A substantial body of evidence indicates that reduced plasma adiponectin levels may be key in the development of insulin resistance, type 2 diabetes and the metabolic syndrome. Glucocorticoids decrease the levels of adiponectin in animals and humans. Cortisone is transformed to its active form cortisol, via 11β-hydroxysteroid dehydrogenase (HSD) type 1. This study sought to ascertain if inhibition of 11β HSD1 with a new selective inhibitor, BVT116429, affects the concentrations of circulating adiponectin with concomitant effects on glucose homeostasis in diabetic mice.
KKAy mice were treated with BVT116429 (3, 10, 30 mg/kg), rosiglitazone (5 mg/kg) or vehicle once daily for ten days. Plasma adiponectin levels rose in mice treated with BVT116429 and this was found to be both the hexameric and the high molecular weight multimeric forms of adiponectin. Seven days of treatment with the 11β HSD1-inhibitor BVT116429 decreased basal insulin levels but no changes in glucose tolerance were seen. After ten days of treatment, fasting blood glucose level was decreased by BVT116429 comparable to the effects of rosiglitazone. Another 11β HSD1 inhibitor, BVT2733, improved HbA1c but had no effect on adiponectin.
Inhibition of 11β HSD1 can be expected to be beneficial for treating the pathology of type 2 diabetes mellitus. The differences seen in adiponectin between BVT116429 and BVT2733 could be explained by different pharmacodynamics exerted by the compounds in different tissues in the body. Increases in adiponectin concentrations may be an integral component in the mechanism of action of this new11β HSD1 inhibitor and may be a useful marker of efficacy during the clinical development of 11β HSD1 inhibitor compounds.
To determine the effects of high sucrose diets on vascular reactivity. We hypothesized that similar to high fat diets (HFD), HSD feeding would lead to increased adiposity resulting in inflammation and oxidative stress-mediated impairment of vasodilation.
Male Sprague-Dawley rats were fed control chow (Chow), HSD or HFD diets for 6 weeks. The role of inflammation and oxidative stress on impaired vasodilation were assessed in isolated mesenteric arterioles.
HSD and HFD induced increased adiposity, oxidative stress and inflammation. HFD rats developed fasting hyperglycemia. Both HSD and HFD rats developed impaired glucose tolerance and hyperleptinemia. Nitric oxide (NO)-mediated vasodilation was significantly attenuated in both HSD and HFD rats but was normalized by treatment with antioxidants or anti-inflammatory drugs. Endothelial NO synthase (eNOS) protein expression was not affected by diet. Sensitivity to NO was reduced since NOS inhibition attenuated vasodilation in Chow rats but did not further impair vasodilation in HSD or HFD rats. Likewise, responsiveness to a NO donor was attenuated in both experimental groups.
Oxidative stress diminishes vasodilatory responsiveness in HSD and HFD rats through ROS-mediated scavenging of NO and decreased smooth muscle sensitivity to NO. Inflammation also plays a significant role in the impaired vasodilation.
11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) catalyses intracellular regeneration of active glucocorticoids, notably in liver and adipose tissue. 11β-HSD1 is increased selectively in adipose tissue in human obesity, a change implicated in the pathogenesis of metabolic syndrome. With high fat (HF)-feeding, adipose tissue 11β-HSD1 is down-regulated in mice, plausibly to counteract metabolic disease. Transcription of 11β-HSD1 is directly regulated by members of the CCAAT/enhancer binding protein (C/EBP) family. Here we show that while total C/EBPβ in adipose tissue is unaltered by HF diet, the ratio of the C/EBPβ isoforms liver-enriched inhibitor protein (LIP) and liver-enriched activator protein (LAP) (C/EBPβ-LIP:LAP) is increased in subcutaneous adipose. This may cause changes in 11β-HSD1 expression since genetically modified C/EBPβ(+/L) mice, with increased C/EBPβ-LIP:LAP ratio, have decreased subcutaneous adipose 11β-HSD1 mRNA levels, whereas C/EBPβΔuORF mice, with decreased C/EBPβ-LIP:LAP ratio, show increased subcutaneous adipose 11β-HSD1. C/EBPβ-LIP:LAP ratio is regulated by endoplasmic reticulum (ER) stress and mTOR signalling, both of which are altered in obesity. In 3T3-L1 adipocytes, 11β-HSD1 mRNA levels were down-regulated following induction of ER stress by tunicamycin but were up-regulated following inhibition of mTOR by rapamycin. These data point to a central role for C/EBPβ and its processing to LIP and LAP in transcriptional regulation of 11β-HSD1 in adipose tissue. Down-regulation of 11β-HSD1 by increased C/EBPβ-LIP:LAP in adipocytes may be part of a nutrient-sensing mechanism counteracting nutritional stress generated by HF diet.
