Lipoprotein lipase (EC 3.1.1.34; LPL) is a key enzyme regulating the disposal of lipid fuels in the body. It is expressed in a number of peripheral tissues including adipose tissue, skeletal and cardiac muscle and mammary gland. Its role is to hydrolyse triacylglycerol (TG) circulating in the TG-rich lipoprotein particles in order to deliver fatty acids to the tissue. It appears to act preferentially on chylomicron-TG, and therefore may play a particularly important role in regulating the disposition of dietary fatty acids. LPL activity is regulated according to nutritional state in a tissue-specific manner according to the needs of the tissue for fatty acids. For instance, it is highly active in lactating mammary gland; in white adipose tissue it is activated in the fed state and suppressed during fasting, whereas the reverse is true in muscle. Such observations have led to the view of LPL as a metabolic gatekeeper, especially for dietary fatty acids. However, closer inspection of its action in white adipose tissue reveals that this picture is only partially true. Normal fat deposition in adipose tissue can occur in the complete absence of LPL, and conversely, if LPL activity is increased by pharmacological means, increased fat storage does not necessarily follow. LPL appears to act as one member of a series of metabolic steps which are regulated in a highly coordinated manner. In white adipose tissue, it is clear that there is a major locus of control of fatty acid disposition downstream from LPL. This involves regulation of the pathway of fatty acid uptake and esterification, and appears to be regulated by a number of factors including insulin, acylation-stimulating protein and possibly leptin.

The effects of dietary red pepper added to high-fat (HF) and high-carbohydrate (HC) meals on energy metabolism were examined in thirteen Japanese female subjects. After ingesting a standardized dinner on the previous evening, the subjects took an experimental breakfast (1883 kJ) under the following four conditions: HF meal, HF and red-pepper (10 g) meal, HC meal, or HC and red-pepper meal. Palatability of the experimental meals was measured immediately after the meals. Expired air was collected before and for 210 min after the meal to determine energy expenditure and macronutrient oxidation. Diet-induced thermogenesis was significantly higher after the HC meals than after the HF meals. Lipid oxidation was significantly lower and carbohydrate oxidation was significantly higher after the HC meals than after the HF meals. Addition of red pepper to the experimental meals significantly increased diet-induced thermogenesis and lipid oxidation, particularly after the HF meal. On the other hand, carbohydrate oxidation was significantly decreased by the addition of red pepper to the experimental meals. Addition of red pepper to the HC meal increased the perceived oiliness of the meal to the same level as that of the HF meals. These results indicate that red pepper increases diet-induced thermogenesis and lipid oxidation. This increase in lipid oxidation is mainly observed when foods have a HF content whereas the increase in the perceived oiliness of the meal was found under the HC meal conditions.

Effects of progressive endurance training on energy expenditure (EE) were studied in thirteen elderly sedentary subjects (62.8 (sd 2.3) years) after 7 and 14 weeks of training. Daily EE (DEE) and energy cost of the various usual activities were measured over 48 h by whole-body indirect calorimetry. Free-living DEE (DEEFLC) was calculated from 7 d activity recordings and the energy costs of activities were measured in the calorimeters using the factorial method. DEEFLC did not vary significantly throughout the training period despite the additional energy cost of training sessions (0·60 (sd 0·15) MJ/d), because energy expended during free-living activities (EEACT) decreased by 4·8 (sd 7·1) % (P < 0·05) and 7·7 (sd 8·6) % (P < 0·01) after 7 and 14 weeks of training respectively. Measurements in the calorimeters showed that sleeping metabolic rate transiently increased by 4·6 (sd 3·2) % after 7 weeks of training (P < 0·001) and returned to its initial level after 14 weeks of training. BMR was 7·6 (sd 7·0)%(P < 0·01) and 4·1 (sd 6·1)% (P = NS) higher after 7 and 14 weeks of training respectively, than before training. Likewise, diet-induced thermogenesis increased from 3·7 (sd 2·5) to 7·2 (sd 2·8) % energy intake after 7 weeks of training (P < 0·05), and returned to its initial level after 14 weeks of training (4·2 (sd 2·6) % energy intake). Despite these changes, energy expended during activities and the corresponding DEE did not vary throughout the training period. It was concluded that: (1) DEEFLC remained constant throughout the training period due to a compensatory decrease in free-living EEACT; (2) progressive endurance training induced a transient increase in sleeping metabolic rate, BMR and diet-induced thermogenesis after 7 weeks which was not reflected in the energy expended during activities and DEE.

