©Journal of Sports Science and Medicine (2009) 8, 252-258 http://www.jssm.org Research article Initial metabolic state and exercise-induced endotoxaemia are unrelated to gastrointestinal symptoms during exercise José Moncada-Jiménez 1 , Eric Plaisance 2, Michael L. Mestek 2, Felipe Araya-Ramírez 2, Lance Ratcliff 3, James K. Taylor 4, Peter W. Grandjean 2 and Luis F. AragónVargas 1,5 1 School of Physical Education and Sports, Universidad de Costa Rica, Costa Rica, 2 Department of Kinesiology and 3 Department of Nutrition and Food Sciences, Auburn University, AL, USA, 4 Division of Clinical Laboratory Science, Auburn University-Montgomery, Montgomery, AL, USA 5 The Gatorade Sports Science Institute, Barrington, IL, USA filou and Triantafilou, 2002). This complex is considered Abstract a marker of bacterial translocation and transport responsi- The aim of the study was to investigate the association between ble for initiating a cell-mediated signal response (Nanbo the initial metabolic state and exercise-induced endotoxaemia on et al., 1999; van Deventer et al., 1988; 1998; Camus et al., the appearance of gastrointestinal symptoms (GIS) during exer- 1997). cise. Eleven males (36.6 ± 4.9 yrs, 1.7 ± 0.1 m, 74.5 ± 7.7 kg, DEXA body fat % 17.2 ± 6.6, VO2max 57.4 ± 7.4 ml·kg-1·min-1) Large amounts of endotoxins normally reside underwent two isoenergetic diets designed to change their initial within the human intestines. Bacterial translocation from metabolic status by either depleting or maintaining their hepatic the intestines to the portal circulation towards the liver and muscular glycogen content. These diets and accompanying might occur when factors such as a reduction in splanch- exercise sessions were performed by each participant in the days nic blood flow, intense physical exercise, long stays at before completing a laboratory-based duathlon (5-km run, 30- altitude, or high body core temperature affect the integrity km cycling, 10-km run). Blood samples were obtained before, of the intestinal wall (Hales and Sakurada, 1998; Hall et immediately and 1- and 2-h following the duathlon for determi- al., 2001; Peters et al., 2001a; Wagenmakers, 1992). Dur- nation of insulin (IN), glucagon (GL), endotoxin, aspartic ami- ing high-intensity and/or prolonged exercise blood flow to notransferase (AST), and alanine aminotransferase (ALT) mark- ers. GIS were assessed by survey before and after exercise. Diet the splanchnic areas decreases by approximately 50% content produced a different energy status as determined by from the resting state (Pals et al., 1997). This reduction in macronutrient content and the IN/GL ratio (p < 0.05), and mild blood flow is correlated to the intensity and duration of exercise-induced endotoxaemia was observed in both experi- the exercise (Otte et al., 2001). A reduction in visceral mental duathlons. Regardless of the diet, the AST/ALT ratio blood flow might elicit intestinal ischemia, compromising following exercise and in the recovery phase indicated hepato- intestinal wall integrity and leading to even higher levels cyte and liver parenchyma structural damage. In spite of GIS, no of circulating endotoxins. Furthermore, a reduction in significant correlations between endotoxin levels and GIS were visceral blood flow has been related to gastrointestinal found. In conclusion, increased markers of endotoxaemia ob- problems such as side-pain, flatulence, nausea and vomit- served with the high-intensity exercise were unrelated to hepatic function and/or GIS before and after exercise. ing (Peters et al., 2001b). Thus, there is consistent evidence showing that Key words: Liver structure, endurance, lipopolysaccharide, endotoxaemia occurs during endurance exercise (Brock- endotoxaemia, exercise. Utne et al., 1988; Jeukendrup et al., 2000) and that there might be a link to GIS and other medical conditions such as heat-stroke (Peters et al., 2001b; Ryan, 1993). Al- Introduction though Jeukendrup et al. (2000), did not report a correla- tion between endotoxin and GIS; Brock-Utne et al. Gastrointestinal symptoms (GIS) before, during, and after (1988), found a correlation between endotoxin levels and a competition are reported by approximately 20%–50% of athletes suffering from nausea, vomiting, and diarrhea. the athletes participating in endurance events