bims-mimcad 2024-07-21 papers

Issue of 2024–07–21
seven papers selected by
Henver Brunetta, University of Guelph

Physiol Genomics. 2024 Jul 15.

A matter of food and substrain: obesogenic diets induce differential severity of cardiac remodeling in C57Bl/6J and C57Bl/6N substrains.

Lorena Cascarano, Hrag Esfahani, Pierre Michel, Caroline Bouzin, Chantal Dessy, Jean-Luc Balligand, Lauriane Y M Michel.

The prevalence of metabolic syndrome in cardiac diseases such as heart failure with preserved ejection fraction (HFpEF) prompts the scientific community to investigate its adverse effects on cardiac function and remodeling. However, the selection of a preclinical model of obesity-induced cardiac remodeling has proven more challenging with inconsistencies often found in very similar mouse models. Here, we investigated the implication of genetic background as well as diet composition to identify a suitable model of diet-induced cardiac alterations. C57Bl/6J and C57Bl/6N male mice were subjected to distinct obesogenic diets consisting of high-fat and moderate-sucrose content (HF-S) or High-Sucrose and moderate-lipid content (F-HS) versus matching control diets. 5-month dietary intervention with obesogenic diets induced weight gain, adipocyte hypertrophy and increased visceral and subcutaneous fat mass in both substrains. Obese mice showed similar impairment of glucose disposition and insulin tolerance, both strains developing insulin resistance within two months. However, echocardiographic follow-up and histological analysis confirmed that HF-S diet increases cardiac hypertrophy, interstitial fibrosis as well as left atrial area in the C57Bl/6J strain only. On the contrary C57Bl/6N exhibit cardiac eccentric remodeling under control diets, possibly owing to a genetic mutation in the myosin light-chain-kinase 3 (Mylk3) gene, specific to this substrain, which was not further enhanced under obesogenic diets. Altogether, the present results highlight the importance of carefully selecting the suitable mouse strain and diets to model diet-induced cardiac remodeling. In this regard, C57Bl/6J mice develop significant cardiac remodeling in response to HF-S, and seem a suitable model for cardiometabolic disease.

Keywords: adipocytes; heart failure; metabolic syndrome; myocardial remodelling; obesity

DOI: https://doi.org/10.1152/physiolgenomics.00044.2024

Cardiovasc Diabetol. 2024 Jul 18. 23(1): 258

In-depth phosphoproteomic profiling of the insulin signaling response in heart tissue and cardiomyocytes unveils canonical and specialized regulation.

Jonathan Samuel Achter, Estefania Torres Vega, Andrea Sorrentino, Konstantin Kahnert, Katrine Douglas Galsgaard, Pablo Hernandez-Varas, Michael Wierer, Jens Juul Holst, Jørgen Frank Pind Wojtaszewski, Robert William Mills, Rasmus Kjøbsted, Alicia Lundby.

