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 (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.

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 17β-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.

Early weaning alters the thermogenic capacity of brown adipose tissue in adult male and female rats

PURPOSE

Early weaning (EW) is a risk factor for obesity development. Brown adipose tissue (BAT) hypofunction is related to obesity onset. Here, we evaluated whether sympathetic nervous system (SNS) activity in BAT and the thermogenic function of BAT are decreased in adulthood in obese rats from two EW models.

METHODS

At the time of birth, lactating Wistar rats and their pups (three males and three females) were separated into three groups: the control group, in which pups consumed milk throughout lactation; the non-pharmacological EW (NPEW) group, in which suckling was interrupted with a bandage during the last 3 days of lactation; and the pharmacological EW (PEW) group, in which dams were treated with bromocriptine (0.5 mg/twice a day) 3 days before weaning. The offspring were sacrificed on PN180.

RESULTS

Adult male rats from both EW models exhibited lower BAT SNS activity. Female rats from the PEW group showed a decrease in BAT SNS activity. The protein levels of UCP1 were lower in the NPEW males, while PGC1α levels were lower in both PEW and NPEW males. Both groups of EW females showed reductions in the levels of β3-AR, TRβ1, and PGC1α. The UCP1 protein level was reduced only in the NPEW females. The EW groups of both sexes had lower AMPK protein levels in BAT. In the hypothalamus, only the PEW females showed an increase in AMPK protein levels. In both groups of EW males, adrenal catecholamine was increased and tyrosine hydroxylase was decreased, while in EW females, adrenal catecholamine was decreased.

CONCLUSIONS

Early weaning alters the thermogenic capacity of BAT, which partially contributes to obesity in adulthood, and there are sex-related differences in these alterations.

Treatment with Ilex paraguariensis (yerba mate) aqueous solution prevents hepatic redox imbalance, elevated triglycerides, and microsteatosis in overweight adult rats that were precociously weaned

Early weaning (EW) leads to overweight, visceral obesity, hyperleptinemia, and insulin resistance in adulthood. Treatment with Ilex paraguariensis (yerba mate) improves obesity and insulin resistance in these animals. Here, we evaluated the effects of chronic treatment with yerba mate on the redox balance and liver morphology of overweight early-weaned rats. To induce EW, we wrapped the dams with bandages to interrupt milk access during the last 3 days of lactation. Control pups (C) had free access to maternal milk for the full 21 days of lactation. On postnatal day (PN) 150, EW offspring were subdivided into the EW+YM group, which received the aqueous extract of yerba mate (1 g/kg bw by gavage once a day for 30 days) and the EW group, which received water by gavage for the same period. All rats were euthanized on PN180. The EW group showed higher bound carbonyl (a marker of total protein oxidation), higher TBARS levels (a marker of lipid peroxidation), and lower superoxide dismutase (SOD) activity in liver tissue than the C group, as well as higher triglyceride content and microsteatosis. In plasma, the EW offspring showed higher TBARS levels. One month of yerba mate treatment normalized these parameters. Thus, we have shown evidence that yerba mate improved antioxidant defenses and mitigated liver dysfunction in overweight adult rats that were weaned prematurely.

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 β3-AR, TRα1, and TRβ1 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.

Early redox imbalance is associated with liver dysfunction at weaning in overfed rats

Neonatal overfeeding induced by litter size reduction leads to further obesity and other metabolic disorders, such as liver oxidative stress and microsteatosis at adulthood. We hypothesized that overfeeding causes an early redox imbalance at weaning, which could programme the animals to future liver dysfunction. Thus, we studied lipogenesis, adipogenesis, catecholamine status and oxidative balance in weaned overfed pups. To induce early overfeeding, litters were adjusted to three pups at the 3rd day of lactation (SL group). The control group contained 10 pups per litter until weaning (NL group). Peripheral autonomic nerve function was determined in vivo at 21 days old. Thereafter, pups were killed for further analysis. Differences were considered significant when P < 0.05. The SL pups presented with a higher visceral adipocyte area, higher content of lipogenic enzymes (ACC, FAS) and with a lower content of adipogenic factors (CEBP, PPARγ) in visceral adipose tissue (VAT). Although autonomic nerve activity and adrenal catecholamine production were not significantly altered, catecholamine receptor (β3ADR) content was lower in VAT. The SL pups also presented with higher triglyceride, PPARγ, PPARα and PGC1α contents in liver. In plasma and liver, the SL pups showed an oxidative imbalance, with higher lipid peroxidation and protein oxidation. The SL group presented with a higher serum alanine aminotransferase (ALT). The early increase in lipogenesis in adipose tissue and liver in weaned overfed rats suggests that the higher oxidative stress and lower catecholamine content in VAT are associated with the early development of liver dysfunction and adipocyte hypertrophy.

Calcium reduces vitamin D and glucocorticoid receptors in the visceral fat of obese male rats

Rats overfed during lactation show higher visceral adipose tissue (VAT) mass and metabolic dysfunctions at adulthood. As both vitamin D and glucocorticoids change adipogenesis, parameters related to metabolism and action of these hormones in the adipocyte can be altered in rats raised in small litters (SL). We also studied the antiobesity effects of high calcium diet since it decreases visceral fat in obesity models. On postnatal day (PN) 3, litter size was adjusted to 3pups/dam (SL) to induce overfeeding. Control litters (NL) remained with 10pups/dam until weaning. From PN120 to PN180, half of the SL rats were fed standard chow (SL) and the other half was fed a calcium-supplemented chow (SL-Ca, 10g CaCO3/kg). Both SL groups were heavier and hyperphagic when compared with the NL group; however, SL-Ca rats ate less than SL. SL-Ca rats had decreased VAT mass and adipocyte size, associated with lower hypothalamic NPY content, VAT fat acid synthase content and leptinemia. At PN120, SL rats had increased plasma 25(OH)D3, Cyp27b1 mRNA and glucocorticoid receptor (GR-α) in the VAT, but lower vitamin D receptor (Vdr) mRNA. At PN180, Cyp27b1 and GR-α remained higher, while Vdr normalized in SL rats. SL-Ca rats had normal VAT Cyp27b1 and GR-α, but lower Vdr Thus, higher body mass and glucocorticoid receptors in the VAT of SL rats are normalized by calcium-enriched diet, and Vdr expression in this tissue is reduced, suggesting a possible role of glucocorticoids and vitamin D in calcium action in the adipocyte.

Effect of Early Overfeeding on Palatable Food Preference and Brain Dopaminergic Reward System at Adulthood: Role of Calcium Supplementation

Rats raised in small litters (SL) are obese and hyperphagic. In the present study, we evaluated whether obesity is associated with changes in the mesocorticolimbic dopaminergic reward system in these animals at adulthood. We also assessed the anti-obesity effects of dietary calcium supplementation. To induce early overfeeding, litters were adjusted to three pups on postnatal day (PN)3 (SL group). Control litters were kept with 10 pups each until weaning (NL group). On PN120, SL animals were subdivided into two groups: SL (standard diet) and SL-Ca [SL with calcium supplementation (10 g calcium carbonate/kg rat chow) for 60 days]. On PN175, animals were subjected to a food challenge: animals could choose between a high-fat (HFD) or a high-sugar diet (HSD). Food intake was recorded after 30 min and 12 h. Euthanasia occurred on PN180. SL rats had higher food intake, body mass and central adiposity. Sixty days of dietary calcium supplementation (SL-Ca) prevented these changes. Only SL animals preferred the HFD at 12 h. Both SL groups had lower tyrosine hydroxylase content in the ventral tegmental area, lower dopaminergic transporter content in the nucleus accumbens, and higher type 2 dopamine receptor (D2R) content in the hypothalamic arcuate nucleus (ARC). They also had higher neuropeptide Y (NPY) and lower pro-opiomelanocortin contents in the ARC. Calcium treatment normalised only D2R and NPY contents. Precocious obesity induces long-term effects in the brain dopaminergic system, which can be associated with an increased preference for fat at adulthood. Calcium treatment prevents this last alteration, partially through its actions on ARC D2R and NPY proteins.

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.

