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Life Extension Magazine

LE Magazine September 2001


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Prevention of type 2 diabetes: role of metformin.

Metformin lowers moderate (nondiabetic) fasting hyperglycaemia in individuals at risk for type 2 diabetes without causing hypoglycaemia. In addition, it has demonstrated favourable action on several cardiovascular risk factors that are often present in these individuals: it favours the maintenance of diet-induced weight loss and its associated improvement in fibrinolysis; and it lowers plasma concentrations of fasting insulin, total and low density lipoprotein-cholesterol, free fatty acids, and of two markers of endothelial damage-tissue plasminogen activator antigen and von Willebrand factor. These effects together with the good tolerability profile of the drug position metformin as a first-line agent for the prevention of type 2 diabetes.

Drugs 1999;58 Suppl 1:71-3; discussion 75-82

The effect of metformin on the metabolic abnormalities associated with upper-body fat distribution. BIGPRO Study Group.

OBJECTIVE: The constellation of anomalies associated with insulin resistance is a plausible additional cause of ischemic cardiovascular disease and of NIDDM. To test this hypothesis in a primary prevention trial, the effects of metformin as a potential candidate for intervention in the insulin resistance syndrome (IRS) were evaluated in 324 middle-aged subjects with upper-body obesity. RESEARCH DESIGN AND METHODS: Trial patients were selected on the basis of a high waist-to-hip ratio. They were randomly allocated to receive either metformin or placebo, following a double-blind procedure. After 1 year of treatment, the main clinical and biological parameters of the IRS were assessed and their evolution compared between treatment groups. RESULTS: Compared with placebo, metformin induced a significant weight loss, a better maintenance of fasting blood glucose, total and LDL cholesterol levels, and a greater decrease of fasting plasma insulin concentration. Moreover, tissue-type plasminogen activator antigen, a marker of fibrinolytic impairment, showed a significant decrease under metformin. By contrast, metformin treatment had no significant effect on blood pressure or serum triglyceride and HDL cholesterol concentrations. The main side effect of metformin was diarrhea. CONCLUSIONS: The BIGuanides and Prevention of Risks in Obesity (BIGPRO1) results suggest that metformin would be a suitable candidate for long-term intervention for the prevention of diabetes but that its use in a trial of primary prevention of cardiovascular diseases requires either a reevaluation of its properties toward the most potentially atherogenic anomalies of the IRS or a better definition of the target population.

Diabetes Care 1996 Sep;19(9):920-6

Metformin-induced resumption of normal menses in 39 of 43 (91%) previously amenorrheic women with the polycystic ovary syndrome.

