An abundant biliary metabolite derived from dietary omega-3 polyunsaturated fatty acids regulates triglycerides.

Omega-3 fatty acids from fish oil reduce triglyceride levels in mammals, yet the mechanisms underlying this effect have not been fully clarified, despite the clinical use of omega-3 ethyl esters to treat severe hypertriglyceridemia and reduce cardiovascular disease risk in humans. Here, we identified in bile a class of hypotriglyceridemic omega-3 fatty acid-derived N-acyl taurines (NATs) that, after dietary omega-3 fatty acid supplementation, increased to concentrations similar to those of steroidal bile acids. The biliary docosahexaenoic acid-containing (DHA-containing) NAT C22:6 NAT was increased in human and mouse plasma after dietary omega-3 fatty acid supplementation and potently inhibited intestinal triacylglycerol hydrolysis and lipid absorption. Supporting this observation, genetic elevation of endogenous NAT levels in mice impaired lipid absorption, whereas selective augmentation of C22:6 NAT levels protected against hypertriglyceridemia and fatty liver. When administered pharmacologically, C22:6 NAT accumulated in bile and reduced high-fat diet-induced, but not sucrose-induced, hepatic lipid accumulation in mice, suggesting that C22:6 NAT is a negative feedback mediator that limits excess intestinal lipid absorption. Thus, biliary omega-3 NATs may contribute to the hypotriglyceridemic mechanism of action of fish oil and could influence the design of more potent omega-3 fatty acid-based therapeutics.

Antisense Oligonucleotide Reverses Leukodystrophy in Canavan Disease Mice.

Marked elevation in the brain concentration of N-acetyl-L-aspartate (NAA) is a characteristic feature of Canavan disease, a vacuolar leukodystrophy resulting from deficiency of the oligodendroglial NAA-cleaving enzyme aspartoacylase. We now demonstrate that inhibiting NAA synthesis by intracisternal administration of a locked nucleic acid antisense oligonucleotide to young-adult aspartoacylase-deficient mice reverses their pre-existing ataxia and diminishes cerebellar and thalamic vacuolation and Purkinje cell dendritic atrophy. Ann Neurol 2020;87:480-485.

DDAH-1 via HIF-1 target genes improves cerebral ischemic tolerance after hypoxic preconditioning and middle cerebral artery occlusion-reperfusion.

Dimethylarginine dimethylamino hydrolase-1 (DDAH-1) as an indirect regulator of nitric oxide (NO) metabolism, its role in hypoxic preconditioning (HPC) and ischemic tolerance (IT) of ischemic stroke has still been unknown and needs to be elucidated. Herein, DDAH-1 knock-out (KO) and wild-type (WT) rats underwent HPC and middle cerebral artery occlusion/reperfusion (MCAO/R) model. After 24 h, neurological severity scores, TTC staining and TUNEL assay were used to evaluate neurological damages. To explore the mechanism, the expression of hypoxia inducible factor (HIF-1α) and its target genes were assessed by Western blot and RT-qPCR. NO and ADMA contents were also tested. In addition, supplementation of l-arginine to DDAH-1 KO rats was used to explore the role of DDAH-1 in regulating NO. After HPC the ischemic outcome improved in both KO and WT rats, while KO rats showed attenuated IT exhibiting less expression of HIF-1α and its target genes, lower NO but higher ADMA content. The supplement of l-arginine to KO rats partly alleviated neurological damages accompanied with higher expression of HIF-1α. To sum up, DDAH-1 could regulate the level of NO and enhance IT following HPC and MCAO model via activating the expression of HIF-1α and its target genes.

Disruption of fatty acid amide hydrolase activity prevents the effects of chronic stress on anxiety and amygdalar microstructure.

