Exopolysaccharide β-(2,6)-levan-type fructans have a molecular-weight-dependent modulatory effect on Toll-like receptor signalling

SCOPE

Fructans are a group of dietary fibers which are known to have many beneficial effects including immune-modulating effects. A family of fructans are β-(2,6)-linked levan-type fructans that are known to serve as exopolysaccharides in the cell wall of many species of bacteria including commensal bacteria and probiotics. It is still largely unknown whether and how they can serve as immunomodulating molecules.

RESULTS

Microbial β-(2,6)-fructans were found to induce TLR-dependent activation of THP-1 cells, in a dose-dependent fashion. Low molecular weight (Mw), medium Mw and high Mw β-(2,6)-fructans activated both TLR2 and 4 in a dose- and molecular weight-dependent fashion. In addition, it was found that β-(2,6)-fructans were able to inhibit signalling of various TLRs with the strongest effect on TLR5 and 8, which were inhibited by all the β-(2,6)-fructans in a dose- and molecular weight-dependent fashion. The final effect of this activation and inhibition of TLRs on cytokine responses in human dendritic cells (DCs) was minor which may be explained by the counter-activating effects of the different β-(2,6)-linked levan-type fructans on inhibition of TLR signalling in the DCs.

CONCLUSION

A mechanism by which exopolysaccharide levan β-(2,6)-fructans can be immune-modulating is by impacting TLR signalling. This knowledge could lead to food in which exopolysaccharide levan β-(2,6)-fructans are added for preventing disorders where TLR-signalling is modulated.

Crystal type, chain length and polydispersity impact the resistant starch type 3 immunomodulatory capacity via Toll-like receptors

Food ingredients that can activate and improve immunological defense, against e.g., pathogens, have become a major field of research. Resistant starches (RSs) can resist enzymes in the upper gastrointestinal (GI) tract and induce health benefits. RS-3 physicochemical characteristics such as chain length (DP), A- or B-type crystal, and polydispersity index (PI) might be crucial for immunomodulation by activating human toll-like receptors (hTLRs). We hypothesize that crystal type, DP and PI, alone or in combination, impact the recognition of RS-3 preparations by hTLRs leading to different RS-3 immunomodulatory effects. We studied the activation of hTLR2, hTLR4, and hTLR5 by 0.5, 1 and 2 mg/mL of RS-3. We found strong activation of hTLR2-dependent NF-kB activation with PI <1.25, DP 18 as an A- or B-type crystal. At different doses, NF-kB activation was increased from 6.8 to 7.1 and 10-fold with A-type and 6.2 to 10.2 and 14.4-fold with B-type. This also resulted in higher cytokine production in monocytes. Molecular docking, using amylose-A and B, demonstrated that B-crystals bind hTLR2 promoting hTLR2-1 dimerization, supporting the stronger effects of B-type crystals. Immunomodulatory effects of RS-3 are predominantly hTLR2-dependent, and activation can be tailored by managing crystallinity, chain length, and PI.

In Silico Structural Protein Evaluation of the Phenylalanine Hydroxylase p.(Tyr77His) Variant Associated with Benign Hyperphenylalaninemia as Identified through Mexican Newborn Screening

Hyperphenylalaninemia (HPA), which includes phenylketonuria (PKU), is a genetic autosomal recessive disorder arising from a deficiency in the enzyme named phenylalanine hydroxylase (PAH). Affected patients can experience severe and irreversible neurological impairments when phenylalanine (Phe) blood concentration exceeds 360 μmol/L (6 mg/dL). Here, we describe a female HPA patient who was born in Mexico to Cuban non-consanguineous parents and identified by newborn screening, and who bears the previously unreported PAH NM_000277.3(PAH):c.[229T>C];[1222C>T] or p.[Tyr77His];[Arg408Trp] genotype. At diagnosis, the patient showed a Phe blood level of 321 μmol/L (5.3 mg/dL), indicative of mild HPA. Neither of the PAH variants found in this patient had been previously reported in the mutational PAH spectrum of the Mexican population. The c.229T>C or p.(Tyr77His) PAH variant was previously related to mild HPA in the Swedish population. Our in silico structural analysis and molecular docking showed that mutated His 77 residue is located in the allosteric site of PAH at the interface of the two monomers. The PDBsum in silico tool predicted that this variant would cause minimal structural disturbance of the protein interface in the presence of Phe at the allosteric site. Docking studies revealed that these structural changes might be attenuated by the allosteric effect of Phe. Given the classic PKU phenotype conditioned by the "Celtic" or c.[1222C>T] or p.(Arg408Trp) PAH variant, which is the second variant in this patient, we propose that p.(Tyr77His) has a hypomorphic feature that could explain her mild HPA phenotype. Our results show the importance of following up on cases detected by NBS and the value of genetic studies and in silico tools that aid in the establishment of correct therapeutic strategies.

β(2 → 1)-β(2 → 6) and β(2 → 1) fructans protect from impairment of intestinal tight junction's gene expression and attenuate human dendritic cell responses in a fructan-dependent fashion

β(2 → 1)-β(2 → 6) branched graminan-type fructans (GTFs) and β(2 → 1) linear fructans (ITFs) possess immunomodulatory properties and protect human intestinal barrier function, however the mechanisms underlying these effects are not well studied. Herein, GTFs and ITFs effects with different degree of polymerization (DP) values on tight junctions (TJs) genes CLDN-1, -2 and -3, CDH1, OCLN and TJP1 were studied in Caco-2 gut epithelial cells, under homeostatic and inflammatory conditions. Also, cytokine production in dendritic cells (DCs) was studied. Higher DP fructans decreased the expression of the pore forming CLDN-2. Higher DP GTFs enhanced CLDN-3, OCLN, and TJP-1. Fructans prevented mRNA dysregulation of CLDN-1, -2 and -3 induced by the barrier disruptors A23187 and deoxynivalenol in a fructan-type dependent fashion. The production of pro-inflammatory cytokines MCP-1/CCL2, MIP-1α/CCL3 and TNFα by DCs was also attenuated in a fructan-type dependent manner and was strongly attenuated by DCs cultured with medium of Caco-2 cells which were pre-exposed to fructans. Our data show that specific fructans have TJs and DCs modulating effects and contribute to gut homeostasis. This might serve to design effective dietary means to prevent intestinal inflammation.

