Exercise Alleviates Lipid-Induced Insulin Resistance in Human Skeletal Muscle–Signaling Interaction at the Level of TBC1 Domain Family Member 4

Excess lipid availability causes insulin resistance. We examined the effect of acute exercise on lipid-induced insulin resistance and TBC1 domain family member 1/4 (TBCD1/4)-related signaling in skeletal muscle. In eight healthy young male subjects, 1 h of one-legged knee-extensor exercise was followed by 7 h of saline or intralipid infusion. During the last 2 h, a hyperinsulinemic-euglycemic clamp was performed. Femoral catheterization and analysis of biopsy specimens enabled measurements of leg substrate balance and muscle signaling. Each subject underwent two experimental trials, differing only by saline or intralipid infusion. Glucose infusion rate and leg glucose uptake was decreased by intralipid. Insulin-stimulated glucose uptake was higher in the prior exercised leg in the saline and the lipid trials. In the lipid trial, prior exercise normalized insulin-stimulated glucose uptake to the level observed in the resting control leg in the saline trial. Insulin increased phosphorylation of TBC1D1/4. Whereas prior exercise enhanced TBC1D4 phosphorylation on all investigated sites compared with the rested leg, intralipid impaired TBC1D4 S341 phosphorylation compared with the control trial. Intralipid enhanced pyruvate dehydrogenase (PDH) phosphorylation and lactate release. Prior exercise led to higher PDH phosphorylation and activation of glycogen synthase compared with resting control. In conclusion, lipid-induced insulin resistance in skeletal muscle was associated with impaired TBC1D4 S341 and elevated PDH phosphorylation. The prophylactic effect of exercise on lipid-induced insulin resistance may involve augmented TBC1D4 signaling and glycogen synthase activation.Studies in human and rodent models have revealed deleterious effects of excess lipid availability on peripheral insulin sensitivity (1,2). Intracellular increases in fatty acid metabolites, such as diacylglycerol (DAG) and ceramide, may play critical roles in mediating lipid-induced insulin resistance by inducing serine phosphorylation of insulin-receptor substrate 1 (IRS-1) (3–6) and consequently inhibiting downstream signaling to GLUT4 translocation. However, recent reports challenge such causality. These studies revealed unaltered signal transduction at the level of IRS-1, IRS-1–associated phosphatidylinositol-3-kinase (PI3K) activity, Akt, and TBC1 domain family member 4 (TBC1D4) phosphorylation (phospho-Akt-substrate [PAS] an unspecific antibody recognizing phosphorylated Akt substrate motifs), after 2–7 h of lipid infusion (7–11). When DAG and/or ceramide levels were reported, no changes in skeletal muscle DAG or ceramide levels were found after lipid infusion (7,11).We recently showed that lactate release in human skeletal muscle is augmented along with reduced respiratory exchange ratio (RER) values during lipid infusion (11). This could indicate suppressed activity of the pyruvate dehydrogenase (PDH) complex, which in turn could lead to a reduction in glucose uptake according to the Randle cycle (12). Here, we wished to investigate whether this increase in leg lactate release and reduced RER values were accompanied by altered regulation of PDH, measured by site-specific phosphorylation.Exercise increases peripheral insulin sensitivity (13–15). After an acute bout of exercise, the ability for insulin to stimulate glucose uptake in skeletal muscle is increased several hours into recovery (14,16). This effect can be ascribed to adaptations in the exercised muscle rather than changes in systemic factors (13,17,18) and is observed in both healthy and insulin-resistant states (e.g., obesity) (19) and type 2 diabetes (20). A recent study has shown that a single bout of exercise can prevent subsequent lipid-induced impairments in whole-body glucose tolerance assessed by an intravenous glucose tolerance test (IVGTT) (2). It was hypothesized that repartitioning fatty acids toward intramuscular triacylglycerol (IMTG) synthesis and storage rather than DAG or ceramide might be a primary mediator of the beneficial effects of exercise on lipid-induced impairments in glucose tolerance (2). Enhanced insulin sensitivity after a bout of exercise is associated with increased GLUT4 recruitment to the plasma membrane (21) and not with altered protein synthesis (e.g., GLUT4 protein) (22), but has not been associated with altered signal transduction through the insulin receptor, IRS-1, PI3K, or Akt (13,22,23). Recently, the hypothesis was put forward (24) that the guanosine triphosphatase (GTPase) activating proteins TBC1 domain family member 1 (TBC1D1) and 4 (TBC1D4) might serve as points of convergence for insulin dependent and independent signaling pathways to GLUT4 translocation. In agreement with this hypothesis, PAS phosphorylation of TBC1D4 is elevated along with insulin-stimulated glucose uptake for up to 27 h after exercise in skeletal muscle of rats (25), and we recently showed that phosphorylation of TBC1D4 on specific residues was elevated 4 h after a single bout of exercise in human skeletal muscle (26).TBC1D4/D1 are multikinase substrates proposed to be involved in contraction- and insulin-stimulated glucose uptake in mice (27,28), and exercise and insulin both substantially increase TBC1D4/D1 phosphorylation in human skeletal muscle (29,30). TBC1D4/D1 contain several phosphorylation sites distinctly phosphorylated by various kinases, including Akt and 5′AMP-activated protein kinase (AMPK) (28,31–33). Phosphorylation of TBC1D4/D1 and subsequent 14-3-3 binding is proposed to lead to inactivation of the GTPase-activating proteins, decreasing their inhibitory function on the GLUT4 translocation process and thus, potentially, increasing the GLUT4 capacity of the surface membrane.In the current study we tested the hypothesis that prior exercise prevents subsequent lipid-induced insulin resistance in human skeletal muscle through regulation of the signaling molecules TBC1D4/TBC1D1.     

