(P22-009-25) Assessing the Effects of Different Dietary Fiber Interventions on Kidney Health and Vitamin D Homeostasis in a Preclinical Model of Type 1 Diabetes

Objectives: Type I diabetes (T1D) is an autoimmune disease that if left uncontrolled, increases the risk of renal injury, which can lead to nutritional deficiencies (e.g., vitamin D). We have shown that a dietary intervention with resistant starch (RS, 20%) normalized growth patterns and attenuated vitamin D metabolism, due to the protection of renal health in streptozotocin (STZ)-induced T1D Sprague Dawley (SD) rats. RS elicited the stated effects without improving fasting blood glucose (FBG). This study aimed to evaluate how a 5-day diet intervention with either 5% or 10% RS or WO prior to STZ administration could maintain kidney health, vitamin D balance, and growth patterns.

Methods: SD rats (n=56, 4 wk) were randomly assigned to one of four diets: AIN-93G with 0% RS (control), 5% RS, 10% RS, or WO diet (5% fiber). Macronutrients of the RS and WO diets were adjusted to match the control and remain isocaloric. After 5 days, 49 rats were administered an intraperitoneal (i.p.) injection of STZ, while 7 rats on the control diet received an i.p. of the vehicle (citrate buffered saline) as a non-diabetic control (NDC). After 3 wk, rats were fasted for 6 hr to collect urine, feces, and FBG before euthanization.

Results: Though neither of the fiber diets improved FBG, the WO diet increased weight gain, food intake, and food efficiency compared to the diabetic control (DC). WO also decreased urinary vitamin D binding protein (U DBP) excretion and serum C-reactive protein levels by 71% and 14%, respectively. Both RS diets were effective at protecting renal health as evidenced by a decrease in the urinary excretion of glucose, ketones, and volume. Notably, the 10% RS diet decreased relative kidney weight by 17%, normalized urinary creatinine and decreased urinary total protein (UPCR) and U DBP by 57% and 60%, respectively, compared to the DC group. The 5% RS diet maintained serum 25D levels, though excretion of UPCR and the vitamin D metabolites remained elevated.

Conclusions: Our results suggest that both RS and WO diets, at low to moderate levels, elicited positive yet different impacts on health in T1D rats. Timing of the fiber intervention was crucial in eliciting observed effects.

Funding Sources: Our work was funded by a USDA-NIFA grant to MR and USDA-NIFA-AFRI Predoctoral Fellowship to CC.