Selenoprotein P-1 (SEPP1) as an Early Biomarker of Myocardial Injury in Patients Undergoing Cardiopulmonary Bypass

Background: Biomarkers development for prognostication or prediction of perioperative myocardial disease is critical for the evolution of treatment options in patients undergoing cardiac surgery. The aim of our prospective monocentric study was to investigate the role of selenoprotein 1 (SEEP 1) as a potential biomarker for assessing the risk of myocardial injury after cardiac surgery. Methods: Circulating SEPP1 was measured in the blood of 45 patients before surgery and at 4 h, 8 h and 12 h after CPB by enzyme-linked immunosorbent assay (ELISA); (3) Results: circulating SEPP-1 levels measured 4 h after surgery were strongly correlated with CK-MB levels measured at 48 h (R = 0.598, p < 0.0001) and at 72 h (R = 0.308, p = 0.05). Close correlations were also found between 4 h SEPP-1 and Hs-c troponin values measured at 24 h (R = 0.532, p < 0.0001), 48 h (R = 0.348, p = 0.01) and 72 h (R = 0.377, p = 0.02), as well as with cardiopulmonary bypass (CPB) (R = 0.389, p = 0.008) and cross-clamp time (R = 0.374, p = 0.001); (4) Conclusions: Early SEPP1 measurement after CPB may hold great potential for identifying cardiac surgery patients at risk of developing perioperative myocardial injury.

Role of kidney function on Nrf2 mRNA levels in type 2 diabetes

INTRODUCTION

Diabetic kidney disease (DKD) is a major complication in patients with diabetes and the main contributor to the chronic kidney disease (CKD) global burden. Oxidative stress is a crucial factor in DKD pathogenesis but the role of the antioxidant nuclear factor erythroid 2-related factor 2 (Nrf2) and its molecular regulators has been poorly investigated in man.

RESEARCH DESIGN AND METHODS

In this case-control study, we analyzed the roles of Nrf2, a transcription factor shielding cells from oxidative stress, its repressor Kelch-like ECH-associated protein 1 (Keap1) and six microRNAs (miRNAs) that potentially suppress Nrf2. We categorized 99 participants into 3 groups: 33 non-dialysis patients with type 2 diabetes with DKD, 33 patients with type 2 diabetes without DKD and 33 control subjects and quantified the gene expression (messenger RNA (mRNA)) levels of Nrf2, Keap1 and 6 miRNAs. Moreover, we studied the correlation between gene expression levels and clinical indicators of kidney health.

RESULTS

In patients with diabetes with DKD, Nrf2 mRNA levels were significantly lower than in patients without DKD (p=0.01) and controls (p=0.02), whereas no difference in Nrf2 expression levels existed between patients without DKD and controls. Conversely, in patients with and without DKD, Keap1 expression levels were significantly higher than in controls. Of the six miRNAs studied, miRNA 30e-5p showed differential expression, being markedly reduced in patients with DKD (p=0.007). Nrf2 mRNA levels directly correlated with estimated glomerular filtration rate (eGFR) in patients with DKD (r=0.34, p=0.05) and in a formal mediation analysis the eGFR emerged as the first factor in rank for explaining the difference in Nrf2 mRNA levels between patients with and without DKD.

CONCLUSIONS

The observed dysregulation in the Nrf2-Keap1 axis and the unique expression pattern of miRNA30e-5p in DKD underscore the need for more focused research in this domain that can help identify novel intervention strategies for DKD in patients with type 2 diabetes.

Neuropeptide Y gene polymorphisms and chronic kidney disease progression

BACKGROUND

Neuropeptide Y (NPY) is a neurotransmitter expressed in both the central and peripheral nervous systems, which is involved in regulating a multitude of physiological processes ranging from arterial pressure, energy balance, the immune response and inflammation and renal electrolyte transport. In a cohort of chronic kidney disease (CKD) patients, we recently showed that high plasma NPY levels predict renal disease progression independently of hypertension and other risk factors but the causal nature of this association remains unproven.

METHODS

In the same cohort of the previous study, we tested the relationship of NPY gene variability, as assessed by five single nucleotide polymorphisms (SNPs) that explained the whole gene variability, with the incidence rate of a predefined combined renal endpoint (dialysis/transplantation/estimated glomerular filtration rate reduction >30%) over a median follow up of 36 months (inter-quartile range 35-37 months) in 735 ethnically homogeneous patients with stage 2-5 CKD.

RESULTS

Two variants [rs16131 (recessive model for the T risk allele: TT, n  = 563; CT + CC, n  = 172) and rs16140 (dominant model for the G risk allele: GG + CG, n  = 413; CC, n  = 322)] were coherently associated with the incidence rate of renal events [hazard ratio (HR) ranging from 1.39 to 1.57, P  ≤ 0.015] and this was also true when the two SNPs were jointly introduced into the same Cox model ( P  ≤ 0.043). The analysis of the biological interaction showed a significant synergism between the NPY rs16131 and rs16140 variants. Indeed, patients harboring NPY rs16131 TT and NPY rs16140 GG + CG risk genotypes had a much higher HR of renal events [HR: 1.80, 95% confidence interval (CI):1.16-2.79, P  = 0.009] than that expected in the absence of biological interaction under both the additive and multiplicative models and the attributable proportion due to interaction (AP) was 25% and 38% on crude and adjusted analyses, respectively.

CONCLUSION

This study, based on the Mendelian randomization approach and using NPY gene variants as instrumental variables to test the link between NPY and CKD progression, is in line with findings indicating that high plasma NPY levels predict an increased risk for renal events and lend support to the hypothesis that NPY is causally involved in renal disease progression.

