Atherosclerotic cardiovascular disease remains the leading cause of morbidity and mortality worldwide. Atherosclerosis develops over several decades and is mediated by a complex interplay of cellular mechanisms that drive a chronic inflammatory milieu and cell-to-cell interactions between endothelial cells, smooth muscle cells and macrophages that promote plaque development and progression. While there has been significant therapeutic advancement, there remains a gap where novel therapeutic approaches can complement current therapies to provide a holistic approach for treating atherosclerosis to orchestrate the regulation of complex signalling networks across multiple cell types and different stages of disease progression. MicroRNAs (miRNAs) are emerging as important post-transcriptional regulators of a suite of molecular signalling pathways and pathophysiological cellular effects. Furthermore, circulating miRNAs have emerged as a new class of disease biomarkers to better inform clinical diagnosis and provide new avenues for personalised therapies. This review focusses on recent insights into the potential role of miRNAs both as therapeutic targets in the regulation of the most influential processes that govern atherosclerosis and as clinical biomarkers that may be reflective of disease severity, highlighting the potential theranostic (therapeutic and diagnostic) properties of miRNAs in the management of cardiovascular disease.

Angiogenesis, the process of forming new blood vessels, is crucial in the physiological response to ischemia, though it can be detrimental as part of inflammation and tumorigenesis. We have previously shown that high-density lipoproteins (HDL) modulate angiogenesis in a context-specific manner via distinct classical signalling pathways, enhancing hypoxia-induced angiogenesis while suppressing inflammatory-driven angiogenesis. Whether additional novel targets exist to account for these effects are unknown. A microarray approach identified two novel genes, cyclic-adenosine-monophosphate-response-element-binding protein 3 regulatory factor (CREBRF) and tripartite motif-containing protein 2 (TRIM2) that were upregulated by reconstituted HDL (rHDL). We measured CREBRF and TRIM2 expression in human coronary artery endothelial cells following incubation with rHDL and exposure to either hypoxia or an inflammatory stimulus. We found that CREBRF and TRIM2 mRNA were significantly upregulated by rHDL, particularly in response to its phospholipid component 1-palmitoyl-2-linoleoyl-phosphatidylcholine, however, protein expression was not significantly altered. Knockdown of TRIM2 impaired endothelial cell tubulogenesis in vitro in both hypoxia and inflammation, implying a necessary role in angiogenesis. Furthermore, TRIM2 knockdown attenuated rHDL-induced tubule formation in hypoxia, suggesting that it is important in mediating the pro-angiogenic action of rHDL. Our study has implications for understanding the regulation of angiogenesis in both of these pathophysiological contexts by HDL.

Diabetes mellitus is estimated to affect up to 700 million people by the year 2045, contributing to an immense health and economic burden. People living with diabetes have a higher risk of developing numerous debilitating vascular complications, leading to an increased need for medical care, a reduced quality of life and increased risk of early death. Current treatments are not satisfactory for many patients who suffer from impaired angiogenesis in response to ischaemia, increasing their risk of ischaemic cardiovascular conditions. These vascular pathologies are characterised by endothelial dysfunction and abnormal angiogenesis, amongst a host of impaired signaling pathways. Therapeutic stimulation of angiogenesis holds promise for the treatment of diabetic vascular complications that stem from impaired ischaemic responses. However, despite significant effort and research, there are no established therapies that directly stimulate angiogenesis to improve ischaemic complications such as ischaemic heart disease and peripheral artery disease, highlighting the immense unmet need. However, despite significant effort and research, there are no established therapies that directly stimulate angiogenesis in a clinical setting, highlighting the immense unmet need. MicroRNAs (miRNAs) are emerging as powerful targets for multifaceted diseases including diabetes and cardiovascular disease. This review highlights the potential role of microRNAs as therapeutic targets for rescuing diabetes-impaired angiogenesis, with a specific focus on miR-181c, which we have previously identified as an important angiogenic regulator. Here we summarise the pathways currently known to be regulated by miR-181c, which include the classical angiogenesis pathways that are dysregulated in diabetes, mitochondrial function and axonal guidance, and describe how these relate both directly and indirectly to angiogenesis. The pleiotropic actions of miR-181c across multiple key angiogenic signaling pathways and critical cellular processes highlight its therapeutic potential as a novel target for treating diabetic vascular complications.

