BACKGROUND AND HYPOTHESIS:The endogenous opioid proenkephalin (PENK) has been identified as an independent risk marker for acute cardiovascular diseases and acute kidney injury. However, its regulation, its association with other cardiometabolic markers and its prognostic role in patients with chronic kidney disease (CKD) have not been thoroughly investigated. METHODS:PENK serum levels were cross-sectionally related to renal and cardiometabolic markers across three large cohorts (total N = 4722), including the Leipzig-CKD cohort (N = 581), as well as the population-based LIFE-Adult (N = 3093) and Sorbs (N = 1048) cohort. Furthermore, a longitudinal analysis was performed in the Leipzig-CKD cohort to assess the association between circulating PENK levels at baseline and a composite 4-point major adverse renal events (4P-MAKE) endpoint comprising incident or worsening kidney disease, development of kidney failure (KF) requiring kidney replacement therapy or kidney transplantation, and renal deaths. RESULTS:In the entire cross-sectional cohort (N = 4722), PENK levels were strongly and inversely correlated with markers of renal function, i.e. estimated glomerular filtration rate (eGFR), creatinine and urinary albumin-creatinine ratio. In multivariable analysis, eGFR was the strongest, independent and inverse predictor of circulating PENK levels after adjustment for age and sex, as well as markers of obesity, glucose intolerance, dyslipidemia and inflammation. Multivariable Cox regression analysis revealed that baseline circulating PENK levels were strongly associated with an increased risk of the 4P-MAKE over a median follow-up of 8.7 years. Each doubling of PENK levels was associated with a >2-fold increase in the risk of developing 4P-MAKE, even after adjusting for various clinical and metabolic variables. PENK provided added value for predicting adverse renal outcomes. CONCLUSIONS:PENK levels are strongly, independently, and inversely associated with renal function in cross-sectional analysis. Furthermore, baseline circulating PENK levels are predictive of a 4P-MAKE in patients and added independent, prognostic value for identification of patients at risk for adverse renal outcomes.

Lipoedema is a chronic adipose tissue disorder often misdiagnosed as obesity due to overlapping symptoms and a lack of biomarkers. In this study, we analysed 13 adipocytokines in 79 women and identified chemerin, FGF21 and adiponectin as key biomarkers for distinguishing lipoedema. Decision tree models achieved up to 95% sensitivity, supporting the potential of these biomarkers for improving diagnostic accuracy, particularly in women with overweight or obesity.

Introduction:Kallikrein-related peptidase 7 (KLK7) is a protease implicated in metabolic disease and obesity. Patients with chronic kidney disease (CKD) exhibit several cardio-metabolic comorbidities and increased mortality. The goal of this study was to investigate the associations of KLK7 levels with renal function and clinical outcomes in patients with CKD. Methods:Baseline KLK7 serum levels were cross-sectionally related to renal and cardiometabolic markers in the Leipzig-CKD cohort (n=542). Longitudinal Cox Regression analyses (n=472) were performed to associate baseline circulating KLK7 concentrations and risk of major adverse renal (MARE) and cardiovascular (MACE) events, as well as all-cause mortality. Additionally, mRNA expression of Klk7 and related genes was examined in CKD versus control mice using bulk RNA sequencing. Results:KLK7 levels were inversely associated with markers of renal function, i.e. estimated glomerular filtration rate (eGFR), and inflammation, i.e. C-reactive protein, in multivariable regression. Longitudinal analyses associated higher baseline KLK7 with lower all-cause (adjusted HR [95% CI]: 0.65 [0.49-0.86], p=0.003) and non-cardiovascular (adjusted HR [95% CI]: 0.56 [0.40-0.78], p=0.001) mortality over a median follow-up of 7.6 years. A KLK7 threshold of 1383.6 pg/ml stratified patients into low- and high-risk groups for mortality. No associations were found for MARE or MACE. In tissues of CKD and control mice, no significant changes in Klk7 mRNA expression were found. Discussion:Circulating KLK7 associates inversely with renal function and inflammation, likely reflecting reduced renal clearance. Higher circulating KLK7 independently predicts lower all-cause mortality, whereas baseline KLK7 was not related to composite renal and CV outcomes.

