Histologic and electron microscopy findings in myocardium of treated Fabry disease

Fabry Disease: Cardiac Implications and Molecular Mechanisms

PURPOSE OF REVIEW

This review explores the interplay among metabolic dysfunction, oxidative stress, inflammation, and fibrosis in Fabry disease, focusing on their potential implications for cardiac involvement. We aim to discuss the biochemical processes that operate in parallel to sphingolipid accumulation and contribute to disease pathogenesis, emphasizing the importance of a comprehensive understanding of these processes.

RECENT FINDINGS

Beyond sphingolipid accumulation, emerging studies have revealed that mitochondrial dysfunction, oxidative stress, and chronic inflammation could be significant contributors to Fabry disease and cardiac involvement. These factors promote cardiac remodeling and fibrosis and may predispose Fabry patients to conduction disturbances, ventricular arrhythmias, and heart failure. While current treatments, such as enzyme replacement therapy and pharmacological chaperones, address disease progression and symptoms, their effectiveness is limited. Our review uncovers the potential relationships among metabolic disturbances, oxidative stress, inflammation, and fibrosis in Fabry disease-related cardiac complications. Current findings suggest that beyond sphingolipid accumulation, other mechanisms may significantly contribute to disease pathogenesis. This prompts the exploration of innovative therapeutic strategies and underscores the importance of a holistic approach to understanding and managing Fabry disease.

Lysosomal storage diseases

Lysosomes are cytoplasmic organelles that contain a variety of different hydrolases. A genetic deficiency in the enzymatic activity of one of these hydrolases will lead to the accumulation of the material meant for lysosomal degradation. Examples include glycogen in the case of Pompe disease, glycosaminoglycans in the case of the mucopolysaccharidoses, glycoproteins in the cases of the oligosaccharidoses, and sphingolipids in the cases of Niemann-Pick disease types A and B, Gaucher disease, Tay-Sachs disease, Krabbe disease, and metachromatic leukodystrophy. Sometimes, the lysosomal storage can be caused not by the enzymatic deficiency of one of the hydrolases, but by the deficiency of an activator protein, as occurs in the AB variant of GM2 gangliosidosis. Still other times, the accumulated lysosomal material results from failed egress of a small molecule as a consequence of a deficient transporter, as in cystinosis or Salla disease. In the last couple of decades, enzyme replacement therapy has become available for a number of lysosomal storage diseases. Examples include imiglucerase, taliglucerase and velaglucerase for Gaucher disease, laronidase for Hurler disease, idursulfase for Hunter disease, elosulfase for Morquio disease, galsulfase for Maroteaux-Lamy disease, alglucosidase alfa for Pompe disease, and agalsidase alfa and beta for Fabry disease. In addition, substrate reduction therapy has been approved for certain disorders, such as eliglustat for Gaucher disease. The advent of treatment options for some of these disorders has led to newborn screening pilot studies, and ultimately to the addition of Pompe disease and Hurler disease to the Recommended Uniform Screening Panel (RUSP) in 2015 and 2016, respectively.

Enzyme replacement therapy improves cardiovascular responses to orthostatic challenge in Fabry patients

OBJECTIVE

Fabry patients have autonomic dysfunction but usually do not present clinically overt signs of orthostatic dysregulation. This study evaluated orthostatic regulation and baroreflex sensitivity (BRS) in untreated Fabry patients and possible baroreflex improvement with enzyme replacement therapy (ERT).

METHODS

In 22 Fabry patients (aged 28W8 years), we assessed electrocardiographic RR intervals (RRIs), SBP, DBP and respiratory frequency, in supine and standing position, before and after 18 (11 patients) or 23 months (11 patients) of biweekly alpha-galactosidase A infusions (1.0 mg/kg agalsidase beta). We determined spectral powers of mainly sympathetically mediated low-frequency (0.04-0.15 Hz) and parasympathetically mediated high-frequency (0.15-0.5 Hz) RRI fluctuations, and sympathetic low-frequency powers of blood pressure fluctuations. We normalized RRI powers by relating low-frequency and high-frequency powers to total powers (low-frequency + high-frequency powers), assessed the RRI low-frequency/high-frequency ratio reflecting sympathicovagal balance. As a measure of BRS, we used the alpha-index, obtained as square root of the ratio between powers of simultaneous spectral analyses of spontaneous low-frequency variabilities in RRIs and SBP (coherence>0.5). We compared parameters in supine and standing position of untreated and treated patients with those of 15 healthy age-matched (27+/-5 years) men (repeated-measure analysis of variance, significance at P<0.05).

RESULTS

Supine biosignals were similar in all groups. Upon standing, RRIs were lower in controls and patients after ERT than in patients before ERT (P<0.05); normalized RRI high-frequency powers as well as BRS decreased, whereas DBP, low-frequency/high-frequency ratios and sympathetic low-frequency powers of SBP increased in controls and treated patients only (P<0.05).

CONCLUSION

Reduced increase in heart rate, blood pressure and sympathetic activation, and limited cardiovagal withdrawal and BRS adjustment seen in untreated Fabry patients upon standing normalized after 18 and 23 months of ERT demonstrating improved baroreflex function, which, in turn, is an established parameter of improved disease prognosis.