Glucose-6-phosphate dehydrogenase deficiency in Tunisia: molecular data and phenotype-genotype association

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common human enzyme defect. In this study, we aimed to perform a molecular investigation of G6PD deficiency in Tunisia and to associate clinical manifestations and the degree of deficiency with the genotype. A total of 161 Tunisian subjects of both sexes were screened by spectrophotometric assay for enzyme activity. Out of these, 54 unrelated subjects were selected for screening of the most frequent mutations in Tunisia by PCR/RFLP, followed by size-based separation of double-stranded fragments under non-denaturing conditions on a denaturing high performance liquid chromatography system. Of the 56 altered chromosomes examined, 75 % had the GdA(-) mutation, 14.28 % showed the GdB(-) mutation and no mutations were identified in 10.72 % of cases. Hemizygous males with GdA(-) mutation were mostly of class III, while those with GdB(-) mutation were mainly of class II. The principal clinical manifestation encountered was favism. Acute hemolytic crises induced by drugs or infections and neonatal jaundice were also noted. Less severe clinical features such as low back pain were present in heterozygous females and in one homozygous female. Asymptomatic individuals were in majority heterozygote females and strangely one hemizygous male. The spectrum of mutations seems to be homogeneous and similar to that of Mediterranean countries; nevertheless 10.72 % of cases remain with undetermined mutation thus suggesting a potential heterogeneity of the deficiency at the molecular level. On the other hand, we note a better association of the molecular defects with the severity of the deficiency than with clinical manifestations.

Chromosomal mapping of pancreatic islet morphological features and regulatory hormones in the spontaneously diabetic (Type 2) Goto-Kakizaki rat

Insulin resistance and altered endocrine pancreas function are central pathophysiological features of type 2 diabetes mellitus (T2DM). The Goto-Kakizaki (GK) rat is a model of spontaneous T2DM characterised by reduced beta cell mass and genetically determined glucose intolerance and altered insulin secretion. To identify genetic determinants of endocrine pancreas histopathology, we carried out quantitative trait locus (QTL) mapping of histological phenotypes (beta cell mass -BCM and insulin-positive cell area -IPCA) and plasma concentration of hormones and growth factors in a F2 cohort derived from GK and normoglycemic Brown Norway rats. Although IPCA and BCM in the duodenal region of the pancreas were highly positively correlated (P < 10⁻⁶), and similarly in the splenic region, both measures were poorly correlated when comparing duodenal and splenic phenotypes. Strongest evidence of linkage to pancreas morphological traits was obtained between BCM and chromosome 10 (LOD 3.2). Evidence of significant linkage (LOD 4.2) to plasma corticosterone was detected in a region of chromosome 1 distal to other QTLs previously identified in the GK. Male-specific genetic effects were detected, including linkages (LOD > 4) to growth hormome (GH) on chromosome 6 and prolactin on chromosome 17. These data suggest independent genetic control of the structure and function of ontologically different regions of the endocrine pancreas. Novel QTLs for corticosterone, prolactin and GH may contribute to diabetes in the GK. The QTLs that we have identified in this, and previous genetic studies collectively underline the complex and multiple mechanisms involved in diabetes in the GK strain.

S26948, a new specific peroxisome proliferator activated receptor gamma modulator improved in vivo hepatic insulin sensitivity in 48 h lipid infused rats

We examined whether S26948, a new specific peroxisome proliferator activated receptor gamma modulator prevented insulin-resistance induced by a 48 h intralipid-infusion in normal rat (IL rats). The effect of S26948 (30 mg/kg) was compared to rosiglitazone (10 mg/kg). Rats were catheterized in the right jugular vein 4 days before the beginning of the 48 h lipid or saline infusions. Animals were intraperitoneally injected once daily with vehicle, S26948 or rosiglitazone. At the end of the infusion the rats underwent either a glucose tolerance test or a euglycemic-hyperinsulinemic clamp. Finally isolation and incubation of hepatocytes in another series of rats were performed. Intralipid infusion leads to a 4-fold increase in plasma free fatty acid concentration compared to controls (C). Both S26948 and rosiglitazone decreased plasma free fatty acid concentration in IL rats compared to vehicle treated IL rats. Glucose-induced insulin secretion was significantly increased in IL compared to C and was associated with insulin resistance. Both S26948 and rosiglitazone treatments normalized glucose-induced insulin secretion and improved insulin action in IL rats. However, S26948 specifically improved hepatic insulin sensitivity whereas rosiglitazone improved both hepatic insulin sensitivity and insulin-stimulated glucose utilization. Finally, studies on isolated hepatocytes showed differential effect of both compounds on gene expression of key enzymes of glucose metabolism. Our data show that non thiazolidinedione S26948 may represent an alternative way for the management of dysregulated hepatic insulin sensitivity.

