Use of Elamipretide in patients assigned treatment in the compassionate use program: Case series in pediatric patients with rare orphan diseases.

Several mitochondrial diseases are caused by pathogenic variants that impair membrane phospholipid remodeling, with no FDA-approved therapies. Elamipretide targets the inner mitochondrial membrane where it binds to cardiolipin, resulting in improved membrane stability, cellular respiration, and ATP production. In clinical trials, elamipretide produced clinical and functional improvements in adults and adolescents with mitochondrial disorders, such as primary mitochondrial myopathy and Barth syndrome; however, experience in younger patients is limited and to our knowledge, these are the first case reports on the safety and efficacy of elamipretide treatment in children under 12 years of age. We describe the use of elamipretide in patients with mitochondrial disorders to provide dosing parameters in patients aged <12 years.

Long term follow-up in two siblings with Sengers syndrome: Case report.

BACKGROUND: Sengers syndrome is characterized by congenital cataract, hypertrophic cardiomyopathy, mitochondrial myopathy, and lactic acidosis associated with mutations in AGK gene. Clinical course ranges from a severe fatal neonatal form, to a more benign form allowing survival into adulthood, to an isolated form of congenital cataract. Thus far few reported cases have survived the second decade at their latest examination, and no natural history data are available for the disease. CASE PRESENTATION: Here we provide a 20-year follow-up in two siblings with a benign form of Sengers syndrome, expanding the phenotypical spectrum of the disease by reporting a condition of ovarian agenesis. CONCLUSION: To our knowledge, this report provides the first longitudinal data of Sengers syndrome patients.

Characterization of a Novel Splicing Variant in Acylglycerol Kinase (AGK) Associated with Fatal Sengers Syndrome.

Mitochondrial functional integrity depends on protein and lipid homeostasis in the mitochondrial membranes and disturbances in their accumulation can cause disease. AGK, a mitochondrial acylglycerol kinase, is not only involved in lipid signaling but is also a component of the TIM22 complex in the inner mitochondrial membrane, which mediates the import of a subset of membrane proteins. AGK mutations can alter both phospholipid metabolism and mitochondrial protein biogenesis, contributing to the pathogenesis of Sengers syndrome. We describe the case of an infant carrying a novel homozygous AGK variant, c.518+1G>A, who was born with congenital cataracts, pielic ectasia, critical congenital dilated myocardiopathy, and hyperlactacidemia and died 20 h after birth. Using the patient's DNA, we performed targeted sequencing of 314 nuclear genes encoding respiratory chain complex subunits and proteins implicated in mitochondrial oxidative phosphorylation (OXPHOS). A decrease of 96-bp in the length of the AGK cDNA sequence was detected. Decreases in the oxygen consumption rate (OCR) and the OCR:ECAR (extracellular acidification rate) ratio in the patient's fibroblasts indicated reduced electron flow through the respiratory chain, and spectrophotometry revealed decreased activity of OXPHOS complexes I and V. We demonstrate a clear defect in mitochondrial function in the patient's fibroblasts and describe the possible molecular mechanism underlying the pathogenicity of this novel AGK variant. Experimental validation using in vitro analysis allowed an accurate characterization of the disease-causing variant.

Acylglycerol Kinase-Targeted Therapies in Oncology.

Acylglycerol kinase (AGK) is a recently discovered mitochondrial lipid kinase, and mutation of its gene is the fundamental cause of Sengers syndrome. AGK is not only involved in the stability of lipid metabolism but also closely related to mitochondrial protein transport, glycolysis, and thrombocytopoiesis. Evidence indicates that AGK is an important factor in the occurrence and development of tumors. Specifically, AGK has been identified as an oncogene that partakes in the regulation of tumor cell growth, invasion, metastasis, and drug resistance. The versatility of AGK and its unique role in different types of cancerous and normal cells greatly piqued our interest. We believe that AGK is a promising target for cancer therapy. Therefore, this review summarizes the main research advances concerning AGK, including the discovery of its physiological/pathogenic mechanisms, and provides a reference for the feasible evaluation of AGK as a therapeutic target for human diseases, particularly tumors.

