Effect of amino acid supplementation on insulin sensitivity in elderly

Abstract

Recent reports show that increased protein intake in the context of weight loss improves glucose control. The aim of this study was to examine if supplementation of a weight-maintaining diet with essential amino acids (EAA) is effective in improving insulin sensitivity in elderly. Eight insulin-resistant elderly (66 ± 2 (SE) years, 4 females, 4 males) ingested 11 g of EAA two times a day, between meals for 16 weeks. Diet and activity were not otherwise modified. Insulin sensitivity was determined by an oral glucose tolerance test, and body composition was measured by DEXA, at baseline, and every four weeks. One-way repeated measures ANOVA was used. EAA supplementation significantly improved the Matsuda index (p = 0.019). From a baseline value of 3.8 ± 0.4, the Matsuda index increased to 4.0 ± 0.9, 5.6 ± 1.0, 6.1 ± 1.4, and 5.3 ± 0.9 at week 4, 8, 12, and 16, respectively. The effect of EAA supplementation on insulin sensitivity varied between subjects, with the changes in the Matsuda index ranging from −1.76 to 6.73. A positive correlation between the baseline value and the change in Matsuda index was found at 12 weeks (r = 0.762, p = 0.021), whereas a trend was observed after 8 weeks (r = 0.643, p = 0.071). There was also an improvement in lean body mass (p = 0.066) and leg lean mass (p = 0.049) during the study, but no correlation between changes in lean mass and Matsuda index was seen. In conclusion, supplementation of the diet with EAA improves glucose control in insulin-resistant elderly to a variable extent. (Studies performed at GCRC, UTMB, funded by M01 RR 00073 and P30 AG024832)