Obesity and Its Impact on Transplantation and Alloimmunity

Health Care Provider Clustering Using Fusion Penalty in Quasi-Likelihood

There has been growing research interest in developing methodology to evaluate the health care providers' performance with respect to a patient outcome. Random and fixed effects models are traditionally used for such a purpose. We propose a new method, using a fusion penalty to cluster health care providers based on quasi-likelihood. Without any priori knowledge of grouping information, our method provides a desirable data-driven approach for automatically clustering health care providers into different groups based on their performance. Further, the quasi-likelihood is more flexible and robust than the regular likelihood in that no distributional assumption is needed. An efficient alternating direction method of multipliers algorithm is developed to implement the proposed method. We show that the proposed method enjoys the oracle properties; namely, it performs as well as if the true group structure were known in advance. The consistency and asymptotic normality of the estimators are established. Simulation studies and analysis of the national kidney transplant registry data demonstrate the utility and validity of our method.

Comparison of abdominal adipose tissue versus body mass index (BMI) as a predictor of complications and survival in liver transplantation

INTRODUCTION

Because of the obesity epidemic, more obese patients are on liver transplant (LT) waiting lists. The diseases associated with obesity may increase complications and limit survival after LT. However, there is no established measure or cut-off point to determine this impact and aid decision making. The aim of the present study is to evaluate obesity in patients undergoing LT via BMI and CT-based measurement of adipose tissue (AAT). These parameters will be used to predict the risk of postoperative complications and 5-year survival.

METHODS

A retrospective, single-center study was carried out at a tertiary Spanish hospital, including all patients who received LT between January 2012 and July 2019 (n = 164). The patients were adults who underwent LT using the 'piggyback' technique, preserving the recipient vena cava. Visceral adipose tissue (VAT) and BMI were calculated to examine correlations with postoperative complications and 5-year survival.

RESULTS

No significant association was found between postoperative complications by Comprehensive Complication Index, BMI, AAT/height, subcutaneous fat/height and VAT/height. Kaplan-Meier curves for 5-year survival compared LT recipients with BMI < 30.45 versus ≥30.45, with an estimated survival of 58.97 months versus 43.11 months, respectively (P < .001) (Fig. 3) and for LT recipients with an AAT/height <27.35 mm versus ≥27.35 mm, with an estimated survival of 57.69 months versus 46.34 months (P = .001).

CONCLUSIONS

This study does not show a higher rate of postoperative complications in obese patients. There is a significantly lower long-term survival in patients with AAT/height ≥27.35 mm and BMI ≥ 30.45. BMI is a valid estimate of obesity and is predictive of survival.

[The Role of the Anaesthesiologist in Liver Transplantation - Preoperative Evaluation]

Preoperative evaluation prior to listing for orthotopic liver transplantation (LT) requires a careful multidisciplinary approach with specialized teams including surgeons, hepatologists and anesthesiologists in order to improve short- and long-term clinical outcomes. Due to inadequate supply of donor organs and changing demographics, patients listed for LT have become older, sicker and share more comorbidities. As cardiovascular events are the leading cause for early mortality precise evaluation of risk factors is mandatory. This review focuses on the detection and management of coronary artery disease, cirrhotic cardiomyopathy, portopulmonary hypertension and hepatopulmonary syndrome in patients awaiting LT. Further insights are being given into scoring systems, patients with Acute-on-chronic-liver-failure (ACLF), frailty, NASH cirrhosis and into psychologic evaluation of patients with substance abuse.

The combinatorial effect of age and biological sex on alloimmunity and transplantation outcome

Both age and biological sex affect transplantation outcomes. We have recently shown in a large volume clinical analysis utilizing the SRTR data that graft survival is inferior in young female kidney transplant recipients. In this multi-factorial analysis, older female recipients presented with a trend towards improved transplant outcomes compared to both young female recipients and male recipients of any age. Those data supported by reports of those of others suggest that sex and age impact alloimmune responses both, individually and synergistically. Biological sex and hormone levels change throughout a lifetime with recognized effects on longevity in addition to an impact on the development and course of several disease preconditions. Detailed mechanisms of those sex and age-specific aspects have thus far been studied outside of transplantation. Effects on alloimmunity are largely unknown. Moreover, the combinatorial impact that both, biological sex and age have on transplant outcomes is not understood. Here, we summarize available data that analyze how age in combination with biological sex may shape alloimmune responses and affect transplant outcomes.

