Restricted Diet Prevents Negative Effects of OVX on Soft Tissue Composition

In this episode, Rana Samadfam, Principal Scientist, Bone Biology at Charles River, provides a brief overview of her poster to be presented at the 2013 Society of Toxicology (SOT) Annual Meeting, on Wednesday March 13.

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POSTER ABSTRACT:

Ovariectomy (OVX) in rats is associated with weight gain and loss of bone mass. The increased body weight is in part attributed to increases in growth, consistent with OVX-induced hyperphagia. The objective of this study was to determine the effects of OVX on body composition in aged rats (over 6 months of age) with or without food restriction. PMI Nutrition International diet was used for all animals with animals assigned to the restricted diet groups receiving 21 g/day. Body composition was evaluated at baseline and at 4, 8, 12 and 19/20 weeks post surgery using DXA (Dual Energy X-ray Absorptiometry) and/or pQCT (Peripheral Quantitative Computed Tomography). DXA evaluation showed increases in whole body area and BMC for OVX rats on both restricted and unrestricted diet compared to their corresponding sham controls, with greater increases for animals fed ad libitum. Overall, BMD for OVX groups were comparable to baseline values whereas increases up to 2 and 6% were noted for sham controls respectively on the restricted and fed ad libitum. Significant increases were noted over the study period in muscle mass for rats on restricted diet, with trends for increases in fat mass. For ad libitum fed rats, although an increase in muscle mass was noted 4 weeks following surgery compared to sham controls, muscle mass gradually declined over the remaining study period with lower values 20 weeks post surgery. Fat mass increased for this group. When muscle mass and fat mass values were adjusted for body weight, no significant differences were noted between OVX and sham controls for animals on the restricted diet, indicating that the increased body weight is the result of proportional increases in muscle and fat mass, likely related to the effect of OVX on skeletal growth. For animals fed ad libitum, significant decreases in lean mass with significant increases in fat mass were noted when adjusted for body weight, compared to sham controls, indicating negative effects on soft tissue composition. Data from the restricted diet group suggest that calorie restriction prevents OVX- induced muscle loss and fat gain.