Severe early onset osteopenia and osteoporosis caused by antiepileptic drugs

We describe two adult patients with epilepsy who received long-term antiepileptic drug therapy, a woman aged 39 years and a man aged 38 years, in whom severe osteopenia and osteoporosis, respectively, were diagnosed. Both had had epilepsy since childhood, both were seizure free and off medication for several years before the epilepsy started again. The female patient first sustained a complicated pelvis fracture after minor trauma. Next, both patients had infractions of several thoracic vertebrae after a generalised tonic-clonic seizure. Dual-energy X-ray absorptiometry for measurement of the bone mineral density revealed osteopenia in both. Bone biopsy was only performed in the male patient and showed moderate osteoporosis. Taking into consideration the young age for osteopenia and osteoporosis and the absence of other underlying causes, the long-term anticonvulsant therapy is the most likely cause of the development of osteopenia and osteoporosis in these patients. Reviewing recent literature data, advice from healthcare organisations and medical guidelines, the authors were surprised by the lack of protocols and preventive measures for patients with epilepsy who have been on antiepileptic drug therapy for many years. With this article we stress the urgent need to develop protocols and guidelines for preventive interventions.

Endothelium-dependent vasodilatation, plasma markers of endothelial function, and adrenergic vasoconstrictor responses in type 1 diabetes under near-normoglycemic conditions

It is unknown whether and to what extent changes in various endothelial functions and adrenergic responsiveness are related to the development of microvascular complications in type 1 diabetes. Therefore, endothelium-dependent and endothelium-independent vasodilatation, endothelium-dependent hemostatic factors, and one and two adrenergic vasoconstrictor responses were determined in type 1 patients with and without microvascular complications. A total of 34 patients with type 1 diabetes were studied under euglycemic conditions on two occasions (11 without microangiopathy, 10 with proliferative and preproliferative retinopathy previously treated by laser coagulation, 13 with microalbuminuria, and 12 healthy volunteers also were studied). Forearm vascular responses to brachial artery infusions of N(G)-monomethyl-L-arginine (L-NMMA), sodium nitroprusside, acetylcholine (ACh), clonidine, and phenylephrine were determined. The ACh infusions were repeated during coinfusion of L-arginine. Furthermore, plasminogen activator inhibitor type 1 (PAI-1) activity, tissue plasminogen activator antigen levels, von Willebrand factor antigen levels, tissue factor pathway inhibitor (TFPI) activity, and endothelin-1 levels were measured. No differences in endothelium-dependent or endothelium-independent vasodilatation or adrenergic constriction were observed between the diabetic patients and the healthy volunteers. In comparison to the first ACh infusion, the maximal response to repeated ACh during L-arginine administration was reduced in the diabetic patients, except in the patients with proliferative and preproliferative retinopathy previously treated by laser coagulation. In these patients, the combined infusion of L-arginine and ACh resulted in an enhanced response. TFPI activity was elevated, and PAI-1 activity was reduced in the type 1 diabetic patients. Furthermore, PAI-1 activity was positively correlated with urinary albumin excretion (r = 0.48, P < 0.01) and inversely correlated with the vasodilatory response to the highest ACh dose (r = -0.37, P < 0.05). The response to the highest ACh and L-NMMA dose were positively correlated with mean arterial blood pressure (r = 0.32, P < 0.01; r = 0.41, P < 0.01, respectively). Forearm endothelium-dependent and endothelium-independent vasodilatation and adrenergic responsiveness were unaltered in type 1 diabetic patients with and without microvascular complications. Relative to healthy control subjects, endothelium-dependent vasodilatation was depressed during a repeated ACh challenge (with L-arginine coinfusion) in the diabetic patients without complications or with microalbuminuria. In contrast, this vasodilatation was enhanced in the patients with retinopathy. Elevation of TFPI was the most consistent marker of endothelial damage of all the endothelial markers measured.

The enhanced pressor response in type 2 diabetes is not based upon a generalized increase in vascular responsiveness

OBJECTIVE

The present study was performed to discriminate between central and peripheral effects of noradrenaline (NA) in normotensive, non-obese, type 2 diabetic patients.

