Deficiency Of Β-glucocerebrosidase Research Articles

Diet, β-glucocerebrosidase deficiency, and Parkinson’s disease

Diet, β-glucocerebrosidase deficiency, and Parkinson’s disease

Gaucher disease type 3c: Expanding the clinical spectrum of an ultra-rare disease.

Gaucher disease (GD) type 3 is an autosomal recessive lysosomal disease caused by deficiency of β-glucocerebrosidase (GCase) and encompasses a spectrum of cardiac, neurological, and ophthalmological abnormalities. Although the clinical presentations can be diverse, a recognized clinical trajectory points to an early onset, predominantly before 18 years. GD type 3c is primarily caused by homozygosity for GBA pathogenic variant c.1342G>C (p.Asp448His; historically referred to as D409H) and includes visceral, hematological, skeletal, and cardiac abnormalities. Notably, GD type 3c is distinct from other GD types because it is primarily characterized by valvular heart disease. Yet, with less than 50 patients with GD type 3c reported to date, the phenotypic spectrum and extent of cardiac involvement remains ill-defined. We present a 20-year-old female with an atypical presentation of GD type 3c consisting of chronic intermediate uveitis as the presenting feature and the presence of extensive polyneuropathy starting in adolescence which has been previously unreported in GD type 3c. Distinctively, she has maintained normal cardiac function. Moreover, we compare our case with those reported in the literature to broaden awareness of the varied initial presentations of this disease. The diverse presentations seen in GD type 3c, underscored by our case and those previously reported, demonstrate the need for standardized evaluation and management protocols.

Long- and Short-Term Glucosphingosine (lyso-Gb1) Dynamics in Gaucher Patients Undergoing Enzyme Replacement Therapy.

Background: Gaucher disease (GD) is a lysosomal storage disorder caused by mutations in the GBA1 gene, leading to β-glucocerebrosidase deficiency and glucosylceramide accumulation. Methods: We analyzed short- and long-term dynamics of lyso-glucosylceramide (lyso-Gb1) in a large cohort of GD patients undergoing enzyme replacement therapy (ERT). Results: Eight-years analysis of lyso-Gb1 revealed statistically insignificant variability in the biomarker across the years and relatively high individual variability in patients' results. GD type 1 (GD1) patients exhibited higher variability compared to GD type 3 (GD3) patients (coefficients of variation: 34% and 23%, respectively; p-value = 0.0003). We also investigated the short-term response of the biomarker to enzyme replacement therapy (ERT), measuring lyso-Gb1 right before and 30 min after treatment administration. We tested 20 GD patients (16 GD1, 4 GD3) and observed a rapid and significant reduction in lyso-Gb1 levels (average decrease of 17%; p-value < 0.0001). This immediate response reaffirms the efficacy of ERT in reducing substrate accumulation in GD patients but, on the other hand, suggests the biomarker's instability between the infusions. Conclusions: These findings underscore lyso-Gb1's potential as a reliable biomarker for monitoring efficacy of treatment. However, individual variability and dry blood spot (DBS) testing limitations urge a further refinement in clinical application. Our study contributes valuable insights into GD patient management, emphasizing the evolving role of biomarkers in personalized medicine.

Targeting neuronal lysosomal dysfunction caused by β-glucocerebrosidase deficiency with an enzyme-based brain shuttle construct

Mutations in glucocerebrosidase cause the lysosomal storage disorder Gaucher’s disease and are the most common risk factor for Parkinson’s disease. Therapies to restore the enzyme’s function in the brain hold great promise for treating the neurological implications. Thus, we developed blood-brain barrier penetrant therapeutic molecules by fusing transferrin receptor-binding moieties to β-glucocerebrosidase (referred to as GCase-BS). We demonstrate that these fusion proteins show significantly increased uptake and lysosomal efficiency compared to the enzyme alone. In a cellular disease model, GCase-BS rapidly rescues the lysosomal proteome and lipid accumulations beyond known substrates. In a mouse disease model, intravenous injection of GCase-BS leads to a sustained reduction of glucosylsphingosine and can lower neurofilament-light chain plasma levels. Collectively, these findings demonstrate the potential of GCase-BS for treating GBA1-associated lysosomal dysfunction, provide insight into candidate biomarkers, and may ultimately open a promising treatment paradigm for lysosomal storage diseases extending beyond the central nervous system.

