Niels Sörensen

Classification of newly diagnosed diabetic patients as insulin-requiring or non-insulin-requiring based on clinical and biochemical variables.

In a prospective study of 41 consecutively referred newly diagnosed diabetic patients, we evaluated the predictive value of fasting and glucagon-stimulated C-peptide values, ketonuria, age, and body weight in the classification of subjects as insulin-requiring (IR) or non-insulin-requiring (NIR). The patients were followed up for ≥12 mo and classified as NIR if adequate glycemic control could be achieved without insulin (i.e., fasting plasma glucose < 8 mM and no glycosuria). Patients who needed insulin to obtain this status were classified as IR. We found that all subjects with plasma C-peptide values >0.60 nM 6 min after intravenous glucagon were NIR, whereas all IR subjects together with 3 NIR subjects had C-peptide values below this limit. All NIR subjects but 1 had fasting C-peptide values > 0.30 nM, and all IR subjects but 1 had C-peptide values below this limit. Seventy-five percent of the subjects could be correctly classified by use of age and percent desirable body weight. Thus, all subjects > 40 yr old and >100% ideal body weight were NIR, and all subjects below both these limits were IR. Ketonuria was found in 10 of 12 IR subjects and in 10 of 29 NIR subjects. We conclude that 1) 75% of the subjects could be correctly classified by use of age and percent desirable body weight only and 2) C-peptide measurements are useful in the classification of newly diagnosed diabetes, whereas presence of ketonuria is of limited value.

Phosphatidylinositol 3′-Kinase/AKT Signaling Is Activated in Medulloblastoma Cell Proliferation and Is Associated with Reduced Expression of PTEN

Purpose: Medulloblastomas represent the most frequent malignant brain tumors of childhood. They are supposed to originate from cerebellar neural precursor cells. Recently, it has been shown that Sonic Hedgehog–induced formation of medulloblastoma in an animal model is significantly enhanced by activation of the phosphatidylinositol 3′-kinase (PI3K) signaling pathway. Experimental Design: To examine a role for PI3K/AKT signaling in the molecular pathogenesis of human medulloblastoma, we did an immunohistochemical study of the expression of Ser473-phosphorylated (p)-AKT protein in 22 medulloblastoma samples: All samples displayed p-AKT expression. To investigate if an activated PI3K/AKT pathway is required for medulloblastoma cell growth, we treated five human medulloblastoma cell lines with increasing concentrations of the PI3K inhibitor LY294002 and analyzed cellular proliferation and apoptosis. The antiproliferative effect could be antagonized by overexpressing constitutively active AKT. As the activation of PI3K/AKT signaling may be associated with alterations of the PTEN gene located at 10q23.3, a chromosomal region subject to frequent allelic losses in medulloblastoma, we screened PTEN for mutations and mRNA expression. Results: Proliferation of all of the medulloblastoma cell lines was dependent on PI3K/AKT signaling, whereas apoptosis was not prominently affected. Allelic loss was detected in 16% of the cases. One medulloblastoma cell line was found to carry a truncating mutation in the PTEN coding sequence. Even more important, PTEN mRNA and protein levels were found to be significantly lower in medulloblastomas compared with normal cerebellar tissue of different developmental stages. Reduction of PTEN expression was found to be associated with PTEN promoter hypermethylation in 50% of the tumor samples. Conclusions: We conclude that activation of the PI3K/AKT pathway constitutes an important step in the molecular pathogenesis of medulloblastoma and that dysregulation of PTEN may play a significant role in this context.

