Visfatin, a new adipocytokine, is predominantly related to inflammation/endothelial damage in kidney allograft recipients

Association of visceral adipose tissue with albuminuria and interaction between visceral adiposity and diabetes on albuminuria

AIMS

To explore the correlation between visceral adipose tissue and albuminuria, and whether there is interaction between visceral adipose tissue and diabetes on albuminuria.

METHODS

The study subjects were adult subjects (age ≥ 18 years) from the National Health and Nutrition Examination Surveys (NHANES) database of the USA in 2017-2018. Visceral fat area (VFA) was measured by dual-energy X-ray absorptiometry (DXA). Subjects were divided into three groups according to VFA: low (VFA 0-60cm2), medium (VFA 60-120 cm2) and high (VFA ≥ 120 cm2). Albuminuria was defined as urinary albumin-to-creatinine ratio (UACR) ≥ 30 mg/g. The statistical analysis software used is STATA 17.0.

RESULTS

Data pertaining to 2965 participants (2706 without albuminuria) were included in the analysis. High VFA is an independent risk factor for albuminuria (OR 1.367, 95% CI 1.023-1.827). In the low-VFA group, there is no significant association between diabetes and albuminuria (OR 1.415, 95% CI 0.145-13.849). In the medium-VFA group, diabetes is an independent risk factor for albuminuria (OR 2.217, 95% CI 1.095-4.488). In the high-VFA group, diabetes is also an independent risk factor for albuminuria (OR 5.150, 95% CI 3.150-8.421). There is an additive interaction between high VFA (VFA ≥ 120 cm2) and diabetes on the effect of albuminuria (RERI 3.757, 95% CI 0.927-6.587, p = 0.009), while no multiplication interaction (OR 1.881, 95% CI 0.997-1.023, p = 0.141).

CONCLUSIONS

High VFA may represent an independent risk factor for albuminuria. The amount of visceral fat may affect the effect of diabetes on albuminuria. The higher the visceral fat, the stronger the correlation between diabetes and albuminuria should be present. We suppose an additive interaction between VFA and diabetes on the effect of albuminuria.

Contribution of membrane raft redox signalling to visfatin-induced inflammasome activation and podocyte injury

Recently we have shown that adipokine visfatin-induced NLRP3 inflammasome activation contributes to podocyte injury. However, the molecular mechanisms of how visfatin-induces the Nlrp3 inflammasome activation and podocyte damage is still unknown. The present study tested whether membrane raft (MR) redox signalling pathway plays a central role in visfatin-induced NLRP3 inflammasomes formation and activation in podocytes. Upon visfatin stimulation an aggregation of NADPH oxidase subunits, gp91phox and p47phox was observed in the membrane raft (MR) clusters, forming a MR redox signalling platform in podocytes. The formation of this signalling platform was blocked by prior treatment with MR disruptor MCD or NADPH oxidase inhibitor DPI. In addition, visfatin stimulation significantly increased the colocalization of Nlrp3 with Asc or Nlrp3 with caspase-1, IL-β production, cell permeability in podocytes compared to control cells. Pretreatment with MCD, DPI, WEHD significantly abolished the visfatin-induced colocalization of NLRP3 with Asc or NLRP3 with caspase-1, IL-1β production and cell permeability in podocytes. Furthermore, Immunofluorescence analysis demonstrated that visfatin treatment significantly decreased the podocin and nephrin expression (podocyte damage) and prior treatments with DPI, WEHD, MCD attenuated this visfatin-induced podocin and nephrin reduction. In conclusion, our results suggest that visfatin stimulates membrane raft clustering in the membrane of podocytes to form redox signaling platforms by aggregation and activation of NADPH oxidase subunits enhancing O2·- production and leading to NLRP3 inflammasome activation in podocytes and ultimate podocyte injury.

