Importance of longer fatty acids in obesity
Intake of excess calories results in an increase in lipid supply to the body either as fat intake via food or an increase in fatty acid synthesis. There are two types of adipose tissue in mammals – brown adipose tissue (BAT) and white adipose tissue (WAT). BAT is especially abundant in newborns and hibernating animals and generates heat in animals (thermogenesis) that cannot shiver. Fatty acids can be stored, exported to other tissues, oxidised to re-release energy or metabolised to form other tissues. One fundamental question that has so far attracted little research is the balancing act between oxidation and storage. One possible control mechanism is that of fatty acid length and the EU-funded project 'Elongase 6 and thermogenesis' (Elovl6 Thermogenesis) investigated the role of a key enzyme in the process, a fatty acid elongase 6, Elovl6. Mice do not indulge in shivering as a response to lower environmental temperatures and were thus an ideal model to subject to trials. Studying growth curves of wild type versus Elovl6 knock-out mice pups, without the gene, project researchers found that although they had the same weight at birth, the knock-out pups were smaller up until three weeks. After that, surprisingly, catch up growth occurred until both groups were equal at six weeks. To research the possible mechanisms involved, the scientists examined gene expression regarding lipid metabolism in BAT and WAT in knock-out mice at the post-weaning stage. Increased levels of alternative elongases were found and these may constitute an effort to compensate for lack of Elovl6. Project scientists suggested that disruption of fatty acid chain length could alter energy balance and result in reduced weight gain. This could be the case particularly in tissues with high metabolic rates and a dependence on lipid for fuel such as BAT. The switch in fuel source at weaning may be responsible for the recovery and, furthermore, weight gain is mediated by activation of compensatory elongases. A fascinating insight into the role of fatty acid metabolism in growth and development has been achieved by the project. This knowledge base may be applied to identification of inherited errors of metabolism. The part played by fatty acid elongation in the development of obesity may also be elucidated.
