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Biomedical subjects

I C Roberts-Thomson

Publications and source records attributed to I C Roberts-Thomson.

At least 37 records · Page 2Linked to original sources
PubMed2003

CARD15/NOD2 risk alleles in the development of Crohn's disease in the Australian population.

We have previously reported strong evidence for linkage between IBD1 and Crohn's disease (CD) in Australian Crohn's disease families. Three risk alleles for Crohn's disease, (Arg702Trp (C/T), Gly908Arg (G/C) and 980fs981 (-/C), were recently identified in the CARD15/NOD2 gene on chromosome 16, implicating this as the IBD1 locus. Using a novel diagnostic PCR-RFLP, we have examined the frequency of these alleles in 205 multiplex IBD families, 107 sporadic Crohn's disease cases and 409 normal individuals. We demonstrate that the three risk alleles are more frequent in Crohn's disease, than in controls, with allelic frequencies of 0.11, 0.02 and 0.07 respectively. Heterozygosity for individual variants conferred a three-fold increase in risk for Crohn's disease while substantially higher risks were associated with being homozygous or compound heterozygous. Despite a significantly lower population allele frequency for the frameshift mutation than reported by other groups, we see a similar contribution by this allele to the risk of developing Crohn's disease. While the three risk alleles influence susceptibility to Crohn's disease in Australia, we show that these alleles do not fully explain the linkage evidence and suggest that there are very likely additional IBD1 susceptibility alleles yet to be described in Australian CD at the NOD2 locus. We also show a second linkage peak in Australian CD that provides some support for a second disease susceptibility locus on chromosome 16.

Alleles↗
PubMed2001

Metabolic genotypes and risk for colorectal cancer.

BACKGROUND: Inherited polymorphisms that influence carcinogen metabolism or the composition of bile may influence the risk for the development of colorectal cancer. METHODS: The frequency of polymorphisms involving N-acetyltransferase 1 (NAT1), NAT2, cytochrome P450 1A1 (CYP1A1), CYP2D6, CYP2E1, glutathione S-transferase M1 (GSTM1), GSTT1 and apolipoprotein E were compared in 219 white adults with sporadic colorectal cancer and 200 white controls attending for blood donation at a blood bank. Polymorphisms were determined by using restriction fragment length polymorphism (RFLP) after amplification of genomic DNA by polymerase chain reaction (PCR). Data were analyzed by using standard statistical methods for a case- control study, and reported as odds ratios (OR) with 95% confidence intervals (CI). RESULTS: None of the genotypes, either alone or in combination, showed a strong association with colorectal cancer. Inheritance of the GSTT1 null genotype conferred a twofold risk of cancer that was statistically significant with crude data (OR 2.18; 95% CI 1.38-3.43), but not after adjustment for age (OR 1.91; 95% CI 0.99-3.70). There was also a trend towards a lower risk for proximal (right-sided) cancers in patients with apolipoprotein epsilon4 (OR 0.64; 95% CI 0.31-1.33). CONCLUSION: No strong associations have been found between metabolic genotypes and colorectal cancer risk in Australia. Large studies will be required to confirm weak associations and to establish relationships between cancer risk, metabolic genotypes and exposure to dietary or other environmental carcinogens.

Acetyltransferases↗
PubMed2001

The role of small intestinal bacterial overgrowth, intestinal permeability, endotoxaemia, and tumour necrosis factor alpha in the pathogenesis of non-alcoholic steatohepatitis.

BACKGROUND: Small intestinal bacterial overgrowth may contribute to the development of non-alcoholic steatohepatitis, perhaps by increasing intestinal permeability and promoting the absorption of endotoxin or other enteric bacterial products. AIMS: To investigate the prevalence of small intestinal bacterial overgrowth, increased intestinal permeability, elevated endotoxin, and tumour necrosis factor alpha (TNF-alpha) levels in patients with non-alcoholic steatohepatitis and in control subjects. PATIENTS AND METHODS: Twenty two patients with non-alcoholic steatohepatitis and 23 control subjects were studied. Small intestinal bacterial overgrowth was assessed by a combined (14)C-D-xylose and lactulose breath test. Intestinal permeability was assessed by a dual lactulose-rhamnose sugar test. Serum endotoxin levels were determined using the limulus amoebocyte lysate assay and TNF-alpha levels using an ELISA. RESULTS: Small intestinal bacterial overgrowth was present in 50% of patients with non-alcoholic steatosis and 22% of control subjects (p=0.048). Mean TNF-alpha levels in non-alcoholic steatohepatitis patients and control subjects were 14.2 and 7.5 pg/ml, respectively (p=0.001). Intestinal permeability and serum endotoxin levels were similar in the two groups. CONCLUSIONS: Patients with non-alcoholic steatohepatitis have a higher prevalence of small intestinal bacterial overgrowth, as assessed by the (14)C-D-xylose-lactulose breath test, and higher TNF-alpha levels in comparison with control subjects. This is not accompanied by increased intestinal permeability or elevated endotoxin levels.

Adult↗