Muscle UCP3 Research Articles

Reduction of hyperglycemia in STZ-induced diabetic mice by prophylactic treatment with heat-killed Mycobacterium aurum: possible effects on glucose utilization, mitochondrial uncoupling, and oxidative stress in liver and skeletal muscle.

In addition to conventional treatment and modifications in physical activity and diet, alternative strategies have been investigated to manage, prevent, or delay diabetes in humans. In this regard, one strategy has relied on the immunomodulatory properties of mycobacteria, whereby Bacillus Calmette-Guerin, an attenuated live strain of Mycobacterium bovis, has been shown to improve glycemic control in patients with diabetes and to alleviate hyperglycemia in selected murine models of diabetes. A novel heat-killed (HK) whole-cell preparation of Mycobacterium aurum (M. aurum) is currently under development as a potential food supplement; nevertheless, its potential bioactivity remains largely unknown. Thus, the present study investigated the potential prophylactic anti-diabetic effects of HK M. aurum in streptozotocin (STZ)-induced diabetic mice. Mice were divided into three groups: the STZ-induced diabetic group was injected with a single intraperitoneal high dose of STZ, the HK M. aurum-treated diabetic group was prophylactically treated with three doses of HK M. aurum 6 weeks before STZ injection, and the control non-diabetic group was given three intradermal injections of borate-buffered saline and an intraperitoneal injection of citrate buffer. Liver lactate dehydrogenase (LDH), uncoupling protein 2 (UCP2), and glucose transporter 2 (GLUT2) and skeletal muscle LDH, UCP3, and GLUT4 protein expression levels in different mouse groups were determined by Western blot. Our results indicated that HK M. aurum did not cause any significant changes in glycemic levels of normal non-diabetic mice. Prophylactic administration of three doses of HK M. aurum to diabetic mice resulted in a significant reduction in their blood glucose levels when compared to those in control diabetic mice. Prophylactic treatment of diabetic mice with HK M. aurum significantly restored their disturbed protein expression levels of liver UCP2 and LDH as well as of skeletal muscle UCP3. On the other hand, prophylactic treatment of diabetic mice with HK M. aurum had no significant effect on their liver GLUT2 and skeletal muscle GLUT4 and LDH protein expression levels. Our findings provide the first evidence that HK M. aurum possesses a hyperglycemia-lowering capacity and might support its future use as a food supplement for the amelioration of diabetes.

Enriched functional milk fat ameliorates glucose intolerance and triacylglycerol accumulation in skeletal muscle of rats fed high-fat diets.

We examined the effect of a functional milk fat (FMF) on the glucose metabolism and its association with the intramuscular triacylglycerol (TAG) content in rats fed high-fat diets. Male Wistar rats were fed for 60days with S7 (soybean oil 7%), S30 (soybean oil 30%), MF30 (soybean oil 3% + milk fat 27%), or FMF30 (soybean oil 3% + FMF 27%) diets. An oral glucose tolerance test was performed. The levels of key metabolites in gastrocnemius muscle and mRNA levels of genes involved in glucose and lipid metabolism in muscle, epididymal white adipose tissue (EWAT), and serum were assessed. The S30 diet induced glucose intolerance and led to TAG, citrate, and glucose accumulation in muscle. Moreover, we observed a downregulation of uncoupling proteins (Ucp2 and Ucp3) and insulin receptor substrate-1 (Irs1) genes, lower carnitine palmitoyl transferase-1b (CPT-1b), and phosphofructokinase-1 (PFK1) activities in muscle and lower expression of adiponectin (Adipoq) in EWAT. The FMF30 diet ameliorated the glucose intolerance and normalized the glucose and TAG levels in muscle, preventing the accumulation of citrate and enhancing glucose utilization by the PFK1. The beneficial effects might also be related to the higher expression of Adipoq in EWAT, its receptor in muscle (Adipor1), and the expression of Ucp2, Ucp3, and Irs1 in muscle, restoring the alterations observed with the S30 diet. FMF30 modulated key genes involved in glucose and lipid metabolism in skeletal muscle, improving the glucose utilization and preventing TAG, glucose, and citrate accumulation.

Investigation of obesogenic effects of hexachlorobenzene, DDT and DDE in male rats

