Effects of alfacalcidol on muscle strength, muscle fatigue, and bone mineral density in normal and ovariectomized rats

Vitamin D affects not only bone but also muscle to prevent falls and osteoporotic fractures. However, these effects on muscle and the mechanisms of fall prevention are still unclear. The purpose of this study was to investigate the effects of alfacalcidol [1α(OH)D(3)] on muscle strength, muscle fatigue, and bone mineral density (BMD) in ovariectomized rats. Seven-month-old female Wistar rats were orally administered 1α(OH)D(3) or its vehicle everyday for 4 weeks after ovariectomy (OVX) or sham operation. Calf muscle strength and fatigue were evaluated by electrical stimulation of the sciatic nerve under general anesthesia. 1α(OH)D(3) administration significantly increased the maximum muscle strength in the sham-operated (P < 0.01) and the OVX (P < 0.01) groups compared to their respective control groups. However, 1α(OH)D(3) administration did not significantly affect muscle fatigue in these groups. The BMD of the femur in the 1α(OH)D(3)-treated OVX group was significantly higher than that in the vehicle-treated OVX group (P = 0.04). These results suggested that 1α(OH)D(3) increases muscle strength but does not affect muscle fatigue in this rat model. The effectiveness of activated vitamin D in preventing bone fractures may be partly owing to its effect on muscle strength in addition to its known effect on bone metabolism.     

Effects of alfacalcidol on circulating cytokines and growth factors in rat skeletal muscle

Supra-physiological levels of vitamin D induce skeletal muscle atrophy, which may be particularly detrimental in already sarcopaenic elderly. Neither the cause nor whether the atrophy is fibre type specific are known. To obtain supraphysiological levels of circulating vitamin D (1,25(OH)₂D₃) 27.5-month-old female Fischer₃₄₄ × Brown Norway F1 rats were orally treated for 6 weeks with vehicle or the vitamin D analogue alfacalcidol. Alfacalcidol treatment induced a 22% decrease in body mass and 17% muscle atrophy. Fibre atrophy was restricted to type IIb fibres in the low-oxidative part of the gastrocnemius medialis only (−22%; P < 0.05). There was a concomitant 1.6-fold increase in mRNA expression of the ubiquitin ligase MuRF-1 (P < 0.001), whereas those of insulin-like growth factor 1 and myostatin were not affected. Circulating IL-6 was unaltered, but leptin and adiponectin were decreased (−39%) and increased (64%), respectively. The treated rats also exhibited a reduced food intake. In conclusion, supraphysiological levels of circulating 1,25(OH)₂D₃ cause preferential atrophy of type IIb fibres, which is associated with an increased expression of MuRF-1 without evidence of systemic inflammation. The atrophy and loss of body mass in the presence of supra-physiological levels of vitamin D are primarily due to a reduced food intake.     

Effects of ovariectomy and estrogen on skeletal muscle function in growing rats

This study examined the effect of estrogen replacement on soleus muscle size and contractile function in ovariectomized rats during physiological growth. Seven week old female Sprague-Dawley rats were assigned to one of three treatment groups: (1) control animals (SHAM), (2) ovariectomized animals without estrogen replacement (OVX/CO), and (3) ovariectomized animals with 17 beta-estradiol replacement (OVX/E2). OVX/CO and OVX/E2 animals were pair-fed to SHAM animals to rule out the potentially confounding effect of differences in food intake. Rats were sacrificed 4 weeks after surgery and the soleus muscle was removed for analysis. Estrogen replacement reduced body weight, relative body weight gain, and soleus muscle fiber size despite all groups having a similar food intake. Ovariectomy alone had no effect on any of these parameters suggesting that estrogen may inhibit skeletal muscle growth when it is the only ovarian hormone present. Neither ovariectomy nor estrogen replacement affected maximal specific isometric force. Estrogen replacement increased half relaxation time. Ovariectomy resulted in a reduction in time to peak tension that was reversed with estrogen replacement. This reduction was not accompanied by a change in myosin heavy chain composition implying that calcium handling may have been altered. Results from this study suggest that estrogen affects skeletal muscle growth and twitch kinetics.     