Maternal prolactin inhibition causes changes in leptin at 22- and 30-day-old pups

Breastfeeding is associated with obesity prevention. We showed previously that prolactin inhibition at the end of lactation causes hyperleptinemia at weaning (PN21) and programs for obesity, insulin resistance, dyslipidemia, and leptin resistance (PN180). Here, we evaluate the source of neonatal hyperleptinemia and how it develops during the nutritional transition from milk through solid food. Lactating rats were treated with bromocriptine (BRO), a prolactin inhibitor, 0.5 mg twice a day, or saline (CON) for the last 3 days of lactation. All parameters were studied at PN22 and PN30. At PN22, BRO-treated rats showed lower food intake, body mass, and body length. At PN30, only body length and mesenteric fat mass were lower. Despite normal plasma leptin levels at PN22, the adipose tissue leptin mRNA expression was lower, while plasma leptin was higher in PN30, possibly due to a higher adipose mesenteric tissue production. At PN22, the hypothalamus seems to be more sensitive to leptin, since OBR and STAT3 are higher. Conversely, at PN30 leptin signaling pathway is suggestive of leptin resistance with lower STAT3 and higher SOCS3 in hypothalamus and consequently higher NPY. Glycemia was lower at PN22 and higher at PN30, without changes in plasma insulin levels. At PN30, BRO-treated rats had other metabolic changes such as higher plasma cholesterol, lower HDL-c, higher hepatic cholesterol and AST, suggesting a liver dysfunction. Our data show that milk supply can exert a crucial role in the imprinting of a second leptin peak, which is important for survival adaptation to adverse nutritional conditions.

Resveratrol treatment rescues hyperleptinemia and improves hypothalamic leptin signaling programmed by maternal high-fat diet in rats

PURPOSE

Perinatal high-fat diet is associated with obesity and metabolic diseases in adult offspring. Resveratrol has been shown to exert antioxidant and anti-obesity actions. However, the effects of resveratrol on leptinemia and leptin signaling are still unknown as well as whether resveratrol treatment can improve metabolic outcomes programmed by maternal high-fat diet. We hypothesize that resveratrol treatment in male rats programmed by high-fat diet would decrease body weight and food intake, and leptinemia with changes in central leptin signaling.

METHODS

Female Wistar rats were divided into two groups: control group (C), which received a standard diet containing 9 % of the calories as fat, and high-fat group (HF), which received a diet containing 28 % of the calories as fat. Dams were fed in C or HF diet during 8 weeks before mating and throughout gestation and lactation. C and HF male offspring received standard diet throughout life. From 150 until 180 days of age, offspring received resveratrol (30 mg/Kg body weight/day) or vehicle (carboxymethylcellulose).

RESULTS

HF offspring had increased body weight, hyperphagia and increased subcutaneous and visceral fat mass compared to controls, and resveratrol treatment decreased adiposity. HF offspring had increased leptinemia as well as increased SOCS3 in the arcuate nucleus of the hypothalamus, which suggest central leptin resistance. Resveratrol treatment rescued leptinemia and increased p-STAT3 content in the hypothalamus with no changes in SOCS3, suggesting improvement in leptin signaling.

CONCLUSIONS

Collectively, our data suggest that resveratrol could reverse hyperleptinemia and improve central leptin action in adult offspring from HF mothers attenuating obesity.

Effects of maternal nicotine exposure on thyroid hormone metabolism and function in adult rat progeny

Postnatal nicotine exposure leads to obesity and hypothyroidism in adulthood. We studied the effects of maternal nicotine exposure during lactation on thyroid hormone (TH) metabolism and function in adult offspring. Lactating rats received implants of osmotic minipumps releasing nicotine (NIC, 6 mg/kg per day s.c.) or saline (control) from postnatal days 2 to 16. Offspring were killed at 180 days. We measured types 1 and 2 deiodinase activity and mRNA, mitochondrial α-glycerol-3-phosphate dehydrogenase (mGPD) activity, TH receptor (TR), uncoupling protein 1 (UCP1), hypothalamic TRH, pituitary TSH, and in vitro TRH-stimulated TSH secretion. Expression of deiodinase mRNAs followed the same profile as that of the enzymatic activity. NIC exposure caused lower 5'-D1 and mGPD activities; lower TRβ1 content in liver as well as lower 5'-D1 activity in muscle; and higher 5'-D2 activity in brown adipose tissue (BAT), heart, and testis, which are in accordance with hypothyroidism. Although deiodinase activities were not changed in the hypothalamus, pituitary, and thyroid of NIC offspring, UCP1 expression was lower in BAT. Levels of both TRH and TSH were lower in offspring exposed to NIC, which presented higher basal in vitro TSH secretion, which was not increased in response to TRH. Thus, the hypothyroidism in NIC offspring at adulthood was caused, in part, by in vivo TRH-TSH suppression and lower sensitivity to TRH. Despite the hypothyroid status of peripheral tissues, these animals seem to develop an adaptive mechanism to preserve thyroxine to triiodothyronine conversion in central tissues.

Resveratrol prevents hyperleptinemia and central leptin resistance in adult rats programmed by early weaning

We have previously shown that early weaning in rats increases the risk of obesity and insulin resistance at adulthood, and leptin resistance can be a prime factor leading to these changes. Resveratrol is reported to decrease oxidative stress, insulin resistance, and cardiovascular risk. However, there is no report about its effect on leptin resistance. Thus, in this study we have evaluated resveratrol-preventing effect on the development of visceral obesity, insulin, and leptin resistance in rats programmed by early weaning. To induce early weaning, lactating dams were separated into 2 groups: early weaning (EW)--dams were wrapped with a bandage to interrupt lactation in the last 3 days of lactation and control (C)--dams whose pups had free access to milk during throughout lactation period (21 days). At 150 days-old, EW offspring were subdivided into 2 groups: EW+res--treated with resveratrol solution (30 mg/kg BW/day) or EW--receiving equal volume of vehicle solution, both given by gavage during 30 days. Control group received vehicle solution. Resveratrol prevented the higher body weight, hyperphagia, visceral obesity, hyperleptinemia, hyperglycemia, insulin resistance, and hypoadiponectinemia at adulthood in animals that were early weaned. Leptin resistance, associated with lower JAK2 and pSTAT3 and higher NPY in hypothalamus of EW rats were also normalized by resveratrol. The present results suggest that resveratrol is useful as therapeutic tool in treating obesity, mainly because it prevents the development of central leptin resistance.

Bone structure and strength are enhanced in rats programmed by early overfeeding

Childhood obesity is growing in prevalence. Obesity and bone dysfunctions may be related disorders, and therefore our aim was to study the impact of the early overfeeding (EO) in offspring bone health since weaning up to adulthood. To induce EO during lactation, litter size was adjusted to 3 male rats per litter (SL). Litter containing 10 pups per mother was the control (NL). Bone tissue was evaluated by dual-energy X-ray absorptiometry, computed tomography, microcomputed tomography, biomechanical tests, and serum analyses. SL offspring presented higher body weight, fat mass, lean mass from 21 up to 180 days, hyperphagia, and higher visceral fat mass. Bone analysis showed that SL offspring presented higher total bone mineral density (BMD) only at 180 days, and higher total bone mineral content and higher bone area from 21 until 180 days. At 180 days, SL offspring presented higher femur BMD and fourth lumbar vertebra (LV4) BMD, higher femoral head radiodensity and LV4 vertebral body radiodensity, lower trabecular pattern factor and trabecular separation, however with higher trabecular number, higher maximal load, resilience, stiffness and break load, and lower break deformation. SL group had, at 180 days, higher osteocalcin and lower C-terminal cross-linked telopeptide of type I collagen (CTX I). We have shown that the excess of fat mass contributed to an increased bone mass, and hypothesized that this increase could be mediated by the hypothyroidism and previous higher thyroid hormone action and hyperleptinemia at weaning. Furthermore, the increased biomechanical loading due to increased body weight probably help us to understand the protective effects obesity exerts upon bone health.

Effects of running wheel training on adult obese rats programmed by maternal prolactin inhibition

The inhibition of maternal prolactin production in late lactation leads to metabolic syndrome and hypothyroidism in adult offspring. Physical training is a therapeutic strategy that could prevent or reverse this condition. We evaluated the effects of a short-duration low-intensity running wheel training program on the metabolic and hormonal alterations in rats. Lactating Wistar rats were treated with bromocriptine (Bro, 1 mg twice a day) or saline on days 19, 20, and 21 of lactation, and the training of offspring began at 35 days of age. Offspring were divided into sedentary and trained controls (C-Sed and C-Ex) and sedentary and trained Bro-treated rats (Bro-Sed and Bro-Ex). Chronic exercise delayed the onset of weight gain in Bro-Ex offspring, and the food intake did not change during the experimental period. At 180 days, visceral fat mass was higher (+46%) in the Bro-Sed offspring than in C-Sed and Bro-Ex rats. As expected, running capacity was higher in trained animals. Most parameters observed in the Bro-Sed offspring were consistent with hypothyroidism and metabolic syndrome and were reversed in the Bro-Ex group. Chronic exercise did not influence the muscle glycogen in the C-Ex group; however, liver glycogen was higher (+30%) in C-Ex group and was unchanged in both Bro offspring groups. Bro-Ex animals had higher plasma lactate dehydrogenase levels, indicating skeletal muscle damage and intolerance of the training program. Low-intensity chronic training is able to normalize many clinical aspects in Bro animals; however, these animals might have had a lower threshold for exercise adaptation than the control rats.

