The neuroprotective effect of ghrelin has recently been reported in Alzheimer's disease (AD). Ghrelin is converted from des-acyl ghrelin to the activated form, acyl ghrelin, by membrane bound o-acyltransferase 4 (MBOAT4), and then binds to growth hormone secretagogue receptor (GHS-R). We examined the levels of plasma acyl/des-acyl ghrelin in 75 AD subjects and age- and sex-matched controls, as well as the DNA methylation and mRNA expression of MBOAT4 and GHS-R in peripheral leukocytes. The acyl ghrelin concentration was significantly higher in AD subjects than in controls (2.18 ± 1.25 vs. 1.49 ± 2.3, p = 0.001). The methylation rate of MBOAT4 CpG 2 was significantly lower in AD subjects than in controls (4.0 ± 0.9 vs. 4.7 ± 1.2, p < 0.001). The mRNA expression levels of MBOAT4 and GHS-R1b were significantly higher in AD subjects than in controls (MBOAT4: 1.10 ± 0.48 vs. 1.0 ± 0.55, p = 0.049; GHS-R1b: 1.76 ± 3.18 vs. 1.0 ± 1.56, p = 0.030). These changes in the ghrelin cascade in peripheral blood may reflect those in the brain, and may be a neuroprotective biomarker in AD.
Keywords: Acyl ghrelin; Alzheimer's disease; Des-acyl ghrelin; Growth hormone secretagogue receptor; Membrane bound O-acyltransferase 4; Rivastigmine.
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