Abnormal atrial histology was uniformly found in multiple biopsy specimens in all patients with LAF. It was compatible with a diagnosis of myocarditis in 66% of patients (active in 25%) and of noninflammatory localized cardiomyopathy in 17% and was represented by patchy fibrosis in 17%. The cause of the pathological changes, which were found only in atrial septal biopsies but not in biventricular biopsies, in 75% of patients remains unknown.

In liver the mitochondrial sirtuin, SIRT5, controls ammonia detoxification by regulating CPS1, the first enzyme of the urea cycle. However, while SIRT5 is ubiquitously expressed, urea cycle and CPS1 are only present in the liver and, to a minor extent, in the kidney. To address the possibility that SIRT5 is involved in ammonia production also in nonliver cells, clones of human breast cancer cell lines MDA-MB-231 and mouse myoblast C2C12, overexpressing or silenced for SIRT5 were produced. Our results show that ammonia production increased in SIRT5-silenced and decreased in SIRT5-overexpressing cells. We also obtained the same ammonia increase when using a new specific inhibitor of SIRT5 called MC3482. SIRT5 regulates ammonia production by controlling glutamine metabolism. In fact, in the mitochondria, glutamine is transformed in glutamate by the enzyme glutaminase, a reaction producing ammonia. We found that SIRT5 and glutaminase coimmunoprecipitated and that SIRT5 inhibition resulted in an increased succinylation of glutaminase. We next determined that autophagy and mitophagy were increased by ammonia by measuring autophagic proteolysis of long-lived proteins, increase of autophagy markers MAP1LC3B, GABARAP, and GABARAPL2, mitophagy markers BNIP3 and the PINK1-PARK2 system as well as mitochondrial morphology and dynamics. We observed that autophagy and mitophagy increased in SIRT5-silenced cells and in WT cells treated with MC3482 and decreased in SIRT5-overexpressing cells. Moreover, glutaminase inhibition or glutamine withdrawal completely prevented autophagy. In conclusion we propose that the role of SIRT5 in nonliver cells is to regulate ammonia production and ammonia-induced autophagy by regulating glutamine metabolism.

Background-Fabry disease (FD) has been recognized as the cause of left ventricular hypertrophy in 6% of men with late-onset hypertrophic cardiomyopathy (HCM). Although FD is considered a recessive X-linked disorder, affected women are increasingly reported. The aim of our study was to determine the prevalence of FD in female patients with HCM. Methods and Results-Thirty-four consecutive women (mean age, 50Ϯ13.6 years) who received an ECG and echocardiographic diagnosis of HCM were submitted to an invasive cardiac study that included a biventricular endomyocardial biopsy. Tissue samples were analyzed for histology and electron microscopy. Peripheral blood activity of ␣-galactosidase (␣-Gal) A was assessed in all patients. None of them had a family history of FD. Histology and electron microscopy showed in 4 patients (12%; mean age, 51.5Ϯ3.9 years) the presence of cell vacuoles characterized by the accumulation of glycolipid material organized in concentric lamellar structures, diagnostic for FD. In the remaining patients, histology was consistent with HCM. In all the female carriers, the heart was the only organ clinically involved in the disease, showing concentric hypertrophy in 2 patients, asymmetric hypertrophy in 1, and apical hypertrophy in 1. The ␣-Gal A enzymatic activity was 44Ϯ14% of control values. Genetic analysis showed the presence of ␣-Gal A gene mutation in all 4 cases. Conclusions-FD may account for up to 12% of females with late-onset HCM. Those heterozygous for FD with left ventricular hypertrophy are potential candidates for enzyme enhancement/replacement therapy.

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Background-Chest pain is frequently reported in Fabry disease (FD). However, its mechanism and clinical relevance are unclear. Methods and Results-Basal troponin I level, exercise stress test, single-photon emission computed tomography imaging with 99m Tc sestamibi, coronary angiography with thrombolysis in myocardial infarction (TIMI) frame count and left ventricular angiography and endomyocardial biopsy were obtained in 13 patients with FD with angina. Ratio of external to lumen diameter of intramural arteries (E/L ratio), myocyte diameter, and extent of fibrosis were morphometrically evaluated by using tissue sections. Controls for coronary angiography and histology were 25 patients with FD without angina and 20 mitral stenosis patients with normal left ventricular function. Troponin I level was elevated in 6 of the 13 patients. Exercise stress test showed evidence of myocardial ischemia, and single-photon emission computed tomography was positive for stress-induced perfusion defects in all patients with FD with angina. Epicardial coronaries were structurally normal but showed slow flow in all and were associated with aneurisms of posterior left ventricular wall in 3 cases. Histology showed remarkable lumen narrowing of most intramural arteries (mean E/L ratioϭ3.5Ϯ1.2; PϽ0.001 versus both control groups), because of hypertrophy and proliferation of smooth muscle and endothelial cells, both engulfed by glycosphingolipids. Replacement fibrosis exceeded that of both controls (PϽ0.001). Small vessel disease correlated with coronary slow flow and extent of fibrosis, but did not with patients' age, sex, and degree of left ventricular hypertrophy.