Estrogen-mediated regulation of mitochondrial gene expression

In vivo arterial stiffness, but not isolated artery endothelial function, varies with the mouse estrous cycle

With the increasing appreciation for sex as a biological variable and the inclusion of female mice in research, it is important to understand the influence of the estrous cycle on physiological function. Sex hormones are known to modulate vascular function, but the effects of the mouse estrous cycle phase on arterial stiffness, endothelial function, and arterial estrogen receptor expression remain unknown. In 23 female C57BL/6 mice (6 mo of age), we determined the estrous cycle stage via vaginal cytology and plasma hormone concentrations. Aortic stiffness, assessed by pulse wave velocity, was lower during the estrus phase compared with diestrus. In ex vivo assessment of isolated pressurized mesenteric and posterior cerebral arteries, the responses to acetylcholine, insulin, and sodium nitroprusside, as well as nitric oxide-mediated dilation, were not different between estrous cycle phases. In the aorta, expression of phosphorylated estrogen receptor-α was higher for mice in estrus compared with mice in proestrus. In the cerebral arteries, gene expression for estrogen receptor-β (Esr2) was lowest for mice in estrus compared with diestrus and proestrus. These results demonstrate that the estrus phase is associated with lower in vivo large artery stiffness in mice. In contrast, ex vivo resistance artery endothelial function is not different between estrous cycle phases. Estrogen receptor expression is modulated by the estrus cycle in an artery-dependent manner. These results suggest that the estrous cycle phase should be considered when measuring in vivo arterial stiffness in young female mice.NEW & NOTEWORTHY To design rigorous vascular research studies using young female rodents, the influence of the estrous cycle on vascular function must be known. We found that in vivo aortic stiffness was lower during estrus compared with the diestrus phase in female mice. In contrast, ex vivo mesenteric and cerebral artery endothelial function did not differ between estrous cycle stages. These results suggest that the estrous cycle stage should be accounted for when measuring in vivo arterial stiffness.

The role of mtDNA haplogroups on metabolic features in narcolepsy type 1

Narcolepsy type 1 (NT1) is due to selective loss of hypocretin (hcrt)-producing-neurons. Hcrt is a neuropeptide regulating the sleep/wake cycle, as well as feeding behavior. A subset of NT1 patients become overweight/obese, with a dysmetabolic phenotype. We hypothesized that mitochondrial DNA (mtDNA) sequence variation might contribute to the metabolic features in NT1 and we undertook an exploratory survey of mtDNA haplogroups in a cohort of well-characterized patients. We studied 246 NT1 Italian patients, fully defined for their metabolic features, including obesity, hypertension, low HDL, hypertriglyceridemia and hyperglycemia. For haplogroup assignment, the mtDNA control region was sequenced in combination with an assessment of diagnostic markers in the coding region. NT1 patients displayed the same mtDNA haplogroups (H, HV, J, K, T, U) frequency as those reported in the general Italian population. The majority of NT1 patients (64%) were overweight: amongst these, 35% were obese, 48% had low HDL cholesterol levels, and 31% had hypertriglyceridemia. We identified an association between haplogroups J, K and hypertriglyceridemia (P=0.03, 61.5% and 61.5%, respectively vs. 31.3% of the whole sample) and after correction for age and sex, we observed a reduction of these associations (OR=3.65, 95%CI=0.76-17.5, p=0.106 and 1.73, 0.52-5.69, p=0.368, respectively). The low HDL level showed a trend for association with haplogroup J (P=0.09, 83.3% vs. 47.4% of the whole sample) and after correction we observed an OR=6.73, 95%CI=0.65-69.9, p=0.110. Our study provides the first indication that mtDNA haplogroups J and K can modulate metabolic features of NT1 patients, linking mtDNA variation to the dysmetabolic phenotype in NT1.

Mechanisms Underlying the Regulation of Mitochondrial Respiratory Chain Complexes by Nuclear Steroid Receptors

Mitochondrial respiratory chain complexes play important roles in energy production via oxidative phosphorylation (OXPHOS) to drive various biochemical processes in eukaryotic cells. These processes require coordination with other cell organelles, especially the nucleus. Factors encoded by both nuclear and mitochondrial DNA are involved in the formation of active respiratory chain complexes and 'supercomplexes', the higher-order structures comprising several respiratory chain complexes. Various nuclear hormone receptors are involved in the regulation of OXPHOS-related genes. In this article, we review the roles of nuclear steroid receptors (NR3 class nuclear receptors), including estrogen receptors (ERs), estrogen-related receptors (ERRs), glucocorticoid receptors (GRs), mineralocorticoid receptors (MRs), progesterone receptors (PRs), and androgen receptors (ARs), in the regulatory mechanisms of mitochondrial respiratory chain complex and supercomplex formation.