Interaction of dichloromethylene diphosphonate and vitamin D on bone of thyroparathyroidectomized rats.

Dichloromethylene diphosphonate (Cl2MDP) antagonized the action of vitamin D on bone in thyroparathyroidectomized rats by reducing the metabolic activity of osteoblasts and osteocytes and decreasing the number of osteoclasts. Ultrastructurally, osteoblasts in Cl2MDP-treated rats were interpreted to be less active in bone matrix synthesis. Osteocytes in Cl2MDP-treated rats were interpreted ultrastructurally to be inactive; there was no evidence of bone resorption when compared to osteocytes in rats given vitamin D alone. Abnormal osmiophilic densities in the pericellular bone matrix of rats given vitamin D alone were not present in rats given vitamin D and Cl2MDP. The ultrastructure of osteoclasts was unaltered by Cl2MDT. These cellular changes were associated with a decrease in serum calcium and increase in bone ash and magnesium concentration in rats given high levels (10 mg/kg) of Cl2MDP. Bone adenosine triphosphatase and alkaline phosphatase activities were not affected by Cl2MDP. These results suggest that Cl2MDP may limit the hypercalcemia of hypervitaminosis D by directly inhibiting bone cells in addition to its physicochemical action.     

Autologous bone marrow-derived cells enhance muscle strength following skeletal muscle crush injury in rats

Insufficient post-traumatic skeletal muscle regeneration with consecutive functional deficiency continues to be a serious problem in orthopedic and trauma surgery. Transplantation of autologous muscle precursor cells has shown encouraging results in muscle trauma treatment but is associated with significant donor site morbidity. In contrast to this, bone marrow-derived (BMD) cells can be obtained without any functional deficit by puncture. The goal of this study was to examine whether regular muscle regeneration can be improved by local application of autologous BMD cells in a rat model of blunt skeletal muscle trauma. One week after standardized open blunt crush injury to the left soleus muscle, 10(6) autologous BMD cells were injected into the traumatized muscle of male Sprague Dawley rats. Rats of the control group received saline solution as treatment. Three weeks after application, the fast twitch and tetanic contraction capacity of the soleus muscles was measured bilaterally by stimulating the sciatic nerves. Contraction forces of injured soleus muscles in control animals recovered to 39 +/- 10% (tetanic) and 59 +/- 12% (fast twitch) of the contralateral noninjured soleus muscles (p < 0.001). In contrast, autologous BMD cell injection significantly restored contractile forces to 53 +/- 8% (tetanic) and 72 +/- 13% (fast twitch) compared to those observed in contralateral noninjured soleus muscles. Thus, muscle function was significantly increased by BMD cell treatment (tetanic, p = 0.014; fast twitch, p = 0.05). In conclusion, autologous BMD cell grafting leads to an increase in contraction force, 14% in tetanic and 13% in fast twitch stimulation, demonstrating its potential to improve functional outcome after skeletal muscle crush injury.     

Effects of repeated lengthening contractions on skeletal muscle adaptations in female rats

We examined the adaptation of plantar flexor muscles of female rats to 6 weeks (5 days/week) of lengthening contractions. After repeated lengthening contractions, a decrease in myofiber area of gastrocnemius medialis (26%) was accompanied by an increase in extracellular matrix (ECM) (42%) and collagen content (30.9%) without changes in muscle mass. Decrease in myofiber area (13%) and muscle mass of soleus (19%) was associated with increased collagen content (28%) and ECM (15%). Relative number of soleus myofibers stained for fast myosin increased by 26%. For plantaris, increases in collagen content (32.3%), percent ECM (17%), and myofiber area (6%) were recorded. We also observed (1) increases (3.3%) in the collagen content of the Achilles tendon, (2) no change in the crosslink content of any of the tissues tested, and (3) no difference in the force-frequency relationship of the plantar flexor muscles. Substantial decreases in myofiber areas with increases in muscle connective tissue by 6 weeks of repeated lengthening contractions did not appear to result in isometric force loss.     

