RESUMEN
Obesity is associated with increased plasma glycerol levels. The coordinated regulation of glycerol channels in adipose tissue (AQP7) and the liver (AQP9) has been suggested as an important contributor to the pathophysiology of type-2-diabetes mellitus, as it would provide glycerol for hepatic synthesis of glucose and triglycerides. The regulation of AQP7 and AQP9 is influenced by sex. This study investigates the effect of a high-fat diet (HFD) on glycerol metabolism in mice and the influence of sex and GLP-1-receptor agonist treatment. Female and male C57BL/6JRj mice were fed either a control diet or a HFD for 12 or 24 weeks. Liraglutide was administered (1 mg/kg/day) to a subset of female mice. After 12 weeks of HFD, females had gained less weight than males. In adipose tissue, only females demonstrated an increased abundance of AQP7, whereas only males demonstrated a significant increase in glycerol kinase abundance and adipocyte size. 24 weeks of HFD resulted in a more comparable effect on weight gain and adipose tissue in females and males. HFD resulted in marked hepatic steatosis in males only and had no significant effect on the hepatic abundance of AQP9. Liraglutide treatment generally attenuated the effects of HFD on glycerol metabolism. In conclusion, no coordinated upregulation of glycerol channels in adipose tissue and liver was observed in response to HFD. The effect of HFD on glycerol metabolism is sex-specific in mice, and we propose that the increased AQP7 abundance in female adipose tissue could contribute to their less severe response to HFD.
Asunto(s)
Adipocitos/metabolismo , Dieta Alta en Grasa/efectos adversos , Hígado Graso/metabolismo , Glicerol/metabolismo , Hígado/metabolismo , Triglicéridos/metabolismo , Adipocitos/patología , Animales , Acuaporinas/metabolismo , Hígado Graso/etiología , Hígado Graso/patología , Femenino , Hígado/patología , Masculino , Tasa de Depuración Metabólica , Ratones , Ratones Endogámicos C57BL , Factores SexualesRESUMEN
OBJECTIVES: Disuse is characterized by a rapid and profound bone resorption. Zoledronic acid (Zol) inhibits osteoclastic bone resorption. The aim of the study was to prevent disuse osteopenia with Zol and investigate gene expression markers of osteoclastic differentiation. METHODS: Disuse osteopenia was induced by injecting botulinum toxin (BTX) into the right hind limb of 16-week-old C57BL/6J female mice. Zol (100 µg/kg) was injected s.c. once at study start. The immobilized bones were investigated with DEXA, microCT, mechanical testing, dynamic bone histomorphometry, and RT-qPCR. RESULTS: The BTX-injections resulted in a loss of cortical and trabecular bone as well as mechanical strength compared to intact baseline and control mice. Treatment with Zol prevented the loss of bone and mechanical strength. Interestingly, treatment with Zol resulted in a higher expression of Nfatc1 and Dcstamp, which are markers osteoclastic differentiation. CONCLUSIONS: Zol effectively prevented BTX-induced disuse osteopenia. Furthermore, gene expression markers of osteoclastic differentiation were increased in Zol treated immobilized mice, indicating that Zol only affect mature bone resorbing osteoclasts in vivo. However, the current findings are preliminary and calls for further studies.
Asunto(s)
Conservadores de la Densidad Ósea/farmacología , Enfermedades Óseas Metabólicas/prevención & control , Diferenciación Celular/efectos de los fármacos , Fémur/efectos de los fármacos , Expresión Génica/efectos de los fármacos , Osteoclastos/efectos de los fármacos , Ácido Zoledrónico/farmacología , Animales , Densidad Ósea/efectos de los fármacos , Conservadores de la Densidad Ósea/uso terapéutico , Enfermedades Óseas Metabólicas/inducido químicamente , Toxinas Botulínicas Tipo A , Hueso Esponjoso/diagnóstico por imagen , Hueso Esponjoso/efectos de los fármacos , Femenino , Fémur/diagnóstico por imagen , Ratones , Osteoclastos/citología , Microtomografía por Rayos X , Ácido Zoledrónico/uso terapéuticoRESUMEN
Osteopenia and osteoporosis predominately occur in the fully grown skeleton. However, it is unknown whether disuse osteopenia in skeletally mature, but growing, mice resembles that of fully grown mice. Twenty-four 16-week-old (young) and eighteen 44-week-old (aged) female C57BL/6J mice were investigated. Twelve young and nine aged mice were injected with botulinum toxin in one hind limb; the remaining mice served as controls. The mice were euthanized after 3 weeks of disuse. The femora were scanned by micro-computed tomography (µCT) and bone strength was determined by mechanically testing the femoral mid-diaphysis and neck. At the distal femoral metaphysis, the loss of trabecular bone volume fraction (BV/TV) differed between the young and aged mice. However, at the distal femoral epiphysis, no age-dependent differences were observed. Thinning of the trabeculae was not affected by the age of the mice at either the distal femoral metaphysis or the epiphysis. Furthermore, the aged mice lost more bone strength at the femoral mid-diaphysis, but not at the femoral neck, compared to the young mice. In general, the bone loss induced by botulinum toxin did not differ substantially between young and aged mice. Therefore, the loss of bone in young mice resembles that of aged mice, even though they are not fully grown.
