β3-Adrenergic receptor stimulation induces E-selectin-mediated adipose tissue inflammation

Obesity-related glomerulopathy: recent advances in inflammatory mechanisms and related treatments

Obesity-related glomerulopathy, which is an obesity-triggered kidney damage, has become a significant threat to human health. Several studies have recently highlighted the critical role of inflammation in obesity-related glomerulopathy development. Additionally, excess adipose tissue and adipocytes in patients with obesity produce various inflammatory factors that cause systemic low-grade inflammation with consequent damage to vascular endothelial cells, exacerbating glomerular injury. Therefore, we conducted a comprehensive review of obesity-related glomerulopathy and addressed the critical role of obesity-induced chronic inflammation in obesity-related glomerulopathy pathogenesis and progression, which leads to tubular damage and proteinuria, ultimately impairing renal function. The relationship between obesity and obesity-related glomerulopathy is facilitated by a network of various inflammation-associated cells (including macrophages, lymphocytes, and mast cells) and a series of inflammatory mediators (such as tumor necrosis factor α, interleukin 6, leptin, adiponectin, resistin, chemokines, adhesion molecules, and plasminogen activator inhibitor 1) and their inflammatory pathways. Furthermore, we discuss a recently discovered relationship between micronutrients and obesity-related glomerulopathy inflammation and the important role of micronutrients in the body's anti-inflammatory response. Therefore, assessing these inflammatory molecules and pathways will provide a strong theoretical basis for developing therapeutic strategies based on anti-inflammatory effects to prevent or delay the onset of kidney injury.

The GPR84 molecule is a mediator of a subpopulation of retinal microglia that promote TNF/IL-1α expression via the rho-ROCK pathway after optic nerve injury

Resident microglia are important to maintain homeostasis in the central nervous system, which includes the retina. The retinal microglia become activated in numerous pathological conditions, but the molecular signatures of these changes are poorly understood. Here, using an approach based on FACS and RNA-seq, we show that microglial gene expression patterns gradually change during RGC degeneration induced by optic nerve injury. Most importantly, we found that the microglial cells strongly expressed Tnf and Il1α, both of which are known to induce neurotoxic reactive astrocytes, and were characterized by Gpr84high -expressing cells in a particular subpopulation. Moreover, ripasudil, a Rho kinase inhibitor, significantly blunted Gpr84 expression and cytokine induction in vitro and in vivo. Finally, GPR84-deficient mice prevented RGC loss in optic nerve-injured retina. These results reveal that Rho kinase-mediated GPR84 alteration strongly contribute to microglial activation and promote neurotoxicity, suggesting that Rho-ROCK and GPR84 signaling may be potential therapeutic targets to prevent the neurotoxic microglial phenotype induced by optic nerve damage, such as occurs in traumatic optic neuropathy and glaucoma.

Tregs in visceral adipose tissue up-regulate circadian-clock expression to promote fitness and enforce a diurnal rhythm of lipolysis

Regulatory T cells (T_regs) in nonlymphoid organs provide critical brakes on inflammation and regulate tissue homeostasis. Although so-called "tissue T_regs" are phenotypically and functionally diverse, serving to optimize their performance and survival, up-regulation of pathways related to circadian rhythms is a feature they share. Yet the diurnal regulation of T_regs and its consequences are controversial and poorly understood. Here, we profiled diurnal variations in visceral adipose tissue (VAT) and splenic T_regs in the presence and absence of core-clock genes. VAT, but not splenic, T_regs up-regulated their cell-intrinsic circadian program and exhibited diurnal variations in their activation and metabolic state. BMAL1 deficiency specifically in T_regs led to constitutive activation and poor oxidative metabolism in VAT, but not splenic, T_regs. Disruption of core-clock components resulted in loss of fitness: BMAL1-deficient VAT T_regs were preferentially lost during competitive transfers and in heterozygous T_reg^Bmal1Δ females. After 16 weeks of high-fat diet feeding, VAT inflammation was increased in mice harboring BMAL1-deficient T_regs, and the remaining cells lost the transcriptomic signature of bona fide VAT T_regs. Unexpectedly, VAT T_regs suppressed adipocyte lipolysis, and BMAL1 deficiency specifically in T_regs abrogated the characteristic diurnal variation in adipose tissue lipolysis, resulting in enhanced suppression of lipolysis throughout the day. These findings argue for the importance of the cell-intrinsic clock program in optimizing VAT T_reg function and fitness.

Inhibitory Effect of Lactobacillus delbrueckii subsp. bulgaricus KSFY07 on Kappa-Carrageenan-Induced Thrombosis in Mice and the Regulation of Oxidative Damage

A mouse thrombosis model was established by kappa-carrageenan to observe the inhibitory effect of Lactobacillus delbrueckii subsp. bulgaricus KSFY07 (LDSB-KSFY07) on thrombosis and the oxidative stress response. Mouse serum, liver tissue-related indicators, and intestinal microbial composition were measured by examining the expression of microbes in mouse faeces using a biochemical kit, slice observations, and quantitative polymerase chain reaction (qPCR) experiments. The results showed that LDSB-KSFY07 effectively reduced the degree of black tail in thrombotic mice, increased activated partial thromboplastin time (APTT), and decreased thrombin time (TT), fibrinogen (FIB), and prothrombin time (PT) in thrombotic mice. LDSB-KSFY07 was also able to reduce malondialdehyde (MDA) levels and increase superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) levels in the serum and liver tissues of thrombotic mice. Pathological observations showed that LDSB-KSFY07 reduced liver tissue lesions and tail vein thrombosis. Further, experimental results showed that LDSB-KSFY07 was able to upregulate the mRNA expression of copper/zinc-SOD (Cu/Zn-SOD), manganese-SOD, and GSH-Px in the liver tissue of thrombotic mice. Moreover, LDSB-KSFY07 was also able to downregulate the mRNA expression of NF-κB p65, intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin in tail vein vascular tissue. Meanwhile, LDSB-KSFY07 could raise plasminogen activator inhibitor-1 (PAI-1) mRNA expression and reduce tissue plasminogen activator (t-PA) expression in heart and tail vein vascular tissues of thrombotic mice. A mouse faeces examination revealed that LDSB-KSFY07 could also upregulate Bacteroides, Lactobacterium, and Bifidobacterium microbial expression and downregulate Firmicutes expression in the gut. These results indicate that LDSB-KSFY07 was able to inhibit mouse thrombosis and reduce liver oxidative stress damage in thrombus mice and show that high concentrations of LDSB-KSFY07 provided a better response similar to that of the drug heparin.

Comparison of visceral fat lipolysis adaptation to high-intensity interval training in obesity-prone and obesity-resistant rats

BACKGROUND/OBJECTIVES

Visceral obesity is one of the key features of metabolic syndrome. High-intensity interval training (HIIT) could effectively reduce visceral fat, but its effects show strong heterogeneity in populations with different degrees of obesity. The mechanism may be related to the differential adaptation to training between obesity phenotypes, namely obesity prone (OP) and obesity resistant (OR). The aim of the present study was to compare adaptive changes of visceral adipose lipolysis adaptation to HIIT between OP and OR animals and further explore the upstream pathway.

