Lipogenic gene expression and substrate sensitivity in the bovine mammary gland shape milk fat composition
Milk fat is produced by mammary epithelial cells (MEC) through a conserved mechanism shared among all fat-producing cells across biological kingdoms. Although highly conserved, different tissues and organisms produce distinctive fat compositions. Notably, ruminant milk fat is characterized by enrichment in short and medium chain fatty acids. We hypothesized that this unique profile is driven by…
Milk fat is produced by mammary epithelial cells (MEC) in a manner similar to fat production in other tissues. However, ruminant milk fat contains a higher concentration of short and medium chain fatty acids. To investigate whether mammary epithelial cells (MEC) exhibit unique metabolic characteristics responsible for this distinctive composition, researchers compared MEC to udder-derived fibroblasts.
When exposed to acetate, MEC displayed increased expression of enzymes involved in short-chain fatty acid synthesis (ACSS1 and DGAT), while the expression of enzymes for long-chain fatty acid synthesis (ACSL1) decreased. Additionally, acetate treatment in MEC led to higher levels of medium chain fatty acids compared to fibroblasts.
Through genetic manipulation, the researchers confirmed that ACSS1 plays a crucial role in the production of medium chain fatty acids within MEC. Upon acetate treatment, MEC underwent a comprehensive metabolic shift, primarily involving the breakdown of amino acids, energy metabolism, and polar lipid metabolism. These findings reveal that MEC effectively utilize acetate for de novo fatty acid synthesis, with a pronounced preference for producing medium chain fatty acids.
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