Effects of Fat and Carbohydrate Energy Supply Ratio on Fat Metabolism and Intestinal Microbiota in Rats

Abstract

The proportions of fat and carbohydrate in diet have an important impact on lipid metabolism, glucose metabolism and health. On the premise of consistent dietary available energy (metabolic energy), the effects of different fat and carbohydrates energy supply ratios in diet on fat metabolism and gut microbiota were studied. Sixty-four 9-weeks-old SPF grade male SD rats aged 9 weeks were randomly divided into 4 groups including: HFf group (energy supply ratio of fat to carbohydrate (F/C) 40% : 45%), MFf group (F/C 31% : 54%), LFf group (F/C 21% : 64%) and CON group (control diet). The results showed that there were no significant differences in body weight, blood glucose, blood lipid and liver steatosis among all groups (P > 0.05). The liver triglyceride and abdominal adiponectin of HFf group were significantly higher than those of the other three groups (P < 0.05). Compared to the CON group, the acetyl-CoA carboxylase (ACC) gene expression in the liver of HFf group decreased, while the expressions of lipid synthesis genes, fatty acid transporter (FAT/CD36), sterol regulatory element binding protein (SREBP1), and adipocyte differentiation gene peroxisome proliferator-activated receptor (PPARγ) increased in HFf group (P < 0.05). Compared with CON group, the cholesterol synthesis factor hydroxymethylglutarate monoacyl CoA (HMG-CoA) gene expression in the liver of HFf, MFf and LFf groups were all increased (P < 0.05). In addition, the higher dietary F/C (40% : 45% and 30% : 55%) resulted in impaired gut villi development, which led to decreasing abundance of beneficial bacteria but increasing abundance of potentially pathogenic bacteria. In conclusion, under the same dietary available energy, although the diet of the high-fat group contained a high proportion of fat, it also contained a high content of cellulose, which effectively alleviated the weight gain and blood glucose and lipid abnormalities caused by the high-fat diet. However, there were still symptoms such as increased liver fat and impaired intestinal health, and the F/C in the diet of rats should not exceed 30%. This provides a theoretical reference for the appropriate proportion of macronutrients in the diet.

Keywords

• fat and carbohydrate energy supply ratio
• fat metabolism
• intestinal microbiota
• rat