Plasma adiponectin concentrations in patients with chronic renal failure: relationship with metabolic risk factors and ischemic heart disease

Adiponectin protects against myocardial ischemia-reperfusion injury: a systematic review and meta-analysis of preclinical animal studies

BACKGROUND

Myocardial ischemia-reperfusion injury (MIRI) is widespread in the treatment of ischemic heart disease, and its treatment options are currently limited. Adiponectin (APN) is an adipocytokine with cardioprotective properties; however, the mechanisms of APN in MIRI are unclear. Therefore, based on preclinical (animal model) evidence, the cardioprotective effects of APN and the underlying mechanisms were explored.

METHODS

The literature was searched for the protective effect of APN on MIRI in six databases until 16 November 2023, and data were extracted according to selection criteria. The outcomes were the size of the myocardial necrosis area and hemodynamics. Markers of oxidation, apoptosis, and inflammation were secondary outcome indicators. The quality evaluation was performed using the animal study evaluation scale recommended by the Systematic Review Center for Laboratory animal Experimentation statement. Stata/MP 14.0 software was used for the summary analysis.

RESULTS

In total, 20 papers with 426 animals were included in this study. The pooled analysis revealed that APN significantly reduced myocardial infarct size [weighted mean difference (WMD) = 16.67 (95% confidence interval (CI) = 13.18 to 20.16, P < 0.001)] and improved hemodynamics compared to the MIRI group [Left ventricular end-diastolic pressure: WMD = 5.96 (95% CI = 4.23 to 7.70, P < 0.001); + dP/dtmax: WMD = 1393.59 (95% CI = 972.57 to 1814.60, P < 0.001); -dP/dtmax: WMD = 850.06 (95% CI = 541.22 to 1158.90, P < 0.001); Left ventricular ejection fraction: WMD = 9.96 (95% CI = 7.29 to 12.63, P < 0.001)]. Apoptosis indicators [caspase-3: standardized mean difference (SMD) = 3.86 (95% CI = 2.97 to 4.76, P < 0.001); TUNEL-positive cells: WMD = 13.10 (95% CI = 8.15 to 18.05, P < 0.001)], inflammatory factor levels [TNF-α: SMD = 4.23 (95% CI = 2.48 to 5.98, P < 0.001)], oxidative stress indicators [Superoxide production: SMD = 4.53 (95% CI = 2.39 to 6.67, P < 0.001)], and lactate dehydrogenase levels [SMD = 2.82 (95% CI = 1.60 to 4.04, P < 0.001)] were significantly reduced. However, the superoxide dismutase content was significantly increased [SMD = 1.91 (95% CI = 1.17 to 2.65, P < 0.001)].

CONCLUSION

APN protects against MIRI via anti-inflammatory, antiapoptotic, and antioxidant effects, and this effect is achieved by activating different signaling pathways.

Metabolism regulator adiponectin prevents cardiac remodeling and ventricular arrhythmias via sympathetic modulation in a myocardial infarction model

The stellate ganglia play an important role in cardiac remodeling after myocardial infarction (MI). This study aimed to investigate whether adiponectin (APN), an adipokine mainly secreted by adipose tissue, could modulate the left stellate ganglion (LSG) and exert cardioprotective effects through the sympathetic nervous system (SNS) in a canine model of MI. APN microinjection and APN overexpression with recombinant adeno-associated virus vector in the LSG were performed in acute and chronic MI models, respectively. The results showed that acute APN microinjection decreased LSG function and neural activity, and suppressed ischemia-induced ventricular arrhythmia. Chronic MI led to a decrease in the effective refractory period and action potential duration at 90% and deterioration in echocardiography performance, all of which was blunted by APN overexpression. Moreover, APN gene transfer resulted in favorable heart rate variability alteration, and decreased cardiac SNS activity, serum noradrenaline and neuropeptide Y, which were augmented after MI. APN overexpression also decreased the expression of nerve growth factor and growth associated protein 43 in the LSG and peri-infarct myocardium, respectively. Furthermore, RNA sequencing of LSG indicated that 4-week MI up-regulated the mRNA levels of macrophage/microglia activation marker Iba1, chemokine ligands (CXCL10, CCL20), chemokine receptor CCR5 and pro-inflammatory cytokine IL6, and downregulated IL1RN and IL10 mRNA, which were reversed by APN overexpression. Our results reveal that APN inhibits cardiac sympathetic remodeling and mitigates cardiac remodeling after MI. APN-mediated gene therapy may provide a potential therapeutic strategy for the treatment of MI.

The evolving role of adiponectin as an additive biomarker in HFrEF

Heart failure (HF) is a growing health problem. Despite improved management and outcome, the number of patients with HF is expected to keep rising in the following years. In recent research, adiponectin was shown to exert beneficial effects in the cardiovascular system, but the protein was also implicated in the development and progression of HF. The objective of this review is to provide an overview of current knowledge on the role of adiponectin in HF with reduced ejection fraction. We discuss the cardioprotective and (anti-) inflammatory actions of adiponectin and its potential use in clinical diagnosis and prognosis.

RBP4: A Culprit for Insulin Resistance in End Stage Renal Disease That Can Be Cleared by Hemodiafiltration

INTRODUCTION

Retinol Binding Protein 4 (RBP4) is mainly excreted by the kidney and plays a pivotal role in insulin resistance (IR). In our study, we evaluated the association between RBP4 and IR in hemodialysis subjects (HD). We also assessed how circulating RBP4 could be influenced by kidney transplant or different dialytic techniques.

METHODS

RBP4 serum levels were evaluated in HD (n = 16) and matched healthy controls (C; n = 16). RBP4 and glucose transporter type 4 (GLUT4) mRNA expressions were also determined in adipose tissue. Circulating RBP4 was evaluated after kidney transplant (n = 7) and in hemodialysis patients (n = 10) enrolled in a cross-over study treated with standard bicarbonate dialysis (BD) or hemodiafiltration (HDF).

RESULTS

HOMA index (P < 0.05) and serum RBP4 (P < 0.005) were higher in HD compared to C. RBP4 levels positively correlated with fasting serum glucose (P < 0.05). RBP4 mRNA was lower in HD compared to C (P < 0.05) and positively correlated with kidney function (P < 0.05) and GLUT4 mRNA (P < 0.001). Transplant or HDF reduced circulating RBP4 (P < 0.01 and P < 0.05, resp.). Our results demonstrate that IR is associated with high circulating RBP4 and that suppressed RBP4 adipose tissue expression is accompanied by reduced GLUT4 expression in HD. Renal transplantation or HDF are effective in lowering serum RBP4 levels.

