Contractions Activate Hormone-Sensitive Lipase in Rat Muscle by Protein Kinase C and Mitogen-Activated Protein Kinase

Intramuscular triacylglycerol is an important energy store and is also related to insulin resistance. The mobilization of fatty acids from this pool is probably regulated by hormone-sensitive lipase (HSL), which has recently been shown to exist in muscle and to be activated by both adrenaline and contractions. Adrenaline acts via cAMP-dependent protein kinase (PKA). The signalling mediating the effect of contractions is unknown and was explored in this study. Incubated soleus muscles from 70 g male rats were electrically stimulated to perform repeated tetanic contractions for 5 min. The contraction-induced activation of HSL was abolished by the protein kinase C (PKC) inhibitors bisindolylmaleimide I and calphostin C and reduced 50 % by the mitogen-activated protein kinase kinase (MEK) inhibitor U0126, which also completely blocked extracellular signal-regulated kinase (ERK) 1 and 2 phosphorylation. None of the inhibitors reduced adrenaline-induced HSL activation in soleus muscle. Both phorbol-12-myristate-13-acetate (PMA), which activates PKC and, in turn, ERK, and caffeine, which increases intracellular Ca²⁺ without eliciting contraction, increased HSL activity. Activated ERK increased HSL activity in supernatant from basal but not from electrically stimulated muscle. In conclusion, in muscle, PKC can stimulate HSL through ERK. Contractions and adrenaline enhance muscle HSL activity by different signalling mechanisms. The effect of contractions is mediated by PKC, at least partly via the ERK pathway.     

‘Someone to hold the hand over me’: the significance of transpersonal ‘attachment’ relationships of Danish cancer survivors

The aim of this article is to present findings about self‐reported spirituality of a group of Danish cancer survivors. The findings derive from a qualitative study that was carried out during rehabilitation week courses at a Danish rehabilitation centre. Methods comprised participant observation, semi‐structured interviews and focus group interviews. Employing interpretative phenomenological analysis as analytical strategy, a prominent part of the informants’ self‐reported spirituality was found to centre around a perceived sense of relatedness to a transpersonal entity that transcends the self and extends beyond spatial‐temporal boundaries. Three transpersonal entities were identified: ‘God’, a ‘guardian angel’ and a ‘deceased family member’. The key findings of the study demonstrate that the transpersonal entities were experienced as empowering and supportive resources during cancer treatment and rehabilitation and that they were furthermore perceived as responsible for the informants’ healing and survival. These findings are interpreted through the lenses of two interrelated theoretical frameworks: Hay and Nye's approach to spirituality as ‘relational consciousness’ and Kirkpatrick and colleagues’ understanding of religion and/or spirituality as attachment relationships. These two theoretical understandings are suggested as useful frameworks for capturing spiritual dimensions of cancer survivors’ meaning making and coping in a secular society.     

Meal-stimulated glucagon release is associated with postprandial blood glucose level and does not interfere with glycemic control in children and adolescents with new-onset type 1 diabetes

CONTEXT: The role of glucagon in hyperglycemia in type 1 diabetes is unresolved, and in vitro studies suggest that increasing blood glucose might stimulate glucagon secretion. OBJECTIVE: Our objective was to investigate the relationship between postprandial glucose and glucagon level during the first 12 months after diagnosis of childhood type 1 diabetes. DESIGN: We conducted a prospective, noninterventional, 12-month follow-up study conducted in 22 centers in 18 countries. PATIENTS: Patients included 257 children and adolescents less than 16 yr old with newly diagnosed type 1 diabetes; 204 completed the 12-month follow-up. SETTING: The study was conducted at pediatric outpatient clinics. MAIN OUTCOME MEASURES: We assessed residual beta-cell function (C-peptide), glycosylated hemoglobin (HbA(1c)), blood glucose, glucagon, and glucagon-like peptide-1 (GLP-1) release in response to a 90-min meal stimulation (Boost) at 1, 6, and 12 months after diagnosis. RESULTS: Compound symmetric repeated-measurements models including all three visits showed that postprandial glucagon increased by 17% during follow-up (P = 0.001). Glucagon levels were highly associated with postprandial blood glucose levels because a 10 mmol/liter increase in blood glucose corresponded to a 20% increase in glucagon release (P = 0.0003). Glucagon levels were also associated with GLP-1 release because a 10% increase in GLP-1 corresponded to a 2% increase in glucagon release (P = 0.0003). Glucagon levels were not associated (coefficient -0.21, P = 0.07) with HbA(1c), adjusted for insulin dose. Immunohistochemical staining confirmed the presence of Kir6.2/SUR1 in human alpha-cells. CONCLUSION: Our study supports the recent in vitro data showing a stimulation of glucagon secretion by high glucose levels. Postprandial glucagon levels were not associated with HbA(1c), adjusted for insulin dose, during the first year after onset of childhood type 1 diabetes.     

