Metformin therapy reduces the risk of malignancy after heart transplantation

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.

Diabetes medication following heart transplantation: a focus on novel cardioprotective therapies-a joint review from endocrinologists and cardiologists

There is accumulating evidence that novel glucose-lowering agents infer potent cardiovascular and renal benefits. Therefore, it is imperative to reassess the management of post-transplant diabetes mellitus and consider the role of newer agents. With improved transplant-related survival and high prevalence of post-transplant diabetes, management of long-term complications such as diabetes are increasingly important. There are limited guidelines to assist in choice of appropriate agents after solid organ transplantation. Traditional therapies including insulin and sulfonylureas may still have a role; however, other agents should be considered prior. The evidence of novel glucose-lowering agents in post-transplant care is limited, and most studies have focused on kidney transplant recipients. While there are some parallels between renal and cardiac transplant recipients, the potential cardiovascular benefits, particularly on cardiac fibrosis are unique to cardiac transplantation. The treatment of diabetes, with a focus on additional cardiac and renal benefits, needs to be brought to the forefront of post-transplant care with incorporation of recent evidence outside of transplantation. The role for novel glucose-lowering agents in cardiac transplant recipients will be explored, with a summary of available evidence.

Diabetes Is an Independent Risk Factor for Cancer after Heart and/or Lung Transplantation

Background: De novo cancers are feared complications after heart or lung transplantation. Recent data suggest that diabetes mellitus (DM) might also be a risk factor for cancer. We hypothesized that transplanted diabetic patients are at greater risk of developing cancer compared to non-diabetic ones. Methods: We reviewed 353 patients post-heart and/or -lung transplantation from our center between October 1999 and June 2021. Patients with follow-up <180 days (n = 87) were excluded from the analysis. The remaining 266 patients were divided into patients who had preoperative DM (n = 88) or developed it during follow-up (n = 40) and patients without DM (n = 138). Results: The diabetic cohort showed higher rates of malignancies in all patients (30.33 vs. 15.97%, p = 0.005) and in the matched population (31.9 vs. 16.1%, p < 0.001). There were also significantly more solid tumors (17.9 vs. 9.4%, p = 0.042; matched: 16.6 vs. 9.1%, p = 0.09) The presence of diabetes was associated with a 13% increased risk of cancer when compared to non-diabetic patients. New-onset post-transplant diabetes doubled the likelihood of cancer development. Conclusions: Pre-transplant diabetes mellitus increases the risk of cancer after heart and/or lung transplantation. However, new-onset diabetes after transplantation is associated with a much greater cancer risk. This information is relevant for screening during follow-up.

Third dose of the BNT162b2 vaccine in heart transplant recipients: Immunogenicity and clinical experience

BACKGROUND

The repeated waves of the COVID-19 pandemic have highlighted the necessity to optimize vaccine responses in immunocompromised populations. We investigated the safety and immunogenicity of a third, booster, dose of the Pfizer BNT162b2 vaccine in heart transplant (HT) patients.

METHODS

The cohort comprised 96 adult HT patients who received a third homologous dose of the BNT162b2 vaccine 168 days after the second dose. The vaccine-induced antibody responses of both receptor-binding domain (RBD) IgG and neutralizing antibodies were assessed in all patients, with a positive antibody response being defined as the presence of either IgG anti-RBD or neutralizing antibodies. For a subset of patients, T cell response was also studied.

RESULTS

The third dose was associated with a low rate of adverse events, mostly mild pain at the injection site. No serious adverse events were recorded, and there were no episodes of rejection. At 18 days following the third dose of the vaccine, the positive antibody response increased from 23% to 67%, with a corresponding increase in neutralizing capacity. The third dose elicited SARS-CoV-2 neutralization titers >9-fold and IgG anti-RBD antibodies >3-fold of the range achieved after the two primary doses. Mycophenolate use, lower eGFR and higher C-reactive protein were independently associated with a reduced likelihood of generating an immune response. Importantly, a specific T-cell response following the third dose was evident in the majority of transplant recipients.

CONCLUSIONS

An homologous third booster dose of the BNT162b2 vaccine gave overall consistent tolerability and a good safety profile, while eliciting humoral and cellular immune responses.

Impact of metformin on malignancy in solid organ transplantation

Malignancy after solid organ transplant is a common occurrence that is associated with increased morbidity and mortality. Literature in the general diabetic population has identified possible antineoplastic properties of metformin. This retrospective study aims to determine if metformin results in a malignancy risk reduction in a cohort of diabetic kidney, liver, and heart transplant recipients. The population included transplant recipients without use of metformin at any time point (DMO arm, n = 147) and those with use of metformin (DMM arm, n = 172); the two arms were matched based on organ type and transplant date prior to application of exclusion criteria. Recipients with prior malignancy, malignancy before diabetes diagnosis, and metformin duration <30 days were excluded. The primary endpoint of malignancy first occurrence post-transplant was not found to be statistically significant at 1, 5, 10, and 15 years. In the subgroup of heart transplant recipients, there was a significant reduction in malignancy at 15 years post-transplant. Older age and Caucasian race were identified as significant risk factors for malignancy, while never smoker was a protective factor. Metformin use in this solid organ transplant cohort was not found to significantly reduce malignancy risk compared to use of other anti-diabetic agents.

