A downregulation of SIRT3 was also observed in hearts of mice fed a high-fat diet, in obese, and type 2 diabetic db/db mice, and in rodents with streptozotocin-induced type 1 diabetes, suggesting that downregulation of SIRT3 in the heart may also be a hallmark of the metabolic syndrome and diabetes mellitus, although a downregulation of SIRT3 was not observed in every single study (24, 28, 50–52). Here, SIRT3 is linked to type 1 diabetes mellitus.