Intracerebroventricular injection of adiponectin regulates locomotor activity in rats

Enhancing exercise motivation is the best way to prevent obesity and diabetes. In this study, we examined whether adiponectin affects locomotion activity in Wister and Spontaneously-Running Tokushima-Shikoku (SPORTS) rats using two types of behavioral assays : home cage and wheel running activity. SPORTS rats were established from an original line from Wister strain that had shown high level of wheel running activity in our laboratory. Injection of adiponectin into the lateral ventricle of Wister rats and SPORTS rats decreased home cage activity, but no change was observed in the food intake and oxygen consumption. This result indicates the possibility that adiponectin can reduce non-exercise activity thermogenesis (NEAT) and physical activity via the central nervous system. In contrast, injection of adiponectin did not change wheel running activity in SPORTS rats. We produced hypothalamus-destructed model rat using monosodium glutamate (MSG) to elucidate the regulation site of adiponectin. Injection of adiponectin into MSG-treated SPORTS rats did not change amount of home cage activity and food intake, suggesting that adiponectin action on home cage activity was in the hypothalamic area. These results suggest that adiponectin regulates locomotion activity through mediobasal hypothalamus

肥満によって遊離する脂肪細胞由来のDNA断片が脂肪組織の炎症とインスリン抵抗性を引き起こす

Obesity stimulates chronic inflammation in adipose tissue, which is associated with insulin resistance, although the underlying mechanism remains largely unknown. Here we showed that obesity-related adipocyte degeneration causes release of cell-free DNA (cfDNA), which promotes macrophage accumulation in adipose tissue via Toll-like receptor 9 (TLR9), originally known as a sensor of exogenous DNA fragments. Fat-fed obese wild-type mice showed increased release of cfDNA, as determined by the concentrations of single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) in plasma. cfDNA released from degenerated adipocytes promoted monocyte chemoattractant protein-1 (MCP-1) expression in wild-type macrophages, but not in TLR9-deficient (Tlr9−/−) macrophages. Fat-fed Tlr9−/− mice demonstrated reduced macrophage accumulation and inflammation in adipose tissue and better insulin sensitivity compared with wild-type mice, whereas bone marrow reconstitution with wild-type bone marrow restored the attenuation of insulin resistance observed in fat-fed Tlr9−/− mice. Administration of a TLR9 inhibitory oligonucleotide to fat-fed wild-type mice reduced the accumulation of macrophages in adipose tissue and improved insulin resistance. Furthermore, in humans, plasma ssDNA level was significantly higher in patients with computed tomography–determined visceral obesity and was associated with homeostasis model assessment of insulin resistance (HOMA-IR), which is the index of insulin resistance. Our study may provide a novel mechanism for the development of sterile inflammation in adipose tissue and a potential therapeutic target for insulin resistance

グレリンの脳室内投与はラットにおいて回転カゴ運動を減少させる

There is an increasing interest in elucidating the molecular mechanisms by which voluntary exercise is regulated. In this study, we examined how the central nervous system regulates exercise. We used SPORTS rats, which were established in our laboratory as a highly voluntary murine exercise model. SPORTS rats showed lower levels of serum ghrelin compared with those of the parental line of Wistar rats. Intrac-erebroventricular and intraperitoneal injection of ghrelin decreased wheel-running activity in SPORTS rats. In addition, daily injection of the ghrelin inhibitor JMV3002 into the lateral ventricles of Wistar rats increased wheel-running activity. Co-administration of obestatin inhibited ghrelin-induced increases in food intake but did not inhibit ghrelin-induced suppression of voluntary exercise in rats. Growth hormone secretagogue receptor (GHSR) in the hypothalamus and hippocampus of SPORTS rats was not difference that in control rats. We created an arcuate nucleus destruction model by administering monosodium glutamate (MSG) to neonatal SPORTS rats. Injection of ghrelin into MSG-treated rats decreased voluntary exercise but did not increase food intake, suggesting that wheel-running activity is not controlled by the arcuate nucleus neurons that regulate feeding. These results provide new insights into the mechanism by which ghrelin regulates voluntary activity independent of arcuate nucleus neurons