Polyunsaturated fatty acid saturation by gut lactic acid bacteria affecting host lipid composition

In the representative gut bacterium Lactobacillus plantarum, we identified genes encoding the enzymes involved in a saturation metabolism of polyunsaturated fatty acids and revealed in detail the metabolic pathway that generates hydroxy fatty acids, oxo fatty acids, conjugated fatty acids, and partially saturated trans-fatty acids as intermediates. Furthermore, we observed these intermediates, especially hydroxy fatty acids, in host organs. Levels of hydroxy fatty acids were much higher in specific pathogen-free mice than in germ-free mice, indicating that these fatty acids are generated through polyunsaturated fatty acids metabolism of gastrointestinal microorganisms. These findings suggested that lipid metabolism by gastrointestinal microbes affects the health of the host by modifying fatty acid composition.Dietary fats are metabolized not only by humans but also by microbes in our gastrointestinal tracts. Microorganisms in the gastrointestinal tract interact with their host in many ways and contribute significantly to the maintenance of host health (1). Lipid metabolism by gastrointestinal microbes generates multiple fatty acid species, such as conjugated fatty acids and trans-fatty acids, that can affect host lipid metabolism (2). However, lipid metabolism by gastrointestinal microbes has not been explored in detail. Saturation metabolism of polyunsaturated fatty acids, a representative mode of lipid metabolism by gastrointestinal microbes, is a detoxifying metabolism of anaerobic bacteria, such as lactic acid bacteria, that reside in colon and intestine. This process transforms growth-inhibiting free polyunsaturated fatty acids into less toxic free saturated fatty acids (3). This saturation metabolism generates characteristic fatty acids (e.g., conjugated fatty acids and trans-fatty acids, which are well known to present in ruminant-derived foods and exert various physiological activities).“Conjugated fatty acid” is a collective term for positional and geometric isomers of fatty acids with conjugated double bonds. In particular, conjugated linoleic acids (CLAs), such as cis-9,trans-11-CLA and trans-10,cis-12-CLA, reduce carcinogenesis (4), atherosclerosis (5), and body fat (6). With regard to lipid metabolism, CLA is a potent peroxisome proliferator-activated receptor (PPAR)α agonist (7), and treatment with CLA increases the catabolism of lipids in the liver of rodents (8). Based on these findings, CLA is now commercialized as a functional food for control of body weight, especially in the United States and European countries.On the other hand, consumption of trans-fatty acids increases the risk of coronary heart disease by increasing LDL and reducing HDL cholesterol levels (9). Consequently, trans-fatty acids are considered to be harmful for health, and nutritional authorities have recommended that consumption of trans-fatty acids be reduced to trace amounts (10). Therefore, it is important to control fatty acid saturation processes that generate these fatty acids (11); however, the precise metabolic pathway and enzymes involved have not been clearly identified.Our analyses on conjugated fatty acid synthesis in representative gut bacteria, the lactic acid bacteria (12–15), demonstrated that Lactobacillus plantarum AKU 1009a (AKU Culture Collection, Faculty of Agriculture, Kyoto University) can transform the cis-9,cis-12 diene structure of C18 fatty acids such as linoleic acid, α-linolenic acid, and γ-linolenic acid into the conjugated diene structures cis-9,trans-11 and trans-9,trans-11 (16–21). In addition, this strain can saturate these conjugated dienes into the trans-10 monoene. Our subsequent metabolic analysis indicated that 10-hydroxy-12-octadecenoic acid is an intermediate of CLA synthesis, and further investigations of hydroxy fatty acid metabolism by lactic acid bacteria revealed that CLA is produced from hydroxy fatty acids such as ricinoleic acid in castor oil (22–25). In cell-free extracts from this strain, we identified the enzymes involved in CLA synthesis (26). Three enzymes, CLA-HY, CLA-DH, and CLA-DC, are necessary for synthesis of conjugated fatty acids such as CLA. Only the combined action of these three enzymes can generate CLA from linoleic acid, with 10-hydroxy-cis-12-octadecenoic acid arising as an intermediate (Fig. 1B, 3). The reactions catalyzed by each enzyme, however, were not revealed in those studies. Through genomic analysis in L. plantarum WCFS1, we found that cla-dh (GenBank accession no. {"type":"entrez-nucleotide","attrs":{"text":"NC_004567","term_id":"380031102","term_text":"NC_004567"}}NC_004567; region: 59613-60473) and cla-dc (GenBank accession no. {"type":"entrez-nucleotide","attrs":{"text":"NC_004567","term_id":"380031102","term_text":"NC_004567"}}NC_004567; region: 60505-61350) are located in a cluster with another gene, cla-er (GenBank accession no. {"type":"entrez-nucleotide","attrs":{"text":"NC_004567","term_id":"380031102","term_text":"NC_004567"}}NC_004567; region: 61378-62031) (Fig. 1A). In light of this, we tried to identify the function of the gene product (CLA-ER) together with those of CLA-HY, CLA-DH, and CLA-DC.Open in a separate windowFig. 1.Gene clusters for polyunsaturated fatty acid metabolism and GC chromatograms. (A) Gene clusters for fatty acid metabolic enzymes in L. plantarum. (B) GC chromatograms of substrate (1); reaction with CLA-HY (2); reaction with CLA-HY, CLA-DH, and CLA-DC together with FAD and NADH (3); and reaction with CLA-HY, CLA-DH, CLA-DC, and CLA-ER together with FAD and NADH (4). I.S., internal standard.     

Cytokine production by endothelial cells infected with human T cell lymphotropic virus type I.