Hyperactivation of the amygdala following chronic stress is believed to be one of the primary mechanisms underlying the increased propensity for anxiety-like behaviors and pathological states; however, the mechanisms by which chronic stress modulates amygdalar function are not well characterized. The aim of the current study was to determine the extent to which the endocannabinoid (eCB) system, which is known to regulate emotional behavior and neuroplasticity, contributes to changes in amygdalar structure and function following chronic stress. To examine the hypothesis, we have exposed C57/Bl6 mice to chronic restraint stress, which results in an increase in fatty acid amide hydrolase (FAAH) activity and a reduction in the concentration of the eCB N-arachidonylethanolamine (AEA) within the amygdala. Chronic restraint stress also increased dendritic arborization, complexity and spine density of pyramidal neurons in the basolateral nucleus of the amygdala (BLA) and increased anxiety-like behavior in wild-type mice. All of the stress-induced changes in amygdalar structure and function were absent in mice deficient in FAAH. Further, the anti-anxiety effect of FAAH deletion was recapitulated in rats treated orally with a novel pharmacological inhibitor of FAAH, JNJ5003 (50 mg per kg per day), during exposure to chronic stress. These studies suggest that FAAH is required for chronic stress to induce hyperactivity and structural remodeling of the amygdala. Collectively, these studies indicate that FAAH-mediated decreases in AEA occur following chronic stress and that this loss of AEA signaling is functionally relevant to the effects of chronic stress. These data support the hypothesis that inhibition of FAAH has therapeutic potential in the treatment of anxiety disorders, possibly by maintaining normal amygdalar function in the face of chronic stress.

Evaluation of the emotional phenotype and serotonergic neurotransmission of fatty acid amide hydrolase-deficient mice.

RATIONALE: By enhancing brain anandamide tone, inhibitors of fatty acid amide hydrolase (FAAH) induce anxiolytic-like effects in rodents and enhance brain serotonergic transmission. Mice lacking the faah gene (FAAH(-/-)) show higher anandamide levels. However, their emotional phenotype is still debated and their brain serotonergic tone remained unexplored. OBJECTIVES AND METHODS: In this study, we tested FAAH(-/-) mice in the social interaction and the open field tests performed under different lighting conditions (dim and bright) since variations of the experimental context were proposed to explain opposite findings. Moreover, by microdialysis performed under dim light, we analyzed their serotonergic transmission in frontal cortex (FC) and ventral hippocampus (vHIPP). RESULTS: In both light conditions, FAAH(-/-) mice showed reduced emotionality, compared to wt controls, as suggested by the increased rearing and reduced thigmotaxis displayed in the open field and by the longer time spent in social interaction. Basal serotonergic tone was higher in the FC of mutant mice as compared to control mice, while no difference was observed in the vHIPP. K(+)-induced depolarization produced similar increases of serotonin in both areas of both genotypes. An acute treatment with the CB1 antagonist rimonabant completely abolished the emotional phenotype of FAAH(-/-) mice and prevented the K(+)-stimulated release of serotonin in their FC and vHIPP, without producing any effect in wt mice. CONCLUSIONS: Our results support the role of FAAH in the regulation of emotional reactivity and suggest that anandamide-mediated hyperactivation of CB1 is responsible for the emotional phenotype of FAAH(-/-) mice and for their enhanced serotonergic tone.

Targeting fatty acid amide hydrolase (FAAH) to treat pain and inflammation.

The endogenous cannabinoid N-arachidonoyl ethanolamine (anandamide; AEA) produces most of its pharmacological effects by binding and activating CB(1) and CB(2) cannabinoid receptors within the CNS and periphery. However, the actions of AEA are short lived because of its rapid catabolism by fatty acid amide hydrolase (FAAH). Indeed, FAAH knockout mice as well as animals treated with FAAH inhibitors are severely impaired in their ability to hydrolyze AEA as well as a variety of noncannabinoid lipid signaling molecules and consequently possess greatly elevated levels of these endogenous ligands. In this mini review, we describe recent research that has investigated the functional consequences of inhibiting this enzyme in a wide range of animal models of inflammatory and neuropathic pain states. FAAH-compromised animals reliably display antinociceptive and anti-inflammatory phenotypes with a similar efficacy as direct-acting cannabinoid receptor agonists, such as Delta(9)-tetrahydrocannabinol (THC), the primary psychoactive constituent of Cannabis sativa. Importantly, FAAH blockade does not elicit any apparent psychomimetic effects associated with THC or produce reinforcing effects that are predictive of human drug abuse. The beneficial effects caused by FAAH blockade in these models are predominantly mediated through the activation of CB(1) and/or CB(2) receptors, though noncannabinoid mechanisms of actions can also play contributory or even primary roles. Collectively, the current body of scientific literature suggests that activating the endogenous cannabinoid system by targeting FAAH is a promising strategy to treat pain and inflammation but lacks untoward side effects typically associated with Cannabis sativa.

Clinical findings and a therapeutic trial in the first patient with beta-ureidopropionase deficiency.