Hydrocephalus in craniosynostosis: a review

IntroductionVentricular dilatation in the presence of primary craniosynostosis is a unique condition with respect to pathogenesis, clinical significance, and morphological appearance. It is rarely observed in nonsyndromic craniosynostosis, and in these cases usually attributable to coincidental disorders. Conversely, it is a common feature of syndromic craniosynostosis, affecting at least 40% of patients with Crouzon’s, Pfeiffer’s or the Apert syndrome. Shunt-dependent hydrocephalus is predominantly associated with Crouzon or Pfeiffer syndrome while in the Apert syndrome the usual finding is nonprogressive ventriculomegaly which, however, may also occur in some cases of Crouzon syndrome.PathogenesisThe pathogenesis of progressive hydrocephalus remains somewhat obscure, a hypoplastic posterior fossa and a venous outlet occlusion at the skull base being the main causative factors discussed in literature. Ventriculomegaly may reflect primary brain maldevelopment or in some cases even a compensated state of increased cerebrospinal fluid (CSF) outflow resistance.Clinical evaluation Clinical evaluation is mainly aimed at identifying progressive hydrocephalus, but diagnosis is hampered by the fact that classical clinical signs may be absent, and that ventricular dilatation will often become evident only after decompressive cranial surgery. Moreover, mild ventriculomegaly may in some cases coexist with intracranial hypertension from craniostenosis. Therefore, careful monitoring of intracranial pressure and ventricular size in the pre- and postoperative period is a diagnostic mainstay.Conclusion In true hydrocephalus ventriculo-peritoneal shunting is currently the single promising mode of treatment.

Saethre–Chotzen syndrome caused by TWIST 1 gene mutations: functional differentiation from Muenke coronal synostosis syndrome

The Saethre–Chotzen syndrome (SCS) is an autosomal dominant craniosynostosis syndrome with uni- or bilateral coronal synostosis and mild limb deformities. It is caused by loss-of-function mutations of the TWIST 1 gene. In an attempt to delineate functional features separating SCS from Muenkes syndrome, we screened patients presenting with coronal suture synostosis for mutations in the TWIST 1 gene, and for the Pro250Arg mutation in FGFR3. Within a total of 124 independent pedigrees, 39 (71 patients) were identified to carry 25 different mutations of TWIST 1 including 14 novel mutations, to which six whole gene deletions were added. The 71 patients were compared with 42 subjects from 24 pedigrees carrying the Pro250Arg mutation in FGFR3 and 65 subjects from 61 pedigrees without a detectable mutation. Classical SCS associated with a TWIST 1 mutation could be separated phenotypically from the Muenke phenotype on the basis of the following features: low-set frontal hairline, gross ptosis of eyelids, subnormal ear length, dilated parietal foramina, interdigital webbing, and hallux valgus or broad great toe with bifid distal phalanx. Functional differences were even more important: intracranial hypertension as a consequence of early progressive multisutural fusion was a significant problem in SCS only, while mental delay and sensorineural hearing loss were associated with the Muenkes syndrome. Contrary to previous reports, SCS patients with complete loss of one TWIST allele showed normal mental development.

Melatonin Treatment in Obese Patients with Childhood Craniopharyngioma and Increased Daytime Sleepiness

Craniopharyngioma is a rare dysontogenetic benign tumor. Patients frequently suffer from endocrine deficiencies, sleep disturbances and obesity due to pituitary and hypothalamic lesions. A self-assessment daytime sleepiness questionnaire (German version of the Epworth Sleepiness Scale [ESS]) was used to evaluate 79 patients with childhood craniopharyngioma. Because hypothalamic lesions may explain daytime sleepiness in craniopharyngioma patients, salivary melatonin and cortisol concentrations were examined in severely obese (BMI≥4SD) and non severely obese (BMI<4SD) craniopharyngioma patients (n=79), patients with hypothalamic pilocytic astrocytoma (n=19), and control subjects (n=30). Using a general linear model procedure analyzing the influence of BMI and tumor diagnosis on diurnal salivary melatonin we found that morning salivary melatonin levels were related to BMI (F test: p-value=0.004) and tumor diagnosis (F-test: p-value=0.032). Also for nighttime salivary melatonin levels significant relations with BMI (p-value in F-test: <0.001) and tumor diagnosis (p-value in F-test: 0.025) were detectable. Melatonin concentrations in saliva of craniopharyngioma patients collected at nighttime or in the morning showed a negative correlation (Spearman’s rho: −0.42; p=0.001; Spearman’s rho: −0.31; p=0.020) with the patient’s ESS score. Severely obese craniopharyngioma patients and severely obese hypothalamic tumor patients had similar patterns of melatonin secretion. Differences in terms of diurnal salivary cortisol concentrations were not detectable when patient groups and controls were compared. As decreased nocturnal melatonin levels were associated with increased daytime sleepiness, BMI and hypothalamic tumor diagnosis, we initiated an experimental melatonin substitution in 10 adult obese patients (5f/5m) with childhood craniopharyngioma. In all 10 patients with childhood craniopharyngioma the degree of daytime sleepiness significantly improved based on activity diaries, ESS, self assessment questionnaires and actimetry. We speculate that hypothalamic lesions might be responsible for both obesity and daytime sleepiness. As first experiences with experimental melatonin substitution were promising, further randomized double-blinded studies on the beneficial effects of melatonin substitution on daytime sleepiness and weight control in these patients are warranted.