Obesity has become a very important public health problem and is increasing globally. Genetics, individual and environmental factors play roles in the etiology of this complex disorder. Recently, several environmental pollutants have been suggested to have obesogenic activities. Peroxisome proliferator activating receptor gamma (PPARγ), uncoupling protein-1 (UCP1) and their expression in white adipose tissue (WAT) and brown adipose tissue (BAT) play key roles in adipogenesis. UCP3 and irisin were reported to play roles in non-shivering thermogenesis. Our primary aim was to investigate obesogenic effects of hexachlorobenzene (HCB), dichlorodiphenyltrichloroethane (DDT) and dichlorodiphenyldichloroethylene (DDE) in rats. In addition, thermoregulatory effects of HCB, DDT and DDE were also investigated by analyzing the levels of Ucp3 and irisin. Thirty-two adult male Sprague-Dawley rats were randomly divided into four groups as control, HCB, DDT and DDE. Animals were administered with organochlorine pesticides (OCPs; 5 mg/kg bw) by oral gavage every other day for five weeks. At the end of the experimental period, the animals were sacrificed, BAT and WAT samples were collected to analyze Pparγ, Ucp1 and Ucp3 levels. Moreover, skeletal muscle samples were collected to examine Ucp3 and irisin levels. Serum glucose, cholesterol and triglyceride levels were also determined. Body weight and core temperature of the animals were not significantly affected by any of the OCP administration. Serum glucose, cholesterol and triglyceride levels were similar among the experimental groups. Pparγ expression was significantly elevated by HCB administration only in WAT (p < 0.05). On the other hand, both Pparγ and Ucp1 expressions were diminished in WAT and BAT (p < 0.01) by DDT treatment, while in WAT, DDE significantly decreased Pparγ expression without altering its expression in BAT (p < 0.001). Ucp3 and irisin levels in skeletal muscle were not altered. Our findings show that both DDT and DDE reduce the browning of WAT by suppressing white adipocytes and thus may have obesogenic activity in male rats without altering thermoregulation. In addition, HCB, DDT and DDE-induced alterations in expression of Pparγ and Ucp1 in WAT implicates differential regulation of adipogenic processes.

Reversal of temperature responses to methylone mediated through bi-directional fecal microbiota transplantation between hyperthermic tolerant and naïve rats

ABSTRACT The synthetic cathinone (“bath salt”) methylone induces a hyperthermia response and with chronic administration tolerance to this hyperthermia has been reported. The microbiome-gut-brain axis has been implicated in multiple bodily systems and pathologies, and intentional manipulation of the gut-microbiome has yielded clinically significant results. Here, we examined the effects of bi-directional Fecal Microbiota Transplantation (FMT) between methylone-induced hyperthermic tolerant (MHT) and methylone-naïve (MN) rats. Rats treated with methylone once per week developed tolerance to methylone-induced hyperthermia by the fourth week. Once tolerant, daily bi-directional FMT between the two groups were performed for seven days prior to the next methylone treatment. The FMT abated the developed tolerance in the MHT group. When treated with methylone for the first time following FMT, recipient MN rats displayed significant tolerance to hyperthermia despite it being their initial drug treatment. Post-FMT, MHT rats displayed elevations in norepinephrine and expression of UCP1, UCP3 and TGR5 in brown adipose tissue, with reductions in expression of TGR5 and UCP3 in skeletal muscle. The pre- and post-FMT methylone tolerance phenotypes of transplant recipients are concurrent with changes in the relative abundance of several classes of Proteobacteria, most evident for Gammaproteobacteria and Alphaproteobacteria. MHT recipients demonstrated a marked increase in the relative proportion of the Firmicutes class Erysipelotrichia. These findings suggest that transplantation of gut-microbiomes can confer phenotypic responses to a drug and that the microbiome may be playing a major role in sympathomimetic-mediated hyperthermia. Abbreviations: 3,4-methylenedioxymethamphetamine (MDMA); methylone-induced hyperthermic tolerant (MHT); methylone-naïve (MN); fecal microbiota transplantation (FMT); uncoupling protein (UCP); subcutaneous (sc); intraperitoneal (ip); brown adipose tissue (BAT); skeletal muscle (SKM); sympathetic nervous system (SNS); norepinephrine (NE); quantitative PCR (qRT-PCR); quantification cycle (Cq); High Performance Liquid Chromatography-Electrochemical Detection (HPLC-EC); amplicon sequence variants (ASVs); principal coordinates analysis (PCoA); permutational multivariate analysis (PERMANOVA)

Anti‐obesity effect of Premature Citrus Extract in high‐fat diet induced obesity mice

