Estimating body composition in late gestation: a new hydration constant for body density and total body water

Maternal Lipid Metabolism Is Associated With Neonatal Adiposity: A Longitudinal Study

CONTEXT

Pregnancy is characterized by progressive decreases in glucose insulin sensitivity. Low insulin sensitivity resulting in hyperglycemia is associated with higher neonatal adiposity. However, less is known regarding lipid metabolism, particularly lipid insulin sensitivity in pregnancy and neonatal adiposity.

OBJECTIVE

Because higher maternal prepregnancy body mass index is strongly associated with both hyperlipidemia and neonatal adiposity, we aimed to examine the longitudinal changes in basal and clamp maternal lipid metabolism as contributors to neonatal adiposity.

METHODS

Twelve women planning a pregnancy were evaluated before pregnancy, in early (12-14 weeks), and late (34-36 weeks) gestation. Body composition was estimated using hydrodensitometry. Basal and hyperinsulinemic-euglycemic clamp glucose and glycerol turnover (GLYTO) were measured using 2H2-glucose and 2H5-glycerol and substrate oxidative/nonoxidative metabolism with indirect calorimetry. Total body electrical conductivity was used to estimate neonatal body composition.

RESULTS

Basal free-fatty acids decreased with advancing gestation (P = 0.0210); however, basal GLYTO and nonoxidative lipid metabolism increased over time (P = 0.0046 and P = 0.0052, respectively). Further, clamp GLYTO and lipid oxidation increased longitudinally over time (P = 0.0004 and P = 0.0238, respectively). There was a median 50% increase and significant positive correlation during both basal and clamp GLYTO from prepregnancy through late gestation. Neonatal adiposity correlated with late pregnancy basal and clamp GLYTO (r = 0.6515, P = 0.0217; and r = 0.6051, P = 0.0371).

CONCLUSIONS

Maternal prepregnancy and late pregnancy measures of basal and clamp lipid metabolism are highly correlated. Late pregnancy basal and clamp GLYTO are significantly associated with neonatal adiposity and account for ~40% of the variance in neonatal adiposity. These data emphasize the importance of maternal lipid metabolism relating to fetal fat accrual.

Rationale and study design for lifestyle intervention in preparation for pregnancy (LIPP): A randomized controlled trial

INTRODUCTION

Maternal obesity increases neonatal risk for obesity and metabolic syndrome later in life. Prior attempts to break this intergenerational obesity cycle by limiting excessive gestational weight gain have failed to reduce neonatal adiposity. Alternatively, pre-conception lifestyle interventions may improve the in utero metabolic milieu during early pregnancy leading to improved fetal outcomes. This randomized controlled trial (RCT) is evaluating whether a lifestyle intervention to reduce weight and improve maternal metabolism in preparation for pregnancy (LIPP) attenuates neonatal adiposity, compared to standard medical advice.

MATERIAL AND METHODS

Overweight/class 1 obese women after a previous pregnancy, ~12 weeks postpartum, preparing for a subsequent pregnancy, will be block randomized (1:1) to either LIPP or standard of care in a parallel design. Randomization is stratified by lactation status and overweight vs. class 1 obesity. The LIPP program consists of intensive short-term weight loss followed by weight maintenance until conception using supervised exercise and a low glycemic Mediterranean diet.

PRIMARY OUTCOMES

Group differences in neonatal adiposity at birth assessed by PEA POD and placental mitochondrial lipid metabolism.

SECONDARY OUTCOMES

Group differences in maternal pregravid and gestational body composition, insulin sensitivity, β-cell function, fasting metabolic and inflammatory biomarkers, and overall quality of life. Exploratory outcomes include umbilical cord blood insulin resistance, lipid profile and inflammation.

DISCUSSION

This RCT will determine the efficacy of maternal weight loss prior to pregnancy on reducing neonatal adiposity. Findings may change standard obstetrical care by providing Level 1 evidence on lifestyle interventions improving neonatal outcomes for women planning for pregnancy.

CLINICAL TRIAL REGISTRATION

NCT03146156.

Increased Visceral Adipose Tissue Without Weight Retention at 59 Weeks Postpartum

OBJECTIVE

This study aimed to determine whether controlling maternal gestational weight gain (GWG) influences adipose tissue distribution at 1 year postpartum.

METHODS

Women with overweight or obesity (n = 210, BMI ≥ 25 or ≥ 30) were randomized to a lifestyle intervention (LI) designed to control GWG or to usual obstetrical care (UC). Measures included anthropometry, whole-body magnetic resonance imaging for visceral (VAT), intermuscular, and subcutaneous adipose tissue, and cardiometabolic risk factors in pregnancy (15 and 35 weeks) and after delivery (15 and 59 weeks).

RESULTS

Baseline (15 weeks) characteristics were similar (mean [SD]: age, 33.8 [4.3] years; weight, 81.9 [13.7] kg; BMI, 30.4 [4.5]; gestational age at randomization, 14.9 [0.8] weeks). LI had less GWG (1.79 kg; P = 0.003) and subcutaneous adipose tissue gain at 35 weeks gestation (P < 0.01). UC postpartum weight (2.92 kg) was higher at 15 weeks but not different from baseline or LI at 59 weeks postpartum. Postpartum VAT increased from baseline in LI by 0.23 kg at 15 weeks and 0.55 kg at 59 weeks; in UC, it increased by 0.34 kg at 15 and 59 weeks. Intermuscular adipose tissue remained elevated in LI (0.22 kg) at 59 weeks. VAT was associated with several cardiometabolic risk factors at 59 weeks.

