1212-P: Adipose Tissue Mitochondrial Function in Humans with Varying Liver Histology

Abstract

Adipose dysfunction may drive the development of insulin resistance, type 2 diabetes (T2D) and nonalcoholic (NA) fatty liver disease (NAFLD), comprising NA fatty liver and steatohepatitis (NAFL and NASH). Possible underlying mechanism comprise impaired lipid storage or mitochondrial oxidation favoring increased fatty acid flux to other tissues. Thus, we examined subcutaneous (SAT) and visceral adipose tissue (VAT) mitochondrial capacity in humans with different degrees of insulin resistance and histologically proven NAFLD. Obese people without NAFL (OBE-CON, n=20, 38±8 years, body mass index 53±6 kg/m2, 10% T2D), with NAFL (OBE-NAFL, n=20, 40±8 years, 51±5 kg/m2, 25% T2D) or NASH (OBE-NASH, n=20, 42±10 years, 51±6 kg/m2, 40% T2D) underwent metabolic phenotyping and tissue biopsies. O2 flux rates from different substrates were measured with high resolution respirometry in SAT and VAT. In VAT, maximal uncoupled respiration was lower in OBE-NAFL (least square means (LSM): 0.46 pmol*mg wet weight–1*s–1 [95% confidence interval 0.21;0.71], p<0.05) and OBE-NASH (LSM: 0.51 [0.26;0.76], p<0.001) compared to OBE-CON. Similar differences were seen for state 3 respiration related to complex I (glutamate) or combined complex I and II activity (succinate). In Pearson correlation analysis, combined complex I and II activity in VAT positively correlated with whole-body insulin sensitivity (M value; r= 0.29, p<0.05). VAT mitochondrial content, as assessed from mitochondrial DNA copy number, was not different between the groups. Protein expression of electron transport chain complexes was similar in VAT and SAT of all groups, except for complex IV that tended to be lower in VAT in OBE-NASH than in OBE-CON (p=0.065). Of note, in SAT, oxidative capacity was comparable between groups despite a higher mitochondrial mass in OBE-NASH than in OBE-CON (p=0.045). In conclusion, oxidative capacity is downregulated in VAT, but not in SAT of obese humans with NAFLD, which may be related to the degree of insulin resistance. Disclosure K. Pafili: None. M. Schlensak: None. M. Roden: Advisory Panel; Self; Allergan plc, Bristol-Myers Squibb Company, Novo Nordisk A/S, Research Support; Self; Boehringer Ingelheim International GmbH, Danone Nutricia, Sanofi-Aventis Deutschland GmbH. S. Kahl: None. D. Pesta: None. K. Strassburger: None. L. Mastrototaro: None. J. Puetzer-furmanczak: None. B. Dewidar: None. T. Sarabhai: None. I. Esposito: None.