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BACKGROUND/OBJECTIVES: To investigate the association of adiponectin and its gene polymorphisms with metabolic syndrome (MetS) and cardiovascular disease (CVD) risk factors in Chinese adolescents. SUBJECTS/METHODS: This cross-sectional study enrolled 919 healthy middle school students (aged 11-16 years; 46.7% females). All participants underwent anthropometric and biochemical examinations, and MetS was diagnosed using 2007 International Diabetes Federation criteria. The presence of adiponectin and its genotypes of single nucleotide polymorphisms (SNPs) rs266729 (-11377C/G), rs2241766 (+45T/G) and rs1501299 (+276G/T) was detected. RESULTS: (1) Serum adiponectin levels were negatively correlated with numerous CVD risk factors (all P < 0.05), and following adjustments for confounding factors, a lower adiponectin level was an independent risk factor for MetS (odds ratio = 5.59;95% confidence interval: 1.90, 16.41). Central obesity and low levels of high-density lipoprotein cholesterol were positively associated with MetS and reduced serum adiponectin levels. (2) The genotype and frequencies of SNP-11377 and SNP+276 in a MetS group and non-MetS group were not significantly different. Subjects with genotype SNP+45 GG were at higher risk for MetS compared with subjects with genotypes SNP+45 TT (P = 0.033) orTT+TG (P = 0.021). Subjects with genotype SNP+276 TT or TT+TG had higher levels of serum adiponectin compared with subjects with SNP+276 GG (P = 0.012 and 0.014, respectively). CONCLUSIONS: Adiponectin may be used as a predictive biomarker of MetS, and shows a significant association with CVD risk factors in Chinese adolescents. Adiponectin gene polymorphisms are associated with serum adiponectin concentrations and the presence of MetS. European Journal of Clinicai Nutrition (2015) 69, 62-67; doi: 10.1038/ejcn.2014.152; published online 30 July 2014, INTRODUCTION Adiponectin has been shown to increase insulin sensitivity, demonstrate anti-inflammatory and anti-atherosclerotic effects and be involved in the pathogenesis of metabolic syndrome (MetS). (1) Although a recent study of [...]

Endocrine effects of adipose-derived adiponectin on skeletal muscle have been shown to account, at least in part, for the anti-diabetic effects of this adipokine. Recently, the concept of myokines has gained credence, and the potential for skeletal muscle to produce adiponectin has been suggested. Here we demonstrated an increased level of adiponectin mRNA and protein expression as well as protein secretion in response to rosiglitazone treatment in L6 muscle cells. This correlated with the ability of rosiglitazone to enhance insulin sensitivity for stimulation of protein kinase B (Akt) phosphorylation and glucose transport; rosiglitazone also corrected high-glucose-induced insulin resistance in L6 cells. Overexpression of adiponectin confirmed the functional significance of local production of adiponectin in muscle cells via elevated glucose uptake and increased insulin sensitivity. In obese diabetic db/db mice, there was a change in the adiponectin expression profile in soleus and extensor digitorum longus (EDL) muscle with less high molecular weight (HMW) and more medium (MMW)/low (LMW) molecular weight species detected. Induction of obesity and insulin resistance in rats by feeding a high-fat high-sucrose diet also led to decreased muscle HMW adiponectin content that could be corrected by rosiglitazone treatment. In summary, we show the ability of skeletal muscle cells to produce adiponectin, which can mediate autocrine metabolic effects, thus establishing adiponectin as a bona fide myokine. We also demonstrate that skeletal muscle adiponectin production is altered in animal models of obesity and diabetes and that these changes can be corrected by rosiglitazone. adiponectin; myokine; glucose uptake; obesity; insulin sensitivity

Tre-2, BUB2, CDC16, 1 domain family member 4 (TBC1D4) (AS160) is a Rab-GTPase activating protein implicated in insulin-stimulated glucose transporter 4 (GLUT4)translocation in adipocytes and myotubes. To determine whether loss-of-function mutations in TBC1D4 might impair GLUT4 translocation and cause insulin resistance in humans, we screened the coding regions of this gene in 156 severely insulin-resistant patients. A female presenting at age 11 years with acanthosis nigricans and extreme postprandial hyperinsulinemia was heterozygous for a premature stop mutation (R363X) in TBC1D4. After demonstrating reduced expression of wild-type TBC1D4 protein and expression of the truncated protein in lymphocytes from the proband, we further characterized the biological effects of the truncated protein in 3T3L1 adipocytes. Prematurely truncated TBC1D4 protein tended to increase basal cell membrane GLUT4 levels (P = 0.053) and significantly reduced insulin-stimulated GLUT4 cell membrane translocation (P < 0.05). When coexpressed with wild-type TBC1D4, the truncated protein dimerized with full-length TBC1D4, suggesting that the heterozygous truncated variant might interfere with its wild-type counterpart in a dominant negative fashion. Two overweight family members with the mutation also manifested normal fasting glucose and insulin levels but disproportionately elevated insulin levels following an oral glucose challenge. This family provides unique genetic evidence of TBC1D4 involvement in human insulin action. glucose transport | insulin resistance | AS160