Adiponectin, leptin, nitric oxide, and C-reactive protein levels in kidney transplant recipients: comparison with the hemodialysis and chronic renal failure

BACKGROUND

Cardiovascular disease (CVD) is the leading cause of mortality and morbidity in patients with chronic kidney disease (CKD) including kidney transplant recipients (KTR). Secondary lipid metabolism disorders, endothelial dysfunction, and inflammation enhance the risk of CVD development in these patients. The aim of the present study was to investigate the lipid profile, adiponectin, leptin, nitric oxide (NO), and high sensitivity C-reactive protein (hs-CRP) levels in KTR and to compare these parameters with those of the patients with chronic renal failure (CRF), hemodialysis (HD) patients, and healthy controls.

METHODS

Serum adiponectin and leptin levels were measured by radioimmunoassay; hs-CRP was determined immunoturbidimetrically. Determination of NO was based on the Griess reaction.

RESULTS

Compared with the control group, serum NO and adiponectin levels were significantly higher in the KTR, CRF, and HD groups; hs-CRP levels were significantly higher in the KTR and HD groups; leptin levels were significantly higher in the KTR. In addition, serum NO level was significantly higher in the KTR compared to CRF cases. Adiponectin correlated positively with high density lipoprotein-cholesterol in the control and patient groups. A positive correlation was observed between hs-CRP and NO in the KTR and the patients with CRF. Serum adiponectin levels were inversely correlated with hs-CRP and leptin in the HD group.

CONCLUSION

KTR suffer from inflammation and accompanying changes in levels of adipocytokines and NO which contribute to the increased risk of CVD in these patients.

Influence of body fatness distribution and total lean mass on aortic stiffness in nonobese individuals

BACKGROUND

Subjects with normal body mass index but high body fat percentage have higher cardiovascular risk than subjects with normal weight and low fat mass. However, the association of fat distribution and lean mass with carotid-femoral pulse wave velocity (cfPWV) among nonobese apparently healthy individuals has never been assessed.

METHODS

In 136 nonobese volunteers (mean age = 45±9 years; 57% women) without manifest cardiovascular disease, cfPWV was measured by applanation tonometry. Fat and lean mass were measured by dual-energy x-ray absorptiometry.

RESULTS

In univariate analysis, total fat (r = 0.17; P < 0.01), trunk fat (r = 0.27; P < 0.01), and trunk/total fat ratio (r = 0.32; P < 0.01) were correlated with cfPWV. After adjustment for age and mean arterial pressure, only central fat distribution (trunk/total fat ratio) was significantly associated with cfPWV. In the fully adjustment model, there was a significant interaction between fat distribution and lean mass. When the study sample was grouped by fat distribution and total lean mass medians, subjects with central fat distribution and low lean mass (group 4) had higher log-transformed cfPWV than the noncentral fat/low lean mass group (group 2) (0.89, 95% confidence interval (CI) = 0.86-0.92 vs. 0.85, 95% CI = 0.83-0.87; P < 0.01) or the noncentral fat/high lean mass group (group 1) (0.89, 95% CI = 0.86-0.92 vs. 0.84, 95% CI = 0.81-0.87; P < 0.01) after adjustments. Aortic stiffness increased from group 1 to group 4 (P for linear trend < 0.001).

CONCLUSIONS

Among normal weight individuals without manifest cardiovascular disease, the combination of central fat distribution and low lean mass is associated with higher cfPWV. These factors are more closely related to cfPWV than total fat mass.

Increased myocardial ischemia-reperfusion injury in renal failure involves cardiac adiponectin signal deficiency

Plasma levels of adiponectin (APN) are significantly increased in patients with renal dysfunction and are inversely related to the risk of cardiovascular mortality. The present study was designed to determine the role of APN in myocardial ischemia-reperfusion (MI/R) injury in mice with renal failure and delineate the underlying mechanisms. Renal failure was induced by subtotal nephrectomy (SN). Human recombinant globular domain of adiponectin (gAd) or full-length adiponectin (fAd) was administered via intraperitoneal injection once daily for 7 consecutive days after SN, and in vivo MI/R was introduced 3 wk later. Both plasma and urinary levels of APN increased significantly in SN mice. Compared with sham-operated mice, cardiac function was significantly depressed, and myocardial infarct size and apoptosis increased in SN mice following MI/R. The aggravated MI/R injury was further intensified in APN-knockout mice and markedly ameliorated by treatment with gAd but not fAd. Moreover, SN increased myocardial NO metabolites, superoxide, and their cytotoxic reaction product peroxynitrite, upregulated inducible NO synthase expression, and decreased endothelial NOS phosphorylation. In addition, SN mice also exhibited reduced APN receptor-1 (AdipoR1) expression and AMPK activation. All these changes were further amplified in the absence of APN but reversed by gAd treatment. The present study demonstrates that renal dysfunction increases cardiac susceptibility to ischemic-reperfusion injury, which is associated with downregulated APN/AdipoR1/AMPK signaling and increased oxidative/nitrative stress in local myocardium, and provides the first evidence for the protective role of exogenous supplement of gAd on MI/R outcomes in renal failure.

Plasma adiponectin levels for prediction of cardiovascular risk among hemodialysis patients

Adiponectin (ADPN) is an endogenous insulin sensitizing and anti-inflammatory hormone, released by the adipose tissue. We investigated the clinical and biochemical correlates of plasma ADPN levels and the predictive value of ADPN with respect to survival rates and cardiovascular (CV) events was tested prospectively in a cohort of hemodialysis (HD) patients. We measured baseline ADPN in 110 HD patients, in addition to, 34 healthy subjects to serve as reference group. ADPN levels, were related to different clinical and biochemical cardiovascular risk factors such as increased body mass index (BMI), serum triglycerides (TG), duration of HD, smoking, mean arterial blood pressure (MBP), heart rate (HR), high density (HDL) cholesterol, low density (LDL) cholesterol, serum glucose, hemoglobulin and C-reactive protein (CRP) levels in HD patients. Plasma ADPN levels were higher (P = 0.000) among HD patients (15.06 ± 3.54 μg/mL) than among reference subjects (6.52 ± 1.07 μg/mL), were independent of age, and higher among women (16.13 ± 3.09 μg/mL) than among men (13.94 ± 3.65 μg/mL). Plasma ADPN levels were inversely related to BMI, TG, CRP and glucose levels. Furthermore, plasma ADPN levels were directly related to HDL-cholesterol and Kt/V. Plasma ADPN levels were lower (P = 0.000) among patients who experienced new CV events (11.13 ± 2.15 μg/mL) than among event-free patients (16.82 ± 2.45 μg/mL), and seem to predict cardiovascular outcomes. The inverse relationships between ADPN and several cardiovascular risk factors indicate that ADPN may have a protective role in the prevention of CV events.