The clinical, neurophysiological and neuroradiological work-up as well as the results of a specific treatment trial are presented of the first patient diagnosed with beta-ureidopropionase deficiency (E.C. 3.5.1.6, McKusick 606673). The patient presented with an early-onset dystonic movement disorder, severe developmental delay with marked impairment of visual responsiveness in combination with severely delayed myelination in magnetic resonance imaging studies. In addition, there were partial optic atrophy, pigmentary retinopathy and mild cerebellar hypoplasia. The enzyme defect was expected to lead to intracerebral deficiency of beta-alanine which seems to be a neuromodulator at inhibitory synapses. Therefore, a therapeutic trial with supplementation of beta-alanine was undertaken over 1.5 years with no convincing clinical improvement.

Structure and function of fatty acid amide hydrolase.

Fatty acid amide hydrolase (FAAH) is a mammalian integral membrane enzyme that degrades the fatty acid amide family of endogenous signaling lipids, which includes the endogenous cannabinoid anandamide and the sleep-inducing substance oleamide. FAAH belongs to a large and diverse class of enzymes referred to as the amidase signature (AS) family. Investigations into the structure and function of FAAH, in combination with complementary studies of other AS enzymes, have engendered provocative molecular models to explain how this enzyme integrates into cell membranes and terminates fatty acid amide signaling in vivo. These studies, as well as their biological and therapeutic implications, are the subject of this review.

Localization of biotinidase in the brain: implications for its role in hearing loss in biotinidase deficiency.

Biotinidase deficiency is an autosomal recessively inherited disorder characterized by neurological and cutaneous features, including sensorineural hearing loss. Although many of the features of the disorder are reversible following treatment with biotin, the hearing loss appears to be irreversible. To better characterize the nature of the hearing loss in this disorder, location of the expression and presence of biotinidase within the brain was examined using Northern blot analysis, in vitro hybridization of a cDNA panel, and immunohistochemical staining. Results indicate low, but detectable expression of biotinidase throughout the brain, but increased concentrations of biotinidase within the dorsal cochlear nucleus, ventral cochlear nucleus, and superior olivary complex of the brainstem, as well as, in the hair cells and spiral ganglion of the cochlea. These findings suggest that biotinidase and possibly biotin plays an important role in hearing.

Molecular characterisation of 34 patients with biotinidase deficiency ascertained by newborn screening and family investigation.

This study characterises the spectrum of biotinidase mutations in 21 patients (17 families) with profound biotinidase deficiency (BD) and 13 unrelated patients with partial BD using a denaturing gradient gel electrophoretic mutation screening and selective sequencing approach. In 29 from 30 unrelated families we found biallelic mutations including four common mutations, D444H (frequency 23.3%), G98:d7i3(20.0%), Q456H(20.0%), T532M (15.0%) and nine rare mutations (V62M, R157H, A171T+D444H, C423W, D543H, L279W, N172S, V109G, 12236G-A) with frequencies less than 5.0%. Only three profound BD patients with G98:d7i3/G98:d7i3 and Q456H/Q456H genotypes and residual biotinidase activities of 0.0%, and 0.9% of normal activity developed clinical symptoms before biotin supplementation at 8 weeks of age. All other patients remained asymptomatic within the first months of life or even longer without treatment. Two patients homozygous for the frameshift mutation G98:d7i3 had no measurable residual enzyme activity. Twelve patients with partial BD had the D444H mutation in at least one allele. We conclude that, based on mutation analysis and biochemical examinations of the enzyme, it is currently not clearly predictable whether an untreated patient will develop symptoms or not, although it seems that patients with activities lower than 1% are at a high risk for developing symptoms of the disease early in life.

Biotinidase deficiency--a treatable entity.

Biotinidase deficiency is a well recognised treatable cause of a wide spectrum of progressive neurological symptoms. Recent reports have stressed the need to screen children with early onset of seizures, encephalopathy, neurodevelopmental delay, skin rash and alopecia. Enzyme estimation remains the conclusive test. We present a patient with biotinidase deficiency suspected on the above clinical grounds and diagnosed on the basis of metabolic acidosis, raised blood lactate, ketonuria and positive dinitrophenylhydrazine (DNPH) test and confirmed on urinary organic acid profile. Supplementation with biotin resulted in marked clinical improvement and normalisation of metabolic parameters. Thus the clinician should be alert to simple clinical pointers which aid in early diagnosis of these disorders.

