Impact of an obesogenic diet program on bone densitometry, micro architecture and metabolism in male rat.

International audienceABSTRACT: Background The relationships between fat mass and bone tissue are complex and not fully elucidated. A high-fat/high-sucrose diet has been shown to induce harmful effects on bone micro architecture and bone biomechanics of rat. When such diet leads to obesity, it may induce an improvement of biomechanical bone parameters in rodent. Here, we examined the impact of a high-fat/high-sucrose diet on the body composition and its resulting effects on bone density and structure in male rats. Forty three Wistar rats aged 7 months were split into 3 groups: 1 sacrificed before diet (BD, n=14); 1 subjected to 16 weeks of high-fat/high-sucrose diet (HF/HS, n=14); 1 subjected to standard diet (Control, n=15). Abdominal circumference and insulin sensitivity were measured and visceral fat mass was weighed. The bone mineral density (BMD) was analyzed at the whole body and tibia by densitometry. Microcomputed tomography and histomorphometric analysis were performed at L2 vertebrae and tibiae to study the trabecular and cortical bone structures and the bone cell activities. Osteocalcin and CTX levels were performed to assess the relative balance of the bone formation and resorption. Differences between groups have been tested with an ANOVA with subsequent Scheffe post-hoc test. An ANCOVA with global mass and global fat as covariates was used to determine the potential implication of the resulting mechanical loading on bone. RESULTS: The HF/HS group had higher body mass, fat masses and abdominal circumference and developed an impaired glucose tolerance compared to Control group (p<0.001). Whole body bone mass (p<0.001) and BMD (p<0.05) were higher in HF/HS group vs. Control group. The trabecular thickness at vertebrae and the cortical porosity of tibia were improved (p<0.05) in HF/HS group. Bone formation was predominant in HF/HS group while an unbalance bone favoring bone resorption was observed in the controls. The HF/HS and Control groups had higher total and abdominal fat masses and altered bone parameters vs. BD group. Conclusions The HF/HS diet had induced obesity and impaired glucose tolerance. These changes resulted in an improvement of quantitative, qualitative and metabolic bone parameters. The fat mass increase partly explained these observations

Differential effect of exercise training duration on bone tissue in male obese rat

The association of a well-balanced diet with exercise is a key strategy to treat obesity. Whereas exercise is known to induce beneficial effects on bone, data concerning these effects in a weight loss program in rat are lacking. Because weight loss is linked to a concomitant bone loss, we wondered if exercise training duration may differently affect the bone tissue in such a program. This study aimed to investigate bone responses to two different durations of exercise training combined with a well-balance diet in obese rats. Fifty nine Wistar male rats were previously fed with a high fat/high sucrose diet (HF/HS) for 4 months to induce obesity. A control group (n = 15) was fed with a standard diet (HF/HS vs. Control = T0). Then, all rats were given a well-balanced diet and assigned to 4 different modalities: one month of exercise training (treadmill: 50 min/day, 5 days/week) or sedentarity (T1), two months of exercise or sedentarity (T2). The body composition and BMD were assessed by DXA. Visceral fat mass was weighed and insulin sensitivity was tested. Trabecular micro-architecture of tibia and L2 vertebrae (L2) and the cortical analysis of tibia were performed by 3D microtomography. Osteocalcin and CTX levels were assessed. At T0, the HF/HS diet group had developed a total and abdominal obesity and an impaired glucose tolerance compared with the Control group (p < 0.05). Most of the bone parameters were improved in HF/HS group vs. the Control group: higher total BMC and BMD, lower cortical porosity of tibia and higher Tb.Th of L2 (p < 0.05). One month of exercise (T1) had not affected the body composition and bone parameters except an improvement of insulin sensitivity (p < 0.05) and a tendency to increase BV/TV of tibia (p < 0.06). At T2, the total and fat masses were reduced in exercised group vs. sedentary group (p < 0.01). Regarding the bone parameters, CTX level decreased (p < 0.05), the Tb.Sp of L2 tended to decrease (p < 0.06), the degree of anisotropy (DA) of tibia increased (p < 0.05), and DA of L2 tended to increase (p < 0.06) in exercised group vs. sedentary group. In conclusion, 2 months of exercise had reduced obesity parameters, decreased resorption and improved a part of trabecular parameters of bone tissue whereas 1 month of exercise did not induce such improvement. A two-month program composed of a well balanced diet combined with exercise training is able to treat obesity and to protect bone tissue in male obese rat whereas one month program is not efficient

