MR spectroscopy of cerebral white matter in type 2 diabetes; no association with clinical variables and cognitive performance

Correlation between cerebral neurotransmitters levels by proton magnetic resonance spectroscopy and HbA1c in patients with type 2 diabetes

BACKGROUND

Cognitive dysfunction is the main manifestation of central neuropathy. Although cognitive impairments tend to be overlooked in patients with diabetes mellitus (DM), there is a growing body of evidence linking DM to cognitive dysfunction. Hyperglycemia is closely related to neurological abnormalities, while often disregarded in clinical practice. Changes in cerebral neurotransmitter levels are associated with a variety of neurological abnormalities and may be closely related to blood glucose control in patients with type 2 DM (T2DM).

AIM

To evaluate the concentrations of cerebral neurotransmitters in T2DM patients exhibiting different hemoglobin A1c (HbA1c) levels.

METHODS

A total of 130 T2DM patients were enrolled at the Department of Endocrinology of Shanghai East Hospital. The participants were divided into four groups according to their HbA1c levels using the interquartile method, namely Q1 (< 7.875%), Q2 (7.875%-9.050%), Q3 (9.050%-11.200%) and Q4 (≥ 11.200%). Clinical data were collected and measured, including age, height, weight, neck/waist/hip circumferences, blood pressure, comorbidities, duration of DM, and biochemical indicators. Meanwhile, neurotransmitters in the left hippocampus and left brainstem area were detected by proton magnetic resonance spectroscopy.

RESULTS

The HbA1c level was significantly associated with urinary microalbumin (mALB), triglyceride, low-density lipoprotein cholesterol (LDL-C), homeostasis model assessment of insulin resistance (HOMA-IR), and beta cell function (HOMA-β), N-acetylaspartate/creatine (NAA/Cr), and NAA/choline (NAA/Cho). Spearman correlation analysis showed that mALB, LDL-C, HOMA-IR and NAA/Cr in the left brainstem area were positively correlated with the level of HbA1c (P < 0.05), whereas HOMA-β was negatively correlated with the HbA1c level (P < 0.05). Ordered multiple logistic regression analysis showed that NAA/Cho [Odds ratio (OR): 1.608, 95% confidence interval (95%CI): 1.004-2.578, P < 0.05], LDL-C (OR: 1.627, 95%CI: 1.119-2.370, P < 0.05), and HOMA-IR (OR: 1.107, 95%CI: 1.031-1.188, P < 0.01) were independent predictors of poor glycemic control.

CONCLUSION

The cerebral neurotransmitter concentrations in the left brainstem area in patients with T2DM are closely related to glycemic control, which may be the basis for the changes in cognitive function in diabetic patients.

Utility of MRI in Quantifying Tissue Injury in Cervical Spondylotic Myelopathy

Cervical spondylotic myelopathy (CSM) is a progressive disease that worsens over time if untreated. However, the rate of progression can vary among individuals and may be influenced by various factors, such as the age of the patients, underlying conditions, and the severity and location of the spinal cord compression. Early diagnosis and prompt treatment can help slow the progression of CSM and improve symptoms. There has been an increased use of magnetic resonance imaging (MRI) methods in diagnosing and managing CSM. MRI methods provide detailed images and quantitative structural and functional data of the cervical spinal cord and brain, allowing for an accurate evaluation of the extent and location of tissue injury. This review aims to provide an understanding of the use of MRI methods in interrogating functional and structural changes in the central nervous system in CSM. Further, we identified several challenges hindering the clinical utility of these neuroimaging methods.

Altered Spontaneous Brain Activity in Patients With Diabetic Osteoporosis Using Regional Homogeneity: A Resting-State Functional Magnetic Resonance Imaging Study

Background

The pathophysiological mechanism of cognitive impairment by osteoporosis in type 2 diabetes mellitus (T2DM) remains unclear. This study aims to further investigate the regional spontaneous brain activity changes of patients with diabetic osteoporosis (DOP), and the correlation between abnormal brain regions and bone metabolites.

Methods

A total of 29 subjects with T2DM were recruited, including fourteen patients with DOP and thirteen patients without osteoporosis (Control group). Based on the resting-state functional magnetic resonance imaging (rs-fMRI) datasets acquired from all the subjects, a two-sample t-test was performed on individual normalized regional homogeneity (ReHo) maps. Spearman correlation analysis was performed between the abnormal ReHo regions with the clinical parameters and Montreal Cognitive Assessment (MOCA) scores.

