I had not heard of the term “exposome” until last week (Gastroenterology 2012; 142: 1403-4).  However, this term was coined in 2005 (Cancer Epidemiol Biomarkers Prev 2005; 14: 1847-50).    This term is meant to describe the environmental analog of the genome.

Particularly with the gastrointestinal tract, environmental exposures are often considered a cofactor in disease development.  While there has been an increased understanding of the role of genes in the development of disease, it is abundantly clear that environment exposures can independently cause disease or act as a ‘second hit.’  The gastrointestinal tract is exposed to fluids which contain a multitude of elements and microorganisms, and to foods with their variability in nutrients, microbes and pollutants.  Other environmental factors include smoking, ionizing radiation, noise, breastfeeding, medications, and antimicrobials.

This cited commentary explains how environmental scientists are trying to unravel the ‘exposome.’

• Bottom-up strategy:  measure external sources of the individual exposome at multiple time points.  This strategy may benefit from improvement in informatics, remote & personal sensing devices.
• Top-down strategy: examines internal milieu including blood, biologic specimens, and transcriptomics/proteonomics.  Early examples include distinct signatures associated with specific environmental exposures.

Both strategies require validation to understand how external exposures trigger internal changes and disease expression.  Promising fields in gastroenterology for the study of the exposome include IBD, gastrointestinal cancers, functional disorders, and even obesity.  It is likely that studies of the exposome will answer questions about why the frequency of so many diseases are changing much more readily than studies of the genome.

Related blog posts:

Eat your veggies…if you don’t want to get sick

Why are we seeing so many more cases

Additional references:

• -PLoS One 2010; 5 e10746.  Novel associations between type 2 diabetes and specific chemical exposures.
• -Nature 2006; 444: 1027-31.  Obesity-associated gut microbiome.
• -BMC Med Genomics 2010; 3: 17.  Chemical factors associated with disease-related gene expression data.