The role of uncoupling proteins in the regulation of metabolism

Potential Role of Pig UCP3 in Modulating Adipocyte Browning via the Beta-Adrenergic Receptor Signaling Pathway

Adipose tissue plays an important role in regulating body temperature and metabolism, with white adipocytes serving as storage units for energy. Recent research focused on the browning of white adipocytes (beige adipocytes), causing thermogenesis and lipolysis. The process of browning is linked to the activation of uncoupling protein (UCP) expression, which can be mediated by the β3 adrenergic receptor pathway. Transcriptional factors, such as peroxisome proliferator activated receptor γ (PPARγ) and PPARγ coactivator 1 alpha, play vital roles in cell fate determination for fat cells. Beige adipocytes have metabolic therapeutic potential to combat diseases such as obesity, diabetes mellitus, and dyslipidemia, owing to their significant impact on metabolic functions. However, the molecular mechanisms that cause the induction of browning are unclear. Therefore, research using animal models and primary culture is essential to provide an understanding of browning for further application in human metabolic studies. Pigs have physiological similarities to humans; hence, they are valuable models for research on adipose tissue. This study demonstrates the browning potential of pig white adipocytes through primary culture experiments. The results show that upregulation of UCP3 gene expression and fragmentation of lipid droplets into smaller particles occur due to isoproterenol stimulation, which activates beta-adrenergic receptor signaling. Furthermore, PPARγ and PGC-1α were found to activate the UCP3 promoter region, similar to that of UCP1. These findings suggest that pigs undergo metabolic changes that induce browning in white adipocytes, providing a promising approach for metabolic research with potential implications for human health. This study offers valuable insights into the mechanism of adipocyte browning using pig primary culture that can enhance our understanding of human metabolism, leading to cures for commonly occurring diseases.

A New Strategy for Targeting UCP2 to Modulate Glycolytic Reprogramming as a Treatment for Sepsis A New Strategy for Targeting UCP2

Sepsis is a severe and life-threatening disease caused by infection, characterized by a dysregulated immune response. Unfortunately, effective treatment strategies for sepsis are still lacking. The intricate interplay between metabolism and the immune system limits the treatment options for sepsis. During sepsis, there is a profound shift in cellular energy metabolism, which triggers a metabolic reprogramming of immune cells. This metabolic alteration impairs immune responses, giving rise to excessive inflammation and immune suppression. Recent research has demonstrated that UCP2 not only serves as a critical target in sepsis but also functions as a key metabolic switch involved in immune cell-mediated inflammatory responses. However, the regulatory mechanisms underlying this modulation are complex. This article focuses on UCP2 as a target and discusses metabolic reprogramming during sepsis and the complex regulatory mechanisms between different stages of inflammation. Our research indicates that overexpression of UCP2 reduces the Warburg effect, restores mitochondrial function, and improves the prognosis of sepsis. This discovery aims to provide a promising approach to address the significant challenges associated with metabolic dysfunction and immune paralysis.

Visceral Adipose Tissue Bioenergetics Varies According to Individuals' Obesity Class

Obesity is associated with complex adipose tissue energy metabolism remodeling. Whether AT metabolic reprogramming differs according to body mass index (BMI) and across different obesity classes is unknown. This study’s purpose was to evaluate and compare bioenergetics and energy substrate preference of visceral adipose tissue (VAT) pertaining to individuals with obesity class 2 and class 3. VAT obtained from patients with obesity (n = 15) class 2 (n = 7; BMI 37.53 ± 0.58 kg/m2) or class 3 (n = 8; BMI 47.79 ± 1.52 kg/m2) was used to assess oxygen consumption rate (OCR) bioenergetics and mitochondrial substrate preferences. VAT of patients with obesity class 3 presented significantly higher non-mitochondrial oxygen consumption (p < 0.05). In VAT of patients with obesity class 2, inhibition of pyruvate and glutamine metabolism significantly decreased maximal respiration and spare respiratory capacity (p < 0.05), while pyruvate and fatty acid metabolism inhibition, which renders glutamine the only available substrate, increased the proton leak with a protective role against oxidative stress (p < 0.05). In conclusion, VAT bioenergetics of patients with obesity class 2 depicts a greater dependence on glucose/pyruvate and glutamine metabolism, suggesting that patients within this BMI range are more likely to be responsive to interventions based on energetic substrate modulation for obesity treatment.

Protective Role of Mitochondrial Uncoupling Proteins against Age-Related Oxidative Stress in Type 2 Diabetes Mellitus

The accumulation of oxidative damage to DNA and other biomolecules plays an important role in the etiology of aging and age-related diseases such as type 2 diabetes mellitus (T2D), atherosclerosis, and neurodegenerative disorders. Mitochondrial DNA (mtDNA) is especially sensitive to oxidative stress. Mitochondrial dysfunction resulting from the accumulation of mtDNA damage impairs normal cellular function and leads to a bioenergetic crisis that accelerates aging and associated diseases. Age-related mitochondrial dysfunction decreases ATP production, which directly affects insulin secretion by pancreatic beta cells and triggers the gradual development of the chronic metabolic dysfunction that characterizes T2D. At the same time, decreased glucose oxidation in skeletal muscle due to mitochondrial damage leads to prolonged postprandial blood glucose rise, which further worsens glucose homeostasis. ROS are not only highly reactive by-products of mitochondrial respiration capable of oxidizing DNA, proteins, and lipids but can also function as signaling and effector molecules in cell membranes mediating signal transduction and inflammation. Mitochondrial uncoupling proteins (UCPs) located in the inner mitochondrial membrane of various tissues can be activated by ROS to protect cells from mitochondrial damage. Mitochondrial UCPs facilitate the reflux of protons from the mitochondrial intermembrane space into the matrix, thereby dissipating the proton gradient required for oxidative phosphorylation. There are five known isoforms (UCP1-UCP5) of mitochondrial UCPs. UCP1 can indirectly reduce ROS formation by increasing glutathione levels, thermogenesis, and energy expenditure. In contrast, UCP2 and UCP3 regulate fatty acid metabolism and insulin secretion by beta cells and modulate insulin sensitivity. Understanding the functions of UCPs may play a critical role in developing pharmacological strategies to combat T2D. This review summarizes the current knowledge on the protective role of various UCP homologs against age-related oxidative stress in T2D.

Real ambient particulate matter-induced lipid metabolism disorder: Roles of peroxisome proliferators-activated receptor alpha

A growing body of evidence associated particulate matter (PM) exposure with lipid metabolism disorders, yet, the underlying mechanism remains to be elucidated. Among the major lipid metabolism modulators, peroxisome proliferator-activated receptor (PPAR) alpha plays an important role. In the current study, an individually ventilated cage (IVC) system was used to expose C57/B6 mice to real-ambient PM for six weeks, with or without co-treatment of PPAR alpha agonist WY14,643. The general parameters, liver and adipose tissue pathology, serum lipids, metal deposition and lipid profile of liver were assessed. The results indicated that six weeks of real-ambient PM exposure induced dyslipidemia, including increased serum triglycerides (TG) and decreased high density lipoprotein cholesterol (HDL-C) level, along with steatosis in liver, increased size of adipocytes in white adipose tissue (WAT) and whitening of brown adipose tissue (BAT). ICP-MS results indicated increased Cr and As deposition in liver. Lipidomics analysis revealed that glycerophospholipids and cytochrome P450 pathway were most significantly affected by PM exposure. Several lipid metabolism-related genes, including CYP4A14 in liver and UCP1 in BAT were downregulated following PM exposure. WY14,643 treatment alleviated PM-induced dyslipidemia, liver steatosis and whitening of BAT, while enhancing CD36, SLC27A1, CYP4A14 and UCP1 expression. In conclusion, PPAR alpha pathway participates in PM-induced lipid metabolism disorder, PPAR alpha agonist WY14,643 treatment exerted protective effects on PM-induced dyslipidemia, liver steatosis and whitening of BAT, but not on increased adipocyte size of WAT.

