Uncoupling proteins: their roles in adaptive thermogenesis and substrate metabolism reconsidered

Mitochondria Need Their Sleep: Redox, Bioenergetics, and Temperature Regulation of Circadian Rhythms and the Role of Cysteine-Mediated Redox Signaling, Uncoupling Proteins, and Substrate Cycles

Although circadian biorhythms of mitochondria and cells are highly conserved and crucial for the well-being of complex animals, there is a paucity of studies on the reciprocal interactions between oxidative stress, redox modifications, metabolism, thermoregulation, and other major oscillatory physiological processes. To address this limitation, we hypothesize that circadian/ultradian interaction of the redoxome, bioenergetics, and temperature signaling strongly determine the differential activities of the sleep–wake cycling of mammalians and birds. Posttranslational modifications of proteins by reversible cysteine oxoforms, S-glutathionylation and S-nitrosylation are shown to play a major role in regulating mitochondrial reactive oxygen species production, protein activity, respiration, and metabolomics. Nuclear DNA repair and cellular protein synthesis are maximized during the wake phase, whereas the redoxome is restored and mitochondrial remodeling is maximized during sleep. Hence, our analysis reveals that wakefulness is more protective and restorative to the nucleus (nucleorestorative), whereas sleep is more protective and restorative to mitochondria (mitorestorative). The “redox–bioenergetics–temperature and differential mitochondrial–nuclear regulatory hypothesis” adds to the understanding of mitochondrial respiratory uncoupling, substrate cycling control and hibernation. Similarly, this hypothesis explains how the oscillatory redox–bioenergetics–temperature–regulated sleep–wake states, when perturbed by mitochondrial interactome disturbances, influence the pathogenesis of aging, cancer, spaceflight health effects, sudden infant death syndrome, and diseases of the metabolism and nervous system.

WITHDRAWN: Mitochondria need their sleep: Sleep-wake cycling and the role of redox, bioenergetics, and temperature regulation, involving cysteine-mediated redox signaling, uncoupling proteins, and substrate cycles

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Positive Effects of a Mediterranean Diet Supplemented with Almonds on Female Adipose Tissue Biology in Severe Obesity

It has been suggested that weight-loss-independent Mediterranean diet benefits on cardiometabolic health and diabetes prevention may be mediated, at least in part, through the modulation of white adipose tissue (WAT) biology. This study aimed to evaluate the short-term effects of a dietary intervention based on the Mediterranean diet supplemented with almonds (MDSA) on the main features of obesity-associated WAT dysfunction. A total of 38 women with obesity were randomly assigned to a 3-month intervention with MDSA versus continuation of their usual dietary pattern. Subcutaneous (SAT) and visceral adipose tissue (VAT) biopsies were obtained before and after the dietary intervention, and at the end of the study period, respectively. MDSA favored the abundance of small adipocytes in WAT. In SAT, the expression of angiogenesis genes increased after MDSA intervention. In VAT, the expression of genes implicated in adipogenesis, angiogenesis, autophagy and fatty acid usage was upregulated. In addition, a higher immunofluorescence staining for PPARG, CD31+ cells and M2-like macrophages and increased ADRB1 and UCP2 protein contents were found compared to controls. Changes in WAT correlated with a significant reduction in circulating inflammatory markers and LDL-cholesterol levels. These results support a protective effect of a Mediterranean diet supplemented with almonds on obesity-related WAT dysfunction.

Bioenergetic Aspects of Mitochondrial Actions of Thyroid Hormones

Much is known, but there is also much more to discover, about the actions that thyroid hormones (TH) exert on metabolism. Indeed, despite the fact that thyroid hormones are recognized as one of the most important regulators of metabolic rate, much remains to be clarified on which mechanisms control/regulate these actions. Given their actions on energy metabolism and that mitochondria are the main cellular site where metabolic transformations take place, these organelles have been the subject of extensive investigations. In relatively recent times, new knowledge concerning both thyroid hormones (such as the mechanisms of action, the existence of metabolically active TH derivatives) and the mechanisms of energy transduction such as (among others) dynamics, respiratory chain organization in supercomplexes and cristes organization, have opened new pathways of investigation in the field of the control of energy metabolism and of the mechanisms of action of TH at cellular level. In this review, we highlight the knowledge and approaches about the complex relationship between TH, including some of their derivatives, and the mitochondrial respiratory chain.

Dynamic changes in energy expenditure in response to underfeeding: a review

The observation that 64% of English adults are overweight or obese despite a rising prevalence in weight-loss attempts suggests our understanding of energy balance is fundamentally flawed. Weight-loss is induced through a negative energy balance; however, we typically view weight change as a static function, in that energy intake and energy expenditure are independent variables, resulting in a fixed rate of weight-loss assuming a constant energy deficit. Such static modelling provides the basis for the clinical assumption that a 14644 kJ (3500 kcal) deficit translates to a 1 lb weight-loss. However, this '3500 kcal (14644 kJ) rule' is consistently shown to significantly overestimate weight-loss. Static modelling disregards obligatory changes in energy expenditure associated with the loss of metabolically active tissue, i.e. skeletal muscle. Additionally, it disregards the presence of adaptive thermogenesis, the underfeeding-associated fall in resting energy expenditure beyond that caused by loss of fat-free mass. This metabolic manipulation of energy expenditure is observed from the onset of energy restriction to maintain weight at a genetically pre-determined set point. As a result, the observed magnitude of weight-loss is disproportionally less, followed by earlier weight plateau, despite strict compliance to a dietary intervention. By simulating dynamic changes in energy expenditure associated with underfeeding, mathematical modelling may provide a more accurate method of weight-loss prediction. However, accuracy at an individual level is limited due to difficulty estimating energy requirements, physical activity and dietary intake in free-living individuals. In the present paper, we aim to outline the contribution of dynamic changes in energy expenditure to weight-loss resistance and weight plateau.

Therapeutic potential of mitochondrial uncouplers for the treatment of metabolic associated fatty liver disease and NASH

Background

Mitochondrial uncouplers shuttle protons across the inner mitochondrial membrane via a pathway that is independent of adenosine triphosphate (ATP) synthase, thereby uncoupling nutrient oxidation from ATP production and dissipating the proton gradient as heat. While initial toxicity concerns hindered their therapeutic development in the early 1930s, there has been increased interest in exploring the therapeutic potential of mitochondrial uncouplers for the treatment of metabolic diseases.

Scope of review

In this review, we cover recent advances in the mechanisms by which mitochondrial uncouplers regulate biological processes and disease, with a particular focus on metabolic associated fatty liver disease (MAFLD), nonalcoholic hepatosteatosis (NASH), insulin resistance, and type 2 diabetes (T2D). We also discuss the challenges that remain to be addressed before synthetic and natural mitochondrial uncouplers can successfully enter the clinic.

Major conclusions

Rodent and non-human primate studies suggest that a myriad of small molecule mitochondrial uncouplers can safely reverse MAFLD/NASH with a wide therapeutic index. Despite this, further characterization of the tissue- and cell-specific effects of mitochondrial uncouplers is needed. We propose targeting the dosing of mitochondrial uncouplers to specific tissues such as the liver and/or developing molecules with self-limiting properties to induce a subtle and sustained increase in mitochondrial inefficiency, thereby avoiding systemic toxicity concerns.

