Exercise training attenuates the hypermuscular phenotype and restores skeletal muscle function in the myostatin null mouse

Myostatin regulates both muscle mass and muscle metabolism. The myostatin null (MSTN(-/-)) mouse has a hypermuscular phenotype owing to both hypertrophy and hyperplasia of the myofibres. The enlarged muscles display a reliance on glycolysis for energy production; however, enlarged muscles that develop in the absence of myostatin have compromised force-generating capacity. Recent evidence has suggested that endurance exercise training increases the oxidative properties of muscle. Here, we aimed to identify key changes in the muscle phenotype of MSTN(-/-) mice that can be induced by training. To this end, we subjected MSTN(-/-) mice to two different forms of training, namely voluntary wheel running and swimming, and compared the response at the morphological, myocellular and molecular levels. We found that both regimes normalized changes of myostatin deficiency and restored muscle function. We showed that both exercise training regimes increased muscle capillary density and the expression of Ucp3, Cpt1α, Pdk4 and Errγ, key markers for oxidative metabolism. Cross-sectional area of hypertrophic myofibres from MSTN(-/-) mice decreased towards wild-type values in response to exercise and, in this context, Bnip3, a key autophagy-related gene, was upregulated. This reduction in myofibre size caused an increase of the nuclear-to-cytoplasmic ratio towards wild-type values. Importantly, both training regimes increased muscle force in MSTN(-/-) mice. We conclude that impaired skeletal muscle function in myostatin-deficient mice can be improved through endurance exercise-mediated remodelling of muscle fibre size and metabolic profile.     

Exercise training prevents skeletal muscle damage in an experimental sepsis model

OBJECTIVE:

Oxidative stress plays an important role in skeletal muscle damage in sepsis. Aerobic exercise can decrease oxidative stress and enhance antioxidant defenses. Therefore, it was hypothesized that aerobic exercise training before a sepsis stimulus could attenuate skeletal muscle damage by modulating oxidative stress. Thus, the aim of this study was to evaluate the effects of aerobic physical preconditioning on the different mechanisms that are involved in sepsis-induced myopathy.

METHODS:

Male Wistar rats were randomly assigned to either the untrained or trained group. The exercise training protocol consisted of an eight-week treadmill program. After the training protocol, the animals from both groups were randomly assigned to either a sham group or a cecal ligation and perforation surgery group. Thus, the groups were as follows: sham, cecal ligation and perforation, sham trained, and cecal ligation and perforation trained. Five days after surgery, the animals were euthanized and their soleus and plantaris muscles were harvested. Fiber cross-sectional area, creatine kinase, thiobarbituric acid reactive species, carbonyl, catalase and superoxide dismutase activities were measured.

RESULTS:

The fiber cross-sectional area was smaller, and the creatine kinase, thiobarbituric acid reactive species and carbonyl levels were higher in both muscles in the cecal ligation and perforation group than in the sham and cecal ligation and perforation trained groups. The muscle superoxide dismutase activity was higher in the cecal ligation and perforation trained group than in the sham and cecal ligation and perforation groups. The muscle catalase activity was lower in the cecal ligation and perforation group than in the sham group.

CONCLUSION:

In summary, aerobic physical preconditioning prevents atrophy, lipid peroxidation and protein oxidation and improves superoxide dismutase activity in the skeletal muscles of septic rats.     