β-Glucocerebrosidase Deficiency Activates an Aberrant Lysosome-Plasma Membrane Axis Responsible for the Onset of Neurodegeneration.

β-glucocerebrosidase is a lysosomal hydrolase involved in the catabolism of the sphingolipid glucosylceramide. Biallelic loss of function mutations in this enzyme are responsible for the onset of Gaucher disease, while monoallelic β-glucocerebrosidase mutations represent the first genetic risk factor for Parkinson’s disease. Despite this evidence, the molecular mechanism linking the impairment in β-glucocerebrosidase activity with the onset of neurodegeneration in still unknown. In this frame, we developed two in vitro neuronal models of β-glucocerebrosidase deficiency, represented by mouse cerebellar granule neurons and human-induced pluripotent stem cells-derived dopaminergic neurons treated with the specific β-glucocerebrosidase inhibitor conduritol B epoxide. Neurons deficient for β-glucocerebrosidase activity showed a lysosomal accumulation of glucosylceramide and the onset of neuronal damage. Moreover, we found that neurons react to the lysosomal impairment by the induction of their biogenesis and exocytosis. This latter event was responsible for glucosylceramide accumulation also at the plasma membrane level, with an alteration in lipid and protein composition of specific signaling microdomains. Collectively, our data suggest that β-glucocerebrosidase loss of function impairs the lysosomal compartment, establishing a lysosome–plasma membrane axis responsible for modifications in the plasma membrane architecture and possible alterations of intracellular signaling pathways, leading to neuronal damage.

Screening for exonic mutation L444P in Indonesian patients with gaucher disease using exons 9–11

Objective: Gaucher disease (GD) is the most common lysosomal storage disorder. It is caused by a deficiency of β-glucocerebrosidase (GCase, encoded by GBA) and its inheritance is autosomal recessive. Analyses of common mutations in GBA have been performed in China, Singapore, Taiwan, and Thailand, but not previously in Indonesia. The objective of this study was to identify a common exonic mutation in exons 9–11 of GBA in GD patients in Indonesia. Materials and Methods: Genetic analysis was performed using blood samples from two GD patients and thirty non-GD patients. Peripheral leukocyte samples were collected at the Dr. Cipto Mangunkusumo Referral Hospital, Jakarta, Indonesia. The polymerase chain reaction was performed to amplify exons 9–11 of the GBA gene using specific primers, then the product was digested with Nci I restriction enzyme, and the sequence confirmed by sequence analysis. Results: This identified an L444P mutation located in exon 10. This missense mutation changes amino acid 483 of GCase from leucine to proline and is categorized as a pathogenic variant. Conclusion: This identification of the L444P mutation adds to a database for determining the prevalence of GD in Indonesia. However, further research is needed to ascertain the impact of the L444P mutation on the structure of GCase and to explore any mutations in the other exons.

Tandem mass spectrometry assay of β-glucocerebrosidase activity in dried blood spots eliminates false positives detected in fluorescence assay.

Deficiency of β-Glucocerebrosidase (GBA) activity causes Gaucher Disease (GD). GD can be diagnosed by measuring GBA activity (Beutler and Kuhl, 1990). In this study, we assayed dried blood spots from a cohort (n=528) enriched for GBA mutation carriers (n=78) and GD patients (n=18) using both the tandem mass spectrometry (MS/MS) and fluorescence assays and their respective synthetic substrates. The MS/MS assay differentiated normal controls, which included GBA mutation carriers, from GD patients with no overlap. The fluorescence assay did not always differentiate normal controls including GBA mutation carriers from GD patients and false positives were observed. The MS/MS assay improved specificity compared to the fluorescence assay.