Anemia and reduced renal function are independent predictors of elevated serum adiponectin in elderly women

AIM

Although higher adiponectin levels predict a low risk of type 2 diabetes, elevated adiponectin levels predict higher mortality in older persons.

METHODS

We examined the associations of adiponectin with anthropometric, metabolic and hematological variables and renal function in 361 community-dwelling elderly women aged 76±8. Renal function was assessed using the estimated glomerular filtration rate (eGFR).

RESULTS

By univariate analysis, hemoglobin (r=-0.307, p<0.001) and creatinine-based eGFR (r=-0.121, p<0.05) were inversely associated with adiponectin. After adjustment for percentage body fat, HDL cholesterol and serum leptin, hemoglobin and creatinine-based eGFR remained independent predictors of adiponectin (standardized β coefficient=-0.248, p<0.0001, and -0.101, p=0.03, respectively). A similar but stronger relationship was observed between adiponectin and cystatin C-based eGFR (standardized β coefficient=-0.180, p=0.02). Elderly women with anemia had higher serum adiponectin than those without anemia (17.7±9.1 vs. 14.1±7.0 µg/mL, p=0.001). Women with creatinine-based eGFR <45 mL/min/1.73 m2 (19.2±10.6 µg/mL) had higher adiponectin than those with eGFR ≥45 -< 60 mL/min/1.73 m(2) (14.4±6.9 µg/mL) and those with eGFR ≥60 mL/min/1.73 m(2) (14.5±7.4 µg/mL, p<0.05).

CONCLUSIONS

We conclude that hemoglobin and eGFR are independently associated with serum adiponectin in community-dwelling elderly women. Anemia and reduced renal function may contribute to elevated adiponectin levels in the elderly and may represent important confounders of the relationship between elevated adiponectin and mortality in this population.

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.

The association between chronic kidney disease and cardiovascular disease risk factors in atomic bomb survivors

Atomic bomb (A-bomb) radiation is associated with cardiovascular disease (CVD) and metabolic CVD risk factors. Chronic kidney disease (CKD) is also known to be a risk factor for CVD and little is known whether CKD is associated with A-bomb radiation. To examine whether CKD is associated with CVD risk factors or with A-bomb radiation in A-bomb survivors, we classified renal dysfunction in 1,040 A-bomb survivors who were examined in 2004-2007 as normal [n = 121; estimated glomerular filtration rate (eGFR) ≥ 90 ml/min/1.73 m(2)]; mild (n = 686; eGFR 60-89 ml/min/1.73 m(2)); moderate (n = 217; eGFR 30-59 ml/min/1.73 m(2)); or severe (n = 16; eGFR <30 ml/min/1.73 m(2)). Also, we diagnosed subjects in the moderate and severe renal dysfunction groups as having CKD (n = 233; eGFR <59 ml/min/1.73 m(2)). After adjusting for age, gender, and smoking and drinking habits, we looked for an association between renal dysfunction and hypertension, diabetes mellitus (DM), hyperlipidemia, and metabolic syndrome (MetS), and between renal dysfunction and A-bomb radiation. Hypertension [odds ratio (OR), 1.57; 95% confidence interval (CI), 1.12-2.20, P = 0.009]; DM (OR, 1.79; 95% CI, 1.23-2.61, P = 0.002); hyperlipidemia (OR, 1.55; 95% CI, 1.12-2.14, P = 0.008); and MetS (OR, 1.86; 95% CI, 1.32-2.63, P < 0.001) were associated with CKD (moderate/severe renal dysfunction), and hyperlipidemia and MetS were also associated with mild renal dysfunction. CKD (OR/Gy, 1.29; 95% CI, 1.01-1.63, P = 0.038) and severe renal dysfunction (OR/Gy, 3.19; 95% CI, 1.63-6.25, P < 0.001) were significantly associated with radiation dose. CKD associated with radiation may have played a role in the development of CVD among A-bomb survivors.

Circulating adiponectin is associated with renal function independent of age and serum lipids in west africans

Adiponectin, a protein secreted by adipose tissue, has been associated with renal dysfunction. However, these observations have not been adequately investigated in large epidemiological studies of healthy individuals in general and in African populations in particular. Hence, we designed this study to evaluate the relationship between adiponectin and renal function in a large group of nondiabetic West Africans. Total adiponectin was measured in 792 participants. MDRD and Cockroft-Gault (CG-) estimated GFR were used as indices of renal function. Linear and logistic regression models were used to determine the relationship between adiponectin and renal function. Adiponectin showed an inverse relationship with eGFR in univariate (Beta_MDRD = −0.18, Beta_CG = −0.26) and multivariate (Beta_MDRD = −0.10, Beta_CG = −0.09) regression analyses. The multivariate models that included age, sex, BMI, hypertension, smoking, HDL-C, LDL-C, triglycerides, and adiponectin explained 30% and 55.6% of the variance in GFR estimated by MDRD and CG methods, respectively. Adiponectin was also a strong predictor of moderate chronic kidney disease (defined as eGFR < 60 mL/min/1.73 m²). We demonstrate that adiponectin is associated with renal function in nondiabetic West Africans. The observed relationship is independent of age and serum lipids. Our findings suggest that adiponectin may have clinical utility as a biomarker of renal function.

