Traditional Japanese medicine Kamikihito ameliorates sucrose preference, chronic inflammation and obesity induced by a high fat diet in middle-aged mice.

The high prevalence of obesity has become a pressing global public health problem and there exists a strong association between increased BMI and mortality at a BMI of 25 kg/m2 or higher. The prevalence of obesity is higher among middle-aged adults than among younger groups and the combination of aging and obesity exacerbate systemic inflammation. Increased inflammatory cytokines such as interleukin 6 and tumor necrosis factor alpha (TNFα) are hallmarks of obesity, and promote the secretion of hepatic C-reactive protein (CRP) which further induces systematic inflammation. The neuropeptide oxytocin has been shown to have anti-obesity and anti-inflammation effects, and also suppress sweet-tasting carbohydrate consumption in mammals. Previously, we have shown that the Japanese herbal medicine Kamikihito (KKT), which is used to treat neuropsychological stress disorders in Japan, functions as an oxytocin receptors agonist. In the present study, we further investigated the effect of KKT on body weight (BW), food intake, inflammation, and sweet preferences in middle-aged obese mice. KKT oral administration for 12 days decreased the expression of pro-inflammatory cytokines in the liver, and the plasma CRP and TNFα levels in obese mice. The effect of KKT administration was found to be different between male and female mice. In the absence of sucrose, KKT administration decreased food intake only in male mice. However, while having access to a 30% sucrose solution, both BW and food intake was decreased by KKT administration in male and female mice; but sucrose intake was decreased in female mice alone. In addition, KKT administration decreased sucrose intake in oxytocin deficient lean mice, but not in the WT lean mice. The present study demonstrates that KKT ameliorates chronic inflammation, which is strongly associated with aging and obesity, and decreases food intake in male mice as well as sucrose intake in female mice; in an oxytocin receptor dependent manner.

Identification of oxytocin expression in human and murine microglia.

BACKGROUND: Oxytocin is a neuropeptide synthesized in the hypothalamus. In addition to its role in parturition and lactation, oxytocin mediates social behavior and pair bonding. The possibility of using oxytocin to modify behavior in neurodevelopmental disorders, such as autism spectrum disorder, is of clinical interest. Microglia are tissue-resident macrophages with roles in neurogenesis, synapse pruning, and immunological mediation of brain homeostasis. Recently, oxytocin was found to attenuate microglial secretion of proinflammatory cytokines, but the source of this oxytocin was not established. This prompted us to investigate whether microglia themselves were the source. METHODS: We examined oxytocin expression in human and murine brain tissue in both sexes using immunohistochemistry. Oxytocin mRNA expression and secretion were examined in isolated murine microglia from wild type and oxytocin-knockout mice. Also, secretion of oxytocin and cytokines was measured in cultured microglia (MG6) stimulated with lipopolysaccharide (LPS). RESULTS: We identified oxytocin expression in microglia of human brain tissue, cultured microglia (MG6), and primary murine microglia. Furthermore, LPS stimulation increased oxytocin mRNA expression in primary murine microglia and MG6 cells, and oxytocin secretion as well. A positive correlation between oxytocin and IL-1ß, IL-10 secretion emerged, respectively. CONCLUSION: This may be the first demonstration of oxytocin expression in microglia. Functionally, oxytocin might regulate inflammatory cytokine release from microglia in a paracrine/autocrine manner.

Surface translocation of Kir2.1 channel induces IL-1ß secretion in microglia.

One of the major properties of microglia is to secrete cytokines as a reaction to stress such as lipopolysaccharide (LPS) application. The mechanism of cytokine secretion from the microglia upon stress through the inflammasome-mediated release process is well studied, and the voltage-gated Kv1.3 channel is known to play an important role in this process. Most previous studies investigated long-term inflammasome-mediated cytokine release (at least over 4 h) and there are only a few studies on the acute reaction (within minutes order) of the microglia to stress and its cytokine secretion capacity. In this study, we found that LPS induced an increase in Kir2.1 current within 15 min after administration but had no effect on voltage-dependent outward currents. Moreover, cytological and western blot analysis revealed that the increase in the Kir2.1 channel current after LPS administration was induced by the translocation of Kir2.1 from the cytoplasm to the cell surface. From an experiment using the inhibitor and trafficking mutation of Kir2.1, an increase in Kir2.1 was found to contribute to the secretion of the inflammatory cytokine, IL-1ß. Although the physiological significance of this acute IL-1ß secretion remains unclear, our present data imply that Kir2.1 translocation functions as a regulator of IL-1ß secretion, and therefore becomes a potential target to control cytokine release from microglia.

Structure based analysis of KATP channel with a DEND syndrome mutation in murine skeletal muscle.

Developmental delay, epilepsy, and neonatal diabetes (DEND) syndrome, the most severe end of neonatal diabetes mellitus, is caused by mutation in the ATP-sensitive potassium (KATP) channel. In addition to diabetes, DEND patients present muscle weakness as one of the symptoms, and although the muscle weakness is considered to originate in the brain, the pathological effects of mutated KATP channels in skeletal muscle remain elusive. Here, we describe the local effects of the KATP channel on muscle by expressing the mutation present in the KATP channels of the DEND syndrome in the murine skeletal muscle cell line C2C12 in combination with computer simulation. The present study revealed that the DEND mutation can lead to a hyperpolarized state of the muscle cell membrane, and molecular dynamics simulations based on a recently reported high-resolution structure provide an explanation as to why the mutation reduces ATP sensitivity and reveal the changes in the local interactions between ATP molecules and the channel.