BAFopathies' DNA methylation epi-signatures demonstrate diagnostic utility and functional continuum of Coffin-Siris and Nicolaides-Baraitser syndromes

Coffin–Siris and Nicolaides–Baraitser syndromes (CSS and NCBRS) are Mendelian disorders caused by mutations in subunits of the BAF chromatin remodeling complex. We report overlapping peripheral blood DNA methylation epi-signatures in individuals with various subtypes of CSS (ARID1B, SMARCB1, and SMARCA4) and NCBRS (SMARCA2). We demonstrate that the degree of similarity in the epi-signatures of some CSS subtypes and NCBRS can be greater than that within CSS, indicating a link in the functional basis of the two syndromes. We show that chromosome 6q25 microdeletion syndrome, harboring ARID1B deletions, exhibits a similar CSS/NCBRS methylation profile. Specificity of this epi-signature was confirmed across a wide range of neurodevelopmental conditions including other chromatin remodeling and epigenetic machinery disorders. We demonstrate that a machine-learning model trained on this DNA methylation profile can resolve ambiguous clinical cases, reclassify those with variants of unknown significance, and identify previously undiagnosed subjects through targeted population screening.

Mutations in genes encoding subunits of the BAF complex can cause Coffin–Siris and Nicolaides–Baraitser syndromes. Here the authors identify overlapping DNA methylation signatures in individuals with subtypes of these two syndromes that suggest a functional link and can be used to diagnose subjects with unclear clinical presentations.

Genomic DNA Methylation Signatures Enable Concurrent Diagnosis and Clinical Genetic Variant Classification in Neurodevelopmental Syndromes

Pediatric developmental syndromes present with systemic, complex, and often overlapping clinical features that are not infrequently a consequence of Mendelian inheritance of mutations in genes involved in DNA methylation, establishment of histone modifications, and chromatin remodeling (the "epigenetic machinery"). The mechanistic cross-talk between histone modification and DNA methylation suggests that these syndromes might be expected to display specific DNA methylation signatures that are a reflection of those primary errors associated with chromatin dysregulation. Given the interrelated functions of these chromatin regulatory proteins, we sought to identify DNA methylation epi-signatures that could provide syndrome-specific biomarkers to complement standard clinical diagnostics. In the present study, we examined peripheral blood samples from a large cohort of individuals encompassing 14 Mendelian disorders displaying mutations in the genes encoding proteins of the epigenetic machinery. We demonstrated that specific but partially overlapping DNA methylation signatures are associated with many of these conditions. The degree of overlap among these epi-signatures is minimal, further suggesting that, consistent with the initial event, the downstream changes are unique to every syndrome. In addition, by combining these epi-signatures, we have demonstrated that a machine learning tool can be built to concurrently screen for multiple syndromes with high sensitivity and specificity, and we highlight the utility of this tool in solving ambiguous case subjects presenting with variants of unknown significance, along with its ability to generate accurate predictions for subjects presenting with the overlapping clinical and molecular features associated with the disruption of the epigenetic machinery.

Sustained zero-order delivery of GC-1 from a nanochannel membrane device alleviates metabolic syndrome

BACKGROUND/OBJECTIVES

Our objective was to assess the sustained, low-dose and constant administration of the thyroid receptor-β (TRβ)-selective agonist GC-1 (sobetirome) from a novel nanochannel membrane device (NMD) for drug delivery. As it known to speed up metabolism, accomplish weight loss, improve cholesterol levels and possess anti-diabetic effects, GC-1 was steadily administered by our NMD, consisting of an implantable nanochannel membrane, as an alternative to conventional daily administration, which is subject to compliance issues in clinical settings.

SUBJECTS/METHODS

Diet-induced obese C57BL/J6 male mice were fed a very high-fat diet (VHFD) and received NMD implants subcutaneously. Ten mice per group received capsules containing GC-1 or phosphate-buffered saline (control). Weight, lean and fat mass, as well as cholesterol, triglycerides, insulin and glucose, were monitored for 24 days. After treatment, plasma levels of thyroid-stimulating hormone (TSH) and thyroxine were compared. mRNA levels of a panel of thermogenic markers were examined using real-time PCR in white adipose tissue (WAT) and brown adipose tissue (BAT). Adipose tissue, liver and local inflammatory response to the implant were examined histologically. Pancreatic islet number and β-cell area were assessed.

RESULTS

GC-1 released from the NMD reversed VHFD-induced obesity and normalized serum cholesterol and glycemia. Significant reductions in body weight and fat mass were observed within 10 days, whereas reductions in serum cholesterol and glucose levels were seen within 7 days. The significant decrease in TSH was consistent with TRβ selectivity for GC-1. Levels of transcript for Ucp1 and thermogenic genes PGC1a, Cidea, Dio2 and Cox5a showed significant upregulation in WAT in NMD-GC-1-treated mice, but decreased in BAT. Although mice treated by NMD-GC-1 showed a similar number of pancreatic islets, they exhibited significant increase in β-cell area.

CONCLUSIONS

Our data demonstrate that the NMD implant achieves steady administration of GC-1, offering an effective and tightly controlled molecular delivery system for treatment of obesity and metabolic disease, thereby addressing compliance.

