タウリンと骨格筋の血糖取り込み

日本において糖尿病は国民病と言えるほど罹患者の多い疾患であるが、タウリンには糖尿病による高血糖状態を改善する効果がある。骨格筋はインスリンや運動（筋収縮）の作用で血糖を取り込み、血糖値を低下させる重要な器官である。本稿では「膵臓からのインスリン分泌」と「骨格筋における血糖取り込み」にタウリンが及ぼす影響についてまとめた。タウリンは、膵臓からのインスリン分泌や、インスリンシグナル関連因子、そして糖輸送体GLUT4の発現量を高めるようだ。しかし、タウリンがインスリン標的器官である骨格筋における血糖取り込みに及ぼす影響ついては十分に研究されておらず、タウリンが骨格筋の血糖取り込みを高める機序については、これから更なる研究が必要である

Sleep Quality is associated with Central Arterial Stiffness in Postmenopausal Women : A Cross-sectional Pilot Study

This study aimed to investigate the associations between sleep quality and arterial stiffness in healthy postmenopausal women. A total of 31 healthy postmenopausal women aged between 50 and 74 years participated in this study. Objectively and subjectively measured sleep quantity and quality were concomitantly obtained by a waist-worn actigraphy, Pittsburgh Sleep Quality Index (PSQI) questionnaire, and daily sleep diary. Carotid-femoral pulse wave velocity (cfPWV), brachial-ankle PWV (baPWV), and femoral-ankle PWV (faPWV) were measured as indices of arterial stiffness. Based on the PSQI score, the participants were divided into good (PSQI 5.5; n = 10) sleepers. Self-reported sleep duration was significantly longer in poor sleepers than in good sleepers. However, there was no difference in total sleep time measured by actigraphy between the two groups. Additionally, sleep latency and wake after sleep onset significantly increased, and sleep efficiency significantly decreased in poor sleepers than in good sleepers. The cfPWV and baPWV were significantly higher in poor sleepers than in good sleepers, even after adjustment for risk factors (i.e., age, blood pressure, and physical activity), but no difference in faPWV. These results suggest that decreased sleep quality is associated with an increase in central arterial stiffness in postmenopausal women

N-acetyltaurine and Acetylcarnitine Production for the Mitochondrial Acetyl-CoA Regulation in Skeletal Muscles during Endurance Exercises

During endurance exercises, a large amount of mitochondrial acetyl-CoA is produced in skeletal muscles from lipids, and the excess acetyl-CoA suppresses the metabolic flux from glycolysis to the TCA cycle. This study evaluated the hypothesis that taurine and carnitine act as a buffer of the acetyl moiety of mitochondrial acetyl-CoA derived from the short- and long-chain fatty acids of skeletal muscles during endurance exercises. In human subjects, the serum concentrations of acetylated forms of taurine (NAT) and carnitine (ACT), which are the metabolites of acetyl-CoA buffering, significantly increased after a full marathon. In the culture medium of primary human skeletal muscle cells, NAT and ACT concentrations significantly increased when they were cultured with taurine and acetate or with carnitine and palmitic acid, respectively. The increase in the mitochondrial acetyl-CoA/free CoA ratio induced by acetate and palmitic acid was suppressed by taurine and carnitine, respectively. Elevations of NAT and ACT in the blood of humans during endurance exercises might serve the buffering of the acetyl-moiety in mitochondria by taurine and carnitine, respectively. The results suggest that blood levels of NAT and ACT indicate energy production status from fatty acids in the skeletal muscles of humans undergoing endurance exercise

Acute bout of exercise downregulates thioredoxin-interacting protein expression in rat contracting skeletal muscles

We previously reported that in rat skeletal muscle, disuse (i.e., decreased muscle contractile activity) rapidly increases thioredoxin-interacting protein (TXNIP), which is implicated in the reduced glucose uptake. Accordingly, we sought herein to (a) determine the effect of exercise (i.e., increased muscle contractile activity) on muscle TXNIP protein expression, and (b) elucidate the mechanisms underlying the changes of TXNIP protein expression in response to exercise. Rat epitrochlearis and soleus muscles were dissected out after an acute bout of 3-hr swimming (without weight loading) or 3-hr treadmill running (15% grade at 9m/min). In a separate protocol, the isolated epitrochlearis and soleus muscles were incubated for 3 hr with AMP-dependent protein kinase activator AICAR. Immediately after the cessation of the 3-hr swimming, the TXNIP protein was decreased in epitrochlearis but not in soleus muscle. Conversely, 3-hr treadmill running decreased the TXNIP protein in soleus but not in epitrochlearis muscle. TXNIP protein was decreased concomitantly with reduced postexercise muscle glycogen, showing that a decrease in TXNIP protein expression occurs in muscles that are recruited during exercise. In addition, 3-hr incubation with AICAR decreased TXNIP protein in both isolated epitrochlearis and soleus muscles. Our results suggest that (a) an acute bout of exercise downregulates TXNIP protein expression in rat contracting skeletal muscles, and (b) the reduction in TXNIP protein expression in contracting muscles is probably mediated by AMPK activation, at least in part

Attenuation of indirect markers of eccentric exercise-induced muscle damage by curcumin