The right place for metformin today

Metformin is the most widely used glucose lowering drug worldwide in the treatment of patients with type 2 diabetes, since we have experience with this drug for more than 60 years about the efficacy and safety. Metformin is very effective in HbA1c lowering associated with some weight loss, but does not increase risk for hypoglycemia. At the moment all guidelines in the world recommend to use metformin in monotherapy in patients with newly diagnosed diabetes or in combination with other antidiabetic drugs with documented CV (and renal) benefit in cardiovascular outcome trials (CVOT). Although a randomized placebo controlled CVOT with metformin is lacking, many observational studies in patients with coronary heart disease, heart failure and chronic kidney disease have demonstrated consistent beneficial effects. A recent metanalysis of 26 observational studies including 815 839 patients showed that metformin use was associated with a significantly lower rate of all-cause mortality (HR: 0.74; 95% CI: 0.68-0.81). Whether this very consistent reduction of all-cause mortality is related to the incidence/outcome of several cancers has still to be investigated. In the future early combination therapy of metformin e.g. with SGLT-2 inhibitors should be more often used.

Metformin therapy in patients with diabetes mellitus is associated with a reduced risk of vasculopathy and cardiovascular mortality after heart transplantation

Background

Cardiac allograft vasculopathy (CAV) is a major cause of morbidity and mortality following heart transplantation (HT). Reduced cardiovascular mortality and morbidity have been reported in non-HT patients treated with metformin. Given the high prevalence of type 2 diabetes mellitus (T2DM) in HT patients, we investigated the association between metformin therapy and cardiovascular outcomes after HT.

Methods

The study population comprised 103 DM patients who had undergone HT between 1994 and 2018 and were prospectively followed-up. We excluded from the study patients with type 1 diabetes mellitus. Fifty-five HT patients (53%) in the cohort were treated with metformin. Clinical data were recorded on prospectively designed forms. The primary outcomes included CAV, survival, and the combined end-point of CAV or cardiovascular mortality.

Results

Kaplan–Meier survival analysis showed that the CAV rate at 20 years of follow-up was lower in DM patients treated with metformin than in those who were not (30 vs. 65%; log-rank p = 0.044). Similarly, the combined risk of CAV or cardiovascular mortality was lower in the metformin-treated patients than in those not receiving metformin (32 vs. 68%; log rank p = 0.01). Consistently, multivariate analysis adjusted for age and comorbidities showed that metformin therapy was independently associated with a significant 90% reduction (95% confidence interval 0.02–0.46, p = 0.003) in the risk for the development of CAV, and a 91% reduction (95% confidence interval 0.02–0.42; p = 0.003) in the risk for CAV or cardiovascular mortality.

Conclusions

In diabetic HT patients, metformin therapy is independently associated with a significant reduction in the long-term risk for CAV and the combined end-point of CAV or cardiovascular mortality after HT.

The change of immunosuppressive regimen from calcineurin inhibitors to mammalian target of rapamycin (mTOR) inhibitors and its effect on malignancy following heart transplantation

Malignancy is a significant cause of mortality after organ transplantation. There is an increased rate of malignancy following heart transplantation (HTx) compared to the general population and other organ transplant recipients. Post-HTx patients with a history of malignancy are also at a higher risk of developing new malignancies or exacerbation of their existing malignancies. Mammalian target of Rapamycin inhibitors (mTORIs) are newly introduced immunosuppressive drugs with a unique mechanism of action. By changing the immunosuppressive regimen from classic drugs, especially calcineurin inhibitors (CNIs) to mTORIs, the rate of developing de novo malignancies and the relapse of former malignancies is significantly reduced. However, issues like allograft function, total surveillance of patients, and post-transplantation complications should be considered during the conversion of drug regimens utilizing CNIs to drug regimens employing mTORIs. We reviewed different post-heart transplant maintenance immunosuppressive regimens and their effect on post-HTx malignancies with a focus on mTORIs, compared safety against effectiveness, and gathered conclusions based on our review of the literature, which may lead clinicians to make a better evidence-based decision regarding post-HTx maintenance immunosuppressive drug regimens. Overall, CNI to mTORI conversion in post-HTx maintenance immunosuppressive drug regimens was associated with a reduced rate of developing malignancy in post-HTx patients. Furthermore, nephrotoxicity decreased significantly while using mTORIs in combination with lower doses of CNIs and the rejection rate was equivalent to CNI-only regimens. In conclusion, mTORI-based maintenance immunosuppressive drug regimens seem to be safe and beneficial when considering efficacy vs. adverse effects, and all-cause mortality rates are significantly lower in patients switched to mTORIs when compared to CNI recipients.

Pleiotropic Effects of Metformin on Cancer

Metformin (MTF) is a natural compound derived from the legume Galega officinalis. It is the first line antidiabetic drug for type 2 diabetes (T2D) treatment. One of its main antidiabetic effects results from the reduction of hepatic glucose release. First scientific evidence for the anticancer effects of MTF was found in animal research, published in 2001, and some years later a retrospective observational study provided evidence that linked MTF to reduced cancer risk in T2D patients. Its pleiotropic anticancer effects were studied in numerous in vitro and in vivo studies at the molecular and cellular level. Although the majority of these studies demonstrated that MTF is associated with certain anticancer properties, clinical studies and trials provided a mixed view on its beneficial anticancer effects. This review emphasizes the pleiotropic effects of MTF and recent progress made in MTF applications in basic, preclinical, and clinical cancer research.