Summary theme 6

Semester 2.2, theme 6, endocrine systems

Week 21 , Overweight, metabolic syndrome and type 2 diabetes mellitus

1. understand metabolism; absorption, transport, storage and breakdown of nutrients

Absorption happens in the GI tract. Per substance it is different how they are stored and how they
are broken down.
Carbohydrate metabolism:
- absorption: in jejunum as
monosaccharide absorbed and
transported in mainly the form glucose
- storage: glucose is stored as glycogen.
in the liver and in muscles
* glucose  G6P is only reversable in
liver cells, in renal tubular and
intestinal epithelium
* glycogen can also be stored as fat. Can
happen only in the presence of insulin.
concerted in triglycerides via acetyl-CoA.
- breakdown: glycogenolysis and glucose
into the energy metabolism

Regulation: Insulin and glucagon play a big role. Also epinephrine. ATP, ADP and ADP effect glycolysis.
Citric ion causes glycolysis not to be ahead of Krebs cycle. Cortisol is important in the regulation of
gluconeogenesis.
* somatostatin inhibits both insulin and glucagon. It delays assimilation of nutrients from the GI.

Protein metabolism
- absorption: in jejunum as AA, also transported as AAs in ionized state.
- storage: in cells, AA form proteins and thus low [free AA] in cell. Aminotransferase for AAprotein
* also plasma proteins (albumin, globulin, fibrinogen)
* tissue proteins : plasma proteins = 33:1
* can also be stored as fat: concerted into Acetyl-CoA and then into triglycerides.
- breakdown: too much proteins  protein  AA  fat or glycogen
* adrenocortical hormones: protein  AA

Regulation: AAprotein Protein AA
- GH and insulin - adrenocortical hormones
- testosterone/oestrogen  also more plasma proteins
- thyroxine (higher cell metabolism)

Fat metabolism
- Digestion: triglycerides  monoglycerides + FA
- Absorption: monoglycerides + FA  triglycerides  chylomicrons  lymph
- Transport: 95% of lipids in blood is in lipoproteins. Free FA bind with albumin in the blood.
- Storage: triglycerides are stored in fat cells

, * conversion of triglycerides is mainly in the liver
- Breakdown: beta-oxidation: triglycerides  glycerol + FA  glycerol into glycolytic pathway and FA
into mitochondria for beta-oxidation: formation acetyl CoA.
* much FA in blood?  much ketone bodies  acetone breath (i.e. in starvation, DM, high fat
diet)

Regulation: Conversion of carbs into fat storage happens due to insulin
- epinephrine, norepinephrine, corticotropin hormones  the breakdown of triglycerides
- thyroid hormone  fat mobilization

2. know about the role of various organs in metabolism

Liver: important in the storage of glycogen. But also the conversion of a lot of substances.
Brain: uses a lot of energy, mostly glucose. Only after longer period of adaption, fat can be used.
Muscles: storage of glycogen.

3. know about with the relationship between carbohydrates, lipids and proteins

Carbohydrates are the main source of energy. Only if not available, lipids will be used. If
glucose is not present and needed: gluconeogenesis: glucose made out of fats and proteins.
* alanine  pyruvic acid  glucose
* fats can via acetyl-CoA, as well as proteins.

4. know about with the regulation of food intake

Feeding centre: lateral nuclei of hypothalamus. Orexigenic substances.
- insulin, leptin, CCK  NPY-AGRP nuclei  more food intake and less energy expenditure
Satiety centre: ventromedial nuclei of hypothalamus. Anorexigenic substances.
- Ghrelin  POMC-CART  a-MSH  less food intake and more energy expense
* MCR-4 mutation? = associated with obesity