To examine the effects suplementation of a high fat diet with varying levels of whey protein isolate have on adiposity and weight gain in C57BL/6 mice and to examine the impact these diary whey proteins have on the compostion of the gut microbiota.. Whey protein isolate at varying doses differentia

Whey protein isolate (WPI) reduces weight gain and adiposity, and yet little is known about the related bioactivity and its mechanism of action. Moreover, although obesity-related phenotypes in humans and animal models have been associated with altered gut microbiota profiles, it is not known whether WPI could modify the composition of these microorganisms. To this end, we investigated the WPI dose effects on energy balance in C57BL/6J mice. Mice were fed a low fat diet (10% kJ) or a high fat diet (HFD; 45% kJ) for 21 weeks with either casein (20% kJ, HFD) or WPI (20%, 30% or 40% kJ). WPI dose-independently normalised energy intake in HFD-fed mice. In contrast, the protein challenge dose dependently reduced HFD-induced weight gain, fat mass and plasma triacylglycerol, non-esterified fatty acids, glucose and leptin levels, while it increased lean mass, oxygen consumption and dark phase locomotor activity. WPI proportionally reduced adipose mRNA expression of UCP-2, TNFα and CD68 and increased expression of β3-AR, LPL, IR, IRS-1 and GLUT4. Notably, the metabolic effects observed in 20/30% WPI fed mice were more pronounced in the 40% WPI group. High throughput sequence-based analysis of faecal microbial populations revealed that feeding WPI significantly increased Lactobacillaceae/Lactobacillus and decreased Clostridiaceae/Clostridium in HFD fed mice, with clustering of gut microbiota in 30/40% WPI groups away from HFD and 20% WPI groups. Taken together, our data show that the bioactivity in the WPI is effective on mechanisms regulating energy intake in HFD-fed mice irrespective of the dose used, while a higher WPI dose is required to influence the metabolic health and gut microbiota in these animals, with lower doses still providing a distinctly modulatory signature on each of the latter parameters. The data may suggest distinct WPI-related bioactivities influencing energy balance.