The cost of diabetic foot ulcers and amputations to the National Health Service in England.

AIM: To estimate the healthcare costs of diabetic foot disease in England. METHODS: Patient-level data sets at a national and local level, and evidence from clinical studies, were used to estimate the annual cost of health care for foot ulceration and amputation in people with diabetes in England in 2014-2015. RESULTS: The cost of health care for ulceration and amputation in diabetes in 2014-2015 is estimated at between £837 million and £962 million; 0.8% to 0.9% of the National Health Service (NHS) budget for England. More than 90% of expenditure was related to ulceration, and 60% was for care in community, outpatient and primary settings. For inpatients, multiple regression analysis suggested that ulceration was associated with a length of stay 8.04 days longer (95% confidence interval 7.65 to 8.42) than that for diabetes admissions without ulceration. CONCLUSIONS: Diabetic foot care accounts for a substantial proportion of healthcare expenditure in England, more than the combined cost of breast, prostate and lung cancers. Much of this expenditure arises through prolonged and severe ulceration. If the NHS were to reduce the prevalence of diabetic foot ulcers in England by one-third, the gross annual saving would be more than £250 million. Diabetic foot ulceration is a large and growing problem globally, and it is likely that there is potential to improve outcomes and reduce expenditure in many countries.

In vivo glycosylation of mucin tandem repeats.

The biochemical and biophysical properties of mucins are largely determined by extensive O-glycosylation of serine- and threonine-rich tandem repeat (TR) domains. In a number of human diseases aberrant O-glycosylation is associated with variations in the properties of the cell surface-associated and secreted mucins. To evaluate in vivo the O-glycosylation of mucin TR domains, we generated recombinant chimeric mucins with TR sequences from MUC2, MUC4, MUC5AC, or MUC5B, which were substituted for the native TRs of epitope-tagged MUC1 protein (MUC1F). These hybrid mucins were extensively O-glycosylated and showed the expected association with the cell surface and release into culture media. The presence of different TR domains within the chimeric mucins appears to have limited influence on their posttranslational processing. Alterations in glycosylation were detailed by fast atom bombardment mass spectrometry and reactivity with antibodies against particular blood-group and tumor-associated carbohydrate antigens. Future applications of these chimeras will include investigations of mucin posttranslational modification in the context of disease.

Genetic remodeling of protein glycosylation in vivo induces autoimmune disease.

Autoimmune diseases are among the most prevalent of afflictions, yet the genetic factors responsible are largely undefined. Protein glycosylation in the Golgi apparatus produces structural variation at the cell surface and contributes to immune self-recognition. Altered protein glycosylation and antibodies that recognize endogenous glycans have been associated with various autoimmune syndromes, with the possibility that such abnormalities may reflect genetic defects in glycan formation. We show that mutation of a single gene, encoding alpha-mannosidase II, which regulates the hybrid to complex branching pattern of extracellular asparagine (N)-linked oligosaccharide chains (N-glycans), results in a systemic autoimmune disease similar to human systemic lupus erythematosus. alpha-Mannosidase II-deficient autoimmune disease is due to an incomplete overlap of two conjoined pathways in complex-type N-glycan production. Lymphocyte development, abundance, and activation parameters are normal; however, serum immunoglobulins are increased and kidney function progressively falters as a disorder consistent with lupus nephritis develops. Autoantibody reactivity and circulating immune complexes are induced, and anti-nuclear antibodies exhibit reactivity toward histone, Sm antigen, and DNA. These findings reveal a genetic cause of autoimmune disease provoked by a defect in the pathway of protein N-glycosylation.

FAB-MS characterization of sialyl Lewis x determinants on polylactosamine chains of human airway mucins secreted by patients suffering from cystic fibrosis or chronic bronchitis.

