👤 Ankita Sharma

Apolipoprotein (apo) A-V is a low abundance protein with a profound influence on plasma triacylglycerol levels. In human populations, single nucleotide polymorphisms and mutations in APOA5 positively correlate with hypertriglyceridemia. As an approach to preventing the deleterious effects of chronic hypertriglyceridemia, apoA-V gene therapy has been pursued. Recombinant adeno-associated virus (AAV) 2/8 harboring the coding sequence for human apoA-V or a control AAV2/8 was transduced into hypertriglyceridemic apoa5 (-/-) mice. After injection of 1×10(12) viral genome AAV2/8-apoA-V, maximal plasma levels of apoA-V protein were achieved at 3 to 4 weeks, after which the concentration slowly declined. Complementing the appearance of apoA-V was a decrease (50±6%) in plasma triacylglycerol content compared with apoa5 (-/-) mice treated with AAV2/8-β-galactosidase. After 8 weeks the mice were euthanized and plasma lipoproteins separated. AAV2/8-apoA-V-transduced mice displayed a dramatic reduction in very low-density lipoprotein triacylglycerol content. Vector generated apoA-V in plasma associated with both very low-density lipoprotein and high-density lipoprotein fractions. Taken together, the data show that gene transfer of apoA-V improves the severe hypertriglyceridemia phenotype of apoa5 (-/-) mice. Given the prevalence of hypertriglyceridemia, apoA-V gene therapy offers a potential strategy for maintenance of plasma triacylglycerol homeostasis. Show less

Apolipoprotein (apo) A-V functions to modulate intracellular and extracellular triacylglycerol metabolism. The present review addresses molecular mechanisms underlying these effects. The relevance of apoA-V to human disease conditions is illustrated by the strong correlation between single nucleotide polymorphisms in APOA5, elevated plasma triacylglycerol and dyslipidemic disease. Despite undergoing processing for secretion from hepatocytes, a portion of apoA-V escapes this destiny and accumulates as a component of cytosolic lipid droplets. Expression of recombinant apoA-V in hepatocarcinoma cells results in increased lipid droplet size and number at the expense of triacylglycerol secretion.ApoA-V modulates atherosclerosis in hypercholesterolemic apoE null mice. ApoE null/human apoA-V transgenic mice had reduced levels of triacylglycerol and cholesterol in plasma along with decreased aortic lesion size. ApoA-V modulates triacylglycerol metabolic fate. Following its synthesis, apoA-V enters the endoplasmic reticulum and associates with membrane defects created by triacylglycerol accumulation. Association of apoA-V with endoplasmic reticulum membrane defects promotes nascent lipid droplets budding toward the cytosol. Despite its low concentration in plasma (∼150 ng/ml), apoA-V modulates lipoprotein metabolism by binding to glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1. This interaction effectively localizes triacylglycerol-rich lipoproteins in the vicinity of glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein1's other ligand, lipoprotein lipase. Show less

Liver X receptors (LXRs) α and β are ligand-activated transcription factors belonging to the family of nuclear receptors. LXRs play role in control of lipid homeostasis, glucose metabolism, inflammation, and proliferation. LXRs are expressed in gallbladder cholangiocytes and recent studies have shown that LXR-β (-/-) Mice exhibit an estrogen-dependent gallbladder carcinogenesis. However, there are no studies reported in humans. Therefore, using case-control design in the present study, we have evaluated the associations of LXR-α (rs7120118) and LXR-β (rs35463555 and rs2695121) genetic variants with gallbladder cancer (GBC) susceptibility in 400 cases and 200 controls. Genotypes were determined by TaqMan probes. Statistical analysis was done by SPSS and SNPstats. In silico analysis was performed using Bioinformatics tools (F-SNP, FAST-SNP). LXR-β genotypes (rs35463555) [GA + AA] and (rs2695121) [TC + CC] were associated with risk of GBC [OR = 1.46, p = 0.03; OR = 1.52, p = 0.01, respectively] as compared to healthy controls whereas LXR-α (rs7120118) was not associated with GBC risk. LXR-β haplotype [Ars35463555-Crs2695121] showed statistical significant association with GBC [OR = 5.0, p = 0.03]. On stratification based on gender, LXR-β [GA + AA] and [TC + CC] genotypes were found to be significantly associated in females GBC patients [OR = 1.5, p = 0.04; OR = 1.7, p = 0.005, respectively]. The LXR-β [TC + CC] associated with GBC patients with gallstones [OR; 1.8, p = 0.002]. The genetic risk by LXR-β was not modulated by tobacco consumption or age of onset. In silico analysis using FAST-SNP showed "Low-medium risk" by LXR-β (rs2695121) T > C variation. Our results suggest that LXR-β polymorphisms influence gallbladder cancer susceptibility through estrogen and gallstone-dependent pathways. Show less

