aP2-Cre Mediated Ablation of GHS-R Attenuates Adiposity and Improves Insulin Sensitivity during Aging
- Authors
- Lin, Ligen; Lee, Jong Han; Wang, Ruitao; Wang, Ru; Sheikh-Hamad, David; Zang, Qun S.; Sun, Yuxiang
- Issue Date
- Oct-2018
- Publisher
- MDPI
- Keywords
- ghrelin; GHS-R; tissue-specific knockdown mice; thermogenesis; UCP1; adipose tissues
- Citation
- INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, v.19, no.10
- Journal Title
- INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
- Volume
- 19
- Number
- 10
- URI
- https://scholarworks.bwise.kr/gachon/handle/2020.sw.gachon/3259
- DOI
- 10.3390/ijms19103002
- ISSN
- 1422-0067
- Abstract
- Ghrelin via its receptor, the growth hormone secretagogue receptor (GHS-R), increases food intake and adiposity. The tissue-specific functions of GHS-R in peripheral tissues are mostly unknown. We previously reported that while GHS-R expression is very low in white and brown fat of young mice, expression increases during aging. To investigate whether GHS-R has cell-autonomous effects in adipose tissues, we generated aP2-Cre-mediated GHS-R knockdown mice (aP2-Cre/Ghsr(f/f)). We studied young (5-6 months) and old (15-17 months) aP2-Cre/Ghsr(f/f) mice and their age-matched controls. Interestingly, young aP2-Cre/Ghsr(f/f) mice had normal body weight but reduced fat; old mice showed pronounced reductions of both body weight and body fat. Calorimetry analysis revealed that aP2-Cre/Ghsr(f/f) mice had normal food intake and locomotor activity at both young and old age; but intriguingly, while energy expenditure was normal at young age, it was significantly increased at old age. Both young and old aP2-Cre/Ghsr(f/f) mice exhibited improved insulin sensitivity and glucose tolerance. Importantly, old aP2-Cre/Ghsr(f/f) mice maintained higher core body temperature at 4 degrees C, and showed higher expression of the thermogenic uncoupling protein 1 (UCP1) gene. The ex vivo studies further demonstrated that GHS-R deficient white adipocytes from old mice exhibit increased glucose uptake and lipolysis, promoting lipid mobilization. Despite the fact that the in vivo phenotypes of aP2-Cre/Ghsr(f/f) mice may not be exclusively determined by GHS-R knockdown in adipose tissues, our data support that GHS-R has cell-autonomous effects in adipocytes. The anabolic effect of GHS-R in adipocytes is more pronounced in aging, which likely contributes to age-associated obesity and insulin resistance.
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