Auxiliary roles of nardilysin in the early diagnosis of acute coronary syndrome: a prospective cohort study, the Nardi-ACS study

Acute coronary syndrome (ACS) includes myocardial infarction (MI) and unstable angina (UA). MI is defined by elevated necrosis markers, preferably high-sensitivity cardiac troponins (hs-cTn). However, it takes hours for cTn to become elevated after coronary occlusion; therefore, difficulties are associated with diagnosing early post-onset MI or UA. The aim of this prospective cohort study was to examine the diagnostic ability of serum nardilysin (NRDC) for the early detection of ACS. This study consisted of two sequential cohorts, the Phase I cohort, 435 patients presenting to the emergency room (ER) with chest pain, and the Phase II cohort, 486 patients with chest pain who underwent coronary angiography. The final diagnosis was ACS in 155 out of 435 patients (35.6%) in the phase I and 418 out of 486 (86.0%) in the phase II cohort. Among 680 patients who presented within 24 h of onset, 466 patients (68.5%) were diagnosed with ACS. Serum NRDC levels were significantly higher in patients with ACS than in those without ACS. The sensitivity of NRDC in patients who presented within 6 h after the onset was higher than that of hsTnI, and the AUC of NRDC within 1 h of the onset was higher than that of hsTnI (0.718 versus 0.633). Among hsTnI-negative patients (300 of 680 patients: 44.1%), 136 of whom (45.3%) were diagnosed with ACS, the sensitivity and the NPV of NRDC were 73.5 and 65.7%, respectively. When measured in combination with hsTnI, NRDC plays auxiliary roles in the early diagnosis of ACS.

CRISPR-Cas9-guided amplification-free genomic diagnosis for familial hypercholesterolemia using nanopore sequencing

Familial hypercholesterolemia is an inherited disorder that remains underdiagnosed. Conventional genetic testing methods such as next-generation sequencing (NGS) or target PCR are based on the amplification process. Due to the efficiency limits of polymerase and ligase enzymes, these methods usually target short regions and do not detect large mutations straightforwardly. This study combined the long-read nanopore sequencing and CRISPR-Cas9 system to sequence the target DNA molecules without amplification. We originally designed and optimized the CRISPR-RNA panel to target the low-density lipoprotein receptor gene (LDLR) and proprotein convertase subtilisin/kexin type 9 gene (PCSK9) from human genomic DNA followed by nanopore sequencing. The average coverages for LDLR and PCSK9 were 106× and 420×, versus 1.2× for the background genome. Among them, continuous reads were 52x and 307x, respectively, and spanned the entire length of LDLR and PCSK9. We identified pathogenic mutations in both coding and splicing donor regions in LDLR. We also detected an 11,029 bp large deletion in another case. Furthermore, using continuous long reads generated from the benchmark experiment, we demonstrated how a false-positive 670 bp deletion caused by PCR amplification errors was easily eliminated.

KUS121, a VCP modulator, has an ameliorating effect on acute and chronic heart failure without calcium loading via maintenance of intracellular ATP levels

AIMS

As heart failure (HF) progresses, ATP levels in myocardial cells decrease, and myocardial contractility also decreases. Inotropic drugs improve myocardial contractility but increase ATP consumption, leading to poor prognosis. Kyoto University Substance 121 (KUS121) is known to selectively inhibit the ATPase activity of valosin-containing protein, maintain cellular ATP levels, and manifest cytoprotective effects in several pathological conditions. The aim of this study is to determine the therapeutic effect of KUS121 on HF models.

METHODS AND RESULTS

Cultured cell, mouse, and canine models of HF were used to examine the therapeutic effects of KUS121. The mechanism of action of KUS121 was also examined. Administration of KUS121 to a transverse aortic constriction (TAC)-induced mouse model of HF rapidly improved the left ventricular ejection fraction and improved the creatine phosphate/ATP ratio. In a canine model of high frequency-paced HF, administration of KUS121 also improved left ventricular contractility and decreased left ventricular end-diastolic pressure without increasing the heart rate. Long-term administration of KUS121 to a TAC-induced mouse model of HF suppressed cardiac hypertrophy and fibrosis. In H9C2 cells, KUS121 reduced ER stress. Finally, in experiments using primary cultured cardiomyocytes, KUS121 improved contractility and diastolic capacity without changing peak Ca2+ levels or contraction time. These effects were not accompanied by an increase in cyclic adenosine monophosphate or phosphorylation of phospholamban and ryanodine receptors.

CONCLUSIONS

KUS121 ameliorated HF by a mechanism totally different from that of conventional catecholamines. We propose that KUS121 is a promising new option for the treatment of HF.

Inhibition of microRNA-33b in humanized mice ameliorates nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) can lead to cirrhosis and hepatocellular carcinoma in their advanced stages; however, there are currently no approved therapies. Here, we show that microRNA (miR)-33b in hepatocytes is critical for the development of NASH. miR-33b is located in the intron of sterol regulatory element-binding transcription factor 1 and is abundantly expressed in humans, but absent in rodents. miR-33b knock-in (KI) mice, which have a miR-33b sequence in the same intron of sterol regulatory element-binding transcription factor 1 as humans and express miR-33b similar to humans, exhibit NASH under high-fat diet feeding. This condition is ameliorated by hepatocyte-specific miR-33b deficiency but unaffected by macrophage-specific miR-33b deficiency. Anti-miR-33b oligonucleotide improves the phenotype of NASH in miR-33b KI mice fed a Gubra Amylin NASH diet, which induces miR-33b and worsens NASH more than a high-fat diet. Anti-miR-33b treatment reduces hepatic free cholesterol and triglyceride accumulation through up-regulation of the lipid metabolism-related target genes. Furthermore, it decreases the expression of fibrosis marker genes in cultured hepatic stellate cells. Thus, inhibition of miR-33b using nucleic acid medicine is a promising treatment for NASH.

Glycogen synthase 1 targeting reveals a metabolic vulnerability in triple-negative breast cancer

BACKGROUND

Hypoxia-induced glycogen turnover is implicated in cancer proliferation and therapy resistance. Triple-negative breast cancers (TNBCs), characterized by a hypoxic tumor microenvironment, respond poorly to therapy. We studied the expression of glycogen synthase 1 (GYS1), the key regulator of glycogenesis, and other glycogen-related enzymes in primary tumors of patients with breast cancer and evaluated the impact of GYS1 downregulation in preclinical models.

METHODS

mRNA expression of GYS1 and other glycogen-related enzymes in primary breast tumors and the correlation with patient survival were studied in the METABRIC dataset (n = 1904). Immunohistochemical staining of GYS1 and glycogen was performed on a tissue microarray of primary breast cancers (n = 337). In four breast cancer cell lines and a mouse xenograft model of triple-negative breast cancer, GYS1 was downregulated using small-interfering or stably expressed short-hairpin RNAs to study the effect of downregulation on breast cancer cell proliferation, glycogen content and sensitivity to various metabolically targeted drugs.

RESULTS

High GYS1 mRNA expression was associated with poor patient overall survival (HR 1.20, P = 0.009), especially in the TNBC subgroup (HR 1.52, P = 0.014). Immunohistochemical GYS1 expression in primary breast tumors was highest in TNBCs (median H-score 80, IQR 53-121) and other Ki67-high tumors (median H-score 85, IQR 57-124) (P < 0.0001). Knockdown of GYS1 impaired proliferation of breast cancer cells, depleted glycogen stores and delayed growth of MDA-MB-231 xenografts. Knockdown of GYS1 made breast cancer cells more vulnerable to inhibition of mitochondrial proteostasis.