OXPHOS bioenergetic compensation does not explain disease penetrance in Leber hereditary optic neuropathy

Leber hereditary optic neuropathy (LHON) is one of the most common primary mitochondrial diseases. It is caused by point mutations in mitochondrial DNA (mtDNA) genes and in some cases, it can result in irreversible vision loss, primarily in young men. It is currently unknown why LHON mutations affect only some carriers and whether bioenergetic compensation enables unaffected carriers to overcome mitochondrial impairment and preserve cellular function. Here, we conducted bioenergetic metabolic assays and RNA sequencing to address this question using male-only, age-matched, m.11778G > A lymphoblasts and primary fibroblasts from both unaffected carriers and affected individuals. Our work indicates that OXPHOS bioenergetic compensation in LHON peripheral cells does not explain disease phenotype. We show that complex I impairment is similar in cells from unaffected carrier and affected patients, despite a transcriptional downregulation of metabolic pathways including glycolysis in affected cells relative to carriers detected by RNA sequencing. Although we did not detect OXPHOS bioenergetic compensation in carrier cells under basal conditions, our results indicate that cells from affected patients suffer a growth impairment under metabolic challenge compared to carrier cells, which were unaffected by metabolic challenge. If recapitulated in retinal ganglion cells, decreased susceptibility to metabolic challenge in unaffected carriers may help preserve metabolic homeostasis in the face of the mitochondrial complex I bioenergetic defect.

Manipulating and elucidating mitochondrial gene expression with engineered proteins

Many conventional, modern genome engineering tools cannot be used to study mitochondrial genetics due to the unusual structure and physiology of the mitochondrial genome. Here, we review a number of newly developed, synthetic biology-based approaches for altering levels of mutant mammalian mitochondrial DNA and mitochondrial RNAs, including transcription activator-like effector nucleases, zinc finger nucleases and engineered RNA-binding proteins. These approaches allow researchers to manipulate and visualize mitochondrial processes and may provide future therapeutics. This article is part of the theme issue 'Linking the mitochondrial genotype to phenotype: a complex endeavour'.

PTCD1 Is Required for 16S rRNA Maturation Complex Stability and Mitochondrial Ribosome Assembly

The regulation of mitochondrial RNA life cycles and their roles in ribosome biogenesis and energy metabolism are not fully understood. We used CRISPR/Cas9 to generate heart- and skeletal-muscle-specific knockout mice of the pentatricopeptide repeat domain protein 1, PTCD1, and show that its loss leads to severe cardiomyopathy and premature death. Our detailed transcriptome-wide and functional analyses of these mice enabled us to identify the molecular role of PTCD1 as a 16S rRNA-binding protein essential for its stability, pseudouridylation, and correct biogenesis of the mitochondrial large ribosomal subunit. We show that impaired mitoribosome biogenesis can have retrograde signaling effects on nuclear gene expression through the transcriptional activation of the mTOR pathway and upregulation of cytoplasmic protein synthesis and pro-survival factors in the absence of mitochondrial translation. Taken together, our data show that impaired assembly of the mitoribosome exerts its consequences via differential regulation of mitochondrial and cytoplasmic protein synthesis.

Humanin, a Mitochondrial-Derived Peptide Released by Astrocytes, Prevents Synapse Loss in Hippocampal Neurons

