The main purpose of this study is to study the phenomenon of insulin resistance in patients after carotid revascularization surgery through population-based, randomized, double-blind, placebo-controlled trial.

Trial Title: Insulin Resistance in Patients After Carotid Revascularization. Protocol: Investigators recruited eligible Han Chinese participants (aged 40-80) who were diagnosed with carotid stenosis and had indications for carotid revascularization surgery. Participants were excluded if participants had undergone surgical contraindication, or psychiatric disorders, or cancer, or pregnant, or lactating, or taking antipsychotic drugs during perioperative period. Participants were randomly divided into groups of oral melatonin, and blank control. Participants in groups of oral melatonin took melatonin orally 6mg/day from 3 days before operation to 3 days after operation. Blood samples (about 6 milliliter) were taken at baseline, the first, the second, and the third morning after the operation, all in the fasting state. Through a series hospital clinical laboratory and related ELISA kits to detect the insulin, C-peptide and glucose in serum. Superoxide dismutase (SOD), malonaldehyde (MDA), catalase(CAT), endothelial nitric oxide synthase (eNOS), Interleukin 6 (IL-6), tumour necrosis factor(TNF-α), were included for analysis to verify whether melatonin have protective effect for inflammation and oxidative stress in patients under carotid revascularization, which might be the mechanism of insulin resistance after surgery. This trial is approved by the Ethics Committee of Peking Union Medical College Hospital (No. ZS-1468). All participants completed a questionnaire and signed an informed consent document. Otherwise, participants will get appropriate economic compensation. Trial associates monitored compliance with the masking procedure throughout the trial. All participants and study investigators were unaware of treatment allocation throughout the study. The randomization codes remained sealed until after data collection and cleaning, and completion of a masked analysis. The study team monitored and classified protocol deviations. Investigators summarized baseline clinical and demographic characteristics with descriptive statistics and then determined by the Univariate Analysis of Variance. All the data analyses were done using statistical software SPSS 20.0.

Expected results: Postoperative levels of insulin resistance in both groups are higher than the preoperative. Compared with the blank control group, patients taking melatonin might have lower postoperative levels of insulin resistance, inflammation and oxidative stress.

Consent document: The potential risk, research as a treatment drug of melatonin may delay the metabolism of antipsychotic antipsychotic drug, so when investigators recruit psychiatric disorders or taking antipsychotic drugs orally during the 2 weeks of the trial should exclusion. As a Health care medicine, Melatonin is not suitable for children, so investigators selected recruiting participants under the age of 40 to 80.

The measure to minimize the risk, fully inform the participants and their families the trial's advantages, disadvantages and desired effect. All participants totally agree with the subjects. In this process, at least three or more effective way to get contact with the medical staff or doctor and ensure that those unexpected accident should deserve effective tackle. Participants guarantee to comply with the criterion before start of the trial. Our research involves the application of melatonin is through the china food and drug administration (CFDA) approved to ensure its safety (include its chemical composition, structure, content parameters, main raw material and appropriate crowd). All staff is qualified medical professionals to guarantee the safety of all participants.

The potential risks or discomfort, or inconvenience, or benefits for participants: So far, effective of melatonin in human include regulating sleep, anti-tumor, immune regulation, regulating of inflammation and immune and regulating blood lipid metabolism is confirmed. Adverse reactions is the delay of antipsychotic drug metabolism (so nearly one month ago and during period of the trial participants should not taking antipsychotic drugs) during the trial. The basic principle during the trial is ensure safety of participants.

The relevant content consultation: Everyone have the right to consultation the research content through telephone: +86 01069152500 (principal investigator) and +86 01069155817(Ethics committee).

The rights of withdrew from the trial: Participate in the trial is completely voluntary. If for any reason, participants not willing to participate in, or do not wish to continue to participate in this trial, will not affect the rights and interests of participants. In addition, participants have the right to withdraw this trial at any time. If participants do not accord to the doctor instructions, or for the sake of patients' health and benefits, the doctor or the researchers may also require participants to quit the trial.

The compensation of research: If the participants have any unexpected accident relation with the trial, the compensation and responsibility will be provided by Peking Union Medical College Hospital.

Privacy protection: The privacy of every participant will be protected. The results of the trial in academic publications will not leak any information to identify your personal identity. Peking Union Medical College Hospital will save everybody's data and guarantee not leak without authorization.

Investigators declare no competing interests.

Inclusion Criteria:

• diagnosed with carotid stenosis
• had indications for carotid revascularization

Exclusion Criteria:

• surgical contraindication
• cardiovascular disease
• psychiatric disorders
• cancer
• pregnant
• lactating
• taking antipsychotic drugs during perioperative period
• history of trauma during perioperative period