Total lipid and phospholipid recovery as well as amino acid quality and composition from cuttlefish (Sepia officinalis) and sardine (Sardina pilchardus) were compared. Enzymatic hydrolyses were performed using the three proteases Protamex, Alcalase, and Flavourzyme by the pH-stat method (24 h, pH 8, 50 degrees C). Three fractions were generated: an insoluble sludge, a soluble aqueous phase, and an oily phase. For each fraction, lipids, phospholipids, and proteins were quantified. Quantitative and qualitative analyses of the raw material and hydrolysates were performed. The degree of hydrolysis (DH) for cuttlefish viscera was 3.2% using Protamex, 6.8% using Flavourzyme, and 7% using Alcalase. DH for sardine viscera was 1.9% (using Flavourzyme), 3.1% (using Protamex) and 3.3% (using Alcalase). Dry matter yields of all hydrolysis reactions increased in the aqueous phases. Protein recovery following hydrolysis ranged from 57.2% to 64.3% for cuttlefish and 57.4% to 61.2% for sardine. Tissue disruption following protease treatment increased lipid extractability, leading to higher total lipid content after hydrolysis. At least 80% of the lipids quantified in the raw material were distributed in the liquid phases for both substrates. The hydrolysed lipids were richer in phospholipids than in the lipids extracted by classical chemical extraction, especially after Flavourzyme hydrolysis for cuttlefish and Alcalase hydrolysis for sardine. The total amino acid content differed according to the substrate and the enzyme used. However, regardless of the raw material or the protease used, hydrolysis increased the level of essential amino acids in the hydrolysates, thereby increasing their potential nutritional value for feed products.

a b s t r a c tThe quality of gilthead sea bream from distinct production systems and geographical locations in Southern Europe was evaluated to differentiate aquaculture products from extensive, integrated and semi-intensive systems from the ones produced intensively. This work analysed the external appearance of fish, yields after filleting as well as nutritional, sensory and histological characteristics of the muscle. The results showed that the yellow-golden line between eyes and the shiny red spot on the gill cover can be important and easy criteria to discriminate aquaculture products. Trimming losses are higher in fish from intensive systems. Lipid content of fish from extensive systems was significantly lower than values observed for fish reared intensively. Samples from the integrated and extensive systems showed the best n-3/n-6 ratio, contrarily to intensive systems, but it is difficult to establish clear quality markers to differentiate gilthead sea bream according to the rearing system. Regarding sensory characteristics, the sea bream flesh from intensive systems seems firmer and denser, having smaller white fibres and higher density of fibres in the dorsal muscle. The taste and odour of fatty fish was less strong in fish reared in non-intensive conditions, but extensive rearing in earthen pond is more propitious to the development of certain characteristics related to the environment.

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The present work aimed to study in rats whether substitution of a low level of fish oil (FO; 2.2% of calories) into a low-fat diet (6.6% of calories from fat as peanut-rape oil or control diet) 1) has a tissue-specific effect on insulin signaling pathway and 2) prevents dexamethasone-induced alteration of insulin signaling in liver, muscle, and adipose tissue. Sixteen rats were used for study of insulin signaling, and sixteen rats received an oral glucose load (3 g/kg). Eight rats/group consumed control diet or diet containing FO over 5 wk. Four rats from each group received a daily intraperitoneal injection of saline or dexamethasone (1 mg ⅐ kg Ϫ1 ⅐ day Ϫ1 ) for the last 5 days of feeding. In liver, FO decreased phosphatidylinositol 3Ј-kinase (PI 3Ј-kinase) activity by 54% compared with control diet. A similar result was obtained in muscle. In both liver and muscle, FO clearly amplified the effect of dexamethasone. FO did not alter early steps of insulin signaling, and in muscle GLUT4 protein content remained unaltered. In adipose tissue, FO increased PI 3Ј-kinase activity by 74%, whereas dexamethasone decreased it by 65%; inhibition of PI 3Ј-kinase activity by dexamethasone was similar in rats fed FO or control diet, and GLUT4 protein content was increased by 61% by FO. Glycemic and insulinemic responses to oral glucose were not modified by FO. In conclusion, FO increased PI 3Ј-kinase activity in adipose tissue while inhibiting it in liver and muscle. The maintenance of whole body glucose homeostasis suggests an important role of adipose tissue for control of glucose homeostasis. eicosapentaenoic acid; docosahexaenoic acid; insulin resistance; polyunsaturated fatty acids INSULIN RESISTANCE is a common characteristic of type 2 diabetes, obesity, and metabolic syndrome (31), which results from genetic background and/or environmental factors (39). In patients with type 2 diabetes, liver, skeletal muscle, and adipose tissue are resistant to insulin action (8). In skeletal muscle of patients with type 2 diabetes, tyrosine phosphorylation of insulin receptor (IR) and insulin receptor substrate-1 (IRS-1) and phosphatidylinositol (PI) 3Ј-kinase activity are markedly impaired (5), whereas expressions of IR, IRS-1, or the p85␣ subunit of PI 3Ј-kinase remain unaltered (17). Muscle GLUT4 protein is decreased and GLUT4 translocation is reduced by 90% during hyperinsulinemia (27). These alterations of insulin signaling in muscle participate in the decrease in muscle glucose transport, one of the main features of type 2 diabetes (7). In adipose tissue, basal expression of GLUT4 and IRS-1 are reduced, and upregulation of p85␣ by insulin is completely blunted (11).In rats, a high-fat diet (60% of calories from fat as safflower oil) inhibits liver and muscle PI 3Ј-kinase activity (35). In addition, muscle GLUT4 content and adipose tissue GLUT4 gene expression are reduced (35). These alterations likely explain the impairment of glucose transport in these tissues and at whole body level (33). When fish oil (FO), rich in long-chai...

Le Foll C, Corporeau C, Le Guen V, Gouygou J-P, Bergé J-P, Delarue J. Long-chain n-3 polyunsaturated fatty acids dissociate phosphorylation of Akt from phosphatidylinositol 3Ј-kinase activity in rats.