In situ hybridization study of myelin protein mRNA in rats with an experimental diabetic neuropathy

Distribution of protein zero (P₀) and myelin basic protein (MBP) mRNAs in the sciatic nerve from rats with alloxan-induced diabetes was analyzed at two different time points using in situ hybridization. Some animals of each diabetic group were treated with insulin. Densitometric quantitation of silver clusters revealed that 5 weeks after diabetes induction P₀ mRNA only is significantly increased, while at 14 weeks both P₀ and MBP mRNA contents are markedly higher than controls. Insulin treatment normalizes glycemia levels and slightly counteracts increased P₀ mRNA at both stages of diabetes. An increase in MBP mRNA is observed in chronic diabetic animals only, and is unaltered by the normoglycemic effect of insulin. The increased transcript levels of P₀ and MBP suggest that Schwann cells can modulate gene expression of myelin-specific proteins in response to diabetic-induced metabolic derangement. Such a change may represent a higher turnover of myelin proteins as an attempt by the Schwann cells to repair the diabetes-induced nerve damage. The observed pattern of transcript amount is only slightly influenced by insulin treatment.