Cloned 20 years ago, GLUT2 is a facilitative glucose transporter in the liver, pancreas, intestine, kidney, and brain. It ensures large bidirectional fluxes of glucose in and out the cell due to its low affinity and high capacity. It also transports other dietary sugars, such as fructose and galactose, within the range of physiological concentrations. Sugars and hormones regulate its gene expression. The contribution of GLUT2 to human metabolic diseases previously appeared modest. However, in the past decade, three major features of the GLUT2 protein have been revealed. First, GLUT2 mutations cause the severe but rare Fanconi-Bickel syndrome, mainly characterized by glycogenosis. Recently, a GLUT2 polymorphism has been associated with preferences for sugary food. Second, the GLUT2 location at the cell surface is regulated; this governs cellular activities dependent on glucose in the intestine and possibly those in the liver and pancreas. For instance, GLUT2 translocation from an intracellular pool to the apical membrane after a sugar meal transiently increases sugar uptake by enterocytes (reviewed in 32). Third, GLUT2 functions as a membrane receptor of sugar. Independently of glucose metabolism, GLUT2 detects the presence of extracellular sugar and transduces a signal to modulate cell functions, including [beta]-cell insulin secretion, renal reabsorption, and intestinal absorption according to the sugar environment. These recent developments are examined here in heath and metabolic disease, highlighting various unanswered questions. glucose transporter 2; Fanconi-Bickel syndrome; pancreas; apical membrane; sugar sensing

Animals are remarkably efficient in absorbing dietary fat and assimilating this energy-dense nutrient into the white adipose tissue (WAT) for storage. Although this metabolic efficiency may confer an advantage in times of calorie deprivation, it contributes to obesity and associated metabolic disorders when dietary fat is abundant (1,2). Here we show that the intestinal lipid synthesis enzyme acyl CoA:monoacylglycerol acyltransferase-2 (MGAT2) has a crucial role in the assimilation of dietary fat and the accretion of body fat in mice. Mice lacking MGAT2 have a normal phenotype on a low-fat diet. However, on a high-fat diet, MGAT2-deficient mice are protected against developing obesity, glucose intolerance, hypercholesterolemia and fatty livers. Caloric intake is normal in MGAT2-deficient mice, and dietary fat is absorbed fully. However, entry of dietary fat into the circulation occurs at a reduced rate. This altered kinetics of fat absorption apparently results in more partitioning of dietary fat toward energy dissipation rather than toward storage in the WAT. Thus, our studies identify MGAT2 as a key determinant of energy metabolism in response to dietary fat and suggest that the inhibition of this enzyme may prove to be a useful strategy for treating obesity and other metabolic diseases associated with excessive fat intake., Dietary fat, as triacylglycerol, is a major source of calories, accounting for over 30% of daily intake in most developed countries (3). The assimilation of triacylglycerol as body fat is [...]

Prolonged activation of p70 S6 kinase (S6K) by insulin and nutrients leads to inhibition of insulin signaling via negative feedback input to the signaling factor IRS-1. Systemic deletion of S6K protects against diet-induced obesity and enhances insulin sensitivity in mice. Herein, we present evidence suggesting that hypothalamic S6K activation is involved in the pathogenesis of diet-induced hepatic insulin resistance. Extending previous findings that insulin suppresses hepatic glucose production (HGP) partly via its effect in the hypothalamus, we report that this effect was blunted by short-term high-fat diet (HFD) feeding, with concomitant suppression of insulin signaling and activation of S6K in the mediobasal hypothalamus (MBH). Constitutive activation of S6K in the MBH mimicked the effect of the HFD in normal chow--fed animals, while suppression of S6K by overexpression of dominant-negative S6K or dominant-negative raptor in the MBH restored the ability of MBH insulin to suppress HGP after HFD feeding. These results suggest that activation of hypothalamic S6K contributes to hepatic insulin resistance in response to short-term nutrient excess., Introduction Insulin resistance plays an important role in the pathogenesis of type 2 diabetes. It is well established that excess nutrient intake and chronic hyperinsulinemia cause insulin resistance. The mammalian [...]

