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Dive into the research topics where Jan W. A. Smit is active.

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Featured researches published by Jan W. A. Smit.


Journal of the American College of Cardiology | 2003

Diastolic dysfunction is associatedwith altered myocardial metabolism inasymptomatic normotensive patientswith well-controlled type 2 diabetes mellitus

Michaela Diamant; Hildo J. Lamb; Ymte Groeneveld; Edwin L. Endert; Jan W. A. Smit; Jeroen J. Bax; Johannes A. Romijn; Albert de Roos; Jasper K. Radder

AbstractObjectives: This study evaluated myocardial function in relation to high-energy phosphate (HEP) metabolism in asymptomatic patients with uncomplicated type 2 diabetes mellitus using magneti...


Circulation | 2002

Elevated Numbers of Tissue-Factor Exposing Microparticles Correlate With Components of the Metabolic Syndrome in Uncomplicated Type 2 Diabetes Mellitus

Michaela Diamant; Rienk Nieuwland; Renée F. Pablo; Augueste Sturk; Jan W. A. Smit; Jasper K. Radder

Background—Type 2 diabetes is associated with accelerated atherosclerosis. Because cell-derived microparticles support coagulation and inflammation, they may be involved in atherogenesis. We characterized circulating microparticles both in patients with uncomplicated, well-regulated type 2 diabetes and in healthy subjects, as well as their relationship with coagulation and metabolic control. Methods and Results—Microparticles were isolated from plasma, stained with annexin V, cell-specific monoclonal antibodies (MoAbs) and a MoAb directed against tissue factor (TF), and analyzed by flow cytometry. Microparticle numbers and origin were comparable in the two groups, but the median number of TF-positive microparticles was twice as high in patients than in controls (P =0.018). Patients had higher percentages of TF-positive microparticles from T-helper cells (P =0.045), granulocytes (P =0.004), and platelets (P =0.002). Subpopulations of TF-positive microparticles from platelets and T-helper cells exposed granulocytic markers. Correlations were found between the numbers of various TF-positive microparticle subpopulations and body mass index, fasting plasma glucose and insulin, or tumor necrosis factor-&agr; and serum HDL cholesterol. Microparticles from patients generated less thrombin in vitro (P =0.007). Microparticle numbers did not correlate with in vivo coagulation markers prothrombin fragment F1+2 and thrombin-antithrombin complexes. Conclusions—TF, possibly of granulocytic origin, is exposed on microparticle subpopulations in asymptomatic patients with well-regulated type 2 diabetes. TF-positive microparticles are associated with components of the metabolic syndrome but not with coagulation. Thus, TF on microparticles may be involved in processes other than coagulation, including transcellular signaling or angiogenesis.


Clinical Endocrinology | 2005

High prevalence of long‐term cardiovascular, neurological and psychosocial morbidity after treatment for craniopharyngioma

Alberto M. Pereira; Eva M. Schmid; Pieter J. Schutte; Joan H. C. Voormolen; Nienke R. Biermasz; Sjoerd W. van Thiel; Eleonora P. M. Corssmit; Jan W. A. Smit; Ferdinand Roelfsema; Johannes A. Romijn

Introduction  The treatment of craniopharyngiomas is associated with long‐term morbidity.


Clinical Endocrinology | 2003

Effects of low-iodide diet on postsurgical radioiodide ablation therapy in patients with differentiated thyroid carcinoma

Maurice J. H. M. Pluijmen; Carmen F. A. Eustatia-Rutten; Bernard M. Goslings; Marcel P. M. Stokkel; Alberto M. Pereira Arias; Michaela Diamant; Johannes A. Romijn; Jan W. A. Smit

objective Most patients with differentiated thyroid carcinoma (DTC) undergo total thyroidectomy followed by routine radioiodide thyroid remnant ablation. Most centres that routinely perform radioiodide ablation prescribe a low‐iodide diet (LID) to increase the radioiodide accumulation in thyroid remnants. The efficacy of an LID on thyroid remnant ablation, however, has never been demonstrated convincingly.