Results

In the DOP group, we demonstrated the significantly increased ReHo values in the left middle temporal gyrus (MTG), right superior occipital gyrus (SOG), aright superior parietal lobule (SPL), right angular gyrus (AG), and left precuneus (PE). Additionally, we also found a significant positive correlation between increased ReHo values in the left MTG and the average bone mineral density (BMD AVG), and average T scores (T AVG). The ReHo values of the right SOG and right SPL showed a negative correlation with MOCA scores, as well as a negative correlation between increased ReHo values in the right SPL and osteocalcin (OC) level.

Conclusion

Patients with DOP showed increased spontaneous activity in multiple brain regions. The results indicated that osteoporosis exacerbated cognitive impairment and brain damage. Also, the OC might be considered as a bone marker to track the progression of cognitive impairment.

Disturbances in brain energy metabolism in insulin resistance and diabetes and Alzheimer's disease - Learnings from brain imaging biomarkers

Medical imaging techniques, such as structural and functional magnetic resonance imaging and positron emission tomography, have been used to gain a better understanding of the alterations of the metabolic processes in the brain relating to type 2 diabetes melltius, insulin resistance and Alzheimer's disease. These studies have shown that there are several similarities in the effects that these seemingly disparate diseases have on the brain, and that some of the abnormalities are reversed by metabolic interventions. This review provides an overview of the overlap between these diseases using medical imaging, focusing on glucose metabolism, mitochondrial function and lipid metabolism.

ALTERED BRAIN ACTIVITY IN PATIENTS WITH DIABETIC RETINOPATHY USING REGIONAL HOMOGENEITY: A RESTING-STATE fMRI STUDY

Objective: Previous neuroimaging studies have shown that diabetic retinopathy (DR) is accompanied by abnormal spontaneous brain activity. The purpose of the current study was to investigate changes in brain neural homogeneity in patients with DR using regional homogeneity (ReHo). Methods: A total of 56 subjects were recruited, including 28 patients with DR (16 female and 12 male patients) and 28 healthy controls (HCs) (16 female and 12 male patients) approximately matched for age and sex. All subjects underwent resting-state functional magnetic resonance imaging scans. The ReHo method was applied to explore neural homogeneity in the brain. The patients with DR were distinguished from HCs following the construction of receiver operating characteristic curves. The ReHo method was applied to assess changes in synchronous neural activity. Results: Compared to HCs, the ReHo values in the left and right posterior lobes of the cerebellum in patients with DR were significantly increased, whereas ReHo values in the right anterior cingulate gyrus, right cuneus, bilateral precuneus, and left-middle frontal gyrus were significantly decreased. In addition, the ReHo value in the right cuneus showed a positive correlation with the best corrected visual acuity in patients with DR. Conclusion: Dysfunctional brain homology may reveal the pathological mechanisms underlying the visual pathways of patients with DR. Abbreviations: AUC = area under the curve; BA = Brodmann area; DR = diabetic retinopathy; fMRI = functional magnetic resonance imaging; HC = healthy control; MRI = magnetic resonance imaging; rs-fMRI = resting-state fMRI; ReHo = regional homogeneity; ROC = receiver operating characteristic.

