Immediately Postexercise Research Articles

A novel genetic model provides a unique perspective on the relationship between postexercise glycogen concentration and increases in the abundance of key metabolic proteins after acute exercise.

Some acute exercise effects are influenced by postexercise (PEX) diet, and these diet-effects are attributed to differential glycogen resynthesis. However, this idea is challenging to test rigorously. Therefore, we devised a novel genetic model to modify muscle glycogen synthase 1 (GS1) expression in rat skeletal muscle with an adeno-associated virus (AAV) short hairpin RNA knockdown vector targeting GS1 (shRNA-GS1). Contralateral muscles were injected with scrambled shRNA (shRNA-Scr). Muscles from exercised (2-hour-swim) and time-matched sedentary (Sed) rats were collected immediately postexercise (IPEX), 5-hours-PEX (5hPEX), or 9-hours-PEX (9hPEX). Rats in 5hPEX and 9hPEX experiments were refed (RF) or not-refed (NRF) chow. Muscles were analyzed for glycogen, abundance of metabolic proteins (pyruvate dehydrogenase kinase 4, PDK4; peroxisome proliferator-activated receptor γ coactivator-1α, PGC1α; hexokinase II, HKII; glucose transporter 4, GLUT4), AMP-activated protein kinase phosphorylation (pAMPK), and glycogen metabolism-related enzymes (glycogen phosphorylase, PYGM; glycogen debranching enzyme, AGL; glycogen branching enzyme, GBE1). shRNA-GS1 versus paired shRNA-Scr muscles had markedly lower GS1 abundance. IPEX versus Sed rats had lower glycogen and greater pAMPK, and neither of these IPEX-values differed for shRNA-GS1 versus paired shRNA-Scr muscles. IPEX versus Sed groups did not differ for abundance of metabolic proteins, regardless of GS1 knockdown. Glycogen in RF-rats was lower for shRNA-GS1 versus paired shRNA-Scr muscles at both 5hPEX and 9hPEX. HKII protein abundance was greater for 5hPEX versus Sed groups, regardless of GS1 knockdown or diet, and despite differing glycogen levels. At 9hPEX, shRNA-GS1 versus paired shRNA-Scr muscles had greater PDK4 and PGC1α abundance within each diet group. However, the magnitude of PDK4 or PGC1α changes was similar in each diet group regardless of GS1 knockdown although glycogen differed between paired muscles only in RF-rats. In summary, we established a novel genetic approach to investigate the relationship between muscle glycogen and other exercise effects. Our results suggest that exercise-effects on abundance of several metabolic proteins did not uniformly correspond to differences in postexercise glycogen.

588-P: Probing the Role of Muscle Glycogen Resynthesis on Postexercise AMPK Activation and Metabolic Protein Abundance Using a Novel Genetic Model

Acute exercise can alter the abundance of key metabolic proteins in skeletal muscle. These effects are influenced by postexercise (PEX) refeeding. Muscle glycogen resynthesis is a putative mediator of these refeeding effects. However, it is challenging to test this idea, because glycogen resynthesis is only one of many outcomes with refeeding. Therefore, we devised a novel genetic model to modify muscle expression of glycogen synthase 1 (GS1) using injection of rat skeletal muscle with adeno-associated viral (AAV) vectors for short hairpin RNA targeting GS1 (shRNA-GS1). Contralateral muscles were injected with scrambled shRNA (shRNA-Scr). Rats were sedentary (SED) or exercised (120min swim-exercise). Muscles were collected immediately postexercise (IPEX) and 9-hours PEX (9hPEX), along with time-matched SED controls. The 9hPEX and their SED-control rats were either refed (RF) or not-refed (NRF). Muscles were analyzed for glycogen and phosphorylation and abundance of key metabolic proteins. Muscles injected with shRNA-GS1 vs shRNA-Scr had lower GS1 abundance in all groups. Regardless of genotype, in IPEX vs SED rats: glycogen fell to similarly low values and phosphorylation of AMPK Thr172 (pAMPK) and its substrate ACC Ser79 (pACC) were comparably increased. Muscle glycogen was increased in all groups of 9h-RF rats, but it was lower for shRNA-GS1 vs shRNA-Scr from RF-9hPEX rats. In the NRF-9hPEX rats, pAMPK and pACC were greater for shRNA-GS1 vs shRNA-Scr muscles. Muscle pyruvate dehydrogenase kinase-4 abundance from 9hPEX rats (both NRF and RF) was greater for shRNA-GS1 vs shRNA-Scr. Hexokinase II (HKII) abundance was greater for 9hPEX vs SED in NRF rats regardless of genotype. In RF-9hPEX rats, HKII abundance was greater for shRNA-GS1 vs shRNA-Scr. These results support the idea that some PEX effects on metabolic protein abundance are influenced by muscle GS1 abundance and the extent of glycogen resynthesis Disclosure S.Kwak: None. A.Zheng: None. E.B.Arias: None. H.Wang: None. X.Pan: None. D.Duan: None. Y.Yue: None. G.D.Cartee: None. Funding National Institutes of Health (R01DK071771); University of Michigan

Resistance Exercise Increases Gastrointestinal Symptoms, Markers of Gut Permeability, and Damage in Resistance-Trained Adults.

