Endocrine Disorders in Primary Mitochondrial Disease

Endocrine manifestations and long-term outcomes of patients with mitochondrial diseases

BACKGROUND

Endocrine dysfunctions are commonly associated with mitochondrial diseases. This study aimed to investigate clinical characteristics and outcomes of endocrine manifestations in patients with mitochondrial diseases.

METHODS

This study included 54 patients from 47 families with mitochondrial diseases who were genetically confirmed; 49 patients with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS), four with Pearson syndrome, and one with Kearns-Sayre syndrome (KSS). Clinical and endocrine findings were retrospectively reviewed.

RESULTS

The median age at diagnosis was 18.5 years (range, 0.1 - 49 years). In 49 patients with MELAS, the mean height and weight standard deviation scores were - 2.0 ± 1.3 and - 2.6 ± 1.6, respectively, with 44.9% (n = 22) of the patients exhibiting short stature at diagnosis. Twenty-three (46.9%) patients with MELAS were diagnosed with diabetes mellitus (DM) at a median age of 26 years (range, 12 - 50 years). Interestingly, papillary thyroid cancer was observed in 10.2% of patients (n = 5) with MELAS at a mean age of 34.1 ± 6.9 years. One patient with MELAS and one with KSS exhibited hypoparathyroidism. Patients with Pearson syndrome and KSS exhibited more severe short stature. Adrenal insufficiency was noted in 50% of the patients with Pearson syndrome.

CONCLUSIONS

In 20% of patients with MELAS, endocrine dysfunctions including having a short stature, DM, and hypoparathyroidism preceded the onset of neurological manifestations. Papillary thyroid cancer occurred in 10% of patients with MELAS. Patients with Pearson syndrome and KSS showed profound growth retardation and multisystem dysfunctions, such as chronic kidney disease and neurological defects, which contributed to increased mortality.

Endocrine Dysfunction in Primary Mitochondrial Diseases

Primary mitochondrial disorders (PMD) are genetic disorders affecting the structure or function of the mitochondrion. Mitochondrial functions are diverse, including energy production, ion homeostasis, reactive oxygen species regulation, antioxidant defense, and biosynthetic responsibilities, notably including steroidogenesis. Mitochondria provide the energy to drive intracellular production and extracellular secretion of all hormones. The understanding of the endocrine consequences of PMD is key to timely identification of both endocrine complications in PMD patients, and PMD presenting primarily with endocrine disease. This is a narrative review on the endocrine manifestations of PMD, underlying disease mechanisms, and current and emerging approaches to diagnosing and treating these complex disorders. Diabetes is the most frequent endocrine manifestation of PMD, but growth hormone deficiency, adrenal insufficiency, hypogonadism, and parathyroid dysfunction may occur. Despite the intricate involvement of the thyroid gland in metabolic regulation, there is little evidence for a causal relationship between thyroid dysfunction and PMD. In conclusion, endocrine dysfunction is observed in PMD with varying incidence depending on the specific mitochondrial disorder and the endocrine organ in question. Diagnosis of PMD in a patient with endocrine-presenting features requires a high level of clinical suspicion, particularly when apparently unrelated comorbidities co-exist. Similarly, endocrine pathology may be subtle in patients with known PMD, and thorough consideration must be given to ensure timely diagnosis and treatment. The scope for novel therapeutics for this group of devastating conditions is enormous; however, several challenges remain to be overcome before hopes of curative treatments can be brought into clinical practice.

Endocrine Disorders in Children with Primary Mitochondrial Diseases: Single Center Experience

Objective

Endocrine abnormalities may be the only clinical manifestation of primary mitochondrial disorders. The aim of this study was to evaluate the endocrinological characteristics of mitochondrial disease (MD) in a cohort from a single center.

Methods

Pediatric patients diagnosed with MD were categorized on the basis of their specific genetic abnormalities. The auxologic data, pubertal development, and, based on their clinical symptoms, hormonal profiles were obtained.

Results

Twelve of the cohort of 26 patients (46%) were female. In 15 (57.6%), the MD was caused by nuclear DNA mutations (nDNA group). Four patients had Leigh syndrome, two patients had Leber’s Hereditary Optic Neuropathy syndrome, two patients had Mitochondrial Encephalopathy Lactic Acidosis and Stroke Like episodes, and one patient had Kearns-Sayre syndrome clinical phenotype. The median age at diagnosis was 2.91 (0.59-16.8) years, and the median age at first endocrine evaluation was 4.62 (1.26-18) years. The mean height standard deviation score (SDS) was -1.34±2.12, and the mean body mass index SDS was -0.82±1.96 for all patients. Of the 26 patients, 6 (23%) had a range of hormonal deficits. Ovarian insufficiency, central adrenal insufficiency, central hypothyroidism, diabetes mellitus, and critical illness-related adrenal insufficiency were all observed. Three of the patients were initially monitored in the endocrine clinic for hormone deficiencies but it was later determined that the hormonal abnormalities were caused by underlying MD.

Conclusion

Individuals diagnosed with MD, particularly those with specific genetic abnormalities, are considered a high-risk group for developing hormonal deficits. Endocrine abnormalities may be one of the primary early warning symptoms for MD.

