Probiotic properties of Lactobacillus rhamnosus GL68 with cholesterol-lowering and antioxidant activities in vitro and its effects on SD rats fed with a high-fat diet.

INTRODUCTION: Some probiotic microorganisms have been proven to offer several health benefits. However, there are few reports on lactic acid bacteria with cholesterol-lowering and antioxidant activities in vitro and on their probiotic effects on hosts. This study screened and identified probiotics with cholesterol-lowering activity in vitro and researched their antioxidant activity and probiotic property in vitro, along with their beneficial effects on high-fat diet-induced rats in vivo.

METHODS: The cholesterol-lowering rate in the cell-free supernatant was used to evaluate the cholesterol-lowering activity of isolates. Tolerance to acid and bile salt and antibacterial activity were assessed to investigate their potential probiotic characteristics, and antibiotic susceptibility was evaluated. DPPH and hydroxyl radical scavenging rate of cell-free supernatant was used to evaluate the antioxidant activity in vitro. Body mass, Lee's index, liver index, blood lipid, liver enzymes levels, histological analysis of liver and pancreas, gut microbiota structure, and short-chain fatty acids were used to evaluate the beneficial effects on high-fat diet-induced rats.

RESULTS: A strain with 71.2 ± 0.9% cholesterol-lowering rate was screened and identified as Lactobacillus rhamnosus GL68, and its acid and bile salt tolerance were, respectively, 92.1 ± 4.3% and 88.3 ± 3.2%, and it has antibiotic susceptibility. DPPH and hydroxyl radical scavenging rates were 84.6 ± 1.3% and 79.3 ± 1.1%, respectively. Administering L. rhamnosus GL68 to the high-fat diet group significantly reduced weight gain, Lee's index, and liver index by 22.01, 17.71, and 19.35%, respectively. Additionally, it downregulated total cholesterol, total triglycerides, low-density lipoprotein cholesterol, alanine aminotransferase, and aspartate aminotransferase levels by 29.88, 52.89, 27.51, 26.10, and 26.27%, respectively. Furthermore, it raised high-density lipoprotein cholesterol levels by 20.03%. Administering L. rhamnosus GL68 upregulated liver superoxide dismutase and glutathione peroxidase levels by 41.39 and 71.02%, respectively. It downregulated liver malondialdehyde levels by 37.82%. Administering L. rhamnosus GL68 ameliorated hepatic inflammation and ballooning degeneration, glandular atrophy, and vesicular degeneration. It also reshaped gut microbiota at the genus level, and showed a positive correlation with short-chain fatty acids in the feces of high-fat diet rats.

DISCUSSION: L. rhamnosus GL68 with cholesterol-lowering and antioxidant activity in vitro can be used as a potential probiotic to administer high-fat diet-induced lipid metabolism disorder and gut microbiota disorders, and alleviate liver and pancreatic damage.