A study report on a patient with mitochondrial isolated complex I deficiency, the most frequently encounter OXPHOs defect expressed in skin fibroblasts and muscle tissue is presented. Results showed that the expression and activity of complex 1 and the mitochondrial depolarization could be partially reduced with a baculovirus system expressing the NDUFA2 gene on chromosome 5.

This study was undertaken to test the hypothesis that short-term exposure (4 h) to physiological hyperinsulinemia in normal, healthy subjects without a family history of diabetes would induce a low grade inflammatory response independently of glycemic status. Twelve normal glucose tolerant subjects received a 4-h euglycemic hyperin-sulinemic clamp with biopsies of the vastus lateralis muscle. Microarray analysis identified 121 probe sets that were significantly altered in response to physiological hyperinsulinemia while maintaining euglycemia. In normal, healthy human subjects insulin increased the mRNAs of a number of inflammatory genes (CCL2, CXCL2 and THBD) and transcription factors (ATF3, BHLHB2, HES1, KLF10, JUNB, FOS, and FOSB). A number of other genes were upregulated in response to insulin, including RRAD, MT, and SGK. CITED2, a known coactivator of PPAR[alpha], was significantly downregulated. SGK and CITED2 are located at chromosome 6q23, where we previously detected strong linkage to fasting plasma insulin concentrations. We independently validated the mRNA expression changes in an additional five subjects and closely paralleled the results observed in the original 12 subjects. A saline infusion in healthy, normal glucosetolerant subjects without family history of diabetes demonstrated that the genes altered during the euglycemic hyperinsulinemic clamp were due to hyperinsulinemia and were unrelated to the biopsy procedure per se. The results of the present study demonstrate that insulin acutely regulates the levels of mRNAs involved in inflammation and transcription and identifies several candidate genes, including HES1 and BHLHB2, for further investigation. gene expression; muscle; insulin action; euglycemic hyperinsulinemic clamp; inflammation

The osteoblast-specific secreted molecule osteocalcin behaves as a hormone regulating glucose metabolism and fat mass in two mutant mouse strains. Here, we ask two questions: is the action of osteocalcin on [beta] cells and adipocytes elicited by the same concentrations of the molecule, and more importantly, does osteocalcin regulate energy metabolism in WT mice? Cell-based assays using isolated pancreatic islets, a [beta] cell line, and primary adipocytes showed that picomolar amounts of osteocalcin are sufficient to regulate the expression of the insulin genes and [beta] cell proliferation markers, whereas nanomolar amounts affect adiponectin and Pgc1[alpha] expression in white and brown adipocytes, respectively. In vivo the same difference exists in osteocalcin's ability to regulate glucose metabolism on the one hand and affect insulin sensitivity and fat mass on the other hand. Furthermore, we show that long-term treatment of WT mice with osteocalcin can significantly weaken the deleterious effect on body mass and glucose metabolism of gold thioglucose-induced hyperphagia and high-fat diet. These results establish in WT mice the importance of this novel molecular player in the regulation of glucose metabolism and fat mass and suggest that osteocalcin may be of value in the treatment of metabolic diseases. fat | insulin | diet-induced obesity | diet-induced diabetes | adiponectin

The sirtuins are a group of proteins linked to aging, metabolism and stress tolerance in several organisms. Among the many genes that have been shown to affect aging in model organisms, sirtuin genes are unique in that their activity level is positively correlated with lifespan (i.e. they are anti-aging genes). Sirtuins are a druggable class of enzymes (i.e. amenable to intervention by small molecules) that could have beneficial effects on a variety of human diseases. In view of the many functions of Sirtuin 1 (SIRT1) in cells, this review focuses on its role in regulating important aspects of mitochondrial biology. Mitochondria have been linked to aging, and also to diseases of aging. Thus, sirtuins might provide a key link between mitochondrial dysfunction, aging and metabolic disease.

ABSTRACT Background Macrosomia is associated with considerable neonatal and maternal morbidity. Factors that predict macrosomia are poorly understood. The increased rate of macrosomia in the offspring of pregnant women with [...]

The discovery of a new inherited metabolic disorder, dolichol kinase (DK1) deficiency that is responsible for the final step of the de novo biosynthesis of dolichol phosphate, is described. The results have shown that two homozygous mutations in the human homologue of the yeast DK1 caused a lethal phenotype, with death in early infancy.