METHODS

OP and OR Sprague Dawley rats were established after feeding a high-fat diet for 6 weeks; they were then divided into HIIT (H-OP and H-OR) and control (C-OP and C-OR) groups. After 12 weeks of HIIT or a sedentary lifestyle, animals were fasted for 12 h and then sacrificed for histology as well as gene and protein analysis. Visceral adipocytes were isolated without fasting for catecholamine stimulation and β3-adrenergic receptor (β3-AR) blockade in vitro to evaluate the role of upstream pathways.

RESULTS

After training, there were no differences in weight loss or food intake between OP and OR rats (P > 0.05). However, the visceral fat mass, adipocyte volume, serum triglycerides and liver lipids of OP rats decreased by more than those of OR rats (P < 0.05). Meanwhile, the cell lipolytic capacity and the increase in the expression of β3-AR were higher in the OP compared with OR groups (P < 0.05). Although training did not increase sympathetic nervous system activity (P > 0.05), the cell sensitivity to catecholamine increased significantly in the OP compared with OR groups (P < 0.05). Following blocking β3-AR, the increased sensitivity disappeared.

CONCLUSION

With HIIT, OP rats lost more visceral fat than OR rats, which was related to stronger adaptive changes in lipolysis. Increased β3-AR expression mediated this adaptation.

Lactobacillus plantarum HFY05 Attenuates Carrageenan-Induced Thrombosis in Mice by Regulating NF-κB Pathway-Associated Inflammatory Responses

In this study, a carrageenan-induced thrombus model was established in mice to observe the ability of Lactobacillus plantarum KFY05 (LP-KFY05) to inhibit thrombosis through an NF-κB-associated pathway. Biochemical analysis, microscopical observations, quantitative polymerase chain reactions (qPCR) and western blot analysis were used to examine relevant serum and tissue indexes, and the composition of intestinal microorganisms was determined by examining the abundance of microorganisms in feces. The results showed that LP-KFY05 could markedly reduce the degree of black tail in thrombotic mice; increase the activated partial thromboplastin time (APTT); and decrease the thrombin time (TT), fibrinogen (FIB) level, and prothrombin time (PT). LP-KFY05 could also reduce tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), and interleukin-1 beta (IL-1β) levels in sera and renal tissues of thrombotic mice. Hematoxylin and eosin staining showed that LP-KFY05 could alleviate renal tissue lesions and tail vein thrombosis. qPCR results showed that LP-KFY05 could down-regulate nuclear factor kappa-B (NF-κB) p65, IL-6, TNF-α, and interferon γ (IFN-γ) mRNA expression in renal tissues, as well as NF-κB p65, intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin mRNA expression in tail vein vascular tissues of thrombotic mice. Western blot analysis showed that LP-KFY05 also down-regulated NF-κB protein expression in renal and tail vein vascular tissues of thrombotic mice. Lastly, LP-KFY05 increased the abundances of Bacteroidetes, Lactobacillus, and Bifidobacterium, as well as decreased the abundance of Firmicutes. These results show that LP-KFY05 can reduce inflammation and inhibit thrombosis in thrombotic mice, and the effects of high concentrations of LP-KFY05 were most pronounced, which were similar to the effects of dipyridamole.

E-Selectin-Dependent Inflammation and Lipolysis in Adipose Tissue Exacerbate Steatosis-to-NASH Progression via S100A8/9

BACKGROUND & AIMS

Nonalcoholic steatohepatitis (NASH) is a leading cause of chronic liver disease, characterized by steatosis and hallmark liver neutrophil infiltration. NASH also is associated with adipose tissue inflammation, but the role of adipose tissue inflammation in NASH pathogenesis remains obscure. The aim of this study was to investigate the interplay between neutrophil recruitment in adipose tissue and the progression of NASH.

METHODS

A mouse model of NASH was obtained by high-fat diet (HFD) feeding plus adenovirus-Cxcl1 overexpression (HFD^+AdCxcl1). Genetic deletion of E-selectin (Sele) and treatment with an S100A9 inhibitor (Paquinimod) were investigated using this model.

RESULTS

By analyzing transcriptomic data sets of adipose tissue from NASH patients, we found that E-selectin, a key adhesion molecule for neutrophils, is the highest up-regulated gene among neutrophil recruitment-related factors in adipose tissue of NASH patients compared with those in patients with simple steatosis. A marked up-regulation of Sele in adipose tissue also was observed in HFD^+AdCxcl1 mice. The HFD^+AdCxcl1-induced NASH phenotype was ameliorated in Sele knockout mice and was accompanied by reduced lipolysis and inflammation in adipose tissue, which resulted in decreased serum free fatty acids and proinflammatory adipokines. S100A8/A9, a major proinflammatory protein secreted by neutrophils, was highly increased in adipose tissue of HFD^+AdCxcl1 mice. This increase was blunted in the Sele knockout mice. Therapeutically, treatment with the S100A9 inhibitor Paquinimod reduced lipolysis, inflammation, and adipokine production, ameliorating the NASH phenotype in mice.

CONCLUSIONS

E-selectin plays an important role in inducing neutrophil recruitment in adipose tissue, which subsequently promotes inflammation and lipolysis via the production of S100A8/A9, thereby exacerbating the steatosis-to-NASH progression. Targeting adipose tissue inflammation therefore may represent a potential novel therapy for treatment of NASH.

Oxidative Phosphorylation-Mediated E-Selectin Upregulation Is Associated With Endothelia-Monocyte Adhesion in Human Coronary Artery Endothelial Cells Treated With Sera From Patients With Kawasaki Disease

Background and aims: E-selectin is a cell adhesion molecule of the vascular endothelium that mediates leukocyte rolling in the early inflammatory responses in many diseases including Kawasaki disease (KD). Previous studies have demonstrated that the expression levels of E-selectin was significantly increased in the sera of KD patients and in endothelial cells of KD patient's autopsy. In this study, we aimed to examine E-selectin levels in endothelial cells treated with sera from KD patients and explore the underlying mechanisms. Methods: Human coronary artery endothelial cells (HCAECs) were randomly incubated with sera from either healthy children [healthy control (HC group)] or pediatric KD patients [assigned as KD with coronary artery lesion (KD-CAL+ group) and KD without coronary artery lesion (KD-CAL- group)]. E-selectin levels were determined by RT-qPCR, Western blotting, and immunofluorescence. Cell adhesion assay was performed to quantify the role of E-selectin in intercellular adhesion. High-throughput cell RNA sequencing followed by functional validation was performed to explore the underlying mechanism. Results: E-selectin levels were significantly increased in KD-CAL+ group vs. HC group and KD-CAL- group. Compared with the KD-CAL- group, endothelia-monocyte adhesion was increased in the KD-CAL+ group, while E-selectin-specific siRNA could significantly rescue it. High-throughput cell RNA sequencing analysis also found a significant difference in oxidative phosphorylation (OXPHOS) levels between KD-CAL+ group and KD-CAL- group. Functional validation results further confirmed that the OXPHOS was upregulated in the KD-CAL+ group and KD-CAL- group compared to that in the HC group, while the KD-CAL+ group exhibited a higher OXPHOS than the KD-CAL- group. We also found that the E-selectin levels and endothelia-monocyte adhesion were significantly decreased by OXPHOS inhibitor oligomycin in the KD-CAL+ group and KD-CAL- group, respectively. Conclusion: Sera from KD patients stimulate OXPHOS levels and enhance E-selectin expression in HCAECs, which may contribute to the development of CAL in KD patients.