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.

Two models of early weaning decreases bone structure by different changes in hormonal regulation of bone metabolism in neonate rat

During the last decade a great concern has developed for determining what factors influence bone mineral accretion in healthy children. Mother's milk represents the primary source of calcium and other nutrients in the neonate. The development of bone and adipose tissue has common origins. Since early weaning decreases adipogenesis in neonate, our aim was to evaluate bone metabolism in 2 models of early weaning (EW) in neonate rats. Lactating rats were separated into 3 groups: control: pups had free access to milk; MEW: dams were involved with a bandage mechanically (M) interrupting lactation in the last 3 days; and PEW: dams were pharmacologically (P) treated to block prolactin (0.5 mg bromocryptine/twice a day) 3 days before standard weaning. Significant difference had p<0.05. At weaning, MEW and PEW pups presented lower body weight (-18% and -15%), total body fat (-26% and -27%), total bone mineral density (-7% and -6%), total bone mineral content (-30% and -32%), bone area (-28% and -30%), serum osteocalcin (-20% and -55%), and higher C-terminal cross-linked telopeptide of type I collagen (CTX-I) (1.3 and 1.1-fold increase). However, serum ionized calcium was lower only in MEW pups (-34%), 25-hydroxyvitamin D was higher (1.4-fold increase), and PTH was lower (-26%) only in PEW group. The present study shows that both early weaning models leads to an impairment of osteogenesis associated with lower adipogenesis by different mechanisms, involving mainly changes in vitamin D and PTH.

Developmental plasticity of endocrine disorders in obesity model primed by early weaning in dams

Early weaning is associated with changes in the developmental plasticity. Here, we studied the adipocytes morphology, adipokines expression or content in adipose tissue as well as adrenal and thyroid function of neonate and adult offspring primed by early weaning. After birth, lactating rats were divided into 2 groups: EW (early weaning)--dams were wrapped with a bandage to block access to milk during the last 3 days of lactation, and Control--dams whose pups had free access to milk throughout lactation (21 days). At postnatal day (PN) 21, EW pups had lower visceral and subcutaneous adipocyte area (-67.7% and -62%, respectively), body fat mass (-26%), and leptin expression in visceral adipocyte (-64%) but higher leptin expression in subcutaneous adipocyte (2.9-fold increase). Adrenal evaluations were normal, but neonate EW pups presented lower serum T3 (-55%) and TSH (-44%). At PN 180, EW offspring showed higher food intake, higher body fat mass (+21.6%), visceral and subcutaneous adipocyte area (both 3-fold increase), higher leptin (+95%) and ADRβ3 (2-fold increase) content in visceral adipose tissue, and higher adiponectin expression in subcutaneous adipose tissue (+47%) but lower in visceral adipose tissue (-40%). Adult EW offspring presented higher adrenal catecholamine content (+31%), but no changes in serum corticosterone or thyroid status. Thus, early weaning primed for hypothyroidism at weaning, which can be associated with the adipocyte hypertrophy at adulthood. The marked changes in catecholamine adrenal content and visceral adipocyte ADRB3 are generally found in obesity, contributing to the development of other cardiovascular and metabolic disturbances.

Effects of a moderate physical training on the leptin synthesis by adipose tissue of adult rats submitted to a perinatal low-protein diet

The aim of the study was to verify if moderate physical training affects leptin content in visceral and subcutaneous adipose tissue of adult rats subjected to a low-protein diet during the perinatal period. Male Wistar rats were divided into 2 groups according to their mother's diet during gestation and lactation: control (17% casein, C, n=12) and low-protein (8% casein, LP, n=12). On postnatal day 60, half of each group was submitted to moderate physical training (8 wks, 5 d · wk - 1, 60 min · d - 1, at 70% of VO2max, T) or not. After the physical training period, visceral and subcutaneous adipose tissues were removed. Leptin content was evaluated by western blotting. Starting from the fifth week on, T pups showed a reduction in the body weight. Similarly, LP+T offspring showed a lower body weight starting from the sixth week on. Western blotting analysis showed that leptin content in the visceral tissue was higher in the LP rats (p<0.01) and it was reversed in LP+T. No difference was found in the subcutaneous tissue. Moderate physical training attenuated the effects of a perinatal low-protein diet on the leptin content in visceral adipose tissue in adult offspring.

Maternal high-fat diet induces obesity and adrenal and thyroid dysfunction in male rat offspring at weaning

Maternal nutritional status affects the future development of offspring. Both undernutrition and overnutrition in critical periods of life (gestation or lactation) may cause several hormonal changes in the pups and programme obesity in the adult offspring. We have shown that hyperleptinaemia during lactation results in central leptin resistance, higher adrenal catecholamine secretion, hyperthyroidism, and higher blood pressure and heart rate in the adult rats. Here, we evaluated the effect of a maternal isocaloric high-fat diet on breast milk composition and its impact on leptinaemia, energy metabolism, and adrenal and thyroid function of the offspring at weaning. We hypothesised that the altered source of fat in the maternal diet even under normal calorie intake would disturb the metabolism of the offspring. Female Wistar rats were fed a normal (9% fat; C group) or high-fat diet (29% fat as lard; HF group) for 8 weeks before mating and during pregnancy and lactation. HF mothers presented increased total body fat content after 8 weeks (+27%, P < 0.05) and a similar fat content at the end of lactation. In consequence, the breast milk from the HF group had higher concentration of protein (+18%, P < 0.05), cholesterol (+52%, P < 0.05) and triglycerides (+86%, P < 0.05). At weaning, HF offspring had increased body weight (+53%, P < 0.05) and adiposity (2 fold, P < 0.05), which was associated with lower β3-adrenoreceptor content in adipose tissue (-40%, P < 0.05). The offspring also presented hyperglycaemia (+30%, P < 0.05) and hyperleptinaemia (+62%, P < 0.05). In the leptin signalling pathway in the hypothalamus, we found lower p-STAT3/STAT3 (-40%, P < 0.05) and SOCS3 (-55%, P < 0.05) content in the arcuate nucleus, suggesting leptin resistance. HF offspring also had higher adrenal catecholamine content (+17%, P < 0.05), liver glycogen content (+50%, P < 0.05) and hyperactivity of the thyroid axis at weaning. Our results suggest that a high fat diet increases maternal body fat and this additional energy is transferred to the offspring during lactation, since at weaning the dams had normal fat and the pups were obese. The higher fat and protein concentrations in the breast milk seemed to induce early overnutrition in the HF offspring. In addition to storing energy as fat, the HF offspring had a larger reserve of glycogen and hyperglycaemia that may have resulted from increased gluconeogenesis. Hyperleptinaemia may stimulate both adrenal medullary and thyroid function, which may contribute to the development of cardiovascular diseases. These early changes induced by the maternal high-fat diet may contribute to development of metabolic syndrome.

Developmental plasticity in thyroid function primed by maternal hyperleptinemia in early lactation: a time-course study in rats

Pups whose mothers were leptin-treated during the last 3 days of lactation have thyroid dysfunction at adulthood. However, there was no report about leptin treatment in the first days of life or about its action on thyroid function during development. Here, we evaluated the effects of maternal leptin treatment on the first 10 days of lactation upon thyroid function of the offspring at 21, 30, and 180 days old. At birth, lactating Wistar rats were divided into: Leptin (Lep) - leptin-treated (8 μg/100 g of body weight, s.c.) for the first 10 days of lactation and Control (C, saline-treated). Mothers were killed at the end of lactation and their offspring at 21, 30, and 180 days old. Triiodothyronine (T3), thyroxine (T4), thyrotropin (TSH), and leptin levels in serum and milk were measured. Liver mitochondrial glycerolphosphate dehydrogenase (mGPD) activity was determined. Significant differences had p<0.05. At the end of lactation, Lep mothers had higher milk T3 (+ 30%), while their offspring had higher serum T3 (+ 20%) and TSH (+ 84%). At 30 days-old, Lep offspring showed lower TSH ( - 48%), T3 ( - 20%), and mGPDm ( - 42%). At 180 days-old, Lep group presented hyperleptinemia (1.4-fold increase), higher serum T3 (+ 22%), and lower mGPD activity ( - 57%). Maternal hyperleptinemia on lactation causes hypothyroidism in the pups at 30 days, which may program for higher serum T3 at adulthood. In conclusion, maternal hyperleptinemia during lactation, that is common in obese mothers, may have an impact in future disease development, such as thyroid dysfunction.

