AMP-activated protein kinase (AMPK) ␤ subunits (␤1 and ␤2) provide scaffolds for binding ␣ and ␥ subunits and contain a carbohydrate-binding module important for regulating enzyme activity. We generated C57Bl/6 mice with germline deletion of AMPK ␤2 (␤2 KO) and examined AMPK expression and activity, exercise capacity, metabolic control during muscle contractions, aminoimidazole carboxamide ribonucleotide (AICAR) sensitivity, and susceptibility to obesity-induced insulin resistance. We find that ␤2 KO mice are viable and breed normally. ␤2 KO mice had a reduction in skeletal muscle AMPK ␣1 and ␣2 expression despite up-regulation of the ␤1 isoform. Heart AMPK ␣2 expression was also reduced but this did not affect resting AMPK ␣1 or ␣2 activities. AMPK ␣1 and ␣2 activities were not changed in liver, fat, or hypothalamus. AICAR-stimulated glucose uptake but not fatty acid oxidation was impaired in ␤2 KO mice. During treadmill running ␤2 KO mice had reduced maximal and endurance exercise capacity, which was associated with lower muscle and heart AMPK activity and reduced levels of muscle and liver glycogen. Reductions in exercise capacity of ␤2 KO mice were not due to lower muscle mitochondrial content or defects in contraction-stimulated glucose uptake or fatty acid oxidation. When challenged with a high-fat diet ␤2 KO mice gained more weight and were more susceptible to the development of hyperinsulinemia and glucose intolerance. In summary these data show that deletion of AMPK ␤2 reduces AMPK activity in skeletal muscle resulting in impaired exercise capacity and the worsening of diet-induced obesity and glucose intolerance.The AMP-activated protein kinase (AMPK) 5 is an evolutionary conserved serine/threonine protein kinase that functions as a metabolic regulatory enzyme at both the intracellular and whole body level (1, 2). As a metabolic stress-sensing enzyme, AMPK is activated through phosphorylation of Thr 172 in the ␣-catalytic subunit by upstream kinases, liver kinase B1 (LKB1) and calcium/calmodulin-dependent kinase kinase in response to physiological processes that consume ATP (exercise) or inhibit ATP production (ischemia or hypoxia) (3). Following activation, AMPK acutely regulates lipid, protein, and carbohydrate metabolism through phosphorylation induced changes that alter enzyme activities by switching off ATP consuming anabolic pathways and switching on ATP generating catabolic pathways (4). In addition to these acute effects, AMPK regulates transcription factors to influence gene expression (4). Modulation of AMPK activity by hormones and cytokines adds a complex layer of regulation allowing energy supply and demand within a cell to be integrated with the energy requirements of the whole organism (5).AMPK functions as an ␣␤␥ heterotrimer where the C terminus of the ␤ isoforms (␤1 and ␤2) contains the subunit-binding sequence that is essential for binding the ␥ and ␣ subunits (6, 7). In addition to their structural role in maintaining the AMPK heterotrimer, AMPK ␤ subunits contain an evolutionary ...

. Progressive increase in human skeletal muscle AMPK␣2 activity and ACC phosphorylation during exercise. Am J Physiol Endocrinol Metab 282: E688-E694, 2002; 10.1152/ajpendo.00101.2001.-The effect of prolonged moderate-intensity exercise on human skeletal muscle AMP-activated protein kinase (AMPK)␣1 and -␣2 activity and acetyl-CoA carboxylase (ACC␤) and neuronal nitric oxide synthase (nNOS) phosphorylation was investigated. Seven active healthy individuals cycled for 30 min at a workload requiring 62.8 Ϯ 1.3% of peak O2 consumption (V O2 peak) with muscle biopsies obtained from the vastus lateralis at rest and at 5 and 30 min of exercise. AMPK␣1 activity was not altered by exercise; however, AMPK␣2 activity was significantly (P Ͻ 0.05) elevated after 5 min (ϳ2-fold), and further elevated (P Ͻ 0.05) after 30 min (ϳ3-fold) of exercise. ACC␤ phosphorylation was increased (P Ͻ 0.05) after 5 min (ϳ18-fold compared with rest) and increased (P Ͻ 0.05) further after 30 min of exercise (ϳ36-fold compared with rest). Increases in AMPK␣2 activity were significantly correlated with both increases in ACC␤ phosphorylation and reductions in muscle glycogen content. Fat oxidation tended (P ϭ 0.058) to increase progressively during exercise. Muscle creatine phosphate was lower (P Ͻ 0.05), and muscle creatine, calculated free AMP, and free AMP-to-ATP ratio were higher (P Ͻ 0.05) at both 5 and 30 min of exercise compared with those at rest. At 30 min of exercise, the values of these metabolites were not significantly different from those at 5 min of exercise. Phosphorylation of nNOS was variable, and despite the mean doubling with exercise, statistically significance was not achieved (P ϭ 0.304). Western blots indicated that AMPK␣2 was associated with both nNOS and ACC␤ consistent with them both being substrates of AMPK␣2 in vivo. In conclusion, AMPK␣2 activity and ACC␤ phosphorylation increase progressively during moderate exercise at ϳ60% of V O2 peak in humans, with these responses more closely coupled to muscle glycogen content than muscle AMP/ ATP ratio. adenosine monophosphate-activated protein kinase; acetylcoenzyme A carboxylase-␤; neuronal nitric oxide synthase; prolonged exercise; humans AMP-ACTIVATED PROTEIN KINASE (AMPK) plays an important role in coordinating metabolism with a number of physiological processes (16,22). In rat skeletal muscle, activation of AMPK appears to lead to enhanced fat oxidation and glucose uptake (3,19,25). In transgenic mice expressing a dominant negative mutant of AMPK, there is impaired glucose uptake in response to both contraction and hypoxia (26). There are two isoforms of AMPK, AMPK␣1 and -␣2, expressed in skeletal muscle. Maximal sprint exercise [ϳ200% peak O 2 consumption (V O 2 peak )] over 30 s in humans causes a large increase in the calculated free AMP and free AMP-to-ATP ratio (AMP/ATP) (28) and activates both AMPK␣1 and -␣2 (6). AMPK␣1 is not activated during lower intensity exercise such as at 50 or 70% V O 2 peak , or after 5 min of exercise at 90% V O 2 peak after 55 min of cy...