The Association Between Diabetes and Olfactory Function in Adults

Diabetes is a significant chronic disease that in limited studies has been linked with olfactory dysfunction. We investigated the cross-sectional association between diabetes and olfactory dysfunction in 3151 adults aged ≥40 years who participated in US National Health and Nutrition Examination Survey 2013-2014 with information on olfactory dysfunction and diabetes. Diabetes was defined from fasting serum glucose ≥126 mg/dL, oral glucose tolerance test ≥200 mg/dL, HbA1c levels ≥6.5%, physician-diagnosed diabetes, or current use of oral hypoglycemic agents and/or insulin. Self-reported olfactory dysfunction was defined as a positive answer to any of the following questions: 1) "Have you had problem with smell in the past 12 months?"; 2) "Have you had a change in the ability to smell since age 25?", or 3) "Do you have phantom smells?". Participants were considered to have severe hyposmia or anosmia if they had <5 correct answers in the 8-item pocket smell test. Analyses were adjusted for the main confounders, including olfactory dysfunction risk factors. Compared to non-diabetics, diabetics under insulin treatment showed a higher prevalence of phantom odors [OR(95% CI): 2.42 (1.16; 5.06)] and a non-significant higher prevalence of severe hyposmia/anosmia [OR(95% CI): 1.57 (0.89; 2.78)]. Amongst diabetics, there was a significant trend to severe hyposmia/anosmia for those on more aggressive treatments [OR (95% CI) including oral and insulin treatment compared to those who reported no use of drug treatment, respectively: 1.33 (0.60; 2.96) and 2.86 (1.28; 6.40); P trend 0.01]. No association was observed between diabetes duration and prevalence of olfactory dysfunction.

Altered brain metabolites in patients with diabetes mellitus and related complications - evidence from 1H MRS study

In recent years, diabetes mellitus (DM) has been acknowledged as an important factor for brain disorders. Significant alterations in brain metabolism have been demonstrated during the development of DM and its complications. Magnetic resonance spectroscopy (MRS), a cutting-edge technique used in biochemical analyses, non-invasively provides insights into altered brain metabolite levels in vivo This review aims to discuss current MRS data describing brain metabolite levels in DM patients with or without complications. Cerebral metabolites including N-acetylaspartate (NAA), creatine (Cr), choline (Cho), myo-inositol (mI), glutamate, and glutamine were significantly altered in DM patients, suggesting that energy metabolism, neurotransmission, and lipid membrane metabolism might be disturbed during the progression of DM. Changes in brain metabolites may be non-invasive biomarkers for DM and DM-related complications. Different brain regions presented distinct metabolic signatures, indicating region-specific diabetic brain damages. In addition to serving as biomarkers, MRS data on brain metabolites can also shed light on diabetic treatment monitoring. For example, exercise may restore altered brain metabolite levels and has beneficial effects on cognition in DM patients. Future studies should validate the above findings in larger populations and uncover the mechanisms of DM-induced brain damages.

Magnetic resonance spectroscopy of the frontal region in patients with metabolic syndrome: correlation with anthropometric measurement

PURPOSE

To demonstrate 1H-MR spectroscopy of the frontal region in patients with metabolic syndrome and to correlate the metabolic ratios with anthropometric measurement.

MATERIAL AND METHODS

A prospective study was conducted upon 20 patients with metabolic syndrome (10 male, 10 female; mean age 52 years) and 20 age- and sex-matched volunteers. Patients were mild-moderate (n = 14) and marked and morbid obesity (n = 6). Patients and volunteers underwent 1H-MR spectroscopy of the frontal region. The Ch/Cr and NAA/Cr ratio were calculated and correlated with anthropometric measurement.

RESULTS

The Cho/Cr and NAA/Cr of patients with Mets (1.03 ± 0.08 and 1.62 ± 0.08) were significantly different (p = 0.001) to those of volunteers (0.78 ± 0 and 1.71 ± 0.61, respectively). The Cho/Cr and NAA/Cr cutoffs used to differentiate patients from volunteers were 0.89 and 1.77 with areas under the curve of 0.992 and 0.867 and accuracy of 97% and 93%, respectively. There was a significant difference in Cho/Cr and NAA/Cr between patients with marked-morbid obesity and moderate-mild obesity (p = 0.001 respectively).

CONCLUSIONS

We concluded that NAA/Cr and Cho/Cr ratios of the frontal region can differentiate patients with metabolic syndrome from volunteers and are well correlated with the anthropometric measurement.

