Predictors for a dementia gene mutation based on gene-panel next-generation sequencing of a large dementia referral series.

Next-generation genetic sequencing (NGS) technologies facilitate the screening of multiple genes linked to neurodegenerative dementia, but there are few reports about their use in clinical practice. Which patients would most profit from testing, and information on the likelihood of discovery of a causal variant in a clinical syndrome, are conspicuously absent from the literature, mostly for a lack of large-scale studies. We applied a validated NGS dementia panel to 3241 patients with dementia and healthy aged controls; 13,152 variants were classified by likelihood of pathogenicity. We identified 354 deleterious variants (DV, 12.6% of patients); 39 were novel DVs. Age at clinical onset, clinical syndrome and family history each strongly predict the likelihood of finding a DV, but healthcare setting and gender did not. DVs were frequently found in genes not usually associated with the clinical syndrome. Patients recruited from primary referral centres were compared with those seen at higher-level research centres and a national clinical neurogenetic laboratory; rates of discovery were comparable, making selection bias unlikely and the results generalisable to clinical practice. We estimated penetrance of DVs using large-scale online genomic population databases and found 71 with evidence of reduced penetrance. Two DVs in the same patient were found more frequently than expected. These data should provide a basis for more informed counselling and clinical decision making.

Prevalence of attention deficit hyperactivity disorder symptoms in patients with schizophrenia.

OBJECTIVE: To investigate the frequency of childhood and adult attention deficit hyperactivity disorder (ADHD) symptoms in a cohort of patients with schizophrenia (SCZ). METHODS: A systematic review was conducted to evaluate existing evidence. Two self-report questionnaires were used to investigate adult ADHD and childhood ADHD symptoms in 126 patients with ICD-10 diagnoses of SCZ. RESULTS: Five studies were included in the systematic review, with the prevalence of childhood and adult ADHD in SCZ subjects ranging between 17-57% and 10-47% respectively. Within our cohort, 47% of patients reported positive screening for ADHD symptoms either in childhood or adulthood. 23% reported symptomatology consistent with both childhood and adult ADHD. CONCLUSIONS: We demonstrate a greater presence of ADHD symptomatology in SCZ compared to that reported for ADHD in the general population. Our findings highlight the importance of improved clinical assessment and treatment considerations in a subgroup of patients with SCZ.

Cortical venous disease severity in MELAS syndrome correlates with brain lesion development.

PURPOSE: MELAS syndrome is a mitochondrial disorder typified by recurrent stroke-like episodes, seizures, and progressive brain injury. Abnormal mitochondria have been found in arterial walls implicating a vasculogenic etiology. We have observed abnormal cortical vein T2/FLAIR signal in MELAS patients, potentially representing wall thickening and sluggish flow. We sought to examine the relationship of hyperintense veins and brain lesions in MELAS. METHODS: Imaging databases at two children's hospitals were searched for brain MRIs from MELAS patients. Artifact, sedated exams, and lack of 2D-T2/FLAIR sequences were exclusion criteria. Each exam was assigned a venous score based on number of T2/FLAIR hyperintense veins: 1 = <10, 2 = 10 to 20, 3 = >20. Cumulative brain lesions and venous score in MELAS and aged-matched normal exams were compared by Mann-Whitney test. RESULTS: A total of 106 exams from 14 unique MELAS patients (mean 16 ± 3 years) and 30 exams from normal aged-matched patients (mean 15 ± 3 years) were evaluated. Median venous score between MELAS and control patients significantly differed (3 versus 1; p < 0.001). In the MELAS group, venous score correlated with presence (median = 3) or absence (median = 1) of cumulative brain lesions. In all 8 MELAS patients who developed lesions, venous hyperintensity was present prior to, during, and after lesion onset. Venous score did not correlate with brain lesion acuity. CONCLUSION: Abnormal venous signal correlates with cumulative brain lesion severity in MELAS syndrome. Cortical venous stenosis, congestion, and venous ischemia may be mechanisms of brain injury. Identification of cortical venous pathology may aid in diagnosis and could be predictive of lesion development.

Overt hepatic encephalopathy: development of a novel clinician reported outcome tool and electronic caregiver diary.

