Growth In Metabolic Syndrome Research Articles

Myeloid Derived miR‐21 Influences Coronary Collateral Growth in Metabolic Syndrome

Well‐developed coronary collaterals prove to be highly beneficial in salvaging ischemic myocardium, preserving cardiac function, and improving patient outcome post‐occlusion. However, this process is impaired in patients with metabolic syndrome. A more complete understanding of the underlying mechanism, cell types, and genes causing the impaired coronary collateral growth (CCG) response have yet to be elucidated. Better understanding of the process of CCG will lead to potential therapeutics to induce CCG and circumvent ischemic injury. MicroRNA‐21 (miR‐21) has been studied in cancer, with its central role in the down‐regulation of pro‐apoptotic genes leading to sustained cellular proliferation. However, miR‐21 has recently been reported to modulate inflammation after myocardial infarction (MI) and to play a role in the development of atherosclerosis. Furthermore, miR‐21 has been shown to be involved in macrophage polarization, where it generally serves to reduce inflammatory markers and promote anti‐inflammatory markers. In addition, miR‐21 dysregulation has been rooted in the diabetic population wherein lies a systemic inflammatory state. In this study, we investigated the role of miR‐21 during CCG in diabetes mellitus, which is a major risk factor for the development of cardiovascular disease. Our preliminary data suggested that down‐regulating miR‐21 rescues the impaired CCG in diet‐induced diabetic animals. Given that miR‐21 is highly abundant in immune cells, we sought to further study if miR‐21 regulates CCG by modulating the inflammatory response. While macrophages have been extensively studied during MI events or in atherosclerosis conditions, their roles during CCG are not well‐defined. Thus, we utilize a myeloid specific (Lyz2) miR‐21 knockout to investigate the impact of miR‐21 in macrophages on CCG within the context of diabetes. First, colony stimulating factor‐1 directed bone marrow derived macrophages from miR‐21 Lyz2‐knockout mice were subjected to high glucose (4.5 g/L) and / or hypoxia (3% oxygen) to mimic diabetic conditions. Interestingly, the knockout macrophages have differences in their spindle like projections even before beginning treatment. This possibly suggests greater baseline activation compared to the control. We also observe morphological differences after treatment. The expression profile will give more accurate results. In vivo, CCG is blunted in the miR‐21 Lyz2‐knockout animals subjected to the repetitive ischemia protocol. This suggests that miR‐21 in the myeloid lineage is critical for CCG in healthy non‐diabetic mice. Further studies of CCG in the miR‐21 Lyz2‐knockout mice fed high fat and high sugar diet will give us more insight into the mechanisms underlying impaired CCG in diabetes.Support or Funding InformationThe research is funded by National Institutes of Health grant 2R01HL103227‐05 (Zhang, Yin), 1R01HL135110‐01 (WMC, LY), 1 R01 HL137008‐01A1 (LY), 1R15HL115540‐01 (LY) and 14BGIA18770028 from American Heart Association.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Impact of MicroRNA‐21 Knockout on Coronary Collateral Growth in Metabolic Syndrome

A highly‐functional coronary collateral circulation proves beneficial during acute coronary occlusions such as myocardial infarctions, but the molecular drivers of coronary collateral growth (CCG) have yet to be completely understood. Our previous work shows that CCG is impaired in Zucker Obese Fatty (ZOF) rats (a rat model of metabolic syndrome). These results are consistent with what is seen in human patients with metabolic syndrome. Our gene expression profiling of rat hearts during repetitive ischemia (RI) in ZOF rats and Zucker lean (ZLN) rats showed microRNA‐21 (miR‐21) to be one of the most upregulated genes, and was found to be significantly increased in ZOF rat hearts compared to ZLN rat hearts. This expression was also validated by quantitative RT‐PCR. Interestingly, miR‐21 was reported to play a critical role during CCG in a JCR rats (another rat model of metabolic syndrome) where treatment with a miR‐21 antagomir improved RI‐induced CCG. Since miR‐21 antagomirs may target any metabolically active tissue such as liver, intestine and heart, it is unknown how the knockdown of miR‐21 ameliorate CCG. The miR‐21 knockout (KO) mouse will help us to investigate this question. First, we mapped out where miR‐21 expression occurs by LacZ staining in a miR‐21 mice with a LacZ gene knockin. Staining has shown that there is an abundance of miR‐21 expressed in the heart, aorta, and muscle vasculature of mice. We then investigated the impact that genetic ablation of miR‐21 has on coronary collateral formation in a mouse model of metabolic syndrome induced by a high fat high sugar (HFHS) diet. A pneumatic balloon is surgically placed over the left anterior descending artery (LAD), and after a recovery period the mice underwent RI protocol. CCG was measured by myocardial blood flow with contrast echocardiography and by collateral numbers using micro‐computed tomography (microCT). Interestingly, the right coronary artery (RCA) of miR‐21 KO mice were poorly perfused, possibly suggesting miR‐21 is a player in coronary artery development or potentially in the development of atherosclerotic lesions. Impaired CCG of mice on HFHS diet was restored by miR‐21 KO. Moreover, miR‐21 expression levels were increased in induced vascular progenitor and endothelial cells subjected to high fat and high glucose treatment. miR‐21 expression was also increased in diabetic (db/db) and obese (ob/ob) mice. These data suggest that miR‐21 is a key player in the cardiovascular system in metabolic syndrome and is likely to be involved in the impairment of CCG in metabolic syndrome.Support or Funding InformationThe research is funded by National Institutes of Health grant 2R01HL103227‐05( Zhang, Yin), 1R01HL135110‐01 (WMC, LY), 1 R01 HL137008‐01A1 (LY), 1R15HL115540‐01 (LY) and 14BGIA18770028 from American Heart Association.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Elevated 20-HETE impairs coronary collateral growth in metabolic syndrome via endothelial dysfunction.