This study aimed to determine the influence of acute resistance exercise (RE) and biological sex on subjective gastrointestinal (GI) symptoms, GI epithelial damage, and GI permeability in resistance-trained males and females. Thirty resistance-trained men ( n = 15) and women ( n = 15) completed an RE bout and a nonexercise control (CON) session in a randomized counterbalanced design. The RE protocol used a load of 70% one-repetition maximum for 4 sets of 10 repetitions with a 90-s rest period length between sets and a 120-s rest period between exercises (squat, seated shoulder press, deadlift, bent-over row, and leg press). Blood samples were collected before exercise (PRE), immediately postexercise (IP), and 15-, 30-, and 60-min postexercise. Participants completed GI symptom questionnaires to assess subjective GI symptoms PRE, IP, and 60-min postexercise. Blood samples were assayed to quantify small intestine damage (I-FABP) and GI permeability (lactulose-rhamnose [L/R] ratio). Data were analyzed via separate repeated-measures ANOVA, and area under the curve (AUC) analyses were completed via one-way ANOVA. Participants reported greater GI symptoms in RE at IP compared with CON ( P < 0.001) with 70% of participants reporting at least one GI symptom with no differences between sexes. Nausea was the most reported GI symptom (63.3%), followed by vomiting (33.3%). I-FABP and L/R ratio did not exhibit differential responses between conditions. However, L/R ratio AUC was greater in males after RE than male CON ( P = 0.002) and both conditions for females ( P < 0.05). Furthermore, I-FABP AUC in the male RE condition was greater than both female conditions ( P < 0.05). Resistance-trained individuals experience GI distress after RE, with males incurring the greatest increases in markers of GI damage and permeability.

Acute Response of Blood Lipids and Lipoproteins to Different Intensities of Exercise in Obese Males

This study aimed to examine the response of lipid and lipoprotein levels following different intensities of exercise in obese males. Fifteen obese (body mass index &gt; 30 kg/m2), sedentary (less than 2 days per week of physical activity) males, aged 18–30 years, participated in this randomized, cross-over study. The participants performed a single bout of cycling exercise (average energy expenditure: ~300 kcal) at two different intensities [lower-intensity: 50% of maximal heart rate and higher-intensity: 80% of maximal heart rate] in a random order. Overnight fasting blood samples were collected at baseline, immediately post-exercise (IPE), 1-hr PE, and 24-hr PE for each intensity of exercise to determine the profile of blood lipids and lipoproteins [total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C)]. A 2(intensity) × 4(time) analysis of variance with repeated measures was used to examine the main and interaction differences in intensity and time on the profile of blood lipids and lipoproteins. The blood lipids and lipoproteins were not significantly altered following either lower or higher intensity exercise. There was no significant interaction between intensity and time. The results suggest that regardless of exercise intensity, an acute bout of aerobic exercise requiring 300 kcal energy expenditure may not be enough to significantly alter blood lipids and lipoproteins in physically healthy obese males. Therefore, it is recommended that future research determine whether different intensities of chronic exercise requiring the same or higher volume of energy expenditure can positively alter the blood lipid profiles in obese males.

Exercise effects on γ3-AMPK activity, Akt substrate of 160 kDa phosphorylation, and glucose uptake in muscle of normal and insulin-resistant female rats.

Previous studies demonstrated that acute exercise can enhance glucose uptake (GU), γ3-AMP-activated protein kinase (AMPK) activity, and Akt substrate of 160 kDa (AS160) phosphorylation in skeletal muscles from low-fat diet (LFD)- and high-fat diet (HFD)-fed male rats. Because little is known about exercise effects on these outcomes in females, we assessed postexercise GU by muscles incubated ± insulin, delta-insulin GU (GU of muscles incubated with insulin minus GU uptake of paired muscles incubated without insulin), and muscle signaling proteins from female rats fed a LFD or a brief HFD (2 wk). Rats were sedentary (LFD-SED, HFD-SED) or swim exercised. Immediately postexercise (IPEX) or 3 h postexercise (3hPEX), epitrochlearis muscles were incubated (no insulin IPEX; ±insulin 3hPEX) to determine GU. Muscle γ3-AMPK activity (IPEX, 3hPEX) and phosphorylated AS160 (pAS160; 3hPEX) were also assessed. γ3-AMPK activity and insulin-independent GU of IPEX rats exceeded sedentary rats without diet-related differences in either outcome. At 3hPEX, both GU by insulin-stimulated muscles and delta-insulin GU exceeded their respective diet-matched sedentary controls. GU by insulin-stimulated muscles, but not delta-insulin GU for LFD-3hPEX, exceeded HFD-3hPEX. LFD-3hPEX versus LFD-SED had greater γ3-AMPK activity and greater pAS160. HFD-3hPEX exceeded HFD-SED for pAS160 but not for γ3-AMPK activity. pAS160 and γ3-AMPK at 3hPEX did not differ between diet groups. These results revealed that increased γ3-AMPK activity at 3hPEX was not essential for greater GU in insulin-stimulated muscle or greater delta-insulin GU in HFD female rats. Similarly elevated γ3-AMPK activity in LFD-IPEX versus HFD-IPEX and pAS160 in LFD-3hPEX versus HFD-3hPEX may contribute to the comparable delta-insulin GU at 3hPEX in both diet groups.NEW & NOTEWORTHY Glucose uptake (GU) and phosphorylated AS160 (pAS160) by insulin-stimulated muscles at 3 h postexercise (3hPEX) exceeded diet-matched controls in female low-fat diet-fed (LFD) or high-fat diet-fed (HFD) rats. GU with insulin for LFD-3hPEX exceeded HFD-3hPEX, whereas pAS160 was similar between these groups. γ3-AMPK immediately postexercise (IPEX) was similarly elevated in LFD and HFD, but only LFD-3hPEX had increased γ3-AMPK. These results suggest that greater γ3-AMPK at IPEX and pAS160 at 3hPEX may contribute to elevated GU with insulin, but greater γ3-AMPK at 3hPEX was dispensable for female HFD rats.

