Hyperlipidemia and Allograft Rejection

Minimizing Metabolic and Cardiac Risk Factors to Maximize Outcomes After Liver Transplantation

Cardiovascular disease (CVD) is a leading complication after liver transplantation and has a significant impact on patients' outcomes posttransplant. The major risk factors for post-liver transplant CVD are age, preexisting CVD, nonalcoholic fatty liver disease, chronic kidney disease, and metabolic syndrome. This review explores the contemporary strategies and approaches to minimizing cardiometabolic disease burden in liver transplant recipients. We highlight areas for potential intervention to reduce the mortality of patients with metabolic syndrome and CVD after liver transplantation.

The Biological Parallels Between Atherosclerosis and Cardiac Allograft Vasculopathy: Implications for Solid Organ Chronic Rejection

Atherosclerosis and solid organ chronic rejection are pervasive chronic disease states that account for significant morbidity and mortality in developed countries. Recently, a series of shared molecular pathways have emerged, revealing biological parallels from early stages of development up to the advanced forms of pathology. These shared mechanistic processes are inflammatory in nature, reflecting the importance of inflammation in both disorders. Vascular inflammation triggers endothelial dysfunction and disease initiation through aberrant vasomotor control and shared patterns of endothelial activation. Endothelial dysfunction leads to the recruitment of immune cells and the perpetuation of the inflammatory response. This drives lesion formation through the release of key cytokines such as IFN-y, TNF-alpha, and IL-2. Continued interplay between the adaptive and innate immune response (represented by T lymphocytes and macrophages, respectively) promotes lesion instability and thrombotic complications; hallmarks of advanced disease in both atherosclerosis and solid organ chronic rejection. The aim of this study is to identify areas of overlap between atherosclerosis and chronic rejection. We then discuss new approaches to improve current understanding of the pathophysiology of both disorders, and eventually design novel therapeutics.

Value of blood lipid in predicting graft dysfunction after organ and tissue transplantation: A study of Mendelian randomization

Background

While immunosuppressive regimens have improved outcomes in solid organ transplantation, non-immune factors have also been identified as contributors to graft prognosis. Age, gender, hormones, heredity, and other diseases have been recognized to affect organ transplantation. However, the causal relationship between blood lipids and graft dysfunction remains unverified in human clinical investigations. In this study, we employed two-sample Mendelian randomization (MR) to examine the causality between different types of blood lipids and graft dysfunction following organ and tissue transplantation.

Methods

We conducted a two-sample MR study using available genome-wide association summary data from the online database MRBASE (http://app.mrbase.org/), which encompasses over 11 billion associations between genetic factors and health-related outcomes, enabling researchers to explore various potential determinants of poor health. The exposure factors included four types of blood lipids: high-density lipoprotein, low-density lipoprotein, cholesterol, and triglycerides. For each exposure factor, three databases were selected for analysis. The outcome factor was the failure and rejection of transplanted organs and tissues. All databases consisted of European population samples, without specific subgroups. The related studies were conducted between 2016 and 2022, and the "TwoSampleMR" R package was employed for variant selection.

Results

A total of 13 sample groups were collected and analyzed. The results revealed a causal association between blood lipids and graft dysfunction following organ and tissue transplantation. Specifically, the two-sample MR analysis confirmed that low-density lipoprotein and cholesterol levels were significant risk factors for increased graft dysfunction risk after transplantation. Moreover, high-density lipoprotein potentially reduced the risk of allograft dysfunction, while triglycerides possibly elevated the risk.

Conclusions

Our recent study provides the initial confirmation that blood lipids may initiate causal pathological processes leading to graft dysfunction after organ and tissue transplantation.

Hyperglycemia and Hyperlipidemia with Kidney or Liver Transplantation: A Review

Although solid organ transplantation in persons with diabetes mellitus is often associated with hyperglycemia, the risk of hyperlipidemia in all organ transplant recipients is often underestimated. The diagnosis of diabetes often predates transplantation; however, in a moderate percentage of allograft recipients, perioperative hyperglycemia occurs triggered by antirejection regimens. Post-transplant prescription of glucocorticoids, calcineurin inhibitors and mTOR inhibitors are associated with increased lipid concentrations. The existence of diabetes mellitus prior to or following a liver transplant is associated with shorter times of useful allograft function. A cycle involving Smad, TGF beta, m-TOR and toll-like receptors has been identified in the contribution of rejection and aging of allografts. Glucocorticoids (prednisone) and calcineurin inhibitors (cyclosporine and tacrolimus) induce hyperglycemia associated with insulin resistance. Azathioprine, mycophenolate and prednisone are associated with lipogenesis. mTOR inhibitors (rapamycin) are used to decrease doses of atherogenic agents used for immunosuppression. Post-transplant medication management must balance immune suppression and glucose and lipid control. Concerns regarding rejection often override those relative to systemic and organ vascular aging and survival. This review focuses attention on the underlying mechanism of relationships between glycemia/lipidemia control, transplant rejection and graft aging.

Cardiac allograft vasculopathy: current review and future research directions

Cardiac allograft vasculopathy (CAV) is a pathologic immune-mediated remodelling of the vasculature in transplanted hearts and, by impairing perfusion, is the major cause of late graft loss. Although best understood following cardiac transplantation, similar forms of allograft vasculopathy occur in other vascularized organ grafts and some features of CAV may be shared with other immune-mediated vasculopathies. Here, we describe the incidence and diagnosis, the nature of the vascular remodelling, immune and non-immune contributions to pathogenesis, current therapies, and future areas of research in CAV.