The genetic, biochemical, and clinical characteristics of short-chain acyl-coenzyme A dehydrogenase deficiency (SCADD) patients in the Netherlands and their relatives are described to explore the genotype to phenotype relation. It is observed that SCADD is far more common than assumed and clinical symptoms in SCADD are nonspecific, generally uncomplicated, often transient and not correlated with specific SCAD-encoding (ACADS) genotype.

To investigate the association between hyperinsulinemia and cardiac hypertrophy, we treated rats with insulin for 7 wk and assessed effects on myocardial growth, vascularization, and fibrosis in relation to the expression of angiotensin II receptors (AT-R). We also characterized insulin signaling pathways believed to promote myocyte growth and interact with proliferative responses mediated by G protein-coupled receptors, and we assessed myocardial insulin receptor substrate-1 (IRS-1) and p 110[alpha] catalytic and p85 regulatory subunits of phospatidylinositol 3 kinase (PI3K), Akt, MEK, ERK1/2, and $6 kinase-1 (S6K1). Left ventricular (LV) geometry and performance were evaluated echocardiographically. Insulin decreased AT1a-R mRNA expression but increased protein levels and increased AT2-R mRNA and protein levels and phosphorylation of IRS-1 (Ser374/Tyr989), MEK1/2 (Ser218/Ser222), ERK1/2 (Thr202/Tyr204), S6K1 (Thr421/ Ser424/Thr389), Akt (Thr308/Thr308), and P13K p110[alpha] but not of p85 (Tyr508). Insulin increased LV mass and relative wall thickness and reduced stroke volume and cardiac output. Histochemical examination demonstrated myocyte hypertrophy and increases in interstitial fibrosis. Metoprolol plus insulin prevented the increase in relative wall thickness, decreased fibrosis, increased LV mass, and improved function seen with insulin alone. Thus our data demonstrate that chronic hyperinsulinemia decreases AT1a-to-AT2 ratio and increases MEK-ERK1/2 and S6K1 pathway activity related to hypertrophy. These changes might be crucial for increased cardiovascular growth and fibrosis and signs of impaired LV function. renin-angiotensin system; hypertrophy; mitogen-activated protein kinase; phosphatidylinositol 3 kinase doi:10.1152/ajpheart.00974.2005

Hypoalbuminemia is accompanied by hypercholesterolemia in both nephrotic syndrome and hereditary analbuminemia. Hypercholesterolemia is more severe in the female than in the male Nagase analbuminemic rats (NAR). The sex difference in plasma cholesterol diminishes alter ovariectomy (OVX) and reappears after estrogen replacement in the NAR. The molecular mechanism responsible for the sex difference in severity of hypercholesterolemia in NAR is not known and was investigated here. To this end, hepatic hydroxylmethylglutaryl (HMG)-CoA reductase, cholesterol 7[alpha]-hydroxylase, and LDL receptor were determined in male, female, and OVX female NAR and Sprague-Dawley (SD) rats. Plasma cholesterol, triglycerides, and hepatic HMG-CoA reductase activities were greater in both female and male NAR than in SD rats. This was coupled with upregulation of cholesterol 7[alpha]-hydroxylase in both male and female NAR compared with SD controls. LDL receptor in male NAR was similar to that in male SD rats but was significantly reduced in female NAR. OVX partially, but significantly, reduced plasma cholesterol and triglyceride levels in female NAR. This was coupled with a significant rise in hepatic cholesterol 7[alpha]-hydroxylase and a modest increase in hepatic LDL receptor. In contrast, OVX resulted in a mild elevation of plasma cholesterol and no significant changes in total hepatic HMG-CoA reductase, cholesterol 7[alpha]-hydroxylase, or LDL receptor in female SD rats. Thus the greater severity of hypercholesterolemia in the female NAR appears to be due, in part, to a combination of the constrained compensatory upregulation of cholesterol 7[alpha]-hydroxylase and LDL receptor deficiency. hyperlipidemia; hypercholesterolemia; nephrotic syndrome; proteinuria; low-density lipoprotein; hydroxymethylglutaryl-CoA reductase; bile acids

