Effect of chain length of short-chain fatty acids on their effect on intracranial pressure in rabbits

The short-chain fatty acids propionic, butyric, valeric, isovaleric and octanoic produced elevations in intracranial pressure during intravenous infusion in rabbits. Serum concentrations of these compounds are elevated in patients with Reye's syndrome, and may contribute to the intracranial pressure elevations found in these patients.

Influence of fasting and transit on ruminal and blood metabolites in beef steers

Nine ruminally cannulated steers (average weight 477 kg) were randomly assigned to serve as controls (C) or to be fasted (F) or fasted and transported (FT). C steers were allowed free access to alfalfa hay, water and plain salt during the experiment; F steers were deprived of feed and water for 32 hr, and FT steers were deprived of feed and water and transported for 32 hr in a gooseneck trailer. After 32 hr, F and FT steers were allowed access to alfalfa hay, salt and water. Rumen samples were withdrawn via cannula at 0, 18, 32, 36, 46, 56, 80 and 104 hr after the start of the experiment. Jugular blood was sampled at the same times, except for 36 and 46 hours. Rumen pH of F and FT steers increased (P less than .05) during the 32 hr fasting/transit period over that of C steers and then decreased (P less than .05) on refeeding. Total VFA concentrations were lower in F steers (39.5 mmoles/liter) at 32 hr than in FT steers (202.2 mmoles/liter). Total counts of rumen bacteria and protozoa were lower (P less than .05) in F and FT steers than in C steers at all times except 0 and 104 hr, and recovery of microbial numbers was slower in FT and in F steers. VFA data suggest rumen motility may be impaired in FT steers compared with that in F steers. Blood glucose was higher (P less than .05) at 18 an 32 hr in FT than in F steers. Serum glutamic oxaloacetic transaminase was higher (P less than .05) at 18 hr (104.7 IU/liter) in FT steers than in steers in the other two groups (average 84.3 IU/liter). Serum Fe tended to be lower at 18 and 32 hr in FT steers than in F and C steers, and serum triglycerides were lower (P less than .05) in FT steers at 32 and 56 hr than in C. Most other blood constituents were not greatly affected by treatment. These data suggest that the physiological response of fasting alone differs considerably from that of fasting and transit stress, because transit appears to impose influences on rumen fermentation and blood chemistry beyond those imposed by fasting.

Volatile fatty acids in human peripheral and portal blood: quantitative determination vacuum distillation and gas chromatography

In order to determine volatile fatty acids (VFA) in human blood, gas chromatographic analyses were performed after blood samples had been pre-treated by a vacuum distillation procedure with subsequent evaporation. Results of the reproducibility study, investigated by pre-treating five aliquots of one human serum sample showed C.V. values ranging from 7.4 to 18.2. Normal serum VFA values were determined in individual serum samples collected from healthy subjects and compared to those present in serum from patients undergoing gall-bladder surgery. The serum VFA values were comparable in the two groups. In the surgical patients, blood was also collected from the portal circulation. All portal serum VFA values, except that of iso-butyric acid, were higher than those found in the samples collected from the peripheral arm vein. VFA values were also determined in serum specimens obtained from blood collected from the arm vein of patients with extensive cirrhosis of the liver. The VFA values showed marked individual variations and were higher than those found in peripheral samples from healthy subjects and patients undergoing gall-bladder surgery, but were lower than those found in samples from the portal circulation from the surgical patients.

Gas-liquid chromatography in routine processing of blood cultures for detecting anaerobic bacteraemia

Gas-liquid chromatography was performed on 233 positive blood cultures and findings were compared with culture results. Obligate anaerobic bacteria were recovered from 78 out of 79 blood cultures containing butyric or iso-valeric acids, or both; from 28 out of 69 blood cultures containing succinic acid; and from only one out of 41 blood cultures containing succinic but not butyric or iso-valeric acid. Good correlations (88%) were found for the recovery of anaerobic bacteria and the detection of butyric and/or iso-valeric acids. Detecting volatile fatty acids by gas-liquid chromatography performed on blood cultures at the first signs of growth can therefore provide an early and reliable indication of the presence of anaerobic bacteria.

Origin and utilization of volatile fatty acids in the rat

The arteriovenous differences in the caecum of the rat have been compared for volatile fatty acids (VFA) and for electrolytes. Our results suggest the possibility of an exchange between VFA and chloride at the level of the caecal wall, rather than a net exchange between VFA and bicarbonate; however, the role of bicarbonate or Cl- at the cellular level is still unknown. Acetate uptake by the liver was enhanced when acetate in the afferent plasma was increased in fed as in starved rats, showing that acetyl CoA synthetase was still active during starvation. A release of endogenous acetate was only observed in situations of very active ketogenesis (starvation at the end of pregnancy). In physiological conditions, propionate and butyrate reaching the liver were almost quantitatively removed. However, butyrate was taken up by the liver at a higher rate than propionate after intracecal loads. Propionate was very efficiently utilized as a glucogenic substrate and without noticeable disturbance of lactate metabolism. After administration of acetate loads in starved rats, hepatic ketogenesis increased slightly. There was a marked difference between ketogenesis from butyrate in fed and starved rats. The low ketogenesis from butyrate in the fed rats stressed the important role of metabolic pathways of acetyl-CoA utilization in the control of ketogenesis. In contrast to alanine or lactate, propionate was poorly antiketogenic in the rat.