The exercise-instrumental music program and irisin levels in younger non-professional athletes

A passive lifestyle and lack of exercise are triggering factors in increasing metabolic syndrome, whereas metabolic syndrome is associated with increased morbidity and mortality. This study aimed to analyse an exercise-based non-pharmacological approach combined with instrumental music to the plasma levels of irisin. The study employed a randomised pretest-posttest-only group design recruiting 30 male participants. The individuals aged between 19-21 years, body mass index (BMI) 18.5-24.9 kg/m2, normal blood pressure, normal resting heart rate (RHR), VO2max 40-50 ml/kg bodyweight/min, normal haemoglobin (Hb). The subjects were randomly divided into three groups, MIE (n=10, moderate-intensity exercise), MIEM (n=10, moderate-intensity exercise + instrumental music), and HIE (n=10, high-intensity exercise). Blood sampling was collected from pre- and 5 min post-exercise treatment. ELISA method was used to measure the circulating irisin levels. The non-parametric Kruskal-Wallis test, Mann Whitney test and Spearman correlation were chosen to analyse the data. The results showed that there is no significant difference in pre-exercise irisin levels (ng/ml) in MIE (1.58±0.89), MIEM (1.77±3.12), and HIE (1.65±0.88) with a P-value of 0.098. Importantly, the alteration of irisin levels post-exercise program revealed that the level of this peptide (ng/ml) is higher in HIE (7.28±5.11) compared to MIE (1.95±1.85) and MIEM (4.16±3.40) with a P-value of 0.019. The plasma levels of irisin significantly correlate to energy expenditure (r=0.353, P≤0.01), plasma peroxisome proliferator-activated receptor gamma coactivator-1α (r=0.597, P≤0.001), and high-density lipoprotein (r=0.513, P≤0.01). In summary, increased irisin secretion may directly contribute to the gradual alteration of energy expenditure and correlate to physical exercise intensity-related musical treatment.

Effects of a high-fat diet and global aryl hydrocarbon receptor deficiency on energy balance and liver retinoid status in male Sprague-Dawley rats

The physiological functions of the aryl hydrocarbon receptor (AHR) are only beginning to unfold. Studies in wildtype and AHR knockout (AHRKO) mice have recently disclosed that AHR activity is required for obesity and steatohepatitis to develop when mice are fed with a high-fat diet (HFD). In addition, a line of AHRKO mouse has been reported to accumulate retinoids in the liver. Whether these are universal manifestations across species related to AHR activity level is not known yet. Therefore, we here subjected wildtype and AHRKO male rats (on Sprague-Dawley background) to HFD feeding coupled with free access to 10% sucrose solution and water; controls received a standard diet and water. Although the HFD-fed rats consumed more energy throughout the 24-week feeding regimen, they did not get overweight. However, relative weights of the brown and epididymal adipose tissues were elevated in HFD-fed rats, while that of the liver was lower in AHRKO than wildtype rats. Moreover, the four groups exhibited diet- or genotype-dependent differences in biochemical variables, some of which suggested marked dissimilarities from AHRKO mice. Expression of pro- and anti-inflammatory genes was induced in livers of HFD-fed AHRKO rats, but histologically they did not differ from others. HFD reduced the hepatic concentrations of retinyl palmitate, 9-cis-4-oxo-13,14-dihydroretinoic acid and (suggestively) retinol, whereas AHR status had no effect. Hence, the background strain/line of AHRKO rat is resistant to diet-induced obesity, and AHR does not modulate this or liver retinoid concentrations. Yet, subtle AHR-dependent differences in energy balance-related factors exist despite similar weight development.

Pathological and Pharmacological Roles of Mitochondrial Reactive Oxygen Species in Malignant Neoplasms: Therapies Involving Chemical Compounds, Natural Products, and Photosensitizers

Oxidative stress plays an important role in cellular processes. Consequently, oxidative stress also affects etiology, progression, and response to therapeutics in various pathological conditions including malignant tumors. Oxidative stress and associated outcomes are often brought about by excessive generation of reactive oxygen species (ROS). Accumulation of ROS occurs due to dysregulation of homeostasis in an otherwise strictly controlled physiological condition. In fact, intracellular ROS levels are closely associated with the pathological status and outcome of numerous diseases. Notably, mitochondria are recognized as the critical regulator and primary source of ROS. Damage to mitochondria increases mitochondrial ROS (mROS) production, which leads to an increased level of total intracellular ROS. However, intracellular ROS level may not always reflect mROS levels, as ROS is not only produced by mitochondria but also by other organelles such as endoplasmic reticulum and peroxisomes. Thus, an evaluation of mROS would help us to recognize the biological and pathological characteristics and predictive markers of malignant tumors and develop efficient treatment strategies. In this review, we describe the pathological significance of mROS in malignant neoplasms. In particular, we show the association of mROS-related signaling in the molecular mechanisms of chemically synthesized and natural chemotherapeutic agents and photodynamic therapy.

6-Amino[1,2,5]oxadiazolo[3,4-b]pyrazin-5-ol Derivatives as Efficacious Mitochondrial Uncouplers in STAM Mouse Model of Nonalcoholic Steatohepatitis

Small molecule mitochondrial uncouplers have recently garnered great interest for their potential in treating nonalcoholic steatohepatitis (NASH). In this study, we report the structure-activity relationship profiling of a 6-amino[1,2,5]oxadiazolo[3,4-b]pyrazin-5-ol core, which utilizes the hydroxy moiety as the proton transporter across the mitochondrial inner membrane. We demonstrate that a wide array of substituents is tolerated with this novel scaffold that increased cellular metabolic rates in vitro using changes in oxygen consumption rate as a readout. In particular, compound SHS4121705 (12i) displayed an EC50 of 4.3 μM in L6 myoblast cells and excellent oral bioavailability and liver exposure in mice. In the STAM mouse model of NASH, administration of 12i at 25 mg kg-1 day-1 lowered liver triglyceride levels and improved liver markers such as alanine aminotransferase, NAFLD activity score, and fibrosis. Importantly, no changes in body temperature or food intake were observed. As potential treatment of NASH, mitochondrial uncouplers show promise for future development.

[1,2,5]Oxadiazolo[3,4-b]pyrazine-5,6-diamine Derivatives as Mitochondrial Uncouplers for the Potential Treatment of Nonalcoholic Steatohepatitis

Small molecule mitochondrial uncouplers are emerging as a new class of molecules for the treatment of nonalcoholic steatohepatitis. We utilized BAM15, a potent protonophore that uncouples the mitochondria without depolarizing the plasma membrane, as a lead compound for structure-activity profiling. Using oxygen consumption rate as an assay for determining uncoupling activity, changes on the 5- and 6-position of the oxadiazolopyrazine core were introduced. Our studies suggest that unsymmetrical aniline derivatives bearing electron withdrawing groups are preferred compared to the symmetrical counterparts. In addition, alkyl substituents are not tolerated, and the N-H proton of the aniline ring is responsible for the protonophore activity. In particular, compound 10b had an EC₅₀ value of 190 nM in L6 myoblast cells. In an in vivo model of NASH, 10b decreased liver triglyceride levels and showed improvement in fibrosis, inflammation, and plasma ALT. Taken together, our studies indicate that mitochondrial uncouplers have potential for the treatment of NASH.

Long-term effects of prior diets, dietary transition and pregnancy on adipose gene expression in dairy heifers

Adipose tissue is highly involved in whole-body metabolism and is the main site for lipid synthesis, storage and mobilization in ruminants. Therefore, knowledge about adipose tissue responses to different diets is important, especially in growing heifers as the feeding regimes of replacement heifers affect their future success as dairy cows. However, at gene expression level such knowledge is limited. As part of a larger feed trial, adipose tissue biopsies from 24 Norwegian Red heifers were collected at 12 months of age (12MO) and at month seven of gestation (PREG) and analyzed by next-generation mRNA sequencing. Between these two sampling points, all heifers had gone through a successful conception and a feed change from four dietary treatments of high or low energy (HE/LE) and protein (HP/LP) content (treatments LPHE, HPHE, LPLE and HPLE) to a low-energy, low-protein pregnancy feed given to all animals. Gene expression differences between different feed treatments at 12MO are described in an earlier publication from our group. The main objectives of this study were to investigate the long-term effects of diets differing in protein and energy density level on gene expression in adipose tissue of growing replacement dairy heifers. To achieve this, we examined the post-treatment effects between the treatment groups at month seven of gestation; 6 months after the termination of experimental feeding, and the long-term gene expression changes occurring in the adipose tissue between 12MO and PREG. Post-treatment group comparisons showed evidence of long-term effects of dietary treatment on adipose gene expression. Differences between protein treatments were smaller than between energy treatments. Adipose gene expression changes from 12MO to PREG were much larger for the HE than the LE treatments and seemed to mostly be explained by the characteristics of the diet change. 97 genes displayed a unidirectional expression change for all groups from 12MO to PREG, and are considered to be treatment-independent, possibly caused by pregnancy or increased age. This study provides candidate genes and key regulators for further studies on pregnancy preservation (TGFB1, CFD) and metabolic regulation and efficiency (PI3K, RICTOR, MAP4K4,) in dairy cattle.

