Changes of maternal serum leptin levels during pregnancy

Serum leptin levels and relationship with maternal weight gain at term among obese and non-obese pregnant women in Enugu, Nigeria: a comparative cross-sectional study

OBJECTIVE

To determine and compare the mean maternal serum leptin levels, the prevalence of high serum leptin levels and mean gestational weight gain at term among obese and non-obese pregnant women in Enugu, Nigeria.

METHODS

This cross-sectional comparative study enrolled obese and non-obese pregnant women. The serum leptin levels of the women were determined using an enzyme-linked immunosorbent assay kit. Anthropometric and sociodemographic data were obtained and compared. Mean weight gain during pregnancy was determined.

RESULTS

A total of 170 pregnant women were included in the study. The mean ± SD serum leptin level (99.39 ± 50.2 ng/ml) and the prevalence of hyperleptinaemia (81 of 85 patients; 95.3%) among the obese pregnant women at term were significantly higher than those of the non-obese pregnant women (48.98 ± 30.35 ng/ml/65 of 85 patients; 76.5%). The mean percentage weight gain was significantly higher in the non-obese women compared with the obese women at term. The predictors of high maternal serum leptin level at term among the participants were the employment status and levels of education of the participants.

CONCLUSION

Maternal serum leptin level, maternal weight gain and prevalence of hyperleptinaemia at term were significantly higher in the obese compared with the non-obese pregnant women.

Pathomechanisms of Prenatally Programmed Adult Diseases

Based on epidemiological observations Barker et al. put forward the hypothesis/concept that an adverse intrauterine environment (involving an insufficient nutrient supply, chronic hypoxia, stress, and toxic substances) is an important risk factor for the development of chronic diseases later in life. The fetus responds to the unfavorable environment with adaptive reactions, which ensure survival in the short run, but at the expense of initiating pathological processes leading to adult diseases. In this review, the major mechanisms (including telomere dysfunction, epigenetic modifications, and cardiovascular-renal-endocrine-metabolic reactions) will be outlined, with a particular emphasis on the role of oxidative stress in the fetal origin of adult diseases.

Adipokines underlie the early origins of obesity and associated metabolic comorbidities in the offspring of women with pregestational obesity

Maternal pregestational obesity is a well-known risk factor for offspring obesity, metabolic syndrome, cardiovascular disease and type 2 diabetes. The mechanisms by which maternal obesity can induce alterations in fetal and later neonatal metabolism are not fully elucidated due to its complexity and multifactorial causes. Two adipokines, leptin and adiponectin, are involved in fetal and postnatal growth trajectories, and both are altered in women with pregestational obesity. The placenta synthesizes leptin, which goes mainly to the maternal circulation and in lesser amount to the developing fetus. Maternal pregestational obesity and hyperleptinemia are associated with placental dysfunction and changes in nutrient transporters which directly affect fetal growth and development. By the other side, the embryo can produce its own leptin from early in development, which is associated to fetal weight and adiposity. Adiponectin, an insulin-sensitizing adipokine, is downregulated in maternal obesity. High molecular weight (HMW) adiponectin is the most abundant form and with most biological actions. In maternal obesity lower total and HMW adiponectin levels have been described in the mother, paralleled with high levels in the umbilical cord. Several studies have found that cord blood adiponectin levels are related with postnatal growth trajectories, and it has been suggested that low adiponectin levels in women with pregestational obesity enhance placental insulin sensitivity and activation of placental amino acid transport systems, supporting fetal overgrowth. The possible mechanisms by which maternal pregestational obesity, focusing in the actions of leptin and adiponectin, affects the fetal development and postnatal growth trajectories in their offspring are discussed.

The concurrent validity between leptin, BMI and skin folds during pregnancy and the year after

Background:

From a public health perspective it is important to know which of the currently used methods to estimate changes in maternal body fat during pregnancy and the year thereafter is the most adequate.

Objectives:

To evaluate the concurrent validity between leptin and surrogates of fat measures: body mass index (BMI) and the sum of four skin folds.

Design:

Data from the New Life(style) intervention study were analysed as a cohort study.

Setting:

Midwife practices in The Netherlands.

Population:

Healthy pregnant nulliparous women.

Methods:

Anthropometric measurements were done and blood was collected at 15, 25 and 35 weeks of pregnancy and at 6, 26 and 52 weeks after delivery. Data were used if at least 4 out of the 6 measurements were available, leaving 87 women in the analyses. Spearman's correlation coefficients between leptin and BMI and between leptin and the sum of skin folds were calculated for each time point and for the changes between the time points.

