RESUMO
BACKGROUND: The use of chromium supplements is widespread for the prevention and treatment of diabetes mellitus but there are conflicting reports on efficacy, possibly reflecting discrepant effects across different populations. In the present studies, we test the hypothesis that chromium supplementation raises serum chromium levels and correspondingly improves insulin sensitivity. METHODS: A double blind placebo-controlled randomized trial was conducted on 31 non-obese, normoglycemic subjects. After baseline studies, the subjects were randomized to placebo or chromium picolinate 500 µg twice a day. The primary endpoint was change in insulin sensitivity as measured by euglycemic hyperinsulinemic clamp. Pre-specified secondary endpoints included fasting lipids, blood pressure, weight, body composition measured by DXA scan. RESULTS: After 16 weeks of chromium picolinate therapy there was no significant change in insulin sensitivity between groups (p=0.83). There was, however, a strong association between serum chromium and change in insulin resistance (ß = -0.83, p=0.01), where subjects with the highest serum chromium had a worsening of insulin sensitivity. This effect could not be explained by changes in physiological parameters such as body weight, truncal fat and serum lipids with chromium therapy. CONCLUSIONS: Chromium therapy did not improve insulin sensitivity in non-obese normoglycemic individuals. Further, subjects who have high serum chromium levels paradoxically had a decline in insulin sensitivity. Caution therefore should be exercised in recommending the use of this supplement. TRIAL REGISTRATION: The study was registered on the NIH registry (clinicaltrials.gov) and the identifier is NCT00846248.
RESUMO
BACKGROUND: The purpose of this study was to determine whether a preparation of controlled-release alpha lipoic acid (CRLA) influences features of the polycystic ovary syndrome (PCOS). METHODS: We administered CRLA 600 mg twice daily for 16 weeks to six lean, nondiabetic patients with PCOS. Insulin sensitivity was measured by the euglycemic, hyperinsulinemic clamp. Plasma lipids were measured by vertical ultracentrifugation. Oxidative stress markers were measured in serum. RESULTS: At the end of 16 weeks of CRLA treatment, there was a 13.5% improvement in insulin sensitivity as determined by the euglycemic, hyperinsulinemic clamp (p < .03). There was also a lowering of triglyceride levels (p < .04) and a shift in the distribution of low-density lipoprotein (LDL) particles toward the larger, more buoyant LDL subclass fraction. Two of the subjects who were not on oral contraception had an increased number of menstrual cycles. Controlled-release alpha lipoic acid treatment, however, was neither associated with an increase in plasma antioxidant capacity nor with a reduction in plasma lipid oxidation products. CONCLUSIONS: These data suggest that the CRLA has positive effects on the PCOS phenotype. The effects of CRLA, however, may have been exerted through a mechanism not involving changes in oxidative stress.