BACKGROUND: Insulin signaling regulates cardiac substrate utilization and is implicated in physiological adaptations of the heart. Alterations in the signaling response within the heart are believed to contribute to pathological conditions such as type-2 diabetes and heart failure. While extensively investigated in several metabolic organs using phosphoproteomic strategies, the signaling response elicited in cardiac tissue in general, and specifically in the specialized cardiomyocytes, has not yet been investigated to the same extent.
METHODS: Insulin or vehicle was administered to male C57BL6/JRj mice via intravenous injection into the vena cava. Ventricular tissue was extracted and subjected to quantitative phosphoproteomics analysis to evaluate the insulin signaling response. To delineate the cardiomyocyte-specific response and investigate the role of Tbc1d4 in insulin signal transduction, cardiomyocytes from the hearts of cardiac and skeletal muscle-specific Tbc1d4 knockout mice, as well as from wildtype littermates, were studied. The phosphoproteomic studies involved isobaric peptide labeling with Tandem Mass Tags (TMT), enrichment for phosphorylated peptides, fractionation via micro-flow reversed-phase liquid chromatography, and high-resolution mass spectrometry measurements.
RESULTS: We quantified 10,399 phosphorylated peptides from ventricular tissue and 12,739 from isolated cardiomyocytes, localizing to 3,232 and 3,128 unique proteins, respectively. In cardiac tissue, we identified 84 insulin-regulated phosphorylation events, including sites on the Insulin Receptor (InsrY1351, Y1175, Y1179, Y1180) itself as well as the Insulin receptor substrate protein 1 (Irs1S522, S526). Predicted kinases with increased activity in response to insulin stimulation included Rps6kb1, Akt1 and Mtor. Tbc1d4 emerged as a major phosphorylation target in cardiomyocytes. Despite limited impact on the global phosphorylation landscape, Tbc1d4 deficiency in cardiomyocytes attenuated insulin-induced Glut4 translocation and induced protein remodeling. We observed 15 proteins significantly regulated upon knockout of Tbc1d4. While Glut4 exhibited decreased protein abundance consequent to Tbc1d4-deficiency, Txnip levels were notably increased. Stimulation of wildtype cardiomyocytes with insulin led to the regulation of 262 significant phosphorylation events, predicted to be regulated by kinases such as Akt1, Mtor, Akt2, and Insr. In cardiomyocytes, the canonical insulin signaling response is elicited in addition to regulation on specialized cardiomyocyte proteins, such as Kcnj11Y12 and DspS2597. Details of all phosphorylation sites are provided.
CONCLUSION: We present a first global outline of the insulin-induced phosphorylation signaling response in heart tissue and in isolated adult cardiomyocytes, detailing the specific residues with changed phosphorylation abundances. Our study marks an important step towards understanding the role of insulin signaling in cardiac diseases linked to insulin resistance.

Keywords: Cardiac signaling; Cardiometabolic; Insulin resistance; Insulin signaling; Kinase; Metabolism; Phosphoproteomics; Phosphorylation; Proteomics; Tbc1d4

DOI: https://doi.org/10.1186/s12933-024-02338-4

Nat Metab. 2024 Jul 15.

Reduced adipocyte glutaminase activity promotes energy expenditure and metabolic health.

Glutamine and glutamate are interconverted by several enzymes and alterations in this metabolic cycle are linked to cardiometabolic traits. Herein, we show that obesity-associated insulin resistance is characterized by decreased plasma and white adipose tissue glutamine-to-glutamate ratios. We couple these stoichiometric changes to perturbed fat cell glutaminase and glutamine synthase messenger RNA and protein abundance, which together promote glutaminolysis. In human white adipocytes, reductions in glutaminase activity promote aerobic glycolysis and mitochondrial oxidative capacity via increases in hypoxia-inducible factor 1α abundance, lactate levels and p38 mitogen-activated protein kinase signalling. Systemic glutaminase inhibition in male and female mice, or genetically in adipocytes of male mice, triggers the activation of thermogenic gene programs in inguinal adipocytes. Consequently, the knockout mice display higher energy expenditure and improved glucose tolerance compared to control littermates, even under high-fat diet conditions. Altogether, our findings highlight white adipocyte glutamine turnover as an important determinant of energy expenditure and metabolic health.

DOI: https://doi.org/10.1038/s42255-024-01083-y

Circ Res. 2024 Jul 16.

Glucagon Receptor Antagonist for Heart Failure With Preserved Ejection Fraction.

Chen Gao, Zhaojun Xiong, Yunxia Liu, Meng Wang, Menglong Wang, Tian Liu, Jianfang Liu, Shuxun Ren, Nancy Cao, Hai Yan, Daniel J Drucker, Christoph Daniel Rau, Tomohiro Yokota, Jijun Huang, Yibin Wang.

