Young Investigators’ session
Mitochondrial function and insulin
resistance in humans with obesity,
diabetes mellitus and non-alcoholic
fatty liver disease (NAFLD)
C. Koliaki (Greece)
Hepatic mitochondrial function in humans
with insulin resistance and NAFLD
15th MGSD Meeting, Young Investigators’ session
Chrysi Koliaki, MD PhD
Greece
Athens, 28.04.2017
Conflict of interest
No financial relationships
to disclose
Research fellowship
Postdoctoral research
Background (I)
 Mitochondrial function and its association with insulin resistance in different
tissues, is a hot topic of metabolic research worldwide.
 Liver is a key organ involved in energy homeostasis and pathogenesis of type 2
diabetes mellitus (T2DM) and NAFLD.
 NAFLD comprises benign steatosis (non-alcoholic fatty liver, NAFL),
steatohepatitis (NASH), cirrhosis and hepatocellular carcinoma, and associates
with both hepatic and peripheral insulin resistance.
Roden M. Nat. Clin. Pract. Endocrinol. Metab. 2006;2:335–348
Background (II)
 Mitochondria are dynamic intracellular organelles
 Major orchestrator of cellular energy metabolism
β-oxidation
 tricarboxylic acid cycle (TCA)
 adenosine triphosphate (ATP) synthesis through oxidative
phosphorylation (OXPHOS)
 reactive oxygen species (ROS) formation and detoxification

Murphy MP. Biochem. J. 2009;417:1–13
Background (III)
In skeletal muscle, insulin resistance may coexist with lower mitochondrial density, reduced
OXPHOS gene expression and ATP synthesis.
 Whether similar mitochondrial alterations are also present in livers of insulin resistant
humans remains unclear.
 While there was some evidence for impaired hepatic mitochondrial function in T2DM and
NASH, other investigators reported an increased hepatic mitochondrial function in obese
humans with NAFLD.
 Prior to our study, no data on simultaneous direct measurement of
mitochondrial content and capacity were available in livers of humans at
different stages of insulin resistance and NAFLD.

Mootha VK et al. Nat. Genet. 2003;34:267–273; Morino K et al. J. Clin. Invest. 2005;115:3587–3593;
Szendroedi J et al. PLoS Med. 2007;4:e154; Szendroedi J et al. Hepatology 2009;50:1079–1086; PerezCarreras M et al. Hepatology 2003;38:999–1007; Sunny NE et al. Cell Metab. 2011;14:804–810
Our study
 Registered clinical trial, NCT01477957
 Ex vivo high-resolution respirometry (HRR) to quantify hepatic mitochondrial
respiration
 Combined with measures of mitochondrial content
 Intra-operative liver samples from obese humans
 without NAFL (OBE NAFL-), n=18
 with NAFL (OBE NAFL+), n=16
 with NASH (OBE NASH), n=7
 lean humans without NAFLD (CON), n=12
Methods

Metabolic characterization (euglycemic-hyperinsulinemic clamps with [6,62H ]glucose)
2

Intra-operative liver biopsies (200-700 mg tissue)

Liver histology (steatosis, NAFLD score)

Ex vivo high resolution respirometry in liver tissue & isolated mitochondria
(Oroboros oxygraphs, Innsbruck)

Citrate synthase activity (CSA) and mtDNA for mitochondrial content

TBARS (thiobarbituric acid reactive substances) for lipid peroxidation

H2O2 production for oxidative stress

Gene expression analyses
Study groups
Obese groups without NASH exhibit
upregulated hepatic mitochondrial respiration
Koliaki et al. Cell Metab. 2015;21:739–746
Obese with NASH have more mitochondria but increased
proton leakage
Koliaki et al. Cell Metab. 2015;21:739–746
Obese with NAFL and NASH exhibit impaired mitochondrial
biogenesis
Koliaki et al. Cell Metab. 2015;21:739–746
Only NASH patients present with hepatic
oxidative DNA damage
Koliaki et al. Cell Metab. 2015;21:739–746
Hepatic mitochondrial adaptation in NAFLD
Hypothesis of hepatic mitochondrial flexibility
Tissue-specific alterations of mitochondrial content
and function in states of insulin resistance
Major publications
 Koliaki C et al. Adaptation of hepatic mitochondrial function in humans with non-
alcoholic fatty liver is lost in steatohepatitis. Cell Metab 2015; 21:739-746
 Koliaki C, Roden M. Alterations of Mitochondrial Function and Insulin Sensitivity in
Human Obesity and Diabetes Mellitus. Annu Rev Nutr 2016; 36:337-67
 Koliaki C, Roden M. Do mitochondria care about insulin resistance?
Mol Metab 2014; 3:351-3
 Koliaki C, Roden M. Hepatic energy metabolism in human diabetes mellitus, obesity
and non-alcoholic fatty liver disease. Mol Cell Endocrinol 2013; 379:35-42
Significance of data
The pathophysiologic concept of “hepatic mitochondrial flexibility”
at early stages of human obesity-associated insulin resistance, could
serve as a relevant future target for the prevention and treatment of
NAFLD and other metabolic diseases.
Future perspectives
 We aim to expand our data on mitochondrial function and insulin
resistance by recruiting additional patients from Obesity Outpatient
Clinics in Greece, undergoing bariatric surgery, liver biopsies and
metabolic phenotyping, in order to further corroborate our concept of
hepatic mitochondrial adaptation to insulin resistance and NAFLD.
Acknowledgements
 Prof. Michael Roden for guidance and support
 Study volunteers
 KT, ME, KR for technical assistance
 National Foundation of State Scholarships of Greece
 EFSD, Albert Renold Research Fellowship
 Ministry of Science and Research of the State of North Rhine-
Westphalia (MIWF NRW)
 German Federal Ministry of Health (BMG)
Thank you!