Exploring the Cholesterol-Modifying Abilities of Lactobacilli Cells in Digestive Models and Dairy Products

This study aimed to investigate the ability of lactic acid bacteria to remove cholesterol in simulated gastric and intestinal fluids. The findings showed that the amount of cholesterol removed was dependent on the biomass, viability, and bacterial strain. Some cholesterol binding was stable and not released during gastrointestinal transit. The presence of cholesterol affected the fatty acid profile of bacterial cells, potentially influencing their metabolism and functioning. However, adding cholesterol did not significantly impact the survival of lactic acid bacteria during gastrointestinal transit. Storage time, passage, and bacterial culture type did not show significant effects on cholesterol content in fermented dairy products. Variations in cell survival were observed among lactic acid bacteria strains in simulated gastric and intestinal fluids, depending on the environment. Higher milk protein content was found to be more protective for bacterial cells during gastrointestinal transit than fat content. Future research should aim to better understand the impact of cholesterol on lactic acid bacteria metabolism and identify potential health benefits.

Effects of probiotics and prebiotics on blood lipids

Since the early work of Mann and Spoerry, probiotics in the form of fermented milk products have been reputed to have cholesterol-lowering properties in humans. However, studies conducted since the early 1970s have produced equivocal findings, with interpretation of the outcomes complicated by use of excessive quantities of product, inadequate sample sizes, failure to control nutrient intake and energy expenditure and variations in baseline blood lipids. More recent studies are of better quality, but fail to provide convincing evidence that ‘live’ fermented milk products have cholesterol-lowering efficacy in man. Future studies using probiotics should ensure adequate sample sizes sufficient to detect relatively small changes in blood cholesterol and should be conducted over longer periods of time. The recent introduction of the concept of prebiotics has directed attention towards the possibility that alterations in gut microflora induced by the fermentation of non-digestible components of the diet may also have the potential to influence systemic lipid metabolism. This possibility has been strengthened by the observation that in animals, dietary oligofructosaccharides cause suppression of hepatic triglyceride and VLDL synthesis, resulting in marked reductions in triglyceride, and to a lesser extent cholesterol, levels. Evidence for similar effects in humans is sparse and more studies are needed, particularly with respect to effects on postprandial triglyceride concentrations.

The scale of the evidence base on the health effects of conventional yogurt consumption: findings of a scoping review

BACKGROUND

The health effects of conventional yogurt have been investigated for over a century; however, few systematic reviews have been conducted to assess the extent of the health benefits of yogurt.

OBJECTIVE

The aim of this scoping review was to assess the volume of available evidence on the health effects of conventional yogurt.

METHODS

The review was guided by a protocol agreed a priori and informed by an extensive literature search conducted in November 2013. Randomized controlled trials were selected and categorized according to the eligibility criteria established in the protocol.

RESULTS

213 studies were identified as relevant to the scoping question. The number of eligible studies identified for each outcome were: bone health (14 studies), weight management and nutrition related health outcomes (81 studies), metabolic health (6 studies); cardiovascular health (57 studies); gastrointestinal health (24 studies); cancer (39 studies); diabetes (13 studies), Parkinson's disease risk (3 studies), all-cause mortality (3 studies), skin complaints (3 studies), respiratory complaints (3 studies), joint pain/function (2 studies); the remaining 8 studies reported a variety of other outcomes. For studies of a similar design and which assessed the same outcomes in similar population groups, we report the potential for the combining of data across studies in systematic reviews.

CONCLUSIONS

This scoping review has revealed the extensive evidence base for many outcomes which could be the focus of systematic reviews exploring the health effects of conventional yogurt consumption.

Genetic and proteomic analysis of factors affecting serum cholesterol reduction by Lactobacillus acidophilus A4

This article identifies novel factors involved in cholesterol reduction by probiotic bacteria, which were identified using genetic and proteomic approaches. Approximately 600 Lactobacillus acidophilus A4 mutants were created by random mutagenesis. The cholesterol-reducing ability of each mutant was determined and verified using two different methods: the o-phthalaldehyde assay and gas chromatographic analysis (GC). Among screened mutants, strain BA9 showed a dramatically diminished ability to reduce cholesterol, as demonstrated by a 7.7% reduction rate, while the parent strain had a more than 50% reduction rate. The transposon insertion site was mapped using inverse PCR (I-PCR), and it was determined using bioinformatic methods that the deleted region contained the Streptococcus thermophilus catabolite control protein A gene (ccpA). In addition, we have shown using two-dimensional gel electrophoresis (2-DE) that several proteins, including a transcription regulator, FMN-binding protein, major facilitator superfamily permease, glycogen phosphorylase, the YknV protein, and fructose/tagatose bisphosphate aldolase, were strongly regulated by the ccpA gene. In addition, in vivo experiments investigating ccpA function were conducted with rats. Rats fed wild-type L. acidophilus A4 showed a greater than 20% reduction in total serum cholesterol, but rats fed BA9 mutant L. acidophilus showed only an approximately 10% reduction in cholesterol. These results provide important insights into the mechanism by which these lactic acid bacteria reduce cholesterol.

