Association of MTHFR C677T and A1298C Polymorphisms in Metabolic Alterations, Neuroimaging, and Cognitive Decline in Alzheimer's Disease: Case-Control and Bioinformatics Insights.

Alzheimer's disease (AD) is a multifactorial neurodegenerative disorder influenced by genetic, metabolic, and lifestyle factors. Polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene, notably C677T and A1298C, may increase AD susceptibility through disruptions in one-carbon metabolism and homocysteine accumulation. This study examined the association of MTHFR C677T and A1298C variants with metabolic alterations, cognitive decline, and AD risk. A case-control study was conducted with 120 AD patients and 120 cognitively healthy controls. Cognitive function was assessed using the Hindi Mini-Mental State Examination (HMMSE) and Hindi Mattis Dementia Rating Scale (HMDRS). MRI evaluated white matter hyperintensities and cortical atrophy. Biochemical markers, including homocysteine, folate, and vitamin B12, were measured. Genotyping was performed via TaqMan SNP assays. Functional enrichment and protein-protein interaction analyses were conducted to investigate molecular mechanisms. AD cases demonstrated elevated homocysteine and blood glucose, reduced folate, and impaired cognition. Both MTHFR C677T and A1298C polymorphisms were significantly associated with AD risk under dominant and over-dominant models (ORs 3.41-4.09). Risk-allele carriers exhibited pronounced metabolic alterations. Bioinformatics analyses revealed disruption in one-carbon metabolism, oxidative stress defense, and vascular pathways, with indirect interactions between MTHFR and key AD genes (APP, PSEN1/2, MAPT, APOE, CLU, PICALM, SORL1). MTHFR C677T and A1298C variants contribute to AD susceptibility through metabolic and vascular mechanisms that exacerbate cognitive decline. Integrating genetic, biochemical, and cognitive assessments highlights potential targets for early prevention and therapeutic interventions.