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

Pro-atherogenic medical conditions are associated with widespread regional brain metabolite abnormalities in those with alcohol use disorder

AIMS

Widespread brain metabolite abnormalities in those with alcohol use disorder (AUD) were reported in numerous studies, but the effects of the pro-atherogenic conditions of hypertension, type 2 diabetes mellitus, hepatitis C seropositivity, and hyperlipidemia on metabolite levels were not considered. These conditions were associated with brain metabolite abnormalities in those without AUD. We predicted treatment-seeking individuals with AUD and pro-atherogenic conditions (Atherogenic+) demonstrate lower regional metabolite markers of neuronal viability [N-acetylaspartate (NAA)] and cell membrane turnover/synthesis [choline-containing compounds (Cho)], compared with those with AUD without pro-atherogenic conditions (Atherogenic-) and healthy controls (CON).

METHODS

Atherogenic+ (n = 59) and Atherogenic- (n = 51) and CON (n = 49) completed a 1.5 T proton magnetic resonance spectroscopic imaging study. Groups were compared on NAA, Cho, total creatine, and myoinositol in cortical gray matter (GM), white matter (WM), and select subcortical regions.

RESULTS

Atherogenic+ had lower frontal GM and temporal WM NAA than CON. Atherogenic+ showed lower parietal GM, frontal, parietal and occipital WM and lenticular nuclei NAA level than Atherogenic- and CON. Atherogenic- showed lower frontal GM and WM NAA than CON. Atherogenic+ had lower Cho level than CON in the frontal GM, parietal WM, and thalamus. Atherogenic+ showed lower frontal WM and cerebellar vermis Cho than Atherogenic- and CON.

CONCLUSIONS

Findings suggest proatherogenic conditions in those with AUD were associated with increased compromise of neuronal integrity and cell membrane turnover/synthesis. The greater metabolite abnormalities observed in Atherogenic+ may relate to increased oxidative stress-related compromise of neuronal and glial cell structure and/or impaired arterial vasoreactivity/lumen viability.

The association between the severity of diabetic retinopathy and cognitive impairment: a cross-sectional study

PURPOSE

To assess the correlation among cognitive impairment (CI) and the degree of diabetic retinopathy (DR).

METHODS

The current analytic cross-sectional study has been carried out on two hundred ten individuals having diabetes mellitus type 2. Individuals were split into 7 groups in order of severity of DR in the worse eye with 30 cases in each group. Cognition function has been determined utilizing mini-mental state examination (MMSE) and montreal cognitive assessment (MoCA) tests.

RESULTS

Comparing the severity of CI using both MMSE and MoCA tests, statistically substantial differences have been discovered among individuals without DR, those having non-proliferative diabetic retinopathy (NPDR), and proliferative diabetic retinopathy (PDR) (p < 0.001). The greatest percentage of severe and moderate CI was seen in the PDR group. Regarding the severity of CI, there has been a statistically substantial difference among NPDR and PDR groups, as well as among no-DR and PDR groups (p < 0.001). Moreover, the severity of CI in the MMSE and MoCA tests had a negative connection with the grades of DR (r = - 0.522, P < 0.001 and r = - 0.540, P < 0.001, respectively).

CONCLUSION

We discovered a negative connection between the grades of DR and the severity of CI that persisted as a significant finding, showing that patients with more severe DR tended to have higher levels of CI. These results might offer retinal examination or retinal photography as a promising strategy for mass screening of CI in diabetic patients, especially if it is combined with artificial intelligence and telemedicine.

Alterations of the glutamatergic system in diabetes mellitus

Diabetes mellitus (DM) is a chronic disease characterized by elevated blood glucose levels caused by a lack of insulin production (type 1 diabetes) or insulin resistance (type 2 diabetes). It is well known that DM is associated with cognitive deficits and metabolic and neurophysiological changes in the brain. Glutamate is the main excitatory neurotransmitter in the central nervous system that plays a key role in synaptic plasticity, learning, and memory processes. An increasing number of studies have suggested that abnormal activity of the glutamatergic system is implicated in the pathophysiology of DM. Dysfunction of glutamatergic neurotransmission in the central nervous system can provide an important neurobiological substrate for many disorders. Magnetic resonance spectroscopy (MRS) is a non-invasive technique that allows a better understanding of the central nervous system factors by measuring in vivo the concentrations of brain metabolites within the area of interest. Here, we briefly review the MRS studies that have examined glutamate levels in the brain of patients with DM. The present article also summarizes the available data on abnormalities in glutamatergic neurotransmission observed in different animal models of DM. In addition, the role of gut microbiota in the development of glutamatergic alterations in DM is addressed. We speculate that therapeutic strategies targeting the glutamatergic system may be beneficial in the treatment of central nervous system-related changes in diabetic patients.

