High prevalence of chitotriosidase deficiency in Peruvian Amerindians exposed to chitin-bearing food and enteroparasites

Clusters of rare disorders and congenital anomalies in South America

Objective

To map geographic clusters of rare disorders and congenital anomalies reported in South America.

Methods

Qualitative systematic review conducted in Medline/PubMed, Lilacs, and Scielo electronic databases to identify studies meeting eligibility criteria. The strategy resulted in 1 672 unique articles, from which 164 were selected for full reading by a pair of reviewers.

Results

Fifty-five articles reported at least one cluster of genetic disorders or congenital anomalies in South American territory. From these papers, 122 clusters were identified, of which half (61) were related to autosomal recessive disorders. Sixty-five (53.3%) of the clusters were located in Brazil.

Conclusions

The results of the review reinforce that rare diseases and congenital anomalies can occur in a non-random way in space, which is discussed in the perspective of the complex history of formation, social organization, and genetic structure of the South American population. Mapping clusters in population medical genetics can be an important public health tool, given that such places concentrate cases of rare diseases that frequently require multiprofessional, specialized care. Therefore, these results can support important agendas in public health related to rare diseases and congenital anomalies, such as health promotion and surveillance.

L. Chitins and chitinase activity in airway diseases

Chitin, one of the most abundant biopolymers on Earth, is bound and degraded by chitinases, specialized enzymes that are similarly widespread in nature. Chitin catabolism affects global carbon and nitrogen cycles through a host of diverse biological processes, but recent work has focused attention on systems of chitin recognition and degradation conserved in mammals, connecting an ancient pathway of polysaccharide processing to human diseases influenced by persistent immune triggering. Here we review current advances in our understanding of how chitin-chitinase interactions affect mucosal immune feedback mechanisms essential to maintaining homeostasis and organ health.

Regulation and Role of Chitotriosidase during Lung Infection with Klebsiella pneumoniae

Chitinases and chitinase-like proteins are an evolutionary conserved group of proteins. In the absence of chitin synthesis in mammals, the conserved presence of chitinases suggests their roles in physiology and immunity, but experimental evidence to prove these roles is scarce. Chitotriosidase (chit1) is one of the two true chitinases present in mammals and the most prevalent chitinase in humans. In this study, we investigated the regulation and the role of chit1 in a mouse model of Klebsiella pneumoniae lung infection. We show that chitinase activity in bronchoalveolar lavage fluid is significantly reduced during K. pneumoniae lung infection. This reduced activity is inversely correlated with the number of neutrophils. Further, instilling neutrophil lysates in lungs decreased chitinase activity. We observed degradation of chit1 by neutrophil proteases. In a mouse model, chit1 deficiency provided a significant advantage to the host during K. pneumoniae lung infection by limiting bacterial dissemination. This phenotype was independent of inflammatory changes in chit1-/- mice as they exerted a similar inflammatory response. The decreased dissemination resulted in improved survival in chit1-/- mice infected with K. pneumoniae in the presence or absence of antibiotic therapy. The beneficial effects of chit1 deficiency were associated with altered Akt activation in the lungs. Chit1-/- mice induced a more robust Akt activation postinfection. The role of the Akt pathway in K. pneumoniae lung infection was confirmed by using an Akt inhibitor, which impaired health and survival. These data suggest a detrimental role of chit1 in K. pneumoniae lung infections.

Innate Immunity of the Lung: From Basic Mechanisms to Translational Medicine

The respiratory tract is faced daily with 10,000 L of inhaled air. While the majority of air contains harmless environmental components, the pulmonary immune system also has to cope with harmful microbial or sterile threats and react rapidly to protect the host at this intimate barrier zone. The airways are endowed with a broad armamentarium of cellular and humoral host defense mechanisms, most of which belong to the innate arm of the immune system. The complex interplay between resident and infiltrating immune cells and secreted innate immune proteins shapes the outcome of host-pathogen, host-allergen, and host-particle interactions within the mucosal airway compartment. Here, we summarize and discuss recent findings on pulmonary innate immunity and highlight key pathways relevant for biomarker and therapeutic targeting strategies for acute and chronic diseases of the respiratory tract.

Spontaneous Chitin Accumulation in Airways and Age-Related Fibrotic Lung Disease

The environmentally widespread polysaccharide chitin is degraded and recycled by ubiquitous bacterial and fungal chitinases. Although vertebrates express active chitinases from evolutionarily conserved loci, their role in mammalian physiology is unclear. We show that distinct lung epithelial cells secrete acidic mammalian chitinase (AMCase), which is required for airway chitinase activity. AMCase-deficient mice exhibit premature morbidity and mortality, concomitant with accumulation of environmentally derived chitin polymers in the airways and expression of pro-fibrotic cytokines. Over time, these mice develop spontaneous pulmonary fibrosis, which is ameliorated by restoration of lung chitinase activity by genetic or therapeutic approaches. AMCase-deficient epithelial cells express fibrosis-associated gene sets linked with cell stress pathways. Mice with lung fibrosis due to telomere dysfunction and humans with interstitial lung disease also accumulate excess chitin polymers in their airways. These data suggest that altered chitin clearance could exacerbate fibrogenic pathways in the setting of lung diseases characterized by epithelial cell dysfunction.

