Mohamed Mohamed Soliman
Biochemistry Department, Faculty of Veterinary Medicine, Benha University, Egypt
Currently: College of Applied Medical Sciences. Medical Laboratory Department, Taif University, Saudi Arabia
Obesity is a worldwide disease, associated with oxidative stress, metabolic disorders in heart and vessels as well as diabetes in humans. Oxidative stress is an important pathogenic mechanism of obesity-associated metabolic syndrome. Adipose tissue is known to secret variable bioactive substances known as adipocytokines, as adiponectin and leptin that regulate peripheral glucose and energy expenditure. Leptin levels correlate with adiposity, while adiponectin decreases in obese subjects and is associated with improving insulin sensitivity. Moreover adipose tissue can acts as asource for fat soluble vitamins as vitamin A and E. The active form of vitamin A is Retinoic Acid (RA), the carboxylic acid form of vitamin A, is a nutrient derivative with many remarkable effects on adipocytes biology and whole body adiposity. Vitamin A can improve glucose tolerance and insulin sensitivity probably through adipokines expression. Vitamin A supplementation increases thermogenic potential in brown adipose tissue and muscle. On the same line Vitamin E is the major fat-soluble dietary antioxidant. Vitamin E has eight isoforms and a-tocopherol is the most common isoform. It has a beneficial effect on insulin sensitivity and there is an inverse relationship between plasma alpha-tocopherol concentration and the incidence of type 2 diabetes. We studied the gene expression of carbohydrate and lipid metabolism in obese rats after oral administration for 2 months. The interesting point in vitamin A and E action is that occur without modulation of insulin secretion in insulin resistance. Vitamin A and E administration reduced significantly the increase in body weight and food intake and normalized the alterations in lipid profiles in obese rats compared to normal rats. Moreover, both vitamins decreased the fat accumulation in liver tissues of obese rats. They up-regulated mRNA expression of Pyruvate Kinase (PK) and Glucose Transporter-2 (GLUT-2), and increased lipolysis and cholesterol metabolism through up-regulation of lipoprotein lipase (LPL), Sterol Responsible Element Binding Protein-1a (STREBP-1a) and STREBP-1c mRNA expression. We concluded that vitamin A and E regulate gene expression of carbohydrate and lipid metabolism, and ameliorated changes associated with obesity induced by high fat diet.