Clinical management and clinical trials of patients with overt hepatic encephalopathy (OHE) are compromised by lack of standardized and reproducible tools for its clinical diagnosis or for caregiver (CG) identification of OHE manifestations which merit medical evaluation. Using an iterative Delphi method, Steering Committee and international hepatologist panel, the West Haven (WH) scale was modified to develop and operationalize a clinician tool for OHE identification and grading (HE Grading Instrument, HEGI™). Major diagnostic criteria included disorientation to time, place, and person, asterixis, lethargy, and coma. Minimum HEGI requirements for OHE diagnosis included: (1) disorientation, or (2) presence of both lethargy and asterixis, or (3) coma. Inter- and intra-rater HEGI reproducibility were 97 % and 98 %, respectively. When applied to a phase II clinical trial population of 178 patients with 388 OHE episodes, HEGI demonstrated excellent concordance with investigator judgement. Additionally, a multi-stage study was conducted to develop a daily CG e-diary, based on OHE manifestations recognizable by CG including speech difficulties, unusual behavior, forgetfulness, confusion, disorientation and level of consciousness. The e-diary was designed for use on smart phone, laptop or desktop, utilized branching logic and skip patterns, incorporated automatic daily completion reminders and real time alerts to clinical sites to facilitate daily standardized CG input and was found to be user friendly and understandable. The HEGI and e-diary, which were developed using methodology accepted by regulatory authorities, are designed to facilitate the design and interpretation of clinical trials for OHE and improve outcomes for OHE patients in clinical practice.

Genome-wide association study of Alzheimer's disease with psychotic symptoms.

Psychotic symptoms occur in ~40% of subjects with Alzheimer's disease (AD) and are associated with more rapid cognitive decline and increased functional deficits. They show heritability up to 61% and have been proposed as a marker for a disease subtype suitable for gene mapping efforts. We undertook a combined analysis of three genome-wide association studies (GWASs) to identify loci that (1) increase susceptibility to an AD and subsequent psychotic symptoms; or (2) modify risk of psychotic symptoms in the presence of neurodegeneration caused by AD. In all, 1299 AD cases with psychosis (AD+P), 735 AD cases without psychosis (AD-P) and 5659 controls were drawn from Genetic and Environmental Risk in AD Consortium 1 (GERAD1), the National Institute on Aging Late-Onset Alzheimer's Disease (NIA-LOAD) family study and the University of Pittsburgh Alzheimer Disease Research Center (ADRC) GWASs. Unobserved genotypes were imputed to provide data on >1.8 million single-nucleotide polymorphisms (SNPs). Analyses in each data set were completed comparing (1) AD+P to AD-P cases, and (2) AD+P cases with controls (GERAD1, ADRC only). Aside from the apolipoprotein E (APOE) locus, the strongest evidence for association was observed in an intergenic region on chromosome 4 (rs753129; 'AD+PvAD-P' P=2.85 × 10(-7); 'AD+PvControls' P=1.11 × 10(-4)). SNPs upstream of SLC2A9 (rs6834555, P=3.0 × 10(-7)) and within VSNL1 (rs4038131, P=5.9 × 10(-7)) showed strongest evidence for association with AD+P when compared with controls. These findings warrant further investigation in larger, appropriately powered samples in which the presence of psychotic symptoms in AD has been well characterized.

The APPLE Tree programme: Active Prevention in People at risk of dementia through Lifestyle, bEhaviour change and Technology to build REsiliEnce-randomised controlled trial.

BACKGROUND: Large-scale trials of multidomain interventions show that modifying lifestyle and psychological risk factors can slow cognitive decline. We aim to determine if a lower intensity, personally tailored secondary dementia prevention programme for older people with subjective or mild objective memory decline, informed by behaviour change theory, reduces cognitive decline over 2 years. METHODS: A multi-site, single-blind randomised controlled trial recruiting 704 older adults at high dementia risk due to mild cognitive impairment (MCI) or subjective cognitive decline (SCD). Participants are randomised using 1:1 allocation ratio to the APPLE Tree intervention versus control arm (dementia prevention information), stratified by site. The intervention explores and implements strategies to promote healthy lifestyle, increase pleasurable activities and social connections and improve long-term condition self-management. Two facilitators trained and supervised by a clinical psychologist deliver ten, 1-h group video call sessions over 6 months (approximately every fortnight), video-call 'tea breaks' (less structured, facilitated social sessions) in intervening weeks and individual goal-setting phone calls every 2 weeks. From 6 to 12 months, participants meet monthly for 'tea breaks', with those not attending receiving monthly goal-setting phone calls. Participants receive a food delivery, pedometer and website access to cognitive training and information about lifestyle modification. Follow-ups for all outcome measures are at 12 and 24 months. The primary outcome is cognition (Neuropsychological Test Battery (NTB) score) at 24 months. Secondary outcomes are quality of life, cost per quality-adjusted life year (QALY) and wellbeing and lifestyle factors the intervention targets (diet, vascular risk, body weight, activity, sleep, anxiety, depression, social networks and loneliness, alcohol intake and smoking). Participants from purposively selected sites participate in qualitative process evaluation interviews, which will be analysed using thematic analytic methods. DISCUSSION: If effective, the intervention design, involving remote delivery and non-clinical facilitators, would facilitate intervention roll-out to older people with memory concerns. TRIAL REGISTRATION: ISRCTN17325135 . Registration date 27 November 2019.