BackgroundObesity is a worldwide health threat. Premature citrus extract (PCE) are known to contain high concentrations of flavonoids, polyphenols, and organic acids with health functions. The current study aimed to investigate the anti‐obesity effect of PCE on a high‐fat diet (HFD)‐induced obesity mice.MethodMice were fed on chow or HFD with or without Orlistat (ORL), Hesperidin (HES), and PCE treatment for 10 weeks. Triglyceride (TG) content and total cholesterol (TC), and low‐density lipoprotein cholesterol (LDL‐c), and high‐density lipoprotein cholesterol (HDL‐c) levels were determined by TG, HDL and LDL Assay Kit (BioAssay System). The phosphorylation levels of AMP‐activated protein kinase (AMPK) and acetyl Co‐A carboxylase (ACC); the expression of sterol regulatory element binding protein‐2 (SREBP‐2), 3‐hydroxy‐3‐methylglutaryl coenzyme A reductase (HMGCR), Acyl‐coenzyme A: cholesterol acyltransferases (ACAT‐1) and mitochondrial uncoupling proteins (UCP‐3) were observed via western blot analysis.ResultsPCE and HES administered group significantly reduced the weights of body, liver, and white adipose tissue compared to the HFD group. Supplementation with PCE and HES significantly decreased the levels of TG, TC, and (LDL‐c), and increased (HDL‐c) levels in serum compared to the HFD group. Furthermore, treatment with PCE and HES significantly decreased the levels of TG and TC in the liver whereas increased the levels of TG and TC in feces compared to the HFD group. Western blot analysis revealed that PCE and HES increased the phosphorylation levels of both AMPK and ACC and significantly decreased the expression levels of SREBP‐2, HMGCR, and ACAT‐1 in the liver compared to the HFD group. In addition, both PCE and HES increased the expression level of UCP‐3 in skeletal muscle tissue.ConclusionOverall results suggest that PCE and HES exerts an anti‐obesity effect via activation of AMPK and associated signaling cascades related to lipid metabolism in HFD‐induced obesity mice

A Mix of Dietary Fibres Changes Interorgan Nutrients Exchanges and Muscle-Adipose Energy Handling in Overfed Mini-Pigs.

This study evaluates the capacity of a bread enriched with fermentable dietary fibres to modulate the metabolism and nutrients handling between tissues, gut and peripheral, in a context of overfeeding. Net fluxes of glucose, lactate, urea, short chain fatty acids (SCFA), and amino acids were recorded in control and overfed female mini-pigs supplemented or not with fibre-enriched bread. SCFA in fecal water and gene expressions, but not protein levels or metabolic fluxes, were measured in muscle, adipose tissue, and intestine. Fibre supplementation increased the potential for fatty acid oxidation and mitochondrial activity in muscle (acox, ucp2, sdha and cpt1-m, p < 0.05) as well as main regulatory transcription factors of metabolic activity such as pparα, pgc-1α and nrf2. All these features were associated with a reduced muscle fibre cross sectional area, resembling to controls (i.e., lean phenotype). SCFA may be direct inducers of these cross-talk alterations, as their feces content (+52%, p = 0.05) was increased in fibre-supplemented mini-pigs. The SCFA effects could be mediated at the gut level by an increased production of incretins (increased gcg mRNA, p < 0.05) and an up-regulation of SCFA receptors (increased gpr41 mRNA, p < 0.01). Hence, consumption of supplemented bread with fermentable fibres can be an appropriate strategy to activate muscle energy catabolism and limit the establishment of an obese phenotype.

LANCL1 binds abscisic acid and stimulates glucose transport and mitochondrial respiration in muscle cells via the AMPK/PGC-1α/Sirt1 pathway

ObjectiveAbscisic acid (ABA) is a plant hormone also present and active in animals. In mammals, ABA regulates blood glucose levels by stimulating insulin-independent glucose uptake and metabolism in adipocytes and myocytes through its receptor LANCL2. The objective of this study was to investigate whether another member of the LANCL protein family, LANCL1, also behaves as an ABA receptor and, if so, which functional effects are mediated by LANCL1. MethodsABA binding to human recombinant LANCL1 was explored by equilibrium-binding experiments with [3H]ABA, circular dichroism, and surface plasmon resonance. Rat L6 myoblasts overexpressing either LANCL1 or LANCL2, or silenced for the expression of both proteins, were used to investigate the basal and ABA-stimulated transport of a fluorescent glucose analog (NBDG) and the signaling pathway downstream of the LANCL proteins using Western blot and qPCR analysis. Finally, glucose tolerance and sensitivity to ABA were compared in LANCL2−/− and wild-type (WT) siblings. ResultsHuman recombinant LANCL1 binds ABA with a Kd between 1 and 10 μM, depending on the assay (i.e., in a concentration range that lies between the low and high-affinity ABA binding sites of LANCL2). In L6 myoblasts, LANCL1 and LANCL2 similarly, i) stimulate both basal and ABA-triggered NBDG uptake (4-fold), ii) activate the transcription and protein expression of the glucose transporters GLUT4 and GLUT1 (4-6-fold) and the signaling proteins AMPK/PGC-1α/Sirt1 (2-fold), iii) stimulate mitochondrial respiration (5-fold) and the expression of the skeletal muscle (SM) uncoupling proteins sarcolipin (3-fold) and UCP3 (12-fold). LANCL2−/− mice have a reduced glucose tolerance compared to WT. They spontaneously overexpress LANCL1 in the SM and respond to chronic ABA treatment (1 μg/kg body weight/day) with an improved glycemia response to glucose load and an increased SM transcription of GLUT4 and GLUT1 (20-fold) of the AMPK/PGC-1α/Sirt1 pathway and sarcolipin, UCP3, and NAMPT (4- to 6-fold). ConclusionsLANCL1 behaves as an ABA receptor with a somewhat lower affinity for ABA than LANCL2 but with overlapping effector functions: stimulating glucose uptake and the expression of muscle glucose transporters and mitochondrial uncoupling and respiration via the AMPK/PGC-1α/Sirt1 pathway. Receptor redundancy may have been advantageous in animal evolution, given the role of the ABA/LANCL system in the insulin-independent stimulation of cell glucose uptake and energy metabolism.

