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Prediabetes and post-transplant diabetes mellitus affect about 20-30% of renal transplant patients. The latter is a risk factor for cardiovascular disease. However, no clear evidence linking prediabetes and cardiovascular disease is available. To study this we analyzed the impact of prediabetes on cardiovascular disease in 603 renal transplant patients followed with repeated oral glucose tests for up to five years and a long term survival evaluation. Prediabetes and post-transplant diabetes mellitus were defined at 12 months after transplantation to avoid their high reversibility rate before this period. 73 cardiovascular events were observed. The incidence of events was significantly higher in patients with either prediabetes, (17%; 0.023 person/year) or post-transplant diabetes mellitus (20%; 0.028 person/year) than in normal individuals, (7%; 0.0095 person/year). The incidence of events was comparable between prediabetes and post-transplant diabetes mellitus. Prediabetes at 12 months was a risk factor for cardiovascular events in univariate and multivariate Cox survival analyses (hazard ratio 2.24, 95% confidence interval 1.11-4.52). Prediabetes at three months and hemoglobin A1c at 12 months were not significantly associated with cardiovascular disease. Thus, prediabetes is a risk factor for cardiovascular disease in renal transplantation, a population at high risk for cardiovascular events. Since prediabetes is potentially a reversible condition, there is an opportunity to prevent cardiovascular disease in this population.

Background: Prediabetes and post-transplant diabetes mellitus (PTDM) affect about 20-30% of renal transplant patients. PTDM is a risk factor for cardiovascular disease. However, no clear evidence linking prediabetes and cardiovascular disease is available. Methods: We analyzed the impact of prediabetes on cardiovascular disease in 603 renal transplant patients followed with repeated OGTTs up to 5 years and a long term survival evaluation. Findings: Prediabetes and PTDM were defined at 12 months after transplantation to avoid their high reversibility rate before this period. 73 cardiovascular events were observed. The incidence of events was higher in patients with prediabetes, 28 (17%) or PTDM 20 (20%) than in normal subjects, 25 (7%), p = 0·001 and < 0·0001, respectively. The incidence of events was comparable between prediabetes and PTDM (p = 0·27). Prediabetes at 12 months was a risk factor for cardiovascular events in univariate and multivariate COX survival analyses (HR:2·24 95% CI 1·11-4·52). Prediabetes at 3 months and HbA1c at 12 months were not significant. Interpretation: Prediabetes was a risk factor for cardiovascular disease in renal transplantation, a population at high risk for cardiovascular events. Prediabetes is a potentially reversible condition, which offers the opportunity to prevent cardiovascular disease in this population. Funding Statement: Instituto de Salud Carlos III: The authors would like to acknowledge (a) the IMBRAIN project (FP7-RE6-POT-2012-CT2012- 31637-IMBRAIN) funded under the 7th Frameworks Programme (capacities), (b) the Instituto de Salud Carlos III (Fondo de Investigacioen Sanitaria: FIS) and Fondos FEDER for the following grants: PI 07/0732, the REDINREN RD/0021/0008 and PI10/02428 and (c) the funding of the Spanish Research Network for Kidney Diseases (REDINREN RD12/0021/0008). Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: This study was approved by the Ethics Committee of each hospital and followed the Declaration of Helsinki.

BACKGROUND The long-term clinical evolution of prediabetes and post-transplant diabetes mellitus (PTDM) is unknown. METHODS We analysed, in this cohort study, the reversibility, stability and progression of PTDM and prediabetes in 672 patients using repeated oral glucose tolerance tests (OGTTs) for ≤5 years. RESULTS Most patients were on tacrolimus, steroids and mycophenolate. About half developed either PTDM or prediabetes. The incidence of PTDM was 32% and bimodal: early PTDM (≤3 months) and late PTDM. Early PTDM reverted in 31%; late PTDM developed in patients with post-transplant prediabetes. The use of OGTTs was necessary to detect around half of PTDM. Pretransplant obesity was a major risk factor for early PTDM, for its persistence and for late PTDM {odds ratio [OR] 1.18 [95% confidence interval (CI) 1.09-1.28]}. At 3 months, higher HbA1c promoted [OR 2.37 (95% CI 1.38-4.06)], while insulin sensitivity protected against [OR 0.64 (95% CI 0.48-0.86)] late PTDM. At 3 months, 28% had prediabetes; of these, 36% remained stable, 43% normalized and 21% developed late PTDM. Pretransplant obesity [OR 1.20 (95% CI 1.04-1.39)] and higher HbA1c [OR 3.80 (95% CI 1.45-9.94)] at 3 months promoted while insulin sensitivity protected against [OR 0.57 (95% CI 0.34-0.95)] evolution from prediabetes to late PTDM. Immunosuppressive levels or acute rejection did not influence PTDM. Most (84%) of the patients with normal tests at 3 months remained stable without evolving into PTDM; 14% developed prediabetes. CONCLUSIONS PTDM and prediabetes are very common in renal transplantation. Classic metabolic factors like obesity, prediabetes and insulin resistance promote the evolution of PTDM and prediabetes. Patients with normal glucose metabolism rarely develop PTDM. OGTT is necessary to detect PTDM and prediabetes and thus should be included in clinical practice.