Long-chain fatty acids (LCFAs)가 림프계로 들어가 순환되는 경로

Q:

how are LCFAs transproted to lymphatic system? describe the pathway

 

LCFA가 어떻게 림프계로 들어갈수 있지? 경로를 알려줘

 

 

A:

Long-chain fatty acids (LCFAs) undergo a more complex absorption and transport process than medium-chain fatty acids (MCFAs). Here's how LCFAs are transported to the lymphatic system:

1. Digestion and Emulsification: LCFAs are primarily found in dietary fats and oils. In the stomach, lipases begin to digest triglycerides, but the process is limited. The real digestion occurs in the small intestine, where bile salts secreted from the liver and stored in the gallbladder emulsify dietary fats. This emulsification breaks down large fat globules into smaller micelles, increasing the surface area for pancreatic lipases to act on.
2. Hydrolysis: In the small intestine, pancreatic lipases hydrolyze triglycerides into monoglycerides and free fatty acids. This step is crucial for allowing the fatty acids to be absorbed into the intestinal cells (enterocytes).
3. Absorption: The monoglycerides and LCFAs are then absorbed by the enterocytes lining the small intestine. Inside the enterocytes, these fats re-esterify to form triglycerides.
4. Formation of Chylomicrons: The newly formed triglycerides are packaged with cholesterol, proteins, and phospholipids into lipoprotein particles called chylomicrons. Chylomicrons are large lipoprotein particles that are the primary carriers of dietary lipids.
5. Exocytosis into Lymphatic System: Chylomicrons are too large to enter the capillaries directly. Instead, they are transported out of the enterocytes by exocytosis and enter the lymphatic system through specialized lymphatic vessels called lacteals found in the villi of the intestine.
6. Transport in Lymph: Once in the lymphatic system, chylomicrons travel through the lymphatic vessels and eventually reach the thoracic duct, the largest lymphatic vessel in the body.
7. Entry into Bloodstream: The thoracic duct empties the lymph, containing the chylomicrons, into the bloodstream at the junction of the left subclavian and left internal jugular veins.
8. Metabolism and Uptake: Once in the bloodstream, chylomicrons deliver triglycerides to various tissues, such as muscle and adipose tissue, where lipoprotein lipase (LPL) hydrolyzes the triglycerides into free fatty acids for uptake and use as energy or storage. The remnants of chylomicrons are eventually taken up by the liver for recycling or excretion.

This process highlights the complex journey LCFAs take from dietary intake through to their integration into the body's metabolic systems, contrasting with the more straightforward pathway utilized by MCFAs.

 

 

장쇄지방산(LCFAs)은 중쇄지방산(MCFAs)보다 더 복잡한 흡수 및 수송 과정을 거칩니다. LCFAs가 림프계로 수송되는 과정은 다음과 같습니다:

 

소화 및 유화: LCFAs는 주로 식이 지방과 기름에 존재합니다. 위에서 지방분해효소가 트리글리세리드를 부분적으로 분해하지만, 실제 소화는 소장에서 일어납니다. 간에서 분비되고 담낭에 저장된 담즙염이 식이 지방을 유화시켜 큰 지방 글로불을 작은 마이셀로 분해하여 표면적을 넓혀 췌장 지방분해효소가 작용할 수 있게 합니다.

가수분해: 소장에서 췌장 지방분해효소가 트리글리세리드를 모노글리세리드와 유리지방산으로 가수분해합니다. 이 단계는 지방산이 장세포(enterocyte)로 흡수되는 데 필수적입니다.

흡수: 모노글리세리드와 LCFAs는 소장을 덮고 있는 장세포에 의해 흡수됩니다. 장세포 내부에서 이 지방들은 다시 트리글리세리드로 재에스테르화됩니다.

카일로미크론 형성: 새로 형성된 트리글리세리드는 콜레스테롤, 단백질, 인지질과 함께 카일로미크론이라는 지단백질 입자로 포장됩니다. 카일로미크론은 식이 지질의 주요 운반체인 큰 지단백질 입자입니다.

림프계로의 배출: 카일로미크론은 모세혈관으로 직접 들어갈 수 없을 정도로 너무 큽니다. 대신 장세포에서 배출되어 소장 융모에 있는 특수 림프관인 락테알을 통해 림프계로 들어갑니다.

림프 내 수송: 림프계로 들어간 카일로미크론은 림프관을 따라 이동하여 결국 가장 큰 림프관인 흉관에 도달합니다.

혈류 유입: 흉관은 림프와 함께 카일로미크론을 좌측 쇄골하정맥과 좌측 내경정맥 교차 지점에 비워 혈류로 들어가게 합니다.

대사 및 섭취: 혈류에 있는 카일로미크론은 지단백지방분해효소에 의해 트리글리세리드가 유리지방산으로 가수분해되어 근육, 지방조직 등 여러 조직에 유리지방산을 전달하며, 여기서 에너지원이나 저장용으로 사용됩니다. 카일로미크론의 잔여물은 결국 간에 의해 재활용되거나 배출됩니다.

이 과정은 LCFAs가 식이섭취에서부터 체내 대사계로 통합되기까지의 복잡한 여정을 보여주며, MCFAs가 거치는 보다 단순한 경로와는 대조적입니다