Physiological Mechanisms in the Adaptive Response of Metabolic Rates to Energy Restriction

Resveratrol-Induced Effects on Body Fat Differ Depending on Feeding Conditions

Science constantly seeks to identify new molecules that could be used as dietary functional ingredients in the fight against obesity and its co-morbidities. Among them, polyphenols represent a group of molecules of increasing interest. One of the most widely studied polyphenols is resveratrol (trans-3,4',5-trihydroxystilbene), which has been proposed as an "energy restriction mimetic" because it can exert energy restriction-like effects. The aim of this review is to analyze the effects of resveratrol on obesity under different feeding conditions, such as overfeeding, normal feeding, and energy restriction, in animals and humans. The vast majority of the studies reported have addressed the administration of resveratrol to animals alongside an obesogenic diet. Under these experimental conditions usually a decreased body weight amount was found. To date, studies that focus on the effects of resveratrol under normal feeding or energy restriction conditions in animals and humans are scarcer. In these studies no changes in body fat were reported. After analyzing the results obtained under overfeeding, normal feeding, and energy restriction conditions, it can be stated that resveratrol is useful in reducing body fat accumulation, and thus preventing obesity. Nevertheless, for ethical reasons, these results have been obtained in animals. By contrast, there are no evidences showing the usefulness of this phenolic compound in reducing previously accumulated body fat. Consequently, as of yet, there is not scientific support for proposing resveratrol as a new anti-obesity treatment tool.

EUREKA

Recent research findings reveal that human bioenergetics belongs to the class of multi-loop nonlinear feedback systems—the same class of systems that system dynamics aims to study. In this paper the author aims to demonstrate the utility of utilizing simple—bathtub like—system dynamics models to gain insight into human weight and energy regulation and (in the process) help debunk widespread misconceptions that are hindering prevention and treatment efforts. Specifically, the author presents a series of models, starting with one that captures conventional wisdom about human energy regulation. This baseline model is critiqued and its limitations—and pitfalls—exposed through model experimentation. The model is then incrementally refined in a spiral of modeling-experimentation-learning steps, to arrive at a structure that integrates emerging (advanced) conceptualization(s) of human weight/energy regulation. In the concluding section, the author builds upon the insights gained from this modeling exercise to propose recommendations for obesity treatment and prevention.

Feed restriction and a diet's caloric value: The influence on the aerobic and anaerobic capacity of rats

BACKGROUND

The influence of feed restriction and different diet's caloric value on the aerobic and anaerobic capacity is unclear in the literature. Thus, the objectives of this study were to determine the possible influences of two diets with different caloric values and the influence of feed restriction on the aerobic (anaerobic threshold: AT) and anaerobic (time to exhaustion: Tlim) variables measured by a lactate minimum test (LM) in rats.

METHODS

We used 40 adult Wistar rats. The animals were divided into four groups: ad libitum commercial Purina® diet (3028.0 Kcal/kg) (ALP), restricted commercial Purina® diet (RAP), ad libitum semi-purified AIN-93 diet (3802.7 Kcal/kg) (ALD) and restricted semi-purified AIN-93 diet (RAD). The animals performed LM at the end of the experiment, 48 h before euthanasia. Comparisons between groups were performed by analysis of variance (p < 0,05).

RESULTS

At the end of the experiment, the weights of the rats in the groups with the restricted diets were significantly lower than those in the groups with ad libitum diet intakes. In addition, the ALD group had higher amounts of adipose tissue. With respect to energetic substrates, the groups subjected to diet restriction had significantly higher levels of liver and muscle glycogen. There were no differences between the groups with respect to AT; however, the ALD group had lower lactatemia at the AT intensity and higher Tlim than the other groups.

CONCLUSIONS

We conclude that dietary restriction induces changes in energetic substrates and that ad libitum intake of a semi-purified AIN-93 diet results in an increase in adipose tissue, likely reducing the density of the animals in water and favouring their performance during the swimming exercises.

Effects of an intervention and maintenance weight loss diet with and without exercise on anthropometric indices in overweight and obese healthy women

BACKGROUND AND AIMS

There is growing evidence that excess body weight and body fat levels may lead to various diseases. A low-calorie diet has been found to reduce body weight and fat; however, 95% of patients regain the weight within a short period of time. The aim of this study was to investigate the effects of a reduced-calorie diet with and without exercise on body composition profile as well as to evaluate maintenance of weight loss 18 weeks after the intervention had concluded.

METHODS

Two hundred and six overweight and/or obese women were randomized by a computer to either diet only (DO) or diet and exercise (DE) for an 18-week intervention period and 18 weeks of maintenance. Statistical significance was set at p < 0.05.

