Biomedical subjects

S A Wootton

Publications and source records attributed to S A Wootton.

At least 19 recordsLinked to original sources

PubMed2006

The benefits of oestrogens on postprandial lipid metabolism are lost in post-menopausal women with Type 2 diabetes.

AIMS: Women with Type 2 diabetes appear to lose the protection against cardiovascular disease (CVD) afforded by oestrogens. We examined the effects of oestrogen hormone replacement therapy (HRT) on postprandial clearance of dietary fat in non-diabetic and diabetic post-menopausal women. METHODS: In a cross-sectional study, fasting subjects [HRT+ and HRT- control and diabetic women; Type 2 diabetes (DM) HRT+n = 8, DM HRT-n = 14, control HRT+n = 7, control HRT-n = 11] consumed a meal containing the stable isotope 1,1,1-[13]C-tripalmitin, with blood and breath sampled for 6 and 24 h, respectively, in the postprandial period. RESULTS: In diabetic women, there were no differences between the HRT+ and HRT- groups for any of these parameters. In contrast, in HRT+ compared with HRT- control women, the triglyceride (TG) area under the curve was lower [AUC; HRT+ median (range) 7.7 (4.1, 12.8) mmol/l per 6 h, HRT- 9.7 (3.9, 18.5) mmol/l per 6 h, P < 0.05] and [13]C-palmitic acid in the TG fraction was also lower [HRT+ 23.2 (10.3, 41.3) ng/ml per 6 h, HRT- 47.7 (12.6, 77.2) ng/ml per 6 h, P < 0.05], suggesting the lower postprandial triglyceridaemia associated with HRT in non-diabetic women is because of better chylomicron clearance. CONCLUSIONS: The oestrogen-associated advantage in clearance of dietary lipid we observed in non-diabetic post-menopausal women is not seen in post-menopausal diabetic women. This is likely to promote an atherogenic lipoprotein profile and may contribute to the loss of CVD protection seen in diabetic women.

Blood Glucose↗

PubMed2005

Measured versus predicted energy expenditure in children with inactive Crohn's disease.

INTRODUCTION: The aim of the study was to assess if the estimated average requirements for energy for normal children (EAR) and the Schofield equation could reliably predict energy requirements in children with inactive Crohn's disease (CD). METHODS: Twenty-three children with inactive CD were studied, median age 14.3 years (range 7.8-16.9). Resting energy expenditure (REE) was measured by indirect calorimetry and compared with that predicted using the Schofield equation (BMR). Total energy expenditure (TEE) was measured using REE and a 3-day activity diary and compared with EAR. RESULTS: REE ranged from 79% to 136% of BMR. Mean REE was not significantly greater than mean BMR (P=0.25 2-tailed t-test). TEE ranged from 72% to 163% of estimated average requirements for energy for children of that weight (EARw). EARw tended to underestimate TEE in large children and overestimate TEE in small children (Bland-Altman plot R=0.5, P=0.002). EARw was a poor predictor of TEE (R=0.35, P=0.1). EAR underestimated energy requirements by >500 kcal/day in 40% of the children. CONCLUSIONS: The Schofield equation and EAR are unreliable methods of predicting total energy requirements in children with inactive CD with a significant potential to underestimate energy needs. When energy requirements were greater than EAR it was due to physical activity and body habitus rather than raised REE.

Adolescent↗

PubMed2004

Laboratory markers predict bone loss in Crohn's disease: relationship to blood mononuclear cell function and nutritional status.

BACKGROUND: Crohn's disease is associated with reduced bone density. The power of simple markers of systemic inflammation to identify higher rates of bone loss, in Crohn's disease, is uncertain. This relationship and the role of circulating (peripheral blood) mononuclear cells were investigated in a case-control study. METHODS: Urinary deoxypyridinoline/creatinine and serum osteocalcin concentrations were compared in male and premenopausal females with "active" Crohn's disease (C-reactive protein > or = 10 and/or erythrocyte sedimentation rate > or = 20) (n = 22) and controls with "quiescent" Crohn's disease (C-reactive protein < 10 and erythrocyte sedimentation rate < 20) (n = 21). No patients were receiving corticosteroid therapy. Production of tumour necrosis factor-alpha, interferon-gamma and prostaglandin E(2) by peripheral blood mononuclear cells were measured. RESULTS: Active Crohn's disease was associated with a higher deoxypyridinoline/creatinine (P = 0.02) and deoxypyridinoline/creatinine:osteocalcin ratio (P =0.01) compared with quiescent Crohn's disease, but similar osteocalcin (P = 0.24). These were not explained by vitamin D status, dietary intake or nutritional status. However, production of interferon-gamma by concanavalin A-stimulated peripheral blood mononuclear cells was lower in active Crohn's disease (P = 0.02) and correlated negatively with the deoxypyridinoline/creatinine:osteocalcin ratio (r = -0.40, P = 0.004). CONCLUSION: In Crohn's disease, raised C-reactive protein and erythrocyte sedimentation rate may indicate higher rates of bone loss and, if persistent, the need to assess bone mass even where disease symptoms are mild. This may be partly explained by altered production of interferon-gamma by peripheral blood mononuclear cells.

