Magnesium, insulin resistance and body composition in healthy postmenopausal women

Objective: This study was conducted to determine the association between magnesium (Mg), body composition and insulin resistance in 136 sedentary postmenopausal women, 50 to 77 years of age. Methods: Diabetics, hypertensives and women on hormonal replacement therapy were excluded and the remaining 74 were divided according to BMI≥25 (obese: OG) and BMI<25 kg/m2 (non-obese: NOG). Nutritional data disclosed that intakes were high for protein and saturated fat, low for carbohydrates, polyunsaturated fat and Mg and normal for the other nutrients, according to recommended dietary allowances (RDA). Mg values in red blood cells (RBC-Mg) and plasma (P-Mg), were determined, as were fasting glucose, and insulin levels, Homeostasis Model Assessment (HOMA), body mass index (BMI), body fat percent (BF %), abdominal fat (AF) and free fat mass (FFM). Results: RBC-Mg values were low in both groups when compared with normal values. There were significant differences in body composition parameters, HOMA and insulin levels, with higher basal insulin levels in OG. RBC-Mg was directly correlated with insulin, HOMA and FFM in both groups, according to Pearson correlations. HOMA in OG was also directly correlated with BMI, FFM and AF. In NOG, HOMA was only correlated with FFM. The low RBC-Mg levels observed were probably due to low Mg intake and to deregulation of factors that control Mg homeostasis during menopause. Conclusions: Both Mg deficit and obesity may independently lead to a higher risk for insulin resistance and cardiovascular disease.

Insulin resistance does not play a major role in lipid and apolipoprotein profile in obese women

Background: Obesity is associated with increased atherogenesis through alterations in lipids, among other potential factors. Some of those abnormalities might be mediated by insulin resistance (IR). Aims: To compare lipid and apolipoprotein profile between lean and obese women; to evaluate the influence of IR on lipid and apolipoprotein profile, in obese women. Methods: We studied 112 obese and 100 normal-weight premenopausal women without known cardiovascular disease. Both groups were characterized for anthropometrics and a fasting blood sample was collected for assessment of glucose, insulin, triglycerides, cholesterol (total, LDL and HDL), and apolipoproteins A-I, A-II, B, C-II, C-III, and E; IR was assessed by the homeostatic model assessment (HOMA-IR). We compared lipids between obese and lean women; we looked for correlation of those levels with anthropometrics and IR (independently from anthropometrics) in obese women. Results: Obese women were characterized by mean age=34.6±8.3 years, BMI=43.6±7.9 kg/m2, waist circumference (Wc)=117.5±15.1 cm, and HOMA-IR=4.28±3.5. Lean women (age=34.2±8.3 years, BMI=21.4±1.7 kg/m2, Wc=71.7±5.8 cm, and HOMA-IR=1.21±0.76) presented with significantly lower levels of total cholesterol (P=0.001), LDL-cholesterol (P<0.001), and triglycerides (P<0.001); they presented higher levels of HDL-cholesterol (P<0.001), Apo A-I (P<0.001) and Apo A-II (P=0.037). HOMA-IR showed no significant association with apolipoproteins. HOMA-IR was inversely associated with HDL-cholesterol (P=0.048; r=−0.187) but that association disappeared when we adjusted for waist circumference. Only triglycerides were directly associated with HOMA-IR (P<0.001; r=0.343) independently from anthropometrics. Conclusion: We confirm that obese women present worst lipid and apolipoprotein profile. However, with the exception for triglycerides, insulin resistance per se does not play a major role in lipid and apolipoprotein abnormalities observed in obese women.