A Review of Disparities and Unmet Newborn Screening Needs over 33 Years in a Cohort of Mexican Patients with Inborn Errors of Intermediary Metabolism

Advances in an early diagnosis by expanded newborn screening (NBS) have been achieved mainly in developed countries, while populations of middle- and low-income countries have poor access, leading to disparities. Expanded NBS in Mexico is not mandatory. Herein, we present an overview of the differences and unmet NBS needs of a group of Mexican patients with inborn errors of intermediary metabolism (IEiM), emphasizing the odyssey experienced to reach a diagnosis. We conducted a retrospective observational study of a historical cohort of patients with IEiM from a national reference center. A total of 924 patients with IEiM were included. Although 72.5% of the diseases identified are detectable by expanded NBS, only 35.4% of the patients were screened. The mortality in the unscreened group was almost two-fold higher than that in the screened group. Patients experienced a median diagnostic delay of 4 months, which is unacceptably long considering that to prevent disability and death, these disorders must be treated in the first days of life. Patients had to travel long distances to our reference center, contributing to their unacceptable diagnostic odyssey. This study highlights the urgent need to have an updated, expanded NBS program with adequate follow up in Mexico and promote the creation of regional medical care centers. We also provide compelling evidence that could prove valuable to decision makers overseeing public health initiatives for individuals impacted by IEiM from middle- and low-income countries.

TLR 2/1 interaction of pectin depends on its chemical structure and conformation

Citrus pectins have demonstrated health benefits through direct interaction with Toll-like receptor 2. Methyl-ester distribution patterns over the homogalacturonan were found to contribute to such immunomodulatory activity, therefore molecular interactions with TLR2 were studied. Molecular-docking analysis was performed using four GalA-heptamers, GalA₇Me⁰, GalA₇Me^1,6, GalA₇Me^1,7 and GalA₇Me^2,5. The molecular relations were measured in various possible conformations. Furthermore, commercial citrus pectins were characterized by enzymatic fingerprinting using polygalacturonase and pectin-lyase to determine their methyl-ester distribution patterns. The response of 12 structurally different pectic polymers on TLR2 binding and the molecular docking with four pectic oligomers clearly demonstrated interactions with human-TLR2 in a structure-dependent way, where blocks of (non)methyl-esterified GalA were shown to inhibit TLR2/1 dimerization. Our results may be used to understand the immunomodulatory effects of certain pectins via TLR2. Knowledge of how pectins with certain methyl-ester distribution patterns bind to TLRs may lead to tailored pectins to prevent inflammation.

The BMI Z-Score and Protein Energy Ratio in Early- and Late-Diagnosed PKU Patients from a Single Reference Center in Mexico

The relationship between protein and energy and their appropriate proportions in hyperphenylalaninemia (HPA) or phenylketonuria (PKU) patients in terms of growth have been poorly studied, especially in those diagnosed late. We aimed to describe the protein energy ratio (P:E) and its association with body mass index (BMI) in 638 dietetic and anthropometric assessments from 54 early- or late-diagnosed HPA/PKU patients. Dietetic and anthropometric data were analyzed and classified according to BMI Z-Score and type of diagnosis, early by newborn screening (NBS) or late. Correlation between BMI Z-Score and P:E ratio was established. Percent of dietary protein from Phe-free metabolic formula was analyzed. According to the BMI Z-Score, the majority of assessments were eutrophic (69.4%). The median P:E ratio was >4 in most of the overweight assessments. Remarkably, the underweight group consumed the highest proportion of Phe-free metabolic formula (74.5%). A positive correlation between BMI Z-Score and P:E ratio was found. The highest proportion of underweight was found in the late-diagnosed patients. Our findings might be related to their nutritional history previous to the HPA/PKU treatment. Thus, complex nutritional outcome of the late-diagnosed HPA/PKU patients deserves actions to guarantee the early diagnosis, closer nutritional follow-up and alternative therapeutic approaches.

β(2 → 1)-β(2 → 6) branched graminan-type fructans and β(2 → 1) linear fructans impact mucus-related and endoplasmic reticulum stress-related genes in goblet cells and attenuate inflammatory responses in a fructan dependent fashion

Dietary fibers such as fructans have beneficial effects on intestinal health but it is unknown whether they impact goblet cells (GCs). Here we studied the effects of inulin-type fructans (ITFs) and graminan-type fructans (GTFs) with different molecular weights on mucus- and endoplasmic reticulum (ER) stress-related genes in intestinal GCs. To that end, GCs were incubated in the presence of ITFs or GTFs, or ITFs and GTFs + TNFα or the N-glycosylation inhibitor tunicamycin (Tm). IL-8 production by GCs was studied as a marker of inflammation. Effects between ITFs and GTFs were compared. We found a beneficial impact of GTFs especially on the expression of RETNLB. GTF II protects from the TNFα-induced gene expression dysregulation of MUC2, TFF3, GAL3ST2, and CHST5. Also, all the studied fructans prevented Tm-induced dysregulation of GAL3ST2. Interestingly, only the short chain fructans ITF I and GTF I have anti-inflammatory properties on GCs. All the studied fructans except ITF I decreased the expression of the ER stress-related HSPA5 and XBP1. All these benefits were fructan-structure and chain length dependent. Our study contributes to a better understanding of chemical structure-dependent beneficial effects of ITFs and GTFs on gut barrier function, which could contribute to prevention of gut inflammatory disorders.

