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  • Author: Jing Zhang x
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Yuhui Liu, Le Zhang, Jing Li, Zhongyan Shan and Weiping Teng

Marginal iodine deficiency is a major health problem in pregnant women, but its impact on nerve and intelligence development in offspring has been rarely reported. Our study aimed to investigate the effects of maternal marginal iodine deficiency on nerve and cognitive development in offspring and the related mechanisms. Marginal iodine-deficient rats were given 3 μg iodine per day, while normal control rats were given 4 μg iodine daily. Western blot was used to detect the amounts of brain-derived neurotropic factor (BDNF) and early growth response protein 1 (EGR1) in the hippocampus of each group. Immunohistochemistry was used to measure c-jun and c-fos expression in the hippocampal CA1 region. Finally, the water maze method was used to measure spatial performance. Free thyroxine (FT4) levels in marginal iodine-deficient rats decreased by about 30%. Seven days after birth, EGR1 and BDNF protein levels significantly decreased in the hippocampus of marginal iodine deficiency rats compared with the normal control group. In addition, c-jun and c-fos expression in the hippocampus of 40-day-old rats was decreased in marginal iodine-deficient rats, compared with control. The spatial learning and memory ability of 40-day-old marginal iodine-deficient rats had a downward trend compared with the normal control group. FT4 significantly decreased after pregnancy in rats with marginal iodine deficiency, affecting the expression of related proteins in the brain of offspring.

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Li Ding, Yue Yin, Lingling Han, Yin Li, Jing Zhao and Weizhen Zhang

Neurogenin3-driven deletion of tuberous sclerosis complex 1 (Tsc1) activated mechanistic target of rapamycin complex 1 (mTORC1) measured by the upregulation of mTOR and S6 phosphorylation in islet cells. Neurogenin3-Tsc1−/− mice demonstrated a significant increase in average islet size and mean area of individual islet cell. Insulin mRNA and plasma insulin levels increased significantly after weaning. Glucagon mRNA and plasma levels increased in neonate followed by modest reduction in adult. Somatostatin mRNA and plasma levels markedly increased. Neurogenin3-Tsc1−/− mice fed standard chow demonstrated a significant improvement in glucose tolerance and no alteration in insulin sensitivity. In Neurogenin3-Tsc1−/− mice fed 45% high-fat diets, both glucose tolerance and insulin sensitivity were significantly impaired. Rapamycin reversed the activation of mTORC1, attenuated β cells hypertrophy and abolished the improvement of glucose tolerance. TSC1-mTORC1 signaling plays an important role in the development of pancreatic endocrine cells and in the regulation of glucose metabolism.

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Jacob C Garza, Chung Sub Kim, Jing Liu, Wei Zhang and Xin-Yun Lu

Pharmacological and genetic studies have suggested that melanocortin-4 receptor (MC4R) signaling in the paraventricular nucleus of hypothalamus (PVN) regulates appetite and energy balance. However, the specific role of MC4R signaling in PVN neurons in these processes remains to be further elucidated in normally developed animals. In the present study, we employed RNA interference to determine whether MC4R knockdown in the PVN modulates food intake and body weight in adult rats. Adeno-associated viral (AAV) vectors encoding short hairpin RNAs targeting MC4R (AAV-shRNA-MC4R) were generated to induce MC4R knockdown in the PVN. By in situ hybridization, we detected a high-level expression of Dicer, a key enzyme required for shRNA-mediated gene silencing, along the entire rostrocaudal extent of the PVN. Bilateral injection of AAV-shRNA-MC4R vectors into the PVN of the adult rat resulted in significant and specific reduction of MC4R mRNA expression. Animals with MC4R knockdown exhibited an increase in food intake and excessive body weight gain when exposed to a high-fat diet. Our results provide evidence that AAV-mediated silencing of MC4R on PVN neurons promotes hyperphagia and obesity in response to the dietary challenge in the adult animal.