RESULTS

Body mass index (BMI) was reduced by 5.1 in the DE group compared to 3.2 in the DO group 18 weeks after the intervention period had ended; waist circumference (WC) was 14.2 cm lower in the exercise group and 8 cm lower in the diet alone group, and body fat was reduced by 15.5% in the DE group, while no changes were observed in the DO group.

CONCLUSION

A combination of a reduced-calorie diet with exercise may successfully reduce weight, BMI, WC and body fat levels.

Intake and utilization of energy from ammonia-treated and untreated wheat straw by steers and wether sheep given a basal diet of grass pellets and hay

Two experiments, experiment 1 with six steers in a 3 × 3 Latin-square design and experiment 2 with four wether sheep in a cross-over design, were conducted to study the effect of species and ammonia treatment on intake and utilization of the energy of untreated wheat straw. Treatments were: (1) untreated wheat straw offered ad libitum on top of a basal diet (B) consisting of hay (0·25) and grass pellets (0·75) (UWS), (2) ammoniated wheat straw offered ad libitum plus B (AWS) and (3) ammoniated wheat straw offered at a restricted level plus B (AWS-). B was offered as a maintenance diet for both species and AWS- was only studied in steers. Voluntary intake of AWS zvas higher than that of UWS. No significant differences emerged between whole rations UWS and AWS with regard to energy digestion (ED), energy metabolizability (ρ = metabolizable energy (ME) I gross energy (GE)) and losses of digestible energy (DE) in urine and methane (average 187 J/KJ DE), but the efficiency of utilization of ME for growth (kg) was significantly higher for AWS than for UWS. ED and ρ of the straw part of the ration was significantly higher for AWS than for UWS. AWS- and AWS did not differ significantly with regard to ED, ρ and DE losses in methane and urine. Steers had a higher intake per kg0·75 per day than wether sheep. Across species, digestible energy intake (DEI) of the whole ad libitum fed diets was related to live weight (M)0·946 (s.e. of exponent 0·0152). ED and ρ of the straw part of the rations did not differ significantly between species, but steers had a significantly higher ED and ρ of β than wether sheep. Steers excreted a significantly lower proportion of DE in urine and a significantly higher proportion of DE in methane than did wethers. Total energy losses in urine and methane, however, did not differ between species.

Responses of young calves, on two levels of feeding, to transportation

The effect of transportation on energy metabolism in young calves was assessed at two feeding levels by indirect calorimetry during a 5·5-day experimental period. Twenty-six Holstein-Friesian male calves were assigned in a 2 × 2 factorial arrangement of treatments. Calves were fed below or near the maintenance requirements (270 or 420 k) metabolizable energy per kg M0·75 per day). At 5 days of age, 13 calves were transported. The applied transportation procedure was aimed to mimic common transport of young calves. The other 13 calves were controls. Metabolizability of dietary energy was low (0·808), but similar for control and transported calves. Despite the similar salivary cortisol concentrations after transportation, heat production was higher by 23 kJ/kg M0·75 per day in transported than in control calves. Calves were not in a steady-state regarding their energy metabolism. Heat production decreased with time. Both transportation and feeding level influenced the decline in heat production with time. Only during the first 3 days after transportation was heat production enhanced, suggesting a relatively short-term effect of transportation in young calves. The impact of transportation on heat production and time related alterations in heat production were not related to the calfs activity.

Energy expenditure in anorexia nervosa: can fat-free mass as measured by bioelectrical impedance predict energy expenditure in hospitalized patients?

Anorexia nervosa (AN) is associated with a reduced metabolically active fat-free mass (FFM) and basal metabolic rate (BMR). Excessive refeeding results in major fat deposition which is not well tolerated by patients. Prediction of BMR is, therefore, a clinical issue during refeeding, but measurement by indirect calorimetry is time-consuming and not widely available. The study aim was to determine if and when BMR could be estimated from prediction formulas based on FFM derived from bioelectrical impedance analysis (BIA) in AN patients during refeeding. Indirect calorimetry and BIA were prospectively measured bi-weekly in 9 AN patients (body mass index 13.7 +/- 0.5 kg/m2) for 10 weeks of refeeding. Initial BMR was 969 +/- 46.7 kcal/d and 27.7 +/- 1.4 kcal/kg FFM, and at week 10 increased to 1360 +/- 44.6 kcal/d and 35.8 +/- 0.8 kcal/kg FFM. While correlations improved with increasing weight, FFM and body mass index, prediction formulas are insufficient to permit prediction of BMR based on weight or FFM, even after 10 weeks of refeeding. To allow for optimal nutritional support, indirect calorimetry measurements may be useful in the early weeks of refeeding because of a large variability of basal metabolic rate between patients.

