Breast cancer-secreted factors induce atrophy and reduce basal and insulin-stimulated glucose uptake by inhibiting Rac1 activation in rat myotubes

Abstract

Background. Metabolic disorders are prevalent in women with breast cancer and breast cancer survivors. Such disorders increase breast cancer mortality and likelihood of relapse 2-and 3-fold, respectively. However, there is a severe lack of research into the physiological sequelae of breast cancer, including the metabolic health consequences. The aim of the present study was to provide novel insights into the causes of metabolic disturbances associated with breast cancer by investigating the effects of breast cancer on insulin sensitivity in skeletal muscle.Method. L6 myotubes stably expressing GLUT4 were incubated for 72 hours in normal growth medium or medium supplemented with 25% conditioned media (CM) from either MCF7 or BT474 breast cancer cells. Basal and insulin-(100nM) stimulated GLUT4 translocation, 2-deoxyglucose (2DG) uptake, and intracellular insulin signaling was determined in day 7 myotubes.Results. Basal-and insulin-stimulated GLUT4 translocation was reduced in L6 myotubes incubated with MCF7 (basal: -7%, insulin: -14%, p<0.01) or BT474 (basal: -16%, insulin: -8%, p<0.01) breast cancer CM. Insulin-stimulated 2DG uptake in L6 myotubes was also reduced by MCF7 (-5%, p<0.05) and BT474 (-10%, p<0.05) breast cancer CM. Insulin-stimulated p-Akt Thr308 (but not p-Akt Ser473 ) phosphorylation tended to be reduced (-25%, p<0.1) in L6 myotubes incubated with MCF7 or BT474 breast cancer CM, while p-TBC1D4 Thr642 phosphorylation was enhanced (+34%, p<0.05) by MCF7 breast cancer CM. Conclusion.We conclude that breast cancer reduces muscle insulin responsiveness, evidenced as reduced insulin-stimulated GLUT4 translocation, downregulated glucose uptake, and blunted intracellular insulin sigaling in L6 myotubes incubated with breast cancer cell CM. Thus, skeletal muscle insulin resistance might contribute to metabolic disorders prevalent in women with breast cancer and could be a potential treatment target. Introduction.Cancer is the second most deadly disease worldwide [1, 2] but fortunately, more people are now surviving their cancer. The majority of cancer survivors constitute women who have survived breast cancer. However, the breast cancer recurs in 10-50% of breast cancer survivors [3]. Recent epidemiological studies have revealed that 60-80% of women with breast cancer develop metabolic disorders [4][5][6]. Metabolic disorders negatively impact on disease prognosis, as it increases the likelihood of breast cancer recurrence 3-fold [7, 8]. Furthermore, the presence of metabolic disorders, increases mortality among women with breast cancer 2-fold [9]. Thus, it is clearly necessary to treat metabolic disorders in breast cancer patients and survivors, but because the cause is unknown and the problem is underappreciated, current treatment is limited. Thus, there is a severe lack of research into the physiological sequelae of cancer and/or treatment, including the metabolic health consequences of breast cancer [10].The metabolic dysfunctions observed in breast cancer, include obesity, hyperglycemia, hyperinsulinem...

Genetically Encoded Synthetic Beta Cells for Insulin Biosynthesis and Release under Hyperglycemic Conditions

“…To evaluate the bioactivity of the produced insulin, namely, promoting glucose uptake into cells, a fluorescent glucose analog, 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino]-2-deoxy-D-glucose (2-NBDG) was employed (Figure 3e). [29,30] MCF-7 cells were first subjected to serum-starvation for 4 h to eliminate the effects of serum [31] before supplying with 2-NBDG and standard insulin (100 nmol) or insulin produced from the Synthetic cell group (100 nmol as calculated from ELISA result from Figure 3c). The living cells were then analyzed by flow cytometry (Figure 3f), which exhibited a marked 3.65% and 7.51% increase in glucose uptake in the Synthetic cell group and standard insulin group (100 nmol), compared to the negative control group (no insulin added).…”