Gluconeogenesis

Gluconeogenesis is a metabolic process that generates glucose from non-carbohydrate sources, such as amino acids, lactate, and glycerol. This process is crucial for maintaining normal blood sugar levels, particularly in the presence of exhaustion of liver glycogen reserves 1. In mice with tumors, gluconeogenesis is one of the factors maintaining normal blood sugar levels, and hyperglycemia induced by glucose leads to an increase in liver glycogen content and a decrease in the intensity of gluconeogenesis 1.

Gluconeogenesis from fructose predominates in periportal regions of the liver lobule, and rates of glucose and lactate production from fructose are around 100 and 75 micromoles per gram per hour, respectively 3. This process is also stimulated by extracellular ATP, which triggers an initial increase in intracellular calcium concentration in hepatocytes 6.

However, gluconeogenesis is also a pathological process, particularly in the context of stress and diabetes. Stress tends to be anti-metabolic initially, and gluconeogenesis is the prime driver of the symptoms of diabetes 5. Insulin helps to lower blood glucose levels in type 2 diabetic patients by stopping the process of excessive gluconeogenesis, rather than by increasing glucose uptake into cells 5.

The relationship between gluconeogenesis and cancer is also complex. An enzyme that activates glycolysis, PFKFB4, is normally increased by oxygen deprivation and the hypoxia-inducible factor (HIF), but it is also increased by heme oxygenase, which removes heme and inhibits gluconeogenesis 4. Lactic acid produced by glycolysis can also stimulate the formation of new blood vessels by inducing VEGF, a growth factor essential for cancer growth 4.

In conclusion, gluconeogenesis is a multifaceted process that plays a crucial role in maintaining normal blood sugar levels, but is also a pathological process in the context of stress and diabetes. Its relationship with cancer is complex and involves the interplay of various metabolic pathways.