Dopaminergic Dysfunction Is More Symmetric in Dementia with Lewy Bodies Compared to Parkinson's Disease

BACKGROUND

The α-syn Origin site and Connectome model (SOC) proposes that α-synucleinopathies can be divided into two categories: the asymmetrical brain-first, and more symmetrical body-first Lewy body disease. We have hypothesized that most patients with dementia with Lewy bodies (DLB) belong to the body-first subtype, whereas patients with Parkinson's disease (PD) more often belong to the brain-first subtype.

OBJECTIVE

To compare asymmetry of striatal dopaminergic dysfunction in DLB and PD patients using [18F]-FE-PE2I positron emission tomography (PET).

METHODS

We analyzed [18F]-FE-PE2I PET data from 29 DLB patients and 76 PD patients who were identified retrospectively during a 5-year period at Dept. of Neurology, Aarhus University Hospital. Additionally, imaging data from 34 healthy controls was used for age-correction and visual comparison.

RESULTS

PD patients showed significantly more asymmetry in specific binding ratios between the most and least affected putamen (p < 0.0001) and caudate (p = 0.003) compared to DLB patients. PD patients also had more severe degeneration in the putamen compared to the caudate in comparison to DLB patients (p < 0.0001) who had a more universal pattern of striatal degeneration.

CONCLUSION

Patients with DLB show significantly more symmetric striatal degeneration on average compared to PD patients. These results support the hypothesis that DLB patients may be more likely to conform to the body-first subtype characterized by a symmetrical spread of pathology, whereas PD patients may be more likely to conform to the brain-first subtype with more lateralized initial propagation of pathology.

In vivo vesicular acetylcholine transporter density in human peripheral organs: an [18F]FEOBV PET/CT study

Background

The autonomic nervous system is frequently affected in some neurodegenerative diseases, including Parkinson’s disease and Dementia with Lewy bodies. In vivo imaging methods to visualize and quantify the peripheral cholinergic nervous system are lacking. By using [¹⁸F]FEOBV PET, we here describe the peripheral distribution of the specific cholinergic marker, vesicular acetylcholine transporters (VAChT), in human subjects. We included 15 healthy subjects aged 53–86 years for 70 min dynamic PET protocol of peripheral organs. We performed kinetic modelling of the adrenal gland, pancreas, myocardium, renal cortex, spleen, colon, and muscle using an image-derived input function from the aorta. A metabolite correction model was generated from venous blood samples. Three non-linear compartment models were tested. Additional time-activity curves from 6 to 70 min post injection were generated for prostate, thyroid, submandibular-, parotid-, and lacrimal glands.

Results

A one-tissue compartment model generated the most robust fits to the data. Total volume-of-distribution rank order was: adrenal gland > pancreas > myocardium > spleen > renal cortex > muscle > colon. We found significant linear correlations between total volumes-of-distribution and standard uptake values in most organs.

Conclusion

High [¹⁸F]FEOBV PET signal was found in structures with known cholinergic activity. We conclude that [¹⁸F]FEOBV PET is a valid tool for estimating VAChT density in human peripheral organs. Simple static images may replace kinetic modeling in some organs and significantly shorten scan duration.

Clinical Trial Registration Trial registration: NCT, NCT03554551. Registered 31 May 2018. https://clinicaltrials.gov/ct2/show/NCT03554551?term=NCT03554551&draw=2&rank=1.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13550-022-00889-9.

NMDA receptor ion channel activation detected in vivo with [18F]GE-179 PET after electrical stimulation of rat hippocampus

