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

Maternal nicotine exposure impairs brown adipose tissue via AMPK-SIRT1-PGC-1α signals in male offspring

AIMS

Maternal nicotine exposure during pregnancy and lactation is associated with obesity in offspring. Brown adipose tissue (BAT) is correlated with energy metabolism and obesity. In this study, we explored the mechanism of maternal nicotine exposure on BAT changes in male offspring.

MAIN METHODS

Pregnant rats were randomly assigned to nicotine (1.0 mg/kg twice per day, subcutaneous administration) or control groups. In vitro, C3H10T1/2 cells were induced to differentiate into mature brown adipocytes, and 0-50 μM nicotine was given to C3H10T1/2 cells during the differentiation process.

KEY FINDINGS

Nicotine-exposed males had white-like adipocytes and abnormal mitochondria structure in iBAT at 26 weeks. The expression of mitochondrial genes, UCP1 and AMPK-SIRT1-PGC-1α pathway were downregulated in the nicotine group at 26 weeks rather than 4 weeks. In vitro, 50 μM nicotine decreased the expression of mitochondrial genes, UCP1 and AMPK-SIRT1-PGC-1α pathway in brown adipocytes.

SIGNIFICANCE

Maternal nicotine exposure showed the "programming" effect on the decreased brown-like phenotype in BAT of adult male offspring via downregulating AMPK-SIRT1-PGC-1α pathway. This impairment of BAT may be a potential mechanism of nicotine-induced obesity in male offspring.

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.

Effects of prenatal nicotine exposure on hepatic glucose and lipid metabolism in offspring rats and its hereditability

Prenatal nicotine exposure (PNE) could induce an increased susceptibility to multiple chronic diseases in adult offspring, that mainly caused by intrauterine maternal glucocorticoid (GC) over-exposure. We investigated the changes and inheritability of hepatic glucose and lipid metabolism caused by PNE, to decipher the possible intrauterine programming mechanism. Pregnant Wistar rats were administered subcutaneously with 2 mg/kg·d nicotine from gestational day (GD) 9∼20, and second-generation (F2) were set according to the mating between control females and PNE males. The results showed that serum phenotypes and hepatic enzymes of glucose and lipid metabolism were lower in F1 fetal rats of PNE but higher in the F1 adult rats. Meanwhile, the activated states of hepatic glucocorticoid-activation system, including type 1 and type 2 11β-hydroxysteroid dehydrogenases (Hsd11b1/2), nuclear receptor subfamily 3, group C, member 1 (Nr3c1) and CCAAT enhancer binding protein α (Cebpa), were positively correlated with serum corticosterone levels but negatively correlated with the histone acetylation (H3K27ac) and expression levels of insulin-like growth factor 1 (Igf1) before and after birth. Furthermore, serum phenotypes and hepatic enzymes of glucose and lipid metabolism were lower in both F2 fetal and adult rats of PNE, which were consistent with the hepatic changes of GC-IGF1 axis and the glucocorticoid-activation system. In conclusion, PNE could lead to inheritable changes of hepatic glucose and lipid metabolism, which are related to the intrauterine programming of GC-IGF1 axis induced by the glucocorticoid-activation system.

Attenuated cholesterol metabolism pathway suppresses regulatory T cell development in prenatal nicotine exposed female mice

The recession of regulatory T cells (Tregs) contributes to development of autoimmune disease. Our previous study suggested that prenatal nicotine exposure (PNE) inhibited Tregs frequency in offspring, but the mechanisms are still uncertain. This study aimed to explore the molecular mechanisms of PNE-induced Tregs inhibition from the perspective of cellular cholesterol homeostasis both in vivo and in vitro. PNE mice model were established by 3 mg/kg/d nicotine administration in Balb/c strain from gestational day (GD) 9 to GD 18. The results showed that PNE significantly decreased thymic Tregs frequency in neonatal offspring. The activation of mTOR and downregulation of p-STAT5/Foxp3 pathway of Tregs were observed in PNE offspring. Mechanism study found that PNE elevated ATP-binding cassette transporter G1 (ABCG1) expression and decreased intracellular cholesterol content of Tregs in offspring, indicating impaired intracellular cholesterol homeostasis. Similar results were observed in 1 μM nicotine-treated primary thymocytes in vitro. Further, cholesterol-replenishment can abrogate nicotine-induced mTOR activation and the following suppression of p-STAT5/Foxp3 pathway and Tregs frequency. In addition, Abcg1 siRNA transfection can partly reverse the nicotine-decreased intracellular cholesterol content and cell frequency of Tregs. In conclusion, this study showed that PNE could suppress Tregs development in female mice by up-regulating ABCG1-dependent cholesterol efflux, and suggested that PNE-induced thymic Tregs recession of offspring at early life was the developmental origin mechanism of immune dysfunction in later life.

