The Impact of Food Deprivation on Cardiovascular Physiology

Introduction: Despite the commonality of fasting, there still remains a lack of scientific research, specifically in regard to the impact of fasting on cardiovascular physiology. Thus, the goal of this research project was to further explore the relationship between fasting and cardiovascular physiology. Hypothesis: The hypothesis of this research project was that a 24-hr fast would likely lead to increased BP and HR, along with blood biomarker changes, and that experiencing this 24-hr fast twice a week would lead to reduced BP and HR along with altered circulating blood biomarker levels. Methods: In order to test these hypotheses, cardiovascular and blood biomarker factors were assessed both before, during and after a 24-hr fast, and throughout a 4-wk period of two 24-hr fasts per week. Results: After the 24-hr fast there was increased resting BP (SBP, p=0.062; DBP, p=0.101) and HR (p=0.125), in addition to decreased overall average ambulatory BP (SBP, p=0.159; DBP, p=0.167) and HR (p=0.076) throughout the 24-hr fast. Blood glucose (p=0.012) and plasma NPY (p=0.007) were decreased, and plasma ghrelin (p=0.171) and plasma LEAP2 (p=0.203) were increased after the 24-hr fast. Resting BP (SBP, p=0.004; DBP, p=0.202) was decreased, and autonomic function showed a shift toward lessened sympathetic activity (↑ RRI, p=0.125; ↓ RRI-LF/HF ratio, p=0.293) at the end of the 4 weeks of fasting, and the decrease in BP was seen as early as 2 weeks of fasting. Plasma ghrelin (p=0.372) was increased at the end of the 4 weeks of fasting with little to no change in blood glucose (p=1.000), plasma LEAP2 (p=1.000) and plasma NPY (p=1.000). Plasma LEAP2 (p=0.693) and plasma NPY (p=0.473) did decrease after 2 weeks of fasting before returning to approximately baseline levels after 4 weeks of fasting. The cardiovascular changes from 24 hours of fasting were most correlated to blood glucose and plasma ghrelin, and the changes from 4 weeks of fasting were most correlated to plasma ghrelin and plasma NPY. Discussion: It appears that fasting may have a mild impact on cardiovascular physiology; both during a 24-hr fast and as an adaptation to 4 weeks of fasting

Effects of Acute Cold Exposure on Plasma Biomarkers Associated with Cardiovascular Disease Risk

Background and Aims: The underlying cause of the majority of the cases of CVD is atherosclerosis, which is a condition initiated and progressed by chronic inflammation and hyperlipidemia. We are interested in evaluating the efficacy of cold-exposure to increase shivering- and non-shivering thermogenesis energy expenditure (RMR) as a non-pharmaceutical weight loss tool analogous to low intensity exercise. Naturally, we are concurrently evaluating the possible effects of cold exposure on risk factors associated with CVD risk. Inflammatory cytokines and lipid mediators are used as biomarkers for CVD risk. This proposed study aims to measure cardiovascular inflammatory and lipid biomarkers to expand our knowledge of cold exposure and CVD risk. The two biomarkers collected during this study were Interleukin-1 Beta (IL-β) and Chemokine Ligand 2 (CCL2). The hypothesis was that there would be no change in biomarker values before and after cold exposure. Methods: Twenty subjects were recruited and subjected to a 30-min cold exposure test while a metabolic cart collected metabolic data via indirect calorimetry. Venous plasma collected at: pre cold exposure, immediately after cold exposure, and 2 hours post cold exposure was centrifuged for subsequent biomarkers analysis. Results: RMR increases dramatically during acute cold exposure during shivering and remains increased 5 minutes after the cessation of shivering. Five minutes post-cold exposure, RMR rapidly decreases to pre-cold exposure RMR and is maintained for up to 120 minutes. There was no change in CCL2 values when comparing the three stages. IL-β values increased between blood draws immediately after cold exposure and 2 hours post cold exposure, however this increase was not statistically significant. Conclusions: With these pilot results, we conclude that cold exposure has no effect on biomarkers for CVD risk. However, this study was limited by 1) accuracy of analysis techniques, 2) cold exposure protocol, 3) analysis of only two representative biomarkers. Further biomarker analysis is underway for a more comprehensive picture of the purported cold exposure effects

Research notes: Soybean linkage tests

F2 linkage results are presented in Table 1 with a=XY, b=Xy, c=xY and d = xy for the gene pairs 1 i sted in the form of Xx and Yy. Percentage recombination was obtained from the ratio of products following the method of Inmer and Henderson (1943). Results from testing F3 seeds and seedlings to determine F2 phenotypes indicate possible linkage between seed coat peroxidase (ep) and root fluorescence (fr)

