Clinical Characteristics and Patterns of Immune Responses in COVID-19 Patients From a Rural Community Hospital.

Background Although demographic and clinical factors such as age, certain comorbidities, and sex have been associated with COVID-19 outcomes, these studies were largely conducted in urban populations affiliated with large academic medical centers. There have been very few studies focusing on rural populations that also characterize broader changes in inflammatory cytokines and chemokines. Methodology A single-center study was conducted between June 2020 and March 2021 in Abilene, Texas, USA. Patients were included if they presented to the hospital for treatment of COVID-19, had extra biological materials from routine care available, and were between the ages of 0 to 110 years. There were no exclusion criteria. Patient characteristics, symptom presentation, and clinical laboratory results were extracted from electronic health records. Blood specimens were analyzed by protein microarray to quantitate 40 immunological biomarkers. Results A total of 122 patients were enrolled, of whom 81 (66%) were admitted to the general non-critical inpatient unit, 37 (30%) were admitted to the intensive or critical care units, and four (3.2%) were treated outpatient. Most hospitalized COVID-19 patients in this rural population were elderly, male, obese, and retired individuals. Predominant symptoms for non-critical patients were shortness of breath, fever, and fatigue. Ferritin levels for outpatient patients were lower on average than those in an inpatient setting and lactate dehydrogenase (LDH) levels were noted to be lower in non-critical and outpatient than those in the intensive care unit setting. Inflammatory biomarkers were positively correlated and consistent with inflammatory cascade. Interleukin (IL)-10 was positively correlated while platelet-derived growth factor was negatively correlated with inflammatory biomarkers. Patients ≥65 years had significantly higher levels of LDH and seven cytokines/chemokines (granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin IL-1b, IL-6, IL-10, IL-11, macrophage inflammatory protein (MIP)-1d, and IL-8) while levels of five other immune molecules (intercellular adhesion molecule 1 (ICAM-1), monocyte chemoattractant protein 1 (MCP-1), tissue inhibitor of metalloproteinase 2 (TIMP-2), IL-2, and IL-4) were significantly lower compared to those <65 years. Females had significantly higher levels of LDH and 10 cytokines/chemokines (GM-CSF, IL-1b, IL-6, IL-10, IL-11, IL-15, IL-16, MIP-1a, MIP-1d, and IL-8) while levels of TIMP-2 and IL-4 were significantly lower than male patients. Conclusions The clinical characteristics of this rural cohort of hospitalized patients differed somewhat from nationally reported data. The contributions of social, environmental, and healthcare access factors should be investigated. We identified age and sex-associated differences in immunological response markers that warrant further investigation to identify the underlying molecular mechanisms and impact on COVID-19 pathogenesis.

Rate control with intravenous diltiazem, verapamil, and metoprolol in acute atrial fibrillation with rapid ventricular rate.

INTRODUCTION: Diltiazem is a preferred agent for rate control in atrial fibrillation due to its quick onset, minimal side effects, and low cost. Due to its intermittent national shortage since February 2018, the utilization of intravenous metoprolol and verapamil has increased. This study investigated the effect of intravenous diltiazem, metoprolol, and verapamil on rate control in patients with atrial fibrillation with rapid ventricular rate. METHODS: This study was a retrospective, single-center, cohort study conducted in patients with acute atrial fibrillation receiving intravenous diltiazem, metoprolol, or verapamil for rapid ventricular rate between 1 January 2012 and 31 August 2018. The primary outcome was the incidence of patients who achieved a rate less than 100 bpm within 1 h of treatment. Secondary outcomes included time to achieve rate control, heart rate at 30 min and 1 h after administration, bradycardia and hypotension incidence, the requirement of other rate control agent(s), inpatient admission, length of stay, and mortality. RESULTS: A total of 73 patients were included in the study. At 1 h after receiving the initial rate control drug, there was no statistically significant difference between diltiazem, metoprolol, and verapamil in achieving rate control. Median time to ventricular rate control was 166 min in the diltiazem group, 297 min in the metoprolol group, and 100.5 min in the verapamil group. CONCLUSION: There was no difference in achieving rate control when using intravenous diltiazem, metoprolol, or verapamil. Any of the three rate control agents may be used for rate control. However, further studies are needed to determine which agent is superior for rate control.

Stratifying Therapeutic Enoxaparin Dose in Morbidly Obese Patients by BMI Class: A Retrospective Cohort Study.

