In the century-long evolution of insulin pharmaceuticals, each transformative advancement in this drug class has been closely tied to the ability to obtain new insulin isoforms for research. Despite this, the recently discovered naturally occurring isoforms of glycosylated human insulin have remained largely unattainable for proper characterization. Herein, we demonstrate for the first time that total chemical synthesis can be used to generate all isoforms. This achievement required maintaining the correct positions of the interchain disulfide bonds while effectively removing protecting groups on complex glycans. Notably, the availability of seven glycoforms reveals the important effects of natural sialylated glycans in suppressing insulin self-association and enhancing its solubility, surpassing the performance of currently employed rapid-acting insulin drugs. This work not only offers a readily adaptable platform for exploring natural O-glycosylation in other therapeutic proteins and peptides but also lays the groundwork for further research into harnessing natural glycosylation for therapeutic applications.

A total of 1151 subjects were enrolled in this study.Metabolic syndrome (MS) was diagnosed according to the International Diabetes Federation (IDF) criteria.Significant differences in waist circumference,body mass index(BMI),diastolic blood pressure(DBP),systolic blood pressure(SBP),fat mass,Fat％ in different serum TSH levels were found.There were positive relation between fasting plasma glucose,DBP,SBP,and serum FT4 levels,between high density lipoprotein-cholesterol,DBP,SBP,waist circumference,fat mass,Fat％,and serum FT3 levels,even after adjustment for age and sex.Serum FT3 and FT4 levels were higher in the MS group than those in the control group.