Low pre-transplant adiponectin multimers are associated with adverse allograft outcomes in kidney transplant recipients a 3-year prospective study

Adiponectin/leptin ratio as a predictor of acute rejection in early post-transplant period in patients after kidney transplantation

Introduction

Adipokines are largely involved in the regulation of immune system activity. While leptin is the main pro-inflammatory marker of adipose tissue, adiponectin is characterized by anti-inflammatory effects. The aim of our study was to determine the risk of acute graft rejection in protocol biopsy depending on the adiponectin/leptin (A/L) ratio in patients after kidney transplantation (KT).

Materials and methods

A total of 104 patients were included in the prospective analysis, in whom the levels of adipokines were examined pre-transplant, in the 3rd month after KT and the A/L ratio was calculated. In the 3rd month after KT, all patients underwent protocol biopsy of the graft and examination of donor-specific antibodies (DSA) using the Luminex method.

Results

After adjusting for differences in the basic characteristics of the donor and recipient, we identified a subgroup with A/L ratio < 0.5 pre-transplant [HR 1.6126, (P = 0.0133)] and 3 months after KT [HR 1.3150, (P = 0.0172)] as independent risk factor for acute graft rejection. In the subsequent specification of the rejection episode, we identified the risk ratio A/L < 0.5 before KT [HR 2.2353, (P = 0.0357)] and 3 months after KT [HR 3.0954, (P = 0.0237)] as independent risk factor for the development of acute humoral rejection with DSA positivity.

Conclusion

This is the first study to investigate the relationship between A/L ratio and immunological risk in terms of the development of rejection changes in patients after KT. In our study, we found that A/L ratio < 0.5 is an independent risk factor for the development of acute humoral rejection and de novo DSA production in the third month after KT.

Adiponectin is unrelated to kidney function or injury markers in renal transplant recipients: A one-year follow-up study

BACKGROUND

Adiponectin (ADPN) is a biologically active cytokine produced by adipose tissue. This protein exhibits anti-inflammatory, antioxidant, antifibrotic, and insulin-sensitizing properties. As ADPN is primarily eliminated by the kidneys, it is a potential biomarker of chronic kidney disease progression. This study aimed to analyze the fluctuations in ADPN levels after kidney transplantation during a one-year follow-up and to compare them to significant renal (eGFR, NGAL) and metabolic (insulin, glucose, lipids, HOMA-IR) markers.

METHODS

Insulin, ADPN, NGAL, and basic biochemical parameters were evaluated in 51 healthy controls and 39 patients right before kidney transplantation and at five time points following transplantation (5-7 days, one month, three months, six months, and twelve months).

RESULTS

Mean ADPN levels dropped significantly right after transplantation (from 35.449 to 30.920 µg/ml, p = 0.001) and decreased gradually over a year. From the third month after the transplantation, ADPN levels were comparable to healthy individuals. At the pre-transplant time point, ADPN correlated only with insulin (r = -0.60, p < 0.001) and HOMA-IR (r = -0.55, p < 0.001). At the timepoints after transplantation, ADPN correlated only with NGAL at three months (r = -0.70, p = 0.048). The correlation of ADPN with HOMA-IR found at pre-transplant was not significant at any post-transplant time point, but at one and three months after transplant, the correlations reached a borderline significance (p = 0.07 and p = 0.08, respectively).

CONCLUSIONS

Successful kidney transplantation is followed by a gradual and significant ADPN decrease. In pre- and post-transplant patients, ADPN is unrelated to kidney function defined by GFR, but to glucose metabolism. Most of the analyzed metabolic and kidney parameters, apart from NGAL, stabilize within three months after transplantation.

Weight gain post-heart transplantation is associated with an increased risk for allograft vasculopathy and rejection

OBJECTIVE

Obesity and overweight are associated with an increased risk for cardiovascular disease. Since fat mass (FM) and fat-free mass (FFM) both contribute to total body weight (TBW), we characterized the post-heart transplantation (HT) change in TBW and its implications for outcomes.

METHODS

Post-HT changes in TBW, FM, and FFM were reviewed for 211 HT patients assessed during 1997-2017. Endpoints included cardiac allograft vasculopathy (CAV) and rejection.

