Cerebellar Glucose During Fasting and Acute Hyperglycemia in Nondiabetic Men and in Men with Type 1 Diabetes

Balanced Steady-State Free Precession Enables High-Resolution Dynamic 3D Deuterium Metabolic Imaging of the Human Brain at 7T

OBJECTIVES

Deuterium (2H) metabolic imaging (DMI) is an emerging magnetic resonance technique to non-invasively map human brain glucose (Glc) uptake and downstream metabolism following oral or intravenous administration of 2H-labeled Glc. The achievable spatial resolution is limited due to inherently low sensitivity of DMI. This hinders potential clinical translation. The purpose of this study was to improve the signal-to-noise ratio (SNR) of 3D DMI via a balanced steady-state free precession (bSSFP) acquisition scheme combined with fast non-Cartesian spatial-spectral sampling to enable high-resolution dynamic imaging of neural Glc uptake and glutamate+glutamine (Glx) synthesis of the human brain at 7T.

MATERIALS AND METHODS

Six healthy volunteers (2 f/4 m) were scanned after oral administration of 0.8 g/kg [6,6']-2H-Glc using a novel density-weighted bSSFP acquisition scheme combined with fast 3D concentric ring trajectory (CRT) k-space sampling at 7T. Time-resolved whole brain DMI datasets were acquired for approximately 80 minutes (7 minutes per dataset) after oral 2H-labeled Glc administration with 0.75 mL and 0.36 mL isotropic spatial resolution and results were compared to conventional spoiled Free Induction Decay (FID) 2H-MRSI with CRT readout at matched nominal spatial resolution. Dynamic DMI measurements of the brain were accompanied by simultaneous systemic Glc measurements of the interstitial fluid using a continuous Glc monitoring (CGM) sensor (on the upper arm). The correlation between brain and interstitial Glc levels was analyzed using linear mixed models.

RESULTS

The bSSFP-CRT approach achieved SNRs that were up to 3-fold higher than conventional spoiled FID-CRT 2H-MRSI. This enabled a 2-fold higher spatial resolution. Seventy minutes after oral tracer uptake comparable 2H-Glc, 2H-Glx, and 2H-water concentrations were detected using both acquisition schemes at both, regular and high spatial resolutions (0.75 ml and 0.36 mL isotropic). The mean Areas Under the Curve (AUC) for interstitial fluid Glc measurements obtained using a CGM sensor was 509 ± 65 mM·min. This is 3.4 times higher than the mean AUC of brain Glc measurements of 149 ± 43 mM·min obtained via DMI. The linear mixed models fitted to assess the relationship between CGM measures and brain 2H-Glc yielded statistically significant slope estimates in both GM (β1 = 0.47, P = 0.01) and WM (β1 = 0.36, P = 0.03).

CONCLUSIONS

In this study we successfully implemented a balanced steady-state free precession (bSSFP) acquisition scheme for dynamic whole-brain human DMI at 7T. A 3-fold SNR increase compared to conventional spoiled acquisition allowed us to double the spatial resolution achieved using conventional FID-CRT DMI. Systemic continuous glucose measurements, combined with dynamic DMI, demonstrate significant potential for clinical applications. This could help improve our understanding of brain glucose metabolism by linking it to time-resolved peripheral glucose levels. Importantly, these measurements are conducted in a minimally invasive and physiological manner.

Balanced steady state free precession enables high-resolution dynamic 3D Deuterium Metabolic Imaging of the human brain at 7T

Objectives

Deuterium (2H) Metabolic Imaging (DMI) is an emerging magnetic resonance technique to non-invasively map human brain glucose (Glc) uptake and downstream metabolism following oral or intravenous administration of 2H-labeled Glc. The achievable spatial resolution is limited due to inherently low sensitivity of DMI. This hinders potential clinical translation. The purpose of this study was to improve the signal-to-noise ratio (SNR) of 3D DMI via a balanced steady state free precession (bSSFP) acquisition scheme combined with fast non-Cartesian spatial-spectral sampling to enable high resolution dynamic imaging of neural Glc uptake and glutamate+glutamine (Glx) synthesis of the human brain at 7T.

