Stem Cell Transplantation Increases Antioxidant Effects in Diabetic Mice

Intra bone marrow-bone marrow transplantation (IBM- BMT) + thymus transplantation (TT) has been shown to reduce the incidence of graft versus host disease (GVHD) and restore donor-derived T cell function. In addition, an increase in insulin sensitivity occurred in db/db mice after IBM-BMT+TT treatment. Heme oxygenase (HO)-1 is a stress inducible enzyme which exert antioxidant, antiapoptotic, and immune-modulating properties. We examined whether IBM-BMT+TT could modulate the expression of HO-1 in the kidneys of db/db mice. Six-week-old db/db mice with blood glucose levels higher than 250 mg/dl were treated with IBM-BMT+TT. Six weeks later, the db/db mice showed decreased body weight, blood glucose levels and insulin, and increased plasma adiponectin levels. The upregulation of HO-1 was associated with significantly (p<0.05) increased levels of peNOS and pAKT, but decreased levels of iNOS in the kidneys of db/db mice. Plasma creatinine levels also decreased (p<0.05), and the expression of type IV collagen was improved. Thus IBM-BMT+TT unregulated the expression of HO-1, peNOS and pAKT, while decreasing iNOS levels in the kidney of db/db mice. This was associated with an improvement in renal function.     

L-4F treatment reduces adiposity, increases adiponectin levels, and improves insulin sensitivity in obese mice

We hypothesized that the apolipoprotein mimetic peptide L-4F, which induces arterial anti-oxidative enzymes and is vasoprotective in a rat model of diabetes, would ameliorate insulin resistance and diabetes in obese mice. L-4F (2 mg/kg/d) administered to ob/ob mice for 6 weeks limited weight gain without altering food intake, decreased visceral (P < 0.02) and subcutaneous (P < 0.045) fat content, decreased plasma IL-1beta and IL-6 levels (P < 0.05) and increased insulin sensitivity, resulting in decreased glucose (P < 0.001) and insulin (P < 0.036) levels. In addition, L-4F treatment increased aortic and bone marrow heme oxygenase (HO) activity and decreased aortic and bone marrow superoxide production (P < 0.001). L-4F treatment increased serum adiponectin levels (P < 0.037) and decreased adipogenesis in mouse bone marrow (P < 0.039) and in cultures of human bone marrow-derived mesenchymal stem cells (P < 0.022). This was manifested by reduced adiposity, improved insulin sensitivity, improved glucose tolerance, increased plasma adiponectin levels, and reduced IL-1beta and IL-6 levels in obese mice. This study highlights the existence of a temporal relationship between HO-1 and adiponectin that is positively affected by L-4F in the ob/ob mouse model of diabetes, resulting in the amelioration of the deleterious effects of diabetes.     

The L-4F mimetic peptide prevents insulin resistance through increased levels of HO-1, pAMPK, and pAKT in obese mice

We examined mechanisms by which L-4F reduces obesity and diabetes in obese (ob) diabetic mice. We hypothesized that L-4F reduces adiposity via increased pAMPK, pAKT, HO-1, and increased insulin receptor phosphorylation in ob mice. Obese and lean mice were divided into five groups: lean, lean-L-4F-treated, ob, ob-L-4F-treated, and ob-L-4F-{"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002. Food intake, insulin, glucose adipocyte stem cells, pAMPK, pAKT, CB1, and insulin receptor phosphorylation were determined. Subcutaneous (SAT) and visceral adipose tissue (VAT) were determined by MRI and hepatic lipid content by magnetic resonance spectroscopy. SAT and VAT volumes decreased in ob-L-4F-treated animals compared with control. L-4F treatment decreased hepatic lipid content and increased the numbers of small adipocytes (P < 0.05) and phosphorylation of insulin receptors. L-4F decreased CB1 in SAT and VAT and increased pAKT and pAMPK in endothelium. L-4F-mediated improvement in endothelium was prevented by {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002. Inhibition of pAKT and pAMPK by {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002 was associated with an increase in glucose levels. Upregulation of HO-1 by L-4F produced adipose remodeling and increased the number of small differentiated adipocytes. The anti-obesity effects of L-4F are manifested by a decrease in visceral fat content with reciprocal increases in adiponectin, pAMPK, pAKT, and phosphorylation of insulin receptors with improved insulin sensitivity.     