Executive function deficits and glutamatergic protein alterations in a progressive 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mouse model of Parkinson's disease

Changes in executive function are at the root of most cognitive problems associated with Parkinson's disease. Because dopaminergic treatment does not necessarily alleviate deficits in executive function, it has been hypothesized that dysfunction of neurotransmitters/systems other than dopamine (DA) may be associated with this decrease in cognitive function. We have reported decreases in motor function and dopaminergic/glutamatergic biomarkers in a progressive 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) Parkinson's mouse model. Assessment of executive function and dopaminergic/glutamatergic biomarkers within the limbic circuit has not previously been explored in our model. Our results show progressive behavioral decline in a cued response task (a rodent model for frontal cortex cognitive function) with increasing weekly doses of MPTP. Although within the dorsolateral (DL) striatum mice that had been given MPTP showed a 63% and 83% loss of tyrosine hydroxylase and dopamine transporter expression, respectively, there were no changes in the nucleus accumbens or medial prefrontal cortex (mPFC). Furthermore, dopamine-1 receptor and vesicular glutamate transporter (VGLUT)-1 expression increased in the mPFC following DA loss. There were significant MPTP-induced decreases and increases in VGLUT-1 and VGLUT-2 expression, respectively, within the DL striatum. We propose that the behavioral decline following MPTP treatment may be associated with a change not only in cortical-cortical (VGLUT-1) glutamate function but also in striatal DA and glutamate (VGLUT-1/VGLUT-2) input.

Neuronal gamma-aminobutyric acid (GABA) type A receptors undergo cognate ligand chaperoning in the endoplasmic reticulum by endogenous GABA

GABA_A receptors mediate fast inhibitory neurotransmission in the brain. Dysfunction of these receptors is associated with various psychiatric/neurological disorders and drugs targeting this receptor are widely used therapeutic agents. Both the efficacy and plasticity of GABA_A receptor-mediated neurotransmission depends on the number of surface GABA_A receptors. An understudied aspect of receptor cell surface expression is the post-translational regulation of receptor biogenesis within the endoplasmic reticulum (ER). We have previously shown that exogenous GABA can act as a ligand chaperone of recombinant GABA_A receptors in the early secretory pathway leading us to now investigate whether endogenous GABA facilitates the biogenesis of GABA_A receptors in primary cerebral cortical cultures. In immunofluorescence labeling experiments, we have determined that neurons expressing surface GABA_A receptors contain both GABA and its degradative enzyme GABA transaminase (GABA-T). Treatment of neurons with GABA-T inhibitors, a treatment known to increase intracellular GABA levels, decreases the interaction of the receptor with the ER quality control protein calnexin, concomittantly increasing receptor forward-trafficking and plasma membrane insertion. The effect of GABA-T inhibition on the receptor/calnexin interaction is not due to the activation of surface GABA_A or GABA_B receptors. Consistent with our hypothesis that GABA acts as a cognate ligand chaperone in the ER, immunogold-labeling of rodent brain slices reveals the presence of GABA within the rough ER. The density of this labeling is similar to that present in mitochondria, the organelle in which GABA is degraded. Lastly, the effect of GABA-T inhibition on the receptor/calnexin interaction was prevented by pretreatment with a GABA transporter inhibitor. Together, these data indicate that endogenous GABA acts in the rough ER as a cognate ligand chaperone to facilitate the biogenesis of neuronal GABA_A receptors.

The phenotype of Floating-Harbor syndrome: clinical characterization of 52 individuals with mutations in exon 34 of SRCAP

BACKGROUND

Floating-Harbor syndrome (FHS) is a rare condition characterized by short stature, delays in expressive language, and a distinctive facial appearance. Recently, heterozygous truncating mutations in SRCAP were determined to be disease-causing. With the availability of a DNA based confirmatory test, we set forth to define the clinical features of this syndrome.

METHODS AND RESULTS

Clinical information on fifty-two individuals with SRCAP mutations was collected using standardized questionnaires. Twenty-four males and twenty-eight females were studied with ages ranging from 2 to 52 years. The facial phenotype and expressive language impairments were defining features within the group. Height measurements were typically between minus two and minus four standard deviations, with occipitofrontal circumferences usually within the average range. Thirty-three of the subjects (63%) had at least one major anomaly requiring medical intervention. We did not observe any specific phenotype-genotype correlations.

CONCLUSIONS

This large cohort of individuals with molecularly confirmed FHS has allowed us to better delineate the clinical features of this rare but classic genetic syndrome, thereby facilitating the development of management protocols.

Hydrogen sulfide preconditions the db/db diabetic mouse heart against ischemia-reperfusion injury by activating Nrf2 signaling in an Erk-dependent manner

Hydrogen sulfide (H2S) therapy protects nondiabetic animals in various models of myocardial injury, including acute myocardial infarction and heart failure. Here, we sought to examine whether H2S therapy provides cardioprotection in the setting of type 2 diabetes. H2S therapy in the form of sodium sulfide (Na2S) beginning 24 h or 7 days before myocardial ischemia significantly decreased myocardial injury in db/db diabetic mice (12 wk of age). In an effort to evaluate the signaling mechanism responsible for the observed cardioprotection, we focused on the role of nuclear factor E2-related factor (Nrf2) signaling. Our results indicate that diabetes does not alter the ability of H2S to increase the nuclear localization of Nrf2, but does impair aspects of Nrf2 signaling. Specifically, the expression of NADPH quinine oxidoreductase 1 was increased after the acute treatment, whereas the expression of heme-oxygenase-1 (HO-1) was only increased after 7 days of treatment. This discrepancy was found to be the result of an increased nuclear expression of Bach1, a known repressor of HO-1 transcription, which blocked the binding of Nrf2 to the HO-1 promoter. Further analysis revealed that 7 days of Na2S treatment overcame this impairment by removing Bach1 from the nucleus in an Erk1/2-dependent manner. Our findings demonstrate for the first time that exogenous administration of Na2S attenuates myocardial ischemia-reperfusion injury in db/db mice, suggesting the potential therapeutic effects of H2S in treating a heart attack in the setting of type 2 diabetes.

