KIN 404 2 Flashcards
By how much can total daily energy expenditure vary in two adults in similar size? Why?
1500 kcal/day…occupation
What is BMR, and how is it measured?
Basal metabolic rate…laying awake but resting, stress free in the morning after sleep, not digesting food (post-absoprtive state) and in the absence of thermoregulatory heat production…direct or indirect calorimetry
What is RMR?
Resting Metabolic Rate…similar to BMR but not measured in the morning after sleep (usually 10% of BMR)
What is MMR?
Minimal Metabolic Rate…metabolic rate in carious conditions that cause the rate to fall below BMR (sleep decreases 10%, anesthesia, continued starvation decreases it by 10%)
What is FMR?
Field Metabolic Rate…total daily energy expenditure (TDEE) is higher than BMR due to energy requirements of feeding, cold exposure and muscle use
What is maximal metabolic rate?
Maximal steady-state metabolic rate during hard eercise (20 x BMR in trained athlete and 12 x BMR in sedentary person)
What are the major oxygen consuming organs of the body?
Skeletal muscle, liver, brain, heart, lung kidney, GI tract
What are the top 3 organs for body O2 % use?
Brain, skeletal muscle and liver
What us the % breakdown of metabolic pathways and cellular processes to daily energy expenditure?
Basal Metabolic Rate 60-70%, Physical Activity (15-30%), thermic effect of feeding (8-12%), other such as adaptive thermogenesis, growth and reproduction (2-3%)
What are the two components of physical activity?
exercise and non-exercise activity thermogenesis (NEAT)
What is the % of basal metabolic rate?
Mitochondrial Proton Leak (20%), Protein Synthesis (25-30%), Na+-K+-ATPase (19-28%), Ca2+-ATPase (4-8%), Glucogeogenesis (7-10%), Ureagenesis (3%), Actomyosin ATPase (2-8%), other (13-30%)
How much does Thermic Effect of Feeding stimulate the metabolic rate by 1-2 hours after a meal in humans?
approximately 25%
What are the components of the thermic effect of feeding?
Metabolism of ingested AA in liver for glucose, fat, urea and protein synthesis (~35-45%). Swallowing, digestion and absoprtion of food and enzyme secretion (~25-30%. SNS activation (~30-40%).
Steps in the overview of the acute control of brown adipose tissue (BAT)
1) PVN/VMN secretes MCH and CART 2) MCH and CART activate the SNS to release NE 3) Beta-3 adrenergic receptor on BAT and increases cAMP within the cell 4) Activates PKA which activates HSL 5) Lipolysis to release FFA from TG 6) FFA substrate for thermogenesis and activator of UCP-1
What allosterically activates UCP-1?
FFA
Thermogenesis is due to activation of?
UCP-1 through lipolysis
WHere is UCP1 found?
Only in the mitochondria of BROWN FAT
Thermogenesis in BAT at a given moment is determined by the degree of ___________ at that moment and can alter within seconds, but the ______________ for thermogenesis is determined by the degree of _______________ of the tissue (x-ais) which needs days or weeks to be significantly altered.
activation, capacity, recruitment
WHere are the sites of BAT in adult humans found by FDG PET?
neck, supraclavicular, medistinum, paravertebral, suprarenal
What is FDG PET?
Fluorodeoxy glucose positron emission tomography
How was it determined that adult humans do indeed have brown adipose tissue?
Gave them FDG PET scans in warm environment, and there was no BAT activation. Repeated the study with a SNS beta blocker, and again no activation…shows that adults have BAT that is activated by cold and by SNS activation
2 studies have shown that mice overexpressing human UCP-3 in skeletal muscle are hyperphagic and lean, and those that overexpress UCP-1 in skeletal muscle are resistant to diet-induced obesity and insulin resistance…what does this show?
Promoting inefficient metabolism in muscle represents a potential treatment for obesity and diabetes
2 studies have shown that mice lacking mitochondrial uncoupling protein are cold-sensitive but not obese and transgenetic mice that have BAT ablated develop obesity…what does this show?