CONCLUSIONS

Our findings highlight GYS1 as potential therapeutic target in breast cancer, especially in TNBC and other highly proliferative subsets.

Overview of the 84th Annual Scientific Meeting of the Japanese Circulation Society - Change Practice!

Due to the COVID-19 pandemic, the 84^thAnnual Meeting of the Japanese Circulation Society (JCS) was held in a web-based format for the first time in its history as "The Week for JCS 2020" from Monday, July 27 to Sunday, August 2, 2020. All sessions, including general abstracts, were streamed live or on-demand. The main theme of the meeting was "Change Practice!" and the aim was to organize the latest findings in the field of cardiovascular medicine and discuss how to change practice. The total number of registered attendees was over 16,800, far exceeding our expectations, and many of the sessions were viewed by far more people than at conventional face-to-face scientific meetings. At this conference, the power of online information dissemination was fully demonstrated, and the evolution of online academic meetings will be a direction that cannot be reversed in the future. The meeting was completed with great success, and we express our heartfelt gratitude to all affiliates for their enormous amount of work, cooperation, and support.

microRNA-33 maintains adaptive thermogenesis via enhanced sympathetic nerve activity

Adaptive thermogenesis is essential for survival, and therefore is tightly regulated by a central neural circuit. Here, we show that microRNA (miR)-33 in the brain is indispensable for adaptive thermogenesis. Cold stress increases miR-33 levels in the hypothalamus and miR-33^−/− mice are unable to maintain body temperature in cold environments due to reduced sympathetic nerve activity and impaired brown adipose tissue (BAT) thermogenesis. Analysis of miR-33^f/f dopamine-β-hydroxylase (DBH)-Cre mice indicates the importance of miR-33 in Dbh-positive cells. Mechanistically, miR-33 deficiency upregulates gamma-aminobutyric acid (GABA)_A receptor subunit genes such as Gabrb2 and Gabra4. Knock-down of these genes in Dbh-positive neurons rescues the impaired cold-induced thermogenesis in miR-33^f/fDBH-Cre mice. Conversely, increased gene dosage of miR-33 in mice enhances thermogenesis. Thus, miR-33 in the brain contributes to maintenance of BAT thermogenesis and whole-body metabolism via enhanced sympathetic nerve tone through suppressing GABAergic inhibitory neurotransmission. This miR-33-mediated neural mechanism may serve as a physiological adaptive defense mechanism for several stresses including cold stress.

Adaptive thermogenesis is regulated by central neuronal circuits. Here, the authors show that microRNA-33 in the brain contributes to the maintenance of brown adipose tissue thermogenesis and whole-body energy balance via enhanced sympathetic nerve tone, and regulating the expression of GABAa receptor subunits.

CXCR4-Binding Positron Emission Tomography Tracers Link Monocyte Recruitment and Endothelial Injury in Murine Atherosclerosis

OBJECTIVE

vMIP-II (viral macrophage inflammatory protein 2)/vCCL2 (viral chemotactic cytokine ligand 2) binds to multiple chemokine receptors, and vMIP-II-based positron emission tomography tracer (64Cu-DOTA-vMIP-II: vMIP-II tracer) accumulates at atherosclerotic lesions in mice. Given that it would be expected to react with multiple chemokine receptors on monocytes and macrophages, we wondered if its accumulation in atherosclerosis lesion-bearing mice might correlate with overall macrophage burden or, alternatively, the pace of monocyte recruitment. Approach and Results: We employed a mouse model of atherosclerosis regression involving adenoassociated virus 8 vector encoding murine Apoe (AAV-mApoE) treatment of Apoe-/- mice where the pace of monocyte recruitment slows before macrophage burden subsequently declines. Accumulation of 64Cu-DOTA-vMIP-II at Apoe-/- plaque sites was strong but declined with AAV-mApoE-induced decline in monocyte recruitment, before macrophage burden reduced. Monocyte depletion indicated that monocytes and macrophages themselves were not the only target of the 64Cu-DOTA-vMIP-II tracer. Using fluorescence-tagged vMIP-II tracer, competitive receptor blocking with CXCR4 antagonists, endothelial-specific Cre-mediated deletion of CXCR4, CXCR4-specific tracer 64Cu-DOTA-FC131, and CXCR4 staining during disease progression and regression, we show endothelial cell expression of CXCR4 is a key target of 64Cu-DOTA-vMIP-II imaging. Expression of CXCR4 was low in nonplaque areas but strongly detected on endothelium of progressing plaques, especially on proliferating endothelium, where vascular permeability was increased and monocyte recruitment was the strongest.

CONCLUSIONS

Endothelial injury status of plaques is marked by CXCR4 expression and this injury correlates with the tendency of such plaques to recruit monocytes. Furthermore, our findings suggest positron emission tomography tracers that mark CXCR4 can be used translationally to monitor the state of plaque injury and monocyte recruitment.

Functional non-coding RNAs in vascular diseases

Recently, advances in genomic technology such as RNA sequencing and genome‐wide profiling have enabled the identification of considerable numbers of non‐coding RNAs (ncRNAs). MicroRNAs have been studied for decades, leading to the identification of those with disease‐causing and/or protective effects in vascular disease. Although other ncRNAs such as long ncRNAs have not been fully described yet, recent studies have indicated their important functions in the development of vascular diseases. Here, we summarize the current understanding of the mechanisms and functions of ncRNAs, focusing on microRNAs, circular RNAs and long ncRNAs in vascular diseases.

Lionheart LincRNA alleviates cardiac systolic dysfunction under pressure overload

Recent high-throughput approaches have revealed a vast number of transcripts with unknown functions. Many of these transcripts are long noncoding RNAs (lncRNAs), and intergenic region-derived lncRNAs are classified as long intergenic noncoding RNAs (lincRNAs). Although Myosin heavy chain 6 (Myh6) encoding primary contractile protein is down-regulated in stressed hearts, the underlying mechanisms are not fully clarified especially in terms of lincRNAs. Here, we screen upregulated lincRNAs in pressure overloaded hearts and identify a muscle-abundant lincRNA termed Lionheart. Compared with controls, deletion of the Lionheart in mice leads to decreased systolic function and a reduction in MYH6 protein levels following pressure overload. We reveal decreased MYH6 results from an interaction between Lionheart and Purine-rich element-binding protein A after pressure overload. Furthermore, human LIONHEART levels in left ventricular biopsy specimens positively correlate with cardiac systolic function. Our results demonstrate Lionheart plays a pivotal role in cardiac remodeling via regulation of MYH6.

Kuwabara et al. identify a novel long intergenic noncoding RNA (lincRNA), termed Lionheart, upregulated in pressure overloaded hearts in mice. Deleting this gene results in decreased systolic function and reduction in MYH6 protein levels following pressure overload. They demonstrate that Lionheart interacts with PURA, preventing its binding to the promoter region of Myh6 locus, leading to reduced MYH6 protein expression.

Homeobox A4 suppresses vascular remodeling by repressing YAP/TEAD transcriptional activity

The Hippo signaling pathway is involved in the pathophysiology of various cardiovascular diseases. Yes-associated protein (YAP) and transcriptional enhancer activator domain (TEAD) transcriptional factors, the main transcriptional complex of the Hippo pathway, were recently identified as modulators of phenotypic switching of vascular smooth muscle cells (VSMCs). However, the intrinsic regulator of YAP/TEAD-mediated gene expressions involved in vascular pathophysiology remains to be elucidated. Here, we identified Homeobox A4 (HOXA4) as a potent repressor of YAP/TEAD transcriptional activity using lentiviral shRNA screen. Mechanistically, HOXA4 interacts with TEADs and attenuates YAP/TEAD-mediated transcription by competing with YAP for TEAD binding. We also clarified that the expression of HOXA4 is relatively abundant in the vasculature, especially in VSMCs. In vitro experiments in human VSMCs showed HOXA4 maintains the differentiation state of VSMCs via inhibition of YAP/TEAD-induced phenotypic switching. We generated Hoxa4-deficient mice and confirmed the downregulation of smooth muscle-specific contractile genes and the exacerbation of vascular remodeling after carotid artery ligation in vivo. Our results demonstrate that HOXA4 is a repressor of VSMC phenotypic switching by inhibiting YAP/TEAD-mediated transcription.