Adult↗

PubMed2003

Essential fatty acid status in paediatric Crohn's disease: relationship with disease activity and nutritional status.

BACKGROUND: Active paediatric Crohn's disease is associated with nutritional deficiencies and altered nutrient intake. The availability of essential fatty acids (linoleic and alpha-linolenic acids) or their derivatives (arachidonic and eicosapentaenoic acids) may alter in plasma and cell membrane phospholipid in protein-energy malnutrition in children and in Crohn's disease in adults. AIM: To investigate the relationship of fatty acid phospholipid profiles with disease activity and nutritional status in paediatric Crohn's disease. METHODS: The fatty acid (proportionate) composition of plasma and erythrocyte phosphatidylcholine was determined in 30 patients (10.3-17.0 years) stratified into active and quiescent Crohn's disease (paediatric Crohn's disease activity index) and high and low body mass (body mass index centile). RESULTS: In plasma phosphatidylcholine, active disease activity was associated with a lower level of alpha-linolenic acid compared with that in quiescent disease (P < 0.05). A body mass index below the 50th centile was associated with active Crohn's disease, low linoleic and alpha-linolenic acids and high arachidonic acid (P < 0.05) in plasma phosphatidylcholine, and low alpha-linolenic acid in erythrocyte phosphatidylcholine. These findings could not be explained through differences in habitual dietary fat intake. CONCLUSION: In paediatric Crohn's disease, a low body mass index centile and high disease activity are associated with altered profiles of essential fatty acids and their derivatives, which may reflect altered metabolic demand.

Adolescent↗

PubMed2003

Conversion of alpha-linolenic acid to palmitic, palmitoleic, stearic and oleic acids in men and women.

The purpose of this study was to determine whether adult humans can recycle carbon from alpha-linolenic acid (18:3n-3) into saturated (SFA) and monounsaturated (MUFA) fatty acids. Six men and six women consumed 700 mg [U-13C]-18:3n-3. Blood was collected over 21 days and breath over 24h. [13C]-labelled SFA and MUFA were detected in plasma phosphatidylcholine (PC) and triacylglycerol (TAG). Total labelled fatty acid incorporation into SFA and MUFA was five- and 25-fold greater in PC than TAG in men and women, respectively. [13C]-16:0 was the major labelled fatty acid in both fractions. Total [13C] incorporation into SFA and MUFA was 20% greater in men than women, and related positively (r(2) = 0.35, P<0.05) to the fractional recovery of labelled 18:3n-3 as 13CO2 on breath. These results suggest that the extent of partitioning towards beta-oxidation and carbon recycling may regulate the availability of 18:3n-3 for conversion to longer-chain fatty acids.

Adult↗

PubMed2003

Effect of meal sequence on postprandial lipid, glucose and insulin responses in young men.

OBJECTIVE: To investigate whether the postprandial changes in plasma triacylglycerol (TAG), nonesterified fatty acids (NEFA), glucose and insulin concentrations in young men were the same if an identical meal was fed at breakfast and lunch, and if the response to lunch was modified by consumption of breakfast. METHODS: In two trials (1 and 2) healthy subjects (age 22+/-1 y, body mass index 22+/-2 kg/m(2)) were fed the same mixed macronutrient meal at breakfast at 08:00 h and lunch at 14:00 h. In the third trial, no breakfast was fed and the overnight fast extended until lunch at 14:00 h. Addition of [1,1,1-(13)C]tripalmitin to one meal in each trial was used to distinguish between endogenous and meal-derived lipids. RESULTS: The postprandial changes in TAG, NEFA and glucose concentrations were similar in trials 1 and 2. The change in plasma total TAG concentration was about two fold less (P<0.05) after lunch compared to breakfast. Postprandial NEFA suppression was the same after breakfast and lunch. Glucose and insulin responses were significantly greater following lunch suggesting decreasing insulin sensitivity during the day. Consumption of breakfast did not alter the postprandial total TAG or NEFA responses after lunch. Measurement of [(13)C]palmitic acid concentration showed that handling of TAG and NEFA from the meal was the same after breakfast and lunch, and was not altered by consumption of breakfast. CONCLUSIONS: Overall, these data suggest that in young, healthy men regulation of plasma TAG from endogenous sources, principally VLDL, but not chylomicrons during the postprandial period leads to differences in the magnitude of lipaemic response when the same meal was consumed at breakfast or at lunch 6 h later.

