Hong Min Kim

Blockade of CCL2/CCR2 signalling ameliorates diabetic nephropathy in db/db mice

BACKGROUND CCL2/C-C chemokine receptor 2 (CCR2) signalling is suggested to play a significant role in various kidney diseases including diabetic nephropathy. We investigated the renoprotective effect of a CCR2 antagonist, RS102895, on the development of diabetic nephropathy in a type 2 diabetic mouse model. METHODS Six-week-old diabetic db/db and non-diabetic db/m mice were fed either normal chow or chow mixed with 2 mg/kg/day of RS102895 for 9 weeks. We investigated the effects of CCR2 antagonism on blood glucose, blood pressure, albuminuria and the structure and ultrastructure of the kidney. RESULTS Diabetes-induced albuminuria was significantly improved after CCR2 antagonist treatment, and glucose intolerance was improved in the RS102895-treated diabetic mice. RS102895 did not affect blood pressure, body weight or kidney weight. Mesangial expansion, glomerular basement membrane thickening and increased desmin staining in the diabetic kidney were significantly improved after RS102895 treatment. The up-regulation of vascular endothelial growth factor mRNA expression and the down-regulation of nephrin mRNA expression were markedly improved in the kidneys of RS102895-treated diabetic mice. Increased renal CD68 and arginase II and urinary malondialdehyde in diabetes were effectively attenuated by RS102895 treatment. CONCLUSION Blockade of CCL2/CCR2 signalling by RS102895 ameliorates diabetic nephropathy not only by improving blood glucose levels but also by preventing CCL2/CCR2 signalling from altering renal nephrin and VEGF expressions through blocking macrophage infiltration, inflammation and oxidative stress in type 2 diabetic mice.

Peroxisome proliferator-activated receptor δ agonist attenuates hepatic steatosis by anti-inflammatory mechanism

Although peroxisome proliferator receptor (PPAR)-α and PPAR-γ agonist have been developed as chemical tools to uncover biological roles for the PPARs such as lipid and carbohydrate metabolism, PPAR-δ has not been fully investigated. In this study, we examined the effects of the PPAR-δ agonist GW0742 on fatty liver changes and inflammatory markers. We investigated the effects of PPAR-δ agonist GW0742 on fatty liver changes in OLETF rats. Intrahepatic triglyceride contents and expression of inflammatory cytokines such as tumor necrosis factor-α (TNF-α) and monocyte chemo-attractant protein-1 (MCP-1) and also, PPAR-γ coactivator (PGC)-1α gene were evaluated in liver tissues of OLETF rats and HepG2 cells after GW0742 treatment. The level of TNF-α and MCP-1 was also examined in supernatant of Raw264. 7 cell culture. To address the effects of GW0742 on insulin signaling, we performed in vitro study with AML12 mouse hepatocytes. Rats treated with GW0742 (10 mg/kg/day) from 26 to 36 weeks showed improvement in fatty infiltration of the liver. In liver tissues, mRNA expressions of TNF-α, MCP-1, and PGC-1α were significantly decreased in diabetic rats treated with GW0742 compared to diabetic control rats. We also observed that GW0742 had inhibitory effects on palmitic acid-induced fatty accumulation and inflammatory markers in HepG2 and Raw264.7 cells. The expression level of Akt and IRS-1 was significantly increased by treatment with GW0742. The PPAR-δ agonist may attenuate hepatic fat accumulation through anti-inflammatory mechanism, reducing hepatic PGC-1α gene expression, and improvement of insulin signaling.

Prospective study of serum uric acid levels and incident metabolic syndrome in a Korean rural cohort

OBJECTIVE Recent studies have demonstrated an association between serum uric acid (SUA) levels and metabolic syndrome (MetS). However, paucity of available data regarding the cause and effect relationship between SUA and MetS in healthy adults is still a big challenge which remains to be studied. Therefore, we investigated whether SUA predicts new onset of MetS in a population-based cohort study. METHODS The study included 1590 adults (661 men and 929 women) aged 40-70 years without MetS at baseline (2005-2008) and subjects were prospectively followed for 2.6 years. To evaluate the relationship between SUA and MetS, we divided the aforementioned subjects into quintiles (SUA-I to SUA-V) from the lowest to the highest values of SUA. SUA was measured by the enzymatic colorimetric method. We used category-free net reclassification improvement (NRI) and integrated discrimination improvement (IDI) to characterize the performance of predicted model. RESULTS During a mean of 2.6 years of follow-up, 261(16.4%) adults developed MetS. MetS variables were significantly related to the baseline SUA level. Waist circumference (WC), blood pressure (BP), and serum triglyceride (TG) were significantly higher in the highest quintile of SUA compared to the lowest SUA quintile in men and women. After adjustment for age, total cholesterol and low-density lipoprotein cholesterol (LDL-C) in men and women, subjects in the fifth quintiles of SUA showed significantly higher ORs for incident MetS. The association between hyperuricemia and new onset of MetS were consistently stronger in women than men. Additionally, among women, we found an improvement in the area under the ROC curve in the models that added SUA to core components of MetS. CONCLUSION Our study suggests that SUA is significantly correlated with future risk of WC, BP, TG and may predicted as a risk factor for developing MetS. SUA may have a clinical role in predicting new-onset metabolic syndrome among women. Large prospective study is needed to reveal the clinical significance of SUA in metabolic disease.