Disease registries and rare disorders: The virtuous example of mitochondrial medicine

Primary mitochondrial disorders (PMDs) are an extraordinarily complex group of rare disorders caused by impairment of the mitochondrial electron transport chain, or respiratory chain. Studying genotype-phenotype relationships in PMDs is a complex task. The clinical variability is large even in individuals with the same genotype, and the statistical power is low in single-center studies because of their rarity. To better define the clinical phenotypes associated with PMDs, in the last 15 years a significant multicenter effort has led to nation-wide studies on large cohorts of patients. Many national registries of mitochondrial patients have been developed in recent years, and now there is a strong effort towards international (and even global) registries. This review will revise the notable advances obtained with such studies in recent years, and will discuss the actual developments and future perspectives.

Mitophagy Unveiled: Exploring the Nexus of Mitochondrial Health and Neuroendocrinopathy

Mitochondria play a pivotal role in cellular metabolism, energy production, and apoptotic signaling, making mitophagy, the selective degradation of damaged mitochondria, crucial for mitochondrial health. Dysregulation of mitophagy has been implicated in various neuroendocrinopathies, yet the mechanisms linking these processes remain poorly understood. This review aims to explore the intersection between mitophagy and neuroendocrinopathy, addressing the critical gaps in knowledge regarding how mitochondrial dysfunction may contribute to the pathophysiology of neuroendocrine disorders. We conducted a comprehensive literature review of studies published on mitophagy and neuroendocrinopathies, focusing on data that elucidate the pathways involved and the clinical implications of mitochondrial health in neuroendocrine contexts. Our findings indicate that altered mitophagy may lead to the accumulation of dysfunctional mitochondria, contributing to neuroendocrine dysregulation. We present evidence linking impaired mitochondrial clearance to disease models of conditions such as metabolic syndrome, depression, and stress-related disorders, highlighting the potential for therapeutic interventions targeting mitophagy. While significant advances have been made in understanding mitochondrial biology, the direct interplay between mitophagy and neuroendocrinopathies remains underexplored. This review underscores the necessity for further research to elucidate these connections, which may offer novel insights into disease mechanisms and therapeutic strategies for treating maladaptive neuroendocrine responses.

A case with short stature and proteinuria: atypical presentation of a family with m.3243A>G mutation

BACKGROUND

The mitochondrial DNA (mtDNA) m.3243A>G mutation is one of the most common pathogenic mtDNA variants. The phenotypes associated with this mutation range from asymptomatic induviduals to well-defined clinical syndromes, or non-syndromic mitochondrial disorders. Variable clinical features in pediatric cases may cause difficulty in diagnosis. Kidney involvement in this mutation is uncommon and reported on a case-by-case basis. Here, we report on a patient with m.3243A>G mutation, who presented with short stature and proteinuria, and his family, who share the same genotype but exhibit different heteroplasmy levels in different tissues and variable phenotypes.

CASE PRESENTATION

A 15-year-old male patient was admitted to the pediatric endocrinology department with short stature. His examinations revealed nephrotic range proteinuria, hearing loss, impaired glucose tolerance, and Wolf-Parkinson-White syndrome. From family history, it was learned that diabetes mellitus (DM) and progressive sensorineural hearing loss were common in this family. The patient's mother, who had chronic kidney disease, DM, and hearing loss, had died suddenly for an unknown reason. Considering the family history, a genetic analysis was performed for mitochondrial disease. Mitochondrial DNA analysis revealed a m.3243A>G mutation with 47% heteroplasmy in blood, 62% heteroplasmy in buccal cells, and 96% heteroplasmy in urothelial cells in our patient.

CONCLUSIONS

Short stature without any other complaint and renal involvement are rare findings in m.3243A>G mutation. In patients presenting with proteinuria, in the presence of conditions affecting many systems such as endocrine system pathologies, hearing loss, and cardiac pathologies, and in the presence of individuals with a similar family history of multiple organ involvement, mitochondrial diseases should be considered, and examined from this perspective. Our case illustrates the value of a detailed medical and family history.

SLC30A9: an evolutionarily conserved mitochondrial zinc transporter essential for mammalian early embryonic development

SLC30A9 (ZnT9) is a mitochondria-resident zinc transporter. Mutations in SLC30A9 have been reported in human patients with a novel cerebro-renal syndrome. Here, we show that ZnT9 is an evolutionarily highly conserved protein, with many regions extremely preserved among evolutionarily distant organisms. In Drosophila melanogaster (the fly), ZnT9 (ZnT49B) knockdown results in acutely impaired movement and drastic mitochondrial deformation. Severe Drosophila ZnT9 (dZnT9) reduction and ZnT9-null mutant flies are pupal lethal. The phenotype of dZnT9 knockdown can be partially rescued by mouse ZnT9 expression or zinc chelator TPEN, indicating the defect of dZnT9 loss is indeed a result of zinc dyshomeostasis. Interestingly, in the mouse, germline loss of Znt9 produces even more extreme phenotypes: the mutant embryos exhibit midgestational lethality with severe development abnormalities. Targeted mutagenesis of Znt9 in the mouse brain leads to serious dwarfism and physical incapacitation, followed by death shortly. Strikingly, the GH/IGF-1 signals are almost non-existent in these tissue-specific knockout mice, consistent with the medical finding in some human patients with severe mitochondrial deficiecny. ZnT9 mutations cause mitochondrial zinc dyshomeostasis, and we demonstrate mechanistically that mitochondrial zinc elevation quickly and potently inhibits the activities of respiration complexes. These results reveal the critical role of ZnT9 and mitochondrial zinc homeostasis in mammalian development. Based on our functional analyses, we finally discussed the possible nature of the so far identified human SLC30A9 mutations.