SREBF1/MicroRNA-33b Axis Exhibits Potent Effect on Unstable Atherosclerotic Plaque Formation In Vivo

Objective- Atherosclerosis is a common disease caused by a variety of metabolic and inflammatory disturbances. MicroRNA (miR)-33a within SREBF2 (sterol regulatory element-binding factor 2) is a potent target for treatment of atherosclerosis through regulating both aspects; however, the involvement of miR-33b within SREBF1 remains largely unknown. Although their host genes difference could lead to functional divergence of miR-33a/b, we cannot dissect the roles of miR-33a/b in vivo because of lack of miR-33b sequences in mice, unlike human. Approach and Results- Here, we analyzed the development of atherosclerosis using miR-33b knock-in humanized mice under apolipoprotein E-deficient background. MiR-33b is prominent both in human and mice on atheroprone condition. MiR-33b reduced serum high-density lipoprotein cholesterol levels and systemic reverse cholesterol transport. MiR-33b knock-in macrophages showed less cholesterol efflux capacity and higher inflammatory state via regulating lipid rafts. Thus, miR-33b promotes vulnerable atherosclerotic plaque formation. Furthermore, bone marrow transplantation experiments strengthen proatherogenic roles of macrophage miR-33b. Conclusions- Our data demonstrated critical roles of SREBF1-miR-33b axis on both lipid profiles and macrophage phenotype remodeling and indicate that miR-33b is a promising target for treating atherosclerosis.

Identification of Differential Roles of MicroRNA-33a and -33b During Atherosclerosis Progression With Genetically Modified Mice

Background

MicroRNA (miR)‐33 targets cholesterol transporter ATP‐binding cassette protein A1 and other antiatherogenic targets and contributes to atherogenic progression. Its inhibition or deletion is known to result in the amelioration of atherosclerosis in mice. However, mice lack the other member of the miR‐33 family, miR‐33b, which exists in humans and other large mammals. Thus, precise evaluation and comparison of the responsibilities of these 2 miRs during the progression of atherosclerosis has not been reported, although they are essential.

Methods and Results

In this study, we performed a comprehensive analysis of the difference between the function of miR‐33a and miR‐33b using genetically modified mice. We generated 4 strains with or without miR‐33a and miR‐33b. Comparison between mice with only miR‐33a (wild‐type mice) and mice with only miR‐33b (miR‐33a^−/−/miR‐33b^+/+) revealed the dominant expression of miR‐33b in the liver. To evaluate the whole body atherogenic potency of miR‐33a and miR‐33b, we developed apolipoprotein E–deficient/miR‐33a^+/+/miR‐33b^−/− mice and apolipoprotein E–deficient/miR‐33a^−/−/miR‐33b^+/+ mice. With a high‐fat and high‐cholesterol diet, the apolipoprotein E–deficient/miR‐33a^−/−/miR‐33b^+/+ mice developed increased atherosclerotic plaque versus apolipoprotein E–deficient/miR‐33a^+/+/miR‐33b^−/− mice, in line with the predominant expression of miR‐33b in the liver and worsened serum cholesterol profile. By contrast, a bone marrow transplantation study showed no significant difference, which was consistent with the relevant expression levels of miR‐33a and miR‐33b in bone marrow cells.

Conclusions

The miR‐33 family exhibits differences in distribution and regulation and particularly in the progression of atherosclerosis; miR‐33b would be more potent than miR‐33a.

Interleukin-17 Drives Interstitial Entrapment of Tissue Lipoproteins in Experimental Psoriasis

Lipoproteins trapped in arteries drive atherosclerosis. Extravascular low-density lipoprotein undergoes receptor uptake, whereas high-density lipoprotein (HDL) interacts with cells to acquire cholesterol and then recirculates to plasma. We developed photoactivatable apoA-I to understand how HDL passage through tissue is regulated. We focused on skin and arteries of healthy mice versus those with psoriasis, which carries cardiovascular risk in man. Our findings suggest that psoriasis-affected skin lesions program interleukin-17-producing T cells in draining lymph nodes to home to distal skin and later to arteries. There, these cells mediate thickening of the collagenous matrix, such that larger molecules including lipoproteins become entrapped. HDL transit was rescued by depleting CD4⁺ T cells, neutralizing interleukin-17, or inhibiting lysyl oxidase that crosslinks collagen. Experimental psoriasis also increased vascular stiffness and atherosclerosis via this common pathway. Thus, interleukin-17 can reduce lipoprotein trafficking and increase vascular stiffness by, at least in part, remodeling collagen.

Hepatokine α1-Microglobulin Signaling Exacerbates Inflammation and Disturbs Fibrotic Repair in Mouse Myocardial Infarction

Acute cardiac rupture and adverse left ventricular (LV) remodeling causing heart failure are serious complications of acute myocardial infarction (MI). While cardio-hepatic interactions have been recognized, their role in MI remains unknown. We treated cultured cardiomyocytes with conditioned media from various cell types and analyzed the media by mass spectrometry to identify α1-microglobulin (AM) as an Akt-activating hepatokine. In mouse MI model, AM protein transiently distributed in the infarct and border zones during the acute phase, reflecting infiltration of AM-bound macrophages. AM stimulation activated Akt, NFκB, and ERK signaling and enhanced inflammation as well as macrophage migration and polarization, while inhibited fibrogenesis-related mRNA expression in cultured macrophages and cardiac fibroblasts. Intramyocardial AM administration exacerbated macrophage infiltration, inflammation, and matrix metalloproteinase 9 mRNA expression in the infarct and border zones, whereas disturbed fibrotic repair, then provoked acute cardiac rupture in MI. Shotgun proteomics and lipid pull-down analysis found that AM partly binds to phosphatidic acid (PA) for its signaling and function. Furthermore, systemic delivery of a selective inhibitor of diacylglycerol kinase α-mediated PA synthesis notably reduced macrophage infiltration, inflammation, matrix metalloproteinase activity, and adverse LV remodeling in MI. Therefore, targeting AM signaling could be a novel pharmacological option to mitigate adverse LV remodeling in MI.

Loss of periostin ameliorates adipose tissue inflammation and fibrosis in vivo

Recent evidence suggests that the accumulation of macrophages as a result of obesity-induced adipose tissue hypoxia is crucial for the regulation of tissue fibrosis, but the molecular mechanisms underlying adipose tissue fibrosis are still unknown. In this study, we revealed that periostin (Postn) is produced at extraordinary levels by adipose tissue after feeding with a high-fat diet (HFD). Postn was secreted at least from macrophages in visceral adipose tissue during the development of obesity, possibly due to hypoxia. Postn-/- mice had lower levels of crown-like structure formation and fibrosis in adipose tissue and were protected from liver steatosis. These mice also showed amelioration in systemic insulin resistance compared with HFD-fed WT littermates. Mice deficient in Postn in their hematopoietic compartment also had lower levels of inflammation in adipose tissue, in parallel with a reduction in ectopic lipid accumulation compared with the controls. Our data indicated that the regulation of Postn in visceral fat could be beneficial for the maintenance of healthy adipose tissue in obesity.

