Lactobacillus plantarum Reduces Low-Grade Inflammation and Glucose Levels in a Mouse Model of Chronic Stress and Diabetes

This study aimed to examine the effects of Lactobacillus plantarum, a lactic acid bacteria strain isolated from kimchi, on the development of low-grade inflammation and type 2 diabetes mellitus (T2DM) exacerbated by chronic stress. C57BL/6 mice were fed either a high-fat diet (HFD) and randomized into an HFD group or a group that was fed an HFD and subjected to chronic cold exposure-related stress (HFDS), or mice were fed a normal diet (ND) and randomized into an ND group or a group that was fed an ND and subjected to chronic cold exposure-related stress (NDS). Lactobacillus plantarum LRCC5310 (108, 1010 CFU) and LRCC5314 (108, 1010 CFU) as well as L. gasseri BNR17 (108 CFU), as a positive control, were administered orally twice every day to all the mice for 12 weeks. The expression of Glut4 and adiponectin, main glucose transporter-related genes, was upregulated in the LRCC5310- and LRCC5314-treated groups. Levels of serum proinflammatory cytokines (tumor necrosis factor-α [TNF-α], interleukin-6 [IL-6]) and of mRNAs of proinflammatory genes (Tnf-α, Il-6, Ccl2, leptin) were elevated in HFDS mice. The expression of proinflammatory genes was downregulated in LRCC5310- and LRCC5314-treated groups; this was not the case for Tnf-α expression in HFDS mice. Levels of serum corticosterone and mRNA levels of stress-related genes (Npy, Y2r) were decreased in lactic acid bacteria (LAB)-fed groups, with only LRCC5314 downregulating Npy expression in HFDS mice. These results suggest that the LAB strains can normalize the expression of metabolic genes, inhibit inflammatory responses, and suppress stress in HFDS mice.