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LE Magazine July 2005

Grape seed extract

Intracellular mediators of procyanidin-induced lipolysis in 3T3-L1 adipocytes.

We have previously reported that grape seed procyanidins stimulate long-term lipolysis on 3T3-L1 fully differentiated adipocytes. To unravel the molecular mechanism by which procyanidins exert this effect, we checked the involvement of two main cellular targets in adipose cells: protein kinase A (PKA) and peroxisome proliferator-activated receptor-gamma (PPAR-gamma). Procyanidin treatment increased intracellular cAMP levels in 3T3-L1 adipocytes, and their lipolytic effect was inhibited by simultaneous treatment with H89, a PKA specific inhibitor. BRL49653, a very highly specific ligand of PPAR-gamma, totally abolished the lipolytic effect of procyanidins. Simultaneous to this long-term lipolytic effect, the mRNA levels of some differentiation adipocyte markers decreased, although there were no changes in the triglyceride content of the cells. BRL49653 did not antagonize the decrements of differentiation markers. These results support a mediation of PPAR-gamma and PKA on the lipolytic effects of procyanidins on 3T3-L1 adipocytes.

J Agric Food Chem. 2005 Jan 26;53(2):262-6

Grape seed proanthocyanidins extract promotes bone formation in rat’s mandibular condyle.

We studied the effect of dietary supplementation with grape seed proanthocyanidins extract (GSPE) 3 mg added in 100 g high-calcium diet with a calcium content of 1697 mg 100 g(-1) on mandibular condyle bone debility, which was induced by a low-calcium diet. Forty Wistar male rats, 5 week old, were randomly divided into control (Co), low-calcium diet (LC), low-calcium/high-calcium diet (LCH), and low-calcium/high-calcium with supplementary GSPE diet (LCHG) groups for 6 wk. Bone formation of the mandibular condyle was measured using peripheral quantitative computed tomography (pQCT). Significant differences were not seen among the four groups for body weight, measured weekly. The LCHG group scored significantly higher in cortical bone density, total bone cross-sectional area, cortical bone cross-sectional area, cortical bone mineral content, total bone density, total bone mineral content, and in the stress-strain index to the reference axis x when compared with the LCH group. We concluded that a high-calcium diet combined with GSPE supplementation is more effective in reversing mandibular condyle bone debility in rats than is a low-calcium diet, standard diet, or high-calcium diet alone.

Eur J Oral Sci. 2005 Feb;113(1):47-52

Pharmacological preconditioning with resveratrol: role of CREB-dependent Bcl-2 signaling via adenosine A3 receptor activation.

Recent studies demonstrated that resveratrol, a grape-derived polyphenolic phytoalexin, provides pharmacological preconditioning (PC) of the heart through a NO-dependent mechanism. Because adenosine receptors play a role in PC, we examined whether they play any role in resveratrol PC. Rats were randomly assigned to groups perfused for 15 min with 1) Krebs-Henseleit bicarbonate buffer (KHB) only; 2) KHB containing 10 microM resveratrol; 3) 10 microM resveratrol + 1 microM 8-cyclopentyl-1,3-dimethylxanthine (CPT; adenosine A(1) receptor blocker); 4) 10 microM resveratrol + 1 microM 8-(3-chlorostyryl) caffeine (CSC; adenosine A(2a) receptor blocker); 5) 10 microM resveratrol + 1 microM 3-ethyl-5-benzyl-2-methyl-4-phenylethynyl-6-phenyl-1,4-(+/-)-dihydropyridine-3,5-dicarboxylate (MRS-1191; adenosine A(3) receptor blocker); or 6) 10 microM resveratrol + 3 microM 2-(4-morpholinyl)-8-phenyl-1(4H)-benzopyran-4-one hydrochloride [LY-294002, phosphatidylinositol (PI)3-kinase inhibitor], and groups perfused with adenosine receptor blockers alone. Hearts were then subjected to 30-min ischemia followed by 2-h reperfusion. The results demonstrated significant cardioprotection with resveratrol evidenced by improved ventricular recovery and reduced infarct size and cardiomyocyte apoptosis. CPT and MRS 1191, but not CSC, abrogated the cardioprotective abilities of resveratrol, suggesting a role of adenosine A(1) and A(3) receptors in resveratrol PC. Resveratrol induced expression of Bcl-2 and caused its phosphorylation along with phosphorylation of cAMP response element-binding protein (CREB), Akt, and Bad. CPT blocked phosphorylation of Akt and Bad without affecting CREB, whereas MRS 1191 blocked phosphorylation of all compounds, including CREB. LY-294002 partially blocked the cardioprotective abilities of resveratrol. The results indicate that resveratrol preconditions the heart through activation of adenosine A(1) and A(3) receptors, the former transmitting a survival signal through PI3-kinase-Akt-Bcl-2 signaling pathway and the latter protecting the heart through a CREB-dependent Bcl-2 pathway in addition to an Akt-Bcl-2 pathway.

Am J Physiol Heart Circ Physiol. 2005 Jan;288(1):H328-35

Resveratrol: Preventing properties against vascular alterations and ageing.

