ADIPOCYTE TURNOVER Adipose tissues expand via three mechanisms: increase in the size of pre-existing adipocytes (hypertrophy), formation of small new adipocytes (hyperplasia), or by both mechanisms. According to Spalding et al. (2008), about 10% of adipose cells are renewed per year at all adult ages and body weights but without any significant increase in the overall number of adipocytes. Studies have shown that during childhood or adolescence there could be an increase in the number of adipocytes but that this number remains fairly constant in adults regardless of the weight and gender of the individual (Arner et al., 2010). This is to say that there seem to be no net loss of adipocytes in the body of a human, the overall number of adipocytes …show more content…
Rather, they are specialized to convert these nutrients into chemical energy in the form of heat. This form of thermogenesis is referred to as the non-shivering thermogenesis, and this is important in the body’s defense against cold and also obesity (Ye et al., 2013). These adipocytes which perform these role have numerous mitochondria with unique mitochondrial genetic program which promotes mitochondrial biogenesis, energy uncoupling and dissipation leading to heat generation (Kajimura et al., 2010). Normally, energy in the form of adenosine triphosphate (ATP) is generated in the mitochondria of cells when protons that have accumulated in the intermembranous space flow back into the mitochondrial cristae through the numerous ATP synthetase on the inner mitochondrial walls. On the other hand, the abundant mitochondria in brown adipocytes have specialized proteins called the uncoupling protein 1 (UCP1) or thermogenin which is permeable to these protons such that these protons flow across the inner mitochondrial membrane through these thermogenins (instead of through the ATP synthetase channel) thereby resulting in energy dissipation in the form of heat (Cannon and Nedergaard,