Inflammasome signaling could be used to sense and respond to endogenous damage in brown but not white adipose tissue of a hibernating ground squirrel

Small mammalian hibernators use metabolic suppression to enhance survival during the winter. Torpor is punctuated by periods of euthermia used to clear metabolic by-products and damaged cell components. The current study was performed to determine if the innate immune system, specifically NLRP and AIM2 inflammasome signaling, may detect and respond to cell stress during hibernation. Nlrp3, Casp1, and Il1b genes were significantly upregulated in brown adipose tissue (BAT) during arousal with respect to the euthermic control, suggesting increased NLRP3 inflammasome priming. NLRP3, IL-18, and gasdermin D protein levels increased during torpor, indicating a lag between inflammasome priming and formation. AIM2 and gasdermin D levels increased in BAT during arousal, as did caspase-1 activity. Thus, non-shivering thermogenesis may generate pro-inflammatory triggers of inflammasome signaling. This study is the first to support a role for inflammasome signaling in sensing cellular perturbations at various points of the torpor-arousal cycle, in metabolically-active BAT, but not white adipose tissue (WAT).

Sleep and body temperature in TNFα knockout mice: The effects of sleep deprivation, β3-AR stimulation and exogenous TNFα

Increased production of pro-inflammatory cytokines is assumed to mediate increased sleep under inflammatory conditions, such as systemic infections or recovery from sleep loss. The role of cytokines in sleep regulation under normal conditions is less clear. In the present study, we investigated the role of endogenous tumor necrosis factor alpha (TNFα) in sleep regulation using TNFα knockout (KO) mice. Under control conditions at thermoneutral ambient temperature, total sleep time did not differ between TNFα KO and wild-type (WT) mice, but TNFα KO mice had increased rapid-eye-movement sleep (REMS), accompanied by decreased motor activity and body temperature. Exposure to 17 °C induced decreases in total sleep time similarly in both genotypes. Sleep deprivation by gentle handling elicited robust rebound increases in non-rapid-eye movement sleep (NREMS), REMS and electroencephalographic (EEG) slow-wave activity (SWA), accompanied by suppressed motor activity and decreased body temperature; there was no significant difference between the responses of WT and KO mice. Systemic injection of the beta3-adrenergic receptor (β3-AR) agonist CL-316,243 induced increases in NREMS and body temperature. The temperature response, but not the sleep effect, was attenuated in the KO animals. Systemic injection of TNFα induced increased NREMS, reduced REMS and biphasic temperature responses in both genotypes. In the KO mice, the NREMS-promoting effects of exogenously administered TNFα was decreased, while REMS suppression was enhanced, and the first, hypothermic, phase of temperature response was attenuated. Overall, TNFα KO mice did not show any deficiency in sleep regulation which suggests that the role of endogenous TNFα in sleep regulation is less pronounced than previously suggested.

Bidirectional crosstalk between neutrophils and adipocytes promotes adipose tissue inflammation

Chronic activation of the IL-1β system in adipose tissue on metabolic disorders is well demonstrated. However, a mechanism for its expression and activation in the tissue has remained unexplored. Here, we demonstrate that IL-1β transcript was enriched in neutrophils of white adipose tissue (WAT) from lean mice. Mechanistically, the interaction of neutrophils with adipocytes induced IL-1β expression via NF-κB pathway. Lipolysis of adipocytes accumulated neutrophils prior to macrophages in WAT and produced high levels of IL-1β via an inflammasome pathway. Leukotriene B₄ (LTB₄) production in WAT also contributed to neutrophil accumulation. Furthermore, an LTB₄-inflammasome axis contributed to the expression of chemotactic molecules involved in high-fat diet-induced macrophage infiltration into WAT. We have identified previously unappreciated roles for neutrophils in the development of adipose tissue inflammation: robust IL-1β production and infiltration of macrophages to initiate chronic inflammation.-Watanabe, Y., Nagai, Y., Honda, H., Okamoto, N., Yanagibashi, T., Ogasawara, M., Yamamoto, S., Imamura, R., Takasaki, I., Hara, H., Sasahara, M., Arita, M., Hida, S., Taniguchi, S., Suda, T., Takatsu, K. Bidirectional crosstalk between neutrophils and adipocytes promotes adipose tissue inflammation.

Tumor Necrosis Factor-α in Heart Failure: an Updated Review

PURPOSE OF THE REVIEW

Proinflammatory cytokines are consistently elevated in congestive heart failure. In the current review, we provide an overview on the current understanding of how tumor necrosis factor-α (TNFα), a key proinflammatory cytokine, potentiates heart failure by overwhelming the anti-inflammatory responses disrupting the homeostasis.

RECENT FINDINGS

Studies have shown co-relationship between severity of heart failure and levels of the proinflammatory cytokine TNFα and one of its secondary mediators interleukin-6 (IL-6), suggesting their potential as biomarkers. Recent efforts have focused on understanding the mechanisms of how proinflammatory cytokines contribute towards cardiac dysfunction and failure. In addition, how unchecked proinflammatory cytokines and their cross-talk with sympathetic system overrides the anti-inflammatory response underlying failure. The review offers insights on how TNFα and IL-6 contribute to cardiac dysfunction and failure. Furthermore, this provides a forum to begin the discussion on the cross-talk between sympathetic drive and proinflammatory cytokines and its determinant role in deleterious outcomes.

