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Objective: The current focus of kisspeptin research is an exploration of its key role in the hypothalamic control of human and animal fertility. Notwithstanding the importance of these studies, strong evidence exists that the gene encoding human kisspeptin, KISS1, is present in several peripheral sites, including the placenta. We also provided evidence that kiss1 is also expressed and regulated in rodent adipose tissue. This study describes a pilot investigation into the possibility that human female adipose tissue might also express the KISS1 gene. Methods: Samples of fat were taken from women undergoing open abdominal surgery, for example, during caesarian section. Two small samples of fat were obtained, one from subcutaneous tissue ( n = 35) and one from the omentum ( n = 32). RNA was isolated from all fat samples and KISS1 mRNA was detected by realtime RT-PCR. Results: KISS1 gene expression was detected at varying levels in all samples of fat tissue but levels were significantly higher in subcutaneous fat. There was no significant correlation between KISS1 gene expression and body mass index (BMI) in subcutaneous fat ( P = 0.43), but there was a significant positive correlation ( P = 0.01) between KISS1 mRNA levels and BMI in omental adipose tissue. Conclusion: We have shown for the first time that human female adipose tissue may be a source of kisspeptins. Further studies are required to establish whether kisspeptins of adipose tissue origin might be correlated with some aspects of infertility. [ABSTRACT FROM AUTHOR]

Sleep research in Drosophila is not only here to stay, but is making impressive strides toward helping us understand the biological basis for and the purpose of sleep--perhaps one of the most complex and enigmatic of behaviors. Thanks to over a decade of sleep-related studies in lies, more molecular methods are being applied than ever before toward understanding the genetic basis of sleep disorders. The advent of high-throughput technologies that can rapidly interrogate whole genomes, epigenomes and proteomes, has also revolutionized our ability to detect genetic variants that might be causal for a number of sleep disorders. In the coming years, mutational studies in model organisms such as Drosophila will need to be functionally connected to information being generated from these whole-genome approaches in humans. This will necessitate the development of appropriate methods for interpolating data and increased analytical power to synthesize useful network(s) of sleep regulatory pathways --including appropriate discriminatory and predictive capabilities. Ultimately, such networks will also need to be interpreted in the context of fundamental neurobiological substrates for sleep in any given species. In this review, we highlight some emerging approaches, such as network analysis and mathematical modeling of sleep distributions, which can be applied to contemporary sleep research as a first step to achieving these aims. These methodologies should favorably impact not only a mechanistic understanding of sleep, but also future pharmacological intervention strategies to manage and treat sleep disorders in humans. [ABSTRACT FROM AUTHOR]

Delayed gastric emptying symptoms are often reported after chemotherapy. This study aims to characterise the effects of chemotherapy on gastric neuro-muscular function. Patients undergoing elective surgery for oesophago-gastric cancer were recruited. Acetylcholinesterase, nNOS, ghrelin receptor and motilin expressions were studied in gastric sections from patients receiving no chemotherapy (n = 3) or oesophageal (n = 2) or gastric (n = 2) chemotherapy. A scoring system quantified staining intensity (0-3; no staining to strong). Stomach sections were separately suspended in tissue baths for electrical field stimulation (EFS) and exposure to erythromycin or carbachol; three patients had no chemotherapy; four completed cisplatin-based chemotherapy within 6 weeks prior to surgery. AChE expression was markedly decreased after chemotherapy (scores 2.3 ± 0.7, 0.5 ± 0.2 and 0 ± 0 in non-chemotherapy, oesophageal- and gastric-chemotherapy groups (p < 0.03 each) respectively. Ghrelin receptor and motilin expression tended to increase (ghrelin: 0.7 ± 0.4 vs 2.0 ± 0.4 and 1.2 ± 0.2 respectively; p = 0.04 and p = 0.2; motilin: 0.7 ± 0.5 vs 2.2 ± 0.5 and 2.0 ± 0.7; p = 0.06 and p = 0.16). Maximal contraction to carbachol was 3.7 ± 0.7 g and 1.9 ± 0.8 g (longitudinal muscle) and 3.4 ± 0.4 g and 1.6 ± 0.6 (circular) in non-chemotherapy and chemotherapy tissues respectively (p < 0.05 each). There were loss of AChE and reduction in contractility to carbachol. The tendency for ghrelin receptors to increase suggests an attempt to upregulate compensating systems. Our study offers a mechanism by which chemotherapy markedly alters neuro-muscular gastric function. [ABSTRACT FROM AUTHOR]

Orexin peptides and their cognate receptors were discovered 14 years ago. They soon took a very central position in the regulation of sleep and wakefulness. Active studies have further elucidated these functions as well as the role of orexins in, for instance, appetite, metabolism, analgesia, addiction, and stress response. This review summarizes all the important fields but especially aims at focusing on novel findings and future directions. [ABSTRACT FROM AUTHOR]

Components of purinergic signalling are expressed in the early embryo raising the possibility that ATP, ADP and adenosine may contribute to the mechanisms of embryonic development. We summarize the available data from four developmental models-mouse, chick, Xenopus and zebrafish. While there are some notable examples where purinergic signalling is indeed important during development, e.g. development of the eye in the frog, it is puzzling that deletion of single components of purinergic signalling often results in rather minor developmental phenotypes. We suggest that a key step in further analysis is to perform combinatorial alterations of expression of purinergic signalling components to uncover their roles in development. We introduce the concept that purinergic signalling could create novel morphogenetic fields to encode spatial location via the concentration of ATP, ADP and adenosine. We show that using minimal assumptions and the known properties of the ectonucleotidases, complex spatial patterns of ATP and adenosine can be set up. These patterns may provide a new way to assess the potential of purinergic signalling in developmental processes. [ABSTRACT FROM AUTHOR]

We have elucidated the alteration in hippocampal and cerebellum function following chronic cisplatin treatment in male and female rats. Hippocampus and cerebellum related behavioral dysfunction in cisplatin-treated [intraperitoneally, 5 mg/(kg/week) for 5 weeks from 23-day-old] rats were analyzed using explorative, motor function, learning, and memory tasks (grasping, rotarod, open field, and Morris water maze tests). Exposure to cisplatin impaired the motor coordination in male and female rats. Exposure to cisplatin was reflected by a decrease in grasping time compared to vehicle-treated controls (saline) only in male rat while there were not any differences in female rats. When the rearing frequency, total distance moved and velocity of their recorded in open fieldtest, both males and females were dramatically affected by exposure to cisplatin. Compared to the saline, male and female rats trained 5 weeks after cisplatin injection showed significant memory deficits in the Morris water maze test. However, hippocampal and cerebellum functions of male and female rats were profoundly affected by exposure to cisplatin while no sex differences in the most variable were evident. [ABSTRACT FROM AUTHOR]