ApoA1

Insulin resistance is a risk factor in the development of type 2 diabetes and is a major cause of atherosclerosis. Reduction in heme oxygenase (HO-1) has been shown to exacerbate vascular dysfunction and insulin resistance in obese mice and involves a decrease in adiponectin levels. Adiponectin is released from mesenchymal stem cell (MSC)-derived adipocytes, its levels are decreased in type 2 diabetes. We hypothesized that the apoA1 mimetic peptide, L-4F, will target the expression of the HO-1-adiponectin axis and reverse adipocyte dysfunction both in vivo and in vitro. The administration of L-4F [2 mg/Kg/daily (i.p.) for 4-week to 8-week-old obese (ob) mice restored adipocyte function, increased adiponectin release (p &lt; 0.05) and decreased the levels of IL-1 and IL-6 (p &lt; 0.05)]. These perturbations were associated with an increase in insulin sensitivity (p &lt; 0.01 vs. untreated ob mice) and decreased glucose levels (309 + 42 vs. 201 + 8 mg/d after L-4F treatment). Treatment of both mesenchymal stem cell (MSC)-derived adipocytes with L-4F (50 μg/ml) increased adiponectin (p &lt; 0.05), decreased IL-1 and IL-6 (p &lt; 0.05) levels and increased MSC-derived adipocyte cell numbers by 50% in S phase (p &lt; 0.05). MSC-derived adipocytes treated with L-4F increased WNT10b and decreased Peg 1/Mest. Inhibition of HO activity reversed the decrease in the adipogenic response gene, Peg 1/Mest. An increase of HO-1 expression by L-4F increased insulin-receptor phosphorylation. These findings support the hypothesis that L-4F increases early adipocyte markers, HO-1-adiponectin, WNT10b and decreases Peg1/Mest, negative regulators of adipocyte differentiation.     

ApoA1: Mimetic peptide reverses adipocyte dysfunction in vivo and in vitro via an increase in heme oxygenase (HO-1) and Wnt10b

Insulin resistance is a risk factor in the development of type 2 diabetes and is a major cause of atherosclerosis. Reduction in heme oxygenase (HO-1) has been shown to exacerbate vascular dysfunction and insulin resistance in obese mice and involves a decrease in adiponectin levels. Adiponectin is released from mesenchymal stem cell (MSC)-derived adipocytes, its levels are decreased in type 2 diabetes. We hypothesized that the apoA1 mimetic peptide, L-4F, will target the expression of the HO-1-adiponectin axis and reverse adipocyte dysfunction both in vivo and in vitro. The administration of L-4F [2 mg/Kg/daily (i.p.) for 4-week to 8-week-old obese (ob) mice restored adipocyte function, increased adiponectin release (p < 0.05) and decreased the levels of IL-1 and IL-6 (p < 0.05)]. These perturbations were associated with an increase in insulin sensitivity (p < 0.01 vs. untreated ob mice) and decreased glucose levels (309 + 42 vs. 201 + 8 mg/d after L-4F treatment). Treatment of both mesenchymal stem cell (MSC)-derived adipocytes with L-4F (50 µg/ml) increased adiponectin (p < 0.05), decreased IL-1 and IL-6 (p < 0.05) levels and increased MSC-derived adipocyte cell numbers by 50% in S phase (p < 0.05). MSC-derived adipocytes treated with L-4F increased WNT10b and decreased Peg 1/Mest. Inhibition of HO activity reversed the decrease in the adipogenic response gene, Peg 1/Mest. An increase of HO-1 expression by L-4F increased insulin-receptor phosphorylation. These findings support the hypothesis that L-4F increases early adipocyte markers, HO-1-adiponectin, WNT10b and decreases Peg1/Mest, negative regulators of adipocyte differentiation.Key words: diabetes, osteoporosis, osteoblasts, BMP2, heme oxygenase     

Improved myocardial perfusion in chronic diabetic mice by the up‐regulation of pLKB1 and AMPK signaling

