Yuichi Akasaki

Sfrp5 Is an Anti-Inflammatory Adipokine That Modulates Metabolic Dysfunction in Obesity

Fats Mixed Messages Certain metabolic disorders, such as type 2 diabetes, are more prone to arise in obese individuals, a link that has been attributed, in part, to the detrimental activities of adipokines—proteins secreted by fat cells. Most adipokines disrupt glucose homeostasis by promoting inflammation and insulin resistance. Ouchi et al. (p. 454, published online 17 June; see the Perspective by Oh and Olefsky) identify a new adipokine, secreted frizzled-related protein 5 (Sfrp5), which has the opposite effect: It is anti-inflammatory and appears to promote metabolic health. In obese mice, Sfrp5 suppresses the activation of key inflammatory cells (macrophages) residing within adipose tissue by inhibiting the c-Jun N-terminal kinase (JNK) signaling pathway. Further study of this Sfrp5-JNK1 regulatory axis in fat may offer therapeutic opportunities for obesity-linked metabolic disorders. Fat cells secrete an anti-inflammatory factor that has beneficial effects on metabolic health. Adipose tissue secretes proteins referred to as adipokines, many of which promote inflammation and disrupt glucose homeostasis. Here we show that secreted frizzled-related protein 5 (Sfrp5), a protein previously linked to the Wnt signaling pathway, is an anti-inflammatory adipokine whose expression is perturbed in models of obesity and type 2 diabetes. Sfrp5-deficient mice fed a high-calorie diet developed severe glucose intolerance and hepatic steatosis, and their adipose tissue showed an accumulation of activated macrophages that was associated with activation of the c-Jun N-terminal kinase signaling pathway. Adenovirus-mediated delivery of Sfrp5 to mouse models of obesity ameliorated glucose intolerance and hepatic steatosis. Thus, in the setting of obesity, Sfrp5 secretion by adipocytes exerts salutary effects on metabolic dysfunction by controlling inflammatory cells within adipose tissue.

FGF21 is an Akt-regulated myokine

Fibroblast growth factor‐21 (FGF21) functions as a metabolic regulator. The FGF21 transcript is reported to be abundantly expressed in liver, but little is known about the regulation of FGF21 expression in other tissues. In this study, we show that levels of FGF21 protein expression were similar in skeletal muscle and liver from fasted mice. FGF21 transcript and protein expression were upregulated in gastrocnemius muscle of skeletal muscle‐specific Akt1 transgenic mice. Serum concentration of FGF21 was also increased by Akt1 transgene activation. In cultured skeletal muscle cells, FGF21 expression and secretion was regulated by insulin, Akt transduction and LY294002. These data indicate that skeletal muscle is a source of FGF21 and that its expression is regulated by a phosphatidylinosistol 3‐kinase (PI3‐kinase)/Akt1 signaling pathway‐dependent mechanism.

Glycolytic fast-twitch muscle fiber restoration counters adverse age-related changes in body composition and metabolism.

Aging is associated with the development of insulin resistance, increased adiposity, and accumulation of ectopic lipid deposits in tissues and organs. Starting in mid‐life there is a progressive decline in lean muscle mass associated with the preferential loss of glycolytic, fast‐twitch myofibers. However, it is not known to what extent muscle loss and metabolic dysfunction are causally related or whether they are independent epiphenomena of the aging process. Here, we utilized a skeletal‐muscle‐specific, conditional transgenic mouse expressing a constitutively active form of Akt1 to examine the consequences of glycolytic, fast‐twitch muscle growth in young vs. middle‐aged animals fed standard low‐fat chow diets. Activation of the Akt1 transgene led to selective skeletal muscle hypertrophy, reversing the loss of lean muscle mass observed upon aging. The Akt1‐mediated increase in muscle mass led to reductions in fat mass and hepatic steatosis in older animals, and corrected age‐associated impairments in glucose metabolism. These results indicate that the loss of lean muscle mass is a significant contributor to the development of age‐related metabolic dysfunction and that interventions that preserve or restore fast/glycolytic muscle may delay the onset of metabolic disease.

Insulin-like 6 is induced by muscle injury and functions as a regenerative factor

The insulin-like family of factors are involved in the regulation of a variety of physiological processes, but the function of the family member termed insulin-like 6 (Insl6) in skeletal muscle has not been reported. We show that Insl6 is a myokine that is up-regulated in skeletal muscle downstream of Akt signaling and in regenerating muscle in response to cardiotoxin (CTX)-induced injury. In the CTX injury model, myofiber regeneration was improved by the intramuscular or systemic delivery of an adenovirus expressing Insl6. Skeletal muscle-specific Insl6 transgenic mice exhibited normal muscle mass under basal conditions but elevated satellite cell activation and enhanced muscle regeneration in response to CTX injury. The Insl6-mediated regenerative response was associated with reductions in muscle cell apoptosis and reduced serum levels of creatine kinase M. Overexpression of Insl6 stimulated proliferation and reduced apoptosis in cultured myogenic cells. Conversely, knockdown of Insl6 reduced proliferation and increased apoptosis. These data indicate that Insl6 is an injury-regulated myokine that functions as a myogenic regenerative factor.

Waon therapy mobilizes CD34+ cells and improves peripheral arterial disease

BACKGROUND We previously reported that Waon therapy upregulates endothelial nitric oxide synthase protein, and augments ischemia-induced angiogenesis in mice with hindlimb ischemia, and it improves limb ischemia in patients with peripheral arterial disease (PAD). The aim of this study was to investigate the underlying mechanism of Waon therapy for the treatment of patients with PAD, and to determine whether Waon therapy can mobilize blood-derived progenitor cells. METHODS 21 consecutive PAD patients received standard medications, and were randomly divided into control (n=10) and Waon therapy groups (n=11). The Waon therapy group received Waon therapy daily for 6 weeks. The control group continued conventional therapy for 6 weeks. Leg pain was scored using a visual analogue scale. The ankle-brachial pressure index (ABPI) and the 6-min walking distance were measured at baseline and 6 weeks after therapy. Frequency of circulating CD34+ progenitor cell numbers was measured by quantitative real-time polymerase chain reaction, and the serum nitrate and nitrite levels were also measured at baseline and 6 weeks after therapy. RESULTS The leg pain score, ABPI and the 6-min walking distance improved significantly after 6 weeks in the Waon therapy group, but not in the control group. Frequency of circulating CD34+ cells increased after 6 weeks of Waon therapy [2.0 ± 1.2 (×10(-4)) at baseline to 3.9 ± 1.9 (×10(-4)), p=0.015], while it remained unchanged in the control group [1.8 ± 1.8 (×10(-4)) at baseline to 1.2 ± 0.9 (×10(-4))]. Serum nitrate and nitrite levels increased significantly after Waon therapy (29.6 ± 17.6 to 36.0 ± 17.7 μmol/ml, p<0.05), but not in the control group (34.4 ± 9.4 to 38.3 ± 8.8 μmol/ml). CONCLUSION Waon therapy mobilized circulating endothelial progenitor cells and improved limb ischemia in patients with PAD. Waon therapy is a highly promising therapy for patients with PAD.

Tacrolimus-eluting stent inhibits neointimal hyperplasia via calcineurin/NFAT signaling in porcine coronary artery model

AIMS The purpose is to elucidate the mechanism by which a newly developed tacrolimus-eluting stent (TES) prevents neointimal hyperplasia after stenting. METHODS AND RESULTS The three major coronary arteries in juvenile swine were randomized to implantation of either a TES or bare metal stent (BMS). Twelve weeks after stenting, the TES showed 29% less neointimal area than the BMS. Immunohistochemical staining showed that the expression of calcineurin was up-regulated in the neointima and media after stenting, and the TES inhibited this up-regulation. Western blotting demonstrated that the expression of calcineurin, nuclear factor of activated T cell (NFAT), and interleukin-2 (IL-2) was lower with the TES than with the BMS. To confirm the effect of tacrolimus on vascular smooth muscle cells (VSMCs) and its mechanism, cultured rat VSMCs were incubated with 12.5 microM of tacrolimus (tacrolimus group) or without tacrolimus (control group). The cell number of the tacrolimus group was significantly lower than that of the control group at 48 h of incubation. Western blotting demonstrated that tacrolimus decreased the expression of calcineurin, NFATc4, and IL-2 of cultured VSMCs. We confirmed that calcineurin small-interfering RNA (siRNA) decreased cell proliferation and the expression of NFATc4 and IL-2 in cultured VSMCs compared with negative control-siRNA. CONCLUSION The newly developed TES inhibited neointimal hyperplasia after stenting via the calcineurin/NFAT/IL-2 signaling pathway, which is one of several mechanisms through which TES inhibits restenosis. Calcineurin may be an important molecular target to prevent restenosis after stenting.

Novel Therapy for Atherosclerosis Using Recombinant Immunotoxin Against Folate Receptor β-Expressing Macrophages.

Background Folate receptor β (FRβ) is induced during macrophage activation. A recombinant immunotoxin consisting of the truncated Pseudomonas exotoxin A (PE38) conjugated to an anti-FRβ antibody (anti–FRβ-PE38) has been reported to kill activated macrophages in inflammatory diseases. To elucidate the effect of an immunotoxin targeting FRβ on atherosclerosis, we determined the presence of FRβ-expressing macrophages in atherosclerotic lesions and administered the FRβ immunotoxin in apolipoprotein E–deficient mice. Methods and Results The FRβ-expressing macrophages were observed in atherosclerotic lesions of apolipoprotein E–deficient mice. At 15 or 35 weeks of age, the apolipoprotein E–deficient mice were divided into 3 groups and were intravenously administered 0.1 mg/kg of anti–FRβ-PE38 (immunotoxin group), 0.1 mg/kg of PE38 (toxin group), or 0.1 mL of saline (control group) every 3 days, for a total of 5 times for each age group. The mice were analyzed at 21 or 41 weeks of age. Treatment with the immunotoxin resulted in 31% and 22% reductions in atherosclerotic lesions of the 21- and 41-week-old mice, respectively (P<0.05). Administration of immunotoxin reduced the numbers of FRβ- and tumor necrosis factor-α–expressing macrophages, reduced cell proliferation, and increased the number of apoptotic cells (P<0.05). Real-time polymerase chain reaction demonstrated that the expression of FRβ and tumor necrosis factor-α mRNA was significantly decreased in the immunotoxin group (P<0.05). Conclusions These results suggest that FRβ-expressing macrophages exist in the atherosclerotic lesions of apolipoprotein E–deficient mice and that FRβ immunotoxin administration reduces the progression of atherosclerotic lesions in younger and older individuals. The recombinant FRβ immunotoxin targeting activated macrophages could provide a novel therapeutic tool for atherosclerosis. (J Am Heart Assoc. 2012;1:e003079 doi: 10.1161/JAHA.112.003079.)

Interferon-α Therapy following Autologous Peripheral Blood Stem Cell Transplantation for Adult T Cell Leukemia/Lymphoma

In the present report, we describe a case of adult T cell leukemia/lymphoma (ATLL), a 58-year-old woman, successfully treated with interferon (IFN)-α following autologous peripheral blood stem cell transplantation (auto-PBSCT). The patient remains in remission with full performance status for more than 12 months. Auto-PBSCT reduced the abdominal lymphoma mass and IFN-α eliminated residual tumor cells, possibly through the induction of specific T-cell subsets expressing CD3, CD8 on their surfaces and either IFN-γ or tumor necrosis factor (TNF)-α in cytoplasm. We have treated a total of 4 ATLL patients with auto-PBSCT, including the case presented herein. All other patients treated with auto-PBSCT were not followed by adjuvant chemotherapy or cytokine therapy and relapsed within 3 months after auto-PBSCT. This evidence suggests that the therapeutic success of the present case was attributable to the administration of IFN-α immunotherapy following auto-PBSCT.

Metabolomic Analysis of Akt1-Mediated Muscle Hypertrophy in Models of Diet-Induced Obesity and Age-Related Fat Accumulation

Akt1 is a serine/threonine kinase that promotes cell growth and survival. Previously, Akt1 activation in a double transgenic (DTG) mouse model fed a high-fat/high-sucrose (HF/HS) diet was found to promote type IIb muscle growth and to lead to a significant reduction in obesity. Here, we have used metabolomics to examine the metabolic perturbations in blood serum and liver and gastrocnemius tissues of the DTG mice. Multivariate statistics highlighted consistent metabolic changes in gastrocnemius muscle following Akt1 activation, which included significant reductions of serine and histidine-containing dipeptides (anserine and carnosine), in addition to increased concentrations of phosphorylated sugars. In addition, Akt1-mediated regression in obesity could be associated with increased glycolysis in gastrocnemius muscle as well as increased gluconeogenesis, glycogenolysis, and ketogenesis in the liver. In old DTG animals, Akt1 activation was found to improve glucose metabolism and confer a beneficial effect in the regression of age-related fat accumulation. This study identifies metabolic changes induced by Akt1-mediated muscle growth and demonstrates a cross-talk between distant organs that leads to a regression of fat mass. The current findings indicate that agents that promote Akt1 induction in muscle have utility in the regression of obesity.

The Impact of Autophagy on Cardiovascular Senescence and Diseases

The risk of cardiovascular disease increases with age, causing chronic disability, morbidity, and mortality in the elderly. Cardiovascular aging and disease are characterized by heart failure, cardiac ischemia-reperfusion injury, cardiomyopathy, hypertension, arterial stiffness, and atherosclerosis. As a cell ages, damaged organelles and abnormal proteins accumulate. A system for removing these cytoplasmic substrates is essential for maintaining homeostasis. Autophagy assists tissue homeostasis by forming a pathway by which these substances are degraded. Growing evidence suggests that autophagy plays a role in age-related and disease states of the cardiovascular system, and it may even be effective in preventing or treating cardiovascular disease. On the other hand, overexpression of autophagy in the heart and arteries can produce detrimental effects. We summarize the current understanding of the close relationship between autophagy and cardiovascular senescence.