The positron emission tomography (PET) tracer [¹⁸F]GE-179 binds to the phencyclidine (PCP) site in the open N-methyl-D-aspartate receptor ion channel (NMDAR-IC). To demonstrate that PET can visualise increased [¹⁸F]GE-179 uptake by active NMDAR-ICs and that this can be blocked by the PCP antagonist S-ketamine, 15 rats had an electrode unilaterally implanted in their ventral hippocampus. Seven rats had no stimulation, five received pulsed 400 µA supra-threshold 60 Hz stimulation alone, and three received intravenous S-ketamine injection prior to stimulation. Six other rats were not implanted. Each rat had a 90 min [¹⁸F]GE-179 PET scan. Stimulated rats had simultaneous depth-EEG recordings of induced seizure activity. [¹⁸F]GE-179 uptake (volume of distribution, V_T) was compared between hemispheres and between groups. Electrical stimulation induced a significant increase in [¹⁸F]GE-179 uptake at the electrode site compared to the contralateral hippocampus (mean 22% increase in V_T, p = 0.0014) and to non-stimulated comparator groups. Rats injected with S-ketamine prior to stimulation maintained non-stimulated levels of [¹⁸F]GE-179 uptake during stimulation. In conclusion, PET visualisation of focal [¹⁸F]GE-179 uptake during electrically activated NMDAR-ICs and the demonstration of specificity for PCP sites by blockade with S-ketamine support the in vivo utility of [¹⁸F]GE-179 PET as a use-dependent marker of NMDAR-IC activation.

Regional and interindividual relationships between cerebral perfusion and oxygen metabolism

Quantitative measurements of resting cerebral blood flow (CBF) and metabolic rate of oxygen (CMRO₂) show large between-subject and regional variability, but the relationships between CBF and CMRO₂ measurements regionally and globally are not fully established. Here, we investigated the between-subject and regional associations between CBF and CMRO₂ measures with independent and quantitative PET techniques. We included resting CBF and CMRO₂ measurements from 50 healthy volunteers (aged 22-81 yr), and calculated the regional and global values of oxygen delivery (Do₂) and oxygen extraction fraction (OEF). Linear mixed-model analysis showed that CBF and CMRO₂ measurements were closely associated regionally, but no significant between-subject association could be demonstrated, even when adjusting for arterial Pco₂ and hemoglobin concentration. The analysis also showed regional differences of OEF, reflecting variable relationship between Do₂ and CMRO₂, resulting in lower estimates of OEF in thalami, brainstem, and mesial temporal cortices and higher estimates of OEF in occipital cortex. In the present study, we demonstrated no between-subject association of quantitative measurements of CBF and CMRO₂ in healthy subjects. Thus, quantitative measurements of CBF did not reflect the underlying between-subject variability of oxygen metabolism measures, mainly because of large interindividual OEF variability not accounted for by Pco₂ and hemoglobin concentration.NEW & NOTEWORTHY Using quantitative PET-measurements in healthy human subjects, we confirmed a regional association of CBF and CMRO₂, but did not find an association of these values across subjects. This suggests that subjects have an individual coupling between perfusion and metabolism and shows that absolute perfusion measurements does not serve as a surrogate measure of individual measures of oxygen metabolism. The analysis further showed smaller, but significant regional differences of oxygen extraction fraction at rest.

In vivo quantification of glial activation in minipigs overexpressing human α-synuclein

Parkinson's disease is characterized by a progressive loss of substantia nigra (SN) dopaminergic neurons and the formation of Lewy bodies containing accumulated alpha-synuclein (α-syn). The pathology of Parkinson's disease is associated with neuroinflammatory microglial activation, which may contribute to the ongoing neurodegeneration. This study investigates the in vivo microglial and dopaminergic response to overexpression of α-syn. We used positron emission tomography (PET) and the 18 kDa translocator protein radioligand, [¹¹ C](R)PK11195, to image brain microglial activation and (+)-α-[¹¹ C]dihydrotetrabenazine ([¹¹ C]DTBZ), to measure vesicular monoamine transporter 2 (VMAT2) availability in Göttingen minipigs following injection with recombinant adeno-associated virus (rAAV) vectors expressing either mutant A53T α-syn or green fluorescent protein (GFP) into the SN (4 rAAV-α-syn, 4 rAAV-GFP, 5 non-injected control minipigs). We performed motor symptom assessment and immunohistochemical examination of tyrosine hydroxylase (TH) and transgene expression. Expression of GFP and α-syn was observed at the SN injection site and in the striatum. We observed no motor symptoms or changes in striatal [¹¹ C]DTBZ binding potential in vivo or striatal or SN TH staining in vitro between the groups. The mean [¹¹ C](R)PK11195 total volume of distribution was significantly higher in the basal ganglia and cortical areas of the α-syn group than the control animals. We conclude that mutant α-syn expression in the SN resulted in microglial activation in multiple sub- and cortical regions, while it did not affect TH stains or VMAT2 availability. Our data suggest that microglial activation constitutes an early response to accumulation of α-syn in the absence of dopamine neuron degeneration.