To verify the influence of food consistency on satiety mechanisms we evaluated the effects of the same meal in solid–liquid (SM) and homogenized (HM) form on satiety sensation, gastric emptying rate and plasma cholecystokinin (CCK) concentration. Eight healthy men, aged 21-28 (mean 24·5) years were given two meals (cooked vegetables 250 g, cheese 35 g, croutons 50 g and olive oil 25 g, total energy 2573 kJ, with water 300 ml) differing only in physical state: SM and HM. The subjects consumed the meals in randomized order on non-consecutive days. The sensations of fullness, satiety and desire to eat were evaluated by means of a questionnaire, gastric emptying was assessed by ultrasonographic measurement of antral area, and plasma CCK concentration was measured by radioimmunoassay. The vegetable-rich meal was significantly more satiating (P < 0·05) when in the HM form than when eaten in a SM state. Furthermore, the overall gastric emptying time was significantly slowed (255 (sem 11) min after HM v. 214 (sem 12) min after SM; P < 0·05) and CCK peak occurred later (94 (sem 12) min after HM v. 62 (sem 11) min after SM; NS) when the food was consumed in the HM form. Independently of the type of meal, antral area was significantly related to fullness sensations (r2 0·46, P = 0·004). These results demonstrate that meal consistency is an important physical food characteristic which influences both gastric emptying rate and satiety sensation. Moreover, the relationship observed between antral area and fullness sensation confirms that antral distension plays a part in the regulation of eating behaviour.

I intake and I deficiency were investigated in thirty vegans (eleven males and nineteen females) consuming their habitual diet. I intake was estimated using the chemical analysis of 4 d weighed duplicate diet collections. The probability of I-deficiency disorders (IDD) was judged from the measurement of urinary I excretion in 24 h urine specimens during the 4 d. There was wide variation in I intake. Mean I intake in males was lower than the reference nutrient intake (RNI; Department of Health, 1991) and mean intake in females was above the RNI, although 36% males and 63% females had I intakes below the lower RNI. Mean I intake in subjects who consumed seaweed (n 3) was in excess of the RNI, and approached the provisional maximum tolerable daily intake (World Health Organization/Food and Agriculture Organization Joint Expert Committee on Food Additives, 1989). The probability of IDD in the group investigated was moderate to severe: three of five subgroups were classified as moderate and two subgroups were classified as severe IDD possibility. The findings highlight that vegans are an ‘at risk’ group for I deficiency. The I status of vegans and the subclinical effects of low I intakes and infrequent high I intakes on thyroid function in this group should be further studied. Our work has also raised the question of adequate I intakes in groups where cow's milk is not consumed, and has exposed a need for more research in this area.

Two N balance experiments using growing pigs were conducted to study the effect of essential:total (E:T) N ratio on N retention and utilization. Purified diets contained casein and crystalline amino acids as the sole sources of N. E:T values ranged from 0·25 to 0·86 while either the concentration of total N (Expt. 1) or essential N (Expt 2) was kept constant. At a constant concentration of total dietary N, N retention and total N utilization were maximized with an E:T value of approximately 0·6, while essential N utilization gradually decreased as E:T increased. At a constant level of essential N, N retention remained unchanged until the E:T value reached 0·48 and then decreased. In Expt 2, maximum total N utilization was attained with an E:T value of 0·66 while N excretion and essential N utilization decreased with increased E:T value. These results suggest that under conditions of optimal protein utilization, essential amino acids are partially degraded and used for the synthesis of non-essential amino acids.

In patients who require enteric tube-feeding the osmolality of the formulas is assumed to play an important role. There is the dilemma that osmolality increases as the digestibility of formulas is enhanced by means of degradation of the nutrients. Hitherto there have been no reports of whether there are differences in nutrient absorption and water fluxes between iso-osmotic polymeric and hyperosmotic oligomeric diets. We therefore investigated absorption of nutrients and net fluxes of water during perfusion of a 1·5 m jejunal segment with oligomeric, polymeric and commercial oligopeptide diets either in the absence of pancreatic juice or with concomitant infusion of pancreatic enzymes. In the absence of pancreatic juice the absorption rates of the polymeric diet and the commercial oligopeptide diets reached 58·0 and 84·5 % respectively of that of a completely-hydrolysed hyperosmotic oligomeric diet. The concomitant infusion of pancreatic enzymes with the polymeric and oligopeptide diets significantly increased the absorption rates of nutrients and energy. The highest absorption rate of energy occurred with the commercial formula Survimed® (Fresenius, Bad Homburg, Germany), probably due to an optimal composition of the macronutrients. The increase in absorption due to the degradation of nutrients by pancreatic enzymes was associated with an increase in net water secretion and flow-rate, reaching similar values to those with the hyperosmotic oligomeric diet. It may be concluded that iso-osmotic oligopeptide formulas require further pancreatic hydrolysis for optimum absorption. In patients with normal pancreatic secretion, oligopeptide formulas have no advantage over polymeric diets. In patients with reduced pancreatic secretion, either completely-hydrolysed hyperosmotic oligomeric diets or polymeric diets supplemented with pancreatic enzymes are appropriate.