Astroglial cells are crucial for central nervous system (CNS) homeostasis. They undergo complex morpho-functional changes during aging and in response to hormonal milieu. Ovarian hormones positively affect different astroglia parameters, including regulation of cell morphology and release of neurotrophic and neuroprotective factors. Thus, ovarian hormone loss during menopause has profound impact in astroglial pathophysilogy and has been widely associated to the process of brain aging. Humanin (HN) is a secreted mitochondrial-encoded peptide with neuroprotective effects. It is localized in several tissues with high metabolic rate and its expression decreases with age. In the brain, humanin has been found in glial cells in physiological conditions. We previously reported that surgical menopause induces hippocampal mitochondrial dysfunction that mimics an aging phenotype. However, the effect of ovarian hormone deprivation on humanin expression in this area has not been studied. Also, whether astrocytes express and release humanin and the regulation of such processes by ovarian hormones remain elusive. Although humanin has also proven to be beneficial in ameliorating cognitive impairment induced by different insults, its putative actions on structural synaptic plasticity have not been fully addressed. In a model of surgical menopause in rats, we studied hippocampal humanin expression and localization by real-time quantitative polymerase chain reaction (RT-qPCR) and double immunohistochemistry, respectively. Humanin production and release and ovarian hormone regulation of such processes were studied in cultured astrocytes by flow cytometry and ELISA, respectively. Humanin effects on glutamate-induced structural synaptic alterations were determined in primary cultures of hippocampal neurons by immunocytochemistry. Humanin expression was lower in the hippocampus of ovariectomized rats and its immunoreactivity colocalized with astroglial markers. Chronic ovariectomy also promoted the presence of less complex astrocytes in this area. Ovarian hormones increased humanin intracellular content and release by cultured astrocytes. Humanin prevented glutamate-induced dendritic atrophy and reduction in puncta number and total puncta area for pre-synaptic marker synaptophysin in cultured hippocampal neurons. In conclusion, astroglial functional and morphological alterations induced by chronic ovariectomy resemble an aging phenotype and could affect astroglial support to neuronal function by altering synaptic connectivity and functionality. Reduced astroglial-derived humanin may represent an underlying mechanism for synaptic dysfunction and cognitive decline after menopause.

Amyloid precursor protein-mediated mitochondrial regulation and Alzheimer's disease

Despite clear evidence of a neuroprotective physiological role of amyloid precursor protein (APP) and its non-amyloidogenic processing products, APP has been investigated mainly in animal and cellular models of amyloid pathology in the context of Alzheimer's disease. The rare familial mutations in APP and presenilin-1/2, which sometimes drive increased amyloid β (Aβ) production, may have unduly influenced Alzheimer's disease research. APP and its cleavage products play important roles in cellular and mitochondrial metabolism, but many studies focus solely on Aβ. Mitochondrial bioenergetic metabolism is essential for neuronal function, maintenance and survival, and multiple reports indicate mitochondrial abnormalities in patients with Alzheimer's disease. In this review, we focus on mitochondrial abnormalities reported in sporadic Alzheimer's disease patients and the role of full-length APP and its non-amyloidogenic fragments, particularly soluble APPα, on mitochondrial bioenergetic metabolism. We do not review the plethora of animal and in vitro studies using mutant APP/presenilin constructs or experiments using exogenous Aβ. In doing so, we aim to invigorate research and discussion around non-amyloidogenic APP processing products and the mechanisms linking mitochondria and complex neurodegenerative disorders such as sporadic Alzheimer's disease. LINKED ARTICLES: This article is part of a themed section on Therapeutics for Dementia and Alzheimer's Disease: New Directions for Precision Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.18/issuetoc.

Estrogens regulate life and death in mitochondria

Estrogens coordinate and integrate cellular metabolism and mitochondrial activities by direct and indirect mechanisms mediated by differential expression and localization of estrogen receptors (ER) in a cell-specific manner. Estrogens regulate transcription and cell signaling pathways that converge to stimulate mitochondrial function- including mitochondrial bioenergetics, mitochondrial fusion and fission, calcium homeostasis, and antioxidant defense against free radicals. Estrogens regulate nuclear gene transcription by binding and activating the classical genomic estrogen receptors α and β (ERα and ERβ) and by activating plasma membrane-associated mERα, mERβ, and G-protein coupled ER (GPER, GPER1). Localization of ERα and ERβ within mitochondria and in the mitochondrial membrane provides additional mechanisms of regulation. Here we review the mechanisms of rapid and longer-term effects of estrogens and selective ER modulators (SERMs, e.g., tamoxifen (TAM)) on mitochondrial biogenesis, morphology, and function including regulation of Nuclear Respiratory Factor-1 (NRF-1, NRF1) transcription. NRF-1 is a nuclear transcription factor that promotes transcription of mitochondrial transcription factor TFAM (mtDNA maintenance factorFA) which then regulates mtDNA-encoded genes. The nuclear effects of estrogens on gene expression directly controlling mitochondrial biogenesis, oxygen consumption, mtDNA transcription, and apoptosis are reviewed.

