New-onset diabetes after kidney transplantation-changes and challenges

Preventing and managing hyperglycemia in kidney transplant patients

PURPOSE OF REVIEW

New onset diabetes after kidney transplantation (NODAT) remains a common complication after transplantation and is associated with significant morbidity and mortality. The review will examine recent advances in our knowledge of this metabolic disorder and speculate upon future development.

RECENT FINDINGS

Research continues to broaden the horizon of existing and emerging risk factors that contribute to development of NODAT. Attempts to use this knowledge to develop quantitative risk scoring composites have been made, utilizing either pretransplant or 1-year posttransplantation variables, with variable success. Reassuringly a number of clinical trials have been published, or are currently in progress, that utilize pharmacological intervention for both prevention and management of NODAT. These are both in the form of differential immunosuppressant regimens or use of antiglycemic agents. Upcoming results will prove crucial in developing a genuine evidence-base for NODAT management.

SUMMARY

Rather than simple translation of data from the general to kidney transplant population, clinicians must appreciate that NODAT constitutes a distinct metabolic entity with unique pathophysiology. As such targeted strategies to prevent and manage NODAT require focused investigation to deal with this common complication.

Metformin for patients with diabetes and concomitant renal restrictions--is there an evidence base?

Despite its array of benefits that comparatively outweigh alternative oral anti-glycaemic agents, the ability of clinicians to prescribe metformin is restricted. There are numerous contra-indications and cautions concerning the putative risks of metformin-related side effects that necessitate cessation of metformin. Notably the often stated, yet completely unsubstantiated, heightened risk for development of lactic acidosis in the context of renal insufficiency or a kidney transplant is particularly contentious. In this article, I will critique current regulatory advice and argue for further research to evaluate the safety and efficacy of metformin use in populations where the benefits of metformin are likely to far outweigh any infinitesimal risk (such as advanced chronic kidney disease and those after kidney transplantation). The only way to settle this debate is for well-designed trials and registry analyses to ascertain the safety and efficacy of metformin in these 'high-risk' populations. That is what evidence-based medicine demands and unfortunately is long overdue.

Novel views on new-onset diabetes after transplantation: development, prevention and treatment

New-onset diabetes after transplantation (NODAT) is associated with increased risk of allograft failure, cardiovascular disease and mortality, and therefore, jeopardizes the success of renal transplantation. Increased awareness of NODAT and the prediabetic states (impaired fasting glucose and impaired glucose tolerance, IGT) has fostered previous and present recommendations, based on the management of type 2 diabetes mellitus (T2DM). Unfortunately, the idea that NODAT merely resembles T2DM is potentially misleading, because the opportunity to initiate adequate anti-hyperglycaemic treatment early after transplantation might be given away for 'tailored' immunosuppression in patients who have developed NODAT or carry personal risk factors. Risk factor-independent mechanisms, however, seem to render postoperative hyperglycaemia with subsequent development of overt or 'full-blown' NODAT, the unavoidable consequence of the transplant and immunosuppressive process itself, at least in many cases. A proof of the concept that timely preventive intervention with exogenous insulin against post-transplant hyperglycaemia may decrease NODAT was recently provided by a small clinical trial, which is awaiting confirmation from a multicentre study. However, because early insulin therapy aimed at beta-cell protection seems to contrast the currently recommended, stepwise approach of 'watchful waiting' prior to pancreatic decompensation, we here aim at reviewing recent concepts regarding the development, prevention and treatment of NODAT, some of which seem to challenge the traditional view on T2DM and NODAT. In summary, we suggest a novel, risk factor-independent management approach to NODAT, which includes glycaemic monitoring and anti-hyperglycaemic treatment in virtually everybody after transplantation. This approach has widespread implications for future research and is intended to tackle NODAT and also ultimately cardiovascular disease.

Validity of glycated haemoglobin to diagnose new onset diabetes after transplantation

Diagnosing new onset diabetes after transplantation (NODAT) by glycated haemoglobin (HbA1c) has not been validated against the gold-standard oral glucose tolerance test (OGTT). We analysed the predictive and optimum value of HbA1c to diagnose NODAT amongst nondiabetic renal transplant recipients. Assessment of glucose metabolism (OGTT and HbA1c) was prospectively undertaken at 3 and 12 months post-transplantation in 71 nondiabetic renal transplant recipients. Receiver operator characteristic (ROC) curve analyses were performed to determine accuracy, sensitivity, specificity and area under curve (c-statistic). Incidence of NODAT at 3 and 12 months post-transplantation was 14.3% and 9.5% respectively. At 3 months, optimum HbA1c cut-off value for predicting NODAT based on fasting glucose was 7.35 [AUC 1.00 (sensitivity 100.0%, specificity 100.0%, P = 0.004)] and for postprandial glucose-defined NODAT was 6.20 [AUC 0.98 (sensitivity 100.0%, specificity 88.9%, P < 0.001)]. At 12 months, optimum HbA1c cut-off value for both fasting- and postprandial glucose-defined NODAT was 6.45 [AUC 0.92 (sensitivity 100.0%, specificity 87.5%, P = 0.048) and AUC 0.84 (sensitivity 75.0%, specificity 89.5%, P = 0.026) respectively]. Concordance between diagnosis of NODAT (OGTT+, HbA1c+) and nondiagnosis of NODAT (OGTT-, HbA1c-) was 88.9% and 98.7% respectively. To conclude, HbA1c (≥6.5%) can be utilized to diagnose NODAT beyond 3 months post-transplantation but the OGTT remains the gold-standard tool.

Longitudinal analysis of vascular function and biomarkers of metabolic bone disorders before and after renal transplantation

BACKGROUND/AIMS

The role of chronic kidney disease-mineral bone disorder (CKD-MBD) reversibility in the amelioration of vascular function and in the reduction of the risk for cardiovascular events after renal transplantation is still unknown.

METHODS

We investigated the longitudinal relationship between the main biomarkers of CKD-MBD and the evolution of vascular function [flow-mediated dilatation (FMD)] after transplantation in a series of 161 patients with kidney failure maintained on chronic dialysis (5D-CKD).

RESULTS

Before transplantation, FMD in patients was markedly lower (-40%, p < 0.001) than in well-matched healthy subjects and increased by 27% after transplantation (p = 0.001). Fibroblast growth factor 23 (FGF23), 25-hydroxy-vitamin D (25OHVD) and serum phosphate (p < 0.01) were independently associated with simultaneous changes in FMD. Changes in classical risk factors and in risk factors related to CKD like the glomerular filtration rate, serum albumin, C-reactive protein and insulin resistance failed to independently explain the variability in FMD changes after transplantation.

CONCLUSION

Endothelium-dependent vasodilatation improves after kidney transplantation, which is parallel to the dramatic fall in FGF23, the reduction in serum phosphorus and the increase in 25OHVD levels. If these associations are causal, a part of decline in cardiovascular risk after transplantation is related to partial resolution of CKD-MBD.