Exercise and training effects on ceramide metabolism in human skeletal muscle

In rat skeletal muscle prolonged exercise affects the content and composition of ceramides, but in human skeletal muscle no data are available on this compound. Our aim was to examine the content of ceramide- and sphingomyelin fatty acids and neutral, Mg(2+)-dependent sphingomyelinase activity in skeletal muscle in untrained and trained subjects before and after prolonged exercise. Healthy male subjects were recruited into an untrained (n = 8, VO2,max 3.8 +/- 0.2 1 min1) and a trained (n = 8, Vo2,max 5.1 +/- 0.1 1 min2) group. Before and after a 3-h exercise bout (58 +/- 1% VO2,max) a muscle biopsy was excised from the vastus lateralis. Ceramide and sphingomyelin were isolated using thin-layer chromatography. The content of individual ceramide fatty acids and sphingomyelin fatty acids was measured by means of gas-liquid chromatography. The activity of neutral, Mg(2+)-dependent sphingomyelinase was measured using N-[14CH3]-sphingomyelin as a substrate. Prior to exercise, the muscle total ceramide fatty acid content in both groups was similar (201 +/- 18 and 197 +/- 9 nmol g(-1) in the untrained and trained group, respectively) and after exercise a 25% increase in the content was observed in each group. At rest, the muscle total sphingomyelin fatty acid content was higher in untrained than in trained subjects (456 +/- 10, 407 +/- 7 nmol g(-1), respectively; P < 0.05). After exercise a 20% increase (P < 0.05) in total sphingomyelin was observed only in the trained subjects. The muscle neutral, Mg(2+)-dependent sphingomyelinase activity was similar in the two groups at rest and a similar reduction was observed after exercise in both groups (untrained from 2.19 +/- 0.08 to 1.78 +/- 0.08 and trained from 2.31 +/- 0.12 to 1.80 +/- 0.09 nmol (mg protein) (-1) h(-1); P < 0.05 in each case). In conclusion, we have reported, for the first time, the values for ceramide fatty acid content and neutral, Mg2(+)-dependent sphingomyelinase activity in human skeletal muscle. The results indicate that acute prolonged exercise affects ceramide metabolism in human skeletal muscle both in untrained and in trained subjects and this may influence muscle cell adaptation and metabolism.     

Age-related activation of mitochondrial caspase-independent apoptotic signaling in rat gastrocnemius muscle

Mitochondria-mediated apoptosis represents a central process driving age-related muscle loss. However, the temporal relation between mitochondrial apoptotic signaling and sarcopenia as well as the regulation of release of pro-apoptotic factors from the mitochondria has not been elucidated. In this study, we investigated mitochondrial apoptotic signaling in skeletal muscle of rats across a wide age range. We also investigated whether mitochondrial-driven apoptosis was accompanied by changes in the expression of Bcl-2 proteins and components of the mitochondrial permeability transition pore (mPTP). Analyses were performed on gastrocnemius muscle of 8-, 18-, 29- and 37-month-old male Fischer344 x Brown Norway rats (9 per group). Muscle weight declined progressively with advancing age, concomitant with increased apoptotic DNA fragmentation. Cytosolic and nuclear levels of apoptosis inducing factor (AIF) and endonuclease G (EndoG) increased in old and senescent animals. In contrast, cytosolic levels of cytochrome c were unchanged with age. Mitochondrial Bcl-2, Bax and Bid increased dramatically in 37-month-old rats, with no changes in the Bax/Bcl-2 ratio in any of the age groups. Finally, expression of cyclophilin D (CyPD) was enhanced at very old age. Our findings indicate that the mitochondrial caspase-independent apoptotic pathway may play a more prominent role in skeletal muscle loss than caspase-mediated apoptosis.     

Adaptations in rat skeletal muscle following long-term resistance exercise training

The purpose of this investigation was to determine whether long-term, heavy resistance training would cause adaptations in rat skeletal muscle structure and function. Ten male Wistar rats (3 weeks old) were trained to climb a 40-cm vertical ladder (4 days/week) while carrying progressively heavier loads secured to their tails. After 26 weeks of training the rats were capable of lifting up to 800?g or 140% of their individual body mass for four sets of 12–15 repetitions per session. No difference in body mass was observed between the trained rats and age-matched sedentary control rats. Absolute and relative heart mass were greater in trained rats than control rats. When expressed relative to body mass, the mass of the extensor digitorum longus (EDL) and soleus muscles was greater in trained rats than control rats. No difference in absolute muscle mass or maximum force-producing capacity was evident in either the EDL or soleus muscles after training, although both muscles exhibited an increased resistance to fatigue. Individual fibre hypertrophy was evident in all four skeletal muscles investigated, i.e. EDL, soleus, plantaris and rectus femoris muscles of trained rats, but muscle fibre type proportions within each of the muscles tested remained unchanged. Despite an increased ability of the rats to lift progressively heavier loads, this heavy resistance training model did not induce gross muscle hypertrophy nor did it increase the force-producing capacity of the EDL or soleus muscles.     

