Mangiferin Ameliorates Obesity-Associated Inflammation and Autophagy in High-Fat-Diet-Fed Mice: In Silico and In Vivo Approaches

Abstract

Obesity-induced insulin resistance is the fundamental cause of metabolic syndrome. Accordingly, we evaluated the effect of mangiferin (MGF) on obesity and glucose metabolism focusing on inflammatory response and autophagy. First, an in silico study was conducted to analyze the mechanism of MGF in insulin resistance. Second, an in vivo experiment was conducted by administering MGF to C57BL/6 mice with high-fat-diet (HFD)-induced metabolic disorders. The in silico analysis revealed that MGF showed a high binding affinity with macrophage-related inflammatory cytokines and autophagy proteins. In the in vivo study, mice were divided into three groups: normal chow, HFD, and HFD + MGF 150 mg/kg. MGF administration to obese mice significantly improved the body weight, insulin-sensitive organs weights, glucose and lipid metabolism, fat accumulation in the liver, and adipocyte size compared to HFD alone. MGF significantly reduced the macrophages in adipose tissue and Kupffer cells, inhibited the gene expression ratio of tumor necrosis factor-α and F4/80 in adipose tissue, reduced the necrosis factor kappa B gene, and elevated autophagy-related gene 7 and fibroblast growth factor 21 gene expressions in the liver. Thus, MGF exerted a therapeutic effect on metabolic diseases by improving glucose and lipid metabolism through inhibition of the macrophage-mediated inflammatory responses and activation of autophagy.

Keywords: Anemarrhenae rhizoma; autophagy; inflammation; insulin resistance; mangiferin; obesity.

Figure 1

Hub genes of mangiferin (MGF) and insulin resistance and functional enrichment analysis. (a) The 59 overlapping genes between MGF and insulin resistance. (b) GO enrichment analysis. (c) KEGG pathway enrichment analysis. GO, gene ontology; KEGG, Kyoto Encyclopedia of Genes and Genomes.

Figure 2

Molecular docking between the MGF and target proteins. (a) MGF and TNF-α. (b) MGF and IL-6. (c) MGF and NF-κB. (d) MGF and AKT1. (e) MGF and ATG7. (f) MGF and FGF21. Binding energies are expressed on the middle top section of each sub-panel. The top three shortest interaction distances are displayed in pink, and the interacting amino acids are shown in yellow. MGF, mangiferin; TNF-α, tumor necrosis factor-α; IL-6, interleukin-6; NF-κB, nuclear factor kappa B; ATG7, autophagy-related gene 7; FGF21, fibroblast growth factor 21.

Figure 3

Weight-related indexes of each experimental group (a) Timeline of body weight gain. (b) Change in body weight. (c) Epididymal fat pad weight. (d) Liver weight. (e) Calorie intake. Data are expressed as mean ± standard error of mean. ### p < 0.001 indicates the results of comparison with the NC group, and * p < 0.05 and ** p < 0.01 indicate the results of comparison with the HFD group. NC, normal chow; HFD, high-fat diet; MGF, HFD + MGF 150 mg/kg/day; MGF, mangiferin.

Figure 4

Glucose-metabolism-related outcomes. (a) Fasting blood glucose (FBG). (b) Oral glucose tolerance test (OGTT). (c) AUC of OGTT. (d) iAUC of OGTT. (e) Serum insulin level. (f) HOMA-IR. Data are expressed as mean ± standard error of mean. # p < 0.05, ## p < 0.01, and ### p < 0.001 indicate the results of comparison with the NC group, and * p < 0.05 and *** p < 0.001 indicate the results of comparison with the HFD group. NC, normal chow; HFD, high-fat diet; MGF, HFD + MGF 150 mg/kg/day; MGF, mangiferin; FBG, fasting blood glucose; AUC, area under the curve; iAUC, incremental area under the curve; OGTT, oral glucose tolerance test; HOMA-IR, homeostatic model assessment for insulin resistance.

Figure 5

Lipid profiles of each experimental group. (a) Total cholesterol (TC). (b) LDL cholesterol. (c) HDL cholesterol. (d) Phospholipid. (e) Nonesterified fatty acids (NEFA). (f) OFTT. (g) AUC of OFTT. Data are expressed as mean ± standard error of mean. # p < 0.05, ## p < 0.01, and ### p < 0.001 indicate the results of comparison with the NC group, and * p < 0.05 and ** p < 0.01 indicate the results of comparison with the HFD group. NC, normal chow; HFD, high-fat diet; MGF, HFD + MGF 150 mg/kg/day; MGF, mangiferin; TC, total cholesterol; LDL, low-density lipoprotein; HDL, high-density lipoprotein; TG, triglyceride; AUC, area under the curve; OFTT, oral fat tolerance test.

Figure 6

Analysis of ATMs and gene expression of the mRNA level in adipose tissue. (a) Flow cytometry of total ATMs. (b) Percentage of total ATMs. (c) Flow cytometry of CD11c+ and CD206 + ATMs. (d) Percentage of CD11c + ATMs. (e) Percentage of CD206+ ATMs. Expressions of (f) F4/80, (g) TNF-α, and (h) IL-6. Data are expressed as mean ± standard error of mean. # p < 0.05, ## p < 0.01, and ### p < 0.001 indicate the results of comparison with the NC group, and * p < 0.05, ** p < 0.01 indicates the results of comparison with the HFD group. NC, normal chow; HFD, high-fat diet; MGF, HFD + MGF 150 mg/kg/day; MGF, mangiferin; ATMs, adipose tissue macrophages; TNF-α, tumor necrosis factor-α; IL-6, interleukin-6.

Figure 7

Analysis of KCs and gene expression of the mRNA level in liver tissue. (a) Flow cytometry of total KCs. (b) Percentage of total KCs. Expressions of (c) NF-κB, (d) AKT, (e) ATG7, and (f) FGF21. Data are expressed as mean ± standard error of mean. # p < 0.05, ## p < 0.01, and ### p < 0.001 indicate the results of comparison with the NC group, and * p < 0.05 and ** p < 0.01, *** p < 0.001 indicate the results of comparison with the HFD group. NC, normal chow; HFD, high-fat diet; MGF, HFD + MGF 150 mg/kg/day; MGF, mangiferin; KCs, Kupffer cells; NF-κB, nuclear factor kappa B; ATG7, autophagy-related gene 7; FGF21, fibroblast growth factor 21.

Figure 8

Histological changes in liver and epididymal fat tissues. (a) Histological images of the liver. (b) Fatty area in the liver. (c) Histological images of epididymal fat. (d) Adipocyte size. Data are expressed as mean ± standard error of mean. Bar indicates 100 µm. ### p < 0.001 indicates the results of comparison with the NC group, and *** p < 0.001 indicates the results of comparison with the HFD group. NC, normal chow; HFD, high-fat diet; MGF, HFD + MGF 150 mg/kg/day; MGF, mangiferin.