Kiyomi Saito

Cardioprotective Effects of Short-Term Caloric Restriction Are Mediated by Adiponectin via Activation of AMP-Activated Protein Kinase

Background— Overeating and obesity are major health problems in developed countries. Caloric restriction (CR) can counteract the deleterious aspects of obesity-related diseases and prolong lifespan. We have demonstrated that short-term CR improves myocardial ischemic tolerance and increases adiponectin levels. Here, we investigated the specific role of adiponectin in CR-induced cardioprotection. Methods and Results— Adiponectin antisense transgenic (Ad-AS) mice and wild-type (WT) mice were randomly assigned to a group fed ad libitum and a CR group (90% of caloric intake of ad libitum for 3 weeks, then 65% for 2 weeks). Isolated perfused mouse hearts were subjected to 25 minutes of ischemia, followed by 60 minutes of reperfusion. CR increased serum adiponectin levels by 84% in WT mice. Gel filtration analysis of the oligomeric complex distribution showed that CR produced a marked increase in the high–molecular-weight complex of adiponectin in WT mice; in contrast, CR did not change serum adiponectin levels or their oligomeric pattern in Ad-AS mice. CR improved the recovery of left ventricular function after ischemia/reperfusion and limited infarct size in WT mice; these effects were completely abrogated in Ad-AS mice. CR also increased the phosphorylated form of AMP-activated protein kinase and acetyl-CoA carboxylase in WT but not in Ad-AS mice. Recombinant adiponectin restored CR-induced cardioprotection in Ad-AS mice, and inhibition of AMP-activated protein kinase phosphorylation completely abrogated CR-induced cardioprotection in WT mice. Conclusion— The cardioprotective effects of short-term CR are mediated by increased production of adiponectin and the associated activation of AMP-activated protein kinase.

Adiponectin protects against doxorubicin-induced cardiomyopathy by anti-apoptotic effects through AMPK up-regulation

AIMS Adiponectin (APN) has been reported to protect against ischaemia-reperfusion injury and hypertrophy. However, few reports have investigated the cardioprotective effects of APN in doxorubicin (DOX)-induced cardiomyopathy; therefore, we studied the cardioprotective mechanisms of APN in this model. METHODS AND RESULTS In an in vivo study, we quantified the cardiac pathohistology of C57BL/6 mice [wild-type (WT) mice], APN transgenic mice with high APN concentrations [APN transgenic sense (SE) mice], and those with reduced APN concentrations [APN transgenic antisense (AS) mice] after intraperitoneal injections of DOX (4 mg/kg) weekly for 6 weeks. The survival rate after 14 days was significantly increased in APN-SE mice (WT vs. APN-AS vs. APN-SE: 40 vs. 17 vs. 73%, P < 0.05). We assessed myocardial pathohistological changes and observed that fibrosis and apoptosis were significantly decreased in APN-SE mice compared with those of the other groups. We also assessed DOX-induced apoptotic mechanisms in vitro using cultured cardiomyocytes isolated from neonatal WT mice. The expression of adenosine monophosphate-activated protein kinase (AMPK) and anti-apoptotic factor Bcl-2 increased, but that of pro-apoptotic factor Bax decreased in cardiomyocytes treated with highly concentrated APN. The protective effects of APN were reversed by the addition of an AMPK inhibitor (dorsomorphin) to the culture medium. CONCLUSION These data suggest that APN improved cardiac function through anti-apoptotic effects by up-regulation of AMPK in DOX-induced cardiomyopathy in mice.

The novel acute phase protein, IHRP, inhibits actin polymerization and phagocytosis of polymorphonuclear cells

Objective and Design: In the present study, the involvement of the binding of IHRP (inter-alpha-trypsin inhibitor family heavy chain-related protein) and actin in phagocyte activity was investigated.¶Materials and Methods: The actin polymerization and the phagocytic activity of the polymorphonuclear (PMN) cells were studied in the presence of IHRP.¶Results: IHRP inhibited the polymerization of actin and the phagocytic activity of the PMN cells.¶Conclusion: 1) IHRP may bind to actin released from the damaged cells and suppress its toxic action by preventing the formation of actin fibril. 2) IHRP may bind to cell surface actin on PMN cells and inhibit their phagocytic activities. 3) From these results, IHRP may act as an anti-inflamma-tory protein.

Adiponectin enhances calcium-dependency of mouse bladder contraction mediated by protein kinase Cα expression

Adiponectin is an adipose tissue–secreted protein and is a multifunctional adipocytokine. However, the association of adiponectin with bladder contraction has not been investigated. In this study, the adiponectin-sense transgenic mouse (Adip-Sen mouse; age, 16–24 weeks; male) and age-matched controls (C57Bl mouse) were studied. The Adip-Sen mouse showed a significant increase in plasma adiponectin levels (56.2%; P < 0.01), compared with those in the C57Bl mouse, without affecting other lipid parameters. Isometric force development in bladder smooth muscle tissues were detected using an organ-bath system. Although carbachol (CCh)–induced (0.1–100 µM) time- and dose-dependent contractions in Adip-Sen mouse bladder were slightly enhanced, compared with those in the C57Bl mouse during a low range (0.3–1.0 µM) of CCh, differences could not be detected with other CCh concentrations. However, the reduction in contraction under Ca2+-replaced conditions was significantly different between Adip-Sen and C57Bl mice (94.1 and 66.3% of normal contraction, respectively; n = 5). A parameter of Ca2+ sensitivity, the relation between intracellular Ca2+ concentration and contraction, was increased in the Adip-Sen mouse, compared with that in the C57B1 mouse. This Ca2+ dependency in the Adip-Sen mouse was reduced by a protein kinase C (PKC) inhibitor, but not by a Rho kinase inhibitor. Expression of the calcium-dependent isoform of PKC, PKCα, was increased in the Adip-Sen mouse bladder, and CCh-induced phosphorylation of PKCα was also enhanced, compared with those in the C57Bl mouse. In conclusion, adiponectin is associated with bladder smooth muscle contraction, which involves an increase in Ca2+ dependency of contraction mediated by PKCα expression.

Potentiated macrophage activation by acid sensing under low adiponectin levels

Adiponectin can protect against inflammation; one of the mechanisms involves direct, inhibition of macrophages (MΦ). We postulated that adiponectin anti-sense transgenic (AsTg) mice raised in our laboratory are prone to inflammation because of systemic low adiponectin levels. The writhing response to acetic acid was utilized as an in vivo inflammatory model, and using Ca(2)(+), response to the acid was exploited in vitro to evaluate the function of resident peritoneal MΦ. The in vivo response to the acid was increased and the Ca(2)(+) response of MΦ was enhanced in AsTg mice, compared with those in wild type (WT) mice. In parallel with these enhanced responses, MΦ from AsTg mice augmented TNF-α and IL-6 mRNA expression. We further analyzed the enhancement in activity of MΦ from AsTg mice by acid sensing using specific inhibitors, amiloride for acid-sensing ion channels (ASICs) and KB-R7943 for Na(+)/Ca(2)(+) exchangers (NCXs). Our results indicated that in AsTg mice, the Ca(2)(+) response to the acid was facilitated in MΦ by a low threshold of ASIC1 and NCX1 molecules and the activity of these channel was possibly regulated by adiponectin.