Genotypic spectrum underlying tetrahydrobiopterin metabolism defects: Experience in a single Mexican reference center

Background: Pterin profiles or molecular analyses of hyperphenylalaninemia (HPA) caused by phenylalanine hydroxylase (PAH) deficiency or tetrahydrobiopterin deficiency (BH4D) are not always available in low- or middle-income countries, including Mexico, limiting information regarding the phenotypic and genotypic characteristics of patients exhibiting BH4D.

Objective: To report the genotypes underlying BH4D and the clinical presentation in unrelated Mexican HPA pediatric patients with normal PAH genotypes who attended a single metabolic reference center in Mexico.

Methods: Automated Sanger sequencing of the PTS, QDPR, and PCBD1 genes of 14 HPA patients was performed. Predicted effects on protein structure caused by missense variants were assessed by in silico protein modeling.

Results and discussion: A high prevalence of BH4D was noted in our HPA cohort (9.8%, N = 14/142). Clinically relevant biallelic genotypes were identified in the PTS (N = 7/14 patients), QDPR (N = 6/14 patients), and PCBD1 (N = 1/14 patients) genes. Four novel QDPR variants [c.714dup or p.(Leu239Thrfs*44), c.106-1G>T or p.(?), c.214G>T or p.(Gly72*), and c.187_189dup or p.(Gln63dup)] were identified. In silico protein modeling of six missense variants of PTS [p.(Thr67Met), p.(Glu81Ala), and p.(Tyr113Cys)], QDPR [p.(Cys161Phe) and p.(Pro172Leu)], and PCBD1 [p.(Glu97Lys)] supports their pathogenicity. Progressive neurological symptoms (mainly intellectual and motor impairment and even death in three patients) were noted in all patients with biallelic QDPR genotypes and in 5/7 patients bearing biallelic PTS genotypes. The single homozygous PCBD1 p.(Glu97Lys) patient remains asymptomatic.

Conclusion: A higher proportion of BH4D (9.8 vs. 1%–2% worldwide), attributable to a heterogeneous mutational spectrum and wide clinical presentation, was noted in our Mexican HPA cohort, with the PTS-related HPA disorder being the most frequent. Sequencing-based assays could be a reliable approach for diagnosing BH4D in our population.

Actualización para el tratamiento de la hiperamonemia aguda en pacientes con errores innatos del metabolismo

La hiperamonemia aguda (HAA) es una urgencia médica que causa daño neurológico y puede conducir a daño neurológico o incluso la muerte. En los pacientes con errores innatos del metabolismo (EIM) se presenta con mayor frecuencia, sobre todo en eventos de descompensación metabólica, ameritando atención de terapia intensiva. Los EIM que principalmente causan HAA incluyen los defectos del ciclo de la urea, acidemias orgánicas, defectos de oxidación de ácidos grasos y los defectos del ciclo de la carnitina. Ante un evento de HAA el objetivo primordial es preservar la vida y la integridad del sistema nervioso central, disminuyendo los niveles sanguíneos de amonio hasta valores normales, mediante tratamiento médico urgente, soporte vital y nutrición individualizada. El conocer los medicamentos y métodos disponibles para la remoción del amonio, así como las necesidades energéticas, proteicas, suplementos, cofactores y vitaminas, es muy importante para la correcta toma de decisiones médicas y nutricionales en cada paciente tomando en cuenta su condición clínica, bioquímica y enfermedad de base. El objetivo de este trabajo es presentar conceptos actuales sobre el tratamiento de la HAA en pacientes con EIM. 

The Giardial Arginine Deiminase Participates in Giardia-Host Immunomodulation in a Structure-Dependent Fashion via Toll-like Receptors

Beyond the problem in public health that protist-generated diseases represent, understanding the variety of mechanisms used by these parasites to interact with the human immune system is of biological and medical relevance. Giardia lamblia is an early divergent eukaryotic microorganism showing remarkable pathogenic strategies for evading the immune system of vertebrates. Among various multifunctional proteins in Giardia, arginine deiminase is considered an enzyme that plays multiple regulatory roles during the life cycle of this parasite. One of its most important roles is the crosstalk between the parasite and host. Such a molecular "chat" is mediated in human cells by membrane receptors called Toll-like receptors (TLRs). Here, we studied the importance of the 3D structure of giardial arginine deiminase (GlADI) to immunomodulate the human immune response through TLRs. We demonstrated the direct effect of GlADI on human TLR signaling. We predicted its mode of interaction with TLRs two and four by using the AlphaFold-predicted structure of GlADI and molecular docking. Furthermore, we showed that the immunomodulatory capacity of this virulent factor of Giardia depends on the maintenance of its 3D structure. Finally, we also showed the influence of this enzyme to exert specific responses on infant-like dendritic cells.

Metabolic Reprogramming in SARS-CoV-2 Infection Impacts the Outcome of COVID-19 Patients

Severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) infection triggers inflammatory clinical stages that affect the outcome of patients with coronavirus disease 2019 (COVID-19). Disease severity may be associated with a metabolic imbalance related to amino acids, lipids, and energy-generating pathways. The aim of this study was to characterize the profile of amino acids and acylcarnitines in COVID-19 patients. A multicenter, cross-sectional study was carried out. A total of 453 individuals were classified by disease severity. Levels of 11 amino acids, 31 acylcarnitines, and succinylacetone in serum samples were analyzed by electrospray ionization-triple quadrupole tandem mass spectrometry. Different clusters were observed in partial least squares discriminant analysis, with phenylalanine, alanine, citrulline, proline, and succinylacetone providing the major contribution to the variability in each cluster (variable importance in the projection >1.5). In logistic models adjusted by age, sex, type 2 diabetes mellitus, hypertension, and nutritional status, phenylalanine was associated with critical outcomes (odds ratio=5.3 (95% CI 3.16-9.2) in the severe vs. critical model, with an area under the curve of 0.84 (95% CI 0.77-0.90). In conclusion the metabolic imbalance in COVID-19 patients might affect disease progression. This work shows an association of phenylalanine with critical outcomes in COVID-19 patients, highlighting phenylalanine as a potential metabolic biomarker of disease severity.

