8-Prenyl daidzein and 8-prenyl genistein from germinated soybean modulate inflammatory response in activated macrophages.

Soy isoflavones have been shown to have anti-inflammatory properties; however, the anti-inflammatory effects of isoflavone metabolites produced during soybean germination remain unclear. We found that the daidzein and genistein derivatives, 8-prenyl daidzein (8-PD) and 8-prenyl genistein (8-PG), demonstrated a more potent effect than daidzein and genistein on repressing inflammatory responses in macrophages. Although IkB protein levels were unaltered, 8-PD and 8-PG repressed nuclear factor kappa B (NF-κB) activation, which was associated with reduced ERK1/2, JNK, and p38 MAPK activation and suppressed mitogen- and stress-activated kinase 1 phosphorylation. Inflammatory responses induced by the medium containing hypertrophic adipocyte secretions were successfully suppressed by 8-PD and 8-PG treatment. In the ex vivo study, 8-PD and 8-PG significantly inhibited proinflammatory C-C motif chemokine ligand 2 (CCL2) secretion from the adipose tissues of mice fed a long-term high-fat diet. The data suggest that 8-PD and 8-PG could regulate macrophage activation under obesity conditions.

7-Ketocholesterol-Induced Micro-RNA-107-5p Increases Number and Activity of Osteoclasts by Targeting MKP1.

Osteoclasts (OCs), which are responsible for bone resorption, play a critical role in cholesterol-induced bone loss and recent studies have suggested that various micro-RNAs (miRs) contribute to modulating OCs. We hypothesized that 7-ketocholesterol (7-KC), a metabolite responsible for cholesterol-induced bone loss, induces miR-107-5p, which affects OCs. Overexpression and knock-down of miR-107-5p were performed using miR-107-5p mimic and anti-miR-107-5p, respectively. The effects of miR-107-5p on OCs were analyzed by tartrate-resistant alkaline phosphatase staining, qPCR, and Western blot. MiR-107-5p was upregulated after 7-KC exposure in receptor activator of nuclear factor kappa-Β ligand-stimulated OCs. Furthermore, miR-107-5p upregulation was also observed in tibiae from an atherogenic diet-fed mice compared with mice fed with a normal diet. MiR-107-5p overexpression enhanced the area and number of OCs, whereas inhibiting the endogenous expression of miR-107-5p generated by 7-KC had the opposite effect. Among the possible candidates, mitogen-activated protein kinase phosphatase-1, a stress-responsive dual-specificity phosphatase that inactivates mitogen-activated protein kinase (MKP1), has been proven to be a target gene of miR-107-5p, as demonstrated by the direct interaction between miR-107-5p and the 3'-untranslated region of MKP1. Collectively, our findings demonstrate that 7-KC-induced miR-107-5p promotes differentiation and function of OCs by downregulating MKP1.

Cellular source of hypothalamic macrophage accumulation in diet-induced obesity.

BACKGROUND: Obese mice on a high-fat diet (HFD) display signs of inflammation in the hypothalamic arcuate nucleus (ARC), a critical area for controlling systemic energy metabolism. This has been suggested as a key mechanism of obesity-associated hypothalamic dysfunction. We reported earlier that bone marrow-derived macrophages accumulate in the ARC to sustain hypothalamic inflammation upon chronic exposure to an HFD. However, the mechanism underlying hypothalamic macrophage accumulation has remained unclear. METHODS: We investigated whether circulating monocytes or myeloid precursors contribute to hypothalamic macrophage expansion during chronic HFD feeding. To trace circulating myeloid cells, we generated mice that express green fluorescent protein (GFP) in their lysozyme M-expressing myeloid cells (LysMGFP mice). We conducted parabiosis and bone marrow transplantation experiments using these animals. Mice received an HFD for 12 or 30 weeks and were then sacrificed to analyze LysMGFP cells in the hypothalamus. Hypothalamic vascular permeability in the HFD-fed obese mice was also tested by examining the extravascular leakage of Evans blue and fluorescence-labeled albumin. The timing of LysMGFP cell entry to the hypothalamus during development was also evaluated. RESULTS: Our parabiosis and bone marrow transplantation experiments revealed a significant infiltration of circulating LysMGFP cells into the liver, skeletal muscle, choroid plexus, and leptomeninges but not in the hypothalamic ARC during chronic HFD feeding, despite increased hypothalamic vascular permeability. These results suggested that the recruitment of circulating monocytes is not a major mechanism for maintaining and expanding the hypothalamic macrophage population in diet-induced obesity. We demonstrated instead that LysMGFP cells infiltrate the hypothalamus during its development. LysMGFP cells appeared in the hypothalamic area from the late embryonic period. This cellular pool suddenly increased immediately after birth, peaked at the postnatal second week, and adopted an adult pattern of distribution after weaning. CONCLUSIONS: Bone marrow-derived macrophages mostly populate the hypothalamus in early postnatal life and may maintain their pool without significant recruitment of circulating monocytes throughout life, even under conditions of chronic HFD feeding.

