Urinary Excretion Of Dicarboxylic Acids Research Articles

Carnitine Supplementation Ameliorates the Steatosis and Ketosis Induced by Pivalate in Rats

These studies examined the effect in rats of carnitine supplementation on variables of fat metabolism altered by administration of sodium pivalate, a compound which induces a carnitine deficiency. Weanling male rats received 20 mmol/L sodium pivalate or 20 mmol/L sodium bicarbonate in their drinking water for 2 wk. They were food-deprived for 24 h, and to maximize fatty acid oxidation, were cold-stressed for 4 h. In Experiment 1, group 1 received the bicarbonate, group 2 received the pivalate, group 3 received the pivalate and 0.46 mmol L-carnitine in the diet/d, while group 4 received the pivalate and 0.95 mmol L-carnitine in the diet/d. In Experiment 2, group 1 received unsupplemented drinking water, group 2 received the bicarbonate, group 3 received the pivalate, and group 4 received the pivalate and 0.95 mmol L-carnitine in the diet/d. Pivalate-treated rats given the low carnitine diet had plasma and liver triglyceride levels (Experiment 1), plasma β-hydroxybutyrate concentrations (Experiments 1 and 2) and urinary dicarboxylic acid excretion (Experiment 2) significantly greater than those of controls (P < 0.05). The reduced tissue carnitine concentrations, starvation ketosis and lipid accumulation in the liver are findings also reported for human secondary carnitine deficiency due to organic acidurias. Supplementing the diet with L-carnitine at the level of 0.95 mmol/d significantly raised plasma and tissue carnitine concentrations and reduced the plasma β-hydroxybutyrate and liver triglyceride concentrations to levels not significantly different than control values. Carnitine supplementation ameliorates the degree of liver lipid accumulation and exaggerated starvation ketosis induced by pivalate.

Plasma and urine metabolic profiles are reflective of altered beta-oxidation in non-diabetic obese subjects and patients with type 2 diabetes mellitus.

ObjectivesThe two primary pathophysiological characteristics of patients with type 2 diabetes mellitus (T2DM) are insulin resistance (IR) and beta cell dysfunction. It has been proposed that the development of IR is secondary to the accumulation of triacylglycerols and fatty acids in the muscle and liver, which is in turn thought to be secondary to an enzymatic defect in mitochondrial beta-oxidation. The purpose of the present study was to analyze the molecules of intermediary metabolism to determine if an alteration in mitochondrial function exists in T2DM patients and, if so, to determine whether this alteration is caused by excess nutrients or an enzymatic defect.Design and methodsSeventy-seven subjects were recruited and divided into four groups (21 T2DM patients, 17 non-diabetic overweight/obese subjects, 20 offspring of T2DM patients, and 19 healthy subjects). Anthropometric parameters were determined by air plethysmography, and biochemical and metabolic parameters were measured, including 31 acylcarnitines (ACs) and 13 amino acids quantified by MS/MS and 67 organic acids measured by GC/MS.ResultsPatients with T2DM showed elevation of short-chain ACs (C2, C4), a glycogenic amino acid (valine), a glycogenic and ketogenic amino acid (tyrosine), and a ketogenic amino acid (leucine) as well as altered excretion of dicarboxylic acids. T2DM offspring with abnormal glucose tolerance test GTT showed increased levels of C16. Subjects in the obese group who were dysglycemic also showed altered urinary excretion of dicarboxylic acids and lower levels of a long-chain AC (C14:2).ConclusionsThese results suggest that mitochondrial beta-oxidation is altered in T2DM patients and that the alteration is most likely caused by nutrient overload through a different pathway from that observed in obese subjects.

Clinical and Biochemical Findings of a Patient With Thanatophoric Dysplasia Type I: Additional Finding of Dicarboxylic Aciduria

Abstract Objective: A long-surviving thanatophoric dysplasia type I patient to age of 6 years is presented. Results and Conclusions: Molecular studies revealed a heterozygous point mutation, S249C in the fibroblast growth factor receptor 3 gene. Most of the clinical course was similar to previous reports, including hearing loss and acanthosis nigricans. Abnormal urinary excretion of dicarboxylic acids and 3-hydroxydicarboxylic acids was observed. We hypothesize that this was a consequence of the FGFR3 mutation.

