Differentiation, growth and development of adipose tissues

Abstract

Adipose tissue is the main energy buffer between the input of nutrients and the physiological needs of many animals. In meat producing animals, they have also a role in the determination of carcass and meat quality. This article is concerned with adipose tissue structure, adipose cell differentiation and finally with adipose tissue growth and development in cattle. Three major steps are considered in the cellular development of adipose tissue : proliferation of precursor cells (adipoblasts), differentiation of these cells into functional adipose cells (adipocytes) and lastly enlargment of the adipocytes. All these developmental steps are under hormonal control. The ontogeny of the various adipose tissues of cattle takes place during foetal life. During this period, these tissues contain uncoupling protein, specific to brown adipose tissue. This protein, which has an important role in the regulation of thermogenesis in new-born animals, disappears after birth. Cell proliferation is more active during foetal life, whereas cell hypertrophy mainly takes place after birth. Adipose tissue represents 5 % of the body weight of new-born calves and this remains constant for 3 months. Afterwards, this percentage increases more and more rapidly reaching approximately 25 % in mature cattle. Subcutaneous and abdominal fatty tissues have a faster growth rate than intermuscular fat. Development of adipose tissues, and fat partition between anatomical sites are variable according to the breed of animals. Increasing (or decreasing) the level of food intake increases (or decreases) selectively adipose tissue growth, but this effect is mainly mediated by adipose cell size. The regulation of adipose tissue growth by the monitoring of adipose cell number is not yet possible.