Categories and frequencies of leisureactivities employed by 156 randomly selected males and females aged 40-44, 50-54, 60-64 were investigated by structured interviews and were related to leisuresatisfaction, to experienced health and socio-economic status. In equal numbers (15) of males and females from each group and in 24 males (60 +_6 years) with intermittent claudication (Cl) isokinetic plantar flexion performance was investigated with registrations of peak torque (PT), contractional work (CW), active range-of-motion (RoM) and integrated electromyograms from all threee triceps surae heads. Subjects performed a few maximum plantarflexions at different velocities of angular motion and also up to 200 consecutive plantar flexions at 60 °/s. The males aged 40-44 were re -investigated after two years additionally using electromyographic power frequency analyses. Leisure choice was mainly age and sex independent and extensively included outdoor activities. Leisure satisfaction was positively associated with relative frequency of activities. Symptoms of bodily discomfort, in particular backpain, were quite common and apparently caused relatively low level of mutual leisure activities. Thus, with in this age span, leisure activities appear rather rigid but often successfully, adhered to . Common ailments influence partnership mutuality negatively. Plantar flexion PT and CW are adequately p re dicta ble by sex, age and crural circumference. Uniformly a 3:2 male/female ratio characterizes mechanical output and iEMG. The latter is velocity independent. Output decreases with increasing age. Hence the output/excitation balance (CW/iEMG) is age, but not sex, dependent. CI-patients produce less PT and CW than do controls. Independently of this disease, of age and sex, PT and CW describe parallel negative exponential functions of velocity. During repeated manoeuvres plantar flexion output and iEMG initially drop, there after to maintain nearly steady-state levels. Throughout up to 200 contractions CW/iEMG was unaltered in the clinically healthy. Test/re-test with two years interval yielded nearly identical results. Leftshifts in mean power frequency in parallel with output-drop imply that the latter probably is due to FT-motor unit fatigue. For CW, but not for PT, the drop became slower and the (relative) steady-state level higher with increasing age, indicating significant increase in endurance with age. In the Cl-patients, output, but not excitation, decreased after a few repititions. Therefore, CW/iEMG fell dramatically, implying intramuscular fatigue. Taken together with findings of close associations between total cumulated work and measured/expected maximum walking tole rance it is suggested that measurements of CW and calculations of CW/iEMG are of clinical value. / <p>Härtill 5 uppsatser</p> / digitaliserinlg@umu.se

The human body consists of about 40 % skeletal muscles which control the body’s movement, ability to stand up, force generation, locomotion, heat production and are also the body’s protein reservoir. Muscle mass is controlled by the relationship between protein synthesis and protein degradation. Atrophy, a decrease in muscle mass, can be trigged by disuse, immobilization, inflammation and cancer. Hypertrophy, an increase in muscle mass, can occur after increased mechanical load, high usage and/or anabolic stimulation. The aim of this thesis was to investigate changes in expression and post translational modifications of some factors involved in the regulation of protein synthesis and protein degradation in 6-days denervated atrophic hind-limb muscles (anterior tibial and pooled gastrocnemius and soleus muscles) and in 6-days denervated hypertrophic hemidiaphragm muscle in mice. Protein expression and post translational modifications were studied semi-quantitatively using Western blots with whole muscle homogenates and separated nuclear and cytosolic fractions from both innervated and denervated muscles.  An increase in protein synthesis after denervation in both atrophic and hypertrophic muscles was suggested after studies of factors downstream of mTOR (paper I).  Other results suggest that FoxO1 and MuRF1 (paper II) participate in the tissue remodeling that occurs after denervation. A differential response of MK2 phosphorylation in denervated hypertrophic and atrophic muscles was confirmed (paper III). An increase in phosphorylation of the MK2 substrate Hsp 25 in all denervated muscles studied (paper III) indicates that other factors than MK2 are involved in regulating this phosphorylation. eIF4G phosphorylation at S1108 was investigated (paper IV) and a decrease was observed in atrophic muscle but an increase in hypertrophic muscle. The results in this thesis suggest that there are several factors that control protein degradation and protein synthesis in denervated atrophic and hypertrophic skeletal muscles. This is an intricate labyrinth with many different cell signaling factors, the function of which are still far from fully understood.

