Effects of oxytocin upon the endocrine pancreas secretion and glucose turnover in normal man

Abstract

Abstract. In normal man oxytocin infusion under basal conditions and at pharmacological doses evoked a rapid surge in plasma glucose and glucagon levels followed by a later increase in plasma insulin levels. Simultaneous [D-3H]glucose infusion indicated that oxytocin also produced a prompt and significant increase in hepatic glucose output with a secondary increase in glucose disappearance rate. Eight healthy volunteers were studied during euglycemic glucose clamp and simultaneous [D-3H]glucose infusion, during suppression of endogenous pancreatic secretion by cyclic somatostatin (250 μg/h) and during exogenous glucagon (67 ng/min) and insulin (0.15 mU · kg−1 · min−1 from 0 to 120 min and 0.40 mU · kg−1 · min−1 from 121 to 240 min) replacement. During the first 60 min oxytocin (0.2 U/min) evoked a transient but significant increase in plasma glucose levels and hepatic glucose output with a simultaneous suppression of the glucose infusion rate. No difference in glucose disappearance and metabolic clearance rates were recorded throughout the clamp irrespective of whether oxytocin was infused or not. So we conclude that oxytocin exerts a hyperglycemic effect through an A-cell stimulation and a glycogenolytic action.

Hypoglycemia-Induced Arginine Vasopressin and Oxytocin Release Is Mediated by Glucoreceptors Located Inside the Blood-Brain Barrier

“…The role of AVP and OT during hypoglycemia is still unclear. Both hormones are presumed to contribute to glucose homeo stasis because of their hyperglycemic effects [18][19][20][21][22][23][24], However, these actions have been described at concentra tions higher than those reported during ITT in normal human subjects. On the other hand, elevated AVP and OT responses to hypoglycemia have been found in diabetics [25][26][27], Furthermore, posterior pituitary hormones are known to act as neuromodulators of other hormonal se cretions.…”

The effects of oxytocin on eating behaviour and metabolism in humans

“…Furthermore, in response to insulin-induced hypoglycaemia, oxytocin infused intravenously at this dose attenuated the drop in levels of glucose, increased levels of glucagon and adrenaline and reduced cortisol levels 111,112 . Using a euglyceamic euinsulinaemic clamp, it was also shown that the same dose of intravenous oxytocin increased hepatic glucose output in healthy young men aged 22-28 yrs 113 .…”

Alpha cell function in health and disease: influence of glucagon-like peptide-1

“…Although other non-glucose secretagogues, such as isoproterenol, are also used in provocative tests of beta cell function [26], bolus administration of isoproterenol is less effective than arginine in stimulation of acute glucagon release in humans [27]. Acute insulin-induced hypoglycaemia has also been used to assess alpha cell [9] NEFA [8] Parasympathetic nerves [10] Ketones [7] Adrenaline (epinephrine) [112] Insulin [113] Oxytocin [114] Somatostatin [115] Vasopressin [116] Secretin [117] GIP [118] GLP-1 [54] PACAP [119] Carbohydrate meal [18] GRP [120] CCK [121] VIP [122] Protein meal [18] Stress [20] Hypoglycaemia [3] GRP gastrin-releasing peptide; PACAP pituitary adenylate cyclaseactivating polypeptide; VIP vasoactive intestinal polypeptide function in humans [28], although arginine stimulation tests clearly pose less risk and are more routinely employed.…”