Although a large body of structural data exists for bronchial mucins from cystic fibrosis (CF) and chronic bronchitis (CB) patients, little is known about terminal structures carried on poly-N-acetyllactosamine antennae. Such structures are of interest because they are potential ligands for bacterial adhesins and other lectins. In this study, we have used fast atom bombardment mass spectrometry (FAB-MS) to examine terminal sequences released by endo-beta-galactosidase from O-glycans obtained by reductive elimination of bronchial mucins purified from the sputum of 8 CF and 8 CB patients. Our data show that, although the polylactosamine antennae of CF and CB mucins have several terminal sequences in common, they differ significantly in their sialyl Lewis(x) (NeuAcalpha2-3Galbeta1-4[Fucalpha1-3]GlcNAcbeta1-) content. Thus all examined mucins from CF patients carry sialyl Lewis(x) on their polylactosamine antennae, whereas this type of epitope is present on only three out of the eight CB mucins examined, notably in the airways of one CB patient which were heavily infected by Pseudomonas aeruginosa as are the airways of all the CF patients. This suggests that, in airway mucins, the expression of sialyl Lewis(x) on polylactosamine antennae is probably more related to inflammation and infection than to a direct effect of the CF defect.

Modeling human congenital disorder of glycosylation type IIa in the mouse: conservation of asparagine-linked glycan-dependent functions in mammalian physiology and insights into disease pathogenesis.

The congenital disorders of glycosylation (CDGs) are recent additions to the repertoire of inherited human genetic diseases. Frequency of CDGs is unknown since most cases are believed to be misdiagnosed or unrecognized. With few patients identified and heterogeneity in disease signs noted, studies of animal models may provide increased understanding of pathogenic mechanisms. However, features of mammalian glycan biosynthesis and species-specific variations in glycan repertoires have cast doubt on whether animal models of human genetic defects in protein glycosylation will reproduce pathogenic events and disease signs. We have introduced a mutation into the mouse germline that recapitulates the glycan biosynthetic defect responsible for human CDG type IIa (CDG-IIa). Mice lacking the Mgat2 gene were deficient in GlcNAcT-II glycosyltransferase activity and complex N-glycans, resulting in severe gastrointestinal, hematologic, and osteogenic abnormalities. With use of a lectin-based diagnostic screen for CDG-IIa, we found that all Mgat2-null mice died in early postnatal development. However, crossing the Mgat2 mutation into a distinct genetic background resulted in a low frequency of survivors. Mice deficient in complex N-glycans exhibited most CDG-IIa disease signs; however, some signs were unique to the aged mouse or are prognostic in human CDG-IIa. Unexpectedly, analyses of N-glycan structures in Mgat2-null mice revealed a novel oligosaccharide branch on the "bisecting" N-acetylglucosamine. These genetic, biochemical, and physiologic studies indicate conserved functions for N-glycan branches produced in the Golgi apparatus among two mammalian species and suggest possible therapeutic approaches to GlcNAcT-II deficiency. Our findings indicate that human genetic disease due to aberrant protein glycosylation can be modeled in the mouse to gain insights into N-glycan-dependent physiology and the pathogenesis of CDG-IIa.

Structural analysis of sequences O-linked to mannose reveals a novel Lewis X structure in cranin (dystroglycan) purified from sheep brain.

The Lewis X epitope, Galbeta1-4(Fucalpha1-3)GlcNAc-R, has been implicated in cell-cell recognition events in a number of systems including the central nervous system and is expressed on diverse glycoconjugates including cell adhesion molecules, glycolipids, and the proteoglycan phosphacan. Although Lewis X sequences 3-linked to mannose have been described within proteoglycan fractions of mammalian brain, these have not been reported in other contexts and have been widely believed to be peculiar constituents of brain proteoglycans. In the present paper, we confirm the existence of Lewis X structures O-linked to mannose within the mammalian brain, demonstrate that these structures are present on a well defined mucin-like glycoprotein, cranin (dystroglycan), and report studies suggesting that the linkages involved may be predominantly 2-linked to mannose. Mannose-linked Lewis X is the latest in an increasing list of oligosaccharide recognition "tags" that have been shown to be expressed on cranin (dystroglycan) purified from brain.