Association Between Serum Leptin Level and Mortality in Kidney Transplant Recipients

New Insights into Adiponectin and Leptin Roles in Chronic Kidney Disease

Chronic kidney disease (CKD) is commonly associated with a high burden of comorbidities and poor clinical outcomes. Malnutrition–inflammation–atherosclerosis syndrome is common in the more severe stages of CKD, suggesting a close interplay for these three comorbid conditions. Both malnutrition and obesity are associated with a disturbed adipokine profile and inflammation, contributing to a higher risk of cardiovascular disease (CVD) events. Adiponectin and leptin have important roles in carbohydrate and lipid metabolism, and in the inflammatory process. The effects of adiponectin and leptin alterations in CKD, which are usually increased, and their association with the different comorbidities found in CKD, will be focused on to understand their crosstalk with the risk of CVD events. Nonetheless, although adiponectin and leptin contribute to a higher risk of CVD events, further studies are warranted to fully clarify their roles, especially when different comorbidities exist.

Pro-Inflammatory Profile of Adipokines in Obesity Contributes to Pathogenesis, Nutritional Disorders, and Cardiovascular Risk in Chronic Kidney Disease

Obesity is a disease which leads to the development of many other disorders. Excessive accumulation of lipids in adipose tissue (AT) leads to metabolic changes, including hypertrophy of adipocytes, macrophage migration, changes in the composition of immune cells, and impaired secretion of adipokines. Adipokines are cytokines produced by AT and greatly influence human health. Obesity and the pro-inflammatory profile of adipokines lead to the development of chronic kidney disease (CKD) through different mechanisms. In obesity and adipokine profile, there are gender differences that characterize the male gender as more susceptible to metabolic disorders accompanying obesity, including impaired renal function. The relationship between impaired adipokine secretion and renal disease is two-sided. In the developed CKD, the concentration of adipokines in the serum is additionally disturbed due to their insufficient excretion by the excretory system caused by renal pathology. Increased levels of adipokines affect the nutritional status and cardiovascular risk (CVR) of patients with CKD. This article aims to systematize the current knowledge on the influence of obesity, AT, and adipokine secretion disorders on the pathogenesis of CKD and their influence on nutritional status and CVR in patients with CKD.

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.

Association of serum adiponectin and leptin levels with renal function in kidney transplant recipients with or without new-onset diabetes after transplantation

PURPOSE

To evaluate serum adiponectin and leptin concentration in new-onset diabetes after transplantation (NODAT) and non-NODAT patients and association with renal function in kidney transplant recipients (KTRs).

PATIENTS AND METHODS

A study of 314 consecutive adults KTRs divided into four groups: 236 individuals without NODAT who had renal insufficiency (RI; n = 56) or normal renal function (n = 180) and 78 patients with NODAT who had RI (n = 17) or normal renal function (n = 61). NODAT was diagnosed based on venous fasting blood glucose or HbA1c with the criteria of the American Diabetes Association. Renal insufficiency was defined according to KDOQI 2002 guidelines.

RESULTS

In the NODAT group, the median level of serum adiponectin was lower than that of non-NODAT one (30 µg/ml vs 37.15 µg/ml, p < 0.001); in contrast, the median leptin concentration was higher (4.27 ng/ml vs 4.05 ng/ml, p = 0.024). In the RI group, both median serum adiponectin and leptin levels were higher than those of non-RI one (Adiponectin: 40.01 µg/ml vs 33.7 µg/ml; Leptin: 4.51 ng/ml vs 3.91 ng/ml, p < 0.001 both). We found that BMI was related to both adiponectin and leptin levels in both NODAT, non-NODAT, and all subject groups, based on univariate and multivariate linear regression analysis.

CONCLUSION

New-onset diabetes after transplantation, BMI, and renal insufficiency were affected to the serum level of adiponectin and leptin in KTRs.

Association between serum osteoprotegerin level and mortality in kidney transplant recipients - a prospective observational cohort study

Paradoxically, higher serum levels of osteoprotegerin (OPG: a vascular calcification inhibitor) have been associated with increased arterial stiffness, risk of cardiovascular disease and all-cause mortality. A few studies reported that post-transplant OPG levels are associated with mortality in kidney transplant (KT) recipients. In this study, this association was assessed in a cohort of prevalent KT recipients, adjusting for previously untested potential confounders, including fibroblast growth factor 23 (FGF23) and interleukin 6 (IL-6). Socio-demographic and clinical parameters, medical and transplant history, and laboratory data were collected from 982 prevalent KT recipients. The association between serum OPG and all-cause mortality over a 6-year follow-up period was examined using Kaplan-Meier survival curves and multivariable-adjusted Cox regression models. Participants with high serum OPG were more likely female, older, deceased donor KT recipients and have more comorbidity, lower eGFR, higher FGF23, higher IL-6, and longer dialysis vintage. Each 1 pmol/l higher serum OPG level was associated with a 49% higher risk of mortality (hazard ratio (HR) [95% confidence interval (CI)]: 1.49 [1.40-1.61]). This association persisted after adjusting for confounders (HR [95% CI]: 1.20 [1.10-1.30]). In conclusion, serum OPG was associated with all-cause mortality independent of several novel confounders in prevalent KT recipients.

