Acute myocardial infarction (MI) accelerates cardiomyocyte apoptosis, which underpins ventricular remodelling and dysfunction. The hormone ghrelin mitigates this remodelling, but the mechanisms remain unclear. Specific microRNAs (miRs) are key modulators and reliable biomarkers of early-stage apoptosis. We hypothesized that ghrelin targets anti-apoptotic miR-499 and miR-133 following MI to suppress cardiac apoptosis and thus mitigate cardiac dysfunction. C57/B6 mice received an injection of ghrelin (150 µg/kg, s.c.) or saline following left anterior descending coronary artery ligation (MI). Plasma levels of miR-499 and miR-133 at 3 or 24 h post-MI were measured using real-time PCR. Echocardiography and TUNEL staining were used to assess progressive cardiac function/structure and cardiomyocyte apoptosis, respectively. Myocardial ischaemia adversely decreased the levels of anti-apoptotic miR-499 by 3 h post-MI and increased the proportion of TUNEL-positive apoptotic cardiomyocytes by 24 h post-MI, contributing to cardiac remodelling and dysfunction by 2 weeks post-MI. Ghrelin prevented this MI-induced decrease in miR-499 by 3 h post-MI, then further increased the levels of miR-499 and miR-133 by 24 h. These ghrelin-mediated changes in microRNA were associated with a significant decrease in cardiomyocyte apoptosis and, consequently, significantly improved cardiac function and structure by 2 weeks post-MI. These results highlight miRs as effective biomarkers for the early detection of ischaemia-induced apoptotic signalling. Moreover, ghrelin appears to mitigate ischaemia-induced apoptosis by increasing the levels of anti-apoptotic miR-499 and miR-133, further solidifying ghrelin as a new therapeutic strategy for the clinical treatment of heart failure.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Dysregulation of cardiac-enriched microRNA (miRNA) expression is linked to age-associated cardiovascular diseases (CVDs). However, the sex-specificity and age at which dysregulation occurs remain unclear. Given the conserved nature of miRNAs and short lifespan of Drosophila melanogaster (fruit flies), we investigated age-related changes in the expression of cardiac enriched miRNAs (miR-1, -9, -34a, and -133, target miRNAs) and their impact on the cardiac tube in male and female flies. Cardiac tube tissues were collected from male and female flies (n = 5/group) at 7-day intervals from day 7 to day 70. miRNAs and predicted target mRNA gene (KCNQ, MRTF, and CCN) expression were quantified by RT-qPCR (n = 4-6/group). Myofibril diameter was assessed by Masson's trichrome staining (n = 4-6) to determine the structural effects of hypertrophic miR-9. In females, miR-1 was downregulated with age (P ≤ 0.0001), whereas in males, miR-9 (P ≤ 0.0001) and miR-34a (P = 0.0017) were downregulated. Interestingly, miR-133 was downregulated in both sexes (P ≤ 0.0001). In males, MRTF (miR-9 target) and CCN (miR-133 target) expression increased with age (P = 0.016 and P = 0.013, respectively), whereas in females, KCNQ (miR-1 target) and CCN expression decreased (P = 0.03 and P = 0.002, respectively). Myofibril thickness significantly increased with age in both sexes (P < 0.0001). miR-9 downregulation may contribute to this effect in males, whereas the mechanism in females remains unclear. This study provides novel insights into sex-specific miRNA dysregulation in cardiac aging, emphasizing the need to consider sex differences in miRNA-mediated cardiovascular aging and the potential of miRNAs as diagnostic tools in age-related CVDs.NEW & NOTEWORTHY Advancements in healthcare and diet have increased life expectancy, doubling the population aged 60 and above by 2050. However, this longevity raises the risk of chronic diseases, especially cardiovascular diseases. We examined age-related changes in cardiovascular-enriched microRNAs in the Drosophila melanogaster heart. This first-of-its-kind observational study tracks microRNA changes across life stages. It highlights sex-specific expression of miRNAs, providing crucial insights into cardiac aging. It lays a strong foundation for future research on microRNA in heart health.

