Hélène Alami-Durante

Growth and meat quality relations in carp

Abstract Growth proceeds through an harmonious development of major tissues, namely bone, muscle and adipose tissues. Changes in chemical composition result from differential growth of these tissues. Little is known about the relative changes in morphometric traits during development of carp or about their genetic basis, but it seems that valuable criteria for selection on suitability for processing could be found in the mechanisms of bone and muscle development. The development of fatty tissues associated with growth of carp is stimulated by the use of lipid-enriched or high-energy artificial diets. Fat is accumulated in specific adipose tissues and the analysis of the relative development of these tissues could give valuable information on the over-accumulation of fat and its distribution in the whole body. Accumulation of fat has either positive or negative consequences for sensory evaluation depending on the source and the composition of fat. The main characteristics of muscle and connective tissues are presented in this paper. Different muscle tissues comprising different fibre types are found in cyprinids. These tissues together with adipose tissues compose the edible part of carp and explain most of protein retention. Protein content and composition are stable during development. Furthermore, a wide variability in the characteristics of muscle and connective tissues persists in commercial-size fish related to their mode of development. It is especially true for the main contractile protein: myosin. This is illustrated on expression of isoform of myosin but in early stages. The changes in the characteristics of the tissues and of the flesh after death and during postmortem storage and processing are reviewed. The structural components and the organization of tissues are very specific in fish and more sensitive to destruction. Thus, the degradative processes that affect the flesh during storage and processing have important consequences for sensory evaluation of the flesh which in freshwater species is generally rather soft and with neutral odour and taste. In this paper the possible role of biological characteristics of the flesh and of its constitutive tissues in quality is analyzed for the effect of body weight and for the effect of acclimation temperature. Temperature induces specific compensation for the maintenance of basic processes and the consequences for quality are analysed as well.

Skeletal muscle cellularity and expression of myogenic regulatory factors and myosin heavy chains in rainbow trout (Oncorhynchus mykiss): Effects of changes in dietary plant protein sources and amino acid profiles

The nutritional regulation of skeletal muscle growth is very little documented in fish. The aim of the study presented here was to determine how changes in dietary plant protein sources and amino acid profiles affect the muscle growth processes of fish. Juvenile rainbow trout (Oncorhynchys mykiss) were fed two diets containing fish meal and a mixture of plant protein sources either low (control diet) or rich in soybean meal (diet S). Both diets were supplemented with crystalline indispensable amino acids (IAA) to match the rainbow trout muscle IAA profile. Diet S was also supplemented with glutamic acid, an AA present in high quantities in trout muscle. Rainbow trout fed diets C and S were not significantly different in terms of overall somatic growth or daily nitrogen gain, although their parameters of dietary protein utilisation differed. Distribution of skeletal white muscle fibre diameter and expression of certain selected muscle genes were also affected by dietary changes. In the white muscle, diet S led to a significant decrease (x0.9) in the mean and median diameters of muscle fibres, to a significant decrease (x0.6) in the expression of MyoD and to a significant increase (x1.7) in the expression of fast-MHC, with no significant changes in myogenin expression. There was no change in the expression of the genes analysed in lateral red muscle (MyoD, MyoD2, myogenin and slow-MHC). These results demonstrated that changes occurred in skeletal white muscle cellularity and expression of MyoD and fast-MHC, although overall growth and protein accretion were not modified, when a diet rich in soybean meal and glutamic acid was ingested. Present findings also indicated that the white and red muscles of rainbow trout are differently affected by nutritional changes.

Postprandial Regulation of Growth- and Metabolism-Related Factors in Zebrafish

Zebrafish (Danio rerio) have been proposed as a possible model organism for nutritional physiology. However, this potential has not yet been realized and studies on the field remain scarce. In this work, we investigated in this species the effect of a single meal as well as that of an increase in the ratio of dietary carbohydrates/proteins on the postprandial expression of several hepatic and muscle metabolism-related genes and proteins. Fish were fed once either a commercial diet (experiment 1) or one of two experimental diets (experiment 2) containing different protein and carbohydrate levels after 72 h of starvation. Refeeding induced the postprandial expression of genes of glycolysis (GK, HK1) and lipogenesis (FAS, G6PDH, ACCa) and inhibited those of gluconeogenesis (cPEPCK) and beta-oxidation (CPT1b) in the viscera. In the muscle, refeeding increased transcript levels of myogenesis (Myf5, Myogenin), inhibited those of Ub-proteasomal proteolytic system (Atrogin1, Murf1a, Murf1b), and induced the activation of key signaling factors of protein synthesis (Akt, 4EBP1, S6K1, S6). However, diet composition had a low impact on the studied factors. Together, these results highlight some specificity of the zebrafish metabolism and demonstrate the interest and the limits of this species as a model organism for nutritional physiology studies.

