Analysis of association between components of the folate metabolic pathway and autism spectrum disorder in eastern Indian subjects.

BACKGROUND: Folate has a pivotal role in maintaining different cellular processes including DNA integrity and neurotransmitter levels. Further, folate deficiency was reported in subjects with neuropsychiatric disorders including autism spectrum disorder (ASD). METHODS AND RESULTS: We recruited ASD probands following the Diagnostic and Statistical Manual of Mental Disorder-IV/-5. Severity was assessed by the Childhood Autism Rating Scale2-Standard Test (CARS2-ST). Functional SNPs in reduced folate carrier1 (rs1051266), methylenetetrahydrofolate dehydrogenase (rs2236225), methylenetetrahydrofolate methyltransferase (rs1805087), methylenetetrahydrofolate reductase (rs1801133 and rs1801131), cystathionine-beta- synthase (rs5742905), and serine hydroxymethyltransferase (rs1979277) genes were analyzed in the ASD probands (N = 203), their parents and controls (N = 250) by PCR/TaqMan based methods. Plasma homocysteine and vitamin B12 levels were examined by Enzyme-Linked ImmunoSorbent Assay. Statistical analysis revealed higher frequencies of rs1051266 and rs1805087 "A" alleles (P = 8.233e-005 and P = 0.010 respectively) and rs1051266 "AA" genotype (P = 0.02) in the ASD probands. Gender based stratified analysis revealed higher frequency of rs1051266 "AA" in the male probands (P = 0.001) while frequencies of rs1805087 "A" (P = 0.001) and "AA" (P < 0.05), and rs2236225 "CC" (P = 0.03) were higher in the females. The case-control analysis also exhibited a significant difference in the occurrence of biallelic and triallelic haplotypes. rs1051266 "A", rs1979277 "T" and rs5742905 "C" alleles showed biased parental transmission (P = 0.02). CARS2-ST scores were higher in the presence of rs5742905 "T" while scores were lower in the presence of rs1979277 "T" and rs1051266 "A". ASD probands showed vitamin B12 deficiency. CONCLUSION: Based on these observations, we infer that components needed for proper folate metabolism may influence ASD severity in this population.

Association of Dopamine Transporter Gene with Heroin Dependence in an Indian Subpopulation from Manipur.

Dopamine transporter (DAT) or solute carrier family 6 member 3 (SLC6A3) is a transmembrane protein regulating dopaminergic neurotransmission. It has been implicated in playing important roles in the dopaminergic reward pathways, and thus, DAT1 is a strong candidate gene for association studies with heroin dependence. A case-control study involving 279 individuals (147 controls and 132 heroin-dependent cases) was conducted. Ten polymorphisms of the DAT1 (SLC6A3) gene were analysed for its association with heroin dependence. Following the Hardy-Weinberg equilibrium (HWE) test, genetic association analyses were performed for the study groups. The post hoc statistical power of the study was 0.655 (65.5%). Single-nucleotide polymorphism (SNP) rs246997 was found to be significantly associated with heroin dependence at allelic, genotypic, and haplotypic levels. A significant difference in the distribution of 11R allele and 10R/11R genotype of rs28363170 between heroin-dependent cases and controls was also observed. Nominal significance at degrees of freedom (df) = 5 was also observed for rs28363170. Five bimarker-based haplotype combinations were also found to be associated with heroin dependence. For the first time, 13R allele (7R/13R genotype) and 14R allele (7R/14R genotype) were identified for rs3836790 in the population. The study also reports that the 11R allele and 10R/11R genotype of rs28363170 is associated with protection against heroin dependence. 7R and 6R alleles were also found to be the common alleles of rs3836790 in the study population. The study provides evidence for the association of polymorphisms of DAT1 (SLC6A3) with heroin dependence.

A single nucleotide polymorphism in OPRM1(rs483481) and risk for heroin use disorder.