OBJECTIVE: To investigate the ability of human T cell lymphotropic virus type I (HTLV-I) to infect endothelial cells and induce cytokine production by these cells. METHODS: Human umbilical vein endothelial cells (HUVEC) were cocultured with HTLV-I infected T cell line (MT-2 cells) or uninfected T cell line (CEM cells). RESULTS: Following coculture with MT-2 cells, endothelial cells expressed HTLV-I specific core antigens. Endothelial cells cocultured with MT-2 cells produced significant amounts of several cytokines, including interleukin (IL)-1 alpha, IL-6, granulocyte colony stimulating factor (G-CSF), and granulocyte/macrophage colony stimulating factor (GM-CSF), compared with endothelial cells cocultured with CEM cells. Coculturing of endothelial cells with MT-2 and CEM cells failed to produce detectable amounts of IL-1 beta and tumour necrosis factor alpha (TNF-alpha). The production of cytokines by endothelial cells cocultured with MT-2 cells was more persistent than that by endothelial cells cocultured with CEM cells after several passages. Furthermore, the production was blocked by cocultivation of endothelial cells and MT-2 cells using the Millicell system. Finally, after cocultivation of endothelial cells and MT-2 cells, endothelial cells positive for HTLV-I antigen were stained by anti-GM-CSF antibody. CONCLUSIONS: HTLV-I can infect endothelial cells, resulting in their active production of several cytokines, such as IL-1 alpha, IL-6, G-CSF, and GM-CSF. These findings strongly suggest that the excess production of these cytokines by HTLV-I infected endothelial cells may be involved in the pathogenesis of HTLV-I associated inflammatory diseases.     

Involvement of maxi-KCa channel activation in atrial natriuretic peptide-induced vasorelaxation

Large conductance, voltage- and Ca²⁺-sensitive K⁺ (maxi-K_Ca) channels play an important role in the regulation of vascular smooth muscle excitability and contractility. The activity of maxi-K_Ca channels is modified by a variety of intracellular messengers including cGMP, as well as by voltage and Ca²⁺. In the present study, we investigated the functional relevance of maxi-K_Ca channels in atrial natriuretic peptide (ANP)-mediated vasorelaxation in the isolated rat mesenteric artery. ANP produced concentration-dependent relaxation in the de-endothelialized rat mesenteric artery . Iberiotoxin, a specific blocker of maxi-K_Ca channels, greatly attenuated the ANP-induced vasorelaxation. Similarly, a large portion of the vascular relaxation induced by 8-Bromo-cGMP, a membrane permeable analogue of cGMP, was inhibited by iberiotoxin. These results indicate that activation of maxi-K_Ca channels contributes substantially to the vascular relaxation produced by ANP in the rat mesenteric artery. Intracellular cGMP, increased by ANP, and the subsequent activation of cGMP-dependent protein kinase (PKG) may play a central role in the activation of maxi-K_Ca channels in the ANP-produced vascular relaxation. Received: 3 February 1998 / Accepted: 12 March 1998     

Brain activation of patients with obsessive-compulsive disorder during neuropsychological and symptom provocation tasks before and after symptom improvement: a functional magnetic resonance imaging study.

BACKGROUND: Functional neuroimaging studies have implicated hyperactivity of the frontal cortex in obsessive-compulsive disorder (OCD); however, relationships between abnormal brain activity, clinical improvement, and neuropsychological function have not been clarified in OCD. To clarify the pathophysiology of this disorder, regional changes in brain function were examined during administration of cognitive and symptom provocation tasks in patients with OCD before and after treatment. METHODS: Ten outpatients with OCD participated in the study. Functional magnetic resonance imaging (fMRI) was performed before and after treatment. Stroop and symptom provocation tasks were administered during fMRI. Each patient was randomly allocated to receive either pharmacotherapy with fluvoxamine 200 mg/day (n = 4) or behavior therapy (n = 6) for 12 weeks. RESULTS: After 12-week treatment, mean (+/- SD) total score on the Yale-Brown Obsessive-Compulsive Scale decreased from 29.00 +/- 3.59 to 14.60 +/- 9.22, representing symptomatic improvement from moderate to mild. After symptom improvement, symptom provocation-related activation in the orbitofrontal, dorsolateral-prefrontal, and anterior cingulate cortices decreased. Conversely, Stroop task-related activation in the parietal cortex and cerebellum increased. CONCLUSIONS: After improvement of OCD with either fluvoxamine or behavioral therapy, hyperactivation of the frontal lobe related to a symptom-provocative state decreases, and posterior brain activity related to action-monitoring function increases.     

Islet cell antibodies in patients with autoimmune thyroid disease

Islet cell antibodies (ICAs) were assayed in 316 patients with autoimmune thyroid disease (AITD; 190 with Graves' disease, 126 with Hashimoto's thyroiditis), 53 patients with insulin-dependent diabetes mellitus (IDDM), and 144 healthy control subjects. ICAs were measured by an immunohistochemical method with peroxidase-labeled protein A and human pancreatic tissues. The prevalence of ICAs in patients with AITD was 7.6% (24 of 316), whereas the prevalence in control subjects was 0.7% (1 of 144). Among 24 ICA+ patients, 20 (83%) had IDDM. In these 20 patients, the duration of diabetes from clinical onset was 5.4 +/- 5.1 yr. ICAs in patients with IDDM alone were positive in 90.9% at 1 yr and 7.7% at 5 yr after the onset of diabetes. These data have shown that most ICA+ patients with AITD have IDDM and that the prevalence of ICAs in patients with AITD in Japanese is as high as that found among whites, whereas the incidence of IDDM in Japanese is approximately one-thirtieth or one-fiftieth of that in whites.