scholarly journals β-Adrenergically Stimulated Fat Oxidation Is Diminished in Middle-Aged Compared to Young Subjects*

1999 ◽  
Vol 84 (10) ◽  
pp. 3764-3769
Author(s):  
E. E. Blaak ◽  
M. A. van Baak ◽  
W. H. M. Saris
Keyword(s):  
Skeletal Muscle ◽  
Energy Expenditure ◽  
Total Energy ◽  
Fat Oxidation ◽  
Substrate Utilization ◽  
Total Energy Expenditure ◽  
Adrenergic Stimulation ◽  
Middle Aged ◽  
Older Subjects ◽  
Young Subjects

Abstract The effect of aging on β-adrenergically mediated substrate utilization was investigated in nine young (25.2 ± 1.7 yr old) and eight older males (52.9 ± 2.1 yr old), matched for body weight and body composition. In a first experiment, the nonselectiveβ -agonist isoprenaline (ISO) was infused in increasing standardized doses, and during each infusion period energy expenditure and substrate utilization were determined by indirect calorimetry. In a second experiment, forearm skeletal muscle metabolism was studied during a standardized infusion dose of ISO (19 ng/kg fat-free mass·min). During β-adrenergic stimulation there was an increased carbohydrate oxidation (at an ISO infusion dose of 24 ng/kg fat-free mass·min, 31% vs. 21% of total energy expenditure; P < 0.05) and a decreased fat oxidation (51 vs. 62 of total energy expenditure; P < 0.05) in older compared to young subjects. Skeletal muscle lactate release significantly increased in the older subjects (from −175 ± 32 to −366 ± 66 nmol/100 mL forearm tissue·min), whereas there was no change in young subjects (from− 32 ± 21 to 23 ± 57 nmol/100 mL forearm tissue·min; interaction group × ISO, P < 0.01). Additionally, there was a tendency toward a blunted ISO-induced increase in nonesterified fatty acid uptake in the older subjects (interaction group × ISO, P = 0.062). Thus, middle-aged subjects have a blunted ability to oxidize fat during β-adrenergic stimulation compared to young subjects. This diminished fat oxidation may be an important etiological factor in the age-related increase in body fatness and obesity by favoring fat storage above oxidation.

scholarly journals Does skeletal muscle carnitine availability influence fuel selection during exercise?

2017 ◽  
Vol 77 (1) ◽  
pp. 11-19 ◽  
Author(s):  
Francis B. Stephens
Keyword(s):  
Skeletal Muscle ◽  
Energy Expenditure ◽  
Total Energy ◽  
Exercise Intensity ◽  
Human Subjects ◽  
Maximal Oxygen Consumption ◽  
Fat Oxidation ◽  
Total Energy Expenditure ◽  
Fuel Selection

Fat and carbohydrate are the major fuel sources utilised for oxidative, mitochondrial ATP resynthesis during human skeletal muscle contraction. The relative contribution of these two substrates to ATP resynthesis and total energy expenditure during exercise can vary substantially, and is predominantly determined by fuel availability and exercise intensity and duration. For example, the increased ATP demand that occurs with an increase in exercise intensity is met by increases in both fat and carbohydrate oxidation up to an intensity of approximately 60–70 % of maximal oxygen consumption. When exercise intensity increases beyond this workload, skeletal muscle carbohydrate utilisation is accelerated, which results in a reduction and inhibition of the relative and absolute contribution of fat oxidation to total energy expenditure. However, the precise mechanisms regulating muscle fuel selection and underpinning the decline in fat oxidation remain unclear. This brief review will primarily address the theory that a carbohydrate flux-mediated reduction in the availability of muscle carnitine to the mitochondrial enzyme carnitine palmitoyltransferase 1, a rate-limiting step in mitochondrial fat translocation, is a key mechanism for the decline in fat oxidation during high-intensity exercise. This is discussed in relation to recent work in this area investigating fuel metabolism at various exercise intensities and taking advantage of the discovery that skeletal muscle carnitine content can be nutritionally increased in vivo in human subjects.

