Differential gene regulation of GHSR signaling pathway in the arcuate nucleus and NPY neurons by fasting, diet-induced obesity, and 17β-estradiol

Abstract

Ghrelin’s receptor, growth hormone secretagogue receptor (GHSR), is highly expressed in the arcuate nucleus (ARC) and in neuropeptide Y (NPY) neurons. Fasting, diet-induced obesity (DIO), and 17β-estradiol (E2) influence ARC Ghsr expression. It is unknown if these effects occur in NPY neurons. Therefore, we examined the expression of Npy, Agrp, and GHSR signaling pathway genes after fasting, DIO, and E2 replacement in ARC and pools of NPY neurons. In males, fasting increased ARC Ghsr and NPY Foxo1 but decreased NPY Ucp2. In males, DIO decreased ARC and NPY Ghsr and Cpt1c. In fed females, E2 increased Agrp, Ghsr, Cpt1c, and Foxo1 in ARC. In NPY pools, E2 decreased Foxo1 in fed females but increased Foxo1 in fasted females. DIO in females suppressed Agrp and augmented Cpt1c in NPY neurons. In summary, genes involved in GHSR signaling are differentially regulated between the ARC and NPY neurons in a sex-dependent manner.

The interaction of fasting, caloric restriction, and diet-induced obesity with 17β-estradiol on the expression of KNDy neuropeptides and their receptors in the female mouse

“…Uterine weight was increased by E2B treatment in both LFD- (p < 0.0001) and HFD- (p < 0.0001) fed animals (Table 2; steroid: F(1, 36) = 55.13, p < 0.0001). Uterine weight relative to body weight was increased in E2B- compared to oil-treated animals in both LFD- and HFD-fed animals, as we have previously reported (Yasrebi et al, 2016). Plasma E2 concentrations were elevated in E2B-treated animals, within both diets (Yasrebi et al, 2016).…”

“…In one study, Kiss1 mRNA expression in the ARC was unchanged with administration of ghrelin in a fed or fasted state (Forbes et al, 2009). In another, ghrelin depolarized more KNDy neurons in E2-treated females than in oil-treated females, which was due to an increase Ghsr expression in the ARC by E2 (Frazao et al, 2014, Yasrebi et al, 2016). …”

“…In Experiments #4–5, we collected Tac2 neurons to determine cell-type specific changes in gene expression similar to our previous publication (Yasrebi et al, 2016). Briefly, animals were sedated with ketamine (100 μl of 100 mg/ml stock, i.p.)…”

“…For ARC, cDNA was synthesized from 200 ng of total RNA, following our previous publication (Yasrebi et al, 2016). A 1:20 dilution of the cDNA was produced using nuclease-free water (Gene Mate) for a final cDNA concentration of 0.5 ng/μl and stored at −20°C.…”

Identification of mutations through dominant screening for obesity using C57BL/6 substrains

“…Unlike obesity in Sim1 or Mc4r mutant mice, the obesity induced in the high-fat diet rodent model is relevant to human obesity which is strongly associated with the recent availability of high-calorie food. Prolonged high-fat diet feeding promotes leptin-resistance18 and alters hypothalamic gene expression patterns, such as decreased Agrp and Ghrh mRNA levels without significant change in Pomc mRNA level41495051, which is consistent with the current results for DIO mice. Common changes between DIO mice and genetically obese mice, such as decreased Agrp and Avp mRNA levels, might be secondary to obesity-associated changes, including increased leptin and insulin levels and polyuria52.…”