Metabolic changes in adipose tissues in response to β3 -adrenergic receptor activation in mice

Brown and beige adipocytes dissipate energy as heat. Thus, the activation of brown adipocytes and the emergence of beige adipocytes in white adipose tissue (WAT) are suggested to be useful for preventing and treating obesity. Although β₃ -adrenergic receptor activation is known to stimulate lipolysis and activation of brown and beige adipocytes, fat depot-dependent changes in metabolite concentrations are not fully elucidated. The current study examined the effect of treatment with CL-316,243, a β₃ -adrenergic receptor agonist, on the relative abundance of metabolites in interscapular brown adipose tissue (iBAT), inguinal WAT (ingWAT), and epididymal WAT (epiWAT). Intraperitoneal injection of CL-316,243 (1 mg/kg) for 3 consecutive days increased the relative abundance of several glycolysis-related metabolites in all examined fat depots. The cellular concentrations of metabolites involved in the citric acid cycle and of free amino acids were also increased in epiWAT by CL-316,243. CL-316,243 increased the expression levels of several enzymes and transporters related to glucose metabolism and amino acid catabolism in ingWAT and iBAT but not in epiWAT. CL-316,243 also induced the emergence of more beige adipocytes in ingWAT than in epiWAT. Furthermore, adipocytes surrounded by macrophages were detected in the epiWAT of mice given CL-316,243. The current study reveals the fat depot-dependent modulation of cellular metabolites in CL-316,243-treated mice, presumably resulting from differential regulation of cell metabolism in different cell populations.

Spermidine/spermine N1-acetyltransferase-mediated polyamine catabolism regulates beige adipocyte biogenesis

OBJECTIVE

Cold and β3-adrenergic receptor (AR) agonists activate beige adipocyte biogenesis in white adipose tissue (WAT). The two stimuli also induce expression of inflammatory cytokines in WAT. The low-grade inflammation may further promote WAT browning. However, the mechanisms to reconcile these two biological processes remain to be elucidated. In this study, we aim to investigate the roles of the rate-limiting polyamine catabolic enzyme spermidine/spermine N1-acetyltransferase (SAT1) in regulating beige adipocyte biogenesis and inflammation.

METHODS

Adipose-specific SAT1 knockout mice (SAT1-aKO) were generated by crossing adiponectin-cre to SAT1-lox/lox mice. Metabolic phenotype was investigated. Primary pre-adipocytes were isolated from inguinal WAT (iWAT) and differentiated to adipocytes for studying beige adipocyte biogenesis.

RESULT

The expression and enzymatic activity of SAT1 were up-regulated in iWAT upon cold and β3-AR stimulation. SAT1-aKO mice developed late-onset obesity on a high-fat diet with impaired cold-induced beige adipocyte biogenesis and energy expenditure. RNA-seq analysis of iWAT from cold-challenged SAT1-aKO mice revealed that, in addition to beige adipocyte biogenesis signatures, the immune response markers were highly enriched among reduced genes. In cultured adipocytes, SAT1 overexpression or pharmacological activation with N1, N11-diethylnorspermine (DENSpm) elevated oxygen consumption and increased the expression of beige adipocyte marker UCP1 and PGC-1α. DENSpm treatment of adipocytes also increased the expression of inflammatory genes. SAT1 activation enhanced hydrogen peroxide production in adipocytes. Antioxidant N-acetylcysteine abrogated the elevated UCP1 expression and reversed some inflammatory genes induced by SAT1 activation.

CONCLUSIONS

SAT1 activation plays a key role in cold and β3-AR agonist-induced beige adipocyte biogenesis and low-grade inflammation.

Proinflammatory Cytokines Mediate GPCR Dysfunction

Proinflammatory reaction by the body occurs acutely in response to injury that is considered primarily beneficial. However, sustained proinflammatory cytokines observed with chronic pathologies such as metabolic syndrome, cancer, and arthritis are detrimental and in many cases is a major cardiovascular risk factor. Proinflammatory cytokines such as interleukin-1, interleukin-6, and tumor necrosis factor α (TNFα) have long been implicated in cardiovascular risk and considered to be a major underlying cause for heart failure (HF). The failure of the anti-TNFα therapy for HF indicates our elusive understanding on the dichotomous role of proinflammatory cytokines on acutely beneficial effects versus long-term deleterious effects. Despite these well-described observations, less is known about the mechanistic underpinnings of proinflammatory cytokines especially TNFα in pathogenesis of HF. Increasing evidence suggests the existence of an active cross-talk between the TNFα receptor signaling and G-protein-coupled receptors such as β-adrenergic receptor (βAR). Given that βARs are the key regulators of cardiac function, the review will discuss the current state of understanding on the role of proinflammatory cytokine TNFα in regulating βAR function.

Exercise-induced changes in stress hormones and cell adhesion molecules in obese men

Purpose

The current study examined the relationship between exercise-induced changes in stress hormones (epinephrine, norepinephrine, and cortisol) and vascular inflammatory markers (soluble intracellular adhesion molecule-1 [sICAM-1], soluble endothelial selectin [sE-selectin], and soluble vascular adhesion molecule-1 [sVCAM-1]) in obese men over a 24-hour period following exercise at lower and higher intensity.

Patients and methods

Fifteen physically inactive, obese, college-aged men performed a single bout of cycling exercise at lower and higher intensities (lower intensity: 50% of maximal heart rate, and higher intensity: 80% of maximal heart rate) in random order. Overnight fasting blood samples were collected at baseline, immediately postexercise (IPE), 1-hour PE (1-h PE), and 24-hour PE. Changes in stress hormones and inflammatory markers were analyzed with a repeated-measures analysis of variance using Bonferroni multiple comparisons and a linear regression analysis (p<0.05).

Results

sICAM-1, sVCAM-1, epinephrine, and norepinephrine did not change over time, while sE-selectin was significantly lower at 1-h PE (10.25±1.07 ng/mL, p=0.04) than at baseline (12.22±1.39 ng/mL). Cortisol and sICAM-1 were negatively related at 1-h PE following lower-intensity exercise (r²=0.34, p=0.02), whereas cortisol and sVCAM-1 were positively related at IPE following higher-intensity exercise (r²=0.36, p=0.02).

Conclusion

Regardless of intensity, an acute bout of aerobic exercise may lower sE-selectin in sedentary obese men. Responses of cortisol are dependent on exercise intensity, and cortisol may be a key stress hormone playing a major role in regulating sICAM-1 and sVCAM-1.

Butyrate stimulates adipose lipolysis and mitochondrial oxidative phosphorylation through histone hyperacetylation-associated β3 -adrenergic receptor activation in high-fat diet-induced obese mice