Adult↗

PubMed2002

Influence of glucose ingestion by humans during recovery from exercise on substrate utilisation during subsequent exercise in a warm environment.

Carbohydrate (CHO) ingestion during short-term recovery from prolonged running has been shown to increase the capacity for subsequent exercise in a warm environment. The aim of this study was to examine the effects of the amount of glucose given during recovery on substrate storage and utilisation during recovery and subsequent exercise in a warm environment. A group of 11 healthy male volunteers took part in two experiments in a controlled warm environment (35 degrees C, 40% relative humidity), 1 week apart. On each occasion the subjects completed two treadmill runs (T1 and T2) at a speed equivalent to 60% of maximal oxygen uptake, for 90 min, until they were fatigued, or until aural temperature (T(aur)) reached 39 degrees C. The two runs were separated by a 4 h recovery period (REC), during which subjects consumed 55 g of naturally enriched [U-(13)C]-glucose in the form of a 7.5% carbohydrate-electrolyte solution (CES, mass of solution 667 g) immediately after T1. The subjects then consumed either: the same quantity of CES, or an equivalent volume of an electrolyte placebo, at 60, 120 and 180 min during REC, providing a total of 220 g (C220) or 55 g (C55) of [U-(13)C]-glucose, respectively. Expired gases were collected at 15 min intervals during exercise and 60 min intervals during REC, for determination of total CHO and fat oxidation by indirect respiratory calorimetry, and orally ingested [U-(13)C]-glucose oxidation, estimated from the (13)C:(12)C ratio of expired CO(2). Substrate metabolism did not differ between conditions during T1. Despite the fact that total CHO (P < 0.05) and ingested glucose oxidation (P < 0.01) were greater during REC of the C220 condition, glycogen synthesis was estimated to be approximately fivefold greater (P < 0.01) than in the C55 condition. During T2 the rate of total CHO oxidation was higher (P < 0.01) and total fat oxidation lower (P < 0.01) at all times during the C220 compared to the C55 condition. The greater CHO oxidation during C220 appeared to be met from ingested sources, as the rate of [U-(13)C]-glucose oxidation was greater (P < 0.01) at all times during T2, compared to C55. Whilst more of the ingested substrate remained unoxidised on completion of T2 during C220, exercise duration was similar in the two experimental conditions, and was limited by thermoregulatory incapacity (T(aur) > 39 degrees C) rather than substrate availability per se.

Administration, Oral↗

PubMed2002

The paradox of improved antiretroviral therapy in HIV: potential for nutritional modulation?

Chronic infection with HIV type 1 is associated with alterations in macronutrient metabolism, specifically elevated plasma lipids, glucose and reduced insulin sensitivity. These alterations are most severe in patients at the later stages of AIDS, indicating a relationship with disease progression. Recently, a metabolic syndrome, termed lipodystrophy, has been described in successfully-treated HIV patients in whom the altered macronutrient metabolism of HIV infection appears to be amplified markedly, with concurrent alterations in adipose tissue patterning. This syndrome presents a paradox, as before the development of highly-active antiretroviral therapy (HAART) the most severe perturbations in metabolism were observed in the sickest patients. Now, the patients that respond well to therapy are showing metabolic perturbations much greater than those seen before. The implications of this syndrome are that, whilst life expectancy may be increased by reducing viral load, there are concomitant increases in the risk of cardiovascular disease, diabetes and pancreatitis within this patient population. The aetiology of the syndrome remains unclear. In a collaborative trial with the Chelsea and Westminster Hospital in London we have used stable-isotope-labelled fatty acids to examine the hypothesis that treatment with HAART causes a delayed clearance of dietary lipid from the circulation, resulting in the retention of lipid within plasma and the downstream changes in insulin and glucose homeostasis. This hypothesis would indicate a role for low-fat diets, exercise and drugs that reduce plasma lipid or insulin resistance, in modulating the response to antiretroviral therapy in HIV infection.

