Type 2 diabetes affects the microstructure of the brain

In a recent study published in the journal Scientific reportsresearchers examine microstructural changes in brain tissue in patients with type 2 diabetes (T2D) using diffusion-mean (DM)-based whole-brain diffusion tensor imaging (DTI) procedures that distinguish acute from chronic stages of tissue change. This study hypothesized that patients with T2D will exhibit impaired MD values ​​in the domains of mood regulation and cognition compared to healthy individuals.

Study: Microstructural changes in brain tissue contribute to cognitive and mood deficits in adults with type 2 diabetes mellitus. Image Credit: Elif Bayraktar / Shutterstock.com

Background

T2D, a chronic metabolic disorder, has been shown to impair cognition and mood and therefore is often considered an early risk factor for Alzheimer’s disease (AD) and vascular dementia. Indeed, epidemiological studies have shown that T2DM increases the risk of

cognitive deficits and mood disorders by 1.5 and 2 times, respectively.

Structural magnetic resonance imaging (MRI), due to its insufficient sensitivity to tissue changes, cannot detect subtle aberrations of brain tissue. However, DTI, a non-invasive procedure, shows changes in the microstructural organization of the brain in gray and white matter. DTI also measures MD, which reflects the movement of water molecules, revealing the nature of brain tissue damage and its extent in patients with T2D.

To date, researchers have not examined direct correlations between tissue changes in brain sites mediating cognition and mood as a function of DM. Similarly, symptom scores for mood and cognition in patients with T2D were not reported.

About the study

In the current study, researchers recruited 68 people with T2DM who were taking medication from the Gonda Diabetes Center at the University of California, Los Angeles (UCLA), in addition to 101 healthy controls without diabetes. The people in the two study cohorts were between 40 and 65 years old.

The Diabetes Complication Severity Index (DCSI) of each patient’s clinical record was determined. Symptoms of anxiety and depression were assessed by the Beck Anxiety Inventory (BAI) and the Beck Depression Inventory (BDI-II), respectively. BDI-II or BAI values ​​greater than nine indicated depression or anxiety, respectively. The Montreal Cognitive Assessment (MoCA) was also administered, with scores of 26 or greater indicating no cognitive impairment.

DTI data were collected using a one-shot echo planar imaging technique, partially parallel self-calibrating generalized acquisition (GRAPPA), with an acceleration factor of two. Then, visual assessment of T1-, T2-, and PD-weighted images of all subjects was performed for various pathologies, including cystic lesions, infarcts, or tumors.

MD maps derived from all DTI series were quantified and realigned to remove any variation in head movement or other imaging artifacts and averaged. Non-diffusion-weighted images were also realigned and averaged.

Statistical parametric maps showing brain sites with significant differences in MD between groups were overlaid on a mean anatomical image for identification via MRIcroN software. This provided region of interest (ROI) values ​​on brain regions showing significant associations with mood and cognition values ​​between T2DM and controls. Whole-brain MD maps were also correlated voxel-by-voxel with mood and cognition scores, including subscores for BAI, BDI-II, and MoCA, using partial correlations.

Altered brain structure in diabetics

Widespread microstructural disturbances were observed in brain regions controlling cognitive and mood functions in people with T2DM compared to controls. Most of these changes were in the chronic stage, with only a few sites in the acute stage. Patients with T2D also had impairments in visual-spatial cognitive, language, and attention subdomains, as well as higher depression and anxiety scores than healthy controls.

Cognitive and mood-regulating networks are distributed over a large area of ​​the human brain. Thus, significant microstructural tissue changes in these areas play a unique role in cognitive and mood deficits in patients with T2D.

These results provide important insights into these changes, as well as microstructural neuropathological changes that may contribute to mood and cognitive dysfunctions in patients with T2DM. Notably, all disturbances in the microstructural integrity of brain tissue occurred primarily in the temporal, parietal, temporal, and subcortical cortices.

Similar to previous studies, regions that exhibited chronic tissue changes with increased MD values ​​in patients with T2DM included brain fibers connecting the cerebellum to the vermis and the anterior crus to the cortices, including the frontal, precentral, and superior parietal gyri .

conclusion

Study results demonstrate how DM can facilitate early detection of microstructural brain tissue changes in cognitive and mood-regulating regions in patients with T2D, which cause mood alteration and cognitive deficits .