Results:

Correlations between leptin and BMI varied from 0.69 to 0.81. Correlations between leptin and the sum of skin folds were comparable, varying between 0.65 and 0.81.

Correlations between changes in leptin and changes in BMI and the sum of skin folds, respectively, were much lower compared with cross-sectional correlations.

Conclusion:

Because of the high correlation among the three methods and because of the overlapping intervals, all methods seem to be equally adequate to estimate changes in maternal body fat during pregnancy and the year thereafter.

Third trimester plasma adiponectin and leptin in gestational diabetes and normal pregnancies

The aim of this study was to compare pregnant women with and without gestational diabetes (GDM) with regard to third trimester adiponectin, leptin and insulin resistance, as well as to investigate their relation to fetal growth and macrosomia. 134 pregnant women were enrolled in the study: 86 with GDM and 48 controls. Maternal plasma adiponectin, leptin, fasting insulin, glucose and fetal biometry were measured between 27 and 32 weeks of gestation. Birthweight and delivery data were also assessed. Adiponectin in GDM patients was lower when compared to non-diabetic women while mean leptin concentration was not different. In GDM group only mothers' weight gain until third trimester was significantly different between the groups of patients with normal and accelerated fetal growth. No correlation of adiponectin and leptin with fetal growth was shown. Mothers' weight gain until third trimester and mean fasting glucose between 33 and 34 weeks of gestation were associated with neonatal macrosomia. There were no differences in adiponectin and leptin between mothers of macrosomic and non-macrosomic neonates. Fetal growth seems not to be related to third trimester adiponectin and leptin concentrations, while increased third trimester fasting glucose may be an independent risk factor of macrosomia.

Dietary sucrose intake is related to serum leptin concentration in overweight pregnant women

BACKGROUND

Overweight, characterized by low-degree systemic inflammation, predisposes women to impaired glucose metabolism during pregnancy. Adipokine leptin participates in the regulation of energy balance and immune action.

AIMS OF THE STUDY

Objective of the study was to evaluate if aberrations in glucose metabolism during pregnancy are related to leptin concentration and whether serum leptin concentration is affected by diet composition.

SUBJECTS AND METHODS

Normal-weight (n = 61) and overweight or obese (BMI > 25, n = 42) pregnant women visited study clinic at third trimester of pregnancy and one month postpartum. Serum fasting leptin and insulin as well as plasma glucose concentrations were measured, insulin resistance (HOMA) and sensitivity (QUICKI) calculated, and dietary intake from food records determined.

RESULTS

In overweight women leptin concentration was significantly higher both in pregnancy, 45.27 (95% CI 39.40-51.14) ng/ml, and postpartum, 31.84 (27.38-36.30) ng/ml, than in normal-weight women, 31.09 (95% CI 27.80-34.37) ng/ml and 16.23 (13.93-18.53) ng/ml, respectively. Equally, blood glucose concentration during pregnancy was higher, 4.82 (4.67-4.97)mmol/l, and insulin concentration, 15.34 (12.00-18.68) mU/l, more pronounced in overweight compared to normal-weight women, 4.51 (4.42-4.61) mmol/l and 8.28 (7.21-9.36) mU/l, respectively. Significantly higher HOMA and lower QUICKI were also detected in overweight compared to normal-weight women. At third trimester of pregnancy, leptin concentration correlated positively with insulin concentration in normal-weight (r = 0.561, P = 0.002) and overweight women (r = 0.736, P < 0.001), as well as with HOMA (r = 0.568, P = 0.002 and r = 0.731, P < 0.001, respectively) whereas negative association was found with QUICKI in normal-weight (r = -0.484, P = 0.011) and overweight women (r = -0.711, P < 0.001). Importantly, serum leptin concentration was affected by dietary sucrose intake both as quantitatively (r = 0.424, P = 0.009) and relative to energy intake (r = 0.408, P = 0.012) in overweight but not in normal-weight pregnant women.

CONCLUSIONS

Overweight-related elevation in serum leptin is associated with impaired regulation of glucose metabolism during pregnancy. The novel finding that dietary sucrose intake is related to serum leptin concentration is in line with the current dietary recommendations to overweight pregnant women with impaired glucose metabolism advising the lower intake of sucrose during pregnancy.