In Vitro and In Vivo Effects of Fermented Oyster-Derived Lactate on Exercise Endurance Indicators in Mice.

Exogenous lactate administration has more recently been investigated for its various prophylactic effects. Lactate derived from potential functional foods, such as fermented oyster extract (FO), may emerge as a practical and effective method of consuming exogenous lactate. The current study endeavored to ascertain whether the lactate derived from FO may act on muscle cell biology, and to what extent this may translate into physical fitness improvements. We examined the effects of FO in vitro and in vivo, on mouse C2C12 cells and exercise performance indicators in mice, respectively. In vitro, biochemical analysis was carried out to determine the effects of FO on lactate content and muscle cell energy metabolism, including adenosine triphosphate (ATP) activity. Western blot analysis was also utilized to measure the protein expression of total adenosine monophosphate-activated protein kinase (AMPK), p-AMPK (Thr172), lactate dehydrogenase (LDH), succinate dehydrogenase (SDHA) and peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) in response to FO administration. Three experimental groups were formed: a positive control (PC) treated with 1% horse serum, FO10 treated with 10 μg/mL and FO50 treated with 50 μg/mL. In vivo, the effects of FO supplementation on exercise endurance were measured using the Rota-rod test, and Western blot analysis measured myosin heavy-chain 2 (MYH2) to assess skeletal muscle growth, alongside p-AMPK, total-AMPK, PGC-1α, cytochrome C and UCP3 protein expression. Biochemical analysis was also performed on muscle tissue to measure the changes in concentration of liver lactate, lactate dehydrogenase (LDH), glycogen and citrate. Five groups (n = 10/per group) consisted of a control group (CON), exercise group (Ex), positive control treated with Ex and 500 mg/kg Taurine (Ex-Tau), Ex and 100 mg/kg FO supplementation (Ex-FO100) and Ex and 200 mg/kg FO supplementation (Ex-FO200) orally administered over the 4-week experimental period.FO50 significantly increased PGC-1α expression (p < 0.001), whereas both FO10 and FO50 increased the expression of p-AMPK (p < 0.001), in C2C12 muscle cells, showing increased signaling important for mitochondrial metabolism and biogenesis. Muscle lactate levels were also significantly increased following FO10 (p < 0.05) and FO50 (p < 0.001). In vivo, muscle protein expression of p-AMPK (p < 0.05) and PGC-1α were increased, corroborating our in vitro results. Cytochrome C also significantly increased following FO200 intake. These results suggest that the effects of FO supplementation may manifest in a dose-response manner. FO administration, in vitro, and supplementation, in vivo, both demonstrate a potential for improvements in mitochondrial metabolism and biogenesis, and even for potentiating the adaptive effects of endurance exercise. Mechanistically, lactate may be an important molecule in explaining the aforementioned positive effects of FO.

P734Research on the mechamism of renal sympathetic denervation in the treatment of insulin resistance

Abstract Background Insulin resistance is the main pathogenesis of type 2 diabetes. In order to better control the blood glucose of diabetic patients, the key is to improve the insulin sensitivity. With the in-depth study on the mechanism of insulin resistance, sympathetic nerve is an important part of it, but the specific mechanism is not clear. Objective This experiment aims to observe the effects of RDN on insulin resistance and skeletal muscle mitochondrial function in spontaneous diabetes ZDF rats. Methods 6 SPF healthy male ZDF (fa/+) rats were selected as control group, 12 healthy males ZDF (fa/fa) rats were randomly divided into sham group and RDN group. In the sham group and RDN group, the rats were treated with sham operation or bilateral renal sympathetic denervation respectively. Insulin sensitivity was tested in all rats with Hyperinsulinemic-euglycemic clamp test 2 weeks after RDN. The skeletal muscle ATPsyn, COXIV, UCP3 and SOD2 were tested by Western-blot method. Results The result showed that 2 weeks after RDN, the blood glucose level of the RDN group decreased significantly (P=0.000) when compared with the sham group. The glucose infusion rate (GIR) in sham and RDN group decreased significantly when compared with the control group (P=0.000). After RDN, the GIR in RDN group increased significantly. ATPsyn, COXIV which were the key enzyme of oxidative metabolism in skeletal muscle mitochondria decreased significantly in the sham and RDN group when compared with control group (P=0.001). However, parameters improved dramatically after RDN (P=0.001). Table 1. Comparision of Baseline in each group 2 weeks after RDN Control (n=6) Sham (n=6) RDN (n=6) Pa Pb Pc Weight (g) 311.1±8.5 410.8±10.7 377.9±15.3 0.000 0.001 0.002 BBG (mmol/L) 5.97±0.16 21.42±1.45 7.91±0.54 0.000 0.001 0.000 BISN (ng/mL) 100.67±4.18 162.17±3.13 134.67±2.50 0.000 0.001 0.001 TG (mmol/L) 2.71±0.28 6.90±0.24 4.88±0.23 0.000 0.001 0.002 TC (mmol/L) 2.38±0.17 6.98±0.15 5.40±0.09 0.000 0.000 0.000 HDL-C (mmol/L) 7.92±0.44 2.95±0.22 5.35±0.19 0.000 0.000 0.000 LDL-C (mmol/L) 3.72±0.37 4.12±0.17 3.98±0.17 0.001 0.000 0.000 aCompared with Control Group and Sham Group. bCompared with RDN Group and Sham Group. cCompared with Sham Group and RDN Group. Relative results Conclusion Our results showed that RDN improved the insulin sensitivity in diabetes rats. The mechanism may be related to the decrease of oxidative stress and function improvement in skeletal muscle mitochondrial by RDN.

