Noncompetitive immunoassay optimized for pharmacokinetic assessments of biologically active efruxifermin

Efruxifermin (EFX) is a homodimeric human IgG1 Fc-FGF21 fusion protein undergoing investigation for treatment of liver fibrosis due to nonalcoholic steatohepatitis (NASH), a prevalent and serious metabolic disease for which there is no approved treatment. Biological activity of FGF21 requires its intact C-terminus, which enables binding to its obligate co-receptor β-Klotho on the surface of target cells. This interaction is a prerequisite for FGF21 signal transduction through its canonical FGF receptors: FGFR1c, 2c, and 3c. Therefore, the C-terminus of each FGF21 polypeptide chain must be intact, with no proteolytic truncation, for EFX to exert its pharmacological activity in patients. A sensitive immunoassay for quantification of biologically active EFX in human serum was therefore needed to support pharmacokinetic assessments in patients with NASH. We present a validated noncompetitive electrochemiluminescent immunoassay (ECLIA) that employs a rat monoclonal antibody for specific capture of EFX via its intact C-terminus. Bound EFX is detected by a SULFO-TAG™-conjugated, affinity purified chicken anti-EFX antiserum. The ECLIA reported herein for quantification of EFX demonstrated suitable analytical performance, with a sensitivity (LLOQ) of 20.0 ng/mL, to support reliable pharmacokinetic assessments of EFX. The validated assay was used to quantify serum EFX concentrations in a phase 2a study of NASH patients (BALANCED) with either moderate-to-advanced fibrosis or compensated cirrhosis. The pharmacokinetic profile of EFX was dose-proportional and did not differ between patients with moderate-to-advanced fibrosis and those with compensated cirrhosis. This report presents the first example of a validated pharmacokinetic assay specific for a biologically active Fc-FGF21 fusion protein, as well as the first demonstration of use of a chicken antibody conjugate as a detection reagent specific for an FGF21 analog.

Efruxifermin in non-alcoholic steatohepatitis: a randomized, double-blind, placebo-controlled, phase 2a trial

Preclinical and clinical data suggest that fibroblast growth factor 21 (FGF21) is anti-fibrotic, improves metabolic status and has potential to treat non-alcoholic steatohepatitis (NASH). We assessed the safety and efficacy of efruxifermin, a long-acting Fc-FGF21 fusion protein, for the treatment of NASH. BALANCED was a randomized, placebo-controlled study in patients with NASH conducted at 27 centers in the United States (ClinicalTrials.gov NCT03976401 ). Eighty patients, stratified by hepatic fat fraction (HFF) and fibrosis stage, were randomized using a centrally administered minimization algorithm 1:1:1:1 to receive placebo (n = 21) or efruxifermin 28 mg (n = 19), efruxifermin 50 mg (n = 20) or efruxifermin 70 mg (n = 20) via weekly subcutaneous injection for 16 weeks. The primary endpoint-absolute change from baseline in HFF measured as magnetic resonance imaging-proton density fat fraction at week 12-was met. For the full analysis set, the least squares mean absolute changes (one-sided 97.5% confidence interval) from baseline in HFF were -12.3% (-infinity (-inf), -10.3), -13.4% (-inf, -11.4) and -14.1% (-inf, -12.1) in the 28-, 50- and 70-mg groups, respectively, versus 0.3% (-inf, 1.6) in the placebo group, with statistically significant differences between efruxifermin groups and placebo (P < 0.0001 each). Overall, 70 of 79 patients who received the study drug (89%) experienced at least one treatment-emergent adverse event (TEAE), with the majority grade 1-2 (64 (81%)), five (6%) grade 3 and one grade 4. The most commonly reported drug-related TEAEs were grade 1-2 gastrointestinal (36 (46%)). Treatment with efruxifermin significantly reduced HFF in patients with F1-F3 stage NASH, with an acceptable safety profile.

Generation of Affinity Purified Antibody Reagents for Specific Determination of Efruxifermin in Biological Matrices

