Caffeine attenuates metabolic syndrome in diet-induced obese rats

Objective: Caffeine is a constituent of many non-alcoholic beverages. Pharmacological actions of caffeine include the antagonism of adenosine receptors and the inhibition of phosphodiesterase activity. The A1 adenosine receptors present on adipocytes are involved in the control of fatty acid uptake and lipolysis. In this study, the effects of caffeine were characterized in a diet-induced metabolic syndrome in rats. Methods: Rats were given a high-carbohydrate, high-fat diet (mainly containing fructose and beef tallow) for 16 wk. The control rats were given a corn starch diet. Treatment groups were given caffeine 0.5 g/kg of food for the last 8 wk of the 16-wk protocol. The structure and function of the heart and the liver were investigated in addition to the metabolic parameters including the plasma lipid components. Results: The high-carbohydrate, high-fat diet induced symptoms of metabolic syndrome, including obesity, dyslipidemia, impaired glucose tolerance, decreased insulin sensitivity, and increased systolic blood pressure, associated with the development of cardiovascular remodeling and nonalcoholic steatohepatitis. The treatment with caffeine in the rats fed the high-carbohydrate, high-fat diet decreased body fat and systolic blood pressure, improved glucose tolerance and insulin sensitivity, and attenuated cardiovascular and hepatic abnormalities, although the plasma lipid concentrations were further increased. Conclusion: Decreased total body fat, concurrent with increased plasma lipid concentrations, reflects the lipolytic effects of caffeine in adipocytes, likely owing to the caffeine antagonism of A1 adenosine receptors on adipocytes.