An assessment of thermoneutral housing conditions on murine cardiometabolic function.

Mouse models are used to model human diseases and perform pharmacological efficacy testing to advance therapies to humans; most of these studies are conducted in room temperature conditions. At room temperature (22°C), mice are cold-stressed and must use brown adipose tissue (BAT) to maintain body temperature. This cold stress increases catecholamine tone to maintain adipocyte lipid release via lipolysis, which will fuel adaptive thermogenesis. Maintaining rodents at thermoneutral temperatures (28°C) ameliorates the need for adaptive thermogenesis, thus reducing catecholamine tone and BAT activity. Cardiovascular tone is also determined by catecholamine levels in rodents, as ß-adrenergic stimuli are primary drivers of not only lipolytic but also ionotropic and chronotropic responses. As mice have increased catecholamine tone at room temperature, we investigated how thermoneutral housing conditions would impact cardiometabolic function. Here, we show a rapid and reversible effect of thermoneutrality on both heart rate and blood pressure in chow-fed animals, which was blunted in animals fed a high-fat diet. Animals subjected to transverse aortic constriction displayed compensated hypertrophy at room temperature, whereas animals displayed less hypertrophy and a trend toward worse systolic function at thermoneutrality. Despite these dramatic changes in blood pressure and heart rate at thermoneutral housing conditions, enalapril effectively improved cardiac hypertrophy and gene expression alterations. There were surprisingly few differences in cardiac parameters in high-fat-fed animals at thermoneutrality. Overall, these data suggest that thermoneutral housing may alter some aspects of cardiac remodeling in preclinical mouse models of heart failure.NEW & NOTEWORTHY Thermoneutral housing conditions cause rapid and reversible changes in mouse heart rate and blood pressure. Despite dramatic reductions in heart rate and blood pressure, thermoneutrality reduced the compensatory hypertrophic response in a pressure overload heart failure model compared with room temperature housing, and ACE inhibitors were still efficacious to prevent pressure overload-induced cardiac remodeling. The effects of thermoneutrality on heart rate and blood pressure are abrogated in the context of diet-induced obesity.

Small molecule branched-chain ketoacid dehydrogenase kinase (BDK) inhibitors with opposing effects on BDK protein levels.

Branched chain amino acid (BCAA) catabolic impairments have been implicated in several diseases. Branched chain ketoacid dehydrogenase (BCKDH) controls the rate limiting step in BCAA degradation, the activity of which is inhibited by BCKDH kinase (BDK)-mediated phosphorylation. Screening efforts to discover BDK inhibitors led to identification of thiophene PF-07208254, which improved cardiometabolic endpoints in mice. Structure-activity relationship studies led to identification of a thiazole series of BDK inhibitors; however, these inhibitors did not improve metabolism in mice upon chronic administration. While the thiophenes demonstrated sustained branched chain ketoacid (BCKA) lowering and reduced BDK protein levels, the thiazoles increased BCKAs and BDK protein levels. Thiazoles increased BDK proximity to BCKDH-E2, whereas thiophenes reduced BDK proximity to BCKDH-E2, which may promote BDK degradation. Thus, we describe two BDK inhibitor series that possess differing attributes regarding BDK degradation or stabilization and provide a mechanistic understanding of the desirable features of an effective BDK inhibitor.

Lymphangiogenic therapy prevents cardiac dysfunction by ameliorating inflammation and hypertension.

The lymphatic vasculature is involved in the pathogenesis of acute cardiac injuries, but little is known about its role in chronic cardiac dysfunction. Here, we demonstrate that angiotensin II infusion induced cardiac inflammation and fibrosis at 1 week and caused cardiac dysfunction and impaired lymphatic transport at 6 weeks in mice, while co-administration of VEGFCc156s improved these parameters. To identify novel mechanisms underlying this protection, RNA sequencing analysis in distinct cell populations revealed that VEGFCc156s specifically modulated angiotensin II-induced inflammatory responses in cardiac and peripheral lymphatic endothelial cells. Furthermore, telemetry studies showed that while angiotensin II increased blood pressure acutely in all animals, VEGFCc156s-treated animals displayed a delayed systemic reduction in blood pressure independent of alterations in angiotensin II-mediated aortic stiffness. Overall, these results demonstrate that VEGFCc156s had a multifaceted therapeutic effect to prevent angiotensin II-induced cardiac dysfunction by improving cardiac lymphatic function, alleviating fibrosis and inflammation, and ameliorating hypertension.