Sex-specific variations in global DNA methylation levels with age: a population-based exploratory study from North India

Global DNA Methylation Levels Viz-a-Viz Genetic and Biochemical Variations in One Carbon Metabolic Pathway: An Exploratory Study from North India

Despite the importance of one carbon metabolic pathway (OCMP) in modulating the DNA methylation process, only a few population-based studies have explored their relationship among healthy individuals. This study aimed to understand the variations in global DNA methylation levels with respect to selected genetic (CBS 844ins68, MTRR A66G, MTR A2756G, and MTHFR C677T polymorphisms) and biochemical (folate, vitamin B12, and homocysteine) markers associated with OCMP among healthy North Indian adults. The study has been conducted among 1095 individuals of either sex (69.5% females), aged 30-75 years. A sample of 5 mL of blood was collected from each participant. Homocysteine, folate, and vitamin B12 levels were determined using the chemiluminescence technique. Restriction digestion was performed for genotyping MTRR A66G, MTR A2756G, and MTHFR C677T polymorphisms and allele-specific PCR amplification for CBS 844ins68 polymorphism. Global DNA methylation levels were analyzed using ELISA-based colorimetric technique. Of the selected genetic and biochemical markers, the mutant MTRR A66G allele was positively associated with global DNA methylation levels. Further, advanced age was inversely associated with methylation levels. MTRR 66GG genotype group was hypermethylated than other genotypes in folate replete and vitamin B12 deficient group (a condition prevalent among vegetarians), suggesting that the G allele may be more efficient than the wild-type allele in such conditions. Global DNA methylation levels appeared to be more influenced by genetic than biochemical factors. MTRR 66G allele may have a selective advantage in vitamin B12 deficient conditions. Further research should be undertaken to understand how genetics affects epigenetic processes.

Hypertension and global DNA methylation: a population-based study in rural, Punjab, India

Hypertension is a significant public health concern and a modifiable risk factor for increased mortality worldwide. It is reported to be influenced by gene-environment interactions and micronutrient intake. This study aims to understand the relationship between global DNA methylation levels and hypertension, independently and in the context of micronutrient status, among rural population in Punjab, India. A total of 2300 individuals, aged 30-75 years, (54.9% females) were screened for blood pressure. Of 2300 screened individuals, 900 (age sex matched 450 cases and 450 controls of hypertension) individuals were selected to examine the relationship between hypertension, global DNA methylation (5mC), and biochemicals (Folate, Vitamin B12, and Homocysteine). Folate, vitamin B12, and homocysteine levels were estimated using chemiluminescence technique. The ELISA-based colorimetric technique was used for performing peripheral blood leucocyte (PBL) global DNA methylation (5mC). Statistical analyses were performed using SPSS version 22.0. Hypertensives were found to have significantly lower levels of global DNA methylation than normotensives (0.65 vs. 0.72 respectively; p-value = 0.01*). Individuals in the 1st quartile of 5mC were at significantly (OR: 1.671; 95% CI: 1.206-2.315; p-value = 0.01*) increased risk for hypertension in comparison to those in the 4th quartile (reference). Further hypertensives on medication with controlled blood pressure (BP) were significantly hypermethylated as compared to hypertensives on medication with uncontrolled BP (0.70 vs. 0.62 respectively; p-value = 0.04*). Folate appeared to mediate global DNA methylation among hypertensives on medication-controlled BP. Further hypertension driven hypomethylation hints towards accelerated biological aging among younger hypertensives. Hypertension may be associated with Global DNA hypomethylation in the studied rural population of Punjab, India. Folate sufficiency may prove to be an aid in improving the methylation levels among the cases of hypertension who were on medication and had controlled BP.

Current Challenges of Methylation-Based Liquid Biopsies in Cancer Diagnostics

In current clinical practice, effective cancer testing and screening paradigms are limited to specific types of cancer, exhibiting varying efficiency, acceptance, and adherence. Cell-free DNA (cfDNA) methylation profiling holds promise in providing information about the presence of malignity regardless of its type and location while leveraging blood-based liquid biopsies as a method to obtain analytical samples. However, technical difficulties, costs and challenges resulting from biological variations, tumor heterogeneity, and exogenous factors persist. This method exploits the mechanisms behind cfDNA release but faces issues like fragmentation, low concentrations, and high background noise. This review explores cfDNA methylation's origins, means of detection, and profiling for cancer diagnostics. The critical evaluation of currently available multi-cancer early detection methods (MCEDs) as well as tests targeting single genes, emphasizing their potential and limits to refine strategies for early cancer detection, are explained. The current methodology limitations, workflows, comparisons of clinically approved liquid biopsy-based methylation tests for cancer, their utilization in companion diagnostics as well as the biological limitations of the epigenetics approach are discussed, aiming to help healthcare providers as well as researchers to orient themselves in this increasingly complex and evolving field of diagnostics.