Treatment-naïve Gaucher disease patients achieve therapeutic goals and normalization with velaglucerase alfa by 4 years in phase 3 trials

Gaucher disease is an inherited metabolic disease characterized by β-glucocerebrosidase deficiency and commonly treated with enzyme replacement therapy (ERT). The efficacy of ERT with velaglucerase alfa was assessed based on the achievement of published therapeutic goals and the normalization of disease parameters in 39 treatment-naïve patients with type 1 Gaucher disease, 6 to 62years of age, enrolled in phase 3 clinical trials. After 4years of ERT, therapeutic goals for thrombocytopenia and splenomegaly had been achieved in 100% of patients; goals for anemia and hepatomegaly had been achieved in 95% and 94% of patients, respectively. Consistent with the goal for bone mineral density, lumbar spine bone density improved in 87% of patients ≥18years of age. At year 4, compared with clinical ranges for healthy individuals, 86% of patients with a low baseline hemoglobin concentration had normalized, 60% with a low baseline platelet count had normalized, 67% with baseline splenomegaly had normalized, 58% with hepatomegaly had normalized, and lumbar spine bone density had normalized in 53% of adults. The decade-old therapeutic goals do not reflect the potential for normalization of clinical parameters in ERT-treated patients. Goals consistent with normalization or near-normalization should be considered. ClinicalTrials.gov identifiers: NCT00430625, NCT00553631, NCT00635427.

The influence of genetic variability and proinflammatory status on the development of bone disease in patients with Gaucher disease.

Gaucher disease, the most common lysosomal storage disorder, is caused by β-glucocerebrosidase deficiency. Bone complications are the major cause of morbidity in patients with type 1 Gaucher disease (GD1). Genetic components strongly influence bone remodelling. In addition, chronic inflammation produced by Gaucher cells induces the production of several cytokines, which leads to direct changes in the bone remodelling process and can also affect the process indirectly through other immune cells. In this study, we analysed the association between bone mineral density (BMD), bone marrow burden score, and relevant genetic polymorphisms related to bone metabolism, as well as profiles of proinflammatory cytokines in a GD1 cohort. This study included 83 patients distributed according to bone status. BMD was measured with DXA and broadband ultrasound attenuation; bone marrow involvement was evaluated using MRI. We also analysed 26 SNPs located in 14 genes related to bone metabolism. To assess proinflammatory status, we analysed IL-4, IL-6, IL-7, IL-10, IL-13, MIP-1α, MIP-1β, and TNFα in plasma samples from 71 control participants and GD1 patients. SNP genotype proportions and BMD differed significantly between ESRI c.453-397T>C and VDR c.1024+283G>A variants. We also observed significant associations between GD1 genotypes and bone affectation. When patients were stratified by spleen status, we observed significant correlations between non-/splenectomized groups and Spanish MRI (S-MRI) score. Across genotype proportions of non-/splenectomized patients and S-MRI, we observed significant differences in ESRI c.453-397T>C, VDR c.-83-25988G>A, and TNFRSF11B c.9C>G polymorphisms. We observed different significant proinflammatory profiles between control participants, treatment-naïve patients, and patients on enzyme replacement therapy (ERT); between non-/splenectomized patients (between untreated and ERT-treated patients) and among those with differing GBA genotypes. The data suggest that patients with GD1 have increased susceptibility to developing bone disease owing to the coexistence of genetic variants, and that genetic background in GD1 is fundamental to regulate the impact of proinflammatory status on the development of bone disease.

