The acute effects of Pterocarpus Marsupium supplementation on insulin-dependent and insulin-independent signaling pathways at rest, after an oral glucose tolerance test and after intense exercise in overweight pre-diabetic females.

Increasing physical activity and modifying diet to incorporate more phytonutrients has been suggested as a way to prevent the progression of insulin resistance (IR) into cardiometabolic disease. Pterocarpus Marsupium (PM), a phytonutrient compound shown to improve hyperglycemia, could potentially improve IR. The primary purpose of this study was to examine the effects of PM on insulin sensitivity and blood lipids in overweight and obese, sedentary women classified as prediabetic. Further, to examine the effects of acute ingestion of PM on insulin- and exercise-mediated glucose disposal following an oral glucose tolerance test (OGTT) and aerobic exercise bout, and to understand the mechanisms by which PM supplementation may affect specific muscle gene expression. A double-blind, randomized, placebo controlled study was conducted. Participants consumed 250 mg of either PM (n=8) or placebo (PL, n=8) twice daily for 6 days. Blood and muscle samples were obtained prior to supplementation, prior to and following OGTT, and prior to and following an exercise bout. Following OGTT, plasma glucose levels were higher at 30 minutes (p<0.001) and 1 hour post-OGTT (p=0.001) in both PM and PL groups. Similarly, plasma insulin levels were higher 30 minutes (p=0.023), 1 hour (p=0.023), and 2 hours post-OGTT (p=0.003) in both PM and PL groups. Additionally, serum glucose levels decreased from 30 minutes to 1 hour postexercise (p = 0.011), and from 30 minutes to 2 hours postexercise (p = 0.013) in both PM and PL groups. A significant increase in mRNA expression of Akt2 (p = 0.001), AMPK (p = 0.001), AS160 (p = 0.02), and PPARα (p = 0.025) was observed one hour after OGTT. The findings suggest that 250 mg of PM twice daily does not improve insulin sensitivity or fasting lipid levels in this population. However, this is the first study to report the novel finding of an increase in skeletal muscle mRNA expression of Akt2, AMPK, AS160, and PPARα in response to an OGTT. The observed increase, and subsequent decrease, in serum glucose levels after brief, maximal exertion exercise was also novel.