Enhancement of Tumor-Specific T Cell–Mediated Immunity in Dendritic Cell–Based Vaccines by Mycobacterium tuberculosis Heat Shock Protein X

Despite the potential for stimulation of robust antitumor immunity by dendritic cells (DCs), clinical applications of DC-based immunotherapy are limited by the low potency in generating tumor Ag-specific T cell responses. Therefore, optimal conditions for generating potent immunostimulatory DCs that overcome tolerance and suppression are key factors in DC-based tumor immunotherapy. In this study, we demonstrate that use of the Mycobacterium tuberculosis heat shock protein X (HspX) as an immunoadjuvant in DC-based tumor immunotherapy has significant potential in therapeutics. In particular, the treatment aids the induction of tumor-reactive T cell responses, especially tumor-specific CTLs. The HspX protein induces DC maturation and proinflammatory cytokine production (TNF-α, IL-1β, IL-6, and IFN-β) through TLR4 binding partially mediated by both the MyD88 and the TRIF signaling pathways. We employed two models of tumor progression and metastasis to evaluate HspX-stimulated DCs in vivo. The administration of HspX-stimulated DCs increased the activation of naive T cells, effectively polarizing the CD4+ and CD8+ T cells to secrete IFN-γ, as well as enhanced the cytotoxicity of splenocytes against HPV-16 E7 (E7)–expressing TC-1 murine tumor cells in therapeutic experimental animals. Moreover, the metastatic capacity of B16-BL6 melanoma cancer cells toward the lungs was remarkably attenuated in mice that received HspX-stimulated DCs. In conclusion, the high therapeutic response rates with tumor-targeted Th1-type T cell immunity as a result of HspX-stimulated DCs in two models suggest that HspX harnesses the exquisite immunological power and specificity of DCs for the treatment of tumors.

Oleanolic acid and N-acetylcysteine ameliorate diabetic nephropathy through reduction of oxidative stress and endoplasmic reticulum stress in a type 2 diabetic rat model

BACKGROUND Hyperglycemia-induced endoplasmic reticulum (ER) stress and oxidative stress could be causes of renal fibrosis in diabetes. Oleanolic acid (OA) naturally occurs in fruits and vegetables. It has anti-inflammatory, antihyperlipidemic and antioxidant effects. N-acetylcysteine (NAC) is a precursor of glutathione, which has a strong antioxidant effect in the body. In this study, we investigated the therapeutic effects of OA and NAC in diabetic nephropathy (DN). METHODS Otsuka Long-Evans Tokushima Fatty rats were treated with OA (100 mg/kg/day) or NAC (300 mg/kg/day) for 20 weeks by oral gavage. RESULTS The OA or NAC administration increased blood insulin secretion and superoxide dismutase levels, and decreased triglycerides and urinary albumin/creatinine levels. In the kidney, the damaged renal structure recovered with OA or NAC administration, through an increase in nephrin and endothelial selective adhesion molecules and a decrease in transforming growth factor-β/p-smad2/3 and ER stress. Reactive oxygen species and ER stress were increased by high glucose and ER stress inducers in cultured mesangial cells, and these levels recovered with OA (5.0 μM) or NAC (2.5 mM) treatment. CONCLUSION The findings in this study suggest that OA and NAC have therapeutic effects for DN through an antioxidant effect and ER stress reduction.

Taurine Alleviates the Progression of Diabetic Nephropathy in Type 2 Diabetic Rat Model

The overexpression of vascular endothelial growth factor (VEGF) is known to be involved in the pathogenesis of diabetic nephropathy. In this study, the protective effects of taurine on diabetic nephropathy along with its underlying mechanism were investigated. Experimental animals were divided into three groups: LETO rats as normal group (n = 10), OLETF rats as diabetic control group (n = 10), and OLETF rats treated with taurine group (n = 10). We treated taurine (200 mg/kg/day) for 20 weeks and treated high glucose (HG, 30 mM) with or without taurine (30 mM) in mouse cultured podocyte. After taurine treatment, blood glucose level was decreased and insulin secretion was increased. Taurine significantly reduced albuminuria and ACR. Also it decreased glomerular volume, GBM thickness and increased open slit pore density through decreased VEGF and increased nephrin mRNA expressions in renal cortex. The antioxidant effects of taurine were confirmed by the reduction of urine MDA in taurine treated diabetic group. Also reactive oxygen species (ROS) levels were decreased in HG condition with taurine treated podocytes compared to without taurine. These results indicate that taurine lowers glucose level via increased insulin secretion and ameliorates the progression of diabetic nephropathy through antifibrotic and antioxidant effects in type 2 diabetes rat model.