Increased dietary fat intake is associated with obesity, insulin resistance, and metabolic disease. In transgenic mice, adipose tissue-specific overexpression of the glucocorticoid-amplifying enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) exacerbates high-fat (HF) diet-induced visceral obesity and diabetes, whereas 11β-HSD1 gene knockout ameliorates this, favoring accumulation of fat in nonvisceral depots. Paradoxically, in normal mice HF diet-induced obesity (DIO) is associated with marked downregulation of adipose tissue 11β-HSD1 levels. To identify the specific dietary fats that regulate adipose 11β-HSD1 and thereby impact upon metabolic disease, we either fed mice diets enriched (45% calories as fat) in saturated (stearate), monounsaturated (oleate), or polyunsaturated (safflower oil) fats ad libitum or we pair fed them a low-fat (11%) control diet for 4 wk. Adipose and liver mass and glucocorticoid receptor and 11β-HSD1 mRNA and activity levels were determined. Stearate caused weight loss and hypoinsulinemia, partly due to malabsorption, and this markedly increased plasma corticosterone levels and adipose 11β-HSD1 activity. Oleate induced pronounced weight gain and hyperinsulinemia in association with markedly low plasma corticosterone and adipose 11β-HSD1 activity. Weight gain and hyperinsulinemia was less pronounced with safflower compared with oleate despite comparable suppression of plasma corticosterone and adipose 11β-HSD1. However, with pair feeding, safflower caused a selective reduction in visceral fat mass and relative insulin sensitization without affecting plasma corticosterone or adipose 11β-HSD1. The dynamic depot-selective relationship between adipose 11β-HSD1 and fat mass strongly implicates a dominant physiological role for local tissue glucocorticoid reactivation in fat mobilization.
glucocorticoid; dietary fats
Background: Adipose hypertrophy limits fat cell oxygenation, promotes scarring, and associates with increased local glucocorticoid regeneration (higher 11βHSD1 enzyme).
Results: 11βHSD1 knock-out mice have reduced scarring and better vascularization and oxygenation in their adipose tissue.
Conclusion: Elevated adipose 11βHSD1 contributes to obesity pathogenesis by suppressing adipose angiogenesis.
Significance: Enhancement of adipose oxygenation and vascularization is a novel therapeutic modality for 11βHSD1 inhibitors.
In obesity, rapidly expanding adipose tissue becomes hypoxic, precipitating inflammation, fibrosis, and insulin resistance. Compensatory angiogenesis may prevent these events. Mice lacking the intracellular glucocorticoid-amplifying enzyme 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1−/−) have “healthier” adipose tissue distribution and resist metabolic disease with diet-induced obesity. Here we show that adipose tissues of 11βHSD1−/− mice exhibit attenuated hypoxia, induction of hypoxia-inducible factor (HIF-1α) activation of the TGF-β/Smad3/α-smooth muscle actin (α-SMA) signaling pathway, and fibrogenesis despite similar fat accretion with diet-induced obesity. Moreover, augmented 11βHSD1−/− adipose tissue angiogenesis is associated with enhanced peroxisome proliferator-activated receptor γ (PPARγ)-inducible expression of the potent angiogenic factors VEGF-A, apelin, and angiopoietin-like protein 4. Improved adipose angiogenesis and reduced fibrosis provide a novel mechanism whereby suppression of intracellular glucocorticoid regeneration promotes safer fat expansion with weight gain.
Adipose Tissue; Collagen; Extracellular Matrix Proteins; Fibroblast; Hypoxia; Angiogenesis; Fibrosis; Glucocorticoids
11β-Hydroxysteroid dehydrogenase type-1 (11β-HSD1) converts inert cortisone into active cortisol, amplifying intracellular glucocorticoid action. 11β-HSD1 deficiency improves cardiovascular risk factors in obesity but exacerbates acute inflammation. To determine the effects of 11β-HSD1 deficiency on atherosclerosis and its inflammation, atherosclerosis-prone apolipoprotein E-knockout (ApoE-KO) mice were treated with a selective 11β-HSD1 inhibitor or crossed with 11β-HSD1-KO mice to generate double knockouts (DKOs) and challenged with an atherogenic Western diet. 11β-HSD1 inhibition or deficiency attenuated atherosclerosis (74–76%) without deleterious effects on plaque structure. This occurred without affecting plasma lipids or glucose, suggesting independence from classical metabolic risk factors. KO plaques were not more inflamed and indeed had 36% less T-cell infiltration, associated with 38% reduced circulating monocyte chemoattractant protein-1 (MCP-1) and 36% lower lesional vascular cell adhesion molecule-1 (VCAM-1). Bone marrow (BM) cells are key to the atheroprotection, since transplantation of DKO BM to irradiated ApoE-KO mice reduced atherosclerosis by 51%. 11β-HSD1-null macrophages show 76% enhanced cholesterol ester export. Thus, 11β-HSD1 deficiency reduces atherosclerosis without exaggerated lesional inflammation independent of metabolic risk factors. Selective 11β-HSD1 inhibitors promise novel antiatherosclerosis effects over and above their benefits for metabolic risk factors via effects on BM cells, plausibly macrophages.—Kipari, T., Hadoke, P. W. F., Iqbal, J., Man, T. Y., Miller, E., Coutinho, A. E., Zhang, Z., Sullivan, K. M., Mitic, T., Livingstone, D. E. W., Schrecker, C., Samuel, K., White, C. I., Bouhlel, M. A., Chinetti-Gbaguidi, G., Staels, B., Andrew, R., Walker, B. R., Savill, J. S., Chapman, K. E., Seckl, J. R. 11β-hydroxysteroid dehydrogenase type 1 deficiency in bone marrow-derived cells reduces atherosclerosis.