There is increasing evidence that poor early growth confers an increased risk of type 2 diabetes, hypertension, and other features of the metabolic syndrome in later life. We hypothesized that this may result from poor nutrition during early life exerting permanent effects on the structure and function of key metabolic organ systems. To study the long-term impact of early-life under-nutrition on susceptibility to visceral adiposity, we used a rat model of maternal protein restriction (MPR) in which dams were fed a low-protein diet (containing 8% instead of 20% protein in control diet) throughout pregnancy and lactation. MPR offspring were born smaller than controls (offspring of dams on control diet) and in adulthood developed visceral adiposity. We compared the pattern of gene expression in visceral adipose tissue (VAT) between MPR offspring and controls with Affymetrix rat expression arrays. Of the total number of genes and expressed sequence tags analyzed (15,923 probe sets), 9,790 (61.5%) were expressed in VAT. We identified 650 transcripts as differentially expressed [is greater than or equal to] 1.5-fold in the VAT of MPR offspring. Gene ontology analysis revealed a global upregulation of genes involved in carbohydrate, lipid, and protein metabolism. A number of genes involved in adipocyte differentiation, angiogenesis, and extracellular matrix remodeling were also upregulated. However, in marked contrast to other rodent models of obesity, the expression of a large number of genes associated with inflammation was reduced in this rat model. Thus visceral adiposity in this early-life programmed rat model is marked by dynamic changes in the transcriptional profile of VAT. Our data provide new insights into the molecular mechanisms that underlie the early-life programming of visceral adiposity. visceral adipose tissue; maternal protein restriction; DNA microarray

Epidemiologic data demonstrate a positive association between obesity and certain measures related to the metabolic syndrome that differ among individuals of different ethnic/racial backgrounds. The effect of genetic and environmental factors on these differences is not completely understood; however, insightful information can be obtained by taking into account the degree of ancestral admixture in populations. Key words: obesity, racial differences, genetic admixture

Mucolipidosis IV (MLIV) is an autosomal recessive disorder of unknown etiology characterized by severe visual impairment and psychomotor retardation. Recently, there has been considerable interest in positional cloning of the MLIV gene. It is unknown whether MLIV is a genetically homogenous disorder. In this paper, we present experiments that determined whether the MLIV phenotype in fibroblasts could be corrected by fusing normal cells to MLIV cells and fusing fibroblasts from pairs of patients. All of our MLIV patients fulfilled several diagnostic criteria that we developed. In addition, we found high sensitivity to chloroquine in cultured fibroblasts from MLIV patients. We found that normal cells corrected the MLIV phenotype. Fusion products of normal and MLIV fibroblasts, but not MLIV fibroblasts themselves, were relatively protected against chloroquine selection. In addition, 74% of the normal-to-patient fusion products had reduced levels or total loss of MLIV characteristic autofluorescence. However, there was no complementation of the phenotype in fibroblast cultures from any of our MLIV patients, including those of non-Jewish ancestry. In fusion products of MLIV cultures from 24 patients, 90-100% of the cells remained autofluorescent. These results indicate that all of our known MLIV patients, regardless of ancestry or severity of the developmental defect, have a single mutated gene.

Partial lipodystrophy (PLD), or Dunnigan-Kobberling syndrome, is a defect in regional depositing of adipose tissue. New data including conclusive evidence for linkage of the PLD locus to microsatellite markers on chromosome 1q21 and no evidence of heterogeneity are important for the effort to characterize and isolate the PLD gene. The syndrome is transmitted as a highly penetrant autosomal dominant disorder characterized by having no fat tissue in limbs and trunk areas and having fat retained on the face, at periserous sites, and in retro-orbital space. It is more evident in females than in males. Metabolic syndrome X is associated. A genomewide search was done with two multigeneration families with a total of 18 members. .

Two exon-skipping mutations appear to be the molecular basis of succinic semialdehyde dehydrogenase (SSADH) deficiency or 4-hydroxylbutyric aciduria. SSADH is a rare metabolic disorder of 4-aminobutyric acid degradation identified in about 150 patients. The found mutations alter highly conserved sequences at intron-exon boundaries and keep the RNA -splicing mechanism from recognizing the normal splice junction as it should. Each family segregated a mutation in a different splice site. Exon skipping was the result with a frameshift and premature termination in one case. In the other there was in-frame deletion in the resulting protein. Family members were heterozygotes for the splicing abnormality, evidence of autosomal recessive inheritance. Two point mutation in the SSADH genes derived from four patients were identified.

