Nude mice as a model for gonadotropin-induced adrenocortical neoplasia

Excess dietary zinc drives a Cushing's-like syndrome in ovariectomized mice - Implications for postmenopausal obesity

Postmenopausal women have an increased risk of obesity, but the underlying cause is not clear. We unexpectedly found that excess dietary zinc induced severe obesity and a Cushing's-like syndrome without increased food intake in ovariectomized (Ovx) but not in sham-operated mice. Zinc accumulated in the adrenal glands and inhibited adrenal 17,20-lyase activity and steroid synthesis. As adrenal steroids are the only source of estrogen in Ovx mice, estrogen deficiency induced adrenal hyperplasia, glucocorticoid overproduction, and consequent development of a Cushing's-like syndrome. Adrenal steroid supplementation prevented the effects of zinc. Plasma zinc was positively correlated with cortisol level and negatively correlated with the levels of adrenal steroids and estrogen in obese postmenopausal women. The finding of a link between dietary zinc, estrogen deficiency, and postmenopausal obesity, implies that postmenopausal obesity might be prevented by supplementation with a adrenal steroid and avoiding excess dietary zinc.

Expression of sfrp1 and activation of the Wnt pathway in the adrenal glands of healthy ferrets and neutered ferrets with hyperadrenocorticism

Gonadectomy induces the pathogenesis of luteinising hormone receptor positive, androgen and oestrogen producing tumours in the adrenal cortex of ferrets. In mice, the castration-dependent appearance of adrenocortical tumours has been attributed to loss of expression of the tumour suppressor gene Secreted Frizzled Related Protein 1 (sfrp1), a dominant inhibitor of the Wnt pathway, which controls cell proliferation and 'cell faith' decisions. This study investigated whether sfrp1 and the Wnt pathway play a similar role in the pathogenesis of hyperadrenocorticism in ferrets. The expression of sfrp1 and three target genes of the Wnt pathway (c-myc, axin2 and cyclinD1) in seven adrenal glands from healthy ferrets and in 13 adrenocortical tumours were studied by quantitative real-time PCR. Nuclear β-catenin staining was assessed by immunohistochemistry. Sfrp1 mRNA expression was up-regulated and axin2 and cyclinD1 were down-regulated in the tumour group in comparison with the control group. Decreased nuclear β-catenin staining supported the decrease in active Wnt signalling in adrenocortical tumours in ferrets. Therefore, it is unlikely that the involvement of sfrp1 and the Wnt pathway in the pathogenesis of adrenocortical tumours in ferrets is similar to that described in mice.

Role of the GATA family of transcription factors in endocrine development, function, and disease

The WGATAR motif is a common nucleotide sequence found in the transcriptional regulatory regions of numerous genes. In vertebrates, these motifs are bound by one of six factors (GATA1 to GATA6) that constitute the GATA family of transcriptional regulatory proteins. Although originally considered for their roles in hematopoietic cells and the heart, GATA factors are now known to be expressed in a wide variety of tissues where they act as critical regulators of cell-specific gene expression. This includes multiple endocrine organs such as the pituitary, pancreas, adrenals, and especially the gonads. Insights into the functional roles played by GATA factors in adult organ systems have been hampered by the early embryonic lethality associated with the different Gata-null mice. This is now being overcome with the generation of tissue-specific knockout models and other knockdown strategies. These approaches, together with the increasing number of human GATA-related pathologies have greatly broadened the scope of GATA-dependent genes and, importantly, have shown that GATA action is not necessarily limited to early development. This has been particularly evident in endocrine organs where GATA factors appear to contribute to the transcription of multiple hormone-encoding genes. This review provides an overview of the GATA family of transcription factors as they relate to endocrine function and disease.

Adrenocortical tumorigenesis, luteinizing hormone receptor and transcription factors GATA-4 and GATA-6

Luteinizing hormone (LH/hCG) responsiveness of normal and pathological human adrenal glands as well as the possibility of constitutive expressions of luteinizing hormone receptor (LHR) in adrenal cortex has been reported. Some recent studies showed a correlation between the LHR and abundant GATA-4 expression in both metastasizing and non-metastasizing human adrenocortical tumors, but not in normal adrenals, implicating the putative relevance of LHR and GATA-4 for adrenocortical pathophysiology. However, the physio- and pathophysiological significance of LHR and GATA-4 in the mechanism of adrenocortical tumorigenesis remains unclear. The paucity of suitable models for adrenal tumorigenesis makes the establishment of proper animal models highly important. LHR expression in the murine adrenal gland is an exception and not found in wild-type (WT) animal. We have previously shown that ectopic LHR expression in the murine adrenal gland can be induced by chronically elevated LH levels. We have generated a gonadotropin-responsive adrenal tumor model in gonadectomized transgenic (TG) mice expressing the inhibin alpha promoter/Simian Virus 40 T antigen transgene (inhalpha/Tag). Given the induction of expression and regulation of GATA-4 and GATA-6 zinc finger transcription factors in the gonads by gonadotropins, this review will explore their relationship to LHR expression and their role in adrenocortical tumorigenesis. A functional link between LHR and GATA-4 actions in the adrenal pathophysiology is proposed.

The past, present and future of nongonadal LH/hCG actions in reproductive biology and medicine

The past and present published studies reaffirm that nongonadal LH and hCG actions are real and here to stay. These actions have led to a better understanding of the biology of the hormones and more importantly begin to pave the way for novel therapies in reproductive medicine and in other areas.