Extracellular nucleotides induce cellular responses in the central nervous system (CNS) through the activation of ionotropic P2X and metabotropic P2Y nucleotide receptors. Activation of these receptors regulates a wide range of physiological and pathological processes. In this review, we present an overview of the current literature regarding P2X and P2Y receptors in the CNS with a focus on the contribution of P2X7 and P2Y receptor-mediated responses to neuroinflammatory and neuroprotective mechanisms. [ABSTRACT FROM AUTHOR]

We investigated the possible modulation of the intestinal contractility by uracil nucleotides (UTP and UDP), using as model the murine small intestine. Contractile activity of a mouse ileum longitudinal muscle was examined in vitro as changes in isometric tension. Transcripts encoding for uracil-sensitive receptors was investigated by RT-PCR. UDP induced muscular contractions, sensitive to PPADS, suramin, or MRS 2578, P2Y receptor antagonist, and mimicked by PSB 0474, P2Y-receptor agonist. UTP induced biphasic effects characterized by an early inhibition of the spontaneous contractile activity followed by muscular contraction. UTP excitatory effects were antagonized by PPADS, suramin, but not by MRS 2578, whilst the inhibitory effects were antagonized by PPADS but not by suramin or MRS 2578. UTPγS, P2Y/ receptor agonist but not 2-thio-UTP, P2Y receptor agonist, mimicked UTP effects. The inhibitory effects induced by UTP was abolished by ATP desensitization and increased by extracellular acidification. UDP or UTP responses were insensitive to TTX, atropine, or L-NAME antagonized by U-73122, inhibitor of phospholipase C (PLC) and preserved in the presence of nifedipine or low Ca solution. Transcripts encoding the uracil nucleotide-preferring receptors were expressed in mouse ileum. Functional postjunctional uracil-sensitive receptors are present in the longitudinal muscle of the mouse ileum. Activation of P2Y receptors induces muscular contraction, whilst activation of P2Y receptors leads to inhibition of the contractile activity. Indeed, the presence of atypical UTP-sensitive receptors leading to muscular contraction is suggested. All uracil-sensitive receptors are linked to the PLC pathway. [ABSTRACT FROM AUTHOR]

This study explores the pharmacokinetics of 22- S-hydroxycholesterol (22SHC) in vivo in rats. We also carried out a metabolic study to explore whether the beneficial effects observed of 22SHC on glucose and lipid metabolism in vitro could be seen in vivo in rats. In the pharmacokinetic study, rats were given 50 mg/kg of [H]22- S-hydroxycholesterol before absorption, distribution and excretion were monitored. In the metabolic study, the effect of 22SHC (30 mg/kg/day for 3 weeks) in rats on body weight gain [chow and high-fat diet (HFD)], serum lipids triacylglycerol (TAG) content and gene expression in liver and skeletal muscle were examined. Results showed that 22SHC was well absorbed after oral administration and distributed to most organs and mainly excreted in feces. Rats receiving 22SHC gained less body weight than their controls regardless whether the animals received chow diet or HFD. Moreover, we observed that animals receiving HFD had elevated levels of serum TAG while this was not observed for animals on HFD supplemented with 22SHC. The amount of TAG in liver was reduced after 22SHC treatment in animals receiving either chow diet or HFD. Gene expression analysis revealed that two genes (carnitine palmitoyltransferase 2 and uncoupling protein 3) involved in fatty acid oxidation and energy dissipation were increased in liver. Ucp3 expression (both protein and mRNA level) was increased in skeletal muscle, but insulin-stimulated glucose uptake and TAG content were unchanged. In conclusion, 22SHC seems to be an interesting model substance in the search of treatments for disorders involving aberrations in lipid metabolism. [ABSTRACT FROM AUTHOR]

The purinergic 1 receptor (P2RY1) has been implicated in development of heart disease and in individual pharmacodynamic response to anticoagulant therapies. However, the association of polymorphisms in the P2RY1 gene with myocardial infarction (MI), and its associated conditions, has yet to be reported in the literature. We evaluated seven known SNPs in P2RY1 for association with MI in a Latvian population. Seven independent parameters that are related to MI [body mass index (BMI), type 2 diabetes (T2D), angina pectoris, hypertension, hyperlipidemia, atrial fibrillation and heart failure] were investigated. No significant association with MI was observed for any of the polymorphisms. Those SNPs for which the P value was close to significance were located in coding or promoter regions. Intriguingly, carriers of the minor allele in the P2RY1 gene locus showed a tendency towards higher onset age for MI, suggesting a possible protective effect of these SNPs against MI or their contribution in progression as opposed to onset. Finally, a linkage disequilibrium (LD) plot was generated for these polymorphisms in the Latvian population. The results of this study suggest that the role of P2RY1 in individuals from Latvian population is likely to be principally involved in platelet aggregation and thromboembolic diseases, and not as a significant contributing factor to the global metabolic syndrome. [ABSTRACT FROM AUTHOR]

Objective:The objective of the study was to look for uncoupling protein 3 (UCP3) gene variants in early-onset severe childhood obesity and to determine their effect on long-chain fatty acid oxidation and triglyceride storage.Methods and results:We identified four novel mutations in the UCP3 gene (V56M, A111V, V192I and Q252X) in 200 children with severe, early-onset obesity (body mass index-standard deviation score >2.5; onset: <4 years) living in Southern Italy. We evaluated the role of wild-type (wt) and mutant UCP3 proteins in palmitate oxidation and in triglyceride storage in human embryonic kidney cells (HEK293). Palmitate oxidation was ∼60% lower (P<0.05; P<0.01) and triglyceride storage was higher in HEK293 cells expressing the four UCP3 mutants than in cells expressing wt UCP3. Moreover, mutants V56M and Q252X exerted a dominant-negative effect on wt protein activity (P<0.01 and P<0.05, respectively). Telmisartan, an angiotensin II receptor antagonist used in the management of hypertension, significantly (P<0.05) increased palmitate oxidation in HEK293 cells expressing wt and mutant proteins (P<0.05; P<0.01), including the dominant-negative mutants.Conclusions:These data indicate that protein UCP3 affects long-chain fatty acid metabolism and can prevent cytosolic triglyceride storage. Our results also suggest that telmisartan, which increases fatty acid oxidation in rat skeletal muscle, also improves UCP3 wt and mutant protein activity, including the dominant-negative UCP3 mutants. [ABSTRACT FROM AUTHOR]

The article presents information on a study conducted on the role of Toll-like receptor 4 (TLR4) signaling in intracerebral hemorrhage (ICH)-induced inflammation. The study concluded that heme induces microglial activation through TLR4, and ultimately increases cytokine expression and inflammatory injury in ICH.

