Leptin, the ob gene product, in female health and disease

Breast-feeding duration for the prevention of excess body weight of mother-child pairs concurrently: a 2-year cohort study

OBJECTIVE

To examine the association between breast-feeding duration and the risk of excess body weight (children >85th percentile, mothers BMI≥25·0 kg/m2) concurrently in mother-child pairs two years after delivery.

DESIGN

Prospective cohort study in Joinville, Brazil. Multivariable logistic regression was used to examine the independent relationship between breast-feeding duration and risk of excess body weight.

SETTING

Brazilian public maternity hospital.

SUBJECTS

Three hundred and five mother-child pairs.

RESULTS

At 2-year follow-up, 23·6 % of mother-child pairs had excess body weight. Children breast-fed for <2 months were more likely to have excess body weight than children breast-fed for ≥6 months (OR=2·4; 95 % CI 1·1, 5·1). Breast-feeding for <2 months was also associated with a greater likelihood of maternal excess body weight compared with those who breast-fed for ≥6 months (OR=2·9; 95 % CI 1·1, 8·1). There was a progressive increase in the likelihood of mother-child pairs having excess body weight as breast-feeding duration decreased. In addition to breast-feeding duration, other independent determinants of excess body weight were pre-pregnancy weight, gestational weight gain and number of pregnancies in mothers, and birth weight in children.

CONCLUSIONS

Breast-feeding for a longer duration has a parallel protective effect on the risk of excess body weight in mother-child pairs two years after birth. Since members of the same family could be influenced by the same risk factors, continued promotion and support of breast-feeding may help to attenuate the rising prevalence of overweight in mother-child pairs.

Effect of increased dietary salinity on the reproductive status and energy intake of xeric and mesic populations of the spiny mouse, Acomys

The possible role of increased dietary salinity as a proximate regulator of reproduction in xeric population of golden spiny mice (Acomys russatus) and mesic population of common spiny mice (A. cahirinus) was tested. In the wild, as the dry season progresses, evaporative water loss in the vegetation increases. This leads to increase in particle concentration of plant tissues. Thus, species consuming a plant diet are exposed to increased dietary salinity. Both male and female individuals of A. russatus were subjected to gradually increasing dietary salinity (0.9%, 2.5%, 3.5%, and 5%) while those of A. cahirinus only up to 3.5% for a total period of 8 and 6 weeks, respectively. Urine osmolarity showed a significant increase under 3.5% and 5% salinity in A. russatus and 2.5% and 3.5% in A. cahirinus. Testis mass and spermatogenesis were significantly reduced while uterine mass and vaginal estrus cycles were not affected in A. russatus. None of the parameters was significantly affected in A. cahirinus. Increase in salinity also significantly reduced body mass in A. russatus but not in A. cahirinus. Mass-specific daily digestible energy intake was not significantly affected by increased salinity in both species. Recovery individuals regained body mass quickly and surpassed initial values after four weeks. However, testis mass and spermatogenesis did not show recovery. The results suggest that increase in dietary salinity could be used as a proximate signal to regulate reproduction in A. russatus by halting it in males, as the dry season progresses while such role in the mesic population of A. cahirinus is unlikely.

Insulin and leptin relations in obesity: a multimedia approach

Obesity has been recognized as a worldwide public health problem. It significantly increases the chances of developing several diseases, including Type II diabetes. The roles of insulin and leptin in obesity involve reactions that can be better understood when they are presented step by step. The aim of this work was to design software with data from some of the most recent publications on obesity, especially those concerning the roles of insulin and leptin in this metabolic disturbance. The most notable characteristic of this software is the use of animations representing the cellular response together with the presentation of recently discovered mechanisms on the participation of insulin and leptin in processes leading to obesity. The software was field tested in the Biochemistry of Nutrition web-based course. After using the software and discussing its contents in chatrooms, students were asked to answer an evaluation survey about the whole activity and the usefulness of the software within the learning process. The teaching assistants (TA) evaluated the software as a tool to help in the teaching process. The students' and TAs' satisfaction was very evident and encouraged us to move forward with the software development and to improve the use of this kind of educational tool in biochemistry classes.

A differential response in the reproductive system and energy balance of spiny mice Acomys populations to vasopressin treatment

Increased dietary salinity suppressed reproduction of the xeric adapted golden spiny mouse, Acomys russatus. Testicular and uterine mass were reduced, suppressed spermatogenesis and vaginal closure were observed. The anti-diuretic hormone, vasopressin (VP), was suggested to mediate such effects. However, increased dietary salinity did not affect reproductive status of a mesic adapted population of the common spiny mouse, A. cahirinus. In the present study, the effect of exogenous VP on the reproductive status and energy balance of both males and females of A. russatus and of a mesic population of A. cahirinus was tested. Vasopressin (Sigma, 50 microg/kg) was injected intraperitoneally in three-day intervals for four weeks. In VP-treated A. russatus, spermatogenesis was significantly suppressed while the change in testis mass did not show significant difference. Both control and VP-treated females lost body mass (W(b)) significantly and the latter also exhibited a higher energy expenditure compared to their male counterparts. VP did not affect reproductive status in both sexes of A. cahirinus. Also it did not have a significant effect on W(b), energy intake, and energy expenditure in this species. Our results support the idea that VP mediates the effects of increased diet salinity on reproduction in A. russatus. The results also reinforce previous knowledge that different physiological systems could be integrated by a single biochemical signal.

