Branched esters of palmitic acid and hydroxystearic acid (PAHSA) are anti-inflammatory and antidiabetic lipokines that connect glucose and lipid metabolism. We aimed to characterize involvement of the 5-PAHSA regioisomer in the adaptive metabolic response of white adipose tissue (WAT) to cold exposure (CE) in mice, exploring the cross talk between glucose utilization and lipid metabolism. CE promoted local production of 5- and 9-PAHSAs in WAT. Metabolic labeling of de novo lipogenesis (DNL) using 2H2O revealed that 5-PAHSA potentiated the effects of CE and stimulated triacylglycerol (TAG)/fatty acid (FA) cycling in WAT through impacting lipogenesis and lipolysis. Adipocyte lipolytic products were altered by 5-PAHSA through selective FA re-esterification. The impaired lipolysis in global adipose triglyceride lipase (ATGL) knockout mice reduced free PAHSA levels and uncovered a metabolite reservoir of TAG-bound PAHSAs (TAG estolides) in WAT. Utilization of 13C isotope tracers and dynamic metabolomics documented that 5-PAHSA primes adipocytes for glucose metabolism in a different way from insulin, promoting DNL and impeding TAG synthesis. In summary, our data reveal new cellular and physiological mechanisms underlying the beneficial effects of 5-PAHSA and its relation to insulin action in adipocytes and independently confirm a PAHSA metabolite reservoir linked to ATGL-mediated lipolysis.

-Quantity of components of the labial gland secretion of bumblebee males changes significantly during ageing of males. In B. terrestris, compounds showing the EAG-activity to virgin queens are ethyl dodecanoate, 2,3-dihydrofarnesal, 2,3-dihydrofarnesol, hexadecanol, octadeca-9,12,15-trienol, and geranylcitronellol. The EAG-active compounds found in B.lucorum are ethyl dodecanoate, ethyl tetradec-7-enoate, ethyl tetradec-9-enoate, ethyl hexadec-9-enoate, hexadecanol, hexadec-7-enal, octadeca-9,12-dienol, octadeca-9,12,15-trienol and octadecanol. Quantification of these compounds based on a calibration showed that the main components were present in milligram amounts in both species. Different concentration pattern of active compounds was observed in the species studied. Compounds reached maximal amounts about seventh day after eclosion. Then, a rapid concentration decrease occurs in B. terrestris whereas the amounts of active compounds stay approximately constant or decreases only slowly in B. lucorum. These results were also confirmed by means of optical microscopy. B. terrestris secretory cells undergo apoptosis since the fifth to the tenth day of life, whilst they live and show secretory activity through the whole life of B. lucorum males.

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