Energetic and myocellular pathways in cardiac and skeletal muscle following anthracycline chemotherapy

Background

Anthracycline-related cardiac dysfunction is a recognised consequence of cancer therapies. Here we assess resting cardiac and skeletal muscle energic status as an early mechanistic pathway of myocyte derangement and explore molecular targets of skeletal myocyte metabolism, protein synthesis/degradation and mitochondrial biogenesis signalling.

Methods

We conducted a prospective, mechanistic, observational, longitudinal study of chemotherapy-naive breast cancer patients undergoing anthracycline-based chemotherapy, compared to a healthy control group. 31P-Magnetic Resonance spectroscopy in cardiac and skeletal muscle (phosphocreatine/gamma adenosine triphosphate (PCr/yATP) and inorganic phosphate/phosphocreatine (Pi/PCr) ratios respectively), cardiac magnetic resonance (CMR) imaging inclusive of T1 and T2 mapping, echocardiography-derived global longitudinal strain function, serum NT-pro-BNP and skeletal muscle biopsies from the right vastus lateralis were assessed before and after 3 cycles of Flurouracil, Epirubicin and Cyclophosphamide followed by 3 cycles of Docetaxel. Statistical significance was set at p<0.05.

Results

Twenty-five female breast cancer patients (median age 53 years, range 32–74 years) receiving a mean epirubicin dose 307 mg/m2) and twenty-eight controls (median age 44 years, range 23–65) were recruited. All study assessments in breast cancer patients at pre-chemotherapy stage were comparable to the matched healthy controls. However, following chemotherapy, breast cancer patients demonstrated a small but significant reduction in cardiac function (global longitudinal strain −22.9±3.9 vs −19.1±3.3%, p=0.01 and CMR-derived ejection fraction 65±5 vs 62±4%, p=0.047), a mild increase in CMR-derived indexed left ventricular volumes (end diastolic 65±10 vs 74±11 ml/m2, p=0.014 and end systolic 23±5 vs 28±5 ml/m2, p=0.01) as well as an increase in left ventricular T1 and T2-mapping (1289±29 vs 1321±31 ms, p=0.004 and 50±4 vs 55±7 ms, p=0.027, respectively) and serum NT-Pro-BNP (49±25 vs 108±84 pg/m, p=0.008). After epirubicin, there was significant reduction in cardiac PCr/yATP ratio (2.0±0.7 vs 1.2±0.6, p=0.007) and a significant increase in skeletal muscle Pi/PCr ratio (0.13±0.04 vs 0.22±0.2, p=0.008) – Figure 1.

Following chemotherapy, there was significant upregulation of skeletal myocyte protein synthesis (mammalian target of rapamycin, 0.44±0.4 vs 0.53±0.2, p<0.001) and degradation (Calcium/calmodulin dependent protein kinase II, 1.4±0.7 vs 2.7±1.1, p<0.001), metabolism (peroxisome proliferator-activated receptor gamma, 0.35±0.2 vs 0.60±0.1, p<0.001) and muscle mass regulator myostatin-2 (0.16±0.1 vs 0.24±0.1, p<0.001).

Conclusion

Contemporary doses of epirubicin for breast cancer result in significant reduction of cardiac and skeletal muscle high energy 31P-metabolism alongside skeletal myocellular alterations of protein synthesis and metabolic regulation pathways.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Tenovus ScotlandNHS Grampian Endowment fund

Renin-angiotensin and endothelin systems in patients post takotsubo syndrome

Background

We investigate if renin-angiotensin and endothelin-1 response pathways follow the same pattern of recovery as left ventricular ejection fraction in patients with takotsubo syndrome.

Purpose

To provide better insight into the pathophysiology underlying this condition.

Methods

Ninety takotsubo syndrome patients [n=30 in each of “acute”, “convalescent” (3–5 months) and “recovered” (>1 year) groups] who were on minimal or no medication and were free of any significant cardiac/metabolic co-morbidities, and 30 healthy controls were studied. Serum concentrations of renin, angiotensin converting enzyme, angiotensin II, big endothelin-1, endothelin-1 were measured using commercially available ELISA, and BNP was measured using an immunoassay.