BACKGROUND: Enoxaparin is a low-molecular weight heparin (LMWH) commonly used for treatment of venous thromboembolism and acute coronary syndromes. The recommended dose for these conditions is weight-based (1 mg/kg) and doesn't require dose-capping. However, previous studies have shown that in those with a body mass index (BMI) > 40 kg/m2, this dose results in supratherapeutic levels. OBJECTIVE: This study investigated enoxaparin dosing in morbidly obese patients with a goal of identifying a dose with the greatest chance of producing favorable anti-factor Xa (anti-Xa) levels. METHODS: This retrospective cohort study by electronic chart review was used to record data of patients who received enoxaparin with anti-Xa level monitoring between 2012 and 2017. The primary outcome was the enoxaparin dose that results in a therapeutic anti-Xa level (0.5-1.0 IU/mL) among three BMI groups. Secondary outcomes were bleeding and thromboembolic events. RESULTS: Two hundred forty-one patients were included in the study, and 132 achieved a therapeutic dose. For those with a BMI of 40-50 kg/m2, the median therapeutic dose was 0.97 mg/kg every 12 h. In subjects with a BMI of 50-60 kg/m2, the median therapeutic dose was 0.70 mg/kg. Finally, the median therapeutic dose for subjects with a BMI over 60 kg/m2 was 0.71 mg/kg. In all three groups, 53-65% of patients had a supratherapeutic anti-Xa level while less than 10% had a subtherapeutic level. Relatively few patients (4.1%) experienced major bleeding and only one thromboembolic event was reported. CONCLUSION: Standard dosing of enoxaparin in morbidly obese patients will most likely lead to supratherapeutic anti-Xa levels and thus further investigation is warranted to better determine appropriate dosing.

Benefits of Beta-Blockade in Sepsis and Septic Shock: A Systematic Review.

BACKGROUND: Sepsis and septic shock are inflammatory disorders associated with high rates of mortality. Patients with sepsis and septic shock frequently become tachycardic as a result of the utilization of vasopressor therapy and cardiac overcompensation owing to hypotension, predisposing patients to an increased risk of atrial fibrillation. Previously, it was thought that beta-blocker therapy in patients with sepsis would exacerbate hypotension; however, recent studies have shown that may not be the case. OBJECTIVE: This review aims to ascertain whether beta-blocker therapy reduces heart rate in patients with sepsis without a corresponding decrease in blood pressure, and if beta-blockade has a beneficial effect on mortality. METHODS: Several databases including Cochrane, EMBASE, PubMed, SCOPUS, and Web of Science were scoured for trials pertaining to the utilization of beta-blockers in sepsis and septic shock, and trials that were either prospective or controlled were included in this review. RESULTS: In the initial search, 1839 articles were found, and those were subsequently reduced to 14 trials (five randomized controlled trials, nine non-randomized trials) that were deemed appropriate for inclusion in this review. All included trials displayed beneficial effects on heart rate without any detriments to blood pressure. Of the six trials that assessed mortality, four showed substantial benefits. CONCLUSION: The majority of the trials assessed in this review displayed beneficial results for beta-blocker use in patients with sepsis. However, owing to the deficit of large-scale randomized controlled trials addressing this topic, further research is needed to ensure the veracity of these results.

Clinical Outcomes of Extended-Spectrum Beta-Lactamase-Producing Enterobacteriaceae Infections with Susceptibilities among Levofloxacin, Cefepime, and Carbapenems.

PURPOSE: Highly resistant Gram-negative bacterial infections are associated with high mortality. Increasing resistance to standard therapy illustrates the need for alternatives when treating resistant organisms, especially extended-spectrum beta-lactamase- (ESBL-) producing Enterobacteriaceae. METHODS: A retrospective chart review at a community hospital was performed. Patients who developed ESBL-producing infections were included. Patients less than eighteen years old, who were pregnant, or who were incarcerated were excluded. The primary outcome was hospital mortality. The secondary outcomes included intensive care unit (ICU) mortality, ICU length of stay, and hospital length of stay. RESULTS: 113 patients with ESBL-producing infections met the criteria for review. Hospital mortality: carbapenem (16.6%), cefepime (0%), and levofloxacin (15.3%) (p=0.253). ICU mortality: carbapenem (4.5%), cefepime, (0%), and levofloxacin (3.7%) (p=0.616). Mean ICU and hospital length of stay: carbapenem (9.8 ± 16, 12.1 ± 1 days), cefepime (7.8 ± 6, 11.1 ± 10.5 days), and levofloxacin (5.4 ± 4.1, 11.1 ± 10.4 days) (p=0.805, 0.685). No predictors were clearly found between the source of infection and mortality. CONCLUSION: Cefepime or levofloxacin can be a potential alternative agent for infections with ESBL-producing Enterobacteriaceae, and larger clinical trials investigating these outcomes are warranted.