Fasting - the ultimate diet?

Adult humans often undertake acute fasts for cosmetic, religious or medical reasons. For example, an estimated 14% of US adults have reported using fasting as a means to control body weight and this approach has long been advocated as an intermittent treatment for gross refractory obesity. There are unique historical data sets on extreme forms of food restriction that give insight into the consequences of starvation or semi-starvation in previously healthy, but usually non-obese subjects. These include documented medical reports on victims of hunger strike, famine and prisoners of war. Such data provide a detailed account on how the body adapts to prolonged starvation. It has previously been shown that fasting for the biblical period of 40 days and 40 nights is well within the overall physiological capabilities of a healthy adult. However, the specific effects on the human body and mind are less clearly documented, either in the short term (hours) or in the longer term (days). This review asks the following three questions, pertinent to any weight-loss therapy, (i) how effective is the regime in achieving weight loss, (ii) what impact does it have on psychology? and finally, (iii) does it work long-term?

Serum leptin and insulin levels in lactating protein-restricted rats: implications for energy balance

The present study analysed the effect of protein restriction on serum insulin and leptin levels and their relationship with energy balance during lactation. Four groups of rats received isocaloric diets containing 170 g protein/kg or 60 g protein/kg from pregnancy until the 14th day of lactation: control non-lactating, control lactating (both fed a control diet), low-protein non-lactating and low-protein lactating. Energy intake, body composition, energy balance, serum insulin and leptin concentrations and the relationship between these hormones and several factors related to obesity were analysed. Low-protein-intake lactating rats exhibited hypoinsulinaemia, hyperleptinaemia, hypophagia and decreased energy expenditure compared with control lactating rats. The protein level in the carcasses was lower in the low-protein lactating group than in the control lactating group, resulting in a higher fat content in the first group compared with the latter. Body fat correlated inversely with serum insulin and positively with serum leptin level. There was a significant negative correlation between serum leptin and energy intake, and a positive relationship between energy intake and serum insulin level in lactating rats and in the combined data from both groups. Energy expenditure was correlated positively with serum insulin and negatively with serum leptin in lactating rats and when data from control non-lactating and lactating rats were pooled. Lactating rats submitted to protein restriction, compared with lactating control rats, showed that maternal reserves were preserved owing to less severe negative energy balance. This metabolic adaptation was obtained, at least in part, by the hypoinsulinaemia that resulted in increased insulin sensitivity favouring enhanced fat deposition, hyperleptinaemia and hypophagia.

Consequences of inadequate food energy and negative energy balance in humans

Energy deficiency is probably best measured in adults by the body mass index (BMI). Acute energy deficiency (AED) is associated with body weight loss, along with changes in body composition, as well as a reduced BMR and physical activity. Chronic energy deficiency (CED) is an inadequacy in food to which individuals adapt, at some cost. Individuals with this have never 'lost' weight: they have simply grown less. They adapt to the decreased food energy by reductions in their total energy expenditure (TEE), linked mainly to a lower body size, and to their physical activity. It seems unlikely that enhanced metabolic efficiency contributes substantially to energy saving in CED. Supplementation of energy deficient individuals is accompanied by significant fat deposition; this may have deleterious consequences. Women in many developing countries achieve a successful outcome to pregnancy in spite of being chronically undernourished. Reductions in basal metabolism and behavioural changes in the form of diminished physical activity could meet most of the extra energy needed for pregnancy. Milk energy output is maintained within the expected range in undernourished lactating mothers. Energy deficiency in children is best measured by height-for-age for stunting, and weight-for-height for wasting. Deficits in behavioural and functional parameters in children exist with undernutrition, and can be reduced by early nutritional supplementation along with the appropriate environment.