Role of Gut Microbiota in Overweight Susceptibility in an Adult Population in Italy

Although the gut microbiota is known to affect body weight, its relationship with overweight/obesity is unclear. Our aim was to characterize microbiota composition in a cohort from the southernmost area of Italy. We investigated whether an altered gut microbiota could play an etiological role in the pathogenesis of overweight/obesity. A total of 163 healthy adults were enrolled. Microbiome analysis was performed via 16S rRNA gene sequencing. We found significant phylum variations between overweight (N = 88) and normal-weight (N = 75) subjects. Bacteroidetes and Proteobacteria were higher in overweight participants (p = 0.004; p = 0.03), and Firmicutes and Verrucomicrobia were lower (p = 0.02; p = 0.008) compared to normal-weight participants. Additionally, Akkermansia and Bifidobacterium (genus level) were significantly lower in the overweight group, as well as Akkermansia muciniphila at the species level. The Firmicutes/Bacteroidetes ratio (F/B ratio), an index of dysbiosis, was found to be inversely associated with BMI in linear and logistic regression models (p = 0.001; p = 0.005). The association remained statistically significant after adjustment for potential confounders. This cross-sectional study contributes to defining the gut microbiota composition in an adult population living in southern Italy. It confirms the relationship between overweight susceptibility and the dysbiosis status, highlighting the possible etiological role of the F/B ratio in disease susceptibility.

Inflammation biomarkers and inflammatory genes expression in metabolically healthy obese patients

BACKGROUND AND AIMS

Obesity without metabolic alterations (Metabolically Healthy Obesity, MHO) is a condition with a risk of death and cardiovascular disease lower than that of obesity associated with metabolic alterations (Metabolically Unhealthy Obesity, MUO) and similar to that of healthy non obese individuals. Inflammation is considered as a key risk factor mediating the adverse health outcomes in obesity.

METHODS AND RESULTS

We compared circulating levels of thirteen major cytokines and adipokines and the expression profiles of fifteen pro-inflammatory and two anti-inflammatory genes in visceral and subcutaneous adipose tissue in a series of 16 MHO patients and in 32 MUO patients that underwent bariatric surgery. MHO was defined according to the most applied definition in current literature. Serum levels of a large set of major cytokines and adipokines did not differ between MHO and MUO patients (p ≥ 0.15). Analyses of the expression profile of pro-inflammatory and anti-inflammatory genes in subcutaneous and visceral adipose tissue failed to show differences between MHO and MUO patients (p ≥ 0.07). Sensitivity analyses applying two additional definitions of MHO confirmed the results of the primary analysis.

CONCLUSION

In a series of metabolically healthy obese patients neither circulating levels of major cytokines and adipokines nor the gene expression profile of a large set of pro-inflammatory and anti-inflammatory genes in subcutaneous and visceral fat differed from those in metabolically unhealthy obese patients.

MO354: Selenium-Binding Protein 1 (Sepp1) as an Early Sensitive Biomarker of Acute Kidney Injury in Patients Undergoing Cardiopulmonary Bypass

BACKGROUND AND AIMS

Acute kidney injury (AKI) often occurs in patients undergoing major cardiac surgery with cardiopulmonary bypass (CPB). Despite renal ischemia remains the key trigger, sustained oxidative stress is now acknowledged as a significant contributor. Selenium-binding protein 1 (SEPP1) is an intracellular protein whose blood levels increase in response to systemic cardiovascular and oxidative stress, as well as in the course of chronic kidney injury.

METHOD

In this pilot prospective study, we measured circulating SEPP1 levels in a cohort of 45 patients undergoing cardiac surgery with CPB in order to test its possible role in predicting the following occurrence of AKI. Serum samples of SEPP1 were collected before CPB (baseline) and at 4, 8 and 12 h after the end of the procedure and measured with a commercially available ELISA kit.

RESULTS

In the whole cohort, there was a significant statistical trend in SEPP1 levels from baseline to 12 h after CPB [39 (10–45) versus 3263 (1886–5042) ng/mL; P &lt; 0.0001]. Within 48 h from CPB end, 12/45 patients (27%) developed AKI, as defined as an increase in serum creatinine &gt;0.3 mg/dL or an absolute 1.5-fold increase from baseline and/or a reduced urine output (&lt;0.5 mL/kg/h). Circulating SEPP1 displayed an earlier and more prominent increase in AKI patients as compared with others [4 h SEPP1: 52 (39–233) versus 546 (260–1000) ng/mL; P &lt; 0.001]. 8 h SEPP1: 638 (437–1254) versus 1959 (1055–5303) ng/mL; P &lt; 0.001; difference between overall trends: P &lt; 0.001 (Fig. 1). At ROC analyses, either 4 or 8 h circulating SEPP1 had a remarkable diagnostic capacity in identifying AKI patients (AUCs 0.854 and 0.790, both P &lt; 0.001). The crude OR of AKI in patients with 4 and 8 h SEPP1 above the best ROC-derived cut-off values (178 and 1840 ng/mL, respectively) was 22 (95%CI 2.5–192.9) and 14.5 (95% CI 2.9–71.2), respectively. At multivariate analysis, such a risk was independent from potential confounders, including CPB duration, clamping time and age.

CONCLUSION

Increased SEPP1 levels in patients undergoing CPB may reflect a sustained response to systemic oxidative stress. Such a response becomes more prominent when renal damage is also occurring. Studies on larger and more heterogeneous cohorts are needed to confirm whether SEPP1 may be a candidate as an early and specific biomarker of AKI in this high-risk setting.

