kiss1-protein--human and Hypoglycemia

There is a significant unmet need for a safe and effective therapy for the treatment of children with congenital hyperinsulinism. We hypothesized that amplification of the glucagon signaling pathway could ameliorate hyperinsulinism associated hypoglycemia. In order to test this we evaluated the effects of loss of Prkar1a, a negative regulator of Protein Kinase A in the context of hyperinsulinemic conditions. With reduction of Prkar1a expression, we observed a significant upregulation of hepatic gluconeogenic genes. In wild type mice receiving a continuous infusion of insulin by mini-osmotic pump, we observed a 2-fold increase in the level of circulating ketones and a more than 40-fold increase in Kiss1 expression with reduction of Prkar1a. Loss of Prkar1a in the Sur1-/- mouse model of KATP hyperinsulinism significantly attenuated fasting induced hypoglycemia, decreased the insulin/glucose ratio, and also increased the hepatic expression of Kiss1 by more than 10-fold. Together these data demonstrate that amplification of the hepatic glucagon signaling pathway is able to rescue hypoglycemia caused by hyperinsulinism.

Topics: Animals; Congenital Hyperinsulinism; Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; Cyclic AMP-Dependent Protein Kinases; Disease Models, Animal; Gluconeogenesis; Glucose; Hypoglycemia; Insulin; Ketones; Kisspeptins; Liver; Mice; Mice, Knockout; Signal Transduction; Sulfonylurea Receptors

Stress suppresses pulsatile luteinising hormone (LH) secretion in a variety of species, although the mechanism underlying this inhibition of reproductive function remains unclear. Metabolic stress, particularly hypoglycaemia, is a clinically-relevant stress type that is modelled with bolus insulin injection (insulin-induced hypoglycaemia). The present study utilised ovariectomised C57BL/6 mice to test the hypothesis that acute hypoglycaemia suppresses pulsatile LH secretion via central mechanisms. Pulsatile LH secretion was measured in 90-minute sampling periods immediately prior to and following i.p. injection of saline or insulin. The secretion of LH was not altered over time in fed animals or acutely fasted (5 hours) animals following an i.p. saline injection. By contrast, insulin elicited a robust suppression of pulsatile LH secretion in fasted animals, preventing LH pulses in five of six mice. To identify the neuroendocrine site of impairment, a kisspeptin challenge was performed in saline or insulin pre-treated animals in a cross-over design. LH secretion in response to exogenous kisspeptin was not different between animals pre-treated with saline or insulin, indicating normal gonadotrophin-releasing hormone cell and pituitary responses during acute hypoglycaemia. Based on this finding, the effect of insulin-induced hypoglycaemia on arcuate kisspeptin (Kiss1) cell function was determined using c-Fos as a marker of neuronal activation. Insulin caused a significant suppression in the percentage of Kiss1 cells in the arcuate nucleus that contained c-Fos compared to saline-injected controls. Taken together, these data support the hypothesis that insulin-induced hypoglycaemia suppresses pulsatile LH secretion in the female mouse via predominantly central mechanisms, which culminates in the suppression of the arcuate Kiss1 population.

Topics: Animals; Arcuate Nucleus of Hypothalamus; Fasting; Female; Hypoglycemia; Insulins; Kisspeptins; Luteinizing Hormone; Mice; Mice, Transgenic; Neurons; Ovariectomy; Proto-Oncogene Proteins c-fos

This study investigated whether kisspeptin-10 (KP-10) prevents diabetic rhesus monkeys from insulin-induced hypoglycemic shock.. Thirty-six adult male rhesus monkeys were used, six in each group. Diabetes was induced with streptozotocin (45 mg/kg b.w.; single dose i.v.). Groups were as: saline control, insulin alone, pre-insulin (treated with KP-10, 30 min before insulin), post-insulin (treated with KP-10, 30 min after insulin), treated with premix dose of KP-10 (50 μg) and insulin, and the group treated with the kisspeptin antagonist P234 (50 μg). Following an overnight fast, each animal was subjected to respective treatment, and blood glucose concentrations were recorded every 30-min interval for 3 h.. Intergroup comparisons demonstrated that treatment with KP-10 prior to insulin administration and kisspeptin-insulin premix treatment allowed blood glucose levels to rise to significantly higher levels (. KP-10 bears therapeutic potential to prevent hypoglycemic shock that may sometimes occur during intensive insulin therapy. Several pharmacological aspects of its interaction with insulin and other drugs, however, remain to be investigated.