Background: The selection of stable and suitable reference genes for real-time quantitative PCR (RT-qPCR) is a crucial prerequisite for reliable gene expression analysis under different experimental conditions. The present study aimed to identify reference genes as internal controls for gene expression studies by RT-qPCR in azole-stimulated Candida glabrata. Results: The expression stability of 16 reference genes under fluconazole stress was evaluated using fold change and standard deviation computations with the hkg Finder tool. Our data revealed that the mRNA expression levels of three ribosomal RNAs (RDN5.8, RDN18, and RDN25) remained stable in response to fluconazole, while PGK1, UBC7, and UBC13 mRNAs showed only approximately 2.9-, 3.0-, and 2.5-fold induction by azole, respectively. By contrast, mRNA levels of the other 10 reference genes (ACT1, EF1α, GAPDH, PPIA, RPL2A, RPL10, RPL13A, SDHA, TUB1, and UBC4) were dramatically increased in C. glabrata following antifungal treatment, exhibiting changes ranging from 4.5- to 32.7-fold. We also assessed the expression stability of these reference genes using the 2-ΔΔCT method and three other software packages. The stability rankings of the reference genes by geNorm and the 2-ΔΔCT method were identical to those by hgk Finder, whereas the stability rankings by BestKeeper and NormFinder were notably different. We then validated the suitability of six candidate reference genes (ACT1, PGK1, RDN5.8, RDN18, UBC7, and UBC13) as internal controls for ten target genes in this system using the comparative CT method. Our validation experiments passed for all six reference genes analyzed except RDN18, where the amplification efficiency of RDN18 was different from that of the ten target genes. Finally, we demonstrated that the relative quantification of target gene expression varied according to the endogenous control used, highlighting the importance of the choice of internal controls in such experiments. Conclusions: We recommend the use of RDN5.8, UBC13, and PGK1 alone or the combination of RDN5.8 plus UBC13 or PGK1 as reference genes for RT-qPCR analysis of gene expression in C. glabrata following azole treatment. In contrast, we show that ACT1 and other commonly used reference genes (GAPDH, PPIA, RPL13A, TUB1, etc.) were not validated as good internal controls in the current model. [ABSTRACT FROM AUTHOR]

Background: Diets producing a high glycemic response result in exaggerated insulin secretion which induces hepatic lipogenesis, contributing to development of insulin resistance and fatty liver. Viscous dietary fibers blunt the postprandial rise in blood glucose, however their effect on type 2 diabetes and obesity are not entirely known. This study examined the effect of chronic consumption of the viscous, non-fermentable dietary fiber, hydroxypropyl methylcellulose (HPMC), on glucose control, insulin resistance and liver lipids in an obese diabetic rat model. Methods: Three groups of Zucker Diabetic Fatty (ZDF) rats were fed diets containing either 5% non-viscous cellulose (control), low viscosity HPMC (LV-HPMC) or high viscosity HPMC (HV- HPMC) for six weeks. Zucker lean littermates consuming cellulose served as a negative control. Markers of glucose control, including oral glucose tolerance test, glycated hemoglobin and urinary glucose, were measured as well as adiposity and the accumulation of liver lipids. Results: The HPMC diets increased the viscosity of the small intestinal contents and reduced the postprandial rise in blood glucose. The food efficiency ratio was greater with HPMC feeding compared to the obese control and urinary excretion of glucose and ketone bodies was reduced. The two HPMC groups had lower glycated hemoglobin and kidney weights and a reduced area under the curve during a glucose tolerance test, indicating improved glucose control. Epididymal fat pad weight as percent of body weight was reduced in the HV-HPMC group compared to the obese control group. The HV-HPMC group also had lower concentrations of liver lipid and cholesterol and reduced liver weight. However, HV-HPMC feeding did not affect hepatic gene expression of SREBP-1c or FAS. Muscle concentration of acylcarnitines, a lipid intermediate in fatty acid β-oxidation, was not different between the HPMC groups and obese control, suggesting no change in muscle fatty acid oxidation by HPMC. Conclusions: Consumption of the viscous non-fermentable fiber HPMC decreased diabetic wasting, improved glucose control and reduced insulin resistance and fatty liver in a model of obesity with diabetes. [ABSTRACT FROM AUTHOR]

P2Y receptors are G protein-coupled receptors composed of eight known subunits (P2Y), which are involved in different functions in neural tissue. The present study investigates the expression pattern of P2Y receptors in the rat central nervous system (CNS) using immunohistochemistry and in situ hybridization. The specificity of the immunostaining has been verified by preabsorption, Western blot, and combined use of immunohistochemistry and in situ hybridization. Neurons expressing P2Y receptors were distributed widely in the rat CNS. Heavy P2Y receptor immunostaining was observed in the magnocellular neuroendocrine neurons of the hypothalamus, red nucleus, pontine nuclei, mesencephalic trigeminal nucleus, motor trigeminal nucleus, ambiguous nucleus, inferior olive, hypoglossal nucleus, and dorsal motor vagus nucleus. Both neurons and astrocytes express P2Y receptors. P2Y receptor immunostaining signals were mainly confined to cell bodies and dendrites of neurons, suggesting that P2Y receptors are mainly involved in regulating postsynaptic events. In the hypothalamus, all the vasopressin (VP) and oxytocin (OT) neurons and all the orexin A neurons were immunoreactive for P2Y receptors. All the neurons expressing P2Y receptors were found to express N-methyl- d-aspartate receptor 1 (NR1). These data suggest that purines and pyrimidines might be involved in regulation of the release of the neuropeptides VP, OT, and orexin in the rat hypothalamus via P2Y receptors. Further, the physiological and pathophysiological functions of the neurons may operate through coupling between P2Y receptors and NR1. [ABSTRACT FROM AUTHOR]

Hypothalamic orexin neurons project to the hindbrain, and 4th-ventricle intracerebroventricular (4th-icv) injection of orexin-A treatment increases food intake. We assessed the effects of hindbrain orexin-A and the orexin-1-receptor antagonist SB334867 on meal pattern in rats consuming standard chow. When injected 4th-icv shortly before dark onset, lower doses of orexin-A increased food intake over a 2-h period by increasing the size of the first meal relative to vehicle, whereas the highest dose increased food intake by causing the second meal to be taken sooner. Conversely, hindbrain SB334867 reduced food intake by decreasing the size of the first meal of the dark phase. We also examined the effects of 4th-icv orexin-A and SB334867 on locomotor activity. Only the highest dose of orexin-A increased activity, and SB334867 had no effect. In addition, hindbrain SB334867 induced c-Fos in the nucleus of the solitary tract. These data support the suggestion that endogenous hindbrain orexin-A acts to limit satiation. Both orexin-A and the pancreatic satiation hormone amylin require an intact area postrema to affect food intake, so we asked whether 4th-icv orexin-A impairs the satiating effect of peripheral amylin treatment. Amylin reduced the size of the first meal of the dark cycle when rats were pretreated with 4th-icv saline, yet amylin was ineffective after 4th-icv orexin-A pretreatment. Using double-label immunohistochemistry, we determined that some orexin-A fibers in the area postrema are located in proximity to amylin-responsive neurons. Therefore, hindbrain orexin-A may increase food intake, in part, by reducing the ability of rats to respond to amylin during a meal. [ABSTRACT FROM AUTHOR]

