The presentation is targeted for MBBS, MD, BDS students describing the fate of dietary lipids in our body

1. Digestion and absorption of Lipids
Prof (Dr) Viyatprajna Acharya MD, PhD

2. Major dietary lipids- TAG
Minor quantity- cholesterol & PL
Avg. normal Indian diet- 20-30 gm/day
Western diet- 2-3 times more fat

3. Overview of fat digestion
Very minor digestion in stomach
Fat digested mainly into monoglycerides & fatty
acids by lipase enzyme from pancreas
Bile aids digestion & absorption
Triglycerides resynthesized from absorbed fat,
incorporated into chylomicrons & transferred to
lymph
Usually < 5% fat excreted in faeces

4. Triglyceride Digestion and Absorption
 Mouth
•Lingual lipase
• Optimum pH- 2.5-5
• Acts on short chain TG
• More significant in infants
• also emulsification from dietary phospholipids, lingual lipase
• emulsification especially important, because digestive secretions all water-
based

5. Stomach
 Gastric lipase – acid stable (pH 5.4)
 Secreted by chief cells
 Stomach churning helps to physically
separate fats
 30% digestion of fat in stomach

6. Intestine
Emulsification- Pre-requisite of digestion
Favored by-
Bile salts
Peristalsis
Phospholipids
Lipolytic enzymes
1. Pancreatic lipase with co-lipase (Presence of co-lipase is
obligatory for lipase action )
2. Cholesterol esterase
3. Phospholipase A2

11. LIPASE SITE OF
ACTION
PREFERRED
SUBSTRATE
PRODUCTS
Lingual lipase Mouth,
Stomach
TAG, medium chain
FA
FFA+DAG
Pancreatic lipase+ Co-
lipase
Small Intestine TAG, LCFA FFA+2 MAG
Int. lipase+ bile acids Small Intestine TAG, MCFA 3FFA+GLYCEROL
PLA2+ Bile acids Small Intestine PLs with UFA on
position 2
UFA, Lysolecithin
LPL+ Insulin Capillary walls TAGs in chylomicron
or VLDL
FFA+ Glycerol
HS Lipase Adipocytes TAG in adipose
tissue
FFA+ Glycerol

12. Disorders of fat absorption
Defective digestion: steatorrhoea
>6gm fat in stool/day
Defective absorption: Malabsorption syndrome
Chyluria

13. OLESTRA???

14. For more PPT on Medical Biochemistry
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