Tinamous (Tinamidae) have the smallest heart in relation to body mass compared to any other flying bird today (Bishop 1997). This means that heart size is likely to restrict aerobic metabolism. Tinamous inhabit areas from sea level to 4800 m a.s.l., which means that the high altitude living species, Nothoprocta ornata (NO), is exposed to hypoxia. In this study the activity of the two metabolic enzymes Lactate Dehydrogenase (LDH) and Citrate Synthase (CS) was measured and the ratio between the enzyme activities calculated to examine if the small heart of the tinamous affects their aerobic/anaerobic metabolism. The activity of the two enzymes was measured in the heart and the gastrocnemius muscle in the three species Nothoprocta ornata (NO), Nothoprocta perdicaria (NP) and Gallus gallus (GG). CS activity was significantly higher in the heart compared to the skeletal muscle and LDH activity was significant higher in the skeletal muscle than in the heart in all three species. The LDH/CS ratio was significantly higher in NO’s skeletal muscle than in chickens but there was no significant difference between species in the heart. The higher ratio in NO´s muscle could be a sign of a higher anaerobic metabolism that is used in the muscles to compensate for the small heart NO have. In conclusion, the Tinamous

Skeletal muscle is one of the largest tissues in humans and provides many pivotal functions to support life. Abnormality in skeletal muscle functions can lead to disease. For example, insulin resistance in skeletal muscle leads to type II diabetes. The underlying mechanisms that control energy balance in skeletal muscle remain largely elusive, especially at the genetic level. Here in the second chapter, I showed that MyoD mediated the transcriptional regulation of ACSL5, a mitochondrial protein, in C2C12 myoblasts via two E-box elements. A SNP rs2419621 (T) created a de novo E-box that together with the two pre-existing proximal E-boxes strongly enhances ACSL5 expression in both CV1 and C2C12 cells. In the third chapter, I identified a novel VGLL4-interacting protein IRF2BP2 and verified the interaction with co-immunoprecipitation and mammalian two-hybrid assays. Functionally, overexpression of IRF2BP2 and transcription factor TEAD1 activates mouse VEGF-A promoter in CV1 cells and enhances the biosynthesis of VEGF-A in C2C12 myoblasts. In vivo studies showed that ischemia induced the expression of IRF2BP2 by more than three fold, suggesting that IRF2BP2 could play a pivotal role during tissue ischemia. IRF2BP2 is a nuclear protein in both mouse cardiac myocytes and C2C12 myoblasts as demonstrated by immunohistochemistry and immunocytochemistry, respectively. Therefore, I sought to delineate the mechanism for the nuclear shuttling of IRF2BP2 in the fourth chapter. With various DNA alternations, I mapped the NLS to an evolutionarily conserved sequence 354ARKRKPSP361 in IRF2BP2. Deletion of the positively charged amino acids resulted in the abolishment of the NLS signal. Next, I showed that phosphorylation of serine 360 (S360) mediates the nuclear import of the protein. Whereas an alanine substitution (S360A) at the site resulted in perinuclear accumulation of the protein, an aspartic acid substitution (S360D) forced the nuclear accumulation. Nevertheless, the forced accumulation of the S360D mutant did not enhance the activation of VEGF-A promoter in CV1 cells as did the wild-type protein. My studies revealed two novel mechanisms by which skeletal muscle could harvest energy, thus providing new insight into the energy metabolism in skeletal muscle

Background: Patients with heart failure (HF) are characterized by exercise intolerance, breathlessness, fatigue and excessive neurohormonal activation associated with premature mortality. Recently, inflammatory activation has been described as an important factor in the progression of HF. Increased levels of certain pro-inflammatory cytokines (e.g., TNF-ɑ, IL-6) have been related to increased severity of left ventricular dysfunction, the activation of the sympathetic and renin-angiotensin systems and the catabolism of skeletal muscle. Although exercise training is important in the management of HF, acute bouts of exercise may lead to increases in proinflammatory cytokines. It is believed that the skeletal muscle abnormalities associated with HF may increase the risk of damage to skeletal muscle, (i.e., exercise-induced muscle injury (EIMI) with associated inflammatory activation) especially following unaccustomed exercise training. Recently, several training methods have been proposed for patients with HF that challenge the traditional “steady-state” (SS) training model, including interval training (IT). Interval training methods employ greater muscular loading than SS and therefore may increase the risk of inflammatory system activation EIMI, and/or reduced muscle function. There is no study that has examined the effects of IT on EIMI, muscle function and/or inflammatory markers. Material and Methods: Fourteen male participants with HF (mean age: 59 +/- 7.8 yrs; mean VO2 peak: 13.64 +/- 4.5 ml/kg/m-1; EF < 45%) were matched (for body mass and aerobic fitness) and randomized into SS or IT for 20 minutes. The IT involved 2 minute work:recovery phases of 90% and 40% of heart rate reserve, respectively. The SS involved continuous exercise at 65% of heart rate reserve. Biochemical markers of muscle damage and acute inflammation, concentric and eccentric isokinetic muscle torque, and subjective indicators of delayed onset muscle soreness (DOMS) and lower extremity function were evaluated at baseline, and then immediately following the training bout, and at 6, 24, and 48 hours post. Results: There were no significant differences between the IT and the SS training group for markers of skeletal muscle injury or inflammatory activation. Conclusions: The findings from the present study suggest that IT or SS do not result in excessive inflammatory system activation or skeletal muscle injury. These results have important implications for clinicians prescribing exercise regimes for HF patients who may be starting back into activity after a prolonged sedentary period. Additionally, results from this study indicate that there is a need for future research looking at the actual and perceived effect of even a single about of exercise on lower extremity function.

Nuclear hormone receptors (NRs) are ligand-dependent DNA binding proteins that translate nutritional and physiological signals into gene regulation. The significance of NRs in human health and disease is underscored by the availability of drugs that targets NRs for treating several diseases. In this context, a subgroup of NR family has been proposed to regulate metabolism in a cell/tissue specific manner. The Rev-erb subgroup of NRs consists of two isoforms Rev-erb and Rev-erb. These two receptors have been shown to regulate different aspects of human physiology such as metabolism, inflammation, and circadian rhythm. Many NRs are expressed in skeletal muscle, a major mass peripheral tissue that accounts for ~40% of the total body weight and energy expenditure. This lean tissue is a major site for lipid and glucose homeostasis. Skeletal muscle express and secrete cytokines which perform autocrine and paracrine function with other tissues such as adipose. Accordingly, skeletal muscle plays important role in blood lipid profile, insulin sensitivity and progression of diseases such as type 2 diabetes and obesity. In addition, many studies have shown that NRs in skeletal muscle regulate glucose, lipid and energy homeostasis. Therefore, understanding the function of NRs in skeletal muscle provides a platform for potential new therapeutic treatments for metabolic disease. Rev-erb is expressed in skeletal muscle; however the function of this receptor in skeletal muscle metabolism has not been examined. Nevertheless, considering the importance of Rev-erb subfamily in metabolism, circadian control and the role of skeletal muscle in lipid homeostasis, the function of Rev-erb in skeletal muscle metabolism needs to be further investigated. We tested the hypothesis that Rev-erb (directly and/or indirectly) regulated the genetic programs that control lipid homeostasis in skeletal muscle. Initially, we exogenously expressed a truncated version of Rev-erb without the ligand-binding domain (Rev-erb) in vitro (in the C2C12 skeletal muscle cell culture system); and in vivo (in mouse tibialis anterior muscle. Moreover, we also attenuated Rev-erb expression in skeletal muscle cells using siRNAs targeting N-terminus and hinge regions of Rev-erb. We performed candidate based expression profiling utilizing quantitative RT-PCR analysis on the Taqman Low Density Array (TLDA) platform to identify putative downstream primary and/or secondary targets of Rev-erb action in skeletal muscle cells in the context of metabolism and muscle growth. Exogenous expression of Rev-erb in skeletal muscle cells in vitro decreased the expression of several genes involved in fatty acid/lipid absorption (including Cd36, and Fabp3 and 4). Interestingly, the mRNA encoding the master lipogenic regulator, SREBP-1c was also increased after ectopic Rev-erb expression. Moreover, we observed significant induction in the mRNAs encoding interleukin-6 and IKB that are involved in the regulation of the inflammatory cascade. Finally, we also observed