Adiponectin is present in the urine in its native conformation, and specifically reduces the secretion of MCP-1 by proximal tubular cells

Fecal and Urinary Adipokines as Disease Biomarkers

The use of biomarkers is of great clinical value for the diagnosis and prognosis of disease and the assessment of treatment efficacy. In this context, adipokines secreted from adipose tissue are of interest, as their elevated circulating levels are associated with a range of metabolic dysfunctions, inflammation, renal and hepatic diseases and cancers. In addition to serum, adipokines can also be detected in the urine and feces, and current experimental evidence on the analysis of fecal and urinary adipokine levels points to their potential as disease biomarkers. This includes increased urinary adiponectin, lipocalin-2, leptin and interleukin-6 (IL-6) levels in renal diseases and an association of elevated urinary chemerin as well as urinary and fecal lipocalin-2 levels with active inflammatory bowel diseases. Urinary IL-6 levels are also upregulated in rheumatoid arthritis and may become an early marker for kidney transplant rejection, while fecal IL-6 levels are increased in decompensated liver cirrhosis and acute gastroenteritis. In addition, galectin-3 levels in urine and stool may emerge as a biomarker for several cancers. With the analysis of urine and feces from patients being cost-efficient and non-invasive, the identification and utilization of adipokine levels as urinary and fecal biomarkers could become a great advantage for disease diagnosis and predicting treatment outcomes. This review article highlights data on the abundance of selected adipokines in urine and feces, underscoring their potential to serve as diagnostic and prognostic biomarkers.

Urinary levels of energy metabolism hormones in association with the proportional intake of maternal milk and weight gain in very preterm neonates

BACKGROUND

This study prospectively investigated the levels of energy metabolism hormones in very preterm neonates to identify their change over time, association with intake of maternal milk, and weight gain velocity.

METHODS

We measured and compared the leptin, adiponectin, ghrelin, and insulin-like growth factor I (IGF-1) levels in the urine of 70 very preterm neonates, before the initiation of any enteral feeding (baseline level) and twice within 14 days on full enteral feeding (FEF). Regression models identified the role of intake of maternal milk on the levels of the tested energy metabolism hormones in the enteral-fed infants. We also analyzed the adequacy of the weight gain velocity defined by the fetal-infant growth reference (FIGR). We also collected and analyzed the infants' clinical and feeding characteristics during the birth hospitalization.

RESULTS

The preterm infants' baseline levels of the energy metabolism hormones significantly predicted their increase at the end of two weeks of observation on FEF. The leptin level was associated with increased intake of maternal milk, whereas the feeding volume was associated with increased ghrelin and IGF-1, and decreased leptin and adiponectin. Infants with comparable FIGR had higher leptin levels than those with inadequate weight gain velocity.

CONCLUSION

Early postnatal levels of leptin, adiponectin, ghrelin, and IGF-1 predicted the increase of these hormones in the fully enteral fed very preterm neonates. Moreover, greater intake of maternal milk by the study infants contributed to an increased leptin-associated weight gain velocity.

Adiponectin protects obesity-related glomerulopathy by inhibiting ROS/NF-κB/NLRP3 inflammation pathway

BACKGROUND

Adiponectin is an adipocytokine that plays a key regulatory role in glucose and lipid metabolism in obesity. The prevalence of obesity has led to an increase in the incidence of obesity-related glomerulopathy (ORG). This study aimed to identify the protective role of adiponectin in ORG.

METHODS

Small-interfering RNA (siRNA) against the gene encoding adiponectin was transfected into podocytes. The oxidative stress level was determined using a fluorometric assay. Apoptosis was analyzed by flow cytometry. The expressions of podocyte markers and pyrin domain containing protein 3 (NLRP3) inflammasome-related proteins were measured by qRT-PCR, immunohistochemistry, and Western blot.