α-Cedrene protects rodents from high-fat diet-induced adiposity via adenylyl cyclase 3.

OBJECTIVE: The increasing global prevalence of obesity and its associated disorders points to an urgent need for the development of novel and effective strategies for the prevention of weight gain. Here, we investigated the potential of α-cedrene, a volatile sesquiterpene compound derived from cedarwood oil, in regulation of obesity and delineated the mechanisms involved. METHODS: For the prevention of obesity, C57BL/6 N mice were fed a high-fat diet (HFD) and were orally administered either with vehicle or α-cedrene for 8 weeks. For the therapy of obesity, obese Sprague Dawley rats, induced by a HFD for 8 weeks, were orally treated either with vehicle or α-cedrene for 12 weeks. To determine whether the action of α-cedrene was Adcy3 dependent, Adcy3 heterozygous null mice (Adcy3+/-) and wild-type controls were fed either HFD or α-cedrene supplemented HFD for 17 weeks. RESULTS: Oral α-cedrene administration prevented or reversed HFD-induced obesity and abnormal metabolic aberrations in rodents, without affecting their food intake. Downregulation of Adcy3 expression by small interfering RNA abrogated the beneficial effects of α-cedrene on the oxygen consumption rate and intracellular lipid accumulation in 3T3-L1 adipocytes. Similarly, in Adcy3+/- mice, the α-cedrene-driven suppression of body weight gain observed in wild-type mice was substantially (~50%) attenuated. Expression of thermogenic and lipid oxidation genes was increased in adipose tissues of α-cedrene-treated mice, with concomitant downregulation of adipogenic gene expression. These beneficial molecular changes elicited by α-cedrene were blunted in adipose tissues of Adcy3+/- mice. CONCLUSIONS: Our results highlight the potential of α-cedrene for antiobesity interventions and suggest that the antiobesity effect of α-cedrene is mediated by Adcy3 in adipose tissues.

Fibroblast growth factor 21 deficiency aggravates obesity-induced hypothalamic inflammation and impairs thermogenic response.

OBJECTIVE AND DESIGN: Hypothalamic inflammation is closely associated with metabolic dysregulation. Fibroblast growth factor 21 (FGF21) is known to be an important metabolic regulator with anti-inflammatory properties. In this study, we investigated the effects of FGF21 deficiency on obesity-induced hypothalamic inflammation and thermogenic responses. MATERIALS AND METHODS: FGF21-deficient mice and/or wild-type (WT) mice were fed a high-fat diet (HFD) for 12 weeks. RESULTS: FGF21-deficient mice fed an HFD showed increased levels of inflammatory cytokines compared with WT obese control, and this was accompanied by upregulation of gliosis markers in the hypothalamus. Expression of heat-shock protein 72, a marker of neuronal damage, was increased in the FGF21-deficient obese mice, and the expression of hypothalamic neuronal markers involved in anti-thermogenic or thermogenic responses was altered. Moreover, the protein level of uncoupling protein 1 and other thermogenic genes were markedly reduced in the brown adipose tissue of the FGF21-deficient obese mice. CONCLUSIONS: These findings suggest that FGF21 deficiency aggravates obesity-induced hypothalamic inflammation and neuronal injury, leading to alterations in hypothalamic neural circuits accompanied by a reduction of the thermogenic response.

The hepatokine FGF21 is crucial for peroxisome proliferator-activated receptor-α agonist-induced amelioration of metabolic disorders in obese mice.

