Allyl-containing sulfides in garlic increase uncoupling protein content inbrown adipose tissue, and noradrenaline and adrenaline secretion in rats

The effects of garlic supplementation on triglyceride metabolism were inves tigated by measurements of the degree of thermogenesis in interscapular bro wn adipose tissue (IBAT), and noradrenaline and adrenaline secretion in rat s fed two types of dietary fat. In Experiment 1, rats were given isoenerget ic high-fat diets containing either shortening or lard with or without garl ic powder supplementation (8 g/kg of diet). After 28 d feeding, body weight , plasma triglyceride levels and the weights of perirenal adipose tissue an d epididymal fat pad were significantly lower in rats fed diets supplemente d with garlic powder than in those fed diets without garlic powder. The con tent of mitochondrial protein and uncoupling protein (UCP) in IBAT, and uri nary noradrenaline and adrenaline excretion were significantly greater in r ats fed a lard diet with garlic powder than in those fed the same diet with out garlic. Other than adrenaline secretion, differences due to garlic were significant in rats fed shortening, also. In Experiment 2, the effects of various allyl-containing sulfides present in garlic on noradrenaline and ad renaline secretion were evaluated. Administration of diallyldisulfide, dial lyltrisulfide and alliin, organosulfur compounds present in garlic, signifi cantly increased plasma noradrenaline and adrenaline concentrations, wherea s the administration of disulfides without allyl residues, diallylmonosulfi de and S-allyl-L-cysteine did not increase adrenaline secretion. These resu lts suggest that in rats, allyl-containing sulfides in garlic enhance therm ogenesis by increasing UCP content in IBAT, and noradrenaline and adrenalin e secretion.