Abstract
Purpose: Mitochondrial dysfunction in adipose tissue has emerged as key to the development of obesity and diabetes. Salvianolic acid B (SalB) is a water-soluble ingredient derived from Salvia miltiorrhiza that has been shown to possess potential anti-obese and anti-diabetic activities. However, the cellular mechanism of SalB on mitochondrial function with respect to these metabolic disorders has not been elucidated. Therefore, we aim to investigate the effects of SalB on mitochondrial function in 3T3-L1 adipocytes and analyze the underlying molecular mechanism.Methods: The effects of SalB on adipocyte differentiation, glucose uptake, and glycerol release were evaluated in 3T3-L1 adipocytes. Differentiated adipocytes were treated with SalB (50 μM) with or without PPARγ antagonist (GW9662, 20 μM) for 48 h, and mitochondrial oxygen consumption rate (OCR) as well as extracellular acidification rate (ECAR) were assessed using an XF Extracellular Flux Analyzer. The mitochondrial distribution of adipocytes was assessed using Mito Tracker Green (MTG) and observed under a fluorescent microscope. In addition, the mRNA expression levels of peroxisome proliferators-activated receptor γ/α (PPARγ/α), CCAAT/enhancer binding proteinα (C/EBPα), Nuclear respiratory factor 1/2 (NRF1/2), Uncoupling protein 2 (UCP2), and phosphofructokinase 2/fructose-2, 6-bisphosphatase 2 (PFKFB2) were detected by RT-PCR. Finally, changes in the protein levels of peroxisome proliferators-activated receptor γ coactivator-1α (PGC-1α) were determined by western blotting and immunofluorescence analysis.Results: Treatment with SalB increased glucose uptake and mitochondrial respiration, reduced glycerol release and promoted adipocyte differentiation by increasing mRNA expression of adipogenic transcription factors including PPARγ, C/EBPα, and PPARα. Furthermore, SalB enhanced adipocytes mitochondrial content, mitochondrial respiration and glycolysis capacity, which had been attenuated by GW9662 treatment through the increased expression of PGC-1α.Conclusion: Our results provide novel insights into the role of PGC-1α and mitochondria as probable mediators of SalB activity in the regulation of adipocyte differentiation in 3T3-L1 adipocytes.
Highlights
Obesity is becoming a global public health problem due to the current lifestyle of energy-rich food consumption and physical inactivity, it is predicted that up to 58% of the world’s adult population will be overweight or obese by 2030 (Kelly et al, 2008; Tremmel et al, 2017)
Cell viability decreased by 17.8% when the cells were incubated in medium with 125 μM SalB (P < 0.01). 3T3-L1 preadipocytes were incubated with the cocktail method without or with SalB (0, 25, 50 and 100 μM) for 8 days, and the accumulated oil droplets were visualized by staining with Oil Red O to identify differentiated cells
GW9662 combined with SalB increased the expression of these genes by 122.7, 45.7, 75.1, and 32.5%, respectively, compared with the GW9662 group. These results suggest that SalB can improve mitochondrial glycolytic function through upregulating the related genes expression after inhibiting the PPARγ activation
Summary
Obesity is becoming a global public health problem due to the current lifestyle of energy-rich food consumption and physical inactivity, it is predicted that up to 58% of the world’s adult population will be overweight or obese by 2030 (Kelly et al, 2008; Tremmel et al, 2017). Mitochondria are essential organelles that provide energy for cellular metabolic activity in form of adenosine triphosphate (ATP) and are considered the “power house” of the cell (Zhang et al, 2007). Multiple studies found that marked changes in mitochondrial mass, oxygen consumption, glycolysis capacity take place during adipogenesis programming and throughout the progression of metabolic disease (Zhang et al, 2013; Miller et al, 2015; Basse et al, 2017; Shiau et al, 2017). Since the adipocyte differentiation program requires large amount of ATP when cells become fully metabolically active, mitochondria are thought to be necessary regulators of this process (Heidari et al, 2018). The modulation of mitochondrial oxygen consumption and glycolytic capacity may have therapeutic potential for the treatment of important pathophysiological conditions related to energy metabolism
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