Effect of Caloric Restriction on Male Wistar Rats

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Effect of Caloric Restriction on Male Wistar Rats

• J. Lambert
• Supervisors J.M. LaMothe, R.F. Zernicke and R.
  Reimer
• Markin-Flanagan Symposium

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Background Caloric Restriction

• Shown to increase both mean and maximal life-span
  in a variety of animals
• Study methodologies have varied
• age
• period and degree of restriction
• vitamin/mineral status
• gender

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Background Biomechanics

• Geometric or Morphometric properties
• Structural properties
• Material properties

Load
Slope stiffness
Deformation
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Talbott, Rothkopf, Shapses (1998)

• Findings
• "younger" (3 mo.) and "older" (10 mo.) female
  Sprague-Dawley rats
• restriction of calcium, calories, or both
  resulted in an elevated rate of bone resorption
  in both younger and older rats
• only the CR group had elevated bone formation
• final bone mineral density was lower in the older
  CR group but not the younger

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Talbott, et al. (2001)

• Findings
• Mature" (5 mo.) and "aged" (12 mo.) female
  Sprague-Dawley rats
• Ad libitum or 40 reduction in caloric intake for
  a period of 9 weeks
• CR caused a loss in body mass, which was found to
  reduce bone strength in the aged but not mature
  rats
• Adult-onset CR elevates bone resorption and
  decreases whole-body bone mineral density in aged
  but not mature rats

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LaMothe, Hepple, and Zernicke (2003)

• Results
• CR rats had significantly decreased tibial
  morphometric and structural properties
• CR rats had significantly diminished L6 height,
  load at proportional limit, and maximal load
• CR adversely affected bone geometry and mechanics

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Purpose

• To determine the effect of caloric restriction,
  with maintenance of vitamin and mineral intake,
  on mechanical and structural properties of bone
  in 12-month-old male Wistar rats.

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MethodsAnimals

• Seventeen 12-month-old adult male Wistar rats
• Ad Libitum (n8)
• Calorically restricted (n9) at 35 for 5 months
• Tibiae and the sixth lumbar vertebrae (L6)
• µCT scanning biomechanical testing ash analysis

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Methods?CT scanning
?CT scanner Skyscan
diamond wafer saw Buehler Isomet
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Methods ?CT scanning
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Methods Biomechanical Testing
Model 1122, Instron
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Methods Biomechanical Testing
Load-deformation curves generated
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Results Body Mass
Body mass was found to be significantly lower in
the CR group by almost 30 (p0.000).
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Results Tibial Morphometrics

Before adjustment for body mass ? area (15)

• CR group after
• adjustment for body mass
• ? area (15)

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Results Tibial Mechanical Properties

• Before body mass adjustment, there were no
• significant differences

• CR group after adjustment for body mass
• ? maximal load (15)
• ? stiffness (20)

Stiffness (kN/mm/g)
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Results L6 Morphometrics

• Before adjustment for body mass there were no
  significant differences
• After adjustment for body mass L6 area was
  significantly greater in the CR rats

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Results L6 Mechanical Properties

• There were no significant differences between
  groups prior to adjustment for body mass
• After adjustment for body mass

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Results Tibial and L6 Material Properties

• Max stress and mineral ash fraction were not
  significantly different between groups in tibiae
  and L6

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Discussion

• Body mass of CR animals significantly lower than
  the ad libitum animals, which is consistent with
  many studies (Banu et al., 2001)

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Tibial Properties

• Tibiae from CR rats were significantly smaller
  until corrected for body mass when they became
  significantly larger
• Suggests bone growth per unit body mass was not
  diminished with the CR-paradigm
• After adjusting for body mass, tibial maximal
  load and stiffness became significantly greater
  in the CR group

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Tibial Properties

• Material properties did not show significant
  decrements therefore bone material integrity was
  not affected with CR
• Therefore, differences in maximal load and
  stiffness (structural properties) must be
  primarily due to differences in morphometric
  properties (length, mass, and area)

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L6 Properties

• After adjustment for body mass morphometric
  parameters were significantly greater in CR rats
• No significant differences between groups in
  material properties
• Current level of CR did not affect material
  properties and structural properties were not
  jeopardized
• Material and morphometric integrity were
  maintained with a short period of CR in
  skeletally mature rats

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Conclusion

• Changes in body mass due to CR accounted for
  minimal differences in L6 and tibial mechanics
• Overall, in the present study CR did not
  adversely affect tibial and L6 mechanics in spite
  of a 35 restriction in caloric intake

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Acknowledgements

• Markin-Flanagan Studentship
• Dr. Aaron Tubman
• Dr. Raylene Reimer
• Jeremy Lamothe
• Dr. Ron Zernicke
• Dr. Roland Auer (performed caloric restriction)