Mitochondria couple respiration to ATP synthesis through an electrochemical proton gradient. Proton leak across the inner membrane allows adjustment of the coupling efficiency. The aim of this review is threefold: 1) introduce the unfamiliar reader to proton leak and its physiological significance, 2) review the role and regulation of uncoupling proteins, and 3) outline the prospects of proton leak as an avenue to treat obesity, diabetes, and age-related disease. [ABSTRACT FROM AUTHOR]

Mammalian cytosolic glutathione transferases (GSTs) can be grouped into seven classes. Of these, the sigma class is also widely distributed in nature, with isoforms found in both vertebrates and invertebrates. It contains examples of proteins that have evolved specialized functions, such as the cephalopod lens S-crystallins, the mammalian hematopoietic prostaglandin D2 synthase, and the helminth 28-kDa antigen. In mammals, the sigma-class GST has both anti- and proinflammatory functions, depending on the type of immune response, and an immunomodulatory function is also associated with the enzyme from helminth parasites. In the fly, it is associated with a specific detoxication activity toward lipid oxidation products. Mice genetically depleted of the sigma-class GST, or transgenically overexpressing it, have provided insight into the physiological roles of the GST. Inhibitors of the mammalian enzyme developed by structure-based methods are effective in controlling allergic response. This review covers the structure, function, and pharmacology of vertebrate and invertebrate GSTs. [ABSTRACT FROM AUTHOR]

Background Acute administration of the antitumoral drug cisplatin can induce nausea/emesis and diarrhea. The long-term effects of cisplatin on gastrointestinal motility, particularly after repeated administration, are not well known. Because cisplatin is highly neurotoxic, myenteric neurons can be affected. Our aim was to study the prolonged effects of repeated cisplatin administration in a rat model, focusing on gastrointestinal motor function and myenteric neurons. Methods Rats received saline or cisplatin (1 or 3 mg kg−1, i.p.) once weekly for 5 weeks. One week after treatment, both upper gastrointestinal transit and colonic activity were evaluated, and tissue samples from ileum, colon and rectum were processed for histological analysis. Intestinal transit was measured invasively (charcoal method). Colonic activity was determined electromyographically. The gut wall structure was evaluated in sections using conventional histology and immunohistochemistry. Whole-mount preparations from the distal colon were labeled for different markers, including nitric oxide synthase (NOS) and calcitonin-gene related peptide (CGRP) to determine relative proportions of myenteric neurons vs the total neuronal population labeled with HuC/D. Key Results One week after repeated cisplatin exposure, the upper gastrointestinal transit rate and colonic activity were dose-dependently reduced. The number of NSE- or HuC/D-immunoreactive myenteric neurons per ganglion was decreased; the proportion of CGRP-immunoreactive neurons was decreased, whereas that of NOS-immunoreactive cells was increased. Conclusions & Inferences Chronic cisplatin may induce an enteric neuropathy characterized by changes in myenteric neurons associated with marked gastrointestinal motor dysfunction. [ABSTRACT FROM AUTHOR]

In this work we review recent findings that explain how mitochondrial bioenergetic functions and redox state respond to a hyperlipidemic in vivo environment and may contribute to the maintenance of a normal metabolic phenotype. The experimental model utilized to evidence these adaptive mechanisms is especially useful for these studies since it exhibits genetic hypertriglyceridemia and avoids complications introduced by high fat diets. Liver from hypertrigliceridemic (HTG) mice have a greater content of glycerolipids together with increased mitochondrial free fatty acid oxidation. HTG liver mitochondria have a higher resting respiration rate but normal oxidative phosphorylation efficiency. This is achieved by higher activity of the mitochondrial potassium channel sensitive to ATP (mitoK). The mild uncoupling mediated by mitoK accelerates respiration rates and reduces reactive oxygen species generation. Although this response is not sufficient to inhibit lipid induced extra-mitochondrial oxidative stress in whole liver cells it avoids amplification of this redox imbalance. Furthermore, higher mitoK activity increases liver, brain and whole body metabolic rates. These mitochondrial adaptations may explain why these HTG mice do not develop insulin resistance and obesity even under a severe hyperlipidemic state. On the contrary, when long term high fat diets are employed, insulin resistance, fatty liver and obesity develop and mitochondrial adaptations are inefficient to counteract energy and redox imbalances. [ABSTRACT FROM AUTHOR]

Controversy exists on whether uncoupling protein 3 (UCP3) positively or negatively influences insulin sensitivity in vivo, and the underlying signaling pathways have been scarcely studied. We studied how a progressive reduction in UCP3 expression (using UCP3 +/+, UCP3 +/−, and UCP3 −/− mice) modulates insulin sensitivity and related metabolic parameters. In order to further validate our observations, we also studied animals in which insulin resistance was induced by administration of a high-fat diet (HFD). In UCP3 +/− and UCP3 −/− mice, gastrocnemius muscle Akt/protein kinase B (Akt/PKB) (serine 473) and AMP-activated protein kinase (AMPK) (threonine 171) phosphorylation, and glucose transporter 4 (GLUT4) membrane levels were reduced compared to UCP3 +/+ mice. The HOMA-IR index (insulin resistance parameter) was increased both in the UCP3 +/− and UCP3 −/− mice. In these mice, insulin administration normalized Akt/PKB phosphorylation between genotypes while AMPK phosphorylation was further reduced, and sarcolemmal GLUT4 levels were induced but did not reach control levels. Furthermore, non-insulin-stimulated muscle fatty acid oxidation and the expression of several involved genes both in muscle and in liver were reduced. HFD administration induced insulin resistance in UCP3 +/+ mice and the aforementioned parameters resulted similar to those of chow-fed UCP3 +/− and UCP3 −/− mice. In conclusion, high-fat-diet-induced insulin resistance in wild-type mice mimics that of chow-fed UCP3 +/− and UCP3 −/− mice showing that progressive reduction of UCP3 levels results in insulin resistance. This is accompanied by decreased fatty acid oxidation and a less intense Akt/PKB and AMPK signaling. [ABSTRACT FROM AUTHOR]

The hormone leptin controls food intake and body weight through its receptor in the hypothalamus, and may modulate physiological functions such as reproduction, sleep or circadian timing. In the present study, the effects of leptin on the resetting of the circadian clock, the hypothalamic suprachiasmatic nucleus (SCN) and on the activity of the hypocretinergic system were examined in vivo, with comparative analysis between male and female mice. A single leptin injection (5 mg/kg) at both the onset and offset of the activity period did not alter locomotion of mice housed under a 12 : 12 h light/dark cycle and did not shift the circadian behavioral rhythm of mice housed in constant darkness. By contrast, leptin potentiated the phase-shifting effect of a 30-min light-pulse on behavioural rhythms during the late subjective night, although only in females. This was accompanied by a higher induction of the clock genes Per1 and Per2 in the SCN. A 2-week chronic exposure to a physiological dose of leptin (100 μg/kg per day) decreased locomotor activity, expression of hypocretin receptor 1 and 2, as well as the number of hypocretin-immunoreactive neurones only in female mice, whereas the number of c-fos-positive hypocretinergic neurones was reduced in both genders. These results highlight a dimorphic effect of leptin on the hypocretinergic system and on the response of the circadian clock to light. Leptin may thus modulate the sleep/wake cycle and circadian system beside its well-established action on food intake and regulation of body weight. [ABSTRACT FROM AUTHOR]