Floating-Harbor syndrome and polycystic kidneys associated with SRCAP mutation

Floating-Harbor syndrome (FHS) is a rare genetic disorder recently shown to be caused by mutations in the Snf2-related CREB-binding protein activator protein gene (SRCAP). It comprises three key clinical features of characteristic facies, expressive and receptive speech impairment and short stature. We report on a patient with this syndrome associated with early adult-onset hypertension and bilateral polycystic kidneys. Family screening for polycystic kidney disease was negative and mutations in polycystic kidney disease 1 and 2 genes (PKD1 and PKD2) were absent. Sequencing of the SRCAP gene demonstrated a de novo mutation matching one of the known FHS-associated mutations. The patient required treatment with anti-hypertensives and will require lifelong renal monitoring. We suggest this patient's presentation may be due to the pleiotropic effects of SRCAP mutations. Further, the protein encoded by SRCAP is known to interact with CREB-binding protein, the product of the gene mutated in Rubinstein-Taybi syndrome, which is associated with renal abnormalities. A literature review of the renal findings in patients with Floating-Harbor syndrome identified another patient with possible polycystic kidneys, two patients with early onset hypertension, and a young patient with a ruptured intracranial aneurysm, which can be a feature of classic adult polycystic kidney disease. Collectively, these findings suggest that all patients with Floating-Harbor syndrome should undergo regular blood pressure monitoring and screening for polycystic kidneys by ultrasound at the time of the FHS diagnosis with imaging to be repeated during adulthood if a childhood ultrasound was negative.

Abstract 96: Thioredoxin-1 Is Essential for Hydrogen Sulfide-Mediated Cardioprotection in the Setting of Ischemic-Induced Heart Failure

Background: Numerous studies have reported the cytoprotective effects of hydrogen sulfide (H2S) in various models of myocardial injury. Here we examined the role that thioredoxin-1 (Trx1) plays in mediating the protective effects of H2S in a model of heart failure.

Methods and Results: Mice were subjected to 60 min of left coronary artery ischemia followed by 4 wks of reperfusion (R) at which time left ventricular dimensions and function were assessed. Mice received saline (Veh) or H2S in the form of sodium sulfide (Na2S, 100 μ g/kg) at the time of R followed by daily i.v. injections for the first 7 days of R. Mice treated with Na2S experienced less left ventricular dilatation and hypertrophy, displayed improved left ventricular ejection fraction, and displayed improved contractility and relaxation when compared to Veh-treated mice. Studies aimed at evaluating the underlying cardioprotective mechanisms found that Na2S treatment increased the expression of Trx1. Further analysis revealed that this was accompanied by an increase in phosphorylation of apoptosis signaling kinase-1 (ASK1) at serine residue 966 (inhibitory site), as well as a decrease in the phosphorylation of JNK and p38 (downstream targets of ASK1). We also found that Na2S treatment did not improve cardiac dilatation, cardiac dysfunction, or cardiac hypertrophy in cardiac specific Trx1 dominant negative transgenic (Trx1 dnTg) mice when compared to Veh-treated mice.

Conclusion: These findings provide important information that the upregulation of cardiac Trx1 by H2S in the setting of ischemic-induced heart failure sets into motion events, including ASK1 inhibition, which ultimately leads to cardioprotection.

Abstract P282: Increased Nuclear Localization of Fyn May Limit the Cardioprotective Effects of Hydrogen Sulfide by Interfering with Nrf2 Signaling

Background: Hydrogen sulfide (H2S) therapy reduces myocardial infarct size by up to 56% in non-diabetic mice. Here, we sought to examine if H2S could provide cardioprotection in the setting of diabetes.

Methods and Results: Diabetic mice (db/db) were subjected to 30 min of left coronary artery occlusion (LCA) followed by reperfusion for 24 hours at which time the extent of myocardial infarction was evaluated. Sodium sulfide (Na2S, 100 μ g/kg) administered at the time of reperfusion decreased infarct size relative the area-at-risk by 18% compared to vehicle treated animals (p<0.001). Previously, Na2S has been shown to increase the nuclear localization of Nrf-2 and upregulates its downstream target, heme oxygenase (HO)-1, in non-diabetic mice. To investigate if this cascade contributed to the observed cardioprotection, Na2S was administered (tail vein) to non-diabetic and diabetic mice and heart tissue was excised 1 hr and 24 hrs later. One hr following the administration of Na2S, the nuclear expression of Nrf2 was increased in both groups. In contrast, Na2S only increased the expression of HO-1 (24 hrs) in the non-diabetic heart. Further studies investigating Fyn, a tyrosine kinase known to inhibit Nrf2 signaling, revealed an upregulation of nuclear Fyn expression in the diabetic heart compared to the non-diabetic heart.

Conclusion: This data demonstrates the complexity of therapeutic intervention for diabetics following myocardial ischemia, as the robust cardioprotective effects of H2S in the non-diabetic state were found to be diminished in the diabetic state. This data also suggests that interference of Nrf2 signaling by Fyn may be responsible for the loss of protection.

