Impaired adipose tissue (AT) function closely associates with obesity, type 2 diabetes and nonalcoholic fatty liver disease (NAFLD) . Mitochondrial oxidative phosphorylation (OXPHOS) capacity of AT improves after weight loss surgery. However, it is not clear if the improvement is affected by the presence of NAFLD before surgery. We examined 52 severely obese people exhibiting no histological liver disease (OBE_CON) , simple steatosis (OBE_NAFL) or steatohepatitis (OBE_NASH) before (0 weeks) , 12 and 52 weeks after bariatric surgery. Whole-body insulin sensitivity was measured by hyperinsulinemic euglycemic clamps. OXPHOS capacity of subcutaneous AT was assessed by high-resolution respirometry. Transcript levels of TNFα in AT were quantified by RT-PCR. Before surgery, OBE_NASH presented with lower insulin sensitivity and higher HbA1c compared to OBE_CON and OBE_NAFL (all p<0.05) whereas OXPHOS capacity in AT was comparable between the groups. Maximum coupled respiration declined at week 12 by 17% from week 0 in OBE_CON only (p<0.05) . From 12 to 52 weeks, AT maximum coupled respiration markedly increased by 82 and 49% in OBE_CON and OBE_NAFL (both p<0.001) but only by 28% in OBE_NASH (p=0.05; maximum coupled OXPHOS at week 52: OBE_CON vs. OBE_NASH p<0.05) . The changes in AT maximum coupled respiration from 12 to 52 weeks correlated negatively with changes in AT TNFα levels in OBE_CON (β=-0.83, p<0.001) and negatively with changes in systemic C-reactive protein levels in OBE_NASH (β=-0.34, p<0.05) . Maximal noncoupled OXPHOS yielded similar changes and correlations.
In conclusion, in severe obesity, weight loss-related improvements in AT OXPHOS capacity may be mediated to a great extent by reduced AT inflammation in people without liver disease; however, with pre-surgery manifestation of NASH and worsening of metabolic control, residual systemic subclinical inflammation may attenuate the improvement of AT OXPHOS capacity after bariatric surgery.
S.Kahl: None. G.Heilmann: None. I.Esposito: None. M.Schlensak: None. M.Roden: Advisory Panel; Eli Lilly and Company, Research Support; Boehringer Ingelheim International GmbH, Nutricia, Speaker's Bureau; Novo Nordisk. K.Strassburger: None. S.Gancheva: None. N.Saatmann: None. C.Granata: None. C.Herder: Research Support; Sanofi. K.Pafili: None. J.Puetzer-furmanczak: None. T.Sarabhai: None.
German Federal Ministry of Health; Ministry of Culture and Science of the State North Rhine-Westphalia;German Federal Ministry of Education and Research;European Funds for Regional Development (EFRE-0400191) ;EUREKA Eurostars-2 (E!113230DIA-PEP) ;German Science Foundation (CRC/SFB1116/2 B12; RTG/GRK 2576 vivid, Project 3) ;Schmutzler Stiftung