Kidney Week

Abstract: SA-PO510

Downregulation of EHHADH and Tubular Dysfunction in Diabetic Nephropathy

Session Information

• Diabetic Kidney Disease: Basic - III
  November 09, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Diabetic Kidney Disease

• 601 Diabetic Kidney Disease: Basic

Authors

• Whitman, Jacob, Vanderbilt University Medical Center, Nashville, Tennessee, United States

Jacob Whitman,

• Yang, Haichun, Vanderbilt University Medical Center, Nashville, Tennessee, United States

Haichun Yang,

• Harris, Raymond C., Vanderbilt University Medical Center, Nashville, Tennessee, United States

Raymond C. Harris,

• Fogo, Agnes B., Vanderbilt University Medical Center, Nashville, Tennessee, United States

Agnes B. Fogo,

Background

The pathophysiology of diabetic nephropathy (DN) is not well understood. In a previous study, we analyzed renal cortical tissue from the db/db/eNOS^-/- murine DN model by RNA-seq, identified altered novel genes with human orthologs, and assessed mRNA expression of these genes in human DN versus control. Ehhadh was downregulated in human DN. Ehhadh encodes for a peroxisomal protein that catalyzes the second and third committed steps in the peroxisomal beta-oxidation pathway (PBO), which is responsible for oxidizing long-chain and complex fatty acids. We investigated the potential role of Ehhadh in DN.

Methods

Biopsies with mild (n=20), moderate (n=19), or severe (n=20) DN were compared to normal controls (n=20). Ehhadh protein expression and localization were scored and compared to morphologic lesions, clinical data, and follow-up. Multiplex analyses examined the relationship of Ehhadh and KIM1 expression. Subcellular localization of Ehhadh and peroxisomal membrane protein ABCD3 was analyzed via super-resolution microscopy (SIM). Ehhadh mRNA expression in a high-glucose assay of cultured human proximal tubular cells (PTC) was assessed by qPCR.

Results

In normal controls, Ehhadh protein was strongly expressed in tubular epithelium and was significantly reduced in moderate and severe DN groups versus control. Downregulation of tubular Ehhadh significantly correlated with increased interstitial fibrosis (r²=0.587, p<0.0001), increased serum creatinine (r²=0.488, p<0.0001), and increased UPCR (r²=0.327, p<0.005). Ehhadh expression correlated positively with renal survival (p=0.054). Ehhadh exhibited complementary expression with KIM1 with no co-localization in tubules. SIM analyses of Ehhadh and ABCD3 indicated that tubular downregulation of Ehhadh in DN precedes loss of peroxisomal membranes. Ehhadh transcription was significantly downregulated in PTC under high-glucose conditions.

Conclusion

Ehhadh downregulation is associated with tubular injury and worse renal survival in human diabetic nephropathy. We postulate that the dysmetabolism caused by downregulation of Ehhadh and PBO promotes increased levels of complex lipid products in PTC, possibly contributing to progression and tubulointerstitial fibrosis.

Funding

• Other NIH Support