Dibenzoylmethane Exerts Metabolic Activity through Regulation of AMP-Activated Protein Kinase (AMPK)-Mediated Glucose Uptake and Adipogenesis Pathways

Dibenzoylmethane (DBM) has been shown to exert a variety of beneficial effects on human health. However, the mechanism of action is poorly understood. In this study, DBM increased phosphorylation of AMP-activated protein kinase (AMPK) and stimulated glucose uptake in a skeletal muscle cell line. Both knockdown of AMPK with siRNA and inhibition with AMPK inhibitor blocked DBM-induced glucose uptake. DBM increased the concentration of intracellular calcium and glucose uptake due to DBM was abolished by STO-609 (a calcium/calmodulin-dependent protein kinase inhibitor). DBM stimulated phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK), which was blocked by pretreatment with compound C, an AMPK inhibitor. The expression of glucose transporter type 4 (GLUT4) was increased by DBM. The translocation of GLUT4 to the plasma membrane was also increased by DBM in AMPK dependently. In addition, DBM suppressed weight gain and prevented fat accumulation in the liver and abdomen in mice fed a high-fat diet. In pre-adipocyte cells, DBM decreased the activity of acetyl-CoA carboxylase (ACC), the rate-limiting enzyme of fatty acid synthesis. Expression of the adipogenic gene, fatty acid synthase (FAS), was suppressed by DBM in an AMPK-dependent manner. These results showed that the beneficial metabolic effects of DBM might be due to regulation of glucose uptake via AMPK in skeletal muscle and inhibition of adipogenesis in pre-adipocytes.

Mycobacterium tuberculosis MmsA, a novel immunostimulatory antigen, induces dendritic cell activation and promotes Th1 cell-type immune responses

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis, is an outstanding pathogen that modulates the host immune response. This inconvenient truth drives the continual identification of antigens that generate protective immunity, including Th1-type T cell immunity. Here, the contribution of methylmalonate semialdehyde dehydrogenase (MmsA, Rv0753c) of Mtb to immune responses was examined in the context of dendritic cell (DC) activation and T cell immunity both in vitro and in vivo. The results showed that MmsA induced DC activation by activating the MAPK and NF-κB signaling pathways. Additionally, MmsA-treated DCs activated naïve T cells, effectively polarized CD4(+) and CD8(+) T cells to secrete IFN-γ and IL-2, and induced T cell proliferation. These results indicate that MmsA is a novel DC maturation-inducing antigen that drives the Th1 immune response. Thus, MmsA was found to potentially regulate immune responses via DC activation toward Th1-type T cell immunity, enhancing our understanding of Mtb pathogenesis.

Dehydrozingerone exerts beneficial metabolic effects in high-fat diet-induced obese mice via AMPK activation in skeletal muscle

Dehydrozingerone (DHZ) exerts beneficial effects on human health; however, its mechanism of action remains unclear. Here, we found that DHZ suppressed high‐fat diet‐induced weight gain, lipid accumulation and hyperglycaemia in C57BL/6 mice and increased AMP‐activated protein kinase (AMPK) phosphorylation and stimulated glucose uptake in C2C12 skeletal muscle cells. DHZ activated p38 mitogen‐activated protein kinase (MAPK) signalling in an AMPK‐dependent manner. Inhibiting AMPK or p38 MAPK blocked DHZ‐induced glucose uptake. DHZ increased GLUT4 (major transporter for glucose uptake) expression in skeletal muscle. Glucose clearance and insulin‐induced glucose uptake increased in DHZ‐fed animals, suggesting that DHZ increases systemic insulin sensitivity in vivo. Thus, the beneficial health effects of DHZ could possibly be explained by its ability to activate the AMPK pathway in skeletal muscle.

Essential Engagement of Toll-Like Receptor 2 in Initiation of Early Protective Th1 Response against Rough Variants of Mycobacterium abscessus

ABSTRACT Although Mycobacterium abscessus (M. abscessus) is becoming more prevalent in patients without overt immunodeficiency, little is known about the factors that contribute to disease susceptibility. This study was undertaken to investigate how Toll-like receptor 2 (TLR2) functionally contributes to the generation of protective immunity against M. abscessus in a morphotype-specific manner. We found that Tlr2 −/− mice were extremely susceptible to an intravenous (i.v.) model of infection by M. abscessus rough variants, displaying uncontrolled infection in the lungs and a significantly lower survival rate than with wild-type (WT) mice. This uncontrolled infection resulted from failures in the following processes: (i) production of the crucial cytokines gamma interferon (IFN-γ), tumor necrosis factor alpha (TNF-α), and interleukin 12p70 (IL-12p70); (ii) early infiltration of neutrophils, monocytes, and dendritic cells (DCs) in the lungs of Tlr2 −/− mice; (iii) rapid influx of CD4+ and CD8+ T cells; and (iv) the expansion of memory/effector T cells. Notably, systemic administration of M. abscessus culture filtrate-treated syngeneic DCs from WT mice greatly strengthened immune priming in vivo, resulting in a dramatic reduction in bacterial growth and improved long-term survival in Tlr2 −/− mice, with a recovery of protective immunity. Our findings demonstrate that TLR2 is an essential contributor to instructive and effector immunity during M. abscessus infection in a morphotype-specific manner.