Chronic triiodothyronine supplementation does not improve the lipoprotein disorders of mildly uremic rats

The present study was performed to appreciate the potential role that thyroid deficiency could play in the energy homeostasis and lipid metabolism of experimental chronic renal failure. For this purpose, 12 uremic rats that were supplemented with T₃ (0.4 μg/100 g body weight/day) during 5 weeks by means of osmotically driven minipumps were compared to 12 unsupplemented uremic rats and 12 control rats. The chronic supplementation of uremic rats with T₃ induced no significant change in body weight gain or in the serum concentration of insulin, glucose, glycerol, nonesterified fatty acids, total triglycerides (TG), total cholesterol, and total choline phospholipids. Similarly, the metabolism of TG-rich lipoproteins was not affected by the supplementation with T₃ in these uremic rats as appreciated by TG production or TG degradation (adipose tissue lipoprotein lipase activity). T₃ administration induced a significant decrease in serum β-hydroxybutyrate concentration and an increase in serum lactate concentration. Furthermore, heparin-releasable hepatic TG lipase activity as expressed per total liver mass was decreased in uremic rats treated with T₃. The latter changes were observed in the absence of modifications of serum glucose or TG concentration. We conclude from these observations that rats with a moderate degree of chronic uremic do not seem to have a cellular thyroid deficiency sufficient to disturb their energy or lipid metabolism.