CONCLUSIONS

Despite no weight retention at 59 weeks postpartum, women had increased VAT by ~30%. Postpartum modifiable behaviors are warranted to lower the risk of VAT retention.

Body Composition During Pregnancy Differs by Obesity Class

OBJECTIVE

The aim of this study is to characterize changes in body composition during pregnancy in women with obesity.

METHODS

Fifty-four healthy women with obesity (class 1, 30-34.9 kg/m² : n = 25; class 2, 35-39.9 kg/m² : n = 21; class 3, ≥ 40.0 kg/m² : n = 8) expecting a singleton pregnancy were studied. Body composition was measured in early pregnancy (13-16 weeks), midpregnancy (24-27 weeks), and late pregnancy (35-37 weeks) using air displacement plethysmography, stable isotopes, and skinfold thickness measurements. Fasting glucose, insulin, and leptin were measured.

RESULTS

The gain in fat-free mass was lower in the second trimester compared with the third (2.7 ± 0.2 to 5.3 ± 0.2 kg; P < 0.001), whereas fat mass accumulation declined over time (0.6 ± 0.3 to -0.7 ± 0.4 kg; P = 0.005). Women with class 1 and 2 obesity gained 1.1 ± 0.7 kg of fat mass during pregnancy, while women with class 3 obesity lost 4.1 ± 0.6 kg (both P < 0.001). The difference in fat accumulation between obesity classes was observed only in the second trimester (P = 0.02). Gestational weight gain was associated positively with changes in plasma concentrations of insulin, leptin, and insulin resistance (all P < 0.01).

CONCLUSIONS

Gestational weight gain in pregnancy differs by obesity class and trimester. Women with class 3 obesity gain less body weight and fat mass. Fat mass gain is most likely preventable in the second trimester.

Body Composition During Pregnancy: Longitudinal Changes and Method Comparisons

The Pregnancy Obesity Nutrition and Child Health study is a longitudinal study of reproductive health. Here we analyzed body composition of normal-weight and obese Swedish women by three methods during each trimester of pregnancy. Cross-sectional and longitudinal fat mass estimates using quantitative magnetic resonance (QMR) and bioelectrical impedance analysis (BIA) (Tanita MC-180MA-III) were compared with fat mass determined by air displacement plethysmography (ADP) in pregnancy weeks 8-12, 24-26, and 35-37 in normal-weight women (n = 122, BMI = 22.1 ± 1.6 kg/m²) and obese women (n = 29, BMI = 34.6 ± 3.6 kg/m²). ADP results were calculated from pregnancy-adjusted fat-free mass densities. Mean fat mass by QMR and ADP were similar in obese women, although with wide limits of agreement. In normal-weight women, QMR overestimated mean fat mass in all trimesters, with systematic overestimation at low fat mass values in trimesters 1 and 3. In obese women, fat mass by BIA was grossly underestimated and imprecise in all trimesters, especially at higher values in trimester 2. In normal-weight women, fat mass by BIA was moderately lower than by ADP in trimester 1, similar in trimester 2, and moderately higher in trimester 3. QMR and ADP assessed fat mass changes similarly in obese women, whereas BIA overestimated fat mass changes in normal-weight women. Mean fat mass and fat mass changes by QMR and pregnancy-adjusted ADP were similar in pregnant obese women. Mean fat mass by QMR and fat mass changes by BIA were higher than corresponding values determined by pregnancy-adjusted ADP in normal-weight women.

Towards Prepared mums (TOP-mums) for a healthy start, a lifestyle intervention for women with overweight and a child wish: study protocol for a randomised controlled trial in the Netherlands

INTRODUCTION

Periconception obesity is associated with a higher risk for adverse perinatal outcomes such as gestational diabetes mellitus, preeclampsia, large for gestational age, operative delivery and preterm birth. Lifestyle interventions during pregnancy have resulted in insufficient effects on reducing these perinatal complications. A few reasons for this disappointing effect can be suggested: (1) the time period during pregnancy for improvement of developmental circumstances is too short; (2) the periconception period in which complications originate is not included; and (3) lifestyle interventions may not have been sufficiently multidisciplinary and customised. A preconception lifestyle intervention might be more effective to reduce perinatal complications. Therefore, the aim of the Towards Prepared mums study is to evaluate the effect of a lifestyle intervention starting prior to conception on lifestyle behaviour change.

METHODS AND ANALYSIS

This protocol outlines a non-blinded, randomised controlled trial. One hundred and twelve women (18-40 years of age) with overweight or obesity (body mass index≥25.0 kg/m2) who plan to conceive within 1 year will be randomised to either the intervention or care as usual group. The intervention group will receive a multidisciplinary, customised lifestyle intervention stimulating physical activity, a healthy diet and smoking cessation, if applicable. The lifestyle intervention and monitoring will take place until 12 months postpartum. The primary outcome is difference in weight in kg from baseline to 6 weeks postpartum. Secondary outcomes are gestational weight gain, postpartum weight retention, smoking cessation, dietary and physical activity habits. Furthermore, exploratory outcomes include body composition, cardiometabolic alterations, time to pregnancy, need for assisted reproductive technologies, perinatal complications of mother and child, and lung function of the child. Vaginal and oral swabs, samples of faeces, breast milk, placenta and cord blood will be stored for evaluation of microbial flora, epigenetic markers and breast milk composition. Furthermore, a cost-effectiveness analysis will take place.

