A Comparative Study Of Dietary Patterns Of Milk Protein And Whey Protein For The Prevention Of Obesity

High-protein diets have a positive effect on short-term weight loss and metabolic improvement as a form of macronutrient regulation.Whether dietary intervention strategies with milk protein sources differ in their efficacy in preventing the development of obesity needs to be further investigated.The aim of this paper was to investigate the effects of milk protein and whey protein on obesity in rats on a high-protein diet and to explore the possible mechanisms,with the aim of providing a valuable theoretical basis for the screening and application of beneficial proteins in high-protein diets.The details of the study and the results are as follows:First,the effects of milk protein and whey protein on growth performance and lipid metabolism of rats were analyzed.Eighty male SPF Sprague Dawley rats were randomly divided into milk protein group(milk protein concentrate,MPC)and whey protein group(whey protein concentrate,WPC),and each group was divided into four levels:low-fat low protein(LFD-14%),low-fat high protein(LFD-40%),high-fat low protein(HFD-14%)and high-fat high protein(HFD-40%),sampling and analysis after 12 weeks of feeding.The results showed that the energy intake and body weight of rats in high-fat groups increased significantly with increasing fat content in the diet.The addition of 40%MPC significantly reduced body weight,body fat percentage,plasma lipids and leptin levels in obese rats,while there was a trend of reduction in the 40%WPC group but no significant difference.Real-time PCR analysis showed that 40%MPC feeding significantly reduced the expression of hepatic lipid synthesis genes(ACC,FAS and SCD1)and upregulated the expression of catabolic genes(HSL,CPT1,ACOX1,FGF21,PPAR?)and thermogenic gene UCP1 in the high-fat group.In addition,there was no significant effect of 14%or 40%MPC and WPC on the growth performance of rats in the low-fat group,but the body fat percentage of rats in the MPC group was lower compared with WPC at the same diet composition,indicating that MPC was more effective in improving body energy metabolism and controlling the development of obesity.Then,the effects of milk protein versus whey protein on muscle protein metabolism and redox homeostasis in rats were investigated.The results showed that 40%MPC and 40%WPC feeding significantly increased rat skeletal muscle rate and CS value,enhanced muscle protein synthesis by upregulating protein synthesis genes(eif4E,m TOR,S6k1 and Akt)and downregulating catabolic genes(Mu RF1,FOXO3a,MAFbx and Ubiquitin)expression,and the effect of MPC was better than that of WPC.Measurement of redox-related indexes revealed that with the increase of MPC content in the high-fat diets,the levels of plasma,liver and muscle GSH/GSSG and T-AOC increased and the levels of plasma and muscle lipid peroxidation products MDA decreased significantly in rats,while WPC had no significant effect on the above indexes.In addition,both high-protein diets significantly increased plasma urea nitrogen levels in rats,but had no effect on plasma creatinine levels and kidney tissue structure,indicating that short-term high-protein feeding did not cause renal function damage in rats.Finally,based on the analysis of amino acid composition between MPC and WPC,which revealed a large difference in cysteine content,the possible mechanisms of high-protein dietary intervention in obesity were explored in depth using plasma amino acid levels and metabolic transformation in rats as an entry point.The results showed that compared with 40%WPC,40%MPC feeding significantly reduced plasma cystine levels of rats in the high-fat group.Enhanced the transsulfuration pathway by upregulating the expression levels of key enzymes CBS,CTH and signaling factor ATF4,and increased plasma and tissue H₂S levels.Correlation analysis revealed that plasma H₂S levels were significantly and positively correlated with hepatic lipolysis gene(FGF21,PPAR?,ACOX1,CPT1)expression and HDL-C levels,and negatively correlated with hepatic lipid synthesis gene(ACC,SCD1)expression and TG,LDL-C,TC levels.Meanwhile,plasma H₂S levels were significantly and positively correlated with plasma T-AOC,GSH-Px,GSH/GSSG levels and negatively correlated with MDA levels.The above results suggest that the improvement of lipid metabolism and redox homeostasis in obese rats by MPC may be related to the increase of endogenous H₂S levels.In conclusion,the addition of 40% MPC to high-fat diets was more effective than WPC in preventing obesity,improving lipid metabolism and redox homeostasis,and promoting muscle protein deposition in rats.Differences in amino acid composition and cysteine content of dietary protein affected amino acid metabolism and transsulfuration pathways in vivo,which might be one of the reasons for the differences in the efficacy of different high-protein dietary patterns to intervention in obesity.