Effects of two Lactobacillus strains on lipid metabolism and intestinal microflora in rats fed a high-cholesterol diet

Ning Xie,Yong Tang,Ya-Ni Yin,Nian Fu,Fang-Gen Lu,Xin Zhao,Xue-Hong Wang,Zheng-Gen Wang,Jun-Wen Yang,Chun-Lian Wang,Xiao-Wei Liu,Yi Cui

doi:10.1186/1472-6882-11-53

Abstract

BackgroundThe hypocholesterolemic effects of lactic acid bacteria (LAB) have now become an area of great interest and controversy for many scientists. In this study, we evaluated the effects of Lactobacillus plantarum 9-41-A and Lactobacillus fermentum M1-16 on body weight, lipid metabolism and intestinal microflora of rats fed a high-cholesterol diet.MethodsForty rats were assigned to four groups and fed either a normal or a high-cholesterol diet. The LAB-treated groups received the high-cholesterol diet supplemented with Lactobacillus plantarum 9-41-A or Lactobacillus fermentum M1-16. The rats were sacrificed after a 6-week feeding period. Body weights, visceral organ and fat pad weights, serum and liver cholesterol and lipid levels, and fecal cholesterol and bile acid concentrations were measured. Liver lipid deposition and adipocyte size were evaluated histologically.ResultsCompared with rats fed a high-cholesterol diet but without LAB supplementation, serum total cholesterol, low-density lipoprotein cholesterol and triglycerides levels were significantly decreased in LAB-treated rats (p < 0.05), with no significant change in high-density lipoprotein cholesterol levels. Hepatic cholesterol and triglyceride levels and liver lipid deposition were significantly decreased in the LAB-treated groups (p < 0.05). Accordingly, both fecal cholesterol and bile acids levels were significantly increased after LAB administration (p < 0.05). Intestinal Lactobacillus and Bifidobacterium colonies were increased while Escherichia coli colonies were decreased in the LAB-treated groups. Fecal water content was higher in the LAB-treated groups. Compared with rats fed a high-cholesterol diet, administration of Lactobacillus plantarum 9-41-A resulted in decreases in the body weight gain, liver and fat pad weight, and adipocytes size (p < 0.05).ConclusionsThis study suggests that LAB supplementation has hypocholesterolemic effects in rats fed a high-cholesterol diet. The ability to lower serum cholesterol varies among LAB strains. Our strains might be able to improve the intestinal microbial balance and potentially improve intestinal transit time. Although the mechanism is largely unknown, L. plantarum 9-41-A may play a role in fat metabolism.

Highlights

The hypocholesterolemic effects of lactic acid bacteria (LAB) have become an area of great interest and controversy for many scientists
Since Mann and Spoerry [3] discovered the hypocholesterolemic effects of fermented milk ingested by the Massai tribes people, the relationship between lactic acid bacteria (LAB) and the serum cholesterol has become a focus of great interest
Several hypotheses have been proposed to explain these findings: (1) consumption of cholesterol by intestinal bacteria, reducing the amount of cholesterol available for absorption [11,12]; (2) cholesterol may be bound to the bacterial cellular surface [13] or incorporated into the bacterial cellular membranes [14] or converted into coprostanol by cholesterol reductase, which is produced by strains of lactobacilli [15]; (3) inhibition of micelle formation by certain probiotic strains [16]; (4) short-chain fatty acids produced upon selective fermentation of food by intestinal bacterial microflora may lower plasma cholesterol levels [17]; and (5) some bacterial species excrete bile salt hydrolase, leading to increased bile excretion in feces [18]

Summary

Introduction

The hypocholesterolemic effects of lactic acid bacteria (LAB) have become an area of great interest and controversy for many scientists. Since Mann and Spoerry [3] discovered the hypocholesterolemic effects of fermented milk ingested by the Massai tribes people, the relationship between lactic acid bacteria (LAB) and the serum cholesterol has become a focus of great interest. Studies evaluating this relationship have found that lactobacilli or bifidobacteria can exhibit hypocholesterolemic properties in animal models [4,5,6] and in humans [7,8,9,10]. More information is required to strengthen the proposed hypotheses and improve our undetstanding of how bacteria affect cholesterol metabolism, which might lead to more appropriate use of probiotics

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