Peroxisome Proliferator-Activated Receptors and Caloric Restriction-Common Pathways Affecting Metabolism, Health, and Longevity

Caloric restriction (CR) is a traditional but scientifically verified approach to promoting health and increasing lifespan. CR exerts its effects through multiple molecular pathways that trigger major metabolic adaptations. It influences key nutrient and energy-sensing pathways including mammalian target of rapamycin, Sirtuin 1, AMP-activated protein kinase, and insulin signaling, ultimately resulting in reductions in basic metabolic rate, inflammation, and oxidative stress, as well as increased autophagy and mitochondrial efficiency. CR shares multiple overlapping pathways with peroxisome proliferator-activated receptors (PPARs), particularly in energy metabolism and inflammation. Consequently, several lines of evidence suggest that PPARs might be indispensable for beneficial outcomes related to CR. In this review, we present the available evidence for the interconnection between CR and PPARs, highlighting their shared pathways and analyzing their interaction. We also discuss the possible contributions of PPARs to the effects of CR on whole organism outcomes.

Nutritional management of a kitten with thermal burns and septicaemia

Case summary

A 3-month-old entire female British Shorthair cat presented for further management of thermal burns after falling into a bath of scalding water. On presentation to the primary care clinician the kitten was obtunded, markedly painful and relatively bradycardic, consistent with a state of shock. The haircoat was wet, with erythematous skin and sloughing from the digital pads and anal mucosa. The primary care clinician administered opioid analgesia, sedation, antibiotics and started intravenous (IV) fluid therapy prior to referral. On arrival to the referral hospital the kitten was obtunded with respiratory and cardiovascular stability but was overtly painful and resistant to handling. The kitten required intensive management with IV and regional analgesia, IV broad-spectrum antibiosis, IV fluid therapy, enteral nutrition and wound management, including surgical debridement and topical antibiotic therapy. Septicaemia developed during the hospitalisation. Multidrug-resistant Escherichia coli and Pseudomonas aeruginosa were cultured, and antibiosis was escalated to IV imipenem. Acute respiratory distress syndrome was suspected following the development of dyspnoea. Early enteral nutrition within 24 h of admission was initiated using an oesophageal feeding tube and a veterinary therapeutic liquid diet. Over the ensuing 72 h the kitten started voluntary intake of food alongside oesophageal tube feeds. The kitten experienced continued weight loss despite the provision of nutritional support to meet, and then later exceed, the estimated resting energy requirements. Caloric intake was gradually increased to a total of 438% of the calculated resting energy requirement using the most recent daily body weight, eventually resulting in stabilisation of weight loss and weight gain.

Relevance and novel information

There is limited published information on the nutritional management of veterinary patients with thermal burn injury. Hypermetabolic states related to burn injuries are induced and maintained by complex interactions of catecholamines, stress hormones and inflammatory cytokines on proteolysis, lipolysis and glycogenolysis. Secondary infections are common following burn injury and the subsequent proinflammatory state perpetuates hypermetabolism and catabolism. These states present a challenge in both predicting and providing adequate nutrition, particularly in a paediatric septic patient. This subset of patients should be monitored closely during hospitalisation to ensure body weight and condition are maintained (while taking into consideration hydration status), and caloric intake is adjusted accordingly to meet nutritional support goals. Extensive research exists regarding the nutritional requirements and metabolic derangements of people with thermal burns. However, the importance of maintaining body weight and body condition in veterinary burn patients, and the association between nutritional support and reduced morbidity and mortality, has not been investigated and remains to be elucidated.

Danggui Buxue Tang, a Chinese Herbal Decoction Containing Astragali Radix and Angelicae Sinensis Radix, Modulates Mitochondrial Bioenergetics in Cultured Cardiomyoblasts

Danggui Buxue Tang (DBT) is an ancient herbal mixture containing Astragali Radix and Angelicae Sinensis Radix, and which are commonly consumed for "qi-invigorating" (i.e., stimulating vital energy/energy metabolism) as traditional Chinese medicine (TCM). The pharmacological activities of DBT in anti-oxidation, estrogenic, hematopoietic, and immunogenic have been reported; however, the role of DBT in cellular energy metabolism has not been determined. Here, we employed an extracellular flux analyzer to evaluate the mitochondrial respiration of cultured H9C2 cardiomyoblasts in present of DBT. The herbal extract of DBT was qualified chemically for the major ingredients, i.e. astragaloside, calycosin, formononetin, Z-ligustilide, and ferulic acid. The anti-oxidant activities of DBT, as well as its major ingredients, were determined by Folin-Ciocalteu assay, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, and protective effect in tert-butyl hydroperoxide (tBHP)-treated cultured cardiomyoblasts. In addition, a real-time oxygen consumption rate (OCR) in herbal extract-treated cultured cardiomyoblasts was revealed by using a Seahorse extracellular flux analyzer. In addition, the transcript expressions of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PCG-1α) and other genes relating to mitochondria biogenesis were determined in cardiomyoblasts under different herbal treatments. DBT possessed the strongest anti-oxidant activity and protective effects on the oxidatively stressed cardiomyoblasts. By revealing the OCR in mitochondria, the health state of cultured cardiomyoblasts under DBT was improved via increase of basal respiration, proton leak, non-mitochondria, and adenosine triphosphate (ATP) production. Furthermore, the transcriptional activities of genes responsible for mitochondrial biogenesis and DNA replication were stimulated by application of DBT in cultures.

Reduced Skeletal Muscle Protein Turnover and Thyroid Hormone Metabolism in Adaptive Thermogenesis That Facilitates Body Fat Recovery During Weight Regain

Objective: The recovery of body composition after weight loss is characterized by an accelerated rate of fat recovery (preferential catch-up fat) resulting partly from an adaptive suppression of thermogenesis. Although the skeletal muscle has been implicated as an effector site for such thrifty (energy conservation) metabolism driving catch-up fat, the underlying mechanisms remain to be elucidated. We test here the hypothesis that this thrifty metabolism driving catch-up fat could reside in a reduced rate of protein turnover (an energetically costly "futile" cycle) and in altered local thyroid hormone metabolism in skeletal muscle. Methods: Using a validated rat model of semistarvation-refeeding in which catch-up fat is driven solely by suppressed thermogenesis, we measured after 1 week of refeeding in refed and control animals the following: (i) in-vivo rates of protein synthesis in hindlimb skeletal muscles using the flooding dose technique of ¹³C-labeled valine incorporation in muscle protein, (ii) ex-vivo muscle assay of net formation of thyroid hormone tri-iodothyronine (T3) from precursor hormone thyroxine (T4), and (iii) protein expression of skeletal muscle deiodinases (type 1, 2, and 3). Results: We show that after 1 week of calorie-controlled refeeding, the fractional protein synthesis rate was lower in skeletal muscles of refed animals than in controls (by 30-35%, p < 0.01) despite no between-group differences in the rate of skeletal muscle growth or whole-body protein deposition-thereby underscoring concomitant reductions in both protein synthesis and protein degradation rates in skeletal muscles of refed animals compared to controls. These differences in skeletal muscle protein turnover during catch-up fat were found to be independent of muscle type and fiber composition, and were associated with a slower net formation of muscle T3 from precursor hormone T4, together with increases in muscle protein expression of deiodinases which convert T4 and T3 to inactive forms. Conclusions: These results suggest that diminished skeletal muscle protein turnover, together with altered local muscle metabolism of thyroid hormones leading to diminished intracellular T3 availability, are features of the thrifty metabolism that drives the rapid restoration of the fat reserves during weight regain after caloric restriction.