RESULTS

Podocytes treated with palmitic acid (PA) showed downregulated expressions of podocyte markers, increased apoptosis, upregulated levels of NLRP3 inflammasome-related proteins, increased production of inflammatory cytokines (IL-18 and IL-1β), and induced activation of NF-κB as compared to the vehicle-treated controls. Decreased adiponectin expression was observed in the serum samples from high fat diet (HFD)-fed mice. Decreased podocin expression and upregulated NLRP3 expression were observed in the kidney samples from high fat diet (HFD)-fed mice. Treatment with adiponectin or the NLRP3 inflammasome inhibitor, MCC950, protected cultured podocytes against podocyte apoptosis and inflammation. Treatment with adiponectin protected mouse kidney tissues against decreased podocin expression and upregulated NLRP3 expression. The knockout of adiponectin gene by siRNA increased ROS production, resulting in the activation of NLRP3 inflammasome and the phosphorylation of NF-κB in podocytes. Pyrrolidine dithiocarbamate, an NF-κB inhibitor, prevented adiponectin from ameliorating FFA-induced podocyte injury and NLRP3 activation.

CONCLUSIONS

Our study showed that adiponectin ameliorated PA-induced podocyte injury in vitro and HFD-induced injury in vivo via inhibiting the ROS/NF-κB/NLRP3 pathway. These data suggest the potential use of adiponectin for the prevention and treatment of ORG.

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.

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.

Advances in understanding the role of adiponectin in renal fibrosis

Renal fibrosis is characterized by the proliferation of renal intrinsic cells, activation of renal interstitial fibroblasts and deposition of extracellular matrix (ECM), processes that lead to the progressive loss of renal function. Renal fibrosis is characterized by the proliferation of renal intrinsic cells, activation of renal interstitial fibroblasts, and septal fibrosis is recognized as a marker for the progression of chronic kidney disease, a condition that is associated with high morbidity and mortality and is a significant public health burden. Despite extensive studies, there are no effective treatments for renal fibrosis. Adiponectin (APN) is a protein mainly produced by adipocytes that has anti-inflammatory and anti-atherosclerotic effects, improves insulin resistance and provides other salutary effects. Recent studies found that APN can inhibit ECM deposition by inhibiting inflammation and oxidative stress, and by regulating the TGF-β, AMPK, MCP-1 and other signalling pathways. Many recent studies have examined the roles of these pathways in the pathogenesis of renal fibrosis. In this article, we review the pathogenic mechanism of APN in renal fibrosis and provide a theoretical basis for delaying and blocking renal fibrosis by alteration of APN activity.

Physiological role of adiponectin in different tissues: a review

Adiponectin is the most important adipokine secreted by the adipose tissue. It carries out an important role in setting up the metabolism and improving the function of various organs. Adiponectin in the kidneys prevents degradation of the renal arteries, reduces protein excretion, and improves filtration. This role is accomplished by regulating anabolic pathways and reducing oxidative stress in the renal tissue. This hormone in the liver prevents the accumulation of fat and free radicals that cause damage to liver cells and tissue. This adipokine, by preventing inflammatory processes, oxidative stress, obesity and insulin resistance, improves vascular function and prevents the development of atherosclerosis. It seems that adiponectin can also be a therapeutic target for many metabolic diseases. This study aims to clarify the adipose tissue discharge. Here, the diverse physiological actions of adiponectin were reviewed to provide an overview of its therapeutic potential in different metabolic disorders.

The role of adiponectin in placentation and preeclampsia

Preeclampsia is not fully understood; and few biomarkers, therapeutic targets, and therapeutic agents for its management have been identified. Original investigative findings suggest that abnormal placentation triggers preeclampsia and leads to hypertension, proteinuria, endothelial dysfunction, and inflammation, which are characteristics of the disease. Because of the regulatory roles that it plays in several metabolic processes, adiponectin has become a cytokine of interest in metabolic medicine. In this review, we have discussed the role of adiponectin in trophoblast proliferation, trophoblast differentiation, trophoblast invasion of the decidua, and decidual angiogenesis, which are the major phases of placentation. Also, we have highlighted the physiological profile of adiponectin in the course of normal pregnancy. Moreover, we have discussed the involvement of adiponectin in hypertension, endothelial dysfunction, inflammation, and proteinuria. Furthermore, we have summarized the reported relationship between the maternal serum adiponectin level and preeclampsia. The available evidence indicates that adiponectin level physiologically falls as pregnancy advances, regulates placentation, and exhibits protective effects against the symptoms of preeclampsia and that while hyperadiponectinemia is evident in normal-weight preeclamptic women, hypoadiponectinemia is evident in overweight and obese preeclamptic women. Therefore, the clinical use of adiponectin as a biomarker, therapeutic target, or therapeutic agent against the disease looks promising and should be considered.

