Inhibition of smooth muscle cell proliferation by adiponectin requires proteolytic conversion to its globular form.

Accelerated atherosclerosis is the primary cardiovascular manifestation of diabetes and correlates inversely with levels of circulating adiponectin, an anti-atherosclerotic adipokine that declines in diabetes. We therefore initiated a study to examine the mechanisms by which adiponectin, a hormone released from adipose tissue, influences the proliferation of vascular smooth muscle cells (SMCs). Addition of adiponectin to quiescent porcine coronary artery SMCs increased both protein and DNA synthesis and concurrently activated ERK1/2 and Akt. By contrast, globular adiponectin, a truncated form of this protein, exhibited anti-mitogenic properties as indicated by the inhibition of protein and DNA synthesis in SMCs stimulated with platelet-derived growth factor (PDGF). Whereas globular adiponectin did not stimulate growth-related signal transduction pathways, it was able to block the PDGF-dependent phosphorylation of eukaryotic elongation factor 2 kinase, a regulator of protein synthesis. Proteolysis of adiponectin with trypsin, which produces globular adiponectin, reversed the growth-stimulating actions of the undigested protein. As the existence of globular adiponectin remains controversial, western blotting was used to establish its presence in rat serum. We found that globular adiponectin was detectable in rat serum, but this result was not obtained with all antibodies. The contrasting properties of adiponectin and its globular form with respect to SMC proliferation suggest that protection against atherosclerosis may therefore be mediated, in part, by the level of globular adiponectin.

Biological response of hepatomas to an extract of Fagopyrum esculentum M. (buckwheat) is not mediated by inositols or rutin.

Buckwheat contains d-chiro-inositol (D-CI) and myo-inositol (MI), possible insulin-mimetic compounds; thus, this study investigated the insulin-mimetic activities of a buckwheat concentrate (BWC), D-CI, and MI on insulin signal transduction pathways and glucose uptake with H4IIE rat hepatoma cells. BWC stimulated phosphorylation of p42/44 extracellular-related kinase (p42/44 ERK) and its downstream target, p70(S6K), on Thr(421). In contrast, D-CI, MI, rutin, or its agylcone form, quercetin, did not activate these signal transduction proteins. Phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK), another target of insulin, was also up-regulated upon BWC treatment. The effects of BWC on glucose uptake were subsequently investigated using H4IIE cells. Insulin and D-CI stimulated glucose uptake, whereas BWC inhibited basal and insulin-stimulated glucose uptake. Although results from this work suggest that BWC has insulin-mimetic effects on select protein phosphorylation events in H4IIE cells, D-CI and MI were not the active components responsible for the observed effects. The inhibition of glucose uptake by BWC suggests that buckwheat may affect hepatic glucose metabolism, possibly by inhibiting glucose flux. Furthermore, the fact that D-CI and MI stimulated glucose uptake in H4IIE cells suggests that other compounds are responsible for inhibition of glucose uptake by BWC.

Seasonal variation and bioactivity in the leaf oil of Liriodendron tulipifera growing in Huntsville, Alabama.

The seasonal variation in the chemical composition of the leaf essential oil of Liriodendron tulipifera has been analyzed by GC-MS. Two individual trees were sampled five times during the course of the growing season. Twenty components were identified in the leaf oils, which were dominated by sesquiterpene hydrocarbons, principally germacrene D and beta-elemene, in the early part of the season (42-44% and 18-23%, respectively,) but monoterpene hydrocarbons, largely (Z)-beta-ocimene, dominated the later season leaf oils (40-60%). The leaf oils exhibited in-vitro antibacterial activity against Bacillus cereus and Staphylococcus aureus as well as cytotoxic activity on MDA-MB-231 and Hs 578T human breast tumor cells.

Essential oil compositions and cytotoxic activities of Dendropanax capillaris, Oreopanax nubigenus, and Schefflera rodrigueziana from Monteverde, Costa Rica.

The leaf essential oils of Dendropanax capillaris, Oreopanax nubigenus and Schefflera rodrigueziana (Araliaceae) were isolated by hydrodistillation and analyzed by GC-MS. The leaf oil of Dendropanax capillaris was composed of only four compounds, beta-pinene (25.3%), 6-3-carene (44.7%), daucene (17.1%), and dauca-5,8-diene (12.9%). Oreopanax nubigenus leaf oil was dominated by the sesquiterpene hydrocarbons germacrene D (70.1%) and beta-caryophyllene (11.8%), while Schefflera rodrigueziana leaf oil was made up entirely of sesquiterpene hydrocarbons, mostly germacrene D (27.6%), beta-cubebene (27.2%), beta-caryophyllene (12.2%), beta-cubebene (11.1%), and alpha-copaene (10.8%). Both O. nubigenus and S. rodrigueziana leaf oils showed notable in-vitro cytotoxicity on MDA-MB-231 cells, which may be attributable to the relatively high concentrations of germacrene D and beta-caryophyllene in those oils.