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I. INTRODUCTION A. Is There a Set Point for Body Weight? The maintenance of an adequate body weight is a major determinant of the survival of higher organisms including mammals. [...]

Research shows that the tumor suppressor gene TSC2 regulates the common mTOR pathway, involved in protein synthesis, cell growth, and viability in response to cellular energy status. Results show that under energy-deprived conditions, TSC2 is phosphorylated, enhancing its activity, to facilitate translation regulation and cell size control during tuberous sclerosis complex (TSC).

Results show the mechanism of proton-transfer mediated by the architecture of the cluster binding region of a native protein, that contains no water molecules, and similar to a more flexible and open structure with access to solvent molecules. Data indicate that electrostatic coupling is critical for maintaining proton transfer efficiency both to and from the cluster.

Research elucidates catalysis of poly-ubiquitin chain formation, from a structural point of view, facilitated by the Uev.Ubc13 heterodimer. Data indicate that poly-ubiquitin chain formation involves interactions between components of Lys(sup)63-linked poly-ubiquitin conjugation machinery. Furthermore, results discuss affinity, stoichiometry, specificity, and binding kinetics between the acceptor ubiquitin and the reactants.

Results show that furfural tolerance appears to be directly coupled to the ability to convert furfural to less inhibitory compounds in Saccharomyces cerevisiae under both aerobic and anaerobic growth conditions. Data indicate that furfural is solely converted to furoic acid during respiratory growth. Furthermore, furfural affects fluxes mediating energy metabolism as indicated by a 50% increase in the respiratory activity durign furfural conversion.

This article describes the microbial electricity production by microbial fuel cells attached to an electrode. Research indicates that Geobacter sulfurreducens enhance the effectiveness of microbial fuel cells by attaching to electrodes and oxidizing organic substrates with transfer of electrons to an electrode quantitatively.

Seventy-seven diets were fed to 61-kg growing pigs at a feeding level close to their ad libitum intake and to nonlactating, nonpregnant sows slightly above their maintenance energy level (2.4 kg/d). The main objectives of this study were to compare the total tract digestibility of dietary energy or nutrients of the 77 diets in growing pigs and adult sows and to analyze the effect of diet chemical composition on total tract digestibility in both groups of pigs. Diets were formulated to represent a range of chemical compositions as large as those found in most practical situations. The DE and ME values and total tract digestible nutrient contents of diets were measured for each group of animals; each diet was measured in four to five animals per group, and collection of urine and feces lasted 10 d. The results were used to establish equations for predicting DE and ME values, total tract digestible nutrient contents, and total tract digestibility coefficients of energy from chemical characteristics for each group of animals. The results show that the total tract digestibility of energy or nutrients was higher (P [is less than] 0.01) in adult sows than in growing pigs; the total tract digestibility coefficients of energy, crude protein, ether extract, and NDF averaged 85.2, 85.1, 37.1, and 64.4%, respectively, for sows and 82.1, 80.3, 31.6, and 56.3%, respectively, for growing pigs. The ME/DE ratio was lower (P [is less than] 0.01) in sows (94.8%) than in growing pigs (96.5%), as a result of higher urinary energy losses in sows. The difference in DE values (on average, 0.6 MJ/kg of DM) between adult sows and growing pigs was not constant (P [is less than] 0.01) but increased with dietary fiber content (3.3, 8.6, and 10.1 kJ for each gram of NDF, ADF, and crude fiber increase in the diet, respectively), which suggests that the origin of the difference between the two physiological stages is mainly due to a higher rate of degradation of dietary fiber in the hindgut of sows. The DE and ME values could be accurately predicted from total tract digestible nutrients or from chemical characteristics for each physiological stage. Equations for predicting urinary energy loss from urinary N are also proposed. From a practical point of view, it is suggested to use two energy values for pig feeds: one applicable to growing-finishing pigs and one to adult sows. Equations for predicting DE in adult sows from energy values obtained in growing pigs are proposed. Key Words: Digestibility, Energy Value, Fiber, Pigs, Prediction, Sows

Melanocortins play a critical role in appetite and body weight regulation, because manipulations of this pathway can lead to the development of obesity in several animal models. The purpose of this study was to use a melanocortin receptor agonist and antagonist to evaluate the involvement of melanocortins in feeding, energy metabolism, and body weight regulation in lean and obese Zucker rats. Central administration of a melanocortin receptor antagonist (SHU9119) elevated food intake and body weight of lean Zucker rats but had little effect in obese Zucker rats. In contrast, the melanocortin receptor agonist MTII reduced food intake in both lean and obese rats but was more potent in the obese Zucker rats. These data indicate the existence of functional melanocortin receptors in both lean and obese Zucker rats but suggest that obese Zucker rats have reduced endogenous melanocortin tone. In addition to its effects on food intake, MTII infusion elevated oxygen consumption and decreased respiratory quotient dose dependently during the light cycle. Our data suggest that a melanocortin receptor agonist can induce weight loss by increasing energy expenditure and promoting body fat utilization in addition to its inhibitory effects on food intake in both obese and lean Zucker rats. obesity; indirect calorimetry; oxygen consumption; respiratory quotient; agonist; antagonist