atherogenesis; glucocorticoids; inflammation
Obesity became major health problem in the world, the objective of this work was to examine the effect of high sucrose and high fat diet to induce obesity on antioxidant defense system, biochemical changes in blood and tissue of control, non treated and treated groups by administration of Garcinia cambogia, and explore the mechanisms that link obesity with altered renal function
Rats were fed a standard control diet for 12 week (wk) or a diet containing 65% high sucrose (HSD) or 35% fat (HFD) for 8 wk and then HFD group divided into two groups for the following 4 wks. One group was given Garcinia+HFD, the second only high fat, Also the HSD divided into two groups, 1st HSD+Garcinia and 2nd HSD. Blood and renal, mesenteric, Perirenal and epididymal adipose tissues were collected for biochemical assays.
HFD and HSD groups of rats showed a significant increase in feed intake, Body weight (BW) and body mass index (BMI). Also there were significant increases in weights of mesenteric, Perirenal and epididymal adipose tissues in HFD and HSD groups.
HFD and HSD affect the kidney by increasing serum urea and creatinine levels and decreased level of nitric oxide (NO) and increased blood glucose, low density lipoproteins (LDL), triacylglycerol (TG), total cholesterol (TC) and malondialdehyde (MDA). Glucose 6-phosphate dehydrogenase (G6PD) activities were significantly decreased in HFD while there were significant increases in HSD and HSD+G groups p ≤ 0.05 compared with control. Moreover, renal catalase activities and MDA levels were significantly increased while NO level was lowered. These changes improved by Garcinia that decreased the oxidative stress biomarkers and increased NO level.
There were significant positive correlations among BMI, kidney functions (Creatinine and urea), TG and Oxidative markers (renal MDA and catalase).
Rats fed a diet with HFD or HSD showed, hypertriglyceridemia, increased LDL production, increased oxidative stress and renal alteration. Moreover, suggesting association between lipid peroxidation, obesity and nephropathy, while Garcinia ameliorated the damaging effects of the HFD or HSD and decreased feed intake, MDA level and decreased oxidative stress in renal tissues.
To determine the effects of niacin on adiponectin and markers of adipose tissue inflammation in a mouse model of obesity.
Materials and Methods
Male C57BL/6 mice were placed on a control or high-fat diet (HFD) and were maintained on such diets for the duration of the study. After 6 weeks on the control or high fat diets, vehicle or niacin treatments were initiated and maintained for 5 weeks. Identical studies were conducted concurrently in HCA2−/− (niacin receptor−/−) mice.
Niacin increased serum concentrations of the anti-inflammatory adipokine, adiponectin by 21% in HFD-fed wild-type mice, but had no effect on lean wild-type or lean or HFD-fed HCA2−/− mice. Niacin increased adiponectin gene and protein expression in the HFD-fed wild-type mice only. The increases in adiponectin serum concentrations, gene and protein expression occurred independently of changes in expression of PPARγ C/EBPα or SREBP-1c (key transcription factors known to positively regulate adiponectin gene transcription) in the adipose tissue. Further, niacin had no effect on adipose tissue expression of ERp44, Ero1-Lα, or DsbA-L (key ER chaperones involved in adiponectin production and secretion). However, niacin treatment attenuated HFD-induced increases in adipose tissue gene expression of MCP-1 and IL-1β in the wild-type HFD-fed mice. Niacin also reduced the expression of the pro-inflammatory M1 macrophage marker CD11c in HFD-fed wild-type mice.
Niacin treatment attenuates obesity-induced adipose tissue inflammation through increased adiponectin and anti-inflammatory cytokine expression and reduced pro-inflammatory cytokine expression in a niacin receptor-dependent manner.
This study evaluated the relationship between ulcerative colitis and obesity, which are both chronic diseases characterized by inflammation and increases in immune cells and pro-inflammatory cytokines.
Mice with chronic ulcerative colitis induced by 2 cycles of dextran sodium sulfate (DSS) in the first and fourth week of the experiment were fed a high-fat diet (HFD) to induce obesity by 8 weeks. The animals were divided into 4 \ groups (control, colitis, HFD and colitis + HFD).
Obesity alone did not raise histopathology scores, but the combination of obesity and colitis worsened the scores in the colon compared to colitis group. Despite the reduction in weight gain, there was increased inflammatory infiltrate in both the colon and visceral adipose tissue of colitis + HFD mice due to increased infiltration of macrophages, neutrophils and lymphocytes. Intravital microscopy of VAT microvasculature showed an increase in leukocyte adhesion and rolling and overexpression of adhesion molecules compared to other groups. Moreover, circulating lymphocytes, monocytes and neutrophils in the spleen and cecal lymph nodes were increased in the colitis + HFD group.