ETHICS AND DISSEMINATION

Ethical approval was obtained from the Medical Ethical Committee of Maastricht University Medical Centre+ (NL52452.068.15/METC152026). Knowledge derived from this study will be made available by publications in international peer-reviewed scientific journals and will be presented at (inter)national scientific conferences. A dissemination plan for regional and national implementation of the intervention is developed.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT02703753.

Gestation-Specific Changes in the Anatomy and Physiology of Healthy Pregnant Women: An Extended Repository of Model Parameters for Physiologically Based Pharmacokinetic Modeling in Pregnancy

BACKGROUND

In the past years, several repositories for anatomical and physiological parameters required for physiologically based pharmacokinetic modeling in pregnant women have been published. While providing a good basis, some important aspects can be further detailed. For example, they did not account for the variability associated with parameters or were lacking key parameters necessary for developing more detailed mechanistic pregnancy physiologically based pharmacokinetic models, such as the composition of pregnancy-specific tissues.

OBJECTIVES

The aim of this meta-analysis was to provide an updated and extended database of anatomical and physiological parameters in healthy pregnant women that also accounts for changes in the variability of a parameter throughout gestation and for the composition of pregnancy-specific tissues.

METHODS

A systematic literature search was carried out to collect study data on pregnancy-related changes of anatomical and physiological parameters. For each parameter, a set of mathematical functions was fitted to the data and to the standard deviation observed among the data. The best performing functions were selected based on numerical and visual diagnostics as well as based on physiological plausibility.

RESULTS

The literature search yielded 473 studies, 302 of which met the criteria to be further analyzed and compiled in a database. In total, the database encompassed 7729 data. Although the availability of quantitative data for some parameters remained limited, mathematical functions could be generated for many important parameters. Gaps were filled based on qualitative knowledge and based on physiologically plausible assumptions.

CONCLUSION

The presented results facilitate the integration of pregnancy-dependent changes in anatomy and physiology into mechanistic population physiologically based pharmacokinetic models. Such models can ultimately provide a valuable tool to investigate the pharmacokinetics during pregnancy in silico and support informed decision making regarding optimal dosing regimens in this vulnerable special population.

Advances in assessing body composition during pregnancy

The prevalence of excess gestational weight gain is increasing worldwide and is associated with pregnancy complications, including gestational diabetes mellitus, pre-eclampsia, preterm birth, macrosomia, and development of obesity in offspring. Whereas gestational weight gain positively correlates with the gain in fat mass (FM), fat-free mass (FFM) gain is relatively consistent across pregnancies. Commonly used methods to assess body composition include anthropometry, densitometry (air displacement plethysmography, underwater weighing), and hydrometry (isotope dilution, bioimpedance analysis). While these techniques can be applied to pregnancy, they require specific adjustments to assumptions inherent within each method, most importantly to accommodate for the hydration of FFM which is transient throughout gestation. Here we discuss the application of the abovementioned methods to pregnant women and the relevant adjustments needed to more accurately calculate FM based on body weight, body volume, or total body water. We also present a novel application of classical data to provide FFM density estimates for pregnant women at any stage of pregnancy. Use of these adjustments will help standardize assumptions on FFM hydration and minimize error in FM estimation. Techniques still fail, however, to fully distinguish tissue gains between mother and fetus. To fill this important gap, imaging techniques such as ultrasound and magnetic resonance imaging are being used more frequently and will provide more insight into fetal development, fetal adiposity, and depot specificity of maternal FM acquisition. Efforts to synchronize protocols are necessary to allow seamless comparison of data to advance the understanding of maternal body composition changes that contribute to pregnancy-related complications.

Variations in resting energy expenditure: impact on gestational weight gain

BACKGROUND

There are significant variations in gestational weight gain, with many women gaining in excess of the Institute of Medicine guidelines. Unfortunately, efforts to improve appropriate gestational weight gain have had only limited success. To date, interventions have focused primarily on decreasing energy intake and/or increasing physical activity. Maternal resting energy expenditure, which comprises ∼60% of total energy expenditure compared with the ∼20% that comes from physical activity, may be an important consideration in understanding variations in gestational weight gain.

OBJECTIVE

Our objective was to quantify the changes in resting energy expenditure during pregnancy and their relationship to gestational weight gain and body composition changes among healthy women. We hypothesized that greater gestational weight gain, and fat mass accrual in particular, are inversely related to variations in resting energy expenditure.

STUDY DESIGN

We conducted a secondary analysis of a prospective cohort studied before conception and late pregnancy (34-36 weeks). Body composition (estimated using hydrodensitometry) and resting energy expenditure (estimated using indirect calorimetry) were measured. The relationship between the changes in resting energy expenditure and gestational weight gain and the change in fat mass and fat-free mass were quantified. Resting energy expenditure was expressed as kilocalories per kilogram of fat-free mass per day (kilocalories per kilogram of fat-free mass^-1/day^-1) and kilocalories per day. Correlations are reported as r.