Results

Left ventricular ejection fraction was 38±1.6% in acute, 63±2.0% in convalescent and 64±2.6% in recovered takotsubo syndrome patients. As shown in Figure 1, serum renin concentrations are persistently elevated after a takotsubo episode (p=0.03 vs controls). Angiotensin converting enzyme levels are significantly depressed during the acute phase compared to convalescent (p=0.004), recovered takotsubo (p=0.02) or controls (p=0.03). Angiotensin II is increased in takotsubo patients (p<0.001 vs controls) remaining persistently elevated long-term in the recovered group (p=0.03 vs controls). B-type natriuretic peptide concentrations remain elevated after a Takotsubo episode compared to controls (p=0.003). Big endothelin-1 levels are unchanged, but endothelin-1 is significantly lower after takotsubo syndrome compared to controls (p=0.03).

Conclusions

Despite “normalisation” of the left ventricular ejection fraction, there is long-term maladaptive activation of renin-angiotensin system in takotsubo syndrome patients. This suggests therapy aimed at modulating this pathway may be beneficial in the long-term.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): British Heart Foundation

OUES from submaximal cardiopulmonary exercise

Introduction

Cardiopulmonary exercise testing (CPEX) provides valuable diagnostic and prognostic cardiopulmonary function data. However, in clinical setting a maximal test is not always achievable. The Oxygen Efficiency Uptake Slope (OUES) has been proposed as a possible submaximal measure of cardiopulmonary function as it remains relatively stable during the final quartile of the exercise test. This study explored the validity of OUES as a surrogate marker for cardiopulmonary function in the event of a submaximal test.

Methods

Four groups of subjects [128 healthy controls (73 M), 44 asymptomatic hypertensive (HT) patients (26 M), 67 adult cardiac congenital heart disease (ACHD) patients (44 M) and 35 Heart Failure with preserved Ejection Fraction (HFpEF) (10M) patients] were recruited after informed consent. All subjects underwent clinical assessment, resting ECG, blood pressure and spirometry prior to a treadmill CPEX to volitional exhaustion and a respiratory exchange ratio (RER) of at least 1.1 using the same testing protocol. Peak VO2 (ml/min) was recorded from the last 5s of the maximal test (RER=1.1) and OUES was calculated from complete (RER=1.1) and truncated (RER=0.9) gas exchange data. The linear relationships between absolute peak VO2 and OUES from complete and truncated gas exchange data were assessed using Pearson's correlation coefficient. Subsequently, the two correlations obtained in each patient group were compared. Statistical significance was set at p<0.01.

Results

Mean and 95% confidence intervals of the peak VO2 for males and females in each decile of life examined in the 4 subject groups are shown in the Figure. Peak VO2 values achieved in each of the patient groups were significantly lower when matched for age and sex compared to healthy participants (HT p=0.006, ACHD patients p<0.001 and HFpEF patients p<0.001).

In all 4 groups there was a good correlation between absolute peak VO2 and the OUES at RER 1.1 (healthy volunteers r=0.910, p<0.001, HT r=0.899, p<0.001, ACHD r=0.816, p<0.001 and HFpEF r=0.846, p<0.001). Correlations were inferior for absolute peak VO2 and OUES at RER 0.9 (healthy volunteers r=0.74, p<0.001, HT r=0.780, p<0.001, ACHD r=0.651, p<0.001 and HFpEF r=0.817, p<0.001). Correlations between absolute peak VO2 vs OUES at RER of 1.1 and 0.9 were significantly different only for healthy controls (p=0.001, Z-score = −4.649), but not for HT (p=0.05, Z-score = −1.909), ACHD (p=0.04, Z-score = −2.080) or HFpEF (p=0.7, Z-score = −0.377) patients.

Conclusion

Our data support the use of submaximal OUES at an RER of 0.9 as a surrogate marker for absolute peak VO2 obtained at an RER of 1.1, especially in patients, in whom it can often be difficult to achieve maximal exercise.