Evaluation of apparent diffusion coefficient measurements of brain injury in type 2 diabetics with retinopathy by diffusion-weighted MRI at 3.0 T

Diabetes is often associated with impairments in brain functioning. However, the injury of specific functioning areas of the brain is not clear. To address this problem, the present study was designed to investigate possible brain functioning change in specific brain areas, particularly in areas associated with vision function, in patients with proliferative and nonproliferative diabetic retinopathy (PDR and NPDR) using the diffusion-weighted imaging technology. Conventional MRI was performed in 45 diabetic patients, 30 of whom had diabetic retinopathy (DR) involvement (half PDR, and half NPDR) and 15 of whom were diabetic patients without retinopathy and with normal ophthalmologic examination. The apparent diffusion coefficient (ADC) values were calculated in the orbitofrontal cortex (OFC), cingulated gyrus, thalamus, dorsomedial and dorsolateral frontal cortex, and corona radiate. The ADC values of the OFC, cingulated gyrus, and visual cortex were significantly increased in patients with PDR and NPDR compared with both patients without retinopathy and the control group (P<0.01). The ADC values of the OFC, cingulated gyrus, and visual cortex were significantly increased in patients with PDR compared with NPDR. The duration of disease and values of hemoglobin A1c were significantly correlated with ADC values of the OFC, cingulated gyrus, and visual cortex, respectively (P<0.01 or <0.05). We observed significantly increased ADC values of the visual center (OFC, cingulated gyrus, and visual cortex), supporting the association between DR and impairment in brain functioning. Diffusion-weighted imaging may serve to assess subclinical neurological involvement in DR, even when brain structural changes are absent.

Biomarkers for cognitive decline in patients with diabetes mellitus: evidence from clinical studies

Diabetes mellitus is considered as an important factor for cognitive decline and dementia in recent years. However, cognitive impairment in diabetic patients is often underestimated and kept undiagnosed, leading to thousands of diabetic patients suffering from worsening memory. Available reviews in this field were limited and not comprehensive enough. Thus, the present review aimed to summarize all available clinical studies on diabetic patients with cognitive decline, and to find valuable biomarkers that might be applied as diagnostic and therapeutic targets of cognitive impairment in diabetes. The biomarkers or risk factors of cognitive decline in diabetic patients could be classified into the following three aspects: serum molecules or relevant complications, functional or metabolic changes by neuroimaging tools, and genetic variants. Specifically, factors related to poor glucose metabolism, insulin resistance, inflammation, comorbid depression, micro-/macrovascular complications, adipokines, neurotrophic molecules and Tau protein presented significant changes in diabetic patients with cognitive decline. Besides, neuroimaging platform could provide more clues on the structural, functional and metabolic changes during the cognitive decline progression of diabetic patients. Genetic factors related to cognitive decline showed inconsistency based on the limited studies. Future studies might apply above biomarkers as diagnostic and treatment targets in a large population, and regulation of these parameters might shed light on a more valuable, sensitive and specific strategy for the diagnosis and treatment of cognitive decline in diabetic patients.

Metabolic profile of visual cortex in diabetic rats measured with in vivo proton MRS

The purpose of the present study was to characterize the metabolic profile of the visual cortex in streptozotocin-induced Type 1 diabetic rats by means of in vivo proton MRS. Several metabolite concentration ratios in the visual cortex were calculated. In addition, postmortem histologic analyses for retinal ganglion cell (RGC) loss, optic nerve injury and visual cortex alterations were monitored. The results showed that diabetes induced several changes in visual cortex metabolites, such as reduced N-acetylaspartate, glutamate, γ-aminobutyric acid, taurine and choline-containing compound levels. Nevertheless, myo-inositol levels increased significantly as compared with controls. Remarkable RGC loss and optic nerve degeneration were observed by morphological analysis. Moreover, the results showed significant neuronal loss and glial activation in the visual cortex. These findings indicated that, besides vascular abnormalities, neuronal loss and degeneration in the visual pathway were induced due to disrupted glucose homeostasis in diabetes. Metabolic or functional abnormalities were induced in cerebral neurons of the visual cortex by diabetes.

Cerebral Pathology and Cognition in Diabetes: The Merits of Multiparametric Neuroimaging

Type 2 diabetes mellitus is associated with accelerated cognitive decline and various cerebral abnormalities visible on MRI. The exact pathophysiological mechanisms underlying cognitive decline in diabetes still remain to be elucidated. In addition to conventional images, MRI offers a versatile set of novel contrasts, including blood perfusion, neuronal function, white matter microstructure, and metabolic function. These more-advanced multiparametric MRI contrasts and the pertaining parameters are able to reveal abnormalities in type 2 diabetes, which may be related to cognitive decline. To further elucidate the nature of the link between diabetes, cognitive decline, and brain abnormalities, and changes over time thereof, biomarkers are needed which can be provided by advanced MRI techniques. This review summarizes to what extent MRI, especially advanced multiparametric techniques, can elucidate the underlying neuronal substrate that reflects the cognitive decline in type 2 diabetes.