Cardiovascular diseases are the leading cause of death in developed countries where the common pathological substrate underlying this process is atherosclerosis. Several new concepts have emerged in relation to mechanisms that contribute to the regulation of the vascular diseases and associated inflammatory effects. Recently, potential antioxidants (vitamin E, polyphenols) have received much attention as potential anti-atherosclerotic agents. Among the polyphenols with health benefic properties, resveratrol, a phytoalexin of grape, seem to be a good candidate protecting the vascular walls from oxidation, inflammation, platelet aggregation, and thrombus formation. In this review, we focus onthe mechanism of resveratrol cardiovascular benefic effects. We analyze, in relation with the different steps of atherosclerotic process, the resveratrol properties at multiple levels, such as cellular signaling, enzymatic pathways, apoptosis, and gene expression. We show and discuss the relationship with reactive oxygen species, regulation of pro-inflammatory genes including cycloxygenases and cytokines in molecular inflammatory and aging processes, and how the regulation of these activites by resveratrol can lead to a prevention of vascular diseases.

Mol Nutr Food Res. 2005 Apr 14


Advanced glycation endproducts—role in pathology of diabetic complications.

Diabetes mellitus is a common endocrine disorder characterised by hyperglycaemia and predisposes to chronic complications affecting the eyes, blood vessels, nerves and kidneys. Hyperglycaemia has an important role in the pathogenesis of diabetic complications by increasing protein glycation and the gradual build-up of advanced glycation endproducts (AGEs) in body tissues. These AGE form on intra- and extracellular proteins, lipids, nucleic acids and possess complex structures that generate protein fluorescence and cross-linking. Protein glycation and AGE are accompanied by increased free radical activity that contributes towards the biomolecular damage in diabetes. There is considerable interest in receptors for AGEs (RAGE) found on many cell types, particularly those affected in diabetes. Recent studies suggest that interaction of AGEs with RAGE alter intracellular signalling, gene expression, release of pro-inflammatory molecules and free radicals that contribute towards the pathology of diabetic complications. This review introduces the chemistry of glycation and AGEs and examines the mechanisms by which they mediate their toxicity. The role of AGEs in the pathogenesis of retinopathy, cataract, atherosclerosis, neuropathy, nephropathy, diabetic embryopathy and impaired wound healing are considered. There is considerable interest in anti-glycation compounds because of their therapeutic potential. The mechanisms and sites of action of selected inhibitors, together with their potential in preventing diabetic complications are discussed.

Diabetes Res Clin Pract. 2005 Jan;67(1):3-21

Incidence of newly diagnosed diabetes attributable to atypical antipsychotic medications.

OBJECTIVE: The purpose of the study was to determine the proportion of patients with schizophrenia with a stable regimen of antipsychotic monotherapy who developed diabetes or were hospitalized for ketoacidosis. METHOD: Patients with schizophrenia for whom a stable regimen of antipsychotic monotherapy was consistently prescribed during any 3-month period between June 1999 and September 2000 and who had no diabetes were followed through September 2001 by using administrative data from the Department of Veterans Affairs. Cox proportional hazards models were developed to identify the characteristics associated with newly diagnosed diabetes and ketoacidosis. RESULTS: Of the 56,849 patients identified, 4,132 (7.3%) developed diabetes and 88 (0.2%) were hospitalized for ketoacidosis. Diabetes risk was highest for clozapine (hazard ratio=1.57) and olanzapine (hazard ratio=1.15); the diabetes risks for quetiapine (hazard ratio=1.20) and risperidone (hazard ratio=1.01) were not significantly different from that for conventional antipsychotics. The attributable risks of diabetes mellitus associated with atypical antipsychotics were small, ranging from 0.05% (risperidone) to 2.03% (clozapine). CONCLUSIONS: Although clozapine and olanzapine have greater diabetes risk, the attributable risk of diabetes mellitus with atypical antipsychotics is small.

Am J Psychiatry. 2004 Sep;161(9):1709-11

Hyperglycemia associated with antipsychotic treatment in a multicenter drug safety project.

The introduction of new antipsychotics has resulted in the availability of drugs with improved safety and tolerability as well as proven efficacy compared to the older antipsychotics. New compounds might show new or different adverse effects that arise in the post-marketing phase when a greater number of patients are treated. One goal of the drug safety program in psychiatry AMSP (Arzneimittelsicherheit in der Psychiatrie) is the detection and description of severe, new, or rare adverse drug reactions (ADRs). Between 1993 and 2000, 122,562 patients were monitored in 35 psychiatric institutions, 86,349 patients of which received antipsychotics. Hyperglycemia related to antipsychotics was observed in association with only two compounds so far: clozapine and olanzapine (clozapine 2 cases, olanzapine 7 cases). In 6 of 9 patients, weight gain preceded hyperglycemia. The relative frequency of these adverse drug related events was 0.013% for clozapine and 0.075% for olanzapine. The symptomatology included reversible hyperglycemia, worsening of existing diabetes, and new-onset diabetes. Control for glycemic dysregulation should be maintained in clinical practice with these drugs.