Recovery using “float” from high intensity stress on growth hormone-like molecules in resistance trained men

ObjectiveThe purpose of this study was to examine the influence of a novel “floatation-restricted environmental stimulation therapy” (floatation-REST) on growth hormone responses to an intense resistance exercise stress. DesignNine resistance trained men (age: 23.4 ± 2.5 yrs.; height: 175.3 ± 5.4 cm; body mass: 85.3 ± 7.9 kg) completed a balanced, crossover-controlled study design with two identical exercise trials, differing only in post-exercise recovery intervention (i.e., control or floatation-REST). A two-week washout period was used between experimental conditions. Plasma lactate was measured pre-exercise, immediately post-exercise and after the 1 h. recovery interventions. Plasma iGH was measured pre-exercise, immediately-post exercise, and after the recovery intervention, as well as 24 h and 48 h after the exercise test. The bGH-L was measured only at pre-exercise and following each recovery intervention. ResultsFor both experimental conditions, a significant (P ≤ 0.05) increase in lactate concentrations were observed immediately post-exercise (~14 mmol • L-1) and remained slightly elevated after the recovery condition. The same pattern of responses was observed for iGH with no differences from resting values at 24 and 48 h of recovery. The bGH-L showed no exercise-induced changes following recovery with either treatment condition, however concentration values were dramatically lower than ever reported. ConclusionThe use of floatation-REST therapy immediately following intense resistance exercise does not appear to influence anterior pituitary function in highly resistance trained men. However, the lower values of bGH suggest dramatically different molecular processing mechanisms at work in this highly trained population.

Fiber type-specific effects of acute exercise on insulin-stimulated AS160 phosphorylation in insulin-resistant rat skeletal muscle.

Muscle is a heterogeneous tissue composed of multiple fiber types. Earlier research revealed fiber type-selective postexercise effects on insulin-stimulated glucose uptake (ISGU) from insulin-resistant rats (increased for type IIA, IIB, IIBX, and IIX, but not type I). In whole muscle from insulin-resistant rats, the exercise increase in ISGU is accompanied by an exercise increase in insulin-stimulated AS160 phosphorylation (pAS160), an ISGU-regulating protein. We hypothesized that, in insulin-resistant muscle, the fiber type-selective exercise effects on ISGU would correspond to the fiber type-selective exercise effects on pAS160. Rats were fed a 2-wk high-fat diet (HFD) and remained sedentary (SED) or exercised before epitrochlearis muscles were dissected either immediately postexercise (IPEX) or at 3 h postexercise (3hPEX) using an exercise protocol that previously revealed fiber type-selective effects on ISGU. 3hPEX muscles and SED controls were incubated ± 100µU/mL insulin. Individual myofibers were isolated and pooled on the basis of myosin heavy chain (MHC) expression, and key phosphoproteins were measured. Myofiber glycogen and MHC expression were evaluated in muscles from other SED, IPEX, and 3hPEX rats. Insulin-stimulated pAktSer473 and pAktThr308 were unaltered by exercise in all fiber types. Insulin-stimulated pAS160 was greater for 3hPEX vs. SED on at least one phosphosite (Ser588, Thr642, and/or Ser704) in type IIA, IIBX, and IIB fibers, but not in type I or IIX fibers. Both IPEX and 3hPEX glycogen were decreased versus SED in all fiber types. These results provided evidence that fiber type-specific pAS160 in insulin-resistant muscle may play a role in the previously reported fiber type-specific elevation in ISGU in some, but not all, fiber types.

Fiber type-selective exercise effects on AS160 phosphorylation.