Regional cerebral effects of ketone body infusion with 3-hydroxybutyrate in humans: Reduced glucose uptake, unchanged oxygen consumption and increased blood flow by positron emission tomography. A randomized, controlled trial

Ketone bodies are neuroprotective in neurological disorders such as epilepsy. We randomly studied nine healthy human subjects twice—with and without continuous infusion of 3-hydroxybutyrate–to define potential underlying mechanisms, assessed regionally (parietal, occipital, temporal, cortical grey, and frontal) by PET scan. During 3-hydroxybutyrate infusions concentrations increased to 5.5±0.4 mmol/l and cerebral glucose utilisation decreased 14%, oxygen consumption remained unchanged, and cerebral blood flow increased 30%. We conclude that acute 3-hydroxybutyrate infusion reduces cerebral glucose uptake and increases cerebral blood flow in all measured brain regions, without detectable effects on cerebral oxygen uptake though oxygen extraction decreased. Increased oxygen supply concomitant with unchanged oxygen utilisation may contribute to the neuroprotective effects of ketone bodies.

Early synaptic dysfunction induced by α-synuclein in a rat model of Parkinson's disease

Evidence suggests that synapses are affected first in Parkinson’s disease (PD). Here, we tested the claim that pathological accumulation of α-synuclein, and subsequent synaptic disruption, occur in absence of dopaminergic neuron loss in PD. We determined early synaptic changes in rats that overexpress human α-synuclein by local injection of viral-vectors in midbrain. We aimed to achieve α-synuclein levels sufficient to induce terminal pathology without significant loss of nigral neurons. We tested synaptic disruption in vivo by analyzing motor defects and binding of a positron emission tomography (PET) radioligand to the vesicular monoamine transporter 2, (VMAT2), [¹¹C]dihydrotetrabenazine (DTBZ). Animals overexpressing α-synuclein had progressive motor impairment and, 12 weeks post-surgery, showed asymmetric in vivo striatal DTBZ binding. The PET images matched ligand binding in post-mortem tissue, and histological markers of dopaminergic integrity. Histology confirmed the absence of nigral cell death with concomitant significant loss of striatal terminals. Progressive aggregation of proteinase-K resistant and Ser129-phosphorylated α-synuclein was observed in dopaminergic terminals, in dystrophic swellings that resembled axonal spheroids and contained mitochondria and vesicular proteins. In conclusion, pathological α-synuclein in nigro-striatal axonal terminals leads to early axonal pathology, synaptic disruption, dysfunction of dopaminergic neurotransmission, motor impairment, and measurable change of VMAT2 in the absence of cell loss.

In Alzheimer's Disease, 6-Month Treatment with GLP-1 Analog Prevents Decline of Brain Glucose Metabolism: Randomized, Placebo-Controlled, Double-Blind Clinical Trial

In animal models, the incretin hormone GLP-1 affects Alzheimer’s disease (AD). We hypothesized that treatment with GLP-1 or an analog of GLP-1 would prevent accumulation of Aβ and raise, or prevent decline of, glucose metabolism (CMR_glc) in AD. In this 26-week trial, we randomized 38 patients with AD to treatment with the GLP-1 analog liraglutide (n = 18), or placebo (n = 20). We measured Aβ load in brain with tracer [¹¹C]PIB (PIB), CMR_glc with [¹⁸F]FDG (FDG), and cognition with the WMS-IV scale (ClinicalTrials.gov NCT01469351). The PIB binding increased significantly in temporal lobe in placebo and treatment patients (both P = 0.04), and in occipital lobe in treatment patients (P = 0.04). Regional and global increases of PIB retention did not differ between the groups (P ≥ 0.38). In placebo treated patients CMR_glc declined in all regions, significantly so by the following means in precuneus (P = 0.009, 3.2 μmol/hg/min, 95% CI: 5.45; 0.92), and in parietal (P = 0.04, 2.1 μmol/hg/min, 95% CI: 4.21; 0.081), temporal (P = 0.046, 1.54 μmol/hg/min, 95% CI: 3.05; 0.030), and occipital (P = 0.009, 2.10 μmol/hg/min, 95% CI: 3.61; 0.59) lobes, and in cerebellum (P = 0.04, 1.54 μmol/hg/min, 95% CI: 3.01; 0.064). In contrast, the GLP-1 analog treatment caused a numerical but insignificant increase of CMR_glc after 6 months. Cognitive scores did not change. We conclude that the GLP-1 analog treatment prevented the decline of CMR_glc that signifies cognitive impairment, synaptic dysfunction, and disease evolution. We draw no firm conclusions from the Aβ load or cognition measures, for which the study was underpowered.

