N-glycosylation of plasma proteins as monitoring marker of metabolic syndrome

Abstract

Metabolički sindrom obuhvaća poremećaje poput visceralne pretilosti te inzulinske rezistencije koja često prethodi šećernoj bolesti tipa 2. Istraživanja su spomenute poremećaje povezala s promjenama N-glikozilacije proteina plazme, jedne od najčešćih i najkompleksnijih post-translacijskih modifikacija. Glavni ciljevi ovog doktorskog rada jesu identificirati N-glikanske strukture prisutne na proteinima plazme koje: a) omogućavaju predikciju i rano prepoznavanje pojedinaca s povećanim rizikom razvoja inzulinske rezistencije i šećerne bolesti tipa 2 i b) su povezane s indeksom tjelesne mase te pretilošću i promjenama indeksa tjelesne mase kod pojedinaca podvrgnutih operaciji želuca. Analizirani su uzorci krvne plazme oko 2 000 ispitanika iz TwinsUK registra sakupljani u više vremenskih točaka tijekom 20 godina pri čemu su bilježeni detaljni podaci o zdravstvenom statusu ispitanika poput dijagnoze inzulinske rezistencije i šećerne bolesti tipa 2, te uzorci krvne plazme 37 pretilih ispitanika okupljenih u Sveučilišnoj bolnici Oxford gdje su bili podvrgnuti restriktivnoj dijeti i operaciji želuca, a krv im je uzrokovana kontinuirano tijekom studije. Izolirani, pročišćeni te fluorescentno obilježeni N-glikani proteina plazme i imunoglobulina G analizirani su HILIC-UPLC metodom. Statistička obrada dobivenih rezultata pokazala je da se N-glikani proteina plazme u pojedinaca koji će razviti šećernu bolest tipa 2 i inzulinsku rezistenciju značajno razlikuju od ispitanika koji će ostati zdravi te se primijećene promjene počinju pojavljivati godinama prije službene dijagnoze što omogućuje uspješno pravovremeno identificiranje pojedinaca visokorizičnih za poremećaj u metabolizmu glukoze. Nadalje, opažene promjene N-glikana proteina plazme i imunoglobulina G u pretilih pojedinaca uslijed mršavljenja rezultat su podvrgavanja restriktivnoj dijeti i operaciji želuca. Iste promjene su primijećene i uslijed longitudinalnog praćenja pojedinaca kojima se mijenjao indeks tjelesne mase. Zaključno, primjenom N-glikana kao biljega ranog izdvajanja visokorizičnih pojedinaca te kao biljega praćenja metaboličkoga i upalnog statusa organizma, može se na vrijeme prevenirati i odgoditi razvoj ozbiljnih komorbiditeta koji se povezuju s metaboličkim sindromom, te čak i spriječiti pojavu samog sindroma, ali i pratiti učinkovitost terapijskog pristupa.Metabolic syndrome includes disorders such as visceral obesity and insulin resistance, which often precedes type 2 diabetes. Studies have linked these disorders to changes in plasma N-glycosylation, one of the most common and complex post-translational modifications. The main objectives of this study are to identify N-glycan structures present on plasma proteins that: a) allow prediction and early identification of individuals at increased risk of developing insulin resistance and type 2 diabetes and b) are associated with body mass index and obesity and body mass index changes in individuals undergoing bariatric surgery (restrictive gastric surgery). Blood plasma samples of about 2000 subjects from the TwinsUK registry collected at multiple time points over 20 years were analysed, recording detailed data on the health status of subjects, as well as blood plasma samples of 37 obese subjects gathered at the Oxford University Hospital where they were subjected to a restrictive diet and bariatric surgery, and their blood was sampled continuously throughout the study. Isolated, purified and fluorescently labelled plasma protein and immunoglobulin G N-glycans were analysed by HILIC-UPLC method. Statistical processing of the obtained results showed that plasma protein N-glycans in individuals to be diagnosed with type 2 diabetes and insulin resistance differ significantly from healthy controls, and that the observed changes begin to appear years before official diagnosis, which allows successful timely identification of individuals at high risk of impaired glucose metabolism. Furthermore, observed significant changes in plasma and immunoglobulin G N-glycans in obese individuals due to weight loss are the result of being subjected to a low-calorie, restrictive diet and bariatric surgery. The same changes were observed due to longitudinal follow-up of individuals with changes in their body mass index. In conclusion, the use of N-glycans as markers of timely identification of high-risk individuals and as monitoring markers of metabolic and inflammatory status of the organism, can prevent and delay the development of serious comorbidities associated with metabolic syndrome, and even prevent the occurrence of the syndrome itself, but also can monitor the efficacy of used therapeutic approach