The discovery of apolipoprotein A-V (apoA-V) in 2001 has raised a number of intriguing questions about its role in lipid transport and triglyceride (TG) homeostasis. Genome wide association studies (GWAS) have consistently identified APOA5 as a contributor to plasma TG levels. Single nucleotide polymorphisms (SNP) within the APOA5 gene locus have been shown to correlate with elevated plasma TG. Furthermore, transgenic and knockout mouse models support the view that apoA-V plays a critical role in maintenance of plasma TG levels. The present review describes recent concepts pertaining to apoA-V SNP analysis and their association with elevated plasma TG. The interaction of apoA-V with glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1 (GPIHBP1) is discussed relative to its postulated role in TG-rich lipoprotein catabolism. The potential role of intracellular apoA-V in regulation of TG homeostasis, as a function of its ability to associate with cytosolic lipid droplets, is reviewed. While some answers are emerging, numerous mysteries remain with regard to this low abundance, yet potent, modulator of TG homeostasis. Given the strong correlation between elevated plasma TG and heart disease, there is great scientific and public interest in deciphering the numerous biological riddles presented by apoA-V. This article is part of a Special Issue entitled Triglyceride Metabolism and Disease. Show less

An accumulation of data from in vitro to in vivo model system has established a pivotal role of three crucial ligand activated nuclear receptors RXR, LXR-alpha and VDR for their ability to regulate an array of genes involved in regulation of fundamental cellular processes to patho-physiological situations. Keeping in view RXR as a common heterodimeric partner for LXR-alpha and VDR, the present study was designed to dissect the interrelationship between these three nuclear receptors in peripheral blood mononuclear cellular model. The present study revealed that all the three nuclear receptors displayed auto regulation in response to their specific ligands; Both LXR-alpha and VDR regulated the expression of their heterodimeric partner RXR; and VDR was regulated by LXR-alpha through its ability to modulate SREBP response element present in the promoter region of VDR gene. Based on these findings, the role of these nuclear receptors could be better understood in various nuclear receptor mediated pathological processes. Show less

Triglycerides is an independent risk factor for coronary artery disease (CAD) and is especially important in Indians because of high prevalence of hypertriglyceridemia in this population. Both genetic and environmental factors determine triglyceride levels. In a birth cohort from India, hypertriglyceridemia was found in 41% of men and 11% of women. Subjects who had high triglycerides had more rapid body mass index (BMI) or weight gain than rest of the cohort throughout infancy, childhood and adolescence. We analysed polymorphisms in APOA5, hepatic lipase and PPARγ genes and investigated their association with birth weight and serial changes in BMI. Polymorphisms in APOA5 (-1131T > C, S19W), PPARγ (Pro12Ala) and hepatic lipase (-514C > T) were studied by polymerase chain reaction (PCR) followed by restriction digestion in 1492 subjects from the New Delhi Birth Cohort (NDBC). We assessed whether these polymorphisms influence lipid and other variables and serial changes in BMI, both individually and together.The risk allele of APOA5 (-1131C) resulted in 23.6 mg/dl higher triglycerides as compared to normal allele (P < 0.001). Risk allele of HL (-514T) was associated with significantly higher HDL2 levels (P = 0.002). Except for the marginal association of PPARγ Pro12Ala variation with a lower conditional weight at 6 months, (P = 0.020) and APOA5 S19W with a higher conditional BMI at 11 yrs of age (P = 0.030), none of the other associations between the gene polymorphisms and serial changes in body mass index from birth to young adulthood were significant. The promoter polymorphism in APOA5 was associated with raised serum triglycerides and that of HL with raised HDL2 levels. None of the polymorphisms had any significant relationship with birth weight or serial changes in anthropometry from birth to adulthood in this cohort. Show less

