Effect of short-term, high-intensity exercise training on human skeletal muscle citrate synthase maximal activity: single versus multiple bouts per session.

The legs of 9 men (age 21 ± 2 years, 45 ± 4 mL/(kg·min)) were randomly assigned to complete 6 sessions of high-intensity exercise training, involving either one or four 5-min bouts of counterweighted, single-leg cycling. Needle biopsies from vastus lateralis revealed that citrate synthase maximal activity increased after training in the 4-bout group (p = 0.035) but not the 1-bout group (p = 0.10), with a significant difference between groups post-training (13%, p = 0.021). Novelty Short-term training using brief intense exercise requires multiple bouts per session to increase mitochondrial content in human skeletal muscle.

Sarcolemmal loss of active nNOS (Nos1) is an oxidative stress-dependent, early event driving disuse atrophy.

Skeletal muscle atrophy following unloading or immobilization represents a major invalidating event in bedridden patients. Among mechanisms involved in atrophy development, a controversial role is played by neuronal NOS (nNOS; NOS1), whose dysregulation at the protein level and/or subcellular distribution also characterizes other neuromuscular disorders. This study aimed to investigate unloading-induced changes in nNOS before any evidence of myofiber atrophy, using vastus lateralis biopsies obtained from young healthy subjects after a short bed-rest and rat soleus muscles after exposure to short unloading periods. Our results showed that (1) changes in nNOS subcellular distribution using NADPH-diaphorase histochemistry to detect enzyme activity were observed earlier than using immunofluorescence to visualize the protein; (2) loss of active nNOS from the physiological subsarcolemmal localization occurred before myofiber atrophy, i.e. in 8-day bed-rest biopsies and in 6 h-unloaded rat soleus, and was accompanied by increased nNOS activity in the sarcoplasm; (3) nNOS (Nos1) transcript and protein levels decreased significantly in the rat soleus after 6 h and 1 day unloading, respectively, to return to ambulatory levels after 4 and 7 days of unloading, respectively; (4) unloading-induced nNOS redistribution appeared dependent on mitochondrial-derived oxidant species, indirectly measured by tropomyosin disulfide bonds which had increased significantly in the rat soleus already after a 6 h-unloading bout; (5) activity of displaced nNOS molecules is required for translocation of the FoxO3 transcription factor to myofiber nuclei. FoxO3 nuclear localization in rat soleus increased after 6 h unloading (about four-fold the ambulatory level), whereas it did not when nNOS expression and activity were inhibited in vivo before and during 6 h unloading. In conclusion, this study demonstrates that the redistribution of active nNOS molecules from sarcolemma to sarcoplasm not only is ahead of the atrophy of unloaded myofibers, and is induced by increased production of mitochondrial superoxide anion, but also drives FoxO3 activation to initiate muscle atrophy. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Regional regulation of focal adhesion kinase after concentric and eccentric loading is related to remodelling of human skeletal muscle.

AIMS: We assessed focal adhesion kinase (FAK) response to concentric (CON) vs eccentric (ECC) resistance training (RT) at two vastus lateralis (VL) sites, and the relationships between FAK, muscle protein synthesis (MPS) and morphological remodelling. METHODS: Six young males trained both legs unilaterally 3 times/week for 8 weeks; one leg performed CON RT, the contralateral performed ECC RT. Muscle biopsies were collected after training from VL mid-belly (MID) and distal (distal) sites at 0, 4, 8 weeks. Focal adhesion kinase content and activation were evaluated by immunoblotting. MPS was assessed by deuterium oxide tracer; morphological adaptations were evaluated by ultrasound and DXA. RESULTS: pY397-FAK 8 weeks levels were ~4-fold greater after ECC at the distal site compared to CON (P < .05); pY397FAK to total FAK ratio was greater in ECC vs CON at 4 (~2.2-fold, P < .05) and 8 weeks (~9-fold, P < .001) at the distal site. Meta-vinculin was found transiently increased at 4 weeks at the distal site only after ECC RT. ECC presented greater fascicle length (Lf) increases (10.5% vs 4%), whereas CON showed greater in pennation angle (PA) changes (12.3% vs 2.1%). MPS did not differ between exercise types or muscle sites at all time points. distal pY397-FAK and pY397-FAK/FAK values correlated to changes in Lf at 8 weeks (r = .76, P < .01 and r = .66, P < .05 respectively). CONCLUSION: Focal adhesion kinase phosphorylation was greater at 8 weeks after ECC RT and was muscle region-specific. FAK activity correlated to contraction-dependent architectural remodelling, suggesting a potential role of FAK in orienting muscle structural changes in response to distinct mechanical stimuli.

