During the past few years, there have been two major developments, if not revolutions, in the field of energy balance and weight regulation. The first at the molecular level, which was catalysed by developments in DNA screening technology together with the mapping of the human genome, has been the tremendous advances made in the identification of molecules that play a role in the control of food intake and metabolic rate. The second, at the systemic level, which centered upon the use of modern technologies or more robust analytical techniques for assessing human energy expenditure in response to starvation and overfeeding, has been the publication of several papers providing strong evidence that adaptive thermogenesis plays a much more important role in the regulation of body weight and body composition than previously thought. Within these same few years, several new members of the mitochondrial carrier protein family have been identified in a variety of tissues and organs. All apparently possess uncoupling properties in genetically-modified systems, with two of them (uncoupling protein (UCP) 2 and UCP3) being expressed in adipose tissues and skeletal muscles, which are generally recognised as important sites for variations in thermogenesis and/or in substrate oxidation. Considered as breakthrough discoveries, the cloning of these genes has generated considerable optimism for rapid advances in our molecular understanding of adaptive thermogenesis, and for the identification of new targets for pharmacological management of obesity and cachexia. The present paper traces first, from a historical perspective, the landmark events in the field of thermogenesis that led to the identification of these genes encoding candidate UCP, and then addresses the controversies and on-going debate about their physiological importance in adaptive thermogenesis, in lipid oxidation or in oxidative stress. The general conclusion is that UCP2 and UCP3 may have distinct primary functions, with UCP3 implicated in regulating the flux of lipid substrates across the mitochondria and UCP2 in the control of mitochondrial generation of reactive oxygen species. The distinct functions of these two UCP1 homologues have been incorporated in a conceptual model to illustrate how UCP2 and UCP3 may act in concert in the overall regulation of lipid oxidation concomitant to the prevention of lipid-induced oxidative damage.

Statistical analysis of data collected in experimental or observational studies is an important part of nutritional research. If it is not done appropriately, there is a risk that information in the data is lost, or that conclusions are misleading. The present article does not attempt a full review of the subject of statistics, but attempts to list aspects where care is needed.

The regulation of intracellular ascorbic acid (AsA) levels may be under the control of an AsA-specific membrane transporter. The present study investigates AsA uptake and expression of Na-dependent vitamin C transporter (SVCT) mRNA in the mouse osteoblastic cell line, MC3T3-E1. Among eight compounds tested, dexamethasone (Dex) all-trans retinoic acid, transforming growth factor β, prostaglandin E2 and transferrin significantly (P<0·01, P<0·01, P<0·05 and P<0·01 respectively) stimulated the update of AsA into MC3T3-E1 cells. Among these five, Dex was the most active, inducing mSVCT2 mRNA and the uptake of AsA in a time- and concentration-dependant manner. Dex did not induce mSVCT1 mRNA. These results suggest that the Dex-induced stimulation of AsA incorporation into osteoblastic cells is mediated by the induction of mSVCT2. Since Dex reduced alkaline phosphatase activity in MC3T3-E1 cells in our culture conditions, Dex-induced stimulation of AsA incorporation might not be the result of differentiation. Hormone-regulated changes of SVCT expression may have an important role in cell functions.

The effects of dietary supplementation with either sucrose or starch (50 g/kg regular food for 2 weeks) on central 5-hydroxytryptamine (5HT; serotonin) release were investigated in freely-moving rats. It has been suggested that the amount of transmitter that serotoninergic neurons release might be altered by food intake. We monitored the effects of sucrose and starch on concentrations of extracellular 5HT, its metabolite 5-hydroxyindoleacetic acid (5HIAA), γ-aminobutyric acid (GABA) and dopamine in the hippocampus, using in vivo microdialysis. The major finding was that baseline levels of extracellular hippocampal 5HT in rats with ad libitum access to food supplemented with sucrose were significantly higher compared with the starch control group. We then verified that sucrose supplementation affected the potency of S(+)fenfluramine to increase hippocampal 5HT levels. In both groups of rats, acute intraperitoneal injection (1 mg/kg) of this anorectic drug induced a response curve of the extracellular hippocampal 5HT levels, with a shape that corresponded with earlier data for different brain areas often using up to 10-fold higher doses of S(+)fenfluramine. Nevertheless, we showed that throughout the experiment the absolute values of the sucrose response curve remained higher than in the starch group. On the other hand, S(+)fenfluramine exerted longer lasting effects in the starch group, as compared with the sucrose group. Significant decreases in levels of extracellular hippocampal 5HIAA levels following S(+)fenfluramine administration were simultaneously observed. A practical implication of the present findings is that dietary sucrose may bias the results of studies investigating brain serotoninergic mechanisms and the effects of (anorectic) drugs interacting with 5HT systems in the hippocampus.

