Viviane Van Hoof

Interpretation and Clinical Significance of Alkaline Phosphatase Isoenzyme Patterns

AbstractAlkaline phosphatase (ALP, EC 3.1.3.1.) is a membrane-bound metalloenzyme that consists of a group of true isoenzymes, all glycoproteins, encoded for by at least four different gene loci: tissue-nonspecific, intestinal, placental, and germ-cell ALP. Through posttranslational modifications of the tissue-nonspecific gene, for example, through differences in carbohydrate composition, bone and liver ALP are formed. Nowadays, most commercially available methods for separating or measuring ALP isoenzymes are easy to perform and sensitive and allow for reproducible and quantitative results. As more isoenzymes and isoforms have been characterized, confusion has arisen due to the many different names they were given. For the sake of simplicity and because of structural analogies, we propose an alternative nomenclature for the ALP isoenzymes and isoforms based on their structural characteristics: soluble, dimeric (Sol), anchor-bearing (Anch), and membrane-bound (Mem) liver, bone, intestinal, and placental A...

Functional Adiponectin Resistance at the Level of the Skeletal Muscle in Mild to Moderate Chronic Heart Failure

Background—Adiponectin is an antiinflammatory, insulin-sensitizing, and antiatherogenic adipocytokine that plays a fundamental role in energy homeostasis. In patients with chronic heart failure (CHF), high circulating adiponectin levels are associated with inverse outcome. Recently, adiponectin expression has been identified in human skeletal muscle fibers. We investigated the expression of adiponectin, the adiponectin receptors, and genes involved in the downstream lipid and glucose metabolism in the skeletal muscle of patients with CHF. Methods and Results—Muscle biopsies (vastus lateralis muscle) were obtained from 13 patients with CHF and 10 healthy subjects. mRNA transcript levels of adiponectin, adiponectin receptors (AdipoR1 and AdipoR2), and downstream adiponectin-related enzymes were quantified by real-time reverse transcriptase polymerase chain reaction. Adiponectin expression in the skeletal muscle of patients with CHF was 5-fold higher than in healthy subjects (P<0.001), whereas AdipoR1 was downregulated (P=0.005). In addition, the expression of the main genes involved in downstream pathway (peroxisome proliferator-activated receptor-&agr; [PPAR-&agr;] and both AMP-activated protein kinase-&agr;1 and -&agr;2 subunits) as well as their target genes in lipid (acyl-coenzyme A dehydrogenase C-14 to C-12 straight chain) and glucose metabolism (hexokinase-2) were significantly reduced in CHF. The strong positive correlation found between AdipoR1 and PPAR-&agr;/AMP-activated protein kinase gene expression was confirmed in PPAR-&agr; null mice, suggesting a cause-and-effect relationship. Immunohistochemical staining confirmed the presence of adiponectin in the skeletal muscle. Conclusions—Despite increased adiponectin expression in the skeletal muscle, patients with CHF are characterized by downregulation of AdipoR1 that is most probably linked to deactivation of the PPAR-&agr;/AMP-activated protein kinase pathway. These facts suggest functional adiponectin resistance at the level of the skeletal muscle in CHF.

Useful biochemical markers for diagnosing renal osteodystrophy in predialysis end-stage renal failure patients

BACKGROUND Various biochemical markers have been evaluated in dialysis patients for the diagnosis of renal osteodystrophy (ROD). However, their value in predialysis patients with end-stage renal failure (ESRF) is not yet clear. METHODS Bone histomorphometric evaluation was performed and biochemical markers of bone turnover were determined in serum of an unselected predialysis ESRF population (N = 84). RESULTS Significant (P < 0.005) differences between the five groups with ROD (ie, normal bone [N = 32], adynamic bone [ABD; N = 19], hyperparathyroidism [N = 8], osteomalacia [OM; N = 10], and mixed lesion [N = 15]) were noted for intact parathyroid hormone, total (TAP) and bone alkaline phosphatase (BAP), osteocalcin (OC), and serum calcium levels. Serum creatinine and (deoxy)pyridinoline levels did not differ between groups. For the diagnosis of ABD, an OC level of 41 microg/L or less (< or =7.0 nmol/L) had a sensitivity of 83% and specificity of 67%. The positive predictive value (PPV) for the population under study was 47%. The combination of an OC level of 41 ng/L or less (< or =7.0 nmol/L) with a BAP level of 23 U/L or less increased the sensitivity, specificity, and PPV to 72%, 89%, and 77%, respectively. ABD and normal bone taken as one group could be detected best by a BAP level of 25 U/L or less and TAP level of 84 U/L or less, showing sensitivities of 72% and 88% and specificities of 76% and 60%, corresponding with PPVs of 89% and 85%, respectively. In the absence of aluminum or strontium exposure, serum calcium level was found to be a useful index for the diagnosis of OM. CONCLUSION OC, TAP, BAP, and serum calcium levels are useful in the diagnosis of ABD, normal bone, and OM in predialysis patients with ESRF.