Analysis of magnetic resonance splectroscopy characteristics in patients with type 2 diabetes complicated with stroke

In this study, we investigated the metabolism of white matter by magnetic resonance spectroscopy (MRS) in stroke complicated with diabetes mellitus in combination with glycosylated hemoglobin (HbAlc) detection and clinical neurological deficit score (NIHSS). Fifty-three patients with stroke within 24 h after onset were collected and scanned by MRS. The biochemical, clinical and imaging characteristics of patients were analyzed. Patients were divided into three groups according to HbAlc levels: Good glycemic control (A): &lt; 6.5%; satisfactory glycemic control (B): 6.5–7.5% and poor glycemic control (C): &gt; 7.5%. The results showed that HbA1c levels were positively correlated with NIHSS in patients with acute ischemic stroke (AIS). There is significant difference in NAA/Cr between the infarcted site of the three groups and the mirror site. HbA1C level was negatively correlated with NAA/Cr in patients with AIS, and there was no significant correlation between NIHSS score and NAA/Cr. The data above demonstrated that the MRS imaging can be used to explain the adverse effects of hyperglycated hemoglobin on brain parenchyma from the perspective of imaging. This imaging technique and clinical NIHSS score have a high consistency in evaluating stroke.

Concomitant functional impairment and reorganization in the linkage between the cerebellum and default mode network in patients with type 2 diabetes mellitus

BACKGROUND

Increasing evidence shows that the default mode network (DMN) and cerebellum are prone to structural and functional abnormalities in patients with type 2 diabetes mellitus (T2DM). However, the type of change in the functional connection between the DMN and cerebellum is still unknown.

METHODS

In this study, seed-based functional connectivity (FC) analysis was used to examine the intrinsic FC of the cerebellum-DMN between healthy controls (HCs) and T2DM patients. Pearson correlation analysis was used to explore the relationship between clinical variables and changes in FC.

RESULTS

Compared with HCs, T2DM patients showed significantly increased FC of the left crus I-left medial superior frontal gyrus, left crus I-right medial superior frontal gyrus, and right crus I-left medial orbitofrontal cortex. Compared with HCs, T2DM patients showed decreased FC of the lobule IX-the right angular gyrus. Moreover, diabetes duration was positively correlated with increased FC of the left crus I-right medial superior frontal gyrus (r=0.438, P=0.007).

CONCLUSIONS

Concomitant functional impairment and reorganization in the linkage between the cerebellum and DMN in patients with T2DM may be a biomarker of early brain damage that can help us better understand the pathogenesis of cognitive impairment in T2DM.

A Comprehensive Review of Neuronal Changes in Diabetics

There has been an exponential rise in diabetes mellitus (DM) cases on a global scale. Diabetes affects almost every system of the body, and the nervous system is no exception. Although the brain is dependent on glucose, providing it with the energy required for optimal functionality, glucose also plays a key role in the regulation of oxidative stress, cell death, among others, which furthermore contribute to the pathophysiology of neurological disorders. The variety of biochemical processes engaged in this process is only matched by the multitude of clinical consequences resulting from it. The wide-ranging effects on the central and peripheral nervous system include, but are not limited to axonopathies, neurodegenerative diseases, neurovascular diseases, and general cognitive impairment. All language search was conducted on MEDLINE, COCHRANE, EMBASE, and GOOGLE SCHOLAR till September 2021. The following search strings and Medical Subject Headings (MeSH terms) were used: "Diabetes Mellitus," "CNS," "Diabetic Neuropathy," and "Insulin." We explored the literature on diabetic neuropathy, covering its epidemiology, pathophysiology with the respective molecular pathways, clinical consequences with a special focus on the central nervous system and finally, measures to prevent and treat neuronal changes. Diabetes is slowly becoming an epidemic, rapidly increasing the clinical burden on account of its wide-ranging complications. This review focuses on the neuronal changes occurring in diabetes such as the impact of hyperglycemia on brain function and structure, its association with various neurological disorders, and a few diabetes-induced peripheral neuropathic changes. It is an attempt to summarize the relevant literature about neuronal consequences of DM as treatment options available today are mostly focused on achieving better glycemic control; further research on novel treatment options to prevent or delay the progression of neuronal changes is still needed.

