Life Extension Final Clerance Sale


Table of Contents
image Treatment of mild hyperhomocystinemia in vascular disease patients
image Can Lowering Homocysteine Levels Reduce Cardiovascular Risk?
image Hyperhomocysteinaemia and end stage renal disease
image High dose-B-vitamin treatment of hyperhomocysteinemia in dialysis patients.
image Long-term folic acid (but not pyridoxine) supplementation lowers elevated plasma homocysteine level in chronic renal failure.
image The role of folic acid in deficiency states and prevention of disease.
image Prevention of neural tube defects.
image Vitamins as homocysteine-lowering agents.
image Homocysteine: Relation with ischemic vascular diseases.
image Drug therapy during pregnancy.
image Clinical rise of a combination containing phosphocreatinine as adjuvant to physiokinesiotherapy
image Gastrointestinal infections in children
image Folic acid supplementation improves erythropoietin response.
image Megaloblastic anemia in patients receiving total parenteral nutrition without folic acid or vitamin B12 supplementation.
image [Is it necessary to supplement with folic acid patients in chronic dialysis treated with erythropoietin?]
image [Primary prophylaxis against cerebral toxoplasmosis. Efficacy of folinic acid in the prevention of hematologic toxicity of pyrimethamine]
image [Myelopathy and macrocytic anemia associated with a folate deficiency. Cure by folic acid]
image Acute folate deficiency associated with intravenous nutrition with aminoacid-sorbitol-ethanol: prophylaxis with intravenous folic acid.
image Common mutation in methylenetetrahydrofolate reductase: Correlation with homocysteine metabolism and late-onset vascular disease
image Homocystinuria: What about mild hyperhomocysteinaemia?
image Dietary methionine imbalance, endothelial cell dysfunction and atherosclerosis
image Homocysteine, folate, and vascular disease
image Hyperhomocysteinemia and venous thromboembolic disease.
image Homocyst(e)ine: an important risk factor for atherosclerotic vascular disease.
image [Homocysteine, a risk factor of atherosclerosis]
image Hyperhomocysteinemia induced by folic acid deficiency and methionine load--applications of a modified HPLC method.
image [Hyperhomocysteinemia]
image Hyperhomocysteinaemia: a role in the accelerated atherogenesis of chronic renal failure?
image Hyperhomocysteinaemia and endothelial dysfunction in young patients with peripheral arterial occlusive disease.
image Vitamin status in patients with inflammatory bowel disease
image Sulfasalazine inhibits the absorption of folates in ulcerative colitis
image The effect of folic acid supplementation on the risk for cancer or dysplasia in ulcerative colitis
image Localized deficiencies of folic acid in aerodigestive tissues
image Male rats fed methyl- and folate-deficient diets with or without niacin develop hepatic carcinomas associated with decreased tissue NAD concentrations and altered poly(ADP-ribose) polymerase activity
image Vitamins as therapy in the 1990s
image Association of esophageal cytological abnormalities with vitamin and lipotrope deficiencies in populations at risk for esophageal cancer
image Intestinal folate transport: Identification of a cDNA involved in folate transport and the functional expression and distribution of its mRNA
image Colorectal cancer and folate status: A nested case-control study among male smokers
image Apoptosis in blood diseases: Review - New data
image Non-glutamate type pyrrolo(2,3-d)pyrimidine antifolates. II. Synthesis and antitumor activity of N5-substituted glutamine analogs
image Identification of in vivo target RNA sequences bound by thymidylate synthase
image Elevated cyclooxygenase-2 levels in Min mouse adenomas
image Levels of folic acid in plasma and in red blood cells of colorectal cancer patients
image Exon-specific DNA hypomethylation of the p53 gene of rat colon induced by dimethylhydrazine: Modulation by dietary folate
image Dietary folate and folylpolyglutamate synthetase activity in normal and neoplastic murine tissues and human tumor xenografts
image Folate deficiency causes uracil misincorporation into human DNA and chromosome breakage: Implications for cancer and neuronal damage
image Exploitation of folate and antifolate polyglutamylation to achieve selective anticancer chemotherapy
image Potent inhibition of human folylpolyglutamate synthetase by suramin
image Epithelial cell folate depletion occurs in neoplastic but not adjacent normal colon mucosa
image Relationship of plasma folic acid and status of DNA methylation in human gastric cancer
image Nutrition and ulcerative colitis
image Influence of dietary folate on folate receptor expression
image Folate, vitamin B12, and neuropsychiatric disorders.
image [Folate and the nervous system (author's transl)]
image [Neutropenia in HIV infection]
image Will an increased dietary folate intake reduce the incidence of cardiovascular disease?
image Genetic polymorphism of methylenetetrahydrofolate reductase and myocardial infarction: A case-control study
image Folate status is the major determinant of fasting total plasma homocysteine levels in maintenance dialysis patients.
image Macrocytosis and cognitive decline in Down's syndrome.
image Nutrient intake and food use in an Ojibwa-Cree community in Northern Ontario assessed by 24h dietary recall
image [Patients with type-II diabetes mellitus and neuropathy have nodeficiency of vitamins A, E, beta-carotene, B1, B2, B6, B12 and folic acid]
image Tissue concentrations of water-soluble vitamins in normal and diabetic rats.
image Effects of oral contraceptives on nutritional status.
image Partial amelioration of AZT-induced macrocytic anemia in the mouse by folic acid.
image [Anemias due to disorder of folate, vitamin B12 and transcobalamin metabolism]
image Ineffective hematopoiesis in folate-deficient mice.
image Premature infants require additional folate and vitamin B-12 to reduce the severity of the anemia of prematurity.
image Apoptosis mediates and thymidine prevents erythroblast destruction in folate deficiency anemia.
image Interactions between folate and ascorbic acid in the guinea pig.
image Relations of vitamin B-12, vitamin B-6, folate, and homocysteine to cognitive performance in the Normative Aging Study.
image Vitamin intake: A possible determinant of plasma homocyst(e)ine among middle-aged adults
image Atherogenesis and the homocysteine-folate-cobalamin triad: Do we need standardized analyses?
image Hyperhomocysteinemia confers an independent increased risk of atherosclerosis in end-stage renal disease and is closely linked to plasma folate and pyridoxine concentrations.
image [Homocysteine, a less well-known risk factor in cardiac and vascular diseases]
image Homocysteine and coronary atherosclerosis.
image Is metabolic evidence for vitamin B-12 and folate deficiency more frequent in elderly patients with Alzheimer's disease?
image Folate, vitamin B12 and cognitive impairment in patients with Alzheimer's disease
image Vitamin B12 and folate concentrations in serum and cerebrospinal fluid of neurological patients with special reference to multiple sclerosis and dementia


Localized deficiencies of folic acid in aerodigestive tissues

Heimburger D.C.; Colby F.; Benitez L.; Raiten D.J.; Butterworth C.E.