Earlier research using muscle tissue demonstrated that postexercise elevation in insulin-stimulated glucose uptake (ISGU) occurs concomitant with greater insulin-stimulated Akt substrate of 160 kDa (AS160) phosphorylation (pAS160) on sites that regulate ISGU. Because skeletal muscle is a heterogeneous tissue, we previously isolated myofibers from rat epitrochlearis to assess fiber type-selective ISGU. Exercise induced greater ISGU in type I, IIA, IIB, and IIBX but not IIX fibers. This study tested if exercise effects on pAS160 correspond with previously published fiber type-selective exercise effects on ISGU. Rats were studied immediately postexercise (IPEX) or 3.5 h postexercise (3.5hPEX) with time-matched sedentary controls. Myofibers dissected from the IPEX experiment were analyzed for fiber type (myosin heavy chain isoform expression) and key phosphoproteins. Isolated muscles from the 3.5hPEX experiment were incubated with or without insulin. Myofibers (3.5hPEX) were analyzed for fiber type, key phosphoproteins, and GLUT4 protein abundance. We hypothesized that insulin-stimulated pAS160 at 3.5hPEX would exceed sedentary controls only in fiber types characterized by greater ISGU postexercise. Values for phosphorylation of AMP-activated kinase substrates (acetyl CoA carboxylaseSer79 and AS160Ser704) from IPEX muscles exceeded sedentary values in each fiber type, suggesting exercise recruitment of all fiber types. Values for pAS160Thr642 and pAS160Ser704 from insulin-stimulated muscles 3.5hPEX exceeded sedentary values for type I, IIA, IIB, and IIBX but not IIX fibers. GLUT4 abundance was unaltered 3.5hPEX in any fiber type. These results advanced understanding of exercise-induced insulin sensitization by providing compelling support for the hypothesis that enhanced insulin-stimulated phosphorylation of AS160 is linked to elevated ISGU postexercise at a fiber type-specific level independent of altered GLUT4 expression.

High-Intensity Aerobic Exercise Acutely Increases Brain-derived Neurotrophic Factor.

This study examined the effects of AEx, of different intensities, on serum BDNF and cortisol in individuals with and without depression. Thirteen participants with depression (10 females; age = 27.2 ± 6.9 yr; Montgomery-Äsberg Depression Rating Scale = 21.7 ± 4.7) and 13 control participants (10 females; age 27.2 ± 7.2 yr; Montgomery-Äsberg Depression Rating Scale = 0.5 ± 0.9) participated. Experimental visits consisted of 15 min of low-intensity cycling (LO) at 35% heart rate reserve, high-intensity cycling (HI) at 70% heart rate reserve, or sitting (CON). During each visit, blood samples were obtained at baseline, immediately postexercise (IP), and then every 15 min postexercise for 1 h (15P, 30P, 45P, and 60P). Group, condition, and time differences in BDNF and cortisol were assessed. There were no group differences in cortisol and BDNF. Secondary analysis revealed that BDNF increased in an intensity-dependent nature at IP, and cortisol was significantly elevated at 15P after HI. Changes in BDNF and cortisol showed significant linear relationships with changes in HR. HI AEx can elicit acute, transient increases in BDNF and cortisol in young, healthy, and physically active, nondepressed and mild to moderately depressed individuals. This work suggests that AEx has potential to significantly affect the central nervous system function, and the magnitude of such effect may be directly driven by exercise intensity.

Skeletal muscle fiber type-selective effects of acute exercise on insulin-stimulated glucose uptake in insulin-resistant, high-fat-fed rats.

Insulin-stimulated glucose uptake (GU) by skeletal muscle is enhanced several hours after acute exercise in rats with normal or reduced insulin sensitivity. Skeletal muscle is composed of multiple fiber types, but exercise's effect on fiber type-specific insulin-stimulated GU in insulin-resistant muscle was previously unknown. Male rats were fed a high-fat diet (HFD; 2 wk) and were either sedentary (SED) or exercised (2-h exercise). Other, low-fat diet-fed (LFD) rats remained SED. Rats were studied immediately postexercise (IPEX) or 3 h postexercise (3hPEX). Epitrochlearis muscles from IPEX rats were incubated in 2-deoxy-[3H]glucose (2-[3H]DG) without insulin. Epitrochlearis muscles from 3hPEX rats were incubated with 2-[3H]DG ± 100 µU/ml insulin. After single fiber isolation, GU and fiber type were determined. Glycogen and lipid droplets (LDs) were assessed histochemically. GLUT4 abundance was determined by immunoblotting. In HFD-SED vs. LFD-SED rats, insulin-stimulated GU was decreased in type IIB, IIX, IIAX, and IIBX fibers. Insulin-independent GU IPEX was increased and glycogen content was decreased in all fiber types (types I, IIA, IIB, IIX, IIAX, and IIBX). Exercise by HFD-fed rats enhanced insulin-stimulated GU in all fiber types except type I. Single fiber analyses enabled discovery of striking fiber type-specific differences in HFD and exercise effects on insulin-stimulated GU. The fiber type-specific differences in insulin-stimulated GU postexercise in insulin-resistant muscle were not attributable to a lack of fiber recruitment, as indirectly evidenced by insulin-independent GU and glycogen IPEX, differences in multiple LD indexes, or altered GLUT4 abundance, implicating fiber type-selective differences in the cellular processes responsible for postexercise enhancement of insulin-mediated GLUT4 translocation.

Postexercise improvement in glucose uptake occurs concomitant with greater γ3-AMPK activation and AS160 phosphorylation in rat skeletal muscle.

