Vascular remodeling induced by naturally occurring unsaturated lysophosphatidic acid in vivo.

BACKGROUND: We previously identified unsaturated (16:1, 18:1, and 18:2) but not saturated (12:0, 14:0, 16:0, and 18:0) lysophosphatidic acids (LPAs) as potent factors for vascular smooth muscle cell (VSMC) dedifferentiation. Unsaturated LPAs strongly induce VSMC dedifferentiation via the coordinated activation of the extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (p38MAPK), resulting in the proliferation and migration of dedifferentiated VSMCs. Here, we investigated the effects of 18:1 and 18:0 LPAs (as representative unsaturated and saturated LPAs, respectively) on the vasculature in vivo. METHODS AND RESULTS: Rat common carotid arteries (CCAs) were treated transiently with 18:1 or 18:0 LPA and then examined by histological and biochemical analyses. The 18:1 but not 18:0 LPA potently induced vascular remodeling that was composed primarily of neointima. The incorporation of [3H]18:1 LPA into the CCAs revealed that a sufficient amount of unmetabolized [3H]18:1 LPA to induce VSMC dedifferentiation was present in the vascular wall. The 18:1 LPA-induced neointimal formation in vivo was also dependent on the coordinated activation of ERK and p38MAPK. Unlike balloon-injured CCAs, the 18:1 LPA-treated CCAs showed a histological similarity to human atherosclerotic arteries. CONCLUSIONS: This is the first report demonstrating a role for a naturally occurring unsaturated LPA in inducing vascular remodeling in vivo and provides a novel animal model for neointimal formation.

Negligible changes in piglet serum clinical indicators or organ weights due to dietary single-cell long-chain polyunsaturated oils.

Single-cell oils are currently included in human infant formula as sources of the long-chain polyunsaturates (LCP) docosahexaenoic acid (DHA) and arachidonic acid (AA) in many countries, but have not yet been approved for use in the USA. We prepared four bovine-milk-based formulas with AA/DHA=0, 34/17, 68/34 and 170/85 (mg per 100 kcal formula) provided by two commercial single-cell oils. These levels correspond approximately to 0, 1, 2 and 5 times the concentrations used in infant formulas and, due to greater consumption of formula per unit body weight, resulted in daily consumption of approximately 0, 3, 6 and 16 times those anticipated for human infants. All other dietary fat (47% of calories) was provided by a vegetable oil blend used in commercial human infant formulas. Domestic piglets were allowed to nurse with the sow for 24 h after parturition, then removed to individual cages and maintained on one of the four diets. At 30 days of age the piglets were sacrificed, and serum collected and organs weighed. With litters treated as a blocked variable, no significant differences among groups were found by analysis of variance for the following serum assays: alkaline phosphatase, alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood urea nitrogen (BUN), creatinine, albumin, glucose, cholesterol, triglycerides, and total protein. No significant differences were found for hematocrit or body weight. No significant differences were found among groups for weights of liver, brain, heart, lung, spleen, kidneys or lung, analyzed as absolute weight and as a fraction of body weight. Hematoxylin/eosin liver sections examined by light microscopy showed no abnormalities as evaluated by an independent pathologist. DHA content in liver and heart and AA content in heart showed significant dose-related accumulation (P<0.05) and confirmed enhanced tissue accretion of DHA and AA from both oils. We conclude that single-cell oils in formula consumed for 1 month in amounts up to 16-fold greater than proposed for human infants in the USA did not result in clinical chemistry or histopathologic indications of toxic effects in neonatal pigs.

Maternal body weight gain and fetus development of rats fed a moderately altered olive oil.

