Metabolic dysfunction-associated steatotic liver disease (MASLD) is closely associated with obesity. Excess cholesterol, the hepatic and circulating levels of which are regulated by proprotein convertase subtilisin/kexin type 9 (PCSK9), exacerbates MASLD. Data on hepatic and circulating PCSK9 protein expression in MASLD are inconsistent, and PCSK9 levels in different adipose tissues have not been well studied. Here, we used two MASLD mouse models that develop hepatic steatosis, one with weight gain and one with weight loss. These models enable distinguishing between the effects of obesity and MASLD. In the high-fat diet model, hepatic PCSK9 protein was normal. PCSK9 protein was increased in the serum and epididymal fat of the mice. In mice fed a methionine-choline-deficient diet, PCSK9 protein was normal in the liver, brown fat, subcutaneous fat, epididymal, and perirenal adipose tissue. Serum PCSK9 levels were reduced, suggesting that the lower fat mass of these mice contributed to the reduction. It is noteworthy that PCSK9 expression was low in adipocytes compared to hepatocytes. In addition, stromal vascular cells residing within adipose tissue contribute to PCSK9 protein levels in adipose tissue. PCSK9 protein was similar in subcutaneous, epididymal, and perirenal adipose tissue and was lowest in brown adipose tissue, indicating a more prominent expression in white adipose tissues. The current study shows that PCSK9 is expressed in both white and brown adipose tissues, and suggests that obesity rather than liver steatosis is associated with higher serum PCSK9 levels.

The aim of this study was to examine associations involving serum proprotein convertase subtilisin/kexin type 9 (PCSK9) in metabolic disturbances observed in women with polycystic ovary syndrome (PCOS), with particular emphasis on the potential impact of tobacco smoke exposure. The study included 88 women: 60 with PCOS (23 smokers and 37 non-smokers) and 28 without PCOS. Selected biochemical and molecular biomarkers related to lipid metabolism, oxidative stress, and inflammation were assessed. No significant differences in PCSK9 levels were observed among non-smoking women with PCOS, smoking women with PCOS, and non-smoking women without PCOS. However, in women with PCOS, excess body weight and insulin resistance were associated with increased PCSK9 concentrations. Significant correlations between PCSK9, lipid profile parameters, and the Castelli and triglycerides-glucose indices suggest a potential role of PCSK9 as a biomarker of dyslipidemia and cardiometabolic risk. Elevated PCSK9 levels may contribute not only to increased low-density lipoprotein cholesterol but also to enhanced formation of oxidized low-density lipoprotein, which is particularly detrimental to cardiovascular and metabolic health. Vitamin D levels were more strongly associated with smoking status and insulin resistance than with excess body weight. Overall, these findings indicate that PCSK9 regulation in PCOS may be driven predominantly by metabolic factors rather than PCOS status or smoking per se, and that metabolic status and vitamin D deficiency should be considered when assessing cardiometabolic risk in this population.

Proprotein convertase 1/3 (PC1/3), encoded by PCSK1, is expressed in neuronal and endocrine cell types, where it activates a number of protein precursors that play roles in energy homeostasis. Biallelic PCSK1 loss-of-function mutations cause a polyendocrinopathy; a total of 34 patients were reported. An infant with congenital malabsorptive diarrhea of all carbohydrates underwent exome sequencing (ES), with particular consideration of PC1/3 deficiency, but no mutations were found. The onset of obesity in the second year of life increased suspicion of PC1/3 deficiency in the proband, as well as in his equally affected cousin. Transcript analysis revealed minor amounts of an aberrant PCSK1 transcript containing intron 9 sequence and encoding a premature stop codon (p.Pro400Valfs*35). A deep intronic PCSK1 variant, NG_021161.1(NM_000439.5):c.1196+2681T>A, was found to segregate in the proband's family with the disease. A minigene approach demonstrated that the identified deep-intronic variant underlies pseudo-exon inclusion of the intron 9 sequence in the transcript. The characteristic phenotype of PC1/3 deficiency might require extended genetic testing to make a timely diagnosis.

