Submitted to: Calcified Tissues International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/30/2015
Publication Date: 8/1/2015
Publication URL: http://handle.nal.usda.gov/10113/61260
Citation: Cao, J.J., Picklo, M.J. 2015. Involuntary wheel running decreases adiposity, improves but does not fully protect against negative skeletal effects of obesity induced by a high-fat diet in rats. Calcified Tissues International. 97(2):145-155.
Interpretive Summary: Excessive adiposity induced by a high-fat diet is detrimental to bone structure and strength in various animal models. Exercise is recommended as a means to maintain healthy body weight and for the reduction of health disorders in obese and non-obese individuals while antioxidant micronutrients such as vitamin C and E, have been commonly used as supplements for the purpose of health promotion and disease prevention. We investigated that whether exercise or anti-oxidant supplementation with vitamin C and E during exercise benefits bone structure and affects markers of bone metabolism in a diet-induced obese rat model. We demonstrate that 1) Excessive adiposity is detrimental to bone structure in obese prone rats; 2) Involuntary exercise with running wheel decreases body fat percent, suppresses bone turnover and improves bone microarchitecture but does not fully protect against detrimental skeletal effects of excessive adiposity; 3) Vitamin C and E supplementation had no beneficial effects on bone structure and biomarkers of bone turnover during exercise.
Technical Abstract: Excessive adiposity induced by a high-fat diet is detrimental to bone structure and strength in various animal models. This study investigated whether exercise or anti-oxidant supplementation with vitamin C and E during exercise counteracts bone structure deterioration at different skeletal sites and influences markers of bone metabolism in a diet-induced obese rat model. Obese prone Sprague Dawley rats, 6-wk old, were fed a normal-fat diet (NF, 10% kcal as fat, n=14) and a high-fat diet (HF, 45% kcal as fat with extra fat from lard) ad libitum for 14 wks. Then, rats on the high-fat diet were assigned randomly to three treatment groups for additional 12 wks: HF; HF + exercise (HF+Ex); and HF with vitamin C (0.5 g ascorbate/kg diet) and vitamin E (0.4 g a-tocopherol acetate/kg diet) supplementation + exercise (HF+Ex+VCE), 14 animals in each group. Animals were forced to exercise on a running wheel for 5 d/wk for 7 wks at a graduated rate until reaching 1.2 km/ 2-hr session and maintained at the same rate by another 5 wks. At completion of the study, body weight and fat (%) were similar among NF, HF+Ex, and HF+Ex+VCE whereas HF had greater body weight and fat (%) than other groups. Compared to NF, HF had elevated serum leptin, tartrate-resistant acid phosphatase (TRAP), and IGF-1, increased trabecular separation, and structural model index, decreased bone mineral density, trabecular connectivity density, and trabecular number in distal femur, while HF+Ex and HF+Ex+VCE had elevated serum TRAP, decreased bone volume/total volume and trabecular number of distal femurs. Compared to HF, HF+Ex and HF+Ex+VCE had decreased serum TRAP and osteocalcin and improved bone structural properties of the distal femur. However, trabecular indices of the 2nd lumbar vertebrae (L2) and cortical variables of mid-shaft femurs were similar among HF, HF+Ex and HF+Ex+VCE. HF+Ex and HF+Ex+VCE had similar bone structural properties at distal femurs. These findings suggest that exercise, while decreasing body fat and improving bone structure, does not fully protect against the negative skeletal effects of excessive adiposity induced by a high-fat diet. Furthermore, vitamin C and E supplementation has no additional benefits on bone structural properties during exercise. Keywords: antioxidant, bone, exercise, high-fat, vitamin C and E