Skeletal muscles of hibernating black bears show minimal atrophy and phenotype shifting despite prolonged physical inactivity and starvation

Hibernating mammals experience prolonged periods of torpor and starvation during winter for up to 5–7 months. Though physical inactivity and malnutrition generally lead to profound loss of muscle mass and metabolic dysfunction in humans, hibernating bears show limited muscle atrophy and can successfully maintain locomotive function. These physiological features in bears allow us to hypothesize that hibernating bears uniquely alter the regulation of protein and energy metabolism in skeletal muscle which then contributes to “muscle atrophy resistance” against continued physical inactivity. In this study, alteration of signaling pathways governing protein and energy metabolisms was examined in skeletal muscle of the Japanese black bear (Ursus thibetanus japonicus). Sartorius muscle samples were collected from bear legs during late November (pre-hibernation) and early April (post-hibernation). Protein degradation pathways, through a ubiquitin-proteasome system (as assessed by increased expression of murf1 mRNA) and an autophagy-dependent system (as assessed by increased expression of atg7, beclin1, and map1lc3 mRNAs), were significantly activated in skeletal muscle following hibernation. In contrast, as indicated by a significant increase in S6K1 phosphorylation, an activation state of mTOR (mammalian/mechanistic target of rapamycin), which functions as a central regulator of protein synthesis, increased in post-hibernation samples. Gene expression of myostatin, a negative regulator of skeletal muscle mass, was significantly decreased post-hibernation. We also confirmed that the phenotype shifted toward slow-oxidative muscle and mitochondrial biogenesis. These observations suggest that protein and energy metabolism may be altered in skeletal muscle of hibernating bears, which then may contribute to limited loss of muscle mass and efficient energy utilization.

Oxidative damage mediated iNOS and UCP-2 upregulation in rat brain after sub-acute cyanide exposure: dose and time-dependent effects

Cyanide-induced chemical hypoxia is responsible for pronounced oxidative damage in the central nervous system. The disruption of mitochondrial oxidative metabolism has been associated with upregulation of uncoupling proteins (UCPs). The present study addresses the dose- and time-dependent effect of sub-acute cyanide exposure on various non-enzymatic and enzymatic oxidative stress markers and their correlation with inducible-nitric oxide synthase (iNOS) and uncoupling protein-2 (UCP-2) expression. Animals received (oral) triple distilled water (vehicle control), 0.25 LD50 potassium cyanide (KCN) or 0.50 LD50 KCN daily for 21 d. Animals were sacrificed on 7, 14 and 21 d post-exposure to measure serum cyanide and nitrite, and brain malondialdehyde (MDA), reduced glutathione (GSH), glutathione disulfide (GSSG), cytochrome c oxidase (CCO), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR) and catalase (CA) levels, together with iNOS and UCP-2 expression, and DNA damage. The study revealed that a dose- and time-dependent increase in cyanide concentration was accompanied by corresponding CCO inhibition and elevated MDA levels. Decrease in GSH levels was not followed by reciprocal change in GSSG levels. Diminution of SOD, GPx, GR and CA activity was congruent with elevated nitrite levels and upregulation of iNOS and UCP-2 expression, without any DNA damage. It was concluded that long-term cyanide exposure caused oxidative stress, accompanied by upregulation of iNOS. The upregulation of UCP-2 further sensitized the cells to cyanide and accentuated the oxidative stress, which was independent of DNA damage.

Serum levels of uncoupling proteins in patients with differential insulin resistance: A community-based cohort study

The uncoupling protein (UCP) belongs to a family of energy-dissipating proteins in mitochondria. Increasing evidences have indicated that UCPs have immense impact on glucose homeostasis and are key proteins in metabolic syndrome. For applying the findings to clinical practice, we designed a study to explore the association between serum UCPs 1-3 and insulin resistance. This investigation prospectively recorded demographical parameter and collected blood samples of 1071 participants from 4 districts in Northeastern Taiwan during the period from August 2013 to July 2014. Propensity score matching by age and sex in patients with top and bottom third homeostasis model assessment of insulin resistance (HOMA-IR) levels was performed, and 326 subjects were enrolled for further studies. The mean age of the patients was 59.4 years and the majority of them (65.5%) were females. The prevalence of metabolic syndrome was 35.5%. Our results demonstrated that serum UCPs 1-3 were significantly associated with differences in HOMA-IR levels. Multiple logistic regression analysis indicated that low UCP 1 and features of metabolic syndrome, namely hypertension, diabetes, body mass index, and high-density lipoprotein, were independent determinants for high HOMA-IR levels. We thus determined that low serum UCP 1 is a predictor for high resistance to insulin.

Mitochondrial function and bioenergetic trade-offs during lactation in the house mouse (Mus musculus)

Energy allocation theory predicts that a lactating female should alter the energetic demands of its organ systems in a manner that maximizes nutrient allocation to reproduction while reducing nutrient use for tasks that are not vital to immediate survival. We posit that organ‐specific plasticity in the function of mitochondria plays a key role in mediating these energetic trade‐offs. The goal of this project was to evaluate mitochondrial changes that occur in response to lactation in two of the most energetically demanding organs in the body of a rodent, the liver and skeletal muscle. This work was conducted in wild‐derived house mice (Mus musculus) kept in seminatural enclosures that allow the mice to maintain a natural social structure and move within a home range size typical of wild mice. Tissues were collected from females at peak lactation and from age‐matched nonreproductive females. Mitochondrial respiration, oxidative damage, antioxidant, PGC‐1α, and uncoupling protein levels were compared between lactating and nonreproductive females. Our findings suggest that both liver and skeletal muscle downregulate specific antioxidant proteins during lactation. The liver, but not skeletal muscle, of lactating females displayed higher oxidative damage than nonreproductive females. The liver mass of lactating females increased, but the liver displayed no change in mitochondrial respiratory control ratio. Skeletal muscle mass and mitochondrial respiratory control ratio were not different between groups. However, the respiratory function of skeletal muscle did vary among lactating females as a function of stage of concurrent pregnancy, litter size, and mass of the mammary glands. The observed changes are predicted to increase the efficiency of skeletal muscle mitochondria, reducing the substrate demands of skeletal muscle during lactation. Differences between our results and prior studies highlight the role that an animals’ social and physical environment could play in how it adapts to the energetic demands of reproduction.

BAR502, a dual FXR and GPBAR1 agonist, promotes browning of white adipose tissue and reverses liver steatosis and fibrosis

Non-alcoholic steatohepatitis (NASH) is a highly prevalent chronic liver disease. Here, we have investigated whether BAR502, a non-bile acid, steroidal dual ligand for FXR and GPBAR1, reverses steato-hepatitis in mice fed a high fat diet (HFD) and fructose. After 9 week, mice on HFD gained ≈30% of b.w (P < 0.01 versus naïve) and were insulin resistant. These overweighting and insulin resistant mice were randomized to receive HFD or HFD in combination with BAR502. After 18 weeks, HFD mice developed NASH like features with severe steato-hepatitis and fibrosis, increased hepatic content of triacylglycerol and cholesterol and expression of SREPB1c, FAS, ApoC2, PPARα and γ, α-SMA, α1 collagen and MCP1 mRNAs. Treatment with BAR502 caused a ≈10% reduction of b.w., increased insulin sensitivity and circulating levels of HDL, while reduced steatosis, inflammatory and fibrosis scores and liver expression of SREPB1c, FAS, PPARγ, CD36 and CYP7A1 mRNA. BAR502 increased the expression of SHP and ABCG5 in the liver and SHP, FGF15 and GLP1 in intestine. BAR502 promoted the browning of epWAT and reduced liver fibrosis induced by CCl₄. In summary, BAR502, a dual FXR and GPBAR1 agonist, protects against liver damage caused by HFD by promoting the browning of adipose tissue.

