Pathophysiology of Carnitine Palmitoyltransferase 2 (CPT2) Deficiency in the Dahl Salt-sensitive R at

Abstract

Carnitine palmitoyltransferase 2 (CPT2) is an essential enzyme of the carnitine shuttle, which facilitates fatty acid -oxidation in mitochondria. This study aims to characterize the various effects of CPT2 deficiency on the Dahl salt-sensitive (SS) rat metabolome and its concomitant influence on renal homeostasis. CRISPR/Cas9 was used to insert a single base pair into the SS Cpt2 gene, causing a frameshift mutation found to be lethal in homozygotes (SSCpt2−/−). Western blotting and qPCR analysis of renal cortex tissue confirmed a reduced expression of CPT2 in heterozygous (SSCpt2+/-) rats compared to wild-type (WT) littermates; therefore, male and female heterozygotes were used for all experiments. Lipid metabolomics of renal cortex samples collected from SSCpt2+/- animals at 8 weeks old on a baseline 0.4% NaCl diet revealed a significant upregulation in inflammatory lipids such as 11-HETE (p<0.01) and 12-HHT (p<0.05) when compared to WT littermates. Urine analysis from the SSCpt2+/- group demonstrated a severe reduction in acetoacetic acid production (p<0.001), indicating ketogenesis is likely impacted by the loss of CPT2 in -oxidation. Additionally, TCA cycle metabolites fumaric acid (p<0.05) and oxaloacetic acid (p<0.01) are significantly downregulated in urine from SSCpt2+/- animals. Radio telemeters were implanted into the rats at 8 weeks of age to continuously record mean arterial pressure (MAP) and monitor the development of SS hypertension over the course of several dietary treatment protocols. Three weeks of either a 4% NaCl high-salt (HS) diet or a HS + ketogenic (HSK) diet with equivalent caloric content (4:1 caloric ratio, fat: carbohydrate) were administered to the animals. No difference in MAP elevation occurred between groups after the HS challenge alone, but SSCpt2+/- animals on the HSK diet had a significantly attenuated development of hypertension (p=0.03). Further metabolic analysis after the HSK diet illustrated that both groups had similar increases in long-chain fatty acids, liver enzymes, and cholesterol levels with a decrease in short-chain fatty acids. These experiments show that the partial loss of CPT2 in the Dahl SS rat leads to dysregulation across multiple metabolic pathways. Moreover, a ketogenic diet appears to protect heterozygous animals from the development of salt-sensitive hypertension. Funding: NIH R35 HL135749 and VA I01 BX004024. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.