In the postprandial state, insulin may also control NEFA appearance through enhanced trapping into the adipose tissue of NEFA derived from intravascular triglyceride lipolysis. To determine the contribution of suppression of intracellular lipolysis in the modulation of plasma NEFA metabolism by insulin during enhanced intravascular triglyceride lipolysis, 10 healthy nonobese subjects underwent pancreatic clamps at fasting vs. high physiological insulin level with intravenous infusion of heparin plus Intralipid. Nicotinic acid was administered orally during the last 2 h of each 4-h clamp to inhibit intracellular lipolysis and assess insulin's effect on plasma NEFA metabolism independently of its effect on intracellular lipolysis. Stable isotope tracers of palmitate, acetate, and glycerol were used to assess plasma NEFA metabolism and total triglyceride lipolysis in each participant. The glycerol appearance rate was similar during fasting vs. high insulin level, but plasma NEFA levels were significantly lowered by insulin. Nicotinic acid significantly blunted the insulin-mediated suppression of plasma palmitate appearance and oxidation rates by ϳ60 and ϳ70%, respectively. In contrast, nicotinic acid did not affect the marked stimulation of palmitate clearance by insulin. Thus most of the insulin-mediated reduction of plasma NEFA appearance and oxidation can be explained by suppression of intracellular lipolysis during enhanced intravascular triglyceride lipolysis in healthy humans. Our results also suggest that insulin may affect plasma NEFA clearance independently of the suppression of intracellular lipolysis. intracellular lipolysis; lipid oxidation; postprandial state; lipid metabolism

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We screened urine for chemical individuality in over 1 million newborn infants, by various chromatographic (thin-layer), chemical and spectrophotometric methods, 12 procedures in all. The programme is part of the Quebec Network of Genetic Medicine. Voluntary urine screening began in 1971 and has evolved with changes in choice of tests and times of sample collection. Urine samples were collected on filter paper at either 5, 14 or 21 days after birth; results were best with the 21-day test. Compliance is over 94% with the latter and over 98% with requests for repeat samples. Screening is centralized in one laboratory; follow-up diagnosis, counselling and management are done at four regional centres. Incidence of phenotypes ranged from 1:4300 live births (for expressed cystinuria alleles) to 1 per million (for hyperargininaemia). Over 20 inherited Mendelian disorders were identified. 30 patients required aggressive medical management. We show how this programme can be used for neuroblastoma screening.

A decrease in the formation/secretion of bile has been well documented in animals on total parenteral nutrition (TPN). Either an excess or an imbalance of amino acids (AA) has been most often implicated. In view of recent work showing that taurine promotes bile flow, bile acid secretion, and protects against hepatotoxic bile acids, the effect of adding taurine (15 mg/dL) to an AA solution was examined in guinea pigs on TPN for 3 days. The TPN-taurine group had a larger bile flow than the group without taurine and had bile acid secretory rates (BASR) similar to those of controls who were on saline by central catheter and had free access to food. Bile composition showed an increase in the secondary bile acid, 7-ketolithocholate and a concomitant decrease in chenodeoxycholate (CDC) in both experimental groups. Taurine led to a reversal of the usual predominance of glycine over taurine conjugated bile acids as well as to increases in HCO3 in cholesterol secretion. In response to a challenge with a large load of CDC, the TPN-taurine animals increased their BASR beyond those observed in the two other groups. These observations suggest that the addition of taurine to TPN solutions could play a role in the prevention of altered biliary function associated with AA solutions.