The present study examines whether the consumption of a moderately altered olive oil influenced body weight gain and food efficiency ratio of pregnant rats as well as placental and fetal development. Olive oil used for frying 15 times undergoes a relatively slight alteration involving a statistically significant increase in polar content (9.0+/-0.1 mg/100 mg oil vs 2.0+/-0.1 mg/100 mg oil; p < 0.001). The methyl ester content also increased (5.1+/-0.8 mg/100 mg oil vs 1.8+/-0.5 mg/100 mg oil; p < 0.02), while the linoleic acid and oleic acid contents decreased significantly (6.2+/-0.6% oil vs 7.2+/-0.2% oil and 75.8+/-0.6% vs 78.9+/-0.2%, respectively, both p < 0.05). Wistar rats were divided into four groups, two of which included pregnant rats (P1 and P2) and the other two, non-pregnant rats (NP1 and NP2). Groups NP1 and P1 received a diet containing 15% of fat as unused olive oil, while groups NP2 and P2 were fed a diet with a fat content of 15% as the olive oil used in 15 fryings. Pregnancy increased food intake, body weight, weight gain and food efficiency ratio (P1 vs NP1, and P2 vs NP1), while consumption of the used olive oil diet with respect to the unused oil diet did not alter food intake, body weight, weight gain and food efficiency ratio, placental weight, fetal weight and the number of fetuses in P2 rats with respect to P1 ones. These results suggest that in pregnant rats consumption of olive oil with a moderate level of alteration, as the only dietary fat source, exerts no detrimental effects on the mother weight gain or conceptus development.

Toxicity of polyunsaturated fatty acid esters for human monocyte-macrophages: the anomalous behaviour of cholesteryl linolenate.

We have investigated the toxicity to human monocytemacrophages, and susceptibility to oxidation, of different individual dietary fatty acids in cholesterol esters and triglycerides, added to the cell cultures as coacervates with bovine serum albumin. Toxicity was assessed using release of radioactivity from cells preloaded with tritiated adenine. Lipid oxidation was measured by gas chromatography (GC). The triglycerides showed a direct relationship between toxicity and increasing unsaturation, which in turn correlated with increasing susceptibility to oxidation. Triolein (18:1; omega-9) and trilinolein (18:2; omega-6) were non-toxic. Trilinolenin (18:3; omega-3) was toxic only after prolonged incubation. Triarachidonin (20:4; omega-6), trieicosapentaenoin (20:5; omega-3) and tridocosahexaenoin (22:6; omega-3) were profoundly and rapidly toxic. There was a similar relationship between toxicity and increasing unsaturation for most of the cholesterol esters, but cholesteryl linolenate was apparently anomalous, being non-toxic in spite of possessing three double bonds and being extensively oxidised. Probucol and DL-alpha-tocopherol conferred protection against the toxicity of cholesteryl arachidonate and triarachidonin. The oxidation in these experiments was largely independent of the presence of cells. GC indicated that formation of 7-oxysterols might contribute to the toxicity of cholesteryl linoleate. The toxicity of triglycerides suggests that polyunsaturated fatty acid peroxidation products are also toxic. Possible mechanisms of cytotoxicity and relevance to atherosclerosis are discussed.

Early indicators of exocrine pancreas carcinogenesis produced by non-genotoxic agents.

In the past 40 years the incidence of pancreatic cancer in many Western countries had increased. Since no single factor responsible for the development of pancreatic cancer has been identified, it is believed that non-genotoxic factors may play an important role in the pathogenesis of this highly fatal form of cancer. Focal abnormalities of acinar cells, referred to as atypical acinar cell foci or nodules, occur spontaneously in rats and some other species. Their incidence increases with age from zero at birth to about 75% in 2-year-old rats. These spontaneous lesions have a phenotype that cannot be distinguished from the putative, atypical preneoplastic, acinar cell foci induced in rat pancreas by the carcinogen azaserine. Unsaturated fat (corn oil) has been found to increase the incidence of atypical acinar cell nodules and adenomas in the pancreas of non-carcinogen-treated rats without influencing the weight of the pancreas. Furthermore, unsaturated fat has a specific promoting effect on the growth potential of atypical acinar cell foci and nodules induced in rat pancreas by azaserine, resulting in an increase in the number and size of these lesions. Rats fed raw soya flour or trypsin inhibitors develop an enlarged pancreas as a result of hypertrophy and hyperplasia. They also develop acidophilic atypical acinar cell foci and nodules, adenomas and adenocarcinomas after being fed full-fat raw soya flour for 2 years. It may be concluded from the observations in rat pancreas that non-genotoxic compounds or conditions that enhance pancreatic growth may be classified as non-genotoxic pancreatic tumour promoters. The observations with corn oil, however, indicate that there may be non-genotoxic compounds that specifically enhance growth of spontaneous initiated atypical acinar cell foci without causing hyperplasia of the pancreas. The possible mechanisms whereby unsaturated fat and trypsin inhibitors exert their effects on exocrine pancreatic carcinogenesis are discussed.