Gastrointestinal Cell Injury and Percieved Symptoms after Running the Boston Marathon

Gastrointestinal (GI) disturbances are a prevalent cause of marathon related complaints, and in extreme cases can promote life-threatening conditions such as exertional heat stroke. PURPOSE: Our aim was to study intestinal cell injury (via intestinal fatty acid binding protein [I-FABP]) and perceived GI distress symptoms among marathon runners. Potential risk factors (e.g., inadequate sleep) that could exacerbate GI disturbances in healthy, trained endurance runners were also examined. METHODS: A parallel mixed-methods study design was utilized. 2019 Boston Marathon participants were recruited via email. Before the race subjects completed surveys describing demographics and training history. Immediately pre-race, post-race, and 24-hours post-race participants completed a GI questionnaire to assess presence and severity of symptoms, a survey regarding risk factors (e.g., recent illness, medications) that could promote GI disturbances, and provided a urine sample. Due to weather, blood samples were only collected immediately and 24-hours post-race. RESULTS: A total of 40 runners (males: n = 19, age = 44.9 ± 10.8 years; females: n = 21, age = 44.8 ± 10.6 years) completed this study. I-FABP significantly decreased from post-race (3367.5 ± 2633.5 pg/ml) to 24-hours post-race (1657.3 ± 950.7 pg/ml, t(39) = -4.228, p \u3c .001, d = -.669). A significant difference in overall GI symptom scores across the three time points occurred (F(2, 39) = 41.37, p \u3c .001). Compared to pre-race (.09 ± .12) and 24-hour post-race (.44 ± .28), the highest average score occurred post-race (.84 ± .68). Post-race I-FABP (r = .31, p = .048) and post-race urine specific gravity (r = .33, p = .041) were significantly correlated with post-race GI symptom scores. CONCLUSION: Our study further supports the individualized presentation of GI disturbances, with participants experiencing a wide range of risk factors that can influence the extent of GI damage and perceived symptoms during and after exercise

Liposomal-encapsulated Ascorbic Acid: Influence on Vitamin C Bioavailability and Capacity to Protect against Ischemia–Reperfusion Injury

Intravenous administration of vitamin C has been shown to decrease oxidative stress and, in some instances, improve physiological function in adult humans. Oral vitamin C administration is typically less effective than intravenous, due in part to inferior vitamin C bioavailability. The purpose of this study was to determine the efficacy of oral delivery of vitamin C encapsulated in liposomes. On 4 separate randomly ordered occasions, 11 men and women were administered an oral placebo, or 4 g of vitamin C via oral, oral liposomal, or intravenous delivery. The data indicate that oral delivery of 4 g of vitamin C encapsulated in liposomes (1) produces circulating concentrations of vitamin C that are greater than unencapsulated oral but less than intravenous administration and (2) provides protection from ischemia–reperfusion-mediated oxidative stress that is similar to the protection provided by unencapsulated oral and intravenous administrations

Concurrent Beet Juice and Carbohydrate Ingestion: Influence on Glucose Tolerance in Obese and Nonobese Adults

Insulin resistance and obesity are characterized by low nitric oxide (NO) bioavailability. Insulin sensitivity is improved with stimulation of NO generating pathways. Consumption of dietary nitrate (NO3-) increases NO formation, via NO3- reduction to nitrite (NO2-) by oral bacteria. We hypothesized that acute dietary nitrate (beet juice) ingestion improves insulin sensitivity in obese but not in nonobese adults. 12 nonobese (body mass index: 26.3±0.8 kg/m2 (mean ± SE)) and 10 obese adults (34.0±0.8 kg/m2) ingested beet juice, supplemented with 25 g of glucose (carbohydrate load: 75 g), with and without prior use of antibacterial mouthwash to inhibit NO3- reduction to NO2-. Blood glucose concentrations after beet juice and glucose ingestion were greater in obese compared with nonobese adults at 60 and 90 minutes (P=0.004). Insulin sensitivity, as represented by the Matsuda Index (where higher values reflect greater insulin sensitivity), was lower in obese compared with nonobese adults (P=0.009). Antibacterial mouthwash rinsing decreased insulin sensitivity in obese (5.7±0.7 versus 4.9±0.6) but not in nonobese (8.1±1.0 versus 8.9±0.9) adults (P=0.048). In conclusion, insulin sensitivity was improved in obese but not in nonobese adults following coingestion of beet juice and glucose when oral bacteria nitrate reduction was not inhibited. Obese adults may benefit from ingestion of healthy nitrate-rich foods during meals

Regulators of human white adipose browning: evidence for sympathetic control and sexual dimorphic responses to sprint interval training.

The conversion of white adipose to the highly thermogenic beige adipose tissue has been proposed as a potential strategy to counter the unfavorable consequences of obesity. Three regulators of this conversion have recently emerged but information regarding their control is limited, and contradictory. We present two studies examining the control of these regulators. Study 1: In 10 young men, the plasma concentrations of irisin and fibroblast growth factor 21 (FGF21) were determined prior to and during activation of the sympathetic nervous system via hypoxic gas breathing (FIO2 = 0.11). The measurements were performed twice, once with and once without prior/concurrent sympathetic inhibition via transdermal clonidine administration. FGF21 was unaffected by basal sympathetic inhibition (338±113 vs. 295±80 pg/mL; P = 0.43; mean±SE), but was increased during hypoxia mediated sympathetic activation (368±135); this response was abrogated (P = 0.035) with clonidine (269±93). Irisin was unaffected by sympathetic inhibition and/or hypoxia (P>0.21). Study 2: The plasma concentration of irisin and FGF21, and the skeletal muscle protein content of fibronectin type III domain containing 5 (FNDC5) was determined in 19 young adults prior to and following three weeks of sprint interval training (SIT). SIT decreased FGF21 (338±78 vs. 251±36; P = 0.046) but did not affect FNDC5 (P = 0.79). Irisin was decreased in males (127±18 vs. 90±23 ng/mL; P = 0.045) and increased in females (139±14 vs. 170±18). Collectively, these data suggest a potential regulatory role of acute sympathetic activation pertaining to the browning of white adipose; further, there appears to be a sexual dimorphic response of irisin to SIT

Effect of sprint interval training on exercise performance and brown fat regulators.

<p>Time to exhaustion (A), plasma fibroblast growth factor 21 (FGF21) (B), fibronectin type III domain containing 5 (FNDC5) protein expression (C), and plasma irisin (D) prior to (Pre-SIT) and following (Post-SIT) three weeks of sprint interval training (SIT). Data are mean ± SE * <i>P</i><0.05 compared to Pre-SIT. + <i>P</i> = 0.001 compared to males Post-SIT.</p

Circulating catecholamine response to hypoxia and clonidine.

<p>Plasma norepinephrine (A) and epinephrine (B) in response to normoxic (F_IO2  = 0.21) and hypoxic gas (F_IO2  = 0.11) breathing with and without concomitant sympathetic inhibition (48-h transdermal administration of the centrally acting α2-adrenergic receptor agonist clonidine). Data are mean ± SE. Hypoxic gas breathing increased norepinephrine (<i>P</i> = 0.001) and epinephrine (<i>P</i><0.001). Clonidine attenuated the rise in norepinephrine (<i>P</i> = 0.014) and epinephrine (<i>P</i> = 0.061).</p