1.
Role of ammonia and inflammation in minimal hepatic encephalopathy.
Shawcross, DL, Wright, G, Olde Damink, SW, Jalan, R
Metabolic brain disease. 2007;(1):125-38
Abstract
BACKGROUND Minimal hepatic encephalopathy (MHE) is common in cirrhosis but its pathophysiologic basis remains undefined. We evaluated whether the presence of MHE was associated with severity of liver disease, ammonia levels or the presence of inflammation and assessed factors determining neuropsychological deterioration accompanying induction of hyperammonemia. METHODS Eighty four cirrhotics were studied. A neuropsychological test battery was performed and blood taken for ammonia, WCC, CRP, nitrate/nitrite, IL-6 and amino acids, before and after, induction of hyperammonemia by administration of a solution mimicking the amino acid composition of haemoglobin (60) or placebo (24). RESULTS The presence and severity of MHE were independent of severity of liver disease and ammonia concentration but markers of inflammation were significantly higher in those with MHE compared with those without. Induction of hyperammonemia produced deterioration in one or more neuropsychological tests by > or =1 SD in 73.3%. This was independent of the magnitude of change in plasma ammonia and severity of liver disease but was significantly greater in those with more marked inflammation. CONCLUSION Our data show that inflammation is an important determinant of the presence and severity of MHE. The change in neuropsychological function following induced hyperammonemia is greater in those with more severe inflammation.
2.
Short-term low-carbohydrate diet dissociates lactate and ammonia thresholds in men.
Langfort, J, Czarnowski, D, Zendzian-Piotrowska, M, Zarzeczny, R, Górski, J
Journal of strength and conditioning research. 2004;(2):260-5
Abstract
A low-carbohydrate (L-CHO) diet has been shown to shift the lactate threshold toward higher workloads. The aim of the present study was to examine the effect of an L-CHO diet on the ammonia threshold and to compare it with the lactate threshold in men. The plasma catecholamine threshold was also measured. Eight young, untrained men participated in the study. Two exercise tests with graded workload were performed. The workload was increased every 3 minutes by 40 W until volitional exhaustion. The first test was performed after 3 days of a controlled mixed diet. After the first test, the mixed diet was switched to a L-CHO diet. Three days later the same test was repeated. The blood concentration of lactate, ammonia, noradrenaline, and adrenaline was measured before and after each workload in both groups. It was found that the concentration of the examined compounds in the blood increases exponentially with graded workload after each kind of diet. This led us to calculate the blood ammonia, lactate, epinephrine, and norepinephrine thresholds. The thresholds were defined as points at which the concentration of a given compound starts to increase in a nonlinear fashion, which is calculated using 2 segmental linear regressions. After the mixed diet, the threshold for each compound occurs at the same workload. The L-CHO diet resulted in dissociation of the lactate threshold from the ammonia threshold: the lactate threshold was shifted toward a higher workload, whereas the ammonia threshold was shifted toward a lower workload. The norepinephrine threshold was also shifted toward a lower workload, and the epinephrine threshold remained unchanged. The results obtained indicate that an L-CHO diet accelerates production of ammonia and delays production of lactate during graded exercise, as well as that diet must be strictly controlled when ammonia and lactate thresholds are measured.
3.
Effect of vegetables, tea, and soy on endogenous N-nitrosation, fecal ammonia, and fecal water genotoxicity during a high red meat diet in humans.
Hughes, R, Pollock, JR, Bingham, S
Nutrition and cancer. 2002;(1):70-7
Abstract
Red meat increases colonic N-nitrosation, and this may explain the positive epidemiological relationship between red meat intake and colorectal cancer risk. Vegetables, tea, and soy have been shown to block N-nitroso compound (NOC) formation and are associated with protection against colorectal cancer. To determine whether these supplements affect fecal NOC excretion during consumption of a high red meat (420 g/day) diet, 11 male volunteers were studied over a randomized series of 15-day dietary periods. Seven of these subjects completed a further dietary period to test the effects of soy (100 g/day). Soy significantly suppressed fecal apparent total NOC (ATNC) concentration (P = 0.02), but supplements of vegetables (400 g/day as 134 g broccoli, 134 g brussels sprouts, and 134 g petits pois) and tea extract (3 g/day) did not affect mean levels of fecal ATNC, nitrogen and ammonia excretion, and fecal water genotoxicity. However, fecal weight was increased (P < 0.001) and associated with reduced transit time (r = 0.594, P < 0.0001), so that contact between ATNC, nitrite, and ammonia and the large bowel mucosa would have been reduced. Longer transit times were associated with elevated fecal ATNC concentrations (r = 0.42, P = 0.002). Fecal nitrite was significantly suppressed during the tea supplement compared with the meat-only (P = 0.0028) and meat + vegetables diets (P = 0.005 for microgram NO2/g).
4.
Effect of carbohydrate ingestion on ammonia metabolism during exercise in humans.
Snow, RJ, Carey, MF, Stathis, CG, Febbraio, MA, Hargreaves, M
Journal of applied physiology (Bethesda, Md. : 1985). 2000;(5):1576-80
Abstract
The present study was undertaken to examine the effect of carbohydrate ingestion on plasma and muscle ammonia (NH(3) denotes ammonia and ammonium) accumulation during prolonged exercise. Eleven trained men exercised for 2 h at 65% peak pulmonary oxygen consumption while ingesting either 250 ml of an 8% carbohydrate-electrolyte solution every 15 min (CHO) or an equal volume of a sweet placebo. Blood glucose and plasma insulin levels during exercise were higher in CHO, but plasma hypoxanthine was lower after 120 min (1.7 +/- 0.3 vs. 2.6 +/- 0.1 micromol/l; P < 0. 05). Plasma NH(3) levels were similar at rest and after 30 min of exercise in both trials but were lower after 60, 90, and 120 min of exercise in CHO (62 +/- 9 vs. 76 +/- 9 micromol/l; P < 0.05). Muscle NH(3) levels were similar at rest and after 30 min of exercise but were lower after 120 min of exercise in CHO (1.51 +/- 0.21 vs. 2.07 +/- 0.23 mmol/kg dry muscle; P < 0.05; n = 5). These data are best explained by carbohydrate ingestion reducing muscle NH(3) production from amino acid degradation, although a small reduction in net AMP catabolism within the contracting muscle may also make a minor contribution to the lower tissue NH(3) levels.