Energy Expenditure following Acute Cold Exposure

TACSM Abstract - Energy Expenditure following Acute Cold Exposure Stelly S, Bravo D, Hines N, Koehler L, Levi M and Fogt D Exercise Biochemistry & Metabolism Laboratory; Department of Kinesiology, Health & Nutrition; The University of Texas at San Antonio; San Antonio, TX Category: Masters Advisor / Mentor: Fogt, Donovan ([email protected]) ABSTRACT Whole body energy expenditure (i.e., RMR) increases during acute cold exposure. Whether this increase in energy expenditure persists in the post-cold term in humans due to non-shivering thermogenesis has not yet been evaluated. Therefore we tested the hypothesis that RMR would be different directly following acute cold exposure. RMR (kcal•min-1) was assessed via indirect calorimetry on eight (8) males and seven (7) females at six time points: prior to cold exposure (T1), at the end of 30 minutes of cold exposure (T2), immediately post-cold-post-shivering (T3), at 35 minutes post-cold (T4), at 75 minutes post-cold (T5), and at 115 minutes post-cold (T6). This RMR data for the aforementioned time points was analyzed using paired, dependent t-tests and one way ANOVA; the significance level was placed at p \u3c 0.05. The RMR data for each time point was as follows: T1 (1.19±0.21), T2 (2.30±0.94), T3 (1.37±0.25), T4 (1.12±0.19), T5 (1.14±0.22), and T6 (1.14±0.22). The analysis of the RMR data showed a significant difference between the cold (T2) data and all other time points (T1, T3, T4, T5, and T6). Additionally there was a significant difference between the pre-cold (T1) and the immediately post-cold (T3) data. However there was no significant difference between the pre-cold (T1) data when compared with the remaining post-cold data (T4 – T6). These results suggest that the human body is capable of returning RMR to baseline levels relatively immediately following the cessation of acute cold exposure

Effects of Vaporized Nicotine on Resting Metabolic Rate and Physical Work Capacity

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Research notes: Soybean linkage tests

F2 linkage results are presented in Table 1 with a=XY, b=Xy, c=xY and d = xy for the gene pairs 1 i sted in the form of Xx and Yy. Percentage recombination was obtained from the ratio of products following the method of Inmer and Henderson (1943). Results from testing F3 seeds and seedlings to determine F2 phenotypes indicate possible linkage between seed coat peroxidase (ep) and root fluorescence (fr).</p

Acute Fasting Increases Vagal Tone and Reduces Ambulatory Arterial Pressure

Obesity is a chronic metabolic disorder associated with increased risk of cardiovascular disease, and intermittent fasting might mitigate risk. Intermittent fasting creates a negative energy balance that results in weight loss, but the cardiovascular benefits of fasting have not been studied thoroughly. The purpose of this study was to investigate the influences of an acute 24-hr fast on cardiovascular control and hemodynamics. Ours was a randomized, crossover design with autonomic testing occurring 3-hrs postprandial (fed) and 24-hrs postprandial (fast). A standardized meal was provided for both conditions. 24-hrs before autonomic testing participants wore an ambulatory blood pressure (ABP) cuff which recorded 3 brachial pressures per hr during the day and 2 pressures per hr at night. 24-hour ABP was averaged and compared via a paired t-test (N=17, 6 Female; fed vs. fasted). 3 participants did not meet inclusion criteria of at least 20 valid day and 7 valid night recordings. Twenty young (23±0.7 yrs), normotensive, non-obese (25±0.8 BMI), participants completed the autonomic test. We measured blood glucose (GLU), ketones (β-OHB), and triglycerides (TRG) to confirm a successful fast. With subjects in a supine position during the autonomic test, we recorded the ECG and beat-to-beat arterial pressure (finger plethysmography). Cardiovagal baroreflex sensitivity (cvBRS) was determined by beat-to-beat changes in R-R interval (RRI) and systolic pressure (SAP) using the sequence method. Only sequences with linear r values \u3e0.7 were accepted (cvBRS-up N=18; cvBRS-down N=20). Spectral analysis was used to assess heart rate variability. The high frequency (HFnu; 0.15-0.40 Hz) and low frequency (Lfnu; 0.04-0.15 Hz) components were normalized to total power. Subjects rested quietly for 10 min while breathing in time to a computer display prompting them to breathe at a frequency of 15 breaths/min. The last 8 min of the autonomic test were averaged and compared via a paired t-test (N = 20, 7 Female; fed vs. fasted). Data are expressed as mean±SE. P-values ≤ 0.05 were considered significant and are indicated by an asterisk (*). Changes in TRG, GLU and β-OHB with fasting were consistent with expectations: TRG and GLU decreased (TRG; 114±11 fed vs. 68±6* mg/dL fast)(GLU; 99±3 fed vs. 80±2* mg/dL fast), and β-OHB increased (β-OHB; 0.13±.03 fed vs. 0.57±.12* mmol/L fast). Overall SAP and diastolic (DAP) ABP decreased in the fasted condition (SAP;111±1.5 fed vs. 109±1.5* mmHg fast) (DAP; 66±1.4 fed vs. 64±1.5* mmHg fast). During the autonomic test, RRI, cvBRS-up, cvBRS-down, and HFnu increased, and LFnu decreased in the fasted condition. (RRI; 991±35 fed vs. 1053±45* ms fast)(cvBRS-up 19.5±3 fed vs. 26.4±6* ms/mmHg fast) (cvBRs-down; 15.3±1 fed vs. 21.5±3* ms/mmHg fast) (HFnu; 54.4±3 fed vs. 61.4±4* a.u. fast) (LFnu; 45.6±3 fed vs. 38.6±3* a.u. fast). Our results suggest that acute fasting may convey cardioprotective benefits through enhanced vagal tone and reduced 24-hr ambulatory arterial pressure