Microbiota-dependent and -independent effects of obesity on transplant rejection and hyperglycemia

Obesity is associated with dysbiosis and a state of chronic inflammation that contributes to the pathogenesis of metabolic diseases, including diabetes. We have previously shown that obese mice develop glucose intolerance, increased alloreactivity, and accelerated transplant rejection. In the present study, we investigated the influence of the microbiota on diet-induced obesity (DIO)-associated transplant rejection and hyperglycemia. Antibiotic treatment prolonged graft survival and reduced fasting glycemia in high-fat diet (HFD)-fed specific-pathogen-free (SPF) mice, supporting a role for the microbiota in promoting accelerated graft rejection and hyperglycemia induced by DIO. Further supporting a microbiota-dependent effect, fecal microbiota transfer from DIO SPF mice into germ-free mice also accelerated graft rejection when compared with lean mice-fecal microbiota transfer. Notably, HFD could be also detrimental to the graft independently from microbiota, obesity, and hyperglycemia. Thus, whereas HFD-associated hyperglycemia was exclusively microbiota-dependent, HFD affected transplant outcomes via both microbiota-dependent and -independent mechanisms. Importantly, hyperglycemia in DIO SPF mice could be reduced by the addition of the gut commensal Alistipes onderdonkii, which alleviated both HFD-induced inflammation and glucose intolerance. Thus, microbial dysbiosis can be manipulated via antibiotics or select probiotics to counter some of the pathogenic effects of obesity in transplantation.

Taurodeoxycholic acid and valine reverse obesity-associated augmented alloimmune responses and prolong allograft survival

Obesity initiates a chronic inflammatory network linked to perioperative complications and increased acute rejection rates in organ transplantation. Bariatric surgery is the most effective treatment of obesity recommended for morbidly obese transplant recipients. Here, we delineated the effects of obesity and bariatric surgery on alloimmunity and transplant outcomes in diet-induced obese (DIO) mice. Allograft survival was significantly shorter in DIO-mice. When performing sleeve gastrectomies (SGx) prior to transplantation, we found attenuated T cell-derived alloimmune responses resulting in prolonged allograft survival. Administering taurodeoxycholic acid (TDCA) and valine, metabolites depleted in DIO-mice and restored through SGx, prolonged graft survival in DIO-mice comparable with SGx an dampened Th1 and Th17 alloimmune responses while Treg frequencies and CD4+ T cell-derived IL-10 production were augmented. Moreover, in recipient animals treated with TDCA/valine, levels of donor-specific antibodies had been reduced. Mechanistically, TDCA/valine restrained inflammatory M1-macrophage polarization through TGR5 that compromised cAMP signaling and inhibited macrophage-derived T cell activation. Consistently, administering a TGR5 agonist to DIO-mice prolonged allograft survival. Overall, we provide novel insights into obesity-induced inflammation and its impact on alloimmunity. Furthermore, we introduce TDCA/valine as a noninvasive alternative treatment for obese transplant patients.

Undernutrition and Hypoleptinemia Modulate Alloimmunity and CMV-specific Viral Immunity in Transplantation

BACKGROUND

Immunological mechanisms linking undernutrition to infection and the alloimmune response are poorly understood in transplantation. We aimed to determine how undernutrition and hypoleptinemia impact T-cell allospecific and cytomegalovirus (CMV) viral-specific immunity in a murine model.

METHODS

Fed, fasted for 48 h (model of undernutrition), and fasted with leptin injections (leptin rescue), C57BL/6 mice received skin grafts from either C57BL/6 (syngeneic) or BALB/c (allogeneic) mice donors. Allograft rejection and survival were monitored. Fed, fasted, and leptin rescue C57BL/6 mice were inoculated with murine cytomegalovirus (mCMV). Mouse spleens were retrieved for T-cell flow cytometry analysis, mCMV DNA extraction, and quantitative polymerase chain reaction. Serum leptin levels were measured with ELISA.