Insulin receptor binding and insulin action in human fat cells: Effects of obesity and fasting

We have studied (125I)-insulin binding and insulin dose response relationships of (14C)-methylglucose transport conversion of (14C)-glucose to CO2 and total lipids, and lipolysis at 37 degrees C and pH 7.4 in adipocytes from obese patients before (n = 15) and after fasting for 10 days (n = 6). Studies of adipocytes from obese before fasting showed a significant reduction of insulin binding when expressed to cell surface area and rightward shifts of the insulin dose response curves (decreased insulin sensitivity) for glucose transport, glucose oxidation, lipogenesis and antilipolysis. The decreased insulin sensitivity of adipocytes from obese was most likely the functional consequence of the impaired insulin binding. Moreover, decreased maximal glucose transport capacities were present in rat cells from obese both in the basal and maximally insulin stimulated states. Similarly, the percentage response above basal level to maximal insulin stimulation of glucose oxidation and lipogenesis was impaired to these cells. The latter findings suggest post receptor defects localized both to the transport system per se and to intracellular mechanisms involved in the metabolism of glucose. Conversely, the post receptor pathways for the insulin induced antilipolysis was intact in fat cells from obese man. Studies after fasting showed an increase of adipocyte insulin binding accompanied by an increased sensitivity to the antilipolytic effect of insulin with unchanged maximal responsiveness. However, due to marked post receptor alterations, the insulin stimulated glucose utilization was severely blunted. Thus, the glucose transport system of adipocytes from all fasted subjects was totally unresponsive to insulin, while some of the fasted patients had a slight response of glucose oxidation and lipogenesis in the presence of insulin in maximally effective concentrations.

Abdominal obesity is associated with insulin resistance and reduced glycogen synthase activity in skeletal muscle

Insulin resistance is commonly associated with obesity. The present study was performed to investigate the relative importance of total fat mass versus localization of adipose tissue in insulin-stimulated glucose disposal (Rd) and skeletal muscle glycogen synthase (GS) activity in obese individuals. Twenty obese women with an average body mass index (BMI) of 37.8 +/- 1.3 kg/m2 and a waist to hip ratio (WHR) ranging from 0.78 to 1.02 were examined during basal conditions and following hyperinsulinemia (hyperinsulinemic euglycemic clamp). To accurately determine body composition, the following three methods were used: anthropometric measurements, dual-energy x-ray absorptiometry scanning (DEXA-scan), and bioelectric impedance measurements. In addition, indirect calorimetry and muscle biopsy were performed. Insulin-stimulated glucose Rd was negatively correlated with WHR (R = -.52, P < .025) whereas there were no correlations with BMI or percent fat (R = .16, NS and R = .16, NS, respectively). Furthermore, a negative correlation between WHR and insulin stimulation of GS activity in skeletal muscle was found (R = -.62, P < .005). In contrast, BMI and percent fat were not correlated with the insulin effect on GS activity in skeletal muscle (R = .34, NS and R = -.35, NS, respectively). The concentration of nonesterified fatty acids (NEFA) during hyperinsulinemia was strongly correlated with WHR and abdominal localization of adipose tissue (determined by DEXA-scan; R = .60, P < .005 and R = .60, P < .007, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of HIC‐1 methylation and transcription in human ependymomas

