Pre-exercise protein intake is associated with reduced time in hypoglycaemia among adolescents with type 1 diabetes

AIM

Secondary analyses were conducted from a randomized trial of an adaptive behavioural intervention to assess the relationship between protein intake (g and g/kg) consumed within 4 h before moderate-to-vigorous physical activity (MVPA) bouts and glycaemia during and following MVPA bouts among adolescents with type 1 diabetes (T1D).

MATERIALS AND METHODS

Adolescents (n = 112) with T1D, 14.5 (13.8, 15.7) years of age and 36.6% overweight/obese, provided measures of glycaemia using continuous glucose monitoring [percentage of time above range (>180 mg/dl), time in range (70-180 mg/dl), time below range (TBR; <70 mg/dl)], self-reported physical activity (previous day physical activity recalls), and 24 h dietary recall data at baseline and 6 months post-intervention. Mixed effects regression models adjusted for design (randomization assignment, study site), demographic, clinical, anthropometric, dietary, physical activity and timing covariates estimated the association between pre-exercise protein intake on percentage of time above range, time in range and TBR during and following MVPA.

RESULTS

Pre-exercise protein intakes of 10-19.9 g and >20 g were associated with an absolute reduction of -4.41% (p = .04) and -4.83% (p = .02) TBR during physical activity compared with those who did not consume protein before MVPA. Similarly, relative protein intakes of 0.125-0.249 g/kg and ≥0.25 g/kg were associated with -5.38% (p = .01) and -4.32% (p = .03) absolute reductions in TBR during physical activity. We did not observe a significant association between protein intake and measures of glycaemia following bouts of MVPA.

CONCLUSIONS

Among adolescents with T1D, a dose of ≥10 g or ≥0.125 g/kg of protein within 4 h before MVPA may promote reduced time in hypoglycaemia during, but not following, physical activity.

GPAT1 Activity and Abundant Palmitic Acid Impair Insulin Suppression of Hepatic Glucose Production in Primary Mouse Hepatocytes

BACKGROUND

Glycerol-3-phosphate acyltransferase (GPAT) activity is correlated with obesity and insulin resistance in mice and humans. However, insulin resistance exists in people with normal body weight, and individuals with obesity may be metabolically healthy, implying the presence of complex pathophysiologic mechanisms underpinning insulin resistance.

OBJECTIVE

We asked what conditions related to GPAT1 must be met concurrently for hepatic insulin resistance to occur.

METHODS

Mouse hepatocytes were overexpressed with GPATs via adenoviral infection or exposed to high or low concentrations of glucose. Glucose production by the cells and phosphatidic acid (PA) content in the cells were assayed, GPAT activity was measured, relative messenger RNA expressions of sterol-regulatory element-binding protein 1c (SREBP1c), carbohydrate response element-binding protein (ChREBP), and GPAT1 were analyzed, and insulin signaling transduction was examined.

RESULTS

Overexpressing GPAT1 in mouse hepatocytes impaired insulin's suppression of glucose production, together with an increase in both N-ethylmaleimide-resistant GPAT activity and the content of di-16:0 PA. Akt-mediated insulin signaling was inhibited in hepatocytes that overexpressed GPAT1. When the cells were exposed to high-glucose concentrations, insulin suppression of glucose production was impaired, and adding palmitic acid exacerbated this impairment. High-glucose exposure increased the expression of SREBP1c, ChREBP, and GPAT1 by ∼2-, 5-, and 5.7-fold, respectively. The addition of 200 mM palmitic acid or linoleic acid to the culture media did not change the upregulation of expression of these genes by high glucose. High-glucose exposure increased di-16:0 PA content in the cells, and adding palmitic acid further increased di-16:0 PA content. The effect was specific to palmitic acid because linoleic acid did not show these effects.

CONCLUSION

These data demonstrate that high-GPAT1 activity, whether induced by glucose exposure or acquired by transfection, and abundant palmitic acid can impair insulin's ability to suppress hepatic glucose production in primary mouse hepatocytes.

Post-Exercise Protein Intake May Reduce Time in Hypoglycemia Following Moderate-Intensity Continuous Exercise among Adults with Type 1 Diabetes

Little is known about the role of post-exercise protein intake on post-exercise glycemia. Secondary analyses were conducted to evaluate the role of post-exercise protein intake on post-exercise glycemia using data from an exercise pilot study. Adults with T1D (n = 11), with an average age of 33.0 ± 11.4 years and BMI of 25.1 ± 3.4, participated in isoenergetic sessions of high-intensity interval training (HIIT) or moderate-intensity continuous training (MICT). Participants completed food records on the days of exercise and provided continuous glucose monitoring data throughout the study, from which time in range (TIR, 70-180 mg/dL), time above range (TAR, >180 mg/dL), and time below range (TBR, <70 mg/dL) were calculated from exercise cessation until the following morning. Mixed effects regression models, adjusted for carbohydrate intake, diabetes duration, and lean mass, assessed the relationship between post-exercise protein intake on TIR, TAR, and TBR following exercise. No association was observed between protein intake and TIR, TAR, or TBR (p-values ≥ 0.07); however, a borderline significant reduction of -1.9% (95% CI: -3.9%, 0.0%; p = 0.05) TBR per 20 g protein was observed following MICT in analyses stratified by exercise mode. Increasing post-exercise protein intake may be a promising strategy to mitigate the risk of hypoglycemia following MICT.

