Low-density lipoprotein receptor-related protein 1 deficiency in cardiomyocytes reduces susceptibility to insulin resistance and obesity.

BACKGROUND: Low-density lipoprotein receptor-related protein 1 (LRP1) plays a key role in fatty acid metabolism and glucose homeostasis. In the context of dyslipemia, LRP1 is upregulated in the heart. Our aim was to evaluate the impact of cardiomyocyte LRP1 deficiency on high fat diet (HFD)-induced cardiac and metabolic alterations, and to explore the potential mechanisms involved. METHODS: We used TnT-iCre transgenic mice with thoroughly tested suitability to delete genes exclusively in cardiomyocytes to generate an experimental mouse model with conditional Lrp1 deficiency in cardiomyocytes (TNT-iCre+-LRP1flox/flox). FINDINGS: Mice with Lrp1-deficient cardiomyocytes (cm-Lrp1-/-) have a normal cardiac function combined with a favorable metabolic phenotype against HFD-induced glucose intolerance and obesity. Glucose intolerance protection was linked to higher hepatic fatty acid oxidation (FAO), lower liver steatosis and increased whole-body energy expenditure. Proteomic studies of the heart revealed decreased levels of cardiac pro-atrial natriuretic peptide (pro-ANP), which was parallel to higher ANP circulating levels. cm-Lrp1-/- mice showed ANP signaling activation that was linked to increased fatty acid (FA) uptake and increased AMPK/ ACC phosphorylation in the liver. Natriuretic peptide receptor A (NPR-A) antagonist completely abolished ANP signaling and metabolic protection in cm-Lrp1-/- mice. CONCLUSIONS: These results indicate that an ANP-dependent axis controlled by cardiac LRP1 levels modulates AMPK activity in the liver, energy homeostasis and whole-body metabolism.

GSK3ß inhibition and canonical Wnt signaling in mice hearts after myocardial ischemic damage.

AIMS: Myocardial infarction induces myocardial injury and tissue damage. During myocardial infarction strong cellular response is initiated to salvage the damaged tissues. This response is associated with the induction of different signaling pathways. Of these, the canonical Wnt signaling is increasingly important for its prosurvival cellular role, making it a good candidate for the search of new molecular targets to develop therapies to prevent heart failure in infarcted patients. METHODS: Herein we report that GSK3ß regulates the canonical Wnt signaling in C57Bl6 mice hearts. GSK3ß is a canonical Wnt pathway inhibitor. Using GSK3ß inhibitors and inducing myocardial injury (MI) in Lrp5-/- mice model we show that GSK3ß phosphorylation levels regulate downstream canonical Wnt pathway genes in the ischemic heart. In the setting of MI, myocardial damage assessment usually correlates with functional and clinical outcomes. Therefore, we measured myocardial injury size in Wt and Lrp5-/- mice in the presence and absence of two different GSK3 inhibitors prior to MI. Myocardial injury was independent of GSK3 inhibitor treatments and GSK3ß expression levels. RESULTS: These studies support a central role for GSK3ß in the activation of the canonical Wnt pathway in the Wt heart. Although LRP5 is protective against myocardial injury, GSK3ß expression levels do not regulate heart damage.

Translating the microRNA signature of microvesicles derived from human coronary artery smooth muscle cells in patients with familial hypercholesterolemia and coronary artery disease.