Funding Acknowledgement

Type of funding sources: None.

Inflammatory cytokines, high-sensitivity C-reactive protein, and risk of one-year vascular events, death, and poor functional outcome after stroke and transient ischemic attack

Background

Inflammation driven by pro-inflammatory cytokines is a new therapeutic target in coronary disease. Few data exist on the association of key upstream cytokines and post-stroke recurrence. In a prospective cohort study, we investigated the association between pivotal cytokines, high-sensitivity C-reactive protein (hsCRP) and one-year outcomes.

Methods

BIO-STROKETIA is a multi-center prospective cohort study of non-severe ischemic stroke (modified Rankin score ≤ 3) and transient ischemic attack. Controls were patients with transient symptoms attending transient ischemic attack clinics with non-ischemic final diagnosis. Exclusion criteria were severe stroke, infection, and other pro-inflammatory disease; hsCRP and cytokines (interleukin (IL) 6, IL-1β, IL-8, IL-10, IL-12, interferon-γ (IFN-γ), tumor-necrosis factor-α (TNF-α)) were measured. The primary outcome was one-year recurrent stroke/coronary events (fatal and non-fatal).

Results

In this study, 680 patients (439 stroke, 241 transient ischemic attack) and 68 controls were included. IL-6, IL-1β, IL-8, IFN-γ, TNF-α, and hsCRP were higher in stroke/transient ischemic attack cases (p ≤ 0.01 for all). On multivariable Cox regression, IL-6, IL-8, and hsCRP independently predicted one-year recurrent vascular events (adjusted hazard ratios (aHR) per-quartile increase IL-6 1.31, confidence interval (CI) 1.02–1.68, p = 0.03; IL-8 1.47, CI 1.15–1.89, p = 0.002; hsCRP 1.28, CI 1.01–1.62, p = 0.04). IL-6 (aHR 1.98, CI 1.26–3.14, p = 0.003) and hsCRP (aHR 1.81, CI 1.20–2.74, p = 0.005) independently predicted one-year fatality. IL-6 and hsCRP (adjusted odds ratio per-unit increase 1.02, CI 1.01–1.04) predicted poor functional outcome, with a trend for IL-1β (p = 0.054).

Conclusion

Baseline inflammatory cytokines independently predicted late recurrence, supporting a rationale for randomized trials of anti-inflammatory agents for prevention after stroke and suggesting that targeted therapy to high-risk patients with high baseline inflammation may be beneficial.

P6203Intramyocellular lipid saturation as a new metabolic biomarker

Background

Endurance trained athletic healthy volunteers (Athl-HV) and type 2 diabetes patients (T2D) have higher levels of lipids in their skeletal myocytes compared to healthy controls. Despite apparently similar metabolic storage, they are at opposite ends of insulin sensitivity and cardio-metabolic risk.

Purpose

We investigated if the degree of saturation of the IntraMyoCellular Lipids (IMCL) will differentiate Athl-HV from T2D; and explored if an exercise intervention will induce changes in the IMCL saturation.

Methods

Male, age matched Athl-HV and T2D were enrolled (n=25/group). Athl-HV had ≥5 years endurance training, T2D were sedentary. Subjects were studied at baseline and after an exercise intervention (4 week deconditioning in Athl-HV and supervised bike training at ≥65% of peakVO2, 5 hours/week x 8 weeks in T2D). All subjects underwent cardio-pulmonary exercise testing (CPET), blood sampling for insulin sensitivity (QUICKI*) and single voxel 1H-magnetic resonance spectroscopy (1H-MRS) of the right vastus lateralis. 1H-MRS was acquired on 3T Philips Achieva with a 16-channel coil, point-resolved spectroscopy, variable pulse power and optimized relaxation delay water suppression and analysed in LCModel. We derived fractional lipid mass (fLM) and fractions of saturated (fSL) and unsaturated (fUL) lipids. Data were analysed by t tests, shown as mean±SEM, statistical significance p<0.05.

