Plasma Kynurenine Predicts Severity and Complications of Heart Failure and Associates with Established Biochemical and Clinical Markers of Disease.

BACKGROUND: Kynurenine, a metabolite of the L-tryptophan pathway, plays a pivotal role in neuro-inflammation, cancer immunology, and cardiovascular inflammation, and has been shown to predict cardiovascular events. OBJECTIVES: It was our objective to increase the body of data regarding the value of kynurenine as a biomarker in chronic heart failure (CHF). METHODS: We investigated the predictive value of plasma kynurenine in a CHF cohort (CHF, n = 114); in a second cohort of defibrillator carriers with CHF (AICD, n = 156), we determined clinical and biochemical determinants of the marker which was measured by enzyme immunoassay. RESULTS: In the CHF cohort, both kynurenine and NT-proBNP increased with NYHA class. Univariate binary logistic regression showed kynurenine to predict death within a 6-month follow-up (OR 1.43, 95% CI 1.03-2.00, p = 0.033) whereas NT-proBNP did not contribute significantly. Kynurenine, like NT-proBNP, was able to discriminate at a 30% threshold of left ventricular ejection fraction (LVEF; AUC-ROC, both 0.74). Kynurenine correlated inversely with LVEF (ϱ = -0.394), glomerular filtration fraction (GFR; ϱ = -0.615), and peak VO2 (ϱ = -0.626). Moreover, there was a strong correlation of kynurenine with NT-proBNP (ϱ = 0.615). In the AICD cohort, multiple linear regression analysis demonstrated highly significant associations of kynurenine with GFR, hsCRP, and tryptophan, as well as a significant impact of age. CONCLUSIONS: This work speaks in favor of kynurenine being a new and valuable biomarker of CHF, with particular attention placed on its ability to predict mortality and reflect exercise capacity.

Homoarginine Associates with Zonulin and Tryptophan - Findings in a High-Risk Cohort of Patients Carrying an AICD.

BACKGROUND: Homoarginine (hArg) is known to have an impact on nitric oxide (NO) metabolism. It seems to increase NO generation and/or availability, thereby enhancing endothelial function. In addition, hArg is connected to energy metabolism since the key enzyme, L-arginine-glycine amidinotransferase (AGAT) for hArg synthesis in the kidneys, is also involved in the synthesis of energy metabolites like guanidinoacetate. Former studies indicate that low levels of hArg are linked to cardiovascular disease and increased all-cause mortality. METHODS: This study investigated the dependence of plasma hArg on various biochemical and clinical factors in 229 patients carrying an automatic, implantable cardioverter/defibrillator (AICD) using multiple linear regression analysis (Generalized Linear Model, GLM). RESULTS: GLM revealed a highly significant, positive association between hArg and zonulin (p < 0.001). hArg was also positively correlated with tryptophan (p = 0.004), BMI (p = 0.02), and body weight (p = 0.02). Patients with hsCRP above 10 mg/L had significantly lower hArg concentrations than patients with hsCRP ≤ 10 mg/L. CONCLUSIONS: The highly significant positive association of hArg with zonulin is a novel finding which may indicate a different meaning of circulating versus local (gut) zonulin. Therefore, further experimental and clinical investigation is needed to explore this association, focusing on possible pathophysiological pathways and the role of circulating zonulin levels in cardiovascular disease. The positive correlation of hArg and Trp also deserves further research because both amino acids might have a protective effect on cardiovascular disease by inhibition of the enzyme alkaline phosphatase. Eventually, our study associates low hArg concentrations with chronic low-grade inflammation and parameters of malnutrition in cardiovascular high-risk patients.

Plasma Zonulin and its Association with Kidney Function, Severity of Heart Failure, and Metabolic Inflammation.

