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Abstract Background N-glycosylation is one of the most important post-translational modifications. Many studies have shown that N-glycosylation has a significant effect on the secretion level of heterologous glycoproteins in yeast cells. However, there have been few studies reporting a clear and unified explanation for the intracellular mechanism that N-glycosylation affect the secretion of heterologous glycoproteins so far. Pichia pastoris is an important microbial cell factory producing heterologous protein. It is of great significance to study the effect of N-glycosylation on the secretion level of heterologous protein. Camel chymosin is a glycoprotein with higher application potential in cheese manufacturing industry. We have expressed camel prochymosin in P. pastoris GS115, but the lower secretion level limits its industrial application. This study attempts to increase the secretion level of prochymosin through N-glycosylation, and explore the molecular mechanism of N-glycosylation affecting secretion. Results Adding an N-glycosylation site at the 34th amino acid of the propeptide of prochymosin significantly increased its secretion in P. pastoris. N-glycosylation improved the thermostability of prochymosin without affecting the enzymatic activity. Immunoprecipitation coupled to mass spectrometry (IP-MS) analysis showed that compared with the wild prochymosin (chy), the number of proteins interacting with N-glycosylated mutant (chy34) decreased, and all differential interacting proteins (DIPs) were down-regulated in chy34-GS115 cell. The DIPs in endoplasmic reticulum were mainly concentrated in the misfolded protein pathway. Among the five DIPs in this pathway, overexpression of BiP significantly increased the secretion of chy. The knockout of the possible misfolded protein recognition elements, UDP-glycose:glycoprotein glucosyltransferase 1 and 2 (UGGT1/2) had no effect on the growth of yeast cells and the secretion of prochymosin. Conclusions In conclusion, N-glycosylation increased the secretion of prochymosin in P. pastoris trough the adjustment of intracellular interacted proteins. The results of our study may help to elucidate the molecular mechanism of N-glycosylation affecting secretion and provide a new research method to improve the secretion of heterologous glycoprotein in P. pastoris.

Abstract Background Chitosan supplementation has been shown to modulate glycemic levels; however, studies have reported conflicting results. The present meta-analysis with trial sequential analysis was conducted to verify the overall influence of chitosan on glycemic levels in patients with metabolic syndrome. Methods The PubMed, Cochrane library, and EMBASE databases were systematically searched for randomized controlled studies of chitosan intake and glycemic levels. Results A total of ten clinical trials including 1473 subjects were included in this meta-analysis. Pooled effect sizes were determined by random-effects meta-analysis. Subgroup analysis was performed to analyze the sources of heterogeneity and their influence on the overall results. The results revealed a significant reduction in fasting glucose levels (SMD: − 0.39 mmol/L, 95% CI: − 0.62 to − 0.16) and hemoglobin A1c (HbA1c) levels (SMD: -1.10; 95% CI: − 2.15 to − 0.06) following chitosan supplementation but no effect on insulin levels (SMD: − 0.20 pmol/L, 95% CI: − 0.64 to 0.24). Subgroup analyses further demonstrated significant reductions in fasting glucose levels in subjects administered 1.6–3 g of chitosan per day and in studies longer than 13 weeks. Trial sequential analysis of the pooled results of the hypoglycemic effect demonstrated that the cumulative Z-curve crossed both the conventional boundary and trial sequential monitoring boundary for glucose and HbA1c. Conclusions The glucose level of patients who are diabetic and obese/overweight can be improved by supplementation with chitosan for at least 13 weeks at 1.6–3 g per day. Additional clinical research data are needed to confirm the role of chitosan, particularly in regulating glycosylated hemoglobin and insulin.

Abstract Background To further explore characteristics of myopia and changes in factors associated with myopia among students at Inner Mongolia Medical University. Methods Two cross-sectional censuses were conducted in 2011 and 2013. Participants were medical students residing on campus in 2011 and 2013. Logistic regression analysis was performed to ascertain associations with basic information, genetic factors, environmental factors. The χ2 test was used to test for differences in prevalence between 2011 and 2013. Prevalence was calculated at various myopia occurrence times among different parental myopia statuses. Results A total of 11,138 students enrolled from 2007 to 2012 completed the questionnaire. The prevalence of myopia in 2011 and 2013 was 70.50% and 69.21%, respectively, no statistically significant difference existed between the two censuses (p = 0.12). Both censuses were completed by 1015 students. There were no differences among the various year of study in 2011 or 2013. Myopic prevalence increased with an increased number of myopic parents: the prevalence if both parents were myopic was over 90%, nearly 80% if one parent was myopic, and less than 70% with non-myopic parents (p