Exercise protects against myocardial ischemia-reperfusion injury via stimulation of β(3)-adrenergic receptors and increased nitric oxide signaling: role of nitrite and nitrosothiols

RATIONALE

Exercise training confers sustainable protection against ischemia-reperfusion injury in animal models and has been associated with improved survival following a heart attack in humans. It is still unclear how exercise protects the heart, but it is apparent that endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) play a role.

OBJECTIVE

To determine the role of β(3)-adrenergic receptors (β(3)-ARs), eNOS activation, and NO metabolites (nitrite and nitrosothiols) in the sustained cardioprotective effects of exercise.

METHODS AND RESULTS

Here we show that voluntary exercise reduces myocardial injury in mice following a 4-week training period and that these protective effects can be sustained for at least 1 week following the cessation of the training. The sustained cardioprotective effects of exercise are mediated by alterations in the phosphorylation status of eNOS (increase in serine 1177 and decrease in threonine 495), leading to an increase in NO generation and storage of NO metabolites (nitrite and nitrosothiols) in the heart. Further evidence revealed that the alterations in eNOS phosphorylation status and NO generation were mediated by β(3)-AR stimulation and that in response to exercise a deficiency of β(3)-ARs leads to an exacerbation of myocardial infarction following ischemia-reperfusion injury.

CONCLUSIONS

Our findings clearly demonstrate that exercise protects the heart against myocardial ischemia-reperfusion injury by stimulation of β(3)-ARs and increased cardiac storage of nitric oxide metabolites (ie, nitrite and nitrosothiols).

Phenylalanine biosynthesis in Arabidopsis thaliana. Identification and characterization of arogenate dehydratases

There is much uncertainty as to whether plants use arogenate, phenylpyruvate, or both as obligatory intermediates in Phe biosynthesis, an essential dietary amino acid for humans. This is because both prephenate and arogenate have been reported to undergo decarboxylative dehydration in plants via the action of either arogenate (ADT) or prephenate (PDT) dehydratases; however, neither enzyme(s) nor encoding gene(s) have been isolated and/or functionally characterized. An in silico data mining approach was thus undertaken to attempt to identify the dehydratase(s) involved in Phe formation in Arabidopsis, based on sequence similarity of PDT-like and ACT-like domains in bacteria. This data mining approach suggested that there are six PDT-like homologues in Arabidopsis, whose phylogenetic analyses separated them into three distinct subgroups. All six genes were cloned and subsequently established to be expressed in all tissues examined. Each was then expressed as a Nus fusion recombinant protein in Escherichia coli, with their substrate specificities measured in vitro. Three of the resulting recombinant proteins, encoded by ADT1 (At1g11790), ADT2 (At3g07630), and ADT6 (At1g08250), more efficiently utilized arogenate than prephenate, whereas the remaining three, ADT3 (At2g27820), ADT4 (At3g44720), and ADT5 (At5g22630) essentially only employed arogenate. ADT1, ADT2, and ADT6 had k(cat)/Km values of 1050, 7650, and 1560 M(-1) S(-1) for arogenate versus 38, 240, and 16 M(-1) S(-1) for prephenate, respectively. By contrast, the remaining three, ADT3, ADT4, and ADT5, had k(cat)/Km values of 1140, 490, and 620 M(-1) S(-1), with prephenate not serving as a substrate unless excess recombinant protein (>150 microg/assay) was used. All six genes, and their corresponding proteins, are thus provisionally classified as arogenate dehydratases and designated ADT1-ADT6.

Colchicine poisoning

Colchicine poisoning is an unusual but serious form of drug intoxication. Although relatively uncommon, colchicine poisoning may produce life-threatening systemic effects that must be recognized and treated by the emergency physician. This alkaloid found in Colchicum autumnale is used primarily in the treatment of gout. In toxic doses it produces nausea and vomiting, and bone marrow suppression often leading to sepsis, hypocalcemia, adult respiratory distress syndrome, and direct cardiotoxic effects. Treatment requires early recognition and supportive care including fluid and electrolyte replacement and occasionally blood component replacement therapy. Recent experiments using colchicine-specific antibodies have demonstrated beneficial effects on colchicine intoxication.

Comparative antioxidant activity of tocotrienols and other natural lipid-soluble antioxidants in a homogeneous system, and in rat and human lipoproteins

The antioxidant activity of tocotrienols toward peroxyl radicals was compared with that of other natural lipid-soluble antioxidants in three different systems by measuring the temporal disappearance of antioxidants and the formation of lipid hydroperoxides. In homogeneous solution, the initial rates of consumption of the various antioxidants, assessed by competition experiments between pairs of antioxidants for radicals, decreased in the order: ubiquinol-10 approximately ubiquinol-9 > alpha-tocopherol approximately alpha-tocotrienol > beta-carotene approximately lycopene > gamma-tocopherol approximately gamma-tocotrienol. Following in vitro incubation of human plasma with alpha-tocotrienol, this form of vitamin E was present in all classes of lipoproteins isolated from the supplemented plasma. Dietary supplementation of rats and humans with a tocotrienol-rich preparation resulted in a dose-dependent appearance of alpha- and gamma-tocotrienols in plasma and all circulating lipoproteins, respectively. Exposure of such enriched rat plasma to aqueous peroxyl radicals resulted in simultaneous consumption of the alpha- and then gamma-isomers of vitamin E. The sequence of radical-induced consumption of antioxidants in freshly isolated, in vitro and in vivo tocotrienol-enriched low density lipoprotein (LDL) was again ubiquinol-10 > alpha-tocotrienol approximately alpha-tocopherol > carotenoids > gamma-tocopherol approximately gamma-tocotrienol. Under conditions where radicals were generated at constant rates, the rate of lipid hydroperoxide formation in LDL was not constant. It proceeded in at least three stages separated by the phase of ubiquinol-10 consumption and, subsequently, that of alpha-tocopherol/alpha-tocotrienol. Our results show that dietary tocotrienols become incorporated into circulating human lipoproteins where they react with peroxyl radicals as efficiently as the corresponding tocopherol isomers.