Neuropeptide Y as a risk factor for cardiorenal disease and cognitive dysfunction in CKD: translational opportunities and challenges

Neuropeptide Y (NPY) is a 36-amino-acid peptide member of a family also including peptide YY and pancreatic polypeptide, which are all ligands to Gi/Go coupled receptors. NPY regulates several fundamental biologic functions including appetite/satiety, sex and reproduction, learning and memory, cardiovascular and renal function and immune functions. The mesenteric circulation is a major source of NPY in the blood in man and this peptide is considered a key regulator of gut–brain cross talk. A progressive increase in circulating NPY accompanies the progression of chronic kidney disease (CKD) toward kidney failure and NPY robustly predicts cardiovascular events in this population. Furthermore, NPY is suspected as a possible player in accelerated cognitive function decline and dementia in patients with CKD and in dialysis patients. In theory, interfering with the NPY system has relevant potential for the treatment of diverse diseases from cardiovascular and renal diseases to diseases of the central nervous system. Pharmaceutical formulations for effective drug delivery and cost, as well as the complexity of diseases potentially addressable by NPY/NPY antagonists, have been a problem until now. This in part explains the slow progress of knowledge about the NPY system in the clinical arena. There is now renewed research interest in the NPY system in psychopharmacology and in pharmacology in general and new studies and a new breed of clinical trials may eventually bring the expected benefits in human health with drugs interfering with this system.

Serum gamma-glutamyltransferase, oxidized LDL and mortality in the elderly

BACKGROUND

Serum gamma-glutamyltransferase (GGT) is a liver enzyme involved in the metabolism of glutathione (GSH), a major antioxidant in humans. GGT is a risk factor for mortality in young and middle-aged individuals but this association has been poorly investigated in the elderly.

METHODS

We studied the relationship between GGT and all-cause mortality and tested whether oxidized low-density lipoproteins (oxLDL) modify this association in a cohort of 1038 elderly individuals.

RESULTS

During the observation time (median 9 years), 401 individuals died. In a Cox regression model adjusting for potential confounders, GGT was an independent risk factor for all-cause mortality [HR (20U/L increase in serum GGT): 1.11, 95% CI 1.02-1.21, P = 0.02]. Furthermore, increasing levels of oxLDL amplified the risk excess for all-cause mortality associated with GGT (P for the effect modification = 0.003).

CONCLUSIONS

In the elderly, serum GGT is an independent risk factor for all-cause mortality and circulating oxLDL amplify the magnitude of this association.

Circulating adiponectin modifies the FGF23 response to vitamin D receptor activation: a post hoc analysis of a double-blind, randomized clinical trial

Background

The fibroblast growth factor 23 (FGF23) response to phosphate load is suppressed in adiponectin gene null mice and substantially amplified in mice overexpressing the same gene and vitamin D receptor (VDR) activation markedly enhances FGF23 gene expression.

Methods

We performed an analysis of the static (baseline adiponectin levels) and dynamic (fluctuations in adiponectin levels) interactions of serum adiponectin with the FGF23 response to paricalcitol and placebo in the setting of a double-blind, randomized clinical trial in chronic kidney disease (CKD) patients (NCT01680198).

Results

As compared with placebo, VDR activation by paricalcitol markedly increased serum FGF23 levels (P < 0.001), and such an increase was amplified in patients in the 4th adiponectin quartile as compared with other quartiles (P = 0.009) while no such an effect was noted in the placebo group (P = 0.49). Both baseline adiponectin (P for interaction = 0.009) and fluctuations in adiponectin levels following paricalcitol and placebo (P for interaction = 0.003) strongly modified the difference in the FGF23 response to these treatments. These interactions were specific because no similar effect modification by other factors with the FGF23 response to VDR activation was found. Furthermore, in a global correlation analysis, adiponectin and FGF23 were interrelated independent of the estimated glomerular filtration rate and other potential confounders (β = 0.22, P = 0.003).

Conclusions

Adiponectin is a strong modifier of the FGF23 response to VDR activation in CKD patients. The adiponectin-FGF23 link discovered in genetically engineered mice is of mechanistic relevance in the FGF23 response to VDR activation in CKD patients.

Vitamin D receptor activation by paricalcitol and insulin resistance in CKD

BACKGROUND AND AIMS

The nature of the link (causal vs non-causal) between low 1,25-OH vitamin D and insulin resistance (IR) in patients with chronic kidney disease (CKD) remains elusive. We have now made a post hoc analysis of the effect of vitamin D receptor activation by paricalcitol on IR in the complete dataset of a double-blind, randomized, placebo controlled trial, the Paricalcitol and ENdothelial fuNction in chronic kidneY disease (PENNY).

METHODS AND RESULTS

Eighty-eight patients with stage 3-4 CKD were randomized (1:1) to receive 2 μg/day paricalcitol or matching placebo for 12 weeks. IR was measured by five IR indices: the homeostasis model assessment of insulin resistance (HOMA-IR), the quantitative insulin sensitivity check index (QUICKI), the McAuley index, the HOMA corrected for adiponectin (HOMA-AD) and the Leptin-adiponectin ratio (LAR). As compared to placebo, paricalcitol produced the expected small rise in serum calcium (+0.07 mmol/L, P = 0.01) and phosphate (+0.08 mmol/L, P = 0.034) and the expected parathyroid hormone suppression (-96 pg/ml, P < 0.001). However, the drug largely failed to affect the five indices of IR which remained unchanged both in the active and the placebo arm (paricalcitol vs placebo, P ranging from 0.25 to 0.62) and no effect modification of paricalcitol on IR by vitamin D or other parameters was registered.