In vitro adsorption of possible aetiological factors of hepatic encephalopathy

Four different adsorbents (activated charcoal, XAD-4, a strong base anion and a strong acid cation-exchange resin) were tested in vitro for their capacity to remove substances that may be important in the development of hepatic encephalopathy. Separate columns packed with one of these adsorbents were perfused for three hours with a reconstituted plasma solution containing simultaneously high concentrations of amino-acids, ammoniumchloride, short-chain fatty acids, octopamine and bile salts. Effective removal of all these substances was only obtained when either activated charcoal, or XAD-4, were combined with the cation-exchange resin. Possible implications for the treatment of hepatic coma are discussed.

Blood acid-base equilibrium in experimental acidosis of the rumen in sheep

Blood acid-base equilibrium in experimental acidosis of the rumen in sheep. Acta Physiol. Pol., 1979, 30 (4): 543--551. Experimental acidosis of the rumen was induced in sheep infusing into it through a fistula a solution of saccharose and solutions of different volatile fatty acids and lactic acid. Arterial-blood acid-base equilibrium indices were determined by the Astrup micromethod with an Acid-Base-Cart ABC-1 unit. It was found that during saccharose-acidosis partly compensated metabolic acidosis develops and that acid-base equilibrium disturbances are caused by all volatile fatty acids and lactic acid. When they are infused in equimolar amounts into the rumen the strongest and earliest disturbances in that equilibrium are caused by acetic acid, followed by butyric, lactic and propionic acids.

Brain metabolism and specific transport at the blood-brain barrier after portocaval anastomosis in the rat

The rapid metabolism of [1-14C]butyrate and [2-14C]pyruvate in the brain was studied after intracarotid injection in control rats and rats given an end-to-side portocaval anastomosis (PCA). At 10 or 50 sec after injection there was a 40-50% lowering of the total amount of radioactivity in the brain of operated rats for both compounds. The percentage distribution of label in various metabolic fractions, e.g. amino acids, was unaltered by PCA. The results from the metabolic studies focused on an impaired transport of short chain monocarboxylic acids between blood and brain in rats with a PCA. The brain uptake index (BUI) of acetate, butyrate, pyruvate and glucose was determined by rapid intracarotid injection of the 14C test compound plus 3H2O as a reference marker. At 3 weeks after PCA, transport of all 3 monocarboxylic acids into brain was reduced by 40-50%. The reduction in [2-14C]pyruvate uptake was absent at one week, but thereafter, up to 50 weeks after operation, was consistently present. Eadie-Hofstee analysis of influx at varying substrate concentrations indicated a reduction in Vmax values of pyruvate and butyrate uptake without changes in Km. The calculated influx rate of glucose in operated rats was reduced in direct proportion to the lowering of plasma glucose. Portocaval anastomosis in the rat induces selective changes on substrates that are transported across the blood-brain barrier via a facilitated transport process.

A rapid method for the determination of volatile fatty acids in biological fluids

A rapid and simple method for the determination of volatile fatty acids in plasma and urine without any pretreatment is described. The gas chromatographic method reported here allows us to detect and quantitate in approx. 20 min biological VFA characteristics of various metabolic diseases. Conditions used are very mild so to avoid as much as possible any thermal decomposition of biological compounds.

Biochemical correlates of illness and recovery in Reye's syndrome

Eight patients with Reye's syndrome were followed through the course of their disease with serial measurements of serum concentrations of ammonia, short-chain organic acids, and amino acids. Correlations were made between clinical status and biochemical alterations. Elevated short-chain fatty acids, hyperammonemia, and hyperaminoacidemia were found in all patients studied. Clinical improvement appeared to correlate most closely with clearance of short-chain fatty acids from the serum. These observations suggest that the clinical symptoms are at least in part related to organic acidemia and that treatment directed toward the rapid clearance of these compounds from the system is reasonable.

Plasma short-chain fatty acids in fulminant hepatic failure

The role of short-chain fatty acids in the pathogenesis of coma in patients with fulminant hepatic failure has been studied by gas-liquid chromatography. There was no correlation between the initial or the final plasma levels of short-chain fatty acids in these patients and the clinical outcome of their disease. A primary role for the short-chain fatty acids in the pathogenesis of coma in fulminant hepatic failure is unlikely.

Changes in portal blood metabolites and insulin with feeding steers twice daily

Four Holstein steers surgically prepared with a device for sampling from the portal vein were used to examine changes in concentrations of metabolites and insulin in portal blood with scheduled meals. The animals were fed a complete mixed ration (3.4 kcal/g digestible energy) twice daily at three intakes. Blood was sampled at 30, 15, 10, and 5 min before feeding and at 1, 3, 5, 10, 15, 30, 45, 60, and 120 min after feeding began. Average intakes of food at 30 min for the three intakes were 0 (control), 889 g (restricted), and 1425 g (fed). Packed cell volume increased rapidly within 15 min of initiation of the meal in fed steers, but the maximum change from pre-feeding was 6.6%. Insulin increased within 5 min with the restricted intake and at 15 min in fed steers. Portal volatile fatty acids and beta-hydroxybutyrate also increased within 15 min of initiation of the meal in fed steers, and glucose tended to decrease after feeding. Certain metabolites and insulin of portal bood changed rapidly with feeding. Additional studies are required to establish any role of these blood components in the short-term control of feed intake in steers consuming concentrate feeds.