Nocturnal hypometabolism as an overwintering strategy of red deer (Cervus elaphus)

Herbivores of temperate and arctic zones are confronted during winter with harsh climatic conditions and nutritional shortness. It is still not fully understood how large ungulates cope with this twofold challenge. We found that red deer, similar to many other northern ungulates, show large seasonal fluctuations of metabolic rate, as indicated by heart rate, with a 60% reduction at the winter nadir compared with the summer peak. A previously unknown mechanism of energy conservation, i.e., nocturnal hypometabolism associated with peripheral cooling, contributed significantly to lower energy expenditure during winter. Predominantly during late winter night and early morning hours, subcutaneous temperature could decrease substantially. Importantly, during these episodes of peripheral cooling, heart rate was not maintained at a constant level, as to be expected from classical models of thermoregulation in the thermoneutral zone, but continuously decreased with subcutaneous temperature, both during locomotor activity and at rest. This indicates that the circadian minimum of basal metabolic rate and of the set-point of body temperature regulation varied and dropped to particularly low levels during late winter. Our results suggest, together with accumulating evidence from other species, that reducing endogenous heat production is not restricted to hibernators and daily heterotherms but is a common and well-regulated physiological response of endothermic organisms to energetically challenging situations. Whether the temperature of all tissues is affected, or the body shell only, may simply be a result of the duration and degree of hypometabolism and its interaction with body size-dependent heat loss.

Evaluation of thyroid function in obese dogs and in dogs undergoing a weight loss protocol

Obesity and weight loss have been shown to alter thyroid hormone homeostasis in humans. In dogs, obesity is the most common nutritional problem encountered and weight loss is the cornerstone of its treatment. Therefore, it is important to clarify how obesity and weight loss can affect thyroid function test results in that species. The objectives of this study were to compare thyroid function in obese dogs and in lean dogs and to explore the effects of caloric restriction and weight loss on thyroid hormone serum concentrations in obese dogs. In the first experiment, 12 healthy lean beagles and 12 obese beagles were compared. Thyroid function was evaluated by measuring serum concentrations of total thyroxine (TT4), free thyroxine (FT4), total triiodothyronine (TT3), thyrotropin (TSH), and reverse triiodothyronine (rT3) as well as a TSH stimulation test using 75 microg i.v. of recombinant human TSH. In the second experiment, eight obese beagles were fed an energy-restricted diet [average 63% maintenance energy requirement (MER)] until optimal weight was obtained. Blood samples for determination of TT4, FT4, TT3, TSH and rT3, were taken at the start and then weekly during weight loss. Only TT3 and TT4 serum concentrations were significantly higher in obese dogs as compared to lean dogs. In the second experiment, weight loss resulted in a significant decrease in TT3 and TSH serum concentrations. Thus obesity and energy restriction significantly alter thyroid homeostasis in dogs, but the observed changes are unlikely to affect interpretation of thyroid function test results in clinics.

Comparability of resting energy expenditure in Nigerians and U.S. blacks

OBJECTIVE

To determine the influence of environmental factors on resting energy expenditure (REE) and its relationship to adiposity in two populations of West African origin, Nigerians and U.S. blacks.

RESEARCH METHODS AND PROCEDURES

REE and body composition were measured in a cross-sectional sample of 89 Nigerian adults (39 women and 50 men), and 181 U.S. black adults (117 women and 65 men). Both groups represent randomly selected population samples. REE was measured by indirect calorimetry after an overnight fast in both sites using the same instrument. Body composition was estimated using bioelectrical impedance analysis (BIA) in 72 Nigerians and 156 U.S. participants. Multivariate regression analysis was used to determine the significant predictors of REE. The analyses were repeated in a set of 17 Nigerians and 28 U.S. blacks in whom body composition was measured using deuterium dilution.

RESULTS

U.S. black adults were significantly heavier and had both more fat-free mass (FFM) and body fat than Nigerians. FFM was the only significant determinant of REE in both population groups, whether body composition was measured using BIA or deuterium dilution. The relationship between REE and body composition did not differ by site. There was no relationship between REE and adiposity.

DISCUSSION

Differences in current environmental settings did not impact REE. The differences observed in mean levels of body fat between Nigerians and U.S. blacks were not the result of differences in REE adjusted for body composition.

Hormones and metabolites of arctic foxes (Alopex lagopus) in response to season, starvation and re-feeding

Svalbard's arctic foxes experience large seasonal variations in light, temperature and food supply throughout the year, which may result in periods of starvation. The aim of this work is to investigate if there are seasonal variations in post-absorptive plasma thyroid hormones (free thyroxin (fT(4)), free triiodothyronine (fT(3)) and reverse triiodothyronine (rT(3))) and metabolites (free fatty-acids (FFA) and beta-hydroxybutyrate (beta-OHB)) with season and their response to starvation and re-feeding. The concentrations of post-absorptive free triiodothyronine were significantly higher in November than May, while those of thyroxin, reverse triiodothyronine, free fatty-acids and beta-hydroxybutyrate remained unchanged. Possible explanations for the seasonal variations in free triiodothyronine are discussed. There were no significant changes from post-absorptive concentrations of thyroxin and reverse triiodothyronine in starved and re-fed foxes. However, free triiodothyronine concentrations decreased during starvation and increased again with re-feeding both in May and November. Starvation induced high levels of free fatty acids in both May and November, indicating increased lipolysis. There was a significant increase in beta-hydroxybutyrate in November only, indicating that arctic foxes are capable of protein conservation during starvation.

