Highly increased insulin secretion in a patient with postprandial hypoglycemia: role of glucagon-like peptide-1 (7-36) amide

Expression of sweet taste receptor and gut hormone secretion in modelled type 2 diabetes

Sweet taste receptors (STRs) are expressed in L cells which secret glucagon-like peptide-1 (GLP-1) in the gut. The STR blocker lactisole reduces GLP-1 secretion and increases blood glucose levels. Therefore, we investigated the expression of sweet taste molecules in the proximal and distal small intestine, and gut hormone secretion, in healthy control and type 2 diabetic rats. Two groups of rats (Sprague Dawley (SD), and Zucker diabetic fatty (ZDF)) were involved in the study. Each group (n=10) received an intragastric glucose infusion (50% glucose solution, 2g/kg body weight). Blood samples were taken for measurement of blood glucose, plasma insulin, and GLP-1 concentrations. One week later, we obtained small intestinal tissue and detected the expression of STRs and glucose transporters (GTs) by real time polymerase chain reaction (Real Time-PCR). Sweet taste molecules of T1R2, T1R3, α-gustducin and TRPM5 in ileum were dramatically higher than those in duodenum (P<0.01 for each). T1R3, α-gustducin and TRPM5 expression were less in the ileum of ZDF than those in SD (P<0.05 for each), while expression of glucose transporter 2 (GLUT-2) in ileum was significantly higher in ZDF rats. Plasma GLP-1 levels were higher in ZDF rats than SD rats at t=0, 15, 30, 60 and 120min (P<0.01). In conclusion, transcript levels of ileal T1R3 and GLUT-2 are disordered in ZDF rats suggesting that intestinal sweet taste receptor expression is associated with altered glucose metabolism. The mechanism needs further investigation, but might provide a potential therapy in the treatment of type 2 diabetes.

Hyperinsulinaemic hypoglycaemia in children and adults

Pancreatic β cells are functionally programmed to release insulin in response to changes in plasma glucose concentration. Insulin secretion is precisely regulated so that, under normal physiological conditions, fasting plasma glucose concentrations are kept within a narrow range of 3·5-5·5 mmol/L. In hyperinsulinaemic hypoglycaemia, insulin secretion becomes dysregulated (ie, uncoupled from glucose metabolism) so that insulin secretion persists in the presence of low plasma glucose concentrations. Hyperinsulinaemic hypoglycaemia is the most common cause of severe and persistent hypoglycaemia in neonates and children. At a molecular level, mutations in nine different genes can lead to the dysregulation of insulin secretion and cause this disorder. In adults, hyperinsulinaemic hypoglycaemia accounts for 0·5-5·0% of cases of hypoglycaemia and can be due either to β-cell tumours (insulinomas) or β-cell hyperplasia. Rapid diagnosis and prompt management of hyperinsulinaemic hypoglycaemia is essential to avoid hypoglycaemic brain injury, especially in the vulnerable neonatal and childhood periods. Advances in the field of hyperinsulinaemic hypoglycaemia include use of rapid molecular genetic testing for the disease, application of novel imaging techniques (6-[fluoride-18]fluoro-levodopa [¹⁸F-DOPA] PET-CT and glucagon-like peptide 1 (GLP-1) receptor imaging), and development of novel medical treatments (eg, long-acting octreotide formulations, mTOR inhibitors, and GLP-1 receptor antagonists) and surgical therapies (eg, laparoscopic surgery).

Idiopathic postprandial hyperinsulinaemic hypoglycaemia

BACKGROUND

Idiopathic postprandial hyperinsulinaemic hypoglycaemia (PPHH) has rarely been reported in the paediatric age. The objective of this study was to describe the clinical characteristics, diagnosis and management in a group of children with PPHH.

METHODS

Six children (three females) with a mean follow-up of 3.5±3.0 years at a single tertiary paediatric hospital. All had 24-h blood glucose monitoring, diagnostic fast and prolonged oral glucose tolerance test (OGTT). Follow-up included: 24-h blood glucose monitoring or continuous glucose monitoring system, prolonged OGTT and/or mixed meal (MM) test.

RESULTS

Age at diagnosis ranged from 5.4 to 15.7 years and auxology parameters were within normal range in all subjects. All the children had a normal fasting tolerance for age. Prolonged OGTT demonstrated symptomatic hypoglycaemia after 120 min in all the patients with simultaneous detectable serum insulin concentration. Acarbose was tried in three patients, having a positive effect on glycaemic and symptom control, but due to side effects, only two patients continued acarbose in the long run. Diazoxide proved to be beneficial in one patient. The rest of the patients were managed with frequent feeds but despite this, prolonged OGTT/MM demonstrated on-going PPHH.

CONCLUSIONS

Prolonged OGTT is necessary to diagnose PPHH in children. Acarbose is beneficial in children with PPHH, although not well tolerated. Patients managed exclusively on frequent feeds demonstrated persistent hypoglycaemia on OGTT. The underlying cause of the PPHH in these patients remains unknown.

Post prandial plasma glucose level less than the fasting level in otherwise healthy individuals during routine screening

During routine screening, some otherwise healthy individuals who showed remarkably lower post prandial (at 2 hour) plasma glucose without any symptom were subjected to extended glucose tolerance test and a few of them to extended post meal tolerance test as well. It was observed that post prandial (at 2 hour) plasma glucose after glucose administration was significantly lower than the fasting level (p<0.05-p<0.001). However, post prandial plasma glucose at 2 hour after their usual meal exhibited a significantly higher level than the fasting and post glucose level (p<0.05-p<0.001). Glucose appears to be a stronger agent than the more natural mixed meal in these individuals in causing post prandial lowering of plasma glucose. Hence, these individuals are to be evaluated with their usual meals before considering further investigations. Like upper limit, there is the need to have a consensus lower limit of reference interval of blood glucose level.

Postprandial reactive hypoglycemia in an oldest-old patient effectively treated with low-dose acarbose

We recently encountered a 96-year-old Japanese woman who suffered from frequent hypoglycemia. Endocrinological and imaging data eliminated the possibility of insulinoma, whereas oral glucose tolerance testing revealed impaired glucose tolerance and subsequent reactive hypoglycemia. The patterns between insulin or C-peptide secretions and glucose excursions demonstrated that the discrepancy occurred in the late postprandial stage. Administration of small doses of alpha-glucosidase inhibitor (alpha-GI) dramatically inhibited the rapid rise and subsequent precipitous fall of plasma glucose. Reactive hypoglycemia may be one of the important cause of hypoglycemia in the elderly, and alpha-GI could effectively and safely prevent such hypoglycemic attacks in those patients.