بسم الله الرحمن الرحيم

• Carbohydrate Metabolism

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• prof.dr azza elkattawy

�BLOOD GLUCOSE�

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prof.dr.Azza M.Elkattawy

�BLOOD GLUCOSE�

diet

GLUCONEOGENESIS,

GLYCOGENOLYSIS

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oxidation

glycogenesis

lipogenesis

Excretion in urine

factors Regulate the Concentration of the Blood Glucose level

A- Hormonal Factors

B-hepatic Factor

C-renal threshold of the Glucose,GIT, adipose tissue ,skeletal muscles

D- coenzyme necessary for oxidation of glucose

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prof.dr.Azza M.Elkattawy

A- Hormonal Factors �1- Insulin

Insulin Plays a Central Role in Regulating Blood Glucose

It is produced by the β cells of the islets of

Langerhans in the pancreas in response to hyperglycemia.

controlling glycolysis,

stimulate=glycogenesis,lipogenesis

Inhibit= gluconeogenesis,glycogenolysis

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prof.dr.Azza M.Elkattawy

2-Glucagon Opposes the Actions of Insulin�

Glucagon is the hormone produced by the α cells of the pancreatic islets.

Both hepatic glycogenolysis and gluconeogenesis contribute to the hyperglycemic effect of glucagon,

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prof.dr.Azza M.Elkattawy

3-Anterior pituitary hormones

The anterior pituitary gland secretes hormones that tend to elevate the blood glucose and therefore antagonize the action of insulin.

growth hormone it decreases glucose uptake in muscle.Some of this effect may not be direct, since it stimulates mobilization of free fatty acids from adipose tissue, which themselves inhibit glucose utilization. Inhibit glucokinase enzyme

ACTH (corticotropin)

and possibly other “diabetogenic”hormones

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prof.dr.Azza M.Elkattawy

4-The glucocorticoids (11-oxysteroids)

are secreted by the adrenal cortex and increase gluconeogenesis.

- glucocorticoids inhibit the utilization of glucose in extra hepatic tissues.

This is a result of enhanced hepatic uptake of amino acids and increased activity of aminotransferases and key enzymes of gluconeogenesis

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prof.dr.Azza M.Elkattawy

5-Epinephrine

it is secreted by the adrenal medulla as a result of stressful stimuli and leads to glycogenolysis

in liver and muscle owing to stimulation of phosphorylase via generation of cAMP.

In muscle, glycogenolysis results in increased glycolysis, whereas in liver glucose is the main product leading to increase in blood glucose.

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prof.dr.Azza M.Elkattawy

B-hepatic factor

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prof.dr.Azza M.Elkattawy

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• The liver after a carbohydrates meal, becomes a net consumer of glucose (normally the liver is glucose producing rather than glucose utilizing tissue).
• It retains roughly 60 of every 100 g of glucose presented by the portal system.

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• The majority of glucose is taken by it to be oxidized by increased glycolysis and increased HMS or to be stored as glycogen (increased glycogenesis).

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• In the fasting state, it adds glucose to blood through increased glycogenolysis and increased gluconeogenesis.

��C-Renal Threshold for Glucose� �

When the blood glucose rises to relatively high levels, the kidney also exerts a regulatory effect.

Glucose is continuously filtered by the glomeruli but is normally completely reabsorbed in the renal tubules by active transport.

The capacity of the tubular system to reabsorb glucose is limited to a rate of about 180 mg/100ml blood,

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prof.dr.Azza M.Elkattawy

C-Renal Threshold for Glucose�

in hyperglycemia the glomerular filtrate may contain more glucose than can be reabsorbed, resulting in glucosuria.

Glucosuria occurs when the venous blood glucose concentration exceeds 9.5–10.0 mmol/L; this is termed the renal threshold for glucose.

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prof.dr.Azza M.Elkattawy

�Adipose tissue: �

• After intake of carbohydrate meal, there are increased glucose transport into adipocytes (very sensitive to insulin concentration) increased glycolysis and increased HMP.
• Also, storage of excess glucose as triglycerides in adipose tissue occurs (lipogenesis).

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�Skeletal muscles: �

• After carbohydrate rich meal, there will be transient increase in blood glucose and insulin increased glucose transport into the skeletal muscle cells increased metabolism of glucose to provide the energy needed by the cells. Also, the excess glucose will be stored as glycogen (increased glycogenesis).

D-Coenzymes necessary for oxidation of glucose

1-TPP FROM B1

2- FLAVIN FROM B2

3,4- NAD,NADP FROM NICOTINIC ACID

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prof.dr.Azza M.Elkattawy

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prof.dr.Azza M.Elkattawy