Increased alloreactivity and adverse outcomes in obese kidney transplant recipients are limited to those with diabetes mellitus.

Previous studies on patient and allograft outcomes of obese kidney transplant recipients (KTRs) remain controversial. To what extent obesity-related comorbidities contribute to adverse outcomes, however, hasn't been addressed. We studied all KTRs from 2005 to 2012. 29 (4%), 317 (48%), 217 (33%), 76 (12%), and 21 KTRs (4%) were identified as underweight, normal-weight, overweight, obese, and morbid obese, respectively. 33 of 97 obese KTRs (34%) had pre-existent diabetes. Samples were collected before transplantation and at +1, +2, +3months posttransplantation. Donor-reactive T-cells were measured using an interferon-γ Elispot assay. Obese KTRs showed an increased incidence pre-existent diabetes (p<0.001), but no differences for hypertension and coronary artery disease (p>0.05). Among obese KTRs, those with pre-existent diabetes showed inferior patient and allograft survival, worse allograft function, delayed graft function, and prolonged hospitalization (p<0.05). Interestingly, no differences were observed between obese non-diabetic, normal-weight diabetic, and normal-weight non-diabetic KTRs (p>0.05). Obese diabetic KTRs showed higher frequencies of donor-reactive T-cells pretransplantation (p<0.05). Our results suggest that the increased risk of mortality, allograft loss, delayed graft function, and prolonged hospitalization in obese KTRs is limited to those with diabetes. A state of obesity-related inflammation plus hyperglycemia may trigger increased alloreactivity and should call for adequate immunosuppression.