Cardiac-specific deficiency of 3-hydroxy-3-methylglutaryl coenzyme A lyase in mice causes cardiomyopathy and a distinct pattern of acyl-coenzyme A-related biomarkers.

Deficiency of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) lyase (HL) is an autosomal recessive inborn error of acyl-CoA metabolism affecting the last step of leucine degradation. Patients with HL deficiency (HLD) can develop a potentially fatal cardiomyopathy. We created mice with cardiomyocyte-specific HLD (HLHKO mice), inducing Cre recombinase-mediated deletion of exon 2 at two months of age. HLHKO mice survive, but develop left ventricular hypertrophy by 9 months. Also, within minutes after intraperitoneal injection of the leucine metabolite 2-ketoisocaproate (KIC), they show transient left ventricular hypocontractility and dilation. Leucine-related acyl-CoAs were elevated in HLHKO heart (e.g., HMG-CoA, 34.0 ± 4.4 nmol/g versus 0.211 ± 0.041 in controls, p < 0.001; 3-methylcrotonyl-CoA, 5.84 ± 0.69 nmol/g versus 0.282 ± 0.043, p < 0.001; isovaleryl-CoA, 1.86 ± 0.30 nmol/g versus 0.024 ± 0.014, p < 0.01), a similar pattern to that in liver of mice with hepatic HL deficiency. After KIC loading, HMG-CoA levels in HLHKO heart were higher than under basal conditions, as were the ratios of HMG-CoA/acetyl-CoA and of HMG-CoA/succinyl-CoA. In contrast to the high levels of multiple leucine-related acyl-CoAs, biomarkers in urine and plasma of HLHKO mice show isolated hyper-3-methylglutaconic aciduria (700.8 ± 48.4 mmol/mol creatinine versus 37.6 ± 2.4 in controls, p < 0.001), and elevated C5-hydroxyacylcarnitine in plasma (0.248 ± 0.014 μmol/L versus 0.048 ± 0.005 in controls, p < 0.001). Mice with liver-specific HLD were compared, and showed normal echocardiographic findings and normal acyl-CoA profiles in heart. This study of nonhepatic tissue-specific HLD outside of liver reveals organ-specific origins of diagnostic biomarkers for HLD in blood and urine and shows that mouse cardiac HL is essential for myocardial function in a cell-autonomous, organ-autonomous fashion.

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