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LE Magazine August 2008


Role of insulin resistance and hyperglycemia in the development of atherosclerosis.

Insulin resistance (IR) is the underlying defect in >90% of patients with type 2 diabetes mellitus and the major pathologic mechanism for the associated susceptibility to premature cardiovascular disease (CVD). The progression of IR to diabetes parallels the progression of endothelial dysfunction to atherosclerosis. The downregulation of the antiatherogenic phosphatidylinositol-3-kinase-mediated insulin receptor-signaling pathway, and maintained activity of the proatherogenic mitogenic-activated protein kinase pathway in insulin-resistant states, leads to accelerated atherosclerosis. Efforts to prevent or slow the epidemic of atherothrombotic CVD must focus on the reversal of the disturbances in glucose and lipid homeostasis through the amelioration of IR.

Am J Cardiol. 2007 Feb 19;99(4A):6B-14B

Inflammatory biomarkers and risks of myocardial infarction, stroke, diabetes, and total mortality: implications for longevity.

Inflammation is recognized as a major etiologic determinant of multiple disease states including myocardial infarction, stroke, diabetes, and metabolic syndrome, and individuals with elevated levels of the inflammatory biomarker high-sensitivity C-reactive protein (hsCRP) are at increased risk of mortality and morbidity from these conditions. Novel screening algorithms, such as the Reynolds Risk Score, that incorporate inflammation can greatly improve risk detection in primary prevention. In high-risk secondary prevention settings such as acute coronary syndrome patients being treated with statin therapy, achieving low levels of plasma hsCRP concentration appears to be of similar importance as achieving low levels of LDL cholesterol. Whether inflammation in general or CRP in particular are appropriate targets for therapy remains controversial and is under investigation. Several novel methods to reduce CRP have been proposed, including direct inhibitors as well as antisense technologies.

Nutr Rev. 2007 Dec;65(12 Pt 2):S253-9

Inflammation, insulin resistance, and obesity.

Obesity, in particular visceral obesity, has strong associations with cardiovascular disease and is related to many factors that are constituents of the metabolic syndrome. Increasing evidence suggests that features of the metabolic syndrome, including visceral obesity, are associated with a low-grade inflammatory state. Indeed, visceral fat is a source of several molecules, such as leptin, adiponectin, tumor necrosis factor-alpha, and interleukin 6, that are collectively called adipokines. All of them may induce a proinflammatory state and oxidative damage, leading to initiation and progression of atherosclerosis. Reduced-energy diets might represent an effective and healthful approach for long-term weight loss in patients with metabolic syndrome by reducing the underlying inflammatory condition.

Curr Atheroscler Rep. 2004 Nov;6(6):424-31

Effect of DHEA on abdominal fat and insulin action in elderly women and men: a randomized controlled trial.

CONTEXT: Dehydroepian-drosterone (DHEA) administration has been shown to reduce accumulation of abdominal visceral fat and protect against insulin resistance in laboratory animals, but it is not known whether DHEA decreases abdominal obesity in humans. DHEA is widely available as a dietary supplement without a prescription. OBJECTIVE: To determine whether DHEA replacement therapy decreases abdominal fat and improves insulin action in elderly persons. DESIGN AND SETTING: Randomized, double-blind, placebo-controlled trial conducted in a US university-based research center from June 2001 to February 2004. PARTICIPANTS: Fifty-six elderly persons (28 women and 28 men aged 71 [range, 65-78] years) with age-related decrease in DHEA level. INTERVENTION: Participants were randomly assigned to receive 50 mg/d of DHEA or matching placebo for 6 months. MAIN OUTCOME MEASURES: The primary outcome measures were 6-month change in visceral and subcutaneous abdominal fat measured by magnetic resonance imaging and glucose and insulin responses to an oral glucose tolerance test (OGTT). RESULTS: Of the 56 men and women enrolled, 52 underwent follow-up evaluations. Compliance with the intervention was 97% in the DHEA group and 95% in the placebo group. Based on intention-to-treat analyses, DHEA therapy compared with placebo induced significant decreases in visceral fat area (-13 cm2 vs +3 cm2, respectively; P = .001) and subcutaneous fat (-13 cm2 vs +2 cm2, P = .003). The insulin area under the curve (AUC) during the OGTT was significantly reduced after 6 months of DHEA therapy compared with placebo (-1119 muU/mL per 2 hours vs +818 muU/mL per 2 hours, P = .007). Despite the lower insulin levels, the glucose AUC was unchanged, resulting in a significant increase in an insulin sensitivity index in response to DHEA compared with placebo (+1.4 vs -0.7, P = .005). CONCLUSION: DHEA replacement could play a role in prevention and treatment of the metabolic syndrome associated with abdominal obesity.

JAMA. 2004 Nov 10;292(18):2243-8