Genetic control of plasma lipid levels in a cross derived from normoglycaemic Brown Norway and spontaneously diabetic Goto-Kakizaki rats

AIMS/HYPOTHESIS

Dyslipidaemia is a main component of the insulin resistance syndrome. The inbred Goto-Kakizaki (GK) rat is a model of spontaneous type 2 diabetes and insulin resistance, which has been used to identify diabetes-related susceptibility loci in genetic crosses. The objective of our study was to test the genetic control of lipid metabolism in the GK rat and investigate a possible relationship with known genetic loci regulating glucose homeostasis in this strain.

MATERIALS AND METHODS

Plasma concentration of triglycerides, phospholipids, total cholesterol, HDL, LDL and VLDL cholesterol were determined in a cohort of 151 hybrids of an F2 cross derived from GK and non-diabetic Brown Norway (BN) rats. Data from the genome-wide scan of the F2 hybrids were used to test for evidence of genetic linkage to the lipid quantitative traits.

RESULTS

We identified statistically significant quantitative trait loci (QTLs) that control the level of plasma phospholipids and triglycerides (chromosome 1), LDL cholesterol (chromosome 3) and total and HDL cholesterol (chromosomes 1 and 5). These QTLs do not coincide with previously identified diabetes susceptibility loci in a similar cross. The significance of lipid QTLs mapped to chromosomes 1 and 5 is strongly influenced by sex.

CONCLUSION/INTERPRETATION

We established that several genetic loci control the quantitative variations of plasma lipid variables in a GKxBN cross. They appear to be distinct from known GK diabetes QTLs, indicating that lipid metabolism and traits directly relevant to glucose and insulin regulation are controlled by different gene variants in this strain combination.

[Difference albumin-transferrin interest in the iron deficiency detection in a cohort of 1288 schoolchildren in the district of Tunis]

Iron deficiency (ID) is the most common nutritional deficiency worldwide especially among young children, women in pregnancy and breastfeeding. This study was undertaken to assess the prevalence of ID in 1288 pupil ranging in age from 11 to 14 years. Haemoglobin (Hb), mean corpuscular volume (MCV), mean corpuscular Hb (MCH), serum iron (Fe) serum transferrin (Trf), serum ferritin (Ft) and an inflammtory proteic profil (IPP) were measured. The IPP combines the analysis of protein variations: protein results are converted in percent of normal values referenced for the technique used. It has been suggested that on the protein profile, an increase in serum transferrin level compared to a normal serum albumin level (DAT: difference albumin-transferrin), appears early in the course of ID. Iron deficiency was defined by a low serum ferritin (< 15 ng/mL) and/or a pathologic DAT (> 28%). Approximately, 33.8% of children had Ft < 15 ng/mL and 12,8% had DAT > 28% while ferritin values were in the normal range. Diagnosis performance (sensitivity, specificity and diagnosis efficacy) of ferritin and DAT were compared to the performance of high serum transferrin receptor (sTfR) values in 2 populations presenting or not a biological inflammation. Only the diagnosis efficacy of DAT was constant in both situations. In conclusion, the serum ferritin concentration is the first indicator of body storage iron identifying ID, however normal or elevated values of ferritin may be difficult to interpret particulary in the presence of inflammation. sTfR and DAT values are thus reliable indicators of ID in such circumstances.

[Children's accidents in rural environment: study of 324 cases]

The child's accidents constitute a problem of public health. The purpose of our work is to study the epidemiological factors and peculiarities of the accident at the child in a farming locality (locality of Jbeniana). The survey is made to the service of Emergencies of the Regional hospital of Jbeniana on one year (of May 2000 to April 2001). 324 cases of accidents at children of lower or equal age to 14 years have been counted. Our set is constituted of 246 boys (76%) and 78 girls (24%). In 1/3 of cases age is included between 2 and 5 years, in_of cases between 6 and 10 years. The domestic accident represents the most frequent circumstance (72% of cases), follow-up of circulation accidents (12.9%), falls represents the most frequent domestic accident mechanism (38%). In 57% of circulation accidents, the child is a passenger or driver of two-wheeled vehicle. Lesion balance shows that in 47.2% of cases the child presents superficial lesions. A badly adapted environment is found in 31.4% of cases. A failing of the setting is noted in 44% of cases. The prevention to be efficient should take into account of the inherent measurements to the accident (environment, cultural and psychological factors).