Effect of fermented milk (yogurt) containing Lactobacillus acidophilus L1 on serum cholesterol in hypercholesterolemic humans

OBJECTIVE

Two controlled clinical studies were performed to examine effects of consumption of one daily serving of fermented milk (FM) (yogurt) on serum lipids.

METHODS

In the first study, subjects were randomly allocated to FM containing Lactobacillus acidophilus L1 of human origin or to FM containing L. acidophilus ATCC 43211 of swine origin. In this single-blind study, subjects consumed one 200 ml serving of FM daily for 3 weeks. The second study was a double-blind, placebo-controlled, cross-over study. Subjects completed a 4-week first treatment, had a 2-week washout, and completed a second 4-week treatment. In the second study subjects consumed FM containing L. acidophilus L1 or placebo FM over 4 weeks.

RESULTS

In the first study, FM containing L. acidophilus L1 was accompanied by a 2.4% (p<0.05) reduction of serum cholesterol concentration. In the second study, strain L1 reduced serum cholesterol concentration by 3.2% (p<0.05) in the first treatment period. In the second treatment period there were no significant changes in serum cholesterol concentration. Combined analysis of the two L1 treatment studies demonstrated a 2.9% (p<0.01) reduction in serum cholesterol concentration.

CONCLUSION

Since every 1% reduction in serum cholesterol concentration is associated with an estimated 2% to 3% reduction in risk for coronary heart disease, regular intake of FM containing an appropriate strain of L. acidophilus has the potential of reducing risk for coronary heart disease by 6 to 10%.

Review article: the use of biotherapeutic agents in the prevention and treatment of gastrointestinal disease

There is presently a lack of well conducted clinical trials demonstrating any significant benefits of probiotics in humans. With the exception of diarrhoea due to rotavirus infection in children there is little evidence from randomized, double-blind, placebo-controlled studies that bacterial probiotics have a significant beneficial action in preventing diarrhoea of any cause. The yeast Saccharomyces boulardii has been shown to be of benefit in the prevention of antibiotic-associated diarrhoea but not in preventing infection with Clostridium difficile. S. boulardii may also be of benefit in preventing relapse of C. difficile infection. Because of the simplicity of in vitro systems and some animal models, beneficial characteristics of probiotics such as the ability of bacteria to bind to epithelial surfaces are not always transferable to humans. Thus any postulated benefit from consumption of probiotic bacteria should only be accepted as fact after testing in clinical studies. This review outlines our present knowledge of the mode of action of probiotics and presents the data from clinical trials on their use.

Influence of yogurt and acidophilus yogurt on serum cholesterol levels in mice

The effects of yogurt and acidophilus yogurt on the weight gain, serum cholesterol, high density lipoprotein cholesterol, low density lipoprotein cholesterol, triglycerides, and the numbers of fecal lactobacilli and coliforms were investigated in mice assigned to three dietary treatments for 56 d: 1) commercial rodent chow and water (control), 2) commercial rodent chow and yogurt made from milk inoculated with a 3% (vol/vol) liquid culture of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus (yogurt), and 3) commercial rodent chow plus yogurt made from milk inoculated with a 0.01% (wt/vol) freeze-dried culture of Streptococcus thermophilus plus Lactobacillus acidophilus. The weight gains of mice receiving yogurt or acidophilus yogurt were higher than those of the mice in the control group. The mean values for serum cholesterol concentrations and LDL cholesterol concentrations were significantly decreased when acidophilus yogurt was fed on d 28 and 56. High density lipoprotein cholesterol and triglycerides were not affected by yogurt or acidophilus yogurt. The highest number of fecal lactobacilli was found in mice receiving acidophilus yogurt, and the number of fecal coliforms of that group was also lower than in the other two groups.