Effect of tapering after a period of high-volume sprint interval training on running performance and muscular adaptations in moderately trained runners.

The effect of tapering following a period of high-volume sprint interval training (SIT) and a basic volume of aerobic training on performance and muscle adaptations in moderately trained runners was examined. Eleven (8 men, 3 women) runners [maximum oxygen uptake (V̇o2max): 56.8 ± 2.9 ml·min-1·kg-1; mean ± SD] conducted high-volume SIT (HV; 20 SIT sessions; 8-12 × 30 s all-out) for 40 days followed by 18 days of tapering (TAP; 4 SIT sessions; 4 × 30 s all-out). Before and after HV as well as midway through and at the end of TAP, the subjects completed a 10-km running test and a repeated running test at 90% of vV̇o2max to exhaustion (RRT). In addition, a biopsy from the vastus lateralis muscle was obtained at rest. Performance during RRT was better ( P < 0.01) at the end of TAP than before HV (6.8 ± 0.5 vs. 5.6 ± 0.5 min; means ± SE), and 10-km performance was 2.7% better ( P < 0.05) midway through (40.7 ± 0.7 min) and at the end of (40.7 ± 0.6 min) TAP than after HV (41.8 ± 0.9 min). The expression of muscle Na+-K+-ATPase (NKA)α1, NKAß1, phospholemman (FXYD1), and sarcoplasmic reticulum calcium transport ATPase (SERCA1) increased ( P < 0.05) during HV and remained higher during TAP. In addition, oxygen uptake at 60% of vV̇o2max was lower ( P < 0.05) at the end of TAP than before and after HV. Thus short-duration exercise capacity and running economy were better than before the HV period together with higher expression of muscle proteins related to Na+/K+ transport and Ca2+ reuptake, while 10-km performance was not significantly improved by the combination of HV and tapering. NEW & NOTEWORTHY Short-duration performance became better after 18 days of tapering from ~6 wk of high-volume sprint interval training (SIT), whereas 10-km performance was not significantly affected by the combination of high-volume SIT and tapering. Higher expression of muscle NKAα1, NKAß1, FXYD1, and SERCA1 may reflect faster Na+/K+ transport and Ca2+ reuptake that could explain the better short-duration performance. These results suggest that the type of competition should determine the duration of tapering to optimize performance.

Dicarbonyl stress and glyoxalase enzyme system regulation in human skeletal muscle.

Skeletal muscle insulin resistance is a hallmark of Type 2 diabetes (T2DM) and may be exacerbated by protein modifications by methylglyoxal (MG), known as dicarbonyl stress. The glyoxalase enzyme system composed of glyoxalase 1/2 (GLO1/GLO2) is the natural defense against dicarbonyl stress, yet its protein expression, activity, and regulation remain largely unexplored in skeletal muscle. Therefore, this study investigated dicarbonyl stress and the glyoxalase enzyme system in the skeletal muscle of subjects with T2DM (age: 56 ± 5 yr.; BMI: 32 ± 2 kg/m2) compared with lean healthy control subjects (LHC; age: 27 ± 1 yr.; BMI: 22 ± 1 kg/m2). Skeletal muscle biopsies obtained from the vastus lateralis at basal and insulin-stimulated states of the hyperinsulinemic (40 mU·m-2·min-1)-euglycemic (5 mM) clamp were analyzed for proteins related to dicarbonyl stress and glyoxalase biology. At baseline, T2DM had increased carbonyl stress and lower GLO1 protein expression (-78.8%), which inversely correlated with BMI, percent body fat, and HOMA-IR, while positively correlating with clamp-derived glucose disposal rates. T2DM also had lower NRF2 protein expression (-31.6%), which is a positive regulator of GLO1, while Keap1 protein expression, a negative regulator of GLO1, was elevated (207%). Additionally, insulin stimulation during the clamp had a differential effect on NRF2, Keap1, and MG-modified protein expression. These data suggest that dicarbonyl stress and the glyoxalase enzyme system are dysregulated in T2DM skeletal muscle and may underlie skeletal muscle insulin resistance. Whether these phenotypic differences contribute to the development of T2DM warrants further investigation.

