A Discussion on Isolation and Identification of Lactobacillus plantarum HFY05 from Natural Fermented Yak Yogurt and Its Effect on Alcoholic Liver Injury in Mice

Yak yogurt is a type of naturally fermented dairy product prepared by herdsmen in the Qinghai-Tibet
Plateau, which is rich in microorganisms. In this study, a strain of Lactobacillus plantarum was
isolated and identified from yak yogurt in Hongyuan, Sichuan Province and named Lactobacillus
plantarum HFY05 (LP-HFY05). LP-HFY05 was compared with a common commercial strain of
Lactobacillus delbrueckii subsp. bulgaricus (LDSB). LP-HFY05 showed better anti-artificial gastric
acid and bile salt effects than LDSB in in vitro experiments, indicating its potential as a probiotic. In
animal experiments, long-term alcohol gavage induced alcoholic liver injury. LP-HFY05 effectively
reduced the liver index of mice with liver injury, downregulated the levels of aspartate
aminotransferase, alanine aminotransferase, alkaline phosphatase, triglyceride, total cholesterol,
blood urea nitrogen, nitric oxide, and MDA and upregulated the levels of albumin, superoxide
dismutase (SOD), catalase (CAT), and glutathione peroxidase in the serum of liver-injured mice. LPHFY05
also reduced the levels of interleukin (IL)-6, IL-12, tumor necrosis factor-alpha, and interferongamma
in the serum of liver-injured mice. The pathological observations showed that LP-HFY05
reduced the damage to liver cells caused by alcohol. Quantitative polymerase chain reaction and
Western blot assays further showed that LP-HFY05 upregulated neuronal nitric oxide synthase,
endothelial nitric oxide synthase, manganese-SOD, cuprozinc-SOD, CAT, and inhibitor of κB-α mRNA
and protein expression and downregulated the expression of nuclear factor-κB-p65 and inducible
nitric oxide synthase in the livers of liver-injured mice. A fecal analysis revealed that LP-HFY05
regulated the microbial content in the intestinal tract of mice with liver injury, increased the content of
beneficial bacteria, including Bacteroides, Bifidobacterium, and Lactobacillus and reduced the content
of harmful bacteria, including Firmicutes, Actinobacteria, Proteobacteria, and Enterobacteriaceae,
thus, regulating intestinal microorganisms to protect against liver injury. The effect of LP-HFY05 on
liver-injured mice was better than that of LDSB, and the effect was similar to that of silymarin. LPHFY05
is a high-quality microbial strain with a liver protective effect on experimental mice with
alcoholic liver injury. This study showed that LP-HFY05 reduced the liver index of liver-injured mice
and downregulated the levels of AST, ALT, ALP, TG, TC, BUN, NO, and MDA and upregulated the
levels of ALB, SOD, CAT, and GSH-Px in the serum of liver-injured mice. LP-HFY05 also
downregulated the serum levels of IL-6, IL-12, TNF-α, and IFN-γ in the liver-injured mice. qPCR
and Western blot experiments further confirmed that LP-HFY05 effectively upregulated nNOS, eNOS,
Mn-SOD, Cu/Zn-SOD, CAT, and IκB-α mRNA and protein expression and downregulated NF-κB-p65
and iNOS expression in the liver tissues of liver-injured mice.