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11 recordsLinked to original sources
PubMed1976

Effect of propionic acid on fatty acid oxidation and ureagenesis.

Propionic acid significantly inhibited 14CO2 production from [1-14C] palmitate at a concentration of 10 muM in control fibroblasts and 100 muM in methylmalonic fibroblasts. This inhibition was similar to that produced by 4-pentenoic acid. Methylmalonic acid also inhibited 14CO2 production from [1-14C] palmitate, but only at a concentration of 1 mM in control cells and 5 mM in methylmalonic cells. Propionic acid (5 mM) also inhibited ureagenesis in rat liver slices when ammonia was the substrate but not with aspartate and citrulline as substrates. Propionic acid had no direct effect on either carbamyl phosphate synthetase or ornithine transcarbamylase. These findings may explain the fatty degeneration of the liver and the hyperammonemia in propionic and methylmalonic acidemia.

Ammonia↗
PubMed1979

The effects of glucagon on protein metabolism in normal man.

Plasma glucagon rises after major injury and could act to increase gluconeogenesis and ureagenesis in the post-traumatic state. This study documents the effect of prolonged glucagon infusion on ureagenesis and nitrogen excretion, as well as possible sources of the increased ureagenesis, in normal man. Four healthy men fasted for 6 days during intravenous infusion of glucose (750 gmday), establishing a steady state of minimal ureagenesis. Glucagon (1 mg/day) then was added to the infusion for 5 days. Glucose alone was given for the final 2 days. Forearm muscle flux of metabolites was determined by standard arterial-deep venous sampling and capacitance plethysmography. Glucagon concentration was suppressed during glucose infusion (11 +/- 13 pg/ml) and rose to levels seen in subjects with major trauma during glucagon infusion (669 +/- 138 pg/ml). Glucose infusion stabilized urine nitrogen excretion at 1.54 +/- 0.42 gm of N/sq m/day. Nitrogen excretion increased to 2.40 +/- 0.53 gm of N/sq m/day with glucagon infusion, with urea accounting for the increased excretion. Excretion of 3-methylhistidine was unchanged. Plasma amino acid concentration was strikingly reduced on the first day of glucagon infusion, where it stabilized. Forearm flux showed a slight net release of amino acid nitrogen during glucose infusion. Addition of glucagon to the glucose infusion resulted in a net uptake of nitrogen by forearm skeletal muscle. These evidences strong suggest that glucagon infusion in normal man increases ureagenesis, not only at the expense of the free amino acid pool, but by the hydrolysis of visceral protein as well, with muscle protein being maintained.

Amino Acids↗
PubMed1977

Influence of physiologic hyperglucagonemia on urinary glucose, nitrogen, and electrolyte excretion in diabetes.

To evaluate the effect of physiologic hyperglucagonemia on nitrogen and glucose metabolism and on urinary electrolyte excretion, pancreatic glucagon was administered as a continuous 3-day infusion to three adult-onset non-insulin-dependent diabetics and two insulin-treated juvenile diabetics while on a constant dietary intake. The glucagon infusion resulted in increases in plasma glucagon which were 4-6 fold greater than control values. Despite prolonged hyperglucagonemia, urinary glucose excretion was unchanged. Similarly, urinary urea nitrogen and total nitrogen excretion were not altered by glucagon administration. Urinary sodium tended to rise, albeit not significantly (p less than .01), on the first infusion day, but later declined to control values despite increasing plasma glucagon concentrations. Urinary chloride, potassium, calcium, phosphorus excretion remained unchanged. We conclude that continuous physiologic increments in plasma glucagon do not enhance glycosuria or increase protein catabolism and ureagenesis in diabetes when insulin is available. The augmented protein catabolism and glucogenesis that accompany diabetic ketoacidosis cannot be explained primarily on the basis of hyperglucagonemia.

Adult↗
PubMed1976

Carbohydrate metabolism in trauma.