such as Therefore, a potential role of endotoxins has been sug- marathon, cycling and triathlon (Gil et al., 1998; Peters et gested (Gil et al, 1998; Peters et al., 2001b) that might al., 2001a). In spite of the high frequency of GIS such as partially explain the appearance of GIS during endurance bloating, side-pain, nausea, and diarrhea, the exact exercise. physiological mechanisms responsible for such distur- An exercise-induced endotoxaemia model similar bances are not fully-understood. Endotoxaemia has been to the one proposed by Hales and Sakurada (1998) might suggested as an underlying cause responsible for the dele- be valid to assess the impact of high-intensity and long terious effect of strenuous physical exercise on athletes, duration exercise on physiological variables. First, during who in extreme conditions might require medical atten- exercise, endotoxins will translocate at a higher rate from tion (e.g., heat-stroke) (Hales and Sakurada, 1998; Ryan, a possibly compromised intestinal wall. Second, under 1993). Endotoxaemia is characterized by the presence of these circumstances, the liver may be unable to clear toxins in the blood, generally lipopolysaccharides (LPS) endotoxins and therefore elevated concentrations of these from gram-negative bacteria that bind to LPS-binding bacteria may cause disturbances in cardiovascular func- protein (LBP) to form the LPS-LBP complex (Trianta- tion. Received: 13 October 2008 / Accepted: 23 March 2009 / Published (online): 01 June 2009 Moncada-Jiménez et al. 253 Based on this model, we hypothesized that the each participant. Participants were instructed to rest (i.e., liver’s ability to clear endotoxins can be impaired if its no exercise) the day before the exercise intervention and energy level is low since this metabolic process is energy- to avoid unusually consumed foods that might cause GIS dependent. In other words, we hypothesized that the en- such as fiber-rich and spicy foods, caffeinated drinks, and zymatic indicators of structural hepatic changes will pre- controlled drugs such as alcohol, tobacco, and/or non- vent liver to clear endotoxins. Thus, endotoxins will be steroidal anti-inflammatory drugs (NSAIDs) (Lambert et responsible for producing gastrointestinal distress (Hales al, 2007; Van Nieuwenhoven et al., 1999; Ryan et al., and Sakurada, 1998), and might be a limiting factor for 1996). athletes exercising at high-intensity and for prolonged events. Therefore, the aim of the study was to investigate Exercise intervention the association between the initial metabolic state and Two-days before completing a duathlon, participants on exercise-induced endotoxaemia on hepatic structure and the high-CHO diet were instructed to return to the labora- the appearance of gastrointestinal symptoms during high- tory to complete a 60-min sub-maximal (70% VO2max) jog intensity endurance exercise. on the treadmill, and one-day before the duathlon, partici- pants were instructed to rest. During the 48-h in which Methods participants consumed the high-fat diet, they were re- quired to run on a treadmill for 60-min (70% VO2max) Participants and study protocol two-days before the duathlon and 45-min at the same A crossover design was used and experimental conditions intensity on the day prior to the duathlon. The exercise were randomly assigned to the participants. Thus, each regimens combined with the dietary manipulations were athlete performed the experiment on two different occa- used to change the initial metabolic state of the partici- sions, separated by at least 7 days. The Institutional Re- pants prior to when they report for the duathlon (Sherman view Board from Auburn University approved the study. et al., 1981). Written informed consent was obtained from each subject. Eleven males 20 to 44 years of age who had a maximal Experimental exercise session (duathlon) oxygen consumption (VO2max) ≥ 50 ml·kg-1·min-1 as de- On the day of the duathlon participants arrived at the termined in a treadmill-based graded exercise test (GXT) laboratory, returned empty food packages, and were were allowed to participate in the study. Volunteers were instructed to void their bladders before body weight was not allowed to participate if they reported or exhibited measured. Then, they were instructed to sit quietly for 5- anemia, had