TITLE:
High-Lard and High-Fish Oil Diets Differ in Their Effects on Insulin Resistance Development, Mitochondrial Morphology and Dynamic Behaviour in Rat Skeletal Muscle
AUTHORS:
Lillà Lionetti, Raffaella Sica, Maria Pia Mollica, Rosalba Putti
KEYWORDS:
High-Fish Oil Diet; High-Lard Diet; Skeletal Muscle; Mitochondrial Fusion; Mitochondrial Fission; Insulin-Resistance
JOURNAL NAME:
Food and Nutrition Sciences,
Vol.4 No.9A,
August
30,
2013
ABSTRACT: Fish oil (mainly omega 3
polyunsaturated fatty acids), differently from lard (mainly saturated fatty
acids) has been suggested to have anti-inflammatory effects associated with
amelioration of insulin sensibility. An important role in skeletal muscle
insulin resistance development has been recently attributed to mitochondrial
dynamic behavior. Mitochondria are dynamic organelles that frequently undergo
fission/fusion processes and a shift toward fission process has been associated
with skeletal muscle mitochondrial dysfunction and insulin resistance
development. The present work aimed to evaluate if the replacement of lard with
fish oil in high-fat diet positively affect skeletal muscle mitochondrial dynamic
behavior in association with the improvement of insulin-resistance. Body weight gain, systemic insulin-resistance
(glucose/insulin ratio), serum TNFα levels and skeletal muscle lipid content were assessed in rats fed a high-lard
or high-fish-oil diet for 6 weeks. In skeletal muscle sections, immunohistochemical
analysis were performed to detect the presence of insulin receptor substrate 1
(IRS1) and tyrosine phosphorylated IRS1 (key factor in insulin signalling pathway)
as well as to detect the main proteins involved in mitochondrial fusion (MFN2
and OPA1) and fission (DRP1 and Fis1) processes. Skeletal muscle mitochondrial
ultrastructural features were assessed by electron microscopy. High-fish oil feeding induced lower
body weight gain, systemic inflammation and insulin-resistance development as
well as skeletal muscle lipid accumulation compared to high-lard feeding.
Skeletal muscle sections from high-fish oil fed rats exhibited a greater number
of immunoreactive fibers for MFN2 and OPA1 proteins as well as weaker
immunostaining for DRP1 and Fis1 compared to sections from high-lard fed rats.
Electron microscopy observations suggested a prominent presence of fission
events in L rats and fusion events in F rats. The positive effect of the replacement
of lard with fish oil in high-fat diet on systemic and skeletal muscle insulin
sensibility was associated to changes in mitochondrial dynamic behavior.