Abstract
AimInhibition of sodium/glucose cotransporter 2 (SGLT2), the key transport protein in renal glucose reabsorption, promotes glucose excretion and represents a new concept in the therapy of type-2 diabetes. In addition, SGLT2 inhibition elevates circulating glucagon concentrations and enhances hepatic glucose production. Since SGLT2 is expressed in human pancreatic α-cells and regulates glucagon release, we tested whether common variants of the SGLT2 gene SLC5A2 associate with altered plasma glucagon concentrations in the fasting state and upon glucose challenge.MethodsA study population of 375 healthy subjects at increased risk for type-2 diabetes, phenotyped by a 5-point oral glucose tolerance test (OGTT) and genotyped for recently described SLC5A2 tagging single nucleotide polymorphisms (SNPs), was selected for plasma glucagon measurements.ResultsAfter adjustment for gender, age, body mass index, and insulin sensitivity, the four tagging SNPs (rs9924771, rs3116150, rs3813008, rs9934336), tested separately or as genetic score, were neither significantly nor nominally associated with plasma glucagon concentrations at any time during the OGTT, with the inverse AUC of glucagon or the glucagon fold-change during the OGTT (p ≥ 0.2, all). Testing for genotype-related differences in the time course of the glucagon response using MANOVA did also not reveal any significant or nominal associations (p ≥ 0.5, all).ConclusionWe could not obtain statistically significant evidence for a role of common SLC5A2 variants in the regulation of glucagon release in the fasting state or upon glucose challenge. Moreover, the reported nominal effects of individual SLC5A2 variants on fasting and post-challenge glucose levels may probably not be mediated by altered glucagon release.
Highlights
Even though very well soluble in water, less than one percent of glucose filtered by the healthy kidney is excreted in the urine [1]
The reported nominal effects of individual SLC5A2 variants on fasting and post-challenge glucose levels may probably not be mediated by altered glucagon release
Two sodium-dependent glucose transporters, i.e., sodium/ glucose cotransporter (SGLT) 1 and 2, are the major transport proteins responsible for renal glucose reabsorption: more than 90 percent of glucose is reabsorbed by sodium/glucose cotransporter 2 (SGLT2) and nearly three percent by SGLT1 [2]
Summary
Even though very well soluble in water, less than one percent of glucose filtered by the healthy kidney is excreted in the urine [1]. Two sodium-dependent glucose transporters, i.e., sodium/ glucose cotransporter (SGLT) 1 and 2, are the major transport proteins responsible for renal glucose reabsorption: more than 90 percent of glucose is reabsorbed by SGLT2 and nearly three percent by SGLT1 [2]. In the pathophysiological state of hyperglycemia, glucose is excreted by glucosuria due to substrate saturation of the SGLTs [2]. This renal glucose loss is insufficient to normalize the elevated blood glucose levels of diabetic patients. The rise in glucose reabsorption up to the SGLTs’ transport maximum is considered to contribute to sustained hyperglycemia [1]
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