RESULTS

Fasted mice had prolonged rejection-free and graft survival compared with fed mice (P = 0.0002 and P = 0.043). Leptin administration did not alter rejection-free survival or allograft failure. CD8+ central memory T cell and CD8+ effector T cell proportions were significantly lower in fasted mice receiving allogeneic skin transplants compared with fed mice (P = 0.0009 and P = 0.0015). Fasted mice had higher viral loads (P = 0.0028) and impaired mCMV-specific interferon-gamma-producing CD8+ T cells (P = 0.0007), which improved with leptin rescue (P = 0.032).

CONCLUSIONS

Undernutrition and its associated hypoleptinemia correlated with impaired allospecific and viral-specific immunities. Leptin administration decreased mCMV viral burden and increased mCMV-specific T-cell immunity, however, it did not increase rejection or worsen graft survival in complete major histocompatibility complex-mismatched skin allografts. Leptin may be a potential adjunctive therapy for CMV viremia in undernourished transplant recipients.

Obesity-related IL-18 Impairs Treg Function and Promotes Lung Ischemia-reperfusion Injury

RATIONALE

Primary graft dysfunction (PGD) is a severe form of acute lung injury, leading to increased early morbidity and mortality after lung transplantation. Obesity is a major health problem, and recipient obesity is one of the most significant risk factors for developing PGD.

OBJECTIVES

We hypothesized that T-regulatory (Treg) cells are able to dampen early ischemia/reperfusion events and thereby decrease risk of PGD, whereas that action is impaired in obese recipients.

METHODS

We evaluated Treg, T cells and inflammatory markers, plus clinical data, in 79 lung and 41 liver or kidney transplant recipients and studied two groups of mice on high fat diet (HFD), who developed ("inflammatory" HFD) or not ("healthy" HFD) low-grade inflammation with decreased Treg function.

RESULTS

We identified increased levels of IL-18 as a previously unrecognized mechanism that impairs Treg suppressive function in obese individuals. IL-18 decreases levels of FOXP3, the key Treg transcription factor, decreases FOXP3 di- and oligomerization and increases the ubiquitination and proteasomal degradation of FOXP3. IL-18-treated Tregs or Treg from obese mice fail to control PGD, while IL-18 inhibition ameliorates lung inflammation. The IL-18 driven impairment in Treg suppressive function pre-transplant was associated with increased risk and severity of PGD in clinical lung transplant recipients.

CONCLUSION

Obesity-related IL-18 induces Treg dysfunction that may contribute to the pathogenesis of PGD. Evaluation of Treg suppressive function along with IL-18 levels may serve as screening tools to identify pre-transplant obese recipients with increased risk of PGD.

Rapamycin delays allograft rejection in obese graft recipients through induction of myeloid-derived suppressor cells

Obesity has become a relevant problem in transplantation medicine with steadily increasing numbers of obese graft recipients. However, the effect of immunomodulatory drugs on transplant-related outcomes among obese patients are unknown. Therefore, we evaluated the impact of rapamycin on allograft rejection and alloimmune response in a murine model of diet-induced obesity and fully-mismatched skin transplantation. Rapamycin significantly delayed allograft rejection in obese recipient mice compared to treated lean mice (14.5 days vs. 10.7 days, p = 0.005). Treatment with rapamycin increased frequencies of monocytic myeloid-derived suppressor cells (M-MDSCs), augmented the immunosuppressive activity of M-MDSCs on T cells through indoleamine 2,3-dioxygenase pathway and shifted CD4⁺T cells towards regulatory T cells in obese graft recipients. In summary, our results demonstrate that rapamycin delays allograft rejection in obese graft recipients by enhancing suppressive immune cell function and shifting immune cell subsets towards anti-inflammatory conditions.

Impact of high body mass index on allograft outcomes in kidney transplant recipients with presensitization to human leukocyte antigen

Background

This study aimed to investigate whether high body mass index (BMI) and presensitization to human leukocyte antigen (HLA) in kidney transplant recipients (KTRs) affected allograft outcomes.

Methods

From January 2010 to December 2018, 1,290 kidney transplantations (KTs) were performed at the Seoul St Mary’s Hospital. Of these, 682 cases of ABO-compatible living donor KT patients were enrolled. They were divided into four groups (low BMI-non-sensitized, high BMI-non-sensitized, low BMI-sensitized, and high BMI-sensitized) according to the median BMI value (22.7 kg/m²) and HLA presensitization status (anti-HLA antibody mean fluorescence intensity > 3,000). Short-term and long-term allograft outcomes were compared between groups.