Uncoupling Protein, UCP-4 May Be Involved in Neuronal Defects During Aging and Resistance to Pathogens in Caenorhabditis elegans

Uncoupling proteins (UCPs) are mitochondrial inner membrane proteins that function to dissipate proton motive force and mitochondrial membrane potential. One UCP has been identified in Caenorhabditis elegans (C. elegans), namely UCP-4. In this study, we examined its expression and localization using a GFP marker in C. elegans. ucp-4 was expressed throughout the body from early embryo to aged adult and UCP-4 was localized in the mitochondria. It is known that increased mitochondrial membrane protential leads to a reactive oxygen species (ROS) increase, which is associated with age-related diseases, including neurodegenerative diseases in humans. A ucp-4 mutant showed increased mitochondrial membrane protential in association with increased neuronal defects during aging, and the neurons of ucp-4 overexpressing animals showed decreased neuronal defects during aging. These results suggest that UCP-4 may be involved in neuroprotection during aging via relieving mitochondrial membrane protential. We also investigated the relationship between UCP-4 and innate immunity because increased ROS can affect innate immunity. ucp-4 mutant displayed increased resistance to the pathogen Staphylococcus aureus compared to wild type. The enhanced immunity in the ucp-4 mutant could be related to increased mitochondrial membrane protential, presumably followed by increased ROS. In summary, UCP-4 might have an important role in neuronal aging and innate immune responses through mediating mitochondrial membrane protential.

Metallothioneins 1 and 2 Modulate Inflammation and Support Remodeling in Ischemic Cardiomyopathy in Mice

Aims. Repetitive brief ischemia and reperfusion (I/R) is associated with left ventricular dysfunction during development of ischemic cardiomyopathy. We investigated the role of zinc-donor proteins metallothionein MT1 and MT2 in a closed-chest murine model of I/R. Methods. Daily 15-minute LAD-occlusion was performed for 1, 3, and 7 days in SV129 (WT)- and MT1/2 knockout (MT(-/-))-mice (n = 8-10/group). Hearts were examined with M-mode echocardiography and processed for histological and mRNA studies. Results. Expression of MT1/2 mRNA was transiently induced during repetitive I/R in WT-mice, accompanied by a transient inflammation, leading to interstitial fibrosis with left ventricular dysfunction without infarction. In contrast, MT(-/-)-hearts presented with enhanced apoptosis and small infarctions leading to impaired global and regional pump function. Molecular analysis revealed maladaptation of myosin heavy chain isoforms and antioxidative enzymes in MT1/2(-/-)-hearts. Despite their postponed chemokine induction we found a higher total neutrophil density and macrophage infiltration in small infarctions in MT(-/-)-hearts. Subsequently, higher expression of osteopontin 1 and tenascin C was associated with increased myofibroblast density resulting in predominately nonreversible fibrosis and adverse remodeling in MT1/2(-/-)-hearts. Conclusion. Cardioprotective effects of MT1/2 seem to be exerted via modulation of contractile elements, antioxidative enzymes, inflammatory response, and myocardial remodeling.

Omega-9 Oleic Acid Induces Fatty Acid Oxidation and Decreases Organ Dysfunction and Mortality in Experimental Sepsis

Sepsis is characterized by inflammatory and metabolic alterations, which lead to massive cytokine production, oxidative stress and organ dysfunction. In severe systemic inflammatory response syndrome, plasma non-esterified fatty acids (NEFA) are increased. Several NEFA are deleterious to cells, activate Toll-like receptors and inhibit Na⁺/K⁺-ATPase, causing lung injury. A Mediterranean diet rich in olive oil is beneficial. The main component of olive oil is omega-9 oleic acid (OA), a monounsaturated fatty acid (MUFA). We analyzed the effect of OA supplementation on sepsis. OA ameliorated clinical symptoms, increased the survival rate, prevented liver and kidney injury and decreased NEFA plasma levels in mice subjected to cecal ligation and puncture (CLP). OA did not alter food intake and weight gain but diminished reactive oxygen species (ROS) production and NEFA plasma levels. Carnitine palmitoyltransferase IA (CPT1A) mRNA levels were increased, while uncoupling protein 2 (UCP2) liver expression was enhanced in mice treated with OA. OA also inhibited the decrease in 5' AMP-activated protein kinase (AMPK) expression and increased the enzyme expression in the liver of OA-treated mice compared to septic animals. We showed that OA pretreatment decreased NEFA concentration and increased CPT1A and UCP2 and AMPK levels, decreasing ROS production. We suggest that OA has a beneficial role in sepsis by decreasing metabolic dysfunction, supporting the benefits of diets high in monounsaturated fatty acids (MUFA).

Exercise Increases and Browns Muscle Lipid in High-Fat Diet-Fed Mice

Muscle lipid increases with high-fat feeding and diabetes. In trained athletes, increased muscle lipid is not associated with insulin resistance, a phenomenon known as the athlete's paradox. To understand if exercise altered the phenotype of muscle lipid, female C57BL/6 mice fed CTL or high-fat diet (HFD for 6 or 18 weeks) were further divided into sedentary or exercising groups (CTL-E or HFD-E) with voluntary access to running wheels for the last 6 weeks of experiments, running 6 h/night. Diet did not affect running time or distance. HFD mice weighed more than CTL after 18 weeks (p < 0.01). Quadriceps muscle TG was increased in running animals and in sedentary mice fed HFD for 18 weeks (p < 0.05). In exercised animals, markers of fat, Plin1, aP2, FSP27, and Fasn, were increased significantly in HFD groups. Ucp1 and Pgc1a, markers for brown fat, increased with exercise in the setting of high fat feeding. Fndc5, which encodes irisin, and CytC were sensitive to exercise regardless of diet. Plin5 was increased with HFD and unaffected by exercise; the respiratory exchange ratio was 15% lower in the 18-week HFD group compared with CTL (p < 0.001) and 10% lower in 18 weeks HFD-E compared with CTL-E (p < 0.001). Increased Ucp1 and Pgc1a in exercised muscle of running mice suggests that a beige/brown fat phenotype develops, which differs from the fat phenotype that induces insulin resistance in high fat feeding. This suggests that increased muscle lipid may develop a "brown" phenotype in the setting of endurance exercise training, a shift that is further promoted by HFD.

The effect of delivery type on uncoupling protein-2 levels

OBJECTIVE

Uncoupling proteins (UCPs) are carrier proteins located in the mitochondrial inner membrane that disturb the proton gradient by re-transporting protons and that thus inhibit ATP synthesis. UCP-2 is found in in several tissues, particularly the brain. This study was performed to examine the effects of mode of delivery on UCP-2 in humans.

METHODS

The study was performed prospectively. Cord blood specimens were collected for measurement of blood gasses, full-blood count, total and direct bilirubin levels and UCP-2. UCP-2 levels were measured using an enzyme-linked immunosorbent assay (ELISA) kit. Results were expressed as nanogram per milliliter.

RESULTS

The study was performed with 120 healthy term babies, 60 born by normal spontaneous vaginal delivery (NSVD) and 60 by cesarean/section (C/S). There was significant difference in UCP-2 levels between the two groups. UCP-2 levels were significantly higher in the cases born by NSVD then in the cases born by C/S.

CONCLUSION

This study showed that a correlation exists between mode of delivery and UCP-2 in humans. As UCP-2 is described as playing a significant role in the formation of nerve cells and deficiency of this protein during development of the brain may lead to behavioral problems extending to adulthood, we think that increasing UCP-2 levels through normal delivery will protect all organs, and particularly the brain, against oxidative damage and play a role in preventing organ dysfunctions.

Isoproterenol Increases Uncoupling, Glycolysis, and Markers of Beiging in Mature 3T3-L1 Adipocytes

Beta-adrenergic activation stimulates uncoupling protein 1 (UCP1), enhancing metabolic rate. In vitro, most work has studied brown adipocytes, however, few have investigated more established adipocyte lines such as the murine 3T3-L1 line. To assess the effect of beta-adrenergic activation, mature 3T3-L1s were treated for 6 or 48 hours with or without isoproterenol (10 and 100 μM) following standard differentiation supplemented with thyroid hormone (T3; 1 nM). The highest dose of isoproterenol increased lipid content following 48 hours of treatment. This concentration enhanced UCP1 mRNA and protein expression. The increase in UCP1 following 48 hours of isoproterenol increased oxygen consumption rate. Further, coupling efficiency of the electron transport chain was disturbed and an enhancement of glycolytic rate was measured alongside this, indicating an attempt to meet the energy demands of the cell. Lastly, markers of beige adipocytes (protein content of CD137 and gene transcript of CITED1) were also found to be upregulated at 48 hours of isoproterenol treatment. This data indicates that mature 3T3-L1 adipocytes are responsive to isoproterenol and induce UCP1 expression and activity. Further, this finding provides a model for further pharmaceutical and nutraceutical investigation of UCP1 in 3T3-L1s.

