Edgard Delvin

Bone response to phosphate salts, ergocalciferol, and calcitriol in hypophosphatemic vitamin D-resistant rickets.

We treated 11 children with vitamin D-resistant rickets with a phosphate mixture either alone (1.2 to 3.6 g per day) or combined with ergocalciferol (vitamin D2, to 50 x 103 IU per day) or with calcitriol (1,25-dihydroxyvitamin D3, 0.25 to 1 microgram per day). Serum calcitriol concentrations were normal in all patients. Calcitriol therapy circulating levels of the hormone to values above normal and increased intestinal phosphate absorption. In some patients this regimen decreased the need for phosphate supplements. None of the treatment regimens corrected the renal phosphate leak. Radiologic studies and bone histomorphometric analyses showed that phosphate (alone or with ergocalciferol) induced the mineralization of the growth plate but not of the endosteal bone surface. Combined calcitriol and phosphate therapy for a total of 2850 patient-days greatly improved the mineralization of trabecular bone. Short-term episodes of hypercalcemia were easily controlled by changes in calcitriol dosage. The data indicate that the combined calcitriol and phosphate regimen is useful in the treatment of vitamin D-resistent rickets.

Blood Pressure and Adiposity in Children and Adolescents

Background—Although obesity is associated with important hemodynamic disturbances, there are few data on population-wide blood pressure (BP) distribution in children and adolescents in this era of endemic pediatric obesity. Methods and Results—We conducted a school-based survey of a representative sample of youth aged 9, 13, and 16 years in Quebec, Canada. Resting BP was measured with an oscillometric device in 3589 subjects (80% response). Additional measures included height, weight, and subscapular and triceps skinfold thickness, an age-appropriate questionnaire, and a fasting blood draw. Mean (SD) systolic/diastolic BP (SBP/DBP) levels in 9-, 13-, and 16-year-olds were 103 (9)/57 (6), 113 (12)/58 (7), and 124 (14)/61 (7) mm Hg in males and 103 (10)/57 (6), 111 (11)/60 (7), and 114 (11)/62 (7) mm Hg in females. The prevalence of high-normal or elevated SBP was 12%, 22%, and 30% among 9-, 13-, and 16-year-old males, respectively, and 14%, 19%, and 17% among same-aged females. The prevalence of high-normal or elevated DBP was <1%. In multiple linear regression analysis, body mass index was consistently associated with SBP and DBP in all age-gender groups. Conclusions—Mean SBP and the prevalence of high-normal and elevated SBP are elevated in children and adolescents. Public policy, public health programs, and clinical preventive measures are urgently needed to address the obesity epidemic and its hemodynamic consequences.

Insulin resistance syndrome in a representative sample of children and adolescents from Quebec, Canada

OBJECTIVES: To estimate the prevalence of insulin resistance syndrome (IRS) in a representative sample of youth. To test for the independent contribution of insulin resistance (IR) and adiposity to clustering of metabolic risk factors. To identify the underlying components of IRS. To examine the relationship between adiposity and fasting plasma levels of free fatty acids (FFA).METHODS: In 1999, we conducted a school-based survey of a representative sample of youth aged 9, 13 and 16 y in Quebec, Canada. Age-specific questionnaire data, standardized clinical measurements and a fasting blood sample were available for 2244 subjects. Fasting insulin and HOMA were used as surrogate measures of IR.RESULTS: In all age–sex groups, adiposity indices, blood pressure (BP), plasma glucose and triglycerides (TG) increased significantly with increasing insulin quartiles while HDL cholesterol (HDL-C) decreased. The overall prevalence of IRS defined as hyperinsulinaemia combined with two or more risk factors including overweight, high systolic BP, impaired fasting glucose, high TG and low HDL-C, was 11.5% (95% CI: 10.2–12.9). There were no significant differences in the prevalence of IRS across ages or between sexes. The independent contribution of adiposity to clustering of risk factors was stronger than that of fasting insulin (or HOMA-IR). Factor analysis revealed three factors (BMI/insulin/lipids, BMI/insulin/glucose and diastolic/systolic BP) consistent across ages suggesting that more than one pathophysiologic process underlies IRS. Although elevation of FFA might be in the causal pathway linking obesity to IR, we did not detect any consistent association between measures of fatness and fasting plasma FFA.CONCLUSION: IRS is highly prevalent in youth, even among children as young as age 9 y. Factor analysis identifies three physiologic domains within IRS with a unifying role for markers of IR and adiposity.