Genetic Ablation of MicroRNA-33 Attenuates Inflammation and Abdominal Aortic Aneurysm Formation via Several Anti-Inflammatory Pathways

OBJECTIVE

Abdominal aortic aneurysm (AAA) is an increasingly prevalent and ultimately fatal disease with no effective pharmacological treatment. Because matrix degradation induced by vascular inflammation is the major pathophysiology of AAA, attenuation of this inflammation may improve its outcome. Previous studies suggested that miR-33 (microRNA-33) inhibition and genetic ablation of miR-33 increased serum high-density lipoprotein cholesterol and attenuated atherosclerosis.

APPROACH AND RESULTS

MiR-33a-5p expression in central zone of human AAA was higher than marginal zone. MiR-33 deletion attenuated AAA formation in both mouse models of angiotensin II- and calcium chloride-induced AAA. Reduced macrophage accumulation and monocyte chemotactic protein-1 expression were observed in calcium chloride-induced AAA walls in miR-33^-/- mice. In vitro experiments revealed that peritoneal macrophages from miR-33^-/- mice showed reduced matrix metalloproteinase 9 expression levels via c-Jun N-terminal kinase inactivation. Primary aortic vascular smooth muscle cells from miR-33^-/- mice showed reduced monocyte chemotactic protein-1 expression by p38 mitogen-activated protein kinase attenuation. Both of the inactivation of c-Jun N-terminal kinase and p38 mitogen-activated protein kinase were possibly because of the increase of ATP-binding cassette transporter A1 that is a well-known target of miR-33. Moreover, high-density lipoprotein cholesterol derived from miR-33^-/- mice reduced expression of matrix metalloproteinase 9 in macrophages and monocyte chemotactic protein-1 in vascular smooth muscle cells. Bone marrow transplantation experiments indicated that miR-33-deficient bone marrow cells ameliorated AAA formation in wild-type recipients. MiR-33 deficiency in recipient mice was also shown to contribute the inhibition of AAA formation.

CONCLUSIONS

These data strongly suggest that inhibition of miR-33 will be effective as a novel strategy for treating AAA.

Thermoneutrality but Not UCP1 Deficiency Suppresses Monocyte Mobilization Into Blood

RATIONALE

Ambient temperature is a risk factor for cardiovascular disease. Cold weather increases cardiovascular events, but paradoxically, cold exposure is metabolically protective because of UCP1 (uncoupling protein 1)-dependent thermogenesis.

OBJECTIVE

We sought to determine the differential effects of ambient environmental temperature challenge and UCP1 activation in relation to cardiovascular disease progression.

METHODS AND RESULTS

Using mouse models of atherosclerosis housed at 3 different ambient temperatures, we observed that cold temperature enhanced, whereas thermoneutral housing temperature inhibited atherosclerotic plaque growth, as did deficiency in UCP1. However, whereas UCP1 deficiency promoted poor glucose tolerance, thermoneutral housing enhanced glucose tolerance, and this effect held even in the context of UCP1 deficiency. In conditions of thermoneutrality, but not UCP1 deficiency, circulating monocyte counts were reduced, likely accounting for fewer monocytes entering plaques. Reductions in circulating blood monocytes were also found in a large human cohort in correlation with environmental temperature. By contrast, reduced plaque growth in mice lacking UCP1 was linked to lower cholesterol. Through application of a positron emission tomographic tracer to track CCR2⁺ cell localization and intravital 2-photon imaging of bone marrow, we associated thermoneutrality with an increased monocyte retention in bone marrow. Pharmacological activation of β3-adrenergic receptors applied to mice housed at thermoneutrality induced UCP1 in beige fat pads but failed to promote monocyte egress from the marrow.

CONCLUSIONS

Warm ambient temperature is, like UCP1 deficiency, atheroprotective, but the mechanisms of action differ. Thermoneutrality associates with reduced monocyte egress from the bone marrow in a UCP1-dependent manner in mice and likewise may also suppress blood monocyte counts in man.

Development of a Patient-Derived Induced Pluripotent Stem Cell Model for the Investigation of SCN5A-D1275N-Related Cardiac Sodium Channelopathy

BACKGROUND

TheSCN5Agene encodes the α subunit of the cardiac voltage-gated sodium channel, Na_V1.5. The missense mutation, D1275N, has been associated with a range of unusual phenotypes associated with reduced Na_V1.5 function, including cardiac conduction disease and dilated cardiomyopathy. Curiously, the reported biophysical properties ofSCN5A-D1275N channels vary with experimental system.Methods and Results:First, using a human embryonic kidney (HEK) 293 cell-based heterologous expression system, theSCN5A-D1275N channels showed similar maximum sodium conductance but a significantly depolarizing shift of activation gate (+10 mV) compared to wild type. Second, we generated human-induced pluripotent stem cells (hiPSCs) from a 24-year-old female who carried heterozygousSCN5A-D1275N and analyzed the differentiated cardiomyocytes (CMs). AlthoughSCN5Atranscript levels were equivalent between D1275N and control hiPSC-CMs, both the total amount of Na_V1.5 and the membrane fractions were reduced approximately half in the D1275N cells, which were rescued by the proteasome inhibitor MG132 treatment. Electrophysiological assays revealed that maximum sodium conductance was reduced to approximately half of that in control hiPSC-CMs in the D1275N cells, and maximum upstroke velocity of action potential was lower in D1275N, which was consistent with the reduced protein level of Na_V1.5.

CONCLUSIONS

This study successfully demonstrated diminished sodium currents resulting from lower Na_V1.5 protein levels, which is dependent on proteasomal degradation, using a hiPSC-based model forSCN5A-D1275N-related sodium channelopathy.

Dynamic changes of serum microRNA-122-5p through therapeutic courses indicates amelioration of acute liver injury accompanied by acute cardiac decompensation

AIMS

Recent studies have shown that serum microRNA (miR) abundance is informative for the diagnosis or prognosis of heart failure. However, the dynamics and kinetics of miRs in acute heart failure are largely unknown. Serial measurement and analysis of serum miRs changes in individuals along their therapeutic course could reduce inter-individual variation and should detect potentially important serum miRs related to disease mechanisms. Based on this concept, we profiled serum miR signatures of blood samples that were obtained sequentially on the day of admission and on hospital Day 7.

METHODS AND RESULTS

This prospective, observational study included 42 consecutive acute heart failure patients (74 ± 1 years old, 24 male). From admission to Day 7, most of the patients showed clinical improvement. In such a cohort, we detected several fluctuations of serum miRs by two distinct screening methods (quantitative PCR and high-throughput sequencing). One of these fluctuating serum miRs, miR-122-5p, decreased significantly from Day 1 to Day 7 [median arbitrary unit (1st:3rd quantile value); 4.62 [2.39:12.3] to 3.07 [1.67:5.39], P = 0.007]. This fluctuation was significantly correlated with changes in serum liver function markers (estimated coefficient and 95% confidence interval; vs change in aspartate aminotransferase 1.69, 0.890-2.484, P < 0.001 and r = 0.560, vs change in alanine aminotransferase 1.09, 0.406-1.771, P = 0.007 and r = 0.428).

CONCLUSIONS

The serum miR signature of patients with acute heart failure might indicate the severity of the disease or patients' response to therapeutic intervention. Notably, serum miR-122-5p levels reflect liver damage in this condition.

Prevention of neointimal formation using miRNA-126-containing nanoparticle-conjugated stents in a rabbit model

Background

Despite recent progress with drug-eluting stents, restenosis and thrombosis after endovascular intervention are still major limitations in the treatment of cardiovascular diseases. These problems are possibly caused by inappropriate inhibition of neointimal formation and retardation of re-endothelialization on the surface of the stents. miR-126 has been shown to have the potential to enhance vascular endothelial cell proliferation.