Diabetes mellitus increases the risk of developing cardiovascular diseases such as coronary artery disease and heart failure. Studies have shown that the heart failure risk is increased in diabetic patients even after adjusting for coronary artery disease and hypertension. Although the cause of this increased heart failure risk is multifactorial, increasing evidence suggests that derangements in cardiac energy metabolism play an important role. In particular, abnormalities in cardiomyocyte mitochondrial energetics appear to contribute substantially to the development of cardiac dysfunction in diabetes. This review will summarize these abnormalities in mitochondrial function and discuss potential underlying mechanisms. [ABSTRACT FROM PUBLISHER]

Ischemic preconditioning (IPC) produces cardioprotection by phosphorylation of glycogen synthase kinase-3β (GSK-3β) that inhibits the opening of mitochondrial permeability transition pore (MPTP). The activity of glycogen GSK-3β is elevated during diabetes mellitus (DM). This study investigated the role of GSK-3β in attenuation of cardioprotective effect of IPC in diabetic rat. DM was induced by single administration of streptozotocin (STZ, 50 mg/kg, i.p.). Isolated perfused heart was subjected to 30 min of ischemia followed by 120 min of reperfusion. Myocardial infarct size was estimated by triphenyltetrazolium chloride (TTC) staining and lactate dehydrogenase (LDH) and creatine kinase-MB (CK-MB) was analyzed in coronary effluent. IPC significantly decreased myocardial infarct size and release of LDH and CK-MB from normal rat heart. The cardioprotective effect of IPC was significantly attenuated in diabetic rat. Four episodes of preconditioning by either of GSK-3β inhibitors, lithium chloride (LiCl, 20 mM), indirubin-3 monooxime (1 μM), and SB216763 (3 μM) significantly reduced the LDH and CK-MB release and decreased infarct size in diabetic rat heart. Perfusion of atractyloside, an opener of MPTP, significantly attenuated, the cardioprotective effect of IPC in normal rat heart, and of GSK-3β inhibitor induced preconditioning in the DM rat heart. Our results suggest that preconditioning with GSK-3β inhibitors in diabetic rat heart may provide a more consistent cardioprotection, as compared to IPC. Also, the mechanism of diabetes mellitus-induced attenuation of cardioprotective effect of IPC involves activation of GSK-3β, due to impaired protective upstream signaling pathways and opening of MPTP during reperfusion. [ABSTRACT FROM AUTHOR]

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High glucose (HG) has been shown to induce insulin resistance in both type 1 and type 2 diabetes. However, the molecular mechanism behind this phenomenon is unknown. Insulin receptor substrate (IRS) proteins are the key signaling molecules that mediate insulin's intracellular actions. Genetic and biological studies have shown that reductions in IRS1 and/or IRS2 protein levels are associated with insulin resistance. In this study we have shown that proteasome degradation of IRS1, but not of IRS2, is involved in HG-induced insulin resistance in Chinese hamster ovary (CHO) cells as well as in primary hepatocytes. To further investigate the molecular mechanism by which HG induces insulin resistance, we examined various molecular candidates with respect to their involvement in the reduction in IRS1 protein levels. In contrast to the insulin-induced degradation of IRS1, HG-induced degradation of IRS1 did not require IR signaling or phosphatidylinositol 3-kinase/Akt activity. We have identified glycogen synthase kinase 3β (GSK3β or GSK3B as listed in the MGI Database) as a kinase required for HG-induced serine332 phosphorylation, ubiquitination, and degradation of IRS1. Overexpression of IRS1 with mutation of serine332 to alanine partially prevents HG-induced IRS1 degradation. Furthermore, overexpression of constitutively active GSK3β was sufficient to induce IRS1 degradation. Our data reveal the molecular mechanism of HG-induced insulin resistance, and support the notion that activation of GSK3β contributes to the induction of insulin resistance via phosphorylation of IRS1, triggering the ubiquitination and degradation of IRS1. [ABSTRACT FROM AUTHOR]

Lipocalin-type prostaglandin (PG) D synthase is expressed in adipose tissues and involved in the regulation of glucose tolerance and atherosclerosis in type 2 diabetes. However, the physiological roles of PGD2 in adipogenesis in vivo are not clear, as lipocalin-type prostaglandin D synthase can also act as a transporter for lipophilic molecules, such as retinoids. We generated transgenic (TG) mice overexpressing human hematopoietic PGDS (H-PGDS) and investigated the in vivo functions of PGD2 in adipogenesis. PGD2 production in white adipose tissue of H-PGDS TG mice was increased approximately seven-fold as compared with that in wild-type (WT) mice. With a high-fat diet, H-PGDS TG mice gained more body weight than WT mice. Serum leptin and insulin levels were increased in H-PGDS TG mice, and the triglyceride level was decreased by about 50% as compared with WT mice. Furthermore, in the white adipose tissue of H-PGDS TG mice, transcription levels of peroxisome proliferator-activated receptor γ, fatty acid binding protein 4 and lipoprotein lipase were increased approximately two-fold to five-fold as compared with those of WT mice. Finally, H-PGDS TG mice showed clear hypoglycemia after insulin clamp. These results indicate that TG mice overexpressing H-PGDS abundantly produced PGD2 in adipose tissues, resulting in pronounced adipogenesis and increased insulin sensitivity. The present study provides the first evidence that PGD2 participates in the differentiation of adipocytes and in insulin sensitivity in vivo, and the H-PGDS TG mice could constitute a novel model mouse for diabetes studies. [ABSTRACT FROM AUTHOR]

The mammalian homolog of the fish calcium regulatory hormone stanniocalcin-1 (STC 1) is ubiquitously expressed and likely functions in an autocrine/paracrine fashion. Mammalian STC1 does not appear to exert significant effects on serum calcium, and its physiological role remains to be determined. In macrophages, STC1 decreases intracellular calcium and cell mobility; attenuates the response to chemoattractants; and diminishes superoxide generation through induction of uncoupling protein-2 (UCP2). In cytokine-treated endothelial cells, STC 1 attenuates superoxide generation and the activation of inflammatory pathways [c-Jun NH2-terminal kinase (JNK) and NF-κB]; maintains the expression of tight junction proteins, preserving the endothelial monolayer seal; and decreases transendothelial migration of leukocytes. Combined, the effects of STC1 on endothelial cells and macrophages predict potent anti-inflammatory action. Indeed, application of the anti-glomerular basement membrane (GBM) glomerulonephritis model to STC1 transgenic mice that display increased expression of STC1 transgene in endothelial cells and macrophages yields renal protection. Our data suggest that STC1 activates antioxidant pathways in endothelial cells and macrophages and displays cytoprotective and anti-inflammatory actions. [ABSTRACT FROM AUTHOR]

The article discusses the regulation of myocardial fatty acid β-oxidation and the contribution of its alterations to heart disease. It states that fatty acid β-oxidation can increase or decrease to adjust to changes in cardiac energy demand. Furthermore, the contribution of oxidation to cardiac energy metabolism ranges from 100% of the total energy requirement of the heart to being a small contributor. It emphasizes the pathway of oxidation and the factors that affect it.