Polygenic dissection of the bipolar phenotype.

BACKGROUND: Recent data provide strong support for a substantial common polygenic contribution (i.e. many alleles each of small effect) to genetic susceptibility for schizophrenia and overlapping susceptibility for bipolar disorder. AIMS: To test hypotheses about the relationship between schizophrenia and psychotic types of bipolar disorder. METHOD: Using a polygenic score analysis to test whether schizophrenia polygenic risk alleles, en masse, significantly discriminate between individuals with bipolar disorder with and without psychotic features. The primary sample included 1829 participants with bipolar disorder and the replication sample comprised 506 people with bipolar disorder. RESULTS: The subset of participants with Research Diagnostic Criteria schizoaffective bipolar disorder (n = 277) were significantly discriminated from the remaining participants with bipolar disorder (n = 1552) in both the primary (P = 0.00059) and the replication data-sets (P = 0.0070). In contrast, those with psychotic bipolar disorder as a whole were not significantly different from those with non-psychotic bipolar disorder in either data-set. CONCLUSIONS: Genetic susceptibility influences at least two major domains of psychopathological variation in the schizophrenia-bipolar disorder clinical spectrum: one that relates to expression of a 'bipolar disorder-like' phenotype and one that is associated with expression of 'schizophrenia-like' psychotic symptoms.

A threonine to isoleucine missense mutation in the pericentriolar material 1 gene is strongly associated with schizophrenia.

Markers at the pericentriolar material 1 gene (PCM1) have shown genetic association with schizophrenia in both a University College London (UCL) and a USA-based case-control sample. In this paper we report a statistically significant replication of the PCM1 association in a large Scottish case-control sample from Aberdeen. Resequencing of the genomic DNA from research volunteers who had inherited haplotypes associated with schizophrenia showed a threonine to isoleucine missense mutation in exon 24 which was likely to change the structure and function of PCM1 (rs370429). This mutation was found only as a heterozygote in 98 schizophrenic research subjects and controls out of 2246 case and control research subjects. Among the 98 carriers of rs370429, 67 were affected with schizophrenia. The same alleles and haplotypes were associated with schizophrenia in both the London and Aberdeen samples. Another potential aetiological base pair change in PCM1 was rs445422, which altered a splice site signal. A further mutation, rs208747, was shown by electrophoretic mobility shift assays to create or destroy a promoter transcription factor site. Five further non-synonymous changes in exons were also found. Genotyping of the new variants discovered in the UCL case-control sample strengthened the evidence for allelic and haplotypic association (P=0.02-0.0002). Given the number and identity of the haplotypes associated with schizophrenia, further aetiological base pair changes must exist within and around the PCM1 gene. PCM1 protein has been shown to interact directly with the disrupted-in-schizophrenia 1 (DISC1) protein, Bardet-Biedl syndrome 4, and Huntingtin-associated protein 1, and is important in neuronal cell growth. In a separate study we found that clozapine but not haloperidol downregulated PCM1 expression in the mouse brain. We hypothesize that mutant PCM1 may be responsible for causing a subtype of schizophrenia through abnormal cell division and abnormal regeneration in dividing cells in the central nervous system. This is supported by our previous finding of orbitofrontal volumetric deficits in PCM1-associated schizophrenia patients as opposed to temporal pole deficits in non-PCM1-associated schizophrenia patients. Caution needs to be exercised in interpreting the actual biological effects of the mutations we have found without further cell biology. However, the DNA changes we have found deserve widespread genotyping in multiple case-control populations.

Case-control studies show that a non-conservative amino-acid change from a glutamine to arginine in the P2RX7 purinergic receptor protein is associated with both bipolar- and unipolar-affective disorders.

