Cumulative hyperinsulinemia, hyperglycaemia, and insulin resistance from mid-adolescence through young adulthood with carotid intima-media thickness progression: a 9-year longitudinal study

Background

In a recent meta-analysis of randomized clinical trials conducted among adults, carotid intima-media thickness (cIMT) progression was established as a predictor of cardiovascular morbidity and mortality. However, due to the paucity of hard outcomes among adolescents and young adults, a single cIMT measure has largely been used as a marker of preclinical atherosclerotic changes. The repeated measure of cIMT in the young population is scarce thus a knowledge gap exists on the associations of metabolic indices with cIMT progression.

Purpose

To investigate the associations of cumulative fasting plasma glucose, insulin, and homeostatic model assessment of insulin resistance (HOMA-IR) with cIMT progression in adolescence.

Methods

We studied 1779 British 15-year-olds (50% females) followed up for 9 years. Fasting insulin and glucose were measured in line with standard protocols at ages 15, 17, and 24 years, respectively. HOMA-IR was computed for each time point. Metabolic indices were age and sex-specifically dichotomized as ≥75%, indicating high category and <75% indicating moderate or reference category. cIMT from the right and left common carotid arteries at 17 years was assessed by ultrasound using a linear 12-MHz transducer (Vivid7, GE Medical, Chicago, Illinois) and cIMT from the right and left common carotid arteries at 24 years was measured using an ultrasound machine (CardioHealth Panasonic and a 13.5 MHz linear array broadband transducer (probe; centre frequency 9.0 MHz). We conducted linear mixed-effect model analyses and adjusted for statistically significant determinants of cIMT progression, viz: sex, age, high sensitivity C-reactive protein, insulin or glucose, dual-energy Xray absorptiometry measured total fat mass and lean mass, systolic blood pressure, diastolic blood pressure, smoking status, and ActiGraph measured sedentary time and light physical activity. Covariates were repeatedly measured.

Results

Participants mean (SD) age in years at different time points were 15.43 (0.29), 17.69 (0.31), and 24.53 (0.72). Cumulative high exposures to glucose: effect estimate 0.009 mm [95% CI −0.003 to 0.021; p=0.130], insulin: 0.002 mm [−0.030 to 0.013; p=0.704], and HOMA-IR: 0.003 mm [−0.009 to 0.016; p=0.608] from 15 to 24 years of age were not associated with the 7-year cIMT progression after full covariate adjustments. Sex-based analyses were consistent with the group analyses in both males and females.

Conclusion

These findings suggest that hyperinsulinemia, hyperglycaemia, and elevated insulin resistance from mid-adolescence through young adulthood may not be associated with progressive carotid wall thickening during late adolescence through young adulthood. Future studies investigating the role of other metabolic indices such as cumulative elevated lipid exposures on cIMT progression in the young population are warranted.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Finnish Cultural Foundation

CXCR3 and CCR5 ligands in rheumatoid arthritis synovium

The pathogenesis of rheumatoid arthritis (RA) may be mediated by Th1-type T cells. Since chemokine receptors CXCR3 and CCR5 are preferentially expressed on Th1 cells, we tested the expression and regulation of several chemokines, including those that signal through CXCR3 (interferon-gamma-inducible protein of 10 kDa, IP-10, CXCL10; and monokine induced by interferon-gamma, Mig, CXCL9) and CCR5 (macrophage inflammatory protein (Mip)-1 alpha, CCL3; and Mip-1 beta, CCL4) in RA synovial fluids, synovial tissues, and blood. Synovial fluid (SF) protein levels of IP-10 (32.1 +/- 10.5 ng/ml), Mig (15.0 +/- 6.4 ng/ml), Mip-1 beta (0.7 +/- 0.3 ng/ml), and Mip-1 alpha (0.8 +/- 0.1 ng/ml) were 100-, 50-, 25-, and 2-fold elevated in RASF compared to control SF (P < 0.001, P < 0.001, P < 0. 001, and P < 0.02, respectively). Tissue levels of IP-10, Mig, and Mip-1 beta were significantly higher in RA than in OA (P < 0.01). Serum levels of IP-10 (3.1 +/- 1.2 ng/ml) were higher in patients with seropositive RA compared to controls (1.2 +/- 0.2 ng/ml) (P < 0.02). There was a gradient of IP-10, Mig, Mip-1 alpha, and Mip-1 beta from the blood into the synovial fluid in RA. Infiltrating T cells around high endothelial venules in RA synovium and 90 +/- 3% of SF CD3(+)CD4(+) T cells expressed CXCR3, and 85 +/- 2% of SF CD3(+)CD4(+) T cells expressed CCR5. Chemokines, including IP-10, Mig, Mip-1 alpha, and Mip-1 beta, may participate in the selective recruitment of CCR5(+)CXCR3(+) T cells to the inflamed synovium.