17β-Estradiol Directly Lowers Mitochondrial Membrane Microviscosity and Improves Bioenergetic Function in Skeletal Muscle

Menopause results in a progressive decline in 17β-estradiol (E2) levels, increased adiposity, decreased insulin sensitivity, and a higher risk for type 2 diabetes. Estrogen therapies can help reverse these effects, but the mechanism(s) by which E2 modulates susceptibility to metabolic disease is not well understood. In young C57BL/6N mice, short-term ovariectomy decreased-whereas E2 therapy restored-mitochondrial respiratory function, cellular redox state (GSH/GSSG), and insulin sensitivity in skeletal muscle. E2 was detected by liquid chromatography-mass spectrometry in mitochondrial membranes and varied according to whole-body E2 status independently of ERα. Loss of E2 increased mitochondrial membrane microviscosity and H₂O₂ emitting potential, whereas E2 administration in vivo and in vitro restored membrane E2 content, microviscosity, complex I and I + III activities, H₂O₂ emitting potential, and submaximal OXPHOS responsiveness. These findings demonstrate that E2 directly modulates membrane biophysical properties and bioenergetic function in mitochondria, offering a direct mechanism by which E2 status broadly influences energy homeostasis.

Adjunctive Steroid Therapy for Treatment of Pediatric Septic Shock

Septic shock remains the major cause of childhood morbidity and mortality worldwide. Although early sepsis recognition, fluid resuscitation, timely administration of antimicrobials, and vasoactive-inotropic drug infusions are all key to achieving good sepsis outcomes, therapy using various steroid drug classes remains an attractive adjunctive intervention to minimize the duration of septic shock and transition to multiple organ dysfunction syndrome. All steroid drug classes possess biological plausibility to affect a beneficial clinical effect among children with septic shock, but none has undergone rigorous, prospective assessment in a large, high-quality pediatric interventional trial.

The Role of Estrogen in Cardiac Metabolism and Diastolic Function

Heart failure with preserved ejection fraction (HFpEF) has similar prevalence and prognosis as HF with reduced EF, but there is no approved treatment for HFpEF. HFpEF is common in postmenopausal women, which suggests that the absence of estrogen (E2) plays a role in its pathophysiology. With the country's growing elderly population, the prevalence of HFpEF is rapidly increasing. This has triggered a renewed urgency in finding novel approaches to preventing and slowing the progression of HFpEF. In this review, we address the role of E2 in left ventricular diastolic function and how it impacts women with HFpEF as well as animal models. We also discuss the primary potential mechanisms that represent critical nodes in the mechanistic pathways of HFpEF and how new treatments could be developed to target those mechanisms.

Amyloid precursor protein drives down-regulation of mitochondrial oxidative phosphorylation independent of amyloid beta

Amyloid precursor protein (APP) and its extracellular domain, soluble APP alpha (sAPPα) play important physiological and neuroprotective roles. However, rare forms of familial Alzheimer’s disease are associated with mutations in APP that increase toxic amyloidogenic cleavage of APP and produce amyloid beta (Aβ) at the expense of sAPPα and other non-amyloidogenic fragments. Although mitochondrial dysfunction has become an established hallmark of neurotoxicity, the link between Aβ and mitochondrial function is unclear. In this study we investigated the effects of increased levels of neuronal APP or Aβ on mitochondrial metabolism and gene expression, in human SH-SY5Y neuroblastoma cells. Increased non-amyloidogenic processing of APP, but not Aβ, profoundly decreased respiration and enhanced glycolysis, while mitochondrial DNA (mtDNA) transcripts were decreased, without detrimental effects to cell growth. These effects cannot be ascribed to Aβ toxicity, since higher levels of endogenous Aβ in our models do not cause oxidative phosphorylation (OXPHOS) perturbations. Similarly, chemical inhibition of β-secretase decreased mitochondrial respiration, suggesting that non-amyloidogenic processing of APP may be responsible for mitochondrial changes. Our results have two important implications, the need for caution in the interpretation of mitochondrial perturbations in models where APP is overexpressed, and a potential role of sAPPα or other non-amyloid APP fragments as acute modulators of mitochondrial metabolism.

In Vitro Evaluation of Mitochondrial Function and Estrogen Signaling in Cell Lines Exposed to the Antiseptic Cetylpyridinium Chloride

BACKGROUND

Quaternary ammonium salts (QUATS), such as cetylpyridinium chloride (CPC) and benzalkonium chloride (BAK), are frequently used in antiseptic formulations, including toothpastes, mouthwashes, lozenges, throat and nasal sprays, and as biocides. Although in a recent ruling, the U.S. Food and Drug Administration (FDA) banned CPC from certain products and requested more data on BAK's efficacy and safety profile, QUATS, in general, and CPC and BAK, in particular, continue to be used in personal health care, food, and pharmaceutical and cleaning industries.

OBJECTIVES

We aimed to assess CPC's effects on mitochondrial toxicity and endocrine disruption in vitro.

