12-hydroxy-5-8-10-14-eicosatetraenoic-acid and Body-Weight

Diabetes is associated with increased production of 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE]. The mechanisms involved in this process remain unclear. We hypothesized that hyperglycemia and angiotensin II (ANG II) regulate renal 12(S)-HETE production via a balance between angiotensin AT(1) and AT(2) receptors activities. Using a microdialysis technique, renal interstitial fluid (RIF) levels of ANG II and 12(S)-HETE were monitored in normal control and streptozotocin-induced diabetic rats at baseline and then weekly thereafter for 12 wk. In a second group of normal and diabetic rats, 3 wk after development of diabetes, we monitored RIF 12(S)-HETE levels in response to acute AT(1) receptor blockade with valsartan or AT(2) receptor blockade with PD123319 individually or combined. Two weeks after induction of diabetes there was a 404% increase in ANG II (P < 0.05), a 149% increase in 12S-HETE (P < 0.05), and a 649% increase in urinary albumin excretion (P < 0.05). These levels remained elevated throughout the study. PD123319 given alone had no effect on 12(S)-HETE. Valsartan decreased 12(S)-HETE by 61.6% (P < 0.0001), a response that was abrogated when PD123319 was given with valsartan. These data demonstrate that hyperglycemia increases renal ANG II and 12(S)-HETE levels. The increase in 12(S)-HETE is mediated via AT(1) receptor. The attenuation of the effects of AT(1) receptor blockade by PD123319 suggests that AT(2) receptor contributes to the downregulation of renal 12(S)-HETE production.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Angiotensin II; Angiotensin II Type 1 Receptor Blockers; Angiotensin II Type 2 Receptor Blockers; Animals; Blood Glucose; Blood Pressure; Body Weight; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Hypoglycemic Agents; Imidazoles; In Vitro Techniques; Insulin; Kidney; Male; Microdialysis; Pyridines; Rats; Rats, Sprague-Dawley; Receptor, Angiotensin, Type 1; Receptor, Angiotensin, Type 2; Tetrazoles; Valine; Valsartan

Human esophageal adenocarcinoma (EAC) develops in a sequence from gastroesophageal reflux disease (GERD), columnar-lined esophagus (CLE), dysplasia, and eventually to EAC. We established a rat surgical EAC model with esophagogastroduodenal anastomosis (EGDA) to mimic the staged process of esophageal adenocarcinogenesis. Profiling of the AA metabolites with mass spectrometry showed that prostaglandin E2 (PGE2), leukotriene B4 (LTB4), 15-hydroeicosatetraenoic acid (HETE), 12-HETE, 8-HETE and 5-HETE all increased at the esophagoduodenal junction after EGDA as compared with the proximal esophagus, with PGE2 as the major metabolite. Consistent with this profile, cyclooxygenase 2 (Cox2) was overexpressed in the basal cell layer of esophageal squamous epithelium, CLE cells and EAC tumor cells of the EGDA rats, as compared with the normal esophageal epithelium. Sulindac (a Cox inhibitor), nordihydroguaiaretic acid (NDGA, a lipoxygenase inhibitor) and alpha-difluoromethylornithine (DFMO, an ornithine decarboxylase inhibitor) were tested for their possible inhibitory actions against the formation of EAC in the rat EGDA model. In a short-term study (for 4 weeks after surgery), dietary administration of both sulindac (300 and 600 p.p.m.) and NDGA (100 p.p.m.) effectively reduced the EGDA-induced inflammation. In a long-term chemoprevention study (for 40 weeks after surgery), 300 p.p.m. sulindac, alone or in combination with 100 p.p.m. NDGA or 0.5% DFMO, decreased the tumor incidence from 57.7 to 26.9%, or 16.7 or 20%, respectively (P < 0.05). NDGA alone (100 and 200 p.p.m.) slightly decreased the tumor incidence to 52.4 and 37%, respectively, although the difference was not statistically significant. DFMO alone did not show significant effects on tumor incidence. Inhibition of tumor formation by sulindac was correlated with lowered levels of PGE2. In conclusion, sulindac exerted its chemopreventive effect against the formation of EAC in the rat EGDA model possibly through its inhibition of Cox.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Animals; Arachidonic Acid; Body Weight; Cyclooxygenase 2; Dinoprostone; Eflornithine; Esophageal Neoplasms; Esophagus; Gas Chromatography-Mass Spectrometry; Hydroxyeicosatetraenoic Acids; Immunoenzyme Techniques; In Situ Hybridization; Inflammation; Isoenzymes; Leukotriene B4; Male; Masoprocol; Mass Spectrometry; Neoplasms; Prostaglandin-Endoperoxide Synthases; Rats; Rats, Sprague-Dawley; Sulindac; Time Factors

