Ethnic differences in pancreatic fat accumulation and its relationship with other fat depots and inflammatory markers

Abstract

Objective: Visceral adipose tissue (VAT) and hepatic fat are associated with insulin resistance and vary by sex and ethnicity. Recently, pancreatic fat fraction (PFF) has also been linked with increasing obesity. Our aim was to assess ethnic and sex differences in PFF and its relationship to other fat depots, circulating free fatty acids (FFA), insulin secretion and sensitivity, and inflammation in obese adolescents and young adults.

Research design and methods: We examined 138 (40 males, 98 females) obese Hispanics and African Americans (13-25 years). Subcutaneous adipose tissue and VAT volumes, hepatic fat fraction (HFF), and PFF were determined by magnetic resonance imaging. Insulin sensitivity and β-cell function were assessed during an intravenous glucose tolerance test.

Results: Hispanics had higher PFF than African Americans (7.3 ± 3.8 vs. 6.2 ± 2.6%, P = 0.03); this ethnic difference was higher in young adults compared with children and adolescents (ethnicity × age: P = 0.01). Males had higher PFF than females (P < 0.0001). PFF was positively correlated with VAT (r = 0.45, P < 0.0001), HFF (r = 0.29, P < 0.0001), and FFA (r = 0.32, P = 0.001). PFF positively correlated with inflammatory markers but lost significance when adjusted for VAT. In multiple stepwise regression analysis, VAT and FFA were the best predictors of PFF (adjusted R(2) = 0.40). There were no significant correlations between PFF and markers of insulin sensitivity or β-cell function.

Conclusions: PFF is higher in Hispanics than African Americans, and this difference increases with age. In young obese individuals, PFF is related to VAT, HFF, and circulating FFA, thus possibly contributing to their increased risk for type 2 diabetes and related metabolic disorders.

Trial registration: ClinicalTrials.gov NCT00697580.

Figure 1

SAT (A), VAT (B), HFF (C), and PFF (D) by age and ethnic groups. All data show means ± SE and were analyzed by using 2-factor ANOVA; the Tukey-Kramer test was used during post hoc comparisons. AA, African American; Hisp, Hispanic. *Significant (P < 0.05) effect of ethnicity; †significant (P < 0.05) effect of age.

Figure 2

Unadjusted relationships between PFF and FFA (A), VAT (B), and HFF (C). In the overall group, PFF was positively correlated with FFA (r = 0.32, P = 0.001), VAT (r = 0.45, P < 0.0001), and HFF (r = 0.29, P < 0.0001). ●, Hispanics; ○, African Americans.