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Considering the insufficient supply of long-chain polyunsaturated [omega]-3 fatty acids often prevailing in Western populations, this report deals mainly with alterations of [Ca.sup.2+] fluxes and [Ca.sup.2+]-dependent insulin secretory events in isolated pancreatic islets from [omega]-3-depleted rats. In terms of [sup.45][Ca.sup.2+] handling, the islets from [omega]-3-depleted rats, compared with those from normal animals, displayed an unaltered responsiveness to an increase in extracellular [K.sup.+] concentration, a lower inflow rate and lower fractional outflow rate of the divalent cation, and higher [sup.45][Ca.sup.2+]-labeled cellular pool(s) at isotopic equilibrium. The latter anomaly was corrected 120 min after intravenous injection of a novel medium-chain triglyceride-fish oil (MCT:FO) emulsion, distinct from a control [omega]-3-poor MCT-olive oil (MCT:OO) emulsion. At 8.3 mM D-glucose, insulin release was higher in islets from [omega]-3-depleted rats vs. control animals, coinciding with a higher cytosolic [Ca.sup.2+] concentration. The relative magnitude of the increase in insulin output attributable to a rise in D-glucose as well as extracellular [Ca.sup.2+] or [K.sup.2+] concentration, to the absence vs. presence of verapamil and to the presence vs. absence of extracellular [Ca.sup.2+], theophylline, phorbol 12-myristate 13-acetate, or [Ba.sup.2+], was always more pronounced in islets from [omega]-3-depleted rats injected with the MCT:OO compared with the MCT:FO emulsion. A comparable situation prevailed when comparing islets from noninjected [omega]-3-depleted and normal rats. In light of these and previous findings, we propose that an impairment of [Na.sup.+], [K.sup.+]-ATPase activity plays a major, although not an exclusive, role in the perturbation of [Ca.sup.2+] fluxes and [Ca.sup.2+]-dependent secretory events in the islets from [omega]-3-depleted rats. long-chain polyunsaturated [omega]-3 fatty acid-depleted rats; calcium fluxes; pancreatic islets doi:10.1152/ajpendo.00455.2005

Decreased body fat mass and liver steatosis have been reported in mice fed diets containing the conjugated linoleic acid trans-10,cis-12-C18:2 (CLA2), but not in those fed diets containing cis-9,trans-11-C18:2 (CLA1). Because the decrease in fatty acid (FA) oxidation may cause fat accumulation, we questioned whether the effects of both CLAs on enzyme activities and mRNA expression were related to liver FA oxidation. To address this question, 7-wk-old male C57BL/6J mice were fed for 4 wk a diet supplemented with 1% CLA1, CLA2, or cis-9-C18:1 (control) esterified as triacylglycerols. In CLA2-fed mice, the proportions of CLA2 in the total FA of liver lipids were substantially lower than those of CLA1 in mice fed CLA1. The mitochondrial protein content per total liver was about 56% greater in CLA2-fed mice than in CLA1-fed mice and controls. Mitochondrial carnitine palmitoyltransferase I (CPT I) and carnitine-dependent palmitate oxidation activities were also significantly greater in CLA2-fed mice than in the two other groups. The amounts of malonyl-CoA per gram of liver and the sensitivity of CPT I to malonyl-CoA inhibition were greater in both groups of CLA-fed mice than in the controls. L-CPT I mRNA expression doubled in CLA2-fed mice and was 3 and 2 times greater for M-CPT I in the CLA1 and CLA2 groups, respectively, compared with controls. Peroxisomal FA oxidation-related activities and acyl-CoA oxidase mRNA expression were increased in CLA1-fed mice, and to a larger extent in CLA2-fed mice, relative to controls. These data indicate that FA oxidation capacities were increased in mice fed CLA2, but were likely depressed in vivo through malonyl-CoA inhibition. KEY WORDS: * acetyl-CoA carboxylase * acyl-CoA oxidase * carnitine palmitoyltransferase I * malonyl-CoA * regulation