Regeneration pattern of cardiac and skeletal muscle after transplantation into a skeletal muscle bed in rats

Background: The ability of skeletal muscle to regenerate after injury is well established. In contrast, cardiac muscle is incapable of regeneration and recovery after injury. The aim of the present study was to evaluate and compare the regeneration pattern of cardiac and skeletal muscle after transplantation into a skeletal muscle bed in rats. Methods: The following group of transplants were performed at the site prepared by removing the host extensor digitorum longus (EDL) muscle. The first group consisted of cardiac muscle transplanted as one piece or after mincing into 1-mm pieces. The second group included cotransplants of cardiac and skeletal muscle minces that were intermixed. Entire EDL muscle or minced EDL muscle were also transplanted for comparison. Rats were sacrificed 3–30 days after transplantation for morphological analysis. Results: The results demonstrated that skeletal muscle transplants underwent rapid regeneration, and by 30 days the entire muscle was filled with regenerated myofibers. In transplants of cardiac muscle significant inflammation, myocardial degeneration and necrosis were observed. In spite of the necrosis and fibrosis, the presence of a few regenerated myotubes in the outer region was observed. In cardiac and skeletal muscle cotransplants, the inflammation was restricted to cardiac tissue; however, by 30 days the entire contransplant was filled with regenerated myotubes and myofibers. Conclusions: These results show that skeletal muscle is capable of growth, regeneration, and integration with the cardiac muscle after cotransplantation. Combination of skeletal and cardiac muscle may prove useful in defining the cellular processes necessary for enhancing cardiac repair after injury. © 1995 Wiley-Liss, Inc.     

Effects of exercise on the adenosinetriphosphatase activity in skeletal and heart muscle of rats

Summary Fifty-eight male albino rats of the Sprague-Dawley strain with an average beginning weight of 340 grams were exercised for 5 weeks on a training program consisting of one-half hour daily swim in water at 37 °C. Pair-fed, non swimming animals served as controls. ATPase activities were determined on the heart ventricles and gastrocnemii. The results were expressed in terms of unit, actual total and relative total activities. The exercise significantly altered the enzymatic activities of the heart ventricles (P相似文献   

Effects of chronic intermittent asphyxia on haematocrit, pulmonary arterial pressure and skeletal muscle structure in rats

Sleep-disordered breathing in humans is a common condition associated with serious cardiovascular and other abnormalities. The prevalence and pathogenesis of increased haematocrit and pulmonary hypertension is controversial and it has been suggested that these changes only occur in patients who also have daytime continuous hypoxaemia. The hypothesis tested here is that the chronic intermittent hypoxia and asphyxia associated with sleep-disordered breathing causes erythropoiesis and pulmonary hypertension and that this occurs in the absence of periods of continuous hypoxia. In humans and animals with obstructive sleep apnoea, there are abnormalities of upper airway muscle structure that have been ascribed to increased load placed on these muscles. An alternative hypothesis is that chronic intermittent hypoxia and asphyxia cause changes in upper airway muscle structure and function. To test these hypotheses, rats were exposed to intermittent hypoxia and asphyxia for 8 h per day for 5 weeks. This caused an increase in haematocrit, right ventricular weight and pulmonary arterial pressure. There were only slight changes in diaphragm, upper airway and limb muscle structure and force production but in general, muscle fatigability was increased. In conclusion chronic intermittent hypoxia and asphyxia cause an increase in haematocrit and pulmonary arterial pressure in the absence of periods of continuous hypoxia. Chronic intermittent hypoxia and asphyxia have little effect on skeletal muscle structure and force production but increase muscle fatigue. Increased upper airway muscle fatigue could lead to a vicious cycle of further compromise in upper airway patency and further hypoxia and asphyxia.     

