A simple blood test expedites the diagnosis of glucose transporter type 1 deficiency syndrome.

Glucose transporter type 1 (GLUT1) deficiency syndrome (GLUT1-DS) leads to a wide range of neurological symptoms. Ketogenic diets are very efficient to control epilepsy and movement disorders. We tested a novel simple and rapid blood test in 30 patients with GLUT1-DS with predominant movement disorders, 18 patients with movement disorders attributed to other genetic defects, and 346 healthy controls. We detected significantly reduced GLUT1 expression only on red blood cells from patients with GLUT1-DS (23 patients; 78%), including patients with inconclusive genetic analysis. This test opens perspectives for the screening of GLUT1-DS in children and adults with cognitive impairment, movement disorder, or epilepsy. Ann Neurol 2017;82:133-138.

A double-blind, placebo-controlled trial of triheptanoin in adult polyglucosan body disease and open-label, long-term outcome.

BACKGROUND: Adult polyglucosan body disease (APBD) is a progressive neurometabolic disorder caused by a deficiency of glycogen branching enzyme. We tested the efficacy of triheptanoin as a therapy for patients with APBD based on the hypothesis that decreased glycogen degradation leads to brain energy deficit. METHODS AND RESULTS: This was a two-site, randomized crossover trial of 23 patients (age 35-73 years; 63% men) who received triheptanoin or vegetable oil as placebo. The trial took place over 1 year and was followed by a 4-year open-label phase. Generalized linear mixed models were used to analyze this study. At baseline, using the 6-min walk test, patients could walk a mean of 389 ± 164 m (range 95-672; n = 19), highlighting the great clinical heterogeneity of our cohort. The overall mean difference between patients on triheptanoin versus placebo was 6 m; 95% confidence interval (CI) -11 to 22; p = 0.50. Motion capture gait analysis, gait quality, and stair climbing showed no consistent direction of change. All secondary endpoints were statistically nonsignificant after false discovery rate adjustment. Triheptanoin was safe and generally well tolerated. During the open-label phase of the study, the most affected patients at baseline kept deteriorating while mildly disabled patients remained notably stable up to 4 years. CONCLUSIONS: We cannot conclude that triheptanoin was effective in the treatment of APBD over a 6-month period, but we found it had a good safety profile. This study also emphasizes the difficulty of conducting trials in very rare diseases presenting with a wide clinical heterogeneity. ClinicalTrials.gov Identifier: NCT00947960.

Molecular screening of a large cohort of Moroccan patients with congenital hypopituitarism.

BACKGROUND/OBJECTIVES: Congenital hypopituitarism is a rare disease which, for most patients, has no identified molecular cause. We aimed to document the molecular basis of growth retardation in a Moroccan cohort. DESIGN/PATIENTS: 80 index cases [54 with isolated growth hormone deficiency (IGHD), 26 with combined pituitary hormone deficiency (CPHD)] were screened for molecular defects in GH1 (including LCR-GH1), GHRHR, GHSR, GHRH, PROP1, POU1F1, HESX1, LHX3, LHX4 and SOX3. RESULTS: Five different deleterious mutations were identified in 14 patients from eight families. In the IGHD group, three genes were found to be involved: GH1, GHRHR and GHSR. In the CPHD group, PROP1 was the only mutated gene. In addition, two heterozygous variations whose deleterious effect remains to be demonstrated were identified (in GH1 and LHX4), and two polymorphisms (missense variations) were detected (in LHX3 and in GHSR). The prevalence of mutations in this Moroccan GHD cohort was 10% (8/80), 11·1% (6/54) in the IGHD group and 7·7% (2/26) in the CPHD group. CONCLUSION: This is the first molecular screening of congenital GHD in a Moroccan population and, like other studies, mutations were preferentially identified in familial cases (75%); mutations in genes such as POU1F1, HESX1, SOX3, LHX3 and LHX4 are extremely rare. The p.R73C PROP1 mutation was the most frequent mutation in CPHD; this should be the first one to screen in this population. Our results should contribute to a better diagnosis and management of this heterogeneous disease condition.