In 43 amenorrheic women with polycystic ovary syndrome (PCOS), 31 (74%) with fasting hyperinsulinemia (> or =20 microU/mL), our aim was to determine whether metformin (Bristol-Myers Squibb, Princeton, NJ), which reduces hyperinsulinemia, would reverse the endocrinopathy of PCOS, allowing resumption of regular normal menses. A second aim was to assess the effects of weight loss versus other metformin-induced effects on ovarian function, and to determine if there were different responses to metformin between those who lost weight and those who did not. A third aim was to assess associations between PCOS, 4G/5G polymorphism in the promoter sequence of the plasminogen activator inhibitor-1 gene (PAI-1 gene), and PAI activity (PAI-Fx). Of the 43 women, 40 (93%) had normal fasting blood glucose and 37 had normal hemoglobin A1C (HgA1C); only three (7%) had type 2 diabetes mellitus. Metformin (1.5 to 2.25 g/d) was given for 6.1+/-5.1 months (range, 1.5 to 24), to 16 patients for less than 3 months, to 12 for 3 to 6 months, and to 15 for at least 6 months. On metformin, 39 of 43 patients (91%) resumed normal menses. The percentage of women resuming normal menses did not differ among treatment duration groups (P<.1) or among dose groups (P>.1). The body mass index (BMI) decreased from 36.4 + 7 Kg/m2 at study entry to 35.1+/-6.7 on metformin (P=.0008). Of 43 patients, 28 (67%) lost weight (1 to 69 pounds), with nine (21%) losing at least 12 pounds. On metformin, the median fasting serum insulin decreased from 26 microU/mL to 22 (P=.019), testosterone decreased from 61 ng/dL to 47 (P=.003), and estradiol increased from 41 pg/mL to 71 (P=.0001). Metformin-induced improvements in ovarian function were independent of weight loss (testosterone decrease, P<.002; estradiol increase, P<.0004). The change in response variables on metformin did not differ (P>.05) between those who lost weight and those who did not, excepting Lp(a), which increased 4 mg/dL in those who lost weight and decreased 9 mg/dL in those who did not (P = .003). The change in response variables on metformin did not differ among the five quintiles of weight loss, excepting fasting glucose (P<.05), which increased 6 mg/dL in those who lost the least weight on metformin versus those in the 60th to 80th percentile for weight loss, in whom glucose decreased 33 mg/dL. Although the pretreatment fasting serum insulin was not significantly correlated with testosterone (r=.24, P=.13) or androstenedione (r=.27, P=.09), on metformin, the change in insulin correlated positively with the change in testosterone (r=.35, P=.047) and with the change in androstenedione (r=.48, P=.01). Patients were more likely than normal controls (83% v 64%, P=.016) to be heterozygous or homozygous for 4G polymorphism of the PAI-1 gene and were also more likely to have high PAI-Fx (> or =22 U/mL, 28% v3%, chi(2)=10.1, P=.001). Metformin reduces the endocrinopathy of PCOS, allowing resumption of normal menses in most (91%) previously amenorrheic women with PCOS.

Metabolism 1999 Apr;48(4):511-9

Metformin therapy in polycystic ovary syndrome reduces hyperinsulinemia, insulin resistance, hyperandrogenemia, and systolic blood pressure, while facilitating normal menses and pregnancy.

Using polycystic ovary syndrome (PCOS) as a model of insulin resistance and hyperandrogenism, our specific aim was to assess the effect of metformin on lipoproteins, sex hormones, gonadotropins, and blood pressure in 26 women with PCOS who were studied at baseline, received metformin 1.5 g/d for 8 weeks, and were then restudied. None of the women had normal menstrual cycles, 100% had multiple subcapsular follicules by pelvic ultrasound, 90% were hirsute, and 85% had high free testosterone. Comparing post-metformin versus baseline levels, the Quetelet Index (QI) decreased 1.5% (P = .04) and the waist to hip ratio (WHR) decreased 2.8% (P = .003). After covariance adjusting for changes in the QI and WHR, on metformin the area under the insulin curve (IA) during oral glucose tolerance testing decreased 35% (P = .04), and the insulin area to glucose area ratio decreased 31% (P = .03). On metformin, covariance-adjusted systolic blood pressure (SBP) decreased (P = .04) and apo A-1 increased (P = .05). On metformin, with improvement in insulin sensitivity, there were sharp reductions in covariance-adjusted luteinizing hormone ([LH] P = .0007), total testosterone ([T] P = .0004), free T (P = .0001), androstenedione (P = .002), dehydroepiandrosterone sulfate ([DHEAS] P = .006), and the free androgen index ([FAI] P = .0005), with increments in follicle-stimulating hormone ([FSH] P = .04) and sex hormone-binding globulin ([SHBG] P = .04).

Metabolism 1994 May;43(5):647-54

Alzheimer’s disease

Causative genes in Alzheimer’s disease.

