Nicotine exposure affects mother's and pup's nutritional, biochemical, and hormonal profiles during lactation in rats

Neonatal nicotine exposure affects adult rat hepatic pathways involved in endoplasmic reticulum stress and macroautophagy in a sex-dependent manner

Nonalcoholic fatty liver disease (NAFLD) involves changes in hepatic pathways, as lipogenesis, oxidative stress, endoplasmic reticulum (ER) stress, and macroautophagy. Maternal nicotine exposure exclusively during lactation leads to fatty liver (steatosis) only in the adult male offspring, not in females. Therefore, our hypothesis is that neonatal exposure to nicotine sex-dependently affects the signaling pathways involved in hepatic homeostasis of the offspring, explaining the hepatic lipid accumulation phenotype only in males. For this, between postnatal days 2 and 16, Wistar rat dams were implanted with osmotic minipumps, which released nicotine (NIC; 6 mg/Kg/day) or vehicle. The livers of offspring were evaluated at postnatal day 180. Only the male offspring that had been exposed to nicotine neonatally showed increased protein expression of markers of unfolded protein response (UPR), highlighting the presence of ER stress, as well as disruption of the activation of the macroautophagy repair pathway. These animals also had increased expression of diacylglycerol O-acyltransferase 1 and 4-hydroxynonenal, suggesting increased triglyceride esterification and oxidative stress. These parameters were not altered in the female offspring that had been neonatally exposed to nicotine, however they exhibited increased phospho adenosine monophosphate-activated protein kinase pAMPK expression, possibly as a protective mechanism. Thus, the disturbance in the hepatic homeostasis by UPR, macroautophagy, and oxidative stress modifications seem to be the molecular mechanisms underlying the liver steatosis in the adult male offspring of the nicotine-programming model. This highlights the importance of maternal smoking cessation during breastfeeding to decrease the risk of NAFLD development, especially in males.

The impact of e-cigarette exposure on different organ systems: A review of recent evidence and future perspectives

The use of electronic cigarettes (e-cigs) is rapidly increasing worldwide and is promoted as a smoking cessation tool. The impact of traditional cigs on human health has been well-defined in both animal and human studies. In contrast, little is known about the adverse effects of e-cigs exposure on human health. This review summarizes the impact of e-cigs exposure on different organ systems based on the rapidly expanding recent evidence from experimental and human studies. A number of growing studies have shown the adverse effects of e-cigs exposure on various organ systems. The summarized data in this review indicate that while e-cigs use causes less adverse effects on different organs compared to traditional cigs, its long-term exposure may lead to serious health effects. Data on short-term organ effects are limited and there is no sufficient evidence on long-term organ effects. Moreover, the adverse effects of secondhand and third hand e-cigs vapour exposure have not been thoroughly investigated in previous studies. Although some studies demonstrated e-cigs used as a smoking cessation tool, there is a lack of strong evidence to support it. While some researchers suggested e-cigs as a safer alternative to tobacco smoking, their long-term exposure health effects remain largely unknown. Therefore, more epidemiological and prospective studies including mechanistic studies are needed to address the potential adverse health effects of e-cigs to draw a firm conclusion about their safe use. A wide variation in e-cigs products and the lack of standardized testing methods are the major barriers to evaluating the existing data. Specific regulatory guidelines for both e-cigs components and the manufacturing process may be effective to protect consumer health.

Developmental nicotine exposure and masculinization of the rat preoptic area

Nicotine is a neuroteratogenic component of tobacco smoke, e-cigarettes, and other products and can exert sex-specific effects in the developing brain, likely mediated through sex hormones. Estradiol modulates expression of nicotinic acetylcholine receptors in rats, and plays critical roles in neurodevelopmental processes, including sexual differentiation of the brain. Here, we examined the effects of developmental nicotine exposure on the sexual differentiation of the preoptic area (POA), a brain region that normally displays robust structural sexual dimorphisms and controls adult mating behavior in rodents. Using a rat model of gestational exposure, developing pups were exposed to nicotine (2 mg/kg/day) via maternal osmotic minipump (subcutaneously, sc) throughout the critical window for brain sexual differentiation. At postnatal day (PND) 4, a subset of offspring was analyzed for epigenetic effects in the POA. At PND40, all offspring were gonadectomized, implanted with a testosterone-releasing capsule (sc), and assessed for male sexual behavior at PND60. Following sexual behavior assessment, the area of the sexually dimorphic nucleus of the POA (SDN-POA) was measured using immunofluorescent staining techniques. In adults, normal sex differences in male sexual behavior and in the SDN-POA area were eliminated in nicotine-treated animals. Using novel analytical approaches to evaluate overall masculinization of the adult POA, we identified significant masculinization of the nicotine-treated female POA. In neonates (PND4), nicotine exposure induced trending alterations in methylation-dependent masculinizing gene expression and DNA methylation levels at sexually-dimorphic differentially methylated regions, suggesting that developmental nicotine exposure is capable of triggering masculinization of the rat POA via epigenetic mechanisms.

Can breastfeeding affect the rest of our life?

The breastfeeding period is one of the most important critical windows in our development, since milk, our first food after birth, contains several compounds, such as macronutrients, micronutrients, antibodies, growth factors and hormones that benefit human health. Indeed, nutritional, and environmental alterations during lactation, change the composition of breast milk and induce alterations in the child's development, such as obesity, leading to the metabolic dysfunctions, cardiovascular diseases and neurobehavioral disorders. This review is based on experimental animal models, most of them in rodents, and summarizes the impact of an adequate breast milk supply in view of the developmental origins of health and disease (DOHaD) concept, which has been proposed by researchers in the areas of epidemiology and basic science from around the world. Here, experimental advances in understanding the programming during breastfeeding were compiled with the purpose of generating knowledge about the genesis of chronic noncommunicable diseases and to guide the development of public policies to deal with and prevent the problems arising from this phenomenon. This review article is part of the special issue on "Cross talk between periphery and brain".

