The complex role of adiponectin in chronic kidney disease

Exploring Adiponectin in Autosomal Dominant Kidney Disease: Insight and Implications

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a common monogenic disorder characterized by renal cysts and progressive renal failure. In kidney diseases, adipose tissue undergoes functional changes that have been associated with increased inflammation and insulin resistance mediated by release of adipokines. Adiponectin is involved in various cellular processes, such as energy and inflammatory and oxidative processes. However, it remains to be determined whether adiponectin is involved in the concomitant metabolic dysfunctions present in PKD. In this scenario, we aimed to analyze: (a) PPARγ, ADIPOQ, ADIPOR1 and ADIPOR2 gene variations in 92 ADPKD patients through PCR-Sanger sequencing; and (b) adiponectin levels and its oligomerization state by ELISA and Western Blot. Our results indicated that: (a) 14 patients carried the PPARγ SNP, 29 patients carried the ADIPOQ SNP rs1501299, and 25 patients carried the analyzed ADIPOR1 SNPs. Finally, 82 patients carried ADIPOR2 SNPs; and (b) Adiponectin is statistically lower in ADPKD patients compared to controls, and further statistically lower in ESRD than in non-ESRD patients. An inverse relationship between adiponectin and albumin and between adiponectin and creatinine and a direct relationship between adiponectin and eGFR were found. Interestingly, significantly lower levels of adiponectin were found in patients bearing the ADIPOQ rs1501299 SNP and associated with low levels of eGFR. In conclusion, adiponectin levels and the presence of ADIPOQ rs1501299 genotype are significantly associated with a worse ADPKD phenotype, indicating that both could potentially provide important insights into the disease. Further studies are warranted to understand the pathophysiological role of adiponectin in ADPKD patients.

Association Between Adipokine Profile, Systemic Inflammation, Muscle and Protein Energy Wasting in Children With Chronic Kidney Disease

OBJECTIVES

This cross-sectional study explores the association of adipokines and interleukin-6 (IL-6) with muscle and protein energy wasting (PEW) in children with chronic kidney disease (CKD).

METHODS

We measured serum adiponectin, leptin, resistin and IL-6 in 53 patients with CKD stage 3-5. Lean tissue (LTI) and fat tissue index (FTI) were estimated by bioimpedance analysis spectroscopy. PEW was defined as muscle wasting [LTI adjusted to height age (LTI HA) z-score < -1.65 SD) and at least 2 of the following: reduced body mass [body mass index adjusted to height age (BMI HA) z-score < -1.65 SD), poor growth [height z-score < -1.88 SD], questionnaire-based decreased appetite, and serum albumin ≤3.8 g/dL.

RESULTS

PEW, observed in 8 (15.1%) patients, was more prevalent in CKD stage 5 (P = .010). Among the adipokines, adiponectin, and resistin levels were significantly higher in CKD stage 5 (P < .001, P = .005). Adiponectin was correlated to LTI HA z-score (Rs = -0.417, P = .002), leptin to FTI z-score (Rs = 0.620, P < .001), while no correlation was observed between resistin and body composition parameters. Resistin was the only adipokine correlated to IL-6 (Rs = 0.513, P < .001). After adjustment for CKD stage and patient age, PEW was associated with adiponectin and IL-6 rise by 1 μg/mL and 10 pg/mL respectively (odds ratio (OR) 1.240, 95% confidence interval (CI) 1.040, 1.478 and OR 1.405, 95% CI 1.075-1.836) but not with leptin, while resistin association with PEW lost its significance.

CONCLUSIONS

In pediatric CKD, adiponectin is associated with muscle wasting, leptin with adiposity and resistin with systemic inflammation. Adiponectin and cytokine IL-6 may serve as PEW biomarkers.

Trends in insulin resistance: insights into mechanisms and therapeutic strategy

The centenary of insulin discovery represents an important opportunity to transform diabetes from a fatal diagnosis into a medically manageable chronic condition. Insulin is a key peptide hormone and mediates the systemic glucose metabolism in different tissues. Insulin resistance (IR) is a disordered biological response for insulin stimulation through the disruption of different molecular pathways in target tissues. Acquired conditions and genetic factors have been implicated in IR. Recent genetic and biochemical studies suggest that the dysregulated metabolic mediators released by adipose tissue including adipokines, cytokines, chemokines, excess lipids and toxic lipid metabolites promote IR in other tissues. IR is associated with several groups of abnormal syndromes that include obesity, diabetes, metabolic dysfunction-associated fatty liver disease (MAFLD), cardiovascular disease, polycystic ovary syndrome (PCOS), and other abnormalities. Although no medication is specifically approved to treat IR, we summarized the lifestyle changes and pharmacological medications that have been used as efficient intervention to improve insulin sensitivity. Ultimately, the systematic discussion of complex mechanism will help to identify potential new targets and treat the closely associated metabolic syndrome of IR.

Kidney Damage Caused by Obesity and Its Feasible Treatment Drugs

The rapid growth of obesity worldwide has made it a major health problem, while the dramatic increase in the prevalence of obesity has had a significant impact on the magnitude of chronic kidney disease (CKD), especially in developing countries. A vast amount of researchers have reported a strong relationship between obesity and chronic kidney disease, and obesity can serve as an independent risk factor for kidney disease. The histological changes of kidneys in obesity-induced renal injury include glomerular or tubular hypertrophy, focal segmental glomerulosclerosis or bulbous sclerosis. Furthermore, inflammation, renal hemodynamic changes, insulin resistance and lipid metabolism disorders are all involved in the development and progression of obesity-induced nephropathy. However, there is no targeted treatment for obesity-related kidney disease. In this review, RAS inhibitors, SGLT2 inhibitors and melatonin would be presented to treat obesity-induced kidney injury. Furthermore, we concluded that melatonin can protect the kidney damage caused by obesity by inhibiting inflammation and oxidative stress, revealing its therapeutic potential.

