Abnormal Thyroid Hormone Status Differentially Affects Bone Mass Accrual and Bone Strength in C3H/HeJ Mice: A Mouse Model of Type I Deiodinase Deficiency.

C3H/HeJ (C3H) mice are deficient of type I deiodinase (D1), an enzyme that activates thyroid hormone (TH), converting thyroxine (T4) to triiodothyronine (T3). Nevertheless, C3H mice present normal serum T3 and a gross euthyroid phenotype. To investigate if a global D1 deficiency interferes in the TH effects on bone, we compared bone growth, bone mass accrual and bone strength of C3H and C57BL/6J (B6) mice under abnormal TH status. Four-week-old female mice of both strains were grouped as Euthyroid, Hypothyroid (pharmacologically-induced), 1xT4 and 10xT4 (hypothyroid animals receiving 1- or 10-fold the physiological dose of T4 /day/16 weeks). Hypothyroidism and TH excess similarly impaired body weight (BW) gain and body growth in both mice strains. In contrast, whereas hypothyroidism only slightly impaired bone mineral density (BMD) accrual in B6 mice, it severely impaired BMD accrual in C3H mice. No differences were observed in serum and bone concentrations of T3 between hypothyroid animals of both strains. Interestingly, treatment with 10xT4 was less deleterious to BMD accrual in C3H than in B6 mice and resulted in less elevated T3 serum levels in B6 than in C3H mice, which is probably explained by the lower D1 activity in C3H mice. In addition, hypothyroidism decreased bone strength only in C3H but not in B6 mice, while TH excess decreased this parameter in both strains. These findings indicate that D1 deficiency contributes to the TH excess-induced differences in bone mass accrual in C3H vs. B6 mice and suggest that deiodinase-unrelated genetic factors might account for the different skeleton responses to hypothyroidism between strains.

Biomechanical properties: effects of low-level laser therapy and Biosilicate® on tibial bone defects in osteopenic rats.

PURPOSE: The aim of this study was to investigate the effects of laser therapy and Biosilicate® on the biomechanical properties of bone callus in osteopenic rats. METHODS: Fifty female Wistar rats were equally divided into 5 groups (n=10/group): osteopenic rats with intact tibiae (SC); osteopenic rats with unfilled and untreated tibial bone defects (OC); osteopenic rats whose bone defects were treated with Biosilicate® (B); osteopenic rats whose bone defects were treated with 830-nm laser, at 120 J/cm2 (L120) and osteopenic rats whose bone defects were treated with Biosilicate® and 830-nm laser, at 120 J/cm2 (BL120). Ovariectomy (OVX) was used to induce osteopenia. A non-critical bone defect was created on the tibia of the osteopenic animals 8 weeks after OVX. In Biosilicate® groups, bone defects were completely filled with the biomaterial. For the laser therapy, an 830-nm laser, 120 J/cm2 was used. On day 14 postsurgery, rats were euthanized, and tibiae were removed for biomechanical analysis. RESULTS: Maximal load and energy absorption were higher in groups B and BL120, according to the indentation test. Animals submitted to low-level laser therapy (LLLT) did not show any significant biomechanical improvement, but the association between Biosilicate® and LLLT was shown to be efficient to enhance callus biomechanical properties. Conversely, no differences were found between study groups in the bending test. CONCLUSIONS: Biosilicate® alone or in association with low level laser therapy improves biomechanical properties of tibial bone callus in osteopenic rats.

Expression of myostatin, myostatin receptors and follistatin in diabetic rats submitted to exercise.

Myostatin (MSTN) has been implicated in metabolic adaptation to physiological stimuli, such as physical exercise, which is linked to improved glucose homeostasis. The aim of the present study was to evaluate the influence of exercise on the expression of MSTN, MSTN receptors (ActRIIB and ALK4) and follistatin (FS) in the muscle and fat of streptozotocin-induced diabetic rats. Control and diabetic rats were randomly assigned to a swimming training group (EC and ED, respectively) and a sedentary group (SC and SD, respectively). Exercising animals swam for 45 min at 0900 and 1700 hours, 5 day/week, for 4 weeks. The mRNA expression of MSTN, ActRIIB, ALK4 and FS mRNA was quantified by real-time reverse transcription-polymerase chain reaction. Expression of MSTN and FS mRNA increased in the muscle and subcutaneous fat of SD compared with SC rats. Expression of ActRIIB mRNA was increased in the muscle, mesenteric fat and brown adipose tissue (BAT) of SD compared with SC rats, whereas ALK4 mRNA expression was only increased in the BAT of SD compared with SC rats. After training, MSTN and ActRIIB expression was lower in the BAT of EC compared with SC rats. Expression of MSTN mRNA increased in the mesenteric fat of ED compared with SD rats, whereas FS mRNA expression decreased in the muscle, mesenteric and subcutaneous fat and BAT. Lower ALK4 mRNA expression was noted in the BAT of ED compared with SD rats. These results indicate that MSTN, its receptors and FS expression change in both the muscle and fat of diabetic rats and that the expression of these factors can be modulated by exercise in diabetes.

