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.

Editorial, see p 229AMP-activated protein kinase (AMPK) is a major cellular sensor of energy availability. Liver kinase B1 (LKB1) and Ca 2+ /calmodulin-dependent protein kinase kinase β can act as major upstream kinases of AMPK in mammalian cells and phosphorylate AMPK at Thr 172 . 5 LKB1 forms a heterotrimeric complex with ste20-related adaptor and calcium-binding protein 39 (Cab39, also known as MO25α). 6 Although several lines of evidence indicate that AMPK phosphorylation is attenuated in diet-induced obesity (DIO) mouse hearts, 7,8 the mechanisms by which AMPK phosphorylation is decreased are not fully understood.MicroRNAs (miRNAs or miRs) are a large class of small noncoding RNAs. miRNAs suppress the translation of a target mRNA depending on the complementarity between the 5′ side seed sequence of a miRNA and the 3′ untranslated region (3′UTR) of the target mRNA. Although several reports indicate that miRNAs are involved in diabetic cardiomyopathy in a type 1 DM model of streptozotocin-induced diabetic mice, 9-11 miRNA functions in diabetic hearts induced especially by type 2 DM remain to be elucidated.In the present study, we used DIO mice to identify differentially regulated miRNAs in hearts. One of these miRNAs, miR-451, was upregulated in the hearts, and palmitic acid stimulation increased miR-451 levels in neonatal rat cardiac myocytes (NRCMs). miR-451 directly targeted Cab39 in NRCMs, and loss of miR-451 function partly rescued lipotoxicity in vitro. Furthermore, we revealed that high-fat diet (HFD)-induced cardiac hypertrophy was ameliorated in cardiomyocyte-specific miR-451 knockout (miR-451 cKO) mice. Finally, we showed that AMPK phosphorylation was increased and mammalian target of rapamycin (mTOR) phosphorylation was decreased in the HFD-fed miR-451 cKO mice compared with the HFD-fed control mice. These data strongly suggest that cardiac-specific inhibition of miR-451 is a strategy for treating diabetic cardiomyopathy. MethodsDetailed methods are provided in the Online Data Supplement. Results miRNA-451 Expression Is Significantly Increased in DIO Mouse HeartsTo clarify miRNA expression changes in DIO mouse hearts, we used HFD-fed C57BL/6 mice. This is a well-established obesity and type 2 DM model, 12 and the C57BL/6 mice become obese depending on the duration of HFD feeding, as shown in Figure 1A. In line with our and other reports, 8,12,13 liver weights approximately doubled, and fasting blood sugar concentrations increased significantly by 1.5-fold after feeding 45 kcal% fat-containing HFD for 20 weeks ( Figure 1B and 1C). These data suggest that this mouse model had marked insulin resistance and fatty liver and mimicked obesity with type 2 DM in humans.To evaluate miRNA expression changes in the heart, we performed microarray analyses of miRNAs extracted from the hearts of mice fed HFD for 8 and 20 weeks. We focused on miRNAs meeting the following 3 criteria. The miRNA was evidently expressed in the heart (miRNA spot intensity, >100), the expression levels increased depending on the dura...

Background: Premature menopause is an independent risk factor for cardiovascular disease in women, but mechanisms underlying this association remain unclear. Clonal hematopoiesis of indeterminate potential (CHIP), the age-related expansion of hematopoietic cells with leukemogenic mutations without detectable malignancy, is associated with accelerated atherosclerosis. Whether premature menopause is associated with CHIP is unknown. Methods: We included postmenopausal women from the UK Biobank (N=11,495) aged 40-70 years with whole exome sequences and from the Women's Health Initiative (WHI, N=8,111) aged 50-79 years with whole genome sequences. Premature menopause was defined as natural or surgical menopause occurring before age 40 years. Co-primary outcomes were the presence of (1) any CHIP and (2) CHIP with variant allele frequency (VAF) >0.1. Logistic regression tested the association of premature menopause with CHIP, adjusted for age, race, the first 10 principal components of ancestry, smoking, diabetes mellitus, and hormone therapy use. Secondary analyses considered natural vs. surgical premature menopause and gene-specific CHIP subtypes. Multivariable-adjusted Cox models tested the association between CHIP and incident coronary artery disease (CAD). Results: The sample included 19,606 women, including 418 (2.1%) with natural premature menopause and 887 (4.5%) with surgical premature menopause. Across cohorts, CHIP prevalence in postmenopausal women with vs. without a history of premature menopause was 8.8% vs. 5.5% (P<0.001), respectively. After multivariable adjustment, premature menopause was independently associated with CHIP (all CHIP: OR 1.36, 95% 1.10-1.68, P=0.004; CHIP with VAF >0.1: OR 1.40, 95% CI 1.10-1.79, P=0.007). Associations were larger for natural premature menopause (all CHIP: OR 1.73, 95% CI 1.23-2.44, P=0.001; CHIP with VAF >0.1: OR 1.91, 95% CI 1.30-2.80, P<0.001) but smaller and non-significant for surgical premature menopause. In gene-specific analyses, only DNMT3A CHIP was significantly associated with premature menopause. Among postmenopausal middle-aged women, CHIP was independently associated with incident coronary artery disease (HR associated with all CHIP: 1.36, 95% CI 1.07-1.73, P=0.012; HR associated with CHIP with VAF >0.1: 1.48, 95% CI 1.13-1.94, P=0.005). Conclusions: Premature menopause, especially natural premature menopause, is independently associated with CHIP among postmenopausal women. Natural premature menopause may serve as a risk signal for predilection to develop CHIP and CHIP-associated cardiovascular disease.

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