No description available.

Parkinson's disease (PD) is the second most prevalent age-related neurodegenerative disease and currently affects over 8 million people worldwide. The primary features of PD include cognitive, behavioral, and motor function deficits induced primarily by the progressive loss of dopaminergic neurons within the substantia nigra of the basal ganglia (BG). Motor coordination becomes severely affected over the course of the disease, causing patients to experience tremors at rest, bradykinesia, and body rigidity. The availability of treatment options has increased the quality of life for patients experiencing the early stages of PD; however, there exists no cure and treatment options are limited for those experiencing severe, advanced disease symptoms. Genetic studies in PD patients have led to the identification of causative genes, but revealed that less than 20% of cases can be attributed to monogenic variations. Evidence strongly indicates that the majority of PD cases are idiopathic and likely driven due to gene by environmental interactions. Reflective of this idea, recent research efforts have turned to genome-wide association studies (GWAS) to provide indications of gene variations, that while not causative of PD, incur increased risk within patient populations. GWAS findings play a particularly crucial role in neurodegenerative interventions, as early identification of patient risk may allow for preventative therapeutics to delay disease onset or reduce symptom severity. Amongst the many gene variants identified as incurring increased PD risk, single-nucleotide polymorphisms (SNPs) in the loci for CD38 that cause reduced gene expression are consistently identified as increasing risk. The cluster of differentiation 38 (CD38) protein serves two major roles: one as a receptor for immunological response and a second as an ectoenzyme that modulates bioenergetic functions. The particular functions of CD38 are highly relevant to neurodegenerative contexts, as changes in central nervous system (CNS) inflammatory status and means of cellular energy production typically precede pathological indications. In the brain, CD38 expression is most enriched in astrocytes in BG regions, including substantia nigra, midbrain, and striatum. However, it is not known how CD38 deficiency may contribute to astrocytic dysfunction and neuropathological features of PD. This dissertation describes how CD38 influences astrocytic gene expression and cellular bioenergetics. Astrocyte RNA was sequenced from the BG of one-year old male Cd38+/+, Cd38+/-, and Cd38-/- mice by magnetic-activated cell sorting (MACS) to acquire astrocyte isolates. Numerous differentially expressed genes (DEGs) were identified in Cd38 Cd38+/- and Cd38-/- astrocytes that relate to regulation of cellular health, responses to stress, and bioenergetic functions. GO analysis further suggested mitochondrial dysfunction in both Cd38+/- and Cd38-/- astrocytes. In a subsequent set of experiments evaluating mitochondrial function by Seahorse XF96 platform, Cd38+/- and Cd38-/- astrocytes displayed altered bioenergetic function. The results herein demonstrate that astrocytic Cd38 expression regulates cellular function and implicates transcriptional changes associated with the hallmarks of neurodegeneration. These findings serve to provide future direction for studies evaluating the relationship between CD38 function and astrocytes as it relates to neurodegenerative PD risk. / Doctor of Philosophy / Parkinson's disease (PD) is the second most common age-related neurodegenerative disease and currently affects over 8 million people worldwide. The primary features of PD include cognitive, behavioral, and motor function deficits induced primarily by the progressive loss of specialized neurons within the substantia nigra of the basal ganglia (BG) brain region. Motor coordination becomes severely affected over the course of the disease, causing patients to experience body tremors, slowness, and rigidity. The availability of treatment options has increased the quality of life for patients experiencing the early stages of PD; however, there exists no cure and little treatment options for those experiencing severe, advanced disease symptoms. Genetic studies in PD patients have led to the identification of causative genes, but revealed that less than 20% of cases can be attributed to specific, individual variations. Evidence strongly indicates that the majority of PD cases are likely caused by small gene changes that interact with environmental factors. Recent research efforts have turned to genome-wide association studies (GWAS) to identify these small changes, that while not causative of PD, may increase risk within patient populations. GWAS findings play a particularly crucial role in treating neurodegenerative diseases, as early identification of patient risk may allow for preventative therapeutics to slow disease onset or reduce symptom severity. Amongst the many small gene changes identified as increasing PD risk, changes in the gene CD38 that cause reduced gene expression are consistently identified as increasing risk. The cluster of differentiation 38 (CD38) protein serves two major roles: one as a receptor for immune responses and a second as an enzyme that impacts how cells produce energy. The functions of CD38 are highly relevant to neurodegenerative contexts, as changes in central nervous system (CNS) inflammatory status and means of cellular energy production typically precede disease pathology. In the brain, CD38 expression is most enriched in