Clinical correlates of red blood cell omega-3 fatty acid content in male veterans with peripheral arterial disease

The Fish Oil to Reduce Tobacco Use iN Expectant mothers (FORTUNE) feasibility trial

BACKGROUND

Three small clinical trials have suggested that supplementation with n-3 long-chain polyunsaturated fatty acids (eicosapentaenoic acid and docosahexaenoic acid) found in fish oils may reduce nicotine cravings and at higher doses reduce cigarette consumption. Pregnant women who smoke have fewer pharmacologic options to aid them with smoking cessation. Although n-3 long-chain polyunsaturated fatty acid supplementation has been studied in pregnancy, few studies have evaluated doses of ≥4 g per day, and no previous studies have selectively enrolled pregnant women who smoke. High-dose n-3 long-chain polyunsaturated fatty acids may aid cessation but could be poorly tolerated in pregnant women who smoke because of gastrointestinal side effects.

OBJECTIVE

We conducted a feasibility trial to determine the tolerability of high-dose n-3 long-chain polyunsaturated fatty acid supplementation in pregnant women who smoked. We hypothesized that n-3 long-chain polyunsaturated fatty acid doses of 4.2 g a day would be well-tolerated relative to an olive oil placebo. We assessed red blood cell phospholipid membrane concentrations at baseline and end of therapy (4 weeks) and piloted outcomes for a future efficacy trial of n-3 long-chain polyunsaturated fatty acid supplementation for smoking cessation in pregnancy.

STUDY DESIGN

We recruited 28 pregnant women between the gestational ages of 6 and 36 weeks who reported daily cigarette smoking and were motivated to quit to participate in a double-blind placebo-controlled randomized feasibility trial of 4.2 g per day of n-3 long-chain polyunsaturated fatty acid supplementation. Participants reported cigarettes per day, completed the Fagerström Test for Cigarette Dependence, and provided blood, urine, and exhaled CO samples. We used repeated-measures analysis of variance to pilot analyses of changes in cigarettes per day and Fagerström Test for Cigarette Dependence scores.

RESULTS

At baseline, red blood cell membrane eicosapentaenoic acid concentrations were negatively correlated with cigarettes per day (r=-0.44; P=.04). By 4 weeks, circulating n-3 long-chain polyunsaturated fatty acid levels increased by 18% in the n-3 long-chain polyunsaturated fatty acid supplementation arm vs a decrease of 3% in the placebo arm. Occurrence of gastrointestinal side effects such as burping, heartburn, diarrhea, abdominal pain, or nausea did not differ statistically between study arms. At 4 weeks, participants allocated to the n-3 long-chain polyunsaturated fatty acids arm reported a median of 3 cigarettes per day (interquartile range, 1-8) vs 7 cigarettes per day (interquartile range, 1-14) in the placebo arm, which was not statistically significant (P=.99). Participants allocated to the n-3 long-chain polyunsaturated fatty acids arm had a decrease of 1 (interquartile range, 0-1) on the Fagerström Test for Cigarette Dependence score vs 0 (interquartile range, 0-0) for placebo (P=.46).

CONCLUSION

High-dose n-3 long-chain polyunsaturated fatty acids may be tolerated in pregnant women who smoke; however, there was a high level of participant dropout, with more participants allocated to the fish oil arm becoming lost to follow-up. These results will inform the design of a future large-scale randomized controlled trial to test the impact of fish oil supplements on smoking cessation in pregnancy.

Investigating N-3 Fatty Acids to prevent Neonatal Tobacco-related outcomeS (INFANTS): study protocol for a double-blind, randomized, placebo-controlled parallel clinical trial of n-3 polyunsaturated fatty acids in pregnant smokers

