To determine the effect of fasting on SIRT7, we cultured cancer cell lines under conditions of normal glucose concentration (mouse mammary tumor 4T1 cells, approximately 10 mM; human breast cancer MDA-231 and MCF-7 cells, approximately 5 mM), low-glucose concentration (1 mM) or GD to mimic the normal diet, hypoglycemia, or acute energy stress as previously reported27,28. The gene discussed is SIRT7; the disease is breast carcinoma.