Relationships between regional and ectopic adiposity and insulin sensitivity in early and late pregnancy.

Objective To determine relationships between measurements of total body, visceral, and ectopic (liver, skeletal muscle) fat with insulin sensitivity in pregnancy. Research Design and Methods Pregnant women of varying pre-pregnancy weights were prospectively studied in early (n=59) and late (n=47) gestation. At each visit participants underwent body composition measurements including fat mass (FM), fat-free mass (FFM), abdominal subcutaneous (SAT), visceral (VAT) fat, ectopic lipid amounts in liver (IHL) and calf skeletal muscle (IMCL, EMCL) and hyperinsulinemia-euglycemic clamp to determine insulin sensitivity (Rd), endogenous glucose production (EGP), hepatic insulin sensitivity index (HISI), and free fatty acid (FFA) levels. Results In early pregnancy, Rd ((mg/kg FFM/min)/IU/mL) inversely correlated (P-values < .05) with body mass index (BMI), FM, SAT, VAT, IHL, IMCL, and FFA. HISI inversely correlated (P-values < .05) with BMI, FM, SAT, VAT, IMCL, and FFA, but not IHL. In late pregnancy, however, neither EGP ((mg/kg FFM/min)/IU/mL) nor Rd correlated with regional or ectopic fat measures, but HISI remained inversely correlated with BMI, FM, SAT, VAT, and IMCL. Early pregnancy IHL levels did not predict late pregnancy insulin sensitivity. Pregnant women with pre-pregnancy obesity were more insulin resistant but gained less gestational weight, VAT, and SAT, and experienced less decline in insulin sensitivity, than normal pre-pregnancy weight women. Conclusions Insulin resistance in early pregnancy is strongly associated with total, regional, and ectopic adiposity. However, in late pregnancy, factors other than regional and ectopic adiposity predominately influence insulin sensitivity. Pre-pregnancy weight categories proportionately alter gestational weight gain, adiposity distribution, and glucometabolic responses.