Carbohydrates: Role, Metabolism and Related Diseases

Carbohydrates are one of the essential nutrient groups, playing a crucial role in the body as the primary energy source, forming structural components of cells and participating in complex biochemical processes.

Carbohydrate Metabolism

Carbohydrate Breakdown Process:

• Enzymes involved:

• Phosphorylase: Breaks down α-1,4 bonds in glycogen chains.

• Glucano transferase: Transfers branches in glycogen molecules.

• 1,6-glucosidase: Breaks down α-1,6 bonds in glycogen chains.

• Phosphoglucosemutase: Converts glucose-1-P to glucose-6-P.

Carbohydrate Synthesis Process:

• Enzymes involved:

• Glycogen synthase: Synthesizes straight α-1,4 chains in glycogen chains.

• Amylose (1-4 1-6) transglucosesidase: Synthesizes branched α-1,6 chains in glycogen chains.

• UDP-Glu-Gal phosphat uridyltransferase: Converts Galactose-1-P to Glucose-1-P.

• UDP-Gal epimerase: Converts Galactose-1-P to Glucose-1-P.

Genetic Diseases Related to Carbohydrates

1. G-6-PD Deficiency (Glucose-6-phosphate dehydrogenase):

• Cause: Deficiency of the G6PD enzyme in the pentose phosphate pathway, leading to NADPH deficiency.

• Consequences: Hemolysis when using drugs that generate oxidizing radicals (such as Primaquin, Aspirin…).

• Mechanism: NADPH reduces oxidized glutathione to its reduced form, helping to break down H2O2 (H2O2 reduces red blood cell lifespan, damages cell membranes, leading to hemolysis).

2. Inherited Galactose Blood Disorder (Galactosemia):

• Cause: Deficiency of the UDP-glu-gal-uridyltransferase enzyme.

• Consequences: Accumulation of galactose in the body, causing mental retardation, cataracts, and enlarged liver.

• Treatment: Stop breastfeeding, replace with lactose-free milk.

Diseases Related to Carbohydrate Metabolism

1. Pancreatic Diabetes:

• Type 1:

• Occurs in children.

• Insulin is not secreted.

• Cause: Immune system attacks pancreatic beta cells.

• Treatment: Insulin supplementation (injection).

• Type 2:

• Occurs in older adults, obese individuals.

• Insulin is secreted but does not maintain normal glucose levels.

• Cause: Target cells do not respond to insulin (insulin resistance, due to cortisol, GH).

• Treatment: Diet modification, insulin-stimulating medications.

2. Spontaneous Hypoglycemia:

• Cause: Pancreatic cell tumor causing increased insulin secretion, leading to increased glucose conversion to glycogen.

• Consequences: Hypoglycemia, hypoglycemic coma.

3. Carbohydrate Metabolism in Starvation and Satiety:

• During Starvation:

• Adrenaline, glucagon convert glycogen to glucose in the liver.

• Glucagon synthesizes glucose.

• Glucocorticoids synthesize glucose from muscle amino acids.

• Adrenaline, GH break down lipids.

• The liver converts fatty acids to ketone bodies for tissue use to minimize glucose consumption.

• During Satiety:

• Liver, muscle: Insulin increases glucose conversion to glycogen.

• Increased triglyceride synthesis in adipose tissue.

• Brain: Glucose is oxidized to provide ATP.

Conclusion

Carbohydrates play a vital role in the body, and diseases related to carbohydrate metabolism can lead to serious complications. Understanding the mechanisms of carbohydrate metabolism and related diseases can help us take effective preventative measures and treatments.