Changes in gut-brain axis parameters in adult rats of both sexes with different feeding pattern that were early nicotine-exposed

Nicotine is an endocrine disruptor and imprinting factor during breastfeeding that can cause food intake imbalance in the adulthood. As nicotine affects the intestinal microbiota, altering the composition of the bacterial communities and short-chain fatty acids (SCFAs) synthesis in a sex-dependent manner, we hypothesized that nicotine could program the gut-brain axis, consequently modifying the eating pattern of adult male and female rats in a model of maternal nicotine exposure (MNE) during breastfeeding. Lactating Wistar rat dams received minipumps that release 6 mg/kg/day of nicotine (MNE group) or saline for 14 days. The progeny received standard diet from weaning until euthanasia (26 weeks of age). We measured: in vivo electrical activity of the vagus nerve; c-Fos expression in the nucleus tractus solitarius, gastrointestinal peptides receptors, intestinal brain-derived neurotrophic factor (BDNF), SCFAs and microbiota. MNE females showed hyperphagia despite normal adiposity, while MNE males had unchanged food intake, despite obesity. Adult MNE offspring showed decreased Bacteroidetes and increased Firmicutes, Actinobacteria and Proteobacteria. MNE females had lower fecal acetate while MNE males showed higher vagus nerve activity. In summary nicotine exposure through the milk induces long-term intestinal dysbiosis, which may affect eating patterns of adult offspring in a sex-dependent manner.

Effect of E-cigarettes aerosol exposure during lactation in rats: Hormonal and biochemical aspects

Electronic cigarettes (e-cigarettes) have been marketed as a less lethal substitute for smoking traditional cigarettes. This study aims to investigate the impact of e-cigarettes aerosol exposure on lactating dams and pups, whose dams were exposed. Lactating dams received fresh air (control) or e-cigarettes aerosol during lactation (day 4-21). Maternal exposure to e-cigarettes aerosol during lactation induced significant reduction (P < 0.0001) in the fat content of the milk and serum Leptin level (P < 0.005) compared to control dams. Furthermore, pups whose dams were exposed to e-cigarettes during lactation showed an increased level of glucose, thyroxine and decreased level of insulin. The exposure to e-cigarettes aerosol during lactation altered the composition of milk as well as the hormonal and biochemical profile in dams and pups. This result, if observed in women using e-cigarettes, suggests that e-cigarettes' use during lactation may have consequences on the milk production and hormonal and biochemical profile in breastfeeding mothers and nursing babies.

Calcium-Deficiency during Pregnancy Affects Insulin Resistance in Offspring

Prenatal malnutrition is known to affect the phenotype of the offspring through changes in epigenetic regulation. Growing evidence suggests that epigenetics is one of the mechanisms by which nutrients and minerals affect metabolic traits. Although the perinatal period is the time of highest phenotypic plasticity, which contributes largely to developmental programming, there is evidence of nutritional influence on epigenetic regulation during adulthood. Calcium (Ca) plays an important role in the pathogenesis of insulin resistance syndrome. Cortisol, the most important glucocorticoid, is considered to lead to insulin resistance and metabolic syndrome. 11β-hydroxysteroid dehydrogenase-1 is a key enzyme that catalyzes the intracellular conversion of cortisone to physiologically active cortisol. This brief review aims to identify the effects of Ca deficiency during pregnancy and/or lactation on insulin resistance in the offspring. Those findings demonstrate that maternal Ca deficiency during pregnancy may affect the epigenetic regulation of gene expression and thereby induce different metabolic phenotypes. We aim to address the need for Ca during pregnancy and propose the scaling-up of clinical and public health approaches that improved pregnancy outcomes.

Neonatal nicotine exposure changes insulin status in fat depots: sex-related differences

Nicotine is the main psychoactive substance present in cigarette smoke that is transferred to the baby by breast milk. In rats, maternal nicotine exposure during breastfeeding induces obesogenesis and hormone dysfunctions in adult male offspring. As glucocorticoid (GC), insulin, and vitamin D change both adipogenesis and lipogenesis processes, we assessed parameters related to metabolism and action of these hormones in visceral and subcutaneous adipose tissues (VAT and SAT) of adult male and female rats in a model of neonatal nicotine exposure. At postnatal (PN) day 2, dams were kept with six pups (three per sex) and divided into nicotine and control groups for implantation of osmotic minipumps that released 6 mg/kg nicotine or saline, respectively. At PN180, fat mass, hormone levels, and protein contents of biomarkers of the GC activation and receptor (11beta-hydroxysteroid dehydrogenase type 1 and glucocorticoid receptor alpha), insulin signaling pathway [insulin receptor beta (IRβ), phosphorylated insulin receptor substrate 1, insulin receptor substrate 1 (IRS1), phosphorylated serine/threonine kinase (pAKT), serine/threonine kinase, glucose transporter type 4 (GLUT4)], and vitamin D activation and receptor (1α-hydroxylase and vitamin D receptor) were evaluated. While nicotine-exposed males showed increased fat mass, hypercorticosteronemia, hyperinsulinemia, and higher 25-hydroxyvitamin D, these alterations were not observed in nicotine-exposed females. Nicotine-exposed males only showed lower IRS1 in VAT, while the females had hyperglycemia, higher pAKT in VAT, while lower IRβ, IRS1, and GLUT4 in SAT. Parameters related to metabolism and action of GC and vitamin D were unaltered in both sexes. We evidence that exposure exclusively to nicotine during breastfeeding affects the hormone status and fat depots of the adult progeny in a sex-dependent manner.

Pancreatic steatosis in adult rats induced by nicotine exposure during breastfeeding

PURPOSE

Maternal nicotine exposure negatively impacts offspring's health and metabolism, leading to obesity and insulin resistance. Here we investigated the pancreatic islet function, glycemic homeostasis, and insulin signaling in adult rat offspring that were nicotine-exposed during breastfeeding.

METHODS

For this, lactating Wistar rat dams were divided into two groups: Nicotine (implanted with osmotic minipumps containing 6 mg/Kg, NIC) and Control (saline, CON). Solutions were released from postnatal (PN) day 2-16. At PN110 and PN170, 10 offspring per litter/sex/group were submitted to the oral glucose tolerance test (OGTT). PN180 offspring were killed and glycemia, insulinemia, adiponectinemia, pancreas morphology as well as pancreatic islet protein expression (related to insulin secretion) and skeletal muscle (related to insulin action) were evaluated. Males and females were compared to their respective controls.

