High force eccentric exercise enhances serum tartrate-resistant acid phosphatase-5b and osteocalcin.

We investigated the effects of eccentric contractions (ECs) on bone metabolism markers and the relationship between bone metabolism and skeletal muscle related protein. Seventeen young untrained men were divided into two groups and performed either 60 or 30 maximal ECs. We measured serum levels of osteocalcin (OC), bone alkaline phosphatase, cross-linked N-telopeptide of type I collagen (NTx), and tartrate-resistant acid phosphatase 5b (TRACP-5b), growth hormone (GH), and insulin-like growth factor-1 (IGF-1). Blood samples were collected for up to five days after ECs. OC with 60 ECs were significantly higher than with 30 ECs (2 hours; p<0.05, day 1 and day 5; p<0.01). TRACP-5b with 60 ECs were significantly higher than with 30 ECs (day 3 and day 5; p<0.001). IGF-1 and OC were significantly positively correlated with 60 ECs (2 hours, day 1, and day 5; p<0.05). There were also significant positive correlations between IGF-1 and NTx with 60 ECs (2 hours, p<0.01; day 1, p<0.05). We found that one bout of severe ECs caused increases in OC and TRACP-5b, which promote increased bone metabolism. Our results suggest that contraction-induced IGF-1 may activate OC and NTx in acute response.

Effect of eccentric contractions of elbow flexor on bone formation and resorption markers.

AIM: This study aimed to investigate the effects of eccentric contractions (ECs) of the biceps brachii muscle on bone metabolism markers. METHODS: Eight untrained subjects (20.0±0.5 years) performed 5 sets of 6 maximal ECs of the elbow flexors with a 2-min rest interval between each set. Blood samples were collected at 6 time points: before (Pre) ECs, immediately after (Post) ECs, and two hours (2 hours), 1 (day 1), 3 (days 3), and 5 days (days 5) after ECs. We measured the levels of the bone formation marker osteocalcin (OC) and the resorption marker tartrate-resistant acid phosphatase 5b (TRACP-5b). In addition, we measured the isometric tetanic torque and the levels of myoglobin (Mb), creatine kinase (CK), blood lactate, and insulin-like growth factor-1 (IGF-1). RESULTS: The results showed 1) CK and Mb levels increased significantly by days 3 and 5 (P<0.05); 2) OC levels significantly decreased in Post and 2 hours (P<0.01) and TRACP-5b levels significantly increased in Post (P<0.01); 3) OC positively correlated with the total work output in Post, 2 hours, and days 5 (Post: r=0.79, P<0.05; 2 hours: r=0.82, P<0.01; days 5: r=0.79, P<0.05); and 4) TRACP-5b levels positively correlated with IGF-1 levels (r=0.69, P<0.01). CONCLUSION: We conclude that a single bout of ECs of the biceps has a negative effect on bone metabolism in the acute phase.

The cartilage intermediate layer protein gene is associated with lumbar disc degeneration in collegiate judokas.

Lumbar disc degeneration is frequently seen in athletes. Lumbar disc diseases include a spectrum of diseases and/or symptoms, including lumbar disc degeneration. Some reports suggest an association between lumbar disc diseases and a functional single-nucleotide polymorphism (SNP;1184T/C, rs 2073711) of the cartilage intermediate layer protein ( CILP) gene. We hypothesized that lumbar disc degeneration occurrence may be significantly associated with SNP variants at the CILP gene in Japanese collegiate judo athletes. Eighty-nine Japanese judo athletes participated in this study. T2-weighted magnetic resonance imaging was used to define lumbar disc degeneration. Genotyping of the CILP gene (1184T/C) was performed using DNA sequencing. By using logistic regression analysis, significant associations of lumbar disc degeneration with the CILP C allele (odds ratio=4.1, 95% confidence interval: 1.57-10.71) and body weight (odds ratio=1.06, 95% confidence interval: 1.02-1.09) were observed. We conclude that the CILP gene 1184T/C polymorphism is a significant risk factor for lumbar disc degeneration occurrence in Japanese collegiate judo athletes.

Muscle plasticity related to changes in tubulin and αB-crystallin levels induced by eccentric contraction in rat skeletal muscles.

We used the model of eccentric contraction of the hindlimb muscle by Ochi et al. to examine the role of eccentric contraction in muscle plasticity. This model aims to focus on stimulated skeletal muscle responses by measuring tissue weights and tracing the quantities of αB-crystallin and tubulin. The medial gastrocnemius muscle (GCM) responded to electrically induced eccentric contraction (EIEC) with significant increases in tissue weight (p < 0.01) and the ratio of tissue weight to body weight (p < 0.05); however, there was a decrease in soleus muscle weight after EIEC. EIEC in the GCM caused contractile-induced sustenance of the traced proteins, but the soleus muscle exhibited a remarkable decrease in α-tubulin and a 19% decrease in αB-crystallin. EIEC caused fast-to-slow myosin heavy chain (MHC) isoform type-oriented shift within both the GCM and soleus muscle. These results have shown that different MHC isoform type-expressing slow and fast muscles commonly undergo fast-to-slow type MHC isoform transformation. This suggests that different levels of EIEC affected each of the slow and fast muscles to induce different quantitative changes in the expression of αB-crystallin and α-tubulin.

