Plasma met-enkephalin in type I diabetes.

Physiological and pathological evidence suggests that opioid peptides may play a role in glucose homeostasis. We measured plasma levels of beta-endorphin (beta-END) and met-enkephalin (met-ENK) in 22 type I diabetic patients and 15 healthy women (control group). No differences were observed in plasma beta-END levels, whereas plasma met-ENK levels were significantly higher (Student's t test, P less than .005) in diabetics than in controls before (68 +/- 3 pg/mL v 32 +/- 7 pg/mL) and 1 hour after, a standard meal and administration of insulin therapy (81 +/- 9 pg/mL v 32 +/- 7 pg/mL). This is the first report of met-ENK levels in insulin-dependent diabetes mellitus (IDDM), and an impaired feedback of insulin/met-ENK is suggested.