Liver enzymes but not free fatty acid levels predict markers of insulin sensitivity in overweight and obese, nondiabetic adults

Nutr Res. 2013 Oct;33(10):781-8. doi: 10.1016/j.nutres.2013.07.019. Epub 2013 Aug 26.

Abstract

Although obesity is a key predisposing risk factor in the development of insulin resistance (IR) and type 2 diabetes mellitus, not all obese individuals develop IR. This study aimed to identify key anthropometric and biochemical parameters that predict insulin sensitivity in overweight and obese adults. Based on previous literature, we hypothesized that markers of insulin sensitivity would be negatively correlated with plasma concentrations of free fatty acids and liver enzymes. Forty nondiabetic adult participants (body mass index ≥ 25.0 kg/m²) were recruited. Data collection included anthropometric measurements and fasting plasma samples for the quantification of liver enzymes (alanine transaminase, aspartate transaminase, γ-glutamyl transpeptidase), blood lipid profile, and markers of insulin sensitivity. Questionnaires relating to dietary intake, physical activity, and fatigue were also completed. Insulin and Homeostasis Model of Assessment (HOMA) scores were significantly correlated with indirect measures of central obesity (P < .05). Glycosylated hemoglobin, insulin, and HOMA scores for IR were all positively correlated with selected liver function markers (P < .05). Scores of HOMA-IR were significantly positively correlated with plasma phospholipid levels of n-3 fatty acids (P = .04) and ratio of n-3/n-6 fatty acids (P < .05) and negatively correlated with n-6 fatty acids (P = .03). No significant correlations were found between markers of insulin sensitivity and cholesterol levels, physical activity, or self-reported fatigue. These results have reinforced the integral role of liver function in the development of IR. Despite previous data linking elevations in free fatty acid to the development of IR, we found no relationship between these variables in this study.

Keywords: ALT; AST; BMI; CV; DHA; EPA; FFAs; GGT; HOMA; Homeostasis Model of Assessment; Human; ICAM-1; IR; Insulin; LDL; Liver; NQSP; National Glycohemoglobin Standardization Program; Obesity; PUFA; Spearman correlation coefficients; T2DM; WC; WHtR; alanine transaminase; aspartate transaminase; body mass index; coefficients of variation; docosahexaenoic acid; eGFR; eicosapentaenoic acid; estimated glomerular filtration rate; free fatty acids; insulin resistance; intercellular adhesion molecule 1; low-density lipoprotein; n-3 Fatty acids; n-6 Fatty acids; polyunsaturated fatty acids; r; type 2 diabetes mellitus; waist circumference; waist-to-height ratio; γ-glutamyl transpeptidase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Alanine Transaminase / blood
  • Aspartate Aminotransferases / blood
  • Biomarkers / blood
  • Body Mass Index*
  • Cholesterol / blood
  • Diabetes Mellitus
  • Exercise / physiology
  • Fatigue / metabolism
  • Fatty Acids, Nonesterified / blood*
  • Fatty Acids, Omega-3 / blood
  • Fatty Acids, Omega-6 / blood
  • Female
  • Glycated Hemoglobin A / metabolism*
  • Humans
  • Insulin / blood*
  • Insulin Resistance*
  • Liver / enzymology
  • Liver / physiopathology*
  • Male
  • Middle Aged
  • Obesity / blood
  • Obesity / enzymology
  • Obesity / physiopathology*
  • Obesity, Abdominal / blood
  • Obesity, Abdominal / enzymology
  • Obesity, Abdominal / physiopathology
  • Overweight
  • Phospholipids / blood
  • Reference Values
  • gamma-Glutamyltransferase / blood

Substances

  • Biomarkers
  • Fatty Acids, Nonesterified
  • Fatty Acids, Omega-3
  • Fatty Acids, Omega-6
  • Glycated Hemoglobin A
  • Insulin
  • Phospholipids
  • Cholesterol
  • gamma-Glutamyltransferase
  • Aspartate Aminotransferases
  • Alanine Transaminase