Energy and Obesity

Question 1

What is the respiratory quotient?

Answer 1

RQ=ratio of CO2 produced by a fuel (e.g. carbs/fat) to O2 used to burn the fuel

Question 2

What fuel is used with a RQ = 1?

Answer 2

oxidizing carbs

Question 3

What fuel is used with RQ= 0.7?

Answer 3

oxidizing fat

Question 4

What fuel is used with RQ= 0.8?

Answer 4

oxidizing fats and carbs

Question 5

What is the RQ for protein oxidation?

Answer 5

~0.81

Question 6

What does an RQ > 1.1 indicate?

Answer 6

fat synthesis

RARE: if force-fed carbs all day

Question 7

What are long term signals of body fat?

Answer 7

insulin and leptin

Question 8

Short term signals of body fat

Answer 8

signals from gut: ghrelin, CCK, GLP-1, PYY, apoA IV

leptin modulates sensitivity to short therm signals (CCK)

Question 9

What are adiposity signals?

Answer 9

leptin (from fat) and insulin (from pancreas)

Question 10

What are satiation signals?

Answer 10

CCK, GLP-1, gastric distension

Question 11

What are orexigenic signals? (tell you to eat eat eat)

Answer 11

ghrelin
orexin
galanin
MCH (melanin concentrating hormone)
GABY -gamma amino butyric acid
PYY NRY neuropeptide Y

Question 12

What are anorexigenic signals? (tell you not to eat)

Answer 12

gastric distension
CCK
GLP-1 (glucagon like peptide 1)
insulin
leptin
lipid
protein/AAs
glucose

Question 13

What are the effects of leptin?

Answer 13

Letpin –> (+) POMC –> catabolic response –> stop eating/increase expenditure

Leptins also takes away the inhibition PY neurons to inhibit appetite

Question 14

What are the risk factors for weight gain?

Answer 14

• relatively low RMR (body temp)
• high RQ
• high insulin sensitivity
• low spontaneous physical activity

Question 15

What happens?

Parabiosis: ob next to normal

Answer 15

ob shrinks

Why?
ob has no leptin
leptin from normal crosses over and restores body weight of ob

Question 16

What happens?

Parabiosis: db next to norm

(note: db = agouti: blocked melanin formation which is involved in food intake)

Answer 16

norm shrinks

Why?
db has LOTs of leptin but faulty receptor for leptin in brain
next to the normal, the overproduced (compensated) leptin from db crosses over to norm and inhibits food/increases expenditure of normal)

Question 17

What happens?

Parabiosis: ob next to db

Answer 17

Ob strinks

ob gets leptin from db but db still can’t respond

Question 18

What did we learn from ob/db parabiosis?

Answer 18

leptin produced by adiopose –> goes brain –> stim energy expenditure and decrease food intake

Question 19

Barker hypothesis

Answer 19

epigenitc changes: hypothesis to explain relationships btwn SGA and metabolic syndrome DM2

Question 20

What was learned from Fecal transplants betwn lean and obese twins into gnotobiotic (germ-free) mice?

Answer 20

Lean mouse donor: body mass composition did not change in recipient

Obese mouse donor: body mass composition of recipient increases

Question 21

Which appears to be dominant: obese twin fecal biome or lean twin fecal biome?

Answer 21

lean

put lean and obese together in a germ free it will end up looking like a lean

Question 22

What happened when…?

transplanted fecal material from lean and obese twins into gnotobiotic mice

Answer 22

mice repliacted phenotype (adiposity) of donor twin, but consumed equal amts of food

microbiota resembled donors

Question 23

What happened when…?

mixed two mice in common cage: one that received lean and one that received obese (keep in mind, mice eat poop)

Answer 23

“obese” mice housed with “lean” mice became leaner and microbiota reverted to “lean” pattern

germ free co-housed with both types became leaner

Question 24

UCP1

Answer 24

brings protons back into mitochondria w/o making ATP, but you DO make a lot of heat

-in intact cells, UCP1 is constantly inhibited by ATP in cytosol

-IF COLD:
NE stimulates lipolysis of lipid droplet to release FFA which stimulate UCP1 (overtake ATP’s normal inhibition of UCP1) –> heat and uncoupling of

Question 25

Brown adipose tissue

Answer 25

many mito, lipid droplets, highly vascularized, beta3 adrenergic receptors

EXISTS FOR HEAT GENERATION (new born, hibernation)