In situ protein Kinase C activity is increased in cultured fibroblasts from Type 1 diabetic patients with nephropathy

Abstract

Aims/hypothesis. To verify whether individual susceptibility to diabetic nephropathy resides in an intrinsic difference in Protein Kinase C (PKC) activity. Methods. We compared the effect of different glucose concentrations on PKC activity, PKC isoform expression and diacylglycerol (DAG) content in cultured fibroblasts from 14 Type 1 diabetic patients who developed nephropathy with those in cells from 14 patients without nephropathy. We recruited 14 normal subjects as control patients. Forearm skin fibroblasts were cultured in either normal (5 mmol/l) or high (20 mmol/l) glucose concentrations. Results. In normal glucose, in situ PKC activity was higher in Type 1 patients with nephropathy (10.1±1.4 pmol/min/mg protein; p<0.01) than in those without (6.8±0.8) and the normal control subjects (6.3±0.5). This difference was due to increased concentrations of PKCα isoform in the membrane fraction of fibroblasts from patients with nephropathy. DAG content was also higher in cells from Type 1 patients with nephropathy. Incubation in high glucose concentration caused a further increase in PKC activity and DAG content in quiescent fibroblasts from patients with diabetic nephropathy, with no significant changes in cells from diabetic patients without nephropathy and normal control subjects. Conclusion/interpretation. Differences in PKC activation could contribute to the individual susceptibility to renal damage in Type 1 diabetic patients. [Diabetologia (2003) 46:524-530]

Diabetic Nephropathy Is Associated With Gene Expression Levels of Oxidative Phosphorylation and Related Pathways

“…More direct evidence supporting the above hypothesis comes from studies that found increased oxidative stress and impaired antioxidant enzyme responses to high glucose in cultured skin fibroblasts from type 1 diabetic patients with diabetic nephropathy (9,10). These studies (9,10) are consistent with earlier work linking behaviors of cultured skin fibroblasts to diabetic nephropathy risk (11)(12)(13)(14)(15)(16).…”

Endothelial Progenitor Cells and Vascular Biology in Diabetes Mellitus: Current Knowledge and Future Perspectives

“…Thus, high glucose may have effects on EPCs in vivo that are not observable in the culture systems. Accordingly, we have previously reported that hyperglycemia acutely increases activity of both MAP kinases and PKC in human circulating PBMCs in vivo [103][104][105]: the same effects are likely to intervene also in circulating EPCs, as a subgroup of PBMCs, even if future studies will be needed to confirm this hypothesis.…”

Cellular basis of diabetic nephropathy: III. In vitro GLUT1 mRNA expression and risk of diabetic nephropathy in Type 1 diabetic patients

“…Multiple studies [8,10,12,31,32] have outlined skin fibroblast cellular markers for Type 1 diabetic patients at increased risk of DN. The present study, along with our previous findings of decreased latent TGF-β binding protein-1 mRNA expression levels in "slow-track" Type 1 diabetic patients compared with "fast-track" patients and control subjects [11], indicates that there are also in vitro cellular behaviours associated with protection from DN.…”