METHODS

Study I: In 10 patients and 10 healthy volunteer (HV) cumulative doses of NA were infused intravenously until mean arterial pressure (MAP) rose with 20 mmHg, and subsequently the effects on the forearm blood flow (FBF) was measured. Also, the FBF response to intra-arterial NA (0.025, 0.1, 0.4 micrograms min-1) was measured. Study II: In 13 patients and 14 HV the venous constrictor response to a cumulative local infusion of NA in a dorsal hand vein was determined.

RESULTS

In study I the circulating plasma NA concentrations inducing a rise in MAP of 20 mmHg, were lower in the type 2 patients relative to the HV (p < 0.01). The relationship between changes in pressure and changes in heart rate were similar in both groups. Moreover, FBF responsiveness to intra-arterial NA was not different between the two groups. The slopes of the delta MAP/NA regression lines were correlated with basal insulin levels and relative insulin resistance in the healthy volunteers (R = 0.77, p < 0.01, and R = 0.83, p < 0.01), but not in the type 2 diabetic patients. In study II no differences were observed in the dose generating half maximum (ED50) and the maximum (Emax) response to NA between the type 2 patients and the HV.

CONCLUSIONS

Non-obese normotensive type 2 patients have an increased pressor response to NA, which is not based upon a defect in skeletal muscle resistance arterioles, peripheral veins, or a defect in the baroreceptor system. Therefore, in type 2 diabetes the noradrenergic responsiveness of other vascular beds, such as the splanchnic or renal, must be enhanced.

Impaired arterial but not venous responsiveness to nitroglycerin in non-insulin-dependent diabetes mellitus

In earlier studies, the response of the arterioles to nitroglycerin (NTG) was found to be impaired in non-insulin-dependent diabetes mellitus (NIDDM) patients. NTG has major therapeutic effects in reducing cardiac after- and preload. Thus, the vasorelaxing efficacy of a therapeutic dose of 0-4 mg of NTG sublingually (s.l.) was evaluated in the conduit femoral artery and large veins of normotensive, normoalbuminuric NIDDM patients. After NTG, the increase in the femoral artery diameter was significantly lower in the NIDDM patients than in control subjects: 0.49 (0.29-0.79) vs. 0.75 (0.47-1.00) mm respectively (median, interquartile ranges). NTG resulted in an increase of pulse wave transit time in the aorta in control subjects but not in the NIDDM patients: from 64 (60-73) to 70 (63-80) ms, P < 0.02; and from 62 (53-69) to 66 (51-72) ms, P = NS, respectively. The reduction in the venous tone of the forearm to NTG was similar in both groups. These results suggest that the response to NTG is impaired in the arterial system but not in the venous system in well-regulated NIDDM patients without diabetic complications.

Peripheral blood flow and noradrenaline responsiveness: the effect of physiological hyperinsulinemia

OBJECTIVE

Insulin seems to have vasodilator properties, but it is unclear if insulin in postprandial concentrations is a specific vasodilator of skeletal muscle resistance arterioles only or that various types of vessels are affected. The aim of the present study was to determine the direct effects and the time course of regional/local physiological hyperinsulinemia on skeletal muscle arterioles, skin blood flow and peripheral venous tone and the responsiveness of these different vascular beds to noradrenaline.

METHODS

In protocol I (n = 12) we infused insulin into the brachial artery for 180 min (3.5 mU/min) and evaluated the effects on forearm (muscle) blood flow (FBF) and skin blood flow (SBF). Furthermore, noradrenaline (0.025, 0.01 and 0.4 microgram/min) was infused (i.a.) at baseline, at 90 and 180 min after the start of insulin. In protocol 2 (n = 10) the same regional forearm hyperinsulinemia was achieved, but now the local venous responsiveness to noradrenaline (1.7-55 ng/min, at baseline and at 90 and 180 min) was measured in a dorsal hand vein. In protocol 3 we evaluated the local effects of different doses of insulin (1-100 mU/min) infused directly into hand veins preconstricted with phenylephrine.

RESULTS

Forearm hyperinsulinemia (approximately 50 mU/l) led to a significant increase in FBF after 180 min (median 26%, interq ranges 5-50, P < 0.05), while SBF was not altered. Forearm hyperinsulinemia did not affect the noradrenergic responsiveness in skeletal muscle or skin. Infused locally into hand veins only the highest dose of insulin (100 mU/min) caused a minor venodilation (7% [2.4-12.5], P < 0.05).

