Diabetes mellitus is a systemic disorder that increases infection susceptibility. The most common site of infection is the urinary tract. Urinary tract infection (UTI) is more common, more severe, and has worse outcomes in people with diabetes. To date, the mechanisms that predispose people with diabetes to UTI have not been elucidated. This project will evaluate how insulin regulates innate immune mechanisms in the kidney?s intercalated cells. Surmounting evidence from our research group and others suggests that intercalated cells (IC) play a critical role in antibacterial defenses against uropathogenic E. coli (UPEC). Our research shows that insulin resistance and Type 2 diabetes mellitus increases UTI risk. When the insulin receptor is selectively deleted in murine ICs, UPEC susceptibility significantly increases in vivo. Also, we have demonstrated that insulin induces antimicrobial peptide (AMP) expression in primary human renal epithelial cells via the phosphatidylinositide 3-kinase (PI3K/AKT) signaling pathway. Specifically, our data show that insulin induces Ribonuclease 7 (RNase 7) production, the most potent AMP in the human urinary tract, to shield the urothelium from UPEC. Together, these data provide strong support for our hypothesis that insulin signaling plays an essential role in innate IC defenses by regulating PI3K/AKT activity and downstream AMP production. Building on these previous studies, we propose a comprehensive analysis of insulin?s ability to regulate IC defense mechanisms.
Aim 1 will evaluate how insulin resistance and Type 2 diabetes mellitus affects IC antibacterial defenses.
Aim 2 will identify how IC insulin receptor deletion impacts AMP transcription and whether targeted PI3K/AKT activation induces AMP expression.
Aim 3 will use a novel transgenic humanized mouse model to assess how insulin resistance and insulin therapy impacts the production of RNase 7 and its antimicrobial activity in vivo. The long-term objective of this project is to improve the care of diabetic patients with UTI by identifying novel therapeutic options. By evaluating the role of insulin signaling in host defense, completion of these Aims can have profound influence on the health of people with diabetes as they may develop insulin-signaling targets, like PI3K/AKT and RNase 7, as new therapeutics that prevent UTI, extending UTI treatment options beyond the scope of antibiotics.

Public Health Relevance

Urinary tract and kidney infections are serious infections that can cause many health complications and death in people with diabetes. Research now suggests that specialized cells in the kidney are important to fighting urinary tract infections. By studying how insulin regulates the antibacterial mechanisms in these cells, we can gain insight into why people with diabetes develop infections and develop new options to treat and prevent them.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Kidney Molecular Biology and Genitourinary Organ Development (KMBD)
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Rankin, Tracy L
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Nationwide Children's Hospital
United States
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