Meropenem-vaborbactam: a carbapenem and beta-lactamase inhibitor with activity against carbapenem-resistant Enterobacteriaceae.

Meropenem-vaborbactam is a carbapenem and ß-lactamase inhibitor combination that is newly indicated for the treatment of complicated urinary tract infections (cUTI), including adult pyelonephritis. Vaborbactam was developed due to emergence of carbapenem-resistant strains of Enterobacteriaceae. In a phase I trial, patients that received meropenem-vaborbactam 2-2 g intravenously over 3 h every 8 h, Cmax was 58.2 ± 10.8 µg/mL for meropenem and 59.0 ± 8.4 µg/mL for vaborbactam. AUC0-8 was 186 ± 33.6 µg â€¢ h/mL for meropenem and 204 ± 34.6 µg â€¢ h/mL for vaborbactam. Vss = 16.3 ± 2.6 L for meropenem and 17.6 ± 2.6 L for vaborbactam. Protein binding for vaborbactam averaged 33% in humans. Plasma clearance ranged from 10.42 ± 1.85 to 14.77 ± 2.84 L/h. One phase III trial evaluated efficacy for meropenem-vaborbactam 2-2 g intravenously every 8 h versus piperacillin-tazobactam 4-0.5 g intravenously every 8 h in complicated UTI. It found non-inferiority and statistical superiority for meropenem in overall success at the end of treatment primary end point. In another phase III trial evaluating efficacy in carbapenem-resistant Enterobacteriaceae (CRE) infections, meropenem-vaborbactam 2-2 g intravenously every 8 h was associated with decreased 28-day mortality and increased clinical cure compared with a best available therapy group.

Correction to: Continuous Infusion Versus Intermittent Bolus of Beta-Lactams in Critically Ill Patients with Respiratory Infections: A Systematic Review and Meta-analysis.

Unfortunately, ≥ was found missing between scores and 20 in conclusion section of the online published article. The original article was corrected.

Continuous Infusion Versus Intermittent Bolus of Beta-Lactams in Critically Ill Patients with Respiratory Infections: A Systematic Review and Meta-analysis.

BACKGROUND: Critically ill patients display altered pharmacokinetics and pharmacodynamics and are more likely to be infected with more resistant pathogens. Beta-lactam antibiotics exhibit time-dependent pharmacodynamics; therefore, it is postulated that continuous infusion (CI) may optimize these parameters. OBJECTIVE: To perform a systematic review and meta-analysis of the available literature comparing CI versus intermittent bolus (IB) of beta-lactam antibiotics in critically ill adult patients with respiratory infections to determine if clinical benefits exist. METHODS: PubMed, EMBASE, and Web of Science were searched. Thirteen randomized controlled trials were included in the meta-analyses of clinical cure and/or mortality. Four retrospective studies reporting clinical cure and/or mortality, and 11 studies that reported pharmacokinetic/pharmacodynamic parameters were included in the systematic review. RESULTS: The majority of patients in both groups maintained the percentage of time the free drug concentration exceeded the minimum inhibitory concentration (%fT > MIC) targets throughout the treatment, with differences favoring CI being more prevalent when the MIC of the offending pathogen increased. CI of beta-lactam antibiotics in critically ill adult patients with respiratory infections significantly improved clinical cure rates when compared to IB (risk ratio [RR] 1.177; 95% CI 1.065-1.300). No significant differences in mortality rates were seen when patients were treated with either dosing modality (RR 0.845; 95% CI 0.644-1.108). CONCLUSIONS: CI of beta-lactam antibiotics is associated with better cure rates and higher %fT > MIC when administered to critically ill patients with respiratory infections, but may be most beneficial in severely ill patients with more resistant Gram-negative bacterial infections.