Relationship between structure and function of dietary fibre: a comparative study of the effects of three galactomannans on cholesterol metabolism in the rat

Male adult rats were fed on diets containing 80 g/kg galactomannans with different galactose (G): mannose (M) ratios/kg. The galactomannans were compared with purified cellulose (Solkaflok) and the animal were also fed on a basal diet free from fibre. All diets contained cholesterol (10 g/kg) and sodium cholate (2 g/kg). The three galactomannans were fenugreek gum (1G:1M), guar gum (1G:2M) and locust-bean gum (1G:4M). In comparison with the fibre-free and Solkaflok diets, all three galactomannans lowered the concentrations of cholesterol in both liver and blood plasma. The galactomannans also decreased the rate of hepatic synthesis of cholesterol. Dietary galactomannans increased caecal volatile fatty acids, particularly propionic, increased the weight of the caecum and its contents and increased the amount of water in the faeces. The increase in propionic acid production was significantly related to a decrease in caecal pH, but not to changes in plasma cholesterol or hepatic cholesterol synthesis. These effects were significantly influenced by chemical composition and structure of the galactomannan; they were most evident when the proportion of galactose in the galactomannan was highest (i.e. fenugreek gum). The three galactomannans also differed markedly in their effects on the viscosity of the digesta, but the galactomannan which gave the highest viscosity was least effective in lowering plasma cholesterol. A separate experiment with perfused loops of small intestine in vivo showed that the most effective galactomannan, fenugreek gum, had no direct effect on cholesterol absorption.

Research note: effects of dietary fats on hepatic cholesterol synthesis in Japanese quail

Blood lipid concentrations and hepatic cholesterol synthesis were compared in Japanese quail fed diets containing fats with different fatty acid profiles. The quail fed a diet containing tuna oil had the lowest blood cholesterol concentration; those fed beef drippings the highest, and those fed safflower oil or linseed oil had intermediate concentrations. Rates of hepatic cholesterol synthesis mirrored the results for serum cholesterol concentration. Serum triglyceride concentrations were lower in the quail fed the two diets containing n-3 fatty acids in comparison with the beef and safflower treatment groups.

Effect of diet and substrate on the in vitro measurement of cholesterol and fatty-acid synthesis in hepatic tissue of Japanese quail

A comparison of acetate, glucose, mevalonate, or water as radioactive substrates for the hepatic synthesis of cholesterol, fatty acids, and glyceride-glycerol was made in Japanese quail fed diets containing either beef fat or tuna oil. The quail fed a diet containing beef fat were fatter and had a significantly higher (P less than .01) concentration of serum cholesterol (5.6 mM per L) than that measured in the serum of quail given tuna oil (4.1 mM per L). Both in vitro cholesterol and fatty-acid synthesis were greater in the quail fed a diet of beef fat than in those fed a diet containing tuna oil. The results showed that mevalonate was the most-suitable radioactive substrate for measuring cholesterol synthesis, whereas glucose was the most-suitable radioactive substrate for measuring fatty-acid and glyceride-glycerol synthesis.

Induction of vitellogenin in primary monolayer cultures of cockerel hepatocytes

A primary monolayer culture system from cockerel hepatocytes was established. The cultures synthesize and secrete proteins that comigrate with authentic serum proteins on polyacrylamide gels and are found in the same relative abundance. Addition of estradiol increased the synthesis of apoprotein B, found in very low density lipoprotein, under all culture conditions. Vitellogenin synthesis could not be induced directly by estradiol. However, when serum was obtained from cockerels injected with estradiol 4 days before blood collection and included in the culture medium, the cultures secreted a protein identified immunologically as vitellogenin by affinity chromatography. Furthermore, addition of growth hormone or prolactin to cultured cockerel hepatocyte monolayers resulted in the synthesis and secretion of a polypeptide that comigrates with authentic vitellogenin on polyacrylamide gels.

Inhibition by potential metabolic inhibitors of in vitro adipose tissue lipogenesis

To study the pathway of lactate utilization as a carbon source for fatty acid synthesis, the effect of (-)-hydroxycitrate, agaric acid, sodium oxamate, 2-n-butyl malonate and alpha-cyano-4-hydroxycinnamate on the rate of in vitro conversion of lactate, acetate and glucose to fatty acids was measured in bovine and rat adipose tissues. Sodium oxamate and hydroxycitrate caused less fatty acid to be synthesized from lactate in bovine adipose tissue. Hydroxycitrate depressed fatty acid synthesis from glucose in rat adipose tissue. alpha-Cyano-4-hydroxycinnamate was an effective inhibitor of lipogenesis from all substrates and may act as a specific inhibitor in adipose tissue. Although the inhibitors were absorbed poorly into adipocytes, the results indicate that conversion of lactate to fatty acids probably occurs by way of the citrate cleavage pathway.

