Functional Gly297Ser Variant of the Physiological Dysglycemic Peptide Pancreastatin Is a Novel Risk Factor for Cardiometabolic Disorders.

Pancreastatin (PST), a chromogranin A-derived potent physiological dysglycemic peptide, regulates glucose/insulin homeostasis. We have identified a nonsynonymous functional PST variant (p.Gly297Ser; rs9658664) that occurs in a large section of human populations. Association analysis of this single nucleotide polymorphism with cardiovascular/metabolic disease states in Indian populations (n = 4,300 subjects) displays elevated plasma glucose, glycosylated hemoglobin, diastolic blood pressure, and catecholamines in Gly/Ser subjects as compared with wild-type individuals (Gly/Gly). Consistently, the 297Ser allele confers an increased risk (∼1.3-1.6-fold) for type 2 diabetes/hypertension/coronary artery disease/metabolic syndrome. In corroboration, the variant peptide (PST-297S) displays gain-of-potency in several cellular events relevant for cardiometabolic disorders (e.g., increased expression of gluconeogenic genes, increased catecholamine secretion, and greater inhibition of insulin-stimulated glucose uptake) than the wild-type peptide. Computational docking analysis and molecular dynamics simulations show higher affinity binding of PST-297S peptide with glucose-regulated protein 78 (GRP78) and insulin receptor than the wild-type peptide, providing a mechanistic basis for the enhanced activity of the variant peptide. In vitro binding assays validate these in silico predictions of PST peptides binding to GRP78 and insulin receptor. In conclusion, the PST 297Ser allele influences cardiovascular/metabolic phenotypes and emerges as a novel risk factor for type 2 diabetes/hypertension/coronary artery disease in human populations.

Catestatin Gly364Ser Variant Alters Systemic Blood Pressure and the Risk for Hypertension in Human Populations via Endothelial Nitric Oxide Pathway.

Catestatin (CST), an endogenous antihypertensive/antiadrenergic peptide, is a novel regulator of cardiovascular physiology. Here, we report case-control studies in 2 geographically/ethnically distinct Indian populations (n≈4000) that showed association of the naturally-occurring human CST-Gly364Ser variant with increased risk for hypertension (age-adjusted odds ratios: 1.483; P=0.009 and 2.951; P=0.005). Consistently, 364Ser allele carriers displayed elevated systolic (up to ≈8 mm Hg; P=0.004) and diastolic (up to ≈6 mm Hg; P=0.001) blood pressure. The variant allele was also found to be in linkage disequilibrium with other functional single-nucleotide polymorphisms in the CHGA promoter and nearby coding region. Functional characterization of the Gly364Ser variant was performed using cellular/molecular biological experiments (viz peptide-receptor binding assays, nitric oxide [NO], phosphorylated extracellular regulated kinase, and phosphorylated endothelial NO synthase estimations) and computational approaches (molecular dynamics simulations for structural analysis of wild-type [CST-WT] and variant [CST-364Ser] peptides and docking of peptide/ligand with ß-adrenergic receptors [ADRB1/2]). CST-WT and CST-364Ser peptides differed profoundly in their secondary structures and showed differential interactions with ADRB2; although CST-WT displaced the ligand bound to ADRB2, CST-364Ser failed to do the same. Furthermore, CST-WT significantly inhibited ADRB2-stimulated extracellular regulated kinase activation, suggesting an antagonistic role towards ADRB2 unlike CST-364Ser. Consequently, CST-WT was more potent in NO production in human umbilical vein endothelial cells as compared with CST-364Ser. This NO-producing ability of CST-WT was abrogated by ADRB2 antagonist ICI 118551. In conclusion, CST-364Ser allele enhanced the risk for hypertension in human populations, possibly via diminished endothelial NO production because of altered interactions of CST-364Ser peptide with ADRB2 as compared with CST-WT.

Genotyping and meta-analysis of KIF6 Trp719Arg polymorphism in South Indian Coronary Artery Disease patients: A case-control study.

