Silvana Almeida

Oxytocin modulates social interaction but is not essential for sexual behavior in male mice.

Recently, several studies have shown different conclusions regarding the effect of oxytocin (OT) on the social behaviors of male mice. Most of these studies used exogenous OT, but currently, investigations of the neural bases of social behavior are increasingly employing gene inactivation. This study aimed to analyze the role of OT in the modulation of social behaviors (i.e., sexual and social interaction behaviors) in male mice with selective deletions of the OT gene (OTKO) and the influence of this deletion in basal vasopressin (AVP) plasma concentrations. Our results showed that in the social interaction test, OTKO mice exhibited lower levels of social behaviors and higher levels of non-social behaviors compared to the wild type (WT) group. Additionally, the OTKO group showed a decrease in the number of agonistic behaviors delivered, and consequently, their dominance score was lower than that of the WT group. In the ethological analysis, the OTKO group had a lower aggressive performance and increased social investigation than the WT group. No significant differences were observed in the sexual behavior between groups. Finally, we found lower AVP plasma concentrations in the OTKO compared with the WT group. In conclusion, our data suggest that OT modulates social investigation behavior and the aggressiveness of male mice. The decrease in AVP concentrations in the OTKO group allows us to infer that AVP is physiologically relevant to these behavioral modulations. However, sexual behaviors do not seem to be affected by the lack of OT or by a decrease in the AVP concentration.

Progesterone and maternal aggressive behavior in rats

Females usually display low levels of aggressiveness; however, during lactation, the aggressive behavior against intruders to the nest area is an important component of the maternal behavioral repertoire. The present study aimed to analyze the influence of progesterone (P4) on the maternal aggressive behavior in rats. Lactating rat were ovariectomized on the first day after delivery and, on the 6th postpartum day, aggressive behaviors against a male intruder were recorded. Also in the 6th PPD, the effects of a P4 receptor antagonist (RU 486) as well as of finasteride - which inhibits the conversion of P4 to its metabolite allopregnanolone - on the aggressive behavior of non-ovariectomized lactating rats were analyzed. Finally, plasma concentration of prolactin was measured on the 8th PPD. This study shows, for the first time, that ovariectomy just after parturition reduces some aspects of the maternal behavior (frequency of licking) and the aggressive behavior and increased plasma prolactin. On the other hand, the administration of RU486 induced a marked increase in the aggressiveness of lactating females. No changes were detected after finasteride injection. Gonadal hormones after parturition seem necessary for the development of maternal aggressive behavior. Furthermore, our results suggest that the increase in P4 levels throughout the postpartum period could be one of the causes for the natural reduction of the aggressive behavior in lactating rats.

Analysis of transcriptional levels of the oxytocin receptor in different areas of the central nervous system and behaviors in high and low licking rats

The natural variation in maternal care is an interesting model to analyze the physiological mechanisms that lead to differences in the mother-infant interaction. Several studies have shown differences in the expression of brain receptors such as the dopamine, estrogen and oxytocin receptors in areas classically involved in the onset and/or maintenance of maternal behavior: the medial preoptic area, the nucleus accumbens, the amygdala, the lateral septum, and the bed nucleus of the stria terminalis. The present study examined the responses of HL and LL rats in several behavioral tests and analyzes the transcription of the oxytocin receptor (OXTR) in the olfactory bulb (OB), the prefrontal cortex (FPC), the hippocampus (HP) and the striatum (ST) in different patterns of licking behavior. Our results showed that, in the second week postpartum, HL and LL mothers did not show behavioral differences in the elevated plus maze (EPM), the forced swimming test (FST) or the open field test. In the maternal aggressive behavior test, HL females showed a higher frequency of biting compared to LL females, but no significant differences in other aggressive behaviors were detected. LL mothers had higher levels of transcriptional OXTR in the OB and in the HP when compared to HL mothers. No differences in other areas were detected when compared LL and HL. These findings suggest that variations in maternal behavior may be associated with biting behavior of mothers and that OXTR participates in modulation of maternal behavior in rats, while other emotional behaviors are less related to such behavior.

Gene expression in the CNS of lactating rats with different patterns of maternal behavior.