The accurate measurement of sympathetic nerve activity is essential for advancing knowledge related to the mechanisms that underpin sympathetic activation in diseased states, such as acute heart failure. Considering sympathetic outflow throughout the body is differentially modulated, the most reliable method of measuring sympathetic traffic to individual organs is by way of direct electrophysiological recording of nerve activity. However, the surgical approach of accessing, exposing, and isolating the sympathetic nerve of interest is technically demanding, especially in the small size of a standard laboratory rat, one of the most common models for measuring SNA. Moreover, preserving the health of the nerve while attaching it to electrodes for recording requires careful diligence. The complexity of recording from specifically the cardiac sympathetic nerve remains a significant challenge due to the difficulty of accessing the nerve within the thorax cavity. Here, we describe in detail the process of surgically isolating the cardiac sympathetic nerve activity in a rat for accurately recording and quantifying sympathetic nerve activity.

Diabetic heart disease is a leading cause of morbidity and mortality in individuals with type 2 diabetes mellitus (T2DM). A major yet frequently under-recognized component of diabetic heart disease is cardiac autonomic neuropathy (CAN), a condition characterized by dysregulated sympathetic and parasympathetic drive to the heart. Current pharmacological treatments for diabetic CAN are often ineffective, having been extrapolated from other health conditions. These therapies predominantly target the peripheral symptoms of elevated sympathetic activity, whilst largely neglecting its origins in sympathoexcitatory regions of the central autonomic network. Sympathetic control of cardiac function originates from the hypothalamus, medulla oblongata, midbrain, and pons, and is relayed through the intermediolateral cell column of the thoracic spinal cord and the intrinsic cardiac nervous system. Targeting the central autonomic network to modulate cardiac sympathetic drive presents a promising novel therapeutic avenue for the treatment of diabetic CAN. This review briefly summarizes established knowledge regarding the pathophysiology and management of diabetic CAN, and the implications of recent findings of increased neuronal activation in central sympathoregulatory regions early in the development of T2DM. Increased cardiac sympathetic in the intital stages of T2DM might represent a novel therapeutic target to reduce the impact of CAN and thereby improve outcomes in patients with T2DM.

The stress axis is always active, even in the absence of any threat. This manifests as hourly pulses of corticosteroid stress hormone secretion over the day. Corticotropin-releasing hormone (CRH) neurons in the paraventricular nucleus of the hypothalamus (CRHPVN) control both the neuroendocrine stress axis as well as stress-associated behaviors. However, it is currently unclear how the resting activity of these neurons is coordinated with both spontaneous behavior and ultradian pulses of corticosteroid secretion. To investigate this, we performed fiber photometry recordings of CRHPVN neuron activity in Crh-Ires-Cre mice and a newly generated line of Crh-Ires-Cre rats. In both mice and rats, CRHPVN neurons displayed an ultradian rhythm of activity with reoccurring upstates of activity approximately once per hour over the 24-h day. Upstates in activity were coordinated with increases in animal activity/arousal. Chemogenetic activation of CRHPVN neurons was also sufficient to induce behavioral arousal. In rats, increases in CRH neural activity preceded some pulses of corticosteroid secretion but not others. Thus, while CRHPVN neurons display an ultradian rhythm of activity over the 24-h day that is coordinated with behavioral arousal, the relationship between CRHPVN activity and pulses of corticosteroid secretion is not one-to-one.

Abstract Background: miRNAs have been shown to be dysregulated in Neuropathic pain conditions such as diabetic painful neuropathy (DPN). While invasive techniques such as blood samples are routinely used to collect and analyse miRNAs, the use of non-invasive techniques such as salivary samples for analysing miRNAs involved in neuropathic pain has been minimal. Therefore, the objective of this study was to determine if miRNAs involved in neuropathic pain can be measured reliably in salivary samples comprising of healthy European and Pacific population. Methods: Participants were recruited via advertisements on notice boards, social media, word of mouth, and pamphlets. Saliva samples were collected from healthy European and Pacifica Participants. Samples were stored in -80ºC until analysis. Total RNA was extracted using miRNEasy kit (Qiagen) following manufacturer’s protocol and the concentration was measured using Nanodrop (Thermofisher). Results: A total of 37 healthy participants (19 European and 18 Pacifica; age range: 22-57 years) were included in the study. Results showed that four different miRNAs (miR-16, miR-124, miR-132 and miR-134) that have been demonstrated to be associated with DPN were expressed and reliably measured in all the salivary samples. Conclusion: all the miRNAs identified in our study have been shown to be involved in neuropathic pain and inflammation. Hence, further research is required in this area to investigate the feasibility of extracting and analysing these miRNAs in people with neuropathic pain.