any gastrointestinal disorders, and/or other min. During the 5-min rest period, participants completed chronic disorders, were current cigarette smokers, and/or a “gastrointestinal symptom survey”. This is a modified were under any current nonsteroidal anti-inflammatory visual scale (Morton and Callister, 2002) used to obtain drug (NSAID) (Lambert et al., 2007). information about the anatomical location and the specific Volunteers who apparently met the inclusion crite- GIS felt. The 18 GIS list was obtained from the literature ria arrived to the Exercise Technology Laboratory at (belching, bloating, diarrhea, dizziness, flatulence/gas, Auburn University and underwent body composition headache, heartburn, intestinal cramps, muscle cramps, assessment to determine body fat mass via dual energy x- nausea, side-pain/side stitch, stomach cramps, stomach ray absorptiometry (DEXA), and a GXT on a treadmill to upset, urge to defecate, urge to urinate, urge to vomit, determine VO2max via respiratory gas analysis. Indications vomiting, and/or other). We did not ask the magnitude to stop the GXT were to achieve at least two of the fol- (i.e., how hard/light was felt) of the symptom, rather to lowing criteria: a) a request to stop the test, b) respiratory indicate (in the visual scale) the anatomical area in which exchange ratio (RER) ≥ 1.15, and/or c) a plateau of the the symptom was experienced. VO2 curve < 2 ml·kg-1·min-1 with increased workload. Next, a fasting blood sample was obtained. Fol- lowing the initial blood draw, participants were provided Initial metabolic state manipulation with a standardized breakfast of two slices of white bread, Participants were instructed to record their food consump- one slice of American cheese, water and a small banana to tion over a three-day period (2 weekdays and 1 weekend- eat while resting in a comfortable chair. This breakfast day) in a food log to determine food preferences and provided 1570.1 kJ (375 kcal) and was consumed in about energy needs (Economos et al., 1993). A registered dieti- 10-min. After a rest period of 60-min, participants had 10- tian analyzed food logs and designed two individual diets; min to warm up and then started the duathlon in the fol- one high in fat and one high in carbohydrates (CHO). lowing order: a) treadmill run of 5-km (Run-1); b) 30-km These diets met the participant’s daily energy needs; stationary cycle (Bike); and c) 10-km treadmill run (Run- however, their nutrient content was different. A nutrient 2). The subjects ran at 0% grade and were allowed to composition of 60% CHO, 25% fat, and 15% protein was modify only the treadmill speed. For the cycling part of the goal for the high-CHO diet; and 20% CHO, 65% fat, the race, participants had previously attached their own and 15% protein for the high-fat diet (Sherman et al., bicycles to a CompuTrainer™ (Racer Mate, Inc., Seattle, 1981). WA). Total time was recorded for further analysis. During Diets consisted of commercially-available pre- the duathlon the participants were given the opportunity packaged foods provided by the researchers and were to drink chilled water ad libitum; solid foods were given to each participant 72-h before an exercise trial. avoided at all times. The environmental conditions of Allotments for breakfast, lunch, dinner, and snacks 48-h temperature and relative humidity in the laboratory during before experimental exercise session were provided to the duathlon were 20-21°C and 50-60%, respectively. 254 Metabolic state and exercise-induced endotoxaemia Participants were asked to give their best effort adjustment for multiple comparisons). Finally, a Chi2 (χ2) during the duathlon. Volume of oxygen (VO2), heart rate test was carried to analyze gastrointestinal problems and (beats·min-1), and GIS were monitored for at least two endotoxaemia. minutes during the duathlon. VO2 and heart rate were used to assure an exercise intensity ≥ 70% VO2max. Par- Results ticipants were instructed to increase their effort if exercise intensity was < 70% of their individual VO2max. Table 1 shows the physical characteristics of the eleven Participants completed the “gastrointestinal symp- healthy athletes participating in the study. Participants tom survey” along with each of the blood samples. Once trained for middle and long distance