31 research outputs found
Visceral fat mass determination in rodent: validation of dual-energy x-ray absorptiometry and anthropometric techniques in fat and lean rats
<p>Abstract</p> <p>Background</p> <p>Because abdominal obesity is predisposed to various metabolic disorders, it is of major importance to assess and track the changes with time of this specific fat mass. The main issue for clinicians or researchers is to use techniques for assessing abdominal fat deposition and its accumulation or changes over time, without sacrificing of experimental subjects. In the rat, techniques to investigate in-vivo visceral fat mass are lacking. The purpose of the study was to validate indirect Dual-energy X-ray Absorptiometry technique and abdominal circumference measurement as tools to predict visceral adipose tissue in rats.</p> <p>Forty-three Wistar male rats from different body weight, fat mass and ages were included in the study. Visceral fat mass was assessed by weighing the total perirenal and peri-epididymal adipose tissues after dissection. Statistical methods were used to discriminate the best region of interest allowing the in-vivo measure of Central Fat Mass by DXA. Abdominal circumference was measured at the same time as the DXA scan.</p> <p>Results</p> <p>A region of interest including Central Fat Mass from the whole body DXA scan (extending from L2 to L5 vertebrae), correlated strongly with <it>ex-vivo </it>Fat Mass (r = 0.94, p < 0.001). Abdominal circumference correlated significantly with <it>ex-vivo </it>Fat Mass (r = 0.82, p < 0.001) and Central Fat Mass (0.90, p < 0.001) in the whole group of rats. When dividing the whole group into lean and fat rats, correlations remained significant between Central Fat Mass and <it>ex-vivo </it>Fat Mass but disappeared for the lean group between abdominal circumference and <it>ex-vivo </it>Fat Mass.</p> <p>Conclusions</p> <p>This study validates the Central Fat Mass determined by DXA as a non-sacrificial technique to assess visceral fat for in-vivo investigations in rats. The abdominal circumference measure appears useful in studying overweight or obese rats. These two techniques could be convenient tools in follow-up and longitudinal studies.</p
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
Interventions nutritionnelles, exercice physique et perturbations métaboliques : réponses micro-architecturales, densitométrique, biomécaniques et cellulaires du tissu osseux chez le rat mùle. Induction de l'obésité et prise en charge.
Si lâobĂ©sitĂ© a longtemps Ă©tĂ© considĂ©rĂ©e comme protectrice pour le squelette, sa prise en charge nutritionnelle sâaccompagne dâune perte osseuse. Dans le but dâĂ©tudier les mĂ©canismes liant le tissu adipeux et le tissu osseux, des rats ont Ă©tĂ© nourris avec un rĂ©gime riche en graisse et en sucre afin dâinduire une obĂ©sitĂ© et ses complications mĂ©taboliques. Puis, ces rats ont suivi un programme de prise en charge de lâobĂ©sitĂ© associant un rĂ©Ă©quilibrage nutritionnel Ă de lâactivitĂ© physique. Des investigations de la densitĂ©, de la micro architecture trabĂ©culaire, de la qualitĂ© corticale, des propriĂ©tĂ©s biomĂ©caniques et des paramĂštres cellulaires du tissu osseux ont Ă©tĂ© rĂ©alisĂ©es sur le squelette des rats. LâobĂ©sitĂ© induite a amĂ©liorĂ© les paramĂštres densitomĂ©triques et corticaux des rats. La prise en charge de lâobĂ©sitĂ© a entraĂźnĂ© des effets contrastĂ©s. Le rĂ©Ă©quilibrage de lâalimentation nâa pas altĂ©rĂ© la densitĂ© ni les paramĂštres biomĂ©caniques et corticaux du tissu osseux des rats en dĂ©pit dâaltĂ©rations de la micro architecture et des perturbations lâactivitĂ© cellulaire osseuse. Lâexercice a augmentĂ© la densitĂ© minĂ©rale osseuse du tibia des rats. Nos rĂ©sultats montrent que lâinclusion de lâexercice dans un programme de prise en charge de lâobĂ©sitĂ© permet de potentialiser la perte de masse grasse et de maintenir lâintĂ©gritĂ© du squelette. En Ă©tudiant lâimpact dâun rĂ©gime obĂ©sogĂšne et de la prise en charge de lâobĂ©sitĂ© sur le tissu osseux chez le rat, ce travail de thĂšse apporte sa contribution dans la comprĂ©hension des mĂ©canismes liant le tissu adipeux et le tissu osseux.While obesity has long been considered protective of bone tissue, its nutritional management is linked to a concomitant bone loss. In order to access these mechanisms, male rats were given a high fat / high sucrose diet to induce obesity and its resulting metabolic disorders. Then, these rats participated in a well balanced nutritional program combined, or not, with physical activity in order to treat their obesity. Investigations on density, trabecular micro-architecture, cortical quality, biomechanical properties and cellular parameters of bone tissue were performed on ratâs skeleton. Obesity had improved the bone density and cortical parameters of rats. Obesity management had induced mixed effects. The well balanced diet did alter neither the bone density nor biomechanical and cortical parameters despite the presence of alterations in the trabecular micro architecture and some disturbances of bone cellular activity. Exercise by itself had increased the tibia bone mineral density. Our results show that including exercise in obesity management allows increasing the fat mass loss and maintaining the skeleton integrity. By studying the impact of an obesogenic diet and obesity treatment on bone tissue in rats, this study brings its contribution to the understanding of the mechanisms linking adipose tissue and bone tissue
Mechanically Driven CounterâRegulation of Cortical Bone Formation in Response to SclerostinâNeutralizing Antibodies