Efruxifermin (EFX) is a novel Fc-fusion analog of human fibroblast growth factor 21 (FGF21), currently in clinical development as a potential treatment for non-alcoholic steatohepatitis (NASH). Each molecule of EFX consists of two modified FGF21 molecules, each attached at their N-termini to a human IgG1 Fc domain by a short polyglycine-serine linker. The FGF21 moiety of EFX incorporates three amino acid substitutions (L98R, P171G, and A180E relative to native FGF21). Two of these are proximal to the C-terminus (P171G and A180E), and reduce cleavage and inactivation by an endogenous protease, fibroblast activation protein (FAP), thereby prolonging its half-life. Fusion to human IgG1 Fc domain further extends circulating half-life, enabling once-weekly subcutaneous dosing. Accordingly, to support on-going clinical development of EFX, a specific assay is needed to distinguish intact EFX from both endogenous FGF21 and any in vivo biotransformation products of EFX that display reduced pharmacology. To maximize the antigenicity of EFX, FGF21 amino acid sequences were compared across species. Based on this, an antibody generation campaign was initiated in both rabbits and chickens. Comparison of titer responses against EFX and human FGF21 suggested that antisera from chickens was superior to rabbit antisera. Following a scaled-up, 12-week antibody campaign, antisera were purified by a combination of batch and column chromatographic procedures. By exploiting differences in structure and amino acid sequence of EFX relative to human FGF21, a purification strategy was designed to isolate chicken antibodies with increased specificity for EFX unique sequences. This reagent is being used as a capture antibody in the development of a noncompetitive ECLIA employing chemiluminescence detection. Presently, a number of different antibodies are being evaluated for potential pairing with the specific capture. We conclude that application of affinity purified chicken anti-EFX IgY will enable sensitive and specific determination of EFX in biological matrices with decreased cross-reactivity from endogenous hFGF21 and EFX metabolites.

Human sebum requires de novo lipogenesis, which is increased in acne vulgaris and suppressed by acetyl-CoA carboxylase inhibition

Sebum plays important physiological roles in human skin. Excess sebum production contributes to the pathogenesis of acne vulgaris, and suppression of sebum production reduces acne incidence and severity. We demonstrate that sebum production in humans depends on local flux through the de novo lipogenesis (DNL) pathway within the sebocyte. About 80 to 85% of sebum palmitate (16:0) and sapienate (16:1n10) were derived from DNL, based on stable isotope labeling, much higher than the contribution of DNL to triglyceride palmitate in circulation (~20%), indicating a minor contribution by nonskin sources to sebum lipids. This dependence on local sebocyte DNL was not recapitulated in two widely used animal models of sebum production, Syrian hamsters and Göttingen minipigs. Confirming the importance of DNL for human sebum production, an acetyl-CoA carboxylase inhibitor, ACCi-1, dose-dependently suppressed DNL and blocked synthesis of fatty acids, triglycerides, and wax esters but not free sterols in human sebocytes in vitro. ACCi-1 dose-dependently suppressed facial sebum excretion by ~50% (placebo adjusted) in human individuals dosed orally for 2 weeks. Sebum triglycerides, wax esters, and free fatty acids were suppressed by ~66%, whereas non-DNL-dependent lipid species, cholesterol, and squalene were not reduced, confirming selective modulation of DNL-dependent lipids. Last, individuals with acne vulgaris exhibited increased sebum production rates relative to individuals with normal skin, with >80% of palmitate and sapienate derived from DNL. These findings highlight the importance of local sebocyte DNL for human skin sebaceous gland biology and illuminate a potentially exploitable therapeutic target for the treatment of acne vulgaris.

Once-weekly administration of a long-acting fibroblast growth factor 21 analogue modulates lipids, bone turnover markers, blood pressure and body weight differently in obese people with hypertriglyceridaemia and in non-human primates

AIMS

To assess the safety, tolerability, pharmacokinetics and pharmacodynamics of PF-05231023, a long-acting fibroblast growth factor 21 (FGF21) analogue, in obese people with hypertriglyceridaemia on atorvastatin, with or without type 2 diabetes.

METHODS

Participants received PF-05231023 or placebo intravenously once weekly for 4 weeks. Safety (12-lead ECGs, vital signs, adverse events [AEs], laboratory tests) and longitudinal weight assessments were performed. Blood samples were collected for pharmacokinetic and pharmacodynamic analyses. Cardiovascular safety studies were also conducted in telemetered rats and monkeys. Blood pressure (BP; mean, systolic and diastolic) and ECGs were monitored.

RESULTS

A total of 107 people were randomized. PF-05231023 significantly decreased mean placebo-adjusted fasting triglycerides (day 25, 33%-43%) and increased HDL cholesterol (day 25, 15.7%-28.6%) and adiponectin (day 25, 1574 to 3272 ng/mL) across all doses, without significant changes in body weight (day 25, -0.45% to -1.21%). Modest decreases from baseline were observed for N-terminal propeptides of type 1 collagen (P1NP) on day 25, although C-telopeptide cross-linking of type 1 collagen (CTX-1) increased minimally. Systolic, diastolic BP, and pulse rate increased in a dose- and time-related manner. There were 5 serious AEs (one treatment-related) and no deaths. Three participants discontinued because of AEs. The majority of AEs were gastrointestinal. PF-05231023 increased BP and heart rate in rats, but not in monkeys.

CONCLUSIONS

Once-weekly PF-05231023 lowered triglycerides markedly in the absence of weight loss, with modest changes in markers of bone homeostasis. This is the first report showing increases in BP and pulse rate in humans and rats after pharmacological administration of a long-acting FGF21 molecule.