UCP-1 is not the only system involved in thermogenesis even within BAT, so there may be other energy consuming processes that can be targeted for promoting inefficient metabolism.
What is the estimated contribution of SERCAs to daily energy expenditure?
~18% in skeletal muscle…60% of daily energy expenditure is from BMR. Of that 60%, 20% of it comes from skeletal muscle and muscle consumes 40-45% of that ATP at rest, therefore, ~18% of RMR comes from skeletal muscle!
What is BTS?
a drug that inhibits actin-myosin ATPase, so when muscle contracts there is no force production, but there is still Ca2+ release and change in membrane potential, so SERCA and Na+/K+ ATPase are still wokring
How much of the resting muscle VO2 is from SERCA?
40-45%
How is MgCl2 used to assess the contribution of SERCA activity to resting metabolic rate in isolated mouse skeletal muscles?
MgCl2 blocks Ca2+ leak so SERCA is not needed at rest to pump Ca2+ back into SR. So, when the calcium leak channel is blocked, the VO2 of the muscle will drop in proportion to the amount of O2 mitochondria are using at rest
What are some things that phyisologically reduce SR Ca2+ transport efficiency?
phospholamban, sarcolipin, HUFAs and cold acclimation
What are some things that pharmacologically reduce SR Ca2+ transport efficiency?
L-thyroxine (hyperthyroid), low iodine diet (hypothyroid), tamoxifen
What are 2 things that pharmacologically increase the efficiency of SERCA?
curcumin and fluoride
What is sarcolipin?
An 31 AA, integral membrane protein that ineracts with Ca2+ binding domain of SERCA to reduce its efficiency…causes calcium slippage by drastically reducing the affinity of calcium before the E2 confirmation is reached, thereby, allowing Ca2+ to slip back into the cytosol because there is a lower concentration there compared to inside the SR
The major energy consuming process that contributed to BMR in the G tract is?
Protein synthesis
Which of the following 2 processes combined contribute to ~50% of whole body BMR? a) actiomyosin ATPase and Na+/K+ ATPas b) mitochondrial uncoupling and ureagenesis c) actomyosin ATPase and gluconeogenesis d) Na+/K+ ATPase and protein synthesis e) digstion of food and mitochondrial uncoupling
d) Na+/K+ ATPase and protein synthesis (19-28% and 25-30%)
Which of the following is true? a) deletion of UCP-1 gene does NOT increase obesity at room temperature b) genetic ablation of BAT does not increase obesity of room temperature c) overexpression of UCP-1 reduces the efficiency of Ca2+ pumps in skeletal muscle d) a and b e) all the above
a) deletion of UCP-1 gene does NOT increase obesity in mice at room temperature
Deletion of SLN would be expected to cause… a) decrease in exercise induced thermogenesis b) decrease in BMR c) decreased efficiency of Ca2+ transport d) only a and b e) all the above
d) a and b only
Deletion of sarcolipin was shown to cause… a) decreased resting energy expenditure in ST skeletal muscle b) decreased contribution of SERCA pumps to REE in ST skeletal muscle c) decreased whole body BMR d) a and b only e) all of the above
b) decreased contribution of SERCA pumps to REE in ST skeletal muscle (i.e. soleus)
Which is true? a) SLN-null mice fed a chow diet are more glucose intolerant than age matched WT b) SLN content in BAT is increased in HF WT mice c) SLN-null mice have lower cage activity than age-matched WT mice c) SLN-null mice have lower cage activity than age-matched WT mice d) differences in diet-induced obesity between WT and SLN null mice are smaller following propanolol treatment e) none of the above
e) none of the above
How much do SERCAs contribute to daily energy expenditure?
~18%
What % of resting muscle VO2 come sfrom SERCA?
~40-45%
What is adaptive thermogenesis?
The energy expenditure that occurs in response to environmental temperature or diet…variable and regulated by the brain, responds to temperature and diet, occurs in brown adipocyte mitochondria
What does SLN ablation do to Ca2+ transport efficiency in soleus?
increases Ca2+ transport efficiency in the soleus
The relative contribution of SERCA to resting soleus VO2 is _______ in chow-fed SLN KO mice
lower