Methods and results

We designed and constructed a 27-nt double strand RNA (dsRNA) conjugated to cholesterol, which has high membrane permeability, and formed mature miR-126 after transfection. For site-specific induction of miR-126, we utilized poly (DL-lactide-co-glycolide) nanoparticles (NPs). miR-126-dsRNA-containing NPs (miR-126 NPs) significantly reduced the protein expression of a previously identified miR-126 target, SPRED1, in human umbilical vascular endothelial cells (HUVECs), and miR-126 NPs enhanced the proliferation and migration of HUVECs. On the other hand, miR-126 NPs reduced the proliferation and migration of vascular smooth muscle cells, via the suppression of IRS-1. Finally, we developed a stent system that eluted miR-126. This delivery system exhibited significant inhibition of neointimal formation in a rabbit model of restenosis.

Conclusions

miR-126 NP-conjugated stents significantly inhibited the development of neointimal hyperplasia in rabbits. The present study may indicate the possibility of a novel therapeutic option to prevent restenosis after angioplasty.

MicroRNA-33 Controls Adaptive Fibrotic Response in the Remodeling Heart by Preserving Lipid Raft Cholesterol

RATIONALE

Heart failure and atherosclerosis share the underlying mechanisms of chronic inflammation followed by fibrosis. A highly conserved microRNA (miR), miR-33, is considered as a potential therapeutic target for atherosclerosis because it regulates lipid metabolism and inflammation. However, the role of miR-33 in heart failure remains to be elucidated.

OBJECTIVE

To clarify the role of miR-33 involved in heart failure.

METHODS AND RESULTS

We first investigated the expression levels of miR-33a/b in human cardiac tissue samples with dilated cardiomyopathy. Increased expression of miR-33a was associated with improving hemodynamic parameters. To clarify the role of miR-33 in remodeling hearts, we investigated the responses to pressure overload by transverse aortic constriction in miR-33-deficient (knockout [KO]) mice. When mice were subjected to transverse aortic constriction, miR-33 expression levels were significantly upregulated in wild-type left ventricles. There was no difference in hypertrophic responses between wild-type and miR-33KO hearts, whereas cardiac fibrosis was ameliorated in miR-33KO hearts compared with wild-type hearts. Despite the ameliorated cardiac fibrosis, miR-33KO mice showed impaired systolic function after transverse aortic constriction. We also found that cardiac fibroblasts were mainly responsible for miR-33 expression in the heart. Deficiency of miR-33 impaired cardiac fibroblast proliferation, which was considered to be caused by altered lipid raft cholesterol content. Moreover, cardiac fibroblast-specific miR-33-deficient mice also showed decreased cardiac fibrosis induced by transverse aortic constriction as systemic miR-33KO mice.

CONCLUSION

Our results demonstrate that miR-33 is involved in cardiac remodeling, and it preserves lipid raft cholesterol content in fibroblasts and maintains adaptive fibrotic responses in the remodeling heart.

Post-translational Modifications of SIBLING Proteins and Their Roles in Osteogenesis and Dentinogenesis

The extracellular matrix (ECM) of bone and dentin contains several non-collagenous proteins. One category of non-collagenous protein is termed the SIBLING (Small Integrin-Binding LIgand, N-linked Glycoprotein) family, that includes osteopontin (OPN), bone sialoprotein (BSP), dentin matrix protein 1 (DMP1), dentin sialophosphoprotein (DSPP), and matrix extracellular phosphoglycoprotein (MEPE). These polyanionic SIBLING proteins are believed to play key biological roles in the mineralization of bone and dentin. Although the specific mechanisms involved in controlling bone and dentin formation are still unknown, it is clear that some functions of the SIBLING family members are dependent on the nature and extent of post-translational modifications (PTMs), such as phosphorylation, glycosylation, and proteolytic processing, since these PTMs would have significant effects on their structure. OPN and BSP are present in the ECM of bone and dentin as full-length forms, whereas amino acid sequencing indicates that DMP1 and DSPP exist as proteolytically processed fragments that result from scission of X-Asp bonds. We hypothesized that the processing of DMP1 and DSPP is catalyzed by the PHEX enzyme, since this protein, an endopeptidase that is predominantly expressed in bone and tooth, has a strong preference for cleavage at the NH2-terminus of aspartyl residue. We envision that the proteolytic processing of DMP1 and DSPP may be an activation process that plays a significant, crucial role in osteogenesis and dentinogenesis, and that a failure in this processing would cause defective mineralization in bone and dentin, as observed in X-linked hypophosphatemic rickets.

Abstract 277: Microrna-33 Promotes Cardiac Fibrosis by Maintaining Cellular Lipid Homeostasis

Background: A highly conserved microRNA, miR-33 is considered as a potential therapeutic target for atherosclerosis, because recent reports, including ours, indicated miR-33 has atherogenic effects by reducing HDL-C. However, the functions of miR-33 in heart failure remain to be elucidated.

Methods and results: To clarify the functions of miR-33 involved in cardiac hypertrophy and fibrosis in vivo, we investigated the responses to pressure overload by transverse aortic constriction (TAC) in miR-33 deficient (KO) mice. When subjected to TAC, miR-33 expression level was significantly up-regulated in wild-type (WT) left ventricles, whereas miR-33 KO hearts displayed no less hypertrophic responses than WT hearts. However, interestingly, histological and gene expression analyses showed ameliorated cardiac fibrosis in miR-33 KO hearts compared to WT hearts. Furthermore, we generated cardiac fibroblast specific miR-33 deficient mice, which also showed ameliorated cardiac fibrosis when they were subjected to TAC. We also found that cardiac fibroblasts were mainly responsible for miR-33 expression in the heart, because its expression was about 4-folds higher in isolated primary cardiac fibroblasts than cardiomyocytes. Deficiency of miR-33 impaired cell proliferation in primary fibroblasts, which was considered due to altered lipid raft cholesterol content by up-regulated ATP-binding cassette transporter A1/G1.

Conclusion: Deficiency of miR-33 impaired fibroblast proliferation in vitro, and ameliorated cardiac fibrosis induced by pressure overload in vivo.

Expression Patterns of miRNA-423-5p in the Serum and Pericardial Fluid in Patients Undergoing Cardiac Surgery

BACKGROUND

Recently, it has been reported that specific microRNA (miRNA) levels are elevated in serum and can be used as biomarkers in patients with cardiovascular diseases. However, miRNAs expression profiles and their sources in pericardial fluid (PF) are unclear.

METHODS AND RESULTS

The purpose of this study was to identify the levels of miRNAs in PF in relation to those in the serum in patients undergoing cardiac surgery. Serum (S) and PF from patients undergoing coronary artery bypass graft (CABG) due to stable angina pectoris (sAP) and unstable AP (uAP) and aortic valve replacement due to aortic stenosis (AS) were analyzed for the detection of miRNAs. We named these samples S-sAP, S-uAP, S-AS, PF-sAP, PF-uAP, and PF-AS, respectively. We first measured the levels of miR-423-5p, which was recognized previously as a biomarker for heart failure. miR-423-5p levels were significantly higher in PF than serum. Although there was no difference in miR-423-5p levels among the PF-AS, PF-sAP, and PF-uAP, its levels were significantly elevated in S-uAP compared with those in S-AS and S-sAP. In order to clarify the source of miR-423-5p in PF, we measured the levels of muscle-enriched miR-133a and vascular-enriched miR-126 and miR-92a in the same samples. miR-133a levels were significantly higher in serum than in PF, and it was elevated in S-uAP compared with S-AS. miR-126 level was significantly increased in serum compared with PF, and the level of miR-92a the similar tendency. miR-423-5p is located in the first intron of NSRP1. There is another miRNA, miR-3184, encoded in the opposite direction in the same region. In vitro experiments indicated that the duplex of miR-423-5p and miR-3184-3p was more resistant to RNase than the duplex of miR-423-5p and miR-133-3p, which may help to stabilize miR-423-5p in the PF.