RESULTS

Median TBW increased by 7.3% at 1 year, with a significant rise in the obese category (28% vs. 13%, p < 0.001) and with FM versus FFM making the main contribution (23% vs. 3%, p < 0.001). When patients were divided according to median TBW change ("high" vs. "low"), Kaplan-Meier analysis showed that 10-year freedom from CAV (log-rank p < 0.005) and rejection (log-rank p < 0.01) was significantly higher for the "low" TBW change group. Consistently, multivariable analyses showed that the "high" group was independently associated with significant 3.5-fold and 4.2-fold increased risks for CAV (95% CI 1.4-8.7, p = 0.01) and rejection (95% CI 1.2-15.4, p = 0.03), respectively.

CONCLUSIONS

Weight gain, contributed mostly by FM, is independently associated with an increased risk for CAV and rejection. Follow-up emphasis should be placed on weight gain and preventative measures.

Adipocytokines in renal transplant recipients

In the last two decades, perceptions about the role of body fat have changed. Adipocytes modulate endocrine and immune homeostasis by synthesizing hundreds of hormones, known as adipocytokines. Many studies have been investigating the influences and effects of these adipocytokines and suggest that they are modulated by the nutritional and immunologic milieu. Kidney transplant recipients (KTRs) are a unique and relevant population in which the function of adipocytokines can be examined, given their altered nutritional and immune status and subsequent dysregulation of adipocytokine metabolism. In this review, we summarize the recent findings about four specific adipocytokines and their respective roles in KTRs. We decided to evaluate the most widely described adipocytokines, including leptin, adiponectin, visfatin and resistin. Increasing evidence suggests that these adipocytokines may lead to cardiovascular events and metabolic changes in the general population and may also increase mortality and graft loss rate in KTRs. In addition, we present findings on the interrelationship between serum adipocytokine levels and nutritional and immunologic status, and mechanisms by which adipocytokines modulate morbidity and outcomes in KTRs.

Hypoadiponectinemia correlates with arterial stiffness in kidney transplantation patients

BACKGROUND

Adiponectin is a fat-derived hormone produced and secreted exclusively by adipocytes that have anti-atherosclerotic effects. The aim of this study was to evaluate the relationship between fasting serum adiponectin levels and arterial stiffness among kidney transplant (KT) patients.

METHODS

Fasting blood samples were obtained from 69 KT patients. Brachial-ankle pulse wave velocity (baPWV) was measured in the right or left brachial artery to the ankle segments using an automatic pulse wave analyzer. Plasma adiponectin levels were measured using a commercial enzyme-linked immunosorbent assay kit. Left or right baPWV values of >14.0 m/s were used to define the high arterial stiffness group.

RESULTS

Thirty-five KT patients (35/69; 50.7 %) were defined in high arterial stiffness group. Diabetes (P = 0.013), smoking (P = 0.001), KT duration (P < 0.001), body weight (P = 0.013), waist circumference (P = 0.013), body mass index (P = 0.001), fasting glucose (P = 0.013), systolic blood pressure (P < 0.001), diastolic blood pressure (P = 0.008), and pulse pressure (P = 0.003) were higher, while serum adiponectin level (P = 0.004) was lower in high arterial stiffness group compared with low arterial stiffness group. Multivariate logistic regression analysis showed that adiponectin (odds ratio 0.90, 95 % confidence interval 0.81-0.99, P = 0.034) was still the independent predictors of arterial stiffness among the KT patients.

CONCLUSION

Serum fasting adiponectin level was inversely associated with arterial stiffness among KT patients.

Increased recipient body mass index is associated with acute rejection and other adverse outcomes after kidney transplantation

BACKGROUND

Outcomes of kidney transplant recipients with increased body mass index (BMI) remain controversial. We studied the relationship between BMI and clinically relevant outcomes among kidney transplant recipients at a large center.

