New paper on insulin’s effect on lipolysis

J Clin Endocrinol Metab. 2011 May 18. [Epub ahead of print]

Higher Acute Insulin Response to Glucose May Determine Greater 
Free Fatty Acid Clearance in African-American Women.

Chow CC, Periwal V, Csako G, Ricks M, Courville AB, Miller BV 3rd, Vega GL,
Sumner AE.

Laboratory of Biological Modeling (C.C.C., V.P.), National Institute of Diabetes
and Digestive and Kidney Diseases, National Institutes of Health, Bethesda,
Maryland 20892; Departments of Laboratory Medicine (G.C.) and Nutrition (A.B.C.),
Clinical Center, National Institutes of Health, and Clinical Endocrinology Branch
(M.R., B.V.M., A.E.S.), National Institute of Diabetes and Digestive and Kidney
Diseases, National Institutes of Health, Bethesda, Maryland 20892; and Center for
Human Nutrition (G.L.V.), University of Texas Southwestern Medical Center at
Dallas, Dallas, Texas 75235.

Context: Obesity and diabetes are more common in African-Americans than whites.
Because free fatty acids (FFA) participate in the development of these
conditions, studying race differences in the regulation of FFA and glucose by
insulin is essential. Objective: The objective of the study was to determine
whether race differences exist in glucose and FFA response to insulin. Design:
This was a cross-sectional study. Setting: The study was conducted at a clinical
research center. Participants: Thirty-four premenopausal women (17
African-Americans, 17 whites) matched for age [36 ± 10 yr (mean ± sd)] and body
mass index (30.0 ± 6.7 kg/m(2)). Interventions: Insulin-modified frequently
sampled iv glucose tolerance tests were performed with data analyzed by separate
minimal models for glucose and FFA. Main Outcome Measures: Glucose measures were
insulin sensitivity index (S(I)) and acute insulin response to glucose (AIRg).
FFA measures were FFA clearance rate (c(f)). Results: Body mass index was similar
but fat mass was higher in African-Americans than whites (P < 0.01). Compared
with whites, African-Americans had lower S(I) (3.71 ± 1.55 vs. 5.23 ± 2.74
[×10(-4) min(-1)/(microunits per milliliter)] (P = 0.05) and higher AIRg (642 ±
379 vs. 263 ± 206 mU/liter(-1) · min, P < 0.01). Adjusting for fat mass,
African-Americans had higher FFA clearance, c(f) (0.13 ± 0.06 vs. 0.08 ± 0.05
min(-1), P < 0.01). After adjusting for AIRg, the race difference in c(f) was no
longer present (P = 0.51). For all women, the relationship between c(f) and AIRg
was significant (r = 0.64, P < 0.01), but the relationship between c(f) and S(I)
was not (r = -0.07, P = 0.71). The same pattern persisted when the two groups
were studied separately. Conclusion: African-American women were more insulin
resistant than white women, yet they had greater FFA clearance. Acutely higher
insulin concentrations in African-American women accounted for higher FFA
clearance.

PMID: 21593106  [PubMed - as supplied by publisher]