Solute carrier family 16 member 1 as a potential prognostic factor for pancreatic ductal adenocarcinoma and its influence on tumor immunity.

Background: Solute carrier family 16 member 1 (SLC16A1) serves as a biomarker in numerous types of cancer. Tumor immune infiltration has drawn increasing attention in cancer progression and treatment. The objective of our study was to explore the association between SLC16A1 and the tumor immune microenvironment in pancreatic ductal adenocarcinoma (PDAC). Methods: Data were obtained from The Cancer Genome Atlas. The xCell web tool was used to calculate the proportion of immune cells according to SLC16A1 expression. To further explore the mechanism of SLC16A1, immunity-related genes were screened from differentially expressed genes through weighted gene coexpression network analysis, examined via Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses, and filtrated using univariate Cox regression and least absolute shrinkage and selection operator regression model combined correlation analysis (P<0.05). Next, CIBERSORT was used to analyze the correlation between immune cells and five important genes. SLC16A1 expression and its clinical role in pancreatic cancer was clarified via immunohistochemical staining experiments. Finally, the effects of SLC16A1 on the results of cancer immunity were evaluated by in vitro experiments. Results: SLC16A1 was overexpressed in PDAC tissues and could be an independent prognostic factor. SLC16A1 was significantly negatively correlated with overall survival and suppressed the tumor immunity of PDAC. In clinic, SLC16A1 expression was significantly positively correlated with tumor progression and poor prognosis. We also found that SLC16A1 could suppress the antitumor ability of CD8+ T cells. Conclusions: SLC16A1 is a biomarker for the prognosis of PDAC and can influence the immune environment of PDAC. These findings provide new insights into the treatment of PDAC.

Alleviated NCOA4-mediated ferritinophagy protected RA FLSs from ferroptosis in lipopolysaccharide-induced inflammation under hypoxia.

OBJECTIVE: Ferroptosis is a reactive oxygen species (ROS)- and iron-dependent form of non-apoptotic cell death process. Previous studies have demonstrated that ferroptosis participates in the development of inflammatory arthritis. However, the role of ferroptosis in rheumatoid arthritis (RA) inflammatory hypoxic joints remains unclear. This study sought to explore the underlying mechanism of ferroptosis on lipopolysaccharide (LPS)-induced RA fibroblast-like synoviocytes (FLSs). METHODS: FLSs, isolated from patients with RA, were treated with LPS and ferroptosis inducer (erastin and RSL-3), and ferroptosis inhibitor (Fer-1 and DFO), respectively. The cell viability was measured by CCK-8. The cell death was detected by flow cytometer. The proteins level were tested by Western blot. The cytosolic ROS and lipid peroxidation were determined using DCFH-DA and C11-BODIPY581/591 fluorescence probes, respectively. The small interfering RNA (siRNA) was used to knock down related proteins. The levels of malondialdehyde (MDA), 4-hydroxynonenal (4-HNE), iron, inflammatory cytokines (IL6 and IL8), and LDH were analyzed by commercial kits. RESULTS: Ferroptosis was activated by LPS in RA FLS with increased cellular damage, ROS and lipid peroxidation, intracellular Fe and IL8, which can be further amplified by ferroptosis inducer (erastin and RSL-3) and inhibited by ferroptosis inhibitor (Fer-1 and DFO). Mechanistically, LPS triggered ferroptosis via NCOA4-mediated ferritinophagy in RA FLSs, and knockdown of NCOA4 strikingly prevent the process of ferroptosis. Intriguingly, LPS-induced RA FLSs became insensitive to ferroptosis and NCOA4-mediated ferritinophagy under hypoxia compared with normoxia. Knockdown of HIF-1α reverted ferroptosis and ferritinophagy evoking by LPS-induced RA FLSs inflammation under hypoxia. In addition, low dose of auranofin (AUR) induced re-sensitization of ferroptosis and ferritinophagy through inhibiting the expression of HIF-1α under hypoxia. CONCLUSIONS: NCOA4-mediated ferritinophagy was a key driver of ferroptosis in inflammatory RA FLSs. The suppression of NCOA4-mediated ferritinophagy protected RA FLSs from ferroptosis in LPS-induced inflammation under hypoxia. Targeting HIF-1α/NCOA4 and ferroptosis could be an effective and valuable therapeutic strategy for synovium hyperplasia in the patients with RA.