An enzymatic assay for activity of lipoprotein lipase

An enzymatic method for the determination of the amount of free fatty acids released from triglyceride by lipoprotein lipase is described. The quantity of free fatty acids present in media before and after incubation is measured spectrophotometrically by the oxidation of NADH in the final reaction of a series of coupled enzymatic reactions. This assay for lipoprotein lipase is unlike previously described assays in that radioactive substrates or titration procedures are not used in the free fatty acid determination. In addition, another method for assay of lipoprotein lipase activity that involves the separation of free fatty acids from triglycerides by adsorption chromatography with Florisil as a stationary phase is described.

Comparison of plasma very low density lipoproteins and lipogenic enzymes as predictors of fat content and food conversion efficiency in selected lines of broiler chickens

Activities of lipogenic enzymes and plasma very low density lipoprotein (VLDL) concentrations were measured in lines of chickens with large differences in food conversion efficiency (FCE) and body fat. Hepatic activities of malate dehydrogenase [EC 1.1.1.40 (MD)] and ATP citrate lyase [EC 4.1.3.8 (CL)] were correlated with the proportion of both abdominal and total body fat (r = 0.50) but were poorly correlated with gain: food ratio. Activities of MD and CL in plasma were low and variable and were not correlated with any other characteristics. Plasma VLDL concentration was significantly correlated with the proportion of abdominal and total body fat (r = 0.59), and gain: food ratio (r = 0.36).

Insulin responsiveness in non-fa/fa and fa/fa Zucker rats: effects of adipocyte size

Epididymal adipose tissue from non-fa/fa (lean) and fa/fa (obese) 14.5-week-old Zucker rats was used to study the influence of insulin and genotype on uptake of glucose and palmitate into adipocytes of different sizes. After incubation with radioactive substrate, adipocytes were inactivated and fixed by addition of osmium tetroxide; fixed adipocytes were isolated and separated by screening on the basis of size. Rates of substrate uptake into triacylglycerols were measured in adipocytes of each of ten size categories. Uptake rates of both glucose and palmitate increased as adipocyte size increased. Insulin had no effect on glucose uptake per adipocyte for fa/fa rats but had a highly significant (P less than 0.01) stimulatory effect on that for non-fa/fa rats. This stimulation became significantly greater with increasing adipocyte size. When insulin was included in the incubation media, glucose uptake rates were similar between similar sizes of adipocytes from non-fa/fa and fa/fa rats. Absence of insulin from the incubation media, however, resulted in lower rates of glucose uptake by adipocytes from non-fa/fa rats. Glucose uptake was maximal in adipocytes from fa/fa rats, even in the absence of insulin. Net uptake of palmitate into triacylglycerols was not influenced by insulin; a significant interaction was observed, however, between adipocyte size and genotype. Large adipocytes from fa/fa rats had greater rates of palmitate uptake than did adipocytes of similar size from non-fa/fa rats. The reverse was true for adipocytes less than 125 micron in diameter. The results of this study show that response to insulin of adipocytes of difference sizes varies with adipocyte size and with genotype.

Conversion of glucose, acetate and lactate to CO2 and fatty acids in liver and adipose tissue of prairie voles (Microtus ochrogaster)

Production of CO2 and fatty acids from acetate, glucose and lactate was determined in slices of liver and adipose tissue from prairie voles fed either a high-starch or a high-cellulose diet. Acetate and lactate were oxidized to CO2 and converted to fatty acids at greater rates than was glucose in both liver and adipose tissue. Fatty acid synthesis occurred at greater rates in adipose tissue than in liver. Fatty acid synthesis per adipocyte increased with increased adipocyte diameter. Fiber content of diets had only minimal effect on metabolic activities of liver and adipose tissue.

The cellular and metabolic organization of ovine subcutaneous adipose tissue

The cellular organization and lipogenic capacity ([14C]acetate incorporation per l06 cells) of sections, parallel to the skin, of subcutaneous adipose tissue from the rump, shoulder and brisket regions of fat sheep were studied. Adipocytes from the brisket (134 �m in mean diameter; 1.35 nl in mean volume) were smaller than those from the shoulder (213 �m; 4.77 nl) or rump (202 �m; 4.69 nl). Furthermore, cells from the brisket incorporated significantly less [I4C]acetate than those from either the shoulder or rump, which were not significantly different in lipogenic capacity. The frequency distributions of diameters of cells from the rump and shoulder were predominantly normal, but those of brisket cells were positively skewed. Adipocytes were larger and lipogenesis was greater in sections closer to the skin than in sections closer to the muscle for each region. This gradient of cell size and lipogenic capacity indicates that ovine subcutaneous adipose tissue is not homogeneous but is organized in structure and metabolism.

Relationships among growth, adipose cell size, and lipid metabolism in ruminant adipose tissue

In early postnatal development, growth of adipose tissue is due to both cellular hypertrophy and hyperplasia. Adipose cell (adipocyte) hypertrophy is the major mechanism in fattening of ruminants grown to market weight, although evidence is accumulating that preadipose cells can proliferate postnatally, even in mature animals. In interfasicular adipose tissue (marbling), however, small adipose cells are present and their number makes a positive contribution to the size of this fat depot in ruminants of market weight. Present information does not indicate whether these small cells are newly synthesized cells or are cells that differentiated early in postnatal development and fill with lipid at some later time. Limitations on detecting small adipose cells in cell-counting techniques are partly responsible for conflicting conclusions on the cellular basis for adiposity. Nutritional modification of adipose cell number has been reported in rodents. However, the extreme nutritional modifications required to alter cell number have little practical application in the growth of ruminants for meat production. Adipose cells of various sizes respond differently in the esterification and synthesis of fatty acids. The greater rates of lipid synthesis from acetate in large adipose cells may be related to increased uptake of substrate in cells with a large surface area.

