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Background: Sarcopenic obesity, a loss of muscle and a concomitant increase in ectopic fat, is reported to increase in life-style related diseases. Especially the prevalence of sarcopenia is greater in patients with type 2 diabetes mellitus (T2DM) than in non-diabetic subjects. Increase in fat filtration enhances insulin resistance and is associated with metabolic risk factors. However, the detailed mechanism of such ectopic fat filtration in muscle of T2DM patients has not been well investigated. Here, we assessed muscle regeneration using muscle-injured models in obese diabetic mice.Methods: Male eight-week-old wild-type mice (C57BL6) and T2DM mice (KKAy) were undergone intramuscular injection of cardiotoxin (Ctx) (100uL/10uM) into tibia. After two weeks, muscle were removed and stained with hematoxylin and eosin. KKAy replaced by bone marrow prepared from GFP-transgenic mice were generated by 8 Gy whole body X-ray irradiation. Cell-differentiation was evaluated by immunofluorescent analysis. Some mice were treated with all trans-retinoic acid (ATRA) and PPAR-gamma antagonist, GW9662.Results: In 26 week-old KKAy, magnetic resonance imaging analysis showed that intramuscular fat deposition was estimated as higher intensity compared with C57BL6 mice. Treatment with Ctx showed a significant increase in honey comb structure which was perilipin positive. KKAy mice exhibited impaired muscle regeneration. Tibial muscle weight was approximately a half in Ctx-injured KKAy. Such change was also observed in another diabetic mouse model, db/db, but not in streptozocin-induced diabetic mice. Fat formation was remarkably increased in aged KKAy compared with younger mice. Several fat formation was GFP-positive in GFP-chimeric mice indicating that fat tissue was partially generated from marrow cells. Fat formation was desmin-negative and vimentin-positive indicating that these are mesenchymal origin. Treatment with ATRA reduced fat filtration. On the other hand, treatment with GW9662 enhanced fat filtration.Conclusion: Obese diabetic mice showed significantly impaired muscle regeneration with replacement of fat deposition, suggesting that diabetes enhanced sarcopenic obesity possibly due to inhibitory effect of cell differentiation. [ABSTRACT FROM AUTHOR]

Background: We have previously reported that treatment with angiotensin II type-2 (AT2) receptor agonist (compound 21; C21) ameliorated insulin resistance with the improvement of adipocyte dysfunction in obese type 2 diabetic mouse model, KKAy. Until quite recently, adipose tissue has been divided into two groups that have directory-opposed capacities; white adipose tissue is best known for its role in energy store, while brown adipose tissue functions for energy expenditure (thermogenesis). In addition, new clusters of adipocyte with thermogenic capability have been discovered in white adipose tissue, which are distinct origins from brown adipose tissue. These adipocytes have been named ‘beige’. However, the role of AT2 receptor signaling in white-to-beige fat conversion is not known.Methods: KKAy mice were subjected to i.p. injection of C21 (10ug/kg/day) for 2 weeks. After the treatment, the expression of thermogenic genes (Ucp1, Cidea, Pgc1α) in adipose tissue were determined with real-time RT-PCR. Next, we examined the difference in conversion from white to beige fat between wild-type (WT) mice and AT2 receptor knockout (AT2KO) mice. Eight-week-old mice were fed a high-fat and high-cholesterol diet (HFCD) (10% coconut oil + 1.25% cholesterol) for 2 weeks. To examine the effect of exercise on fat conversion, 9-week-old mice were forced swim test (2 minх3 times/day) for 7days. After the swim test, mice were sacrificed for examinations.Results: In KKAy mice, treatment of C21 increased the expression of thermogenic genes in subcutaneous fat, but not in visceral fat. Adipose tissue weight was not changed by treatment of C21. In AT2KO mice fed HFCD for 2 weeks, visceral fat was greater than that in WT mice, but subcutaneous fat was not. The expression of thermogenic genes in subcutaneous fat was lower in AT2KO mice than in WT mice. In both mice, swim exercise increased the expression of thermogenic genes; however, the up-regulation of these genes in AT2KO mice did not reach the level of that in WT mice.Conclusion: These results suggest that AT2 receptor signaling has an important role in white-to-beige fat conversion, and therefore AT2 receptor signaling might be a potential therapeutic target for lipid metabolic disorders. [ABSTRACT FROM AUTHOR]

