Diabetic Cardiovascular Risk and Carnitine Deficiency —Carnitine Deficiency in Clinical Diabetes Mellitus

Background: Type 1 diabetes mellitus increases the risk of coronary heart disease. The Pittsburgh IDDM morbidity and mortality study reported greater than 10 fold coronary heart disease mortality compared with US national data [1]. Adults with diabetes have heart disease death rates 2 to 4 times higher than adults without diabetes [2]. Diabetic cardiomyopathy explains much of this survival difference and carnitine deficiency is a cause of cardiomyopathy. Research Design and Methods: Adult subjects (40) with type 1 diabetes mellitus were seen for a routine annual visit having no clinical complaints. Fasting serum samples were collected for annual chemistries and the measurement of carnitine. Results: The mean total (40.8 ± 8.8) [40 - 80 nmol/ml] and free (32.9 ± 7.9) [30 - 60 nmol/ml] carnitine levels for this group included 43% low total and 28% low free carnitine. The mean esterified/free (E/F) carnitine ratio (0.25 ± 0.09) for this group was elevated indicating carnitine insufficiency. Conclusions: Fatty acids are the primary energy source for diabetic heart muscle, and carnitine is essential for intracellular fatty acid transport and ATP production. Therefore, mild carnitine deficiency can compromise fatty acid energy production in a failing heart. Carnitine deficiency in subjects at high risk for cardiovascular failure is a possible unrecognized reason for the 4 fold increased death rate in patients with type 1 diabetes. Supplementation with oral carnitine could reduce that increased risk of heart failure, in patients with type 1 diabetes. Intravenous carnitine may be life saving when managing acute cardiac failure in patients with diabetes mellitus. Normal carnitine levels in patients with type 1 diabetes may provide a biochemical environment that prevents the long recognized idiopathic heart failure that occurs in insulin requiring diabetics as first reported in the 1974 Framingham Study.