(P19-031-25) Increased Insulin Sensitivity in Diabetic UC Davis Type 2 Diabetes Mellitus Rats Upregulates the Protein Expression of Phd2 and Occludin

Objectives: Increasing evidence suggests that insulin resistance disrupts colonic energy metabolism and barrier function; however, it is not known whether therapeutic interventions reverse these disturbances. This study aims to evaluate how improvements in glucose homeostasis influence colonic epithelial energy metabolism in diabetic UC Davis Type 2 Diabetes Mellitus (UCD‑T2DM) rats.

Methods: Male UCD T2DM rats (age: 173.4±41.4 days) 6 weeks post-onset of diabetes were randomly assigned to receive twice daily subcutaneous injections of PBS (control; n=12) or a 0.5 mg/kg dose of leptin (n=12) for 4-weeks and fed ad libitum chow diet (Inotiv 2018) throughout the intervention. An oral glucose tolerance test (OGTT) was conducted at baseline and at the end of the intervention. Pimonidazole (PMZ) was injected intraperitoneally 1 hr prior to euthanasia for colonic hypoxia assessment. Ileum and colon tissues were formalin-fixed for histology and immunohistochemistry. Colon tissue was flash frozen and assessed by rt qPCR and western blot analyses. Colon contents were collected and assessed for short-chain fatty acids by LC MS/MS.

Results: After 4 weeks of treatment Glucose OGTT integration area was significantly lower in treated animals compared to controls (26,340 vs 40,151 mg/dL 120 min; P < 0.01), whereas insulin OGTT integration area did not differ. Ileal villi height was significantly reduced in leptin-treated rats, however, no differences between groups were observed in colonic crypt depth. PMZ intensity in colon immunohistological stains did not differ between groups. Colon butyric acid levels were higher in treated rats with no difference observed for acetic and propionic acids. Gene expression abundances of colon tissue Ldha and Pparg were lower in treated rats; however, no differences were observed in protein expression. Protein expression of distal colon tissue Phd2 and Ocln was higher in treated rats.

Conclusions: Leptin-induced improvements in insulin sensitivity in the UCD T2DM Rat Model, which spontaneously develops obesity and diabetes under normal feeding conditions, are associated with colonocyte indicators of energy metabolism and tight junction expression. Further investigation is required to determine whether these observations result in functional outcomes.

Funding Sources: Major funding was provided by USDA-ARS Project 6026-51000-012-06S.