Sengers syndrome: a rare case of cardiomyopathy combined with congenital cataracts in an infant: post-mortem case report.

Sengers syndrome is a rare autosomal recessive disorder caused by a mutation in the Acylglycerol Kinase (AGK) gene with subsequent mitochondrial dysfunction. It is a combination of cardiomyopathy, skeletal myopathy, congenital bilateral cataracts, and lactic acidosis following exertion. The current study describes an extremely rare case of Sengers syndrome that is diagnosed during post-mortem examination. A four-month-old female child underwent sudden cardiac arrest immediately following the induction of general anesthesia for lens extraction surgery. This infant was the first child born to healthy, non-consanguineous, Egyptian parents. There were unremarkable medical problems either during pregnancy or during delivery. This infant was born at term with a normal APGAR score and weight. She had congenital bilateral cataracts since birth, easily-fatigued, and delayed milestones for her age. A post-mortem examination revealed a hypertrophied heart that weighed 96.6 grams with left ventricular hypertrophy. The left ventricle free wall thickness was 1cm, and an interventricular septum thickness of 1.3 cm. Histopathologically, the myocardium showed myocytes disarray. Also, the myocytes were hypertrophied, and vacuolated. The Gömöri trichrome stain revealed vacuolated cardiomyocytes surrounded by collagenous connective tissue, and the Periodic Acid Schiff (PAS) stain excluded that these vacuolations were related to glycogen storage disease. Focal lymphocytic infiltrations were observed within the myocardium. Thus, Sengers syndrome should be taken into consideration as a possible diagnosis whenever a congenital cataract is present for clinical and medicolegal cases.

Case Report: Two Chinese Infants of Sengers Syndrome Caused by Mutations in AGK Gene.

Sengers syndrome (OMIM #212350) is a rare autosomal recessive disorder due to mutations in acylglycerol kinase (AGK) gene. We report two cases that were diagnosed clinically and confirmed genetically. Both infants had typical clinical features characterized by hypertrophic cardiomyopathy, bilateral cataracts, myopathy, and lactic acidosis, and heart failure was the most severe manifestation. Genetic testing of a boy revealed a homozygous pathogenic variant for Sengers syndrome in AGK (c.1131+2T>C) which was classified as likely pathogenic according to the ACMG guideline; besides, his skeletal muscle biopsy and transmission electron microscope presented obvious abnormity. One girl had compound heterozygous (c.409C>T and c.390G>A) variants of AGK gene that was identified in the proband and further Sanger sequencing indicated that the parents carried a single heterozygous mutation each. After the administration of "cocktail" therapy including coenzyme Q10, carnitine, and vitamin B complex, as well as ACEI, heart failure and myopathy of the boy were significantly improved and the condition was stable after 1-year follow-up, while the cardiomyopathy of the girl is not progressive but the plasma lactate acid increased significantly. We present the first report of two infants with Sengers syndrome diagnosed via exome sequencing in China.

Metabolic Alterations Caused by Defective Cardiolipin Remodeling in Inherited Cardiomyopathies.

The heart is the most energy-consuming organ in the human body. In heart failure, the homeostasis of energy supply and demand is endangered by an increase in cardiomyocyte workload, or by an insufficiency in energy-providing processes. Energy metabolism is directly associated with mitochondrial redox homeostasis. The production of toxic reactive oxygen species (ROS) may overwhelm mitochondrial and cellular ROS defense mechanisms in case of heart failure. Mitochondria are essential cell organelles and provide 95% of the required energy in the heart. Metabolic remodeling, changes in mitochondrial structure or function, and alterations in mitochondrial calcium signaling diminish mitochondrial energy provision in many forms of cardiomyopathy. The mitochondrial respiratory chain creates a proton gradient across the inner mitochondrial membrane, which couples respiration with oxidative phosphorylation and the preservation of energy in the chemical bonds of ATP. Akin to other mitochondrial enzymes, the respiratory chain is integrated into the inner mitochondrial membrane. The tight association with the mitochondrial phospholipid cardiolipin (CL) ensures its structural integrity and coordinates enzymatic activity. This review focuses on how changes in mitochondrial CL may be associated with heart failure. Dysfunctional CL has been found in diabetic cardiomyopathy, ischemia reperfusion injury and the aging heart. Barth syndrome (BTHS) is caused by an inherited defect in the biosynthesis of cardiolipin. Moreover, a dysfunctional CL pool causes other types of rare inherited cardiomyopathies, such as Sengers syndrome and Dilated Cardiomyopathy with Ataxia (DCMA). Here we review the impact of cardiolipin deficiency on mitochondrial functions in cellular and animal models. We describe the molecular mechanisms concerning mitochondrial dysfunction as an incitement of cardiomyopathy and discuss potential therapeutic strategies.