Iron deficiency induces thymus atrophy in laboratory animals and very likely in humans by unknown mechanisms. The atrophy is associated with impaired cell-mediated immunity. In this study, we tested the hypothesis that thymus atrophy is a result of increased apoptosis and reduced thymocyte proliferation. Thymocytes were obtained from twenty-seven control, twenty-seven pairfed, twenty-seven iron-deficient (ID) mice; twelve and fourteen ID mice that received the control diet (0·9 mmol/kg versus 0·09 mmol/kg for the ID diet) for 1 d (repletion, R1) and 3 d (R3), respectively. Cell cycle analysis and apoptosis were studied by flow cytometry using propidium iodide staining and terminal deoxyuridine nick end labeling of DNA breaks assay respectively. When mice were killed, haemoglobin, haematocrit, and liver iron stores of ID, R1, and R3 mice were 25–40 % of those of control and pairfed mice (P<0·01). Absolute and relative thymus weights and thymocyte numbers were 19 to 68 % lower in ID, R1, and R3 than in control and pairfed groups (P<0·05). We found no significant difference among groups in the percentage of cells undergoing apoptosis. A higher percentage of thymocytes from ID and R1 mice than those of control, pairfed, and R3 mice were in the resting phase of the normal cell cycle (P<0·05). Conversely, a lower percentage of thymocytes from ID and R1 mice than those from control, pairfed, and R3 mice were in the DNA synthesis phase and late phase of DNA synthesis and onset of mitosis (G2-M) (P<0·05). Indicators of iron status positively correlated (r 0·3 to 0·56) with the percentage of thymocytes in the G2-M phase (P<0·05). Results suggest that reduced cell proliferation but not increased apoptosis is the cause of thymus atrophy associated with iron deficiency.

Our objective was to determine whether dietary supplementation with phosphatidylcholine (PC) plus vitamin B12 could afford beneficial effects on biochemical and biophysical events in the brain of senescence-accelerated mouse (SAM) substrain SAMP8. We measured learning behaviour, hippocampal protein kinase C (PKC) activity, cerebral antioxidant status, phospholipid composition and fatty acid composition in 6-month-old SAMP8 and in age-matched controls (SAM substrain SAMR1). In comparison with SAMR1, SAMP8 showed a significant elevation in total grading score of senescence (P<0·05) and a significant decline in acquisition (P<0·05). SAMP8 had a lower hippocampal PKC activity and cerebral PKC-β mRNA abundance than SAMR1. SAMP8 had increased cerebral lipid peroxide levels and proportion of sphingomyelin, and a lower proportion of 20 : 4n-6 and 22 : 6n-3 in cerebral phosphtidylethanolamine than SAMR1. SAMP8 fed the PC combined with vitamin B12 diet had an increased PKC activity and a higher proportion of 22 : 6n-3 than SAMP8 fed the control diet. These results indicate the potential benefit of PC combined with vitamin B12 as a dietary supplement.

The present study investigated the extent of expectancy in the ability of glucose to affect cognitive performance. Using a within-subjects design, subjects (n 26) completed four experimental sessions (in counterbalanced order and after an initial practice session) during which they were given a 500 ml drink 30 min prior to completing a cognitive assessment battery. In addition, all subjects completed a baseline practice session during which they were given no drink. During two of the sessions, subjects were given a drink containing 50 g glucose and on the other two they were given a drink containing aspartame. A balanced placebo design was used, such that for half the sessions subjects were accurately informed as to the content of the drink (glucose or aspartame), whereas in the other two sessions they were misinformed as to the content of the drink. The task battery comprised a 6 min visual analogue of the Bakan vigilance task, an immediate verbal free-recall task, an immediate verbal recognition memory task and a measure of motor speed (two-finger tapping). Blood glucose and self-reported mood were also recorded at several time points during each session. Glucose administration was found to improve recognition memory times, in direct contrast to previous findings in the literature. Glucose administration also improved performance on the Bakan task (relative to the control drink), but only in sessions where subjects were informed that they would receive glucose and not when they were told that they would receive aspartame. There were no effects either of the nature of the drink or expectancy on the other measures. These results are interpreted in terms of there being some contribution of expectancy concerning the positive effects of glucose on cognition in studies which have not used an equi-sweet dose of aspartame as a control drink.