Age-related changes in force and efficiency in rat skeletal muscle

We investigated the effect of age on (the reduction of) work output, efficiency and muscle fibre type composition. Rat medial gastrocnemius muscles of three age-groups performed a series of 15 repeated contractions within 6 s (blood flow was arrested). Stimulation and shortening velocities were chosen as optimal for each group, while all muscles shortened over the same relative fibre lengths. The fibre type composition showed a higher proportion of the oxidative type IIBd fibres in the middle-aged group [5 months old; 39.8 ± 6.8 vs. 23.6 ± 4.2% of the fibre area in the young rats (1.3 months old)] in contrast to the type IIBm fibres (52.9 vs. 67.9%, respectively), while the old group (22 months old) was not different from the middle-aged group. Work output in the last contraction (relative to the first contraction) was not different between the age-groups (53.1 ± 18.1; 48.± 6.5 and 61.1± 6.2%, respectively). High-energy phosphate utilization was not different between the groups (150.6 ± 11.2; 154.6 ± 15.6 and 157.2 ± 7.0 μmol g^-1 dry wt, respectively). However, the efficiency was 30% lower in the muscles of the youngest group, which corresponds with a lower specific power and specific tension. Since the change in fibre type composition is unlikely to be the cause of the low efficiency in the young animals, the causes remain unclear, but may be related to the rapid growth of the young rats in our study.     

Nandrolone decanoate pre-treatment attenuates unweighting-induced functional changes in rat soleus muscle

Extracellular nucleotides have been shown to induce vasodilatation of conductance arteries by release of the endothelium-derived hyperpolarizing factor (EDHF). As small resistance arteries are of greater importance for blood pressure regulation, a whole rat mesenteric arterial bed preparation was used in the present study when evaluating the physiological relevance for EDHF in mediating nucleotide dilatation. Dilatory responses were examined after pre-contraction with noradrenaline in the presence of 10 mM indomethacin. Adenosine-5'-O-thiodiphosphate (ADPbetaS), adenosine triphosphate (ATP) and uridine triphosphate (UTP) induced vasodilatation (pEC50=6.5-7 and E(max)=40-70%), while uridine diphosphate (UDP) was ineffective. Endothelium-derived hyperpolarizing factor was studied in the presence of 0.5 mM Nvarpi-nitro-L-arginine (L-NOARG). ADPbetaS and UTP induced strong and potent EDHF-dilatations, while ATP only had a weak effect (E(max)=25%). After P2X1 receptor desensitization with 10 microM alphabeta-methylene-adenosine triphosphate, the ATP response was significantly increased (E(max)=65%). Putatively, this could be because of simultaneous activation of both endothelial P2Y receptors and P2X1 receptors on smooth muscle cells, which resulted in the release of EDHF and subsequent hyperpolarization, and depolarization, respectively. Nitric oxide (NO) was studied in the presence of 60 mM K+. ADPbetaS, ATP and UTP induced weak NO dilatations, suggesting a minor role for NO as compared with EDHF. In conclusion, extracellular nucleotides stimulate dilatation by activating P2Y(1) and P2Y(2)/P2Y(4) receptors, but not P2Y(6) receptors. The dilatory responses are mediated primarily by EDHF in the peripheral vascular bed.     