To determine altered gene expression profiles in subcutaneous adipose and skeletal muscle from nondiabetic, insulin-resistant individuals compared with insulin-sensitive individuals matched for BMI. A total of 62 nondiabetic individuals were chosen for extremes of insulin sensitivity (31 insulin-resistant and 31 insulin-sensitive subjects; 40 were European American and 22 were African American) and matched for age and obesity measures. Global gene expression profiles were determined and compared between ethnic groups and between insulin-resistant and insulin-sensitive participants individually and using gene-set enrichment analysis. African American and European American subjects differed in 58 muscle and 140 adipose genes, including many inflammatory and metabolically important genes. Peroxisome proliferator-activated receptor γ cofactor 1A (PPARGC1A) was 1.75-fold reduced with insulin resistance in muscle, and fatty acid and lipid metabolism and oxidoreductase activity also were downregulated. Unexpected categories included ubiquitination, citrullination, and protein degradation. In adipose, highly represented categories included lipid and fatty acid metabolism, insulin action, and cell-cycle regulation. Inflammatory genes were increased in European American subjects and were among the top Kyoto Encyclopedia of Genes and Genomes pathways on gene-set enrichment analysis. FADS1, VEGFA, PTPN3, KLF15, PER3, STEAP4, and AGTR1 were among genes expressed differentially in both adipose and muscle. Adipose tissue gene expression showed more differences between insulin-resistant versus insulin-sensitive groups than the expression of genes in muscle. We confirm the role of PPARGC1A in muscle and show some support for inflammation in adipose from European American subjects but find prominent roles for lipid metabolism in insulin sensitivity independent of obesity in both tissues. Show less

The role of phosphatases in the impairment of MAPK signaling, which is directly responsible for Leishmania-induced macrophage dysfunction, is still poorly understood. Gene expression profiling revealed that Leishmania donovani infection markedly up-regulated the expression of three phosphatases: MKP1, MKP3, and PP2A. Inhibition of these phosphatases prior to infection points toward preferential induction of the Th2 response through deactivation of p38 by MKP1. On the other hand, MKP3 and PP2A might play significant roles in the inhibition of iNOS expression through deactivation of ERK1/2. Among various PKC isoforms, PKCzeta was associated with induction of MKP3 and PP2A in infected macrophages, whereas PKCepsilon was correlated with MKP1 induction. Inhibition of phosphatases in L. donovani-infected BALB/c mice shifted the cytokine balance in favor of the host by inducing TNF-alpha and iNOS expression. This was validated by cystatin, an immunomodulator and curing agent for experimental visceral leishmaniasis, which showed that inhibition of MKPs and PP2A activity may be necessary for a favorable T cell response and suppression of organ parasite burden. This study, for the first time, suggests the possibility of the involvement of MAPK-directed phosphatases in the establishment of L. donovani infection. Show less