The effect of temperature (23 or 33 [degrees] C) and feeding level on components of energy balance was studied in seven groups of individually reared Pietrain x (Landrace x Large White) littermate piglets. Within each litter, one pig was reared at 23 [degrees] C and given a predefined feeding level close to ad libitum (23AL pigs), one was reared at 33 [degrees] C and also fed close to ad libitum (33AL), and one was reared at 23 [degrees] C and pair-fed to the 33AL pig (23PF). Piglets of one litter were acclimated during 2 to 4 wk to their experimental temperature in temperature-controlled rooms before being transferred (one per week) to a respiration chamber for measurement of nitrogen and energy balances. The average initial BW was 22.4 kg. The data on [O.sub.2] consumption, [CO.sub.2] production, and physical activity were collected over seven consecutive days and used to calculate total heat production ([HP.sub.tot]) and its components: fasting heat production (FHP), heat production due to physical activity ([HP.sub.act]), and thermic effect of feed (TEF). A preliminary trial was conducted in which heat production was measured in three piglets according to a Latin square design at 23, 25, and 27 [degrees] C. Total heat production was, but activity-free heat production was not, affected by temperature, and no firm conclusions could be drawn as to whether 23 [degrees] C was within the thermoneutral zone of fed piglets. In Trial 2, the combination of increased temperature and reduced feed intake resulted in a 20% lesser heat production in 33AL than in 23AL pigs. This was due to a reduction in both TEF (-39%) and FHP (0.642 vs 0.808 MJ [multiplied by] [d.sup.-1] [multiplied by] kg [BW.sup.-0.60]). Despite the shorter duration of standing activity, [HP.sub.act] was slightly higher at 33 [degrees] C, probably due to hyperventilation at this temperature. With similar feeding levels (23PF vs 33AL), [HP.sub.tot] and activity-free heat production were less at 33 [degrees] C and energy retention as protein (+6%) and fat (+31%) was increased. Because [HP.sub.act] was similar for both treatments, the greater energy retention for 33AL seemed to be due to a greater utilization of feed energy or to a reduced maintenance requirement (i.e., reduced FHP). However, the type of stress imposed on 23PF and 33AL pigs was different and may have affected energy metabolism. The results suggest that the reduction in heat production of piglets at high ambient temperatures is caused by a reduction in voluntary feed intake and differences in energetic efficiency. The mechanisms for the lesser efficiency at 23 [degrees] C compared to 33 [degrees] C (at the same level of feed intake) remain unclear. Key Words: Energy Metabolism, Environmental Temperature, Feed Intake, Heat Production, Physical Activity, Piglets

Swimmers, like all athletes, require a well-balanced diet with adequate energy intake for normal daily activities and the demands of training and competition. Investigators have typically studied nutritional status of [...]

Energetic response to repeated restraint stress in rapidly growing mice. Am J Physiol Endocrinol Metab 279: E33-E43, 2000.--There is a cost of stress that may result in the loss of normal biological function (e.g., growth). Repeated, and even single, applications of stressors have been shown to induce negative energy balance in rodents. However, here we addressed whether this energetic response changes during multiple stress exposure and whether there is complete recovery subsequent to the cessation of stress exposure. These questions were addressed in growing C57Bl/6 mice (31 day) by determining at different times the energetic and endocrine responses after the exposure to restraint (R) stress for 4 h applied once (R1), repeatedly over 3 days (R3), or repeatedly over 7 days (R7). Compared with control values, R elevated (P [is less than] 0.05) plasma corticosterone and reduced plasma insulin-like growth factor I on all days of exposure to the stressor. Seven days, but not 1 or 3 days of R, decreased the net growth (126%, P [is less than] 0.05) and deposition of fat (71%, P [is less than] 0.05) and lean (60%, P [is less than] 0.05) energy over the 7 days. Only R7 depressed the 7-day metabolizable energy intake (P [is less than] 0.05), and R7, but not R1 or R3, increased the overall energy expenditure (10%, P [is less than] 0.05). Our results demonstrate that repeated episodes of stress are energetically costly to the rapidly growing animal, but compensatory mechanisms mitigate this cost of repeated stress exposure and permit complete recovery of energy balance after the cessation of stress application. growth; energy partitioning; feed intake; corticosterone