Interrelationships of maternal serum leptin, body mass index and gestational age

BACKGROUND

The aim of this study was to evaluate the interrelationships between maternal serum leptin level and body mass index (BMI) at different gestational ages or during the whole pregnancy.

METHODS

A total of 374 blood samples were obtained from 114 pregnant women when they visited the prenatal clinic for registration, Down syndrome screening test, 50 g oral glucose challenge test, hepatitis B markers test, and near or at the time of delivery. Serum leptin levels were measured by immunoradiometric assay. Linear regression analysis, 1-way ANOVA and post hoc tests were used to analyze the data.

RESULTS

Throughout the course of pregnancy, maternal serum leptin concentration was significantly correlated with gestational age (p = 0.001, r = 0.179). A good correlation was also found between gestational age and maternal serum leptin level in the second trimester (p = 0.021, r = 0.158). A significant decline in maternal serum leptin was found in the third trimester (p = 0.011, r = 0.237). There were good correlations between maternal leptin and BMI in all 3 trimesters (p = 0.002 in the first trimester, p < 0.001 in the second trimester, p = 0.007 in the third trimester) and through the whole pregnancy (p < 0.001). Maternal BMI was related to gestational age in the second trimester (p < 0.001) and the whole pregnancy (p < 0.001), but not in the first (p = 0.404) and third trimesters (p = 0.053).

CONCLUSION

Maternal serum leptin concentration was significantly related to gestational age (except in the first trimester) and BMI in the 3 trimesters and throughout pregnancy. Serum leptin concentration peaked during the early third trimester and declined significantly thereafter. Maternal BMI was related to gestational age in the second trimester and the whole pregnancy.

The influence of leptin on placental and fetal volume measured by three-dimensional ultrasound in the second trimester

For a couple of years mechanisms influencing placental and fetal growth and the functioning of leptin, the protein product of the ob/ob gene, have been subjects of intensive research. This study's aim was to investigate whether maternal serum leptin and amniotic fluid leptin have an influence on placental and fetal size measured by three-dimensional ultrasound in the second trimester. To determine this, 40 women with a singleton intrauterine pregnancy at the time of the amniocentesis were included in the study. Placental and fetal volume measurements were obtained and correlated to maternal serum leptin, amniotic fluid leptin, body mass index and gestational age. Multiple regression analysis identified amniotic fluid leptin as an independent negative predictor of placental and fetal volume (r = -2.29, p = 0.032 and r = -0.95, p = 0.011, respectively). In contrast, there was no correlation between maternal serum leptin and placental or fetal volume. The median leptin level in amniotic fluid (9.5 ng/ml) was significantly lower than in maternal blood (18.6 ng/ml). However, there was no significant correlation between maternal serum leptin and amniotic fluid leptin (r = 0.208, n.s.). Body mass index did not reveal any significant influences on placental or fetal volume. The relatively high level of amniotic fluid leptin and its inverse correlation on placental and fetal volume in the second trimester suggest that it possibly plays a role as an anti-placental growth hormone or feedback modulator of substrate supply to the fetus and placenta.

Maternal serum, amniotic fluid and cord leptin levels at term: their correlations with fetal weight

AIMS

To investigate the relationship between fetal weight and leptin levels in maternal serum, amniotic fluid and umbilical cord.

METHODS

Forty pregnant women presenting for antenatal care at early weeks of gestation were enrolled for the study. Maternal and cord blood samples for leptin measurement were obtained at birth. Amniotic fluid samples were recovered by amniotomy performed during labor. Maternal body mass index and placental weight were also recorded. Leptin measurement was carried out using the ELISA method. Spearman's correlation test was used for comparison of non-parametric data.

RESULTS

Leptin concentration in venous cord blood correlated significantly with birth weight and placental weight whereas maternal serum and amniotic fluid leptin levels did not show correlation with birth weight. There were no significant correlations between leptin levels in maternal serum, cord blood and amniotic fluid.

CONCLUSION

We conclude that lack of correlation between leptin levels in mother, cord and amniotic fluid suggest that these compartments may be non-communicating separate units or have different mechanisms regulating leptin synthesis or degradation, and that leptin in maternal blood and amniotic fluid may not have a direct effect on fetal growth but rather a different role in pregnancy.

Cerebrospinal fluid leptin levels in preeclampsia: relation to maternal serum leptin levels

BACKGROUND

To determine whether cerebrospinal fluid (CSF) and circulating levels of leptin differ between women with preeclampsia and women who had an uncomplicated pregnancy.