Interprofessional education and distance education: A review and appraisal of the current literature.

BACKGROUND: Interprofessional education (IPE) is becoming essential for students and healthcare professionals. An evolving approach to implement it is via distance education. Distance education can provide a viable solution to deliver IPE in a variety of settings. METHODS: A literature search on PubMed and Academic Search Complete databases was conducted, revealing 478 articles ranging from the years of 1971-2015. The articles were screened for relevance using the following inclusion criteria: 1) Is this study implementing IPE? 2) Is this study utilizing the instructional delivery method of distance education? 3) Does this study contain students from two or more healthcare professions? RESULTS: Fifteen studies met the inclusion criteria and were systematically analyzed to identify data relevant for this review. Findings from this review provide a description of the teaching methods involved in distance education in promoting IPE and an assessment of the continuing use of distance education to foster IPE. Success varied depending upon on the distance-based instructional model utilized to facilitate IPE. IMPLICATIONS: Incorporating distance education to implement IPE can be an opportunity to develop team collaboration and communication skills among students. Teaching models presented in this review have the potential to be adapted to methods that leverage the power of evolving technology. Further research is needed to understand which distance education instructional delivery models best maximize the IPE experience.

Efficacy of standard dose unfractionated heparin for venous thromboembolism prophylaxis in morbidly obese and non-morbidly obese critically Ill patients.

To determine the efficacy of standard dose unfractionated heparin (UFH) for venous thromboembolism (VTE) prophylaxis in critically ill morbidly obese patients. Retrospective single-center observational cohort study in a single tertiary teaching hospital intensive care units (ICUs) in Multiparameter Intelligent Monitoring in Intensive Care II Clinical Database. Patients 18 years or older, admitted to the ICU, and received either UFH 5000 units subcutaneously twice daily or UFH 5000 units three times daily for VTE prophylaxis between 2001 and 2008 were included. Total 243 patients in the BMI ≥ 40 kg/m2 group and 2813 patients in the BMI < 40 kg/m2 group were identified. There was no difference in VTE incidence between the two groups. However, a strong linear association was found showing as BMI increased so did the rate of VTE incidence. Morbidly obese patients had longer hospital (17 vs. 14 days, P = 0.016) and ICU length of stay (10 vs. 8 days, P = 0.007). After controlling Padua score, logistic regression analysis revealed the odds of VTE increased by a factor of 1.026 for each one-unit increase in BMI. Additionally, having a BMI ≥ 40 kg/m2 was associated with a greater likelihood of VTE incidence in males (OR 3.92) but not in females. In patients treated with standard dose UFH, morbid obesity does not increase VTE risk overall. However, BMI has a strong linear relationship with VTE incidence and morbid obesity is more likely associated with greater hospital and ICU length of stay.

Monitoring Enoxaparin with Antifactor Xa Levels in Obese Patients.

STUDY OBJECTIVES: To characterize antifactor Xa peak levels (as therapeutic, subtherapeutic, and supratherapeutic) in morbidly obese patients receiving treatment doses of enoxaparin, using a therapeutic range of 0.5-1.1 units/ml, and to assess the occurrence of bleeding complications in these patients. DESIGN: Retrospective cohort study. SETTING: Community hospital. PATIENTS: Ninety-nine morbidly obese patients (body mass index [BMI] higher than 40 kg/m(2) or total body weight more than 150 kg) who received at least three doses of the standard treatment dosage of enoxaparin and had steady-state antifactor Xa peak levels between April 2009 and January 2014. MEASUREMENTS AND MAIN RESULTS: Data were collected from patients' medical records on age, sex, height, weight, BMI, serum creatinine concentration, creatinine clearance (using lean body weight as well as adjusted body weight), antifactor Xa level, and time of blood collection for measurement of antifactor Xa level. Enoxaparin therapy was monitored by using antifactor Xa levels; steady-state enoxaparin antifactor Xa levels were measured 4 hours after administration of the third dose for peak level monitoring. The primary outcome was the proportion of patients whose steady-state antifactor Xa peak values were in the therapeutic (0.5-1.1 units/ml), subtherapeutic, and supratherapeutic ranges. The secondary outcome was occurrence of major bleeding. Univariate regression analysis was performed to identify the correlation between baseline patient characteristics and antifactor Xa levels. Most of the patients (50 [50.5%]) had supratherapeutic levels, 35 (35.4%) had levels within the therapeutic peak range (0.5-1.1 units/ml), and 14 (14.1%) had subtherapeutic levels. No bleeding was observed in any of the 99 patients. Univariate analysis revealed a negative association between antifactor Xa levels and serum creatinine concentration (r = -0.262, p=0.009). CONCLUSION: Based on the results of this study, monitoring antifactor Xa levels is warranted to ensure the safety and efficacy of enoxaparin in the obese patient population (defined as a total body weight more than 150 kg or BMI higher than 40 kg/m(2)). Enoxaparin dose individualization and antifactor Xa level monitoring need further validation with clinical outcomes.