Abstract Background Obesity is a multifactorial disease reaching pandemic proportions with increasing healthcare costs, advocating the development of better prevention and treatment strategies. Previous research indicates that the gut microbiome plays an important role in metabolic, hormonal, and neuronal cross-talk underlying eating behavior. We therefore aim to examine the effects of prebiotic and neurocognitive behavioral interventions on food decision-making and to assay the underlying mechanisms in a Randomized Controlled Trial (RCT). Method This study uses a parallel arm RCT design with a 26-week intervention period. We plan to enroll 90 participants (male/diverse/female) living with overweight or obesity, defined as either a Waist-to-Hip Ratio (WHR) ≥ 0.9 (male)/0.85 (diverse, female) or a Body Mass Index (BMI) ≥ 25 kg/m2. Key inclusion criteria are 18–60 years of age and exclusion criteria are type 2 diabetes, psychiatric disease, and Magnetic Resonance Imaging (MRI) contraindications. The interventions comprise either a daily supplementary intake of 30 g soluble fiber (inulin), or weekly neurocognitive behavioral group sessions, compared to placebo (equicaloric maltodextrin). At baseline and follow-up, food decision-making is assessed utilizing task-based MRI. Secondary outcome measures include structural MRI, eating habits, lifestyle factors, personality traits, and mood. Further, we obtain fecal and blood samples to investigate gut microbiome composition and related metabolites. Discussion This study relies on expanding research suggesting that dietary prebiotics could improve gut microbiome composition, leading to beneficial effects on gut-brain signaling and higher-order cognitive functions. In parallel, neurocognitive behavioral interventions have been proposed to improve unhealthy eating habits and metabolic status. However, causal evidence on how these “bottom-up” and “top-down” processes affect food decision-making and neuronal correlates in humans is still scarce. In addition, microbiome, and gut-brain-axis-related mediating mechanisms remain unclear. The present study proposes a comprehensive approach to assess the effects of these gut-brain-related processes influencing food decision-making in overweight and obesity. Trial registration ClinicalTrials.gov NCT05353504. Retrospectively registered on 29 April 2022.

Introduction: Chronic kidney disease (CKD) is associated with an increased risk for cardiovascular mortality. Despite this, the recommended European cardiovascular risk prediction model for primary prevention (SCORE2) is not validated for people with CKD. Recently, the American Heart Association (AHA) emphasized the cardiovascular-kidney-metabolic (CKM) syndrome linking cardiovascular health, obesity/diabetes, and CKD. Hence, a new prediction model, PREVENT, was developed, incorporating kidney function.

Measurements of plasma metanephrines and methoxytyramine provide a sensitive test for diagnosis of pheochromocytoma/paraganglioma. False-positive results remain a problem, particularly in patients taking norepinephrine reuptake-blocking drugs. Therefore, in this retrospective observational study, we measured plasma metanephrines and methoxytyramine in 61 patients taking norepinephrine reuptake blockers (tricyclic antidepressants or serotonin-norepinephrine reuptake inhibitors) and 17 others taking selective serotonin reuptake inhibitors, all without pheochromocytoma/paraganglioma. We highlight a singular case with strongly elevated plasma normetanephrine and methoxytyramine concentrations associated with norepinephrine reuptake blockade. Data were compared to results from 252 and 1804 respective patients with and without tumors. Plasma normetanephrine was 40% higher (P < 0.0001) in patients on norepinephrine reuptake blockers and methoxytyramine was 127% higher (P = 0.0062) in patients taking tricyclic antidepressants compared to patients not taking uptake blockers and without tumors. The corresponding false-positive rates rose (P < 0.0001) from 4.8% to 23.0% for normetanephrine and from 0.9% to 28.6% for methoxytyramine. Selective serotonin reuptake inhibitors did not increase plasma concentrations of metabolites. In the highlighted case, plasma normetanephrine and methoxytyramine were elevated more than six times above upper reference limits. A pheochromocytoma/paraganglioma, however, was excluded by functional imaging. All biochemical test results normalized after discontinuation of norepinephrine reuptake blockers. These findings clarify that norepinephrine reuptake blockers usually result in mild elevations of normetanephrine and methoxytyramine that, nevertheless, significantly increase the number of false-positive results. There can, however, be exceptions where increases in normetanephrine and methoxytyramine reach pathological levels. Such exceptions may reflect failure of centrally mediated sympathoinhibition that normally occurs with the norepinephrine reuptake blockade.

AIM:Although of potential biomedical relevance, dipeptide metabolism has hardly been studied. We found the dipeptidase carnosinase-2 (CN2) to be abundant in human proximal tubules, which regulate water and solute homeostasis. We therefore hypothesized, that CN2 has a key metabolic role, impacting proximal tubular transport function. METHODS:A knockout of the CN2 gene (CNDP2-KO) was generated in human proximal tubule cells and characterized by metabolomics, RNA-seq analysis, paracellular permeability analysis and ion transport. RESULTS:CNDP2-KO in human proximal tubule cells resulted in the accumulation of cellular dipeptides, reduction of amino acids and imbalance of related metabolic pathways, and of energy supply. RNA-seq analyses indicated altered protein metabolism and ion transport. Detailed functional studies demonstrated lower CNDP2-KO cell viability and proliferation, and altered ion and macromolecule transport via trans- and paracellular pathways. Regulatory and transport protein abundance was disturbed, either as a consequence of the metabolic imbalance or the resulting functional disequilibrium. CONCLUSION:CN2 function has a major impact on intracellular amino acid and dipeptide metabolism and is essential for key metabolic and regulatory functions of proximal tubular cells. These findings deserve in vivo analysis of the relevance of CN2 for nephron function and regulation of body homeostasis.

