Accelerated oligosaccharide absorption and altered serum metabolites during oral glucose tolerance test in young Japanese with impaired glucose tolerance

摘要

Aims/Introduction Impaired glucose tolerance (IGT) is a subtype of prediabetes, a condition having high risk for development to diabetes mellitus, but its pathophysiology is not fully understood. In the present study, we examined metabolic changes in IGT by using two types ( D‐ glucose [Glc] and partial hydrolysate of starch [PHS]) of oral glucose tolerance tests (OGTTs), with emphasis on serum incretins and metabolites. Materials and Methods We carried out the two types of OGTT (Glc/OGTT and PHS/OGTT) in 99 young Japanese individuals who had tested either positive (GU+; n = 48) or negative (GU?; n = 51) for glycosuria. After OGTT, they were sub‐grouped into five categories: normal glucose tolerance (NGT) in the GU? group (GU?/NGT; n = 49), NGT in the GU+ group (GU+/NGT; n = 28), IGT ( n = 12), diabetes mellitus ( n = 1) and renal glycosuria ( n = 9). Serum incretin and metabolites of GU?/NGT and IGT were then measured. Results When the serum insulin level at each time‐point during PHS/OGTT was expressed as its ratio relative to Glc/OGTT, it was increased time‐dependently in GU?/NGT, but not in IGT. Such an increase in the ratio was also detected of serum incretin levels in GU?/NGT, but not in IGT, suggesting a lack of deceleration of oligosaccharide absorption in IGT. Metabolome analysis showed a difference in the serum levels of two metabolites of unknown function in mammals, methylcysteine and sedoheptulose 1,7‐bisphosphate, between GU?/NGT and IGT. Conclusions Comparison of PHS/OGTT and Glc/OGTT showed that oligosaccharide absorption was accelerated in IGT. Methylcysteine and sedoheptulose 1,7‐bisphosphate could be novel markers for dysregulated glucose metabolism.