Abstract
Chronic over-nutrition is a major contributor to the spread of obesity and its related metabolic disorders. Development of therapeutics has been slow compared to the speedy increase in occurrence of these metabolic disorders. We have identified a natural compound, mangiferin (MGF) (a predominant component of the plants of Anemarrhena asphodeloides and Mangifera indica), that can protect against high fat diet (HFD) induced obesity, hyperglycemia, insulin resistance and hyperlipidemia in mice. However, the molecular mechanisms whereby MGF exerts these beneficial effects are unknown. To understand MGF mechanisms of action, we performed unbiased quantitative proteomic analysis of protein profiles in liver of mice fed with HFD utilizing 15N metabolically labeled liver proteins as internal standards. We found that out of 865 quantified proteins 87 of them were significantly differentially regulated by MGF. Among those 87 proteins, 50% of them are involved in two major processes, energy metabolism and biosynthesis of metabolites. Further classification indicated that MGF increased proteins important for mitochondrial biogenesis and oxidative activity including oxoglutarate dehydrogenase E1 (Dhtkd1) and cytochrome c oxidase subunit 6B1 (Cox6b1). Conversely, MGF reduced proteins critical for lipogenesis such as fatty acid stearoyl-CoA desaturase 1 (Scd1) and acetyl-CoA carboxylase 1 (Acac1). These mass spectrometry data were confirmed and validated by western blot assays. Together, data indicate that MGF upregulates proteins pivotal for mitochondrial bioenergetics and downregulates proteins controlling de novo lipogenesis. This novel mode of dual pharmacodynamic actions enables MGF to enhance energy expenditure and inhibit lipogenesis, and thereby correct HFD induced liver steatosis and prevent adiposity. This provides a molecular basis supporting development of MGF or its metabolites into therapeutics to treat metabolic disorders.
Highlights
Metabolic disorders, including diabetes and liver steatosis, are currently epidemic, driven by increased prevalence of obesity as a result of sedentary lifestyles and high-calorie diets [1,2]
Along with other phenotypic effects such as adiposity and insulin resistance, we observed that high fat diet (HFD) feeding caused a 2–6 fold increase in TG, cholesterol and low density lipoprotein (LDL) in blood of mice, as compared to chow feeding (Figure 2)
Treatment with 0.5% MGF resulted in 50% reduction in cholesterol and LDL in HFD-fed groups
Summary
Metabolic disorders, including diabetes and liver steatosis, are currently epidemic, driven by increased prevalence of obesity as a result of sedentary lifestyles and high-calorie diets [1,2]. The molecular mechanisms of metabolic dysregulation leading to obesity and its related pathological conditions remain poorly understood, no effective therapy is currently available. We and others have identified a natural compound, mangiferin (MGF), that could increase insulin sensitivity and mitigate hyperglycemia in diabetic animal models [3,4,5]. Treatment with extract from African mango for over a period of 10 weeks resulted in significant weight loss of up to 12 kilograms in overweight and obese subjects, accompanied with improvements in total cholesterol, LDL and fasting blood glucose [59]. The molecular mechanisms of MGF actions are poorly understood
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