For most mammalian species, maternal behavior has an essential role in the development of the offspring. The frequency of licking/grooming (LG) the pups has been used as a parameter to evaluate maternal care, having mothers with high (HL) or low (LL) frequencies of LG. This study aimed to analyze the gene expression of the receptors for dopamine (Drd1a), prolactin (Prlr), serotonin (Htr1a, Htr1b), estrogen (Esr1, Esr2), and of Bdnf in the olfactory bulb (OB), hippocampus (HP), prefrontal cortex (PFC), and striatum (ST) of Wistar rats from three groups: LL (n = 8); HL (n = 8); virgin females in diestrus (D; n = 6). Maternal behavior was studied between the 1st and 7th postpartum days. Brain parts were analyzed by qRT-PCR. LL showed a decrease in the frequency of nursing, and an increase of remaining off the pups. There was an increase in gene expression of Drd1a, Prlr, Htr1a, Htr1b and Esr1 in the OB of HL, compared to LL. In the HP, Drd1a, Prlr and Htr1a were differently expressed when comparing HL, or LL, with D. The main finding is that HL had higher gene expression levels in the OB, which is a crucial structure to promote behavioral differences.

SNPs in the APM1 gene promoter are associated with adiponectin levels in HIV-infected individuals receiving HAART.

Objective: This study aimed to investigate the association between 4 polymorphisms in the leptin, leptin receptor, and adiponectin (APM1) genes and the occurrence of lipodystrophy and dyslipidemia in HIV-infected patients receiving highly active antiretroviral therapy (HAART). Materials and Methods: Genotypes of 410 HIV-infected patients on HAART were investigated. Anthropometric (weight, height, waist circumference and skinfolds thickness) and biochemical (blood lipids, glucose, leptin, and adiponectin levels) parameters were evaluated. Genotype frequencies were compared between patients with or without lipodystrophy. Mean biochemical and anthropometric parameters were compared between the different genotypes. Results: Lipodystrophy prevalence was 53.4%. Genotype frequencies were not different between patients with or without lipodystrophy. Carriers of the A allele for the APM1-11391 G>A and of the C allele for APM1-11377 C>G presented higher adiponectin levels compared to other genotypes, and carriers of the -11391A-11377C haplotype when compared with carriers of other haplotypes. Conclusions: SNPs in APM1 gene are associated with adiponectin levels in HIV-infected patients receiving HAART and may thus affect the occurrence of metabolic alterations in these patients. No influence of the leptin and leptin receptor gene polymorphisms on the occurrence of lipodystrophy and dyslipidemia was observed.

Polymorphisms in LEPR, PPARG and APM1 genes: associations with energy intake and metabolic traits in young children.

OBJECTIVE To assess the association of single nucleotide polymorphisms (SNPs) in five genes - leptin, leptin receptor (LEPR), adiponectin (APM1), peroxisome proliferator-activated receptor gamma (PPARG) and uncoupling protein 1 - with anthropometric, metabolic, and dietary parameters in a Southern Brazilian cohort of 325 children followed up from birth to 4 years old. MATERIALS AND METHODS SNPs were analyzed using polymerase chain reaction-based procedures, and their association with phenotypes was evaluated by t-test, analysis of variance, and general linear models. RESULTS LEPR223Arg allele (rs1137101) was associated with higher daily energy intake at 4 years of age (P = 0.002; Pcorrected = 0.024). PPARG 12Ala-carriers (rs1801282) presented higher glucose levels than Pro/Pro homozygotes (P = 0.007; Pcorrected = 0.042). CONCLUSIONS Two of the six studied SNPs presented consistent associations, showing that it is already possible to detect the influences of genetic variants on susceptibility to overweight in 4-year-old children.

Examining the Role of Vasopressin in the Modulation of Parental and Sexual Behaviors

Vasopressin (VP) and VP-like neuropeptides are evolutionarily stable peptides found in all vertebrate species. In non-mammalian vertebrates, vasotocin (VT) plays a role similar to mammalian VP, whereas mesotocin and isotocin are functionally similar to mammalian oxytocin (OT). Here, we review the involvement of VP in brain circuits, synaptic plasticity, evolution, and function, highlighting the role of VP in social behavior. In all studied species, VP is encoded on chromosome 20p13, and in mammals, VP is produced in specific hypothalamic nuclei and released by the posterior pituitary. The role of VP is mediated by the stimulation of the V1a, V1b, and V2 receptors as well as the oxytocinergic and purinergic receptors. VT and VP functions are usually related to osmotic and cardiovascular homeostasis when acting peripherally. However, these neuropeptides are also critically involved in the central modulation of social behavior displays, such as pairing recognition, pair-bonding, social memory, sexual behavior, parental care, and maternal and aggressive behavior. Evidence suggests that these effects are primarily mediated by V1a receptor in specific brain circuits that provide important information for the onset and control of social behaviors in normal and pathological conditions.