Antiretroviral Therapy, Highly Active↗

PubMed2002

Maldigestion and malabsorption of dietary lipid during severe childhood malnutrition.

BACKGROUND: Diets rich in lipid are used to provide energy density in treating children with severe malnutrition, but the extent to which their digestion and absorption can cope with the load effectively is uncertain. AIM: To determine the extent of impaired digestion or absorption, in three groups of eight malnourished children (aged 5-23 months) using isotopic probes of the predominant fatty acids in coconut and corn oil used to fortify the diet. METHODS: Each child received oral doses of one of three (13)C labelled triglycerides (trilaurin, triolein, or trilinolein). The recovery of (13)C label in stool either as triglyceride (TAG) or fatty acid (FA), was used to assess digestion and absorption. In a separate test, the recovery of label in stool following an oral dose of [(13)C]-glycocholate was measured to assess bile salt malabsorption. RESULTS: The median recovery of label in stool was 9% (range 1-29%) of administered dose. Following treatment there was a reduction in stool (13)C excretion for the labelled TAG (<1%). In half the subjects, label was recovered as TAG in stool (median 0.6%, range 0-44%). Most label in stool was recovered as FA (median 30%, range 0-100%). Following [(13)C]-glycocholate, label was recovered in excess in about one third of studies. CONCLUSION: Abnormalities in the gastrointestinal handling of lipid were observed in over 50% of children with severe malnutrition, reflecting problems in absorption, although impaired solubilisation or hydrolysis could also be contributory factors. The underlying lesion improves as treatment progresses, leading to concomitant improvement in function.

Carbon Isotopes↗

PubMed2001

Exogenous carbohydrate oxidation from drinks ingested during prolonged exercise in a cold environment in humans.

Six healthy male volunteers performed four rides to exhaustion on a cycle ergometer at approximately 80% of maximal oxygen consumption. Subjects ingested a bolus volume of fluid (7.14 ml/kg) immediately before exercise and additional fluid volumes (1.43 ml/kg) every 10 min during exercise. The fluids ingested were either a flavored water control or glucose-electrolyte beverages with glucose concentrations of 2, 6, or 12%. The beverages were labeled with [U-(13)C]glucose (99.2%: 0.05 g/l). Exercise capacity was not different (P = 0.13) between trials; median (range) exercise time was 83.52 (79.85--89.68), 103.19 (78.82--108.22), 100.37 (80.60--124.07), and 94.76 (76.78--114.25) min in the 0, 2, 6, and 12% trials, respectively. The oxidation of exogenous glucose in each 15-min period was significantly lower in the 2% trial (P = 0.02) than in the 6 and 12% trials where oxidation rates were between 0.5 and 0.7 g/min. No difference in endogenous glucose oxidation was observed between trials (P = 0.71). These findings indicate that the oxidation of exogenous glucose during exercise of this intensity and duration in a cold environment is similar to that observed in warmer conditions. Thus a low oxidation of exogenous substrate is unlikely to be a factor limiting the effectiveness of carbohydrate-electrolyte drink ingestion on exercise capacity in a cold environment.

Acclimatization↗

PubMed2001

Effects of prior moderate exercise on exogenous and endogenous lipid metabolism and plasma factor VII activity.

Moderate exercise reduces postprandial triacylglycerol concentrations, which are a risk marker for coronary heart disease. The present study sought to determine the qualitative nature of exercise-induced changes in lipid metabolism and their association (if any) with changes in factor VII activation. Eleven normotriglyceridaemic men, aged 51.7+/-6.1 years (mean+/-S.D.), participated in two oral fat tolerance tests after different pre-conditions: control (no exercise), and exercise (90 min of brisk walking the day before). Venous blood samples were obtained in the fasted state and for 8 h after ingestion of a high-fat meal (1.32 g of fat, 1.36 g of carbohydrate, 0.30 g of protein and 10 mg of [1,1,1-(13)C] tripalmitin x kg(-1) body mass). Prior exercise reduced postprandial plasma triacylglycerol concentrations by 25+/-3% (mean+/-S.E.M.), with lower concentrations in the Svedberg flotation rate (Sf) 20--400 (very-low-density lipoprotein) fraction accounting for 79+/-10% of this reduction. There was no effect on plasma factor VII coagulant activity or on the concentration of the active form of factor VIIa. Prior exercise increased postprandial serum 3-hydroxybutyrate and plasma fatty acid concentrations, decreased serum postprandial insulin concentrations and increased exogenous (8 h (13)C breath excretion of 15.1+/-0.9% of ingested dose compared with 11.9+/-0.8%; P=0.00001) and endogenous postprandial fat oxidation. These data raise the possibility that reduced hepatic secretion of very-low-density lipoprotein plays a role in the attenuation of plasma triacylglycerol concentrations seen after exercise, although it is possible that increased triacylglycerol clearance also contributes to this effect.