Gray Matter Abnormalities in Type 1 and Type 2 Diabetes: A Dual Disorder ALE Quantification

Aims/hypothesis: Diabetes mellitus (DM) is associated with comorbid brain disorders. Neuroimaging studies in DM revealed neuronal degeneration in several cortical and subcortical brain regions. Previous studies indicate more pronounced brain alterations in type 2 diabetes mellitus (T2DM) than in type 1 diabetes mellitus (T1DM). However, a comparison of both types of DM in a single analysis has not been done so far. The aim of this meta-analysis was to conduct an unbiased objective investigation of neuroanatomical differences in DM by combining voxel-based morphometry (VBM) studies of T1DM and T2DM using dual disorder anatomical likelihood estimation (ALE) quantification.

Methods: PubMed, Web of Science and Medline were systematically searched for publications until June 15, 2020. VBM studies comparing gray matter volume (GMV) differences between DM patients and controls at the whole-brain level were included. Study coordinates were entered into the ALE meta-analysis to investigate the extent to which T1DM, T2DM, or both conditions contribute to gray matter volume differences compared to controls.

Results: Twenty studies (comprising of 1,175 patients matched with 1,013 controls) were included, with seven studies on GMV alterations in T1DM and 13 studies on GMV alterations in T2DM. ALE analysis revealed seven clusters of significantly lower GMV in T1DM and T2DM patients relative to controls across studies. Both DM subtypes showed GMV reductions in the left caudate, right superior temporal lobe, and left cuneus. Conversely, GMV reductions associated exclusively with T2DM (>99% contribution) were found in the left cingulate, right posterior lobe, right caudate and left occipital lobe. Meta-regression revealed no significant influence of study size, disease duration, and HbA1c values.

Conclusions/interpretation: Our findings suggest a more pronounced gray matter atrophy in T2DM compared to T1DM. The increased risk of microvascular or macrovascular complications, as well as the disease-specific pathology of T2DM may contribute to observed GMV reductions.

Systematic Review Registration: [PROSPERO], identifier [CRD42020142525].

The neurometabolic profiles of GABA and Glutamate as revealed by proton magnetic resonance spectroscopy in type 1 and type 2 diabetes

Glucose metabolism is pivotal for energy and neurotransmitter synthesis and homeostasis, particularly in Glutamate and GABA systems. In turn, the stringent control of inhibitory/excitatory tonus is known to be relevant in neuropsychiatric conditions. Glutamatergic neurotransmission dominates excitatory synaptic functions and is involved in plasticity and excitotoxicity. GABAergic neurochemistry underlies inhibition and predicts impaired psychophysical function in diabetes. It has also been associated with cognitive decline in people with diabetes. Still, the relation between metabolic homeostasis and neurotransmission remains elusive.

Two 3T proton MR spectroscopy studies were independently conducted in the occipital cortex to provide insight into inhibitory/excitatory homeostasis (GABA/Glutamate) and to evaluate the impact of chronic metabolic control on the levels and regulation (as assessed by regression slopes) of the two main neurotransmitters of the CNS in type 2 diabetes (T2DM) and type 1 diabetes (T1DM).

Compared to controls, participants with T2DM showed significantly lower Glutamate, and also GABA. Nevertheless, higher levels of GABA/Glx (Glutamate+Glutamine), and lower levels of Glutamate were associated with poor metabolic control in participants with T2DM. Importantly, the relationship between GABA/Glx and HbA_1c found in T2DM supports a relationship between inhibitory/excitatory balance and metabolic control. Interestingly, this neurometabolic profile was undetected in T1DM. In this condition we found strong evidence for alterations in MRS surrogate measures of neuroinflammation (myo-Inositol), positively related to chronic metabolic control.