Unusual D‐Lactic Acid Acidosis from Propylene Glycol Metabolism in Overdose

Objective: To report a case of D‐lactic acid acidosis owing to massive oral ingestion of propylene glycol. Case Report: A 72‐year old man with known congestive failure was admitted to the ICU with encephalopathy. Twelve hours prior to admission he had erroneously ingested a large amount of propylene glycol (PG). The laboratory revealed high anion gap (anion gap = 27 meq/l) acidosis (arterial pH = 7.16) and an increased osmolal gap. Toxicological analysis revealed a low serum propylene glycol level. Biochemical analysis indicated that very high amounts of D‐lactic acid (up to 110 mmol/l), but not of the usual type of L‐lactic acid, were responsible for the metabolic acidosis. Hemodialysis was initiated and associated with a decline of both the acidosis and D‐lactic acid levels. The patient regained conciousness. Conclusion: Ingestion of massive doses of propylene glycol, previously not reported as a cause of D‐lactic acidosis, should be added to the differential diagnosis of this rare condition.

Red cell distribution width as a marker of impaired exercise tolerance in patients with chronic heart failure

Exercise intolerance predicts mortality in patients with chronic heart failure (CHF). Recently, increased red cell distribution width (RDW) has emerged as an additional powerful predictor of poor outcome. We investigated the relationship between RDW and exercise capacity in patients with CHF. In addition, the association between training‐induced improved maximal aerobic capacity (VO2peak) and RDW was studied.

Role of Dietary Phosphorus and Degree of Uremia in the Development of Renal Bone Disease in Rats

The remnant kidney rat model has been extensively used for the evaluation of bone changes due to uremia. The present study aimed to assess the effect of the dietary phosphorus availability and of the severity of renal failure on bone histomorphometric changes and various biochemical markers over time in this model. Chronic renal failure (CRF) was induced in male Wistar rats by 5/6th nephrectomy. Half of the number of animals received a standard rat diet (STD) (0.67% P, containing low bioavailable phosphorus of plant origin); the other animals were fed a high phosphorus diet (HPD) (0.93% P, containing inorganic phosphorus with high bioavailability). Every two weeks, blood and urine samples were collected. At sacrifice after 6 or 12 weeks, bone samples were taken for the measurement of histological and histodynamic parameters. Serum creatinine measurements indicated the development of mild to moderate renal failure in both diet groups. Phosphaturia was unexpectedly low in all animals that received the STD, indicating relative phosphorus depletion despite the normal dietary phosphorus content. In the HPD CRF group, a decrease in calcemia and a rise in phosphatemia were seen after 12 weeks of CRF, which were more pronounced in animals with higher serum creatinine. Serum iPTH levels were distinctly increased in CRF rats fed a HPD, especially those with more pronounced renal failure. Serum osteocalcin and to a lesser extend tartrate-resistant acid phosphatase and urinary pyridinoline and deoxypyridinoline crosslinks were higher in the CRF animals compared to the shams, particularly in the animals of the HPD group with more pronounced CRF. In both diet groups, the CRF animals had significantly higher amounts of osteoid compared to shams. Only the animals that received a HPD developed distinct histological signs of secondary hyperparathyroidism (sHPTH), that is, an increased bone formation rate, mineral apposition rate, osteoblast perimeter, and eroded perimeter. Again, this effect was most prominent in rats with more severe CRF. In conclusion, data of the present study indicate that in experimental studies using the remnant kidney rat model, both the dietary phosphorus bioavailability and the degree of renal failure in the development of hyperparathyroidism should be considered.

Comparison of two commercially available systems for the electrophoretic separation of alkaline phosphatase isoenzymes

Abstract Two commercially available electrophoretic methods for the separation of the human serum enzyme alkaline phosphatase (ALP, EC 3.1.3.1) were evaluated: the Isopal system (Beckman, Brea, CA, USA) was compared with the Iso-PAL system (Sebia, Issy-les-amoulineux, France). Both use agarose as supporting medium to separate ALP into its clinically relevant isoenzymes: bone, liver, high-Mr (or “fast liver”), intestinal and placental ALP. With both methods, additional fractions for bone, liver and intestinal ALP were found, true isoforms that were called “variant” fractions. The migration pattern differed considerably between the systems, owing to the use of different detergents. Bone and liver ALP were partially separated with both methods. However, when bone ALP exceeded 50% of the total ALP activity, sample treatment was necessary, either with neuraminidase (Beckman) or by applying the sample on a second gel containing wheat-germ lectin to precipitate bone ALP (Sebia). The within-and between-gel reproducibilities of both systems were comparable and remained between 2 and 6% for normal isoenzyme activities. Both systems correlated well, except for high Mr ALP. The Sebia system was more sensitive for detecting intestinal ALP, whereas higher liver and bone variant ALP activities were detected with the Beckman system. It is concluded that both methods are convenient for routine use in the clinical laboratory.