Nonalcoholic steatohepatitis: Association of insulin resistance and mitochondrial abnormalities

The pathogenesis of nonalcoholic steatohepatitis (NASH) is unknown. We tested the hypothesis that NASH is associated with 2 defects: (1) peripheral insulin resistance, which increases lipolysis, delivery of free fatty acids (FFA) to the liver, and hepatic fatty acid beta oxidation, thereby creating oxidative stress; and (2) an abnormality within the hepatocytes that might render them more susceptible to injury from oxidative stress. The hypothesis was tested by evaluation of (1) insulin resistance by a 2-step hyperinsulinemic (10 and 40 mU. m(-2). min(-1)) euglycemic clamp; (2) insulin effects on lipolysis by enrichment of [U-(13)C]glycerol; (3) frequency and severity of structural defects in hepatocyte mitochondria in vivo; (4) fatty acid beta oxidation from serum [beta-OH butyrate], release of water-soluble radioactivity from (3)H-palmitate by cultured fibroblasts and urinary dicarboxylic acid excretion; and (5) hepatic lipid peroxidation by immunohistochemical staining for 3-nitrotyrosine (3-NT). Subjects with NASH (n = 6-10 for different studies) were compared with those with fatty liver (n = 6) or normal controls (n = 6). NASH and fatty liver were both associated with insulin resistance, with mean glucose infusion rates (normal/fatty liver/NASH) of step 1, 4.5/1.6/0.9; step 2, 9.5/7.7/4.5 (P < 0.03 for both steps). Although baseline rates of glycerol appearance were higher in those with NASH than in those with fatty liver (means, 14.6 vs. 21.6 micromol. kg(-1). min(-1); P < 0.05), neither group significantly suppressed glycerol appearance at insulin infusion rates of 10 mU. m(-2). min(-1). NASH was associated with loss of mitochondrial cristae and paracrystalline inclusions in 9 of 10 subjects, compared with 0 of 6 subjects with fatty liver. However, no evidence of a generalized defect in fatty acid beta oxidation was noted in any group. Also, mean [beta-OH butyrate] was highest in those with NASH (means, 90 vs. 110 vs. 160 micromol/L; P < 0.04). Increased staining for 3-NT was present in fatty liver, and even greater staining was seen in NASH. These data indicate that peripheral insulin resistance, increased fatty acid beta oxidation, and hepatic oxidative stress are present in both fatty liver and NASH, but NASH alone is associated with mitochondrial structural defects.

Dicarboxylic acids as markers of fatty acid peroxidation in diabetes

Increased urinary excretion of dicarboxylic acids (DAs) has been well known in patients with diabetic ketoacidosis (DKA). It was known that small amounts of such DAs were also detected in urine from healthy humans. Upon chemical, radiation-induced or enzymatic oxidation, cis-polyunsaturated fatty acids (PUFA) have previously been shown to generate saturated short- and medium-chain length DAs. In diabetes, it was confirmed that the imbalance between the generation of free radicals and antioxidant defense systems increases oxidative stress and leads to the damage of lipid, which contains PUFA. Some peroxidation products of PUFA, such as malondialdehyde and conjugated diene, are generally known to be elevated in patients with diabetes. The present study was undertaken to determine if urinary excretion of DAs is elevated in diabetic patients without DKA. Urine samples from ten non-ketoacidotic patients with type 2 diabetes and ten healthy subjects were examined for DAs by combined gas chromatography and mass spectrometry with selected ion monitoring. The diabetic subjects had significantly ( P<0.001) more increased DAs excretion in urine than corresponding healthy subjects. The yields of DAs in each group decreased in the order adipic>suberic>sebacic acid. Being stable and easily detectable compounds, DAs may be considered potential markers of oxidative attack on PUFA in diabetes.