TRPV4 in adipose tissue ameliorates diet-induced obesity by promoting white adipocyte browning.

The induction of adipocyte browning to increase energy expenditure is a promising strategy to combat obesity. Transient receptor potential channel V4 (TRPV4) functions as a nonselective cation channel in various cells and plays physiological roles in osmotic and thermal sensations. However, the function of TRPV4 in energy metabolism remains controversial. This study revealed the role of TRPV4 in adipose tissue in the development of obesity. Adipose-specific TRPV4 overexpression protected mice against diet-induced obesity (DIO) and promoted white fat browning. TRPV4 overexpression was also associated with decreased adipose inflammation and improved insulin sensitivity. Mechanistically, TRPV4 could directly promote white adipocyte browning via the AKT pathway. Consistently, adipose-specific TRPV4 knockout exacerbated DIO with impaired thermogenesis and activated inflammation. Corroborating our findings in mice, TRPV4 expression was low in the white adipose tissue of obese people. Our results positioned TRPV4 as a potential regulator of obesity and energy expenditure in mice and humans.

Nicotinamide mononucleotide alters body composition and ameliorates metabolic disorders induced by a high-fat diet.

Obesity is caused by an imbalance between calorie intake and energy expenditure, leading to excessive adipose tissue accumulation. Nicotinamide adenine dinucleotide (NAD+ ) is an important molecule in energy and signal transduction, and NAD+ supplementation therapy is a new treatment for obesity in recent years. Liver kinase B1 (LKB1) is an energy metabolism regulator. The relationship between NAD+ and LKB1 has only been studied in the heart and has not yet been reported in obesity. Nicotinamide mononucleotide (NMN), as a direct precursor of NAD+ , can effectively enhance the level of NAD+ . In the current study, we showed that NMN intervention altered body composition in obese mice, characterized by a reduction in fat mass and an increase in lean mass. NMN reversed high-fat diet-induced blood lipid levels then contributed to reducing hepatic steatosis. NMN also improved glucose tolerance and alleviated adipose tissue inflammation. Moreover, our data suggested that NMN supplementation may be depends on the NAD+ /SIRT6/LKB1 pathway to regulate brown adipose metabolism. These results provided new evidence for NMN in obesity treatment.

LKB1 on POMC neurons affect the formation of diet-induced obesity by regulating the expression of HDAC1.

BACKGROUND: Obesity is considered a major public health issue worldwide. Liver Kinase B1 (LKB1) is a serine/threonine kinase, peripheral LKB1 is involved in obesity by regulating adipogenesis, but the role of central LKB1 in the development of obesity remains unclear. OBJECTIVE: This study aims to explore the main role of LKB1 in POMC neurons on obesity, and reveal the underlying mechanism of central LKB1 affecting obesity through quantitative proteomics. METHODS: We constructed POMC neuron specific LKB1 knockout mice (PomcLkb1 KO) and exposed them to high fat diet intervention for three months. The effect of LKB1 knockout on obesity was evaluated by monitoring body weight, food intake and measuring fat content. The hypothalamus tissues were collected for proteomic analysis and validated by RT-PCR. RESULTS: The degree of obesity was aggravated in PomcLkb1 KO mice fed with high fat diet. Proteomic results showed that only Histone deacetylase 1 (HDAC1) was down-regulated in the hypothalamus of PomcLkb1 KO mice. Our research also found that LKB1 knockout on POMC neurons led to reduction of Peroxisome proliferator-activated receptor γ (PPARγ). Meanwhile, the software predicted that the transcription factor PPARγ binds to the HDAC1 promoter. Therefore, we speculated that central LKB1 may regulate diet-induced obesity development by influencing HDAC1/PPARγ expression. CONCLUSION: We firstly found that central LKB1 may affect the development of obesity by regulating the expression of HDAC1, which provides a new idea for the central regulatory mechanism of obesity.