CONCLUSIONS

Our results suggested that miR-423-5p is enriched in PF, and serum miR-423-5p may be associate with uAP. Its expression pattern was different to that of muscle- and vascular-enriched miRNAs, miR-133a, miR-126, and miR-92a.

An in situ hybridization study of perlecan, DMP1, and MEPE in developing condylar cartilage of the fetal mouse mandible and limb bud cartilage

The main purpose of this in situ hybridization study was to investigate mRNA expression of three bone/cartilage matrix components (perlecan, DMP1, and MEPE) in developing primary (tibial) and secondary (condylar) cartilage. Perlecan mRNA expression was first detected in newly formed chondrocytes in tibial cartilage at E13.0, but this expression decreased in hypertrophic chondrocytes at E14.0. In contrast, at E15.0, perlecan mRNA was first detected in the newly formed chondrocytes of condylar cartilage; these chondrocytes had characteristics of hypertrophic chondrocytes, which confirmed the previous observation that progenitor cells of developing secondary cartilage rapidly differentiate into hypertrophic chondrocytes. DMP1 mRNA was detected in many chondrocytes within the lower hypertrophic cell zone in tibial cartilage at E14.0. In contrast, DMP1 mRNA expression was only transiently detected in a few chondrocytes of condylar cartilage at E15.0. Thus, DMP1 may be less important in the developing condylar cartilage than in the tibial cartilage. Another purpose of this study was to test the hypothesis that MEPE may be a useful marker molecule for cartilage. MEPE mRNA was not detected in any chondrocytes in either tibial or condylar cartilage; however, MEPE immunoreactivity was detected throughout the cartilage matrix. Western immunoblot analysis demonstrated that MEPE antibody recognized two bands, one of 67 kDa and another of 59 kDa, in cartilage-derived samples. Thus MEPE protein may gradually accumulate in the cartilage, even though mRNA expression levels were below the limits of detection of in situ hybridization. Ultimately, we could not designate MEPE as a marker molecule for cartilage, and would modify our original hypothesis.

MicroRNA-155-5p is associated with oral squamous cell carcinoma metastasis and poor prognosis

BACKGROUND

Abnormal miRNA expression was recently implicated in the metastasis of oral squamous cell carcinoma (OSCC) and with a poor prognosis. The initiation of the invasion-metastasis cascade involves epithelial-mesenchymal transition (EMT). Our aim was to clarify how miRNA, especially miR-155-5p misexpression contributes to OSCC metastasis through EMT.

METHODS

We collected tumor samples from 73 subjects with OSCC. The samples were analyzed by quantitative reverse-transcription polymerase chain reaction (qRT-PCR), and correlations between miR-155-5p levels and clinical characteristics were investigated. OSCC cell lines were analyzed by miRNA microarray and by transfection with a miR-155-5p mimic or inhibitor, followed by proliferation and wound-healing migration assays. qRT-PCR analyses of EMT makers in cells transfected with miR-155-5p inhibitor were performed.

RESULTS

We found high miR-155-5p expression in tissue samples from subjects with OSCC that had metastasized to cervical lymph nodes. HSC-3 cells also strongly expressed miR-155-5p. The epithelial marker E-cadherin was strongly expressed in HSC-3 cells transfected with miR-155-5p inhibitor, and we observed elevated SOCS1 and decreased STAT3 expression in these cells.

CONCLUSIONS

Our results suggest that miR-155-5p causes OSCC to metastasize, and could serve as a novel therapeutic target for OSCC.

Abstract 214: MicroRNA-451 Aggravates Lipotoxic Cardiomyopathy Through Suppression of the LKB1/AMPK Signaling Pathway

Rationale: In some type 2 diabetes mellitus (T2D) patients without hypertension, cardiac hypertrophy and attenuated cardiac function are observed, and this insult is termed “diabetic cardiomyopathy.” Tons of evidence suggests that microRNAs are involved in cardiac diseases. However, the functions of microRNAs in the diabetic cardiomyopathy induced by T2D and obesity are not fully understood.

Methods and Results: C57BL/6 mice were fed a high-fat diet (HFD) for 20 weeks, which induced obesity and T2D. MicroRNA microarray and real-time PCR revealed that miR-451 levels were significantly increased in the T2D mouse hearts (n=4-5, p<0.05). Because excess supply of saturated fatty acids is a cause of diabetic cardiomyopathy, we stimulated neonatal rat cardiac myocytes (NRCMs) with palmitate in physiological albumin concentration and confirmed that miR-451 expression was increased in a dose-dependent manner (n=6-12, p<0.01). Loss of miR-451 function ameliorated palmitate-induced lipotoxicity in NRCMs (n=4, p<0.05). Calcium-binding protein 39 (Cab39) is a scaffold protein of liver kinase B1 (LKB1), an upstream kinase of AMP-activated protein kinase (AMPK). Cab39 was a direct target of miR-451 in NRCMs and Cab39 overexpression rescued the palmitate-induced lipotoxicity in NRCMs (n=4, p<0.01). To clarify miR-451 functions in vivo, we generated cardiomyocyte-specific miR-451 knockout (cKO) mice. HFD-induced cardiac hypertrophy and contractile reserves were ameliorated in cKO mice compared with HFD-fed control mice. Protein levels of Cab39 and phosphorylated AMPK were increased and phosphorylated mammalian target of rapamycin (mTOR) was reduced in HFD-fed cKO mouse hearts compared with HFD-fed control mouse hearts (n=10-12, p<0.05). We also measured the lipotoxic intermediates, triglyceride and ceramide, in these mouse hearts using HPLC-evaporative light scattering detector (ELSD). Although there was no difference in triglyceride levels (n=3-5), ceramide level was decreased in HFD-fed cKO mice compared with HFD-fed control mice (n=3-5, p<0.05).

Conclusions: Our results indicate that miR-451 exacerbates diabetic cardiomyopathy. miR-451 is a potential therapeutic target for cardiac disease caused by T2D and obesity.

Abstract 190: Serum HDL-C Decreases in MicroRNA-33b Knock-in Mice for an Intron of Sterol Regulatory Element-binding Factor 1 (Srebf1)

Background: MicroRNAs (miRs) are small non-protein-coding RNAs that bind to specific mRNAs and inhibit translation or promote mRNA degradation. Recent reports, including ours, indicated that miR-33 (miR-33a) located within the intron of sterol regulatory element-binding factor (SREBF) 2 controls cholesterol homeostasis. Primates, but not rodents, express a second miR-33 gene (miR-33b) from an intron of SREBF1. To address miR-33b function in vivo, we developed humanized mice, in which a miR-33b transgene is inserted within a Srebf1 intron.

Methods: The human miR-33b sequence was introduced into intron 16 of mouse Srebf1 because miR-33b is located in intron 16 of human SREBF1 and there are high homologies in exons 16 and 17 between human and mouse. The expression of serum miRNA was normalized with cel-miR-39 as a spike-in control.