Lipoprotein(a) is a risk factor for cardiovascular events and modifies the benefit of PCSK9 (proprotein convertase subtilisin/kexin type 9) inhibitors. Lipoprotein(a) concentration can be measured with immunoassays reporting mass or molar concentration or a reference measurement system using mass spectrometry. Whether the relationships between lipoprotein(a) concentrations and cardiovascular events in a high-risk cohort differ across lipoprotein(a) methods is unknown. We compared the prognostic and predictive value of these types of lipoprotein(a) tests for major adverse cardiovascular events (MACE). The ODYSSEY OUTCOMES trial (Evaluation of Cardiovascular Outcomes After an Acute Coronary Syndrome During Treatment With Alirocumab) compared the PCSK9 inhibitor alirocumab with placebo in patients with recent acute coronary syndrome. We compared risk of a MACE in the placebo group and MACE risk reduction with alirocumab according to baseline lipoprotein(a) concentration measured by Siemens N-latex nephelometric immunoassay (IA-mass; mg/dL), Roche Tina-Quant turbidimetric immunoassay (IA-molar; nmol/L), and a noncommercial mass spectrometry-based test (MS; nmol/L). Lipoprotein(a) values were transformed into percentiles for comparative modeling. Natural cubic splines estimated continuous relationships between baseline lipoprotein(a) and outcomes in each treatment group. Event rates were also determined across baseline lipoprotein(a) quartiles defined by each assay. Among 11 970 trial participants with results from all 3 tests, baseline median (Q1, Q3) lipoprotein(a) concentrations were 21.8 (6.9, 60.0) mg/dL, 45.0 (13.2, 153.8) nmol/L, and 42.2 (14.3, 143.1) nmol/L for IA-mass, IA-molar, and MS, respectively. The strongest correlation was between IA-molar and MS (r=0.990), with nominally weaker correlations between IA-mass and MS (r=0.967) and IA-mass and IA-molar (r=0.972). Relationships of lipoprotein(a) with MACE risk in the placebo group were nearly identical with each test, with estimated cumulative incidences differing by ≤0.4% across lipoprotein(a) percentiles, and all were incrementally prognostic after accounting for low-density lipoprotein cholesterol levels (all spline P≤0.0003). Predicted alirocumab treatment effects were also nearly identical for each of the 3 tests, with estimated treatment hazard ratios differing by ≤0.07 between tests across percentiles and nominally less relative risk reduction by alirocumab at lower percentiles for all 3 tests. Absolute risk reduction with alirocumab increased with increasing lipoprotein(a) measured by each test, with significant linear trends across quartiles. In patients with recent acute coronary syndrome, 3 lipoprotein(a) tests were similarly prognostic for MACE in the placebo group and predictive of MACE reductions with alirocumab at the cohort level. URL: https://www.clinicaltrials.gov; Unique identifier: NCT01663402.

Long noncoding RNAs are involved in the pathogenesis of atherosclerosis. As long noncoding RNAs maternally expressed gene 3 (Meg3) prevents cellular senescence of hepatic vascular endothelium and obesity-induced insulin resistance, we decided to examine its role in cellular senescence and atherosclerosis. By analyzing our data and human and mouse data from the Gene Expression Omnibus database, we found that Meg3 expression was reduced in humans and mice with cardiovascular disease, indicating its potential role in atherosclerosis. In Ldlr-/- mice fed a Western diet for 12 weeks, Meg3 silencing by chemically modified antisense oligonucleotides attenuated the formation of atherosclerotic lesions by 34.9% and 20.1% in male and female mice, respectively, revealed by en-face Oil Red O staining, which did not correlate with changes in plasma lipid profiles. Real-time quantitative PCR analysis of cellular senescence markers p21 and p16 revealed that Meg3 deficiency aggravates hepatic cellular senescence but not cellular senescence at aortic roots. Human Meg3 transgenic mice were generated to examine the role of Meg3 gain-of-function in the development of atherosclerosis induced by PCSK9 overexpression. Meg3 overexpression promotes atherosclerotic lesion formation by 29.2% in Meg3 knock-in mice independent of its effects on lipid profiles. Meg3 overexpression inhibits hepatic cellular senescence, while it promotes aortic cellular senescence likely by impairing mitochondrial function and delaying cell cycle progression. Our data demonstrate that Meg3 promotes the formation of atherosclerotic lesions independent of its effects on plasma lipid profiles. In addition, Meg3 regulates cellular senescence in a tissue-specific manner during atherosclerosis. Thus, we demonstrated that Meg3 has multifaceted roles in cellular senescence and atherosclerosis.