Increased GABA concentrations in type 2 diabetes mellitus are related to lower cognitive functioning

Type 2 diabetes mellitus is associated with accelerated cognitive decline. The underlying pathophysiological mechanisms still remain to be elucidated although it is known that insulin signaling modulates neurotransmitter activity, including inhibitory γ-aminobutyric acid (GABA) and excitatory glutamate (Glu) receptors. Therefore, we examined whether levels of GABA and Glu are related to diabetes status and cognitive performance.Forty-one participants with type 2 diabetes and 39 participants without type 2 diabetes underwent detailed cognitive assessments and 3-Tesla proton MR spectroscopy. The associations of neurotransmitters with type 2 diabetes and cognitive performance were examined using multivariate regression analyses controlling for age, sex, education, BMI, and percentage gray/white matter ratio in spectroscopic voxel.Analysis revealed higher GABA+ levels in participants with type 2 diabetes, in participants with higher fasting blood glucose levels and in participants with higher HbA1c levels, and higher GABA+ levels in participants with both high HbA1c levels and less cognitive performance.To conclude, participants with type 2 diabetes have alterations in the GABAergic neurotransmitter system, which are related to lower cognitive functioning, and hint at the involvement of an underlying metabolic mechanism.

Memory and executive functions in persons with type 2 diabetes: a meta-analysis

Literature suggests that persons with type 2 diabetes mellitus (T2DM) are at risk for cognitive impairment, hence dementia. Common domains reported to be affected in those with T2DM are memory and executive functions. The extent of influence of T2DM on these domains has varied among studies. A systematic review and meta-analysis was carried out to understand whether sub-domains contributed to the variations observed in published research. We searched 'PubMed', 'ScienceDirect', 'SciVerseHub', 'Psychinfo', 'Proquest' 'Ebsco' and 'J-gate Plus' databases for published studies on cognition and T2DM among persons aged 50 years and older. Memory, executive functions and processing speed domain and sub-domain scores were extracted; effect sizes (Cohen's d) were calculated and analysed. Eight hundred seventeen articles were found. After various levels of filtering, 15 articles met the inclusion criteria for quantitative analyses. The analyses indicated that in comparison to controls, persons with T2DM showed decrements in episodic memory (d = -0.51), logical memory (d = -0.24), sub-domain of executive functions which included phonemic fluency (d = -0.35) and cognitive flexibility (d = 0.52), and speed of processing (d = -0.22). We found no difference in the sub-domains of verbal short-term memory and working memory. The meta-analysis revealed a detrimental effect of T2DM on cognitive sub-domains, namely, episodic memory and cognitive flexibility. There was a trend for the logical memory, phonemic fluency and processing speed to be affected. The analysis indicates that T2DM is a detrimental factor on certain cognitive sub-domains, rendering the person vulnerable to subsequent dementia. Copyright © 2016 John Wiley & Sons, Ltd.

In Vivo NMR Studies of the Brain with Hereditary or Acquired Metabolic Disorders

Metabolic disorders, whether hereditary or acquired, affect the brain, and abnormalities of the brain are related to cellular integrity; particularly in regard to neurons and astrocytes as well as interactions between them. Metabolic disturbances lead to alterations in cellular function as well as microscopic and macroscopic structural changes in the brain with diabetes, the most typical example of metabolic disorders, and a number of hereditary metabolic disorders. Alternatively, cellular dysfunction and degeneration of the brain lead to metabolic disturbances in hereditary neurological disorders with neurodegeneration. Nuclear magnetic resonance (NMR) techniques allow us to assess a range of pathophysiological changes of the brain in vivo. For example, magnetic resonance spectroscopy detects alterations in brain metabolism and energetics. Physiological magnetic resonance imaging (MRI) detects accompanying changes in cerebral blood flow related to neurovascular coupling. Diffusion and T1/T2-weighted MRI detect microscopic and macroscopic changes of the brain structure. This review summarizes current NMR findings of functional, physiological and biochemical alterations within a number of hereditary and acquired metabolic disorders in both animal models and humans. The global view of the impact of these metabolic disorders on the brain may be useful in identifying the unique and/or general patterns of abnormalities in the living brain related to the pathophysiology of the diseases, and identifying future fields of inquiry.

