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Title: Exercise induced inflammation and the effect of omega-3 polyunsaturated fatty acids on physiological variables associated with endurance performance
Author: Hale, Lucy
ISNI:       0000 0004 8504 9013
Awarding Body: University of Kent
Current Institution: University of Kent
Date of Award: 2018
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The purpose of this thesis was to investigate the effect of a dietary intervention designed to increase tissue incorporation of omega 3 polyunsaturated fatty acids (n3 PUFA) on oxygen consumption during submaximal exercise, and to investigate the acute inflammatory cytokine response to different intensities of cycling in trained men. Study 1. The cytokine response to two cycling modalities: 1) pre-loaded performance trial and 2) high intensity interval trial. This study investigated the effect of two cycling protocols on plasma concentrations of pro-inflammatory and anti-inflammatory cytokines. Fourteen moderately trained healthy males completed two cycling protocols 1 week apart, 1) a 1-hour pre - loaded cycling time trial with the first 45 minutes corresponding ~70% of maximal work load and 2), 12 x 1 minute high intensity intervals corresponding to 100% of maximal workload (workload was based on an incremental test to exhaustion). Blood samples were obtained from the antecubital vein pre and immediately post each exercise trial, for the determination of plasma cytokine concentrations. Additional saliva samples were collected at the same time points to validate their relationship and agreement with plasma samples for measurement of IL-1ß. Results: IL-6 increased more markedly following the pre-loaded time trial (mean ± standard deviation), 2.56 ± 3.30 pg./ ml to 6.68 ± 4.48 pg./ ml respectively (a 161% increase) compared to the interval trial 2.16 ± 2.05 pg./ ml to 2.95 ± 2.24 pg./ ml (a 37% increase) (time * trial interaction p = 0.015). IL-4 and MCP-1 concentrations increased, and VEGF decreased following both trials combined (main effect of time IL-4, p = 0.013, MCP-1, p = 0.002, VEGF, p = 0.016). No changes were observed in other cytokine concentrations. A significant correlation between plasma and saliva IL-1ß concentration was only observed in samples obtained post the time trial (r = 0.807, p = 0.009), expressed as concentration: osmolality, r = 0.781, p = 0.013). In conclusion, a 1-hour pre-loaded cycling trial resulted in a greater increase in IL-6 compared with 12 x 1min interval trial. Acute post exercise increases in IL-4 and MCP-1, and a decrease in VEGF were observed post both trials on average. Furthermore, the relationship between plasma and saliva for the measurement of IL-1ß concentration was inconsistent and lacked agreement. Saliva did not prove to be a valid alternative method of measurement to blood plasma for the measurement of IL-1ß. Study 2. Validation of the use of a fingertip capillary dry blood spot method to determine percentage incorporation of n-3 PUFA and n6 into erythrocyte cell membranes. This study investigated the relationship and agreement between dry blood spot samples (DBS), and isolated erythrocytes (from venepuncture whole blood samples), for the measurement of percentage PUFA status in 10-trained cyclists. Blood samples were collected on three occasions over an 8-week period (baseline, at 4 weeks and at 8 weeks) to determine percentage tissue incorporation of total n6 PUFA, AA, LA, total n-3 PUFA, EPA and DHA. On each occasion, two sample types were obtained from each participant. 1), isolated erythrocytes from whole blood taken from the participant's antecubital vein. 2), a whole blood fingertip capillary sample spotted on to a Guthrie absorbent card pre-soaked in butylated hydroxytoluene. The n-3 PUFA and n-6 PUFA content of both samples was determined by gas chromatography and mass spectrometry. Results: Isolated erythrocyte samples had a significantly higher percentage content of EPA, AA, total n-6, EPA + DHA and n-6/ n-3 PUFA and a lower content of ALA when compared to fingertip capillary DBS samples. No differences between methods were observed for DHA and total n-3 PUFA values. Linear regression showed there was