Maternal tobacco smoke exposure during lactation inhibits catecholamine production by adrenal medullae in adult rat offspring

Previously, we have shown that maternal smoke exposure during lactation, even when pups are not exposed, affects biochemical profiles in the offspring at weaning, eliciting lower body adiposity, hyperinsulinemia, hypocorticosteronemia and lower adrenal catecholamine content. However, the future impact of tobacco exposure is still unknown. As postnatal nicotine exposure causes short- and long-term effects on pups' biochemistry and endocrine profiles, we have now evaluated some endocrine and metabolic parameters of the adult offspring whose mothers were tobacco exposed during lactation. For this, from day 3 to 21 of lactation, rat dams were divided in: 1) SE group, cigarette smoke-exposed (1.7 mg nicotine/cigarettes for 1 h, 4 times/day, daily), without their pups, and 2) C group, exposed to air, in the same conditions. Offspring were killed at 180-days-old. Body weight and food intake were evaluated. Blood, white adipose tissue, adrenal, and liver were collected. All significant data were p<0.05. The adult SE offspring showed no change in body weight, cumulative food intake, serum hormone profile, serum lipid profile, or triglycerides content in liver. However, in adrenal gland, adult SE offspring showed lower catecholamine content ( - 50%) and lower tyrosine hydroxylase protein expression ( - 56%). Despite the hormonal alterations during lactation, tobacco smoke exposure through breast milk only programmed the adrenal medullary function at adulthood and this dysfunction can have consequence on stress response. Thus, an environment free of smoke during lactation period is essential to improve health outcomes in adult offspring.

Maternal prolactin inhibition during lactation affects physical performance evaluated by acute exhaustive swimming exercise in adult rat offspring

Maternal prolactin inhibition at the end of lactation programs for metabolic syndrome and hypothyroidism in adult offspring, which could negatively affect exercise performance. We evaluated the effects of maternal hypoprolactinemia in late lactation on physical performance in adult progeny. Lactating Wistar rats were treated with bromocriptine (BRO, 1 mg per day) or saline on days 19, 20, and 21 of lactation and offspring were followed until 180 days old. Physical performance was recorded in untrained rats at 90 and 180 days by an acute exhaustive swimming test (exercise group-Ex). At day 90, BRO offspring showed higher visceral fat mass, higher plasma thiobarbituric acid reactive substances, lower total antioxidant capacity, higher liver glycogen, lower glycemia, and normal insulinemia. Although thyroid hormones (TH) levels were unchanged, mitochondrial glycerol phosphate dehydrogenase (mGPD) activity was lower in muscle and in brown adipose tissue (BAT). At this age, BRO-Ex offspring showed higher exercise capacity, lower blood lactate, higher serum T3, and higher muscle and BAT mGPD activities. At day 180, BRO offspring showed central obesity, hypothyroidism, insulin resistance, and lower EDL (extensor digitorum longus) muscle glycogen with unaltered plasma oxidative stress markers. This group showed no alteration of exercise capacity or blood lactate. After exercise, EDL and liver glycogen were lower, while T3 levels, BAT and muscle mGPD activities were normalized. Liver glycogen seem to be related with higher exercise capacity in younger BRO offspring, while the loss of this temporary advantage maybe related to the hypothyroidism and insulin resistance developed with age.

Postnatal low protein diet programs leptin signaling in the hypothalamic-pituitary-thyroid axis and pituitary TSH response to leptin in adult male rats

Maternal protein restriction (PR) during lactation programs a lower body weight, hyperthyroidism, leptin resistance, and over-expression of leptin receptor in the pituitary gland at adulthood. Because leptin regulates energy homeo-stasis and the hypothalamus-pituitary-thyroid (HPT) axis, we evaluated adipocyte morphology, the leptin signaling pathway in the HPT axis and the in vitro thyrotropin (TSH) response to leptin in adult progeny in this model. At birth, dams were separated in control diet with 23% protein or PR diet with 8% protein. After weaning, offspring received a normal diet. Adult PR offspring showed lower adipocytes area, higher leptin:visceral fat ratio, lower hypothalamic signal transducer and activator of transcription 3 (STAT3), higher pituitary leptin receptor (Ob-R) and lower thyroid janus tyrosine kinase 2 (JAK2) contents. Regarding the in vitro study, 10(-7)  M leptin stimulated TSH secretion in C offspring at 30 min, but had no effect in PR offspring. At 120 min, 10(-7)  M leptin decreased TSH secretion in C offspring and increased in PR offspring. Maternal nutritional status during lactation programs for adipocyte atrophy, higher relative leptin secretion and changes in the downstream leptin signaling in the HPT axis and the TSH response to leptin, suggesting a role for leptin in the development of the HPT axis and helping to explain thyroid dysfunction and leptin resistance in this programming model. Because leptin stimulates thyroid function, it is unlikely that these alterations were responsible for the increased in serum T4 and T3. Therefore, neonatal PR programs a hyperthyroidism, lower adipogenesis, and impairment of leptin action.

The Δ337T mutation on the TRβ causes alterations in growth, adiposity, and hepatic glucose homeostasis in mice

Mice bearing the genomic mutation Δ337T on the thyroid hormone receptor β (TRβ) gene present the classical signs of resistance to thyroid hormone (TH), with high serum TH and TSH. This mutant TR is unable to bind TH, remains constitutively bound to co-repressors, and has a dominant negative effect on normal TRs. In this study, we show that homozygous (TRβΔ337T) mice for this mutation have reduced body weight, length, and body fat content, despite augmented relative food intake and relative increase in serum leptin. TRβΔ337T mice exhibited normal glycemia and were more tolerant to an i.p. glucose load accompanied by reduced insulin secretion. Higher insulin sensitivity was observed after single insulin injection, when the TRβΔ337T mice developed a profound hypoglycemia. Impaired hepatic glucose production was confirmed by the reduction in glucose generation after pyruvate administration. In addition, hepatic glycogen content was lower in homozygous TRβΔ337T mice than in wild type. Collectively, the data suggest that TRβΔ337T mice have deficient hepatic glucose production, by reduced gluconeogenesis and lower glycogen deposits. Analysis of liver gluconeogenic gene expression showed a reduction in the mRNA of phosphoenolpyruvate carboxykinase, a rate-limiting enzyme, and of peroxisome proliferator-activated receptor-γ coactivator 1α, a key transcriptional factor essential to gluconeogenesis. Reduction in both gene expressions is consistent with resistance to TH action via TRβ, reproducing a hypothyroid phenotype. In conclusion, mice carrying the Δ337T-dominant negative mutation on the TRβ are leaner, exhibit impaired hepatic glucose production, and are more sensitive to hypoglycemic effects of insulin.

Calcium supplementation reverts central adiposity, leptin, and insulin resistance in adult offspring programed by neonatal nicotine exposure

Obesity is a worldwide epidemic. Calcium influences energy metabolism regulation, causing body weight loss. Because maternal nicotine exposure during lactation programs for obesity, hyperleptinemia, insulin resistance (IR), and hypothyroidism, we decided to evaluate the possible effect of dietary calcium supplementation on these endocrine dysfunctions in this experimental model. Osmotic minipumps containing nicotine solution (N: 6 mg/kg per day for 14 days) or saline (C) were s.c. implanted in lactating rats 2 days after giving birth (P2). At P120, N and C offspring were subdivided into four groups: 1) C - standard diet; 2) C with calcium supplementation (CCa, 10 g calcium carbonate/kg rat chow); 3) N - standard diet; and 4) N with calcium supplementation (NCa). Rats were killed at P180. As expected, N offspring showed higher visceral and total body fat, hyperleptinemia, lower hypothalamus leptin receptor (OB-R) content, hyperinsulinemia, and higher IR index. Also, higher tyrosine hydroxylase (TH) expression (+51%), catecholamine content (+37%), and serum 25-hydroxyvitamin D(3) (+76%) were observed in N offspring. Dietary calcium supplementation reversed adiposity, hyperleptinemia, OB-R underexpression, IR, TH overexpression, and vitamin D. However, this supplementation did not reverse hypothyroidism. In NCa offspring, Sirt1 mRNA was lower in visceral fat (-37%) and higher in liver (+42%). In conclusion, dietary calcium supplementation seems to revert most of the metabolic syndrome parameters observed in adult offspring programed by maternal nicotine exposure during lactation. It is conceivable that the reduction in fat mass per se, induced by calcium therapy, is the main mechanism that leads to the increment of insulin action.

