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Biomedical subjects

B J Potter van Loon

Publications and source records attributed to B J Potter van Loon.

12 recordsLinked to original sources
PubMed1996

Acute cardiorespiratory failure as presenting symptom of chronic lymphocytic leukemia.

A patient with acute cardiorespiratory failure caused by hyperleukocytosis due to chronic lymphocytic leukaemia (CLL) is described. Although acute pulmonary failure due to leukostasis is a known and often postmortem finding in patients with acute myelocytic leukaemia (AML) or chronic myelocytic leukaemia (CML) in blastic crises, it is rare in CLL.

Acute Disease↗
PubMed1994

Insulin-induced decline of plasma amino acid concentrations in obese subjects with and without non-insulin-dependent diabetes.

Obesity-associated hyperaminoacidemia is traditionally interpreted as a consequence of insulin resistance. We performed two different experiments to investigate the effects of both obesity-associated insulin resistance and the insulin resistance of non-insulin-dependent diabetes mellitus (NIDDM) on amino acid metabolism. In the first experiment, we measured postabsorptive amino acid concentrations and their decline in response to an oral carbohydrate load in 19 obese nondiabetic women and 19 normal-weight nondiabetic controls. Obese subjects were more resistant to insulin with respect to its effects on glucose metabolism than normal-weight controls, as calculated by the method described by Matthews. However, postabsorptive plasma concentrations of the so-called large neutral amino acids (LNAA), namely phenylalanine, tyrosine, valine, leucine, and isoleucine, and their decrease in response to carbohydrate consumption were similar in both groups. In the second experiment, we compared the decrease of plasma concentrations of LNAA during a euglycemic, hyperinsulinemic clamp in obese subjects with and without NIDDM. Peripheral glucose uptake (PGU) was more impaired in NIDDM subjects compared with obese controls. Furthermore, hepatic glucose production (HGP) was less attenuated by insulin infusion in NIDDM than in control subjects. Postabsorptive plasma LNAA concentrations were not different in the two groups. Values obtained in either group were not different from the postabsorptive concentrations in the normal-weight control subjects of experiment 1. All amino acid levels decreased substantially in response to insulin infusion. The magnitude of the decrease was not significantly different in the two groups, except for a slightly greater decrease of the plasma isoleucine concentration in obese control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

The cardiovascular risk factor plasminogen activator inhibitor type 1 is related to insulin resistance.

The cardiovascular risk factor plasminogen activator inhibitor type 1 (PAI-1) has been associated with abdominal obesity, hypertension, hypertriglyceridemia, hyperinsulinemia, glucose intolerance, and type II diabetes, conditions known to be linked with insulin resistance. To determine whether PAI-1 is related to insulin resistance, we studied nine obese nondiabetics and 10 obese type II diabetics by means of a sequential hyperinsulinemic euglycemic clamp study. Plasma PAI-1 antigen (Ag) correlated significantly with peripheral insulin resistance, represented by the insulin level at which peripheral glucose uptake (PGU) is half-maximal ([ED50PGU] r = .87, P < .001). Multiple regression analysis including indices of hepatic and peripheral insulin action, fasting plasma insulin levels, triglyceride levels, blood pressure (BP), waist to hip ratio (WHR), and body mass index (BMI) disclosed ED50PGU to account for 76% of the variance of PAI-1 Ag. We suggest that PAI-1 contributes to the increased cardiovascular risk encountered with insulin resistance.

Antigens↗
PubMed1993

Long term use of captopril or nifedipine in normotensive microalbuminuric patients with insulin-dependent diabetes mellitus.

Several studies have suggested that ACE-inhibition may be effective in postponing the onset of nephropathy in insulin-dependent diabetic subjects. In contrast, other drugs might have opposing effects. To study the long term effects of either captopril or nifedipine in normotensive, microalbuminuric patients with insulin-dependent diabetes mellitus, eighteen subjects received either placebo (n = 5, P), 20 mg nifedipine daily (n = 7, N) or 50 mg captopril daily (n = 6, C) for one year. Baseline clinical and laboratory variables were comparable in the three groups. Glomerular filtration rate (GFR), effective renal plasma flow (ERPF) and blood pressure did not differ between groups before and after one years medication. UAER did not change in the captopril and the placebo group (C: -12.6% (-58.1 to 51.8%)' P: -17.3 (-55.9 to 99.3%), medians and ranges. In contrast, in the patients that received nifedipine, UAER rose by 43.1% (-8.5 to 261.8%), (p < 0.05 Baseline vs one year, and one year nifedipine vs captopril and placebo). We therefore conclude, that long-term use of nifedipine increases UAER in normotensive microalbuminuric insulin-dependent subjects, in contrast to captopril or placebo. Whether this enhancement of microalbuminuria exerts an adverse effect on renal function in the long-term is yet unknown, but caution seems warranted.

Adult↗
PubMed1992

The amount of plasminogen, tissue-type plasminogen activator and plasminogen activator inhibitor type 1 in human thrombi and the relation to ex-vivo lysibility.