Non-esterified erythrocyte linoleic acid, arachidonic acid, and subjective sleep outcomes

OBJECTIVE

This study investigated whether non-esterified erythrocyte omega-6 PUFAs were associated with subjective assessment of sleep quality and duration, and risk for obstructive sleep apnea.

METHODS

In this secondary analysis of the cross-sectional OPPERA-II study, 538 adults completed the Pittsburgh Sleep Quality Index (PSQI), reported their usual hours of sleep, and answered STOP screening questions for obstructive sleep apnea. Circulating non-esterified erythrocyte concentrations of omega-6 PUFA linoleic acid and arachidonic acid were quantified by liquid chromatography tandem mass spectroscopy. Sleep outcomes were dichotomized as poor (PSQI ≤5) vs good (PSQI ≥6) sleep quality, insufficient or excessive (≤6 or >9 h) vs good (7-9 h) sleep duration, and high (≥2 affirmative responses) vs low (<2 affirmative responses) risk for obstructive sleep apnea. Non-esterified omega-6 PUFAs and the continuous covariates of body mass index, Short Form (SF) 12 Health Survey Physical and Mental Component scores and resting measures of systolic and diastolic blood pressure were standardized for multivariable analysis. Categorical covariates were study site, age, sex, and race/ethnicity. Multivariable-adjusted logistic regression first estimated odds ratios (OR) and 95% confidence limits (CL) for sleep outcomes using linoleic acid as the main exposure. Analysis was then repeated using arachidonic acid as the main exposure.

RESULTS

In the multivariable-adjusted model, each standard deviation increase in non-esterified erythrocyte linoleic acid was associated with higher odds of poor sleep quality (OR=1.2, 95% CL: 1.1, 1.5), insufficient or excessive sleep (OR= 1.3, 95% CL: 1.1, 1.6) and high-risk for obstructive sleep apnea (OR=1.3, 95% CL: 1.1, 1.6). Likewise, for each standard deviation increase in non-esterified erythrocyte arachidonic acid, odds increased of poor sleep quality (OR=1.2, 95% CL: 1.1, 1.5), and insufficient or excessive sleep (OR=1.2, 95% CL: 1.1, 1.5). Odds of being high risk for obstructive sleep apnea increased with greater circulating arachidonic acid, but the association did not reach statistical significance (OR=1.1, 95% CL: 0.9, 1.4).

CONCLUSION

Non-esterified erythrocyte linoleic acid and arachidonic acid were associated with poor sleep quality and insufficient or excessive sleep duration. Linoleic acid, but not arachidonic acid, was also associated with high risk for obstructive sleep apnea.

Behavioral changes in FPR2/ALX and Chemr23 receptor knockout mice are exacerbated by prenatal alcohol exposure

Introduction

Prenatal alcohol exposure (PAE) causes neuroinflammation that may contribute to the pathophysiology underlying Fetal Alcohol Spectrum Disorder. Supplementation with omega-3 polyunsaturated fatty acids (PUFAs) has shown success in mitigating effects of PAE in animal models, however, the underlying mechanisms are unknown. Some PUFA metabolites, specialized pro-resolving mediators (SPMs), play a role in the resolution phase of inflammation, and receptors for these are in the brain.

Methods

To test the hypothesis that the SPM receptors FPR2 and ChemR23 play a role in PAE-induced behavioral deficits, we exposed pregnant wild-type (WT) and knockout (KO) mice to alcohol in late gestation and behaviorally tested male and female offspring as adolescents and young adults.

Results

Maternal and fetal outcomes were not different among genotypes, however, growth and behavioral phenotypes in the offspring did differ and the effects of PAE were unique to each line. In the absence of PAE, ChemR23 KO animals showed decreased anxiety-like behavior on the elevated plus maze and FPR2 KO had poor grip strength and low activity compared to age-matched WT mice. WT mice showed improved performance on fear conditioning between adolescence and young adulthood, this was not seen in either KO.

Discussion

This PAE model has subtle effects on WT behavior with lower activity levels in young adults, decreased grip strength in males between test ages, and decreased response to the fear cue indicating an effect of alcohol exposure on learning. The PAE-mediated decreased response to the fear cue was also seen in ChemR23 KO but not FPR2 KO mice, and PAE worsened performance of adolescent FPR2 KO mice on grip strength and activity. Collectively, these findings provide mechanistic insight into how PUFAs could act to attenuate cognitive impairments caused by PAE.

A High Protein Diet Is Associated with Improved Glycemic Control Following Exercise among Adolescents with Type 1 Diabetes

Nutritional strategies are needed to aid people with type 1 diabetes (T1D) in managing glycemia following exercise. Secondary analyses were conducted from a randomized trial of an adaptive behavioral intervention to assess the relationship between post-exercise and daily protein (g/kg) intake on glycemia following moderate-to-vigorous physical activity (MVPA) among adolescents with T1D. Adolescents (n = 112) with T1D, 14.5 (13.8, 15.7) years of age, and 36.6% overweight or obese, provided measures of glycemia using continuous glucose monitoring (percent time above range [TAR, >180 mg/dL], time-in-range [TIR, 70-180 mg/dL], time-below-range [TBR, <70 mg/dL]), self-reported physical activity (previous day physical activity recalls), and 24 h dietary recall data at baseline and 6 months post-intervention. Mixed effects regression models adjusted for design (randomization assignment, study site), demographic, clinical, anthropometric, dietary, physical activity, and timing covariates estimated the association between post-exercise and daily protein intake on TAR, TIR, and TBR from the cessation of MVPA bouts until the following morning. Daily protein intakes of ≥1.2 g/kg/day were associated with 6.9% (p = 0.03) greater TIR and -8.0% (p = 0.02) less TAR following exercise, however, no association was observed between post-exercise protein intake and post-exercise glycemia. Following current sports nutrition guidelines for daily protein intake may promote improved glycemia following exercise among adolescents with T1D.