Pharmacopsychiatry. 2004 Mar;37 Suppl 1:S79-83

Daily stress and glycaemic control in Type 1 diabetes: individual differences in magnitude, direction, and timing of stress-reactivity.

The aim of this study was to investigate the relationships between daily stress and glycaemic control in 54 people with Type 1 diabetes over 21 days. Measures included daily reports of stress (hassles), four-times-daily blood glucose measurements, and HbA1c levels. Time-series analyses revealed considerable variation between individuals in the nature and extent of blood glucose response to stress (stress-reactivity). In approximately one-third of the sample, stress was significantly associated with either same- or next-day blood glucose levels (r-range: -0.79 to 0.58). The majority of stress-reactive individuals (20.4% of the sample) demonstrated a positive association between hassles and same-day blood glucose levels. A much less common effect was found in two individuals (3.7%), where hassles were related to decreased same-day blood glucose. ‘Stress-reactive’ individuals tended to have high HbA1c values at baseline (t(52) = 2.2; P < 0.05), and significant relationships between emotion-focused coping and blood glucose levels (r = 0.93; P < 0.01). In conclusion, although a significant majority of this sample was resistant to the effects of stress, marked individual differences were found in the nature and extent of stress-reactivity. Our study goes beyond other published results as it is longitudinal, uses time-series analyses and includes a relatively larger sample. Clinicians need to be aware of these individual differences in order to advise patients about anticipating and preventing stress-related disruptions of glycaemic control.

Diabetes Res Clin Pract. 2004 Dec;66(3):237-44

Moderate alcohol intake and markers of inflammation and endothelial dysfunction among diabetic men.

AIMS/HYPOTHESIS: Type 2 diabetes mellitus is characterised by heightened inflammation and endothelial dysfunction. Moderate alcohol intake has been associated with a reduced risk of cardiovascular disease in type 2 diabetic patients. It remains to be determined whether there is an association between alcohol and inflammation in individuals with diabetes. METHODS: We investigated the relationship between alcohol intake and inflammation in 726 of 18,159 men who returned blood samples in the Health Professionals Follow-up Study and had confirmed type 2 diabetes at blood draw. RESULTS: In age-adjusted analyses, alcohol intake was associated with lower levels of HbA1c, fibrinogen, soluble tumour necrosis factor receptor-2 (sTNF-R2) and soluble vascular adhesion molecule-1 (sVCAM-1), and with higher levels of HDL cholesterol and adiponectin (p value for trends <0.05). After adjustment for age, HbA1c, insulin use, fasting status, smoking, BMI, physical activity, aspirin use, prevalence of cardiovascular disease and dietary factors, each additional drink per day was related to increased HDL cholesterol (0.053 mmol/l, p<0.0001) and adiponectin (0.8 microg/ml, p=0.01), and decreased sTNFR-2 (73 pg/ml, p=0.03), fibrinogen (0.302 micromol/l, p=0.02) and sVCAM-1 (33 ng/ml, p=0.02). The relationship between alcohol and inflammatory biomarkers persisted when subjects were stratified according to HbA1c levels. CONCLUSIONS/INTERPRETATION: Moderate alcohol intake may have a beneficial effect on markers of inflammation and endothelial dysfunction in type 2 diabetic patients.

Diabetologia. 2004 Oct;47(10):1760-7

Acute alcohol consumption improves insulin action without affecting insulin secretion in type 2 diabetic subjects.

OBJECTIVE: Long-term exposure to alcohol is associated with an improvement in insulin sensitivity. At this time, however, there is no definitive proof that alcohol per se has an effect on the insulin sensitivity index (S(i)) in type 2 diabetes patients. The aim of the present study was to assess the role of acute moderate alcohol intake on insulin sensitivity and insulin secretion in comparable subjects with and without type 2 diabetes. RESEARCH DESIGN AND METHODS: Frequently sampled intravenous glucose tolerance tests (FSIGTs) were performed twice on eight healthy and eight type 2 diabetic volunteers. Forty grams of alcohol (vodka 40% wt/vol) or tap water were sipped from time -60 min to the end of the FSIGT. RESULTS: Lactate area under the curve (AUC) was higher in both groups during the alcohol study than in the control study. Free fatty acid (FFA) AUC was higher in type 2 diabetic subjects than in control subjects; alcohol slightly reduced FFA by 17% in control subjects (34 +/- 4 mmol. min(-1). l(-1); P = 0.1) but significantly decreased FFA by 23% in type 2 diabetic subjects (54 +/- 10; P = 0.007). Beta-cell response was markedly reduced in type 2 diabetic subjects regardless of the type of study. Alcohol significantly increased S(i) in both groups. CONCLUSIONS: Acute alcohol consumption improves insulin action without affecting beta-cell secretion. This effect may be partly due to the inhibitory effect of alcohol on lipolysis. Alcohol intake increases insulin sensitivity and may partly explain both the J-shaped relationship between the prevalence of diabetes and the amount of alcohol consumption and the decreased mortality for myocardial infarction.

Diabetes Care. 2004 Jun;27(6):1369-74

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