Discovery of a Selective Covalent Inhibitor of Lysophospholipase-like 1 (LYPLAL1) as a Tool to Evaluate the Role of this Serine Hydrolase in Metabolism

Lysophospholipase-like 1 (LYPLAL1) is an uncharacterized metabolic serine hydrolase. Human genome-wide association studies link variants of the gene encoding this enzyme to fat distribution, waist-to-hip ratio, and nonalcoholic fatty liver disease. We describe the discovery of potent and selective covalent small-molecule inhibitors of LYPLAL1 and their use to investigate its role in hepatic metabolism. In hepatocytes, selective inhibition of LYPLAL1 increased glucose production supporting the inference that LYPLAL1 is a significant actor in hepatic metabolism. The results provide an example of how a selective chemical tool can contribute to evaluating a hypothetical target for therapeutic intervention, even in the absence of complete biochemical characterization.

Branched-chain amino acid restriction in Zucker-fatty rats improves muscle insulin sensitivity by enhancing efficiency of fatty acid oxidation and acyl-glycine export

Objective

A branched-chain amino acid (BCAA)-related metabolic signature is strongly associated with insulin resistance and predictive of incident diabetes and intervention outcomes. To better understand the role that this metabolite cluster plays in obesity-related metabolic dysfunction, we studied the impact of BCAA restriction in a rodent model of obesity in which BCAA metabolism is perturbed in ways that mirror the human condition.

Methods

Zucker-lean rats (ZLR) and Zucker-fatty rats (ZFR) were fed either a custom control, low fat (LF) diet, or an isonitrogenous, isocaloric LF diet in which all three BCAA (Leu, Ile, Val) were reduced by 45% (LF-RES). We performed comprehensive metabolic and physiologic profiling to characterize the effects of BCAA restriction on energy balance, insulin sensitivity, and glucose, lipid and amino acid metabolism.

Results

LF-fed ZFR had higher levels of circulating BCAA and lower levels of glycine compared to LF-fed ZLR. Feeding ZFR with the LF-RES diet lowered circulating BCAA to levels found in LF-fed ZLR. Activity of the rate limiting enzyme in the BCAA catabolic pathway, branched chain keto acid dehydrogenase (BCKDH), was lower in liver but higher in skeletal muscle of ZFR compared to ZLR and was not responsive to diet in either tissue. BCAA restriction had very little impact on metabolites studied in liver of ZFR where BCAA content was low, and BCKDH activity was suppressed. However, in skeletal muscle of LF-fed ZFR compared to LF-fed ZLR, where BCAA content and BCKDH activity were increased, accumulation of fatty acyl CoAs was completely normalized by dietary BCAA restriction. BCAA restriction also normalized skeletal muscle glycine content and increased urinary acetyl glycine excretion in ZFR. These effects were accompanied by lower RER and improved skeletal muscle insulin sensitivity in LF-RES fed ZFR as measured by hyperinsulinemic-isoglycemic clamp.

Conclusions

Our data are consistent with a model wherein elevated circulating BCAA contribute to development of obesity-related insulin resistance by interfering with lipid oxidation in skeletal muscle. BCAA-dependent lowering of the skeletal muscle glycine pool appears to contribute to this effect by slowing acyl-glycine export to the urine.

•

Feeding a BCAA restricted diet improves skeletal muscle insulin sensitivity in Zucker fatty rats.

•

BCKDH activity is decreased in liver and increased in skeletal muscle in Zucker fatty versus lean rats.

•

High BCAA levels drive the obesity-associated decline in circulating and muscle glycine levels.

•

BCAA-driven glycine depletion restricts formation of acyl-glycine adducts for excretion in urine.

•

High BCAA/low glycine reduces efficiency of fat oxidation in muscle leading to acyl CoA buildup.

A Long-Acting FGF21 Molecule, PF-05231023, Decreases Body Weight and Improves Lipid Profile in Non-human Primates and Type 2 Diabetic Subjects

FGF21 plays a central role in energy, lipid, and glucose homeostasis. To characterize the pharmacologic effects of FGF21, we administered a long-acting FGF21 analog, PF-05231023, to obese cynomolgus monkeys. PF-05231023 caused a marked decrease in food intake that led to reduced body weight. To assess the effects of PF-05231023 in humans, we conducted a placebo-controlled, multiple ascending-dose study in overweight/obese subjects with type 2 diabetes. PF-05231023 treatment resulted in a significant decrease in body weight, improved plasma lipoprotein profile, and increased adiponectin levels. Importantly, there were no significant effects of PF-05231023 on glycemic control. PF-05231023 treatment led to dose-dependent changes in multiple markers of bone formation and resorption and elevated insulin-like growth factor 1. The favorable effects of PF-05231023 on body weight support further evaluation of this molecule for the treatment of obesity. Longer studies are needed to assess potential direct effects of FGF21 on bone in humans.