Prospective Multicenter Validation of a Simple Blood Test for the Diagnosis of Glut1 Deficiency Syndrome.

BACKGROUND AND OBJECTIVE: GLUT1 deficiency syndrome (Glut1DS) is a treatable neurometabolic disease that causes a wide range of neurologic symptoms in children and adults. However, its diagnosis relies on an invasive test, that is, a lumbar puncture (LP) to measure glycorrhachia, and sometimes complex molecular analyses of the SLC2A1 gene. This procedure limits the number of patients able to receive the standard of care. We wished to validate the diagnostic performance of METAglut1, a simple blood test that quantifies GLUT1 on the erythrocyte surface. METHODS: We performed a multicenter validation study in France, involving 33 centers. We studied 2 patient cohorts: a prospective cohort consisting of patients with a clinical suspicion of Glut1DS explored through the reference strategy, that is, LP and analyses of the SLC2A1 gene, and a retrospective cohort that included patients previously diagnosed with Glut1DS. All patients were blind-tested with METAglut1. RESULTS: We analyzed 428 patients in the prospective cohort, including 15 patients newly diagnosed with Glut1DS, and 67 patients in the retrospective cohort. METAglut1 was 80% sensitive and >99% specific for the diagnosis of Glut1DS. Concordance analyses showed a substantial agreement between METAglut1 and glycorrhachia. In the prospective cohort, the positive predictive value of METAglut1 was slightly higher than that of glycorrhachia. METAglut1 succeeded to identify patients with Glut1DS with SCL2A1 mosaicism and variants of unknown significance. DISCUSSION: METAglut1 is an easily performed, robust, and noninvasive diagnostic test for the diagnosis of Glut1DS, which allows wide screening of children and adults, including those with atypical forms of this treatable condition. CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that a positive METAglut1 test accurately distinguishes patients with suspected GLUT1 deficiency syndrome from other neurologic syndromes as compared with invasive and genetic testing.

Multiparametric characterization of white matter alterations in early stage Huntington disease.

Huntington's disease (HD) is a monogenic, fully penetrant neurodegenerative disorder. Widespread white matter damage affects the brain of patients with HD at very early stages of the disease. Fixel-based analysis (FBA) is a novel method to investigate the contribution of individual crossing fibers to the white matter damage and to detect possible alterations in both fiber density and fiber-bundle morphology. Diffusion-weighted magnetic resonance spectroscopy (DW-MRS), on the other hand, quantifies the motion of brain metabolites in vivo, thus enabling the investigation of microstructural alteration of specific cell populations. The aim of this study was to identify novel specific microstructural imaging markers of white matter degeneration in HD, by combining FBA and DW-MRS. Twenty patients at an early stage of HD and 20 healthy controls were recruited in a monocentric study. Using diffusion imaging we observed alterations to the brain microstructure and their morphology in patients with HD. Furthermore, FBA revealed specific fiber populations that were affected by the disease. Moreover, the mean diffusivity of the intra-axonal metabolite N-acetylaspartate, co-measured with N-acetylaspartylglutamate (tNAA), was significantly reduced in the corpus callosum of patients compared to controls. FBA and DW-MRS of tNAA provided more specific information about the biological mechanisms underlying HD and showed promise for early investigation of white matter degeneration in HD.

Multiparametric in vivo analyses of the brain and spine identify structural and metabolic biomarkers in men with adrenomyeloneuropathy.