Portal blood insulin and metabolite changes with spontaneous feeding in steers

Four Holstein steers surgically prepared with a device for sampling blood from the portal vein were used to study changes in metabolites and insulin of portal blood associated with spontaneous meal feeding. The animals were fed a complete mixed ration (3.4 kcal/g digestible energy) in individual, electronically controlled feeding units. Blood was sampled before, during, and after meals. During the meal, blood samples were at 2-min intervals. Blood was sampled at 50 individual meals. Average meal length was 15.0 min and average consumption per meal was 631.7 g. Portal insulin increased within 2 min of meal initiation and remained elevated for the first 14 min of meals. Free fatty acids also increased at 8, 10, 12, 16, and 18 min after meal initiation. There were no consistent changes in packed cell volume, glucose, beta-hydroxybutyrate, or volatile fatty acids during this time. On control days when no feed was consumed, there were no significant changes in concentrations of metabolites or insulin. The increase in insulin of portal blood, which occurs upon meal initiation, preceded changes in metabolites. Therefore, the rapid change in insulin may be the result of a reflex neural stimulation rather than the result of a metabolite stimulating release of insulin.

A simple quantitative method to determine short chain fatty acid levels in biological fluids

A simple method has been developed for quantitative acetic, propionic, isobutyric, butyric, isovaleric, valeric, isocaproic, and caproic acids in intestinal fluids, feces and blood. The method utilizes extraction with ether and gas chromatography. It is accurate over a wide range of SCFA concentrations and appears to be applicable to any biological fluid.

Alterations in volatile free fatty acids of blood after hepatectomy

Volatile free fatty acids (VFA) in blood increased approximately twofold in dogs subjected to total hepatectomy. The average total plasma VFA preoperatively was 1,585 mug percent and shortly before death, postoperatively, was 2,798 mug percent. The corresponding red cell concentrations were essentially the same. Acetic acid was 81 percent of the total VFA, propionic acid 7 percent, isobutyric acid 4 percent, butyric acid one percent, and isovaleric acid 5 percent. There was little or no isovalerate in red cells. The increments in the individual fatty acids after hepatectomy were highly variable, but the average increase with time was almost linear. The increase in VFA probably reflects an increased utilization of the branched-chain aminoacids by extrahepatic tissues.

Jamaican vomiting sickness. Biochemical investigation of two cases

We identified methylenecyclopropylacetic acid, a known metabolite of hypoglycin A, in the urine of two patients with Jamaican vomiting sickness. Excretion of unusual dicarboxylic acids such as 2-ethylmalonic, 2-methylsuccinic, glutaric, adipic and dicarboxylic acids with eight and 10 carbon chains were also detected in both patients. The amounts of these dicarboxylic acids were 70 to 1000 times higher than normal. These metabolites have also been identified in urine of hypoglycin-treated rats. This evidence links hypoglycin A to Jamaican vomiting sickness as its causative agent. Urinary excretion of short-chain fatty acids was also increased up to 300 times higher than normal. These results indicate that, despite their clinical and histologic similarities, the cause and biochemical mechanisms of Jamaican vomiting sickness differ distinctly from those of Reye's syndrome in which these abnormal urinary metabolites are not appreciably increased.

[Variations in the pattern of ruminal volatile free fatty acids, acetoacetate and glucose in the blood plasma of lactating cows after a period of fasting and renewed feeding]

3 lactating cows were fasted for 4 days and then again received food. The trial was performed to investigate the effect of fasting on the concentration and molar proportion of volatile fatty acids in the rumen, on the concentration of free fatty acids and glucose in blood plasma and on the acetoacetate concentration in the blood. Fasting produced a considerable decrease in the total concentration of volatile fatty acids. Processes of ruminal fermentation were characterized, during the fasting period, by a continuous increase in the molar proportions of acetic acid, isobutyric acid and isovaleric acid whereas a significant decline observed to occur in the molar proportions of propionic acid and butyric acid. The reciprocal behaviour of acetate and propionate under conditions of fasting lead to a linear increase in the C2 to C3 ratio from 4.4 : 1 to 9,6 : 1. With renewed food supply all fermentation data returned to normal levels. The concentrations of blood glucose declined after 24 hrs of fasting, remained at the same level for the following 2 days and rose again to normal values on the 4th day of fasting. The concentration of acetoacetate decreased significantly on the first day of fasting to values that were 4 times as high as the initial value. The concentration of free fatty acids in blood plasma increased tremendously to a value 40 times as high as that observed at the beginning of the fasting period. It proved to be a good indicator for the energy requirements of the organism.