Journal of Inherited Metabolic Disease (2018) 41 (Suppl 1):S37–S219 https://doi.org/10.1007/s10545-018-0233-9 ABSTRACTS Oral Presentations PARALLEL SESSION 1A: Clycosylation and cardohydrate disorders O-002 Link between glycemia and hyperlipidemia in Glycogen Storage O-001 Disease type Ia Hoogerland J A1, Hijmans B S1, Peeks F1, Kooijman S3, 4, Bos T2, Fertility in classical galactosaemia, N-glycan, hormonal and inflam- Bleeker A1, Van Dijk T H2, Wolters H1, Havinga R1,PronkACM3, 4, matory gene expression interactions Rensen P C N3, 4,MithieuxG5, 6, Rajas F5, 6, Kuipers F1, 2,DerksTGJ1, Reijngoud D1,OosterveerMH1 Colhoun H O1,Rubio-GozalboME2,BoschAM3, Knerr I4,DawsonC5, Brady J J6,GalliganM8,StepienKM9, O'Flaherty R O7,MossC10, 1Dep Pediatrics, CLDM, Univ of Groningen, Groningen, Barker P11, Fitzgibbon M C6, Doran P8,TreacyEP1, 4, 9 Netherlands, 2Lab Med, CLDM, Univ of Groningen, Groningen, Netherlands, 3Dep of Med, Div of Endocrinology, LUMC, Leiden, 1Dept Paediatrics, Trinity College Dublin, Dublin, Ireland, 2Dept Paeds and Netherlands, 4Einthoven Lab Exp Vasc Med, LUMC, Leiden, Clin Genetics, UMC, Maastricht, Netherlands, 3Dept Paediatrics, AMC, Netherlands, 5Institut Nat Sante et Recherche Med, Lyon, Amsterdam, Netherlands, 4NCIMD, TSCUH, Dublin, Ireland, 5Dept France, 6Univ Lyon 1, Villeurbanne, France Endocrinology, NHS Foundation Trust, Birmingham, United Kingdom, 6Dept Clin Biochem, MMUH, Dublin, Ireland, 7NIBRT Glycoscience, Background: Glycogen Storage Disease type Ia (GSD Ia) is an NIBRT, Dublin, Ireland, 8UCDCRC,UCD,Dublin,Ireland,9NCIMD, inborn error of glucose metabolism characterized by fasting hypo- MMUH, Dublin, Ireland, 10Conway Institute, UCD, Dublin, Ireland, glycemia, hyperlipidemia and fatty liver disease. We have previ- 11CBAL, NHS Foundation, Cambridge, United Kingdom ously reported considerable heterogeneity in circulating triglycer- ide levels between individual GSD Ia patients, a phenomenon that Background: Classical Galactosaemia (CG) is caused by deficiency of is poorly understood. Interestingly, hypertriglyceridemia in GSD galactose-1-phosphate uridylyltransferase (GALT). Long-term complica- Ia patients appears to be related to glycemic control, but the tions persist in treated patients despite dietary galactose restriction with mechanisms that link glycemia to hyperlipidemia remain significant variations in outcomes suggesting epigenetic glycosylation in- unresolved. fluences. Primary Ovarian Insufficiency (POI) is a very significant compli- Methods: We performed a systematic analysis of whole-body tri- cation affecting females with follicular depletion noted in early life. glyceride metabolism in fed (normoglycemic) and fasted Methods: We studied specific glycan synthesis, leptin system and inflam- (hypoglycemic) hepatocyte-specific glucose-6-phosphatase defi- matory gene expression in white blood cells as potential biomarkers of cient (L-G6pc−/−) mice, a liver-specific model for GSD Ia. infertility in 54 CG adults (27 females and 27 males) (age range 17–51 y) Results: L-G6pc−/− mice exhibited fatty liver disease as compared on a galactose-restricted diet in a multi-site Irish and Dutch study. Gene to wildtype controls under both conditions, but the increase in expression profiles were tested for correlation with a serum Ultra hepatic triglyceride content was highest in fasted L-G6pc−/− mice. Performance Liquid Chromatography (UPLC)-Immunoglobulin (IgG)- Hepatic de novo fatty acid synthesis substantially contributed to N-glycan galactose incorporation assay and endocrine measurements. hepatic triglyceride accumulation in fed L-G6pc−/− mice. In con- Results: 25 females (93% of subjects) had clinical and biochemical trast, in fasted L-G6pc−/− mice, de novo lipogenesis was of less evidence of POI. As expected, the female patients, the majority of importance and increased liver fat was paralleled by enhanced whom were on hormone replacement therapy, and the controls of adipose tissue lipolysis. Plasma lipoprotein analysis showed that both genders showed a positive correlation between log leptin and VLDL-triglyceride and cholesterol levels were increased in L- BMI but this correlation was not apparent in CG male subjects. The G6pc−/− mice under both conditions, but that VLDL levels were key glycan synthesis modifier genes MGAT3 and FUT8 which influ- significantly higher in fasted versus fed L-G6pc−/− mice. VLDL ence glycan chain bisecting and fucosylation and subsequently cell production rates were doubled under both conditions in L-G6pc−/− signalling and adhesion were significantly upregulated (p< 0.01 and mice, while VLDL catabolism was inhibited only in hypoglycemic p< 0.05) as was the glycan synthesis gene ALG9 (p< 0.01). Both the L-G6pc−/− mice. LEP and LEPR genes were upregulated (p< 0.01). The inflammatory Discussion: Our data show that hypoglycemia in GSD Ia pro- genes ANXA1 and ICAM1 and the apoptosis gene SEPT4 were also motes adipose tissue lipolysis and arrests VLDL catabolism. upregulated, (p< 0.01). These mechanisms likely also contribute to aggravation of Discussion: These findings further elaborate on the systemic glycosyla- fatty liver and hyperlipidemia in patients with poorly con- tion and cell signalling abnormalities evident in CG which likely influ- trolled glycemia and may contribute to clinical heterogeneity ence the pathophysiology of POI. in GSD Ia.v S38 J Inherit Metab Dis (2018) 41 (Suppl 1):S37–S219 O-003 Tracing the fate of galactose in PGM1-CDG mannosidase gene MAN2B2, affecting lysosomal integrity and the glyco- sylation pathway. Methods: Exome sequencing was employed to identify disease-causing Radenkovic S R1, 2, 3,BirdMJB1, 4,WongSYW5,VerheijenJV6, mutations in a patient born to consanguineous parents. The patient pre- Witters P W7, Altassan R A9, Vermeersch P V4, 8,CassimanDC1, 7, sented with profound immune deficiency, strabismus, dysmorphisms, ab- Ghesquiere B G2, 3, Morava E M6, 7 normal chest configuration, and a history of stroke. Pathogenic effects of the mutation were investigated in vitro by mass spectrometry, MALDI- 1Lab Hepato, Dep CHROMETA, KU Leuven, Leuven, Belgium, TOF free glycan profile analysis and Western blotting in immortalized 2Vesalius Research Center, VIB, Leuven, Belgium, 3Dep Onc, KU lymphocytes and fibroblasts. Leuven, Leuven, Belgium, 4Clin Dep Lab Med, Univ Hosp Leuven, Results: Exome sequencing identified a predicted pathogenic biallelic Leuven, Belgium, 5Hayward Gen Cent, Tulane Univ School Med, New mutation p.D38N in MAN2B2. Pedigree analysis confirmed segregation Orleans, Louisiana, United States, 6Cent Ind Med, Dep Clin Genom, of the homozygous mutation with disease. Free glycan profiling showed Mayo Clin, Rochester, Minnesota, United States, 7Metab Cent, Dep accumulation of GlcNAc2Man2 with terminal 1,6 Mannose motif in Ped, Univ Hosp Leuven, Leuven, Belgium, 8Dep Cardiovasc Sciences, patient cells, indicative of a deficiency of 1,6 mannosidase KU Leuven, Leuven, Belgium, 9Med Gen Dep, Montr Child Hosp, activity.Glycosylation analysis showed increased expression of McGill Un, Montreal, Canada hypoglycosylated ICAM-1, and decreased levels of glycosylated ICAM-1 protein in patient immune cells compared to control. Background: Phosphoglucomutase-1 (PGM1) mutations have recently Glycosylated LAMP2 protein was found decreased in patient cells com- been reclassified as a congenital disorder of glycosylation (PGM1- paredtocontrol. CDG; MIM 612941). PGM1 interconverts glucose-1-P to glucose-6-P, Discussion: Our data suggest the MAN2B2 gene as a novel autosomal and is a key enzyme sitting at the crossroads of glycogenesis, glycogen- recessive disease gene leading to congenital disorder of glycosylation and olysis, glycolysis, nucleotide sugar biosynthesis, the hexosamine biosyn- affecting lysosomal trafficking. Disruption of MAN2B2 enzymatic activ- thesis pathway, and the pentose phosphate pathway (PPP). PGM1-CDG ity and subsequent impairment of α1,6-mannosidosis leads to abnormal is also one of the few multisystem CDGs with a largely effective treat- mannosylation of glycans. Bone-marrow transplantation restores the met- ment – galactose, which has been shown in open label trials to be both abolic defect. safe and reduce symptoms in patients. How galactose benefits these pa- tients though is not understood. Methods: To probe the biochemical basis to galactose treatment, we O-005 employed tracer based metabolomics, a technique capable of tracking the activity of multiple pathways simultaneously. Control and PGM1- CDG fibroblasts were cultured with the tagged sugars (13C) glucose, with Ngly1 pathogenic variant causing deglycosylation defect, masquerad- and without galactose. The 13C tracer is then incorporated into connected ing as mitochondrial hepatocerebral cytopathy pathways after which, the cells were harvested to enable detection of metabolites by the mass-spectrometry. Mandel H1, 5,KalfonL1, Tobar A2, 3, Zohar Y4, 5,BarisHN5, 6,Falik Results: Our results suggest that the mechanism by which galactose ben- Zaccai T1, 7,IancuTC8 efits these patients is by restoring depleted levels of the activated sugars UDP-glucose and -galactose, thus restarting stalled glycosylation in these 1Hum Genet Galilee Med Ctr, Nahria, Israel, 2Pathology Schneider Med patients. Further, our data indicates that glucose is utilised differently in Ctr, Petach tikva, Israel, 3Sackler Fac Med Tel Aviv Univ, Tel Aviv, Israel, the presence of galactose. 4Pathoogy Rambam Health care campus, Haifa, Israel, 5Rappaport Fac Discussion: Our results suggest there