Peanut skin phenolic extract attenuates hyperglycemic responses in vivo and in vitro

Diabetes affects at least 285 million people globally, and this number continues to increase. Clinical complications include impaired glucose metabolism, hyperglycemia, dyslipidemia, atherosclerosis and non-alcoholic fatty liver disease. Evidence has shown that natural phenolics play a protective effect on both the development and management of type 2 diabetes. This study evaluated effects of the extract from peanut skins containing polyphenols on induced-hyperglycemia using in vivo and in vitro methods. A human hepatocellular liver carcinoma cell line (HepG2) was used to investigate the effect of the peanut skin extract on cell viability after exposure to high glucose concentrations. In vivo, the effect of peanut skin extract on an oral glucose tolerance was investigated in human subjects. Fifteen participants aged 21-32 underwent an oral glucose tolerance test with five treatments: 1) 50-gram glucose solution (reference); 2). 50-gram glucose solution, followed by 12 mg of vegi-capsulated maltodextrin; 3) 50-gram glucose solution, followed by 120 mg of vegi-capsulated maltodextrin-encapsulated peanut skin extract; 4). 50-gram glucose solution, followed by 28 grams of unfortified coated peanuts; 5) 50-gram glucose solution, followed by 28 grams of chili lime coated peanuts fortified with encapsulated peanut skin extract. Glucose levels were measured using a continuous monitor. Peanut skin extract was found to attenuate the decrease in cell viability in high glucose treated HepG2 cells, showing a protective effect against hyperglycemia induced cell death. No difference in the glycemic response area under the curve between any treatments using the tolerance test, but the treatment of the peanut skin extract with the glucose reference resulted in a significantly lower peak blood glucose response at 45 minutes, indicating that it was effective at reducing the glycemic response. The present study shows that the phenolic extract of peanut skins has an antidiabetic effect, further confirming their value as a functional food ingredient.