Ultrastructure and function of the fractalkine mucin domain in CX(3)C chemokine domain presentation

Fractalkine (FKN), a CX(3)C chemokine/mucin hybrid molecule on endothelium, functions as an adhesion molecule to capture and induce firm adhesion of a subset of leukocytes in a selectin- and integrin-independent manner. We hypothesized that the FKN mucin domain may be important for its function in adhesion, and tested the ability of secreted alkaline phosphatase (SEAP) fusion proteins containing the entire extracellular region (FKN-SEAP), the chemokine domain (CX3C-SEAP), or the mucin domain (mucin-SEAP) to support firm adhesion under flow. CX3C-SEAP induced suboptimal firm adhesion of resting peripheral blood mononuclear cells, compared with FKN-SEAP, and mucin-SEAP induced no firm adhesion. CX3C-SEAP and FKN-SEAP bound to CX(3)CR1 with similar affinities. By electron microscopy, fractalkine was 29 nm in length with a long stalk (mucin domain), and a globular head (CX(3)C). To test the function of the mucin domain, a chimeric protein replacing the mucin domain with a rod-like segment of E-selectin was constructed. This chimeric protein gave the same adhesion of peripheral blood mononuclear cells as intact FKN, both when immobilized on glass and when expressed on the cell surface. This implies that the function of the mucin domain is to provide a stalk, extending the chemokine domain away from the endothelial cell surface to present it to flowing leukocytes.

Myocardial infarction and remodeling in mice: effect of reperfusion

Anatomic and functional changes after either a permanent left anterior descending coronary artery occlusion (PO) or 2 h of occlusion followed by reperfusion (OR) in C57BL/6 mice were examined and compared with those in sham-operated mice. Both interventions generated infarcts comprising 30% of the left ventricle (LV) measured at 24 h and equivalent suppression of LV ejection velocity and filling velocity measured by Doppler ultrasound at 1 wk. Serial follow-up revealed that the ventricular ejection velocity and filling velocity returned to the levels of the sham-operated controls in the OR group at 2 wk and remained there; in contrast, PO animals continued to display suppression of both systolic and diastolic function. In contrast, ejection fractions of PO and OR animals were depressed equivalently (50% from sham-operated controls). Anatomic reconstruction of serial cross sections revealed that the percentage of the LV endocardial area overlying the ventricular scar (expansion ratio) was significantly larger in the PO group vs. the OR group (18 +/- 1.7% vs. 12 +/- 0.9%, P < 0.05). The septum that was never involved in the infarction had a significantly (P < 0.002) increased mass in PO animals (22.5 +/- 1.08 mg) vs. OR (17.8 +/- 1.10 mg) or sham control (14.8 +/- 0.99 mg) animals. Regression analysis demonstrated that the extent of septal hypertrophy correlated with LV expansion ratio. Thus late reperfusion appears to reduce the degree of infarct expansion even under circumstances in which it no longer can alter infarct size. We suggest that reperfusion promoted more effective ventricular repair, less infarct expansion, and significant recovery or preservation of ventricular function.