Effect of Glucose and Insulin on Lipoprotein Lipase Activity in Adipose Tissue and Milk

Twelve pairs of Holstein cows were infused intravenously every 7th day with 3 liters of .9% saline or 25% glucosesaline for 24-h periods in a double reversal experiment to study the effect of glucose on lipoprotein lipase activity in adipose tissue and milk. The mean enzyme activities ( μ eq of fatty acids released per h per g of tissue or per ml of milk) for cows during saline and glucose treatments were: 22.2 and 26.8 in the adipose tissue and 332 and 342 in milk. Blood glucose of saline and glucose-infused cows was 54.6 and 96.9 mg/100ml. Both blood glucose and lipoprotein lipase activity in adipose tissue were higher during glucose treatment than during saline treatment and were correlated .31. After the adipose tissue biopsy at the end of the infusion, six cows received 40 to 80 IU of insulin intravenously. Lipoprotein lipase activity in adipose tissue taken 15min after insulin injection was 31 compared to 23 in the pre-insulin samples. Adipose tissue samples from two nonlactating Holstein cows were incubated for 2.5h at 38C in: (a) 5ml buffer, (b) buffer + 10mg glucose, (c) buffer + 50 mU insulin, and (d) buffer + 10mg glucose + 50 mU insulin. At the end of die incubation the mean lipoprotein lipase activities for treatments a, b, c, and d were 4.6, 7.7, 9.3, and 10.3.