*Purpose: Insulin is produced by pancreatic beta-cells by cleavage of a prohormone precursor into equal parts insulin and C-peptide. C-peptide has been shown to have renoprotective properties including decreasing microalbuminuria, reduced hyperfiltration injury, and regression of diabetic histologic changes on kidney biopsy when administered to type 1 diabetics. In animal models, C-peptide also protects against ischemia-reperfusion injury. How pre-transplant C-peptide levels relate to outcomes after kidney transplantation has not been previously explored.

*Methods: We identified a cohort of non-diabetic adult patients who underwent kidney transplant in Halifax, Nova Scotia between January 1, 2016-December 31, 2018 who had fasting C-peptide levels measured immediately prior to transplant. The association of pre-transplant C-peptide level dichotomized around the median and i. delayed graft function (DGF), ii. proteinuria and iii. median estimated glomerular filtration rate (eGFR) at one year was determined and statistical differences were identified using Fischer’s exact or Wilcoxon rank-sum methods where appropriate. C-peptide level was also examined as a continuous variable and categorized into quartiles. We used multivariable linear regression to determine the association of pre-transplant C-peptide level with eGFR at one year post-transplant.

*Results: Mean and median pre-transplant C-peptide levels were 3458 and 3118 pmol/L, respectively. As such, in an initial analysis, pre-transplant C-peptide level was dichotomized at 3000 pmol/L. The incidence of DGF was higher 8/31 (25.8%) amongst those with low C-peptide levels, compared with 6/33 (18.2%) for those with levels ≥ 3000. The eGFR was lower at 1 year in those with a C-peptide < 3000 compared with ≥ 3000 (49.8 ± 4.1 versus 60.0 ± 4.2, p-value 0.0877). When C-peptide was instead categorized based on quartile, eGFR again increased steadily from the lowest to highest quartile, Table 1, likewise, the percentage with proteinuria at 1 year also increased. When C-peptide was treated as a continuous variable, the association between C-peptide and eGFR at one year post transplant was significant (coefficient = 0.0043, 95% CI 0.00038-0.0081, p-value 0.032).

*Conclusions: A higher pre-transplant C-peptide level is associated with a lower risk of DGF, and a higher eGFR and lower proportion with proteinuria at one year after kidney transplant.

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