METHOD

Mitochondrial O₂ consumption and adenosine triphosphate (ATP) synthesis rates of osteosarcoma cybrid cells were measured before and after CPC and BAK treatment. Antiestrogenic effects of the compounds were measured by a luciferase-based assay using recombinant human breast carcinoma cells (VM7Luc4E2, ERalpha-positive).

RESULTS

CPC inhibited both mitochondrial O₂ consumption [half maximal inhibitory concentration (IC₅₀): 3.8μM] and ATP synthesis (IC₅₀: 0.9μM), and additional findings supported inhibition of mitochondrial complex 1 as the underlying mechanism for these effects. In addition, CPC showed concentration-dependent antiestrogenic activity half maximal effective concentration [(EC₅₀): 4.5μM)]. BAK, another antimicrobial QUATS that is structurally similar to CPC, and the pesticide rotenone, a known complex 1 inhibitor, also showed mitochondrial inhibitory and antiestrogenic effects. In all three cases, there was overlap of the antiestrogenic activity with the mitochondrial inhibitory activity.

CONCLUSIONS

Mitochondrial inhibition in vitro occurred at a CPC concentration that may be relevant to human exposures. The antiestrogenic activity of CPC, BAK, rotenone, and triclosan may be related to their mitochondrial inhibitory activity. Our findings support the need for additional research on the mitochondrial inhibitory and antiestrogenic effects of QUATS, including CPC and BAK. https://doi.org/10.1289/EHP1404.

Pediatric Multiple Organ Dysfunction Syndrome: Promising Therapies

OBJECTIVE

To describe the state of the science, identify knowledge gaps, and offer potential future research questions regarding promising therapies for children with multiple organ dysfunction syndrome presented during the Eunice Kennedy Shriver National Institute of Child Health and Human Development Workshop on Pediatric Multiple Organ Dysfunction Syndrome (March 26-27, 2015).

DATA SOURCES

Literature review, research data, and expert opinion.

STUDY SELECTION

Not applicable.

DATA EXTRACTION

Moderated by an expert from the field, issues relevant to the association of multiple organ dysfunction syndrome with a variety of conditions were presented, discussed, and debated with a focus on identifying knowledge gaps and research priorities.

DATA SYNTHESIS

Summary of presentations and discussion supported and supplemented by relevant literature.

CONCLUSIONS

Among critically ill children, multiple organ dysfunction syndrome is relatively common and associated with significant morbidity and mortality. For outcomes to improve, effective therapies aimed at preventing and treating this condition must be discovered and rigorously evaluated. In this article, a number of potential opportunities to enhance current care are highlighted including the need for a better understanding of the pharmacokinetics and pharmacodynamics of medications, the effect of early and optimized nutrition, and the impact of effective glucose control in the setting of multiple organ dysfunction syndrome. Additionally, a handful of the promising therapies either currently being implemented or developed are described. These include extracorporeal therapies, anticytokine therapies, antitoxin treatments, antioxidant approaches, and multiple forms of exogenous steroids. For the field to advance, promising therapies and other therapies must be assessed in rigorous manner and implemented accordingly.

MECHANISMS IN ENDOCRINOLOGY: Nutrition as a mediator of oxidative stress in metabolic and reproductive disorders in women

Nutrition can generate oxidative stress and trigger a cascade of molecular events that can disrupt oxidative and hormonal balance. Nutrient ingestion promotes a major inflammatory and oxidative response at the cellular level in the postprandial state, altering the metabolic state of tissues. A domino of unfavorable metabolic changes is orchestrated in the main metabolic organs, including adipose tissue, skeletal muscle, liver and pancreas, where subclinical inflammation, endothelial dysfunction, mitochondrial deregulation and impaired insulin response and secretion take place. Simultaneously, in reproductive tissues, nutrition-induced oxidative stress can potentially violate delicate oxidative balance that is mandatory to secure normal reproductive function. Taken all the above into account, nutrition and its accompanying postprandial oxidative stress, in the unique context of female hormonal background, can potentially compromise normal metabolic and reproductive functions in women and may act as an active mediator of various metabolic and reproductive disorders.