A single exercise session can increase insulin-stimulated glucose uptake (GU) by skeletal muscle, concomitant with greater Akt substrate of 160 kDa (AS160) phosphorylation on Akt-phosphosites (Thr642 and Ser588) that regulate insulin-stimulated GU. Recent research using mouse skeletal muscle suggested that ex vivo 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) or electrically stimulated contractile activity-inducing increased γ3-AMPK activity and AS160 phosphorylation on a consensus AMPK-motif (Ser704) resulted in greater AS160 Thr642 phosphorylation and GU by insulin-stimulated muscle. Our primary goal was to determine whether in vivo exercise that increases insulin-stimulated GU in rat skeletal muscle would also increase γ3-AMPK activity and AS160 site-selective phosphorylation (Ser588, Thr642, and Ser704) immediately postexercise (IPEX) and/or 3 h postexercise (3hPEX). Epitrochlearis muscles isolated from sedentary and exercised (2-h swim exercise; studied IPEX and 3hPEX) rats were incubated with 2-deoxyglucose to determine GU (without insulin at IPEX; without or with insulin at 3hPEX). Muscles were also assessed for γ1-AMPK activity, γ3-AMPK activity, phosphorylated AMPK (pAMPK), and phosphorylated AS160 (pAS160). IPEX versus sedentary had greater γ3-AMPK activity, pAS160 (Ser588, Thr642, Ser704), and GU with unaltered γ1-AMPK activity. 3hPEX versus sedentary had greater γ3-AMPK activity, pAS160 Ser704, and GU with or without insulin; greater pAS160 Thr642 only with insulin; and unaltered γ1-AMPK activity. These results using an in vivo exercise protocol that increased insulin-stimulated GU in rat skeletal muscle are consistent with the hypothesis that in vivo exercise-induced enhancement of γ3-AMPK activation and AS160 Ser704 IPEX and 3hPEX are important for greater pAS160 Thr642 and enhanced insulin-stimulated GU by skeletal muscle.

Exercise-induced changes in stress hormones and cell adhesion molecules in obese men.

PurposeThe current study examined the relationship between exercise-induced changes in stress hormones (epinephrine, norepinephrine, and cortisol) and vascular inflammatory markers (soluble intracellular adhesion molecule-1 [sICAM-1], soluble endothelial selectin [sE-selectin], and soluble vascular adhesion molecule-1 [sVCAM-1]) in obese men over a 24-hour period following exercise at lower and higher intensity.Patients and methodsFifteen physically inactive, obese, college-aged men performed a single bout of cycling exercise at lower and higher intensities (lower intensity: 50% of maximal heart rate, and higher intensity: 80% of maximal heart rate) in random order. Overnight fasting blood samples were collected at baseline, immediately postexercise (IPE), 1-hour PE (1-h PE), and 24-hour PE. Changes in stress hormones and inflammatory markers were analyzed with a repeated-measures analysis of variance using Bonferroni multiple comparisons and a linear regression analysis (p<0.05).ResultssICAM-1, sVCAM-1, epinephrine, and norepinephrine did not change over time, while sE-selectin was significantly lower at 1-h PE (10.25±1.07 ng/mL, p=0.04) than at baseline (12.22±1.39 ng/mL). Cortisol and sICAM-1 were negatively related at 1-h PE following lower-intensity exercise (r2=0.34, p=0.02), whereas cortisol and sVCAM-1 were positively related at IPE following higher-intensity exercise (r2=0.36, p=0.02).ConclusionRegardless of intensity, an acute bout of aerobic exercise may lower sE-selectin in sedentary obese men. Responses of cortisol are dependent on exercise intensity, and cortisol may be a key stress hormone playing a major role in regulating sICAM-1 and sVCAM-1.

Relationship Between Autophagy and Heat Shock Response in Peripheral Blood Mononuclear Cells Following Resistance Exercise

Autophagy and protein degradation occur during the proximal hours (hr) post-exercise (PE) and are then followed by a gradual transition to protein synthesis. Previous works suggest that this biphasic relationship is mediated in-part by the heat shock response which may influence autophagy activity and may be influenced by the presence of amino acids. PURPOSE: To determine the effect of acute resistance exercise and branched-chain amino acid (BCAA) supplementation on autophagy and the heat shock response. METHODS: Twenty males (22.3±1.5yr, 86.4±15.6kg; 175.4±6.7cm) were randomly assigned to complete 8 days of 0.22 g/kg/d BCAA or placebo (PL) supplementation. On day 5 participants performed a bout of eccentric resistance exercise. Peripheral blood mononuclear cells (PBMC) were isolated pre-exercise, immediately post-exercise (IPE), and 2, 4, 24, 48, and 72hr. PBMC protein expression of autophagy markers (LC3I & II, & p62) and HSP70 were measured using Western blot. All autophagy and heat shock markers were assessed in relation to a standard baseline (1.0RQ). Red cell lysate was collected pre-exercise, IPE, and 1, 2, 4, and 24hr to assess glutathione/total glutathione ratio (GSSG/tGSH). RESULTS: No group differences (p>0.05) were detected for protein expression of autophagy markers, HSP70, or GSSG/tGSH ratio at any time-point. When combining groups, LC3II decreased significantly (p<0.01) at 2 (0.51±0.38RQ) and 4 (0.41±0.36RQ) hr PE. p62 decreased significantly (p<0.001) at IP (0.56±0.33RQ), 2 (0.24±0.23RQ), and 4 (0.33±0.31RQ) hr PE and significantly increased (p<0.01) at 24 (1.43±0.44RQ) hr PE. HSP70 increased significantly (p<0.001) increased at 48 (1.59±0.96RQ) and 72 (4.71±3.84RQ) hr PE. GSSG/tGSH ratio significantly (p<0.05) increased from baseline (0.11±0.04RQ) at 1 (0.39±0.05RQ), 2 (0.69±0.22RQ), and 4 (0.39±0.17RQ) hr post-exercise. CONCLUSION: These data support previous work that the heat shock response may exert regulatory control of autophagy in-part through HSP70. HSP70 may assist in transitioning the cell from an initial degradation phase immediately following exercise towards protein synthesis in the latter phases of the post-exercise period. The initial autophagy upregulation may be influenced by oxidative stress.