Results

In the high BMI-sensitized group, the decline in allograft function was higher than that in the other three groups. Death-censored graft loss (DCGL) rates were highest in the high BMI-sensitized group (4 of 21 [19.0%], p = 0.04). In the multivariable Cox regression hazard regression model analysis, the hazard ratio (HR) for DCGL was intensified when high BMI and presensitization statuses were combined (HR, 3.75; p = 0.03); these statuses significantly interacted with each other (p-value for interaction = 0.008).

Conclusion

Our results suggest that presensitization to HLA and high BMI might have an interactive adverse impact on allograft outcomes in KTRs.

Renal transplantation outcomes in obese patients: a French cohort-based study

Background

Whilst there are a number of publications comparing the relationship between body mass index (BMI) of kidney transplant recipients and graft/patient survival, no study has assessed this for a French patient cohort.

Methods

In this study, cause-specific Cox models were used to study patient and graft survival and several other time-to-event measures. Logistic regressions were performed to study surgical complications at 30 days post-transplantation as well as delayed graft function.

Results

Among the 4691 included patients, 747 patients were considered obese with a BMI level greater than 30 kg/m². We observed a higher mortality for obese recipients (HR = 1.37, p = 0.0086) and higher risks of serious bacterial infections (HR = 1.24, p = 0.0006) and cardiac complications (HR = 1.45, p < 0.0001). We observed a trend towards death censored graft survival (HR = 1.22, p = 0.0666) and no significant increased risk of early surgical complications.

Conclusions

We showed that obesity increased the risk of death and serious bacterial infections and cardiac complications in obese French kidney transplant recipients. Further epidemiologic studies aiming to compare obese recipients versus obese candidates remaining on dialysis are needed to improve the guidelines for obese patient transplant allocation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-021-02278-1.

Changes in Body Mass Index and Outcomes After Kidney Transplant: A Single-Center, Retrospective, Observational Study

OBJECTIVES

We aimed to describe changes in body mass index after kidney transplant and to assess how these changes influence long-term outcomes.

MATERIALS AND METHODS

Data were collected from kidney transplant recipients seen at our center between January 2007 and July 2016. Changes in body mass index over the posttransplant period were modeled using a generalized estimating equation, with changes calculated for each patient from pretransplant to 6 months posttransplant. Calculations were then categorized into 3 body mass index groups: stable (change of ± 1.5 kg/m² or less), reduced (reduction of > 1.5 kg/m²), and increased (increase of > 1.5 kg/m²). Outcomes among groups were compared.

RESULTS

Among 1344 total patients, the geometric mean pretransplant body mass index was 27.3 kg/m². This declined significantly (P < .001) to a geometric mean of 25.6 kg/m² at 1 month posttransplant, before increasing and stabilizing to pretransplant levels by 36 months (geometric mean body mass index of 27.2 kg/m² ; P = .522). Of 822 patients with body mass index measurements at 6 months, 303 had reduced, 388 had stable, and 131 had increased levels relative to pretransplant levels. On multivariate analyses, 12-month creatinine levels were significantly higher in the reduced cohort, with adjusted levels of 160.6 versus 135.0 μmol/L for the stable cohort. However, no significant associations were detected between 6-month body mass index changes and patient survival, graft survival, incidences of posttransplant diabetes and cancer, and a range of other clinical and histologic outcomes (all P > .05).

CONCLUSIONS

Our data demonstrated that body mass index was significantly reduced in the first month after kidney transplant before increasing to pretransplant levels during years 3 to 5. Furthermore, patients who retained decreased levels at 6 months had impaired graft function in long-term follow-up. These observations conflict with the existing literature and warrant further investigations.

Obesity in Kidney Transplantation: Impact on Transplant Candidates, Recipients, and Donors

Obesity is now common among children and adults who are kidney transplant candidates and recipients. It is associated with an increased risk of cardiovascular disease and kidney failure. This also pertains to potential living kidney donors with obesity. Obese patients with end-stage renal disease benefit from transplantation as do nonobese patients, but obesity is also associated with more risk. A complicating factor is that obesity is also associated with increased survival on maintenance dialysis in adults, but not in children. The assessment of obesity and body habitus should be individualized. Body mass index is a common but imperfect indicator of obesity. The medical management of obesity in renal failure patients is often unsuccessful. Bariatric surgery, specifically laparoscopic sleeve gastrectomy, can result in significant weight loss with reduced morbidity, but many patients do not agree to undergo this treatment. The best approach to manage obese transplant candidates and recipients is yet unresolved.