The New England Journal of Medicine | 2017

Thyroid Hormone Therapy for Older Adults with Subclinical Hypothyroidism

David J. Stott; Nicolas Rodondi; Patricia M. Kearney; Ian Ford; Rudi G. J. Westendorp; Simon P. Mooijaart; Naveed Sattar; Carole Elodie Aubert; Drahomir Aujesky; Douglas C. Bauer; Christine Baumgartner; Manuel R. Blum; John Browne; Stephen Byrne; Tinh-Hai Collet; Olaf M. Dekkers; Wendy P. J. den Elzen; Robert S. Du Puy; Graham Ellis; Martin Feller; Carmen Floriani; Kirsty Hendry; Caroline Hurley; J. Wouter Jukema; Sharon Kean; Maria Kelly; Danielle Krebs; Peter Langhorne; Gemma McCarthy; Vera J. C. McCarthy

BACKGROUND The use of levothyroxine to treat subclinical hypothyroidism is controversial. We aimed to determine whether levothyroxine provided clinical benefits in older persons with this condition. METHODS We conducted a double‐blind, randomized, placebo‐controlled, parallel‐group trial involving 737 adults who were at least 65 years of age and who had persisting subclinical hypothyroidism (thyrotropin level, 4.60 to 19.99 mIU per liter; free thyroxine level within the reference range). A total of 368 patients were assigned to receive levothyroxine (at a starting dose of 50 μg daily, or 25 μg if the body weight was <50 kg or the patient had coronary heart disease), with dose adjustment according to the thyrotropin level; 369 patients were assigned to receive placebo with mock dose adjustment. The two primary outcomes were the change in the Hypothyroid Symptoms score and Tiredness score on a thyroid‐related quality‐of‐life questionnaire at 1 year (range of each scale is 0 to 100, with higher scores indicating more symptoms or tiredness, respectively; minimum clinically important difference, 9 points). RESULTS The mean age of the patients was 74.4 years, and 396 patients (53.7%) were women. The mean (±SD) thyrotropin level was 6.40±2.01 mIU per liter at baseline; at 1 year, this level had decreased to 5.48 mIU per liter in the placebo group, as compared with 3.63 mIU per liter in the levothyroxine group (P<0.001), at a median dose of 50 μg. We found no differences in the mean change at 1 year in the Hypothyroid Symptoms score (0.2±15.3 in the placebo group and 0.2±14.4 in the levothyroxine group; between‐group difference, 0.0; 95% confidence interval [CI], ‐2.0 to 2.1) or the Tiredness score (3.2±17.7 and 3.8±18.4, respectively; between‐group difference, 0.4; 95% CI, ‐2.1 to 2.9). No beneficial effects of levothyroxine were seen on secondary‐outcome measures. There was no significant excess of serious adverse events prespecified as being of special interest. CONCLUSIONS Levothyroxine provided no apparent benefits in older persons with subclinical hypothyroidism. (Funded by European Union FP7 and others; TRUST ClinicalTrials.gov number, NCT01660126.)


Amyloid | 2002

AL amyloidosis treated with induction chemotherapy with VAD followed by high dose melphalan and autologous stem cell transplantation.

van Gameren; Bpc Hazenberg; Pl Jager; Jan W. A. Smit; Edo Vellenga

Abstract High dose melphalan (HDM) followed by reinfusion of autologous blood stem cells (ASCT) has been applied in AL amyloidosis. Vincristine, doxorubicin, and dexamethasone (VAD) rapidly decrease light chain production in multiple myeloma. In a Phase I/II study of VAD followed by HDM and ASCT in AL amyloidosis, toxicity, feasibility, and response to this regimen were evaluated. Over a 5-year period 38 patients with AL amyloidosis were seen of which 12 out of 18 eligible patients participated in the study. VAD induced a distinct clonal response in 50% (6/12) of the patients, but without clinical improvement. In 11 patients HDM and ASCT was applied. Six months after ASCT 78% (7/9) of the surviving patients showed partial clonal response and none responded completely. Clinical condition evidently improved in 67% (6/9) of survivors, whereby clinical response, clinical response, performance score, and SAP scintigraphs were concordant. Therefore a complete clonal response is not a prerequisite for clinical improvement. With median follow-up after ASCT of 25 months, 75% of the study group patients were alive. Mortality was strongly depending on the number of organs involved. Patients treated with HDM and ASCT had better survival than those not eligible (P < 0.0005).