Complicated Intra-Abdominal Infections: The Old Antimicrobials and the New Players.

Complicated intra-abdominal infections (cIAIs) are an important cause of morbidity and mortality worldwide. They are diagnosed when the initial abdominal organ infection has spread into the peritoneal space. Successful treatment relies on adequate source control and appropriate empiric antimicrobial therapy. Inappropriate antimicrobial therapy may result in poor patient outcomes and increases in healthcare costs. Current guidelines recommend several single and combination antimicrobial regimens; however, empiric antimicrobial treatment has been complicated by the increasing rates of resistant organisms, especially the extended-spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae. Additionally, the overuse of carbapenems to combat these resistant pathogens has contributed to the rise of carbapenemase-producing microorganisms, especially Klebsiella pneumoniae. This increasing resistance has prompted the development of novel antimicrobials like ceftazidime-avibactam and ceftolozane-tazobactam, whose activity extends to ESBL-producing microorganisms. Furthermore, the optimal duration of antimicrobial therapy is still unknown, and further research is necessary to find a definitive answer. This review will focus on antimicrobial therapies recommended by the current guidelines, the individual properties of these agents, appropriate duration of therapy, recent clinical trials, and place in therapy of the antimicrobial agents recently approved for the treatment of cIAIs.

Comparison of unfractionated heparin protocols using antifactor Xa monitoring or activated partial thrombin time monitoring.

OBJECTIVE: To determine whether there is a difference between an activated partial thromboplastin time (aPTT) based unfractionated heparin (UFH) protocol versus an antifactor Xa based UFH protocol with respect to 24-hour attainment of therapeutic levels. METHODS: This was an observational study performed at a 500 bed private, community hospital. The study included inpatients from January 2008 to December 2009 on our institution's aPTT UFH protocol and inpatients from July 2010 to March 2011 on our institution's antifactor Xa UFH protocol. The two groups were compared to determine whether a higher percentage of patients reached therapeutic goal within 24 hours of UFH initiation. Secondary outcomes evaluated the percentage of patients at therapeutic goal within 6 and 12 hours, incidence of bleeding, and number of UFH dosage adjustments within 24 hours between the two groups. RESULTS: One hundred twenty-one patients met inclusion criteria for this study; 79 in the aPTT group and 42 in the antifactor Xa group. At 24 hours, 74% of patients in the antifactor Xa group were at goal, versus 63% of patients in the aPTT group (p = 0.242). Nearly 57% of patients in the antifactor Xa group were at goal versus 27% in the aPTT group within 6 hours (p = 0.001). Subjects in the antifactor Xa group averaged 1.00 dosage adjustments per subject as compared to an 1.71 dosage adjustments per subject in the aPTT group within the first 24 hours (p = 0.003). CONCLUSION: The antifactor Xa assay should be used to monitor UFH versus aPTT due to less variability in measurements, the absence of a need for calibration with new reagents/coagulometers, quicker attainment of therapeutic levels, fewer dose adjustments, and similar bleeding rates.

Treatment of community-acquired pneumonia.

Community-acquired pneumonia is the sixth leading cause of death in the USA. Adherence to the 2007 Infectious Diseases Society of America/American Thoracic Society community-acquired pneumonia guidelines has been associated with improved clinical outcomes. However, choice between guideline-recommended treatments is at the discretion of the prescribing clinician. This review is intended to discuss the characteristics of these treatment options including dosing frequency, dose adjustment for renal/hepatic dysfunction, serious/common adverse events, drug interactions, lung penetration, pharmacokinetic-pharmacodynamic target and effect of obesity to help guide antimicrobial selection. An increasing portion of patients are receiving expanded empiric coverage for methicillin-resistant Staphylococcus aureus as recommended by the American Thoracic Society and Infectious Diseases Society of America for healthcare-associated pneumonia. However, this expanded coverage may not be achieving the desired improvements in clinical outcomes. We expect this increasingly diverse spectrum of patients with pneumonia to eventually result in the merger of these two guidelines to include all patients with pneumonia.