Purpose: Polyphenolic curcumin is known to have potent anti-inflammatory effects; thus the present study investigated the hypothesis that curcumin ingestion would attenuate muscle damage after eccentric exercise. Methods: Fourteen untrained young men (24 ± 1 years) performed 50 maximal isokinetic (120°/s) eccentric contractions of the elbow flexors of one arm on an isokinetic dynamometer and the same exercise with the other arm 4 weeks later. They took 150 mg of curcumin (theracurmin) or placebo (starch) orally before and 12 h after each eccentric exercise bout in a randomised, crossover design. Maximal voluntary contraction (MVC) torque of the elbow flexors, range of motion of the elbow joint, upper-arm circumference, muscle soreness, serum creatine kinase (CK) activity, and plasma interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) concentration were measured before, immediately after, and 24, 48, 72 and 96 h after each eccentric exercise. Changes in these variables over time were compared between curcumin and placebo conditions by two-way repeated measures ANOVA. Results: MVC torque decreased smaller and recovered faster (e.g., 4 days post-exercise: −31 ± 13 % vs. −15 ± 15 %), and peak serum CK activity was smaller (peak: 7684 ± 8959 IU/L vs. 3398 ± 3562 IU/L) for curcumin than placebo condition (P \u3c 0.05). However, no significant differences between conditions were evident for other variables, and no significant changes in IL-6 and TNF-α were evident after exercise. Conclusion: It is concluded that theracurmin ingestion attenuates some aspects of muscle damage such as MVC loss and CK activity increase

Taurine supplementation enhances endurance capacity by delaying blood glucose decline during prolonged exercise in rats

Taurine enhances physical performance; however, the underlying mechanism remains unclear. This study examined the effect of taurine on the overtime dynamics of blood glucose concentration (BGC) during endurance exercise in rats. Male F344 rats were subjected to transient treadmill exercise until exhaustion following 3 weeks of taurine supplementation or non-supplementation (TAU and CON groups). Every 10 min during exercise, BGC was measured in blood collected through cannulation of the jugular vein. Gluconeogenesis-, lipolysis-, and fatty acid oxidation-related factors in the plasma, liver, and skeletal muscles were also analyzed after 120-min run. Exercise time to exhaustion was significantly longer with taurine supplementation. BGC in the two groups significantly increased by 40 min and gradually and significantly decreased toward the respective exhaustion point. The decline in BGC from the peak at 40 min was significantly slower in the TAU group. The time when the once-increased BGC regressed to the 0-time level was significantly and positively correlated with exercise time until exhaustion. At the 120-min point, where the difference in BGC between the two groups was most significant, plasma free fatty acid concentration and acetyl-carnitine and N-acetyltaurine concentrations in skeletal muscle were significantly higher in the TAU group, whereas glycogen and glucogenic amino acid concentrations and G6Pase activity in the liver were not different between the two groups. Taurine supplementation enhances endurance capacity by delaying the decrease in BGC toward exhaustion through increases of lipolysis in adipose tissues and fatty acid oxidation in skeletal muscles during endurance exercise

Aerobic exercise training enhances cerebrovascular pulsatility response to acute aerobic exercise in older adults

The brain\u27s low resistance ensures a robust blood flow throughout systole and diastole and is susceptible to flow pulsatility. Increased cerebral pulsatility contributes to the progression of cerebrovascular disease. Although aerobic exercise affects vascular function, little is known about the effect of exercise on the cerebral pulsatility index in older adults. The aim of this study was to investigate the effect of exercise training on the post‐exercise cerebral pulsatility response in older adults. Ten healthy older adults participated in a 12‐week exercise training intervention. Before and after the intervention, we measured the pulsatility index of the middle cerebral artery by means of transcranial Doppler method at baseline and following a cycling exercise bout performed at an intensity corresponding to the ventilatory threshold. Before exercise training, there was no significant change in the cerebral pulsatility response to an acute bout of cycling exercise. However, after the intervention, cerebral pulsatility decreased significantly following 30 min of an acute cycling exercise (P < 0.05). This study demonstrated that cerebral pulsatility index did not change following an acute bout of cycling exercise at an intensity corresponding to ventilatory threshold, but that, after 12 weeks of exercise training, cerebral pulsatility index was reduced at 30 min after a single bout of cycling exercise. These results suggest that long‐term aerobic exercise training may enhance the post‐exercise reduction in pulsatility index in older adults

骨格筋糖代謝ならびにアミノ酸代謝関連の遺伝子発現に及ぼすタウリン投与の影響

骨格筋の糖代謝ならびにセリン・グリシン・スレオニンのアミノ酸代謝の遺伝子発現に及ぼすタウリン投与の影響を明らかにすることを目的とした。ラットへ2週間タウリンを経口投与し、腓腹筋内側頭白色部の遺伝子発現をDNAマイクロアレイ法にて網羅的に解析を行った。その結果、タウリン投与によって、骨格筋の糖代謝ならびにセリン・グリシン・スレオニンのアミノ酸代謝には影響を及ぼさなかった。タウリン投与のエネルギー代謝への影響は骨格筋よりむしろ肝臓など他の臓器への作用が関連する可能性が示唆された