Impact of Proestrus on Gene Expression in the Medial Preoptic Area of Mice

The antero-ventral periventricular zone (AVPV) and medial preoptic area (MPOA) have been recognized as gonadal hormone receptive regions of the rodent brain that-via wiring to gonadotropin-releasing hormone (GnRH) neurons-contribute to orchestration of the preovulatory GnRH surge. We hypothesized that neural genes regulating the induction of GnRH surge show altered expression in proestrus. Therefore, we compared the expression of 48 genes obtained from intact proestrous and metestrous mice, respectively, by quantitative real-time PCR (qPCR) method. Differential expression of 24 genes reached significance (p < 0.05). Genes upregulated in proestrus encoded neuropeptides (kisspeptin (KP), galanin (GAL), neurotensin (NT), cholecystokinin (CCK)), hormone receptors (growth hormone secretagogue receptor, μ-opioid receptor), gonadal steroid receptors (estrogen receptor alpha (ERα), progesterone receptor (PR), androgen receptor (AR)), solute carrier family proteins (vesicular glutamate transporter 2, vesicular monoamine transporter 2), proteins of transmitter synthesis (tyrosine hydroxylase (TH)) and transmitter receptor subunit (AMPA4), and other proteins (uncoupling protein 2, nuclear receptor related 1 protein). Proestrus evoked a marked downregulation of genes coding for adenosine A2a receptor, vesicular gamma-aminobutyric acid (GABA) transporter, 4-aminobutyrate aminotransferase, tachykinin precursor 1, NT receptor 3, arginine vasopressin receptor 1A, cannabinoid receptor 1, ephrin receptor A3 and aldehyde dehydrogenase 1 family, member L1. Immunocytochemistry was used to visualize the proteins encoded by Kiss1, Gal, Cck and Th genes in neuronal subsets of the AVPV/MPOA of the proestrous mice. The results indicate that gene expression of the AVPV/MPOA is significantly modified at late proestrus including genes that code for neuropeptides, gonadal steroid hormone receptors and synaptic vesicle transporters. These events support cellular and neuronal network requirements of the positive estradiol feedback action and contribute to preparation of the GnRH neuron system for the pre-ovulatory surge release.

Influence of expression of UCP3, PLIN1 and PPARG2 on the oxidation of substrates after hypocaloric dietary intervention

BACKGROUND & AIMS

In addition to environmental and psychosocial factors, it is known that genetic factors can also influence the regulation of energy metabolism, body composition and determination of excess weight. The objective of this study was to evaluate the influence of UCP3, PLIN1 and PPARG2 genes on the substrates oxidation in women with grade III obesity after hypocaloric dietary intervention.

SUBJECTS/METHODS

This is a longitudinal study with 21 women, divided into two groups: Intervention Group (G1): 11 obese women (Body Mass Index (BMI) ≥40 kg/m²), and Control Group (G2): 10 eutrophic women (BMI between 18.5 kg/m² and 24.9 kg/m²). Weight (kg), height (m), BMI (kg/m²), substrate oxidation (by Indirect Calorimetry) and abdominal subcutaneous adipose tissue were collected before and after the intervention. For the dietary intervention, the patients were hospitalized for 6 weeks receiving 1200 kcal/day.

RESULTS

There was a significant weight loss (8.4 ± 4.3 kg - 5.2 ± 1.8%) and reduction of UCP3 expression after hypocaloric dietary intervention. There was a positive correlation between carbohydrate oxidation and UCP3 (r = 0.609; p = 0.04), PLIN1 (r = 0.882; p = 0.00) and PPARG2 (r = 0.791; p = 0.00) expression before dietary intervention and with UCP3 (r = 0.682; p = 0.02) and PLIN1 (r = 0.745; p = 0.00) genes after 6 weeks of intervention. There was a negative correlation between lipid oxidation and PLIN1 (r = -0.755; p = 0.00) and PPARG2 (r = 0.664; p = 0.02) expression before dietary intervention and negative correlation with PLIN1 (r = 0.730; p = 0.02) expression after 6 weeks of hypocaloric diet.

CONCLUSION

Hypocaloric diet reduces UCP3 expression in individuals with obesity and the UCP3, PLIN1 and PPARG2 expression correlate positively with carbohydrate oxidation and negatively with lipid oxidation.

Beneficial effects of metformin on energy metabolism and visceral fat volume through a possible mechanism of fatty acid oxidation in human subjects and rats

OBJECTIVE

Metformin is known to have a beneficial effect on body weight and body composition, although the precise mechanism has not been elucidated yet. The aim of this study is to investigate the effects of metformin on energy metabolism and anthropometric factors in both human subjects and rats.

METHODS

In human studies, metformin (1500mg/day) was administered to 23 healthy subjects and 18 patients with type 2 diabetes for 2 weeks. Metabolic parameters and energy metabolism were measured during a meal tolerance test in the morning before and after the treatment of metformin. In animal studies, 13 weeks old SD rats were fed 25-26 g of standard chow only during 12-hours dark phase with either treated by metformin (2.5mg/ml in drinking water) or not for 2 weeks, and metabolic parameters, anthropometric factors and energy metabolism together with expressions related to fat oxidation and adaptive thermogenesis were measured either in fasting or post-prandial state at 15 weeks old.

RESULTS

Post-prandial plasma lactate concentration was significantly increased after the metformin treatment in both healthy subjects and diabetic patients. Although energy expenditure (EE) did not change, baseline respiratory quotient (RQ) was significantly decreased and post-prandial RQ was significantly increased vice versa following the metformin treatment in both groups. By the administration of metformin to SD rats for 2 weeks, plasma levels of lactate and pyruvate were significantly increased in both fasting and post-prandial states. RQ during a fasting state was significantly decreased in metformin-treated rats compared to controls with no effect on EE. Metformin treatment brought about a significant reduction of visceral fat mass compared to controls accompanied by an up-regulation of fat oxidation-related enzyme in the liver, UCP-1 in the brown adipose tissue and UCP-3 in the skeletal muscle.

CONCLUSION

From the results obtained, beneficial effects of metformin on visceral fat reduction has been demonstrated probably through a mechanism for a potential shift of fuel resource into fat oxidation and an upregulation of adaptive thermogenesis independent of an anorexigenic effect of this drug.

Expression of Lung Uncoupling Protein-2 mRNA is Modulated Developmentally and by Caloric Intake

Lung expresses a high concentration of uncoupling protein-2 (UCP-2) mRNA, but neither its pulmonary regulation nor function is known. We measured lung UCP-2 mRNA expression in two animal models: in neonatal rats when both the metabolic rate, as measured by oxygen consumption, and levels of serum free fatty acids (FFAs) increase and in adult mice during decreased food intake, when levels of serum FFAs increase but the metabolic rate decreases. In rat lung, the concentration of UCP-2 mRNA was low and unchanged during late gestation, increased approximately twofold within 6 hrs after birth, and, compared with late gestation, remained approximately threefold higher from day 1 to adulthood. The early postnatal rise in the lung UCP-2 mRNA concentration was partially blocked by an antithyroid drug and was increased by treatment with triiodothyronine. Unlike lung, heart UCP-2 mRNA levels were lower during adulthood than at day 15. In adult mice, lung UCP-2 mRNA concentrations increased approximately fivefold within 12 hrs of 67% calorie restriction (CR), remained elevated during 2 weeks of CR, fell to control levels within 24 hrs of refeeding (CR-RF), and positively correlated with serum FFA concentrations. Heart UCP-2 expression during CR and CR-RF was similar to that of lung; liver UCP-2 mRNA levels were slightly lower during CR and returned to control levels during CR-RF. These data suggest that the regulation of UCP-2 is at least partly tissue-specific and that, in the adult mouse, lung UCP-2 is regulated not by oxygen consumption but by FFAs. Moreover, lung UCP-2 mRNA levels in mice fed ad libitum was increased by the intraperitoneal administration of Intralipid, a 20% fat emulsion. On the basis of these data in adult mice, together with the findings of others that levels of FFAs increase by 2 hrs after birth, we propose lung UCP-2 is regulated by FFA.