Influence of acute fasting on cerebrovascular reactivity during mental stress

Acute fasting has been adopted in fitness communities, and has been practiced for religious purposes. Short‐term fasting does not affect cognitive function, and therefore may not affect cerebrovascular responsiveness. Cerebral blood flow velocity increases with mental stress, however the combined influences of an acute fast and mental stress on cerebrovascular responses are unknown. The purpose of this study was to describe the effects of a 24‐hour, water‐only fast on cerebral blood flow velocity responses to mental stress in a small cohort of research volunteers. Eight young healthy participants (7 males, average age of 25 yrs) completed the protocol in a fed state (4 hours post‐prandial) and in a fasted state (24–25 hours post‐prandial). Whole blood was collected and analyzed before experimentation for β‐Ketones, total cholesterol, HDL, LDL, triglycerides (TRG), and glucose. With participants in a supine position, we recorded the electrocardiogram, beat‐to‐beat arterial pressure (finger plethysmography), and cerebral artery blood flow velocity (transcranial Doppler). After a 5‐min baseline, participants performed 5‐min of mental stress via mental arithmetic (rapid continuous subtraction). Mental stress reactivity was calculated as the mean stress response for each minute of mental stress minus the corresponding 5‐min baseline. The minute‐by‐minute reactivity was analyzed with repeated measures ANOVA. Blood variables were analyzed with paired t‐tests. Data were expressed as mean ± SE. Baseline blood variables were different in the fasted compared with the fed state: TRG (112±14 fed vs. 68±13 mg/dL fasted; p\u3c.01) Glucose (101±5 fed vs. 79±6 mg/dL fasted; p\u3c.01) and β‐Ketone (.1±.01 fed vs. .5±.2 mmol/L fasted; p\u3c.05). Mean arterial pressures and heart rate reactivities to mental stress were not affected by fasting. Mean cerebral blood flow velocity reactivity to mental stress was reduced in the fasted compared with the fed condition (condition × time, p\u3c.01), with a particular divergent responsiveness during the third minute of mental stress. The results we present are new, but preliminary. We did not attempt to ascribe mechanisms to fasting and cerebral blood flow velocity reactivity during mental stress. The changes we observed with our preliminary data set suggest that fasting, and associated changes of plasma glucose, β‐Ketone and TRG may be associated with reductions of cerebral blood flow velocity during mental stress

Controlled breathing and autonomic rhythms: Influence of auditory versus visual cues

We compared standard metrics of autonomic control in 20 humans (10 female) during spontaneous and controlled breathing. Subjects controlled breathing at 0.25 Hz following a metronome (auditory) or scrolling waveforms (visual). Respiratory rates and heart rates were lower during spontaneous breathing compared with auditory and visual. One heart rate variability metric was higher during visual compared with spontaneous breathing, but baroreflex sensitivity and muscle sympathetic nerve activity were not affected by breathing cues. A majority of subjects (86%) perceived that breathing to auditory cues was more difficult compared with visual cues, but this elevated perceived stress did not manifest physiologically