Marinette van der Graaf

Combined quantitative dynamic contrast-enhanced MR imaging and (1)H MR spectroscopic imaging of human prostate cancer.

To differentiate prostate carcinoma from healthy peripheral zone and central gland using quantitative dynamic contrast‐enhanced (DCE) magnetic resonance (MR) imaging and two‐dimensional 1H MR spectroscopic imaging (MRSI) combined into one clinical protocol.

Proton MR spectroscopy of prostatic tissue focused on the detection of spermine, a possible biomarker of malignant behavior in prostate cancer

To investigate whether polyamines may be valuable diagnostic and prognostic markers in prostate cancer, the presence of alyamines was studied in various human prostatic tissues using both proton magnetic resonance (MR) spectroscopy and righ-pressure liquid chromatography (HPLC). The HPLC results showed that normal and benign hyperplastic prostatic tissues re characterized by a high content of spermine. Spermine levels were reduced in tumor tissue, especially in prostatic carcinoma h metastases, and in xenografts of human prostatic carcinoma cells. These preliminary results indicate that spermine may be d as a biomarker for malignant behavior. The MR spectroscopy study showed that it is possible to detect spermine resonances prostatic biopsy material by one-dimensional and two-dimensional J-resolved MR spectroscopy at high field (600 MHz). ocalized one-dimensional in vitro MR spectra obtained at the clinical field strength of 1.5 T showed spermine signals in the region between 3.0 and 3.3 ppm. In in vivo MR spectra of the human prostate, however, these signals were obscured by esonances of choline (3.2 ppm) and creatine (3.0 ppm).

Clinical and biochemical effects of zileuton in patients with the Sjögren-Larsson syndrome

Abstract. The Sjögren-Larsson syndrome (SLS) is an inborn error of lipid metabolism, characterised clinically by congenital ichthyosis, mental retardation and spasticity. Patients also suffer from severe pruritus. The degradation of leukotriene (LT) B4 is one of the defective metabolic routes in SLS. Zileuton inhibits the synthesis of LTB4 and the cysteinyl leukotrienes. Five SLS patients were treated with zileuton for 3 months. Favourable effects were found on pruritus score (P=0.006), general well-being, and background activity of electroencephalographic studies. Neuropsychological test results did not change significantly. There was, however, a clinically important trend towards improvement in the speed of information processing. Results of cerebral MRI and proton magnetic resonance spectroscopy did not change during therapy. Urinary concentrations of LTB4 and ω-OH-LTB4 decreased significantly (P=0.02 and P=0.003 respectively), while their concentrations in CSF were normal at baseline and remained so after therapy. Conclusion: patients with Sjögren-Larsson syndrome might benefit from treatment with zileuton, especially with respect to the agonising pruritus. The findings reported here, point to a crucial role for leukotriene B4 in the pathogenesis of pruritus.

Steady-State Brain Glucose Concentrations During Hypoglycemia in Healthy Humans and Patients With Type 1 Diabetes

The objective of this study was to investigate the relationship between plasma and brain glucose levels during euglycemia and hypoglycemia in healthy subjects and patients with type 1 diabetes mellitus (T1DM). Hyperinsulinemic euglycemic (5 mmol/L) and hypoglycemic (3 mmol/L) [1-13C]glucose clamps were performed in eight healthy subjects and nine patients with uncomplicated T1DM (HbA1c 7.7 ± 1.4%). Brain glucose levels were measured by 13C magnetic resonance spectroscopy. Linear regression analysis was used to fit the relationship between plasma and brain glucose levels and calculate reversible Michaelis-Menten (MM) kinetic parameters. Brain glucose values during euglycemia (1.1 ± 0.4 μmol/g vs. 1.1 ± 0.3 μmol/g; P = 0.95) and hypoglycemia (0.5 ± 0.2 μmol/g vs. 0.6 ± 0.3 μmol/g; P = 0.52) were comparable between healthy subjects and T1DM patients. MM kinetic parameters of combined data were calculated to be maximum transport rate/cerebral metabolic rate of glucose (Tmax/CMRglc) = 2.25 ± 0.32 and substrate concentration at half maximal transport (Kt) = 1.53 ± 0.88 mmol/L, which is in line with previously published data obtained under hyperglycemic conditions. In conclusion, the linear MM relationship between plasma and brain glucose can be extended to low plasma glucose levels. We found no evidence that the plasma to brain glucose relationship or the kinetics describing glucose transport over the blood–brain barrier differ between healthy subjects and patients with uncomplicated, reasonably well-controlled T1DM.

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.

Sjögren–Larsson syndrome in clinical practice

This review article gives a state-of-the-art synopsis of current pathophysiological concepts in Sjögren–Larsson syndrome (SLS) mainly based upon original research data of the authors in one of the world’s largest clinical SLS study cohorts. Clinical features are discussed in order of appearance, and diagnostic tests are set out to guide the clinician toward the diagnosis SLS. Furthermore, current and future treatment strategies are discussed to render a comprehensive review of the topic.

