[The pathogenesis of diabetic and hepatic neuropathies]

The pathomechanism of neuropathies associated with diabetes and chronic liver diseases are poorly understood. Both metabolic and vascular factors are involved in the pathogenesis of diabetic neuropathy. It seems likely, that microangiopathy on the one hand and changes of various metabolic pathways due to hyperglycaemia on the other hand are much more related to each other than it was suggested previously. Nitric oxide may be the link between the metabolic and vascular hypotheses of diabetic neuropathy. Both reduced endoneurinal blood flow and increased oxidative stress leads to reduced nitric oxide synthetase activity. There are widespread inter-relationships between the most relevant metabolic changes included polyol pathway hyperactivity, reduced myoinosit concentration, advanced glycation end products formation, increased oxidative stress and lipid peroxidation. Changes of hemorheological conditions and primary hemostasis leeds to hyperviscosity just as to increased activity of the coagulation system. Among patients with chronic alcoholic liver diseases the direct toxic effect of alcohol is of particular relevance, however, malabsorption, impairment of axoplasmatic transport, changes of intermedier metabolism as well as thiamine and pyridoxine deficiency are of importance as well. The role of decreased insulin sensitivity and various degrees of glucose intolerance related to chronic liver diseases are still underestimated. Impairment of proteoglycan metabolism as well as increased oxydative stress are thought to be important factors in the pathogenesis of both diabetic and hepatic neuropathies. Glucose autooxidation and enhanced lipid peroxidation contribute to increased oxidative stress in patients with diabetes and chronic liver diseases as well. Vitamin E deficiency, autoimmun processes, circulating immune complexes, cryoglobulinemia, just as changes of vascular responsiveness associated with nitric oxide activity plays a role in the development of neural damage of hepatic origin. Most likely, similarly to diabetes mellitus, vascular changes contribute to the development of neuropathy in patients with chronic liver diseases.