Previous studies related impaired myocardial microcirculation in diabetes to oxidative stress and endothelial dysfunction. Thus, this study was aimed to determine the effect of up‐regulating pAMPK‐pAKT signaling on coronary microvascular reactivity in the isolated heart of diabetic mice. We measured coronary resistance in wild‐type and streptozotocin (STZ)‐treated mice, during perfusion pressure changes. Glucose, insulin, and adiponectin levels in plasma and superoxide formation, NOx levels and heme oxygenase (HO) activity in myocardial tissue were determined. In addition, the expression of HO‐1, 3‐nitrotyrosine, pLKB1, pAMPK, pAKT, and peNOS proteins in control and diabetic hearts were measured. Coronary response to changes in perfusion pressure diverged from control in a time‐dependent manner following STZ administration. The responses observed at 28 weeks of diabetes (the maximum time examined) were mimicked by L‐NAME administration to control animals and were associated with a decrease in serum adiponectin and myocardial pLKB1, pAMPK, pAKT, and pGSK‐3 expression. Cobalt protoporphyrin treatment to induce HO‐1 expression reversed the microvascular reactivity seen in diabetes towards that of controls. Up‐regulation of HO‐1 was associated with an increase in adiponectin, pLKB1, pAKT, pAMPK, pGSK‐3, and peNOS levels and a decrease in myocardial superoxide and 3‐nitrotyrosine levels. In the present study we describe the time course of microvascular functional changes during the development of diabetes and the existence of a unique relationship between the levels of serum adiponectin, pLKB1, pAKT, and pAMPK activation in diabetic hearts. The restoration of microvascular function suggests a new therapeutic approach to even advanced cardiac microvascular derangement in diabetes. J. Cell. Biochem. 109: 1033–1044, 2010. © 2010 Wiley‐Liss, Inc.     

Stem Cell Transplantation Upregulates Sirt1 and Antioxidant Expression,Ameliorating Fatty Liver in Type 2 Diabetic Mice

Nonalcoholic fatty liver disease (NAFLD) is associated with insulin resistance, oxidative stress, and obesity. The db/db mouse model displays increased levels of insulin resistance, obesity, and an over-accumulation of hepatic triglycerides, making it an excellent model for studying NAFLD. In db/db mice, intra-bone marrow-bone marrow transplantation plus thymus transplantation (IBM-BMT+TT) improves type 2 diabetes mellitus (T2 DM) by normalizing the T-cell imbalance. We hypothesized that this approach would improve Sirt1 expression in the liver and benefit liver development.The db/db mice were treated with IBM-BMT+TT, and plasma MCP-1, IL-6, adiponection, LDL, Sirt1, and HO-1 levels were then assessed. Stem cell transplantation decreased the levels of plasma inflammatory cytokines and LDL while it increased the expression of Sirt1 and HO-1, resulting in decreased progression of fatty liver. Moreover, Sirt1 and HO-1 expression were both detected in the thymus and many HO-1-positive cells were observed in the bone marrow.This is the first report of stem cell transplantation improving the antioxidant function in the liver, thymus, and bone marrow of db/db mice by increasing the levels of Sirt1 and HO-1. This approach may prove useful in the treatment of nonalcoholic steatohepatitis and its clinical manifestations.     

High-fat diet exacerbates renal dysfunction in SHR: reversal by induction of HO-1-adiponectin axis

High-dietary fat intake is a major risk factor for development of metabolic and cardiovascular-renal dysfunction including obesity, coronary artery disease, hypertension, and chronic renal failure. We examined the effect of a high-fat diet on renal function and morphology in spontaneously hypertensive rats (SHR), a phenotype designed to mimic metabolic syndrome. High-fat diet induced increase (P < 0.05) in blood pressure, body weight, and renal lipid deposition in these rats. This increase in body weight was accompanied by elevations (P < 0.05) of blood glucose and low-density lipoprotein (LDL) levels, a decrease (P < 0.05) in adiponectin and increases (P < 0.05) in plasma monocyte chemotactic protein-1 (MCP-1) along with renal macrophage infiltration. These pathophysiological perturbations were attenuated (P < 0.05) by heme oxygenase-1 (HO-1) induction by treatment with cobalt protoporphyrin (CoPP). Further effects of CoPP included increased (P < 0.05) renal expression of adiponectin along with enhancement (P < 0.05) of pAKT, pAMPK, and p-eNOS in SHRs fed a high-fat diet. Prevention of such beneficial effects of CoPP by the concurrent administration of the heme-HO inhibitor stannous mesoporphyrin (SnMP) corroborates the role of HO system in mediating such effects. Taken together, our results demonstrate that high-fat diet induces a metabolic syndrome-like phenotype in hypertensive rats, which is amenable to rescue by increases in HO-1- and adiponectin-dependent pathways.     

