## 1 Introduction  
Probiotics, defined as live microorganisms that (when ingested) provide health benefits to the host, are used when people eat fermented foods [1]. Many microorganisms have currently been used or considered for use as probiotics. Several studies have proven the functional features of _Lactobacillus_. _Lactobacillus fermentum_ LF31 and _Lactobacillus coryniformis_ were found to exert antioxidative effects [2, 3]. _Lactobacillus plantarum_ NCU116 could enhance the mucosal immunity of the intestine and regulate Th17/Treg balance [4]. _Lactobacillus_ GG was shown to exert an antidiabetic effect [5], and _Lactobacillus paracaei_ Jhus66 could effectively protect the liver [6]. _Bifidobacterium_ and _Streptococcus_ have also been used as probiotics [7; 8]. However, most studies have limited their focus to the beneficial effects of live microorganisms, and a number of experts have recently investigated whether the cellular components of live microorganisms also played any role. Thus, the beneficial effects of live and dead microorganisms should be compared to determine which microorganisms are effective. Considering the advantages of dead microorganisms has also been useful in industrial production and consumer usage, such as increased convenience in storage and transport, lengthened shelf-life extension, and improved safety. Thus, evaluating the effects of dead microorganisms has practical significance [9]. Diabetes, a metabolic disease group with high blood glucose as the main feature, is associated with numerous genetic and environmental factors. With changes in diet and lifestyle, the incidence of diabetes has increased year by year [10]. Type 2 diabetes is the foremost type of diabetes worldwide [11]. A number of mechanisms underlying type 2 diabetes have been identified, including glycogenesis, glycolysis, fatty acid biosynthesis, glucose uptake, lipogenesis, lipolysis, and the insulin signaling pathway. However, the definite etiology and pathogenesis of the disease remain unclear [12]. The liver is the main organ of metabolism, detoxification, and immunity; it is also the center of glucose metabolism [13]. Thus, the liver plays an important role in keeping the body healthy. In previous studies on diabetes, the role of the liver was self-evident. One study demonstrated that fatty liver and insulin resistance were involved in metabolic syndrome. Among patients with type 2 diabetes, 50% to 70% of the patients suffered from fatty liver, and the percentage increased to 95% in patients with obesity [14; 15]. Persistent high blood glucose was associated with excessive generation of reactive oxygen species in the body with diabetes, and this could induce oxidative tissue damage particularly in the liver, pancreas, and kidney [16]. Thus, the effects of research targets (e.g., probiotics, polysaccharides and polypeptides) on the liver of mice with diabetes need to be evaluated. These finding could provide a theoretical basis for its hypoglycemic activity. Numerous methods for modeling diabetes have been developed. Among these techniques, the construction of a diabetic model with streptozotocinocin (STZ) combined with high-fat diet has been widely used. STZ, a monofunctional nitrosourea derivative, was first isolated from _Streptomyces achromogenes_[17; 18]. It is also an alkylating agent and can lead to cell death. When cytotoxicity acts on \(\beta\)-cells, insulin release decreases, and blood glucose in the body rises [19]. In addition, a high-fat diet can lead to obesity and insulin resistance [20]. Therefore, diabetes induced by a high-fat diet combined with STZ can better simulate the pathogenesis of human type 2 diabetes and can be used widely in studies on hypoglycemic activity. In the current study, _Lactobacillus fermentum_ (LF) and _Lactobacillus plantarum_ (LP) were isolated from Chinese pickles by using traditional pure culture techniques and then deposited in the China General Microbiological Culture Collection Center (CGMCC).