Lipidomic profiling of plasma and urine from patients with Gaucher disease during enzyme replacement therapy by nanoflow liquid chromatography–tandem mass spectrometry

Gaucher disease (GD) is a rare genetic disorder that arises from lipid species, especially monohexosylceramide (MHC), accumulating in different organs. GD results from a β-glucocerebrosidase deficiency, causing metabolic or neurologic complications. This study comprehensively profiled lipids from patients and healthy controls to discover active lipid species related to GD. Most studies have evaluated lipids from one type of biological sample, such as plasma, urine, or spinal fluid, which are the main sources of lipids in human bodies. The purpose of this study, however, was to collect and assess both plasma and urine samples from a group of individuals, explore the lipids, and select characteristic species that show significant differences between controls and patients from the two sources. Also, the response of lipids to enzyme replacement therapy (ERT), which is targeted to reduce excessive lipid accumulation within lysosomes, was investigated by obtaining plasma and urine from patients after receiving the therapy. Most lipid species were found in both plasma and urine but their concentrations differed, and some species were found in either plasma or urine only. Out of 125 plasma and 105 urinary lipids that were identified by nLC–ESI–MS/MS, 20 plasma and 10 urinary lipids were selected as characteristic species for having average concentrations that were significantly increased or decreased in patients by greater than 2-fold. Moreover, the concentrations of most lipids that showed greater than 2-fold of difference in patients decreased after ERT indicating that these species were directly or indirectly affected by the therapy.

Consanguinity and founder effect for Gaucher disease mutation G377S in a population from Tabuleiro do Norte, Northeastern Brazil.

Gaucher's disease (GD) is caused by a β-glucocerebrosidase deficiency, leading to the accumulation of glucocerebroside in the reticuloendothelial system. The prevalence of GD in Tabuleiro do Norte (TN) (1:4000) is the highest in Brazil. The purpose of this study was to present evidence of consanguinity and founder effect for the G377S mutation (c.1246G>A) among GD patients in TN based on enzyme, molecular and genealogical studies. Between March 2009 and December 2010, 131 subjects at risk for GD (GC in dried blood ≤2.19 nmol/h/ml) and 5 confirmed GD patients from the same community were submitted for molecular analysis to characterize the genetic profile of the population. Based on the enzymatic and molecular analysis, the subjects were classified into three categories: affected (n = 5), carrier (n = 20) and non-carrier (n = 111). All carriers were (G377S/wt). Affected subjects were homozygous (G377S/G377S). The identification of a single mutation in carriers and homozygotes from different generations, the history of the community and the genealogy study suggest that the high prevalence of GD in this population may be due to a combination of consanguinity and founder effect for the G377S mutation.

B cell lymphoma and myeloma in murine Gaucher's disease.

Multiple myeloma and B cell lymphoma are leading causes of death in Gaucher's disease but the nature of the stimulus driving the often noted clonal expansion of immunoglobulin-secreting B cells and cognate lymphoid malignancy is unknown. We investigated the long-term development of B cell malignancies in an authentic model of non-neuronopathic Gaucher's disease in mice: selective deficiency of β-glucocerebrosidase in haematopoietic cells [Gba(tm1Karl/tm1Karl)Tg(Mx1-cre)1Cgn/0, with excision of exons 9-11 of the murine GBA1 gene, is induced by poly[I:C]. Mice with Gaucher's disease showed visceral storage of β-glucosylceramide and greatly elevated plasma β-glucosylsphingosine [median 57.9 (range 19.8-159) nm; n = 39] compared with control mice from the same strain [median 0.56 (range 0.04-1.38) nm; n = 29] (p < 0.0001). Sporadic fatal B cell lymphomas developed in 11 of 21 GD mice (6-24 months) but only two of eight control animals developed tumours by age 24 months. Unexpectedly, most mice with overt lymphoma had absent or few Gaucher cells but local inflammatory macrophages were present. Eleven of 39 of Gaucher mice developed monoclonal gammopathy, but in the control group only one animal of 25 had clonal immunoglobulin abnormalities. Seven of 10 of the B cell lymphomas were found to secrete a monoclonal paraprotein and the lymphomas stained intensely for pan-B cell markers; reactive T lymphocytes were also present in tumour tissue. In the Gaucher mouse strain, it was notable that, as in patients with this disease, CD138(+) plasma cells frequently surrounded splenic macrophages engorged with glycosphingolipid. Our strain of mice, with inducible deficiency of β-glucocerebrosidase in haematopoietic cells and a high frequency of sporadic lethal B cell malignancies, faithfully recapitulates human Gaucher's disease: it serves as a tractable model to investigate the putative role of bioactive sphingolipids in the control of B cell proliferation and the pathogenesis of myelomatosis-the most prevalent human cancer associated with this disorder.