The Acetyl Group Buffering Action of Carnitine Acetyltransferase Offsets Macronutrient-Induced Lysine Acetylation of Mitochondrial Proteins

Lysine acetylation (AcK), a posttranslational modification wherein a two-carbon acetyl group binds covalently to a lysine residue, occurs prominently on mitochondrial proteins and has been linked to metabolic dysfunction. An emergent theory suggests mitochondrial AcK occurs via mass action rather than targeted catalysis. To test this hypothesis, we performed mass spectrometry-based acetylproteomic analyses of quadriceps muscles from mice with skeletal muscle-specific deficiency of carnitine acetyltransferase (CrAT), an enzyme that buffers the mitochondrial acetyl-CoA pool by converting short-chain acyl-CoAs to their membrane permeant acylcarnitine counterparts. CrAT deficiency increased tissue acetyl-CoA levels and susceptibility to diet-induced AcK of broad-ranging mitochondrial proteins, coincident with diminished whole body glucose control. Sub-compartment acetylproteome analyses of muscles from obese mice and humans showed remarkable overrepresentation of mitochondrial matrix proteins. These findings reveal roles for CrAT and L-carnitine in modulating the muscle acetylproteome and provide strong experimental evidence favoring the nonenzymatic carbon pressure model of mitochondrial AcK.

Impact of combined resistance and aerobic exercise training on branched-chain amino acid turnover, glycine metabolism and insulin sensitivity in overweight humans

AIMS/HYPOTHESES

Obesity is associated with decreased insulin sensitivity (IS) and elevated plasma branched-chain amino acids (BCAAs). The purpose of this study was to investigate the relationship between BCAA metabolism and IS in overweight (OW) individuals during exercise intervention.

METHODS

Whole-body leucine turnover, IS by hyperinsulinaemic-euglycaemic clamp, and circulating and skeletal muscle amino acids, branched-chain α-keto acids and acylcarnitines were measured in ten healthy controls (Control) and nine OW, untrained, insulin-resistant individuals (OW-Untrained). OW-Untrained then underwent a 6 month aerobic and resistance exercise programme and repeated testing (OW-Trained).

RESULTS

IS was higher in Control vs OW-Untrained and increased significantly following exercise. IS was lower in OW-Trained vs Control expressed relative to body mass, but was not different from Control when normalised to fat-free mass (FFM). Plasma BCAAs and leucine turnover (relative to FFM) were higher in OW-Untrained vs Control, but did not change on average with exercise. Despite this, within individuals, the decrease in molar sum of circulating BCAAs was the best metabolic predictor of improvement in IS. Circulating glycine levels were higher in Control and OW-Trained vs OW-Untrained, and urinary metabolic profiling suggests that exercise induces more efficient elimination of excess acyl groups derived from BCAA and aromatic amino acid (AA) metabolism via formation of urinary glycine adducts.

CONCLUSIONS/INTERPRETATION

A mechanism involving more efficient elimination of excess acyl groups derived from BCAA and aromatic AA metabolism via glycine conjugation in the liver, rather than increased BCAA disposal through oxidation and turnover, may mediate interactions between exercise, BCAA metabolism and IS.

TRIAL REGISTRATION

Clinicaltrials.gov NCT01786941.

Isocitrate-to-SENP1 signaling amplifies insulin secretion and rescues dysfunctional β cells

Insulin secretion from β cells of the pancreatic islets of Langerhans controls metabolic homeostasis and is impaired in individuals with type 2 diabetes (T2D). Increases in blood glucose trigger insulin release by closing ATP-sensitive K+ channels, depolarizing β cells, and opening voltage-dependent Ca2+ channels to elicit insulin exocytosis. However, one or more additional pathway(s) amplify the secretory response, likely at the distal exocytotic site. The mitochondrial export of isocitrate and engagement with cytosolic isocitrate dehydrogenase (ICDc) may be one key pathway, but the mechanism linking this to insulin secretion and its role in T2D have not been defined. Here, we show that the ICDc-dependent generation of NADPH and subsequent glutathione (GSH) reduction contribute to the amplification of insulin exocytosis via sentrin/SUMO-specific protease-1 (SENP1). In human T2D and an in vitro model of human islet dysfunction, the glucose-dependent amplification of exocytosis was impaired and could be rescued by introduction of signaling intermediates from this pathway. Moreover, islet-specific Senp1 deletion in mice caused impaired glucose tolerance by reducing the amplification of insulin exocytosis. Together, our results identify a pathway that links glucose metabolism to the amplification of insulin secretion and demonstrate that restoration of this axis rescues β cell function in T2D.