Distribution of serum adiponectin isoforms in pediatric patients with steroid-sensitive nephrotic syndrome

BACKGROUND

Serum adiponectin circulates in three multimeric isoforms: high-molecular-weight (HMW), middle-molecular-weight (MMW), and low-molecular-weight (LMW) isoforms. Potential change in the circulating adiponectin levels in patients with nephrotic syndrome (NS) remain unknown. This study aimed to assess the levels of total adiponectin and the distribution of its isoforms in pediatric patients with NS.

METHODS

We sequentially measured total adiponectin and each adiponectin isoform levels at the onset of NS, initial remission, and during the remission period of the disease in 31 NS patients. We also calculated the ratios of HMW (%HMW), MMW (%MMW), and LMW (%LMW) to total adiponectin incuding 51 control subjects.

RESULTS

The median of total serum adiponectin levels in patients were 36.7, 36.7, and 20.2 μg/mL at the onset, at initial remission, and during the remission period of NS, respectively. These values were significantly higher than those in control subjects. The median values of %HMW, %MMW, and %LMW values were 56.9/27.0/14.1 at the onset, 62.0/21.8/13.4 at the initial remission, and 58.1/21.7/17.5 at during the remission period of NS, respectively. Compared with control subjects, %HMW at initial remission and %MMW at the onset were high, and the %LMW values at the onset and at initial remission were low.

CONCLUSIONS

In patients with NS, total serum adiponectin levels increase at the onset of the disease, and the ratio of adiponectin isoforms changes during the course of the disease. Further studies are needed to delineate the mechanisms between proteinuria and adiponectin isoforms change.

Effects of Obesity and Diabetes on Sperm Cell Proteomics in Rats

Infertility caused by male factors is potentially associated with metabolic disorders such as obesity and/or diabetes. This experimental study was conducted in a male rodent model to assess the effects of different diseases on semen quality and sperm proteomics. Ten Wistar rats were used for each treatment. Rats were fed commercial food provided controllably to the control group and the diabetic group, and a hypercaloric diet supplemented with 5% sucrose in water was provided ad libitum to the obese group for 38 weeks. Diabetes was induced with 35 mg/kg streptozotocin. After euthanasia, testicles, spermatozoa, fat, and blood (serum) samples were collected. Spermatozoa were evaluated for quality and subjected to proteomics analyses. Histology and cytology of the testis, and serum leptin, adiponectin, interleukin 8 (IL-8), blood glucose, and testosterone levels, were also assessed. Body weight, retroperitoneal and testicular fat, and the Lee index were also measured. Obesity and diabetes were induced. The diabetic group showed noticeable changes in spermatogenesis and sperm quality. The mass spectrometry proteomics data have been deposited in Mendeley Data (doi: 10.17632/rfp7kfjcsd.5). Fifteen proteins varied in abundance between groups, especially proteins related to energy production and structural function of the spermatozoa, suggesting disturbances in energy production with a subsequent alteration in sperm motility in both groups, but with a compensatory response in the obese group.

Effect of parathyroidectomy on bone tissue biomarkers and body composition in patients with chronic kidney disease and secondary hyperparathyroidism

BACKGROUND/OBJECTIVE

Loss of renal function may induce secondary hyperparathyroidism (s-HPT), which triggers several complications leading to an extreme decline in quality of life and increased mortality in affected patients. We evaluated whether parathyroidectomy (PTx), as surgical treatment for s-HPT, modifies body composition, and hormones involved in the protein-energy metabolism of affected patients.

SUBJECTS/METHODS

Overall, 30 s-HPT patients were evaluated at two times, before PTx (pre PTx) and 6 months after PTx (post PTx). Patients were evaluated by biochemistry analysis, anthropometry, electrical bioimpedance (BIA), food intake diary, handgrip strength, and modified global subjective nutritional assessment (SGA).

RESULTS

After PTx, patients showed decreased serum levels of total and ionic calcium, as well as decreased alkaline phosphatase and PTH, and increased 25 (OH) vitamin D. These results demonstrate that PTx was efficient to correct part of the mineral disorder. We also observed an increase in caloric intake, body weight, body mass index (BMI), phase angle, handgrip strength, SGA score, and a decreasing in the percentage of weight loss. The osteocalcin concentration of both carboxylated (cOC) and undercarboxylated form was diminished post PTx. The cOC correlated with bone metabolism markers and SGA score.

CONCLUSIONS

PTx modified body composition improving nutritional status and preventing the progression of weight loss with increased of energy intake, BMI, handgrip strength, phase angle of BIA, and SGA score. The present study also suggests an association of cOC with bone markers and SGA score. Further studies are needed to better clarify these associations with larger sample size.

Adiponectin in Chronic Kidney Disease

Adiponectin is the adipokine associated with insulin sensitization, reducing liver gluconeogenesis, and increasing fatty acid oxidation and glucose uptake. Adiponectin is present in the kidneys, mainly in the arterial endothelium and smooth muscle cells, as well as in the capillary endothelium, and might be considered as a marker of many negative factors in chronic kidney disease. The last few years have brought a rising body of evidence that adiponectin is a multipotential protein with anti-inflammatory, metabolic, anti-atherogenic, and reactive oxygen species (ROS) protective actions. Similarly, adiponectin has shown many positive and direct actions in kidney diseases, and among many kidney cells. Data from large cross-sectional and cohort studies showed a positive correlation between serum adiponectin and mortality in chronic kidney disease. This suggests a complex interaction between local adiponectin action, comorbidities, and uremic milieu. In this review we discuss the role of adiponectin in chronic kidney disease.