Resistance training increases glucose uptake and transport in rat skeletal muscle

The aim of this investigation was to determine if resistance training exercise improved glucose uptake and transport in rodent skeletal muscle. Sprague-Dawley rats were assigned to one of the three groups: control (CON), resistance trained (RT) and aerobic exercise trained (AT). Resistance trained rats were placed in a rodent squat apparatus and performed three sets of 10 repetitions at 75% of their one repetition maximum 3 days week-1 for 12 weeks. Aerobic exercise training consisted of running the rats 3 days week-1 for 45 min over a 12-week period on a motor-driven treadmill (32 m min-1, 15% grade). Following the training period, all animals were subjected to hind limb perfusion in the presence of 500 microU mL-1 insulin. Hind limb glucose uptake was similar in the RT (9.91 +/- 0.7 micromol g-1 h-1) and AT (10.23 +/- 1.0 micromol g-1 h-1) animals and significantly greater than control (CON) (6.40 +/- 0.6 micromol g-1 h-1). Rates of 3-O-methyl-d-glucose transport in the RT animals were elevated in the muscles utilized for RT while in the AT animals rates of 3-O-methyl-d-glucose transport were increased in those muscles recruited for running. The increased rates of 3-O-methyl-d-glucose transport in the skeletal muscles of the resistance trained and aerobic exercise trained animals appeared to be, in part, because of an increased GLUT4 protein concentration. These findings suggest that both resistance or aerobic training exercise can improve insulin-stimulated skeletal muscle glucose uptake and transport, but the training adaptations are restricted to the muscles recruited for the exercise performance.     

Aerobic training reverses high-fat diet-induced pro-inflammatory signalling in rat skeletal muscle

High-fat feeding activates components of the pro-inflammatory pathway and increases co-immunoprecipitation of suppressor of cytokine signalling (SOCS)-3 with both the insulin receptor (IR)-β subunit and IRS-1, which together contribute to keeping PI-3 kinase from being fully activated. However, whether aerobic training reverses these impairments is unknown. Sprague-Dawley rats were fed a chow (CON, n = 8) or saturated high-fat (n = 16) diets for 4 weeks. High-fat-fed rats were then allocated (n = 8/group) to either sedentary (HF) or aerobic exercise training (HFX) for an additional 4 weeks after which all animals underwent hind limb perfusions. Insulin-stimulated red quadriceps 3-O-methylglucose transport rates and PI-3 kinase activity were greater (p < 0.05) in CON and HFX compared to HF. IRS-1 tyrosine phosphorylation was increased (p < 0.05) and IRS-1 serine 307 phosphorylation was decreased (p < 0.05) in HFX compared to HF. IR-β subunit co-immunoprecipitation with IRS-1 was increased in HFX compared to HF. SOCS-3 co-immunoprecipitation with both the IR-β subunit and IRS-1 was decreased (p < 0.05) in HFX compared to HF. IKKα/β serine phosphorylation, and IκBα serine phosphorylation were decreased (p < 0.05) while IκBα protein concentration was increased in HFX compared to HF. By decreasing the association of SOCS-3 with both the IR-β subunit and IRS-1 the interaction between IRS-1 and the IR-β subunit was normalized in the HFX, and may have contributed to skeletal muscle PI-3 kinase being fully activated by insulin. Additionally, the reduction in IKKα/β serine phosphorylation in HFX may have contributed to decreasing IRS-1 serine phosphorylation, and in turn, promoted the normalization of insulin-stimulated activation of PI-3 kinase.     

