Comparative study of probiotic effects of Lactobacillus and Bifidobacteria strains on cholesterol levels, liver morphology and the gut microbiota in obese mice

Abstract

Background: Microbiome-modulating interventions are promising for treatment and prevention of metabolic syndrome. The number of probiotic strains demonstrated ability to decrease cholesterol level in vivo, however, it was poorly confirmed in a clinical setting. The aim was to study the effects of L. acidophilus IMV B-7279, L. casei IMV B-7280, B. animalіs VKL and B. animalіs VKB separately and in various compositions on the level of serum cholesterol, gut microbiota contents and liver morphology on a high-calorie-induced obesity model in BALB/c mice.

Materials and methods: We used for the study female BALB/c mice 6-8 weeks old (18-24 g). Experimental animals were fed by a fat-enriched diet (FED), and 8 experimental groups were formed (12 mice in each group) to test strains of probiotic bacteria L. delbrueckii subsp. bulgaricus IMV B-7281, L. casei IMV B-7280, B. animalіs VKL and B. animalіs VKB and compositions. We used ultrasound for in vivo assessment of the liver and visceral (mesenteric) fat size. In the blood serum of the obese mice, the level of cholesterol was estimated. The liver morphology and gut microbiota of obese mice were studied.

Results: We revealed that after treatment with all of the studied probiotic bacteria and compositions of B. animalis VKL/B. animalis VKB/L. casei IMV B-7280, the weight of obese mice decreased, and cholesterol and its fraction levels in serum were reduced. The size of the liver slightly decreased after treatment with L. delbrueckii subsp. bulgaricus IMV B-7281, B. аnimalis VKB or probiotic compositions; we observed reduction of the mesenteric fat size after injection of all these probiotic bacteria (separately) and probiotic compositions. We defined the strain-dependent effects on serum lipid profiles, liver morphology and the gut microbiota. The B. animalis VKL/B. animalis VKB/L. casei IMV B-7280 composition effectively recovered the liver morphological structure of obese mice. The number of Lactobacillus spp., Bifidobacterium spp. and coliform bacteria increased, the number of staphylococci and streptococci reduced, and the number of microscopic fungi significantly decreased in the gut of obese mice after treatment with L. casei IMV B-7280, L. delbrueckii subsp. bulgaricus IMV B-7281, B. animalis (separately) or their compositions.

Conclusion: L. casei IMV B-7280 (separately) and a composition of B. animalis VKL/B. animalis VKB/L. casei IMV B-7280 are effective at decreasing the weight of obese mice, decreasing cholesterol level, restoring the liver morphology and beneficially modulating the gut microbiome in high-calorie-induced obesity.

Keywords: Bifidobacterium; Cholesterol; Gut microbiota; Lactobacillus; Liver; Metabolic syndrome; Mouse model: mesenteric fat; Obesity; Predictive preventive personalized medicine; Ultrasound.

Fig. 1

Ultrasound examination of mice along the experiment; (A) obese mouse (general view); (B) cross-section abdominal scan (transverse organo-complex record); (C) organs evaluation on US, L liver, K kidney

Fig. 2

Ultrasound examination (A) to obtain longitudinal scans of the abdominal cavity of mice along the experiment (sagittal organo-complex records); B measurement of visceral (mesenteric) fat

Fig. 3

Ultrasound examination of the liver (A) during the experiment; (B) the enlarged liver of obese mouse; (C) liver size decreasing after treatment

Fig. 4

Cholesterol levels; (A) the concentration of total, free and ester cholesterol in the blood serum of BALB/c line mice that received FED; (B) changes of total cholesterol levels in the blood serum during the experiment in all groups

Fig. 5

Liver tissue of intact (A, B) and obese (C, D) mice. (A, B) structure of liver tissue is preserved as normal, pathologic changes not detected. (C, D) fatty degeneration/necrosis of hepatocytes (A – x200 magnification, B – x400 magnification)

Fig. 6

Liver tissue of mice that received FED and L. casei IMV B-7280 (A), B. animalіs VKL (B), B. animalis VKL/B. animalis VKB/L. casei IMV B-7280 (C), B. animalis VKB (D, E), L. delbrueckii subsp. bulgaricus IMV B-7281 (F), B. animalis VKB/B. animalis VKL composition (G). (A) restoring liver structure, lipid inclusions are detected in hepatocytes. Partial necrosis and fatty degeneration of hepatocytes (x400 magnification). (B) restoring structure, lipid inclusions in hepatocytes and existing isolated sites with lymphocytes and macrophages infiltrates are detected; partial necrosis and fatty degeneration of hepatocytes (×400 magnification). (C) restoring structure, degenerative changes not detected. Partial necrosis of hepatocytes (x400 magnifications). (D, E) partial necrosis and fatty degeneration of hepatocytes (D – ×1000 magnification, E – ×400 magnification). (F) necrosis and fatty degeneration of hepatocytes (×400 magnification). (G) necrosis and fatty degeneration of hepatocytes (×400 magnification)