Three linkage studies of bipolar disorder have implicated chromosome 12q24.3 with lod scores of over 3.0 and several other linkage studies have found lods between 2 and 3. Fine mapping within the original chromosomal linkage regions has identified several loci that show association with bipolar disorder. One of these is the P2RX7 gene encoding a central nervous system-expressed purinergic receptor. A non-synonymous single nucleotide polymorphism, rs2230912 (P2RX7-E13A, G allele) and a microsatellite marker NBG6 were both previously found to be associated with bipolar disorder (P=0.00071 and 0.008, respectively). rs2230912 has also been found to show association with unipolar depression. The effect of the polymorphism is non-conservative and results in a glutamine to arginine change (Gln460Arg), which is likely to affect P2RX7 dimerization and protein-protein interactions. We have confirmed the allelic associations between bipolar disorder and the markers rs2230912 (P2RX7-E13A, G allele, P=0.043) and NBG6 (P=0.010) in a London-based sample of 604 bipolar cases and 560 controls. When we combined these data with the published case-control studies of P2RX7 and mood disorder (3586 individuals) the association between rs2230912 (Gln460Arg) and affective disorders became more robust (P=0.002). The increase in Gln460Arg was confined to heterozygotes rather than homozygotes suggesting a dominant effect (odds ratio 1.302, CI=1.129-1.503). Although further research is needed to prove that the Gln460Arg change has an aetiological role, it is so far the most convincing mutation to have been found with a role for increasing susceptibility to bipolar and genetically related unipolar disorders.

DISC1 association, heterogeneity and interplay in schizophrenia and bipolar disorder.

Disrupted in schizophrenia 1 (DISC1) has been associated with risk of schizophrenia, schizoaffective disorder, bipolar disorder, major depression, autism and Asperger syndrome, but apart from in the original translocation family, true causal variants have yet to be confirmed. Here we report a harmonized association study for DISC1 in European cohorts of schizophrenia and bipolar disorder. We identify regions of significant association, demonstrate allele frequency heterogeneity and provide preliminary evidence for modifying interplay between variants. Whereas no associations survived permutation analysis in the combined data set, significant corrected associations were observed for bipolar disorder at rs1538979 in the Finnish cohorts (uncorrected P=0.00020; corrected P=0.016; odds ratio=2.73+/-95% confidence interval (CI) 1.42-5.27) and at rs821577 in the London cohort (uncorrected P=0.00070; corrected P=0.040; odds ratio=1.64+/-95% CI 1.23-2.19). The rs821577 single nucleotide polymorphism (SNP) showed evidence for increased risk within the combined European cohorts (odds ratio=1.27+/-95% CI 1.07-1.51), even though significant corrected association was not detected (uncorrected P=0.0058; corrected P=0.28). After conditioning the European data set on the two risk alleles, reanalysis revealed a third significant SNP association (uncorrected P=0.00050; corrected P=0.025). This SNP showed evidence for interplay, either increasing or decreasing risk, dependent upon the presence or absence of rs1538979 or rs821577. These findings provide further support for the role of DISC1 in psychiatric illness and demonstrate the presence of locus heterogeneity, with the effect that clinically relevant genetic variants may go undetected by standard analysis of combined cohorts.

Whole-genome association study of bipolar disorder.

We performed a genome-wide association scan in 1461 patients with bipolar (BP) 1 disorder, 2008 controls drawn from the Systematic Treatment Enhancement Program for Bipolar Disorder and the University College London sample collections with successful genotyping for 372,193 single nucleotide polymorphisms (SNPs). Our strongest single SNP results are found in myosin5B (MYO5B; P=1.66 x 10(-7)) and tetraspanin-8 (TSPAN8; P=6.11 x 10(-7)). Haplotype analysis further supported single SNP results highlighting MYO5B, TSPAN8 and the epidermal growth factor receptor (MYO5B; P=2.04 x 10(-8), TSPAN8; P=7.57 x 10(-7) and EGFR; P=8.36 x 10(-8)). For replication, we genotyped 304 SNPs in family-based NIMH samples (n=409 trios) and University of Edinburgh case-control samples (n=365 cases, 351 controls) that did not provide independent replication after correction for multiple testing. A comparison of our strongest associations with the genome-wide scan of 1868 patients with BP disorder and 2938 controls who completed the scan as part of the Wellcome Trust Case-Control Consortium indicates concordant signals for SNPs within the voltage-dependent calcium channel, L-type, alpha 1C subunit (CACNA1C) gene. Given the heritability of BP disorder, the lack of agreement between studies emphasizes that susceptibility alleles are likely to be modest in effect size and require even larger samples for detection.