β(2→1) chicory and β(2→1)-β(2→6) agave fructans protect the human intestinal barrier function in vitro in a stressor-dependent fashion

Dietary fibers such as fructans can protect the intestinal epithelial barrier integrity, but the mechanisms underlying this protection are not completely understood. We aimed to study the protective effect of β(2→1)-β(2→6) branched graminan-type fructans (GTFs) on gut epithelial barrier function that was disrupted by three different agents which impact the barrier function via different cellular mechanisms. The effects of GTFs were compared with those of linear β(2→1) inulin-type fructans (ITFs). T84 intestinal epithelial monolayers were incubated with GTFs and ITFs. Afterwards, the monolayers were challenged with the barrier disruptors calcium ionophore A23187, 12-myristate 13-acetate (PMA) and deoxynivalenol (DON). Transepithelial resistance was measured with an electric cell-substrate impedance sensing system. All fructans studied prevented the barrier disruption induced by A23187. ITF II protected from the disruptive effects of PMA. However, none of the studied fructans influenced the disruption induced by DON. As a measure of disruption-induced inflammation, interleukin-8 (IL-8) production by the intestinal epithelium was determined by ELISA. The production of IL-8 induced by A23187 was decreased by all fructans, whereas IL-8 production induced by DON decreased only upon pre-treatment with ITF II. None of the studied fructans prevented PMA induced IL-8 production. GTFs just like ITFs can influence the barrier function and inflammatory processes in gut epithelial cells in a structure-dependent fashion. These distinct protective effects are dependent on the different signaling pathways that lead to gut barrier disruption.

β(2→6)-Type fructans attenuate proinflammatory responses in a structure dependent fashion via Toll-like receptors

Graminan-type fructans (GTFs) have demonstrated immune benefits. However, mechanisms underlying these benefits are unknown. We studied GTFs interaction with Toll-like receptors (TLRs), performed molecular docking and determined their impact on dendritic cells (DCs). Effects of GTFs were compared with those of inulin-type fructans (ITFs). Whereas ITFs only contained β(2→1)-linked fructans, GTFs showed higher complexity as it contains additional β(2→6)-linkages. GTFs activated NF-κB/AP-1 through MyD88 and TRIF pathways. GTFs stimulated TLR3, 7 and 9 while ITFs activated TLR2 and TLR4. GTFs strongly inhibited TLR2 and TLR4, while ITFs did not inhibit any TLR. Molecular docking demonstrated interactions of fructans with TLR2, 3, and 4 in a structure dependent fashion. Moreover, ITFs and GTFs attenuated pro-inflammatory cytokine production of stimulated DCs. These findings demonstrate immunomodulatory effects of GTFs via TLRs and attenuation of cytokine production in dendritic cells by GTFs and long-chain ITF.

An Updated PAH Mutational Spectrum of Phenylketonuria in Mexican Patients Attending a Single Center: Biochemical, Clinical-Genotyping Correlations

Establishing the genotypes of patients with hyperphenylalaninemia (HPA)/phenylketonuria (PKU, MIM#261600) has been considered a cornerstone for rational medical management. However, knowledge of the phenylalanine hydroxylase gene (PAH) mutational spectrum in Latin American populations is still limited. Herein, we aim to update the mutational PAH spectrum in the largest cohort of HPA/PKU Mexican patients (N = 124) reported to date. The biallelic PAH genotype was investigated by Sanger automated sequencing, and genotypes were correlated with documented biochemical phenotypes and theoretical tetrahydrobiopterin (BH₄) responsiveness. Patients were biochemically classified as having classic PKU (50%, 62/124), mild PKU (20.2%, 25/124) and mild HPA (29.8%, 37/124). Furthermore, 78.2% of the included patients (97/124) were identified by newborn screening. A total of 60 different pathogenic variants were identified, including three novel ones (c. 23del, c. 625_626insC and c. 1315 + 5_1315 + 6insGTGTAACAG), the main categories being missense changes (58%, 35/60) and those affecting the catalytic domain (56.6%, 34/60), and c. 60 + 5G > T was the most frequent variant (14.5%, 36/248) mainly restricted (69.2%) to patients from the central and western parts of Mexico. These 60 types of variants constituted 100 different biallelic PAH genotypes, with the predominance of compound-heterozygous ones (96/124, 77%). The expected BH₄ responsiveness based on the PAH genotype was estimated in 52% of patients (65/124), mainly due to the p. (Val388Met) (rs62516101) allele. Instead, our study identified 27 null variants with an allelic phenotype value of zero, with a predominance of c. 60 + 5G > T, which predicts the absence of BH₄ responsiveness. An identical genotype reported in BIOPKUdb was found in 92/124 (74%) of our patients, leading to a genotype–phenotype concordance in 80/92 (86.9%) of them. The high number of variants found confirms the heterogeneous and complex mutational landscape of HPA/PKU in Mexico.

Multilevel Approach for the Treatment of Giardiasis by Targeting Arginine Deiminase

Giardiasis represents a latent problem in public health due to the exceptionally pathogenic strategies of the parasite Giardia lamblia for evading the human immune system. Strains resistant to first-line drugs are also a challenge. Therefore, new antigiardial therapies are urgently needed. Here, we tested giardial arginine deiminase (GlADI) as a target against giardiasis. GlADI belongs to an essential pathway in Giardia for the synthesis of ATP, which is absent in humans. In silico docking with six thiol-reactive compounds was performed; four of which are approved drugs for humans. Recombinant GlADI was used in enzyme inhibition assays, and computational in silico predictions and spectroscopic studies were applied to follow the enzyme's structural disturbance and identify possible effective drugs. Inhibition by modification of cysteines was corroborated using Ellman's method. The efficacy of these drugs on parasite viability was assayed on Giardia trophozoites, along with the inhibition of the endogenous GlADI. The most potent drug against GlADI was assayed on Giardia encystment. The tested drugs inhibited the recombinant GlADI by modifying its cysteines and, potentially, by altering its 3D structure. Only rabeprazole and omeprazole decreased trophozoite survival by inhibiting endogenous GlADI, while rabeprazole also decreased the Giardia encystment rate. These findings demonstrate the potential of GlADI as a target against giardiasis.

