High Serum Leptin in Patients with Chronic Graft-Versus-Host Disease after Hematopoietic Stem Cell Transplantation

Pre-Transplant Serum Leptin Levels and Relapse of Acute Myeloid Leukemia after Allogeneic Transplantation

Weight loss and metabolic activity influence outcome after allogeneic stem cell transplantation (alloSCT). This study evaluates pre-conditioning Leptin, a peptide hormone involved in metabolism and immune homeostasis, as a prognostic factor for survival, relapse and non-relapse mortality (NRM) following alloSCT. Leptin serum levels prior to conditioning were determined in a cohort of patients transplanted for various hematologic malignancies (n = 524) and correlated retrospectively with clinical outcome. Findings related to patients with acute leukemia (AL) from this sample were validated in an independent cohort. Low pre-conditioning serum Leptin was an independent prognostic marker for increased risk of relapse (but not of NRM and overall mortality) following alloSCT for AL of intermediate and advanced stage (beyond first complete remission). Multivariate analysis revealed a hazard ratio (HR) for relapse of 0.75 per log2 increase (0.59–0.96, p = 0.020). This effect was similar in an independent validation cohort. Pre-conditioning serum Leptin was validated as a prognostic marker for early relapse by fitting the multivariate Cox model to the validation data. Pre-conditioning serum Leptin levels may serve as an independent prognostic marker for relapse following alloSCT in intermediate and advanced stage AL patients. Prospective studies are required to prove whether serum Leptin could be used for guiding nutritional intervention in patients with AL undergoing alloSCT.

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.

Monogenic Immune Diseases Provide Insights Into the Mechanisms and Treatment of Chronic Graft-Versus-Host Disease

Chronic graft-versus-host disease (GvHD) has become a leading cause of morbidity and mortality following allogeneic hematopoietic stem cell transplantation (HSCT) and can burden patients with devastating and lifelong health effects. Our understanding of the pathogenic mechanisms underlying chronic GvHD remains incomplete and this lack of understanding is reflected by lack of clear therapeutic approaches to steroid refractory disease. Observations predominantly from mouse models and human correlative studies currently support a three phase model for the initiation and development of chronic GvHD: 1) early inflammation and tissue damage triggers the innate immune system. This leads to inflammatory cytokine/chemokine patterns that recruit effector immune cell populations; 2) chronic inflammation causes the loss of central and peripheral tolerance mechanisms leading to emergence of pathogenic B and T cell populations that promote autoimmune and alloimmune reactions; 3) the dysregulated immunity causes altered macrophage polarization, aberrant tissue repair leading to scarring and end organ fibrosis. This model has led to the evaluation of many new therapies aimed at limiting inflammation, targeting dysregulated signaling pathways and restoring tolerance mechanisms. However, chronic GvHD is a multisystem disease with complex clinical phenotypes and it remains unclear as to which cluster of patients will respond best to specific therapeutic strategies. However, it is possible to gain novel insights from immune-related monogenic diseases. These diseases either share common clinical manifestations, replicate steps from the three phase chronic GvHD model or serve as surrogates for perfectly targeted drugs being investigated in chronic GvHD therapy. In this review, we will summarize the evidence from these monogenic immune related diseases that provide insight into pathogenic pathways in chronic GvHD, rationales for current therapies and novel directions for future drug discovery.

Distinct Regulatory and Effector T Cell Metabolic Demands during Graft-Versus-Host Disease

Despite graft-versus-host disease (GVHD) prophylactic agents, the success and wider utilization of allogeneic hematopoietic stem cell transplantation (allo-HSCT) is limited by GVHD. Increasing donor graft regulatory T cell (Treg):effector T cell (Teff) ratios can substantially reduce GVHD in cancer patients, but pre-HSCT conditioning regimens and GVHD create a challenging inflammatory environment for Treg stability, persistence, and function. Metabolism plays a crucial role in T cell and Treg differentiation, and development of effector function. Although glycolysis is a main driver of allogeneic T cell-driven GVHD, oxidative phosphorylation is a main driver of Treg suppressor function. This review focuses on recent advances in our understanding of Treg metabolism in the context of GVHD, and discusses potential therapeutic applications of Tregs in the prevention or treatment of GVHD in cancer patients.