Our results suggest a role for Glutamate as a global marker of T2DM and a sensitive marker of glycemic status. GABA/Glx may provide a signature of cortical metabolic state in poorly controlled patients as assessed by HbA_1c levels, which indicate long-term blood Glucose control. These findings are consistent with an interplay between abnormal neurotransmission and metabolic control in particular in type 2 diabetes thereby revealing dissimilar contributions to the pathophysiology of neural dysfunction in both types of diabetes.

A novel hippocampus metabolite signature in diabetes mellitus rat model of diabetic encephalopathy

Diabetic encephalopathy (DE) is one of the chronic complications of diabetes. Even then, the molecular mechanism underlying DE remains unexplored. In this study, we have made an attempt to investigate the metabolic changes associated with the streptozocin (STZ)-induced cognitive dysfunction in the hippocampus of the rat model, a classical rodent model for DE, with the help of Gas Chromatography-Mass Spectrometry-based method. The STZ injections led to the rise of mean blood glucose levels in the diabetes mellitus (DM) group of rats as compared to the control (CON) group of rats throughout the experiment. However, we did not find any significant difference between the blood glucose levels of the DM & the CON groups of rats before the STZ injection. The results indicated a behavioral and morphological cognitive dysfunction in the DM groups of rats. The metabolomic investigation of these DE rats demonstrated a lower level of N-acetylaspartate and dihydroxyacetone phosphate accompanied by a higher level of homocysteine and glutamate as against the CON group of rats. The outcome of this study may unravel the underlying pathophysiological mechanism of DE. Also, the metabolomic data from this study may provide a platform for the development of DE biomarkers.

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.

Plasma N-Acetylaspartate Is Related to Age, Obesity, and Glucose Metabolism: Effects of Antidiabetic Treatment and Bariatric Surgery

Background: N-acetylaspartate (NAA) is synthesized only by neurons and is involved in neuronal metabolism and axonal myelination. NAA is the strongest signal on brain magnetic resonance spectroscopy, and its concentration have been associated with cognitive dysfunction in neurodegenerative diseases, obesity, and type 2 diabetes (T2D). Materials and Methods: We explored the impact of obesity and T2D on circulating NAA as well as the impact of bariatric surgery and antidiabetic treatments. We developed an LC-MS method for the accurate measurements of fasting plasma NAA levels in 505 subjects (156 subjects with normal glucose tolerance, 24 subjects with impaired glucose tolerance, and 325 patients with T2D) to examine the associations of NAA with obesity and dysglycemia. To validate cross-sectional findings, plasma NAA was measured 6 months after Roux-en-Y Gastric Bypass (RYGB) in 55 morbidly obese subjects, and after 1 year of antidiabetic treatment (with dapagliflozin, exenatide, or dapagliflozin plus exenatide) in 192 T2D patients. Results: In the whole population, NAA was associated with age (r = 0.31, p <0.0001) and BMI (r = -0.20, p <0.0001). Independently of age and BMI, NAA was reciprocally related to HbA1c and fasting plasma glucose (partial r = -0.13, both p = 0.01). Surgically-induced weight loss raised NAA (by 18 nmol/L on average, p <0.02). Glucose lowering treatment increased NAA in proportion to the drop in HbA1c (r = 0.31, p <0.0001) regardless of the agent used. Conclusions: Circulating NAA concentrations are modulated by age, obesity, and glycemic control. Whether they may mark for the corresponding metabolic effects on brain function remains to be established by joint measurements of spectroscopic signal and cognitive function.

Correlation Between Diabetic Cognitive Impairment and Diabetic Retinopathy in Patients With T2DM by 1H-MRS

Objective: To explore the correlation between diabetic cognitive impairment (DCI) and diabetic retinopathy (DR) through examining the cognitive function and the metabolism of the cerebrum in Type 2 diabetes mellitus (T2DM) by ¹H-MRS.