RESULTS

Adult NIC offspring of both sexes showed glucose intolerance in the OGTT. Despite normoglycemia, NIC males showed hyperinsulinemia while females, although normoinsulinemic, had hyperglycemia. Both sexes showed increased IRI, reduced adiponectin/visceral fat mass ratio and higher ectopic deposition of lipids in the pancreatic tissue adipocytes. In pancreatic islets, NIC males showed lower PDX-1 expression while females had higher PDX-1 and GLUT2 expressions plus lower α2 adrenergic receptor. In the muscle, NIC offspring of both sexes showed reduction of GLUT4 expression; NIC males also had lower insulin receptor and pAKT expressions.

CONCLUSIONS

Thus, glycemic homeostasis and peripheral insulin signaling in adult offspring of both sexes are affected by nicotine exposure through the milk, increasing the risk for type 2 diabetes development.

Early life nicotine exposure alters mRNA and microRNA expressions related to thyroid function and lipid metabolism in liver and BAT of adult wistar rats

In rats, maternal nicotine exposure during lactation induces obesity, thyroid dysfunction, brown adipose tissue (BAT) hypofunction and liver alterations in adult offspring. Both thyroid function and lipid metabolism are influenced by gene silencing mediated by microRNAs (miRNAs). Here we investigated long-term effects of early nicotine exposure on molecular and epigenetic mechanisms closely related to thyroid and lipid metabolism, through the expression of mRNAs and miRNAs in BAT and liver of adult male and female offspring. At postnatal day 2 (PND2), lactating control (CON) or nicotine (NIC) dams were subcutaneously implanted with osmotic minipumps containing, respectively, saline or 6 mg/kg nicotine. Litters were adjusted to 3 males and 3 females. Offspring's euthanasia occurred at PND180. In the BAT, NIC females showed higher Dio2 mRNA expression, while miR-382* expression was not altered in both sexes. In the liver, NIC offspring of both sexes showed lower Dio1 mRNA expression and higher miR-224 expression, while only NIC females had higher miR-383 and miR-21 expressions. NIC offspring of both sexes showed higher mRNA expression of SCD1 in the liver; NIC males had decreased CPT1 expression, whereas NIC females had increased FASN, miR-370 and miR-122 expressions. Regardless of sex, alterations in liver Dio1, miR-224 and SCD1 expressions are involved in the disturbances caused by maternal nicotine exposure during breastfeeding. Interestingly, females had more altered miRs in the liver. Early nicotine exposure induces a sex dimorphism, particularly regarding hepatic lipid metabolism, through miRs expression.

Maternal waterpipe tobacco smoke exposure during lactation induces hormonal and biochemical changes in rat dams and offspring

Waterpipe smoking is common among pregnant and breastfeeding women. Herein, the effects of waterpipe tobacco smoke (WTS) exposure during lactation on milk composition, hormonal levels and biochemical profile in dams and pups were investigated. Lactating Wistar rats were randomly assigned to receive either WTS (2 hours per day) or fresh air (control group). Milk was collected on day 21 and analysed for protein, lactose and total fat. Blood, from dams and pups, was analysed for insulin, glucose, lipid profile, leptin, prolactin and corticosterone. WTS exposure during lactation increased the blood level of HDL and corticosterone in dams (P < .05). However, the level of milk lactose and blood glucose was reduced in dams after the exposure to WTS during lactation (P < .05). WTS during lactation significantly increased levels of triglycerides, LDL and leptin (P < .05), and a trend of increase in blood level of nicotine and prolactin in pups. Levels of other parameters were not affected by WTS exposure in dams and pups. In conclusion, WTS exposure during lactation altered the milk composition and altered lipid profile, glucose homeostasis and hormonal levels in dams and pups. It is necessary to adopt strategies to enhance tobacco cessation during breastfeeding.

Nicotine exposure during lactation causes disruption of hedonic eating behavior and alters dopaminergic system in adult female rats

Tobacco smoke during gestation is associated with increased consumption of palatable foods by the offspring in humans and rats. Postpartum relapse is observed in lactating women who quit smoking during pregnancy, putting their children at risk of adverse health outcomes caused by secondhand smoke. Nicotine is transferred through milk and alters the dopaminergic reward system of adult male rats, reducing dopamine action in the nucleus accumbens (NAc) and hypothalamic arcuate nucleus. Here, we evaluated the long-term effects of nicotine-only exposure during lactation on eating behavior, anxiety, locomotion, dopaminergic system, hypothalamic leptin signaling and nicotinic receptor in the adult female rat progeny. Two days after birth (PN2), Wistar rat dams were separated into control and nicotine (Nic) groups for implantation of osmotic minipumps that released respectively saline or 6 mg/kg nicotine. Lactating dams were kept with 6 pups. After weaning (PN21; nicotine withdrawal), only the female offspring were studied. Euthanasia occurred at PN180. Nic females showed hyperphagia, preference for a high-sucrose diet, increased anxiety-like behavior, lower tyrosine hydroxylase (TH), lower dopamine transporter and higher dopamine receptor (Drd2) in NAc; lower Drd1 in prefrontal cortex and lower TH in dorsal striatum (DS). These animals showed changes that can explain their hyperphagia, such as: lower leptin signaling pathway (Lepr^b, pJAK2, pSTAT3) and Chrna7 expression in hypothalamus. Neonatal nicotine exposure affects the brain reward system of the female progeny differently from males, mainly decreasing dopamine production in NAc and DS. Therefore, Nic females are more susceptible to develop food addiction and obesity.

The effect of tobacco smoking during pregnancy and breastfeeding on human milk composition-a systematic review

Tobacco smoking is still a widespread habit in pregnant and breastfeeding women. While the role of these risk factors on neonatal outcomes has been deeply studied, their effect on human milk composition is still not completely clear. This study aimed to report the most up to date evidence about the alteration of breast milk composition of smoking breastfeeding mothers compared to non-smoking ones. We performed a systematic review by searching PubMed, Embase, and Cochrane Library databases. Evaluated data were extracted and critically analyzed by two independent authors. PRISMA guidelines were applied, and the risk of bias was assessed (ROBINS), as was the methodological quality of the included studies (GRADE). After applying the inclusion criteria, we included 20 studies assessed as medium or high quality. In all the studies, we analyzed data regarding 1769 mothers (398 smokers and 971 nonsmokers). Smoking was associated with a lower content of lipids, calories, and proteins. Moreover, it was characterized by decreased antioxidant properties and an altered immune status. Smoking during pregnancy and breastfeeding is significantly associated with an alteration of milk metabolic properties. Further studies are needed to investigate how these changes can alter newborns' development and outcomes and which molecular patterns are involved.