The Underutilization, Adverse Reactions and Efficacy of Statins after Liver Transplant: A Meta-Analysis and Systematic Review

(1) Background: Treatment of dyslipidemia via statin therapy in the non-liver transplant (LT) population is associated with a mortality benefit; however, the impact of statin therapy in post-LT population is not well-defined. This meta-analysis seeks to investigate the safety and efficacy of statin therapy in post-LT patients. (2) Methods: A systematic literature search on Medline and EMBASE database was conducted. A single-arm proportional meta-analysis and conventional pair-wise meta-analysis were performed to compare different outcomes with a random effects model. (3) Results: A total of 11 studies were included in this study, with 697 LT recipients identified to be on statin therapy. Statins were underutilized with only 32% (95% CI: 0.15–0.52) of 1094 post-LT patients on therapy. The incidence of adverse events of 14% (95% CI: 0.05–0.25) related to statin therapy was low. A significant mortality benefit was noted in patients on statin therapy with HR = 0.282 (95% CI: 0.154–0.517, p < 0.001), and improved lipid profiles post LT. The use of statins also significantly decreased odds of graft rejection (OR = 0.33; 95% CI: 0.15–0.73) and hepatocellular carcinoma (HCC) recurrence (HR = 0.32, 95% CI: 0.11–0.89). (4) Conclusions: Statin therapy is safe and efficacious in post-LT patients. Future studies to evaluate the effects of interactions between statins and immunosuppressant therapy are warranted.

Cardiac allograft vasculopathy: Differences of absolute and relative intimal hyperplasia in children versus adults in optical coherence tomography

BACKGROUND

Intracoronary imaging enables an early detection of intimal changes. To what extend the development of absolute and relative intimal hyperplasia in intracoronary imaging differs depending on age and post-transplant time is not known.

METHODS

Aim of our retrospective study was to compare findings between 24 pediatric (cohort P) and 21 adult HTx patients (cohort A) using optical coherence tomography (OCT) at corresponding post-transplant intervals (≤5 years: P1 (n = 11) and A1 (n = 10); >5 and ≤ 10 years: P2 (n = 13) and A2 (n = 11),. Coronary intima thickness (IT), media thickness (MT) and intima to media ratio (I/M) were assessed per quadrant. Maximal IT >0.3 mm was considered absolute, I/M > 1 relative intimal hyperplasia.

RESULTS

Compared to A1, I/M was significantly higher in P1 (maximal I/M: P1: 5.41 [2.81-13.39] vs. A1: 2.30 [1.55-3.62], p = 0.005), whereas absolute IT values were comparable. In contrast, I/M was comparable between P2 and A2, but absolute IT were significantly higher in A2 (maximal IT: P2: 0.16 mm [0.11-0.25] vs. A2: 0.40 mm [0.30-0.71], p < 0.001). A2 presented with higher absolute IT (maximal: A1: 0.16 mm [0.12-0.44] vs. A2: 0.40 mm [0.30-0.71], p = 0.02) and I/M (maximal I/M A1: 2.30 [1.55-3.62] vs. A2: 3.79 [3.01-5.62], p = 0.04).

CONCLUSION

Our results suggest an age- and time-dependent difference in the prevalence of absolute and relative intimal hyperplasia in OCT, with an early peak in children and a progressive increase in adults.

A Triple-Blind Randomized Controlled Trial on Impacts of Pioglitazone on Oxidative Stress Markers in Diabetic Kidney Transplant Recipients

Background: Oxidative stress as a major mediator of adverse outcomes in kidney transplant recipients who are prone to oxidative stress-mediated injury by pre-transplant and post-transplant conditions. Objectives: The purpose of this study was to assess the effects of Pioglitazone on oxidative stress biomarkers and blood glucose control in diabetic patients receiving insulin after kidney transplantation. Methods: In a triple-blind randomized placebo-controlled trial, sixty-two kidney transplanted diabetic patients (40 men and 24 women) were followed for 4 months after randomly assigned to the placebo group and Pioglitazone group (30 mg/d). All of the patients continued their insulin therapy irrespective of the group that they were assigned to evaluate the effects of the addition of pioglitazone on blood glucose and oxidative stress biomarkers, Malondialdehyde (MDA) and total protein carbonyls (TPC) serum levels. Results: At baseline, there were no statistically significant differences in glycemic control levels and oxidative markers between the two groups. After 4 months of intervention, a significant improvement occurred in Hemoglobin A1c (HBA1c) in the Pioglitazone group. The changes of HBA1c during 4 months of follow up in the Pioglitazone group show improvement in glucose control were as HBA1c in the placebo group increased by 0.3% (P = 0.0001). Moreover, at the end of the study, the MDA level was significantly lower in the Pioglitazone group (P < 0.0001, 1.22 - 3.90). Regarding the serum level of TPC, the changes were not statistically different at baseline and also at the end of the study between two groups. Conclusions: Administration of Pioglitazone in addition to insulin in diabetic kidney transplant patients not only improved glycemic control (evidenced by HBA1c) but also significantly decreased oxidative stress markers such as MDA.