Novel single skeletal muscle fiber analysis reveals a fiber type-selective effect of acute exercise on glucose uptake.

One exercise session can induce subsequently elevated insulin sensitivity that is largely attributable to greater insulin-stimulated glucose uptake by skeletal muscle. Because skeletal muscle is a heterogeneous tissue comprised of diverse fiber types, our primary aim was to determine exercise effects on insulin-independent and insulin-dependent glucose uptake by single fibers of different fiber types. We hypothesized that each fiber type featuring elevated insulin-independent glucose uptake immediately postexercise (IPEX) would be characterized by increased insulin-dependent glucose uptake at 3.5 h postexercise (3.5hPEX). Rat epitrochlearis muscles were isolated and incubated with 2-[3H]deoxyglucose. Muscles from IPEX and sedentary (SED) controls were incubated without insulin. Muscles from 3.5hPEX and SED controls were incubated ± insulin. Glucose uptake (2-[3H]deoxyglucose accumulation) and fiber type (myosin heavy chain isoform expression) were determined for single fibers dissected from the muscles. Major new findings included the following: 1) insulin-independent glucose uptake was increased IPEX in single fibers of each fiber type (types I, IIA, IIB, IIBX, and IIX), 2) glucose uptake values from insulin-stimulated type I and IIA fibers exceeded the values for the other fiber types, 3) insulin-stimulated glucose uptake for type IIX exceeded IIB fibers, and 4) the 3.5hPEX group vs. SED had greater insulin-stimulated glucose uptake in type I, IIA, IIB, and IIBX but not type IIX fibers. Insulin-dependent glucose uptake was increased at 3.5hPEX in each fiber type except for IIX fibers, although insulin-independent glucose uptake was increased IPEX in all fiber types (including type IIX). Single fiber analysis enabled the discovery of this fiber type-related difference for postexercise, insulin-stimulated glucose uptake.

Associations Between Antioxidant Capacity And Insulin Sensitivity At Baseline But Not Following Six-weeks Of HIIT Or MIT In Obese Males.

Obesity is an independent risk factor for type 2 diabetes and cardiovascular disease. Oxidative stress or low total antioxidant capacity has been shown to be associated with decreased insulin sensitivity (SI) in overweight/obese individuals. Exercise training has been shown to improve systemic antioxidant capacity (TAC) and SI; however whether or not correlations between SI and TAC observed under untrained conditions are associated following exercise training is less clear. PURPOSE: The purpose of this study was twofold: 1) to determine if SI was correlated with serum TAC in a cohort of overweight/obese men at baseline and following six-weeks of exercise training; and 2) to determine if the relationships between SI and TAC responded differently following High Intensity Interval (HIIT) vs Moderate Intensity-Training (MIT). METHODS: 16 sedentary, overweight/obese young men (age = 20 ± 1.5 years, body mass index = 29.5 ± 3.3 kg/m2) were randomly assigned to HIIT or MIT and evaluated at baseline and post-training. Baseline and post training assessments included DXA for body composition assessment, oral glucose tolerance test to measure SI, and the oxygen radical absorbance capacity assay to assess TAC. Additionally, acute serum TAC responses were assessed at pre-exercise (PRE), immediately post exercise (IPE) and 30 minutes post exercise (30min-Post) at baseline and six-weeks post training. RESULTS: A significant correlation was observed between SI and TAC at baseline (R2=0.548, P=0.001). SI significantly improved from baseline to post-training in both groups (P=0.037), with no significant time x group interactions for HIIT or MIT. No significant changes in TAC were found from baseline to post-training. No significant correlations were found between SI and TAC in the trained condition. A significant increase in TAC was observed IPE compared to pre-exercise at baseline and six-weeks post training following HIIT (P<0.05). A significant decrease in TAC was found 30min-Post compared to IPE six-weeks post training in HIIT and MIT. CONCLUSION: The observed baseline correlation between SI and TAC did not persist after training, which suggests that factors other than changes in TAC may be mediating the exercise-induced improvement in SI. Ongoing studies will attempt to identify exercise-induced mediators in SI.

Acute Exercise and Oxidative Stress: CrossFit(™) vs. Treadmill Bout.

