Insulin resistance and tissue glycogen content in the tumor-bearing state

Insulin resistance in cancer patients may play an important role in post-operative outcomes.

In an effort to understand the mechanism responsible, we measured glucose uptake by euglycemic hyperinsulinemic glucose clamp, glycogen content in skeletal muscle, liver, and adipose tissue by an enzymatic method, and facilitative glucose transporter mRNA by reverse transcription polymerase chain reaction (RT-PCR), in 10 patients with gastrointestinal cancers. Glucose uptake was also examined in 5 volunteers.

The M value was significantly smaller in cancer patients (6.11 +/- 2.49 mg/kg/min) than in controls (8.55 +/- 0.91 mg/kg/min). A significant decrease in glucose storage was also observed in cancer patients compared with that of controls, 3.18 +/- 2.46 and 4.95 +/- 0.55 mg/kg/min, respectively. The glycogen content of skeletal muscle from cancer patients averaged 12.1 +/- 2.7 micrograms/mg tissue and was correlated with the M value (r = 0.75, p < 0.05). Muscle glycogen had an even stronger correlation to glucose storage (r = 0.964, p < 0.05). The glycogen content of liver averaged 105.4 +/- 79.0 micrograms/mg tissue but was not related to the M value. Glycogen in adipose tissue was not measurable by this method. Muscle and liver samples were positive for periodic and Schiff (PAS) stain, while the stain in adipose tissue was very weak. Glucose transporter 4 mRNA was the dominant facilitative glucose transporter in skeletal muscle.

These results suggest that patients with gastrointestinal (GI) cancer and insulin resistance have decreased glycogen storage in skeletal muscle. These may be the patients who are in need of pre-operative nutritional support.