Mechanisms of Adiponectin Action: Implication of Adiponectin Receptor Agonism in Diabetic Kidney Disease

Adiponectin, an adipokine secreted by adipocytes, exerts favorable effects in the milieu of diabetes and metabolic syndrome through its anti-inflammatory, antifibrotic, and antioxidant effects. It mediates fatty acid metabolism by inducing AMP-activated protein kinase (AMPK) phosphorylation and increasing peroxisome proliferative-activated receptor (PPAR)-α expression through adiponectin receptor (AdipoR)1 and AdipoR2, respectively, which in turn activate PPAR gamma coactivator 1 alpha (PGC-1α), increase the phosphorylation of acyl CoA oxidase, and upregulate the uncoupling proteins involved in energy consumption. Moreover, adiponectin potently stimulates ceramidase activity associated with its two receptors and enhances ceramide catabolism and the formation of its anti-apoptotic metabolite, sphingosine 1 phosphate (S1P), independently of AMPK. Low circulating adiponectin levels in obese patients with a risk of insulin resistance, type 2 diabetes, and cardiovascular diseases, and increased adiponectin expression in the state of albuminuria suggest a protective and compensatory role for adiponectin in mitigating further renal injury during the development of overt diabetic kidney disease (DKD). We propose AdipoRon, an orally active synthetic adiponectin receptor agonist as a promising drug for restoration of DKD without inducing systemic adverse effects. Its renoprotective role against lipotoxicity and oxidative stress by enhancing the AMPK/PPARα pathway and ceramidase activity through AdipoRs is revealed here.

Adiponectin protects against uric acid‑induced renal tubular epithelial inflammatory responses via the AdipoR1/AMPK signaling pathway

Adiponectin (APN) exerts anti‑inflammatory effects in various cells. Uric acid (UA) induces inflammation in proximal renal tubular epithelial cells (PTECs). It remains unknown whether APN protects against UA‑induced inflammation. In the present study, human PTECs were incubated with 100 µg/ml soluble (S) UA in the presence or absence of globular (g) APN, APN receptor 1 (AdipoR1)‑short hairpin RNA lentivirus or compound C. Reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) assays were performed to assess APN mRNA expression. Immunoblotting was used to assess the protein expression of APN, AdipoR1, NACHT, leucine rich repeat and pyrin domain‑containing protein 3 (NLRP3) and the activation of tumor necrosis factor (TNF) α and adenosine monophosphate‑activated protein kinase (AMPK). ELISA analyses were performed to assess supernatant levels of interleukin (IL)‑1β and TNFα. It was observed that SUA significantly enhanced APN mRNA and protein expression (both P<0.05) and increased NLRP3 (P<0.001) and TNFα (P<0.05) protein levels, as well as supernatant levels of IL‑1β (P<0.01) and TNFα (P<0.001) compared with untreated cells. gAPN administration significantly limited TNFα synthesis and secretion (both P<0.001), significantly decreased IL‑1β release (P<0.01), impacted NLRP3 protein expression and augmented AdipoR1 protein (P<0.01) and AMPK phosphorylation (P<0.05) levels compared with SUA‑treated cells. AdipoR1 knockdown significantly promoted the synthesis (P<0.05) and release of TNFα (P<0.001), significantly increased IL‑1β supernatant levels (P<0.01) and exhibited little influence on NLRP3 production (P>0.05) compared with the SUA‑treated cells. Secreted TNFα levels were significantly increased upon the inhibition of AMPK (P<0.05) and protein levels of IL‑1β, NLRP3 and TNFα in cell lysates were not significantly affected (P>0.05). In summary, the data demonstrated that SUA promoted APN expression in PTECs and that gAPN attenuated SUA‑induced inflammation through the AdipoR1/AMPK signaling pathway. AdipoR1 knockdown and AMPK inactivation increased SUA‑induced inflammatory damage in PTECs. These findings may help to further understand and regulate UA‑associated inflammation in proximal renal tubules.