Insulin increases plasma nonesterified fatty acid (NEFA) clearance in humans, but whether this is independent of change in plasma NEFA appearance is currently unknown. Nine nondiabetic men (age: 28 Ϯ 3 yr, body mass index: 27.2 Ϯ 1.7 kg/m 2 ) underwent euglycemic clamps to maintain low (LINS) vs. high (HINS) physiological insulin levels for 6 h. An intravenous infusion of heparin ϩ Intralipid (HI) was performed during 4 of the 6 h of the clamps (in the last 4 h at LINS and in the first 4 h at HINS), whereas saline infusion (SAL) was administered in the remaining 2 h to modulate plasma NEFA levels independently of plasma insulin levels. Four experimental conditions were obtained in each individual: LINS with saline (LINS/SAL) and with HI infusion (LINS/HI) and HINS with saline (HINS/SAL) and with HI infusion (HINS/HI). Plasma palmitate appearance during HINS/SAL was lower than during the three other experimental conditions (P Ͻ 0.05). In contrast, plasma linoleate appearance, as expected, was increased by HI independently of insulin level (P Ͻ 0.02). Plasma palmitate clearance during HINS/SAL was higher than LINS/SAL and LINS/HI (P Ͻ 0.008), and this increase was blunted during HINS/HI. We observed a linear decrease in plasma palmitate clearance with increasing plasma NEFA appearance independent of insulin levels. Plasma NEFA levels increased exponentially with increase in plasma NEFA appearance. We conclude that insulin stimulates plasma NEFA clearance by reducing the endogenous appearance rate of NEFA. The relationship between plasma NEFA level and appearance rate is nonlinear.human; insulin action; lipid metabolism; fatty acid metabolism UNDERSTANDING THE REGULATION of plasma nonesterified fatty acid (NEFA) is very important to elucidate its potential role in the development of various pathological conditions, including type 2 diabetes (27). Prolonged experimental elevation of plasma NEFA in humans reproduces the cardinal pathophysiological features of type 2 diabetes, including reduced insulinmediated glucose utilization, impaired glucose-mediated insulin secretion, and increased endogenous glucose production (10, 36, 39). Epidemiological studies have linked elevated plasma NEFA levels to insulin resistance and type 2 diabetes (15,26,35), and reduced suppression of postprandial plasma NEFA concentration is among the earliest metabolic abnormalities seen in the natural history of type 2 diabetes (3).Insulin potently suppresses plasma NEFA appearance. It is often assumed that plasma NEFA level is an accurate reflection of plasma NEFA appearance rate in various physiological and pathophysiological conditions known to affect plasma NEFA levels through change in plasma insulin level, i.e., that plasma NEFA clearance does not change with changing levels of plasma insulin. However, this may not necessarily be the case, because insulin has been shown to stimulate NEFA transport across plasma cell membranes (6). Elevation of plasma insulin level was associated with enhanced plasma NEFA clearance in human studies durin...

Amniocentesis was performed at 17.3 weeks in a pregnancy with severe intrauterine growth retardation. Cytogenetic studies on amniocytes were normal, 46,XX, and the pregnancy was continued. The diagnosis of Smith-Lemli-Opitz syndrome was suspected in the neonatal period and confirmed by the presence of 7-dehydrocholesterol (7-DHC) in the plasma (0.4 mmol/l, normal = not detectable) associated with a low total cholesterol concentration (0.4 mmol/l, normal = 2.56 +/- 0.23). Retrospective analysis of the amniotic fluid sample revealed an elevated level of 7-DHC (0.022 mmol/l; normal = undetectable). Therefore measurement of 7-DHC levels in amniotic fluid during the second trimester of pregnancy is useful for the prenatal diagnosis of Smith-Lemli-Opitz syndrome in families at risk and should be considered in cases of severe growth retardation of unknown aetiology for which amniotic fluid is available and in which a normal chromosomal pattern in amniocytes is present.

Fabry disease is an X-linked lysosomal storage disorder of glycosphingolipid catabolism resulting from a deficiency of the enzyme alpha-galactosidase A, and leading to the progressive accumulation of one biomarker, globotriaosylceramide (Gb(3)), predominantly elevated in the urine of these patients. We have developed a technique for the analysis of total Gb(3) in urine samples collected on filter paper, using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with a triple quadrupole instrument. Existing Gb(3) techniques being both time- and labour-intensive, this filter paper method eliminates lipid extraction, glycolipid isolation, centrifugation and evaporation steps, while maintaining sensitivity and efficiency. The stability of Gb(3) on filter paper was good for a 7-week period under different temperature conditions. Normal control values were established and the technique was tested with anonymized samples from Fabry hemizygotes and heterozygotes. The levels of total Gb(3) in all classical hemizygotes were well above the control values and all heterozygotes, except two nonexcretors, were above the reference level. The proposed novel filter paper method favours the collection, storage and shipment of samples. It is simple and efficient for a feasibility study, potentially applicable to the determination of total urinary Gb(3) in the newborn population as part of a screening programme, and could also be used in high-risk screening laboratories. Since the incidence of Fabry disease is hard to establish, owing to the heterogeneous clinical expression of the visible phenotype, this feasibility study could help determine its actual incidence in the Quebec population.

Hartnup disorder is an autosomal recessive impairment of amino acid transport in kidney and intestine. Mutations in SLC6A19 have been shown to cosegregate with the disease in the predicted recessive manner; however, in two previous studies (Seow et al., Nat Genet 2004;36:1003-1007; Kleta et al., Nat Genet 2004;36:999-1002), not all causative alleles were identified in all affected individuals, raising the possibility that other genes may contribute to Hartnup disorder. We have now investigated six newly acquired families of Australian and Canadian (Province of Quebec) origin and resequenced the entire coding region of SLC6A19 in families with only a single disease allele identified. We also studied one American family in whom no mutations had been identified in a previous study (Kleta et al., Nat Genet 2004;36:999-1002). We have identified seven novel mutations in SLC6A19 that show functional obliteration of the protein in vitro, explaining Hartnup disorder in all reported families so far. We demonstrate that Hartnup disorder is allelically heterogeneous with two mutated SLC6A19 alleles, whether identical or not, necessary for manifestation of the characteristic aminoaciduria in affected individuals. This study resolves the previous hypothesis that other genes contribute to the Hartnup phenotype.