CONCLUSION

Paricalcitol treatment for 12 weeks does not improve IR in patients with stage 3-4 CKD. Low vitamin D receptor activation is not a causal factor for IR in the CKD population.

Oxidized LDL, Gamma-Glutamyltransferase and Adverse Outcomes in Older Adults

OBJECTIVES

Gamma-glutamyltransferase (GGT) is a biomarker of liver disease and oxidative stress which was associated with all-cause and cardiovascular (CV) mortality in the general population and in patients with high risk conditions. This study aims at assessing whether oxLDL modifies the relationship between GGT, all-cause, and CV mortality in elderly individuals from the general population.

DESIGN

Observational longitudinal study.

SETTING

Population-based cohort of older individuals (>65 years) free of liver disease.

PARTICIPANTS

One thousand and thirty-eight individuals from the Invecchiare in Chianti (InCHIANTI) study.

MEASUREMENTS

Serum GGT level, oxidized low-density lipoprotein (oxLDL), CV comorbidities, all-cause and CV mortality.

RESULTS

The median age of the study population (n = 1,038) was 74 years (inter-quartile range: 69-79), 152 individuals (15%) had past CV events. During a median follow-up of 9 years, 401 individuals died, 168 of them (42%) for CV causes. In adjusted analyses, GGT predicted all-cause mortality (HR for 20 U/L increase in serum GGT: 1.11, 95% CI: 1.02-1.21, P = .02) and CV mortality (HR: 1.17, 95% CI: 1.03-1.33; P = .02). Furthermore, in an analysis for interaction circulating oxLDL amplified the effect of GGT on all-cause mortality (P = .003).

CONCLUSION

Circulating oxLDL amplifies the effect of GGT on mortality in the elderly. The mechanism for this association remains unknown and requires further research, including studying the potential role of GGT in oxidative stress. These results are consistent with the hypothesis of a causal role of GGT in the CV morbidity and mortality in older individuals and indicate that oxLDL plays a crucial role in the interpretation of the link between GGT and the risk of adverse clinical events in this population.

Insulin resistance in chronic kidney disease: a systematic review

Insulin resistance (IR) is an early metabolic alteration in chronic kidney disease (CKD) patients, being apparent when the glomerular filtration rate is still within the normal range and becoming almost universal in those who reach the end stage of kidney failure. The skeletal muscle represents the primary site of IR in CKD, and alterations at sites beyond the insulin receptor are recognized as the main defect underlying IR in this condition. Estimates of IR based on fasting insulin concentration are easier and faster but may not be adequate in patients with CKD because renal insufficiency reduces insulin catabolism. The hyperinsulinemic euglycemic clamp is the gold standard for the assessment of insulin sensitivity because this technique allows a direct measure of skeletal muscle sensitivity to insulin. The etiology of IR in CKD is multifactorial in nature and may be secondary to disturbances that are prominent in renal diseases, including physical inactivity, chronic inflammation, oxidative stress, vitamin D deficiency, metabolic acidosis, anemia, adipokine derangement, and altered gut microbiome. IR contributes to the progression of renal disease by worsening renal hemodynamics by various mechanisms, including activation of the sympathetic nervous system, sodium retention, and downregulation of the natriuretic peptide system. IR has been solidly associated with intermediate mechanisms leading to cardiovascular (CV) disease in CKD including left ventricular hypertrophy, vascular dysfunction, and atherosclerosis. However, it remains unclear whether IR is an independent predictor of mortality and CV complications in CKD. Because IR is a modifiable risk factor and its reduction may lower CV morbidity and mortality, unveiling the molecular mechanisms responsible for the pathogenesis of CKD-related insulin resistance is of importance for the identification of novel therapeutic targets aimed at reducing the high CV risk of this condition.

Insulin resistance in chronic kidney disease: a systematic review

Insulin resistance (IR) is an early metabolic alteration in chronic kidney disease (CKD) patients, being apparent when the glomerular filtration rate is still within the normal range and becoming almost universal in those who reach the end stage of kidney failure. The skeletal muscle represents the primary site of IR in CKD, and alterations at sites beyond the insulin receptor are recognized as the main defect underlying IR in this condition. Estimates of IR based on fasting insulin concentration are easier and faster but may not be adequate in patients with CKD because renal insufficiency reduces insulin catabolism. The hyperinsulinemic euglycemic clamp is the gold standard for the assessment of insulin sensitivity because this technique allows a direct measure of skeletal muscle sensitivity to insulin. The etiology of IR in CKD is multifactorial in nature and may be secondary to disturbances that are prominent in renal diseases, including physical inactivity, chronic inflammation, oxidative stress, vitamin D deficiency, metabolic acidosis, anemia, adipokine derangement, and altered gut microbiome. IR contributes to the progression of renal disease by worsening renal hemodynamics by various mechanisms, including activation of the sympathetic nervous system, sodium retention, and downregulation of the natriuretic peptide system. IR has been solidly associated with intermediate mechanisms leading to cardiovascular (CV) disease in CKD including left ventricular hypertrophy, vascular dysfunction, and atherosclerosis. However, it remains unclear whether IR is an independent predictor of mortality and CV complications in CKD. Because IR is a modifiable risk factor and its reduction may lower CV morbidity and mortality, unveiling the molecular mechanisms responsible for the pathogenesis of CKD-related insulin resistance is of importance for the identification of novel therapeutic targets aimed at reducing the high CV risk of this condition.