Materials and Methods

Six healthy volunteers (2f/4m) were scanned after oral administration of 0.8 g/kg [6,6']-2H-Glc using a novel density-weighted bSSFP acquisition scheme combined with fast 3D concentric ring trajectory (CRT) k-space sampling at 7T. Time-resolved whole brain DMI datasets were acquired for approximately 80 min (7 min per dataset) after oral 2H-labeled Glc administration with 0.75ml and 0.36ml isotropic spatial resolution and results were compared to conventional spoiled Free Induction Decay (FID) 2H-MRSI with CRT readout at matched nominal spatial resolution.Dynamic DMI measurements of the brain were accompanied by simultaneous systemic Glc measurements of the interstitial tissue using a continuous Glc monitoring (CGM) sensor (on the upper arm). The correlation between brain and interstitial Glc levels was analyzed using linear mixed models.

Results

The bSSFP-CRT approach achieved SNRs that were up to 3-fold higher than conventional spoiled FID-CRT 2H-MRSI. This enabled a 2-fold higher spatial resolution. Seventy minutes after oral tracer uptake comparable 2H-Glc, 2H-Glx and 2H-water concentrations were detected using both acquisition schemes at both, regular and high spatial resolutions (0.75ml and 0.36 ml isotropic). The mean Areas Under the Curve (AUC) for interstitial fluid Glc measurements obtained using a continuous Glc monitoring (CGM) sensor was 509±65 mM·min. This is 3.4 times higher than the mean AUC of brain Glc measurements of 149±43 mM·min obtained via DMI. The linear mixed models fitted to assess the relationship between CGM measures and brain 2H-Glc yielded statistically significant slope estimates in both GM (β1 = 0.47, p = 0.01) and WM (β1 = 0.36, p = 0.03).

Conclusion

In this study we successfully implemented a balanced steady state free precession (bSSFP) acquisition scheme for dynamic whole-brain human DMI at 7T. A 3-fold SNR increase compared to conventional spoiled acquisition allowed us to double the spatial resolution achieved using conventional FID-CRT DMI. Systemic continuous glucose measurements, combined with dynamic DMI, demonstrate significant potential for clinical applications. This could help to improve our understanding of brain glucose metabolism by linking it to time-resolved peripheral glucose levels. Importantly, these measurements are conducted in a minimally invasive and physiological manner.

Whole-brain deuterium metabolic imaging via concentric ring trajectory readout enables assessment of regional variations in neuronal glucose metabolism

Deuterium metabolic imaging (DMI) is an emerging magnetic resonance technique, for non-invasive mapping of human brain glucose metabolism following oral or intravenous administration of deuterium-labeled glucose. Regional differences in glucose metabolism can be observed in various brain pathologies, such as Alzheimer's disease, cancer, epilepsy or schizophrenia, but the achievable spatial resolution of conventional phase-encoded DMI methods is limited due to prolonged acquisition times rendering submilliliter isotropic spatial resolution for dynamic whole brain DMI not feasible. The purpose of this study was to implement non-Cartesian spatial-spectral sampling schemes for whole-brain 2H FID-MR Spectroscopic Imaging to assess time-resolved metabolic maps with sufficient spatial resolution to reliably detect metabolic differences between healthy gray and white matter regions. Results were compared with lower-resolution DMI maps, conventionally acquired within the same session. Six healthy volunteers (4 m/2 f) were scanned for ~90 min after administration of 0.8 g/kg oral [6,6']-2H glucose. Time-resolved whole brain 2H FID-DMI maps of glucose (Glc) and glutamate + glutamine (Glx) were acquired with 0.75 and 2 mL isotropic spatial resolution using density-weighted concentric ring trajectory (CRT) and conventional phase encoding (PE) readout, respectively, at 7 T. To minimize the effect of decreased signal-to-noise ratios associated with smaller voxels, low-rank denoising of the spatiotemporal data was performed during reconstruction. Sixty-three minutes after oral tracer uptake three-dimensional (3D) CRT-DMI maps featured 19% higher (p = .006) deuterium-labeled Glc concentrations in GM (1.98 ± 0.43 mM) compared with WM (1.66 ± 0.36 mM) dominated regions, across all volunteers. Similarly, 48% higher (p = .01) 2H-Glx concentrations were observed in GM (2.21 ± 0.44 mM) compared with WM (1.49 ± 0.20 mM). Low-resolution PE-DMI maps acquired 70 min after tracer uptake featured smaller regional differences between GM- and WM-dominated areas for 2H-Glc concentrations with 2.00 ± 0.35 mM and 1.71 ± 0.31 mM, respectively (+16%; p = .045), while no regional differences were observed for 2H-Glx concentrations. In this study, we successfully implemented 3D FID-MRSI with fast CRT encoding for dynamic whole-brain DMI at 7 T with 2.5-fold increased spatial resolution compared with conventional whole-brain phase encoded (PE) DMI to visualize regional metabolic differences. The faster metabolic activity represented by 48% higher Glx concentrations was observed in GM- compared with WM-dominated regions, which could not be reproduced using whole-brain DMI with the low spatial resolution protocol. Improved assessment of regional pathologic alterations using a fully non-invasive imaging method is of high clinical relevance and could push DMI one step toward clinical applications.