Genetic strain-dependent protein metabolism and muscle hypertrophy under chronic isometric training in rat gastrocnemius muscle.

Genetic strain-dependent reactivity to mechanical stimuli in rat skeletal muscle has not been examined. This study aimed to examine whether genetic strain-dependency is associated with reactivity in protein metabolism and the resultant muscle hypertrophy after isometric resistance training (RT). The right triceps of Sprague-Dawley (SD) and Wistar rats underwent 12 sessions of RT. After RT, a transition from the IIb to the IIx myosin heavy-chain isoform was observed in both strains. In SD rats, the lateral gastrocnemius muscle (LG) mass of the trained legs (TRN) was significantly higher than that of the control legs (CON) (7.8 %, P<0.05). Meanwhile, in Wistar rats, the LG mass was unchanged. In SD rats, the levels of 70-kDa ribosomal protein S6 kinase (p70S6k) and forkhead box 3a (FOXO3a) phosphorylation in the TRN were significantly greater than those of the CON (2.2- and 1.9-fold, respectively; P<0.05). The expression of muscle ring finger-1 (MuRF1) and muscle atrophy F-box (MAFbx/atrogin-1) in the TRN were significantly lower than those of the CON (0.6- and 0.7-fold, respectively; P<0.05). However, in Wistar rats, there was no significant difference. These results suggest a genetic strain difference in protein metabolism. This phenomenon may be useful for studying individual differences in response to RT.

Blood flow-restricted training does not improve jump performance in untrained young men.

The purpose of this study was to investigate the effect of blood flow-restricted training (BFRT) on jump performance in relation to changes in muscle strength. Seventeen untrained young men were assigned into either BFRT or normal training (NORT) groups and performed low-intensity [30-40% of one-repetition maximum (1RM)] resistance exercise (horizontal squat, 3-4 sets × 15-30 repetitions) twice a week for 10 weeks. The BFRT performed the exercise with their proximal thighs compressed by air-pressure cuffs for the purpose of blood flow restriction. Squat 1RM, muscle cross-sectional area (CSA) of quadriceps femoris, and countermovement jump (CMJ) height were measured before and after the 10-wk training period. Squat 1RM increased greater in BFRT than in NORT (19.3% vs. 9.7%, P < 0.01). Although the CSA increase was independent of groups, it tended to be larger in BFRT than in NORT (8.3% vs. 2.9%, P = 0.094). On the other hand, CMJ height did not change after the training (P = 0.51). In conclusion, the present study showed that BFRT induced muscle hypertrophy and strength increase, whereas it did not increase CMJ height in previously untrained young men. It is suggested that BFRT is ineffective in improving jump performance.

Functional characterization of Musca glutamate- and GABA-gated chloride channels expressed independently and coexpressed in Xenopus oocytes.

Ligand-gated chloride channels (LGICs) are important targets for insecticides and parasiticides. Genes encoding subunits of two LGICs, a glutamate-gated chloride channel (MdGluCl-alpha) and a gamma-aminobutyric acid (GABA)-gated chloride channel (MdRdl), were cloned from house-flies (Musca domestica L.). These genes were first expressed independently in Xenopus laevis oocytes by cRNA injection in order to investigate the pharmacology of these ligand-gated channels using two-electrode voltage-clamp electrophysiology. It was found that L-glutamate and GABA activated the MdGluCl-alpha homo-oligomers with an EC(50) value of 30 microM and the MdRdl homo-oligomers with an EC(50) value of 101 microM, respectively. Both channels were chloride ion-permeable, and the MdRdl channel was more sensitive to chloride channel blockers, such as gamma-hexachlorocyclohexane (gamma-HCH), fipronil and picrotoxinin, than the MdGluCl-alpha channel. MdGluCl-alpha required only 1-2 days of incubation after cRNA injection to be expressed in oocytes, whereas 4-7 days of incubation was necessary to achieve MdRdl expression. However, when the cRNA of MdGluCl-alpha was injected at a dose of 1% (w/w) 1 day after the injection of the cRNA of MdRdl, a significant increase in the current amplitude of responses to GABA was observed, and the incubation period necessary for MdRdl expression became shorter. These results suggest that MdGluCl-alpha assists in the expression of MdRdl when the two are coexpressed.