Publications by authors named "Niels Gregersen"

152 Publications

Use of Molecular Genetic Analyses in Danish Routine Newborn Screening.

Int J Neonatal Screen 2021 Jul 26;7(3). Epub 2021 Jul 26.

Research Unit for Molecular Medicine, Department of Clinical Medicine, Aarhus University and Aarhus University Hospital, 8200 Aarhus, Denmark.

Historically, the analyses used for newborn screening (NBS) were biochemical, but increasingly, molecular genetic analyses are being introduced in the workflow. We describe the application of molecular genetic analyses in the Danish NBS programme and show that second-tier molecular genetic testing is useful to reduce the false positive rate while simultaneously providing information about the precise molecular genetic variant and thus informing therapeutic strategy and easing providing information to parents. When molecular genetic analyses are applied as second-tier testing, valuable functional data from biochemical methods are available and in our view, such targeted NGS technology should be implemented when possible in the NBS workflow. First-tier NGS technology may be a promising future possibility for disorders without a reliable biomarker and as a general approach to increase the adaptability of NBS for a broader range of genetic diseases, which is important in the current landscape of quickly evolving new therapeutic possibilities. However, studies on feasibility, sensitivity, and specificity are needed as well as more insight into what views the general population has towards using genetic analyses in NBS. This may be sensitive to some and could have potentially negative consequences for the NBS programme.
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http://dx.doi.org/10.3390/ijns7030050DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8395600PMC
July 2021

Bioenergetic and Proteomic Profiling of Immune Cells in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients: An Exploratory Study.

Biomolecules 2021 06 29;11(7). Epub 2021 Jun 29.

Department of Clinical Physiology and Nuclear Medicine, Nordsjaellands Hospital, 2400 Hilleroed, Denmark.

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a heterogeneous, debilitating, and complex disease. Along with disabling fatigue, ME/CFS presents an array of other core symptoms, including autonomic nervous system (ANS) dysfunction, sustained inflammation, altered energy metabolism, and mitochondrial dysfunction. Here, we evaluated patients' symptomatology and the mitochondrial metabolic parameters in peripheral blood mononuclear cells (PBMCs) and plasma from a clinically well-characterised cohort of six ME/CFS patients compared to age- and gender-matched controls. We performed a comprehensive cellular assessment using bioenergetics (extracellular flux analysis) and protein profiles (quantitative mass spectrometry-based proteomics) together with self-reported symptom measures of fatigue, ANS dysfunction, and overall physical and mental well-being. This ME/CFS cohort presented with severe fatigue, which correlated with the severity of ANS dysfunction and overall physical well-being. PBMCs from ME/CFS patients showed significantly lower mitochondrial coupling efficiency. They exhibited proteome alterations, including altered mitochondrial metabolism, centred on pyruvate dehydrogenase and coenzyme A metabolism, leading to a decreased capacity to provide adequate intracellular ATP levels. Overall, these results indicate that PBMCs from ME/CFS patients have a decreased ability to fulfill their cellular energy demands.
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http://dx.doi.org/10.3390/biom11070961DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8301912PMC
June 2021

Variants in the ethylmalonyl-CoA decarboxylase (ECHDC1) gene: a novel player in ethylmalonic aciduria?

J Inherit Metab Dis 2021 09 8;44(5):1215-1225. Epub 2021 Jun 8.

Research Unit for Molecular Medicine, Department for Clinical Medicine, Aarhus University and Aarhus University Hospital, Aarhus, Denmark.

Ethylmalonic acid (EMA) is a major and potentially cytotoxic metabolite associated with short-chain acyl-CoA dehydrogenase (SCAD) deficiency, a condition whose status as a disease is uncertain. Unexplained high EMA is observed in some individuals with complex neurological symptoms, who carry the SCAD gene (ACADS) variants, c.625G>A and c.511C>T. The variants have a high allele frequency in the general population, but are significantly overrepresented in individuals with elevated EMA. This has led to the idea that these variants need to be associated with variants in other genes to cause hyperexcretion of ethylmalonic acid and possibly a diseased state. Ethylmalonyl-CoA decarboxylase (ECHDC1) has been described and characterized as an EMA metabolite repair enzyme, however, its clinical relevance has never been investigated. In this study, we sequenced the ECHDC1 gene (ECHDC1) in 82 individuals, who were reported with unexplained high EMA levels due to the presence of the common ACADS variants only. Three individuals with ACADS c.625G>A variants were found to be heterozygous for ECHDC1 loss-of-function variants. Knockdown experiments of ECHDC1, in healthy human cells with different ACADS c.625G>A genotypes, showed that ECHDC1 haploinsufficiency and homozygosity for the ACADS c.625G>A variant had a synergistic effect on cellular EMA excretion. This study reports the first cases of ECHDC1 gene defects in humans and suggests that ECHDC1 may be involved in elevated EMA excretion in only a small group of individuals with the common ACADS variants. However, a direct link between ECHDC1/ACADS deficiency, EMA and disease could not be proven.
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http://dx.doi.org/10.1002/jimd.12394DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8518634PMC
September 2021

Open-geometry modal method based on transverse electric and transverse magnetic mode expansion for orthogonal curvilinear coordinates.

Phys Rev E 2021 Mar;103(3-1):033301

Department of Photonics Engineering, Technical University of Denmark, Ørsteds Plads, Building 343, DK-2800 Kongens Lyngby, Denmark.