Relationship between expression of muscle-specific uncoupling protein 2 messenger RNA and genetic selection toward growth in channel catfish

This study tested the hypothesis that increased growth in channel catfish is associated with expression of the genes that code for uncoupling proteins (UCP) 2 and 3, members of the mitochondrial channel proteins involved in nutrient sensing and metabolism. The specific objective was to contrast the levels of UCP2 messenger RNA (mRNA) in fast vs slow growing catfish as well as in fed vs fasted catfish. Two distinct UCP2 transcripts were identified and named UCP2a and UCP2b, respectively. Nucleotide and amino acid sequence of catfish UCP2s were highly similar to UCP2 and other UCPs from other fish and mammals (>75%). Expression of UCP2a mRNA was detectable at very low levels in various metabolically active tissues, whereas the expression of UCP2b mRNA was readily detectable in the muscle and heart. In a 21-wk feeding study, fish that grew faster had a greater percent body fat at the end of the study (P < 0.01). Expression of UCP2b mRNA tended to be lower (P < 0.10) in fast growing fish in the middle of the study although levels were similar at the beginning and the end of the study. In the fed vs fasted study, expression of UCP2b mRNA in muscle was increased (P < 0.05) in fish assigned to 30 d of fasting. Our results suggest that, based on the nucleotide and amino acid sequence similarities and tissue mRNA distribution, catfish UCP2b may be the analog to UCP3. Moreover, our results suggest selection toward growth and associated fat accumulation appears to be independent of muscle UCP2b mRNA expression and UCP2b-mediated mechanisms.

Oestradiol modulates the effects of leptin on energy homeostasis by corticotrophin-releasing factor type 2 receptor

In addition to its action in the control of the hypothalamic-pituitary-adrenal axis, corticotrophin-releasing factor (CRF) has been described as an anorexigenic neuropeptide, modulating food intake and energy expenditure. CRF synthesis is influenced by leptin, which would act to increase CRF neurone activation in the paraventricular nucleus (PVN). Gonadal hormones also participate in the regulation of energy homeostasis. The reduction of food intake and body weight gain in ovariectomised (OVX) rats treated with oestradiol is associated with an increase in CRF mRNA expression in the PVN. The present study aimed to investigate the role of CRF as a mediator of leptin responsiveness in the presence of oestradiol. Wistar female rats were bilaterally OVX and divided into three groups: OVX, OVX+E (i.e. treated with oestradiol) and OVX+PF (i.e. OVX pairfed with OVX+E). The rats received daily s.c. injections of either oestradiol cypionate or vehicle for 8 days. To evaluate the role of CRF on the effects of leptin, we performed an i.c.v. leptin injection (10 μg/5 μl) with or without previous i.c.v. treatment with an CRF-R2 antagonist. We observed that oestradiol replacement in OVX rats reduced body weight gain and food intake. The effects of exogenous leptin administration with respect to decreasing food intake and body weight, and increasing uncoupling protein-1 expression in the brown adipose tissue and neuronal activation in the arcuate nucleus, were reversed by previous administration of a CRF-R2 antagonist only in oestradiol-treated OVX rats. These effects appear to be mediated by CRF-2 receptor because the antagonist of this receptor reversed the action of oestradiol on the effects of leptin.

Relationship between the acyl chain length of paradol analogues and their antiobesity activity following oral ingestion

6-Paradol is known to activate thermogenesis in brown adipose tissue (BAT), and paradol analogues with different acyl chain lengths possess different pungency thresholds. In this study, the influence of the acyl chain length on the antiobesity activity of the paradol analogues was investigated. The antiobesity activity of 6-paradol in mice fed a high-fat diet for 8 weeks was greater than that of dihydrocapsiate. A comparison of the antiobesity activities of zingerone and 6-paradol showed that the length of the acyl chain in the paradol analogue was important for strong activity. Furthermore, the antiobesity activities of 6-, 8-, and 12-paradol appeared to decrease in an acyl chain length-dependent manner. The mechanism of the antiobesity activity of 6-paradol was enhanced by increasing levels of energy metabolism in the BAT, as well as an increase in the expression of uncoupling proteins 1 via the activation of sympathetic nerve activity.

Identification of uncoupling protein 4 from the blood-sucking insect Rhodnius prolixus and its possible role on protection against oxidative stress

Uncoupling proteins (UCPs) play a critical role in the control of the mitochondrial membrane potential (ΔΨm) due to their ability to dissipate the proton gradient, which results in the uncoupling of mitochondrial respiration from ATP production. Most reactive oxygen species generation in mitochondria occurs in complex III, due to an increase of semiquinone (Q(-)) half-life. When active, UCPs can account as a potential antioxidant system by decreasing ΔΨm and increasing mitochondrial respiration, thus reducing Q(-) life time. The hematophagous insect Rhodnius prolixus, a vector of Chagas disease, is exposed to a huge increase in oxidative stress after a blood meal because of the hydrolysis of hemoglobin and the release of the cytotoxic heme molecule. Although some protective mechanisms were already described for this insect and other hematophagous arthropods, the putative role of UCP proteins as antioxidants in this context has not been explored. In this report, two genes encoding UCP proteins (RpUcp4 and RpUcp5) were identified in the R. prolixus genome. RpUcp4 is the predominant transcript in most analyzed organs, and both mRNA and protein expression are upregulated (13- and 3-fold increase, respectively) in enterocytes the first day after the blood feeding. The increase in UCP4 expression is coincident with the decrease in hydrogen peroxide (H2O2) generation by midgut cells. Furthermore, in mitochondria isolated from enterocytes, the modulation of UCP activity by palmitic acid and GDP resulted in altered ΔΨm, as well as modulation of H2O2 generation rates. These results indicate that R. prolixus UCP4 may function in an antioxidation mechanism to protect the midgut cells against oxidative damage caused by blood digestion.

High-fat diet induces site-specific unresponsiveness to LPS-stimulated STAT3 activation in the hypothalamus

Hypophagia induced by inflammation is associated with Janus kinase (JAK)-2/signal transducer and activator of transcription (STAT) 3 signaling pathway, and leptin-mediated hypophagia is also mediated by JAK2-STAT3 pathway. We have previously reported that lipopolysaccharide (LPS) did not reduce food intake in leptin-resistant high-fat diet (HFD) rats but maintained body weight loss. We investigated whether changes in p-STAT3 expression in the hypothalamus and brain stem could account for the desensitization of hypophagia in HFD animals after a low LPS dose (100 μg/kg). Wistar rats fed standard diet (3.95 kcal/g) or HFD (6.3 kcal/g) for 8 wk were assigned into control diet-saline, control diet-LPS, HFD-saline, and HFD-LPS groups. LPS reduced feeding in the control diet but not HFD. This group showed no p-STAT3 expression in the paraventricular nucleus (PVN) and ventromedial hypothalamic nucleus (VMH), but sustained, though lower than control, p-STAT3 in the nucleus of the solitary tract (NTS) and raphe pallidus (RPa). LPS decreased body weight in HFD rats and increased Fos expression in the NTS. LPS increased body temperature, oxygen consumption, and energy expenditure in both control diet and HFD rats, and this response was more pronounced in HFD-LPS group. Brown adipose tissue (BAT) thermogenesis and increased energy expenditure seem to contribute to body weight loss in HFD-LPS. This response might be related with increased brain stem activation. In conclusion, LPS activates STAT3-mediated pathway in the hypothalamus and brain stem, leading to hypophagia, however, LPS effects on food intake, but not body weight loss, are abolished by leptin resistance induced by HFD. The preserved STAT3 phosphorylation in the brain stem suggests that unresponsiveness to LPS on STAT3 activation under HFD might be selective to the hypothalamus.