BACKGROUND: Heart failure with preserved ejection fraction (HFpEF) is an emerging major unmet need and one of the most significant clinic challenges in cardiology. The pathogenesis of HFpEF is associated with multiple risk factors. Hypertension and metabolic disorders associated with obesity are the 2 most prominent comorbidities observed in patients with HFpEF. Although hypertension-induced mechanical overload has long been recognized as a potent contributor to heart failure with reduced ejection fraction, the synergistic interaction between mechanical overload and metabolic disorders in the pathogenesis of HFpEF remains poorly characterized.
METHOD: We investigated the functional outcome and the underlying mechanisms from concurrent mechanic and metabolic stresses in the heart by applying transverse aortic constriction in lean C57Bl/6J or obese/diabetic B6.Cg-Lepob/J (ob/ob) mice, followed by single-nuclei RNA-seq and targeted manipulation of a top-ranked signaling pathway differentially affected in the 2 experimental cohorts.
RESULTS: In contrast to the post-trans-aortic constriction C57Bl/6J lean mice, which developed pathological features of heart failure with reduced ejection fraction over time, the post-trans-aortic constriction ob/ob mice showed no significant changes in ejection fraction but developed characteristic pathological features of HFpEF, including diastolic dysfunction, worsened cardiac hypertrophy, and pathological remodeling, along with further deterioration of exercise intolerance. Single-nuclei RNA-seq analysis revealed significant transcriptome reprogramming in the cardiomyocytes stressed by both pressure overload and obesity/diabetes, markedly distinct from the cardiomyocytes singularly stressed by pressure overload or obesity/diabetes. Furthermore, glucagon signaling was identified as the top-ranked signaling pathway affected in the cardiomyocytes associated with HFpEF. Treatment with a glucagon receptor antagonist significantly ameliorated the progression of HFpEF-related pathological features in 2 independent preclinical models. Importantly, cardiomyocyte-specific genetic deletion of the glucagon receptor also significantly improved cardiac function in response to pressure overload and metabolic stress.
CONCLUSIONS: These findings identify glucagon receptor signaling in cardiomyocytes as a critical determinant of HFpEF progression and provide proof-of-concept support for glucagon receptor antagonism as a potential therapy for the disease.

Keywords: cardiology; heart failure; hypertension; risk factors; stroke volume

DOI: https://doi.org/10.1161/CIRCRESAHA.124.324706

Acta Physiol (Oxf). 2024 Jul 17. e14202

HIF-1α limits myocardial infarction by promoting mitophagy in mouse hearts adapted to chronic hypoxia.

Petra Alanova, Lukas Alan, Barbora Opletalova, Romana Bohuslavova, Pavel Abaffy, Katerina Matejkova, Kristyna Holzerova, Daniel Benak, Nina Kaludercic, Roberta Menabo, Fabio Di Lisa, Bohuslav Ostadal, Frantisek Kolar, Gabriela Pavlinkova.

AIM: The transcriptional factor HIF-1α is recognized for its contribution to cardioprotection against acute ischemia/reperfusion injury. Adaptation to chronic hypoxia (CH) is known to stabilize HIF-1α and increase myocardial ischemic tolerance. However, the precise role of HIF-1α in mediating the protective effect remains incompletely understood.
METHODS: Male wild-type (WT) mice and mice with partial Hif1a deficiency (hif1a+/-) were exposed to CH for 4 weeks, while their respective controls were kept under normoxic conditions. Subsequently, their isolated perfused hearts were subjected to ischemia/reperfusion to determine infarct size, while RNA-sequencing of isolated cardiomyocytes was performed. Mitochondrial respiration was measured to evaluate mitochondrial function, and western blots were performed to assess mitophagy.
RESULTS: We demonstrated enhanced ischemic tolerance in WT mice induced by adaptation to CH compared with their normoxic controls and chronically hypoxic hif1a+/- mice. Through cardiomyocyte bulk mRNA sequencing analysis, we unveiled significant reprogramming of cardiomyocytes induced by CH emphasizing mitochondrial processes. CH reduced mitochondrial content and respiration and altered mitochondrial ultrastructure. Notably, the reduced mitochondrial content correlated with enhanced autophagosome formation exclusively in chronically hypoxic WT mice, supported by an increase in the LC3-II/LC3-I ratio, expression of PINK1, and degradation of SQSTM1/p62. Furthermore, pretreatment with the mitochondrial division inhibitor (mdivi-1) abolished the infarct size-limiting effect of CH in WT mice, highlighting the key role of mitophagy in CH-induced cardioprotection.
CONCLUSION: These findings provide new insights into the contribution of HIF-1α to cardiomyocyte survival during acute ischemia/reperfusion injury by activating the selective autophagy pathway.

