Elsevier

Molecular Metabolism

Volume 4, Issue 1, January 2015, Pages 39-50
Molecular Metabolism

Original article
High fat diet-induced modifications in membrane lipid and mitochondrial-membrane protein signatures precede the development of hepatic insulin resistance in mice

https://doi.org/10.1016/j.molmet.2014.11.004Get rights and content
Under a Creative Commons license
open access

Abstract

Objective

Excess lipid intake has been implicated in the pathophysiology of hepatosteatosis and hepatic insulin resistance. Lipids constitute approximately 50% of the cell membrane mass, define membrane properties, and create microenvironments for membrane-proteins. In this study we aimed to resolve temporal alterations in membrane metabolite and protein signatures during high-fat diet (HF)-mediated development of hepatic insulin resistance.

Methods

We induced hepatosteatosis by feeding C3HeB/FeJ male mice an HF enriched with long-chain polyunsaturated C18:2n6 fatty acids for 7, 14, or 21 days. Longitudinal changes in hepatic insulin sensitivity were assessed via the euglycemic-hyperinsulinemic clamp, in membrane lipids via t-metabolomics- and membrane proteins via quantitative proteomics-analyses, and in hepatocyte morphology via electron microscopy. Data were compared to those of age- and litter-matched controls maintained on a low-fat diet.

Results

Excess long-chain polyunsaturated C18:2n6 intake for 7 days did not compromise hepatic insulin sensitivity, however, induced hepatosteatosis and modified major membrane lipid constituent signatures in liver, e.g. increased total unsaturated, long-chain fatty acid-containing acyl-carnitine or membrane-associated diacylglycerol moieties and decreased total short-chain acyl-carnitines, glycerophosphocholines, lysophosphatidylcholines, or sphingolipids. Hepatic insulin sensitivity tended to decrease within 14 days HF-exposure. Overt hepatic insulin resistance developed until day 21 of HF-intervention and was accompanied by morphological mitochondrial abnormalities and indications for oxidative stress in liver. HF-feeding progressively decreased the abundance of protein-components of all mitochondrial respiratory chain complexes, inner and outer mitochondrial membrane substrate transporters independent from the hepatocellular mitochondrial volume in liver.

Conclusions

We assume HF-induced modifications in membrane lipid- and protein-signatures prior to and during changes in hepatic insulin action in liver alter membrane properties – in particular those of mitochondria which are highly abundant in hepatocytes. In turn, a progressive decrease in the abundance of mitochondrial membrane proteins throughout HF-exposure likely impacts on mitochondrial energy metabolism, substrate exchange across mitochondrial membranes, contributes to oxidative stress, mitochondrial damage, and the development of insulin resistance in liver.

Keywords

Hepatosteatosis
Proteomics
Metabolomics
Diabetes
Clamp
Mitochondria

Abbreviations

2-[14C]DG
2-[1-14C]deoxyglucose
GIR
glucose infusion rate
Rd
rate of disappearance
Ra
rate of appearance
EGP
endogenous (hepatic) glucose production
AUC
area under the curve
HF
high-fat diet
LF
low-fat diet
WAT
white adipose tissue
ROS
reactive oxygen species
DAG
diacylglycerol
TAG
triacylglycerol
WAT
white adipose tissue
NEFA
non-esterified fatty acids
ALT
alanine aminotransferase
Basal
17 h fasting
Rg
glucose metabolic index
PCaa
diacylglycerophosphocholine
PCae
glycerophosphocholine
lysoPC
lysophosphatidylcholines
SM
sphingolipid
B
basal
IS
insulin-stimulated

Cited by (0)

9

Chair for Molecular Animal Breeding and Biotechnology.