While the increased incidence of coronary atherosclerosis in diabetes has been appreciated for some time, in recent years an additional cause for serious heart dysfunction in this disease has been recognized; this disorder has been termed diabetic cardiomyopathy and is characterized by the accumulation of periodic acid-Schiff reactive material surrounding the heart fibers and the small blood vessels. Although on a histochemical basis this material appears to be glycoprotein, its molecular nature is unknown. A major difficulty in trying to understand this pathological condition is the fact that very little attention has been given to a study of the complex carbohydrates of the normal heart, including those present in the sarcolemma, the basement membrane and the interstitium. The proposed research will approach this problem from a biochemical point of view by comparing the glycoconjugates present in normal and diabetic myocardium. Components to be studied will include cell surface glycoproteins, structural glycoproteins such as laminin and fibronectin and the proteoglycans and collagens of the basement membrane and interstitium. Initial studies will be performed on hearts form normal and diabetic rats; since rats made hypertensive as well as diabetic have been reported to develop the lesions more rapidly, the effect of hypertension singly and with diabetes will also be studied. Subsequently, heart tissue obtained at autopsy from diabetic and nondiabetic individuals will be examined. The biosynthesis of selected glycoproteins will be measured in normal rat heart by perfusion or in vivo techniques and compared to that occurring in the hearts of the experimental models, since it is likely that changes in the rate of synthesis of the carbohydrate-containing molecules will be detected earlier than their accumulation. The capacity of myocardial cells in culture to synthesize extracellular and cell surface components will also be measured. Methods will include sequential extraction of membrane-bound and matrix components, including blycoproteins, proteoglycans and collagens; glycoproteins will also be prepared by detergent solubilization of sarcolemma prepared by density gradient centrifugation. Characterization of macromolecules will be performed by sodium dodecyl sulfate-gel electrophoresis combined with immunoblotting, gel filtration, ion exchange and lectin chromatography, digestion with various proteases as well as by amino acid and sugar analyses. Quantitation will be accomplished by radioimmunoassay.