Stroke in rats produced by carotid injection of sodium arachidonate.

Unilateral cerebrovascular occlusion was produced in heparinized rats within 60 seconds after an injection of sodium arachidonate (in doses exceeding 0.45 milligram per kilogram) into the carotid artery. Electroencephalographic activity over the affected cerebral hemisphere was suppressed, and cerebral blood flow decreased by half. Microscopic examination revealed complete obstruction of the hemispheric microcirculation by platelet aggregates.

Rare variant analysis in multiply affected families, association studies and functional analysis suggest a role for the ITGΒ4 gene in schizophrenia and bipolar disorder.

Recent results imply that rare variants contribute to the risk of schizophrenia. Exome sequence data from the UK10K project was used to identify three rare, amino acid changing variants in the ITGB4 gene which segregated with schizophrenia in two families: rs750367954, rs147480547 and rs145976111. Association analysis was carried out in the exome-sequenced Swedish schizophrenia study and in UCL schizophrenia and bipolar cases and controls genotyped for these variants. A gene-wise weighted burden test was performed on a trio sample of schizophrenia cases and their parents. rs750367954 was seen in two Swedish cases and in no controls. The other two variants were commoner in cases than controls in both Swedish and UCL cohort samples and an overall burden test was significant at p=0.0000031. The variants were not observed in the trio sample but ITGB4 was most highly ranked out of 14,960 autosomal genes in a gene-wise weighted burden test. The effect of rs147480547 and rs145976111 was studied in human neuroblastoma SH-SY5Y cells. Cells transfected with both variants had increased proliferation at both 24 and 48h (p=0.013 and p=0.05 respectively) compared to those with wild-type ITGB4. Taken together, these results suggest that rare variants in ITGB4 which affect function may contribute to the aetiology of schizophrenia and bipolar disorder.

Activators of the nuclear hormone receptors PPARalpha and FXR accelerate the development of the fetal epidermal permeability barrier.

Members of the superfamily of nuclear hormone receptors which are obligate heterodimeric partners of the retinoid X receptor may be important in epidermal development. Here, we examined the effects of activators of the receptors for vitamin D3 and retinoids, and of the peroxisome proliferator activated receptors (PPARs) and the farnesoid X-activated receptor (FXR), on the development of the fetal epidermal barrier in vitro. Skin explants from gestational day 17 rats (term is 22 d) are unstratified and lack a stratum corneum (SC). After incubation in hormone-free media for 3-4 d, a multilayered SC replete with mature lamellar membranes in the interstices and a functionally competent barrier appear. 9-cis or all-trans retinoic acid, 1,25 dihydroxyvitamin D3, or the PPARgamma ligands prostaglandin J2 or troglitazone did not affect the development of barrier function or epidermal morphology. In contrast, activators of the PPARalpha, oleic acid, linoleic acid, and clofibrate, accelerated epidermal development, resulting in mature lamellar membranes, a multilayered SC, and a competent barrier after 2 d of incubation. The FXR activators, all-trans farnesol and juvenile hormone III, also accelerated epidermal barrier development. Activities of beta-glucocerebrosidase and steroid sulfatase, enzymes previously linked to barrier maturation, also increased after treatment with PPARalpha and FXR activators. In contrast, isoprenoids, such as nerolidol, cis-farnesol, or geranylgeraniol, or metabolites in the cholesterol pathway, such as mevalonate, squalene, or 25-hydroxycholesterol, did not alter barrier development. Finally, additive effects were observed in explants incubated with clofibrate and farnesol together in suboptimal concentrations which alone did not affect barrier development. These data indicate a putative physiologic role for PPARalpha and FXR in epidermal barrier development.

Review article: the current pharmacological therapies for hepatic encephalopathy.