CrossFit™, a popular high-intensity training modality, has been the subject of scrutiny, with concerns of elevated risk of injury and health. Despite these concerns empirical evidence regarding physiologic stresses including acute oxidative stress is lacking. Therefore, the purpose of this investigation was to examine the acute redox response to a CrossFit™ bout. Furthermore, these findings were compared to a high-intensity treadmill bout as a point of reference. Ten males 26.4 ± 2.7 yrs having three or more months of CrossFit™ experience participated in the present study. Blood plasma was collected at four time points: Pre-exercise (PRE), immediately-post-exercise (IPE), 1 hr-post (1-HP) and 2 hr-post (2-HP), to examine oxidative damage and antioxidant capacity. Regarding plasma oxidative damage, CrossFit™ and Treadmill elicited a time-dependent increase of lipid peroxides 1-HP (CrossFit™=+143%, Treadmill=+115%) and 2-HP (CrossFit™=+256%, Treadmill+167%). Protein Carbonyls were increased IPE in CF only (+5%), while a time-dependent decrease occurred 1-HP (CrossFit™=−16%, Treadmill=−8%) and 2-HP (CF=−16%, TM=−1%) compared to IPE. Regarding antioxidant capacity, Ferric Reducing Antioxidant Power also demonstrated a time-dependent increase within CrossFit™ and Treadmill: IPE (CrossFit™=+25%, Treadmill=+17%), 1-HP (CrossFit™=+26%, Treadmill=+4.8%), 2-HP (CrossFit™=+20%, Treadmill=+12%). Total Enzymatic Antioxidant Capacity showed a time-dependent decrease in IPE (CrossFit™=−10%, Treadmill=−12%), 1-HP (CrossFit™=−12%, Treadmill=−6%), 2-HP (CrossFit™=−7%, Treadmill=−11%). No trial-dependent differences were observed in any biomarker of oxidative stress. The CrossFit™ bout elicited an acute blood oxidative stress response comparable to a traditional bout of high-intensity treadmill running. Results also confirm that exercise intensity and the time course of exercise recovery influence oxidative responses.

Cytokine Responses to Acute Intermittent Aerobic Exercise in Children With Prader-Willi Syndrome and Nonsyndromic Obesity.

Prader-Willi Syndrome (PWS), the best characterized form of syndromic obesity, presents with abnormally high fat mass. In children, obesity presents with low-grade systemic inflammation. This study evaluated if PWS and/or nonsyndromic obesity affected cytokine responses to intermittent aerobic exercise in children. Eleven children with PWS (11 ± 2 y, 45.4 ± 9.5% body fat), 12 children with obesity (OB) (9 ± 1 y, 39.9 ± 6.8% body fat), and 12 lean (LN) children (9 ± 1 y, 17.5 ± 4.6% body fat) participated. Children completed 10 2-min cycling bouts of vigorous intensity, separated by 1-min rest. Blood samples were collected preexercise (PRE), immediately postexercise (IP), and 15, 30, and 60 min into recovery to analyze possible changes in cytokines. In all groups, IL-6 and IL-8 concentrations were greater during recovery compared with PRE. PWS and OB exhibited higher IL-6 area under the curve (AUC) than LN (p < .01 for both). PWS demonstrated higher IL-8 AUC than LN (p < .04). IL-10, TNF-α, and IFN-γ did not change with exercise (p > .05 for all). Results indicate that children with PWS respond with increased Il-6 and IL-8 concentrations to acute exercise similarly to controls. Excess adiposity and epigenetic modifications may explain the greater integrated IL-6 and IL-8 responses in PWS compared with controls.

Evaluating Stress Hormones’ Responses to Exercise in Lean versus Obese Children using Different Methodologies

Previous studies have evaluated the role of obesity on stress hormones’ responses to exercise. Responses were typically evaluated by analyzing the; 1) change in absolute concentration of the hormone over time; 2) calculated area under the curve (AUC); and 3) calculated percent change from baseline (PRE) to various time points. It was hypothesized that depending on the method used to assess changes from PRE, results and conclusions may differ in groups that present PRE differences. PURPOSE: This study determined whether three different methods to assess changes in hormonal concentrations over time yielded results leading to similar conclusions. METHODS: Eleven lean (LN: 8M/3F; age = 9.3 ± 1.2 y; body fat = 17.3 ± 4.8 %) and 11 obese (OB: 7M/4F; age = 9.0 ± 1.1 y; body fat = 39.0 ± 6.4 %) children completed a 30-min discontinuous submaximal bike test. Blood samples were collected at PRE, immediately post-exercise (IP), and 15, 30 and 60 min into recovery. Epinephrine (EPI), norepinephrine (NE) and growth hormone (GH) were analyzed using ELISA. Data were analyzed by: M1 = 2 (group) x 5 (time) repeated measures ANOVA for absolute concentrations; M2 = ANOVA for AUC; and M3 = 2 (group) x 4 (time) ANOVA for percent changes from PRE. RESULTS: M1 and M3 detected an interaction for EPI as IP > all times in LN only (p < 0.01 for both methods). For NE, M1 found a time effect (IP > all times; p < 0.01 for all) and M3 found group (LN > OB; p = 0.04) and time effects (PRE to IP > all times; p < 0.01 for all). M1 showed an interaction for GH with IP > all times in LN and OB (p < 0.01 for both) though at IP, LN > OB (p < 0.01). In contrast, M3 found a time effect (PRE to IP > PRE to 30 and 60 min; p < 0.01 for both). M2 supported M1’s findings, but not M3, for all hormones. CONCLUSION: Findings indicate that evaluating hormonal concentration changes over time using calculated percent change from PRE resulted in different conclusions compared to absolute changes over time or AUC. This difference was specific for GH, as M3 may have accounted for differences at PRE between groups. Therefore, researchers are encouraged to decide a priori the method for analysis based on whether the objective is to compare possible absolute concentration exposure of hormones to tissues, integrated responses or relative changes from PRE as interpretation of results may differ when PRE differences exist between groups.