Muscle ceramide content in man is higher in type I than type II fibers and not influenced by glycogen content

The purpose was to determine the relation between visual feedback gain and variability in force and whether visual gain-induced changes in force variability were associated with frequency-specific force oscillations and changes in the neural activation of the agonist muscle. Fourteen young adults (19–29 years) were instructed to accurately match the target force at 2 and 10% of their maximal voluntary contraction with abduction of the index finger. Force was maintained at specific visual feedback gain levels that varied across trials. Each trial lasted 20 s and the amount of visual feedback was varied by changing the visual gain from 0.5 to 1,474 pixels/N (13 levels; equals ~0.001–4.57°). Force variability was quantified as the standard deviation of the detrended force data. The neural activation of the first dorsal interosseus (FDI) was measured with surface electromyography. The mean force did not vary significantly with the amount of visual feedback. In contrast, force variability decreased from low gains compared to moderate gains (0.5–4 pixels/N: 0.09 ± 0.04 vs. 64–1,424 pixels/N: 0.06 ± 0.02 N). The decrease in variability was predicted by a decrease in the power of force oscillations from 0–1 Hz (~50%) and 3–7 Hz (~20%). The activity of the FDI muscle did not vary across the visual feedback gains. These findings demonstrate that in young adults force variability can be decreased with increased visual feedback gain (>64 pixels/N vs. 0.5–4 pixels/N) due to a decrease in the power of oscillations in the force from 0–1 and 3–7 Hz.     

Regulation and role of hormone-sensitive lipase in rat skeletal muscle

Intramyocellular triacylglycerol (TG) is an important energy store, and the energy content of this depot is higher than the energy content of the muscle glycogen depot. It has recently been shown that the mobilization of fatty acids from this TG pool may be regulated by the neutral lipase hormone-sensitive lipase (HSL). This enzyme is known to be rate limiting for intracellular TG hydrolysis in adipose tissue. The presence of HSL has been demonstrated in all muscle fibre types by Western blotting of muscle fibres isolated by collagenase treatment or after freeze-drying. The content of HSL varies between fibre types, being higher in oxidative fibres than in glycolytic fibres. When analysed under conditions optimal for HSL, neutral lipase activity in muscle can be stimulated by adrenaline as well as by contractions. These increases are abolished by the presence of anti-HSL antibody during analysis. Moreover, immunoprecipitation with affinity-purified anti-HSL antibody causes similar reductions in muscle HSL protein concentration and in measured neutral lipase responses to contractions. The immunoreactive HSL in muscle is stimulated by adrenaline via beta-adrenergic activation of cAMP-dependent protein kinase (PKA). From findings in adipocytes it is likely that PKA phosphorylates HSL at residues Ser(563), Ser(659) and Ser(660). Contraction probably also enhances muscle HSL activity by phosphorylation, because the contraction-induced increase in HSL activity is elevated by the protein phosphatase inhibitor okadaic acid and reversed by alkaline phosphatase. A novel signalling pathway in muscle by which HSL activity may be stimulated by protein kinase C (PKC) via extracellular signal-regulated kinase (ERK) has been demonstrated. In contrast to previous findings in adipocytes, in muscle the activation of ERK is not necessary for stimulation of HSL by adrenaline. However, contraction-induced HSL activation is mediated by PKC, at least partly via the ERK pathway. In fat cells ERK is known to phosphorylate HSL at Ser(600). Hence, phosphorylation of different sites may explain the finding that in muscle the effects of contractions and adrenaline on HSL activity are partially additive. In line with the view that the two stimuli act by different mechanisms, training increases contraction-mediated HSL activation but diminishes adrenaline-mediated HSL activation in muscle. In conclusion, HSL is present in skeletal muscle and can be activated by phosphorylation in response to both adrenaline and muscle contractions. Training increases contraction-mediated HSL activation, but decreases adrenaline-mediated HSL activation in muscle.     

The urokinase receptor as a potential target in cancer therapy

The glycolipid-anchored receptor for urokinase-type plasminogen activator (uPAR) is essential for cell-surface associated plasminogen activation and is overexpressed at the invasive tumor-stromal microenvironment in many human cancers. In line with this, uPAR and uPA levels in both resected tumor tissue and plasma are of independent prognostic significance for patient survival in several types of human cancer. As the expression of both uPAR and its cognate protease ligand thus appears to be correlated with tumor malignancy, the uPA-uPAR interaction represents an attractive target for the development of either antagonists with possible anti-invasive effects or cytotoxic agents with anti-tumor effects. In this review we discuss recent achievements in the development of protein and peptide based drug candidates targeting uPAR. The majority of these compounds has been optimized for human uPAR and exhibits a pronounced species-specificity showing little or no reactivity with murine uPAR. This evidently complicates their application in preclinical intervention studies, since an intimate interplay between the tumor and its associated stroma is a distinct feature of the invasive phenotype of many human cancers. The virtues and drawbacks of various mouse tumor models as surrogates for human cancer are also discussed in relation to uPAR targeting.     