Ependymomas are among the most common brain tumors in children. They develop from ependymal cells lining the ventricular system of the CNS. Previous studies have demonstrated a significant rate of allelic loss at chromosome 17p13.3. The HIC‐1 putative tumor‐suppressor gene, which exhibits hypermethylation and loss of expression in various tumor entities including medulloblastomas and gliomas, maps to the affected region. In the present study, we analyzed HIC‐1 in ependymomas. Therefore, we applied methylation‐specific PCR of the 5′‐untranslated region as well as of a central region of HIC‐1 and bisulfite sequencing to determine the methylation status in 52 ependymomas of different histologic subtypes, grades and locations. In addition, we used a competitive RT‐PCR approach for sensitive assessment of HIC‐1 transcripts. Hypermethylation of at least one of the 2 analyzed regions was found in 43/52 (83%) cases. There was a significant correlation between hypermethylation of HIC‐1 and nonspinal localization (p = 0.019) as well as age. Of 27 ependymomas, 22 (81%) showed absent or low expression of HIC‐1. The elevated methylation of HIC‐1 in nonspinal ependymomas supports the hypothesis that spinal and nonspinal ependymomas represent genetically distinct entities.

Increased insulin binding to adipocytes and monocytes and increased insulin sensitivity of glucose transport and metabolism in adipocytes from non-insulin-dependent diabetics after a low-fat/high-starch/high-fiber diet

Nine non-insulin-dependent diabetics were studied before and after 3 weeks on an isoenergetic high-fiber/high-starch/low-fat diet (alternative diet), and nine non-insulin-dependent diabetics were studied on their usual diet. In the group that ate the alternative diet, the intake of fiber and starch increased 120% and 53%, whereas fat intake decreased 31%. Diabetes control improved as demonstrated by decreased fasting plasma glucose (P less than 0.05) and 24-hour urinary glucose excretion (P less than 0.05). The in vivo insulin action increased (KIVITT increased, P less than 0.05) with no change in fasting serum insulin levels. In fat cells obtained from patients in the alternative-diet group, insulin receptor binding increased (P less than 0.05) after the change of diet. Insulin binding to purified monocytes (more than 95% monocytes) also increased (P less than 0.05), whereas no change was found in insulin binding to erythrocytes. When lipogenesis was studied at a tracer glucose concentration at which glucose transport seems to be rate limiting, insulin sensitivity increased (P less than 0.02). This is the predicted consequence of increased receptor binding. Moreover, when CO2 production and lipogenesis were studied at a higher glucose concentration, where steps beyond transport seem to be rate limiting for glucose metabolism, increased insulin sensitivity was also observed. In contrast, no change was found in maximal insulin responsiveness. Fat and blood cells from the patients who continued on their usual diet showed no changes of the mentioned quantities.(ABSTRACT TRUNCATED AT 250 WORDS)

Cutaneous lesions in occult spinal dysraphism—correlation with intraspinal findings

ObjectsThis study was conducted to investigate the frequency and type of cutaneous stigmata in different forms of occult spinal dysraphism (OSD) and their correlation to the underlying malformation.MethodsFourteen different forms of spinal malformations were identified in 358 operated patients with OSD. Most frequent findings (isolated or in combinations) were spinal lipoma, split cord malformation, pathologic filum terminale, dermal sinus, meningocele manqué, myelocystocele and caudal regression. Stigmata were present in 86.3% of patients, often in various combinations. Using a binary logistic regression analysis, significant correlations with distinct malformations were found for subcutaneous lipomas, skin tags, vascular nevi, pori, hairy patches, hypertrichosis, meningoceles and “cigarette burn” marks.ConclusionsCutaneous markers in a high percentage accompany spinal malformations. Due to the correlations of different stigmata to distinct malformations, they can aid the clinician in further diagnostic and therapeutic work.