Mitochondrial Actions of Thyroid Hormone

The hypermetabolic effects of thyroid hormones (THs), the major endocrine regulators of metabolic rate, are widely recognized. Although, the cellular mechanisms underlying these effects have been extensively investigated, much has yet to be learned about how TH regulates diverse cellular functions. THs have a profound impact on mitochondria, the organelles responsible for the majority of cellular energy production, and several studies have been devoted to understand the respective importance of the nuclear and mitochondrial pathways for organelle activity. During the last decades, several new aspects of both THs (i.e., metabolism, transport, mechanisms of action, and the existence of metabolically active TH derivatives) and mitochondria (i.e., dynamics, respiratory chain organization in supercomplexes, and the discovery of uncoupling proteins other than uncoupling protein 1) have emerged, thus opening new perspectives to the investigation of the complex relationship between thyroid and the mitochondrial compartment. In this review, in the light of an historical background, we attempt to point out the present findings regarding thyroid physiology and the emerging recognition that mitochondrial dynamics as well as the arrangement of the electron transport chain in mitochondrial cristae contribute to the mitochondrial activity. We unravel the genomic and nongenomic mechanisms so far studied as well as the effects of THs on mitochondrial energetics and, principally, uncoupling of oxidative phosphorylation via various mechanisms involving uncoupling proteins. The emergence of new approaches to the question as to what extent and how the action of TH can affect mitochondria is highlighted. © 2016 American Physiological Society. Compr Physiol 6:1591-1607, 2016.

Metabolic changes over the course of aging in a mouse model of tau deposition

Weight loss and food intake disturbances that often precede cognitive decline and diagnosis have been extensively reported in Alzheimer's disease patients. Previously, we observed that transgenic mice overexpressing tau seemed to eat more food yet weigh less than nontransgenic littermates. Thus, the present longitudinal study measured the time course of changes in metabolic state over the lifespan of the tau depositing Tg4510 mouse model of tau deposition. Although body weight was comparable to nontransgenic littermates at 2 months of age, Tg4510 mice weighed less at older ages. This was accompanied by the accumulation of tau pathology and by dramatically increased activity in all phases of the 24-hour cycle. Resting metabolic rate was also increased at 7 months of age. At 12 months near the end of the Tg4510 lifespan, there was a wasting phase, with a considerable decrease of resting metabolic rate, although hyperactivity was maintained. These diverse changes in metabolism in a mouse model of tau deposition are discussed in the context of known changes in energy metabolism in Alzheimer's disease.

UCP1 and UCP3 Expression Is Associated with Lipid and Carbohydrate Oxidation and Body Composition

BACKGROUND/OBJECTIVE

Uncoupling proteins (UCPs) are located in the inner membrane of mitochondria. These proteins participate in thermogenesis and energy expenditure. This study aimed to evaluate how UCP1 and UCP3 expression influences substrate oxidation and elicits possible changes in body composition in patients submitted to bariatric surgery.

SUBJECTS/METHODS

This is a longitudinal study comprising 13 women with obesity grade III that underwent bariatric surgery and 10 healthy weight individuals (control group). Body composition was assessed by bioelectrical impedance. Carbohydrate and fat oxidation was determined by indirect calorimetry. Subcutaneous adipose tissue was collected for gene expression analysis. QPCR was used to evaluate UCP1 and UCP3 expression.

RESULTS

Obese patients and the control group differed significantly in terms of lipid and carbohydrate oxidation. Six months after bariatric surgery, the differences disappeared. Lipid oxidation correlated with the percentage of fat mass in the postoperative period. Multiple linear regression analysis showed that the UCP1 and UCP3 genes contributed to lipid and carbohydrate oxidation. Additionally, UCP3 expression was associated with BMI, percentage of lean body mass, and percentage of mass in the postoperative period.

CONCLUSIONS

UCP1 and UCP3 expression is associated with lipid and carbohydrate oxidation in patients submitted to bariatric surgery. In addition, UCP3 participates in body composition modulation six months postoperatively.

Reactive oxygen species, heat stress and oxidative-induced mitochondrial damage. A review

In recent years there has been enormous interest in researching oxidative stress. Reactive oxygen species (ROS) are derived from the metabolism of oxygen as by-products of cell respiration, and are continuously produced in all aerobic organisms. Oxidative stress occurs as a consequence of an imbalance between ROS production and the available antioxidant defence against them. Nowadays, a variety of diseases and degenerative processes such as cancer, Alzheimer's and autoimmune diseases are mediated by oxidative stress. Heat stress was suggested to be an environmental factor responsible for stimulating ROS production because of similarities in responses observed following heat stress compared with that occurring following exposure to oxidative stress. This manuscript describes the main mitochondrial sources of ROS and the antioxidant defences involved to prevent oxidative damage in all the mitochondrial compartments. It also deals with discussions concerning the cytotoxic effect of heat stress, mitochondrial heat-induced alterations, as well as heat shock protein (HSP) expression as a defence mechanism.

Perspectives on mitochondrial uncoupling proteins-mediated neuroprotection

The integrity of mitochondrial function is essential to cell life. It follows that disturbances of mitochondrial function will lead to disruption of cell function, expressed as disease or even death. Considering that neuronal uncoupling proteins (UCPs) decrease reactive oxygen species (ROS) production at the expense of energy production, it is important to understand the underlying mechanisms by which UCPs control the balance between the production of adenosine triphosphate (ATP) and ROS in the context of normal physiological activity and in pathological conditions. Here we review the current understanding of neuronal UCPs-mediated respiratory uncoupling process by performing a survey in their physiology and regulation. The latest findings regarding neuronal UCPs physiological roles and their involvement and interest as potential targets for therapeutic intervention in brain diseases will also be exploited.

The role of thyroid hormones as inductors of oxidative stress and neurodegeneration

Reactive oxygen species (ROS) are oxidizing agents amply implicated in tissue damage. ROS production is inevitably linked to ATP synthesis in most cells, and the rate of production is related to the rate of cell respiration. Multiple antioxidant mechanisms limit ROS dispersion and interaction with cell components, but, when the balance between ROS production and scavenging is lost, oxidative damage develops. Many traits of aging are related to oxidative damage by ROS, including neurodegenerative diseases. Thyroid hormones (THs) are a major factor controlling metabolic and respiratory rates in virtually all cell types in mammals. The general metabolic effect of THs is a relative acceleration of the basal metabolism that includes an increase of the rate of both catabolic and anabolic reactions. THs are related to oxidative stress not only by their stimulation of metabolism but also by their effects on antioxidant mechanisms. Thyroid dysfunction increases with age, so changes in THs levels in the elderly could be a factor affecting the development of neurodegenerative diseases. However, the relationship is not always clear. In this review, we analyze the participation of thyroid hormones on ROS production and oxidative stress, and the way the changes in thyroid status in aging are involved in neurodegenerative diseases.