events such as triath- the experimental session was completed, the subjects lon and marathon. They trained on average 11 h·wk-1, were provided with rehydration fluids, fruit, and an ap- including running on average 13 km·wk-1 and cycling 24 pointment for the next visit to the laboratory. to 40 km·wk-1. Resting Hb and Hct values were within normal ranges for adult males. Blood sampling and analysis Venous blood samples for each participant were collected Table 1. Descriptive statistics for athletes (n = 11). before, immediately after, and 1- and 2-h following the Variable Mean (±SD) duathlon. Two-7 ml serum tubes were obtained at each Age (years) 36.6 (4.9) blood sampling time point. Only the blood samples for Height (m) 1.70 (.10) glucagon analyses were collected in chilled lavender-top Body mass (kg) 74.5 (7.7) tubes containing 100 µL of aprotinin (Sigma, Aprotinin, Body fat mass (DEXA, %) 17.2 (6.6) -1 -1 Cat# A6279). Immediately following the blood draw, a VO2max (ml · kg · min ) 57.4 (7.4) small portion of the sample was collected in three micro- capillary tubes and spun to determine hematocrit (Hct). The fasting mean IN/GL ratio in the high-fat diet To determine hemoglobin (Hb) concentration another (0.27 ± 0.10) was lower (p ≤ 0.05) than the ratio on the portion of fresh blood (10 µL) was also immediately high-CHO diet (0.39 ± 0.20), indicating participant’s transferred into a tube containing a previously prepared compliance to the dietary regimen. Participants in the Hb reagent solution (2.5 mL Sodium Lauryl Sulfate). This high-fat diet consumed 11.59 ± 1.58 MJ distributed in mixture was transferred into a cuvette and read at 540 Nm meals consisting of 21% CHO, 67% fat, and 11% protein. in a spectrophotometer. In the high-CHO diet, energy intake was 11.50 ± 1.48 MJ The remainder of the blood sample was allowed to distributed in meals consisting of 63% CHO, 25% fat, and clot and serum was separated by centrifugation at 1500 g 11% protein. In the high-fat diet, the athletes consumed for 15-min. Serum aliquots were prepared and stored at – 2.8, 1.9, and 1.0 g·kg-1 body weight of fat, CHO, and 80°C for further analysis of glucose (Glucose Flex® Di- protein, respectively. In the high-CHO diet, fat, CHO, and mension®, Dade Behring Inc., Deerfield, IL), AST (AST protein consumed were 0.8, 6.3, and 1.0 g·kg-1 body Flex® Dimension®, Dade Behring Inc., Deerfield, IL), and weight, respectively. Fiber content of each diet was 31.63 ALT (ALT Flex® Dimension®, Dade Behring Inc., Deer- ± 16.41 g·d-1 for the high-fat diet and 42.02 ± 15.93 g·d-1 field, IL). Enzyme linked-immuno-sorbent assay (ELISA) for the high-CHO diet (p = 0.292). kits were used for determination of insulin (IN), glucagon No differences in duathlon performance were ob- (GL) (LINCO, St. Charles, MO), LPS-LBP complex as a served between the high-fat trial (136.38 ± 20.09 min) measure of endotoxaemia (Cell Sciences, Inc., Canton, and the high-CHO trial (134.88 ± 20.89 min). Regardless MA). Plasma concentration of LPS-LBP complex was of the diet, subjects performed the duathlon at 71.07 ± corrected to take into consideration changes in plasma 1.97% of their individually determined VO2max; achieving volume occurred during exercise (Dill and Costill, 1974). higher %VO2max in the run-1 (79.10 ± 2.59%) than in the cycle (64.20 ± 2.19%) and run-2 (69.90 ± 2.49%) (p ≤ Statistical analysis 0.001). Heart rate response, estimated as a percentage of Data were analyzed with the Statistical Package for the HRmax, was higher in the run-1 (88 ± 2%) compared to the Social Sciences (SPSS®), version 15.0 for Windows. Data bike (84 ± 2%) and run-2 (86 ± 2%) (p = 0.011). are presented as mean ± standard deviation (SD), and Analysis of hydration status at the end of the statistical significance was set a priori at p ≤ 0.05. Paired duathlon indicated higher dehydration after the high-fat t-tests were used to determine significant mean differ- diet trial (-1.6 ± 1.2% body mass) compared to the high- ences between experimental conditions in the dependent CHO diet trial (-1.0 ± 1.4% body mass) (p = 0.007). variables IN/GL ratio, performance time in the duathlon, For hepatic integrity markers AST, ALT, and diet content composition, and hydration status. Factorial 2 AST/ALT ratio, no significant combined effects were (diets) x 4 (pre-exercise, immediately after exercise, 1-h found between diet conditions and measurement time. post-exercise, 2-h post-exercise) repeated measures analy- Independently of measurement time, AST concentrations ses of variance (ANOVA) were computed to analyze were higher in the high-fat diet trial compared to the high- AST, ALT, the AST/ALT ratio, and LPS-LBP complex. CHO diet trial (39.23 ± 3.54 U/L vs. 29.40 ± 1.75 U/L) (p Metabolic indicators (i.e., VO2, %VO2) were analyzed by = 0.007). Regardless of the diet, AST levels increased a 2 (diets) x 3 (run-1, bike, run-2) factorial, repeated- from baseline (28.53 ± 2.03 U/L), to immediately measures ANOVA. For all ANOVA tests, appropriate following exercise (36.58 ± 2.52 U/L), and remained follow-up analyses were computed if significant interac- elevated 1- and 2-h following exertion (35.42 ± 2.50 U/L tions and/or main effects were found (i.e., Bonferroni and 36.72 ± 2.81 U/L, respectively) (p ≤ 0.001). Moncada-Jiménez et al. 255 1.4 b b b1.2 1.0 a 0.8 0.6 0.4 0.2 0.0 Baseline Immediately + 1 h + 2 h p < 0.05, a < b Figure 1. AST/ALT ratio for 11 males following a duathlon (mean ± SD). Also, regardless of the diet, ALT levels increased only Table 2. Frequency of participants with GI symptoms and from baseline (34.15 ± 1.74 U/L) to immediately follow- exercise-induced endotoxaemia following exercise under a ing exercise (35.83 ± 2.05 U/L) (p = 0.010). high-fat and a high-CHO diet (n = 11). Independently of measurement time, AST/ALT ra- Endotoxaemia immediately tio was higher in the low-CHO diet trial compared to the after exercise high-CHO diet trial (1.15 ± 0.12 vs. 0.89 ± 0.04) (p = Gastrointestinal LPS-LBP > 5 LPS-LBP < 5 Symptoms pg·ml-1 pg·ml-1 0.042). Regardless of the diet, AST/ALT ratios increased Yes 2 3 from baseline (0.84 ± 0.05), to immediately following High-fat diet No 4 2 exercise (1.03 ± 0.06), and remained elevated 1- and 2-h Yes 2 3 following exertion (1.08 ± 0.07 and 1.14 ± 0.11, respec- High-CHO diet No 3 3 tively) (p ≤ 0.001) (Figure 1). High-fat χ2 = 0.711; p = 0.399, High-CHO χ2 = 0.100; p = 0.752. Intestinal permeability and bacterial translocation as determined by the LPS-LBP complex increased from We estimated a GIS/time indicator by taking the baseline regardless of the dietary manipulation (p ≤ 0.05). number of reported GIS and dividing them by the cumula- LPS-LBP complex concentrations increased from base- tive time subjects performed exercise. Thus, in general, -1 line to immediately following exercise (∆ = 16.34%) and there were 0.35 episodes/h regardless of the diet, 0.51 -1 -1 decreased from baseline to 1- (∆ = - 0.79%) and 2-h (∆ = episodes/h in the high-fat diet, and 0.20 episodes/h in - 4.10%) following exercise. the high-CHO diet. GIS reported were belching, flatu- Mild endotoxaemia was found at baseline in 27% lence, intestinal cramps, nausea, side-pain/stitch, stomach of the participants (n = 3) who followed the high-fat diet upset, urge to vomit, vomiting, and constipation. The compared to 9% (n = 1) who followed the high-CHO diet. anatomical region where participants felt a GIS following These figures increased to 55% (n = 6) immediately fol- duathlon in the high-CHO diet is depicted in Figure 2. No lowing exercise in the high-fat diet, compared to 45% (n specific anatomical regions for GIS were reported during = 5) in the high-CHO diet. One-hour after exercise, 36% the high-fat diet. (n = 4) and 30% (n = 3) of the athletes in the high-fat and the high-CHO diets had endotoxaemia. Finally, 2-h fol- lowing exercise, endotoxaemia was found only in 9% (n = 1) and 10% (n = 1) of the athletes in the high-fat and high-CHO diets, respectively. The highest measured value for a participant was 16.7 pg·ml-1, immediately after exer- cise in the high-fat diet condition. Table 2 shows the incidence of GIS for both diet conditions. No significant associations were found be- tween GIS and endotoxaemia in either diet (high-fat, p = 0.399 vs. high-CHO, p = 0.752). Three participants (27%) reported GIS under both dietary conditions; four partici- pants (36%) did not report GIS in either dietary trial. Finally, 2 participants (18%) in the high-fat diet and 2 participants (18%) in the high-CHO diet trials reported GIS. Figure 2. Anatomical region where participants felt GIS in the high-CHO diet