astrocytes, specialized brain cells that supports neurons, in regions affected by PD. However, it is not known how CD38 deficiency may contribute to astrocytic dysfunction and neuropathological features of PD. This dissertation describes how CD38 influences astrocytic gene expression and cellular bioenergetics. Astrocyte RNA was sequenced from the BG of one-year old male Cd38+/+, Cd38+/- (50% CD38 loss), and Cd38-/- (100% CD38 loss) mice by magnetic-activated cell sorting (MACS) to acquire astrocytes. Numerous changes in gene expression were identified in Cd38 Cd38+/- and Cd38-/- astrocytes that relate to regulation of cellular health, responses to stress, and energy functions. Further analysis looking at functions, suggested mitochondrial abnormalities in both Cd38+/- and Cd38-/- astrocytes. In a subsequent set of experiments evaluating mitochondrial function by Seahorse XF96 platform, Cd38+/- and Cd38-/- astrocytes displayed altered energetic function. The results herein demonstrate that astrocytic Cd38 expression regulates cellular function and implicates transcriptional changes associated with the hallmarks of neurodegeneration. These findings serve to provide future direction for studies evaluating the relationship between CD38 function and astrocytes as it relates to neurodegenerative PD risk.

In forested ecosystems, salamanders occupy important ecological roles as predator, prey and as potential regulators of ecological processes. The effects of forest management, particularly clearcut harvesting, on salamanders have been well documented; removal of overstory trees negatively affects abundances of salamanders. However, the length of time that salamander populations remain depressed following forest harvesting and factors limiting population recovery have been a source of controversy in the literature and are the goal of this dissertation. As part of the Southern Appalachian Silviculture and Biodiversity (SASAB) project (Chapter 1), a long-term replicated field experiment designed to evaluate a range of silvicultural treatments on biodiversity, I evaluated specific hypotheses related to salamander populations, their prey, and their habitat. First, I examined long-term trends in salamander abundances across a range of silvicultural treatments to determine whether negative effects of forest harvesting persisted for 13-years after harvest (Chapter 2) and to document the effects of multiple harvests on salamanders (Chapter 3). The relative abundances of terrestrial salamanders were quantified in six silvicultural treatments and an unharvested control and on six replicated field sites with night-time, area-constrained searches. Across 13-years of post-harvest data, terrestrial salamander abundances generally were lower in silvicultural treatments with some disturbance to the canopy (group selection harvest through silvicultural clearcut). Further, a comparison of demography of common species of salamanders suggested that differences in habitat quality existed between harvested and unharvested experimental units (EUs). A second harvest in the shelterwood plots to remove overwood had a cumulative negative effect on salamanders at one of two sites studied. Additionally, I conducted a sensitivity and elasticity analysis for eastern red-backed salamanders (Plethodon cinereus) and modeled population growth to evaluate the contribution of demographic parameters to population recovery. These analyses indicated that adult survival was the parameter with the greatest influence on the population growth rate and that >60 years would be required for recovery of salamander populations to preharvest levels even if habitat conditions were restored to preharvest conditions immediately. Next, I quantified the bioenergetics of salamanders across a disturbance gradient to evaluate whether changes to (1) invertebrate prey, (2) energy expenditure for basic maintenance costs, and or (3) an index to body condition could help explain observed changes to abundances or demography of salamanders from forest harvesting (Chapter 4). Although I did not detect a difference in abundances of invertebrates along the disturbance gradient, I determined that salamanders in recently disturbed forest stands expended approximately 33% more energy for basic maintenance costs in an active season and the body condition of salamanders was greater at one of two sites in disturbed EUs. Thus, the bioenergetics of terrestrial salamanders may have been affected by increasing temperatures from silvicultural disturbance and may cause salamanders to allocate less energy to reproduction or growth because of increased maintenance costs. In collaboration with Eric Sucre, Department of Forestry at Virginia Tech, I examined the effects of salamanders on invertebrates and ecosystem processes, specifically leaf litter decomposition. We constructed 12 in situ field mesocosms and I manipulated densities of red-backed salamanders into zero, low, and high density treatments. From June 2006-June 2008, I estimated invertebrate abundances, rates of leaf litter decomposition and food habits of salamanders across treatments. I found that invertebrate abundances were more affected by season than by the density of salamanders and that rates of leaf litter decomposition did not differ among salamander treatments. Salamanders were euryphagic and consumed more (by abundance and volume) herbivorous invertebrates than predators or detritivores. Finally, I modeled habitat relationships of terrestrial salamanders at two spatial scales on the SASAB study sites (Chapter 6). I quantified