Biochemical Aspects of GI Disease and Nutrition Flashcards
What does the following terms mean?
Dietary reference value
Recommended daily intake
Recommended daily amount
Estimated average requirement
Reference nutrient intake
Lower reference nutrient intake
What should you ask during a clinical assessment for GI diseae and Nutrition?
What is normal for patient – Weight (loss or gain; intentional unintentional)
• Family weight
– Food intake
– Chewing/swallowing
– GI symptoms
• Nausea, vomiting, altered bowel habit
– Drugs/alcoho
How do you measure the following functional assessments?
- Muscles mass
- Hepatic Secretory Proteins
- Immune Response in malnourished patients
Muscle mass - Grip strength/isometric knee extension/response to electrical stimulation
Hepatic secretory proteins - albumin (<35g/L), transferrin (<1.5 g/L)
Immune response in malnourished patients – Cell mediated immunity
Malnutrition
Up to 40% can be malnourished in hospital
what complication can happen due to the following:
Impaired immune response
Decreased respiratory muscle strength
Impaired wound healing
Inactivity
Decreased skeletal muscle strength
Impaired thermoregulation
Malabsorption’ – Wide group of conditions associated with disordered biochemistry – No specific clinical presentation • May be a group of signs or symptoms
Impaired immune response - Infection
Decreased respiratory muscle strength - Increased incidence of chest infection
Impaired wound healing - Prolonged recovery
Inactivity - Thromboembolism, pressure sores
Decreased skeletal muscle strength - Fatigue, inactivity, falls
Impaired thermoregulation - Hypothermia
What are the causes for the following presentation?
Pale bulky (offensive) stools - fat malabsorption or digestion
Abdominal distention, borborygmi (gurgling in stomach), watery diarrhoea and xs flatus
Vague malaise, tiredness and weightloss
Anaemia
Easy bruising or bleeding
Failure to thrive (infants)
What are different sources of energy?
What prediction equations are there to calculate GI disease?
Carbohydrates • Fats • Protein • Vitamins • Minerals • Fibre
Energy Requirements – Calorimetry • Estimation from body weight – 25-35 kcal/kg/24h • Prediction equations – Schofield equation – Harris-Benedict equation – Ireton-Jones formula
What is the difference between intrinsic and extrinsic sugar?
What are starches made up of?
What are digestive ezymes that break up carbohydrate?
How are carbohydates absorbed?
Where is amylase produced and what does it help digest?
Sugars – Intrinsic • Naturally e.g. as part of the cellular structure
– Extrinsic • Non natural e.g. refined sugar
Starches • α glucan polysaccharides • Amylose – Straight chain glucose polymer with molecular mass 100 000 Da
• Amylopectin – Branched chain glucose polymer with molecular mass >1 000 000 Da
- Digestive Enzymes - Salivary amylase, pancreatic amylase, and brush border enzymes (dextrinase, glucoamylase, lactase, maltase, and sucrase)
Absorption – Secondary active transport (cotransport) with Na+ – Facilitated diffusion of some monosaccharides • Enter the capillary beds in the villi • Transported to the liver via the hepatic portal vein
• Digestion – Amylase • Salivary and pancreatic • Digestion of α-1,4 bonds in starch • Produces – Maltose – Maltotriose – Short branched oligosaccarhides – α-limit dextrins
What are the actions of the following enzymes and what are the actions and products?
Maltase
Sucrase
Isomaltase
Sucrase -isomaltase
Lactase
What percentage of carbs are not absorbed?
Carbohydrates in the bowel is metabolised by bacteria to produce what?
Who commonly has primary lactase deficiency? What are causes of secondary lactase deficiency?
