Objective:

To establish whether prolonged small bowel transit time (SBTT) and/or gastric pH mediate a relationship between vagal dysfunction (VD) and small intestinal bacterial overgrowth (SIBO) in people with HIV (PWH).

Background:

HIV-associated autonomic neuropathy (HIV-AN) is common and VD is part of HIV-AN. However, the associations between VD and end organ dysfunction are unknown.  This is particularly relevant in the gastrointestinal (GI) system given vagal control proximal GI motility, and the role of increased translocation of GI microbial products as a stimulus for abnormal immune activation in PWH.

Design/Methods:

This is an ongoing cross-sectional study which (as of this writing) has complete baseline data on 50 people with well-controlled HIV. Participants underwent: 1) a standardized battery of autonomic function tests (AFTs), 2) glucose breath testing for SIBO; and 3) assessment of GI transit times and pH using a wireless motility capsule (WMC). VD was defined as a Composite Autonomic Severity Score (CASS) cardiovagal sub-score of at least one (based on the AFTs).

Results:

The mean age of participants was 50 (SD=12) years; 78% were men; 46% black, 24% white and 24% Hispanic/Latinx. Twenty-nine (58%) participants met criteria for VD and 24 (48%) met criteria for SIBO. Among participants with VD, SIBO (defined as the increase in methane and hydrogen content in the breath following glucose ingestion) was significantly greater (22.8 vs 11.5 ppm; p=0.038). There was also an association between SBTT and SIBO (B= 0.097, p=0.011) However, participants with VD did not experience prolonged SBTT (5.8 vs. 5.1 hours, p=0.492) or differences in minimum gastric pH (1.2 vs .99, p=0.483).

Conclusions: