Yasuko Nakano

The fat-derived hormone adiponectin reverses insulin resistance associated with both lipoatrophy and obesity.

Adiponectin is an adipocyte-derived hormone. Recent genome-wide scans have mapped a susceptibility locus for type 2 diabetes and metabolic syndrome to chromosome 3q27, where the gene encoding adiponectin is located. Here we show that decreased expression of adiponectin correlates with insulin resistance in mouse models of altered insulin sensitivity. Adiponectin decreases insulin resistance by decreasing triglyceride content in muscle and liver in obese mice. This effect results from increased expression of molecules involved in both fatty-acid combustion and energy dissipation in muscle. Moreover, insulin resistance in lipoatrophic mice was completely reversed by the combination of physiological doses of adiponectin and leptin, but only partially by either adiponectin or leptin alone. We conclude that decreased adiponectin is implicated in the development of insulin resistance in mouse models of both obesity and lipoatrophy. These data also indicate that the replenishment of adiponectin might provide a novel treatment modality for insulin resistance and type 2 diabetes.

Comparison of Serum High-Molecular Weight (HMW) Adiponectin With Total Adiponectin Concentrations in Type 2 Diabetic Patients With Coronary Artery Disease Using a Novel Enzyme-Linked Immunosorbent Assay to Detect HMW Adiponectin

Adiponectin (Acrp30), an adipocyte-derived protein, exists in serum as a trimer, a hexamer, and a high–molecular weight (HMW) form, including 12–18 subunits. Because HMW adiponectin may be biologically active, we measured it in serum using a novel enzyme-linked immunosorbent assay (ELISA) confirmed by gel filtration chromatography that the ELISA detected mainly adiponectin with 12–18 subunits, and we compared HMW with total adiponectin concentration in patients with type 2 diabetes. We next investigated the relationship between serum HMW and coronary artery disease (CAD) in 280 consecutive type 2 diabetic patients, including 59 patients with angiographically confirmed CAD. Total adiponectin was measured in serum by a commercially available ELISA. Like serum total adiponectin, HMW adiponectin correlated positively with HDL cholesterol and negatively with triglyceride, insulin sensitivity, creatinine clearance, and circulating inflammatory markers. Total and HMW adiponectin were significantly higher in women than in men, as was the HMW-to-total adiponectin ratio. Serum HMW and the HMW-to-total adiponectin ratio were significantly lower in men with than without CAD (P < 0.05, respectively). In women, the ratio, but neither total nor HMW adiponectin, tended to be lower when CAD was present. In conclusion, determination of HMW adiponectin, especially relative to total serum adiponectin, is useful for evaluating CAD in type 2 diabetic patients.

SP-40,40 is a constituent of Alzheimer's amyloid

SummaryCerebrospinal fluid (CSF), serum and seminal plasma contain a small amount of SP-40,40, a modulatory protein of the human complement system. The SP-40,40 in each body fluid was different in molecular size on SDS-PAGE, and glioblastoma cells, hepatoma cells and testicular tumor cells produced SP-40,40, while neuroblastoma cells did not. Therefore, it was estimated that CSF SP-40,40 originated in glia cells, serum SP-40,40 in liver cells and seminal plasma SP-40,40 in testicular cells. SP-40,40 concentrations in CSF of the patients with Alzheimers disease and the patients with cerebral tumor were higher than those of normal donors. β-Amyloid deposits in the brains of the patients with Alzheimers disease were stained with an anti-SP-40,40 monoclonal antibody (mAb) but not with an anti-S-protein mAb, while cellular processes around β-amyloid were stained with an anti-S-protein mAb but not with an anti-SP-40,40 mAb. Therefore, β-amyloid contained SP-40,40 in a form different from that in the soluble membrane attack complex (SMAC, SC5b-9) of the complement, which contains S-protein as well as SP-40,40.

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.

A novel enzyme-linked immunosorbent assay specific for high-molecular-weight adiponectin

Human plasma contains at least three forms of adiponectin: a trimer, a hexamer, and a high-molecular-weight (HMW) multimer. We purified HMW adiponectin from human plasma using its affinity to gelatin and obtained monoclonal antibodies against it. On Western blot analysis, the reactivity of these monoclonal antibodies was shown to be restricted to a non-heat-denatured form of adiponectin molecules. On heating, the collagen-like domain of adiponectin molecules became denatured, and thus the trimer form could not be maintained. From these, monoclonal antibodies against HMW adiponectin were suggested to react with the intact trimer of adiponectin. With these monoclonal antibodies, we developed a sandwich ELISA system for quantifying adiponectin in human serum. Its specificity was verified by analysis of serum fractions separated by gel-filtration chromatography, and our ELISA system was found to be HMW adiponectin-specific. With this novel ELISA, the HMW adiponectin concentrations were 8.4 ± 5.5 μg/ml (mean ± SD) in healthy women and 6.2 ± 3.6 μg/ml in healthy men. Also, serum with a lower HMW adiponectin concentration was shown to have a lower HMW ratio (i.e., HMW adiponectin/total adiponectin).

High molecular weight adiponectin activates AMPK and suppresses cytokine-induced NF-κB activation in vascular endothelial cells

Various isoforms of adiponectin circulate in the plasma. We purified high molecular weight (HMW) adiponectin from human plasma. HMW adiponectin was observed to activate AMP‐activated protein kinase (AMPK), thereby increasing the phosphorylation of eNOS and NO production in endothelial cells. On the other hand, cells preincubated with HMW adiponectin had reduced TNFα‐induced NF‐κB activation. HMW adiponectin by itself was found to modestly activate NF‐κB, which was significantly enhanced by inhibition of AMPK/eNOS activation. Thus, HMW adiponectin might have dual action, both pro and anti‐inflammatory. An initial period of NF‐κB activation by HMW adiponectin might be proinflammatory, but it could be counteracted by activation of AMPK/eNOS, which lead to a potential reduction in a second activation of NF‐κB against inflammatory stimuli.

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.

Neutrophil TRPM2 channels are implicated in the exacerbation of myocardial ischaemia/reperfusion injury

AIMS Transient receptor potential melastatin 2 (TRPM2) highly expressed in immunocytes is a Ca(2+)-permeable non-selective cation channel activated by oxidative stress. Myocardial ischaemia/reperfusion (I/R) injury is characterized by acute inflammation associated with the augmentation of oxidative stress. We hypothesized that TRPM2 is implicated in the exacerbation of myocardial I/R injury. METHODS AND RESULTS Wild-type (Trpm2(+/+)) and Trpm2 knockout (Trpm2(-/-)) mice were subjected to ligation of the left main coronary artery followed by reperfusion. Myocardial infarction following I/R, but not ischaemia alone, was reduced more in Trpm2(-/-)mice than in Trpm2(+/+) mice and cardiac contractile functions were also improved in Trpm2(-/-)mice. TRPM2 was highly expressed in the polymorphonuclear leucocytes (PMNs) rather than in the heart. The number of neutrophils and myeloperoxidase (MPO) activity in the reperfused area following ischaemia was lowered in Trpm2(-/-) mice. When Trpm2(+)(/+) or Trpm2(-/-) PMNs were administered to the Trpm2(-/-) heart ex vivo through the perfusate or in vivo by iv injection, Trpm2(+)(/+) PMNs produced enlargement of the infarct size. Following in vitro regional I/R, a pharmacological inhibitor of TRPM2 reduced the infarct size. The combination of H(2)O(2) and leukotriene B(4) (LTB(4)) increased intracellular Ca(2+) concentration and their adhesion to endothelial cells in Trpm2(+)(/+) but not in Trpm2(-/-)PMNs. CONCLUSION These findings indicate that neutrophil TRPM2 is implicated in the exacerbation of myocardial reperfusion injury. Accumulation of neutrophils in the reperfused area mediated by TRPM2 activation is likely to play a crucial role in myocardial I/R injury.

Adiponectin induces NF-κB activation that leads to suppression of cytokine-induced NF-κB activation in vascular endothelial cells: globular adiponectin vs. high molecular weight adiponectin

Adiponectin circulates in plasma as various isoforms. However, the biological activity of each isoform has not been firmly established. High molecular weight (HMW) adiponectin may be the active form of adiponectin, while a proteolytic cleavage product of adiponectin, known as globular adiponectin (gAd), has recently been shown to activate vascular endothelial cells. We compared HMW adiponectin with gAd to investigate whether they could activate nuclear factor kappa B (NF-κB) and suppress cytokine-induced NF-κB activation in vascular endothelial cells. HMW adiponectin was found to activate NF-κB modestly compared to the activation observed with gAd. HMW adiponectin requires a shorter incubation period to demonstrate inhibition against tumour necrosis factor alpha (TNFα)-induced NF-κB activation, compared with gAd. gAd strongly activates NF-κB, thereby inducing the expression of various pro-inflammatory and adhesion molecule genes, and requires a longer incubation period to show inhibition against cytokine-induced NF-κB activation. Thus, HMW adiponectin might function to protect against inflammatory stimuli, while cleavage of adiponectin at inflammatory sites might enhance the inflammatory process.

A genome‐wide association study for racing performances in Thoroughbreds clarifies a candidate region near the MSTN gene

Using 1400 microsatellites, a genome-wide association study (GWAS) was performed to identify genomic regions associated with lifetime earnings and performance ranks, as determined by the Japan Racing Association (JRA). The minimum heritability (h(2) ) was estimated at 7-8% based on the quantitative trait model, suggesting that the racing performance is heritable. Following GWAS with microsatellites, fine mapping led to identification of three SNPs on ECA18, namely, g.65809482T>C (P=1.05E-18), g.65868604G>T (P=6.47E-17), and g.66539967A>G (P=3.35E-14) associated with these performance measures. The haplotype of these SNPs, together with a recently published nearby SNP, g.66493737C>T (P=9.06E-16) in strong linkage disequilibrium, also showed a very clear association with the performance (P<1E-05). The candidate genomic region contained eight genes annotated by ENSEMBL, including the myostatin gene (MSTN). These findings suggest the presence of a gene affecting the racing performance in Thoroughbred racehorses in this region on ECA18.