title: Unraveling the interplay between GPx4 genotype, carbonyl stress and cardiovascular diseases
title: harnessing the therapeutic potential of carnosine
titleType: Subtitle
Creators: name: Berdaweel, Islam A.
Publisher: name: University of Iowa
Year: 2023
Subjects: carbonyl stress
Cardiac fibrosis
Carnosine
Glutathione peroxidase 4

description: Lipid peroxidation (LPO) is increasingly recognized as a pathological factor in cardiovascular disease (CVD), through interconnected oxidative-inflammatory pathways. Recent studies have shown that LPO products are predictive markers for CVD and are significantly elevated in specific cardiovascular events, indicating their significance in this context. Notably, Glutathione peroxidase 4 (GPx4), a LPO inhibiting enzyme, was found to be significantly lower in the myocardium of patients who have diabetes and correlates with the severity of diabetes nephropathy. Moreover, several GPX4 gene variants were found to be associated with CVD occurrence and to affect GPx4 enzyme level/activity. Importantly, the two most common risk factors for CVD, namely diabetes and obesity, are characterized by heightened LPO and systemic inflammation. Cardiac fibrosis is a hallmark of the myocardial tissue of diabetics and obese patients and contributes significantly to the pathogenesis of heart failure and arrhythmias. Carnosine, a naturally occurring histidine dipeptide, is a pleiotropic molecule that has been proven to be an effective quencher of various LP products. Additionally, ample preclinical and clinical evidence indicate that carnosine has a role in the prevention and treatment of the cardiometabolic complications associated with obesity and type 2 diabetes. Based on this evidence, this thesis tests two main hypotheses: 1) We hypothesize that single nucleotide polymorphism (SNP) in the GPX4 gene is associated with increased risk of poly unsaturated fatty acid (POAF) in humans and are associated with GPx4 enzyme content/activity. 2)We hypothesize that carnosine supplementation can mitigate cardiac fibrosis associated with diet-induced obesity in a model of enhanced LPO of GPx4-deficient mouse model (GPx4+/-).
description: To test the first hypothesis, a comprehensive sequencing analysis was conducted on the coding region of GPX4 located on chromosome 19, involving a cohort of 189 patients who underwent elective coronary artery bypass graft surgery. Concurrently, GPx4 enzyme content and activity were assessed in the corresponding atrial myocardium samples from these patients. We identified five GPX4 gene variants associated with increased risk of POAF (permutated p-value of ≤ 0.05), while eight variants were associated with alterations in myocardial GPx4 content/activity (p-value of &lt; 0.05). Notably, one of these variants (rs713041) is a known modifier of CVD risk.
description: To test the carnosine effectiveness in mitigating cardiac fibrosis, wild-type (WT) and GPx4+/− male mice were fed on either standard chow (CNTL) or high fat high sucrose diet (HFHS) for 16 weeks. Seven weeks after starting the diet two groups of the HFHS - WT and GPx4+/− were started on 80 mM carnosine treatment, added to their drinking water throughout the entire study period. We observed a moderate glycemic control enhancement with carnosine treatment in both genotypes with HFHS diet, while we didn’t observe changes in insulin sensitivity. Remarkably, despite our finding that carnosine therapy has no significant impact on overall gene expression as it was revealed by the transcriptomic analysis, it was noteworthy carnosine substantially increased the expression of cardiac GPx4 in both WT and GPx4+/− mice following the HFHS diet. Interestingly, carnosine demonstrated a significant reduction in protein carbonyls and iron levels in both genotypes on the HFHS diet. Notably, our study revealed a strong antifibrotic effect of carnosine treatment on the hearts of obese mice, accompanied by a significant anti-collagen cross-linking effect.
description: Collectively, this thesis accentuated the importance of GPx4 variants as potential modifiers for POAF risk and demonstrated a GPx4 enzyme genotype-phenotype associations. Additionally, this thesis highlighted the potential of carnosine in mitigating cardiac fibrosis associated with obesity under GPx4 deficiency and emphasized the importance of key mechanisms involved in its activity. These results may offer a novel perspective on the treatment of cardiac fibrosis in obesity.