Obesity causes excess fat accumulation in white adipose tissues (WAT) and also in other insulin-responsive organs such as the skeletal muscle, increasing the risk for insulin resistance, which can lead to obesity-related metabolic disorders. Peroxisome proliferator-activated receptor-α (PPARα) is a master regulator of fatty acid oxidation whose activator is known to improve hyperlipidemia. However, the molecular mechanisms underlying PPARα activator-mediated reduction in adiposity and improvement of metabolic disorders are largely unknown. In this study we investigated the effects of PPARα agonist (fenofibrate) on glucose metabolism dysfunction in obese mice. Fenofibrate treatment reduced adiposity and attenuated obesity-induced dysfunctions of glucose metabolism in obese mice fed a high-fat diet. However, fenofibrate treatment did not improve glucose metabolism in lipodystrophic A-Zip/F1 mice, suggesting that adipose tissue is important for the fenofibrate-mediated amelioration of glucose metabolism, although skeletal muscle actions could not be completely excluded. Moreover, we investigated the role of the hepatokine fibroblast growth factor 21 (FGF21), which regulates energy metabolism in adipose tissue. In WAT of WT mice, but not of FGF21-deficient mice, fenofibrate enhanced the expression of genes related to brown adipocyte functions, such as Ucp1, Pgc1a, and Cpt1b Fenofibrate increased energy expenditure and attenuated obesity, whole body insulin resistance, and adipocyte dysfunctions in WAT in high-fat-diet-fed WT mice but not in FGF21-deficient mice. These findings indicate that FGF21 is crucial for the fenofibrate-mediated improvement of whole body glucose metabolism in obese mice via the amelioration of WAT dysfunctions.

10-oxo-12(Z)-octadecenoic acid, a linoleic acid metabolite produced by gut lactic acid bacteria, enhances energy metabolism by activation of TRPV1.

Gut microbiota can regulate the host energy metabolism; however, the underlying mechanisms that could involve gut microbiota-derived compounds remain to be understood. Therefore, in this study, we investigated the effects of KetoA [10-oxo-12(Z)-octadecenoic acid]-a linoleic acid metabolite produced by gut lactic acid bacteria-on whole-body energy metabolism and found that dietary intake of KetoA could enhance energy expenditure in mice, thereby protecting mice from diet-induced obesity. By using Ca2+ imaging and whole-cell patch-clamp methods, KetoA was noted to potently activate transient receptor potential vanilloid 1 (TRPV1) and enhance noradrenalin turnover in adipose tissues. In addition, KetoA up-regulated genes that are related to brown adipocyte functions, including uncoupling protein 1 (UCP1) in white adipose tissue (WAT), which was later diminished in the presence of a ß-adrenoreceptor blocker. By using obese and diabetic model KK-Ay mice, we further show that KetoA intake ameliorated obesity-associated metabolic disorders. In the absence of any observed KetoA-induced antiobesity effect or UCP1 up-regulation in TRPV1-deficient mice, we prove that the antiobesity effect of KetoA was caused by TRPV1 activation-mediated browning in WAT. KetoA produced in the gut could therefore be involved in the regulation of host energy metabolism.-Kim, M., Furuzono, T., Yamakuni, K., Li, Y., Kim, Y.-I., Takahashi, H., Ohue-Kitano, R., Jheng, H.-F., Takahashi, N., Kano, Y., Yu, R., Kishino, S., Ogawa, J., Uchida, K., Yamazaki, J., Tominaga, M., Kawada, T., Goto, T. 10-oxo-12(Z)-octadecenoic acid, a linoleic acid metabolite produced by gut lactic acid bacteria, enhances energy metabolism by activation of TRPV1.

Over-expression of PPARα in obese mice adipose tissue improves insulin sensitivity.

Peroxisome proliferator-activated receptor α (PPARα) is important in the regulation of lipid metabolism and expressed at high levels in the liver. Although PPARα is also expressed in adipose tissue, little is known about the relationship between its activation and the regulation of glucose metabolism. In this study, we developed adipose tissue specific PPARα over-expression (OE) mice. Metabolomics and insulin tolerance tests showed that OE induces branched-chain amino acid (BCAA) profile and improvement of insulin sensitivity. Furthermore, LC-MS and PCR analyses revealed that OE changes free fatty acid (FFA) profile and reduces obesity-induced inflammation. These findings suggested that PPARα activation in adipose tissue contributes to the improvement of glucose metabolism disorders via the enhancement of BCAA and FFA metabolism.

Monoterpene phenolic compound thymol promotes browning of 3T3-L1 adipocytes.