Delivery mode-associated gut microbiota in the first 3 months of life in a country with high obesity rates: A descriptive study

Delivery methods during childbirth and their related gut microbiota profiles have important impacts on health later in life, they can contribute to the development of diseases such as obesity, whose highest prevalence rate is found among the Mexican child population. Coincidentally, Mexico has one of the highest global average annual rate increase in cesarean births (C-section). Since Mexico leads the world in childhood obesity, studying the relationship between childbirth delivery methods and gut microbiota profiles in this vulnerable population may be used to identify early risk factors for obesity in other developed and developing countries. The objective of this study is to determine the association between child delivery method and gut microbiota profiles in healthy Mexican newborns.Fecal samples of 57 term infants who participated in a randomized clinical trial in 2013 to study the safety of Agave fructans in newborns, were used in this study. DNA samples were extracted and used to characterize the microbiota composition using high-throughput 16S rRNA gene sequencing. The samples were further divided based on childbirth delivery method, as well as early diet. Gut microbiota profiles were determined and analyzed using cluster analysis followed by multiple correspondence analysis.An unusual high abundance of Proteobacteria was found in the gut microbiota of all Mexican infants studied, regardless of delivery method. Feces from infants born by C-section had low levels of Bacteroidetes, high levels of Firmicutes, especially Clostridium and Enterococcus, and a strikingly high ratio of Firmicutes/Bacteroidetes (F:B). Profiles enriched in Bacteroidetes and low F:B ratios, were strongly associated with vaginal delivery.The profile of gut microbiota associated with feces from Mexican infants born by C-section, may be added to the list of boosting factors for the worrying obesity epidemic in Mexico.

Mutational spectrum of Mexican patients with tyrosinemia type 1: In silico modeling and predicted pathogenic effect of a novel missense FAH variant

Background

Tyrosinemia type 1 (HT1, MIM#276700) is caused by a deficiency in fumarylacetoacetate hydrolase (FAH) and it is associated with severe liver and renal disfunction. At present, the mutational FAH (15q25.1, MIM*613871) spectrum underlying HT1 in the Mexican population is unknown. The objective of this study was to determine the FAH genotypes in eight nonrelated Mexican patients with HT1, who were diagnosed clinically.

Methods

Sequencing of FAH and their exon–intron boundaries and in silico protein modeling based on the crystallographic structure of mouse FAH.

Results

We identified pathogenic variants in 15/16 studied alleles (93.8%). Nine different variants were found. The most commonly detected HT1‐causing allele was NM_000137.2(FAH):c.3G > A or p.(?) [rs766882348] (25%, n = 4/16). We also identified a novel missense variant NM_000137.2(FAH):c.36C > A or p.(Phe12Leu) in a homozygous patient with an early and fatal acute form. The latter was classified as a likely pathogenic variant and in silico protein modeling showed that Phe‐12 residue substitution for Leu, produces a repulsion in all possible Leu rotamers, which in turn would lead to a destabilization of the protein structure and possible loss‐of‐function.

Conclusion

HT1 patients had a heterogeneous mutational and clinical spectrum and no genotype–phenotype correlation could be established.

On the molecular and cellular effects of omeprazole to further support its effectiveness as an antigiardial drug

Research on Giardia lamblia has accumulated large information about its molecular cell biology and infection biology. However, giardiasis is still one of the commonest parasitic diarrheal diseases affecting humans. Additionally, an alarming increase in cases refractory to conventional treatment has been reported in low prevalence settings. Consequently, efforts directed toward supporting the efficient use of alternative drugs, and the study of their molecular targets appears promising. Repurposing of proton pump inhibitors is effective in vitro against the parasite and the toxic activity is associated with the inhibition of the G. lamblia triosephosphate isomerase (GlTIM) via the formation of covalent adducts with cysteine residue at position 222. Herein, we evaluate the effectiveness of omeprazole in vitro and in situ on GlTIM mutants lacking the most superficial cysteines. We studied the influence on the glycolysis of Giardia trophozoites treated with omeprazole and characterized, for the first time, the morphological effect caused by this drug on the parasite. Our results support the effectiveness of omeprazole against GlTIM despite of the possibility to mutate the druggable amino acid targets as an adaptive response. Also, we further characterized the effect of omeprazole on trophozoites and discuss the possible mechanism involved in its antigiardial effect.

Mutational spectrum of PTS gene and in silico pathological assessment of a novel variant in Mexico

BACKGROUND

Tetrahydrobiopterin (BH4) is the cofactor for 6-pyruvoyl-tetrahydropterin synthase (PTPS); it is involved in BH4 biosynthesis and is encoded by PTS gene. Its deficiency (PTPSD) is characterized by hyperphenylalaninemia (HPA) and deficit in central monoamine neurotransmitters. We describe the clinical and mutational spectrum of five patients with PTPSD, from four unrelated Mexican families. All patients had symptomatic diagnosis and presented severe early neurological manifestations and HPA.

METHODS

Clinical and biochemical data from studied patients were recorded. Responsible PTPSD genotypes was determined by direct and bidirectional Sanger DNA sequencing of the six PTS coding exons and their exon-intron borders, and these were directly searched in the available relatives. The novel PTS missense variant [NM_3000317.2:331G > T, p.(Ala111Ser)] was subjected to in silico, to predict a possible deleterious effect.