Uric acid upregulates the adiponectin‑adiponectin receptor 1 pathway in renal proximal tubule epithelial cells

Adiponectin (APN) is a protein hormone that is primarily derived from adipocytes. It can also be secreted by renal cells. Hypoadiponectinemia has been documented in patients with hyperuricemia, however, whether soluble uric acid (SUA) regulates the expression of APN and APN receptor 1 (AdipoR1) in renal proximal tubule epithelial cells (PTECs) remains to be elucidated. The present study investigated the expression of APN and AdipoR1 in cultured PTECs that were exposed to SUA through immunofluorescence and western blot analysis. In addition, Sprague-Dawley rats with oxonic acid-induced hyperuricemia (HUA) with or without febuxostat treatment were employed as an animal model to measure 24 h urine protein, serum creatinine, urea nitrogen, uric acid and homeostasis model assessment of insulin resistance. Renal pathology was evaluated using hematoxylin and eosin and immunohistochemical staining. APN and AdipoR1 expression in the renal cortex were evaluated by western blotting. The results demonstrated that, in PTECs, the expression of APN and AdipoR1 was constant and increased upon SUA exposure. Similar observations were made within the proximal renal tubules of rats, and the oxonic acid-induced increases in APN and AdipoR1 were offset by febuxostat treatment. Furthermore, SUA-treated PTECs exhibited an increase in the expression of NLR family pyrin domain-containing (NLRP) 3, which was dose-dependent. NLRP3 expression was also significantly increased in the renal cortex of HUA rats compared with control and febuxostat-treated rats. In conclusion, SUA enhanced the expression of APN and AdipoR1 in PTECs, which was associated with an increase in NLRP3 expression. The APN-AdipoR1 pathway was demonstrated to have an important role in in vitro and in vivo models of renal proximal tubule inflammatory injury. Therefore, this pathway may be a potential therapy target in urate nephropathy.

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.

Associations of serum adiponectin with markers of cardio-metabolic disease risk in Indigenous Australian adults with good health, diabetes and chronic kidney disease

The higher serum adiponectin concentrations observed in females are often attributed to differences in adiposity or sex hormones. There is little data describing adiponectin in Indigenous Australians, and no studies examining its association with cardio-metabolic disease risk markers and chronic kidney disease (CKD).

AIM

To describe the relationship of serum adiponectin with cardio-metabolic disease risk markers and kidney function in a community-based sample of Indigenous Australian adults, with particular reference to sex-specific differences.

METHODS

A cross-sectional analysis of a community-based volunteer sample of 548 Indigenous Australian adults (62% female), stratified into five cardio-metabolic risk groups ranging from good health (strata-1) to high cardio-metabolic risk and low measured glomerular filtration rate (mGFR, <60ml/min/1.73m²) (strata-5). We examined serum adiponectin concentrations with cardio-metabolic risk markers, albuminuria and mGFR.

RESULTS

Indigenous Australian females had a lower than expected adiponectin concentration (3.5μg/ml), which was higher than males in strata 1-4 (as in other populations), but not in strata-5 (mGFR<60, p=0.19), and higher leptin: adiponectin ratio than other populations (7.8ng/μg - strata-1, healthy females; 12.2ng/μg - strata-3, females with diabetes and mGFR≥90). Female-gender, HDL-cholesterol (positive), mGFR and waist: hip ratio (WHR) (inverse) were independently associated with log-adiponectin when mGFR≥60; when mGFR<60, female-gender was associated with 0.27 units lower log-adiponectin.