Adiponectin in renal fibrosis

Renal fibrosis is an inevitable consequence of parenchymal scarring and is the common final pathway that mediates almost all progressive renal diseases. Adiponectin, a hormone produced by adipose tissue, possesses potent anti-insulin, anti-inflammatory, and anti-fibrotic properties. Reportedly, adiponectin serves as an important messenger that facilitates complex interactions between adipose tissue and other metabolically related organs. In recent years, a growing body of evidence supports adiponectin involvement in renal fibrosis. These studies provide a deeper understanding of the molecular mechanism of action of adiponectin in renal fibrosis and also offer a potential preventive and therapeutic target for renal fibrosis. In this review, the physiological role of adiponectin is briefly introduced, and then the mechanism of adiponectin-mediated renal fibrosis and the related signaling pathways are described. Finally, we summarize the findings regarding the clinical value of adiponectin in renal fibrotic diseases and prospected its application potential.

Adiponectin for the treatment of diabetic nephropathy

The metabolic burden caused by hyperglycemia can result in direct and immediate metabolic injuries, such as oxidative stress and tissue inflammation, in the kidney. Furthermore, chronic hyperglycemia can lead to substantial structural changes such as formation of advanced glycation end-products, glomerular and tubular hypertrophy, and tissue fibrosis. Glomerular hypertrophy renders podocytes vulnerable to increased glomerular filtration, leading to podocyte instability and loss. Thus, prevention of glomerular hypertrophy and attenuation of glomerular hyperfiltration may have therapeutic potential for diabetic nephropathy (DN). Adiponectin is an adipokine that improves insulin sensitivity in obesity-related metabolic disorders, including diabetes, but its efficacy is unknown. Moreover, the recently developed adiponectin receptor agonist, AdipoRon, shows therapeutic potential for DN. In this review, we focus on the role of glomerular hypertrophy in the pathogenesis of DN and discuss the role of adiponectin in its prevention.

The Impact of Insulin Resistance and Chronic Kidney Disease on Inflammation and Cardiovascular Disease

There is extensive evidence showing that insulin resistance (IR) is associated with chronic low-grade inflammation. Furthermore, IR has been shown to increase the risk for cardiovascular disease (CVD), even in nondiabetic patients, and is currently considered as a “nontraditional” risk factor contributing to CVD by promoting hypertension, oxidative stress, endothelial dysfunction, dyslipidemia, and type 2 diabetes mellitus. However, chronic kidney disease (CKD) is also considered a state of low-grade inflammation. In addition, CKD is considered an IR state and has been described as an independent risk factor for the development of CVD, as even early-stage CKD is associated with an estimated 40% to 100% increase in CVD risk. There is also strong evidence indicating that inflammation per se plays a crucial role in both the initiation and progression of CVD. Given the above, the combined effect of IR and CKD may significantly increase the risk of inflammation and CVD. This review aims to focus on the complex interplay between IR, CKD, inflammation, and CVD and will present and discuss the current clinical and scientific data pertaining to the impact of IR and CKD on inflammation and CVD.

The complex effects of adipokines in the patients with kidney disease

Kidney diseases are categorized as the highest prevalent ones with worldwide noticeable incidence. They cause accelerated cardiovascular diseases and noticeable mortalities. Adipose tissue and its messengers, adipokines, are reported to have the highest relationship with end-stage renal diseases or chronic kidney diseases. Over recent years, with shifting of scientists’ mindset from a simple overview of adipose tissue as a fat store to the complex paradigm of this issue as a multipotential secretory organ, the importance of studies on this tissue has emerged.

Associations of Adiponectin, Leptin Levels, and the Change of Body Composition in Patients on Peritoneal Dialysis: A Prospective Cohort Study

Background

Although the association between adipokines such as adiponectin, leptin, and body composition has been noted, whether they could predict the change of fat mass and lean body mass is unknown. We aimed to examine these associations in patients on peritoneal dialysis (PD) through a prospective cohort study.

Methods

Body composition (by dual-energy x-ray absorptiometry) including fat mass and lean body mass were examined at baseline and then at year 3. Serum leptin and adiponectin levels were measured. Demographic data, comorbidity, biochemical data, inflammation (high-sensitive C-reactive protein [hs-CRP]) and insulin resistance (homeostatic model assessment [HOMA-IR]) were also examined.

Results

At baseline, serum adiponectin levels were significantly inversely correlated with weight, lean body mass index (LBMI), fat mass index (FMI), lean body mass (LBM), and fat mass (FM) in 213 prevalent patients. At year 3, FMI, LBMI, FM, and the percentage of FM (FM%) increased while the percentage of LBM (LBM%) significantly decreased despite unchanged weight and LBM among the remaining 112 patients. After adjustment for demographic data, comorbidities, hs-CRP, HOMA-IR, and daily energy intake (DEI), serum adiponectin at baseline was not associated with increases in LBMI, FMI, and FM, but independently associated with an increase in FM% and a decrease in LBM%. The predictive effect of high-serum adiponectin level on mortality disappeared after adjusting for diabetes and cardiovascular disease. Serum leptin was not associated with any changes in body composition during the follow-up, nor with the mortality in this cohort.

Conclusions

A high adiponectin level could predict an increase in FM% and a decrease in LBM% during a 3-year follow-up in PD patients. Serum adiponectin could not independently predict mortality in PD patients.

