Prospective Assessment of Alzheimer's Disease-Like Hypometabolism Pattern in the Brain of Diabetics in Contrast to Non-diabetics on Positron Emission Tomography-Computed Tomography Images Using Fluorodeoxyglucose in India.

Background: Diabetes mellitus (DM) is a known risk factor for cognitive decline and Alzheimer's disease (AD), possibly due to insulin resistance and impaired cerebral glucose metabolism. Fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) imaging has shown AD-like hypometabolism patterns in diabetic individuals in various global studies. However, such data is lacking in the Indian population. This study investigated the presence of AD-like hypometabolism in Indian diabetic patients compared to non-diabetic controls.

Aim And Objective: This study aimed to evaluate whether the Indian diabetic patients show AD-like reduction in brain glucose metabolism, as several studies reported AD-like hypometabolism in the brain at very early stages before making a clinical diagnosis of probable AD.

Materials And Methods: A prospective, observational study was conducted on 78 patients (39 diabetics and 39 non-diabetics; age range 43-87 years) at a tertiary care center. After excluding patients with a recent history of stroke, transient ischemic attack, or structural brain abnormalities, all participants underwent dedicated brain FDG PET-CT imaging just after a whole-body scan. Scans were analyzed using CORTEX-ID software (GE Healthcare, Chicago, IL, USA), comparing cerebral glucose metabolism to age-matched normative data. Regional hypometabolism was normalized to thalamic activity. Appropriate tests of significance were used, and P< 0.05 was considered statistically significant.  Results: The study included 78 patients, 39 diabetics and 39 non-diabetic controls, matched for sex (19 males and 20 females in each group). Diabetic patients had a higher mean age (66.4 ± 10.6 years). The Mini-Mental State Examination (MMSE) score was lower in diabetics (25.3 ± 2.3) than in controls (26.8 ± 1.9). About 5.1% of diabetic patients showed an AD-like pattern, and the remaining 94.9% did not show an AD-like pattern on the FDG PET-CT scan. An AD-like pattern was not seen in any patient among the non-diabetic control group. No statistically significant association was found between the AD-like pattern in the brain on FDG PET-CT and diabetes (P 0.494).

Conclusions: No significant incidence of "AD-like pattern" in the brain on PET-CT images using FDG was seen in this research study on the Indian diabetic populations. However, abnormal brain scans with no AD-like hypometabolism patterns possibly suggested other etiologies, likely depression. More prospective multicentric research studies on a large Indian diabetic population with age-matched non-diabetic control groups need to be explored for definite conclusions.