Gillian A. Gray

Background and Purpose: Plasma glucocorticoids increase acutely after MI, thereafter tissue levels are amplified selectively within cells expressing 11‐ ß hydroxysteroid dehydrogenase type 1 (11‐ßHSD1) that regenerates active glucocorticoids from circulating metabolites. Glucocorticoids initially protect cardiomyocytes and prevent excessive inflammation after MI but can also suppress wound repair leading to functional decline. We investigate 11‐ßHSD1 inhibition after MI to prevent deterioration of cardiac function and its impact on wound repair. Experimental Approach: Adult female Gottingen mini‐pigs underwent percutaneous balloon MI/reperfusion and were randomised to receive either oral 11‐ßHSD1 inhibitor AZD8329 (n = 11) or vehicle (n = 9), from 2 until 27 days later, with concurrent administration of relevant therapeutic intervention (anti‐platelet, statin and ACE inhibitor). Key Results: AZD8329 treatment increased plasma accumulation of cortisone substrate showing successful 11‐ßHSD1 inhibition. Gadolinium‐enhanced magnetic resonance imaging (MRI) showed equivalent infarct size in both groups prior to commencing treatment. Twenty‐eight days after MI cardiac function and left ventricle area were preserved in the AZD8329 treated group relative to vehicle. There was no impact of 11‐ßHSD1 inhibitor on neovascularisation or infarct area. Mass spectrometry imaging revealed AZD8329 binding to the healing infarct and altered regulation of extracellular matrix processing was highlighted by birefringence microscopy and proteomic analysis. Conclusions and Implications: Pharmacological inhibition of 11‐ßHSD1 after MI prevents deterioration of cardiac function and detrimental remodelling. 11‐ßHSD1 inhibitors have safely reached Phase 2 clinical trials in diabetes and dementia, and could be repurposed as an addition to standard care after MI to prevent the development of heart failure.

Spinal Muscular Atrophy is an autosomal dominant disease caused by mutations and deletions within the SMN1 gene, with predominantly childhood onset. Although primarily a motor neuron disease, defects in non-neuronal tissues are described in both patients and mouse models. Here, we have undertaken a detailed study of the heart in the Smn2B/− mouse models of SMA, and reveal a thinning of the ventriclar walls as previously described in more severe mouse models of SMA. However most structural changes are resolved by accounting for the smaller body size of the SMA mouse, as was also confirmed in the SMN∆7 model. Echocardiography revealed increased systolic function, which was particularly pronounced in subsets of mice and an increase in global longitudinal strain, collectively indicative of increased cardiac stress in the Smn2B/− mouse model. We have used TMT proteomics to perform a longitudinal study of the proteome of the hearts of Smn2B/− mice and reveal a progressive dysregulation of LXR/RXR signalling which is a regulator of lipid metabolism. We further show consistent perturbations in lipid metabolism in the Smn2B/−, Smn−/−;SMN2;SmnΔ7and SmnΔ7/Δ7;SMN2 mouse models of SMA on the day of birth. This work indicates that although structural changes in the heart can be overstated by failing to account for body size, there are functional defects which could predispose the heart to subsequent failure. We identify a common molecular signature across mouse models pointing to a dysregulation in lipid metabolism, and suggest that manipulation of LXR/RXR signalling offers an opportunity to impact upon these pathways.

Alström syndrome (AS), a multisystem disorder caused by biallelic ALMS1 mutations, features major early morbidity and mortality due to cardiac complications. The latter are biphasic, including infantile dilated cardiomyopathy and distinct adult-onset cardiomyopathy, and poorly understood. We assessed cardiac function of Alms1 knockout (KO) mice by echocardiography. Cardiac function was unaltered in Alms1 global KO mice of both sexes at postnatal day 15 (P15) and 8 weeks. At 23 weeks, female − but not male − KO mice showed increased left atrial area and decreased isovolumic relaxation time, consistent with early restrictive cardiomyopathy, as well as reduced ejection fraction. No histological or transcriptional changes were seen in myocardium of 23-week-old female Alms1 global KO mice. Female mice with Pdgfra-Cre-driven Alms1 deletion in cardiac fibroblasts and in a small proportion of cardiomyocytes did not recapitulate the phenotype of global KO at 23 weeks. In conclusion, only female Alms1-deficient adult mice show echocardiographic evidence of cardiac dysfunction, consistent with the cardiomyopathy of AS. The explanation for sexual dimorphism remains unclear but might involve metabolic or endocrine differences between sexes.