Effect of elevated FFA on carbohydrate and lipid oxidation during prolonged exercise in humans

1986 ◽  
Vol 60 (3) ◽  
pp. 893-900 ◽  
Author(s):  
E. Ravussin ◽  
C. Bogardus ◽  
K. Scheidegger ◽  
B. LaGrange ◽  
E. D. Horton ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Energy Expenditure ◽  
Total Energy ◽  
Prolonged Exercise ◽  
Total Energy Expenditure ◽  
Constant Infusion ◽  
Base Line ◽  
O2 Uptake ◽  
Glucose Ingestion ◽  
Exercise In Humans

Increased availability of circulating free fatty acids (FFA) inhibits the rate of glycolysis in heart and resting skeletal muscle (Randle effect). Whether elevated FFA may play a role in decreasing carbohydrate oxidation during prolonged exercise in humans is more controversial. Using respiratory exchange measurements, we measured substrate utilization during 2.5 h of exercise at approximately 44 +/- 1% maximal O2 uptake (VO2 max) in the presence or absence of elevated FFA levels. After 30 min of base-line determinations, 1,000 U heparin was given intravenously and a 3-h constant infusion of Intralipid 10% (150 g/h) and heparin (500 U/h) was started. After an additional 30 min of rest, subjects exercised for 2.5 h (study 1, n = 6). In another five subjects (study 2) 100 g glucose was ingested after 30 min of exercise. The same protocols (studies 1 and 2) were also performed during a 0.9%-saline infusion. During exercise, without glucose ingestion, higher FFA concentrations prevailed during the Intralipid infusion (1,122 +/- 40 vs. 782 +/- 65 mumol/l), but the relative contributions of carbohydrate (49 +/- 4 vs. 50 +/- 4%) or lipid (49 +/- 4 vs. 47 +/- 6%) oxidation to the total energy expenditure were different only during the first 30 min of exercise. Similarly, higher FFA levels (1,032 +/- 62 vs. 568 +/- 46 mumol/l) did not alter the relative contributions of carbohydrate (62 +/- 4 vs. 69 +/- 2%) or lipid (36 +/- 4 vs. 29 +/- 2%) oxidation to the total energy expenditure after glucose feeding.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Ingested Fat Oxidation Contributes 8% of 24-h Total Energy Expenditure in Moderately Obese Subjects

2005 ◽  
Vol 135 (9) ◽  
pp. 2159-2165 ◽  
Author(s):  
Bakary J. Sonko ◽  
Paul V. Fennessey ◽  
Joseph E. Donnelly ◽  
Daniel Bessesen ◽  
Teresa A. Sharp ◽  
...  
Keyword(s):  
Energy Expenditure ◽  
Total Energy ◽  
Fat Oxidation ◽  
Total Energy Expenditure ◽  
Obese Subjects

scholarly journals 2536

2017 ◽  
Vol 1 (S1) ◽  
pp. 11-11
Author(s):  
David M. Presby ◽  
Rebecca M. Foright ◽  
Julie A. Houck ◽  
Ginger C. Johnson ◽  
L. Allyson Checkley ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Weight Loss ◽  
Energy Expenditure ◽  
Metabolic Rate ◽  
Total Energy ◽  
Weight Regain ◽  
Resting Metabolic Rate ◽  
Weight Loss Maintenance ◽  
Oxidative Capacity ◽  
Total Energy Expenditure