Results

CPET and insulin sensitivity are presented in Table 1. T2D had higher fLM in the skeletal muscle compared to Athl-HV, at baseline (p=0.003) and after the exercise intervention (p=0.009), Figure 1A. At baseline, T2D had a different phenotype with a lower fSL and higher fUL compared to Athl-HV (82±3 vs 88±1% and 18±3 vs 12±1%, p=0.02 for both). Whilst deconditioning did not attract any significant changes in either fSL or fUL in Athl-HV (88±1 to 86±1% and 12±1 to 14±1, p=0.2), in contrast, with exercise training T2D significantly increased fSL (82±3 to 88±1%) and decreased their fUL (18±3 to 12±1%) (both p=0.01). Figure 1B and 1C.

CPET and insulin sensitivity results Athl-HV Baseline Athl-HV Deconditioning p value T2D Baseline T2D After Training p value VO2 peak, (mL/kg/min) 45.0±0.9† 41.7±0.9‡ <0.0001 23.6±0.6† 30.3±0.6‡ <0.0001 QUICKI* 0.346±0.002† 0.343±0.003‡ 0.2 0.308±0.004† 0.317±0.004‡ 0.02 *QUICKI: Quantitative Insulin Sensitivity Check Index; †Athl-HV vs T2D at baseline p≤0.001, ‡Athl-HV vs T2D after exercise intervention p≤0.001.

Figure 1

Conclusion

We demonstrate for the first time, in vivo, significant differences in the IMCL amount and saturation between Athl-HV and T2D. IMCL saturation was changed by exercise training in T2D to mirror the phenotype seen in Athl-HV uncovering a new, independent biomarker of improved cardio-metabolic health.

Acknowledgement/Funding

British Heart Foundation Project Grant no. PG/15/88/31780

A randomised controlled trial comparing a dietary antiplatelet, the water-soluble tomato extract Fruitflow, with 75 mg aspirin in healthy subjects

BACKGROUND/OBJECTIVES

Increasing numbers of food ingredients are gaining acknowledgement, via regulated health claims, of benefits to human health. One such is a water-soluble tomato extract, Fruitflow (FF), a dietary antiplatelet. We examined relative platelet responses to FF and to 75 mg aspirin (ASA) in healthy subjects.

SUBJECTS/METHODS

A total of 47 healthy subjects completed a double-blinded randomised controlled trial following a crossover design. Acute and 7-day treatments with 75 mg ASA were compared with control with and without concomitant FF, over a 5-h timecourse. Platelet aggregation response agonist, platelet thromboxane A2 release, plasma clotting times and time to form a primary haemostatic clot (PFA-100 closure time, TTC) were measured.

RESULTS

Administration of all treatments lowered platelet function and thromboxane A2 generation, and extended the TTC, relative to baseline (P<0.001) and to control (P<0.001). Plasma clotting times were not affected. A single 75 mg dose of ASA showed approximately equal efficacy to a dose of FF, whereas daily 75 mg ASA was approximately three times as effective after 7 days (P=0.002). Platelet responses were heterogenous with distinct weak and strong responder groups. Weak ASA responders retained a functional platelet response to collagen agonist and were responsive to FF. Concomitant FF and ASA did not lead to significant additive effects.

CONCLUSIONS

The suppression of platelet function observed after consuming FF is approximately one-third that of daily 75 mg ASA. The reversible action of FF renders it less likely to overextend the time to form a primary haemostatic clot than ASA, an important safety consideration for primary prevention.

Falls and fractures 2 years after acute stroke: the North Dublin Population Stroke Study

BACKGROUND

Stroke patients are at increased risk of falls and fractures. The aim of this study was to determine the rate, predictors and consequences of falls within 2 years after stroke in a prospective population-based study in North Dublin, Ireland.

DESIGN

Prospective population-based cohort study.

SUBJECTS

567 adults aged >18 years from the North Dublin Population Stroke Study.

METHODS

Participants were enrolled from an Irish urban population of 294,592 individuals, according to recommended criteria. Patients were followed for 2 years. Outcome measures included death, modified Rankin Scale (mRS), fall and fracture rate.