Clinical Endocrinology | 2003

Sandostatin LAR in acromegaly: a 6-week injection interval suppresses GH secretion as effectively as a 4-week interval.

Nienke R. Biermasz; Niels C. van den Oever; Marijke Frölich; Alberto M. Pereira Arias; Jan W. A. Smit; Johannes A. Romijn; Ferdinand Roelfsema

introduction Depot preparations of long‐acting somatostatin analogues are being used increasingly in the treatment of GH hypersecretion in patients with acromegaly, either as primary treatment or as secondary treatment following incomplete surgery. In 60% of these patients, Sandostatin long‐acting release (LAR), the depot preparation of octreotide, achieves effective suppression of serum GH (< 5 mU/l) and IGF‐I levels. The advice is to administer Sandostatin LAR at 4‐week intervals. After injection, serum octreotide shows an initial peak and thereafter maximal values between 14 and 42 days. There have been suggestions that the dose interval of this preparation could be increased, resulting in reduced costs, although this concept has not been confirmed by studies.


Thrombosis Research | 1995

BASAL TISSUE FACTOR EXPRESSION IN ENDOTHELIAL-CELL CULTURES IS CAUSED BY CONTAMINATING SMOOTH-MUSCLE CELLS - REDUCTION BY USING CHYMOTRYPSIN INSTEAD OF COLLAGENASE

AndréB. Mulder; Nel R. Blom; Jan W. A. Smit; Marcel H.J. Ruiters; Jan van der Meer; M. Ruud Halie; Victor J.J. Bom

A discrepancy exists between basal tissue factor (TF) expression found in endothelial cell cultures and the failure to detect TF in unpertubated endothelial cells in vivo. We demonstrated that basal TF expression in endothelial cell cultures originated from contaminating cells. These cells were ultrastructurally and flowcytometrically identified as smooth muscle cells. The cell cultures had been obtained from collagenase-treated human umbilical cord vessels. Histologic studies revealed that after collagenase treatment the basement membrane was digested and underlying structures were disrupted at some areas of the vein. We selected chymotrypsin as an alternative for the isolation of endothelial cells. Using chymotrypsin, the endothelial lining was selectively lost leaving the basement membrane undisturbed. Furthermore, use of chymotrypsin instead of collagenase minimized the level of basal TF activity. Taken together, we demonstrated that basal TF expression in endothelial cell cultures is caused by contaminating smooth muscle cells. This contamination can strongly be reduced using chymotrypsin instead of collagenase for isolation of endothelial cells.


PLOS ONE | 2013

Cardioprotective properties of omentin-1 in type 2 diabetes: evidence from clinical and in vitro studies.

Sabrina Greulich; Weena J.Y. Chen; Bujar Maxhera; Luuk J. Rijzewijk; Rutger W. van der Meer; Jacqueline T. Jonker; Heidi Mueller; Daniella Herzfeld de Wiza; Ralf-Ruediger Floerke; Konstantinos Smiris; Hildo J. Lamb; Albert de Roos; Jeroen J. Bax; Johannes A. Romijn; Jan W. A. Smit; Payam Akhyari; Artur Lichtenberg; Juergen Eckel; Michaela Diamant; D. Margriet Ouwens

