Nutrients and Metabolism

Question 1

describe the 6 major classes of nutrients

Answer 1

1. carbohydrates: provide energy
   -sugars
   -starches
   -fibers
2. proteins: provide energy
   -amino acids
3. fats: provide energy
   -fatty acids
4. vitamins:
   -water soluble
   -fat soluble
   -vitamin-like compounds
5. minerals:
   -macro minerals
   -micro mineraks
6. water

Question 2

describe energy balance

Answer 2

1. calories in, calories out
2. positive energy balance:
   -weight gain
   -necessary during growth, gestation, and lactation
3. neutral energy balance: weight stable
4. negative energy balance:
   -weight loss
   -necessary for achieving gradual weight loss

Question 3

describe the levels of energy in food

Answer 3

1. gross energy: all of it
2. digestible energy: after energy lost in feces
3. metabolizable energy:
   -after energy lost in urine and gases from the GI tract
4. net energy:
   -after energy lost as heat in the digestion, absorption, and use of food
   -called heat increment or specific dynamic action
5. NEm: for maintenance
6. NEp: for production, which occurs only if there is NE remaining after what is used for maintenance

Question 4

describe genesis versus lysis

Answer 4

genesis: production
-glycogenesis: production of glycogen stores
-gluconeogenesis: production of new glucose from glycerol, lactate, and amino acids

lysis: breakdown
-glycogenolysis: breakdown of glycogen in the liver
-glycolysis: breakdown of glucose; converts glucose to pyruvate and produces energy (ATP)

Question 5

describe the citric acid cycle/krebs cycle (broad)

Answer 5

connects glucose, amino acids, and fatty acids through acetyl-CoA

produces energy (ATP)

Question 6

describe the electron transport chain (3)

Answer 6

1. group of proteins and organic molecules found in the inner membrane of mitochondria
2. chain members transfer electrons in a series of oxidation-reduction (redox) reactions to form a proton gradient that drives energy (ATP) production
3. primary source of energy (ATP) production

Question 7

describe lipogenesis (2)

Answer 7

1. production of triglyceride (fat) from glucose
2. beta oxidation: breakdown of fatty acids to produce energy (ATP)

Question 8

describe amino acid metabolism

Answer 8

production of non-essential amino acids, cellular proteins, and urea from ammonia

Question 9

describe sources of vitamins (5)

Answer 9

1. many must be provided through the diet (essential vitamins)
   -vitamin A: all species
   -vitamin D: dogs, cats, and animals housed indoors without a UVB light source
   -B vitamins: monogastrics: dogs, cats, swine, poultry
2. ruminants (rumen microbes) and hindgut fermenters (hindgut microbes) can synthesize B vitamins
3. water soluble B vitamins: required as enzymatic cofactors for proper function of all metabolic pathways, but no storage so must get every day! (except cobalamine)
4. deficiency: lack of vitamin(s) necessary in amount necessary to support normal physiologic function
5. toxicity:
   -excess of vitamin(s) in amount necessary to support normal physiologic function

Question 10

describe water soluble versus fat soluble vitamins

Answer 10

water soluble:
1. digestion and absorption: absorbed in the small intestine
2. storage: limited (required daily)
3. deficiency: occurs quickly in monogastrics due to lack of storage
4. toxicity: generally not reported (excess is excreted through urine)

fat-soluble:
1. digestion and absorption: required dietary fat, pancreatic lipase, and bile salts to form lipid micelles

2. storage: liver and adipose tissue
3. deficiency: occurs slowly
4. toxicity: especially vitamins A and D

Question 11

describe the DVM + PhD nutritionist definition of ketogenic diet

Answer 11

1. high fat, carb-restricted with primary goal of inducing urinary ketosis
2. evidence by acetone and diacetic acid (acetoacetic acid) in urine

3 mimics a starvation state without calorie restriction: neutral energy balance

BUT no consensus in vet med for ketogenic diets in canines

so parr:
1. classic human approach: high fat low protein low carb: palatability issues
2. alternative for humans: medium chain triglycerides = less carb and protein restriction

3. proposed definition for dogs: high fat, adequate protein, low carb, calorie restricted that mimics acetonemia (ketosis) created by starvation; provides only 75-80% of daily caloric intake for patient so weight loss WILL occur

Question 12

differentiate dietary fats (2)

Answer 12

1. medium chain triglycerides:
   -C8-12 (fewer carbons)
   -once ingested, can be absorbed or at least partially absorbed without needing to go through lymphatic system and can go directly to the portal vein bound to albumin so go directly to the mitochondria more quickly
   -don’t know cutoff for absorption though so some could be utilized like long chain too
   -not essential, no CCK stimulation in humans, no bile or pancreatic enzymes required, carnitine not required to enter mitochondria
2. long chain triglycerides:
   -C14-24
   -still need SOME in diet for life
   -once ingested, need to form chylomicrons (absorbed via lymphatic system (micelles)), enter bloodstream through thoracic duct, and then peripheral tissues start utilizing before mitochondrial use)
   -essential FAs, CCK stimulation in humans, bile and pancreatic enzymes required, require carnitine to enter mitochondria

Question 13

what is the issue with ketogenic diets in dogs? (3)

Answer 13

1. dogs are very resilient against ketosis and ketogenesis = difficult to induce ketosis
   -thought to be because they are much better at peripheral utilization of ketone bodies (don’t build up, used immediately in health)
2. exceptions: only really become ketotic when sick!
   -diabetic ketoacidosis
   -pregnancy: insulin resistance, gestational diabetes
3. can’t use ketones to differentiate disease states in animals because dogs are so efficient at using ketones

Question 14

what is the only current slightly ketogenic veterinary diet available?

Answer 14

1. purine neurocare diet:
   -MCTs may be more ketogenic than LCTs as they are rapidly transported to the liver via portal vein and converted to ketone bodies

-not necessarily high fat hight protein though

-found to provide balanced nutrition for growth of puppies and maintenance of adult dogs including growth of large size dogs (not designed for weight loss)

Question 15

what about coconut oil?

Answer 15

contains very little of the essential fatty acids for dogs and cats so DONT use to balance a homemade diet and DONT use as the fat source if stupidly trying to induce ketogenesis in your dog

-very palatable and provides energy so used IN vet diets, but if you use this alone you are an idiot and will give your cat hepatic lipidosis, idiot