Mapping α2 adrenoceptors of the human brain with 11C-yohimbine

A previous study from this laboratory suggested that (11)C-yohimbine, a selective α2-adrenoceptor antagonist, is an appropriate ligand for PET of α2 adrenoceptors that passes readily from blood to brain tissue in pigs but not in rodents. To test usefulness in humans, we determined blood-brain clearances, volumes of distribution, and receptor availability by means of PET with (11)C-yohimbine in healthy male adults.

METHODS

We recorded the distribution of (11)C-yohimbine with 90-min dynamic PET and sampled arterial blood to measure intact (11)C-yohimbine in plasma. For analysis, we coregistered PET images to individual MR images and automatically identified 27 volumes of interest. We used 1-tissue-compartment graphical analysis with 6 linearized solutions of the fundamental binding equation, with the metabolite-corrected arterial plasma curves as input function, to estimate the kinetic parameters of (11)C-yohimbine. With the lowest steady-state distribution volume (VT), determined in the corpus callosum, we calculated the binding potential (receptor availability) of the radioligand in other regions.

RESULTS

The linear regressions yielded similar estimates of the kinetic parameters. The cortical values of VT ranged from 0.82 mL cm(-3) in the right frontal cortex to 0.46 mL cm(-3) in the corpus callosum, with intermediate VT values in subcortical structures. Binding potentials averaged 0.6-0.8 in the cortex and 0.2-0.5 in subcortical regions.

CONCLUSION

The maps of (11)C-yohimbine binding to α2 adrenoceptors in human brain had the highest values in cortical areas and hippocampus, with moderate values in subcortical structures, as found also in vitro. The results confirm the usefulness of the tracer (11)C-yohimbine for mapping α2 adrenoceptors in human brain in vivo.

Glucagon-like peptide-1 (GLP-1) raises blood-brain glucose transfer capacity and hexokinase activity in human brain

In hyperglycemia, glucagon-like peptide-1 (GLP-1) lowers brain glucose concentration together with increased net blood-brain clearance and brain metabolism, but it is not known whether this effect depends on the prevailing plasma glucose (PG) concentration. In hypoglycemia, glucose depletion potentially impairs brain function. Here, we test the hypothesis that GLP-1 exacerbates the effect of hypoglycemia. To test the hypothesis, we determined glucose transport and consumption rates in seven healthy men in a randomized, double-blinded placebo-controlled cross-over experimental design. The acute effect of GLP-1 on glucose transfer in the brain was measured by positron emission tomography (PET) during a hypoglycemic clamp (3 mM plasma glucose) with (18)F-fluoro-2-deoxy-glucose (FDG) as tracer of glucose. In addition, we jointly analyzed cerebrometabolic effects of GLP-1 from the present hypoglycemia study and our previous hyperglycemia study to estimate the Michaelis-Menten constants of glucose transport and metabolism. The GLP-1 treatment lowered the vascular volume of brain tissue. Loading data from hypo- to hyperglycemia into the Michaelis-Menten equation, we found increased maximum phosphorylation velocity (V max) in the gray matter regions of cerebral cortex, thalamus, and cerebellum, as well as increased blood-brain glucose transport capacity (T max) in gray matter, white matter, cortex, thalamus, and cerebellum. In hypoglycemia, GLP-1 had no effects on net glucose metabolism, brain glucose concentration, or blood-brain glucose transport. Neither hexokinase nor transporter affinities varied significantly with treatment in any region. We conclude that GLP-1 changes blood-brain glucose transfer and brain glucose metabolic rates in a PG concentration-dependent manner. One consequence is that hypoglycemia eliminates these effects of GLP-1 on brain glucose homeostasis.

