Serum Vitamin D and Its Upregulated Protein, Thioredoxin Interacting Protein, Are Associated With Beta-Cell Dysfunction in Adult Patients With Type 1 and Type 2 Diabetes

Can J Diabetes. 2018 Dec;42(6):588-594. doi: 10.1016/j.jcjd.2018.02.012. Epub 2018 Mar 2.


Objectives: Diabetes mellitus is characterized by either complete deficiency of insulin secretion, as in type 1 diabetes, or decompensation of the pancreatic beta cells in type 2 diabetes. Both vitamin D (vitD) and thioredoxin interacting protein (TXNIP) have been shown to be involved in beta-cell dysfunction. Therefore, this study was designed to examine vitD and TXNIP serum levels in patients with diabetes and to correlate these levels with beta-cell function markers in both types of diabetes.

Methods: The routine biochemical parameters and the serum levels of vitD and TXNIP were measured in 20 patients with type 1 diabetes and 20 patients with type 2 diabetes. The levels were then compared to those of 15 healthy control volunteers. Insulin, C-peptide and proinsulin (PI), vitD and TXNIP were measured by ELISA. Beta-cell dysfunction was assessed by homeostatic model assessment (HOMA-beta), proinsulin-to-C-peptide (PI/C) and proinsulin-to-insulin (PI/I) ratios. Correlations among various parameters were studied.

Results: Patients with type 1 diabetes had significantly lower HOMA-beta, vitD and TXNIP levels; however, they had higher PI/C levels than the control group. Meanwhile, patients with type 2 diabetes had significantly higher C-peptide, proinsulin, PI/C, HOMA-insulin resistance (HOMA-IR) and lower HOMA-beta and vitD levels, with no significant difference in TXNIP levels as compared to the control group. In addition, vitD was significantly correlated positively with HOMA-beta and TXNIP and negatively with PI, PI/C, PI/I and HOMA-IR. TXNIP correlated positively with HOMA-beta and negatively with PI/C.

Conclusions: Our data showed that vitD and TXNIP were associated with different beta-cell dysfunction markers, indicating their potential abilities to predict the beta-cell status in people with diabetes.

Keywords: beta-cell dysfunction; diabète sucré de type 1; diabète sucré de type 2; dysfonction des cellules bêta; protéines d'interaction avec la thiorédoxine; thioredoxin interacting protein (TXNIP); type 1 diabetes mellitus; type 2 diabetes mellitus; vitamin D; vitamine D.

MeSH terms

  • C-Peptide / blood
  • Carrier Proteins / blood*
  • Diabetes Mellitus, Type 1 / blood*
  • Diabetes Mellitus, Type 2 / blood*
  • Female
  • Homeostasis
  • Humans
  • Insulin / blood
  • Insulin-Secreting Cells*
  • Male
  • Middle Aged
  • Pancreatic Diseases / blood*
  • Proinsulin / blood
  • Vitamin D / blood*


  • C-Peptide
  • Carrier Proteins
  • Insulin
  • TXNIP protein, human
  • Vitamin D
  • Proinsulin