A vectorial modal method is presented based on transverse magnetic and transverse electric mode expansion, which significantly simplifies the evaluation of the operator matrix. The method, which features a true open boundary condition, is introduced for an orthogonal curvilinear coordinate system with the specific examples of circular and elliptical geometries presented. We validate the method by considering challenging problems, such as the calculation of spontaneous emission rates, of modal reflection coefficients and of the effect of the emitter spatial misalignment on the spontaneous emission β factor. Results are compared with literature.
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http://dx.doi.org/10.1103/PhysRevE.103.033301DOI Listing
March 2021

Time-bin entangled photon pairs from quantum dots embedded in a self-aligned cavity.

Opt Express 2021 Feb;29(3):4174-4180

We introduce a scalable photonic platform that enables efficient generation of entangled photon pairs from a semiconductor quantum dot. Our system, which is based on a self-aligned quantum dot- micro-cavity structure, erases the need for complex steps of lithography and nanofabrication. We experimentally show collection efficiency of 0.17 combined with a Purcell enhancement of up to 1.7. We harness the potential of our device to generate photon pairs entangled in time bin, reaching a fidelity of 0.84(5) with the maximally entangled state. The achieved pair collection efficiency is 4 times larger than the state-of-the art for this application. The device, which theoretically supports pair extraction efficiencies of nearly 0.5 is a promising candidate for the implementation of bright sources of time-bin, polarization- and hyper entangled photon pairs in a straightforward manner.
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http://dx.doi.org/10.1364/OE.411021DOI Listing
February 2021

Bezafibrate activation of PPAR drives disturbances in mitochondrial redox bioenergetics and decreases the viability of cells from patients with VLCAD deficiency.

Biochim Biophys Acta Mol Basis Dis 2021 06 5;1867(6):166100. Epub 2021 Feb 5.

Research Unit for Molecular Medicine, Department of Clinical Medicine, Aarhus University and Aarhus University Hospital, Palle Juel-Jensens Boulevard 99, 8200 Aarhus, Denmark. Electronic address:

Very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency is the most common inborn long-chain fatty acid oxidation (FAO) disorder. VLCAD deficiency is characterized by distinct phenotypes. The severe phenotypes are potentially life-threatening and affect the heart or liver, with a comparatively milder phenotype characterized by myopathic symptoms. There is an unmet clinical need for effective treatment options for the myopathic phenotype. The molecular mechanisms driving the gradual decrease in mitochondrial function and associated alterations of muscle fibers are unclear. The peroxisome proliferator-activated receptor (PPAR) pan-agonist bezafibrate is a potent modulator of FAO and multiple other mitochondrial functions and has been proposed as a potential medication for myopathic cases of long-chain FAO disorders. In vitro experiments have demonstrated the ability of bezafibrate to increase VLCAD expression and activity. However, the outcome of small-scale clinical trials has been controversial. We found VLCAD deficient patient fibroblasts to have an increased oxidative stress burden and deranged mitochondrial bioenergetic capacity, compared to controls. Applying heat stress under fasting conditions to bezafibrate pretreated patient cells, caused a marked further increase of mitochondrial superoxide levels. Patient cells failed to maintain levels of the essential thiol peptide antioxidant glutathione and experienced a decrease in cellular viability. Our findings indicate that chronic PPAR activation is a plausible initiator of long-term pathogenesis in VLCAD deficiency. Our findings further implicate disruption of redox homeostasis as a key pathogenic mechanism in VLCAD deficiency and support the notion that a deranged thiol metabolism might be an important pathogenic factor in VLCAD deficiency.
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http://dx.doi.org/10.1016/j.bbadis.2021.166100DOI Listing
June 2021

Riboflavin Deficiency-Implications for General Human Health and Inborn Errors of Metabolism.

Int J Mol Sci 2020 May 28;21(11). Epub 2020 May 28.

Research Unit for Molecular Medicine, Department for Clinical Medicine, Aarhus University and Aarhus University Hospital, 8200 Aarhus N, Denmark.

As an essential vitamin, the role of riboflavin in human diet and health is increasingly being highlighted. Insufficient dietary intake of riboflavin is often reported in nutritional surveys and population studies, even in non-developing countries with abundant sources of riboflavin-rich dietary products. A latent subclinical riboflavin deficiency can result in a significant clinical phenotype when combined with inborn genetic disturbances or environmental and physiological factors like infections, exercise, diet, aging and pregnancy. Riboflavin, and more importantly its derivatives, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), play a crucial role in essential cellular processes including mitochondrial energy metabolism, stress responses, vitamin and cofactor biogenesis, where they function as cofactors to ensure the catalytic activity and folding/stability of flavoenzymes. Numerous inborn errors of flavin metabolism and flavoenzyme function have been described, and supplementation with riboflavin has in many cases been shown to be lifesaving or to mitigate symptoms. This review discusses the environmental, physiological and genetic factors that affect cellular riboflavin status. We describe the crucial role of riboflavin for general human health, and the clear benefits of riboflavin treatment in patients with inborn errors of metabolism.
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http://dx.doi.org/10.3390/ijms21113847DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7312377PMC
May 2020

Increased antioxidant response in medium-chain acyl-CoA dehydrogenase deficiency: does lipoic acid have a protective role?

Pediatr Res 2020 10 11;88(4):556-564. Epub 2020 Feb 11.

Research Unit for Molecular Medicine, Department of Clinical Medicine, Aarhus University Hospital and Faculty of Health, Aarhus University, Aarhus, Denmark.

Background: Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency (MCADD) is the most frequent fatty acid oxidation (FAO) defect in humans. MCAD-deficient fibroblasts are more resistant to oxidative stress-induced cell death than other FAO defects and healthy controls.

Methods: Herein we investigate the antioxidant response and mitochondrial function in fibroblasts from MCAD-deficient patients (c.985 A>G/c.985 A>G) and healthy controls.

