78 research outputs found

    Quantitative Modeling of GRK-Mediated β2AR Regulation

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    We developed a unified model of the GRK-mediated β2 adrenergic receptor (β2AR) regulation that simultaneously accounts for six different biochemical measurements of the system obtained over a wide range of agonist concentrations. Using a single deterministic model we accounted for (1) GRK phosphorylation in response to various full and partial agonists; (2) dephosphorylation of the GRK site on the β2AR; (3) β2AR internalization; (4) recycling of the β2AR post isoproterenol treatment; (5) β2AR desensitization; and (6) β2AR resensitization. Simulations of our model show that plasma membrane dephosphorylation and recycling of the phosphorylated receptor are necessary to adequately account for the measured dephosphorylation kinetics. We further used the model to predict the consequences of (1) modifying rates such as GRK phosphorylation of the receptor, arrestin binding and dissociation from the receptor, and receptor dephosphorylation that should reflect effects of knockdowns and overexpressions of these components; and (2) varying concentration and frequency of agonist stimulation “seen” by the β2AR to better mimic hormonal, neurophysiological and pharmacological stimulations of the β2AR. Exploring the consequences of rapid pulsatile agonist stimulation, we found that although resensitization was rapid, the β2AR system retained the memory of the previous stimuli and desensitized faster and much more strongly in response to subsequent stimuli. The latent memory that we predict is due to slower membrane dephosphorylation, which allows for progressive accumulation of phosphorylated receptor on the surface. This primes the receptor for faster arrestin binding on subsequent agonist activation leading to a greater extent of desensitization. In summary, the model is unique in accounting for the behavior of the β2AR system across multiple types of biochemical measurements using a single set of experimentally constrained parameters. It also provides insight into how the signaling machinery can retain memory of prior stimulation long after near complete resensitization has been achieved

    Effect of Exercise Interventions on Health-Related Quality of Life After Stroke and Transient Ischemic Attack: A Systematic Review and Meta-Analysis

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    Exercise interventions have been shown to help physical fitness, walking and balance after stroke, but data is lacking on whether such interventions lead to improvements in health-related quality of life (HRQoL). In this systematic review and meta-analysis, thirty randomised controlled trials (n=1,836 patients) were found from PubMed, OVID MEDLINE, Web of Science, CINAHL, SCOPUS, The Cochrane Library and TRIP databases when searched from 1966 to Feb 2020, that examine the effects of exercise interventions on HRQoL after strokem or transient ischaemic attack (TIA). Exercise interventions resulted in small to moderate beneficial effects on HRQoL at intervention end (standardised mean difference (SMD) -0.23; 95% CI -0.40 to -0.07) that appeared to diminish at longer term follow up (SMD -0.11; 95%CI -0.26 to 0.04). Exercise was associated with moderate improvements in physical health (SMD -0.33; 95% CI -0.61 to -0.04) and mental health (SMD -0.29; 95% CI -0.49 to -0.09) domains of HRQoL while effects on social or cognitive composites showed little difference. Interventions that were initiated within 6 months, lasted at least 12 weeks in duration, involved at least 150 minutes per week, and included resistance training appeared most effective. Exercise can lead to moderate beneficial effects on HRQoL and should be considered an integral part of stroke rehabilitatio

    Prognostic biomarker potential of quantifying endotrophin in serum from pancreas cancer patients.

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    e16804 Background: Pancreas cancer (PC) is the most stroma rich tumor type defined by increased collagen deposition and remodeling (desmoplasia/tumor fibrosis), which result in poor prognosis and lack of treatment response. The cleavage product of the type VI collagen alpha 3 (COL6a3) chain, also knowns as endothrophin, has been shown to signaling properties and affect several pro-tumorigenic events by augmenting desmoplasia, angiogenesis, inflammation and tumor growth. Here we evaluate the clinical utility of a biomarker (PRO-C6) quantifying endothrophin in serum from patients with PC. Methods: Serum PRO-C6 was measured by ELISA (Nordic Bioscience) in 814 PC patients (n = 15, 201, 164 and 434 for stage 1-4, respectively) and 87 patients with benign conditions from the clinical study BIOPAC (NCT03311776, Denmark). PC was histologically confirmed, and patients received standard of treatment (surgical resection or palliative chemotherapy). PRO-C6 was compared between PC and benign conditions and correlated to stage. Association between OS and PRO-C6 in PC patients was analyzed by Kaplan-Meyer curves and Cox regression analysis alone, and after adjusting for age, gender, BMI, diabetes, smoking, performance status, cachexia, CA19-9, stage and metastatic sites. Results: PRO-C6 was elevated in PC compared to benign disease (p = 0.009) and increased with tumor stage (p = 0.0006). When dividing PRO-C6 into quartiles (Q1-Q4) a stepwise decrease was detected in median OS time (Q1:380 days, Q2:264 days, Q3:236 days, Q4:176 days, p &lt; 0.0001). Patients in Q4 had 85% increased risk of dying compared to Q1 (HR:1.85, p &lt; 0.0001). High PRO-C6 (Q4) remained associated with poor OS after adjusting for co-variates (HR: 1.66, p = 0.0018). Conclusions: Pretreatment serum PRO-C6 (a measure of the COL6a3 chain/endothrophin) is associated with PC and has independent prognostic value. This suggests that endothrophin, and the desmoplastic reaction, plays a key role in PC and indicate that PRO-C6 may provide means for a theragnostic approach for stratifying and treating PC patients in the future. Clinical trial information: NCT03311776 . </jats:p
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