Proinflammatory Cytokine and Adipokine Levels in Adult Unrelated Marrow Donors Are Not Associated with Hematopoietic Cell Transplantation Outcomes

Graft-versus-host disease (GVHD) is a frequent cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (allo-HCT). GVHD occurs when donor lymphocytes are activated by inflammatory cytokines and alloantigens. The role of donor biologic characteristics, such as basal inflammation, has not been investigated as a risk factor for GVHD but is theoretically transferrable to the recipient. We evaluated donor serum and plasma concentrations of cytokines and adipokines (IL-1β, IL-6, tumor necrosis factor [TNF]-α, leptin, suppression of tumorigenicity-2, and adiponectin) from test (n = 210) and replication (n = 250) cohorts of matched, unrelated transplant peripheral blood stem cell recipients identified through the Center for International Blood and Marrow Transplantation Research between 2000 and 2011 for hematologic malignancies. Hazard ratios were estimated for acute (grades II to IV and III to IV) and chronic GVHD, overall survival, disease-free survival, transplant-related mortality, and relapse for each cytokine or adipokine, adjusting for significant covariates. The lowest cytokine quartile was considered as the reference group for each model. To account for multiple testing P < .01 was considered the threshold for significance. In the test cohort a borderline significant association was identified between donor serum IL-1β concentrations and grades III to IV acute GVHD in the recipient (P = .01), and a significant inverse association was identified between donor TNF-α concentrations and chronic GVHD (P = .006). These findings were not validated in the replication cohort. Although the initial associations between cytokine levels and allo-HCT outcomes were not validated, the idea that donor characteristics may be transferable to the recipient remains an exciting area for future research.

Prospective evaluation of metabolic syndrome and its features in a single-center series of hematopoietic stem cell transplantation recipients

Available studies on metabolic syndrome (MS) after hematopoietic stem cell transplantation (HSCT) are retrospective with heterogeneous inclusion criteria, and little is known about the early post-transplant phase. In our prospective study, clinical and laboratory data were collected in 100 HSCT recipients, 48 allogeneic and 52 autologous, at baseline, at + 30, + 100 and + 360 days. At baseline, MS was observed in 24 patients, significantly associated with insulin resistance and leptin on multivariate analysis. At + 30, the diagnosis of MS was confirmed in 43 patients, significantly related to insulin resistance and allogeneic transplants. If the whole series was considered, patients with MS had significantly higher mortality from any cause. The baseline presence of any MS feature was a predictor of + 30 MS. Isolated occurrences of MS features were related to hyperleptinemia and hyperinsulinemia, except in the case of low HDL cholesterol, linked to adiponectin and resistin. Our data confirm that patients undergoing HSCT have a high prevalence of MS, with hyperleptinemia playing a major role. The early peak of new MS cases is primarily attributable to insulin resistance, notably but not exclusively immunosuppression-induced; the subsequent long-term increase in MS cases may be an effect of persistent adipokine imbalance.

Metabolic Syndrome in Long-Term Survivors of Hematopoietic Stem-Cell Transplantation

Since its introduction more than 50 years ago, hematopoietic stem-cell transplantation (HSCT) has transformed from an inescapably fatal procedure to one where cure from malignant and other nonmalignant hematologic diseases is becoming increasingly common. Nevertheless, longevity is not entirely restored. New causes of mortality have emerged; of particular importance is that of increased cardiovascular disease (CVD), related to metabolic syndrome and its components. Controversy exists over whether the metabolic abnormalities induced are a direct effect of HSCT itself or a consequence of other therapies involved. Analysis of the mechanisms that promote the changes in metabolic components will give insight into future HSCT therapy as well as CVD pathogenesis and prevention.

