From the biopsy samples, the investigators obtained preadipocytes ”the precursors to fat cells that have the potential to differentiate, or mature, into fat-containing adipocytes. They then allowed the precursor cells to mature for 14 days in culture media containing normal glucose (the main sugar found in the bloodstream and the principal source of energy in the body), high glucose or high fructose. The researchers assessed cell differentiation by measuring activity of an enzyme (GPDH) and the abundance of the adipocyte fatty acid binding protein, which are both present only in mature fat cells.

Fructose, the research team found, had different effects to that of glucose and caused the fat cells to differentiate more ”that is, to form more mature fat cells ”but only in visceral fat.

For both types of fat cells, maturation in fructose decreased the cells' insulin sensitivity, which is the ability to successfully take up glucose from the bloodstream into fat and muscles. Decreased insulin sensitivity is a characteristic of Type 2 diabetes.

Although prolonged exposure to fructose had a negative effect on insulin sensitivity, when Coade and her co-workers exposed mature fat cells, rather than preadipocytes, to fructose for 48 hours, the cells' insulin sensitivity increased. The reason why is unknown. However, she said, "Fructose alters the behavior of human fat cells if it is present as the fat cells mature. We can maybe compare this [timing] to periods in children when they are making their fat."

SOURCE The Endocrine Society