Obesity= a group of disorders of energy balance in which surplus energy
is stored as fat.
BMI
Weight/ height 2
Main problem is that elevated body weight does not mean its fat, could
also be muscle.
Condition called sarcopenia (muscle wastage) reduced lean body mass so
often compensated by fat mass.
Waste circumference.
Measuring of waste to see the amount of abdominal fat.
Effects of obesity
Has different effects depending on the location of the adipose tissue.
1. Apple shaped= large amount of visceral fat, fat surrounds the
organs
2. Pear shaped= fat on hips, buttock, and thighs.
Problems with excessive visceral fat
- Type 2 diabetes
- Respiratory disorders
- Reproductive disorders
- Cancer of colon, prostate etc.
Obesity also exhibits low grade inflammation; the adipose tissue is
infiltrated with macrophages therefore have increased concentration of
inflammatory mediators e.g. IL-6 etc.
Genetics of obesity
This genetic defect is rare in humans, but it does produce obesity in
homozygous individuals.
Leptin is a small protein produced by white adipose tissue therefore more
fat means more leptin.
Leptin interacts with receptors in the hypothalamus to inhibit food intake
and increase energy expenditure.
Obese humans are leptin resistant. Fall in leptin causes intense drive to
eat.
Heritable changes in DNA methylation and histone modifications causes
change in gene expression which can cause obese children.
Fatty acids
, 1. Triacylglycerol- energy storage, the acyl chains carry the energy.
2. Phospholipids- membrane structure
3. Prostaglandins- signalling molecule
4. Myristylation (attach irreversibly to glycine residues) and
palmitoylation (reversibly attaches to cysteine) - attachment to
proteins, examples of post translational modification.
Fatty acid synthesis in adipose tissue
- Glucose is taken up by the cell via GLUT4 transporters.
- Goes through glycolysis where its phosphorylated and turns into
pyruvate.
- Pyruvate is turned into acetyl CoA (pyruvate dehydrogenase)
- Acetyl CoA is converted into Malonyl CoA (Acetyl CoA
carboxylase)
- Synthesises long chain fatty acids.
Synthesises happens in the cytoplasm of the cell, acetyl CoA is generated
in the mitochondria. Inner membrane of mitochondria is impermeable to
acetyl CoA, so it combines with oxaloacetate and turns into citrate.
Citrate can leave the mitochondrial membrane. Acetyl CoA is released,
and oxaloacetate is regenerated.
There is no oxaloacetate transporter, so NADH converts it to
Malate and releases NADPH which is then converted to pyruvate
and pyruvate is able to re-enter to mitochondria and turns into
oxaloacetate again and reused.
is stored as fat.
BMI
Weight/ height 2
Main problem is that elevated body weight does not mean its fat, could
also be muscle.
Condition called sarcopenia (muscle wastage) reduced lean body mass so
often compensated by fat mass.
Waste circumference.
Measuring of waste to see the amount of abdominal fat.
Effects of obesity
Has different effects depending on the location of the adipose tissue.
1. Apple shaped= large amount of visceral fat, fat surrounds the
organs
2. Pear shaped= fat on hips, buttock, and thighs.
Problems with excessive visceral fat
- Type 2 diabetes
- Respiratory disorders
- Reproductive disorders
- Cancer of colon, prostate etc.
Obesity also exhibits low grade inflammation; the adipose tissue is
infiltrated with macrophages therefore have increased concentration of
inflammatory mediators e.g. IL-6 etc.
Genetics of obesity
This genetic defect is rare in humans, but it does produce obesity in
homozygous individuals.
Leptin is a small protein produced by white adipose tissue therefore more
fat means more leptin.
Leptin interacts with receptors in the hypothalamus to inhibit food intake
and increase energy expenditure.
Obese humans are leptin resistant. Fall in leptin causes intense drive to
eat.
Heritable changes in DNA methylation and histone modifications causes
change in gene expression which can cause obese children.
Fatty acids
, 1. Triacylglycerol- energy storage, the acyl chains carry the energy.
2. Phospholipids- membrane structure
3. Prostaglandins- signalling molecule
4. Myristylation (attach irreversibly to glycine residues) and
palmitoylation (reversibly attaches to cysteine) - attachment to
proteins, examples of post translational modification.
Fatty acid synthesis in adipose tissue
- Glucose is taken up by the cell via GLUT4 transporters.
- Goes through glycolysis where its phosphorylated and turns into
pyruvate.
- Pyruvate is turned into acetyl CoA (pyruvate dehydrogenase)
- Acetyl CoA is converted into Malonyl CoA (Acetyl CoA
carboxylase)
- Synthesises long chain fatty acids.
Synthesises happens in the cytoplasm of the cell, acetyl CoA is generated
in the mitochondria. Inner membrane of mitochondria is impermeable to
acetyl CoA, so it combines with oxaloacetate and turns into citrate.
Citrate can leave the mitochondrial membrane. Acetyl CoA is released,
and oxaloacetate is regenerated.
There is no oxaloacetate transporter, so NADH converts it to
Malate and releases NADPH which is then converted to pyruvate
and pyruvate is able to re-enter to mitochondria and turns into
oxaloacetate again and reused.
