Flávia Braidotti Stevanato

Ácidos graxos poli-insaturados n-3 e n-6: metabolismo em mamíferos e resposta imune

A experimentacao animal apresenta uma grande importância para o desenvolvimento da ciencia. O uso de camundongos em experimentos ocorre devido a semelhanca destes animais com os seres humanos, facil criacao e manutencao e resposta experimental bastante rapida. Esses animais possuem as mesmas enzimas dessaturases e elongases que os humanos, por isso sao usados em pesquisas envolvendo incorporacao e sintese de acidos graxos em tecidos. Os acidos graxos da familia omega-3 e omega-6 sao de suma importância na dieta humana, pois estes nao sao sintetizados pela sintese de novo e sao precursores dos acidos graxos poli-insaturados de cadeia muito longa, como os acidos eicosapentaenoico, docosahexaenoico e araquidonico. Estes desempenham funcoes importantes no organismo, como a sintese de eicosanoides que estao envolvidos diretamente no sistema imune e nas respostas inflamatorias. A razao entre o consumo de acidos graxos n-6 e n-3 na dieta e um importante fator para determinar a ingestao adequada de acidos graxos bem como prevenir o aparecimento de doencas. Este artigo tem como objetivo avaliar a incorporacao de acidos graxos em tecidos de animais e discutir a importância dos acidos da familia n-3 e seus metabolitos no sistema imunologico.

Fatty acids and nutrients in the flour made from tilapia (Oreochromis niloticus) heads

The objective of this work was to analyze the fatty acid composition and nutrient potential of flour made from tilapia heads, which are normally discarded during the filleting operation. Significant differences were found between the proximate composition (moisture, ash, protein and total lipids) of the in natura tilapia and the flour, due to the drying process. The predominant fatty acids in the heads (in natura and in the flour) were palmitic acid (1,999 mg.100 g -1 and 7,699 mg.100 g -1 , respectively), oleic acid (3,128 mg.100 g -1 and 11,447 mg.100 g -1 , respectively), and linoleic acid (1,018 mg.100 g -1 and 3,784 mg.100 g -1 , respectively). The results lead us to conclude that tilapia head flour offers high levels of protein (38.41%), total lipids (35.46%), and ash (minerals) (19.38%). The content of omega-3 (731 mg.100 g -1 ) were proved to be satisfactory. Also, n-6/n-3 ratio was 6.15 and PUFA/SFA ratio was 0.47, which are in agreement with the recommended levels. Thus, tilapia heads can be used as a low-cost raw material for food fit for human consumption.

Avaliação química e sensorial da farinha de resíduo de tilápias na forma de sopa

Fish heads are normally discarded during fish processing and are not used as food. This study therefore investigated the chemical and fatty acids composition of fish meal produced from tilapia heads. An evaluation was made of the sensorial, chemical and fatty acids characteristics of broth and soup containing this fish meal. The purpose of the study was to analyze the composition and acceptance of products containing fish meal, aiming at its use in human food, especially in school meals. The results indicated that the fish meal contained contents of protein (38.4%), ashes (19.4%) and lipids (35.5%). The soup containing fish meal was well accepted by elementary schoolchildren. Moreover, the fatty acids composition of the lipid content indicated the presence of several omega-3 acids, especially alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and an excellent PUFA/SFA ratio. All these parameters indicate that fish meal made from discarded tilapia heads is an acceptable, nutritious and healthy source of food for humans.

Composição e estabilidade lipídica da farinha de espinhaço de tilapia

Espinhacos de tilapias (Oreochromis niloticus) sao partes do peixe de composicao desconhecida. A composicao lipidica dos espinhacos nao e citada na literatura, bem como a estabilidade da farinha do espinhaco durante o armazenamento. Nesse sentido, realizou se estudo de processamento dos espinhacos envolvendo etapas de coccao, trituracao, secagem, peneiramento e armazenamento da farinha. A farinha ficou armazenada sob refrigeracao por um periodo de 90 dias, sendo sua qualidade monitorada por meio da composicao em acidos graxos, indice de acidez e analises microbiologicas. Os resultados da composicao centesimal foram de 14,2% (umidade), 40,8% (proteina), 18,3% (residuo mineral fixo) e 25,3% de lipidios totais. Nos lipidios totais foi identificado um total de 24 acidos graxos, com predominância dos acidos graxos (porcentagem media) de 27.4% (acido palmitico, 16:0), 35,15% (acido oleico, 18:1n-9) e 11,82% (acido linoleico, 18:2n-6) e, em menor proporcao: 0,88% (acido alfa-linolenico, 18:3n-3), 0,08% (acido eicosapentaenoico, 20:5n-3) e 0,59 (acido docosahexaenoico, 22:6n-3). Durante os 90 dias de armazenamento, foram observadas algumas alteracoes no indice de acidez e composicao de alguns acidos graxos, no entanto, para 60 dias de armazenamento, nao foram observadas alteracoes na composicao de nenhum acido graxo, do indice de acidez e nas analises microbiologicas.

Production of TNF-α, nitric oxide and hydrogen peroxide by macrophages from mice with paracoccidioidomycosis that were fed a linseed oil-enriched diet

Omega-3 polyunsaturated fatty acids (n-3 PUFA) can modulate the immune system and their primary effect is on macrophage function. Paracoccidioidomycosis (PCM) is an endemic systemic mycosis in Latin America that is caused by the dimorphic fungus Paracoccidioides brasiliensis (Pb). Macrophages are the main defence against this pathogen and have microbicidal activity that is dependent on interferon-Γ and tumour necrosis factor (TNF)-α. These cytokines stimulate the synthesis of nitric oxide (NO) and hydrogen peroxide (H₂O₂), leading to the death of the fungus. To study the effect of n-3 PUFA on the host immune response during experimental PCM, macrophages that were obtained from animals infected with Pb18 and fed a diet enriched by linseed (LIN) oil were cultured and challenged with the fungus in vitro. The macrophage function was analysed based on the concentrations of TNF-α, NO and H₂O₂. LIN oil seems to influence the production of TNF-α during the development of disease. A diet enriched with LIN oil influences the microbicidal activity of the macrophages by inducing the production of cytokines and metabolites such as NO and H₂O₂, predominantly in the chronic phase of infection.

Incorporation of n-3 fatty acids by the liver of mice fed linseed oil as a function of feeding duration

The objective of this study was to evaluate the incorporation of omega-3 fatty acids (n-3 FA) on male Swiss mice livers receiving diets based on linseed oil (LO) for up to 56 days. The mice were sacrificed at 7, 14, 28, 42, 56 days and FA concentration was analyzed by gas chromatography. A total of 13 FA were identified on LO feeds presenting alpha-linolenic acid (LNA) contents of 26.97 %. A total 22 FA were identified in the livers of the mice. Part of the LNA was converted into n-3 FA (20:3n-3, eicosapentaenoic acid-EPA, 22:5n-3, and docosahexaenoic acid-DHA), and some of the LNA was stored in the liver. LNA, EPA and DHA concentrations (mg/g total lipids ) from 0 days for up 56 days increased from 1.29 to 18.90 (LNA), 0.20 to 18.90 (EPA) and 41.26 to 99.17 (DHA).The concentration of n-3 FA in the livers varied with the duration of the LO diet. During LO feed, n-6 FA concentration fell and n-3 FA concentration rose through the experimental period.