Clinical forms and epidemiology of lesions
Diabetes mellitus triggers diffuse or focal damage to peripheral and autonomic nerve fibers.
- Diabetic polyneuropathy unites a complex of clinical and subclinical syndromes.
- Painful form is registered in 6–34% of patients.
- Cardiac form of autonomic disorders is recognized as the most severe condition with a high risk of sudden cardiac death.
Carbohydrate metabolism as the basis of antioxidant defense
The functional capacity of the glutathione antioxidant system directly depends on glucose metabolism.
- Pentose phosphate pathway oxidizes glucose-6-phosphate using the enzyme glucose-6-phosphate dehydrogenase, converting $NADP^+$ to $NADPH$.
- The resulting $NADPH$ activates glutathione reductase, which reduces oxidized glutathione ($GSSG$) to its active form ($GSH$).
- Glutathione peroxidase uses reduced glutathione to neutralize hydrogen peroxide.
Deficiency of this mechanism leads to oxidative damage to proteins and cells.
Hyperglycemia and oxidative stress
Chronic hyperglycemia and insulin resistance form a destructive pathogenetic cycle.
- Excess glucose activates the polyol pathway, where aldose reductase depletes $NADPH$ reserves by competing with protective enzymes.
- Enhanced oxidation of substrates in mitochondria increases the generation of free radicals.
- Non-enzymatic glycation of proteins forms advanced glycation end products that suppress antioxidant enzymes (catalase, superoxide dismutase).
Stress-response mechanisms
Any stress reactions via the sympathoadrenal system activate lipid peroxidation and the release of counter-regulatory hormones. Adrenaline, glucagon, and glucocorticoids enhance glycogenolysis and maintain hyperglycemia, uniting metabolic disorders and oxidative stress into a single loop.
The pentose pathway yields NADPH, glutathione reductase rescues the cell, and hyperglycemia destroys everything through the polyol shunt.
Class and exam questions
What percentage do polyneuropathies constitute among all diabetic neuropathies?
Diabetic polyneuropathy accounts for 90% of all possible neuropathy variants in diabetes mellitus.
Why is the cardiac form of autonomic disorders considered particularly dangerous?
Cardiac autonomic disturbances are recognized as the most severe complication of diabetes, as patients fall into the high-risk group for sudden cardiac death.
How does carbohydrate metabolism fuel antioxidant defense?
The oxidative branch of the pentose phosphate pathway produces NADPH via the enzyme glucose-6-phosphate dehydrogenase, which is necessary for glutathione reduction and peroxide neutralization.
What does activation of the polyol pathway lead to in diabetes?
The polyol pathway consumes the NADPH cofactor to convert excess glucose into sorbitol, depleting antioxidant defense and enhancing oxidative stress.
What else to study on this topic
- The role of mitochondrial dysfunction and neuronal apoptosis in type 1 and type 2 diabetes mellitus
- The impact of hypothyroidism on the development of peripheral polyneuropathy and carpal tunnel syndrome
- Mechanisms of advanced glycation end-product (AGE) formation and their effect on vessels and nerves
- The role of methemoglobin reductase in coupling glycolysis with hemoglobin protection
- Pathogenetic features of hypercortisolism and its similarity to diabetic complications
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