Abstract: SA-PO108
Regulation of Renal Gluconeogenesis in Acidotic Proximal Tubule-(PT) Targeted Dual Insulin/Insulin-Like-Growth Factor (IGF) Receptor Knockout Mice
Session Information
- Diabetic Kidney Disease: Basic - III
October 27, 2018 | Location: Exhibit Hall, San Diego Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Diabetic Kidney Disease
- 601 Diabetic Kidney Disease: Basic
Authors
- Fluitt, Maurice B., Georgetown University, Washington, District of Columbia, United States
- Aljaylani, Abdullah, Georgetown University, Washington, District of Columbia, United States
- Tiwari, Swasti, Sanjay Gandhi PGI, Lucknow, India
- Ecelbarger, Carolyn M., Georgetown University, Washington, District of Columbia, United States
Background
Acidosis is associated with an increase in renal gluconeogenesis due to upregulation of ammoniagenesis, which liberates α-ketoglutarate, a substrate for gluconeogenesis. Insulin and IGF1 have been postulated to upregulate transport of glutamine into PT (precursor of ammoniagenesis), but may also be associated with decreased gluconeogenic capacity by phosphorylating forkhead box protein 01 (FOX01). Thus, net regulation of renal gluconeogenesis by insulin in the context of acidosis is uncertain.
Methods
We bred PT-select dual Insr/Igf1r knockout mice with Cre-recombinase driven by the γ-glutamyltransferase promoter. Male and female KO and WT littermates were made acidotic by consuming 280 mM NH4Cl in the drinking water for 7 days.
Results
Male KO mice demonstrated a 23% increase in fasting glucose (18-hr) with acid loading, while this increase was 2% in the WT males. In contrast, female WT mice had a mean 8% decrease and KO a 5% increase, indicating less sensitivity of females. Acid-treated male KO mice had lower blood pH and bicarbonate as compared to same sex WT (significant interaction). Female mice did not show this genotype dichotomy. Ex vivo capacity to synthesize glucose (with unlimited substrate) was measured in proximal tubule suspensions harvested from acid- and control- treated WT and KO mice. PT harvested from control KO males produced 56% more glucose then WT males. In agreement, the ratio of phosphorylated (Serine 256) FOX01 to total FOX01 was 37% lower in PT from the KO versus WT male mice. Acid loading increased glucose producing capacity of PT only in the WT males, while reducing the pFOX01/FOX01 ratio in all groups. In agreement, in males, acidosis significantly increased renal protein abundances of two rate-limiting enzymes in gluconeogenesis, i.e., fructose bisphosphatase-1 (FBP1) and phosphoenolpyruvate carboxykinase (PEPCK). The increase in FBP1 was 2-fold higher in the KO mice; however, KO mice also had significantly lower cortical expression of glucose-6-phosphatase (terminal gluconeogenic enzyme).
Conclusion
Chronic acidosis increases the capacity of the PT to produce glucose. Insulin and/or IGF1 appear to be involved in homeostatic regulation of this production via FOX01.
Funding
- Clinical Revenue Support