OBJECTIVE: Progressive myelopathy causes severe handicap in men with adrenomyeloneuropathy (AMN), an X-linked disorder due to ABCD1 pathogenic variants. At present, treatments are symptomatic but disease-modifying therapies are under evaluation. Given the small effect size of clinical scales in AMN, biomarkers with higher effect size are needed. Here we used high-resolution magnetic resonance techniques to identify non-invasive in vivo biomarkers of the brain and spine with high effect sizes. METHODS: We performed a multiparametric imaging and spectroscopy study in 23 male patients with AMN (age: 44 ± 11) and 23 male controls (age: 43 ± 11) of similar age and body-mass index. We combined (i) macrostructural analyses of the spine, using cross-sectional area (CSA) and magnetization transfer ratio (MTR), (ii) microstructural analyses of the spine and the brain, using diffusion tensor and the newly developed fixel-based analysis, and (iii) advanced metabolic analyses of the spine using metabolite cycling coupled to a semi-LASER sequences. RESULTS: Macrostructural alterations (decrease in CSA and MTR) were observed in patients at all spinal cord levels studied (C1-T2 for CSA and C1-C5 for MTR) (p < 0.001). Microstructural alterations were observed in the spine and brain on diffusion tensor and fixel-based metrics though the latter showed higher effect sizes. Metabolic alterations were observed in patients as a decreased total N-acetylaspartate/myo-inositol ratio (p < 0.001). Overall, MTR showed the highest effect size. CONCLUSION: This cross-sectional study supports the use of multiparametric techniques that elucidate the structural, microstructural and metabolic alterations in AMN. These outcome measures should be tested longitudinally and in clinical trials.

Loss of constitutive activity of the growth hormone secretagogue receptor in familial short stature.

The growth hormone (GH) secretagogue receptor (GHSR) was cloned as the target of a family of synthetic molecules endowed with GH release properties. As shown recently through in vitro means, this receptor displays a constitutive activity whose clinical relevance is unknown. Although pharmacological studies have demonstrated that its endogenous ligand--ghrelin--stimulates, through the GHSR, GH secretion and appetite, the physiological importance of the GHSR-dependent pathways remains an open question that gives rise to much controversy. We report the identification of a GHSR missense mutation that segregates with short stature within 2 unrelated families. This mutation, which results in decreased cell-surface expression of the receptor, selectively impairs the constitutive activity of the GHSR, while preserving its ability to respond to ghrelin. This first description, to our knowledge, of a functionally significant GHSR mutation, which unveils the critical importance of the GHSR-associated constitutive activity, discloses an unusual pathogenic mechanism of growth failure in humans.

No effect of triheptanoin on exercise performance in McArdle disease.

OBJECTIVE: To study if treatment with triheptanoin, a 7-carbon triglyceride, improves exercise tolerance in patients with McArdle disease. McArdle patients have a complete block in glycogenolysis and glycogen-dependent expansion of tricarboxylic acid cycle (TCA), which may restrict fat oxidation. We hypothesized that triheptanoin metabolism generates substrates for the TCA, which potentially boosts fat oxidation and improves exercise tolerance in McArdle disease. METHODS: Double-blind, placebo-controlled, crossover study in patients with McArdle disease completing two treatment periods of 14 days each with a triheptanoin or placebo diet (1 g/kg/day). Primary outcome was change in mean heart rate during 20 min submaximal exercise on a cycle ergometer. Secondary outcomes were change in peak workload and oxygen uptake along with changes in blood metabolites and respiratory quotients. RESULTS: Nineteen of 22 patients completed the trial. Malate levels rose on triheptanoin treatment versus placebo (8.0 ± SD2.3 vs. 5.5 ± SD1.8 µmol/L, P < 0.001), but dropped from rest to exercise (P < 0.001). There was no difference in exercise heart rates between triheptanoin (120 ± SD16 bpm) and placebo (121 ± SD16 bpm) treatments. Compared with placebo, triheptanoin did not change the submaximal respiratory quotient (0.82 ± SD0.05 vs. 0.84 ± SD0.03), peak workload (105 ± SD38 vs. 102 ± SD31 Watts), or peak oxygen uptake (1938 ± SD499 vs. 1977 ± SD380 mL/min). INTERPRETATION: Despite increased resting plasma malate with triheptanoin, the increase was insufficient to generate a normal TCA turnover during exercise and the treatment has no effect on exercise capacity or oxidative metabolism in patients with McArdle disease.