Differential localization and anabolic responsiveness of mTOR complexes in human skeletal muscle in response to feeding and exercise.

Mechanistic target of rapamycin (mTOR) resides as two complexes within skeletal muscle. mTOR complex 1 [mTORC1-regulatory associated protein of mTOR (Raptor) positive] regulates skeletal muscle growth, whereas mTORC2 [rapamycin-insensitive companion of mTOR (Rictor) positive] regulates insulin sensitivity. To examine the regulation of these complexes in human skeletal muscle, we utilized immunohistochemical analysis to study the localization of mTOR complexes before and following protein-carbohydrate feeding (FED) and resistance exercise plus protein-carbohydrate feeding (EXFED) in a unilateral exercise model. In basal samples, mTOR and the lysosomal marker lysosomal associated membrane protein 2 (LAMP2) were highly colocalized and remained so throughout. In the FED and EXFED states, mTOR/LAMP2 complexes were redistributed to the cell periphery [wheat germ agglutinin (WGA)-positive staining] (time effect; P = 0.025), with 39% (FED) and 26% (EXFED) increases in mTOR/WGA association observed 1 h post-feeding/exercise. mTOR/WGA colocalization continued to increase in EXFED at 3 h (48% above baseline) whereas colocalization decreased in FED (21% above baseline). A significant effect of condition (P = 0.05) was noted suggesting mTOR/WGA colocalization was greater during EXFED. This pattern was replicated in Raptor/WGA association, where a significant difference between EXFED and FED was noted at 3 h post-exercise/feeding (P = 0.014). Rictor/WGA colocalization remained unaltered throughout the trial. Alterations in mTORC1 cellular location coincided with elevated S6K1 kinase activity, which rose to a greater extent in EXFED compared with FED at 1 h post-exercise/feeding (P < 0.001), and only remained elevated in EXFED at the 3 h time point (P = 0.037). Collectively these data suggest that mTORC1 redistribution within the cell is a fundamental response to resistance exercise and feeding, whereas mTORC2 is predominantly situated at the sarcolemma and does not alter localization.

Pure exercise intolerance and ophthalmoplegia associated with the m.12,294G > A mutation in the MT-TL2 gene: a case report.

BACKGROUND: Pure exercise intolerance associated with exclusive affection of skeletal muscle is a very rare phenotype of patients with mitochondrial myopathy. Moreover, the exercise intolerance in these rare patients is yet not well explored, as most of known cases have not been assessed by objective testing, but only by interview. We report a patient with a mitochondrial DNA (mtDNA) mutation that gives rise to an exclusive myopathy associated with exercise intolerance and ophthalmoplegia. We quantified the patient's exercise intolerance through detailed exercise testing. CASE PRESENTATION: A 39-year-old man presented with exercise intolerance and chronic progressive external ophthalmoplegia. Sequencing of the entire mtDNA identified a m.12,294G > A mutation in the MT-TL2 gene. The mutation was heteroplasmic in skeletal muscle (75%) while undetectable in blood, urinary sediment, and buccal mucosa as well as in tissues from the patient's mother. The mutation affected a highly conserved site in the anticodon stem of the mitochondrial transfer RNA Leucine (CUN) molecule and lead to a severe combined respiratory chain defect. Exercise physiological studies in the patient demonstrated a significantly reduced maximal oxygen uptake of 20.4 ml O2 × min-1 × kg-1 (about half of normal) as well as threefold elevated lactate/pyruvate ratios. CONCLUSION: The findings of our study support that the m.12,294G > A mutation is pathogenic. Likely, the mutation arose sporadically in early embryogenesis after differentiation of the mesoderm into muscle progenitor cells, leading to a pure myopathic phenotype.

Two-week inhalation of budesonide increases muscle Na,K ATPase content but not endurance in response to terbutaline in men.

