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.

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 (Leprb, 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.

Nicotine exposure during breastfeeding reduces sympathetic activity in brown adipose tissue and increases in white adipose tissue in adult rats: Sex-related differences.

Nicotine transfer via breast milk induces obesity in the adult offspring. We hypothesize that sympathetic nervous system (SNS) activity, brown adipose tissue (BAT) thermogenesis and white adipose tissue (WAT) lipogenesis/adipogenesis are altered in adult rats that were exposed to nicotine exclusively during the breastfeeding period. Lactating Wistar rats were separated into two groups: nicotine (NIC), dams implanted with osmotic minipumps containing 6 mg/kg of nicotine at postnatal day (PN) 2; control, dams were implanted with saline-containing minipumps. Euthanasia occurred at PN120 or PN180. NIC offspring had lower BAT SNS activity and higher BAT lipid content. NIC males showed lower UCP1, ß3-AR and CPT1a, while NIC females showed lower UCP1, TRα1, CPT1a, suggesting lower thermogenesis. NIC males showed higher WAT SNS activity, WAT ß3-AR, adrenal catecholamine, FAS, PPARγ and adipocytes area, while NIC females showed higher ACC, FAS, CEBPß and PPARγ. These findings indicate increased lipogenesis/adipogenesis in both sexes, with a possible compensatory sympathetic activated-lipolysis in males. NIC males had higher hypothalamic pAMPK/AMPK, explaining the lower BAT sympathetic activity. Neonatal nicotine exposure reduces BAT SNS activity and thermogenesis, and, only in males, increases WAT adipogenesis/lipogenesis, despite higher WAT SNS activity. These alterations can be associated with obesogenesis in this programming model.

Hypothalamic Neuropeptides Expression and Hypothalamic Inflammation in Adult Rats that Were Exposed to Tobacco Smoke during Breastfeeding: Sex-Related Differences.

The hypothalamus controls food intake and energy expenditure. In rats, maternal exposure to nicotine during breastfeeding alters the hypothalamic circuitry of the adult offspring, resulting in leptin resistance, neuropeptides changes and gliosis. Tobacco smoke exposure during lactation causes greater adiposity, hyperphagia and hyperleptinemia in the adult progeny. To understand the central mechanisms underlying the obese phenotype of adult rats that were directly and indirectly exposed to cigarette smoke during lactation, we investigated leptin signaling, orexigenic and anorexigenic neuropeptides expression, as well as astrocyte and microglia markers in hypothalamus. From postnatal day (PND) 3 to 21, Wistar lactating rat dams and their pups were divided into two groups: SE, smoke-exposed in a cigarette-smoking machine (four times/day); Crtl, exposed to filtered air. Offspring of both sexes were euthanized at PND180. The leptin pathway was not altered in SE animals from both sexes. SE males showed increased NPY (arcuate nucleus, ARC), CRH (paraventricular nucleus, PVN), as well as higher GFAP fiber density (ARC and PVN) and IL6 protein content. TRH (PVN) immunohistochemistry was reduced. SE females had lower CART-positive cells (ARC) and lower α-MSH immunostaining intensity (PVN and lateral hypothalamus), with no change of GFAP or IL-6. The protein contents of CX3CR1 (marker of activated microglia) and α7nAChR (anti-inflammatory marker) were not altered in both SE males and females. Neonatal cigarette smoke is deleterious to the hypothalamic circuitry, inducing changes in energy homeostasis favoring hyperphagia and decreased energy expenditure at adulthood in both sexes; however sex-dependent mechanisms were observed.

Cigarette smoke during lactation in rat female progeny: Late effects on endocannabinoid and dopaminergic systems.

