Aims The objectives of this study were to investigate the safety, tolerability, pharmacokinetics and pharmacodynamics of single and multiple oral doses of ONO-7684, a novel activated factor XI (FXIa) inhibitor, in healthy subjects. Methods This was a first-in-human (FIH), randomised, placebo-controlled, double-blind, single and multiple dose study in healthy subjects under fed and fasted conditions. This study consisted of two parts: single ascending dose (Part A; 1, 5, 20, 80, 150 or 300 mg ONO-7684 or placebo) and multiple ascending doses (Part B; 80, 150 or 250 mg ONO-7684 or placebo daily for 14 days). In both parts, subjects were randomised in a 3:1 ratio to receive ONO-7684 or placebo. Results ONO-7684 was well tolerated at all dose levels tested following both single and repeated doses, with a low overall incidence of treatment-emergent adverse events. There was no evidence to suggest a bleeding risk. Dose proportionality in exposure was observed for the range of 1-300 mg ONO-7684 in Part A. In Part A, the half-life of ONO-7684 administered in the fasted state ranged from 16.0 to 19.8 hours. In Part B, the half-life of ONO-7684 administered in the fed state ranged from 22.1 to 27.9 hours, supporting once daily oral dosing. ONO-7684 strongly inhibited factor XI coagulation activity (FXI:C) and increased activated partial thromboplastin time (aPTT), with a mean maximum on treatment percentage inhibition versus baseline of 92% and a mean maximum on treatment ratio-to-baseline of 2.78, respectively, at 250 mg ONO-7684 daily. Conclusions The data generated in this FIH study demonstrate the promising potential of oral FXIa inhibition and ONO-7684 for indications requiring anticoagulation.

Acromegaly is a chronic systemic disease characterized by facial and peripheral changes caused by soft tissue overgrowth and is associated with multiple comorbidities. Despite available surgical and medical therapies, suitable treatments for acromegaly are still lacking. Efficient drug development requires an understanding of the exposure-response (E-R) relationship based on nonclinical and early clinical studies. We aimed to establish a platform to facilitate the development of novel drugs to treat acromegaly. We evaluated the E-R relationship of the growth hormone (GH)-inhibitory effect of the somatostatin analog octreotide under growth hormone-releasing hormone + arginine stimulation in healthy participants and compared the results with historical data for patients with acromegaly. This randomized five-way crossover study included two placebo and three active-treatment periods with different doses of octreotide acetate. GH secretion in the two placebo periods was comparable, which confirmed the reproducibility of the response with no carryover effect. GH secretion was inhibited by low-, medium-, and high-dose octreotide acetate in a dose-dependent manner. We also examined the E-R relationship in monkeys as a preclinical drug evaluation study and in rats as a more convenient and simple system for screening candidate drugs. The E-R relationships and EC50 values were similar among animals, healthy participants, and patients with acromegaly, which suggests that GH stimulation studies in early research and development allowed simulation of the drug response in patients with acromegaly. SIGNIFICANCE STATEMENT: This study demonstrated similar exposure-response relationships in terms of the growth hormone-inhibitory effect of octreotide after growth hormone-releasing hormone stimulation among healthy participants, monkeys, and rats. The research methods and analyses utilized in this study will be useful for simulating the dosages and therapeutic effects of drugs for acromegaly and will facilitate the research and development of novel therapeutic agents with similar modes of action.