abundance of salamanders with area-constrained searches during warm rainy nights and measured forest characteristics related to foraging or refugia habitats or that described the overstory and understory of forest stands. At the scale of the 30 m2 transect and the 10 m2 sub-transect, abundance of salamanders was best described by models that incorporated descriptors of canopy cover and woody and herbaceous understory vegetation. Thus, terrestrial salamanders may have responded positively to forest stands with a mature overstory and structurally diverse understory for foraging habitat. Collectively, these data suggest that recovery of salamander populations after forest harvesting will take approximately 60 years, and that life history characteristics (low fecundity, late sexual maturity) and possibly changes to bioenergetics may contribute to the slow recovery. Further, silvicultural practices that retain some canopy trees through a rotation may have a more rapid return of salamander populations to preharvest levels and may encourage development of understory structure for salamander foraging. Although these data fill some gaps in knowledge of relationships between silviculture and terrestrial salamanders, many questions about long-term effects of disturbances on populations and habitats remain. My modeling of recovery of salamander populations depended on estimates of a survival from a congener, and I did not document whether forest harvesting decreases survival of terrestrial salamanders. Lastly, the influence of stochastic events on population dynamics particularly in disturbed stands was not examined in this dissertation. Therefore, future research on the SASAB study sites should continue to track abundances and demography across the disturbance gradient, acquire age-specific estimates of survival, determine whether salamanders exhibit density dependence, develop estimates of entire energy budgets, and use manipulative laboratory experiments to describe the role of plethodontid salamanders in ecosystem functions. / Ph. D.

Mitochondrial structure and function are inextricably linked ("structure-function"), with decrements in structure-function evident across diseases. Barriers to new therapies include a complete understanding of the underlying molecular culprits, as well as effective mitochondria-targeted therapies that mitigate injury. In these works, we investigate the role of cristae-shaping factors like cardiolipin in health and disease. In a series of studies, we tested the effects of the cell-permeable tetrapeptides, elamipretide and a postulated peptide, (arginine-tyrosine-lysine-phenylalanine; "RYKF"), on the recovery of mitochondrial structure-function after injury. Elamipretide is a clinical-stage compound currently under investigation for genetic and age-related mitochondrial diseases, yet the mechanism of action is not completely understood. We used a combination of physiological models, mitochondrial imaging, and biomimetic membrane studies to test the hypothesis that elamipretide and RYKF-cardiolipin interactions improved mitochondrial structure-function. Post-ischemic treatment with elamipretide sustained mitochondrial function across electron transport chain complexes. Endogenous RYKF expression similarly improved mitochondrial respiration after peroxide and hypoxia nutrient deprivation injuries. Using two parallel electron microscopy paradigms, we show elamipretide and RYKF treatment led to maintenance of mitochondrial ultrastructure and notably, improved cristae interconnectedness. Finally, we utilized a novel biomimetic membrane system to model the pathological mitochondrial membrane and found that elamipretide and RYKF both improved biophysical pressure-area relationships through a mechanism that appears to involve aggregating cardiolipin. Our data indicate that targeting pathophysiological mitochondrial membranes with cationic, lipophilic peptides can improve bioenergetics by sustaining cristae networks and support interdependent relationships between mitochondrial structure and function. / Doctor of Philosophy / Mitochondria, the powerhouses of the cell, form energy networks that produce over 90% of the body’s energy. Mitochondrial dysfunction is implicated across diseases, yet no FDA-approved treatments exist that improve mitochondrial energy production. In this study, we tested the effects of elamipretide, a peptide that localizes to mitochondria. Although elamipretide is currently in clinical trials for several diseases characterized by energetic deficiencies, its mechanism of action is not fully understood. Since mitochondrial structure and function are directly linked, we modeled heart attacks in cultured cells and rat hearts to test the hypothesis that elamipretide and a postulated analog, RYKF, glue damaged mitochondrial membranes back together to preserve structure and function during disease. In hearts subjected to a heart attack, elamipretide significantly protected mitochondrial energy production. Similarly, RYKF protected mitochondrial function in muscle cells exposed to peroxide stress. In damaged hearts imaged with electron microscopy, elamipretide and RYKF treatment significantly improved mitochondrial structure and notably, improved the interconnectedness of mitochondrial energy networks. Furthermore, elamipretide and RYKF improved the integrity of diseased mitochondrial membranes. Together, these data support our hypothesis that elamipretide and RYKF act as mitochondrial adhesion molecules to protect mitochondrial structure and sustain energy production during disease.

