Insulin deficiency and reduced expression of lipogenic enzymes in cardiomyopathic hamster

Evidence is given that the heart of the cardiomyopathic UM-X7.1 hamster has a lipid composition different from that of the same tissue isolated from a nimals of the Syrian hamster parent strain. Also, noncardiac tissues from c ardiomyopathic and healthy hamsters exhibit significant compositional diffe rences. On the basis of these preliminary observations, a comparative study of the hepatic biosynthesis of lipids in cardiomyopathic and healthy Syria n hamsters was undertaken. The results obtained indicate that the cardiomyo pathic hamster is characterized by a generalized disturbance of lipid metab olism, In particular, the fatty acid synthase and stearoyl-CoA desaturase a ctivities were significantly lower in the liver of UM-X7.1 hamsters than. i n age-matched healthy controls fed the same diet. Northern blot analysis of the mRNAs encoding the two enzymatic proteins and the "lipogenic" S14 nucl ear protein indicated that the transcription of the respective genes was im paired in UM-X7.1. Short-term dietary manipulations modulated the expressio n of the above-mentioned genes both in cardiomyopathic and healthy animals. However, dietary carbohydrates were less effective in inducing the express ion of lipogenic enzymes in UM-X7.1 Liver than healthy controls, The main d eterminant of the metabolic defect pointed out in the present work appears to be represented by the low insulin level detectable in the plasma of the cardiomyopathic hamster.