Brain region-specific disruption of mitochondrial bioenergetics in cynomolgus macaques fed a Western versus a Mediterranean diet

Mitochondrial dysfunction is evident in diseases affecting cognition and metabolism such as Alzheimer's disease and type 2 diabetes. Human studies of brain mitochondrial function are limited to postmortem tissue, preventing the assessment of bioenergetics by respirometry. Here, we investigated the effect of two diets on mitochondrial bioenergetics in three brain regions: the prefrontal cortex (PFC), the entorhinal cortex (ERC), and the cerebellum (CB), using middle-aged nonhuman primates. Eighteen female cynomolgus macaques aged 12.3 ± 0.7 yr were fed either a Mediterranean diet that is associated with healthy outcomes or a Western diet that is associated with poor cognitive and metabolic outcomes. Average bioenergetic capacity within each brain region did not differ between diets. Distinct brain regions have different metabolic requirements related to their function and disease susceptibility. Therefore, we also examined differences in bioenergetic capacity between brain regions. Mitochondria isolated from animals fed a Mediterranean diet maintained distinct differences in mitochondrial bioenergetics between brain regions, whereas animals fed the Western diet had diminished distinction in bioenergetics between brain regions. Notably, fatty acid β-oxidation was not affected between regions in animals fed a Western diet. In addition, bioenergetics in animals fed a Western diet had positive associations with fasting blood glucose and insulin levels in PFC and ERC mitochondria but not in CB mitochondria. Altogether, these data indicate that a Western diet disrupts bioenergetic patterns across brain regions and that circulating blood glucose and insulin levels in Western-diet fed animals influence bioenergetics in brain regions susceptible to Alzheimer's disease and type 2 diabetes.NEW & NOTEWORTHY We show that compared with cynomolgus macaques fed a Mediterranean diet, a Western diet resulted in diminished bioenergetic pattern between brain regions related to blood glucose and insulin levels, specifically in brain regions susceptible to neurodegeneration and diabetes. In addition, fatty acid metabolism not directly linked to the TCA cycle and glucose metabolism did not show differences in bioenergetics due to diet.

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.

Dynamic Changes of Amplitude of Low-Frequency Fluctuations in Patients With Diabetic Retinopathy

Background: Growing evidence demonstrate that diabetic retinopathy (DR) patients have a high risk of cognitive decline and exhibit abnormal brain activity. However, neuroimaging studies thus far have focused on static cerebral activity changes in DR patients. The characteristics of dynamic cerebral activity in patients with DR are poorly understood.

Purpose: The purpose of the study was to investigate the dynamic cerebral activity changes in patients with DR using the dynamic amplitude of low-frequency fluctuation (dALFF) method.

Materials and methods: Thirty-four DR patients (18 men and 16 women) and 38 healthy controls (HCs) (18 males and 20 females) closely matched in age, sex, and education were enrolled in this study. The dALFF method was used to investigate dynamic intrinsic brain activity differences between the DR and HC groups.

Results: Compared with HCs, DR patients exhibited increased dALFF variability in the right brainstem, left cerebellum_8, left cerebellum_9, and left parahippocampal gyrus. In contrast, DR patients exhibited decreased dALFF variability in the left middle occipital gyrus and right middle occipital gyrus.

Conclusion: Our study highlighted that DR patients showed abnormal variability of dALFF in the visual cortices, cerebellum, and parahippocampal gyrus. These findings suggest impaired visual and motor and memory function in DR individuals. Thus, abnormal dynamic spontaneous brain activity might be involved in the pathophysiology of DR.