Adiponectin Improves Cardiomyocyte Contractile Function in db/db Diabetic Obese Mice

Low levels of adiponectin, a fat‐derived hormone, are found to be correlated with coronary heart disease, type 2 diabetes, obesity, and insulin resistance. Conversely, high adiponectin levels are predictive of reduced coronary risk in long‐term epidemiologic studies. However, the precise role of adiponectin in cardiomyocyte function is still not clear. This study was designed to examine the role of adiponectin in cardiac contractile function in the db/db model of diabetic obesity. Mechanical properties and intracellular Ca²⁺ transients were evaluated in cardiomyocytes from lean control and db/db mice with or without adiponectin (10 µg/ml) treatment. Expression and phosphorylation of IRS‐1, Akt, c‐Jun, and c‐Jun N terminal kinase (JNK) as well as markers of endoplasmic reticulum (ER) stress were evaluated using western blotting. Cardiomyocytes from db/db mice exhibited greater cross‐sectional area, depressed peak shortening (PS), and maximal velocity of shortening/re‐lengthening as well as prolonged duration of re‐lengthening. Consistently, myocytes from db/db mice displayed a reduced electrically stimulated rise in intracellular Ca²⁺ and prolonged intracellular Ca²⁺ decay, which were abrogated by adiponectin treatment. Ratios between phosphorylated c‐Jun and c‐Jun as well as phosphorylated IRS‐1 and IRS‐1 were increased in db/db mice, the effect of which was attenuated by adiponectin. Levels of the phosphorylated ER stress makers PERK (Thr980), IRE‐1, and eIF2α were significantly elevated in db/db mice compared with lean controls, although the effect was unaffected by adiponectin. Collectively, our data suggest that adiponectin improves cardiomyocyte dysfunction in db/db diabetic obese mice through a mechanism possibly related to c‐Jun and IRS‐1.     

Adipose Overexpression of Heme Oxygenase-1 Does Not Protect against High Fat Diet-Induced Insulin Resistance in Mice

Heme oxygenase-1 (HO-1) is a stress-responsive enzyme with potent anti-oxidant and anti-inflammatory activities. Previous studies have shown that systemic induction of HO-1 by chemical inducers reduces adiposity and improves insulin sensitivity. To dissect the specific function of HO-1 in adipose tissue, we generated transgenic mice with adipose HO-1 overexpression using the adipocyte-specific aP2 promoter. The transgenic (Tg) mice exhibit similar metabolic phenotype as wild type (WT) control under chow-fed condition. High fat diet (HFD) challenge significantly increased the body weights of WT and Tg mice to a similar extent. Likewise, HFD-induced glucose intolerance and insulin resistance were not much different between WT and Tg mice. Analysis of the adipose tissue gene expression revealed that the mRNA levels of adiponectin and interleukin-10 were significantly higher in chow diet-fed Tg mice as compared to WT counterparts, whereas HFD induced downregulation of adiponectin gene expression in both Tg and WT mice to a similar level. HFD-induced proinflammatory cytokine expression in adipose tissues were comparable between WT and transgenic mice. Nevertheless, immunohistochemistry and gene expression analysis showed that the number of infiltrating macrophages with preferential expression of M2 markers was significantly higher in the adipose tissue of obese Tg mice than WT mice. Further experiment demonstrated that myeloid cells from Tg mice expressed higher level of HO-1 and exhibited greater migration response toward chemoattractant in vitro. Collectively, these data indicate that HO-1 overexpression in adipocytes does not protect against HFD-induced obesity and the development of insulin resistance in mice.     

Structural and functional analysis of pancreatic islets preserved by pioglitazone in db/db mice

