Ghrelin is a novel peptide that acts on the growth hormone (GH) secretagogue receptor in the pituitary and hypothalamus. It may function as a third physiological regulator of GH secretion, along with GH-releasing hormone and somatostatin. In addition to the action of ghrelin on the GH axis, it appears to have a role in the determination of energy homeostasis. Although feeding suppresses ghrelin production and fasting stimulates ghrelin release, the underlying mechanisms controlling this process remain unclear. The purpose of this study was to test the hypotheses, by use of a stepped hyperinsulinemic eu-hypo-hyperglycemic glucose clamp, that either hyperinsulinemia or hypoglycemia may influence ghrelin production. Having been stable in the period before the clamp, ghrelin levels rapidly fell in response to insulin infusion during euglycemia (baseline ghrelin 207 Ϯ 12 vs. 169 Ϯ 10 fmol/ml at t ϭ 30 min, P Ͻ 0.001). Ghrelin remained suppressed during subsequent periods of hypoglycemia (mean glucose 53 Ϯ 2 mg/dl) and hyperglycemia (mean glucose 163 Ϯ 6 mg/dl). Despite suppression of ghrelin, GH showed a significant rise during hypoglycemia (baseline 4.1 Ϯ 1.3 vs. 28.2 Ϯ 3.9 g/l at t ϭ 120 min, P Ͻ 0.001). Our data suggest that insulin may suppress circulating ghrelin independently of glucose, although glucose may have an additional effect. We conclude that the GH response seen during hypoglycemia is not regulated by circulating ghrelin. growth hormone; somatostatin; hypothalamus; hypoglycemia; glucose clamp GHRELIN IS A NOVEL PEPTIDE that acts on the growth hormone (GH) secretagogue receptor in the pituitary and hypothalamus, possibly functioning as a third physiological regulator of GH secretion along with GHreleasing hormone (GHRH) and somatostatin. In addition to the action of ghrelin on the GH axis, it appears to have a role in the determination of energy homeostasis (3, 12, 13). Ghrelin acts as an orexigenic hormone, stimulating both neuropeptide Y (NPY) and agoutirelated peptide, and thus feeding (14, 21). Although feeding suppresses ghrelin production and fasting stimulates ghrelin release, the underlying mechanisms controlling these processes remain unclear (4,19). This relationship is the opposite of that seen with leptin (14), which has been shown to be increased by insulin (18). Specifically, the roles that alterations in plasma glucose and insulin have in regulating ghrelin secretion have not been established. To address this issue, we employed a stepped hyperinsulinemic eu-hypo-hyperglycemic glucose clamp. This procedure allowed us to examine the ghrelin response to marked variations in circulating concentrations of insulin and glucose in human subjects. METHODSEleven young adult volunteers (9 women, 2 men) participated in the study. The age of the subjects was 24 Ϯ 4 yr (range 18-31 yr), and the body mass index was 22.1 Ϯ 2.8 kg/m 2 (18.4-26.6 kg/m 2 ). All subjects were healthy and taking no medication. They were instructed to maintain their normal physical activity and to consume a normal diet contai...

SummaryBackgroundThe achievement of glycaemic control remains challenging for patients with type 1 diabetes. We assessed the effectiveness of day-and-night hybrid closed-loop insulin delivery compared with sensor-augmented pump therapy in people with suboptimally controlled type 1 diabetes aged 6 years and older.MethodsIn this open-label, multicentre, multinational, single-period, parallel randomised controlled trial, participants were recruited from diabetes outpatient clinics at four hospitals in the UK and two centres in the USA. We randomly assigned participants with type 1 diabetes aged 6 years and older treated with insulin pump and with suboptimal glycaemic control (glycated haemoglobin [HbA1c] 7·5–10·0%) to receive either hybrid closed-loop therapy or sensor-augmented pump therapy over 12 weeks of free living. Training on study insulin pump and continuous glucose monitoring took place over a 4-week run-in period. Eligible subjects were randomly assigned using central randomisation software. Allocation to the two study groups was unblinded, and randomisation was stratified within centre by low (<8·5%) or high (≥8·5%) HbA1c. The primary endpoint was the proportion of time that glucose concentration was within the target range of 3·9–10·0 mmol/L at 12 weeks post randomisation. Analyses of primary outcome and safety measures were done in all randomised patients. The trial is registered with ClinicalTrials.gov, number NCT02523131, and is closed to accrual.FindingsFrom May 12, 2016, to Nov 17, 2017, 114 individuals were screened, and 86 eligible patients were randomly assigned to receive hybrid closed-loop therapy (n=46) or sensor-augmented pump therapy (n=40; control group). The proportion of time that glucose concentration was within the target range was significantly higher in the closed-loop group (65%, SD 8) compared with the control group (54%, SD 9; mean difference in change 10·8 percentage points, 95% CI 8·2 to 13·5; p<0·0001). In the closed-loop group, HbA1c was reduced from a screening value of 8·3% (SD 0·6) to 8·0% (SD 0·6) after the 4-week run-in, and to 7·4% (SD 0·6) after the 12-week intervention period. In the control group, the HbA1c values were 8·2% (SD 0·5) at screening, 7·8% (SD 0·6) after run-in, and 7·7% (SD 0·5) after intervention; reductions in HbA1c percentages were significantly greater in the closed-loop group compared with the control group (mean difference in change 0·36%, 95% CI 0·19 to 0·53; p<0·0001). The time spent with glucose concentrations below 3·9 mmol/L (mean difference in change −0·83 percentage points, −1·40 to −0·16; p=0·0013) and above 10·0 mmol/L (mean difference in change −10·3 percentage points, −13·2 to −7·5; p<0·0001) was shorter in the closed-loop group than the control group. The coefficient of variation of sensor-measured glucose was not different between interventions (mean difference in change −0·4%, 95% CI −1·4% to 0·7%; p=0·50). Similarly, total daily insulin dose was not different (mean difference in change 0·031 U/kg per day, 95% CI −0·005 to 0·067; p=0·09...