Leptin as an immunomodulator

Leptin is an adipocyte-derived hormone/cytokine that links nutritional status with neuroendocrine and immune functions. In humans, leptin influences energy homeostasis and regulates neuroendocrine function primarily in states of energy deficiency. Initially described as an antiobesity hormone, leptin has subsequently been shown also to influence basal metabolism, hematopoiesis, thermogenesis, reproduction, and angiogenesis. As a cytokine, leptin can affect thymic homeostasis and the secretion of acute-phase reactants such as interleukin-1 (IL-1) and tumor-necrosis factor-alpha (TNF-α). Leptin links nutritional status and proinflammatory T helper 1 (Th1) immune responses and the decrease in leptin plasma concentration during food deprivation leads to impaired immune function. Similar to other pro-inflammatory cytokines, leptin promotes Th1-cell differentiation and can modulate the onset and progression of autoimmune responses in several animal models of disease. Here, we review the advances and controversy for a role of leptin in the pathophysiology of immune responses and discuss novel possible therapeutic implications for leptin modulators.

A comparison between metabolic syndrome post-hematopoietic stem cell transplantation and spontaneously occurring metabolic syndrome

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) is used in the treatment of several hematological and non-hematological disorders. An increasing number of long-term survivors recover from their primary disease, but they are at risk of adverse late effects, including metabolic syndrome (MS), which seems to be common in long-term survivors of HSCT.

AIM

To compare common metabolic parameters and adipohormone profiles in post-transplant and spontaneously occurring or "classic" MS patients.

SUBJECTS AND METHODS

Post-transplant MS patients (15 women and 14 men; 49.8±9.3 yr) were compared to "classic" MS patients (15 women and 14 men; 52.9±8.0 yr). For each subject a record of conventional clinical parameters was made; moreover, serum leptin, insulin, quantitative C-reactive protein (CRP), tumor necrosis factor-α [TNF-α], and adiponectin concentrations were measured.

RESULTS

The patients with post-HSCT MS had significantly higher levels of leptin, CRP, and TNF-α than the patients with "classic" MS. A generalized linear model comprising serum insulin (p=0.022), body mass index (p<0.001), gender (p<0.001), and group (i.e. healthy, post-HSCT with MS, or suffering from "classic" MS; p<0.001) explained serum leptin variability (adjusted R(2)=0.741). Serum leptin concentrations and BMI were related in the patients with "classic" MS but not in those with post-HSCT MS.

CONCLUSIONS

A possible pathogenetic mechanism in the development of MS after HSCT could be hyperleptinemia. A potential interaction among circulating leptin, components of MS, and immune function might explain the role of this adipokine in mediating cardiovascular risk after HSCT.

Increased cardiometabolic traits in pediatric survivors of acute lymphoblastic leukemia treated with total body irradiation

Survivors of childhood acute lymphoblastic leukemia (ALL) may face an increased risk of metabolic and cardiovascular late effects. To determine the prevalence of and risk factors for adverse cardiometabolic traits in a contemporary cohort of pediatric ALL survivors, we recruited 48 off-therapy patients in remission treated with conventional chemotherapy and 26 treated with total body irradiation (TBI)-based hematopoietic cell transplantation (HCT) in this cross-sectional pilot study. At a median age of 15 years (range, 8-21 years), HCT survivors were significantly more likely than non-HCT survivors to manifest multiple cardiometabolic traits, including central adiposity, hypertension, insulin resistance, and dyslipidemia. Overall, 23.1% of HCT survivors met the criteria for metabolic syndrome (≥ 3 traits), compared with 4.2% of non-HCT survivors (P = .02). HCT survivors also had increased C-reactive protein and leptin levels and decreased adiponectin, suggestive of underlying inflammation and increased visceral fat. In multivariate analyses, history of HCT remained associated with ≥ 2 traits (odds ratio [OR]. 5.13; 95% confidence interval [CI], 1.54-17.15) as well as with ≥ 3 traits (OR, 16.72; 95% CI, 1.66-168.80). Other risk factors included any cranial radiation exposure and family history of cardiometabolic disease. In summary, pediatric ALL survivors exposed to TBI-based HCT as well as to any cranial radiation may manifest cardiometabolic traits at an early age and should be screened accordingly.