Are Females More Prone Than Males to Become Obese After Kidney Transplantation?

Background

Being overweight for kidney transplant recipients can cause serious side effects. Weight gain affects two-thirds of kidney transplant recipients and has been attributed to a more liberal diet after transplantation, recovery of appetite due to lack of uremic toxicity, corticosteroid use, and inadequate lifestyle changes. The aim of this study was to assess gender-dependent profile of body mass index (BMI) changes after kidney transplantation (KTx).

Material/Methods

Sixty-two kidney transplant recipients (38 males and 24 females), aged 46.0±12.8 years at KTx, were observed according to weight gain after KTx. BMI was calculated before transplantation (pre-KTx) and at 6, 12, and 24 months post-KTx.

Results

During the 24-month observation period, we found an increase in the incidence of kidney transplant recipients being overweight or obese (pre-KTx 43.5% increase and 24-month post-Ktx 61.3% increase, P=0.036). We analyzed a number of factors that could potentially influence a 24-month BMI gain including age at KTx, gender, pre-KTx BMI, time on dialysis, pre-KTx glucose metabolism disorder, and post-KTx diabetes mellitus. For female recipients, there was a significant step-wise post-KTx increase in BMI during the 24-month observation period. The overall pre-KTx to 24-month net increase for female BMI was 2 times greater than that observed for male recipients (1.90±2.20 kg/m² versus 0.89±1.85 kg/m², P<0.001).

Conclusions

Weight gain after KTx was observed in both sexes, but the net BMI increase was more than 2 times greater in females than in males at 24-months post-KTx. This indicated the need for diet education and strict weight control in kidney transplant recipients, especially in female patients.

Systematic review with meta-analysis: post-operative complications and mortality risk in liver transplant candidates with obesity

BACKGROUND

International guidelines rate class III (morbid) obesity (body mass index [BMI]≥40 kg/m2 ) as a relative contraindication for liver transplantation (LT) requiring further research. Moreover, data on the mortality risk in candidates with a BMI: 30-34.9 and 35-39.9 kg/m2 (class I and class II obesity, respectively) are weak.

AIM

To compare post-operative complications and mortality risks in all obese candidates vs candidates with a BMI: 18.5-29.9 (normal/overweight) assumed as controls.

METHODS

We searched the Cochrane library, PubMed, Scopus, Web-of-Science and article reference lists, restricted to the English language, and selected cohort studies analysing the following outcomes: all-causes mortality (at 30 days, 1-2-3-5 years), post-operative and cardiopulmonary complications, hospital and intensive care unit (ICU) length of stay. Two reviewers independently extracted the studies data and a third one resolved discrepancies.

RESULTS

Twenty-four studies comprising 132 162 patients met the inclusion criteria. As compared to controls, mortality risk was increased at all time-periods (except at 3 years) for a BMI≥40, at 30 days for a BMI: 30-34.9 and in none of the considered time-periods for a BMI: 35-39.9. Post-operative complications were significantly higher for a BMI>30 and 30-34.9. Due to the shortage/absence of data, we evaluated cardiopulmonary complications, hospital and ICU length of stay only in the BMI≥30 category. In these patients, only cardiopulmonary complications were increased as compared to controls.

CONCLUSIONS

Morbid obesity has an impact on patients' survival after LT. However, since even a BMI>30 increases post-transplant complications, new strategies should be included in the LT programme to favour weight loss in all obese candidates.

High-Fat Diet-Induced Obesity Enhances Allograft Rejection

BACKGROUND

Obesity promotes a state of low-grade inflammation that exacerbates chronic inflammatory diseases, such as asthma and inflammatory bowel disease. In transplantation, the survival of organs transplanted into obese patients is reduced compared with allografts in lean recipients. However, whether this is due to increased alloimmunity remains to be addressed conclusively.

METHODS

We used a mouse model of high-fat diet (HFD)-induced obesity and assessed immune responses to allogeneic stimulation in vitro, allogeneic splenocyte immunization in vivo, and allogeneic heart transplantation.

