*Purpose: Post-transplant diabetes mellitus (PTDM) increases adverse outcomes. The risk factors for PTDM have not been fully delineated. Glucose metabolism links closely to cholesterol metabolism. The apolipoprotein B/A1 (Apo B/A1) ratio is associated with insulin resistance but has not been evaluated in kidney transplant recipients as a cause for PTDM.

*Methods: We identified 1104 previously non-diabetic adults who received a kidney transplant between January 1, 1998 and December 1, 2015 and were followed at one transplant centre for at least 6 months. Recipients provided testing for serum ApoB and ApoA1 concentrations from 2010, either at 3 months post-transplant for new transplant recipients, or the next clinic visit for prevalent recipients. Late post-transplant diabetes mellitus (PTDM) diagnoses occurring more than 3 months post-transplant using Canadian Diabetes Association criteria post-apolipoprotein testing were recorded until May 1, 2016.

*Results: There were 53 incident late PTDM cases, or 1.71 cases per 100 patient-years. Late PTDM differed between the highest and lowest quartiles for ApoB/A1 ratio, 2.47 per 100 patient-years v 0.88 per 100 patient-years (p=0.005 for difference). In multiple Cox regression analysis, first measured serum ApoB concentration better predicted subsequent PTDM than LDL-C (HR: 12.34 per 1 g/dL increase, p<0.001 versus HR 1.60 per g/dL, p=0.015), while HDL-C (p=0.14) and triglyceride (p=0.21) concentrations did not predict PTDM. By contrast to ApoB, ApoA1 was protective against PTDM in statin users (HR 0.17 per 1 g/dL, p=0.016).

*Conclusions: Apolipoproteins B and A1 better predict late PTDM than conventional markers of cholesterol metabolism. Routine apolipoprotein measurement post-kidney transplantation, if validated in other cohorts, may facilitate investigating mechanisms for PTDM, and might ultimately contribute to monitoring and reducing long-term post-transplant cardiovascular risk.

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