Coenzyme Q10 depletion in medical and neuropsychiatric disorders: potential repercussions and therapeutic implications

Coenzyme Q10 (CoQ10) is an antioxidant, a membrane stabilizer, and a vital cofactor in the mitochondrial electron transport chain, enabling the generation of adenosine triphosphate. It additionally regulates gene expression and apoptosis; is an essential cofactor of uncoupling proteins; and has anti-inflammatory, redox modulatory, and neuroprotective effects. This paper reviews the known physiological role of CoQ10 in cellular metabolism, cell death, differentiation and gene regulation, and examines the potential repercussions of CoQ10 depletion including its role in illnesses such as Parkinson's disease, depression, myalgic encephalomyelitis/chronic fatigue syndrome, and fibromyalgia. CoQ10 depletion may play a role in the pathophysiology of these disorders by modulating cellular processes including hydrogen peroxide formation, gene regulation, cytoprotection, bioenegetic performance, and regulation of cellular metabolism. CoQ10 treatment improves quality of life in patients with Parkinson's disease and may play a role in delaying the progression of that disorder. Administration of CoQ10 has antidepressive effects. CoQ10 treatment significantly reduces fatigue and improves ergonomic performance during exercise and thus may have potential in alleviating the exercise intolerance and exhaustion displayed by people with myalgic encepholamyletis/chronic fatigue syndrome. Administration of CoQ10 improves hyperalgesia and quality of life in patients with fibromyalgia. The evidence base for the effectiveness of treatment with CoQ10 may be explained via its ability to ameliorate oxidative stress and protect mitochondria.

ROS and Sympathetically Mediated Mitochondria Activation in Brown Adipose Tissue Contribute to Methamphetamine-Induced Hyperthermia

Methamphetamine (Meth) abuse has been shown to induce alterations in mitochondrial function in the brain as well as to induce hyperthermia, which contributes to neurotoxicity and Meth-associated mortality. Brown adipose tissue (BAT), a thermogenic site known to be important in neonates, has recently regained importance since being identified in significant amounts and in correlation with metabolic balance in human adults. Given the high mitochondrial content of BAT and its role in thermogenesis, we aimed to investigate whether BAT plays any role in the development of Meth-induced hyperthermia. By ablating or denervating BAT, we identified a partial contribution of this organ to Meth-induced hyperthermia. BAT ablation decreased temperature by 0.5°C and reduced the length of hyperthermia by 1 h, compared to sham-operated controls. BAT denervation also affected the development of hyperthermia in correlation with decreased the expression of electron transport chain molecules, and increase on PCG1a levels, but without affecting Meth-induced uncoupling protein 1 upregulation. Furthermore, in isolated BAT cells in culture, Meth, but not Norepinephrine, induced H2O2 upregulation. In addition, we found that in vivo Reactive Oxygen Species (ROS) play a role in Meth hyperthermia. Thus, sympathetically mediated mitochondrial activation in the BAT and Meth-induced ROS are key components to the development of hyperthermia in Meth abuse.

Polymorphisms of the UCP2 gene are associated with body fat distribution and risk of abdominal obesity in Spanish population

BACKGROUND

Increased accumulation of fat results from an imbalance between energy expenditure and intake, being modulated by different environmental and genetic factors. Uncoupling proteins (UCPs) are mitochondrial carrier proteins able to spend energy generating heat. Therefore, variations in these genes are good candidates as potential modulators of body fat accumulation. Our aim was to investigate the possible association of genetic variations of the gene codifying the UCP2 protein with obesity and fat distribution.

DESIGN

We performed a cross-sectional study in 2367 individuals from two population-based studies from different regions of Spain. The Hortega Study included 1436 individuals (693 women) 21-85 years old, and the Pizarra Study included 931 individuals (584 women) 18-65 years old. We evaluated three polymorphisms of the UCP2 gene.

RESULTS

The TT genotype of the rs660339 polymorphism and the AA genotype of the rs659366 polymorphism of the UCP2 gene were significantly associated with higher waist circumference in the Hortega Study. Furthermore, subjects carrying both genotypes (TT+AA) also showed higher central adiposity compared with other genotypes. This association was also present in the Pizarra Study. Moreover, in the pooled population, we found a stronger association with waist circumference. Even, we found association with BMI. Furthermore, rs659366 polymorphism was associated with the risk of abdominal obesity (P= 0·04: OR = 1·3; CI = 1·01-1·67).

CONCLUSIONS

Polymorphisms of the UCP2 gene (rs660339 and rs659366) were associated with central obesity. This study shows association between the UCP2 gene and the susceptibility to obesity and body fat distribution in a south European population.

mRNA expression of genes regulating oxidative phosphorylation in the muscle of beef cattle divergently ranked on residual feed intake

Our objective was to evaluate the effects of phenotypic ranking on residual feed intake (RFI) on the transcription of genes 1) involved in the respiratory chain complex and 2) coding for transcriptional factors regulating mitochondrial biogenesis, across two contrasting diet types. Beef heifers (n = 86) fed a diet comprising 70:30 concentrate-corn silage [low forage (LF)] over a 82-day period were ranked on RFI. The 10 highest (feed inefficient, high-RFI) and 10 lowest (feed efficient, low-RFI) ranking animals were selected for the current study. Biopsies of the M. longissimus dorsi were harvested following initial selection (LF diet) and again following a 6 wk period while the animals were offered a high-forage (HF) grass silage-only diet. Real-time PCR was used to quantify mRNA transcripts of 17 genes associated with cellular energetic efficiency. The mRNA expression of UCP3 tended to be upregulated (2.2-fold, P = 0.06) for the high-RFI compared with the low-RFI animals. mRNA transcripts coding for the transcription factor PGC-1α was 1.7-fold higher (P = 0.01) in low compared with high-RFI animals. A phenotype × diet interaction was evident for the abundance of ANT1 mRNA transcript, with greater (P = 0.04) expression levels detected in the low-RFI phenotype during the HF period, but no difference (P = 0.50) between phenotypes during the LF period. A phenotype × diet interaction was also evident for COX II with greater expression levels detected (P = 0.04) in the low compared with the high RFI phenotype while on LF but not the HF diet (P = 0.22). These data suggest an association between cellular energetic efficiency and RFI in cattle.

Arginine-vasopressin directly promotes a thermogenic and pro-inflammatory adipokine expression profile in brown adipocytes

Arginine-vasopressin (AVP) - via activation of the hypothalamic-pituitary-adrenal (HPA) axis - may play a role in the regulation of energy homeostasis and related cardiovascular complications. Brown adipose tissue (BAT) - via dissipation of energy in the form of heat - contributes to whole body energy balance. BAT expresses vasopressin receptors. We investigated direct effects of AVP on brown adipose endocrine and metabolic functions. UCP-1 protein expression in differentiated brown adipocytes was induced after acute exposure of adipocytes to AVP. This effect was time-dependent with a maximum increase after 8h. AVP also induced a time- and dose-dependent increase in p38 MAP kinase phosphorylation. Pharmacological inhibition of p38 MAP kinase with SB 202190 abolished the induction of UCP-1 protein expression. Furthermore, while acute AVP treatment enhanced mRNA expression of MCP-1 and IL-6, adiponectin mRNA expression was reduced. Yet, on the level of intracellular glucose uptake, there was no AVP-induced change of adipose insulin-induced glucose uptake. Finally, there was no difference in lipid accumulation between control and AVP-treated cells. Taken together, our data demonstrate direct effects of AVP on thermogenic, inflammatory, and glucoregulatory gene expression in brown adipocytes, thus expanding the hitherto known spectrum of this neuropeptides's biological effects and suggesting a direct adipotropic role as a stress-promoting factor.

Do UCP2 and mild uncoupling improve longevity?

Mild uncoupling of mitochondrial respiration is considered to prolong life span of organisms by reducing the production of reactive oxygen species (ROS). Experimental evidence against this hypothesis has been brought forward by premature senescence in cell cultures treated with uncouplers. Exposing HUVEC to a mixture of nutritionally important fatty acids (oil extract of chicken yolk) mild uncoupling with "naturally acting substances" was performed. This treatment also resulted in premature senescence although ROS production did not increase. Fatty acids activate uncoupling proteins (UCP) in the inner mitochondrial membrane. UCP2 expression proved to be sensitive to the presence of fatty acids but remains unchanged during the ageing process. UCP3 expression in senescent HUVEC and avUCP expression in senescent CEF were considerably less than in young cultures. No indication for protonophoric reduction of mitochondrial membrane potential was found in UCP2 overexpressing HeLa cells and only little in HUVEC. ROS levels increased instead of being reduced in these cells. Stable transfection with UCP2-GFP was possible only in chick embryo fibroblasts and HeLa cells and resulted in decreased proliferation. Stable transfection of HUVEC with UCP2-GFP resulted in death of cultures within one or two weeks. The reason for this behaviour most probably is apoptosis preceded by mitochondrial fragmentation and loss of membrane potential.