Asunto(s)
Envejecimiento/patología , Desarrollo Óseo , Enfermedades Óseas Metabólicas/inducido químicamente , Enfermedades Óseas Metabólicas/patología , Huesos/patología , Absorciometría de Fotón , Animales , Fenómenos Biomecánicos , Peso Corporal , Enfermedades Óseas Metabólicas/diagnóstico por imagen , Enfermedades Óseas Metabólicas/fisiopatología , Huesos/diagnóstico por imagen , Huesos/fisiopatología , Toxinas Botulínicas , Femenino , Fracturas del Fémur/diagnóstico por imagen , Fracturas del Fémur/patología , Fracturas del Fémur/fisiopatología , Fémur/diagnóstico por imagen , Fémur/patología , Fémur/fisiopatología , Imagenología Tridimensional , Ratones Endogámicos C57BL , Tamaño de los Órganos , Microtomografía por Rayos XRESUMEN
In rodents, lactation is associated with a considerable and very rapid bone loss, which almost completely recovers after weaning. The aim of the present study was to investigate whether the bisphosphonate Zoledronate (Zln) can inhibit lactation induced bone loss, and if Zln interferes with recovery of bone mass after lactation has ceased. Seventy-six 10-weeks-old NMRI mice were divided into the following groups: Baseline, Pregnant, Lactation, Lactation+Zln, Recovery, Recovery+Zln, and Virgin Control (age-matched). The lactation period was 12days, then the pups were removed, and thereafter recovery took place for 28days. Zln, 100µg/kg, was given s.c. on the day of delivery, and again 4 and 8days later. Mechanical testing, µCT, and dynamic histomorphometry were performed. At L4, lactation resulted in a substantial loss of bone strength (-55% vs. Pregnant, p<0.01), BV/TV (-40% vs. Pregnant, p<0.01), and trabecular thickness (Tb.Th) (-29% vs. Pregnant, p<0.001). Treatment with Zln completely prevented lactation induced loss of bone strength, BV/TV, and Tb.Th at L4. Full recovery of micro-architectural and mechanical properties was found 28days after weaning in vehicle-treated mice. Interestingly, the recovery group treated with Zln during the lactation period had higher BV/TV (+45%, p<0.01) and Tb.Th (+16%, p<0.05) compared with virgin controls. Similar results were found at the proximal tibia and femur. This indicates that Zln did not interfere with the bone formation taking place after weaning. On this background, we conclude that post-lactation bone formation is not dependent on a preceding lactation induced bone loss.