Opioid receptor mu1 (OPRM1) is the target of many opioid drugs, and it is known to have affinity toward both endogenous and exogenous opioids, opiate and opioid analgesic drugs. The present study was undertaken to explore association of single nucleotide polymorphisms (SNPs) in the OPRM1 gene with heroin use disorder. Ten OPRM1 polymorphisms were analyzed in 132 cases and 147 healthy controls. The SNP rs483481 showed significant allelic, genotypic and haplotypic association (Allelic: p-value = 0.003, OR = 1.75, CI = 1.21-2.55) (Genotypic: p-value = 0.003, OR = 1.72, CI = 1.08-2.75) with heroin use disorder. Allelic and genotypic association remained significant even after multiple testing corrections with 1000 permutations. A significant positive correlation between 'Number of times drug abstained' and 'rs483481-AA genotype' (p-value = 0.002; Pearson correlation = 0.265) was also observed. One-way ANOVA analysis demonstrated significant association of rs483481 with 'number of times drug abstained' (F = 4.86, p-value =0.009). 'A' allele and 'AA' genotype of marker rs483481 seem to confer protective effect while 'G' allele and 'GG' genotype potentiates risk for heroin use disorder. OPRM1 is found to be associated with heroin use disorder in the studied Manipuri cohort. The study suggests that individuals with G allele and GG genotypes at rs483481 could be more vulnerable to heroin dependence, and it could be taken into consideration in prevention and intervention programs.

Autistic traits and components of the folate metabolic system: an explorative analysis in the eastern Indian ASD subjects.

Objectives: Proper metabolism of the folate is crucial for maintaining DNA integrity, chromosome structure, methylation, as well as gene expression, and thus, folate is speculated to contribute to the etiology of different disorders. Since the etiology of autism spectrum disorder (ASD) is believed to be influenced by both genetic and environmental factors, we hypothesized that functional single nucleotide polymorphisms (SNPs) affecting folate metabolic pathway may have a causal role in the etiology of ASD. Methods: We analyzed three SNPs, rs2071010, rs2298444 and rs1801198 (in the folate receptor 1, folate receptor 2 and transcobalamin 2, respectively), in 867 ethnically matched subjects including 206 ASD probands and 286 controls. Plasma vitamin B6 and folate were measured in age-matched probands and controls. Results: ASD probands showed a higher frequency of rs2298444 'A' allele (P = 0.01) and genotypes with 'A' allele (P = 0.03) when compared with the controls. rs1801198 'C' allele and 'CG' genotype also showed higher occurrence in the probands (P = 0.009 and 0.005, respectively). Gender-based stratified analysis revealed a significant higher frequency of rs2298444 'A' allele (P = 0.003), genotypes with rs2298444 'A' allele (P = 0.003) and rs1801198 CG (P = 0.001) in the male probands. Studied variants also showed statistically significant associations with ASD-associated traits measured by the Childhood Autism Rating Scale. ASD subjects exhibited gross deficiency in vitamin B6 level when compared with age-matched controls (P < 0.001), which correlated with risk genetic variants. Discussion: We infer from this pioneering study on eastern Indian subjects that vitamin B6 deficiency, along with risk gene variants, may affect ASD-associated symptoms, warranting further investigation in large cohorts.

Attention deficit-hyperactivity disorder suffers from mitochondrial dysfunction.

BACKGROUND: Pathophysiology of attention-deficit hyperactivity disorder (ADHD) is not known, and therefore the present study investigated mitochondrial defects, if any in cybrids created from patients and control population. METHODS: To investigate mitochondrial pathology in ADHD, cybrids cell lines were created from ADHD probands and controls by fusing their platelets with ρ0-cells prepared from SH-SY5Y neuroblastoma cell line. Cellular respiration, oxidative stress, mitochondrial membrane potential and morphology were evaluated employing oxygraph, mitochondria-specific fluorescence staining and evaluation by FACS, and immunocytochemistry. HPLC-electrochemical detection, quantitative RT-PCR and Blue Native PAGE were employed respectively for assays of serotonin, mitochondrial ATPase 6/8 subunits levels and complex V activity. RESULTS: Significantly low cellular and mitochondrial respiration, ATPase6/8 transcripts levels, mitochondrial complex V activity and loss of mitochondrial membrane potential and elevated oxidative stress were observed in ADHD cybrids. Expression of monoamine oxidizing mitochondrial enzymes, MAO-A and MAO-B levels remained unaffected. Two-fold increase in serotonin level was noted in differentiated cybrid-neurons. CONCLUSIONS: Since cybrids are shown to replicate mitochondrial defects seen in post-mortem brains, these observed defects in ADHD cybrids strongly suggest mitochondrial pathology in this disorder. GENERAL SIGNIFICANCE: Mitochondrial defects are detected in ADHD cybrids created from patients' platelets, implying bioenergetics crisis in the mitochondria could be a contributory factor for ADHD pathology and/or phenotypes.