Adiponectin attenuates kidney injury and fibrosis in deoxycorticosterone acetate-salt and angiotensin II-induced CKD mice

Adiponectin (ApN) is a multifunctional adipokine. However, high, rather than low, concentrations of ApN are unexpectedly found in patients with chronic kidney disease (CKD) via an as yet unknown mechanism, and the role of ApN in CKD is unclear. Herein, we investigated the effect of ApN overexpression on progressive renal injury resulting from deoxycorticosterone acetate-salt (DOCA) and angiotensin II (ANG II) infusion using a transgenic, inducible ApN-overexpressing mouse model. Three groups of mice [wild type receiving no infusion (WT) and WT and cytochrome P450 1a1 (cyp1a1)-ApN transgenic mice (ApN-Tg) receiving DOCA+ANG II infusion (WT/DOCA+ANG II and ApN-Tg/DOCA+ANG II)] were assigned to receive normal food containing 0.15% of the transgene inducer indole-3-carbinol (I3C) for 3 wk. In the I3C-induced ApN-Tg/DOCA+ANG II mice, not the WT or WT/DOCA+ANG II mice, overexpression of ApN in liver resulted in 3.15-fold increases in circulating ApN compared with nontransgenic controls. Of note, the transgenic mice receiving DOCA+ANG II infusion were still hypertensive but had much less albuminuria and glomerular and tubulointerstitial fibrosis, which were associated with ameliorated podocyte injury determined by ameliorated podocyte loss and foot process effacement, and alleviated tubular injury determined by ameliorated mRNA overexpression of kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin and mRNA decreases of cubilin and megalin in tubular cells, compared with WT/DOCA+ANG II mice. In addition, renal production of NF-κB-p65, NAPDH oxidase 2, and p47 ^phox and MAPK-related cellular proliferation, which were induced in WT/DOCA+ANG II mice, were markedly reduced in ApN-Tg/DOCA+ANG II mice. These results indicate that elevated ApN in the CKD mouse model is renal protective. Enhancing ApN production or signaling may have therapeutic potential for CKD.

High serum adiponectin is associated with anemia development in chronic kidney disease: The results from the KNOW-CKD study

BACKGROUND

Adiponectin is an adipokine secreted by adipocytes. A low adiponectin level is a significant risk factor of diabetes mellitus and cardiovascular disease. Recent studies have shown that adiponectin is negatively associated with hematopoiesis and predicts the development of anemia in the general population. In chronic kidney disease (CKD) patients, circulating adiponectin level is paradoxically elevated and the role of adiponectin is complex. Therefore, we evaluated the relationship between adiponectin and anemia in these patients.

METHODS

This prospective longitudinal study included 2113 patients from the KNOW-CKD study (KoreaN cohort study for Outcome in patients With CKD), after excluding 125 without data on adiponectin levels. Hemoglobin levels were measured yearly during a mean follow-up period of 23.7 months. Anemia was defined as hemoglobin levels of <13.0 and 12.0 g/dL for men and women, respectively.

RESULTS

Mean patient age was 53.6 ± 12.2 years, and 1289 (61%) were men. The mean estimated glomerular filtration rate (eGFR) was 50.4 ± 30.2 mL min^-1 1.73 m^-2. Serum adiponectin level was inversely associated with body mass index, eGFR, log-transformed C-reactive protein, and positively with Charlson comorbidity index, urine protein to creatinine ratio, and high density lipoprotein cholesterol. In addition, serum adiponectin level was also negatively correlated with hemoglobin level and reticulocyte production index in both men and women. In multivariable linear regression analysis after adjustment of multiple confounders, adiponectin was negatively associated with hemoglobin (men, β = -0.219, P < .001; women, β = -0.09, P = .025). Among 1227 patients without anemia at baseline, 307 newly developed anemia during the follow-up period. In multivariable Cox regression analysis after adjustment of confounders, high adiponectin level was significantly associated with an increased risk of incident anemia (per 1 µg/mL increase, hazard ratio, 1.02; 95% confidence interval 1.01-1.04; P = .001).

CONCLUSIONS

A high serum adiponectin level is independently associated with a low hemoglobin level and predicts the development of anemia in patients with CKD. These findings reveal the potential role of adiponectin in CKD-related anemia.

The polyunsaturated fatty acid balance in kidney health and disease: A review

Epidemiological studies show that circulating polyunsaturated fatty acids contribute to preserve renal function. In renal disease states there is generally a lack of omega-3 long chain polyunsaturated fatty acids (n-3 LCPUFA) as measured in biological samples, but despite intense research for more than 30 years, it is still unclear how and to what extent their supplementation would benefit kidney disorders. Studies evaluating the n-6 series and the kidney are less frequent. The last compilation of clinical trials with n-3 LCPUFA supplements focusing on renal function and damage dates back to 2012. We here discuss n-3 and n-6 fatty acids in relation to the kidney summarizing single- and double blind randomized controlled trials performed between 2012 and 2016. Nine were sub-studies/post-hoc analyses of previous parent trials. Twelve out of the twenty trials reported on fatty acid profile or fatty acid species. Factors that may explain inconsistent results obtained after supplementation with the n-3 LCPUFA EPA and DHA in kidney disease are discussed such as baseline levels determining response, drug interaction. The need of evaluating fatty acid status before and after intervention is emphasized, to match changes in outcome measure with changes of any fatty acid potentially involved.

Associations of adiponectin and leptin levels with protein-energy wasting, in end stage renal disease patients

OBJECTIVE

The aim of the study was to examine the prevalence of protein-energy wasting (PEW) in hemodialysis (HD) and peritoneal dialysis (PD) patients in our center and determine whether adiponectin and leptin are involved in the development of PEW.

DESIGN

Prospective (18 months).

SETTING

University Hospital of Heraklion, Crete, Greece.

SUBJECTS

Seventy-four end-stage-renal-disease patients, 47 on HD and 27 on PD.

MAIN OUTCOME MEASURES

At three sequential time points (baseline, 6 and 18 months) anthropometric, nutritional and inflammatory status data were collected. Serum adiponectin and leptin were also assessed at each time point. Patients were allocated to 3 strata according to PEW severity (0, 1-2 and ≥3 criteria for PEW).

