title: Circulating glucagon-like peptide-1 increases in response to short-term overfeeding in men.
abstract: BACKGROUND
  Glucagon-like Peptide-1 (GLP-1) is an incretin hormone secreted from the gastrointestinal tract that facilitates the glucose-dependent insulin response. Additionally, GLP-1 is thought to be involved in energy homeostasis. Currently little is known about GLP-1's responsiveness to an energy surplus, a fundamental cause of obesity and diabetes. Our objective was to examine the response of serum GLP-1 to short-term (7 day) overfeeding in young men.
  
  
  METHODS
  Seventy-two young men from the Canadian province of Newfoundland were recruited for the study. For 7-days, the subjects consumed 70% more calories than required at baseline.Various measurements including: anthropometrics, body composition, markers of glucose/lipid metabolism and serum total GLP-1, were taken at a fasted state before (day 1) and after (day 8) the challenge. Paired t-test analyses were used to assess the change in variables after the overfeeding period. Additionally, the relationship between serum GLP-1 and the measured variables at baseline and change due to overfeeding were analyzed.
  
  
  RESULTS
  Serum GLP-1 was significantly increased in all groups in response to the 7-day energy surplus, indicating the increase was independent of adiposity status. There was no significant difference in fasting GLP-1 at baseline between the normal weight and overweight/obese groups. At baseline, GLP-1 concentration negatively correlated with HDL-cholesterol and positively correlated with triacylglycerols and markers of insulin resistance in the overweight/obese group. Also GLP-1 was negatively correlated with change in percent gynoid fat in the overweight/obese subjects. Percent change in GLP-1 was negatively associated with percent change in gynoid fat in the normal weight group and positively associated with percent change in cholesterol in the overweight/obese group. Percentage change of circulating triacylglycerols was positively associated with percent change in GLP-1 in both adiposity groups.
  
  
  CONCLUSIONS
  Our findings showed that GLP-1 serum concentration is not a significant factor in determining obesity status. The increase of GLP-1 in all subjects regardless of obesity status, suggest GLP-1 serves as a protective role, counteracting energy surplus.
authors.affiliation: Division of Medicine, Faculty of Medicine, Health Sciences Center, Memorial University of Newfoundland, 300 Prince Phillip Drive, St, John's, NL, A1B 3V6, Canada. gsun@mun.ca.
authors.forename: Danny
authors.initials: D
authors.lastname: Wadden
authors.forename: Farrell
authors.initials: F
authors.lastname: Cahill
authors.forename: Peyvand
authors.initials: P
authors.lastname: Amini
authors.forename: Edward
authors.initials: E
authors.lastname: Randell
authors.forename: Sudesh
authors.initials: S
authors.lastname: Vasdev
authors.forename: Yanqing
authors.initials: Y
authors.lastname: Yi
authors.forename: Jon
authors.initials: J
authors.lastname: Church
authors.forename: Guang
authors.initials: G
authors.lastname: Sun