trial. B= Resting; I= Immediately after duathlon. AST/ALT 256 Metabolic state and exercise-induced endotoxaemia Discussion to be jeopardized in our participants. Changes of liver structure observed in this study were similar to findings The aim of the study was to investigate the effect of the reported in highly trained competitive cyclists (Mena et initial metabolic state and exercise-induced endotoxaemia al., 1996), marathoners (Smith et al., 2004), and other on the appearance of GIS during high-intensity endurance athletes performing a series of physical activities (Fojt et exercise in males. al., 1976; Schlang and Kirkpatrick, 1961). In this study, we tried to modify the initial meta- Since endotoxaemia has been proposed as a poten- bolic state by short-term diet and exercise. We did not tial mechanism explaining the appearance of GIS in ath- measure hepatic or muscular glycogen stores directly to letes, we expected to find a significant correlation be- determine metabolic state. Sherman et al. (1981), com- tween endotoxaemia and GIS such as nausea, vomiting, bined training runs (~60-min, 73% VO ) and diet (104 and diarrhea (Brock-Utne et al., 1988; van Deventer et al., 2max g CHO/d-1 for 48-h), then directly measured muscle gly- 1990). However, similar to Jeukendrup et al. (2000); we cogen by biopsies, and found a dramatic reduction in did not find a correlation between endotoxaemia and GIS. glycogen levels. Similarly, Widrick et al. (1993), com- Indeed, GIS were virtually absent in the subjects partici- bined exercise (60-min, 70% VO ) and diet (181 g pating in our study. We documented only one case of 2max CHO/d-1 for 48-h), and also found significant reductions belching, dizziness, headache, stomach upset, nausea and in muscle glycogen content. In this study we followed an vomiting 1-h after the duathlon in the high-fat diet. The intermediate protocol; we provided athletes with ~141 g participant remained in the laboratory for observation and CHO/d-1 for 48-h and supervised treadmill training runs symptoms resolved one hour after vomiting. Another (60-min, 70% VO ). Therefore we expected reduced subject complained of tightness in the upper abdominal 2max muscle (i.e., diet + training) and liver (i.e., diet + training area. However, this complaint was unrelated to our ex- + overnight fast) glycogen stores. Both, the combination perimental intervention (i.e., diet, exercise). Finally, two of a reduced CHO diet, treadmill exercise, and fasting participants reported having a transient side-stitch in the allowed us to confidently assume that both, muscle and lower abdominal area during exercise that lasted less than liver reserves, were low. 10-min and did not interfere with their performance. We also support the energy status change with the We hypothesized that the combination of both, a information provided by glucoregulatory hormones IN high intensity and long duration exercise, would reduce and GL. A subject in the absorptive state is expected to splanchnic blood flow allowing bacteria to translocate show higher IN concentrations than during post- from the intestines to the portal circulation to finally reach absorptive state; while a subject in the post-absorptive the liver (Gil et al., 1998; Pals et al., 1997; Otte et al., state or fasting is expected to show higher GL than IN 2001; Nielsen et al., 2002). In the present study, the mean levels (Vander et al., 1998). Therefore, an elevated IN/GL exercise intensity elicited by the subjects during the ratio would indicate an absorptive state and a hypoglyce- duathlon in both dietary conditions was high enough to mic state mediated by IN (i.e., high glycogen stores and cause intestinal permeability and bacterial translocation high energy status). A reduced IN/GL ratio would indi- from baseline as demonstrated by the increased LPS-LBP cate a post-absorptive state, meaning a higher glyco- complex values. Regardless of the dietary trial, the sub- genolysis rate and gluconeogenesis in order to maintain jects performed the duathlon at approximately 70% of normal blood glucose levels (i.e., low glycogen stores and their individual VO2max and this exercise intensity caused low energy status) (Brooks et al., 2000). In addition, total bacterial translocation as measured after exercise. Similar liver glycogen content is dramatically