Transcriptional expression study in the central nervous system of rats: what gene should be used as internal control?

Objective A growing number of published articles report the expression of specific genes with different behavior patterns in rats. The levels of messenger ribonucleic acid transcripts are usually analyzed by reverse transcription followed by polymerase chain reaction and quantified after normalization with an internal control or reference gene (housekeeping gene). Nevertheless, housekeeping genes exhibit different expression in the central nervous system, depending on the physiological conditions and the area of the brain to be studied. The choice of a good internal control gene is essential for obtaining reliable results. This study evaluated the expression of three housekeeping genes (beta-actin, cyclophilin A, and ubiquitin C) in different areas of the central nervous system in rats (olfactory bulb, hippocampus, striatum, and prefrontal cortex). Methods Wistar rats (virgin females, n=6) during the diestrum period were used. Total ribonucleic acid was extracted from each region of the brain; the complementary deoxyribonucleic acid was synthesized by reverse transcription and amplified by real-time quantitative polymerase chain reaction using SYBR™ Green and primers specific for each one of the reference genes. The stability of the expression was determined using NormFinder. Results Beta-actin was the most stable gene in the hippocampus and striatum, while cyclophilin A and ubiquitin C showed greater stability in the prefrontal cortex and the olfactory bulb, respectively. Conclusion Based on our study, further studies of gene expression using rats as animal models should take into consideration these results when choosing a reliable internal control gene.

SLC6A14 and 5-HTR2C polymorphisms are associated with food intake and nutritional status in children

BACKGROUND Serotonin plays a critical role in the regulation of food intake. The solute carrier family 6 member 14 (SLC6A14) and serotonin receptor 2C (5-HTR2C) genes are involved in the bioavailability and action of this neurotransmitter. OBJECTIVE Evaluation of the association of six polymorphisms in these genes with food intake and nutritional status in children followed to 7-8years of age. DESIGN Blood samples and the biodemographic data of 344 children were collected at three development stages, in a cross-sectional study undertaken with the cohort from a randomized trial. Polymorphisms were analyzed using polymerase chain reaction-based techniques. RESULTS At 7 to 8years of age, carriers of the A alleles for both the SLC6A14 rs2312054 and SLC6A14 rs12391221 polymorphisms showed higher food intake, except for the sugar-dense food (SDF) intake parameter, than T/T and C/C homozygotes, respectively. Boy carriers of the C allele of rs2071877 had a higher sum of triceps and subscapular folds than T allele carriers at 7 to 8years old. For 5-HTR2C gene variants, A allele carriers (rs3813928) and T allele carriers (rs3813929) had higher food intake at 3 to 4years old than G/G and C/C homozygotes, respectively, except for SDF. At this age, the intake of energy-dense foods was higher in carriers of the T allele (rs3813929) than in C/C homozygotes. CONCLUSION This study provides evidence that genetic variants of these proteins might be involved in the determination of food intake and nutritional status in children.

The lactase persistence genotype is a protective factor for the metabolic syndrome

The Metabolic Syndrome (MetS) is defined as a pattern of metabolic disturbances, which include central obesity, insulin resistance and hyperglycemia, dyslipidemia, and hypertension. Milk has been promoted as a healthy beverage that can improve the management of MetS. Most human adults, however, down-regulate the production of intestinal lactase after weaning. Lactase encoded by the LCT gene is necessary for lactose digestion. The -13910C > T SNP (rs4988235) is responsible for the lactase persistence phenotype in European populations. We herein investigated whether the lactase persistence genotype is also associated with the MetS in subjects from a Brazilian population of European descent. This study consisted of 334 individuals (average age of 41 years) genotyped by PCR-based methods for the -13910C > T SNP. Clinical data were assessed and the genotypes were tested for their independent contribution to the MetS using chi-square tests and multiple logistic regression analysis. Univariate analyses showed that hypertension and MetS prevalence were higher in individuals with the lactase non-persistence genotype than in lactase persistence subjects. Furthermore, lactase persistence was associated with a lower risk for MetS (OR = 0.467; 95% CI 0.264–0.824; p = 0.009). These results suggest that LCT genotypes can be a valuable tool for the management of MetS treatment.