Cardiolipin remodeling in Barth syndrome and other hereditary cardiomyopathies.

Mitochondria play a prominent role in cardiac energy metabolism, and their function is critically dependent on the integrity of mitochondrial membranes. Disorders characterized by mitochondrial dysfunction are commonly associated with cardiac disease. The mitochondrial phospholipid cardiolipin directly interacts with a number of essential protein complexes in the mitochondrial membranes including the respiratory chain, mitochondrial metabolite carriers, and proteins critical for mitochondrial morphology. Barth syndrome is an X-linked disorder caused by an inherited defect in the biogenesis of the mitochondrial phospholipid cardiolipin. How cardiolipin deficiency impacts on mitochondrial function and how mitochondrial dysfunction causes cardiomyopathy has been intensively studied in cellular and animal models of Barth syndrome. These findings may also have implications for the molecular mechanisms underlying other inherited disorders associated with defects in cardiolipin, such as Sengers syndrome and dilated cardiomyopathy with ataxia (DCMA).

Atypical Presentation of Sengers Syndrome: A Novel Mutation Revealed with Postmortem Genetic Testing.

INTRODUCTION: Sengers syndrome is an autosomal recessive disorder characterized by congenital cataracts, hypertrophic cardiomyopathy, skeletal myopathy and lactic acidosis. The causative AGK mutations have been identified with whole exome sequencing. CLINICAL REPORT: We report on a 9-month-old infant with episodic lactic acidosis who died before a definitive diagnosis could be established. Postmortem genomic autopsy revealed a novel homozygous NM_018238: c.1215dupG; p.Phe406Valfs*4 mutation in AGK (OMIM 610345) confirming the diagnosis of Sengers syndrome. CONCLUSION: This report provides further evidence that reverse genetics is a useful approach in patients who do not manifest the hallmark features of known and recognizable syndromes.

The role of mitochondrial cardiolipin in heart function and its implication in cardiac disease.

Mitochondria play an essential role in the energy metabolism of the heart. Many of the essential functions are associated with mitochondrial membranes and oxidative phosphorylation driven by the respiratory chain. Mitochondrial membranes are unique in the cell as they contain the phospholipid cardiolipin. The important role of cardiolipin in cardiovascular health is highlighted by several cardiac diseases, in which cardiolipin plays a fundamental role. Barth syndrome, Sengers syndrome, and Dilated cardiomyopathy with ataxia (DCMA) are genetic disorders, which affect cardiolipin biosynthesis. Other cardiovascular diseases including ischemia/reperfusion injury and heart failure are also associated with changes in the cardiolipin pool. Here, we summarize molecular functions of cardiolipin in mitochondrial biogenesis and morphology. We highlight the role of cardiolipin for the respiratory chain, metabolite carriers, and mitochondrial metabolism and describe links to apoptosis and mitochondria specific autophagy (mitophagy) with possible implications in cardiac disease.

Novel Loss of Function in the AGK Gene: Rare Cause of End-Stage Heart Failure.

The authors present a case of mitochondrial cardiomyopathy due to a novel mutation of AGK gene that led to progressive heart failure. The cardiac magnetic resonance image findings of diffusely elevated relaxation time and increase in extracellular volume in the myocardium without early or late gadolinium enhancement may suggest mitochondrial cardiomyopathy. The authors emphasized the multidisciplinary team approach in the care of patients with mitochondrial cardiomyopathies. (Level of Difficulty: Advanced.).