Effects of fatty acids on mitochondrial beta-oxidation enzyme gene expression in renal cell lines

Regulatory effects of fatty acids on gene expression of medium-chain acyl-CoA dehydrogenase (MCAD), a mitochondrial beta-oxidation enzyme, were investigated in rabbit kidney cell lines derived from proximal tubule (RC.SV1), thick ascending limb of Henle's loop (RC.SV2), or collecting duct (RC.SV3). Exposure to long-chain fatty acids led to significant increases (2-fold) in MCAD mRNA abundance in RC.SV1 and RC.SV2 cells; kinetics and dose-response studies established that maximal MCAD gene stimulation was reached 4 h after addition of 50 microM oleate (C18:1) in the culture medium. These effects of fatty acids were totally abolished in the presence of 1 microg/ml actinomycin D, a transcription inhibitor. Staining of cellular lipids revealed that fatty acid-induced gene stimulation could occur in the absence of cellular fatty acid accumulation. Altogether, these data indicate that small changes in cellular fatty acid flux can have direct short-term effects on fatty acid oxidation enzyme gene expression in renal cells, and this might take part in the regulation of cellular fatty acid homeostasis in response to changes in tubular fluid composition.

Regulation of fatty acid transport protein and mitochondrial and peroxisomal beta-oxidation gene expression by fatty acids in developing rats

Regulation of genes involved in fatty acid (FA) utilization in heart and liver of weanling rats was investigated in response to variations in dietary lipid content and to changes in intracellular FA homeostasis induced by etomoxir, a blocker of FA import into mitochondria. Northern-blot analyses were performed using cDNA probes specific for FA transport protein, a cell membrane FA transporter; long-chain- and medium-chain acyl-CoA dehydrogenases, which catalyze the first step of mitochondrial FA beta-oxidation; and acyl-CoA oxidase, a peroxisomal FA beta-oxidation marker. High-fat feeding from postnatal d 21 to 28 resulted in a coordinate increase (58 to 136%) in mRNA abundance of all genes in heart. In liver, diet-induced changes in mitochondrial and peroxisomal beta-oxidation enzyme mRNAs (from 52 to 79%) occurred with no change in FA transport protein gene expression. In both tissues, the increases in mRNA levels went together with parallel increases in enzyme activity. Changes in FA homeostasis resulting from etomoxir administration led to a marked stimulation (76 to 180%) in cardiac expression of all genes together with parallel increases in enzyme activities. In the liver, in contrast, etomoxir stimulated the expression of acyl-CoA oxidase gene only. Feeding rats a low-fat diet containing 0.5% clofibrate, a ligand of peroxisome proliferator-activated receptor alpha, resulted in similar inductions of beta-oxidation enzyme genes in both tissues, whereas up-regulation of FA transport protein gene was restricted to heart. Altogether, these data suggest that changes in FA homeostasis in immature organs resulting either from high-fat diet or beta-oxidation blockade can efficiently be transduced to the level of gene expression, resulting in tissue-specific adaptations in various FA-using enzymes and proteins.

Dietary lipids regulate beta-oxidation enzyme gene expression in the developing rat kidney

This study examines the ability of dietary lipids to regulate gene expression of mitochondrial and peroxisomal fatty acid beta-oxidation enzymes in the kidney cortex and medulla of 3-wk-old rats and evaluates the role of glucagon or of the alpha-isoform of peroxisome proliferator-activated receptor (PPARalpha) in mediating beta-oxidation enzyme gene regulation in the immature kidney. The long-chain (LCAD) and medium-chain acyl-CoA dehydrogenases (MCAD) and acyl-CoA oxidase (ACO) mRNA levels were found coordinately upregulated in renal cortex, but not in medulla, of pups weaned on a high-fat diet from day 16 to 21. Further results establish that switching pups from a low- to a high-fat diet for only 1 day was sufficient to induce large increases in cortical LCAD, MCAD, and ACO mRNA levels, and gavage experiments show that this upregulation of beta-oxidation gene expression is initiated within 6 h following lipid ingestion. Treatment of pups with clofibrate, a PPARalpha agonist, demonstrated that PPARalpha can mediate regulation of cortical beta-oxidation enzyme gene expression, whereas glucagon was found ineffective. Thus dietary lipids physiologically regulate gene expression of mitochondrial and peroxisomal beta-oxidation enzymes in the renal cortex of suckling pups, and this might involve PPARalpha-mediated mechanisms.