Tolerance to starvation in children on long-term total parenteral nutrition

To evaluate the consequences of long-term cyclic total parenteral nutrition (TPN) on metabolicpathways which contribute to energy metabolism, adaptation to starvation was studied in a group of seven children 2–7 years old, on long-term cyclic TPN. In addition to clinical monitoring, the following biological parameters were measured: blood levels of glucose, free fatty acids, ketone bodies and carnitine, and urinary excretion of dicarboxylic acids. Five of the seven children had good clinical tolerance up to 30 h of fasting. This indicated that metabolic changes arising from prolonged cyclic TPN are easily reversed when such children are fasting. The other two children had to be refed after 22 and 24 h, respectively. Both had metabolic signs of impaired hepatic fatty acid oxidation or ketogenesis. These metabolic changes might reflect the liver failure caused by TPN in these children, and stresses the fact that prolonged starvation has to be carefully monitored in patients with liver dysfunction secondary to TPN.

Fuel homeostasis and carnitine metabolism in rats with secondary biliary cirrhosis

Energy metabolism is abnormal in patients and experimental animals with liver cirrhosis. To help better understand the abnormalities, fuel homeostasis and carnitine metabolism were studied in fed and 24-hr-starved rats with secondary biliary cirrhosis induced by bile duct ligation for 4 wk. Plasma ketone body concentrations were decreased by 67% in starved, bile duct-ligated rats compared with control rats. In contrast, plasma nonesterified fatty acid concentrations were not different between bile duct-ligated and control rats in the fed or the fasted state. Plasma triglyceride concentrations showed the expected decrease with starvation in control rats, but were increased with starvation in bile duct-ligated rats. Urinary excretion of dicarboxylic acids was increased in both fed and fasted bile duct ligated-rats compared with the respective control groups. Compared with control rats, hepatic total carnitine content (per gram of liver) was increased by 24% in fed and by 36% in fasted, bile duct-ligated rats. Fed, bile duct-ligated rats had an increased short-chain acylcarnitine-to-carnitine ratio in liver, plasma and urine compared with control rats. Analysis of the hepatic coenzyme A pool showed decreased coenzyme A content in fed and fasted bile duct-ligated rats compared with control rats. Hepatic long-chain acylcarnitine and long-chain acyl-coenzyme A content increased with starvation both in control and bile duct-ligated rats. The rise in plasma nonesterified fatty acid concentration and hepatic long-chain acylcarnitine and long-chain acylcoenzyme A contents with starvation in bile duct-ligated rats are consistent with unaltered hepatic availability of fatty acids.(ABSTRACT TRUNCATED AT 250 WORDS)

7 Defects of fatty-acid oxidation in muscle

Long-chain fatty acids (LCFA) are oxidized by muscle mitochondria after transport in the cytosol by fatty-acid-binding protein(s) and their activation by a thiokinase. Carnitine, two forms of carnitine palmitoyltransferase(s) and carnitine acylcarnitine translocase are involved in LCFA gating. A primary genetic carnitine deficiency occurs in children with dilated cardiomyopathy, hypoglycaemia and low carnitine content in plasma, liver and muscle, owing to a defect in a common high-affinity transport system. This high-affinity transport in muscle differs from a low-affinity transport that has modifications during muscle maturation. The genetic enzyme defects of beta-oxidation (long-chain acyl-CoA dehydrogenase, medium- and short-chain acyl-CoA-dehydrogenase) present with Reye-like attacks that may lead to non-ketotic hypoglycaemia, coma and sudden infant death syndrome. There is elevated urinary excretion of dicarboxylic acids, acylcarnitines and acylglycines. Secondary carnitine deficiency may occur. ETF and ETF dehydrogenase deficiencies may present in a neonatal form with congenital anomalies, or in a later-onset form with ethylmalonic adipic aciduria. A still-unidentified defect leads to LCFA accumulation in fibroblasts, bone marrow, liver and muscle cells in a multisystem triglyceride disorder.

Urinary Dicarboxylic Acids in X‐Linked Adrenoleukodystrophy

The urinary excretion of dicarboxylic acids in X-linked adrenoleukodystrophy (X-ALD) was studied. The dicarboxylic acid profile in X-ALD did not show any specific pattern, unlike Zellweger syndrome and neonatal adrenoleukodystrophy. Medium-chain dicarboxylic acids with an even number of carbon atoms (adipic, suberic, sebacic) and an odd number of carbon atoms (pimelic, azelaic) were excreted within the normal ranges. Dicarboxylic acids with more than 10 carbon atoms were not found. These findings may be due to the normal beta-oxidation system of dicarboxylic acids in X-ALD.