RESULTS

Among 51 women, preconception body mass index was 23.0 (4.7) kg/m²; gestational weight gain was 12.8 (4.7) kg. Preconception and late pregnancy resting energy expenditure (kilocalories per day) correlated positively with the change in fat-free mass (r = 0.37, P = .008; r = 0.51, P = .001). Late-pregnancy resting energy expenditure (kilocalories per kilogram of fat-free mass^-1/day^-1) was inversely associated with the change in fat mass (r = -0.34, P = .02) and gestational weight gain (r = -0.29, P = .04). From before pregnancy through late gestation, the increase in resting energy expenditure (kilocalories per day) correlated positively with the change in fat-free mass (r = 0.44, P = .002) and negatively with the change in fat mass (r = -0.27, P = .06).

CONCLUSION

The change in resting energy expenditure from before conception through late gestation correlated positively with changes in fat-free mass but negatively with fat mass accrual. Women with smaller increases in resting energy expenditure across pregnancy had greater gestational weight gain, specifically more adipose tissue. These data suggest that resting energy expenditure is an important factor in gestational weight gain, particularly excess fat mass accrual. Future lifestyle intervention studies need to consider clinically feasible means of estimating resting energy expenditure and, in response, tailor nutrient intake and composition recommendations. Implementing and testing such interventions would be a novel approach to improve compliance with gestational weight gain guidelines.

Maternal fat, but not lean, mass is increased among overweight/obese women with excess gestational weight gain

BACKGROUND

Weight gain in pregnancy is an essential physiologic adaptation that supports growth and development of a fetus and is distributed among lean mass that includes total body water and fat mass gains. Although gestational weight gain provides a source of energy for the mother and fetus, excess gestational weight gain may underlie reported associations between parity and future metabolic disorders and is linked to postpartum weight retention and insulin resistance. Although weight gain often is proposed as a modifiable variable to mitigate adverse maternal and offspring health outcomes, our knowledge of specific maternal body composition changes with weight gain and the potential metabolic consequences is limited. Furthermore, although gestational weight gain alters maternal body composition, the impact of excess weight gain on fat and lean mass is not well-studied. Understanding the accrual of fat and lean body mass may improve our understanding of the role of excessive gestational weight gain and metabolic dysfunction.

OBJECTIVE

The purpose of our study was to quantify the relationship between gestational weight gain and maternal fat and lean body mass accrual and to compare fat and lean body mass accrual according to the 2009 Institute of Medicine Guidelines for Gestational Weight Gain in Pregnancy adherence. We hypothesized that exceeding current weight gain guidelines would be associated with greater fat, compared with lean body, mass accrual.

STUDY DESIGN

This is a secondary analysis of a randomized controlled trial of 49 overweight/obese women; all 49 are included in this secondary analysis. Maternal weight and body composition were collected in early (13 0/6 to 16 6/7 weeks gestation) and late (34 0/7 to 36 6/7 weeks gestation) pregnancy with the use of air densitometry. Correlations were drawn between gestational weight gain and change in fat and lean body mass. We compared change in fat and lean body mass by adherence to the 2009 Institute of Medicine Guidelines for Gestational Weight Gain in Pregnancy. Nonparametric tests and chi-square analyses were performed; a probability value of <.05 was significant.

RESULTS

Early pregnancy body mass index was 30.3 kg/m(2) (interquartile range [IQR], 28.5-35.2 kg/m(2)); women gained 9.0 kg (IQR, 5.3-13.2 kg). Overweight and obese women were equally likely to gain excess weight (48% vs 35%; P = .6). Weight gain correlated strongly with fat mass change (r = 0.87; P < .001); women with excess vs adequate vs inadequate weight gain had greater fat mass change overall (5.2 [IQR, 4.2-8.1] vs 0.2 [IQR, -0.4-2.2] vs -2.7 [IQR, -5.2- -0.7] kg, respectively; P < .001) and in all pairwise comparisons. Weight gain also correlated with lean body mass change (r = 0.52; P = .001), but women with excess vs adequate weight gain had similar lean body mass change (8.4 [IQR, 7.2-10.1] vs 7.8 [IQR, 6.0-8.7] kg; P = .1).

CONCLUSION

Excess gestational weight gain is associated primarily with maternal fat, but not with lean body mass accrual. Our results may help explain the reason that excess gestational weight gain or fat mass accrual is associated with long-term obesity, metabolic dysfunction, and cardiovascular disease risk.

Comparison of multiple methods to measure maternal fat mass in late gestation

BACKGROUND

Measurements of maternal fat mass (FM) are important for studies of maternal and fetal health. Common methods of estimating FM have not been previously compared in pregnancy with measurements using more complete body composition models.

OBJECTIVES

The goal of this pilot study was to compare multiple methods that estimate FM, including 2-, 3- and 4-compartment models in pregnant women at term, and to determine how these measures compare with FM by dual-energy X-ray absorptiometry (DXA) 2 wk postpartum.

DESIGN

Forty-one healthy pregnant women with prepregnancy body mass index (in kg/m(2)) 19 to 46 underwent skinfold thickness (SFT), bioelectrical impedance analysis (BIA), body density (Db) via air displacement plethysmography (ADP), and deuterium dilution of total body water (TBW) with and without adjustments for gestational age using van Raaij (VRJ) equations at 37-38 wk of gestation and 2 wk postpartum to derive 8 estimates of maternal FM. Deming regression analysis and Bland-Altman plots were used to compare methods of FM assessment.