Effect of Acute Hypoglycemia on Human Cerebral Glucose Metabolism Measured by 13C Magnetic Resonance Spectroscopy

OBJECTIVE To investigate the effect of acute insulin-induced hypoglycemia on cerebral glucose metabolism in healthy humans, measured by 13C magnetic resonance spectroscopy (MRS). RESEARCH DESIGN AND METHODS Hyperinsulinemic glucose clamps were performed at plasma glucose levels of 5 mmol/L (euglycemia) or 3 mmol/L (hypoglycemia) in random order in eight healthy subjects (four women) on two occasions, separated by at least 3 weeks. Enriched [1-13C]glucose 20% w/w was used for the clamps to maintain stable plasma glucose labeling. The levels of the 13C-labeled glucose metabolites glutamate C4 and C3 were measured over time in the occipital cortex during the clamp by continuous 13C MRS in a 3T magnetic resonance scanner. Time courses of glutamate C4 and C3 labeling were fitted using a one-compartment model to calculate metabolic rates in the brain. RESULTS Plasma glucose 13C isotopic enrichment was stable at 35.1 ± 1.8% during euglycemia and at 30.2 ± 5.5% during hypoglycemia. Hypoglycemia stimulated release of counterregulatory hormones (all P < 0.05) and tended to increase plasma lactate levels (P = 0.07). After correction for the ambient 13C enrichment values, label incorporation into glucose metabolites was virtually identical under both glycemic conditions. Calculated tricarboxylic acid cycle rates (VTCA) were 0.48 ± 0.03 μmol/g/min during euglycemia and 0.43 ± 0.08 μmol/g/min during hypoglycemia (P = 0.42). CONCLUSIONS These results indicate that acute moderate hypoglycemia does not affect fluxes through the main pathways of glucose metabolism in the brain of healthy nondiabetic subjects.

Symptomatic lipid storage in carriers for the PNPLA2 gene.

Neutral lipid storage disease comprises a heterogeneous group of inherited disorders characterized by severe accumulation of cytoplasmic triglyceride droplets in several tissues and neutrophils. A novel type of autosomal recessive lipid myopathy due to PNPLA2 mutations was recently described with associated cardiac disease, myopathy and frequent infections, but without ichthyosis. Here we describe the clinical and biochemical characteristics of a long surviving patient and report on four carrier family members with diverse clinical involvement. Interestingly, heterozygous patients show neutral lipid storage in muscle and in the keratocytes of the skin, Jordans’ bodies, mild myopathy and frequent infections. Biochemical analysis of fibroblasts obtained from patients revealed increased triglyceride storage and reduced lipid droplet-associated triglyceride hydrolase activity. Together, our data implicate that the wild-type allele cannot fully compensate for the mutated dysfunctional allele of PNPLA2 leading to triglyceride accumulation in muscle and mild myopathy in PNPLA2 mutation carriers. The presence of neutral lipid droplets in the skin in PNPLA2 mutation carriers strengthens the link between NLSD and other neutral lipid storage diseases with ichthyosis.

Brain glucose metabolism during hypoglycemia in type 1 diabetes: insights from functional and metabolic neuroimaging studies

Hypoglycemia is the most frequent complication of insulin therapy in patients with type 1 diabetes. Since the brain is reliant on circulating glucose as its main source of energy, hypoglycemia poses a threat for normal brain function. Paradoxically, although hypoglycemia commonly induces immediate decline in cognitive function, long-lasting changes in brain structure and cognitive function are uncommon in patients with type 1 diabetes. In fact, recurrent hypoglycemia initiates a process of habituation that suppresses hormonal responses to and impairs awareness of subsequent hypoglycemia, which has been attributed to adaptations in the brain. These observations sparked great scientific interest into the brain’s handling of glucose during (recurrent) hypoglycemia. Various neuroimaging techniques have been employed to study brain (glucose) metabolism, including PET, fMRI, MRS and ASL. This review discusses what is currently known about cerebral metabolism during hypoglycemia, and how findings obtained by functional and metabolic neuroimaging techniques contributed to this knowledge.

Pioglitazone improves insulin resistance and decreases blood pressure in adult patients with congenital adrenal hyperplasia.

CONTEXTnPatients with congenital adrenal hyperplasia (CAH) are chronically treated with supraphysiological doses of glucocorticoids, which are known to induce insulin resistance. Thiazolidinediones might reverse this effect and improve insulin sensitivity.nnnOBJECTIVESnTo assess insulin sensitivity in CAH patients and the effect of pioglitazone treatment on insulin sensitivity in CAH patients. Secondary objectives were the effects of treatment with pioglitazone on blood pressure, body fat distribution, lipid, and steroid profiles.nnnDESIGNnRandomized placebo controlled crossover trial.nnnPARTICIPANTSnTwelve CAH patients and 12 body mass and age-matched control subjects.nnnINTERVENTIONnSixteen-week treatment with pioglitazone (45 mg/day) or placebo.nnnMAIN OUTCOME MEASUREnInsulin sensitivity measured by euglycemic clamp and oral glucose tolerance test. Further measures were 24-h blood pressure profiles, body fat distribution measured by magnetic resonance imaging, dual energy x-ray absorptiometry (DEXA) and bioimpedance procedures, liver fat by magnetic resonance spectroscopy, lipid, and steroid profiles.nnnRESULTSnCAH patients were insulin resistant compared with healthy controls. Treatment with pioglitazone significantly improved insulin sensitivity in CAH patients (glucose infusion rate (GIR) from 28.5+/-11.6 to 38.9+/-11.0 micromol/kg per min, P=0.000, GIR in controls 46.2+/-23.4 micromol/kg per min, P<0.05 versus CAH). Treatment with pioglitazone decreased blood pressure (systolic: 124.0+/-13.6 vs 127.0+/-14.9 mmHg, P<0.001, diastolic: 72.8+/-11.5 vs 77.4+/-12.6 mmHg, P<0.001). No changes in body fat distribution, lipid, and steroid profiles were observed.nnnCONCLUSIONSnCAH patients are insulin resistant compared with matched control subjects. Treatment with pioglitazone improves insulin sensitivity and decreases blood pressure in CAH patients.