Dietary supplementation of tetradecylthioacetic acid increases feed intake but reduces body weight gain and adipose depot sizes in rats fed on high-fat diets

AIM

The pan-peroxisome proliferator-activated receptor (PPAR) ligand and fatty acid analogue tetradecylthioacetic acid (TTA) may reduce plasma lipids and enhance hepatic lipid metabolism, as well as reduce adipose tissue sizes in rats fed on high-fat diets. This study further explores the effects of TTA on weight gain, feed intake and adipose tissue functions in rats that are fed a high-fat diet for 7 weeks.

METHODS

The effects on feed intake and body weight during 7 weeks' dietary supplement with TTA ( approximately 200 mg/kg bw) were studied in male Wistar rats fed on a lard-based diet containing approximately 40% energy from fat. Adipose tissue mass, body composition and expression of relevant genes in fat depots and liver were measured at the end of the feeding.

RESULTS

Despite higher feed intake during the final 2 weeks of the study, rats fed on TTA gained less body weight than lard-fed rats and had markedly decreased subcutaneous, epididymal, perirenal and mesenteric adipose depots. The effects of TTA feeding with reduced body weight gain and energy efficiency (weight gain/feed intake) started between day 10 and 13. Body contents of fat, protein and water were reduced after feeding lard plus TTA, with a stronger decrease in fat relative to protein. Plasma lipids, including Non-Esterified Fatty Acids (NEFA), were significantly reduced, whereas fatty acid beta-oxidation in liver and heart was enhanced in lard plus TTA-fed rats. Hepatic UCP3 was expressed ectopically both at protein and mRNA level (>1900-fold), whereas Ucp1 mRNA was increased approximately 30-fold in epididymal and approximately 90-fold in mesenteric fat after lard plus TTA feeding.

CONCLUSION

Our data support the hypothesis that TTA feeding may increase hepatic fatty acid beta-oxidation, and thereby reduce the size of adipose tissues. The functional importance of ectopic hepatic UCP3 is unknown, but might be associated with enhanced energy expenditure and thus the reduced feed efficiency.

Cigarette smoking induces overexpression of a fat-depleting gene AZGP1 in the human

BACKGROUND

Smokers weigh less and have less body fat than nonsmokers. Increased body fat and weight gain are observed following smoking cessation. To assess a possible molecular mechanism underlying the inverse association between smoking and body weight, we hypothesized that smoking may induce the expression of a fat-depleting gene in the airway epithelium, the cell population that takes the brunt of the stress of cigarette smoke.

METHODS

To assess whether smoking up-regulates expression in the airway epithelium of genes associated with weight loss, microarray analysis was used to evaluate genes associated with fat depletion in large airway epithelial samples obtained by fiberoptic bronchoscopy from healthy smokers and healthy nonsmokers. As a candidate gene we further evaluated the expression of alpha(2)-zinc-glycoprotein 1 (AZGP1), a soluble protein that stimulates lipolysis, induces a reduction in body fat in mice, is associated with the cachexia related to cancer, and is known to be expressed in secretory cells of lung epithelium. AZGP1 protein expression was assessed by Western analysis and localization in the large airway epithelium by immunohistochemistry.

RESULTS

Both microarray and TaqMan analysis demonstrated that AZGP1 messenger RNA levels were higher in the large airway epithelium of healthy smokers compared to healthy nonsmokers (p < 0.05, all comparisons). Western analysis of airway biopsy specimens from smokers compared with those from nonsmokers demonstrated up-regulation of AZGP1 at the protein level, and immunohistochemical analysis demonstrated up-regulation of AZGP1 in secretory as well as neuroendocrine cells of smokers.

CONCLUSIONS

In the context that AZGP1 is involved in lipolysis and fat loss, its overexpression in the airway epithelium of chronic smokers may represent one mechanism for the weight difference in smokers vs nonsmokers.

Molecular characterization and expression of a novel homolog of uncoupling protein 5 (UCP5) from the eastern oyster Crassostrea virginica (Bivalvia: Ostreidae)

Uncoupling proteins (UCPs) belong to the mitochondrial anion carrier gene family which has been implicated in diverse physiological functions ranging from thermoregulation to antioxidant defense. In mammals, the UCP family is well characterized and contains five members (UCP1-5). In contrast, invertebrate homologues of uncoupling proteins are much less studied both from the viewpoints of structure and function. In this study we report nucleotide and predicted protein structure of an important member of UCP family, UCP5 from eastern oysters Crassostrea virginica. UCP5 from oysters appears to be a close homolog of the mammalian brain mitochondrial carrier protein (BMCP1, or UCP5) and is the first full-length UCP described from a Lophotrochozoan invertebrate. Evolutionary analysis of UCP sequences indicates at least three monophyletic UCP branches (UCP1-3, UCP4 and UCP5) that have diverged early in the evolution, prior to the divergence of vertebrates and invertebrates. In oysters, two forms of UCP5 transcript are found (UCP5S and UCP5L) that differ by 152 bp in length due to the presence of an intron in UCP5L. UCP5 was expressed in all studied oyster tissues, unlike mammals, where UCP5 is predominantly expressed in brains and male gonads. Hypoxia-reoxygenation stress, sublethal Cd exposure (50 ?g L(?1) Cd for 56 days) and acclimation to different temperatures (12 and 20 °C) had no significant effect on UCP5 mRNA expression in oysters indicative of its relative unimportance in antioxidant defense and temperature adaptation of oyster mitochondria. These data suggest that despite the relatively high degree of evolutionary conservation of the UCP5 amino acid sequence, its functional significance in mitochondria changed in the course of evolution of mollusks and vertebrates.

A casein diet added isoflavone-enriched soy protein favorably affects biomarkers of steatohepatitis in obese Zucker rats

OBJECTIVE

Dietary supplementation of a soy protein enriched with isoflavones (HDI) has been shown to improve fatty liver in obese rats. The main objective of this study was to investigate whether HDI would influence the inflammatory status in livers of obese rats with fatty liver.

METHODS

Male obese Zucker fa/fa rats were fed casein (controls) or casein supplemented with HDI (containing 4.00 g of genistein and 4.50 g of daidzein per kilogram of diet) for 6 wk.

RESULTS

The HDI-fed rats had a markedly lower hepatic concentration of triacylglycerol when compared with controls. The decreased aspartate transaminase/alanine transaminase ratio in plasma, together with lower circulating levels of alkaline phosphatase and bile acids after HDI feeding, implied an improved hepatitis. This was supported by decreased plasma and hepatic mRNA levels of tumor necrosis factor-alpha, lower plasma levels of interleukin-1beta and monocyte chemoattractant protein-1, and an increased anti-inflammatory fatty acid index in plasma. HDI also seemed to protect the rats from oxidative damage, because the level of lipid peroxides in triacylglycerol-rich lipoproteins after in vitro copper oxidation was lower for HDI-fed rats when compared with controls.

CONCLUSION

These results show that isoflavone-enriched soy protein favorably affects biomarkers of hepatic inflammation in obese Zucker fa/fa rats with fatty liver. Thus, dietary soy proteins enriched in isoflavones may be a promising agent to improve steatohepatitis in patients.

A claim in search of evidence: reply to Manger's thermogenesis hypothesis of cetacean brain structure

In a recent publication in Biological Reviews, Manger (2006) made the controversial claim that the large brains of cetaceans evolved to generate heat during oceanic cooling in the Oligocene epoch and not, as is the currently accepted view, as a basis for an increase in cognitive or information-processing capabilities in response to ecological or social pressures. Manger further argued that dolphins and other cetaceans are considerably less intelligent than generally thought. In this review we challenge Manger's arguments and provide abundant evidence that modern cetacean brains are large in order to support complex cognitive abilities driven by social and ecological forces.