Current perspectives on the causes of neural tube defects resulting from diabetic pregnancy

Maternal diabetes increases the risk for neural tube, and other, structural defects. The mother may have either type 1 or type 2 diabetes, but the diabetes must be existing at the earliest stages of pregnancy, during which organogenesis occurs. Abnormally high glucose levels in maternal blood, which leads to increased glucose transport to the embryo, is responsible for the teratogenic effects of maternal diabetes. Consequently, expression of genes that control essential developmental processes is disturbed. In this review, some of the biochemical pathways by which excess glucose metabolism disturbs neural tube formation are discussed. Research from the author's laboratory has shown that expression of Pax3, a gene required for neural tube closure, is significantly reduced by maternal diabetes, and this is associated with significantly increased neural tube defects (NTD). Pax3 encodes a transcription factor that has recently been shown to inhibit p53-dependent apoptosis. Evidence in support of this model, in which excess glucose metabolism inhibits expression of Pax3, thereby derepressing p53-dependent apoptosis of neuroepithelium and leading to NTD will be discussed.

Measurement of serum leptin concentrations in university undergraduates by competitive ELISA reveals correlations with body mass index and sex

Synthesized mainly in adipocytes, leptin is a peptide hormone that plays a key role in the regulation of body weight and composition. The serum leptin concentrations of 193 Singapore university medical and bioscience undergraduates aged 19-26 yr were measured using a competitive ELISA kit, and their leptin levels were correlated with sex and body mass index (BMI). Mean leptin levels were more than twice as high in females than in males of corresponding weight status, especially among females of healthy weight who exhibited levels that were 5.7 times higher. Overweight individuals generally demonstrated higher circulating leptin concentrations than healthy-weight and underweight participants. The differences in mean leptin levels between underweight and overweight males (P = 0.006), as well as between healthy-weight and overweight males (P = 0.011) were statistically significant. Comparison tests of leptin levels between healthy-weight and underweight females were highly significant (P = 0.001). Highly significant linear correlations between BMI and the logarithm of leptin concentration were observed in the female (r = 0.44) and male (r = 0.36) groups. These results reiterate the impact of gonadal steroids as mediators of the apparent sexual dimorphism in circulating leptin. The findings also corroborate evidence that adiposity determines leptin levels. This laboratory exercise has educational value for undergraduates by determining their BMIs, by alluding to the importance of maintaining healthy body composition, and by emphasizing the molecular mechanisms of body weight regulation and obesity, with special reference to leptin. This practical study also exemplifies the principles and applications of the competitive ELISA technique and integrates certain key concepts of physiology, molecular biology, immunology, and medicine.

Prospective assessment of exclusive breastfeeding in relation to weight change in women

OBJECTIVE

To study prospectively the relation of parity, prepregnancy body mass index (BMI), and exclusive breastfeeding to weight gain.

DESIGN

The cohort of the Nurse's Health Study II, with analysis restricted to women who were aged 24 to 40 y at baseline (1989), who had a history of no more than one past full-term pregnancy at baseline, gave birth to one child between 1990 and 1991, but had no other pregnancies during the follow-up.

SUBJECTS

1538 of the 33 082 nulliparous women and 2810 of the 20 261 primiparous, in 1989.

MEASUREMENTS

Introduction of daily formula/milk was assumed to represent the end of exclusive breastfeeding period. Duration of exclusive breastfeeding was categorized into 0, 1-3, 4-7, 8-11, and 12 months or more.

RESULTS

After adjusting for age, physical activity, and BMI in 1989, lactation was associated with a weight gain from 1989 to 1993 of approximately 1 kg (statistically significant only for women nulliparous in 1989 with a BMI <25 kg/m(2) (P=0.02) and for those women primiparous in 1989, with a BMI >/=25 kg/m(2) (P=0.04)) comparing women who breastfed with women who did not, and duration of lactation was unrelated to the magnitude of weight change (P>0.40 for all comparisons).

CONCLUSIONS

Although promotion of breastfeeding has high priority because of its enormous advantages for a newborn child, the associated maternal weight reduction is minimal. Dietary guidelines for pregnant and breastfeeding women should include ways to prevent weight retention after parity.

Leptin's sexual dimorphism results from genotype by sex interactions mediated by testosterone

OBJECTIVE

Recent studies have reported the existence of marked sexual dimorphism in serum leptin levels in humans, with women having approximately three times the levels of men. As we have shown for other measures of adiposity, such sexual dimorphism can arise from a special case of genotype by environment interaction, that of genotype by sex interaction.

RESEARCH METHODS AND PROCEDURES

Using maximum likelihood-based variance decomposition techniques, we examined the genetic and environmental architecture of sexual dimorphism in serum leptin levels in 1147 Mexican Americans from the San Antonio Family Heart Study.

RESULTS

Both the genetic and environmental variances for this trait differed significantly between the sexes (p < 0.001 and p < 0.01, respectively), with women displaying larger values for both components. We found significant evidence that different genes influence variation in serum leptin levels between the two sexes (p = 0.05). Furthermore, this pattern of sexual dimorphism in serum leptin levels persisted even after accounting for the effects of either the percentage of body fat or total body fat. However, this pattern of sexual dimorphism was eliminated after accounting for the effects of testosterone.

DISCUSSION

These findings suggest that the sexual dimorphism seen in leptin levels is not simply explained as differences in total adiposity between the sexes. We conclude that the genes, which influence variation in serum leptin levels, are differentially expressed depending on sex, and that the sexes also show differences in response of the expression of this obesity-related trait to unmeasured residual effects.