Gene Nutrient Interactions in Kidney Function

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Acute kidney disease (AKD) and chronic kidney disease (CKD) are interconnected, pathological syndromes that are quite common in the USA. CKD affects greater than 10% of the world’s population and is an increasing global health burden. The prevalence of CKD in the USA is ~12-14%. Diabetes and hypertension cause ~ two-thirds of CKD cases, while glomerulonephritis, nephrolithiasis, polycystic kidney disease, and toxicants are less common causes. Both AKD and CKD are associated with major cardiovascular complications. Thus, both new treatments for CKD and a deeper understanding of the genesis of CKD are greatly needed. Vitamin A (all-trans retinol, VA), a micronutrient and essential vitamin necessary for life, can only be obtained from our diets. Vitamin A (retinol) is required for kidney development, but much less is known about the functions of this important micronutrient, vitamin A, in the adult kidney. Vitamin A’s metabolites (e.g. retinoic acid (RA)) primarily act by binding to three distinct retinoic acid receptors (RARs) and modifying transcription. In R01 DK113088, a new R01 grant funded in December, 2017, we hypothesized that RARβ played a protective role against CKD and that a RARβ2 selective agonist could inhibit the development of CKD associated with obesity. We have proved these hypotheses and we will build on our exciting results and expand our research into new, but complementary directions. Our hypothesis for Aim (1) is that the RARβ2 selective agonist, AC261066, will be effective in reducing the pathological sequelae after more than one type of kidney injury, not just lipotoxicity-related injury associated with obesity-induced chronic kidney disease. For Aim (2), we hypothesize that vitamin A, via each retinoic acid receptor, including RARγ, which we are just beginning to study, has key actions in multiple, different cell types in the adult kidney and that mice deficient in RARs in specific kidney cells may be models of various human kidney diseases. We propose two specific aims: Specific Aim (1): Because we have evidence that a selective RARβ2 agonist has a therapeutic impact on the development of CKD in one mouse model, we propose to test the efficacy of this RARβ2 agonist in two additional CKD models, potentially creating a rationale to use AC261066 as a lead compound for treatment of CKD and to define its gene targets. Specific Aim (2): Our genetic approach to study the micronutrient vitamin A has been fruitful and has generated several potentially useful models of various types of CKD. Furthermore, our results suggest that the interaction of the kidney with other organ systems varies in different mouse models. Thus, we propose to evaluate the actions of the retinoic acid receptors α, β, and γ in specific cell types in the kidney. We will, through this research, understand the pathologies of CKDs in more depth, elucidate how these pathologies relate to nutrition and aberrant vitamin A signaling, discover new, useful models of CKD, and advance the development of a novel therapeutic for CKD.