Dietary Fiber Improves Lipid Metabolism through Changes in Gut Microbiota and their Metabolites in High-Fat Diet Fed Rats

Abstract

Background and Aims: A high-fat diet can induce hepatic steatosis, hyperlipidemia, obesity, diabetes, and other lipid metabolism disorders through the regulation of lipid metabolism signaling pathways in the liver. The objective of this study was to investigate the influence of dietary fiber on the composition of the intestinal microbiota to improve lipid metabolism. Materials and Methods: Male Sprague Dawley (SD) rats were divided into four groups: a Control group (ZC), a high-fat diet group (HF), a fiber diet group (GQ), and a combination of high-fat and fiber diet group (GZGQ). Following four weeks of feeding with experimental diets, the rats were euthanized, and the blood sample was collected from the abdominal aorta. Plasma levels of triglyceride (TG), total cholesterol (TC), low-density lipoprotein (LDL-C), and high-density lipoprotein cholesterol (HDL-C) were assessed. Furthermore, total DNA was extracted from a 100 mg stool sample. The 16S ribosomal RNA gene sequencing and quadrupole time-of-flight mass spectrometry coupled with high-performance liquid chromatography to detect the structure and metabolites of rat intestinal gut flora. Linear discriminant analysis effect size was used to determine the major communities or species across various experimental groups. Results: Using high-throughput 16S rRNA gene sequencing, 8, 6, 2, and 5 unique bacteria were observed in the ZC, GQ, HF, and GZGQ group, respectively. Compared to the Control group, the proportion of thick-walled phyla decreased in the GQ and GZGQ groups and increased in the HF group. The relative abundance of Bacteroidales S24-7 group, Bacteroides, and Ruminococcus gnavus group was significantly higher in the GQ and GZGQ groups (p < 0.05), whereas the relative abundance of some bacteria was elevated in the HF group. Moreover, it was found that the atorvastatin-induced metabolites were elevated in the HF group. Furthermore, choline content was significantly increased in the GZGQ group, and levocarnitine content was significantly lower in both the GQ and GZGQ groups. Additionally, dietary fiber reduced the levels of TC, TG, and LDL-C in high-fat rats. Conclusions: These findings indicate that through the gut microbiota, dietary fiber regulates dyslipidemia, increases choline and L-carnitine, and reduces the risk of diseases associated with a high-fat diet.