Key Biochemical Aspects of Obesity Flashcards
Define the term obesity
When an individual is carrying an excess amount of adipose tissue. An excess of adipose tissue has many comorbidities. In terms of BMI, obesity is 30 or more.
How is BMI calculated and what are its limitations? Suggest alternative measurements
weight in kg/height in m, squared. BMI is easy to calculate and it works in general but it doesn’t take muscle into account. Other measurements are wasit:hip ratio, waist circumference, skin fold thickness. Body fat % could be another way but hard to measure. Some people store fat viscerally and others peripherally. Viscerally is more dangerous and so skinny people may be less healthy if they store all their fat viscerally.
Describe the role that adipocytes play in obesity
Adipocytes are fat storing cells and the main component of adipose tissue. Display hypertrophy (getting bigger) and hyperplasia (proliferation). They can change how much fat they store, mainly as triglycerides, by up to 4x. This is what constitutes gaining weight.
Describe the components that make up adipose tissue and the adipokines that they release.
Adipocytes, fibroblast cells, and immune cells. Leptin is the key adipokine released, and it turns off starvation signals. If organisms have no leptin, they have sever weight gain. Giving them leptin supresses weight gain.
Describe the role of ghrelin and where it is secreted from
Ghrelin is the hormones secreted by the stomach when the stomach is empty. Promotes hunger.
Describe how leptin and ghrelin work together to regulate the gut brain axis
Leptin is constitutively released by the adipose tissue, so levels are fairly constant over time. An increase in adiposity = an increase in leptin. Ghrelin is released when the stomach is empty so more frequently. The balance between ghrelin and leptin determine levels of hunger or satiety
Describe which part of the brain regulates the gut-brain axis and how it does it
The hypothalamus integrates the signals from letpin and ghrelin. The hypothalamus contains the Arcuate Nucleus, which contains two sets of neurons with opposing functions. The POMC neurons are anorexigenic (inhibit hunger) and the AgRP neurons are orexigenic (stimulate hunger).
