CPT1A protects against renal fibrosis in mouse model of diabetic kidney disease

Abstract

Objective To determine the effect of carnitine palmitoyl-transferase 1A (CPT1A) on renal interstitial fibrosis in diabetic kidney disease (DKD). Methods A total of 16 4-week-old male C57BL/6 mice were randomly divided into Control (Ctrl) group (n=8) and DKD group (n=8). The mice of Ctrl group were fed with normal diet, and those from the DKD group were inflicted with intraperitoneal streptozotocin injection plus high fat diet (STZ/HFD) to induce DKD model. Their 24-hour urine were collected, and fasting blood glucose level and body weight were measured every 4 weeks. After 16 weeks of modeling, the mice (aged 20 weeks) were sacrificed, and the levels of serum creatinine, urine creatinine and urine albumin were measured. PAS and Masson stainings were used to analyze the renal glomerulus morphology and interstitial fibrosis. Immunohistochemical assay and Western blotting were performed to detect the expression of CPT1A and fibrosis markers. In in vitro study, human proximal tubular epithelial HK-2 cells were divided into Ctrl group, HG group (30 mmol/L glucose treatment), and M group (30 mmol/L mannitol treatment). After treatment for 48 h, the protein levels of CPT1A and fibrosis markers were detected with Western blotting. After HK-2 cells were transfected with CPT1A overexpression plasmid and then treated with 30 mmol/L glucose, cell morphological changes and the expression of CPT1A and fibrosis markers were observed. Results The mice of the DKD group had obvious glomerulus hypertrophy, mesangial expansion and renal interstitial fibrosis, increased levels of serum creatinine and urine albumin/creatinine ratio (P < 0.05), decreased CPT1A expression, and elevated protein levels of fibrosis markers when compared with the mice of the Ctrl group. In in vitro experiment, HG treatment induced the morphological changes of HK-2 cells into long spindle-shape, decreased level of CPT1A, and increased levels of fibrosis markers, which were not affected by alterations of osmotic pressure. However, CPT1A overexpression significantly reversed these HG-induced morphological changes and high expression of fibrosis markers. Conclusion Overexpression of CPT1A may show potential inhibitory effect on renal interstitial fibrosis in DKD mice.

Keywords

• carnitine palmitoyl-transferase 1a
• diabetic kidney disease
• renal interstitial fibrosis
• human proximal tubular cells