Caloric Regimens Research Articles

Costs of exploratory behavior: the energy trade-off hypothesis and the allocation model tested under caloric restriction

In order to maintain the energy balance, animals often exhibit several physiological adjustments when subjected to a decrease in resource availability. Specifically, some rodents show increases in behavioral activity in response to food restriction; a response regarded as a paradox because it would imply an investment in locomotor activity, despite the lack of trophic resources. Here, we aim to explore the possible existence of trade-offs between metabolic variables and behavioral responses when rodents are faced to stochastic deprivation of food and caloric restriction. Adult BALB/c mice were acclimatized for four weeks to four food treatments: two caloric regimens (ad libitum and 60% restriction) and two periodicities (continuous and stochastic). In these mice, we analyzed: exploratory behavior and home-cage behavior, basal metabolic rate, citrate synthase and cytochrome oxidase c enzyme activity (in liver and skeletal muscle), body temperature and non-shivering thermogenesis. Our results support the model of allocation, which indicates commitments between metabolic rates and exploratory behavior, in a caloric restricted environment. Specifically, we identify the role of thermogenesis as a pivotal budget item, modulating the reallocation of energy between behavior and basal metabolic rate. We conclude that brown adipose tissue and liver play a key role in the development of paradoxical responses when facing decreased dietary availability.

Effects of caloric restriction on retinal aging and neurodegeneration.

Glaucoma is the most common neurodegenerative cause of irreversible blindness worldwide. Restricted caloric regimens are an attractive approach for delaying the progression of neurodegenerative diseases. Here we review the current literature on the effects of caloric restriction on retinal neurons, under physiological and pathological conditions. We focused on autophagy as one of the mechanisms modulated by restricted caloric regimens and involved in the death of retinal ganglion cells (RGCs) over the course of glaucoma.

Adaptive Physiological and Morphological Adjustments Mediated by Intestinal Stem Cells in Response to Food Availability in Mice

Several studies have evaluated plastic changes in the morphology of the digestive tract in rodents subjected to caloric restriction or restricted availability. Nevertheless, studies that link these morphological responses to physiological consequences are scarce. In order to investigate short-term plastic responses in the intestine, we acclimated adult Mus musculus (BALB/c) males for 20 days to four distinctive treatments: two caloric regimens (ad libitum and 60% of calorie ingestion) and two levels of periodicity of the regimens (continuous and stochastic treatment). At the end of the treatment we analyzed the cell proliferation and cell death dynamics of small intestinal crypts in these animals. In addition, we measured organ masses and lengths, hydrolytic digestive enzyme activities, and energy output from feces. Finally, in order to explore the metabolic changes generated by these dietary conditions we assessed the catabolic activity (i.e., enzymes) of the liver. Our results show that individuals acclimated to a continuous and 60% regimen presented longer intestines in comparison to the other treatments. Indeed, their intestines grew with a rate of 0.22 cm/day, generating a significant caloric reduction in the content of their feces. Besides, both mass and intestinal lengths were predicted strongly by the stabilization coefficient of BrdU+ proliferating cells per crypt, the latter correlating positively with the activity of n-aminopeptidases. Interestingly, by using pharmacological inhibition of the kinase mammalian target of rapamycin complex 1 (mTORC1) by Rapamycin, we were able to recapitulate similar changes in the proliferation dynamics of intestinal stem cells. Based on our results, we propose that the impact of caloric restriction on macroscopic variation in morphology and functional changes in digestive n-aminopeptidases occurs through synchronization in the proliferation rate of stem and/or progenitor cells located in the small intestinal crypts and requires mTORC1 as a key mediator. Hence, we suggest that an excessive stem and progenitor activity could result in increased crypts branching and might therefore underlie the reported intestinal tissue expansion in response to short-term caloric restriction. Summarizing, we demonstrate for the first time that short-term caloric restriction induces changes in the level of cell proliferation dynamics explaining in part digestive tract plasticity in adaptive performance.