NEW FINDINGS

What is the central question of this study? Butyrate can prevent diet-induced obesity through increasing energy expenditure. However, it is unclear whether β₃ -adrenergic receptors (ARβ3) mediate butyrate-induced adipose lipolysis. What is the main finding and its importance? Short-term oral administration of sodium butyrate is effective in alleviating diet-induced obesity through activation of ARβ3-mediated lipolysis in white adipose tissue. Butyrate can prevent diet-induced obesity through increasing energy expenditure. However, it is unclear whether ARβ3 mediates butyrate-induced adipose lipolysis. In this study, weaned mice were were fed control (Con) or high-fat (HF) diet for 8 weeks to establish obesity. High-fat diet-induced obese mice maintained on the HF diet were divided into two subgroups; the HFB group was gavaged with 80 mg sodium butyrate (SB) per mouse every other day for 10 days, whereas the HF group received vehicle. Chromatin immunoprecipitation assay was performed to determine the status of histone H3 lysine 9 acetylation (H3K9Ac) on the promoter of the β₃ -adrenergic receptor (ARβ3) gene in epididymal white adipose tissue. It was shown that five gavage doses of SB significantly alleviated HF diet-induced obesity and restored plasma leptin concentration to the control level. Protein contents of ARβ3 and PKA, as well as ATGL and p-HSL (Ser563), were significantly upregulated in the HFB group compared with the HF group. Mitochondrial oxidative phosphorylation was enhanced by SB treatment. Sodium butyrate significantly increased the expression of four out of 13 mitochondrial DNA-encoded genes and significantly upregulated the protein contents of peroxisome proliferator-activated receptor-γ coactivator 1α and COX4. Moreover, SB administration enhanced the expression of ARβ3 and its downstream signalling. The G protein-coupled receptor 43 and p-CREB (Ser133) were significantly stimulated by SB. In addition, an active transcription marker, H3K9Ac, was significantly enriched on the promoter of the ARβ3 gene. Our results indicate that short-term oral administration of SB is effective in alleviating diet-induced obesity through activation of the ARβ3-mediated lipolysis in the epididymal white adipose tissue.

Thermoneutrality but Not UCP1 Deficiency Suppresses Monocyte Mobilization Into Blood

RATIONALE

Ambient temperature is a risk factor for cardiovascular disease. Cold weather increases cardiovascular events, but paradoxically, cold exposure is metabolically protective because of UCP1 (uncoupling protein 1)-dependent thermogenesis.

OBJECTIVE

We sought to determine the differential effects of ambient environmental temperature challenge and UCP1 activation in relation to cardiovascular disease progression.

METHODS AND RESULTS

Using mouse models of atherosclerosis housed at 3 different ambient temperatures, we observed that cold temperature enhanced, whereas thermoneutral housing temperature inhibited atherosclerotic plaque growth, as did deficiency in UCP1. However, whereas UCP1 deficiency promoted poor glucose tolerance, thermoneutral housing enhanced glucose tolerance, and this effect held even in the context of UCP1 deficiency. In conditions of thermoneutrality, but not UCP1 deficiency, circulating monocyte counts were reduced, likely accounting for fewer monocytes entering plaques. Reductions in circulating blood monocytes were also found in a large human cohort in correlation with environmental temperature. By contrast, reduced plaque growth in mice lacking UCP1 was linked to lower cholesterol. Through application of a positron emission tomographic tracer to track CCR2⁺ cell localization and intravital 2-photon imaging of bone marrow, we associated thermoneutrality with an increased monocyte retention in bone marrow. Pharmacological activation of β3-adrenergic receptors applied to mice housed at thermoneutrality induced UCP1 in beige fat pads but failed to promote monocyte egress from the marrow.

CONCLUSIONS

Warm ambient temperature is, like UCP1 deficiency, atheroprotective, but the mechanisms of action differ. Thermoneutrality associates with reduced monocyte egress from the bone marrow in a UCP1-dependent manner in mice and likewise may also suppress blood monocyte counts in man.

The role of the brown adipose tissue in β3-adrenergic receptor activation-induced sleep, metabolic and feeding responses

Brown adipose tissue (BAT) is regulated by the sympathetic nervous system via β3-adrenergic receptors (β3-AR). Here we tested the hypothesis that pharmacological stimulation of β3-ARs leads to increased sleep in mice and if this change is BAT dependent. In wild-type (WT) animals, administration of CL-316,243, a selective β3-AR agonist, induced significant increases in non-rapid-eye movement sleep (NREMS) lasting for 4–10 h. Simultaneously, electroencephalographic slow-wave activity (SWA) was significantly decreased and body temperature was increased with a delay of 5–6 h. In uncoupling protein 1 (UCP-1) knockout mice, the middle and highest doses of the β3-AR agonist increased sleep and suppressed SWA, however, these effects were significantly attenuated and shorter-lasting as compared to WT animals. To determine if somnogenic signals arising from BAT in response to β3-AR stimulation are mediated by the sensory afferents of BAT, we tested the effects of CL-316,243 in mice with the chemical deafferentation of the intra-scapular BAT pads. Sleep responses to CL-316,243 were attenuated by ~50% in intra-BAT capsaicin-treated mice. Present findings indicate that the activation of BAT via β3-AR leads to increased sleep in mice and that this effect is dependent on the presence of UCP-1 protein and sleep responses require the intact sensory innervation of BAT.

Neutrophil Elastase Regulates Emergency Myelopoiesis Preceding Systemic Inflammation in Diet-induced Obesity

Inflammation plays a significant role in the development of obesity-related complications, but the molecular events that initiate and propagate such inflammation remain unclear. Here, we report that mice fed a high-fat diet (HFD) for as little as 1-3 days show increased differentiation of myeloid progenitors into neutrophils and monocytes but reduced B lymphocyte production in the bone marrow. Levels of neutrophil elastase (NE) and the nuclear factors CCAAT/enhancer-binding protein α (C/EBPα) and growth factor-independent 1 (GFI-1) are elevated in hematopoietic stem and progenitor cells from HFD-fed mice, but mice lacking either NE or C/EBPα are resistant to HFD-induced myelopoiesis. NE deletion increases expression of the inhibitory isoform of p30 C/EBPα, impairs the transcriptional activity of p42 C/EBPα, and reduces expression of the C/EBPα target gene GFI-1 in hematopoietic stem and progenitor cells, suggesting a mechanism by which NE regulates myelopoiesis. Furthermore, NE deletion prevents HFD-induced vascular leakage. Thus, HFD feeding rapidly activates bone marrow myelopoiesis through the NE-dependent C/EBPα-GFI-1 pathway preceding vascular damage and systemic inflammation.

Fasting rapidly increases fatty acid oxidation in white adipose tissue of young broiler chickens

Upregulating the fatty acid oxidation capacity of white adipose tissue in mice protects against diet-induced obesity, inflammation and insulin resistance. Part of this capacity results from induction of brown-like adipocytes within classical white depots, making it difficult to determine the oxidative contribution of the more abundant white adipocytes. Avian genomes lack a gene for uncoupling protein 1 and are devoid of brown adipose cells, making them a useful model in which to study white adipocyte metabolism in vivo. We recently reported that a brief (5 hour) period of fasting significantly upregulated many genes involved in mitochondrial and peroxisomal fatty acid oxidation pathways in white adipose tissue of young broiler chickens. The objective of this study was to determine if the effects on gene expression manifested in increased rates of fatty acid oxidation. Abdominal adipose tissue was collected from 21 day-old broiler chicks that were fasted for 3, 5 or 7 hours or fed ad libitum (controls). Fatty acid oxidation was determined by measuring and summing ¹⁴CO₂ production and ¹⁴C-labeled acid-soluble metabolites from the oxidation of [1-¹⁴C] palmitic acid. Fasting induced a progressive increase in complete fatty acid oxidation and citrate synthase activity relative to controls. These results confirm that fatty acid oxidation in white adipose tissue is dynamically controlled by nutritional status. Identifying the underlying mechanism may provide new therapeutic targets through which to increase fatty acid oxidation in situ and protect against the detrimental effects of excess free fatty acids on adipocyte insulin sensitivity.

