Research Article Details

Article ID: A23972
PMID: 23334462
Source: Diabetologia
Title: Adipose tissue is inflamed in NAFLD due to obesity but not in NAFLD due to genetic variation in PNPLA3.
Abstract: AIMS/HYPOTHESIS: The rs738409 C>G single-nucleotide polymorphism in PNPLA3 leads to a missense mutation (I148M) which increases liver fat but does not cause insulin resistance. We hypothesised that patients with non-alcoholic fatty liver disease (NAFLD) due to the PNPLA3 variant ('PNPLA3 NAFLD'&#8201;=&#8201;PNPLA3-148MM) do not have adipose tissue (AT) inflammation in contrast with those with NAFLD due to obesity ('obese NAFLD'). METHODS: Biopsy specimens of AT were taken, and PNPLA3 genotype and liver fat ((1)H-magnetic resonance spectroscopy) were determined in 82 volunteers, who were divided into groups based on either median BMI (obese 36.2&#8201;&#177;&#8201;0.7&#160;kg/m(2); non-obese 26.0&#8201;&#177;&#8201;0.4&#160;kg/m(2)) or PNPLA3 genotype. All groups were similar with respect to age and sex. The PNPLA3 subgroups were equally obese (PNPLA3-148MM, 31.1&#8201;&#177;&#8201;1.3&#160;kg/m(2); PNPLA3-148II, 31.2&#8201;&#177;&#8201;0.8&#160;kg/m(2)), while the obese and non-obese subgroups had similar PNPLA3 genotype distribution. Gene expression of proinflammatory (MCP-1, CD68) and anti-inflammatory (Twist1, ADIPOQ) markers was measured using quantitative real-time RT-PCR. RESULTS: Liver fat was similarly increased in obese NAFLD (9.5&#8201;&#177;&#8201;1.3% vs 5.1&#8201;&#177;&#8201;0.9%, obese vs non-obese, p&#8201;=&#8201;0.007) and PNPLA3 NAFLD (11.4&#8201;&#177;&#8201;1.7% vs 5.3&#8201;&#177;&#8201;0.8%, PNPLA3-148MM vs PNPLA3-148II, p&#8201;<&#8201;0.001). Fasting serum insulin was higher in the obese than the non-obese group (76&#8201;&#177;&#8201;6 vs 47&#8201;&#177;&#8201;6&#160;pmol/l, p&#8201;<&#8201;0.001), but similar in PNPLA3-148MM and PNPLA3-148II (60&#8201;&#177;&#8201;8 vs 62&#8201;&#177;&#8201;5&#160;pmol/l, NS). In obese vs non-obese, MCP-1 and CD68 mRNAs were upregulated, whereas those of Twist1 and ADIPOQ were significantly downregulated. AT gene expression of MCP-1, CD68, Twist1 and ADIPOQ was similar in PNPLA3-148MM and PNPLA3-148II groups. CONCLUSIONS/INTERPRETATION: PNPLA3 NAFLD is characterised by an increase in liver fat but no insulin resistance or AT inflammation, while obese NAFLD has all three of these features.
DOI: 10.1007/s00125-013-2829-9