Results: MCAD-deficient fibroblasts showed increased level of mitochondrial superoxide, while lipids were less oxidatively damaged, and higher amount of manganese superoxide dismutase were detected compared to healthy controls, showing forceful antioxidant system in MCADD. We showed increased maximal respiration and reserve capacity in MCAD-deficient fibroblasts compared to controls, indicating more capacity through the tricarboxylic acid (TCA) cycle and subsequently respiratory chain. This led us to study the pyruvate dehydrogenase complex (PDC), the key enzyme in the glycolysis releasing acetyl-CoA to the TCA cycle. MCAD-deficient fibroblasts displayed not only significantly increased PDC but also increased lipoylated PDC protein levels compared to healthy controls.

Conclusions: Based on these findings, we raise the interesting hypothesis that increased PDC-bound lipoic acid, synthesized from accumulated octanoic acid in MCADD, may affect the cellular antioxidant pool in MCADD.
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http://dx.doi.org/10.1038/s41390-020-0801-1DOI Listing
October 2020

Design of Quantum Dot-Nanowire Single-Photon Sources that are Immune to Thermomechanical Decoherence.

Phys Rev Lett 2019 Dec;123(24):247403

Univ. Grenoble Alpes, CEA, IRIG, PHELIQS, "Nanophysique et semiconducteurs" group, F-38000 Grenoble, France.

Nanowire antennas embedding a single quantum dot (QD) have recently emerged as versatile platforms to realize bright sources of quantum light. In this theoretical work, we show that the thermally driven, low-frequency vibrations of the nanowire have a major impact on the QD light emission spectrum. Even at liquid helium temperatures, these prevent the emission of indistinguishable photons. To overcome this intrinsic limitation, we propose three designs that restore photon indistinguishability thanks to a specific engineering of the mechanical properties of the nanowire. We anticipate that such a mechanical optimization will also play a key role in the development of other high-performance light-matter interfaces based on nanostructures.
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http://dx.doi.org/10.1103/PhysRevLett.123.247403DOI Listing
December 2019

Danish expanded newborn screening is a successful preventive public health programme.

Dan Med J 2020 Jan;67(1)

Introduction: Newborn screening is a public health programme for early diagnosis of treatable diseases.

Methods: The subjects included were newborns born 2002-2019. Expanded newborn screening (eNBS) for metabolic diseases was introduced as a pilot project from 2002 to 2009, followed by routine screening with informed dissent. A total of 967,780 newborns were screened; 82,930 were unscreened. Furthermore, a historic cohort of clinically diagnosed children born in the 1992-2001 period was included. Children in the unscreened and historic cohorts were evaluated for the same diseases as were the screened children. Dried blood spot samples were collected locally and sent for screening analyses. We recorded newborns with true and false positive results as well as false negative results and their clinical signs at screening and at the last follow-up.

Results: A total of 603 samples were screen positive: 354 false positives and 249 true positives (222 newborns and 27 mothers). The positive predictive value (PPV) was 41% for the entire screening period; 62% for 2018. The false positive rate (FPR) was 0.036% overall; 0.024% for 2018. The overall prevalence of diseases was 1:3,900; in the historic cohort, the prevalence of the same diseases was 1:8,300; 7.3% had symptoms at the time of screening. At follow-up, 93% of the children had no clinically significant sequelae. Among 82,930 unscreened newborns, 27 (1:3,000) had eNBS panel diseases, some with severe manifestations.

Conclusions: This update of eNBS in Denmark confirms that eNBS is a successful preventive public health programme. Early treatment in a latent phase of disease is effective and screening should be extended to other diseases not currently in the programme.

Funding: The work was supported by grants from The Ronald McDonald Børnefond, Danmarks Sundhedsfond, Direktør Ib Henriksens Fond, Ragnhild Ibsens Legat til Medicinsk Forskning, Gerda og Aage Haenschs Fond, Dronning Louises Børnehospitals Forskningsfond, Læge Sofus Carl Emil Friis og Hustru Olga Doris Friis's Legat, Aase and Ejnar Danielsens Fond, Oda og Hans Svenningsens Fond, Fonden af 1870, Vanførefonden, Fonden til Lægevidenskabens Fremme and Danish Medical Research Council.

Trial Registration: not relevant.
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January 2020

[Psychological, neurological and cell-mediated mechanisms by mindfulness-based therapy].

Ugeskr Laeger 2019 Jul;181(30)

In this review, we present clinical studies on mindfulness-based therapy (MBT) with a focus on mediating mechanisms for its health promoting effects. These constitute awareness, self-compassion, regulation of dysfunctional patterns of thoughts and emotions, neural network and cellular processes. Among cellular processes are inflammation, oxidative stress, mitochondrial dysfunction and telomere shortening, which all contribute to the molecular pathophysiology of several of today's lifestyle diseases. Finally, we address applications, where strong evidence exists for the clinical impact of MBT.
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July 2019

[Myalgic encephalomyelitis or chronic fatigue syndrome].

Ugeskr Laeger 2019 Jun;181(24)

In this review, we discuss the myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), which is characterised by extreme mental and physical fatigue with associated symptoms of pain, disturbed sleep, cognitive and autonomic dysfunction, as well as post-exertional malaise. This con-dition is often preceded by an infection, severe physiological and/or psychological strain. Over the last decades, research has demonstrated mitochondrial, neuroendocrine, immuno-logical, and metabolic perturbations in patients with ME/CFS, giving hope for the development of new biomarkers and new treatment modalities.
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June 2019

Mitochondrial fatty acid oxidation and the electron transport chain comprise a multifunctional mitochondrial protein complex.

J Biol Chem 2019 08 24;294(33):12380-12391. Epub 2019 Jun 24.

Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261; Department of Human Genetics, University of Pittsburgh Graduate School of Public Health, Pittsburgh, Pennsylvania 15261; Center for Rare Disease Therapy, UPMC Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania 15224. Electronic address:

Three mitochondrial metabolic pathways are required for efficient energy production in eukaryotic cells: the electron transfer chain (ETC), fatty acid β-oxidation (FAO), and the tricarboxylic acid cycle. The ETC is organized into inner mitochondrial membrane supercomplexes that promote substrate channeling and catalytic efficiency. Although previous studies have suggested functional interaction between FAO and the ETC, their physical interaction has never been demonstrated. In this study, using blue native gel and two-dimensional electrophoreses, nano-LC-MS/MS, immunogold EM, and stimulated emission depletion microscopy, we show that FAO enzymes physically interact with ETC supercomplexes at two points. We found that the FAO trifunctional protein (TFP) interacts with the NADH-binding domain of complex I of the ETC, whereas the electron transfer enzyme flavoprotein dehydrogenase interacts with ETC complex III. Moreover, the FAO enzyme very-long-chain acyl-CoA dehydrogenase physically interacted with TFP, thereby creating a multifunctional energy protein complex. These findings provide a first view of an integrated molecular architecture for the major energy-generating pathways in mitochondria that ensures the safe transfer of unstable reducing equivalents from FAO to the ETC. They also offer insight into clinical ramifications for individuals with genetic defects in these pathways.
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http://dx.doi.org/10.1074/jbc.RA119.008680DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6699831PMC
August 2019

All-Optical Mapping of the Position of Quantum Dots Embedded in a Nanowire Antenna.

Nano Lett 2018 10 7;18(10):6434-6440. Epub 2018 Sep 7.

Univ. Grenoble Alpes, CEA, INAC, PHELIQS , "Nanophysique et semiconducteurs" group, F-38000 Grenoble , France.

Nanowire antennas embedding single quantum dots (QDs) have recently emerged as a versatile solid-state platform for quantum optics. Within the nanowire section, the emitter position simultaneously determines the strength of the light-matter interaction, as well as the coupling to potential decoherence channels. Therefore, to quantitatively understand device performance and guide future optimization, it is highly desirable to map the emitter position with an accuracy much smaller than the waveguide diameter, on the order of a few hundreds of nanometers. We introduce here a nondestructive, all-optical mapping technique that exploits the QD emission into two guided modes with different transverse profiles. These two modes are fed by the same emitter and thus interfere. The resulting intensity pattern, which is highly sensitive to the emitter position, is resolved in the far-field using Fourier microscopy. We demonstrate this technique on a standard microphotoluminescence setup and map the position of individual QDs in a nanowire antenna with a spatial resolution of ±10 nm. This work opens important perspectives for the future development of light-matter interfaces based on nanowire antennas. Beyond single-QD devices, it will also provide a valuable tool for the investigation of collective effects that imply several emitters coupled to an optical waveguide.
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http://dx.doi.org/10.1021/acs.nanolett.8b02826DOI Listing
October 2018

Biomarker Discovery by Mass Spectrometry in Cerebrospinal Fluid and Plasma after Global Hypoxia-Ischemia in Newborn Piglets.

Neonatology 2018 19;114(4):307-314. Epub 2018 Jul 19.

Research Unit for Molecular Medicine, Aarhus, Denmark.

Background: Biomarkers may qualify diagnosis, treatment allocation, and prognostication in neonatal encephalopathy. Biomarker development is challenged by competing etiologies, inter-individual genetic variability, and a lack of specific neonatal markers. To address these challenges, we used a standardized neonatal hypoxic-ischemic (HI) encephalopathy model with pre- and post-HI sampling of cerebrospinal fluid (CSF) and plasma.

Objectives: The study aimed to identify novel candidate protein biomarkers of HI encephalopathy in a newborn piglet model in CSF and plasma.

Methods: FiO2 was lowered to 4% in 6 newborn piglets, then adjusted over a 45-min period keeping the amplitude integrated-EEG < 7 µV to induce HI encephalopathy. CSF and plasma was sampled pre-HI and 2 h after HI, protein levels were then analyzed by mass spectrometry.

Results: Protein levels after HI changed significantly for 18 CSF proteins and 37 plasma proteins. CSF and plasma data showed distinct information, although peptidyl-prolyl cis-trans isomerase A had elevated levels in both fluids. HI regulation involved functional groups such as the antioxidant system, cell proliferation, cell structure, and apoptosis. S100-A8, which increased the most in CSF (9.5 fold), is known to be involved in inflammatory and immune response and to be highly regulated during injury. In plasma, increased proteins included FABP1 (31.8 fold) and proteins with antioxidant (SOD1, GPX3) and lectin function (REG3A, LGALS3).

Conclusions: In this exploratory study, we have identified candidate biomarkers for HI in CSF and plasma, many not previously associated with HI. Identified proteins are promising candidates for further validation in time series experiments and clinical studies.
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http://dx.doi.org/10.1159/000490393DOI Listing
September 2019

A Novel Synonymous Variant in the AVP Gene Associated with Autosomal Dominant Familial Neurohypophyseal Diabetes Insipidus Causes Partial RNA Missplicing.

Neuroendocrinology 2018 27;107(2):167-180. Epub 2018 Jun 27.

Department of Biomedicine, Aarhus University, Aarhus, Denmark.

Objective: Autosomal dominant familial neurohypophyseal diabetes insipidus (adFNDI) is characterized by severe polyuria and polydipsia and is caused by variations in the gene encoding the AVP prohormone. This study aimed to ascertain a correct diagnosis, to identify the underlying genetic cause of adFNDI in a Swedish family, and to test the hypothesis that the identified synonymous exonic variant in the AVP gene (c.324G>A) causes missplicing and endoplasmic reticulum (ER) retention of the prohormone.