Circadian disruption increases the development of cardiovascular disease and diabetes. We found that circadian disruption causes glucose intolerance, cardiac fibrosis and adipocyte tissue dysfunction in male sand rats, Psammomys obesus. Whether these effects occur in female P. obesus is unknown. Male and female P. obesus were fed a high energy diet and exposed to a neutral (12 light:12 dark, control) or short (5 light:19 dark, circadian disruption) photoperiod for 20 weeks. Circadian disruption impaired glucose tolerance in males but not females. It also increased cardiac perivascular fibrosis and cardiac expression of inflammatory marker Ccl2 in males, with no effect in females. Females had reduced proapoptotic Bax mRNA and cardiac Myh7:Myh6 hypertrophy ratio. Cardiac protection in females occurred despite reductions in the clock gene Per2. Circadian disruption increased adipocyte hypertrophy in both males and females. This was concomitant with a reduction in adipocyte differentiation markers Pparg and Cebpa in males and females, respectively. Circadian disruption increased visceral adipose expression of inflammatory mediators Ccl2, Tgfb1 and Cd68 and reduced browning marker Ucp1 in males. However, these changes were not observed in females. Collectively, our study show that sex differentially influences the effects of circadian disruption on glucose tolerance, cardiac function and adipose tissue dysfunction.

BACKGROUND: Impaired angiogenic responses to ischemia underlie diabetic vascular complications. Reconstituted high-density lipoproteins (rHDLs) have proangiogenic effects in diabetes. The PDK4 (pyruvate dehydrogenase kinase 4)/PDC (pyruvate dehydrogenase complex) axis is an oxygen-conserving mechanism that preserves endothelial cell function in hypoxia. We aimed to determine the role of the PDK4/PDC axis in angiogenesis, the effect of diabetes on its regulation in response to ischemia, and the proangiogenic properties of rHDL. METHODS: Expression of PDK4 and phosphorylated PDC (pPDC) were measured in PBS- or rHDL-treated wounds of nondiabetic and streptozotocin-induced diabetic mice and PBS- or rHDL-treated endothelial cells exposed to glucose and hypoxia. The importance of PDK4 in the action of rHDL was determined by siRNA knockdown in vitro and PDK4 inhibitor in vivo. Chromatin immunoprecipitation assay was performed to identify the mechanism for PDK4 induction by rHDL. RESULTS: PDK4 and pPDC were elevated early (24 hours) post-induction of wound ischemia in nondiabetic wounds, which did not occur in diabetic mice. Topical rHDL rescued this impairment, enhancing PDK4 (68%; P =0.0041) and pPDC (165%; P =0.029) in diabetic wounds. Wound neovascularization (62%; P <0.05) and closure (154%; P <0.001) were increased in diabetic rHDL-treated wounds. In vitro, PDK4 and pPDC levels were increased with hypoxia (65%, P =0.043 and 64%, P =0.026, respectively). High glucose did not elicit a further stepwise induction in PDK4/pPDC, with aberrant increases in mitochondrial respiration (19%; P =0.026), and impaired angiogenic functions. Importantly, rHDL increased PDK4 and pPDC 2-fold, returning mitochondrial respiration and angiogenic functions to normal glucose levels. PDK4 inhibition ameliorated the proangiogenic effects of rHDL. rHDL increased FOXO1 (forkhead box O1) binding to the PDK4 promoter and suppressed FOXO1 phosphorylation, presenting FOXO1 as a mechanism for rHDL-mediated induction of PDK4. CONCLUSIONS: The PDK4/PDC axis response to ischemia is impaired in diabetes and is important for the proangiogenic effects of rHDL.