Obesidade: atualização sobre sua etiologia, morbidade e tratamento

As tendências de transição nutricional ocorridas neste século direcionam para uma dieta mais ocidentalizada, a qual, aliada à diminuição progressiva da atividade física, converge para o aumento no número de casos de obesidade em todo o mundo. Isso representa aumento na morbidade e na mortalidade associadas à obesidade, já que esta é fator de risco para várias doenças como diabetes tipo II, hipertensão, doenças cardiovasculares e cálculo na vesícula biliar. A obesidade se apresenta não apenas como problema científico e de saúde pública, porém como grande indústria que envolve o desenvolvimento de fármacos, de alimentos modificados e estratégias governamentais estimulando a prática regular de atividade física e a orientação alimentar a fim de promover melhores hábitos. Assim, o conhecimento das causas e estratégias preventivas da obesidade é o objeto de estudo de pesquisadores de diferentes centros. Esse artigo tem como objetivo rever esses estudos, abordando o aumento na prevalência e incidência da obesidade, doenças relacionadas ao excesso de peso e os tratamentos para redução da gordura corporal.

Differentiation-dependent inhibition of proteolysis by norepinephrine in brown adipocytes

The objective was to evaluate whether norepinephrine (NE) and other hormonal factors have direct effects on protein degradation in brown fat cells. NE inhibited proteolysis by 35-45% in mouse brown adipocytes differentiated in culture. Insulin also inhibited protein degradation but significantly less than NE, whereas glucagon and leptin had no effect. The inhibitory effect of NE was partially antagonized by propranolol but not by prazosin, and dose-response curves with BRL-37344 (a beta(3)-agonist), isoproterenol (a beta(1)/beta(2)-agonist) and dobutamide (a beta(1)-agonist) were consistent with the involvement of a beta(3)-adrenergic receptor. Furthermore, forskolin mimicked the effects of NE, whereas additions of A-23187 or phorbol esters had no effect, alone or in combination with NE or forskolin. Thus inhibition of proteolysis by NE likely involves a beta(3)-adrenergic receptor-mediated increase in cAMP. In contrast, NE, BRL-37344, and dobutamide had no effect on proteolysis in preadipocytes. Inhibition of proteolysis by NE was due at least in part to inhibition of autophagy. Thus inhibition of proteolysis by NE and insulin in mature brown adipocytes is likely an important process contributing to brown fat growth and atrophy under many physiological or pathological conditions.

Nutritionally-directed compensatory growth enhances mammary development and lactation potential in rats

A nutritionally-regulated compensatory growth regimen imposed during a growing period from prepuberty to gestation can significantly affect mammary development and subsequent lactation performance. The objectives of this study were as follows: 1) to determine whether a compensatory nutrition regimen enhances lactation potential for the first and second lactation cycles and 2) to determine the extent to which a compensatory nutrition regimen modulates cell proliferation, differentiation, and apoptosis and expression of genes in mammary tissues of female rats. Female Sprague-Dawley rats (n = 122, 35 d of age) were randomly assigned either to the control group, with free access to diet, or to a stair-step compensatory nutrition feeding regimen, with an alternating 2-2-3-3-wk schedule. The regimen began with an energy-restricted diet (40% restriction) for 2 wk, followed by the control diet for 2 wk; this step was then repeated at 3-wk intervals. Pups of dams from the compensatory nutrition regimen group gained more during mid-lactation than did control group pups. Mammary tissues were obtained from early (d 2) and late (d 19) lactating rats. Mammary tissue from the compensatory nutrition group exhibited increased cell proliferation and greater gamma-glutamyltranspeptidase and ornithine decarboxylase gene expressions than did tissue from the control group during early lactation of both cycles. Mammary tissue from the compensatory nutrition group also had fewer apoptotic cells than tissue from the control group during late lactation of the first lactation cycle. These results suggest that the compensatory nutrition regimen imposed during the peripubertal developmental phase stimulated mammary growth and enhanced lactation performance by affecting the expression of genes that regulate the cell cycle.

