linoleic-acid and Nutrition-Disorders

The term 'essential fatty acid' is ambiguous and inappropriately inclusive or exclusive of many polyunsaturated fatty acids. When applied most rigidly to linoleate and alpha-linolenate, this term excludes the now well accepted but conditional dietary need for two long chain polyunsaturates (arachidonate and docosahexaenoate) during infancy. In addition, because of the concomitant absence of dietary alpha-linolenate, essential fatty acid deficiency is a seriously flawed model that has probably led to significantly overestimating linoleate requirements. Linoleate and alpha-linolenate are more rapidly beta-oxidized and less easily replaced in tissue lipids than the common 'non-essential' fatty acids (palmitate, stearate, oleate). Carbon from linoleate and alpha-linolenate is recycled into palmitate and cholesterol in amounts frequently exceeding that used to make long chain polyunsaturates. These observations represent several problems with the concept of 'essential fatty acid', a term that connotes a more protected and important fatty acid than those which can be made endogenously. The metabolism of essential and non-essential fatty acids is clearly much more interconnected than previously understood. Replacing the term 'essential fatty acid' by existing but less biased terminology, i.e. polyunsaturates, omega3 or omega6 polyunsaturates, or naming the individual fatty acid(s) in question, would improve clarity and would potentially promote broader exploration of the functional and health attributes of polyunsaturated fatty acids.

Topics: alpha-Linolenic Acid; Animals; Dietary Fats; Fatty Acids, Essential; Fatty Acids, Omega-3; Fatty Acids, Unsaturated; Humans; Linoleic Acid; Nutrition Disorders; Nutritional Physiological Phenomena

Fatty acids have both stimulatory and inhibitory effects on insulin secretion. Long-term exposure to fatty acids results in impaired insulin secretion whilst acute exposure has generally been found to enhance insulin release. However, there are conflicting data in the literature as to the relative efficacy of various fatty acids and on the glucose dependency of the stimulatory effect. Moreover, there is little information on the responses of human islets in vitro to fatty acids. We have therefore studied the acute effects of a range of fatty acids on insulin secretion from rat and human islets of Langerhans at different glucose concentrations. Fatty acids (0.5 mM) acutely stimulated insulin release from rat islets of Langerhans in static incubations in a glucose-dependent manner. The greatest effect was seen at high glucose concentration (16.7 mM) and little or no response was elicited at 3.3 or 8.7 mM glucose. Long-chain fatty acids (palmitate and stearate) were more effective than medium-chain (octanoate). Saturated fatty acids (palmitate, stearate) were more effective than unsaturated (palmitoleate, linoleate, elaidate). Stimulation of insulin secretion by fatty acids was also studied in perifused rat islets. No effects were observed at 3.3 mM glucose but fatty acids markedly potentiated the effect of 16.7 mM glucose. The combination of fatty acid plus glucose was less effective when islets had been first challenged with glucose alone. The insulin secretory responses to fatty acids of human islets in static incubations were similar to those of rat islets. In order to examine whether the responses to glucose and to fatty acids could be varied independently we used an animal model in which lactating rats are fed a low-protein diet during early lactation. Islets from rats whose mothers had been malnourished during lactation were still able to respond effectively to fatty acids despite a lowered secretory response to glucose. These data emphasise the complex interrelationships between nutrients in the control of insulin release and support the view that fatty acids play an important role in glucose homeostasis during undernutrition.

Topics: Animals; Caprylates; Cells, Cultured; Fatty Acids; Fatty Acids, Monounsaturated; Female; Glucose; Humans; Insulin; Insulin Secretion; Islets of Langerhans; Lactation; Linoleic Acid; Models, Animal; Nutrition Disorders; Oleic Acid; Oleic Acids; Palmitates; Rats; Rats, Wistar; Stearates; Stimulation, Chemical

We studied the effects of wintertime undernutrition on the fatty acid composition of bone marrow triacylglycerols (TAGs) of legs in freely-ranging reindeer calves (<1 year) and adult hinds by comparing reindeer in poor condition slaughtered in February with reindeer in good condition slaughtered in October. Significant reductions were found in the proportions of the major monounsaturated fatty acid, or oleic acid, and in linoleic and alpha-linolenic acids in the femur TAGs of the undernourished reindeer as compared with the reindeer in good condition. As a result of these changes, the unsaturation index (UI) of the femur TAGs was reduced by 11% both in the calves and hinds. Similarly, there were also significant reductions in the proportions of oleic and linoleic acid in the metatarsal TAGs in the undernourished hinds, but only in linoleic acid in the calves. The UI of the metatarsal TAGs of the hinds was reduced by 7%, but that of the calves remained unchanged. The results suggest selective mobilization of oleic acid and the principal C18-polyunsaturated fatty acids from bone marrow TAGs in the undernourished reindeer during winter. These changes decrease the unsaturation degree of bone marrow fats, and, if advanced, may impair their fluidity and the functioning of the legs in the cold.

Topics: Age Factors; alpha-Linolenic Acid; Animals; Bone Marrow; Fatty Acids, Monounsaturated; Fatty Acids, Unsaturated; Female; Femur; Linoleic Acid; Male; Nutrition Disorders; Oleic Acid; Reindeer; Seasons; Triglycerides

A study of plasmatic fatty acids was carried out on a group of paediatric patients suffering from cystic fibrosis. These data have been compared with those obtained by others authors. High levels of saturated fatty acids and a reduction of polyunsaturates have been found. The ratio of eicosatrienoic acid to arachidonic acid is high in this group of patients, which indicates a certain lack of essential fatty acids.

Topics: 8,11,14-Eicosatrienoic Acid; Adolescent; Arachidonic Acid; Arachidonic Acids; Child; Child, Preschool; Cystic Fibrosis; Dietary Fats; Fatty Acids; Female; Humans; Infant; Linoleic Acid; Linoleic Acids; Male; Nutrition Disorders

Treatment of human alpha-linolenic acid deficiency (ALAD) with ethyl linolenate is reported. The patient's scaly dermatitis nearly disappeared after 5-d supplementation with 0.1 mL ethyl linolenate. Pretreatment content of various n-3 fatty acids in RBC was 0-15% of healthy controls. After 14 d of supplementation, cholesterol and triglycerides were reduced by 70% of pretreatment values, 22:5n-3 and 22:6n-3 increased three- to fourfold while 18:3n-3 and 20:5n-3 remained low, indicating a rapid elongation and desaturation of 18:3n-3 in ALAD. Urinary excretion of PGI2-M was approximately 10 times higher than in healthy control subjects, while PGI3-M excretion was low. Linolenate supplementation increased PGI2-M excretion twofold, while PGI3-M remained near detection limit. Platelet capacity to synthesize TXA2, and urinary excretion of TXB2+3-M were nearly unaffected by supplementation. The results confirm that the minimal daily requirement of alpha-linolenic acid is 0.2-0.3% of total energy.

Topics: Aged; Aged, 80 and over; Diet; Eicosanoic Acids; Epoprostenol; Erythrocytes; Fatty Acids; Female; Humans; Linoleic Acid; Linoleic Acids; Linolenic Acids; Nutrition Disorders; Thromboxanes

Topics: Animals; Aspartate Aminotransferases; Diet; Dietary Fats; Edible Grain; Fatty Acids; Linoleic Acid; Linoleic Acids; Lipids; Liver Diseases; Muscular Dystrophies; Nutrition Disorders; Research; Swine; Swine Diseases; Vitamin E