Total hip arthroplasty in Parkinson's disease patients: a propensity score-matched analysis with minimum 2-year surveillance

INTRODUCTION

Parkinson's disease (PD) patients experience chronic pain related to osteoarthritis at comparable rates to the general population. While total hip arthroplasty (THA) effectively improves pain, functionality, and quality of life in PD patients, long-term outcomes following THA are under-reported. This study sought to investigate whether PD patients have an increased risk of complications and revision following THA in comparison to the general population.

METHODS

Utilising New York State's Statewide Planning and Research Cooperative System, all PD patients who underwent THA from 2009 to 2011 with minimum 2-year follow-up were identified. A control group (no-PD) was created via 1:1 propensity score-matching by age, gender, and Charlson/Deyo score. Univariate analysis compared demographics, complications, and revisions. Multivariate binary stepwise logistic regression identified independent predictors of outcomes.

RESULTS

470 propensity score-matched patients (PD: n = 235; no-PD: n = 235) were identified. PD patients demonstrated higher rates of overall and postoperative wound infection (p < 0.05), with comparable individual and overall complication and revision rates. PD did not increase odds of complications or revisions. PD patients had lengthier hospital stay (4.97 vs. 4.07 days, p = 0.001) and higher proportion of second primary THA >2-years postoperatively (69.4% vs. 59.6%, p = 0.027). Charlson/Deyo index was the greatest predictor of any surgical complication (OR = 1.17, p = 0.029). Female sex was the strongest predictor of any medical complication (OR = 2.21, p < 0.001).

DISCUSSION

Despite lengthier hospital stays and infection-related complications, PD patients experienced comparable complication and revision rates to patients from the general population undergoing THA.

Altered Cerebellar-Cerebral Circuits in Patients With Type 2 Diabetes Mellitus

The role of the cerebellum in type 2 diabetes mellitus (T2DM) has been receiving increased attention. However, the functional connectivity (FC) between the cerebellar subregions and the cerebral cortex has not been investigated in T2DM. Therefore, the purpose of this study was to investigate cerebellar-cerebral FC and the relationship between FC and clinical/cognitive variables in patients with T2DM. A total of 34 patients with T2DM and 30 healthy controls were recruited for this study to receive a neuropsychological assessment and undergo resting-state FC. We selected four subregions of the cerebellum (bilateral lobules IX, right and left Crus I/II, and left lobule VI) as regions of interest (ROIs) to examine the differences in cerebellar-cerebral circuits in patients with T2DM compared to healthy controls. Correlation analysis was performed to examine the relationship between FC and clinical/cognitive variables in the patients. Compared to healthy controls, patients with T2DM showed significantly decreased cerebellar-cerebral FC in the default-mode network (DMN), executive control network (ECN), and visuospatial network (VSN). In the T2DM group, the FC between the left cerebellar lobule VI and the right precuneus was negatively correlated with the Trail Making Test A (TMT-A) score (r = −0.430, P = 0.013), after a Bonferroni correction. In conclusion, patients with T2DM have altered FC between the cerebellar subregions and the cerebral networks involved in cognitive and emotional processing. This suggests that a range of cerebellar-cerebral circuits may be involved in the neuropathology of T2DM cognitive dysfunction.

Effect of Parkinson's disease on primary total joint arthroplasty outcomes: A meta-analysis of matched control studies

BACKGROUND

Currently, no meta-analysis exists elucidate the outcomes of total joint arthroplasty (TJA) in patients with Parkinson's disease (PD). The aim of this study was to investigate the outcomes of TJA in patients with PD with respect to complication and revision in comparison to a TJA cohort without PD.

METHODS

MEDLINE, Scopus, EMBASE, and Cochrane Library databases were searched with English language restrictions. The primary outcome measures were complications and revision, whereas the secondary outcomes included length of stay (LOS) and total charge.

RESULTS

Seven studies with a total of 124163 patients were included. The most important finding from our study was that PD patients had a 42% higher risk for any medical complication (P = 0.004) and a 65% higher risk for any surgical complication (P = 0.01) compared to the matched cohort. Specifically, PD was associated with increased superficial wound infection (P = 0.006), dislocation (P = 0.01), deep vein thrombosis (DVT) (P = 0.02), LOS (P = 0.0005), and total hospital charges (P < 0.00001). However, PD did not increase the risks for periprosthetic infection (P = 0.32) and revision (P = 0.17).

