Inhibition of carnitine palymitoyltransferase1b induces cardiac hypertrophy and mortality in mice

Abstract

Recent reports suggest that short-term pharmacological carnitine palmitoyltransferase 1 (Cpt1) inhibition improves skeletal muscle glucose tolerance and insulin sensitivity. Although this appears promising for the treatment of diabetes, these Cpt1 inhibitors are not specific to skeletal muscle and target multiple Cpt1 isoforms. To assess the effects of inhibiting the Cpt1b isoform we generated mice with a heart- and skeletal muscle-specific deletion of the Cpt1b, Cpt1b(HM-/-). These mice seem to develop normally with similar bodyweights as control mice. However, premature mortality was observed by 15 weeks of age in the Cpt1b(HM-/-) mice. The hearts of Cpt1b(HM-/-) mice were four times the size of controls. Cpt1b(HM-/-) mice were also subject to stress-induced seizures that accompanied an increased risk for premature mortality. Our data suggests that prolonged Cpt1b inhibition poses severe cardiac risk and emphasizes that attempts to improve insulin sensitivity by targeting Cpt1 with current inhibitors is not viable.

Keywords: cardiac hypertrophy; carnitine palmitoyltransferase; fatty acid oxidation; observational study.

Figure 1

Targeted deletion of CPT1b. (A) Strategy used for the generation of CPT1bHM−/− mice. (B) CPT1b mRNA expression (C) Bodyweight. (n= 5–8 per group) A Student’s T-test was performed to determine statistical significance, * denotes p < 0.05.

Figure 2

CPT1bHM−/− mice display cardiac hypertrophy and increased mortality. (A) H&E Staining of hearts from CPT1bfl/fl and CPT1bHM−/− mice. (B) Heart weight (C) Sectioned hearts were stained for neutral lipid via oil red O staining and quantified (D) Quantitative RT-PCR of mitochondrial and glucose metabolism enzymes (E) Survival curve. (n= 5–8 per group) A Student’s T-test was performed to determine statistical significance, * denotes p < 0.05.