Asunto(s)
Resorción Ósea/tratamiento farmacológico , Resorción Ósea/prevención & control , Huesos/patología , Difosfonatos/uso terapéutico , Imidazoles/uso terapéutico , Lactancia/efectos de los fármacos , Absorciometría de Fotón , Fosfatasa Alcalina/sangre , Animales , Peso Corporal/efectos de los fármacos , Densidad Ósea/efectos de los fármacos , Resorción Ósea/sangre , Huesos/diagnóstico por imagen , Huesos/efectos de los fármacos , Difosfonatos/farmacología , Femenino , Fémur/diagnóstico por imagen , Fémur/efectos de los fármacos , Fémur/patología , Fracturas Óseas/patología , Imidazoles/farmacología , Ratones , Tamaño de los Órganos/efectos de los fármacos , Osteogénesis/efectos de los fármacos , Fosfatasa Ácida Tartratorresistente/sangre , Destete , Microtomografía por Rayos X , Ácido ZoledrónicoRESUMEN
Strontium ranelate (SrR) has both bone anabolic and anti-resorption properties and has therefore the potential to increase the healing of bone defects. The aim of the present study was to investigate the effect of systemic treatment with SrR during the healing of cortical bone defects in rats. In addition, the vertebral bodies were examined in order to elucidate the effect of short-term treatment with SrR on intact trabecular bone. Sixty 16-week-old female Wistar rats were randomized into four groups. A cylindrical defect was drilled through the anterior cortex of the mid-femoral diaphysis in both hind limbs. Two of the groups were treated with SrR (900 mg/kg b.w.) mixed into the food and two groups served as controls. The animals were euthanized after either 3 or 8 weeks of treatment. Healing of the defects was analyzed with µCT, mechanical testing, and stereology. Treatment with SrR resulted in increased thickness of the defects after 3 weeks of treatment, whereas no effect on bone volume fraction (BV/TV), mechanical properties (maximum strength and maximum stiffness), periosteal callus volume, or osteoclast-covered bone surfaces (Oc.S/BS) after either 3 or 8 weeks of treatment was found. Furthermore, SrR increased the bone material density (ρ) of the vertebral bodies, and tended to increase BV/TV after 8 weeks of treatment (p = 0.087). The mechanical properties of the vertebral bodies were not influenced by SrR treatment. In conclusion, 3 weeks of treatment with SrR increased the thickness of the healing mid-femoral cortical bone defects in rats, but did not influence BV/TV, mechanical properties, periosteal callus volume, or Oc.S/BS after either 3 or 8 weeks. Furthermore, SrR had no effect on the microstructure and mechanical properties of the vertebral bodies.
Asunto(s)
Conservadores de la Densidad Ósea/farmacología , Fémur/efectos de los fármacos , Tiofenos/farmacología , Cicatrización de Heridas/efectos de los fármacos , Animales , Densidad Ósea/efectos de los fármacos , Modelos Animales de Enfermedad , Femenino , Fémur/lesiones , Ratas , Ratas Wistar , Microtomografía por Rayos XRESUMEN
Skeletal unloading results in a rapid thinning of the trabecular bone network, but it is unknown whether vertical and horizontal trabeculae are equally affected. Therefore, the purpose of the present study was to investigate whether horizontal and vertical trabeculae were thinned similarly during skeletal unloading in rats. Fifty-seven 16-week-old female Wistar rats were randomized into six groups: baseline; control 4 weeks; botulinum toxin A (BTX) 4 weeks; control 8 weeks; BTX 8 weeks; and two BTX injections 8 weeks (BTX + BTX8). The BTX animals were injected in the right hind limb with 4 IU BTX at the start of the study, while the BTX + BTX8 were also injected with 2 IU BTX after 4 weeks. The animals were killed after 0, 4, or 8 weeks. The distal femoral metaphyses were µCT scanned, and the strengths of the femoral necks, mid-diaphyses, and distal femoral metaphyses were ascertained. Disuse resulted in a significant loss of BV/TV, thinning of the trabeculae, and decrease in the degree of anisotropy, and in a significant reduced bone strength after both 4 and 8 weeks. The ratio of horizontal to vertical trabecular thickness (Tb.Th.horz/Tb.Th.vert) and the ratio of horizontal to vertical bone volume (BV.horz/BV.vert) were significantly higher in BTX animals than in control animals. In addition, the horizontal and vertical trabecular thickness probability density functions were more similar in BTX animals than in control animals. In conclusion, skeletal unloading decreased BV/TV, Tb.Th, the degree of anisotropy, and mechanical strength, while BV.horz/BV.vert and Tb.Th.horz/Tb.Th.vert were increased. This indicates that the more loaded vertical trabeculae are pronouncedly more thinned than the less loaded supporting horizontal trabeculae during unloading.