Design/patients: Three affected family members were admitted for fluid deprivation test and dDAVP (1-deamino-8-d-arginine-vasopressin) challenge test. Direct sequencing of the AVP gene was performed in the affected subjects, and genotyping of the identified variant was performed in family members. The variant was examined by expression of AVP minigenes containing the entire coding regions as well as intron 2 of AVP.

Methods/results: Clinical tests revealed significant phenotypical variation with both complete and partial adFNDI phenotype. DNA analysis revealed a synonymous c.324G>A substitution in one allele of the AVP gene in affected family members only. Cellular studies revealed both normally spliced and misspliced pre-mRNA in cells transfected with the AVP c.324G>A minigene. Confocal laser scanning microscopy showed collective localization of the variant prohormone to ER and vesicular structures at the tip of cellular processes.

Conclusion: We identified a synonymous variant affecting the second nucleotide of exon 3 in the AVP gene (c.324G>A) in a family in which adFNDI segregates. Notably, we showed that this variant causes partial missplicing of pre-mRNA, resulting in accumulation of the variant prohormone in ER. Our study suggests that even a small amount of aberrant mRNA might be sufficient to disturb cellular function, resulting in adFNDI.
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http://dx.doi.org/10.1159/000491579DOI Listing
January 2019

Benchmarking five numerical simulation techniques for computing resonance wavelengths and quality factors in photonic crystal membrane line defect cavities.

Opt Express 2018 Apr;26(9):11366-11392

We present numerical studies of two photonic crystal membrane microcavities, a short line-defect cavity with a relatively low quality (Q) factor and a longer cavity with a high Q. We use five state-of-the-art numerical simulation techniques to compute the cavity Q factor and the resonance wavelength λ for the fundamental cavity mode in both structures. For each method, the relevant computational parameters are systematically varied to estimate the computational uncertainty. We show that some methods are more suitable than others for treating these challenging geometries.
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http://dx.doi.org/10.1364/OE.26.011366DOI Listing
April 2018

Novel and recurrent variants in AVPR2 in 19 families with X-linked congenital nephrogenic diabetes insipidus.

Eur J Pediatr 2018 Sep 28;177(9):1399-1405. Epub 2018 Mar 28.

Department of Pediatrics and Adolescent Medicine and Department of Clinical Medicine, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark.

Congenital nephrogenic diabetes insipidus (CNDI) is characterized by the reduced ability of renal collecting duct cells to reabsorb water in response to the antidiuretic effect of vasopressin. Chronic polyuria and polydipsia are the hallmarks of the disease. Approximately 90% of all patients with CNDI have X-linked inherited disease caused by variants in the arginine vasopressin receptor 2 (AVPR2) gene. We present genetic findings in 34 individuals from 19 kindreds including one or more family members with CNDI. Coding regions of AVPR2 were sequenced bi-directionally. We identified eight novel disease-causing variants in AVPR2, p.Arg68Alafs*124, p.Ser171Arg, p.Gln174Pro, p.Trp200Arg, p.Gly201Cys, p.Gly220Arg, p.Val226Glu, and p.Gln291Pro in nine kindreds. In all three families with more than one affected individual, the novel variants segregated with the disease. We also identified eight recurrent disease-causing variants, p.Val88Met, p.Leu111Valfs*80, p.Arg113Trp, p.Tyr124*, p.Ser167Leu, p.Thr207Asn, p.Arg247Alafs*12, and p.Arg337* in ten kindreds. Our findings contribute to the growing list of AVPR2 variants causing X-linked CNDI.

Conclusion: Being a rapid diagnostic tool for CNDI, direct sequencing of AVPR2 should be encouraged in newborns with familial predisposition to CNDI. What is Known: • Disease-causing variants in AVPR2 cause X-linked congenital nephrogenic diabetes insipidus (CNDI). • DNA sequencing of AVPR2 is rapid, facilitates differential diagnosis, early intervention, and genetic diagnosis thus reducing morbidity in CNDI. What is New: • We identified eight novel disease-causing variants in AVPR2: p.Arg68Alafs*124, p.Ser171Arg, p.Gln174Pro, p.Trp200Arg, p.Gly201Cys, p.Gly220Arg, p.Val226Glu, and p.Gln291Pro, thereby adding to the growing list of AVPR2 disease-causing variants and emphasizing the importance of genetic testing in CNDI.
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http://dx.doi.org/10.1007/s00431-018-3132-zDOI Listing
September 2018

Novel Variant in a Patient with Congenital Nephrogenic Diabetes Insipidus.

Case Rep Nephrol Dial 2017 Sep-Dec;7(3):130-137. Epub 2017 Sep 27.

Department of Biomedicine, Aarhus University, Aarhus, Denmark.

Early diagnosis and treatment of congenital nephrogenic diabetes insipidus (CNDI) are essential due to the risk of intellectual disability caused by repeated episodes of dehydration and rapid rehydration. Timely genetic testing for disease-causing variants in the arginine vasopressin receptor 2 () gene is possible in at-risk newborns with a known family history of X-linked CNDI. In this study, a Swedish male with no family history was diagnosed with CNDI at 6 months of age during an episode of gastroenteritis. We analyzed the coding regions of by PCR and direct DNA sequencing and identified an 80-bp duplication in exon 2 (GenBank NM_000054.4; c.800_879dup) in the proband. This variant leads to a frameshift and introduces a stop codon four codons downstream (p.Ala294Profs*4). The variant gene product either succumbs to nonsense-mediated decay or is translated to a truncated nonfunctional vasopressin V2 receptor. This variant was absent in four unaffected family members, including his parents, as well as in 100 alleles from healthy controls, and is thus considered a novel disease-causing variant. Identification of the disease-causing variant facilitated precise diagnosis of CNDI in the proband. Furthermore, it allows future genetic counseling in the family. This case study highlights the importance of genetic testing in sporadic infant cases with CNDI that can occur due to variants in or several generations of female transmission of the disease-causing variant.
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http://dx.doi.org/10.1159/000480009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5696758PMC
September 2017

An intronic variation in SLC52A1 causes exon skipping and transient riboflavin-responsive multiple acyl-CoA dehydrogenation deficiency.