CONCLUSION

Regional forearm physiological hyperinsulinemia has a vasodilator effect on resistance vessels in skeletal muscle, but is slow in onset (180 min). However, skin vasculature and peripheral veins are not affected by this hyperinsulinemia.

Local 24-h hyperglycemia does not affect endothelium-dependent or -independent vasoreactivity in humans

Hyperglycemia induces regional hemodynamic changes, as suggested by animal studies. These hemodynamic changes may play an initiating role in the pathogenesis of diabetic microangiopathy. The aim of the present study was to evaluate the effects of acute local hyperglycemia for 24 h on basal human forearm muscle and skin blood flow and endothelium-dependent and -independent vasoreactivity. Local hyperglycemia (approximately 15 mM) was induced by infusion of 5% glucose into the brachial artery of the nondominant arm. In control experiments, the same individual amount of glucose was infused intravenously in the dominant arm to correct for possible systemic effects of the infused glucose. Vasoreactivity of the forearm vasculature was evaluated by local infusion of acetylcholine (ACh), sodium nitroprusside (SNP), NG-monomethyl-L-arginine (L-NMMA), and norepinephrine (NE) into the brachial artery. Regional hemodynamic measurements were performed at baseline and after 6, 12, and 24 h of local hyperglycemia. Median (with interquartile range) basal forearm (muscle) blood flow (FBF) was not influenced by the 24-h local hyperglycemia [infused-to-contralateral arm FBF ratio for glucose 1.32 (1.16-1.64) vs. control 1.54 (1.34-1.69)]. Skin microcirculatory blood flow (laser Doppler flowmetry, LDF) was not influenced by the 24-h local hyperglycemia [LDF ratio for glucose 1.00 (0.62-1.56) vs control 0.80 (0.58-1.14)]. In addition, the vasoreactivity of both muscle and skin (not shown) vasculature to ACh [percent change in FBF ratio for glucose 167% (81-263) vs. control 148% (94-211)], SNP [for glucose 486% (178-586) vs. control 293% (196-454)], L-NMMA [for glucose -36% (-56 to -22) vs. control -41% (-51 to -24)], and NE [for glucose -48% (-72 to -41) vs. control -66% (-79 to -33)] was also not affected by the local hyperglycemia. Thus, in contrast to animal studies, our results suggest that a moderate-to-severe hyperglycemia does not affect the regulation of basal blood flow or endothelium-dependent or -independent vasoreactivity in humans.

The effects of 7-hour local hyperglycaemia on forearm macro and microcirculatory blood flow and vascular reactivity in healthy man

Animal studies suggest that hyperglycaemia directly affects local blood flow and vascular reactivity. We studied the effects of 7 h of local forearm hyperglycaemia, on forearm (muscle) and skin microcirculatory blood flow in 12 healthy men. Furthermore, the effects of this local hyperglycaemia on forearm vasoreactivity to noradrenaline were studied. Using the perfused forearm technique, a local hyperglycaemia of approximately 16 mmol/l was induced by continuous intraarterial infusion of 5% glucose. All subjects received both glucose and placebo (0.9% NaCl) infusions on two different occasions, in random order and blinded for the subjects. Forearm (muscle) blood flow and vascular reactivity to noradrenaline were measured using venous occlusion plethysmography. Skin microcirculatory blood flow was evaluated using intravital capillary microscopy (nutritive blood flow) and laser-Doppler fluxmetry (thermoregulatory blood flow). Measurements were performed at baseline, after 4 h, and after 7 h of intraarterial glucose or placebo infusion. During local glucose infusion there was a slight increase in the levels of insulin, C-peptide, systemic glucose, and blood pressure, compared to the placebo experiments. No differences were observed in forearm blood flow and laser-Doppler flux ratio (infused: contralateral arm), as well as in capillary blood cell velocity between glucose and placebo experiments. Noradrenaline produced similar reductions in forearm blood flow ratio during glucose and placebo experiments. We conclude that in contrast to animal studies, local hyperglycaemia (approximately 16 mmol/l) for 7 h does not affect forearm macro and microcirculatory blood flow or vascular reactivity to noradrenaline in man.

