Interleukin-6, Diabetes, and Metabolic Syndrome in a Biracial Cohort: The Reasons for Geographic and Racial Differences in Stroke Cohort

OBJECTIVE

Black Americans have a greater risk of type 2 diabetes than White Americans. The proinflammatory cytokine interleukin-6 (IL-6) is implicated in diabetes pathogenesis, and IL-6 levels are higher in Black individuals. This study investigated associations of IL-6 with incident diabetes and metabolic syndrome in a biracial cohort.

RESEARCH DESIGN AND METHODS

The Reasons for Geographic and Racial Differences in Stroke (REGARDS) study enrolled 30,239 Black and White adults age ≥45 years in 2003-2007, with a follow-up ∼9.5 years later. Baseline plasma IL-6 was measured in 3,399 participants at risk of incident diabetes and 1,871 at risk of metabolic syndrome. Relative risk (RR) by IL-6 was estimated with modified Poisson regression for both groups.

RESULTS

Incident diabetes occurred in 14% and metabolic syndrome in 20%; both rates rose across IL-6 quartiles. There was a three-way interaction of IL-6, race, and central adiposity for incident diabetes (P = 8 × 10-5). In Black participants with and without central adiposity, RRs were 2.02 (95% CI 1.00-4.07) and 1.66 (1.00-2.75) for the fourth compared with first IL-6 quartile, respectively. The corresponding RRs were 1.73 (0.92-3.26) and 2.34 (1.17-4.66) in White participants. The pattern was similar for IL-6 and metabolic syndrome.

CONCLUSIONS

Although IL-6 was higher in Black than in White participants and those with central adiposity, the association of IL-6 with diabetes risk was statistically significant only among White participants without central adiposity. The association with metabolic syndrome risk was similarly stronger in low-risk groups. The results support the concept of interventions to lower inflammation in diabetes prevention, but to reduce race disparities, better biomarkers are needed.

Gene-flow between populations of cotton bollworm Helicoverpa armigera (Lepidoptera: Noctuidae) is highly variable between years

Both large and small scale migrations of Helicoverpa armigera Hübner in Australia were investigated using AMOVA analysis and genetic assignment tests. Five microsatellite loci were screened across 3142 individuals from 16 localities in eight major cotton and grain growing regions within Australia, over a 38-month period (November 1999 to January 2003). From November 1999 to March 2001 relatively low levels of migration were characterized between growing regions. Substantially higher than average gene-flow rates and limited differentiation between cropping regions characterized the period from April 2001 to March 2002. A reduced migration rate in the year from April 2002 to March 2003 resulted in significant genetic structuring between cropping regions. This differentiation was established within two or three generations. Genetic drift alone is unlikely to drive genetic differentiation over such a small number of generations, unless it is accompanied by extreme bottlenecks and/or selection. Helicoverpa armigera in Australia demonstrated isolation by distance, so immigration into cropping regions is more likely to come from nearby regions than from afar. This effect was most pronounced in years with limited migration. However, there is evidence of long distance dispersal events in periods of high migration (April 2001-March 2002). The implications of highly variable migration patterns for resistance management are considered.

Can a signal sequence become too hydrophobic?

We have characterized several mutants that contain alterations in the hydrophilic domain (N region) of the pseudorabies virus glycoprotein gC signal sequence. In general, our results agree with previous findings and indicate that basic residues in the N region are not essential for efficient export of gC in infected cells. While reducing the N region to a net neutral charge led to a slight impairment of membrane translocation, a substantial gC export defect was not observed until a net negative charge was introduced. However, there was one exception to this pattern. The substitution of a leucine for an arginine at the carboxyl terminus of the N region led to a considerable export defect despite maintaining a net positive charge. As a consequence of the substitution, the mutant signal sequence was 1.5 times more hydrophobic than wild type, but we found that the defect could be largely corrected if an additional alteration that lessened the overall hydrophobicity of the gC signal sequence was incorporated. We suggest that an upper limit of hydrophobicity may exist for eukaryotic signal sequences; exceeding this value could lead to an export defect.

Characterization of the prv43 gene of pseudorabies virus and demonstration that it is not required for virus growth in cell culture

We have determined the complete DNA sequence of the prv43 gene of a swine herpesvirus, pseudorabies virus. prv43 is 1119 bp in length with a G+C content of 74.5% and is predicted to encode a multiply hydrophobic protein with a molecular mass of 38 kDa. prv43 is colinear with the herpes simplex virus type 1 UL43 locus, and the prv43 and UL43 gene products are predicted to be 47% similar and 23% identical. prv43 is an early gene, producing a 1.2-kb transcript that is easily detected at 2 hr postinfection but not at 6 hr postinfection. We have constructed a prv43 deletion mutant that does not express a prv43 transcript. This mutant did not appear to be defective for viral growth and demonstrated that the gene is nonessential for virus growth in cell culture.

The amino-terminal one-third of pseudorabies virus glycoprotein gIII contains a functional attachment domain, but this domain is not required for the efficient penetration of Vero cells

We have examined the attachment and penetration phenotypes of several glycoprotein gIII mutants of pseudorabies virus (PRV) and have identified the first one-third of gIII as a region that mediates efficient virus attachment to PK15 and Vero cells. This portion of gIII, amino acids 25 through 157 of the wild-type sequence, appeared to support attachment by binding to heparinlike molecules on cell surfaces. Virions containing the first one-third of gIII were sensitive to heparin competition and showed greatly reduced infectivity on cells treated with heparinase. PRV virions lacking the first one-third of the mature glycoprotein exhibited only residual binding to cells if challenged by vigorous washing with phosphate-buffered saline at 2 h postinfection at 4 degrees C. This residual binding was resistant to heparin competition, and strains lacking the first one-third of gIII were able to infect cells treated with heparinase as effectively as untreated cells. When we determined the penetration phenotypes for each strain, we found that gIII-mediated virus attachment was necessary for timely penetration of PK15 cells but remarkably was not required for efficient virus penetration of Vero cells. Moreover, wild-type PRV was actually prohibited from rapid penetration of Vero cells by a gIII-heparan sulfate interaction. Our results indicate that initial virus binding to heparan sulfate via glycoprotein gIII is not required for efficient PRV infection of all cell types and may in fact be detrimental in some instances.