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Baffled by some of the words? Check out the Key terms page 

Clinical Obesity 

overweight to a degree which causes medical complications

Leptin is secreted by cells in adipose tissue and acts on the hypothalamus of the brain to inhibit appetite

KEY CONCEPT: 

What is Leptin? 

Leptin is a hormone secreted from fat cells which helps to regulate body weight. The name leptin is derived from the Greek word ‘leptos’ meaning thin. It is sometimes referred to as the ‘Fat Controller’.

What is adipose tissue? 

Adipose tissue, or fat, is an anatomical term for loose connective tissue composed of adipocytes.

 

a cell specialized for the storage of fat, found in connective tissue.

 

 

 

What is the hypotahlamus ? 

 

 

 

a region of the forebrain below the thalamus that coordinates both the autonomic nervous system and the activity of the pituitary, controlling body temperature, thirst, hunger, and other homeostatic systems, and involved in sleep and emotional activity.

 

 

 

 

Many laboratory mice, are referred to as "homozygous", in terms of single cell mutations, which lead to them becoming severely obese. 

 

There are two kinds of mutations; 

 

Ob/ob = this refers to the mutations which take place in the gene for leptin which is a hormone leptin. 

 

After being injected with leptin the mice return to their normal body weight. 

 

The term db/db refers to the mutations in the gene which code for the receptor of leptin. 

 

 

 

 

 

 

Leptins in Humans 

Human leptin refers to a protein which consists of 167 amino acids. 

Made in the adipocytes (fat cells) of the white adipose tissue, the level of the leptin also happens to be directly proportional to the total value of fat the body aquires. 

 

Leiptin acts according to the receptors located in the hypothalamus part of the brain which; 

 

counteracts the effects of neurpeptide Y (this refers to a "potent" feeding stimulant which is secreted in teh gut in addition to the hypothalamus) 

 

Counteracts the effects of anadamide (this is another example of stimulat which feeds on potent; it binds to the same recepotrs as THC) 

 

 

 

  • promotes the synthesis of α-MSH, an appetite suppressant;

  • the result: inhibition of food intake.

This inhibition is long-term, this is quite different to 

  • the quick inhibition of eating throughout cholecystokinin (CCK) and

  • the slower ability to suppress  hunger between meals caused  by PPY3-36

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The absence of a functional hormone (or its receptor) leads to uncontrolled food intake and this eventually leads to obesity.

 

 

 

Interesting video on Adipose tissue 

Figure 1 : Leptin

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