RESULTS

Adiponectin and leptin levels were greater among PD compared to HD patients (p≤0.035). Adiponectin levels were incrementally greater across increasing strata of PEW (p≤0.002). Leptin showed the opposite trend, with lower levels in malnourished patients and higher levels in patients with zero PEW criteria (p≤0.042). Alterations of adiponectin levels during the observation period were dependent on PEW stratum (p≤0.021) and mode of dialysis (p≤0.002), after adjustment for age, dialysis vintage, gender and fat mass index. Particularly, adiponectin levels increased over time in HD patients with ≥3 criteria for PEW, whereas adiponectin levels decreased in PD patients with ≥3 criteria for PEW throughout the study. Leptin alterations over time were not affected by dialysis mode or PEW stratification.

CONCLUSIONS

Our study provides evidence that increased adiponectin and decreased leptin levels are independently associated with PEW and thus, poor prognosis.

Comparative Assessment of Serum Adipokines Zinc-α2-glycoprotein and Adipose Triglyceride Lipase, and Cardiovascular Risk Factors Between Normal Weight and Obese Patients with Hemodialysis

BACKGROUND

Little is known about the potential relationship of obesity, adipose tissue and novel adipokines with cardiometabolic risk factors in end-stage renal disease. Zinc-α2-glycoprotein (ZAG) and adipose triglyceride lipase (ATGL) are novel adipokines with proposed desirable effects on inflammation, and lipid and glucose metabolism. The aim of this study was to investigate serum concentrations of ZAG and ATGL, and the relationship of these adipokines with cardiovascular risk factors in normal weight (NW) and obese (OB) patients undergoing hemodialysis.

METHODS

Patients with regular hemodialysis including 44 normal weight (18.5<BMI<25 kg/m²) and 44 obese (BMI≥30 kg/m²) were enrolled. Serum lipid profile, high-sensitivity C-reactive protein (hsCRP) and nitric oxide metabolites along with ZAG and ATGL concentrations were assessed.

RESULTS

ZAG concentrations were significantly lower in OB compared to NW group (100 ± 34 vs. 106 ± 31 ng/ml; p = 0.007). No significant difference was observed in ATGL between the two groups. A significant inverse correlation between ZAG and HDL (r = ‒0.236, p = 0.048) and a marginal inverse correlation between ATGL and HDL (r = ‒0.211, p = 0.078) were observed in all patients. ZAG had positive correlations with triglyceride/HDL (r = 0.279, p = 0.019), cholesterol/HDL (r = 0.319, p = 0.007), and LDL/HDL (r = 0.26, p = 0.029) ratios. Among cardiovascular risk factors, only LDL/HDL ratio and hsCRP were significantly higher in OB patients (p = 0.009 and p = 0.038, respectively).

CONCLUSIONS

Serum concentrations of ZAG, but not ATGL, were significantly lower in the OB group. It appears that obesity overrides the role of hemodialysis in determining ZAG concentration. In contrast, uremic condition might overshadow the role of obesity in determining levels of traditional cardiovascular risk factors.

Alterations of HDL Particles in Children with End-stage Renal Disease

Background

Unfavorable lipid profile presents one of most important risk factor for cardiovascular disease in renal pathology. Myeloperoxidase (MPO) as enzyme which oxidizes lipoproteins and paraoxonase1 (PON1) as anti-oxidative enzyme have been involved in pathogenesis of cardiovascular disease. In the present study we sought to assess oxidative stress status, lipoprotein subclasses distribution as well as functionality of high density lipoprotein (HDL) trough MPO/PON1 ratio in children with chronic kidney disease (CKD) and children after renal transplantation.

Methods

PON1 activity and oxidative stress parameters were measured spectrophotometrically, while MPO concentration was determined using immunoassay. Separation of lipoprotein subclasses was performed by vertical gradient gel electrophoresis in 19 children with different stage of CKD and 19 post-transplantation patients (PT).

Results

CKD patients had increased MPO/PON1 ratio and higher prevalence of smaller HDL subclasses when compared to PT subjects. Also, there was a significant positive correlation between MPO level and MPO/PON1 ratio with relative proportion of smaller HDL subclasses.

Conclusion

Children with CKD have impaired HDL distribution that is improved after kidney transplantation. Since that measurement of HDL distribution and functionality are not routinely available, MPO/PON1 ratio may be useful marker that could provide necessary information.

Adiponectin, lipids and atherosclerosis

PURPOSE OF REVIEW

Adiponectin is an adipokine with anti-inflammatory, antioxidant, antiatherogenic, pro-angiogenic, vasoprotective and insulin-sensitizing properties. Several factors may influence adiponectin levels, such as genetic polymorphisms, obesity / body fat distribution, diet and exercise as well as cardiovascular risk factors such as sleep deprivation and smoking as well as medications. Adiponectin has been proposed as a potential prognostic biomarker and a therapeutic target in patients with cardiometabolic diseases.

RECENT FINDINGS

This narrative review discusses the associations of adiponectin with obesity-related metabolic disorders (metabolic syndrome, nonalcoholic fatty liver disease, hyperuricaemia and type 2 diabetes mellitus). We also focus on the links between adiponectin and lipid disorders and with coronary heart disease and noncardiac vascular diseases (i.e. stroke, peripheral artery disease, carotid artery disease, atherosclerotic renal artery stenosis, abdominal aortic aneurysms and chronic kidney disease). Further, the effects of lifestyle interventions and drug therapy on adiponectin levels are briefly reviewed.

SUMMARY

Based on available data, adiponectin represents a multifaceted biomarker that may beneficially affect atherosclerosis, inflammation and insulin resistance pathways. However, there are conflicting results with regard to the associations between adiponectin levels and the prevalence and outcomes of cardiometabolic diseases. Further research on the potential clinical implications of adiponectin in the diagnosis and treatment of such diseases is needed.

