Inflammatory hypothesis as a link between Alzheimer's disease and diabetes mellitus.
OBJECTIVE
The aim of the present study was to evaluate whether there was an inflammation-mediated link between Alzheimer's disease (AD) and type 2 diabetes mellitus (DM) status.


METHODS
An age-matched control group and patient groups designated as AD without treatment (AD); AD under cholinesterase inhibitors (AD-CEI); DM without treatment (DM); DM under oral antidiabetic agents (DM-OAD); AD under treatment, who had newly diagnosed DM (AD-CEI+DM); and DM under treatment, who had newly diagnosed probable AD (DM-OAD+AD) were studied. Serum inflammation status was evaluated by the determination of serum C-reactive protein (CRP), tumor necrosis factor-alpha, interleukin (IL)-1β and IL-6 levels. CRP levels were determined by an immunonephelometric method. The others were assayed by enzyme-linked immunosorbent assay methods.


RESULTS
IL-1β levels were found to be significantly lower in the DM group than in the control group (P < 0.01). The AD group had significantly higher serum IL-1β levels than the DM group (P < 0.01). IL-6 levels were significantly higher in the AD and DM groups than in controls (P < 0.01 and P < 0.01). Serum tumor necrosis factor-alpha and CRP levels in the AD (P < 0.05 and P < 0.001, respectively) and DM groups (P < 0.05 and P < 0.001, respectively) were significantly higher when compared with the controls. The presence of AD or DM or therapies of the diseases did not significantly change in serum tumor necrosis factor-alpha levels. The AD-CEI + DM and DM-OAD+AD groups had significantly higher CRP levels than the AD-CEI group (P < 0.05) and DM-OAD groups (P < 0.001), respectively. Serum CRP levels showed a positive correlation with Mini-Mental State Examination scores (r = 0.339, P < 0.01).


CONCLUSIONS
Our findings support the presence of a low-grade systemic inflammation link between AD and DM. Geriatr Gerontol Int 2016; 16: 1161-1166.
Department of Neurology, Istanbul University Cerrahpasa Medical Faculty, Istanbul, Turkey.
Melda
M
Bozluolcay
Department of Biochemistry, Istanbul University Cerrahpasa Medical Faculty, Istanbul, Turkey. gulnurandican@gmail.com.
Gülnur
G
Andican
Department of Biochemistry, Istanbul University Cerrahpasa Medical Faculty, Istanbul, Turkey.
Sinem
S
Fırtına
Department of Neurology, Istanbul University Cerrahpasa Medical Faculty, Istanbul, Turkey.
Gökhan
G
Erkol
Department of Biochemistry, Istanbul University Cerrahpasa Medical Faculty, Istanbul, Turkey.
Dildar
D
Konukoglu
D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000097:blood* / Q000188:drug therapy / Q000453:epidemiology / Q000503:physiopathology; D002097:C-Reactive Protein / Q000032:analysis; D016022:Case-Control Studies; D016207:Cytokines / Q000097:blood*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000188:drug therapy / Q000453:epidemiology / Q000503:physiopathology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007249:Inflammation / Q000097:blood / Q000453:epidemiology / Q000503:physiopathology; D018836:Inflammation Mediators / Q000097:blood*; D015850:Interleukin-6 / Q000097:blood; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012016:Reference Values; D018570:Risk Assessment; D012720:Severity of Illness Index; D012737:Sex Factors; D014409:Tumor Necrosis Factor-alpha / Q000097:blood
D016207:Cytokines; D018836:Inflammation Mediators; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha; D002097:C-Reactive Protein
Alzheimer's disease; cytokine; diabetes mellitus; inflammation; interleukin