While chronic systemic administration of glucocorticoids increases muscle Na+ ,K+ ATPase content, such effect is unexplored after therapeutic inhalation. We investigated the effect of therapeutic inhalation of the glucocorticoid budesonide on Na+ ,K+ ATPase content of skeletal muscle in men. Ten healthy trained subjects, aged 23 ± 4 years (mean ± 95% CI), participated in the study. Before and after 2 weeks of daily inhalation of budesonide (1.6 mg/day), a biopsy was taken from the vastus lateralis muscle for measurement of Na+ ,K+ ATPase content and blood samples were drawn for determination of plasma budesonide, cortisol, and K+ . Subjects' performance during cycling to fatigue at 90% of incremental peak power output (iPPO) was measured in response to 4 mg inhaled terbutaline to maximally stimulate Na+ ,K+ ATPase activity. Plasma concentrations of budesonide rose to 5.0 ± 1.6 nM with the intervention, whereas no changes were observed in plasma cortisol. Muscle Na+ ,K+ ATPase content increased (P ≤ 0.01) by 46 ± 34 pmol/(g wet wt) (17% increase) with the intervention. Cycling performance at 90% of iPPO did not change (P = 0.21) with the intervention (203 vs 214 s) in response to terbutaline. The present observations show that therapeutic inhalation of glucocorticoids increases muscle Na+ ,K+ ATPase content, but does not enhance high-intensity cycling endurance in response to terbutaline.

Microvascular Endothelial Dysfunction in Sedentary, Obese Humans Is Mediated by NADPH Oxidase: Influence of Exercise Training.

OBJECTIVE: The objectives of this study were to determine the impact of in vivo reactive oxygen species (ROS) on microvascular endothelial function in obese human subjects and the efficacy of an aerobic exercise intervention on alleviating obesity-associated dysfunctionality. APPROACH AND RESULTS: Young, sedentary men and women were divided into lean (body mass index 18-25; n=14), intermediate (body mass index 28-32.5; n=13), and obese (body mass index 33-40; n=15) groups. A novel microdialysis technique was utilized to detect elevated interstitial hydrogen peroxide (H2O2) and superoxide levels in the vastus lateralis of obese compared with both lean and intermediate subjects. Nutritive blood flow was monitored in the vastus lateralis via the microdialysis-ethanol technique. A decrement in acetylcholine-stimulated blood flow revealed impaired microvascular endothelial function in the obese subjects. Perfusion of apocynin, an NADPH oxidase inhibitor, lowered (normalized) H2O2 and superoxide levels, and reversed microvascular endothelial dysfunction in obese subjects. After 8 weeks of exercise, H2O2 levels were decreased in the obese subjects and microvascular endothelial function in these subjects was restored to levels similar to lean subjects. Skeletal muscle protein expression of the NADPH oxidase subunits p22phox, p47phox, and p67phox was increased in obese relative to lean subjects, where p22phox and p67phox expression was attenuated by exercise training in obese subjects. CONCLUSIONS: This study implicates NADPH oxidase as a source of excessive ROS production in skeletal muscle of obese individuals and links excessive NADPH oxidase-derived ROS to microvascular endothelial dysfunction in obesity. Furthermore, aerobic exercise training proved to be an effective strategy for alleviating these maladies.

COX Inhibitor Influence on Skeletal Muscle Fiber Size and Metabolic Adaptations to Resistance Exercise in Older Adults.

Common cyclooxygenase (COX)-inhibiting drugs enhance resistance exercise induced muscle mass and strength gains in older individuals. The purpose of this investigation was to determine whether the underlying mechanism regulating this effect was specific to Type I or Type II muscle fibers, which have different contractile and metabolic profiles. Muscle biopsies (vastus lateralis) were obtained before and after 12 weeks of knee-extensor resistance exercise (3 days/week) from healthy older men who consumed either a placebo (n = 8; 64±2 years) or COX inhibitor (acetaminophen, 4 gram/day; n = 7; 64±1 years) in double-blind fashion. Muscle samples were examined for Type I and II fiber cross-sectional area, capillarization, and metabolic enzyme activities (glycogen phosphorylase, citrate synthase, ß-hydroxyacyl-CoA-dehydrogenase). Type I fiber size did not change with training in the placebo group (304±590 µm(2)) but increased 28% in the COX inhibitor group (1,388±760 µm(2), p < .1). Type II fiber size increased 26% in the placebo group (1,432±499 µm(2), p < .05) and 37% in the COX inhibitor group (1,825±400 µm(2), p < .05). Muscle capillarization and enzyme activity were generally maintained in the placebo group. However, capillary to fiber ratio increased 24% (p < .1) and citrate synthase activity increased 18% (p < .05) in the COX inhibitor group. COX inhibitor consumption during resistance exercise in older individuals enhances myocellular growth, and this effect is more pronounced in Type I muscle fibers.