BACKGROUND

Tobacco use during pregnancy is the most important modifiable risk factor associated with adverse pregnancy outcomes, increasing the risk of preterm birth, intrauterine growth restriction and sudden infant death syndrome. Fewer than half of pregnant smokers can quit on their own. Identifying safe and effective therapies to prevent tobacco-related adverse pregnancy outcomes and/or increase smoking cessation in pregnant women would have a substantial public health impact. Cigarette smoking is associated with a relative deficiency in circulating n-3 long-chain polyunsaturated fatty acid (n-3 LCPUFA) levels. A recent analysis found that smokers taking n-3 LCPUFAs during pregnancy had a reduction in preterm labor risk when compared to non-smokers. Studies have shown that supplemental n-3 LCPUFAs may also reduce nicotine cravings and daily cigarette use. Thus, smokers may benefit from supplemental n-3 LCPUFAs by lowering the risk of preterm labor and/or increased smoking cessation. To address important remaining knowledge gaps, we propose the Investigating N-3 Fatty Acids to prevent Neonatal Tobacco related outcomeS (INFANTS).

METHODS

The INFANTS study is a multicenter, randomized, double-blind, placebo-controlled study that will randomize 400 pregnant smokers to either supplemental n-3 LCPUFAs or placebo. Participants will be enrolled between 12 and 24 weeks' gestation and followed until 6 weeks after delivery. We will recruit from clinical centers throughout Middle Tennessee. We will assess smoking behavior after 12 weeks of supplementation using self-report and validated biomarkers of tobacco exposure. We will measure response to supplementation using biological markers of n-3 LCPUFA status. Our primary endpoint will be preterm labor as reflected by gestational age at delivery. Our secondary endpoint will be change from baseline in cigarettes per day at 12 weeks.

DISCUSSION

This study tests the hypothesis that smoking-induced n-3 LCPUFA deficiencies contribute to tobacco-related adverse pregnancy outcomes and that supplementation of n-3 LCPUFAs in pregnant smokers may prevent these complications. If our study demonstrates that supplemental n-3 LCPUFAs are effective at reducing the risk of tobacco-related adverse neonatal outcomes and/or reducing tobacco use during pregnancy, our results could have an immediate and major impact on pregnancy care and neonatal outcomes.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04417595. Registered on April 21, 2020.

The impact of nutrition on the development and progression of peripheral artery disease: A systematic review

BACKGROUND & AIMS

This systematic review sought to identify and summarize existing evidence for the impact of nutrition on the development, progression, and outcomes of peripheral artery disease (PAD).

METHODS

We performed a systematic literature search of available studies published between January 1974 and December 2019. Randomized controlled trials (RCT), observational studies, and cross-sectional studies reporting either the primary or secondary prevention of PAD with nutritional intake were included. The quality assessment was performed for the RCTs, without pooling a meta-risk estimate.

RESULTS

Among a total of 8502 records screened, 186 full texts were assessed for eligibility, and 82 studies (30% RCT) were analyzed. The nutrients were structured in fruits, vegetables and antioxidants, fats and oils, dietary fiber, meat, proteins, vitamins and trace elements, and diets and lifestyle. The findings of the current systematic review indicate that the Mediterranean diet, nuts, and polyunsaturated fat are associated with a lower incidence of PAD and saturated fat, cholesterol, and processed meat were associated with higher rates of cardiovascular events in patients suffering from PAD.

CONCLUSIONS

The current review found evidence of a beneficial impact of the Mediterranean diet including nuts in this target population. More RCTs and high-quality registries are needed that focus on nutritional habits among patients with PAD to design appropriate preventive programs.

Predicting the effects of supplemental EPA and DHA on the omega-3 index

BACKGROUND

Supplemental long-chain omega-3 (n-3) fatty acids (EPA and DHA) raise erythrocyte EPA + DHA [omega-3 index (O3I)] concentrations, but the magnitude or variability of this effect is unclear.

OBJECTIVE

The purpose of this study was to model the effects of supplemental EPA + DHA on the O3I.

METHODS

Deidentified data from 1422 individuals from 14 published n-3 intervention trials were included. Variables considered included dose, baseline O3I, sex, age, weight, height, chemical form [ethyl ester (EE) compared with triglyceride (TG)], and duration of treatment. The O3I was measured by the same method in all included studies. Variables were selected by stepwise regression using the Bayesian information criterion.