Mol Genet Metab 2017 12 2;122(4):182-188. Epub 2017 Nov 2.

Department of Biochemistry and Molecular Biology, The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense, Denmark. Electronic address:

Vitamin B2, riboflavin is essential for cellular function, as it participates in a diversity of redox reactions central to human metabolism, through its role as precursor for the cofactors flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which are electron carriers. The electron transfer flavoprotein (ETF) and its dehydrogenase (ETFDH), uses FAD as cofactor. The ETF and ETFDH are forming the electron transport pathway for many mitochondrial flavoprotein dehydrogenases involved in fatty acid, amino acid and choline metabolism. A variation in either ETF or ETFDH causes multiple acyl-CoA dehydrogenation deficiency (MADD), but genetic variations in the riboflavin metabolism or transportation of riboflavin can also cause MADD. The most common variations are located in the riboflavin transporter 2 (RFVT2) and 3 (RFVT3), that are highly expressed in brain and intestinal tissues, respectively. Deficiency of riboflavin transporter 1 (RFVT1), encoded by the SLC52A1 gene, highly expressed in the placenta, has only been reported once. We here report a case of transient MADD, caused by a heterozygous intronic variation, c.1134+11G>A, in the SLC52A1 gene encoding RFVT1. This variation creates a binding site for the splice inhibitory hnRNP A1 protein and causes exon 4 skipping. Riboflavin deficiency and maternal malnutrition during pregnancy might have been the determining factor in the outcome of this case.
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http://dx.doi.org/10.1016/j.ymgme.2017.10.014DOI Listing
December 2017

Modeling open nanophotonic systems using the Fourier modal method: generalization to 3D Cartesian coordinates.

J Opt Soc Am A Opt Image Sci Vis 2017 Sep;34(9):1632-1641

Recently, an open geometry Fourier modal method based on a new combination of an open boundary condition and a non-uniform k-space discretization was introduced for rotationally symmetric structures, providing a more efficient approach for modeling nanowires and micropillar cavities [J. Opt. Soc. Am. A33, 1298 (2016)JOAOD61084-752910.1364/JOSAA.33.001298]. Here, we generalize the approach to three-dimensional (3D) Cartesian coordinates, allowing for the modeling of rectangular geometries in open space. The open boundary condition is a consequence of having an infinite computational domain described using basis functions that expand the whole space. The strength of the method lies in discretizing the Fourier integrals using a non-uniform circular "dartboard" sampling of the Fourier k space. We show that our sampling technique leads to a more accurate description of the continuum of the radiation modes that leak out from the structure. We also compare our approach to conventional discretization with direct and inverse factorization rules commonly used in established Fourier modal methods. We apply our method to a variety of optical waveguide structures and demonstrate that the method leads to a significantly improved convergence, enabling more accurate and efficient modeling of open 3D nanophotonic structures.
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http://dx.doi.org/10.1364/JOSAA.34.001632DOI Listing
September 2017

Fasting induces prominent proteomic changes in liver in very long chain Acyl-CoA dehydrogenase deficient mice.

Biochem Biophys Rep 2016 Dec 17;8:333-339. Epub 2016 Sep 17.

Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, USA.

Very long chain acyl-CoA dehydrogenase (VLCAD) deficiency (VLCADD) is a clinically heterogeneous disorder of mitochondrial fatty acid β-oxidation usually identified through newborn screening. Genotype-phenotype correlations have been defined, but considerable clinical heterogeneity still exists. Symptoms are often induced by physiological stress such as fasting or intercurrent illness, setting it as an important example of environmental effects altering clinical course in an individual with a genetic disease. However, neither the cellular changes that predispose to this phenomenon nor the alterations it induces are well characterized. We examined the effects of fasting in a knockout mouse model to explore changes in global mitochondria protein profiles in liver and to investigate the physiologically relevant changes that lead to the clinical presentations. An isobaric tags for relative and absolute quantification (iTRAQ) labeling approach was employed to examine mitochondrial proteome changes in VLCAD deficient compared to wild type mice in the fed and fasted states. We identified numerous proteomic changes associated with the gene defect and fasting within relevant metabolic pathways. Few changes induced by fasting were shared between the VLCAD deficient and wild type mice, with more alterations found in the deficient mice on fasting. Particularly, fasting in the deficient mice could reverse the protective response in oxidative phosphorylation pathway seen in wild type animals. In addition, we found that changes in chaperone proteins including heat shock protein 60 (HSP60) and 10 (HSP10) during fasting differed between the two genotypes, highlighting the importance of these proteins in VLCAD deficiency. Finally, the effects on the liver proteome imposed by changes in fasted VLCAD deficient mice indicates that this environmental factor may be an inducer of both cellular and physiological changes.
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http://dx.doi.org/10.1016/j.bbrep.2016.08.014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5613767PMC
December 2016

Ketone Body Acetoacetate Buffers Methylglyoxal via a Non-enzymatic Conversion during Diabetic and Dietary Ketosis.