RESULTS

Systematic differences in FM estimates were found. Methods for FM estimates from lowest to highest were 4-compartment, DXA, TBW(VRJ), 3-compartment, Db(VRJ), BIA, air displacement plethysmography body density, and SFT ranging from a mean ± SD of 29.5 ± 13.2 kg via 4-compartment to 39.1 ± 11.7 kg via SFT. Compared with postpartum DXA values, Deming regressions revealed no substantial departures from trend lines in maternal FM in late pregnancy for any of the methods. The 4-compartment method showed substantial negative (underestimating) constant bias, and the air displacement plethysmography body density and SFT methods showed positive (overestimating) constant bias. ADP via Db(VRJ)and 3-compartment methods had the highest precision; BIA had the lowest.

CONCLUSIONS

ADP that uses gestational age-specific equations may provide a reasonable and practical measurement of maternal FM across a spectrum of body weights in late pregnancy. SFT would be acceptable for use in larger studies. This trial was registered at clinicaltrials.gov as NCT02586714.

Are the metabolic changes of pregnancy reversible in the first year postpartum?

AIMS/HYPOTHESIS

Maternal metabolic alterations are essential to achieve healthy pregnancy outcomes, but increasing maternal parity may be associated with long-term metabolic dysfunction risk. As existing data are limited by study design, our aim was to employ robust metabolic measures to determine whether or not physiological pregnancy alterations in maternal metabolic function persist at 1 year postpartum.

METHODS

We evaluated 21 healthy women, of whom 11 had an interval pregnancy (IP) and assessment at preconception, during pregnancy and 1 year postpartum, and 10 had no IP and assessment at baseline and a 1 year interval. Assessment measures included body composition, insulin sensitivity and response, and basal metabolic rate. For each measure, IP vs no IP and time intervals within each group were compared using nonparametric analyses, reporting median (IQR).

RESULTS

IP and no IP women were similar at enrolment, and no IP women had similar metabolic profiles at enrolment and the 1 year interval. IP women exhibited expected metabolic changes during pregnancy compared with preconception. In IP women, preconception and postpartum measures, including fat mass (20.7 [13.7-37.4] kg vs 18.4 [13.8-41.3] kg; p = 0.2), total insulin response (AUC 11,459 [9,230-13,696] pmol/ml × min vs 11,522 [5,882-17,404] pmol/ml × min; p = 0.9), insulin sensitivity (0.12 [0.06-0.13] mg [kg fat-free mass (FFM)](-1) min(-1) vs 0.11 [0.10-0.15] mg [kg FFM](-1) min(-1); p = 0.1) and basal metabolic rate (0.092 [0.092-0.105] kJ min(-1) FFM vs 0.096 [0.088-0.096] kJ min(-1) FFM; p = 0.5), were similar.

CONCLUSIONS/INTERPRETATION

Our findings suggest pregnancy might not irreversibly alter maternal metabolic profile, measured at preconception through to 1 year postpartum. This result might be explained by a return to pre-pregnancy weight.

A randomized longitudinal dietary intervention study during pregnancy: effects on fish intake, phospholipids, and body composition

Background

Fish and meat intake may affect gestational weight gain, body composition and serum fatty acids. We aimed to determine whether a longitudinal dietary intervention during pregnancy could increase fish intake, affect serum phospholipid fatty acids, gestational weight gain and body composition changes during pregnancy in women of normal weight participating in the Pregnancy Obesity Nutrition and Child Health study. A second aim was to study possible effects in early pregnancy of fish intake and meat intake, respectively, on serum phospholipid fatty acids, gestational weight gain, and body composition changes during pregnancy.

Methods

In this prospective, randomized controlled study, women were allocated to a control group or to a dietary counseling group that focused on increasing fish intake. Fat mass and fat-free mass were measured by air-displacement plethysmography. Reported intake of fish and meat was collected from a baseline population and from a subgroup of women who participated in each trimester of their pregnancies. Serum levels of phospholipid arachidonic acid (s-ARA), eicosapentaenoic acid (s-EPA), and docosahexaenoic acid (s-DHA) were measured during each trimester.

Results

Weekly fish intake increased only in the intervention group (n = 18) from the first to the second trimester (median difference 113 g, p = 0.03) and from the first to the third trimester (median difference 75 g, p = 0.01). In the first trimester, fish intake correlated with s-EPA (r = 0.36, p = 0.002, n = 69) and s-DHA (r = 0.34, p = 0.005, n = 69), and meat intake correlated with s-ARA (r = 0.28, p = 0.02, n = 69). Fat-free mass gain correlated with reported meat intake in the first trimester (r = 0.39, p = 0.01, n = 45).

Conclusions

Dietary counseling throughout pregnancy could help women increase their fish intake. Intake of meat in early pregnancy may increase the gain in fat-free mass during pregnancy.