High circulating glucose and non-esterified free fatty acid (NEFA) levels can cause pancreatic β-cell failure. The molecular mechanisms of this β-cell glucolipotoxicity are yet to be established conclusively. In this thesis by exploring mitochondrial energy metabolism in INS-1E insulinoma cells and isolated pancreatic islets, a role of mitochondria in pancreatic β-cell glucolipotoxicity is uncovered. It is reported that prolonged palmitate exposure at high glucose attenuates glucose-stimulated mitochondrial respiration which is coupled to ADP phosphorylation. These mitochondrial defects coincide with an increased level of mitochondrial reactive oxygen species (ROS), impaired glucose-stimulated insulin secretion (GSIS) and decreased cell viability. Palmitoleate, on the other hand, does not affect mitochondrial ROS levels or cell viability and protects against the adverse effects of palmitate on these phenotypes. Interestingly, palmitoleate does not significantly protect against mitochondrial respiratory or insulin secretion defects and in pancreatic islets tends to limit these functions on its own. Furthermore, strong evidence suggests that glucolipotoxic-induced ROS are of a mitochondrial origin and these ROS are somehow linked with NEFA-induced loss in cell viability. To explore the mechanism of glucolipotxic-induced mitochondrial ROS and associated cell loss, uncoupling protein-2 (UCP2) protein levels and activity were probed in NEFA exposed INS-1E cells. It is concluded that UCP2 neither mediates palmitate-induced mitochondrial ROS production and the related cell loss, nor protects against these deleterious effects. Instead, UCP2 dampens palmitoleate protection against palmitate toxicity. Collectively, these data shed important new light on the area of glucolipotoxicity in pancreatic β-cells and provide novel insights into the pathogenesis of Type 2 diabetes.

No description available.

Four experiments were carried out with laying hens to evaluate the effects of body weight, age, dietary protein, and tallow levels on performance, nutrient intake and energy utilization. In the first experiment, Single Comb White Leghorn birds were divided into four body weight groups at the onset of egg production. Voluntary feed intake was 18% less for the lightest (1.39 kg) in comparison with the heaviest group (1.83 kg). Egg weight was directly related to body weight with the heavy birds producing an average egg weighing 65.3 g and the lightest birds having an average egg weight of 58.9 g. Feed conversion was also significantly better for the lighter birds. Maintenance requirements for the heaviest and lightest birds were 60.5 and 57.9% of metabolizable energy consumed, respectively. Metabolizable energy intakes above maintenance were 131 kcal/d for the heavy birds and only 119 kcal for the light group. A composite regression analysis indicated a maintenance requirement of 127.7 kcal/d/kg('0(.)75) and an energetic efficiency of 75.2% for the conversion of metabolizable energy to net energy. In order to evaluate the effects of age and body weight on laying hen performance, the last three experiments were designed using old, molted, and young hens which were divided into the heaviest and lightest body weight groups. The old birds were 72 weeks old, the molted birds were 106 weeks old, and the young birds were 27 weeks old at the start of the studies. In each experiment the birds were fed ten experimental diets with 12, 14, 16, 18, and 20% dietary protein in combination of 1 and 4% supplemental fat. Egg output was increased with the supplementation of tallow in only the young birds; while energy retentions were improved in the old and molted birds with fat feeding. Average energy retentions per kg physiological body weight were 58.8, 41.7, and 38.6 kcal for the young, molted, and old hens, respectively. The light-bodied birds showed 9% better gross energetic efficiencies than the heavy-bodied birds. Estimated daily protein intake requirements were 16.8, 13.3, and 12.8 g/d to support production levels of 84, 64, and 66% for the young, old, and molted birds, respectively.