To evaluate preventive effects of pioglitazone on pancreatic beta-cell damage in C57BL/KsJ db/db mice, an obese diabetic animal model, the pancreatic islets were compared morphologically between pioglitazone-treated (100 mg/kg daily po) and untreated db/db mice (n = 7 for each) after a 12-wk intervention (6-18 wk of age). The fasting blood glucose level was significantly improved by the treatment with pioglitazone (260 +/- 12 vs. 554 +/- 62 mg/dl, P < 0.05). The islet mass in the pancreas was significantly greater in pioglitazone-treated mice than in untreated mice (10.2 +/- 1.1 vs. 4.6 +/- 0.2 mg, P < 0.01). Subsequently, biochemical and physiological analyses of the beta-cell function were employed using pioglitazone-treated and untreated db/db mice (n = 6 for each) and pioglitazone-treated and untreated db/+ mice (n = 6 for each). After 2 wk of treatment (10-12 wk of age), the plasma levels of triglyceride and free fatty acid were significantly decreased, whereas the plasma adiponectin level increased significantly compared with the untreated group (65.2 +/- 18.0 vs. 18.3 +/- 1.3 microg/ml, P < 0.05). Pioglitazone significantly reduced the triglyceride content in the islets (43.3 +/- 3.6 vs. 65.6 +/- 7.6 ng/islet, P < 0.05) with improved glucose-stimulated insulin secretion. Pioglitazone showed no significant effects on the biochemical and physiological parameters in db/+ mice. The present study first demonstrated that pioglitazone prevents beta-cell damage in an early stage of the disease progression in db/db mice morphologically and physiologically. Our results suggest that pioglitazone improves glucolipotoxicity by increasing insulin sensitivity and reducing fat accumulation in the pancreatic islets.     

SGK1 抑制剂改善糖代谢紊乱的作用研究

目的:观察血清和糖皮质激素诱导的蛋白激酶1(serum and glucocorticoid-induced protein kinase1,SGK1)抑制剂对db/db小鼠糖代谢紊乱的改善作用,初步探讨该作用是否与改善脂肪组织功能紊乱有关。方法:将db/db小鼠随机分为db/db组、抑制剂组,同时设db/m组,db/db组、db/m组小鼠给予普通饲料喂养,抑制剂组小鼠给予含SGK1抑制剂的饲料喂养,干预8周。观察体重、摄食量、空腹血糖(fasting blood glucose,FBG)、糖化血红蛋白(glycosylated hemoglobin,Hb A1C),干预8周后行腹腔葡萄糖耐量试验(intraperitoneal glucose tolerance test,IPGTT)、腹腔胰岛素耐量试验(intraperitoneal insulin tolerance test,IPITT)。酶联免疫吸附测定(enzyme linked immunosorbent assay,ELISA)法检测血清空腹胰岛素(fasting insulin,FINS)水平,计算胰岛素抵抗指数(homeostasis model assessment of insulin resistance,HOMA-IR)及胰岛素敏感性指数(insulin sensitivity index,ISI)。实时定量荧光PCR(real-time PCR)法检测脂肪组织中SGK1、脂肪细胞因子m RNA表达水平。结果:干预8周后,抑制剂组体重、FBG、Hb A1C、IPGTT、IPITT均低于db/db组(P0.05),摄食量无明显差异。与db/db组相比,抑制剂组血清FINS有下降趋势,HOMA-IR明显降低,ISI明显升高(P0.05)。SGK1抑制剂干预治疗后,脂肪组织中SGK1、单核细胞趋化因子-1(monocyte chemotactic protein-1,MCP-1)、凝血酶元激活因子的抑制因子-1(plasminogen activator inhibitor 1,PAI-1)m RNA表达下降(P0.05),脂联素(adiponectin)m RNA表达无明显变化。结论:SGK1抑制剂干预治疗可一定程度改善db/db小鼠糖代谢紊乱,该作用可能部分与改善脂肪组织功能紊乱有关。     

Fructose Mediated Non-Alcoholic Fatty Liver Is Attenuated by HO-1-SIRT1 Module in Murine Hepatocytes and Mice Fed a High Fructose Diet

Background

Oxidative stress underlies the etiopathogenesis of nonalcoholic fatty liver disease (NAFLD), obesity and cardiovascular disease (CVD). Heme Oxygenase-1 (HO-1) is a potent endogenous antioxidant gene that plays a key role in decreasing oxidative stress. Sirtuin1 (SIRT1) belongs to the family of NAD-dependent de-acyetylases and is modulated by cellular redox.

Hypothesis

We hypothesize that fructose-induced obesity creates an inflammatory and oxidative environment conducive to the development of NAFLD and metabolic syndrome. The aim of this study is to determine whether HO-1 acts through SIRT1 to form a functional module within hepatocytes to attenuate steatohepatitis, hepatic fibrosis and cardiovascular dysfunction.

