Lipoprotein lipase activity and mRNA are up-regulated by refeeding in adipose tissue and cardiac muscle of sheep

Previous studies in rodents have shown that the lipoprotein lipase (LPL) re gulation is complex and often opposite in adipose tissue (AT) and muscle in response to the same nutritional treatment. However, neither LPL responses nor the molecular mechanisms involved in the nutritional regulation have b een studied in both AT and muscle of ruminant species. To explore this, we measured the LPL activity and mRNA levels in perirenal AT and cardiac muscl e (CM) of control, 7-d-underfed or 14-d-refed ewes. Underfeeding decreased (P < 0.01) LPL activity both in AT (-59%) and CM (-31%), and these activiti es were restored (P ( 0.01) by refeeding (AT, +248%; CM, +34%). Variations of LPL mRNA level measured by real-time reverse transcription-polymerase ch ain reaction or by Northern blot followed variations of LPL activity: under feeding decreased AT- and CM-LPL mRNA levels (-58 and -53%, respectively), and refeeding restored (P ( 0.01) them in CM (+117%) and increased them ove r the baseline in AT (+640%). Quantification of either 3.4- or 3.8-kb LPL m RNA levels revealed a predominant (P ( 0.001) expression of the 3.4-kb mRNA in AT (60%) and of the 3.8-kb mRNA in CM (56%), without any preferential r egulation of one of these mRNA species by the nutritional status. This work reveals a tissue-specific expression pattern of the ovine LPL gene and a p retranslational nutritional regulation of its expression, which is achieved in the same direction in perirenal AT and CM. The different regulation of CM-LPL between ewes and rats probably arises from peculiarities of ruminant species for nutrient digestion and absorption and liver lipogenesis.