Objectives:The involvement of skeletal muscle mitochondrial uncoupling protein-3 (UCP3) in the control of energy expenditure in skeletal muscle and at the whole-body level is still a matter of debate. We previously reported that UCP3 downregulation is linked to an enhanced mitochondrial energy metabolism in rat skeletal muscle as a result of acute capsiate treatment. Here, we aimed at investigating noninvasively the effects of chronic capsiate ingestion on metabolic changes occurring in exercising gastrocnemius muscle and at the whole-body level.Methods:We used an original experimental setup allowing a complete noninvasive investigation of gastrocnemius muscle function in situ using 31-phosphorus magnetic resonance spectroscopy. Whole-body fat composition was determined using magnetic resonance imaging and UCP3 gene expression was measured by quantitative real-time RT-PCR analysis.Results:We found that a 14-day daily administration of capsiate (100 mg kg−1 body weight) reduced UCP3 gene expression and increased phosphocreatine level at baseline and during the stimulation period in gastrocnemius muscle. During muscle stimulation, pHi showed a larger alkalosis in the capsiate group suggesting a lower glycolysis and a compensatory higher aerobic contribution to ATP production. Although the capsiate-treated rats were hyperphagic as compared to control animals, they showed a lower weight gain coupled to a decreased abdominal fat content.Conclusion:Overall, our data indicated that capsiate administration contributes to the enhancement of aerobic ATP production and the reduction of body fat content coupled to a UCP3 gene downregulation. [ABSTRACT FROM AUTHOR]

Abstract  The aim of this study was to evaluate the impact of three different chromium forms as chromic chloride (CrCl), chromium picolinate (CrPic), and a newly synthesized complex of chromium chelated with small peptides (CrSP) on glucose uptake and metabolism in vitro. In cultured skeletal muscle cells, chromium augmented insulin-stimulated glucose uptake and metabolism as assessed by a reduced glucose concentration of culture medium. At the molecular level, insulin significantly increased the mRNA levels of insulin receptor (IR), glucose transporter 4 (GLUT4), glycogen synthase (GS), and uncoupling protein-3 (UCP3), and these impacts can be enhanced by the addition of chromium, especially in the form of CrSP. Collectively, results of this study demonstrate that chromium improves glucose uptake and metabolism through upregulating the mRNA levels of IR, GLUT4, GS, and UCP3 in skeletal muscle cells, and CrSP has higher efficacy on glucose uptake and metabolism compared to the forms of CrCl and CrPic. [ABSTRACT FROM AUTHOR]

OBJECTIVE--Transgenic expression of diacylglycerol acyltransferase-1 (DGAT1) in skeletal muscle leads to protection against fat-induced insulin resistance despite accumulation of intramuscular triglyceride, a phenomenon similar to what is known as the "athlete paradox." The primary objective of this study is to determine how DGAT1 affects muscle fatty acid oxidation in relation to whole-body energy metabolism and insulin sensitivity. RESEARCH DESIGN AND METHODS--We first quantified insulin sensitivity and the relative tissue contributions to the improved whole-body insulin sensitivity in muscle creatine kisase (MCK)-DGAT1 transgenic mice by hyperinsulinemic-euglycemic clamps. Metabolic consequences of DGAT1 overexpression in skeletal muscles were determined by quantifying triglyceride synthesis/storage (anabolic) and fatty acid oxidation (catabolic), in conjunction with gene expression levels of representative marker genes in fatty acid metabolism. Whole-body energy metabolism including food consumption, body weights, oxygen consumption, locomotor activity, and respiration exchange ratios were determined at steady states. RESULTS--MCK-DGAT1 mice were protected against muscle lipoptoxicity, although they remain susceptible to hepatic lipotoxicity. While augmenting triglyceride synthesis, DGAT1 overexpression also led to increased muscle mitochondrial fatty acid oxidation efficiency, as compared with wild-type muscles. On a high-fat diet, MCK-DGAT1 mice displayed higher basal metabolic rates and 5-10% lower body weights compared with wild-type littermates, whereas food consumption was not different. CONCLUSIONS--DGAT1 overexpression in skeletal muscle led to parallel increases in triglyceride synthesis and fatty acid oxidation. Seemingly paradoxical, this phenomenon is characteristic of insulin-sensitive myofibers and suggests that DGAT1 plays an active role in metabolic "remodeling" of skeletal muscle coupled with insulin sensitization. Diabetes 58:2516-2524, 2009 [ABSTRACT FROM AUTHOR]

Systemic inflammation is associated with either fever or hypothermia. Fever, a response to mild systemic inflammation, is mediated by cyclooxygenase (COX)-2 and not by COX-1. However, it is still disputed whether COX-2, COX-1, neither, or both mediate(s) responses to severe systemic inflammation, and, in particular, the hypothermic response. We compared the effects of SC-236 (COX-2 inhibitor) and SC-560 (COX-! inhibitor) on the deep body temperature (Tb) of rats injected with a lower (10 μg/kg iv) or higher (1,000 μg/kg iv) dose of LPS at different ambient temperatures (TaS). At a neutral Ta (30°C), the rats responded to LPS with a polyphasic fever (lower dose) or a brief hypothermia followed by fever (higher dose). SC-236 (2.5 mg/kg iv) blocked the fever induced by either LPS dose, whereas SC-560 (5 mg/kg iv) altered neither the febrile response to the lower LPS dose nor the fever component of the response to the higher dose. However, SC-560 blocked the initial hypothermia caused by the higher LPS dose. At a subneutral Ta, (22°C), the rats responded to LPS with early (70-90 min, nadir) dose-dependent hypothermia. The hypothermic response to either dose was enhanced by SC-236 but blocked by SC-560. The hypothermic response to the higher LPS dose was associated with a fall in arterial blood pressure. This hypotensive response was attenuated by either SC-236 or SC-560. At the onset of LPS-induced hypothermia and hypotension, the functional activity of the COX-1 pathway (COX-1-mediated PGE2 synthesis ex vivo) increased in the spleen but not liver, lung, kidney, or brain. The expression of splenic COX-1 was unaffected by LPS. We conclude that COX-1, but not COX-2, mediates LPS hypothermia, and that both COX isoforms are required for LPS hypotension. [ABSTRACT FROM AUTHOR]

