Biochemical characterization of patients with dihydrolipoamide dehydrogenase deficiency

Dihydrolipoamide dehydrogenase (DLD; E3) oxidizes lipoic acid. Restoring the oxidized state allows lipoic acid to act as a necessary electron sink for the four mitochondrial keto-acid dehydrogenases: pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, branched-chain α-keto-acid dehydrogenase, and 2-oxoadipate dehydrogenase. DLD deficiency (DLDD) is caused by biallelic pathogenic variants i

Case report: Two unexpected cases of DGUOK-related mitochondrial DNA depletion syndrome presenting with hyperinsulinemic hypoglycemia

Timely diagnosis of persistent neonatal hypoglycemia is critical to prevent neurological sequelae, but diagnosis is complicated by the heterogenicity of the causes. We discuss two cases at separate institutions in which clinical management was fundamentally altered by the results of molecular genetic testing. In both patients, critical samples demonstrated hypoketotic hypoglycemia and a partial glycemic response to glucagon stimulation, thereby suggesting hyperinsulinism (HI). However, due to rapid genetic testing, both patients were found to have deoxyguanosine kinase (DGUOK)-related mitochondrial DNA depletion syndrome, an unexpected diagnosis. Patients with this disease typically present with either hepatocerebral disease in the neonatal period or isolated hepatic failure in infancy. The characteristic features involved in the hepatocerebral form of the disease include lactic acidosis, hypoglycemia, cholestasis, progressive liver failure, and increasing neurologic dysfunction. Those with isolated liver involvement experience hepatomegaly, cholestasis, and liver failure. Although liver transplantation is considered, research has demonstrated that for patients with DGUOK-related mitochondrial DNA depletion syndrome and neurologic symptoms, early demise occurs. Our report advocates for the prompt initiation of genetic testing in patients presenting with persistent neonatal hypoglycemia and for the incorporation of mitochondrial DNA depletion syndromes in the differential diagnosis of HI

It is Time for Zero Tolerance for Sexual Harassment in Academic Medicine

While there are more women in leadership positions in academic medicine now than ever before in our history, evidence from recent surveys of women and from graduating medical students demonstrates that sexual harassment continues in our institutions. Our ability to change the culture is hampered by fear of reporting episodes of harassment, which is largely due to fear of retaliation. We describe some efforts in scientific societies that are addressing this and working to establish safe environments at national meetings. We must also work at the level of each institution to make it safe for individuals to come forward, to provide training for victims and for bystanders, and to abolish locker room talk that is demeaning to women

Efeitos da administração a longo prazo de dietas com diferentes teores de sódio sobre a função renal de ratos hipertensos

A alta ingestão de sódio contribui significativamente para o desenvolvimento da hipertensão e suas complicações. Dentre estas, a doença renal crônica. Entretanto, os mecanismos moleculares responsáveis pelos danos renais e pela renoproteção produzidos por dietas de alto e baixo sal, respectivamente, são pouco compreendidos. Objetivo: Investigar os efeitos a longo prazo de dietas com diferentes teores de cloreto de sódio sobre a função renal de ratos espontaneamente hipertensos (SHR) focando nos mecanismos moleculares envolvidos no manejo renal de albumina e componentes do sistema renina angiotensina renal (SRA). Métodos: ratos SHR machos recém-desmamados (4 semamas) foram alimentados durante 6 meses com dietas diferindo apenas no teor de NaCl: dieta padrão de sal (NS: 0.3 %), dieta de baixo sal (LS: 0.03%) e dieta de alto teor de sal ( HS: 3%). Foram realizadas análises de função e morfologia renal, avaliação da expressão de componentes-chave envolvidos no manejo renal de albumina, incluindo as proteínas da slit membrane (nefrina e podocina) e do aparato endocítico do túbulo proximal (megalina e cubilina). Além disso, a expressão ea atividade dos componentes do RAS (enzima conversora de angiotensina ACE, ACE2, AT1, AT2 e Mas) também foram examinados. Resultados: HS agravou a hipertensão nos ratos SHR, provocou hipertrofia glomerular, diminuição da expressão renal de nefrina e ECA2, levou à perda da integridade morfológica dos processos podais e ao aumento da proteinúria caracterizado pela perda de albumina e proteínas de alto peso molecular. Por outro lado, a hipertensão grave foi atenuada e disfunção renal foi prevenida pela dieta LS, já que, a proteinúria foi muito menor nestes animais quando comparados aos SHR NS. Tais achados foram associados com uma diminuição da razão de proteína e de atividade das enzimas ECA/ECA2 nos rins e aumento da expressão renal de cubilina. Conclusão: Portanto, os resultados sugerem que a dieta a baixa ingestão de sódio atenua a progressão da hipertensão em ratos SHR e preserva a função renal. Os mecanismo que parcialmente podem explicar estes resultados incluem a modulação intra-renal do balanço ECA/ECA2 e o aumento da expressão renal de cubilina. Contudo, a alta ingestão de sódio agrava a lesão renal hipertensiva e reduz a expressão de nefrina, um componente chave slit diaphragm

