Although exercise is effective in improving obesity and hyperinsulinemia, the exact influence of exercise on the capillary density of skeletal muscles remains unknown. The aim of this study was to investigate the effects of low-intensity exercise training on metabolism in obesity with hyperinsulinemia, focusing specifically on the capillary density within the skeletal muscle. Otsuka Long-Evans Tokushima fatty (OLETF) rats were used as animal models of obesity with hyperinsulinemia, whereas Long-Evans Tokushima Otsuka (LETO) rats served as controls (no obesity, no hyperinsulinemia). The animals were randomly assigned to either non-exercise or exercise groups (treadmill running for 60 min/day, for 4 weeks). The exercise groups were further divided into subgroups according to training mode: single bout (60 min, daily) vs. multiple bout (three bouts of 20 min, daily). Fasting insulin levels were significantly higher in OLETF than in LETO rats. Among OLETF rats, there were no significant differences in fasting glucose levels between the exercise and the non-exercise groups, but the fasting insulin levels were significantly lower in the exercise group. Body weight and triacylglycerol levels in the liver were significantly higher in OLETF than in LETO rats; however, among OLETF rats, these levels were significantly lower in the exercise than in the non-exercise group. The capillary-to-fiber ratio of the soleus muscle was significantly higher in OLETF than in LETO rats; however, among OLETF rats, the ratio was lower in the exercise group than in the non-exercise group. No significant differences in any of the studied parameters were noted between the single-bout and multiple-bout exercise training modes among either OLETF or LETO rats. These results suggest that low-intensity exercise training improves insulin sensitivity and fatty liver. Additionally, the fact that attenuation of excessive capillarization in the skeletal muscle of OLETF rats was accompanied by improvement in increased body weight.

Bmp plays an important role in cardiomyocyte differentiation, but the function of Smad4 in Bmp signaling remains elusive. Here, we show that disruption of the Smad4 gene in cardiac progenitors expressing Sfrp5 led to embryonic lethality with hypoplastic heart formation. Although the expression of Nkx2-5 is regulated by Bmp signaling, expression of Nkx2-5 was weakly detected in the mutant heart. However, the nuclear translocation of Nkx2-5 was impaired. Expression of CK2 or PP1, which could alter the phosphorylation status of the NLS of Nkx2-5, was not affected, but Nkx2-5 was found to bind to Smad4 by co-immunoprecipitation experiments. Introduction of Smad4 into cells derived from Smad4 conditional knockout embryonic hearts restored the nuclear localization of Nkx2-5, and exogenous Nkx2-5 failed to translocate into the nucleus of Smad4-depleted fibroblasts. These results suggest that Smad4 plays an essential role in cardiomyocyte differentiation by controlling not only transcription but also the nuclear localization of Nkx2-5.

Aortic aneurysm refers to dilatation of the aorta due to loss of elasticity and degenerative weakening of its wall. A preventive role for osteoprotegerin (Opg) in the development of abdominal aortic aneurysm has been reported in the CaCl 2-induced aneurysm model, whereas Opg was found to promote suprarenal aortic aneurysm in the AngII-induced ApoE knockout mouse aneurysm model. To determine whether there is a common underlying mechanism to explain the impact of Opg deficiency on the vascular structure of the two aneurysm models, we analyzed suprarenal aortic tissue of 6-month-old ApoE-/-Opg-/mice after AngII infusion for 28 days. Less aortic dissection and aortic lumen dilatation, more adventitial thickening, and higher expression of collagen I and Trail were observed in ApoE-/-Opg-/mice relative to ApoE-/-Opg +/+ mice. An accumulation of α-smooth muscle actin and vimentin double-positive myofibroblasts was noted in the thickened adventitia of ApoE-/-Opg-/mice. Our results suggest that fibrotic remodeling of the aorta induced by myofibroblast accumulation might be an important pathological event which tends to limit AngIIinduced aortic dilatation in ApoE-/-Opg-/mice.