Mechanisms and pathologies of human mitochondrial DNA replication and deletion formation

Human mitochondria possess a multi-copy circular genome, mitochondrial DNA (mtDNA), that is essential for cellular energy metabolism. The number of copies of mtDNA per cell, and their integrity, are maintained by nuclear-encoded mtDNA replication and repair machineries. Aberrant mtDNA replication and mtDNA breakage are believed to cause deletions within mtDNA. The genomic location and breakpoint sequences of these deletions show similar patterns across various inherited and acquired diseases, and are also observed during normal ageing, suggesting a common mechanism of deletion formation. However, an ongoing debate over the mechanism by which mtDNA replicates has made it difficult to develop clear and testable models for how mtDNA rearrangements arise and propagate at a molecular and cellular level. These deletions may impair energy metabolism if present in a high proportion of the mtDNA copies within the cell, and can be seen in primary mitochondrial diseases, either in sporadic cases or caused by autosomal variants in nuclear-encoded mtDNA maintenance genes. These mitochondrial diseases have diverse genetic causes and multiple modes of inheritance, and show notoriously broad clinical heterogeneity with complex tissue specificities, which further makes establishing genotype-phenotype relationships challenging. In this review, we aim to cover our current understanding of how the human mitochondrial genome is replicated, the mechanisms by which mtDNA replication and repair can lead to mtDNA instability in the form of large-scale rearrangements, how rearranged mtDNAs subsequently accumulate within cells, and the pathological consequences when this occurs.

Beneficial Effects of Ursodeoxycholic Acid on Metabolic Parameters and Oxidative Stress in Patients with Type 2 Diabetes Mellitus: A Randomized Double-Blind, Placebo-Controlled Clinical Study

Background

Oxidative stress and inflammation are closely related pathophysiological processes, both occurring in type 2 diabetes mellitus (T2DM). In addition to the standard treatment of T2DM, a potential strategy has been focused on the use of bile acids (BAs) as an additional treatment. Ursodeoxycholic acid (UDCA), as the first BA used in humans, improves glucose and lipid metabolism and attenuates oxidative stress. The aim of this study was to evaluate the potential metabolic, anti-inflammatory, and antioxidative effects of UDCA in patients with T2DM.

Methods

This prospective, double-blind, placebo-controlled clinical study included 60 patients with T2DM, randomly allocated to receive UDCA or placebo. Subjects were treated with 500 mg tablets of UDCA or placebo administered three times per day (total dose of 1500 mg/day) for eight weeks. Two study visits, at the beginning (F0) and at the end (F1) of the study, included the interview, anthropometric and clinical measurements, and biochemical analyses.

Results

UDCA treatment showed a significant reduction in body mass index (p = 0.024) and in diastolic blood pressure (p = 0.033), compared to placebo. In addition, there was a statistically significant difference in waist circumference in the UDCA group before and after treatment (p < 0.05). Although no statistical significance was observed at the two-month follow-up assessment, an average decrease in glucose levels in the UDCA group was observed. After two months of the intervention period, a significant decrease in the activity of liver enzymes was noticed. Furthermore, a significant reduction in prooxidative parameters (TBARS, NO2-, H2O2) and significant elevation in antioxidative parameters such as SOD and GSH were found (p < 0.001).

Conclusions

The eight-week UDCA administration showed beneficial effects on metabolic and oxidative stress parameters in patients with T2DM. Thus, UDCA could attenuate the progression and complications of diabetes and should be considered as an adjuvant to other diabetes treatment modalities. This trial is registered with NCT05416580.

Endocrine features of primary mitochondrial diseases

PURPOSE OF REVIEW

Primary mitochondrial diseases are one of the most prevalent groups of multisystem genetic disorders. Endocrinopathies associated with mitochondrial diseases may have clinical features that are distinct from the more common forms. We provide an overview of mitochondrial disorder genetics and phenotypes, focusing on recent studies regarding identification and treatment of associated endocrinopathies.

RECENT FINDINGS

Known endocrine phenotypes of mitochondrial disorders continue to expand, and now include growth hormone deficiency, hypogonadism, precocious puberty, hypoparathyroidism, hypo- and hyperthyroidism, diabetes, and adrenal insufficiency. Recent studies suggest several genotype-phenotype correlations, including those related to nuclear variants. Diagnosis is important, as special considerations should be made in the management of endocrinopathies in mitochondrial patients. Finally, new mitochondrial replacement strategies may soon be available for women interested in preventing mitochondrial disease transmission to offspring.

SUMMARY

Patients with multiple endocrinopathies or atypical endocrinopathies should be evaluated for primary mitochondrial disease, as a diagnosis may impact management of these individuals.

Endocrine Challenges in Myoclonic Epilepsy With Ragged Red Fibers Syndrome: A Case Report

Myoclonic epilepsy with ragged red fibers (MERRF) syndrome is a primary mitochondrial disorder characterized by myoclonus, epilepsy, ataxia, and muscle fiber abnormalities. While traditionally associated with neurological features, MERRF's multisystem nature extends to endocrine dysfunction, including diabetes mellitus, thyroid disorders, and adrenal abnormalities. This case report explores the multifaceted nature of MERRF syndrome by presenting the clinical journey of a 70-year-old woman who sought care at the endocrinology clinic due to coexisting Addison's disease and diabetes mellitus, marked by recurrent hypoglycemia and suboptimal metabolic control. Over time, she developed a history of myoclonic epilepsy, effectively managed with lamotrigine, along with mild sensory axonal polyneuropathy and ataxia. The patient was diagnosed with MERRF syndrome following her son's diagnosis, which had a severe form. This case underscores the intricate interplay between mitochondrial dysfunction and endocrine manifestations in MERRF syndrome, highlighting the importance of a comprehensive and multidisciplinary approach to patient care. MERRF syndrome's array of endocrine manifestations substantially impacts patients' quality of life and morbidity. A comprehensive approach, uniting endocrinologists, neurologists, geneticists, and other specialists, is essential for effective patient care. Further research is warranted to unravel the complex mitochondrial-endocrine interactions in MERRF syndrome, offering potential insights for improved management.

