In brown adipocytes Benador et. al. have recently
shown that LD binding can lead to the formation of a
specific sub-population of mitochondria, characterized
by a specific metabolic signature and termed them
?peridroplet mitochondria? (Benador et al., 2018).
Consistent with the model by Freyre et al., peridroplet
mitochondria do not specialize in oxidizing fatty acids,
but are involved in the synthesis of TAGs. This result is
perhaps even more surprising than in white adipocytes,
because brown adipocytes are known to efficiently con-
sume fatty acids mobilized from TAGs for thermogene-
sis. Direct physical contact between mitochondria and
LDs was so far considered critical for efficient oxidation
of TAGs. The careful metabolic analysis by Benador
et al. revealed, however, that oxidation reactions in
mitochondria that co-purified with LDs are not
uncoupled from ATP synthesis. The higher oxidative
capacity, and enhanced flux through the tricarboxylic
acid (TCA) cycle of LD-bound mitochondria rather
led to higher levels of ATP production. Unexpectedly,
the substrates supplying energy for ATP synthesis were
pyruvate, malate, and succinate instead of free fatty
acids. According to the authors, augmented synthesis
of ATP improved the ATP dependent activation of die-
tary fatty acids (FAs) by attaching coenzyme A (CoA).
A high level of FA-CoAs was in turn necessary
to increase the esterification with diacylglycerols
(DAGs) in order to produce TAGs, confirming an ana-
bolic function of mitochondria that interact with LDs
(Benador et al., 2019
https://journals.sagepub.com/doi/full/10.1177/2515256421993708https://journals.sagepub.com/na101/home/literatum/publisher/sage/journals/content/ctca/2021/ctca_4/2515256421993708/20210228/images/large/10.1177_2515256421993708-fig1.jpeg
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