Our results demonstrated the relationship between ulcerative colitis and obesity as aggravating factors for each disease, with increased inflammation in the colon and adipose tissue and systemic alterations observed in the spleen, lymph nodes and bloodstream.
ulcerative colitis; obesity; high-fat diet-induced obesity and inflammation
Tissue glucocorticoid levels in the liver and adipose tissue are regulated by regeneration of inactive glucocorticoid by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) and inactivation by 5α- and 5β-reductases. A low carbohydrate diet increases hepatic 11β-HSD1 and reduces glucocorticoid metabolism during weight loss in obese humans. We hypothesized that similar variations in macronutrient proportions regulate glucocorticoid metabolism in obese rats. Male Lister Hooded rats were fed an obesity-inducing ad libitum ‘Western’ diet (37% fat, n = 36) for 22 weeks, then randomised to continue this diet (n = 12) or to switch to either a low carbohydrate (n = 12) or a moderate carbohydrate (n = 12) diet for the final 8 weeks. A parallel lean control group were fed an ad libitum control diet (10% fat, n = 12) throughout. The low and moderate carbohydrate diets decreased hepatic 11β-HSD1 mRNA compared with the Western diet (both 0.7±0.0 vs 0.9±0.1 AU; p<0.01), but did not alter 11β-HSD1 in adipose tissue. 5α-Reductase mRNA was increased on the low carbohydrate compared with the moderate carbohydrate diet. Compared with lean controls, the Western diet decreased 11β-HSD1 activity (1.6±0.1 vs 2.8±0.1 nmol/mcg protein/hr; p<0.001) and increased 5α-reductase and 5β-reductase mRNAs (1.9±0.3 vs 1.0±0.2 and 1.6±0.1 vs 1.0±0.1 AU respectively; p<0.01) in the liver, and reduced 11β-HSD1 mRNA and activity (both p<0.01) in adipose tissue. Although an obesity-inducing high fat diet in rats recapitulates the abnormal glucocorticoid metabolism associated with human obesity in liver (but not in adipose tissue), a low carbohydrate diet does not increase hepatic 11β-HSD1 in obese rats as occurs in humans.
The study objective was to determine the key early mechanisms underlying the beneficial redistribution, function, and inflammatory profile of adipose tissue in 11β-hydroxysteroid dehydrogenase type 1 knockout (11β-HSD1−/−) mice fed a high-fat (HF) diet.
RESEARCH DESIGN AND METHODS
By focusing on the earliest divergence in visceral adiposity, subcutaneous and visceral fat depots from 11β-HSD1−/− and C57Bl/6J control mice fed an HF diet for 4 weeks were used for comparative microarray analysis of gene expression, and differences were validated with real-time PCR. Key changes in metabolic signaling pathways were confirmed using Western blotting/immunoprecipitation, and fat cell size was compared with the respective chow-fed control groups. Altered adipose inflammatory cell content and function after 4 weeks (early) and 18 weeks (chronic) of HF feeding was investigated using fluorescence (and magnetic)-activated cell sorting analysis, immunohistochemistry, and in situ hybridization.
In subcutaneous fat, HF-fed 11β-HSD1−/− mice showed evidence of enhanced insulin and β-adrenergic signaling associated with accretion of smaller metabolically active adipocytes. In contrast, reduced 11β-HSD1−/− visceral fat accumulation was characterized by maintained AMP kinase activation, not insulin sensitization, and higher adipocyte interleukin-6 release. Intracellular glucocorticoid deficiency was unexpectedly associated with suppressed inflammatory signaling and lower adipocyte monocyte chemoattractant protein-1 secretion with strikingly reduced cytotoxic T-cell and macrophage infiltration, predominantly in visceral fat.
Our data define for the first time the novel and distinct depot-specific mechanisms driving healthier fat patterning and function as a result of reduced intra-adipose glucocorticoid levels.
High-fat diet (HFD)-induced adipose tissue inflammation is a critical feature of diet-induced insulin resistance (IR); however, the contribution of interleukin-1 receptor I (IL-1RI)-mediated signals to this phenotype has not been defined. We hypothesized that lack of IL-1RI may ameliorate HFD-induced IR by attenuating adipose tissue inflammation.
RESEARCH DESIGN AND METHODS
Glucose homeostasis was monitored in chow- and HFD-fed wild-type (WT) and IL-1RI−/− mice by glucose tolerance and insulin tolerance tests. Macrophage recruitment and cytokine signature of adipose tissue macrophages was evaluated. Insulin sensitivity and cytokine secretion from adipose explants was quantified. Cytokine secretion and adipocyte insulin sensitivity was measured in cocultures of WT or IL-1RI−/− macrophages with 3T3L1 adipocytes. Synergistic effects of IL-1β with tumor necrosis factor (TNF)-α on inflammation was monitored in WT and IL-1RI−/− bone-marrow macrophages and adipose explants.
Lean and obese IL-1RI−/− animals exhibited enhanced glucose homeostasis by glucose tolerance test and insulin tolerance test. M1/M2 macrophage number in adipose tissue was comparable between genotypes; however, TNF-α and IL-6 secretion was lower from IL-1RI−/− adipose tissue macrophages. IL-1RI−/− adipose exhibited enhanced insulin sensitivity, elevated pAKT, lower cytokine secretion, and attenuated induction of phosphorylated signal transducer and activator of transcription 3 and suppressor of cytokine signaling molecule 3 after HFD. Coculture of WT, but not IL-1RI−/− macrophages, with 3T3L1 adipocytes enhanced IL-6 and TNF-α secretion, reduced adiponectin secretion, and impaired adipocyte insulin sensitivity. TNF-α and IL-1β potently synergized to enhance inflammation in WT macrophages and adipose, an effect lost in the absence of IL-1RI.