Low-fat diets, in which carbohydrates replace some of the fat, decrease serum cholesterol. This decrease is due to decreases in LDL-cholesterol but in part to possibly harmful decreases in HDL-cholesterol. High-oil diets, in which oils rich in monounsaturated fat replace some of the saturated fat, decrease serum cholesterol mainly through LDL-cholesterol. We used these two diets to investigate whether a change in HDL-cholesterol would change flow-mediated vasodilation, a marker of endothelial function. We fed thirty-two healthy volunteers two controlled diets in a 2×3·5 weeks' randomised cross-over design to eliminate variation in changes due to differences between subjects. The low-fat diet contained 59·7 % energy (en%) as carbohydrates and 25·7 en% as fat (7·8 en% as monounsaturates); the oil-rich diet contained 37·8 en% as carbohydrates and 44·4 en% as fat (19·3 en% as monounsaturates). Average (SD) SERUM HDL-CHOLESTEROL AFTER THE LOW-FAT DIET WAS 0·21 (sd 0·12) mmol/l (8·1 mg/dl) lower than after the oil-rich diet. Serum triacylglycerols were 0·22 (sd 0·28) mmol/l (19·5 mg/dl) higher after the low-fat diet than after the oil-rich diet. Serum LDL and homocysteine concentrations remained stable. Flow-mediated vasodilation was 4·8 (SD 2·9) after the low-fat diet and 4·1 (SD 2·7) after the oil-rich diet (difference 0·7 %; 95 % CI -0·6, 1·9). Thus, although the low-fat diet produced a lower HDL-cholesterol than the high-oil diet, flow-mediated vasodilation, an early marker of cardiovascular disease, was not impaired.

The effects of red wine and ethanol on plasma lipoproteins and the fatty acid composition of kidney lipids and erythrocytes phospholipids were studied. Lipid peroxidation is one of the main deleterious effects of oxidant attack on biomolecules, due to the disruption of the structural integrity of membranes. The vulnerability of the kidney to oxidative damage has been partly attributed to its high content of long-chain polyunsaturated fatty acids. Antioxidants, such as flavonoids, would be a means of reducing the risk of oxidative damage to membranes. Nutritional sources rich in antioxidants, including those provided by wine, are expected to attenuate the effects of oxidative challenges. Adult rats were fed red wine rich in flavonols, ethanol (125 ml/l), or alcohol-free red wine. The control group drank water. After 10 weeks, blood samples served to measure plasma lipoproteins and antioxidant capacity. Kidney lipids and erythrocyte phospholipids were extracted. The samples were assayed by GLC. Energy intake did not differ between all the groups, but the weight gain of the ethanol group was less than the other three groups. Blood HDL and triacylglycerols were increased by both ethanol and red wine. Ethanol decreased arachidonic and docosahexaenoic acids in both kidney lipids and erythrocyte phospholipids, as compared with either water, red wine or alcohol-free red wine groups. These results indicate that non-alcoholic components of red wine could contribute to avoiding the unfavourable effects of ethanol on plasma lipoproteins, kidney lipids and membrane erythrocyte phospholipids.

