Lens Metabolism

1 Lens Metabolism

Hexokinaseenzyme Glucose G6P 2 Lens Metabolism

Hexokinase Glucose G6P 3 Lens Metabolism

Hexokinase Glucose G6P

Anaerobicmetabolic Glycolysispathway (majority of glucose)

F6P

Pyruvate

Krebs/TCA 4 Lens Metabolism

Hexokinase Glucose G6P

Anaerobic Glycolysis (majority of glucose)

F6P

Pyruvate

Krebs/TCA 5 Lens Metabolism

Hexokinase Glucose G6P

Anaerobic metabolic HMPpathway Shunt Glycolysis (majority of glucose) (5% of glucose)

F6P

Pyruvate

Krebs/TCA 6 Lens Metabolism

Hexokinase Glucose G6P

Anaerobic HMP Shunt Glycolysis (majority of glucose) (5% of glucose)

F6P

Pyruvate

Krebs/TCA 7 Lens Metabolism

Hexokinase Glucose G6P

Aldose Reductaseenzyme

Anaerobic product HMP Shunt Sorbitol Glycolysis (majority of glucose) (5% of glucose)

Fructoseproduct F6P

Pyruvate

Krebs/TCA 8 Lens Metabolism

Hexokinase Glucose G6P

Aldose Reductase

Anaerobic HMP Shunt Sorbitol Glycolysis (majority of glucose) (5% of glucose)

Fructose F6P

Pyruvate

Krebs/TCA 9 Lens Metabolism

Hexokinase Glucose G6P

Aldose Reductase

Anaerobic HMP Shunt Sorbitol Glycolysis (majority of glucose) (5% of glucose) In a high-glucose environment, these accumulate in the lens, increasing osmotic pressure within it. This results in swelling, cytoskeletal disruption, and ultimately a diabetic cataract Fructose F6P

Pyruvate

Krebs/TCA 10 Lens Metabolism

Hexokinase Galactose Glucose G6P

Aldose Reductase

Anaerobic HMP Shunt Sorbitol Glycolysis (majority of glucose) (5% of glucose) In a high-glucose environment, these accumulate in the lens, increasing osmotic pressure within it. This results in swelling, cytoskeletal disruption, and ultimately a diabetic cataract Fructose F6P

Pyruvate

Galactitolproduct Krebs/TCA 11 Lens Metabolism

Hexokinase Galactose Glucose G6P

Aldose Reductase

Anaerobic HMP Shunt Sorbitol Glycolysis (majority of glucose) (5% of glucose) In a high-glucose environment, these accumulate in the lens, increasing osmotic pressure within it. This results in swelling, cytoskeletal disruption, and ultimately a diabetic cataract Fructose F6P

Pyruvate Galactitol Krebs/TCA 12 Lens Metabolism

Hexokinase Galactose Glucose G6P

Aldose Reductase

Anaerobic HMP Shunt Sorbitol Glycolysis (majority of glucose) (5% of glucose) In a high-glucose environment, these accumulate in the lens, increasing osmotic pressure within it. This results in swelling, cytoskeletal disruption, and ultimately a diabetic cataract Fructose F6P

In a high-galactose environment (ie, in galactosemia), aldose reductase converts galactose to galactitol, which Pyruvate is an inert end-product. The accumulation of galactitol Galactitol increases osmotic pressure within the lens, resulting in swelling, cytoskeletal disruption, and ultimately a galactosemia cataract Krebs/TCA 13 Lens metabolism is dependent upon the presence of glucose, not oxygen. Even in zero-oxygen environment (such as can be created in the lab), a lens will remain transparent ands viable so longLens as it has an adequateMetabolism glucose supply. However, in the reverse environmental situation— that is, one in which oxygen is abundant but glucose is absent—the lens will become cloudy and nonviable in a matter of hours.

Hexokinase Galactose Glucose G6P

Aldose Reductase

Anaerobic HMP Shunt Sorbitol Glycolysis (majority of glucose) (5% of glucose) In a high-glucose environment, these accumulate in the lens, increasing osmotic pressure within it. This results in swelling, cytoskeletal disruption, and ultimately a diabetic cataract Fructose F6P

In a high-galactose environment (ie, in galactosemia), aldose reductase converts galactose to galactitol, which Pyruvate is an inert end-product. The accumulation of galactitol Galactitol increases osmotic pressure within the lens, resulting in swelling, cytoskeletal disruption, and ultimately a galactosemia cataract Krebs/TCA