Associations between visceral adiposity index and incident nephropathy outcomes in diabetic patients: Insights from the ACCORD trial

AIMS

Visceral adiposity index (VAI) was a reliable marker for visceral adiposity accumulation and dysfunction. The association between VAI and nephropathy outcomes remains uncertain in patients with type 2 diabetes (T2DM). We aimed to evaluate the longitudinal relationships between VAI and incident nephropathy outcomes in T2DM patients.

MATERIALS AND METHODS

Ten thousand one hundred and thirty two participants with T2DM from the ACCORD trial were included in the present study. Cumulative average VAI based on VAI measurements at baseline and follow-up was used to represent long-term VAI status. The primary outcome was the incident composite nephropathy outcome defined as: (1) serum creatinine doubling or >20 ml/min decrease in eGFR; or (2) development of macro-albuminuria; or (3) renal failure or end stage kidney disease (dialysis) or serum creatinine >3.3 mg/dl.

RESULTS

During 26,168 person-years follow-up duration, 6094 (60.1%) participants developed the incident composite nephropathy outcome. When assessing cumulative average VAI as quartiles, compared with those in the 1-2 quartiles (<2.6), a significantly higher risk of incident composite nephropathy outcomes was observed among participants in the 3-4 quartiles (≥2.6, adjusted HR: 1.09, 95% CI: 1.01, 1.18). Moreover, the positive association was consistent in participants with or without single abnormal VAI components, including general obesity, abdominal obesity, elevated triglycerides, and low high-density lipoprotein cholesterol, or with different numbers of abnormal VAI components. Additionally, the positive association was stronger in participants with cumulative average systolic blood pressure <130 mmHg (vs. ≥130 mmHg; p-interaction < 0.001).

CONCLUSIONS

In T2DM patients, higher cumulative average VAI was associated with a higher risk of incident composite nephropathy outcomes.

CLINICAL TRIAL REGISTRATION

clinicaltrials.gov, identifier: NCT00000620.

Visfatin as a Promising Marker of Cardiometabolic Risk

Adipose tissue is an endocrine organ that produces molecules with important functions in the human body called adipokines. Visfatin can be secreted from various sources, such as macrophages, chondrocytes and amniotic epithelial cells other than adipose tissue. The main effect of visfatin is to promote inflammatory processes. In addition, visfatin has pivotal effects on the entire cardiovascular system, such as endothelial dysfunction, atherosclerosis, plaque rupture and mobilization, myocardial damage, fibrosis and new vessel formation. Vascular pathologies in other tissues also mediate its effects. Visfatin changes in a similar manner to cardiac markers in acute myocardial infarction, and the most cited feature in research studies is that it may be a cardiovascular risk marker. Visfatin is therefore expected to be widely used in cardiovascular pathology in the near future. Visfatin has many target tissues and various effects that occur in relatively complex biological pathways, making it difficult to understand visfatin adequately. In this review, we provide comprehensive information about this promising molecule.

NAMPT and NAPRT: Two Metabolic Enzymes With Key Roles in Inflammation

Nicotinamide phosphoribosyltransferase (NAMPT) and nicotinate phosphoribosyltransferase (NAPRT) are two intracellular enzymes that catalyze the first step in the biosynthesis of NAD from nicotinamide and nicotinic acid, respectively. By fine tuning intracellular NAD levels, they are involved in the regulation/reprogramming of cellular metabolism and in the control of the activity of NAD-dependent enzymes, including sirtuins, PARPs, and NADases. However, during evolution they both acquired novel functions as extracellular endogenous mediators of inflammation. It is well-known that cellular stress and/or damage induce release in the extracellular milieu of endogenous molecules, called alarmins or damage-associated molecular patterns (DAMPs), which modulate immune functions through binding pattern recognition receptors (PRRs), such as Toll-like receptors (TLRs), and activate inflammatory responses. Increasing evidence suggests that extracellular (e)NAMPT and eNAPRT are novel soluble factors with cytokine/adipokine/DAMP-like actions. Elevated eNAMPT were reported in several metabolic and inflammatory disorders, including obesity, diabetes, and cancer, while eNAPRT is emerging as a biomarker of sepsis and septic shock. This review will discuss available data concerning the dual role of this unique family of enzymes.