Effects of vitamin D on renal fibrosis in diabetic nephropathy model rats

This study is to investigate the effects of vitamin D on renal fibrosis in rat diabetic nephropathy models, as well as the changes and interactions in the expressions of renal fibrogenesis- and inflammation-related genes. Rat diabetic nephropathy models were established by high-fat diets, which were subjected to TGF-β1 manipulation, as well as vitamin D treatment. H&E staining, Masson staining, and TEM detection were performed to assess the effects of vitamin D treatment and/or TGF-β1 manipulation on pathological changes in the renal tissues in these rat diabetic nephropathy models. Immunohistology and real-time PCR were used to evaluate the expressions of TGF-β1, MCP-1, CTGF, and VDR. Histological staining and TEM detection showed that, in both TGF-β1 over-expressed and interfered groups, vitamin D administration alleviated the renal fibrosis, compared with the vehicle treatment. Similar results were observed with the immunohistological staining. Real-time PCR analysis indicated that, when TGF-β1 was over-expressed in diabetic nephropathy, the expressions of MCP-1 and CTGF were also up-regulated, which would be decreased by the treatment of vitamin D. On the other hand, when TGF-β1 was interfered in DN, the expressions of MCP-1 and CTGF were relatively down-regulated, which would be further lowered by vitamin D administration. The mRNA expression of VDR was elevated by vitamin D treatment in these diabetic nephropathy models. Active vitamin D₃ and lentivirus-mediated TGF-β1 interference could effectively reduce the renal fibrosis and protect the renal function in diabetic nephropathy rat models, which makes a promising therapeutic strategy for the disease.     

Symptomatic myositis-myalgia in hypercholesterolemic statin-treated patients with concurrent vitamin D deficiency leading to statin intolerance may reflect a reversible interaction between vitamin D deficiency and statins on skeletal muscle

Myositis-myalgia is the most common cause of statin intolerance, leading to cessation of statin use, with consequent failure to lower LDL cholesterol to target levels for primary and secondary prevention of cardiovascular disease (CVD). We hypothesize that symptomatic myositis-myalgia in hypercholesterolemic statin-treated patients with concurrent 25 (OH) vitamin D deficiency and statin intolerance may reflect a reversible interaction between vitamin D deficiency and statins on skeletal muscle. In hypercholesterolemic, vitamin D deficient patients, intolerant to statins because of myositis-myalgia, three non-blinded clinical case series have uniformly demonstrated that after supplementation with oral vitamin D2 which normalizes serum 25 (OH) vitamin D levels, statins can be successfully re-instituted in >90% of patients, without recurrent myositis-myalgia, with reduction of LDL cholesterol to target levels. Empirically, in 68 hypercholesterolemic patients, unable to tolerate ? 1 statin because of myositis-myalgia, selected by low (<32 ng/ml) serum 25 (OH) vitamin D, we have prospectively assessed whether resolution of vitamin D deficiency would result in statin tolerance, free of myositis-myalgia. On no statins, 50,000 units of vitamin D2 was given twice/week for 3 weeks, and was then continued once/week. After 3 weeks on vitamin D supplementation, statins were restarted, and patients were re-assessed after 3 months on statins while continuing vitamin D supplementation. At 3 months follow-up, on vitamin D supplementation and re-instituted statins, 62 of 68 (91%) previously statin-intolerant patients now tolerated statins well and were asymptomatic without myositis-myalgia. In these 68 patients, on vitamin D supplementation and statins, mean ± SD vitamin D rose from 22 ± 7 to 43 ± 13 ng/ml (p < 0.0001), and LDL cholesterol fell from 162 ± 55 to 101 ± 35 mg/dl (p < 0.0001). Despite published and new empirical evidence, the medical establishment has refused to accept the hypothesis, requiring placebo-controlled, double-blind studies, none having been reported to date. A placebo-controlled, double-blind study is needed to document that normalization of serum 25 (OH) vitamin D levels in vitamin D deficient, statin intolerant patients would facilitate re-introduction of statins with concurrent freedom from myositis-myalgia. The ability to reverse myositis-myalgia in vitamin D deficient, statin intolerant, hypercholesterolemic patients by vitamin D supplementation would be extraordinarily valuable, facilitating reinstitution of statins to lower LDL cholesterol to reduce risk of CVD events. We hypothesize that symptomatic myositis-myalgia in hypercholesterolemic statin-treated patients with concurrent vitamin D deficiency producing statin intolerance may reflect a reversible interaction between vitamin D deficiency and statins on skeletal muscle.     