Methods: Fifty-three patients with T2DM were enrolled for this study. According to the fundus examination, the patients were divided into the DR group (n = 26) and the T2DM without DR group (T2DM group, n = 27). Thirty healthy adults were selected as a control group (HC group, n = 30). Cognitive function was measured by Montreal Cognitive Assessment (MoCA). The peak areas of N-acetylaspartate (NAA), Cho-line (Cho), Creatine (Cr), and Myo-inositol (mI) as well as their ratios were detected by proton magnetic resonance spectroscopy (¹H-MRS). The difference analysis between the three groups was performed by one-way ANOVA. When p < 0.05, LSD-t was applied. A partial correlation analysis (with age as a covariate) was used to analyze the correlation between metabolites in the DR group and MoCA scores. Among all T2DM patients, Chi-square test age, gender, education level, BMI, SBP, DBP, FPG, HbA1c, TC, TG, HDL-C, LDL-C, DR, and DCI correlation were measured. Differences were statistically significant while P < 0.05.

Results: 1. The scores of MoCA in the DR group or in the T2DM group were significantly less than those in the HC group (F = 3.54, P < 0.05), and the scores of MoCA in the DR group were significantly less than those in the other groups (F = 3.61, P < 0.05). 2. There were significant differences for NAA in the bilateral hippocampus in DR patients, T2DM patients, and healthy controls (P < 0.05). 3. The NAA/Cr was significantly positively correlated with the score of MoCA in DR patients' left hippocampus (r = 0.781, P < 0.01). 4. Chi-square analysis found that there was a correlation between DR and DCI (x² = 4.6, df = 1, p = 0.032, plt: 0.05). There was no correlation between other influencing factors and DCI (P > 0.05).

Conclusion: DCI is closely correlated with the DR in patients with T2DM. Hippocampal brain metabolism may have some changes in two sides of NAA in patients with DR, ¹H-MRS may provide effective imaging strategies and methods for the early diagnosis of brain damage and quantitative assessment cognitive function in T2DM.

Higher GABA concentration in the medial prefrontal cortex of Type 2 diabetes patients is associated with episodic memory dysfunction

Type 2 diabetes (T2D) is associated with an accelerated episodic memory decline, but the underlying pathophysiological mechanisms are not well understood. Hallmarks of T2D comprise impairment of insulin secretion and insulin sensitivity. Insulin signaling modulates cerebral neurotransmitter activity, including the excitatory glutamate and inhibitory gamma-aminobutyric acid (GABA) systems. Here we tested the hypothesis that the glutamate and GABA systems are altered in T2D patients and this relates to memory decline and insulin resistance. Using 1 H-magnetic resonance spectroscopy (MRS), we examined glutamate and GABA concentrations in episodic memory relevant brain regions (medial prefrontal cortex and precuneus) of T2D patients and matched controls. Insulin sensitivity was measured by hyperinsulinemic-euglycemic clamps and memory performance was assessed using a face-profession associations test. T2D patients exhibited peripheral insulin resistance and had a decreased memory for face-profession associations as well as elevated GABA concentration in the medial prefrontal cortex but not precuneus. In addition, medial prefrontal cortex GABA concentration was negatively associated with memory performance suggesting that abnormal GABA levels in the medial prefrontal cortex are linked to the episodic memory decline that occurs in T2D patients.

Altered Whole-Brain Functional Topological Organization and Cognitive Function in Type 2 Diabetes Mellitus Patients