Developmental plasticity in adrenal function and leptin production primed by nicotine exposure during lactation: gender differences in rats

Neonate male rats whose mothers were nicotine-treated during lactation have higher adiposity, hyperleptinemia, and adrenal dysfunction. At adulthood, they still present higher adiposity and hyperleptinemia, but there was no report about their adrenal function. Also, there was no report of this developmental plasticity on females. Here, we evaluated the adrenal function and leptin content in adipocytes and muscle of male and female adult offspring whose mothers were nicotine-treated during lactation. On the 2nd postnatal day (PN2), dams were subcutaneously implanted with osmotic minipumps releasing nicotine (NIC-6 mg/kg/day) or saline for 14 days (12 litters/group and 2 rats/litter). Male and female offspring were killed on PN180. Significant data were p<0.05. Male NIC offspring presented higher adrenal catecholamine content (+ 89%) and TH expression (+ 38%), lower "in vitro" catecholamine release (- 19%), and higher adrenergic β3 receptor (ADRB3, + 59%) content in visceral adipose tissue (VAT). Serum corticosterone was higher (+ 77%) in male NIC group, coherent with the increase of both CRH and ACTH immunostaining in hypothalamus and pituitary, respectively. Leptin content was higher in VAT (+ 23%), which may justify the observed hyperleptinemia. Female NIC offspring presented lower ADRB3 content in VAT (- 39%) and lower leptin content in subcutaneous adipose tissue (SAT) (- 46%), but higher leptin content in soleus muscle (+ 22%), although leptinemia was normal. We evidenced a sex dimorphism in the model of maternal nicotine exposure during lactation. The adrenal function in adult offspring was primed only in male offspring while the female offspring displayed relevant alterations in leptin content on muscle and adipocytes.

Maternal prolactin inhibition during lactation is associated to renal dysfunction in their adult rat offspring

The renal function of rats whose mothers had hypoprolactinemia at the end of lactation was evaluated during development. Lactating Wistar rats were treated with bromocriptine (BRO, 1 mg twice a day, s.c.) or saline on days 19, 20, and 21 of lactation, and their male offspring were followed from weaning until 180 days old. 1 rat from each of the 12 litters/group was evaluated at 2 time points (90 and 180 days). Body and kidney weights, sodium, potassium, and creatinine were measured. Values were considered significant when p<0.05. Adult BRO-treated offspring presented higher body weight (+10%), lower relative renal weight at 90 and 180 days (-9.2% and -15.7%, respectively), glomerulosclerosis, and peritubular fibrosis. At 90 and 180 days, creatinine clearance was lower (-32% and -30%, respectively), whereas serum potassium was higher (+19% and +29%, respectively), but there were no changes in serum sodium. At 180 days, higher proteinuria (+36%) and serum creatinine levels (+20%) were detected. Our data suggest that prolactin inhibition during late lactation programs renal function damage in adult offspring that develops gradually, first affecting the creatinine clearance and potassium serum levels with further development of hyperproteinuria and higher serum creatinine, without affecting sodium. Thus, precocious weaning programs some components of the metabolic syndrome, which can be a risk factor for further development of kidney disease.

Maternal flaxseed diet during lactation programs thyroid hormones metabolism and action in the male adult offspring in rats

Flaxseed has several benefits for health such as improvement in lipid profile; and since thyroid hormones increases cholesterol biliary excretion, we decide to evaluate the programming effect of maternal flaxseed diet during lactation upon thyroid hormone metabolism and action in the adult offspring in rats. At birth, lactating rats were divided into: flaxseed dams (F) - diet with 25% of flaxseed - and controls dams (C). F and C pups received normal diet after weaning and male offspring were sacrificed at 21 and 180 days old. We evaluated serum T3, T4, and TSH; type 1 and 2 deiodinase activities (D1 and D2) in the liver, thyroid, brown adipose tissue (BAT), and pituitary; thyroid hormone receptor (TRβ1) expression and mitochondrial glycerophosphate-dehydrogenase activity (GPDm) in the liver. F offspring showed lower T3 levels at weaning (-30%, p<0.05) probably caused by lower liver D1 activity (-32%, p<0.05) and higher TSH levels (+84.6%, p<0.05) characterizing a profile of hypothyroidism. At 180 days old, F offspring had lower T4 and thyroid D1 and D2 activities (-28.3%, -18.5%, and -44.2%, respectively, p<0.05) and higher BAT D2 activity (+34.5%, p<0.05). We suggest that adult F animals present an inappropriate TSH action on the thyroid, since thyroid deiodinase was lower. Serum T3 was normal probably due to a higher BAT D2 activity and may reflect the tissue T3 concentration because liver D1, TRβ1, and GPDm were normal. Thus, maternal flaxseed diet during lactation may affect the thyroid hormones metabolism in a long-term.

Higher white adipocyte area and lower leptin production in adult rats overfed during lactation

Litter size reduction during lactation is a good model for childhood obesity since it induces overnutrition and programming for obesity at adulthood. Adult offspring develop higher fat mass content, hyperinsulinemia and insulin resistance, hypertension, lower HDL cholesterol, hyperphagia, and leptin resistance. Leptin resistance is often associated with hyperleptinemia. Although we observed higher SOCS3 and lower STAT3 in the hypothalamus of rats raised in small litters featuring a central leptin resistance, they showed unexpected normoleptinemia at 180 days old. Then, to clarify why early overfed rats did not develop hyperleptinemia when adult, we studied the leptin production by the visceral and subcutaneous adipose tissue and skeletal muscle as well as the morphology in the 2 different fat depots. To induce EO, litter size was reduced to 3 pups/litter (SL group) on the 3 (rd) day of life. In controls (NL group), litter size was adjusted to 10 pups/litter. Rats were killed at 180 days old. The programming of adipose tissue morphology by early overnutrition is specific between the different fat depots with hypertrophy only in the visceral compartment. In addition, the visceral adipocyte showed lower leptin content that may indicate a reduced leptin synthesis. These data suggest that adipocytes from SL rats are dysfunctional, since a higher leptin production in larger adipose cells is expected. In conclusion, postnatal nutrition is determinant for future leptin production by different fat depots as well as adipocyte morphology. These changes seem to be related to the severity of obesity and its metabolic consequences.

Effects of tobacco smoke exposure during lactation on nutritional and hormonal profiles in mothers and offspring

Exposure to tobacco smoke is related to changes in energy balance regulation and several endocrine dysfunctions. Previously, we showed that maternal nicotine (the main addictive compound of tobacco) exposure exclusively during lactation affects biochemical profiles in mothers, milk, and pups. As the possible consequences for mothers and offspring of maternal smoking during lactation are still unknown, we evaluated the effects of tobacco smoke exposure on nutritional, biochemical, and hormonal parameters in dams and pups at weaning. After 72 h from birth, lactating rats were divided into two groups: smoke-exposed (S) in a cigarette-smoking machine, 4 × 1 h per day throughout the lactation period without pups; control (C), rats were treated the same as the experimental group but exposed to filtered air. Dams and pups were killed at weaning (21 days of lactation). Body weight and food intake were evaluated. Milk, blood, visceral fat, adrenal, and carcass were collected. S dams showed hyperprolactinemia (+50%), hypoinsulinemia (-40%), hypoleptinemia (-46%), as well as lower triglycerides (-53%) and very low-density lipoprotein cholesterol (-50%). Milk of S dams had higher lactose (+52%) and triglycerides (+78%). S pups presented higher body protein (+17%), lower total (-24%) and subcutaneous fat contents (-25%), hypoglycemia (-11%), hyperinsulinemia (+28%), hypocorticosteronemia (-40%), lower adrenal catecholamine content (-40%), hypertriglyceridemia (+34%), higher high-density lipoprotein cholesterol (+16%), and lower low-density lipoprotein cholesterol (-45%). In conclusion, tobacco smoke exposure leads to changes in nutritional, biochemical, and hormonal parameters in dams and, passively through the milk, may promote several important metabolic disorders in the progeny.