Comparison of the effects of low-level laser therapy and low-intensity pulsed ultrasound on the process of bone repair in the rat tibia.

BACKGROUND: Electrophysical agents such as Ultrasound (US) and low-level laser therapy (LLLT) have been increasingly used in physical therapy practice. Studies suggest that these devices are able to stimulate osteoblast proliferation and osteogenesis at the fracture site, resulting in a greater deposition of bone mass and speeding up the consolidation process. OBJECTIVE: The aim of this study was to analyze the effects of US and LLLT on the bone healing process, through biomechanical and histological analysis of the bone callus. METHODS: A total of 30 rats were randomly allocated into three groups: control group fracture without treatment (GC); fracture group treated with pulsed US, burst 1.5 MHz, 200 us, 1 KHz, 30 mW/cm² (GUS) and fracture group treated with laser 830 nm, 100 mW, 120 J/cm² (GL). Bone defects were performed with a circular drill of 2mm in diameter in the animal's tibias. The treatments were carried out after surgery consisting of 7 applications every 48 hours. After 14 days the animals were sacrificed and the tibias were removed to perform the analysis, being the right tibia designated for biomechanical analysis, while the left tibia for histological analysis. RESULTS: The biomechanical analysis showed no statistically significant difference between biomechanical properties of the CG, CL and GUS. In morphometric analysis, both GUS and GL showed a significantly higher woven bone tissue area compared to the control group. However, when the two treatment modalities were compared, there were no statistical differences between them. CONCLUSION: Both devices used in this study were able to accelerate the bone healing process in rats.

Comparação dos efeitos do laser de baixa potência e do ultrassom de baixa intensidade no processo de reparo ósseo em tíbia de rato / Comparison of the effects of low-level laser therapy and low-intensity pulsed ultrasound on the process of bone repair in the rat tibia

CONTEXTUALIZAÇÃO: Recursos eletrofísicos, como o ultrassom (US) e a terapia laser de baixa potência (LLLT), vêm sendo cada vez mais utilizados na prática fisioterapêutica. Estudos sugerem que esses recursos são capazes de estimular a proliferação de osteoblastos e a osteogênese no local da fratura, promovendo maior deposição de massa óssea e acelerando o processo de consolidação. OBJETIVO: Analisar os efeitos do US e da LLLT no processo de consolidação óssea por meio das análises biomecânica e histológica do calo ósseo. MÉTODOS: Foram utilizados 30 ratos machos, distribuídos aleatoriamente em três grupos: grupo controle fratura, sem tratamento (GC); grupo fratura tratado com US pulsado com burst de 1,5 MHz, 200us, 1KHz, 30 mW/cm² (GUS) e grupo fratura tratado com laser 830nm, 100mW, 120J/cm² (GL). Foram realizados defeitos ósseos circulares com broca de 2 mm de diâmetro nas tíbias dos animais. Os tratamentos foram realizados a cada 48 horas, totalizando sete aplicações e, no 14º dia, os animais foram sacrificados. A tíbia direita foi designada para análise biomecânica, enquanto a esquerda, para análise histológica. RESULTADOS: A análise biomecânica não mostrou diferença estatisticamente significativa entre as propriedades biomecânicas do GC, GL e GUS. Na análise morfométrica, tanto GUS quanto GL apresentaram área de osso neoformado estatisticamente maior em relação ao GC. No entanto, quando as duas modalidades de tratamento foram comparadas, não foram encontradas diferenças estatísticas entre elas. CONCLUSÃO: Ambos os recursos utilizados neste estudo foram capazes de acelerar o processo de reparo ósseo em ratos.

BACKGROUND: Electrophysical agents such as Ultrasound (US) and low-level laser therapy (LLLT) have been increasingly used in physical therapy practice. Studies suggest that these devices are able to stimulate osteoblast proliferation and osteogenesis at the fracture site, resulting in a greater deposition of bone mass and speeding up the consolidation process. OBJECTIVE: The aim of this study was to analyze the effects of US and LLLT on the bone healing process, through biomechanical and histological analysis of the bone callus. METHODS: A total of 30 rats were randomly allocated into three groups: control group fracture without treatment (GC); fracture group treated with pulsed US, burst 1.5 MHz, 200us, 1KHz, 30 mW/cm² (GUS) and fracture group treated with laser 830nm, 100mW, 120J/cm² (GL). Bone defects were performed with a circular drill of 2mm in diameter in the animal's tibias. The treatments were carried out after surgery consisting of 7 applications every 48 hours. After 14 days the animals were sacrificed and the tibias were removed to perform the analysis, being the right tibia designated for biomechanical analysis, while the left tibia for histological analysis. RESULTS: The biomechanical analysis showed no statistically significant difference between biomechanical properties of the CG, CL and GUS. In morphometric analysis, both GUS and GL showed a significantly higher woven bone tissue area compared to the control group. However, when the two treatment modalities were compared, there were no statistical differences between them. CONCLUSION: Both devices used in this study were able to accelerate the bone healing process in rats.