Department of Nutrition Sciences, University of Alabama, Birmingham, AL 35294 USA

ANN. NEW YORK ACAD. SCI. (USA), 1992, 669/- (87-96)

The notion that requirements for folic acid may be higher in some tissues than others, resulting in localized deficiencies in spite of blood levels in the normal range was first suggested by the observation of megaloblastic changes in the cervical epithelium that responded to folate supplementation. Theoretically, such deficiencies may arise from elevated folate turnover in response to rapid tissue proliferation or repair; inactivation or alteration of its function by external agents such as tobacco, alcohol, or drugs; or altered metabolism or tissue uptake caused by an inborn error. Marginal dietary intake could aggravate these effects on cells at risk. Evidence for the possible existence of localized folate deficiencies in the aerodigestive tract includes lower circulating folate levels in smokers as compared with nonsmokers; yet lower circulating levels in smokers with bronchial metaplasia; lower folate levels in scrapings of the buccal mucosa of smokers than non-smokers; apparent improvement in bronchial atypical metaplasia in smokers supplemented with folic acid; lower erythrocyte folate levels and higher prevalence of cellular features compatible with folate deficiency in geographic areas and individuals in South Africa at high risk for esophageal cancer; and a trend toward a lower prevalence of colonic dysplasia in ulcerative colitis patients who use folic acid supplements. These observations, as well as animal and in vitro studies, also suggest that folate deficiency may be co-carcinogenic. Further research in this area will be aided by the development of animal models of localized folate deficiency and of methodologies capable of measuring folate levels in minute quantities of tissues and exfoliated cells.

Male rats fed methyl- and folate-deficient diets with or without niacin develop hepatic carcinomas associated with decreased tissue NAD concentrations and altered poly(ADP-ribose) polymerase activity

Journal of Nutrition (USA), 1997, 127/1 (30-36)

Folate is an essential cofactor in the generation of endogenous methionine, and there is evidence that folate deficiency exacerbates the effects of a diet low in choline and methionine, including alterations in poly(ADP-ribose) polymerase (PARP) activity, an enzyme associated with DNA replication and repair. Because PARP requires NAD as its substrate, we postulated that a deficiency of both folate and niacin would enhance the development of liver cancer in rats fed a diet deficient in methionine and choline. In two experiments, rats were fed choline- and folate-deficient, low methionine diets containing either 12 or 8% casein (12% MCFD, 8% MCFD) or 6% casein and 6% gelatin with niacin (MCFD) or without niacin (MCFND) and were compared with folate-supplemented controls. Liver NAD concentrations were lower in all methyl-deficient rats after 2-17 mo. At 17 mo, NAD concentrations in other tissues of rats fed these diets were also lower than in controls. Compared with control values, liver PARP activity was enhanced in rats fed the 12% MCFD diet but was lower in MCFND-fed rats following a further reduction in liver NAD concentration. These changes in PARP activity associated with lower NAD concentrations may slow DNA repair and enhance DNA damage. Only rats fed the MCFD and MCFND diets developed hepatocarcinomas after 12-17 mo. In Experiment 2, hepatocarcinomas were found in 100% of rats fed the MCFD and MCFND diets. These preliminary results indicate that folic acid deficiency enhances tumor development. Becausetions of NAD in these animals were also low, further studies are needed to clearly define the role of niacin in methyldeficient rats.

Vitamins as therapy in the 1990s

Journal of the American Board of Family Practice (USA), 1995, 8/3 (206-216)

Background: At one time vitamins were considered as essential nutrients needed only in very small amounts to prevent deficiency syndromes. Many vitamins and their derivatives, however, are currently being used in the mainstream of medicine as therapeutic modalities. Methods: A MEDLINE literature search for clinical reviews and original studies on the use of vitamins in medicine was conducted along with a search of the obtained papers' bibliographies. The primary years of search were 1990-1994. Research reports written before 1990 were used after cross-referencing from more recent articles. Results and Conclusions: Based on the literature review, several recommendations for the use of vitamins for treatment and prevention are presented. They include topical vitamin A derivatives (tretinoin) for the treatment of acne and age-related skin damage, oral vitamin A derivatives for severe cystic acne (isotretinoin) and psoriasis (etretinate), vitamin D3 for the treatment and prevention of osteoporosis in postmenopausal females, topical vitamin D in psoriasis patients, and niacin for serum cholesterol reduction. Folate appears to decrease the incidence of neural tube defects if given in the preconception phase of pregnancy. Finally, recent preliminary evidence suggests the possible benefit of antioxidants (vitamins C, E, and beta-carotene) in the prevention of atherosclerosis and cancer.

Association of esophageal cytological abnormalities with vitamin and lipotrope deficiencies in populations at risk for esophageal cancer

ANTICANCER RES. (Greece), 1988, 8/4 (711-716)

Esophageal brush cytological screening was undertaken and blood concentrations of micronutrients (vitamins A, E, B12, folic acid and methionine) determined from adults at risk for esophageal carcinoma (EC) in Transkei and Ciskei, Southern Africa. Age-standardised EC rates per 100,000 per annum for both sexes in high, intermediate and low risk districts in Transkei were 74, 51 and 34, respectively. Corresponding rates in high and low EC risk districts in Ciskei were 129 and 9, respectively. Esophageal cytological changes including esophagitis, signs of folic acid deficiency, cellular atypia, dysplasia and cancer, were more prevalent in patients from high than from low EC risk areas. Dietary questionnaires revealed that corn was the main dietary staple in all populations, but that lower intakes of green vegetables, fruits and animal protein occurred in the high risk areas. Significantly lower concentrations of vitamins A, E, B12 and folic acid were present in the blood of patients presenting with cellular dysplasia or malignancy than in cytologically normal patients and in patients from the low risk areas. Concentrations of red cell and plasma folate were significantly lower in patients presenting with cytological signs of folic acid deficiency or cellular atypia. The association of vitamin A, vitamin E and folic acid deficiencies with specific esophageal cytological abnormalities in populations at risk for EC is reported for the first time.