Methodology used in studies reporting chronic kidney disease prevalence: a systematic literature review

Background

Many publications report the prevalence of chronic kidney disease (CKD) in the general population. Comparisons across studies are hampered as CKD prevalence estimations are influenced by study population characteristics and laboratory methods.

Methods

For this systematic review, two researchers independently searched PubMed, MEDLINE and EMBASE to identify all original research articles that were published between 1 January 2003 and 1 November 2014 reporting the prevalence of CKD in the European adult general population. Data on study methodology and reporting of CKD prevalence results were independently extracted by two researchers.

Results

We identified 82 eligible publications and included 48 publications of individual studies for the data extraction. There was considerable variation in population sample selection. The majority of studies did not report the sampling frame used, and the response ranged from 10 to 87%. With regard to the assessment of kidney function, 67% used a Jaffe assay, whereas 13% used the enzymatic assay for creatinine determination. Isotope dilution mass spectrometry calibration was used in 29%. The CKD-EPI (52%) and MDRD (75%) equations were most often used to estimate glomerular filtration rate (GFR). CKD was defined as estimated GFR (eGFR) <60 mL/min/1.73 m² in 92% of studies. Urinary markers of CKD were assessed in 60% of the studies. CKD prevalence was reported by sex and age strata in 54 and 50% of the studies, respectively. In publications with a primary objective of reporting CKD prevalence, 39% reported a 95% confidence interval.

Conclusions

The findings from this systematic review showed considerable variation in methods for sampling the general population and assessment of kidney function across studies reporting CKD prevalence. These results are utilized to provide recommendations to help optimize both the design and the reporting of future CKD prevalence studies, which will enhance comparability of study results.

A genetic marker of hyperuricemia predicts cardiovascular events in a meta-analysis of three cohort studies in high risk patients

INTRODUCTION

The strongest genetic marker of uric acid levels, the rs734553 SNP in the GLUT9 urate transporter gene, predicts progression to kidney failure in CKD patients and associates with systolic BP and carotid intima media thickness in family-based studies.

METHODS

Since genes are transmitted randomly (Mendelian randomization) we used this gene polymorphism as an unconfounded research instrument to further explore the link between uric acid and cardiovascular disease (cardiovascular death, and non-fatal myocardial infarction and stroke) in a meta-analysis of three cohort studies formed by high risk patients (MAURO: 755 CKD patients; GHS: 353 type 2 diabetics and coronary artery disease and the TVAS: 119 patients with myocardial infarction).

RESULTS

In separate analyses of the three cohorts, the incidence rate of CV events was higher in patients with the rs734553 risk (T) allele (TT/GT) than in those without (GG patients) and the HR in TT/GT patients in the three cohorts (range 1.72-2.14) coherently signaled an excessive cardiovascular risk with no heterogeneity (I2 = 0.01). The meta-analytical estimate (total number of patients, n = 1227; total CV events, n = 222) of the HR for the combined end-point in TT/GT patients was twice higher (pooled HR: 2.04, 95% CI: 1.11-3.75, P = 0.02) than in GG homozygotes.

CONCLUSIONS

The T allele of the rs734553 polymorphism in the GLUT9 gene predicts a doubling in the risk for incident cardiovascular events in patients at high cardiovascular risk. Findings in this study are compatible with the hypothesis of a causal role of hyperuricemia in cardiovascular disease in high risk conditions.

Association between resistin levels and all-cause and cardiovascular mortality: a new study and a systematic review and meta-analysis

Context

Studies concerning the association between circulating resistin and mortality risk have reported, so far, conflicting results.

Objective

To investigate the association between resistin and both all-cause and cardiovascular (CV) mortality risk by 1) analyzing data from the Gargano Heart Study (GHS) prospective design (n=359 patients; 81 and 58 all-cause and CV deaths, respectively); 2) performing meta-analyses of all published studies addressing the above mentioned associations.

Data Source and Study Selection

MEDLINE and Web of Science search of studies reporting hazard ratios (HR) of circulating resistin for all-cause or CV mortality.

Data Extraction

Performed independently by two investigators, using a standardized data extraction sheet.

Data Synthesis

In GHS, adjusted HRs per one standard deviation (SD) increment in resistin concentration were 1.28 (95% CI: 1.07-1.54) and 1.32 (95% CI: 1.06-1.64) for all-cause and CV mortality, respectively. The meta-analyses included 7 studies (n=4016; 961 events) for all-cause mortality and 6 studies (n=4,187: 412 events) for CV mortality. Pooled HRs per one SD increment in resistin levels were 1.21 (95% CI: 1.03-1.42, Q-test p for heterogeneity<0.001) and 1.05 (95% CI: 1.01-1.10, Q-test p for heterogeneity=0.199) for all-cause and CV mortality, respectively. At meta-regression analyses, study mean age explained 9.9% of all-cause mortality studies heterogeneity. After adjusting for age, HR for all-cause mortality was 1.24 (95% CI: 1.06-1.45).

Conclusions

Our results provide evidence for an association between circulating resistin and mortality risk among high-risk patients as are those with diabetes and coronary artery disease.

Synergism between asymmetric dimethylarginine (ADMA) and a genetic marker of uric acid in CKD progression

BACKGROUND & AIMS

We have recently reported that a polymorphism (rs734553) in a major urate transporter gene (GLUT9) is a strong predictor of incident renal events in stage 2-5 CKD patients implying that life-time exposure to high uric acid levels may be causally implicated in CKD progression. Since disturbed NO bioavailability is a major pathway whereby high uric may cause renal damage, we tested the interaction between the major endogenous inhibitor of NO synthase, asymmetric-dimethylargine (ADMA), and the rs734553 polymorphism for CKD progression in the same cohort.

