Interindividual differences contribute to variation in microbiota composition more than hormonal status: A prospective study.

Aims: Ovarian hormone deficiency is one of the main risk factors for osteoporosis and bone fractures in women, and these risks can be mitigated by menopausal hormone therapy. Recent evidence suggests that gut microbiota may link changes in estrogen levels and bone metabolism. This study was conducted to investigate the potential relationship between hormonal and bone changes induced by oophorectomy and subsequent hormonal therapy and shifts in gut microbiota composition. Methods: We collected 159 stool and blood samples in several intervals from 58 women, who underwent bilateral oophorectomy. Changes in fecal microbiota were assessed in paired samples collected from each woman before and after oophorectomy or the start of hormone therapy. Bacterial composition was determined by sequencing the 16S rRNA gene on Illumina MiSeq. Blood levels of estradiol, FSH, biomarkers of bone metabolism, and indices of low-grade inflammation were measured using laboratory analytical systems and commercial ELISA. Areal bone mineral density (BMD) of the lumbar spine, proximal femur, and femur neck was measured using dual-energy X-ray absorptiometry. Results: We found no significant changes in gut microbiota composition 6 months after oophorectomy, despite major changes in hormone levels, BMD, and bone metabolism. A small decrease in bacterial diversity was apparent 18 months after surgery in taxonomy-aware metrics. Hormonal therapy after oophorectomy prevented bone loss but only marginally affected gut microbiota. There were no significant differences in ß-diversity related to hormonal status, although several microbes (e.g., Lactococcus lactis) followed estrogen levels. Body mass index (BMI) was the most significantly associated with microbiota variance. Microbiota was not a suitable predictive factor for the state of bone metabolism. Conclusions: We conclude that neither the loss of estrogens due to oophorectomy nor their gain due to subsequent hormonal therapy is associated with a specific gut microbiota signature. Sources of variability in microbiota composition are more related to interindividual differences than hormonal status.

Menopausal Transition: Prospective Study of Estrogen Status, Circulating MicroRNAs, and Biomarkers of Bone Metabolism.

Objective: Osteoporosis is associated with an impaired balance between bone resorption and formation, which in turn leads to bone loss and fractures. Many recent studies have underlined the regulatory role of microRNAs (miRNAs) in bone remodeling processes and their potential as biomarkers of osteoporosis. The purpose of this study was to prospectively examine the association of circulating miRNAs and bone biomarkers with estrogen status in women before and after oophorectomy, as well as in oophorectomized women on estrogen therapy. Methods: In this prospective study, we included 11 women before oophorectomy and hysterectomy and at 201 ± 24 days after the surgery. Another 11 women were evaluated 508 ± 127 days after oophorectomy and hysterectomy and after an additional 203 ± 71 days of estradiol treatment. Serum miRNAs were profiled by sequencing. Estrogen status and biomarkers of bone metabolism were quantified. Bone mineral density was assessed in the lumbar spine. Results: Our analysis revealed 17 miRNAs associated with estrogen levels. Of those miRNAs that were upregulated with estrogen deficiency and downregulated after estrogen therapy, miR-422a correlated with serum beta-carboxy-terminal type I collagen crosslinks (ß-CTX) and procollagen 1 N-terminal propeptide (P1NP); and miR-1278 correlated with serum ß-CTX, P1NP, osteocalcin, sclerostin, and Dickkopf-1(Dkk1). In contrast, we found an inverse association of miR-24-1-5p with estrogen status and a negative correlation with serum ß-CTX, P1NP, osteoprotegerin, and sclerostin levels. Conclusion: The reported miRNAs associated with estrogen status and bone metabolism could be potential biomarkers of bone pathophysiology and would facilitate studies on the prevention of postmenopausal osteoporosis. Our findings require validation in an extended cohort.

The relationship of mitochondrial dysfunction and the development of insulin resistance in Cushing's syndrome.

PURPOSE: Cushing's syndrome is characterized by metabolic disturbances including insulin resistance. Mitochondrial dysfunction is one pathogenic factor in the development of insulin resistance in patients with obesity. We explored whether mitochondrial dysfunction correlates with insulin resistance and other metabolic complications. PATIENTS AND METHODS: We investigated the changes of mRNA expression of genes encoding selected subunits of oxidative phosphorylation system (OXPHOS), pyruvate dehydrogenase (PDH) and citrate synthase (CS) in subcutaneous adipose tissue (SCAT) and peripheral monocytes (PM) and mitochondrial enzyme activity in platelets of 24 patients with active Cushing's syndrome and in 9 of them after successful treatment and 22 healthy control subjects. RESULTS: Patients with active Cushing's syndrome had significantly increased body mass index (BMI), homeostasis model assessment of insulin resistance (HOMA-IR) and serum lipids relative to the control group. The expression of all investigated genes for selected mitochondrial proteins was decreased in SCAT in patients with active Cushing's syndrome and remained decreased after successful treatment. The expression of most tested genes in SCAT correlated inversely with BMI and HOMA-IR. The expression of genes encoding selected OXPHOS subunits and CS was increased in PM in patients with active Cushing's syndrome with a tendency to decrease toward normal levels after cure. Patients with active Cushing's syndrome showed increased enzyme activity of complex I (NQR) in platelets. CONCLUSION: Mitochondrial function in SCAT in patients with Cushing's syndrome is impaired and only slightly affected by its treatment which may reflect ongoing metabolic disturbances even after successful treatment of Cushing's syndrome.