OBJECTIVES/SPECIFIC AIMS: Obesity is a rapidly growing epidemic and long-term interventions aimed to reduce body weight are largely unsuccessful due to an increased drive to eat and a reduced metabolic rate established during weight loss. Previously, our lab demonstrated that exercise has beneficial effects on weight loss maintenance by increasing total energy expenditure above and beyond the cost of an exercise bout and reducing the drive to eat when allowed to eat ad libitum (relapse). We hypothesized that exercise’s ability to counter these obesogenic-impetuses are mediated via improvements in skeletal muscle oxidative capacity, and tested this using a mouse model with augmented oxidative capacity in skeletal muscle. METHODS/STUDY POPULATION: We recapitulated the exercise-induced improvements in oxidative capacity using FVB mice that overexpress lipoprotein lipase in skeletal muscle (mLPL). mLPL and wild type (WT) mice were put through a weight-loss-weight-regain paradigm consisting of a high fat diet challenge for 13 weeks, with a subsequent 1-week calorie-restricted medium fat diet to induce a ~15% weight loss. This newly established weight was maintained for 2 weeks and followed with a 24-hour relapse. Metabolic phenotype was characterized by indirect calorimetry during each phase. At the conclusion of the relapse day, mice were sacrificed and tissues were harvested for molecular analysis. RESULTS/ANTICIPATED RESULTS: During weight loss maintenance, mLPL mice had a higher metabolic rate (p=0.0256) that was predominantly evident in the dark cycle (p=0.0015). Furthermore, this increased metabolic rate was not due to differences in activity (p=0.2877) or resting metabolic rate (p=0.4881). During relapse, mLPL mice ingested less calories and were protected from rapid weight regain (p=0.0235), despite WT mice exhibiting higher metabolic rates during the light cycle (p=0.0421). DISCUSSION/SIGNIFICANCE OF IMPACT: These results highlight the importance of muscular oxidative capacity in preventing a depression in total energy expenditure during weight loss maintenance, and in curbing overfeeding and weight regain during a relapse. Moreover, our data suggest that the thermic effect of food is responsible for the differences in metabolic rate, because no differences were found in activity or resting metabolic rate. Additional studies are warranted to determine the molecular mechanisms driving the ability of oxidative capacity to assist with weight loss maintenance.

Effect of Protein Ingestion on Energy Expenditure and Substrate Utilization after Exercise in Middle-Aged Women

2007 ◽  
Vol 17 (6) ◽  
pp. 544-555 ◽  
Author(s):  
Melissa J. Benton ◽  
Pamela D. Swan
Keyword(s):  
Energy Expenditure ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Fat Oxidation ◽  
Substrate Utilization ◽  
Protein Supplementation ◽  
Exercise Session ◽  
Middle Aged ◽  
Post Exercise ◽  
Baseline Values

Research suggests that ingesting protein after resistance exercise (RE) increases muscle protein synthesis and results in greater muscle gains. The effect on energy expenditure and substrate utilization, however, is unclear. This study evaluated the effect of RE and post exercise protein on recovery energy expenditure and substrate utilization in 17 women (age 46.5 ± 1.2 y). A whey-protein supplement (120 kcal, 30 g protein) was ingested immediately after 1 bout of RE (PRO) and a non caloric placebo after another (PLA). VO2 and respiratory-exchange ratio (RER) were measured before and for 120 min after each exercise session. RE resulted in a significant increase in VO2 that persisted through 90 min of recovery (P < 0.01) and was not affected by protein supplementation. RE significantly lowered RER, resulting in an increase in fat oxidation for both PLA and PRO (P < 0.01). For PRO, however, RER returned to baseline values earlier than for PLA, resulting in a reduced fat-oxidation response (P = 0.02) and earlier return to pre exercise baseline values than for PLA. Substrate utilization was significantly different between conditions (P = 0.02), with fat contributing 77.76% ± 2.19% for PLA and 72.12% ± 2.17% for PRO, while protein oxidation increased from 17.18% ± 1.33% for PLA to 20.82% ± 1.47% for PRO. Post exercise protein did not affect energy expenditure, but when protein was available as an alternate fuel fat oxidation was diminished. Based on these findings it might be beneficial for middle-aged women to delay protein intake after RE to maximize fat utilization.

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