Effective treatment options for hepatic encephalopathy are limited. Based on the principle that intestinal-derived ammonia contributes to the pathogenesis of hepatic encephalopathy, current therapeutic approaches are directed at reducing bacterial production of ammonia and enhancing its elimination. Non-absorbable disaccharides are first-line therapy for hepatic encephalopathy, but published clinical studies evaluating their safety and efficacy are limited. Alternative therapies such as benzodiazepine receptor antagonists, branched-chain amino acids, and l-ornithine-l-aspartate also have limited clinical data supporting their use. Studies of antibiotics indicate that they are effective in the treatment of hepatic encephalopathy, but adverse effects and concerns about long-term safety have limited the widespread use of most. Rifaximin is a minimally absorbed antibiotic that concentrates in the gastrointestinal tract and is excreted mostly unchanged in faeces. It has been studied extensively in the treatment of hepatic encephalopathy and appears to confer therapeutic benefits greater than those of placebo and non-absorbable disaccharides and at least comparable with those of systemic antibiotics. Rifaximin was also well tolerated in patients with hepatic encephalopathy and is not associated with clinical drug interactions or clinically relevant bacterial antibiotic resistance. In conclusion, non-absorbed antibiotics such as rifaximin offer a favourable benefit-risk ratio in the treatment of hepatic encephalopathy and may help to improve patient outcomes.

Genome-wide association study of borderline personality disorder reveals genetic overlap with bipolar disorder, major depression and schizophrenia.

Borderline personality disorder (BOR) is determined by environmental and genetic factors, and characterized by affective instability and impulsivity, diagnostic symptoms also observed in manic phases of bipolar disorder (BIP). Up to 20% of BIP patients show comorbidity with BOR. This report describes the first case-control genome-wide association study (GWAS) of BOR, performed in one of the largest BOR patient samples worldwide. The focus of our analysis was (i) to detect genes and gene sets involved in BOR and (ii) to investigate the genetic overlap with BIP. As there is considerable genetic overlap between BIP, major depression (MDD) and schizophrenia (SCZ) and a high comorbidity of BOR and MDD, we also analyzed the genetic overlap of BOR with SCZ and MDD. GWAS, gene-based tests and gene-set analyses were performed in 998 BOR patients and 1545 controls. Linkage disequilibrium score regression was used to detect the genetic overlap between BOR and these disorders. Single marker analysis revealed no significant association after correction for multiple testing. Gene-based analysis yielded two significant genes: DPYD (P=4.42 × 10-7) and PKP4 (P=8.67 × 10-7); and gene-set analysis yielded a significant finding for exocytosis (GO:0006887, PFDR=0.019; FDR, false discovery rate). Prior studies have implicated DPYD, PKP4 and exocytosis in BIP and SCZ. The most notable finding of the present study was the genetic overlap of BOR with BIP (rg=0.28 [P=2.99 × 10-3]), SCZ (rg=0.34 [P=4.37 × 10-5]) and MDD (rg=0.57 [P=1.04 × 10-3]). We believe our study is the first to demonstrate that BOR overlaps with BIP, MDD and SCZ on the genetic level. Whether this is confined to transdiagnostic clinical symptoms should be examined in future studies.

Intestinal fatty acid binding protein may favor differential apical fatty acid binding in the intestine.

The intestinal mucosa metabolizes fatty acids differently when presented to the lumenal or basolateral membrane. Expression of both liver and intestinal fatty acid binding proteins (L- and I-FABPs) uniquely in the enterocyte offers a possible explanation of this phenomenon. An organ explant system was used to analyze the relative binding of fatty acids to each protein. More fatty acid was bound to L-FABP than to I-FABPs (28% vs. 6% of cytosolic radioactivity), no matter on which side the fatty acid was added. However, a 2-3-fold increase in fatty acid binding to the intestinal paralog was noted after apical addition of palmitic or oleic acid in mucosa from chow fed rats. When oleic acid was added apically, a 1.4-fold increase in binding to I-FABP was observed in mucosa derived from chronically fat fed rats, consistent with the previously observed 50% increase in the content of that protein. Immunocytochemical localization of both FABPs in vivo demonstrated an apical cytoplasmic localization in the fasting state, and redistribution to the entire cytoplasm after fat feeding. These data are consistent with the hypothesis that I-FABP may contribute to the metabolic compartmentalization of apically presented fatty acids in the intestine.

Induction of fatty acid binding protein by peroxisome proliferators in primary hepatocyte cultures and its relationship to the induction of peroxisomal beta-oxidation.