Association of polymorphisms in leptin and adiponectin genes with long-term outcomes in renal transplant recipients

The effect of polymorphims in leptin and adiponectin genes on long-term outcomes of renal transplantation is unknown. In 349 renal transplant recipients (RTR), we aimed to determine associations between five SNPs in the leptin receptor (LEPR) and adiponectin (ADIPOQ) genes and these outcomes. Follow-up time ranged from 2 to 25 years (mean 10.29 ± 5.16 years). Two SNPs showed associations with long-term outcomes and their statistical significance greatly increased after 39 RTR with a history of cardiovascular events prior to transplantation were removed from the analysis. Adjusted odds ratios (OR) for LEPR rs1805094 and ADIPOQ rs1501299 and risk of graft loss were 0.35 (0.16-0.74) p = 0.006 and 2.37 (1.28-4.37) p = 0.006, respectively. The assessment of risk for global mortality revealed OR values of 0.20 (0.06-0.62), p = 0.005, and 2.43 (1.08-5.44), p = 0.031 for LEPR rs1805094 and ADIPOQ rs1501299, respectively. Our results show that polymorphism in genes involved in leptin and adiponectin function modify long-term outcomes in renal transplantation.

Galectin-1-induced tolerogenic dendritic cells combined with apoptotic lymphocytes prolong liver allograft survival

Donor-derived tolerogenic dendritic cells (DCs) and apoptotic lymphocytes (ALs) are practical tools for controlling rejection after transplantation by targeting direct and indirect allorecognition pathways, respectively. To date, few studies have investigated the combination of donor-derived tolerogenic DCs and ALs infusion in organ transplantation protection. In the present study, we generated galectin-1-induced tolerogenic DCs (DC_gal-1s) and ultraviolet irradiation-induced ALs with stable immune characteristics in vitro and potential immune regulatory activity in vivo. A rat model of acute liver transplant rejection was established, and the intrinsic tolerogenic profiles associated with the short-term alleviation of rejection and the long-term maintenance of tolerance in the absence of immunosuppressive drugs were evaluated. The DC_gal-1-AL treatment prolonged allograft survival more significantly than a transfusion of DC_gal-1s or ALs alone. This benefit was associated with CD4⁺ Treg cell expansion and decreased interferon (IFN)-γ⁺ T cell levels. Moreover, DC_gal-1-AL treatment led to different cytokine/chemokine changes in the allograft and peripheral blood, that indicated an alleviation of local and systemic inflammation on day 7 post-transplantation. TGF-β1 and TGF-β2 were significantly increased in the long-term surviving allografts after DC_gal-1-AL treatment. Our results indicate that the combination of DC_gal-1s with ALs effectively prolongs liver allograft survival and represents a novel therapeutic strategy for liver transplant rejection.

Leptin, cardiovascular diseases and type 2 diabetes mellitus

Leptin, an adipokine that is implicated in the control of food intake via appetite suppression, may also stimulate oxidative stress, inflammation, thrombosis, arterial stiffness, angiogenesis and atherogenesis. These leptin-induced effects may predispose to the development of cardiovascular diseases. In the present review we discuss the evidence linking leptin levels with the presence, severity and/or prognosis of both coronary artery disease and non-cardiac vascular diseases such as stroke, carotid artery disease, peripheral artery disease (PAD) and abdominal aortic aneurysms (AAA) as well as with chronic kidney disease (CKD) and type 2 diabetes mellitus (T2DM). Leptin levels have been positively associated with the presence, severity, extent and lesion complexity of coronary atherosclerosis as well as with the presence, severity and poor clinical outcomes of both ischemic and hemorrhagic strokes. But conflicting results also exist. Furthermore, leptin was reported to independently predict common carotid intima-media thickness and carotid plaque instability. A link between hyperleptinemia and PAD has been reported, whereas limited data were available on the potential association between leptin and AAA. Elevated leptin concentrations have also been related to CKD incidence and progression as well as with insulin resistance, T2DM, micro- and macrovascular diabetic complications. Statins and antidiabetic drugs (including sitagliptin, metformin, pioglitazone, liraglutide and empagliflozin) may affect leptin levels. Further research is needed to establish the potential use (if any) of leptin as a therapeutic target in these diseases.