The three-gene paraoxonase family: Physiologic roles, actions and regulation

The paraoxonase (PON) gene family is composed of three members (PON1, PON2, PON3) that share considerable structural homology and are located adjacently on chromosome 7 in humans. By far the most-studied member is PON1, a high-density lipoprotein-associated esterase/lactonase, also endowed with the capacity to hydrolyze organophosphates, but all the three proteins prevent oxidative stress and fight inflammation. They therefore seem central to a wide variety of human illnesses, including atherosclerosis, diabetes mellitus, mental disorders and inflammatory bowel disease. The major goal of this review is to highlight the regulation of each of the paraoxonase components by diverse nutritional molecules and pharmacological agents as well as a number of pathophysiological events, such as oxidative stress and inflammation. Considerable and detailed cell-based studies and animal model experiments have been provided to allow a thorough scrutiny of PON modulation, which will increase our understanding and ability to target these genes in order to efficiently increase their transcriptional activity and decrease the risks of developing different disorders.

Distribution of Fasting Plasma Insulin, Free Fatty Acids, and Glucose Concentrations and of Homeostasis Model Assessment of Insulin Resistance in a Representative Sample of Quebec Children and Adolescents

BACKGROUND Plasma fasting insulin and the homeostasis model assessment of insulin resistance (HOMA-IR) are markers of IR, which, at least in part, mediates the relation of obesity to increased cardiovascular risk. Increased free fatty acids (FFAs) may be involved in the pathogenesis of IR. Our objectives were to describe the distributions of fasting plasma insulin, glucose, and FFAs and HOMA-IR in youth and to assess the relationship between FFAs and markers of IR. METHODS Fasting plasma insulin, glucose, and FFAs were measured in a representative sample of Quebec youth comprising 2244 individuals 9, 13, and 16 years of age. RESULTS In all age and sex groups, glucose exhibited remarkably tight distributions (median CV, 7.1%) in contrast to insulin, HOMA-IR, and FFAs (median CVs, 52%, 54% and 45%, respectively). For every percentile examined, 9-year-olds had lower insulin concentrations and HOMA-IR values than 13- and 16-year-olds. We observed strong correlations between insulin concentrations and HOMA-IR values, as well as close similarity in their rankings of individuals. The mean concentrations of glucose were higher in our population than in other Caucasian pediatric populations. No positive correlations were detected between FFAs and markers of IR. CONCLUSIONS We report some of the first data on the distributions of fasting plasma insulin, HOMA-IR, and FFAs from a representative sample of youth. HOMA-IR does not appear more informative than fasting insulin as a marker of IR. Our findings on higher mean glucose concentrations in this population require confirmation in other representative samples of youth to assess whether the North American distribution of glucose concentrations is shifting positively.

