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Open Access Research

Effects of diet-induced obesity and voluntary wheel running on the microstructure of the murine distal femur

Hongqiang Ma1, Tuomas Turpeinen2, Mika Silvennoinen3, Sira Torvinen3, Rita Rinnankoski-Tuikka3, Heikki Kainulainen3, Jussi Timonen2, Urho M Kujala1, Paavo Rahkila1 and Harri Suominen1*

Author Affiliations

1 Department of Health Sciences, University of Jyväskylä, Finland

2 Department of Physics, University of Jyväskylä, Finland

3 Department of Biology of Physical Activity, University of Jyväskylä, Finland

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Nutrition & Metabolism 2011, 8:1  doi:10.1186/1743-7075-8-1

Published: 17 January 2011

Abstract

Background

Obesity and osteoporosis, two possibly related conditions, are rapidly expanding health concerns in modern society. Both of them are associated with sedentary life style and nutrition. To investigate the effects of diet-induced obesity and voluntary physical activity we used high resolution micro-computed tomography (μCT) together with peripheral quantitative computed tomography (pQCT) to examine the microstructure of the distal femoral metaphysis in mice.

Methods

Forty 7-week-old male C57BL/6J mice were assigned to 4 groups: control (C), control + running (CR), high-fat diet (HF), and high-fat diet + running (HFR). After a 21-week intervention, all the mice were sacrificed and the left femur dissected for pQCT and μCT measurements.

Results

The mice fed the high-fat diet showed a significant weight gain (over 70% for HF and 60% for HFR), with increased epididymal fat pad mass and impaired insulin sensitivity. These obese mice had significantly higher trabecular connectivity density, volume, number, thickness, area and mass, and smaller trabecular separation. At the whole bone level, they had larger bone circumference and cross-sectional area and higher density-weighted maximal, minimal, and polar moments of inertia. Voluntary wheel running decreased all the cortical bone parameters, but increased the trabecular mineral density, and decreased the pattern factor and structure model index towards a more plate-like structure.

Conclusions

The results suggest that in mice the femur adapts to obesity by improving bone strength both at the whole bone and micro-structural level. Adaptation to running exercise manifests itself in increased trabecular density and improved 3D structure, but in a limited overall bone growth