Distinct patterns of tissue-specific lipid accumulation during the induction of insulin resistance in mice by high-fat feeding.

AIMS/HYPOTHESIS: While it is well known that diet-induced obesity causes insulin resistance, the precise mechanisms underpinning the initiation of insulin resistance are unclear. To determine factors that may cause insulin resistance, we have performed a detailed time-course study in mice fed a high-fat diet (HFD). METHODS: C57Bl/6 mice were fed chow or an HFD from 3 days to 16 weeks and glucose tolerance and tissue-specific insulin action were determined. Tissue lipid profiles were analysed by mass spectrometry and inflammatory markers were measured in adipose tissue, liver and skeletal muscle. RESULTS: Glucose intolerance developed within 3 days of the HFD and did not deteriorate further in the period to 12 weeks. Whole-body insulin resistance, measured by hyperinsulinaemic-euglycaemic clamp, was detected after 1 week of HFD and was due to hepatic insulin resistance. Adipose tissue was insulin resistant after 1 week, while skeletal muscle displayed insulin resistance at 3 weeks, coinciding with a defect in glucose disposal. Interestingly, no further deterioration in insulin sensitivity was observed in any tissue after this initial defect. Diacylglycerol content was increased in liver and muscle when insulin resistance first developed, while the onset of insulin resistance in adipose tissue was associated with increases in ceramide and sphingomyelin. Adipose tissue inflammation was only detected at 16 weeks of HFD and did not correlate with the induction of insulin resistance. CONCLUSIONS/INTERPRETATION: HFD-induced whole-body insulin resistance is initiated by impaired hepatic insulin action and exacerbated by skeletal muscle insulin resistance and is associated with the accumulation of specific bioactive lipid species.

AMP-activated protein kinase (AMPK)α2 plays a role in determining the cellular fate of glucose in insulin-resistant mouse skeletal muscle.

AIMS/HYPOTHESIS: We determined whether: (1) an acute lipid infusion impairs skeletal muscle AMP-activated protein kinase (AMPK)α2 activity, increases inducible nitric oxide synthase (iNOS) and causes peripheral insulin resistance in conscious, unstressed, lean mice; and (2) restoration of AMPKα2 activity during the lipid infusion attenuates the increase in iNOS and reverses the defect in insulin sensitivity in vivo. METHODS: Chow-fed, 18-week-old C57BL/6J male mice were surgically catheterised. After 5 days they received: (1) a 5 h infusion of 5 ml kg(-1) h(-1) Intralipid + 6 U/h heparin (Lipid treatment) or saline (Control); (2) Lipid treatment or Control, followed by a 2 h hyperinsulinaemic-euglycaemic clamp (insulin clamp; 4 mU kg(-1) min(-1)); and (3) infusion of the AMPK activator, 5-aminoimidazole-4-carboxamide 1-ß-D-ribofuranoside (AICAR) (1 mg kg(-1) min(-1)), or saline during Lipid treatment, followed by a 2 h insulin clamp. In a separate protocol, mice producing a muscle-specific kinase-dead AMPKα2 subunit (α2-KD) underwent an insulin clamp to determine the role of AMPKα2 in insulin-mediated muscle glucose metabolism. RESULTS: Lipid treatment decreased AMPKα2 activity, increased iNOS abundance/activation and reduced whole-body insulin sensitivity in vivo. AICAR increased AMPKα2 activity twofold; this did not suppress iNOS or improve whole-body or tissue-specific rates of glucose uptake during Lipid treatment. AICAR caused a marked increase in insulin-mediated glycogen synthesis in skeletal muscle. Consistent with this latter result, lean α2-KD mice exhibited impaired insulin-stimulated glycogen synthesis even though muscle glucose uptake was not affected. CONCLUSIONS/INTERPRETATION: Acute induction of insulin resistance via lipid infusion in healthy mice impairs AMPKα2, increases iNOS and causes insulin resistance in vivo. However, these changes do not appear to be interrelated. Rather, a functionally active AMPKα2 subunit is required for insulin-stimulated muscle glycogen synthesis.