reduced following a results immediately after exercise have been previously 12-h fasting and/or a low carbohydrate diet (Houston, reported in marathon and ultraendurance events (Jeuken- 1995). We observed significant differences in the IN/GL drup et al., 2000; Øktedalen et al., 1992). ratio between dietary conditions, indicating a change in Although there were no direct correlations between the initial energy status mediated by a combined effect of endotoxaemia and GIS, we cannot rule out the endotox- the diet and exercise regimen. aemia model for explaining at least some of the gastroin- Even though a potential low energy level was testinal distress felt by athletes. Several individual charac- achieved at baseline in the high-fat diet trial, as shown by teristics may explain the variation in how an athlete re- a reduced IN/GL ratio, we did not find a significant asso- sponds to exercise, especially as it relates to gastrointesti- ciation between LPS-LBP complex and hepatic markers nal distress and/or exercise-induced endotoxaemia. A list AST and ALT following exercise. Our findings are simi- of psychological (e.g., pre-competitive anxiety), pre- lar to those reported when studying hepatocyte function in exercise presentation (e.g., diet, rest, fitness), physiologi- fasted and semifasted rats (Latour et al., 1999). In this cal function (e.g., buffering capacity, endotoxin clearance, study, the AST/ALT ratio was > 1.0 immediately follow- blood flow redistribution to vital organs), and environ- ing exercise and in the recovery phase (i.e., 1- and 2-h ment conditions (e.g., heat, cold, humidity), and variables post-exercise), indicating hepatocyte and liver paren- that might explain gastrointestinal distress still deserve chyma structural damage. Indeed, ALT, a more specific further investigation. Other factors might include, for marker of liver damage (Sherlock and Dooley, 2001), instance, the fiber content of the diet before the trials increased from baseline to immediately following exer- might impact the orocecal transit time producing gastroin- cise, suggesting hepatocyte damage (i.e., structure) possi- testinal distress. In addition, the fat and CHO content of bly explained by the combined effect of exercise intensity the diet, as well as hydration status during the race might and duration. Nevertheless, liver function did not appear impact the gastrointestinal system. In this study, the fiber Moncada-Jiménez et al. 257 content was similar between diets (combined mean ~36.8 Harris, A., Lindeman, A.K. and Martin, B.J. (1991) Rapid orocecal g·d-1), slightly above than the 20-35 g·d-1 recommended transit in chronically active persons with high energy intake. range for healthy adults (Marlett et al., 2002). Since it has Journal of Applied Physiology 70, 1550-1553. Houston, M.E. (1995) Biochemistry primer for exercise science. Human been reported that physically-active people have rapid Kinetics, Champaign, IL. orocecal transit time (i.e., higher gastrointestinal system Jeukendrup, A.E., Vet-Joop, K., Sturk, A., Stegen, J.H.J.C., Senden, J., motility) (Harris et al., 1991), we assumed that the impact Saris, W.H.M. and Wagenmakers, A.J.M. (2000) Relationship of the fiber content of the diets on the gastrointestinal between gastro-intestinal complaints and endotoxaemia, cyto-kine release and the acute-phase reaction during and after a system would be negligible. Thus, we did not find an long-distance triathlon in highly trained men. Clinical Science association between fiber content and GIS before, during 98, 47-55. or after exercise even in the presence of higher dehydra- Lambert, G.P., Boylan, M., Laventure, J.P., Bull, A. and Lanspa, S. tion levels in the high-fat diet. In addition, in spite of a (2007) Effect of Aspirin and Ibuprofen on GI permeability dur-ing exercise. International Journal of Sports Medicine 28, 722- having two significantly different diet composition (i.e., 726. high-fat vs. high-CHO), the fat content did not influence Latour, M.G., Brault, A., Huet, P.M. and Lavoie, J.M. (1999) Effects of the gastrointestinal system during the trials. We did not acute physical exercise on hepatocyte volume and function in find evidence to support that fat content might have rat. American Journal of Physiology 276, R1258-R1264. Marlett, J.A., McBurney, M.I. and