Naoki Kodo

The Effect of Carnitine on Ketogenesis in Perfused Livers from Juvenile Visceral Steatosis Mice with Systemic Carnitine Deficiency

Juvenile visceral steatosis (JVS) mice have been reported to have systemic carnitine deficiency, and the carnitine concentration in the liver of JVS mice was markedly lower than that of controls (11.6 ± 2.6 versus 393.5 ± 56.4 nmol/g of wet liver). To evaluate the role of carnitine in mitochondrial β-oxidation in liver, we examined the effects of carnitine on ketogenesis in perfused liver from control and JVS mice. In control mice, ketogenesis was increased by the infusion of 0.3 mM oleate, but not by L-carnitine. In contrast, although ketogenesis in JVS mice was not increased by the infusion of oleate, it was increased 2.5-fold by the addition of 1000μM L-carnitine. Addition of 50, 100, and 200 μM L-carnitine increased ketogenesis in a dose-dependent manner. The infusion of 0.3 mM octanoate or butyrate increased ketogenesis in a carnitine-independent fashion in both control and JVS mice. These findings suggest that endogenous long chain fatty acids from accumulated triglycerides may be used as substrates in the presence of carnitine in JVS mice. The relationship between ketogenesis and free carnitine concentration was examined in livers from JVS mice. Ketogenesis increased as free carnitine levels increased until concentrations exceeded about 100 nmol/g of wet liver (340 μM). The free carnitine concentration required for half-maximal ketone body production in liver of JVS mice was 45μM (13 nmol/g of wet liver), which corresponds to a Km value of carnitine palmitoyltransferase I. We conclude that carnitine is a rate-limiting factor for β-oxidation in liver only when the carnitine level in liver is very low.

Effect of sports activity on carnitine metabolism Measurement of free carnitine, γ-butyrobetaine and acylcarnitines by tandem mass spectrometry

The effects of sports activity on carnitine metabolism were studied using mass spectrometry. Serum levels of free carnitine, acylcarnitines (acetylcarnitine, propionylcarnitine, C4-, C5- and C8-acylcarnitine) and gamma-butyrobetaine, a carnitine precursor, were determined by tandem mass spectrometry in liquid secondary ion mass ionization mode. The coefficients of variation at three different concentrations were 2.8-7.9% for gamma-butyrobetaine, and 1.2 to approximately 6.7% for free carnitine. The recoveries added to serum were 109.1% for gamma-butyrobetaine, 89.3% for free carnitine. Sports activity caused increased serum levels of gamma-butyrobetaine, acetylcarnitine, C4- and C8-acylcarnitines and decreased serum levels of free carnitine. This method requires a small amount of sample volume (20 microl of serum) and short total instrumental time for the analysis (1 h for preparation, 2 min per sample for mass spectrometric analysis). Therefore, this method can be applied to study carnitine metabolism under various conditions that affect fatty acid oxidation.

Gluconeogenesis and ketogenesis in perfused livers from short-chain acyl-CoA dehydrogenase-deficient mice.

Recently, several cases of short-chain acyl-CoA dehydrogenase (SCAD) deficiency (McKusick 201470) in humans have been described. Symptoms of this disorder are variable (Turnbull et al 1984; Amendt et al 1987; Coates et al 1988) and metabolic characteristics are not well understood. A mutant mouse (BALB/cBYJ) with no SCAD activity in liver, which is the first animal model of fatty acid oxidation disorders, has been reported (Wood et al 1989). To investigate the metabolic characteristics in these mice, we performed a series of experiments using liver perfusion techniques and HPLC

Abnormal serum phenylalanine-tyrosine ratio and hyperferritinemia in malignant histiocytosis

Nine cases of childhood malignant histiocytosis (MH) showed an abnormally high serum phenylalanine (Phe)/tyrosine (Tyr) ratio (3.47 +/- 1.32) coincident with hyperferritinemia (50,800 +/- 33,600 ng/ml). Lactate dehydrogenase activity was also increased in these patients. These values were compared with data on sera from two groups of patients, acute leukemia cases (n = 14) and measles cases (n = 13), and with control values from normal healthy children (n = 38). The Phe/Tyr ratio was 1.57 +/- 0.54 for the acute leukemia (p less than 0.01) and 2.58 +/- 1.46 for the measles cases (NS), serum ferritin was 245 +/- 124 ng/ml for acute leukemia (p less than 0.01) and 167 +/- 117 ng/ml for measles (p less than 0.01). Accordingly, the concurrence of both abnormalities is considered to be characteristic for MH. It was also found that both serum Phe/Tyr ratio and ferritin levels reflect the disease activity, indicating that these two factors are useful prognostic indicators in the treatment of patients with MH.

Tryptophan therapy for non-ketotic hyperglycinaemia

Non-ketototic hyperglycinaemia (NKH; McKusick 238300) is a rare inherited metabolic disease caused by a defect of glycine cleavage enzyme. Increased glycine level in cerebrospinal fluid (CSF) is thought to cause the symptoms such as seizure, hyperkinesia and involuntary explosive movement. Sodium benzoate can decrease the glycine level in serum and CSF and is widely used in the treatment of NKH (Wolff et al 1986); however, it is not enough to control these symptoms. Recently the modulation of the N-methyl-D-aspartic (NMBA) receptor has been extensively studied and therapy for NtH is focusing on this aspect (Ohya et al 1991)

Hyperphenylalaninemia in Malignant Histiocytosis and Virus-Associated Hemophagocytic Syndrome

It has been known for more than 2 decades that amino acid changes accompany various forms of infectious diseases. In some of these infections, an elevation in the phenylalanine/tyrosine ratio has been reported (1–4). Similar amino acid changes have also been described in protein calorie malnutrition (5) and chronic renal insufficiency (6). So far, however, such changes have not been clearly described in patients with hematologic neoplasias, especially for proliferative disorders of mononuclear macrophages. Nor has the actual occurrence of hyperphenylalaninemia in association with infectious or neoplastic disorders been reported. Recently, we encountered 2 patients with malignant histiocytosis (MH) (7) and a case of virus‐associated hemophagocytic syndrome (VAHS) (8). In all three patients the disease took a very rapid and fatal course with multiple organ dysfunction associated with hyperphenylalaninemia (>400 μmol/l) and an increased serum phenylalanine/tyrosine (Phe/Tyr) ratio (>4.00) (Table 1).

Methylmalonic aciduria with pathological fracture.

Larsson A, Mattsson B, Wauters EAK et al (1981) 5-Oxoprolinuria due to hereditary 5oxoprolinase deficiency in two brothers A new inborn error of the gamma-glutamyl cycle. Acta Paediatr Scand 70: 301-307. Roesel RA, Hommes FA, Samper L (1981) Pyroglutamic aciduria (5-oxoprolinuria) without glutathione synthetase deficiency and with decreased pyroglutamate hydrolase activity. J Inher Metab Dis 4: 89-92.