Adiponectin and Its Receptors in Diabetic Kidney Disease: Molecular Mechanisms and Clinical Potential

Diabetic kidney disease (DKD) is a major complication for diabetic patients. Adiponectin is an insulin sensitizer and anti-inflammatory adipokine and is mainly secreted by adipocytes. Two types of adiponectin receptors, AdipoR1 and AdipoR2, have been identified. In both type 1 and type 2 diabetes (T2D) patients with DKD, elevated adiponectin serum levels have been observed, and adiponectin serum level is a prognostic factor of end-stage renal disease. Renal insufficiency and tubular injury possibly play a contributory role in increases in serum and urinary adiponectin levels in diabetic nephropathy by either increasing biodegradation or elimination of adiponectin in the kidneys, or enhancing production of adiponectin in adipose tissue. Increases in adiponectin levels resulted in amelioration of albuminuria, glomerular hypertrophy, and reduction of inflammatory response in kidney tissue. The renoprotection of adiponectin is associated with improvement of the endothelial dysfunction, reduction of oxidative stress, and upregulation of endothelial nitric oxide synthase expression through activation of adenosine 5'-monophosphate-activated protein kinase by AdipoR1 and activation of peroxisome proliferator-activated receptor (PPAR)-α signaling pathway by AdipoR2. Several single nucleotide polymorphisms in the AdipoQ gene, including the promoter, are associated with increased risk of the development of T2D and DKD. Renin-angiotensin-aldosterone system blockers, adiponectin receptor agonists, and PPAR agonists (e.g., tesaglitazar, thiazolidinediones, fenofibrate), which increase plasma adiponectin levels and adiponectin receptors expression, may be potential therapeutic drugs for the treatment of DKD.

WAT-on-a-chip: a physiologically relevant microfluidic system incorporating white adipose tissue

Organ-on-a-chip systems possess a promising future as drug screening assays and as testbeds for disease modeling in the context of both single-organ systems and multi-organ-chips. Although it comprises approximately one fourth of the body weight of a healthy human, an organ frequently overlooked in this context is white adipose tissue (WAT). WAT-on-a-chip systems are required to create safety profiles of a large number of drugs due to their interactions with adipose tissue and other organs via paracrine signals, fatty acid release, and drug levels through sequestration. We report a WAT-on-a-chip system with a footprint of less than 1 mm2 consisting of a separate media channel and WAT chamber connected via small micropores. Analogous to the in vivo blood circulation, convective transport is thereby confined to the vasculature-like structures and the tissues protected from shear stresses. Numerical and analytical modeling revealed that the flow rates in the WAT chambers are less than 1/100 of the input flow rate. Using optimized injection parameters, we were able to inject pre-adipocytes, which subsequently formed adipose tissue featuring fully functional lipid metabolism. The physiologically relevant microfluidic environment of the WAT-chip supported long term culture of the functional adipose tissue for more than two weeks. Due to its physiological, highly controlled, and computationally predictable character, the system has the potential to be a powerful tool for the study of adipose tissue associated diseases such as obesity and type 2 diabetes.

Sustained High Levels of Both Total and High Molecular Weight Adiponectin in Plasma during the Convalescent Phase of Haemorrhagic Fever with Renal Syndrome Are Associated with Disease Severity

Haemorrhagic fever with renal syndrome (HFRS) is characterised by an uncontrolled immune response that causes vascular leakage. Adiponectin (APN) is an adipocytokine involved in prorevascularisation and immunomodulation. To investigate the possible effects of APN in the pathogenesis of HFRS, total and high molecular weight (HMW) APN levels in the plasma of patients with HFRS were quantified using enzyme-linked immunosorbent assay (ELISA). Compared with those in healthy controls, the plasma total and HMW APN levels in patients were elevated to different degrees from the fever onset and remained high at the convalescent phase. Consistent with these results, western blot analysis additionally showed that low molecular weight (LMW), middle molecular weight (MMW), and HMW APN levels were all elevated and contributed to the elevation of the total APN level. Importantly, sustained high levels of total and HMW APN at the convalescent phase were significantly higher in patients with critical disease than those in patients with mild or moderate disease. Moreover, total and HMW APN levels negatively correlated with white blood cell count and positively correlated with platelet count and serum albumin level. These results may provide insights into understanding the roles of total and HMW APN in the pathogenesis of HFRS.

Inflammatory Cytokines as Uremic Toxins: "Ni Son Todos Los Que Estan, Ni Estan Todos Los Que Son"

Chronic kidney disease is among the fastest growing causes of death worldwide. An increased risk of all-cause and cardiovascular death is thought to depend on the accumulation of uremic toxins when glomerular filtration rate falls. In addition, the circulating levels of several markers of inflammation predict mortality in patients with chronic kidney disease. Indeed, a number of cytokines are listed in databases of uremic toxins and uremic retention solutes. They include inflammatory cytokines (IL-1β, IL-18, IL-6, TNFα), chemokines (IL-8), and adipokines (adiponectin, leptin and resistin), as well as anti-inflammatory cytokines (IL-10). We now critically review the cytokines that may be considered uremic toxins. We discuss the rationale to consider them uremic toxins (mechanisms underlying the increased serum levels and evidence supporting their contribution to CKD manifestations), identify gaps in knowledge, discuss potential therapeutic implications to be tested in clinical trials in order to make this knowledge useful for the practicing physician, and identify additional cytokines, cytokine receptors and chemokines that may fulfill the criteria to be considered uremic toxins, such as sIL-6R, sTNFR1, sTNFR2, IL-2, CXCL12, CX3CL1 and others. In addition, we suggest that IL-10, leptin, adiponectin and resistin should not be considered uremic toxins toxins based on insufficient or contradictory evidence of an association with adverse outcomes in humans or preclinical data not consistent with a causal association.