METHODS & RESULTS

Over a 29 ± 11 months follow-up the risk for incident renal events was higher in patients harboring the risk allele of the polymorphism (T) as compared to those without the risk allele (HR: 2.35, 95% CI: 1.25-4.42, P = 0.008) (p = 0.01). Similarly, patients with ADMA > median value had an increased risk for the same outcome (HR: 1.37, 95% CI: 1.06-1.76, P = 0.016). Interaction analysis showed a strong amplification by ADMA of the risk for renal events associated to the T allele because in adjusted (P = 0.016) and bootstrapping validated (P = 0.020) analyses the risk excess associated to this allele was progressively higher across increasing ADMA levels.

CONCLUSIONS

The rs734553 polymorphism, the strongest genetic marker of uric acid levels discovered so far, interacts with ADMA in determining the risk for CKD progression in CKD patients. This synergic interaction conforms to biological knowledge indicating that disturbed NO bio-availability is a critical pathway whereby life time exposure to high uric acid may engender renal damage.

Association of IL-6 and a functional polymorphism in the IL-6 gene with cardiovascular events in patients with CKD

BACKGROUND AND OBJECTIVES

High serum IL-6 is a major risk factor for cardiovascular disease (CVD) in the general population. This cytokine is substantially increased in patients with CKD, but it is still unknown whether the link between IL-6 and CVD in CKD is causal in nature.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In a cohort of 755 patients with stages 2-5 CKD, consecutively recruited from 22 nephrology units in southern Italy, this study assessed the relationship of serum IL-6 with history of CVD, as well as with incident cardiovascular (CV) events (mean follow up±SD, 31±10 months) and used the functional polymorphism (-174 G/C) in the promoter of the IL-6 gene to investigate whether the link between IL-6 and CV events is causal.

RESULTS

In adjusted analyses, serum IL-6 above the median value was associated with history of CVD (P<0.001) and predicted the incidence rate of CV events (hazard ratio, 1.66; 95% confidence interval [95% CI], 1.11 to 2.49; P=0.01). Patients homozygous for the risk allele (C) of the -174 G/C polymorphism had higher levels of IL-6 than did those with other genotypes (P=0.04). Homozygous CC patients more frequently had a history of CVD (odds ratio, 2.15; 95% CI, 1.15 to 4.00; P=0.02) as well as a 87% higher rate of incident CV events (hazard ratio, 1.87; 95% CI, 1.02 to 3.44; P=0.04) compared with other genotypes.

CONCLUSIONS

In patients with stages 2-5 CKD, high serum IL-6 is associated with history of CVD and predicts incident CV events. The parallel relationship with history of CVD and incident CV events of the -174 G/C polymorphism in the IL-6 gene suggests that IL-6 may be causally involved in the high CV risk in this population.

Joint effect of insulin signaling genes on all-cause mortality

OBJECTIVE

We have previously reported the combined effect of SNPs perturbing insulin signaling (ENPP1 K121Q, rs1044498; IRS1 G972R, rs1801278; TRIB3 Q84R, rs2295490) on insulin resistance (IR), type 2 diabetes (T2D) and cardiovascular events. We here investigated whether such a combined effect affects also all-cause mortality in a sample of 1851 Whites of European ancestry.

METHODS

We investigated a first sample of 721 patients, 232 deaths, 3389 person-years (py). Replication was assessed in two samples of patients with T2D: the Gargano Mortality Study (GMS) of 714 patients, 127 deaths, 5426 py and the Joslin Kidney Study (JKS) comprising 416 patients, 214 deaths, 5325 py.

RESULTS

In the first sample, individuals carrying 1 or ≥ 2 risk alleles had 33% (p = 0.06) and 51% (p = 0.02) increased risk of mortality, as compared with individuals with no risk alleles. A similar, though not significant, trend was obtained in the two replication samples only for subject carrying ≥ 2 risk alleles. In a pooled analysis, individuals carrying ≥ 2 risk alleles had higher mortality rate as compared to those carrying 0 risk alleles (HR = 1.34, 95%CI = 1.08-1.67; p = 0.008), and as compared to those carrying only one risk allele (HR = 1.41, 95%CI = 1.13-1.75; p = 0.002). This association was independent from several possible confounders including sex, age, BMI, hypertension and diabetes status.

CONCLUSION

Our data suggest that variants affecting insulin signaling exert a joint effect on all-cause mortality and is consistent with a role of abnormal insulin signaling on mortality risk.

Pro- and anti-inflammatory cytokine gene expression in subcutaneous and visceral fat in severe obesity

BACKGROUND AND AIMS

Pro-inflammatory molecules produced by adipose tissue have been implicated in the risk of cardiovascular (CV) disease in obesity. We investigated the expression profile of 19 pro-inflammatory and seven anti-inflammatory genes in subcutaneous adipose tissue (SAT) and in visceral adipose tissue (VAT) in 44 severely obese individuals who underwent bariatric surgery.

METHODS AND RESULTS

SAT and VAT expressed an identical series of pro-inflammatory genes. Among these genes, 12 were significantly more expressed in SAT than in VAT while just one (IL18) was more expressed in VAT. The remaining genes were equally expressed. Among pro-inflammatory cytokines, both IL6 and IL8 were about 20 times more intensively expressed in SAT than in VAT. The expression of nine genes was highly associated in SAT and VAT. Only for three pro-inflammatory cytokines (IL8, IL18, SAA1) in SAT the gene expression in adipose tissue associated with the circulating levels of the corresponding gene products while no such an association was found as for VAT.

