Menstrual Cycle Phase Has No Influence on Performance-Determining Variables in Endurance-Trained Athletes: The FENDURA Project.

PURPOSE: This study aimed to investigate the effect of the MC and endogenous sex hormone concentrations on performance-determining variables in three distinct MC phases in endurance-trained females. METHODS: Twenty-one eumenorrheic trained/highly trained endurance athletes completed a standardized test battery during the early follicular phase (EFP), ovulatory phase (OP), and midluteal phase (MLP) for either one ( n = 7) or two test cycles ( n = 14). MC phases were determined using calendar-based counting, urinary ovulation testing, and verified with serum hormone analysis. MCs were retrospectively classified as eumenorrheic or disturbed. Disturbed MCs were excluded from analysis. The test battery consisted of 4-6 × 5-min submaximal stages with stepwise speed increases, a 30-s all-out double-poling ski ergometer test, and a maximal incremental treadmill running test. RESULTS: At a group level, there was no effect of MC phase or the serum concentrations of estrogen and progesterone on peak oxygen uptake (V̇O 2peak ), oxygen uptake at 4 mmol·L -1 blood lactate concentration, time to exhaustion, running economy, or mean 30-s power output (MPO 30s ). Serum testosterone concentration was positively associated with MPO 30s ( P = 0.016). Changes in V̇O 2peak from EFP to MLP were inconsistent between individuals and across cycles. CONCLUSIONS: None of the measured performance-determining variables were influenced by MC phase or serum estrogen or progesterone concentrations. Although some individual patterns could be observed, there was no indication that any single MC phase is consistently associated with improved or impaired V̇O 2peak on a group level.

Condensed Internet-delivered prolonged exposure provided soon after trauma: a randomised trial.

BACKGROUND: Exposure to trauma is common and can have a profoundly negative impact on mental health. Interventions based on trauma-focused cognitive behavioural therapy have shown promising results to facilitate recovery. The current trial evaluated whether a novel, scalable and digital early version of the intervention, Condensed Internet-Delivered Prolonged Exposure (CIPE), is effective in reducing post-traumatic stress symptoms. METHOD: A single-site randomised controlled trial with self-referred adults (N = 102) exposed to trauma within the last 2 months. The participants were randomised to 3 weeks of CIPE or a waiting list (WL) for 7 weeks. Assessments were conducted at baseline, week 1-3 (primary endpoint), week 4-7 (secondary endpoint) and at 6-month follow-up. The primary outcome measure was PTSD Checklist for DSM-5 (PCL-5). RESULTS: The main analysis according to the intention-to-treat principle indicated statistically significant reductions in symptoms of post-traumatic stress in the CIPE group as compared to the WL group. The between-group effect size was moderate at week 3 (bootstrapped d = 0.70; 95% CI 0.33-1.06) and large at week 7 (bootstrapped d = 0.83; 95% CI 0.46-1.19). Results in the intervention group were maintained at the 6-month follow-up. No severe adverse events were found. CONCLUSIONS: CIPE is a scalable intervention that may confer early benefits on post-traumatic stress symptoms in survivors of trauma. The next step is to compare this intervention to an active control group and also investigate its effects when implemented in regular care.

Effect moderators in Internet-based exposure therapy for fibromyalgia: The role of pain intensity.

BACKGROUND: A recent randomized controlled trial (N = 140) was indicative of large and sustained average improvements of Internet-based exposure for fibromyalgia, as compared to a waitlist. However, little is known about who benefits the most from this treatment. OBJECTIVES: To test for potential moderating effects of age, educational attainment, the duration of fibromyalgia, baseline overall fibromyalgia severity, pain intensity, fibromyalgia-related avoidance behaviour and symptom preoccupation on the waitlist-controlled effect of 10 weeks of Internet-based exposure for fibromyalgia. METHODS: Secondary analysis of a randomized controlled trial (ClinicalTrials.gov NCT02638636). We used linear mixed effects models to determine whether the waitlist-controlled effect of exposure therapy on overall fibromyalgia severity (Fibromyalgia Impact Questionnaire) differed as a function of the potential moderators. RESULTS: Only pain intensity (0-10) was found to be a significant moderator, where a higher baseline pain intensity predicted a more limited waitlist-controlled effect of Internet-based exposure (B = 3.48, 95% CI: 0.84-6.13). Standardized point estimates of effects were small for the sociodemographic variables, and in the moderate range for some clinical variables that did not reach statistical significance such as behavioural avoidance and time with the fibromyalgia diagnosis. CONCLUSIONS: Results suggest that Internet-based exposure treatment was more useful for participants with lower baseline levels of pain, and less so for participants with higher baseline levels of pain. The treatment had relatively similar effects across the other tested moderators. SIGNIFICANCE: This study evaluated potential effect moderators in exposure-based treatment for fibromyalgia. Results indicated that a higher level of pain intensity at baseline was predictive of a less favourable outcome. It may be extra important to monitor progression for these patients and to provide additional therapeutic support when needed.