RESULTS

Diminished fetal movements were perceived as a uniform characteristic in the studied group. DNA sequencing showed two known p.(Arg25∗) and p.(Val132TyrFs∗19) and the novel missense p.(Ala111Ser) PTS variants, the latter representing potentially a frequent PTPSD-responsible allele (50%, 4/8) in Mexican patients. In silico protein modeling analysis of the p.(Ala111Ser) variant revealed loss of hydrophobic interactions between the alanine and neighboring valines, suggesting that these changes in polarity may be detrimental for enzyme function, structure and/or stability.

CONCLUSIONS

This work contributes to the knowledge of PTPS molecular spectrum. The delayed diagnosis of these patients emphasizes the importance of considering BH4 metabolism defects in the differential diagnosis of HPA, especially for countries that are beginning their HPA newborn screening programs.

In silico prediction of the pathogenic effect of a novel variant of BCKDHA leading to classical maple syrup urine disease identified using clinical exome sequencing

Maple syrup urine disease (MSUD) is a metabolic disorder caused by mutations in three of the branched-chain α-keto acid dehydrogenase complex (BCKDC) genes. Classical MSUD symptom can be observed immediately after birth and include ketoacidosis, irritability, lethargy, and coma, which can lead to death or irreversible neurodevelopmental delay in survivors. The molecular diagnosis of MSUD can be time-consuming and difficult to establish using conventional Sanger sequencing because it could be due to pathogenic variants of any of the BCKDC genes. Next-generation sequencing-based methodologies have revolutionized the molecular diagnosis of inborn errors in metabolism and offer a superior approach for genotyping these patients. Here, we report an MSUD case whose molecular diagnosis was performed by clinical exome sequencing (CES), and the possible structural pathogenic effect of a novel E1α subunit pathogenic variant was analyzed using in silico analysis of α and β subunit crystallographic structure. Molecular analysis revealed a new homozygous non-sense c.1267C>T or p.Gln423Ter variant of BCKDHA. The novel BCKDHA variant is considered pathogenic because it caused a premature stop codon that probably led to the loss of the last 22 amino acid residues of the E1α subunit C-terminal end. In silico analysis of this region showed that it is in contact with several residues of the E1β subunit mainly through polar contacts, hydrogen bonds, and hydrophobic interactions. CES strategy could benefit the patients and families by offering precise and prompt diagnosis and better genetic counseling.

Crisis neuropática por suspensión de nitisinona en una paciente con tirosinemia: informe de un caso

Se presenta el caso de una paciente con tirosinemia hepatorrenal (TYR- 1) que, debido a la interrupción por cuatro semanas de tratamiento con nitisinona, tuvo una grave crisis neurológica de pseudoporfiria caracterizada por vómito, dolor abdominal, irritabilidad e hipertensión arterial, con gran elevación de la succinilacetona y alfafetoproteína. La crisis requirió tratamiento intrahospitalario. Una semana después de reiniciar la administración del fármaco revirtió totalmente. Este caso enfatiza la importancia de mantener el tratamiento ininterrumpido con nitisinona en pacientes con tirosinemia hepatorrenal. También es útil para reconocer el cuadro clínico y la fisiopatología de las crisis neurológicas características de esta enfermedad.

Kernicterus in a boy with ornithine transcarbamylase deficiency: A case report

Ornithine transcarbamylase deficiency (OTCD) is an X-linked urea cycle defect associated with severe and usually fatal hyperammonemia. This study describes a patient with early onset lethal OTCD due to a known pathogenic variant (c.298+1G>A), as well as the novel autopsy finding of kernicterus with relatively low blood concentration of unconjugated bilirubin (UCB) (11.55 mg/dL). The patient was a full-term male with a family history of two previous male siblings who died as newborns after acute neurologic deterioration. The patient's symptoms began at 24 h of life with lethargy that rapidly progressed to coma upon admission to the neonatal intensive care unit. Although hyperammonemia and hyperbilirubinemia were documented, hemofiltration could not be performed. OTCD diagnosis was biochemically established. Despite nutritional intervention and treatment for hyperammonemia, the patient died on the sixth day of life. At autopsy, external brain examination revealed a marked yellow pigmentation typical of kernicterus that included gray matter, particularly the thalamus and basal ganglia; dentate nuclei of the cerebellum and brain stem gray matter were also affected. Microscopic findings were consistent with the classical description of tissue damage in OTCD, including the presence of Alzheimer type II astrocytes in basal ganglia, necrosis, neuronal loss with spongiform degeneration and macrophage infiltration surrounded by astroglia. This condition may be an important comorbidity in newborns with hyperammonemia.

Hepatorenal Tyrosinemia in Mexico: A Call to Action

Hepatorenal tyrosinemia is a treatable metabolic disease characterized by progressive liver failure, renal damage and pronounced coagulopathy. Its clinical diagnosis is difficult because of its low prevalence and heterogeneous symptoms. In developed countries, expanded newborn screening, based on succinylacetone quantification by tandem mass spectrometry, has been very valuable in the early detection of hepatorenal tyrosinemia, providing the opportunity for rapid treatment of affected patients. In developing countries without systematic expanded newborn screening, however, diagnosis and treatment of this disease remain major challenges, as genetic diseases in these countries are not a health priority and there are few referral centers for infants with inherited errors of metabolism. This chapter describes the diagnosis, follow-up and outcome of 20 Mexican patients with hepatorenal tyrosinemia. This chapter also constitutes a call to action to pediatricians, gastroenterologists, geneticists and other health professionals, and to academic organizations, health authorities and patient advocacy groups, to promote early patient detection and treatment, reducing the unacceptably high mortality rate (75%) in Mexican infants with this potentially deadly but eminently treatable condition.