Right Dorsolateral Frontal Lobe N-Acetyl Aspartate and Myoinositol Concentration Estimation in Type 2 Diabetes with Magnetic Resonance Spectroscopy

INTRODUCTION

Chronic hyperglycaemia in type 2 diabetes, effects the central nervous system by altering the concentrations of brain metabolites like N-acetyl aspartate (NAA) and myoinositol (mI), which are indicators of neuronal integrity and glial cell damage respectively. Dorsolateral frontal lobe is associated with aspects of cognition especially right frontal lobe is involved in episodic memory retrieval, ninety percent of the diabetic cases are type 2 in nature globally and yoga is very effective in stabilizing the brain metabolites by bringing the blood glucose levels to near or within the physiological range in type 2 diabetes.

AIM AND OBJECTIVES

The aim of the study was to observe the effects of yogasana and pranayama on glycosilated haemoglobin (HbA1c) levels and right dorsolateral frontal cortical NAA and mI concentration in type 2 diabetic subjects.

MATERIALS AND METHODS

It's a case control study. Sixty eight type 2 diabetic subjects of both the sex, aged between 35-65 years are included in the study, subjects are divided in to test and control group 34 each. Test group subjects did the yogasana and pranayama for a period of 6 months, 6 days in a week, 45-60 minutes daily under the supervision of a qualified yoga teacher. Control group subjects are not on any specific exercise regimen. Both the group subjects are taking oral hypoglycaemic agents. HbA1c levels are measured using the Bio-Rad D-10™ haemoglobin A1c program and Magnetic Resonance Spectroscopy (MRS) is used in assessing the metabolite concentrations.

STATISTICAL ANALYSIS

Analysis of data was done by using unpaired t-test. P-value for HbA1c level is <0.001, which is highly significant statistically. P-value for NAA was < 0.02 and for myoinositol was < 0.01, which are statistically significant.

RESULTS

HbA1c levels in control and test group subjects are 7.7 ± 1.84 and 6.02 ± 0.46 respectively. NAA concentrations in the right dorsolateral frontal lobe of control and test group are 1.44 ± 0.15 and 1.54 ± 0.19 respectively. The mI concentrations in the right dorsolateral frontal lobe of control and test group are 0.61 ± 0.22 and 0.47 ± 0.24 respectively.

CONCLUSION

Yogasana and pranayama minimized the neuronal and glial cellular damage in test group, which is evident by minimal changes in right dorsolateral frontal lobe NAA and mI levels in type 2 diabetic subjects.

Effects of a high-caloric diet and physical exercise on brain metabolite levels: a combined proton MRS and histologic study

Excessive intake of high-caloric diets as well as subsequent development of obesity and diabetes mellitus may exert a wide range of unfavorable effects on the central nervous system (CNS). It has been suggested that one mechanism in this context is the promotion of neuroinflammation. The potentially harmful effects of such diets were suggested to be mitigated by physical exercise. Here, we conducted a study investigating the effects of physical exercise in a cafeteria-diet mouse model on CNS metabolites by means of in vivo proton magnetic resonance spectroscopy ((1)HMRS). In addition postmortem histologic and real-time (RT)-PCR analyses for inflammatory markers were performed. Cafeteria diet induced obesity and hyperglycemia, which was only partially moderated by exercise. It also induced several changes in CNS metabolites such as reduced hippocampal glutamate (Glu), choline-containing compounds (tCho) and N-acetylaspartate (NAA)+N-acetyl-aspartyl-glutamic acid (NAAG) (tNAA) levels, whereas opposite effects were seen for running. No association of these effects with markers of central inflammation could be observed. These findings suggest that while voluntary wheel running alone is insufficient to prevent the unfavorable peripheral sequelae of the diet, it counteracted many changes in brain metabolites. The observed effects seem to be independent of neuroinflammation.