Tobacco smoking during breastfeeding increases the risk of developing metabolic syndrome in adulthood: Lessons from experimental models

Metabolic syndrome (MetS) is characterized by increased abdominal fat, dyslipidemia, diabetes mellitus and hypertension. A high MetS prevalence is strongly associated with obesity. Obesity is a public health problem in which several complex factors have been implicated, including environmental pollutants. For instance, maternal smoking seems to play a role in obesogenesis in childhood. Given the association between endocrine disruptors, obesity and metabolic programming, over the past 10 years, our research group has contributed to studies based on the hypothesis that early exposure to nicotine/tobacco causes offspring to become MetS-prone. The mechanism by which tobacco smoking during breastfeeding induces metabolic dysfunctions is not completely understood; however, increased metabolic programming has been shown in studies that focus on this topic. Here, we reviewed the literature mainly based in light of our latest data from experimental models. Nicotine or tobacco exposure during breastfeeding induces several endocrine dysfunctions in a sex- and tissue-specific manner. This review provides an updated summary regarding the hypothesis that early exposure to nicotine/tobacco causes offspring to become MetS-prone. An understanding of this issue can provide support to prevent long-term disorders, mainly related to the risk of obesity and its comorbidities, in future generations.

Programming of hepatic lipid metabolism in a rat model of postnatal nicotine exposure - Sex-related differences

Maternal nicotine exposure during lactation induces liver damage in adult male rats. However, the mechanism in males is unknown and females have not been tested. Here, we determined the liver lipid composition and lipogenic enzymes in male and female offspring at two ages in a model of postnatal nicotine exposure. Osmotic minipumps were implanted in lactating Wistar rat dams at postnatal day (PND) 2 to release 6 mg/kg/day of nicotine (NIC group) or saline (CON group) for 14 days. Offspring received a standard diet from weaning until euthanasia at PND120 (1 pup/litter/sex) or PND180 (2 pups/litter/sex). At PND120, NIC males showed lower plasma triglycerides (TG), steatosis degree 1, higher hepatic cholesterol (CHOL) ester, free fatty acids, monoacylglycerol content as well as acetyl-coa carboxylase-1 (ACC-1) and fatty acid synthase (FAS) protein expression in the liver compared to CON males. At this age, NIC females had preserved hepatocytes architecture, higher plasma CHOL, higher CHOL ester and lower total CHOL content in the liver compared to CON females. At PND180, NIC males showed steatosis degrees 1 and 2, higher TG, lower free fatty acids and total CHOL content in the liver and an increase in ACC-1 hepatic protein expression. NIC females had higher plasma TG and CHOL levels, no change in hepatic morphology, lower CHOL ester and free fatty acids in the liver, which also showed higher total ACC-1 and FAS protein expression. Maternal nicotine exposure induces long-term liver dysfunction, with an alteration in hepatic cytoarchitecture that was aggravated with age in males. Concerning females, despite unchanged hepatic cytoarchitecture, lipid metabolism was compromised, which deserves further attention.

Molecular mechanisms for nicotine intoxication

Nicotine, one of the more than 4700 ingredients in tobacco smoke, is a neurotoxin and once used as pesticides in agriculture. Although its use in agriculture is prohibited in many countries, nicotine intoxication is still a problem among the workers in tobacco farms, and young children as well as adults due to the accidental or suicidal ingestions of nicotine products. Understanding the mechanism of nicotine intoxication is important not only for the prevention and treatment but also for the appropriate regulatory approaches. Here, we review pharmacokinetics of nicotine and the molecular mechanisms for acute and chronic intoxication from nicotine that might be relevant to the central and the peripheral nervous system. We include green tobacco sickness, acute intoxication from popular nicotine products, circadian rhythm changes, chronic intoxication from nicotine through prenatal nicotine exposure, newborn behaviors, and sudden infant death syndrome.

Mothering under the influence: how perinatal drugs of abuse alter the mother-infant interaction

Although drug-abusing women try to moderate their drug and alcohol use during pregnancy, they often relapse at a time when childcare needs are high and maternal bonding is critical to an infant's development. In the clinical setting, the search for the neural basis of drug-induced caregiving deficits is complex due to several intervening variables. Rather, the preclinical studies that control for drug dose and regimen, as well as for gestational and postpartum environment, allow a precise determination of the effects of drugs on maternal behaviour. Given the relevance of the issue, this review will gather reports on the phenotypic correlates of maternal behaviour in preclinical studies, and focus on the detrimental consequences on the mother-infant interaction exerted by the perinatal use of alcohol, nicotine, cannabis, cocaine and stimulants and opiates. The drug-induced disruptions of this maternal repertoire are associated with adverse maternal and infant outcomes. A comprehensive overview will help promote the refinement of the treatment approaches toward maternal drug use disorders and maternal misbehaviour, in favour of augmented parenting resiliency.

Maternal diet-induced obesity during suckling period programs offspring obese phenotype and hypothalamic leptin/insulin resistance

During the early post-natal period, offspring are vulnerable to environmental insults, such as nutritional and hormonal changes, which increase risk to develop metabolic diseases later in life. Our aim was to understand whether maternal obesity during lactation programs offspring to metabolic syndrome and obese phenotype, in addition we aimed to assess the peripheral glucose metabolism and hypothalamic leptin/insulin signaling pathways. At delivery, female Wistar rats were randomly divided in two groups: Control group (CO), mothers fed a standard rodent chow (Nuvilab); and Diet-induced obesity group (DIO), mothers who had free access to a diet performed with 33% ground standard rodent chow, 33% sweetened condensed milk (Nestlé), 7% sucrose and 27% water. Maternal treatment was performed throughout suckling period. All offspring received standard rodent chow from weaning until 91-day-old. DIO dams presented increased total body fat and insulin resistance. Consequently, the breast milk from obese dams had altered composition. At 91-day-old, DIO offspring had overweight, hyperphagia and higher adiposity. Furthermore, DIO animals had hyperinsulinemia and insulin resistance, they also showed pancreatic islet hypertrophy and increased pancreatic β-cell proliferation. Finally, DIO offspring showed low ObRb, JAK2, STAT-3, IRβ, PI3K and Akt levels, suggesting leptin and insulin hypothalamic resistance, associated with increased of hypothalamic NPY level and decreased of POMC. Maternal obesity during lactation malprograms rat offspring to develop obesity that is associated with impairment of melanocortin system. Indeed, rat offspring displayed glucose dyshomeostasis and both peripheral and central insulin resistance.