Abstract ONO-5788 is a novel low molecular weight orally administered molecule with potent and selective agonistic effects at the human SST2 receptor subtype. ONO-5788 could offer the advantages of a more convenient route of administration for patients with acromegaly and other indications and also a preferential safety profile compared to injections. Methods: This First in Human study includes a double-blind, randomized, placebo-controlled, single ascending dose (SAD) part (including an assessment of food effect) in healthy adult male and female volunteers, 18-55 years of age. 34 males and 14 females were enrolled. Subjects were randomised to ONO-5788 or placebo (6:2 ratio) in each cohort with escalating doses of ONO-5788 (0.4, 1.6, 5, 20, 50 or 120mg) assessed. The first 2 dose levels were dosed as an oral liquid solution, the 4 remaining dose levels were dosed as oral API in capsule. Findings: Preliminary blinded data suggested no significant safety issues during administration of single doses of ONO-5788. A low incidence of mild to moderate gastrointestinal adverse events was observed at the higher doses (loose stools n=4; abdominal cramping n=3; abdominal discomfort, abdominal tenderness, discolouration of stools, pale stools, dyspepsia, nausea, all n=2). There were no safety findings for safety labs, ECGs or vital signs and no SAEs were reported. A transient increase in serum glucose was noted at 6 hours post-dose (3 hours post-meal) which followed a dose-response pattern when comparing mean glucose values across all 6 cohorts; all subjects were asymptomatic and no intervention was required. Pharmacokinetics of ONO-5788 and its active metabolite (ONO-ST1-641) were well characterized at the doses tested. Parent drug concentrations were notably higher than the active metabolite (approximately 40-fold greater). A 300-fold dose range was explored (0.4mg to 120mg) but, using arithmetic mean Cmax, AUClast and AUCinf values, ONO-5788 exposure was approximately 59-90 times higher at the highest dose compared to the lowest and ONO-ST1-641 exposure was 139-193 times higher at the highest dose. There were less than dose-proportional increases in exposure observed with both ONO-5788 and ONO-ST1-641 at doses above 20mg. Lower exposure was observed with food at the 20mg dose. The mean half-life of ONO-5788 ranged between 6.4-22 hours and for ONO-ST1-641 between 62-110 hours. Conclusion: ONO-5788 was found to be well tolerated in this SAD study at all doses tested. The pharmacokinetic profiles of ONO-5788 and its active metabolite were well characterised with a half-life suggesting the potential for once-daily dosing. Safety, tolerability, pharmacokinetics and pharmacodynamics will continue to be assessed in healthy volunteers with multiple dosing, dosing of a cohort of elderly subjects and a proof-of-principle study to further characterize ONO-5788 prior to studies in patients.

ONO-2952, a novel antagonist of translocator protein 18 kDa (TSPO), binds with high affinity to TSPO in rat brain and human tumor cell line membrane preparations. This study used the TSPO-specific PET radioligand [(11) C]PBR28 to confirm binding of ONO-2952 to brain TSPO in human subjects, and evaluate brain TSPO occupancy and its relationship with ONO-2952 plasma concentration. Sixteen healthy subjects received a single oral dose of 200, 60, 20, or 6 mg ONO-2952 (n=4 per dose). Two PET scans with [(11) C]PBR28 were conducted 7 days apart: at baseline and 24 h after ONO-2952 administration. [(11) C]PBR28 regional distribution volume (V-T) was derived with kinetic modeling using the arterial input function and a two tissue compartment model. Nonspecific binding (V-ND) was obtained on an individual basis for each subject using linear regression as the x-intercept of the Lassen plot. The binding potential relative to V-ND (BPND) was derived as the difference between V-T in the ROI (V-T ROI) and V-ND, normalized to V-ND; BPND=(V-T ROI - V-ND)/V-ND. TSPO occupancy was calculated as the change in BPND (BPND) from individual's baseline scan to the on-medication scan to the baseline BPND value. TSPO occupancy by ONO-2952 was dose dependent between 20-200 mg, approaching saturation at 200 mg both in the whole brain and in 15 anatomic regions of interest (ROI). Estimated K-i values ranged from 24.1 to 72.2 nM. This open-label, single-center, single-dose study demonstrated engagement of ONO-2952 to brain TSPO. The relationship between pharmacokinetics and TSPO occupancy observed in this study support the hypothesis that ONO-2952 could potentially modulate neurosteroid production by binding to brain TSPO.

