The role of dietary fat in adipose tissue metabolism

Abstract

Energy intake and expenditure tend on average to remain adjusted to each other in order to maintain a stable body weight, which is only likely to be sustained if the fuel mix oxidised is equivalent to the nutrient content of the diet. Whereas protein and carbohydrate degradation and oxidation are closely adjusted to their intakes, fat balance regulation is less precise and that fat is more likely to be stored than oxidised.It has been demonstrated that dietary fatty acids have an influence not only on the fatty acid composition of membrane phospholipids, thus modulating several metabolic processes that take place in the adipocyte, but also on the composition and the quantity of different fatty acids in adipose tissue. Moreover, dietary fatty acids also modulate eicosanoid presence, which have hormone-like activities in lipid metabolism regulation in adipose tissue.Until recently, the adipocyte has been considered to be no more than a passive tissue for storage of excess energy. However, there is now compelling evidence that adipocytes have a role as endocrine secretory cells. Some of the adipokines produced by adipose tissue, such as leptin and adiponectin, act on adipose tissue in an autocrine/paracrine manner to regulate adipocyte metabolism. Furthermore, dietary fatty acids may influence the expression of adipokines.The nutrients are among the most influential of the environmental factors that determine the way adipose tissue genes are expressed by functioning as regulators of gene transcription. Therefore, not only dietary fat amount but also dietary fat composition influence adipose tissue metabolism. Keywords Dietary fatty acidsAdipose tissue Energy and macronutrient balancesAlthough quite variable from day to day, energy intake and energy expenditure tend to remain adjusted to each other on average in order to maintain a stable body weight. Such a steady state is likely to be sustained only if the fuel mix oxidised by the body is equivalent, in terms of its average composition, to the nutrient content of the diet consumed, so that protein balance, carbohydrate balance and fat balance are all achieved. As a result, long periods of weight stability imply not only that energy intake and energy expenditure are equivalent on average but also that the composition of the fuel mix oxidised is equal on average to the composition of the diet. Consequently, it can be stated that spontaneous adjustment of the rate of oxidation of a substrate to its rate of intake is obviously a major factor facilitating maintenance of substrate balance 1,2 . The rate of aminoacid oxidation and degradation is adjusted to protein intake, so that stable protein content is maintained. The rate of glucose disposal is also closely adjusted to carbohydrate intake because body glycogen reserves are small compared to glucose turnover, not being much larger than the amount of carbohydrate usually consumed and used in one day. Although the conversion of excess carbohydrate into fat can be proposed as a pathway for the disposal of carboh...

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