Coronary collateral growth (CCG) is impaired in metabolic syndrome (MetS). microRNA-145 (miR-145-Adv) delivery to our rat model of MetS (JCR) completely restored and neutrophil depletion significantly improved CCG. We determined whether low endogenous levels of miR-145 in MetS allowed for elevated production of 20-hydroxyeicosatetraenoic acid (20-HETE), which, in turn, resulted in excessive neutrophil accumulation and endothelial dysfunction leading to impaired CCG. Rats underwent 0-9 days of repetitive ischemia (RI). RI-induced cardiac CYP4F (neutrophil-specific 20-HETE synthase) expression and 20-HETE levels were increased (4-fold) in JCR vs. normal rats. miR-145-Adv and 20-HETE antagonists abolished and neutrophil depletion (blocking antibodies) reduced (~60%) RI-induced increases in CYP4F expression and 20-HETE production in JCR rats. Impaired CCG in JCR rats (collateral-dependent blood flow using microspheres) was completely restored by 20-HETE antagonists [collateral-dependent zone (CZ)/normal zone (NZ) flow ratio was 0.76 ± 0.07 in JCR + 20-SOLA, 0.84 ± 0.05 in JCR + 20-HEDGE vs. 0.11 ± 0.02 in JCR vs. 0.84 ± 0.03 in normal rats]. In JCR rats, elevated 20-HETE was associated with excessive expression of endothelial adhesion molecules and neutrophil infiltration, which were reversed by miR-145-Adv. Endothelium-dependent vasodilation of coronary arteries, endothelial nitric oxide synthase (eNOS) Ser1179 phosphorylation, eNOS-dependent NO·- production and endothelial cell survival were compromised in JCR rats. These parameters of endothelial dysfunction were completely reversed by 20-HETE antagonism or miR-145-Adv delivery, whereas neutrophil depletion resulted in partial reversal (~70%). We conclude that low miR-145 in MetS allows for increased 20-HETE, mainly from neutrophils, which compromises endothelial cell survival and function leading to impaired CCG. 20-HETE antagonists could provide viable therapy for restoration of CCG in MetS.NEW & NOTEWORTHY Elevated 20-hydroxyeicosatetraenoic acid (20-HETE) impairs coronary collateral growth (CCG) in metabolic syndrome by eliciting endothelial dysfunction and apoptosis via excessive neutrophil infiltration. 20-HETE antagonists completely restore coronary collateral growth in metabolic syndrome. microRNA-145 (miR-145) is an upstream regulator of 20-HETE production in metabolic syndrome; low expression of miR-145 in metabolic syndrome promotes elevated production of 20-HETE.

MiR-21-mediated decreased neutrophil apoptosis is a determinant of impaired coronary collateral growth in metabolic syndrome.

Coronary collateral growth (CCG) is impaired in metabolic syndrome. microRNA-21 (miR-21) is a proproliferative and antiapoptotic miR, which we showed to be elevated in metabolic syndrome. Here we investigate whether impaired CCG in metabolic syndrome involved miR-21-mediated aberrant apoptosis. Normal Sprague-Dawley (SD) and metabolic syndrome [J. C. Russel (JCR)] rats underwent transient, repetitive coronary artery occlusion [repetitive ischemia (RI)]. Antiapoptotic Bcl-2, phospho-Bad, and Bcl-2/Bax dimers were increased on days 6 and 9 RI, and proapoptotic Bax and Bax/Bax dimers and cytochrome-c release concurrently decreased in JCR versus SD rats. Active caspases were decreased in JCR versus SD rats (~50%). Neutrophils increased transiently on day 3 RI in the collateral-dependent zone of SD rats but remained elevated in JCR rats, paralleling miR-21 expression. miR-21 downregulation by anti-miR-21 induced neutrophil apoptosis and decreased Bcl-2 and Bcl-2/Bax dimers (~75%) while increasing Bax/Bax dimers, cytochrome-c release, and caspase activation (~70, 400, and 400%). Anti-miR-21 also improved CCG in JCR rats (~60%). Preventing neutrophil infiltration with blocking antibodies resulted in equivalent CCG recovery, confirming a major role for deregulated neutrophil apoptosis in CCG impairment. Neutrophil and miR-21-dependent CCG inhibition was in significant part mediated by increased oxidative stress. We conclude that neutrophil apoptosis is integral to normal CCG and that inappropriate prolonged miR-21-mediated survival of neutrophils plays a major role in impaired CCG, in part via oxidative stress generation.