METHODS

We performed an observational cohort study of all recipients of kidney transplants at our center from January 1, 2000 to December 31, 2010 to determine if increased BMI at transplantation is associated with adverse outcomes, including delayed graft function and biopsy-proven acute rejection (BPAR). Recipient BMI was categorized as <20, 20 to 24.9 (reference), 25 to 29.9, 30 to 34.9, and ≥35 kg/m. Potential confounders were included in logistic and Cox proportional hazards models.

RESULTS

A total of 1151 patients were studied. Recipient BMI of 30 to 34.9 and ≥35 kg/m were associated with an increased risk of delayed graft function (odds ratio [95% confidence interval [CI], 1.92 [1.16-3.19] and 4.49 [2.24-9.00], respectively). BMI≥35 kg/m was also associated with an increased risk of BPAR (hazard ratio [HR; 95% CI], 2.43 [1.48-3.99]), all-cause graft failure (HR [95% CI], 1.97 [1.09-3.56]), and death-censored graft failure (HR [95% CI], 2.43 [1.07-5.51]). Adjustment for acute rejection as a time-varying covariate significantly attenuated the association with graft failure endpoints. There was no significant relation between BMI and death with graft function.

CONCLUSIONS

Increased BMI at kidney transplantation is a predictor of adverse outcomes, including BPAR. The role of pretransplantation weight reduction in improving graft and patient outcomes requires further study.

Evolving concepts and treatment strategies for cardiac allograft vasculopathy

OPINION STATEMENT

The central event in the development of allograft vasculopathy is the inflammatory response to immune-mediated and nonimmune-mediated endothelial damage. This response is characterized by the release of inflammatory cytokines, upregulation of cell-surface adhesion molecules, and subsequent binding of leukocytes. Growth factors stimulate smooth muscle cell proliferation and circulating progenitor cells are recruited to sites of arterial injury leading to neointima formation. Because of its diffuse nature, intravascular ultrasound is more sensitive than angiography for early diagnosis. Proliferation signal inhibitors (PSIs) have the capacity to slow vasculopathy progression by inhibiting smooth muscle cell proliferation, but its side effects profile makes its use as a first line agent difficult. Retransplantation is still the only definitive therapy but is available only in selected cases. The current hope is that immunomodulation at the time of transplant could induce long-term tolerance and graft accommodation, leading to less vasculopathy.

The adipose tissue as an endocrine organ

During the past 2 decades, results of both basic science and clinical studies have changed the physicians' views about adipocyte pathophysiology. Since leptin was discovered in 1994, white adipose tissue was recognized as an endocrine organ and an important source of biologically active substances with local and/or systemic action called adipokines. Inappropriate secretion of several adipokines by the excessive amount of white adipose tissue seems to participate in the pathogenesis of obesity-related pathologic processes including endothelial dysfunction, inflammation, atherosclerosis, diabetes mellitus, and chronic kidney disease. In this review endocrine action of selected adipokines (mainly leptin and adiponectin) in the context of kidney diseases is discussed. Specifically, the role of these adipokines in malnutrition, chronic kidney disease progression, and pathogenesis of cardiovascular complications is presented.

Adiponectin in inflammatory and immune-mediated diseases

Circulating levels of adiponectin (APN) are reduced in obesity and associated comorbidities, with inflammation playing an important role in downregulating APN production. In contrast to obesity and metabolic disease, elevated systemic and local levels of APN are present in patients with inflammatory and immune-mediated diseases, including autoimmune and pulmonary conditions, heart and kidney failure, viral hepatitis, organ transplantation and perhaps critical illness. A positive association between inflammation and APN is usually reported in inflammatory/immune pathologies, in contrast with the negative correlation typical of metabolic disease. This review discusses the role of APN in modulation of inflammation and immunity and the potential mechanisms leading to increased levels of APN in inflammatory/immune diseases, including modification of adipose tissue physiology; relative contribution of different tissues and adipose depots; hormonal, pharmacological, nutritional and life style factors; the potential contribution of the microbiota as well as the role of altered APN clearance and release from T-cadherin-associated tissue reservoirs. Potential reasons for some of the apparently contradictory findings on the role of APN as a modulator of immunity and inflammation are also discussed, including a comparison of types of recombinant APN used for in vitro studies and strain-dependent differences in the phenotype of APN KO mice.