Slc22a5 haploinsufficiency does not aggravate the phenotype of the long‐chain acyl‐CoA dehydrogenase KO mouse

Abstract

Secondary carnitine deficiency is commonly observed in inherited metabolic diseases characterised by the accumulation of acylcarnitines such as mitochondrial fatty acid oxidation (FAO) disorders. It is currently unclear if carnitine deficiency and/or acylcarnitine accumulation play a role in the pathophysiology of FAO disorders. The long-chain acyl-CoA dehydrogenase (LCAD) KO mouse is a model for long-chain FAO disorders and is characterised by decreased levels of tissue and plasma free carnitine. Tissue levels of carnitine are controlled by SLC22A5, the plasmalemmal carnitine transporter. Here, we have further decreased carnitine availability in the LCAD KO mouse through a genetic intervention by introducing one defective Slc22a5 allele (jvs). Slc22a5 haploinsufficiency decreased free carnitine levels in liver, kidney, and heart of LCAD KO animals. The resulting decrease in the tissue long-chain acylcarnitines levels had a similar magnitude as the decrease in free carnitine.Levels of cardiac deoxycarnitine, a carnitine biosynthesis intermediate, were elevated due to Slc22a5 haploinsufficiency in LCAD KO mice. A similar increase in heart and muscle deoxycarnitine was observed in an independent experiment using Slc22a5 jvs/jvs mice. Cardiac hypertrophy, fasting-induced hypoglycemia and increased liver weight, the major phenotypes of the LCAD KO mouse, were not affected by Slc22a5 haploinsufficiency. This may suggest that secondary carnitine deficiency does not play a major role in the pathophysiology of these phenotypes. Similarly, our data do not support a major role for toxicity of longchain acylcarnitines in the phenotype of the LCAD KO mouse. K E Y W O R D S biosynthesis, carnitine, fatty acid oxidation disorders, haploinsufficiency, modifier

Dietary restriction in the long-chain acyl-CoA dehydrogenase knockout mouse

“…1 A). Although in this study baseline body weights of LCAD KO mice were slightly higher when compared to the WT mice (27.9 ± 0.5 versus 26.1 ± 0.4, respectively, P = 0.0126), this is not a general finding in this animal model [ 10 , 18 , 19 ]. In the first days of the study all mice lost body weight likely due to the stress associated with single housing and the baseline echocardiography.…”

“…Immunoblotting of mouse heart homogenates was performed as described in an earlier study using the same primary antibodies [ 18 ].…”

Electrophysiological Abnormalities in VLCAD Deficient hiPSC-Cardiomyocytes Do not Improve with Carnitine Supplementation

“…The heart lacks enzymes for carnitine synthesis and is therefore dependent on carnitine import from the circulation via the sodium dependent organic cation transporter (OCTN2). In a recent study, it was shown that haploinsufficiency of OCTN2 in lcFAO disorder mice results in decreased free carnitine levels and subsequently decrease in tissue and plasma LCAC accumulation but does not significantly affect clinically relevant outcome parameters (hypoglycemia, heart weight or liver weight) ( Ranea-Robles et al, 2020 ). However, it should be noted that the C14:1-acylcarnitine levels were still higher in lcFAO disorder with OCTN2 haploinsufficiency when compared to wild type in heart, liver and plasma.…”

Dietary restriction in the long-chain acyl-CoA dehydrogenase knockout mouse

“…BNP and MYH7 are well-established markers of cardiac remodeling during pathological hypertrophy. The role of MYL1 in cardiac remodeling is unknown, but we have noted that its expression is decreased in LCAD KO hearts [14]. α-SMA is a marker to detect the presence of myofibroblasts in cardiac fibrosis.…”

“…Immunoblotting of mouse heart homogenates was performed as described in an earlier study using the same primary antibodies [14]. A linear mixed effect model was used to model the echocardiography data using R.…”