Enteropancreatic effects of acute and short-term whey protein preload on metabolic and reproductive parameters in polycystic ovary syndrome

Insulin resistance and hyperglycemia are common in polycystic ovary syndrome (PCOS). This study evaluated effects of whey protein isolate (WPI) preload on postprandial glycemic regulation in women with and without PCOS (PCO and CON respectively). Study design: A repeated measures design was used. Fourteen PCO and 15 CON women underwent 150-min oral glucose tolerance test (OGTT) without WPI preload (Day 0) followed by tests at the beginning and end of a 7-day supplementation (Days 1 and 7 respectively). Participants consumed 35-g WPI bolus per day before a carbohydrate load on each of the seven days. Venous samples were drawn at -30, 0, 15, 30, 60, 90, 120, and 150 min per test. Glucose, insulin, active glucagon-like peptide 1 (aGLP-1) and total glucose-dependent insulinotropic polypeptide (tGIP) were quantified. Methods: Multiplex assays and ELISA were used for quantification of incretins, steroid hormones and insulin respectively. Repeated measures ANCOVA with Bonferroni post hoc tests were used for statistical analyses. P-value ≤ .05 was considered significant. Results: In both groups, postprandial glucose responses decreased on Days 1 and 7 compared to Day 0 but the changes were not statistically significant (p > .05). ‘Group x Day x time’ interaction significantly affected insulin responses (p = .04). Preloading on Days 1 and 7 yielded higher early phase and total postprandial insulin AUC insulin levels in both groups than Day 0 (p < .05). During all OGTTs CON had higher incretin responses than corresponding tests in the PCO group. Conclusions: A 35-g whey bolus before a glucose load amplified insulin release, consequently lowering circulating glucose in PCO and CON. The insulinogenic effect of preloading can be attributed to enhanced incretin responses. Women with PCOS exhibited sustained glycemic control in response to 7-day WPI supplementation compared to women without PCOS. The study concludes that WPI consumption may be effective in achieving glycemic homeostasis in PCOS.