1. Characteristics of energy metabolism in catsIn feline livers, activities of glucokinase as rate limiting enzyme of glycolysis were not observed and glucose transport activities were significantly lower than those in canine livers, whereas gluconeogenetic and lipogenetic enzymes activities were higher than those in canine livers. Feline livers showed unique characteristics in metabolism of glucose and lipid differing from canine livers.2. Onset mechanism of insulin resistance in catsType 2 diabetes mellitus accompanying with obesity was frequently observed in cats compared to in dogs. The onset of diabetes mellitus was considered to be related to insulin resistance frequently observed in cats. In feline livers activity of uptake and utilization of glucose was significantly lower than in canine livers. Cats have metabolic characteristics to be easy to cause hyperglycemia and obesity. The unique glucose-lipid metabolism and insulin signal pathway observed in feline livers was considered to be one of key factors to cause insulin resistance and type 2 diabetes mellitus.3. Development of preventive veterinary medicine for treatments for obesity and diabetes in catsThe most effective treatments for multifactorial diseases like obesity and diabetes are prophylaxis based on early detection and diagnosis. The preventive veterinary medicine is also effective in treatments for obesity and diabetes mellitus in cats. Treatments of metabolic syndrome caused by visceral lipid accumulation are the most important medical problem in human. Metabolic syndrome in cats becomes big problem in veterinary medicine. It is necessary to work out the diagnostic criterion for cats as in human to develop the preventive medicine based on early diagnosis.