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Dan Li, Yan Ji, Chunlan Zhao, Yapeng Yao, Anlan Yang, Honghong Jin, Yang Chen, Mingjun San, Jing Zhang, Mingjiao Zhang, Luqing Zhang, Xuechao Feng and Yaowu Zheng

Oxytocin receptor (OXTR) is a G-protein-coupled receptor and known for regulation of maternal and social behaviors. Null mutation (Oxtr−/−) leads to defects in lactation due to impaired milk ejection and maternal nurturing. Overexpression of OXTR has never been studied. To define the functions of OXTR overexpression, a transgenic mouse model that overexpresses mouse Oxtr under β-actin promoter was developed (++ Oxtr). ++ Oxtr mice displayed advanced development and maturation of mammary gland, including ductal distention, enhanced secretory differentiation and early milk production at non-pregnancy and early pregnancy. However, ++ Oxtr dams failed to produce adequate amount of milk and led to lethality of newborns due to early involution of mammary gland in lactation. Mammary gland transplantation results indicated the abnormal mammary gland development was mainly from hormonal changes in ++ Oxtr mice but not from OXTR overexpression in mammary gland. Elevated OXTR expression increased prolactin-induced phosphorylation and nuclear localization of STAT5 (p-STAT5), and decreased progesterone level, leading to early milk production in non-pregnant and early pregnant females, whereas low prolactin and STAT5 activation in lactation led to insufficient milk production. Progesterone treatment reversed the OXTR-induced accelerated mammary gland development by inhibition of prolactin/p-STAT5 pathway. Prolactin administration rescued lactation deficiency through STAT5 activation. Progesterone plays a negative role in OXTR-regulated prolactin/p-STAT5 pathways. The study provides evidence that OXTR overexpression induces abnormal mammary gland development through progesterone and prolactin-regulated p-STAT5 pathway.

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Jiannan Zhang, Xin Li, Yawei Zhou, Lin Cui, Jing Li, Chenlei Wu, Yiping Wan, Juan Li and Yajun Wang

The interaction of melanocortin-4 (MC4R) and melanocortin-3 (MC3R) receptors with proopiomelanocortin (POMC)-derived peptides (e.g. α-MSH), agouti-related protein (AgRP) and melanocortin-2 receptor accessory protein 2 (MRAP2) is suggested to play critical roles in energy balance of vertebrates. However, evidence on their interaction in birds remains scarce. Our study aims to reveal their interaction in chickens and the results showed that (1) chicken (c-)MC3R and cMC4R expressed in Chinese hamster ovary (CHO) cells can be activated by α-MSH and ACTH1–39 equipotently, monitored by a pGL3-CRE-luciferase reporter system; (2) cMC3R and cMC4R, when co-expressed with cMRAP2 (or cMRAP, a cMRAP2 homolog), show increased sensitivity to ACTH treatment and thus likely act as ACTH-preferring receptors, and the interaction between cMC3R/cMC4R and cMRAP2 was demonstrated by co-immunoprecipitation assay; (3) both cMC3R and cMC4R display constitutive activity when expressed in CHO cells, as monitored by dual-luciferase reporter assay, and cMRAP2 (and cMRAP) can modulate their constitutive activity; (4) AgRP inhibits the constitutive activity of cMC3R/cMC4R, and it also antagonizes ACTH/α-MSH action on cMC4R/cMC3R, indicating that AgRP functions as the inverse agonist and antagonist for both receptors. These findings, together with the co-expression of cMC4R, cMC3R, cMRAP2, cAgRP and cPOMC in chicken hypothalamus detected by quantitative real-time PCR, suggest that within the hypothalamus, α-MSH/ACTH, AgRP and MRAP2 may interact at the MC4R(/MC3R) interface to control energy balance. Furthermore, our data provide novel proof for the involvement of MRAP2 (and MRAP) in fine-tuning the constitutive activity and ligand sensitivity and selectivity of both MC3R and MC4R in vertebrates.