Glukoneogeneesille

Glukoneogeneesille is the Finnish term that corresponds to gluconeogenesis, the metabolic pathway that generates glucose from non-carbohydrate substrates. It primarily occurs in the liver and, to a lesser extent, in the renal cortex. During fasting, prolonged exercise, or carbohydrate restriction, gluconeogenesis helps maintain blood glucose to supply tissues that depend on glucose, such as the brain and red blood cells.

Substrates for gluconeogenesis include lactate, glycerol, and glucogenic amino acids such as alanine and glutamine. In mammals, a typical flux begins with pyruvate or lactate, which are converted through a series of reactions to phosphoenolpyruvate and ultimately to glucose. Key enzymes that bypass irreversible glycolytic steps are pyruvate carboxylase (mitochondrial) and phosphoenolpyruvate carboxykinase, followed by cytosolic enzymes fructose-1,6-bisphosphatase and glucose-6-phosphatase. This arrangement allows the production of glucose without relying on the irreversible glycolytic steps catalyzed by pyruvate kinase, phosphofructokinase-1, and hexokinase/glucokinase.

The pathway is energetically demanding, typically consuming about 6 high-energy phosphate equivalents per glucose molecule. Regulation integrates hormonal signals (glucagon and epinephrine promote gluconeogenesis; insulin inhibits it) and substrate availability. Allosteric control, including levels of fructose-2,6-bisphosphate, modulates the activities of fructose-1,6-bisphosphatase and phosphofructokinase-1, balancing gluconeogenesis with glycolysis. The kidney can contribute during prolonged fasting or extreme metabolic needs.

Clinical relevance includes defects in gluconeogenic enzymes that cause hypoglycemia and metabolic crises. Examples include deficiencies in pyruvate carboxylase or glucose-6-phosphatase.