The regulation of hexose transport under glucose-starvation conditions was studied in cultured human skin fibroblasts. Glucose starvation enhanced the transport of 2-DG and 3-0-methyl-D-glucose (3-OMG) but not of L-glucose. Glucose-starvation enhanced transport was inhibited by cytochalasin B (10 microM). The starvation-induced change in 2-DG transport was due to an increase in the Vmax of both the high and low affinity transport sites (2.8- and 2.4-fold, respectively) with no effect on their Kms. The presence of 5.55 mM glucose, fructose, or L-glucose in the medium resulted in transport increases similar to those seen in glucose-starved cells, while the presence of 5.55 mM glucose, mannose, or 3-OMG repressed 2-DG transport. Glucose-starvation enhancement of 2-DG transport was blocked by cycloheximide (20 micrograms/ml) but not by actinomycin D (0.03 microgram/ml) or alpha-amanitin (3.5 microM). Readdition of glucose (5.55 mM) for six hours to glucose-starved cells led to a rapid decrease in hexose transport that could be blocked by cycloheximide but not actinomycin D. Although readdition of 3-OMG to glucose-starved cells had little effect on reversing the transport increases, glucose plus 3-OMG were more effective than glucose alone. Serum containing cultures (10% v/v) of glucose-fed or glucose-starved cells exhibited rapid decreases in 2-DG transport when exposed to glucose-containing serum-free medium. These decreases were prevented by employing glucose-free, serum-free medium. The data indicate that hexose transport regulation in cultured human fibroblasts involves protein synthesis of hexose carriers balanced by interactions of glucose with a regulatory protein(s) and glucose metabolism as they affect the regulation and/or turnover of the carrier molecules.

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The V_max for saturable (i.e. 2-deoxy-D-glucose) sugar transport in cultured human fibroblasts was found to increase with in vitro ageing when the results were expressed per 106 cells. No age-related changes were observed in the K_m for 2-deoxy-D-glucose transport or in nonsaturable (i.e. L-glucose) sugar uptake.

The replicative ability of fibroblasts derived from normal and type II diabetic (non-insulin-dependent) donors and their DNA synthetic capabilities in response to serum and insulin ( ± dexamethasone) have been studied. Comparative replicative life spans of the fibroblasts studied using several lots of serum showed no significant differences between the two donor groups with any lot of serum (p > 0.05). Insulin (i.e. 700 nM) and serum (10% v/v) stimulation of DNA synthesis in normal and type II diabetic cultures exhibited no differences in responses. The insulinxontrol ratios of the normal vs. type II diabetic were 1.61 ± 0.08 vs. 1.81 ± 0.11, respectively (p > 0.05) while the serumxontrol ratios were 3.55 ± 0.58 vs. 4.02 ± 0.54, respectively (p > 0.05). Dexamethasone amplification of the insulin-stimulated DNA synthetic response over a range of insulin concentrations (i.e. 1.6–66.6 nM) expressed no differences between the two donor groups. Additionally, calculation of the insulin concentration necessary for the half-maximal response showed no differences between the normal and diabetic groups (3.47 ± 0.5 vs. 4.44 ± 0.8 nM, respectively) (p > 0.05). The data suggest that there are no general age-related abnormalities inherent to the type II diabetic cultured cell.