Slavin, J.L. (2002) Position of the played a role in the few GIS reported during exercise. American Dietetic Association Health Implications of Dietary Finally, further studies need to be conducted to determine Fiber. Journal of the American Dietetic Association 102, 993- the influence of different levels of dehydration on the 1000. appearance of GIS. Mena, P., Maynar, M. and Campillo, J.E. (1996) Changes in plasma enzyme activities in profesional racing cyclists. British Journal of Sports Medicine 30, 122-124. Conclusion Morton, D.P., and Callister, R. (2002) Factors influencing exercise- related transient abdominal pain. Medicine & Science in Sports & Exercise 34, 745-749. 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(1990) Experimental endotoxaemia in hu- Effects of nutrition interventions on exercise performance mans: Analysis of cytokine release and coagulation, fibrinoli- E-mail: ratclla@auburn.edu tic, and complement pathways. Blood 76, 2520-2526. James K. TAYLOR van Deventer, S.J.H., Büller, H.R., ten Cate, J.W., Sturk, A. and Pauw, W. (1998) Endotoxaemia: An early predictor of septicaemia in Employment febrile patients. Lancet 331, 605-608. Division of Clinical Laboratory Science, Auburn University- Van Nieuwenhoven, M.A., Brouns, F., and Brummer, R.J.M. (1999) The Montgomery, Alabama, USA effect of physical exercise on parameters of gastrointestinal Degree function. Neurogastroenterology and Motility 11, 431-439. MSc Vander, A.J., Sherman, J.H., and Luciano, D.S. (1998) Human physiol- Research interest ogy: The mechanisms of body function. McGraw-Hill, New Effects of exercise on metabolic syndrome York. E-mail: jtaylor@mail.aum.edu Wagenmakers, A.J. (1992) Amino acid metabolism, muscular fatigue and muscle wasting. Speculations on adaptations at high alti- Peter W. GRANDJEAN tude. International Journal of Sports Medicine 13, s110-s113. Employment Widrick, J.J., Costill, D.L., Fink, W.J., Hickey, M.S., McConell, G.K., Associate professor at the Department of Kinesiology, Auburn and Tanaka. H. (1993) Carbohydrate feedings and exercise per- University, Alabama, USA formance: Effect of initial muscle glycogen concentration. Degree Journal of Applied Physiology 74, 2998-3005. PhD Research interest AUTHORS BIOGRAPHY Effects of exercise on lipid metabolism José MONCADA-JIMÉNEZ E-mail: grandpw@auburn.edu Employment Luis F. ARAGONVARGAS Doctoral student, director of the Laboratory of Human Move- Employment ment Sciences at the School of Physical Education and Sports Professor at the School of Physical Education and Sports at the at the University of Costa Rica, Costa Rica University of Costa Rica, Costa Rica Degree Degree MSc PhD Research interest Research interest The effects of exercise on gastrointestinal and immune re- Sports nutrition, fasting, dehydration and rehydration in sports sponses E-mail: luis.aragon@ucr.ac.cr E-mail: jose.moncada@ucr.ac.cr Eric P. PLAISANCE Prof. José Moncada-Jiménez Employment P.O. Box 239-1200, San José, Costa Rica. Postdoctoral fellow at the Boshell Diabetes and Metabolic Diseases Research Program at Auburn University, Alabama, USA Key points Degree PhD Research interest • Gastrointestinal symptoms before, during, and after The study of physiological and metabolic changes elicited by a competition are reported by approximately 20%– exercise and medications 50% of the athletes participating in endurance events E-mail: plaisep@auburn.edu such as marathon, cycling and triathlon. Michael L. MESTEK • Energy status, exercise-induced endotoxaemia and Employment liver structural damage might be related to gastroin- Research associate at the Integrative Vascular Biology testinal symptoms. Laboratory at University of Colorado, Colorado, USA Degree • In this study, gastrointestinal symptoms observed PhD before and after endurance exercise were unrelated Research interest to endotoxin levels or hepatic structural damage. Effects of aging, cardiometabolic risk factors, HIV-1, and physical activity on vascular endothelial function E-mail: michael.mestek@colorado.edu Felipe ARAYA-RAMIREZ Employment Doctoral student and graduate assistant at the Exercise Technology Laboratory at Auburn University, Alabama, USA Degree MSc Research interest Effects of exercise training in cardiovascular risk reduction in obesity E-mail: arayafe@auburn.edu