Chronic Urotensin-II Administration Improves Whole-Body Glucose Tolerance in High-Fat Diet-Fed Mice.

Urotensin-II (U-II) is an endogenous peptide agonist of a G protein-coupled receptor—urotensin receptor. There are many conflicting findings about the effects of U-II on blood glucose. This study aims to explore the effects of U-II on glucose metabolism in high-fat diet-fed mice. Male C57BL/6J mice were fed a 45% high-fat diet or chow diet and were administered U-II intraperitoneally for in vivo study. Skeletal muscle C2C12 cells were used to determine the effects of U-II on glucose and fatty acid metabolism as well as mitochondrial respiratory function. In this study, we found that chronic U-II administration (more than 7 days) ameliorated glucose tolerance in high-fat diet-fed mice. In addition, chronic U-II administration reduced the weight gain and the adipose tissue weight, including visceral, subcutaneous, and brown adipose tissue, without a significant change in blood lipid levels. These were accompanied by the increased mRNA expression of the mitochondrial thermogenesis gene Ucp3 in skeletal muscle. Furthermore, in vitro treatment with U-II directly enhanced glucose and free fatty acid consumption in C2C12 cells with increased aerobic respiration. Taken together, chronic U-II stimulation leads to improvement on glucose tolerance in high-fat diet-fed mice and this effect maybe closely related to the reduction in adipose tissue weights and enhancement on energy substrate utilization in skeletal muscle.

Occlusal interference induces oxidative stress and increases the expression of UCP3 in the masseter muscle: A rat model

ObjectiveTo determine whether occlusal alteration contributes to masticatory muscle damage by inducing oxidative stress. DesignThirty Sprague-Dawley rats were randomly divided into six groups, including occlusal interference groups (3 days, 7 days, 14 days, 21 days, and removal for 3 days) and a sham group. A rat experimental model of occlusal interference was generated by a 0.6-mm unilateral bite-raise. The rats were euthanised for evaluation of histologic changes in the masseter muscles using haematoxylin-eosin staining. To further investigate the role of oxidative stress and uncoupling protein (UCP3) in the development of occlusal dysfunction-induced masseter damage, levels of UCP3 protein were measured by western blot analysis. ResultsCompared with the sham group, the connective tissue of the masseter muscle was extended partially and inflammatory cells appeared following the induction of malocclusion. With respect to the oxidative stress markers, there were increases in malondialdehyde (MDA) content but decreases in superoxide dismutase (SOD) and glutathione peroxidase (GPX) activities; furthermore, the expression of UCP3 was upregulated. After eliminating the occlusal interference for 3 days, the degree of inflammation was substantially alleviated, the MDA content decreased, and SOD and GPX activities increased. The expression of UCP3 decreased. ConclusionsOcclusal interference induces oxidative stress in the masseter muscle, regulated by UCP3. Overall, these findings have significant implications for the understanding of how occlusal dysfunction causes muscle fatigue and pain.

Oral Ang-(1-7) treatment improves white adipose tissue remodeling and hypertension in rats with metabolic syndrome