Intestinal folate transport: Identification of a cDNA involved in folate transport and the functional expression and distribution of its mRNA

Biochimica et Biophysica Acta - Biomembranes (Netherlands), 1996, 1281/2 (164-172)

Although the mechanism of folate intestinal transport has been the subject of intensive studies, very little is known about the molecular identity of the transport system(s) involved. In this investigation, we screened a mouse intestinal cDNA library using as probe the cDNA clone of a reduced folate carrier (RFC1) of mouse leukemia L1210 cells, and identified a positive clone, IFC1(RFC1). The cloned cDNA consisted of 2274 base pairs with an open reading frame that encodes a putative polypeptide of 512 amino acids with a predicted molecular mass of 58,112 daltons and 12 putative transmembrane domains. The polypeptide appears to carry a net positive charge (pI = 8.6) which may be important for its interaction with the ngeatively charged substrate. Functional identity of the IFC1(RFC1) clone was established by expression in Xenopus oocytes. An 11-folf increase in 5-methyltetrahydrofolate (5-MTHF) uptake in the cRNA injected oocyte was: (1) 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS)-sensitive; and (2) saturable with an apparent K(m) of 1.99 plus or minus 0.32 microM, and a V(max) of 3782 plus or minus 188 fmol/oocyte per h. The distribution of mRNA species complementary to IFC1(RFC1) in different mouse tissues was examined by Northern blot analysis. In addition to the small intestine, expression of ney, large intestine, brain, heart and liver. Furthermore, mRNA species complementary to IFC1(RFC1) were also detected by Northern blot analysis in the small intestine of human and other animal species (rat and rabbit). Expression of mRNA complementary to IFC1(RFC1) was markedly higher in rat intestinal villus cells than in crypt cells. These results represent the first identification of a folate transporter in mammalian intestine.

Colorectal cancer and folate status: A nested case-control study among male smokers

Cancer Epidemiology Biomarkers and Prevention (USA), 1996, 5/7 (487-494)

Evidence is accumulating that folate, a B vitamin found in green leafy vegetables, may affect the development of neoplasia. We examined the relationship between folate status and colorectal cancer in a case-control study nested within the Alpha-Tocopherol Beta-Carotene Study cohort of male smokers 50-69 years old. Serum folate was measured in 144 incident cases (91 colon, 53 rectum) and 276 controls matched to cases on baseline age, clinic, and time of blood collection. Baseline dietary folate was available from a food-use questionnaire for 386 of these men (92%). Conditional logistic regression modeling was used. No statistically significant association was observed between serum folate and colon or rectal cancer. Although a 2-fold increase in rectal cancer risk was suggested for men with serum folate >2.9 ng/ml and those in the highest quartile of energy-adjusted folate intake, there was no evidence of a monotonic dose-response, and all confidence intervals inconfidence interval (CI), 0.16-0.96), 0.34 (95% CI, 0.130.88), and 0.51 (95% CI, 0.20-1.31) were obtained for the second through fourth quartiles of energy-adjusted folate intake, respectively, compared to the first (P for trend = 0.15). Furthermore, men with a high-alcohol, low- folate, low-protein diet were at higher risk for colon cancer than men who consumed a low-alcohol, high-folate, high-protein diet (OR, 4.79; 95% CI, 1.36-16.93). This study suggests a possible association between low folate intake and increased risk of colon cancer (but not rectal cancer) and highlights the need for further studies that measure dietary folate and methionine, along with biochemical measures of folate (i.e., erythrocyte and serum), homocysteine, and vitamin B12.

Apoptosis in blood diseases: Review - New data

Hematology and Cell Therapy (France), 1996, 38/3 (253-264)

In this report we reviewed the recent data regarding the involvement of apoptosis orprogammed cell death in hematological diseases. We summarized new features of apoptosis including high molecular weight DNA fragmentation and programmed cell death of enucleated cells. We described the recent contributions about the three oncogenes bcl-2, p53 and c-myc. New inducers and inhibitors of apoptosis have been reported, particularly the role of stromal environment, thrombopoietin, erythropoietin and flt-3 ligand has been mentioned. Apoptosis has been studied in red cell pathology: polycythemia, thalassemia and deficiency in folates, vitamin B12, iron and G6PD. Recently, the involvement of programmed cell death has been documented in bone marrow failure and myelodysplasia. In Acute Leukemia, the therapeutic action of numerous drugs has been proven by their in vitro apoptotic effect. The resistance of malignant cells to apoptosis, in Chronic Myeloid Leukemia, due to bcr-abl oncogene, has been partially explained by conformational changes in p53 expression and is reversed by retinoic acid. Numerous reports in Chronic Lymphocytic Leukemia have documented the major role of apoptosis in this disease, especially in therapeutic efficacy of Chlorambucil, Fludarabine and Methylxanthine derivatives. At least, in Myeloma, it has been shown that apoptosis is induced byxamethasone and HMBA, and inhibited by interleukine 6 that prevents activation of SAP Kinases.

Non-glutamate type pyrrolo(2,3-d)pyrimidine antifolates. II. Synthesis and antitumor activity of N5-substituted glutamine analogs

Chemical and Pharmaceutical Bulletin (Japan), 1996, 44/8 (1498-1509)

The glutamic acid moiety of N-(4-(3-(2,4-diamino-7H-pyrrolo(2,3-d)pyrimidin-5-yl)propyl) benzoyl)-L-glutamic acid (1b, TNP-351) and related compounds was replaced with some N5-substituted glutamines. Antifolates (4A-S) were effectively prepared by coupling pyrrolo(2,3-d)pyrimidine carboxylic acids (11a,b) with some properly protected N5-substituted glutamine derivatives (10A-S), which were prepared by coupling Boc-Glu-Ome (7) with various amines (8A-S) using a suitable condensing reagent, followed by hydrolysis. The inhibitory effects of the resulting products on dihydrofolate reductase (DHFR), thymidylate synthetase (TS) and the growth of murine fibrosarcoma Meth A cells in culture were examined. All N5- substituted glutamine analogs (4A-S) inhibited DHFR much more strongly than TNP-351 and some analogs exhibited the same potent growth inhibition of Meth A cells as TNP-351. Some typical analogs (4Bb, 4Db, 4F, 4Oa) were also examined for inhibitory effects on the growth of methotrexate (MTX)- resistant human CCRF-CEM cells in culture and for in vivo antitumor activities against murine leukemia and solid tumors. MTX-resistant cells, with a defect in transport and decreased polyglutamylation activity, showed little cross resistance to the analog (4Oa) having a tetrazole moiety as a substituent of glutamine, which exhibited potent antitumor activities. These results demonstrate that the antifolate analogs (4) with N5-substituted glutamine in place of glutamic acid are novel potent DHFR inhibitors with activity against MTX-resistant tumors. The potent antitumor activity of these analogs (4) may result from their effective uptake via reduced folate carrier in combination with their potent inhibition of DHFR.