a significant correlation (R) between the two types of measurement for EPA (R2 = 0.64, p = 0.005) but not for other fatty acids. Bland and Altman analysis showed moderate agreement between methods for EPA (mean difference = 1.12% with 95% limits of agreement -1.43% – 3.67%). In conclusion, the current study suggests fingertip capillary DBS sampling is a valid method for determining the EPA status of individuals but not for other n-3, n-6 PUFAs. Study 3. The effect of an 8-week high n-3 PUFA and low n-6 PUFA (H3-L6) dietary intervention, on erythrocyte fatty acid incorporation, and its effect on the oxygen cost of submaximal exercise and VO2 ? peak in trained cyclists. This study investigated the effect of an 8-week dietary intervention (designed to increase n-3 PUFA and reduce n-6 PUFA (to less than 2.5% of average daily kcal intake)) on VO2 ? peak and oxygen consumption ( VO2 ? ) during submaximal exercise. 14-trained male cyclists were randomly assigned to two independent groups. The experimental group received 8 x 1g capsules per day of n-3 PUFA (2600mg EPA and 1800mg DHA), and followed a dietary intervention designed to reduce n-6 PUFA intake (H3-L6). The placebo group received 8 x 1g capsules per day of organic soy oil and a pseudo dietary intervention that maintained their habitual daily n-6 PUFA intake. Blood samples were obtained from the participant's antecubital vein, pre supplementation, at week 4 and at week 8, for the analysis of erythrocyte incorporation of n-3 PUFA and n-6 PUFA. Pre and post the dietary intervention, participants completed 4 x 7mins submaximal cycling on a Lode ergometer at four discontinuous incremental power outputs. Steady state oxygen consumption ( VO2 ? ), tissue oxygen saturation index (TSI%), deoxygenated haemoglobin (deoxy-HHb), heart rate (HR bpm), blood pressure (BP mmHg), and rating of perceived exertion (RPE), were assessed during each cycling bout. Following a 15-minute rest, participants performed an incremental cycling ramp test to exhaustion (intensity increasing by 30 W·min -1 ) for the determination of VO2 ? peak (L/min). Results: H3-L6 significantly increased erythrocyte % content of total n-3 PUFA, EPA and DHA compared to the placebo group over the 8 week intervention (time * group interaction, total n-3 PUFA, p = <0.001, EPA, p = <0.001, DHA, p = 0.001), and significantly reduced total n-6 PUFA, LA and AA (time * group interaction, total n-6 PUFA, p = <0.001, LA, p = 0.004, AA, p = < 0.001). There were no differences in VO2 ? peak (group * time, p = 0.56). During steady state submaximal cycling, there were no differences in oxygen consumption VO2 ? L/min (group * time * power level, p = 0.49), TSI% (p = 0.43) or deoxy-HHb (p = 0.56). Furthermore, no changes were observed in HR, BP, MAP or RPE. In conclusion, despite the dietary intervention successfully increasing erythrocyte n-3 PUFA percentage and reducing n-6 PUFA incorporation over an 8- week intervention period, there was no effect on oxygen consumption during submaximal exercise or VO2 ? peak performance. In summary, this thesis provides evidence that IL-6 increases more markedly in response to a 1 hour pre-loaded cycling time trial compared to 12 x 1 minute intervals. For both cycling trials combined, there was an increase in antiinflammatory IL-4 and MCP-1, and a decrease in VEGF. Furthermore, saliva did not prove to be a valid alternate measurement method to blood plasma for the measurement of IL-1ß. This thesis demonstrated that an 8-week H3-L6 dietary intervention successfully increased erythrocyte incorporation of n-3 PUFA and reduced n-6 PUFA. However, the intervention failed to induce significant alterations in oxygen consumption during submaximal exercise or VO2 ? peak performance. In addition, when quantifying an individual's n-3 PUFA and n-6 PUFA status, fingertip capillary DBS sampling proved to be a valid method for the measurement of EPA but not for other fatty acids. Therefore, the DBS method was not considered a suitable replacement for the isolated erythrocytes method when quantifying an individual's n-3 PUFA and n-6 PUFA status.
Supervisor: Louis, Passfield ; Davison, Glen Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available