A computational model for mitochondrial function has been developed from oxygen concentration data measured in the Oroboros Oxygraph-2k and oxygen consumption rates measured in the Seahorse XF24 Analyzer. Measurements were acquired using embryonic-cultured cortical neurons and isolated mitochondria from CD1 mice. Based on the biological mechanism of mitochondrial activity, a computational model was developed using biochemical kinetic modelling. To modulate mitochondrial activity, dysfunctions were introduced by injecting the inhibiting reagents oligomycin, rotenone, and antimycin A, and the uncoupling reagent carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP) during measurements. To incorporate these changes, model equations were adapted and globally calibrated to experimental data using the genetic algorithm developed by Jason Fiege of the University of Manitoba by fitting oxygen concentration data. The model was coded in MATLAB R2014a along with the development of a graphical user interface for simulating mitochondrial bioenergetics in silico. / October 2016

Les métaux sont des éléments chimiques ubiquitaires, naturellement présents dans notre environnement et utilisés dans de nombreux secteurs d’activité tels que, l’aérospatial, la cosmétologie ou l’industrie pharmaceutique. De nombreux travaux montrent qu’ils sont susceptibles d’être à l’origine de diverses pathologies. Toutefois, la diversité et les modalités des études réalisées rendent difficiles la comparaison de leurs effets et mécanisme d’action. Dans ce contexte, ce travail concerne l’étude de la cyto-génotoxicité du cadmium, du nickel et de l’aluminium, sur un même modèle cellulaire, le fibroblaste cutané humain. Leur cytotoxicité est évaluée en étudiant leur effet sur la bioénergétique cellulaire par microcalorimétrie et, leur effet sur la viabilité cellulaire est mesuré par des techniques colorimétriques conventionnelles. Leur génotoxicité est déterminée par des techniques spécifiques que sont le test des comètes et des micronoyaux. De plus, une approche de leur interaction avec l’ADN est réalisée par microcalorimétrie. Les résultats montrent que la cytotoxicité du cadmium est supérieure à celle du nickel, elle-même supérieure à celle de l’aluminium. Seuls le cadmium et le nickel sont génotoxiques à pH7 principalement en induisant un effet aneugène. Leur interaction est de type électrostatique anti-coopérative avec les groupements phosphate de l’ADN. Si l’aluminium à pH7, n’exerce pas d’effet génotoxique, son interaction avec l’ADN à pH acide est comparable à celle du cadmium et du nickel. Ce résultat singulier lié à la valeur du pH suggère l’importance de la prise en compte de la spéciation des métaux pour l’étude de leurs effets aussi bien in vitro qu’in vivo / Metals are ubiquitous chemical elements naturally present in our environment and used in many field, like aerospace, cosmetology or pharmaceutical industries. Many works show that metals are involved in diverse diseases. However, the way these studies are led, make the comparison of their effects and mechanism of action delicate. In this context, this work studies the cyto-genotoxicity of cadmium, nickel and aluminum on a single cellular model: normal human dermal fibroblasts. Cytotoxicity is first evaluated by the cell bioenergetics study thanks to microcalorimetry technics, and then the effect on cell viability is measured by conventional colorimetric techniques. Genotoxicity is evaluated by specific technics which are comet and micronuclei assays. Furthermore, thermodynamic properties of the interaction between metals and DNA are determined tanks to microcalorimetry measures. Results show that cadmium cytotoxicity is higher than nickel, itself higher than aluminum. Cadmium and nickel are the only ones genotoxic, they mostly induce aneugenic effects. They present an electrostatic anti-cooperative interaction with DNA phosphate groups. If, at pH 7, aluminum does not induce genotoxicity, his interaction is comparable to cadmium and nickel at acidic pH. This unusual result, related to pH value, highlights the importance of the speciation determination when metal effects are studied, as well in vitro as in vivo