To investigate the in vitro effects of atorvastatin on lipopolysaccharide (LPS)-induced gene expression in endometrial-endometriotic stromal cells. In vitro experimental study using flow cytometry, ELISA, semiquantitative reverse transcriptase polymerase chain reaction, and Western blot. Postgraduate Institute of Medical Education and Research. Twenty-five women undergoing laparoscopy (n = 10) and laparotomy (n = 15). Endometriotic cyst wall (group I) and endometrial biopsy (group II) collection. The endometrial-endometriotic stromal cells were isolated from ectopic (group I) and eutopic (group II) endometrium by established methods, cultured, and stimulated with LPS (1 μg/mL), followed by atorvastatin treatment in a time- and dose-dependent manner to investigate the effects of LPS on proliferation (Ki-67) and expression of cyclooxygenase-2 (COX-2), vascular endothelial growth factor (VEGF), receptor for advanced glycation end products (RAGE), extracellular newly identified RAGE binding protein (EN-RAGE), peroxisome proliferator activated receptor-γ (PPAR-γ), and liver X receptor-α (LXR-α) genes in endometrial-endometriotic stromal cells and on levels of insulin-like growth factor binding protein-1 (IGFBP-1) and 17β-E(2) in endometrial-endometriotic stromal cell culture supernatant. Significant inhibition of Ki-67 and LPS-induced expression of inflammatory and angiogenic genes (COX-2, VEGF, RAGE, and EN-RAGE) was observed in atorvastatin-treated endometrial-endometriotic stromal cells. In contrast, a significant dose- and time-dependent increase in expression of anti-inflammatory genes (PPAR-γ and LXR-α) and levels of IGFBP-1 was observed after atorvastatin treatment in both the groups. However, atorvastatin treatment had no effect on 17β-E(2) levels in endometrial/endometriotic stromal cell culture supernatant. The data of the present study provide new insights for the implication of atorvastatin treatment for endometriosis in humans. Show less

Recent studies on the liver X receptor-alpha (LXR-alpha) have recognized its crucial protective role in the initiation of a cross-talk between lipid metabolism and inflammation regarded as a prerequisite for the development of atherosclerotic lesions. The present study was directed to explore the functional genomics of LXR-alpha gene within blood mononuclear cells of subjects suffering from coronary heart disease (CHD), revealed a paradoxical relationship between blood cellular LXR-alpha mRNA expression and the severity of coronary occlusion. In order to resolve this apparent paradox, the ligand binding domain of LXR-alpha gene was analyzed. The results of such a study revealed that three critical mutations in the domain comprising of amino acids Asp324, Pro327 and Arg328, were responsible for inability of this domain to interact with its natural ligands leading thereby to deregulation of its effector genes that are known to play crucial role in the cross-talk between lipid peroxidation and inflammation. This phenomenon was in conformity with functional assay of LXR-alpha dependent transcriptional activity within cells derived from normal and CHD subjects. Based upon these results we propose that the mutations in the LXR-alpha gene reported here for the first time not only may be exploited for the diagnosis of CHD in human subjects but also could be used as a marker for exploring the predisposition of human subjects towards CHD. Show less

HP1 proteins are thought to be modulators of chromatin organization in all mammals, yet their exact physiological function remains unknown. In a first attempt to elucidate the function of these proteins in vivo, we disrupted the murine Cbx1 gene, which encodes the HP1-beta isotype, and show that the Cbx1(-/-) -null mutation leads to perinatal lethality. The newborn mice succumbed to acute respiratory failure, whose likely cause is the defective development of neuromuscular junctions within the endplate of the diaphragm. We also observe aberrant cerebral cortex development in Cbx1(-/-) mutant brains, which have reduced proliferation of neuronal precursors, widespread cell death, and edema. In vitro cultures of neurospheres from Cbx1(-/-) mutant brains reveal a dramatic genomic instability. Our results demonstrate that HP1 proteins are not functionally redundant and that they are likely to regulate lineage-specific changes in heterochromatin organization. Show less

The survival motor neurons (smn) gene in mice is essential for embryonic viability. In humans, mutation of the telomeric copy of the SMN1 gene causes spinal muscular atrophy, an autosomal recessive disease. Here we report that the SMN protein interacts with the zinc-finger protein ZPR1 and that these proteins colocalize in small subnuclear structures, including gems and Cajal bodies. SMN and ZPR1 redistribute from the cytoplasm to the nucleus in response to serum. This process is disrupted in cells from patients with Werdnig-Hoffman syndrome (spinal muscular atrophy type I) that have SMN1 mutations. Similarly, decreased ZPR1 expression prevents SMN localization to nuclear bodies. Our data show that ZPR1 is required for the localization of SMN in nuclear bodies. Show less