PURPOSE: Appearance of brown-like adipocytes within white adipose tissue depots (browning) is associated with improved metabolic phenotypes, and thus a wide variety of dietary agents that contribute to browning of white adipocytes are being studied. The aim of this study was to assess the browning effect of thymol, a dietary monoterpene phenolic compound, in 3T3-L1 white adipocytes. METHODS: Thymol-induced fat browning was investigated by determining expression levels of brown fat-specific genes and proteins by real-time RT-PCR and immunoblot analysis, respectively. Moreover, the molecular mechanism underlying the fat-browning effect of thymol was investigated by determining expression levels of key players responsible for browning in the presence of kinase inhibitors. RESULTS: Thymol promoted mitochondrial biogenesis and enhanced expression of a core set of brown fat-specific markers as well as increased protein levels of PPARγ, PPARδ, pAMPK, pACC, HSL, PLIN, CPT1, ACO, PGC-1α, and UCP1, suggesting its possible role in browning of white adipocytes, augmentation of lipolysis, fat oxidation, and thermogenesis, and reduction of lipogenesis. Increased expression of UCP1 and other brown fat-specific markers by thymol was tightly coordinated with activation of ß3-AR as well as AMPK, PKA, and p38 MAPK. CONCLUSION: Our findings suggest that 3T3-L1 is a potential cell model for screening browning agents. Thymol plays multiple modulatory roles in the form of inducing the brown-like phenotype as well as enhancing lipid metabolism. Thus, thymol may be explored as a potentially promising food additive for prevention of obesity.

Proinflammatory cytokine interleukin-1ß suppresses cold-induced thermogenesis in adipocytes.

In this study, we investigated the effects of interleukin-1ß (IL-1ß), a typical proinflammatory cytokine on the ß-adrenoreceptor-stimulated induction of uncoupling protein 1 (UCP1) expression in adipocytes. IL-1ß mRNA expression levels were upregulated in white adipose tissues of obese mice and in RAW264.7 macrophages under conditions designed to mimic obese adipose tissue. Isoproterenol-stimulated induction of UCP1 mRNA expression was significantly inhibited in C3H10T1/2 adipocytes by conditioned medium from lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages in comparison with control conditioned medium. This inhibition was significantly attenuated in the presence of recombinant IL-1 receptor antagonist and IL-1ß antibody, suggesting that activated macrophage-derived IL-1ß is an important cytokine for inhibition of ß-adrenoreceptor-stimulated UCP1 induction in adipocytes. IL-1ß suppressed isoproterenol-induced UCP1 mRNA expression in C3H10T1/2 adipocytes, and this effect was partially but significantly abrogated by inhibition of extracellular signal-regulated kinase (ERK). IL-1ß also suppressed the isoproterenol-induced activation of the UCP1 promoter and transcription factors binding to the cAMP response element. Moreover, intraperitoneal administration of IL-1ß suppressed cold-induced UCP1 expression in adipose tissues. These findings suggest that IL-1ß upregulated in obese adipose tissues suppresses ß-adrenoreceptor-stimulated induction of UCP1 expression through ERK activation in adipocytes.

IL-7 receptor deletion ameliorates diet-induced obesity and insulin resistance in mice.

AIM/HYPOTHESIS: Obesity-induced inflammation plays an important role in the development of insulin resistance and type 2 diabetes. Recent studies have demonstrated that adiposity can be improved by ablating certain inflammatory signalling pathways. Although the IL-7 receptor (IL-7R) is mostly known as a key regulator of T lymphocyte development and homeostasis, its role in obesity and metabolic diseases is unknown. Because IL-7 is markedly increased in the serum of obese individuals and IL-7R (also known as IL7R) is overexpressed in white adipose tissue (WAT) in obesity, we studied the metabolic consequences of genetic Il-7r ablation in mice. METHODS: Age-matched Il-7r-deficient (Il-7r KO) and wild-type (WT) littermates were fed a standard chow or high-fat diet (HFD) for 14 weeks. Their serum metabolic variables were measured. The expression of genes and proteins related to insulin resistance and inflammation was evaluated in WAT. RESULTS: We demonstrated that Il-7r KO mice exhibited significantly reduced body weight gain and visceral adiposity compared with WT controls on both chow and HFD. The expression of signalling molecules involved in adipogenesis was reduced in the WAT of Il-7r KO mice. We also found that Il-7r KO mice had significantly enhanced glucose homeostasis and insulin sensitivity. Consistent with an improved metabolic phenotype, proinflammatory cytokine production and macrophage infiltration was attenuated in the WAT of Il-7r KO mice. CONCLUSIONS/INTERPRETATION: The IL-7R plays an important role in the induction of HFD-induced adipogenesis and insulin resistance in mice.