Results: We successfully established miR-33b knock-in (KI) mice with C57BL/6 background and this miR-33b KI strategy did not alter Srebf1 intron 16 splicing, which was confirmed by RT-PCR and sequencing. An LXR agonist T0901317, which induces Srebf1 expression, enhanced miR-33b expression in primary hepatocytes and the liver of miR-33 KI mice. The protein levels of known miR-33a target genes, such as ABCA1, ABCG1, and SREBP-1, were reduced compared with those in wild-type mice. Peritoneal macrophages from the miR-33b KI mice had a reduced cholesterol efflux capacity via apoA-I and HDL-C. Serum HDL-C levels were reduced by almost 35% in miR-33b KI mice. HPLC elution analysis showed that the decreased HDL-C levels were mainly composed of very large-, large-, medium sized HDL-C, which was compatible with the previous results of miR-33a deficient mice. Next, we measured miR-33b levels in serum of human. The expressions of miR-33b-3p were inversely correlated with serum HDL-C levels (P=0.025, R=0.336).

Conclusions: miR-33b KI mice for an intron of Srebf1 showed reduced HDL-C level and serum miR-33b-3p levels were inversely correlated with HDL-C levels in human. These results indicate that miR-33b can be a potential target for raising HDL-C and may account for lower HDL-C levels in humans than those in mice. These mice will aid in elucidating the roles of miR-33s and screening of the drugs that can alter miR-33s levels and activities.

MicroRNAs and High-Density Lipoprotein Cholesterol Metabolism

MicroRNAs (miRNAs) are small non-protein-coding RNAs that negatively regulate gene expression. They bind to the 3'-untranslated region of specific mRNAs and inhibit translation or promote mRNA degradation. Dyslipidemia/hyperlipidemia is a well-accepted risk factor for the development of atherosclerosis. The pathogenesis factors involved in lipid abnormalities are being examined extensively, and there is emerging evidence linking miRNAs to lipid metabolism. Among them, recent studies, including ours, have demonstrated that miRNAs control the expression of genes associated with high-density lipoprotein (HDL) cholesterol (HDL-C) metabolism, including ABCA1, ABCG1, and scavenger receptor class B, type I. Moreover, HDL-C itself was proved to carry miRNAs and deliver them to several different types of cells. In this review, we describe the current understanding of the functions of miRNAs in HDL metabolism and their potential in therapy for treating cardiometabolic diseases.

MicroRNA-33a/b in lipid metabolism – novel “thrifty” models

MicroRNAs (miRNAs; miRs) are small non-protein-coding RNAs that negatively regulate gene expression. They bind to the 3' UTR of specific mRNAs and either inhibit translation or promote mRNA degradation. There is emerging evidence linking miR-33a/b to lipid homoeostasis, targeting ABCA1,SREBF1, etc and it would appear that they have acted as "thrifty genes" during evolution to maintain cholesterol levels both at the cellular and whole body level. As we are now living in a period of "satiation", miR-33a/b no longer seem to be useful and could be potential therapeutic targets for lipid disorders and/or atherosclerosis. In this review, we describe the current understanding of the function of miR-33a/b in lipid homeostasis, focusing on the "thrifty" aspect.

MicroRNA-451 exacerbates lipotoxicity in cardiac myocytes and high-fat diet-induced cardiac hypertrophy in mice through suppression of the LKB1/AMPK pathway

RATIONALE

In some patients with type 2 diabetes mellitus (DM) without hypertension, cardiac hypertrophy and attenuated cardiac function are observed, and this insult is termed diabetic cardiomyopathy. To date, microRNA (miRNAs or miR) functions in diabetic cardiomyopathy remain to be elucidated.

OBJECTIVE

To clarify the functions of miRNAs involved in diabetic cardiomyopathy caused by type 2 DM.

METHODS AND RESULTS

C57BL/6 mice were fed a high-fat diet (HFD) for 20 weeks, which induced obesity and type 2 DM. miRNA microarray analyses and real-time polymerase chain reaction revealed that miR-451 levels were significantly increased in the type 2 DM mouse hearts. Because excess supply of saturated fatty acids is a cause of diabetic cardiomyopathy, we stimulated neonatal rat cardiac myocytes with palmitic acid and confirmed that miR-451 expression was increased in a dose- and time-dependent manner. Loss of miR-451 function ameliorated palmitate-induced lipotoxicity in neonatal rat cardiac myocytes. Calcium-binding protein 39 (Cab39) is a scaffold protein of liver kinase B1 (LKB1), an upstream kinase of AMP-activated protein kinase (AMPK). Cab39 was a direct target of miR-451 in neonatal rat cardiac myocytes and Cab39 overexpression rescued the lipotoxicity. To clarify miR-451 functions in vivo, we generated cardiomyocyte-specific miR-451 knockout mice. HFD-induced cardiac hypertrophy and contractile reserves were ameliorated in cardiomyocyte-specific miR-451 knockout mice compared with control mice. Protein levels of Cab39 and phosphorylated AMPK were increased and phosphorylated mammalian target of rapamycin (mTOR) was reduced in cardiomyocyte-specific miR-451 knockout mouse hearts compared with control mouse hearts.

CONCLUSIONS

Our results demonstrate that miR-451 is involved in diabetic cardiomyopathy through suppression of the LKB1/AMPK pathway.

MicroRNA-33 regulates sterol regulatory element-binding protein 1 expression in mice

MicroRNAs (miRs) are small non-protein-coding RNAs that bind to specific mRNAs and inhibit translation or promote mRNA degradation. Recent reports have indicated that miR-33, which is located within the intron of sterol regulatory element-binding protein (SREBP) 2, controls cholesterol homoeostasis and may be a potential therapeutic target for the treatment of atherosclerosis. Here we show that deletion of miR-33 results in marked worsening of high-fat diet-induced obesity and liver steatosis. Using miR-33(-/-)Srebf1(+/-) mice, we demonstrate that SREBP-1 is a target of miR-33 and that the mechanisms leading to obesity and liver steatosis in miR-33(-/-) mice involve enhanced expression of SREBP-1. These results elucidate a novel interaction between SREBP-1 and SREBP-2 mediated by miR-33 in vivo.

Cardiac-specific inhibition of kinase activity in calcium/calmodulin-dependent protein kinase kinase-β leads to accelerated left ventricular remodeling and heart failure after transverse aortic constriction in mice

Background

The mechanism of cardiac energy production against sustained pressure overload remains to be elucidated.

Methods and Results

We generated cardiac-specific kinase-dead (kd) calcium/calmodulin-dependent protein kinase kinase-β (CaMKKβ) transgenic (α-MHC CaMKKβ^kd TG) mice using α-myosin heavy chain (α-MHC) promoter. Although CaMKKβ activity was significantly reduced, these mice had normal cardiac function and morphology at baseline. Here, we show that transverse aortic binding (TAC) in α-MHC CaMKKβ^kd TG mice led to accelerated death and left ventricular (LV) dilatation and dysfunction, which was accompanied by significant clinical signs of heart failure. CaMKKβ downstream signaling molecules, including adenosine monophosphate-activated protein kinase (AMPK), were also suppressed in α-MHC CaMKKβ^kd TG mice compared with wild-type (WT) mice. The expression levels of peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α, which is a downstream target of both of CaMKKβ and calcium/calmodulin kinases, were also significantly reduced in α-MHC CaMKKβ^kd TG mice compared with WT mice after TAC. In accordance with these findings, mitochondrial morphogenesis was damaged and creatine phosphate/β-ATP ratios assessed by magnetic resonance spectroscopy were suppressed in α-MHC CaMKKβ^kd TG mice compared with WT mice after TAC.

Conclusions

These data indicate that CaMKKβ exerts protective effects on cardiac adaptive energy pooling against pressure-overload possibly through phosphorylation of AMPK and by upregulation of PGC-1α. Thus, CaMKKβ may be a therapeutic target for the treatment of heart failure.