On the basis of our meta-analysis, neutrophil CD64 expression could be a promising and meaningful biomarker for diagnosing bacterial infection. Nevertheless, more large prospective studies should be carried out before the neutrophil CD64 test is used widely in the clinical setting because of the various cut-off values.

Background-Statins exert antiinflammatory and antiproliferative actions independent of cholesterol lowering. To determine whether these actions might affect neointimal formation, we investigated the effect of simvastatin on the response to experimental angioplasty in LDL receptor-deficient (LDLR Ϫ/Ϫ ) mice, a model of hypercholesterolemia in which changes in plasma lipids are not observed in response to simvastatin. Methods and Results-Carotid artery dilation (2.5 atm) and complete endothelial denudation were performed in male C57BL/6J LDLR Ϫ/Ϫ mice treated with low-dose (2 mg/kg) or high-dose (20 mg/kg) simvastatin or vehicle subcutaneously 72 hours before and then daily after injury. After 7 and 28 days, intimal and medial sizes were measured and the intima to media area ratio (I:M) was calculated. Total plasma cholesterol and triglyceride levels were similar in simvastatin-and vehicle-treated mice. Intimal thickening and I:M were reduced significantly by low-and high-dose simvastatin compared with vehicle alone. Simvastatin treatment was associated with reduced cellular proliferation (BrdU), leukocyte accumulation (CD45), and platelet-derived growth factor-induced phosphorylation of the survival factor Akt and increased apoptosis after injury. Conclusions-Simvastatin

The age-related effects of GDF11 have been a subject of controversy. Here, we find that elevated GDF11 causes signs of cachexia in mice: reduced food intake, body weight, and muscle mass. GDF11 also elicited a significant elevation in plasma Activin A, previously shown to contribute to the loss of skeletal muscle. The effects of GDF11 on skeletal muscle could be reversed by administration of antibodies to the Activin type II receptors. In addition to the effects on muscle, GDF11 increased plasma GDF15, an anorectic agent. The anorexia, but not the muscle loss, could be reversed with a GDF15-neutralizing antibody. GDF15 upregulation is due to GDF11-induced recruitment of SMAD2/3 to the GDF15 promoter. Inhibition of GDF15 can restore appetite but cannot restore the GDF11-induced loss of muscle mass, which requires blockade of ActRII signaling. These findings are relevant for treatment of cachexia.

In Zhejiang Province, SFTS is prevalent between May and August among elderly persons who live in hilly areas, and clinical features are not specific. More emphasis should be given to this disease and further training of medical personnel should be carried out to prevent misdiagnosis.