Context Adipokines are linked to the development of cardiovascular dysfunction in type 2 diabetes (DM2). In DM2-patients, circulating levels of omentin-1, an adipokine preferentially expressed in epicardial adipose tissue, are decreased. This study investigated whether omentin-1 has a cardioprotective function. Methods Omentin-1 levels in plasma and cardiac fat depots were determined in DM2-patients versus controls. Moreover, the relation between omentin-1 levels and cardiac function was examined in men with uncomplicated DM2. Finally, we determined whether omentin-1 could reverse the induction of cardiomyocyte dysfunction by conditioned media derived from epicardial adipose tissue from patients with DM2. Results Omentin-1 was highly expressed and secreted by epicardial adipose tissue, and reduced in DM2. Circulating omentin-1 levels were lower in DM2 versus controls, and positively correlated with the diastolic parameters early peak filling rate, early deceleration peak and early deceleration mean (all P<0.05). The improved diastolic function following pioglitazone treatment associated with increases in omentin-1 levels (P<0.05). In vitro, exposure of cardiomyocytes to conditioned media derived from epicardial adipose tissue from patients with DM2 induced contractile dysfunction and insulin resistance, which was prevented by the addition of recombinant omentin. Conclusion These data identify omentin-1 as a cardioprotective adipokine, and indicate that decreases in omentin-1 levels could contribute to the induction of cardiovascular dysfunction in DM2.


European Journal of Endocrinology | 2011

Low prevalence of hypopituitarism after traumatic brain injury: a multicenter study

Nieke E. Kokshoorn; Jan W. A. Smit; W A Nieuwlaat; Jitske Tiemensma; Peter H. Bisschop; R Groote Veldman; Ferdinand Roelfsema; A A M Franken; M. J. E. Wassenaar; Nienke R. Biermasz; Johannes A. Romijn; Alberto M. Pereira

OBJECTIVE Hypopituitarism after traumatic brain injury (TBI) is considered to be a prevalent condition. However, prevalence rates differ considerably among reported studies, due to differences in definitions, endocrine assessments of hypopituitarism, and confounding factors, such as timing of evaluation and the severity of the trauma. Aim To evaluate the prevalence of hypopituitarism in a large cohort of TBI patients after long-term follow-up using a standardized endocrine evaluation. Study design Cross-sectional study. PATIENTS AND METHODS We included 112 patients with TBI, hospitalized for at least 3 days and duration of follow-up >1 year after TBI from five (neurosurgical) referral centers. Evaluation of pituitary function included fasting morning hormone measurements and insulin tolerance test (n=90) or, when contraindicated, ACTH stimulation and/or CRH stimulation tests and a GH releasing hormone-arginine test (n=22). Clinical evaluation included quality of life questionnaires. RESULTS We studied 112 patients (75 males), with median age 48 years and mean body mass index (BMI) 26.7±4.8 kg/m(2). Mean duration of hospitalization was 11 (3-105), and 33% of the patients had a severe trauma (Glasgow Coma Scale <9) after TBI. The mean duration of follow-up was 4 (1-12) years. Hypopituitarism was diagnosed in 5.4% (6/112) of patients: severe GH deficiency (n=3), hypogonadism (n=1), adrenal insufficiency (n=2). Patients diagnosed with pituitary insufficiency had significantly higher BMI (P=0.002). CONCLUSION In this study, the prevalence of hypopituitarism during long-term follow-up after TBI was low. Prospective studies are urgently needed to find reliable predictive tools for the identification of patients with a significant pre-test likelihood for hypopituitarism after TBI.

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Johannes A. Romijn

Leiden University Medical Center

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Alberto M. Pereira

Leiden University Medical Center

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Jeroen J. Bax

Erasmus University Rotterdam

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Marcel P. M. Stokkel

Leiden University Medical Center

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Ferdinand Roelfsema

Leiden University Medical Center

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Edo Vellenga

University Medical Center Groningen

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Nienke R. Biermasz

Autonomous University of Barcelona

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Albert de Roos

Leiden University Medical Center

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Michaela Diamant

VU University Medical Center

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Hans Morreau

Leiden University Medical Center

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