Supplementation of artificial diets for common carp (Cyprinus carpio L.) larvae

Abstract Duplicate groups of full-sib carp (Cyprinus carpio L.) larvae were reared at 24±0.5°C and fed six artificial diets (A to F) with the same protein sources (yeast powder 59%; dry beef liver 41%) and a diet (G) in which half of the protein source was replaced by egg powder. Diets were supplemented with different levels (0%, 5% or 10%) of cod liver oil (CLO), mineral premix (M) and vitamin premix (V). After 21 days on experimental diets (D0–D21), larvae were fed a commercial feed for 10 additional days (D21–D31). On day 21, survival of larvae fed the yeast-liver diet supplemented with CLO (5%), M (5%) and V (5%) (diet A) was 64% and mean body weight was 169 mg. Compared to diet A, diet B (CLO 10%, M 10%, V 10%) did not improve survival (68%) or mean body weight (170 mg). Larvae fed a non-supplemented diet (C) containing only yeast and liver had a lower survival rate (42%) and mean body weight (63 mg). Vitamins appeared to be a limiting factor as the larvae fed diet D with CLO 5%, M 5% and no V exhibited a very low survival rate (13%) and mean body weight (28 mg). The mineral premix also seemed necessary as results obtained with diet E (CLO 5%, V 5%, no M) were similar (survival 52%, mean weight 53 mg) to those obtained with the non-supplemented diet (C). Diet F (M 5%, V 5%, no CLO) led to an excellent survival rate (95%) and mean body weight of 189 mg on day 21. Larvae fed diet G (42.5% yeast-liver mixture, 42.5% egg powder, 5% CLO, 5% M, 5% V) reached an individual mean weight of 140 mg. It was concluded that the mineral and vitamin supplementation of the yeast-liver diets was necessary, whilst an addition of 5% CLO in these diets had a negative effect. Survival of larvae initially fed the best diet (F) was 95% and mean body weight was 755 mg after 10 additional days of feeding (D21–D31) a commercial diet. This confirmed the possibility of rearing carp larvae on artificial food with high survival and growth rates.

Dietary Cholecalciferol Regulates the Recruitment and Growth of Skeletal Muscle Fibers and the Expressions of Myogenic Regulatory Factors and the Myosin Heavy Chain in European Sea Bass Larvae

The aim of this study was to determine whether dietary cholecalciferol affects the recruitment and growth of axial skeletal muscle fibers in first-feeding European sea bass. Larvae were fed diets containing 0.28 (VD-L, low dose), 0.69 (VD-C, control dose), or 3.00 (VD-H, high dose) mg cholecalciferol/kg from 9 to 44 d posthatching (dph). Larvae were sampled at 44 dph for quantification of somatic growth, muscle growth, and muscle growth dynamics and at 22 and 44 dph for the relative quantification of transcripts encoded by genes involved in myogenesis, cell proliferation, and muscle structure. The weight increase of the VD-L-fed larvae was less than that of the VD-H-fed group, whereas that of VD-C-fed larvae was intermediate. The level of expression of genes involved in cell proliferation (PCNA) and early myogenesis (Myf5) decreased between 22 and 44 dph, whereas that of the myogenic determination factor MyoD1 and that of genes involved in muscle structure and function (myosin heavy chain, myosin light chains 2 and 3) increased. Dietary cholecalciferol regulated Myf5, MyoD1, myogenin, and myosin heavy chain gene expression, with a gene-specific shape of response. The maximum hypertrophy of white muscle fibers was higher in larvae fed the VD-C and VD-H diets than in larvae fed the VD-L diet. White muscle hyperplasia was highly stimulated in VD-H-fed larvae compared to VD-L- and VD-C-fed ones. These findings demonstrate a dietary cholecalciferol effect on skeletal muscle growth mechanisms of a Teleost species.

Early decrease in dietary protein:energy ratio by fat addition and ontogenetic changes in muscle growth mechanisms of rainbow trout: short- and long-term effects

As the understanding of the nutritional regulation of muscle growth mechanisms in fish is fragmentary, the present study aimed to (1) characterise ontogenetic changes in muscle growth-related genes in parallel to changes in muscle cellularity; (2) determine whether an early decrease in dietary protein:energy ratio by fat addition affects the muscle growth mechanisms of rainbow trout (Oncorhynchus mykiss) alevins; and (3) determine whether this early feeding of a high-fat (HF) diet to alevins had a long-term effect on muscle growth processes in juveniles fed a commercial diet. Developmental regulation of hyperplasia and hypertrophy was evidenced at the molecular (expression of myogenic regulatory factors, proliferating cell nuclear antigen and myosin heavy chains (MHC)) and cellular (number and diameter of white muscle fibres) levels. An early decrease in dietary protein:energy ratio by fat addition stimulated the body growth of alevins but led to a fatty phenotype, with accumulation of lipids in the anterior part, and less caudal muscle when compared at similar body weights, due to a decrease in both the white muscle hyperplasia and maximum hypertrophy of white muscle fibres. These HF diet-induced cellular changes were preceded by a very rapid down-regulation of the expression of fast-MHC. The present study also demonstrated that early dietary composition had a long-term effect on the subsequent muscle growth processes of juveniles fed a commercial diet for 3 months. When compared at similar body weights, initially HF diet-fed juveniles indeed had a lower mean diameter of white muscle fibres, a smaller number of large white muscle fibres, and lower expression levels of MyoD1 and myogenin. These findings demonstrated the strong effect of early feed composition on the muscle growth mechanisms of trout alevins and juveniles.

Transient up- and down-regulation of expression of myosin light chain 2 and myostatin mRNA mark the changes from stratified hyperplasia to muscle fiber hypertrophy in larvae of gilthead sea bream (Sparus aurata L.)

Hyperplasia and hypertrophy are the two mechanisms by which muscle develops and grows. We study these two mechanisms, during the early development of white muscle in Sparus aurata, by means of histology and the expression of structural and regulatory genes. A clear stage of stratified hyperplasia was identified early in the development of gilthead sea bream but ceased by 35 dph when hypertrophy took over. Mosaic recruitment of new white fibers began as soon as 60 dph. The genes mlc2a and mlc2b were expressed at various levels during the main phases of hyperplasia and hypertrophy. The genes myog and mlc2a were significantly up-regulated during the intensive stratified formation of new fibers and their expression was significantly correlated. Expression of mstn1 and igf1 increased at 35 dph, appeared to regulate the hyperplasia-to-hypertrophy transition, and may have stimulated the expression of mlc2a, mlc2b and col1a1 at the onset of mosaic hyperplasia. The up-regulation of mstn1 at transitional phases in muscle development indicates a dual regulatory role of myostatin in fish larval muscle growth.