Systemic Inflammation in Preclinical Ulcerative Colitis.

BACKGROUND & AIMS: Preclinical ulcerative colitis is poorly defined. We aimed to characterize the preclinical systemic inflammation in ulcerative colitis, using a comprehensive set of proteins. METHODS: We obtained plasma samples biobanked from individuals who developed ulcerative colitis later in life (n = 72) and matched healthy controls (n = 140) within a population-based screening cohort. We measured 92 proteins related to inflammation using a proximity extension assay. The biologic relevance of these findings was validated in an inception cohort of patients with ulcerative colitis (n = 101) and healthy controls (n = 50). To examine the influence of genetic and environmental factors on these markers, a cohort of healthy twin siblings of patients with ulcerative colitis (n = 41) and matched healthy controls (n = 37) were explored. RESULTS: Six proteins (MMP10, CXCL9, CCL11, SLAMF1, CXCL11 and MCP-1) were up-regulated (P < .05) in preclinical ulcerative colitis compared with controls based on both univariate and multivariable models. Ingenuity Pathway Analyses identified several potential key regulators, including interleukin-1ß, tumor necrosis factor, interferon-gamma, oncostatin M, nuclear factor-κB, interleukin-6, and interleukin-4. For validation, we built a multivariable model to predict disease in the inception cohort. The model discriminated treatment-naïve patients with ulcerative colitis from controls with leave-one-out cross-validation (area under the curve = 0.92). Consistently, MMP10, CXCL9, CXCL11, and MCP-1, but not CCL11 and SLAMF1, were significantly up-regulated among the healthy twin siblings, even though their relative abundances seemed higher in incident ulcerative colitis. CONCLUSIONS: A set of inflammatory proteins are up-regulated several years before a diagnosis of ulcerative colitis. These proteins were highly predictive of an ulcerative colitis diagnosis, and some seemed to be up-regulated already at exposure to genetic and environmental risk factors.

A heat and moisture-exchanging mask impairs self-paced maximal running performance in a sub-zero environment.

PURPOSE: Heat-and-moisture-exchanging devices (HME) are commonly used by endurance athletes during training in sub-zero environments, but their effects on performance are unknown. We investigated the influence of HME usage on running performance at - 15 °C. METHODS: Twenty-three healthy adults (15 male, 8 female; age 18-53 years; [Formula: see text] men 56 ± 7, women 50 ± 4 mL·kg-1·min-1) performed two treadmill exercise tests with and without a mask-style HME in a randomised, crossover design. Participants performed a 30-min submaximal warm-up (SUB), followed by a 4-min maximal, self-paced running time-trial (TT). Heart rate (HR), respiratory frequency (fR), and thoracic area skin temperature (Tsk) were monitored using a chest-strap device; muscle oxygenation (SmO2) and deoxyhaemoglobin concentration ([HHb]) were derived from near-infra-red-spectroscopy sensors on m. vastus lateralis; blood lactate was measured 2 min before and after the TT. RESULTS: HME usage reduced distance covered in the TT by 1.4%, despite similar perceived exertion, HR, fR, and lactate accumulation. The magnitude of the negative effect of the HME on performance was positively associated with body mass (r2 = 0.22). SmO2 and [HHb] were 3.1% lower and 0.35 arb. unit higher, respectively, during the TT with HME, and Tsk was 0.66 °C higher during the HME TT in men. HR (+ 2.7 beats·min-1) and Tsk (+ 0.34 °C) were higher during SUB with HME. In the male participants, SmO2 was 3.8% lower and [HHb] 0.42 arb. unit higher during SUB with HME. CONCLUSION: Our findings suggest that HME usage impairs maximal running performance and increases the physiological demands of submaximal exercise.

Morphological, elemental, and boron isotopic insights into pathophysiology of diseased coral growth anomalies.