Glucagon-like peptide-1 decreases intracerebral glucose content by activating hexokinase and changing glucose clearance during hyperglycemia

Type 2 diabetes and hyperglycemia with the resulting increase of glucose concentrations in the brain impair the outcome of ischemic stroke, and may increase the risk of developing Alzheimer's disease (AD). Reports indicate that glucagon-like peptide-1 (GLP-1) may be neuroprotective in models of AD and stroke: Although the mechanism is unclear, glucose homeostasis appears to be important. We conducted a randomized, double-blinded, placebo-controlled crossover study in nine healthy males. Positron emission tomography was used to determine the effect of GLP-1 on cerebral glucose transport and metabolism during a hyperglycemic clamp with (18)fluoro-deoxy-glucose as tracer. Glucagon-like peptide-1 lowered brain glucose (P=0.023) in all regions. The cerebral metabolic rate for glucose was increased everywhere (P=0.039) but not to the same extent in all regions (P=0.022). The unidirectional glucose transfer across the blood-brain barrier remained unchanged (P=0.099) in all regions, while the unidirectional clearance and the phosphorylation rate increased (P=0.013 and 0.017), leading to increased net clearance of the glucose tracer (P=0.006). We show that GLP-1 plays a role in a regulatory mechanism involved in the actions of GLUT1 and glucose metabolism: GLP-1 ensures less fluctuation of brain glucose levels in response to alterations in plasma glucose, which may prove to be neuroprotective during hyperglycemia.

Brain energy metabolism and blood flow differences in healthy aging

Cerebral metabolic rate of oxygen consumption (CMRO(2)), cerebral blood flow (CBF), and oxygen extraction fraction (OEF) are important indices of healthy aging of the brain. Although a frequent topic of study, changes of CBF and CMRO(2) during normal aging are still controversial, as some authors find decreases of both CBF and CMRO(2) but increased OEF, while others find no change, and yet other find divergent changes. In this reanalysis of previously published results from positron emission tomography of healthy volunteers, we determined CMRO(2) and CBF in 66 healthy volunteers aged 21 to 81 years. The magnitudes of CMRO(2) and CBF declined in large parts of the cerebral cortex, including association areas, but the primary motor and sensory areas were relatively spared. We found significant increases of OEF in frontal and parietal cortices, excluding primary motor and somatosensory regions, and in the temporal cortex. Because of the inverse relation between OEF and capillary oxygen tension, increased OEF can compromise oxygen delivery to neurons, with possible perturbation of energy turnover. The results establish a possible mechanism of progression from healthy to unhealthy brain aging, as the regions most affected by age are the areas that are most vulnerable to neurodegeneration.

Glucose metabolism in small subcortical structures in Parkinson's disease

OBJECTIVES

Evidence from experimental animal models of Parkinson's disease (PD) suggests a characteristic pattern of metabolic perturbation in discrete, very small basal ganglia structures. These structures are generally too small to allow valid investigation by conventional positron emission tomography (PET) cameras. However, the high-resolution research tomograph (HRRT) PET system has a resolution of 2 mm, sufficient for the investigation of important structures such as the pallidum and thalamic subnuclei.

MATERIALS AND METHODS

Using the HRRT, we performed [(18)F]-fluorodeoxyglucose (FDG) scans on 21 patients with PD and 11 age-matched controls. We employed three types of normalization: white matter, global mean, and data-driven normalization. We performed volume-of-interest analyses of small subcortical gray matter structures. Voxel-based comparisons were performed to investigate the extent of cortical hypometabolism.

RESULTS

The most significant level of relative subcortical hypermetabolism was detected in the external pallidum (GPe), irrespective of normalization strategy. Hypermetabolism was suggested also in the internal pallidum, thalamic subnuclei, and the putamen. Widespread cortical hypometabolism was seen in a pattern very similar to previously reported patterns in patients with PD.

CONCLUSION

The presence and extent of subcortical hypermetabolism in PD is dependent on type of normalization. However, the present findings suggest that PD, in addition to widespread cortical hypometabolism, is probably characterized by true hypermetabolism in the GPe. This finding was predicted by the animal 2-deoxyglucose autoradiography literature, in which high-magnitude hypermetabolism was also most robustly detected in the GPe.