The global population is estimated to reach 9.8 billion by 2050, of which 2.1 billion will comprise individuals above 60 years of age. As the number of elderly is estimated to double from 2017, it is a victory of the modern healthcare system but also worrisome as ageing, and the onset of chronic disease are correlated. Among other chronic conditions, cardiovascular diseases (CVDs) are the leading cause of death in the aged population. While the underlying cause of the age-associated development of CVDs is not fully understood, studies indicate the role of non-coding RNAs such as microRNAs (miRNAs) and long noncoding RNAs (lnc-RNAs) in the development of age-associated CVDs. miRNAs and lnc-RNAs are non-coding RNAs which control gene expression at the post-transcriptional level. The expression of specific miRNAs and lnc-RNAs are reportedly dysregulated with age, leading to cardiovascular system changes and ultimately causing CVDs. Since miRNAs and lnc-RNAs play several vital roles in maintaining the normal functioning of the cardiovascular system, they are also being explored for their therapeutic potential as a treatment for CVDs. This review will first explore the pathophysiological changes associated with ageing. Next, we will review the known mechanisms underlying the development of CVD in ageing with a specific focus on miRNA and lnc-RNAs. Finally, we will discuss the therapeutic options and future challenges towards healthy cardiac ageing. With the global ageing population on the rise, this review will provide a fundamental understanding of some of the underlying molecular mechanisms of cardiac ageing.

Pericytes (PCs) are abundant yet remain the most enigmatic and ill-defined cell population in the heart. Here, we investigated whether PCs can be reprogrammed to aid neovascularization. Primary PCs from human and mouse hearts acquired cytoskeletal proteins typical of vascular smooth muscle cells (VSMCs) upon exclusion of EGF/bFGF, which signal through ERK1/2, or upon exposure to the MEK inhibitor PD0325901. Differentiated PCs became more proangiogenic, more responsive to vasoactive agents, and insensitive to chemoattractants. RNA sequencing revealed transcripts marking the PD0325901-induced transition into proangiogenic, stationary VSMC-like cells, including the unique expression of 2 angiogenesis-related markers, aquaporin 1 (AQP1) and cellular retinoic acid-binding protein 2 (CRABP2), which were further verified at the protein level. This enabled us to trace PCs during in vivo studies. In mice, implantation of Matrigel plugs containing human PCs plus PD0325901 promoted the formation of αSMA+ neovessels compared with PC only. Two-week oral administration of PD0325901 to mice increased the heart arteriolar density, total vascular area, arteriole coverage by PDGFRβ+AQP1+CRABP2+ PCs, and myocardial perfusion. Short-duration PD0325901 treatment of mice after myocardial infarction enhanced the peri-infarct vascularization, reduced the scar, and improved systolic function. In conclusion, myocardial PCs have intrinsic plasticity that can be pharmacologically modulated to promote reparative vascularization of the ischemic heart.

