Abnormal ghrelin secretion in new onset childhood Type 1 diabetes
KeywordsMeal Test Ghrelin Concentration Ghrelin Secretion Serum Ghrelin Meal Tolerance Test
To the Editor: Ghrelin is a new circulating peptide hormone produced mainly by the stomach  and involved in the regulation of feeding behaviour and energy homeostasis . The concentrations of ghrelin are low in obese subjects [3, 4] and high in anorexic subjects . In normal subjects the ghrelin secretion is stimulated by fasting and reduced by feeding  and by oral glucose load . The mechanism of hormone release from the A-like ghrelin-producing cells  of the gastric mucosa is not yet known.
We examined ghrelin concentrations in 22 children; 11 boys and 11 girls, age 16±3.6 years (mean±SD), BMI 18.0±5.2 kg/m2 (mean±SD) with a new onset of Type 1 diabetes. Blood samples were obtained at diagnosis before and after 10 days of insulin treatment, blood glucose 24.6±8.7 and 6.6±3.0 mmol/l, respectively, and in conjunction with meal tests, carried out in 15 and 20 of the cases at 3 and 9 months after the start of insulin therapy, respectively. At meal tests the patients were fasting over night and had received no insulin in the morning. Then they had a standardised breakfast (20% of their daily energy intake, containing 33% fat, 50% carbohydrates and 17% proteins) and blood was drawn at time zero and after 30, 60, 90, 120, and 150 min. Ghrelin was measured in the samples taken just before the test and when C-peptide reached its maximum. Ghrelin was determined in serum using a radioimmunoassay (Phoenix Pharmaceuticals, Belmont, Calif., USA), which uses 125I-labelled bioactive ghrelin as a tracer and a polyclonal antibody raised in rabbits against the full-length, octanoylated human ghrelin. Intra-assay and inter-assay coefficients of variance were 5.3% and 13.6%, respectively. Statistical significance was evaluated by Mann-Whitney U test and Wilcoxon signed rank test. The study was approved by the Research Ethics Committee at the Faculty of Health Sciences, Linköping.
To our knowledge, there are no previous reports on circulating ghrelin concentrations in patients with Type 1 diabetes. Patients with Type 2 diabetes were included in a previous study  which examined ghrelin concentrations in lean, normal weight and obese non-diabetic subjects and included observations on 42 subjects with Type 2 diabetes, 8 of whom were treated with diet alone, 22 with oral hypoglycaemic agents and 8 with insulin. Fasting plasma ghrelin concentration was negatively correlated with BMI in both subjects with Type 2 diabetes and those without. The plasma ghrelin concentrations of normal subjects decreased significantly after oral glucose administration, and a similar response was observed in patients with Type 2 diabetes after a meal tolerance test, reaching a nadir of 69% of the basal level after the meal. Similarly, a suppressive effect of a mixed liquid meal or oral glucose on serum ghrelin values in healthy human subjects was noted . In contrast, we found that the children with Type 1 diabetes did not respond to meal tests with suppression of ghrelin values. One could speculate that ghrelin concentrations are low at diagnosis before the first insulin injection because of the insulinopaenia, high blood glucose load and deranged lipid metabolism, and then increases at later follow up with more normal blood glucose and metabolic control.
In conclusion, childhood Type 1 diabetes seems to be associated with abnormalities in ghrelin secretion. The circulating concentrations are low prior to insulin treatment and responses to meal tests are absent. As ghrelin is involved in the regulation of feeding behaviour and energy homeostasis, abnormalities in ghrelin secretion may play a role for the metabolic balance in diabetic children.
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