Localization and role of NPC1L1 in cholesterol absorption in human intestine

Recent studies have documented the presence of Niemann-Pick C1-Like 1 (NPC1L1) in the small intestine and its capacity to transport cholesterol in mice and rats. The current investigation was undertaken to explore the localization and function of NPC1L1 in human enterocytes. Cell fractionation experiments revealed an NPC1L1 association with apical membrane of the enterocyte in human jejunum. Signal was also detected in lysosomes, endosomes, and mitochondria. Confirmation of cellular NPC1L1 distribution was obtained by immunocytochemistry. Knockdown of NPC1L1 caused a decline in the ability of Caco-2 cells to capture micellar [14C]free cholesterol. Furthermore, this NPC1L1 suppression resulted in increased and decreased mRNA levels and activity of HMG-CoA reductase, the rate-limiting step in cholesterol synthesis, and of ACAT, the key enzyme in cholesterol esterification, respectively. An increase was also noted in the transcriptional factor sterol-regulatory element binding protein that modulates cholesterol homeostasis. Efforts were devoted to define the impact of NPC1L1 knockdown on other mediators of cholesterol uptake. RT-PCR evidence is presented to show the significant decrease in the levels of scavenger receptor class B type I (SR-BI) with no changes in ABCA1, ABCG5, and cluster determinant 36 in NPC1L1-deficient Caco-2 cells. Together, our data suggest that NPC1L1 contributes to intestinal cholesterol homeostasis and possibly cooperates with SR-BI to mediate cholesterol absorption in humans.

Plasma PCSK9 Is Associated with Age, Sex, and Multiple Metabolic Markers in a Population-Based Sample of Children and Adolescents

BACKGROUND Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a protein convertase that posttranslationally promotes the degradation of the low-density lipoprotein receptor (LDLR) in hepatocytes and increases plasma LDL cholesterol (LDL-C). Heterozygote gain-of-function mutations of PCSK9 are associated with the familial hypercholesterolemia phenotype, whereas loss-of-function variants are associated with reduced LDL-C concentrations and lower coronary risk. Plasma PCSK9 correlates with body mass index, triglyceridemia, total cholesterol, and LDL-C in adults, but no data are available in youth. METHODS We studied 1739 French Canadian youth ages 9, 13, and 16 years who participated in the Quebec Child and Adolescent Health and Social Survey, a province-wide school-based survey conducted in 1999. An ELISA assay was used to measure plasma PSCK9. RESULTS The mean (SD) plasma PCSK9 concentration was 84.7 (24.7) microg/L in the sample. In boys, plasma PCSK9 decreased with age, whereas the inverse was true for girls. There were statistically significant positive associations between PCSK9 and fasting glucose, insulin, and HOMA-IR (homeostasis model assessment of insulin resistance). In multivariable analysis, a 10% higher fasting insulin was associated with a 1%-2% higher PCSK9 in both sexes. There were also positive associations between PCSK9 and total cholesterol, LDL-C, and triglycerides, as well as with HDL-C and apolipoproteins A1 and B. CONCLUSIONS PCSK9 is associated with age, sex, and multiple metabolic markers in youth. A novel finding is that PCSK9 is associated with fasting insulinemia, which suggests that PCSK9 could play a role in the development of dyslipidemia associated with the metabolic syndrome. .

Screening for preeclampsia using first-trimester serum markers and uterine artery Doppler in nulliparous women

OBJECTIVE To evaluate the screening accuracy of pregnancy hypertensive disorders by maternal serum biomarkers and uterine artery Doppler in the first trimester. STUDY DESIGN Prospectively enrolled nulliparous women had uterine artery Doppler and serum measured at 11-13 weeks. Maternal characteristics, uterine artery Doppler, and serum placental biomarkers (pregnancy-associated plasma protein-A, Inhibin-A, placental protein 13, A disintegrin and metalloprotease 12, free β-hCG, placental growth factor) were recorded. RESULTS Among 893 women, 20 (2.2%) had gestational hypertension developed and 40 (4.5%) had preeclampsia developed, including 9 (1.0%) early-onset preeclampsia and 16 (1.8%) severe preeclampsia. A combined screening model with clinical characteristics, pregnancy-associated plasma protein-A, Inhibin-A, and placental growth factor could detect 75% of early-onset preeclampsia at a 10% false-positive rate. After adjustment for clinical variables, uterine artery Doppler, placental protein 13, and A disintegrin and metalloprotease 12 did not improve the diagnostic accuracy. CONCLUSION A combination of clinical characteristics and first-trimester maternal serum biomarkers (pregnancy-associated plasma protein-A, Inhibin-A, and placental growth factor) provides an accurate screening for early-onset preeclampsia in nulliparous women.