Combined MITOchondrial-NUCLEAR (MITO-NUCLEAR) Analysis for Mitochondrial Diseases Diagnosis: Validation and Implementation of a One-Step NGS Method

BACKGROUND

Next-generation sequencing (NGS) technology is revolutionizing diagnostic screening for mitochondrial diseases (MDs). Moreover, an investigation by NGS still requires analyzing the mitochondrial genome and nuclear genes separately, with limitations in terms of time and costs. We describe the validation and implementation of a custom blended MITOchondrial-NUCLEAR (MITO-NUCLEAR) assay for the simultaneous identification of genetic variants both in whole mtDNA and in nuclear genes included in a clinic exome panel. Furthermore, the MITO-NUCLEAR assay, implemented in our diagnostic process, has allowed us to arrive at a molecular diagnosis in a young patient.

METHODS

Massive sequencing strategy was applied for the validation experiments, performed using multiple tissues (blood, buccal swab, fresh tissue, tissue from slide, and formalin-fixed paraffin-embedded tissue section) and two different blend-in ratios of the mitochondrial probes: nuclear probes; 1:900 and 1:300.

RESULTS

Data suggested that 1:300 was the optimal probe dilution, where 100% of the mtDNA was covered at least 3000×, the median coverage was >5000×, and 93.84% of nuclear regions were covered at least 100×.

CONCLUSIONS

Our custom Agilent SureSelect MITO-NUCLEAR panel provides a potential "one-step" investigation that may be applied to both research and genetic diagnosis of MDs, allowing the simultaneous discovery of nuclear and mitochondrial mutations.

Currently available therapies in mitochondrial disease

Mitochondrial diseases are a heterogeneous group of multisystem disorders caused by impaired mitochondrial function. These disorders occur at any age and involve any tissue, typically affecting organs highly dependent on aerobic metabolism. Diagnosis and management are extremely difficult due to various underlying genetic defects and a wide range of clinical symptoms. Preventive care and active surveillance are strategies to try to reduce morbidity and mortality by timely treatment of organ-specific complications. More specific interventional therapies are in early phases of development and no effective treatment or cure currently exists. A variety of dietary supplements have been utilized based on biological logic. For several reasons, few randomized controlled trials have been completed to assess the efficacy of these supplements. The majority of the literature on supplement efficacy represents case reports, retrospective analyses and open-label studies. We briefly review selected supplements that have some degree of clinical research support. In mitochondrial diseases, potential triggers of metabolic decompensation or medications that are potentially toxic to mitochondrial function should be avoided. We shortly summarize current recommendations on safe medication in mitochondrial diseases. Finally, we focus on the frequent and debilitating symptoms of exercise intolerance and fatigue and their management including physical training strategies.

Adrenal Dysfunction in Mitochondrial Diseases

Cortisol is central to several homeostatic mechanisms including the stress and immune response. Adrenal insufficiency and impaired cortisol production leads to severe, potentially fatal disorders. Several fundamental stages of steroidogenesis occur within the mitochondria. These dynamic organelles not only contribute ATP for steroidogenesis, but also detoxify harmful by-products generated during cortisol synthesis (reactive oxygen species). Mutations in nuclear or mitochondrial DNA that impair mitochondrial function lead to debilitating multi-system diseases. Recently, genetic variants that impair mitochondrial function have been identified in people with isolated cortisol insufficiency. This review aimed to clarify the association between mitochondrial diseases and adrenal insufficiency to produce cortisol. Mitochondrial diseases are rare and mitochondrial diseases that feature adrenal insufficiency are even rarer. We identified only 14 cases of adrenal insufficiency in people with confirmed mitochondrial diseases globally. In line with previous reviews, adrenal dysfunction was most prevalent in mitochondrial deletion syndromes (particularly Pearson syndrome and Kearns-Sayre syndrome) and with point mutations that compromised oxidative phosphorylation. Although adrenal insufficiency has been reported with mitochondrial diseases, the incidence reflects that expected in the general population. Thus, it is unlikely that mitochondrial mutations alone are responsible for an insufficiency to produce cortisol. More research is needed into the pathogenesis of adrenal disease in these individuals.

Delay in diagnosing a patient with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome who presented with status epilepticus and lactic acidosis: a case report

Background

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episode syndrome is a rare mitochondrial genetic disorder that can present with a variety of clinical manifestations, including stroke, hearing loss, seizures, and lactic acidosis. The most common genetic mutation associated with this syndrome is M.3243A>G. The main underlying mechanism of the disease relates to protein synthesis, energy depletion, and nitric oxide deficiency. Controlling disease complications and improving patient quality of life are the primary aims of treatment options.

Case presentation

A 28-year-old Arabic female visited Al-Amiri Hospital in Kuwait. The patient was newly diagnosed with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episode syndrome following her admission as a case of status epilepticus requiring further investigation. The patient’s seizures were controlled, and she was evaluated to rule out the most serious complications by carrying out appropriate clinical, laboratory, and radiological imaging. The patient was discharged from the hospital after 2 weeks with a follow-up plan.

