Alkylglycerols in bovine colostrum and milk in relation to precursor levels

Abstract

The concentrations of dihydroxyacetone phosphate (DHAP), glycerol-3-phosphate (GP), glucose and alkylglycerols were measured in bovine colostrum and milk. Concentrations of GP were higher in colostrum than in milk, and corresponded to intracellular concentrations at the onset of lactation. This suggests that GP equilibrates over the apical membrane at onset of lactation, which is believed to occur also in full lactation. The ratio of DHAP to GP showed a peak in colostrum that was more than twice that in milk, indicating that concentration changes in colostrum/milk were not caused by dilution. DHAP was positively correlated to metabolical compounds such as glucose and alkylglycerols. As DHAP is a required precursor for alkylglycerol synthesis, the positive correlation suggests that DHAP may be limiting for alkylglycerol synthesis and thus could explain the elevated levels of alkylglycerols found in colostrum.

Breast milk alkylglycerols sustain beige adipocytes through adipose tissue macrophages

“…It is known that Agmo transcription is diminished by M1-activating stimuli (26, 62) (Supplemental Figure 15, C and D), whereas M2 polarizing signals increase Agmo transcription in ATMs (62). Accordingly, we found that IL-4/STAT6 signaling controlled Agmo transcription and AGMO was expressed and localized to intracellular membranes in IL-4-treated macrophages (Supplemental Figure 15, E and F), which serve as the site of AKG accumulation and PAF synthesis (24,28,68,69).…”

“…Cow milk contains negligible AKGs, which is at odds with the finding of AKG synthesis and release in cow colostrum and milk (68). This may be due to an increased catabolism of AKGs in cow milk (24). Moreover, the amount of milk produced daily by a dairy cow is magnitudes higher than of the other species tested and may lead to the dilution of AKG concentration to a negligible level.…”

“…Lipid vesicles are released together with the apical cell membrane by so-called apocrine secretion (10). AKGs are enriched in the apical cell membrane of the lactating gland cells (24) and synthesized within the cell membranes due to remodeling of other ether lipids (24,28,68,69); hence, apocrine secretion allows AKG enrichment in the milk. Cow milk contains negligible AKGs, which is at odds with the finding of AKG synthesis and release in cow colostrum and milk (68).…”