Exploring leukocyte O-GlcNAcylation as a novel diagnostic tool for the earlier detection of type 2 diabetes mellitus.
BACKGROUND
Because current tests available for the diagnosis of diabetes have shortcomings, a novel screening method for the earlier and more efficient detection of type 2 diabetes would be a significant clinical advance.


OBJECTIVE
The hexosamine biosynthetic pathway usually acts as a fuel sensor, and its activation leads to O-linked β-N-acetylglucosamine (O-GlcNAc) modification of target proteins (O-GlcNAcylation) in a glucose-responsive manner. O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA) are responsible for O-GlcNAc addition and removal, respectively. Because higher hexosamine biosynthetic pathway flux is linked to insulin resistance/type 2 diabetes, we hypothesized that increased O-GlcNAcylation of leukocyte proteins can detect the onset of pre- and overt diabetes.


METHODS
Seventy-four participants from Bellville and Stellenbosch (Western Cape, South Africa) were recruited and classified as normal, prediabetic, and diabetic individuals (American Diabetes Association criteria).


METHODS
Leukocytes isolated from study subjects were evaluated for O-GlcNAc, OGA, and O-GlcNAc transferase expression by flow cytometry and immunofluorescence microscopy.


RESULTS
Flow cytometric analysis of leukocyte subtypes revealed increased O-GlcNAcylation in granulocytes vs. lymphocytes (P < 0.001). Diabetic individuals displayed higher leukocyte O-GlcNAcylation (P < 0.01), whereas granulocyte analysis showed an increase for prediabetic subjects (P < 0.01). However, OGA expression increased in leukocytes of diabetic subjects and is likely an adaptation to attenuate higher O-GlcNAcylation observed (P < 0.001).


CONCLUSIONS
Together our data demonstrate that leukocyte (particularly granulocyte) O-GlcNAcylation could help detect pre- and overt diabetes and offer clinical value as unique markers for the earlier and more efficient detection of type 2 diabetes.
Cardio-Metabolic Research Group, Department of Physiological Sciences, Stellenbosch University, Room 2005, Mike De Vries Building, Merriman Avenue, Stellenbosch 7600, South Africa.
Clare
C
Springhorn
Tandi E
TE
Matsha
Rajiv T
RT
Erasmus
M Faadiel
MF
Essop
D000117:Acetylglucosamine / Q000032:analysis / Q000097:blood / Q000378:metabolism*; D000215:Acylation; D001786:Blood Glucose / Q000032:analysis / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000175:diagnosis* / Q000378:metabolism; D042241:Early Diagnosis; D005215:Fasting / Q000097:blood / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D006442:Glycated Hemoglobin / Q000032:analysis; D006031:Glycosylation; D006801:Humans; D007962:Leukocytes / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D017351:N-Acetylglucosaminyltransferases / Q000032:analysis / Q000378:metabolism*; D011236:Prediabetic State / Q000097:blood / Q000175:diagnosis / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000502:physiology
D000117:Acetylglucosamine; D001786:Blood Glucose; D006442:Glycated Hemoglobin; D017351:N-Acetylglucosaminyltransferases; C517652:hemoglobin A1c protein, human; C449880:O-GlcNAc transferase