Obesity impairs skeletal muscle AMPK signaling during exercise: role of AMPKα2 in the regulation of exercise capacity in vivo.

OBJECTIVE: Skeletal muscle AMP-activated protein kinase (AMPK)α2 activity is impaired in obese, insulin-resistant individuals during exercise. We determined whether this defect contributes to the metabolic dysregulation and reduced exercise capacity observed in the obese state. DESIGN: C57BL/6J wild-type (WT) mice and/or mice expressing a kinase dead AMPKα2 subunit in skeletal muscle (α2-KD) were fed chow or high-fat (HF) diets from 3 to 16 weeks of age. At 15 weeks, mice performed an exercise stress test to determine exercise capacity. In WT mice, muscle glucose uptake and skeletal muscle AMPKα2 activity was assessed in chronically catheterized mice (carotid artery/jugular vein) at 16 weeks. In a separate study, HF-fed WT and α2-KD mice performed 5 weeks of exercise training (from 15 to 20 weeks of age) to test whether AMPKα2 is necessary to restore work tolerance. RESULTS: HF-fed WT mice had reduced exercise tolerance during an exercise stress test, and an attenuation in muscle glucose uptake and AMPKα2 activity during a single bout of exercise (P<0.05 versus chow). In chow-fed α2-KD mice, running speed and time were impaired ∼45 and ∼55%, respectively (P<0.05 versus WT chow); HF feeding further reduced running time ∼25% (P<0.05 versus α2-KD chow). In response to 5 weeks of exercise training, HF-fed WT and α2-KD mice increased maximum running speed ∼35% (P<0.05 versus pre-training) and maintained body weight at pre-training levels, whereas body weight increased in untrained HF WT and α2-KD mice. Exercise training restored running speed to levels seen in healthy, chow-fed mice. CONCLUSION: HF feeding impairs AMPKα2 activity in skeletal muscle during exercise in vivo. Although this defect directly contributes to reduced exercise capacity, findings in HF-fed α2-KD mice show that AMPKα2-independent mechanisms are also involved. Importantly, α2-KD mice on a HF-fed diet adapt to regular exercise by increasing exercise tolerance, demonstrating that this adaptation is independent of skeletal muscle AMPKα2 activity.

Impact of macrophage toll-like receptor 4 deficiency on macrophage infiltration into adipose tissue and the artery wall in mice.

AIMS/HYPOTHESIS: Toll-like receptor 4 (TLR4) is a receptor for saturated fatty acids (SFAs), global deficiency of which has been shown to protect against inflammation, insulin resistance and atherosclerotic lesion formation. Because macrophages express Tlr4 and are important in insulin resistance and atherosclerotic lesion formation due to their infiltration of white adipose tissue (WAT) and the artery wall, respectively, we hypothesised that deficiency of macrophage TLR4 could protect against these disorders. METHODS: Bone marrow transplantation of agouti, LDL-receptor deficient (A(y)/a; Ldlr (-/-)) mice with marrow from either C57BL/6 or Tlr4 (-/-) mice was performed. Recipient mice with Tlr4 (+/+) marrow (MthetaTLR4(+/+)) or with Tlr4 (-/-) marrow (MthetaTLR4(-/-)) were then placed on one of four diets: (1) low fat; (2) high fat; (3) high fat rich in SFAs (HF(SFA)); and (4) HF(SFA) supplemented with fish oil. RESULTS: There were no differences in body composition or plasma lipids between MthetaTLR4(+/+) and MthetaTLR4(-/-) mice on any of the diets. However, we observed a decrease in some macrophage and inflammatory markers in WAT of female low fat-fed MthetaTLR4(-/-) mice compared with MthetaTLR4(+/+) mice. MthetaTLR4(-/-) mice fed low-fat diet also displayed decreased atherosclerotic lesion area. There were no differences in macrophage accrual in WAT or atherosclerosis between MthetaTLR4(+/+) and MthetaTLR4(-/-) mice fed any of the high-fat diets. Finally, no difference was seen in insulin sensitivity between MthetaTLR4(+/+) and MthetaTLR4(-/-) mice fed the HF(SFA) diet. CONCLUSIONS/INTERPRETATION: These data suggest that under certain dietary conditions, macrophage expression of Tlr4 can be an important mediator of macrophage accumulation in WAT and the artery wall.