ß-Caryophyllene potently inhibits solid tumor growth and lymph node metastasis of B16F10 melanoma cells in high-fat diet-induced obese C57BL/6N mice.

We reported previously that high-fat diet (HFD) feeding stimulated solid tumor growth and lymph node (LN) metastasis in C57BL/6N mice injected with B16F10 melanoma cells. ß-caryophyllene (BCP) is a natural bicyclic sesquiterpene found in many essential oils and has been shown to exert anti-inflammatory activities. To examine whether BCP inhibits HFD-induced melanoma progression, 4-weeks old, male C57BL/6N mice were fed a control diet (CD, 10 kcal% fat) or HFD (60 kcal% fat + 0, 0.15 or 0.3% BCP) for the entire experimental period. After 16 weeks of feeding, B16F10s were subcutaneously injected into mice. Three weeks later, tumors were resected, and mice were killed 2 weeks post-resection. Although HFD feeding increased body weight gain, fasting blood glucose levels, solid tumor growth, LN metastasis, tumor cell proliferation, angiogenesis and lymphangiogenesis, it decreased apoptotic cells, all of which were suppressed by dietary BCP. HFD feeding increased the number of lipid vacuoles and F4/80+ macrophage (MΦ) and macrophage mannose receptor (MMR)+ M2-MΦs in tumor tissues and adipose tissues surrounding the LN, which was suppressed by BCP. HFD feeding increased the levels of CCL19 and CCL21 in the LN and the expression of CCR7 in the tumor; these changes were blocked by dietary BCP. In vitro culture results revealed that BCP inhibited lipid accumulation in 3T3-L1 preadipocytes; monocyte migration and monocyte chemoattractant protein-1 secretion by B16F10s, adipocytes and M2-MΦs; angiogenesis and lymphangiogenesis. The suppression of adipocyte and M2-cell accumulation and the inhibition of CCL19/21-CCR7 axis may be a part of mechanisms for the BCP suppression of HFD-stimulated melanoma progression.

Carbon monoxide reverses adipose tissue inflammation and insulin resistance upon loss of ovarian function.

We hypothesized that carbon monoxide (CO) might suppress chronic inflammation, which led to metabolic disturbances. Ovariectomy (OVX) was performed in mice to mimic chronic inflammation secondary to loss of ovarian function. OVX increased fat mass and the infiltration of highly inflammatory CD11c cells into adipose tissue (AT), resulting in a disturbance of glucose metabolism. Treatment of CO attenuated these; CO decreased recruitment of CD11c-expressing cells in AT and reduced expression of CD11c in bone marrow-derived macrophages, protecting them from M1 polarization. Upregulated cGMP and decreased reactive oxygen species were responsible for the inhibitory activity of CO on CD11c expression; knockdown of soluble guanylate cyclase or heme oxygenase-1 using small interfering RNAs reduced this inhibition substantially. Improved OVX-induced insulin resistance (IR) by CO was highly associated with its activity to attenuate AT inflammation. Our results suggest a therapeutic value of CO to treat postmenopausal IR by reducing AT inflammation.

Arginase inhibition ameliorates adipose tissue inflammation in mice with diet-induced obesity.

