oa Effect of nonnutritive sweetener stevioside on regulation of adipogenesis and oxidative stress in adipocytes

Effect of non-nutritive sweetener stevioside on regulation of adipogenesis and oxidative stress in adipocytes Jayakumar Jerobin, Manjunath Ramanjaneya, Ilham Bettahi, Siveen Kodappully Sivaraman, Ramzi M Mohammad, Monica Skarulis Young, Abdul Badi Abou Samra Interim Translational Research Institute, Qatar Metabolic Research Institute & Department of Medicine, Hamad Medical Corporation, Doha, Qatar. Introduction The metabolic syndrome which includes obesity, diabetes, polycystic ovarian syndrome and non-alcoholic fatty liver disease is a major health risk in Middle Eastern countries including Qatar. The metabolic syndrome is worsened by unhealthy diet and sedentary lifestyle. Both nutritive and nonnutritive sweeteners (NNS) are consumed by people worldwide, and the consumption of sweeteners above the recommended level contributes to metabolic syndrome. In adipocytes, artificial NNS such as saccharin and acesulfame potassium promotes adipogenesis and suppresses adipose tissue lipolysis. The consumption of artificial NNS saccharin modulates the gut microbiota and promotes glucose intolerance. Currently the artificial NNS are replaced with natural NNS stevioside in foods and beverages since it has low caloric value. Studies have shown that stevioside possess glucose uptake properties which may have a potential role in type 2 diabetes mellitus treatment. This proposed study mainly focuses on the effect of NNS stevioside on regulation of adipogenesis and oxidative stress in matured adipocytes. Methods The 3T3L1 preadipocytes cells were cultured in DMEM medium, and the preadipocyte cells were differentiated in to mature adipocytes by the addition of IBMX, Insulin and Dexamethasone on 0th day. It was replaced with maintenance medium containing insulin on 2,4 and 6th days of differentiation. The stevioside at different dosage (10, 100 and 200 μM) were treated on 0, 2, 4 and 6th days of differentiation in matured adipocytes. Cell viability was analyzed using MTS solution. Oil red¬ O staining was carried out to study the accumulation of lipids in the undifferentiated and matured adipocyte cells. The different oxidative stress markers such as Reactive oxygen species (ROS) and reduced Glutathione were measured using flow cytometry. Western blot and gene expression studies were carried out to study the adipogenesis and insulin sensitivity markers. Results The stevioside was found to be non-toxic to both preadipocyte and adipocytes. On eighth day of differentiation, a significant increase in the accumulation of lipids was observed in the differentiated adipocytes compared to the undifferentiated preadipocytes as analyzed by Oil Red O. The generation of oxidative stress was higher in adipocytes compared to the undifferentiated adipocytes. This was confirmed by increase in the level of reactive oxygen species radicals and reduced glutathione in untreated adipocytes. Treatment with stevioside resulted in inhibition of oxidative stress markers in a dose dependent manner. The protein expression level of early adipogenesis marker such as PPAR-γ and C/EBP-alpha was significantly decreased in stevioside treated adipocytes. Adiponectin, an adipokine found to have association with insulin sensitivity was significantly increased in stevioside treated adipocytes. The protein and gene expression levels of GLUT4 was also found to be significantly increased in stevioside treated matured adipocytes. Conclusion Stevioside reduces oxidative stress by modulating the level of free radicals in maturing adipocytes. Adiponectin an insulin sensitizer which was found to be lower in obese individuals was significantly upregulated in stevioside treated adipocytes. Similarly, the increase in the expression of insulin regulated glucose transporter GLUT-4 in adipocytes indicates that stevioside may possess insulin sensitivity properties in matured adipocytes.