Statistical method for testing the neutral mutation hypothesis by DNA polymorphism.

Metal ions are essential cofactors for a wealth of biological processes, including oxidative phosphorylation, gene regulation and free-radical homeostasis. Failure to maintain appropriate levels of metal ions in humans is a feature of hereditary haemochromatosis, disorders of metal-ion deficiency, and certain neurodegenerative diseases. Despite their pivotal physiological roles, however, there is no molecular information on how metal ions are actively absorbed by mammalian cells. We have now identified a new metal-ion transporter in the rat, DCT1, which has an unusually broad substrate range that includes Fe2+, Zn2+, Mn2+, Co2+, Cd2+, Cu2+, Ni2+ and Pb2+. DCT1 mediates active transport that is proton-coupled and depends on the cell membrane potential. It is a 561-amino-acid protein with 12 putative membrane-spanning domains and is ubiquitously expressed, most notably in the proximal duodenum. DCT1 is upregulated by dietary iron deficiency, and may represent a key mediator of intestinal iron absorption. DCT1 is a member of the 'natural-resistance-associated macrophage protein' (Nramp) family and thus its properties provide insight into how these proteins confer resistance to pathogens.

Cloning and characterization of a mammalian proton-coupled metal-ion transporter

Insulin sensitivity (euglycemic clamp, insulin infusion rate: 40 mU m(-2) min(-1)) was studied in 30 subjects with biopsy-proven nonalcoholic fatty liver disease (NAFLD), normal glucose tolerance, and a BMI <30 kg/m(2) Of those 30 subjects, 9 had pure fatty liver and 21 had evidence of steatohepatitis In addition, 10 patients with type 2 diabetes under good metabolic control and 10 healthy subjects were studied Most NAFLD patients had central fat accumulation, increased triglycerides and uric acid, and low HDL cholesterol, irrespective of BMI Glucose disposal during the clamp was reduced by nearly 50% in NAFLD patients, as well as in patients with normal body weight, to an extent similar to that of the type 2 diabetic patients Basal free fatty acids were increased, whereas insulin-mediated suppression of lipolysis was less effective (-69% in NAFLD vs -84% in control subjects; P = 0003) Postabsorptive hepatic glucose production (HGP), measured by [6,6-(2)H(2)]glucose, was normal In response to insulin infusion, HGP decreased by only 63% of basal in NAFLD vs 84% in control subjects (P = 0002) Compared with type 2 diabetic patients, NAFLD patients were characterized by lower basal HGP, but with similarly reduced insulin-mediated suppression of HGP There was laboratory evidence of iron overload in many NAFLD patients, but clinical, histological, and biochemical data (including insulin sensitivity) were not correlated with iron status Four subjects were heterozygous for mutation His63Asp of the HFE gene of familiar hemochromatosis We concluded that NAFLD, in the presence of normoglycemia and normal or moderately increased body weight, is characterized by clinical and laboratory data similar to those found in diabetes and obesity NAFLD may be considered an additional feature of the metabolic syndrome, with specific hepatic insulin resistance

/pdf/nonalcoholic-fatty-liver-disease-a-feature-of-the-metabolic-tls3hey2y6.pdf

Nonalcoholic fatty liver disease a feature of the metabolic syndrome

Observational epidemiological studies suffer from many potential biases, from confounding and from reverse causation, and this limits their ability to robustly identify causal associations. Several high-profile situations exist in which randomized controlled trials of precisely the same intervention that has been examined in observational studies have produced markedly different findings. In other observational sciences, the use of instrumental variable (IV) approaches has been one approach to strengthening causal inferences in non-experimental situations. The use of germline genetic variants that proxy for environmentally modifiable exposures as instruments for these exposures is one form of IV analysis that can be implemented within observational epidemiological studies. The method has been referred to as 'Mendelian randomization', and can be considered as analogous to randomized controlled trials. This paper outlines Mendelian randomization, draws parallels with IV methods, provides examples of implementation of the approach and discusses limitations of the approach and some methods for dealing with these.

