A Pilot Study to Evaluate the Glucagon-Like Peptide 1 Response to the Challenge of Mixed Meals in Chinese Subjects
Condition: Healthy
Study type: Observational

Summary: 
      The purpose of the study is to standardize a meal test to facilitate future studies of the
      postprandial glucagons-like peptide 1 (GLP-1) response in Chinese subjects. Eighteen healthy
      Chinese subjects, aged between 20-65 years old, without history of diabetes, will be
      recruited for the study. Each subject will receive two mixed meal tests for postprandial
      GLP-1 excursion at random order: 60 % carbohydrate (CHO)/20 % fat vs. 50 % CHO/30 % fat. The
      postprandial glucose, insulin, glucagon and other related hormones responses will also be
      measured. Through the study, we hope to build up a platform for the study of the postprandial
      GLP-1 response and insulin secretion.
    

Detailed description: 
      Glucagon-like peptide 1 (GLP-1) is a 30-amino acid peptide produced in the intestinal
      epithelial endocrine L-cells. It stimulates insulin and suppresses glucagons secretion,
      inhibits gastric emptying, and reduces appetite and food intake. In the fasting state, the
      plasma concentrations of GLP-1 are very low. Levels of circulating GLP-1 rise rapidly after
      food intake. The GLP-1 meal response depends on ingested nutrients. Carbohydrates are strong
      stimuli of GLP-1 release. Protein stimulates GLP-1 release, even more than carbohydrates.
      GLP-1 concentrations also increase after intake of fat, although the elevation is delayed
      compared to the stimulation of carbohydrates. Dietary fibers may also modify the postprandial
      GLP-1 response. Therefore, it is essential for us to characterize nutrient compositions of
      test meals for further studies of meal response of GLP-1.

      Other sampling conditions of the meal tests are also needed to be taking care of. GLP-1 is
      rapidly degraded by the enzyme dipeptidyl peptidase IV (DPP-4). During the meal tests, it is
      important adding enzyme inhibitors into sampling tubes to avoid hormone degradation. Lugari
      et al. collected blood samples into tubes containing EDTA and aprotinin during a meal test.
      They could obtain samples from the same tube for both glucagons and GLP-1 assays. Other study
      groups reported that samples for GLP-1 needed to be collected into Vacutainer tubes prepared
      with EDTA and DPP-4 inhibitor for preventing degradation of GLP-1. Another aim of the present
      study is to compare the differences in GLP-1 concentrations in samples collected by EDTA
      tubes containing aprotinin or a DPP-4 inhibitor during the meal tests.

      Racial differences in GLP-1 levels during oral glucose challenge have been demonstrated
      recently that severely obese African Americans exhibited lower GLP-1 concentrations than
      Caucasians. It is worthwhile to examine the meal response of GLP-1 across ethnicities. The
      current study proposes to observe the GLP-1 response during standardized meal tests in a
      group of Chinese subjects.

      The purpose of the study is to standardize a meal test to facilitate future studies of the
      postprandial GLP-1 response in Chinese subjects. Eighteen healthy Chinese subjects, aged
      between 20-65 years old, without history of diabetes, will be recruited for the study. Each
      subject will receive two mixed meal tests for postprandial GLP-1 excursion at random order:
      60 % carbohydrate (CHO)/20 % fat vs. 50 % CHO/30 % fat. The postprandial glucose, insulin,
      glucagon and other related hormones responses will also be measured. Through the study, we
      hope to build up a platform for the study of the postprandial GLP-1 response and insulin
      secretion.
    

Observational model: Cohort
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        Invited normal healthy volunteers from a research clinic
      
Biospecimen description: 
      Plasma samples retained, with no potential for DNA extraction from any retained samples. The
      retained samples will be destroyed after the results published.
    
Keywords: Chinese; Glucagon-like peptide 1; Glucagon; Insulin; Mixed meals; Healthy Adults