FGF21 does not require interscapular brown adipose tissue and improves liver metabolic profile in animal models of obesity and insulin-resistance

FGF21 is a key metabolic regulator modulating physiological processes and its pharmacological administration improves metabolic profile in preclinical species and humans. We used native-FGF21 and a long-acting FGF21 (PF-05231023), to determine the contribution of liver and brown adipose tissue (BAT) towards metabolic improvements in Zucker rats and DIO mice (DIOs). FGF21 improved glucose tolerance and liver insulin sensitivity in Zuckers without affecting BW and improved liver function by decreased lipogenesis, increased fatty acid oxidation and improved insulin signaling. Through detailed lipidomic analyses of liver metabolites in DIOs, we demonstrate that FGF21 favorably alters liver metabolism. We observed a dose-dependent increase of [(18)F]-FDG-glucose uptake in interscapular BAT (iBAT) of DIOs upon FGF21 administration. Upon excision of iBAT (X-BAT) and administration of FGF21 to mice housed at 80 °F or 72 °F, the favorable effects of FGF21 on BW and glucose excursion were fully retained in both sham and X-BAT animals. Taken together, we demonstrate the liver as an organ that integrates the actions of FGF21 and provide metabolic benefits of FGF21 in Zucker rats and DIOs. Finally, our data demonstrates iBAT does not play a role in mediating favorable metabolic effects of FGF21 administration in DIOs housed at 80 °F or 72 °F.

The hepatoselective glucokinase activator PF-04991532 ameliorates hyperglycemia without causing hepatic steatosis in diabetic rats

Hyperglycemia resulting from type 2 diabetes mellitus (T2DM) is the main cause of diabetic complications such as retinopathy and neuropathy. A reduction in hyperglycemia has been shown to prevent these associated complications supporting the importance of glucose control. Glucokinase converts glucose to glucose-6-phosphate and determines glucose flux into the β-cells and hepatocytes. Since activation of glucokinase in β-cells is associated with increased risk of hypoglycemia, we hypothesized that selectively activating hepatic glucokinase would reduce fasting and postprandial glucose with minimal risk of hypoglycemia. Previous studies have shown that hepatic glucokinase overexpression is able to restore glucose homeostasis in diabetic models; however, these overexpression experiments have also revealed that excessive increases in hepatic glucokinase activity may also cause hepatosteatosis. Herein we sought to evaluate whether liver specific pharmacological activation of hepatic glucokinase is an effective strategy to reduce hyperglycemia without causing adverse hepatic lipids changes. To test this hypothesis, we evaluated a hepatoselective glucokinase activator, PF-04991532, in Goto-Kakizaki rats. In these studies, PF-04991532 reduced plasma glucose concentrations independent of changes in insulin concentrations in a dose-dependent manner both acutely and after 28 days of sub-chronic treatment. During a hyperglycemic clamp in Goto-Kakizaki rats, the glucose infusion rate was increased approximately 5-fold with PF-04991532. This increase in glucose infusion can be partially attributed to the 60% reduction in endogenous glucose production. While PF-04991532 induced dose-dependent increases in plasma triglyceride concentrations it had no effect on hepatic triglyceride concentrations in Goto-Kakizaki rats. Interestingly, PF-04991532 decreased intracellular AMP concentrations and increased hepatic futile cycling. These data suggest that hepatoselective glucokinase activation may offer glycemic control without inducing hepatic steatosis supporting the evaluation of tissue specific activators in clinical trials.

Optimizing glucokinase activator binding kinetics to lower in vivo hypoglycemia risk

GK activators represent a promising strategy for treatment of T2DM; however, drug candidates have failed in clinical trials due to narrow TI between efficacy and hypoglycemia.

Metabolic events associated with the preparation of the fetus for independent life

The metabolic changes late in fetal development that are essential for neonatal survival are discussed. In many species gluconeogenesis develops before birth but provides substrate for intracellular biosynthesis and not for glucose production because of low activities of glucose 6-phosphate translocase. At the time of glycogen deposition in species with a relatively mature brain at birth the translocase develops and glucagon and adrenaline can stimulate glucose production and synthesis to elevate blood glucose concentrations both pre- and postnatally. The other metabolic fuel accumulated before birth, fat, can also be mobilized prenatally and in fetuses that are relatively mature at birth it may be used as an alternative fuel. The fetal rat brain can oxidize fatty acids and the brain of fetuses such as that of the guinea-pig and man can oxidize ketone bodies before birth. The timing and degree of oxidation of ketone bodies relates to the timing of myelination and protects the brain against hypoglycaemia. These late changes in development are associated with a sharp increase in plasma cortisol and adrenaline concentrations and a high fetal insulin concentration.

Duration of protective immunity against ovine haemonchosis following vaccination with the nematode gut membrane antigen H11

To establish for how long protective antibody levels may be maintained, lambs were vaccinated with the gut membrane antigen H11 and challenged with Haemonchus contortus 14, 84, 126 or 168 days later. Compared to controls, mean faecal egg counts of vaccinated lambs were reduced by 97 per cent, 99 per cent, 92 per cent and 86 per cent respectively. Total worm burdens at postmortem five weeks after infection were reduced by 87 per cent, 94 per cent, 92 per cent and 62 per cent respectively. In vaccinated lambs, antibody levels to H11 peaked at about 60 days after the first vaccination and were maintained for the duration of the experiment. There was evidence of secondary antibody responses to H11 following challenge.