Purpose: Peripheral tropomyosin receptor kinase (Trk) A is a promising target for inhibition of the signaling processes that contribute to the manifestation of chronic pain. ONO-4474 is an orally available, peripheral-specific, pan-Trk inhibitor that has shown potent analgesic effects in rat models of NGF-induced hyperalgesia and adjuvant-induced arthritis, and effects comparable to morphine in rat models of monosodium iodoacetate (MIA)-induced osteoarthritis (OA) and cancer induced bone pain. This study was a first in human investigation into the safety, tolerability and pharmacokinetics (PK) of ONO-4474 in healthy subjects. Methods: The safety, tolerability and pharmacokinetics of ONO-4474 were assessed in a multi-part, double-blind, placebo controlled study in healthy subjects (ClinicalTrials.gov: NCT02454387). ONO-4474 was given as single and multiple oral ascending doses to healthy young and elderly subjects. In Part A subjects were healthy males (single ascending dose including food effect; 0.1-1000mg), in Part B subjects were healthy males and females (multiple ascending dose, 50, 200 and 400mg twice-daily [BID] for up to 14 days in the fed state), in Part C subjects were healthy males (single 100mg dose in the fed state) and in Part D subjects were healthy males and females aged 65 and over (elderly, single 100 and 200mg dose in the fed state). In total, 112 subjects were exposed to ONO-4474 over the 4 parts of the study. Results: The majority of adverse events (AEs) reported in the study were mild and resolved. There were no serious AEs reported. Adverse events related to oral sensory disturbances (hypo-, hyper- and paraesthesia) were infrequently reported at single doses higher than 300 mg. These AEs were more frequent and persistent at repeat doses of 400 mg BID resulting in the early termination of this cohort. Adverse events of pain in extremity and musculoskeletal pain were frequently reported at repeat doses of 400 mg BID. Significant elevations in ALT (up to 4 times the upper limit of normal (ULN)) and AST (up to 3 times the ULN) were observed in 2 subjects after 9 days of dosing of ONO-4474 400 mg BID in the fed state, however these were not accompanied by bilirubin elevations, and decreased to normal levels several days after cessation of dosing. There were no clinically significant changes in C-SSRS, vital signs, ECGs, other laboratory parameters, physical examinations and Bond-Lader mood assessments following multiple dosing that were considered investigational product related. Apart from one elderly male subject who had reduced vibratory sense after 200 mg single dose, no other abnormalities were detected during neurological examination in any other subjects. Exposure to ONO-4474 generally increased with dose with increases being slightly lower than dose proportional in the fasted condition and slightly higher than dose proportional in the fed condition. At doses greater than 100 mg, Cmax and AUCinf under fed conditions were 1.1 to 2.6-fold and 1.2 to 2.5-fold greater than in the fasted condition, respectively. Steady state was achieved by Day 6 following multiple BID dosing. The exposures and half-life on Days 7 and 14 did not differ significantly from Day 1 (single dose) suggesting limited accumulation of ONO-4474 after repeat administration. Half-life in the elderly subjects was longer than that of young but overall there was no significant difference in exposure between elderly and young subjects. Conclusions: In this study, 200 mg BID in the fed state was identified as the maximum tolerated repeated dose in this study and overall, there were no safety, tolerability or PK concerns that would preclude further development of ONO-4474 for OA.

We examined the effects of ONO-5334, a cathepsin K inhibitor, on bone markers, BMD, strength and histomorphometry in ovariectomized (OVX) cynomolgus monkeys. ONO-5334 (1.2, 6 and 30mg/kg/day, p.o.), alendronate (0.05mg/kg/2weeks, i.v.), or vehicle was administered to OVX monkeys (all groups N=20) for 16months. A concurrent Sham group (N=20) was also treated with vehicle for 16months. OVX significantly increased bone resorption and formation markers and decreased BMD in lumbar vertebra, femoral neck, proximal tibia and distal radius. Alendronate suppressed these parameters to a level similar to that in the Sham-operated monkeys. ONO-5334 at doses 6 and 30mg/kg decreased bone resorption markers to a level roughly half of that in the Sham group, while keeping bone formation markers level above that in the Sham monkeys. Changes in DXA BMD confirmed that ONO-5334 at doses 6 and 30mg/kg increased BMD to a level greater than that in the Sham group in all examined sites. In the proximal tibia, in vivo pQCT analysis showed that ONO-5334 at doses 6 and 30mg/kg suppressed trabecular BMD loss to the sham level. However, ONO-5334 increased cortical BMD, cortical area and cortical thickness to a level greater than that in the Sham group, suggesting that ONO-5334 improves both cortical BMD and cortical geometry. Histomorphometric analysis revealed that ONO-5334 suppressed bone formation rate (BFR) at osteonal site in the midshaft femur but did not influence OVX-induced increase in BFR at either the periosteal or endocortical surfaces. Unlike alendronate, ONO-5334 increased osteoclasts surface (Oc.S/BS) and serum tartrate-resistant acid phosphatise 5b (TRAP5b) activity, highlighting the difference in the mode of action between these two drugs. Our results suggest that ONO-5334 has therapeutic potential not only in vertebral bones, but also in non-vertebral bones.