Blocking leptin action one week after weaning reverts most of the programming caused by neonatal hyperleptinemia in the adult rat

Hyperleptinemia during lactation programs for higher serum leptin in 30-day-old and adult rats, associated with metabolic changes. Here we evaluated the inhibition of serum leptin at 29 and 30 days on the metabolic phenotype of rats programmed with leptin during lactation. Pups from Wistar rats were saline-injected or leptin-injected from postnatal day 1 to day 10. At 29 and 30 days old, animals were injected with anti-leptin antibody (LA and CA) or saline (LS and CS). In adult animals, higher visceral (+53%) and total fat mass (+33%), hyperleptinemia (+67%), hypertriglyceridemia (+47%), and hypoadiponectinemia (-44%) observed in LS group compared to CS were prevented by immunoneutralization of leptin, since LA group had those parameters values similar to CS group. However, immunoblockade of leptin in normal animals led to the same metabolic changes seen in leptin-treated animals, in addition to lower serum adiponectin (-77% vs. CS) and higher insulin resistance index (+37%). Liver sirtuin1 (SIRT1) was higher (+41%) only in LA group, suggesting a role for SIRT1 in the prevention of leptin programming. Hypothalamic OBR was lower and SOCS3 higher in LS group and these changes were normalized in LA group. In conclusion, blocking leptin action one week after weaning seems to revert most of the alterations observed in rats programmed by neonatal hyperleptinemia. Higher liver SIRT1 expression may be one of the mechanisms involved, leading to a better glucose and lipid metabolism. Our data suggest that the lack or the excess of leptin programs an adverse metabolic phenotype in adulthood.

Prolactin inhibition at mid-lactation influences adiposity and thyroid function in adult rats

Maternal hypoprolactinemia at the end of lactation (a precocious weaning model) increases milk leptin transfer and results in overweight, leptin resistance, and secondary hypothyroidism at adulthood. We studied the effects of prolactin (PRL) inhibition during mid-lactation (a partial malnutrition model) on milk leptin transfer, leptinemia, body composition, and thyroid function. Lactating rats were treated with bromocryptine (BRO, 1 mg/twice daily) or saline on days 7, 8, and 9 of lactation. Offspring were sacrificed 10, 21, and 90 days after birth. After treatment, BRO-treated dams showed hypoprolactinemia and hyperleptinemia, and produced less milk with lower levels of lactose and higher milk triglycerides. Milk leptin levels were lower at weaning. Offspring of BRO-treated dams had lower body weight and length as well as less visceral fat during lactation and adulthood. Total fat was also lower at weaning and adult life, whereas total protein was higher at 90 days-old. BRO offspring presented lower serum T4 and TSH at 10 days-old and weaning, respectively. When adults, these rats exhibited hypoleptinemia, lower levels of thyroid hormones, and higher TSH. Early inhibition of PRL therefore leads to offspring malnutrition and affects subsequent growth. Also, inhibition of PRL during lactation predisposes offspring to hypothyroidism; however, when the inhibition occurs during late lactation, the hypothyroidism is secondary, whereas when it is restricted to mid-lactation, the thyroid hypofunction is primary. The programming effect of milk suppression thus depends on the developmental stage of offspring.

Neonatal nicotine exposure alters leptin signaling in the hypothalamus-pituitary-thyroid axis in the late postnatal period and adulthood in rats

AIMS

Postnatal nicotine exposure causes precocious primary hypothyroidism and programs for overweight, hyperleptinemia and secondary hypothyroidism in adulthood. As leptin and thyroid hormones share the ability to increase energy expenditure, we studied the effects of maternal nicotine exposure during lactation on the leptin signaling in the hypothalamus-pituitary-thyroid axis of suckling and adult offspring.

MAIN METHODS

Two days after delivery, osmotic minipumps were implanted in lactating rats, and nicotine (NIC, 6 mg/kg/day s.c.) or saline (C) was administered for 14days. Offspring were killed at 15 and 180 days-old. Proteins belonging to leptin signaling were analyzed by Western blot. Significant differences had p<0.05.

KEY FINDINGS

In the hypothalamus, NIC offspring showed higher OB-R and pSTAT-3 content (+58%,+1.34x) at 15 days, and lower OB-R, JAK-2 and pSTAT-3 (-61%, -42%, -56%) at 180 days. In the pituitary gland, NIC offspring showed lower JAK-2 content (-52%) at 15 days, but no differences in adulthood. In the thyroid gland, the NIC group presented lower OB-R, JAK-2 and STAT-3 (-44%, -50%, -47%) and higher pSTAT-3 expression (+80%) at 15 days. At 180 days-old, NIC offspring presented higher thyroid OB-R (+1.54x) and lower pSTAT-3 content (-34%).

SIGNIFICANCE

Neonatal primary hypothyroidism induced by maternal nicotine exposure during lactation may be partially explained by decreased leptin signaling in the thyroid, though the early stimulation of the central leptin pathway did not prevent the thyroid dysfunction. Long-term effects of postnatal nicotine exposure on leptin signaling in the hypothalamus and thyroid appear to involve central and peripheral leptin resistance in adulthood.

Leptin treatment during lactation programs leptin synthesis, intermediate metabolism, and liver microsteatosis in adult rats

Epidemiological and experimental studies have associated development of metabolic syndrome with stressful events (nutritional, hormonal, or environmental) in early life. This phenomenon is known as programing and changes in adipokines levels in early life, especially leptin, seem to be involved with its development. We have shown that neonatal hyperleptinemia on lactation programs for leptin resistance, hyperthyroidism, and higher corticosterone and catecholamines levels with cardiovascular consequences. In the present study, we evaluated the effect of hyperleptinemia during lactation on the glucose and lipid metabolism and liver morphology of adult rats, which were saline or leptin-treated (8 microg/100 g of body weight) daily, for the first 10 days of life. Leptin group had lower body mass during treatment, but higher body mass and hyperleptinemia at adulthood, without difference in fat mass. We showed that the probable source of hyperleptinemia is the higher leptin content in the subcutaneous adipose tissue. The programed rats showed hyperinsulinemia and hypoadiponectinemia with higher expression of the hypothalamic Suppressor of Cytokine Signaling 3 (SOCS3), suggesting insulin resistance. Besides, they presented higher liver glycogen and hypertriglyceridemia. We also observed liver microsteatosis in the leptin-programed adult rats. Our data show that neonatal hyperleptinemia alters glucose metabolism, which seems to be partially compensated by the hyperinsulinemia. However, changes in the lipid metabolism are not compensated. It is probable that these changes induced by neonatal hyperleptinemia result from a selective tissue specific resistance both to insulin and leptin at adulthood, and the increase of SOCS3 may play an important role in this process.

Programming of rat adrenal medulla by neonatal hyperleptinemia: adrenal morphology, catecholamine secretion, and leptin signaling pathway

Leptin serum concentration in early life is an important factor for adequate future development of the offspring. Previously, we demonstrated that hyperleptinemia on lactation programmed for hyperleptinemia, central leptin resistance with lower expression of the long form of leptin receptor at hypothalamus, and higher medullary catecholamine levels with cardiovascular consequences at adulthood. The central objective of this study was to determine the direct effect of leptin on adrenal medullary function of adult rats that were leptin treated during lactation. Adrenal morphology was also accessed. Recombinant murine leptin was injected in the pups during the first 10 days of life (group L, leptin-programmed) or at adulthood during 6 days (group LC). The controls of both experiments received saline (groups C and CC). Both treatments resulted in hyperleptinemia at 150 days old (+78% and 2-fold increase, respectively; P < 0.05). Programmed animals showed hypertrophy of adrenal and higher adrenal catecholamine content at 150 days old (3-fold increase, P < 0.05), and no changes were observed in the LC group. However, LC rats had lower adrenal content of tyrosine hydroxylase (-17%, P < 0.05). Leptin-programmed rats had a lower response to leptin in vitro stimulation (-22%, P < 0.05) and lower expression of key proteins of the leptin signaling pathway, leptin receptor and janus tyrosine kinase 2 in the medullas (-61% and -29%, respectively, P < 0.05). However, they presented higher expression of phosphorylated signal transducer and activator of transcription 3 (+2-fold, P < 0.05). Leptin treatment at adulthood did not affect these parameters. The higher catecholamine synthesis and secretion in the leptin-programmed rats observed in our previous study does not seem to be a consequence of the direct effect of leptin on the medullas. We suggest that the hyperleptinemia of the programmed animals increases adrenal medullary function through sympathetic nervous system activation. In conclusion, high leptin levels on lactation program the activity of the sympathoadrenal system at adulthood that may contribute to the development of adult chronic diseases such as hypertension.

