Biomedical subjects

Patricia Aspichueta

Publications and source records attributed to Patricia Aspichueta.

5 recordsLinked to original sources

PubMed2024

A functional genomic framework to elucidate novel causal metabolic dysfunction-associated fatty liver disease genes.

BACKGROUND AND AIMS: Metabolic dysfunction-associated fatty liver disease (MASLD) is the most prevalent chronic liver pathology in western countries, with serious public health consequences. Efforts to identify causal genes for MASLD have been hampered by the relative paucity of human data from gold standard magnetic resonance quantification of hepatic fat. To overcome insufficient sample size, genome-wide association studies using MASLD surrogate phenotypes have been used, but only a small number of loci have been identified to date. In this study, we combined genome-wide association studies of MASLD composite surrogate phenotypes with genetic colocalization studies followed by functional in vitro screens to identify bona fide causal genes for MASLD. APPROACH AND RESULTS: We used the UK Biobank to explore the associations of our novel MASLD score, and genetic colocalization to prioritize putative causal genes for in vitro validation. We created a functional genomic framework to study MASLD genes in vitro using CRISPRi. Our data identify VKORC1 , TNKS , LYPLAL1 , and GPAM as regulators of lipid accumulation in hepatocytes and suggest the involvement of VKORC1 in the lipid storage related to the development of MASLD. CONCLUSIONS: Complementary genetic and genomic approaches are useful for the identification of MASLD genes. Our data supports VKORC1 as a bona fide MASLD gene. We have established a functional genomic framework to study at scale putative novel MASLD genes from human genetic association studies.

Humans↗

PubMed2006

The 2-series prostaglandins suppress VLDL secretion in an inflammatory condition-dependent manner in primary rat hepatocytes.

In the liver, prostaglandins (PG) generated mainly by activated non-parenchymal cells can modulate the parenchymal cell function during homeostasis and inflammation. Whether prostaglandins regulate the hepatocyte VLDL assembling/secretor phenotype in both conditions remains unresolved. We sought to determine whether and how PGE2, PGD2, and PGF2alpha (5 and 50 microM) have a role in VLDL secretion regulation in resting and interleukin-6 (IL-6) stimulated rat hepatocytes. Prostaglandins led to comparable, concentration-dependent reductions in the secretion of VLDL apoB and lipids by resting, 24 h-cultured cells. Moreover, each apoB copy recruited less of each lipid class, correlating with reduced particle size, lipogenesis and cholesterogenesis, and impaired cellular triacylglycerol recycling. Triacylglycerol output reduction occurred early, as the transient PGD2- and PGF2alpha -promoted apoB mRNA decreases. IL-6 markedly increased the apoB mRNA expression and the secretion of its protein in triacylglycerol-poor VLDL. The latter was uniquely blunted by PGE2, which unaffected basal or IL-6-activated apoB gene expression. Collectively, our findings show inflammation condition-based roles for 2-series-prostaglandins in VLDL secretion modulation. Whereas in non-stimulated hepatocytes, they all inhibited VLDL-apoB output, interfered with lipid provision for lipoprotein assembly and may be regarded as pro-steatotic, the anti-inflammatory PGE2 antagonized the IL-6-promoted VLDL secretion contributing in restoring liver homeostasis.

Animals↗

PubMed2006

Impaired response of VLDL lipid and apoB secretion to endotoxin in the fasted rat liver.