STAT3/HIF-1α/fascin-1 axis promotes RA FLSs migration and invasion ability under hypoxia.

Rheumatoid arthritis (RA) synovium was identified as "tumor-like" tissues because of the hypoxic microenvironment, significant cell proliferation, and invasion phenotypes. It was reported that hypoxia promoted tumor aggressiveness via up-regulated expression of fascin-1 in cancer. However, the role of fascin-1 in RA synovial hyperplasia and joint injury progression remains unknown. In the current study, we first identified that both fascin-1 and HIF-1α were highly expressed in the RA synovium, in which they were widely colocalized, compared to osteoarthritis(OA). As well, levels of fascin-1 in RA fibroblast-like synoviocytes(FLSs) were found significantly higher than those in OA FLSs. Further, it was demonstrated that the mRNA and protein levels of fascin-1 in RA FLSs were up-regulated in hypoxia (3 % O2) and experimental hypoxia induced by cobalt chloride. Mechanistically, the HIF-1α-mediated hypoxia environment activated the gene expression of the fascin-1 protein, which in turn promoted the migration and invasion of RA FLSs. Accordingly, the restoration of FLSs migration and invasion was observed following siRNA-mediated silencing of fascin-1 and HIF-1α expression. Notably, under the experimental hypoxia, we found that the expression levels of fascin-1, HIF-1α, and p-STAT3 were increased in a time-dependent manner, and fascin-1and HIF-1α expressions were dependent on p-STAT3. Our results indicated that hypoxia-induced fascin-1 up-regulation promoted RA FLSs migration and invasion through the STAT3/HIF-1α/fascin-1 axis, which might represent a novel therapeutic target for the treatment of RA.

NEK7-Mediated Activation of NLRP3 Inflammasome Is Coordinated by Potassium Efflux/Syk/JNK Signaling During Staphylococcus aureus Infection.

Staphylococcus aureus (S. aureus) is a foodborne pathogen that causes severe diseases, such as endocarditis, sepsis, and bacteremia. As an important component of innate immune system, the NLR family pyrin domain-containing 3 (NLRP3) inflammasome plays a critical role in defense against pathogen infection. However, the cellular mechanism of NLRP3 inflammasome activation during S. aureus infection remains unknown. In the present study, we found that spleen tyrosine kinase (Syk) and c-Jun N-terminal kinase (JNK) were rapidly phosphorylated during S. aureus infection. Moreover, a Syk/JNK inhibitor and Syk/JNK siRNA not only reduced NLRP3 inflammasome-associated molecule expression at the protein and mRNA levels, apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC) speck formation, and interleukin-1ß (IL-1ß), and IL-18 release but also rescued the decreased NIMA-related kinase 7 (NEK7) expression level following suppression of the NEK7-NLRP3 interaction in macrophages. Interestingly, Syk/JNK phosphorylation levels and NLRP3 inflammasome-associated molecule expression were decreased by blockade of K+ efflux. Furthermore, activation of the NLRP3 inflammasome and a lower NEK7 protein level were found in vivo upon S. aureus infection. Taken together, our data indicated that S. aureus infection induces a K+ efflux/Syk/JNK/NEK7-NLRP3 signaling pathway and the subsequent activation of the NLRP3 inflammasome for the release of proinflammatory cytokines. This study expands our understanding of the basic molecular mechanism regulating inflammation and provides potential value for anti-infective drug development against S. aureus infection.

Ginsenoside Rb1 Facilitates Browning by Repressing Wnt/ß-Catenin Signaling in 3T3-L1 Adipocytes.