Cell Chem Biol 2017 Aug;24(8):935-943.e7

Department of Forensic Medicine, Aarhus University, Aarhus 8200, Denmark. Electronic address:

The α-oxoaldehyde methylglyoxal is a ubiquitous and highly reactive metabolite known to be involved in aging- and diabetes-related diseases. If not detoxified by the endogenous glyoxalase system, it exerts its detrimental effects primarily by reacting with biopolymers such as DNA and proteins. We now demonstrate that during ketosis, another metabolic route is operative via direct non-enzymatic aldol reaction between methylglyoxal and the ketone body acetoacetate, leading to 3-hydroxyhexane-2,5-dione. This novel metabolite is present at a concentration of 10%-20% of the methylglyoxal level in the blood of insulin-starved patients. By employing a metabolite-alkyne-tagging strategy it is clarified that 3-hydroxyhexane-2,5-dione is further metabolized to non-glycating species in human blood. The discovery represents a new direction within non-enzymatic metabolism and within the use of alkyne-tagging for metabolism studies and it revitalizes acetoacetate as a competent endogenous carbon nucleophile.
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http://dx.doi.org/10.1016/j.chembiol.2017.07.012DOI Listing
August 2017

Fluxomic evidence for impaired contribution of short-chain acyl-CoA dehydrogenase to mitochondrial palmitate β-oxidation in symptomatic patients with ACADS gene susceptibility variants.

Clin Chim Acta 2017 Aug 19;471:101-106. Epub 2017 May 19.

Department of Biochemistry and Molecular Biology, Laboratory of Hormonology, Metabolism-Nutrition & Oncology (HMNO), Center of Biology and Pathology (CBP) Pierre-Marie Degand, CHRU Lille, France; Univ. Lille, EA 7364 - RADEME - Maladies RAres du Développement et du Métabolisme: du phénotype au génotype et à la Fonction, Lille, France; Inserm, Lille, France. Electronic address:

Background: Despite ACADS (acyl-CoA dehydrogenase, short-chain) gene susceptibility variants (c.511C>T and c.625G>A) are considered to be non-pathogenic, encoded proteins are known to exhibit altered kinetics. Whether or not, they might affect overall fatty acid β-oxidation still remains, however, unclear.

Methods: De novo biosynthesis of acylcarnitines by whole blood samples incubated with deuterated palmitate (16-H,15-H-palmitate) is suitable as a fluxomic exploration to distinguish between normal and disrupted β-oxidation, abnormal profiles and ratios of acylcarnitines with different chain-lengths being indicative of the site for enzymatic blockade. Determinations in 301 control subjects of ratios between deuterated butyrylcarnitine and sum of deuterated C2 to C14 acylcarnitines served here as reference values to state specifically functional SCAD impairment in patients addressed for clinical and/or biological suspicion of a β-oxidation disorder.

Results: Functional SCAD impairment was found in 39 patients. The 27 patients accepting subsequent gene studies were all positive for ACADS mutations. Twenty-six of 27 patients were positive for c.625G>A variant. Twenty-three of 27 patients harbored susceptibility variants as sole ACADS alterations (18 homozygous and 3 heterozygous for c.625G>A, 2 compound heterozygous for c.625G>A/c.511C>T).

Conclusion: Our present fluxomic assessment of SCAD suggests a link between ACADS susceptibility variants and abnormal β-oxidation consistent with known altered kinetics of these variants.
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http://dx.doi.org/10.1016/j.cca.2017.05.026DOI Listing
August 2017

Short-chain acyl-CoA dehydrogenase deficiency: from gene to cell pathology and possible disease mechanisms.

J Inherit Metab Dis 2017 Sep 17;40(5):641-655. Epub 2017 May 17.

Research Unit for Molecular Medicine, Department of Clinical Medicine, Aarhus University Hospital and Faculty of Health, Aarhus University, Palle Juul-Jensens Boulevard 99, Aarhus N, 8200, Denmark.

Short-chain acyl-CoA dehydrogenase deficiency (SCADD) is an inherited disorder of mitochondrial fatty acid oxidation that is characterized by the presence of increased butyrylcarnitine and ethylmalonic acid (EMA) concentrations in plasma and urine. Individuals with symptomatic SCADD may show relatively severe phenotype, while the majority of those who are diagnosed through newborn screening by tandem mass spectrometry may remain asymptomatic. As such, the associated clinical symptoms are very diverse, ranging from severe metabolic or neuromuscular disabilities to asymptomatic. Molecular analysis of affected individuals has identified rare gene variants along with two common gene variants, c.511C > T and c.625G > A. In vitro studies have demonstrated that the common variants as well as the great majority of rare variants, which are missense variants, impair folding, that may lead to toxic accumulation of the encoded protein, and/or metabolites, and initiate excessive production of ROS and chronic oxidative stress. It has been suggested that this cell toxicity in combination with yet unknown factors can trigger disease development. This association and the full implications of SCADD are not commonly appreciated. Accordingly, there is a worldwide discussion of the relationship of clinical manifestation to SCADD, and whether SCAD gene variants are disease associated at all. Therefore, SCADD is not part of the newborn screening programs in most countries, and consequently many patients with SCAD gene variants do not get a diagnosis and the possibilities to be followed up during development.
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http://dx.doi.org/10.1007/s10545-017-0047-1DOI Listing
September 2017

The Novel Ser18del AVP Variant Causes Inherited Neurohypophyseal Diabetes Insipidus by Mechanisms Shared with Other Signal Peptide Variants.

Neuroendocrinology 2018 12;106(2):167-186. Epub 2017 May 12.

