Effect of Fasting on the Content of Thyrotropin-releasing Hormone and its mRNA in the Central Nervous System and Pyroglutamyl Peptidase II Activity in the Anterior Pituitary of Post-Weaned and Adult Rats

Gortari, Patricia de; González-Alzati, Ma. Elena; Cisneros, Miguel; Joseph‐Bravo, Patricia

doi:10.1080/1028415x.2000.11747323

Cited by 10 publications

(5 citation statements)

References 65 publications

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“…PF animals did not show any difference in AH or MBH PPII activity, therefore our results confirmed that there were specific effects of the mineral deficiency in the TRH-degrading activity of the enzyme that could not be due to a negative energy balance. This is in agreement with previous studies with fasted and foodrestricted adult rats (de Gortari et al, 2000;Alvarez-Salas et al, 2012); besides, differential metabolic effects are induced by Zndeficiency and by its associated negative energy balance (Gaetke et al, 2002).…”

Section: Male Adult Ratssupporting

confidence: 93%

“…Although PPII activity has been proposed to participate in the regulatory effects of TH on HPT axis function, it is not known whether TRH‐induced TSH release is affected by changes on PPII activity independently from the direct effects that TH have on TSH expression (Bauer, 1995). For example, the decrease in circulating T 3 levels that occurs during negative energy balance in rats is accompanied by a decrease in TSH serum levels, but not in AH or MBH PPII activity (Alvarez‐Salas et al, 2012; de Gortari et al, 2000). However, without changing TH levels, there is evidence that the systemic administration of a PPII inhibitor along with TRH is able to maintain high circulating TSH levels for a longer time when compared to those of animals injected only with TRH (Scalabrino et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

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Mediobasal hypothalamic and adenohypophyseal TRH‐degrading enzyme (PPII) is down‐regulated by zinc deficiency

Alvarez-Salas

Alcántara-Alonso

Matamoros-Trejo

et al. 2015

Intl J of Devlp Neuroscience

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Thyrotropin-releasing hormone (TRH) synthesized in hypothalamic paraventricular nucleus directs hypothalamus-pituitary-thyroid (HPT) axis function, regulating thyrotropin release from adenohypophysis and thyroid hormones serum concentration. Pyroglutamyl aminopeptidase II (PPII), a Zn-dependent metallopeptidase located in adenohypophysis and medial-basal-hypothalamus degrades TRH released from the median eminence and participates in HPT axis function by regulating TRH-induced thyrotropin release from adenohypophysis. It is unknown whether dietary Zn deficiency down-regulates PPII. Our aim was to compare adenohypohyseal and medial-basal-hypothalamic PPII activity and expression of adult rats fed a Zn-deficient diet (2ppm) throughout their lifespan (DD), prenatally (DC) or after weaning (CD) vs. that of animals fed a control diet (20ppm:CC). Female rats consumed a Zn-deficient or control diet from two weeks before gestation and up to the end of lactation. We analyzed adenohypophyseal and medial-basal-hypothalamic PPII activity of dams and male offspring when adults; its relation to median eminence TRH, serum thyrotropin, leptin and thyroid hormones concentration. Offspring ate the same diet as their dams (CC, DD) or were switched from dietary regime after weaning (CD, DC) and until 2.5 months of age. DD males showed decreased adenohypophyseal and medial-basal-hypothalamic PPII activity, along with high thyrotropin serum concentration. Post-weaning Zn-deficiency (CD) decreased PPII activity only in adenohypophysis and increased thyrotropin circulating levels. Zn-replenishment (DC) normalized PPII activity in both regions and serum thyrotropin concentration. Adenohypophyseal PPII activity decreased and prolactin levels increased in Zn-deficient dams. We concluded that long-term changes in dietary Zn down-regulate PPII activity independently of T3, increasing thyrotropin serum concentration, overall resembling sub-clinical hypothyroidism.