MicroRNA-33b knock-in mice for an intron of sterol regulatory element-binding factor 1 (Srebf1) exhibit reduced HDL-C in vivo

MicroRNAs (miRs) are small non-protein-coding RNAs that bind to specific mRNAs and inhibit translation or promote mRNA degradation. Recent reports, including ours, indicated that miR-33a located within the intron of sterol regulatory element-binding protein (SREBP) 2 controls cholesterol homeostasis and can be a possible therapeutic target for treating atherosclerosis. Primates, but not rodents, express miR-33b from an intron of SREBF1. Therefore, humanized mice, in which a miR-33b transgene is inserted within a Srebf1 intron, are required to address its function in vivo. We successfully established miR-33b knock-in (KI) mice and found that protein levels of known miR-33a target genes, such as ABCA1, ABCG1, and SREBP-1, were reduced compared with those in wild-type mice. As a consequence, macrophages from the miR-33b KI mice had a reduced cholesterol efflux capacity via apoA-I and HDL-C. Moreover, HDL-C levels were reduced by almost 35% even in miR-33b KI hetero mice compared with the control mice. These results indicate that miR-33b may account for lower HDL-C levels in humans than those in mice and that miR-33b is possibly utilized for a feedback mechanism to regulate its host gene SREBF1. Our mice will also aid in elucidating the roles of miR-33a/b in different genetic disease models.

An immunohistochemical study of matrix proteins in the craniofacial cartilage in midterm human fetuses

Immunohistochemical localization of collagen types I, II, and X, aggrecan, versican, dentin matrix protein (DMP)-1, martix extracellular phosphoprotein (MEPE) were performed for Meckel's cartilage, cranial base cartilage, and mandibular condylar cartilage in human midterm fetuses; staining patterns within the condylar cartilage were compared to those within other cartilaginous structures. Mandibular condylar cartilage contained aggrecan; it also had more type I collagen and a thicker hypertrophic cell layer than the other two types of cartilage; these three characteristics are similar to those of the secondary cartilage of rodents. MEPE immunoreactivity was first evident in the cartilage matrix of all types of cartilage in the human fetuses and in Meckel's cartilage of mice and rats. MEPE immunoreactivity was enhanced in the deep layer of the hypertrophic cell layer and in the cartilaginous core of the bone trabeculae in the primary spongiosa. These results indicated that MEPE is a component of cartilage matrix and may be involved in cartilage mineralization. DMP-1 immunoreactivity first became evident in human bone lacunae walls and canaliculi; this pattern of expression was comparable to the pattern seen in rodents. In addition, chondroid bone was evident in the mandibular (glenoid) fossa of the temporal bone, and it had aggrecan, collagen types I and X, MEPE, and DMP-1 immunoreactivity; these findings indicated that chondroid bone in this region has phenotypic expression indicative of both hypertrophic chondrocytes and osteocytes.

MicroRNAs and Lipoprotein Metabolism

MicroRNAs(miRNAs; miRs) are small, non-protein-coding RNAs that negatively regulate the gene expression. They bind to specific mRNAs and inhibit translation or promote mRNA degradation. Recently, some miRNAs have been shown to be involved in lipid homoeostasis. In particular, miR122 and miR-33 have a significant impact on lipid homeostasis and are potential therapeutic targets for treating lipid disorders and/or atherosclerosis. In this review, we describe the current understanding of the function of miRNAs in lipid homeostasis, with a focus on lipoprotein metabolism.

[Effect of starfish (Asterias amurensis) intake on weight gain and blood biochemical values in rats]

We observed the effect of starfish (Asterias amurensis) intake during 67 days, on rats, in terms of the activity of enzymes related to liver function and biochemical values related to weight gain, lipid metabolism and safety. 1. Starfish (Asterias amurensis) did not induce a significant difference of body weight change. 2. Starfish (Asterias amurensis) intake did not affect organ weight. 3. Starfish (Asterias amurensis) intake did not affect lipid metabolism, liver function, or protein nutrition in this experiment.

MicroRNA-33 deficiency reduces the progression of atherosclerotic plaque in ApoE-/- mice

Background

Cholesterol efflux from cells to apolipoprotein A-I (apoA-I) acceptors via the ATP-binding cassette transporters ABCA1 and ABCG1 is thought to be central in the antiatherogenic mechanism. MicroRNA (miR)-33 is known to target ABCA1 and ABCG1 in vivo.

Methods and Results

We assessed the impact of the genetic loss of miR-33 in a mouse model of atherosclerosis. MiR-33 and apoE double-knockout mice (miR-33^−/−Apoe^−/−) showed an increase in circulating HDL-C levels with enhanced cholesterol efflux capacity compared with miR-33^+/+Apoe^−/− mice. Peritoneal macrophages from miR-33^−/−Apoe^−/− mice showed enhanced cholesterol efflux to apoA-I and HDL-C compared with miR-33^+/+Apoe^−/− macrophages. Consistent with these results, miR-33^−/−Apoe^−/− mice showed reductions in plaque size and lipid content. To elucidate the roles of miR-33 in blood cells, bone marrow transplantation was performed in these mice. Mice transplanted with miR-33^−/−Apoe^−/− bone marrow showed a significant reduction in lipid content in atherosclerotic plaque compared with mice transplanted with miR-33^+/+Apoe^−/− bone marrow, without an elevation of HDL-C. Some of the validated targets of miR-33 such as RIP140 (NRIP1) and CROT were upregulated in miR-33^−/−Apoe^−/− mice compared with miR-33^+/+Apoe^−/− mice, whereas CPT1a and AMPKα were not.

Conclusions

These data demonstrate that miR-33 deficiency serves to raise HDL-C, increase cholesterol efflux from macrophages via ABCA1 and ABCG1, and prevent the progression of atherosclerosis. Many genes are altered in miR-33-deficient mice, and detailed experiments are required to establish miR-33 targeting therapy in humans.

Increased microRNA-1 and microRNA-133a levels in serum of patients with cardiovascular disease indicate myocardial damage

BACKGROUND

Recently, elevation of circulating muscle-specific microRNA (miRNA) levels has been reported in patients with acute myocardial infarction. However, it is still unclear from which part of the myocardium or under what conditions miRNAs are released into circulating blood. The purpose of this study was to identify the source of elevated levels of circulating miRNAs and their function in cardiovascular diseases.

METHODS AND RESULTS

Serum levels of miRNA (miR)-1 and miR-133a were increased significantly in patients not only with acute myocardial infarction but also with unstable angina pectoris and Takotsubo cardiomyopathy without elevation of serum creatine phosphokinase or cardiac troponin. MicroRNA microarray analysis of the heart from a mouse model of myocardial infarction indicated that the levels of miR-1, miR-133a, miR-208a, and miR-499 were significantly reduced in the infarcted myocardium. In situ hybridization of miR-133a also showed that miR-133a levels were very low in the infarcted and peri-infarcted myocardium. It has been shown that circulating miRNAs are localized inside exosomes, which are released after Ca(2+) stimulation. We stimulated H9c2 cardiomyoblasts with A23187 and measured miR-133a levels in the exosome fraction of the culture medium. A23187 induced a dose-dependent release of miR-133a, and significant elevation was observed only at concentrations where dead cells were detected. We also found that miR-133a-containing exosomes reduced the luciferase activity of 293FT cells transfected with an miR-133a sensor vector.

CONCLUSIONS

These results suggest that elevated levels of circulating miR-133a in patients with cardiovascular diseases originate mainly from the injured myocardium. Circulating miR-133a can be used as a marker for cardiomyocyte death, and it may have functions in cardiovascular diseases.