RESULTS

Our results indicate that HFD altered the composition and phenotype of splenic antigen-presenting cells that led to their enhanced capacity to stimulate T cells. Immunization with allogeneic splenocytes in vivo resulted in increased alloreactivity, as determined by IFNγ production. Moreover, cardiac allograft rejection in HFD mice was modestly accelerated compared to aged-matched control animals fed a low-fat diet, correlating with enhanced alloreactive T cell function.

CONCLUSIONS

Our results highlight the increased alloresponse triggered by HFD-induced obesity and its negative impact on transplant outcome.

Influence of the recipient body mass index on the outcomes after kidney transplantation

PURPOSE

The relationship between the body mass index (BMI) of kidney transplant recipients and outcomes after kidney transplantation (KT) is not fully understood and remains controversial. We studied the influence of BMI on clinically relevant outcomes in kidney transplant recipients.

METHODS

In this retrospective single-centre study, all patients who underwent kidney transplantation at our institution between January 2007 and December 2012 were included. Demographic data and BMI were correlated with the clinical course of the disease, rejection rates, delayed graft function rates, and graft and patient survival.

RESULTS

During the study period, 384 single KTs (130 women and 254 men) were performed. Seventeen percent of the transplants were transplanted within the Eurotransplant Senior Programme (ESP). Most of the transplants were performed using organs that were obtained from donors after brain death (DBD), and living donor kidney transplants were performed in 22.4% of all transplants. The median BMI of the recipients was 25.9 kg/m². Additionally, 13.5% of the recipients had a BMI of 30-34.9 kg/m² and 3.9% had a BMI >35 kg/m². A BMI >30 kg/m² was significantly associated with primary non-function of the kidney (p = 0.047), delayed graft function (p = 0.008), and a higher rate of loss of graft function (p = 0.015). The glomerular filtration rate 12 months after KT was significantly lower in recipients with a BMI >30 kg/m². Multivariate analysis revealed that recipient BMI, among other factors, was an independent risk factor for delayed graft function and graft survival. Patients with a BMI >30 kg/m² had an almost four times higher risk for surgical site infection than did recipients with a lower BMI.

CONCLUSIONS

Increased BMI at kidney transplantation is a predictor of adverse outcomes, including delayed graft function. These findings demonstrate the importance of the careful selection of patients and pre-transplant weight reduction, although the role of weight reduction for improving graft function is not clear.

Trends in brain-dead organ donor characteristics: a 13-year analysis

BACKGROUND

Driven by disease trends, such as obesity and metabolic syndrome, that are increasingly prevalent in the general population, we aimed to evaluate the comorbidities and attributes of the brain-dead organ donor population over time in a longitudinal study.

METHODS

We compared overall health and baseline attributes of organ donors between 2000-2005 and 2006-2012 using our prospective transplant database. Descriptive and comparative analyses of the 2 historical cohorts were performed.

RESULTS

A total of 1040 brain-dead organ donors were included in our analysis: 496 from the 2000-2005 period and 544 from the 2006-2012 period. Our analysis revealed that donors from the recent (2006-2012) period were more likely to have increased body mass index (26.4 ± 6.0 v. 25.0 ± 4.8, p = 0.003), smoking history (57.0% v. 27.2%, p < 0.001), coronary artery disease (14.3% v. 3.2%, p = 0.015) and dyslipidemia (19.1% v. 4.2%, p < 0.001), but less likely to have concurrent infection (1.1% v. 7.9%, p < 0.001) than those from the earlier period.

CONCLUSION

Our data suggest that the characteristics and comorbidities of brain-dead organ donors have somewhat deteriorated over the last decade. Further studies are needed to evaluate the impact of these health attributes on donated organ utilization and outcomes.

Obesity-Associated Adipose Tissue Inflammation and Transplantation

Obesity is often associated with the development of adipose tissue (AT) inflammation, resulting in metabolic dysfunction and an increased risk for developing type 2 diabetes. It is also associated with multiple chronic diseases, including cardiovascular, liver, and kidney disease, and thus can contribute to organ failure. Several studies have investigated whether there is a correlation between obesity and outcomes in transplantation, but there is currently very limited information on the specific role of AT inflammation in the rejection process or on the overall function of the transplanted organ. Here, we provide a brief review of the current understanding of the cellular mechanisms that control obesity-associated AT inflammation and summarize knowledge about how obesity affects clinical outcomes following solid organ or hematopoietic stem cell transplantation. We also highlight opportunities for more research to better understand how obesity affects outcomes of transplantation.

