naloxone and Hyperinsulinism

Beta-endorphin were detected in the endocrine pancreas and seem able to influence insulin and glucagon release. Hence, endogenous opioids could have a role in glucoregulation and in the pathogenesis of obesity beyond the previously detected effects on appetite. Metabolic abnormalities, such as hyperinsulinemia, insulin-resistance and obesity, are common features of polycystic ovary syndrome (PCOS), and seem to have a pathogenetic role in this disorder. A link between opioids and PCOS-related hyperinsulinism is suggested by the finding of altered central opioid tone and elevated beta-endorphins levels, directly correlated with body weight, in these patients. Furthermore, naloxone and naltrexone significantly reduce the insulin response to glucose load only in hyperinsulinemic PCOS patients. This effect is obtained chiefly through an improvement of insulin clearance. Naltrexone is also able to ameliorate the abnormal gonadotrophins secretion and to improve the ovarian responsiveness in obese PCOS women undergoing ovulation induction with exogenous GnRH. Such effects are believed to be obtained through an amelioration of hyperinsulinemia. Gonadal steroids modulate the opioid system both centrally and in peripheral districts. Nevertheless, the decline of ovarian function does not abolish the opioidergic control of glucoregulation. Post-menopausal period is characterised by a high prevalence of hyperinsulinemia and insulin-resistance. In particular, an association between hyperinsulinemia and increased opioid activity was found in postmenopausal women showing a central body fat distribution. Both naloxone and naltrexone ameliorate the metabolic imbalance also when it appears in the climacteric period, and mainly by increasing insulin clearance. The benefits of naltrexone may represent in the future a useful tool for the treatment of women with hyperinsulinism in the clinical practice.

Topics: Clinical Trials as Topic; Endorphins; Female; Humans; Hyperinsulinism; Insulin Resistance; Menopause; Naloxone; Naltrexone; Narcotic Antagonists; Obesity; Polycystic Ovary Syndrome

To evaluate the influence of the opioid system on glyco-regulation in postmenopausal women before and after hormone replacement therapy (HRT).. Prospective nonrandomized clinical study.. Academic research environment.. Twenty-one healthy normo- or hyperinsulinemic postmenopausal women.. Oral glucose tolerance test (OGTT) (saline study), OGTT with IV injection of naloxone (naloxone study), and hyperinsulinemic euglycemic clamp performed before treatment, after 12 weeks of estrogen replacement therapy (ERT), and after 12 additional weeks of estro-progestin combined therapy (i.e., HRT).. Glucose, insulin, and c-peptide plasma levels assessed in fasting condition and during the two OGTTs (area under the curve [AUC]). Evaluation of fractional hepatic insulin extraction (FHIE) and peripheral sensitivity to insulin.. At baseline, there is a greater increase of the FHIE and a more significant reduction of the insulin AUC in the hyperinsulinemic patients during the naloxone study compared with the saline study. In these women, ERT enhanced the c-peptide AUC and improved the FHIE; naloxone infusion mainly increased these two parameters. HRT did not induce any further change.. Endogenous opioid peptides are involved in the modulation of carbohydrate metabolism in menopause in hyperinsulinemic patients more than in other patients. The favorable changes of the glyco-insulinemic metabolism induced by HRT may be partially due to the induction of the opioidergic activity.

Topics: Area Under Curve; C-Peptide; Drug Synergism; Estrogen Replacement Therapy; Female; Glucose Tolerance Test; Humans; Hyperinsulinism; Insulin; Insulin Antagonists; Insulin Secretion; Middle Aged; Naloxone; Narcotic Antagonists; Postmenopause; Prospective Studies; Sodium Chloride