AIMS: To analyze the impact of atherogenic lipoproteins on the miRNA signature of microvesicles derived from human coronary artery smooth muscle cells (CASMC) and to translate these results to familial hypercholesterolemia (FH) and coronary artery disease (CAD) patients. METHODS: Conditioned media was collected after exposure of CASMC to atherogenic lipoproteins. Plasma samples were collected from two independent populations of diagnosed FH patients and matched normocholesterolemic controls (Study population 1, N=50; Study population 2, N=24) and a population of patients with suspected CAD (Study population 3, N=50). Extracellular vesicles were isolated and characterized using standard techniques. A panel of 30 miRNAs related to vascular smooth muscle cell (VSMC) (patho-)physiology was analyzed using RT-qPCR. RESULTS: Atherogenic lipoproteins significantly reduced levels of miR-15b-5p, -24-3p, -29b-3p, -130a-3p, -143-3p, -146a-3p, -222-3p, -663a levels (P<0.050) in microvesicles (0.1µm-1µm in diameter) released by CASMC. Two of these miRNAs, miR-24-3p and miR-130a-3p, were reduced in circulating microvesicles from FH patients compared with normocholesterolemic controls in a pilot study (Study population 1) and in different validation studies (Study populations 1 and 2) (P<0.050). Supporting these results, plasma levels of miR-24-3p and miR-130a-3p were also downregulated in FH patients compared to controls (P<0.050). In addition, plasma levels of miR-130a-3p were inversely associated with coronary atherosclerosis in a cohort of suspected CAD patients (Study population 3) (P<0.050). CONCLUSIONS: Exposure to atherogenic lipoproteins modifies the miRNA profile of CASMC-derived microvesicles and these alterations are reflected in patients with FH. Circulating miR-130a-3p emerges as a potential biomarker for coronary atherosclerosis.

Stem cells isolated from adipose tissue of obese patients show changes in their transcriptomic profile that indicate loss in stemcellness and increased commitment to an adipocyte-like phenotype.

BACKGROUND: The adipose tissue is an endocrine regulator and a risk factor for atherosclerosis and cardiovascular disease when by excessive accumulation induces obesity. Although the adipose tissue is also a reservoir for stem cells (ASC) their function and "stemcellness" has been questioned. Our aim was to investigate the mechanisms by which obesity affects subcutaneous white adipose tissue (WAT) stem cells. RESULTS: Transcriptomics, in silico analysis, real-time polymerase chain reaction (PCR) and western blots were performed on isolated stem cells from subcutaneous abdominal WAT of morbidly obese patients (ASCmo) and of non-obese individuals (ASCn). ASCmo and ASCn gene expression clustered separately from each other. ASCmo showed downregulation of "stemness" genes and upregulation of adipogenic and inflammatory genes with respect to ASCn. Moreover, the application of bioinformatics and Ingenuity Pathway Analysis (IPA) showed that the transcription factor Smad3 was tentatively affected in obese ASCmo. Validation of this target confirmed a significantly reduced Smad3 nuclear translocation in the isolated ASCmo. CONCLUSIONS: The transcriptomic profile of the stem cells reservoir in obese subcutaneous WAT is highly modified with significant changes in genes regulating stemcellness, lineage commitment and inflammation. In addition to body mass index, cardiovascular risk factor clustering further affect the ASC transcriptomic profile inducing loss of multipotency and, hence, capacity for tissue repair. In summary, the stem cells in the subcutaneous WAT niche of obese patients are already committed to adipocyte differentiation and show an upregulated inflammatory gene expression associated to their loss of stemcellness.

Cholesterol-lowering strategies reduce vascular LRP1 overexpression induced by hypercholesterolaemia.

BACKGROUND: Low density lipoprotein receptor-related protein (LRP1) plays a key role on vascular functionality and is upregulated by hypercholesterolemia and hypertension. To investigate the effect of cholesterol-lowering interventions on vascular LRP1 over expression and whether simvastatin influences LRP1 expression. MATERIAL AND METHODS: Male New Zealand rabbits were recruited into various groups, one group was fed a normal chow diet for 28 days (control group, n = 6), other group (n = 24) was fed a hypercholesterolemic diet (HC), six rabbits were euthanized at day 28 to test the capacity of HC diet to induce early atherosclerosis and the rest at day 60 (n = 18) after receiving either HC diet (HC group, n = 6), HC diet with simvastatin (2·5 mg/kg.day) (HC+simv group, n = 6), or a normal chow diet (NC group, n = 6) for the last 32 days. RESULTS: High-cholesterol diet raised vascular LRP1 concomitantly with increased lipid, VSMC and macrophage content in the arterial intima. Simvastatin and return to normocholesterolemic diet significantly reduced systemic cholesterol levels and vascular lipid content. Interestingly, these interventions also downregulate LRP1 overexpression in the vascular wall although to a different extent (HC+simv: 75 ± 3·6%vs NC: 50 ± 3·5% versus, P = 0·002). Immunohistochemistry studies showed that LRP1 diminushion was associated to a reduction in the number of intimal VSMC in HC+simv.group. Simvastatin per se did not exert any significant effect on LRP1 expression in rabbit aortic smooth muscle cells (rSMC). CONCLUSIONS: Our results demonstrate that cholesterol-lowering interventions exerted down regulatory effects on vascular LRP1 over expression induced by hypercholesterolemia and that simvastatin did not influence LRP1 expression beyond its cholesterol-lowering effects.