CONCLUSION

Female-gender was not associated with higher adiponectin concentrations in Indigenous Australians with mGFR<60ml/min/1.73m². High WHR was frequent in both genders, and inversely associated with adiponectin. Longitudinal studies are needed to examine relationships of serum adiponectin, obesity and cardiovascular disease events in Indigenous Australians.

Urinary adiponectin and albuminuria in non-diabetic hypertensive patients: an analysis of the ESPECIAL trial

Background

Although adiponectin levels have been reported to be correlated with albuminuria, this issue remains unresolved in non-diabetic hypertensive subjects, particularly when urinary adiponectin is considered.

Methods

Urinary adiponectin levels were examined using an enzyme-linked immunosorbent assay in 229 participants. who used olmesartan as a hypertensive agent. Their albuminuria levels were measured for 16 weeks after randomization and initiation of conventional or intensive diet education. Linear or logistic regression models were applied, as appropriate, to explore the relationship with albuminuria itself or its response after the intervention.

Results

Urinary adiponectin levels were positively related to baseline albuminuria level (r = 0.529). After adjusting for several covariates, the adiponectin level was associated with the albuminuria level (β = 0.446). Among the 159 subjects with baseline macroalbuminuria, the risk of consistent macroalbuminuria (> 300 mg/day) at 16 weeks was higher in the 3^rd tertile of adiponectin than in the 1^st tertile (odds ratio = 6.9), despite diet education. In contrast, among all subjects, the frequency of the normoalbuminuria achievement (< 30 mg/day) at 16 weeks was higher in the 1^st tertile than in the 3^rd tertile (odds ratio = 13.0).

Conclusions

Urinary adiponectin may be a useful biomarker for albuminuria or its response after treatment in non-diabetic hypertensive patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-015-0124-3) contains supplementary material, which is available to authorized users.

Adiponectin attenuates Ang Ⅱ-induced TGFβ1 production in human mesangial cells via an AMPK-dependent pathway

Glomerulosclerosis is a key element in end-stage renal failure. Angiotensin II (Ang II) plays an important role in modulating cell growth and extracellular matrix (ECM) synthesis and degradation. Adiponectin, a protein derived from adipocytes, is primarily involved in regulating glucose levels and fatty acid break down. It has recently been shown to have antiatherosclerotic and anti-inflammatory properties. However, the role of adiponectin as a renoprotective agent has not been fully explored. We herein examine the effect of adiponectin on Ang II-induced TGFβ1 and ECM production in human renal mesangial cells (HRMCs) and explore the signaling pathway involved. In this study, we found that both adiponectin receptor 1 and adiponectin receptor 2 are expressed in HRMCs. Adiponectin (10 μg/mL) attenuated the stimulatory effect of Ang II on TGF-β1 and fibronectin. Furthermore, adiponectin activated the AMP-activated protein kinase (AMPK), and the AMPK-specific inhibitor (compound C) blocked AMPK activation. We also determined that compound C blocked the inhibitory effect of adiponectin on Ang II-stimulated TGFβ1 and fibronectin production. In summary, these results demonstrate that adiponectin suppresses Ang II-induced synthesis of ECM in mesangial cells via activation of the AMPK pathway. Based on our data, we suggest that this mechanism could delay the progression of kidney disease.