Obesity, Oxidative Stress, Adipose Tissue Dysfunction, and the Associated Health Risks: Causes and Therapeutic Strategies

Obesity is gaining acceptance as a serious primary health burden that impairs the quality of life because of its associated complications, including diabetes, cardiovascular diseases, cancer, asthma, sleep disorders, hepatic dysfunction, renal dysfunction, and infertility. It is a complex metabolic disorder with a multifactorial origin. Growing evidence suggests that oxidative stress plays a role as the critical factor linking obesity with its associated complications. Obesity per se can induce systemic oxidative stress through various biochemical mechanisms, such as superoxide generation from NADPH oxidases, oxidative phosphorylation, glyceraldehyde auto-oxidation, protein kinase C activation, and polyol and hexosamine pathways. Other factors that also contribute to oxidative stress in obesity include hyperleptinemia, low antioxidant defense, chronic inflammation, and postprandial reactive oxygen species generation. In addition, recent studies suggest that adipose tissue plays a critical role in regulating the pathophysiological mechanisms of obesity and its related co-morbidities. To establish an adequate platform for the prevention of obesity and its associated health risks, understanding the factors that contribute to the cause of obesity is necessary. The most current list of obesity determinants includes genetic factors, dietary intake, physical activity, environmental and socioeconomic factors, eating disorders, and societal influences. On the basis of the currently identified predominant determinants of obesity, a broad range of strategies have been recommended to reduce the prevalence of obesity, such as regular physical activity, ad libitum food intake limiting to certain micronutrients, increased dietary intake of fruits and vegetables, and meal replacements. This review aims to highlight recent findings regarding the role of oxidative stress in the pathogenesis of obesity and its associated risk factors, the role of dysfunctional adipose tissue in development of these risk factors, and potential strategies to regulate body weight loss/gain for better health benefits.

Increased Circulating Visfatin Is Associated With Progression of Kidney Disease in Non-Diabetic Hypertensive Patients

BACKGROUD

Declining renal function is an independent risk factor for all-cause mortality in cardiovascular disease. Visfatin has been described as a marker of inflammation and endothelial dysfunction, but whether circulating visfatin levels are predictive to a subsequent decline in renal function remains unclear.

METHODS

In total, 200 nondiabetic, non-proteinuric hypertensive outpatients with initial serum creatinine (Scr) ≤1.5 mg/dl were enrolled. Plasma visfatin concentration and endothelial function estimated by brachial artery flow-mediated dilatation (FMD) were determined in the study subjects. The primary endpoints were the occurrence of renal events including doubling of Scr, 25% loss of glomerular filtration rate (GFR) from baseline values, and the occurrence of end-stage renal disease during follow-up.

RESULTS

The mean annual rate of GFR decline (ΔGFR/y) was -1.26±2.76 ml/min/1.73 m(2) per year during follow-up (8.6±2.5 years). At baseline, plasma visfatin was negatively correlated with estimated GFR. In longitudinal analysis, the ΔGFR/y was correlated with visfatin, baseline GFR, FMD, systolic blood pressure, and fasting blood glucose (FBG). Multivariate analysis indicated that increased visfatin (r = -0.331, P <0.001), baseline GFR (r = -0.234, P = 0.001), FMD (r = 0.163, P = 0.015), and FBG (r = -0.160, P = 0.015) are independent predictors of ΔeGFR/y. Cox regression model analysis showed that visfatin (hazard ratio (HR), 1.09; 95% confidence interval (CI), 1.05-1.13, P <0.001), FBG (HR, 1.01; 95% CI, 1.00-1.02, P = 0.020), and FMD (HR, 0.87; 95% CI, 0.76-1.00, P = 0.049) were independently associated with the risk of developing future renal events.

CONCLUSIONS

Increased circulating visfatin are associated with subsequent decline in renal function in nondiabetic hypertensive patients.