Adiponectin and atherosclerosis risk factors in African hemodialysis patients: a population at low risk for atherosclerotic cardiovascular disease

Atherosclerotic cardiovascular disease (CVD) is the major cause of morbidity and mortality in hemodialysis (HD) patients. Adiponectin (ADPN), a recently discovered collagen-like protein, is secreted exclusively by adipocytes. It has anti-atherogenic properties and reduced serum ADPN levels have been shown to be predictive of cardiovascular events. In this study, we determined the atherosclerotic risk and the significance of ADPN levels in our HD patients and also examined its relationship to other traditional CVD risk factors. A cross-sectional study of 84 patients on maintenance HD (58 Blacks and 26 non-Blacks) and 63 healthy controls matched for age, sex and race (35 Blacks and 28 non-Blacks) was undertaken. Serum ADPN levels and other risk factors, including blood pressure, serum lipid, and C-reactive protein, were studied in HD patients and were compared with the controls. Carotid artery intima-media thickness and plaque occurrence was measured by B-mode ultrasonography while echocardiography was done according to American Society of Echocardiography guidelines. Serum ADPN levels were higher in the HD group compared with the control subjects (22.19 ± 0.98 mg/mL vs. 9.93 ± 0.68 mg/mL; P < 0.001). Higher ADPN levels in HD patients were associated with lower triglyceride levels. ADPN correlated positively (r = 0.49, P < 0.0001) with left ventricular mass index (LVMI) in the total study population. ADPN levels were raised in HD patients and correlated with LVMI, possibly because of the confounding effect of low glomerular filtration rate. ADPN levels were inversely related to risk factors for atherosclerosis and may provide possible targets for therapeutic interventions.

Adiponectin: an adipocyte-derived hormone, and its gene encoding in children with chronic kidney disease

Background

The prevalence of cardiovascular disease (CVD) and inflammation is high in patients with chronic kidney disease (CKD). Adiponectin (ADPN) is an adipocytokine that may have significant anti-inflammatory and anti-atherosclerotic effects. Low adiponectin levels have previously been found in patients with high risk for CVD.

Methods

On seventy eight advanced CKD (stages 4 and 5) pediatric patients undergoing maintenance hemodialysis( MHD) or conservative treatment (CT) the following parameters were studied: body mass index, left ventricular mass index(LVMI), serum adiponectin , cholesterol, HDL-cholesterol, high sensitivity C-reactive protein (hs CRP),interleukin 6(IL6) and single-nucleotide polymorphisms (SNPs) in the ADIPOQ gene at positions 45, and 276. Seventy age-and gender-matched healthy subjects served as control subjects.

Results

Markedly (P = 0.01) elevated plasma adiponectin levels were observed in CKD patients, especially CT patients, compared to control subjects. The wild type of ADIPOQ 45T > G (T) allele is the main gene for patients and controls. MHD and CT patients had significantly higher frequency of the TT genotypes of +276G > T gene (P = 0.04) compared with control subjects. A significant positive correlation was observed between plasma adiponectin and IL6 level, whereas negative correlations were found between adiponectin level, cholesterol, HDL cholesterol and hs CRP. In a stepwise backward multiple regression model only IL6 (P = 0.001) was independently associated with plasma adiponectin levels. The adiponectin gene the 276 GT+TT genotypes were associated with a higher level of adiponectin .

Conclusions

The present study demonstrated that ADPN is related to several metabolic and inflammatory CV risk factors in a manner consistent with the hypothesis that this protein might have a protective role against these factors. We observed an association between the +276G>T SNP in the adiponectin gene and CKD in children. Genetic variation of +276 gene seemed to have a positive impact on circulating adiponectin levels in CKD patients.

Relationship between ADIPOQ gene, circulating high molecular weight adiponectin and albuminuria in individuals with normal kidney function: evidence from a family-based study

AIMS/HYPOTHESIS

Insulin resistance is associated with reduced serum adiponectin and increased albuminuria levels. Thus, one would anticipate an inverse relationship between circulating adiponectin and albuminuria. However, several studies have described a 'paradoxical' elevation of serum adiponectin in patients with elevated albuminuria. These findings may have been confounded by the presence of diseases and related treatments known to affect circulating adiponectin and albuminuria. We therefore studied the relationship between circulating adiponectin and albuminuria in the absence of such confounders.

METHODS

To this purpose, the relationship between adiponectin isoforms and albumin:creatinine ratio (ACR) was investigated in a family-based sample of 634 non-diabetic untreated white individuals with normal kidney function. We also investigated whether the two variables share a common genetic background and addressed the specific role of the gene encoding adiponectin on that background by genotyping several ADIPOQ single nucleotide polymorphisms (SNPs).

RESULTS

ACR was directly associated with high molecular weight (HMW) adiponectin isoform (p = 0.024). The two variables shared some genetic correlation (ρ(g) = 0.38, p = 0.04). ADIPOQ promoter SNP rs17300539 was associated with HMW adiponectin (p = 4.8 × 10(-5)) and ACR (p =0.0027). The genetic correlation between HMW adiponectin and ACR was no longer significant when SNP rs17300539 was added to the model, thus reinforcing the role of this SNP in determining both traits.

CONCLUSIONS/INTERPRETATION

Our study shows a positive, independent correlation between HWM adiponectin and ACR. ADIPOQ variability is associated with HMW adiponectin and ACR, and explains some of the common genetic background shared by these traits, thus suggesting that ADIPOQ and HMW adiponectin modulate albuminuria levels.

Serum adiponectin is associated with homocysteine in elderly men and women, and with 5,10-methylenetetrahydrofolate reductase (MTHFR) in a sex-dependent manner

Plasma homocysteine associates positively with cardiovascular disease. C-to-T substitution at base 677 of the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene associates with increased plasma homocysteine. The association of adiponectin with cardiovascular disease is unclear. This study of survivors of a 30-year cohort of the Jewish Israeli population, 310 men and 273 women (mean age, 70.5 ± 7.0 years for both), investigated the relationship between adiponectin and homocysteine, and between adiponectin and the MTHFR C677T genotype. Serum adiponectin associated positively with total homocysteine in both men (r = 0.27, P < .001) and women (r = 0.22, P < .001). In women, the TT MTHFR genotype associated with lower median adiponectin levels, 8.98 mg/L, compared with 9.88 and 10.57 mg/L for TC and CC, respectively (P = .05; CC vs TT, P = .01). In men, the trend was opposite, but not statistically significant: 7.90, 7.03, and 6.88 mg/L for TT, TC, and CC genotypes, respectively (P = .5). This study demonstrated a positive association between homocysteine and adiponectin in both elderly men and women and a statistically significant association between adiponectin and MTHFR C677T genotypes in women only.