Conclusion

This case report emphasizes the importance of considering mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episode syndrome as a potential cause of status epilepticus with lactic acidosis in a young female patient with a past history of stroke-like episodes. It also stresses the most important workup to rule out every possible life-threatening complication to improve patients’ lives.

Genetics of monogenic disorders of calcium and bone metabolism

Disorders of calcium homeostasis are the most frequent metabolic bone and mineral disease encountered by endocrinologists. These disorders usually manifest as primary hyperparathyroidism (PHPT) or hypoparathyroidism (HP), which have a monogenic aetiology in 5%-10% of cases, and may occur as an isolated endocrinopathy, or as part of a complex syndrome. The recognition and diagnosis of these disorders is important to facilitate the most appropriate management of the patient, with regard to both the calcium-related phenotype and any associated clinical features, and also to allow the identification of other family members who may be at risk of disease. Genetic testing forms an important tool in the investigation of PHPT and HP patients and is usually reserved for those deemed to be an increased risk of a monogenic disorder. However, identifying those suitable for testing requires a thorough clinical evaluation of the patient, as well as an understanding of the diversity of relevant phenotypes and their genetic basis. This review aims to provide an overview of the genetic basis of monogenic metabolic bone and mineral disorders, primarily focusing on those associated with abnormal calcium homeostasis, and aims to provide a practical guide to the implementation of genetic testing in the clinic.

A child with mitochondrial DNA deletion presenting diabetes mellitus as an initial symptom

Children with mitochondrial disease may present with diabetes mellitus (DM) without autoimmune antibodies as an initial manifestation, however, it is difficult to make a precise diagnosis in early stages. We present a 2-year-old male patient with mitochondrial disease who showed insulin-dependent DM without autoimmune antibodies as an initial symptom. He later presented with progressive motor deterioration, hearing disability, ptosis, external ophthalmoplegia, and retinitis pigmentosa at 6 years and 6 months. T2- and diffusion-weighted imaging revealed high signal lesions in the subcortical white matter, anterior thalamus, globus pallidus, and brainstem. MR spectroscopy showed elevated lactate and low N-acetylaspartate in the affected white matter. Genetic analysis revealed a single large-scale mitochondrial DNA deletion at 7117-13994, leading to a diagnosis of mitochondrial DNA deletion syndrome associated with insulin-dependent DM. Although the frequency of DM in pediatric mitochondrial disease is low, mitochondrial disease, especially due to mitochondrial DNA deletion, should be considered as a differential diagnosis in those with insulin-dependent DM without autoimmune antibodies, and MRI and MR spectroscopy are recommended for an early diagnosis.

Mitochondria and mitochondrial disorders: an overview update

Mitochondria, the cell powerhouse, are membrane-bound organelles present in the cytoplasm of almost all the eukaryotic cells. Their main function is to generate energy in the form of adenosine triphosphate (ATP). In addition, mitochondria store calcium for the cell signaling activities, generate heat, harbor pathways of intermediate metabolism and mediate cell growth and death. Primary mitochondrial diseases (MDs) form a clinically as well as genetically heterogeneous group of inherited disorders that result from the mitochondrial energetic metabolism malfunctions. The lifetime risk of the MDs development is estimated at 1:1470 of newborns, which makes them one of the most recurrent groups of inherited disorders with an important burden for society.

MDs are progressive with wide range of symptoms of variable severity that can emerge congenitally or anytime during the life. MD can be caused by mutations in the mitochondrial DNA (mtDNA) or nuclear DNA genes. Mutations inducing impairment of mitochondrial function have been found in more than 400 genes. Furthermore, more than 1200 nuclear genes, which could play a role in the MDs’ genetic etiology, are involved in the mitochondrial activities. However, the knowledge regarding the mechanism of the mitochondrial pathogenicity appears to be most essential for the development of effective patient’s treatment suffering from the mitochondrial disease. This is an overview update focused on the mitochondrial biology and the mitochondrial diseases associated genes.

Body Mass Index and Height in the Friedreich Ataxia Clinical Outcome Measures Study

BACKGROUND AND OBJECTIVES

Body mass index (BMI) and height are important indices of health. We tested the association between these outcomes and clinical characteristics in Friedreich ataxia (FRDA), a progressive neuromuscular disorder.

METHODS

Participants (N = 961) were enrolled in a prospective natural history study (Friedreich Ataxia Clinical Outcome Measure Study). Age- and sex-specific BMI and height Z-scores were calculated using CDC 2000 references for participants younger than 18 years. For adults aged 18 years or older, height Z-scores were also calculated, and absolute BMI was reported. Univariate and multivariate linear regression analyses tested the associations between exposures, covariates, and BMI or height measured at the baseline visit. In children, the superimposition by translation and rotation analysis method was used to compare linear growth trajectories between FRDA and a healthy reference cohort, the Bone Mineral Density in Childhood Study (n = 1,535 used for analysis).

RESULTS

Median age at the baseline was 20 years (IQR, 13-33 years); 49% (n = 475) were women. A substantial proportion of children (17%) were underweight (BMI-Z < fifth percentile), and female sex was associated with lower BMI-Z (β = -0.34, p < 0.05). In adults, older age was associated with higher BMI (β = 0.09, p < 0.05). Regarding height, in children, older age (β -0.06, p < 0.05) and worse modified Friedreich Ataxia Rating Scale (mFARS) scores (β = -1.05 for fourth quartile vs first quartile, p < 0.01) were associated with shorter stature. In girls, the magnitude of the pubertal growth spurt was less, and in boys, the pubertal growth spurt occurred later (p < 0.001 for both) than in a healthy reference cohort. In adults, in unadjusted analyses, both earlier age of FRDA symptom onset (=0.09, p < 0.05) and longer guanine-adenine-adenine repeat length (shorter of the 2 GAA repeats, β = -0.12, p < 0.01) were associated with shorter stature. Both adults and children with higher mFARS scores and/or who were nonambulatory were less likely to have height and weight measurements recorded at clinical visits.