Circulating Polyunsaturated Fatty Acids and Pain Intensity in Five Chronic Pain Conditions

Pain intensity is well-known to be influenced by a wide range of biobehavioral variables. Nutritional factors, however, have not been generally considered for their potential importance. This cross-sectional study examined associations between erythrocyte omega-6 (n-6) and omega-3 (n-3) polyunsaturated fatty acids (PUFAs) and pain intensity in 605 adults. Pain intensity was computed on a 0 to 100 numeric rating scale from questions about 5 chronic pain conditions: orofacial pain, headache, low back pain, irritable bowel syndrome, and bodily pain. For each pain condition, multiple linear regression tested the hypothesis that a higher ratio of n-6 arachidonic acid to the sum of n-3 eicosapentaenoic acid and docosahexaenoic acid (AA/(EPA+DHA) was associated with greater pain intensity. In covariate-adjusted analysis, orofacial pain intensity increased 5.7 points (95% CI: 1.4, 9.9) per unit increase in n-6/n-3 PUFA ratio. Likewise, a 1 unit increase in n-6/n-3 PUFA ratio was associated with significant increases in pain intensity (range 5-8 points) of headache pain, low back pain, and bodily pain, but not abdominal pain. Separate multiple linear regression models investigated the independent strength of association of individual PUFAs to the intensity of each pain condition. Overall, n-3 docosahexaenoic acid was most strongly, and inversely, associated with pain intensity. PERSPECTIVE: A higher ratio of n-6/n-3 long-chain polyunsaturated fatty acids was associated greater pain intensity for orofacial pain, headache, low back pain, and bodily pain, but not abdominal pain. The n-6/n-3 PUFA ratio was more consistently associated with pain intensity than any individual constituent of the long-chain PUFA ratio.

Ratio of Omega-6/Omega-3 Polyunsaturated Fatty Acids Associated With Somatic and Depressive Symptoms in People With Painful Temporomandibular Disorder and Irritable Bowel Syndrome

Somatic symptom disturbance is among the strongest predictors of painful temporomandibular disorder (TMD). Related psychological constructs, such as anxiety and depression, respond therapeutically to omega-3 polyunsaturated fatty acids (PUFAs) in clinical trials. This cross-sectional study investigated associations between the omega-6/omega-3 PUFA ratio and somatic symptom disturbance and depressive symptoms in a community-based sample of 501 adults and determined whether these associations differed between adults with and without TMD or irritable bowel syndrome (IBS). Liquid chromatography tandem mass spectrometry quantified PUFAs in circulating erythrocytes. Somatic symptoms and depression were quantified using Symptom Checklist-90-Revised subscales. Presence or absence of TMD and IBS, respectively, were determined by clinical examination and Rome III screening questions. The standardized beta coefficient for the omega-6/omega-3 long-chain PUFA ratio was 0.26 (95% confidence limits (CL): 0.08, 0.43) in a multivariable linear regression model in which somatic symptom disturbance was the dependent variable. When modelling depressive symptoms as the dependent variable, the standardized beta coefficient was 0.17 (95% CL:0.01, 0.34). Both associations were stronger among TMD cases and IBS cases than among non-cases. Future randomized control trials that lower the omega-6/omega-3 PUFA ratio could consider somatic or depressive symptoms as a therapeutic target for TMD or IBS pain. PERSPECTIVE: In people with TMD or IBS, a high n-6/n-3 PUFA ratio was positively associated with somatic symptom disturbance and depressive symptoms. Both measures of psychological distress were elevated in people with painful TMD and IBS. Future randomized clinical trials will determine whether lowering the n-6/n-3 ratio is therapeutic for pain.

Circulating Omega-6 and Omega-3 Polyunsaturated Fatty Acids in Painful Temporomandibular Disorder and Low Back Pain

Preclinical studies demonstrate opposing effects of long-chain polyunsaturated fatty acid (PUFA) metabolites on inflammation and nociception. Omega-6 (n-6) PUFAs amplify both processes while omega-3 (n-3) PUFAs inhibit them. This cross-sectional study examined relationships between PUFAs in circulating erythrocytes and 2 chronic idiopathic pain conditions: temporomandibular disorder (TMD) and low back pain in a community-based sample of 503 U.S. adults. Presence or absence of TMD and low back pain, respectively, were determined by clinical examination and by responses to established screening questions. Liquid chromatography-tandem mass spectrometry quantified PUFAs. In multivariable logistic regression models, a higher ratio of n-6/n-3 long-chain PUFAs was associated with greater odds of TMD (odds ratio ((OR) = 1.75, 95% confidence limits (CL): 1.16, 2.64) and low back pain (OR = 1.63, 95% CL: 1.07, 2.49). Higher levels of the pronociceptive n-6 long-chain arachidonic acid (AA) were associated with a greater probability of both pain conditions for women, but not men. Higher levels of the antinociceptive long-chain n-3 PUFAs eicosapentaenoic and docosahexaenoic acids were associated with a lower probability of both pain conditions for men, but not women. As systemic inflammation is not a hallmark of these conditions, PUFAs may influence idiopathic pain through other mechanisms. PERSPECTIVE: This cross-sectional clinical study found that a higher ratio of circulating n-6/n-3 long-chain PUFAs was associated with greater odds of 2 common chronic overlapping pain conditions. This suggests that the pro and antinociceptive properties of n-6 and n-3 PUFAs, respectively, influence pain independently of their well-established inflammatory pathways.

