The role of age-related DNA methylation in the development of age-related disease

PhD ThesisAlterations in DNA methylation can have dramatic effects on gene transcription, and in particular, hypermethylation of promoter associated CpG islands is known to lead to gene inactivation. Altered patterns of DNA methylation play a key role in the development of cancer and may also play important roles in many other diseases. However, the mechanisms which lead to these changes in DNA methylation are unknown. DNA methylation patterns have also been found to change during normal ageing and these changes have similarities to those that occur during the development of cancer. This suggests that for some age-related diseases, most notably cancer, altered patterns of methylation may be an early initiating event and that disease may develop in cells which already possess changes in their DNA methylation landscape. Therefore, this study was designed to examine how methylation levels at a group of genes alters over the life-course and how these relate to methylation changes observed in major age-related diseases (cancer, specifically acute lymphoblastic leukaemia (ALL) and Hereditary Nonpolyposis Colorectal Cancer (HNPCC) patients, and atherosclerosis). DNA was collected from healthy volunteers from different ages and from ALL, HNPCC and atherosclerosis patients. Methylation was quantified using pyrosequencing. The study produced a number of findings: 1) Genes exhibiting variable methylation in PBL samples from healthy volunteers are also highly methylated in leukaemia, suggesting a common underlying mechanism. 2) Increased methylation levels were observed in lymphoid compared to myeloid cells, in healthy individuals, mirroring the patterns seen in leukaemia. 3) A subset of genes exhibiting variable methylation in PBL samples from healthy volunteers and that are highly methylated in leukaemia are aberrantly methylated in HNPCC patients and atherosclerosis patients, suggesting shared risk factors. 4) While methylation levels increase during ageing, a substantial proportion of methylation is already present at birth and may thus alter disease susceptibility throughout life. 5) Blood samples from ALL patients in remission exhibit increased methylation levels (versus controls), not directly related to their leukaemic clone, and the extent of methylation correlates with overall survival. The studies to date are compatible with a hypothesis in which altered methylation of disease-related genes pre-exists in a subset of haematopoietic cells and that these cells may be at a significantly increased risk of progression to age-related diseases. Furthermore, monitoring DNA methylation may be a valuable tool for early diagnosis of these diseases, as well as for monitoring disease progression in patients

DNA methylation of candidate genes in peripheral blood from patients with type 2 diabetes or the metabolic syndrome

Introduction: The prevalence of type 2 diabetes (T2D) and the metabolic syndrome (MetS) is increasing and several studies suggested an involvement of DNA methylation in the development of these metabolic diseases. This study was designed to investigate if differential DNA methylation in blood can function as a biomarker for T2D and/or MetS. Methods: Pyrosequencing analyses were performed for the candidate genes KCNJ11, PPARγ, PDK4, KCNQ1, SCD1, PDX1, FTO and PEG3 in peripheral blood leukocytes (PBLs) from 25 patients diagnosed with only T2D, 9 patients diagnosed with T2D and MetS and 11 control subjects without any metabolic disorders. Results: No significant differences in gene-specific methylation between patients and controls were observed, although a trend towards significance was observed for PEG3. Differential methylation was observed between the groups in 4 out of the 42 single CpG loci located in the promoters regions of the genes FTO, KCNJ11, PPARγ and PDK4. A trend towards a positive correlation was observed for PEG3 methylation with HDL cholesterol levels. Discussion Altered levels of DNA methylation in PBLs of specific loci might serve as a biomarker for T2D or MetS, although further investigation is required

Blood profile of proteins and steroid hormones predicts weight change after weight loss with interactions of dietary protein level and glycemic index

Weight regain after weight loss is common. In the Diogenes dietary intervention study, high protein and low glycemic index (GI) diet improved weight maintenance. OBJECTIVE: To identify blood predictors for weight change after weight loss following the dietary intervention within the Diogenes study. DESIGN: Blood samples were collected at baseline and after 8-week low caloric diet-induced weight loss from 48 women who continued to lose weight and 48 women who regained weight during subsequent 6-month dietary intervention period with 4 diets varying in protein and GI levels. Thirty-one proteins and 3 steroid hormones were measured. RESULTS: Angiotensin I converting enzyme (ACE) was the most important predictor. Its greater reduction during the 8-week weight loss was related to continued weight loss during the subsequent 6 months, identified by both Logistic Regression and Random Forests analyses. The prediction power of ACE was influenced by immunoproteins, particularly fibrinogen. Leptin, luteinizing hormone and some immunoproteins showed interactions with dietary protein level, while interleukin 8 showed interaction with GI level on the prediction of weight maintenance. A predictor panel of 15 variables enabled an optimal classification by Random Forests with an error rate of 24±1%. A logistic regression model with independent variables from 9 blood analytes had a prediction accuracy of 92%. CONCLUSIONS: A selected panel of blood proteins/steroids can predict the weight change after weight loss. ACE may play an important role in weight maintenance. The interactions of blood factors with dietary components are important for personalized dietary advice after weight loss

Inheritance of protection from osmotic stress

Exposure of mother worms to mild osmotic stress induces gene expression changes in offspring that protect them from strong osmotic stress. Inheritance of protection is now shown to depend on altered insulin-like signalling in the maternal germline, which confers protection through increased expression of zygotic gpdh-2, a rate-limiting enzyme in glycerol biosynthesis