Aging and Gastrointestinal Barrier Function

Not Applicable

Completed

Conditions: Aging
Hyperthermia

Interventions: Other: Controlled hyperthermia

Registration Number: NCT05816551

Lead Sponsor: University of Texas Southwestern Medical Center

Brief Summary: The purpose of this study is to assess the gastrointestinal responses of the elderly and younger populations during hyperthermia.

Detailed Description: Heat waves are lethal and cause a disproportionate number of deaths in the elderly relative to any other age group. Although gastrointestinal barrier dysfunction is a primary cause of heat related illness, little is known about the effects of aging on gastrointestinal barrier function during hyperthermia. The central hypothesis of this work is that the elderly exhibit greater gastrointestinal barrier dysfunction during hyperthermia. Participants will complete a control trial where gastrointestinal permeability (without heating) will be assessed in young and older adults. In the experimental trial, controlled hyperthermia will be achieved using a water perfused, tube lined suit. Core body temperature will be raised to a maximum of 2 degrees Celsius above the baseline value, or an absolute temperature of 39.5 degrees Celsius. Core temperature will not be collected during the control trial. Comprehensive assessments of gastrointestinal barrier function and systemic inflammation will be assessed in young and older adults. The expected outcome of this work will re-shape our understanding of the consequences of aging on gastrointestinal barrier function during heat waves.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 22

Inclusion Criteria

Healthy male and female individuals
18-35 years or 65+ years of age
Free of any underlying moderate to serious medical conditions

Exclusion Criteria

Known heart disease
Any chronic medical conditions requiring regular medical therapy including cancer, diabetes, uncontrolled hypertension, inflammatory bowel disease, and uncontrolled hypercholestrolmia etc;
Abnormality detected on routine screening suggestive of provocable ischemia or previously undetected cardiac disease or resting left bundle branch block on screening electrocardiogram.
Current smokers, as well as individuals who regularly smoked within the past 3 years
Subject with a body mass index ≥35 kg/m2
Pregnant
Use of immunosuppressant drugs within last 4 weeks prior to screening
Use of antibiotics or antimicrobial medication in last month
Any previous abdominal surgery
Use of steroids in last 6 weeks
Regular use of probiotics in last month
Use of laxatives or anti-diarrhetic in last month

Study & Design

Study Type: INTERVENTIONAL

Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Younger participants	Controlled hyperthermia	Individuals aged 18-39 years
Older participants	Controlled hyperthermia	Individuals aged over 65 years

Primary Outcome Measures

Name	Time	Method
Log Lactulose/Rhamnose Following Control Trial	"Visit 1": 3-5 hours after ingestion of multiple sugar drink.	In vivo gastrointestinal permeability measured by quantities of orally ingested multi-sugar drink excreted in urine. The urinary recovery of each ingested sugar (lactulose, sucrose and rhamnose) was determined by multiplying the measured concentration of each sugar by the total volume of urine collected and dividing by the dose administered. Since lactulose is degraded in the colon, we used the ratio urine lactulose to rhamnose (L/R) to determine small intestinal barrier permeability.
Log Lactulose/Rhamnose Following Hyperthermia Trial	"Visit 2": 3-5 hours after ingestion of multiple sugar drink.	In vivo gastrointestinal permeability measured by quantities of orally ingested multi-sugar drink excreted in urine. The urinary recovery of each ingested sugar (lactulose, sucrose and rhamnose) was determined by multiplying the measured concentration of each sugar by the total volume of urine collected and dividing by the dose administered. Since lactulose is degraded in the colon, we used the ratio urine lactulose to rhamnose (L/R) to determine small intestinal barrier permeability.
Log Sucrose Following Control Trial	"Visit 1": 3-5 hours after ingestion of multiple sugar drink.	The urinary recovery of sucrose was determined by multiplying the measured concentration of sucrose by the total volume of urine collected and dividing by the dose administered. Sucrose is broken down rapidly in the duodenum, thus we used the urinary excretion of sucrose to assess and gastroduodenal permeability.
Log Sucrose Following Hyperthermia Trial	"Visit 2": 3-5 hours after ingestion of multiple sugar drink.	The urinary recovery of sucrose was determined by multiplying the measured concentration of sucrose by the total volume of urine collected and dividing by the dose administered. Sucrose is broken down rapidly in the duodenum, thus we used the urinary excretion of sucrose to assess and gastroduodenal permeability.

Secondary Outcome Measures

Name	Time	Method
Change in Core Temperature During Hyperthermia Trial	"Visit 2": At 0 minutes and 50-90minutes into the hyperthermia trial.	Core temperature was measured using an orally ingestible telemetric pill that was taken no less than 1 hour before the baseline period.