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Knowledge of the development and function of fatty tissue in fish has until recently been relatively scarce. A high quantity of fat around the guts means production loss at slaughter, and may also influence fish health. There has therefore been an increasing demand for knowledge on the development and function of fatty tissue in salmon.

Marijana Todorčević’s doctoral work at the Norwegian University of Life Sciences (UMB) shows that the recruitment of new adipose (fat) cells from unspecialised stem cells and the maturation of adipose cells are regulated by a complex network which is not so very different from the development of fatty tissue in humans.

The studies have shown that fatty tissue in salmon has more functions that previously assumed, one of which is to secrete hormone-like substances that are important for the regulation of energy conversion as well as inflammatory reactions. Increased accumulation of fat in adipose cells leads to increased expression of genes coding for endoplasmatic reticulum stress, oxidative stress and inflammation.

Ms Todorčević’s results indicate that the composition and function of fatty tissue influence fish health.

Omega 3

The fats in fish feed are increasingly sourced from plants, and this has led to reduced levels of healthy omega 3 fatty acids in the fatty tissue of fish.

Another important issue addressed in Ms Todorčević’s doctoral work was to examine whether fatty acids from plant oils influence the quantity of gut fat and stress markers in salmon. Her studies showed that fatty acids found abundantly in plant oils lead to a higher degree of fat accumulation in cells and to a higher expression of stress related genes than do fatty acids from omega 3 oils.

However, the thesis also shows that salmon fatty tissue has a number of mechanisms which protect the fat cells against negative effects from excessive fat storage. Fatty tissue has a relatively low capacity for exploiting fatty acids for energy production, but since this tissue may represent a rather high percentage of total body weight, its metabolizing capacity may influence the quantity of gut fat.

Ms Todorčević’s studies show that lipid peroxidation (going rancid) of mitochondrial membranes (the mitochondries are organelles responsible for fat metabolism) leads to decreased fat conversion and thereby influences fat deposition in the fish.

Ms Todorčević is 30 years of age and originally comes from Serbia. She took her Master’s degree in feed technology at UMB at Ås, and started her PhD work at UMB and Nofima in 2005.

Her supervisors have been professor Bente Ruyter and ex senior researcher Anne Vegusdal at Nofima Marin. She defended her thesis on Friday March 5th 2010. The title of her thesis is “Development and functions of adipose tissue in Atlantic salmon”. Ms Todorčević has decided to stay on as a researcher at Nofima Marin.

April 2010

the Fish Site Editor

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