ObjectiveAngiotensin (Ang)-(1-7) has preventive effects on metabolic syndrome (MetS). The aim of this study was to evaluate the therapeutic effect of oral Ang-(1-7) on mean arterial pressure (MAP), insulin resistance (IR), inflammatory process, and remodeling of white adipose tissue (WAT) in rats with established MetS. MethodsRats were subjected to control (CT; AIN-93M) or high-fat (HF) diets for 13 wk to induce MetS and treated with Ang-(1-7) or vehicle (V) for the last 6 wk. At the end of 13 wk, MAP, biochemical and histological parameters, and uncoupling protein (UCP) and inflammatory gene expression were determined by quantitative reverse transcription polymerase chain reaction. ResultsHF-V rats showed increased visceral fat deposition, inflammatory cytokine expression, hyperplasia, and hypertrophy in retroperitoneal (WAT) and brown adipose tissue (BAT). Additionally, the gastrocnemius muscle reduced UCP-3 and increased the UCP-1 expression in BAT. HF-V also elevated levels of plasma insulin, glucose, homeostatic model assessment (HOMA) of IR and HOMA-β, and increased body mass, adiposity, and MAP. Ang-(1-7) treatment in rats with MetS [HF-Ang-(1-7)] reduced WAT area, number of adipocytes, and expression of proinflammatory adipokines in WAT and BAT and increased UCP-3 in gastrocnemius muscle and UCP-1 expression in BAT compared with the HF-V group. These events prevented body mass gain, reduced adiposity, and normalized fasting plasma glucose, insulin levels, HOMA-IR, HOMA-β, and MAP. ConclusionData from the present study demonstrated that oral Ang-(1-7) treatment is effective in restoring biochemical parameters and hypertension in established MetS by improving hypertrophy and hyperplasia in WAT and inflammation in adipose tissue, and regulating metabolic processes in the gastrocnemius muscle and BAT.

Green satsuma mandarin orange (Citrus unshiu) extract reduces adiposity and induces uncoupling protein expression in skeletal muscle of obese mice

Increased fat mass, which is induced by the storage of excess nutrients, is considered a causal factor for various metabolic disorders, including insulin resistance, type 2 diabetes, hyperlipidemia, hyperglycemia, hypertension, atherosclerosis, and non-alcoholic fatty liver disease. Therefore, it is necessary to prevent hyperadiposity to sustain a healthy life. Recently, uncoupling proteins (UCPs) were suggested to be molecular targets for curing obesity and its complications. In this study, green satsuma mandarin orange (Citrus unshiu) extract (GME) increased UCP3 expression in cultured myocytes. In a diet-induced obese animal model, administration of GME reduced fat mass and average fat cell size. Similar to in vitro experiments, GME restored expression of UCP3 in skeletal muscle. Moreover, GME also induced UCP2 expression in skeletal muscle. In conclusion, GME is suggested to be a novel functional dietary supplement for adiposity control through induction of UCPs.

ACE I/D gene variant predicts ACE enzyme content in blood but not the ACE, UCP2, and UCP3 protein content in human skeletal muscle in the Gene SMART study.

Angiotensin-converting enzyme (ACE) is expressed in human skeletal muscle. The ACE I/D polymorphism has been associated with athletic performance in some studies. Studies have suggested that the ACE I/D gene variant is associated with ACE enzyme content in serum, and there is an interaction between ACE and uncoupling proteins 2 and 3 (UCP2 and UCP3). However, no studies have explored the effect of ACE I/D on ACE, UCP2, and UCP3 protein content in human skeletal muscle. Utilizing the Gene SMART cohort ( n = 81), we investigated whether the ACE I/D gene variant is associated with ACE enzyme content in blood and ACE, UCP2, and UCP3 protein content in skeletal muscle at baseline and following a session of high-intensity interval exercise (HIIE). Using a stringent and robust statistical analyses, we found that the ACE I/D gene variant was associated with ACE enzyme content in blood ( P < 0.005) at baseline but not the ACE, UCP2, and UCP3 protein content in muscle at baseline. A single session of HIIE tended (0.005 < P < 0.05) to increase blood ACE content immediately postexercise, whereas muscle ACE protein content was lower 3 h after a single session of HIIE ( P < 0.005). Muscle UCP3 protein content decreased immediately after a single session of HIIE ( P < 0.005) and remained low 3 h postexercise. However, those changes in the muscle were not genotype dependent. In conclusion, The ACE I/D gene variant predicts ACE enzyme content in blood but not the ACE, UCP2, and UCP3 protein content of human skeletal muscle. NEW & NOTEWORTHY This paper describes the association between ACE I/D gene variant and ACE protein content in blood and ACE, UCP2, and UCP3 protein content in skeletal muscle at baseline and after exercise in a large cohort of healthy males. Our data suggest that ACE I/D is a strong predictor of blood ACE content but not muscle ACE content.

Long-term effects of sprint interval training on expression of cardiac genes involved in energy efficiency

The real mechanisms of intensive exercise training-induced energy efficiency have not yet been well examined. Therefore, the aim of the present study was to investigate the effects of sprint interval training (SIT) on gene expression of uncoupling proteins (UCPs) and endothelial nitric oxide synthase (eNOS). For this purpose, 16 Albino Wistar rats (250–300 g) were randomly divided into equal groups of control and sprint training. The animals run on treadmill for 10 weeks, 5 days per week at intensity corresponding to 90–95% maximal oxygen consumption. The gene expression of UCP2, UCP3 and eNOS was analyzed by RT-PCR method in hearts. The data were analyzed by independent samples T test at P < 0.05 level. Sprint interval training significantly decreased mRNA expression of UCP2 (t14 = 4.818, P = 0.001) and UCP3 (t14 = 4.620, P = 0.001) in cardiac muscle of rats. In contrast, mRNA expression of eNOS in cardiac muscle significantly increased following sprint interval training (t14 = 7.967, P = 0.001). This study elucidates that SIT through reduction in gene expression of uncoupling proteins can improve energy efficiency. But, more studies are needed to confirm this hypothesis.