Tobacco smoking and breastfeeding: Effect on the lactation process, breast milk composition and infant development. A critical review

Approximately 10% of women report smoking during pregnancy. The number of breastfeeding women who relapse back to smoking is even greater. Smoking may cause adverse changes to the milk's composition by not only reducing its protective properties, but also by affecting the infant's health. The pathophysiological mechanisms underlying these adverse effects are not entirely known. This article is a review of previous reports about the effects of smoking on the lactation process, breast milk composition and infant development. A systematic search for English language articles published until 2015 was made, using a MEDLINE data. The key search terms were "smoking and breastfeeding", "smoking and lactation", "smoking and milk composition", "nicotine and breast milk". Studies have shown that nicotine levels in breast milk of women who smoke are three times higher than those in the plasma levels. Breast milk volume is reduced and the duration of lactation period is shorter. Smoking causes adverse changes to the milk's composition by not only reducing its protective properties, but also affecting infants' response to breastfeeding and to breast milk.

Exposure to Tobacco Metabolites via Breast Milk and Infant Weight Gain: A Population-Based Study

BACKGROUND

Although the immutable benefits of breastfeeding are well documented, information on the potential consequences of exposure to tobacco metabolites specifically via breastfeeding is sparse.

OBJECTIVE

The aim was to conduct the first study of the association between exposure to tobacco metabolites specifically through breastfeeding and infant weight gain.

METHODS

We used historical data from the US Collaborative Perinatal Project. Mothers were classified as nonsmokers, light smokers (1-19 cigarettes/day), and heavy (20+ cigarettes/day) smokers. In-hospital feeding type was observed during a nursery stay after delivery. We conducted stratified analyses among average-for-gestational-age (AGA; N = 23 571) and small-for-gestational-age (SGA; N = 2552) infants. We isolated the effect of exposure to tobacco metabolites specifically through breastfeeding.

RESULTS

Overall, maternal smoking was associated with change in weight-for-length z-score in a dose-response manner. Change in weight z-score was most pronounced among SGA infants of heavy smokers (breastfed: 0.53; 95% confidence interval [CI], 0.12-0.94; formula fed: 0.17; 95% CI, 0.03-0.30). Exposure to tobacco metabolites specifically through breastfeeding was not associated with additional weight gain among AGA infants. Among the much smaller sample of SGA infants, exposure specifically through breastfeeding was associated with marginally significant additional weight gain (0.46; 95% CI, 0.00-0.91) among infants of heavy smokers.

CONCLUSION

Our findings are in accord with recommendations by health agencies for smokers to breastfeed. However, SGA infants exposed to tobacco metabolites via breastfeeding by heavy smokers appear to gain weight more rapidly than other infants. Practical implications of our findings are discussed.

Effects of prenatal and lactation nicotine exposure on glucose homeostasis, lipogenesis and lipid metabolic profiles in mothers and offspring

There is increasing evidence suggesting that maternal nicotine (NIC) exposure alone can lead to many deleterious consequences in the fetus. In this study, we aimed to evaluate the effects of prenatal and lactation NIC exposure on glucose homeostasis, lipogenesis and lipid metabolism in mothers and pups. After maternal NIC exposure (from gestational day 9 to weaning), NIC mothers showed lower body weight, decreased parametrial white adipose tissue (pWAT) and inguinal WAT weights, lower homeostasis model assessment of beta cell function, higher serum total cholesterol (TC) and low-density lipoprotein cholesterol levels, higher Castelli index values, lower hepatic mRNA levels of sterol regulatory element binding protein-1c (SREBP1c), lipoprotein lipase, acetyl-CoA carboxylase, fatty acid synthase (FAS) and glucose transporters 4 (GLUT4), as well as lower SREBP1c, FAS, leptin and GLUT4 mRNA levels in pWAT. However, female NIC pups presented higher body weights and serum TC levels, and increased trends for high density lipoprotein-cholesterol and Castelli index I. Male NIC pups had higher body weight, serum TC levels and Castelli index I values, and lower glycemia levels. Additionally, hepatic and adipose FAS gene expression from the female NIC pups presented a decreasing trend, while the male NIC pups had lower hepatic FAS expression and higher adipose FAS expression. In conclusion, prenatal and lactation NIC exposure induced deleterious effects on the glucose homeostasis, lipogenesis and lipid metabolism in both mothers and pups, which may promote several important metabolic disorders in the progeny. Additionally, there are gender-specific effects on pups.

Developmental fluoxetine exposure increases behavioral despair and alters epigenetic regulation of the hippocampal BDNF gene in adult female offspring

A growing number of infants are exposed to selective serotonin reuptake inhibitor (SSRI) medications during the perinatal period. Perinatal exposure to SSRI medications alter neuroplasticity and increase depressive- and anxiety-related behaviors, particularly in male offspring as little work has been done in female offspring to date. The long-term effects of SSRI on development can also differ with previous exposure to prenatal stress, a model of maternal depression. Because of the limited work done on the role of developmental SSRI exposure on neurobehavioral outcomes in female offspring, the aim of the present study was to investigate how developmental fluoxetine exposure affects anxiety and depression-like behavior, as well as the regulation of hippocampal brain-derived neurotrophic factor (BDNF) signaling in the hippocampus of adult female offspring. To do this female Sprague-Dawley rat offspring were exposed to prenatal stress and fluoxetine via the dam, for a total of four groups of female offspring: 1) No Stress+Vehicle, 2) No Stress+Fluoxetine, 3) Prenatal Stress+Vehicle, and 4) Prenatal Stress+Fluoxetine. Primary results show that, in adult female offspring, developmental SSRI exposure significantly increases behavioral despair measures on the forced swim test, decreases hippocampal BDNF exon IV mRNA levels, and increases levels of the repressive histone 3 lysine 27 tri-methylated mark at the corresponding promoter. There was also a significant negative correlation between hippocampal BDNF exon IV mRNA levels and immobility in the forced swim test. No effects of prenatal stress or developmental fluoxetine exposure were seen on tests of anxiety-like behavior. This research provides important evidence for the long-term programming effects of early-life exposure to SSRIs on female offspring, particularily with regard to affect-related behaviors and their underlying molecular mechanisms.