Methods and Results

We examined the effect of fructose, on hepatocyte lipid accumulation and fibrosis in murine hepatocytes and in mice fed a high fructose diet in the presence and absence of CoPP, an inducer of HO-1, and SnMP, an inhibitor of HO activity. Fructose increased oxidative stress markers and decreased HO-1 and SIRT1 levels in hepatocytes (p<0.05). Further fructose supplementation increased FAS, PPARα, pAMPK and triglycerides levels; CoPP negated this increase. Concurrent treatment with CoPP and SIRT1 siRNA in hepatocytes increased FAS, PPARα, pAMPK and triglycerides levels suggesting that HO-1 is upstream of SIRT1 and suppression of SIRT1 attenuates the beneficial effects of HO-1. A high fructose diet increased insulin resistance, blood pressure, markers of oxidative stress and lipogenesis along with fibrotic markers in mice (p<0.05). Increased levels of HO-1 increased SIRT1 levels and ameliorated fructose-mediated lipid accumulation and fibrosis in liver along with decreasing vascular dysfunction (p<0.05 vs. fructose). These beneficial effects of CoPP were reversed by SnMP.

Conclusion

Taken together, our study demonstrates, for the first time, that HO-1 induction attenuates fructose-induced hepatic lipid deposition, prevents the development of hepatic fibrosis and abates NAFLD-associated vascular dysfunction; effects that are mediated by activation of SIRT1 gene expression.     

吡格列酮对db/db小鼠骨骼肌蛋白酪氨酸磷酸酶1B表达的影响

目的探讨吡格列酮对db/db小鼠骨骼肌蛋白酪氨酸磷酸酶1B（protein tyrosine phosphatase 1B,PTP1B）表达水平的影响。方法将20只4周龄db/db小鼠随机分为两组（吡格列酮组和db/db对照组）,每组10只,分别给予吡格列酮10mg/kg.d和安慰剂灌胃。另设10只同周龄db/m小鼠,给予安慰剂灌胃作为非糖尿病对照（db/m对照组）。每周监测体重、血糖,4周后用蛋白印迹法检测各组小鼠骨骼肌组织中PTP1B蛋白含量。结果db/db组小鼠骨骼肌PTP1B表达显著高于db/m组,给予吡格列酮干预,血糖、胰岛素抵抗指数显著低于db/db组（P〈0.05）,骨骼肌PTP1B表达水平亦显著降低（P〈0.05）。结论吡格列酮改善胰岛素抵抗,可能与降低骨骼肌PTP1B蛋白表达有关。     

大黄素降糖及改善脂质代谢的实验研究

目的：探讨大黄素对2型糖尿病模型db/db小鼠血糖及血脂水平的影响。方法：4周龄16只db/db雄性小鼠随机分为治疗组和对照组,每组8只;治疗组经灌胃每天给予100mg/kg大黄素;对照组灌胃给予相仿体积的生理盐水,开始10天每天算进食量,每周测空腹血糖及体重1次,连续干预8周,干预前及实验结束前1周测胰岛素耐量,干预结束后于颈动脉取血测血脂水平（HDL-C、LDL-C、TG、TC）。结果：①大黄素干预不影响db/db小鼠的进食量,与对照组比较,P〉0.05;②大黄素可显著减轻db/db小鼠体重,与对照组比较,P〈0.05;③大黄素可改善db/db小鼠胰岛素敏感性,降低小鼠的空腹血糖水平,与对照组比较,P〈0.05或P〈0.01;④大黄素可降低db/db小鼠血TG、TC、LDL-C水平,P〈0.01。结论：大黄素可有效地改善db/db小鼠的糖脂紊乱状态,其降糖及改善血脂代谢机制值得进一步深入研究。     

Exercise restores coronary vascular function independent of myogenic tone or hyperglycemic status in db/db mice