Identification of in vivo target RNA sequences bound by thymidylate synthase

Nucleic Acids Research (United Kingdom), 1996, 24/16 (3222-3228)

We developed an immunoprecipitation-RNA-random PCR (rPCR) method to isolate cellular RNA sequences that bind to the folate-dependent enzyme thymidylate synthase (TS). Using this approach, nine different cellular RNAs that formed a ribonucleoprotein (RNP) complex with thymidylate synthase (TS) in human colon cancer cells were identified. RNA binding experiments revealed that seven of these RNAs bound TS with relatively high affinity (IC50 values ranging from 1.5 to 6 nM). One of the RNAs was shown to encode the interferon (IFN)-induced 15 kDa protein. Western immunoblot analyses demonstrated that the level of IFN-induced 15 kDa protein was significantly decreased in human colon cancer H630-R10 cells compared with parent H630 cells. While the level of IFN-induced 15 kDa mRNA expression was the same in parent and TS-overexpressing cell lines, the level of IFN-induced 15 kDa RNA bound t-R10 cells relative to parent H630 cells. These studies begin to define a number of cellular target RNA sequences with which TS interacts and suggest that these TS protein-cellular RNA interactions may have a biological role.

Elevated cyclooxygenase-2 levels in Min mouse adenomas

Gastroenterology (USA), 1996, 111/4 (1134-1140)

Background and Aims: Mutations in the APC gene result in an increased propensity to develop intestinal neoplasia; however, a complete understanding of the mechanisms resulting in tumor formation has remained elusive. Min mice possess a mutation in the APC gene and display a neoplastic phenotype similar to that observed in familial adenomatous polyposis coli in humans. Cyclooxygenase (COX) inhibitors decrease tumor multiplicity in the Min mouse intestine. The present study was designed to determine if there was an increase in COX-2 in adenomas harvested from Min mouse intestine. Methods: COX-2 messenger RNA levels were determined by Northern blots and reverse- transcription polymerase chain reactions of B6(Min) x 129 mouse-derived tumors. Protein levels and localization were determined by Western blots and immunohistochemical staining. Results: The Northern blots revealed an approximately threefold increase in the level of COX-2 messenger RNA in Min mouse adenoma compared with normal mucosa. COX-2 protein levels in adenomatous tissues were also approximately threefold higher compared with normal mucosa from the same mouse. Immunohistochemical staining with a monospecific COX-2 antibody confirmed that increases in COX-2 immunoreactivity were restricted to dysplastic and neoplastic foci within intestinal mucosa. Conclusions: These data show that COX-2 levels may be increased at an early stage in colorectal neoplasia during polyp formation and before invasion.

Levels of folic acid in plasma and in red blood cells of colorectal cancer patients

Biomedicine and Pharmacotherapy (France), 1996, 50/6-7 (303-305)

The levels of folic acid have been determined by radioimmunological method in the plasma and in the red blood cells of normal subjects and colorectal cancer patients. A decrease was evident both in the plasma and erythrocytes of cancer patients. The possible reasons and applications of this observation are discussed.

Exon-specific DNA hypomethylation of the p53 gene of rat colon induced by dimethylhydrazine: Modulation by dietary folate

American Journal of Pathology (USA), 1996, 149/4 (1129-1137)

Folate deficiency enhances colorectal carcinogenesis in dimethylhydrazine-treated rats. Folate is an important mediator of DNA methylation, an epigenetic modification of DNA that is known to be dysreguioted in the early stages of colorectal cancer. This study investigated the effect of dimethylhydrazine on DNA methylation of the colonic p53 gene and the modulation of this effect by dietary folate. Sprague-Dawley rats were fed diets containing 0, 2, 8, or 40 mg of folate/kg of diet. Five weeks after diet initiation, dimethylhydrazine was injected weekly for fifteen weeks. Folate-depleted and folate-replete control animals did not receive dimethylhydrazine and were fed the 0- and 8-mg folate diets, respectively. The extent of p53 methylation was determined by a quantitative HpaII-polymerase chain reaction. In exons 6 and 7, significant p53 hypomethylation was observed in all dimethylhydrazine-treated rats relative to controls (P < 0.01), independent of dietary folate. In exon 8, significant p53 hypomethylation was observed only in the dimethylhydrazine-treated folate-depleted rats compared with controls (P = 0.038) and was effectively overcome by increasing levels of dietary folate (P = 0.008). In this model, dimethylhydrazine induces exon-specific p53 hypomethylation. In some exons, this occurs independent of dietary folate, easing levels of dietary folate effectively override the induction of hypomethylation in a dose-responsive manner. This may be a mechanism by which increasing levels of dietary folate inhibit colorectal carcinogenesis.

