While many studies of intestinal permeability (IP) are focused on those with gastrointestinal (GI) disorders, there is a rising trend to analyze IP among individuals with mental health conditions including posttraumatic stress disorder (PTSD) with and without diagnosed GI conditions. This interest stems from the association between gut dysbiosis and chronic inflammation, which are mechanisms linked to stress-related somatic and mental health conditions. Efforts to date have resulted in the exploration of non-invasive and feasible measures to identify an IP biomarker that could also serve as a treatment target. Additionally, those conducting studies regarding IP often recruit individuals without health problems and compare levels of biomarkers of IP to those obtained from participants with conditions of interest. This study aimed to assess correlations between blood-based biomarkers of IP, as well as examine the association between blood-based biomarkers of IP and PTSD symptoms. Blood was sampled from seventeen United States military Veterans with variable severity of PTSD symptoms per the posttraumatic checklist for DSM-5 (PCL-5) (n = 6 with scores over 31 indicating clinically meaningful symptoms of PTSD; overall range 0-49, mean 20.8, standard deviation 15.7) and analyzed blood biomarkers of IP including citrulline, diamine oxidase, glucagon-like peptide-2, intestinal fatty-acid binding protein, lipopolysaccharide binding protein, lipopolysaccharide, and zonulin. Correlations between the IP blood-based biomarkers ranged from ρ of -0.31 to 0.35. None of the measured biomarkers were significantly correlated to PTSD symptom severity scores (ρ of -0.34 to 0.05). Although based on limited sample size, our results call into question the specificity of blood-based biomarkers of IP when: (1) studying persons with and without PTSD symptoms in whom clinical GI disorders are not necessarily the focus of the study; and (2) comparing IP results among individuals with well-defined disease states to those without the disease (e.g., controls). Further studies are needed to explore the role of external factors (e.g., nutrition, obesity, alcohol use) on IP and to determine if the biomarkers studied are appropriate for measuring IP in people with a range of symptoms related to PTSD.
Keywords: Blood-based biomarker; Intestinal permeability; PCL-5; PTSD; Posttraumatic stress.