针刺对运动性骨骼肌损伤大鼠骨骼肌线粒体自噬的影响

目的:通过观察针刺对大负荷运动大鼠骨骼肌线粒体自噬相关蛋白表达的影响,探讨针刺在运动性骨骼肌损伤修复中的作用及其机制。方法:将128只成年雄性Sprague-Dawley大鼠随机分为4组:空白对照(control,C;n=8)组、单纯运动(exercise,E;n=40)组、单纯针刺(acupuncture,A;n=40)组和运动针刺(exercise and acupuncture,EA;n=40)组。其中,E和EA组进行1次下坡跑运动,A组和EA组(运动后即刻)施加针刺处理。后3组根据干预后不同时相又分为0 h、12 h、24 h、48 h和72 h亚组(n=8),分别于对应时点分离比目鱼肌进行检测,使用透射电子显微镜观察骨骼肌线粒体超微结构变化;采用ELISA法检测比目鱼肌线粒体定量酶柠檬酸合成酶(CS)的含量变化;应用Western blot法检测骨骼肌PTEN诱导假定激酶1(PINK1)、parkin和微管相关蛋白1轻链3(LC3)的蛋白表达变化。结果:1次大负荷运动后大鼠比目鱼肌线粒体出现明显肿胀和肌膜下积聚等超微结构异常变化,伴有大量自噬体形成;同时CS的含量明显减少(P0.05);线粒体自噬蛋白PINK1、parkin和LC3均出现一过性的表达升高(P0.05)。运动后针刺明显改善了线粒体超微结构的异常变化,减少自噬溶酶体的出现,同时抑制CS的含量减少,下调PINK1、parkin和LC3在线粒体上的表达(P0.05)。结论:1次大负荷运动后骨骼肌线粒体结构和数量受损,通过激活PINK1/parkin途径诱发线粒体自噬的过度发生。大负荷运动后针刺可以缓解骨骼肌线粒体的损伤,其作用机制可能是通过下调线粒体外膜蛋白PINK1表达,抑制其对下游胞浆蛋白parkin的招募,进而影响LC3与线粒体的结合以抑制线粒体自噬过度激活。     

A vitamin D analog ameliorates glomerular injury on rat glomerulonephritis

OCT (22-oxa-calcitriol), a vitamin D analog, has been reported to show strong inhibitory effects on mesangial cell proliferation in vitro. In the present study, we report a study of the effect of OCT on anti-thy-1 glomerulonephritis. Both OCT and 1,25(OH)(2)D(3) significantly inhibited mesangial cell proliferation, the degree of glomerulosclerosis, and albuminuria at day 8 compared to the disease control group. The OCT-treated group showed normal calcium levels but the 1,25(OH)(2)D(3)-treated group showed higher levels. The disease control group showed a marked increase of type I and type IV collagens, and alpha-smooth muscle actin (alpha-SMA) compared to the normal group. The treatment of OCT or 1,25(OH)(2)D(3) significantly reduced the expression of these proteins. The mRNA of the glomeruli of anti-thy-1 model expressed significantly higher levels of type I and type IV collagens, and alpha-SMA at day 8 compared to normal rats. Treatment with OCT or 1,25(OH)(2)D(3) inhibited the mRNA expressions of type I and type IV collagens, as well as that of alpha-SMA. These data demonstrate that OCT inhibits mesangial cell proliferation and extracellular matrix expansion with a low calcemic activity. Disease control rats showed significantly increased levels of transforming growth factor-beta1 protein in the glomeruli, but treatment with OCT or 1,25(OH)(2)D(3) markedly reduced this expression. The levels of mRNA in glomeruli were also consistent with these protein levels. Therefore, the suppressive effect of OCT may be mediated by inhibition of transforming growth factor-beta1. The present results suggest that OCT has potential for use in therapeutic strategy for the treatment of glomerulonephritis without inducing hypercalcemia.     