Induction of protective immunity in cattle against infection with Fasciola hepatica by vaccination with cathepsin L proteinases and with hemoglobin

Two cathepsin L proteinases, cathepsin L1 and cathepsin L2, secreted by liver flukes may be involved in tissue penetration, nutrition, and protection from immune attack. To ascertain the immunoprophylactic potential of these proteinases, and of another molecule, liver fluke hemoglobin (Hb), we performed vaccine trials in cattle. In the first vaccine trial various doses of cathepsin L1 were tested. The mean protection level obtained was 53.7%. In a second vaccine trial cathepsin L1 and Hb elicited 42.5 and 43.8% protection levels, respectively, while a combination of the two molecules induced a significantly higher level of protection (51.9%). Cathepsin L2 was not examined alone; however, vaccination of cattle with a combination of cathepsin L2 and Hb elicited the highest level of protection (72.4%). The animals that received cathepsin L1-Hb or cathepsin L2-Hb showed reduced liver damage as assessed by serum glutamic dehydrogenase and gamma-glutamyl transferase levels. Furthermore, a reduced viability was observed for fluke eggs recovered from all vaccine groups. This anti-embryonation effect of vaccination was particularly evident in the group that received cathepsin L2-Hb where >98% of the eggs recovered did not embryonate to miracidia. Although all vaccine preparations induced high antibody titers which were boosted following the challenge infection, there was no correlation between antibody titers and protection. The results of these trials demonstrate that cathepsin Ls and Hb could form the basis of a molecular vaccine that would not only reduce parasite burden but would also prevent transmission of liver fluke disease.

Vaccination of sheep against haemonchosis with H11, a gut membrane-derived protective antigen from the adult parasite: prevention of the periparturient rise and colostral transfer of protective immunity

Pregnant ewes were immunised with a fraction highly enriched in the membrane glycoprotein antigen H11, isolated from the intestinal brush border of adult Haemonchus contortus. Immunity induced by immunisation was able to abolish almost completely (98-99%) the worm egg output from pregnant ewes challenged with ca. 10,000 infective larvae of H. contortus during the last trimester. Furthermore, lambs born and reared on vaccinated ewes had substantial antibody levels to H11 derived from maternal transfer. This antibody conferred moderate protection against a bolus challenge of ca. 3000 infective larvae of H. contortus in 5-week-old lambs.

Protection against multiply drug-resistant and geographically distant strains of Haemonchus contortus by vaccination with H11, a gut membrane-derived protective antigen

H11 is a "hidden antigen" derived from adult Haemonchus contortus which is capable of conferring a high degree of protection against subsequent challenge. To be commercially useful, any vaccine based on this antigen must protect against field strains and drug-resistant worms. The results show that vaccination with H11 affords high levels of protection against the multiply drug-resistant (MDR) Lawes strain of Haemonchus contortus. Moreover, there was no difference in protection whether the H11 was extracted from drug-resistant or susceptible worms, indicating that multiple drug-resistance does not significantly alter the immunogenicity of H11. Ideally, a commercial vaccine based on this antigen should also be capable of protecting against strains from geographically separate areas, so that it is not necessary to manufacture "region-specific" vaccines. Vaccination with H11 purified from either Australian or U.K. Haemonchus contortus was effective in protecting against subsequent challenge with Australian larvae, indicating that one type of H11 should have world-wide application.

Influence of the beta-agonist salbutamol on claw horn lesions and walking soundness in finishing pigs

The effects of feeding the beta-adrenergic agonist salbutamol to pigs at levels between 0.5 and 5.0 mg/kg feed for different periods were studied in six experiments. The feet and ability to walk of pigs weighing 30 to 100 kg were examined at intervals. False sand-crack, white-line and heel erosion lesions were classified as mild or severe, and corns and wall haemorrhages were also recorded. At each examination the pig was given a grade for the overall severity of its foot lesions. Salbutamol fed at 1.0 to 5.0 mg/kg feed, for as little as 21 to 28 days, increased the frequency (P < 0.05 to 0.001) and often the severity (P < 0.05) of the foot lesions, the higher doses tending to produce more severe lesions, and the overall foot grades deteriorated (P < 0.001). The effects on both sexes were similar. No changes were observed when 0.5 mg/kg was fed for 56 days. Despite the severity of many of the foot lesions, the pigs became lame in only one experiment. Electron microscopy indicated that salbutamol was interfering with horn production, but light microscopy revealed no changes in skin sections. These findings suggested that salbutamol was not directly affecting the function of keratinocytes. Supplementing the diet of the pigs with biotin and methionine did not delay, or prevent, the effects of salbutamol.