Energetic efficiency is important for health (e.g. genesis of obesity in humans), socio-economically important for meat production systems (e.g. feed cost to produce high quality protein) and important for the environment (e.g. use of natural resources and production of green house gases for meat production). Mitochondria are organelles that play an essential role in cellular metabolism and homeostasis related to energy utilization. These processes involve several proteins to ensure continuous availability of energy to the cells. The Shc proteins play a key role in substrate oxidation and energy metabolism. Additionally, the mitochondrial uncoupling proteins (UCPs) participate in physiological processes that may account for variation in energy expenditures in tissues. However, the mechanisms behind energy expenditure in animals are largely unknown. Thus, in order to study the energy metabolism and mitochondria function, studies using a nutritional, biochemical and molecular approaches were conducted with mice and cattle. The purpose of the first study was to determine if Shc proteins influence the metabolic response to acute (5-7 days) feeding of a high fat diet (HFD). To this end, whole animal energy expenditure and substrate oxidation were measured in the Shc knockout (ShcKO) and wild-type (WT) male mice consuming either a control or HFD diet. The activities of enzymes of glycolysis, the citric acid cycle, electron transport chain (ETC), and &beta;-oxidation were investigated in liver and skeletal muscle. The study showed that ShcKO increases (P < 0.05) energy expenditure (EE) adjusted for either total body weight or lean mass. This change in EE could explain the decrease in weight gain observed in ShcKO versus WT mice fed an HFD. Thus, our results indicate that Shc proteins should be considered as potential targets for developing interventions to mitigate weight gain on HFD by stimulating EE. Although decreased levels of Shc proteins influenced the activity of some enzymes in response to high fat feeding, such as increasing the activity of acyl-CoA dehydrogenase, it did not produce concerted changes in enzymes of glycolysis, citric acid cycle or the ETC. However, the physiological significance of these changes in enzyme activities remains to be determined. The purpose of experiment 2 was to study the association among heat production, blood parameters and mitochondrial DNA (mtDNA) copy number in Nellore bulls with high and low residual feed intake (RFI). The RFI values were obtained by regression of dry mater intake (DMI) in relation to average daily gain and mid-test metabolic body weight. Thus, 18 animals (9 in each group) were individually fed in a feedlot for 98 days. The heart rate (HR) of bulls was monitored for 4 consecutive days and used to calculate the estimated heat production (EHP). Electrodes were fitted to bulls with stretch belts and oxygen consumption was obtained using a facemask connected to the gas analyzer and HR was simultaneously measured for 15 minutes period. Daily EHP was calculated multiplying oxygen pulse (O2P) by the average HR, assuming 4.89 kcal/L of O2. Blood parameters such as hematocrit, hemoglobin, and glucose were assayed between 45 and 90 days. Immediately after slaughter, liver, muscle and adipose tissues (subcutaneous and visceral fat) were collected and, subsequently, mtDNA copy number per cell was quantified in tissues by quantitative real-time PCR. The proteome of hepatic tissue and levels of mitochondrial UCPs were also investigated. We found similar EHP and O2 consumption between RFI groups, while low RFI bulls (more efficient in feed conversion) shown lower HR, hemoglobin and hematocrit percentage (P < 0.05), confirming previous data from our group. In addition, 71 protein spots in liver were differentially expressed (P < 0.05) and no differences were detected for UCPs levels between RFI groups. Finally, there was no association between amounts of mtDNA and the RFI phenotypes, suggesting that mitochondrial abundance in liver, muscle, and adipose tissue was similar between efficient and inefficient groups. However, additional studies to confirm this hypothesis are needed. / A eficiência energética é importante para a saúde humana (gênese da obesidade), sistemas