Effects of chronic caffeine intake and low-intensity exercise on skeletal muscle of Wistar rats

Caffeine can affect muscle cell physiology and the inflammatory response during exercise. The purpose of this study was to analyse muscle damage markers and inflammatory cell infiltration into the soleus muscle of sedentary and exercised animals submitted to chronic caffeine intake. Thirty-two male Wistar rats were divided into the following four groups (n = 8 per group): sedentary control (SCO); sedentary + caffeine (SCAF); trained control (TCO); and trained + caffeine (TCAF). The animals were housed in individual cages and received tap water or caffeine (1 mg ml(-1)); they were maintained at rest or submitted to swimming for up to 40 min day(-1) with a 4% load, five times per week for 30 days. Blood samples were collected for analysis of serum lactate, creatine kinase and calcium. The right soleus muscle and the epididymal fat depot were weighed, and the muscle was submitted to histological analysis. Training and caffeine did not change body or muscle weight, food and liquid intake or serum calcium levels among groups. Decreased fat tissue (P < 0.05) was observed in the SCAF (4.05 ± 1.03 g), TCO (4.14 ± 0.78 g) and TCAF groups (4.02 ± 1.02 g) compared with the SCO group (5.31 ± 1.06 g). Serum creatine kinase activity was significantly reduced in the SCAF (787.3 ± 230.3 U l(-1)), TCO (775.3 ± 232.3 U l(-1)) and TCAF groups (379.5 ± 110.5 U l(-1)) compared with the SCO group (1610.2 ± 276.5 U l(-1)). Few damaged muscle fibres (P < 0.05) were found in SCAF (16.7 ± 12.8%) and TCAF groups (17.3 ± 11.7%) compared with the SCO group (53.6 ± 13.9%). The SCAF group presented fewer fields with inflammatory cells (7.6 ± 8.7 fields) compared with the SCO group (123 ± 146 fields). The results suggest that the chronic intake of caffeine, as well as chronic low-intensity exercise, decreased muscle damage and inflammatory infiltration into skeletal muscle.     

Effects of vitamin A on doxorubicin-induced chromosomal aberrations in bone marrow cells of rats

The present study was carried out to evaluate the role of vitamin A (VA) on the induction of chromosomal aberrations (CA) in rat bone marrow cells and to investigate its modulating effect on chromosomal damage induced by doxorubicin (DXR). Wistar rats were treated with VA (7.5, 15 and 30 microg/kg body wt) once a day for 2 days by gavage before injecting DXR (90 mg/kg body wt). Rats in the control group were treated with corresponding doses of water and olive oil. Animals treated with the medium dose of VA (15 microg/kg body wt) plus single dose of DXR presented a statistically significant reduction in total number of CA and in number of abnormal metaphases (P < 0.05). However, when compared with control and DXR groups, the low and high VA doses (7.5 and 30 microg/kg body wt) were found to be less efficient than the medium dose VA (15 microg/kg body wt) in terms of parameters analyzed. Furthermore, the high dose of VA group (30 microg/kg body wt) was found to be clastogenic (P < 0.05). This study concludes that the protective effect of VA against chromosome damage is dose dependent.