Post-glucose-load urinary C-peptide and glucose concentration obtained during OGTT do not affect oral minimal model-based plasma indices

• Published in: Endocrine Vol. 52; no. 2; pp. 253 - 262
• Main Authors: Jainandunsing, Sjaam, Wattimena, J. L. Darcos, Rietveld, Trinet, van Miert, Joram N. I., Sijbrands, Eric J. G., de Rooij, Felix W. M.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-05-2016
• Subjects: Adult; Biomarkers - urine; C-Peptide - urine; Diabetes; Diabetes Mellitus, Type 2 - urine; Endocrinology; Female; Glomerular Filtration Rate; Glucose Tolerance Test; Glycosuria; Humanities and Social Sciences; Humans; Internal Medicine; Male; Medicine; Medicine & Public Health; Middle Aged; Models, Biological; multidisciplinary; Original; Original Article; ROC Curve; Science; Type 2 diabetes; Oral minimal model; Glucose; South Asian; OGTT; C-peptide
• ISSN: 1355-008X; 1559-0100
• DOI: 10.1007/s12020-015-0765-9

The purpose of this study was to investigate how renal loss of both C-peptide and glucose during oral glucose tolerance test (OGTT) relate to and affect plasma-derived oral minimal model (OMM) indices. All individuals were recruited during family screening between August 2007 and January 2011 and underwent a 3.5-h OGTT, collecting nine plasma samples and urine during OGTT. We obtained the following three subgroups: normoglycemic, at risk, and T2D. We recruited South Asian and Caucasian families, and we report separate analyses if differences occurred. Plasma glucose, insulin, and C-peptide concentrations were analyzed as AUCs during OGTT, OMM estimate of renal C-peptide secretion, and OMM beta-cell and insulin sensitivity indices were calculated to obtain disposition indices. Post-glucose load glucose and C-peptide in urine were measured and related to plasma-based indices. Urinary glucose corresponded well with plasma glucose AUC (Cau
r
 = 0.64,
P
 < 0.01; SA
r
 = 0.69,
P
 < 0.01),
S
I
(Cau
r
 = −0.51,
P
 < 0.01; SA
r
 = −0.41,
P
 < 0.01),
Φ
dynamic
(Cau
r
 = −0.41,
P
 < 0.01; SA
r
 = −0.57,
P
 < 0.01), and
Φ
oral
(Cau
r
 = −0.61,
P
 < 0.01; SA
r
 = −0.73,
P
 < 0.01). Urinary C-peptide corresponded well to plasma C-peptide AUC (Cau
r
 = 0.45,
P
 < 0.01; SA
r
 = 0.33,
P
 < 0.05) and OMM estimate of renal C-peptide secretion (
r
 = 0.42,
P
 < 0.01). In general, glucose excretion plasma threshold for the presence of glucose in urine was ~10–10.5 mmol L
−1
in non-T2D individuals, but not measurable in T2D individuals. Renal glucose secretion during OGTT did not influence OMM indices in general nor in T2D patients (renal clearance range 0–2.1 %, with median 0.2 % of plasma glucose AUC). C-indices of urinary glucose to detect various stages of glucose intolerance were excellent (Cau 0.83–0.98; SA 0.75–0.89). The limited role of renal glucose secretion validates the neglecting of urinary glucose secretion in kinetic models of glucose homeostasis using plasma glucose concentrations. Both C-peptide and glucose in urine collected during OGTT might be used as non-invasive measures for endogenous insulin secretion and glucose tolerance state.