Neonatal Nicotine Exposure Leads to Hypothalamic Gliosis in Adult Overweight Rats

Astrocytes and microglia, the immune competent cells of central nercous system, can be activated in response to metabolic signals such as obesity and hyperleptinaemia. In rats, maternal exposure to nicotine during lactation leads to central obesity, hyperleptinaemia, leptin resistance and alterations in hypothalamic neuropeptides in the offspring during adulthood. In the present study, we studied the activation of astrocytes and microglia, as well as the pattern of inflammatory mediators, in adult offspring of this experimental model. On postnatal day 2 (P2), osmotic minipumps releasing nicotine (NIC) (-6 mg/kg/day) or saline for 14 days were s.c. implanted in dams. Male offspring were killed on P180 and hypothalamic immunohistochemistry, retroperitoneal white adipose tissue (WAT) polymerase chain reaction analysis and multiplex analysis for plasma inflammatory mediators were carried out. At P180, NIC astrocyte cell number was higher in the arcuate nucleus (ARC) (medial: +82%; lateral: +110%), in the paraventricular nucleus (PVN) (+144%) and in the lateral hypothalamus (+121%). NIC glial fibrillary acidic protein fibre density was higher in the lateral ARC (+178%) and in the PVN (+183%). Interleukin-6 was not affected in the hypothalamus. NIC monocyte chemotactic protein 1 was only higher in the periventricular nucleus (+287%). NIC microglia (iba-1-positive) cell number was higher (+68%) only in the PVN, as was the chemokine (C-X3-C motif) receptor 1 density (+93%). NIC interleukin-10 was lower in the WAT (-58%) and plasma (-50%). Thus, offspring of mothers exposed to nicotine during lactation present hypothalamic astrogliosis at adulthood and microgliosis in the PVN.

Prenatal stress and early-life exposure to fluoxetine have enduring effects on anxiety and hippocampal BDNF gene expression in adult male offspring

With the growing use of selective serotonin reuptake inhibitor medications (SSRIs) for the treatment of depression during the perinatal period, questions have been raised about the longterm impact of these medications on development. We aimed to investigate how developmental SSRI exposure may alter affect-related behaviors and associated molecular processes in offspring using a rodent model of maternal stress and depression. For this purpose, prenatally stressed or non-stressed male offspring were exposed to fluoxetine (5 mg/kg/day) or vehicle, via lactation, until weaning. Primary results show that postnatal fluoxetine exposure differentially altered anxiety-like behavior by increasing anxiety in non-stressed offspring and decreasing anxiety in prenatally stressed offspring. In the hippocampus, developmental fluoxetine exposure decreased BDNF IV and TrkB mRNA expression. Prenatal stress alone also decreased escape behaviors and decreased hippocampal BDNF IV mRNA expression. These data provide important evidence for the long-term programming effects of early-life exposure to SSRIs on brain and behavior.

Developmental nicotine exposure enhances inhibitory synaptic transmission in motor neurons and interneurons critical for normal breathing

Nicotine exposure in utero negatively affects neuronal growth, differentiation, and synaptogenesis. We used rhythmic brainstems slices and immunohistochemistry to determine how developmental nicotine exposure (DNE) alters inhibitory neurotransmission in two regions essential to normal breathing, the hypoglossal motor nucleus (XIIn), and preBötzinger complex (preBötC). We microinjected glycine or muscimol (GABAA agonist) into the XIIn or preBötC of rhythmic brainstem slices from neonatal rats while recording from XII nerve roots to obtain XII motoneuron population activity. Injection of glycine or muscimol into the XIIn reduced XII nerve burst amplitude, while injection into the preBötC altered nerve burst frequency. These responses were exaggerated in preparations from DNE animals. Quantitative immunohistochemistry revealed a significantly higher GABAA receptor density on XII motoneurons from DNE pups. There were no differences in GABAA receptor density in the preBötC, and there were no differences in glycine receptor expression in either region. Nicotine, in the absence of other chemicals in tobacco smoke, alters normal development of brainstem circuits that are critical for normal breathing.

Maternal tobacco smoke increased visceral adiposity and serum corticosterone levels in adult male rat offspring

BACKGROUND

Maternal tobacco smoke (MTS) predisposes human and rat offspring to visceral obesity in early adulthood. Glucocorticoid excess also causes visceral obesity. We hypothesized that in utero MTS would increase visceral adiposity and alter the glucocorticoid pathway in young adult rats.

METHODS

We developed a novel model of in utero MTS exposure in pregnant rats by exposing them to cigarette smoke from E11.5 to term. Neonatal rats were cross-fostered to control dams and weaned to standard rat chow through young adulthood (postnatal day 60).

RESULTS

We demonstrated increased visceral adiposity (193%)*, increased visceral adipose 11-β hydroxysteroid dehydrogenase 1 mRNA (204%)*, increased serum corticosterone (147%)*, and no change in glucocorticoid receptor protein in adult male MTS rat offspring. Female rats exposed to MTS in utero demonstrated no change in visceral or subcutaneous adiposity, decreased serum corticosterone (60%)*, and decreased adipose glucocorticoid receptor protein (66%)*. *P < 0.05.

CONCLUSION

We conclude that in utero MTS exposure increased visceral adiposity and altered in the glucocorticoid pathway in a sex-specific manner. We speculate that in utero MTS exposure programs adipose dysfunction in adult male rat offspring via alteration in the glucocorticoid pathway.

