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Urine C-peptide creatinine ratio can be used to assess insulin resistance and insulin production in people without diabetes: an observational study
  1. Richard A Oram1,2,
  2. Andrew Rawlingson1,2,
  3. Beverley M Shields1,
  4. Coralie Bingham2,
  5. Rachel E J Besser,
  6. Tim J McDonald1,2,
  7. Bridget A Knight1,
  8. Andrew T Hattersley1
  1. 1NIHR Exeter Clinical Research Facility, University of Exeter Medical School, Royal Devon & Exeter NHS Foundation Trust, Exeter, UK
  2. 2Royal Devon & Exeter NHS Foundation Trust, Exeter, UK
  1. Correspondence to Dr Richard A Oram; r.oram{at}exeter.ac.uk

Abstract

Objectives The current assessment of insulin resistance (IR) in epidemiology studies relies on the blood measurement of C-peptide or insulin. A urine C-peptide creatinine ratio (UCPCR) can be posted from home unaided. It is validated against serum measures of the insulin in people with diabetes. We tested whether UCPCR could be a surrogate measure of IR by examining the correlation of UCPCR with serum insulin, C-peptide and HOMA2 (Homeostasis Model Assessment 2)-IR in participants without diabetes and with chronic kidney disease (CKD).

Design Observational study.

Setting Single-centre clinical research facility.

Participants 37 healthy volunteers and 30 patients with CKD (glomerular filtration rate 15–60) were recruited.

Primary and secondary endpoints Serum insulin, C-peptide and glucose at fasting (0), 30, 60, 90 and 120 min were measured during an oral glucose tolerance test (OGTT). Second-void fasting UCPCR and 120 min post-OGTT UCPCR were collected. HOMA2-IR was calculated using fasting insulin and glucose. The associations between UCPCR and serum measures were assessed using Spearman's correlations.

Results In healthy volunteers, fasting second-void UCPCR strongly correlated with serum insulin (rs=0.69, p<0.0001), C-peptide (rs=0.73, p<0.0001) and HOMA2-IR (rs=−0.69, p<0.0001). 120 min post-OGTT UCPCR correlated strongly with C-peptide and insulin area under the curve. In patients with CKD, UCPCR did not correlate with serum C-peptide, insulin or HOMA2-IR.

Conclusions In participants with normal renal function, UCPCR may be a simple, practical method for the assessment of IR in epidemiology studies.

  • Diabetes & Endocrinology
  • Statistics & Research Methods

This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 3.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See: http://creativecommons.org/licenses/by/3.0/

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