Type 2 diabetes mellitus (T2DM) is associated with cognitive dysfunction and may even progress to dementia. However, the underlying mechanism of altered functional topological organization and cognitive impairments remains unclear. This study explored the topological properties of functional whole brain networks in T2DM patients with graph theoretical analysis using a resting-state functional magnetic resonance imaging (rs-fMRI) technique. Thirty T2DM patients (aged 51.77 ± 1.42 years) and 30 sex-, age-, and education-matched healthy controls (HCs) (aged 48.87 ± 0.98 years) underwent resting-state functional imaging in a 3.0 T MR scanner in addition to detailed neuropsychological and laboratory tests. Then, graph theoretical network analysis was performed to explore the global and nodal topological alterations in the functional whole brain networks of the T2DM patients. Finally, correlation analyses were performed to investigate the relationship between the altered topological parameters, cognitive performances and clinical variables. Compared to HCs, we found that T2DM patients displayed worse performances in general cognitive function and several cognitive domains, including episodic memory, attention and executive function. In addition, T2DM patients showed a higher small-worldness (σ), a higher normalized clustering coefficient (γ) and a higher local efficiency (E_loc). Moreover, decreased nodal topological properties were mainly distributed in the occipital lobes, frontal lobes, left median cingulate and paracingulate gyri, and left amygdala, while increased nodal topological properties were mainly distributed in the right gyrus rectus, right anterior cingulate and paracingulate gyri, right posterior cingulate gyrus, bilateral caudate nucleus, bilateral cerebellum 3, bilateral cerebellum crus 1, vermis (1, 2) and vermis 3. Some disrupted nodal topological properties were correlated with cognitive performance and HbA1c levels in T2DM patients. This study shows altered functional topological organization in T2DM patients, mainly suggesting a compensation mechanism of the functional whole brain network in the relatively early stage to counteract cognitive impairments.

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.

Intragastric balloon therapy leads to normalization of brain magnetic resonance spectroscopic markers of diabetes in morbidly obese patients

Elevated brain myo-inositol (m-Ins) concentration (a putative marker of neuroinflammation) has been reported in patients suffering from type 2 diabetes mellitus (T2DM). Obesity alone and T2DM have been found to be associated with a lower concentration of N-acetyloaspartate and N-acetylaspartylglutamate (tNAA, a marker of neuronal integrity, reflecting neuronal loss or metabolic derangement). It is not clear if these changes reverse with weight loss. The intra-gastric balloon (IGB) is an endoscopic bariatric therapy that leads to massive weight loss and improvement of glycemic control. In this study we evaluated if tNAA/tCr and m-Ins/tCr metabolite ratios are affected by weight loss, where tCr is the signal of creatine containing compounds. Twenty-three morbidly obese patients, 12 of them with T2DM (OD) and 11 without T2DM (OB), as well as 11 healthy controls of normal weight (CON), underwent single voxel spectroscopy at 3 T. Spectra were obtained within a region in the left parietal white matter one month before IGB insertion, three months after IGB insertion, and one month after IGB removal. Before IGB insertion, m-Ins/tCr was 15% higher in OD than in OB (p = 0.005) and 12% higher in OD than in CON (p = 0.03). m-Ins/tCr decreased significantly by 8% over the first three months after IGB insertion (p = 0.01) and remained normal after IGB removal. tNAA/tCr was normal in all groups throughout the study, pointing to normal brain metabolism. Normalization of m-Ins/tCr is consistent with remission of neuroinflammation in patients with T2DM. An evaluation of long-term effects of IGB treatment is necessary.

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.

Metabolic Changes Associated with a Rat Model of Diabetic Depression Detected by Ex Vivo 1H Nuclear Magnetic Resonance Spectroscopy in the Prefrontal Cortex, Hippocampus, and Hypothalamus

Diabetic patients often present with comorbid depression. However, the pathogenetic mechanisms underlying diabetic depression (DD) remain unclear. To explore the mechanisms underpinning the pathogenesis of the disease, we used ex vivo ¹H nuclear magnetic resonance spectroscopy and immunohistochemistry to investigate the main metabolic and pathological changes in various rat brain areas in an animal model of DD. Compared with the control group, rats in the DD group showed significant decreases in neurotransmitter concentrations of glutamate (Glu) and glutamine (Gln) in the prefrontal cortex (PFC), hippocampus, and hypothalamus and aspartate and glycine in the PFC and hypothalamus. Gamma-aminobutyric acid (GABA) was decreased only in the hypothalamus. Levels of the energy product, lactate, were higher in the PFC, hippocampus, and hypothalamus of rats with DD than those in control rats, while creatine was lower in the PFC and hippocampus, and alanine was lower in the hypothalamus. The levels of other brain metabolites were altered, including N-acetyl aspartate, taurine, and choline. Immunohistochemistry analysis revealed that expressions of both glutamine synthetase and glutaminase were decreased in the PFC, hippocampus, and hypothalamus of rats with DD. The metabolic changes in levels of Glu, Gln, and GABA indicate an imbalance of the Glu-Gln metabolic cycle between astrocytes and neurons. Our results suggest that the development of DD in rats may be linked to brain metabolic changes, including inhibition of the Glu-Gln cycle, increases in anaerobic glycolysis, and disturbances in the lactate-alanine shuttle, and associated with dysfunction of neurons and astrocytes.