Genetic Variants in CHIA and CHI3L1 Are Associated with the IgE Response to the Ascaris Resistance Marker ABA-1 and the Birch Pollen Allergen Bet v 1

Helminth infections and allergic diseases are associated with IgE hyperresponsiveness but the genetics of this phenotype remain to be defined. Susceptibility to Ascaris lumbricoides infection and antibody levels to this helminth are associated with polymorphisms in locus 13q33-34. We aimed to explore this and other genomic regions to identify genetic variants associated with the IgE responsiveness in humans. Forty-eight subjects from Cartagena, Colombia, with extreme values of specific IgE to Ascaris and ABA-1, a resistance marker of this nematode, were selected for targeted resequencing. Burden analyses were done comparing extreme groups for IgE values. One-hundred one SNPs were genotyped in 1258 individuals of two well-characterized populations from Colombia and Sweden. Two low-frequency coding variants in the gene encoding the Acidic Mammalian Chitinase (CHIA rs79500525, rs139812869, tagged by rs10494133) were found enriched in high IgE responders to ABA-1 and confirmed by genetic association analyses. The SNP rs4950928 in the Chitinase 3 Like 1 gene (CHI3L1) was associated with high IgE to ABA-1 in Colombians and with high IgE to Bet v 1 in the Swedish population. CHIA rs10494133 and ABDH13 rs3783118 were associated with IgE responses to Ascaris. SNPs in the Tumor Necrosis Factor Superfamily Member 13b gene (TNFSF13B) encoding the cytokine B cell activating Factor were associated with high levels of total IgE in both populations. This is the first report on the association between low-frequency and common variants in the chitinases-related genes CHIA and CHI3L1 with the intensity of specific IgE to ABA-1 in a population naturally exposed to Ascaris and with Bet v 1 in a Swedish population. Our results add new information about the genetic influences of human IgE responsiveness; since the genes encode for enzymes involved in the immune response to parasitic infections, they could be helpful for understanding helminth immunity and allergic responses. We also confirmed that TNFSF13B has an important and conserved role in the regulation of total IgE levels, which supports potential evolutionary links between helminth immunity and allergic response.

Chitotriosidase Activity and Gene Polymorphism in Iranian Patients with Gaucher Disease and Sibling Carriers

OBJECTIVE

Chitotriosidase (CT) activity is a useful biomarker for diagnosis and monitoring of Gaucher disease (GD). Its application is limited by some variants in the CT gene. Two main polymorphisms are 24 bp duplication and G102S led to reduce CT activity. The aim of this study was to determine these variants influencing on plasma CT activity.

MATERIALS & METHODS

Blood samples were collected from 33 patients with GD, 15 sibling carriers and 105 healthy individuals serving as controls. CT activity was measured using 4-methylumbelliferyl-β-D-N,N',N″triacetylchitotrioside substrate in plasma samples. The CT genotypes of 24 bp duplication and G102S variants were determined using PCR and PCR-RFLP.

RESULTS

Untreated GD patients had a significantly higher CT activity compared to treated patients (P = 0.021). In addition, chitotriosidase activity in carriers was higher rather than controls. Allele frequencies of 24 bp duplication in GD patients, sibling carriers and controls were 0.21, 0.266 and 0.29 and for G102S were 0.318, 0.366 and 0.219, respectively. Different G102S genotypes had not significant effect on CT activity. Chitotriosidase activity has a positive correlation with age in normal group, carriers, and negative correlation with hemoglobin in GD patients. Using cut-off level of 80.75 nmol/ml/h, sensitivity and specificity of CT activity were 93.9% and 100%, respectively.

CONCLUSION

Chitotriosidase activity is a suitable biomarker for diagnosis and monitoring of GD. Determination of 24 bp duplication is helpful for more accurate monitoring the GD patient's therapy. However, it seems that, specifying of the G102S polymorphism is not required for Iranian GD patients.

Dup-24 bp in the CHIT1 Gene in Six Mexican Amerindian Populations

Chitotriosidase (CHIT, EC 3.2.1.14) is an enzyme secreted by activated macrophages with the ability to hydrolyze the chitin of pathogens. The high activity of this enzyme has been used as a secondary biomarker of response to treatment in patients with Gaucher disease (OMIM 230800). Within the world's population, approximately 6% is homozygous and 35% is heterozygous for the most common polymorphism in the CHIT1 gene, a 24-bp duplication (dup-24 bp), with homozygosity of this duplication causing inactivation of the enzyme but without major consequences for health. To determine the frequency of the dup-24 bp CHIT1 gene in indigenous populations from Mexico, 692 samples were analyzed: Purepecha (49), Tarahumara (97), Huichol (97), Mayan (139), Tenek (97), and Nahua (213). We found that the groups were in Hardy-Weinberg equilibrium. The dup-24 bp allele frequency was found to be (in order of highest to lowest) 37% (Mayan), 34% (Huichol and Nahua), 33% (Purepecha), 31% (Tenek), and 29% (Tarahumara).