The role of adiponectin in renal physiology and development of albuminuria

Adiponectin is secreted by the adipose tissue and is downregulated in states of obesity and insulin resistance. There is a growing body of evidence indicating that adiponectin has renoprotective effects and protects against the development of albuminuria in rodent experiments. Adiponectin crossing the glomerular filtration barrier possibly inhibits inflammation, fibrosis and oxidative stress in kidneys through activation of AMP-activated protein kinase. Moreover, microalbuminuria is a well established early sign of progressive cardiovascular and renal disease, even in subjects with preserved glomerular filtration rate. Studies investigating the relationship between serum adiponectin levels and urinary albumin excretion rate (UAE) have yielded conflicting data and the mechanisms underlying the interplay between adiponectin and albuminuria remain to be elucidated. This article constitutes a critical review attempting to clarify any remaining confusion about this matter. Furthermore, this article examines the clinical significance of adiponectin-albuminuria interplay, suggesting that adiponectin is possibly involved in the development of albuminuria that is associated with obesity, diabetes and cardiovascular disease and may mediate, at least in part, the actions of medical treatments that influence UAE, such as angiotensin-converting-enzyme inhibitors, angiotensin II receptor blockers, thiazolidinediones, fenofibrate and diet. Further studies to investigate more thoroughly the renoprotective role of adiponectin in the human setting should be carefully planned, focusing on causality and the possible influence of adiponectin on the development of albuminuria in specific clinical settings.

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.

Urinary adiponectin concentration is positively associated with micro- and macro-vascular complications

BACKGROUND

A relationship between plasma adiponectin level and a number of metabolic conditions, including insulin resistance, obesity, and type 2 diabetes, has been reported. This study aimed to assess whether urinary adiponectin concentration is correlated with vascular complications.

METHODS

The study comprised 708 subjects who enrolled in the Seoul Metro City Diabetes Prevention Program and were carefully monitored from September 2008 to December 2008. Levels of urinary adiponectin were measured using an enzyme linked immunosorbent assay (ELISA) kit (AdipoGen, Korea). Urinary albumin excretion was assessed by the ratio of urinary albumin to creatinine (A/C ratio). Participants were divided into three groups based on tertiles of urinary adiponectin concentration, and we investigated whether urinary adiponectin levels are associated with microalbuminuria and pulse wave velocity.

RESULTS

Urinary adiponectin concentrations were significantly higher in subjects with microalbuminuria than subjects with normoalbuminuria (P < 0.001). Urinary adiponectin concentration was positively correlated with age, fasting plasma glucose level, HbA1C level, triglyceride level, HOMA-IR, systolic/diastolic blood pressure, and urinary A/C ratio (all P < 0.05). Subjects in the highest tertile of urinary adiponectin concentration had an increased likelihood of microalbuminuria than those in the lowest tertile (Odds ratio (OR), 6.437; 95% confidence interval (CI), 4.202 to 9.862; P < 0.001). After adjusting for age, sex, and estimated creatinine clearance rate (eCcr), the OR remained significant (OR, 5.607; 95% CI, 3.562 to 8.828; P < 0.001). Backward multiple linear regression analysis revealed urinary adiponectin concentration to be a significant determinant of mean brachial-ankle pulse wave velocity (baPWV).

CONCLUSIONS

An increased urinary adiponectin concentration is significantly associated with microalbuminuria and increased mean baPWV. These results suggest that urinary adiponectin may play an important role as a biomarker for vascular dysfunction.

Changes of adiponectin and its receptors in rats following chronic renal failure

OBJECTIVE

To investigate changes of adiponectin and its receptors (Adipo R) in rats following chronic renal failure.

METHODS

Male SD rats were randomly divided into two groups: control group and chronic renal failure (CRF) group. The CRF group were gavaged with adenine (300 mg/kg/d) for 4 weeks and the control group with drinking water. All rats were anesthetized at 2nd or 4th week and blood and urine samples were collected for detection of renal function, 24 h urine protein and adiponectin concentration. Renal tissues were also collected for HE staining, immunohistochemistry and RT-PCR screening.

RESULTS

Compared with control group, the serum concentrations of urea and creatinine, 24 h urine protein excretion in the CRF group were significantly higher at 2nd week and further increased at 4th week (p < 0.05). The adiponectin levels in serum and urine in the CRF group were significantly higher than those of control group (p < 0.01). The renal expressions of Adipo R1 and Adipo R2 in CRF group were also significantly increased compared to control group (p < 0.01). The increased expressions of Adipo R1 and Adipo R2 were positively related to the adiponectin levels in serum, urine, and 24 h urine protein.