Plasma adiponectin concentration and insulin resistance: role of successful kidney transplantation

Adiponectin (ADPN) has been reported to be inversely correlated with insulin resistance (IR) in uremic subjects and following kidney transplantation. Kidneys have been suggested to play a part in ADPN clearance. This study sought to evaluate this hypothesis. We enrolled 67 candidates with end-stage renal disease (ESRD) along with 30 healthy unrelated donors. Plasma ADPN, IR (based on the homeostasis model assessment for IR index), and glomerular filtration rates were compared between control and patient groups. The correlations of the aforementioned variables were also compared in the patient group 1 day before and 14 days following transplantation. The changes in measured parameters were also compared with control group values. The glomerular filtration rate was significantly decreased among recipients. ADPN levels were remarkably higher in the patient group before transplantation when compared with healthy subjects (P<.001) and remained significantly higher thereafter (P<.001). Insulin resistance was higher, albeit not significantly, among ESRD patients compared with controls (P>.05) and it increased following transplantation (P=.03). There was no correlation between ADPN, IR, and glomerular filtration rate in normal individuals or ESRD patients before or after transplantation. It is our assumption that mechanisms other than kidney function are probably involved in ADPN metabolism in ESRD patients and in the immediate phase following transplantation. It does not seem that ADPN substantially affects IR either in ESRD or transplantation patients.

Metabolic acidosis lowers circulating adiponectin through inhibition of adiponectin gene transcription

BACKGROUND

Metabolic acidosis (MA) adversely affects protein and lipid metabolism as well as endocrine function. Adipose tissue communicates with the rest of the body through synthesis and release adipokines, such as leptin, adiponectin and TNF-alpha. Adiponectin enhances insulin sensitivity and possesses anti-atherogenic and anti-inflammatory properties. Circulating adiponectin correlates inversely with cardiovascular events. It is possible that MA negatively regulates adiponectin contributing to poor patient outcome. The present study investigates the effect of MA on adiponectin in vivo and in vitro.

METHODS

Twenty healthy female volunteers underwent a 7-day course of oral ammonium chloride (NH4Cl)-induced acidosis. Serum adiponectin was determined before and after NH4Cl ingestion. Adipocytes were differentiated from their precursors, human mesenchymal stem cells (hMSCs), in culture. Concentrated HCl was added to the media to lower pH. Adiponectin mRNA and protein were determined at 48 and 96 h by real-time RT-PCR and ELISA, respectively.

RESULTS

After a 7-day course of NH4Cl, serum bicarbonate decreased significantly associated with the increase in urine ammonium and titratable acid. Adiponectin decreased significantly from 10,623 to 9723 pg/mL (P<0.005). MA suppressed adiponectin mRNA in hMSC-derived adipocytes at 48 and 96 h (P<0.01). The amount of adiponectin released into the culture media declined corresponding to the mRNA levels (P<0.001). MA did not affect adipocyte triglyceride or protein content.

CONCLUSIONS

MA lowered circulating adiponectin through inhibition of adiponectin gene transcription in adipocytes.

Associations of circulating adiponectin with measures of vascular function and morphology

CONTEXT

Some previous studies have reported an association between circulating adiponectin and selected measures of vascular function and morphology, but most of these studies have been performed in small samples of patients with preexisting disease.

OBJECTIVE

We aimed to evaluate associations between circulating adiponectin and comprehensive measures of vascular function and morphology in a large sample of individuals from the community.

DESIGN, SETTINGS, AND PARTICIPANTS

We conducted a cross-sectional investigation of 981 70-yr-old participants (50% women) of the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS).

MAIN OUTCOME MEASURES

Measures of outcome included vascular function [common carotid artery (CCA) distensibility, flow-mediated dilation, endothelium-dependent and endothelium-independent vasodilation using invasive methods] and vascular morphology [intima-media (IM) thickness, plaque presence, gray scale median (GSM) in the IM and plaques].

RESULTS

In age- and sex-adjusted models, adiponectin was positively associated with IM-GSM, plaque GSM, CCA distensibility, endothelium-dependent and endothelium-independent vasodilation. In multivariable models (with additional adjustment for body mass index; systolic blood pressure; antihypertensive, antidiabetic, and lipid-lowering medication; fasting blood glucose; total cholesterol; high-density lipoprotein cholesterol; creatinine; and smoking), adiponectin remained positively associated with IM-GSM [beta = 2.06; 95% confidence interval (CI), 0.54, 3.58], plaque GSM (beta = 3.11; 95% CI, 0.36, 5.86), and CCA distensibility (beta = 0.04; 95% CI, 0.00, 0.07).

CONCLUSIONS

Serum levels of adiponectin were positively associated with IM-GSM and plaque GSM (indicating lower fat content in the IM and plaques) and CCA distensibility (indicating higher wall elasticity), independent of potential confounders. Our results imply that adiponectin is associated with less arterial pathology.

Adiponectin in health and disease: evaluation of adiponectin-targeted drug development strategies

Adiponectin is a secretory protein predominantly expressed by adipocytes and released at a high rate into circulation. The ease with which the levels of adiponectin can be measured owing to its high abundance, small diurnal variation and high stability in plasma have made it a popular target for measurements in many clinical studies. It has emerged as a valuable biomarker for insulin sensitivity, cardiovascular risk and inflammation. However, adiponectin levels have been measured in many additional disease states. Preclinical studies not only have implicated adiponectin as an outstanding biomarker but also have demonstrated direct cardio-protective and insulin-sensitizing properties to be associated with the protein. Adiponectin might, therefore, be a viable protein therapeutic that could be supplied in a recombinant form in the context of type 2 diabetes and cardiovascular disease. However, the high abundance, complex tertiary and quaternary structure and rapid turnover might make chronic administration of the protein rather challenging.

Relationship of adiposity with arterial stiffness as mediated by adiponectin in older men and women: the Hoorn Study

OBJECTIVE

To investigate whether adiponectin is associated with arterial stiffness, and whether adiponectin explains the association between body composition and arterial stiffness.

DESIGN

Cross-sectional cohort study.

METHODS

Subjects were participants (n=456, mean age 68.9+/-6.1 years; age range 60-86 years) of the third follow-up examination of the Hoorn Study. Trunk fat, leg fat, trunk lean, and leg lean mass were measured by dual-energy X-ray absorptiometry. Ultrasound was used to measure distensibility and compliance of the carotid, femoral, and brachial arteries, and carotid Young's elastic modulus (as estimates of peripheral arterial stiffness). Results Trunk fat mass was negatively associated with (ln-transformed) adiponectin (standardized beta=-0.49, P<0.001), while leg fat mass was positively associated with adiponectin (beta=0.44, P<0.001), after adjustment for each other, age, and lean mass. After adjustment for age, sex, mean arterial pressure, and estimated glomerular filtration rate, higher adiponectin was associated with decreased peripheral arterial stiffness (beta of mean Z-scores of all three arteries=0.14, P=0.001). However, the associations of trunk fat (beta=-0.26, P<0.001) and leg fat (beta=0.16, P=0.006) with peripheral arterial stiffness were only minimally explained by adiponectin levels.