Venous compliance and the venodilatory effect of nitroglycerin in insulin-dependent diabetic patients with and without (incipient) nephropathy

The venous system plays a pivotal role in volume and blood pressure homeostasis. We tested the hypothesis that the visco-elastic properties of the peripheral venous system are reduced in patients with (incipient) diabetic nephropathy. Twenty-two normotensive patients with long-term insulin-dependent diabetes mellitus (IDDM), 11 without and 11 with (incipient) nephropathy (eight microalbuminuria and three proteinuria, serum creatinine below 100 mumol l-1), and 14 healthy age/sex matched controls were studied. Forearm venous compliance (VENCOMP) was determined using strain gauge plethysmography and direct intravenous pressure measurements. Furthermore, the venodilatory effect of 0.4 mg sublingual nitroglycerin (NTG) was studied. In comparison with healthy controls, VENCOMP was decreased in patients without and with (incipient) nephropathy, without any differences between the two diabetic groups: 0.059 (0.052-0.066), 0.044 (0.038-0.059) and 0.049 (0.046-0.058) ml 100 ml-1 mmHg-1, respectively (medians and interquartile ranges) (P < 0.05). No differences in the increase of forearm volume after NTG were observed: 0.34 (0.11-0.51), 0.37 (0.19-0.50) and 0.39 (0.20-0.55) ml 100 ml-1, respectively. In conclusion, the visco-elastic properties of the peripheral venous system are reduced in patients with long-term IDDM. This reduction is not related to the presence of nephropathy. No major differences were observed in NTG-induced venodilation between diabetic patients and healthy subjects.

Short-term variation in the elastic properties of a muscular artery in humans

1. Information on the interaction between mechanical strain and the elastic properties of large arteries could give insight to the origin of haemodynamic vascular injury, possibly resulting in formation of atherosclerotic plaques. Intra-individual variation in the elastic properties of muscular arteries measured using non-invasive techniques has been observed. This variation could be due to changes in blood pressure, since the elastic properties of muscular arteries are strongly non-linear. 2. The objective of the present study was to evaluate variability in the elastic properties of a muscular artery over a time period of up to 1 h. Furthermore, the relation between changes in elastic properties and alterations in blood pressure was studied. With a non-invasive high-resolution ultrasound technique, the diameter and distension of the femoral artery were assessed by repeated measurements in 10 healthy subjects (mean age 27 +/- 2.9 years) under resting conditions over 40-60 min. Intra-arterial blood pressure of the contralateral common femoral artery and heart rate were recorded simultaneously. From the distension and pulse pressure, the distension/pressure ratio was calculated, a measure of the compliance. For each parameter the variation coefficient was computed. 3. In all subjects a considerable variation was found in distension (mean variation coefficient 14.8%) but not in pulse pressure (mean variation coefficient 3.7%). The expected positive correlation between pulse pressure and distension was absent in eight subjects. As a consequence, large intra-individual variation was found in the distension/pressure ratio (mean variation coefficient 15.3%).(ABSTRACT TRUNCATED AT 250 WORDS)

Diurnal variations in total forearm and skin microcirculatory blood flow in man

The aim of the present study was to determine diurnal variations in total forearm and skin microcirculatory blood flow in healthy man. At six time points between 08.00 and 18.00 hours was measured: blood pressure, forearm blood flow (FBF; strain gauge plethysmography), skin thermoregulatory blood flow (LDF; laser-Doppler fluxmetry), and skin nutritive blood flow (CBV: Capillary Blood Cell Velocity; intravital capillary microscopy) in 15 healthy, fasting, and resting men. FBF increased gradually from 2.8 in the morning to 4.3 ml 100 ml min-1 in the afternoon (p < 0.001). In contrast, LDF decreased, predominantly in the morning, from 18.3 at 09.00 hours to 13.1 at 12.00 hours and to 12.1 perfusion units at 17.30 hours (p < 0.001). However, performing the same protocol starting in the afternoon resulted in a similar initial decrease in LDF, suggesting an acclimatization phenomenon. Although not statistically significant, the decrease in CBV showed a similar pattern as compared to LDF. Blood pressure did not change. In conclusion, forearm blood flow increased during the day, probably due to diurnal variation in muscle flow. The initial decrease we observed in skin thermoregulatory blood flow is probably not related to diurnal variation but due to long-term acclimatization to the experimental conditions. These data suggest different regulatory mechanisms for the different vascular beds studied. Measurements of forearm blood flow should preferably be performed at the same time of day, and skin microcirculatory haemodynamic measurements should be performed after a standard period of acclimatization.