Keywords: cardioprotection; chronic hypoxia; hypoxia‐inducible factor 1 alpha; mitochondria; mitophagy; myocardial infarction

DOI: https://doi.org/10.1111/apha.14202

Obesity (Silver Spring). 2024 Jul 17.

Fas (CD95) expression in adipocytes contributes to diet-induced obesity.

Stephan Wueest, Chiara Scaffidi, Pim P van Krieken, Nils K Konrad, Christian Koch, Michael S F Wiedemann, Anne Goergen, Marcela Borsigova, Ioannis G Lempesis, Jonas Fullin, Konstantinos N Manolopoulos, Steffen Böttcher, Gijs H Goossens, Matthias Blüher, Daniel Konrad.

OBJECTIVE: Induction of browning in white adipose tissue (WAT) increases energy expenditure and may be an attractive target for the treatment of obesity. Since activation of Fas (CD95) induces pathways known to blunt expression of uncoupling protein 1 (UCP1), we hypothesized that Fas expression in adipocytes inhibits WAT browning and thus contributes to the development of obesity.
METHODS: Adipocyte-specific Fas knockout (FasΔadipo) and control littermate (FasF/F) mice were fed a regular chow diet or a high-fat diet (HFD) for 20 weeks. Energy expenditure was assessed by indirect calorimetry, and browning was determined in subcutaneous WAT. In vitro, UCP1 was analyzed in subcutaneous murine adipocytes treated with or without Fas ligand. Moreover, FAS expression in WAT was correlated to UCP1 and percentage of body fat in human individuals.
RESULTS: HFD-fed FasΔadipo mice displayed reduced body weight gain and blunted adiposity compared to control littermates. Concomitantly, whole-body energy expenditure and WAT browning were elevated. In cultured adipocytes, Fas ligand treatment blunted isoproterenol-induced UCP1 protein levels. In support of these findings in rodents, FAS expression in WAT correlated negatively with UCP1 but positively with adiposity in human individuals.
CONCLUSIONS: Fas activation in adipocytes contributes to HFD-associated adiposity in rodents and may be a therapeutic target to reduce obesity and associated diseases.

DOI: https://doi.org/10.1002/oby.24092

Science. 2024 Jul 19. 385(6706): eadm9238

The human mitochondrial mRNA structurome reveals mechanisms of gene expression.

J Conor Moran, Amir Brivanlou, Michele Brischigliaro, Flavia Fontanesi, Silvi Rouskin, Antoni Barrientos.

The human mitochondrial genome encodes crucial oxidative phosphorylation system proteins, pivotal for aerobic energy transduction. They are translated from nine monocistronic and two bicistronic transcripts whose native structures remain unexplored, posing a gap in understanding mitochondrial gene expression. In this work, we devised the mitochondrial dimethyl sulfate mutational profiling with sequencing (mitoDMS-MaPseq) method and applied detection of RNA folding ensembles using expectation-maximization (DREEM) clustering to unravel the native mitochondrial messenger RNA (mt-mRNA) structurome in wild-type (WT) and leucine-rich pentatricopeptide repeat-containing protein (LRPPRC)-deficient cells. Our findings elucidate LRPPRC's role as a holdase contributing to maintaining mt-mRNA folding and efficient translation. mt-mRNA structural insights in WT mitochondria, coupled with metabolic labeling, unveil potential mRNA-programmed translational pausing and a distinct programmed ribosomal frameshifting mechanism. Our data define a critical layer of mitochondrial gene expression regulation. These mt-mRNA folding maps provide a reference for studying mt-mRNA structures in diverse physiological and pathological contexts.

DOI: https://doi.org/10.1126/science.adm9238