Alleviation of high-fat diet-induced atherosclerosis and glucose intolerance by a novel GLP-1 fusion protein in ApoE(-/-) mice

We have previously constructed an engineered anti-diabetic fusion protein using glucagon-like peptide-1 and the globular domain of adiponectin. Herein, we evaluated the therapeutic effects of this fusion protein (GAD) on high-fat diet (HFD)-fed ApoE(-/-) mice. The lipid-lowering effect of GAD was determined in C57BL/6 mice using a lipid tolerance test. The effects of GAD on HFD-induced glucose intolerance, atherosclerosis, and hepatic steatosis were evaluated in HFD-fed ApoE(-/-) mice using glucose tolerance test, histological examinations and real-time quantitative PCR. The anti-inflammation activity of GAD was assessed in vitro on macrophages. GAD improved lipid metabolism in C57BL/6 mice. GAD treatment alleviated glucose intolerance, reduced blood lipid level, and attenuated atherosclerotic lesion in HFD-fed ApoE(-/-) mice, which was associated with a repressed macrophage infiltration in the vessel wall. GAD treatment also blocked hepatic macrophage infiltration and prevented hepatic inflammation. GAD suppressed lipopolysaccharide-triggered inflammation responses on macrophages, which can be abolished by H89, an inhibitor of protein kinase A. These findings demonstrate that GAD is able to generate a variety of metabolic benefits in HFD-fed ApoE(-/-) mice and indicate that this engineered fusion protein is a promising lead structure for anti-atherosclerosis drug discovery.

Sarcolipin knockout mice fed a high-fat diet exhibit altered indices of adipose tissue inflammation and remodeling

OBJECTIVE

To investigate indices of adipose tissue inflammation and remodeling in high-fat diet (HFD) sarcolipin-knockout (SLN(-) (/-) ) mice. SLN regulates muscle-based nonshivering thermogenesis and is up-regulated with HFD. SLN(-) (/-) mice develop greater diet-induced obesity and glucose intolerance. This is accompanied by increases in circulating catecholamines and fatty acids. Catecholamines and fatty acids play a role in the pathology of adipose tissue inflammation.

METHODS

Male mice (wild type and SLN(-) (/-) ) were fed a HFD (42% kcal from fat) for 8 weeks.

RESULTS

SLN(-) (/-) mice displayed greater obesity and glucose intolerance. This was accompanied by higher circulating epinephrine and nonesterified fatty acids. Epididymal but not inguinal subcutaneous adipose tissue from SLN(-) (/-) mice displayed higher interleukin-6, suppressor of cytokine signaling 3, interleukin-1β, and tumor necrosis factor-α mRNA expression, and this was associated with increased markers of macrophage infiltration (F4/80 expression and crown-like structures) and M1 polarization (higher CD11c expression and CD11c/MGL1). Interestingly, this occurred despite SLN(-) (/-) mice having smaller adipocytes.

CONCLUSIONS

In conditions of nutrient excess, SLN(-) (/-) mice display depot-specific increases in indices of adipose tissue inflammation and remodeling. This could be a compensatory response to reductions in muscle-based thermogenesis.

Inositol hexakisphosphate kinase-1 interacts with perilipin1 to modulate lipolysis

Lipolysis leads to the breakdown of stored triglycerides (TAG) to release free fatty acids (FFA) and glycerol which is utilized by energy expenditure pathways to generate energy. Therefore, a decrease in lipolysis augments fat accumulation in adipocytes which promotes weight gain. Conversely, if lipolysis is not complemented by energy expenditure, it leads to FFA induced insulin resistance and type-2 diabetes. Thus, lipolysis is under stringent physiological regulation, although the precise mechanism of the regulation is not known. Deletion of inositol hexakisphosphate kinase-1 (IP6K1), the major inositol pyrophosphate biosynthetic enzyme, protects mice from high fat diet (HFD) induced obesity and insulin resistance. IP6K1-KO mice are lean due to enhanced energy expenditure. Therefore, IP6K1 is a target in obesity and type-2 diabetes. However, the mechanism/s by which IP6K1 regulates adipose tissue lipid metabolism is yet to be understood. Here, we demonstrate that IP6K1-KO mice display enhanced basal lipolysis. IP6K1 modulates lipolysis via its interaction with the lipolytic regulator protein perilipin1 (PLIN1). Furthermore, phosphorylation of IP6K1 at a PKC/PKA motif modulates its interaction with PLIN1 and lipolysis. Thus, IP6K1 is a novel regulator of PLIN1 mediated lipolysis.

"Weighing" the effects of exercise and intrinsic aerobic capacity: are there beneficial effects independent of changes in weight?

It has been known for centuries that regularly performed exercise has beneficial effects on metabolic health. Owing to its central role in locomotion and the fact that it accounts for a large majority of whole-body glucose disposal and fatty acid oxidation, the effects of exercise on skeletal muscle has been a central focus in exercise physiology research. With this being said it is becoming increasingly well recognized that both adipose tissue and liver metabolism are robustly modified by exercise, especially in conditions of obesity and insulin resistance. One of the difficult questions to address is if the effects of exercise are direct or occur secondary to exercise-induced weight loss. The purpose of this review is to highlight recent work that has attempted to tease out the protective effects of exercise, or intrinsic aerobic capacity, against metabolic and inflammatory challenges as it relates to the treatment and prevention of obesity and insulin resistance. Recent studies reporting improvements in liver and adipose tissue insulin action following a single bout of exercise will also be discussed. The research highlighted in this review sheds new insight into protective, anti-inflammatory effects of exercise that occur largely independent of changes in adiposity and body weight.

Rapamycin Blocks Induction of the Thermogenic Program in White Adipose Tissue

Rapamycin extends life span in mice, yet paradoxically causes lipid dysregulation and glucose intolerance through mechanisms that remain incompletely understood. Whole-body energy balance can be influenced by beige/brite adipocytes, which are inducible by cold and other stimuli via β-adrenergic signaling in white adipose depots. Induction of beige adipocytes is considered a promising strategy to combat obesity because of their ability to metabolize glucose and lipids, dissipating the resulting energy as heat through uncoupling protein 1. Here, we report that rapamycin blocks the ability of β-adrenergic signaling to induce beige adipocytes and expression of thermogenic genes in white adipose depots. Rapamycin enhanced transcriptional negative feedback on the β3-adrenergic receptor. However, thermogenic gene expression remained impaired even when the receptor was bypassed with a cell-permeable cAMP analog, revealing the existence of a second inhibitory mechanism. Accordingly, rapamycin-treated mice are cold intolerant, failing to maintain body temperature and weight when shifted to 4°C. Adipocyte-specific deletion of the mTORC1 subunit Raptor recapitulated the block in β-adrenergic signaling. Our findings demonstrate a positive role for mTORC1 in the recruitment of beige adipocytes and suggest that inhibition of β-adrenergic signaling by rapamycin may contribute to its physiological effects.