Asunto(s)
Huesos/diagnóstico por imagen , Absorciometría de Fotón , Animales , Huesos/citología , Huesos/efectos de los fármacos , Toxinas Botulínicas Tipo A/toxicidad , Modelos Animales de Enfermedad , Femenino , Desnervación Muscular/métodos , Fármacos Neuromusculares/toxicidad , Ratas , Ratas Wistar , Microtomografía por Rayos XRESUMEN
Immobilization causes rapid and massive bone loss. By comparing Botulinum Toxin A (BTX)-induced bone loss in mouse strains with different genetic backgrounds we investigated whether the genetic background had an influence on the severity of the osteopenia. Secondly, we investigated whether BTX had systemic effects on bone. Female mice from four inbred mouse strains (BALB/cJ, C57BL/6 J, DBA/2 J, and C3H/HeN) were injected unilaterally with BTX (n = 10/group) or unilaterally with saline (n = 10/group). Mice were euthanized after 21 days, and the bone properties evaluated using µCT, DXA, bone histomorphometry, and mechanical testing. BTX resulted in substantially lower trabecular bone volume fraction (BV/TV) and trabecular thickness in all mouse strains. The deterioration of BV/TV was significantly greater in C57BL/6 J (- 57%) and DBA/2 J (- 60%) than in BALB/cJ (- 45%) and C3H/HeN (- 34%) mice. The loss of femoral neck fracture strength was significantly greater in C57BL/6 J (- 47%) and DBA/2 J (- 45%) than in C3H (- 25%) mice and likewise the loss of mid-femoral fracture strength was greater in C57BL/6 J (- 17%), DBA/2 J (- 12%), and BALB/cJ (- 9%) than in C3H/HeN (- 1%) mice, which were unaffected. Using high resolution µCT we found no evidence of a systemic effect on any of the microstructural parameters of the contralateral limb. Likewise, there was no evidence of a systemic effect on the bone strength in any mouse strain. We did, however, find a small systemic effect on aBMD in DBA/2 J and C3H/HeN mice. The present study shows that BTX-induced immobilization causes the greatest loss of cortical and trabecular bone in C57BL/6 J and DBA/2 J mice. A smaller loss of bone microstructure and fracture strength was seen in BALB/cJ mice, while the bone microstructure and fracture strength of C3H/HeN mice were markedly less affected. This indicates that BTX-induced loss of bone is mouse strain dependent. We found only minimal systemic effects of BTX.
RESUMEN
Immobilization is known to cause a rapid bone loss due to increased osteoclastic bone resorption and decreased osteoblastic bone formation. Zoledronate (Zln) is a potent anti-resorptive pharmaceutical, while intermittent PTH is a potent bone anabolic agent. The aim of the present study was to investigate whether PTH or Zln alone or in combination could prevent immobilization-induced osteopenia. Immobilization was achieved by injecting 4IU Botox (BTX) into the right hind limb musculature. Seventy-two 16-week-old female Wistar rats were randomized into 6 groups; baseline (Base), control (Ctrl), BTX, BTX+PTH, BTX+Zln, and BTX+PTH+Zln. PTH (1-34) (80µg/kg) was given 5days/week and Zln (100µg/kg) was given once at study start. The animals were killed after 4weeks of treatment. The bone properties were evaluated using DEXA, µCT, dynamic bone histomorphometry, and mechanical testing. BTX resulted in lower femoral trabecular bone volume fraction (BV/TV) (-25%, p<0.05), lower tibial trabecular bone formation rate (BFR/BS) (-29%, p<0.05), and lower bone strength (Fmax) at the distal femur (-19%, p<0.001) compared with Ctrl. BTX+PTH resulted in higher femoral BV/TV (+31%, p<0.05), higher tibial trabecular BFR/BS (+297%, p<0.05), and higher Fmax at the distal femur (+11%, p<0.05) compared with BTX. BTX+Zln resulted in higher femoral BV/TV (+36%, p<0.05), lower tibial trabecular BFR/BS (-93%, p<0.05), and higher Fmax at the distal femur (+10%, p<0.05) compared with BTX. BTX+PTH+Zln resulted in higher femoral BV/TV (+70%, p<0.001), higher tibial trabecular BFR/BS (+59%, p<0.05), and higher Fmax at the distal femur (+32%, p<0.001) compared with BTX. In conclusion, BTX-induced immobilization led to lower BV/TV, BFR/BS, and Fmax. In general, PTH or Zln alone prevented the BTX-induced osteopenia, whereas PTH and Zln given in combination not only prevented, but also increased BV/TV and BFR/BS, and maintained Fmax at the distal femoral metaphysis compared with Ctrl.