Topics: Animals; Blood Glucose; Diabetes Mellitus, Experimental; Hypoglycemia; Hypoglycemic Agents; Insulin; Insulin Coma; Kisspeptins; Macaca mulatta; Male

Normal reproductive function is dependent upon availability of glucose and insulin-induced hypoglycaemia is a metabolic stressor known to disrupt the ovine oestrous cycle. We have recently shown that IIH has the ability to delay the LH surge of intact ewes. In the present study, we examined brain tissue to determine: (i) which hypothalamic regions are activated with respect to IIH and (ii) the effect of IIH on kisspeptin cell activation and CRFR type 2 immunoreactivity, all of which may be involved in disruptive mechanisms. Follicular phases were synchronized with progesterone vaginal pessaries and at 28 h after progesterone withdrawal (PW), animals received saline (n = 6) or insulin (4 IU/kg; n = 5) and were subsequently killed at 31 h after PW (i.e., 3 h after insulin administration). Peripheral hormone concentrations were evaluated, and hypothalamic sections were immunostained for either kisspeptin and c-Fos (a marker of neuronal activation) or CRFR type 2. Within 3 h of treatment, cortisol concentrations had increased whereas plasma oestradiol concentrations decreased in peripheral plasma (p < 0.05 for both). In the arcuate nucleus (ARC), insulin-treated ewes had an increased expression of c-Fos. Furthermore, the percentage of kisspeptin cells co-expressing c-Fos increased in the ARC (from 11 to 51%; p < 0.05), but there was no change in the medial pre-optic area (mPOA; 14 vs 19%). CRFR type 2 expression in the lower part of the ARC and the median eminence was not altered by insulin treatment. Thus, disruption of the LH surge after IIH in the follicular phase is not associated with decreased kisspeptin cell activation or an increase in CRFR type 2 in the ARC but may involve other cell types located in the ARC nucleus which are activated in response to IIH.

Topics: Animals; Arcuate Nucleus of Hypothalamus; Estradiol; Female; Follicular Phase; Gene Expression Regulation; Hydrocortisone; Hypoglycemia; Hypothalamus; Insulin; Kisspeptins; Luteinizing Hormone; Progesterone; Proto-Oncogene Proteins c-fos; Receptors, Corticotropin-Releasing Hormone; Reproduction; Sheep

Hypoglycemia inhibits the hypothalamic-pituitary-gonadal (HPG) axis by still incompletely deciphered mechanisms. Many evidences suggest that the hypoglycemia-induced inhibition of the HPG axis involves alteration of the hypothalamic gonadotropin-releasing hormone (GnRH) release, but neuroendocrine factors responsible for this alteration are yet to be completely elucidated. The current study was carried out to ascertain whether insulin-induced hypoglycemic suppression of the HPG axis involves modulation of responsiveness of the GnRH neuron to kisspeptin and excitatory amino acids (EAA) drives. Five intact chair-restraint habituated adult male rhesus monkeys (Macaca mulatta) were given intravenous boli of GnRH, hCG, human kisspeptin-10 (KP10), NMDA (N-methyl-D, L-aspartate, an EAA analogue), and vehicle in both insulin (1 IU/kg)-induced hypoglycemic (IIH) and normal euglycemic conditions. Specific RIAs were used for measuring plasma cortisol and T concentrations. KP10 and NMDA administration stimulated significantly (p<0.005) T secretion in both euglycemic and hypoglycemic monkeys. Mean post-KP10 T concentrations and AUC were comparable between euglycemic and hypoglycemic monkeys. However, mean post-NMDA T levels and AUC in hypoglycemic animals were significantly lower (p<0.01-0.005) as compared to the corresponding values in euglycemic animals. T response to GnRH and hCG was similar between hypoglycemic and euglycemic monkeys. Vehicle did not affect plasma T concentrations in all conditions. Our results demonstrate that while the primate HPG axis response to kisspeptin stimulation remains intact that to EAA excitation is attenuated in hypoglycemic conditions, suggesting that hypogonadism in IIH is contributed, in part, by reduced sensitivity of the GnRH neurons to EAA signaling in the primate hypothalamus.

Topics: Animals; Area Under Curve; Blood Glucose; Chorionic Gonadotropin; Gonadotropin-Releasing Hormone; Humans; Hydrocortisone; Hypoglycemia; Hypothalamo-Hypophyseal System; Injections, Intravenous; Kisspeptins; Macaca mulatta; Male; N-Methylaspartate; Pituitary-Adrenal System; Testosterone; Time Factors