What is the significance of isolated increase of Asialo-GM1 antibodies with nerve conduction suggestive of sensory motor axonal polyneuropathy?

These autoantibodies need to be interpreted with clinical context.

Generally, GM1 IgM antibodies are associated with multifocal motor neuropathy with conduction block (MMN), which is a pure motor syndrome with acquired demyelinating features on nerve conductions/EMG.

GM1 IgG antibodies are typically associated with acute motor axonal neuropathy (AMAN) - a GBS variant. 

If the patient has a clinical history, exam, and electrodiagnostic studies consistent with either of these entities (MMN, AMAN) and the appropriate autoantibody that is one thing. But if the patient has a more chronic and insidious prototypical sensorimotor axonal polyneuropathy I'm not sure that there is an association between the condition and the abnormal laboratory test.