RESULTS

Individuals supplemented with EPA + DHA (n = 846) took a mean ± SD of 1983 ± 1297 mg/d, and the placebo controls (n = 576) took none. The mean duration of supplementation was 13.6 ± 6.0 wk. The O3I increased from 4.9% ± 1.7% to 8.1% ± 2.7% in the supplemented individuals ( P < 0.0001). The final model included dose, baseline O3I, and chemical formulation type (EE or TG), and these explained 62% of the variance in response (P < 0.0001). The model predicted that the final O3I (and 95% CI) for a population like this, with a baseline concentration of 4.9%, given 850 mg/d of EPA + DHA EE would be ∼6.5% (95% CI: 6.3%, 6.7%). Gram for gram, TG-based supplements increased the O3I by about 1 percentage point more than EE products.

CONCLUSIONS

Of the factors tested, only baseline O3I, dose, and chemical formulation were significant predictors of O3I response to supplementation. The model developed here can be used by researchers to help estimate the O3I response to a given EPA + DHA dose and chemical form.

Maximal exercise and erythrocyte fatty-acid status: a lipidomics study

Omega-3 fatty acids have long been ascribed a positive cardiovascular function. However, the plasma measurements invariably ignore 40% of the blood specimen, cells that engage in continuous exchange with their environment. In our study, we included all components of the circulating blood. Erythrocyte or red-blood-cell (RBC) n-3 fatty acid status has been linked to cardiovascular disease and death. A low omega-3 index is an independent risk factor for cardiovascular disease and mortality. We tested the hypothesis that acute, maximal exercise would influence the relationship between RBC and serum fatty acids. RBC fatty acids profiling was achieved using targeted HPLC-MS mass spectrometry. Healthy volunteers performed maximal treadmill exercise testing using the modified Bruce protocol. Central hemodynamics were monitored and maximal workload was assessed in metabolic equivalents (METs). Venous blood was obtained for RBC lipidomics. With the incremental exercise test, no fatty acid-level variations were found in RBCs, while heart rate and arterial blood pressure increased significantly. No changes occurred in the omega-3 quotient, namely the percentage of eicosapentaenoic acid and docosahexaenoic acid in RBC fatty acids in the RBC membrane. Nonetheless, maximal (13.50 ± 1.97 METs) exercise intensity led to a decrease of RBC lauric acid (C12:0) in the recovery period. These data suggest that despite significant hemodynamic effects, short-term maximal exercise is insufficient to alter RBC n-3 and other fatty-acid status, including the omega-3 quotient, in healthy individuals. RBC lauric acid deserves further scrutiny as a potential regulator of cardiovascular and metabolic functions.

Predictors of change in omega-3 index with fish oil supplementation in peripheral artery disease

BACKGROUND

The omega-3 index represents the red blood cell (RBC) content of two major long-chain n-3 polyunsaturated fatty acids (PUFAs), eicosapentaenoic acid, and docosahexaenoic acid. We sought to determine factors associated with a favorable response to fish oil treatment and to characterize changes in RBC PUFAs associated with fish oil supplementation.

METHODS

This study was a secondary analysis of the OMEGA-PAD I trial, a randomized, double-blinded, placebo-controlled trial investigating short-duration, high-dose n-3 PUFA oral supplementation on endothelial function and inflammation in subjects with peripheral arterial disease. Patients with mild to severe claudication received either 4.4 g of fish oil providing 2.6 g of eicosapentaenoic acid and 1.8 g of docosahexaenoic acid daily (n = 40) or placebo capsules (n = 40) for 1 mo. The RBC fatty acid content was measured by gas chromatography and expressed as a percent of total fatty acids. The change in omega-3 index was calculated as the difference between pre- and post-supplementation in the fish oil and placebo groups. Univariate analysis identified predictors of change in omega-3 index, with these variables included in our multivariable model.

RESULTS

In the fish oil group, there was an increase in the omega-3 index (5.1± 1.3% to 9.0± 1.8%; P < 0.0001), whereas there was no change in the control group. Factors associated with a favorable response (i.e., greater than the median change of 4.06%) included a lower body mass index and higher concentrations of low-density lipoproteins. Other demographic and/or lifestyle factors such as age, race, or smoking status were unrelated to the response. Oral n-3 PUFA supplementation also decreased the n-6 PUFA content in RBCs.

