Abstract: SA-PO235
Klotho KL1 Domain Directly Prevents Cardiac Fibrosis in a Rat CKD-MBD Model
Session Information
- CKD-MBD: Basic and Translational
October 26, 2024 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Bone and Mineral Metabolism
- 501 Bone and Mineral Metabolism: Basic
Authors
- Halim, Arvin, Indiana University School of Medicine, Indianapolis, Indiana, United States
- Narayanan, Gayatri, Indiana University School of Medicine, Indianapolis, Indiana, United States
- Srinivasan, Shruthi, Indiana University School of Medicine, Indianapolis, Indiana, United States
- O'Neill, Kalisha, Indiana University School of Medicine, Indianapolis, Indiana, United States
- Chen, Neal X., Indiana University School of Medicine, Indianapolis, Indiana, United States
- Moe, Sharon M., Indiana University School of Medicine, Indianapolis, Indiana, United States
- Lim, Kenneth, Indiana University School of Medicine, Indianapolis, Indiana, United States
Background
α-Klotho has a bifunctional role as a co-receptor for FGF23 and exerts FGF23-independent cardioprotective effects. However, the fragment of Klotho responsible for direct cardioprotective effects is unknown. Our group’s computational modeling suggests that the Klotho KL1 domain (which has a lipid raft binding site and lacks FGF23 binding elements) is the fragment responsible for these effects. This study aimed to assess whether KL1 can exert direct anti-fibrotic effects at the heart in CKD rats.
Methods
Cy/+ male rats (CKD rats) were fed a casein-based diet starting at 22 wks (~50% normal renal function), and then treated daily with intraperitoneal injections of 50 μg/kg KL1 (n=9) or vehicle (n=23) for 5-7 weeks starting at 27 wks. Normal littermates (NL, n=23) were used as controls. At 32-34 weeks (~15% normal renal function), tissues were harvested for molecular and histological analyses. For in vitro fibrosis experiments, human cardiac fibroblasts (HCFs) were exposed to 3.8mM phosphate and 2.0mM calcium (P+C) and treated daily for 5 days with 5nM KL1 or vehicle. For immunofluorescence (IF), HCFs were incubated with 500nM AlexaFluor-tagged KL1 and hybridized with anti-asialoGM1 (GA1) antibody to label lipid rafts.
Results
CKD rats had increased left ventricular (LV) and perivascular fibrosis as assessed by Masson’s Trichome staining (P<0.0001), TGF-β (P<0.004), and LV mass index (LVMI P<0.0004) compared to NL. This was accompanied by mineral dysregulation (high phosphate, iFGF23 and iPTH (P<0.0006)) and reduced renal function (high BUN and creatinine (P<0.0001)) compared to NL rats. Significantly, KL1-treated rats exhibited reduced fibrosis (P<0.01) and TGF-β (P<0.02) in LV tissue. These effects were independent of changes in LVMI, mineral dysregulation, cardiac inflammatory markers (TNFα, IL-6, and MCP-1), and renal function. In HCFs, KL1 reduced collagen type I (P<0.0001) and α-SMA (P<0.02) cultured under P+C stress. IF demonstrated KL1 localization to the membrane, cytoplasm, and nuclei, but not with GA1-containing lipid rafts.
Conclusion
KL1 directly improved cardiac fibrosis independent of alterations in renal function, mineral metabolism, nor inflammation in CKD rats. Further studies are needed to validate these findings and elucidate the receptor(s) of KL1 responsible for its anti-fibrotic effects.
Funding
- Other NIH Support