Response of skeletal muscle UCP2-expression during metabolic adaptation to caloric restriction.

Spendthrift vs. thrifty individuals expend more energy and experience greater weight loss during caloric restriction (CR). Adaptive mechanisms in skeletal muscle, adipose tissue, and on hormone level modulate energy expenditure (EE) during weight loss. Metabolic mechanisms underlying the variability in EE during CR are unclear. The present study explored whether during long-term CR (i) gene expression changes in skeletal muscle and adipose tissue relate with the individual EE response and weight loss, and (ii) altered catecholamine and FGF21-concentrations are associated with measures of metabolic adaptation. In a 10-week inpatient study, 24-h EE was measured before and after 6 weeks of 50% CR in 12 subjects using whole-room indirect calorimetry. Weight loss was assessed and repeated hormone measurements performed. Muscle and adipose tissue biopsies were taken before and after CR, and gene expression was assessed (RNA-Seq). Genes showing the most significant changes after CR were tested for association with EE and followed-up for further association with metabolic measures in a separate phenotyping study (n = 103). Muscle UCP2 showed the strongest change after CR (log2-fold change = -1.57, false discovery rate = 0.10) and was considered the best gene for exploration of metabolic adaptive processes. A greater decrease in UCP2-expression was associated with less weight loss (P = 0.03, r = 0.77) and relatively lower 24-h EE after CR (P = 0.001, r = -0.96). Post-CR changes in FGF21-plasma concentrations correlated with UCP2-expression change (P = 0.02, r = -0.89) and weight loss (P = 0.003, r = -0.83). In a separate metabolic phenotyping study, muscle UCP2-expression correlated with respiratory quotient and macronutrient oxidation. In adipose tissue, no candidate genes for metabolic exploration were found. Changes in muscle UCP2-expression reflect an inter-individual metabolic response to long-term CR and may influence EE and weight loss via modulation of substrate oxidation.

Expression of genes involved in carbohydrate-lipid metabolism in muscle and fat tissues in the initial stage of adult-age obesity in fed and fasted mice.

C57Bl mice exhibit impaired glucose metabolism by the late adult age under standard living conditions. The aim of this study was to evaluate white adipose tissue (WAT), brown adipose tissue (BAT), and skeletal muscle expression of genes involved in carbohydrate‐lipid metabolism at postpubertal stages preceding the late adult age in C57Bl mice. Muscle mRNA levels of uncoupling protein 3 (Ucp3) and carnitine palmitoyltransferase 1 (Cpt1) (indicators of FFA oxidation), WAT mRNA levels of hormone‐sensitive lipase (Lipe) and lipoprotein lipase (Lpl) (indicators of lipolysis and lipogenesis), muscle and WAT mRNA levels of the type 4 glucose transporter Slc2a4 (indicators of insulin‐dependent glucose uptake), and BAT mRNA levels of uncoupling protein 1 (Ucp1) (indicator of thermogenesis) were measured in fed and 16 h‐fasted mice in three age groups: 10‐week‐old (young), 15‐week‐old (early adult), and 30‐week‐old (late adult). Weight gain from young to early adult age was not accompanied by changes in WAT and BAT indexes and biochemical blood parameters. Weight gain from early to late adult age was accompanied by increased WAT and BAT indexes and decreased glucose tolerance. Muscle Ucp3 and Cpt1 mRNA levels and WAT Lipe and Slc2a4 mRNA levels increased from young to early adult age and then sharply decreased by the late adult age. Moreover, BAT Ucp1 mRNA level decreased in the late adult age. Fasting failed to increase muscle Cpt1 mRNA levels in late adult mice. These transcriptional changes could contribute to impaired glucose metabolism and the onset of obesity in late adult mice during normal development.