Activities of mitochondrial respiratory chain complexes in platelets of patients with Alzheimer's disease and depressive disorder.

We analyzed activities of complex I, II, III, and IV, and citrate synthase (CS) in patients with major depressive disorder (MDD) or Alzheimer's disease (AD) presenting with or without depression. Associations of these parameters with disease or disease severity were observed in both AD and MDD; however, mean values of mitochondrial parameters were significantly altered in AD but not in MDD. Potential mitochondrial dysfunction in MDD seems not to be caused by disturbed activity of CS or respiratory complexes. In AD, a decrease in the activity of CS and complex IV may cause mitochondrial dysfunction, whereas an increase in activities of other mitochondrial complexes or their ratios to CS may be an adaptive response. The data indicate that comorbid depression in AD is associated with increased complex II activity. The mitochondrial parameters measured can be included in the panel of biomarkers of AD.

Mitochondrial Respiration in the Platelets of Patients with Alzheimer's Disease.

Mitochondrial dysfunctions significantly contribute to the pathogenesis of Alzheimer's disease (AD). Here, we studied the relationship between AD and changes in the mitochondrial rates of respiration in blood platelets, respiratory chain complexes activity, and coenzyme Q10 plasma concentrations. In intact platelets obtained from AD patients, we observed a decrease in endogenous basal respiration rates, a decrease in the maximal capacity of the electron transport system (ETS), and higher respiratory rates after inhibiting complex I of the ETS. When normalized for citrate synthase activity, rotenone inhibited respiratory rates and complex I activity was significantly altered. In permeabilized platelets, mitochondrial respiration was completely rescued by the addition of complex I substrates. The changes in mitochondrial respiratory parameters were not associated with the progression of AD except for the capacity of the ETS in permeabilized platelets. In AD, complex I activity was increased, complex IV activity was decreased, and coenzyme Q10 plasma concentrations were decreased. Our data indicate that both insufficiency in substrates entering into the oxidative phosphorylation system and functional disturbances in the ETS complex are responsible for the decrease in respiration observed in intact platelets in AD patients. Analyses of complex IV activity, the respiratory rates of intact platelets, and the capacity of the ETS in permeabilized platelets may enable the characterization of mitochondrial dysfunctions in the initial stage of AD.

Inflammatory myopathy associated with statins: report of three cases.

Statins are well-established lipid-lowering drugs that reduce morbidity and mortality due to cardiovascular disease and cause adverse effects relatively rarely. It is still unclear whether statins are capable of inducing an immune-mediated response directed against skeletal muscle. Here, we present the cases of three patients who developed inflammatory myopathy in the course of statin treatment. Moreover, multiple mitochondrial DNA deletions were found in two of them. The ability of statins to induce an immune-mediated response and their interactions with mitochondrial metabolism pathways are discussed.

Neonatal onset of mitochondrial disorders in 129 patients: clinical and laboratory characteristics and a new approach to diagnosis.

INTRODUCTION: Mitochondrial disorders (MD) may manifest in neonates, but early diagnosis is difficult. In this study, clinical and laboratory data were analyzed in 129 patients with neonatal onset of MD to identify any association between specific mitochondrial diseases and their symptoms with the aim of optimizing diagnosis. MATERIALS AND METHODS: Retrospective clinical and laboratory data were evaluated in 461 patients (331 families) with confirmed MD. RESULTS: The neonatal onset of MD was reported in 28% of the patients. Prematurity, intrauterine growth retardation and hypotonia necessitating ventilatory support were present in one-third, cardiomyopathy in 40%, neonatal seizures in 16%, Leigh syndrome in 15%, and elevated lactate level in 87%. Hyperammonemia was observed in 22 out of 52 neonates. Complex I deficiency was identified in 15, complex III in one, complex IV in 23, complex V in 31, combined deficiency of several complexes in 53, and PDH complex deficiency was identified in six patients. Molecular diagnosis was confirmed in 49 cases, including a newborn with a 9134A>G mutation in the MTATP6 gene, which has not been described previously. CONCLUSION: The most significant finding is the high incidence of neonatal cardiomyopathy and hyperammonemia. Based on our experience, we propose a diagnostic flowchart applicable to critically ill neonates suspicious for MD. This tool will allow for the use of direct molecular genetic analyses without the need for muscle biopsies in neonates with Alpers, Barth, MILS and Pearson syndromes, SCO1, SCO2, TMEM70, ATP5E, SUCLG1 gene mutations and PDH complex deficiency.

