(P20-038-23) Colonic Epithelia Hypoxia Remains Constant During the Progression of Diabetes in the UC Davis Type 2 Diabetes Mellitus Rat Model

Objectives: The progression of type 2 diabetes has been associated with alterations of the gut microbiota. Evidence from the UC Davis Type 2 Diabetes Mellitus (UCDT2DM) Rat model, which spontaneously develops diabetes, suggests that diet-independent mechanisms underlie this alteration. Recent studies have suggested that changes in colonocyte metabolism, resulting in a decrease in cellular oxygen consumption, may influence factors promoting pathogenic bacteria expansion. Thus, our objective is to determine whether colonocyte hypoxia decreases during the progression of diabetes in UCDT2DM rats.

Methods: Colon tissues were examined for colonic surface hypoxia staining using pimonidazole (PMZ) in age-matched male UCDT2M Rats (173.8 ± 3.6 days) prior to the onset of diabetes (PD, n=15), within 1-month post onset (RD, n=12), and 3-month post onset (D3M, n=12). All rats were maintained under ad libitum feeding conditions (2018 Telkad Global). Rats were given an IP injection of pimonidazole (PMZ, 60mg/kg body weight) 1-hour prior to euthanization. Colon tissue was fixed in 10% formalin, embedded in paraffin, and processed for immunohistochemistry. Staining intensity of PMZ was determined by averaging 10 unique sites across the colon section. Measurements were collected from the lumen to serosa side at every 10 µm intervals. Colon content microbiome was measured by 16S and content short chain fatty acids were measured by LC-MS.

Results: HbA1c % linearly increased in the PD (5.9 ± 0.1), RD (7.6 ± 0.4), D3M (11.5 ± 0.6) groups, indicating the progression of diabetes in this model. Similar to previous reports, gut microbial composition differed across diabetic groups in the colon (Bray Curtis Dissimilarity; PERMANOVA p-value < 0.05). Intensity of PMZ staining did not differ by diabetic group across any section of the tissue. Colonic content of butyrate was greater in D3M rats (7950 ± 3350 ng/mg) relative to PD rats (3800 ± 2500 ng/mg). There were no differences between groups for acetate or propionate.

Conclusions: Diabetes advancement in the UCDT2DM rat does not alter colonocyte hypoxia. Other mechanisms underlying diabetes associated microbial populations are yet to be identified in this model.

Funding Sources: This study was supported by USDA-ARS Project 6026-51000-010-05S.