Dietary folate and folylpolyglutamate synthetase activity in normal and neoplastic murine tissues and human tumor xenografts

Biochemical Pharmacology (USA), 1996, 52/9 (1477-1479)

The importance of polyglutamation for the activation of natural folates and classical antifolates and recent evidence for the role of dietary folate as a biochemical modulator of antifolate efficacy led us to investigate the influence of changes in dietary folate on folylpolyglutamate synthetase (FPGS) activity. Activities were measured using lometrexol (6R-5,10-dideazatetrahydrofolic acid) as a substrate for FPGS with extracts of murine tissues, murine tumors, and human tumor xenografts from mice on standard diet or low folate diet. Tissues and tumors from mice on standard diet exhibited a 6-fold range of FPGS activity. Kidney had the lowest activity (36 pmol/hr . mg protein), followed by the human xenograft PANC-1 pancreatic carcinoma (46 pmol/hr . mg protein), liver (109 pmol/hr . mg protein), murine C3H mammary tumor (112 pmol/hr . mg protein), and the human xenograft MX-1 mammary carcinoma (224 pmol/hr . mg protein). In response to restricted dietary folate, four out of five tissues had significantly increased (25-50%) FPGS activity. Only the tumor with highest FPGS activity under standard diet conditions (MX-1 mammary) did not respond to low folate diet. The results indicate that changes in dietary folate intake can modulate FPGS activity significantly in vivo and suggest that the tissue distribution and toxicities of classical antifolates requiring polyglutamation for activation and cellular retention will be influenced significantly by folate status of the host.

Folate deficiency causes uracil misincorporation into human DNA and chromosome breakage: Implications for cancer and neuronal damage

Proceedings of the National Academy of Sciences of the United States of

America (USA), 1997, 94/7 (3290-3295)

Folate deficiency causes massive incorporation of uracil into human DNA (4 million per cell) and chromosome breaks. The likely mechanism is the deficient methylation of dUMP to dTMP and subsequent incorporation of uracil into DNA by DNA polymerase. During repair of uracil in DNA, transient nicks are formed; two opposing nicks could lead to chromosome breaks. Both high DNA uracil levels and elevated micronucleus frequency (a measure of chromosome breaks) are reversed by folate administration. A significant proportion of the U.S. populate levels, in the range associated with elevated uracil misincorporation and chromosome breaks. Such breaks could contribute to the increased risk of cancer and cognitive defects associated with folate deficiency in humans.

Exploitation of folate and antifolate polyglutamylation to achieve selective anticancer chemotherapy

Investigational New Drugs (USA), 1996, 14/3 (317-323)

Synthesis of poly(gamma-glutamate) metabolites of natural folates and antifolates is a critical process. Folylpolyglutamates are essential for cell proliferation. Polyglutamates of glutamate (Glu)-containing antifolates are often critical for their cytotoxic action and are relevant to antifolate resistance. However, the role of polyglutamate synthesis in selectivity is less clear. We have undertaken a research program to further define the significance of polyglutamate metabolism and to devise ways to exploit this metabolism to achieve greater therapeutic selectivity in cancer chemotherapy. This article briefly reviews several approaches tested thus far. Inhibition of folylpolyglutamate synthesis should lead to cell death. Current ornithine (Orn)-containing folate-based inhibitors of the enzyme responsible for their synthesis, folylpolyglutamate synthetase (FPGS), are poorly t protonated delta-amine. Replacement of Orn with 4,4-difluoroOrn, the delta-amine of which has a much lower pK(alpha) and is thus less protonated at physiological pH, was explored. Since it is unclear how polyglutamylation contributes to selectivity, we explored generic means either to eliminate or to enhance polyglutamylation. The data indicate that substitution for Glu in an antifolate by some Glu analogs in which the gamma-COOH is either altered or replaced (e.g., gamma-tetrazole-Glu) leads to loss of both FPGS substrate activity and binding; antifolate target specificity is unchanged, while uptake is actually enhanced. Substitution of 3,3-difluoroGlu for Glu leads to enhanced polyglutamylation (although probably only to the diglutamate), retention of target specificity, and at least equal uptake. Comparative studies of the same antifolate containing different replacements for Glu, such as gamma-tetrazole-Glu (no polyglutamylation) or 3,3-difluoroGlu (enhanced polyglutamylation), will be useful in exploring the role and significance of polyglutamylation.

Potent inhibition of human folylpolyglutamate synthetase by suramin

Archives of Biochemistry and Biophysics (USA), 1996, 335/1 (139-144)

Suramin, a bis-hexasulfonated napthylurea, was studied as an inhibitor of human folylpolyglutamate synthetase (FPGS), a crucial enzyme in folate metabolism. Suramin is a more potent (IC50, 0.9 microM) inhibitor of FPGS partially purified from CCRF-CEM human leukemia cells than is bromosulfophthalein (IC50, 17 microM), the first reported nonsubstrate-analog inhibitor of FPGS (J. J. McGuire et al, Adv. Exptl. Med. Biol. 163, 199, 1983). FPGS inhibition by suramin is reversed by bovine serum albumin (which binds suramin). Suramin is a noncompetitive inhibitor with aminopterin (K(ii) = 0.9 microM; K(is) = 1.1 microM) and glutamic acid (K(ii) = 1.0 microM; K(is) = 5.2 microM) as the variable substrates; suramin inhibition tends toward being competitive with respect to the third FPGS substrate, ATP (K(ii) = 3.4 microM; K(is) = 0.35 microM), since the major effect is on its K(m). Suramin is a much less potent inhibitor of two other folate-dependent enzymes, dihydrofolate reductase (IC50, 38 microM; methotrexate (MTX), 0.6 nM) and thymidylate synthase (IC50, 87 microM; MTX, 48 microM). The effects of suramin on growth of CCRF-CEM cells and a MTX-resistant subline (R30dm) expressing low levels of FPGS activity were determined. R3Odm is slightly collaterally sensitive to suramin consistent with FPGS inhibition contributing to the cytotoxic mechanism. These data, and those of Rideout et al. (Int. J. Cancer 61, 840, 1995), demonstrating that the reduced folate carrier system of CCRF-CEM is inhibited, suggest that inhibition of folate metabolism could be involved in the mechanism of action of suramin.

Epithelial cell folate depletion occurs in neoplastic but not adjacent normal colon mucosa

Gastroenterology (USA), 1997, 112/4 (1163-1168)

Background and Aims: Restricted folate supply is associated with the development of carcinoma, and folate supplements have a protective effect in colorectal carcinoma. This effect may be mediated through correction of local folate deficiency. The aim of this study was to define the folate content of neoplastic colonic epithelial cells and its relation to that of adjacent normal tissue and circulating levels. Methods: Epithelial cells were isolated from endoscopic biopsy specimens of normal, adenocarcinoma, adenoma, and adjacent normal colonic mucosa by ion chelation. Intracellular folate levels were determined by microbiological assay. Results: Folate levels in carcinoma specimens were lower than in adjacent normal tissue (P < 0.02). Levels in adenoma epithelial cells were lower than in adjacent normal tissue, although this did not reach statistical significance (P < 0.06). Epithelial cells from normal tissue and mucosa adjacent to tumors and adenomata had similar folate contents. Blood folate and vitamin B12 indices for all groups were normal. Conclusions: Malignant colon epithelial cells show a relative localized folate deficiency. However, there is no evidence for the occurrence of generalized mucosal folate deficiency. This finding suggests that folate supplements do not inhibit carcinogenesis through correction of localized folate depletion.

