The influence of mental stress and a high polyphenol herb and spice blend on postprandial lipemia, oxidative stress and vascular dysfunction
Open Access
- Author:
- Mc Crea, Cindy Eileen
- Graduate Program:
- Biobehavioral Health
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 22, 2015
- Committee Members:
- Sheila Grace West, Dissertation Advisor/Co-Advisor
Penny Margaret Kris Etherton, Committee Member
Laura Klien, Committee Member
Ryan John Elias, Special Member - Keywords:
- spice
herb
vascular function
postprandial
lipemia
triglycerides
stress
oxidative stress
EndoPAT - Abstract:
- Postprandial elevations in triglycerides and glucose may be a novel and powerful predictor of increased CVD risk[1]. Specifically, exaggerated increases in postprandial triglycerides and glucose are believed to promote atherogenesis via increases in inflammation, oxidative stress, endothelial dysfunction, and the production of small dense LDL cholesterol [2-4]. For this reason, dietary interventions which reduce post meal spikes in triglycerides and glucose or the subsequent rise in oxidative stress and endothelial dysfunction may be particularly important for managing CVD risk. First, this dissertation explores the effects of acute stress and a high antioxidant herb and spice blend on postprandial oxidative stress, inflammation and vascular function. Methods: Archived samples from a randomized, crossover clinical trial [5] were used to test the effects of mental stress (Trier Social Stress Test) and rest on postprandial oxidative stress, inflammation and endothelial function following the consumption of a high fat meal with or without 14.5 grams of polyphenol-rich spices (black pepper, cinnamon, cloves, garlic, ginger, oregano, paprika, rosemary, and turmeric). Twenty participants completed 4 visits in this 2x2 factorial design. At each visit, fasted baseline blood samples were collected, participants consumed the test meal and then underwent either the mental stress protocol or rest condition. Additional blood samples were collected at 105, 140, 180, and 210 minutes post meal (corresponding to 10, 45, 90 and 120 minutes post stress). Endpoints included plasma levels of malondialdehyde (MDA), oxidized low density lipoproteins (oxLDL), the inflammatory cytokines interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α). Vascular function was assessed via peripheral arterial tonometry at 240 minutes post meal. Results: Compared to the fasting baseline, the meal increased oxidative stress regardless of the presence or absence of spices (p = 0.003 for MDA and p = 0.02 for oxLDL). Similarly, the meal resulted in increased plasma IL-6 (p <0.001). A stress by time interaction was also present for plasma IL-6 (p = 0.05), such that when stressed, the average change was elevated at time 2 compared to time 3 (1.05 ± 0.25 vs 0.44 ± 0.16, Tukey p = 0.03). However, the direct comparison of IL-6 at time 2 following stress versus rest revealed no difference. There was no effect of spices on oxidative stress, inflammation or vascular function. Second, this dissertation describes a clinical study which examines the effects of an polyphenol-rich spiced meal on postprandial plasma triglyceride concentrations and rates of fecal fat excretion and gut motility. Building on previous studies in which we observed significant reductions in postprandial triglycerides following a meal rich in spices, the purpose of this study is to identify mechanisms by which this effect occurred. Methods: Twelve healthy but overweight men participated in a randomized 2 period cross over study. At each of 2 visits, a fasting blood sample was followed by the consumption of a high fat meal (~1100 kcals, 57g fat) containing blue dye, 2.5g non absorbable fat and with or without the 14.5 g polyphenol-rich herb and spice blend. Within 15 minutes of finishing the meal, participants swallowed a single-use SmartPill wireless motility capsule. Blood was sampled every 60 minutes after the meal for 8 hrs for the analysis of plasma triglycerides and glucose. Fecal deposits were collected until the dyed sample was captured. The sucrose polybehenate test of fecal fat absorption was used to evaluate fat excretion in the dyed samples. Endothelial function (measured via flow-mediated dilation, FMD) was assessed at fasting and 210minutes post meal. Results: Serum triglycerides, glucose and insulin were increased postprandially, as expected. There was no effect of spices on these three endpoints (ps > 0.05). Gastric emptying time was lower after the spice meal compared to control (658 ± 98.2 vs. 884.5 ± 98.2 minutes; p = 0.046), but small bowel and colonic transit time were unaffected by treatment. There was no effect of either meal on brachial artery diameter or FMD (ps > 0.05). The spiced meal increased blood flow compared to the fasting scan (ps = 0.06 and 0.05). Both blood flow volume at the start of the FMD scan (average increase of 57.78 ± 25.34mL/min, post hoc p = 0.037) and following shear stress were increased (average increase of 188.867 ± 66.6 mL/minute post hoc p = 0.012). These findings suggest that spices may influence sympathetic activity. Finally, this dissertation reports the test-retest reliability of pulse amplitude tonometry (PAT). PAT is an alternative to the noninvasive standard procedure of flow-mediated dilation (FMD) for assessing endothelial function. PAT uses automated methods to measures the change in pulse wave amplitude before and during reactive hyperemia (Itamar Medical Ltd, Caesarea, Israel). However, little is known about its ability to reliably assess vascular function in healthy adults across time periods of more than a few hours. Methods: Twenty healthy adults completed two PAT tests separated by a mean of 19.5 days. Standardized conditions included time of day, location, time since and contents of last meal, body position and menstrual phase for premenopausal females. Results: PAT-derived measures of endothelial function (reactive hyperemia index, RHI) and arterial stiffness (augmentation index, AI) showed strong repeatability (intra-class correlations = 0.74 and 0.83, respectively). To guide future research, we also analyzed sample size requirements for a range of effect sizes. A crossover design powered at 0.90 requires 28 participants to detect a 15% change in RHI. Our study is the first to show that PAT measurements are repeatable in adults over an interval greater than 1 week and thus appropriate for gauging change over longer term intervention trials. In conclusion, this dissertation provides evidence that common culinary spices have little impact on metabolic, oxidative and inflammatory processes during the postprandial period. Evidence is also provided for the reliability of an inexpensive and operator-independent method of measuring endothelial dysfunction. The results of this dissertation may be useful in designing interventions to prevent and treat obesity, metabolic syndrome, and CVD.