Lack of IL-1RI protects against HFD-induced IR coincident with reduced local adipose tissue inflammation, despite equivalent immune cell recruitment.
Increased adipose tissue macrophages contribute to obesity-induced metabolic syndrome. Heme oxygenase-1 (HO-1) is a stress-inducible enzyme with potent anti-inflammatory and proangiogenic activities in macrophages. However, the role of macrophage HO-1 on obesity-induced adipose inflammation and metabolic syndrome remains unclear. Here we show that high-fat diet (HFD) feeding in C57BL/6J mice induced HO-1 expression in the visceral adipose tissue, particularly the stromal vascular fraction. When the irradiated C57BL/6J mice reconstituted with wild-type or HO-1+/− bone marrow were fed with HFD for over 24 weeks, the HO-1+/− chimeras were protected from HFD-induced insulin resistance and this was associated with reduced adipose macrophage infiltration and angiogenesis, suggesting that HO-1 affects myeloid cell migration toward adipose tissue during obesity. In vivo and in vitro migration assays revealed that HO-1+/− macrophages exhibited an impaired migration response. Chemoattractant-induced phosphorylation of p38 and focal adhesion kinase (FAK) declined faster in HO-1+/− macrophages. Further experiments demonstrated that carbon monoxide and bilirubin, the byproducts derived from heme degradation by HO-1, enhanced macrophage migration by increasing phosphorylation of p38 and FAK, respectively. These data disclose a novel role of hematopoietic cell HO-1 in promoting adipose macrophage infiltration and the development of insulin resistance during obesity.
Inhibitor of differentiation-3 (Id3) has been implicated in promoting angiogenesis, a key determinant of high fat diet (HFD)-induced visceral adiposity. Yet the role of Id3 in high fat diet (HFD)-induced angiogenesis and visceral adipose expansion is unknown.
Methods and Results
Id3−/− mice demonstrated a significant attenuation of HFD-induced visceral fat depot expansion compared to WT littermate controls. Importantly, unlike other Id proteins, loss of Id3 did not affect adipose depot size in young mice fed chow diet or differentiation of adipocytes in vitro or in vivo. Contrast enhanced ultrasound revealed a significant attenuation of visceral fat microvascular blood volume in HFD-fed mice null for Id3 compared to WT controls. HFD induced Id3 and VEGFA expression in the visceral stromal vascular fraction (SVF) and Id3−/− mice had significantly lower levels of VEGFA protein in visceral adipose tissue compared to WT. Furthermore, HFD-induced VEGFA expression in visceral adipose tissue was completely abolished by loss of Id3. Consistent with this effect, Id3 abolished E12-mediated repression of VEGFA promoter activity.
Results identify Id3 as an important regulator of HFD-induced visceral adipose VEGFA expression, microvascular blood volume, and depot expansion. Inhibition of Id3 may have potential as a therapeutic strategy to limit visceral adiposity.
obesity; visceral adiposity; helix-loop-helix factors; Id3; VEGFA
Intracellular glucocorticoid (GC) receptor (GR) function determines tissue sensitivity to GCs and strongly affects the development of type 2 diabetes and obesity. 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) mediates intracellular steroid exposure to mouse liver GR by prereceptor reactivation of GCs and is crucially dependent on hexose-6-phosphate dehydrogenase (H6PDH)-generating NADPH system. Pharmacological inhibition of 11β-HSD1 improves insulin intolerance and obesity. Here, we evaluated the potential beneficial effects of 11β-HSD1 inhibitor carbenoxolone (CBX) in diet-induced obese (DIO) and insulin-resistant mice by examining the possible influence of CBX on the expression of GR, 11β-HSD1, and H6PDH in vivo and in vitro in hepatocytes. Treatment of DIO mice with CBX markedly reduced hepatic GR mRNA levels and reduced weight gain, hyperglycemia, and insulin resistance. The reduction of hepatic GR gene expression was accompanied by CBX-induced inhibition of both 11β-HSD1 and H6PDH activity and mRNA in the liver. Moreover, CBX treatment also suppressed the expression of both phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase enzyme (G6Pase) mRNA and improved hepatic [1, 2-3H] deoxy-d-glucose uptake in DIO mice. In addition, the treatment of primary cultures of hepatocytes with increasing concentrations of CBX led to a dose-dependent downregulation of GR mRNA levels, which correlated with the suppression of both 11β-HSD1 and H6PDH activity and their gene expression. Addition of CBX to primary hepatocytes also resulted in suppression of both PEPCK and G6Pase mRNA levels. These findings suggest that CBX exerts some of its beneficial effects, at least in part, by inhibiting hepatic GR and H6PDH expression.