Relationship of plasma folic acid and status of DNA methylation in human gastric cancer

Journal of Gastroenterology (Japan), 1997, 32/2 (171-175)

To evaluate the anti-cancer effects of folic acid at the molecular level, we determined plasma folic acid concentration by radioimmuno-assay and the degree of total genomic DNA methylation by incubating DNA with 3H-S-adenosylmethionine (3H-SAM) in the presence of a methylase, and analyzed the methylation status of the c-myc and c-Ha-ras oncogenes by Southern blotting in 21 patients with advanced gastric cancer. The degree of total genomic DNA methylation of cancerous tissues was significantly lower than that of paracancerous and non-cancerous tissues; c-myc and c-Ha-ras oncogenes from cancerous (10/21, 5/10) and paracancerous (13/21, 4/10) tissues were hypomethylated. The plasma folic acid concentration in patients who showed hypomethylation was lower than that patients showing normal methylation. These findings suggest that a decrease in folic acid, and the subsequent DNA hypomethylation, may be invoesis.

Nutrition and ulcerative colitis

Bailliere's Clinical Gastroenterology (United Kingdom), 1997, 11/1

The role of diet in the aetiology and pathogenesis of ulcerative colitis (UC) remains uncertain. Impaired utilization by colonocytes of butyrate, a product of bacterial fermentation of dietary carbohydrates escaping digestion, may be important. Sulphur-fermenting bacteria may be involved in this impaired utilization. Oxidative stress probably mediates tissue injury but is probably not of causative importance. Patients with UC are prone to malnutrition and its detrimental effects. However, there is no role for total parenteral nutrition and bowel rest as primary therapy for UC. The maintenance of adequate nutrition is very important, particularly in the peri-operative patient. In the absence of massive bleeding, perforation, toxic megacolon or obstruction, enteral rather than parenteral nutrition should be the mode of choice. Nutrients may be beneficial as adjuvant therapy. Butyrate enemas have improved patients with otherwise recalcitrant distal colitis in small studies, Non-cellulose fibre supplements are of benefit in rats with experimental colitis. Eicosapentaenoic acid in fish oil has a steroid-sparing effect which, although modest, is important, particularly in terms of reducing the risk of osteoporosis, but it seems to have no role in the patient with inactive disease. gamma-Linolenic acid and anti-oxidants also are showing promise. Nutrielso modify the increased risk of colorectal carcinoma. Oxidative stress can damage tissue DNA but there are no data published at present on possible protection from oral anti-oxidants. Butyrate protects against experimental carcinogenesis in rats with experimental colitis. Folate supplementation is weakly associated with decreased incidence of cancer in UC patients when assessed retrospectively. Vigilance should be maintained for increased micronutrient requirements and supplements given as appropriate. Calcium and low-dose vitamin D should be given to patients on long-term steroids and folate to those on sulphasalazine.

Influence of dietary folate on folate receptor expression

Lilly Corporate Center, Indi(USA), 1996, 2/7 (1135-1141)

Membrane-associated folate receptors (FRs) have been detected in many mammalian species, and multiple isoforms have been identified. The pharmacological properties of FRs from murine kidney, liver, and six murine tumors were characterized. Murine kidney expressed primarily folate-binding protein 1, analogous to human FR-alpha whereas murine liver expressed predominantly folate-binding protein 2, analogous to human FR-beta. Five of six murine tumors expressed high-affinity PRs with pharmacological properties consistent with folate-binding protein 1 isoform expression. Restriction of dietary folate resulted in significant changes in the PR expression in most murine tissues. Kidney and tumor PRs showed a decreased affinity for folic acid, suggesting a change in isoform expression in response to a low folate diet. Density of the PR in the kidney decreased and, in contrast, density of the FR in all tumors increased. The response of tile liver to a low folate diet was unique in that there were no detectable changes in affinity or density of liver FR. Changes in dietary folate that modulate PR isoform expression may have relevance for cancer patients treated with antifolates.

Folate, vitamin B12, and neuropsychiatric disorders.

Nutr Rev (UNITED STATES) Dec 1996, 54 (12) p382-90

Folate and vitamin B12 are required both in the methylation of homocysteine to methionine and in the synthesis of S-adenosylmethionine. S-adenosylmethionine is involved in numerous methylation reactions involving proteins, phospholipids, DNA, and neurotransmitter metabolism. Both folate and vitamin B12 deficiency may cause similar neurologic and psychiatric disturbances including depression, dementia, and a demyelinating myelopathy. A current theory proposes that a defect in methylation processes is central to the biochemical basis of the neuropsychiatry of these vitamin deficiencies. Folate deficiency may specifically affect central monoamine metabolism and aggravate depressive disorders. In addition, the neurotoxic effects of homocysteine may also play a role in the neurologic and psychiatric disturbances that are associated with folate and vitamin B12 deficiency.

[Folate and the nervous system (author's transl)]

Sem Hop (FRANCE) Sep 18-25 1979, 55 (31-32) p1383-7

The responsibility of the folate deficiency in some neuropsychiatric disorders is recent knowledge. The role of the folate on the nervous system is not yet well definite, but the action on the metabolism of the amino-acids, on the purine and the pyrimidine synthesis and on the metabolism of the catecholamins are certainly essential. The neuropsychiatric diseases secondary to the folate deficiency are numerous: dementia, schizophrenia like syndromes, insomnia, irritability, forgetfulness, endogenous depression, organic psychosis, pueperal psychosis, peripheral neuropathy, myelopathy (spinal cord syndrome and/or pyramidal tract damage), restless legs syndrome. Clinically the diagnosis may be difficult with sub acute combined degenration secondary to the pernicious anaemia, and the dosage of the folate (in serum, in red-cells and in cerebrospinal fluid) is necessary. The congenital defects in the uptake or utilization of the folate are associated with neuropsychiatric disturbances. The treatment is easy and safe if the vitamin B12 deficiency is eliminated and if employed with caution in epileptic patients because folate can induced seizures.