Non-ischemic diabetic heart disease (NiDHD) is characterized by diastolic dysfunction and decreased or preserved systolic function, eventually resulting in heart failure. Accelerated apoptotic cell death because of alteration of molecular signaling pathways due to dysregulation in microRNAs (miRNAs) plays a significant role in the development of NiDHD. Here, we aimed to determine the pathological role of cardiomyocyte-enriched pro-apoptotic miR-320 in the development of NiDHD. We identified a marked upregulation of miR-320 that was associated with downregulation of its target protein insulin growth factor-1 (IGF-1) in human right atrial appendage tissue in the late stages of cardiomyopathy in type 2 diabetic db/db mice and high-glucose-cultured human ventricular cardiomyocytes (AC-16 cells). In vitro knockdown of miR-320 in high-glucose-exposed AC-16 cells using locked nucleic acid (LNA) anti-miR-320 markedly reduced high-glucose-induced apoptosis by restoring IGF-1 and Bcl-2. Finally, in vivo knockdown of miR-320 in 24-week-old type 2 diabetic db/db mice reduced cardiomyocyte apoptosis and interstitial fibrosis while restoring vascular density. This resulted in partial recovery of the impaired diastolic and systolic function. Our study provides evidence that miR-320 is a late-responding miRNA that aggravates apoptosis and cardiac dysfunction in the diabetic heart, and that therapeutic knockdown of miR-320 is beneficial in partially restoring the deteriorated cardiac function.

Background: Non-ischemic diabetic heart disease (NiDHD) is characterised by diastolic dysfunction and decreased or preserved systolic function, eventually resulting in heart failure. The fundamental mechanisms leading to NiDHD are still not known. microRNAs (miRNAs) plays a significant role in the development of NiDHD. Objective: To investigate the pathological role of cardiomyocyte enriched pro-apoptotic miR-320 in the development of NiDHD and to determine if therapeutic knockdown of miR-320 can restore impaired cardiac function and angiogenesis in the diabetic heart. Methods and Results: Cardiac tissue were collected from type-2 diabetic individuals undergoing cardiac surgery showed marked upregulation of miR-320, which was associated with downregulation of its direct target pro-survival insulin growth factor-1 (IGF-1) and anti-apoptotic protein Bcl-2. Analysis of cardiac tissue samples collected from type 2 diabetic mice (BKS.Cg-m+/+Leprdb/J) every 4wks, from 8 to 32wks of age showed activation of miR-320 and downregulation of IGF-1 at the later stages of diabetes. To determine if therapeutic knockdown of miR-320 is beneficial, high glucose cultured adult cardiomyocytes were treated with either locked nucleic acid (LNA) anti-precursor (pre)-miR-320 or scrambled (Scr) sequence. Results showed that LNA-anti-pre-320 significantly restored IGF-1 expression and reduced apoptotic cells death (3.1±05 in Scr vs 1.3±0.6 in LNA-anti-pre-320, P<0.01). Finally, to confirm if the effect can be translated in vivo , 24 weeks old type 2 diabetic mice with established systolic dysfunction were injected with LNA-anti-pre-320 once a week for 4wks. Echocardiography confirmed significant restoration of diastolic function and partial restoration of systolic function. Molecular analysis showed marked reduction in miR-320 expression, which was associated with recovery of IGF-1 and Bcl-2. Further, histological analysis confirmed improved angiogenesis and reduced fibrosis in the LNA-anti-pre-320 treated group. Conclusion: miR-320 is a late responding miRNA that aggravates apoptosis and cardiac dysfunction in diabetic heart, and that therapeutic knockdown of miR-320 is beneficial in partially restoring the deteriorated cardiac function.

The majority of the conventional techniques that are utilized for investigating the pathogenesis of cardiovascular disease in preclinical animal models do not permit microlevel assessment of in situ cardiomyocyte and microvascular functions. Therefore, it has been difficult to establish whether cardiac dysfunction in complex multiorgan disease states, such as heart failure with preserved ejection fraction and pulmonary hypertension, have their origins in microvascular dysfunction or rather in the cardiomyocyte. Herein, we describe our approach of utilizing synchrotron radiation microangiography to, first, ascertain whether the growth hormone secretagogue (GHS) hexarelin is a vasodilator in the coronary circulation of normal and anesthetized Sprague-Dawley rats, and next investigate if hexarelin is able to prevent the pathogenesis of right ventricle (RV) dysfunction in pulmonary hypertension in the sugen chronic hypoxia model rat. We show that acute hexarelin administration evokes coronary microvascular dilation through GHS-receptor 1a and nitric oxide, and through endothelium-derived hyperpolarization. Previous work indicated that chronic exogenous administration of ghrelin largely prevented the pathogenesis of pulmonary hypertension in chronic hypoxia and in monocrotaline models. Unexpectedly, chronic hexarelin administration prior to sugen chronic hypoxia did not prevent RV hypertrophy or RV cardiomyocyte relaxation impairment. Small-angle X-ray scattering revealed that super relaxed myosin filaments contributed to diastolic dysfunction, and that length-dependent activation might contribute to sustained contractility of the RV. Thus, synchrotron-based imaging approaches can reveal novel insights into cardiac and coronary functions in vivo.