The cellular basis for growth of the abdominal fat pad in broiler-type chickens

Cellular growth of the abdominal fat pads from Tegel TM70 white broiler chickens was characterized by both hyperplasia and hypertrophy of adipose cells until the chickens were approximately 14 weeks old, after which hypertrophy of existing adipose cells was solely responsible for increases in the mass of these fat deposits. The percent body fat was linearly and positively correlated with the weight of abdominal fat. However, at a constant percent body fat, male birds had a larger deposit of fat in the abdominal region than did females. Thus, a different relationship to predict body fat would be required for each sex. In mature birds the mass of an adipose tissue deposit is generally reflected in the size of adipose cells rather than the number of cells in an adipose organ.

Distribution of milk fat globules in cow's milk high in linoleic acid

The influence of feeding cows formaldehyde-treated polyunsaturated oilseed supplement on fatty acid composition and distribution of particle size of milk fat globules has been studied. Supplement increased linoleic acid in milk fat from 1.7 to 27.4%. Distributions of particle size measured by a Coulter counter showed that milk fat from cows receiving supplement had large milk fat globules than those in milk fat of the same cows when supplementation was discontinued. However. this difference in size could not be attributed to percent linoleic acid in the milk fat since correction of the data of supplemented cows for percent milk fat and size of milk fat globules resulted in particle distributions strikingly similar in shape.

Sire effect on fatty acid composition of ovine adipose tissue

The fatty acid composition of perirenal adipose tissue from 255 purebred and crossbred sheep was examined to determine the genetic effects of sire on each of five fatty acids. The sheep, all rams, were the progeny of 30 Dorset Horn sires. The animals were grazed on pasture and slaughtered at an average age of 21 months, when their mean carcass weight was 30 kilograms. The fatty acids studied and their mean percentage compositions were: stearic, 38%; oleic, 31%; palmitic, 20%; palmitoleic, 2%, and linoleic, 2%. These amounted to over 90% by weight of the tissue sample fatty acids. In addition, numerical functions were constructed as ratios for two pairs of fatty acids, ratio 1 (palmitoleic to palmitic) and ratio 2 (oleic to stearic), for estimation of the desaturase enzyme activity in the tissue samples studied. A Softness Index, expressed as a ratio between monounsaturated and saturated acids, was also included in the analysis. Significant birth year and maternal breed effects were found for all the traits studied. This was in contrast to the regression on slaughter age, which with two exceptions was not a significant source of variation in the data. The sire effect, based on 27 degrees of freedom, was highly significant or significant for all traits except stearic or linoleic acid and ratio 2. These results are discussed with reference to utilization of genetic variation between sites in selective breeding programs to modify fatty acid composition of ovine adipose tissue.

A technique to study the relationship between adipose cell size and lipogenesis in a heterogeneous population of adipose cells

A technique is described for the calculation of the incorporation of radioactive substrate into lipid in adipose cells that have been isolated and separated into groups according to their diameter from a single sample of adipose tissue containing a heterogeneous population of cells. After incorporation of radioactive substrate, a section of adipose tissue is fixed in osmium tetroxide and the fixed cells isolated and separated into specific diameter ranges using a series of nylon screens. The separated cells are weighed, decolorized with hydrogen peroxide, and the radioactivity is determined in the cells from each diameter range. With this method, true comparisons can be made between adipose cell size and lipogenic activity of isolated cells of known diameter which have been subjected to various nutritional or hormonal treatments. Results with sheep adipose tissue show that large adipose cells are considerably more active in the synthesis of lipid than small cells from the same sample of adipose tissue.

Effect of feeding protected lipids on fatty acid synthesis in ovine tissues

The effects of including protected lipid supplements in the sheep diet have been studied by measuring the incorporation of [1-14C]acetate into tissue fatty acids in vivo and in vitro. Supplementing the diet with protected lipid significantly (P > 0.05) depressed lipogenesis in adipose tissue both in vovo and in vitro. However, when protected lipids of different fatty acid composition were given to lambs, the protected safflower oil supplement containing high levels of linoleic acid was the only treatment to cause a significant (P > 0.05) depression in fatty acid synthesis in adipose tissue, the major site of lipogenesis in the sheep. Larger adipose cells in the lipid-supplemented sheep indicate that these sheep were fatter than those receiving the basal diet. Therefore, supplemented wethers deposited more fat than sheep receiving the basal diet and this fat was derived from the supplement rather than from de novo synthesis.

Biotin and the sudden infant death syndrome

A diet which is marginally deficient in the vitamin biotin may cause sudden unexpected death of young broiler chickens when they are exposed to stress. Chickens affected with this disorder have low levels of biotin in their livers. In conditions of biotin insufficiency, we postulate that a similar disorder, triggered by mild stress, may occur in the human infant. We have now used a radiochemical technique to measure the biotin content of 204 livers obtained from infants at autopsy. The levels of biotin in the livers of infants who had died of sudden infant death syndrom (SIDS; cot death) were significantly lower than those in livers of infants of similar age, who had died of explicable causes. These findings support an association of biotin with SIDS.