CONCLUSION

Trunk fat and leg fat are oppositely associated with adiponectin. Although low adiponectin was a determinant of increased peripheral arterial stiffness, it only explained a small part of the association between body fat and peripheral arterial stiffness. This indicated that factors other than adiponectin may be more important in the pathophysiological mechanisms by which abdominal obesity leads to arterial stiffness.

The usefulness of circulating adipokine levels for the assessment of obesity-related health problems

Because the prevalence of obesity has increased dramatically in recent years, one of the key targets of public health is obesity and its associated pathological conditions. Obesity occurs as a result of white adipose tissue enlargement, caused by adipocyte hyperplasia and/or hypertrophy. Recently, endocrine aspects of adipose tissue have become an active research area and these adipose tissue-derived factors are referred to as adipokines. These adipokines interact with a range of processes in many different organ systems and influence a various systemic phenomena. Therefore, dysregulated production of adipokines has been found to participate in the development of metabolic and vascular diseases related to obesity. The obese state is also known to be associated with increased local and systemic inflammation. Adipokines influence not only systemic insulin resistance and have pathophysiological roles in the metabolic syndrome and cardiovascular disease, but also contribute toward an increase in local and systemic inflammation. Thus, circulating levels of adipokines can be used as high-throughput biomarkers to assess the obesity-related health problems, including low grade inflammation. This review focuses on the usefulness of measuring circulating adipokine levels for the assessment of obesity-related health problems.

Plasma adiponectin levels and clinical outcomes among haemodialysis patients

BACKGROUND

Adiponectin (ADPN) levels are consistently elevated among patients with advanced chronic kidney disease, but its relationship with cardiovascular outcomes in this population remains controversial.

METHODS

We measured baseline and yearly plasma ADPN in 182 prevalent haemodialysis patients recruited to the Haemodialysis (HEMO) Study from two Boston centres. Plasma ADPN at baseline and during follow-up was studied in relation to prevalent cardiovascular disease (CVD) and cardiovascular and all-cause mortality.

RESULTS

Baseline plasma ADPN levels were found to be approximately twofold higher than in the general population and correlated inversely with (log-transformed) CRP levels and (log-transformed) body mass index (BMI). Levels measured over time showed a gradual increase (0.95 microg/mL, 95% CI = 0.12-1.78 microg/mL; P = 0.03) by year, although this difference became non-significant after adjustment for covariates. Baseline ADPN levels were lower among patients with pre-existing CVD (adjusted OR of 0.67; P = 0.03). They also predicted all-cause mortality (P < 0.01) and the composite outcome of 'cardiovascular events/cardiovascular mortality' (P < 0.01); levels measured over time predicted the composite outcome of 'cardiovascular events and all-cause mortality' (P < 0.01). These relationships were non-linear (quadratic) with the hazard for each outcome increasing in the lower and upper ranges of the distribution of ADPN, and strengthened after adjustment for baseline covariates including serum albumin, CVD and the flux and dialysis dose categorization of the HEMO study.

CONCLUSIONS

In summary, low plasma levels of ADPN were associated with inflammation and pre-existing CVD; ADPN levels predicted cardiovascular and mortality outcomes, the relationship being extensively confounded by multiple patient-related factors.

Low plasma levels of adiponectin are associated with low risk for future cardiovascular events in patients with clinical evident vascular disease

BACKGROUND

Adiponectin is considered to have anti-inflammatory, insulin-sensitizing, and antiatherosclerotic properties. In the present prospective study, the relationship between metabolic syndrome (Adult Treatment Panel III) and adiponectin plasma levels and the relationship between plasma adiponectin levels and future cardiovascular events were investigated.

METHODS

A case-cohort study of 431 patients with clinical evident vascular disease from the Second Manifestations of ARTerial Disease study. The relationship between adiponectin plasma levels and new vascular events was investigated with Cox regression, adjusted for potential confounders and effect modifiers (age, sex, renal function [modification of diet in renal disease], body mass index, high sensitive C-reactive protein, use of angiotensin converting enzyme-inhibition and/or AII antagonists, and presence of metabolic syndrome or impaired renal function).

RESULTS

Plasma adiponectin levels were lower in patients with metabolic syndrome as compared with patients without (7.9 +/- 0.3 vs 5.2 +/- 0.3 microg/mL) and decreased with the number of components. During a mean follow-up of 2.3 years, 216 patients had a new cardiovascular event. Lower adiponectin plasma levels were associated with a lower risk for future cardiovascular events (hazard ratio 0.50, 95% confidence interval 0.25-0.99). This relationship was not influenced by renal function, body mass index, and renin-angiotensin system-blocking agents or modified by metabolic syndrome and impaired renal function.

CONCLUSION

In patients with clinical evident vascular disease, lower adiponectin levels were associated with a lower cardiovascular risk. Therefore, it may be hypothesized that the potential antiatherosclerotic properties of adiponectin do not apply for patients with already established vascular disease.

Cardiac expression of adiponectin and its receptors in streptozotocin-induced diabetic rats

Adiponectin can improve both glucose metabolism and insulin resistance via the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway. Activated AMPK phosphorylates a variety of intracellular proteins, including acetyl coenzyme A carboxylase (ACC) that is involved in fatty acid oxidation. Adenosine monophosphate-activated protein kinase increases glucose transport by stimulating the translocation of glucose transporter 4 (GLUT4) to the sarcolemma in the heart. Adiponectin exerts its effect through adiponectin receptors, which are predominantly expressed in the liver and skeletal muscle. It is unknown whether the cardiac expression of adiponectin and its receptors is changed in diabetic rats. In the present study, we investigated the protein expression of adiponectin and its receptors in streptozotocin (STZ)-induced diabetic rat hearts. We also explored whether the levels of AMPK, ACC, and GLUT4 will be altered with the changed adiponectin and its receptors in STZ diabetic rat hearts. Plasma and cardiac adiponectin levels were measured by radioimmunoassay. Plasma and cardiac interleukin 6 and plasma tumor necrosis factor alpha (TNF-alpha) were assayed by enzyme-linked immunosorbent assay. Cardiac adiponectin receptors, AMPK-alpha, ACC, GLUT4, and TNF-alpha were analyzed by Western blot in control and STZ diabetic rats. The plasma adiponectin level was decreased, but the cardiac protein expression of adiponectin receptor 1 was increased in diabetic rats. There was no difference in the cardiac adiponectin level and the cardiac adiponectin receptor 2 protein expression between control and diabetic rats. The phosphorylation of AMPK-alpha and protein expression of GLUT4 were decreased, but the phosphorylation of ACC was unchanged in diabetic rat hearts. Plasma and cardiac levels of interleukin 6 and TNF-alpha were increased in diabetic rats. In conclusion, STZ-induced diabetes up-regulates adiponectin receptors in the heart. Despite an increase in cardiac adiponectin receptor 1 expression, there is an increased cardiac inflammatory response and a decreased GLUT4 protein expression associated with a reduction in circulating adiponectin.