Novel HESX1 mutations associated with a life-threatening neonatal phenotype, pituitary aplasia, but normally located posterior pituitary and no optic nerve abnormalities.

CONTEXT: Hesx1 is one of the earliest homeodomain transcription factors expressed during pituitary development. Very few HESX1 mutations have been identified in humans; although in those cases the disease phenotype shows considerable variability, all but one of the patients display an ectopic posterior pituitary and/or optic nerve abnormalities. OBJECTIVE: The objectives of the study were to describe the complex phenotype associated with the panhypopituitarism of two unrelated Italian patients who, at birth, presented with hypoglycemic seizures and respiratory distress complicated by shock, in a familial context of neonatal death in one family and spontaneous miscarriage in both families and to identify the molecular basis of this unusual syndrome. MAIN OUTCOME MEASURES: Magnetic resonance imaging of the pituitary region, study of HESX1 gene and transcripts, and assessment of the ability of mutated HESX1 proteins to repress transcription were measured. RESULTS: Magnetic resonance imaging examination showed an anterior pituitary aplasia in a flat sella turcica and a normally located posterior pituitary in both patients. A constellation of extrapituitary developmental defects were found in the two patients, but without any optic nerve abnormalities. Sequencing of HESX1 exons and their flanking intronic regions revealed two different homozygous mutations. A frameshift (c.449_450delAC) was identified in one case, whereas the other patient carried a splice defect (c.357 + 2Tb > C) confirmed by the study of HESX1 transcripts. If translated, these mutations would lead to the synthesis of truncated proteins partly or entirely lacking the homeodomain, with no transcriptional repression, as shown by their inability to inhibit PROP1 activity. CONCLUSIONS: These observations reveal two novel HESX1 mutations in a so-far-undescribed disease phenotype characterized by a life-threatening neonatal condition associated with anterior pituitary aplasia, in the absence of ectopic posterior pituitary and optic nerve abnormalities, two features classically associated with HESX1 defects.

Alu-element insertion in the homeodomain of HESX1 and aplasia of the anterior pituitary.

The pathophysiology of combined pituitary hormone deficiency is just beginning to be elucidated. None of the genes known to be necessary for pituitary development has so far been involved in pituitary gland aplasia in humans. Among these, Hesx1/HESX1, which encodes a homeobox transcription factor, has been shown to be essential for normal forebrain development in mice, and HESX1 mutations in humans have been associated with various pituitary hormone deficiencies usually combined with optic nerve anomalies. Here we have investigated a consanguineous family in which two siblings displayed a complete absence of the anterior pituitary revealed by a deficit in all anterior pituitary hormones. One patient, who also has retinal coloboma, carries a HESX1 defect in the homozygous state: an Alu insertion in exon 3, a sequence that encodes the major part of the homeodomain. The Alu-containing HESX1 allele generates a major transcript lacking this exon, and a minor one in which exons 2 and 3 are skipped, predicting severely truncated proteins. This observation, which combines pituitary aplasia and retinal coloboma, further illustrates the heterogeneity of HESX1-associated disease phenotypes. Anterior pituitary aplasia is a new example of a human disease caused by a germline retrotransposition event involving an Alu sequence.

Symptomatic heterozygotes and prenatal diagnoses in a nonconsanguineous family with syndromic combined pituitary hormone deficiency resulting from two novel LHX3 mutations.