Uncoupling protein 3 (Ucp3) is a transport protein of the inner mitochondrial membrane and presumably is implicated in the maintenance or tolerance of high lipid oxidation rates. Ucp3 is predominantly expressed in skeletal muscle and brown adipose tissue and is regulated by a transcription factor complex involving peroxisome proliferator-activated receptor-, MyoD, and COUP transcription factor II. By analysis of a mutant Djungarian hamster model lacking Ucp3 transcription specifically in brown adipose tissue, we identified a putative transcription factor-binding site that confers tissue specificity. A naturally occurring intronic point mutation disrupting this site leads to brown adipose tissue-specific loss of Ucp3 expression and an altered body weight trajectory. Our findings provide insight into tissue-specific Ucp3 regulation and, for the first time, unambiguously demonstrate that changes in Ucp3 expression can interfere with body weight regulation. [ABSTRACT FROM AUTHOR]

Recent studies have established that vitamin D plays multiple biological roles beyond calcium metabolism; however, whether vitamin D is involved in energy metabolism is unknown. To address this question, we characterized the metabolic phenotypes of vitamin D receptor (VDR)-null mutant mice. Under a normocalcemic condition, VDR-null mice displayed less body fat mass and lower plasma triglyceride and cholesterol levels compared with wild-type (WT) mice; when placed on a high-fat diet, VDR-null mice showed a slower growth rate and accumulated less fat mass globally than WT mice, even though their food intake and intestinal lipid transport capacity were the same as WT mice. Consistent with the lower adipose mass, plasma leptin levels were lower and white adipocytes were histologically smaller in VDR-null mice than WT mice. The rate of fatty acid β-oxidation in the white adipose tissue was higher, and the expression of uncoupling protein (UCP) 1, UCP2 and UCP3 was markedly upregulated in VDR-null mice, suggesting a higher energy expenditure in the mutant mice. Experiments using primary brown fat culture confirmed that 1 ,25-dihydroxyvitarnin D1 directly suppressed the expression of the UCPs. Consistently, the energy expenditure, oxygen consumption, and CO2 production in VDR-null mice were markedly higher than in WT mice. These data indicate that vitamin D is involved in energy metabolism and adipocyte biology in vivo in part through regulation of β-oxidation and UCP expression. [ABSTRACT FROM AUTHOR]

AMP- activated protein kinase (AMPK) plays an important role in regulating whole body energy homeostasis. Recently, it has been demonstrated that berberine (BBR) exerts antiobesity and antidiabetic effects in obese and diabetic rodent models through the activation of AMPK in peripheral tissues. Here we show that BBR improves lipid dysregulation and fatty liver in obese mice through central and peripheral actions. In obese db/db and ob/ob mice, BBR treatment reduced liver weight, hepatic and plasma triglyceride, and cholesterol contents. In the liver and muscle of db/db mice, BBR promoted AMPK activity and fatty acid oxidation and changed expression of genes involved in lipid metabolism. Additionally, intracerebroventricular administration of BBR decreased the level of malonyl-CoA and stimulated the expression of fatty acid oxidation genes in skeletal muscle. Together, these data suggest that BBR would improve fatty liver in obese subjects, which is probably mediated not only by peripheral AMPK activation but also by neural signaling from the central nervous system. [ABSTRACT FROM AUTHOR]

P2Y receptors have been reported to modulate gastrointestinal functions. The newest family member is the nucleotide-sugar receptor P2Y 14. P2ry14 mRNA was detected throughout the rat gut, with the highest level being in the forestomach. We investigated the role of the receptor in stomach motility using cognate agonists and knockout (KO) mice. In rat isolated forestomach, 100 μM UDP-glucose and 100μM UDP-galactose both increased the baseline muscle tension (BMT) by 6.2 ± 0.6 and 1.6 ± 0.6 mN (P < 0.05, n = 3-4), respectively, and the amplitude of contractions during electrical field stimulation (EFS) by 3.7 ± 1.7 and 4.3 ± 2.5 mN (P < 0.05, n = 3-4), respectively. In forestomach from wild-type (WT) mice, 100 μM UDP-glucose increased the BMT by 1.0 ± 0.1 mN (P <0.05, n = 6) but this effect was lost in the KO mice (change of -0.1 ± 0.1 N, n = 6). The 100 μM UDP-glucose also increased the' contraction amplitude during EFS in this tissue from the WT animals (0.9 ± 0.4 mN, P < 0.05, n = 6) but not from the KO mice (0.0 ± 0.2 mN, n = 6). In vivo, UDP-glucose at 2,000 mg/kg ip reduced gastric emptying in rats by 49.7% (P < 0.05, n = 4-6) and in WT and KO mice by 56.1 and 66.2%, respectively (P < 0.05, n = 7-10) vs. saline-treated control animals. There was no significant difference in gastric emptying between WT and KO animals receiving either saline or D-glucose. These results demonstrate a novel function of the P2Y14 receptor associated with contractility in the rodent stomach that does not lead to altered gastric emptying after receptor deletion and an ability of UDP-glucose to delay gastric emptying without involving the P2Y14 receptor. [ABSTRACT FROM AUTHOR]

Cancer chemotherapy drugs, such as cisplatin, potently produce nausea and vomiting. Acute effects of these treatments are partly controlled by antiemetic drugs, but the delayed effects (>24 h), especially nausea, are more difficult to treat. It is unknown what brain pathways produce this delayed sickness. Our prior data show that brain Fos expression is increased for at least 48 h after cisplatin treatment in the rat, a nonvomiting species. Here, we extend these observations by using house musk shrews (Suncus murinus), a species with an emetic response. Compared with saline injection, cisplatin treatment (30 mg/kg ip) induced Fos expression in hindbrain areas known to play a role in the generation of emesis, the dorsal motor nucleus (DMN), the area postrema, and the nucleus of the solitary tract (NTS), for up to 48 h. Cisplatin also stimulated Fos expression in the parabrachial nucleus (PBN) of the midbrain and the central nucleus of the amygdala (CeA) for at least 48 h after treatment. When animals were pretreated with the antiemetic palonosetron, a long-term serotonin type 3 (5-HT3) receptor antagonist, cisplatin-induced Fos expression was significantly attenuated in the NTS, DMN, and CeA at 6 h but not at 48 h. These results indicate that cisplatin activates a neural system that includes the dorsal vagal complex and forebrain in the musk shrew, which is partially suppressed by a 5-HT3 receptor antagonist. Our findings suggest the existence of an extensive neural system that could be targeted to reduce nausea, vomiting, and malaise in cancer patients receiving chemotherapy. [ABSTRACT FROM AUTHOR]

