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Objective: This study prospectively evaluated the longitudinal changes in insulin sensitivity, insulin response, and endogenous (primarily hepatic) glucose production and suppression during insulin infusion in women with normal glucose tolerance (control) and gestational diabetes mellitus before and during a planned pregnancy.Study Design: Eight control subjects and 7 subjects in whom gestational diabetes mellitus developed were evaluated with an oral glucose tolerance test, an intravenous glucose tolerance test, and hyperinsulinemic-euglycemic clamp with infusion of [6,6 (2)H2 ]glucose before conception and at 12 to 14 and 34 to 36 weeks' gestation. Insulin response was estimated as the area under the curve during the intravenous glucose tolerance test. Basal endogenous glucose production was estimated from isotope tracer dilution during steady state with [6,6 (2)H2 ]glucose and suppression during insulin infusion. Insulin sensitivity to glucose was defined as the glucose infusion rate required to maintain euglycemia during steady-state insulin infusion. Body composition was estimated with hydrodensitometry. Data were analyzed with 2-way analysis of variance with repeated measures for 2 groups.Results: There were increases in first-phase (P =.006) and second-phase (P =. 0001) insulin responses in both groups with advancing gestation, but the increase in second-phase response was significantly greater (P =. 02) in the gestational diabetes mellitus group than in the control group. Basal glucose production increased significantly (P =.0001) with advancing gestation, and there was resistance to suppression during insulin infusion in both groups (P =.0001). There was less suppression of endogenous glucose production however, in the gestational diabetes mellitus group than in the control group (P =. 01). Insulin sensitivity decreased with advancing gestation in both groups (P =.0001), and there was lower insulin sensitivity in the gestational diabetes mellitus group than in the control group (P =. 04). Significant decreases in insulin sensitivity with time (P =. 0001) and between groups (P =.03) remained when the data were adjusted for differences in insulin concentration or residual hepatic glucose production.Conclusion: Obese women in whom gestational diabetes mellitus develops have a significant increase in insulin response but decreases in insulin sensitivity and suppression of hepatic glucose production during insulin infusion with advancing gestation with respect to a matched control group. These metabolic abnormalities in glucose metabolism are the hallmarks of type 2 diabetes, for which these women are at increased risk in later life. [ABSTRACT FROM AUTHOR]

Objective: The objective of this study was to evaluate the longitudinal changes in energy expenditure and body composition in relationship to alterations in carbohydrate metabolism in women with normal and abnormal glucose metabolism. We hypothesized that women with decreased insulin sensitivity before conception would have less fat accretion and smaller increases in energy expenditure.Study Design: Six women with normal glucose tolerance and 10 women with abnormal glucose tolerance were evaluated before conception, and in early (12 to 14 weeks) and late (34 to 36 weeks) gestation. Body composition was estimated by hydrodensitometry, resting energy expenditure, and glucose and fat metabolism by indirect calorimetry, endogenous glucose production by infusion of [6-6 2H2] glucose, and insulin sensitivity using a hyperinsulinemic-euglycemic clamp (40 mU/m2/min).Results: There was a smaller increase in fat mass (1.3 kg [P = .04]) in early pregnancy in women with abnormal glucose tolerance before pregnancy. Indirect calorimetry measured gestational age-related increases in basal oxygen utilization, with or without correction for fat-free mass (VO2, P = .002), resting energy expenditure (expressed in kilocalories, P = .0001), and carbohydrate oxidation (P = .0003). The insulin-mediated elevation in VO2 increased in later gestation VO2 (P = .005), as did resting energy expenditure (P = .0001) and fat oxidation (P = 0.0001). However, there was a decrease in respiratory quotient (P = .0001), carbohydrate oxidation (P = .002), and nonoxidative carbohydrate metabolism (P = .0001) with advancing gestation during insulin infusion. In early pregnancy, changes in fat mass correlated inversely with changes in insulin sensitivity (r= -0.52, P = .04) and changes in basal VO2 correlated inversely with decreases in basal endogenous glucose production (r = -0.74, P = .01).Conclusion: In early gestation, the changes in maternal fat mass and basal oxygen consumption are inversely related to the changes in insulin sensitivity. This response in lean women with decreased insulin sensitivity before conception may have survival value by providing a larger amount of available substrate to meet fetoplacental needs during gestation. [ABSTRACT FROM AUTHOR]

