Homocysteine metabolism and the associations of global DNA methylation with selected gene polymorphisms and nutritional factors in patients with dementia Małgorzata Bednarska-Makaruk a, ⁎,Ałła Graban b , Agata Sobczyńska-Malefora c , Dominic J. Harrington c , Michael Mitchell c , Kieran Voong c , Letian Dai c , Wanda Łojkowska b , Anna Bochyńska b , Danuta Ryglewicz b , Anna Wiśniewska a , Hanna Wehr a a Department of Genetics, Institute of Psychiatry and Neurology, Warsaw, Poland b First Department of Neurology, Institute of Psychiatry and Neurology, Warsaw, Poland c The Nutristasis Unit and the Molecular Haemostasis and Thrombosis Laboratory, Viapath, St. Thomas' Hospital, London, UK abstract article info Article history: Received 27 December 2015 Received in revised form 27 April 2016 Accepted 6 May 2016 Available online 07 May 2016 Epigenetics (particularly DNA methylation) together with environmental and genetic factors, are key to under- standing the pathogenesis of many diseases including dementia. Disturbances in DNA methylation have already been implicated in dementia. Homocysteine metabolism, with folate and vitamin B 12 as essential cofactors, is in- tegral to methylation processes. We evaluated in a case-control study the association of global DNA methylation, homocysteine, folate and vita- min B 12 status with dementia. Selected polymorphisms of genes previously associated with dementia develop- ment and the influence of various factors on DNA methylation were also investigated. 102 patients with dementia (53 with Alzheimer's disease, 17 with vascular dementia and 32 with mixed demen- tia) were recruited. The non-demented controls consisted of 45 age-matched subjects without dementia and 47 individuals with mild cognitive impairment. Global DNA methylation was determined by Imprint Methylated DNA Quantification Kit MDQ1 (Sigma-Aldrich, Gillingham, Dorset, UK). Plasma homocysteine, serum folate and vitamin B 12 were determined by chemiluminescence. Plasma and erythrocyte 5-methyltetrahydrofolate and plasma methylmalonic acid (markers of folate and vitamin B 12 status) were measured by HPLC. APOE, PON1 p.Q192R, MTHFR 677C N T (c.665C N T) and IL1B-511C N T polymorphisms were identified using PCR-RFLP methods. Patients with dementia had significantly higher concentrations of homocysteine (p = 0.012) and methylmalonic acid (p = 0.016) and lower folate (p = 0.002) and plasma 5-methyltetrahydrofolate (p = 0.005) than non- demented subjects. There was no difference in DNA methylation between patients and controls. A non- significant tendency to higher DNA methylation in patients with vascular dementia (p = 0.061) was observed. Multivariate regression analysis of all recruited individuals demonstrated a significant positive association be- tween DNA methylation and folate (p = 0.013), creatinine (p = 0.003) concentrations and IL1B-511 T (p = 0.002) and PON1 192R (p = 0.049) alleles and negative association with fasting glucose (p = 0.004). The biochemical results showed significantly lower folate and vitamin B 12 status in demented patients than con- trols. Global DNA methylation was associated with markers of folate status, creatinine, glucose and PON1 and IL1B polymorphisms. © 2016 Elsevier Inc. All rights reserved. Keywords: Dementia Global DNA methylation Homocysteine Folate Plasma 5-methyltetrahydrofolate Vitamin B12 Plasma methylmalonic acid 1. Introduction Dementia is caused by defects in cerebral structure and function, often manifesting as a progressive deterioration of memory and other cognitive functions. In the elderly Alzheimer's disease (AD) is the most prevalent cause of dementia and results in the irreversible loss of neurons, particularly in the cortex and hippocampus (Sosa-Oritz et al., 2012). Pathological hallmarks of AD include extracellular β-amyloid plaques and intraneuronal neurofibrillary tangles of hyperphosphorylated forms of microtubule-associated protein tau. AD is classified into early onset AD (EOAD, b 65 years of age) accounting for 1–5% of all cases, and late-onset AD (LOAD, N 65 years of age) ac- counting for N 95% of all those affected. Causal mutations in three genes: amyloid precursor protein (APP), presenilin 1 (PSEN1) and Experimental Gerontology 81 (2016) 83–91 ⁎ Corresponding author at: Institute of Psychiatry and Neurology, Department of Genetics, Sobieskiego 9, 02-957 Warsaw, Poland. E-mail address: makaruk@ipin.edu.pl (M. Bednarska-Makaruk). http://dx.doi.org/10.1016/j.exger.2016.05.002 0531-5565/© 2016 Elsevier Inc. All rights reserved. Contents lists available at ScienceDirect Experimental Gerontology journal homepage: www.elsevier.com/locate/expgero