运动诱导的骨骼肌信号机制

背景：运动可通过增强骨骼肌葡萄糖转运及胰岛素活动,来调节葡萄糖内环境。明确这些复杂过程的分子机制将无疑为治疗提供更多的靶向,也为认识这些复杂的生理过程提供最基本的知识。 目的：综述运动诱导骨骼肌葡萄糖转运的分子信号机制。 方法：以“骨骼肌,运动,腺苷酸活化蛋白激酶,葡萄糖摄取,葡萄糖运载体4”为中文检索词,以“skeletal muscle, exercise, AMPK, glucose uptake, GLUT4”为英文检索词。应用计算机检索PubMed数据库和中文期刊全文数据库2011年11月前发表有关运动诱导骨骼肌信号机制的研究文献,排除重复性研究及Meta分析类文章。共保留39篇文献进行综述。 结果与结论：运动/收缩和胰岛素是骨骼肌葡萄糖转运的最有效的和生理相关的刺激,运动诱导的信号机制代表着糖尿病治疗药物学靶点发展的一个重要步骤。运动是通过增加骨骼肌葡萄糖摄取来改善葡萄糖内环境的,而运动诱导的葡萄糖摄取是有多种信号途径来介导的,包括腺苷酸活化蛋白激酶、非典型蛋白激酶C、钙调节依赖蛋白激酶及相对分子质量为160 000的Akt底物等。这些骨骼肌信号机制通过刺激葡萄糖运载体4活动增加来调节葡萄糖的转运。     

Satellite cell ablation attenuates short-term fast-to-slow fibre type transformations in rat fast-twitch skeletal muscle

The purpose of this time-course study was to determine whether satellite cell ablation within rat tibialis anterior (TA) muscles exposed to short-term chronic low-frequency stimulation (CLFS) would limit fast-to-slow fibre type transformations. Satellite cells of the left TA were ablated by exposure to γ-irradiation before 1, 2, 5 or 10 days of CLFS and 1 week later where required. Control groups received only CLFS or a sham operation. Continuous infusion of 5-bromo-2′-deoxyuridine revealed that CLFS first induced an increase in satellite cell proliferation at 1 day, up to a maximum at 10 days over control (mean ± SEM, 5.7 ± 0.7 and 20.4 ± 1.0 versus 1.5 ± 0.2 mm⁻², respectively, P < 0.007) that was abolished by γ-irradiation. Myosin heavy chain mRNA, immunohistochemical and sodium dodecyl sulfate polyacrylamide gel electrophoresis analyses revealed CLFS-induced fast-to-slow fibre type transformation began at 5 days and continued at 10 days; in those muscles that were also exposed to γ-irradiation, attenuation occurred within the fast fibre population, and the final fast-twitch to slow-twitch adaptation did not occur. These findings indicate satellite cells play active and obligatory roles early on in the time course during skeletal muscle fibre type adaptations to CLFS.     

Stoichiometry of phosphocreatine and inorganic phosphate changes in rat skeletal muscle

The apparent T1's of phosphate metabolites were measured during and after series of twitch contractions in gastrocnemius muscles of pentobarbital-anesthetized rats by steady-state progressive saturation using spatially-selective composite pulses. There was no significant change in apparent T1's of inorganic phosphate (Pi), phosphocreatine (PCr), or the three phosphates of ATP. There was a 5-10% decrease in the sum of Pi and PCr integrals, and in the sum of the gamma- and beta- phosphates of ATP during stimulation, but no significant change in the ratio (Pi + PCr)/(gamma-ATP + beta-ATP). The results indicate that there is no selective decrease in NMR observable Pi during or after a series of muscle contractions.     

Exercise training decreases DNA damage and increases DNA repair and resistance against oxidative stress of proteins in aged rat skeletal muscle

Regular physical exercise retards a number of age-associated disorders, in spite of the paradox that free radical generation is significantly enhanced with exercise. Eight weeks of treadmill running resulted in nearly a 40% increase in maximal oxygen uptake in both middle-aged (20-month-old) and aged (30-month-old) rats. The age-associated increase in 8-hydroxy-2'-deoxyguanosine (8-OHdG) content was significantly attenuated in gastrocnemius muscle by exercise. The 8-OHdG repair, as measured by the excision of 32P-labeled damaged oligonucleotide, increased in muscle of exercising animals. The reactive carbonyl derivatives (RCD) of proteins did not increase with aging. However, when the muscle homogenate was exposed to a mixture of 1 mM iron sulfate and 50 mM ascorbic acid, the muscle of old control animals accumulated more RCD than that of the trained or adult groups. The chymotrypsin-like activity of proteasome complex increased in muscle of old trained rats. We suggest that regular exercise-induced adaptation attenuates the age-associated increase in 8-OHdG levels, and increases the activity of DNA repair and resistance against oxidative stress in proteins.     