Nuclear respiratory factor-1 and bioenergetics in tamoxifen-resistant breast cancer cells

Acquired tamoxifen (TAM) resistance is a significant clinical problem in treating patients with estrogen receptor α (ERα)+ breast cancer. We reported that ERα increases nuclear respiratory factor-1 (NRF-1), which regulates nuclear-encoded mitochondrial gene transcription, in MCF-7 breast cancer cells and NRF-1 knockdown stimulates apoptosis. Whether NRF-1 and target gene expression is altered in endocrine resistant breast cancer cells is unknown. We measured NRF-1and metabolic features in a cell model of progressive TAM-resistance. NRF-1 and its target mitochondrial transcription factor A (TFAM) were higher in TAM-resistant LCC2 and LCC9 cells than TAM-sensitive MCF-7 cells. Using extracellular flux assays we observed that LCC1, LCC2, and LCC9 cells showed similar oxygen consumption rate (OCR), but lower mitochondrial reserve capacity which was correlated with lower Succinate Dehydrogenase Complex, Subunit B in LCC1 and LCC2 cells. Complex III activity was lower in LCC9 than MCF-7 cells. LCC1, LCC2, and LCC9 cells had higher basal extracellular acidification (ECAR), indicating higher aerobic glycolysis, relative to MCF-7 cells. Mitochondrial bioenergetic responses to estradiol and 4-hydroxytamoxifen were reduced in the endocrine-resistant cells compared to MCF-7 cells. These results suggest the acquisition of altered metabolic phenotypes in response to long term antiestrogen treatment may increase vulnerability to metabolic stress.

Estrogen and promoter methylation in the regulation of PLA2G7 transcription

In the current study, cell lines including HEK293, SW480, HPASMC, HPCASMC and HAEC were cultured with 5-aza-2-deoxycytidine (DAC) and 17-β-estradiol to investigate whether PLA2G7 transcription was under the control of promoter methylation and 17-β-estradiol. Luciferase reporter gene assays were used to evaluate whether reporter gene activity was enhanced by PLA2G7 promoter fragment. Gene expression and methylation were detected using RT-PCR and pyrosequencing methods, respectively. Endogenous PLA2G7 transcription levels were found to be significantly lower in vascular related cell lines than in the other cell lines. Luciferase reporter gene assays indicated that gene activity was significantly enhanced by PLA2G7 promoter fragment. PLA2G7 transcription was found to be up-regulated with the treatment of DAC. The 17-β-estradiol was found to down-regulate PLA2G7 transcription in all the cell lines. However, 17-β-estradiol did not have significant effect on PLA2G7 methylation. Further chromatin immunoprecipitation assay showed that 17-β-estradiol might regulate gene transcription by affecting the acetylated histone H3 and H4 marks on PLA2G7 promoter. Our results showed that PLA2G7 gene expression was co-regulated by 17-β-estradiol and promoter methylation. Our findings might provide molecular clues for gender disparity in the contribution of PLA2G7 to vascular related diseases such as coronary heart disease.

The role of mitochondrial DNA copy number, variants, and haplotypes in farm animal developmental outcome

The vast majority of cellular energy is generated through the process of oxidative phosphorylation, which takes place in the electron transport chain in the mitochondria. The electron transport chain is encoded by 2 genomes, the chromosomal and the mitochondrial genomes. Mitochondrial DNA is associated with a number of traits, which include tolerance to heat, growth and physical performance, meat and milk quality, and fertility. Mitochondrial genomes can be clustered into groups known as mtDNA haplotypes. Mitochondrial DNA haplotypes are a potential genetic source for manipulating phenotypes in farm animals. The use of assisted reproductive technologies, such as nuclear transfer, allows favorable chromosomal genetic traits to be mixed and matched with sought after mtDNA haplotype traits. As a result super breeds can be generated.

Recessive Mutations in TRMT10C Cause Defects in Mitochondrial RNA Processing and Multiple Respiratory Chain Deficiencies

Mitochondrial disorders are clinically and genetically diverse, with mutations in mitochondrial or nuclear genes able to cause defects in mitochondrial gene expression. Recently, mutations in several genes encoding factors involved in mt-tRNA processing have been identified to cause mitochondrial disease. Using whole-exome sequencing, we identified mutations in TRMT10C (encoding the mitochondrial RNase P protein 1 [MRPP1]) in two unrelated individuals who presented at birth with lactic acidosis, hypotonia, feeding difficulties, and deafness. Both individuals died at 5 months after respiratory failure. MRPP1, along with MRPP2 and MRPP3, form the mitochondrial ribonuclease P (mt-RNase P) complex that cleaves the 5′ ends of mt-tRNAs from polycistronic precursor transcripts. Additionally, a stable complex of MRPP1 and MRPP2 has m¹R9 methyltransferase activity, which methylates mt-tRNAs at position 9 and is vital for folding mt-tRNAs into their correct tertiary structures. Analyses of fibroblasts from affected individuals harboring TRMT10C missense variants revealed decreased protein levels of MRPP1 and an increase in mt-RNA precursors indicative of impaired mt-RNA processing and defective mitochondrial protein synthesis. The pathogenicity of the detected variants—compound heterozygous c.542G>T (p.Arg181Leu) and c.814A>G (p.Thr272Ala) changes in subject 1 and a homozygous c.542G>T (p.Arg181Leu) variant in subject 2—was validated by the functional rescue of mt-RNA processing and mitochondrial protein synthesis defects after lentiviral transduction of wild-type TRMT10C. Our study suggests that these variants affect MRPP1 protein stability and mt-tRNA processing without affecting m¹R9 methyltransferase activity, identifying mutations in TRMT10C as a cause of mitochondrial disease and highlighting the importance of RNA processing for correct mitochondrial function.

