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Urinary excretion of sulphated N-acetylhexosamines in patients with various mucopolysaccharidoses.

ABSTRACT: Sulphated N-acetylhexosamines have been isolated from human urine and tentatively identified as N-acetylglucosamine 6-sulphate (GlcNAc6S), N-acetylgalactosamine 6-sulphate (GalNAc6S), N-acetylgalactosamine 4-sulphate (GalNAc4S) and N-acetylgalactosamine 4,6-disulphate (GalNAc4,6diS). Urine from mucopolysaccharidosis-Type-IIID, -IVA and -VI patients compared with that from normal individuals contains elevated levels of GlcNAc6S (380-fold), GalNAc6S (180-fold) and GalNAc4S (420-fold) respectively. Urine from mucopolysaccharidosis-Type-VI patients also contain more than 600 times the normal level of GalNAc4,6diS. Urine from a mucolipidosis-Type-II and a multiple-sulphatase-deficient patient, and, in general, all mucopolysaccharidosis patients studied, contain at least 5-10-fold elevations of sulphated N-acetylhexosamines over the levels detected in urine from normal controls and a alpha-mannosidosis patient. Urine from patients with clinically mild phenotypes contains less sulphated N-acetylhexosamines than isolated from urine of clinically severe mucopolysaccharidosis patients. The source of the four sulphated N-acetylhexosamines is not known. However, incubation of a series of oligosaccharide substrates, derived from keratan sulphate and chondroitin 6-sulphate and containing non-reducing-end beta-linked 6-sulphated N-acetylhexosamine residues, with homogenates of cultured human skin fibroblasts has indirectly been shown to release GlcNA6S and GalNAc6S respectively. Release of GalNAc4S could not be demonstrated in similar incubations of oligosaccharide substrates derived from chondroitin 4-sulphate and containing non-reducing-end beta-linked GalNAc4S residues. We propose that some, if not all, of the sulphated N-acetylhexosamine present in human urine is derived from the action of beta-N-acetylhexosaminidase on sulphated GlcNAc or GalNAc residues at the non-reducing end of keratan sulphate, dermatan sulphate or chondroitin sulphate.

SUBMITTER: Hopwood JJ

PROVIDER: S-EPMC1145099 | biostudies-other | 1985 Aug

REPOSITORIES: biostudies-other

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Project description:The role of retinal vasculature's dysfunction in the physiopathology of Diabetic Retinopathy (DR) has been extensively described. Recently, the existence of a diabetic choroidal vasculopathy has been proposed. The purpose of this study was to compare choroidal thickness (CT) in nondiabetic patients and in type 2 diabetic patients without retinopathy, using EDI SD-OCT. Additionally, considering the diabetic patient group, compare CT in patients with and without microalbuminuria. This retrospective study selected patients sent from primary health-care centers as part of the national screening of diabetic retinopathy. Inclusion criteria were diagnosis of type 2 diabetes mellitus, absence of diabetic retinopathy, and a 24 hours urinary albumin measurement in the last 3 months at the primary health-care center. Nondiabetic patients were selected from a database in the ophthalmology department, and only healthy patients were included. At the screening visit, all patients performed a complete ophthalmologic examination by the same examiner. All eyes were examined with SD- OCT, and all scans were performed in the EDI mode. Measurements were made at three points: subfoveal, 1500??m temporally and nasally to the foveal center. We included 110 eyes of 110 diabetic patients without diabetic retinopathy and 30 eyes of 30 healthy controls. Mean subfoveal CT was greater in diabetic patients without retinopathy (with normoalbuminuria or microalbuminuria) when compared with nondiabetic patients (p < 0.05). In diabetic patients without retinopathy, the subfoveal and temporal choroid was thicker among patients with microalbuminuria when compared with those of normoalbuminuric patients (p < 0.05). The subfoveal and temporal choroid was thicker among diabetic patients with microalbuminuria compared with nondiabetic patients. (p < 0.05). This study suggests that choroidal changes are present in type 2 diabetic patients even before the clinical development of retinopathy.

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Urinary excretion of sulphated N-acetylhexosamines in patients with various mucopolysaccharidoses.

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