During the initial shock or 'ebb' phase of injury, body glucose (serum glucose concentration X glucose space) is significantly increased but mass flow to peripheral tissue is only slightly altered. During the 'flow' or hypermetabolic phase of injury, mass flow of glucose is markedly increased, related to the extent of injury and directed primarily by increased sympathetic nervous system activity. Increased hepatic gluconeogenesis provides glucose which is converted to three-carbon precursors in the periphery and returns to the liver for reconversion to new glucose, utilising the Cori and alanine cycles. Increased ureagenesis is a consequence of skeletal muscle amino acids contributing to this cycle system. This energy shuttle system produces heat, and the rate of six- to three-carbon cycling correlates closely with the increased oxygen consumption of the injured patient. The glucose cycle may be altered by hormonal administration, food intake, exercise, weight loss, pharmacological manipulation and infection, but the basic reset in hepatic glucose production and energy demands in the injured patient appears essential for the inflammatory response and tissue repair.

Blood Glucose↗
PubMed1977

Effect of 4-pentenoate on rat liver ornithine transcarbamylase.

The effect of 4-pentenoate on rat liver ornithine transcarbamylase was studied. No effect was found. It is concluded that the effect of 4-pentenoic acid on ornithine transcarbamylase reported by others was probably due to technical errors. Available evidence indicates that 4-pentenoate inhibits ureagenesis by interfering with mitochondrial energy metabolism, which in turn impairs mitochondrial ornithine transport or depletes mitochondrial ATP, impairing carbamyl phosphate synthesis, or both.

Animals↗
PubMed1979

Amino acid metabolism in dogs with E. coli bacteremic shock.

In 10 fasting dogs receiving 10(9) viable E. coli bacteria per kilogram intravenously, mean systolic blood pressure decreased from 120.6 +/- 15.1 to 82.2 +/- 12.8 mm Hg. The association of hypoglycemia and increased arterial alanine and glycine with elevated plasma glucagon implied impaired gluconeogenesis. A rapid elevation of blood urea concentration, indicating increased ureagenesis, a fall of blood glucose, and an increase of net urea synthesis relative to that of glucose suggested that an increased proportion of the carbon residues derived from glucogenic amino acids is catabolized via pathways other than gluconeogenesis. In the bacteremic dogs the absolute net release from the leg of valine, isoleucine, and leucine and their net release relative to the net rate of proteolysis were decreased, suggesting increased oxidation of these amino acids in skeletal muscle. An increased net release of alanine relative to the net rate of protein catabolism in muscle was in agreement with this contention.

Alanine↗
PubMed1978

Cerebral and hepatic urea synthesis in patients with chronic renal insufficiency.

Urea production by the liver and the brain was evaluated in patients with chronic renal insufficiency and in subjects with normal renal function by measuring the arterial-venous differences of urea across the hepatosplanchnic bed and the brain. In five out of seven patients with chronic renal insufficiency no urea release into the hepatic veins was observed, whereas a high urea output by the brain was measured in 6 out of 8 patients. In the control group urea was released only into the hepatic veins. These data demonstrate a defect in hepatic urea synthesis and a switch to cerebral ureagenesis in chronic renal insufficiency.

Adult↗
PubMed2025

Use of an oversized AAV8 vector for CPS1 deficiency results in long-term survival and ammonia control.

Carbamoyl phosphate synthetase 1 (CPS1) deficiency, a urea-cycle disorder, results in hyperammonemia initiating a sequence of adverse events that can lead to coma and death if not treated rapidly. There is a high unmet need for an effective therapeutic for this disorder, especially in early neonatal patients where mortality is excessive. However, development of an adeno-associated virus (AAV)-based approach is hampered by large cDNA size and high protein requirement. We developed an oversized AAV vector as a gene therapy to treat CPS1 deficiency. In order to constrain genome size, we utilized small liver-specific promoter/enhancers and a minimal polyadenylation signal. Long-term survival (9 months, end of study) with ammonia control was achieved in AAV8.CPS1-administered Cps1flox/flox mice, while all null vector-injected controls died with marked hyperammonemia; female mice demonstrated improved survival over treated males. While glutamine remained elevated compared to controls, ammonia was controlled in surviving animals. Mice maintained their weights and were not sarcopenic. While drinking water did contain carglumic acid, no nitrogen scavengers were administered. Although there were concerns with vector genomic integrity, these findings demonstrate proof of concept for an oversized gene-therapy approach for a challenging urea-cycle disorder where high-level hepatic protein is essential for survival.

MT: Delivery Strategies↗