Vasoactive enzymes and blood flow responses to passive and active exercise in peripheral arterial disease.

BACKGROUND: Peripheral arterial disease (PAD) is characterised by impaired leg blood flow, which contributes to claudication and reduced exercise capacity. This study investigated to what extent vasoactive enzymes might contribute to altered blood flow in PAD (Fontaine stage II). METHODS: We compared femoral artery blood flow during reactive hyperaemia, leg-extension exercise and passive leg movement, and determined the level of vasoactive enzymes in skeletal muscle samples from the vastus lateralis in PAD (n = 10, 68.5 ± 6.5 years) and healthy controls (CON, n = 9, 62.1 ± 12.3 years). Leg blood flow was measured with Doppler ultrasound and muscle protein levels of phosphorylated endothelial nitric oxide synthase, NADPH oxidase, cyclooxygenase 1 and 2, thromboxane synthase, and prostacyclin synthase were determined. RESULTS: Leg blood flow during the initial 90 s of passive leg movement (242 ± 33 vs 441 ± 75 ml min(-1), P = 0.03) and during reactive hyperaemia (423 ± 100 vs 1255 ± 175 ml min(-1), P = 0.002) was lower in PAD than CON, whereas no significant difference was observed for leg blood flow during exercise (1490 ± 250 vs 1887 ± 349 ml min(-1), P = 0.37). PAD had higher NADPH oxidase than CON (1.04 ± 0.19 vs 0.50 ± 0.06 AU, P = 0.02), with no differences for other enzymes. Leg blood flow during exercise was correlated with prostacyclin synthase (P = 0.001). CONCLUSION: Elevated NADPH oxidase indicates that oxidative stress may be a primary cause of low nitric oxide availability and impaired blood flow in PAD.

Skeletal muscle fiber characteristics and oxidative capacity in hemiparetic stroke survivors.

INTRODUCTION: Skeletal muscle is changed after stroke, but conflicting data exist concerning muscle morphology and oxidative enzyme capacity. METHODS: In 36 chronic stroke patients bilateral rectus femoris muscle biopsies were analyzed, and fiber type proportions and cross-sectional areas were determined by ATPase histochemistry. Enzymatic concentrations of citrate synthase (CS) and 3-Hydroxyacyl-coenzymeA-dehydrogenase (HAD) were determined using freeze-dried muscle tissue. Findings were correlated with clinical outcomes. RESULTS: In the paretic muscles the mean fiber area was smaller (P = 0.0004), and a lower proportion of type 1 fibers (P = 0.0016) and a higher proportion of type 2X fibers (P = 0.0002) were observed. The paretic muscle had lower CS (P = 0.013) and HAD concentrations (P = 0.037). Mean fiber area correlated with muscle strength (r = 0.43; P = 0.041), and CS concentration correlated with aerobic capacity (r = 0.47; P = 0.01). CONCLUSIONS: In stroke survivors there is a phenotypic shift toward more fatigable muscle fibers with reduced oxidative enzymatic capacity that relates to clinical outcomes.

Effect of limited ischemia time on the amount and function of mitochondria within human skeletal muscle cells.

INTRODUCTION: The clinical success of total knee arthroplasty (TKA) depends substantially on the quadriceps muscle function. A frequently applied thigh tourniquet during TKA may induce ischemia related injuries to quadriceps muscle cells. Animal limb muscles subjected to 2-5 h ischemia revealed dysfunctional mitochondria, which in turn compromised the cellular bioenergetics and increased the level of reactive oxygen species. The hypothesis of the present study was that tourniquet application during TKA for 60 min (min) affects the amount and function of mitochondria within musculus vastus medialis cells. MATERIALS AND METHODS: In a randomized clinical trial, 10 patients enrolled to undergo primary TKA. The patients were randomly assigned to the tourniquet (n = 5) or non-tourniquet group (n = 5) after obtaining a written informed consent. For each of the groups, the first muscle biopsy was harvested immediately after performing the surgical approach and the second biopsy exactly 60 min later. All biopsies (5 × 5 × 5 mm) 125 mm3 were harvested from musculus vastus medialis and snap-frozen in liquid nitrogen. The biochemical analysis of the prepared muscle tissues included the measurement of activities of mitochondrial respiratory chain enzyme complexes I-III and citrate synthase. RESULTS: Tourniquet-induced 60 min ischemia time did not significantly change the activities of the mitochondrial respiratory chain enzymes complexes I-III of the skeletal muscle cells. The citrate synthase activities found to be not significantly different between both groups. CONCLUSIONS: The use of tourniquet during TKA within a limited time period of 60 min remained without substantial effects on the amount and function of mitochondria within human skeletal muscle cells.

