Control of skeletal muscle fibres and adipose cells size in the flesh of rainbow trout

Abstract

The distributions of the diameters of skeletal muscle fibres and adipocytes were studied in rainbow trout. The cellularity of perivisceral adipose tissues and subcutaneous ventral and dorsal adipose tissues were characterized more specifically. In these tissues, a population of small adipocytes was distinguishable from larger adipocytes. The same was observed in white muscle. The effects of extrinsic factors (dietary lipid in two different thermal conditions) and intrinsic factors (strains in two different saline conditions, growth hormone) on the long-term response of the cellularity of both muscle and adipose tissues were studied. The effects of thermal environment were tested on fish fed the same ration and the effects of saline environment on fish fed ad libitum. The mean size of white muscle fibres was relatively unaffected by the different treatments tested: genetic origin and dietary lipid in different environmental conditions. There were significant differences in growth rate due to genetic origin and saline environment. The possible involvement of hyperplasia in response to these different factors is discussed. Growth hormone supplementation enhanced the percentage of small diameter fibres indicating a role of this hormone in the control of muscle hyperplastic growth. The mean size of adipose cells was affected only slightly by the different treatments tested. An increase in adipose cell size with aging and lipid content was observed. The percentage of small adipocytes also increased with aging. Thus, it is proposed that the development of adipose tissues, and thus fat retention, both result from the recruitment of new adipocytes and from the increase in size of existing adipocytes. The hyperplastic process contributed significantly to the differences in fat retention due to different treatments tested (strains, thermal and saline environments). When partially substituting fish oils for corn oils in the diet, a large increase in the ventral adipose cell size was seen indicating a potential negative effect of n-6 fatty acids on cell proliferation. Growth hormone treatment, on the contrary, induced a decrease in the size of perivisceral adipocytes. Thus, diet and hormonal status affect adipose cells size through two different metabolic pathways: lipogenesis and lipolysis respectively. 1997 The Fisheries Society of the British Isles

Dietary protein content influences both growth and size distribution of anterior and posterior muscle fibres in juveniles of Pagellus bogaraveo (Brunnich)

“…Overall, these differences only became apparent in fish fed on protein-rich diets ([40%). Increases in the cross-sectional area of white muscle fibres during growth were also observed in other fish species (Weatherley et al 1980;Kiessling et al 1991;Koumans et al 1993;Fauconneau et al 1997;Suresh and Sheehan 1998)-here we further proved that such increases are maximal only above a threshold of diet protein intake.…”

“…Indeed, the smallest fibres are thought to be the newly generated ones (Carpenè and Veggetti 1981;Rowlerson et al 1985). The rates of muscle fibre hypertrophy and hyperplasia for reaching a given girth vary among species and different strains of a species (Weatherley et al 1979) and can be influenced by controlled rearing conditions, such as diet (Kiessling et al 1991;Fauconneau et al 1997;Johnston et al 2002), exercise training (Johnston and Moon 1980) and temperature (Ayala et al 2000(Ayala et al , 2001López-Albors et al 2003).…”

<b>Influence of rearing temperature on muscle growth and adipose tissue in Nile tilapia (<i>Oreochromis niloticus</i>) strains

“…Similar results occurred with fish reared at 28 and 30ºC. Fauconneau et al (1997) analyzed four distinct regions of fat deposition, perivisceral, subcutaneous ventral, dorsal subcutaneous and red muscle of different strains of rainbow trout. At each of these sites, fat cells were found with a variety of size 5-200 microns.…”

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“…The relative contribution of muscle fibre hypertrophy and hyperplasia to the total muscle growth varies according to endogenous and exogenous factors. Some of the most important external factors are temperature (Johnston, 1999;Johnston et al, 1998;Ayala et al, 2000aAyala et al, , 2001aAyala et al, ,b, 2003López Albors et al, 2003;García de la Serrana et al, 2012;Campos et al, 2013a,b), the photoperiod (Johnston et al, 2003a(Johnston et al, , 2004, exercise training (Johnston and Moon, 1980), and diets (Weatherley et al, 1980;Fauconneau et al, 1997).…”