title: The second-meal phenomenon is associated with enhanced muscle glycogen storage in humans.
abstract: The rise in blood glucose after lunch is less if breakfast has been eaten. The metabolic basis of this second-meal phenomenon remains uncertain. We hypothesized that storage of ingested glucose as glycogen could be responsible during the post-meal suppression of plasma NEFAs (non-esterified fatty acids; 'free' fatty acids). In the present study we determined the metabolic basis of the second-meal phenomenon. Healthy subjects were studied on two separate days, with breakfast and without breakfast in a random order. We studied metabolic changes after a standardized test lunch labelled with 3 g of 13C-labelled (99%) glucose. Changes in post-prandial muscle glycogen storage were measured using 13C magnetic resonance spectroscopy. The rise in plasma glucose after lunch was significantly less if breakfast had been taken (0.9+/-0.3 compared with 3.2+/-0.3 mmol/l, with and without breakfast respectively; P<0.001), despite comparable insulin responses. Pre-lunch NEFAs were suppressed after breakfast (0.13+/-0.03 compared with 0.51+/-0.04 mmol/l) and levels correlated positively with the maximum glucose rise after lunch (r=0.62, P=0.001). The increase in muscle glycogen signal was greater 5 h after lunch on the breakfast day (103+/-21 compared with 48+/-12 units; P<0.007) and correlated negatively with plasma NEFA concentrations before lunch (r=-0.48, P<0.05). The second-meal effect is associated with priming of muscle glycogen synthesis consequent upon sustained suppression of plasma NEFA concentrations.
authors.affiliation: Diabetes Research Group, Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, U.K.
authors.forename: Ana
authors.initials: A
authors.lastname: Jovanovic
authors.forename: Emily
authors.initials: E
authors.lastname: Leverton
authors.forename: Bhavana
authors.initials: B
authors.lastname: Solanky
authors.forename: Balasubramanian
authors.initials: B
authors.lastname: Ravikumar
authors.forename: Johanna E M
authors.initials: JE
authors.lastname: Snaar
authors.forename: Peter G
authors.initials: PG
authors.lastname: Morris
authors.forename: Roy
authors.initials: R
authors.lastname: Taylor
mesh_terms: D001786:Blood Glucose / Q000378:metabolism*; D001944:Breath Tests; D002247:Carbon Isotopes / Q000032:analysis; D004435:Eating / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D005934:Glucagon / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000378:metabolism; D008875:Middle Aged; D019518:Postprandial Period / Q000502:physiology; D052097:Quadriceps Muscle / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism
chemical_list: D001786:Blood Glucose; D002247:Carbon Isotopes; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D014280:Triglycerides; D006003:Glycogen; D005934:Glucagon