Identification of differential gene expression profile in circulating lympho-monocytes of apparently healthy young adults in presence of cardiovascular risk factors through whole-genome transcriptomic profile analysis with oligo-RNA microarrays

Abstract

Background and Aims: Preliminary evidence indicates that the gene expression profile of circulating white blood cells is significantly affected by the exposure to cardiovascular (CV) risk factors. However the few available studies have several limitations, including small sample size and narrow range of genes tested. The aim of the present thesis is to provide a review of the current literature on this relationship and the presentation of the results of a clinical research program aimed at investigating the gene expression profile at whole-genome level in peripheral blood mononuclear cells (PBMC) of healthy volunteers in presence of CV risk factors and associated biomarkers. Materials and Methods: In the clinical study, PBMC’s expression profile was evaluated using Agilent whole genome oligonucleotide mRNA microarrays in 167 apparently healthy young-adults, all volunteers in a CV risk assessment study. Enrolled subjects were free of diabetes, CV and inflammatory diseases, and did not take pharmacological medications. Data analysis was performed using methods developed to address differential expression for quantitative phenotypes and enrichment of gene sets in ranked lists of genes. Results. Differential expression profiles were identified in presence of cigarette smoking, high LDL-cholesterol concentrations, increased biomakers associated with CV risk (like IL-6 and TNF-alpha) and in presence of increased carotid intima-media thickness (IMT), a surrogate marker of atherosclerosis. In all these conditions, gene expression profile was characterized by a pro-inflammatory signature. More in detail, cigarette smoking was characterized by an over-expression of groups of genes and molecular pathways involved in the innate immunity, whereas smoking was associated with the over-expression of genes involved in the cell-mediated immunitary response and high IMT was characterized by an over-expression of genes of the mitochondrial respiratory chain. Interestingly, in subjects who smoked and had high LDL-c compared to low LDL-c non-smokers, the transcriptomic profile was characterized by the co-presence of the two bio-signatures and the enrichment of both innate and cell-mediated immunity. The gene expression profile associated with gender, age, and different proportions of leukocyte sub-populations are also presented as collateral results. Conclusions: In conclusion, in apparently healthy young adults, the presence of several CV risk factors such as cigarette smoking, high LDL-cholesterol and thickened IMT are associated with the over-expression of genes related to the inflammatory response. However, different risk factors are characterized by different transcriptomic “signatures”. Presented data and supportive literature suggest that gene expression profile in PBMCs reflects the biological processes involved in the chronic sub-clinical inflammation that is a key patho-physiological element of CV disease.