There is concern that replacement of dietary fat with carbohydrate may not reduce the overall risk of CHD because this replacement strategy elevates postprandial plasma triacylglycerol (TAG) concentrations. The present study was designed to test the hypothesis that daily exercise can offset the augmented postprandial lipaemia associated with a short-term high-carbohydrate diet. Nine healthy, normolipidaemic men aged 33 (SD 4) YEARS CONSUMED A TEST MEAL (G/KG BODY MASS; 1·2 FAT, 1·1 CARBOHYDRATE, 0·2 PROTEIN) ON THREE OCCASIONS: AFTER 3 D ON A TYPICAL WESTERN DIET (46, 38 AND 16 % ENERGY FROM CARBOHYDRATE, FAT AND PROTEIN RESPECTIVELY); AFTER 3 D ON AN ISOENERGETIC HIGH-CARBOHYDRATE DIET (CORRESPONDING VALUES: 70, 15 AND 15 % ENERGY); AFTER 3 D ON THE SAME HIGH-CARBOHYDRATE DIET WITH 30 MIN MODERATE EXERCISE DAILY. FASTING PLASMA TAG CONCENTRATION WAS HIGHER AFTER THE HIGH-CARBOHYDRATE DIET (1·15 (se 0·16) mmol/l) than after the Western diet (0·83 (se 0·10) mmol/l; P=0·03). Similarly, postprandial lipaemia (6 h total area under plasma TAG concentration v. time curve) was higher after the high-carbohydrate diet (12·54 (se 2·07) mmol/l·h) than after the Western diet (9·30 (se 1·30) mmol/l·h; P=0·004). The addition of exercise to the high-carbohydrate diet significantly reduced postprandial lipaemia (9·95 (se 1·94) mmol/l·h; P=0·01 when compared with the high-carbohydrate diet) but not fasting TAG concentration (1·02 (se 0·24) mmol/l). In conclusion, daily exercise prevented the augmentation of postprandial lipaemia attributable to the short-term high-carbohydrate diet and, thus, exercise may be a powerful adjunct to dietary change.

The aim of the present study was to investigate the effects of stearic acid-, oleic acid- and linoleic acid-rich meals on postprandial haemostasis in young healthy volunteers whose background diets had been controlled for 14 d in a residential study. Six healthy male volunteers were assigned randomly to consume diets rich in stearic acid, oleic acid or linoleic acid for 14 d. On day 15, plasma lipids and haematological variables were measured in the fasted state, and 3 and 7 h (factor VII and prothrombin activation peptide fragments, 1 and 2 only) after consumption of a test meal. Test meals provided 40 % of the subjects' daily energy requirement, with 41 % of the energy provided as fat, 17 % energy as protein and 42 % energy as carbohydrate. The mean fat content of the meal was 45 (SD 5) g. Significant alterations from fasted values were observed for activated factor VII (P<0·05 after 7 h), factor VII antigen (P<0·05 after 7 h), prothrombin activation peptide fragments 1 and 2 (P<0·05 after 7 h) and plasminogen activator inhibitor type 1 activity (P<0·01 after 3 h) after consumption of each of the three meals. No significant differences were observed in haemostatic values (factor VII coagulant activity, factor VII antigen, tissue plasminogen activator activity prothrombin activation peptide fragment and plasminogen activator inhibitor type-1) with regard to diet except for activated factor VII at 3 h; values were higher after the oleic acid- and linoleic acid-rich meals than after the stearic acid-rich meal (P<0·05). After consumption of each of the three meals, chylomicrons contained proportionately more palmitic acid than the lipids ingested. The present study shows that there are demonstrable changes in postprandial haemostasis when young healthy volunteers with controlled dietary backgrounds are challenged with a physiological fat load. These changes are independent of the fatty acid composition of the test meals.

The present study was undertaken in order to assess the role of dietary phosphate in growth. A diet deficient in phosphate led to a suppression of growth in juvenile rats. The phenomenon is similar to that described for diets deficient in other essential single components such as Mg, Zn or K. However, unlike the other constituents, dietary phosphate restriction affected the growth rate much more than it altered the serum phosphate concentration; addition of phosphate to the drinking water of rats fed a low-phosphate diet restored the growth rate without a concomitant change in serum phosphate concentration. The suppression of growth rate by the deletion of phosphate was associated with a delayed decrease in food intake. This finding implies that the variation in appetite was secondary to the change in growth. The increase in body weight following phosphate supplementation was associated with a concomitant increment in food intake. The phosphate-dependent growth was, however, evident also in rats that were pair-fed with those that were not supplied with phosphate. It is concluded that dietary phosphate-dependent growth is not mediated by changes in phosphate concentrations in the extracellular fluid. It is plausible that signals arising from receptors for phosphate in the digestive system constitute part of the growth control apparatus in rats.

