Glucose disposal and gluconeogenesis from alanine in tumor-bearing Fischer 344 rats

For the study of glucose carbon recycling and incorporation of carbon atoms from plasma glucose, [3-3H]glucose and [U-14C]alanine were injected into inbred non-tumor-bearing (NTB) and tumor-bearing (TB) male F344 rats. The glucose and alanine kinetics were determined in relation to antecedent food intake and carcass weight loss. Whereas fed NTB and TB rats appropriately experienced reduced glucose disposal with decreased food intake (0.99 vs. 0.29 mg/min -100 g(-1) compared wtih observations in starved NTB rats), starved TB rats exhibited increased glucose utilization. Both fully fed and cachectic TB groups exhibited increased isotopic carbon recycling compared to the carbon recycling of NTB control groups, whereas starved TB rats did not demonstrate increased recycling compared to the carbon recycling (27% of C-atoms recycled). These findings suggest that alterations of glucose turnover, carbon recycling, and gluconeogenesis in the fed host parallel hypophagia and weight loss, regardless of TB status.