Metabolism and nutrition

From Iusmphysiology

• started here on 02/25/11 at 11AM.

Contents 1 Metabolism and Nutrition 1.1 Metabolism 1.2 Energy balance 1.3 Glucose metabolism 1.4 Interconversions 1.5 Energy liberation 1.6 Nutrition 1.6.1 Atkin's diet 1.6.2 CArbs and fats 1.6.3 Proteins 1.6.4 Vitamins and minerals 1.7 Regulation of food intake 1.7.1 Loops 1.7.2 Obesity 1.7.3 Starvation

[edit] Metabolism and Nutrition

[edit] Metabolism

• In a young, healthy person, you need 30 kcal per kg of body mass.
• The BMR is measured under standardizied conditions; this is a clinical definition of resting medabilic rate.
  • A little higher for males than for females.

[edit] Energy balance

• First law of thermodyn:
  • Energy neighter created or destroyed
  • So we take in energy (diet: carbs, fats, prots, vitameins, etc.)
  • And it must equal energy output (detox, movement, etc) + energy we store
  • POstive energy balance = put on weight.
  • Negative energy...

• Second law:
  • Chemical transformations always result in a loss of free energy
  • E = gibbs free energy +
  • As you eat glucose, you have an increase in your internal energy.
  • T*delta-S can never be zero, so if we add no E to the system, deltaG must decline.
  • So if we burn a mole of glucose
  • So we burn some and we store some
  • Storage goes into high energy phosphate bonds.

[edit] Glucose metabolism

• Body stores energy as glycogen and TAGs
• Carbs = 4.1 kcal / g
  • Body has 120 g of glycogen in liver, and 600 g in muscle
  • ABout 3000 kcal which is over your BMR so you can live on your storage for 1.5 days.
• Lipids = 9.4 kcal / g
  • Body has 14 kg of fat = 130K kcal!
  • Can live on his fat for about 63 days.
• Protein = 4.3 kcal / g
  • Serves structural and functional role
  • 14% protein = 20K kcal in protein but only half can be mobilized as energy b/c the other half has impt function
  • Less than 5% of protein catabolism is used for BMR.

[edit] Interconversions

• We can convert between carbs and lipids (lipiogenesis), etc.
• AA can be converted to TAGS or glycogen
• Lipid can only be stored, though, not converted.

[edit] Energy liberation

• Muscle and liver:
  • Epi binds, activates adenylate cyclase, PKA activated, Glycogen phosphorylase activated to break down glycogen.
  • Glucagon has same effect
• Adipocytes
  • Leads to activate ion of lipase to release Fatty acids

[edit] Nutrition

• Water, vitamins, minerals are important to maintain function (hence we can't live wihtout food for 63 days).
• Requirements:
  • Carbs: none, shouldn't differ with activity, age, etc. though.
    • Typically 55-60%
• Lipids: will differ by individual
  • about 25-30% is appropriate, 60% is typical.
• Activity level is impt determinant of changes in caloric intake.

[edit] Atkin's diet

• Not true that wasting occurs
• What really happens is that carbs are low, ketone bodies are high, and glucogenogensis is on b/c glycogen is being broken down.

• In diabetes, ketones are so high you can smell the fruity breath.

[edit] CArbs and fats

• Need palmitic acid, oleic acid in order to make linoleate and linolate.
• Make arachidonic acid (for lots of other things)
• Get these from fish
• Lipoprotein lipase can easily break fats of cis monounsaturated but not trans.
  • So trans stays around longer and causes problems; increases LDL levesl and decreases HDL levels.

[edit] Proteins

• 9 essential aas
• Vegetarians at risk for not getting essential aas.
• Use a scoring system to judge how well a food provides these essential aas:
  • Egg is the standard at 100
  • Each food is scored by it's lowest scoring essential aa relative to the 100 of the egg.
• There is a second scoring system from the WHO
  • BAsed on aa requirements of humans
  • Score of 1 means it meets all the aa needs of the human.
  • Eggs and beans are 1
• Other systems, too:
  • Biological value (BV) looks at how much of the material is actually retained in the body
  • Efficiency ratio (PER) looks at how well the material is converted to body mass
  • Net protein utilization (NPU) looks at how much of the protein is reatined....?

• Need about 0.6g of protein / kg / day
• Recommended at 1.0g for kids and 2.0 g for first 6 months
  • For establishing growing body
• Higher requirements for:
  • Athletes
  • Pregos
  • Burn victims
  • Aids pts (muscle wasting)

[edit] Vitamins and minerals

• Not going to be tested.
• Chromium has a unique way in lowering chol.
• Cr in drinking water inhibitns insulin resistance.
• May be that increase in chol causes an initial impairment of glucose movement.
  • Can initially be fixed with cr.
  • Then later cannot be fixed with cr.

[edit] Regulation of food intake

• Hypothalamus controls sensation of hunger.
• Anorexics inhibit feeding:
  • CRH corticotropic releasing hormone
  • alpha-melanocyte stimulating hormone
  • Cocaine
  • GLP1
• Orexigenics increase feeding:
  • NPY stimulates feeding
  • NE
  • couple others

[edit] Loops

• Short term regulation:
  • GI hormones affect short term regulation; think CCK
  • Insulin released after a meal, decreases feeding
  • Glucose after a meal is high, decreases feeding
  • Glucose is low before a meal, increases feeding
  • CCK works at the ventral medial nucleus
• Long term
  • Leptin released from fat, inhibits feeding center and stimulates the satiety center.
  • Leptin levels correlate well with adiposity.
  • OBOB mice are HUGE and have high levels of leptin and mutated leptin receptors.
• Majority of obese have high leptin levels which means they are partially resistant

[edit] Obesity

• Obesity is a chronic excess of caloric intake.
• 1 kg of fat is 9400 kcal
• Adipocytes can hyperplasia and hypertrophy
  • Plastic increases only in the first few years of life
    • Means later in life more adipocytes can hyperplasia
  • HYperplasia is how older peep get bigger
• Skinny kids less likely to become obese because fewer cells to hypertrophy
• Fat goes to skeletal muscle and liver when adipocytes cannot hyperotrophy any more.
  • Causes lots of metabolic problems.

[edit] Starvation

• Conscientious objectors starved themselves.
• Univ. of Minn wanted to work on starvation
  • So instead of war, people volunteered for starvation study.
• Starvation is a depletion of carbs
• Ulstimately you die for lack of minerals and vitamins.
• First thing to happen is depression and hysterics.
• Slowly took away food over 12 weeks.
• One pt chopped off all of his fingers.
  • Didn't know if he wanted to or if it was an accident.
• So, eat.

• stopped here on 02/25/11 at 12PM.