Lactation is a physiologically demanding period in mink production, during which kit and dam losses may occur. Ambient temperature and quantitative water supply are thought to affect animal performance and well-being, but conclusive data in the literature are sparse. Therefore, effects of ambient temperature (Ta; low, about 5° medium, about 15° high, average 20-25°) and water supply (ad libitum (N), or 10 % extra supplementation in the food (E)) were investigated regarding effects on quantitative water intake and excretion, urine osmolality and solute excretion, and urinary cortisol and catecholamines as stress indicators in an experiment with twelve lactating mink with litters of three to seven kits in three consecutive periods, lasting 3, 3 and 2 d respectively. Kit ages ranged from 15 to 20 d at the end of the experiment. Water requirement for milk production (factorial calculations) and water available for evaporation (balance component) were estimated. Period, and hence mainly Ta, had a significant influence on intake of metabolizable energy, quantitative water intake and excretion, but there was less effect of water supply. The total water intake and excretion were very high in relation to the weight of the animals as an effect of lactation. Water intake and excretion, and urinary Na excretion, seemed to be less accurately regulated compared with corresponding functions in non-lactating animals. Rectal temperature increased with increasing Ta, possibly as a means of decreasing evaporative water loss. Water output in milk was estimated to increase from 118 g/d at low Ta to 134 g/d at high Ta. The amounts of water available for evaporation were estimated to be 42, 58 and 69 g/kg0·75 at low, medium and high Ta. Cortisol data did not indicate that the animals experienced negative stress. It was concluded that prolonged periods of high Ta may be hazardous for lactating mink because of decreased intake of metabolizable energy resulting in energy deficit and excessive mobilization of body reserves simultaneously as the requirement for intake of water increases considerably.

To compare the effects of fish oil and olive oil on the development of atherosclerosis in Watanabe heritable hyperlipidaemic (WHHL) rabbits, 6-week-old animals were given a daily dose (1·5 ml/kg body weight) of fish oil (n 10) or olive oil (n 10) by oral administration for 16 weeks. Plasma cholesterol and triacylglycerols were measured once monthly, and their concentrations in lipoproteins, together with susceptibility of LDL to oxidation were measured in vitro at the termination of the experiment. Aortic atherosclerosis was quantified biochemically and microscopically. After 4 weeks of treatment, and throughout the study thereafter, blood lipids were significantly (P < 0·05) lower in the fish-oil group than in the olive-oil group (cholesterol: 17·0 v. 30·3 mmol/l, triacylglycerols 2·97 v. 6·25 mmol/l, at termination). In the fish-oil group cholesterol was significantly lower in intermediate-density lipoproteins (2·69 v. 6·76 mmol/l) and VLDL (3·36 v. 11·51 mmol/l). Triacylglycerol levels of intermediate-density lipoproteins and VLDL in the fish-oil group were also significantly lower when compared with the olive-oil group (0·54 v 1·36 mmol/l and 0·92 v. 2·87 mmol/l respectively). No group differences were recorded for LDL- and HDL-cholesterol or triacylglycerol levels. A significantly higher oxidation of LDL was recorded 1 h after exposure to CuSO4 in the fish-oil group when compared with the olive-oil group (0·465 v. 0·202, arbitrary units). The following indicators of atherosclerosis development were significantly lower in the fish-oil group than in the olive-oil group: the cholesterol content (mg/g tissue) in the ascending aorta (29·8 v.48·9), the intima:media value (4·81 v. 18·24) and the area of intima (0·10 v. 0·57 mm2) in the thoracic aorta. It was concluded that fish-oil treatment decreased blood lipids and the development of aortic atherosclerosis in WHHL rabbits when compared with olive-oil treatment.

The amount of dietary trace elements absorbed from a meal depends, among other factors, on the quantities of certain minor plant constituents present in the meal. These substances can act as ligands and bind trace elements in the digestive tract in available or unavailable forms for absorption. The present study was designed to investigate the extent to which different polyphenols (PP) may influence Zn and Cu absorption in rats. Different PP of nutritional interest (chlorogenic acid, caffeic acid, catechin and rutin) were studied using meals extrinsically-labelled with stable isotopes67Zn and 65Cu. Male Wistar rats were fed on a non-labelled semi-synthetic diet containing (mg/kg) 38 Fe, 35 Zn and 7·5 Cu for 8 d. PP were dissolved in dimethyl sulfoxide as the solvent and added to the meal at 1 g/kg during 3 d before isotope administration and until the end of the experiment (a further 3 d). The control group received the dimethyl sulfoxide only. After overnight food deprivation, rats were fed on the labelled test meals (4 g diet+0·1 mg 67Zn and 0·1 mg 65Cu) with 0·5 mg Dy as a faecal marker. Faeces and urine pools were collected for 3 d and analysed for 67Zn and65 Cu isotopic enrichment using the inductively-coupled plasma mass spectrometry technique. Zn absorption was significantly less in rats fed on chlorogenic acid or caffeic acid than in the control group. Catechin ingestion non-significantly inhibited 67Zn absorption. However, the PP studied were without effect on Cu absorption. The study illustrates the effect of metal-binding phenolic compounds on mineral nutrition in the rat, and the possible importance of the effects of different foods rich in these compounds on mineral absorption in man.