Diet and gene interactions influence the skeletal response to polyunsaturated fatty acids.

Document Type

Article

Publication Date

11-2014

Institution/Department

MMCRI

Journal Title

Bone

MeSH Headings

Adipose Tissue, Brown, Adipose Tissue, White, Adiposity, Animals, Biomarkers, Biomechanical Phenomena, Body Composition, Bone Density, Bone Marrow, Bone and Bones, Cell Count, Diet, Dietary Supplements, Fatty Acids, Omega-3, Fatty Acids, Omega-6, Female, Femur, Fish Oils, Gene Expression Regulation, Mice, Inbred C3H, Mice, Inbred C57BL, Organ Size, Osteoclasts, Spine, Tibia

Abstract

Diets rich in omega-3s have been thought to prevent both obesity and osteoporosis. However, conflicting findings are reported, probably as a result of gene by nutritional interactions. Peroxisome proliferator-activated receptor-gamma (PPARγ) is a nuclear receptor that improves insulin sensitivity but causes weight gain and bone loss. Fish oil is a natural agonist for PPARγ and thus may exert its actions through the PPARγ pathway. We examined the role of PPARγ in body composition changes induced by a fish or safflower oil diet using two strains of C57BL/6J (B6); i.e. B6.C3H-6T (6T) congenic mice created by backcrossing a small locus on Chr 6 from C3H carrying 'gain of function' polymorphisms in the Pparγ gene onto a B6 background, and C57BL/6J mice. After 9months of feeding both diets to female mice, body weight, percent fat and leptin levels were less in mice fed the fish oil vs those fed safflower oil, independent of genotype. At the skeletal level, fish oil preserved vertebral bone mineral density (BMD) and microstructure in B6 but not in 6T mice. Moreover, fish oil consumption was associated with an increase in bone marrow adiposity and a decrease in BMD, cortical thickness, ultimate force and plastic energy in femur of the 6T but not the B6 mice. These effects paralleled an increase in adipogenic inflammatory and resorption markers in 6T but not B6. Thus, compared to safflower oil, fish oil (high ratio omega-3/-6) prevents weight gain, bone loss, and changes in trabecular microarchitecture in the spine with age. These beneficial effects are absent in mice with polymorphisms in the Pparγ gene (6T), supporting the tenet that the actions of n-3 fatty acids on bone microstructure are likely to be genotype dependent. Thus caution must be used in interpreting dietary intervention trials with skeletal endpoints in mice and in humans.

ISSN

1873-2763

First Page

100

Last Page

107

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