Time course of postprandial hepatic phosphorus metabolites in lean, obese, and type 2 diabetes patients.

BACKGROUND: Impaired energy metabolism is a possible mechanism that contributes to insulin resistance and ectopic fat storage. OBJECTIVE: We examined whether meal ingestion differently affects hepatic phosphorus metabolites in insulin-sensitive and insulin-resistant humans. DESIGN: Young, lean, insulin-sensitive humans (CONs) [mean ± SD body mass index (BMI; in kg/m(2)): 23.2 ± 1.5]; insulin-resistant, glucose-tolerant, obese humans (OBEs) (BMI: 34.3 ± 1.7); and type 2 diabetes patients (T2Ds) (BMI: 32.0 ± 2.4) were studied (n = 10/group). T2Ds (61 ± 7 y old) were older (P < 0.001) than were OBEs (31 ± 7 y old) and CONs (28 ± 3 y old). We quantified hepatic γATP, inorganic phosphate (Pi), and the fat content [hepatocellular lipids (HCLs)] with the use of (31)P/(1)H magnetic resonance spectroscopy before and at 160 and 240 min after a high-caloric mixed meal. In a subset of volunteers, we measured the skeletal muscle oxidative capacity with the use of high-resolution respirometry. Whole-body insulin sensitivity (M value) was assessed with the use of hyperinsulinemic-euglycemic clamps. RESULTS: OBEs and T2Ds were similarly insulin resistant (M value: 3.5 ± 1.4 and 1.9 ± 2.5 mg · kg(-1) · min(-1), respectively; P = 0.9) and had 12-fold (P = 0.01) and 17-fold (P = 0.002) higher HCLs, respectively, than those of lean persons. Despite comparable fasting hepatic γATP concentrations, the maximum postprandial increase of γATP was 6-fold higher in OBEs (0.7 ± 0.2 mmol/L; P = 0.03) but only tended to be higher in T2Ds (0.6 ± 0.2 mmol/L; P = 0.09) than in CONs (0.1 ± 0.1 mmol/L). However, in the fasted state, muscle complex I activity was 53% lower (P = 0.01) in T2Ds but not in OBEs (P = 0.15) than in CONs. CONCLUSIONS: Young, obese, nondiabetic humans exhibit augmented postprandial hepatic energy metabolism, whereas elderly T2Ds have impaired fasting muscle energy metabolism. These findings support the concept of a differential and tissue-specific regulation of energy metabolism, which can occur independently of insulin resistance. This trial was registered at clinicaltrials.gov as NCT01229059.

Correction of Mitochondrial Enzyme Activities in the Skeletal Muscles of Old Rats in Response to Addition of Olive Oil to the Ration.

Activities of mitochondrial electron transport chain enzymes NADH-CoQ oxidoreductase (complex I), cytochrome C-oxidase (complex IV), and citrate synthase were measured by spectrophotometry in m. quadriceps femoris homogenate from old rats receiving olive oil with the ration. Reduced activities of complexes I and IV in old animals were restored to the level of young animals after 6-week consumption of olive oil. Activity of citrate synthase did not change with age. Positive effect of olive oil on fatty-acid composition of the muscle tissue in old animals was demonstrated. The content of summary monounsaturated fatty acids, reduced with aging, and of summary polyunsaturated ones, increasing with age, were restored in old rats to the levels virtually not differing from the levels of young animals.

Enhanced insulin signaling in human skeletal muscle and adipose tissue following gastric bypass surgery.

