title: Effects of caffeine ingestion on NE kinetics, fat oxidation, and energy expenditure in younger and older men.
abstract: Age-related differences in energy expenditure, fat oxidation, and norepinephrine (NE) kinetics after caffeine ingestion were examined using a placebo-controlled double-blind study in 10 older (O, 65-80 yr) and 10 younger (Y, 19-26 yr) men who were moderate consumers of caffeine. Caffeine ingestion resulted in similar increases in Y and O men for plasma caffeine levels (Y = 89 +/- 100 to 6,340 +/- 1,938 ng/ml, P < 0.05; O = 124 +/- 38 to 7,066 +/- 2,366 ng/ml, P < 0.05) and energy expenditure (Y = 11%, 1.38 +/- 0.15 to 1.52 +/- 0.22 kcal/min, P < 0.05; O = 9.5%, 1.15 +/- 0.13 to 1.26 +/- 0.20 kcal/min, P < 0.05). However, caffeine ingestion increased fatty acid concentrations (362 +/- 159 to 803 +/- 253 mumol/l, P < 0.05) and tended to increase rate of appearance of fatty acids (624 +/- 376 to 1,394 +/- 1,331 mumol/l, P = 0.07) in younger but not older men. Rates of fat oxidation and NE appearance and clearance did not significantly differ from baseline values in either group. In conclusion, older and younger men show a similar thermogenic response to caffeine ingestion, whereas older men show a smaller increase in fatty acid availability after a caffeine challenge. These metabolic differences are not related to alterations in NE kinetics or fat oxidation.
authors.affiliation: Department of Medicine, University of Maryland, Baltimore, USA.
authors.forename: P J
authors.initials: PJ
authors.lastname: Arciero
authors.forename: A W
authors.initials: AW
authors.lastname: Gardner
authors.forename: J
authors.initials: J
authors.lastname: Calles-Escandon
authors.forename: N L
authors.initials: NL
authors.lastname: Benowitz
authors.forename: E T
authors.initials: ET
authors.lastname: Poehlman
mesh_terms: D000284:Administration, Oral; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001831:Body Temperature / Q000187:drug effects; D002110:Caffeine / Q000008:administration & dosage / Q000494:pharmacology*; D002250:Carbon Radioisotopes; D002648:Child; D004311:Double-Blind Method; D004734:Energy Metabolism / Q000187:drug effects*; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D006801:Humans; D008066:Lipolysis / Q000187:drug effects; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism*; D010919:Placebos; D011865:Radioisotope Dilution Technique; D012016:Reference Values; D014316:Tritium
chemical_list: D002250:Carbon Radioisotopes; D005230:Fatty Acids, Nonesterified; D010169:Palmitic Acids; D010919:Placebos; D014316:Tritium; D019308:Palmitic Acid; D002110:Caffeine; D009638:Norepinephrine