Thrombolytic therapy successfully reopens obstructed blood vessels in the majority of cases. However, it is not known why a substantial amount of thrombi are resistant to lysis by a fibrinolytic agent. In vitro studies have demonstrated that tissue-type plasminogen activator (t-PA) and plasminogen incorporated in the clot (during formation) increase lysibility. To test whether lysibility of in vivo formed human thrombi is related to their composition, we studied 25 venous thrombi obtained at autopsy and 21 arterial thrombi obtained during embolectomy. Plasminogen activator inhibitor-1 (PAI-1) antigen was measured in a phosphate-buffered saline (PBS) extract of each thrombus; t-PA antigen and plasminogen antigen were determined in a 6 M urea extract of the thrombus, representing bound proteins. Lysibility was measured as weight reduction during 8 h of incubation in PBS containing streptokinase (SK) 100 U/ml, corrected for spontaneous lysis, reflected by weight loss in PBS without SK. In addition, lysibility in SK was compared with lysibility in urokinase (UK) 100 U/ml and in t-PA 200 U/ml. Spontaneous lysis amounted to 29 +/- 5% (mean +/- SEM) and 33 +/- 5% in venous and arterial thrombi, respectively, and inversely correlated with the PAI-1 content of thrombi (r = -0.43, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1992

Fluoxetine increases insulin action in obese nondiabetic and in obese non-insulin-dependent diabetic individuals.

Insulin resistance contributes to the metabolic defects in non-insulin-dependent diabetes mellitus (NIDDM). Anorectic agents have been shown to improve insulin action in NIDDM, irrespective of weight reduction. The serotonin-reuptake inhibiting agent fluoxetine has recently been recognized as an anorectic agent. The effect of fluoxetine on insulin action has not yet been determined. In a double blind placebo controlled crossover study, we examined hepatic and peripheral insulin action by the sequential hyperinsulinemic euglycemic clamp technique with infusion of 3-3H-glucose in eight obese NIDDM and in eight obese nondiabetics, matched for age, sex and body mass index. Body weight was kept constant. After 14 days of fluoxetine, 60 mg daily, in NIDDM half-maximal peripheral glucose uptake was achieved at a lower insulin level than after placebo (ED50pgu 180.5 +/- 25.8 vs 225.3 +/- 39.9 mU/l, P less than 0.05), but not in nondiabetics (140 +/- 15.3 vs 135.3 +/- 22.2 mU/l, n.s.). Maximal peripheral glucose uptake (Vmaxpgu) did not change significantly. Basal hepatic glucose production (HGP) was reduced after fluoxetine in both NIDDM (9.45 vs 10.37 mumol/kg/min) and in nondiabetics (8.57 vs 9.16 mumol/kg/min), although the difference was only significant in nondiabetics (P less than 0.05). Multivariate analysis disclosed no differences in the effect of fluoxetine between NIDDM and nondiabetics. When nondiabetics and NIDDM were considered together, only the most insulin-resistant individuals demonstrated a decrease in ED50pgu (P less than 0.001). Likewise, only the individuals with the most outspoken hepatic insulin resistance demonstrated a decrease in insulin level, at which hepatic glucose production is completely suppressed (HGP0) (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

C-Peptide↗
PubMed1992

Fluoxetine increases insulin action in obese type II (non-insulin dependent) diabetic patients.

Insulin resistance contributes to the metabolic defects in non-insulin dependent diabetes mellitus (NIDDM). Anorectic agents have been shown to improve insulin action in NIDDM, irrespective of weight reduction. In a double-blind placebo-controlled cross-over study, we examined hepatic and peripheral insulin action by the sequential hyperinsulinaemic-euglycaemic clamp technique with infusion of 3-[3H]-glucose in eight obese NIDDM patients and in eight obese non-diabetics, matched for age, sex and body mass index. Body weight was kept constant. After 14 days of fluoxetine, 60 mg daily, in NIDDM half-maximal peripheral glucose uptake was achieved at a lower insulin level than after placebo (ED50pgu: 180.5 +/- 25.8 vs. 225.3 +/- 39.9 mU/l, P < 0.05), but not in non-diabetics (140 +/- 15.3 vs. 135.3 +/- 22.2 mU/l, n.s.). Maximal peripheral glucose uptake (Vmaxpgu) did not change significantly. Multivariate analysis disclosed no differences in the effect of fluoxetine between NIDDM and non-diabetics. When non-diabetics and NIDDM were considered together, only the most insulin-resistant individuals demonstrated a decrease in ED50pgu (P < 0.001). Likewise, only the individuals with the most outspoken hepatic insulin resistance demonstrated a decrease in insulin level, at which hepatic glucose production (HGP) is completely suppressed (HGP0) (P < 0.01). In conclusion, fluoxetine improves peripheral and hepatic insulin action in obese insulin-resistant subjects irrespective of its weight lowering effect.

Blood Glucose↗
PubMed1989

Individuals with only one allele for a functional insulin receptor have a tendency to hyperinsulinaemia but not to hyperglycaemia.

Recently, we described a leprechaun patient with a genetically transmitted severe insulin resistance due to the absence of functional insulin receptors as inferred from the loss of insulin binding to the patients' fibroblasts and the impaired autophosphorylation of the beta-chain of the receptor. This patient was homozygous for the genetic defect which was recently found to be a leucine to proline mutation at position 233 in the alpha-chain of the insulin receptor. In the present study we have examined insulin receptor functions in relatives of this patient. Some of these individuals are heterozygous for the genetic defect and have only one allele coding for a functional insulin receptor. Insulin binding to cultured fibroblasts from the heterozygous individuals is only 20-40% of control values indicating a Mendelian mode of inheritance of the binding defect. In contrast, insulin stimulated autophosphorylation of the beta-chain of the insulin receptor shows normal values, indicating compensation mechanisms operating on this process. The stimulation of the basal level of 2-deoxyglucose uptake by insulin in fibroblasts from the homozygous patient is 1.2 fold whereas the heterozygous and control individuals show stimulation values of approximately 1.65 fold. Basal levels of 2-deoxyglucose uptake are similar in these fibroblasts. Oral glucose tolerance tests on the heterozygous individuals indicate an increased requirement for insulin of the target tissues as concluded from the tendency towards hyperinsulinaemia with no observed hyperglycaemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