CONCLUSIONS

Short-term, high-dose n-3 PUFA supplementation increases the omega-3 index to a greater extent in patients with a lower body mass index and higher total and low-density lipoprotein cholesterol levels.

Risk factors associated with plasma omega-3 fatty acid levels in patients with suspected coronary artery disease

INTRODUCTION

We sought to determine the associations between plasma eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) levels and various cardiovascular risk factors and with the use of fish oil supplements (FOS).

PATIENTS AND METHODS

Patients with suspected coronary artery disease (CAD) undergoing cardiac catheterization (n=433) were studied. Serum fatty acid (FA) composition, the concentrations of lipids and biomarkers of oxidative stress, and dietary/lifestyle factors were measured.

RESULTS

FOS use was associated with a higher plasma EPA+DHA levels (3.7±1.5 vs. 2.6±1.1%, p<0.0001). However, there was no relationship between FOS dose (mg/day) and EPA+DHA levels in 76 patients reporting FOS use (r=-0.21, p=0.07). Lower levels were inversely associated with risk factor profiles including lower ApoB100/ApoA1 ratios (p<0.001).

DISCUSSION AND CONCLUSIONS

Higher EPA+DHA levels characterized patients with lower CAD risk. The lack of relations between FOS dose and plasma EPA+DHA levels likely reflects uncaptured variability in EPA+DHA content of supplements.

Smoking and red blood cell phospholipid membrane fatty acids

Smoking is associated with lower n-3 long chain polyunsaturated fatty acids (LCPUFA) concentrations; however, limited studies have accounted for dietary PUFA intake or whether tobacco dose or smoking duration influences this association. We measured red blood cell phospholipid (RBC) membrane concentrations of fatty acids in 126 current smokers, 311 former smokers, and 461 never smokers using gas liquid chromatography and tandem mass spectrometry. Smokers had lower RBC membrane percentages of total n-3 LCPUFAs compared to former smokers or never smokers (median percent: 5.46, [interquartile range (IQR) 4.52, 6.28] versus 6.39; [IQR: 5.18, 7.85] versus 6.59; [IQR 5.34, 8.01]) (p<0.001) and this association remained after adjusting for dietary PUFA intake. Duration of smoking and cigarettes per day were not associated with RBC membrane n-3 LCPUFA differences. Smoking is associated with lower n-3 LCPUFA RBC membrane percentages and this association was not influenced by diet or smoking dose or duration.

Systemic delivery of proresolving lipid mediators resolvin D2 and maresin 1 attenuates intimal hyperplasia in mice

Vascular injury induces a potent inflammatory response that influences vessel remodeling and patency, limiting long-term benefits of cardiovascular interventions such as angioplasty. Specialized proresolving lipid mediators (SPMs) derived from ω-3 polyunsaturated fatty acids [eicosapentaenoic acid and docosahexaenoic acid (DHA)] orchestrate resolution in diverse settings of acute inflammation. We hypothesized that systemic administration of DHA-derived SPMs [resolvin D2 (RvD2) and maresin 1 (MaR1)] would influence vessel remodeling in a mouse model of arterial neointima formation (carotid ligation). In vitro, SPM treatment inhibited mouse aortic smooth muscle cell migration (IC₅₀ ≅ 1 nM) to a PDGF gradient and reduced TNF-α-stimulated p65 translocation, superoxide production, and proinflammatory gene expression (MCP-1). In vivo, adult FVB mice underwent unilateral carotid artery ligation with administration of RvD2, MaR1, or vehicle (100 ng by intraperitoneal injection at 0, 1, 3, 5, and 7 d after ligation). In ligated carotid arteries at 4 d, SPM treatment was associated with reduced cell proliferation and neutrophil and macrophage recruitment and increased polarization of M2 macrophages in the arterial wall. Neointimal hyperplasia (at 14 d) was notably attenuated in RvD2 (62%)- and MaR1 (67%)-treated mice, respectively. Modulation of resolution pathways may offer new opportunities to regulate the vascular injury response and promote vascular homeostasis.