Reduction of JNK1 expression with antisense oligonucleotide improves adiposity in obese mice

To investigate the role of JNK1 in metabolism, male ob/ob and diet-induced obese mice were treated with a JNK1-specific antisense oligonucleotide (ASO) or control ASO at 25 mg/kg or saline twice/wk for 6 and 7 wk, respectively. JNK1 ASO reduced JNK1 mRNA and activity by 65-95% in liver and fat tissues in both models. Compared with controls, treatment with JNK1 ASO did not change food intake but lowered body weight, fat pad weight, and whole body fat content. The treatment increased metabolic rate. In addition, the treatment markedly reduced plasma cholesterol levels and improved liver steatosis and insulin sensitivity. These positive observations were accompanied by the following changes: 1) increased mRNA levels of AR-beta(3) and UCP1 by >60% in BAT, 2) reduced mRNA levels of ACC1, ACC2, FAS, SCD1, DGAT1, DGAT2, and RBP4 by 30-60% in WAT, and 3) reduced mRNA levels of ACC1, FAS, G-6-Pase, and PKCepsilon by 40-70% and increased levels of UCP2 and PPARalpha by more than twofold in liver. JNK1 ASO-treated mice demonstrated reduced levels of pIRS-1 Ser(302) and pIRS-1 Ser(307) and increased levels of pAkt Ser(473) in liver and fat in response to insulin. JNK1 ASO-transfected mouse hepatocytes showed decreased rates of de novo sterol and fatty acid synthesis and an increased rate of fatty acid oxidation. These results indicate that inhibition of JNK1 expression in major peripheral tissues can improve adiposity via increasing fuel combustion and decreasing lipogenesis and could therefore provide clinical benefit for the treatment of obesity and related metabolic abnormalities.

Uncoupling protein expression in skeletal muscle and adipose tissue in response to in vivo porcine somatotropin treatment

These experiments examined the potential roles of somatropin (pST) and IGF-I in the regulation of uncoupling protein (UCP)2 and UCP3 and their regulatory proteins peroxisome proliferator activated receptor (PPAR) alpha, gamma and delta using in vivo pST treatment of swine and in vitro supplementation of pST or IGF-I to adipose slices. Six, 90kg barrows were treated with recombinant pST (10mg) for 2 week while another six pigs were injected with buffer. Total RNA from outer subcutaneous adipose (OSQ) and middle subcutaneous adipose (MSQ) tissues, leaf fat, liver and longissimus (LM) was amplified by reverse transcription-PCR with quantification of transcripts by capillary electrophoresis with laser-induced fluorescence detection. UCP2 mRNA abundance increased in liver (P<0.001) and all three adipose tissues by pST treatment (P<0.05). Administration of pST increased UCP3 mRNA abundance by 42% in LM (P<0.01). PPARalpha mRNA abundance increased with pST treatment by 29% in liver (P<0.05), while decreasing 25% in LM (P<0.05). PPARgamma mRNA abundance decreased 32% (P<0.01) while PPARdelta increased 48% in LM (P<0.01) with pST administration. In vitro, pST reduced UCP2 mRNA abundance in OSQ and MSQ tissue slices (P<0.05). UCP3 mRNA abundance decreased in OSQ (P<0.05) but increased in MSQ (P<0.05) with pST. In contrast, IGF-I increased UCP2 and UCP3 mRNA abundance in both MSQ and OSQ slices (P<0.05). These experiments suggest pST, IGF-I and metabolic adaptations to pST contribute to regulating UCP2 and UCP3.

Increased uncoupling protein 1 mRNA expression in mice brown adipose tissue after burn injury

Brown adipose tissue (BAT) contains numerous mitochondria and is characterized by the presence of uncoupling protein 1 (UCP1). UCP1 is the main mediator of thermogenesis that plays an important role in the modulation of energy balance. The authors hypothesize that alterations in the expression of UCP1 might be involved in the major metabolic disorders occurring during burn trauma. The present study is designed to explore the potential role of the UCP1 in metabolic disorders after burn injury. The authors have used the real-time reverse transcription-polymerase chain reaction to quantify UCP1 mRNA expression in the mice BAT and white adipose tissue (WAT). UCP1 mRNA expression was up-regulated in BAT, especially at 24 hours after burn. UCP1 mRNA expression was detectable and also up-regulated by burn injury in WAT. The authors provide evidence that one of the mechanisms mediating hypermetabolism and increased energy expenditure in burn injury is a pronounced increase in thermogenic capacity, as illustrated by robust gene expression of UCP1 in BAT and WAT.

Renal contribution to thermolability in rats: role of renal nerves

BACKGROUND

Body temperature is closely regulated via the integration of a number of mechanisms, the study of which has been greatly assisted by the exploitation of comparative physiology. Previous studies have demonstrated that chronic renal failure patients have significantly lower body temperatures than healthy subjects when artifacts from circadian changes were taken into consideration. We hypothesize that the blunting of renal sensory neurons after kidney partial ablation may contribute to the lack of suppression of sympathetic efferent outflow towards BAT, modifying the glucose metabolism signaling pathway, UCP 1 expression and liver mitocondrial respiratory chain activity.

METHODS

To evaluate the influence of renal mass reduction, renal denervation and chronic deafferentation by capsaicin on thermoregulation, glucose metabolism, UCP1 expression and liver mitocondrial respiration, was used respectively, the blocking of heat dissipation by thermoneutral body water immersion, the oxygen consumption by Clark-type electrode, and western blot method.

RESULTS

The study confirmed that, following 5/6 nephrectomy, the basal core temperature of rats was significantly lower than that of control animals when maintained in a thermoneutral body water immersion recipient, as compared to controls. Additionally, we demonstrated that exposure of bilateral renal denervated or of renal chronic capsaicin-treated rats to a similar experimental protocol results in a fast and high rise in rectal temperature response, and this is associated with a significant increase in the basal serine phosphorylation and protein levels of Akt and protein levels of UCP1. This was observed despite unchanged liver mitochondria respiratory control and ADP/O ratios in 5/6 Nx, as well as DNx, when compared to control mitochondria.

CONCLUSIONS

Speculatively, it may be suggested that one of the renal sensory nerve signal defects associated with decreased kidney energy generation, induced by kidney ablation, may result in an inability to control the body temperature.

Organization and evolution of mitochondrial gene clusters in human

Currently, the spatial patterns of mitochondrial genes and how the genomic localization of (pseudo)genes originated from mitochondrial DNA remain largely unexplained. The aim of this study was to elucidate the organization of mitochondrial (pseudo)genes given their evolutionary origin. We used a keyword finding method and a bootstrapping method to estimate parameter values that represent the distribution pattern of mitochondrial genes in the nuclear genome. Almost half of mitochondrial genes showing physical clusters were located in the pericentromeric and subtelomeric regions of the chromosome. Most interestingly, the size of these clusters ranged from 0.085 to 3.2 Mb (average+/-SD 1.3+/-0.73 Mb), which coincides with the size of the evolutionary pocket, or the average size of evolutionary breakpoint regions. Our findings imply that the localization of mitochondrial genes in the human genome is determined independent of adaptation.

The physiological costs of reproduction in small mammals

Life-history trade-offs between components of fitness arise because reproduction entails both gains and costs. Costs of reproduction can be divided into ecological and physiological costs. The latter have been rarely studied yet are probably a dominant component of the effect. A deeper understanding of life-history evolution will only come about once these physiological costs are better understood. Physiological costs may be direct or indirect. Direct costs include the energy and nutrient demands of the reproductive event, and the morphological changes that are necessary to facilitate achieving these demands. Indirect costs may be optional 'compensatory costs' whereby the animal chooses to reduce investment in some other aspect of its physiology to maximize the input of resource to reproduction. Such costs may be distinguished from consequential costs that are an inescapable consequence of the reproductive event. In small mammals, the direct costs of reproduction involve increased energy, protein and calcium demands during pregnancy, but most particularly during lactation. Organ remodelling is necessary to achieve the high demands of lactation and involves growth of the alimentary tract and associated organs such as the liver and pancreas. Compensatory indirect costs include reductions in thermogenesis, immune function and physical activity. Obligatory consequential costs include hyperthermia, bone loss, disruption of sleep patterns and oxidative stress. This is unlikely to be a complete list. Our knowledge of these physiological costs is currently at best described as rudimentary. For some, we do not even know whether they are compensatory or obligatory. For almost all of them, we have no idea of exact mechanisms or how these costs translate into fitness trade-offs.