Transcriptomic indices of fast and slow disease progression in two mouse models of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is heterogeneous with high variability in the speed of progression even in cases with a defined genetic cause such as superoxide dismutase 1 (SOD1) mutations. We reported that SOD1(G93A) mice on distinct genetic backgrounds (C57 and 129Sv) show consistent phenotypic differences in speed of disease progression and life-span that are not explained by differences in human SOD1 transgene copy number or the burden of mutant SOD1 protein within the nervous system. We aimed to compare the gene expression profiles of motor neurons from these two SOD1(G93A) mouse strains to discover the molecular mechanisms contributing to the distinct phenotypes and to identify factors underlying fast and slow disease progression. Lumbar spinal motor neurons from the two SOD1(G93A) mouse strains were isolated by laser capture microdissection and transcriptome analysis was conducted at four stages of disease. We identified marked differences in the motor neuron transcriptome between the two mice strains at disease onset, with a dramatic reduction of gene expression in the rapidly progressive (129Sv-SOD1(G93A)) compared with the slowly progressing mutant SOD1 mice (C57-SOD1(G93A)) (1276 versus 346; Q-value ≤ 0.01). Gene ontology pathway analysis of the transcriptional profile from 129Sv-SOD1(G93A) mice showed marked downregulation of specific pathways involved in mitochondrial function, as well as predicted deficiencies in protein degradation and axonal transport mechanisms. In contrast, the transcriptional profile from C57-SOD1(G93A) mice with the more benign disease course, revealed strong gene enrichment relating to immune system processes compared with 129Sv-SOD1(G93A) mice. Motor neurons from the more benign mutant strain demonstrated striking complement activation, over-expressing genes normally involved in immune cell function. We validated through immunohistochemistry increased expression of the C3 complement subunit and major histocompatibility complex I within motor neurons. In addition, we demonstrated that motor neurons from the slowly progressing mice activate a series of genes with neuroprotective properties such as angiogenin and the nuclear factor (erythroid-derived 2)-like 2 transcriptional regulator. In contrast, the faster progressing mice show dramatically reduced expression at disease onset of cell pathways involved in neuroprotection. This study highlights a set of key gene and molecular pathway indices of fast or slow disease progression which may prove useful in identifying potential disease modifiers responsible for the heterogeneity of human amyotrophic lateral sclerosis and which may represent valid therapeutic targets for ameliorating the disease course in humans.

Determinants of intra-specific variation in basal metabolic rate

Basal metabolic rate (BMR) provides a widely accepted benchmark of metabolic expenditure for endotherms under laboratory and natural conditions. While most studies examining BMR have concentrated on inter-specific variation, relatively less attention has been paid to the determinants of within-species variation. Even fewer studies have analysed the determinants of within-species BMR variation corrected for the strong influence of body mass by appropriate means (e.g. ANCOVA). Here, we review recent advancements in studies on the quantitative genetics of BMR and organ mass variation, along with their molecular genetics. Next, we decompose BMR variation at the organ, tissue and molecular level. We conclude that within-species variation in BMR and its components have a clear genetic signature, and are functionally linked to key metabolic process at all levels of biological organization. We highlight the need to integrate molecular genetics with conventional metabolic field studies to reveal the adaptive significance of metabolic variation. Since comparing gene expressions inter-specifically is problematic, within-species studies are more likely to inform us about the genetic underpinnings of BMR. We also urge for better integration of animal and medical research on BMR; the latter is quickly advancing thanks to the application of imaging technologies and ‘omics’ studies. We also suggest that much insight on the biochemical and molecular underpinnings of BMR variation can be gained from integrating studies on the mammalian target of rapamycin (mTOR), which appears to be the major regulatory pathway influencing the key molecular components of BMR.

Uncoupling protein 2 regulates glucagon-like peptide-1 secretion in L-cells

AIM: To investigate whether uncoupling protein 2 (UCP2) affects oleic acid-induced secretion of glucagon-like peptide-1 (GLP-1) in L-cells.

METHODS: mRNA and protein expression of UCP2 were analyzed in human NCI-H716 cells, which serve as a model for enteroendocrine L-cells, by quantitative reverse transcription-polymerase chain reaction and Western blotting before and after treatment with oleic acid. Localization of UCP2 and GLP-1 in NCI-H716 cells was assessed by immunofluorescence labeling. NCI-H716 cells were transiently transfected with a small interfering RNA (siRNA) that targets UCP2 (siUCP2) or with a non-specific siRNA using Lipofectamine 2000. The concentrations of bioactive GLP-1 in the medium were measured by enzyme linked immunosorbent assay.

RESULTS: Both GLP-1 and UCP2 granules were expressed mainly in the cytoplasm of NCI-H716 cells. NCI-H716 cells that secreted GLP-1 also expressed UCP2. Time-course experiments revealed that release of GLP-1 from NCI-H716 cells into the medium reached a maximum at 120 min and remained stable until at least 180 min after treatment with oleic acid (the level of GLP-1 increased about 2.3-fold as compared with the level of GLP-1 in the control cells, P < 0.05). In an experiment to determine dose dependence, stimulation of NCI-H716 cells with ≤ 8 mmol oleic acid led to a concentration-dependent release of GLP-1 into the medium; 10 mmol oleic acid diminished the release of GLP-1. Furthermore, GLP-1 secretion induced by oleic acid from NCI-H716 cells that were transfected with siUCP2 decreased to 41.8%, as compared with NCI-H716 cells that were transfected with a non-specific siRNA (P < 0.01).

CONCLUSION: UCP2 affected GLP-1 secretion induced by oleic acid. UCP2 plays an important role in L-cell secretion that is induced by free fatty acids.

Activation of the AMP-activated protein kinase by eicosapentaenoic acid (EPA, 20:5 n-3) improves endothelial function in vivo

The aim of the present study was to test the hypothesis that the cardiovascular-protective effects of eicosapentaenoic acid (EPA) may be due, in part, to its ability to stimulate the AMP-activated protein kinase (AMPK)-induced endothelial nitric oxide synthase (eNOS) activation. The role of AMPK in EPA-induced eNOS phosphorylation was investigated in bovine aortic endothelial cells (BAEC), in mice deficient of either AMPKα1 or AMPKα2, in eNOS knockout (KO) mice, or in Apo-E/AMPKα1 dual KO mice. EPA-treatment of BAEC increased both AMPK-Thr172 phosphorylation and AMPK activity, which was accompanied by increased eNOS phosphorylation, NO release, and upregulation of mitochondrial uncoupling protein-2 (UCP-2). Pharmacologic or genetic inhibition of AMPK abolished EPA-enhanced NO release and eNOS phosphorylation in HUVEC. This effect of EPA was absent in the aortas isolated from either eNOS KO mice or AMPKα1 KO mice fed a high-fat, high-cholesterol (HFHC) diet. EPA via upregulation of UCP-2 activates AMPKα1 resulting in increased eNOS phosphorylation and consequent improvement of endothelial function in vivo.

The effects of a cafeteria diet on insulin production and clearance in rats

The aim of the present study was to determine the effects of a cafeteria diet on the function and apoptosis of the pancreas, and the activity and expression of the insulin-degrading enzyme (IDE). Female Wistar rats were fed either with a cafeteria diet or a control diet for 17 weeks, and blood and tissues were then collected for analysis. The cafeteria diet-treated rats had higher plasma insulin and C-peptide levels (P<0·05), showing increased insulin secretion by the pancreas. Insulin protein and gene expression levels were higher in the pancreas of obese rats, as was its transcriptional controller, pancreatic duodenal homeobox 1 (P<0·05). Feeding a cafeteria diet down-regulated the gene expression of the anti-apoptotic marker B-cell/lymphoma 2 (BCL2), and up-regulated the protein levels of BCL2-associated X protein, a pro-apoptotic marker (P<0·05). The cafeteria diet caused lipid accumulation in the pancreas and modified the expression of key genes that control lipid metabolism. To assay whether insulin clearance was also modified, we checked the activity of the IDE, one of the enzymes responsible for insulin clearance. We found increased liver IDE activity (P<0·05) in the cafeteria diet-fed animals, which could, in part, be due to an up-regulation of its gene expression. Conversely, IDE gene expression was unmodified in the kidney and adipose tissue; although when the adipose tissue weight was considered, the insulin clearance potential was higher in the cafeteria diet-treated rats. In conclusion, treatment with a cafeteria diet for 17 weeks in rats mimicked a pre-diabetic state, with ectopic lipid accumulation in the pancreas, and increased the IDE-mediated insulin clearance capability.

