title: Effect of insulin infusion on spillover of meal-derived fatty acids.
abstract: BACKGROUND
  Spillover of chylomicron triglyceride fatty acids directly into the circulation as free fatty acids (FFAs) during lipoprotein lipase hydrolysis may contribute to the elevated total FFAs seen in insulin-resistant states.
  
  
  OBJECTIVE
  The objective of the study was to determine whether spillover is regulated by rates of intracellular lipolysis, we studied overweight and obese nondiabetic subjects (n = 7) on two occasions, during infusion of saline and insulin.
  
  
  METHODS
  During insulin infusion (20 mU · m(-2) · min(-1)), plasma glucose was clamped at the concentration achieved during saline infusion. On both study days, subjects sipped 1-2 oz of a liquid mixed meal every 15 min for 6.5 h to achieve steady-state chylomicron and FFA concentrations. Spillover was measured with infusions of [(3)H]triolein and [U-(13)C] oleate.
  
  
  RESULTS
  Glucose concentrations were similar during saline compared with insulin (113 ± 2 vs. 113 ± 1 mg/dl, P = NS). Insulin levels during saline and insulin infusion were 18 ± 3 and 44 ± 5 μU/ml, respectively. Glucose infusion rate during insulin infusion was 5.5 ± 1.0 mg · kg fat-free mass(-1) · min(-1). Plasma FFA concentrations were lower during insulin compared with saline (75 ± 8 vs. 124 ± 13 μmol/liter, P = 0.002). Oleate rate of appearance was lower during insulin vs. saline (27 ± 3 vs. 36 ± 5 μmol/min, P = 0.004). Spillover was similar during saline and insulin (26 ± 2 vs. 25 ± 2%, P = 0.60).
  
  
  CONCLUSIONS
  These results indicate that suppression of intracellular lipolysis with insulin does not reduce lipoprotein lipase-mediated spillover in humans during meal absorption. It is possible that spillover did not decrease because of an impaired or absent antilipolytic effect of increased insulin concentrations in visceral fat.
authors.affiliation: Endocrine Research Unit, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905, USA.
authors.forename: Kalpana
authors.initials: K
authors.lastname: Muthusamy
authors.forename: Robert H
authors.initials: RH
authors.lastname: Nelson
authors.forename: Ekta
authors.initials: E
authors.lastname: Singh
authors.forename: Danielle
authors.initials: D
authors.lastname: Vlazny
authors.forename: Almira
authors.initials: A
authors.lastname: Smailovic
authors.forename: John M
authors.initials: JM
authors.lastname: Miles
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D005230:Fatty Acids, Nonesterified / Q000097:blood*; D006801:Humans; D007328:Insulin / Q000008:administration & dosage* / Q000097:blood; D008066:Lipolysis / Q000187:drug effects*; D008297:Male; D062407:Meals; D009765:Obesity / Q000097:blood; D050177:Overweight / Q000097:blood*
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin