title: The suppression of ghrelin signaling mitigates age‐associated  thermogenic impairment.
abstract: Aging is associated with severe thermogenic impairment, which contributes to obesity and diabetes in aging. We previously reported that ablation of the ghrelin receptor, growth hormone secretagogue receptor (GHS‐R), attenuates age‐associated obesity and insulin resistance. Ghrelin and obestatin are derived from the same preproghrelin gene. Here we showed that in brown adipocytes, ghrelin decreases the expression of thermogenic regulator but obestatin increases it, thus showing the opposite effects. We also found that during aging, plasma ghrelin and GHS‐R expression in brown adipose tissue (BAT) are increased, but plasma obestatin is unchanged. Increased plasma ghrelin and unchanged obestatin during aging may lead to an imbalance of thermogenic regulation, which may in turn exacerbate thermogenic impairment in aging. Moreover, we found that GHS‐R ablation activates thermogenic signaling, enhances insulin activation, increases mitochondrial biogenesis, and improves mitochondrial dynamics of BAT. In addition, we detected increased norepinephrine in the circulation, and observed that GHS‐R knockdown in brown adipocytes directly stimulates thermogenic activity, suggesting that GHS‐R regulates thermogenesis via both central and peripheral mechanisms.Collectively, our studies demonstrate that ghrelin signaling is an important thermogenic regulator in aging. Antagonists of GHS‐R may serve as unique anti‐obesity agents, combating obesity by activating thermogenesis.
authors.forename: Ligen
authors.initials: L
authors.lastname: Lin
authors.forename: Jong Han
authors.initials: JH
authors.lastname: Lee
authors.forename: Odelia Y N
authors.initials: OY
authors.lastname: Bongmba
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Ma
authors.forename: Xiongwei
authors.initials: X
authors.lastname: Zhu
authors.forename: David
authors.initials: D
authors.lastname: Sheikh-Hamad
authors.forename: Yuxiang
authors.initials: Y
authors.lastname: Sun
mesh_terms: D052437:Adipocytes, Brown / Q000378:metabolism; D000367:Age Factors; D000375:Aging / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D015536:Down-Regulation; D005838:Genotype; D054439:Ghrelin / Q000097:blood / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism; D007473:Ion Channels / Q000378:metabolism; D008297:Male; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism; D009638:Norepinephrine / Q000097:blood; D036361:Peptide Hormones / Q000378:metabolism; D010641:Phenotype; D034622:RNA Interference; D054440:Receptors, Ghrelin / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D022722:Thermogenesis / Q000235:genetics; D013997:Time Factors; D014162:Transfection; D000071256:Uncoupling Protein 1
chemical_list: D054439:Ghrelin; D007328:Insulin; D007473:Ion Channels; D024101:Mitochondrial Proteins; D036361:Peptide Hormones; D054440:Receptors, Ghrelin; D000071256:Uncoupling Protein 1; C512328:obestatin, mouse; D009638:Norepinephrine