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Endurance capacity, not body size, determines physical activity levels: role of skeletal muscle PEPCK.

Novak CM, Escande C, Gerber SM, Chini EN, Zhang M, Britton SL, Koch LG, Levine JA - PLoS ONE (2009)

Bottom Line: To test whether our findings extended to a human population, we measured endurance capacity using a VO(2max) treadmill test and daily activity in a group of non-exercising individuals.Hence, endurance capacity may be the trait that underlies both physical activity levels and leanness.Therefore, the lean phenotype is characterized by high endurance capacity and high activity and may stem from altered skeletal muscle energetics.

View Article: PubMed Central - PubMed

Affiliation: Endocrine Research Unit, Mayo Clinic, Rochester, Minnesota, USA. novak.colleen@mayo.edu

ABSTRACT
Some people remain lean despite pressure to gain weight. Lean people tend to have high daily activity levels, but the source of this increased activity is unknown. We found that leanness cannot be accounted for by increased weight-corrected food intake in two different types of lean rats. As previously reported in lean people, we found that lean rats had higher daily activity levels; lean rats also expended more energy. These lean rats were developed through artificial selection for high aerobic endurance capacity. To test whether our findings extended to a human population, we measured endurance capacity using a VO(2max) treadmill test and daily activity in a group of non-exercising individuals. Similar to lean rats selectively bred for endurance capacity, our study revealed that people with higher VO(2max) also spent more time active throughout the day. Hence, endurance capacity may be the trait that underlies both physical activity levels and leanness. We identified one potential mechanism for the lean, active phenotype in rats, namely high levels of skeletal muscle PEPCK. Therefore, the lean phenotype is characterized by high endurance capacity and high activity and may stem from altered skeletal muscle energetics.

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Related in: MedlinePlus

Lean rats have elevated skeletal muscle PEPCK.Lean, high-endurance rats had higher levels of skeletal muscle PEPCK (A,D) and PEPCK enzymatic activity (B) compared to low-endurance, overweight rats. In rats bred for leanness or obesity on a high-fat diet, heightened skeletal muscle PEPCK was also found in lean compared to obese rats (C, E). *p<0.05.
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pone-0005869-g004: Lean rats have elevated skeletal muscle PEPCK.Lean, high-endurance rats had higher levels of skeletal muscle PEPCK (A,D) and PEPCK enzymatic activity (B) compared to low-endurance, overweight rats. In rats bred for leanness or obesity on a high-fat diet, heightened skeletal muscle PEPCK was also found in lean compared to obese rats (C, E). *p<0.05.

Mentions: Our data suggest that high aerobic endurance may underlie leanness and high daily activity levels. Recently, these same features were described in mice that express high levels of the enzyme PEPCK-C in skeletal muscle [31]. Hakimi et al. (2008) reported that these mice display several of the traits we see in artificially-selected lean rats: they are lean, long-lived, highly active, behaviorally feisty, have increased caloric intake, and have extremely high running endurance [31], [32]. We therefore measured PEPCK and its enzymatic activity in skeletal muscle. PEPCK levels and enzymatic activity were significantly higher in skeletal muscle from lean, high-endurance rats compared to overweight rats (Figure 4A, B, D). High levels of PEPCK were also found in the muscle of obesity-resistant rats compared to diet-induced obese rats (Figure 4C, E). The presence of elevated skeletal muscle PEPCK in two different sets of lean rats selectively bred for two distinct complex traits—diet resistance and high intrinsic running endurance—implies that high levels of skeletal muscle PEPCK may be a common feature of leanness. Taken together with previous studies [31], [32], our data support the proposition that high muscle PEPCK may be an important element of the lean phenotype.


Endurance capacity, not body size, determines physical activity levels: role of skeletal muscle PEPCK.

Novak CM, Escande C, Gerber SM, Chini EN, Zhang M, Britton SL, Koch LG, Levine JA - PLoS ONE (2009)

Lean rats have elevated skeletal muscle PEPCK.Lean, high-endurance rats had higher levels of skeletal muscle PEPCK (A,D) and PEPCK enzymatic activity (B) compared to low-endurance, overweight rats. In rats bred for leanness or obesity on a high-fat diet, heightened skeletal muscle PEPCK was also found in lean compared to obese rats (C, E). *p<0.05.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2690400&req=5

pone-0005869-g004: Lean rats have elevated skeletal muscle PEPCK.Lean, high-endurance rats had higher levels of skeletal muscle PEPCK (A,D) and PEPCK enzymatic activity (B) compared to low-endurance, overweight rats. In rats bred for leanness or obesity on a high-fat diet, heightened skeletal muscle PEPCK was also found in lean compared to obese rats (C, E). *p<0.05.
Mentions: Our data suggest that high aerobic endurance may underlie leanness and high daily activity levels. Recently, these same features were described in mice that express high levels of the enzyme PEPCK-C in skeletal muscle [31]. Hakimi et al. (2008) reported that these mice display several of the traits we see in artificially-selected lean rats: they are lean, long-lived, highly active, behaviorally feisty, have increased caloric intake, and have extremely high running endurance [31], [32]. We therefore measured PEPCK and its enzymatic activity in skeletal muscle. PEPCK levels and enzymatic activity were significantly higher in skeletal muscle from lean, high-endurance rats compared to overweight rats (Figure 4A, B, D). High levels of PEPCK were also found in the muscle of obesity-resistant rats compared to diet-induced obese rats (Figure 4C, E). The presence of elevated skeletal muscle PEPCK in two different sets of lean rats selectively bred for two distinct complex traits—diet resistance and high intrinsic running endurance—implies that high levels of skeletal muscle PEPCK may be a common feature of leanness. Taken together with previous studies [31], [32], our data support the proposition that high muscle PEPCK may be an important element of the lean phenotype.

Bottom Line: To test whether our findings extended to a human population, we measured endurance capacity using a VO(2max) treadmill test and daily activity in a group of non-exercising individuals.Hence, endurance capacity may be the trait that underlies both physical activity levels and leanness.Therefore, the lean phenotype is characterized by high endurance capacity and high activity and may stem from altered skeletal muscle energetics.

View Article: PubMed Central - PubMed

Affiliation: Endocrine Research Unit, Mayo Clinic, Rochester, Minnesota, USA. novak.colleen@mayo.edu

ABSTRACT
Some people remain lean despite pressure to gain weight. Lean people tend to have high daily activity levels, but the source of this increased activity is unknown. We found that leanness cannot be accounted for by increased weight-corrected food intake in two different types of lean rats. As previously reported in lean people, we found that lean rats had higher daily activity levels; lean rats also expended more energy. These lean rats were developed through artificial selection for high aerobic endurance capacity. To test whether our findings extended to a human population, we measured endurance capacity using a VO(2max) treadmill test and daily activity in a group of non-exercising individuals. Similar to lean rats selectively bred for endurance capacity, our study revealed that people with higher VO(2max) also spent more time active throughout the day. Hence, endurance capacity may be the trait that underlies both physical activity levels and leanness. We identified one potential mechanism for the lean, active phenotype in rats, namely high levels of skeletal muscle PEPCK. Therefore, the lean phenotype is characterized by high endurance capacity and high activity and may stem from altered skeletal muscle energetics.

Show MeSH
Related in: MedlinePlus