BACKGROUND The discovery of browning in white adipose tissue has provided new ideas for treating obesity. Many studies have reported that ginsenoside Rb1 (G-Rb1) has activity against diabetes, inflammation, and obesity, but further investigation is needed on the effect and mechanism of G-Rb1 on browning. MATERIAL AND METHODS We treated 3T3-L1 adipocytes with 0-200 µM G-Rb1, and 0.5 µM Compound 3f and 30 µM SKL2001 were used to activate Wnt/b-catenin signaling. Adipocyte activity was evaluated by Cell Counting Kit-8. Oil Red O staining was used to detect the lipid droplets. Quantitative real-time polymerase chain reaction was used to measure the expression of Cd-137, Cited-1, Txb-1, Prdm-16, and Ucp-1 mRNA. Western blotting was used to measure the expression of Ucp-1, pGSK-3ß (Ser 9), GSK- 3ß, and ß-catenin proteins. The expression of Ucp-1 was also detected with immunofluorescence. RESULTS Adipocyte activity was not affected by 0-100 µM G-Rb1. However, G-Rb1 dose-dependently reduced the accumulation of lipid droplets; increased the expression of Cd-137, Cited-1, Txb-1, Prdm-16, and Ucp-1 mRNA; and increased the expression of Ucp-1, pGSK-3ß (Ser 9), GSK-3ß, and ß-catenin proteins. The accumulation of lipid droplets and the expression of Ucp-1 protein decreased as b-catenin increased. CONCLUSIONS G-Rb1 at various concentrations (0-100 µM) promoted the browning of adipocytes in a dose-dependent manner. Further, we confirmed that activation of Wnt/ß-catenin signaling could inhibit browning. Therefore, the browning promoted by G-Rb1 may be associated with the inhibition of Wnt/ß-catenin signaling.

LKB1 up-regulation inhibits hypothalamic inflammation and attenuates diet-induced obesity in mice.

BACKGROUND: Diet-induced obesity (DIO) is associated with chronic, low-grade inflammation in the hypothalamus. The inflammatory pathway of the hypothalamus is activated during obesity, and inhibition of activation of the inflammatory pathway can partially reverse obesity. Therefore, exploring new targets for inhibiting hypothalamic inflammation will provide new ideas for the prevention and treatment of obesity. Liver kinase B1 (LKB1), a serine/threonine kinase, is a tumor suppressor and metabolic regulator. Recent studies have shown that LKB1 has a certain anti-inflammatory effect. However, a role of LKB1 in the regulation of hypothalamic inflammation remains unclear. Therefore, we examined whether LKB1 overexpression in the hypothalamus could weaken the hypothalamic inflammation and inhibit the development of obesity. METHODS: LKB1 overexpressing adeno-associated virus (AAV) particles were injected stereotactically into the third ventricle (3 V) of C57BL/6 mice fed with HFD. We assessed changes in body mass and adiposity, food intake, hypothalamic inflammatory markers, and energy and glucose metabolism. RESULTS: LKB1 up-regulation in hypothalamus attenuated diet-induced hypothalamic inflammation, reduced food intake and body weight gain. In addition, the overexpression of hypothalamic LKB1 increased the insulin sensitivity and improved whole-body lipid metabolism, which attenuated hepatic fat accumulation and serum lipid levels. CONCLUSION: Hypothalamic LKB1 up-regulation attenuates hypothalamic inflammation, and protects against hypothalamic inflammation induced damage to melanocortin system, resulting in lower food intake and lower fat mass accumulation, which consequently protects mice from the development of obesity. Our data suggest LKB1 as a novel negative regulator of hypothalamic inflammation, and also a potentially important target for treating other inflammatory diseases.

Deletion of liver kinase B1 in POMC neurons predisposes to diet-induced obesity.