Smith-Lemli-Opitz syndrome (SLOS), also called RSH syndrome, is reviewed in relation to metabolic morphogenesis and the mutations involved. It is an autosomal recessive, multiple anomaly syndrome that is characterized by genital malformation in males, polydactyly, and craniofacial anomalies including cleft palate. Patients with this syndrome have an increased blood levels of 7-dehydrocholesterol (7DHC), increased by as much as a factor of 2,000. The molecule is the immediate precursor of cholesterol in the Kandutch-Russell cholesterol biosynthesis pathway. The clinical phenotype has been expanded and some near-normal children are included as well as some very defective fetuses that die before birth. Patients' lives are dramatically improved when the cholesterol-deficiency syndrome is treated. Other biochemically undiagnosed malformation syndromes will be investigated for disorders of cholesterol biosynthesis but mutations that bring many malformations have been those of of homeobox genes and other transcription regulators and signaling systems.

A European multicenter study of phenylalanine hydroxylase deficiency has led to a general system for prediction of metabolic phenotype based on genotype and to classification of 105 mutations. Mild hyperphenylalaninemia (MHP) and phenylketonuria (PKU) are allelic disorders caused by mutations in the gene coding for phenylalanine hydroxylase (PAH). Both mutations were found in 686 patients in seven locations in Europe. Based on the phenotypic characteristics of 297 functionally hemizygous patients, 105 of the mutations were assigned to one of four arbitrary phenotype categories. Data show that the PAH-mutation genotype is the primary determinant of metabolic phenotype in most PAH-deficiency patients. The disorder is autosomal recessive.

The role of a functionally silent nucleotide substitution in the sterol 27-hydroxylase gene (CYP 27) in alternative pre-mRNA splicing in patients with cerebrotendinous xanthomatosis (CTX) was investigated. Two Japanese families with CTX with three patients and five heterozygous carriers were used as samples in the experiment. Results show that silent nucleotide substitution leads to alternative pre-mRNA splicing by activating a cryptic 5' splice site at the mutant codon in CTX patients.

A pathological mutation has been reported for the first time in a nuclear complex I gene of the mitochondrial respiratory chain. Twenty complex I-deficient patients with multisystem disorders have been studied. For the human nuclear gene that encodes with 18-kD (AQDQ) subnuit of the mitochondrial respiratory chain complex I, an identified mutation, cDNA cloning, chromosomal localization have been reported. The gene of the cDNA has been mapped to chromosome 5. A homozygous 5-bp duplication was found in a complex I-deficient child with parents heterozygous for the mutation. The duplication was in the 18-kD cDNA and destroys a consensus phosphorylation site. The patient had normal muscle morphology and a surprisingly nonspecific fatal progressive phenotype and no increased lactate concentrations in body fluids. In 19 patients who were complex I-deficient, mutations were not found in the 18-kD gene.

Intrahepatic cholestasis of pregnancy (ICP), marked by elevated maternal serum bile acid levels, occurs in late pregnancy and is often associated with poor perinatal outcomes. In this issue of the [...]

Abstract Recent identification of the urate transporter in the kidney (URAT1, encoded by SLC22A12) led to the molecular elucidation of idiopathic renal hypouricemia, which is a predisposition toward exercise-induce acute [...]

Abstract Growth hormone insensitivity (GHI) has been attributable, classically, to mutations in the gene for the GH receptor. After binding to the GH receptor, GH initiates signal transduction through a [...]

Researchers have made advances recently that have led to greater understanding of the molecular and mutational basis of alkaptonuria, a well-known prototypic metabolic disorder that brings . Soon efforts will be made to treat the disorder using genetic engineering. Such efforts should be made with caution. It would not be an acceptable trade-off to get rid of some alkaptonuric problems in return for giving more serious metabolic problems, perhaps comeing from toxiciy of later tyrosine metabolites.

The amino acid transporter, induced in Xenopus oocytes by the cDNA isolate rBAT, functions as the gene responsible for cystinuria, a metabolic defect. rBAT is the first gene identified in amino acid transport disorder. This amino acid transporter is more representative of the cystinuria gene than theearlier discovered dipolar amino acids.

Free radical chain oxidation of highly oxidizable 7-dehydrocholesterol (7-DHC), initiated by 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), is performed in benzene and oxysterols derived from 7-DHC are isolated and characterized by NMR spectroscopy and mass spectroscopy. The studies have shown that the high reactivity of 7-DHC and the oxyterols generated from its peroxidation have played major roles in the pathogenesis of Smith-Lemli-Opitz syndrome, X-linked dominant chondrodysplasia punctata, and cerebrotendinous xanthomatosis, all of these being metabolic disorders characterized by an elevated level of 7-DHC.