The KIF6 719Arg allele is an interesting genomic variant widely screened in various populations and is reported to be associated with the risk of Coronary Artery Disease (CAD) and statin treatment outcome. Recent population based clinical studies and large-scale meta-analyses pondered over the role of 719Arg variant in CAD risk and treatment response. We screened the KIF6 Trp719Arg polymorphism (rs20455) in south Indian CAD patients in a case-control approach. A total of 1042 samples (510 CAD patients and 532 controls) were screened for the KIF6 Trp719Arg SNP by TaqMan SNP genotyping assay, followed by meta-analysis of the genotype data of non-Europeans reports. The 719Arg risk genotype (GG) was observed in 29.6% of CAD cases and in 30.1% of controls with an odds ratio (OR) of 1.07 (95% CI: 0.76-1.50), p value = 0.709. No significant difference in the genotype frequency was observed between CAD and controls in both dominant model (AG + GG vs AA) and allelic model (719Arg vs 719Trp) with an OR of 1.11 (p = 0.491) and 1.03 (p = 0.767), respectively. The covariate analysis indicated that smoking & alcohol consumption increased the risk for MI among CAD patients. Meta-analysis showed that the KIF6 719Arg allele is not associated with CAD risk in both fixed effect (p = 0.515, OR = 1.023, 95% CI = 0.956-1.094) and random effect (p = 0.547, OR = 1.022, 95% CI = 0.953-1.096). The symmetrical shape of the Egger's funnel plots revealed that there is no publication bias. These results suggest that there is no association of KIF6 719Arg allele with CAD risk in South Indian population and the meta-analysis confirms the same among non-European population.

Altered levels of miR-21, miR-125b-2*, miR-138, miR-155, miR-184, and miR-205 in oral squamous cell carcinoma and association with clinicopathological characteristics.

BACKGROUND: Previous studies have described the aberrantly expressed microRNAs (miRNAs) in oral squamous cell carcinoma (OSCC), and we reasoned that studying frequently deregulated candidate miRNAs in OSCC of Indian ethnicity could aid in better understanding of the genetic/environmental impact on the expression statuses of these miRNAs. Therefore, we evaluated the differential expression of six selected miRNAs namely hsa-miR-21, hsa-miR-125b2*, hsa-miR-138, hsa-miR-155, hsa-miR-184, and hsa-miR-205 in OSCC specimens of Indian ethnicity. METHODS: Two-step Reverse transcriptase quantitative PCR using inventoried TaqMan single miRNA assays was employed to study the expression of the selected miRNAs in 42 OSCC tumors and eight adjacent normal specimens. The expression levels of the miRNAs were tested for any association with clinicopathological parameters. RESULTS: miR-21 was significantly elevated while miR-125b-2* was significantly downregulated in tumors compared to controls (P < 0.01 and P < 0.05 respectively). miR-138 and miR-184 were observed to be predominantly downregulated in the tumor samples. High levels of miR-155 were associated with the habit of chewing tobacco/betel quid. CONCLUSIONS: Our results corroborate the previous findings on the overexpression of mir-21 and downregulation of miR-138 in OSCC. As the expression of miR-184 is controversial in tongue/oral cancer, the downregulation may be specific to tumor anatomical localization. On the other hand, to the best of our knowledge, this is the first report to show the association of miR-155 with tobacco chewing and the downregulation of miR-125b-2* in OSCC. Computational predictions suggest that miR-125b-2* may have a role in alternative splicing.

KIF1Bbeta functions as a haploinsufficient tumor suppressor gene mapped to chromosome 1p36.2 by inducing apoptotic cell death.

Deletion of the distal region of chromosome 1 frequently occurs in a variety of human cancers, including aggressive neuroblastoma. Previously, we have identified a 500-kb homozygously deleted region at chromosome 1p36.2 harboring at least six genes in a neuroblastoma-derived cell line NB1/C201. Among them, only KIF1Bbeta, a member of the kinesin superfamily proteins, induced apoptotic cell death. These results prompted us to address whether KIF1Bbeta could be a tumor suppressor gene mapped to chromosome 1p36 in neuroblastoma. Hemizygous deletion of KIF1Bbeta in primary neuroblastomas was significantly correlated with advanced stages (p = 0.0013) and MYCN amplification (p < 0.001), whereas the mutation rate of the KIF1Bbeta gene was infrequent. Although KIF1Bbeta allelic loss was significantly associated with a decrease in KIF1Bbeta mRNA levels, its promoter region was not hypermethylated. Additionally, expression of KIF1Bbeta was markedly down-regulated in advanced stages of tumors (p < 0.001). Enforced expression of KIF1Bbeta resulted in an induction of apoptotic cell death in association with an increase in the number of cells entered into the G2/M phase of the cell cycle, whereas its knockdown by either short interfering RNA or by a genetic suppressor element led to an accelerated cell proliferation or enhanced tumor formation in nude mice, respectively. Furthermore, we demonstrated that the rod region unique to KIF1Bbeta is critical for the induction of apoptotic cell death in a p53-independent manner. Thus, KIF1Bbeta may act as a haploinsufficient tumor suppressor, and its allelic loss may be involved in the pathogenesis of neuroblastoma and other cancers.