Asunto(s)
Enfermedades Óseas Metabólicas/tratamiento farmacológico , Enfermedades Óseas Metabólicas/prevención & control , Difosfonatos/uso terapéutico , Imidazoles/uso terapéutico , Trastornos Musculares Atróficos/tratamiento farmacológico , Trastornos Musculares Atróficos/prevención & control , Hormona Paratiroidea/uso terapéutico , Absorciometría de Fotón , Animales , Fenómenos Biomecánicos , Enfermedades Óseas Metabólicas/diagnóstico por imagen , Enfermedades Óseas Metabólicas/fisiopatología , Huesos/diagnóstico por imagen , Huesos/efectos de los fármacos , Huesos/patología , Huesos/fisiopatología , Difosfonatos/farmacología , Sinergismo Farmacológico , Femenino , Imagenología Tridimensional , Imidazoles/farmacología , Trastornos Musculares Atróficos/diagnóstico por imagen , Trastornos Musculares Atróficos/fisiopatología , Hormona Paratiroidea/farmacología , Ratas Wistar , Microtomografía por Rayos X , Ácido ZoledrónicoRESUMEN
PTH and strontium ranelate (SrR) have both been shown to reduce bone loss induced by immobilization. PTH is a potent bone anabolic agent, whereas SrR has been suggested to be an antiresorptive as well as a bone anabolic agent. The aim of the study was to investigate whether PTH, SrR, and PTH and SrR in combination could counteract immobilization-induced bone loss in a rat model. Immobilization was induced by injecting 4IU Botox (BTX) into the muscles of the right hind limb. Seventy-two female Wistar rats, 3-months-old, were divided into the following groups: Baseline, Controls, BTX, BTX+PTH, BTX+SrR, and BTX+PTH+SrR (n=12 in each group). PTH was given as injections (SC) at a dosage of 60µg/kg/d, and SrR as 900mg/kg/d in the diet. The experiment lasted for 4weeks. BTX resulted in lower trabecular bone formation rate (-68%) and periosteal bone formation rate (-91%), and a higher fraction of osteoclast-covered surfaces (+53%) compared with controls. This was accompanied by significantly lower trabecular bone volume fraction (-24%), trabecular thickness (-16%), and bone strength (-14% to -32% depending on site). PTH alone counteracted immobilization-induced losses in trabecular (4-fold increase vs. BTX) and periosteal (5-fold increase vs. BTX) bone formation rate, trabecular thickness (+25% vs. BTX) and femoral neck strength (+24% vs. BTX). In contrast, SrR did not influence BTX-induced loss of bone formation rate, trabecular bone volume fraction, trabecular thickness, or bone strength. Finally, no additive effect was found when PTH and SrR treatments were combined. In conclusion, PTH counteracted loss in bone architecture and bone strength in immobilized rats, whereas as no effect of SrR was found. Moreover, no additional effect was found by combining PTH with SrR.
Asunto(s)
Enfermedades Óseas Metabólicas/fisiopatología , Huesos/efectos de los fármacos , Compuestos Organometálicos/farmacología , Hormona Paratiroidea/farmacología , Tiofenos/farmacología , Fosfatasa Alcalina/metabolismo , Animales , Fenómenos Biomecánicos , Peso Corporal/efectos de los fármacos , Huesos/fisiopatología , Femenino , Tamaño de los Órganos/efectos de los fármacos , Ratas , Ratas Wistar , Tomografía Computarizada por Rayos XRESUMEN
Intramuscular injection with botulinum toxin A (BTX) leads to a transient paralysis of the muscles, resulting in a rapid loss of muscle mass and function as well as rapid bone loss (disuse osteoporosis). The purpose of this study was to investigate the temporal development and the site specificity of BTX-induced immobilization on bone strength at five skeletal sites. Three-month-old rats (n = 108) were randomized into nine groups: one served as baseline, while four were injected with BTX and four with saline in the right hind-limb musculature. Animals were killed after 1, 2, 3, or 4 weeks. BTX-induced a significant loss of rectus femoris muscle mass (-61%) and muscle cell cross-sectional area (-59%) as well as bone strength at the femoral neck (-31%), femoral diaphysis (-6%), distal femoral metaphysis (-17%), proximal tibial metaphysis (-31%), and tibial diaphysis (-13%) after 4 weeks. Muscle atrophy occurred in parallel with the bone loss at the femoral neck and proximal tibia, whereas it occurred earlier than the bone loss at the other skeletal sites. At the proximal tibial metaphysis BTX significantly decreased BV/TV (-10%), trabecular thickness (-13%), and bone formation (MS/BS -25%, BFR/BS -50%) and increased osteoclast covered surfaces (+97%) after 4 weeks. In conclusion, BTX-induced a time-dependent loss of bone strength. Moreover, the loss of bone strength differed significantly at the five tested skeletal sites.