Proopiomelanocortin (POMC) neurons in the hypothalamus are direct targets of the adipostatic hormone leptin and contribute to energy homeostasis by integrating peripheral and central information. The melanocortin and beta-endorphin neuropeptides are processed from POMC and putatively coreleased at axon terminals. Melanocortins have been shown by a combination of pharmacological and genetic methods to have inhibitory effects on appetite and body weight. In contrast, pharmacological studies have generally indicated that opioids stimulate food intake. Here we report that male mice engineered to selectively lack beta-endorphin, but that retained normal melanocortin signaling, were hyperphagic and obese. Furthermore, beta-endorphin mutant and wild-type mice had identical orexigenic responses to exogenous opioids and identical anorectic responses to the nonselective opioid antagonist naloxone, implicating an alternative endogenous opioid tone to beta-endorphin that physiologically stimulates feeding. These genetic data indicate that beta-endorphin is required for normal regulation of feeding, but, in contrast to earlier reports suggesting opposing actions of beta-endorphin and melanocortins on appetite, our results suggest a more complementary interaction between the endogenously released POMC-derived peptides in the regulation of energy homeostasis.

Topics: Animals; beta-Endorphin; Eating; Energy Metabolism; Glucose; Homeostasis; Hyperinsulinism; Hyperphagia; Leptin; Male; Mice; Mice, Knockout; Naloxone; Narcotic Antagonists; Neuropeptide Y; Obesity; Reference Values

To evaluate the involvement of endogenous opiates in the pathophysiology of the hyperinsulinism in patients affected by polycystic ovary disease by administering naloxone and naltrexone. We also studied the hormonal status following long-term opioid antagonist administration.. Twenty-one women affected by polycystic ovary disease participated in the study. An oral glucose tolerance test (GTT) was performed at baseline and repeated after short-term naloxone infusion and after 6 weeks of naltrexone administration. Plasma glucose and insulin levels were evaluated in all samples. Gonadotropins, sex hormone-binding globulin, and androgen levels were determined initially and after the naltrexone treatment.. None of the patients showed any alteration of glucose tolerance. Based on the insulin response to the GTT, the patients were classified as normo- or hyperinsulinemic. Opioid antagonist administration significantly reduced the insulin response to the GTT in hyperinsulinemic patients, without affecting their glycemic levels. In normoinsulinemic patients, glucose plasma levels were increased whereas insulin levels were not modified by the treatments. Gonadotropin and androgen plasma concentrations were not modified after naltrexone administration.. This work supports a role for the endogenous opiates in the regulation of exaggerated insulin secretion in patients with polycystic ovary disease. The reduction of insulin secretion failed to demonstrate any hormonal modification in such hyperandrogenized patients.

Topics: Adult; Endorphins; Female; Glucose Tolerance Test; Gonadal Steroid Hormones; Humans; Hyperinsulinism; Insulin; Naloxone; Naltrexone; Obesity; Polycystic Ovary Syndrome; Time Factors

Hyperinsulinism has been associated with infection and endotoxin shock in rodents, dogs, and humans. In dogs with Escherichia coli-induced endotoxin shock, this hyperinsulinism was in response to glucose administration. To determine the role of endogenous opiates in endotoxin-induced glucose-stimulated hyperinsulinism, plasma beta-endorphin, Met-enkephalin, Leu-enkephalin, insulin, and glucose concentrations were measured for 6 h in fasted, anesthetized dogs given LD70 of E. coli endotoxin; endotoxin and glucose; endotoxin, glucose, and naloxone (an opiate antagonist); glucose and naloxone; or glucose alone. Plasma endogenous opiate immunoreactivity was elevated in dogs that received endotoxin, regardless of the presence of glucose or naloxone. The elevation of plasma Met-enkephalin and beta-endorphin preceded the onset of hyperinsulinism, but the elevation of plasma Leu-enkephalin did not. Plasma insulin was elevated 100-fold by 360 min in dogs given endotoxin and glucose. The magnitude of this hyperinsulinism was markedly reduced by naloxone, supporting the hypothesis that endogenous opiates are involved in the development of the glucose-stimulated hyperinsulinism associated with endotoxin shock. Interestingly, naloxone, given in conjunction with glucose, appeared to have a stimulatory effect on insulin secretion.

Topics: Animals; beta-Endorphin; Blood Glucose; Dogs; Endorphins; Endotoxins; Enkephalin, Leucine; Enkephalin, Methionine; Escherichia coli; Glucose; Hyperinsulinism; Insulin; Kinetics; Male; Naloxone; Shock, Septic