METHODS

Maternal serum and CSF leptin concentrations obtained in the third trimester of the gestation were compared in 16 women with mild preeclampsia and 23 normotensive pregnant women who underwent cesarean section. Before administering local anesthetic for spinal anesthesia, 2 mL CSF and 4 mL venous blood sample were taken and were stored at -30 degrees C until serum and CSF leptin levels were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Mean CSF leptin concentrations were not significantly different between the two groups (preeclampsia 9.7 +/- 4.2 ng/mL, normotensive 13.6 +/- 4.3 ng/mL, p = 0.952). Similarly, mean serum leptin concentrations were similar between the two groups (mild preeclampsia 21.7 +/- 7.1 ng/mL, normotensive 18.3 +/- 6.7 ng/mL, p = 0.698). CSF leptin levels are inversely related to the serum leptin concentrations in preeclamptic patients (r = -0.87, p = 0.000). An inverse relationship was also detected between CSF and serum leptin levels in normotensive pregnant subjects (r = -0.66, p = 0.000).

CONCLUSIONS

CSF and serum leptin levels were similar in patients with preeclampsia and normotensive pregnant women. However, the CSF leptin was negatively correlated with the serum leptin concentrations in preeclamptic and normotensive control subjects, suggesting that leptin enters the brain by a saturable transport system. Further work is needed to confirm our findings.

Leptin in pregnancy

Leptin is a 16-kDa polypeptide, encoded in humans by the LEP gene. This protein is probably involved in the regulation of ovarian function, oocyte maturation and embryo development, and in the implantation process. During pregnancy, leptin is produced in the placenta; its values increase in the maternal blood particularly in the second trimester and decline postpartum. Leptin levels may be abnormally high in pregnancies complicated by conditions such as diabetes mellitus and pre-eclampsia. The role of leptin in fetal physiology has not been clarified, although cord blood values correlate significantly with birth weight. It is expected that further research will provide new insight into the physiological importance of leptin in the pregnant woman and fetus.

Maternal serum leptin concentration during the second trimester of pregnancy: association with fetal chromosomal abnormalities

Recent studies suggest that leptin, the product of the obese gene, is produced by the placenta during pregnancy. The present study addressed the question whether second trimester maternal serum leptin could be altered by fetal Down syndrome or Edwards syndrome. Maternal serum leptin concentrations were measured in 18 pregnancies complicated with Down syndrome, six pregnancies complicated with Edwards syndrome and 183 uncomplicated pregnancies during the second trimester of pregnancy. The present results demonstrate that leptin concentrations in uncomplicated pregnancies slightly decrease from the 16th week of pregnancy, reaching a minimum of 18.8 ng/ml around the 20th week, and then rapidly increase to 28.2 ng/ml by the 24th week. Leptin correlation with maternal body weight decreases from r=0.695 at 16-17 week of gestation to r=0.544 at >22 weeks of gestation. There was no significant difference between the mean MoMs of Down syndrome- (0.926) or Edwards syndrome- (0.960) affected pregnancies and normal pregnancies (1.002). A weak correlation (r=0.18, p<0.02) was observed between corrected leptin MoMs and human chorionic gonadotrophin (hCG) MoMs in normal pregnancies. It is assumed that around the 20th week of pregnancy placental leptin production is activated or at least is accelerated and it is added to the amount of leptin produced by maternal adipose tissue. Fetal Down syndrome or Edwards syndrome does not seem to alter maternal leptin concentration and therefore leptin cannot be used as a marker for these chromosomal abnormalities in the early second trimester of pregnancy.

Prospective function of placental leptin at maternal-fetal interface

Leptin is an endocrine and a growth factor which is important for regulation of body fat, feeding, and energy homeostasis. The anti-obesity function of leptin has been recently extended to reproduction, puberty and pregnancy as an endocrine signal to the hypothalamus. Leptin controls the functional integrity of the feto-placental unit thereby maintaining pregnancy by virtue of its immunomodulatory property via T lymphocytes or other proto-oncogenes. Dysregulation of autocrine/paracrine function of leptin at feto-placento-maternal interface may be implicated in the pathogenesis of recurrent miscarriage gestational diabetes, pre-eclampsia and intra-uterine fetal growth retardation including disturbance of fetal bone turnover. This review will focus on the role of leptin in normal and abnormal pregnancy and fetal growth.

The relationships between leptin and inflammatory cytokines in women with pre-eclampsia

OBJECTIVE

To compare maternal serum leptin concentration in women with pre-eclampsia and women with normal pregnancy, and to evaluate the relationships between leptin and several inflammatory cytokines.