Phytate (inositol hexaphosphate; InsP6) was determined in rat tissues fed on diets with different phytate contents, using a GC–mass detection methodology that permitted the evaluation of the total amount of this substance present in such tissues. The highest InsP6 concentrations were found in brain (5·89×10-2 (SE 5·7×10-3) MG/G DM), WHEREAS THE CONCENTRATIONS DETECTED IN KIDNEYS, LIVER AND BONE WERE SIMILAR TO EACH OTHER (1·96×10-3 (se 0·20×10-3), 3·11×10-3 (se 0·24×10-3), 1·77×10-3 (se 0·17×10-3) mg/g DM respectively) and 10-fold less than those detected in brain. When rats were fed on a purified diet in which InsP6 was undetectable, the InsP6 levels of the organs mentioned earlier decreased dramatically (9·0×10-4, 3·8×10-5, 1·4×10-5 mg/g DM in brain, kidneys and liver respectively) and in some cases became undetectable (bone). The addition of InsP6 to this purified diet led to the increase of InsP6 levels in these tissues. This clearly demonstrated that the majority of the InsP6 found in organs and tissues has a dietary origin and is not a consequence of endogenous synthesis. Consequently, considering that InsP6 could be involved in some important biological roles, the value of any diet on supplying this substance is noteworthy.

The objective of the present study was to assess the effect of consumption of a yoghurt-based drink enriched with 1–2 g plant sterols/d on serum lipids, transaminases, vitamins and hormone status in patients with primary moderate hypercholesterolaemia. Thirty patients were randomly assigned to one of two treatment groups: a low-fat low-lactose yoghurt-based drink enriched with 1 g plant sterol extracted from soyabean/d v. a low-fat low-lactose yoghurt, for a period of 4 weeks. After a 2-week wash-out period, patients were crossed over for an additional 4-week period. Second, after a 4-week wash-out period, eleven patients were treated with 2 g plant sterols/d in a second open part of the study for a period of 8 weeks. The yoghurt enriched with plant sterols significantly reduced, in a dose-dependent manner, serum total cholesterol and LDL-cholesterol levels and LDL-cholesterol:HDL-cholesterol (P<0·001), whereas no changes were observed in HDL-cholesterol and triacylglycerol levels, either in the first or the second part of the study. There were only slight, not statistically significant, differences in serum transaminase, vitamin and hormone levels. To conclude, a low-fat yoghurt-based drink moderately enriched with plant sterols may lower total cholesterol and LDL-cholesterol effectively in patients with primary moderate hypercholesterolaemia.

An in vitro method was used to determine the availability of Zn from infant foods containing increasing amounts of phytate, and to quantify the effect of the phytate:Zn molar ratio on the availability. During the in vitro assay, digestive conditions of infants, younger and older than 4 months of age, were carefully simulated since the solubility of phytate–Zn complexes during digestion is pH dependent. Availability was measured with a continuous flow dialysis in vitro procedure with previous intralumen digestive stage. Zn concentrations were determined with flame atomic absorption spectrometry. Phytic acid content was measured with HPLC. Adding phytate to infant formula lowered Zn availability to 2·84 (SD 0·17) % WHEN THE PHYTATE:ZN MOLAR RATIO INCREASED TO 2·2 (P<0·05), AS COMPARED WITH COWS' MILK-BASED FORMULA (6·65 (sd 0·55) %). Availability from vegetables (23·83 (sd 2·17) %) significantly decreased (P<0·05) at a ratio > 7·9 (15·12 (sd 1·63) %). Zn availability from soyabean-based formula (2·26 (sd 0·36) %) was lower (P<0·05) compared with cows' milk-based formula (6·65 (sd 0·55) %). Availability between soyabean- and cows' milk-based formula was similar (P>0·05) when a phytate:Zn ratio of 2·2 (2·84 (sd 0·17) %) was obtained in the cows' milk formula. The negative effect of phytic acid on Zn availability was dependent on the type of the food and the phytate content, and should be considered when using soyabean-based formulas during early infancy.