(RSG) is an insulin-sensitizing thiazolidinedione (TZD) that exerts peroxisome proliferator-activated receptor-␥ (PPAR␥)-dependent and -independent effects. We tested the hypothesis that part of the insulinsensitizing effect of RSG is mediated through the action of AMPactivated protein kinase (AMPK). First, we determined the effect of acute (30 -60 min) incubation of L6 myotubes with RSG on AMPK regulation and palmitate oxidation. Compared with control (DMSO), 200 M RSG increased (P Ͻ 0.05) AMPK␣1 activity and phosphorylation of AMPK (Thr 172 ). In addition, acetyl-CoA carboxylase (Ser 218 ) phosphorylation and palmitate oxidation were increased (P Ͻ 0.05) in these cells. To investigate the effects of chronic RSG treatment on AMPK regulation in skeletal muscle in vivo, obese Zucker rats were randomly allocated into two experimental groups: control and RSG. Lean Zucker rats were treated with vehicle and acted as a control group for obese Zucker rats. Rats were dosed daily for 6 wk with either vehicle (0.5% carboxymethylcellulose, 100 l/100 g body mass), or 3 mg/kg RSG. AMPK␣1 activity was similar in muscle from lean and obese animals and was unaffected by RSG treatment. AMPK␣2 activity was ϳ25% lower in obese vs. lean animals (P Ͻ 0.05) but was normalized to control values after RSG treatment. ACC phosphorylation was decreased with obesity (P Ͻ 0.05) but restored to the level of lean controls with RSG treatment. Our data demonstrate that RSG restores AMPK signaling in skeletal muscle of insulin-resistant obese Zucker rats.lipids; peroxisome proliferator-activated receptor-␥; thiazolidinedione; Zucker rats; adenosine monophosphate-activated protein kinase-␣2 SKELETAL MUSCLE INSULIN RESISTANCE is a common state associated with inactivity, aging, genetic predisposition, and environmental factors and is a hallmark feature of a variety of disease states, including obesity, hyperlipidemia, hypertension, and type 2 diabetes (31). Rosiglitazone (RSG) is a member of the thiazolidinedione (TZD) class of oral antidiabetic agents that improve insulin sensitivity in a range of insulin-resistant states (15,18). TZDs are peroxisome proliferator-activated receptor-␥ (PPAR␥) agonists that, upon activation by fatty acids (FA) or FA-derived compounds, bind to responsive elements located in the promoter regions of many genes and modulate their transcriptive activities (1, 32). Although PPAR␥ plays a role in the TZD-induced insulin sensitization, metabolic responses to TZDs can be dissociated from PPAR␥-induced gene transcription (4,14,29). Furthermore, we (23) have recently reported that RSG improves glucose tolerance by mechanisms other than a reduction of FA accumulation within skeletal muscle. Hence, it is likely that there exists PPAR␥-independent mechanisms by which TZDs improve insulin sensitivity.The AMP-activated protein kinase (AMPK) is a cellular energy sensor that regulates glucose and lipid metabolism by phosphorylating key regulatory enzymes (21, 39). AMPK activation causes many metabolic changes that would be benef...

. Skeletal muscle basal AMP-activated protein kinase activity is chronically elevated in alloxan-diabetic dogs: impact of exercise. J Appl Physiol 95: 1523-1530. First published June 27, 2003 10.1152/japplphysiol.00199.2003.-The effect of diabetes and exercise on skeletal muscle (SkM) AMP-activated protein kinase (AMPK)␣1 and -␣2 activities and site-specific phosphorylation of acetyl-CoA carboxylase was examined in the same six dogs before alloxan (35 mg/kg)-induced diabetes (C) and after 4-5 wk of suboptimally controlled hyperglycemic and hypoinsulinemic diabetes (DHG) in the presence and absence of 300-min phlorizin (50 g ⅐ kg Ϫ1 ⅐ min Ϫ1 )-induced "normoglycemia" (DNG). In each study, the dog underwent a 150-min [3-3 H]glucose infusion period, followed by a 30-min treadmill exercise test (60-70% maximal oxygen capacity) to measure the rate of glucose disposal into peripheral tissues (Rd tissue). SkM biopsies were taken from the thigh (vastus lateralis) before and immediately after exercise. In the C and DHG states, the rise in plasma free fatty acids (FFA) with exercise (ϳ40%) was similar. In the DNG group, preexercise FFA were significantly higher, but the absolute rise in FFA with exercise was similar. However, the exercise-induced increment in Rd tissue was significantly blunted (by ϳ40-50%) in the DNG group compared with the other states. In SkM, preexercise AMPK␣1 and -␣2 activities were significantly elevated (by ϳ60-125%) in both diabetic states, but unlike the C group these activities did not rise further with exercise. Additionally, preexercise acetyl-CoA carboxylase phosphorylation in both diabetic states was elevated by ϳ70-80%, but the increases with exercise were similar to the C group. Preexercise AMPK␣1 and -␣2 activities were negatively correlated with Rd tissue during exercise for the combined groups (both P Ͻ 0.02). In conclusion, the elevated preexercise SkM AMPK␣1 and -␣2 activities contribute to the ongoing basal supply of glucose and fatty acid metabolism in suboptimally controlled hypoinsulinemic diabetic dogs; but whether they also play a permissive role in the metabolic stress response to exercise remains uncertain. hyperglycemia; hypoinsulinemia; acetyl coenzyme A carboxylase; glucose and fatty acid metabolism; phlorizin-induced normoglycemia THE REGULATION OF GLUCOSE and fatty acid (FA) metabolism in skeletal muscle (SkM) during exercise is currently the focus of intense investigation (21, 41). Transmembrane GLUT-4-mediated glucose transport is a major rate-determining site for exercise and insulinstimulated SkM glucose uptake (48), although several other factors, including enhanced capillary recruitment (19) and intracellular enzyme activities (such as pyruvate dehydrogenase) (31), also contribute to the increased glucose uptake and processing observed in exercising SkM. In addition, as the energy demanded by the exercising muscle rises, FA uptake and oxidation are also increased (34, 37). Thus heavily exercising SkM is potentially at risk of outstripping its rising energy needs a...