Hypomagnesemia is associated with new-onset diabetes mellitus following heart transplantation

Hypomagnesaemia, an independent risk factor for the development of post-transplant diabetes mellitus in liver and renal transplant recipients? A systematic review

BACKGROUND

Post-transplantation diabetes mellitus (PTDM) is common after solid organ transplantation. In the past decade, there has been increasing interest in the association between hypomagnesaemia and the development of PTDM. This systematic review aimed to investigate the current knowledge regarding the association between hypomagnesaemia and PTDM in adult liver and renal transplant recipients.

METHODS

A literature search of five databases, Medline, Embase, ProQuest, Scopus and Google Scholar, as well as article reference lists, was performed. Eligible studies that focused on adult liver and renal transplant recipients without pretransplantation hyperglycaemia or diabetes were included. Other eligibility criteria included quantitative studies which reported magnesium concentrations, studies with at least 6 months of follow-up, and studies published in English. The Newcastle-Ottawa Assessment Tool was used for the quality assessment.

RESULTS

In total, 12 studies were included in the final analysis. Eleven focused on renal transplantation and one on liver transplantation. All studies were medium to high quality with eight out of 12 achieving the highest rating of nine. Eight studies found a negative association between either pretransplant or early post-transplant serum magnesium concentration and the risk of PTDM, three studies found no association between these two variables, and one study found a positive association between the magnesium concentration at 8 weeks after transplantation and glycosylated haemoglobin A1C.

CONCLUSIONS

Further large-scale prospective studies with at least 6 months of follow-up are needed to confirm these findings, particularly in liver transplantation, to further clarify and explore the relationship between hypomagnesaemia and PTDM.

Early post-transplant hyperglycemia and post-transplant diabetes mellitus following heart transplantation

INTRODUCTION

Heart transplantation is an important treatment for end-stage heart failure. Early post-transplant hyperglycemia (EPTH) and post-transplant diabetes mellitus (PTDM) are common following heart transplantation and are associated with increased morbidity and mortality.

AREAS COVERED

This review summarizes the clinical characteristics, diagnosis, and treatment of EPTH and PTDM in cardiac transplant patients, incorporating findings from non-cardiac solid organ transplant studies where relevant due to limited heart-specific research.

EXPERT OPINION

EPTH following heart transplantation is common yet understudied and is associated with the later development of PTDM. PTDM is associated with adverse outcomes including infection, renal dysfunction, microvascular disease, and an increased risk of re-transplantation and mortality. Risk factors for EPTH include the post-operative immunosuppression regimen, recipient and donor age, body mass index, infections, and chronic inflammation. Early insulin treatment is recommended for EPTH, whereas PTDM management is varied and includes lifestyle modification, anti-glycemic agents, and insulin. Given the emerging evidence on the transplant benefits associated with effective glucose control, and the cardioprotective potential of newer anti-glycemic agents, further focus on the management of EPTH and PTDM within heart transplant recipients is imperative.

Nonallograft Complications of Lung Transplantation

Long-term exposure to immunosuppressive therapy may exacerbate pre-existing medical comorbidities or result in the development of new chronic medical conditions after lung transplantation. This article focuses on common nonallograft complications with the highest impact on short- and long-term outcomes after transplantation. These include diabetes mellitus, hypertension, dyslipidemia, kidney disease (acute and chronic), and malignancy. We discuss evidence-based strategies for the prevention, diagnosis, and management of these nonallograft complications in this article.

Recommendation on an updated standardization of serum magnesium reference ranges

PURPOSE

Serum magnesium is the most frequently used laboratory test for evaluating clinical magnesium status. Hypomagnesemia (low magnesium status), which is associated with many chronic diseases, is diagnosed using the serum magnesium reference range. Currently, no international consensus for a magnesemia normal range exists. Two independent groups designated 0.85 mmol/L (2.07 mg/dL; 1.7 mEq/L) as the low cut-off point defining hypomagnesemia. MaGNet discussions revealed differences in serum magnesium reference ranges used by members' hospitals and laboratories, presenting an urgent need for standardization.

METHODS

We gathered and compared serum magnesium reference range values from our institutions, hospitals, and colleagues worldwide.

RESULTS

Serum magnesium levels designating "hypomagnesemia" differ widely. Of 43 collected values, only 2 met 0.85 mmol/L as the low cut-off point to define hypomagnesemia. The remainder had lower cut-off values, which may underestimate hypomagnesemia diagnosis in hospital, clinical, and research assessments. Current serum magnesium reference ranges stem from "normal" populations, which unknowingly include persons with chronic latent magnesium deficit (CLMD). Serum magnesium levels of patients with CLMD fall within widely used "normal" ranges, but their magnesium status is too low for long-term health. The lower serum magnesium reference (0.85 mmol/L) proposed specifically prevents the inclusion of patients with CLMD.

CONCLUSIONS

Widely varying serum magnesium reference ranges render our use of this important medical tool imprecise, minimizing impacts of low magnesium status or hypomagnesemia as a marker of disease risk. To appropriately diagnose, increase awareness of, and manage magnesium status, it is critical to standardize lower reference values for serum magnesium at 0.85 mmol/L (2.07 mg/dL; 1.7 mEq/L).

Hypomagnesemia after heart transplantation or left ventricular assist device implant for end-stage heart failure

BACKGROUND

Patients with advanced heart failure undergoing heart transplant (HTx) or left ventricular assist device (LVAD) implant are at high risk of magnesium deficiency, that may favor development of diabetes. We aimed to comparatively assess prevalence and correlates of hypomagnesemia during cardiac rehabilitation between 51 HTx and 46 LVAD recipients.

METHODS AND RESULTS

We measured serum magnesium and correlated it to clinical and laboratory findings upon admission (T₁ ) and at discharge (T2) from cardiac rehabilitation. Among LVAD, magnesium levels increased from admission to discharge. Among HTx, magnesium concentrations were below normal in 33% and 47% at T₁ and T₂ , respectively, and decreased from admission to discharge. HTx on tacrolimus showed greater decreases in magnesium and increases in glucose levels than those on cyclosporine. Magnesium levels were inversely associated with >15 mg/dL increased glucose concentrations between T₂ and T₁ (HR 0.373, 95% CI 0.154-0.903, P = .029) after adjustment for pre-existing diabetes, insulin resistance markers, calcineurin inhibitors (cyclosporine/tacrolimus), prednisone doses, and magnesium supplementation.

CONCLUSION

Hypomagnesemia is rare in LVAD recipients, but common within 1 month from HTx, worsens during rehabilitation, despite immunosuppression tapering and magnesium supplements, and is independently associated to increasing glucose levels. Studies evaluating whether correcting hypomagnesemia improves outcome are warranted.