DISCUSSION

FRDA affects both weight gain and linear growth. These insights will inform assessments of affected individuals in both research and clinical settings.

Mitochondrial DNA: Unraveling the "other" genome

ABSTRACT

The mitochondrial genome, which contains all of the hereditary information within human mitochondria, consists of 16,569 base pairs of double-stranded DNA that encode 37 genes. Pathogenic mutations of mitochondrial DNA (mtDNA) cause dysfunction of the respiratory chain and the process of oxidative phosphorylation (OXPHOS), leading to impaired adenosine triphosphate synthesis. Nuclear DNA (nDNA) mutations can affect structural subunits or assembly factors of one of the five OXPHOS complexes. Mitochondrial diseases are a heterogeneous group of disorders, ranging from mtDNA single-point mutations and large-scale deletions to mitochondrial depletion syndromes, resulting from nDNA pathogenic mutations. Manifestations of mitochondrial disease are multisystemic, and organs with substantial energy requirements are most typically affected. Mitochondrial disorders are progressive in nature, and prognosis is dependent on the organs involved and the rate and severity of disease progression. A multidisciplinary team approach is needed to monitor and manage disease sequelae.

The non-syndromic clinical spectrums of mtDNA 3243A>G mutation

The m.3243A >G mutation in the tRNA Leu (UUR) gene (MT-TL1) of the mitochondrial DNA is the most widely seen pathogenic mtDNA mutation which has major phenotypic variations. The clinical phenotype involves various organs such as the brain and nerves, skeletal muscles, heart, endocrine system, gastrointestinal tract, and skin. Some phenotypes conform to well established syndromes, while most of the symptoms appear individually or concomitant to other syndromes, making identification difficult. Furthermore, some progress has been made on cardiac manifestations as well as complications during pregnancy and perinatal period. This article provides a systematic review of the non-syndromic phenotypes and latest developments in m.3243A>G mutation.

Central precocious puberty may be a manifestation of endocrine dysfunction in pediatric patients with mitochondrial disease

We retrospectively reviewed the data of 140 female pediatric patients with rare mitochondrial diseases (MDs) confirmed using muscle biopsy. We evaluated patients who were diagnosed with central precocious puberty (PP) with early pubertal development to determine whether PP is a clinical manifestation of MDs. We also examined the clinical, auxiological, laboratory, and radiological parameters after 1 year of gonadotropin-releasing hormone treatment for central PP. Among the 140 girls with MDs, 29 had early pubertal development and underwent endocrine evaluation. Ten (7.1%) patients were diagnosed with central PP; the prevalence of central PP was higher than was that previously thought. Patients with central PP exhibited bone age advancement over 1 year and increased sex hormone levels despite their young age at diagnosis. Serum estradiol levels were significantly higher in younger patients than in older patients (P = 0.004). Patients with central PP treated with gonadotropin-releasing hormone had favorable outcomes, and their pubertal development was suppressed for 1 year.Conclusion: Central PP may be a manifestation of endocrine dysfunction in young girls with MDs. What is Known: • The general characteristics of mitochondrial diseases include developmental delays and retarded growth. • Precocious puberty has rarely been suggested as a clinical manifestation of mitochondrial diseases. What is New: • Among the 140 girls with mitochondrial diseases, 10 (7.1%) were diagnosed with central precocious puberty. • Serum estradiol levels were significantly higher in younger patients than in older patients.

Hyperglycemic Crisis in Patients With Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-like Episodes (MELAS)

BACKGROUND

Diabetes mellitus is the most commonly encountered endocrinopathy in patients with mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), which manifests as multisystemic organ failure. Whether the management of diabetes mellitus in MELAS requires special consideration is not fully clarified.

METHODS

In this single-center study, we retrospectively reviewed the medical records of patients with MELAS to elucidate the clinical characteristics of MELAS-associated diabetes mellitus.

RESULTS

Four patients among a total of 25 individuals with MELAS who were treated in the study institution developed diabetes mellitus. One patient had well-controlled diabetes mellitus, whereas the remaining three patients experienced hyperglycemic crisis as the first manifestation of diabetes mellitus. Two of the three patients were children aged four and six years. The hyperglycemic events occurred after surgery, infection, and status epilepticus, respectively. None of the three patients had diabetes mellitus previously based on randomly measured serum glucose levels that were within the normal range before the hyperglycemic crisis. Glycated hemoglobin levels measured during the hyperglycemic crisis indicated prediabetes in two patients and diabetes mellitus in one patient. Two patients recovered, whereas one patient died after developing multiorgan failure.

CONCLUSIONS

Fulminant-onset diabetes mellitus occurring in patients with MELAS underscore the importance of routine measurement for glycated hemoglobin and more intense evaluation of glucose intolerance regardless of the patient age and lack of symptoms. Clinicians should be aware of the potential acute onset of hyperglycemic crisis in patients with MELAS, especially in individuals with aggravating factors.