Body composition, resting and running metabolic rates, and net cost of running in rats during starvation

Resting metabolic rate decreases during starvation. However, effects of starvation on the cost of running are not clear. The aim of this study was to examine the effects of 5 days starvation on body composition, resting metabolic rates, running metabolic rates, and net cost of running in male rats. Five days starvation resulted in reductions of 70% fat, 8% protein and 12% carbohydrates. Mass(-0.75) specific resting metabolic rate was significantly reduced from 3.69 +/- 0.27 to 2.73 +/- 0.17 W kg(-0.75) after 5 days starvation. The reduction in metabolic rate after 5 days starvation was maintained during running, in that running metabolic rate was reduced from 10.65 +/- 0.41 to 8.97 +/- 0.47 W kg(-0.75). The net costs of running were calculated and expressed as the costs of moving 1 kg a distance of 1 m. After 5 days of starvation it was reduced from 31.16 +/- 2.03-29.79 +/- 1.69 J m(-1) kg(-1). The reduction however was not significant. The present results therefore suggest that 5 days starvation resulted in a metabolic depression of the resting metabolic rate that was maintained during running. However, the net cost of running remained unchanged, suggesting that the muscle tissues are not significantly involved in the metabolic changes during starvation.

Composição corporal na desnutrição causada por câncer e doenças benignas do aparelho digestivo

A perda de peso é comum em uma grande variedade de doenças, particularmente entre as neoplasias. O objetivo deste estudo foi o de comparar a composição corporal de pacientes desnutridos portadores de câncer ou doenças benignas do aparelho digestivo, através da impedância bioelétrica. Foram avaliados 35 pacientes desnutridos (Indice de massa corporal < 18,5), de 22 a 70 anos, 26 (74,3%) do sexo masculino e nove (25,7%) do sexo feminino, sendo 17 (48,6%) portadores de neoplasias e 18 (51,4%) com doenças benignas. O grupo com neoplasia apresentou idade superior ao de doenças benignas (55,5±10,4 vs 39,8±9,9; p<0,05). O percentual de perda de peso e os valores de albumina sérica não foram diferentes entre os grupos. O percentual de gordura corporal, de massa magra e de água corporal também não diferiu significantemente. Conclui-se que a variação da composição corporal não é diferente em pacientes desnutridos portadores de doença neoplásica ou benigna do aparelho digestivo, quando eliminada a interferência causada por diferentes graus de perda ponderal.

Splenic and intestinal lymphocyte proliferation response in mice fed milk or yogurt and challenged with Salmonella typhimurium

Two groups of 4-5 week old DBA/2J Nii mice were put on either a yogurt-based (n = 33) or a milk-based (n = 32) diet for a period of 4 weeks. At the end of the feeding trial one sub group of mice each from the two dietary groups was sacrificed for assessment of immune response. The remaining mice were challenged intragastrically with 2 x 10(10) live Salmonella typhimurium organisms and continued on their respective diets for 8 days after which they were also sacrificed. The immune response was measured by tritiated thymidine uptake by splenic or intestinal lymphocytes in response to the mitogens concanavalin A (Con A), Phytohaemaggutinin (PHA), and Lipopolysaccharide from Escherichia coli (LPS). Serum Immunoglobulin A levels were also estimated. Feed efficiency, measured as weight gain per unit energy intake, was significantly higher for the yogurt diet than for the milk diet. The mitogenic response of splenic and intestinal lymphocytes in the two groups of unchallenged mice was not different. In the Salmonella-challenged mice the stimulation index (SI) of splenic lymphocytes from yogurt-fed mice (mean +/- SD) was significantly higher (P = 0.001) in response to Con A (24.71 +/- 3.40) than that of milk-fed mice (15.85 +/- 2.09). Further, in these mice the SI of intestinal lymphocytes from yogurt-fed mice was higher than that of milk-fed mice in response to Con A (7.35 +/- 0.61 vs 5.65 +/- 0.78, P = 0.016) and LPS (9.04 +/- 0.93 vs 6.15 +/- 1.32, P = 0.016). Serum IgA levels in Salmonella-challenged mice were significantly higher 8 days after the challenge in the yogurt-fed group than in the milk-fed group (P < 0.001). The experiments indicate an improvement in local gastrointestinal as well as systemic immunity on a yogurt diet as compared to a milk diet.