Objective: Transcriptional control of angiotensin II type 2 (AT2) receptor expression is not well known and we previously reported that interferon regulatory factor (IRF)-1 plays physiological roles in “growth”-regulated AT2 receptor expression in fibroblast. We studied whether IRF-1 is involved in the attenuation of vascular remodeling in association with AT2 receptor up-regulation.Methods: Inflammatory vascular injury was induced by polyethylene-cuff placement around the mouse femoral artery in male wild-type mice (WT: C57BL/6J strain), IRF-1 knockout mice (IRF-1KO) and AT2 receptor-null mice (AT2KO) at 10 weeks of age. After cuff placement, each mice were treated with an intraperitoneal injection of compound 21 (C21), AT2 receptor agonist, at the dose of 10 μg/kg/day or saline. Formalin-fixed, paraffin-embedded sections were prepared using femoral arteries 14 days after cuff placement and subjected to Elastica van Gieson staining for the evaluation of neointima formation. Superoxide anion production and mRNA expressions 7 days after cuff placement were evaluated by dihydroethidium staining and real-time quantitative RT-PCR respectively.Results: Neointima areas in the injured artery induced by cuff placement were significantly increased in vehicle-treated group of IRF-1KO and AT2KO compared with those in WT. Moreover, we observed that treatment with C21 attenuated neointima formation 76% in WT, but 45% in IRF-1KO. Oxidative stress was more enhanced in vehicle-treated group of IRF-1KO compared with WT. Treatment with C21 markedly inhibited oxidative stress in WT, but not in IRF-1KO. AT2 receptor mRNA expression was significantly decreased in IRF-1KO compared with that in WT; however, IRF-1 mRNA expression did not differ between AT2KO and WT.Conclusion: These results indicate that IRF-1 up-regulates AT2 receptor expression and thereby plays an important role in the inhibition of vascular remodeling, supporting the notion that IRF-1 is one of the key transcriptional factor for AT2 receptor expression and that targeting the immune system is pivotal in the treatment of vascular diseases. [ABSTRACT FROM AUTHOR]

Objective: Recent accumulating evidence suggests that an orally active angiotensin II receptor-neprilysin inhibitor, LCZ696, was supposed to be superior compared to angiotensin II receptor blocker (ARB), valsartan alone in treating cardiovascular disease. We previously reported that ARBs prevent ischemic brain damage using middle cerebral artery occlusion (MCAO) mouse model. Moreover, natriuretic peptides such as atrial natriuretic peptide (ANP) or brain natriuretic peptide (BNP) increased by neprilysin inhibitor are also reported to protect brain damage. Therefore, we investigate the possible protective effects of valsartan (VAL) compared with LCZ696 (LCZ) (VAL+ neprilysin inhibitor; 1:1) on the prevention of ischemic damage after stroke.Methods: Focal brain ischemia was induced by MCAO with the intraluminal filament technique in 10-week male C57BL/6J mice. Mice were treated with VAL (3 mg/kg) or LCZ (6 mg/kg) orally as powder in gelatin mini-capsules daily for 2 weeks before MCAO. Ischemic area was evaluated by triphenyl tetrazolium chloride staining, cerebral blood flow (CBF) by laser-Doppler flowmetry, oxidative stress by dihydroethidium staining.Results: Telemetry method showed that systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) did not change before and after treatments. Protective effect of LCZ treatment on ischemic brain damage in each brain section seemed to be more marked than that of VAL treatment. The average ischemic area ratio showed a significant reduction in VAL and LCZ groups compared with CON group. CBF in the peripheral region around ischemic core was significantly improved after treatments. Moreover, VAL and LCZ treatments significantly decreased the increase of superoxide anion production in the cortex of ischemic side. However, significant differences of CBF and superoxide anion production were not observed in VAL and LCZ.Conclusions: Both valsartan and LCZ696 treatments exerted preventive effects on ischemic stroke. The preventive effect of LCZ696 seemed more prominent than VAL. LCZ696 could be a novel powerful approach to protect brain after stroke. Further investigation has been performed to clarify the protective effect of LCZ696 on ischemic brain damage. [ABSTRACT FROM AUTHOR]