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

We have shown that maternal nicotine exposure during lactation has long-lasting effects on body adiposity and hormonal status of rat offspring. Here, we studied the nutritional and hormonal profiles in this experimental model. Two days after birth, osmotic minipumps were implanted in lactating rats divided into two groups: NIC - continuous s.c. infusions of nicotine (6 mg/kg per day) for 14 days and C - saline. Dams and pups were killed at 15 and 21 days of lactation. Body weight and food intake were evaluated. Milk, blood, visceral fat, carcass, and adrenal gland were collected. All the significant data were P<0.05. At the end of nicotine exposure (15 days), dams presented higher milk production, hyperprolactinemia, and higher serum high-density lipoprotein cholesterol (HDL-C). Milk from NIC dams had higher lactose concentration and energy content. After nicotine withdrawal (21 days), dams showed lower food intake and hyperleptinemia. The 15-day-old NIC pups presented higher total body fat, higher HDL-C, serum leptin, serum corticosterone, and adrenal catecholamine content, but lower tyrosine hydroxylase protein levels. The 21-day-old NIC pups had higher body protein content and serum globulin. Thus, maternal nicotine exposure during lactation results in important changes in nutritional, biochemical, and hormonal parameters in dams and offspring. The pattern of these effects is clearly distinct when comparing the nicotine-exposed group to the withdrawal group, which could be important for the programming effects observed previously.

Temporal evaluation of body composition, glucose homeostasis and lipid profile of male rats programmed by maternal protein restriction during lactation

Neonatal protein restriction causes lower body weight and hormonal dysfunctions in 6 months-old rats. In this model, we studied the body composition, glycogen content, serum lipid, serum protein, and hormones related to glucose homeostasis in the offspring during development. At birth, lactating rats were divided into: control dams - fed a normal diet (23% protein) and protein restricted dams - fed a diet with 8% protein. After weaning, pups received normal diet. Offspring were killed at 21, 90, and 180 days-old. Protein restricted offspring showed lower visceral fat (90th day: 14%; 180th day: 19%) and lower total fat (90th day: 16%; 180th day: 14%) that explain their lower body weight. They presented lower glycemia (180th day: 17%), lower insulinemia (21st day: 63%; 180th day: 24%), higher adiponectinemia (21st day: 169%), higher liver glycogen (21st day: 104%), and higher muscle glycogen (180th day: 106%), suggesting a higher insulin sensitivity. The higher serum corticosterone (50%), higher adrenal total catecholamines content (98%) as well as in vitro catecholamine secretion (26%) of adult protein restricted offspring, suggest a programming stimulatory effect upon adrenal gland. They also presented several biochemical changes, such as lower serum total protein, albumin and globulin (21st day: 17, 21, 12%, respectively), higher LDL-c (21st day: 69%), lower triglycerides (21st day: 42%; 90th day: 39%), and lower total cholesterol (180th day: 16%). Thus, maternal protein restriction during lactation induces an energy-protein malnutrition, characterized by an impairment of the pup's protein anabolism and, after weaning, the lower adiposity suggests lower lipogenesis and higher lipolytic activity, probably caused by catecholamine and glucocorticoid action.

Early maternal hyperleptinemia programs adipogenic phenotype in rats

We have previously reported on the treatment of maternal rats with leptin during the three last days of lactation program for overweight and leptin hypothalamic resistance in the offspring. Here we have investigated whether treatment of maternal rats with leptin in the first ten days of lactation can program metabolic dysfunctions on the adult offspring. Lactating rats were divided into 2 groups: rats (LEP) injected with recombinant mouse leptin (8 microg/100 g/body weight, daily during the first 10 days of lactation) and control group (C) that received the same volume of saline. After weaning, all pups had free access to normal diet, their body weight and food intake were monitored at 4 days interval until 180 days, when they were tested for food intake and response to either leptin (0.5 mg/kg body weight, ip) or saline. The offspring from leptin-treated mothers gained more weight from day 69 onward and had higher food intake from day 145 onward, higher amount of visceral adipose tissue (57%), higher serum glucose (10%), and higher serum leptin (135%) at 180 days compared to control group. The food intake was not reduced as expected after acute injection of leptin in these animals, suggesting resistance to the anorexigenic effect of leptin. We conclude that maternal hyperleptinemia in early lactation programed higher food intake, body weight gain due to higher total and visceral fat mass, and resistance to anorexigenic effect of leptin in the adult offspring even when this hyperleptinemia occurred at the beginning of lactation.

Short- and long-term effects of maternal nicotine exposure during lactation on body adiposity, lipid profile, and thyroid function of rat offspring

Epidemiological studies show a higher prevalence of obesity in children from smoking mothers and smoking may affect human thyroid function. To evaluate the mechanism of smoking as an imprinting factor for these dysfunctions, we evaluated the programming effects of maternal nicotine (NIC) exposure during lactation. Two days after birth, osmotic minipumps were implanted in lactating rats, divided into: NIC (6 mg/kg per day s.c.) for 14 days; Control - saline. All the significant data were P<0.05 or less. Body weight was increased from 165 days old onwards in NIC offspring. Both during exposure (at 15 days old) and in adulthood (180 days old), NIC group showed higher total fat (27 and 33%). In addition, NIC offspring presented increased visceral fat and total body protein. Lipid profile was not changed in adulthood. Leptinemia was higher at 15 and 180 days old (36 and 113%), with no changes in food intake. Concerning the thyroid status, the 15-days-old NIC offspring showed lower serum-free tri-iodothyronine (FT(3)) and thyroxine (FT(4)) with higher TSH. The 180-days-old NIC offspring exhibited lower TSH, FT(3), and FT(4)). In both periods, liver type 1 deiodinase was lower (26 and 55%). We evidenced that NIC imprints a neonatal thyroid dysfunction and programs for a higher adiposity, hyperleptinemia, and secondary hypothyroidism in adulthood. Our study identifies lactation as a critical period to NIC programming for obesity, with hypothyroidism being a possible contributing factor.

Maximum acute exercise tolerance in hyperthyroid and hypothyroid rats subjected to forced swimming

Thyroid dysfunction can compromise physical capacity. Here, we analyze the effects of hyperthyroidism and hypothyroidism on maximum swim time in rats subjected to acute forced swimming, as an indicator of anaerobic capacity. Animals were forced to swim against a load (5% of body weight) attached to the tail and were killed 48 hours after the last test. Hyperthyroid rats were treated with thyroxine (50 mug/100 g body weight, i. p. for 7 days). The hypothyroid group received 0.03% methimazole in the drinking water for 4 weeks. Thyroid state was confirmed by alterations in serum thyroid-stimulating hormone (TSH), triiodothyronine (T3), thyroxine (T4), and liver mitochondrial glycerol phosphate dehydrogenase (mGPD) activity. Hyperthyroid rats presented significantly lower visceral fat mass (VFM) and higher food intake (p<0.05) with unchanged body weight. Maximum swim time (MST), glycogen content (skeletal muscle and liver), and leptin levels were lower while corticosterone was higher (p<0.05). In hypothyroid rats body weight was lower (p<0.05), without changes in VFM. Tested at 7-day intervals, MST was lower for tests 2, 3, and 4 (p<0.05). Muscle glycogen was higher in extensor digitorum longus (EDL) and soleus (p<0.05), without changes in liver. Serum corticosterone was lower, while leptin was higher (p<0.05). These results suggest that in hyperthyroid and hypothyroid rats, thyroid hormones together with corticosterone and/or leptin may impair exercise capacity differently through its known effects on glycogen metabolism.