Recent trials show salicylates improve glycemic control in type 2 diabetes, but the mechanism is poorly understood. Expression of the glucocorticoid-generating enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) in adipose tissue is increased in vitro by proinflammatory cytokines and upregulated in obesity. 11β-HSD1 inhibition enhances insulin sensitivity. We hypothesized that salicylates downregulate 11β-HSD1 expression, contributing to their metabolic efficacy. We treated diet-induced obese (DIO) 11β-HSD1–deficient mice and C57Bl/6 mice with sodium salicylate for 4 weeks. Glucose tolerance was assessed in vivo. Tissue transcript levels were assessed by quantitative PCR and enzyme activity by incubation with 3H-steroid. Two weeks’ administration of salsalate was also investigated in a randomized double-blind placebo-controlled crossover study in 16 men, with measurement of liver 11β-HSD1 activity in vivo and adipose tissue 11β-HSD1 transcript levels ex vivo. In C57Bl/6 DIO mice, salicylate improved glucose tolerance and downregulated 11β-HSD1 mRNA and activity selectively in visceral adipose. DIO 11β-HSD1–deficient mice were resistant to these metabolic effects of salicylate. In men, salsalate reduced 11β-HSD1 expression in subcutaneous adipose, and in vitro salicylate treatment reduced adipocyte 11β-HSD1 expression and induced adiponectin expression only in the presence of 11β-HSD1 substrate. Reduced intra-adipose glucocorticoid regeneration by 11β-HSD1 is a novel mechanism that contributes to the metabolic efficacy of salicylates.
Rats fed high fat (HFD) or high sucrose (HSD) diets develop increased adiposity as well as impaired vasodilatory responsiveness stemming from oxidative stress. Moreover, HFD rats become hypertensive compared to either control (Chow) or HSD fed rats, suggesting elevated vascular tone. We hypothesized that rats with increased adiposity and oxidative stress demonstrate augmented pressure-induced vasoconstriction (i.e. myogenic tone) that could account for the hypertensive state.
Male Sprague-Dawley rats were fed Chow, HFD or HSD for 6 weeks. The effects of oxidative stress and endogenous nitric oxide on myogenic responses were examined in small mesenteric arteries by exposing the arteries to incremental intraluminal pressure steps in the presence of antioxidants or an inhibitor of nitric oxide synthase, LNNA (100 μM).
Contrary to the hypothesis, rats fed either HSD or HFD had significantly impaired myogenic responses despite similar vascular morphology and passive diameter responses to increasing pressures. Vascular smooth muscle (VSM) calcium levels were normal in HFD arteries suggesting that diminished calcium sensitivity was responsible for the impaired myogenic response. In contrast, VSM calcium levels were reduced in HSD arteries but were increased with pre-exposure of arteries to the antioxidants tiron (10 mM) and catalase (1200 U/mL), also resulting in enhanced myogenic tone. These findings show that oxidative stress impairs myogenic tone in arteries from HSD rats by decreasing VSM calcium. Similarly, VSM calcium responses were increased in arteries from HFD rats following treatment with tiron and catalase, but this did not result in improved myogenic tone. Nitric oxide is involved in the impaired myogenic response in HFD, but not HSD, rats since inhibition with LNNA resulted in maximal myogenic responses at lower intraluminal pressures and VSM calcium levels, further implicating reduced calcium sensitivity in the impaired response.
The impaired myogenic responses observed in isolated arteries from HSD and HFD rats are attributed to changes in VSM calcium signaling.
Myogenic tone; Calcium; Oxidative stress; Nitric oxide; Mesenteric arteries
11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) catalyzes the conversion of inactive glucocorticoids to active glucocorticoids and plays an important role in the development of obesity and metabolic syndrome. 11β-HSD1 activity is lower in liver and higher in omental adipose tissue of obese rodent models like obese zucker rats, Ob/Ob and db/db mice. Here, we report the 11β-HSD1 activity in liver and adipose tissue of lean and obese rats of WNIN/Ob strain, a new genetic rat model of obesity. 11β-HSD1 activity in liver, omental and subcutaneous adipose tissues of 3 month-old male WNIN/Ob lean and obese rats was assayed. As observed in other rodent models, 11β-HSD1 activity was lower in liver and higher in omental adipose tissue. In contrast to other rodent obese models, WNIN/Ob obese rats had elevated 11β-HSD1 activity in subcutaneous adipose tissue, which is in line with the observation in human obesity. Here, we conclude that dysregulation of 11β-HSD1 in WNIN/Ob obese rat model is identical to human obesity, which makes it an excellent model for studying the effect of 11β-HSD1 inhibitors in ameliorating obesity and metabolic syndrome.
3-guanidinopropionic acid derivatives reduce body weight in obese, diabetic mice. We have assessed whether one of these analogues, the aminoguanidine carboxylate BVT.12777, opens KATP channels in rat insulinoma cells, by the same mechanism as leptin.