Downregulation of AdipoR1 is Associated with increased Circulating Adiponectin Levels in Serbian Chronic Kidney Disease Patients

BACKGROUND

Since the rise in plasma adiponectin levels in chronic kidney disease (CKD) patients has not yet been elucidated, we sought to investigate if patients on hemodialysis (HD) have altered expression of adiponectin receptors in peripheral blood mononuclear cells (PBMCs) compared to healthy subjects.

METHODS

This study included 31 patients with chronic kidney disease on HD and 33 healthy subjects (CG). Circulating adiponectin levels were measured by ELISA while AdipoR1 and AdipoR2 mRNA levels in PBMCs were determined by real-time PCR.

RESULTS

Plasma adiponectin levels were significantly higher in patients compared to control group (P=0.036). After adjustment for age, BMI and creatinine, this difference became even more significant (P=0.004). In both groups adiponectin correlated with creatinine (CG: r=-0.472, P=0.006; HD: r=-0.375, P=0.038), triglycerides (CG: r=- 0.490, P=0.004; HD: r=-0.488, P=0.005), insulin (CG: r=-0.386, P=0.038; HD: r=-0.506, P=0.012) and high density lipoprotein cholesterol (HDL-C) (CG: r=-0.672, P<0.001; HD: r=-0.584, P=0.001). Significantly lower expression of PBMCs AdipoR1 mRNA was found in patients compared to CG (P=0.034), while AdipoR2 mRNA levels were similarly expressed in PBMCs in both groups.

CONCLUSIONS

Complex pathological processes in CKD cause downregulation of AdipoR1 which could ultimately influence AdipoR1 protein levels leading to a state of ≫adiponectin resistance≪.

[Adiponectin in health and disease]

Over the past 20 years after the discovery of adiponectin, much knowledge about its effect in health and disease has been gained. Adiponectin has antidiabetic, antiatherogenic, anti-inflammatory, immunomodulatory, metabolic, vasoprotective, and antiapoptotic properties. However, an understanding stems from the given literature review that much remains to be explored. Adiponectin has not yet commonly used in clinical practice, but cardiologists, endocrinologists, pediatricians, oncologists, and physicians of many specialties are interested in its preventive and therapeutic applications.

Adiponectin secreted by tubular renal cells during LPS exposure worsens the cellular inflammatory damage

The pathogenetic role of adiponectin (ADPN) in kidney failure is not yet elucidated, since in vitro and in vivo studies have demonstrated that ADPN exerts both anti-inflammatory and pro-inflammatory effects. Starting from our previous findings demonstrating that HK-2 cells express and secrete ADPN, in this study we investigated the autocrine role of ADPN in tubular inflammatory damage induced by lipopolysaccharide (LPS) and the underlying molecular mechanisms. Firstly, we observed that short-term exposure to LPS enhanced ADPN protein expression as well as the adiponectin receptor ADIPOR1 mRNA content together with its signaling pathway downstream, pAMPK/pERK/pJNK, whose up-regulation status was reversed when ADPN gene knockdown occurred. Interestingly, in the same experimental conditions, we observed that ADPN mediated the nuclear translocation of the transcription factors nuclear factor kappa B (NFkB) and pcFos/pcJun (activator protein 1, AP-1), both induced by the pJNK pathway and involved in tumor necrosis factor (TNF)-α transactivation. Indeed, by transient transfection assay, we observed that the LPS-induced increase of TNF-α promoter activity was abrogated in cells pretreated with the inhibitors of NFkB and AP-1. Collectively our results suggest that in HK-2 cells, ADPN produced upon LPS stimulus could worsen the inflammatory damage in an autocrine-dependent manner.

Association of Adiponectin With Body Composition and Mortality in Hemodialysis Patients

BACKGROUND

In the general population, circulating adiponectin is associated with a favorable cardiovascular risk profile (eg, lower triglycerides and body fat) and decreased mortality. Hemodialysis (HD) patients have comparatively higher adiponectin concentrations, but prior studies examining the adiponectin-mortality association in this population have not accounted for body composition or shown a consistent relationship.

STUDY DESIGN

Prospective cohort study.

SETTINGS & PARTICIPANTS

We examined baseline serum adiponectin concentrations in 501 HD patients across 13 dialysis centers from the prospective MADRAD (Malnutrition, Diet, and Racial Disparities in Chronic Kidney Disease) cohort (entry period, October 2011 to February 2013; follow-up through August 2013).

PREDICTOR

Serum adiponectin concentration in tertiles (tertiles 1, 2, and 3 defined as ≤16.1, >16.1-<30.1, and ≥30.1-100.0 μg/mL, respectively). Adjustment variables included case-mix and laboratory test results (age, sex, race, ethnicity, vintage, diabetes, serum albumin, total iron-binding capacity, serum creatinine, white blood cell count, phosphate, hemoglobin, and normalized protein catabolic rate), body composition surrogates (subcutaneous, visceral, and total-body fat and lean body mass), and serum lipid levels (cholesterol, high-density lipoprotein cholesterol, and triglycerides).

OUTCOMES

All-cause mortality using survival (Cox) models incrementally adjusted for case-mix and laboratory test results.

RESULTS

Among 501 HD patients, 50 deaths were observed during 631.1 person-years of follow-up. In case-mix- and laboratory-adjusted Cox analyses, the highest adiponectin tertile was associated with increased mortality versus the lowest tertile (HR, 3.35; 95% CI, 1.50-7.47). These associations were robust in analyses that additionally accounted for body composition (HR, 3.18; 95% CI, 1.61-8.24) and lipid levels (HR, 3.64; 95% CI, 1.34-7.58).

