The correlation of serum adiponectin and insulin resistance with the presence and severity of dementia in non-obese Alzheimer's patients.

BACKGROUND AND AIMS: Alteration in the insulin signaling could contribute to the development of Alzheimer's disease (AD) through metabolic or inflammatory processes, adipokines could affect insulin dysregulation. This study aimed to investigate whether there is a correlation between serum adiponectin level alteration and insulin resistance with the presence and severity of AD, compared to normal controls. METHODS: This analytical observational study was conducted on 60 non-overweight and non-diabetic participants who were assigned to AD patients (n = 34) and healthy volunteers (n = 26). The diagnosis and severity of dementia were evaluated by the same protocol, and the Mini-Mental Score Exam (MMSE) questionnaire was utilized to collect the data. Moreover, adiponectin concentration, fasting blood sugar, and plasma insulin levels were measured using enzyme-linked immunosorbent assay. Furthermore, the homeostasis model assessment for insulin resistance (HOMA-IR) was utilized in this study. RESULTS: The mean ages of the AD patients and control participants were 71.35 and 70.46, respectively. In addition, the mean values of the serum adiponectin level of the participants were 9660 and 12,730 ng/mL in control and AD groups, respectively (P ≤ 0.05). Additionally, the insulin resistance (IR) was 2.90 and 5.10 in the control and AD groups, respectively (P ≤ 0.05). According to the results, there was a significant positive correlation between serum adiponectin level and HOMA-IR in the AD group; however, no significant correlation was observed between serum adiponectin level and MMSE score in this group. The MMSE score of AD patients significantly decreased by 1.2 times with an increase in each score of the IR (P ≤ 0.05). CONCLUSION: A significant direct positive correlation was observed between the serum adiponectin level and IR among the AD patients. However, a significant decrease in cognition levels was detected following an increase in IR scores of the AD patients.

Altered plasma visfatin levels and insulin resistance in patients with Alzheimer's disease.

Central insulin resistance is involved in the pathophysiology of Alzheimer's disease (AD). Visfatin (VIS), an adipokine secreted from peripheral adipose tissue, is involved in energy balance and weight control. Besides its metabolic roles, VIS possesses insulin-mimetic, anti-apoptotic, and neuroprotective properties. In this study, we assessed the presence of a correlation between plasma VIS level and insulin resistance or AD. Sixty participants were enrolled in this study; 34 patients with AD and 26 healthy subjects. All subjects underwent comprehensive evaluations including Mini-mental score exam (MMSE) for the diagnosis of dementia. Subjects with MMSE score < 24 were added to the AD group, while healthy subjects should have a MMSE score > 27. Fasting blood sugar (FBS) and insulin levels were measured by enzyme-linked immunosorbent assay. The results indicate a significant elevation in FBS from 103 ± 3.0 to 147 ± 7.6 in AD patients (p ≤ 0.001). Additionally, 71% of AD patients developed insulin resistance, as the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) index increased from 2.9 ± 0.5 in healthy subjects to 5.2 ± 0.7 in AD patients (p ≤ 0.05). Body mass index and serum insulin level did not show a significant alteration, but serum VIS levels were significantly (p ≤ 0.01) lower in AD patients (11.15 ± 1.9 ng/ml) in comparison to control group (21.09 ± 2.3 ng/ml). There is a negative correlation between plasma VIS level and the HOMA-IR index (p < 0.05). The results of this study present clear evidence for systemic insulin resistance and decreased serum VIS level in non-obese, non-overweight patients with moderate to severe AD.