Question

Regulation of glucose uptake by the cell

An MRI shows a large glioblastoma tumor with areas of necrosis within the tumor (tumor is the bright white area within the brain field on MRI). Use the following series of questions to determine how / if glucose uptake differs in the tumor when compared to the surrounding tissues.

In normal tissue, how is glucose uptake regulated in the following tissues:

● Liver

● Skeletal Muscle

● Brain

● Adipose

How does glucose uptake in normal tissue compare to glucose uptake by tumor cells in the above image and why would this be advantageous to the invasive tumor? What modifications may have occurred in cancer cells to alter glucose uptake as predicted above?

Answer 1

The uptake of glucose in normal cells is monitored in different tissues with the assistance of GLUT or glucose transporters that works to mediate the molecules of glucose down the concentration gradient in various tissues by the process of facilitated diffusion except in gut and kidneys where conduction of glucose molecules occurs by the processes dependent upon energy. Different GLUT work in different tissues, GLUT 2 in the liver, GLUT4 in skeletal muscle, GLUT3 in brain and GLUT4 in adipose tissues. The variation in the uptake of glucose by both tumor and healthy cells is best illustrated by Warburg. In normal cells, the rate of glycolysis is found lower that is succeeded by oxidation of pyruvate in mitochondria. On the other hand, in cancer cells, the rate of glycolysis is greater, which is succeeded by lactic acid fermentation that occurs within the mitochondria. The glycolysis in tumor cells is not associated with Kreb's cycle even in the existence of oxygen, this results in more energy saving in cancer cells. Some of the modifications that take place in cancer cells are uncoupling of glycolysis to Kreb's cycle, a higher rate of glycolysis, lactic acid fermentation succeeded by glycolysis, and inactivity of pyruvate dehydrogenase and activity of lactose dehydrogenase in cancer cells. |