BACKGROUND:ONO-2952 is a novel and selective inhibitor of translocator protein 18 kDa that reduces stress-induced defecation and visceral hyperalgesia in rat models.AIM:To evaluate the efficacy and safety of ONO-2952 in females with irritable bowel syndrome with diarrhoea in an exploratory proof-of-concept study.METHODS:A randomised, double-blind, placebo-controlled study was conducted at 49 US centres. Two hundred subjects with irritable bowel syndrome with diarrhoea (Rome III criteria) were randomised to ONO-2952 20 mg, or 60 mg, or placebo. Subjects recorded irritable bowel syndrome symptoms daily during a 2-week baseline period, the 4-week treatment period and for 4 weeks post-treatment. The co-primary endpoints were change from baseline to week 4 in abdominal pain, stool consistency and stool frequency.RESULTS:Improvements in irritable bowel syndrome symptoms were seen with ONO-2952 over placebo in per-protocol analyses for all three co-primary endpoints, but these did not reach statistical significance at the 5% level. The largest improvement was seen with ONO-2952 60 mg. ONO-2952 was well tolerated with a safety profile similar to that of placebo. Most adverse events were mild or moderate in severity and not treatment related.CONCLUSION:ONO-2952 showed evidence of clinical efficacy in reducing irritable bowel syndrome-related symptoms in female subjects with irritable bowel syndrome with diarrhoea, and further evaluation is, therefore, warranted to assess its potential as a treatment for irritable bowel syndrome with diarrhoea (NCT01844180).

Purpose: To investigate safety, tolerability, and pharmacokinetic properties of single and multiple doses of novel translocator protein 18 kDa antagonist ONO-2952 in healthy subjects.Methods: Double-blind, placebo-controlled single (SAD) and multiple (MAD) dose escalation studies were conducted. Healthy men and women aged 18 to 55 years inclusive and without history of psychiatric disorders were eligible. Forty-eight volunteers received single doses of ONO-2952 (3, 10, 30, 100, 200, or 400 mg) or placebo under fasted conditions (SAD study), and 36 received ONO-2952 (30, 60, or 100 mg/d) or placebo for 21 consecutive days under fed conditions (MAD study). ONO-2952 10 and 200 mg were administered under fasted and fed conditions in the SAD study to investigate the effect of food on the absorption of ONO-2952. Safety assessments included adverse events, vital signs, 12-lead ECGs, and clinical laboratory evaluations. Plasma and urine pharmacokinetic profiles of ONO-2952 were determined.indings: Across both studies, mean age ranged from 29.8 to 39.8 years, most participants were white, and the proportion of female volunteers was 52%. No treatment or dose-related trends in adverse events were observed. The most frequent adverse events were headache and presyncope (n = 2 each [SAD study]) and constipation and headache (n = 3 each [MAD study]). All headache and constipation episodes were possibly related to the study drug. Plasma ONO-2952 concentrations peaked 2.5 to 3.5 hours (SAD study) and 3.0 to 4.0 hours (MAD study) postdose. ONO-2952 systemic exposure increased less than dose proportionally under fasted conditions. Fed conditions September 2015 significantly increased exposure compared with fasted conditions: geometric mean ratios of C-max (90% CIs) were 229% (176-299 [10 mg]) and 778% (623-971 [200 mg]), and AUC(last) were 159% (131-192 [10 mg]) and 382% (288-506 [200 mg]). In the MAD study, the systemic exposure of ONO-2952 increased in a slightly greater than dose-proportional manner. Geometric mean accumulation ratios (95% CI) of AUC24 were 2.50 (2.09-2.98 [30 mg]), 2.23 (1.85 2.68 [60 mg]), and 2.73 (2.10-3.55 [100 mg]); and C-max were 1.65 (1.43-1.90 [30 mg]), 1.56 (1.31-1.85 [60 mg]), and 1.85 (1.38-2.49 [100 mg]). (C) 2015 The Authors. Published by Elsevier HS Journals, Inc.

