L-Ornithine intake affects sympathetic nerve outflows and reduces body weight and food intake in rats.

Ingesting the amino acid l-ornithine effectively improves lipid metabolism in humans, although it is unknown whether it affects the activities of autonomic nerves that supply the peripheral organs related to lipid metabolism, such as adipose tissues. Thus, we investigated the effects of l-ornithine ingestion on autonomic nerves that innervate adipose tissues and the feeding behaviors of rats. Intragastric injection of l-ornithine (2.5%) in urethane-anesthetized rats activated sympathetic nerve activity to white adipose tissue (WAT-SNA), and stimulated sympathetic nerve activity to brown adipose tissue (BAT-SNA). In addition, WAT-SNA responses to l-ornithine were abolished in rats with ablated abdominal vagal nerves. l-ornithine ingestion for 9 weeks also significantly reduced rats' body weight, food intake, and abdominal fat weight. Proopiomelanocortin (POMC) levels in the hypothalamus and uncoupling protein 1 (UCP1) levels in brown adipose tissue were significantly increased in rats that ingested 2.5% l-ornithine for 9 weeks. These results suggested that ingested l-ornithine was taken up in the gastrointestinal organs and stimulated afferent vagal nerves and activated the central nervous system. Subsequently, increased hypothalamic POMC activated sympathetic neurotransmission to adipose tissues and accelerated energy expenditure.

Injection of Lactobacillus casei strain Shirota affects autonomic nerve activities in a tissue-specific manner, and regulates glucose and lipid metabolism in rats.

AIMS/INTRODUCTION: Previously, it was observed that long-term ingestion of a probiotic strain Lactobacillus casei Shirota (LcS) ameliorates insulin resistance and glucose intolerance in rats fed a high-fat diet. In the present study, we examined its possible role in the autonomic nervous system during LcS-induced modulations in glucose and lipid metabolism or cardiovascular functions. MATERIALS AND METHODS: The present study examined the effects of intragastric (IG) LcS injection on autonomic nerve tones in anesthetized rats by electrophysiological method. RESULTS: We found that an IG injection of LcS suppressed neural activity of sympathetic nerves supplying the white adipose tissue of urethane-anesthetized rats in a dose-dependent manner, whereas sympathetic nerve outflow to brown adipose tissue was not affected by the IG LcS injection. Furthermore, the IG LcS injection reduced efferent sympathetic nerve outflow to the adrenal gland and liver, but did not alter gastric vagal nerve activity, renal sympathetic nerve activity, as well as mean arterial pressure. To test the involvement of afferent vagal nerves and the abdominal organs, we examined the adrenal sympathetic response to an LcS injection in rats with ablated afferent vagal nerves, and found that the adrenal sympathetic nerve response to LcS was inhibited in vagotomized rats. In addition, we found that oral ingestion of LcS attenuated the hyperglycemic response to glucose loading and blood glycerol levels in conscious rats. CONCLUSIONS: Our data suggest that LcS might affect tissue-specific autonomic nerves through the afferent vagal nerve pathway to modulate glucose and lipid metabolism.

Soy isoflavone affects the autonomic nervous system in a tissue-specific manner in anesthetized rats.

We examined and compared the effects of taste stimulation by soy saponin as well as soy isoflavone and intragastric (IG) injection of both on the autonomic nerve activities and feeding behavior in rats. We found that taste stimulation by soy saponin or soy isoflavone-rich solution (SIRS) did not affect the activity of the sympathetic nerve supplying the adrenal gland in urethane-anesthetized rats; however, IG injection of SIRS, but not soy saponin, stimulated the adrenal sympathetic nerve activity (ASNA) in a dose-dependent manner. Moreover, IG injection of SIRS significantly suppressed the activity of the vagus nerve innervating the stomach, whereas sympathetic nerve outflows to brown or white adipose tissue were not affected by IG injection of SIRS. To test the involvement of the afferent autonomic nerve in the abdominal organs for regulation of the efferent ASNA by SIRS, we examined the response of the adrenal sympathetic innervation to SIRS injection in rats with ablated afferent vagus or afferent sympathetic nerves. The activating effect of SIRS on the ASNA was inhibited in sympathectomized rats but not in vagotomized rats. Thus, our data suggest that soy isoflavone might affect tissue-specific autonomic nerves through the afferent sympathetic nerve pathway.