Increased cardiac sympathetic nerve activity in type 2 diabetes mellitus (DM) suggests impaired autonomic control of the heart. However, the central regions that contribute to the autonomic cardiac pathologies in type 2 DM are unknown. Therefore, we tested the hypothesis that neuronal activation would be increased in central sympathoregulatory areas in a pre-clinical type 2 DM animal model. Immunohistochemistry in 20-week-old male Zucker diabetic fatty (ZDF) rats revealed an increased number of neurones expressing ΔFosB (a marker of chronic neuronal activation) in the intermediolateral column (IML) of the spinal cord in DM compared to non-diabetic (non-DM) rats (P < 0.05). Rostral ventrolateral medulla (RVLM) neurones activate IML neurones and receive inputs from the hypothalamic paraventricular nucleus (PVN), as well as the nucleus tractus solitarius (NTS) and area postrema (AP), in the brainstem. We observed more ΔFosB-positive noradrenergic RVLM neurones (P < 0.001) and corticotrophin-releasing hormone PVN neurones (P < 0.05) in DM compared to non-DM rats. More ΔFosB-positive neurones were also observed in the NTS (P < 0.05) and AP (P < 0.01) of DM rats compared to non-DM rats. Finally, because DM ZDF rats are obese, we also expected increased activation of pro-opiomelanocortin (POMC) arcuate nucleus (ARC) neurones in DM rats; however, fewer ΔFosB-positive POMC ARC neurones were observed in DM compared to non-DM rats (P < 0.01). In conclusion, increased neuronal activation in the IML of type 2 DM ZDF rats might be driven by RVLM neurones that are possibly activated by PVN, NTS and AP inputs. Elucidating the contribution of central sympathoexcitatory drive in type 2 DM might improve the effectiveness of pharmacotherapies for diabetic heart disease.

Acetylcholine (ACh) plays a crucial role in the function of the heart. Recent evidence suggests that cardiomyocytes possess a non-neuronal cholinergic system (NNCS) that comprises of choline acetyltransferase (ChAT), choline transporter 1 (CHT1), vesicular acetylcholine transporter (VAChT), acetylcholinesterase (AChE) and type-2 muscarinic ACh receptors (M2AChR) to synthesize, release, degrade ACh as well as for ACh to transduce a signal. NNCS is linked to cardiac cell survival, angiogenesis and glucose metabolism. Impairment of these functions are hallmarks of diabetic heart disease (DHD). The role of the NNCS in DHD is unknown. The aim of this study was to examine the effect of diabetes on cardiac NNCS and determine if activation of cardiac NNCS is beneficial to the diabetic heart. Ventricular samples from type-2 diabetic humans and db/db mice were used to measure the expression pattern of NNCS components (ChAT, CHT1, VAChT, AChE and M2AChR) and glucose transporter-4 (GLUT-4) by western blot analysis. To determine the function of the cardiac NNCS in the diabetic heart, a db/db mouse model with cardiac-specific overexpression of ChAT gene was generated (db/db-ChAT-tg). Animals were followed up serially and samples collected at different time points for molecular and histological analysis of cardiac NNCS components and prosurvival and proangiogenic signaling pathways. Immunoblot analysis revealed alterations in the components of cardiac NNCS and GLUT-4 in the type-2 diabetic human and db/db mouse hearts. Interestingly, the dysregulation of cardiac NNCS was followed by the downregulation of GLUT-4 in the db/db mouse heart. Db/db-ChAT-tg mice exhibited preserved cardiac and vascular function in comparison to db/db mice. The improved function was associated with increased cardiac ACh and glucose content, sustained angiogenesis and reduced fibrosis. These beneficial effects were associated with upregulation of the PI3K/Akt/HIF1α signaling pathway, and increased expression of its downstream targets—GLUT-4 and VEGF-A. We provide the first evidence for dysregulation of the cardiac NNCS in DHD. Increased cardiac ACh is beneficial and a potential new therapeutic strategy to prevent or delay the development of DHD.