Background: Alström Syndrome (AS), a multisystem disorder caused by biallelic ALMS1 mutations, features major cardiac complications often causing early mortality. These are biphasic, including infantile dilated cardiomyopathy, and distinct adult-onset cardiomyopathy. Cardiomyocyte maturation defects, cardiac fibrosis and early atherosclerosis have all been invoked as contributors to heart failure in AS, but their relative importance and inter-relationships are unknown. Methods: Cardiac function of global Alms1 knockout mice was assessed by echocardiography at postnatal day 15 (P15) and at 8 and 23 weeks of age. Echocardiography was also undertaken in female mice with Pdgfrα -Cre-driven Alms1 deletion in cardiac fibroblasts and a small proportion of cardiomyocytes. Histological and transcriptional analysis of myocardium at P15 and 24 weeks of age was also performed. Results: Cardiac function was unaltered in knockout mice of both sexes at P15 and 8 weeks of age. At 23 weeks of age female but not male knockout mice showed increased left atrial area, decreased isovolumic relaxation time, and reduced ejection fraction, consistent with early restrictive cardiomyopathy. No histological or transcriptional changes could be identified in myocardium of 23-week old female Alms1 KO mice, however. Pdgfrα -Cre-driven Alms1 KO in females did not recapitulate the phenotype of global KO at 23 weeks. Conclusions: Adult female, but not male, Alms1 -deficient mice show echocardiographic evidence of cardiac dysfunction, consistent with the restrictive cardiomyopathy of AS. The explanation for sexual dimorphism remains unclear, but may involve metabolic or endocrine differences between sexes. No infantile cardiomyopathy was found in this study.

Caloric restriction (CR) reduces the risk of age-related diseases in numerous species, including humans. CR’s metabolic effects, including decreased adiposity and improved insulin sensitivity, are important for its broader health benefits; however, the extent and basis of sex differences in CR’s health benefits are unknown. We found that 30% CR in young (3-month-old) male mice decreased fat mass and improved glucose tolerance and insulin sensitivity, whereas these effects were blunted or absent in young females. Females’ resistance to fat loss was associated with decreased lipolysis, energy expenditure and fatty acid oxidation, and increased postprandial lipogenesis, compared to males. The sex differences in glucose homeostasis were not associated with differential glucose uptake but with altered hepatic ceramide content and substrate metabolism: compared to CR males, CR females had lower TCA cycle activity and higher blood ketone concentrations, a marker of hepatic acetyl-CoA content. This suggests that males use hepatic acetyl-CoA for the TCA cycle whereas in females it accumulates, stimulating gluconeogenesis and limiting hypoglycaemia during CR. In aged mice (18-months old), when females are anoestrus, CR decreased fat mass and improved glucose homeostasis similarly in both sexes. Finally, in a cohort of overweight and obese humans, CR-induced fat loss was also sex- and age-dependent: younger females (45 years) this sex difference was absent. Collectively, these studies identify age-dependent sex differences in the metabolic effects of CR and highlight adipose tissue, the liver and oestrogen as key determinants of CR’s metabolic benefits. These findings have important implications for understanding the interplay between diet and health, and for maximising the benefits of CR in humans.

SUMMARY: Caloric restriction (CR) is a nutritional intervention that reduces the risk of age-related diseases in numerous species, including humans. CR’s metabolic effects, including decreased fat mass and improved insulin sensitivity, play an important role in its broader health benefits. However, the extent and basis of sex differences in CR’s health benefits are unknown. We found that 30% CR in young (3-month-old) male mice decreased fat mass and improved glucose tolerance and insulin sensitivity, whereas these effects were blunted or absent in young female mice. Females’ resistance to fat and weight loss was associated with decreased lipolysis, lower systemic energy expenditure and fatty acid oxidation, and increased postprandial lipogenesis compared to males. Positron emission tomography-computed tomography (PET/CT) with ¹⁸ F-fluorodeoxyglucose ( ¹⁸ F-FDG) showed that peripheral glucose uptake was comparable between sexes. Instead, the sex differences in glucose homeostasis were associated with altered hepatic ceramide content and substrate metabolism: compared to CR males, CR females had lower TCA cycle activity but higher blood ketone concentrations, a marker of hepatic acetyl-CoA content. This suggests that males use hepatic acetyl-CoA for the TCA cycle whereas in females it accumulates, thereby stimulating gluconeogenesis and limiting hypoglycaemia during CR. In aged mice (18-months old), when females are anoestrus, CR decreased fat mass and improved glucose homeostasis to a similar extent in both sexes. Finally, in a cohort of overweight and obese humans CR-induced fat loss was also sex- and age-dependent: younger females (45 years) this sex difference was absent. Collectively, these studies identify age-dependent sex differences in the metabolic effects of CR and highlight adipose tissue, the liver and oestrogen as key determinants of CR’s metabolic benefits. These findings have important implications for understanding the interplay between diet and health and for maximising the benefits of CR in humans. HIGHLIGHTS: Caloric restriction (CR) decreases fat mass and improves glucose homeostasis in young male mice, but young females resist these effects. CR females resist lipolysis, decrease energy expenditure and increase postprandial lipogenesis more than CR males, explaining how females resist fat loss. Sex differences in glucose homeostasis are associated with altered hepatic metabolism and gluconeogenesis, without marked differences in peripheral glucose uptake. CR’s effects on fat loss and glucose homeostasis are comparable in aged male and female mice, implicating oestrogen as the driver of the sexually dimorphic effects in young mice. In humans, females resist CR-induced fat loss in an age-dependent manner, further supporting the role of oestrogen in the sexually dimorphic effects of CR.

