title: Effect of adipose tissue insulin resistance on metabolic parameters and liver histology in obese patients with nonalcoholic fatty liver disease.
abstract: The role of adipose tissue insulin resistance in the pathogenesis of nonalcoholic fatty liver disease (NAFLD) remains unclear. To evaluate this, we measured in 207 patients with NAFLD (age = 51 ± 1, body mass index = 34.1 ± 0.3 kg/m(2) ) and 22 controls without NAFLD (no NAFLD) adipose tissue insulin resistance by means of a validated index (Adipo-IR(i) = plasma free fatty acids [FFA] x insulin [FPI] concentration) and as the suppression of plasma FFA during an oral glucose tolerance test and by a low-dose insulin infusion. We also explored the relationship between adipose tissue insulin resistance with metabolic and histological parameters by dividing them based on quartiles of adipose tissue insulin resistance (Adipo-IR(i) quartiles: Q1 = more sensitive; Q4 = more insulin resistant). Hepatic insulin resistance, measured as an index derived from endogenous glucose production x FPI (HIRi), and muscle insulin sensitivity, were assessed during a euglycemic insulin clamp with 3-[(3) H] glucose. Liver fat was measured by magnetic resonance imaging and spectroscopy, and a liver biopsy was performed to assess liver histology. Compared to patients without steatosis, patients with NAFLD were insulin resistant at the level of adipose tissue, liver, and skeletal muscle and had higher plasma aspartate aminotransferase and alanine aminotransferase, triglycerides, and lower high-density lipoprotein cholesterol and adiponectin levels (all P < 0.01). Metabolic parameters, hepatic insulin resistance, and liver fibrosis (but not necroinflammation) deteriorated as quartiles of adipose tissue insulin resistance worsened (all P < 0.01).
  
  
  CONCLUSIONS
  Adipose tissue insulin resistance plays a key role in the development of metabolic and histological abnormalities of obese patients with NAFLD. Treatment strategies targeting adipose tissue insulin resistance (e.g., weight loss and thiazolidinediones) may be of value in this population.
authors.affiliation: Diabetes, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, USA.
authors.forename: Romina
authors.initials: R
authors.lastname: Lomonaco
authors.forename: Carolina
authors.initials: C
authors.lastname: Ortiz-Lopez
authors.forename: Beverly
authors.initials: B
authors.lastname: Orsak
authors.forename: Amy
authors.initials: A
authors.lastname: Webb
authors.forename: Jean
authors.initials: J
authors.lastname: Hardies
authors.forename: Celia
authors.initials: C
authors.lastname: Darland
authors.forename: Joan
authors.initials: J
authors.lastname: Finch
authors.forename: Amalia
authors.initials: A
authors.lastname: Gastaldelli
authors.forename: Stephen
authors.initials: S
authors.lastname: Harrison
authors.forename: Fermin
authors.initials: F
authors.lastname: Tio
authors.forename: Kenneth
authors.initials: K
authors.lastname: Cusi
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism* / Q000473:pathology; D000328:Adult; D017677:Age Distribution; D000704:Analysis of Variance; D001707:Biopsy, Needle; D015992:Body Mass Index; D016022:Case-Control Studies; D005234:Fatty Liver / Q000453:epidemiology / Q000378:metabolism* / Q000473:pathology*; D005260:Female; D015309:Glucose Clamp Technique / Q000379:methods; D006801:Humans; D006943:Hyperglycemia / Q000175:diagnosis / Q000453:epidemiology; D007150:Immunohistochemistry; D015994:Incidence; D007333:Insulin Resistance / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D065626:Non-alcoholic Fatty Liver Disease; D009765:Obesity / Q000453:epidemiology / Q000378:metabolism* / Q000473:pathology; D011379:Prognosis; D011863:Radioimmunoassay; D012016:Reference Values; D012720:Severity of Illness Index; D017678:Sex Distribution