Aged↗

PubMed2001

Gastrointestinal handling and metabolic disposal of 13C-labelled tripalmitin during rehabilitation from childhood malnutrition.

We investigated the gastrointestinal handling and post-absorptive metabolic handling of [1,1,1-13C]tripalmitin and [1-13C]glycocholate during recovery from severe childhood malnutrition. Eight children were studied on three occasions: at admission (phase 1), during rapid catch-up growth (phase 2) and when weight-for-height had reached 90 % of the reference (phase 3). Breath samples were obtained over a 24 h period and stools were collected over 3 d following the administration of each tracer. At admission, the lipid content of stool expressed as a percentage of ingested lipid was 6 (range 0.7-28.9) but less variation was shown between children at phase 2 (3.3 (range 0.9-4.1)) and phase 3 (1.4 (range 0.4-2.5)). The excretion of 13C in stool varied markedly between children at admission (11.1 (sd 5.4) % administered dose) and during rehabilitation (phase 2, 15.4 (sd 16.5) % administered dose; phase 3, 6.2 (sd 10.2) % administered dose). About 5 % of the absorbed label was recovered on breath at each stage (% absorbed dose; phase 1, 5.1 (sd 6.0); phase 2, 5.2 (sd 3.1); phase 3, 6.4 (sd 6.6)). None of the children exhibited significant bile salt malabsorption as a consequence of small intestinal overgrowth. Of the 13C measured in stool, more label was recovered in fatty acids than triacylglycerols during each of the three phases and this was interpreted to reflect a failure to absorb the products of digestion. The results show that not all the children had problems associated with the digestion and absorption of 13C-labelled tripalmitin in severe malnutrition and during recovery, which was not reflected in gross lipid balance across the gastrointestinal tract. Absorbed lipid was more likely to be deposited as adipose tissue than to satisfy the immediate needs for energy.

Adolescent↗

PubMed2001

Effect of pregnancy on plasma lipid concentration in Trinidadian women. Result of a pilot study.

In Trinidad and Tobago, cardiovascular disease and Type 2 diabetes mellitus are important causes of morbidity and mortality, and birth weight is significantly less than reference standards. Lower birth weight is associated with increased risk of these diseases. Variation in birth weight is due, in part, to deposition of adipose tissue in the foetus during the last trimester at the same time that maternal plasma triacylglycerol (TAG) increases. We conducted a pilot cross-sectional analysis of maternal plasma lipid status and birth weight in healthy, non-pregnant, primigravida Trinidadian women. Non-pregnant and pregnant women, in their second and third trimesters, and at term, were recruited at random from an antenatal clinic. Adult and umbilical cord plasma TAG, non-esterified fatty acids (NEFA) and phosphatidylcholine (PC) concentrations were determined from gas chromatographic analysis of fatty acids. Maternal height, weight, skinfold thickness and infant birth weight were measured. The infants born to Afro-Trinidadian and Indo-Trinidadian women were of low to normal birth weight (medians 3.07 and 3.22 kg, respectively). At term, plasma TAG concentration was approximately two fold (p < 0.05) greater than for non-pregnant women. The increment between 30-34 weeks was 1.5 to 1.9 fold lower than reported in other populations. There was a strong relationship (r = 0.8771, p = 0.019) between maternal and cord plasma TAG and NEFA, but not PC concentrations. There was no significant relationship between maternal TAG concentration at term and birth weight. The result suggests an impaired ability to increase plasma TAG concentrations during late gestation.

Adult↗

PubMed2000

A method for separation of phosphatidylcholine, triacylglycerol, non-esterified fatty acids and cholesterol esters from plasma by solid-phase extraction.