Background/aim: Variability in the severity and age at onset of autosomal dominant familial neurohypophyseal diabetes insipidus (adFNDI) may be associated with certain types of variants in the arginine vasopressin (AVP) gene. In this study, we aimed to describe a large family with an apparent predominant female occurrence of polyuria and polydipsia and to determine the underlying cause.

Methods: The family members reported their family demography and symptoms. Two subjects were diagnosed by fluid deprivation and dDAVP challenge tests. Eight subjects were tested genetically. The identified variant along with 3 previously identified variants in the AVP gene were investigated by heterologous expression in a human neuronal cell line (SH-SY5Y).

Results: Both subjects investigated clinically had a partial neurohypophyseal diabetes insipidus phenotype. A g.276_278delTCC variant in the AVP gene causing a Ser18del deletion in the signal peptide (SP) of the AVP preprohormone was perfectly co-segregating with the disease. When expressed in SH-SY5Y cells, the Ser18del variant along with 3 other SP variants (g.227G>A, Ser17Phe, and Ala19Thr) resulted in reduced AVP mRNA, impaired AVP secretion, and partial AVP prohormone degradation and retention in the endoplasmic reticulum. Impaired SP cleavage was demonstrated directly in cells expressing the Ser18del, g.227G>A, and Ala19Thr variants, using state-of-the-art mass spectrometry.

Conclusion: Variants affecting the SP of the AVP preprohormone cause adFNDI with variable phenotypes by a mechanism that may involve impaired SP cleavage combined with effects at the mRNA, protein, and cellular level.
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http://dx.doi.org/10.1159/000477246DOI Listing
January 2019

Induced pluripotent stem cells derived from a patient with autosomal dominant familial neurohypophyseal diabetes insipidus caused by a variant in the AVP gene.

Stem Cell Res 2017 03 24;19:37-42. Epub 2016 Dec 24.

Department of Biomedicine, Aarhus University, Bartholins Allé 6, 8000 Aarhus C, Denmark.

Autosomal dominant familial neurohypophyseal diabetes insipidus (adFNDI) is caused by variants in the arginine vasopressin (AVP) gene. Here we report the generation of induced pluripotent stem cells (iPSCs) from a 42-year-old man carrying an adFNDI causing variant in exon 1 of the AVP gene using lentivirus-mediated nuclear reprogramming. The iPSCs carried the expected variant in the AVP gene. Furthermore, the iPSCs expressed pluripotency markers; displayed in vitro differentiation potential to the three germ layers and had a normal karyotype consistent with the original fibroblasts. This iPSC line is useful in future studies focusing on the pathogenesis of adFNDI.
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http://dx.doi.org/10.1016/j.scr.2016.12.021DOI Listing
March 2017

Linking telomere loss and mitochondrial dysfunction in chronic disease.

Front Biosci (Landmark Ed) 2017 01 1;22:117-127. Epub 2017 Jan 1.

Research Unit for Molecular Medicine, Department for Clinical Medicine, Aarhus University and Aarhus University Hospital. Palle Juul-Jensens Boulevard 39, 8200 Aarhus N, Denmark.

Telomeres and mitochondria are known to deteriorate over time. Telomere shortening is associated with aging, early senescence, and premature cell death. Mitochondrial dysfunction produces indiscriminate amounts of reactive oxygen species that may lead to oxidative damage to cellular constituents, including telomeric DNA, causing telomere shortening. In fact, primary mitochondrial dysfunction (for example respiratory chain disorders) and secondary mitochondrial dysfunction (such as metabolic diseases, neurodegenerative diseases, cardiovascular diseases, and mood disorders, among others) have been shown to have shorter telomeres than healthy individuals. Drawing a mechanistic connection between telomere function and mitochondria biology will provide a broader perspective for understanding the pathophysiology of diseases and their relation to the aging process, and may provide opportunities for new possible treatments.
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http://dx.doi.org/10.2741/4475DOI Listing
January 2017

Mitochondrial Spare Respiratory Capacity Is Negatively Correlated with Nuclear Reprogramming Efficiency.

Stem Cells Dev 2017 02 28;26(3):166-176. Epub 2016 Nov 28.

1 Department of Biomedicine, Aarhus University , Aarhus C, Denmark .

Nuclear reprogramming efficiency has been shown to be highly variable among different types of somatic cells and different individuals, yet the underlying mechanism remains largely unknown. Several studies have shown that reprogramming of fibroblasts into induced pluripotent stem cells (iPSCs) requires remodeling of mitochondria and a metabolic shift from an oxidative state to a more glycolytic state. In this study, we evaluated the nuclear reprogramming efficiency in relation to mitochondrial bioenergetic parameters of fibroblasts from seven different human individuals. Using the Seahorse extracellular energy flux analyzer, we measured oxygen consumption rate (OCR) profiles of the cells, along with their nuclear reprogramming efficiency into iPSCs. Our results showed that fibroblasts with the lowest mitochondrial spare respiratory capacity (SRC) had the highest nuclear reprogramming efficiency, opposed to fibroblasts with the highest mitochondrial SRC, which showed lowest reprogramming efficiency. Furthermore, we found that targeted fluorescent tagging of endogenous genes (MYH6 and COL2A1) by CRISPR/Cas9-mediated homologous recombination was accompanied by an increase in the SRC level of the modified fibroblasts and impaired reprogramming efficiency. Our findings indicate a negative correlation between high mitochondrial SRC in somatic cells and low reprogramming efficiencies. This type of analysis potentially allows screening and predicting reprogramming efficiency before reprogramming, and further suggests that nuclear reprogramming might be improved by approaches that modulate the SRC.
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http://dx.doi.org/10.1089/scd.2016.0162DOI Listing
February 2017
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