Safety and efficacy of velaglucerase alfa replacement therapy for patients with type 1 Gaucher disease

Gaucher disease is a multisystem disorder caused by deficiency of β-glucocerebrosidase. Exogenously delivered enzyme replacement therapy (ERT) is currently standard of care. Since 1994, intravenously delivered recombinant ERT with imiglucerase (Cerezyme; Genzyme Corporation, Cambridge, MA, USA) improves hematological, visceral and skeletal features of Gaucher disease at dosages of 15–60 units/kg bodyweight/infusion, administered every other week (EOW). Velaglucerase alfa (VPRIV®; Shire HGT, MA, USA) is a human wild-type-sequenced ERT produced in human cell lines using proprietary Gene-Activation® technology (Shire HGT). This article describes the results of a Phase I/II seminal trial in treatment-naive non-neuronopathic patients (including stepwise dose reduction to 30 units/kg/EOW) and three Phase III trials (two doses: 45 or 60 units/kg/EOW; switch-over from imiglucerase at identical dose; head-to-head with imiglucerase, 60 units/kg/EOW) and Phase III extension trial. Velaglucerase alfa was approved in 2010 in many countries; based on clinical trial experience, it is safe and effective in treatment-naive and switch-over patients, children and adults, splenectomized patients and those with an intact spleen.

Enhanced differentiation of osteoclasts from mononuclear precursors in patients with Gaucher disease

Gaucher disease (GD) is an autosomal recessive disorder caused by deficiency of β-glucocerebrosidase. Storage of glucosylceramide in reticuloendothelial cells results in multiorgan pathology including bone disease. Established skeletal disease may remain problematic despite Gaucher-specific treatment. Both osteopenia and osteonecrosis have been described but the underlying pathophysiology, in particular the role of monocyte-derived osteoclasts is not well defined. The objective of this study was to explore the effect of glucocerebrosidase deficiency, inhibition and replacement on osteoclast development and function. In cultures derived from GD patients, or where GBA was chemically inhibited multinucleate giant cells expressing markers of osteoclast differentiation occurred earlier and in greater numbers compared to normal controls and the functional capacity of osteoclasts for bone resorption was enhanced. Increases in osteoclast number and activity correlated with radiological markers of active bone disease. Abnormalities were reversed by addition of specific therapies and were attenuated by co-culture with cells derived from healthy controls (HCs). Numbers of osteoblast lineage cells in the peripheral blood were mismatched to osteoclast precursors indicating uncoupling of osteoblast-osteoclast regulation which may further impact on bone remodelling. Elucidation of the underlying mechanisms of these changes will suggest rational therapies for the most disabling aspect of this condition.

Altered innate function of plasmacytoid dendritic cells restored by enzyme replacement therapy in Gaucher disease

Gaucher disease (GD) is caused by an autosomal-recessive deficiency of β-glucocerebrosidase leading to an accumulation of glucosylceramide in monocytes/macrophage lineage. We analyzed immune cells and especially the function of dendritic cells to evaluate the potential impact of glucosylceramide accumulation in these cells and its possible role in infections and malignancies usually described in this pathology. These analyses were performed for each patient without and under enzyme replacement therapy. Seven GD patients were studied and compared with healthy volunteers. Immune cells (B cells, T cells, NK, dendritic cells), were analyzed by flow cytometry directly on whole blood. Cytokine production by blood dendritic cells was assessed after stimulation by toll-like receptor ligands. Cytokines in sera were measured using a multiplex assay. GD patients displayed decreased numbers of NK cells, γδ2 T cells and increased frequency of memory CD4(+)CD45RO(+) T cells, when compared to healthy controls. Numbers of dendritic cells (myeloid (mDC) and plasmacytoid (pDC) dendritic cells) were also decreased. We demonstrated that pDC from GD patients exhibited a decrease in IFNα production after TLR9 stimulation compared to controls. Importantly, enzyme replacement therapy restored pDC function. Finally, we observed an increase of IL-8 and IL-18 in GD patient sera, which were reduced under enzyme replacement therapy. Our data confirm that patients with GD exhibit altered numbers of innate and T lymphocytes and show for the first time that pDC from GD patients exhibit altered responsiveness to TLR9. These alterations could contribute to a decreased response to pathogens and could favor the development of malignancies.