DESIGN

Prospective clinical study.

SETTING

University Hospital of Puerto Real, Cadiz, Spain.

SAMPLE

Twenty-seven women with pre-eclampsia and 25 normotensive pregnant women.

METHODS

Maternal serum levels of TNF-alpha, TGF-beta1, interleukin 6, and leptin were measured using a commercially available immunoassay.

MAIN OUTCOME MEASURES

Maternal serum levels of leptin and its relationship to levels of TNF-alpha, TGF-beta1 and interleukin 6.

RESULTS

Maternal serum leptin levels were higher in women with pre-eclampsia, but this difference was of borderline statistical significance (median 15.9 ng/mL; interquartile range (5.4-31.9) vs 30.5 ng/mL (13.9-64) (P = 0.05). The concentration of maternal serum leptin was correlated with pre-gestational and gestational body mass index (r = 0.45, P = 0.03; r = 0.44, P = 0.04), TNF-alpha concentration (r = 0.57, P = 0.002) and interleukin-6 level (r = 0.46, P = 0.02) in women with normal pregnancy. In women with pre-eclampsia, only a significant correlation between maternal serum leptin level and TNF-alpha concentration (0.47, P = 0.01) was found.

CONCLUSIONS

The level of maternal serum leptin is increased and correlates positively with the level of TNF-alpha in women with pre-eclampsia. In women with a normal pregnancy leptin levels not only correlate with TNF-alpha, but also with IL-6 and body mass index.

Leptin and the regulation of food intake, energy homeostasis and immunity with special focus on periparturient ruminants

The biology of leptin has been studied most extensively in rodents and in humans. Leptin is involved in the regulation of food intake, energy homeostasis and immunity. Leptin is primarily produced in white adipose tissue and acts via a family of membrane bound receptors, including an isoform with a long intracellular domain (OB-Rb), and many isoforms with short intracellular domains (Ob-Rs). OB-Rb is predominantly expressed in the hypothalamic regions involved in the regulation of food intake and energy homeostasis. The other isoforms are distributed ubiquitously and are found in most peripheral tissues in far greater abundance than OB-Rb. The effects of leptin on food intake and energy homeostasis are central and are mediated via a network of orexigenic neuropeptides (neuropeptide Y, galanin, galanin-like peptide, melanin-concentrating hormone, orexins, agouti-related peptide) and anorexigenic neuropeptides (corticotropin-releasing hormone, pro-opiomelanocortin, alpha-melanocyte stimulating hormone and cocaine- and amphetamine-regulated transcript). In addition, leptin acts directly on immune cells to stimulate hematopoesis, T-cell immunity, phagocytosis, cytokine production, and to attenuate susceptibility to infectious insults. Emerging data in ruminants suggest that leptin is dynamically regulated by many factors and physiological states. Thus, leptin is secreted in a pulsatile fashion, but without a marked diurnal rhythm. A positive relationship between adiposity and plasma leptin concentration exists in growing and lactating ruminants. The concentration of plasma leptin increases during pregnancy, starts to decline 1--2 wk before parturition, and reaches a nadir in early lactation. The reduction of plasma leptin at parturition is likely to promote centrally mediated adaptations required in periods of energy deficit, but could have negative effects on immune cell function. Future research is needed in ruminants to address the roles played by leptin and the central nervous system in orchestrating metabolism during the periparturient period and during infectious diseases.

Body weight and fat deposition in prolactin receptor-deficient mice

To explore the roles of the lactogens in adipose tissue development and function, we measured body weight, abdominal fat content, and plasma leptin concentrations in a unique model of lactogen resistance: the PRL receptor (PRLR)-deficient mouse. The absence of PRLRs in knockout mice was accompanied by a small (5-12%), but progressive, reduction in body weight after 16 weeks of age. Females were affected to a greater degree than males. The reduction in weight in female PRLR-deficient mice (age 8-9 months) was associated with a 49% reduction in total abdominal fat mass and a 29% reduction in fat mass expressed as a percentage of body weight. Lesser reductions were noted in male mice. Plasma leptin concentrations were reduced in females but not in males. That the reductions in abdominal fat may reflect in part the absence of lactogen action in the adipocyte is suggested by the demonstration of PRLR messenger RNA in normal mouse white adipose tissue. Nevertheless, steady state levels of PRLR messenger RNA in mature adipocytes are very low, suggesting that the effects of lactogens might be mediated by other hormones or cellular growth factors. Our observations suggest roles for the lactogens in adipose tissue growth and metabolism in pregnancy and postnatal life.