Glycaemic control for patients with severe acute brain injury: Protocol for a systematic review

Background

Hyperglycaemia is common in patients with acute brain injury admitted to an intensive care unit (ICU). Many studies have found associations between development of hyperglycaemia and increased mortality in hospitalised patients. However, the optimal target for blood glucose control is unknown. We want to conduct a systematic review with meta-analysis and trial sequential analysis to explore the beneficial and harmful effects of restrictive versus liberal glucose control on patient outcomes in adults with severe acute brain injury.

Methods

We will systematically search medical databases including CENTRAL, Embase, MEDLINE and trial registries. We will search the following websites for ongoing or unpublished trials: http://www.controlled-trials.com/ , http://www.clinicaltrials.gov/ , www.eudraCT.com , http://centerwatch.com/ , The Cochrane Library's CENTRAL, PubMed, EMBASE, Science Citation Index Expanded and CINAHL. Two authors will independently review and select trials and extract data. We will include randomised trials comparing levels of glucose control in our analyses and observational studies will be included to address potential harms. The primary outcomes are defined as all-cause mortality, functional outcome and health-related quality of life. Secondary outcomes include serious adverse events including hypoglycaemia, length of ICU stay and duration of mechanical ventilation, and explorative outcomes including intracranial pressure and infection. Trial Sequential Analysis will be used to investigate the risk of type I error due to repetitive testing and to further explore imprecision. Quality of trials will be evaluated using the Cochrane Risk of Bias tool, and quality of evidence will be assessed using the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach.

Discussion

The results of the systematic review will be disseminated through peer-reviewed publication. With the review, we hope to inform future randomised clinical trials and improve clinical practice.     

Post-cardiac arrest intensive care in Sweden: A survey of current clinical practice

Background

European guidelines recommend targeted temperature management (TTM) in post-cardiac arrest care. A large multicentre clinical trial, however, showed no difference in mortality and neurological outcome when comparing hypothermia to normothermia with early treatment of fever. The study results were valid given a strict protocol for the assessment of prognosis using defined neurological examinations. With the current range of recommended TTM temperatures, and applicable neurological examinations, procedures may differ between hospitals and the variation of clinical practice in Sweden is not known.

Aim

The aim of this study was to investigate current practice in post-resuscitation care after cardiac arrest as to temperature targets and assessment of neurological prognosis in Swedish intensive care units (ICUs).

Methods

A structured survey was conducted by telephone or e-mail in all Levels 2 and 3 (= 53) Swedish ICUs during the spring of 2022 with a secondary survey in April 2023.

Results

Five units were not providing post-cardiac arrest care and were excluded. The response rate was 43/48 (90%) of the eligible units. Among the responding ICUs, normothermia (36–37.7°C) was applied in all centres (2023). There was a detailed routine for the assessment of neurological prognosis in 38/43 (88%) ICUs. Neurological assessment was applied 72–96 h after return of spontaneous circulation in 32/38 (84%) units. Electroencephalogram and computed tomography and/or magnetic resonance imaging were the most common technical methods available.

Conclusion

Swedish ICUs use normothermia including early treatment of fever in post-resuscitation care after cardiac arrest and almost all apply a detailed routine for the assessment of neurological prognosis. However, available methods for prognostic evaluation varies between hospitals.     