YME1L controls the accumulation of respiratory chain subunits and is required for apoptotic resistance, cristae morphogenesis, and cell proliferation.

Mitochondrial ATPases associated with diverse cellular activities (AAA) proteases are involved in the quality control and processing of inner-membrane proteins. Here we investigate the cellular activities of YME1L, the human orthologue of the Yme1 subunit of the yeast i-AAA complex, using stable short hairpin RNA knockdown and expression experiments. Human YME1L is shown to be an integral membrane protein that exposes its carboxy-terminus to the intermembrane space and exists in several complexes of 600-1100 kDa. The stable knockdown of YME1L in human embryonic kidney 293 cells led to impaired cell proliferation and apoptotic resistance, altered cristae morphology, diminished rotenone-sensitive respiration, and increased susceptibility to mitochondrial membrane protein carbonylation. Depletion of YME1L led to excessive accumulation of nonassembled respiratory chain subunits (Ndufb6, ND1, and Cox4) in the inner membrane. This was due to a lack of YME1L proteolytic activity, since the excessive accumulation of subunits was reversed by overexpression of wild-type YME1L but not a proteolytically inactive YME1L variant. Similarly, the expression of wild-type YME1L restored the lamellar cristae morphology of YME1L-deficient mitochondria. Our results demonstrate the importance of mitochondrial inner-membrane proteostasis to both mitochondrial and cellular function and integrity and reveal a novel role for YME1L in the proteolytic regulation of respiratory chain biogenesis.

Posterior Reversible Encephalopathy Syndrome (PRES) in 5-year-old girl with nephrotic syndrome.

OBJECTIVE: Posterior Reversible Encephalopathy Syndrome (PRES) is a rare complication of nephrotic syndrome in children. This clinical condition is caused by localized brain angioedema mostly in parieto-occipital region and results in dramatic and acute features as sudden loss of consciousness, epileptic paroxysms, strong headache or visual disturbances. Uncontrolled hypertension often participates in PRES development. CASE: We present the case of a 5-year-old girl treated for relapse of nephrotic syndrome. RESULTS: At the time of edema regression and weight reduction, a sudden loss of consciousness and worsening of hypertension occurred. Brain MRI demonstrated extended multifocal changes strongly suspicious of encephalitis. After exclusion of herpetic encephalitis, the clinical picture was classified as PRES. Successful antihypertensive treatment led to general improvement of the girl's health within 48 hours and resolution of MRI brain hyperintensities occurred within the next three months. CONCLUSIONS: The aim of our case report is to us remind of possible development of PRES at the time of edema regression in nephrotic syndrome.

Novel insights into the assembly and function of human nuclear-encoded cytochrome c oxidase subunits 4, 5a, 6a, 7a and 7b.

Mammalian CcO (cytochrome c oxidase) is a hetero-oligomeric protein complex composed of 13 structural subunits encoded by both the mitochondrial and nuclear genomes. To study the role of nuclear-encoded CcO subunits in the assembly and function of the human complex, we used stable RNA interference of COX4, COX5A and COX6A1, as well as expression of epitope-tagged Cox6a, Cox7a and Cox7b, in HEK (human embryonic kidney)-293 cells. Knockdown of Cox4, Cox5a and Cox6a resulted in reduced CcO activity, diminished affinity of the residual enzyme for oxygen, decreased holoCcO and CcO dimer levels, increased accumulation of CcO subcomplexes and gave rise to an altered pattern of respiratory supercomplexes. An analysis of the patterns of CcO subcomplexes found in both knockdown and overexpressing cells identified a novel CcO assembly intermediate, identified the entry points of three late-assembled subunits and demonstrated directly the essential character as well as the interdependence of the assembly of Cox4 and Cox5a. The ectopic expression of the heart/muscle-specific isoform of the Cox6 subunit (COX6A2) resulted in restoration of both CcO holoenzyme and activity in COX6A1-knockdown cells. This was in sharp contrast with the unaltered levels of COX6A2 mRNA in these cells, suggesting the existence of a fixed expression programme. The normal amount and function of respiratory complex I in all of our CcO-deficient knockdown cell lines suggest that, unlike non-human CcO-deficient models, even relatively small amounts of CcO can maintain the normal biogenesis of this respiratory complex in cultured human cells.

The impact of mitochondrial tRNA mutations on the amount of ATP synthase differs in the brain compared to other tissues.

