Lipogenesis

Lipogenesis is the process by which acetyl-CoA is converted to fatty acids. The former is an intermediate stage in metabolism of simple sugars, such as glucose, a source of energy of living organisms. Through lipogenesis and subsequent triglyceride synthesis, the energy can be efficiently stored in the form of fats.

Lipogenesis encompasses both the process of fatty acid synthesis and triglyceride synthesis (where fatty acids are esterified to glycerol). The products are secreted from the liver in the form of very-low-density lipoproteins (VLDL). VLDL particles are secreted directly into blood, where they mature and function to deliver the endogenously derived lipids to peripheral tissues.

Fatty acids synthesis starts with acetyl-CoA and builds up by the addition of two-carbon units. The synthesis occurs in the cytoplasm of the cell, in contrast to the degradation (oxidation), which occurs in the . Many of the enzymes for the fatty acid synthesis are organized into a multienzyme complex called fatty acid synthase. The major sites of fatty acid synthesis are adipose tissue and the liver.

Insulin is a peptide hormone that is critical for managing the body's metabolism. Insulin is released by the pancreas when blood sugar levels rise, and it has many effects that broadly promote the absorption and storage of sugars, including lipogenesis.

Insulin stimulates lipogenesis primarily by activating two enzymatic pathways. Pyruvate dehydrogenase (PDH), converts pyruvate into acetyl-CoA. Acetyl-CoA carboxylase (ACC), converts acetyl-CoA produced by PDH into malonyl-CoA. Malonyl-CoA provides the two-carbon building blocks that are used to create larger fatty acids.

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