Interactions between the beta-adrenergic agonist salbutamol and genotype on meat quality in pigs

Salbutamol (2.7 ppm) fed to pigs between weaning and slaughter increased ADG (5%), dressing percentage (2%) and cross-sectional area of the longissimus (LD) muscle (14%). In fatter, White-line-sired pigs, but not in leaner, Meat-line-sired animals, it reduced backfat thickness (25%). Liver weight and glycogen concentration also were decreased. In neither genotype were there effects of Salbutamol on pH45, drip loss or reflectance value of the LD, but ultimate pH was elevated in semimembranosus (SM), adductor (AD) and supraspinatus (SS) muscles, resulting in reduced color saturation values. Total muscle heme pigment concentrations were reduced by 10 (SS) to 19% (LD and SM) and the intramuscular fat concentration of the AD, but not the LD, was reduced by 21%. Treated pigs had LD and SM muscles that when measured instrumentally were 15 and 8% tougher, respectively, after cooking, but the texture of the SS was not significantly altered by treatment. Salbutamol increased plasma lactate and creatine phosphokinase (CPK) concentrations. Compared with White-line-sired animals, Meat-line-sired pigs had a higher dressing percentage (2%) and LD muscles with larger cross-sectional area (13%). They also had higher circulating CPK levels.

Studies on the growth of the fetal guinea pig. The effects of nutritional manipulation on prenatal growth and plasma somatomedin activity and insulin-like growth factor concentrations

In guinea pigs between days 41-46 of pregnancy prenatal growth has been manipulated by alteration of nutritional state. Three methods were used. Uterine artery ligation at day 30 of pregnancy depressed fetal growth rate by greater than 50% and was associated with falls in plasma insulin, IGF-1, cortisol, thyroid hormone, glucose, acetate and free fatty acid concentrations and rises in that of IGF-2, glucagon and amino acids. Fetal plasma was inhibitory to sulphate incorporation into pig costal cartilage. Complete food withdrawal from pregnant guinea pigs for 2 days at days 43-44 of pregnancy caused mild fetal growth retardation and similar changes in plasma constituents, except in that plasma IGF-2 concentrations were now depressed and plasma was not inhibitory to sulphate incorporation into pig costal cartilage. Production of hypoglycaemia by 4-times-daily maternal injections of glucose between days 41-46 of pregnancy accelerated fetal growth rate. It also elevated fetal plasma concentrations of insulin, IGF-1, IGF-2, sulphation-promoting activity, thyroid hormones, glucose and free fatty acids and depressed that of glucagon and amino acids. Fetal growth rate during the experimental period showed a good correlation with plasma glucose, insulin and IGF-1 and, to a certain extent, with sulphation-promoting activity. It did not correlate closely with fetal plasma IGF-2 concentration. Hepatic glycogen concentrations showed a good correlation with plasma IGF-2 levels.

The effects of the beta-adrenergic agonist salbutamol on meat quality in pigs

The beta-adrenergic agonist Salbutamol was administered to pigs at 3 ppm in the feed between weaning and slaughter at 85 kg. Growth rate was not affected by Salbutamol. Treated pigs had a higher dressing percentage (2.6%) and produced carcasses that were less fat (17%) and had longissimus (LD) muscles of larger (11%) cross-sectional area. They also had smaller livers that contained less glycogen. The thinner backfat in treated animals was less firm and tended to separate from the underlying lean. However, these changes were attributable solely to the reduced fatness and there was no direct effect of Salbutamol. There were no differences in pH 45 min postmortem, percentage drip loss during storage or reflectance value of the LD between the two groups, indicating no greater propensity for Salbutamol-treated pigs to develop pale, soft, exudative muscle. However, treated pigs had higher final pH values in the muscles; this was reflected in slightly reduced hue and saturation values. These results suggest that the propensity of the pigs to develop dark, firm, dry meat was slightly increased. Salbutamol-treated pigs produced LD muscles that were slightly tougher (22%), had reduced concentration of heme pigments in the muscle, reduced plasma glucose and increased plasma creatine phosphokinase activity. Salbutamol improved lean meat yield but slightly increased the potential to produce dark, firm, dry meat and reduced tenderness.

The effects of salbutamol on blood pressure and heart rate in Large White and Pietrain-cross breeds of pig