AIMS: Liver kinase B1 (LKB1) is a serine/threonine kinase. Although many biological functions of LKB1 have been identified, the role of hypothalamic LKB1 in the regulation of central energy metabolism and susceptibility to obesity is unknown. Therefore, we constructed POMC neuron-specific LKB1 knockout mice (PomcLkb1 KO) and studied it at the physiological, morphological, and molecular biology levels. MAIN METHODS: Eight-week-old male PomcLkb1 KO mice and their littermates were fed a standard chow fat diet (CFD) or a high-fat diet (HFD) for 3 months. Body weight and food intake were monitored. Dual-energy X-ray absorptiometry was used to measure the fat mass and lean mass. Glucose and insulin tolerance tests and serum biochemical markers were evaluated in the experimental mice. In addition, the levels of peripheral lipogenesis genes and central energy metabolism were measured. KEY FINDINGS: PomcLkb1 KO mice did not exhibit impairments under normal physiological conditions. After HFD intervention, the metabolic phenotype of the PomcLkb1 KO mice changed, manifesting as increased food intake and an enhanced obesity phenotype. More seriously, PomcLkb1 KO mice showed increased leptin resistance, worsened hypothalamic inflammation and reduced POMC neuronal expression. SIGNIFICANCE: We provide evidence that LKB1 in POMC neurons plays a significant role in regulating energy homeostasis. LKB1 in POMC neurons emerges as a target for therapeutic intervention against HFD-induced obesity and metabolic diseases.

Liver kinase B1 induces browning phenotype in 3 T3-L1 adipocytes.

Induction of brown adipocytes in white adipose tissue is a promising therapy for combating human obesity and its associated disorders. Liver kinase B1 (LKB1) is a tumor inhibitor and metabolic modulator. Recent data suggest that LKB1 is necessary for adipogenesis, but its role in the browning of white adipocytes remains unknown. The objective of this study was to reveal the effect of LKB1 on browning. In our study, we showed that overexpression of LKB1 in 3 T3-L1 adipocytes up-regulated the expression of brown adipocyte markers, including UCP1, PGC-1α, Cidea, and PRDM16, and beige-cell-specific genes, such as CD137 and Tmem26. It was possible that the expression of UCP1 and other beige markers was increased by activation of PPARγ, resulting in the browning of 3 T3-L1 preadipocytes. The browning effect was abolished by a PPARγ inhibitor (GW9662). Moreover, these effects were dramatically abrogated by silencing of LKB1. Additionally, LKB1 decreased the expression levels of adipogenesis proteins (C/EBPα and SREBP1) and up-regulated lipid catabolism protein, perilipin (PLIN). In summary, the study suggested that LKB1 induces the browning of white adipocytes, in addition to promoting lipid metabolism. Therefore, LKB1 may be a helpful therapeutic candidate for treating obesity.

Intraventricular Injection of LKB1 Inhibits the Formation of Diet-Induced Obesity in Rats by Activating the AMPK-POMC Neurons-Sympathetic Nervous System Axis.

BACKGROUND/AIMS: Obesity is increasingly becoming a major public health problem worldwide. Peripheral LKB1 inhibits white fat generation, but the effect of central LKB1 on diet-induced obesity (DIO) is unknown. Therefore, we examined whether LKB1 over-expression in the hypothalamus can inhibit the development of obesity. METHODS: Adult male Sprague-Dawley rats were anesthetized and placed in a stereotaxic apparatus. LKB1-AAV-EGFP (2.0 × 108 or 2.0 × 1010 vector genomes) or Control-AAV-EGFP (2.0 × 108 vector genomes) was injected into the third ventricle. After administration, the rats were fed a high-fat diet (HFD) for 9 weeks to induce obesity. Rats fed a chow fat diet were used as normal controls. RESULTS: LKB1 delivery decreased body weight, energy intake, fat mass, and serum lipid levels. LKB1 also improved HFD-induced hepatic fatty degeneration. Interestingly, LKB1 over-expression in the hypothalamus activated the AMPK-POMC neurons-sympathetic nervous system (SNS) axis, which can release epinephrine to promote white fat browning. Conversely, the elevated expression of MC3R/MC4R inhibited food intake. These two factors worked together to inhibit the development of obesity. CONCLUSIONS: LKB1 in the hypothalamus may have therapeutic potential for DIO through the activation of the AMPK-POMC neurons-SNS axis.