AIMS: Maternal smoking is considered a risk factor for childhood obesity. In a rat model of tobacco exposure during breastfeeding, we previously reported hyperphagia, overweight, increased visceral fat and hyperleptinemia in adult female offspring. Obesity and eating disorders are associated with impairment in the endocannabinoid (EC) and dopaminergic (DA) systems. Considering that women are prone to eating disorders, we hypothesize that adult female Wistar rats that were exposed to cigarette smoke (CS) during the suckling period would develop EC and DA systems deregulation, possibly explaining the eating disorder in this model. MATERIAL AND METHODS: To mimic maternal smoking, from postnatal day 3 to 21, dams and offspring were exposed to a smoking machine, 4×/day/1 h (CS group). Control animals were exposed to ambient air. Offspring were evaluated at 26 weeks of age. KEY FINDINGS: Concerning the EC system, the CS group had increased expression of diacylglycerol lipase (DAGL) in the lateral hypothalamus (LH) and decreased in the liver. In the visceral adipose tissue, the EC receptor (CB1r) was decreased. Regarding the DA system, the CS group showed higher dopamine transporter (DAT) protein expression in the prefrontal cortex (PFC) and lower DA receptor (D2r) in the arcuate nucleus (ARC). We also assessed the hypothalamic leptin signaling, which was shown to be unchanged. CS offspring showed decreased plasma 17ß-estradiol. SIGNIFICANCE: Neonatal CS exposure induces changes in some biomarkers of the EC and DA systems, which can partially explain the hyperphagia observed in female rats.

Neonatal tobacco smoke reduces thermogenesis capacity in brown adipose tissue in adult rats.

Maternal smoking is a risk factor for progeny obesity. We have previously shown, in a rat model of neonatal tobacco smoke exposure, a mild increase in food intake and a considerable increase in visceral adiposity in the adult offspring. Males also had secondary hyperthyroidism, while females had only higher T4. Since brown adipose tissue (BAT) hypofunction is related to obesity, here we tested the hypothesis that higher levels of thyroid hormones are not functional in BAT, suggesting a lower metabolic rate. We evaluated autonomic nerve activity in BAT and its function in adult rats that were exposed to tobacco smoke during lactation. At birth, litters were adjusted to 3 male and 3 female pups/litter. From postnatal day (PND) 3 to 21, Wistar lactating rats and their pups were divided into SE group, smoke-exposed in a cigarette smoking machine (4 times/day) and C group, exposed to filtered air. Offspring were sacrificed at PND180. Adult SE rats of both genders had lower interscapular BAT autonomic nervous system activity, with higher BAT mass but no change in morphology. BAT UCP1 and CPT1a protein levels were decreased in the SE groups of both genders. Male SE rats had lower ß3-AR, TRα1, and TRß1 expression while females showed lower PGC1α expression. BAT Dio2 mRNA and hypothalamic POMC and MC4R levels were similar between groups. Hypothalamic pAMPK level was higher in SE males and lower in SE females. Thus, neonatal cigarette smoke exposure induces lower BAT thermogenic capacity, which can be obesogenic at adulthood.

High calcium diet improves the liver oxidative stress and microsteatosis in adult obese rats that were overfed during lactation.

Obesity is related to diabetes, higher oxidative stress and nonalcoholic fatty liver disease, and dietetic therapies, for instance calcium-rich diet, can improve these dysfunctions. Rats raised in small litters (SL) had increased fat depots and insulin resistance at adulthood associated with higher liver oxidative stress and microsteatosis. Thus, we evaluated if dietary calcium can improve these changes. In PN3, litter size was adjusted to 3 pups (SL group) to induce overfeeding, while controls had 10 pups until weaning. At PN120, SL group was randomly divided into: rats fed with standard chow or fed with calcium supplementation (SL-Ca group, 10 g/kg chow) for 60 days. At PN180, dietary calcium normalized food consumption, visceral fat, plasma aspartate aminotransferase (AST) and glycaemia. Concerning oxidative balance, calcium restored both higher hepatic lipid peroxidation and protein carbonylation as well as higher plasma lipid peroxidation. Higher fatty acid synthase (FAS) content, steatosis and lower protein kinase B (Akt) in SL group were normalized by dietary calcium and SL-Ca rats had lower hepatic cholesterol. Thus, calcium supplementation improved the insulin sensitivity, redox balance and steatosis in the liver. Therefore, dietary calcium can be a promising therapy for liver disease in the metabolic syndrome.