Circulating polyunsaturated fatty acids, pressure pain thresholds, and nociplastic pain conditions

OBJECTIVE

Polyunsaturated fatty acids (PUFAs) play a role in pain regulation. This study sought to determine whether free PUFAs found in red blood cells also play a role in nociceptive processing. We examined associations between circulating PUFAs and nociceptive thresholds to noxious mechanical stimuli. We also determined whether nociceptive thresholds were associated with nociplastic pain conditions.

METHODS

This cross-sectional study used stored red bloods cells and data from 605 adult participants in the OPPERA-2 study of chronic overlapping pain conditions. In OPPERA-2 adults completed quantitative sensory testing in which pressure algometry measured deep muscular tissue sensitivity at six anatomical sites. Standardized protocols classified adults for presence or absence of five nociplastic pain conditions: temporomandibular disorder, headache, low back pain, irritable bowel syndrome and fibromyalgia. Liquid chromatography tandem mass spectroscopy quantified erythrocyte PUFAs. We conducted three sets of analyses. First, a multivariable linear regression model assessed the association between n-6/n-3 PUFA ratio and the number of overlapping nociplastic pain conditions. Second, a series of 36 multivariable linear regression models assessed covariate-adjusted associations between PUFAs and nociceptive thresholds at each of six anatomical sites. Third, a series of 30 multivariable linear regression models assessed covariate-adjusted associations between nociceptive thresholds at six anatomical sites and each of five pain conditions.

RESULTS

In multiple linear regression, each unit increase in n-6/n-3 PUFA ratio was associated with more pain conditions (β = 0.30, 95% confidence limits: 0.07, 0.53, p = 0.012). Omega-6 linoleic acid and arachidonic acid were negatively associated with lower nociceptive thresholds at three and at five, respectively, anatomical sites. In contrast, omega-3 alpha-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid and the n-6/n-3 PUFA ratio were not associated with nociceptive thresholds at any site. Pain cases had significantly lower nociceptive thresholds than non-case controls at all anatomical sites.

CONCLUSION

A higher n-6/n-3 PUFA ratio was associated with more pain conditions. Omega-6 PUFAs may promote a generalized upregulation of nociceptive processing.

Live cell imaging of oxidative stress in human airway epithelial cells exposed to isoprene hydroxyhydroperoxide

Exposure to respirable air particulate matter (PM2.5) in ambient air is associated with morbidity and premature deaths. A major source of PM2.5 is the photooxidation of volatile plant-produced organic compounds such as isoprene. Photochemical oxidation of isoprene leads to the formation of hydroperoxides, environmental oxidants that lead to inflammatory (IL-8) and adaptive (HMOX1) gene expression in human airway epithelial cells (HAEC). To examine the mechanism through which these oxidants alter intracellular redox balance, we used live-cell imaging to monitor the effects of isoprene hydroxyhydroperoxides (ISOPOOH) in HAEC expressing roGFP2, a sensor of the glutathione redox potential (EGSH). Non-cytotoxic exposure of HAEC to ISOPOOH resulted in a rapid and robust increase in EGSH that was independent of the generation of intracellular or extracellular hydrogen peroxide. Our results point to oxidation of GSH through the redox relay initiated by glutathione peroxidase 4, directly by ISOPOOH or indirectly by ISOPOOH-generated lipid hydroperoxides. We did not find evidence for involvement of peroxiredoxin 6. Supplementation of HAEC with polyunsaturated fatty acids enhanced ISOPOOH-induced glutathione oxidation, providing additional evidence that ISOPOOH initiates lipid peroxidation of cellular membranes. These findings demonstrate that ISOPOOH is a potent environmental airborne hydroperoxide with the potential to contribute to oxidative burden of human airway posed by inhalation of secondary organic aerosols.

Sex Differences in Pulmonary Eicosanoids and Specialized Pro-Resolving Mediators in Response to Ozone Exposure