Liraglutide suppresses proliferation and induces adipogenic differentiation of 3T3-L1 cells via the Hippo-YAP signaling pathway.

Liraglutide, as a glucagon-like peptide­1 analogue, is used to treat type 2 diabetes mellitus and obesity. Previous findings have demonstrated the effects of liraglutide on adipogenesis; however, the underlying mechanism involved in this process remains to be elucidated. In the present study, to certify the effect of liraglutide on adipogenesis and explore the possible underlying mechanism involved in this process, preadipocyte 3T3­L1 cells were cultured in adipocyte­inducing medium and treated with liraglutide. Subsequently, the expression levels of the master transcription factors and adipocyte­specific genes were measured by reverse transcription­quantitative polymerase chain reaction and immunoblotting analysis. Lipid droplet production was detected by Oil red O staining. Cell proliferation was determined by a Cell Counting Kit-8 assay and cell immunofluorescence for Ki67, and apoptosis was assessed by flow cytometry. Next, the expression levels of the core components in the Hippo­yes­associated protein (YAP) signaling pathway as well as YAP­specific target genes were measured. Finally, short interfering RNAs of mammalian ste20 kinase 1/2 (MST1/2), a key protein kinase in the Hippo­YAP pathway, were used to determine whether liraglutide regulated adipogenic differentiation via the Hippo­YAP pathway. It was demonstrated that liraglutide promoted adipogenic differentiation, suppressed proliferation, did not affect apoptosis of 3T3­L1 cells and activated the Hippo­YAP signaling pathway at the initial stage of adipogenesis. Silencing of MST1 counteracted the effect of increasing adipogenesis by liraglutide. These results suggested that liraglutide may activate the Hippo­YAP signaling pathway leading to the inhibition of proliferation of preadipocyte 3T3­L1 cells, and result in cells achieving transformation into mature adipocytes sooner. Taken together, the results of the present study may expand knowledge of the underlying mechanism of liraglutide facilitating adipogenesis, and may contribute to the development of GLP­1 receptor agonists for weight loss and increased insulin sensitivity.

Altered Regional Gray Matter Volume in Obese Men: A Structural MRI Study.

Obesity is associated with a number of health problems, especial insulin resistance and Type 2 diabetes. Our previous study showed that obese males had decreased neural activity in the orbital frontal cortex (OFC) and increased activity in the left putamen (Zhang et al., 2015b), which could indicate altered eating behaviors in obesity related to a hyper-functioning striatum and hypo-functioning inhibitory control. Accordingly, our goal of the current study was to determine whether there are alterations in the brain structures within these two neural systems in obese individuals. Twenty obese men (age: 20-28 years) and 20 age-matched lean male subjects were involved in the current study. Plasma glucose and insulin were tested during hunger state, and homeostasis model assessment of insulin resistance (HOMA-IR) was based on the blood samples. In the study, we used structural MRI and a voxel-based morphometry (VBM) method to investigate regional structures in obese subjects and find out whether there are correlations between the insulin and the brain structures. We found that obese men only showed a significantly increased gray matter volume (GMV) in the left putamen and that the GMV of the left putamen was positively correlated with body mass index, plasma insulin and HOMA-IR. The putamen is a core region participating in insulin signal regulation, and our results showed an abnormal GMV of the putamen is a core alternation in aberrant insulin. Furthermore, the GMV of the OFC was negatively correlated with hunger rating, despite there being no significant difference between the two groups in the OFC. In conclusion, the altered structure and function of the putamen could play important roles in obesity and aberrant insulin.

mTOR remains unchanged in diet-resistant (DR) rats despite impaired LKB1/AMPK cascade in adipose tissue.

