Background/Objective: Long-term intake of a high-fat diet (HFD) leads to obesity and gut dysbiosis. AMP-activated protein kinase (AMPK) is a key regulator of energy metabolism. Herein, we investigated the impacts of Lactobacillus (Lactiplantibacillus) plantarum P111 and Bifidobacterium longum P121, which suppressed dexamethasone-induced adipogenesis in 3T3 L1 cells and increased lipopolysaccharide-suppressed AMPK activation in HepG2 cells, on HFD-induced obesity, liver steatosis, gut inflammation and dysbiosis, and depression/cognitive impairment (DCi)-like behavior in mice. Methods: Obesity is induced in mice by feeding with HFD. Biomarker levels were measured using immunoblotting, enzyme-linked immunosorbent assay, and immunofluorescence staining. Results: Orally administered P111, P121, or their mix LpBl decreased HFD-induced body weight gain, epididymal fat pad weight, and triglyceride (TG), total cholesterol (TC), and lipopolysaccharide levels in the blood. Additionally, they downregulated HFD-increased NF-κB activation and TNF-α expression in the liver and colon, while HFD-decreased AMPK activation was upregulated. They also suppressed HFD-induced DCi-like behavior and hippocampal NF-κB activation, NF-κB-positive cell population, and IL-1β and TNF-α levels, while increasing the hippocampal BDNF-positive cell population and BDNF level. The combination of P111 and P122 (LpBl) also improved body weight gain, liver steatosis, and DCi-like behavior. LpBl also mitigated HFD-induced gut dysbiosis: it decreased Desulfovibrionaceae, Helicobacteriaceae, Coriobacteriaceae, and Streptococcaceae populations and lipopolysaccharide production, which were positively correlated with TNF-α expression; and increased Akkermansiaceae, Bifidobacteriaceae, and Prevotellaceae populations, which were positively correlated with the BDNF expression. Conclusions: P111 and/or P121 downregulated adipogenesis, gut dysbiosis, and NF-κB activation and upregulatde AMPK activation, leading to the alleviation of obesity, liver steatosis, and DCi.
Keywords: Bifidobacterium longum; Lactobacillus plantarum; gut microbiota; liver steatosis; obesity; psychiatric disorder.