Coral growth anomalies (GAs) are tumor-like lesions that are detrimental to colony fitness and are commonly associated with high human population density, yet little is known about the disease pathology or calcification behavior. SEM imagery, skeletal trace elements and boron isotopes (δ11B) have been combined as a novel approach to study coral disease. Low Mg/Ca, and high U/Ca, Mo/Ca, and V/Ca potentially suggest a decreased abundance of "centers of calcification" and nitrogen-fixation in GAs. Estimates of carbonate system parameters from δ11B and B/Ca measurements indicate reduced pH (-0.05 units) and [CO32-] within GA calcifying fluid. We theorize GAs re-allocate resources away from internal pH upregulation to sustain elevated tissue growth, resulting in a porous and fragile skeleton. Our findings show that dystrophic calcification processes could explain structural differences seen in GA skeletons and highlight the use of skeletal geochemistry to shed light on disease pathophysiology in corals.

Symptom Preoccupation in Fibromyalgia: Prevalence and Correlates of Somatic Symptom Disorder in a Self-Recruited Sample.

BACKGROUND: Somatic symptom disorder (SSD) is characterized by a persistent and distressing psychological reaction to somatic symptoms. In pain disorders, the preoccupation with physical symptoms is associated with poor long-term outcomes. SSD may therefore be of use to identify and help chronic pain patients with particular needs. OBJECTIVE: To test the hypothesis that in fibromyalgia, SSD is associated with higher anxiety sensitivity, health anxiety, and reactivity to pain, in addition to lower nonreactivity to inner experiences. In addition, to investigate if individuals with SSD report a larger impact of fibromyalgia core symptoms, more somatic symptoms, and higher psychiatric comorbidity. METHODS: Using data from a clinical trial involving self-referred individuals with fibromyalgia, we compared participants with SSD to participants without SSD using t-tests and logistic regression. RESULTS: Forty-nine out of 140 participants (35%) had SSD. Most findings corroborate that individuals with fibromyalgia who also meet criteria for SSD are worse off in terms of traits previously found to be predictive of a poor course in pain disorders. Post hoc analyses indicated that this could not be explained merely by a higher level of fibromyalgia core symptoms. CONCLUSION: SSD appears to be associated with a higher symptom burden in fibromyalgia, but further research is needed to draw firm conclusions regarding the reliability, acceptability, and utility of the SSD diagnosis in the clinic.

Approach as a key for success: Reduced avoidance behaviour mediates the effect of exposure therapy for fibromyalgia.

Fibromyalgia (FM) is a prevalent chronic pain disorder associated with large suffering and substantial societal costs. Pain-related avoidance behaviour and hypervigilance to bodily symptoms are common in FM and contribute in maintaining and exacerbating the disorder. Exposure therapy targeting avoidance behaviours and hypervigilance has shown promise in the treatment of FM. The present study investigated mediators of treatment outcome in exposure therapy for FM. We used data from a randomised trial, where 140 participants were allocated to 10-week internet-delivered exposure therapy or to a waiting-list control condition. The main outcome variable (FM symptoms) and the hypothesized mediators (FM-related avoidance behaviour, mindful non-reactivity and FM-related worry) were measured weekly throughout treatment. Mediation analyses were conducted using linear mixed effects models with bootstrap replication and time-lagged analysis. Results indicated that all three process variables were significant mediators of FM severity. However, in the time-lagged analyses, only FM-related avoidance behaviour displayed a unidirectional relationship over time with FM symptoms, suggesting a causal effect. Thus, results illustrate that changes in avoidance behaviour mediate the outcome of exposure on FM symptoms, which implies that avoidance behaviour is an important treatment target in exposure therapy.

Cost-Effectiveness and Cost-Utility of Internet-Delivered Exposure Therapy for Fibromyalgia: Results From a Randomized, Controlled Trial.