Background Angiotensin II type 1 receptor blockers (ARBs) have been shown to limit the growth of abdominal aortic aneurysm (AAA), but their efficacy is controversial. This study aimed to investigate the molecular mechanism underlying the protective effect of ARBs against AAA progression. Methods and Results Olmesartan, an ARB, was administered to wild‐type and osteoprotegerin ‐knockout ( Opg ‐KO) mice starting 2 weeks before direct application of CaCl 2 to aortas to induce AAA. The protective effect of olmesartan against AAA in wild‐type and Opg ‐KO mice was compared at 6 weeks after AAA induction. Olmesartan prevented AAA progression in Opg ‐KO mice, including excessive aortic dilatation and collapse of tunica media, but not in wild‐type mice. Deficiency of the Opg gene is known to cause excessive activation of the tumor necrosis factor–related apoptosis‐inducing ligand–induced c‐Jun N‐terminal kinase/matrix metalloproteinase 9 pathway, resulting in prolonged AAA progression. Olmesartan attenuated the upregulation of phosphorylated c‐Jun N‐terminal kinase and matrix metalloproteinase 9 expression in the aortic wall of Opg ‐KO mice. In cultured vascular smooth muscle cells, tumor necrosis factor–related apoptosis‐inducing ligand–induced c‐Jun N‐terminal kinase phosphorylation and matrix metalloproteinase 9 expression were inhibited by angiotensin (1–7), the circulating levels of which are increased by ARBs. Furthermore, administering an angiotensin (1–7) antagonist to Opg ‐KO mice diminished the protective effect of olmesartan against AAA progression. Conclusions Olmesartan prevented AAA progression in Opg‐ KO mice by upregulating angiotensin (1–7), suggesting that angiotensin (1–7) may be a key factor that mediates the protective effect of ARBs.

Objective:Hypertension is one of the major risk factors for onset of abdominal aortic aneurysm (AAA), which is a local enlargement of the abdominal aorta. Therefore, anti-hypertensive drugs, including angiotensin (Ang) II type 1 receptor blocker (ARB), have been expected to limit AAA growth. However, the efficacy of ARB against AAA in clinical settings is controversial. In the present study, we attempted to elucidate a mechanism by which ARB inhibits AAA progression.Design and method:To examine the effect of ARB against AAA progression, olmesartan (20 mg/kg/day) was administered orally to male wild-type mice and osteoprotegerin (Opg)-knockout (KO) mice, from two weeks before the AAA induction by using a CaCl2 application on the abdominal aortae to the sacrifice date. Since Opg could bind to tumor necrosis factor-related apoptosis-inducing ligand (Trail) for inhibiting its activity, deficiency of the Opg gene has been reported to induce overactivation of the Trail induced-c-Jun N-terminal kinase (Jnk)/matrix metalloproteinase 9 (Mmp9) pathway in CaCl2-induced mouse AAA model, resulting in serious AAA progression. Here, we tested whether olmesartan could prevent AAA progression associated with Trail/Jnk/Mmp9 pathway.Results:We found that olmesartan prevented excessive aortic enlargement and serious degenerative change of the aortic tissue in Opg-KO mice at six weeks after AAA induction, but not affected AAA formation in wild-type mice. In Opg-KO mice, olmesartan reduced co-localized expression of phosphorylated Jnk and Mmp9 in the tunica media. Then, we tested whether Ang (1–7), the blood level of which is increased by ARB administration, is associated with the preventive effect of olmesartan, because Ang (1–7) had been reported to reduce the Jnk phosphorylation. Consistent with previous studies, olmesartan increased serum level of Ang (1–7) in our AAA model. In vascular smooth muscle cells, Ang (1–7) inhibited the phosphorylation of Jnk and the increase of downstream Mmp9 mRNA expression induced by Trail. Furthermore, administration of an Ang (1–7) antagonist, A779, to Opg-KO mice diminished the preventive effect of ARB against the AAA progression. Notably, olmesartan slightly lowered blood pressure in Opg-KO mice, while A779 did not affect the blood pressure-lowering effect of olmesartan.Conclusions:Our results indicate that ARB prevents the AAA progression in Opg-KO mice via the inhibition of Trail-induced Jnk-Mmp9 pathway. Furthermore, it is suggested that the increase of Ang (1–7) may play a key role in the preventive effect of ARB on the AAA progression.