High prevalence of metabolic syndrome after allogeneic hematopoietic cell transplantation

We conducted a cross-sectional study to estimate the prevalence of metabolic syndrome, a clustering of risk factors associated with cardiovascular disease, among 86 adults who had allogeneic hematopoietic-cell transplant (HCT) as compared with 258 age- and gender-matched US population controls selected from the 2005-2006 National Health and Nutrition Examination Survey database. The median age at study enrollment was 50 years (range, 21-71), and patients were at a median of 3 years (range, 1-21) from HCT. The prevalence of metabolic syndrome was 49% (95% confidence intervals (CI), 38-60%) among HCT recipients, a 2.2-fold (95% CI, 1.3-3.6, P=0.002) increase compared with controls. The prevalence rates of elevated blood pressure and hypertriglyceridemia were significantly higher among HCT recipients than among controls, but the prevalence rates of abdominal obesity, elevated blood glucose and low high-density lipoprotein cholesterol were not. HCT survivors with metabolic syndrome were more likely to have microalbuminuria (43 vs 10%) and elevated creatinine (31 vs 11%). No patient, donor or transplant characteristics were associated with the diagnosis of metabolic syndrome. We conclude that metabolic syndrome occurs frequently among allogeneic HCT survivors who are seen by transplant physicians. Approaches to screening, prevention and management of metabolic syndrome should be developed for HCT recipients.

Leptin and Inflammation

The past few years of research on leptin have provided important information on the link between metabolism and immune homeostasis. Adipocytes influence not only the endocrine system but also the immune response through several cytokine-like mediators known as adipokines, which include leptin. It is widely accepted that leptin can directly link nutritional status and pro-inflammatory T helper 1 immune responses, and that a decrease of leptin plasma concentration during food deprivation can lead to an impaired immune function. Additionally, several studies have implicated leptin in the pathogenesis of chronic inflammation, and the elevated circulating leptin levels in obesity appear to contribute to the low-grade inflammatory background which makes obese individuals more susceptible to increased risk of developing cardiovascular diseases, type II diabetes, or degenerative disease including autoimmunity and cancer. Conversely, reduced levels of leptin such as those found in malnourished individuals have been linked to increased risk of infection and reduced cell-mediated immune responses. We discuss here the functional influences of leptin in the physiopathology of inflammation, and the effects of leptin in the modulation of such responses.

Prevalence of metabolic syndrome in long-term survivors of hematopoietic stem cell transplantation

Our purpose was to determine the prevalence and features of metabolic syndrome (MS) in a series of long-term hematopoietic stem cell transplantation (HSCT) survivors. We assessed the clinical, metabolic and endocrinological data, and plasma TNF, leptin, resistin and adiponectin levels relating to 85 HSCT recipients. MS was diagnosed on the basis of the National Cholesterol Education Program-Adult Treatment Panel III criteria. Its prevalence was compared with that observed in an Italian population, and its relationship with the clinical and laboratory parameters was assessed univariately and multivariately. Twenty-nine HSCT recipients had MS instead of the 12.8 expected (P<0.0001), with hypertriglyceridemia being the most common feature. Univariate analysis indicated that high insulin and leptin levels, low-adiponectin levels and hypogonadism were significantly related to a diagnosis of MS; multivariate analysis indicated plasma leptin, insulin resistance, age and hypogonadism. We conclude that HSCT recipients are at increased risk of a form of MS that has particular clinical features. Plasma leptin levels are independently related to MS, thus suggesting that leptin resistance may play a role as a pathogenetic clue, as in other conditions in which MS occurs as a secondary phenomenon. MS deserves consideration as a life-threatening complication in patients who are probably cured of their underlying disease.