Fibromyalgia (FM) is a prevalent and debilitating chronic pain disorder associated with a substantial economic burden. Although there are several studies investigating the effectiveness of psychological treatments such as cognitive-behavioral therapy for FM, studies on cost-effectiveness are scarce. The aim of the present study was to investigate the cost-effectiveness of Internet-delivered exposure therapy (iExp) for FM. We used health economic data from a recently conducted randomized, controlled trial, where 140 participants were randomized to either iExp or a waitlist control (WLC) condition. Economic data were collected at pre-treatment, post-treatment, and at the 1-year follow-up. Treatment effectiveness in relation to costs were analyzed using both a societal perspective (including all direct and indirect costs) and a health care unit perspective (including only the direct treatment costs). Bootstrapped net benefit regression analyses were also conducted, comparing the difference in costs and effects between iExp and WLC, within different willingness-to-pay scenarios. Results showed that the incremental cost-effectiveness ratio was -$15,295, indicating that iExp was highly cost-effective as each successfully treated case (treatment responder) was associated with a substantial net reduction in costs. The robustness of the results was tested in 2 different sensitivity analyses, where iExp remained cost-effective, even in a willingness-to-pay-scenario of $0. We conclude that iExp is a cost-effective treatment that generates large societal cost savings. PERSPECTIVE: Health-economic evaluations of psychological interventions for FM are scarce. This study is a cost-effectiveness analysis of Internet-delivered exposure therapy for patients with FM. Results showed that iExp was highly cost-effective compared with no treatment, where each successfully treated case generated a substantial societal cost saving.

Internet-Delivered Exposure Therapy for Fibromyalgia: A Randomized Controlled Trial.

BACKGROUND: Fibromyalgia (FM) is a common and disabling chronic pain disorder, for which existing pharmacological and psychological treatments have yet yielded insufficient effects. Previous literature has shown that exposure therapy may be an effective treatment for chronic pain. This study constitutes the first randomized controlled trial evaluating exposure therapy for FM. METHODS: A total of 140 participants with diagnosed FM were randomized to a 10-week Internet-delivered exposure treatment (iExp; n=70) or a waitlist control condition (WLC; n=70). Primary outcome measure were FM symptoms and impact, and secondary outcome measures were fatigue, disability, quality of life, pain-related distress and avoidance behaviors, insomnia, depression, and anxiety. RESULTS: Data retention was high (100% data completion at posttreatment for primary outcome, 96% at 6-month follow-up and 94% at 12-month follow-up). Results showed that participants in the iExp group made large and superior improvements compared with WLC on FM symptoms and impact (B, -1.93; z, -10.14; P<0.001, between-group Cohen d=0.90), as well as all secondary outcomes (between-group Cohen d ranging from 0.44 to 1.38) with sustained results. CONCLUSIONS: We conclude that iExp seems to be an efficacious treatment for FM compared with no treatment, and the results also highlight the potential increase of accessibility by using the Internet format to deliver psychological treatments for these patients. Future trials with active control conditions are warranted.

Integrating evolutionary and regulatory information with a multispecies approach implicates genes and pathways in obsessive-compulsive disorder.

Obsessive-compulsive disorder is a severe psychiatric disorder linked to abnormalities in glutamate signaling and the cortico-striatal circuit. We sequenced coding and regulatory elements for 608 genes potentially involved in obsessive-compulsive disorder in human, dog, and mouse. Using a new method that prioritizes likely functional variants, we compared 592 cases to 560 controls and found four strongly associated genes, validated in a larger cohort. NRXN1 and HTR2A are enriched for coding variants altering postsynaptic protein-binding domains. CTTNBP2 (synapse maintenance) and REEP3 (vesicle trafficking) are enriched for regulatory variants, of which at least six (35%) alter transcription factor-DNA binding in neuroblastoma cells. NRXN1 achieves genome-wide significance (p = 6.37 × 10-11) when we include 33,370 population-matched controls. Our findings suggest synaptic adhesion as a key component in compulsive behaviors, and show that targeted sequencing plus functional annotation can identify potentially causative variants, even when genomic data are limited.Obsessive-compulsive disorder (OCD) is a neuropsychiatric disorder with symptoms including intrusive thoughts and time-consuming repetitive behaviors. Here Noh and colleagues identify genes enriched for functional variants associated with increased risk of OCD.

On the biosynthesis of 15-HETE and eoxin C4 by human airway epithelial cells.