A single session of aerobic exercise influences paraoxonase 1 activity and concentration (Una sola sesión de ejercicio aeróbico influye en la actividad y concentración de la paraoxonasa)

Our purpose was to examine changes in paraoxonase 1 (PON1) concentration and activity following a single aerobic exercise session. Sixteen men (32 ± 8 yrs.; BMI = 29.4 ± 6.8 kg/m2; % fat = 29 ± 13; VO2max = 38.3 ± 11.9 ml.min-1.kg-1; waist circumference = 93.7 ± 16.0 cm; HDL-C = 1.19 ± 0.21 and triglycerides = 1.22 ± 1.04 mmol’™l-1; direct LDL = 2.69 ± 0.73 mmol’™l-1) expended 400 kcals by treadmill walking at 65% of VO2max. Fasting blood samples were collected before (PRE), immediately post-exercise (IPE), 24 hours post-exercise, and 48 hours post-exercise. PON1 concentration, PON1 activity, lipids, apolipoprotein A1 (Apo A1), apolipoprotein B (Apo B), and thiobarbituric acid reactive substances (TBARS) were analyzed for each time point. The men were divided into two groups based on their body mass index (BMI): Normal weight (NW) and Obese Group. At baseline, PON1 concentration and activity were significantly higher in the NW group as compared to the obese group. In addition, PON1 activity was significantly higher in the NW group as compared to the obese group for all time points. Furthermore, PON1 concentration and activity were significantly increased in the combined group immediately post-exercise and returned to baseline levels within 24 hours. PON1 activity was significantly increased in the Obese group IPE and this was observed with increases in HDLc, Apo A1, and TBARS.Key words. PON1 activity, Exercise, Lipids, Lipoproteins.Resumen. Nuestro objetivo fue examinar los cambios en la concentración y actividad de la paraoxonasa 1 (PON1) luego de una sola sesión de ejercicio aeróbico. Dieciséis hombres (32 ± 8 años; IMC = 29.4 ± 6.8 kg/m2; % grasa = 29 ± 13; VO2max = 38.3 ± 11.9 ml.min-1.kg-1; circunferencia de cintura = 93.7 ± 16.0 cm; HDL-C = 1.19 ± 0.21 y triglicéridos = 1.22 ± 1.04 mmol’™l-1; LDL directo = 2.69 ± 0.73 mmol’™l-1) hicieron ejercicio en una banda sin fin al 65% del VO2max hasta gastar 400 kcal. Se recolectaron muestras sanguíneas en ayuno antes (PRE), inmediatamente finalizado el ejercicio (IPE), 24 y 48 horas posteriores al ejercicio. Para cada una de esas muestras, se analizó la concentración y la actividad de PON1, y la concentración de lípidos, apolipoproteína A1 (Apo A1), apolipoproteína B (Apo B), y sustancias reactivas al ácido tiobarbitúrico (TBARS). Los participantes fueron asignados a dos grupos con base en un índice de masa corporal (IMC): grupo de peso normal (NW) y grupo de personas obesas. Los resultados de línea base indicaron que la concentración y actividad de PON1 fueron significativamente mayores en el grupo NW en comparación con el grupo de personas obesas. También se encontró que la actividad de PON1 fue significativamente mayor en el grupo NW en comparación con el grupo de personas obesas en las demás mediciones. Es más, la concentración y actividad de PON1 aumentó significativamente en ambos grupos combinados inmediatamente luego del ejercicio y regresó a sus niveles basales en 24 horas. La actividad de PON1 aumentó significativamente en el grupo de personas obesas IPE y esto se observó con aumentos en en HDLc, Apo A1 y TBARS.Palabras claves. actividad de PON1, ejercicio, lípidos, lipoproteínas.

Endocrine response to acute resistance exercise in obese versus lean physically active men.

Resistance exercise induces a host of endocrine responses that potentiate its effects on body composition and metabolism. Excess adiposity negatively affects some hormonal responses to exercise in sedentary men. This study compared the resistance exercise (RE)-associated growth hormone (GH), insulin-like growth factor-1 (IGF-1), and testosterone responses in lean vs. obese physically active men. Ten healthy physically active obese males (body fat % 36.2±4.03, age 24.6±3.7years, mass 104.5±15.5kg, height 178.8±6.0cm) were compared to ten lean counterparts (body fat % 12.7±2.9, age 24.6±3.7years, mass 77.1±6.4kg, height 177.2±4.8cm). The muscular endurance RE protocol consisted of six sets of ten repetitions per leg of stepping onto an elevated platform (20% of participant's height) while wearing a weighted-vest (50% of participant's lean mass). Pre-, immediately post-exercise (IP), and three more blood samples were collected during the one-hour recovery. When accounting for baseline differences there were no group by time interactions for GH (p=0.33); or LH (p=0.52). Lean presented a trend towards significance for higher IGF-1 IP (p=0.08) than obese. Testosterone IP was similar in obese and lean, but lower in obese than lean at 30min into recovery (p<0.01). AUC were lower in obese than lean for all hormones (p<0.05 for all). These findings suggest that excess adiposity does not appear to negatively affect the immediate GH and T responses to RE in active males; but possibly negatively affects IGF-1. However, the baseline and integrated concentrations during recovery appear negatively affected by excess adiposity.