Liver kinase B1 (LKB1) plays an important role in adipogenesis, but the underlying molecular mechanism is poorly understood. Here, we explored the functional relationship between LKB1 and the mammalian target of rapamycin (mTOR) in regulating adipogenesis in rats and preadipocytes. We found that LKB1 and the adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) cascade are impaired in the white adipose tissue (WAT) of diet-induced obesity (DIO) and diet-resistant (DR) rats when compared with chow-fed (CF) rats. While DIO activated the mTOR pathway in WAT and led to a more fat mass gain, DR maintained the normal activity of the mTOR pathway and normal weight and percentage of fat mass. We further constructed overexpressed LKB1 (OE) and silenced LKB1 (Si) 3T3-L1 preadipocytes monoclonal cell lines. In the OE cell line, the mTOR pathway was inactivated, and intracellular lipid content was reduced during differentiation. This effect could be reversed by AMPK inhibition. Conversely, in the Si cell line, the mTOR pathway was activated and intracellular lipid content increased. This effect could be reversed by rapamycin, an inhibitor of mTOR. Our results suggest that mTOR mediates the effect of LKB1 on adipogenesis, and normal activity of mTOR in DR rats interferes with the effect of LKB1 in WAT.

Altered baseline brain activity differentiates regional mechanisms subserving biological and psychological alterations in obese men.

Obesity as a chronic disease is a major factor for insulin resistance and Type 2 diabetes, which has become a global health problem. In the present study, we used resting state functional MRI to investigate the amplitude of low frequency fluctuations of spontaneous signal during both hunger and satiety states in 20 lean and 20 obese males. We found that, before food intake, obese men had significantly greater baseline activity in the precuneus and lesser activity in dorsal anterior cingulate cortex (dACC) relative to lean subjects. Furthermore, after food intake, obese males had significantly lesser activity in dACC than lean males. We further found a significant positive correlation between precuneus activation and hunger ratings before food intake, while dACC activity was negatively correlated with plasma insulin levels before and after food intake. These results indicated that both precuneus and dACC may play an important role in eating behavior. While precuneus rather seemed to mediate subjective satiety, dACC levels rather reflected indirect measures of glucose utilization.

Altered baseline brain activities before food intake in obese men: a resting state fMRI study.

Obesity as a chronic disease has become a global epidemic. However, why obese individuals eat more still remains unclear. Recent functional neuroimaging studies have found abnormal brain activations in obese people. In the present study, we used resting state functional MRI to observe spontaneous blood-oxygen-level dependent (BOLD) signal fluctuations during both hunger and satiety states in 20 lean and 20 obese men. Using a regional homogeneity (ReHo) analysis method, we measured temporal homogeneity of the regional BOLD signals. We found that, before food intake, obese men had significantly increased synchronicity of activity in the left putamen relative to lean men. Decreased synchronicity of activity was found in the orbitofrontal cortex (OFC) and medial prefrontal cortex(MPFC) in the obese subjects. And, the ratings of hunger of the obese subjects were higher than those of the lean subjects before food intake. After food intake, we did not find the significant differences between the obese men and the lean men. In all participations, synchronicity of activity increased from the fasted to the satiated state in the OFC. The results indicated that OFC plays an important role in feeding behavior, and OFC signaling may be disordered in obesity. Obese men show less inhibitory control during fasting state. This study has provided strong evidence supporting the hypothesis that there is a hypo-functioning reward circuitry in obese individuals, in which the frontal cortex may fail to inhibit the striatum, and consequently lead to overeating and obesity.

Diet-induced obese rats exhibit impaired LKB1-AMPK signaling in hypothalamus and adipose tissue.