Imbalance of the Osteoprotegerin/RANKL Ratio in Bone Marrow Microenvironment After Allogeneic Hemopoietic Stem Cell Transplantation

BACKGROUND

Bone loss is a common complication after allogeneic stem cell transplantation. Osteoprotegerin (OPG) plays a critical role in bone remodeling by neutralizing the effect of receptor activator of nuclear factor-kappaB ligand (RANKL) on differentiation and activation of osteoclasts. We investigated OPG and RANKL in serum and marrow plasma in transplanted patients.

MATERIALS AND METHODS

In 36 patients and 36 controls, the relationships among bone mineral density, circulating OPG, RANKL, interferon-gamma, and interleukin-6 levels were investigated; in addition, OPG and RANKL were measured in marrow plasma and in conditioned medium of long-term cultures of marrow mesenchymal-derived osteogenic cells.

RESULTS

Lumbar and femoral bone mineral density were lower in patients than in controls (P<0.01). Serum OPG (sOPG) and interferon-gamma were significantly higher in patients than in controls (P<0.05). Patients' interferon-gamma correlated with sOPG levels (r=0.4; P=0.03). Interleukin-6 did not differ between patients and controls. By contrast, OPG levels were lower in patients than in controls in marrow plasma (P<0.001) and in conditioned media after one (P=0.035) and three months (P=0.003) of culture of marrow mesenchymal-derived osteogenic cells. RANKL was similar in patients and controls. The OPG/RANKL ratio "in situ" was significantly lower in patients than in controls (P<0.05). There was no correlation between sOPG and marrow OPG, RANKL levels, densitometric values, and chronic graft-versus-host disease.

CONCLUSION

Our findings suggest that after allogeneic stem cell transplantation: 1) sOPG bear no relationship with OPG in the bone marrow; 2) increased sOPG can be the result of its enhanced production in extra bone tissues triggered by inflammatory cytokines; 3) low bone marrow OPG levels may be partly related to the persistent quantitative and qualitative deficit of osteoblastic precursors; and 4) reduced OPG/RANKL ratio in bone microenvironment may increase bone remodeling by promoting bone resorption.

Hyperleptinemia and its relation with peripheral C34(+)CD7(+) stem cells in renal transplant recipients

OBJECTIVES

Leptin, the Ob gene product, centrally regulates weight control. Transplant recipients are exposed to many factors affecting body mass. Leptin has been reported to activate the peripheral immune system. In this study, we evaluated serum leptin levels and factors contributing to hyperleptinemia; the relationship between serum leptin levels and lymphoid stem and mature cells; and their role in the rejection process in renal transplant recipients.

MATERIALS AND METHODS

Sixty-three renal transplant recipients were included in the study. Patients were grouped according to serum leptin percentiles as hypoleptinemic (n=17), normoleptinemic (n=32), and hyperleptinemic (n=14). We determined serum leptin levels by radioimmunoassay and absolute number of CD34(+), CD7(+), CD34(+)CD7(+) lymphoid stem cells, CD4(+) and CD8(+) lymphocytes in peripheral blood by flow cytometry.

RESULTS

The hyperleptinemic patients constituted 22.3% of the transplant patient. The mean peripheral blood CD34(+)CD7(+) lymphocyte count was significantly higher in hyperleptinemic patients than in normo- or hypoleptinemic patients (6.9, 6.1, and 44.3 cells/mm(3), respectively, P<0.05). There were no significant differences in the mean CD34(+), CD7(+), CD8(+), and CD4(+) lymphocyte count and CD4/CD8 ratio among the groups with respect to serum leptin levels. CD34(+)CD7(+) lymphocyte count was positively correlated with serum leptin levels (r=0.416, P<0.05).

CONCLUSIONS

Hyperleptinemia is not rare during the posttransplant period. Our data support the results of previous experimental studies that have demonstrated the effect of the leptin hormone on lymphoid stem cells. The central and peripheral effects of leptin may differ on lymphoid stem cells and a serum threshold level may apply for the central effects.