RESULTS

At 2 years, 23.5% (124/522) had fallen at least once since their stroke, 14.2% (74/522) had 2 or more falls and 5.4% (28/522) had a fracture. Of 332 survivors at 2 years, 107 (32.2%) had fallen, of whom 60.7% (65/107) had 2 or more falls and 23.4% (25/107) had fractured. In a multivariable model controlling for age and gender, independent risk factors for falling within the first 2 years of stroke included use of alpha-blocker medications for treatment of hypertension (P = 0.02). When mobility measured at Day 90 was included in the model, patients who were mobility impaired (mRS 2-3) were at the highest risk of falling within 2 years of stroke [odds ratio (OR) 2.30, P = 0.003] and those functionally dependent (mRS 4-5) displayed intermediate risk (OR 2.02, P = 0.03) when compared with independently mobile patients.

CONCLUSION

Greater attention to falls risk, fall prevention strategies and bone health in the stroke population are required.

Stroke recurrence within the time window recommended for carotid endarterectomy

OBJECTIVE

In the North Dublin Population Stroke Study, we investigated the risk of recurrent stroke within the 14-day time window recommended for endarterectomy.

METHODS

In a population-based prospective cohort study, all ischemic stroke patients were identified over 1 year and categorized into those with (CS-positive) and without (CS-negative) ipsilateral carotid stenosis (CS) (≥50% lumen narrowing). Nonprocedural stroke recurrence was determined at 72 hours and 7 and 14 days.

RESULTS

Of 365 ischemic stroke patients with carotid imaging, 51 were excluded due to posterior circulation or nonlateralizing stroke, ipsilateral carotid occlusion, or intracranial stenosis, leaving 314 included for analysis (36 CS-positive and 278 CS-negative). Recurrent stroke occurred in 5.6% (2/36) CS-positive and 0.4% (1/278) CS-negative patients by 72 hours of symptom onset (p =0.003), 5.6% (2/36) CS-positive and 0.7% (2/278) CS-negative patients (p =0.01) by 7 days, and in 8.3% (3/36) CS-positive and 1.8% (5/278) CS-negative patients by 14 days (p =0.02). On multivariable Cox regression analysis, CS was the only independent predictor of recurrence at 72 hours (adjusted hazard ratio [HR] 36.1, 95% confidence interval [CI] 1.6-837.5, p =0.03), and 7 days (HR 9.1, 1.1-79.2, p =0.05), with a trend at 14 days (HR 4.6, 0.9-22.8, p =0.06).

CONCLUSIONS

Although only a minority of patients with symptomatic CS had a recurrent stroke within 14 days, early recurrent stroke risk was high, particularly within the first 72 hours. Earlier carotid revascularization or improved acute medical treatment may reduce recurrence in this high-risk group.

Assessment of body image in obesity using a digital morphing technique

BACKGROUND

Historically, body image research has relied on generic, whole body outlines, which may not be suited to obese individuals. The development of computer generated, individualized digital images to represent body image may be more effective.

METHODS

Sixty volunteers participated, with three categories of subject: lean, obese and lean regular exercisers. Body image was assessed using a digital morphing technique in comparison to two standard paper questionnaires.

RESULTS

Using the novel digital morphing tool, obese subjects displayed poorer body awareness (perception) than their lean counterparts (P = 0.03), significantly over-estimating their actual body size. Both genders overestimated body size to a similar degree. For body satisfaction, females wished to be smaller and males to be larger, identifying gender-specific body regions (P < 0.001). Obese subjects showed greatest dissatisfaction (P < 0.001) with body image. There was significant correlation for body image dissatisfaction (P < 0.05) between the digital technique and the questionnaires, which was highest for the figural stimuli questionnaire (r = 0.80, P < 0.001).

CONCLUSIONS

This method represents a novel and alternative approach to rating body image perception (IP) and satisfaction in obese subjects, particularly providing data on specific regional areas. Body image dissatisfaction appears to be both due to poor body IP compounded with the desire to be smaller.

