Abstract
Associations between meat diets and human health have been widely considered. In this study, we focused on long-term effects of different sources of meat protein on liver metabolic enzymes. For 90 days, rats were fed with semisynthetic diets that differed only with protein source. Casein was used as a reference and isolated soybean, fish, chicken, pork, and beef proteins were compared. Changes in liver proteome were determined by isobaric tag for relative and absolute quantitation (iTRAQ) labeling and liquid chromatography electrospray ionization tandem mass spectrometry/mass spectrometry (LC–ESI–MS/MS). Fish and pork protein diets upregulated the gene expression involved in cholesterol synthesis and esterification, and pork protein diet also upregulated the gene expression of high-density lipoprotein receptor and low-density lipoprotein receptor. Chicken, pork, and beef protein diets upregulated the gene expression involved in cholesterol reverse transport and bile acid production, which increased the total cholesterol level in the fish protein diet group. Total cholesterol levels in liver were lower in the pork and beef protein diet groups. Triglyceride levels in liver were lower in chicken, pork, and beef protein diet groups. Peroxisomal proliferator-activated receptor-gamma coactivator-1 was upregulated by chicken, pork and beef protein diets, and promoted the degradation and metabolism of triglyceride, resulting in lower triglyceride in the three diet groups. Meat proteins at a recommended level could be more conducive to cholesterol degradation, triglyceride decomposition, and energy balance maintenance at a healthy level. The findings give a new insight into the associations between meat diet intake and human health.
Highlights
Dietary protein provides the basic nitrogen source necessary for life, and participates in a series of physiological processes such as energy metabolism [1], hormone secretion [2], appetite control [3], and lipid metabolism [4]
In previous studies [12, 16, 20], serum glucose, triglyceride, cholesterol, and other indicators were significantly lower in the beef protein diet group than in the casein, soybean, and other meat protein groups, while the serum triglyceride content was lower in the fish protein diet group than in the casein diet group, and the cholesterol levels were different between the chicken and beef protein diet groups
The degradation of dietary protein into amino acids establishes a relationship with glucose and lipid metabolism through the tricarboxylic acid cycle, and determines the metabolic pathway of intermediates in the branch point of fatty acid metabolism according to the demand of the body [23]
Summary
Dietary protein provides the basic nitrogen source necessary for life, and participates in a series of physiological processes such as energy metabolism [1], hormone secretion [2], appetite control [3], and lipid metabolism [4]. Descovich et al [5] found that protein diets could regulate lipid synthesis and metabolism. Many studies have focused on effects of high protein and protein restriction in diets on growth performance; only few data are available on the diet effect on liver metabolism. Previous studies have shown that diets may differentially regulate the gene expression of enzymes and transporters involved in lipid metabolism. We have investigated the effects of different dietary meat proteins on gene expression in rat liver by transcriptome method, and proposed the relationships of body weight, blood lipid, and amino acid levels with hepatic lipid metabolism, amino acid metabolism, and pancreatic islet signaling pathway [12]. Only few data are available on the effects of meat protein diets on lipid metabolism, and on its underlying mechanisms
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