FORM & FUNCTION (Obesity 1) Flashcards
Obesity:
-over-accumulation of adipose tissue
-increased risk for metabolic disorders (ex. diabetes, steatosis)
-associated with various endocrine alterations (thyroid, insulin, etc.)
Overweight and Obese BW:
-overweight: over 15% of optimal
-obese: over 30% of optimal
Percent of dogs, cats and horses that are overweight or obese:
-dogs: 35-40%
-cats: 25-35%
-horses: 27-35%
Fundamental cause:
-multiple risk factors
-human sociological factors
*when caloric intake is way greater then energy expenditure (metabolism)
Multiple risk factors:
-breed
-age
-sex hormones (neuter/spay
-metabolic disorders (ex. hypothyroidism, hyperadrenocorticism)
-medication (ex. steroids, anticonvulsants, antidepressants and more)
Sex hormones (neuter/spay)
-excess early weight predispose animal to adult obesity (1.5x)
>due to reduction of sex hormones when they are spayed/neutered
Human sociological factors:
-feeding = means of communication
-lifestyle (of owner)
Obesity is a difficult topic:
-more about communication issues than medical
-only 50% of owners know their pets have a weight problem
-MANY believe that food intake has nothing to do with obesity
>will blame inactivity but not too much food!
Fat from digestive CHO, protein or lipids
-excess from diet ends up becoming fat
Fat molecules:
-very metabolically active
>they will grow over time
-they are an endocrine organ when they hypertroph
Fat that has hypertrophied:
-attracts macrophages, lymphocytes, neutrophils and other immune cells
*’adipokines’ dysfunction
High circulating fat with inflammatory markers eventually leads to:
-pancreatitis (pancreas inflammation)
-cirrhosis (liver scaring)
(white) adipose tissue:
-classically though as an organ that ONLY serves to store energy and provid insulation
-recent evidence shows it is an endocrine organ
Adipose tissue: endocrine organ
-controls energy metabolism via hormone and cytokine release (adipokines)
>release of hormones and cytokines can have a hug impact on the body
Leptin: peptide hormone
-made from fat
-secreted into the blood
-acts on the brain
-level is proportional to fat level
Leptin after high fat diet:
-increases for around 8hrs then decreases back to normal state
Major function of leptin:
-regulate appetite (signals to brain to stop eating)
-slow down fat synthesis
-promote fate break down (beta-oxidation)
Leptin and obesity:
-ob/ob alleles
-inability to make it OR development of leptin resistance DIRECTLY leads to obesity
Leptin in liver:
-controls fat metabolism by stimulating AMP kinase activation (AMPK)
>acts to slow down FA biosynthesis by inactivating ACC via AMPK
*promotes fat usage rather than storage
Leptin in muscle:
-stimulates beta-oxidation to reduce body fat mass
>inhibits AMPK and therefore ACC to reduce malonyl CoA accumulation
>reduction of malonyl-CoA will allow for beta-oxidation to continue
No FAS in muscle (leptin):
- but malonyl-CoA are still synthesized by ACC when acetyl-CoA are in excess
*high malonyl-CoA inhibits carnitine attachment=inhibits beta-oxidation
Circulating leptin levels in obese animals:
-constitutively high
*due to development of leptin resistance
Leptin resistance:
-not leptin deficient, but diminished end-organ response
-primarily impairs the satiety effect, but can diminish AMPK regulation in peripheral tissues (liver, muscle)
Tumour necrosis factor-alpha (TNF-a)
-when high levels it disrupts insulin function via 2 mechanisms
-cytokine
-levels are increased when fat is elevated
Development of insulin resistance:
-leads to cells not properly storing glucose/fat
-then leads to progression towards diabetes and steatosis
2 mechanisms how TFN-a disrupts insulin function:
-inhibits IRS-1
-inhibits PP1
TNF-a inhibits IRS-1:
-normal: required for GLUT4 activation
-impairs glucose uptake in muscle and fat
TNF-a inhibits PP1:
-impair glycogen and fat formation (via inhibition of protein phosphatase 1)
-disrupts insulin’s inhibitory effect on hormone-sensitive lipase
TNF-a in obese dogs:
-elevated levels
-insulin resistance development
*more insulin required after a meal to process glucose
-very little changes in pre meal insulin, but changes in post meal insulin
>overtime triggers insulin resistance and leads to type 2 diabetes
Obesity effects:
-joint disorders
-osteoarthritis
-diabetes mellitus
-reduced life span