PageRank analysis reveals topologically expressed genes correspond to psoriasis and their functions are associated with apoptosis resistance

Psoriasis is an inflammatory skin disease. Deceleration in keratinocyte apoptosis is the most significant pathological change observed in psoriasis. To detect a meaningful correlation between the genes and gene functions associated with the mechanism underlying psoriasis, 927 differentially expressed genes (DEGs) were identified using the Gene Expression Omnibus database, GSE13355 [false discovery rate (FDR) <0.01; |log fold change >1] with the package in R langue. The selected DEGs were further constructed using the search tool for the retrieval of interacting genes, in order to analyze the interaction network between the DEGs. Subsequent to PageRank analysis, 14 topological hub genes were identified, and the functions and pathways in the hub genes network were analyzed. The top‑ranked hub gene, estrogen receptor‑1 (ESR1) is downregulated in psoriasis, exhibited binding sites enriched with genes possessing anti‑apoptotic functions. The ESR1 gene encodes estrogen receptor α (ERα); a reduced level of ERα expression provides a crucial foundation in response to the anti‑apoptotic activity of psoriatic keratinocytes by activating the expression of anti‑apoptotic genes. Furthermore, it was detected that the pathway that is associated most significantly with psoriasis is the pathways in cancer. Pathways in cancer may protect psoriatic cells from apoptosis by inhibition of ESR1 expression. The present study provides support towards the investigation of ESR1 gene function and elucidates that the interaction with anti‑apoptotic genes is involved in the underlying biological mechanisms of resistance to apoptosis in psoriasis. However, further investigation is required to confirm the present results.

Sirtuins and the Estrogen Receptor as Regulators of the Mammalian Mitochondrial UPR in Cancer and Aging

By being both the source of ATP and the mediator of apoptosis, the mitochondria are key regulators of cellular life and death. Not surprisingly alterations in the biology of the mitochondria have implications in a wide array of diseases including cancer and age-related diseases such as neurodegeneration. To protect the mitochondria against damage the mitochondrial unfolded protein response (UPR(mt)) orchestrates several pathways, including the protein quality controls, the antioxidant machinery, oxidative phosphorylation, mitophagy, and mitochondrial biogenesis. While several reports have implicated an array of transcription factors in the UPR(mt), most of the focus has been on studies of Caenorhabditis elegans, which led to the identification of ATFS-1, for which the mammalian homolog remains unknown. Meanwhile, there are studies which link the UPR(mt) to sirtuins and transcription factors of the Foxo family in both C. elegans and mammalian cells but those have been largely overlooked. This review aims at emphasizing the potential importance of these studies by building on the large body of literature supporting the key role of the sirtuins in the maintenance of the integrity of the mitochondria in both cancer and aging. Further, the estrogen receptor alpha (ERα) and beta (ERβ) are known to confer protection against mitochondrial stress, and at least ERα has been linked to the UPR(mt). Considering the difference in gender longevity, this chapter also includes a discussion of the link between the ERα and ERβ and the mitochondria in cancer and aging.

The Role of the L-Type Ca2+ Channel in Altered Metabolic Activity in a Murine Model of Hypertrophic Cardiomyopathy

