Diabetologia

, Volume 60, Issue 8, pp 1423–1431

In vivo measurement and biological characterisation of the diabetes-associated mutant insulin p.R46Q (GlnB22-insulin)

  • Julie Støy
  • Jørgen Olsen
  • Soo-Young Park
  • Søren Gregersen
  • Claudia U. Hjørringgaard
  • Graeme I. Bell
Article

Abstract

Aims/hypothesis

Heterozygous mutations in the insulin gene that affect proinsulin biosynthesis and folding are associated with a spectrum of diabetes phenotypes, from permanent neonatal diabetes to MODY. In vivo studies of these mutations may lead to a better understanding of insulin mutation-associated diabetes and point to the best treatment strategy. We studied an 18-year-old woman with MODY heterozygous for the insulin mutation p.R46Q (GlnB22-insulin), measuring the secretion of mutant and wild-type insulin by LC-MS. The clinical study was combined with in vitro studies of the synthesis and secretion of p.R46Q-insulin in rat INS-1 insulinoma cells.

Methods

We performed a standard 75 g OGTT in the 18-year-old woman and measured plasma glucose and serum insulin (wild-type insulin and GlnB22-insulin), C-peptide, proinsulin, glucagon and amylin. The affinity of GlnB22-insulin was tested on human insulin receptors expressed in baby hamster kidney (BHK) cells. We also examined the subcellular localisation, secretion and impact on cellular stress markers of p.R46Q-insulin in INS-1 cells.

Results

Plasma GlnB22-insulin concentrations were 1.5 times higher than wild-type insulin at all time points during the OGTT. The insulin-receptor affinity of GlnB22-insulin was 57% of that of wild-type insulin. Expression of p.R46Q-insulin in INS-1 cells was associated with decreased insulin secretion, but not induction of endoplasmic reticulum stress.

Conclusions/interpretation

The results show that beta cells can process and secrete GlnB22-insulin both in vivo and in vitro. Our combined approach of immunoprecipitation and LC-MS to measure mutant and wild-type insulin may be useful for the study of other mutant insulin proteins. The ability to process and secrete a mutant protein may predict a more benign course of insulin mutation-related diabetes. Diabetes develops when the beta cell is stressed because of increased demand for insulin, as observed in individuals with other insulin mutations that affect the processing of proinsulin to insulin or mutations that reduce the affinity for the insulin receptor.

Keywords

Insulin gene Maturity-onset diabetes of the young Mutant insulin 

Abbreviations

BHK

Baby hamster kidney

eIF2α

Eukaryotic Initiation Factor 2α

ER

Endoplasmic reticulum

NDM

Neonatal diabetes mellitus

Supplementary material

125_2017_4295_MOESM1_ESM.pdf (926 kb)
ESM 1(PDF 925 kb)

Copyright information

© Springer-Verlag Berlin Heidelberg 2017

Authors and Affiliations

  • Julie Støy
    • 1
  • Jørgen Olsen
    • 2
  • Soo-Young Park
    • 3
    • 4
  • Søren Gregersen
    • 5
  • Claudia U. Hjørringgaard
    • 6
  • Graeme I. Bell
    • 3
    • 4
  1. 1.Department of Internal Medicine and EndocrinologyAarhus University HospitalAarhus CDenmark
  2. 2.ADME DepartmentNovo NordiskMåløvDenmark
  3. 3.Department of MedicineUniversity of ChicagoChicagoUSA
  4. 4.Department of Human GeneticsUniversity of ChicagoChicagoUSA
  5. 5.Department of Internal Medicine and EndocrinologyAarhus University HospitalAarhusDenmark
  6. 6.Protein & Peptide ChemistryNovo NordiskMåløvDenmark

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