Low-energy reporting and duration of recording period

Three-day, rather than 7-day, food records are frequently used because mis-reporting of food intake is believed to increase with recording period. Data from the National Diet and Nutrition Survey of adults were used to explore trends in reported energy intake (REI) with day of recording and to compare average REIs from Thursday to Saturday and from Sunday to Tuesday to the complete 7-day record. Although REIs decreased from days 2 to 7, this was by a quantitatively insignificant 49 kJ per day (P=0.026) and well within the measurement error of recorded food intakes. Furthermore, REIs were lowest on the first recording day. The 3- and 7-day averages were similar (mean difference 0.039 (s.d.+/-1.0) MJ (NS), range -3.3 to +4.2 MJ). However, the difference was greater for those reporting higher than average energy intakes because of higher REIs on weekend days. Food intake reporting periods of longer than 3 days and ideally 7 days are preferable.

Comparing different measures of energy expenditure in human subjects resident in a metabolic facility

OBJECTIVE

To compare energy expenditure (EE) measured by doubly labeled water (DLW) with other measures, both physical and based on subjective questionnaires.

DESIGN

A comparison of methods in a stratified sample of adult volunteers.

SETTING

The feeding behaviour suite (FBS) at the Rowett Research Institute, Aberdeen.

SUBJECTS

A total of 59 subjects, stratified for age, sex and body mass index (BMI).

INTERVENTIONS

EE was assessed by DLW (validated using measurements of energy balance), heart rate monitor (HRM), activity monitor (Caltrac), 24-h physical activity diary (PAD) and 7-day physical activity recall. Energy intake was assessed using covert (investigator-weighed) food intake (EI). Data were collected over a 12-day period of residence in the Rowett's FBS.

RESULTS

No methods correlated highly with physical activity assessed by DLW. Physical methods correlated more closely than did subjective recording. All methods (except EI) significantly underestimated EE, estimated by DLW. There were no significant differences in association between methods and sex, age, BMI or fat-free mass.

CONCLUSION

EE is difficult to measure precisely or accurately with current approaches but physical methods are slightly better than subjective accounts.

Energy density and weight of food effect short-term caloric compensation in men

OBJECTIVE

The purpose of the study was to examine the effect of energy density and food weight (volume) on subsequent intake.

DESIGN

Sixteen lean men were each studied four times during a 2-d protocol at the Rowett's Human Nutrition Unit. On day 1, subjects were fed a mandatory diet at 1.6 x resting metabolic rate (RMR). On day 2, during the mandatory morning period (08.30-12.30) subjects consumed a fixed breakfast (08.30) plus a snack (10.30) in one of four treatments [with values in weight (kg), ED (kJ/100g), Energy (MJ)]: (i) zero intake, 0:0:0 (ii) low energy density (LED), 0.615: 400: 2.46; (iii) high energy density (HED), 0.615: 800: 4.92; (iv) 2 x LED, 1.225: 400: 4.91. From 12.30, throughout the remainder of the day, subjects had ad libitum access to 15 high-protein, 15 high-fat and 15 high-carbohydrate foods. Motivation to eat was tracked hourly using 100 mm line scales.

RESULTS

ANOVA showed subjects were hungrier after the zero and LED treatments in the mandatory period (p<0.001). Lunch time EI was 5.0, 3.1, 4.2 and 3.2 MJ on the zero, HED, LED and 2 x LED treatments, respectively (p<0.001). Total ad libitum EI was 11.7, 9.6, 10.3 and 9.5 MJ/d, respectively (p=0.033). Total ad libitum plus mandatory intakes amounted to 11.7, 14.5, 12.6 and 14.4 MJ/d, respectively (p=0.001). Corresponding food intakes were 2.18, 2.39, 2.51 and 3.06 kg/d, respectively (p<0.001).

CONCLUSIONS

The present study showed that subjects respond to both the amount of food eaten in the morning and to the energy density of those foods. However, compensation was only partial and short-term. Subjects only compensated EI by approximately 40% and that compensation only occurred at the next meal.