LIMITATIONS

Residual confounding cannot be excluded.

CONCLUSIONS

Higher adiponectin level is associated with a 3-fold higher death risk in HD patients independent of body composition and lipid levels. Future studies are needed to elucidate underlying mechanisms and determine therapeutic targets associated with improved outcomes in HD patients.

Serum level of adiponectin is a surrogate independent biomarker of radiographic disease progression in early rheumatoid arthritis: results from the ESPOIR cohort

Introduction

Adipokines such as adiponectin, leptin, and visfatin/nicotinamide phosphoribosyltransferase (NAMPT) have recently emerged as pro-inflammatory mediators involved in the pathophysiology of rheumatoid arthritis (RA). We aimed to determine whether serum adipokine levels independently predicted early radiographic disease progression in early RA.

Methods

In total, 791 patients were included from the prospective Etude et Suivi des POlyarthrites Indifférenciées Récentes (ESPOIR) cohort who met the American College of Rheumatology-European League Against Rheumatism criteria for RA (n = 632) or had undifferentiated arthritis (UA) (n = 159). Enzyme-linked immunosorbent assay (ELISA) was used to assess baseline serum levels of adiponectin, leptin, and visfatin/NAMPT. In the RA group, we tested the association of serum adipokine levels and (a) baseline radiographic damage and (b) radiographic disease progression, defined as a change >0 or ≥5 in total Sharp-van der Heijde Score (∆SHS) between inclusion and 1 year (∆SHS ≥1 or rapid radiographic progression: ∆SHS ≥5), adjusting for confounders (age, sex, body-mass index, insulin resistance, C-reactive protein level, Disease Activity Score in 28 joints, Health Assessment Questionnaire score, autoantibody status, steroid use, and radiographic evidence of RA damage at inclusion).

Results

Adiponectin level was independently associated with baseline total SHS (adjusted β = 0.12; P = 0.006). It was also associated with ∆SHS ≥1 (adjusted odds ratio (aOR) = 1.84 (1.25 to 2.72)) involving erosive as well as narrowing disease progression (aOR = 1.73 (1.17 to 2.55) and 1.93 (1.04 to 3.57), respectively). Serum adiponectin level predicted ∆SHS ≥5 (aOR = 2.0 (1.14 to 3.52)). Serum leptin level was independently associated only with ∆SHS >0 (aOR = 1.59 (1.05 to 2.42)). Conversely, serum visfatin/NAMPT level and radiographic disease progression were unrelated. Considering the receiver-operated characteristic curves, the best adiponectin cut-offs were 4.14 μg/ml for ∆SHS ≥1 and 6.04 μg/ml for ∆SHS ≥5, with a good specificity (58% and 75% for ∆SHS ≥1 and ∆SHS ≥5, respectively) and high negative predictive values (75% and 92% for ∆SHS ≥1 or ∆SHS ≥5, respectively).

Conclusion

Serum adiponectin level is a simple useful biomarker associated with early radiographic disease progression in early RA, independent of RA-confounding factors and metabolic status.

Adipokines promote chronic kidney disease

The rapid growth in obesity worldwide contributes to an increase in metabolic syndrome and obesity-related kidney disease with an enhanced increased risk for chronic kidney disease, finally progressing to end-stage renal disease. Adipose tissue is a highly active endocrine organ secreting numerous factors that contribute to renal and cardiovascular complications. In renal damage, various adipokines are involved through mediating endothelial dysfunction, inducing oxidative stress and inflammation as well as stimulating renal sympathetic nervous activity, and it reduces cancellous bone but conversely increases cortical bone. Adipokines may also be involved in the development of renal anaemia. A balance exists between more protective adipokines (adiponectin) and factors mediating pathophysiological effects (angiotensin II, TNFα). Obesity may cause a disruption of this delicate balance, thereby inducing renal disease. Consequently, weight reduction and lifestyle changes affecting all components of the metabolic syndrome are essential to disrupt this vicious cycle.

Leptin as an uremic toxin: Deleterious role of leptin in chronic kidney disease

White adipose tissue secretes a large variety of compounds named adipokines amongst which, leptin exhibits pleiotropic metabolic actions. Leptin is an anorexigenic hormone, secreted in proportion of fat mass, with additional effects on the regulation of inflammation, cardiovascular system, immunity, hematopoiesis and bone metabolism. Chronic kidney disease (CKD) is characterized by an increase of plasma leptin concentration that may be explained by a lack of renal clearance. Hyperleptinemia plays a key role in the pathogenesis of complications associated with CKD such as cachexia, protein energy wasting, chronic inflammation, insulin resistance, cardiovascular damages and bone complications. Leptin is also involved in the progression of renal disease through its pro-fibrotic and pro-hypertensive actions. Most of the adverse effects of leptin have been documented both experimentally and clinically. Leptin may therefore be considered as an uremic toxin in CKD. The aim of this review is to summarize the pathophysiological and clinical role of leptin in in vitro studies, experimental models, as well as in patients suffering from CKD.

The peptidic middle molecules: is molecular weight doing the trick?

Chronic kidney disease (CKD) is characterized by a gradual endogenous intoxication caused by the progressive accumulation of bioactive compounds that in normal conditions would be excreted and/or metabolized by the kidney. Uremic toxicity now is understood as one of the potential causes for the excess of cardiovascular disease and mortality observed in CKD. An important family of uremic toxins is that of the peptidic middle molecules, with a molecular weight ranging between 500 and 60,000 Da, which makes them, as a consequence, difficult to remove in the process of dialysis unless the dialyzer pore size is large enough. This review provides an overview of the main and best-characterized peptidic middle molecules and their role as potential culprits of the cardiometabolic complications inherent to CKD patients.

Adiponectin in inflammatory and immune-mediated diseases

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