Exercise training attenuates acute hyperalgesia in streptozotocin-induced diabetic female rats

OBJECTIVES:

We investigated the effects of chronic (eight weeks) low- to moderate-intensity swimming training on thermal pain sensitivity in streptozotocin-induced diabetic female rats.

METHODS:

Female Wistar rats (n = 51) were divided into the following groups: trained streptozotocin-induced diabetic rats [hyperglycemic trained (HT)], sedentary streptozotocin-induced diabetic rats [hyperglycemic sedentary (HS)], normoglycemic trained rats (NT) and normoglycemic sedentary rats (NS). Diabetes was induced by a single injection of streptozotocin (50 mg/kg, i.p.). One day after the last exercise protocol (60 min/day, five days/week for eight weeks) in the trained groups or after water stress exposure (ten min/twice a week) in the sedentary groups, the rats were subjected to a hot plate test.

RESULTS:

After eight weeks of swimming training, streptozotocin-induced diabetic rats presented a significantly lower body mass (trained: 219.5±29 g, sedentary: 217.8±23 g) compared with the normoglycemic groups (trained: 271±24 g, sedentary: 275.7±32 g). Interestingly, we did not find differences in blood glucose levels (mg/dl) between the trained and sedentary groups of the hyperglycemic or normoglycemic rats (HT: 360.2±66.6, HS: 391.7±66.7, NT: 83.8±14.0, NS: 77.5±10.1). In the hot plate test, the rats from the HT group presented a significantly lower latency than the other rats (HT: 11.7±7.38 s, HS: 7.02±7.38 s, NT: 21.21±7.64 s, NS: 22.82±7.82 s).

CONCLUSION:

Low-to-moderate swimming training for a long duration reduces thermal hyperalgesia during a hot plate test in streptozotocin-induced diabetic female rats.     

Exercise myopathy: selectively enhanced proteolytic capacity in rat skeletal muscle after prolonged running

The proteolytic capacity of rat skeletal muscle was analyzed during the repair of fiber injuries after strenuous exercise. A single bout of prolonged exercise (8 hr running at a speed of 17 m X min-1) caused a slight fiber necrosis and a selective response in the proteolytic activity of rat skeletal muscle. Acid proteolytic capacity (cathepsin D and acid autolysis) was considerably increased on the 4th day after exertion and partially decreased by the 10th day. The acid hydrolytic response was more prominent in red than in white skeletal muscle. Alkaline proteolytic capacity (alkaline and myofibrillar proteases), increased in several atrophic myopathies, was not affected in exercise myopathy. The rate of neutral autolysis slightly increased after exertion. The protein content of skeletal muscle was decreased on the 4th day after exertion. We suggest that the proteolytic responses to acute injuries, as well as to chronic atrophies, are highly selective in skeletal muscle fibers.     

