Impaired proliferation and increased L‐lactate production of dermal fibroblasts in the GK‐rat, a spontaneous model of non‐insulin dependent diabetes mellitus

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Abstract
Intact fibroblast function is required for normal wound healing. Although healing is generally accepted to be disturbed in non-insulin dependent diabetes mellitus, the signals modulating this disturbance are not fully understood. Therefore, we studied dermal fibroblasts from the GK rat, a non-insulin dependent diabetes mellitus model, and the Wistar rat (control) regarding growth characteristics, and L-lactate production at 5.5 mM and 25.5 mM glucose in the absence or presence of protein kinase C-inhibition, or alpha-tocopherol acetate. In addition, growth and L-lactate responses to hyaluronic acid were assessed under normal glucose conditions. At 5.5 mM glucose, the fibroblasts from the GK rat showed a lower proliferation rate during the first 24 hours, measured as DNA content, as compared to Wistar rats, i.e. at 8 hours GK was 57% of control, p < 0.01, at 24 hours GK was 60% of control, p < 0.01. The GK rat fibroblasts accumulated higher L-lactate levels in the media at 24-96 hours. Addition of glucose at a concentration of 25.5 mM decreased the total DNA content in GK rat fibroblast cultures to 74% (p < 0.05) and in control to 87% (p < 0.05), and increased L-lactate levels, measured at 48 hours. A protein kinase C-inhibitor, bisindolylmaleimide IX, increased DNA content and decreased L-lactate in both cell types during culture in high glucose, but only affected GK rat fibroblasts during normal glucose. Hyaluronic acid, increased DNA content in both types of fibroblasts, GK: 139% (p < 0.05), control: 127% (p < 0.05) and reduced L-lactate production. The above observations indicate that GK rat fibroblast proliferation is suppressed when the cells are cultured in high glucose containing media. In addition, protein kinase C and hyaluronic acid might play a role as modulators of fibroblast proliferation during the diabetic state.