The role of dairy protein and dietary calcium in weight regulation and glucose homeostasis.

摘要

Objective. To determine the role of complete dairy foods, individual dairy protein fractions (casein, whey, and leucine), and calcium (Ca) on weight management and glucose homeostasis in Sprague-Dawley diet-induced obese (DIO) rats.;Results. Consistently within and between all studies, complete dairy treated rats had improvements with body weight and composition. During ad libitum feeding, the complete dairy treatment promoted greater fat loss and during ER complete dairy accelerated weight loss with the maintenance of lean body mass (LBM). Additionally, supplementation with HC resulted in increased benefits to body composition. Measurements of glucose homeostasis and insulin sensitivity varied between protein source and Ca, with leucine improving whole body glucose clearance, complete dairy improving baseline measurements of insulin and glucose, and HC resulting in lower glucagon secretion. Hepatic expression of genes related to metabolism (PPARgamma, PGC1alpha, PEPCK, FAS, ACC, and SREBP1c) were altered by protein source and Ca level.;Conclusions. In Sprague-Dawley DIO rats, complete dairy and Ca attenuated weight gain during ad libitum feeding and accelerated weight loss during ER. The precise bioactive component in complete dairy foods responsible for the metabolic changes observed is unknown, as the individual protein fractions of dairy (casein and whey) did not appear to have analogous effects on metabolic parameters. A diet including complete dairy foods may provide some protection against susceptibility to obesity and improve weight loss during restriction.;Methods. Three main studies were performed. Dietary interventions that varied in protein source (complete dairy, casein, whey, or casein+leucine), Ca level [0.67% (LC) or 2.4% (HC)], and energy density [normal energy (NE) or high fat/high sucrose (HFHS)] were tested. Rats consumed the experimental diets either ad libitum or energy restricted to 70% of control ad libitum (ER) intake. Body composition was measured via dual-energy x-ray absorptiometry (DEXA). A meal tolerance test (MTT) or oral glucose tolerance test (OGTT) and/or an insulin tolerance test (ITT) were performed. A euglycemic-hyperinsulinemic clamp was also utilized in the final study to measure whole body glucose uptake. Tissues were collected and gene expression was assessed using real-time PCR and microarray.