Giant lymphadenopathy infiltrated by gaucher cells mimicking lymphoma

Gaucher disease (GD) is a lysosomal storage disease characterized by deficiency of beta-glucocerebrosidase, which results in accumulation of glucocerebroside in reticuloendothelial system, bone marrow infiltration, progressive hepatosplenomegaly, and skeletal complications. Herein we report a 5-year-old female with GD receiving enzyme replacement therapy who had giant mesenteric lymphadenopathies.

Thematic review series: Skin Lipids. Pathogenesis of permeability barrier abnormalities in the ichthyoses: inherited disorders of lipid metabolism

Many of the ichthyoses are associated with inherited disorders of lipid metabolism. These disorders have provided unique models to dissect physiologic processes in normal epidermis and the pathophysiology of more common scaling conditions. In most of these disorders, a permeability barrier abnormality "drives" pathophysiology through stimulation of epidermal hyperplasia. Among primary abnormalities of nonpolar lipid metabolism, triglyceride accumulation in neutral lipid storage disease as a result of a lipase mutation provokes a barrier abnormality via lamellar/nonlamellar phase separation within the extracellular matrix of the stratum corneum (SC). Similar mechanisms account for the barrier abnormalities (and subsequent ichthyosis) in inherited disorders of polar lipid metabolism. For example, in recessive X-linked ichthyosis (RXLI), cholesterol sulfate (CSO(4)) accumulation also produces a permeability barrier defect through lamellar/nonlamellar phase separation. However, in RXLI, the desquamation abnormality is in part attributable to the plurifunctional roles of CSO(4) as a regulator of both epidermal differentiation and corneodesmosome degradation. Phase separation also occurs in type II Gaucher disease (GD; from accumulation of glucosylceramides as a result of to beta-glucocerebrosidase deficiency). Finally, failure to assemble both lipids and desquamatory enzymes into nascent epidermal lamellar bodies (LBs) accounts for both the permeability barrier and desquamation abnormalities in Harlequin ichthyosis (HI). The barrier abnormality provokes the clinical phenotype in these disorders not only by stimulating epidermal proliferation, but also by inducing inflammation.

A retrospective study on enzyme replacement therapy in patients with Gaucher disease