Background Acyl-CoA-binding protein (ACBP)/diazepam-binding inhibitor has recently been characterized as an endocrine factor affecting energy balance and lipid metabolism. However, regulation of ACBP in women with gestational diabetes mellitus (GDM) during pregnancy, as well as postpartum, has not been investigated, so far. Methods ACBP was quantified in 74 women with GDM and 74 healthy, gestational age-matched, pregnant controls using an enzyme-linked immunosorbent assay. Furthermore, ACBP was quantified post-partum in 82 women (i.e. 41 women with previous GDM vs. 41 previous control women). ACBP was related to measures of obesity, hypertension, glucose and lipid metabolism, renal function, and inflammation during pregnancy and postpartum. Results During pregnancy, median [interquartile range] ACBP levels were not significantly different in women with GDM (40.9 [40.0] µg/l) compared to healthy, pregnant controls (29.1 [32.3] µg/l) (p = 0.215). ACBP serum concentrations increased from 30.3 [40.5] µg/l during pregnancy to 59.7 [33.2] µg/l after pregnancy in the entire cohort (p < 0.001). This observed elevation was consistent across both subgroups of women, those with prior GDM and those without. Multivariate analysis revealed that homeostasis model assessment of beta cell function (HOMA2-B) and creatinine positively and independently correlated with serum ACBP after pregnancy, while multivariate analysis during pregnancy showed no significant correlations. Conclusions Circulating ACBP is not a marker of GDM status, but ACBP is decreased during pregnancy, irrespective of GDM status. Furthermore, ACBP is related to beta cell function and renal markers in women after pregnancy.

ObjectiveAcyl-CoA-binding protein (ACBP)/diazepam-binding inhibitor has lately been described as an endocrine factor affecting food intake and lipid metabolism. ACBP is dysregulated in catabolic/malnutrition states like sepsis or systemic inflammation. However, regulation of ACBP has not been investigated in conditions with impaired kidney function, so far.Design/methodsSerum ACBP concentrations were investigated by enzyme-linked immunosorbent assay i) in a cohort of 60 individuals with kidney failure (KF) on chronic haemodialysis and compared to 60 individuals with a preserved kidney function; and ii) in a human model of acute kidney dysfunction (AKD). In addition, mACBP mRNA expression was assessed in two CKD mouse models and in two distinct groups of non-CKD mice. Further, mRNA expression of mACBP was measured in vitro in isolated, differentiated mouse adipocytes - brown and white - after exposure to the uremic agent indoxyl sulfate.ResultsMedian [interquartile range] serum ACBP was almost 20-fold increased in KF (514.0 [339.3] µg/l) compared to subjects without KF (26.1 [39.1] µg/l) (p<0.001). eGFR was the most important, inverse predictor of circulating ACBP in multivariate analysis (standardized β=-0.839; p<0.001). Furthermore, AKD increased ACBP concentrations almost 3-fold (p<0.001). Increased ACBP levels were not caused by augmented mACBP mRNA expression in different tissues of CKD mice in vivo or in indoxyl sulfate-treated adipocytes in vitro.ConclusionsCirculating ACBP inversely associates with renal function, most likely through renal retention of the cytokine. Future studies need to investigate ACBP physiology in malnutrition-related disease states, such as CKD, and to adjust for markers of renal function.

Carnosinase 1 (CN1) is encoded by the Cndp1 gene and degrades carnosine and anserine, two natural histidine-containing dipeptides. In vitro and in vivo studies suggest carnosine- and anserine-mediated protection against long-term sequelae of reactive metabolites accumulating, e.g., in diabetes mellitus. We have characterized the metabolic impact of CN1 in 11- and 55-week-old Cndp1-knockout (Cndp1-KO) mice and litter-matched wildtypes (WT). In Cndp1-KO mice, renal carnosine and anserine concentrations were gender-specifically increased 2- to 9-fold, respectively in the kidney and both most abundant in the renal cortex, but remained unchanged in all other organs and in serum. Renal oxidized/reduced glutathione concentrations, renal morphology and function were unaltered. In Cndp1-KO mice at week 11, renal asparagine, serine and glutamine levels and at week 55, renal arginine concentration were reduced. Renal heat-shock-protein 70 (Hspa1a/b) mRNA declined with age in WT but not in Cndp1-KO mice, transcription factor heat-shock-factor 1 was higher in 55-week-old KO mice. Fasting blood glucose concentrations decreased with age in WT mice, but were unchanged in Cndp1-KO mice. Blood glucose response to intraperitoneal insulin was gender- but not genotype-dependent, the response to intraperitoneal glucose injection was similar in all groups. A global Cndp1-KO selectively, age- and gender-specifically, increases renal carnosine and anserine concentrations, alters renal amino acid- and HSP70 profile and modifies systemic glucose homeostasis. Increase of the natural occurring carnosine and anserine levels in the kidney by modulation of CN1 represents a promising therapeutic approach to mitigate or prevent chronic kidney diseases such as diabetic nephropathy.