Bofutsushosan, an Oriental Herbal Medicine, Attenuates the Weight Gain of White Adipose Tissue and the Increased Size of Adipocytes Associated with the Increase in Their Expression of Uncoupling Protein 1 in High-Fat Diet-Fed Male KK/Ta mice

Bofutsushosan (BOF), an oriental herbal medicine, has been used as an anti-obesity drug in overweight patients. In the present study, to evaluate the anti-obesity and anti-diabetic effects of BOF, we investigated the effects of BOF on the white adipose tissue (WAT) weight, the size of adipocytes, adiponectin expression, and oral glucose tolerance test results in high-fat diet-fed male KK/Ta mice. In addition, the mRNA expression levels of uncoupling protein 1 (UCP1) and UCP2 mRNA in WAT and brown adipose tissue (BAT) were measured. 6-week-old KK/Ta mice were divided into four groups and fed a purified powdered basal diet (the BD group), a purified high-fat (HF) powdered diet containing suet powder at 37.5 g/100 g diet (the HF group), a high-fat diet plus 1.0% bofutsushosan (BOF) treatment (the HF + BOF group), or a high-fat diet plus 1.0% daisaikoto (DAI) treatment (the HF + DAI group) for 4 weeks. The weight of WAT and the size of adipocytes were increased in the HF group compared with those in the BD group, and these increases in the HF group were significantly inhibited in the HF + BOF group, but not affected in the HF + DAI group. There were no statistically significant differences in plasma levels and tissue mRNA levels of adiponectin among the four groups. There were no significant differences in UCP1 mRNA expression of BAT among the four groups. The expression of UCP1 mRNA in WAT was found in the HF + BOF group, but little expression was seen in the WAT of the BD, HF, or HF + DAI groups. The elevated plasma glucose levels and responses after the glucose loading in the HF group tended to decrease in the HF + BOF group. These results suggest that BOF decreases the weight and size gains of WAT along with up-regulating UCP1 mRNA in WAT in high-fat diet-fed mice.

Absence of mitochondrial uncoupling protein 3: effect on thymus and spleen in the fed and fasted mice

Mitochondrial uncoupling protein 3 (UCP3) is constitutively expressed in mitochondria from thymus and spleen of mice, and confocal microscopy has been used to visualize UCP3 in situ in mouse thymocytes. UCP3 is present in mitochondria of thymus and spleen up to at least 16 weeks after birth, but levels decrease by a half in thymus and a fifth in spleen after three weeks, probably reflecting the suckling to weaning transition. UCP3 protein levels increase approximately 3-fold in thymus on starvation, but expression levels in spleen were unaffected by starvation. Lack of UCP3 had little effect on thymus mass or thymocyte number. However, lack of UCP3 affected spleen mass and splenocyte number (in the fasted state) and results in reduced CD4+ single positive cell numbers and reduced double negative cells in the thymus, but as a 2-fold increase in the proportion of CD4(+), CD8(+) and DP cells in spleen. Starvation attenuates these proportionate differences in the spleen. A lack of UCP3 had no apparent effect on basal oxygen consumption of thymocytes or splenocytes or on oxygen consumption due to mitochondrial proton leak. Splenocytes from UCP3 knock-out mice are also more resistant to apoptosis than those from wild-type mice. Overall we can conclude that UCP3 affects thymocyte and spleen cell profiles in the fed and fasted states.

The allenic carotenoid fucoxanthin, a novel marine nutraceutical from brown seaweeds

Obesity and type 2 diabetes are pathologies with rapidly growing prevalence throughout the world. A few molecular targets offer the most hope for anti-obesity and anti-diabetic therapeutics. One of the keys to success will be the induction of uncoupling protein 1 (UCP1) in abdominal white adipose tissue (WAT) and the regulation of cytokine secretions from both abdominal adipose cells and macrophage cells infiltrated into adipose tissue. Anti-obesity and anti-diabetic effects of fucoxanthin, a characteristic carotenoid found in brown seaweeds, have been reported. Nutrigenomic studies reveal that fucoxanthin induces UCP1 in abdominal WAT mitochondria, leading to the oxidation of fatty acids and heat production in WAT. Fucoxanthin improves insulin resistance and decreases blood glucose levels through the regulation of cytokine secretions from WAT. The key structure of carotenoids for the expression of anti-obesity effect is suggested to be the carotenoid end of the polyene chromophore, which contains an allenic bond and two hydroxyl groups.

MicroRNA-15a positively regulates insulin synthesis by inhibiting uncoupling protein-2 expression

MicroRNAs are small noncoding RNAs that have been highly conserved during evolution and have been implicated to play an important role in many diseases, including diabetes. Several reports indicated the function of miRNAs in insulin production. However, the mechanisms by which miRNAs regulate this process remain poorly understood. Here we found that the expression of miR-15a was up-regulated in the presence of high glucose for 1h, whereas prolonged periods of high glucose exposure resulted in depressed expression of miR-15a, and the change in expression levels of miR-15a coincided with insulin biosynthesis. Moreover, ectopic expression of miR-15a promoted insulin biosynthesis in MIN6 cells, whereas its repression was sufficient to inhibit insulin biosynthesis. Further, we verified that miR-15a directly targeted and inhibited uncoupling protein-2 (UCP-2) gene expression. miR-15a mimics inhibited UCP-2 3'UTR luciferase reporter activity. Western blot analysis showed that miR-15a inhibited endogenous UCP-2 protein levels, and resulted in the increase in oxygen consumption and reduced ATP generation. This study suggests miR-15a is a mediator of β cell function and insulin biosynthesis, thus offering a new target for the development of preventive or therapeutic agents against diabetes.

Genes and biochemical pathways in human skeletal muscle affecting resting energy expenditure and fuel partitioning

Genes influencing resting energy expenditure (REE) and respiratory quotient (RQ) represent candidate genes for obesity and the metabolic syndrome because of the involvement of these traits in energy balance and substrate oxidation. We aim to explore the molecular basis for individual variation in REE and fuel partitioning as reflected by RQ. We performed microarray studies in human vastus lateralis muscle biopsies from 40 healthy subjects with measured REE and RQ values. We identified 2,392 and 1,115 genes significantly correlated with REE and RQ, respectively. Genes correlated with REE and RQ encompass a broad array of functions, including carbohydrate and lipid metabolism, gene expression, mitochondrial processes, and membrane transport. Microarray pathway analysis revealed that REE was positively correlated with upregulation of G protein-coupled receptor signaling (meet criteria/total genes: 65 of 283) involved in autonomic nervous system functions, including those receptors mediating adrenergic, dopamine, γ-aminobutyric acid (GABA), neuropeptide Y (NPY), and serotonin action (meet criteria/total genes: 46 of 176). Reduced REE was associated with an increase in genes participating in ubiquitin-proteasome-dependent proteolytic pathways (58 of 232). Serine-type peptidase activity (9 of 76) was positively correlated with RQ, while genes involved in the protein phosphatase type 2A complex (4 of 9), mitochondrial function and cellular respiration (38 of 315), and unfolded protein binding (19 of 97) were associated with reduced RQ values and a preference for lipid fuel metabolism. Individual variations in whole body REE and RQ are regulated by differential expressions of specific genes and pathways intrinsic to skeletal muscle.