Biallelic variants in OGDH encoding oxoglutarate dehydrogenase lead to a neurodevelopmental disorder characterized by global developmental delay, movement disorder, and metabolic abnormalities

PURPOSE: This study aimed to establish the genetic cause of a novel autosomal recessive neurodevelopmental disorder characterized by global developmental delay, movement disorder, and metabolic abnormalities. METHODS: We performed a detailed clinical characterization of 4 unrelated individuals from consanguineous families with a neurodevelopmental disorder. We used exome sequencing or targeted-exome sequencing, cosegregation, in silico protein modeling, and functional analyses of variants in HEK293 cells and Drosophila melanogaster, as well as in proband-derived fibroblast cells. RESULTS: In the 4 individuals, we identified 3 novel homozygous variants in oxoglutarate dehydrogenase (OGDH) (NM_002541.3), which encodes a subunit of the tricarboxylic acid cycle enzyme α-ketoglutarate dehydrogenase. In silico homology modeling predicts that c.566C>T:p.(Pro189Leu) and c.890C>A:p.(Ser297Tyr) variants interfere with the structure and function of OGDH. Fibroblasts from individual 1 showed that the p.(Ser297Tyr) variant led to a higher degradation rate of the OGDH protein. OGDH protein with p.(Pro189Leu) or p.(Ser297Tyr) variants in HEK293 cells showed significantly lower levels than the wild-type protein. Furthermore, we showed that expression of Drosophila Ogdh (dOgdh) carrying variants homologous to p.(Pro189Leu) or p.(Ser297Tyr), failed to rescue developmental lethality caused by loss of dOgdh. SpliceAI, a variant splice predictor, predicted that the c.935G>A:p.(Arg312Lys)/p.(Phe264_Arg312del) variant impacts splicing, which was confirmed through a mini-gene assay in HEK293 cells. CONCLUSION: We established that biallelic variants in OGDH cause a neurodevelopmental disorder with metabolic and movement abnormalities

Biallelic variants in OGDH encoding oxoglutarate dehydrogenase lead to a neurodevelopmental disorder characterized by global developmental delay, movement disorder, and metabolic abnormalities

Purpose: This study aimed to establish the genetic cause of a novel autosomal recessive neurodevelopmental disorder characterized by global developmental delay, movement disorder, and metabolic abnormalities.Methods: We performed a detailed clinical characterization of 4 unrelated individuals from consanguineous families with a neurodevelopmental disorder. We used exome sequencing or targeted-exome sequencing, cosegregation, in silico protein modeling, and functional analyses of variants in HEK293 cells and Drosophila melanogaster, as well as in proband-derived fibroblast cells.Results: In the 4 individuals, we identified 3 novel homozygous variants in oxoglutarate dehydrogenase (OGDH) (NM_002541.3), which encodes a subunit of the tricarboxylic acid cycle enzyme alpha-ketoglutarate dehydrogenase. In silico homology modeling predicts that c.566C > T:p.(Pro189Leu) and c.890C > A:p.(Ser297Tyr) variants interfere with the structure and function of OGDH. Fibroblasts from individual 1 showed that the p.(Ser297Tyr) variant led to a higher degradation rate of the OGDH protein. OGDH protein with p.(Pro189Leu) or p.(Ser297Tyr) variants in HEK293 cells showed significantly lower levels than the wild-type protein. Furthermore, we showed that expression of Drosophila Ogdh (dOgdh) carrying variants homologous to p.(Pro189Leu) or p.(Ser297Tyr), failed to rescue developmental lethality caused by loss of dOgdh. SpliceAI, a variant splice predictor, predicted that the c.935G > A:p.(Arg312Lys)/p.(Phe264_Arg312del) variant impacts splicing, which was confirmed through a mini-gene assay in HEK293 cells.Conclusion: We established that biallelic variants in OGDH cause a neurodevelopmental disorder with metabolic and movement abnormalities.(c) 2022 The Authors. Published by Elsevier Inc. on behalf of American College of Medical Genetics and Genomics. This is an open access article under the CC BY licensePeer reviewe