BVT.12777 hyperpolarized CRI-G1 rat insulinoma cells by activation of KATP channels. In contrast, BVT.12777 did not activate heterologously expressed pancreatic β-cell KATP subunits directly. Although BVT.12777 stimulated phosphorylation of MAPK and STAT3, there was no effect on enzymes downstream of PI3K. Activation of KATP in CRI-G1 cells by BVT.12777 was not dependent on MAPK or PI3K activity. Confocal imaging showed that BVT.12777 induced a re-organization of cellular actin. Furthermore, the activation of KATP by BVT.12777 in CRI-G1 cells was demonstrated to be dependent on actin cytoskeletal dynamics, similar to that observed for leptin.
This study shows that BVT.12777, like leptin, activates KATP channels in insulinoma cells. Unlike leptin, BVT.12777 activates KATP channels in a PI3K-independent manner, but, like leptin, channel activation is dependent on actin cytoskeleton remodelling. Thus, BVT.12777 appears to act as a leptin mimetic, at least with respect to KATP channel activation, and may bypass up-stream signalling components of the leptin pathway.
High-fat diet (HFD) is associated with adipose inflammation, which contributes to key components of metabolic abnormalities. The expanded adipose tissue mass associated with obesity is the result of hyperplasia and hypertrophy of adipocytes. In this study, we investigated the effects of long-term HFD on adipocyte progenitor cell (APC) population and adipose-specific gene profiles in both white and brown adipose, and the role of perivascular adipose in the alteration of vascular function in response to HFD.
Male C57BL/6 mice were fed a standard normal diet (ND) or HFD for about 8 months. Glucose metabolism was assessed by an intraperitoneal glucose tolerance test. APC population and adipose-related gene profile were evaluated, and vascular function was measured in the presence or absence of perivascular adipose. Adiponectin and AMPK activity were also investigated.
HFD induced insulin resistance and glucose intolerance, and resulted in a decrease in APC population in brown, but not in white adipose tissue, when compared with animals fed a ND, with differential alterations of white and brown adipocyte-specific gene expression in brown and white adipose. Additionally, HFD led to altered vascular function in arteries in the presence of perivascular adipose tissue, which is associated with increased superoxide production. Adiponectin and AMPK activity were significantly decreased in response to long-term HFD.
These findings suggest that long-term high-fat intake differentially alters adipocyte progenitor population and adipose-related gene expression in adipose tissue, and adiponectin-AMPK signaling might be involved. In addition, HFD induces changes in perivascular adipose-mediated vascular function.
insulin resistance; obesity; adipocyte progenitor cells; vascular function; AMPK
Obesity-induced diabetes is associated with chronic inflammation and is considered a risk factor for neurodegeneration. We tested the hypothesis that an AMP-activated protein kinase activator, resveratrol (RES), which is known to exert potent anti-inflammatory effects, would attenuate peripheral and central inflammation and improve memory deficit in mice fed a high-fat diet (HFD). C57BL/6J mice were fed an HFD or an HFD supplemented with RES for 20 weeks. Metabolic parameters in serum were evaluated, and Western blot analysis and immunohistochemistry in peripheral organs and brain were completed. We used the Morris water maze test to study the role of RES on memory function in HFD-treated mice. RES treatment reduced hepatic steatosis, macrophage infiltration, and insulin resistance in HFD-fed mice. In the hippocampus of HFD-fed mice, the protein levels of tumor necrosis factor-α and Iba-1 expression were reduced by RES treatment. Choline acetyltransferase was increased, and the phosphorylation of tau was decreased in the hippocampus of HFD-fed mice upon RES treatment. In particular, we found that RES significantly improved memory deficit in HFD-fed mice. These findings indicate that RES reverses obesity-related peripheral and central inflammation and metabolic derangements and improves memory deficit in HFD-fed diabetic mice.
11beta-hydroxysteroid dehydrogenase type 1 (11β-HSD1) regulates local glucocorticoid action in tissues by catalysing conversion of inactive glucocorticoids to active glucocorticoids. 11β-HSD1 inhibition ameliorates obesity and associated co-morbidities. Here, we tested the effect of 11β-HSD inhibitor, carbenoxolone (CBX) on obesity and associated comorbidities in obese rats of WNIN/Ob strain, a new animal model for genetic obesity.
Subcutaneous injection of CBX (50 mg/kg body weight) or volume-matched vehicle was given once daily for four weeks to three month-old WNIN/Ob lean and obese rats (n = 6 for each phenotype and for each treatment). Body composition, plasma lipids and hormones were assayed. Hepatic steatosis, adipose tissue morphology, inflammation and fibrosis were also studied. Insulin resistance and glucose intolerance were determined along with tissue glycogen content. Gene expressions were determined in liver and adipose tissue. CBX significantly inhibited 11β-HSD1 activity in liver and adipose tissue of WNIN/Ob lean and obese rats. CBX significantly decreased body fat percentage, hypertriglyceridemia, hypercholesterolemia, insulin resistance in obese rats. CBX ameliorated hepatic steatosis, adipocyte hypertrophy, adipose tissue inflammation and fibrosis in obese rats. Tissue glycogen content was significantly decreased by CBX in liver and adipose tissue of obese rats. Severe fat loss and glucose- intolerance were observed in lean rats after CBX treatment.