This study examined whether oral administration of an arginase inhibitor regulates adipose tissue macrophage infiltration and inflammation in mice with high fat diet (HFD)-induced obesity. Male C57BL/6 mice (n = 30) were randomly assigned to control (CTL, n = 10), HFD only (n = 10), and HFD with arginase inhibitor N(ω)-hydroxy-nor-l-arginine (HFD with nor-NOHA, n = 10) groups. Plasma and mRNA levels of cytokines in epididymal adipose tissues (EAT), macrophage infiltration into EAT, and macrophage phenotype polarization were measured in the animals after 12 weeks. Additionally, the effects of nor-NOHA on adipose tissue macrophage infiltration and mRNA expression of cytokines were measured in co-cultured 3T3-L1 adipocytes and RAW 264.7 macrophages. Macrophage infiltration into the adipocytes was significantly suppressed by nor-NOHA treatment in adipocyte/macrophage co-culture system and mice with HFD-induced obesity. Pro-inflammatory cytokines, including monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6), were significantly downregulated, and the anti-inflammatory cytokine IL-10 was significantly upregulated in nor-NOHA-treated co-cultured cells. In the mice with HFD-induced obesity, plasma and mRNA levels of MCP-1 significantly reduced after supplementation with nor-NOHA. In addition, oral supplement of nor-NOHA modified M1/M2 phenotype ratio in the EAT. Oral supplementation of an arginase inhibitor, nor-NOHA, altered M1/M2 macrophage phenotype and macrophage infiltration into HFD-induced obese adipose tissue, thereby improved adipose tissue inflammatory response. These results may indicate that arginase inhibition ameliorates obesity-induced adipose tissue inflammation.

10-oxo-12(Z)-octadecenoic acid, a linoleic acid metabolite produced by gut lactic acid bacteria, potently activates PPARγ and stimulates adipogenesis.

Our previous study has shown that gut lactic acid bacteria generate various kinds of fatty acids from polyunsaturated fatty acids such as linoleic acid (LA). In this study, we investigated the effects of LA and LA-derived fatty acids on the activation of peroxisome proliferator-activated receptors (PPARs) which regulate whole-body energy metabolism. None of the fatty acids activated PPARδ, whereas almost all activated PPARα in luciferase assays. Two fatty acids potently activated PPARγ, a master regulator of adipocyte differentiation, with 10-oxo-12(Z)-octadecenoic acid (KetoA) having the most potency. In 3T3-L1 cells, KetoA induced adipocyte differentiation via the activation of PPARγ, and increased adiponectin production and insulin-stimulated glucose uptake. These findings suggest that fatty acids, including KetoA, generated in gut by lactic acid bacteria may be involved in the regulation of host energy metabolism.

Antioxidative Activity of Platinum Nanocolloid and Its Protective Effect Against Chemical-Induced Hepatic Cellular Damage.

Oxidative stress, a major cause of cellular injuries, is closely associated with a variety of chronic diseases such as cancer, liver diseases, degenerative brain disease and aging. In this study, we investigated antioxidant properties of platinum nanocolloid (PNC) against various oxidative stress conditions in vitro/in vivo by treating PNC on liver cell or tissue. Antioxidant activities of the PNC were determined by measuring quenching capacity on reactive oxygen species and its protective action against hydrogen peroxide or CCl4-induced oxidative cellular damage in HepG2 cell or liver tissue of mice. In vitro study, PNC markedly suppressed the production H2O2, ·OH, α,α-diphenyl-ß-picrylhydrazyl radical and nitric oxide in a dose-dependent manner. PNC also inhibited hydrogen peroxide-induced oxidative cellular damage in HepG2 hepatocytes. In vivo study with mice, PNC reduced hepatic lipid peroxidation and CCl4 induced toxicity. Our results support that platinum nanocolloid has antioxidant activities and protects hepatic cellular oxidative damage. Thus platinum nanocolloid may have a potential to be used as an antioxidant supplement.

Involvement of mast cells in adipose tissue fibrosis.

Recently, fibrosis is observed in obese adipose tissue; however, the pathogenesis remains to be clarified. Obese adipose tissue is characterized by chronic inflammation with massive accumulation of immune cells including mast cells. The objective of the present study was to clarify the relationship between fibrosis and mast cells in obese adipose tissue, as well as to determine the origin of infiltrating mast cells. We observed the enhancement of mast cell accumulation and fibrosis in adipose tissue of severely obese diabetic db/db mice. Furthermore, adipose tissue-conditioned medium (ATCM) from severely obese diabetic db/db mice significantly enhanced collagen 5 mRNA expression in NIH-3T3 fibroblasts, and this enhancement was suppressed by the addition of an anti-mast cell protease 6 (MCP-6) antibody. An in vitro study showed that only collagen V among various types of collagen inhibited preadipocyte differentiation. Moreover, we found that ATCM from the nonobese but not obese stages of db/db mice significantly enhanced the migration of bone marrow-derived mast cells (BMMCs). These findings suggest that immature mast cells that infiltrate into adipose tissue at the nonobese stage gradually mature with the progression of obesity and diabetes and that MCP-6 secreted from mature mast cells induces collagen V expression in obese adipose tissue, which may contribute to the process of adipose tissue fibrosis. Induction of collagen V by MCP-6 might accelerate insulin resistance via the suppression of preadipocyte differentiation.