Pelvic floor muscle training with biofeedback and bladder training in elderly women: a feasibility study.

OBJECTIVE: It is generally assumed that interventions used to treat urinary incontinence (UI) in young women could simply be applied to older competent and motivated women, but these assumptions have not been formally tested. The purpose of this study was to determine the feasibility of using physical therapies to treat UI in older women. DESIGN: Twelve-week time series. SETTINGS AND SUBJECTS: We recruited women older than 75 years with UI from an outpatient urology clinic and a waiting list for incontinence surgery. METHODS: After a baseline evaluation, the women collected data on their incontinence symptoms and bladder habits for 3 weeks using the 72-hour voiding diary and the 24-hour pad test. They then received 6 physical therapy treatments consisting of a combination of bladder training and pelvic floor muscle training assisted with biofeedback for 6 weeks. This was followed by another 3-week period of data collection and a final evaluation. RESULTS: Ten women participated in the study; 7 completed it. They were all comfortable with the treatment. They complied with the study demands in terms of attendance at treatment session (100%), data collection (96%), and completion of exercises at home (82%). The authors observed a decrease in the number of incontinent and urgency episodes. CONCLUSION: This preliminary study demonstrates that some women older than 75 years are good candidates to undertake physical therapies for UI and follow study demands. Random controlled studies that include this population will provide evidence regarding the effectiveness of these therapies.     

Percutaneous revascularization in acute myocardial infarction due to left main stem occlusion

Following the encouraging results of trials testing the effect of primary percutaneous coronary intervention (PCI) more cases of left main arterial stenosis (LMS) as culprit lesions in acute myocardial infarction (AMI) are being handled. Not many cases of primary PCI on LMS have been published. We present 12 cases of primary PCI on LMS. Eighty-three percent of the patients presented with cardiogenic shock and only 42% were discharged alive. Due to the high rate of cardiogenic shock at presentation, PCI seems to be the treatment of choice, over coronary artery bypass grafting (CABG), although one might consider using PCI as a bridge over to CABG.     

Parecoxib sodium,a parenteral cyclooxygenase 2 selective inhibitor,improves morphine analgesia and is opioid-sparing following total hip arthroplasty

BACKGROUND: This study examined the opioid-sparing effectiveness, analgesic efficacy, and tolerability of postoperative administration of the parenteral cyclooxygenase 2 selective inhibitor, parecoxib sodium, in total hip arthroplasty patients. METHODS: This was a multicenter, multiple-dose, randomized, double-blind, placebo-controlled study to compare the opioid-sparing effects, analgesic efficacy, and tolerability of postoperative 20 and 40 mg intravenous parecoxib sodium with placebo in hip arthroplasty patients. The first dose of study medication was administered after surgery with an intravenous bolus dose of 4 mg morphine when patients first requested pain medication; remedication with the study medication occurred at 12 and 24 h. Subsequent morphine doses (1-2 mg) were administered by patient-controlled analgesia. Efficacy was assessed by total morphine used, pain relief and pain intensity, time to last dose of morphine, and Global Evaluation rating of the study medication. RESULTS: Parecoxib sodium, 20 and 40 mg, reduced the total amount of morphine required over 36 h by 22.1% (56.5 mg morphine) and 40.5% (43.1 mg morphine), respectively, compared with placebo (72.5 mg morphine; P < 0.01). Patients receiving 20 and 40 mg parecoxib sodium experienced significantly greater maximum pain relief compared with those in the placebo group (P < 0.05). Patients who received 20 and 40 mg parecoxib sodium discontinued PCA morphine earlier than patients receiving placebo and had significantly higher Global Evaluation ratings. Parecoxib sodium, 40 mg, plus morphine demonstrated a significantly lower incidence of fever and vomiting compared with placebo plus morphine. CONCLUSIONS: Administration of parecoxib sodium with PCA morphine resulted in significantly improved postoperative analgesic management as defined by reduction in opioid requirement, lower pain scores, reduced time on PCA morphine, and higher Global Evaluation ratings.     

Expression of either NF-kappaB p50 or p52 in osteoclast precursors is required for IL-1-induced bone resorption.