We conclude that 11β-HSD1 inhibition by CBX decreases obesity and associated co-morbidities in WNIN/Ob obese rats. Our study supports the hypothesis that inhibition of 11β-HSD1 is a key strategy to treat metabolic syndrome. Severe fat loss and glucose -intolerance by CBX treatment in lean rats suggest that chronic 11β-HSD1 inhibition may lead to insulin resistance in normal conditions.
The present study examined the anti-obesity effect and mechanism of action of Korean white ginseng extracts (KGE) using high-fat diet (HFD)-induced obese mice. Mice were fed a low-fat diet (LFD), HFD or HFD containing 0.8 and 1.6% (w/w) KGE diet (HFD + 0.8KGE and HFD + 1.6KGE) for 8 weeks. We also examined the effects of KGE on plasma triglyceride (TG) elevation in mice administrated with oral lipid emulsion. Body weight gain and white adipose tissue (WAT) weight were significantly decreased in the HFD + 1.6KGE group, compared with the HFD group. The plasma TG levels were also significantly reduced in both HFD + 0.8KGE and HFD + 1.6KGE groups, while leptin levels were significantly decreased in only the HFD + 1.6KGE group, compared with the HFD group. The HFD + 1.6KGE group showed significantly lower mRNA levels of lipogenesis-related genes, including peroxisome proliferator-activated receptorγ2 (PPARγ2), sterol regulatory element binding protein-1c (SREBP-1c), lipoprotein lipase (LPL), fatty acid synthase (FAS) and diacylglycerol acyltransferase 1 (DGAT1), compared with the HFD group. In addition, a dose of 1000 mg/kg KGE inhibited the elevation of plasma TG levels compared with mice given the lipid emulsion alone. These results suggest that the anti-obesity effects of KGE may be elicited by regulating expression of lipogenesis-related genes in WAT and by delaying intestinal fat absorption.
Korean white ginseng; High-fat diet-induced obese mice; Lipogenesis-related genes; Intestinal fat absorption
To identify the role of triglyceride-rich lipoproteins (TGRLs) and apoE, a major apolipoprotein in TGRLs, in adipose tissue inflammation with high-fat diet (HFD)–induced obesity.
Male apoE−/− and C57BL/6J wild-type (WT) mice fed HFD for 12 weeks were assessed for metabolic and inflammatory parameters. ApoE−/− and WT mice were orally gavaged with [3H]palmitic acid to examine the role of apoE in fat delivery to adipose tissue. VLDL from obese apoE−/− mice were intravenously injected into lean WT or apoE−/− mice to test potential contribution of TGRLs-derived fat delivery to inflammation in adipose tissue and the role of apoE.
ApoE−/− mice gained less body weight, and had less fat mass and lower triglyceride levels in skeletal muscle than WT. ApoE−/− mice on HFD had better insulin sensitivity than WT even when comparing body weight–matched mice. Compared to WT mice, apoE−/− mice on HFD had lower levels of inflammatory cytokines/chemokines and CD11c in adipose tissue, and lower levels of inflammatory markers in skeletal muscle. At 6 hours after oral gavage with [3H]palmitic acid, incorporation of [3H]palmitic acid into adipose tissue and skeletal muscle was lower in apoE−/− mice. After repeated daily injection for 3 days, VLDL from obese apoE−/− mice induced inflammation in adipose tissue of recipient WT but not apoE−/− mice.
In HFD-induced obesity, apoE plays an important role in inflammation in adipose tissue and skeletal muscle, likely by mediating TGRL-derived fat delivery to these tissues.
adipose tissue; inflammation; insulin resistance; obesity; lipoproteins; apolipoprotein E
The cortisol-regenerating enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) amplifies glucocorticoid levels in liver and adipose tissue. 11β-HSD1 inhibitors are being developed to treat type 2 diabetes. In obesity, 11β-HSD1 is increased in adipose tissue but decreased in liver. The benefits of pharmacological inhibition may be reduced if hepatic 11β-HSD1 is similarly decreased in obese patients with type 2 diabetes. To examine this, we quantified in vivo whole-body, splanchnic, and hepatic 11β-HSD1 activity in obese type 2 diabetic subjects.
RESEARCH DESIGN AND METHODS
Ten obese men with type 2 diabetes and seven normal-weight control subjects were infused with 9,11,12,12-[2H]4cortisol (40%) and cortisol (60%) at 1.74 mg/h. Adrenal cortisol secretion was suppressed with dexamethasone. Samples were obtained from the hepatic vein and an arterialized hand vein at steady state and after oral administration of cortisone (5 mg) to estimate whole-body and liver 11β-HSD1 activity using tracer dilution.
In obese type 2 diabetic subjects, the appearance rate of 9,12,12-[2H]3cortisol in arterialized blood was increased (35 ± 2 vs. 29 ± 1 nmol/min, P < 0.05), splanchnic 9,12,12-[2H]3cortisol production was not reduced (29 ± 6 vs. 29 ± 6 nmol/min), and cortisol appearance in the hepatic vein after oral cortisone was unchanged.
Whole-body 11β-HSD1 activity is increased in obese men with type 2 diabetes, whereas liver 11β-HSD1 activity is sustained, unlike in euglycemic obesity. This supports the concept that inhibitors of 11β-HSD1 are likely to be most effective in obese type 2 diabetic subjects.