Phenylalanine hydroxylase deficiency in Mexico: genotype-phenotype correlations, BH4 responsiveness and evidence of a founder effect

The mutational spectrum of the phenylalanine hydroxylase gene (PAH) in Mexico is unknown, although it has been suggested that PKU variants could have a differential geographical distribution. Genotype-phenotype correlations and genotype-based predictions of responsiveness to tetrahydrobiopterin (BH4 ) have never been performed. We sequenced the PAH gene and determined the geographic origin of each allele, mini-haplotype associated, genotype-phenotype correlations and genotype-based prediction of BH4 responsiveness in 48 Mexican patients. The mutational spectrum included 34 variants with c.60+5G>T being the most frequent (20.8%) and linked to haplotype 4.3 possibly because of a founder effect and/or genetic drift. Two new variants were found c.1A>T and c.969+6T>C. The genotype-phenotype correlation was concordant in 70.8%. The genotype-based prediction to BH4 -responsiveness was 41.7%, this information could be useful for the rational selection of candidates for BH4 testing and therapy.

Resonancia magnética nuclear de encéfalo en pacientes con fenilcetonuria diagnosticada tardíamente

Antecedentes: la fenilcetonuria clásica es una encefalopatía genéticacaracterizada por una inhabilidad de los individuos para metabolizar lafenilalanina, por lo que su concentración plasmática se eleva a nivelestóxicos. Clínicamente se manifiesta como irritabilidad, alteración delsueño, indiferencia al medio, crisis convulsivas, retraso del neurodesarrollo,conducta autista, agresividad y discapacidad intelectual.Objetivo: describir los hallazgos y cuantificar el coeficiente de difusiónaparente en los estudios de imagen de resonancia magnética de cráneo,de pacientes con fenilcetonuria clásica diagnosticada tardíamente enel Instituto Nacional de Pediatría (México).Materiales y métodos: análisis retrospectivo de imágenes cerebralesobtenidas por resonancia magnética en pacientes con fenilcetonuriaclásica. Se utilizó un magneto Signa Excite de 1.5 teslas con antenacerebral de ocho canales de arreglo en fase. Se midió el coeficiente dedifusión aparente en la estación de trabajo Advantage Workstation 4.2p.Resultados: en los pacientes se observaron alteraciones en las sustanciasblanca, gris, o ambas. En la sustancia blanca las lesiones hiperintensasen el área peritrigonal fueron las más frecuentes; se encontraron alteracionesbilaterales en la sustancia blanca frontal, temporal, occipital,subcortical y periventricular. Se observó disminución del coeficientede difusión aparente en la sustancia blanca peritrigonal, occipital,cuerpo calloso, ganglios basales y cerebelo. Un paciente tenía dosquistes aracnoideos.Conclusión: todos los pacientes estudiados tuvieron las anormalidadescaracterísticas de la enfermedad en las imágenes de resonanciamagnética. Los mecanismos causantes de las lesiones cerebrales enla fenilcetonuria, su distribución espacial y su evolución son pococonocidos y requieren de investigaciones posteriores.

Tyrosinemia type I: clinical and biochemical analysis of patients in Mexico

INTRODUCTION

Hepatorenal tyrosinemia (HT1) is a treatable, inherited, metabolic disease characterized by progressive liver failure with pronounced coagulopathy. The aim of this study is to describe the clinical, biochemical, and histopathological findings in a group of Mexican HT1 patients and their outcome.

MATERIAL AND METHODS

Medical records of HT1 patients diagnosed between 1995 and 2011 were analyzed. The diagnosis of HT1 was confirmed by detection of succinylacetone in urine or blood.

RESULTS

Sixteen nonrelated HT1 cases were analyzed. Mean age at clinical onset was 9 months, and the mean age at diagnosis was 16.3 months. Main clinical findings were hepatomegaly, splenomegaly, cirrhosis, liver failure, tubulopathy, nephromegaly, Fanconi syndrome, seizures and failure to thrive. Histopathological findings were cirrhosis, fibrosis and steatosis. The HT1 group had a mortality rate of 78%. Patients who received supportive care or nutritional treatment had a 3-year survival rate of 10%. For those who underwent liver transplantation, the 6-year survival rate was 60%. In most cases pharmacological treatment with nitisinone and special dietary products were not available. The leading causes of death were fulminant liver failure, metastatic hepatocellular carcinoma, and porphyria-like neurologic crisis. Newborn screening programs in combination with the availability of orphan drugs, proper monitoring, genetic counseling, and clinical practice guidelines are needed to enable physicians to identify the disease, delay its progression, and improve patients' quality of life.

CONCLUSION

The devastating natural history of HT1 is still observed in Mexican patients because they are not diagnosed and treated during the early stages of the disease.

Fundamentos teórico-prácticos para la toma correcta de la muestra de sangre del talón para el tamiz neonatal

El tamiz neonatal (TN) es un examen preventivo cuyo beneficio ha sido demostrado científicamente. En todos los países desarrollados el tamiz se realiza con cuatro o cinco gotas de sangre obtenidas mediante la punción del talón del recién nacido con una lanceta; se recolectan en un papel filtro especial (tarjeta de Guthrie). A pesar de su aparente sencillez, a los laboratorios de tamiz llegan muchas muestras mal tomadas o inadecuadas para realizar determinaciones bioquímicas. El objetivo del presente artículo es ofrecer recomendaciones basadas en evidencias científicas para tomar de manera correcta las muestras de sangre en papel filtro para el TN.

[Characterization of inborn errors of intermediary metabolism in mexican patients]

INTRODUCTION

Inborn errors of intermediary metabolism (IEiM) are a group of heterogeneous genetic diseases that are diagnostically challenging and cause significant morbidity and mortality. The aim of this study is to perform a descriptive analysis of the number, type, and clinical features, in a series of cases with IEiM identified through selective diagnosis in a highly specialized pediatric hospital.

MATERIALS AND METHODS

A retrospective study was performed from January of 2000 to December of 2012 by analyzing the files of 204 patients with an IEiM, by selective screening, before and after the implementation of tandem mass spectrometry (MS/MS).

