RESUMO
[Introduction] This study compared the effects of joint immobilization and concurrent electroacupuncture stimulation on fracture line appearance, which is indicative of differences in cortical bone structure, in the femurs of young adult rats. [Materials and Methods] Forty-two 7-week-old Wistar rats were divided into three groups: a hindlimb immobilized group (IM), a hindlimb immobilized group with concurrent electroacupuncture stimulation (IMEA), and an untreated control group (CO). IM and IMEA were immobilized for two weeks with a jacket-type immobilization device that immobilized the hip joint in extension and restricted hip joint adduction and abduction. Acupuncture needles were inserted into the femoral region during the immobilization period in the IMEA group, and continuous alternating current was used for stimulation. A low-frequency stimulator was used to generate electrical current (250 μsec, 50 Hz, 0.24 mA, 500 Ω load resistance), and stimulation was performed daily for two weeks at 10 min/day. The extracted femur was fractured from the anterior part of the diaphysis or metaphyseal end by three-point-bending under constant conditions with 10 mm between the fulcrum and a crosshead speed of 10 mm/min. [Results] IM showed significantly lower Stiffness, Deformation, and Strength values than CO. Bone morphometry parameters also showed lower values for IM. A cement line was observed between lamellar and non-lamellar bone in CO and IMEA, but was indistinct in IM. In CO and IMEA, minute bone fragments were formed in the deep diaphysis region sandwiched between the inner and outer circumferential lamellae, but no such fragments were found in IM. IMEA had less resorption than IM, and lamellar bone with a structure similar to CO was maintained. Moreover, cracks observed in CO and IMEA ran longitudinally in the vicinity of the cement line and rest line, but no such cracks were found in IM. [Discussion and Conclusion] These findings suggest that electroacupuncture mitigates bone weakening in immobilized rat femurs, and this affects the appearance of the fracture line.
RESUMO
This study investigated how dietary fat affects muscle atrophy and lipid metabolism in various muscles during hindlimb immobilization in rats. Twenty-four male Sprague-Dawley rats had their left hindlimb immobilized and were divided into four groups by dietary fat content and composition. The contralateral hindlimb (control) was compared with the immobilized limb in all dietary groups. Rats (n = 6/group) were fed a 4% corn oil diet (CO), 2.6% corn oil + 1.4% fish oil diet (FO), 30% corn oil diet (HCO), or a 30% beef tallow diet (HBT)after their hind limbs were immobilized for 10 days. Data were collected for the gastrocnemius, plantaris and soleus muscles. Muscle atrophy was induced significantly after 10 days of hindlimb immobilization, resulting in significantly decreased muscle mass and total muscle protein content. The protein levels of peroxisome proliferator activated receptor delta (PPARdelta) in the plantaris, gastrocnemius, and soleus increased following hindlimb immobilization irrespective of dietary fat intake. Interestingly, the PPARdelta mRNA level in the plantaris decreased significantly in all groups and that in the FO group was lower than that in the other groups. The soleus PPARdelta mRNA level decreased significantly following hindlimb immobilization in the FO group only. Muscle carnitine palmitoyl transferase 1 (mCPT1) mRNA level was not affected by hindlimb immobilization. However, the mCPT1 mRNA level in the FO group was significantly lower in the plantaris but higher in the soleus than that in the other groups. The pyruvate dehydrogenase kinase 4 (PDK4) mRNA level in the plantaris decreased significantly, whereas that in the soleus increased significantly following hindlimb immobilization. The plantaris, but not soleus, PDK4 mRNA level was significantly higher in the FO group than that in the CO group. The increased PPARdelta protein level following hindlimb immobilization may have suppressed triglyceride accumulation in muscles and different types of dietary fat may have differentially affected muscle atrophy according to muscle type. Our results suggest that omega-3 polyunsaturated fatty acids may suppress muscle atrophy and lipid accumulation by positively affecting the expression level and activity of PPARdelta and PPARdelta-related enzymes, which are supposed to play an important role in muscle lipid metabolism.