Bone metabolism in obese rats programmed by early weaning

OBJECTIVE

Obesity and osteoporosis seem to have a common pathogenesis, especially because bone and adipose tissue have common origins. Since early weaning (EW) decreases adipogenesis and osteogenesis in neonate, further programming for obesity and hyperleptinemia, we hypothesized that these changes in adipogenesis could affect bone metabolism.

MATERIALS/METHODS

Lactating rats were separated into 3 groups: control - dams whose pups ate milk throughout lactation; mechanical EW (MEW) - dams were involved with a bandage interrupting suckling in the last 3days of lactation; pharmacological EW (PEW) - dams were bromocriptine-treated (0.5mg/twice a day via intraperitoneal injection) 3days before weaning. The adult offspring was subjected to dual-energy X-ray absorptiometry and bone tissue was also evaluated by computed tomography, microcomputed tomography and biomechanical tests, beyond serum analyses.

RESULTS

MEW and PEW presented higher total bone mineral density (BMD), total bone mineral content, spine BMD and bone area in postnatal day 150 (PN150). In PN180, both groups also presented increase of these parameters and higher femur BMD and fourth lumbar vertebra (LV4) BMD, femoral head radiodensity and LV4 vertebral body radiodensity, trabecular number, stiffness and break load; lower trabecular separation, maximal deformation and break deformation, and also hyperleptinemia and higher visceral fat mass and 25-hydroxivitamin D, whereas parathyroid hormone was unchanged. Serum C-terminal cross-linked telopeptide of type I collagen was lower for both groups.

CONCLUSIONS

Since both models program for obesity and increased bone mass, and leptin increases plasma vitamin D levels, probably leptin is the link between obesity and higher bone mass.

The hijacking of cellular signaling and the diabetes epidemic: mechanisms of environmental disruption of insulin action and glucose homeostasis

The burgeoning epidemic of metabolic disease causes significant societal and individual morbidity and threatens the stability of health care systems around the globe. Efforts to understand the factors that contribute to metabolic derangements are critical for reversing these troubling trends. While excess caloric consumption and physical inactivity superimposed on a susceptible genetic background are central drivers of this crisis, these factors alone fail to fully account for the magnitude and rapidity with which metabolic diseases have increased in prevalence worldwide. Recent epidemiological evidence implicates endocrine disrupting chemicals in the pathogenesis of metabolic diseases. These compounds represent a diverse array of chemicals to which humans are exposed via multiple routes in adulthood and during development. Furthermore, a growing ensemble of animal- and cell-based studies provides preclinical evidence supporting the hypothesis that environmental contaminants contribute to the development of metabolic diseases, including diabetes. Herein are reviewed studies linking specific endocrine disruptors to impairments in glucose homeostasis as well as tying these compounds to disturbances in insulin secretion and impairments in insulin signal transduction. While the data remains somewhat incomplete, the current body of evidence supports the hypothesis that our chemically polluted environment may play a contributing role in the current metabolic crisis.

The effect of grand maternal nicotine exposure during gestation and lactation on lung integrity of the F2 generation

BACKGROUND

Maternal nicotine exposure during gestation and lactation adversely affects lung development in the offspring. It has been suggested that the "program" that control long-term maintenance of the structural integrity of the lung may be compromised. The aim of the study was to establish whether the effect of grand-maternal nicotine exposure during gestation and lactation can be transferred to the F2 generation.

METHODS

After mating, rats were randomly divided into two groups (F0). One group received nicotine (1 mg/kg body weight/day). The controls receive saline. Body weight (BW), lung volume (Lv), linear intercept (Lm), alveolar wall thickness (Tsept), senescent and proliferating cell numbers were used to evaluate changes in the lung structure of the offspring (F1). The F1 generation was divided into four groups, namely, (1) control (F1 males mated with F1 females, (2) NmCf (F1 nicotine exposed male mated with F1 control female), (3) NfCm (F1 nicotine exposed female mated with F1 control male), and (4) NmNf (F1 male exposed to nicotine mated with F1 female also exposed to nicotine). The F1 nicotine exposed males and females were exposed to nicotine via the placenta and mother's milk (F0 generation) only. The F2 progeny was never exposed to nicotine.

DISCUSSION

Grand-maternal nicotine (F0) resulted in parenchymal deterioration and emphysema in the F2 progeny due to increased numbers of premature senescent cells together with a slower cell proliferation. The transfer of premature aging characteristics from the F1 progeny to the F2 progeny is via the male and female germ cell line.

CONCLUSION

Grand-maternal nicotine exposure induces structural changes in the lungs of the F2 generation that resembled premature aging.

Endocrine effects of tobacco smoke exposure during lactation in weaned and adult male offspring

Children from pregnant smokers show more susceptibility to develop obesity in adult life. Previously, we failed to demonstrate a program for obesity in rat offspring only when the mothers were exposed to tobacco smoke during lactation. Here, we studied the short- and long-term effects of smoke exposure (SE) to both dams and their pups during lactation on endocrine and metabolic parameters. For this, we designed an experimental model where nursing rats and their pups were divided into two groups: SE group, exposed to smoke in a cigarette smoking machine (four times/day, from the third to the 21st day of lactation), and group, exposed to filtered air. Pups were killed at 21 and 180 days. At weaning, SE pups showed lower body weight (7%), length (5%), retroperitoneal fat mass (59%), visceral adipocyte area (60%), and higher subcutaneous adipocyte area (95%) with hypoinsulinemia (-29%), hyperthyroxinemia (59%), hypercorticosteronemia (60%), and higher adrenal catecholamine content (+58%). In adulthood, SE offspring showed higher food intake (+10%), body total fat mass (+50%), visceral fat mass (retroperitoneal: 55%; mesenteric: 67%; and epididymal: 55%), and lower subcutaneous adipocyte area (24%) with higher serum glucose (11%), leptin (85%), adiponectin (1.4-fold increase), total triiodothyronine (71%), free thyroxine (57%), TSH (36%), triglycerides (65%), VLDL cholesterol (+66%), and HDL cholesterol (91%) levels and lower corticosteronemia (41%) and adrenal catecholamine content (57%). Our present findings suggest that tobacco SE to both dams and their pups during lactation causes malnutrition in early life that programs for obesity and hormonal and metabolic disturbances in adulthood, only if the pups are submitted to the same smoke environment as the mother.