BACKGROUND: The tight junction regulator zonulin has attracted clinical attention as a biomarker of increased gastrointestinal permeability. Recent work also suggests zonulin to represent a general regulator of tissue barriers and a player in metabolic inflammation. Here, we investigated the associations of zonulin with chronic heart failure (CHF), kidney function, and metabolic inflammation. METHODS: Using multiple linear regression (Generalized Linear Model), this study determined the association of plasma zonulin with different laboratory and clinical parameters in 225 patients carrying automatic implantable cardioverters/defibrillators (AICD) for primary or secondary prevention. In another 115 patients with diastolic or systolic CHF, we investigated a possible relationship between zonulin and CHF severity. RESULTS: In the AICD cohort, zonulin associated inversely with serum creatinine (p = 0.013), carboxymethyl-lysine calprotectin (p < 0.001), and kynurenine (p = 0.009) and positively with homoarginine (p < 0.001). In the subgroup with type-2 diabetes (T2D) (n = 51), zonulin increased significantly with high-sensitivity CRP (p = 0.014). In the CHF cohort, we found a highly significant rise of NT-proBNP, but not of zonulin with NYHA functional classes I-IV or other parameters of CHF severity. CONCLUSIONS: The inverse associations of zonulin with creatinine and markers of cardio-vascular risk (high CMLcalprotectin and kynurenine, low homoarginine) are novel findings that need further experimental and clinical clarification. Our study indicates zonulin involvement in metabolic inflammation in T2D, but no association with disease status in CHF.

Relaxin-2 does not ameliorate nephropathy in an experimental model of type-1 diabetes.

BACKGROUND/AIMS: In diabetic nephropathy (DN), the current angiotensin-II-blocking pharmacotherapy is frequently failing. For diabetic cardiomyopathy (DC), there is no specific remedy available. Relaxin-2 (Rlx) - an anti-fibrotic, anti-inflammatory, and vasoprotecting peptide ­ is a candidate drug for both. METHODS: Low-dose (32 µg/kg/day) and high-dose (320 µg/kg/day) Rlx were tested against vehicle (n = 20 each) and non-diabetic controls (n = 14) for 12 weeks in a model of type-1 diabetes induced in endothelial nitric oxide synthase knock-out (eNOS-KO) mice by intraperitoneal injection of streptozotocin. RESULTS: Diabetic animals showed normal plasma creatinine, markedly increased albuminuria and urinary malonyldialdehyde, elevated relative kidney weight, glomerulosclerosis, and increased glomerular size, but no relevant interstitial fibrosis. Neither dose of Rlx affected these changes although the drug was active and targeted plasma levels were achieved. Of note, we found no activation of the renal TGF-ß pathway in this model. In the hearts of diabetic animals, no fibrotic alterations indicative of DC could be determined which precluded testing of the initial hypothesis. CONCLUSIONS: We investigated a model showing early DN without overt tubulointerstitial fibrosis and activation of the TGF-ß-Smad-2/3 pathway. In this model, Rlx proved ineffective; however, the same may not apply to other models and types of diabetes.

Autoantibodies against epidermal transglutaminase are a sensitive diagnostic marker in patients with dermatitis herpetiformis on a normal or gluten-free diet.

BACKGROUND: Dermatitis herpetiformis (DH) is a cutaneous manifestation of gluten-sensitive enteropathy (celiac disease). Patients with DH demonstrate circulating IgA antibodies against epidermal transglutaminase (eTG) and tissue transglutaminase (tTG). It has been suggested that eTG is the autoantigen of DH. OBJECTIVE: The purpose of this study was to characterize the autoimmune response to eTG and tTG in patients with DH on a normal or gluten-free diet (GFD). METHODS: Sera from 52 patients with DH were studied for the presence of IgA antibodies to eTG and tTG by enzyme-linked immunosorbant assay. In 38 patients, serum was obtained before initiation of a GFD, whereas 14 patients had been on a GFD for at least 2 years. RESULTS: Autoantibodies against eTG were detected in 36 of 38 patients (95%) and those against tTG in 30 of 38 patients (79%) with DH on a normal diet. Of 14 patients on a long-term GFD, 7 patients were free of DH lesions and did not require dapsone treatment. None of these patients showed circulating antibodies against eTG or tTG. The remaining 7 patients on a GFD were not able to stop taking dapsone. All these patients demonstrated anti-eTG antibodies, whereas only 3 of them showed additional reactivity against tTG. LIMITATION: Autoantibody levels against eTG and tTG before and after introduction of a GFD were not examined in the same patients. CONCLUSION: Our data suggest that antibodies to eTG are the most sensitive serologic marker in treated and untreated patients with DH and confirm the central role of eTG in the pathogenesis of this disease.