Regulatory Effect of High-Protein Diet on Circadian Rhythm of Lipid Metabolism in Obese Mice

This study aimed to investigate the regulatory effect of high-protein diet on circadian rhythm disturbances of lipid metabolism in obese mice induced by high-fat diet. Totally 120 specific pathogen-free (SPF)-grade C57BL/6J mice were randomly divided into normal, high-fat and high-fat/high-protein groups. The metabolic status of mice was monitored at the 4th and 12th week of intervention, and mice were sacrificed at 2, 8, 14, and 20 o’clock after completion of feeding. Lipid levels in blood and liver, the expression of genes related to fat anabolism and catabolism and the expression of circadian rhythm-related genes were measured, and circadian rhythm changes were analyzed. The results showed that highfat feeding caused an increase in body mass and obesity index and a decrease in voluntary activity and caloric expenditure during the active period. The changes were accompanied by dyslipidemia and an abnormal increase in liver lipid levels, manifested by continuous gene expression of acetyl-CoA carboxylase and fatty acid synthetase, key enzymes involved in fat anabolism in liver, at high levels during the active and resting periods, a slow increase in the gene expression of sensitive lipase and acetyl-CoA oxidase, key enzymes involved in fat catabolism in liver, and changes in the diurnal variation pattern. Compared with high-fat intervention, high-protein intervention significantly increased the amount of voluntary activity and energy expenditure during the active period, restored the expression rhythm of fat synthase that was higher during the active period and lower during the rest period, and resulted in high-level expression of ACOX, a key enzyme gene involved in fat catabolism, after ingestion, showing obvious circadian rhythms. Further analysis showed that the improvement effects of high-protein intervention on circadian rhythm disorders of lipid metabolism caused by high-fat diet were closely related to the regulation of the expression of two clock genes in liver, circadian locomotor output cycle kaput (CLOCK) and brain and muscle-Arnt-like protein 1 (BMAL1). In conclusion, high-protein diets can alleviate biological clock disorders in liver induced by high-fat diets and ameliorate hepatic lipid metabolism disorders in mice by stabilizing circadian rhythms.