Regulation of coronary function in diabetic hearts is an important component in preventing ischemic cardiac events but remains poorly studied. Exercise is recommended in the management of diabetes, but its effects on diabetic coronary function are relatively unknown. We investigated coronary artery myogenic tone and endothelial function, essential elements in maintaining vascular fluid dynamics in the myocardium. We hypothesized that exercise reduces pressure-induced myogenic constriction of coronary arteries while improving endothelial function in db/db mice, a model of type 2 diabetes. We used pressurized mouse coronary arteries isolated from hearts of control and db/db mice that were sedentary or exercised for 1 h/day on a motorized exercise-wheel system (set at 5.2 m/day, 5 days/wk). Exercise caused a approximately 10% weight loss in db/db mice and decreased whole body oxidative stress, as measured by plasma 8-isoprostane levels, but failed to improve hyperglycemia or plasma insulin levels. Exercise did not alter myogenic regulation of arterial diameter stimulated by increased transmural pressure, nor did it alter smooth muscle responses to U-46619 (a thromboxane agonist) or sodium nitroprusside (an endothelium-independent dilator). Moderate levels of exercise restored ACh-simulated, endothelium-dependent coronary artery vasodilation in db/db mice and increased expression of Mn SOD and decreased nitrotyrosine levels in hearts of db/db mice. We conclude that the vascular benefits of moderate levels of exercise were independent of changes in myogenic tone or hyperglycemic status and primarily involved increased nitric oxide bioavailability in the coronary microcirculation.     

Effects of macrophage-specific adiponectin expression on lipid metabolism in vivo

Epidemiological studies have associated low circulating levels of the adipokine adiponectin with multiple metabolic disorders, including metabolic syndrome, obesity, insulin resistance, type II diabetes, and cardiovascular disease. Recently, we reported that adiponectin selectively overexpressed in mouse macrophages can improve insulin sensitivity and protect against inflammation and atherosclerosis. To further investigate the role of adiponectin and macrophages on lipid and lipometabolism in vivo, we engineered the expression of adiponectin in mouse macrophages (Ad-TG mice) and examined effects on plasma lipoproteins and on the expression levels of genes involved in lipoprotein metabolism in tissues. Compared with the wild-type (WT) mice, Ad-TG mice exhibited significantly lower levels of plasma total cholesterol (-21%, P < 0.05) due to significantly decreased LDL (-34%, P < 0.05) and VLDL (-32%, P < 0.05) cholesterol concentrations together with a significant increase in HDL cholesterol (+41%, P < 0.05). Further studies investigating potential mechanisms responsible for the change in lipoprotein cholesterol profile revealed that adiponectin-producing macrophages altered expression of key genes in liver tissue, including apoA1, apoB, apoE, the LDL receptor, (P < 0.05), and ATP-binding cassette G1 (P < 0.01). In addition, Ad-TG mice also exhibited higher total and high-molecular-weight adipnection levels in plasma and increased expression of the anti-inflammatory cytokine IL-10 as well as a decrease in the proinflammatory cytokine IL-6 in adipose tissue. These results indicate that macrophages engineered to produce adiponectin can influence in vivo gene expression in adipose tissue in a manner that reduces inflammation and macrophage infiltration and in liver tissue in a manner that alters the circulating lipoprotein profile, resulting in a decrease in VLDL and LDL and an increase in HDL cholesterol. The data support further study addressing the use of genetically manipulated macrophages as a novel therapeutic approach for treatment of cardiometabolic disease.     

Cardioprotection of H2S by downregulating iNOS and upregulating HO-1 expression in mice with CVB3-induced myocarditis

Aims

To explore the effects and potential mechanisms of hydrogen sulfide (H₂S) in CVB3-induced mice with myocarditis.

Main methods

A total of 75 six-week-old inbred male Balb/c mice were divided randomly into four groups (N, C, P and S). Group N was the negative control. The others were inoculated intraperitoneally (i.p.) with CVB3. Subsequently, groups P and S were injected i.p. once a day with DL-Proparglygylcine (PAG) and NaHS respectively. Group C was the positive control. Inducible nitric oxide synthase (iNOS) and heme oxygenase-1(HO-1) expression on cardiac tissues were evaluated by histopathological examination, immunohistochemistry, RT-PCR and Western blot.

Key findings

The heart-weight to body-weight (HW/BW) ratio, the histologic scores and the iNOS mRNA and protein expression levels were higher, and the HO-1 mRNA and protein expression levels were lower in mice treated with PAG than those mice solely inoculated with CVB3. Mice in group S had a significant decreased in the HW/BW ratio, the histologic scores and the iNOS mRNA and protein expression levels, and had a significant increased in the HO-1 mRNA and protein expression levels compared to the mice in group C. H₂S can attenuate inflammatory cell infiltration, alleviate cardiac edema, and limit myocardial lesions.

Significance

Our data support that H₂S can inhibit iNOS overexpression and induce HO-1 expression, both of which contribute to the cardioprotection of H₂S in CVB3-induced mice myocarditis.