Recently, some Alzheimer-associated genes have been found: amyloid precursor protein (APP), apolipoprotein E (apoE), presenilin 1 (PS-1) and presenilin 2 (PS-2). First, we examined mutations of APP, PS-1, and PS-2 genes in familiar Alzheimer’s disease (FAD) (7 cases) found in San-in district by single-strand conformation polymorphism and sequence analysis. These seven cases with FAD did not show any mutations of APP, PS-1, and PS-2 genes. Other susceptibility genes of FAD still remain to be not identified. Many reports have established that apoE genotype distribution for the epsilon 4 allele is a susceptibility factor for the earlier onset and more rapid progression of Alzheimer’s disease (AD). However, the cause of sporadic AD (SAD) has not been elucidated fully. Other genetic factors may be associated with development of SAD. Second, we investigated the association between polymorphisms of the estrogen receptor (ER) alpha gene and SAD. The frequencies of P and X alleles in SAD were significantly higher than those in the control group (p < 0.05). Polymorphisms of the ER alpha gene may be a genetic risk factor for SAD. The apoE genotype is a genetic factor closely related SAD, but it is not full by appreciated how apoE has an effect on developing AD. There are few reports on the quantitative change of apoE, namely the expression of apoE mRNA. Third, ApoE mRNA level in the brains of patients with Alzheimer’s disease (27 cases) and Down’s syndrome (11 cases) was determined by reverse transcriptase-polymerase chain reaction (RT-PCR). ApoE mRNA level in the DS as well as AD was significantly higher than that in control group (p < 0.05, p < 0.05, respectively). High levels of apoE mRNA in AD and DS may play an important role in the development of Alzheimer pathology.

Nippon Ronen Igakkai Zasshi 2001 Mar;38(2):117-20

Cerebral metabolic and cognitive decline in persons at genetic risk for Alzheimer’s disease.

The major known genetic risk for Alzheimer’s disease (AD), apolipoprotein E-4 (APOE-4), is associated with lowered parietal, temporal, and posterior cingulate cerebral glucose metabolism in patients with a clinical diagnosis of AD. To determine cognitive and metabolic decline patterns according to genetic risk, we investigated cerebral metabolic rates by using positron emission tomography in middle-aged and older nondemented persons with normal memory performance. A single copy of the APOE-4 allele was associated with lowered inferior parietal, lateral temporal, and posterior cingulate metabolism, which predicted cognitive decline after 2 years of longitudinal follow-up. For the 20 nondemented subjects followed longitudinally, memory performance scores did not decline significantly, but cortical metabolic rates did. In APOE-4 carriers, a 4% left posterior cingulate metabolic decline was observed, and inferior parietal and lateral temporal regions demonstrated the greatest magnitude (5%) of metabolic decline after 2 years. These results indicate that the combination of cerebral metabolic rates and genetic risk factors provides a means for preclinical AD detection that will assist in response monitoring during experimental treatments.

Proc Natl Acad Sci U S A. 2000 May 23;97(11):5696-8

Beta-amyloid therapies in Alzheimer’s disease.

Neurones in the brain produce beta-amyloid fragments from a larger precursor molecule termed the amyloid precursor protein (APP). When released from the cell, these protein fragments may accumulate in extracellular amyloid plaques and consequently hasten the onset and progression of Alzheimer’s disease (AD). Amyloid-beta fragments are generated through the action of specific proteases within the cell. Two of these enzymes, beta- and gamma-secretase, are particularly important in the formation of beta-amyloid as they cleave within the APP protein to give rise to the N-terminal and C-terminal ends of the beta-amyloid fragment, respectively. Consequently, many researchers are investigating therapeutic approaches that inhibit either beta- or gamma-secretase activity, with the ultimate goal of limiting amyloid-beta; production. An alternative AD therapeutic approach that is being investigated is to employ anti- beta-amyloid antibodies to dissolve plaques that have already formed. Both of these approaches focus on the possibility that accrual of amyloid-beta leads to neuronal degeneration and cognitive impairment characterized by AD and test the hypothesis that limiting amyloid-beta deposition in neuritic plaques may be an effective treatment for AD.

Expert Opin Investig Drugs 2001 Apr;10(4):593-605

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