title: High-altitude acclimation increases the triacylglycerol/fatty acid cycle at rest and during exercise.
abstract: High-altitude acclimation alters lipid metabolism during exercise, but it is unknown whether this involves changes in rates of lipolysis or reesterification, which form the triacylglycerol/fatty acid (TAG/FA) cycle. We combined indirect calorimetry with [2-(3)H]glycerol and [1-(14)C]palmitate infusions to simultaneously measure total lipid oxidation, lipolysis, and rate of appearance (R(a)) of nonesterified fatty acids (NEFA) in high-altitude-acclimated (HA) rats exercising at 60% maximal O(2) uptake (VO(2 max)). During exercise, relative total lipid oxidation (%VO(2)) equaled sea-level control (SL) values; however, acclimation greatly stimulated lipolysis (+75%) but had no effect on R(a) NEFA. As a result, TAG/FA cycling increased (+119%), due solely to an increase in recycling (+144%) within adipocytes. There was no change in either group in these variables with the transition from rest to exercise. We conclude that, in HA, 1) acclimation is a potent stimulator of lipolysis; 2) rats do not modify TAG/FA cycling with the transition to exercise; and 3) in normoxia, HA and SL derive the same fraction of their total energy from lipids and carbohydrates.
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada. grantm@socrates.berkeley.edu
authors.forename: G B
authors.initials: GB
authors.lastname: McClelland
authors.forename: P W
authors.initials: PW
authors.lastname: Hochachka
authors.forename: S P
authors.initials: SP
authors.lastname: Reidy
authors.forename: J M
authors.initials: JM
authors.lastname: Weber
mesh_terms: D000064:Acclimatization; D000531:Altitude; D000818:Animals; D002153:Calorimetry, Indirect; D002245:Carbon Dioxide / Q000097:blood; D002250:Carbon Radioisotopes; D004951:Esterification; D005227:Fatty Acids / Q000097:blood*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005990:Glycerol / Q000378:metabolism; D007700:Kinetics; D008066:Lipolysis; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption; D019308:Palmitic Acid / Q000378:metabolism; D005082:Physical Exertion; D011659:Pulmonary Gas Exchange; D051381:Rats; D017208:Rats, Wistar; D014280:Triglycerides / Q000097:blood*; D014316:Tritium
chemical_list: D002250:Carbon Radioisotopes; D005227:Fatty Acids; D005230:Fatty Acids, Nonesterified; D014280:Triglycerides; D014316:Tritium; D002245:Carbon Dioxide; D019308:Palmitic Acid; D005990:Glycerol; D010100:Oxygen