Urinary Excretion of Dicarboxylic Acids in Term Newborns Fed with 5% Medium‐Chain Triglycerides‐Enriched Formula

Urinary Excretion of Dicarboxylic Acids in Term Newborns Fed with 5% Medium‐Chain Triglycerides‐Enriched Formula

Ketogenesis in hypoglycemic neonates. Carnitine and dicarboxylic acids in neonatal hypoglycemia.

Since hypoglycemic neonates do not exhibit compensative ketosis, we investigated the possible involvement of carnitine deficiency or omega-oxidation in neonatal hypoglycemia. In a first group of 49 neonates, serum free fatty acid, acetoacetate and beta-hydroxybutyrate concentrations were similar in hypoglycemic and normoglycemic neonates. Serum free carnitine concentrations did not show any difference in the hypoglycemic small-for-date infants (median 40 mumol/l, range 16-92 mumol/l) compared to the normoglycemic small-for-date infants (median 30 mumol/l, range 8-64 mumol/l). In a second group of 45 neonates, urinary excretion of dicarboxylic acids (adipic, suberic, sebaric and succinic acids) was similar in hypoglycemic infants compared to normoglycemic neonates. Despite the limitations of interpretation of free carnitine determination, these data do not suggest an impaired beta-oxidation by carnitine depletion or an enzymatic defect in hypoglycemic neonates.

INCREASED β- AND ω-OXIDATION OF FATTY ACIDS IN THE SILVER RUSSELL SYNDROME

We found evidence for an increased oxidation of fatty acids in two Silver-Russell patients (dwarfism of prenatal onset, typical craniofacial appearance and dystrophy).Fasting studies showed elevated blood and urine levels of β-hydroxybutyrate (BHB) and aceto-acetate (AA) and a massive urinary excretion of C6-C12 dicarboxylic acids. After 20 hrs of fasting BHB in blood was 3.50 and 3.50 mmol/1 while AA was 1.02 and 1.12 mmol/1 in the two Silver-Russell dwarfs, respectively. Seven controls of comparable age (1-2½ yr) had significanly lower blood levels of BHB (mean: 1.68 mmol/l) and AA (mean: 0.63 mmol/1). GC-MS analysis of urine organic acids of both Silver-Russell patients showed a very similar pattern with a massive excretion of BHB (<10 mmol/1) and C6-C12 dicarboxylic acids (adipic acid, suberic acid, sebacic acid, C12-dicarboxylic acid, cis/trans unsaturated suberic acid and sebacic acid, cis unsaturated 3-OH-derivates of sebacic acid and C12dicarboxylic acid). In contrast controls had a low excretion of BHB (<1 mmol/l), while C6-C12 dicarboxylic acids were present in very small amounts or not detectable. The combination of both an activated β-oxidation resulting in high blood and urine levels of BHB and AA, and an activated ω-oxidation resulting in a massive urinary excretion of dicarboxylic acids is very typical.We suggest that this increased oxidation of fatty acids is a distinct feature in the Silver-Russell syndrome and might provide an explanation for the dystrophy which is so characteristic.

Urinary excretion of dicarboxylic acids from patients with the zellweger syndrome Importance of peroxisomes in β-oxidation of dicarboxylic acids

The urinary excretion of adipic acid, suberic acid and sebacic acid from two patients with the cerebrohepato-renal syndrome of Zellweger was studied. The patients had a complete lack of peroxisomes in the liver as judged by electron microscopy. In the non-ketotic state, the total excretion of free and conjugated adipic acid, suberic acid and sebacic acid was increased by about 100%, 200% and 350%, respectively, as compared to the corresponding excretion from six healthy infants of the same age. The excretion of free dicarboxylic acid was increased to a considerably lesser extent than the free + conjugated dicarboxylic acid. In view of the presence of adipic acid in urine of the Zellweger patients, it is concluded that peroxisomes are not obligatory for β-oxidation of medium-chain dicarboxylic acids in vivo. The relative accumulation of suberic acid and sebacic acid as compared to adipic acid is, however, consistent with a relative block in the conversion of suberic acid and sebacic acid into adipic acid in patients with the Zellweger syndrome.