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.

Association between serum visfatin and carotid atherosclerosis in diabetic and non-diabetic patients on maintenance hemodialysis

Introduction

Adipose tissue releases bioactive factors termed adipokines. Visfatin is an adipokine that plays an active role promoting vascular inflammation and atherosclerosis. The purpose of this study was to determine the association between serum visfatin levels and carotid atherosclerosis in diabetic and non-diabetic patients on maintenance hemodialysis (HD) in order to clarify the role of serum visfatinas, a risk factor for cardiovascular complications in HD patients.

Methods

Forty patients on maintenance hemodialysis were enrolled in this case-control study in 2015. They were subdivided into two groups, i.e., a diabetic group (n = 20) and a non-diabetic group (n = 20). Twenty healthy subjects who were age and gender matched were included as a control group. Carotid Duplex studies were performed on all patients, and serum visfatin was determined by a competitive enzyme immunoassay.

Results

HD patients showed a highly significant increase in serum visfatin, urea, creatinine, Ca×Ph, K, fasting glucose, triglycerides, LDL levels, and a significant decrease in eGFR, Na, HDL, and Hb compared to the control group. Also, serum visfatin levels showed a highly significant increase in the diabetic HD group compared to both the non-diabetic HD and control groups. Serum visfatin showed a highly significant increase in non-diabetic HD patients compared to the control group. Carotid intima-media thickness (IMT) showed a highly significant increase in HD group compared to the control group. Serum visfatin correlated positively with serum urea, creatinine, glucose, and IMT, but it was negatively correlated with eGFR, Na, and HDL

Conclusion

We concluded that serum visfatin is increased in HD patients with and without diabetes. Moreover, its association with IMT may be involved in the pathogenesis of atherosclerosis in CRF patients.

Obesity in kidney disease: A heavyweight opponent

Obesity is an important worldwide challenge that must be faced in most developed and developing countries because of unhealthy nutritional habits. The consequences of obesity and being overweight are observed in different organs, but the kidney is one of the most affected. Excess adipose tissue causes hemodynamic alterations in the kidney that can result in renal disease. However, obesity is also commonly associated with other comorbidities such as chronic inflammation, hypertension and diabetes. This association of several aggravating factors is still a matter of concern in clinical and basic research because the pathophysiologic mechanisms surrounding chronic kidney disease development in obese patients remain unclear. This review will discuss the consequences of obesity in the context of renal injury.

Aryl hydrocarbon receptor mediates indoxyl sulfate-induced cellular senescence in human umbilical vein endothelial cells

AIM

Vascular senescence, which is accelerated in individuals with chronic kidney disease (CKD), contributes to the development of cardio-renal syndrome, and various uremic toxins may play important roles in the mechanisms underlying this phenomenon. We recently reported that indoxyl sulfate (IS), a uremic toxin, directly activates aryl hydrocarbon receptor (AhR) and generates oxidative stress through NADPH oxidase-4 in human umbilical vein endothelial cells (HUVECs). In the current study, we sought to examine whether IS regulates sirtuin 1 (Sirt1) and affects endothelial senescence via AhR activation.

METHODS

HUVECs were incubated with 500 μmol/L of IS for the indicated time periods. In order to evaluate changes in the senescence of the HUVECs, the number of senescence-associated β-galactosidase (SA β-gal)-positive cells was determined using an image analysis software program. The intracellular nicotinamide phosphoribosyltransferase (iNampt) activity, cellular NAD(＋)/NADPH ratio and Sirt1 activity were analyzed according to a colorimetric assay to determine the mechanism of cellular senescence. Furthermore, we evaluated the involvement of AhR in the senescence-related changes induced by IS using AhR antagonists.

