Cell volume: Role in obesity and its maintenance minireview

Abstract

Keeping volume within certain limits is a prerequisite for cell integrity and proper function. The defense against excess cell swelling is accomplished also by a reduction of the intracellular osmolarity by synthesis of osmotically less active macromolecules from their specific subunits (proteosynthesis and lipogenesis). At the same time proteolysis and lipolysis is inhibited. Conversely, cell shrinkage stimulates lipolysis, degradation of proteins to amino acids, degradation of glycogen to glucosephosphate and simultaneously protein, lipid and glycogen synthesis is inibited. The degradation products are osmotically more active than the macromolecules and their breakdown generates cellular osmolarity resulting in water entry into cells. Recently new interesting view of chronic changes of the cell volume and its role in model of body weight loss and regain in obesity is considered; secretion profile of adipocytes is related to their size. Decrease of body weight is constituted by the drop of fat in adipocytes, they consequently shrink. Surrounding extracellular matrix has to adjust to traction forces. To ascertain a sufficient supply of glucose and fat for re-storage, adipocytes change their pattern of secreted adipokines altering the total body metabolism and promoting energy intake. Shrunken adipocytes show insulin resistance, whereas glucose uptake is facilitated in osmotically swollen adipocytes. Compensating mechanism in patients on very-low calorie diet during weight maintenance period includes increase in water content of adipose tissue correlating with increase of insulin sensitivity. Consideration of participation these mechanisms might bring new insight into understanding of obesity pathophysiology and treatment.