Thyroid function and body weight programming by neonatal hyperthyroidism in rats - the role of leptin and deiodinase activities

Several authors have shown that secondary hypothyroidism was programed by neonatal thyroxine (T4) treatment. However, the associated changes of body weight (BW) were less studied, especially those related to the body fat proportion. Here, we have evaluated the effect of neonatal thyroxine treatment on BW, fat proportion, serum leptin, and thyroid function of 60-day-old rats. Wistar rats were treated with thyroxine (50 microg/100 g BW, ip) (T) or saline (S), during the first 10 days of life. BW, nose-rump length (NRL), and food consumption were monitored for 60 days, when the animals were sacrificed. Thyroid function was evaluated by thyroid radioiodine uptake (RAIU), serum T3, T4, TSH, and liver mitochondrial alpha-glycerophosphate dehydrogenase (mGPD) and type 1 and 2 deiodinases (D1 and D2) activities, which are thyroid hormone-dependent enzymes. T animals showed lower food intake, BW and NRL, but higher total fat mass (+33%) and serum leptin (+46%). They also showed lower serum T3 (-23%), T4 (-32%), TSH (-36%), RAIU (-29%) and mGPD activity (-22%). Hypothalamic and pituitary D2 activities were higher (+24% and 1.4 fold, respectively), while brown adipose tissue (BAT) D2 and skeletal muscle D1 activities were lower (-30% and -62%, respectively). Thus, neonatal hyperthyroidism programs for a higher fat proportion and hyperleptinemia, which can explain the lower food intake. The TH-dependent enzymes activities changed accordingly, except for the decrease in BAT D2, which may be due the role played by the hyperleptinemia. Finally, the decrease in peripheral deiodination may contribute to a lower me-tabolic rate that may increase the adiposity.

Neonatal programming of neuroimmunomodulation--role of adipocytokines and neuropeptides

Programming is an epigenetic phenomenon by which nutrition, environment and stress acting in a critical period earlier in life change the organism's development. This process was evolutionarily selected as an adaptive tool for the survival of organisms living in nutritionally deficient areas and submitted to stressful conditions. Thus, perinatal malnutrition turns on different genes that provide the organism with a thrifty phenotype. In conditions of abundant supply of nutrients, those programmed organisms can be at risk of developing metabolic diseases (obesity, dyslipidemia, diabetes and hypertension). How nutrition or neonatal stress can program the immune system is less well known. Here, we discuss some of the hormonal and metabolic changes that occur in mothers and neonates and how those factors can imprint hormonal or metabolic changes that program neuroimmunomodulatory effects. Some of these changes involve thyroid hormones, leptin, insulin, glucocorticoids and prolactin as potential imprinting factors. Most of them can be transferred through the milk and may change with malnutrition or stress. We discuss the programming effects of these hormones upon body weight, body composition, insulin action, thyroid, adrenal and immune and inflammatory responses, with special emphasis on leptin, a cytokine that seems to play a central role in these events.

Chronic leptin treatment inhibits liver mitochondrial alpha-glycerol-beta-phosphate dehydrogenase in euthyroid rats

Leptin modulates the hypothalamus-pituitary-thyroid axis and peripheral metabolism of thyroid hormones (THs). We have studied the effect of acute and chronic leptin treatment upon liver mitochondrial glycerol phosphate dehydrogenase activity (mGPD), whose expression and activity are TH dependent. We performed 2 experiments: 1) acute leptin treatment - LepA: adult rats received a single leptin injection (8 microg/100 g BW); 2) chronic leptin treatment - LepC: adult rats received leptin (8 microg/100 g BW) daily, for 6 days. In both experiments, control groups were saline-treated. All rats were sacrificed 2 hours after the last dose. Liver mGPD activity was determined by colorimetric method. Liver D1 activity was measured by the release of (125)I from (125)I-rT3. Serum hormones were measured by RIA. LepA rats showed higher serum thyroid stimulating hormone (TSH) (+ 64%, p<0.05), free T4 (+ 34%, p<0.05), free T3 (+ 64%, p<0.05), and liver D1 activity (+ 85%, p<0.05), but no change in mGPD activity. Since THs increase mGPD activity, the unchanged level in the acute experiment is suggestive of an inhibitory role of leptin. LepC rats presented lower mGPD activity (-1.7-fold, p<0.05) and higher liver D1 activity (+ 32%, p<0.05), but no alteration in serum TSH and free THs. Our results show that leptin downregulates mGPD activity, mainly when hyperleptinemia is chronic.

Acute effects of leptin on 5'-deiodinases are modulated by thyroid state of fed rats

Leptin has been shown to modulate deiodinase type 1 (D1) and type 2 (D2) enzymes responsible for thyroxine (T4) to triiodothyronine (T3) conversion. Previously, it was demonstrated that a single injection of leptin in euthyroid fed rats rapidly increased liver, pituitary, and thyroid D1 activity, and simultaneously decreased brown adipose tissue (BAT) and hypothalamic D2 activity. We have now examined D1 and D2 activities, two hours after a single subcutaneous injection of leptin (8 microg/100 g BW) into hypo- and hyperthyroid rats. In hypothyroid rats, leptin did not modify pituitary, liver and thyroid D1, and thyroid D2 activity, while pituitary D2 was decreased by 41% (p<0.05) and hypothalamic D2 showed a 1.5-fold increase. In hyperthyroid rats, thyroid and pituitary D1, and pituitary and hypothalamic D2 were not affected by leptin injection, while liver D1 showed a 42% decrease (p<0.05). BAT D2 was decreased by leptin injection both in hypo- and hyperthyroid states (42 and 48% reduction, p<0.001). Serum TH and TSH showed the expected variations of hypo- and hyperthyroid state, and leptin had no effect. Serum insulin was lower in hypothyroid than in hyperthyroid rats and remained unchanged after leptin. Therefore, acute effects of leptin on D1 and D2 activity, expect for BAT D2, were abolished or modified by altered thyroid state, in a tissue-specific manner, showing an IN VIVO interplay of thyroid hormones and leptin in deiodinase regulation.

Cold exposure restores the decrease in leptin receptors (OB-Rb) caused by neonatal leptin treatment in 30-day-old rats

We had previously shown that neonatal leptin treatment programs thyroid function in adulthood. As both thyroid hormones (TH) and leptin increased thermogenesis, it was interesting to evaluate the effect of cold exposure on the thyroid function of neonate rats treated with leptin. Pups were divided into two groups: Lep, injected with leptin (8 mug/100 g/BW, s.c.) for the first 10 days of lactation and control (C), injected with saline. When they were 30 days old, the groups were subdivided into two subgroups: LepC and CC, which were exposed to 8 degrees C for 12 h and compared with C and Lep groups, maintained at 25 +/- 1 degrees C. Serum leptin, TH, and TSH were measured by RIA. Type I liver deiodinase (D1) and mitochondrial alpha-glycerol-3-phosphate dehydrogenase (mGPD) activities were assayed by the release of (125)I from (125)I-reverse and colorimetric method respectively. Leptin receptor (OB-Rb) was evaluated by western blot. Lep group had hyperleptinemia (+22%) and lower free tri-iodothyronine (FT(3); -33%). Cold exposure increased TH both in LepC and CC groups compared with respective controls free thyroxine (FT(4):+63 and +39%; FT(3):+75 and +40%). Liver D1 activity was lower in Lep (-22%) and increased with cold exposure (LepC +51% and CC +22%). The mGPD activity was lower in Lep (-34%) and increased (fourfold) when this group is cold exposed. Hypothalamic and thyroidal OB-Rb receptors were lower in Lep group (-47 and -36% respectively) and they were restored to normal levels after cold exposure. Leptin-programmed rats had higher TH response after cold exposure. OB-Rb had a fast response to cold exposure normalizing the lower levels observed in the leptin-programmed animals and may contribute to the higher TH cold responses.

Maternal low-protein diet during lactation programmes body composition and glucose homeostasis in the adult rat offspring

Previously we have reported that maternal malnutrition during lactation programmes body weight and thyroid function in the adult offspring. In the present study we evaluated the effect of maternal protein restriction during lactation upon body composition and hormones related to glucose homeostasis in adult rats. During lactation, Wistar lactating rats and their pups were divided into two experimental groups: control (fed a normal diet; 23 % protein) and protein-restricted (PR; fed a diet containing 8 % protein). At weaning, offspring received a normal diet until they were 180 d old. Body weight (BW) and food intake were monitored. Serum, adrenal glands, visceral fat mass (VFM) and carcasses were collected. PR rats showed lower BW ( − 13 %;P < 0·05), VFM ( − 33 %;P < 0·05), total body fat ( − 33 %;P < 0·05), serum glucose ( − 7 %;P < 0·05), serum insulin ( − 26 %,P < 0·05), homeostasis model assessment index ( − 20 %), but higher total adrenal catecholamine content (+90 %;P < 0·05) and serum corticosterone concentration (+51 %;P < 0·05). No change was observed in food intake, protein mass or total body water. The lower BW of PR rats is due to a reduction of white fat tissue, probably caused by an increase in lipolysis or impairment of lipogenesis; both effects could be related to higher catecholaminergic status, as well as to hypoinsulinaemia. To conclude, changes in key hormones which control intermediary metabolism are programmed by maternal protein restriction during lactation, resulting in BW alterations in adult rats.