The effect of mulberry leaf powder and components on preventing obesity and regulating lipid metabolism were investigated in the present study. The mechanism of action was explored by examining the gut microbiota and lipid metabolism-related signaling pathways. As evidenced by the nutritional obesity rats model experiments, the middle concentration mulberry leaf powder (MLP) group (0.8 g/kg⋅d) significantly reduced Lee's index (25.1, compared with model control group [MC] 25.7) and had the strongest lipid metabolism regulation effect. Furthermore, the suppression effects of different mulberry leaf components on nutritional obesity were compared and the mulberry leaf phenolics and fiber mixture (Mulberry leaf mixture [MLM]) group (0.6 g/kg⋅d) was found to have the strongest efficacy (body weight [BW] reduced 12.4%). Real time PCR (RT-qPCR) and western blot analyses demonstrated that MLP (0.8 g/kg⋅d) and its components inhibited adipocyte differentiation and triglyceride synthesis through the PPAR-γ-C/EBP-α signaling pathway, resulting in lipid metabolism regulation. Gut microbiota analysis indicated that MLM (0.6 g/kg⋅d) prevented the reduction in intestinal flora diversity (reach 491 species) caused by highenergy feed, and reduced the Firmicutes/Bacteroidetes ratio (to 7.99%) and the obesity associated flora, Lachnospiraceae (to 19.1%), whereas it improved the content of the beneficial flora, Lactobacilli, Lactobacillus_johnsonii (reach 11.77%).MLM improved the bioaccessibility and bioavailability of the two functional components (phenolics and fiber) and maximized the anti-obesity effect through the gut microbiota-host metabolism pathway. Practical Application: The anti-obesity and lipid metabolism regulation effect of mulberry leaf components were evaluated in this study. The fiber and phenolics of this plant have the potential for development of weight-loss functional foods.
K E Y W O R D Sgut microbiota, lipid metabolism, mulberry leaf, obesity
INTRODUCTIONObesity has become an important global public health problem that is an enormous burden on both families and entire societies (Liang et al., 2020;Ng, 2014). According to the statistics, by 2030, there will be 2.16 billion overweight and 1.12 billion obese people in the word (Apalasamy & Mohamed, 2015). Excessive body fat results in
Mulberry removed monosaccharides (FM) displayed better hypoglycemic activity than untreated mulberry (MP), which may be attributed the stronger effects of FM on activating PI3K/Akt and AMPK signaling pathways.
Gracilaria lemaneiformis polysaccharide (GLP) exhibits good physiological activities, and it is more beneficial as it is degraded. After its degradation by hydrogen peroxide combined with vitamin C (H2O2-Vc) and optimized by Box–Behnken Design (BBD), a new product of GLP-HV will be generated. While using GLP as control, two products of GLP-H (H2O2-treated) and GLP-V (Vc-treated) were also produced. These products chemical characteristics (total sugar content, molecular weight, monosaccharide composition, UV spectrum, morphological structure, and hypolipidemic activity in vitro) were assessed. The results showed that the optimal conditions for H2O2-Vc degradation were as follows: H2O2-Vc concentration was 18.7 mM, reaction time was 0.5 h, and reaction temperature was 56 °C. The total sugar content of GLP and its degradation products (GLP-HV, GLP-H and GLP-V) were more than 97%, and their monosaccharides are mainly glucose and galactose. The SEM analysis demonstrated that H2O2-Vc made the structure loose and broken. Moreover, GLP, GLP-HV, GLP-H, and GLP-V had significantly inhibition effect on α-glucosidase, and their IC50 value were 3.957, 0.265, 1.651, and 1.923 mg/mL, respectively. GLP-HV had the best inhibition effect on α-glucosidase in a dose-dependent manner, which was the mixed type of competitive and non-competitive. It had a certain quenching effect on fluorescence of α-glucosidase, which may be dynamic quenching.
Mulberry has significant hypoglycemic effect and can be used as an auxiliary food for people with type 2 diabetes. However, it is rich in carbohydrate and cannot be consumed directly by diabetic patients. In the study, we fermented the mulberry to reduce the content of glucose and fructose, and added the soybean to reduce the loss of probiotics during fermentation and then determined its hypoglycemic effect. We induced type 2 diabetes mellitus (T2DM) mice by streptozotocin and measured its blood glucose, serum biochemistry, hepatic and pancreatic histopathology, and the diversity of the gut microbiota. After 5 weeks of oral DFMS administration, the glucose tolerance was improved significantly in T2DM mice. Furthermore, there were also significant increases in superoxide dismutase activity and glutathione concentration, and marked reductions in the concentrations of malondialdehyde and free fatty acids. Moreover, DFMS also prevented histopathological changes and the increases in the activities of alanine transaminase and aspartate transaminase. DFMS treatment also markedly increased the richness of the gut microbial community. The abundance of Bacteroidetes was increased, and those of Proteobacteria, Escherichia‐Shigella, and Lactobacillus were reduced. In summary, DFMS has a clear hypoglycemic effect in mice with T2DM.
The objective of this research was to investigate the antioxidant activity of Gracilaria lemaneiformis polysaccharide degradation and its underlying mechanism involved in the Nrf-2/Keap-1 signaling pathway in HepG2 cells with oxidative stress induced by H2O2. The result of the scavenging ability of free radicals showed that GLP-HV (polysaccharide degraded by H2O2–vitamin C (Vc)) performed a better scavenging ability than GLP (G. lemaneiformis polysaccharide). Moreover, the scavenging ability of polysaccharide to these free radicals from strong to weak was as follows: superoxide radical, ferric ion, ABTS+, and DPPH radical, and their IC50 values were 3.56 ± 0.0028, 4.97 ± 0.18, 9.62 ± 0.35, and 23.85 ± 1.78 mg/mL, respectively. Furthermore, GLP-HV obviously relieved oxidative stress in HepG2 cells, which strengthened the activity of T-AOC, CAT, GSH-PX, and SOD, and diminished the intensity of MDA, intracellular ROS, and calcium ion based on the Nrf-2/Keap-1 signaling pathway. The PCR result revealed that polysaccharide upregulated the expression of the genes Nrf-2, HO-1, NQO-1, and ZO-1 and downregulated Keap-1. The correlation between chemical properties and antioxidant mechanism of GLP-HV was evaluated via a heat map. The results illustrated that reducing sugar and active groups presented a positive correlation, and molecular weight and viscosity exhibited a negative relation with antioxidant activity.
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