The association between carotid disease, arterial stiffness and diabetic retinopathy in type 2 diabetes: the Fremantle Diabetes Study Phase II

AIM

To determine whether macrovascular disease assessed by carotid ultrasonography and arterial stiffness by pulse wave velocity are independently associated with diabetic retinopathy in type 2 diabetes.

METHODS

A random subgroup of surviving participants with type 2 diabetes from the Fremantle Diabetes Study Phase II were invited to take part in this sub-study in 2018-2019. In addition to standardized questionnaires, a physical examination and fasting biochemical tests, each underwent dilated colour fundus photography, carotid arterial ultrasonography with measurement of the intima-media thickness (IMT) and quantification of the degree of stenosis, and pulse wave analysis calculation of the carotid-femoral pulse wave velocity (cfPWV). The cross-sectional association between arterial disease parameters and diabetic retinopathy was assessed using generalized estimating equation models which enabled both eyes to be included in the analysis.

RESULTS

Some 270 participants [mean ± sd age 72 ± 9 years, 153 (57%) men and median (IQR) diabetes duration 15 (11-22) years] were included in analysis. Of 524 assessable eyes, 82 (16%) had diabetic retinopathy. In multivariable analysis, significant independent associates of diabetic retinopathy were age at diabetes diagnosis (inversely), HbA_1c , insulin treatment and urinary albumin to creatinine ratio (all P ≤ 0.022), as well as cfPWV [odds ratio (OR) 1.13, 95% confidence interval (CI) 1.03, 1.23 per 1 m/s increase; P = 0.008] and common carotid artery (CCA) IMT ≥1 mm (OR 2.95, 95% CI 1.21, 7.23; P = 0.018).

CONCLUSIONS

The association between diabetic retinopathy and CCA IMT suggests that carotid disease may share cardiovascular risk factors with diabetic retinopathy. The association between diabetic retinopathy and cfPWV may reflect the consequences of altered intravascular haemodynamics.

Two novel quantitative trait loci on mouse chromosomes 6 and 4 independently and synergistically regulate plasma apoB levels

An elevated plasma apolipoprotein B (apoB) level is a strong predictor of atherosclerosis and coronary heart disease. Epidemiologic and family linkage studies have suggested a genetic basis for the wide variations of plasma apoB levels in the general population. Using a human apoB transgenic (HuBTg) mouse model, we have previously shown that hepatic apoB-100 secretion is a major determinant of the high and low plasma human apoB levels in HuBTg mice of the C57BL/6 (B6) and 129/Sv (129) strains, respectively. In the present article, we present the identification of two novel quantitative trait loci (QTL) as major regulators of plasma human apoB levels in the F(2) and N(2) (backcrossed) offspring (n = 572) derived from crosses between the B6 and 129 mouse strains. These loci were designated ApoB regulator genes (Abrg), because the gene products are likely to be involved in the regulation of plasma apoB levels either directly or indirectly. The first locus, designated Abrg1, was mapped to chromosome 6 in 8-week-old male and female mice with a combined logarithm of odds ratio (LOD) score of 14 at the D6Mit55 marker ( approximately 45.9 cM). Abrg1 contributed approximately 35% of the genetic variance. The second locus, designated Abrg2, was mapped to chromosome 4 with an LOD score of 8.6 in 8-week-old male mice but an LOD score of only 2.0 in 8-week-old female mice at the D4Mit27 marker ( approximately 35 cM). Abrg2 contributed approximately 26% of the genetic variance. Epistasis between Abrg1 and Abrg2 was detected and accounted for approximately 12% of the genetic variance. The combination of these two QTL has major effects (>70%) on the regulation of plasma human apoB levels in the tested population. In summary, we have identified two novel loci that have a major role in the regulation of plasma apoB levels and are likely to regulate the secretory pathway of apoB. The human orthologs for the Abrg loci are strong candidates for human disorders characterized by altered plasma apoB levels, such as FCHL and familial hypobetalipoproteinemia.

Oligonucleotides complementary to the Oxytricha nova telomerase RNA delineate the template domain and uncover a novel mode of primer utilization

The telomerase reverse transcriptase uses an essential RNA subunit as a template to direct telomeric DNA synthesis. The 190-nucleotide Oxytricha nova telomerase RNA was identified by using an oligonucleotide probe complementary to the predicted CCCCAAAA template. This RNA displays extensive sequence similarity to the Euplotes crassus telomerase RNA and carries the same 5' CAAAACCCCAAAACC 3' telomeric domain. Antisense oligonucleotides were used to map the boundaries of the functional template and to investigate the mechanism of primer recognition and elongation. On the basis of their ability to inhibit or to prime telomerase, oligonucleotides were classified into three categories. Category 1 oligonucleotides, which extended 5' of residue 42 in the RNA, abolished elongation of (T4G4)3 and (G4T4)3 primers in vitro. In contrast, oligonucleotides terminating between residues 42 and 50 (categories 2 and 3), served as efficient telomerase primers. We conclude that the O. nova template comprises residues 42 to 50 in the 190-nucleotide RNA, a different set of nucleotides than are used by the E. crassus enzyme. Category 2 primer reactions amassed short products, and their abundance could be decreased by altering the 5' sequence of the primer, consistent with the two-primer-binding-site model for telomerase. Category 3 primers generated a bimodal distribution of short and long products, each having a unique elongation profile. The long-product profile is inconsistent with sequence-specific primer alignment. Rather, each primer was extended by the same register of TTTTGGGG repeats, suggesting shuttling to a default position within the template. The parallels between telomerase and RNA polymerase elongation mechanisms are discussed.

Ferrosilite (FeSiO 3 ): Synthesis at High Pressures and Temperatures

The FeSiO(3) (ferrosilite) end member of the pyroxene series is not known as a pure mineral in nature and cannot be synthesized at atmospheric pressure. It is readily synthesized, however, at pressures from 18 to 45 kb and temperatures from 1150 degrees to 1400 degrees C. Its refractive indices approach those predicted for ferrosilite and it melts incongruently to an Fe, SiO(4)-rich liquid plus quartz.