Prenatal nicotine exposure enhances the trigeminocardiac reflex via serotonin receptor facilitation in brainstem pathways

In this study we used a rat model for prenatal nicotine exposure to test whether clinically relevant concentrations of brain nicotine and cotinine are passed from dams exposed to nicotine to her pups, whether this changes the trigeminocardiac reflex (TCR), and whether serotonergic function in the TCR brainstem circuitry is altered. Pregnant Sprague-Dawley dams were exposed to 6 mg·kg(-1)·day(-1) of nicotine via osmotic minipumps for the duration of pregnancy. Following birth dams and pups were killed, blood was collected, and brain nicotine and cotinine levels were measured. A separate group of prenatal nicotine-exposed pups was used for electrophysiological recordings. A horizontal brainstem slice was obtained by carefully preserving the trigeminal nerve with fluorescent identification of cardiac vagal neurons (CVNs) in the nucleus ambiguus. Stimulation of the trigeminal nerve evoked excitatory postsynaptic current in CVNs. Our data demonstrate that prenatal nicotine exposure significantly exaggerates both the TCR-evoked changes in heart rate in conscious unrestrained pups, and the excitatory neurotransmission to CVNs upon trigeminal afferent nerve stimulation within this brainstem reflex circuit. Application of the 5-HT1A receptor antagonist WAY 100635 (100 μM) and 5-HT2A/C receptor antagonist ketanserin (10 μM)significantly decreased neurotransmission, indicating an increased facilitation of 5-HT function in prenatal nicotine-exposed animals. Prenatal nicotine exposure enhances activation of 5-HT receptors and exaggerates the trigeminocardiac reflex.

Maternal nicotine exposure during lactation alters hypothalamic neuropeptides expression in the adult rat progeny

Maternal exposure to nicotine during lactation causes hyperleptinemia in the pups and, at adulthood, these animals are overweight and hyperleptinemic, while, in their hypothalamus, the leptin signaling pathway is reduced, evidencing a central leptin resistance. Then, we evaluated the expression of pro-opiomelanocortin (POMC), alpha-melanocyte stimulating hormone (α-MSH), cocaine and amphetamine-regulated transcript (CART), neuropeptide Y (NPY), agouti-related peptide (AgRP) and others in different hypothalamic nuclei in order to better understand the mechanisms underlying the obese phenotype observed in these animals at adulthood. On the 2nd postnatal day (P2), dams were subcutaneously implanted with osmotic minipumps releasing nicotine (NIC-6 mg/kg/day) or saline for 14 days. Offspring were killed in P180 and immunohistochemistry and Western blot analysis were carried out. Significance data had p<0.05. Adult NIC offspring showed more intense NPY staining in the paraventricular nucleus (PVN) (+21%) and increased number of POMC-positive cells in the: arcuate nucleus (+33%), as an increase in fiber density of α-MSH in PVN (+85%). However, the number of CART-positive cells was reduced in the PVN (-25%). CRH staining was more intense in NIC offspring (+136%). Orexins and AgRP were not altered. Thus, maternal nicotine exposure changes hypothalamic neuropeptides in the adult progeny that is partially compatible with leptin resistance.

Obesity and endocrine dysfunction programmed by maternal smoking in pregnancy and lactation

Obesity is a global epidemic, and maternal smoking has been shown to be associated with the development of childhood obesity. Overall, approximately 40% of children worldwide are exposed to tobacco smoke at home. It is well known that environmental changes within a critical window of development, such as gestation or lactation, can initiate permanent alterations in metabolism that lead to diseases in adulthood, a phenomenon called programming. It is known that programming is based on epigenetic alterations (changes in DNA methylation, histone acetylation, or small interfering RNA expression) that change the expression pattern of several genes. However, little is known concerning the mechanisms by which smoke exposure in neonatal life programs the adipose tissue and endocrine function. Here, we review several epidemiological and experimental studies that confirm the association between maternal nicotine or tobacco exposure during gestation or lactation and the development of obesity and endocrine dysfunction. For example, a positive correlation was demonstrated in rodents between increased serum leptin in the neonatal period and exposure of the mothers to nicotine during lactation, and the further development of leptin and insulin resistance, and thyroid and adrenal dysfunction, in adulthood in the same offspring. Thus, a smoke-free environment during the lactation period is essential to improving health outcomes in adulthood and reducing the risk for future diseases. An understanding of the pathophysiological mechanisms underlying the effects of smoking on programming can provide new insights into therapeutic strategies for obesity.

Role of environmental chemicals in diabetes and obesity: a National Toxicology Program workshop review

BACKGROUND

There has been increasing interest in the concept that exposures to environmental chemicals may be contributing factors to the epidemics of diabetes and obesity. On 11-13 January 2011, the National Institute of Environmental Health Sciences (NIEHS) Division of the National Toxicology Program (NTP) organized a workshop to evaluate the current state of the science on these topics of increasing public health concern.

OBJECTIVE

The main objective of the workshop was to develop recommendations for a research agenda after completing a critical analysis of the literature for humans and experimental animals exposed to certain environmental chemicals. The environmental exposures considered at the workshop were arsenic, persistent organic pollutants, maternal smoking/nicotine, organotins, phthalates, bisphenol A, and pesticides. High-throughput screening data from Toxicology in the 21st Century (Tox21) were also considered as a way to evaluate potential cellular pathways and generate -hypotheses for testing which and how certain chemicals might perturb biological processes related to diabetes and obesity.

CONCLUSIONS

Overall, the review of the existing literature identified linkages between several of the environmental exposures and type 2 diabetes. There was also support for the "developmental obesogen" hypothesis, which suggests that chemical exposures may increase the risk of obesity by altering the differentiation of adipocytes or the development of neural circuits that regulate feeding behavior. The effects may be most apparent when the developmental exposure is combined with consumption of a high-calorie, high-carbohydrate, or high-fat diet later in life. Research on environmental chemical exposures and type 1 diabetes was very limited. This lack of research was considered a critical data gap. In this workshop review, we outline the major themes that emerged from the workshop and discuss activities that NIEHS/NTP is undertaking to address research recommendations. This review also serves as an introduction to an upcoming series of articles that review the literature regarding specific exposures and outcomes in more detail.