High-fat diet induces a neurometabolic state characterized by changes in glutamate and N-acetylaspartate pools associated with early glucose intolerance: An in vivo multimodal MRI study

BACKGROUND

Type-2 diabetes mellitus (T2DM) is a metabolic disorder with a broad range of complications in the brain that depend on the conditions that precede its onset, such as obesity and metabolic syndromes. It has been suggested that neurotransmitter and metabolic perturbations may emerge even before the early stages of T2DM and that high-caloric intake could adversely influence the brain in such states. Notwithstanding, evidence for neurochemical and structural alterations in these conditions are still sparse and controversial.

PURPOSE

To evaluate the influence of high-fat diet in the neurochemical profile and structural integrity of the rodent brain.

STUDY TYPE

Prospective.

SUBJECTS

Wistar rats (n = 12/group).

FIELD STRENGTH/SEQUENCE

A PRESS, ISIS, RARE, and EPI sequences were performed at 9.4T.

ASSESSMENT

Neurochemical and structural parameters were assessed by magnetic resonance spectroscopy, voxel-based morphometry, volumetry, and diffusion tensor imaging.

STATISTICAL TESTS

Measurements were compared through Student and Mann-Whitney tests. Pearson correlation was used to assess relationships between parameters.

RESULTS

Animals submitted to high-caloric intake gained weight (P = 0.003) and developed glucose intolerance (P < 0.001) but not hyperglycemia. In the hippocampus, the diet induced perturbations in glutamatergic metabolites reflected by increased levels of glutamine (P = 0.016) and glutamatergic pool (Glx) (P = 0.036), which were negatively correlated with glucose intolerance (glutamine, r = -0.804, P = 0.029), suggesting a link with neurometabolic dysregulation. At caudate-putamen, high-fat diet led to a surprising increase in the pool of N-acetylaspartate (P = 0.028). A relation with metabolic changes was again suggested by the negative correlation between glucose intolerance and levels of glutamatergic metabolites in this region (glutamate, r = -0.845, P = 0.014; Glx, r = -0.834, P = 0.020). Neither changes in phosphate compounds nor major structural alterations were observed for both regions.

DATA CONCLUSION

We found evidence that high-fat diet-induced obesity leads to distinct early and region-specific metabolic/neurochemical imbalances in the presence of early glucose intolerance even when structural alterations or T2DM are absent.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018.

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.

Beneficial Effects of Yogasanas and Pranayama in limiting the Cognitive decline in Type 2 Diabetes

BACKGROUND

Out of many complications that were observed in type 2 diabetes, cognitive impairment is the most neglected.

AIM AND OBJECTIVES

The aim of the present study is to assess the cognitive decline in type 2 diabetes and to observe the role of yogasanas and pranayama in ameliorating the cognitive decline.

MATERIALS AND METHODS

Sixty eight type 2 diabetic subjects were recruited in the study, 34 of them did specific yogasanas and pranayama (test group) for six months and the remaining age and sex matched 34 subjects were recruited as (control group) who were not on any specific exercise regimen. Glycaemic index was estimated by measuring the glycosylated haemoglobin (HbA1c) concentration with Bio-Rad apparatus and cognition was assessed by using Addenbrook's Cognitive Examination-Revised (ACE-R), which is a neuropsychological battery.

STATISTICAL ANALYSIS

Data was analysed with unpaired student t test. P value<0.05 is considered as statistically significant. Validity was assessed by receiver operating characteristics.

RESULTS

Analysis of data indicated more cognitive scores in the test group when compared with the control group. In test group six months practice of yogasanas and pranayama has also significantly brought down the high glycaemic values which were observed in the control group.

CONCLUSION

These findings allow the study to conclude that regular practice of yogasanas and pranayama has a beneficial effect on cognitive performance in type 2 diabetic subjects by stabilizing blood glucose.

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.