CONCLUSIONS

Patients with PD are at increased risk for medical complication and surgery complications, particularly superficial wound infection, dislocation, and DVT as compared to patients without PD. PD patients also exhibit increased LOS and total hospital charges. However, PD did not increase the risks for periprosthetic infection and revision.

Histological study on the protective role of vitamin B complex on the cerebellum of diabetic rat

BACKGROUND

Disorder in cerebellar structure was reported in diabetes mellitus. B vitamins are involved in many significant metabolic processes within the brain.

AIM OF THE WORK

To detect the protective role of vitamin B complex on the histological structure of the cerebellum of experimentally induced diabetic rat.

MATERIAL & METHODS

Eighteen adult male Wistar rats were divided into two groups. Group I: normal vehicle control (n=6). Group II: streptozotocin-induced diabetic rats (n=12), which was equally divided into two subgroups; IIA (diabetic vehicle control), IIB (diabetic vitamin B complex-treated): streptozotocin-induced diabetic rats treated with vitamin B complex (1mg/kg/day) for 6 weeks. Specimens from the cerebellum were processed for light and electron microscopy.

RESULTS

In vitamin B complex treated group, the histological changes in Purkinje cells, astrocytes and oligodendrocytes were improved compared with the diabetic non-treated group. The white matter revealed intact myelinated axons. Inducible nitric oxide synthase (iNOS) and caspase-3 expression reduced. Glial fibrillary acidic protein (GFAP) expression revealed less activated astroglia. The number of Purkinje cells/mm(2) significantly increased. While, the number of GFAP positive astrocytes/mm(2) significantly decreased. In addition, the blood glucose level was reduced.

CONCLUSION

Vitamin B complex protected the cerebellum from the histological changes which occurred in STZ- induced diabetic rats.

Patients with type 1 diabetes exhibit altered cerebral metabolism during hypoglycemia

Patients with type 1 diabetes mellitus (T1DM) experience, on average, 2 to 3 hypoglycemic episodes per week. This study investigated the effect of hypoglycemia on cerebral glucose metabolism in patients with uncomplicated T1DM. For this purpose, hyperinsulinemic euglycemic and hypoglycemic glucose clamps were performed on separate days, using [1-13C]glucose infusion to increase plasma 13C enrichment. In vivo brain 13C magnetic resonance spectroscopy was used to measure the time course of 13C label incorporation into different metabolites and to calculate the tricarboxylic acid cycle flux (VTCA) by a one-compartment metabolic model. We found that cerebral glucose metabolism, as reflected by the VTCA, was not significantly different comparing euglycemic and hypoglycemic conditions in patients with T1DM. However, the VTCA was inversely related to the HbA1C and was, under hypoglycemic conditions, approximately 45% higher than that in a previously investigated group of healthy subjects. These data suggest that the brains of patients with T1DM are better able to endure moderate hypoglycemia than those of subjects without diabetes.

ImatraNMR: novel software for batch integration and analysis of quantitative NMR spectra

Quantitative NMR spectroscopy is a useful and important tool for analysis of various mixtures. Recently, in addition of traditional quantitative 1D (1)H and (13)C NMR methods, a variety of pulse sequences aimed for quantitative or semiquantitative analysis have been developed. To obtain actual usable results from quantitative spectra, they must be processed and analyzed with suitable software. Currently, there are many processing packages available from spectrometer manufacturers and third party developers, and most of them are capable of analyzing and integration of quantitative spectra. However, they are mainly aimed for processing single or few spectra, and are slow and difficult to use when large numbers of spectra and signals are being analyzed, even when using pre-saved integration areas or custom scripting features. In this article, we present a novel software, ImatraNMR, designed for batch analysis of quantitative spectra. In addition to capability of analyzing large number of spectra, it provides results in text and CSV formats, allowing further data-analysis using spreadsheet programs or general analysis programs, such as Matlab. The software is written with Java, and thus it should run in any platform capable of providing Java Runtime Environment version 1.6 or newer, however, currently it has only been tested with Windows and Linux (Ubuntu 10.04). The software is free for non-commercial use, and is provided with source code upon request.