You have accessJournal of UrologyBladder and Urethra: Anatomy, Physiology and Pharmacology II1 Apr 2015MP21-07 SAFETY, TOLERABILITY AND PHARMACOKINETICS OF SINGLE AND MULTIPLE ASCENDING DOSES OF THE EP2/EP3 RECEPTOR AGONIST ONO-8055, A POTENTIAL NEW THERAPY FOR UNDERACTIVE BLADDER, IN HEALTHY SUBJECTS Christopher Chapple, Mark Bruce, Tomoya Ohno, Tomohiro Kuwayama, and Stephen Deacon Christopher ChappleChristopher Chapple More articles by this author , Mark BruceMark Bruce More articles by this author , Tomoya OhnoTomoya Ohno More articles by this author , Tomohiro KuwayamaTomohiro Kuwayama More articles by this author , and Stephen DeaconStephen Deacon More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2015.02.959AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Underactive bladder (UAB) is a syndrome involving a dysfunctional bladder condition in which patients are unable to produce an effective voiding contraction. ONO-8055 is a potent prostaglandin EP2 and EP3 receptor agonist that has been demonstrated to contract the bladder and relax the urethra in vitro. This study was a first in human investigation into the safety, tolerability and pharmacokinetics (PK) of ONO-8055 in healthy subjects. METHODS This was a single-centre 5-part study in 145 healthy subjects. ONO-8055 was given as single and multiple oral ascending doses to healthy young (Y) and elderly (E) males (M) and females (F). Part A (single ascending dose, 0.5-1000μg, 72YM), Part C (multiple ascending dose, 41 subjects, 100–700μg twice daily [BID] for 7 days in YM, 300–500μg for 13 days in Y/E F), Part D (gender effect, single 300μg dose, 8F) and Part E (age effect, single 300μg dose, 16 E M/F) had a double-blind, placebo-controlled and parallel group design. Part B (food effect, single 300μg dose, 8 YM) had an open-label crossover design. 111 subjects were exposed to ONO-8055 (80 YM, 6 EM, 12 YF and 13 EF). RESULTS There were no serious adverse events (AEs). The majority of AEs reported were gastrointestinal (GI) related, were of mild intensity (93%) and resolved. There were 2 severe AEs - diarrhoea at 300μg BID and frequent bowel movements at 500μg BID both in EF. Overall, the most frequent AE reported was diarrhoea (ONO-8055: 26.1%; Placebo: 17.6%). GI AEs mainly involved loose stools and to a lesser extent increased frequency of stools, and appeared to have a possible dose relationship. Females appeared to be more susceptible to GI AEs than males. There were no clinically significant changes in laboratory tests, vital signs or ECGs. Cmax and AUCinf were dose proportional with single doses up to 8μg and less than proportional 25–1000μg. There was no evidence of deviation from dose proportionality for Cmax or AUCinf with multiple dosing (100–700μg). Steady state was achieved by Day 5. AUCinf was 23% higher in fed vs fasted state (p<0.05). A high fat meal delayed median Tmax (by ∼2.5h, p<0.001). There was no significant effect of age or gender on PK. CONCLUSIONS ONO-8055 was generally well tolerated following single doses up to 1000μg and multiple doses up to 700 μg BID. Overall there were no safety or PK concerns that would preclude further development of ONO-8055 for UAB. © 2015 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 193Issue 4SApril 2015Page: e235 Advertisement Copyright & Permissions© 2015 by American Urological Association Education and Research, Inc.MetricsAuthor Information Christopher Chapple More articles by this author Mark Bruce More articles by this author Tomoya Ohno More articles by this author Tomohiro Kuwayama More articles by this author Stephen Deacon More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Background / Aims: Sleep disorders are often associated to functional gastro-intestinal disorders (FGIDs).The aim of this study is to evaluate prospectively if the presence of sleep disturbances is associated with specific FGID and to assess a possible association to psychological disorders.Methods: Six hundred and eleven consecutive FGID patients (71% female), aged 48.8±16.9 years (M±SD), (BMI 27.0±13.8kg/m 2 ) that have filled both psychological evaluation on anxiety and depression, and a Rome III questionnaire, were included in this study.The patients were classified according the importance of the sleep duration using a 7-points grading scale: Group 1 to 3 , hypersomnia, respectively severe, moderate and mild; Group 4: no