Evaluation of urinary acylglycines by electrospray tandem mass spectrometry in mitochondrial energy metabolism defects and organic acidurias.

We analyzed the urinary acylglycine excretion in 26 patients with mitochondrial energy metabolism disorders and in 55 patients with organic acidurias by electrospray tandem mass spectrometry (ESI-MS/MS), monitoring precursor ions of m/z 90. Urinary concentrations of the different acylglycines were quantified using deuterated internal standards. Normal values for the most important acylglycines were established. In MCAD and MAD (neonatal form) deficiencies, typical excretion patterns of urinary acylglycines were found in all the samples. In isovaleric aciduria, propionic aciduria, and 3-methylcrotonylglycinuria typical glycine conjugates were always found. Methylmalonic aciduria (mutase deficiency), multiple carboxylase deficiency, and 3-hydroxy-3-methylglutaric aciduria revealed pathological acylglycine profiles, even if not specific for the disease. In all these diseases acylglycine excretion seems to be less influenced by the clinical status than organic acid excretion. This method is a useful diagnostic tool for these metabolic disorders, complementary to organic acids and acylcarnitine profiles.

Mutation in a putative glycosylation site (N489T) of biotinidase in the only known Japanese child with biotinidase deficiency.

The only known Japanese child with biotinidase deficiency was identified by newborn screening in Japan. He has 10.8% of mean normal serum biotinyl-hydrolase activity and trace biotinyl-transferase activity. The mutation results in 16% of normal cross-reacting material in serum with antibody to purified normal biotinidase. He is homozygous for a unique mutation, A1466 > C (Asn489Thr) in exon 4 of the biotinidase gene. The mutation appears to abolish a putative glycosylation site in a region in which other missense mutations have been identified, indicating that this region of the enzyme must be important for enzyme activity. This mutation may affect secretion or stability of the enzyme in serum. Interestingly, this child is now 8 years old, has not been on biotin supplementation for 3 years, and has remained asymptomatic.

Mutation (Q456H) is the most common cause of profound biotinidase deficiency in children ascertained by newborn screening in the United States.

Biotinidase deficiency is an autosomal recessive disorder that can result in neurologic and cutaneous symptoms if not treated with biotin supplementation. We have identified the most common cause of profound biotinidase deficiency in children ascertained by newborn screening in the United States. 1368A-->C results in a substitution of histidine for glutamine 456 (Q456H) in exon D of the biotinidase gene. This mutation was found in at least one allele in 14 unrelated children from 27 different families or 15 of 54 alleles studied (28%). This mutation was not identified in 41 normal adults using SSCA, nor was it found in 296 normal newborns using allele-specific oligonucleotide analysis, suggesting that this change is not a polymorphism. In addition, biochemical data from a child homozygous for Q456H suggest that the aberrant enzyme has very low biotinyl-hydrolase activity, lacks biotinyl-transferase activity, and is not recognized by antibody prepared to purified, normal human biotinidase. The ethnic backgrounds of the parents contributing the Q456H allele are varied but are generally northern European.

Canavan disease. Analysis of the nature of the metabolic lesions responsible for development of the observed clinical symptoms.

Canavan disease (CD), a rare recessive autosomal genetic disorder, is characterized by early onset and a progressive spongy degeneration of the brain involving loss of the axon's myelin sheath. After a relatively normal birth, homozygous individuals generally develop clinical symptoms within months, and usually die within several years of the onset of the disease. A biochemical defect associated with this disease results in reduced activity of the enzyme N-acetyl-L-aspartate amidohydrolase (aspartoacylase) and affected individuals have less ability to hydrolyze N-acetyl-L-asparate (NAA) in brain and other tissues. As a result of aspartoacylase deficiency, NAA builds up in extracellular fluids (ECF) and is excreted in urine. From an analysis of the NAA biochemical cycle in various tissues of many vertebrate species, evidence is presented that there may be two distinct NAA circulation patterns related to aspartoacylase activity. These include near-field circulations in the brain and the eye, and a far-field systemic circulation involving the liver and kidney, the purpose of which in each case is apparently to regenerate aspartate (Asp) in order for it to be recycled into NAA as part of the still unknown function of the NAA cycle. Based on the authors' analysis, they have also identified several metabolic outcomes of the genetic biochemical aspartoacylase lesion. First, there is a daily induced Asp deficit in the central nervous system (CNS) that is at least six times the static level of available free Asp. Second, there is up to a 50-fold drop in the intercompartmental NAA gradient, and third, the ability of the brain to perform its normal intercompartmental cycling of NAA to Asp is terminated, and as a result, the only remaining long-term source of Asp for NAA synthesis is via nutritional supplementation of Asp or its metabolic precursors. Finally, the authors identify a potential maternal-fetal interaction that may be responsible for observed normal fetal development in utero, and that provides a rationale for, and suggests how, CD might respond to far-field nutritional, transplantation, or genetic engineering techniques to alter the course of the disease.