de produção de carne (custo dos alimentos para produzir proteínas de alta qualidade) e para o meio ambiente (uso de recursos naturais e mitigação de gases de efeito estufa). As mitocôndrias são organelas que desempenham papel central no metabolismo e homeostase relacionada a utilização da energia. Nas células, diversas proteínas são importantes para melhorar a eficiência energética. Como exemplos, as proteínas de sinalização Shc são fundamentais na oxidação de substratos e metabolismo energético e, nas mitocôndrias, existem as proteínas desacopladoras (UCPs), que participam do gasto energético e produção de calor. Entretanto, os mecanismos que controlam o gasto energético nos animais ainda é bastante desconhecido. Assim, para estudar o metabolismo energético e a função das mitocôndrias foram conduzidos dois estudos utilizando-se estratégias nutricionais, bioquímicas e moleculares com camundongos (1) e bovinos (2). Objetivou-se, no estudo 1, determinar se as proteínas Shc influenciam a resposta metabólica à alimentação contendo dieta rica em gordura (HFD) por 7 dias. Enzimas da via glicolítica, ciclo de Krebs, cadeia transportadora de elétron (CTE) e &beta;-oxidação foram analisadas no fígado e músculo de camundongos com baixa expressão de Shc (knockout ou ShcKO) e comuns (wild-type ou WT) submetidos à uma dieta controle ou à HFD. O gasto energético foi medido por câmara calorimétrica de respiração nos animais. O genótipo ShcKO apresentou maior gasto energético (P < 0.05) ajustado para o peso corporal total ou massa magra. Essa mudança poderia explicar o menor ganho de peso observado no genótipo ShcKO comparado ao WT quando consumindo a HFD. Esses resultados sugerem que as proteínas Shc podem contribuir no desenvolvimento de estratégias para mitigar o ganho de peso. Embora a redução dos níveis de Shc (ShcKO) tenha modificado a atividade de enzimas da &beta;-oxidação em resposta a HFD, tal condição não produziu mudanças semelhantes na via glicolítica, ciclo de Krebs ou CTE. Por isso, mais estudos são necessários para compreender a significância fisiológica dessas alterações. No experimento 2, objetivou-se estudar a associação entre produção de calor, variáveis sanguíneas e número de cópias de DNA mitocondrial (mtDNA) em bovinos Nelore agrupados pelo consumo alimentar residual (CAR). O CAR foi obtido por regressão do consumo de matéria seca em relação ao ganho de peso diário e peso metabólico do teste de desempenho (fase de crescimento). Assim, 18 bovinos (9 alto CAR versus 9 baixo CAR) foram confinados em baias individuais por 98 dias (fase de terminação). Os batimentos cardíacos (BC) dos bovinos foram monitorados por quatro dias consecutivos e, então, utilizados para o cálculo da produção de calor estimada (PCe). O consumo e pulso de oxigênio (O2) foram obtidos por meio de analisador de gás conectado à uma máscara facial, com medição simultânea dos BC por 15 minutos. A PCe diária foi calculada por multiplicação do pulso de O2 pela média dos BC, assumindo-se a constante 4.89 kcal/L de O2. Foram analisadas variáveis sanguíneas como hematócrito, hemoglobina e glicose (alto vs. baixo CAR). Imediatamente após o abate dos animais, amostras de fígado, músculo e tecido adiposo foram coletadas para determinação do mtDNA por PCR em tempo real. Adicionalmente, o proteoma do tecido hepático e os níveis de UCPs nos tecidos foram também investigados. Não houve diferença para PCe e consumo de O2 (P > 0.05) entre os grupos experimentais, entretanto, os animais baixo CAR (mais eficientes em conversão alimentar) demonstraram menor BC, concentração de hemoglobina e percentagem de hematócrito (P < 0.05), confirmando resultados previamente observados em nossos estudos. No fígado, 71 spots proteicos foram diferentes (P < 0.05) entre os grupos alto e baixo CAR, mas nenhuma diferença foi observada para os níveis de UCPs no músculo, fígado ou tecido adiposo. Por fim, não existiu diferença (P > 0.05) entre o número de cópias do mtDNA por célula entre os fenótipos estudados, sugerindo que o número de mitocôndrias e possivelmente a fosforilação oxidativa foi semelhante entre os grupos de animais eficientes e ineficientes. Contudo, são necessários estudos adicionais para confirmar essa hipótese.