Pulmonary hypertension (PH) causes cardiac hypertrophy in the right ventricle (RV) and eventually leads to RV failure due to persistently elevated ventricular afterload. We hypothesized that the mechanical stress on the RV associated with increased afterload impairs vasodilator function of the right coronary artery (RCA) in PH. Coronary vascular response was assessed using microangiography with synchrotron radiation (SR) in two well-established PH rat models, monocrotaline injection or the combined exposure to chronic hypoxia and vascular endothelial growth factor receptor blockade with Su5416 (SuHx model). In the SuHx model, the effect of the treatment with the nonselective endothelin-1 receptor antagonist (ERA), macitentan, was also examined. Myocardial viability was determined in SuHx model rats, using 18F-FDG Positron emission tomography (PET) and magnetic resonance imaging (MRI). Endothelium-dependent and endothelium-independent vasodilator responses were significantly attenuated in the medium and small arteries of severe PH rats. ERA treatment significantly improved RCA vascular function compared with the untreated group. ERA treatment improved both the decrease in ejection fraction and the increased glucose uptake, and reduced RV remodeling. In addition, the upregulation of inflammatory genes in the RV was almost suppressed by ERA treatment. We found impairment of vasodilator responses in the RCA of severe PH rat models. Endothelin-1 activation in the RCA plays a major role in impaired vascular function in PH rats and is partially restored by ERA treatment. Treatment of PH with ERA may improve RV function in part by indirectly attenuating right heart afterload and in part by associated improvements in right coronary endothelial function.NEW & NOTEWORTHY We demonstrated for the first time the impairment of vascular responses in the right coronary artery (RCA) of the dysfunctional right heart in pulmonary hypertensive rats in vivo. Treatment with an endothelin-1 receptor antagonist ameliorated vascular dysfunction in the RCA, enabled tissue remodeling of the right heart, and improved cardiac function. Our results suggest that impaired RCA function might also contribute to the early progression to heart failure in patients with severe pulmonary arterial hypertension (PAH). The endothelium of the coronary vasculature might be considered as a potential target in treatments to prevent heart failure in severe patients with PAH.

Obesity is a risk factor for coronavirus disease 2019 (COVID-19) infection, the prevalence of obese individuals admitted with COVID-19 ranging between 30 and 60%. Herein we determined whether early changes in microRNAs (miRNAs) could be the underlying molecular mechanism increasing the risk of obese individuals to COVID-19 infection. Quantitative real-time PCR analysis of plasma samples for circulating miRNAs showed a significant upregulation of miR-200c and a small increase in miR-let-7b obese individuals. This was associated with significant downregulation of angiotensin-converting enzyme 2 (ACE2). Both the miRNAs are the direct targets of ACE2, the specific functional receptor for severe acute respiratory syndrome coronavirus 2. Correlation analysis confirmed a significant negative correlation between ACE2 and both the miRNAs. Recent studies showed that despite being the functional receptor, inhibition/downregulation of ACE2 did not reduce the severity of COVID-19 infection. In contrast, increased angiotensin II following inhibition of ACE2 may increase the severity of the disease. Taken together, our novel results identify that upregulation of miR-200c may increase the susceptibility of obese individuals to COVID-19. Considering miRNA are the earliest molecular regulators, circulating miR-200c could be a potential biomarker in the early identification of those at the risk of severe COVID-19.