Brain imaging in type 2 diabetes

Type 2 diabetes mellitus (T2DM) is associated with cognitive dysfunction and dementia. Brain imaging may provide important clues about underlying processes. This review focuses on the relationship between T2DM and brain abnormalities assessed with different imaging techniques: both structural and functional magnetic resonance imaging (MRI), including diffusion tensor imaging and magnetic resonance spectroscopy, as well as positron emission tomography and single-photon emission computed tomography. Compared to people without diabetes, people with T2DM show slightly more global brain atrophy, which increases gradually over time compared with normal aging. Moreover, vascular lesions are seen more often, particularly lacunar infarcts. The association between T2DM and white matter hyperintensities and microbleeds is less clear. T2DM has been related to diminished cerebral blood flow and cerebrovascular reactivity, particularly in more advanced disease. Diffusion tensor imaging is a promising technique with respect to subtle white matter involvement. Thus, brain imaging studies show that T2DM is associated with both degenerative and vascular brain damage, which develops slowly over the course of many years. The challenge for future studies will be to further unravel the etiology of brain damage in T2DM, and to identify subgroups of patients that will develop distinct progressive brain damage and cognitive decline.

Assessment of changes in brain metabolites in Indian patients with type-2 diabetes mellitus using proton magnetic resonance spectroscopy

BACKGROUND

The brain is a target for diabetic end-organ damage, though the pathophysiology of diabetic encephalopathy is still not well understood. The aim of the present study was to investigate the effect of diabetes on the metabolic profile of brain of patients having diabetes in comparison to healthy controls, using in-vivo magnetic resonance spectroscopy to get an insight into the pathophysiology of cerebral damages caused due to diabetes.

METHODS

Single voxel proton magnetic resonance spectroscopy (1H-MRS) was performed at 1.5 T on right frontal, right parieto-temporal and right parieto-occipital white matter regions of the brain of 10 patients having type-2 diabetes along with 7 healthy controls. Absolute concentration of N-acetylaspartate (NAA), choline (cho), myo-inositol (mI), glutamate (Glu) and glutamine (Gln), creatine (Cr) and glucose were determined using the LC-Model and compared between the two groups.

RESULTS

The concentration of N-acetylaspartate was significantly lower in the right frontal [4.35 ±0.69 vs. 5.23 ±0.74; p = 0.03] and right parieto-occipital region [5.44 ±0.52 vs.6.08 ±0.25; p = 0.02] of the brain of diabetics as compared to the control group. The concentrations of glutamate and glutamine were found to be significantly higher in the right frontal region of the brain [7.98 ±2.57 vs. 5.32 ±1.43; P = 0.01] in diabetics. Glucose levels were found significantly elevated in all the three regions of the brain in diabetics as compared to the control group. However, no significant changes in levels of choline, myo-inositol and creatine were observed in the three regions of the brain examined among the two groups.

CONCLUSIONS

1H-MRS analysis indicates that type-2 diabetes mellitus may cause subtle changes in the metabolic profile of the brain. Decreased concentrations of NAA might be indicative of decreased neuronal viability in diabetics while elevated concentrations of Gln and Glu might be related to the fluid imbalance resulting from disruption of glucose homeostasis.

Metabolite differences in the lenticular nucleus in type 2 diabetes mellitus shown by proton MR spectroscopy

BACKGROUND AND PURPOSE

Previous studies by using proton MR spectroscopy found metabolite abnormalities in the cerebral cortex and white matter of patients with type 2 diabetes mellitus. The present study was undertaken to detect metabolite differences in the lenticular nuclei and thalamus in patients with T2DM.

MATERIALS AND METHODS

Twenty subjects with T2DM and 22 age-matched control subjects underwent single-voxel MR spectroscopy in the left and right lenticular nuclei and left and right thalami. NAA/Cr and Cho/Cr ratios were calculated. Brain lactic acid, fasting blood glucose, and glycosylated hemoglobin levels were also monitored.

RESULTS

The NAA/Cr ratio was lower in the left lenticular nuclei of subjects with T2DM (P = .007), whereas the Cho/Cr ratio was increased in both the and right lenticular nuclei (P = .001). The NAA/Cr ratio was negatively correlated with FBG in the left (r = -0.573, P = .008) and right nuclei (r = -0.564, P = .010). It was also negatively correlated to HbA1c in the left (r = -0.560, P = .010) and right (r = -0.453, P = .045) nuclei. The Cho/Cr ratio was positively correlated with these variables (P < .05). No significant differences in NAA/Cr or Cho/Cr ratios were observed in the thalamus of patients with T2DM. Lactic acid was not detected in any of the patients in the study.

