F. Hernández y Juan F. Madrid. Universidad de Murcia. Departamento de Biología Celular e Histología
Abstract
The aim of this study was to investigate
lipofuscin origin in brown adipocytes of hyperinsulinaemic
rats and the possible role of lipid
peroxidation and iron in this process. Ultrastructural
examination revealed hyperinsulinaemia-induced
enhancement in the lipofuscin production, accompanied
by an increase of mitochondrial damage in brown
adipocytes. Extensive fusions of lipid droplets and
mitochondria with lysosomes were also observed.
Confocal microscopy showed lipofuscin autofluorescence
emission in brown adipose tissue (BAT)
after excitation at 488 nm and 633 nm, particularly in the
insulin-treated groups. The presence and distribution of
lipid peroxidation product, 4-hydroxy-2-nonenal (4-
HNE), in brown adipocytes was assessed by
immunohistochemical examination revealing its higher
content after treatment with insulin. The iron content
was quantified by electron dispersive X-ray analysis
(EDX) showing its higher content in the hyperinsulinaemic
groups. The ultrastucture of the majority of
lipofuscin granules suggests their mitochondrial origin,
which was additionally confirmed by their colocalization
with ATP synthase. In conclusion, our
results suggest that increased lipofuscinogenesis in the
brown adipocytes of hyperinsulinaemic rats is a
consequence of lipid peroxidation, mitochondrial
damage and iron accumulation