sleep change, Group 5 to 7 insomnia, respectively mild, moderate, and severe.The backwards selection procedure was used for model selection during multivariate logistic regression.Results: 406 patients (66%) reported change of sleep pattern: decreased in 130 (21%), and increased in 276 (45%), while 205 (34%) reported no change.BMI did not differ between the different groups.Patients with increased sleep were the oldest Depression was lower in patients with no change in sleep pattern (P<0.001).Patients with mild change of sleep pattern (group 3 and 5) have depression score higher than patients with no change (P<0.001), and lower than other patients with moderate (Group 2 and 6) or severe (Group 1 and 7) change of sleep pattern (P<0.001).Patients with no sleep change (Group 4) have significant lower anxiety score than patients with moderate change of sleep pattern (Group 2, P<0.001; Group 6, P=0.002) or severe hypersomnia (P=0.001).Among patients that reported an increased sleep, severe hypersomnia is associated to age (P=0.001),high depression (P<0.001),low state anxiety (P=0.036), and increased constipation (P= 0.034;) or fecal incontinence (P=0.022).Moderate hypersomnia is associated to increased depression (P=0.044),state anxiety (P=0.024),constipation (P=0.021),bloating (P=0.026), and proctalgia fugax (P=0.010).Mild hypersomnia is associated to increased mixed IBS (P= 0.047) and fecal incontinence (P=0.032).In patients with no change in sleeping pattern (Group 4), IBS-diarrhea phenotype is a positive descriptor (P=0.018).For patients that report decreased sleep patterns, mild insomnia is associated to high trait anxiety (P=0.048) and low dyspepsia (P=0.011).Moderate insomnia is associated to high depression (P<0.001),low state anxiety (P=0.011), and to an increase of chest pain (P=0.008),IBS-diarrhea (P= 0.009), IBS-mixed (P=0.042) and diarrhea (P=0.021).Severe insomnia is associated to high depression (P=0.003), and an increased frequency of chest pain (P=0.026) and epigastric pain syndrome (P=0.012).Conclusion: This study leads us to consider sleep disorders as potential pathogenic factors in FGIDs.

The tricarboxylic acid (TCA) cycle is the major final common pathway for oxidation of carbohydrates, lipids and some amino acids, which produces reducing equivalents in the form of nicotinamide adenine dinucleotide and flavin adenine dinucleotide that result in production of large amounts of adenosine triphosphate (ATP) via oxidative phosphorylation. Although regulated primarily by the products of ATP hydrolysis, in particular adenosine diphosphate, the rate of delivery of reducing equivalents to the electron transport chain is also a potential regulatory step of oxidative phosphorylation. The TCA cycle is responsible for the generation of ≈67% of all reducing equivalents per molecule of glucose, hence factors that influence TCA cycle flux will be of critical importance for oxidative phosphorylation. TCA cycle flux is dependent upon the supply of acetyl units, activation of the three non-equilibrium reactions within the TCA cycle, and it has been suggested that an increase in the total concentration of the TCA cycle intermediates (TCAi) is also necessary to augment and maintain TCA cycle flux during exercise. This article reviews the evidence of the functional importance of the TCAi pool size for oxidative metabolism in exercising human skeletal muscle. In parallel with increased oxidative metabolism and TCA cycle flux during exercise, there is an exercise intensity-dependent 4- to 5-fold increase in the concentration of the TCAi. TCAi concentration reaches a peak after 10–15 minutes of exercise, and thereafter tends to decline. This seems to support the suggestion that the concentration of TCAi may be of functional importance for oxidative phosphorylation. However, researchers have been able to induce dissociations between TCAi pool size and oxidative energy provision using a variety of nutritional, pharmacological and exercise interventions. Brief periods of endurance training (5 days or 7 weeks) have been found to result in reduced TCAi pool expansion at the start of exercise (same absolute work intensity) in parallel with either equivalent or increased oxidative energy provision. Cycloserine inhibits alanine aminotransferase, which catalyses the predominant anaplerotic reaction in exercising human muscle. When infused into contracting