Overview of Atypical Diabetes

Although type 1 diabetes mellitus and, to a lesser extent, type 2 diabetes mellitus, are the prevailing forms of diabetes in youth, atypical forms of diabetes are not uncommon and may require etiology-specific therapies. By some estimates, up to 6.5% of children with diabetes have monogenic forms. Mitochondrial diabetes and cystic fibrosis related diabetes are less common but often noted in the underlying disease. Atypical diabetes should be considered in patients with a known disorder associated with diabetes, aged less than 25 years with nonautoimmune diabetes and without typical characteristics of type 2 diabetes mellitus, and/or with comorbidities associated with atypical diabetes.

Heteroplasmy and phenotype spectrum of the mitochondrial tRNALeu (UUR) gene m.3243A>G mutation in seven Han Chinese families

The m.3243A > G mutation in the mitochondrial tRNA^{Leu (UUR)} gene is associated with a variety of phenotypic heterogeneity. The clinical spectrum and phenotypic-genotypic correlations in the Chinese patients are poorly understood. In the present study, we reported the clinical and genetic characterization, as well as haplogroups of seven Han Chinese families carrying the m.3243A > G mutation. Of the 39 matrilineal individuals, five suffered from mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS), two had life-threatening mitochondrial myopathy (LTMM), and one patient had neuropathy, ataxia, and retinitis pigmentosa (NARP)-like syndrome. The LTMM and NARP like syndromes enriched the phenotypic profile of the m.3243A > G mutation. The heteroplasmy of the m.3243A > G mutation ranged from 16% to 59% in MELAS, 29% to 79% in LTMM, and 57% in a NARP-like syndrome patient. The levels ranged from 0% to 14% in patients that manifested with pure diabetes and pure hearing loss, and 0% to 5% in 13 normal family members. However, we particularly noticed heteroplasmy in four asymptomatic individuals in one LTMM family carried the heteroplasmy mutation ranged from 22% to 78%, implying that there were other modifying factors in this family. The modulation of the phenotype of mtDNA mutations requires further investigation.

Flavonoids and type 2 diabetes: Evidence of efficacy in clinical and animal studies and delivery strategies to enhance their therapeutic efficacy

Diabetes mellitus type 2 (T2DM) is a metabolic disorder develops due to the overproduction of free radicals where oxidative stress could contribute it. Possible factors are defective insulin signals, glucose oxidation, and degradation of glycated proteins as well as alteration in glutathione metabolism which induced hyperglycemia. Previous studies revealed a link between T2DM with oxidative stress, inflammation and insulin resistance which are assumed to be regulated by numerous cellular networks such as NF-κB, PI3K/Akt, MAPK, GSK3 and PPARγ. Flavonoids are ubiquitously present in the nature and classified according to their chemical structures for example, flavonols, flavones, flavan-3-ols, anthocyanidins, flavanones, and isoflavones. Flavonoids indicate poor bioavailability which could be improved by employing various nano-delivery systems against the occurrences of T2DM. These bioactive compounds exert versatile anti-diabetic activities via modulating targeted cellular signaling networks, thereby, improving glucose metabolism, α -glycosidase, and glucose transport or aldose reductase by carbohydrate metabolic pathway in pancreatic β-cells, hepatocytes, adipocytes and skeletal myofibres. Moreover, anti-diabetic properties of flavonoids also encounter diabetic related complications. This review article has designed to shed light on the anti-diabetic potential of flavonoids, contribution of oxidative stress, evidence of efficacy in clinical, cellular and animal studies and nano-delivery approaches to enhance their therapeutic efficacy. This article might give some new insights for therapeutic intervention against T2DM in near future.

Mitochondrial Dysfunction in Primary Ovarian Insufficiency

Primary ovarian insufficiency (POI) is defined by the loss or dysfunction of ovarian follicles associated with amenorrhea before the age of 40. Symptoms include hot flashes, sleep disturbances, and depression, as well as reduced fertility and increased long-term risk of cardiovascular disease. POI occurs in ∼1% to 2% of women, although the etiology of most cases remains unexplained. Approximately 10% to 20% of POI cases are due to mutations in a single gene or a chromosomal abnormality, which has provided considerable molecular insight into the biological underpinnings of POI. Many of the genes for which mutations have been associated with POI, either isolated or syndromic cases, function within mitochondria, including MRPS22, POLG, TWNK, LARS2, HARS2, AARS2, CLPP, and LRPPRC. Collectively, these genes play roles in mitochondrial DNA replication, gene expression, and protein synthesis and degradation. Although mutations in these genes clearly implicate mitochondrial dysfunction in rare cases of POI, data are scant as to whether these genes in particular, and mitochondrial dysfunction in general, contribute to most POI cases that lack a known etiology. Further studies are needed to better elucidate the contribution of mitochondria to POI and determine whether there is a common molecular defect in mitochondrial function that distinguishes mitochondria-related genes that when mutated cause POI vs those that do not. Nonetheless, the clear implication of mitochondrial dysfunction in POI suggests that manipulation of mitochondrial function represents an important therapeutic target for the treatment or prevention of POI.

Relationship Between Oxidative Stress, ER Stress, and Inflammation in Type 2 Diabetes: The Battle Continues

Type 2 diabetes (T2D) is a metabolic disorder characterized by hyperglycemia and insulin resistance in which oxidative stress is thought to be a primary cause. Considering that mitochondria are the main source of ROS, we have set out to provide a general overview on how oxidative stress is generated and related to T2D. Enhanced generation of reactive oxygen species (ROS) and oxidative stress occurs in mitochondria as a consequence of an overload of glucose and oxidative phosphorylation. Endoplasmic reticulum (ER) stress plays an important role in oxidative stress, as it is also a source of ROS. The tight interconnection between both organelles through mitochondrial-associated membranes (MAMs) means that the ROS generated in mitochondria promote ER stress. Therefore, a state of stress and mitochondrial dysfunction are consequences of this vicious cycle. The implication of mitochondria in insulin release and the exposure of pancreatic β-cells to hyperglycemia make them especially susceptible to oxidative stress and mitochondrial dysfunction. In fact, crosstalk between both mechanisms is related with alterations in glucose homeostasis and can lead to the diabetes-associated insulin-resistance status. In the present review, we discuss the current knowledge of the relationship between oxidative stress, mitochondria, ER stress, inflammation, and lipotoxicity in T2D.