The effect of renal transplantation on adiponectin and its isoforms and receptors

Insulin resistance (IR) and other proatherogenic risk factors associated with end-stage kidney disease (ESKD) are improved by renal transplantation. Adiponectin is a protein with insulin-sensitizing, anti-inflammatory, and antiatherogenic properties. It exists in several isoforms, but the high molecular weight (HMW) isoform correlates best with insulin sensitivity. Paradoxically, the levels of this protein and its HMW isoform are increased in ESKD. We measured the homeostasis model assessment for insulin resistance (HOMA-IR), plasma adiponectin and its isoforms, and messenger RNA for adiponectin receptors (AdipoR1 and AdipoR2) on peripheral blood mononuclear cells in 54 stable transplant recipients, 50 patients established on hemodialysis, and 52 controls; groups were matched for body mass index and sex. HOMA-IR values were significantly higher in patients with ESKD compared with controls (P < .0005) and transplant patients (P < .05) but there was no difference between the latter 2 groups. Adiponectin levels were also higher in patients with ESKD compared with controls (P < .0005), and although levels were lower in the transplant group, they remained higher than in controls (P < .0001). However, although the absolute amount of HMW isoform in transplant patients remained higher than in controls (P < .0001), the proportion was similar, and less than in patients with ESKD (P < .005). The absolute amount of the HMW isoform correlated with superior metabolic indices in all 3 cohorts. AdipoR1 and AdipoR2 messenger RNA levels after transplantation were significantly lower than those of ESKD subjects (P < .0001, P < .01), but transplant patients had less AdipoR1 than controls, although their AdipoR2 levels were higher. AdipoR1 correlated with AdipoR2 in all 3 cohorts. We conclude that HOMA-IR was lower in the transplant group compared with the group on hemodialysis and this coincided with lower total adiponectin levels and absolute amount of the HMW isoform and AdipoR on peripheral blood mononuclear cells. Lower AdipoR after transplantation may be secondary to immunosuppression and/or an improvement in glomerular filtration rate and the uremic milieu.

Association of plasma adiponectin levels with oxidative stress in hemodialysis patients

BACKGROUND

Recent evidence suggests that oxidative stress may be an instigator of the metabolic syndrome, and adiponectin, an adipocyte-derived polypeptide, may modulate oxidative stress, ameliorating the atherosclerotic process.

AIM

Oxidative stress is increased in hemodialysis (HD) patients. We hypothesize that a relationship between plasma levels of adiponectin and markers of inflammation and oxidative stress exists.

METHODS AND RESULTS

In 124 HD patients, plasma adiponectin levels and three separate oxidative stress markers, tumor necrosis factor-alpha as well as high-sensitivity C-reactive protein (hsCRP) were determined. Plasma adiponectin was significantly and negatively correlated with serum hsCRP (r = -0.247, p = 0.008) and plasma malondialdehyde (MDA) levels (r = -0.326; p < 0.001). Multiple regression analyses suggested that plasma MDA, serum HDL cholesterol levels and logarithmically transformed hsCRP were the variables independently associated with plasma adiponectin levels.

CONCLUSION

Plasma adiponectin was significantly associated with plasma MDA, serum HDL cholesterol levels and serum hsCRP levels. Our results suggest the possibility that plasma adiponectin may play a role in alleviating oxidative stress in HD patients.

Plasma and urine levels of resistin and adiponectin in chronic kidney disease

BACKGROUND

Subjects with chronic kidney disease (CKD) have an increased risk of developing coronary atherosclerosis. Adipocyte hormones, resistin and adiponectin are implicated in insulin resistance and atherosclerosis. However, few studies in the literature address the role of adipocyte hormones in CKD. The aim of this study was to compare the levels of resistin, adiponectin and other inflammatory markers in subjects with CKD with those of the control subjects.

MATERIALS AND METHODS

In a cross-sectional study, we measured basal metabolic panel, fasting lipid panel and levels of glucose, resistin, adiponectin, insulin, C-reactive protein (CRP) and TNF-alpha in 43 subjects with CKD compared with those of 34 control subjects. We also measured the resistin and adiponectin levels in urine samples (16).

RESULTS

Subjects with CKD have increased insulin levels and insulin resistance index (IRI). Compared with controls, subjects with CKD had increased levels of resistin (5.12+/-3.2 vs.7.5+/-5.9; p<0.05), CRP (1.7+/-2.2 vs. 5.97+/-6.0; p<0.0005), and TNF-alpha (3.4+/-2.0 vs. 5.2+/-3.5; p<0.005). Resistin levels correlate with CRP and TNF-alpha, even with BMI as a covariate. Although 60% of subjects with CKD have CAD, e plasma levels of adiponectin were not decreased in subjects with CKD compared with controls (17.02+/-9.8 vs. 16.40+/-9.0 with p value 0.78). Urinary adiponectin levels correlate inversely with GFR (r=-0.4; p<0.05) and plasma adiponectin levels (r=0.9; p<0.0001).

CONCLUSIONS

Subjects with CKD had normal levels of plasma adiponectin despite the adverse metabolic environment for CAD. In addition, this study demonstrates the relationship between resistin and TNF-alpha in subjects with CKD and suggests that resistin may play a role in the sub-clinical inflammation associated with CKD, suggesting that adiponectin clearance may be decreased as shown by the inverse correlation of urinary adiponectin with GFR.