The impact of point mutations in mitochondrial tRNA genes on the amount and stability of respiratory chain complexes and ATP synthase (OXPHOS) has been broadly characterized in cultured skin fibroblasts, skeletal muscle samples, and mitochondrial cybrids. However, less is known about how these mutations affect other tissues, especially the brain. We have compared OXPHOS protein deficiency patterns in skeletal muscle mitochondria of patients with Leigh (8363G>A), MERRF (8344A>G), and MELAS (3243A>G) syndromes. Both mutations that affect mt-tRNA(Lys) (8363G>A, 8344A>G) resulted in severe combined deficiency of complexes I and IV, compared to an isolated severe defect of complex I in the 3243A>G sample (mt-tRNA(LeuUUR). Furthermore, we compared obtained patterns with those found in the heart, frontal cortex, and liver of 8363G>A and 3243A>G patients. In the frontal cortex mitochondria of both patients, the patterns of OXPHOS deficiencies differed substantially from those observed in other tissues, and this difference was particularly striking for ATP synthase. Surprisingly, in the frontal cortex of the 3243A>G patient, whose ATP synthase level was below the detection limit, the assembly of complex IV, as inferred from 2D-PAGE immunoblotting, appeared to be hindered by some factor other than the availability of mtDNA-encoded subunits.

Knockdown of human Oxa1l impairs the biogenesis of F1Fo-ATP synthase and NADH:ubiquinone oxidoreductase.

The Oxa1 protein is a founding member of the evolutionarily conserved Oxa1/Alb3/YidC protein family, which is involved in the biogenesis of membrane proteins in mitochondria, chloroplasts and bacteria. The predicted human homologue, Oxa1l, was originally identified by partial functional complementation of the respiratory growth defect of the yeast oxa1 mutant. Here we demonstrate that both the endogenous human Oxa1l, with an apparent molecular mass of 42 kDa, and the Oxa1l-FLAG chimeric protein localize exclusively to mitochondria in HEK293 cells. Furthermore, human Oxa1l was found to be an integral membrane protein, and, using two-dimensional blue native/denaturing PAGE, the majority of the protein was identified as part of a 600-700 kDa complex. The stable short hairpin (sh)RNA-mediated knockdown of Oxa1l in HEK293 cells resulted in markedly decreased steady-state levels and ATP hydrolytic activity of the F(1)F(o)-ATP synthase and moderately reduced levels and activity of NADH:ubiquinone oxidoreductase (complex I). However, no significant accumulation of corresponding sub-complexes could be detected on blue native immunoblots. Intriguingly, the achieved depletion of Oxa1l protein did not adversely affect the assembly or activity of cytochrome c oxidase or the cytochrome bc(1) complex. Taken together, our results indicate that human Oxa1l represents a mitochondrial integral membrane protein required for the correct biogenesis of F(1)F(o)-ATP synthase and NADH:ubiquinone oxidoreductase.

Activities of respiratory chain complexes in isolated platelets in females with anorexia nervosa.

OBJECTIVE: A broad spectrum of endocrine and biochemical disturbances was observed in patients with anorexia nervosa. In addition, metabolic changes may concern the efficiency of mitochondrial energy generating system. In our study we analyzed the activities of respiratory chain complexes in females with anorexia nervosa. METHOD: The activities of respiratory chain complexes I, II, IV, I + III, and citrate synthase serving as the control enzyme were measured spectrophotometrically in isolated platelets in 36 females with anorexia nervosa (BMI 15 +/- 1.7) at the age 18-35 years and in 37 age related female controls (BMI 21 +/- 2.2). RESULTS: In females with anorexia nervosa, the activities of respiratory chain complexes I and II in isolated platelets were significantly higher in comparison with controls. No differences were found in the activities of complexes IV and I + III and citrate synthase. CONCLUSION: Our results suggest higher efficiency of some respiratory chain complexes in platelets in females with anorexia nervosa.

Mitochondrial energy metabolism in very premature neonates.

The activity, amount and protein composition of pyruvate dehydrogenase (PDH) and respiratory chain complexes were studied in muscle mitochondria obtained postmortally from 6 neonates with a gestational age of 23-29 weeks. The activities of PDH and respiratory chain complex III and IV and citrate synthase were significantly lower in comparison with control children aged 0.5-2 and 2-20 years. Protein analyses revealed a parallel decrease in the content of PDH, respiratory chain complexes and their subunits in the cases analyzed. The observed immaturity of the mitochondrial energy-providing system suggests that significant development of mitochondrial energy metabolism occurs during the last 3 months of prenatal development. The metabolic disturbances of mitochondrial energy conversion associated with the low functional capacity and content of PDH and respiratory chain complexes may play an important role in the morbidity of very premature neonates.