2D-1H proton magnetic resonance spectroscopic imaging study on brain metabolite alterations in patients with diabetic hypertension

The aim of the present study was to investigate the possible metabolic alterations in the frontal cortex and parietal white matter in patients with diabetic hypertension (DHT) using proton magnetic resonance (MR) spectroscopic imaging. A total of 33 DHT patients and 30 healthy control subjects aged between 45 and 75 were included in the present study. All subjects were right‑handed. The spectroscopy data were collected using a GE Healthcare 1.5T MR scanner. The multi‑voxels were located in the semioval center (repetition time/echo time=1,500 ms/35 ms). The area of interest was 8x10x2 cm in volume and contained the two sides of the frontal cortex and the parietal white matter. The spectra data were processed using SAGE software. The ratios of brain metabolite concentrations, particularly for N‑acetylaspartate (NAA)/creatine (Cr) and Choline (Cho)/Cr were calculated and analyzed. Statistical analyses were performed using SPSS 17.0. The NAA/Cr ratio of the bilateral prefrontal cortex of the DHT group was significantly lower than that of the control group (left t=‑7.854, P=0.000 and right t=‑5.787, P=0.000), The Cho/Cr ratio was also much lower than the control group (left t=2.422, P=0.024 and right t=2.920, P=0.007). NAA/Cr ratio of the left parietal white matter of the DHT group was extremely lower than that of the control group (t=‑4.199, P=0.000). Therefore, DHT may result in metabolic disorders in the frontal cortex and parietal white matter but the metabolic alterations are different in various regions of the brain. The alteration in cerebral metabolism is associated with diabetes and hypertension. The ratios of NAA/Cr and Cho/Cr are potential metabolic markers for the brain damage induced by DHT.

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.

Daily consumption of white tea (Camellia sinensis (L.)) improves the cerebral cortex metabolic and oxidative profile in prediabetic Wistar rats

Diabetes mellitus (DM) is a major public health problem and its incidence is rising dramatically. The brain, particularly the cerebral cortex, is very susceptible to glucose fluctuations and hyperglycaemia-induced oxidative stress. Tea (Camellia sinensis (L.)) is widely consumed; however, the antidiabetic properties of white tea remain largely unexplored. In the present study, we investigated the effects of daily consumption of white tea on the cerebral cortex of prediabetic rats. The cerebral cortex metabolic profile was evaluated, and the expression levels of GLUT, phosphofructokinase-1, lactate dehydrogenase (LDH) and monocarboxylate transporter 4 were assessed. LDH activity was also determined. The cerebral cortex oxidative profile was determined by evaluating its antioxidant power, lipid peroxidation and protein oxidation levels. Catalase, glutathione, glutamate, N-acetylaspartate, aspartate, choline, γ-aminobutyric acid, taurine and valine contents were determined. Daily consumption of white tea ameliorated glucose tolerance and insulin sensitivity. Moreover, white tea altered the cortex glycolytic profile, modulating GLUT expression and lactate and alanine contents. Finally, white tea consumption restored protein oxidation and lipid peroxidation levels and catalase expression, and improved antioxidant capacity. In conclusion, daily consumption of white tea improved the cerebral cortex metabolic and oxidative profile in prediabetic rats, suggesting it as a good, safe and inexpensive strategy to prevent DM-related effects in the cerebral cortex.

EFFECT OF TYPE 2 DIABETES MELLITUS ON BRAIN METABOLITES BY USING PROTON MAGNETIC RESONANCE SPECTROSCOPY-A SYSTEMATIC REVIEW

Cerebral metabolism will be affected in T2DM either by chronic hyperglycemia or by chronic hypoxia. Proton magnetic resonance spectroscopy (¹H-MRS) of the brain provides detailed information about the structure, dynamics, reaction state and chemical environment of molecules. It also measures the levels of brain metabolites such as myo-inositol (mI), N acetyl aspartate (NAA), creatine (Cr), choline (Cho), glutamate (Glu), glutamine (Gln) and gamma amino butyric acid (GABA). Several studies suggest that people with type 2 diabetes mellitus (T2DM) are at an increased risk of cognitive impairment in comparison with the general population. The altered metabolites may cause cognitive dysfunction in T2DM. This review article concludes that in T2DM, metabolite levels were altered in different regions of brain.