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The opioid system regulates food choice, consumption, and reinforcement processes, especially for palatable meals such as fatty food. β-Endorphin is known as an endogenous opioid peptide produced in neurons of the hypothalamus. In this study, we found that Intralipid (fat emulsion) ingestion increased c-fos expression in β-endorphin neurons. However, intragastric infusion of Intralipid only slightly increased c-fos expression 2h after infusion. Further, dissection of glossopharyngeal nerve, innervating posterior tongue taste buds, partially but significantly decreased the Intralipid-induced c-fos expression. These results indicate that mainly the orosensory stimulation from fat may activate β-endorphin neurons, thereby promoting β-endorphin release., (Copyright © 2012 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.)

Capsaicin, a major ingredient of hot pepper, is considered to exhibit anti-inflammatory properties. Our previous study demonstrated that capsaicin inhibited the production of pro-inflammatory mediators through NF-kappaB inactivation in LPS-stimulated macrophages. In order to further clarify the mechanism underlying the anti-inflammatory action of capsaicin, we investigated whether capsaicin alters PPARgamma activity, which regulates the production of the pro-inflammatory cytokine TNFalpha. Capsaicin significantly inhibited the production of TNFalpha by macrophages in a dose-dependent manner. Simultaneous exposure of the cells to capsaicin and PPARgamma agonist troglitazone or RXR agonist LG100268 resulted in stronger inhibition of TNFalpha production compared to the cells treated with either capsaicin, troglitazone, or LG100268 alone. Luciferase reporter assay revealed that capsaicin induced GAL4/PPARgamma chimera and full length PPARgamma (PPRE) transactivations in a dose-dependent manner. Furthermore, a specific PPARgamma antagonist T0070907 abrogated the inhibitory action of capsaicin on LPS-induced TNFalpha production by RAW 264.7 cells, indicating that capsaicin acts like a ligand for PPARgamma. Our data demonstrate for the first time that the anti-inflammatory action of capsaicin may be mediated by PPARgamma activation in LPS-stimulated RAW 264.7 cells.

Abietic acid is one of the terpenoids, which are multifunctional natural compounds. It has been reported that abietic acid suppresses effects on inflammation. However, the mechanism underlying the anti-inflammatory effects remains unclear. The present work indicates that abietic acid suppresses the protein expression of tumor necrosis factor-alpha and cyclooxygenase 2, which are involved in inflammation, in lipopolysaccharide-stimulated macrophages. Moreover, this effect resembles that of thiazolidinedione, a synthetic peroxisome proliferator-activated receptor-gamma (PPARgamma) ligand. Indeed, abietic acid activates PPARgamma in luciferase reporter assays. The activity of abietic acid induces PPARgamma target gene expression in RAW264.7 macrophages and 3T3-L1 adipocytes. These data indicate that abietic acid is a PPARgamma ligand and that its anti-inflammatory effect is partly due to the activation of PPARgamma in stimulated macrophages. The present work suggests a novel possibility that abietic acid, a naturally occurring compound, can be used not only for anti-inflammation but also for regulating lipid metabolism and atherosclerosis.

Several herbal medicines improve hyperlipidemia, diabetes and cardiovascular diseases. However, the molecular mechanism underlying this improvement has not yet been clarified. In this study, we found that several isoprenols, common components of herbal plants, activate human peroxisome proliferator-activated receptors (PPARs) as determined using the novel GAL4 ligand-binding domain chimera assay system with coactivator coexpression. Farnesol and geranylgeraniol that are typical isoprenols in herbs and fruits activated not only PPARgamma but also PPARalpha as determined using the chimera assay system. These compounds also activated full-length human PPARgamma and PPARalpha in CV1 cells. Moreover, these isoprenols upregulated the expression of some lipid metabolic target genes of PPARgamma and PPARalpha in 3T3-L1 adipocytes and HepG2 hepatocytes, respectively. These results suggest that herbal medicines containing isoprenols with dual action on both PPARgamma and PPARalpha can be of interest for the amelioration of lipid metabolic disorders associated with diabetes.

The putative membrane fatty acid transporter (FAT) protein and its mRNA, originally expressed in adipose tissue, were found in the tongue of rats. Northern blot analysis showed a significant expression of FAT mRNA in the epithelial layer of circumvallate papillae. Immunohistochemical staining revealed that immunoreactivity for FAT is specifically localized in the apical part of taste bud cells, possibly gustatory cells, in the circumvallate papillae.

Monitor peptide (CCK-releasing peptide) mRNA increased on the administration of CCK in rat pancreas and the AR4-2J pancreatic cell line. Subcutaneous injection of CCK into rats at 8 h intervals increased the level of monitor peptide mRNA in the pancreas. Concomitant injection of CCK antagonist CR-1409 strongly decreased it. The monitor peptide mRNA was also increased by CCK in AR4-2J cells and was decreased by the antagonist. These findings suggest that the plasma CCK induced by prolonged intake of a high protein diet may be responsible for the adaptative increase in the monitor peptide as well as exocrine proteases in the pancreas.

A factor which may induce differentiation of intestinal epithelial cell lines in vitro was found in an acid extract of adult rat small intestine. The addition of a partially purified acetic acid extract of rat small intestine to IEC-18 cell culture dishes increased sucrase activity within 48 h. Thymidine incorporation markedly decreased within 24 h. Significant development of microvilli-like structures was observed on the acid extract-treated IEC-18 cells, compared with controls. This activity of rat acid extract was heat-stable and the apparent molecular weight of the factor was 400-800. These findings suggested that the factor may be related to the epithelial differentiation of rat small intestinal crypt cells.