Heterozygous mice (αMHC^403/+) expressing the human disease-causing mutation Arg403Gln exhibit cardinal features of hypertrophic cardiomyopathy (HCM) including hypertrophy, myocyte disarray, and increased myocardial fibrosis. Treatment of αMHC^403/+mice with the L-type calcium channel (I_Ca-L) antagonist diltiazem has been shown to decrease left ventricular anterior wall thickness, cardiac myocyte hypertrophy, disarray, and fibrosis. However, the role of the I_Ca-L in the development of HCM is not known. In addition to maintaining cardiac excitation and contraction in myocytes, the I_Ca-L also regulates mitochondrial function through transmission of movement of I_Ca-L via cytoskeletal proteins to mitochondrial voltage-dependent anion channel. Here, the authors investigated the role of I_Ca-L in regulating mitochondrial function in αMHC^403/+mice. Whole-cell patch clamp studies showed that I_Ca-L current inactivation kinetics were significantly increased in αMHC^403/+cardiac myocytes, but that current density and channel expression were similar to wild-type cardiac myocytes. Activation of I_Ca-L caused a significantly greater increase in mitochondrial membrane potential and metabolic activity in αMHC^403/+. These increases were attenuated with I_Ca-L antagonists and following F-actin or β-tubulin depolymerization. The authors observed increased levels of fibroblast growth factor-21 in αMHC^403/+mice, and altered mitochondrial DNA copy number consistent with altered mitochondrial activity and the development of cardiomyopathy. These studies suggest that the Arg403Gln mutation leads to altered functional communication between I_Ca-L and mitochondria that is associated with increased metabolic activity, which may contribute to the development of cardiomyopathy. I_Ca-L antagonists may be effective in reducing the cardiomyopathy in HCM by altering metabolic activity.

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Heterozygous mice (αMHC^403/+) expressing the human hypertrophic cardiomyopathy (HCM) disease causing mutation Arg403Gln exhibit cardinal features of HCM.

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This study investigated the role of L-type Ca2+ channel (ICa-L) in regulating mitochondrial function in Arg403Gln (αMHC^403/+) mice.

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Activation of ICa-L in αMHC^403/+mice caused a significantly greater increase in mitochondrial membrane potential and metabolic activity when compared to wild-type mice.

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Increases in mitochondrial membrane potential and metabolic activity were attenuated with ICa-L antagonists and when F-actin or β-tubulin were depolymerized.

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ICa-L antagonists may be effective in reducing the cardiomyopathy in HCM by altering metabolic activity.

Mitochondrial Quality Control as a Therapeutic Target

In addition to oxidative phosphorylation (OXPHOS), mitochondria perform other functions such as heme biosynthesis and oxygen sensing and mediate calcium homeostasis, cell growth, and cell death. They participate in cell communication and regulation of inflammation and are important considerations in aging, drug toxicity, and pathogenesis. The cell's capacity to maintain its mitochondria involves intramitochondrial processes, such as heme and protein turnover, and those involving entire organelles, such as fusion, fission, selective mitochondrial macroautophagy (mitophagy), and mitochondrial biogenesis. The integration of these processes exemplifies mitochondrial quality control (QC), which is also important in cellular disorders ranging from primary mitochondrial genetic diseases to those that involve mitochondria secondarily, such as neurodegenerative, cardiovascular, inflammatory, and metabolic syndromes. Consequently, mitochondrial biology represents a potentially useful, but relatively unexploited area of therapeutic innovation. In patients with genetic OXPHOS disorders, the largest group of inborn errors of metabolism, effective therapies, apart from symptomatic and nutritional measures, are largely lacking. Moreover, the genetic and biochemical heterogeneity of these states is remarkably similar to those of certain acquired diseases characterized by metabolic and oxidative stress and displaying wide variability. This biologic variability reflects cell-specific and repair processes that complicate rational pharmacological approaches to both primary and secondary mitochondrial disorders. However, emerging concepts of mitochondrial turnover and dynamics along with new mitochondrial disease models are providing opportunities to develop and evaluate mitochondrial QC-based therapies. The goals of such therapies extend beyond amelioration of energy insufficiency and tissue loss and entail cell repair, cell replacement, and the prevention of fibrosis. This review summarizes current concepts of mitochondria as disease elements and outlines novel strategies to address mitochondrial dysfunction through the stimulation of mitochondrial biogenesis and quality control.

Estrogen: an emerging regulator of insulin action and mitochondrial function

Clinical trials and animal studies have revealed that loss of circulating estrogen induces rapid changes in whole body metabolism, fat distribution, and insulin action. The metabolic effects of estrogen are mediated primarily by its receptor, estrogen receptor-α; however, the detailed understanding of its mechanisms is incomplete. Recent investigations suggest that estrogen receptor-α elicits the metabolic effects of estrogen by genomic, nongenomic, and mitochondrial mechanisms that regulate insulin signaling, substrate oxidation, and energetics. This paper reviews clinical and experimental studies on the mechanisms of estrogen and the current state of knowledge regarding physiological and pathobiological influences of estrogen on metabolism.