Studies examining the effects of low-protein diets on food intake and body weight have shown varied results. Many researchers have found low dietary protein to increase food intake, while others have found no effect or even a decrease. In 63 male Sprague-Dawley rats, we examined several low levels of dietary protein (2%, 5%, 8%, 10%, 15% vs. 20% casein) to determine the dose-response relationships between low dietary protein and food intake, body composition, energy balance and serum leptin concentrations. Food intake, over the range of low dietary protein, showed a quasi bell-shaped response curve with peak intake occurring in rats fed 8-10% casein. Peak feeding occurred at or just below the estimated protein requirement of the rats (10-12.5% casein). Compared to the 20% casein controls, food intake was severely reduced in rats fed 2% casein, while it was greater in the other low-protein groups. The amount of body fat steadily increased between the 15% casein group and the 8% casein group, and sharply declined between the 5% casein group and 2% casein group. The change in body fat reflected both the change in food intake and altered energy partitioning. Serum leptin concentrations were greater in rats fed the 5 and 8% casein diets than in control rats fed 20% casein. Serum leptin concentrations were positively associated with body fat content ([r.sup.2] = 0.763, P [is less than] 0.001). Increased serum leptin concentrations in the presence of increased food intake is suggestive of a state of leptin resistance. This animal model may provide important insights into diet-induced obesity. J. Nutr. 130: 514-521, 2000. KEY WORDS: * protein restriction * food intake * body composition * leptin * rats

Obesity represents a major threat to health and quality of life. Although obesity has strong genetic determinants, the increasing prevalence of obesity in populations around the world suggests that environmental factors are promoting or exacerbating the problem. Experts are calling for public health efforts to deal with the global epidemic of obesity. Such a campaign would require that we identify and modify environmental factors that promote obesity. Our current food supply is high in fat, and high fat diets have been suggested to promote obesity by increasing energy intake, thus increasing the probability of positive energy balance and weight gain. However, others argue that high fat diets are not promoting obesity. In this paper, we review evidence from animal studies, carefully controlled laboratory studies, cross-sectional studies, clinical trials and studies in individuals at high risk to develop obesity. Although there are many environmental factors promoting excess energy intake and discouraging energy expenditure, it is clear that consumption of a high fat diet increases the likelihood of obesity and that the risk of obesity is low in individuals consuming low fat diets. On the basis of the available data, the current public health recommendations to lower dietary fat intake appear to be appropriate. J. Nutr. 130: 284S-288S, 2000. KEY WORDS: * body weight regulation * energy balance

A new layer of gene regulation emerges for the metabolic regulator peroxisome proliferator-activated receptor-[delta] (PPAR-[delta]). A team consisting of a Kruppel-like transcription factor and a SUMO protease regulate the expression [...]

Dietary or energy restriction is the most potent and reproducible known means of reducing cancer risk in mammals. In the specific case of breast cancer, restriction is dominant with relation to genetic susceptibility, carcinogen exposure and specific components of the diet. Similarly, increased body mass index is associated with a twofold increase in postmenopausal breast cancer risk in humans. To further explore the relationship between energy intake and cancer risk, we have identified a biochemical profile that reflects the dietary restriction metabolome. Exploratory studies previously identified subsets of 20-63 redox-active small molecules from sera (measured by HPLC coupled with coulometric detector arrays) that distinguished dietary groups in both male and female rats. Expert system and pattern recognition-based approaches have 85-100% accuracy in distinguishing diet groups by using these profiles, indicating that the metabolites previously determined using principal component analysis and hierarchical cluster analysis contain sufficient information to construct classification models. We have now combined these disparate datasets into a single metabolic profile consisting of 104 chromatographically distinguishable peaks. These analyses bring to light fundamental differences between the metabolic response of females and males to energy restriction (e.g., more metabolites are significantly altered in females). Further analysis with projection methods shows that most samples fall within expected variation, but even most outliers are correctly classified. Significant components identified with projection methods (discriminant analysis) are sufficient to yield >95% accuracy in distinguishing metabolic type. These approaches have further highlighted a limited subset of metabolites that are important for this classification. [Supported by NIA-AG15354.]

Anorexia, hypermetabolism and weight loss are common in advanced cancer. The progressive wasting may be due to diminished dietary intake as well as to increased energy expenditure mediated by metabolic alterations caused by the tumor. We studied dietary intake, resting energy expenditure and weight loss in 297 patients with generalized malignant disease and their relation to survival. Patients were examined cross-sectionally at entry into an outpatient palliative care program that included anti-inflammatory treatment and nutritional counseling. Survivors were studied longitudinally after 4 mo during palliative care. We found at entry that the patients' mean dietary intake was low. Weight loss of >10% was present in 43% of the patients, and hypermetabolism was present in 48%. Dietary intake did not differ between normometabolic and hypermetabolic patients, nor was tumor type or gender related to energy and protein intake. Weight loss could not be accounted for by diminished dietary intake alone. Increased resting energy expenditure was not compensated for by an increase in spontaneous food intake. These findings indicate that feedback regulation of dietary intake in relation to energy expenditure is frequently lost in patients with cancer. Hypermetabolism and weight loss were significant predictors of decreased survival. Mean survival time was about 8 mo; 189 patients survived 4 mo or more, and 153 could be reexamined. At the 4-mo follow-up during palliative care, group mean weight was nearly maintained, with large individual variations. Weight loss during follow-up predicted decreased survival. Energy intake increased slightly, also with great variation, and an increased energy intake predicted longer survival. J. Nutr. 132: 3465S-3466S, 2002. KEY WORDS: * cancer cachexia * dietary intake * energy expenditure * weight loss * survival