The effect of compensatory growth on lipogenesis in ovine carcass adipose tissue

Rates of lipogenesis, as measured by the incorporation in vitvo of [14C]acetate into fatty acids, were measured in wethers which were either fed continuously or subjected to an interval of starvation. Refeeding ad libitum of starved sheep resulted in a faster growth rate; immature sheep after 110 days and mature sheep after 56 days had reached a fat content similar to that in the continuously grown sheep. In continuously grown sheep the rate of lipogenesis in subcutaneous adipose tissue increased with increasing liveweight. Lipogenesis was almost totally eliminated after a period of weight loss. In nutritionally rehabilitated immature and mature sheep, lipogenesis was restored and reached a rate higher than that measured for sheep which were continuously grown on the same diet. In immature sheep lipogenesis responded rapidly to refeeding. However, lipogenesis in mature sheep was slower to respond to increased dietary intake, which indicated that in mature sheep the biochemical pathways of lipid metabolism take several days to respond and reach their full lipogenic potential in response to changes in the physiological state.

Effects of saponins on bile acids and plasma lipids in the rat

1. The effects of feeding isolated saponins on plasma lipid concentrations and on concentrations of biliary and faecal bile acids and neutral sterols were studied in the rat. 2. The animals were given one of four diets, i.e. a standard low-cholesterol synthetic diet, the diet + 10 g saponins/kg, the diet + 10 g cholesterol/kg, the diet + 10 g cholesterol + 10 g saponins/kg. 3. Saponins partially reversed the hypercholesterolaemia caused by the high-cholesterol diet and increased both the rate of bile acid secretion and the faecal excretion of bile acids and neutral sterols. The proportionate contribution of the primary bile acids (particularly chenodeoxycholic) to faecal excretion was also increased by saponins. 4. The results are discussed in relation to the hypothesis that saponins act by inducing the adsorption of bile acids by dietary fibre.

The cellularity of ovine adipose tissue

The cellular growth of adipose tissue from Dorset Horn x Merino wethers was characterized by both hypertrophy and hyperplasia of adipose cells until the sheep were c. 11 months old, after which hypertrophy of existing adipose cells was solely responsible for increases in adipose tissue mass. Omental adipose tissue contained larger adipose cells than either the perirenal or subcutaneous sites. The weight of fat which had been deposited in the boneless carcass meat and the internal adipose tissue depots were linearly and positively correlated with the volume of the adipose cells. Decreases in the mass of adipose tissue, which accompanied nutritional restriction, were due to decreased adipose cell size, since no change was observed in the number of adipose cells per carcass after loss in weight. The cellularity characteristics of rehabilitated sheep were similar to those of sheep which had undergone continuous growth.

Compensatory growth in sheep

Some attributes of the body composition of Dorset Horn x Merino wethers, which were either continuously grown or subjected to one or two periods of starvation-weight loss, realimentation and compensatory growth, were studied. Periods of restricted feed intake were imposed when liveweights were either below (23 kg) or above (43 kg) the level generally regarded as a mature liveweight (c. 31 kg) for such sheep. Loss of liveweight resulted in different responses in the meat of immature and mature animals. The meat from immature sheep was depleted of fat, whereas that from mature sheep increased in fat content. Loss of fat from the meat of immature sheep was associated with both atrophy and hypoplasia of the subcutaneous adipose cells, but in mature sheep there was atrophy without hypoplasia of these adipose cells. Although the greatest loss of fat was from the meat, proportionately more fat was lost from the offal, particularly in mature sheep. The amount of protein in the carcass meat was similar in control, starved, or realimented sheep of the same body weight. During the first few days of realimentation the sheep consumed three to four times as much food per day as during the starvation periods; the apparent digestibility of the food was increased from 53–68% to 80–90%; liveweight gain was 500–600 g/day, and there were increases in fat, water and protein in the meat of realimented animals. Sheep which had been starved and realimented, either once or twice, rapidly achieved liveweights equal to those of continuously grown animals and were similar to them in both body and meat composition.

The effect of dietary fat supplements on cholesterol metabolism in ruminants

The serum cholesterol on ruminant animals rises when supplemental fat is fed in a form that ensures the absorption of long-chain fatty acids. The effects of these fat supplements on cholesterol metabolism have been studied in sheep and goats. The proximal part of the small intestine was the major site of sterol synthesis in sheep. Supplementing the diet with fat significantly enhanced sterolgenesis in the small intestine both in vivo and in vitro, whereas in vitro sterolgenesis appeared to be suppressed in the liver. Increased intestinal sterolgenesis was seen with several varieties of fat, but was greatest when palm oil was fed. The reciprocal findings in the intestine and liver may reflect the increased requirement for cholesterol for the transport of triglyceride in chylomicrons and the secondary inhibiting effect of this cholesterol on sterol synthesis in the liver. Dietary fat supplementation did not alter the excretion of neutral steroids in the feces of goats but did not cause a marked reduction in the excretion of acidic steroids which may have been due to the decreased formation of sterols in the liver. In two lactating goats in which an injection of [14C] cholesterol was followed by daily intraruminal administration of labeled cholesterol, fat supplementation lowered the specific radioactivity of cholesterol in alimentary particles and in milk, being consistent with an increase in intestinally synthesized cholesterol. The hypercholesterolemia that develops in fat-fed ruminants appears to be primarily due to an increased intestinal biosynthesis of cholesterol but may also be partly due to a decreased fecal excretion of bile acids.

The effect of dietary monoterpenes on the cholesterol level of eggs

Monoterpenes were included in the diets of laying hens in an attempt to inhibit the synthesis of cholesterol and hence reduce its amount in egg yolk. However, feeding five monoterpenes, phorone or 200 mg. cholesterol per day to hens did not significantly change the level of cholesterol in the egg yolk. These compounds did not cause signs of ill health in the hen or a decline in egg production.