Renal transplantation in obese patients: experience in an Argentine center

Possible complications of renal transplants in obese patients have raised concerns among nephrologists. We describe the outcomes of 110 renal transplant patients according to body mass index (BMI). Recipient BMI was calculated by using height and weight at time of transplantation and categorized according to World Health Organization guidelines. The patients' BMI values were as follows: underweight, n = 8 (7.27%); normal weight, n = 55 (50%); overweight, n = 30 (27.27%); and obese, n = 17 (15.45%). Mean age was significantly different among groups: underweight, 27.62 ± 7.57 years; normal weight, 44.98 ± 15.55 years; overweight, 50.53 ± 13.90 years; and obese, 52.11 ± 10.41 years (P < .05). Donor age and mean time of dialysis treatment were comparable in all groups. Underweight patients had a significantly larger proportion of living donors than those with higher BMIs. Calculated glomerular filtration rate (using the Modification of Diet in Renal Disease equation) were significantly different among the groups at 30, 60, and 90 days' posttransplantation. At 180 days, however, it was comparable: underweight, 62.96 ± 40.77 mL/min/1.73 m(2); normal weight, 53.55 ± 26.23 mL/min/1.73 m(2); overweight, 47.52 ± 16.37 mL/min/1.73 m(2); and obese, 46.19 ± 17.56 mL/min/1.73 m(2) (P = .34). Incidence of delayed graft function was as follows: underweight, 0%; normal weight, 30.4%; overweight, 53.3%; and obese, 64.1% (P < .05). The incidence of surgical complications, incidence of rejection within the first 6 months' posttransplantation, and graft and patient survival rates over 6 months did not differ among the groups. Because transplantation in obese patients may be associated with higher risks and costs, the evaluation of each center experience is imperative. Longer term assessments are warranted, but our short-term results show that outcomes in overweight or obese renal transplant patients are comparable to those in patients with lower BMI.

Systematic Nutritional Support in Allogeneic Hematopoietic Stem Cell Transplant Recipients

Allogeneic hematopoietic stem cell transplantation (HSCT) has become an established treatment modality for various hematological diseases. However, in allogeneic HSCT, patients often suffer from severe gastrointestinal complications caused by the conditioning regimen and acute/chronic graft-versus-host disease, which requires support by multidisciplinary nutritional support teams (NST). In addition, pretransplantation nutritional status can affect the clinical outcome after allogeneic HSCT. Therefore, it is important to refer the patient to a NST when becoming aware of nutritional problems before allogeneic HSCT. It is also important to follow nutritional status over the long term, as patients often suffer from various nutritional problems, such as malnutrition and metabolic syndrome, even late after allogeneic HSCT. In summary, NST can contribute to the improvement of nutritional status and possibly prognosis at every stage before and after allogeneic HSCT. Here, we aim to give a comprehensive overview of current understanding about nutritional support in allogeneic HSCT and try to provoke a constructive discussion to stimulate further investigation.

Body mass index and outcome in renal transplant recipients: a systematic review and meta-analysis

BACKGROUND

Whether overweight or obese end stage renal disease (ESRD) patients are suitable for renal transplantation (RT) is often debated. The objective of this review and meta-analysis was to systematically investigate the outcome of low versus high BMI recipients after RT.

METHODS

Comprehensive searches were conducted in MEDLINE OvidSP, Web of Science, Google Scholar, Embase, and CENTRAL (the Cochrane Library 2014, issue 8). We reviewed four major guidelines that are available regarding (potential) RT recipients. The methodology was in accordance with the Cochrane Handbook for Systematic Reviews of Interventions and written based on the PRISMA statement. The quality assessment of studies was performed by using the GRADE tool. A meta-analysis was performed using Review Manager 5.3. Random-effects models were used.

