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Background and Purpose Experimental Approach Key Results Conclusions and Implications Cannabis stimulates several G‐protein‐coupled‐receptors and causes bradycardia and hypotension upon sustained consumption. Moreover, in vitro studies suggest an interference of cannabinoid‐signalling with cardiomyocyte contractility and hypertrophy. We aimed at revealing a functional contribution of the cannabinoid‐sensitive receptor GPR55 to cardiomyocyte homeostasis and neurohumorally induced hypertrophy in vivo.Gpr55−/− and wild‐type (WT) mice were characterized after 28‐day angiotensin II (AngII; 1·μg·kg−1 min−1) or vehicle infusion. In isolated adult Gpr55−/− and WT cardiomyocytes, mitochondrial function was assessed under naïve conditions, while cytosolic Ca2+ handling was additionally determined following application of the selective GPR55 antagonist CID16020046.Gpr55 deficiency did not affect angiotensin II (AngII) mediated hypertrophic growth, yet, especially in females, it alleviated maladaptive pro‐hypertrophic and ‐inflammatory gene expression and improved inotropy and adrenergic responsiveness compared to WT. In‐depth analyses implied increased cytosolic Ca2+ concentrations and transient amplitudes, and accelerated sarcomere contraction kinetics in Gpr55−/− myocytes, which could be mimicked by GPR55 blockade with CID16020046 in female WT cells. Moreover, Gpr55 deficiency up‐regulated factors involved in glucose and fatty acid transport independent of the AngII challenge, accelerated basal mitochondrial respiration and reduced basal protein kinase (PK) A, G and C activity and phospholemman (PLM) phosphorylation.Our study suggests GPR55 as crucial regulator of cardiomyocyte hypertrophy and homeostasis presumably by regulating PKC/PKA‐PLM and PKG signalling, and identifies the receptor as potential target to counteract maladaptation, adrenergic desensitization and metabolic shifts as unfavourable features of the hypertrophied heart in females. [ABSTRACT FROM AUTHOR]

(1) Background: Modulators of the Neuropeptide Y (NPY) system are involved in energy metabolism, but the effect of NPY receptor antagonists on metabolic-dysfunction-associated steatotic liver disease (MASLD), a common obesity-related comorbidity, are largely unknown. In this study, we report on the effects of antagonists of the NPY-2 receptor (Y2R) in comparison with empagliflozin and semaglutide, substances that are known to be beneficial in MASLD. (2) Methods: Diet-induced obese (DIO) male Wistar rats were randomized into the following treatment groups: empagliflozin, semaglutide ± PYY3-36, the Y2R antagonists JNJ 31020028 and a food-restricted group, as well as a control group. After a treatment period of 8 weeks, livers were weighed and histologically evaluated. QrtPCR was performed to investigate liver inflammation and de novo lipogenesis (in liver and adipose tissue). Serum samples were analysed for metabolic parameters. (3) Results: Semaglutide + PYY3-36 led to significant weight loss, reduced liver steatosis (p = 0.05), and decreased inflammation, insulin resistance, and leptin levels. JNJ-31020028 prevented steatosis (p = 0.03) without significant weight loss. Hepatic downregulation of de novo lipogenesis-regulating genes (SREBP1 and MLXIPL) was observed in JNJ-31020028-treated rats (p ≤ 0.0001). Food restriction also resulted in significantly reduced weight, steatosis, and hepatic de novo lipogenesis. (4) Conclusions: Body weight reduction (e.g., by food restriction or drugs like semaglutide ± PYY3-36) is effective in improving liver steatosis in DIO rats. Remarkably, the body-weight-neutral Y2R antagonists may be effective in preventing liver steatosis through a reduction in de novo lipogenesis, making this drug class a candidate for the treatment of (early) MASLD. [ABSTRACT FROM AUTHOR]

The stress-responsive epigenetic repressor histone deacetylase 4 (HDAC4) regulates cardiac gene expression. Here we show that the levels of an N-terminal proteolytically derived fragment of HDAC4, termed HDAC4-NT, are lower in failing mouse hearts than in healthy control hearts. Virus-mediated transfer of the portion of the Hdac4 gene encoding HDAC4-NT into the mouse myocardium protected the heart from remodeling and failure; this was associated with decreased expression of Nr4a1, which encodes a nuclear orphan receptor, and decreased NR4A1-dependent activation of the hexosamine biosynthetic pathway (HBP). Conversely, exercise enhanced HDAC4-NT levels, and mice with a cardiomyocyte-specific deletion of Hdac4 show reduced exercise capacity, which was characterized by cardiac fatigue and increased expression of Nr4a1. Mechanistically, we found that NR4A1 negatively regulated contractile function in a manner that depended on the HBP and the calcium sensor STIM1. Our work describes a new regulatory axis in which epigenetic regulation of a metabolic pathway affects calcium handling. Activation of this axis during intermittent physiological stress promotes cardiac function, whereas its impairment in sustained pathological cardiac stress leads to heart failure., Author(s): Lorenz H Lehmann [1, 2, 3]; Zegeye H Jebessa [1, 2]; Michael M Kreusser [1, 2, 3]; Axel Horsch [1, 2]; Tao He [1, 2]; Mariya Kronlage [1, 2, [...]