Body composition changes in pregnancy: measurement, predictors and outcomes

Prevalence of overweight and obesity has risen in the United States over the past few decades. Concurrent with this rise in obesity has been an increase in pregravid body mass index and gestational weight gain affecting maternal body composition changes in pregnancy. During pregnancy, many of the assumptions inherent in body composition estimation are violated, particularly the hydration of fat-free mass, and available methods are unable to disentangle maternal composition from fetus and supporting tissues; therefore, estimates of maternal body composition during pregnancy are prone to error. Here we review commonly used and available methods for assessing body composition changes in pregnancy, including: (1) anthropometry, (2) total body water, (3) densitometry, (4) imaging, (5) dual-energy X-ray absorptiometry, (6) bioelectrical impedance and (7) ultrasound. Several of these methods can measure regional changes in adipose tissue; however, most of these methods provide only whole-body estimates of fat and fat-free mass. Consideration is given to factors that may influence changes in maternal body composition, as well as long-term maternal and offspring outcomes. Finally, we provide recommendations for future research in this area.

Molecular inflammation and adipose tissue matrix remodeling precede physiological adaptations to pregnancy

Changes in adipose tissue metabolism are central to adaptation of whole body energy homeostasis to pregnancy. To gain insight into the molecular mechanisms supporting tissue remodeling, we have characterized the longitudinal changes of the adipose transcriptome in human pregnancy. Healthy nonobese women recruited pregravid were followed in early (8-12 wk) and in late (36-38 wk) pregnancy. Adipose tissue biopsies were obtained in the fasting state from the gluteal depot. The adipose transcriptome was examined via whole genome DNA microarray. Expression of immune-related genes and extracellular matrix components was measured using real-time RT-PCR. Adipose mass, adipocyte size, and cell number increased in late pregnancy compared with pregravid measurements (P < 0.001) but remained unchanged in early pregnancy. The adipose transcriptome evolved during pregnancy with 10-15% of genes being differently expressed compared with pregravid. Functional gene cluster analysis revealed that the early molecular changes affected immune responses, angiogenesis, matrix remodeling, and lipid biosynthesis. Increased expression of macrophage markers (CD68, CD14, and the mannose-6 phosphate receptor) emphasized the recruitment of the immune network in both early and late pregnancy. The TLR4/NF-κB signaling pathway was enhanced specifically in relation to inflammatory adipokines and chemokines genes. We conclude that early recruitment of metabolic and immune molecular networks precedes the appearance of pregnancy-related physiological changes in adipose tissue. This biphasic pattern suggests that physiological inflammation is an early step preceding the development of insulin resistance, which peaks in late pregnancy.

Obesity, insulin resistance, and pregnancy outcome

There has been a significant increase over the past few decades in the number of reproductive age women who are either overweight or obese. Overweight and obese women are at increased risk for having decreased insulin sensitivity as compared with lean or average weight women. The combination of obesity and decreased insulin sensitivity increases the long-term risk of these individuals developing the metabolic syndrome and associated problems of diabetes, hypertension, hyperlipidemia, and cardiovascular disorders. Because of the metabolic alterations during normal pregnancy, particularly the 60% decrease in insulin sensitivity, overweight and obese women are at increased risk of metabolic dysregulation in pregnancy, i.e. gestational diabetes, preeclampsia, and fetal overgrowth. Hence, pregnancy can be considered as a metabolic stress test for the future risk of the metabolic syndrome. In this review, we will review the underlying pathophysiology related to these disorders. Most importantly, an understanding of these risks provides an opportunity for prevention. For example, a planned pregnancy offers an opportunity to address weight control prior to conception. At the very least, by avoiding excessive weight gain during pregnancy, this may prevent excessive weight retention post partum. Finally, based on the concept of in utero programming, these lifestyle measures may not only have short- and long-term benefits for the woman but also for her offspring as well.

Increased skeletal muscle tumor necrosis factor-alpha and impaired insulin signaling persist in obese women with gestational diabetes mellitus 1 year postpartum

OBJECTIVE

Women with gestational diabetes mellitus (GDM) demonstrate chronic and progressive insulin resistance and a markedly increased risk of converting to type 2 diabetes after pregnancy. However, the cellular mechanisms underlying this insulin resistance are unknown.

RESEARCH DESIGN AND METHODS

We investigated the progression of insulin resistance in nine obese women with GDM during late pregnancy (30-36 weeks) and 1 year postpartum. Skeletal muscle biopsies were obtained at each visit, and insulin resistance was determined by the hyperinsulinemic-euglycemic clamp technique.

RESULTS

Insulin resistance was not significantly improved in GDM women (4.1 +/- 0.4 vs. 5.8 +/- 1.1 10(-2) mg x kg FFM x min(-1)/microU x ml(-1)). Subjects did not experience significant weight loss postpartum. Body weight, fat mass, fasting glucose, and plasma tumor necrosis factor (TNF)-alpha remained higher 1 year postpartum than seen in previously studied normal glucose-tolerant women. Skeletal muscle TNF-alpha mRNA was elevated five- to sixfold in GDM women and remained higher 1 year postpartum. While levels of insulin receptor (IR), IR substrate (IRS)-1, and p85 alpha improved postpartum, insulin-stimulated IR tyrosine phosphorylation and receptor tyrosine kinase activity did not significantly improve postpartum in GDM. The levels of (312)Ser-IRS-1 also did not improve postpartum and correlated with TNF-alpha mRNA (r(2) = 0.19, P < 0.03), consistent with a state of subclinical inflammation and chronic skeletal muscle insulin resistance.