Approximately 7 million people are affected by acute myocardial infarction (MI) each year, and despite significant therapeutic and diagnostic advancements, MI remains a leading cause of mortality worldwide. Preclinical animal models have significantly advanced our understanding of MI and have enabled the development of therapeutic strategies to combat this debilitating disease. Notably, some drugs currently used to treat MI and heart failure (HF) in patients had initially been studied in preclinical animal models. Despite this, preclinical models are limited in their ability to fully reproduce the complexity of MI in humans. The preclinical model must be carefully selected to maximise the translational potential of experimental findings. This review describes current experimental models of MI and considers how they have been used to understand drug mechanisms of action and support translational medicine development.LINKED ARTICLES: This article is part of a themed issue on Preclinical Models for Cardiovascular disease research (BJP 75th Anniversary). To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.5/issuetoc

Long non-coding RNAs (lncRNAs) have structural and functional roles in development and disease. We have previously shown that the LINC00961/SPAAR (small regulatory polypeptide of amino acid response) locus regulates endothelial cell function, and that both the lncRNA and micropeptide counter-regulate angiogenesis. To assess human cardiac cell SPAAR expression, we mined a publicly available scRNSeq dataset and confirmed LINC00961 locus expression and hypoxic response in a murine endothelial cell line. We investigated post-natal growth and development, basal cardiac function, the cardiac functional response, and tissue-specific response to myocardial infarction. To investigate the influence of the LINC00961/SPAAR locus on longitudinal growth, cardiac function, and response to myocardial infarction, we used a novel CRISPR/Cas9 locus knockout mouse line. Data mining suggested that SPAAR is predominantly expressed in human cardiac endothelial cells and fibroblasts, while murine LINC00961 expression is hypoxia-responsive in mouse endothelial cells. LINC00961^–/– mice displayed a sex-specific delay in longitudinal growth and development, smaller left ventricular systolic and diastolic areas and volumes, and greater risk area following myocardial infarction compared with wildtype littermates. These data suggest the LINC00961/SPAAR locus contributes to cardiac endothelial cell and fibroblast function and hypoxic response, growth and development, and basal cardiovascular function in adulthood.

Long non-coding RNAs (lncRNAs) have structural and functional roles in development and disease. We have previously shown that the LINC00961/SPAAR locus regulates endothelial cell function, and that both the lncRNA and micropeptide counter-regulate angiogenesis. To assess human cardiac cell SPAAR expression we mined a publicly available scRNSeq dataset and confirmed LINC00961 locus expression and hypoxic response in a murine endothelial cell line. We investigated post-natal growth and development, basal cardiac function, the cardiac functional response and tissue-specific response to myocardial infarction. To investigate the contribution of the LINC00961/SPAAR locus to determination of longitudinal growth, cardiac function, and response to myocardial infarction, we used a novel CRISPR/Cas9 locus knockout mouse line. Data mining suggested that SPAAR is predominantly expressed in human cardiac endothelial cells and fibroblasts, while murine LINC00961 expression is hypoxia-responsive in mouse endothelial cells. LINC00961-/- mice displayed a sex-specific delay in longitudinal growth and development, smaller left ventricular systolic and diastolic areas and volumes, and greater risk area following myocardial infarction compared with wildtype littermates. These data suggest a role for the LINC00961/SPAAR locus in cardiac endothelial cell and fibroblast cell function and hypoxic-response, and in growth and development, and basal cardiovascular function in adulthood.