Table 3.

Characteristics of included studies in mechanism research

Ref.	Detecting items	Research techniques	Main results
Gastric motility
Liu et al[26], 2008	Gastric myoelectrical activity	EGG	Gastric slow wave not altered by TEA
Ji et al[28], 2014	Gastric myoelectrical activity; Gastric emptying	EGG; Radiogram	Increased percentage of normal slow wave in both fasting and postprandial stages in TEA (dP < 0.01) not in sham TEA; accelerated gastric emptying in TEA (fP < 0.001) not in sham TEA
Xu et al[30], 2015	Gastric myoelectrical activity	EGG	Increased dominant power and percentage of normal slow wave in postprandial stage in TEA compared with sham TEA (cP < 0.05)
Zhang et al[31], 2015	Gastric myoelectrical activity; gastric emptying	EGG; B-ultrasound	Improved basic frequency and slow wave frequency in EA compared with CONT (aP < 0.05); increased gastric half-emptying time and antrum movement index in EA compared with CONT (aP < 0.05)
Gastric accommodation
Ji et al[28], 2014	Gastric accommodation	Nutrient drinking test	Improved threshold of satiety volume (dP < 0.01) and maximum tolerance volume (fP < 0.001) in TEA not in sham TEA
Xu et al[30], 2015	Gastric accommodation	Satiety drinking test	Increased maximum tolerable volume in TEA compared with sham TEA (cP < 0.05)
GI hormones
Liu et al[26], 2008	Plasma NPY and motilin levels	Radioimmunoassay	Increased plasma NPY but not motilin level in TEA (cP < 0.05) not in sham TEA
Zhang et al[31], 2015	Plasma motilin level	Radioimmunoassay	Increased plasma motilin level in EA compared with CONT (aP < 0.05)
Qiang et al[33], 2018	Serum ghrelin, CGRP and GLP-1 levels	ELISA	Increased serum ghrelin and GLP-1 levels and decreased CGRP level in EA compared with CONT (aP < 0.05)
Mental status
Ji et al[28], 2014	Anxiety and depression	SAS/SDS	Decreased anxiety (dP < 0.01) and depression (cP < 0.05) scores in TEA not in sham TEA
Jin et al[29], 2015	Anxiety and depression	SAS/SDS	Improved anxiety (kP < 0.0001) and depression (kP < 0.001) status in MA compared with sham MA
Ko et al[32], 2016	Anxiety and depression	STAI/BDI	Decreased anxiety and depression scores in MA (bP < 0.01) not in CONT
Central and autonomic functions
Liu et al[26], 2008	Autonomic function	HRV derived from ECG	In fasting stage, higher HF activity (cP < 0.05) and lower LF/HF ratio (cP < 0.05) in TEA than that before the treatment but not in sham TEA
Zeng et al[27], 2012	Cerebral glycometabolism changes	PET-CT scans	Extensive deactivation in cerebral activities in EA compared with the sham EA(fP < 0.001)
Xu et al[30], 2015	Autonomic function	HRV derived from ECG	Enhanced vagal activity in TEA compared with sham TEA (fP < 0.001)

^aP < 0.05,

^bP < 0.01 vs control group;

^cP < 0.05,

^dP < 0.01,

^fP < 0.001 vs sham TEA;

^kP < 0.001 vs sham EA. BDI: Beck depression inventory; CGRP: Calcitonin gene-related peptide; CONT: Control group; EA: Electroacupuncture; ECG: Electrocardiogram; EGG: Electrogastrogram; GI: Gastrointestinal; GLP-1: Glucagon-like peptide-1; HRV: Heart rate variability; MA: Manual acupuncture; NPY: Neuropeptide Y; SAS: Zung’s self-rating anxiety scale; SDS: Zung’s self-rating depression scale; STAI: State-trait anxiety inventory; PET-CT: Fluorine-18 fluorodeoxy glucose positron emission tomography computed tomography; TEA: Transcutaneous electrical acustimulation; ELISA: Enzyme linked immunosorbent assay.