Question about triglyceride synthesis

[Pinkleton]

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So I'm reading in Kaplan that adipose lacks glycerol kinase, so it can't take glycerol delivered to it by VLDL and turn in into triglycerides for storage. Instead, the DHAP needed for TG synthesis comes from insulin mediated uptake of glucose into the adipocyte.

My question is...how do dietary fats get stored as fat then? It seems like this is implying that our fat stores are exclusively from carbs, and not fats.

 

[NickNaylor]

My understanding is that glycerol kinase is used to produce products for gluconeogenesis, thus it is only present in the liver. Just had a UWorld question on this today but that's all I remember from the explanation/wrote down.

That doesn't really help with how glycerol is produced in adipocytes, but UWorld says that glycerol kinase is unique to the liver.

 

[Pinkleton]

Yeah my head is spinning. Here is a paraphrase from Kaplan (hope that is allowed)

Adipose lacks glycerol kinase and depends strictly on glucose to create DHAP for triglyceride synthesis. Insulin stimulates GLU4, ensuring a good supply of DHAP for TG synthesis.

 

[withrye]

Chylomicrons in the blood can release free fatty acids to adipocytes. The lipoprotein lipase on the adipocyte releases FFAs from the TGs, and the FFAs freely diffuse into the adipocyte. Once inside, glycolysis provides the glycerol (from DHAP) to recombine with the FFA to form TG inside the adipocyte. This is how most dietary TGs get into the adipocyte. Other TGs can get there from synthesized TGs that come from the VLDL made by the liver (as you described in the first post).

 

[Pinkleton]

Chylomicrons in the blood can release free fatty acids to adipocytes. The lipoprotein lipase on the adipocyte releases FFAs from the TGs, and the FFAs freely diffuse into the adipocyte. Once inside, glycolysis provides the glycerol (from DHAP) to recombine with the FFA to form TG inside the adipocyte. This is how most dietary TGs get into the adipocyte. Other TGs can get there from synthesized TGs that come from the VLDL made by the liver (as you described in the first post).

Golden. Thanks 👍