Normal fuel metabolism and alterations in diabetes mellitus

Effective fuel metabolism is dependent on balances among exogenous and endogenous fuel availability, the glucagon/insulin ratio, and tissue insulin sensitivity. Diabetes mellitus results when imbalances occur. The resultant metabolic derangement is accompanied by abnormalities in carbohydrate, protein, and fat metabolism. The two most common forms of diabetes are insulin dependent (IDDM) and noninsulin dependent (NIDDM). IDDM is an autoimmune disease, characterized by insulinopenia and ketosis. NIDDM is related to impaired insulin secretion, defective tissue sensitivity, and abnormalities in glucose transporter proteins. This article describes normal fuel metabolism and traces the abnormal metabolic processes that lead to both IDDM and NIDDM.