New Variant of MELAS Syndrome With Executive Dysfunction, Heteroplasmic Point Mutation in the MT-ND4 Gene (m.12015T>C; p.Leu419Pro) and Comorbid Polyglandular Autoimmune Syndrome Type 2

Background: Mitochondrial diseases are caused by dysfunctions in mitochondrial metabolic pathways. MELAS syndrome is one of the most frequent mitochondrial disorders; it is characterized by encephalopathy, myopathy, lactic acidosis, and stroke-like episodes. Typically, it is associated with a point mutation with an adenine-to-guanine transition at position 3243 of the mitochondrial DNA (mtDNA; m.3243A>G) in the mitochondrially encoded tRNA leucine 1 (MT-TL1) gene. Other point mutations are possible and the association with polyglandular autoimmune syndrome type 2 has not yet been described.

Case presentation: We present the case of a 25-year-old female patient with dysexecutive syndrome, muscular fatigue, and continuous headache. Half a year ago, she fought an infection-triggered Addison crisis. As the disease progressed, she had two epileptic seizures and stroke-like episodes with hemiparesis on the right side. Cerebral magnetic resonance imaging showed a substance defect of the parieto-occipital left side exceeding the vascular territories with a lactate peak. The lactate ischemia test was clearly positive, and a muscle biopsy showed single cytochrome c oxidase-negative muscle fibers. Genetic testing of blood mtDNA revealed a heteroplasmic base exchange mutation in the mitochondrially encoded NADH:ubiquinone oxidoreductase core subunit 4 (MT-ND4) gene (m.12015T>C; p.Leu419Pro; heteroplasmy level in blood 12%, in muscle tissue: 15%). The patient suffered from comorbid autoimmune polyglandular syndrome type 2 with Hashimoto's thyroiditis, Addison's disease, and autoimmune gastritis. In addition, we found increased anti-glutamic acid decarboxylase 65, anti-partial cell, anti-intrinsic factor, and anti-nuclear antibodies.

Conclusion: We present an atypical case of MELAS syndrome with predominant symptoms of a dysexecutive syndrome, two stroke-like episodes, and fast-onset fatigue. The symptoms were associated with a not yet described base and aminoacid exchange mutation in the MT-ND4 gene (m.12015T>C to p.Leu419Pro). The resulting changed protein complex in our patient is part of the respiratory chain multicomplex I and might be the reason for the mitochondriopathy. However, different simulations for pathogenetic relevance are contradictory and rather speak for a benign variant. To our knowledge this case report is the first reporting MELAS syndrome with comorbid polyglandular autoimmune syndrome type 2. Screening for autoimmune alterations in those patients is important to prevent damage to end organs.

Mitochondrial Disease: Advances in clinical diagnosis, management, therapeutic development, and preventative strategies

PURPOSE OF REVIEW

Primary mitochondrial disease encompasses an impressive range of inherited energy deficiency disorders having highly variable molecular etiologies as well as clinical onset, severity, progression, and response to therapies of multi-system manifestations. Significant progress has been made in primary mitochondrial disease diagnostic approaches, clinical management, therapeutic options, and preventative strategies that are tailored to major mitochondrial disease phenotypes and subclasses.

RECENT FINDINGS

The extensive phenotypic pleiotropy of individual mitochondrial diseases from an organ-based perspective is reviewed. Improved consensus on standards for mitochondrial disease patient care are being complemented by emerging therapies that target specific molecular subtypes of mitochondrial disease. Reproductive counseling options now include preimplantation genetic diagnosis at the time of in vitro fertilization for familial mutations in nuclear genes and some mtDNA disorders. Mitochondrial replacement technologies have promise for some mtDNA disorders, although practical and societal challenges remain to allow their further research analyses and clinical utilization.

SUMMARY

A dramatic increase has occurred in recent years in the recognition, understanding, treatment options, and preventative strategies for primary mitochondrial disease.

Effectiveness of Coenzyme Q10 Supplementation for Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis

OBJECTIVE

To evaluate the effectiveness and safety of coenzyme Q10 for patients with type 2 diabetes mellitus (T2DM).

METHODS

Data from randomized controlled trials were obtained to assess the effects of coenzyme Q10 versus placebo or western medicine on patients with T2DM. The study's registration number is CRD42018088474. The primary outcomes included glycosylated hemoglobin, fasting blood glucose, and fasting insulin.

RESULT

Thirteen trials involving 765 patients were included. Compared with the control group, coenzyme Q10 may decrease the HbA1c (WMD -0.29; 95% CI -0.54, -0.03; P = 0.03) and the fasting blood glucose (WMD -11.21; 95% CI -18.99, -3.43; P = 0.005). For fasting insulin, there is also not strong evidence that confirms which one is better because there was no statistical difference (WMD -0.48; 95% CI -2.54, 1.57; P = 0.65).

CONCLUSION

Based on current evidence, coenzyme Q10 may assist glycemic control, decrease TG, and improve HDL-C in patients with T2DM.