ER Status Measured by FISH Is a Better Predictor of Prognosis in ER Positive, Postmenopausal Breast Cancer Patients Treated with Adjuvant Tamoxifen Than ER Status Measured by RT-qPCR or IHC

Background: The estrogen receptor (ER) is the target for endocrine treatment with tamoxifen. It has been suggested that amplification of ESR1 might be a marker of tamoxifen resistance in post-menopausal ER positive breast cancer patients in the adjuvant setting. In this study we aimed to investigate the correlation between copy number changes in the ESR1 gene, ER gene expression (mRNA) and ER protein status measured by immunohistochemistry (IHC) and the association with recurrence status.Materials and methods: A total of 56 breast cancer patients were included in the study. Both frozen and formalin-fixed paraffin-embedded tumor tissue from the primary tumor were available for analysis. All patients were post-menopausal, high-risk, ER positive breast cancer patients allocated to 1, 2 or 5 years of adjuvant tamoxifen treatment following radical surgery. Twenty-eight patients had recurrence with a median time to recurrence of 2.4 years. The other half of the patients were without recurrence at time of follow-up. The median time of follow-up was 12.0 years. The patients were matched 1-to-1 according to clinico-pathological parameters including duration of treatment. The Dako Histology FISH accessory kit was used for analysis of gene copy number, employing a probe covering the ESR1 gene at 6q25 and a reference probe covering the centromere of chromosome 6. The gene expression was analyzed by a pre-designed real-time PCR assay (ID Hs00174860_m1, Applied Biosystems). ER protein expression was visualized by IHC using the NCL-ER-6F11, 1:100 (Novocastra Ltd) antibody, detected by EnVision Flex+ system (Dako).Results: The gene copy number analysis showed amplification (ratio ESR1/CEN-6 ≥2) in 6/28 (21%) of patients with recurrence and in 1/28 (3%) of patients without recurrence. ESR1 deletion (ratio ESR1/CEN-6 &lt; 0.8) was identified in 3 patients, all without recurrence. A lower median gene expression level was observed in tumors from patients with recurrence compared to patients without recurrence (p=0.07). The percentage positive tumor cells (mean 82%) detected by semi-quantitative bright field microscopy was almost equal in the two groups (p=0.70). Only the gene copy number showed a significant difference (p=0.02) between the patient groups having a significantly higher ESR1/CEN-6 ratio in tumors from patients with recurrence compared to patients without recurrence. A weak positive correlation was observed between ESR1 gene copy number and gene expression (p=0.02), in contrast to a non-significant correlation between gene copy number and protein level (p=0.17).Conclusion: This pilot study shows that measuring the ESR1 gene copy number by FISH seems to be more predictive of tamoxifen resistance compared to measuring the expression of ER by either RT-qPCR or IHC, in ER positive post-menopausal breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2004.

Normalization in PET group comparison studies--the importance of a valid reference region

INTRODUCTION

In positron emission tomography (PET) studies of cerebral blood flow (CBF) and metabolism, the large interindividual variation commonly is minimized by normalization to the global mean prior to statistical analysis. This approach requires that no between-group or between-state differences exist in the normalization region. Given the variability typical of global CBF and the practical limit on sample size, small group differences in global mean easily elude detection, but still bias the comparison, with profound consequences for the physiological interpretation of the results.

MATERIALS AND METHODS

Quantitative [15O]H2O PET recordings of CBF were obtained in 45 healthy subjects (21-81 years) and 14 patients with hepatic encephalopathy (HE). With volume-of-interest (VOI) and voxel-based statistics, we conducted regression analyses of CBF as function of age in the healthy group, and compared the HE group to a subset of the controls. We compared absolute CBF values, and CBF normalized to the gray matter (GM) and white matter (WM) means. In additional simulation experiments, we manipulated the cortical values of 12 healthy subjects and compared these to unaltered control data.

RESULTS

In healthy aging, CBF was shown to be unchanged in WM and central regions. In contrast, with normalization to the GM mean, CBF displayed positive correlation with age in the central regions. Very similar artifactual increases were seen in the HE comparison and also in the simulation experiment.

CONCLUSION

Ratio normalization to the global mean readily elevates CBF in unchanged regions when a systematic between-group difference exists in gCBF, also when this difference is below the detection threshold. We suggest that the routine normalization to the global mean in earlier studies resulted in spurious interpretations of perturbed CBF. Normalization to central WM yields less biased results in aging and HE and could potentially serve as a normalization reference region in other disorders as well.