Background: Matrix metalloproteinase (MMP)-9, a member of the MMP superfamily is consistently implicated in the pathophysiology of atherosclerosis and plaque rupture, the most common mechanism responsible for acute coronary syndrome (ACS). Aim: To summarize the role of MMP-9 in atherosclerosis and its potential implications in assessment and treatment of coronary artery disease (CAD). Methods: We reviewed the PubMed database for relevant data regarding the role of MMP-9 in the pathophysiology of atherosclerosis. In the light of these data, we postulate potential implications of MMP-9 in the management and treatment of CAD. Results and conclusions: Existing data strongly support the role of MMP-9 in plaque destabilization and rupture. Based on the current knowledge, MMP-9 can potentially serve as a diagnostic biomarker in ACS and a prognostic biomarker in ACS and chronic CAD patients. MMP-9 is reduced by therapies that are associated with favourable outcome in atherosclerosis and thus may serve as a surrogate biomarker of treatment efficacy. However, large morbidity and mortality trials are still required to confirm that MMP-9 reduction is associated with improved outcome independent of the traditional risk factors (i.e. low-density lipoprotein cholesterol). Given its role in plaque rupture, inhibition of MMP-9 may promote plaque stabilization and consequently reduce cardiovascular events. Yet, the efficacy and safety of MMPs inhibitors should be first studied in preclinical models of atherosclerosis. [ABSTRACT FROM AUTHOR]

Uncoupling protein 3 (UCP3) is a mitochondrial transporter protein which, when over-expressed in mice, is associated with increased metabolic rate, increased feeding and low body weight. This phenotype probably reflects the increased levels of UCP3 partially uncoupling mitochondrial respiration from cellular ATP demands. Consistent with that, mitochondria isolated from muscles of mice that over-express UCP3 are less tightly coupled than those from wild-type mice but the degree of uncoupling is not modulated by likely physiological regulatory factors. To determine whether this also applies to intact muscle fibres, we tested the hypothesis that UCP3 constitutively (i.e. in an unregulated fashion) uncouples mitochondria in muscles from mice that over-expressed human UCP3 (OE mice). The rate of heat production of resting muscles was measured in vitro using bundles of fibres from soleus and extensor digitorum longus muscles of OE, wild-type (WT) and UCP3 knock-out mice. At 20°C, the only significant effect of genotype was that the rate of heat production of OE soleus (3.04 ± 0.16 mW g−1) was greater than for WT soleus (2.31 ± 0.05 mW g−1). At physiological temperature (35°C), the rate of heat production was independent of genotype and equal to the expected in vivo rate for skeletal muscles of WT mice. We conclude that at 35°C, the transgenic UCP3 was not constitutively active, but at 20°C in slow-twitch muscle, it was partially activated by unknown factors. The physiological factor(s) that activate mitochondrial uncoupling by UCP3 in vivo was either not present or inactive in resting isolated muscles. [ABSTRACT FROM AUTHOR]

Energy balance to prevent the development of obesity is dependent on energy expenditure. Although physical activity is the dominant mechanism for dissipating excess energy, a system of thermogenesis that evolved to protect the body from hypothermia is based upon the uncoupling of oxidative phosphorylation in brown adipocytes by the mitochondrial uncoupling protein (UCP1). It has been shown that upregulation of UCP1 by genetic manipulations or pharmacological agents can reduce obesity and improve insulin sensitivity. Recent evidence has shown the existence of two sources for brown adipocytes, one appearing as discrete brown fat depots during fetal development and the other appears during post-natal development as diffuse populations in traditional white fat depots. The latter can be induced by adrenergic stimulation depending on the genetic background of the animals and the nutritional environment. Understanding the biological and environmental factors controlling the expression of these two brown adipocyte populations promises to provide new strategies by which enhanced thermogenesis can be used to reduce obesity.International Journal of Obesity (2008) 32, S32–S38; doi:10.1038/ijo.2008.236 [ABSTRACT FROM AUTHOR]

Human mitochondria can be studied either in biopsies or by measuring flux through ATP synthase and phosphocreatine recovery using magnetic resonance spectroscopy. Myocellular ATP production (flux through ATP synthase [fATP]) increases by up to 90% during 8 h of insulin stimulation. Fasting mitochondrial function is 14–40% lower than in controls in the presence of insulin resistance, as seen in those with type 2 diabetes, their insulin-resistant relatives or the obese. Insulin-stimulated fATP is abolished in insulin-resistant relatives and patients with type 2 diabetes, and patients frequently show decreased mitochondrial size/density. Age, fat mass, physical activity, plasma NEFA and glucose all correlate negatively with mitochondrial function, but it is for methodological reasons difficult to determine whether reduced mitochondrial content or function account for reduced ATP production in insulin resistance. Experimental plasma NEFA elevation appears to inhibit mitochondrial function by interfering with the metabolic actions of insulin, which might explain impaired mitochondrial function in obesity. Alternatively, primary mitochondrial abnormalities, as seen in those with inherited risk of type 2 diabetes, could decrease lipid oxidation, thereby raising circulating and intracellular NEFA levels. In type 2 diabetes, chronic hyperglycaemia and dyslipidaemia could first diminish the function, and subsequently reduce the size or density of mitochondria via oxidative stress and apoptosis. Many questions remain unsolved, including (1) which mechanisms regulate mitochondrial adaptation to nutrient overload; (2) what factors control the expression of genes encoding mitochondrial proteins and other signals involved in mitochondrial biogenesis; (3) which geno/phenotypes are associated with both insulin resistance and mitochondrial abnormalities; and (4) which are the most promising targets for improving mitochondrial fitness in insulin resistance? [ABSTRACT FROM AUTHOR]

Background:Chronically elevated interleukin-6 (IL-6) is implicated in obesity-associated pathologies, where a proportion of this cytokine is derived from adipose tissue. Proinflammatory prostaglandins, which regulate this cytokine elsewhere, are also produced by this tissue.Objective:To investigate whether constitutively active cyclooxygenase (COX)/prostaglandin (PG) pathway in white adipose tissue (WAT) is responsible for basal IL-6 production.Design:The effect of acetylsalicylic acid (ASA), an inhibitor of COX, on IL-6 was assessed in human subjects and mice. COX, downstream PG synthase (PGS) activity and PG receptor signalling were determined in subcutaneous (SC), gonadal (GN) WAT and adipocytes.Methods and Results:In obese humans, low-dose ASA (150 mg day−1 for 10 days) inhibited systemic IL-6 and reduced IL-6 release from SC WAT ex vivo (0.2 mM). Similarly, in mice, ASA (0.2 and 2.0 mg kg−1) suppressed SC WAT 6-keto-PGF1α (a stable metabolite of prostacyclin) and IL-6 release. Although both COX isoforms are comparably expressed, prostacyclin synthase expression is higher in GN WAT, with levels of activity correlating directly with IL-6. Both ASA (5 mM) and NS-398 (COX-2 selective inhibitor 1 μM), but not SC-560 (COX-1 selective inhibitor 1 μM), attenuated IL-6 release from murine WAT in vitro and abolished its depot differences. Prostacyclin receptor (IP) and, to a lesser extent, PGE2 (EP2 and EP4) receptor agonists elevated the release of IL-6 from adipocytes.Conclusions:In adipose tissue, constitutive COX-2-coupled prostacyclin triggers the release of basal IL-6, which in obese subjects is significantly dampened by ASA ingestion, thus offering a novel, modifiable pathway to regulate the potentially pathological component of this cytokine.International Journal of Obesity (2008) 32, 1807–1815; doi:10.1038/ijo.2008.190; published online 4 November 2008 [ABSTRACT FROM AUTHOR]