Intervention trials attempt to clarify the possible effects of certain challenge tests on study subjects (e.g. drugs effectiveness, environmental exposure experiments), while observational studies employ free-living populations to analyze the relationship between a particular effect and possible triggering factors. Based on the hypothesis under investigation, the researcher will choose the appropriate study design. Nevertheless, here we report the utility of combining observational and interventional studies to discover confident biomarkers in the clinical field (1). We contrasted metabolomic profiles related with diabetes and the oral glucose tolerance test (OGTT), a clinical test used to simulate the hyperinsulinemia observed in diabetes. We found that the main metabolic changes occur in the same metabolite classes, including energy-related metabolites, amino acids (especially brain chain amino acids, BCAA) and multiple lipids, such as free fatty acids, acyl-carnitines, triglycerides and phospholipids, among them. Hence, challenge tests such as the OGTT guarantee to be a great strategy to investigate pathological signatures associated with the development of diseases as a previous step before performing validation works in observational studies.

(1) Á. González-Domínguez, A.M. Lechuga-Sancho, R. González-Domínguez. Intervention and Observational Trials are Complementary in Metabolomics: Diabetes and the Oral Glucose Tolerance Test. Curr. Top. Med. Chem. 18 (2018) 896-900