Towards a better interpretation of bone morphology: The effect of obesity on bone

Abstract

The effects of obesity on bone are poorly understood in biological anthropology. By using an experimental approach, we hope to achieve several aims and objectives designed to further our understanding of how obesity affects bone health. The aims also look at trying to understand the implications of the results for understanding past human populations and modern day issues surrounding obesity. To accomplish this, a project has been developed and is outlined below. Bones from lean (control), obese and calorie restricted rats (n=9 rats/group) that were raised in metabolic cages and sacrificed at 17 weeks of age, were studied. The samples were provided by the Nutrition and Obesity Research Group of the University of the Basque Country. The carcasses were micro-CT scanned for linear measurements (LM), geometric morphometric shape analysis (GMSA) and cross sectional shape analysis (CSSA). LM, GMSA and CSSA were performed on a set of 18 landmarks representing the overall shape of the right femur, using the MorphoJ package and Avizo 9.0 software. Cross-sections were obtained at the midshaft and the most lateral point of the third trochanter. The following measurements were collected: maximum length, epiphysis diameter, epiphysis circumference, epicondyle width and epiphysis/epicondyle width ratio. Obese rats had significantly longer but narrower femora. The LM, GMSA and CSSA significantly differentiated between control, obese and calorie restricted. Obese individuals had longer femora with a relatively higher positioned third trochanter but were more gracile and weaker in their diaphyseal strength and rigidity compared to the control sample. These findings confirm that obesity has a significant effect on bone shape and strength but the results from the calorie restricted group demonstrates that these may be reversible. Further research into potential underlying mechanisms, including interactions between bone and lipid cells is required