Ozone (O3) is a criteria air pollutant known to increase the morbidity and mortality of cardiopulmonary diseases. This occurs through a pulmonary inflammatory response characterized by increased recruitment of immune cells into the airspace, pro-inflammatory cytokines, and pro-inflammatory lipid mediators. Recent evidence has demonstrated sex-dependent differences in the O3-induced pulmonary inflammatory response. However, it is unknown if this dimorphic response is evident in pulmonary lipid mediator metabolism. We hypothesized that there are sex-dependent differences in lipid mediator production following acute O3 exposure. Male and female C57BL/6J mice were exposed to 1 part per million O3 for 3 hours and were necropsied at 6 or 24 hours following exposure. Lung lavage was collected for cell differential and total protein analysis, and lung tissue was collected for mRNA analysis, metabololipidomics, and immunohistochemistry. Compared to males, O3-exposed female mice had increases in airspace neutrophilia, neutrophil chemokine mRNA, pro-inflammatory eicosanoids such as prostaglandin E2, and specialized pro-resolving mediators (SPMs) such as resolvin D5 in lung tissue. Likewise, precursor fatty acids (arachidonic and docosahexaenoic acid; DHA) were increased in female lung tissue following O3 exposure compared to males. Experiments with ovariectomized females revealed that loss of ovarian hormones exacerbates pulmonary inflammation and injury. However, eicosanoid and SPM production were not altered by ovariectomy despite depleted pulmonary DHA concentrations. Taken together, these data indicate that O3 drives an increased pulmonary inflammatory and bioactive lipid mediator response in females. Furthermore, ovariectomy increases susceptibility to O3-induced pulmonary inflammation and injury, as well as decreases pulmonary DHA concentrations.

Novel Mechanisms of Ozone-Induced Pulmonary Inflammation and Resolution, and the Potential Protective Role of Scavenger Receptor BI

INTRODUCTION

Increases in ambient levels of ozone (O3), a criteria air pollutant, have been associated with increased susceptibility and exacerbations of chronic pulmonary diseases through lung injury and inflammation. O3 induces pulmonary inflammation, in part by generating damage-associated molecular patterns (DAMPs), which are recognized by pattern recognition receptors (PRRs), such as toll-like receptors (TLRs) and scavenger receptors (SRs). This inflammatory response is mediated in part by alveolar macrophages (AMs), which highly express PRRs, including scavenger receptor BI (SR-BI). Once pulmonary inflammation has been induced, an active process of resolution occurs in order to prevent secondary necrosis and to restore tissue homeostasis. The processes known to promote the resolution of inflammation include the clearance by macrophages of apoptotic cells, known as efferocytosis, and the production of specialized pro-resolving mediators (SPMs). Impaired efferocytosis and production of SPMs have been associated with the pathogenesis of chronic lung diseases; however, these impairments have yet to be linked with exposure to air pollutants.

SPECIFIC AIMS

The primary goals of this study were: Aim 1 - to define the role of SR-BI in O3-derived pulmonary inflammation and resolution of injury; and Aim 2 - to determine if O3 exposure alters pulmonary production of SPMs and processes known to promote the resolution of pulmonary inflammation and injury.

METHODS

To address Aim 1, female wild-type (WT) and SR-BI-deficient, or knock-out (SR-BI KO), mice were exposed to either O3 or filtered air. In one set of experiments mice were instilled with an oxidized phospholipid (oxPL). Bronchoalveolar lavage fluid (BALF) and lung tissue were collected for the analyses of inflammatory and injury markers and oxPL. To estimate efferocytosis, mice were administered apoptotic cells (derived from the Jurkat T cell line) after O3 or filtered air exposure.

To address Aim 2, male WT mice were exposed to either O3 or filtered air, and levels of SPMs were assessed in the lung, as well as markers of inflammation and injury in BALF. In some experiments SPMs were administered before exposure to O3or filtered air, to determine whether SPMs could mitigate inflammatory or resolution responses. Efferocytosis was measured as in Aim 1.

RESULTS

For Aim 1, SR-BI protein levels increased in the lung tissue of mice exposed to O3, compared with mice exposed to filtered air. Compared with WT controls, SR-BI KO mice had a significant increase in the number of neutrophils in their airspace 24 hours post O3 exposure. The oxPL levels increased in the airspace of both WT and SR-BI KO mice after O3 exposure, compared with filtered air controls. Four hours after instillation of an oxPL, SR-BI KO mice had an increase in BALF neutrophils and total protein, and a nonsignificant increase in macrophages compared with WT controls. O3 exposure decreased efferocytosis in both WT and SR-BI KO female mice.

For Aim 2, mice given SPM supplementation before O3 exposure showed significantly increased AM efferocytosis when compared with the O3exposure control mice and also showed some mitigation of the effects of O3 on inflammation and injury. Several SPMs and their precursors were measured in lung tissue using reverse-phase high performance liquid chromatography (HPLC) with tandem mass spectrometry (MS/MS). At 24 hours after O3 exposure 14R-hydroxydocosahexaenoic acid (HDHA) and 10,17-dihydroxydocosahexaenoic acid (diHDoHE) were significantly decreased in lung tissue, but at 6 hours after exposure, levels of these SPMs increased.

CONCLUSIONS

Our findings identify novel mechanisms by which O3 may induce pulmonary inflammation and also increase susceptibility to and exacerbations of chronic lung diseases.

Long-chain omega-3 fatty acids and headache in the U.S. population

The objective of this study was to assess whether dietary intake of long-chain omega-3 polyunsaturated fatty acids (PUFAs) is associated with lower prevalence of headache in the U.S.