[Neutropenia in HIV infection]

An Med Interna (SPAIN) Apr 1997, 14 (4) p199-208

The infection by human immunodeficiency virus (HIV) are commonly associated with haematologic abnormalities (anemia, leucopenia and thrombocytopenia). We review the neutropenia. In patients infected with HIV neutropenia is seen in the 8-50% of them, and also have abnormalities in the neutrophil function. Etiology: Direct injury of HIV on bone marrow, anti-neutrophil antibodies, drugs, opportunistic infections of bone marrow, vitamin B12 and folate deficiency, radiation therapy, and hemophagocytic syndrome. CONSEQUENCES: These patients have a increased risk of infections, since the neutrophils play an important role in the defense against bacterial and certain fungal infections. TREATMENT: It must to treat the causes. When it is not possible, Colony-Stimulating Factor can be use to stimulate the bone marrow granulopoiesis.

Will an increased dietary folate intake reduce the incidence of cardiovascular disease?

Ubbink J.B.; Becker P.J.; Vermaak W.J.H.

Department of Chemical Pathology, University of Pretoria, PO Box 2034, Pretoria 0001 South Africa

Nutrition Reviews (USA), 1996, 54/7 (213-216)

Based on a meta-analysis of published studies, it has been estimated that approximately 10% of coronary artery disease cases are attributable to hyperhomocys(e)inemia. It has also been calculated that food fortification with folate might reduce the number of cases of coronary artery disease in the United States by 50,000 per year. However, the use of statistical concepts to estimate the expected benefits of this intervention strategy may be misleading.

Genetic polymorphism of methylenetetrahydrofolate reductase and myocardial infarction: A case-control study

Schmitz C.; Lindpaintner K.; Verhoef P.; Gaziano J.M.; Buring J.

Division of Cardiovascular Diseases, Brigham and Women's Hospital, 75 Francis St, Boston, MA 02115 USA

Circulation (USA), 1996, 94/8 (1812-1814)

Background: Elevated total plasma homocyst(e)ine (tHcy; the composite of homocysteine-derived moieties in their oxidized and reduced forms) levels are a risk factor for coronary heart disease, stroke, and venous thrombosis. tHcy plasma levels are influenced by folate, vitamins B6 and B12, as well as by hereditary factors. A point mutation (C677T) in the gene encoding methylenetetrahydrofolate reductase, an enzyme involved in homocysteine remethylation, has been reported to render the enzyme thermolabile and less active and has been associated with elevated they in homozygous carriers (+/+ genotype) as well as with increased risk of premature cardiovascular disease. Methods and Results: We investigated whether this mutation influences risk for myocardial infarction (MI) and plasma levels of they and whether this effect may be modified by dietary folate intake in 190 MI cases and 188 control subjects from the Boston Area Health Study. Genotype frequencies were 37.8% for -/-, 47.8% for +/- and 14.4% for +/+ in the control group and 50.0% for -/- 34.7% for +/- and 15.3% for +/+ in the case group. The relative risk for MI associated with the +/+ genotype (compared with +/- and -/-) was 1.1 (95% CI, 0.6 to 1.9; P=.8). Stratification by folate intake values above and below the median did not significantly alter these results. Plasma tHcy levels were 9.9plus or minus2.7 micromol/L in -/- individuals. 10.6plus or minus3.8 micromol/L in +/- individuals, and 9.1plus or minus2.3 micromol/L in +/+ individuals (P(trend)=NS; determined in 68 cases and 59 control subjects). Conclusions: Our data show that homozygosity for the C677T mutation in this largely white, middle-class US population is not associated with increased risk for MI, irrespective of folate intake. This suggests that this mutation does not represent a useful marker for increased cardiovascular risk in this and in similar populations.

Folate status is the major determinant of fasting total plasma homocysteine levels in maintenance dialysis patients.

Bostom A.G.; Shemin D.; Lapane K.L.; Nadeau M.R.; Sutherland P.; Chan J.; Rozen R.; Yoburn D.; Jacques P.F.; Selhub J.; Rosenberg I.H.

Vitamin Bioavailability Laboratory, USDA Human Nutrit. Research Center, Tufts New England Medical Center, 711 Washington Street, Boston, MA 02111 USA

Atherosclerosis (Ireland), 1996, 123/1-2 (193-202)

Limited data are available on the determinants of homocysteinemia or the association between plasma homocysteine (Hey) levels and prevalent cardiovascular disease (CVD) in maintenance dialysis patients. We assessed etiology of renal failure, residual renal function and dialysis adequacy-related variables, and vitamin status, as determinants of fasting total plasma homocysteine (Hcy) in 75 maintenance dialysis patients. We also assessed the potential interactive effect on plasma I-Icy of folate status and a common mutation (ala to val; homozygous val-val frequency similar 10% in methylenetetrihydrofolate reductase (MTHFR), a folate-dependent enzyme crucial for the remethylation of homocysteine (Hcy) to methionine. Lastly, we evaluated whether the Hey levels differed amongst these patients in the presence or absence of prevalent CVD, after adjustment for the traditional CVD risk factors. Fasting total plasma Hey, folate, pyridoxal 5'-phosphate (PLP; active B6), B12, creatinine, glucose, total and HDL cholesterol levels, and presence of the ala to val MTHFR mutation were determined, and clinical CVD and CVD risk factor prevalence were ascertained. General linear modelling/analysis of covariance revealed: (1) folate status and serum creatinine were the only significant independent predictors of fasting Hey; (2) there was a significant interaction between presence of the val mutation and folate status, i.e., among patients with plasma folate below the median (< 29.2 ng/ml), geometric mean Hey levels were 33% greater (29.0 vs. 21.8 microM, P = 0.012) in the pooled homozygotes (val-val) and heterozygotes (ala-val) for the ala to val mutation, vs. normals (ala-ala); (3) there was no association between prevalent CVD and plasma Hey. Given potentially intractable survivorship effects, prospective cohort studies will be required to clarify the relationship between plasma Hcy or any putative CVD risk factor, and incident CVD in dialysis patients. If a positive association between plasma Hcy and incident CVD can be established in maintenance dialysis patients, the current data provide a rationale for additional folic acid supplementation in this patient population.