Energy and protein metabolism in malnutrition due to nonneoplastic gastrointestinal diseases

Although a reduction in both energy expenditure and protein turnover has been demonstrated in starved volunteers, few metabolic data are available for patients in whom malnutrition is due to nonneoplastic gastrointestinal diseases. Chronically malnourished, unstressed adult patients with nonneoplastic gastrointestinal diseases (body mass index, 15.8 +/- 2.5 kg/m2, n = 13) and healthy control subjects (n = 10) were studied in the postabsorptive state using indirect calorimetry, as well as substrate fluxes of L[1-13C]leucine, L-[2-15N]glutamine (seven patients and six controls), and D[6,6-2H2]glucose (seven patients and eight controls). Resting energy expenditure (REE) expressed in kilocalories per 24 hours was significantly lower in patients than in controls; REE expressed per unit of fat-free mass (FFM) was not significantly different in both groups. Whole-body leucine turnover, oxidation, and nonoxidative disposal rates, based on either 13C-leucine or 13C-alpha-ketoisocaproic acid (KIC) enrichments, and glucose turnover rate were not significantly different between malnourished patients and controls. Moreover, glutamine turnover was increased by 28% in malnourished patients as compared with normal volunteers (429.8 +/- 86.8 v 334.9 +/- 15.9 mumol/kg/h, P = .02). These results suggest that hypometabolic adaptation, although previously documented in starved volunteers, is not operative during states of chronic malnutrition due to gastrointestinal disease. The increase in glutamine turnover rate might represent an adaptative mechanism to malnutrition for preservation of visceral mass or function.

Development of metabolic partitioning of energy in young calves

Modifications in thermal demand and energy partitioning in newborn calves were determined over time via indirect calorimetry. One-week-old calves were fed milk replacer at 70 and 110% of the metabolizable energy requirements for maintenance, at ambient temperatures of 7.5 or 19 degrees C, over two consecutive but separately monitored 7-d balance periods. During wk 1, N digestibility, energy digestibility, and energy metabolizability were lower than during wk 2. Heat production decreased, but retention of energy and fat increased, between balance periods. During wk 1, initial IgG concentration in serum was positively correlated with digestibilities of N and energy, and hemoglobin concentration was negatively correlated with heat production. Regression analysis revealed that predicted basal metabolic rate, efficiency of metabolizable energy use, and metabolizable energy requirements for maintenance were lower for wk 2 than for wk 1. Decreased energy utilization in calves on restricted feedings is related to an increase in the utilization of protein as an energy source. Young calves need at least 2 wk to adapt to the combination of new environmental temperature and low feeding amount. Metabolic partitioning of energy may indicate completion of the adaptation stage.

Early skip-a-day feeding of female broiler chicks fed high-protein realimentation diets. Performance and body composition

The effect of an early skip-a-day feeding program on performance and body composition of broiler chicks fed high-protein realimentation diets was studied. One-day-old female broiler chicks were withheld from feed for 2d (0 to 2 d of age), and at 7 d of age three pens of 15 chicks each were randomly assigned to one of five treatments. One treatment (as the control) involved ad libitum access to feed, and other four treatments were subjected to a skip-a-day regimen from 7 to 13 d of age. From 14 to 20 d of age, chicks of the five treatment groups were fed diets containing 21, 21, 25, 30, or 35% protein. Thereafter, chicks were fed a commercial finisher mash diet (18% CP and 3,160 kcal/kg ME) until 56 d of age. Restricted chicks exhibited compensatory growth during the refeeding period, but the 35% CP realimentation diet impaired this phenomenon as indicated by lower recovery index. Chicks of the skip-a-day program, regardless of dietary protein level, had less abdominal fat, as compared with chicks that ate ad libitum. In comparison with the control, less body fat and ash and greater protein contents were observed in chicks fed the 35% CP realimentation diet. Greater or less liver triglyceride content was observed in chicks fed 21% CP, or the 30 and 35% CP realimentation diet, respectively, whereas, less carcass triglyceride content was found in chicks fed 21 or 35% CP realimentation diet, as compared with the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation of energy metabolism to undernutrition in ewes. Contribution of portal-drained viscera, liver and hindquarters