Exercise-mediated IL-6 signaling occurs independent of inflammation and is amplified by training in mouse adipose tissue

The purpose of this investigation was to determine whether exercise-induced increases in adipose tissue interleukin 6 (IL-6) signaling occurred as part of a larger proinflammatory response to exercise and whether the induction of IL-6 signaling with acute exercise was altered in trained mice in parallel with changes in the IL-6 receptor complex. Sedentary and trained C57BL/6J mice were challenged with an acute bout of exercise. Adipose tissue and plasma were collected immediately and 4 h afterward and analyzed for changes in indices of IL-6 signaling, circulating IL-6, markers of adipose tissue inflammation, and expression/content of IL-6 receptor and glycoprotein 130 (gp130). In untrained mice, IL-6 mRNA increased immediately after exercise, and increases in indices of IL-6 signaling were increased 4 h after exercise in epididymal, but not inguinal adipose tissue. This occurred independent of increases in plasma IL-6 and alterations in markers of inflammation. When compared with untrained mice, in trained mice, acute exercise induced the expression of gp130 and IL-6 receptor alpha (IL-6Rα), and training increased the protein content of these. Acute exercise induced the expression, and training increased the protein content, of glycoprotein 130 and IL-6Rα and was associated with a more rapid increase in markers of IL-6 signaling in epididymal adipose tissue from trained compared with untrained mice. The ability of exogenous IL-6 to increase phosphorylation of STAT3 was similar between groups. Our findings demonstrate that acute exercise increases IL-6 signaling in a depot-dependent manner, likely through an autocrine/paracrine mechanism. This response is initiated more rapidly after exercise in trained mice, potentially as a result of increases in IL-6Rα and gp130.

Inducible Deletion of Protein Kinase Map4k4 in Obese Mice Improves Insulin Sensitivity in Liver and Adipose Tissues

Studies in vitro suggest that mitogen-activated protein kinase kinase kinase kinase 4 (Map4k4) attenuates insulin signaling, but confirmation in vivo is lacking since Map4k4 knockout is lethal during embryogenesis. We thus generated mice with floxed Map4k4 alleles and a tamoxifen-inducible Cre/ERT2 recombinase under the control of the ubiquitin C promoter to induce whole-body Map4k4 deletion after these animals reached maturity. Tamoxifen administration to these mice induced Map4k4 deletion in all tissues examined, causing decreased fasting blood glucose concentrations and enhanced insulin signaling to AKT in adipose tissue and liver but not in skeletal muscle. Surprisingly, however, mice generated with a conditional Map4k4 deletion in adiponectin-positive adipocytes or in albumin-positive hepatocytes displayed no detectable metabolic phenotypes. Instead, mice with Map4k4 deleted in Myf5-positive tissues, including all skeletal muscles tested, were protected from obesity-induced glucose intolerance and insulin resistance. Remarkably, these mice also showed increased insulin sensitivity in adipose tissue but not skeletal muscle, similar to the metabolic phenotypes observed in inducible whole-body knockout mice. Taken together, these results indicate that (i) Map4k4 controls a pathway in Myf5-positive cells that suppresses whole-body insulin sensitivity and (ii) Map4k4 is a potential therapeutic target for improving glucose tolerance and insulin sensitivity in type 2 diabetes.

Regulation of β-adrenergic receptor trafficking and lung microvascular endothelial cell permeability by Rab5 GTPase

Rab5 GTPase modulates the trafficking of the cell surface receptors, including G protein-coupled β-adrenergic receptors (β-ARs). Here, we have determined the role of Rab5 in regulating the internalization of β-ARs in lung microvascular endothelial cells (LMECs) and in maintaining the integrity and permeability of endothelial cell barrier. Our data demonstrate that lipopolysaccharide (LPS) treatment disrupts LMEC barrier function and reduces the cell surface expression of β-ARs. Furthermore, the activation of β-ARs, particularly β2-AR, is able to protect the LMEC permeability from LPS injury. Moreover, siRNA-mediated knockdown of Rab5 inhibits both the basal and agonist-provoked internalization of β-ARs, therefore, enhancing the cell surface expression of the receptors and receptor-mediated ERK1/2 activation. Importantly, knockdown of Rab5 not only inhibits the LPS-induced effects on β-ARs but also protects the LMEC monolayer permeability. All together, these data provide strong evidence indicating a crucial role of Rab5-mediated internalization of β-ARs in functional regulation of LMECs.

Mouse models of sepsis elicit spontaneous action potential discharge and enhance intracellular Ca2+ signaling in postganglionic sympathetic neurons

Sepsis is a severe systemic inflammatory disorder that rapidly activates the sympathetic nervous system to enhance catecholamine secretion from postganglionic sympathetic neurons and adrenal chromaffin cells. Although an increase in preganglionic drive to postganglionic sympathetic tissues has been known to contribute to this response for quite some time, only recently was it determined that sepsis also has direct effects on adrenal chromaffin cell Ca2+ signaling and epinephrine release. In the present study, we characterized the direct effects of sepsis on postganglionic sympathetic neuron function. Using the endotoxemia model of sepsis in mice, we found that almost a quarter of postganglionic neurons acquired the ability to fire spontaneous action potentials, which was absent in cells from control mice. Spontaneously firing neurons possessed significantly lower rheobases and fired a greater number of action potentials at twice the rheobase compared to neurons from control mice. Sepsis did not significantly affect voltage-gated Ca2+ currents. However, global Ca2+ signaling was enhanced in postganglionic neurons isolated from 1 to 24 h endotoxemic mice. A similar increase in the amplitude of high-K+-stimulated Ca2+ transients was observed during the cecal ligation and puncture model of sepsis. The enhanced excitability and Ca2+ signaling produced during sepsis likely amplify the effect of increased preganglionic drive on norepinephrine release from postganglionic neurons. This is important, as sympathetic neurons are integral to the anti-inflammatory autonomic reflex that is activated during sepsis.