A well-balanced diet combined or not with exercise induces fat mass loss without any decrease of bone mass despite bone micro-architecture alterations in obese rat

The association of a well-balanced diet with exercise is a key strategy to treat obesity. However, weight loss is linked to an accelerated bone loss. Furthermore, exercise is known to induce beneficial effects on bone. We investigated the impact of a well-balanced isoenergetic reducing diet (WBR) and exercise on bone tissue in obese rats. Sixty male rats had previously been fed with a high fat/high sucrose diet (HF/HS) for 4 months to induce obesity. Then, 4 regimens were initiated for 2 months: HF/HS diet plus exercise (treadmill: 50 min/day, 5 days/week), WBR diet plus exercise, HF/HS diet plus inactivity and WBR diet plus inactivity. Body composition and total BMD were assessed using DXA and visceral fat mass was weighed. Tibia densitometry was assessed by Piximus. Bone histomorphometry was performed on the proximal metaphysis of tibia and on L2 vertebrae (L2). Trabecular micro-architectural parameters were measured on tibia and L2 by 3D microtomography. Plasma concentration of osteocalcin and CTX were measured. Both WBR diet and exercise had decreased global weight, global fat and visceral fat mass (p<0.05). The WBR diet alone failed to alter total and tibia bone mass and BMD. However, Tb.Th, bone volume density and degree of anisotropy of tibia were decreased by the WBR diet (p<0.05). Moreover, the WBR diet had involved a significant lower MS/BS and BFR/BS in 12 (p<0.05). Exercise had significantly improved BMD of the tibia possibly by inhibiting the bone resorption, as evidenced by no change in plasma osteocalcin levels, a decrease of CTX levels (p<0.005) and trabecular osteoclast number (p<0.05). In the present study a diet inducing weight and fat mass losses did not affected bone mass and BMD of obese rats despite alterations of their bone micro-architecture. The moderate intensity exercise performed had improved the tibia BMD of obese rats without any trabecular and cortical adaptation. (C) 2013 Elsevier Inc. All rights reserved

Impact of an obesogenic diet program on bone densitometry, micro architecture and metabolism in male rat

Abstract Background The relationships between fat mass and bone tissue are complex and not fully elucidated. A high-fat/high-sucrose diet has been shown to induce harmful effects on bone micro architecture and bone biomechanics of rat. When such diet leads to obesity, it may induce an improvement of biomechanical bone parameters in rodent. Here, we examined the impact of a high-fat/high-sucrose diet on the body composition and its resulting effects on bone density and structure in male rats. Forty three Wistar rats aged 7 months were split into 3 groups: 1 sacrificed before diet (BD, n = 14); 1 subjected to 16 weeks of high-fat/high-sucrose diet (HF/HS, n = 14); 1 subjected to standard diet (Control, n = 15). Abdominal circumference and insulin sensitivity were measured and visceral fat mass was weighed. The bone mineral density (BMD) was analyzed at the whole body and tibia by densitometry. Microcomputed tomography and histomorphometric analysis were performed at L2 vertebrae and tibia to study the trabecular and cortical bone structures and the bone cell activities. Osteocalcin and CTX levels were performed to assess the relative balance of the bone formation and resorption. Differences between groups have been tested with an ANOVA with subsequent Scheffe post-hoc test. An ANCOVA with global mass and global fat as covariates was used to determine the potential implication of the resulting mechanical loading on bone. Results The HF/HS group had higher body mass, fat masses and abdominal circumference and developed an impaired glucose tolerance (p  Conclusions The HF/HS diet had induced obesity and impaired glucose tolerance. These changes resulted in an improvement of quantitative, qualitative and metabolic bone parameters. The fat mass increase partly explained these observations.</p