POPULATION

This cross-sectional study used data for a nationally representative sample of 12,317 men and women aged ≥ 20 years participating in the National Health and Nutrition Examination Surveys of 1999-2004. Interviewers recorded self-report of severe headache or migraine in the past three months. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were quantified from 24-hour dietary recall using the U.S. Department of Agriculture National Nutrient Database. Serum concentration of C-reactive protein, a marker of inflammation and potential mediator of PUFA's analgesic properties, was quantified by latex-enhanced nephelometry. Multivariable generalized linear models estimated prevalence ratios (PR) with 95% confidence limits (CL) for severe headache or migraine adjusting for NHANES cycle, sociodemographic characteristics, body mass index and total energy intake. The unadjusted prevalence of severe headache or migraine was 22.0% (females 28.2%, males 15.5%). In multivariable analysis, greater intake of omega-3 PUFAs was associated with lower prevalence of severe headache or migraine: PR 0.94 (95% CL: 0.88, 0.99, p = 0.035) per log unit increase in EPA, and PR 0.94 (95% CL: 0.90, 0.99, p = 0.023) per log unit increase in DHA. The strength of association was greater for non-Mexican Hispanics than for other racial/ethnic groups but was not attenuated after adjustment for C-reactive protein. In conclusion, higher dietary intakes of EPA and DHA were associated with lower prevalence of headache supporting the hypothesis that omega-3 PUFAs may prevent or reduce headache.

The effects of diet-induced obesity on B cell function

B-1 and B-2 B cell subsets carry out a diverse array of functions that range broadly from responding to innate stimuli, antigen presentation, cytokine secretion and antibody production. In this review, we first cover the functional roles of the major murine B cell subsets. We then highlight emerging evidence, primarily in preclinical rodent studies, to show that select B cell subsets are a therapeutic target in obesity and its associated co-morbidities. High fat diets promote accumulation of select murine B cell phenotypes in visceral adipose tissue. As a consequence, B cells exacerbate inflammation and thereby insulin sensitivity through the production of autoantibodies and via cross-talk with select adipose resident macrophages, CD4(+) and CD8(+) T cells. In contrast, interleukin (IL)-10-secreting regulatory B cells counteract the proinflammatory profile and improve glucose sensitivity. We subsequently review data from rodent studies that show pharmacological supplementation of obesogenic diets with long chain n-3 polyunsaturated fatty acids or specialized pro-resolving lipid mediators synthesized from endogenous n-3 polyunsaturated fatty acids boost B cell activation and antibody production. This may have potential benefits for improving inflammation in addition to combating the increased risk of viral infection that is an associated complication of obesity and type II diabetes. Finally, we propose potential underlying mechanisms throughout the review by which B cell activity could be differentially regulated in response to high fat diets.

Abstract 337: The Cardiolipin-targeting Peptide Bendavia Preserves Post-ischemic Mitochondrial Energetics by Sustaining Respiratory Supercomplexes

Bendavia is a mitochondria-targeting peptide currently being tested in the EMBRACE-STEMI trial for reducing injury during acute coronary syndromes. We previously showed that the cardioprotective effects of Bendavia involved improving cardiolipin-dependent mitochondrial membrane fluidity. As membrane fluidity influences the ability of proteins to assemble, we hypothesized that a consequence of augmented membrane fluidity would be higher expression of mitochondrial respiratory supercomplexes. Rat hearts (n=42) were subjected to ischemia-reperfusion (I/R) with or without 1nM Bendavia perfusion beginning at the onset of reperfusion. Left ventricular tissue was split into one of two study arms: 1. Supercomplex expression using blue-native gel electrophoresis (BN-PAGE), or 2. High-resolution respirometry using permeabilized ventricular fibers. For BN-PAGE studies, respiratory supercomplex bands were decreased with I/R, and restored with Bendavia (see figure). High-resolution respirometry studies indicated suppressed Complex I-dependent respiration after I/R (208±19 v 42±9 pmol O2/mg*s in control v I/R, respectively; P<0.05). Complex II-dependent respiration was also lower (753±41 v 168±13 pmol/mg*s in control versus I/R; P<0.05). Perfusion with Bendavia during reperfusion significantly increased Complexes I- (100±13pmol O2/mg*s) and II-dependent (334±63 pmol O2/mg*s) respiration (P<0.05 versus untreated IR for both). Taken together, these data suggest that Bendavia’s protective mechanism of action involves preserving supercomplex-dependent mitochondrial function during cardiac reperfusion.

Abstract 225: The Mitochondria-localizing Peptide Bendavia Reduces Cardiac Injury By Targeting Cardiolipin

Bendavia is a cardioprotective mitochondria-targeting peptide that is currently being utilized in the EMBRACE-STEMI clinical trial for acute coronary syndromes (ACS). Across a variety of pre-clinical models examining ACS and heart failure, administration of Bendavia reduces infarction and coronary “no-reflow”, improves function, preserves mitochondrial energetics, and lowers ROS-dependent cell death. Despite the clear effects in mitigating reperfusion injury, Bendavia’s molecular targets and underlying mechanisms are not fully understood. The objective of these studies was to determine Bendavia’s molecular mechanism of action and pharmacokinetic profile. In diabetic animals, Bendavia treatment reversed the decline in 18:2 cardiolipin composition observed in diabetic heart. In vivo (i.v.) administration of 3H-Bendavia showed tissue distribution that correlated with tissue mitochondrial volume density. 3H-Bendavia levels in heart mitochondria peaked 1 hour after treatment, and by 24 hours there was no discernible 3H-Bendavia in the myocardium. Biologic processing of Bendavia results in two major metabolites, and neither of these metabolites showed cardioprotective efficacy, suggesting that the cardioprotection is unique to the intact, tetra-peptide. In isolated heart cells, 3H-Bendavia uptake was found to be independent of mitochondrial membrane potential, and respiratory studies revealed no discernible uncoupling activity. We then tested the hypothesis that Bendavia selectively targeted cardiolipin biophysical organization by synthesizing lipid vesicles of differing phospholipid composition. Fluorescence quenching and electrostatically sensitive probes revealed Bendavia preferentially associated with cardiolipin-enriched lipid vesicles. We modeled changes in inner membrane lipids during cardiac ischemia/reperfusion. Bendavia augmented membrane microviscosity in proportion to the cardiolipin content. As a number of disease states (heart failure, diabetes, ischemia/reperfusion) are characterized by low membrane microviscosity, Bendavia’s putative ability to restore the lipid microenvironment represents a novel paradigm for preserving tissue bioenergetics.

