Diabetes is one of the most common and challenging health problems. Studies in several nations show that polymorphisms within the transcription factor 7-like 2 genes could be associated with type 2 diabetes (T2D). Therefore, a case-control study was conducted to find the association between SNP rs7903146 and T2D in our population. The study consists of 110 patients referring to clinic and 80 healthy controls randomly selected based on WHO guideline. DNA was extracted from blood and genotyped by PCR-RFLP with specific primers to amplify a fragment for restriction enzyme (RsaI). A chi-square test was calculated to compare the proportions of genotypes or alleles. Using a logistic regression model, the odds ratio for risk of developing T2D was calculated with and without adjustment for age, sex, and BMI. The frequency of the T allele of rs7903146 (C/T) polymorphism was significantly higher in diabetic subjects (47.3%) compared to that in normal subjects (34.4%). Logistic regression analysis of the rs7903146 polymorphism showed that the odds ratio was 3.71(95% CI: 1.43-9.56; P: 0.008) for the TT genotype and 1.26 (95% CI: 0.67-2.39; P: 0.516) for the CT genotype when compared with the CC genotype. Odds ratio adjusted for age, sex, and BMI have shown similar results. The results show that rs7903146 of TCF7L2 gene is an important susceptibility gene for T2D mellitus in the province of Isfahan, Iran. Our results support the recent findings that rs7903146 of TCF7L2 gene is an important genetic risk factor for the development of T2D in multiple ethnic groups.

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Pronase digestion Anion-exchange chromatography Highlights• Protocol developed to structurally characterize glycosaminoglycans of proteoglycans.• Comprehensive characterization of cellular glycosaminoglycan structures.• Relative quantification of nonreducing end, internal, and linkage region domains.• Overall chondroitin/dermatan sulfate glycosaminoglycan structures of chromogranin-A.

Proteoglycans (PGs) are proteins with glycosaminoglycan (GAG) chains, such as chondroitin sulfate (CS) or heparan sulfate (HS), attached to serine residues. We have earlier shown that prohormones can carry CS, constituting a novel class of PGs. The mapping of GAG modifications of proteins in endocrine cells may thus assist us in delineating possible roles of PGs in endocrine cellular physiology. With this aim, we applied a glycoproteomic approach to identify PGs, their GAG chains and their attachment sites in insulin-secreting cells. Glycopeptides carrying GAG chains were enriched from human pancreatic islets, rat (INS-1 832/13) and mouse (MIN6, NIT-1) insulinoma cell lines by ion exchange chromatography, depolymerized with GAG lyases, and analyzed by nanoflow liquid chromatography–tandem mass spectrometry (nLC-MS/MS). We identified CS modifications of chromogranin-A (CgA), islet amyloid polypeptide, secretogranin-1 and secretogranin-2, immunoglobulin superfamily member 10, and protein AMBP. Additionally, we identified two HS-modified prohormones (CgA and secretogranin-1), which was surprising, as prohormones are not typically regarded as HSPGs. For CgA, the glycosylation site carried either CS or HS, making it a so-called hybrid site. Additional HS sites were found on syndecan-1, syndecan-4, nerurexin-2, protein NDNF, and testican-1. These results demonstrate that several prohormones, and other constituents of the insulin-secreting cells are PGs. Cell-targeted mapping of the GAG glycoproteome forms an important basis for better understanding of endocrine cellular physiology, and the novel CS and HS sites presented here provide important knowledge for future studies.

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Chondroitin sulfate proteoglycans (CSPGs) are found at cell surfaces and in connective tissues, where they interact with a multitude of proteins involved in various pathophysiological processes. From a methodological perspective, the identification of CSPGs is challenging, as the identification requires the combined sequencing of specific core proteins, together with the characterization of the CS polysaccharide modification(s). According to the current notion of CSPGs, they are often considered in relation to a functional role in which a given proteoglycan regulates a specific function in cellular physiology. Recent advances in glycoproteomic methods have, however, enabled the identification of numerous novel chondroitin sulfate core proteins, and their glycosaminoglycan attachment sites, in humans and in various animal models. In addition, these methods have revealed unexpected structural complexity even in the linkage regions. These findings indicate that the number and structural complexity of CSPGs are much greater than previously perceived. In light of these findings, the prospect of finding additional CSPGs, using improved methods for structural and functional characterizations, and studying novel sample matrices in humans and in animal models is discussed. Further, as many of the novel CSPGs are found in low abundance and with not yet assigned functions, these findings may challenge the traditional notion of defining proteoglycans. Therefore, the concept of proteoglycans is considered, discussing whether “a proteoglycan” should be defined mainly on the basis of an assigned function or on the structural evidence of its existence.

In recent years, several rational designed therapies have been developed for treatment of mucopolysaccharidoses (MPS), a group of inherited metabolic disorders in which glycosaminoglycans (GAGs) are accumulated in various tissues and organs. Thus, improved disease-specific biomarkers for diagnosis and monitoring treatment efficacy are of paramount importance. Specific non-reducing end GAG structures (GAG-NREs) have become promising biomarkers for MPS, as the compositions of the GAG-NREs depend on the nature of the lysosomal enzyme deficiency, thereby creating a specific pattern for each subgroup. However, there is yet no straightforward clinical laboratory platform which can assay all MPS-related GAG-NREs in one single analysis. Here, we developed and applied a GAG domain mapping approach for analyses of urine samples of ten MPS patients with various MPS diagnoses and corresponding aged-matched controls. We describe a nano-LC–MS/MS method of GAG-NRE profiling, utilizing 2-aminobenzamide reductive amination labeling to improve the sensitivity and the chromatographic resolution. Diagnostic urinary GAG-NREs were identified for MPS types IH/IS, II, IIIc, IVa and VI, corroborating GAG-NRE as biomarkers for these known enzyme deficiencies. Furthermore, a significant reduction of diagnostic urinary GAG-NREs in MPS IH (n = 2) and MPS VI (n = 1) patients under treatment was demonstrated. We argue that this straightforward glycomic workflow, designed for the clinical analysis of MPS-related GAG-NREs in one single analysis, will be of value for expanding the use of GAG-NREs as biomarkers for MPS diagnosis and treatment monitoring.