Mitochondrial loss, dysfunction and altered dynamics in Huntington's disease

Although a direct causative pathway from the gene mutation to the selective neostriatal neurodegeneration remains unclear in Huntington's disease (HD), one putative pathological mechanism reported to play a prominent role in the pathogenesis of this neurological disorder is mitochondrial dysfunction. We examined mitochondria in preferentially vulnerable striatal calbindin-positive neurons in moderate-to-severe grade HD patients, using antisera against mitochondrial markers of COX2, SOD2 and cytochrome c. Combined calbindin and mitochondrial marker immunofluorescence showed a significant and progressive grade-dependent reduction in the number of mitochondria in spiny striatal neurons, with marked alteration in size. Consistent with mitochondrial loss, there was a reduction in COX2 protein levels using western analysis that corresponded with disease severity. In addition, both mitochondrial transcription factor A, a regulator of mtDNA, and peroxisome proliferator-activated receptor-co-activator gamma-1 alpha, a key transcriptional regulator of energy metabolism and mitochondrial biogenesis, were also significantly reduced with increasing disease severity. Abnormalities in mitochondrial dynamics were observed, showing a significant increase in the fission protein Drp1 and a reduction in the expression of the fusion protein mitofusin 1. Lastly, mitochondrial PCR array profiling in HD caudate nucleus specimens showed increased mRNA expression of proteins involved in mitochondrial localization, membrane translocation and polarization and transport that paralleled mitochondrial derangement. These findings reveal that there are both mitochondrial loss and altered mitochondrial morphogenesis with increased mitochondrial fission and reduced fusion in HD. These findings provide further evidence that mitochondrial dysfunction plays a critical role in the pathogenesis of HD.

Energy expenditure in obesity associated with craniopharyngioma

BACKGROUND AND PURPOSE

Obesity is a common yet incompletely understood complication of childhood craniopharyngioma. We hypothesized that craniopharyngioma is associated with specific defects in energy balance compared to obese control children.

METHODS

Eleven craniopharyngioma patients were recruited for a study on body composition and energy balance. Eight subjects were obese. The obese craniopharyngioma patients had a mean age (+/-SD) of 11.2 +/- 1.7 years. The average body mass index z score was 2.33 (+/-0.32). A previously studied group of obese children (BMI z score 2.46 +/- 0.46) served as controls. Resting energy expenditure (REE) was determined by indirect calorimetry and body composition by dual energy X-ray absorptiometry in all children.

RESULTS

Obese craniopharyngioma patient subjects had increased mean (+/-standard error) fat-free mass compared to obese controls (57% +/- 0.88 % vs 50.0% +/- 0.87%, p = 0.02). The obese craniopharyngioma patients had a 17% lower REE compared to values expected from the World Health Organization equation (1,541 +/- 112.6 vs 1,809 +/- 151.8 kcal; p = 0.01). In contrast, the obese control children had measured REE within 1% of predicted (1,647 +/- 33.2 vs. 1,652 +/- 40.2; p = 0.8). In a linear regression model, REE remained significantly lower than predicted after controlling for FFM.

CONCLUSIONS

Lower REE may be a factor contributing to obesity in children with craniopharyngioma. Further study is needed into the mechanisms for reduced energy expenditure in patients with craniopharyngioma.

Transport stress in broilers. II. Superoxide production, adenosine phosphate concentrations, and mRNA levels of avian uncoupling protein, avian adenine nucleotide translocator, and avian peroxisome proliferator-activated receptor-gamma coactivator-1alpha in skeletal muscles

The effect of transport stress on superoxide production and adenosine phosphate concentration in addition to avian uncoupling protein (avUCP), avian adenine nucleotide translocator, and avian peroxisome proliferator-activated receptor-gamma coactivator-1alpha mRNA levels of skeletal muscles in broilers was investigated. Arbor Acres chicks (n = 360, 46 d old, males) were randomly allotted to 1 of 5 treatments: unstressed control, 45-min (short-term) transport with 45-min (short-term) recovery, 45-min transport with 3-h (long-term) recovery, 3-h (long-term) transport with 45-min recovery, and 3-h transport with 3-h recovery. Each treatment consisted of 6 replicates with 12 birds each. All birds (except control group) were transported according to a designed protocol. Transport time affected reactive oxygen species production in the thigh muscle (P < 0.05), adenosine triphosphate (ATP) content and energy charge (EC) in both breast and thigh muscles (P < 0.05 for all 4 comparisons), ATP:adenosine diphosphate (ADP) ratio in the breast muscle (P < 0.05), and avUCP mRNA levels in the thigh muscle (P < 0.05). Long-term transport increased (P < 0.05) reactive oxygen species production, ATP content, ATP:ADP ratio, and EC in the thigh muscle, but it decreased ATP content, ATP:ADP ratio, and EC in the breast muscle. Long-term transport increased avUCP mRNA in the thigh muscle (P < 0.05). Long-term recovery increased the ATP (P < 0.05) and ADP (P < 0.05) concentrations, avian adenine nucleotide translocator mRNA (P < 0.05), and avian peroxisome proliferator-activated receptor-gamma coactivator-1alpha mRNA (P < 0.05) in the thigh muscle, whereas EC decreased (P < 0.05) in the breast muscle. There were interactions between transport and recovery time on ATP (P < 0.05), EC (P < 0.05), and avUCP mRNA level (P < 0.05) in the thigh muscle. This study suggests that long-term transport accelerates muscle energy metabolism and lipid peroxidation. A long-term recovery may help alleviate cellular damage and maintain meat quality by reducing the rate of energy metabolism and scavenging of free radicals formed.

Correlation between porcine PPARGC1A mRNA expression and its downstream target genes in backfat and longissimus dorsi muscle

Knowledge of in vivo relationship between the coactivator PPARGC1A and its target genes is very limited, especially in the pig. In this study, a real-time PCR experiment was performed on longissimus dorsi muscle (MLD) and backfat with 10 presumed PPARGC1A downstream target genes, involved in energy and fat metabolism, to identify possible relationships with PPARGC1A mRNA expression in vivo in the pig (n = 20). Except for UCP3 and LPL, a very significant difference in expression was found between MLD and backfat for all genes (P < 0.01). Hierarchical cluster analysis and the significant pairing of mRNA expression data between sampling locations suggested a genetic regulation of the expression of several target genes. A positive correlation with PPARGC1A was found for CPT1B, GLUT4, PDK4, and TFAM (P < 0.0001). A negative correlation was found for UCP2, FABP4, LEP (P < 0.0001), and TNF (P = 0.0071). No significant correlation was detected for UCP3 and LPL. This study provides evidence for a clear difference in mRNA expression of crucial genes in fat and energy metabolism between 2 important tissues. Our data suggest a clear impact of PPARGC1A on energy and lipid metabolism in vivo in the pig, through several of these downstream target genes.

Perspective: Does brown fat protect against diseases of aging?

The most commonly studied laboratory rodents possess a specialized form of fat called brown adipose tissue (BAT) that generates heat to help maintain body temperature in cold environments. In humans, BAT is abundant during embryonic and early postnatal development, but is absent or present in relatively small amounts in adults where it is located in paracervical and supraclavicular regions. BAT cells can 'burn' fatty acid energy substrates to generate heat because they possess large numbers of mitochondria in which oxidative phosphorylation is uncoupled from ATP production as a result of a transmembrane proton leak mediated by uncoupling protein 1 (UCP1). Studies of rodents in which BAT levels are either increased or decreased have revealed a role for BAT in protection against diet-induced obesity. Data suggest that individuals with low levels of BAT are prone to obesity, insulin resistance and cardiovascular disease, whereas those with higher levels of BAT maintain lower body weights and exhibit superior health as they age. BAT levels decrease during aging, and dietary energy restriction increases BAT activity and protects multiple organ systems including the nervous system against age-related dysfunction and degeneration. Future studies in which the effects of specific manipulations of BAT levels and thermogenic activity on disease processes in animal models (diabetes, cardiovascular disease, cancers, neurodegenerative diseases) are determined will establish if and how BAT affects the development and progression of age-related diseases. Data from animal studies suggest that BAT and mitochondrial uncoupling can be targeted for interventions to prevent and treat obesity and age-related diseases. Examples include: diet and lifestyle changes; specific regimens of mild intermittent stress; drugs that stimulate BAT formation and activity; induction of brown adipose cell progenitors in muscle and other tissues; and transplantation of brown adipose cells.