The effects of the beta 2-agonist salbutamol, on pig heart rate and blood pressure were evaluated at the expected commercially used concentration of 3 ppm in final feed, and at three times this level. Salbutamol was administered to pigs previously fed on control diet ('naive'), and in a second study to pigs fed 3 ppm salbutamol for 19 days ('acclimatized'). Heart rate and blood pressure were measured in conscious 30 kg pigs before (pre-ingestive), during (ingestive) and after ingestion (absorptive) of feed containing 3 or 9 ppm salbutamol. To assess any interaction with 'stress genotype' pigs, measurements were performed in Large White and Pietrain-cross breeds. The mean preingestive heart rates for the Large White and Pietrain-cross pigs were 127 and 109 beats/min, respectively. The corresponding figures for mean arterial blood pressure were 121 and 122 mmHg. The act of ingesting control feed caused heart rate to rise by 36-39% and blood pressure to increase by 17-27%. During the absorptive phase for 'naive' pigs fed 3 ppm salbutamol in the diet, blood pressure fell 5-11% and heart rate increased 20-24%, reflecting a classical baroreceptor mediated response. At 9 ppm the fall in blood pressure of 5-11% was similar to that at 3 ppm, while the rise in heart rate was larger at 31-38%. The magnitude of the changes at both 3 and 9 ppm was less than that evoked by the act of ingestion, with the exception of the heart rate response in Large Whites at 9 ppm, which was similar. The responses of the two breeds were comparable, indicating that salbutamol is unlikely to exacerbate the cardiovascular responses seen in potentially stress-susceptible pigs. The acute changes elicited by 3 ppm salbutamol during the absorptive phase in 'naive' pigs were abolished or substantially less in acclimatized pigs, implying a tachyphylaxis to the agonist's actions. This was confirmed by 9 ppm of salbutamol increasing heart rate of 'acclimatized' Large Whites to the same degree as 3 ppm in 'naive' counterparts. The desensitization in Pietrain-cross pigs was even more marked with no increase in heart rate produced by 9 ppm salbutamol following acclimatization. These data, combined with the rapid tachyphylaxis of response, indicate that salbutamol at the intended commercial inclusion of 3 ppm will not compromise the cardiovascular stability of the growing pig at rest.

Studies on the growth of the fetal guinea pig. The effects of ligation of the uterine artery on organ growth and development

The effects of reduced maternal placental blood flow on the growth and development of the fetal guinea pig have been studied by unilateral ligation of the uterine artery at day 30 of pregnancy. Fetal guinea pigs were investigated about 20 or 30 days later. In about one-third of cases fetal death occurred, in another third fetuses less than 60% of normal weight were observed and in the remainder all fetuses were in the normal weight range. In the growth retarded fetuses prenatal growth occurred at about 50% of the rate in control. There was no postnatal 'catch up' as growth still remained lower than in controls. Restricted fetal growth affected particularly development of the visceral tissues in which case size declined in proportion to body weight. Brain and adrenal by comparison were less affected as their contribution to total body weight increased, but even so in the severely retarded fetuses the mass of both fell. The responses of the liver were in general consistent with a delay in the pattern of development. Thus DNA, RNA, protein and haematopoietic cell content changes occurred later than normal. In contrast an enhanced deposition of glycogen was apparent in the liver of the growth-retarded fetus. The results indicate some of the ways in which nutritional deprivation of the fetuses leads to reprogramming of growth and maturation of selected fetal tissues to allow non-essential changes to await more favourable times.

Regulation of glycolytic flux in the heart of the fetal guinea pig

Functional glycolytic capacity and its regulation have been studied in the fetal guinea-pig heart during O2 deprivation in situ and in the Langendorff perfused heart. Anaerobic glycolytic flux, at 2 mumol/min per g wet wt. was similar in the 48-50 and 60-65 days fetal and adult guinea-pig heart, despite lower fetal phosphofructokinase activity. During O2 deprivation in situ and in the perfused heart glucose was the major substrate, with glycogen making a smaller contribution. Glycolytic capacity became more tightly regulated during fetal heart development. Thus at 48-50 days glycolysis was increased during O2 deprivation by substrate supply, but at 60-65 days activation of phosphofructokinase was required also. Low malate/aspartate cycle activity in the fetal heart was suggested by the absence of an increase in malate and alanine at the expense of aspartate. The large proportion of aerobic glycolytic flux converted to lactate concurred with this. Because of the low O2 consumption and relatively high aerobic glycolytic flux, the proportion of glycolytically-derived ATP was 3-4 fold higher in the fetal than adult heart, and may explain its functional resistance to O2 deprivation.

Ultrastructural and enzymatic development of fetal guinea pig heart

The activities of some enzymes of glycolysis, the citric acid cycle, and amino acid metabolism have been measured in the fetal guinea pig heart over the last third of gestation and correlated with heart ultrastructural development. There is little change in glycolytic enzyme activity except for a two- to threefold increase in phosphofructokinase activity. Mitochondrial content and enzyme activities are low in the early fetal heart, and, although content is similar in the late fetus and adult, enzyme activities increase twofold postnatally, indicating fetal heart mitochondria are incompletely developed. The activities of aspartate and particularly alanine aminotransferase are low in the fetal heart. Over the last third of gestation the myofibrillar content of the fetal myocyte increases twofold to the adult value by term. Associated with this is a fourfold rise in myofibrillar and sarcoplasmic reticulum Ca2+-ATPase activity. Na+-K+-ATPase activity is similar in the late fetal and adult heart but one-third lower in the early fetal heart.