Cholesteryl esters of aggregated LDL are internalized by selective uptake in human vascular smooth muscle cells.

OBJECTIVE: Low-density lipoprotein (LDL) receptor-related protein (LRP1) mediates the internalization of aggregated LDL (agLDL)-LDL trapped in the arterial intima bound to proteoglycans-into human vascular smooth muscle cells (VSMC). LRP1-mediated agLDL uptake induces high-intracellular cholesteryl ester (CE) accumulation. The aim of this study was to characterize the mechanism of agLDL internalization in human VSMC. METHODS AND RESULTS: The lipidic component of LDL was labeled with [3H] and the apolipoprotein component with [(125)I]. We found that >90% of intracellular CE derived from agLDL uptake was not associated with apoB100 degradation but was selectively taken up from agLDL. The inhibition of LRP1 expression by small interfering RNA treatment led to a decrease of 80+/-0.05% in agLDL-CE selective uptake. AgLDL induced intracellular CE accumulation without a concomitant CE synthesis. Cytosolic and cytoskeletal proteins were not required for CE transport. Electron and confocal microscopy experiments indicate that CE derived from agLDL accumulated in adipophilin-stained lipid droplets that were not removable by high-density lipoprotein. CONCLUSIONS: Taken together, these results demonstrate that LRP1 mediates the selective uptake of CE from agLDL and that CE derived from agLDL is not intracellularly processed but stored in lipid droplets in human VSMC.

Aggregated low-density lipoprotein uptake induces membrane tissue factor procoagulant activity and microparticle release in human vascular smooth muscle cells.

BACKGROUND: Tissue factor (TF) is the main initiator of the arterial blood coagulation system, and aggregated LDL (agLDL) are found in the arterial intima. Our hypothesis is that agLDL internalization by vascular smooth muscle cells (VSMCs) may trigger TF-procoagulant activity. METHODS AND RESULTS: Cultured human VSMCs were obtained from human coronary arteries of explanted hearts during transplant operations. VSMCs were incubated with native LDL (nLDL) or agLDL. TF mRNA was analyzed by real-time polymerase chain reaction, and cellular and released TF protein antigen were analyzed by Western blot. TF microparticle (MP) content was analyzed by flow cytometry and TF activity by a factor Xa generation test. Both nLDL and agLDL strongly and equally increased TF mRNA and cell membrane protein expression, by approximately 5- and 9-fold, respectively. A sustained TF procoagulant activity was induced by agLDL but not by nLDL (agLDL 2.46+/-0.22 versus nLDL 0.72+/-0.12 mU/mg protein at 12 hours). AgLDL increased TF antigen release (agLDL 5.64+/-0.4 versus nLDL 3.28+/-0.22 AU) and TF MP release (agLDL 89.85+/-8.51 versus nLDL 19.69+/-4.59 TF MP/10(3) cells). TF activation and release induced by agLDL is not related to apoptosis. Blockade of LDL receptor-related protein, a receptor for agLDL, prevented the agLDL-induced release of TF protein and TF MP. CONCLUSIONS: VSMC-TF expression is upregulated by both nLDL and agLDL. However, only agLDL engagement to LDL receptor-related protein induced cellular TF procoagulant activity and TF release by human VSMCs.