Bacterial infection elicits hypertriglyceridemia attributed to increased hepatic production of very low-density lipoprotein (VLDL) particles and decreased peripheral metabolism. The mechanisms underlying VLDL overproduction in sepsis are as yet unclear, but seem to be fed/fasted state-dependent. To learn more about this, we investigated hepatocytes isolated from fasted rats, made endotoxic by 1 mg/kg lipopolysaccharide (LPS) injection, for their ability to secrete the VLDL protein and lipid components. The results were then related to lipogenesis markers and expression of genes critical to VLDL biogenesis. Endotoxic rats showed increased levels of serum VLDL-apoB (10-fold), -triglyceride (2-fold), and -cholesterol (2-fold), whereby circulating VLDL were lipid-poor particles. Similarly, VLDL-apoB secretion by isolated endotoxic hepatocytes was approximately 85% above control, whereas marginal changes in the output of VLDL-lipid classes occurred. This was accompanied by a substantial rise in apoB and a moderate rise in MTP mRNA levels, but with basal de novo formation and efficiency of secretion of triglycerides, cholesterol and cholesteryl esters. These results indicate that during periods of food restriction, endotoxin does not enhance lipid provision to accomplish normal lipidation of overproduced apoB molecules, though this does occur to a sufficient extent to pass the proteasome checkpoint and secretion of lipid-poor, type 2 VLDL takes place.

Animals↗

PubMed2005

Endotoxin promotes preferential periportal upregulation of VLDL secretion in the rat liver.

Zonation affects liver parenchymal cell function and metabolism as well as nonparenchymal cell activation, but whether VLDL production is zonated has yet to be elucidated. Infection induces enhanced VLDL secretion by the liver. Ex vivo studies were undertaken to examine the liver heterogeneity for VLDL formation and secretion and their in vivo response to endotoxin. Highly pure periportal (PP) and perivenous (PV) hepatocytes were isolated from fasted lipopolysaccharide-treated, fasted, and fed rats. They were used to assess their capacity to release VLDL-apolipoprotein B (apoB) and lipid classes in relation to de novo lipid synthesis and the expression of genes crucial to VLDL production. Despite the common superior ability of PP hepatocytes for lipid release and zonal differences in lipid synthesis, zonated secretion of VLDL particles was observed in septic but not in normal fed or fasted livers. The endotoxin-induced apoB secretion was more accentuated in PP hepatocytes; this was accompanied by a preferential PP increase in apoB and microsomal triglyceride transfer protein mRNA levels, whereas lipogenesis indicators were, if anything, similarly modified in hepatocytes of either acinar origin. We conclude that PP and PV hepatocytes exhibited similar capabilities for VLDL formation/secretion in normal conditions; however, the endotoxic pressure did zonate periportally.

Animals↗

PubMed2004

Differential modulation of prostaglandin receptor mRNA abundance by prostaglandins in primary cultured rat hepatocytes.

Prostaglandins (PG) produced by activated non-parenchymal liver cells regulate the function of parenchymal cells through six classes of G-protein-coupled receptors (-R): four receptor subtypes for PGE2, EP1-R-EP4-R and one type each for PGD2, DP-R, and PGF2alpha, FP-R. The mechanisms by which prostaglandins modulate the hepatocyte responding phenotype are poorly characterized. We have studied the concentration and time effect of PGE2, PGD2 and PGF2alpha on the mRNA expression level of their own receptors in the presence or absence of the inflammatory signal interleukin 6 (IL-6). The mRNA levels were determined in primary adult rat hepatocytes upon treatment with either prostaglandin (5 microM or 50 microM), or IL-6 (100 ng/ml), or both, for 4-24 h. A marked, concentration-dependent induction of EP2-R mRNA expression was promoted by PGE2, PGD2 or PGF2alpha after 4 h, whereas EP1-R, EP3-R and EP4-R transcript levels were unaffected. This expression pattern changed substantially upon 24 h. The induction of EP2-R mRNA, persisted, though attenuated. Furthermore, EP1-R mRNA upregulated two-three fold and EP3-R mRNA decreased modestly by 50 microM prostaglandin. None of the treatments affected the FP-R mRNA level, while that of DP-R mRNA was undetectable. In the presence of IL-6, prostaglandins had no such effects, but they did attenuate the IL-6-mediated changes in prostaglandin receptor mRNA expression. The findings indicate that prostaglandins modulate the prostaglandin receptor gene expression programme in primary adult rat hepatocytes in a manner that is specific to the receptor, the concentration and time of exposure, and the inflammatory condition of the cell.

Animals↗