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Section: Male Adult Ratssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Mediobasal hypothalamic and adenohypophyseal TRH‐degrading enzyme (PPII) is down‐regulated by zinc deficiency

Alvarez-Salas

Alcántara-Alonso

Matamoros-Trejo

et al. 2015

Intl J of Devlp Neuroscience

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“…In contrast, our data supported that hypothalamic neurons are firstly responding to low nutrient availability and as a consequence, metabolic rate is adjusted through HPT axis function modulation. For example, negative energy balance decelerates HPT axis and lipids waste in adults, but in weanling rats such adaptation is not successful [ 38 ]. Similarly, in this study, the low Zn intake seemed to activate TRH release from the ME (discussed below) and to increase TSH serum levels, with no abatement of the metabolic rate.…”

Section: Discussionmentioning

confidence: 99%

Intrauterine Zn Deficiency Favors Thyrotropin-Releasing Hormone-Increasing Effects on Thyrotropin Serum Levels and Induces Subclinical Hypothyroidism in Weaned Rats

et al. 2017

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Individuals who consume a diet deficient in zinc (Zn-deficient) develop alterations in hypothalamic-pituitary-thyroid axis function, i.e., a low metabolic rate and cold insensitivity. Although those disturbances are related to primary hypothyroidism, intrauterine or postnatal Zn-deficient adults have an increased thyrotropin (TSH) concentration, but unchanged thyroid hormone (TH) levels and decreased body weight. This does not support the view that the hypothyroidism develops due to a low Zn intake. In addition, intrauterine or postnatal Zn-deficiency in weaned and adult rats reduces the activity of pyroglutamyl aminopeptidase II (PPII) in the medial-basal hypothalamus (MBH). PPII is an enzyme that degrades thyrotropin-releasing hormone (TRH). This hypothalamic peptide stimulates its receptor in adenohypophysis, thereby increasing TSH release. We analyzed whether earlier low TH is responsible for the high TSH levels reported in adults, or if TRH release is enhanced by Zn deficiency at weaning. Dams were fed a 2 ppm Zn-deficient diet in the period from one week prior to gestation and up to three weeks after delivery. We found a high release of hypothalamic TRH, which along with reduced MBH PPII activity, increased TSH levels in Zn-deficient pups independently of changes in TH concentration. We found that primary hypothyroidism did not develop in intrauterine Zn-deficient weaned rats and we confirmed that metal deficiency enhances TSH levels since early-life, favoring subclinical hypothyroidism development which remains into adulthood.

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“…The hormonal effects on PPII activity are preceded by similar changes in PPII mRNA levels (6,9,10), suggesting a control of peptidase biosynthesis. Fasting inhibits adenohypophyseal PPII activity in postweaned but not in adult rats (11).…”

Section: Introductionmentioning

confidence: 99%

Thyrotropin-releasing hormone regulates the diurnal variation of pyroglutamyl aminopeptidase II activity in the male rat adenohypophysis

Vargas

Uribe

Cisneros

et al. 2002

European Journal of Endocrinology

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Effect of Fasting on the Content of Thyrotropin-releasing Hormone and its mRNA in the Central Nervous System and Pyroglutamyl Peptidase II Activity in the Anterior Pituitary of Post-Weaned and Adult Rats

Cited by 10 publications

References 65 publications

Mediobasal hypothalamic and adenohypophyseal TRH‐degrading enzyme (PPII) is down‐regulated by zinc deficiency

Mediobasal hypothalamic and adenohypophyseal TRH‐degrading enzyme (PPII) is down‐regulated by zinc deficiency

Intrauterine Zn Deficiency Favors Thyrotropin-Releasing Hormone-Increasing Effects on Thyrotropin Serum Levels and Induces Subclinical Hypothyroidism in Weaned Rats

Thyrotropin-releasing hormone regulates the diurnal variation of pyroglutamyl aminopeptidase II activity in the male rat adenohypophysis

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