Digestion and absorption of lipids

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 Pancreatic lipase with co-lipase (Presence of co-lipase is obligatory for lipase action ) Cholesterol esterase Phospholipase A2

7. 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

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

9. OLESTRA???

10. For more PPT on Medical Biochemistry Visit www.vpacharya.com