title: Caffeine ingestion decreases glucose disposal during a hyperinsulinemic-euglycemic clamp in sedentary humans.
abstract: The purpose of this investigation was to examine the effect of caffeine (an adenosine receptor antagonist) on whole-body insulin-mediated glucose disposal in resting humans. We hypothesized that glucose disposal would be lower after the administration of caffeine compared with placebo. Healthy, lean, sedentary (n = 9) men underwent two trial sessions, one after caffeine administration (5 mg/kg body wt) and one after placebo administration (dextrose) in a double-blind randomized design. Glucose disposal was assessed using a hyperinsulinemic-euglycemic clamp. Before the clamp, there were no differences in circulating levels of methylxanthines, catecholamines, or glucose. Euglycemia was maintained throughout the clamp with no difference in plasma glucose concentrations between trials. The insulin concentrations were also similar in the caffeine and placebo trials. After caffeine administration, glucose disposal was 6.38 +/- 0.76 mg/kg body wt compared with 8.42 +/- 0.63 mg/kg body wt after the placebo trial. This represents a significant (P < 0.05) decrease (24%) in glucose disposal after caffeine ingestion. In addition, carbohydrate storage was 35% lower (P < 0.05) in the caffeine trial than in the placebo trial. Furthermore, even when the difference in glucose disposal was normalized between the trials, there was a 23% difference in the amount of carbohydrate stored after caffeine administration compared with placebo administration. Caffeine ingestion also resulted in higher plasma epinephrine levels than placebo ingestion (P < 0.05). These data support our hypothesis that caffeine ingestion decreases glucose disposal and suggests that adenosine plays a role in regulating glucose disposal in resting humans.
authors.affiliation: Ohio University Eastern, St. Clairsville, Ohio 43950, USA. greerf@skynet.eastern.ohiou.edu
authors.forename: F
authors.initials: F
authors.lastname: Greer
authors.forename: R
authors.initials: R
authors.lastname: Hudson
authors.forename: R
authors.initials: R
authors.lastname: Ross
authors.forename: T
authors.initials: T
authors.lastname: Graham
mesh_terms: D000284:Administration, Oral; D000328:Adult; D002096:C-Peptide / Q000097:blood; D002110:Caffeine / Q000097:blood / Q000494:pharmacology*; D002151:Calorimetry; D004311:Double-Blind Method; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005947:Glucose / Q000378:metabolism*; D015309:Glucose Clamp Technique; D005990:Glycerol / Q000097:blood; D006801:Humans; D006946:Hyperinsulinism / Q000378:metabolism*; D007328:Insulin / Q000097:blood; D019344:Lactic Acid / Q000097:blood; D008019:Life Style; D008297:Male; D005082:Physical Exertion; D058915:Purinergic P1 Receptor Antagonists
chemical_list: D002096:C-Peptide; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D058915:Purinergic P1 Receptor Antagonists; D019344:Lactic Acid; D002110:Caffeine; D005947:Glucose; D005990:Glycerol