Efficient isolation of individual lipid classes is a critical step in the analysis of plasma and lipoprotein fatty acid compositions. Whilst good separations of total lipid extracts are possible by TLC, this method is time consuming and a major rate-limiting step when processing large numbers of specimens. A method for rapid separation of phosphatidylcholine (PC), non-esterified fatty acids (NEFA), cholesterol ester (CE) and triacylglycerol (TAG) from total plasma lipid extracts by solid-phase extraction (SPE) using aminopropyl silica columns has been developed and validated. Following initial separation of polar and neutral lipids, individual classes were isolated by application of solvents with increasing polarity. Recoveries for combined plasma extraction with chloroform-methanol and SPE were (%): PC 74.2 (SD 7.5), NEFA 73.6 (SD 8.3), CE 84.9 (SD 4.9), and TAG 86.8 (SD 4.9), which were significantly greater for TAG and NEFA than by TLC Both GC-flame ionisation detector and GC-MS analysis of fatty acid methyl esters demonstrated that there was no cross-contamination between lipid classes. Measurements of repeatability of fatty acid composition for TAG, PC, CE and NEFA fractions showed similar CV for each fatty acid. The magnitude of the CV appeared to be related inversely to the fractional fatty acid concentration, and was greatest at concentrations of less than 1 g/100 g total fatty acids. There was no evidence of selective elution of individual fatty acid or CE species. In conclusion, this method represents an efficient, rapid alternative to TLC for isolation of these lipid classes from plasma.

Cholesterol Esters↗

PubMed1999

Effect of fatty acid chain length and saturation on the gastrointestinal handling and metabolic disposal of dietary fatty acids in women.

The gastrointestinal handling and metabolic disposal of [1-13C]palmitic acid, [1-13C]stearic acid and [1-13C]oleic acid administered within a lipid-casein-glucose-sucrose emulsion were examined in normal healthy women by determining both the amount and nature of the 13C label in stool and label excreted on breath as 13CO2. The greatest excretion of 13C label in stool was in the stearic acid trial (9.2% of administered dose) whilst comparatively little label was observed in stool in either the palmitic acid (1.2% of administered dose) or oleic acid (1.9% of administered dose) trials. In both the palmitic acid and oleic acid trials, all of the label in stool was identified as being present in the form in which it was administered (i.e. [13C]palmitic acid in the palmitic acid trial and [13C]oleic acid in the oleic acid trial). In contrast, only 87% of the label in the stool in the stearic acid trial was identified as [13C]stearic acid, the remainder was identified as [13C]palmitic acid which may reflect chain shortening of [1-13C]stearic acid within the gastrointestinal tract. Small, but statistically significant, differences were observed in the time course of recovery of 13C label on breath over the initial 9 h of the study period (oleic acid = palmitic acid > stearic acid). However, when calculated over the 24 h study period, the recovery of the label as 13CO2 was similar in all three trials (approximately 25% of absorbed dose). These results support the view that chain length and degree of unsaturation may influence the gastrointestinal handling and immediate metabolic disposal of these fatty acids even when presented within an emulsion.

Adult↗

PubMed1999

Metabolism of lactose-[13C]ureide and lactose-[15N,15N]ureide in normal adults consuming a diet marginally adequate in protein.

Oral lactose-ureide is resistant to human digestive enzymes, but is fermented by the colonic microflora. Nine normal adults consuming a diet which provided 36 g of protein/day were given oral doses of lactose-[(13)C]ureide and lactose-[(15)N,(15)N]ureide. The appearance on breath of (13)CO(2) derived from lactose-[(13)C]ureide was followed for 48 h. The fate of (15)N derived from lactose-[(15)N, (15)N]ureide was determined by measuring the recovery of (15)N in stools and urine in various forms. About 80% of the label given as lactose-[(13)C]ureide was recovered on the breath, and about 80% of label given as lactose-[(15)N,(15)N]ureide was not recovered in stool, indicating that 80% of the dose was completely fermented. At least 5% of the labelled urea was absorbed and excreted as the intact molecule. Of the (15)N derived from lactose-[(15)N, (15)N]ureide and available for further metabolic interaction, 67% was retained and 33% was excreted in urine. The time taken for [(15)N,(15)N]urea to appear in urine was similar for all subjects, but the appearance of either (13)CO(2) on the breath or [(15)N, (14)N]urea in urine varied. It is concluded that the hydrolysis of the sugar-urea bond may reflect oro-caecal transit time, but that other factors related to colonic bacterial metabolism determine the duration and extent of hydrolysis of urea by urease enzymes. Lactose-ureide can be used to probe the metabolic activity of the colonic microflora in normal individuals.

