KinGdom of MediCine 💊 مملكة الطب:
#Biochemistery
#Carbohydrate_metabolism
#بوست_رقم (18)
الليلة ان شاء الله ح نتكلم عن
Blood glucose Regulation
🌸 Regulation of blood glucose (homeostasis):
اول حاجه خلونا نعرف ال normal blood glucose كم
In fasting state= 60-100 mg/dl (3,6-6,1 mmol/L)
One hour after carbohydrate meal = 120-150 mg/dl (6,7-8,3 mmol/L)
Two hours after carbohydrate meal = 65-140 mg/dl (3,6-7,8 mmol/L)
🔥Note:
For glucose 1 milimole/L (mmol/L) = 18 mg/dl
طيب ح يحصل balance في ال blood glucose كيف؟! عن طريق two factors و hormonal و hepatic and renal mechanisms.
طيب نشوف ال two factors
Factor 1: Rate of glucose enterance into the blood stream.
Blood glucose may be derived from the following sources:
1. From other carbohydrates e.g. Fructose, Galactose,etc..
2. By absorption from the intestine.
3. Glycogenolysis.
4. Gluconeogensis.
Factor 2: Rate of removal from the blood stream. By:
1. Oxidation to supply energy.
2. Glycogenesis.
3. Lipogenesis specially in adipose tissue.
4. Formation of Fructose in seminal fluid, lactose in lactating mammary gland, glycoproteins and glycolipids.
5. Formation of ribose sugers for nucleic acid synthesis.
🌸 Hormonal regulation:
1. Insulin
دا هرمون بتطلعوا لي beta cell موجودة في ال islet of langerhans في ال pancreas
وطبعا زي ماعرفنا زمان انه الهرمون دا بطلع بعد ال meal مباشرة ف طوالي بجي بعمل reduces لل blood glucose level كيف ؟! بإنه بعمل العمليات اللي قلناها في factor 2 فوق ☝️
2. Glucagon:
يلا دا بتطلعوا لي alpha cells of islets of langerhans of pancreas
ودا طوالي بزيد لي من معدل الجلكوز في الدم كييف؟! بواسطة العمليات اللي قلناها في factor 1
3. Catecholamines (epinephrine and norepinephrine):
دي بتطلع لي من ال suprarenal medulla
وبرضو بزيد لي من ال blood glucose level عن طريق شنو لكن؟
By stimulation of glycogenolysis.
🌟they tend to increase blood glucose level even if there is hyperglycemia as in case of stress.
4. Glucocorticoids as cortisol:
دي عبارة عن group of steroid hormones وبتطلع من ال suprarenal cortex.
برضو بتزيد ال level of blood glucose لكن كيف؟!
By stimulation of Gluconeogensis.
5. Growth hormone:
دي بتطلع من ال anterior pituitary gland.
دا بعمل antagonizes لل insulin hormone وبكدا ح يزيد لي ال blood glucose لكن كيف؟!
Through:
1. Inhibition of glucose uptake by cells.
2. Blocks the insulin action at cell membranes.
🌸 Hepatic regulation:
Liver plays a very important role in keeping blood glucose level within range
🍁 During fasting: liver adds glucose to blood by glycogenolysis and gluconeogensis.
🍁 After carbohydrate meal: glucose is transported in portal blood to the liver
حوالي 40% من ال glucose بتمشي لل blood وتحفز ال insulin secretion وبعد كدا taken up by brain ,muscles, adipose tissue and liver
وال 60% المتبقية دي بتاخدها ال liver وتحولها ل glucose-6-P عن طريق Glucokinase enzyme
كدي نتكلم شوية عن ال Glucokinase دا
1. Has low affinity for glucose relative to hexokinase found in most tissues.
بحتاج كمية كبيرة من ال glucose عشان يشتغل لكن ال Hexokinase دا بأقل كمية من الجلكوز بتحفز.
2. Glucokinase is stimulated by insulin secreted in response to hyperglycemia , for this reason, less glucose is taken up by liver during fasting.
طيب ال fate بتاع glucose-6-P شنو؟!
1. Conversion to glycogen (Glycogenesis )
2. Lipogenesis.
🌸 Renal regulation:
Circulating blood glucose is filtered in glomerular filtrate and reabsorbed again by certain tubular enzymes , this saves blood glucose from loss in urine.
اذا ال blood glucose level زااد يعني exceeds certain limits طوالي ال glucose بزيد في ال glomerular flitrate وبتجاوز ال capacity of tubular enzymes to reabsorb ot
عشان كدا ال glucose بظهر في ال urine.
This limit is called renal threshold for glucose reabsorption.
🌸 Definition of renal threshold:
it is blood glucose level above which glucose appears in urine. (Average 180 mg/dl).
عندنا low renal threshold و high renal threshold
نشوف كل واحد براهو
🌸 Low renal threshold:
Where glucose appears in urine even when blood glucose level is low. This occur in :
1. Normally in some persons due
to defective tubular enzymes for glucose reabsorption.
2. In 20% of pregnant females.
🌸 High renal threshold:
Where glucose appears in urine in concentration above the renal threshold (may reach 220 mg/dl or more) , this occurs in :
1. Elderly people due to reduced glomerular filtration rate.
2. In cases of diabetes associated with renal damage.
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