A circadian rhythm in lipid mobilization which is altered in IDDM

It is not clear how circadian lipolysis and circulating concentrations of non-esterified fatty acids (NEFA) are altered in intensively treated insulin-dependent diabetic (IDDM) patients. Ten IDDM patients on an intensive insulin regimen and eight healthy control subjects were investigated under ordinary living conditions for 27 h by microdialysis of subcutaneous adipose tissue. The true tissue glycerol concentration and adipose blood flow changes were monitored as an index of lipolysis. A circadian pattern in adipose tissue lipolysis was observed in both groups, decreasing during the day and increasing during evening-night. The daytime decrease was normal, but the evening-night rise was elevated in IDDM (p = 0.03). Circulating NEFA decreased during the day and increased at night. The latter increase was enhanced threefold in IDDM (p = 0.003) and correlated with fasting glucose levels (r = 0.77). Nocturnal growth hormone (GH) was increased fivefold in IDDM and correlated to nocturnal lipolysis (r = 0.83). Adipose tissue blood flow increased during the night in a similar fashion in both groups. Near-normalization of glucose for 24 h in IDDM did not affect the nocturnal increases in NEFA, GH and lipolysis. In conclusion, a circadian rhythm in lipolysis was found. Increased lipolytic rates during evening-night may at least in part raise nocturnal circulating NEFA. Nocturnal NEFA and lipolysis are further enhanced in IDDM, maybe due to elevated GH, but not to insulinopenia or hyperglycaemia.