RESULTS

After identifying 5,526 studies addressing this topic, 56 studies were included. We extracted data for 37 outcome measures (including data of more than 209,000 RT recipients), of which 26 could be meta-analysed. The following outcome measures demonstrated significant differences in favour of low BMI (<30) recipients: mortality (RR = 1.52), delayed graft function (RR = 1.52), acute rejection (RR = 1.17), 1-, 2-, and 3-year graft survival (RR = 0.97, 0.95, and 0.97), 1-, 2-, and 3-year patient survival (RR = 0.99, 0.99, and 0.99), wound infection and dehiscence (RR = 3.13 and 4.85), NODAT (RR = 2.24), length of hospital stay (2.31 days), operation duration (0.77 hours), hypertension (RR = 1.35), and incisional hernia (RR = 2.72). However, patient survival expressed in hazard ratios was in significant favour of high BMI recipients. Differences in other outcome parameters were not significant.

CONCLUSIONS

Several of the pooled outcome measurements show significant benefits for 'low' BMI (<30) recipients. Therefore, we postulate that ESRD patients with a BMI >30 preferably should lose weight prior to RT. If this cannot be achieved with common measures, in morbidly obese RT candidates, bariatric surgery could be considered.

Obesity-related immune responses and their impact on surgical outcomes

The obesity epidemic represents a critical disease burden with broad clinical consequences. At the same time, obesity has been linked to inferior surgical outcomes and considered a contraindication for some elective surgical procedures. A growing body of mechanistic evidence has accumulated linking obesity to changes of metabolism and immune responses. This concept provides an integrated inflammatory network based on the perception of obesity as a state of chronic low-grade inflammation. With a more detailed understanding of this dynamic network and mechanistic insights, novel treatment and management strategies may be developed with the goal to optimize surgical outcomes in obese patients.

Impact of recipient body mass index on short-term and long-term survival of pancreatic grafts

BACKGROUND

The impact of recipient body mass index on graft and patient survival after pancreas transplantation is not well known.

METHODS

We have analyzed data from all pancreas transplant recipients reported in the Scientific Registry of Transplant Recipients between 1987 and 2011. Recipients were categorized into BMI classes, as defined by the World Health Organization. Short-term (90 days) and long-term (90 days to 5 years) patient and graft survivals were analyzed according to recipient BMI class using Kaplan-Meier estimates. Hazard ratios were estimated using Cox proportional hazard models.

RESULTS

A total of 21,075 adult recipients were included in the analysis. Mean follow-up was 5 ± 1.1 years. Subjects were overweight or obese in 39%. Increasing recipient BMI was an independent predictor of pancreatic graft loss and patient death in the short term (P<0.001), especially for obese class II patient survival (hazard ratio, 2.07; P=0.009). In the long term, obesity, but not overweight, was associated with higher risk of graft failure (P=0.01). Underweight was associated with a higher risk of long-term death (P<0.001).

CONCLUSION

These results question the safety of pancreas transplantation in obese patients and suggest that they may be directed to alternate therapies, such as behavioral modifications or bariatric surgery, before pancreas transplantation is considered.

Impact of pretransplant body mass index on the clinical outcome after allogeneic hematopoietic SCT

To elucidate the impact of pretransplant body mass index (BMI) on the clinical outcome, we performed a retrospective study with registry data including a total of 12 050 patients (age ⩾18 years) who received allogeneic hematopoietic SCT (HSCT) between 2000 and 2010. Patients were stratified as follows: BMI<18.5 kg/m(2), Underweight, n=1791; 18.5⩽BMI<25, Normal, n=8444; 25⩽BMI<30, Overweight, n=1591; BMI⩾30, Obese, n=224. The median age was 45 years (range, 18-77). A multivariate analysis showed that the risk of relapse was significantly higher in the underweight group and lower in the overweight and obese groups compared with the normal group (hazard ratio (HR), 1.16, 0.86, and 0.74, respectively). The risk of GVHD was significantly higher in the overweight group compared with the normal group. The risk of non-relapse mortality (NRM) was significantly higher in the overweight and obese group compared with the normal group (HR 1.19 and HR 1.43, respectively). The probability of OS was lower in the underweight group compared with the normal group (HR 1.10, P=0.018). In conclusion, pretransplant BMI affected the risk of relapse and NRM after allogeneic HSCT. Underweight was a risk factor for poor OS because of an increased risk of relapse. Obesity was a risk factor for NRM.