rat hindlimb muscle, TCAi pool expansion was reduced by 25% with no significant change in oxidative energy provision or power output. Glutamine supplementation has been shown to enhance TCAi pool expansion at the start of exercise with no increase in oxidative energy provision. In summary, there is a consistent dissociation between the extent of TCAi pool expansion at the onset of exercise and oxidative energy provision. At the other end of the spectrum, the parallel loss of TCAi, glycogen and adenine nucleotides and accumulation of inosine monophosphate during prolonged exercise has led to the suggestion that there is a link between muscle glycogen depletion, reduced TCA cycle flux and the development of fatigue. However, analysis of serial biopsies during prolonged exercise demonstrated dissociation between muscle TCAi content and both muscle glycogen content and muscle oxygen uptake. In addition, the delay in fatigue development achieved through increased carbohydrate availability does not attenuate TCAi reduction during prolonged exercise. Therefore, TCAi concentration in whole muscle homogenate does not seem to be of functional importance. However, TCAi content can currently only be measured in whole muscle homogenate rather than the mitochondrial subfraction where TCA cycle reactions occur. In addition, anaplerotic flux rather than TCAi content per se is likely to be of greater importance in determining TCA cycle flux, since TCAi content is probably merely reflective of anaplerotic substrate concentration. Methodological advances are required to allow researchers to address the questions of whether oxidative phosphorylation is limited by mitochondrial TCAi content and/or anaplerotic flux.

There is an up to four-fold increase in the concentration of the tricarboxylic acid (TCA) cycle intermediates at the start of exercise. The rate of TCA cycle flux and, hence, oxidative metabolism may be limited by the concentration of the intermediates in the cycle. The dramatic decline in intramuscular glutamate at the start of exercise, in tandem with increased intramuscular alanine, suggests that glutamate is an important anaplerotic precursor. We hypothesized that oral glutamine might enhance the exercise-induced TCA cycle intermediate pool expansion. Indeed, a greater increase in the sum of muscle citrate, malate, fumarate, and succinate concentrations (∼85% total TCA intermediate pool) occurred at the start of exercise after ingestion of glutamine rather than of placebo or ornithine α-ketoglutarate. However, neither endurance capacity nor the degree of phosphocreatine depletion or lactate accumulation was altered. This suggests that TCA cycle intermediates do not limit flux through the cycle or that more intense exercise is required to show the limitation.

After exhaustive exercise, intravenous or oral glutamine promoted skeletal muscle glycogen storage. However, when glutamine was ingested with glucose polymer, whole-body carbohydrate storage was elevated, the most likely site being liver and not muscle, possibly due to increased glucosamine formation. The rate of tricarboxylic acid (TCA) cycle flux and hence oxidative metabolism may be limited by the availability of TCA intermediates. There is some evidence that intramuscular glutamate normally provides alpha -ketoglutarate to the mitochondrion. We hypothesized that glutamine might be a more efficient anaplerotic precursor than endogenous glutamate alone. Indeed, a greater expansion of the sum of muscle citrate, malate, fumarate and succinate concentrations was observed at the start of exercise (70% VO2max) after oral glutamine than when placebo or ornithine alpha -ketoglutarate was given. However, neither endurance time nor the extent of phosphocreatine depletion or lactate accumulation during the exercise was altered, suggesting either that TCA intermediates were not limiting for energy production or that the severity of exercise was insufficient for the limitation to be operational. We have also shown that in the perfused working rat heart, there is a substantial fall in intramuscular glutamine and alpha -ketoglutarate, especially after ischemia. Glutamine (but not glutamate, alpha -ketoglutarate or aspartate) was able to rescue the performance of the postischemic heart. This ability appears to be connected to the ability to sustain intracardiac ATP, phosphocreatine and glutathione.