Effects of photoperiod and feeding level on adipose tissue and muscle lipoprotein lipase activity and mRNA level in dry non-pregnant sheep

The aim of the present study was to investigate the effects of photoperiod and feeding level on lipid metabolism in ovine perirenal and subcutaneous a dipose tissues (AT) and in skeletal and cardiac muscles. Twenty dry non-pre gnant ovariectomised ewes were divided into two groups and subjected to eit her 8 h or 16 h light/d, and underfed at 22 % energy requirements for 7 d. Half of the ewes in each group were slaughtered and the remaining ewes were refed at 190 % energy requirements for 14 d, until slaughtering. Refeeding increased (2.6-4.3-fold) malic enzyme (ME), fatty acid synthase (FAS), glu cose-6-phosphate dehydrogenase (G6PDH) and glycerol-3-phosphate dehydrogena se (G3PDH) activities in subcutaneous AT as well as lipoprotein lipase (LPL ) activity in perirenal (3.5-fold) and subcutaneous (10-fold) AT and to a l esser extent (1.4-fold) in the skeletal longissimus thoracis and cardiac mu scles. Moreover, variations of LPL mRNA level followed variations of LPL ac tivity: refeeding increased perirenal AT- and cardiac muscle-mRNA levels (7 .4- and 2-fold respectively). The main finding of this study is that, for a given level of food intake, long days (compared with short days) increased the LPL activity in the longissimus thoracis muscle and, in refed ewes, th e activities of LPL and ME in subcutaneous AT. Furthermore, long days incre ased LPL mRNA level in cardiac muscle and perirenal AT. Thus, our results s how that there are direct effects of photoperiod on sheep AT lipogenic pote ntial, as well as on muscle LPL activity, which are not caused by changes i n nutrient availability.