CONCLUSIONS

These results suggest the mechanisms underlying chronic insulin resistance in GDM women may be driven by increased inflammation that impinges on the IR and IRS-1 signaling cascade in skeletal muscle. These findings have important implications for the health of GDM women during subsequent pregnancies and their risk for progression to type 2 diabetes.

Adiponectin in human pregnancy: implications for regulation of glucose and lipid metabolism

AIMS/HYPOTHESIS

Adiponectin is upregulated during adipogenesis and downregulated in insulin-resistant states. The mechanism(s) governing the re-arrangements from adipogenesis to facilitated lipolysis during pregnancy are unknown. Our purpose was to analyse the role of adiponectin relative to the metabolic changes in human pregnancy.

SUBJECTS, MATERIALS AND METHODS

Lean women (BMI <25 kg/m(2)) were evaluated longitudinally before conception, and in early (12-14 weeks) and late (34-36 weeks) pregnancy. Insulin sensitivity was measured using the glucose clamp technique. Venous blood and subcutaneous adipose tissue biopsies were obtained at each time point.

RESULTS

Adiponectin concentrations were lower in the third trimester than in the pregravid condition (9.9+/-1.4 vs 13.5+/-1.8 microg/ml). The hypoadiponectinaemia was reflected by a 2.5-fold decrease in white adipose tissue adiponectin mRNA. These changes were associated with a 25% increase in fat mass (23.7+/-2.9 vs 18.9+/-2.9 kg). Insulin infusion decreased high molecular weight adiponectin complexes in pregravid women (9.9+/-0.6 vs 6.2+/-0.06) and the suppressive effect of insulin was lost during pregnancy. The pregnancy-mediated changes in adiponectin were strongly correlated with basal insulin levels and insulin sensitivity (p<0.0001). The relationship between adiponectin and insulin sensitivity was related to the decreased insulin regulation of glucose utilisation (r=0.55, p<0.001) but not of endogenous hepatic glucose production.

CONCLUSIONS/INTERPRETATION

These data demonstrate that pregnancy is associated with adiponectin changes in lean women. Hypoadiponectinaemia is reflected by a lower amount of high molecular weight adiponectin and by the ratio of high to low molecular weight multimers. The adiponectin changes relate to decreased insulin sensitivity of glucose disposal rather than alterations of lipid metabolism.

Longitudinal changes in energy expenditure and body composition in obese women with normal and impaired glucose tolerance

Our primary objective was to evaluate changes in energy expenditure and body composition in women with normal glucose tolerance (NGT) and gestational diabetes mellitus (GDM). A secondary objective was to examine the relationship between maternal leptin and nutrient metabolism. Fifteen obese women, eight with NGT and seven with GDM, were evaluated before conception (P), at 12-14 wk (E), and at 34-36 wk (L). Energy expenditure and glucose and fat metabolism were measured using indirect calorimetry. Basal hepatic glucose production was measured using [6,6-2H2]glucose and insulin sensitivity by euglycemic clamp. There was a significant increase (6.6 kg, P = 0.0001) in fat mass from P to L. There was a 30% (P = 0.0001) increase in basal O2 consumption (VO2, ml/min). There were no significant changes in carbohydrate oxidation during fasting or storage from P to L. There was, however, a significant (P = 0.0001) 150% increase in basal fat oxidation (mg/min) from P to L. Under hyperinsulinemic conditions, there were similar 25% increases in VO2 (P = 0.0001) from P to L in both groups. Because of the significant increases in insulin resistance from P to L, there was a significant (P = 0.0001) decrease in carbohydrate oxidation and storage. There was a net change from lipogenesis to lipolysis, i.e., fat oxidation (30-40 mg/min, P = 0.0001) from P to L. Serum leptin concentrations had a significant positive correlation with fat oxidation at E (r = 0.76, P = 0.005) and L (r = 0.72, P = 0.009). Pregnancy in obese women is associated with significant increases in fat mass and basal metabolic rate and an increased reliance on lipids both in the basal state and during the clamp. These modifications are similar in women with NGT and GDM. The increased reliance on fat metabolism is accompanied by a concomitant decrease in carbohydrate metabolism during hyperinsulinemia. The increase in fat oxidation may be related to increased maternal serum leptin.