CONTEXT: Only 11 mutations have been reported in the transcription factor LHX3, known to be important for the development of the pituitary and motor neurons. All patients were homozygous, with various syndromic forms of combined pituitary hormone deficiency (CPHD), hampering to allocate, in these consanguineous patients, the respective contribution of LHX3 and additional genes to each symptom. OBJECTIVE: The aim of the study was to report the family history and the molecular basis of a nonconsanguineous patient with syndromic CPHD. PATIENT: The patient, who presented at birth with respiratory distress, had a syndromic CPHD, including severe scoliosis, and normal intelligence. His father and paternal grandmother displayed limited head rotation. RESULTS: Two new LHX3 defects were identified. The paternally inherited c.252-3C>G mutation, which disrupts an acceptor splice site, would lead to severely truncated proteins containing a single LIM domain, resembling LIM-only proteins. Coexpression studies revealed the dominant-negative effect of this LIM-only protein over the wild-type LHX3. The maternally inherited p.Cys118Tyr mutation results in partial loss of transcriptional activity and synergy with POU1F1. Given the severity of the patient's phenotype, two prenatal diagnoses were performed: the first led to pregnancy interruption, the second to the birth of a healthy boy. CONCLUSIONS: This study of the first nonconsanguineous patient with LHX3 mutations demonstrates the pleiotropic roles of LHX3 during development and its full involvement in the complex disease phenotype. Isolated limitation of head rotation may exist in heterozygous carriers and would result from a dominant-negative effect. These data allowed the first prenatal diagnoses of this severe condition to be performed.

Recessive isolated growth hormone deficiency and mutations in the ghrelin receptor.

CONTEXT: Both GH releasing- and orexigenic properties of the gut-to-brain hormone ghrelin are mediated by the GH secretagogue receptor (GHSR). Recently in several patients, a missense mutation (p.A204E) resulting in a complete loss of GHSR constitutive activity has been implicated in short stature with dominant transmission. OBJECTIVE: The objective of the study was to describe the phenotype associated with partial isolated GH deficiency of a young patient born to unrelated parents and identify the molecular basis of his disease. RESULTS: The growth delay (-3.0 sd) was associated with recurrent episodes of abdominal pain, vomiting, ketosis, hypoglycemia, and a low body mass index. GHSR sequencing revealed that the patient was compound heterozygous for two new defects: 1) an early occurring transition predicting a premature stop codon (c.6G>A, p.W2X) inherited from his unaffected father, therefore strongly arguing against haploinsufficiency as a disease mechanism, and 2) a missense mutation (c.709A>T, p.R237W) inherited from his healthy mother, involving an evolutionary invariant residue from the third intracellular loop. In vitro experiments showed that the p.R237W mutation would result in a partial loss of constitutive activity of the receptor, whereas both its ability to respond to ghrelin and its cell surface expression are preserved. CONCLUSION: These data, which describe the first case of recessive partial isolated GH deficiency due to GHSR mutations and emphasize the physiological importance of the GHSR in somatic growth, are discussed in light of the dominantly expressed p.A204E mutation.

Unusual phenotypic features in a patient with a novel splice mutation in the GHRHR gene.

Isolated growth hormone deficiency (IGHD) may be of genetic origin. One of the few genes involved in that condition encodes the growth hormone releasing hormone receptor (GHRHR) that, through its ligand (GHRH), plays a pivotal role in the GH synthesis and secretion by the pituitary. Our objective is to describe the phenotype of two siblings born to a consanguineous union presenting with short stature (IGHD) and Magnetic Resonance Imaging (MRI) abnormalities, and to identify the molecular basis of this condition. Our main outcome measures were clinical and endocrinological investigations, MRI of the pituitary region, study of the GHRHR gene sequence and transcripts. In both patients, the severe growth retardation (-5SD) was combined with anterior pituitary hypoplasia. In addition to these classical phenotypic features for IGHD, one of the patients had a Chiari I malformation, an arachnoid cyst, and a dysmorphic anterior pituitary. A homozygous sequence variation in the consensus donor splice site of intron 1 (IVS1 + 2T > G) of the GHRHR gene was identified in both patients. Using in vitro transcription assay, we showed that this mutation results in abnormal splicing of GHRHR transcripts. In this report, which broadens the phenotype associated with GHRHR defects, we discuss the possible role of the GHRHR in the proper development of extrapituitary structures, through a mechanism that could be direct or secondary to severe GH deficiency.