the marked repression of myostatin mRNA, an important protein implicated in negative regulation of muscle hypertrophy/hyperplasia and a positive regulator of body fat accumulation. In summary, our in vitro study suggested that Rev-erb regulates genes involved in metabolism, inflammation and muscle growth. Quantitative PCR analysis that utilised the Taqman Low Density Array (TLDA) platform revealed Rev-erb siRNA expression down-regulated (in a subtle but significant manner) several genes involved in lipid/glucose homeostasis and the TGF- signalling pathway. Interestingly, genes that are involved in the myostatin and TGF- signalling pathway such as Activin A receptor type 2a (ACVR2A), Smad specific E3 ubiquitin protein ligase 1 (Smurf1), and TGF- receptor 2 (TGFBR2) were identified potential (direct and/or indirect) target of Rev-erb action in skeletal muscle cells. Moreover, genes such as Citrate Synthase (CS), V-akt murine thymoma viral oncogene homolog 2 (Akt2), Peroxisome proliferator- activated receptor- coactivator (PGC)-1 (PGC1) were also significantly modulated by Rev-erb in these analyses. The expression of two mRNAs encoding a) SREBP1c and b) IKB increased by ectopic Rev-erb expression was examined in more detail. These were selected because Rev-erb has been presumed to function as a transcriptional silencer. Secondly, we had demonstrated that in vivo expression of Rev-erb (after injection and electroporation of mouse tibialis anterior muscle) increased SREBP-1c expression, and Rev-erb siRNA studies suggested that this orphan NR was necessary for optimal SREBP-1c mRNA expression. Consequently, we tested the hypothesis that Rev-erb encodes the potential to function as a transcriptional activator in skeletal muscle. To test this hypothesis, we examined whether the SREBP1c and IKB promoters were trans-activated by co-transfected Rev-erb in skeletal muscle cells. We initially tested whether Rev-erb regulates the SREBP1c promoter. Transfection experiments showed Rev-erb expression trans-activated this promoter. This observation was in contrast to previous promoter studies showing that Rev-erb is a potent repressor of gene transcription. Therefore, we subsequently performed an experiment in which we simultaneously used the Rev-erb promoter (previously characterized to be repressed by Rev-erb) and SREBP1c promoter to examine the effect of Rev-erb expression. This experiment showed that Rev-erb repressed the activity of Rev-erb promoter, and in parallel trans-activated the SREBP1c promoter. Bioinformatics analysis identified two regions covering putative Rev-erb response elements RERE1 (-1342 to -1158) and RERE2 (-525 to -401) in the SREBP1c promoter. Chromatin immuno-precipitation assays demonstrated that Rev-erb is selectively recruited to RERE2 between nucleotide positions –525 to –401 in the promoter. Unidirectional deletion analysis of the SREBP1c promoter coupled with the analysis of mutants in the LXR response elements (of the SREBP-1c promoter) confirmed that Rev-erb mediated trans-activation of SREBP1c promoter does not function through LXR response elements. Interestingly, treatment of skeletal muscle cells with Hemin, a molecule recently proposed to function as a ligand for Rev-erbs, increased SREBP1c mRNA expression. In summary these data show that Rev-erb is a novel positive regulator of SREBP1c mRNA expression in skeletal muscle. We subsequently cloned the previously characterised human IKB promoter region spanning the potential ROR and Rev-erb binding site. Transfection experiments showed that in accordance to previously published observation, ROR trans-activated the IKB promoter. However, both Rev-erb and Rev-erb when co-transfected with the IKB promoter had minimal effects on the activity of this promoter. Studies have shown that Rev-erb functions as a competitor for ROR and block ROR mediated trans-activation of its target gene expression. Interestingly, our co-transfection experiments showed that both Rev-erb and Rev-erb blocks ROR-mediated trans-activation of IKB promoter. Together, this data suggests that Rev-erb-mediated regulation of IKB transcription in skeletal muscle cells could occur through indirect mechanisms. In conclusion, our studies have shown Rev-erb directly and indirectly regulates the expression of genes involved in metabolism, inflammation and muscle growth suggesting that Rev-erb in skeletal muscle has the potential to be exploited in a therapeutic manner.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1960. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri--Columbia, 2004. / "December 2004." Typescript. Vita. Includes bibliographical references (leaves 180-210). Also issued on the Internet.