Leptin and maternal growth during adolescent pregnancy

BACKGROUND

Maternal growth on the basis of knee height occurs in nearly 50% of pregnant teenagers and is associated with greater gestational weight gain and accrual of subcutaneous fat in the mother but lower fetal growth compared with nongrowing teenagers and mature pregnant women.

OBJECTIVE

The objective of this study was to determine whether leptin is a biomarker for continued maternal growth.

DESIGN

Leptin concentrations were measured in 162 growing and nongrowing teenage gravidas (aged </=18 y) and in mature gravidas (aged 19-29 y) from the Camden Study at 2 time points during pregnancy and 1 time point postpartum.

RESULTS

Growing teenagers had leptin concentrations that increased with gestation and were higher at 28 wk gestation and postpartum than in nongrowing teenagers and mature gravidas. The differences were related to a leptin surge between entry into the study (16.9 wk) and week 28, primarily in still-growing gravidas. Leptin-surge quartiles were associated with higher knee-height velocity and weight gain, increased skinfold thicknesses in late pregnancy (28 wk) and early postpartum (4-6 wk), and changes in postpartum weight and body mass index. For the highest quartile, low birth weight increased >5-fold, fetal growth restriction increased >6-fold, and infant birth weight decreased by approximately 200 g. Gravidas who developed pregnancy-induced hypertension showed a different pattern-higher leptin concentrations at entry and week 28, no difference in the leptin surge, and no postpartum difference in leptin concentration.

CONCLUSION

A leptin surge by week 28 appears to mark reduced mobilization of maternal fat stores that is associated with maternal growth on the basis of knee height during adolescent pregnancy.

Leptin in pregnancy

Leptin is a polypeptide hormone that aids in the regulation of body weight and energy homeostasis and is linked to a variety of reproductive processes in both animals and humans. Thus, leptin may help regulate ovarian development and steroidogenesis and serve as either a primary signal initiating puberty or as a permissive regulator of sexual maturation. Perhaps significantly, peripheral leptin concentrations, adjusted for adiposity, are dramatically higher in females than in males throughout life. During primate pregnancy, maternal levels that arise from adipose stores and perhaps the placenta increase with advancing gestational age. Proposed physiological roles for leptin in pregnancy include the regulation of conceptus growth and development, fetal/placental angiogenesis, embryonic hematopoiesis, and hormone biosynthesis within the maternal-fetoplacental unit. The specific localization of both leptin and its receptor in the syncytiotrophoblast implies autocrine and/or paracrine relationships in this endocrinologically active tissue. Interactions of leptin with mechanisms regulating pre-eclampsia and maternal diabetes have also been suggested. Collectively, therefore, reports suggest that a better understanding of the regulation of leptin and its role(s) throughout gestation may eventually impact those causes of human perinatal morbidity and mortality that are exacerbated by intrauterine growth retardation, macrosomia, placental insufficiency, or prematurity.

Integration of metabolism and intake regulation: a review focusing on periparturient animals

There has been great interest in dry matter intake regulation in lactating dairy cattle to enhance performance and improve animal health and welfare. Predicting voluntary dry matter intake (VDMI) is complex and influenced by numerous factors relating to the diet, management, housing, environment and the animal. The objective of this review is to identify and discuss important metabolic factors involved in the regulation of VDMI and their integration with metabolism. We have described the adaptations of intake and metabolism and discussed mechanisms of intake regulation. Furthermore we have reviewed selected metabolic signals involved in intake regulation. A substantial dip in VDMI is initiated in late pregnancy and continues into early lactation. This dip has traditionally been interpreted as caused by physical constraints, but this role is most likely overemphasized. The dip in intake coincides with changes in reproductive status, fat mass, and metabolic changes in support of lactation, and we have described metabolic signals that may play an equally important role in intake regulation. These signals include nutrients, metabolites, reproductive hormones, stress hormones, leptin, insulin, gut peptides, cytokines, and neuropeptides such as neuropeptide Y, galanin, and corticotrophin-releasing factor. The involvement of these signals in the periparturient dip in intake is discussed, and evidence supporting the integration of the regulation of intake and metabolism is presented. Still, much research is needed to clarify the complex regulation of VDMI in lactating dairy cows, particularly in the periparturient animal.