RESULTS

IS decreased the iNampt activity, NAD(＋)/NADPH ratio and Sirt1 activity, resulting in an increase in the percentage of SA β-gal-positive cells. On the other hand, the AhR antagonists restored the IS-induced decrease in the NAD(＋) content in association with an improvement in the iNampt activity and ameliorated the senescence-related changes. Taken together, these results indicate that IS impairs the iNampt-NAD(＋)-Sirt1 system via AhR activation, which in turn promotes endothelial senescence.

CONCLUSIONS

The IS-AhR pathway induces endothelial senescence. Therefore, blocking the effects of AhR in the endothelium may provide a new therapeutic tool for treating cardio-renal syndrome.

Obesity in kidney transplantation

Kidney transplantation is the preferred modality of renal replacement therapy. Long-term patient and graft survival have only improved marginally over the recent decade, mainly because of the development of cardiovascular disease after transplantation. Obesity is a risk factor for cardiovascular disease and is common before and after transplantation. This article reviews the literature assessing the role of pre- and post-transplant obesity on patient and graft survival, discusses the underlying obesity-related mechanisms leading to inferior kidney transplant outcomes, and explores the role of nutritional intervention on improving long-term outcomes of transplantation. Although the role of pretransplant obesity remains uncertain, post-transplant obesity increases the risk of graft failure and mortality. Nutritional intervention is effective in achieving post-transplant weight loss, but the effect on long-term outcomes has not been established. Future research should focus on conducting nutritional intervention studies aiming to improve long-term outcomes of kidney transplantation.

Adipokines as a link between obesity and chronic kidney disease

Adipocytes secrete a number of bioactive adipokines that activate a variety of cell signaling pathways in central and peripheral tissues. Obesity is associated with the altered production of many adipokines and is linked to a number of pathologies. As an increase in body weight is directly associated with an increased risk for developing chronic kidney disease (CKD), there is significant interest in the link between obesity and renal dysfunction. Altered levels of the adipokines leptin, adiponectin, resistin, and visfatin can decrease the glomerular filtration rate and increase albuminuria, which are pathophysiological changes typical of CKD. Specifically, exposure of the glomerulus to altered adipokine levels can increase its permeability, fuse the podocytes, and cause mesangial cell hypertrophy, all of which alter the glomerular filtration rate. In addition, the adipokines leptin and adiponectin can act on tubular networks. Thus, adipokines can act on multiple cell types in the development of renal pathophysiology. Importantly, most studies have been performed using in vitro models, with future studies in vivo required to further elucidate the specific roles that adipokines play in the development and progression of CKD.

Visfatin/Nampt: an adipokine with cardiovascular impact

Adipose tissue is acknowledged as an endocrine organ that releases bioactive factors termed adipokines. Visfatin was initially identified as a novel adipokine with insulin-mimetic properties in mice. This adipokine was identical to two previously described molecules, namely, pre-B cell colony-enhancing factor (PBEF) and the enzyme nicotinamide phosphoribosyltransferase (Nampt). Enhanced circulating visfatin/Nampt levels have been reported in metabolic diseases, such as obesity and type 2 diabetes. Moreover, visfatin/Nampt circulating levels correlate with markers of systemic inflammation. In cardiovascular diseases, visfatin/Nampt was initially proposed as a clinical marker of atherosclerosis, endothelial dysfunction, and vascular damage, with a potential prognostic value. Nevertheless, beyond being a surrogate clinical marker, visfatin/Nampt is an active player promoting vascular inflammation, and atherosclerosis. Visfatin/Nampt effects on cytokine and chemokine secretion, macrophage survival, leukocyte recruitment by endothelial cells, vascular smooth muscle inflammation and plaque destabilization make of this adipokine an active factor in the development and progression of atherosclerosis. Further research is required to fully understand the mechanisms mediating the cellular actions of this adipokine and to better characterize the factors regulating visfatin/Nampt expression and release in all these pathologic scenarios. Only then, we will be able to conclude whether visfatin/Nampt is a therapeutical target in cardiometabolic diseases.