Obesity is a risk factor for coronavirus disease 2019 (COVID-19) infection, with studies demonstrating the prevalence of individuals with obesity admitted with COVID-19 ranging between 30 and 60%. We determined whether early changes in microRNAs (miRNAs) are associated with dysregulation of angiotensin-converting enzyme 2 (ACE2), the specific functional receptor for severe acute respiratory syndrome coronavirus 2. ACE2 is a membrane-bound enzyme that catalyzes the conversion of angiotensin II to angiotensin 1-7 the latter having cardioprotective and vasorelaxation effects. Quantitative real-time PCR analysis of plasma samples for circulating miRNAs showed upregulation of miR-200c and miR-let-7b in otherwise healthy individuals with obesity. This was associated with significant downregulation of ACE2, a direct target for both miRNAs, in individuals with obesity. Correlation analysis confirmed a significant negative correlation between ACE2 and both the miRNAs. Studies showed that despite being the functional receptor, inhibition/downregulation of ACE2 did not reduce the severity of COVID-19 infection. In contrast, increased angiotensin II following inhibition of ACE2 may increase the severity of the disease. Taken together, our novel results identify that upregulation of miR-200c may increase the susceptibility of individuals with obesity to COVID-19. Considering miRNA are the earliest molecular regulators, the level of circulating miR-200c could be a potential biomarker in the early identification of those at the risk of severe COVID-19.

Biomedical micro-CT and micro-angiography systems were developed as a cost effective mode for large human lung specimen imaging and intravital small animal imaging, respectively using 36M-pixel and 22M-pixel digital single-lens reflex cameras. An important benefit is that scientific grade cameras for biomedical x-ray imaging are much more expensive than consumer-grade cameras. During the past decade, advances in image sensor technology for consumer appliances have spurred the development of biomedical x-ray imaging systems using commercial digital single-lens reflex cameras fitted with high megapixel CMOS image sensors. The biomedical micro-CT system is highly specialized for visualization of the whole secondary pulmonary lobule in a large human lung specimen. The secondary pulmonary lobule, a fundamental unit of the lung structure, reproduces the lung in miniature. The micro-CT field of view is 40.6-mm-wide × 15.1 mm high with 3.07 μm pixel size. The micro-angiography system was developed for in vivo visualization of coronary, cerebral, and pulmonary arteries in rats and mice with spatial resolution in the micrometer range and temporal resolution in the millisecond range. Furthermore, synchrotron radiation has proved to be a powerful high-resolution and real-time imaging tool. Micro-CT and micro-angiography systems using single lens reflex cameras and synchrotron radiation respectively provide benefits of practical high-resolution wide-field and high-resolution high-speed performance.

Rationale: Diabetic heart disease (DHD) is a debilitating manifestation of type 2 diabetes mellitus. Exercise has been proposed as a potential therapy for DHD, although the effectiveness of exercise in preventing or reversing the progression of DHD remains controversial. Cardiac function is critically dependent on the preservation of coronary vascular function. Objective: We aimed to elucidate the effectiveness and mechanisms by which exercise facilitates coronary and cardiac-protection during the onset and progression of DHD. Methods and Results: Diabetic db/db and nondiabetic mice, with or without underlying cardiac dysfunction (16 and 8 weeks old, respectively) were subjected to either moderate-intensity exercise or high-intensity exercise for 8 weeks. Subsequently, synchrotron microangiography, immunohistochemistry, Western blot, and real-time polymerase chain reaction were used to assess time-dependent changes in cardiac and coronary structure and function associated with diabetes mellitus and exercise and determine whether these changes reflect the observed changes in cardiac-enriched and vascular-enriched microRNAs (miRNAs). We show that, if exercise is initiated from 8 weeks of age, both moderate-intensity exercise and high-intensity exercise prevented the onset of coronary and cardiac dysfunction, apoptosis, fibrosis, microvascular rarefaction, and disruption of miRNA signaling, as seen in the nonexercised diabetic mice. Conversely, the cardiovascular benefits of moderate-intensity exercise were absent if the exercise was initiated after the diabetic mice had already established cardiac dysfunction (ie, from 16 weeks of age). The experimental silencing or upregulation of miRNA-126 activity suggests the mechanism underpinning the cardiovascular benefits of exercise were mediated, at least in part, through tissue-specific miRNAs. Conclusions: Our findings provide the first experimental evidence for the critical importance of early exercise intervention in ameliorating the onset and progression of DHD. Our results also suggest that the beneficial effects of exercise are mediated through the normalization of cardiovascular-enriched miRNAs, which are dysregulated in DHD.