RESULTS

A total of 25 different types of IEiM were found in the 204 files; 102 organic acidurias, 100 aminoacidopathies, and 2 fatty acid oxidation disorders. The introduction of MS/MS increased the number of cases detected by 50%. Patients were referred from 13 different specialists, with pediatricians being the most active. The average interval between onset of symptoms and diagnosis was 18 months.

CONCLUSION

Among the sick Mexican children studied, a wide variety of IEiM was found, propionate defects and maple syrup urine disease being noteworthy. The diagnosis of metabolic disease was delayed in the population studied. These results present evidence to perhaps incorporate IEiM into an expanded newborn screening, or else to perform selective diagnosis in all hospitalized children with suggestive clinical data.

Tandem mass spectrometry newborn screening for inborn errors of intermediary metabolism: abnormal profile interpretation

Expanded newborn screening for inherited metabolic disorders using tandem mass spectrometry was introduced in 1990's and is widely used around the world. In contrast to conventional screening methods, tandem mass spectrometry does not measure single analytes but identifies and quantifies metabolite profiles; one single blood spot analyzed provides information of about 60 metabolites including amino acids, acylcarnitines and related ratios that enable the diagnosis of approximately 50 different diseases. However, the interpretation of these profiles can become quite complex. The aim of this work is to present in an easy and practical manner a comprehensive compilation of information needed for tandem mass neonatal screening profile interpretation, and basic actions for immediate follow up of abnormal results, including the tests that are required for confirmatory purposes. Other conditions not attributable to metabolic disorders which can lead to an abnormal profile of these markers are also described as well as a series of general recommendations which would be useful for health professionals who are beginning newborn screening for inborn errors of intermediary metabolism using tandem mass spectrometry.

Higher incidence of thyroid agenesis in Mexican newborns with congenital hypothyroidism associated with birth defects

BACKGROUND

Congenital hypothyroidism (CH) is the most common endocrine system disorder in newborns. Ectopic thyroid and agenesis are the most frequent thyroid structural malformations. Several reports have shown that CH is associated with birth defects (BD) ranging from congenital heart disease to ocular and gastrointestinal anomalies.

AIMS

We investigated how many and what types of BD were associated with CH in Mexican children.

STUDY DESIGN

Cross-sectional study conducted in patients with confirmed CH.

SETTING

Highly specialized government pediatric center in Mexico City.

SUBJECTS

We included 212 patients with permanent CH identified by newborn screening.

RESULTS

We found that 24% of patients with CH also had BD, and that there was a higher prevalence of thyroid agenesis in the group of patients with CH associated with BD (CH+BD) versus the isolated CH group (p=0.007). There were more females than males in both groups. The most common BD were congenital heart diseases, especially those of the atrial septum, followed by patent ductus arteriosus, found as a single malformation or as part of a complex congenital heart disease. In this study, we found Hirschsprung disease, Beckwith-Wiedemann syndrome, Pierre Robin sequence, Albright's osteodystrophy, VATER association, and frontonasal dysplasia associated with CH.

CONCLUSIONS

In this study population, there was a high prevalence of BD in patients with permanent CH. Thyroid agenesis was the main etiological cause of CH in patients with associated congenital malformations. The high prevalence of CH+BD underlines the need for a comprehensive clinical diagnostic approach of the patients with CH.

Causes of delay in referral of patients with phenylketonuria to a specialized reference centre in Mexico

Objective

To expose causes leading to the delayed arrival of phenylketonuria (PKU) patients at a governmental reference centre (RC), and to describe their clinical characteristics.

Material and methods

PKU files registered during the past 18 years at the National Institute of Pediatrics in Mexico City were evaluated. Patients were classified into two groups according to their age at arrival: Group I (early reference), patients arriving during the first month of life; and Group II (late reference), those who arrived after thirty days of age. Time and causes of delay were documented.

Results

Of 57 recorded files, 10 were classified in Group I and 47 in Group II. Causes leading to the late arrival of Group II patients were absence of routine newborn screening (NBS), PKU not included in the routine NBS, sampling after the recommended age, false negative result, results without interpretation and/or instructions to follow, delayed notification of results, poor medical criteria of attending physician, difficulties in obtaining confirmatory tests, and administrative failures.

Conclusion

The main cause of late referral of PKU patients was the absence of PKU testing. As a developing country, Mexico still faces challenges in the proper functioning and expansion of the NBS programme. Most PKU patients arrived at the RC late, presenting with varying degrees of the clinical spectrum. Incorporating PKU testing into the already established Mexican NBS system and adding quality indicators to guarantee proper operation in all NBS phases is necessary to achieve the goal of identifying, referring, diagnosing, and treating patients promptly.

[Increased mortality and disability in a cohort of Mexican children with maple syrup urine disease]

INTRODUCTION

Maple syrup urine disease (MSUD) is a genetic disorder that produces ketoacidosis crises and neurological complications often leading to death. The age of diagnosis and treatment determine a child's adequate and healthy outcome.

OBJECTIVE

Describe the characteristics of a pediatric Mexican cohort with MSUD.

MATERIAL AND METHODS

Retrospective analysis of MSUD cases seen at our Metabolic Unit between 1991- 2006.

RESULTS

We studied 36 patients; three were initially detected through neonatal screening, one of them done in Mexico and two in the United States. The latter were given timely treatment and developed normally, both intellectually and physically. The patient detected in Mexico was not given adequate treatment and died at 3 months of age. The remaining 33 patients were diagnosed between 2-24 months using standard biochemical tests performed after symptoms became noticeable. All symptomatic patients had high levels of branched-chain amino acids. Hypotonia, refusal to eat and seizures were the most frequent symptoms. The cohort's mortality was 50% (18/36), while 81.2% (13/18) of survivors displayed cognitive impairment.

DISCUSSION

Mexico needs a comprehensive treatment protocol for the care of MSUD patients including newborn screening, early treatment, follow-up and genetic counseling.