Macrocytosis and cognitive decline in Down's syndrome.

British Journal of Psychiatry 1986 Dec Vol 149 797-798

Questions R. L. Welfare and K. E. Hewitt's (see PA, Vol 74:22330) proposal of a causal relationship between cognitive decline and macrocytosis in Down's syndrome, suggesting that both may be related to undetected folate vitamin deficiency.

Nutrient intake and food use in an Ojibwa-Cree community in Northern Ontario assessed by 24h dietary recall

Nutrition Research (USA), 1997, 17/4 (603-618)

As part of a diabetes prevention program in a remote Ojibwa-Cree community in Northern Ontario, 72% of residents >9y of age (729/1019) underwent an oral glucose tolerance test; >98% (718/729) of participants provided a complete 24h dietary recall. Their diet was typical of that for aboriginal North American populations undergoing rapid cultural change, being high in saturated fat (similar13% energy), cholesterol and simple sugars (similar22% energy), low in dietary fibre (11g/d) and nigh in glycaemic index (similar90). There were high prevalences of inadequate intakes of vitamin A (77%), calcium (58%), vitamin C (40%) and folate (37%). Adolescents aged 10-19y consumed more simple sugars and less protein than adults aged >49y and ate more potato chips, flied potatoes, hamburger, pizza, soft drinks and table sugar. Adults >49y retained more traditional eating habits, using more bannock (fried bread) and wild meats than younger individuals. Interventions to prevent diabetes in the community should include culturally appropriate and effective ways to improve the nutritional adequacy of the diet, reduce fat intake and increase the use of less refined carbohydrate foods.

[Patients with type-II diabetes mellitus and neuropathy have nodeficiency of vitamins A, E, beta-carotene, B1, B2, B6, B12 and folic acid]

Med Klin (GERMANY) Aug 15 1993, 88 (8) p453-7

The present study was aimed to determine the vitamin status of vitamins A, E, beta-carotene, B1, B2, B6, B12 and folate in plasma using HPLC and vitamins B1, B2 and B6 in erythrocytes using the apoenzyme stimulation test with the Cobas-Bio analyzer in 29 elderly type II diabetic women with (G1: n = 17, age: 68.6 +/- 3.2 years) and without (G2: n = 12, age: 71.8 +/- 2.7 years) diabetic polyneuropathy. The basic parameters as age, hemoglobin A1c, fructosamine and duration of the disease did not differ in both groups. Furthermore, retinopathy was assessed with fundoscopy and nephropathy with creatinine clearance. The creatinine clearance (G1: 50.6 +/- 3.4 vs. G2: 63.6 +/- 3.7 ml/min, 2p < 0.025) and the percentage of retinopathy (G1: 76.5% vs. G2: 16.7%, 2p = 0.002) were different indicating that G1 had significantly more severe late complications than G2. Current plasma levels of all measured vitamins (A, E, beta-carotene, B1, B2, B6, B12 and folate) and the status of B1, B2 and B6 in erythrocytes did not vary between the two groups (2p > 0.1). In summary, we found a lack of association between the actual vitamin condition in plasma and erythrocytes and diabetic neuropathy.

Tissue concentrations of water-soluble vitamins in normal and diabetic rats.

Int J Vitam Nutr Res (SWITZERLAND) 1993, 63 (2) p140-4

Changes in circulating and tissue concentrations of several vitamins have been reported in diabetic animals and human subjects. In this study, the effect of short-term (2 weeks) streptozotocin diabetes on folate, B6, B12, thiamin, nicotinate, pantothenate, riboflavin and biotin in liver, kidney, pancreas, heart, brain and skeletal muscle of rats was investigated. The tissue distribution of vitamins varied widely in normal rats. Diabetes significantly lowered folate in kidney, heart, brain, and muscle; B6 in brain; B12 in heart; thiamin in liver and heart; nicotinate in liver, kidney, heart and brain; pantothenate in all tissues; riboflavin in liver, kidney, heart, and muscle. These results indicate that experimental diabetes causes a depression of several water-soluble vitamins in various tissues of rats.

Effects of oral contraceptives on nutritional status.

Am Fam Physician (UNITED STATES) Jan 1979, 19 (1) p119-23

Major effects of oral contraceptives on nutritional status are elevation of triglycerides, decline in glucose tolerance, an apparent increase in the need for folate and vitamins C, B2 and B6, and a decrease in iron loss. Women at greater risk of nutritional deficits due to oral contraceptives include those who have just had a baby, are planning to have a baby later, already show nutritional deficiencies, have had recent illness or surgery, have poor dietary habits, are still growing or have a family history of diabetes or heart disease.

Partial amelioration of AZT-induced macrocytic anemia in the mouse by folic acid.

Stem Cells (Dayt) (UNITED STATES) Sep 1993, 11 (5) p393-7

CBA/Ca mice being maintained on azidothymidine (AZT) in drinking water were given vitamin B12 and folate in an effort to ameliorate the macrocytic anemia associated with AZT administration. The B12/folate regimen was ineffectual, but higher doses of folate given daily resulted in an increase in RBC and a decrease in mean corpuscular hemoglobin (MCH) and polychromatophilic erythrocytes (PCE) while mean corpuscular volume (MCV) remained relatively constant. The implications of these findings on RBC production and hemoglobin synthesis are discussed.

[Anemias due to disorder of folate, vitamin B12 and transcobalamin metabolism]

Rev Prat (FRANCE) Jun 1 1993, 43 (11) p1358-63

Macrocytic megaloblastic anemia is the most typical but the latest sign of a cobalamin (vitamin B12) and/or folic acid deficiency or of a congenital abnormality of cobalamin and folate metabolism. Macrocytosis in blood and megaloblastosis in bone marrow are the morphological features of a disturbance in cell division related to a defect in DNA biosynthesis. Macrocytosis without anemia, normocytic normochronic anemia with a low reticulocyte cell count or microcytic hypochromic anemia in case of associated iron deficiency do not exclude a vitamin deficiency. Neurological or psychiatric disorders and immune abnormalities have been reported in patients with vitamin B12 or folate deficiencies or in children with congenital abnormalities of these 2 vitamins; such manifestations may even occur without anemia.