Considering the insufficient supply of long-chain polyunsaturated ta-3 fatty acids often prevailing in Western populations, this report deals mainly with alterations of Ca2+ fluxes and Ca2+-dependent insulin secretory events in isolated pancreatic islets from ω-3-depleted rats. In terms of 45Ca2+ handling, the islets from ω-3-depleted rats, compared with those from normal animals, displayed an unaltered responsiveness to an increase in extracellular K+ concentration, a lower inflow rate and lower fractional outflow rate of the divalent cation, and higher 45Ca2+-labeled cellular pool(s) at isotopic equilibrium. The latter anomaly was corrected 120 min after intravenous injection of a novel medium-chain triglyceride-fish oil (MCT:FO) emulsion, distinct from a control ω-3-poor MCT-olive oil (MCT:OO) emulsion. At 8.3 mM ᴅ-glucose, insulin release was higher in islets from ω-3-depleted rats vs. control animals, coinciding with a higher cytosolic Ca2+ concentration. The relative magnitude of the increase in insulin output attributable to a rise in ᴅ-glucose as well as extracellular Ca2+ or K+ concentration, to the absence vs. presence of verapamil and to the presence vs. absence of extracellular Ca2+, theophylline, phorbol 12 myristate 13-acetate, or Ba2+, was always more pronounced in islets from ω-3-depleted rats injected with the MCT:OO compared with the MCT:FO emulsion. A comparable situation prevailed when comparing islets from noninjected ω-3-depleted and normal rats. In light of these and previous findings, we propose that an impairment of Na+,K+-ATPase activity plays a major, although not an exclusive, role in the perturbation of Ca2+ fluxes and Ca22+-dependent secretory events in the islets from ω-3-depleted rats. [ABSTRACT FROM AUTHOR]

To study the influence on lipid metabolism and platelet aggregation of the fatty acid isomerization that occurs during heat treatment, weanling rats were fed for 8 wk a diet enriched with 5% isomerized (experimental group) or normal (control group) canola oil. Geometrical isomers of alpha-linolenic acid representing 0.2 g/100 g of the experimental diet were incorporated into liver, platelets, aorta and heart, at the expense of their cis homologue and of 18:2(n-6). The major isomer, 9c,12c,15t-18:3, was also metabolized to 5c,8c,11c,14c,17t-20:5 and to an unknown compound, found in liver, platelets and aorta, which has been identified tentatively as 7c, 10c,13c,16c,19t-22:5. The greater 20:4(n-6)/18:2(n-6) ratio in the liver, platelets and heart of the experimental group than the control group indicated an enhancement of desaturation activities. This induced a higher content of long-chain (n-6) fatty acids in the experimental group. Platelet aggregation tended to be slightly higher (P: = 0.065) in the experimental group. We conclude that 0.2 g of trans isomers of alpha-linolenic acid per 100 g of diet was sufficient to be incorporated and metabolized, thus altering the fatty acid profile of rat tissues. [ABSTRACT FROM AUTHOR]

Objective: To collect (i) baseline data and (ii) execute a large multicentre study examining the effect of trans alpha-linolenic acid on its incorporation into plasma lipids and on risk factors for coronary heart disease.Design: Male volunteers were recruited and the habitual diet assessed by a 4-d weighed record. Fatty acid composition of plasma and platelet lipids were determined by gas chromatography at baseline. After a 6 week run-in period on a trans 'free' diet, male volunteers were randomised to consume 0.6 % of energy trans alpha-linolenic acid or to continue with a diet 'low' in trans alpha-linolenic acid for 6 weeks.Setting: Three European university research departments supported by the research and development departments of the food industry.Subjects: Male volunteers (88) recruited by local advertisement.Methods: Replacement of 30 % of the fat of the habitual diet by margarine, oil and foods. Rapeseed oil was deodorised especially to produce the trans 'free' and 'high' trans foods for this study. The incorporation and conversion of trans alpha-linolenic acid into plasma lipids and platelets was assessed by gas chromatography and dietary compliance was verified by 4-d weighed record.Results: Less trans alpha-linolenic acid isomers are incorporated into human plasma lipids in French volunteers than in Dutch or Scottish volunteers consuming their habitual diets. Trans 'free' alpha-linolenic acid-rich oil can be produced by careful deodorization during refining. The 'high' trans diet provided 1410+/-42 mg/d trans isomers of alpha-linolenic acid, whilst the 'low' trans group consumed 60+/-75 mg/d. The change in plasma lipid and platelet fatty acid composition documented that trans linolenic isomers are incorporated and converted to a trans isomer of eicosapentaenoic acid. Only the 15-trans alpha-linolenic acid is incorporated into plasma cholesteryl esters. The group consuming low trans diet had a slightly higher intake of fat, especially saturated and monounsaturated fat.Conclusions: Trans 'free' rapeseed oil, rich in alpha-linolenic acid, can be produced by careful deodorization. Dietary records show good compliance. Dietary trans isomers of alpha-linolenic acid are incorporated in plasma lipids and converted to long-chain polyunsaturated fatty acids. Their effects on risk factors for coronary heart disease and their metabolism will be reported elsewhere.Sponsorship: European Commission (FAIR 95-0594 grant). European Journal of Clinical Nutrition (2000) 54, 104-113 [ABSTRACT FROM AUTHOR]