Estimation of prehepatic insulin secretion: Comparison between standardized C-peptide and insulin kinetic models

Andrea Tura, Giovanni Pacini, Alexandra Kautzky-Willer, Amalia Gastaldelli, Ralph A Defronzo, Ele Ferrannini, Andrea Mari

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Abstract

Our aim was to compare traditional C-peptide-based method and insulin-based method with standardized kinetic parameters in the estimation of prehepatic insulin secretion rate (ISR). One-hundred thirty-four subjects with varying degrees of glucose tolerance received an insulin-modified intravenous glucose tolerance test and a standard oral glucose tolerance test with measurement of plasma insulin and C-peptide. From the intravenous glucose tolerance test, we determined insulin kinetics parameters and selected standardized kinetic parameters based on mean values in a selected subgroup. We computed ISR from insulin concentration during the oral glucose tolerance test using these parameters and compared ISR with the standard C-peptide deconvolution approach. We then performed the same comparison in an independent data set (231 subjects). In the first data set, total ISRs from insulin and C-peptide were highly correlated (R 2 = 0.75, P <.0001), although on average different (103 ± 6 vs 108 ± 3 nmol, P <.001). Good correlation was also found in the second data set (R 2 = 0.54, P <.0001). The insulin method somewhat overestimated total ISR (85 ± 5 vs 67 ± 3 nmol, P =.002), in part because of differences in insulin assay. Similar results were obtained for fasting ISR. Despite the modest bias, the insulin and C-peptide methods were consistent in predicting differences between groups (eg, obese vs nonobese) and relationships with other physiological variables (eg, body mass index, insulin resistance). The insulin method estimated first-phase ISR peak similarly to the C-peptide method and better than the simple use of insulin concentration. The insulin-based ISR method compares favorably with the C-peptide approach. The method will be particularly useful in data sets lacking C-peptide to assess β-cell function through models requiring prehepatic secretion.

Original languageEnglish (US)
Pages (from-to)434-443
Number of pages10
JournalMetabolism: Clinical and Experimental
Volume61
Issue number3
DOIs
StatePublished - Mar 2012

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C-Peptide
Insulin
Glucose Tolerance Test

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

Estimation of prehepatic insulin secretion : Comparison between standardized C-peptide and insulin kinetic models. / Tura, Andrea; Pacini, Giovanni; Kautzky-Willer, Alexandra; Gastaldelli, Amalia; Defronzo, Ralph A; Ferrannini, Ele; Mari, Andrea.

In: Metabolism: Clinical and Experimental, Vol. 61, No. 3, 03.2012, p. 434-443.

Research output: Contribution to journalArticle

Tura, Andrea ; Pacini, Giovanni ; Kautzky-Willer, Alexandra ; Gastaldelli, Amalia ; Defronzo, Ralph A ; Ferrannini, Ele ; Mari, Andrea. / Estimation of prehepatic insulin secretion : Comparison between standardized C-peptide and insulin kinetic models. In: Metabolism: Clinical and Experimental. 2012 ; Vol. 61, No. 3. pp. 434-443.
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