Enhanced microalgal lipid production with media engineering of potassium nitrate as a nitrogen source.

Algal biofuels are far from a commercial reality due to the technical challenges associated with their growth and lipid extraction procedures. In this study, we investigated the effect of 4 different media and 5 different nitrogen sources at 5 levels on the growth, biomass and lipid productivity of Scenedesmus sp and Chlorella sp The hypothesis was that a nitrogen source can be identified that provides enough stress to accumulate lipids without compromising significantly on biomass and lipid productivity. A maximum specific growth rate and doubling per day have been observed with algal species using modified BG-11 medium. Among the tested nitrogen sources, 2.5 mM potassium nitrate as a nitrogen constituent of modified BG-11 medium resulted in higher lipid content and productivity in the case of S. dimorphus (29.15%, 15.449 mg L-1day-1). Another noteworthy outcome of the present study lies in the usage of a smaller amount of the nitrogen source, i.e., 2.5 mM, which is found to be 7 times less than the standard BG11 media (17.60 mM sodium nitrate).

G protein-coupled receptors: signalling and regulation by lipid agonists for improved glucose homoeostasis.

G protein-coupled receptors (GPCRs) play a pivotal role in cell signalling, controlling many processes such as immunity, growth, cellular differentiation, neurological pathways and hormone secretions. Fatty acid agonists are increasingly recognised as having a key role in the regulation of glucose homoeostasis via stimulation of islet and gastrointestinal GPCRs. Downstream cell signalling results in modulation of the biosynthesis, secretion, proliferation and anti-apoptotic pathways of islet and enteroendocrine cells. GPR40 and GPR120 are activated by long-chain fatty acids (>C12) with both receptors coupling to the Gαq subunit that activates the Ca(2+)-dependent pathway. GPR41 and GPR43 are stimulated by short-chain fatty acids (C2-C5), and activation results in binding to Gαi that inhibits the adenylyl cyclase pathway attenuating cAMP production. In addition, GPR43 also couples to the Gαq subunit augmenting intracellular Ca(2+) and activating phospholipase C. GPR55 is specific for cannabinoid endogenous agonists (endocannabinoids) and non-cannabinoid fatty acids, which couples to Gα12/13 and Gαq proteins, leading to enhancing intracellular Ca(2+), extracellular signal-regulated kinase 1/2 (ERK) phosphorylation and Rho kinase. GPR119 is activated by fatty acid ethanolamides and binds to Gαs utilising the adenylate cyclase pathway, which is dependent upon protein kinase A. Current research indicates that GPCR therapies may be approved for clinical use in the near future. This review focuses on the recent advances in preclinical diabetes research in the signalling and regulation of GPCRs on islet and enteroendocrine cells involved in glucose homoeostasis.

Novel phytoandrogens and lipidic augmenters from Eucommia ulmoides.

BACKGROUND: Plants containing compounds such as the isoflavonoids, with female hormone-like effects that bind to human estrogen receptors, are known. But none has been previously shown to have corresponding male hormone-like effects that interact with the human androgen receptor. Here, we report that the tree bark (cortex) of the Gutta-Percha tree Eucommia ulmoides possesses bimodal phytoandrogenic and hormone potentiating effects by lipidic components. METHODS: The extracts of E. ulmoides were tested using in-vitro reporter gene bioassays and in-vivo animal studies. Key compounds responsible for the steroidogenic effects were isolated and identified using solid phase extraction (SPE), high performance liquid chromatography (HPLC), thin layer chromatography (TLC), gas chromatography-mass spectroscopy (GC-MS), electron spray ionisation-mass spectroscopy (ESI-MS) and nuclear magnetic resonance (NMR). RESULTS: The following bioactivities of E. ulmoides were found: (1) a phenomenal tripartite synergism exists between the sex steroid receptors (androgen and estrogen receptors), their cognate steroidal ligands and lipidic augmenters isolated from E. ulmoides, (2) phytoandrogenic activity of E. ulmoides was mediated by plant triterpenoids binding cognately to the androgen receptor (AR) ligand binding domain. CONCLUSION: In addition to well-known phytoestrogens, the existence of phytoandrogens is reported in this study. Furthermore, a form of tripartite synergism between sex steroid receptors, sex hormones and plant-derived lipids is described for the first time. This could have contrasting clinical applications for hypogonadal- and hyperlipidaemic-related disorders.

Tumor cell invasion of collagen matrices requires coordinate lipid agonist-induced G-protein and membrane-type matrix metalloproteinase-1-dependent signaling.