AMPK not only acts as a sensor of cellular energy status but also plays a critical role in the energy balance of the body. In this study, LKB1-AMPK signaling was investigated in diet-induced obese (DIO) and diet resistant (DR) rats. In hypothalamus, DIO rats had lower level of LKB1, AMPKα and pAMPKα than chow-fed or DR rats. Both orexigenic peptide NPY and anorexigenic peptide POMC expression were reduced in hypothalamus of DIO rats. i.c.v. injection of AICAR, an activator of AMPK, increased NPY expression but did not alter POMC expression in DIO rats. In periphery, LKB1 protein content and pAMPKα level were lower in the adipose tissue of DIO rats compared to chow-fed and DR rats. Moreover, pAMPKα and LKB1 protein levels obtained from epididymal fat pad were inversely correlated with epididymal fat mass. LKB1 protein content and pAMPKα in skeletal muscle of DIO rats were not different from those in the muscles of chow-fed and DR rats. In summary, DIO rats, but not DR rats, have impaired LKB1-AMPK signaling in hypothalamus and adipose tissue, suggesting the disturbed energy balance observed in DIO rats is related with abnormalities of AMPK signaling in a tissue specific manner.

Proteomic analysis of rat hypothalamus revealed the role of ubiquitin-proteasome system in the genesis of DR or DIO.

Obesity has become a global epidemic, contributing to the increasing burdens of cardiovascular disease and type 2 diabetes. However, the precise molecular mechanisms of obesity remain poorly elucidated. The hypothalamus plays a major part in regulating energy homeostasis by integrating all kinds of nutritional signals. This study investigated the hypothalamus protein profile in diet-induced obese (DIO) and diet-resistant (DR) rats using two dimensional gel electrophoresis (2-DE) combined with MALDI-TOF/TOF-MS analysis. Twenty-two proteins were identified in the hypothalamus of DIO or DR rats. These include metabolic enzymes, antioxidant proteins, proteasome related proteins, and signaling proteins, some of which are related to AMP-activated protein kinase (AMPK) signaling or mitochondrial respiration. Among these proteins, in comparison with the normal-diet group, Ubiquitin was significantly decreased in DR rats but not changed in DIO rats, while Ubiquitin carboxyl-terminal esterase L1 (UCHL-1) was decreased in DIO rats but not changed in DR rats. The expression level of Ubiquitin and UCHL-1 were further validated using Western blot analysis. Our study reveals that Ubiquitin and UCHL-1 are obesity-related factors in the hypothalamus that may play an important role in the genesis of DR or DIO by interfering with the integrated signaling network that control energy balance and feeding.

Peroxiredoxin1: a potential obesity-related factor in the hypothalamus.

BACKGROUND: Obesity has become a global epidemic and contributes to the increasing burden of type 2 diabetes, cardiovascular disease and some cancers worldwide. However, the precise molecular mechanisms of obesity remain poorly elucidated. Recent data indicate monitoring of brain energy status especially in the hypothalamus, is crucial for energy homeostasis. Anti-oxidant defenses are suggested to play an important role in production of a well-balanced signal, which is necessary for adjusted neuronal activities. MATERIAL/METHODS: Hypothalamus proteomes of the diet-induced obesity (DIO) and diet-resistant (DR) rats were analyzed using 2-dimensional gel electrophoresis (2-DE) combined with MALDI-TOF/TOF-MS analysis. RESULTS: The 2-DE maps showed a resolution of 1280±15, 1250±10, 1260±12 protein spots in normal, DIO and DR groups, respectively. Twenty-two proteins were identified in the hypothalamus of DIO or DR rats. These proteins are involved in metabolism enzymes, antioxidant proteins, proteasome-related proteins and signaling proteins. In comparison with normal-diet group, peroxiredoxin1 (Prx1) was significantly decreased in DR group and it was increased in DIO group. The expression of Prx1 was further validated by Western blot analysis. CONCLUSIONS: The differential expression of Prx1 in DR and DIO groups indicated that the antioxidant protein may play an important role in the genesis of DR or DIO. This study provides new clues to illuminate the mechanisms involved in the progress of DIO and DR in the hypothalamus.