Intestinal cholesterol transport proteins: an update and beyond.

Purpose of review Various studies have delineated the causal role of dietary cholesterol in atherogenesis. Strategies have thus been developed to minimize cholesterol absorption, and cholesterol transport proteins found at the apical membrane of enterocytes have been extensively investigated. This review focuses on recent progress related to various brush-border proteins that are potentially involved in alimentary cholesterol transport. Recent findings Molecular mechanisms responsible for dietary cholesterol and plant sterol uptake have not been completely defined. Growing evidence, however, supports the concept that several proteins are involved in mediating intestinal cholesterol transport, including SR-BI, NPC1L1, CD36, aminopeptidase N, P-glycoprotein, and the caveolin-1/annexin-2 heterocomplex. Other ABC family members (ABCA1 and ABCG5/ABCG8) act as efflux pumps favoring cholesterol export out of absorptive cells into the lumen or basolateral compartment. Several of these cholesterol carriers influence intracellular cholesterol homeostasis and are controlled by transcription factors, including RXR, LXR, SREBP-2 and PPARα. The lack of responsiveness of NPC1L1-deficient mice to ezetimibe suggests that NPC1L1 is likely to be the principal target of this cholesterol-lowering drug. Summary The understanding of the role, genetic regulation and coordinated function of proteins mediating intestinal cholesterol transport may lead to novel ways of treating cardiovascular disease.

An inherited disorder of isoleucine catabolism causing accumulation of alpha-methylacetoacetate and alpha-methyl-beta -hydroxybutyrate, and intermittent metabolic acidosis.

Extract: At least 15 apparently inherited disorders of branched chain amino acid catabolism are now known; the 12th in chronological order of discovery is described in this report. It is a partial defect of the pathway of isoleucine oxidation beyond the level of oxidative decarboxylation and prior to the oxidation of propionate. The impairment of isoleucine catabolism appears to be situated at the “thiolase” reaction which converts α-methylacetoacetyl coenzyme A (CoA) to propionyl-CoA and acetyl-CoA.Two pedigrees (B and M) were investigated in detail. A third (S pedigree) has been brought to our attention for analysis of metabolites in urine but we have not performed additional studies in the latter. Each propositus was ascertained because of intermittent, odorless metabolic acidosis usually precipitated by intercurrent infection. Lethargy and coma occurred frequently during the periods of acidosis. One M sib, also presumably affected, died abroad in such an episode. Symptoms can be ameliorated by a low protein diet and careful attention to the management of intercurrent illness.A large excess of α-methyl-β-hydroxybutyrate and a seemingly smaller excess of α-methylacetoacetate is present at all times in the urine of the three propositions. The M and S propositi also excrete N-tiglylglycine. The amounts of these unusual metabolites increase severalfold during acidosis and after a dietary load of l-isoleucine (75 mg/kg, 3 times daily for 2 days). The urine also contains butanone, particularly during acidosis. The amount of propionate and of glycine and other amino acids in blood and urine is always normal in our patients. Oxidation of l-isoleucine-U-14C to CO2 by cultured skin fibroblasts is about 45% of normal in the B propositus. The precise nature and location of the enzyme defect awaits clarification.Studies of family members reveal that presumed obligate heterozygotes excrete a small excess of α-methyl-β-hydroxybutyrate at all times; the amount can be increased by L-isoleucine feeding. The condition is apparently inherited in autosomal recessive fashion. It is likely that more than one form of mutant allele is responsible for the condition, as it is found in the three different pedigrees described here.Speculation: Investigation of “unexplained,” intermittent metabolic acidosis in childhood has led to the discovery of a “new” disorder of branched chain amino acid catabolism. Gas chromatography coupled with mass spectrometry were important aids to the diagnosis. Rapid escalation of acidosis during catabolic episodes encourages one to suspect that specific metabolites, themselves accumulating during episodic illness, may further inhibit the mutant enzyme. A temperature-sensitive mutant enzyme was not identified in cultured skin fibroblasts.