Induction of heme oxygenase-1 with hemin reduces obesity-induced adipose tissue inflammation via adipose macrophage phenotype switching.

Adipose macrophages with the anti-inflammatory M2 phenotype protect against obesity-induced inflammation and insulin resistance. Heme oxygenase-1 (HO-1), which elicits antioxidant and anti-inflammatory activity, modulates macrophage phenotypes and thus is implicated in various inflammatory diseases. Here, we demonstrate that the HO-1 inducer, hemin, protects against obesity-induced adipose inflammation by inducing macrophages to switch to the M2 phenotype. HO-1 induction by hemin reduced the production of proinflammatory cytokines (TNF-α and IL-6) from cocultured adipocytes and macrophages by inhibiting the activation of inflammatory signaling molecules (JNK and NF-κB) in both cell types. Hemin enhanced transcript levels of M2 macrophage marker genes (IL-4, Mrc1, and Clec10a) in the cocultures, while reducing transcripts of M1 macrophage markers (CD274 and TNF-α). The protective effects of hemin on adipose inflammation and macrophage phenotype switching were confirmed in mice fed a high-fat diet, and these were associated with PPARγ upregulation and STAT6 activation. These findings suggest that induction of HO-1 with hemin protects against obesity-induced adipose inflammation through M2 macrophage phenotype switching, which is induced by the PPARγ and STAT6 pathway. HO-1 inducers such as hemin may be useful for preventing obesity-induced adipose inflammation.

Quercetin protects against obesity-induced skeletal muscle inflammation and atrophy.

Skeletal muscle inflammation and atrophy are closely associated with metabolic impairment such as insulin resistance. Quercetin, a natural polyphenol flavonoid, is known to elicit anti-inflammatory and antioxidant activities. In this study, we investigated its effect on obesity-induced skeletal muscle inflammation and atrophy in mice. Male C57BL/6 mice were fed a regular diet, a high-fat diet (HFD), and an HFD supplemented with quercetin for nine weeks. Quercetin reduced levels of inflammatory cytokines and macrophage accumulation in the skeletal muscle of the HFD-fed obese mice. It also reduced transcript and protein levels of the specific atrophic factors, Atrogin-1 and MuRF1, in the skeletal muscle of the HFD-fed obese mice, and protected against the reduction of muscle mass and muscle fiber size. In vitro, quercetin markedly diminished transcript levels of inflammatory receptors and activation of their signaling molecules (ERK, p38 MAPK, and NF-κB) in cocultured myotubes/macrophages, and this was accompanied by reduced expression of the atrophic factors. Together, these findings suggest that quercetin reduces obesity-induced skeletal muscle atrophy by inhibiting inflammatory receptors and their signaling pathway. Quercetin may be useful for preventing obesity-induced muscle inflammation and sarcopenia.

Berteroin present in cruciferous vegetables exerts potent anti-inflammatory properties in murine macrophages and mouse skin.

Berteroin (5-methylthiopentyl isothiocyanate) is a sulforaphane analog present in cruciferous vegetables, including Chinese cabbage, rucola salad leaves, and mustard oil. We examined whether berteroin exerts anti-inflammatory activities using lipopolysaccharide (LPS)-stimulated Raw 264.7 macrophages and 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced mouse skin inflammation models. Berteroin decreased LPS-induced release of inflammatory mediators and pro-inflammatory cytokines in Raw 264.7 macrophages. Berteroin inhibited LPS-induced degradation of inhibitor of κBα (IκBα) and nuclear factor-κB p65 translocation to the nucleus and DNA binding activity. Furthermore, berteroin suppressed degradation of IL-1 receptor-associated kinase and phosphorylation of transforming growth factor ß activated kinase-1. Berteroin also inhibited LPS-induced phosphorylation of p38 MAPK, ERK1/2, and AKT. In the mouse ear, berteroin effectively suppressed TPA-induced edema formation and down-regulated iNOS and COX-2 expression as well as phosphorylation of AKT and ERK1/2. These results demonstrate that berteroin exhibits potent anti-inflammatory properties and suggest that berteroin can be developed as a skin anti-inflammatory agent.