Objective: Terbutaline, a selective beta2-agonist, is a frequently used tocolytic known to affect maternal metabolism. The purpose of this study was to evaluate the effect of oral terbutaline on maternal glucose metabolism and energy expenditure.Study Design: Six healthy pregnant women with normal glucose tolerance were evaluated between 30 and 34 weeks' gestation. Oral terbutaline was administered to determine the effects on hepatic glucose production with [6-6(2)H2] glucose tracer, insulin sensitivity (hyperinsulinemic-euglycemic clamp), and energy expenditure (indirect calorimetry). Terbutaline, insulin, and glucagon levels were also obtained. Subjects were randomly assigned to either oral terbutaline 5 mg every 6 hours for 24 hours or no medication. Repeat studies were conducted 1 week apart, each subject serving as her own control.Results: In the basal state terbutaline was associated with a trend toward increased basal glucose levels (81.6 +/- 6.6 vs 93.7 +/- 12.0 mg/dl, p = 0.06) but no significant increase in hepatic glucose production (3.2 +/- 0.3 vs 3.6 +/- 0.4 mg/kg fat-free mass/min, p = 0.23). However, there was a significant increase in basal insulin concentration (17.6 +/- 9.2 vs 25.6 +/- 10.4 microU/ml, p = 0.02). There was a 28% decrease in insulin sensitivity as measured by the glucose infusion rate during the euglycemic clamp plus residual hepatic glucose turnover (5.78 +/- 1.91 vs 4.16 +/- 1.49 mg/kg fat-free mass/min, p = 0.005). Glucagon concentration was significantly decreased both in the basal state (163 +/- 26 vs 144 +/- 27 pg/ml, p = 0.0007) and during the clamp (144 +/- 27 vs 133 +/- 27 pg/ml, p = 0.003). Basal oxygen consumption increased 9% (270 +/- 49 vs 294 +/- 50 ml oxygen/min, p = 0.007) and caloric expenditure 14% (1.32 +/- 0.23 vs 1.50 +/- 0.31 kcal/min, p = 0.025) or 260 kcal/day with terbutaline.Conclusion: Decreased peripheral insulin sensitivity, and to a lesser degree increased endogenous glucose production, may represent the pathophysiology of abnormal glucose tolerance observed in many women treated with oral terbutaline. Common side effects such as tremors and tachycardia experienced by many women on a regimen of terbutaline are consistent with our finding of a significant increase in basal energy expenditure. [ABSTRACT FROM AUTHOR]

Objective: Our purpose was to examine the pattern of growth of both fetal lean body mass incorporating bone, brain, and muscle and subcutaneous fat mass during the course of normal pregnancy. We hypothesized that there are detectable differences in the accretion of fat versus lean body mass.Study Design: To establish our method we correlated standardized cross-sectional ultrasonographic images of the fetal extremities with anthropometric assessment of neonatal body composition in 25 subjects. Subsequently 36 nonsmoking women with normal prepregnancy body mass index, normal glucose screening results, and no medical or obstetric complications were recruited. We performed 135 ultrasonographic examinations between 19 and 40 weeks' gestation (mean 3.8 scans per fetus, range 2 to 6) at 4-week intervals. Lean body mass measures included biparietal diameter, head circumference, and femur length. Fetal subcutaneous fat and lean body mass were examined both in the mid upper arm and midthigh by standardized cross-sectional images. All neonates were born between 37 and 42 weeks' gestation and had normal birth weight distribution. Stepwise regression analysis established best-fit equations for fetal measurements obtained ultrasonographically. Independent variables included gestational age, maternal age, weight gain in pregnancy, parity, fetal gender, and maternal prepregnancy weight.Results: Fetal bone growth was best described by a second-order quadratic equation demonstrating deceleration with advancing gestational age (p < 0.0001, R2 0.92 to 0.96). A quadratic equation that accelerates with advancing gestation best described lean body mass accretion in the extremities (p < 0.0001, R2 = 0.85 to 0.86). Fetal fat deposition in the extremities was characterized by an accelerating quadratic equation when plotted against gestational age with maternal age and prepregnancy weight contributing significantly (p < 0.0001, R2 = 0.80 to 0.81).Conclusion: Consistent with our hypothesis, fetal fat and lean body mass demonstrate unique growth profiles. We speculate that, as a result of an accelerated rate of growth in late gestation, the measurement of fetal fat will provide a more sensitive and specific marker of abnormal fetal growth when compared with index values of lean body mass. [ABSTRACT FROM AUTHOR]