CONCLUSIONS

The expression of critical pro-inflammatory genes is substantially higher in SAT than in VAT in individuals with morbid obesity. The variability in circulating levels of pro-inflammatory cytokines is, in small part and just for three pro-inflammatory cytokines, explained by underlying gene expression in SAT but not in VAT. These results point to a compartment-specific adipose tissue contribution to inflammation in obesity and indicate that abdominal SAT contributes more than VAT to the pro-inflammatory milieu associated with severe obesity.

Association of a polymorphism in a gene encoding a urate transporter with CKD progression

BACKGROUND AND OBJECTIVES

Hyperuricemia predicts a high risk for CKD progression but there is no large clinical trial in humans indicating that this relationship is causal in nature. The rs734553 single-nucleotide polymorphism (SNP) of the GLUT9 urate transporter gene was strongly associated with uric acid (UA) levels in a large meta-analysis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This prospective study adopted the Mendelian randomization approach. The rs734553 SNP was used as an instrumental variable to investigate the relationship between UA and renal outcomes in a cohort of 755 patients with CKD who were enrolled between October 18, 2005, and October 2, 2008. The association between the polymorphism and UA was preliminary confirmed in a series of 211 healthy volunteers enrolled between January 1, 2001, and July 12, 2011, from the same geographic area as the patients with CKD. The study end point was a composite renal-end point (i.e., >30% decrease in the GFR, dialysis, or transplantation). Patients were followed up for a median of 36 months.

RESULTS

In healthy individuals, serum UA levels were highest in homozygotes for the T allele (risk allele), intermediate in heterozygotes for the same allele, and lowest in those without the risk allele (P<0.001), but no such relationship was found in patients with CKD. In the CKD cohort, homozygotes (TT) and heterozygotes (GT) for the risk allele had a 2.35 times higher risk (hazard ratio, 2.35; 95% confidence interval, 1.25 to 4.42; P=0.008) of CKD progression. The risk for CKD progression by rs734553 remained unmodified in analyses adjusting for proteinuria, GFR, and other classical and CKD-peculiar risk factors.

CONCLUSIONS

A GLUT9 polymorphism, which is strongly associated with serum UA levels in healthy individuals of the general population with normal renal function, holds a strong predictive power for CKD progression. These findings are compatible with the hypothesis that the link between UA and CKD progression is causal in nature.

Resistin and all-cause and cardiovascular mortality: effect modification by adiponectin in end-stage kidney disease patients

BACKGROUND

Resistin is a major adipose tissue cytokine implicated in insulin resistance, inflammation and vascular damage. This cytokine is raised in patients with end-stage kidney disease (ESKD) but the relationship between resistin and major clinical outcomes has not been investigated in this population.

METHODS

We studied the mutual relationship between resistin and the two major adipokines (adiponectin and leptin) and the interaction between resistin and adiponectin (ADPN) and all-cause and cardiovascular (CV) mortality in a cohort of 231 haemodialysis patients followed up for 57 ± 44 months.

RESULTS

Plasma resistin was substantially raised in ESKD patients when compared with healthy subjects (P < 0.001). On univariate analysis, resistin was related inversely to ADPN (r = -0.14, P = 0.04) and directly to C-reactive protein (r = 0.15, P = 0.03), but was largely independent of leptin (r = 0.08, P = 0.24) and the HOMA-IR index (r = -0.04, P = 0.51). During the follow-up, 165 patients died (96 for CV causes). On both univariate (all-cause mortality: P = 0.004; CV mortality P < 0.001) and multivariate (all-cause mortality: P = 0.01; CV mortality P < 0.001) Cox regression analyses, the effect of resistin on study outcomes was closely dependent on ADPN levels. There was a consistent excess risk for all-cause (P = 0.002) and CV mortality (P = 0.003) by plasma resistin (20 ng/mL) in patients in the first ADPN tertile, but no risk excess for these outcomes was apparent in patients in the third tertile.

CONCLUSION

This study indicates that resistin predicts death and fatal CV events depending on plasma ADPN levels. These findings underscore the importance of the interaction among adipokines for the prediction of adverse clinical outcomes in ESKD.

The fat-mass and obesity-associated gene (FTO) predicts mortality in chronic kidney disease of various severity

BACKGROUND

Polymorphisms in the FTO (fat-mass and obesity-associated) gene have been associated with the body mass index, cancer, type 2 diabetes and hypertension.

METHODS

We investigated the relationship between 17 tag single-nucleotide polymorphisms (SNPs) and all-cause mortality in three cohorts of dialysis patients (CREED-1, North Apulian and CREED-2 cohorts; n = 783) and in one cohort of stage 2-5 CKD patients (n = 757).

RESULTS

We first explored the association between the 17 tag SNPs and all-cause mortality in the CREED-1 cohort and found that patients with the A allele of the FTO rs708259 polymorphism had an elevated risk of mortality (hazard ratio, HR: 1.52, 95% confidence interval (CI) 1.11-2.08; P = 0.008). Similarly, the A allele was associated with an increased risk of death also in the other two dialysis cohorts (North Apulian cohort, risk: +23%; CREED-2 cohort, risk: +21%). The elevated risk portended by this allele was even higher in the stage 2-5 CKD cohort (+97%). However, the risk of mortality associated with the A allele in the three confirmatory cohorts failed to achieve formal statistical significance. In a meta-analysis including the four cohorts (n = 1540; total deaths, n = 381), individuals with the A allele had a 42% excess risk of death (HR: 1.42, 95% CI 1.14-1.76, P = 0.002).