Evidence for fatty acids mediating CL 316,243-induced reductions in blood glucose in mice

CL 316,243, a β3-adrenergic agonist, was developed as an antiobesity and diabetes drug and causes rapid decreases in blood glucose levels in mice. The mechanisms mediating this effect have not been fully elucidated; thus, the purpose of the current study was to examine the role of fatty acids and interleukin-6, reputed mediators of insulin secretion, in this process. To address this question, we used physiological and pharmacological approaches in combination with knockout mouse models. CL 316,243 treatment in male C57BL6 mice increased plasma fatty acids, glycerol, interleukin-6, and insulin and reduced blood glucose concentrations 2 h following injections. The ability of CL 316,243 to increase insulin and fatty acids and reduce glucose was preserved in interleukin-6-deficient mice. CL 316,243-induced drops in blood glucose occurred in parallel with increases in circulating fatty acids but prior to increases in plasma interleukin-6. CL 316,243-mediated increases in plasma insulin levels and reductions in blood glucose were attenuated when mice were pretreated with the lipase inhibitor nicotinic acid or in whole body adipose tissue triglyceride lipase knockout mice. Collectively, our findings demonstrate an important role for fatty acids in mediating the effects of CL 316,243 in mice. Not only do our results provide new insight into the mechanisms of action of CL 316,243, but they also hint at an unappreciated aspect of adipose tissue -pancreas cross-talk.

Proinflammatory cytokines differentially regulate adipocyte mitochondrial metabolism, oxidative stress, and dynamics

Proinflammatory cytokines differentially regulate adipocyte mitochondrial metabolism, oxidative stress, and dynamics. Macrophage infiltration of adipose tissue and the chronic low-grade production of inflammatory cytokines have been mechanistically linked to the development of insulin resistance, the forerunner of type 2 diabetes mellitus. In this study, we evaluated the chronic effects of TNFα, IL-6, and IL-1β on adipocyte mitochondrial metabolism and morphology using the 3T3-L1 model cell system. TNFα treatment of cultured adipocytes led to significant changes in mitochondrial bioenergetics, including increased proton leak, decreased ΔΨm, increased basal respiration, and decreased ATP turnover. In contrast, although IL-6 and IL-1β decreased maximal respiratory capacity, they had no effect on ΔΨm and varied effects on ATP turnover, proton leak, or basal respiration. Only TNFα treatment of 3T3-L1 cells led to an increase in oxidative stress (as measured by superoxide anion production and protein carbonylation) and C16 ceramide synthesis. Treatment of 3T3-L1 adipocytes with cytokines led to decreased mRNA expression of key transcription factors and control proteins implicated in mitochondrial biogenesis, including PGC-1α and eNOS as well as deceased expression of COX IV and Cyt C. Whereas each cytokine led to effects on expression of mitochondrial markers, TNFα exclusively led to mitochondrial fragmentation and decreased the total level of OPA1 while increasing OPA1 cleavage, without expression of levels of mitofusin 2, DRP-1, or mitofilin being affected. In summary, these results indicate that inflammatory cytokines have unique and specialized effects on adipocyte metabolism, but each leads to decreased mitochondrial function and a reprogramming of fat cell biology.

β2- and β3-adrenergic receptors drive COMT-dependent pain by increasing production of nitric oxide and cytokines

Decreased activity of catechol-O-methyltransferase (COMT), an enzyme that metabolizes catecholamines, contributes to pain in humans and animals. Previously, we demonstrated that development of COMT-dependent pain is mediated by both β2- and β3-adrenergic receptors (β2ARs and β3ARs). Here we investigated molecules downstream of β2- and β3ARs driving pain in animals with decreased COMT activity. Based on evidence linking their role in pain and synthesis downstream of β2- and β3AR stimulation, we hypothesized that nitric oxide (NO) and proinflammatory cytokines drive COMT-dependent pain. To test this, we measured plasma NO derivatives and cytokines in rats receiving the COMT inhibitor OR486 in the presence or absence of the β2AR antagonist ICI118,551+β3AR antagonist SR59320A. We also assessed whether the NO synthase inhibitor L-N(G)-nitroarginine methyl ester (L-NAME) and cytokine-neutralizing antibodies block the development of COMT-dependent pain. Results showed that animals receiving OR486 exhibited higher levels of NO derivatives, tumor necrosis factor α (TNFα), interleukin-1β (IL-1β), interleukin-6 (IL-6), and chemokine (C-C motif) ligand 2 (CCL2) in a β2- and β3AR-dependent manner. Additionally, inhibition of NO synthases and neutralization of the innate immunity cytokines TNFα, IL-1β, and IL-6 blocked the development of COMT-dependent pain. Finally, we found that NO influences TNFα, IL-1β, IL-6, and CCL2 levels, whereas TNFα and IL-6 influence NO levels. Altogether, these results demonstrate that β2- and β3ARs contribute to COMT-dependent pain, at least partly, by increasing NO and cytokines. Furthermore, they identify β2- and β3ARs, NO, and proinflammatory cytokines as potential therapeutic targets for pain patients with abnormalities in COMT physiology.

Exercise training protects against an acute inflammatory insult in mouse epididymal adipose tissue

Exercise training reduces systemic and adipose tissue inflammation. However, these beneficial effects seem to be largely tied to reductions in adipose tissue mass. The purpose of the present study was to determine if exercise training confers a protective effect against an acute inflammatory challenge. We hypothesized that the induction of inflammatory markers, such as interleukin 6 (IL-6), suppressor of cytokine signaling 3 (SOCS3), and TNF-α by the beta-3 adrenergic agonist CL 316,243 would be reduced in adipose tissue from trained mice and this would be associated with reductions in transient receptor potential cation channel 4 (TRPV4), a protein recently shown to regulate the expression of proinflammatory cytokines. Exercise training (4 wk of treadmill running, 1 h/day, 5 days/wk) increased markers of skeletal muscle mitochondrial content and the induction of PPAR-gamma coactivator 1 alpha in epididymal adipose tissue. The mRNA expression of IL-6, SOCS3, and TNFα were not different in subcutaneous and epididymal adipose tissue from sedentary and trained mice; however, the CL 316,243-mediated induction of these genes was attenuated ∼50% in epididymal adipose tissue from trained mice as were increases in plasma IL-6. The effects of training were not explained by reductions in lipolytic responsiveness, but were associated with decreases in TRPV4 protein content. These results highlight a previously unappreciated anti-inflammatory effect of exercise training on adipose tissue immunometabolism and underscores the value of assessing adipose tissue inflammation in the presence of an inflammatory insult.

Adipose tissue plasticity from WAT to BAT and in between

Adipose tissue plays an essential role in regulating energy balance through its metabolic, cellular and endocrine functions. Adipose tissue has been historically classified into anabolic white adipose tissue and catabolic brown adipose tissue. An explosion of new data, however, points to the remarkable heterogeneity among the cells types that can become adipocytes, as well as the inherent metabolic plasticity of mature cells. These data indicate that targeting cellular and metabolic plasticity of adipose tissue might provide new avenues for treatment of obesity-related diseases. This review will discuss the developmental origins of adipose tissue, the cellular complexity of adipose tissues, and the identification of progenitors that contribute to adipogenesis throughout development. We will touch upon the pathological remodeling of adipose tissue and discuss how our understanding of adipose tissue remodeling can uncover new therapeutic targets. This article is part of a Special Issue entitled: Modulation of Adipose Tissue in Health and Disease.