Table 1.

Findings of 5-HT/5HIAA levels in different studies including animal and human studies with DM

5-HT metabolite level in the diabetic and normal group (µg L−1)	Determination Method	Types of diabetes or complications	Sample	Main finding	Refs
Diabetic: 1.93 ± 0.07 and healthy: 8.70 ± 0.30	Electrochemical sensing and HPLC	T2D	GI of ZF	Significant reduction in the 5-HT level in diabetic ZF	[18]
NA	A stable isotope dilution direct-infusion method (SIDE-MS assay)	GDM	Plasma and urine	Displaying higher 5-HT levels about disrupted metabolisms, like GDM	[20]
5-HIAA as a mediator of 5-HT 5.2 ± 2.0 and 4.1 ± 1.4	HPLC	T2D/ normoalbuminuric and microalbuminuric patients	WB	Increasing plasma 5-HIAA concentrations associated with impaired systolic and late diastolic, and increasing the resistance of peripheral vascular in diabetic patients	[21]
358.5 and 379.5 (ng/109)	HPLC	T2D and depression	PPP	Finding association between cortisol or 5-HT and platelet markers	[22]
10.2, 6.2, and 8.5 for diabetic groups and 4.8 for the healthy group in PPP 657,485, and 582 for diabetic groups and 713 for the healthy group in WB	HPLC	T2D complicated with chronic kidney (divided into 3 groups and 1 healthy group	PPP, WB	Reduction of the 5-HT level in the plasma and raising 5-HT level in WB, perhaps by suppressing platelet aggregation by administration of iloprost	[19]
5-HIAA 6.9 ± 5.4 Low plasma 3.5 ± 0.8 Moderate plasma 5.7 ± 0.7 High plasma 11.6 ± 7.3	HPLC	T2D- nephropathy	Plasma	Demonstrating relation between plasma 5-HIAA concentration and urinary albumin excretion	[23]
Qualitative consideration	HPLC	ACD- T2D	Plasma	Presenting a major association between plasma 5-HT and atherosclerosis in diabetic patients	[24]

HPLC High performance liquid chromatography; T2D Type 2 diabetes; WB Whole blood; PPP Platelet-rich plasma; 5-HIAA 5-Hydroxyindoleacetic acid; ACD Atherosclerotic cardiovascular disease; GI Gastrointestinal; ZF Zebrafish; GDM Gestational diabetes mellitus