Decreased polyphosphoinositide metabolism accompanies myelinated fiber loss in human peripheral neuropathies

The distribution of incorporated 32P in phospholipids of sural nerve biopsy samples from patients with several peripheral neuropathies was measured. Both the absolute amount and the proportion of isotope in polyphosphoinositides was decreased in nerves that displayed substantial (> 50%) depletion of myelinated fibers as compared to nerves that exhibited minimal depletion. The results suggest that diminished metabolism of these substances is an indicator of myelin loss, and are consistent with the conclusion that polyphosphoinositide turnover in human nerve is nearly entirely localized to the myelin sheath.