Insulin stimulation of glucose transport and metabolism in a human Wilms' tumor-derived myoblast-like cell Line: Modulation of hormone effects by glucose deprivation

✍ Scribed by Sandra K. Lemmon; Maria G. Buse; Donald A. Sens

• Publisher: John Wiley and Sons
• Year: 1985
• Tongue: English
• Weight: 909 KB
• Volume: 125
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041250314

✦ Synopsis

The effects of insulin and glucose on parameters of metabolism were investigated in myoblast-like (MBL) cells, a human myoblast-like cell line derived from a Wilms'tumor. Insulin responses were studied after 4 h r pre-incubation in serum free media, with or without 5 m M glucose. Insulin was added during the last 2 hr. Glucose starvation markedly increased basal glucose transport (measured as 2-deoxyglucose uptake) as well as the net uptake o l ["CC]glucose and [14C]glucose incorporation into glycogen. Insulin stimulated net glucose uptake and incorporation into glycogen in a dose-dependent manner in glucose-led and starved cells. These insulin responses were markedly enhanced in glucose-starved cells. insulin accelerated 2-deoxyglucose transport in glucose-fed cells but did not further stimulate basal glucose transporl in glucose-deprived cells. Insulin increased the incorporation of ['H]leucine into protein in glucose-fed or -starved M B L cells equally. The dose of insulin required for half-maximal insulin responses was similar for all parameters studied. Cycloheximide did not prevent the increased basal glucose incorporation in glucose-starved cells, but markedly inhibited the insulin response, while in glucose-fed cells, cycloheximide stimulated bdsdl glucose incorporation. We conclude that MBL cells resemble fibroblasts in their insulin-independent stimulation of glucose transport in response to glucose-deprivation; when provided with glucose, they respond to insulin like fibroblasts. However, after brief glucose-starvation, t h e stimulated glucose transport system is no longer insulin-responsive in MBL cells, while pathways leading to the synthesis of macromolecules demonstrate preserved or enhanced stimulation by insulin, suggesting that these cells may serve as models to study the regulation of receptor-response coupling by the metabolic milieu.

Rhabdomyogenesis in Wilms' tumor is a well-documented histopathological entity; however, the myoid elements of this tumor have not been fully characterized. We recently reported conditions which allowed the growth and study of this component in vitro, resulting in the placement into cell culture of two separate cell types derived from the myoid component of Wilms' tumors. The first cell type was easily definable as a differentiated skeletal muscle component of these tumors . The second cell type isolated demonstrated the morphological characteristics of myofibroblasts. However, these cells were capable of cell fusion at many points along adjacent cell surfaces and they contained minimal skeletal muscle myosin as well as isoenzymes (B, MB, and M) of creatine kinase. The properties of these myofibroblast-like cells, and the fact that they could only be isolated from Wilms' tumors possessing a myoid component suggested a relationship to muscle cells. Since a n extensive ultrastructural search failed to identify myofibroblasts in the original tumors, these cells were felt to represent myoblasts a t a n early stage of differentiation. Similar cells have been observed growing from in vitro explants of human skeletal muscle (Mendell et al., 1972) and in vivo in alveolar rhabdomyosarcomas . While these cells were originally established in a serum-free growth medium , they continued to proliferate and retained all the above characteristics when returned to a serum containing medium, through 25 subcultures at a 1:3 ratio (Sens, D.A., unpublished).

Because of the unique nature and recent isolation into