The association between maternal nicotine exposure and adipose angiogenesis in female rat offspring: A mechanism of adipose tissue function changes

Maternal smoking during pregnancy and lactation is associated with increased fat mass in the offspring, but the mechanism by which this occurs is not fully understood. Our study focused on the relationships among maternal nicotine exposure, adipose angiogenesis and adipose tissue function in female offspring. Pregnant rats were randomly assigned to nicotine or control groups. Microvascular density, lipid metabolism and α7nAChR-Egr1-FGF2 signaling pathway genes/proteins were tested in 4-, 12- and 26-week female offspring. In vitro, nicotine concentration- and time-response experiments were conducted in 3T3-L1. Lipid metabolism and α7nAChR-Egr1-FGF2 signaling pathway genes/proteins were tested. The conditioned media of differentiated 3T3-L1 treated with nicotine were used to observe tube formation in human umbilical vein endothelial cells (HUVECs). Nicotine-exposed females presented higher adipose microvascular density. The gene expression of α7nAChR, Egr1 and FGF2 was significantly increased in gonadal white adipose tissue (gWAT) and inguinal subcutaneous WAT (igSWAT) of nicotine-exposed females at 4 weeks of age. The protein expression of α7nAChR, Egr1 and FGF2 was increased in gWAT and igSWAT of nicotine-exposed females at 4 weeks of age, and increased in gWAT at 26 weeks. In vitro, nicotine increased the expression of lipid metabolism and α7nAChR-Egr1-FGF2 signaling pathway genes/proteins in a concentration- and time-dependent manner. In the tube formation experiment, adipocytes affected by nicotine promoted HUVEC angiogenesis. Therefore, maternal nicotine exposure promoted the early angiogenesis of adipose tissue via the α7nAChR-Egr1-FGF2 signaling pathway, and this angiogenesis mechanism was associated with increased adipogenesis in adipose tissue of female offspring.

Cigarette Smoke During Breastfeeding in Rats Changes Glucocorticoid and Vitamin D Status in Obese Adult Offspring

Maternal smoking increases obesogenesis in the progeny. Obesity is associated with several hormonal dysfunctions. In a rat model of postnatal tobacco smoke exposure, we previously reported increased central fat depot and disruption of some hormonal systems in the adult offspring. As both glucocorticoids and vitamin D alter lipogenesis and adipogenesis, here we evaluated the metabolism of these two hormones in visceral adipose tissue (VAT) and liver by Western blotting, and possible associations with lipogenesis biomarkers in adult rats that were exposed to tobacco smoke during their suckling period. At postnatal day (PN) 3, dams and offspring of both sexes were exposed (S group) or not (C group) to tobacco smoke, 4 × 1 h/day. At PN180, corticosteronemia was lower in S male and higher in S female offspring, without alterations in peripheral glucocorticoid metabolism and receptor. Adrenal ACTH receptor (MC2R) was higher in both sexes of S group. Despite unchanged serum vitamin D, liver 25-hydroxylase was higher in both sexes of S group. Male S offspring had higher 1α-hydroxylase, acetyl-CoA carboxylase (ACC), and fatty acid synthase (FAS) in VAT. Both sexes showed increased ACC protein content and reduced sirtuin mRNA in liver. Male S offspring had lower liver peroxisome proliferator-activated receptor-α. Tobacco exposure during lactation induced abdominal obesity in both sexes via distinct mechanisms. Males and females seem to develop HPA-axis dysfunction instead of changes in glucocorticoid metabolism and action. Lipogenesis in VAT and liver, as well as vitamin D status, are more influenced by postnatal smoke exposure in male than in female adult rat offspring.