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Impact of TET2 mutations On Responsiveness to Demethylating Agents in MDS

Abstract Abstract 1606 Poster Board I-632 Aberrant epigenetic silencing of tumor suppressor and differentiation genes constitutes an important mechanism in the pathogenesis of MDS and related myeloid malignancies. Demethylationg agents such as azacitidine and decitabine lead to degradation of DNMT1 and may reverse aberrant methylation. While the drugs demonstrate efficacy in MDS, response rates are variable. Thus, many primarily refractory patients are exposed to these therapies unnecessarily. While search for markers of responsiveness included study of methylation status of potential marker promoters or global methylation patterns, to date predictive tests have not been developed. Similarly, mechanisms of epigenetic instability responsible for wide-spread promoter methylation have not been clarified, preventing development of diagnostic markers. TET2 mutations are frequent events in a variety of MDS subtypes, particular chronic myelomonocytic leukemia (CMML) and other MDS/MPN, as well as AML derived from those conditions. It is likely that TET2 alterations are important in the pathogenesis of myeloid malignancies, but little is known regarding the function of TET2. A recent report indicated that a related family member, TET1, converts 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (hmC). Hydroxylation of 5mC prevents DNMT1 from homologous methylation of daughter DNA strands during cell division, thus preventing maintenance methylation (Tahiliani et al. Nature 324, 2009). Consequently, closely related TET2 may play a role in epigenetic regulation. As a consequence, TET2 mutations may lead to accumulation of aberrantly methylated CpG islands. Of utmost importance is whether TET2 mutations or resultant epigenetic silencing of specific gene or gene groups affects response to hypomethylating agents. We hypothesized that TET2 mutations play a role in epigenetic instability and may serve as markers of responsiveness/refractoriness to the therapy with demethylating agents. We have determined TET2 mutational status by sequencing all exons in 32 patients with myeloid malignancies (MDS (N=18) and MDS/MPN (N=14)) who underwent therapy with the demethylating agents azacitidine (N=27) or decitabine (N=5). For definition of response we applied International Working Group Criteria in patients who received a sufficient dose and number of cycles to allow assessment of response. Overall response rate (complete+partial responses (CR+PR) + hematologic improvement (HI)) was achieved for 9/32 patients (28%) after 35 cycles, including 4 patients who achieved CR, 2 PR, and 3 CI. In total, 12 TET2 mutations were identified in 9/32 patients (28%), of whom 5 had MDS/MPN (3 with CMML-1/2) and 4 had sAML. Unique compound heterozygosity was found in 3 patients; consequently biallelic inactivation of TET2 was found in 4 patients. For analyses, patients with partial and complete responses were compared with refractory patients and response was correlated with the presence of TET2 mutations. Among TET2-mutated patients, only 1 patient responded to therapy, whereas 8 additional patients, including 3 patients with biallelic inactivation of the TET2 gene, did not show any improvement (11%). In contrast, among patients with WT TET2 gene, responses were seen in 8/23 patients (35%; p=.19). While the cohort of treated patients was small, our preliminary results indicate that the presence of TET2 mutations may represent a negative predictor of response to demethylating agents. Disclosures No relevant conflicts of interest to declare