Differential effects of a saturated and a monounsaturated fatty acid on MHC class I antigen presentation

Lipid overload, associated with metabolic disorders, occurs when fatty acids accumulate in non-adipose tissues. Cells of these tissues use major histocompatibility complex (MHC) class I molecules to present antigen to T cells in order to eliminate pathogens. As obesity is associated with impaired immune responses, we tested the hypothesis that the early stages of lipid overload with saturated fatty acids (SFA) alters MHC class I antigen presentation. Antigen presenting cells (APC) were treated with either the saturated palmitic acid (PA), abundant in the high fat Western diet, or the monounsaturated oleic acid (OA), a component of the Mediterranean diet. PA-treatment lowered APC lysis by activated cytotoxic T lymphocytes and inhibited APC ability to stimulate naïve T cells. Inhibition of immune responses with PA was due to a significant reduction in MHC class I surface expression, inhibition in the rate of APC-T-cell conjugation, and lowering of plasma membrane F-actin levels. OA-treatment had no effect on antigen presentation and upon exposure with PA, prevented the phenotypic effects of PA. OA-treatment conferred protection against changes in antigen presentation by accumulating fatty acids into triglyceride-rich lipid droplets of APC. Our findings establish for the first time a link between the early stages of lipid overload and antigen presentation and suggest that dietary SFA could impair immunity by affecting MHC I-mediated antigen presentation; this could be prevented, paradoxically, by accumulation of triglycerides rich in monounsaturated fatty acids.

Omega 3-fatty acids: health benefits and cellular mechanisms of action

Epidemiological evidence has established that ingestion of long-chain polyunsaturated omega-3 fatty acids (omega-3 PUFAs), abundant in fish oils, have profound effects on many human disorders and diseases, including cardiovascular disease and cancer. Here we briefly review the dietary recommendations and the food sources that are naturally enriched by these fatty acids. There are also a number of products including eggs, bread, and cereals available to supplement omega-3 fatty acid dietary intake. Some of these supplements are proposed to aid different pathological conditions. While the beneficial effects of omega-3 fatty acids can no longer be doubted, their molecular mechanism of action remains elusive. Without question, the action of omega-3 fatty acids is complex and involves a number of integrated signaling pathways. This review focuses on one of the possible cellular mechanisms by which the omega-3 PUFAs, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), may function. Studies with cancer cells suggest that DHA induces cell cycle arrest and apoptosis by activating protein phosphatases, leading to dephosphorylation of retinoblastoma protein (pRB). Protein phosphatases are also involved with the protein Bcl2, which regulates the release of cytochrome c from mitochondria, and eventually, activation of the apoptotic enzyme caspase 3.

Formation of inverted hexagonal phase in SDPE as observed by solid-state (31)P NMR

Docosahexaenoic acid (DHA), the longest and most unsaturated fatty acid commonly found in biological membranes, is known to affect various membrane properties. In a variety of cell membranes, DHA is primarily incorporated in phosphatidylethanolamines, where its function remains poorly understood. In order to understand the role of DHA in influencing membrane structure, we utilize (31)P NMR spectroscopy to study the phase behavior of 1-stearoyl-2-docosahexaenoyl-sn-glycerophosphoethanolamine (SDPE) in comparison to 1-palmitoyl-2-oleoyl-sn-glycerophosphoethanolamine (POPE) from 20 to 50 degrees C. Spectra of SDPE phospholipids show the formation of inverted hexagonal phase (H(II)) from 20 to 50 degrees C; in contrast, POPE mutilamellar dispersions exist in a lamellar liquid-crystalline phase (L(alpha)) at the same temperatures. The ability of SDPE to adopt nonbilayer phases at a physiological temperature may indicate its role in imparting negative curvature stress upon the membrane and may affect local molecular organization including the formation of lipid microdomains within biological membranes.

Lipid phase separation in phospholipid bilayers and monolayers modeling the plasma membrane

It is postulated that biological membrane lipids are heterogeneously distributed into lipid microdomains. Recent evidence indicates that docosahexaenoic acid-containing phospholipids may be involved in biologically important lipid phase separations. Here we investigate the elastic and thermal properties of a model plasma membrane composed of egg sphingomyelin (SM), cholesterol and 1-stearoyl-2-docosahexaenoyl-sn-glycerophosphoethanolamine (SDPE). Two techniques are employed, pressure-area isotherms on monolayers to examine condensation and interfacial elasticity behavior, and differential scanning calorimetry (DSC) on bilayers to evaluate phase separations. Significant levels of condensation are observed for mixtures of SM and cholesterol. Surface elasticity measurements indicate that cholesterol decreases and SDPE increases the in-plane elasticity of SM monolayers. At X(SDPE)> or =0.15 in SM, a more horizontal region emerges in the pressure-area isotherms indicating 'squeeze out' of SDPE from the monolayers. Addition of cholesterol to equimolar amounts of SM and SDPE further increases the amount of 'squeeze out', supporting the concept of phase separation into a cholesterol- and SM-rich liquid ordered phase and a SDPE-rich liquid disordered phase. This conclusion is corroborated by DSC studies where as little as X(Chol)=0.0025 induces a phase separation between the two lipids.