Sclerostin (Scl) antibodies (Scl-Ab) potently stimulate bone formation, but these effects are transient. Whether the rapid inhibition of Scl-Ab anabolic effects is due to a loss of bone cells' capacity to form new bone or to a mechanostatic downregulation of Wnt signaling once bone strength exceeds stress remains unclear. We hypothesized that bone formation under Scl-Ab could be reactivated by increasing the dose of Scl-Ab and/or by adding mechanical stimuli, and investigated the molecular mechanisms involved in this response, in particular the role of periostin (Postn), a co-activator of the Wnt pathway in bone. For this purpose, C57Bl/6, Postn-/- and Postn+/+ mice were treated with vehicle or Scl-Ab (50 to 100 mg/kg/wk) for various durations and subsequently subjected to tibia axial compressive loading. In wild-type (WT) mice, Scl-Ab anabolic effects peaked between 2 and 4 weeks and declined thereafter, with no further increase in bone volume and strength between 7 and 10 weeks. Doubling the dose of Scl-Ab did not rescue the decline in bone formation. In contrast, mechanical stimulation was able to restore cortical bone formation concomitantly to Scl-Ab treatment at both doses. Several Wnt inhibitors, including Dkk1, Sost, and Twist1, were upregulated, whereas Postn was markedly downregulated by 2 to 4 weeks of Scl-Ab. Mechanical loading specifically upregulated Postn gene expression. In turn, Scl-Ab effects on cortical bone were more rapidly downregulated in Postn-/- mice. These results indicate that bone formation is not exhausted by Scl-Ab but inhibited by a mechanically driven downregulation of Wnt signaling. Hence, increasing mechanical loads restores bone formation on cortical surfaces, in parallel with Postn upregulation
Alternated activation with relaxation of periosteum stimulates bone modeling and remodeling.
Gradual elevation of the periosteum from the original bone surface, based on the principle of distraction osteogenesis, induces endogenous hard and soft tissue formation. This study aimed to assess the impact of alternating protocols of activation with relaxation (periosteal pumping) on bone modeling and remodeling. One hundred and sixty-two adult male Wistar rats were used in this study. Four test groups with different pumping protocols were created based on the relaxation applied. Two control groups underwent an activation period without relaxation or only a single activation. One group was sham-operated. Periosteal pumping without period of activation induced gene expression in bone and bone remodeling, and following activation period enhanced bone modeling. Four test groups and control group with activation period equaled the values of bone modeling at the end-consolidation period, showing significant downregulation of Sost in the bone and periosteum compared to that in the sham group (pâ<â0.001 and pâ<â0.001, respectively). When all test groups were pooled together, plate elevation from the bony surface increased bone remodeling on day 45 of the observation period (pâ=â0.003). Furthermore, bone modeling was significantly affected by plate elevation on days 17 and 45 (pâ=â0.047 and pâ=â0.005, respectively) and by pumping protocol on day 31 (pâ=â0.042). Periosteal pumping was beneficial for increasing bone repair when the periosteum remained in contact with the underlaying bony surface during the manipulation period. Following periosteal elevation, periosteal pumping accelerated bone formation from the bony surface by the modeling process
Ostéoporose chez l'insuffisant rénal: quelle évaluation et quel traitement? Place de la biopsie osseuse
Eight Days of Earth Reambulation Worsen Bone Loss Induced by 1-Month Spaceflight in the Major Weight-Bearing Ankle Bones of Mature Mice
Influence of Fatigue Loading and Bone Turnover on Bone Strength and Pattern of Experimental Fractures of the Tibia in Mice
Bone fragility depends on bone mass, structure, and material properties, including damage. The relationship between bone turnover, fatigue damage, and the pattern and location of fractures, however, remains poorly understood. We examined these factors and their integrated effects on fracture strength and patterns in tibia. Adult male mice received RANKL (2 mg/kg/day), OPG-Fc (5 mg/kg 29/week), or vehicle (Veh) 2 days prior to fatigue loading of one tibia by in vivo axial compression, with treatments continuing up to 28 more days. One day post fatigue, crack density was similarly increased in fatigued tibiae from all treatment groups. After 28 days, the RANKL group exhibited reduced bone mass and increased crack density, resulting in reduced bone strength, while the OPG-Fc group had greater bone mass and bone strength. Injury repair altered the pattern and location of fractures created by ex vivo destructive testing, with fractures occurring more proximally and obliquely relative to non-fatigued tibia. A similar pattern was observed in both non-fatigued and fatigued tibia of RANKL. In contrast, OPG-Fc prevented this fatigue-related shift in fracture pattern by maintaining fractures more distal and transverse. Correlation analysis showed that bone strength was predominantly determined by aBMD with minor contributions from structure and intrinsic strength as measured by nanoindentation and cracks density. In contrast, fracture location was predicted equally by aBMD, crack density and intrinsic modulus. The data suggest that not only bone strength but also the fracture pattern depends on previous damage and the effects of bone turnover on bone mass and structure. These observations may be relevant to further understand the mechanisms contributing to fracture pattern in long bone with different levels of bone remodeling, including atypical femur fracture