CONCLUSION

The A allele of the FTO rs708259 polymorphism is an independent predictor of all-cause mortality in patients with CKD of various severity. These data support our hypothesis that the FTO gene may be a relevant genetic risk factor for mortality in this population.

Plasma cytokines, glomerular filtration rate and adipose tissue cytokines gene expression in chronic kidney disease (CKD) patients

BACKGROUND AND AIM

Systemic inflammation is a hallmark of chronic kidney disease (CKD) and obesity represents a major risk factor for CKD. We investigated the relationship between plasma interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α) and the glomerular filtration rate (GFR) in 75 stage 2-5 CKD patients.

METHODS AND RESULTS

We studied the steady-state relationship between plasma and subcutaneous adipose tissue (SAT) gene expression of the same cytokines in 19 patients and in 17 well-matched healthy subjects (HS) and compared SAT gene expression of these cytokines and of two additional cytokines (IL-1β and IL-8) in CKD patients and in HS. Plasma IL-6 and TNF-α were higher in CKD patients than in HS (P < 0.001). IL-6 was similarly increased in patients with mild, moderate and severe CKD and largely independent of the GFR (r = -0.03, P = NS). TNF-α was inversely related to GFR, which was the first factor in rank (β = -0.37, P = 0.001) explaining the variability in TNF-α in CKD. SAT messenger RNA (mRNA) levels of IL-6, TNF-α, IL- β and IL-8 were similar in CKD patients and in HS. Plasma and SAT mRNA levels of IL-6 and TNF-α levels were largely unrelated.

CONCLUSIONS

Plasma IL-6 rises early in CKD and does not show any further increase at more severe stages of CKD, whereas TNF-α is inversely associated with the GFR indicating a substantial difference in the dynamics of the relationship between these cytokines and renal function. Cytokines are not overexpressed in SAT in these patients, and circulating IL-6 and TNF-α are dissociated from the corresponding mRNA levels in SAT, both in CKD patients and in HS.

Joint effect of insulin signaling genes on cardiovascular events and on whole body and endothelial insulin resistance

OBJECTIVE

Insulin resistance (IR) and cardiovascular disease (CVD) share a common soil. We investigated the combined role of single nucleotide polymorphisms (SNPs) affecting insulin signaling (ENPP1 K121Q, rs1044498; IRS1 G972R, rs1801278; TRIB3 Q84R, rs2295490) on CVD, age at myocardial infarction (MI), in vivo insulin sensitivity and in vitro insulin-stimulated nitric oxide synthase (NOS) activity.

DESIGN AND SETTING

1. We first studied, incident cardiovascular events (a composite endpoint comprising myocardial infarction-MI, stroke and cardiovascular death) in 733 patients (2186 person-years, 175 events). 2. In a replication attempt, age at MI was tested in 331 individuals. 3. OGTT-derived insulin sensitivity index (ISI) was assessed in 829 individuals with fasting glucose <126 mg/dl. 4. NOS activity was measured in 40 strains of human vein endothelial cells (HUVECs).

RESULTS

1. Risk variants jointly predicted cardiovascular events (HR = 1.181; p = 0.0009) and, when added to clinical risk factors, significantly improved survival C-statistics; they also allowed a significantly correct reclassification (by net reclassification index) in the whole sample (135/733 individuals) and, even more, in obese patients (116/204 individuals). 2. Risk variants were jointly associated with age at MI (p = 0.006). 3. A significant association was also observed with ISI (p = 0.02). 4. Finally, risk variants were jointly associated with insulin-stimulated NOS activity in HUVECs (p = 0.009).

CONCLUSIONS

Insulin signaling genes variants jointly affect cardiovascular disease, very likely by promoting whole body and endothelium-specific insulin resistance. Further studies are needed to address whether their genotyping help identify very high-risk patients who need specific and/or more aggressive preventive strategies.

eNOS and caveolin-1 gene polymorphisms interaction and intima media thickness: a proof of concept study in ESRD patients

BACKGROUND

Caveolae are a prominent microdomain in endothelial cells and appropriate localization in caveolae is fundamental for endothelial nitric oxide synthase (eNOS) activity. Since the Glu298Asp variant in the eNOS gene alters caveolar localization of the corresponding enzyme, we tested the interaction between this variant and the rs4730751 polymorphism of the caveolin-1 (CAV-1) gene as related to arterial remodeling in end-stage renal disease (ESRD) patients.

METHODS

One hundred and thirty-three ethnically homogeneous ESRD patients underwent carotid ultrasonographic studies to measure intima-media thickness (IMT) and carotid cross-sectional area (CSA). Genotyping was performed by high-throughput allelic discrimination assays on real-time PCR.

RESULTS

Arterial remodeling was associated to the number of G alleles of CAV-1 polymorphism, GG homozygotes displaying an IMT and a CSA that were, respectively, 16% and 21% higher than those in patients without the risk allele (P < 0.012). In multiple linear regression analyses including the CAV-1 and the eNOS polymorphisms and adjusting for classical risk factors and risk factors peculiar to ESRD both polymorphisms were independent correlates of IMT (CAV-1: β = 0.20, P = 0.01; eNOS β = 0.25, P = 0.001) and CSA (CAV-1: β = 0.20, P = 0.01: eNOS β = 0.13, P = 0.09). Furthermore, strong interactions emerged between the two polymorphisms for explaining the variability in IMT (P = 0.001) and in CSA (P = 0.038) in these patients.

CONCLUSION

Overall these findings form preliminary evidence that disturbed interaction between CAV-1 and eNOS may be of relevance for arterial disease in ESRD and perhaps in other human diseases.