TNF-alpha is a predictor of insulin resistance in human pregnancy

Historically, insulin resistance during pregnancy has been ascribed to increased production of placental hormones and cortisol. The purpose of this study was to test this hypothesis by correlating the longitudinal changes in insulin sensitivity during pregnancy with changes in placental hormones, cortisol, leptin, and tumor necrosis factor (TNF)-alpha. Insulin resistance was assessed in 15 women (5 with gestational diabetes mellitus [GDM] and 10 with normal glucose tolerance) using the euglycemic-hyperinsulinemic clamp procedure, before pregnancy (pregravid) and during early (12-14 weeks) and late (34-36 weeks) gestation. Body composition, plasma TNF-alpha, leptin, cortisol, and reproductive hormones (human chorionic gonadotropin, estradiol, progesterone, human placental lactogen, and prolactin) were measured in conjunction with the clamps. Placental TNF-alpha was measured in vitro using dually perfused human placental cotyledon from five additional subjects. Compared with pregravid, insulin resistance was evident during late pregnancy in all women (12.4 +/- 1.2 vs. 8.1 +/- 0.8 10(-2) mg. kg(-1) fat-free mass. min(-1). microU(-1). ml(-1)). TNF-alpha, leptin, cortisol, all reproductive hormones, and fat mass were increased in late pregnancy (P < 0.001). In vitro, most of the placental TNF-alpha (94%) was released into the maternal circulation; 6% was released to the fetal side. During late pregnancy, TNF-alpha was inversely correlated with insulin sensitivity (r = -0.69, P < 0.006). Furthermore, among all of the hormonal changes measured in this study, the change in TNF-alpha from pregravid to late pregnancy was the only significant predictor of the change in insulin sensitivity (r = -0.60, P < 0.02). The placental reproductive hormones and cortisol did not correlate with insulin sensitivity in late pregnancy. Multivariate stepwise regression analysis revealed that TNF-alpha was the most significant independent predictor of insulin sensitivity (r = -0.67, P < 0.0001), even after adjustment for fat mass by covariance (r = 0.46, P < 0.01). These observations challenge the view that the classical reproductive hormones are the primary mediators of change in insulin sensitivity during gestation and provide the basis for including TNF-alpha in a new paradigm to explain insulin resistance in pregnancy.

Downregulated IRS-1 and PPARgamma in obese women with gestational diabetes: relationship to FFA during pregnancy

Gestational diabetes mellitus (GDM) is associated with elevated postprandial free fatty acids (FFA) and insulin resistance; however, little is known about the cellular mechanisms underlying insulin resistance to suppress lipolysis during gestation. We evaluated the longitudinal changes in insulin suppression of FFA before pregnancy and in early (12-14 wk) and late (34-36 wk) gestation in obese subjects with normal glucose tolerance and in obese GDM subjects. Abdominal subcutaneous adipose tissue biopsies were also obtained during cesarean delivery from normal obese pregnant (Preg-Con), GDM, and nonpregnant obese control (Non-Preg-Con) subjects during gynecological surgery. GDM subjects had higher basal plasma FFA before pregnancy (P = 0.055). Insulin's ability to suppress FFA levels declined from early to late gestation in both GDM and Preg-Con subjects and was significantly less in GDM subjects compared with Preg-Con subjects over time (P = 0.025). Adipose tissue insulin receptor substrate (IRS)-1 protein levels were 43% lower (P = 0.02) and p85alpha subunit of phosphatidylinositol 3-kinase was twofold higher (P = 0.03) in GDM compared with Preg-Con subjects. The levels of peroxisome proliferator-activated receptor-gamma (PPARgamma) mRNA and protein were lower by 38% in Preg-Con (P = 0.006) and by 48% in GDM subjects (P = 0.005) compared with Non-Preg controls. Lipoprotein lipase and fatty acid-binding protein-2 mRNA levels were 73 and 52% lower in GDM compared with Preg-Con subjects (P < 0.002). Thus GDM women have decreased IRS-1, which may contribute to reduced insulin suppression of lipolysis with advancing gestation. Decreased PPARgamma and its target genes may be part of the molecular mechanism to accelerate fat catabolism to meet fetal nutrient demand in late gestation.

Clinically useful estimates of insulin sensitivity during pregnancy: validation studies in women with normal glucose tolerance and gestational diabetes mellitus

OBJECTIVE

We examined whether selected indexes of insulin sensitivity derived from an oral glucose tolerance test (IS(OGTT)) or fasting glucose/insulin levels (IS(QUICKI) and IS(HOMA)) can be used to predict insulin sensitivity in women before and during pregnancy.

RESEARCH DESIGN AND METHODS

A 2-h euglycemic-hyperinsulinemic clamp (5 mmol/l glucose, 40 mU. m(-2). min(-1) insulin) and a 120-min oral glucose tolerance test (75 g load pregravid, 100 g pregnant) were repeated on 15 women (10 with normal glucose tolerance [NGT] and 5 with gestational diabetes mellitus [GDM]) pregravid and during both early (12-14 weeks) and late (34-36 weeks) pregnancy. An index of insulin sensitivity derived from the clamp (IS(CLAMP)) was obtained from glucose infusion rates adjusted for change in fat-free mass and endogenous glucose production measured using [6,6(-2)H(2)]glucose.

RESULTS

Univariate analysis using combined groups and periods of pregnancy resulted in significant correlations between IS(CLAMP) and IS(OGTT) (r(2) = 0.74, P < 0.0001), IS(QUICKI) (r(2) = 0.64, P < 0.0001), and IS(HOMA) (r(2) = 0.53, P < 0.0001). The IS(OGTT) provided a significantly better correlation (P < 0.0001) than either IS(QUICKI) or IS(HOMA.) Multivariate analysis showed a significant group effect (P < 0.0003) on the prediction model, and separate equations were developed for the NGT (r(2) = 0.64, P < 0.0001) and GDM (r(2) = 0.85, P < 0.0001) groups. When subdivided by period of pregnancy, the correlation between IS(CLAMP) and IS(OGTT) pregravid was r(2) = 0.63 (P = 0.0002), during early pregnancy was r(2) = 0.80 (P < 0.0001), and during late pregnancy was r(2) = 0.64 (P = 0.0002).

CONCLUSIONS

Estimates of insulin sensitivity from the IS(OGTT) during pregnancy were significantly better than from fasting glucose and insulin values. However, separate prediction equations are necessary for pregnant women with NGT and women with GDM.