Clinical features and search for genetic determinants of postprandial hypoglycemia.

Objective: To test whether postprandial hypoglycaemia is an extreme and repeatable phenotype of glucose metabolism. Secondly, we explored the genetic determinants of this phenotype.

Design and methods: We conducted this study using data from Pinggu Metabolic Disease Study database (n = 3,345). We selected subjects after an oral glucose tolerance test (OGTT) (2 h, glucose <3 mmol/L_ and compared clinical features with those of normal glucose tolerance (NGT). We additionally selected 75 subjects as super-healthy control group. Whole-exome sequencing (WES) was performed on postprandial hypoglycaemic and super-healthy controls. We also evaluated several candidate genes believed to be important in pancreatic hypoglycaemia.

Results: We found 13 participants (0.39%) had an OGTT 2 h glucose <3 mmol/L. Ten patients were men (76.9%). All 13 participants had insulin > 3 uU/mL when postprandial blood glucose levels were <3 mmol/L. WES analysis identified one gene, paternally expressed 3 (PEG3), which had three rare mutations in four patients (30.8%). Minor allele frequencies (MAF) of rare PEG3 mutations were significantly higher in subjects with postprandial hypoglycaemia than in super-healthy controls. Among all four subjects with PEG3 gene mutations, 71.4% were men, and their body mass index (BMI) was significantly lower than that of the NGT.

Conclusions: Postprandial hypoglycaemia is an extreme and reproducible phenotype in the general population. PEG3 mutations may represent a potential genetic aetiology for postprandial hypoglycaemia. Further research with larger and more diverse populations and a broader genetic focus is needed to understand the genetic basis of postprandial hypoglycaemia.