Several lines of evidence indicate that 15-lipoxygenase type 1 (15-LO-1) plays a pathophysiological role in asthma. The aim for this study was to investigate the 15-LO-1 expression and activity in primary human airway epithelial cells cultivated on micro-porous filters at air-liquid interface. Incubation of human airway epithelial cells with arachidonic acid led to the formation of 15(S)-hydroxy-eicosatetraenoic acid (15-HETE) and exposing the cells to bacteria or physical injury markedly increased their production of 15-HETE. The cells were also found to convert arachidonic acid to eoxin C4 (EXC4). Subcellular fractionation revealed that the conversion of EXA4 to EXC4 was catalyzed by a soluble glutathione transferase (GST). The GST P1-1 enzyme was found to possess the highest activity of the investigated soluble GSTs. Following IL-4 treatment of airway epithelial cells, microarray analysis confirmed high expression of 15-LO-1 and GST P1-1, and immunohistochemical staining of bronchial biopsies revealed co-localization of 15-LO-1 and GST P1-1 in airway epithelial cells. These results indicate that respiratory infection and cell injury may activate the 15-LO pathway in airway epithelial cells. Furthermore, we also demonstrate that airway epithelial cells have the capacity to produce EXC4.

Internet-delivered acceptance and values-based exposure treatment for fibromyalgia: a pilot study.

BACKGROUND: Acceptance and commitment therapy (ACT) is a promising treatment option for fibromyalgia (FM). Studies have shown that many cognitive behavioral protocols can be transferred to the Internet with sustained efficacy. However, no study has investigated the effect on an Internet-delivered ACT-based protocol for FM. This study evaluated the efficacy, acceptability, and the health economic effects of an Internet-delivered acceptance and values-based exposure treatment for FM. METHODS: This open pilot trial included 41 self-referred women with a FM diagnosis. The 10-week Internet-delivered treatment included acceptance, mindfulness, work with life-values, and systematic exposure to FM symptoms and FM-related situations. Participants also had regular contact with an assigned online therapist. Assessments were made at pretreatment, post-treatment, and 6-month follow-up. RESULTS: The treatment was completed by 70% of the participants. Attrition rates were low, with 98% completing the post-treatment assessment and 90% completing the 6-month follow-up assessment. Multiple imputations were used to replace missing values. Pre- to post-treatment within-group effect sizes were in the moderate to large range (Cohen's d = 0.62-1.56) on measures of FM symptoms and impact, disability, quality of life, depression, anxiety, fatigue, and psychological flexibility. All improvements were maintained at follow-up. Economical analyses revealed significant societal cost reductions that offset the treatment costs within 2 months of treatment completion. CONCLUSIONS: An Internet-delivered psychological treatment based on acceptance and exposure principles seems to be an efficacious, acceptable, and cost-effective treatment for FM. Randomized controlled trials are needed to confirm these results.

Pancreatic cancer, healthcare cost, and loss of productivity: a register-based approach.

BACKGROUND: Despite the fact that pancreatic cancer is the fourth leading cause of cancer-related death, there is little empirical evidence on its direct healthcare costs and, especially, its indirect costs due to loss of production. METHODS: The present study is a retrospective analysis of all patients with pancreatic cancer (excluding endocrine cancer) in the primary catchment area of Lund University Hospital, Sweden, during the period 2005-2007. Detailed information on all diagnostic and therapeutic investigations, interventions, and postoperative course and long-term follow-up was collected, as well as absenteeism from work due to the health problem, from which direct costs were calculated. The indirect costs for loss of production due to sickness and premature death were calculated by the human capital method. A total of 83 patients were included, for an incidence rate of 9.9 patients/100,000 inhabitants. RESULTS: Direct treatment cost per pancreatic-cancer patient was estimated at EUR 16,066 for each patient's remaining lifetime. Hospitalization accounted for the major expenditure-60% of the lifetime treatment cost. Patients with resectable tumor had a mean cost of EUR 19,809; locally advanced disease, EUR 14,899; and metastatic disease, 16,179. Younger patients and men had a higher than average lifetime treatment cost. The loss of productivity was estimated at EUR 287,420 per patient younger than 65 years of age, of which premature mortality accounted for 79%. CONCLUSIONS: Adding the cost of palliative care estimated in a previous Swedish study, health-care costs and productivity losses for pancreatic cancer would add up to a substantial economic burden for Sweden at large in 2009 (population 9.1 million), between EUR 86 million and EUR 93 million.

Interleukin-13 stimulation of the mediastinal B-cell lymphoma cell line Karpas-1106P induces a phenotype resembling the Hodgkin lymphoma cell line L1236.