Reverse microdialysis of a dopamine uptake inhibitor in the nucleus accumbens of alcohol-preferring rats: effects on dialysate dopamine levels and ethanol intake

BACKGROUND

The mesolimbic dopamine (DA) system has been implicated in mediating the reinforcing actions of ethanol (EtOH). This study examines the effects of local perfusion of the DA uptake inhibitor GBR12909 (GBR) on (1) DA levels in the nucleus accumbens (NAc) and (2) EtOH drinking in alcohol-preferring rats.

METHODS

Stable drinking of a 15% (v/v) EtOH solution (minimum of 0.75 g/kg body weight) was established in daily 1 hr limited access sessions. Rats were then implanted with bilateral guide cannulae aimed 4 mm above the NAc. After recovery from surgery, concentric microdialysis probes (2 mm dialysis membrane surface) were inserted into the NAc. Most placements were in the shell or overlapping both shell and core. Two days later, the probes were perfused at 1.0 microl/min with artificial cerebral spinal fluid (aCSF) for at least a 90 min washout period followed by collection of five basal samples over 150 min. Rats were then perfused with either aCSF alone or 10, 25, 100, or 200 microM of GBR for 240 min on the first day of microdialysis. During the last 60 min of the drug treatment phase, rats were given their scheduled access to 15% EtOH. All rats were then perfused with aCSF for the last 90 min of the experiment. The following day, the procedure was repeated, but animals that received aCSF on the first day were given a dose of GBR and rats given GBR on the first day received only aCSF.

RESULTS

GBR perfusion increased extracellular NAc DA levels dose dependently to more than 800% of basal levels at 100 to 200 microM but failed to alter EtOH intake (p > 0.05, paired t test) at any concentration tested. Moreover, after 100 microM of GBR perfusion had terminated, the extracellular levels of DA in the NAc remained elevated for approximately 24 hr (790% of day 1 basal; p < 0.05). The increase in dialysate DA levels observed during GBR perfusion with 100 microM was significantly greater for EtOH-experienced rats than for EtOH-naïve rats [F(7,59) = 14.85, p < 0.0001, analysis of variance, Student-Newman-Keuls post hoc test].

CONCLUSIONS

The results suggest (1) that EtOH drinking experience induces neuroadaptations that increase DA release in the NAc, and (2) that additional elevation in synaptic levels of DA in the NAc does not influence the maintenance of ongoing alcohol drinking under scheduled access conditions in alcohol-preferring animals.

Alcohol deprivation effect is prolonged in the alcohol preferring (P) rat after repeated deprivations

BACKGROUND

The alcohol deprivation effect (ADE) is a temporary increase in the ratio of ethanol/total fluid intake and the voluntary intake of ethanol solutions over baseline drinking conditions when ethanol access is reinstated after a period of alcohol deprivation. The ADE has been posited to be an animal model for alcohol craving. The current study examined the effects of initial deprivation length and number of deprivation exposures on the ADE in alcohol-preferring (P) rats.

METHODS

Adult female P rats received 24-hr free-choice access to 10% (v/v) ethanol and water for 6 weeks. Rats were then randomly assigned to five groups deprived of ethanol for 0 (control), 2, 4, 6, or 8 weeks (W). All deprived groups were then given 24-hr access to ethanol for 2 weeks before being deprived of ethanol for another 2 weeks.

RESULTS

After the initial ethanol deprivation period, the deprived groups displayed a similar 2-fold ADE (e.g., 4-W group; 4.6 +/- 0.5 for baseline vs. 10.5 +/- 0.3 g/kg/day for the 1st reinstatement day) during the initial 24-hr period. Ethanol consumption began to return to control levels 48 (7.1 +/- 0.4 g/kg/day) and 72 (6.4 +/- 0.4 g/kg/day) hrs later. In addition, each deprived group showed increases in the ratio of ethanol/total fluid intake upon reinstatement, and there was a tendency for sustained higher ethanol intake ratios during the first 3 postexposure days for the 4-, 6-, and 8-W groups, but only during the first 2 reinstatement days for the 2-W group. The second deprivation did not increase the magnitude of the ADE over that observed in the first deprivation during the initial 24-hr period of re-exposure, but it did prolong the duration of the ADE into the 2nd and 3rd reinstatement day for the 2-, 4-, and 6-W groups and into the 5th reinstatement day for the 8-W group.

CONCLUSIONS

Equivalent robust ADEs can be seen in P rats with deprivation periods of 2-8 W, which suggests that the ADE has a rapid onset and is not affected by the durations of deprivation that were tested. The duration of the ADE was prolonged in P rats exposed to a second deprivation period, suggesting that factors associated with the ADE phenomenon could be strengthened by repeated deprivations.