Double disruption of α2A- and α2C-adrenoceptors results in sympathetic hyperactivity and high-bone-mass phenotype.

Evidence demonstrates that sympathetic nervous system (SNS) activation causes osteopenia via ß(2)-adrenoceptor (ß2-AR) signaling. Here we show that female mice with chronic sympathetic hyperactivity owing to double knockout of adrenoceptors that negatively regulate norepinephrine release, α(2A)-AR and α(2C)-AR (α(2A) /α(2C)-ARKO), present an unexpected and generalized phenotype of high bone mass with decreased bone resorption and increased formation. In α(2A) /α(2C)-ARKO versus wild-type (WT) mice, micro-computed tomographic (µCT) analysis showed increased, better connected, and more plate-shaped trabeculae in the femur and vertebra and increased cortical thickness in the vertebra, whereas biomechanical analysis showed increased tibial and femoral strength. Tibial mRNA expression of tartrate-resistant acid phosphatase (TRACP) and receptor activator of NF-κB (RANK), which are osteoclast-related factors, was lower in knockout (KO) mice. Plasma leptin and brain mRNA levels of cocaine amphetamine-regulated transcript (CART), which are factors that centrally affect bone turnover, and serum levels of estradiol were similar between mice strains. Tibial ß(2)-AR mRNA expression also was similar in KO and WT littermates, whereas α(2A)-, α(2B)- and α(2C)-AR mRNAs were detected in the tibia of WT mice and in osteoblast-like MC3T3-E1 cells. By immunohistochemistry, we detected α(2A)-, α(2B)-, α(2C)- and ß(2)-ARs in osteoblasts, osteoclasts, and chondrocytes of 18.5-day-old mouse fetuses and 35-day-old mice. Finally, we showed that isolated osteoclasts in culture are responsive to the selective α(2)-AR agonist clonidine and to the nonspecific α-AR antagonist phentolamine. These findings suggest that ß(2)-AR is not the single adrenoceptor involved in bone turnover regulation and show that α(2)-AR signaling also may mediate the SNS actions in the skeleton.

Efficiency of intermittent exercise on adiposity and fatty liver in rats fed with high-fat diet.

OBJECTIVE: This study aimed to examine and compare the effects of continuous or intermittent exercises on adiposity and fatty liver in rats fed with high-fat diet. METHODS AND PROCEDURES: Wistar rats were divided according to diet composition-chow diet (C) or high-fat diet (H)-and kinds of exercise-sedentary (S), continuous (CE), or intermittent (IE) exercises. The CE group swam 90 min/day, and the IE group swam 3 x 30 min/day (at 4-h intervals between sessions); both groups exercised 5 days/week during 8 weeks. Body weight and food intake were recorded daily. Lipogenesis rate in vivo was determined by the incorporation of (3)H(2)O into saponified lipids in retroperitoneal (RET), epididymal (EPI), and visceral (VIS) white adipose tissues, brown adipose tissue (BAT), liver (L), and gastrocnemius muscle (GAST) using the gravimetric method. Total cholesterol, high-density lipoprotein (HDL)-cholesterol, and triacylglycerol (TG) were analyzed. RESULTS: The major finding of this study is that IE was more efficient than CE in reducing the adverse effects of high-fat diet and sedentarism. There was an improvement in the lipid profile and a reduction in food intake, body weight gain, visceral and central adiposity, and fatty liver, contributing to the control of obesity and other comorbidities, including nonalcoholic fat liver diseases. DISCUSSION: Earlier studies have discussed the effects of diet consumption on adiposity and their relation to chronic diseases and obesity. This study discusses the effects of high-fat diet consumption and the different kinds of exercise on weight gain, adiposity, fatty liver, and lipid profile in rats. The results may depend on the exercise, time of each session, age, gender, and experimental period.

Involvement of nitric oxide on prolactin release induced by immobilization stress in rats.

The nitric oxide (NO) has important participation in the control of hypothalamic-pituitary axis. The authors investigated the effect of NO donor, isosorbide dinitrate (ISDN), on prolactin (PRL) release induced by immobilization stress (IS) in male rats. Pretreatment with the NO donor, ISDN (2.5; 5 and 10 mg/kg), inhibited about 60-85% of the PRL response to IS. It is concluded that NO does participate in the regulation of PRL response to IS.