Low fat adiponectin expression is associated with oxidative stress in nondiabetic humans with chronic kidney disease--impact on plasma adiponectin concentration

In spite of association between high plasma adiponectin and high metabolic and cardiovascular (CV) risk, highest adiponectin increments retain CV and metabolic protective effects in advanced chronic kidney disease (CKD). Passive accumulation can favor CKD-associated hyperadiponectinemia but potential additional regulation by adipose tissue remains undefined. Oxidative stress (OS) is associated with metabolic and CV disease and with CKD [increasing from conservative treatment (CT) to maintenance hemodialysis (MHD)], and OS can reduce adiponectin expression in experimental models. OS (in the form of plasma thiobarbituric acid-reactive substances: TBARS), subcutaneous adipose adiponectin mRNA, and plasma adiponectin were studied in CKD patients (stages 4 and 5) on CT (n = 7) or MHD (n = 11). Compared with CT and controls (C: n = 6) MHD had highest TBARS and lowest adiponectin mRNA (P < 0.05) with lower adipose adiponectin protein (P < 0.05 vs. CT). MHD also had lower plasma adiponectin than CT, although both had higher adiponectin than C (P < 0.05). In renal transplant recipients (RT: CKD stage 3; n = 5) normal TBARS were, in turn, associated with normal adiponectin mRNA (P < 0.05 vs. MHD). In all CKD (n = 23), adiponectin mRNA was associated positively with adiponectin plasma concentration (P < 0.01). In all subjects (n = 29), adiponectin mRNA was related (P < 0.05) negatively with TBARS after adjusting for plasma C-reactive protein (CRP) or CRP and creatinine. Thus altered OS, adiponectin expression, and plasma concentration represent a novel cluster of metabolic and CV risk factors in MHD that are normalized in RT. The data suggest novel roles of 1) MHD-associated OS in modulating adiponectin expression and 2) adipose tissue in contributing to circulating adiponectin in advanced CKD.

Adiponectin and chronic kidney disease

Enhanced chronic inflammation and reduced insulin sensitivity are often present in chronic kidney disease (CKD). Cardiovascular disease remains a major cause of morbidity and mortality in end-stage renal patients. Adiponectin (ADP) is a hormone exclusively produced by adipocytes and possesses anti-inflammatory and cardioprotective properties. Despite the high prevalence of insulin resistance and cardiovascular disease, levels of ADP are increased among end-stage renal disease patients on hemo or peritoneal dialysis but also among patients with moderate renal failure or with the nephrotic syndrome. Furthermore, lower ADP levels are associated with poor cardiovascular outcome. In this review, we examine ADP modifications in CKD and discuss the different factors that may have an impact on this adipokine metabolism in renal failure.

Adiponectin and mortality in patients undergoing coronary angiography

CONTEXT

The adipokine adiponectin has been suggested to protect against coronary artery disease (CAD). However, studies addressing the association between adiponectin and mortality are sparse.

OBJECTIVE

The objective of the study was to elucidate the relationship between adiponectin and mortality.

DESIGN, SETTING, AND PARTICIPANTS

Adiponectin was determined in 2473 persons with and 673 persons without angiographic CAD. During a mean follow-up period of 5.45 yr, 427 persons with CAD and 55 persons without CAD died.

MAIN OUTCOME MEASURE

Hazard ratios for mortality according to adiponectin levels were measured.

RESULTS

Adiponectin was positively related to female gender, age, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, homocysteine, and N-terminal pro-B-type natriuretic peptide. It was inversely related to glomerular filtration rate, body mass index, and triglycerides and was low in diabetes mellitus and CAD. An increase of 1 sd in adiponectin was associated with unadjusted and fully adjusted hazard ratios for death from any cause of 1.31 [95% confidence interval (CI) 1.20-1.42] and 1.22 (95% CI 1.12-1.34), and for death from cardiovascular causes of 1.32 (95% CI 1.19-1.45) and 1.23 (95% CI 1.11-1.37), respectively. In angiographic CAD, stable CAD, and unstable CAD, the predictive value of adiponectin was similar to that in the entire cohort, but it did not attain statistical significance in persons without angiographic CAD. Adiponectin was also positively related to the risk of death from noncardiovascular causes.

CONCLUSIONS

Despite the common view about adiponectin as a protective molecule in cardiovascular disease, high adiponectin independently predicts all-cause, cardiovascular, and noncardiovascular mortality in individuals with CAD.

Adiponectin and adiponectin receptors in insulin resistance, diabetes, and the metabolic syndrome

Adiponectin is an adipokine that is specifically and abundantly expressed in adipose tissue and directly sensitizes the body to insulin. Hypoadiponectinemia, caused by interactions of genetic factors such as SNPs in the Adiponectin gene and environmental factors causing obesity, appears to play an important causal role in insulin resistance, type 2 diabetes, and the metabolic syndrome, which are linked to obesity. The adiponectin receptors, AdipoR1 and AdipoR2, which mediate the antidiabetic metabolic actions of adiponectin, have been cloned and are downregulated in obesity-linked insulin resistance. Upregulation of adiponectin is a partial cause of the insulin-sensitizing and antidiabetic actions of thiazolidinediones. Therefore, adiponectin and adiponectin receptors represent potential versatile therapeutic targets to combat obesity-linked diseases characterized by insulin resistance. This Review describes the pathophysiology of adiponectin and adiponectin receptors in insulin resistance, diabetes, and the metabolic syndrome.

Carbohydrate metabolism in uraemia

PURPOSE OF REVIEW

Most uraemic patients are insulin resistant. This review focuses on the occurrence, mechanisms and consequences of this insulin resistance. Hypoglycaemia is also possible in a minority of uraemic patients; its causes are discussed at the end of the review.

RECENT FINDINGS

Insulin resistance is detectable when the glomerular filtration rate is below 50 ml/min per 1.73 m in non-diabetic uraemic individuals. Uraemia can alter insulin sensitivity even in diabetic patients; familial insulin resistance may favour the occurrence of diabetic nephropathy. Although reduced glucose non-oxidative disposal is the most evident defect of carbohydrate metabolism, abnormal glucose oxidation, endogenous glucose production and insulin secretion are also contributors. The accumulation of nitrogenous compounds is the most important mechanism of a specific state of insulin resistance in uraemia. Their identification is progressing, particularly in the field of carbamoylated amino acids. The consequences of chronic renal failure such as anaemia, metabolic acidosis and secondary hyperparathyroidism also indirectly play a role.

SUMMARY

The treatment of uraemia by renal replacement therapies or low-protein diets improves insulin sensitivity. However, patients still have a high cardiovascular risk. The identification of the accumulating molecular species that specifically alter insulin sensitivity is therefore of great interest. The favourable effect of non-specific insulin sensitizers such as glitazone may also help to reduce this risk.