Galanin‐Like Peptide (GALP) Neurone‐Specific Phosphoinositide 3‐Kinase Signalling Regulates GALP mRNA Levels in the Hypothalamus of Males and Luteinising Hormone Levels in Both Sexes

Abstract

Galanin-like peptide (GALP) neurons participate in the metabolic control of reproduction and are targets of insulin and leptin regulation. Phosphoinositide 3-kinase (PI3K) is common to the signaling pathways utilized by both insulin and leptin. Therefore, we investigated whether PI3K signaling in neurons expressing GALP plays a role in the transcriptional regulation of the GALP gene and in the metabolic control of luteinizing hormone (LH) release. To this end, we deleted PI3K catalytic subunits, p110α and p110β via conditional gene targeting (cKO) in mice (GALP-p110α/β cKO). To monitor PI3K signaling in GALP neurons these animals were also crossed with Cre-dependent FoxO1GFP reporter mice. Compared to insulin-infused control animals, the PI3K-Akt-dependent FoxO1GFP nuclear exclusion in GALP neurons was abolished in GALP-p110α/β cKO mice. We next used food deprivation to investigate if the GALP-neuron specific ablation of PI3K activity affected the susceptibility of the gonadotropic axis to negative energy balance. Treatment did not affect LH levels in either sex. However, a significant genotype effect on LH levels was observed in females. In contrast, no genotype effect on LH levels was observed in males. A sex-specific genotype effect on hypothalamic GALP mRNA was observed, with fed and fasted GALP-p110α/β cKO males having lower GALP mRNA expression compared to WT fed males. Finally, the effects of gonadectomy and steroid hormone replacement on GALP mRNA levels were investigated. Compared to vehicle-treated mice, steroid hormone replacement reduced MBH GALP expression in WT and GALP-p110α/β cKO animals. In addition, within the castrated and vehicle-treated group and compared to WT, LH levels were lower in GALP-p110α/β cKO males. Double immunofluorescence using GALP-Cre/R26-YFP mice showed androgen and estrogen receptor co-localization within GALP neurons. Our data demonstrate that GALP neurons are direct targets of steroid hormones and that PI3K signaling regulates hypothalamic GALP mRNA expression and LH levels in a sex-specific fashion.

Loss of PI3K p110αin the Adipose Tissue Results in Infertility and Delayed Puberty Onset in Male Mice

“…In the present study, we show that deletion of class IA PI3K catalytic subunit p110 α in adipose tissue results in delayed puberty onset and impaired fertility in males, with adults also showing hyperandrogenemia. The PI3K signaling pathway participates in the regulation of specific aspects of male reproductive function such as gonadotropin release [ 16 , 17 ], gonadal development [ 18 ], and spermatogenesis [ 19 ] acting on both the hypothalamic and the gonad level. To our knowledge, this is the first report to demonstrate that adipose tissue-specific disruption of PI3K signaling impairs male reproductive capacity, independent of a diet manipulation.…”

“…In the latter, PI3K mediates insulin effects on glucose uptake and lipolysis [ 13 – 15 ]. PI3K signaling also participates in the regulation of reproductive function; at the level of the hypothalamus, PI3K regulates the expression of neuropeptides important for fertility and gonadotropin release [ 16 , 17 ]; at the gonad level, PI3K signaling has been shown to regulate gametogenesis and spermatogenesis [ 18 , 19 ]. Class 1A PI3Ks are comprised of a catalytic subunit (p110 α , p110 β , or p110 δ ) bound to one of several regulatory subunits (collectively referred to as p85) [ 5 ].…”

Genetic Variability in Molecular Pathways Implicated in Alzheimer's Disease: A Comprehensive Review

“…Grupe et al reported the association of GALP rs3745833 with increased risk for LOAD (Grupe et al, 2007 ). GALP is a neuropeptide, having important role in the central metabolic control of the reproductive axis (Aziz et al, 2014 ). It is a ligand in G-protein mediated signal transduction in CNS (Robinson et al, 2006 ).…”

Kisspeptin cell-specific PI3K signaling regulates hypothalamic kisspeptin expression and participates in the regulation of female fertility

“…To generate mice in which the genes for the PI3K catalytic subunits p110␣ (Pik3ca) and p110␤ (Pik3cb) are deleted specifically in kisspeptin cells, double-floxed mice, p110␣ flx/flx / p110␤ flx/flx were mated with kisspeptin-IRES-CRE mice (58). Animals were screened for the presence of Cre and floxed p110␣ and p110␤ by PCR of isolated genomic tail DNA as described previously (3,55,58). The resulting F1 animals were then intercrossed to generate KissIC Ϫ p110␣ flx/flx / p110␤ flx/flx and KissIC ϩ p110␣ flx/flx /p110␤ flx/flx animals, referred to here as wild-type (WT) and kiss-p110␣/␤ knockout (KO), respectively.…”

“…Adult male mice of both genotypes were randomly assigned to one of three groups: intact sham operated (controls), Gdx ϩ V, or Gdx ϩ T. At the time of surgery, each animal received a subcutaneous Silastic capsule (1.02 ϫ 2.16 mm od) 5 mm in length filled with crystalline T or left empty (3,60). Adult female mice from each genotype were randomly assigned to one of three groups: intact sham operated (controls), Ovx ϩ V, or Ovx ϩ E 2.…”