Gaucher disease is the most common lysosomal storage disorder. A deficiency of beta-glucocerebrosidase causes accumulation of the glucocerebroside in macrophages throughout the body. This study summarizes the effects of enzyme replacement therapy (ERT) with Imiglucerase in children with Gaucher disease. Data from 72 patients (46 were male and 26 female, age ranged from 16 months to 22 years, median 8 years and 8 months) who were treated in the hospital between May 1999 and October 2005 were collected and analyzed, 57 of the patients had type 1 Gaucher disease, 2 patients with type 2, and 13 patients with type 3. Twenty-two patients had undergone total splenectomy. Imiglucerase was given at an initial dose 60 U/kg body weight by intravenous infusion every 2 weeks. The dose was reduced to 45 U/kg when they had achieved the specified therapeutic goals after 2 years. Clinical outcome data of Imiglucerase treatment were collected using routine Gaucher clinical measures, including growth, hematology, liver and spleen 3-dimensional measurements, and skeletal assessments every 3 - 6 months. Three patients were lost to follow-up, 4 patients died, and 65 patients continued to receive the therapy. Hemoglobin and platelet levels of the patients with intact spleen increased most rapidly from the first 12 months of ERT (P < 0.01). Hemoglobin level of the patients who had undergone splenectomy determined at 30 months of treatment was higher than that of baseline (P < 0.01), but platelet levels were not significantly different (P > 0.05). The volumes of the liver decreased after the 6 months of ERT, decreased in average by (39 +/- 17)% at 24 months (P < 0.01). The volumes of spleen decreased after the 12 months of ERT by (59 +/- 21)% at 24 months (P < 0.01). During the first 12 month, the height and weight of the patients who were 2 - 12 years old increased (8.6 +/- 4.3) cm and (2.6 +/- 1.7) kg, respectively, and those of the patients who were 12 - 18 years old increased (5.2 +/- 3.9) cm and (4.5 +/- 3.3) kg, separately. Bone pain reported by 16 patients relieved after 3 months of treatment. But radiological evidence of bone disease did not change. The signs and symptoms of CNS involvement in patients with type 2 and type 3 disease were not improved. No serious adverse events were reported. ERT with Imiglucerase could improve the quality of life of the patients with Gaucher disease by ameliorating the Gaucher disease-associated anemia, thrombocytopenia, organomegaly, growth retardation and bone pain.

Plasma chitotriosidase activity in β-thalassemia major: a comparative study between Sicilian and Sardinian patients

Background: Chitotriosidase is a functional chitinase secreted by activated macrophages, which is extremely increased in plasma of patients with Gaucher disease (β-glucocerebrosidase deficiency). Recently, we found that chitotriosidase plasma levels were increased to a variable extent in Sicilian patients with β-thalassemia major. The aim of this study is to elucidate the possible mechanisms underlying chitotriosidase overproduction in β-thalassemia major. Methods: Plasma chitotriosidase was measured in 134 patients with β-thalassemia major (64 from Sardinia and 70 from Sicily), which are treated chronically by blood transfusions leading to systemic iron overload. They all have peripheral anemia and enormous enlargement of the reticulo-endothelial system. Results: Plasma chitotriosidase activity was found most frequently elevated among Sardinian (48.4%) than Sicilian (17.1%) patients. In either group, the highest levels of plasma chitotriosidase were observed in patients with the highest degree of iron overload, suggesting that this factor could trigger chitotriosidase overproduction. Conclusions: The higher rate of subjects with increased plasma chitotriosidase values among Sardinian than Sicilian could be related to distinct molecular basis of β-thalassemia and environmental features.

Accumulation of protein-bound epidermal glucosylceramides in β-glucocerebrosidase deficient type 2 Gaucher mice

The epidermal permeability barrier for water is essentially maintained by extracellular lipid membranes within the interstices of the stratum corneum. Ceramides, the main components of these membranes, derive in large part from hydrolysis of glucosylceramides mediated by the lysosomal enzyme β-glucocerebrosidase. As analyzed in this work, the β-glucocerebrosidase deficiency in type 2 Gaucher mice (RecNci I) resulted in an accumulation of all epidermal glucosylceramide species accompanied with a decrease of the related ceramides. However, the levels of one ceramide subtype, which possesses an α-hydroxypalmitic acid, was not altered in RecNci I mice suggesting that the β-glucocerebrosidase pathway is not required for targeting of this lipid to interstices of the stratum corneum. Most importantly, ω-hydroxylated glucosylceramides which are protein-bound to the epidermal cornified cell envelope of the transgenic mice accumulated up to 35-fold whereas levels of related protein-bound ceramides and fatty acids were decreased to 10% of normal control. These data support the hypothesis that in wild-type epidermis ω-hydroxylated glucosylceramides are first transferred enzymatically from their linoleic esters to proteins of the epidermal cornified cell envelope and then catabolized to protein-bound ceramides and fatty acids, thus contributing at least in part to the formation of the lipid-bound envelope.