Adaptation of energy metabolism to undernutrition and to the duration of undernutrition was studied in adult, non-pregnant, non-lactating ewes at the whole-animal, portal-drained viscera, liver and hindquarters levels. Arterio-venous and indirect calorimetry techniques were used. Animals were successively fed at 1 times (3 weeks) and at 0.5 times (7 weeks) their metabolizable energy requirements for maintenance (MEm). Portal, hepatic and hindquarters blood flows in quietly standing ewes decreased by 22, 19 and 11% respectively within the first week of undernutrition and remained at that level thereafter. Standardizing hindquarters blood flow to that in a given posture (quietly standing) reduced blood flow by 9.8%. In the portal-drained viscera and liver, O2 extraction rates decreased, leading to 34 and 38% drops in O2 consumption with underfeeding respectively. In the hindquarters, O2 extraction rate increased, partly counterbalancing the drop in blood flow. Thus O2 consumption of hindquarters tended to decrease but the effect was not significant. All changes appeared to be completed from day 5 of underfeeding. Consequently, the portal-drained viscera, liver and carcass were responsible for 39, 32 and 5% respectively of the drop in whole-animal O2 consumption with underfeeding. At the end of the 0.5 x MEm period, in vivo metabolic rates averaged 1.65, 4.89 and 0.38 mmol O2 consumed/d per g fresh weight of adipose-tissue-free portal-drained viscera, liver and boneless hindquarters respectively. Undernutrition imposed a much greater nutritional challenge to splanchnic tissues than to hindquarters. The former reduced their energy expenditure whereas hindquarters metabolism adapted by counteracting the slight drop in nutrient supply.

Undernutrition in relation to changed tissue composition in wild boar (Sus scrofa)

The effect of long term dietary restriction on the composition of liver, kidney, and several muscles was studied in wild boar (Sus scrofa) in order to evaluate the tissue protein content as an indicator for the nutritional status. Extreme undernutrition was associated with a relatively large weight reduction in liver and kidney. In liver and kidney, total protein content and the protein/DNA ratio were reduced through a reduction in both cell number and cell size. The lower protein/DNA ratios and the increased DNA concentration in the muscle of food restricted animals suggested only a reduction of cell size. The response to undernutrition varied considerably between two muscles. It was concluded that the DNA concentrations and the protein/DNA ratio in several tissues provides an additional tool for assessing nutritional status in living or shot wild boar.

The effect of undernutrition on haematological and serum biochemical variables in wild boar (Sus scrofa)

The effect of induced long term undernutrition on the blood composition of wild boar was studied. During the first weeks, the activity of plasma alkaline phosphatase decreased, while creatinine concentrations increased, and the ratio urea/creatinine decreased, suggesting a renal mechanism as well as recycling of nitrogenous waste products to conserve nitrogen. During the last weeks, haemoglobin and packed cell volume decreased, suggesting protein or mineral deficiencies, and the ratio urea/creatinine increased, indicating substantial endogenous protein catabolism.

Growth and skeletal development in the dog in relation to nutrition; a review

Longitudinal growth of the appendicular skeleton in the growth plates and the adjacent metaphyseal area includes chondrocyte differentiation, proliferation, maturation, and hypertrophy in the physis and bone (re-) modelling in the metaphysis. The rate and extent of longitudinal growth are regulated by interactions between biomechanical factors and endogenous growth regulators, i.e., systemic endocrine factors, and local para or autocrine factors, that act on the growth plate chondrocytes. The most important endogenous regulators of growth and skeletal development are growth hormone (GH) and insulin-like growth factors (IGFs), and calciotropic hormones, i.e., parathyroid hormone (PTH), vitamin D (vitD), and calcitonin (CT). The biochemistry, synthesis, secretion, target organs, and effects of these endogenous factors are reviewed, and the calcium homeostatic mechanisms, dietary intake, bone turnover, and calcium excretion are discussed. Energy, protein, and calcium are nutritional factors of great importance to (skeletal) growth. The effects of low and high dietary intake of these nutrients are discussed, especially with reference to longitudinal growth and disturbances in endochondral ossification.

Net mechanical efficiency during stepping in chronically energy-deficient human subjects

Mechanical efficiency during a step test was measured in chronically energy-deficient (CED) individuals and compared to well-nourished subjects using a whole-body indirect calorimeter. The CED group had significantly higher net mechanical efficiencies than the well nourished subjects. This was also evident in the 15% lower energy costs observed in the CED subjects when expressed as a percentage of the predicted data. Factors such as a higher proportion of slow muscle fibres as well as a greater ergonometric efficiency may contribute to the observed higher muscular efficiency aiding conservation of energy expenditure in these individuals.

Protein and energy interactions throughout life. Metabolic basis and nutritional implications

We review selected aspects of the interactions between protein and energy in human metabolism and nutrition. Following a short account of the underlying metabolic basis for the effects of energy on protein metabolism, the contribution made by whole body protein turnover to the metabolic rate is discussed, including the relationship between protein turnover and energy metabolism at different phases of life. The effects of changes in energy metabolism and intake on the nitrogen economy of the host are also reviewed briefly and we explore the relationship between amino acid oxidation and requirements for indispensable amino acids. Interactions between energy and protein metabolism need to be investigated in greater detail and also they must be considered in relation to further attempts to establish more precisely energy and amino acid requirements of people under various circumstances.