Extending the phenotypic spectrum of Sengers syndrome: Congenital lactic acidosis with synthetic liver dysfunction.

Sengers syndrome is a rare autosomal recessive mitochondrial disease characterized by lactic acidosis, hypertrophic cardiomyopathy and bilateral cataracts. We present here a case of neonatal demise, within the first day of life, who initially presented with severe lactic acidosis, with evidence of both chorioamnionitis and cardiogenic shock. Initial metabolic labs demonstrated a severe lactic acidosis prompting genetic testing which revealed a homozygous pathogenic variant for Sengers syndrome in AGK, c.979A >  T; p.K327*. In addition to the canonical features of Sengers syndrome, our patient is the first reported case with liver dysfunction extending the phenotypic spectrum both in terms of severity and complications. This case also highlights the importance of maintaining a broad differential for congenital lactic acidosis.

Mutation in the AGK gene in two siblings with unusual Sengers syndrome.

Sengers syndrome is a rare autosomal recessive metabolic disorder caused by lack of acylglycerol kinase due to mutations in the AGK gene. It is characterized by congenital cataract, hypertrophic cardiomyopathy, myopathy and lactic acidosis. Two clinical forms have been described: a severe neonatal form, and a more benign form displaying exercise intolerance. We describe two siblings with congenital cataract, cardiomyopathy, hypotonia, intellectual disability and lactic acidosis. Whole exome sequencing revealed a homozygous c.1035dup mutation in the two siblings, supporting a diagnosis of Sengers syndrome. Our patients presented an intermediate form with intellectual deficiency, an unusual feature in Sengers syndrome. This permitted a prenatal diagnosis for a following pregnancy.

Acylglycerol Kinase Mutated in Sengers Syndrome Is a Subunit of the TIM22 Protein Translocase in Mitochondria.

Mutations in mitochondrial acylglycerol kinase (AGK) cause Sengers syndrome, which is characterized by cataracts, hypertrophic cardiomyopathy, and skeletal myopathy. AGK generates phosphatidic acid and lysophosphatidic acid, bioactive phospholipids involved in lipid signaling and the regulation of tumor progression. However, the molecular mechanisms of the mitochondrial pathology remain enigmatic. Determining its mitochondrial interactome, we have identified AGK as a constituent of the TIM22 complex in the mitochondrial inner membrane. AGK assembles with TIMM22 and TIMM29 and supports the import of a subset of multi-spanning membrane proteins. The function of AGK as a subunit of the TIM22 complex does not depend on its kinase activity. However, enzymatically active AGK is required to maintain mitochondrial cristae morphogenesis and the apoptotic resistance of cells. The dual function of AGK as lipid kinase and constituent of the TIM22 complex reveals that disturbances in both phospholipid metabolism and mitochondrial protein biogenesis contribute to the pathogenesis of Sengers syndrome.

Sengers Syndrome-Associated Mitochondrial Acylglycerol Kinase Is a Subunit of the Human TIM22 Protein Import Complex.

Acylglycerol kinase (AGK) is a mitochondrial lipid kinase that catalyzes the phosphorylation of monoacylglycerol and diacylglycerol to lysophosphatidic acid and phosphatidic acid, respectively. Mutations in AGK cause Sengers syndrome, which is characterized by congenital cataracts, hypertrophic cardiomyopathy, skeletal myopathy, exercise intolerance, and lactic acidosis. Here we identified AGK as a subunit of the mitochondrial TIM22 protein import complex. We show that AGK functions in a kinase-independent manner to maintain the integrity of the TIM22 complex, where it facilitates the import and assembly of mitochondrial carrier proteins. Mitochondria isolated from Sengers syndrome patient cells and tissues show a destabilized TIM22 complex and defects in the biogenesis of carrier substrates. Consistent with this phenotype, we observe perturbations in the tricarboxylic acid (TCA) cycle in cells lacking AGK. Our identification of AGK as a bona fide subunit of TIM22 provides an exciting and unexpected link between mitochondrial protein import and Sengers syndrome.