CONCLUSION

The significant changes in expression of adiponectin and its receptors in rat CRF model could be an adaptive response that may provide the basis to understand pathological changes in chronic kidney disease.

Adiponectin in renal disease--a review of the evidence as a risk factor for cardiovascular and all-cause mortality

Adiponectin, an adipokine, was discovered in 1995. The initial evidence led to the study of adiponectin as a determinant of insulin sensitivity and blood glucose levels. The literature then evolved to reports of the inverse association of adiponectin with incident Type 2 diabetes mellitus and coronary heart disease. Shortly thereafter, reports of a positive association with heart failure and mortality appeared and were replicated. We review here the basic science evidence and clinical studies of the role of renal function and kidney disease as a determinant of adiponectin.

Adiponectin, cardiovascular disease, chronic kidney disease: emerging data on complex interactions

Over the past decade, adiponectin has been a subject of interest in many fields of medicine. The effect of adiponectin in metabolism and inflammation has been described for cardiovascular disease (CVD) in animal studies and the general population, generally as a protective factor. Extensive literature pertaining to adult studies indicates that low adiponectin levels are associated with increased CVD morbidity and mortality in the general population and patients with obesity and type 2 diabetes. In chronic kidney disease (CKD), however, despite an increased risk of poor cardiovascular outcomes, blood levels of adiponectin are actually higher than typical physiological levels. These unusual relationships question the protective role of elevated adiponectin in the milieu of CKD. This review summarizes the studies of adiponectin in the general pediatric population and its association with CVD risks in children and adults with CKD. Specific adiponectin values are generally avoided in this review, as there are no standardized normative values at this time - different assays with different "normal" cutoffs have been used and hence comparisons between studies would be invalid.

Adiponectin in amniotic fluid in normal pregnancy, spontaneous labor at term, and preterm labor: a novel association with intra-amniotic infection/inflammation

OBJECTIVE

Adiponectin, an anti-inflammatory and anti-diabetogenic adipokine, has an important regulatory effect on both the innate and adaptive limbs of the immune response. The objective of this study was to determine whether adiponectin is present in amniotic fluid (AF) and if its concentration changes with gestational age, in the presence of labor, and in the presence of intra-amniotic infection (IAI) in patients with spontaneous preterm labor (PTL) and intact membranes.

STUDY DESIGN

This cross-sectional study included 468 patients in the following groups: (1) women in the mid-trimester of pregnancy (14-18 weeks) who underwent amniocentesis for genetic indications and delivered a normal neonate at term (n = 52); (2) normal pregnant women at term with (n = 49) and without (n = 41) spontaneous labor; (3) patients with an episode of PTL and intact membranes who were classified into: (a) PTL who delivered at term (n = 149); (b) PTL who delivered preterm (<37 weeks gestation) without IAI (n = 108); and (c) PTL with IAI (n = 69). Adiponectin concentration in AF was determined by ELISA.

RESULTS

(1) The median AF adiponectin concentration at term was significantly higher than in the mid-trimester (35.6 ng/ml, interquartile range [IQR] 26.4-52.7 vs. 29.9 ng/ml, IQR 19.9-35.2; p = 0.01); (2) among women with PTL and intact membranes, the median AF adiponectin concentration was significantly higher in patients with IAI than in those without IAI who delivered either at term (54.3 ng/ml, 39.0-91.8 vs. 50.1 ng/ml, 33.2-72.8; p = 0.02) or preterm (47.6 ng/ml, 32.6-74.6; p = 0.01); and (3) among women at term, there was no significant difference in the median AF adiponectin concentration between those with and without labor (33.7 ng/ml, IQR 21.7-53.9 vs. 35.6 ng/ml, IQR 26.4-52.7; respectively p = 0.5).

CONCLUSIONS

(1) Adiponectin is a physiologic constituent of AF; and (2) adiponectin concentrations in AF are increased significantly with advancing gestation and in the presence of IAI. Collectively, these findings suggest that adiponectin plays a dynamic role in normal gestation and in the presence of IAI.