Lipolytic Response During Spontaneous Hypoglycaemia in Insulin-Dependent Diabetic Subjects

The adipose tissue lipolytic response to spontaneous, non-experimental hypoglycaemic episodes was investigated in patients with IDDM during ordinary life conditions. The absolute concentration of glucose and glycerol in subcutaneous adipose tissue was monitored in mobile patients with microdialysis in 16 IDDM subjects. The absolute glycerol level in adipose tissue was about five times as high as in venous plasma, whereas the glucose concentration was almost the same in the two compartments. Fourteen hypoglycaemic episodes (glucose < 3.5 mmol/l) were recorded. Adipose tissue glycerol increased markedly by 75% in response to hypoglycaemia and remained increased during at least 4 hours following glucose nadir (F = 3.70, p = 0.003). The circulating levels of free fatty acids increased about three-fold in parallel to the in situ lipolytic response (F = 2.98, p = 0.025). The same lipolytic response was observed whether or not the hypoglycaemic event was perceived by the patient. A rapid decrease in glucose concentration above hypoglycaemic levels did not affect the adipose tissue dialysate glycerol. It is concluded that spontaneous hypoglycaemia elicits a long-term lipolytic response in adipose tissue as evidenced by increased levels of glycerol in adipose tissue with a parallel increase in serum free fatty acids. However, lipolysis is not activated by a rapid glucose decrease per se. The microdialysis method can be used to characterise the lipolytic response to hypoglycaemic episodes in every day life of IDDM patients.

Key words

Lipolysis - Free fatty acids - Glycerol - Insulin - Microdialysis