Adult↗

PubMed1998

The effect of sodium balance on sweat sodium secretion and plasma aldosterone concentration.

The effect of manipulating sodium intake upon sweat sodium secretion was investigated during heat acclimation. Twenty-five male subjects were confined to an environmental chamber at a temperature of 25 degrees C for 3 days, and then acclimated to heat by a further 5 days at 40 degrees C. The subjects' daily sodium intake was controlled throughout as follows: high (HNa), 348.4 (0.8) mmol x day(-1), n=7; moderate (MNa), 174.1 (0.6) mmol x day(-1), n=9; or low (LNa), 66.3 mmol x day(-1), n=9. Sodium losses were estimated from urinary, faecal and sweat collections using a whole-body washdown method. Plasma aldosterone concentration was also measured from venous blood sampled each morning. Measurements of body temperature and heart rate during the heat exposure phase indicated a degree of heat acclimation. During this heat phase there was a reduction (P < 0.01) in sweat sodium secretion for all three conditions which was greatest for the LNa condition, although this finding was not significant (P < 0.1). In the LNa condition, plasma aldosterone concentration increased (P < 0.05) prior to heat exposure, and the secretion of aldosterone was potentiated (P < 0.01) during the heat exposure in comparison with the MNa condition. In contrast, the HNa diet produced a fall (P < 0.05) in plasma aldosterone concentration prior to heat exposure and an attenuation of aldosterone secretion thereafter. These findings are inconsistent with the hypothesis that retention of sweat sodium is dependent upon a net body sodium deficit, but demonstrate that aldosterone secretion is potentiated under such conditions.

Adaptation, Physiological↗

PubMed1998

The effect of age and gender on the metabolic disposal of [1-13C] palmitic acid.

OBJECTIVE: To examine the effect of age and gender on the metabolic disposal of [1-13C]palmitic acid. DESIGN: Cross-sectional. SETTING: Clinical Nutrition and Metabolism Unit at Southampton General Hospital, Institute of Human Nutrition, University of Southampton. SUBJECTS AND MEASUREMENTS: Twelve children (5 boys and 7 girls; aged 5-10 y) and six men (BMI 23.3 +/- 2.6 kg/m2; aged 20-30 y) were recruited. Following oral administration of a bolus dose of [1-13C]palmitic acid (10 mg/kg body weight) consumed with a test meal (1667 kJ) the excretion of 13C-label was measured on breath as 13CO2 over 24 h and in stool over 5 d to account for differences in absorption of [1-13C]palmitic acid. The 13C-enrichment of samples was determined by continuous flow-isotope ratio mass spectrometry. Net substrate oxidation was estimated from gaseous exchange measurements in the postabsorptive state and over 6 h postprandially. RESULTS: The excretion of 13CO2 on breath varied between subjects both in the pattern and amount excreted over 24 h. Breath 13CO2 was not different between boys (61.0 +/- 22.4% of absorbed dose) and girls (54.2 +/- 17.9% of absorbed dose). The excretion of breath 13CO2 was less in the men (35.1 +/- 9.3% of absorbed dose; P = 0.005) and that observed previously by our group in women (30.7 +/- 6.7% of absorbed dose; P = 0.005) than in the children. Net fat oxidation was greater in the children in both the postabsorptive (2.43 +/- 0.78 g/h) and postprandial (11.89 +/- 3.13 g/6 h) states than in the men (0.93 g/h +/- 1.50; P = 0.016; 9.86 +/- 10.53 g/6 h; NS) and women studied previously (0.53 +/- 0.68 g/h; P = 0.003; 0.03 +/- 3.21 g/6 h; P = 0.001). CONCLUSIONS: Our observations that children oxidised nearly twice the amount of [1-13C]palmitic acid than adults in conjunction with greater net fat oxidation in children than adults in both the postabsorptive and postprandial states should be considered before current UK dietary recommendations for fat and saturated fats, developed for adults, are applied to growing children. For dietary recommendations to be developed further more information is required, particularly in groups of infants and the elderly, about the factors that influence the postprandial handling of dietary fat.

Absorption↗