The effect of exercise training on hormone-sensitive lipase in rat intra-abdominal adipose tissue and muscle

1. Adrenaline-stimulated lipolysis in adipose tissue may increase with trai ning. The rate-limiting step in adipose tissue lipolysis is catalysed by th e enzyme hormone-sensitive lipase (HSL). We studied the effect of exercise training on the activity of the total and the activated form of HSL, referr ed to as HSL (DG) and HSL (TG), respectively, and on the concentration of H SL protein in retroperitoneal (RE) and mesenteric (ME) adipose tissue, and in the extensor digitorum. longus (EDL) and soleus muscles in rats. 2. Rats (weighing 96 + 1 g, mean +/- S.E.M.) were either swim trained (T, 1 8 weeks, n = 12) or sedentary (S, n = 12). Then RE and ME adipose tissue an d the EDL and soleus muscles were incubated for 20 min with 4.4 muM adrenal ine. 3. HSL enzyme activities in adipose tissue were higher in T compared with S rats. Furthermore, in RE adipose tissue, training also doubled HSL protein concentration (P < 0.05). In ME adipose tissue, the HSL protein levels did not differ significantly between T and S rats. In muscle, HSL (TG) activit y as well as HSL (TG)/HSL (DG) were. lower in T rats, whereas HSL (DG) acti vity did not differ between groups. Furthermore, HSL protein concentration in muscle did not differ between T and S rats (P > 0.05). 4. In conclusion, training increased the amount of HSL and the sensitivity of HSL to stimulation by adrenaline in intra-abdominal adipose tissue, the extent of the change differing between anatomical locations. In contrast, i n skeletal muscle the amount of HSL was unchanged and its sensitivity to st imulation by adrenaline reduced after training.