What can you use to investigate carbohydrate absorption
Up to 20% of dietary starch is not absorbed
- Carbohydrate in the bowel metabolised by bacteria to produce short chain fatty acids (energy source for colonocytes) + methane + hydrogen
- Primary lactase deficiency – Europeans 5 – 15% have deficiency – Africans/Asians >70% deficiency
- Secondary Lactase deficiency – Inflammatory bowel disease – Chronic alcoholism – Coeliac disease – Tropical Sprue
- Lactose tolerance test – Serial glucose measurements after 50 g lactose
Hydrogen breath tests help to diagnose either intolerance to sugars or small intestinal bacterial overgrowth (SIBO). The test measures how the amount of hydrogen present in your breath changes after you consume a sugar solution.
What oes the following tests indicate?
Glucose hydrogen breath test
Lactose hydrogen breath test
Fructose hydrogen breath test
Sorbitol hydrogen breath test
Lactulose hydroen breath test
– Glucose hydrogen breath test
• bacterial overgrowth in the (upper) small intestine
– Lactose hydrogen breath test
• problem digesting lactose products
– Fructose hydrogen breath test
- Problem digesting fructose e.g. honey, vegetables, fruits and grains. – Sorbitol hydrogen breath test
- Sorbitol is a sugar alcohol (polyol) used to investigate rapid intestinal transit.
– Lactulose hydrogen breath test
• Lactulose - galactose and fructose. Transported intact to the colon measure of orocecal transit time (OCTT).
What are the different types of fats?
How is fat absorbed and digested?
Types of fats: Triacylglycerol – Triglyceride • Phospholipids • Sterols
Fat – Emulsified by bile phospholipid – Stabilised and emulsified by bile salts – Lipase digestion to monoacylglycerol and free fatty acids with pancreatic lipase – Solubilised in micelles
Absorption of glycerol and short chain fatty acids – Absorbed into the capillary blood in villi – Transported via the hepatic portal vein
Absorption of monoglycerides and fatty acids – Cluster with bile salts and lecithin to form micelles – Released by micelles to diffuse into epithelial cells – Combine with proteins to form chylomicrons – Enter lacteals and are transported to systemic circulation
What are the essentials fatty acids such as linoleic acid and alpha linoleic acid precursors of?
– Arachadonic acid • C20:4, ω-6
– Eicosapentaenoic acid • C20:5, ω-3
– Docosahexaenoic acid • C22:6, ω-3
What is fat absorption dependent on?
– Bile production • Dependent on liver secretion – Bile salts – Phospholipid – Cholesterol • Patent ducts
– Pancreatic enzymes • Functioning pancreas
Investigation of Fat absorption
• 14C-Triolein breath test – If 14C-labelled triolein absorbed, 14C02 will appear in breath – But lung/liver disease may give false results
Faecal fat excretion no longer used.
How is protein broken down?
How protein metabolism mesured?
- Nitrogen balance – Patients on ITU or long term nutrition • Nitrogen excretion = urinary nitrogen + faecal nitrogen
- Variability of faecal output • Urinary nitrogen = urinary urea nitrogen + non urea nitrogen – Non urea nitrogen is usually ~ 20% of urinary urea nitrogen – Faecal nitrogen is ‘constant’ ~ 1-2 g/24 hour
- Urinary urea nitrogen can be used as an assessment tool (but) – Becomes less useful with increasing severity of illness
– Inaccurate where there is urine infection (urea-splitting organisms)
How can pancreatic function be investigated?
Serum immunoreactive trypsin indicated what? When is it used for screening cystic fibrosis? Low serum values indivaces what?
Faecal pancreatic elastase-1. – Elastase is a protein-cleaving enzyme produced by the pancreas. – Resistant to degradation by other enzymes – Excreted into the gut – Can be measured in the stool. – Enzyme reduced in pancreatic insufficiency.
• Serum Immunoreactive trypsin (IRT) – Increased IRT indicate obstruction – Used as a screening test for cystic fibrosis in newborn babies. – Low serum values indicate failure of production in pancreatic disease.
What vitamens are fat soluble? How are they absorbed?
What vitamens are water soiuble? How are they absorbed
How is vitamin B12 absorbed?
Which vitamens are aborbed via bacterial metabolism in the large intestine?
Fat-soluble vitamins (A, D, E, and K) are carried by micelles and then diffuse into absorptive cells
– Water-soluble vitamins (vitamin C and B vitamins) are absorbed by diffusion or by passive or active transporters.
