Chronic Obstructive Pulmonary Disease: Genetic Polymorphisms and Intermediary Metabolism Alterations

Abstract

Chronic obstructive pulmonary disease (COPD) is a multifactorial disease characterized by airflow obstruction that is usually progressive and associated with an abnormal inflammatory response of the lungs to noxious particles and gases. Cigarette smoke (CS) is the main risk factor, but only a small proportion of smokers (15-20%) develop symptomatic disease, this suggests that there are individual susceptibility factors involved in disease onset and progression. Considering the impact of environmental and genetic risk factors in COPD, this dissertation sought to uncover genetic susceptibility biomarkers in a population affected by COPD and explore tissue metabolic alterations induced by chronic CS exposure in a mouse model. A case-control study was carried on in a COPD population, aiming to investigate whether polymorphisms of microsomal epoxide hydrolase (EPHX1) gene, and related phenotypes, had any bearing on individual susceptibility to COPD onset and severity. DNA of COPD patients and controls was genotyped for functional polymorphisms of EPHX1 gene (exon 3 Tyr113His, exon 4 His139Arg), and haplotype analysis was performed using PCR-RFLP and PCR-RT techniques. The statistical analysis did not show any significant result about the potential relationship between analyzed SNPs, related phenotypes, and COPD risk and severity. Stable isotope-resolved metabolomics approach was used to study glycolytic pathway alterations induced by chronic CS exposure in lung and liver tissue of an emphysema mouse model. C57BL/6J mice, after CS exposure, were injected via IP injection with glucose tracer containing carbon stable isotope - 13C6-glucose – then, tissues were collected and the incorporation of 13C into metabolites was monitored by mass spectrometry and nuclear magnetic resonance spettroscopy. Lung tissue analyses did not reveal any significant alteration in lung tissue glycolysis of mice exposed to CS. On the other hand, CS may contribute to dysregulated glycolysis, PPP, glycogen synthesis and utilization, in emphysema mouse model liver tissue.