/pdf/mendelian-randomization-using-genes-as-instruments-for-2tocar3o2g.pdf

Mendelian randomization: using genes as instruments for making causal inferences in epidemiology.

Iron has the capacity to accept and donate electrons readily, interconverting between ferric (Fe2+) and ferrous (Fe3+) forms. This capability makes it a useful component of cytochromes, oxygen-bind...

Disorders of iron metabolism.

The human lecithin-cholesterol acyltransferase (LCAT) gene has been sequenced to completion. The gene is divided into six exons spanning approximately 4,200 bp. Exon five codes for amino acids homologous to the interfacial active site of several lipases, and also codes for an amphipathic alpha-helix resembling the carboxy terminus of apolipoprotein E. Blot hybridization data suggest that there is only one LCAT gene in humans. The 1550 base LCAT mRNA can be detected in liver and HepG2 (hepatocyte) cells, but not in small intestine, spleen, pancreas, placenta or adrenal tissue.

Human lecithin-cholesterol acyltransferase gene: complete gene sequence and sites of expression

Multiple RFLPs at the human cholesteryl ester transfer protein (CETP) locus.

Genetic linkage between lipoprotein(a) phenotype and a DNA polymorphism in the plasminogen gene.

Phenotypic evidence indicates that the ability to taste the bitter compounds phenylthiocarbamide (PTC) and 6-n-propylthiouracil (PROP) may protect against cigarette smoking. In this study, PTC gene haplotypes were found to be associated with both the odds of being a smoker and the importance of cigarette taste as a smoking motive. Smokers (n = 384) and nonsmokers (n = 183) were genotyped for polymorphisms that affect taste sensitivity to PTC and PROP. The "taster" PAV haplotype, relative to the "nontaster" AVI haplotype, was predicted to be associated with reduced odds of being a smoker and lower taste motivation as measured by the Wisconsin Inventory of Smoking Dependence Motives-68 taste/sensory processes scale. The results did not support the predicted association between the PAV and AVI haplotypes and smoker odds, but the AAV haplotype, which confers intermediate PTC/PROP taste sensitivity, was associated with reduced smoker prevalence (49% vs. 70%), chi(2)(1, N = 567) = 10.392, p = .001. The predicted relationship between PAV and AVI and taste motivation was found, F(2, 348) = 3.303, p = .038. The results encourage further exploration of the role of taste/sensory processes in tobacco dependence.

/pdf/associations-between-phenylthiocarbamide-gene-polymorphisms-jpxyxsk02w.pdf

Associations Between Phenylthiocarbamide Gene Polymorphisms and Cigarette Smoking

We performed a linkage study of stuttering using 392 markers distributed across the genome in a series of 68 families identified in the general outbred population of North America and Europe. Standardized diagnosis was performed using recorded samples of both conversation and reading, in which stuttering dysfluencies were scored as percentage of dysfluent words and syllables. Analysis was first performed using non-parametric methods implemented in GENEHUNTER, where we obtained maximum statistical support for markers of chromosome 18, with a maximum NPL (Sall) of 1.51 at D18S976. The single largest pedigree within our sample (pedigree 0006) alone gave an NPL of 4.72 at D18S976. For fine mapping, we analyzed 18 markers on chromosome 18 across all families using ALLEGRO. Overall NPL (Srobdom) scores >5 were obtained with markers on 18p, and Z(lr) scores >/=2.5 on 18p and proximal 18q. Furthermore, pedigree 0006 alone gave an NPL (Srobdom) of 5.35. Overall our results suggest chromosome 18 may harbor a predisposing locus for this disorder, and additional genes may exist.

Dennis Drayna

Papers

Human lecithin-cholesterol acyltransferase gene: complete gene sequence and sites of expression

Multiple RFLPs at the human cholesteryl ester transfer protein (CETP) locus.

Genetic linkage between lipoprotein(a) phenotype and a DNA polymorphism in the plasminogen gene.

Associations Between Phenylthiocarbamide Gene Polymorphisms and Cigarette Smoking

Results of a genome-wide linkage scan for stuttering.