The quantitative measurement of antimicrobial resistance in Escherichia coli at the meta-population level (meta-population analysis)

AIMS

To define a method that describes antimicrobial resistance of meta-populations of bacteria in both a quantitative and biologically meaningful way.

METHODS AND RESULTS

Using spiral plating and colony counting technology we obtained, from animal faecal samples, the density of Escherichia coli that grow at different concentrations of antibiotic. A mathematical description of this dose-response curve fitted the data well. The parameters of this model have biological meaning and the model allowed subtle differences between meta-populations to be detected.

CONCLUSIONS

This method, termed MPA (meta-population analysis), is practical and provides a useful quantitative description of antimicrobial resistance in a bacterial meta-population.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study shows that resistance can be defined quantitatively. The method may be used in many epidemiological and clinical studies of antimicrobial resistance in animals and humans.

Effect of an acute fast on energy compensation and feeding behaviour in lean men and women

AIM

Humans appear to defend against energy deficit to a greater extent than energy surplus. Severe dietary energy restriction resulting in 5-30% weight loss often leads to hyperphagia and weight regain in lean subjects. However, the period of time over which fasting is often endured in Western society are far shorter, approximately 1-2 days. This study examined how a 36 h fast effected the subsequent day's energy and nutrient intake in a group of 24 healthy, lean men and women.

METHOD

Subjects underwent two 2 day treatments, termed 'fast' and 'maintenance'. During the 'fast' treatment, subjects were fed a maintenance diet on the day prior to the fast (day -1) to prevent overeating. They then consumed non-energy drinks only, from 20:00 h on day -1 to 08:00 h on day 2 (ad libitum feeding day), thus fasting for 36 h. On the 'maintenance' protocol, subjects received a maintenance diet throughout day 1. Throughout day 2 they had ad libitum access to a range of familiar foods, which were the same for both treatments. Body weight, blood glucose and respiratory quotient were used as compliance checks. Hunger was monitored on day's -1, 1 and 2 for the fast treatment only.

RESULTS

On day 2, average energy intake was 10.2 vs 12.2 MJ/day (s.e.d. 1.0) on the post-maintenance and post-fast periods, respectively (P=0.049). Subjects altered feeding behaviour, in response to the fast, only at breakfast time, selecting a higher-fat meal (P<0.005). Compared to day -1, motivation to eat was elevated during the fast (P<0.05). This continued until breakfast was consumed during the re-feeding period (day 2), when values then returned to baseline.

CONCLUSION

These data suggest that a 36 h fast, which generated a negative energy balance of approximately 12 MJ, did not induce a powerful, unconditioned stimulus to compensate on the subsequent day.

The effect of graded levels of exercise on energy intake and balance in free-living women

AIM

We assessed the effect of graded increases in exercised-induced energy expenditure (EE) on appetite, daily energy intake (EI), total daily EE and body weight in six lean women using a within-subject, repeated measures design.

METHOD

Subjects were each studied three times during 7 day treatments, corresponding to no-exercise (control; Nex; 0 MJ/day), medium exercise level (Mex; approximately 1.9 MJ/day) and high exercise level (Hex; approximately 3.4 MJ/day), with 2 day maintenance beforehand. Subjects self-weighed ad libitum food intake. EE was assessed by continual heart rate monitoring. During waking hours subjects recorded hourly sensations of hunger and appetite.

RESULTS

EE amounted to 9.2, 11.0 and 12.1 MJ/day (F (2, 10)=5.67; P=0.023 (s.e.d.=0.87)) on the Nex, Mex and Hex treatments, respectively. The corresponding values for EI were 8.9, 9.2 and 10.0 MJ/day (F (2, 10)=4.80; P=0.035 (s.e.d.=0.36)). There were very weak treatment effects on hunger. Weight loss was significantly different from zero on the Mex and Hex treatments.

CONCLUSION

Markedly increasing EE through exercise produced significant but partial compensations in EI ( approximately 33% of EE due to exercise). Accurate adjustments of El to acute increases in EE are likely to take weeks rather than days.

