Metabolic effects of whey proteins in an experimental model of diet-induced obesity
Year: 2014
Type: dissertation
Abstract: Milk proteins which make up 3.5% of the bovine milk are classified into casein and whey proteins. A high intake of milk proteins, especially whey proteins, has been shown to exert the beneficial effects on obesity and obesity related diseases in both humans and animals via unknown mechanisms. The aim of the present study was to investigate the potential of different whey proteins, i.e. whey protein isolate (WPI), alpha-lactalbumin (α-lac), lactoferrin (LF) and microfiltered native whey (MFNW), and their mechanisms of actions to prevent and treat diet-induced obesity and its consequences in C57Bl/6J mice. In the present study, all of the tested whey proteins were given as the only protein source in high-fat diets with a constant protein (18 % of the energy): carbohydrate (21 % of the energy): fat (61 % of the energy) ratio. We used weekly body weight measurements, daily food intake monitoring, apparent fat digestibility, dual-energy X-ray absorptiometry, oral glucose tolerance test, monitoring of fat pad weights, as well as biochemical measurements in order to assess the metabolic effects of whey proteins. Compared to casein, WPI (rich in lactoperoxidase, LF, growth factors and immunoglobulins) and LF accelerated weight and fat loss under energy restriction, and inhibited weight and fat regain during the ad libitum feeding after energy restriction without interfering with energy intake or apparent fat digestibility in C57Bl/6J mice. Both WPI and LF ameliorated fatty liver formation, and exerted beneficial effects on glucose tolerance under high-fat-feeding. The beneficial effects of WPI occurred in a dose-dependent manner. In addition, LF reduced the adipose tissue inflammation after weight regain, a property not shared with WPI. The further biochemical analysis indicated that these effects of both WPI and LF are mediated, at least partly, via the inhibition of mTOR nutrient sensing pathway and the activation of SIRT3 in the liver. Alpha-lac has been reported as one of the most effective whey protein fractions for accelerating weight and fat loss during energy restriction in the same mouse model. It was observed that the effects of α-lac on body weight and fat under energy restriction could be reproduced by supplying an amino acid mixture with an identical amino acid profile, which indicates that the anti-obesity effects of α-lac were mainly mediated by its individual amino acid composition. The MFNW produced by polymeric membranes using novel microfiltration technology, prevented weight gain and fat accumulation without interfering with energy intake or glucose homeostasis during ad libitum high-fat-feeding. The findings also suggest that the beneficial effects of MFNW are largely due to its rich α-lac content. In summary, the intake of whey proteins exerts anti-obesity effects in C57Bl/6J mice during high-fat-feeding. WPI and LF enhance weight loss, prevent weight regain and ameliorate obesity induced fatty liver formation. The anti-obesity effects of WPI are attributable, to a large extent, to its LF content. The anti-obesity effects of α-lac are mainly due to its amino acid composition. The observed beneficial effects of MFNW point to a possible method to generate whey proteins with high bioactive value on a large scale.
Source: Työväentutkimus Vuosikirja
Author: Shi Jin
Language: English
Subfield: Endocrine and Autonomic Systems
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2123733522