Implementation of a multi-parameter Point-of-Care-blood test analyzer reduces central laboratory testing and need for blood transfusions in very low birth weight infants.

Blood sampling for laboratory testing is a major cause of iatrogenic blood loss and anemia in neonatal intensive care unit [NICU] patients. The objective of the study was to assess whether the implementation of a multi-parameter Point of Care Test [POCT] (Roche, Cobas b221) analyzer affected blood loss for central laboratory testing and need for red blood cell transfusion in our NICU. This was a retrospective observational cohort study in a NICU with comparison of two serial cohorts of 2 years each. Implementation of a multi-parameter POCT decreased central laboratory performed testing for bilirubin (-32% per patient) and electrolytes (-36% per patient). On average, the net blood volume taken per admitted patient for electrolyte testing decreased with 23.7% and 22.2% for bilirubin testing in the second cohort. After implementation of POCT, fewer very low birth weight infants [VLBWI] required blood transfusion (38.9% vs. 50%, p<.05) as the number of transfusion/infants decreased by 48% (1.57 vs. 2.53, p<0.01). The implementation of POCT was cost-efficient for the Belgian national health insurance, cost reduction -8.3% per neonate. We conclude that implementation of a bedside multi-parameter POCT analyzer decreases transfusions among VLBWI by reducing iatrogenic blood loss for central laboratory testing.

Efficient voltammetric discrimination of free bilirubin from uric acid and ascorbic acid by a CVD nanographite-based microelectrode

We report a novel electrochemical sensor based on nanographite grown on platinum microelectrodes for the determination of bilirubin in the presence of normal concentrations of albumin. The albumin is a protein with an intrinsic ability to bind the bilirubin therefore reducing the concentration of the free electroactive metabolite in human fluids. In addition, the proposed device permits the discrimination of free bilirubin from two interferents, uric acid and ascorbic acid, by the separation of their oxidation peaks in voltammetry. Preliminary measurements in human serum prove that the proposed nanostructured platform can be used to detect bilirubin.

Antihepatotoxic activity of a quantified Desmodium adscendens decoction and D-pinitol against chemically-induced liver damage in rats

ETHNOPHARMACOLOGICAL RELEVANCE The isolation of D-pinitol (or 3-O-methyl-D-chiro-inositol) from an aqueous decoction of Desmodium adscendens (Fabaceae) leaves and twigs is reported. The protective and curative effect of this decoction, in which d-pinitol was quantified, and of pure D-pinitol, against chemically-induced liver damage in rats has been evaluated. MATERIALS AND METHODS Enzyme levels of aspartate transaminase (AST), alanine transaminase (ALT) and alkaline phosphatase (ALP), which are among the usual biomarkers for liver damage, were determined in serum samples of experimental animals. The protective effects against D-galactosamine-induced and ethanol-induced liver damage of a decoction of D. adscendens, quantified on its main constituent D-pinitol, was investigated in rats. In addition, the curative effects of pure D-pinitol and D. adscendens against chronic D-galactosamine-induced and acute acetaminophen-induced hepatotoxicity in rats was studied. Silymarin was used as positive control. RESULTS In a first experiment evaluating the protective effect against acute D-galactosamine-induced liver damage in rats, a significant decrease of AST and ALT was observed for the D. adscendens decoction at a dose equivalent to 5 mg/kg/day and 20 mg/kg/day D-pinitol, as well as 20 mg/kg/day pure D-pinitol. With respect to chronic ethanol-induced liver damage in rats, the protective effects of D. adscendens at doses equivalent to 2 mg/kg/day and 10 mg/kg/day D-pinitol, were not observed for serum AST and ALT levels. However, with respect to reduced mortality of animals, statistical analysis showed a trend towards significance for the Desmodium group receiving a dose equivalent to 10 mg/kg/day D-pinitol, versus the untreated hepatotoxic animals. Additional experiments in rat models of acute acetaminophen-induced and chronic D-galactosamine-induced liver damage indicated that D. adscendens decoction and pure D-pinitol had no curative effect when given in a dose equivalent to 10 mg/kg/day D-pinitol, or up to 20 mg/kg/day as a pure compound daily, respectively. CONCLUSIONS The aqueous decoction of D. adscendens showed a protective effect in rats against liver damage induced by D-galactosamine and ethanol, and this effect is at least in part due to the presence of D-pinitol. However, no curative effect of D. adscendens decoction or D-pinitol on liver damage induced by the tested chemicals could be demonstrated.