New insights on strain-specific impacts of probiotics on insulin resistance: evidence from animal study

сomparative animal study of effectiveness of intermittent administration of lyophilized single-, three- and alive multistrain probiotic in short courses on insulin resistance (IR) in rats with experimental obesity.

70 rats were divided into 7 groups (n = 10 in each). Rats of group I were left intact. Newborn rats in groups II-VII were administered monosodium glutamate (MSG) (4 mg/g) by injection. Rats in group II (MSG-obesity group) were left untreated. The rats in groups III-V received lyophilized mono-probiotics B.animalis VKL, B.animalis VKB, L.casei IMVB-7280 respectively. The rats in group VI received all three of these probiotic strains mixed together. Group VII was treated with multi-probiotic "Symbiter", containing 14 different live probiotic strains (Lactobacillus, Bifidobacterium, Propionibacterium, Acetobacter genera).

Treatment of newborn rats with MSG lead to the development of obesity in all MSG-obesity rats and up to 20-70% after probiotic administration. Additions to probiotic composition, with preference to alive strains (group VII), led to significantly lower rates of obesity, decrease in HOMA-IR (p < 0.001), proinflammatory cytokines levels - IL-1β (p = 0.003), IL-12Bp40 (p < 0.001) and elevation of adiponectin (p = 0.003), TGF-β (p = 0.010) in comparison with MSG-obesity group. Analysis of results in groups treated with single-strain probiotics (groups III-V) shows significant decrease in HOMA-IR, but changes were less pronounced as compared to mixture groups and did not achieve intact rats level. Other metabolic parameters were not affected significantly by single strains.

Our findings provide major clues for how to design and use probiotics with more efficient compositions in obesity and IR management and may bring new insights into how host-microbe interactions contribute to such protective effects.