MiR‐21 normalizes vascular smooth muscle proliferation and improves coronary collateral growth in metabolic syndrome

Inadequate cell proliferation is considered a major causative factor for impaired coronary collateral growth (CCG). Proangiogenic growth factors (GFs) stimulate cell proliferation, but their administration does not promote CCG in patients. These GFs are increased in patients with metabolic syndrome and in animal models, where CCG is impaired. Here, we investigated whether excessive cell proliferation underlies impaired CCG in metabolic syndrome. Normal [Sprague-Dawley (SD)] and metabolic syndrome [James C. Russell (JCR)] rats underwent repetitive ischemia (RI; transient, repetitive coronary artery occlusion and myocardial ischemia). We have shown that CCG was maximal at d 9 of RI in SD rats but did not occur in JCR rats. The increase in cell proliferation (PCNA, Ki-67, cyclin A, phospho- cdc2, p21Waf, p27Kip) was transient (∼4-fold, d 3 RI) in SD rats but greater and sustained in JCR rats (∼8- to 6-fold, d 3-9 RI). In JCR rats, this was associated with increased and sustained miR-21 expression and accumulation of proliferating synthetic vascular smooth muscle cells in the lumen of small arterioles, which failed to undergo outward expansion. Administration of anti-miR-21 blocked RI-induced cell proliferation and significantly improved CCG in JCR rats (∼60%). miR-21-dependent excessive cell proliferation in the later stages of collateral remodeling correlates with impaired CCG in metabolic syndrome.

Corruption of coronary collateral growth in metabolic syndrome: Role of oxidative stress

The myocardium adapts to ischemic insults in a variety of ways. One adaptation is the phenomenon of acute preconditioning, which can greatly ameliorate ischemic damage. However, this effect wanes within a few hours and does not confer chronic protection. A more chronic adaptation is the so-called second window of preconditioning, which enables protection for a few days. The most potent adaptation invoked by the myocardium to minimize the effects of ischemia is the growth of blood vessels in the heart, angiogenesis and arteriogenesis (collateral growth), which prevent the development of ischemia by enabling flow to a jeopardized region of the heart. This brief review examines the mechanisms underlying angiogenesis and arteriogenesis in the heart. The concept of a redox window, which is an optimal redox state for vascular growth, is discussed along with signaling mechanisms invoked by reactive oxygen species that are stimulated during ischemia-reperfusion. Finally, the review discusses of some of the pathologies, especially the metabolic syndrome, that negatively affect collateral growth through the corruption of redox signaling processes.

Redox-sensitive Akt and Src regulate coronary collateral growth in metabolic syndrome

We have recently shown that the inability of repetitive ischemia (RI) to activate p38 MAPK (p38) and Akt in metabolic syndrome [JCR:LA-cp (JCR)] rats was associated with impaired coronary collateral growth (CCG). Furthermore, Akt and p38 activation correlated with optimal O(2)(-). levels and were altered in JCR rats, and redox-sensitive p38 activation was required for CCG. Here, we determined whether the activation of Src, a possible upstream regulator, was altered in JCR rats and whether redox-dependent Src and Akt activation were required for CCG. CCG was assessed by myocardial blood flow (microspheres) and kinase activation was assessed by Western blot analysis in the normal zone and collateral-dependent zone (CZ). RI induced Src activation (approximately 3-fold) in healthy [Wistar-Kyoto (WKY)] animals but not in JCR animals. Akt inhibition decreased (approximately 50%), and Src inhibition blocked RI-induced CCG in WKY rats. Src inhibition decreased p38 and Akt activation. Myocardial oxidative stress (O(2)(-). and oxidized/reduced thiols) was measured quantitatively (X-band electron paramagnetic resonance). An antioxidant, apocynin, reduced RI-induced oxidative stress in JCR rats to levels induced by RI in WKY rats versus the reduction in WKY rats to very low levels. This resulted in a significant restoration of p38 (approximately 80%), Akt (approximately 65%), and Src (approximately 90%) activation in JCR rats but decreased the activation in WKY rats (p38: approximately 45%, Akt: approximately 65%, and Src: approximately 100%), correlating with reduced CZ flow in WKY rats (approximately 70%), but significantly restored CZ flow in JCR rats (approximately 75%). We conclude that 1) Akt and Src are required for CCG, 2) Src is a redox-sensitive upstream regulator of RI-induced p38 and Akt activation, and 3) optimal oxidative stress levels are required for RI-induced p38, Akt, and Src activation and CCG.