CONCLUSIONS

The different metabolic statuses of the lenticular nuclei and thalamus suggest different effects of T2DM in each of these brain nuclei, with the lenticular nuclei being more vulnerable than the thalamus. The abnormal metabolic status was observed before lesions had appeared in these brain areas.

Evaluation of metabolite changes in visual cortex in diabetic retinopathy by MR-spectroscopy

PURPOSE

To evaluate metabolite changes in the visual cortex of diabetic patients with nonproliferative or proliferative diabetic retinopathy by Magnetic Resonance Spectroscopy (MRS).

MATERIALS AND METHODS

15 normal subjects (group 1), 15 patients with diabetes who did not have diabetic retinopathy (group 2), 15 patients with nonproliferative diabetic retinopathy (NPDR) (group 3), and 15 patients with proliferative diabetic retinopathy (PDR) (group 4) were included in the study. Furthermore, diabetic patients were divided into two groups according to HbA1c levels (Group A: 20 patients, HbA1c <8%; Group B: 20 patients, HbA1c >8%). In all cases' left visual cortex, amounts of N-acetyl-aspartate (NAA), choline (Cho), and creatine (Cr) were measured by MRS. NAA/Cr, Cho/Cr, and NAA/Cho ratios were calculated. Furthermore, all cases' complete blood count (CBC) and biochemical parameters were evaluated.

RESULTS

There was no statistically significant difference for NAA/Cr, Cho/Cr, and NAA/Cho ratios between groups 1, 2, 3, and 4 (P>0.05). However there was a statistically significant difference for NAA/Cr and NAA/Cho ratios between groups A and B (P<0.05). There was no statistically significant difference for Cho/Cr ratio between groups A and B (P>0.05).

CONCLUSION

Although NAA/Cr and NAA/Cho ratios decrease in the visual cortex while diabetic retinopathy progresses, these decreases are not statistically significant. While HbA1c levels increase, the NAA concentration decreases in the visual cortex which indicates neuronal loss. The metabolite changes in the visual cortex are associated with acute events rather than chronic.

Quantitative multivoxel proton MR spectroscopy study of brain metabolites in patients with amnestic mild cognitive impairment: a pilot study

INTRODUCTION

The purpose of this study is to investigate brain metabolic changes in patients with amnestic mild cognitive impairment (aMCI) using multivoxel proton MR spectroscopy ((1)H-MVS).

METHODS

Fourteen aMCI patients and fifteen healthy control subjects participated in this experiment. All MR measurements were acquired using a 1.5-T GE scanner. (1)H-MVS point resolved spectroscopy (2D PROBE-CSI PRESS) pulse sequence (TE = 35 ms; TR = 1,500 ms; phase × frequency, 18 × 18) was used for acquiring MRS data. All data were post-processed using Spectroscopy Analysis by General Electric software and linear combination of model (LCModel). The absolute concentrations of N-acetylaspartate (NAA), choline (Cho), myoinositol (MI), creatine (Cr), and the metabolite ratios of NAA/Cr, Cho/Cr, MI/Cr, and NAA/MI were measured bilaterally in the posterior cingulate gyrus (PCG), inferior precuneus (Pr), paratrigonal white matter (PWM), dorsal thalamus (DT), and lentiform nucleus (LN).

RESULTS

Patients with aMCI displayed significantly lower NAA levels in the bilateral PCG (p < 0.01), PWM (p < 0.05), and left inferior Pr (p < 0.05). The metabolite ratio of NAA/MI was decreased in the bilateral PCG (p < 0.01) and PWM (p < 0.05) and in the left DT (p < 0.01). NAA/Cr was decreased in the left PCG (p < 0.01), DT (p < 0.05), right PWM (p < 0.05), and LN (p < 0.05). However, MI/Cr was elevated in the right PCG (p < 0.01) and left PWM (p < 0.05). Significantly increased Cho level was also evident in the left PWM (p < 0.05).

CONCLUSIONS

Our observations of decreased NAA, NAA/Cr, and NAA/MI, in parallel with increased Cho and MI/Cr might be characteristic of aMCI patients.