– Vitamin B12 binds with intrinsic factor, and is absorbed by endocytosis
Vitamin K and B vitamins from bacterial metabolism are absorbed
Where does majority of absorption hapeb?
jenum
What is the function of vitamin A?
What are sources of vitamin A?
What happen if there is a deficiency?
what happens if there is an excess in an acute and chronic sense?
How is it assessed?
Preformed vitamin A – retinol
• Source – Liver, fish oils, dairy
– Carotenoid pigments – β-carotene
• Source – Carrots, dark green leafy vegetables
– Deficiency • Night blindnes
s – XS • Acute – Raised ICP, nausea, vomiting + visual disturbance • Chronic – Liver/bone damage + teratogenicity
– Assessment • Direct measurement
Fat-soluble Vitamins: Vitamin E
It should be proportional to the intake of what
Where is it found in?
What happens if there is a deficiency?
What happens if there is an excess
How is it assessed?
Vitamin E: 8 similar compounds
– Intake proportional to intake of polyunsaturated fatty acids
– Tocopherols • α-tocopherol most abundant
– Tocotrienols
– Found in cell membranes – antioxidant
– Deficiency
- Premature infants – haemolytic anaemia + thrombocytopenia
- Children/young adults – spinocerebellar degeneration
- Parenteral nutrition – XS • Appears relatively non toxic
– Assessment • Direct measurement
What are sources of thiamine (Vit B1)
Thiamine deficiency can lead to beriberi which has dry and wet what is the difference?
What is the commonest cause in first world countries?
How is deficiency assessed?
Is excess an issue?
Sources – Wheat germ, oatmeal & yeast
• Deficiency – Beriberi • Dry – peripheral neuropathy, muscle weakness, fatigue • Wet – oedema, heart failure
– Common in 1st world as • Wernicke’s encephalopathy
Deficiency assessment
- Direct measurement of thiamin available (BEFORE giving thiamin!!)
- Previously Erythrocyte transketolase measurement – not used for assessment
– XS • Non toxic • Not recognised as a problem
Water soluble vitamins- Riboflavin
(Vitamin B2)
What cellular mechanism is this usefull for?
What are the main sources of these?
What happens if there is a deficiency?
How is it assessed?
- Flavoproteins – Flavin mononucleotide (FMN), flavin adenine dinucleotide (FAD) • Electron carrier in biological oxido-reduction systems • Source – Eggs, green vegetables, milk, and meat
- Deficiency • Angular stomatitis, painful red tongue with sore throat • oily scaly skin rashes • eyes sensitive to light • anaemia • birth defects including congenital heart defects and limb deformities.
- Assessment – Urinary excretion (poor measure) – Red cell glutathione reductase (very limited use)
Water soluble vitamins- Nicotinamide (Vitamin B3)
Where are the sources
What disease do you get if have a deficiency in this?
How can you measure it?
‘Niacin’ often used to mean – Nicotinic acid and nicotinamide
• Nicotinic acid previously used to treat hyperlipidaemia
– Nicotinamide
• Found in: – Nicotinamide adenine dinucleotide (NAD+ )
– Nicotinamide adenine dinucleotide phosphate (NADP+ )
- Sources – yeast, meat, milk, and green vegetables
- Deficiency (pellagra) – rare in developed world usually secondary to alcoholism, long term diarrhoea
- Measurement – none readily available
- Replacement is non-toxic
Water soluble vitamins- Vitamin B6
What are the sources
What do you get if you have deficiency in this?
Pyridoxal, pyridoxine, pyridoxamine, + 5’-phosphates
– Sources • fortified breakfast cereals, meat, bananas, chickpeas, potatoes, pistachios
– Deficiency • Seborrhoeic dermatitis, atrophic glossitis, neurologic symptoms of somnolence, confusion and neuropathy & sideroblastic anaemia
– Assessment • Direct measurement of Vitamin B6 (BEFORE giving B6!!)