A metabolite of arachidonic acid, 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE), which can be formed either in the 12-S or 12-R configuration, has a diversity of biological actions and is generated by a number of tissues including the renal glomerulus and the vasculature. As the two isomers have been shown to differ in their effects on epithelial transport mechanisms and vascular responsiveness, we studied their direct effects on the rat isolated kidney, perfused for four consecutive 15-min clearance periods at a pressure of 90 mm Hg with a modified Krebs' buffer containing oncotic agents. At a dose of 20 nmol, both 12(S)- and 12(R)-HETE doubled urine volume (P less than .05) and sodium and potassium excretion rate in the first, postinjection clearance period. The effects of 12(R)-HETE were sustained during all three post-treatment clearance periods, whereas those of 12(S)-HETE were short-lived, excretion rates being similar to control values by the second post-treatment clearance period. At a higher dose of 40 nmol, 12(R)-HETE significantly reduced the usual rate of decline in glomerular filtration rate, characteristic of the rat isolated kidney, and caused an even greater initial increase in urine volume and sodium excretion rate than that achieved with 20 nmol. Renin concentration in the venous effluent was reduced immediately by 12(R)- and 12(S)-HETE (P less than .01), to approximately half of the control value. Again the response to the (R)-isomer was more prolonged. Thus, a 12-HETE of glomerular origin may alter renal function through direct and indirect tubular and hemodynamic effects.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Animals; Body Weight; Electrolytes; Glomerular Filtration Rate; Hydroxyeicosatetraenoic Acids; Kidney; Male; Organ Size; Perfusion; Rats; Rats, Inbred Strains; Renin; Stereoisomerism; Vascular Resistance

The omega 3 class of polyunsaturated fatty acids, particularly eicosapentaenoic acid (EPA, 20:5), has been shown to alter the patterns of arachidonic acid (20:4) metabolism in both in vitro and in vivo systems. To examine further the role of arachidonic acid conversion to prostaglandins (PG) in hypercalcemic mice bearing the PG-producing HSDM1 fibrosarcoma, we have performed experiments in which control and tumor-bearing animals were fed diets either low (0.1-0.2% of total fatty acid) or high (17%) in EPA. In all five experiments performed, tumor-bearing mice eating control diets had markedly elevated (average sixfold above control) plasma concentrations of 13,14-dihydro-15-keto-PGE2 (PGE2-M), while in mice bearing HSDM1 tumors and eating the EPA-enriched menhaden oil diet, the elevation was reduced to only twice control values. The increase in plasma calcium concentration (approximately 2.5 mg/dl above control) in tumor-bearing animals was also reduced significantly (P less than 0.05) to only 1.3 mg/dl above control in mice eating the diet enriched in EPA. Plasma immunoreactive hydroxy fatty acids (i12-HETE) and sulfidopeptide leukotrienes (iSRS) were not elevated in tumor-bearing mice and were unaffected by diet. The contents of PGE2, PGF2 alpha, and 6-keto-PGF1 alpha were lower in tumor tissue from animals eating the diet high in EPA, whereas the tissue contents of i12-HETE and iSRS were not altered by diet. Fatty acid analysis of liver and tumor tissue revealed marked increases in certain omega 3 fatty acids (20:5, 22:5, and 22:6) from animals eating the enriched diet. Body weights, tumor weights, and tumor histology were not significantly altered by diet. To determine whether dietary calcium played a role in the elevation of plasma calcium in mice bearing the HSDM1 tumor and the reduction of plasma calcium in animals fed EPA, we compared results in mice fed diets containing 0.80% (normal) and 0.015% (deficient) calcium. The increases in plasma calcium and PGE2-M observed in tumor-bearing mice were the same on both normal and very low calcium intakes. We conclude, in mice of the Swiss albino strain bearing the HSDM1 fibrosarcoma, that consumption of a diet enriched in EPA reduces the production of cyclooxygenase products of arachidonic acid metabolism and thereby reduces the elevation of plasma calcium concentration. Dietary enrichment with EPA did not alter the production of serologically determined lipoxygenase products of arachidonic acid.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Animals; Arachidonic Acid; Arachidonic Acids; Body Weight; Calcium; Calcium, Dietary; Dietary Fats; Dinoprostone; Fatty Acids; Fibrosarcoma; Fish Oils; Hydroxyeicosatetraenoic Acids; Male; Mice; Oils; Prostaglandins; Prostaglandins E; SRS-A; Tissue Distribution