Dietary cis,trans-18 : 2 isomers impair desaturation and elongation of linoleic acid (Δ9cis,12cis-18 : 2), but little is known of their proportional partitioning between accumulation and oxidation. The present study was therefore designed to assess the accumulation and apparent oxidation of cis,trans-18 : 2 isomers compared with that of trans-18 : 1 isomers and Δ9cis,12cis-18 : 2 in rats. Accumulation is defined as whole-body increase in a fatty acid during a given period (i.e. final body content-initial body content). The apparent oxidation (disappearance) is defined as whole-body utilization of a fatty acid relative to its intake for a given period (intake-excretion-accumulation-longer-chain products)/intake×100). The animals were fed on a diet containing 15 % (w/w) partially hydrogenated rapeseed oil with 1·72 % energy as cis,trans-18 : 2 isomers and varying amounts of Δ9cis,12cis-18 : 2. The apparent oxidation of total cis,trans-18 : 2 isomers (72–76 % dietary intake) was greater than that of Δ9cis,12cis-18 : 2 (38–51 % dietary intake) but it was similar to that of total trans-18 : 1 isomers (78–82 % dietary intake). Among the four isomers, the apparent oxidation of Δ9trans,12trans-18 : 2 was greater than that of the other isomers including Δ9trans,12cis-18 : 2, Δ9cis,12trans-18 : 2 and Δ9cis,13trans-18 : 2. Accumulation of Δ5cis,8cis,11cis,15trans-20 : 4 and Δ5cis,8cis,11cis,14trans-20 : 4 derived from chain-elongation and desaturation of Δ9cis,13trans-18 : 2 and Δ9cis,12trans-18 : 2 was decreased when the dietary Δ9cis,12cis-18 : 2 supply was increased.

The role of the gastrointestinal tract (GIT) in explaining the less efficient utilization of metabolizable energy (ME) in growing lambs fed forage rather than concentrate-based diets was investigated by feeding forage (legume–grass silage) and concentrate (whole shelled maize) diets, at isoenergetic intakes (ME basis), using five groups of lambs. One group of seven lambs was an initial slaughter group and of the two groups (eight lambs per group) fed each diet, one group was fed for 8 weeks, whereas the other group was fed for 16 weeks. All lambs were slaughtered between 18·5 and 20 h following their last meal. Retained energy (as a percentage of ME intake) was higher (concentrate-fed 28, forage-fed 17; P<0·001) for the concentrate-fed animals. Weight-specific mucosal O2 uptake (ml/g DM per h), measured in vitro, was 37 % higher for the forestomach (reticulum, rumen and omasum) and small intestine (jejunum) than for the abomasum and large intestine (caecum and colon), but there was no evidence for a diet effect (except colon; forage-fed 5·3, concentrate-fed 4·2; P=0·036). Total GIT heat loss was estimated as 14 (forage-fed) and 18 (concentrate-fed) % of the whole-body heat loss. Although the GIT did not contribute to increased thermogenesis in the forage-fed lambs in the present study, greater relative contribution of GIT tissue to whole-body mass, i.e. GIT as a percentage of empty-body weight(forage 7·6, concentrate 6·6; P<0·001) in the forage-fed animals supports a role for the GIT in contributing to higher thermogenesis observed in ruminants fed forage as opposed to concentrate diets.

The purpose of the present study was to estimate and compare the effects of macronutrient composition (relative portions of macronutrients) and of non-macronutrient components (e.g. water and fibre) on energy density (energy per unit weight) of the diets of human subjects. We used standard macronutrient energy content values to develop a simple conceptual model and equation for energy density in terms of % energy from dietary fat and % non-macronutrients by weight. To study these effects in self-selected diets of free-living subjects, we used four consecutive days of self-weighed and recorded food records for thirty-two male and thirteen female free-living adult subjects. In the range of typical human diets, the effect of % non-macronutrients by weight was several times greater than that of % energy from dietary fat, both in absolute terms and relative to daily variation in subjects' diets. Both effects were large enough to be physiologically important. Non-macronutrients (% by weight) alone explained much more of the variation in self-selected dietary energy density either between subjects (R2 95 %) or day-to-day (R2 95 %) than did % energy from dietary fat (R2 5 % and 6 % respectively). Omitting beverages gave similar results. The smaller effect of macronutrient composition on energy density of diets is mainly because alterations in macronutrient composition affect only the portion of typical dietary intake that is macronutrients (one-quarter to one-third of weight). Mathematical methods are also useful in analysing observational data and for separating effects of macronutrient composition and non-macronutrients in intervention studies. These results illustrate the importance of considering non-macronutrients in the design and analysis of experimental or observational dietary data.