High-protein hypocaloric vs normocaloric enteral nutrition in critically ill patients: A randomized clinical trial

PurposeAppropriate caloric intake in critically ill patients receiving enteral nutrition is controversial. This study evaluates the impact of different caloric regimens on severity of organ failure measured with Sequential Organ Failure Assessment (SOFA). Materials and methodsWe conducted a randomized prospective controlled trial. Study population included adult intensive care unit (ICU) patients expected to require enteral nutrition for more than 96 hours. Goals in the intervention group were hypocaloric (15 kcal/kg per day) enteral nutrition compared to normocaloric (25 kcal/kg per day) enteral nutrition, both with hyperproteic intake (1.7 g of protein/kg per day). Primary end point was change in SOFA score (ΔSOFA) from baseline at 48 hours. Secondary end points were ΔSOFA at 96 hours, insulin requirements, hyperglycemia or hypoglycemic episodes, length of ICU stay, days on ventilator, and 28-day mortality. ResultsAfter screening 443 patients, 120 patients were analyzed. There were no differences between groups in baseline characteristics. We did not find a statistically significant difference in ΔSOFA at 48 hours. Patients in the hypocaloric group showed lower average daily insulin requirements and percentage of patients requiring any insulin. ConclusionsHyperproteic, hypocaloric nutrition did not show different outcomes compared to normocaloric nutrition, except lower insulin requirements. Hypocaloric nutrition could provide a more physiologic approach with lower need for care and metabolic impact.

Immediate metabolic effects of different nutritional regimens in critically ill medical patients

Metabolic effects of different caloric regimens were investigated in nonsurgical, medical patients with multiple-organ failure (MOF). Seven total parenteral nutrition (TPN) regimens were administered, differing in amount (14, 28, and 56 kcal/kg per day, i.e., hypo-, iso-, and hypercaloric nutrition, respectively) and distribution [carbohydrates (COH), amino acids (AA), long-chain and medium-chain triglycerides (LCT/MCT)] of calories. Each regimen was administered over 12 h. Metabolism was monitored by energy expenditure (EE), body temperature (BT), protein breakdown (PB), and blood glucose and serum lactate levels. Measurements were started within 2 days of MOF onset. The study was conducted in a medical intensive care unit. Twenty patients with MOF on mechanical ventilation (mean Apache II score x = 26) were investigated. The mean values of the EE (x = 31 kcal/kg per day), BT (x = 38 degrees C), PB (x = 1.5 g/kg per day), and lactate (x = 2.0 mmol/l) and glucose level (x = 222 mg/dl) parameters were elevated. EE, BT, and lactate and glucose levels were significantly lower under hypocaloric nutrition than during iso- and hypercaloric nutrition (p < 0.01). Differences in the metabolic effects of LCT and MCT were not significant. PB was significantly elevated under hypercaloric nutrition (p < 0.01). Protein balance was positive under hypercaloric nutrition, and negative under iso- and hypocaloric nutrition. In nonsurgical, medical patients neither hypercaloric nor isocaloric nutritional support prevented protein catabolism; in contrast, they enhanced the metabolic burden measured by EE, thermogenesis, urea production rate, and glucose and lactate levels. A hypocaloric regimen is therefore recommended for these patients during the early phase of MOF.

Comparison of oxygen consumption, carbon dioxide production, and resting energy expenditure in premature and full-term infants

A newly developed closed circuit water-sealed infant calorimeter has been used to measure oxygen consumption (VO2), carbon dioxide production (VCO2), respiratory quotient (RQ) and resting energy expenditure (REE) in 31 infants. There were 17 full-term and 14 premature infants. VO2 was measured volumetrically, keeping the inspired oxygen concentration constant. VCO2 was determined by infrared analysis of the mixed expired gases. Values for REE and RQ were calculated from measurements of VO2 and VCO2. All values were normalized for the infants body weight. Our findings demonstrate significant differences in VO2, VCO2, and REE associated with weight, gestational age, postnatal age, activity, feeding, and sex. In addition, VO2, VCO2, and REE were significantly higher for the premature infants. The water-sealed indirect calorimetry system: (a) is safe and noninvasive, (b) does not interfere with infant tube feeding or IV infusion, (c) permits long-term monitoring of metabolic activity, and (d) allows a more exact matching of oral and intravenous feedings to actual energy expenditure. We are finding that indirect calorimetry removes the guess work from writing daily caloric regimens, with potential advantage for the treatment of sick infants.