Inspiratory muscle training attenuates the human respiratory muscle metaboreflex

We hypothesized that inspiratory muscle training (IMT) would attenuate the sympathetically mediated heart rate (HR) and mean arterial pressure (MAP) increases normally observed during fatiguing inspiratory muscle work. An experimental group (Exp, n = 8) performed IMT 6 days per week for 5 weeks at 50% of maximal inspiratory pressure (MIP), while a control group (Sham, n = 8) performed IMT at 10% MIP. Pre- and post-training, subjects underwent a eucapnic resistive breathing task (RBT) (breathing frequency = 15 breaths min⁻¹, duty cycle = 0.70) while HR and MAP were continuously monitored. Following IMT, MIP increased significantly ( P < 0.05) in the Exp group (−125 ± 10 to −146 ± 12 cmH₂O; mean ± s.e.m. ) but not in the Sham group (−141 ± 11 to −148 ± 11 cmH₂O). Prior to IMT, the RBT resulted in significant increases in HR (Sham: 59 ± 2 to 83 ± 4 beats min⁻¹; Exp: 62 ± 3 to 83 ± 4 beats min⁻¹) and MAP (Sham: 88 ± 2 to 106 ± 3 mmHg; Exp: 84 ± 1 to 99 ± 3 mmHg) in both groups relative to rest. Following IMT, the Sham group observed similar HR and MAP responses to the RBT while the Exp group failed to increase HR and MAP to the same extent as before (HR: 59 ± 3 to 74 ± 2 beats min⁻¹; MAP: 84 ± 1 to 89 ± 2 mmHg). This attenuated cardiovascular response suggests a blunted sympatho-excitation to resistive inspiratory work. We attribute our findings to a reduced activity of chemosensitive afferents within the inspiratory muscles and may provide a mechanism for some of the whole-body exercise endurance improvements associated with IMT.     

Exercise type and volume alter signaling pathways regulating skeletal muscle glucose uptake and protein synthesis

Purpose

The aim of this study was to compare activation of cellular signaling pathways regulating protein synthesis and glucose uptake in skeletal muscle between resistance and endurance exercise. Moreover, the effect of resistance exercise volume was examined.

Methods

Three groups of male volunteers (26 ± 3 years) were examined: 5 × 10 repetition maximum (RM) resistance exercise (RE) with leg press device (5 × 10 RE; n = 8), 10 × 10 RE (n = 11), and endurance exercise (strenuous 50-min walking with extra load on a treadmill; EE; n = 8). Muscle biopsies were obtained from m.vastus lateralis 30 min pre- and post-exercise.

Results

Downstream markers of mTORC1, p-p70S6K^{Thr421/Ser424} and p-rpS6^Ser240/244, increased more after 10 × 10 RE than after 5 × 10 RE (p < 0.05) and EE (p < 0.01–0.001). Exercise-induced changes in p-IRS-I^Ser636/639 that inhibit IRS-I signaling via negative feedback from hyperactivated mTORC1 signaling were greater (p < 0.05) after 10 × 10 RE compared with 5 × 10 RE and EE. The changes in energy sensor p-AMPKα^Thr172 were greater after 10 × 10 RE and EE (p < 0.05–0.01) than after 5 × 10 RE. A major regulator of glucose uptake in muscle, p-AS160^Thr642, increased more after 10 × 10 RE than after 5 × 10 RE (p < 0.01) and EE (p < 0.05).

Conclusion

10 × 10 RE induced greater activation of important signaling proteins regulating glucose uptake (p-AS160) and protein synthesis (p-p70S6K, p-rpS6) than 5 × 10 RE and EE. The present findings further suggest that, especially after 10 × 10 RE, IRS-I signaling is downregulated and that AS160 is activated through AMPK signaling pathway.

     

Oleamide attenuates apoptotic death in cultured rat cerebellar granule neurons

The effect of oleamide on apoptosis was investigated by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction assay, DNA staining assay with propidium iodide and caspase-3 activity analyses. The present results showed that oleamide significantly attenuated the cell death and nuclear condensation of cultured rat cerebellar granule neurons induced by K(+) deprivation in a dose-dependent manner. The oleamide actions were well parallel with the attenuation of caspase-3 activity in the process of apoptotic death. Moreover, neither elaidic acid nor stearic acid, two fatty acids structurally related to oleamide without the Delta(9)-cis double bond, had similar effects on the cell death, suggesting the selectively structural features of oleamide required for this action. These data provided the first evidence of a protective effect of oleamide against apoptosis in a structurally specific manner.