Disorders of phospholipid metabolism: an emerging class of mitochondrial disease due to defects in nuclear genes.

The human nuclear and mitochondrial genomes co-exist within each cell. While the mitochondrial genome encodes for a limited number of proteins, transfer RNAs, and ribosomal RNAs, the vast majority of mitochondrial proteins are encoded in the nuclear genome. Of the multitude of mitochondrial disorders known to date, only a fifth are maternally inherited. The recent characterization of the mitochondrial proteome therefore serves as an important step toward delineating the nosology of a large spectrum of phenotypically heterogeneous diseases. Following the identification of the first nuclear gene defect to underlie a mitochondrial disorder, a plenitude of genetic variants that provoke mitochondrial pathophysiology have been molecularly elucidated and classified into six categories that impact: (1) oxidative phosphorylation (subunits and assembly factors); (2) mitochondrial DNA maintenance and expression; (3) mitochondrial protein import and assembly; (4) mitochondrial quality control (chaperones and proteases); (5) iron-sulfur cluster homeostasis; and (6) mitochondrial dynamics (fission and fusion). Here, we propose that an additional class of genetic variant be included in the classification schema to acknowledge the role of genetic defects in phospholipid biosynthesis, remodeling, and metabolism in mitochondrial pathophysiology. This seventh class includes a small but notable group of nuclear-encoded proteins whose dysfunction impacts normal mitochondrial phospholipid metabolism. The resulting human disorders present with a diverse array of pathologic consequences that reflect the variety of functions that phospholipids have in mitochondria and highlight the important role of proper membrane homeostasis in mitochondrial biology.

Síndrome de Sengers: comunicación de dos casos en Chile / Sengers syndrome: report of two cases in chile

El Síndrome de Sengers es una enfermedad mitocondrial autosómica recesiva, producida por mutación del gen de la Acil-Glicerol Kinasa (AGK), recientemente descubierto. Se caracteriza por cataratas congénitas bilaterales, miocardiopatía hipertrófica y acidosis láctica. Puede tener miopatía esquelética leve, intolerancia al ejercicio y desarrollo mental normal. Los pacientes fallecen tempranamente debido a falla cardíaca. Dada la alta letalidad, lo infrecuente de este síndrome y la presencia de un diagnóstico confirmado, se presenta el caso clínico de 2 hermanos chilenos, fallecidos por la enfermedad, que se presentaron con el cuadro característico de cataratas congénitas bilaterales, miocardiopa-tía hipertrófica y acidosis láctica. El mayor, se operó las cataratas a los 4 meses de edad y falleció a la edad de 13 meses debido a falla cardíaca severa refractaria y falla orgánica múltiple, descompensado por una infección respiratoria. El menor se diagnosticó a los 3 meses de edad y se le confirmó la mutación del gen de AGK en Alemania. Se decidió no operarlo de las cataratas dado el mal pronóstico vital. Presentó progresión de la miocardiopatía hipertrófica y falleció súbitamente a los 8 meses de edad.

Senger's Syndrome is a recessive autosomal mitochondrial disease due to a recently discovered mutation of the Acyl-Glycerol Kinase (AGK) gen,. It is characterized by congenital bilateral cataracts, progressive hypertrophic cardiomyopathy and lactic acidosis. It may present skeletal myopathy, exercise intolerance and usually normal mental development. Patients die early in life due to heart failure. The clinical cases of two brothers with a confirmed diagnosis of Senger's syndrome are reported. The older brother was operated on for cataracts at the age of 4 months and he died when he was 13 months old due to severe refractory heart failure and multi-organ failure, decompensated by a respiratory infection. The younger brother was diagnosed at 3 month of age and the AGK gene mutation was confirmed in Germany. Cataracts were not operated on due to the the patient's extremely poor prognosis. He had progressive hypertrophic cardiomyopathy and died suddenly at 8 month of age.