OBJECTIVE: Primary mediastinal B-cell lymphoma (PMBCL) and Hodgkin lymphoma (HL) share many biological and clinical characteristics supporting a common pathogenetic pathway. Interleukin (IL)-13 has an important pathophysiological role in HL. In this study, we asked the question of whether IL-13 is a major contributor to the observed difference in features of inflammation between HL and PMBCL. MATERIALS AND METHODS: Expression of IL-13 and IL-4 receptors was studied by flow cytometry, expression of a functional cysteinyl leukotriene receptor type 1 (CysLT1R) was investigated by calcium flux measurement, expression and activity of 15-lipoxygenase type 1 (15-LO-1) was determined by Western blot and reversed-phase high-performance liquid chromatography, respectively, and cytokines were quantified by Bioplex detection. RESULTS: Stimulation of the PMBCL cell line Karpas-1106P with IL-13 or IL-4 induced a proinflammatory phenotype similar to that of the HL cell line L1236. Upon interleukin stimulation of the PMBCL cell line, the cellular size increased and cells became multinucleated. Cells also expressed CysLT1R and 15-LO-1, and produced the proinflammatory eoxins. The IL-13 or IL-4 treated PMBCL cell line and the HL cell line secreted a similar set of cytokines such as IL-6, tumor necrosis factor-alpha, interferon-inducible protein-10, interferon-gamma, and RANTES. CONCLUSIONS: IL-13 or IL-4 stimulation of the PMBCL cell line Karpas-1106P induced an inflammatory phenotype that resembles that of the HL cell line. Our results suggest that the autocrine release of IL-13 in HL is one critical factor that can at least partly explain the difference in phenotype between these two lymphoma entities.

Hodgkin Reed-Sternberg cells express 15-lipoxygenase-1 and are putative producers of eoxins in vivo: novel insight into the inflammatory features of classical Hodgkin lymphoma.

Classical Hodgkin lymphoma has unique clinical and pathological features and tumour tissue is characterized by a minority of malignant Hodgkin Reed-Sternberg cells surrounded by inflammatory cells. In the present study, we report that the Hodgkin lymphoma-derived cell line L1236 has high expression of 15-lipoxygenase-1 and that these cells readily convert arachidonic acid to eoxin C(4), eoxin D(4) and eoxin E(4). These mediators were only recently discovered in human eosinophils and mast cells and found to be potent proinflammatory mediators. Western blot and immunocytochemistry analyses of L1236 cells demonstrated that 15-lipoxygenase-1 was present mainly in the cytosol and that the enzyme translocated to the membrane upon calcium challenge. By immunohistochemistry of Hodgkin lymphoma tumour tissue, 15-lipoxygenase-1 was found to be expressed in primary Hodgkin Reed-Sternberg cells in 17 of 20 (85%) investigated biopsies. The enzyme 15-lipoxygenase-1, however, was not expressed in any of 10 biopsies representing nine different subtypes of non-Hodgkin lymphoma. In essence, the expression of 15-lipoxygenase-1 and the putative formation of eoxins by Hodgkin Reed-Sternberg cells in vivo are likely to contribute to the inflammatory features of Hodgkin lymphoma. These findings may have important diagnostic and therapeutic implications in Hodgkin lymphoma. Furthermore, the discovery of the high 15-lipoxygenase-1 activity in L1236 cells demonstrates that this cell line comprises a useful model system to study the chemical and biological roles of 15-lipoxygenase-1.

Interaction of human 15-lipoxygenase-1 with phosphatidylinositol bisphosphates results in increased enzyme activity.

15-lipoxygenase-1 (15-LO-1) can oxygenate both free fatty acids and fatty acids bound to membrane phospholipids. The regulation of the activity of membrane associated 15-LO-1 is poorly understood. Here we demonstrate that calcium ionophore stimulates the translocation of 15-LO-1 to the plasma membrane in human dendritic cells. In a protein-lipid overlay assay, 15-LO-1 was capable of interacting with several phosphoinositides. In the presence of calcium, addition of phosphatidylinositol-4.5-bisphosphate (PI(4.5)P(2)) or PI(3.4)P(2) to the vesicles containing arachidonic acid, led to the formation of approximately three times more 15-HETE than vesicles without phosphoinositides and up to seven times more 15-HETE than vesicles without both calcium and phosphoinositides. The Vmax was unchanged but the apparent Km of 15-LO-1 towards arachidonic acid was significantly lower in the presence of PI(4.5)P(2) or PI(3.4)P(2) in the vesicles in comparison to vesicles with PC only. Taken together, this report demonstrates that human 15-LO-1 binds to PI(4.5)P(2) and PI(3.4)P(2) and that these phospholipids stimulate enzyme activity in the presence of calcium in a vesicle based assay.