The induction of liver fatty acid binding protein (L-FABP) by the peroxisome proliferators bezafibrate and clofibrate was compared with the induction of peroxisomal (cyanide-insensitive) palmitoyl-CoA oxidation in cultured rat hepatocytes maintained on a substratum of laminin-rich (EHS) gel. This substratum was chosen because marked induction of both L-FABP and peroxisomal palmitoyl-CoA oxidation was effected by bezafibrate in hepatocytes supported on EHS gel, whereas only peroxisomal palmitoyl-CoA oxidation was induced in hepatocytes maintained on collagen-coated plates. In control cells on EHS, activity of peroxisomal palmitoyl-CoA oxidation remained stable, while L-FABP abundance declined with time, and L-FABP mRNA was undetectable after 5 days. In cultures exposed to bezafibrate or clofibrate, peroxisomal palmitoyl-CoA oxidation activity was induced earlier and more rapidly than L-FABP. When fibrates were withdrawn, peroxisomal palmitoyl-CoA oxidation declined rapidly, whereas L-FABP continued to increase. L-FABP induction was accompanied by a striking increase in mRNA specifying this protein. Tetradecylglycidic acid, an inhibitor of carnitine palmitoyltransferase I, effectively doubled peroxisomal palmitoyl-CoA oxidation activity. However, tetradecylglycidic acid markedly inhibited fibrate induction of L-FABP and peroxisomal palmitoyl-CoA oxidation but, unexpectedly, did not prevent the fibrate-induced proliferation of peroxisomes. Maximal induction of both L-FABP and peroxisomal palmitoyl-CoA oxidation was produced at a bezafibrate concentration in the culture medium (0.05 mM) much lower than that of clofibrate (0.3 mM). Also, bezafibrate, but not clofibrate, inhibited [1-14C]oleic acid binding to L-FABP with a Ki = 9.5 microM. We conclude that hepatocytes maintained on EHS gel provide an important tool for investigating the regulation of L-FABP. These studies show that the induction of peroxisomal beta-oxidation and L-FABP by peroxisome proliferators are temporally consecutive but closely related processes which may be dependent on a mechanism distinct from that which leads to peroxisome proliferation. Furthermore, the mechanism of action of the more potent peroxisome proliferator, bezafibrate, may be mediated, in part, by interaction of this agent with L-FABP.

Ligandin heterogeneity : evidence that the two non-identical subunits are the monomers of two distinct proteins.

Purified ligandin (Y-protein) a 46000-dalton protein, has been shown to consist of two subunit species (mol. wts. 22 000 and 24 000) on discontinuous polyacrylamide gel electrophoresis in sodium dodecyl sulphate. This technique was used to define further the nature of these subunits. The Y sulphobromophthalein-binding fraction of rat hepatic cytosol was shown to contain three major subunit bands designated subunit Ya, subunit Yb and subunit Yc in ascending order of size. Purified ligandin was found to comprise Ya and Yc subunit species, and also gave two bands on isoelectric focusing. The two subunit species in purified ligandin were partially separated by an additional purification step. Antiserum to ligandin reacted mono-specifically with the purified protein, as well as hepatic, renal and small intestinal mucosa cytosol, but gave lines of identity and partial identity with cytosol from testis, ovary and adrenal gland. The Y fraction of testis was found to contain only Yb and Yc species, while all three major bands were found in liver, kidney and small intestinal mucosa. Phenobarbital treatment increased the concentration of Ya and Yb in the liver, but had little effect on Yc. These findings suggest that the Ya and Yc ligandin subunits are the monomers of two proteins: YaYa and YcYc.

Ligandin concentrations in the steroidogenic tissues of the rat during development.

Ligandin, a ubiquitous multifunctional cytoplasmic protein which exhibits glutathione S-transferase, glutathione peroxidase and delta 5-3-ketosteroid isomerase activities and binds to cortisol metabolites, is present in relatively high concentrations in gonadal and adrenal tissue. In contrast to hepatic ligandin, little is known about the ontogeny of ligandin in steroid-synthesising tissues. We report here the intracellular concentrations of ligandin as well as the serum concentrations of testosterone and progesterone measured by radioimmunoassay at different stages of development in the rat. Ligandin levels in testis, ovary and adrenal tissue were relatively high soon after birth, decreased by day 9 and increased rapidly during puberty to reach adult levels. These changes appeared to be paralleled by changes in the circulating levels of testosterone and progesterone. In contrast, ligandin levels in non-steroidogenically active tissues, such as liver and kidney, were low at birth and rose progressively to reach adult levels. Whereas hepatic ligandin concentration could be increased at all stages of development by phenobarbital induction, no induction occurred in the endocrine tissues.