The first diagnosis of diabetes dates back to Greece, 2,000 years ago. Blood sugar balance, in general, diabetes, in particular, ever since has been the subject of an increasing scientific study. Diabetes affects 16 million people in the United States alone and it is the fourth leading cause of death. Insulin, the hormone produced by pancreas, regulates the uptake and conversion of sugar into heat energy and muscle power. Diabetes is a metabolic disorder and insufficient insulin production leads to Type 1 diabetes or insulin-dependent diabetes mellitus (IDDM). Lipid metabolism is often deranged in diabetics resulting in weight gain and other complications.
More than half of U.S. adults are overweight (body mass index, BMI<25), one-quarter is obese (BMI<30), and 11% of children and adolescents are overweight. Approximately 280,000 deaths are attributable to obesity annually. Sedentary life style is prevalent and only 22% of U.S. adults exercise the recommended five times per week for at least 30 minutes. Healthy weight maintenance involves a delicate balance between energy intake and energy expenditure.
Glucose is the principal nutrient for energy and daily energy balance between intake and expenditure is a determining factor in body weight stability. A long-term positive energy balance leads to weight gain, while a negative balance accounts for weight loss. Obesity is an alarming trend globally and more acute in developed countries due to sedentary life style and rich diets among both adults and children and leads to deleterious consequences such as obesity, syndrome X, insulin resistance, diabetes and other health risks (York D, Bouchard C. How obesity develops, Endocrine, 13 (2), 143-154, 2000). Syndrome X is a metabolic disorder characterized by insulin resistance and central obesity, high cholesterol, high blood pressure and high blood sugar levels. An estimated 20 to 30% of middle-aged Americans suffer from Syndrome X, which is believed to increase risk for diabetes and heart disease. The spread of obesity is considered to be an epidemic in the U.S. and a sensible, sustained weight management is a critical step in this environment (Mokdad A H, Serdula M K, Dietz W H, Bowman B A, Marks J S, Koplan J P. The spread of the obesity epidemic in the United States, 1991-1998, JAMA, 282 (16), 1519-1522, 1999).
Glucose is the most important nutrient for many cells of the body. Glucose transport from the blood into cells, therefore, is one of the most important functions of all cells and some tissues, such as brain, are solely dependent on glucose as an energy source. Insulin regulates glucose uptake into fat and muscle cells through the recruitment of glucose transporter (GLUT)4 from an intracellular membrane storage pool to the plasma membrane. A complex homeostatic mechanism keeps the blood glucose level constant in mammals and most cells contain several types of sodium linked glucose transporters known as GLUT family. Glucose transporters, such as GLUT4, are especially important for regulating intracellular glucose in heart and skeletal muscle cells and in fat cells (brown and white adipocytes). The pancreatic hormone insulin regulates blood sugar levels by a cascade of biochemical steps, including activation and translocation of GLUT4 to cell surface, for glucose transport from blood to cells (Yamasaki K, Effects of some saponins on glucose transport system, Eds. Waller and Yamasaki, 1996. Plenum Press, New York; Maier V H and Gould G W. Long-term insulin treatment of 3T3-L1 adipocytes results in mistargeting of GLUT4: implications for insulin-stimulated glucose transport, Diabetologia, 43, 1273-1281, 2000; Yaworsky K, Somwar R, Ramlal T, Tritschler H J, Klip A. Engagement of insulin-sensitive pathway in the stimulation of glucose transport by a-lipoic acid in 3T3-L1 adipocytes, Diabetologia, 43, 294-303, 2000).
Numerous groups have been systematically searching for an agent to modify glucose transport activity and to find a natural product useful as an anti-diabetic agent. Various medicinal plants from Asia have been used to treat diabetes and the plants exhibiting hypoglycemic effect include Momordica Charantia, Tinospora Cordifolia, Ginseng, etc. (Yamasaki K 1996). Tea preparations from the leaves of Lagerstroemia Speciosa L., traditionally have been used for weight-loss and by diabetics to balance blood sugar levels (Murakami C, Myoga K, Ryoji K, Ohtani K, Kurokawa T, Ishibashi S, Dayrit F, Padolina W G and Yamasaki, K. Screening of plant constituents for effect on glucose transport activity in Ehrlich Ascites tumor cells, Chemical and Pharmaceutical Bulletin, 41 (12), 2129-2131, 1993) and in-vitro studies indicate that Corosolic acid extracted from the leaves of Lagerstroemia Speciosa L, improves the cellular uptake of glucose (Murakami C. et al. 1993). Further studies in diabetic mice indicate the hypoglycemic effects of leaf-extracts from Lagerstroemia Speciosa L. (Kakuda T, Sakane I, Takihara T, Ozaki Y, Takeuchi H and Kuroyanagi M. Hypoglycemic effect of extracts from Lagerstroemia speciosa L. leaves in genetically diabetic KK-AY mice, Biosci. Biotech. Biochem., 60 (2), 204-208, 1996).