Effects of a mixture of organisms, Lactobacillus acidophilus or Streptococcus faecalis on cholesterol metabolism in rats fed on a fat- and cholesterol-enriched diet

The effect of a mixture of organisms (a probiotic mixture) comprising Bacillus, Lactobacillus, Streptococcus, Clostridium, Saccharomyces and Candida (10(7-8) colony-forming units/g rice bran of each component) on lipid metabolism was compared with that of L. acidophilus and that of S. faecalis. There were four treatment groups: rice bran (control), the mixture of organisms, L. acidophilus or S. faecalis (30 g/kg) were given to rats in a fat- and cholesterol-enriched diet for 4 weeks. The serum total cholesterol concentration of the group fed on the mixture of organisms was reduced by 15-33% compared with the other groups at the end of the 4-week feeding period (P < 0.05). This group also had a lower hepatic cholesterol concentration (36-44%) than the two single-bacteria groups (P < 0.05). 3-Hydroxy-3-methylglutaryl-Co A reductase (NADPH; EC 1.1.1.34) activities of the mixed-organism and L. acidophilus groups were significantly lower (61-63%) than those of the other groups (P < 0.05); the activity of the S. faecalis group was also significantly lower (42%) than that of the control group (P < 0.05). The faecal cholesterol and bile acid concentrations of the mixed-organism group increased compared with those of the L. acidophilus and S. faecalis groups (P < 0.05). The capacity of the mixed-organism cells to bind bile salt in vitro was significantly higher (approximately 50%) than that of the single-bacteria cells (P < 0.05). On the other hand, cholesterol micelle formation for the mixed-organism cells was significantly (approximately 9%) lower than that of the single-bacteria cells (P < 0.05). These results indicate that the mixture of organisms decreased the synthesis of cholesterol in the liver and increased the loss of steroids from the intestine, in rats. Thus, the mixture of organisms had a hypocholesterolaemic role.

Intestinal cholesterol metabolism

The handling of cholesterol by the intestine involves a balance between absorption, excretion and metabolism by gut microflora. Between 34-57% of dietary cholesterol is absorbed from the human intestine. Variables effecting the efficiency of cholesterol absorption include the absolute amount of cholesterol consumed, the presence of plant sterols, the fiber content of the diet, transit time and possibly the relative proportions of fatty acids in the diet. On average, 150 mg/day of cholesterol is excreted in the feces. Fecal cholesterol derives from biliary secretions into the intestine, sloughing of epithelial cells and unabsorbed dietary cholesterol. The major metabolic products of cholesterol in the gut are coprostanol, coprostanone, cholestanol, cholestanone and epicoprostanol. Bacterial metabolism of cholesterol can be influenced by diet as evidenced by significant variations among different population groups with different dietary habits. Altered patterns of intestinal bacterial metabolism of cholesterol may place persons at a higher risk of developing colonic disorders. Dairy products have been reported to influence the bacterial metabolism of cholesterol and possibly plasma cholesterol levels although the significance of these findings to overall cholesterol balance needs to be further defined.

Lactobacillus effects on cholesterol: in vitro and in vivo results

A double blind investigation was conducted on the influence of a commercially available tablet containing Lactobacillus acidophilus and Lactobacillus bulgaricus (Lactinex Becton Dickinson Microbiology Systems, Cockeysville, MD) on human serum lipoprotein concentrations. Tablets containing about 2 X 10(6) viable bacteria of Lactobacillus mixtures or placebo tablets were ingested by 354 nonfasting informed subjects in a dose of one tablet each, taken four times a day. There was a 3-wk washout period between two 6-wk treatment periods. The number of viable lactobacillus in unused returned tablets was the same at the end of the study as in the beginning. Analysis of paired data using Wilcoxon signed ranks test showed no major effects on lipoprotein concentrations for either the placebo-treated group or the lactobacilli-treated group. There were no statistically significant differences for low density lipoprotein concentrations between the lactobacilli-treated group and the placebo-treated group. The high density lipoprotein concentrations increased 1.8 to 3.0 mg/dl in both groups for both study periods. For total cholesterol the placebo-treated group experienced a statistically significant increase in the first period according to the Wilcoxon signed ranks test (from 208.0 to 215.0 mg/dl, P less than .001) but not according to a two-sample Student t test. Total cholesterol did not change significantly for the Lactobacillus-treated group in either period. Cardiac risk factor (ratio of total cholesterol to high density cholesterol) did not vary during the study. Lipoprotein values increased immediately following vigorous exercise compared with following 15 min of resting without either placebo or treatment. Sample controls for assay and reassay gave virtually identical values (coefficient of variation 1.6%), confirming that assay results were quite reliable. Thus, ingestion of commercially available Lactobacillus tablets, which contain about 2 X 10(6) cfu/tablet of L. acidophilus and L. bulgaricus cells in a dose of four tablets daily did not affect serum lipoprotein concentrations.