Roux-en-Y gastric bypass (RYGB) leads to increased peripheral insulin sensitivity. The aim of this study was to investigate the effect of RYGB on expression and regulation of proteins involved in regulation of peripheral glucose metabolism. Skeletal muscle and adipose tissue biopsies from glucose-tolerant and type 2 diabetic subjects at fasting and during a hyperinsulinemic-euglycemic clamp before as well as 1 wk and 3 and 12 mo after RYGB were analyzed for relevant insulin effector proteins/signaling components. Improvement in peripheral insulin sensitivity mainly occurred at 12 mo postsurgery when major weight loss was evident and occurred concomitantly with alterations in plasma adiponectin and in protein expression/signaling in peripheral tissues. In skeletal muscle, protein expression of GLUT4, phosphorylated levels of TBC1D4, as well as insulin-induced changes in phosphorylation of Akt and glycogen synthase activity were enhanced 12 mo postsurgery. In adipose tissue, protein expression of GLUT4, Akt2, TBC1D4, and acetyl-CoA carboxylase (ACC), phosphorylated levels of AMP-activated protein kinase and ACC, as well as insulin-induced changes in phosphorylation of Akt and TBC1D4, were enhanced 12 mo postsurgery. Adipose tissue from glucose-tolerant subjects was the most responsive to RYGB compared with type 2 diabetic patients, whereas changes in skeletal muscle were largely similar in these two groups. In conclusion, an improved molecular insulin-sensitive phenotype of skeletal muscle and adipose tissue appears to contribute to the improved whole body insulin action following a substantial weight loss after RYGB.

A polymorphism in the stearoyl-CoA desaturase gene promoter increases monounsaturated fatty acid content in dry-cured ham.

Data on 125 dry-cured hams from purebred Duroc pigs were used to examine whether the favorable effect of the T allele in the promoter region of the stearoyl-CoA desaturase gene (AY487830:g.2228T>C) on monounsaturated fatty acid (MUFA) content in green ham is maintained after the curing process. It is shown that pigs carrying the T allele produced dry-cured hams with increased C16:1, C18:1n-9, C18:1n-7, and MUFA and decreased C18:0 and saturated fatty acid (SFA) content. The TT pigs had 1.39% more MUFA and 1.62% less SFA than the CC animals, while gilts had 0.74% more MUFA and 0.34% less SFA than barrows. The correlation between MUFA in green and dry-cured hams (n=53) was high (r=0.88), with TT pigs being more effective in retaining increased MUFA in green hams until the end of the curing period. It is concluded that increasing the presence of the T allele could have more impact than gender to produce hams with a high level of MUFA.

SERCA1 overexpression minimizes skeletal muscle damage in dystrophic mouse models.

Duchenne muscular dystrophy (DMD) is characterized by progressive muscle wasting secondary to repeated muscle damage and inadequate repair. Elevations in intracellular free Ca²âº have been implicated in disease progression, and sarcoplasmic/endoplasmic reticulum Ca²âº-ATPase 1 (SERCA1) overexpression has been shown to ameliorate the dystrophic phenotype in mdx mice. The purpose of this study was to assess the effects of SERCA1 overexpression in the more severe mdx/Utr(-/-) mouse model of DMD. Mice overexpressing SERCA1 were crossed with mdx/Utr ± mice to generate mdx/Utr(-/-)/+SERCA1 mice and compared with wild-type (WT), WT/+SERCA1, mdx/+SERCA1, and genotype controls. Mice were assessed at ∼12 wk of age for changes in Ca²âº handling, muscle mass, quadriceps torque, markers of muscle damage, and response to repeated eccentric contractions. SERCA1-overexpressing mice had a two- to threefold increase in maximal sarcoplasmic reticulum Ca²âº-ATPase activity compared with WT which was associated with normalization in body mass for both mdx/+SERCA1 and mdx/Utr(-/-)/+SERCA1. Torque deficit in the quadriceps after eccentric injury was 2.7-fold greater in mdx/Utr(-/-) vs. WT mice, but only 1.5-fold greater in mdx/Utr(-/-)/+SERCA1 vs. WT mice, an attenuation of 44%. Markers of muscle damage (% centrally nucleated fibers, necrotic area, and serum creatine kinase levels) were higher in both mdx and mdx/Utr(-/-) vs. WT, and all were attenuated by overexpression of SERCA1. These data indicate that SERCA1 overexpression ameliorates functional impairments and cellular markers of damage in a more severe mouse model of DMD. These findings support targeting intracellular Ca²âº control as a therapeutic approach for DMD.