Leucine deprivation decreases fat mass by stimulation of lipolysis in white adipose tissue and upregulation of uncoupling protein 1 (UCP1) in brown adipose tissue

OBJECTIVE

White adipose tissue (WAT) and brown adipose tissue (BAT) play distinct roles in adaptation to changes in nutrient availability, with WAT serving as an energy store and BAT regulating thermogenesis. We previously showed that mice maintained on a leucine-deficient diet unexpectedly experienced a dramatic reduction in abdominal fat mass. The cellular mechanisms responsible for this loss, however, are unclear. The goal of current study is to investigate possible mechanisms.

RESEARCH DESIGN AND METHODS

Male C57BL/6J mice were fed either control, leucine-deficient, or pair-fed diets for 7 days. Changes in metabolic parameters and expression of genes and proteins related to lipid metabolism were analyzed in WAT and BAT.

RESULTS

We found that leucine deprivation for 7 days increases oxygen consumption, suggesting increased energy expenditure. We also observed increases in lipolysis and expression of beta-oxidation genes and decreases in expression of lipogenic genes and activity of fatty acid synthase in WAT, consistent with increased use and decreased synthesis of fatty acids, respectively. Furthermore, we observed that leucine deprivation increases expression of uncoupling protein (UCP)-1 in BAT, suggesting increased thermogenesis.

CONCLUSIONS

We show for the first time that elimination of dietary leucine produces significant metabolic changes in WAT and BAT. The effect of leucine deprivation on UCP1 expression is a novel and unexpected observation and suggests that the observed increase in energy expenditure may reflect an increase in thermogenesis in BAT. Further investigation will be required to determine the relative contribution of UCP1 upregulation and thermogenesis in BAT to leucine deprivation-stimulated fat loss.

Peroxisome proliferator-activated receptor beta/delta (PPARbeta/delta) acts as regulator of metabolism linked to multiple cellular functions

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors. They function as ligand activated transcription factors. They exist in three isoforms, PPARalpha, PPARbeta (formerly PPARdelta), and PPARgamma. For all PPARs lipids are endogenous ligands, linking them directly to metabolism. PPARs form heterodimers with retinoic X receptors, and, upon ligand binding, modulate gene expression of downstream target genes dependent on the presence of co-repressors or co-activators. This results in cell-type specific complex regulations of proliferation, differentiation and cell survival. Specific synthetic agonists for all PPARs are available. PPARalpha and PPARgamma agonists are already in clinical use for the treatment of hyperlipidemia and type 2 diabetes, respectively. More recently, PPARbeta activation came into focus as an interesting novel approach for the treatment of metabolic syndrome and associated cardiovascular diseases. Although the initial notion was that PPARbeta is expressed ubiquitously, more recently extensive investigations have been performed demonstrating high PPARbeta expression in a variety of tissues, e.g. skin, skeletal muscle, adipose tissue, inflammatory cells, heart, and various types of cancer. In addition, in vitro and in vivo studies using specific PPARbeta agonists, tissue-specific over-expression or knockout mouse models have demonstrated a variety of functions of PPARbeta in adipose tissue, muscle, skin, inflammation, and cancer. We will focus here on functions of PPARbeta in adipose tissue, skeletal muscle, heart, angiogenesis and cancer related to modifications in metabolism and the identified underlying molecular mechanisms.

Peripheral oscillators: the driving force for food-anticipatory activity

Food-anticipatory activity (FAA) and especially the food-entrained oscillator (FEO) have driven many scientists to seek their mechanisms and locations. Starting our research on FAA we, possibly like many other scientists, were convinced that clock genes held the key to the location and the underlying mechanisms for FAA. In this review, which is aimed especially at discussing the contribution of the peripheral oscillators, we have put together the accumulating evidence that the clock gene machinery as we know it today is not sufficient to explain food entrainment. We discuss the contribution of three types of oscillating processes: (i) within the suprachiasmatic nucleus (SCN), neurons capable of maintaining a 24-h oscillation in electrical activity driven by a set of clock genes; (ii) oscillations in metabolic genes and clock genes in other parts of the brain and in peripheral organs driven by the SCN or by food, which damp out after a few cycles; (iii) an FEO which, we propose, is a system built up of different oscillatory processes and consisting of an as-yet-unidentified network of central and peripheral structures. In view of the evidence that clock genes and metabolic oscillations are not essential for the persistence of FAA we propose that food entrainment is initiated by a repeated metabolic state of scarcity that drives an oscillating network of brain nuclei in interaction with peripheral oscillators. This complex may constitute the proposed FEO and is distributed in our peripheral organs as well as within the central nervous system.

Cellular effects of resveratrol in skeletal muscle

Resveratrol is a stilbene found naturally in various plants with the highest concentration in the skin of grapes and peanuts. The function of this compound in plants is to confer resistance against bacterial and fungal infection. The effects of resveratrol in animals and humans are currently an area of intense investigation. Resveratrol has been shown to have a plethora of health benefits including protection against cardiovascular disease, various cancers, type II diabetes, and also has life extending properties. The beneficial effects of resveratrol in skeletal muscle have been given less attention in the literature compared to other tissues. Therefore, the focus of this review is to highlight the cellular effects of resveratrol in skeletal muscle. Resveratrol has been shown to alter protein catabolism and muscle function, and confer resistance against oxidative stress, injury, and cell death of skeletal muscle cells. The mechanisms underlying these resveratrol-induced adaptations in skeletal muscle are discussed.

HIV-1 protease inhibitor induced oxidative stress suppresses glucose stimulated insulin release: protection with thymoquinone

The highly active anti-retroviral therapy (HAART) regimen has considerably reduced the mortality rate in HIV-1 positive patients. However, long-term exposure to HAART is associated with a metabolic syndrome manifesting cardiovascular dysfunction, lipodystrophy, and insulin resistance syndrome (IRS). The inclusion of HIV-1 protease inhibitors (PIs) in HAART has been linked to the induction of IRS. Although several molecular mechanisms of PI-induced effects on insulin action have been postulated, the deleterious effects of PIs on insulin production by pancreatic beta-cells have not been fully investigated and therapeutic strategies to ameliorate insulin dysregulation at this level have not been targeted. The present study showed that exposure to several different PIs, nelfinavir (5-10 microM), saquinavir (5-10 microM) and atazanavir (8-20 microM), decreases glucose stimulated insulin secretion from rat pancreatic beta-cells (INS-1). Nelfinavir significantly increased reactive oxygen species (ROS) generation and suppressed cytosolic, but not mitochondrial superoxide dismutase (SOD) levels. Nelfinvair also decreased both glutathione and ATP and increased UCP2 levels in these cells. Simultaneous treatment with thymoquinone (TQ) (2.5 microM), an active ingredient of black seed oil, significantly inhibited the effect of nelfinavir on augmented ROS production and suppressed SOD levels. Both TQ and black seed oil exposure increased glucose stimulated insulin secretion and ameliorated the suppressive effect of nelfinavir. The present findings imply a direct role of ROS in PI induced deleterious effects on pancreatic beta-cells. Our findings also suggest that TQ may be used as a potential therapeutic agent to normalize the dysregulated insulin production observed in HAART treated patients.