Alcoholic beverage preference and risk of becoming a heavy drinker

BACKGROUND: Studies have suggested that wine drinkers are at lower risk of death than beer or spirits drinkers. The aim of this study is to examine whether the risk of becoming a heavy or excessive drinker differs among individuals who prefer different types of alcoholic beverages. METHODS: In a longitudinal study of 10,330 moderate drinkers from Copenhagen, Denmark, we used logistic regression analyses to address the risk of becoming a heavy or excessive drinker (above 14 and 21 drinks per week, respectively, for women and above 21 and 35 drinks per week for men) according to preference of wine, beer, or spirits. RESULTS: Compared with those who preferred wine, those who preferred beer tended to have increased risk of becoming heavy and excessive drinkers. Women who preferred beer had odds ratios of 1.14 (95% CI = 0.87-1.50) for becoming heavy drinkers and 1.50 (95% CI = 0.93-2.43) for becoming excessive drinkers. For men who preferred beer the ORs were 1.16 (95% CI = 0.84-1.58) and 1.81 (95% CI = 0.85-3.82). CONCLUSION: The finding that moderate wine drinkers appear to be at lower risk of becoming heavy and excessive drinkers may add to the explanation of the reported beverage-specific differences in morbidity and mortality.     

Dissociation of AMP-activated protein kinase activation and glucose transport in contracting slow-twitch muscle

5'AMP-activated protein kinase (AMPK) has been suggested to be a key regulatory protein in exercise signaling of muscle glucose transport. To test this hypothesis, we investigated whether muscle glycogen levels affect AMPK activation and glucose transport stimulation similarly during contractions. Rats were preconditioned by a combination of swimming exercise and diet to obtain a glycogen-supercompensated group (high muscle glycogen content [HG]) with approximately 3-fold higher muscle glycogen levels than a glycogen-depleted group (low muscle glycogen content [LG]). In perfused fast-twitch muscles, contractions induced significant increases in AMPK activity and glucose transport and decreases in acetyl-CoA carboxylase (ACC) activity in both HG and LG groups. Contraction-induced glucose transport was nearly 2-fold (P < 0.05) and AMPK activation was 3-fold (P < 0.05) higher in the LG group compared with the HG group, whereas ACC deactivation was not different between groups. Thus, there was a significant positive correlation between AMPK activity and glucose transport in contracting fast-twitch muscles (r = 0.80, P < 0.01). However, in slow-twitch muscles with HG, glucose transport was increased 6-fold (P < 0.05) during contractions, whereas AMPK activity did not increase. In contracting slow-twitch muscles with LG, the increase in AMPK activity (315%) and the decrease in ACC activity (54 vs. 34% at 0.2 mmol/l citrate, LG vs. HG) was higher (P < 0.05) compared with HG muscles, whereas the increase in glucose transport was identical in HG and LG. In conclusion, in slow-twitch muscles, high glycogen levels inhibit contraction-induced AMPK activation without affecting glucose transport. This observation suggests that AMPK activation is not an essential signaling step in glucose transport stimulation in skeletal muscle.     

Hormone‐sensitive lipase in skeletal muscle: regulatory mechanisms

Aim: The enzymatic regulation of intramuscular triacylglycerol (TG) breakdown has until recently not been well understood. Our aim was to elucidate the role of hormone‐sensitive lipase (HSL), which controls TG breakdown in adipose tissue. Methods: Isolated rat muscle as well as exercising humans were studied. Results: The presence of HSL was demonstrated in all muscle fibre types by Western blotting of muscle fibres isolated by collagenase treatment or after freeze‐drying. The content of HSL varies between fibre types, being higher in oxidative than in glycolytic fibres. Analysed under conditions optimal for HSL, neutral lipase activity in muscle can be stimulated by adrenaline as well as by contractions. These increases are abolished by presence of anti‐HSL antibody during analysis. Moreover, immunoprecipitation with affinity‐purified anti‐HSL antibody causes similar reductions in muscle HSL protein concentration and in measured neutral lipase responses to contractions. The immunoreactive HSL in muscle is stimulated by adrenaline via beta‐adrenergic activation of protein kinase A (PKA). From findings in adipocytes it is likely that PKA phosphorylates HSL at residues Ser⁵⁶³, Ser⁶⁵⁹ and Ser⁶⁶⁰. Contraction probably also enhances muscle‐HSL activity by phosphorylation, because the contraction‐induced increase in HSL activity is increased by the protein phosphatase inhibitor okadaic acid and reversed by alkaline phosphatase. A novel signalling pathway in muscle by which HSL activity may be stimulated by protein kinase C (PKC) via extracellular signal regulated kinase (ERK) has been demonstrated. In contrast to previous findings in adipocytes, in muscle activation of ERK is not necessary for stimulation of HSL by adrenaline. However, contraction‐induced HSL activation is mediated by PKC, at least partly via the ERK pathway. In fat cells ERK is known to phosphorylate HSL at Ser⁶⁰⁰. So, phosphorylation of different sites may explain that in muscle the effects of contractions and adrenaline on HSL activity are partially additive. In line with the view that the two stimuli act by different mechanisms, training increases the contraction‐mediated, but diminishes the adrenaline mediated HSL activation in muscle. Conclusion: The existence and regulation of HSL in skeletal muscle indicate a role of HSL in muscle TG metabolism.