Visfatin impairs endothelium-dependent relaxation in rat and human mesenteric microvessels through nicotinamide phosphoribosyltransferase activity

Visfatin, also known as extracellular pre-B-cell colony-enhancing factor (PBEF) and nicotinamide phosphoribosyltransferase (Nampt), is an adipocytokine whose circulating levels are enhanced in metabolic disorders, such as type 2 diabetes mellitus and obesity. Circulating visfatin levels have been positively associated with vascular damage and endothelial dysfunction. Here, we investigated the ability of visfatin to directly impair vascular reactivity in mesenteric microvessels from both male Sprague-Dawley rats and patients undergoing non-urgent, non-septic abdominal surgery. The pre-incubation of rat microvessels with visfatin (50 and 100 ng/mL) did not modify the contractile response to noradrenaline (1 pmol/L to 30 µmol/L), as determined using a small vessel myograph. However, visfatin (10 to 100 ng/mL) concentration-dependently impaired the relaxation to acetylcholine (ACh; 100 pmol/L to 3 µmol/L), without interfering with the endothelium-independent relaxation to sodium nitroprusside (1 nmol/L to 3 µmol/L). In both cultured human umbilical vein endothelial cells and rat microvascular preparations, visfatin (50 ng/mL) stimulated nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity, as determined by lucigenin-derived chemiluminiscence. The relaxation to ACh impaired by visfatin was restored by the NADPH oxidase inhibitor apocynin (10 µmol/L). Additionally, the Nampt inhibitor APO866 (10 mmol/L to 10 µmol/L), but not an insulin receptor-blocking antibody, also prevented the stimulation of NADPH oxidase and the relaxation impairment elicited by visfatin. Accordingly, the product of Nampt activity nicotinamide mononucleotide (100 nmol/L to 1 mmol/L) stimulated endothelial NADPH oxidase activity and concentration-dependently impaired ACh-induced vasorelaxation. In human mesenteric microvessels pre-contracted with 35 mmol/L potassium chloride, the endothelium-dependent vasodilation to bradykinin (1 nmol/L to 3 µmol/L) was equally impaired by visfatin and restored upon co-incubation with APO866. In conclusion, visfatin impairs endothelium-dependent relaxation through a mechanism involving NADPH oxidase stimulation and relying on Nampt enzymatic activity, and therefore arises as a potential new player in the development of endothelial dysfunction.

Serum visfatin as a non-traditional biomarker of endothelial dysfunction in chronic kidney disease: an Egyptian study

BACKGROUND

Endothelial dysfunction (ED) is closely linked to cardiovascular disease and outcome in patients with chronic kidney disease (CKD). Visfatin is an adipocytokine that recently generated much interest; however, its role in CKD remains to be clarified. This study aimed to assess visfatin in correlation with markers of ED and inflammation in Egyptian patients with CKD.

METHODS

The study included 40 non-diabetic, clinically stable CKD patients and 20 healthy volunteers. Serum levels of visfatin, markers of ED (intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1)) and markers of inflammation (interleukin-6 (IL-6), and C-reactive protein (CRP)) were measured. Endothelial function was evaluated using brachial artery flow-mediated dilatation (FMD).

RESULTS

Serum visfatin, ICAM-1, VCAM-1, CRP, and IL-6 levels were significantly elevated and FMD% was decreased in CKD patients as compared to controls. Visfatin correlated positively with ICAM-1, VCAM-1, CRP, and IL-6 and negatively with FMD% in CKD patients. In a multiple regression model, visfatin was strongly and independently associated with FMD (Beta=-0.02, P<0.001) in CKD patients.

CONCLUSIONS

Serum visfatin is strongly associated with endothelial adhesion molecules and FMD%, suggesting that visfatin is an important promising biomarker for prediction of ED and future cardiovascular risk in CKD patients. Moreover, the relationship between visfatin and IL-6 indicates that circulating visfatin may reflect the sub-clinical inflammatory status. Thus, visfatin might be involved in the complex interactions between ED, inflammation, and atherosclerosis and their major clinical consequences; however, further prospective studies are required to prove this hypothesis.