BAIBA Does Not Regulate UCP-3 Expression in Human Skeletal Muscle as a Response to Aerobic Exercise

ABSTRACTObjective: β-Aminoisobutyric acid (BAIBA) has shown to modulate uncoupling protein (UCP)-1 expression, which is mainly expressed in white adipose tissue; however, no studies to date have analyzed its potential effect on the main uncoupling protein of skeletal muscle, UCP-3. The main goal of this study was to assess the potential effect of acute aerobic exercise on serum BAIBA and skeletal muscle UCP-3. The secondary goal was to assess the potential involvement of the transcription factors proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) and peroxisome proliferator–activated receptor alpha (PPARα), as well as free fatty acids (FFAs) in UCP-3 expression. A tertiary goal of the study was to evaluate the potential effect of consuming a preexercise meal on the outcome of the first 2 objectives.Methods: In a randomized crossover design, untrained participants performed 2 acute cycling sessions (350 kcal at 70% of their VO2peak) after 2 experimental conditions: (1) consumption of a multi-macronutrient shake and (2) a fasting period of 8 hours. Blood samples were taken at baseline, preexercise, postexercise, 1 hour, and 4 hours postexercise, and muscle biopsies were taken at the last 4 time points. UCP-3 protein concentration and expression, as well as the mRNA expression of PGC-1α and PPARα, were measured in muscle, and BAIBA, glucose, and FFA were measured in serum.Results: Aerobic exercise failed to induce a significant effect on serum BAIBA, PGC-1α, and PPARα regardless on the feeding condition. Despite the lack of effect of exercise on the previous variables, UCP-3 expression and protein concentration significantly increased in the shake condition.Conclusion: The expression of human skeletal muscle UCP-3 as a result of exercise might be controlled by factors other than BAIBA.

Irisin in goldfish (Carassius auratus): Effects of irisin injections on feeding behavior and expression of appetite regulators, uncoupling proteins and lipoprotein lipase, and fasting-induced changes in FNDC5 expression

Irisin is a peptide cleaved from the fibronectin type III domain containing protein 5 (FNDC5) gene that is secreted predominantly by muscle cells but also by other tissues including brain and intestine. In mammals, irisin has been shown to have thermogenic actions via the modulation of uncoupling proteins (UCPs) and to affect feeding and energy homeostasis via actions in brain, adipose tissue, liver, muscle and gastrointestinal tract. To examine the role of irisin on feeding and metabolism in fish, the effects of peripheral (intraperitoneal) injections of irisin on feeding behavior, glucose levels and the mRNA expressions of appetite regulators (cocaine and amphetamine regulated transcript CART, agouti related protein AgRP, orexin), UCPs and lipoprotein lipase LPL and brain factors (brain-derived neurotrophic factor , BDNF and tyrosine hydroxylase TH) were assessed in brain, white muscle and intestine. Irisin injections (100ng/g) induced a decrease in food intake and increases in brain orexin, CART1 and CART2, UCP2, BDNF, muscle UCP2 and intestine LPL mRNA expressions but did not affect blood glucose levels, brain AgRP, TH, UCP1, UCP3 and LPL or muscle UCP1, UCP3 and LPL expressions. A partial goldfish FNDC5 cDNA was isolated and the expressions of FDNC5, UCPs, LPL and BDNF were also compared between fed and fasted fish. Fasting induced decreases FNDC5 mRNA expression in the brain and intestine, but not in muscle. Fasting also induced increases in brain BDNF and LPL expressions and increases in UCP1, UCP2, UCP3 and LPL expressions in muscle. Our result suggest that irisin is an anorexigenic factor in fish and its actions might be in part mediated by appetite-regulating factors such as CART and orexins as well as UCP2 and brain factors such as BDNF.

The complementary and divergent roles of uncoupling proteins 1 and 3 in thermoregulation.

Both uncoupling protein 1 (UCP1) and UCP3 are important for mammalian thermoregulation. UCP1 and UCP3 in brown adipose tissue mediate early and late phases of sympathomimetic thermogenesis, respectively. Lipopolysaccharide thermogenesis requires skeletal muscle UCP3 but not UCP1. Acute noradrenaline-induced hyperthermia requires UCP1 but not UCP3. Loss of both UCP1 and UCP3 accelerate the loss of body temperature compared to UCP1KO alone during acute cold exposure. Uncoupling protein 1 (UCP1) is the established mediator of brown adipose tissue-dependent thermogenesis. In contrast, the role of UCP3, expressed in both skeletal muscle and brown adipose tissue, in thermoregulatory physiology is less well understood. Here, we show that mice lacking UCP3 (UCP3KO) have impaired sympathomimetic (methamphetamine) and completely abrogated lipopolysaccharide (LPS) thermogenesis, but a normal response to noradrenaline. By comparison, UCP1 knockout (UCP1KO) mice exhibit blunted methamphetamine and fully inhibited noradrenaline thermogenesis, but an increased febrile response to LPS. We further establish that mice lacking both UCP1 and 3 (UCPDK) fail to show methamphetamine-induced hyperthermia, and have a markedly accelerated loss of body temperature and survival after cold exposure compared to UCP1KO mice. Finally, we show that skeletal muscle-specific human UCP3 expression is able to significantly rescue LPS, but not sympathomimetic thermogenesis blunted in UCP3KO mice. These studies identify UCP3 as an important mediator of physiological thermogenesis and support a renewed focus on targeting UCP3 in metabolic physiology.