Adipokine Gene Expression in Brain and Pituitary Gland

Abstract

The brain has been recognized as a prominent site of peptide biosynthesis for more than 30 years, and many neuropeptides are now known to be common to gut and brain. With these precedents in mind it is remarkable that adipose-derived peptides like leptin have attracted minimal attention as brain-derived putative neuromodulators of energy balance. This review outlines the evidence that several adipose-specific genes are also expressed in the central nervous system and pituitary gland. We, and others, confirmed that the genes for leptin, resistin, adiponectin, FIAF (fasting-induced adipose factor) and adiponutrin are expressed and regulated in these tissues. For example, leptin mRNA was readily detectable in human, rat, sheep and pig brain, but not in the mouse. Leptin expression in rat brain and pituitary was regulated through development, by food restriction, and following traumatic brain injury. In contrast, hypothalamic resistin mRNA was unaffected by age or by fasting, but was significantly depleted by food restriction in mouse pituitary gland. Similar results were seen in the ob/ob mouse, and we noted a marked reduction in resistin-positive hypothalamic nerve fibres. Resistin and fiaf mRNA were also upregulated in hypoxic/ischaemic mouse brain. Our studies on the regulation of neuronal adipokines were greatly aided by the availability of clonal hypothalamic neuronal cell lines. One of these, N-1, expresses both rstn and fiaf together with several other neuropeptides and receptors involved in energy homeostasis. Selective silencing of rstn revealed an autocrine/paracrine regulatory system, mediated through socs-3 expression that may influence the feedback effects of insulin and leptin in vivo. A similar convergence of signals in the pituitary gland could also influence anterior pituitary hormone secretion. In conclusion, the evidence is suggestive that brain and pituitary-derived adipokines represent a local regulatory circuit that may fine tune the feedback effects of adipose hormones in the control of energy balance.

Physical exercise-induced hippocampal neurogenesis and antidepressant effects are mediated by the adipocyte hormone adiponectin

“…This could reflect that the 2-wk training is insufficient to produce a substantial elevation of adiponectin in the circulation (12) or that exercise potentially facilitates the transport of adiponectin from the circulation into the brain. It is also possible that this increase was produced by adipose or nervous tissues inside the brain (33).…”

Brain Activation by Visual Food-Related Stimuli and Correlations with Metabolic and Hormonal Parameters: A fMRI Study

“…This regulation is likely to be highly complex, involving the dopaminergic system, and psychosocial factors including stress [52][53][54][55].…”

Adiponectin and resistin: potential metabolic signals affecting hypothalamo-pituitary gonadal axis in females and males of different species

“…Moreover, in primary rat pituitary cells, GnRH treatment suppressed pituitary adiponectin expression (Kim et al 2013). AdipoRs have been identified in gonadotropin-producing cells in the pars distalis but not in the pars tuberalis in the human pituitary (Wilkinson et al 2007). To our knowledge, a sexual dimorphism has been described in the levels of circulating plasma adiponectin, with males having lower adiponectin levels than females (Arita et al 1999).…”

“…Despite the conflicting evidence as to whether adiponectin can cross the blood-brain barrier, some studies have reported adiponectin and AdipoR expression in the brain and pituitary of various species, including humans, rats, pigs, rodents and chickens (Rodriguez-Pacheco et al 2007, Wilkinson et al 2007, suggesting that adiponectin may be a factor modulating the reproductive functions. AdipoRs have been identified in the hypothalamic GnRH neuron cells (GT1-7) and in human and rodent hypothalami, including in the paraventricular nucleus and in the periventricular areas.…”