title: Age-related changes in insulin sensitivity and β-cell function among European-American and African-American women.
abstract: Type 2 diabetes (T2D) is more prevalent among African-American (AA) than European-American (EA) women for reasons that are unknown. Ethnic differences in physiological processes related to insulin sensitivity (S(I)) and secretion, and age-related changes in these processes, may play a role. The purpose of this study was to identify ethnicity- and age-related differences in S(I) and β-cell responsivity among AA and EA females, and to determine whether these differences are independent of body composition and fat distribution. Healthy, normoglycemic females aged 7-12 years (n = 62), 18-32 years (n = 57), and 40-70 years (n = 49) were recruited for entry into this study. Following an overnight fast, S(I), intravenous glucose tolerance (Kg), acute C-peptide secretion (X0), and basal, first-phase, second-phase, and total β-cell responsivity to glucose (PhiB, Phi1, Phi2, and Phi(TOT), respectively) were measured by an intravenous glucose tolerance test. Total % body fat was assessed by dual-energy X-ray absorptiometry, and intra-abdominal adiposity (IAAT) by computed tomography. Main effects of age group and ethnicity were measured with analysis of covariance, adjusting for % fat, IAAT, and S(I) as indicated. AA had lower S(I), and higher Kg, X0, Phi1, and Phi(TOT) (P < 0.05), which remained after adjustment for % fat and IAAT. Greater X0, Phi1, and Phi(TOT) among AA were independent of S(I). Advancing age was associated with greater Phi2 among both EA and AA. To conclude, inherent ethnic differences in β-cell function exist independently of adiposity and S(I). Future research should examine whether ethnic differences in β-cell physiology contribute to disparities in T2D risk.
authors.affiliation: Department of Nutrition Sciences, University of Alabama at Birmingham, Birmingham, Alabama, USA. pchandle@uab.edu
authors.forename: Paula C
authors.initials: PC
authors.lastname: Chandler-Laney
authors.forename: Radhika P
authors.initials: RP
authors.lastname: Phadke
authors.forename: Wesley M
authors.initials: WM
authors.lastname: Granger
authors.forename: José R
authors.initials: JR
authors.lastname: Fernández
authors.forename: Julian A
authors.initials: JA
authors.lastname: Muñoz
authors.forename: Chiara Dalla
authors.initials: CD
authors.lastname: Man
authors.forename: Claudio
authors.initials: C
authors.lastname: Cobelli
authors.forename: Fernando
authors.initials: F
authors.lastname: Ovalle
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Gower
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D000328:Adult; D001741:Black or African American; D000368:Aged; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D001786:Blood Glucose / Q000378:metabolism; D001823:Body Composition; D002097:C-Reactive Protein / Q000378:metabolism; D002648:Child; D005215:Fasting; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007333:Insulin Resistance / Q000208:ethnology* / Q000502:physiology; D050417:Insulin-Secreting Cells / Q000502:physiology*; D008875:Middle Aged; D012016:Reference Values; D014057:Tomography, X-Ray Computed; D044465:White People; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D002097:C-Reactive Protein