BACKGROUND: Lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P) are bioactive lipid signaling molecules implicated in tumor dissemination. Membrane-type matrix metalloproteinase 1 (MT1-MMP) is a membrane-tethered collagenase thought to be involved in tumor invasion via extracellular matrix degradation. In this study, we investigated the molecular requirements for LPA- and S1P-regulated tumor cell migration in two dimensions (2D) and invasion of three-dimensional (3D) collagen matrices and, in particular, evaluated the role of MT1-MMP in this process. RESULTS: LPA stimulated while S1P inhibited migration of most tumor lines in Boyden chamber assays. Conversely, HT1080 fibrosarcoma cells migrated in response to both lipids. HT1080 cells also markedly invaded 3D collagen matrices (approximatly 700 microm over 48 hours) in response to either lipid. siRNA targeting of LPA1 and Rac1, or S1P1, Rac1, and Cdc42 specifically inhibited LPA- or S1P-induced HT1080 invasion, respectively. Analysis of LPA-induced HT1080 motility on 2D substrates vs. 3D matrices revealed that synthetic MMP inhibitors markedly reduced the distance (approximately 125 microm vs. approximately 45 microm) and velocity of invasion (approximately 0.09 microm/min vs. approximately 0.03 microm/min) only when cells navigated 3D matrices signifying a role for MMPs exclusively in invasion. Additionally, tissue inhibitors of metalloproteinases (TIMPs)-2, -3, and -4, but not TIMP-1, blocked lipid agonist-induced invasion indicating a role for membrane-type (MT)-MMPs. Furthermore, MT1-MMP expression in several tumor lines directly correlated with LPA-induced invasion. HEK293s, which neither express MT1-MMP nor invade in the presence of LPA, were transfected with MT1-MMP cDNA, and subsequently invaded in response to LPA. When HT1080 cells were seeded on top of or within collagen matrices, siRNA targeting of MT1-MMP, but not other MMPs, inhibited lipid agonist-induced invasion establishing a requisite role for MT1-MMP in this process. CONCLUSION: LPA is a fundamental regulator of MT1-MMP-dependent tumor cell invasion of 3D collagen matrices. In contrast, S1P appears to act as an inhibitory stimulus in most cases, while stimulating only select tumor lines. MT1-MMP is required only when tumor cells navigate 3D barriers and not when cells migrate on 2D substrata. We demonstrate that tumor cells require coordinate regulation of LPA/S1P receptors and Rho GTPases to migrate, and additionally, require MT1-MMP in order to invade collagen matrices during neoplastic progression.

Effects of differently oxidized LDL on the expression of pro-inflammatory molecules in human monocytes in vitro.

The oxidation of low-density lipoprotein (LDL) is thought to be a major contributor to the development of atherosclerosis and considerable evidence has accumulated showing that oxidized LDL (ox LDL) induces cell damage and pro-atherogenic events. However, evidence that oxidized LDL directly causes atherosclerosis is lacking. We studied whether native and enzymatically or chemically ox LDL at concentrations of 5 and 100 microg/mL is cytotoxic to or promotes pro-atherogenic activation of human primary monocytes in culture. Both types of ox LDL (100 microg/mL), but not native LDL added to monocytes for 24 h significantly diminish DNA synthesis and increase cell death. In addition, both preparations of ox LDL inhibit cytokine and metalloproteinase production, diminish cellular oxygen consumption and induce PPAR gamma expression. Enzymatically ox LDL, but not LDL oxidized by copper sulfate, also increases the monocyte metabolic rate and induces intracellular lipid accumulation. Low concentrations of either preparation of oxidized and native LDL did not show significant effects on all parameters measured. These data establish a direct link between ox LDL concentration and cytotoxicity and suggest that oxidation by copper of the lipid moiety in LDL and of the protein moiety by enzyme creates ox LDL, which can damage monocytes without release of pro-inflammatory molecular species. In contrast to native and enzymatically ox LDL, copper ox LDL does not induce intracellular lipid accumulation. Differently oxidized LDL molecules may exert distinct effects in lesion development in atherosclerosis.

Possible involvement of protein kinase C in the induction of adipose differentiation-related protein by Sterol ester in RAW 264.7 macrophages.

The accumulation of lipid droplets in macrophages contributes to the formation of foam cells, an early event in atherosclerosis. It is, therefore, important to elucidate the mechanisms by which lipid droplets accumulate and are utilized. Sterol ester (SE)-laden RAW 264.7 macrophages accumulated lipid droplets in a time-dependent manner up to 16 h, which was enhanced by cotreatment with 0.1 microM phorbol 12-myristate 13-acetate (PMA). Inhibition of protein kinase C (PKC) activity by cotreatment with 0.3 microM calphostin C CAL for 16 h resulted in coalescence of small lipid droplets into large ones and increased accumulation of lipid droplets, although to a lesser extent than after PMA cotreatment. Immunostaining for adipose differentiation-related protein (ADRP) revealed a fluorescent rim at the surface of each medium to large lipid droplet. ADRP appearance correlated with lipid droplet accumulation and was regulated by PMA in a time-dependent manner. Induction of ADRP expression by PMA or CAL required SE, since ADRP levels in PMA- or CAL-treated non-SE-laden macrophages were comparable to those in untreated cells. Removal of SE from the incubation medium resulted in the concomitant dissolution of lipid droplets and down-regulation of ADRP. In conclusion, the above results suggest that ADRP may be an important protein in the regulation of lipid droplet metabolism in lipid-laden macrophages and that this regulation may be mediated by PKC activity.