Energy density of foods: effects on energy intake

This article examines the importance of dietary energy density (ED) as a major factor that may influence human appetite and energy intake (EI). The article examines whether the effects of diet composition on appetite and EI can be explained in terms of ED. There is clear evidence that dietary macronutrients exert differential effects on energy intake (EI), both in the laboratory and in real life. Under normal conditions where fat contributes disproportionately to ED, protein, carbohydrate, and fat exert hierarchical effects on satiety in the order protein >carbohydrate > fat. Alcohol appears to stimulate EI. In human appetite studies the main effect of controlling ED is to diminish the impact of differences in the satiating effects of fat and carbohydrate. ED exerts profound effects in constraining EI in short-to-medium term studies. Subjects behave differently in longer term interventions. In short-to-medium term laboratory studies, increases in ED are more effective at increasing EI than at decreasing food intake. In longer term and cross-sectional studies conducted in naturalistic environments, increased ED appears more effective at decreasing food intake and less effective at elevating EI. The available evidence suggests that we should be evolving more complex, multifactor models to account for the observations that both macronutrients and ED affect EI rather than substituting one simplistic model with another.

An investigation into the effects of sodium citrate ingestion on high-intensity exercise performance

This study examined the effect of sodium citrate ingestion on high-intensity cycling performance in repeated 45-sec bouts. Twelve subjects (9 male and 3 female) ingested either a sodium citrate solution (0.3 g x kg-1 body mass[BM]) or a placebo 90 min prior to exercise. Postingestion blood HCO3 concentrations were significantly higher in the citrate trial (p<.01), but there was no difference over the five bouts (p<.05) and postexercise blood lactate concentrations significantly increased over the five bouts (p<0.01), but there were no differences between trials. We conclude that sodium citrate ingestion (0.3 g x kg-1 BM) is not an effective ergogenic aid for high-intensity, intermittent exercise as simulated in this protocol.

Proportions of volatile fatty acids in relation to the chemical composition of feeds based on grass silage

This experiment was designed to quantify the relationships between feed chemistry and the proportions of rumen volatile fatty acids (VFA) across a wide range of feedstuffs. In an experiment using 11 rumencannulated sheep, 16 test feeds were fed at three different inclusion rates in rations that were based on grass silage. The 17 periods of the experiment were each 14 d long. Eight rumen samples were taken every 24 h on d 13 and 14 of each period from which the mean daily proportions of VFA were derived. The effects of an increase in the proportion of test feed in the total feed on proportions of VFA were significant. The observed proportions of VFA were related to the chemical composition of the total feed by principal component regression. The inclusion of the amount of feed offered and the ratio of test feed to total feed in these regressions did not improve their precision; these terms were not significant. The significant terms in the regressions were crude protein, starch, sugar, and cellulose (calculated by difference). The R2 values achieved for the regressions between acetate, propionate, and butyrate (molar proportions) and feed composition were 77.5, 68.0, and 87.3%, respectively. These regressions provided an apparently robust basis for predicting molar proportions of VFA from feed chemistry in feeds based on grass silage.

Superimposing two-dimensional gels to study genetic variation in malaria parasites

Two-dimensional polyacrylamide gel electrophoresis is a valuable tool for studying genetic variation in the human malaria parasite, Plasmodium falciparum. It involves examining the position of protein spots in gel produced from different isolates. Some spots have been seen to vary, while others have had a constant position in all isolates so far examined. These invariant spots provide a reference frame to compare variations in other spots. This paper discusses the usefulness of digital image handling, warping and superimposition in a personal computer environment. Rather than produce a fully automatic interpretation system, we show how the computer may be used as a tool for manipulating gel images, although interpretation of the gels' features remains with the human expert. Autoradiographs are scanned on a desktop scanner, and the images in digital form can be displayed on a monitor attached to a personal computer. The coordinates of the invariant spots on each of several gels are identified by the user. Each of the gels is then warped so that the invariant spots of all the gels coincide as closely as possible. The variable spots are then examined. We have used both affine warping transformations, which match the invariant spots as closely as possible, and thin plate spline transformations, which match them exactly. Colour superimposition proved a useful way of examining the gels.