The Effect of Caloric Restriction on Activity Levels of Young and Old Rats

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The Effect of Caloric Restriction on Activity
Levels of Young and Old Rats

• James Heth
• Faculty Mentor
• Dr. Russ Hepple

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Introduction

• Caloric Restriction (CR) has been shown to
  increase longevity in numerous species
• A current leading theory on the process of aging
  invokes cellular damage caused by production of
  Reactive Oxygen Species (ROS) as a potential
  culprit

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Introduction

• Mitochondria are the main producers of ROS
• May also be the most immediate target of
  oxidative damage, particularly mtDNA

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Introduction

• CR has been shown to reduce the accumulation of
  ROS damage in skeletal muscle
• CR has also been shown to preserve muscle
  function in aging rats
• The effect of CR on activity levels has not been
  well studied

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Introduction

• The current study utilized age-matched Fisher 344
  x Brown Norway F-1 Hybrid (F344BN F-1) rats
• Rectangular mortality curve
• Reduced occurrence of pathologies
• Good model of aging human skeletal muscle

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Purpose

• Examine the effect of a CR diet on the activity
  levels of 8 month old and 35 month old F344BN F-1
  rats

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Method

• Rats were obtained from the National Institute of
  Aging (NIA). The CR rat feeding protocol was as
  follows
• 10 CR at 14 weeks
• 25 CR at 15 weeks
• 40 CR at 16 weeks (maintained throughout
  lifetime)

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Method
Values are mean SE significance at plt0.05
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Method

• Rats were monitored for 22 hour periods (1-3
  periods)
• Physical activity (PA) was measured in a cage
  supported on 2 lever arms.
• Movement of the rat caused deflections, which
  were recorded as a waveform
• Rats were observed to determine the amount of
  deflection caused by grooming behaviour
• Waveform was filtered to obtain activity above
  and below the observed grooming deflections

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Results
Values are mean SE significance at plt0.05 when
these 3 groups are compared with
ANOVA significance at plt0.05 when compared with
Students t-test
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Results
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Results
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Results
VO2max(µmolmin-1100gm-1)
Physical Activity (min)
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Discussion

• Results suggest that PA levels in old rats are
  preserved with a CR diet
• Possible protective effect on mtDNA
• If mitochondria are protected, respiratory chain
  will continue to function at a higher level

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Discussion

• We encountered a large variance in activity
  levels of 8mo Ad Lib rats
• A larger n would reduce variance

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Discussion
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Future Research

• Direct metabolic measures would give a precise
  measure of metabolic activity, which would be
  useful in conjunction with PA measurements

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Acknowledgements

• Dr. Russ Hepple
• Jason Hagen
• Dan Krause
• USRP Programme

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Questions?