Interleukin (IL)-1 is implicated in postmenopausal- and inflammation-mediated bone loss. Its expression is regulated by NF-kappaB and vice versa. To examine the role of NF-kappaB p50 and p52 (they are required for osteoclast formation during embryonic development) in IL-1-induced resorption, we used various NF-kappaB knockout (KO) mice, including p50-/- and p52-/- single KO, p50-/- and p52+/- (3/4KO), and p50-/- and p52-/- double KO (dKO) mice. IL-1 increased blood calcium and bone resorption in wild-type (wt), p50, and p52 single KO mice, but not in 3/4KO or dKO mice. Osteoclast formation was impaired in bone marrow cultures from 3/4KO compared with single KO and wt mice treated with IL-1. IL-1 receptor expression was similar in colony forming unit-granulocyte macrophage (CFU-GM) colony cells from wt and dKO mice. However, IL-1 promoted CFU-GM colony formation and survival as well as the formation, activity, and survival of osteoclasts generated from these colonies from wt mouse splenocytes, but not from dKO splenocytes. No difference in expression of the osteoclast regulatory cytokines, RANKL, and OPG, was observed in osteoblasts from wt and dKO mice. Thus, expression of either NF-kappaB p50 or p52 is required in osteoclasts and their precursors, rather than osteoblasts, for IL-1-mediated bone resorption.     

Trained men display increased basal heat shock protein content of skeletal muscle

PURPOSE: 1) To compare the baseline levels of heat shock and antioxidant protein content in the skeletal muscle of trained and untrained humans and 2) to characterize the exercise-induced stress response of aerobically trained human skeletal muscle to an acute exercise challenge. METHODS: Resting muscle biopsies were obtained from the vastus lateralis muscle of six untrained and six aerobically trained young males. To characterize the stress response of a trained population, the trained subjects also performed a 45-min nondamaging running exercise protocol at an intensity corresponding to 75% of V O2max. Muscle biopsies were obtained from the vastus lateralis muscle at 48 h and 7 d after exercise. RESULTS: Trained subjects displayed significantly higher (P<0.05) resting levels of heat shock protein 60 (HSP60, 25%), alphaB-crystallin (43%), and manganese superoxide (MnSOD, 45%) protein content compared with untrained subjects. Trained subjects also exhibited no significant change (P > 0.05) in resting levels of HSP70 (16%), HSC70 (13%), and total superoxide dismutase (SOD) activity (46%) compared with untrained subjects. Resting HSP27 levels were unaffected by exercise training (P > 0.05). In the trained subjects, exercise failed to induce significant increases (P>0.05)in muscle content of HSP70, HSC70, HSP60, HSP27, alphaB-crystallin, and MnSOD protein content or in the activity of SOD at any time point after exercise. CONCLUSION: This study demonstrates for the first time that trained men display a selective up-regulation of basal heat shock and antioxidant protein content and do not exhibit a stress response to customary running exercise. It is suggested that an increase in these protective systems functions to maintain homeostasis during the stress of exercise by protecting against disruptions to the cytoskeleton/contractile machinery, by maintaining redox balance, and by facilitating mitochondrial biogenesis.     

Intramuscular schwannoma: clinical and magnetic resonance imaging features

INTRODUCTION

Schwannomas that arise within the muscle plane are called intramuscular schwannomas. The low incidence of these tumours and the lack of specific clinical features make preoperative diagnosis difficult. Herein, we report our experience with intramuscular schwannomas. We present details of the clinical presentation, radiological diagnosis and management of these tumours.

METHODS

Between January 2011 and December 2013, 29 patients were diagnosed and treated for histologically proven schwannoma at the National University Hospital, Singapore. Among these 29 patients, eight (five male, three female) had intramuscular schwannomas.

RESULTS

The mean age of the eight patients was 40 (range 27–57) years. The most common presenting feature was a palpable mass. The mean interval between surgical treatment and the onset of clinical symptoms was 17.1 (range 4–72) months. Six of the eight tumours (75.0%) were located in the lower limb, while 2 (25.0%) were located in the upper limb. None of the patients had any preoperative neurological deficits. Tinel’s sign was present in one patient. Magnetic resonance (MR) imaging showed that the findings of split-fat sign, low signal margin and fascicular sign were present in all patients. The entry and exit sign was observed in 4 (50.0%) patients, a hyperintense rim was observed in 7 (87.5%) patients and the target sign was observed in 5 (62.5%) patients. All patients underwent microsurgical excision of the tumour and none developed any postoperative neurological deficits.

CONCLUSION

Intramuscular schwannomas demonstrate the findings of split-fat sign, low signal margin and fascicular sign on MR imaging. These findings are useful for the radiological diagnosis of intramuscular schwannoma.