Biotinidase and its roles in biotin metabolism.

Biotinidase is the enzyme responsible for the recycling of the vitamin biotin. Biotinidase acts as a hydrolase by cleaving biocytin and biotinyl-peptides, thereby liberating biotin for reutilization. Biotinidase is also important for making biotin bioavailable from bound dietary sources. The interest in this enzyme has been increased by the discovery of biotinidase deficiency, an inherited biotin-responsive disorder that can result in neurological and cutaneous abnormalities, but can be treated effectively with biotin supplementation. Biotinidase has recently been shown to be biotinylated in the presence of biocytin, but not biotin, at neutral and alkaline pH. This raises the possibility that biotinidase acts as a biotin-binding or biotin-carrier protein. Biotinidase has also been shown to have biotinyl-transferase activity resulting in the transfer of biotin from biocytin to nucleophilic acceptors, such as histones. Transferase activity occurs at physiological pH and at physiological concentrations of biocytin and, therefore, may be the main function of the enzyme in serum and other tissues. These novel functions of the enzyme may indicate that biotinidase plays a critical role in the metabolism of biotin in nuclei, particularly of neuronal cells. The role of biotinidase in biotin metabolism may be a paradigm for better understanding the metabolism of other vitamins.

Deletion/insertion mutation that causes biotinidase deficiency may result from the formation of a quasipalindromic structure.

Biotinidase is responsible for recycling the vitamin biotin from biocytin that is formed after the proteolytic degradation of the biotin-dependent carboxylases. We have identified a deletion/insertion mutation within exon D of the human biotinidase gene in a child with biotinidase deficiency. The mutation causes a frame shift and premature termination which are predicted to result in a truncated protein. We propose that the mutation occurred during DNA replication by either of two mechanisms. Both mechanisms involve formation of a quasipalindromic hairpin loop in the template and dissociation of DNA polymerase alpha. This mutation supports the formation of palindromic structures as a possible cause of deletions in eukaryotes, and supports the proposal, derived from in vitro studies, that polymerase alpha may preferentially arrest or dissociate at specific template sequences.

The clinical spectrum of biotin-treatable encephalopathies in Saudi Arabia.

Ten patients with biotin-dependent, chronic progressive encephalopathies were studied retrospectively. In four patients, the underlying disease was either total or partial deficiency of biotinidase. In one patient, the disease was caused by a lack of holocarboxylase synthetase activity. Four patients presented with Leigh encephalopathy. However, a biochemical defect could not always be confirmed. All patients required the administration of large doses of biotin to maintain normal neurologic function.

Neonatal screening for biotinidase deficiency in east-Hungary.

There are two types of multiple carboxylase deficiency, the neonatal form with holocarboxylase synthetase defect and the late-onset form with biotinidase deficiency. We report our preliminary experiences in screening for biotinidase deficiency. In total 43,493 infants were screened for the deficiency of the enzyme biotinidase; 0.14% false positive results that necessitated requests for second blood samples and two newborns with a biotinidase defect were identified during our pilot study. The definitive diagnosis required the demonstration of enzyme deficiency in serum. Both of the patients have residual biotinidase activity: 3.59% and 7.55%. These two newborns with biotinidase deficiency are treated with daily supplementation of free biotin. According to our preliminary results biotinidase deficiency satisfies all the criteria for incorporation into the national newborn mass screening.

N-acetylaspartic aciduria in Canavan disease: another proof in two infants.

Increased amounts of urinary N-acetyl-aspartic acid was found in two infants with biopsy proven Canavan disease. The aspartoacylase assay is a new tool for determining both the prenatal and antenatal diagnosis of Canavan disease. This assay should be screened in patients with early onset of psychomotor deterioration, macrocephaly, spasticity/hypotonia and white matter hyperleucency at CT scan.