Low serum 25-hydroxyvitamin D status in the pathogenesis of stress fractures in military personnel: An evidenced link to support injury risk management.

Stress fractures are common amongst healthy military recruits and athletes. Reduced vitamin D availability, measured by serum 25-hydroxyvitamin D (25OHD) status, has been associated with stress fracture risk during the 32-week Royal Marines (RM) training programme. A gene-environment interaction study was undertaken to explore this relationship to inform specific injury risk mitigation strategies. Fifty-one males who developed a stress fracture during RM training (n = 9 in weeks 1-15; n = 42 in weeks 16-32) and 141 uninjured controls were genotyped for the vitamin D receptor (VDR) FokI polymorphism. Serum 25OHD was measured at the start, middle and end (weeks 1, 15 and 32) of training. Serum 25OHD concentration increased in controls between weeks 1-15 (61.8±29.1 to 72.6±28.8 nmol/L, p = 0.01). Recruits who fractured did not show this rise and had lower week-15 25OHD concentration (p = 0.01). Higher week-15 25OHD concentration was associated with reduced stress fracture risk (adjusted OR 0.55[0.32-0.96] per 1SD increase, p = 0.04): the greater the increase in 25OHD, the greater the protective effect (p = 0.01). The f-allele was over-represented in fracture cases compared with controls (p<0.05). Baseline 25OHD status interacted with VDR genotype: a higher level was associated with reduced fracture risk in f-allele carriers (adjusted OR 0.39[0.17-0.91], p = 0.01). Improved 25OHD status between weeks 1-15 had a greater protective effect in FF genotype individuals (adjusted OR 0.31[0.12-0.81] vs. 1.78[0.90-3.49], p<0.01). Stress fracture risk in RM recruits is impacted by the interaction of VDR genotype with vitamin D status. This further supports the role of low serum vitamin D concentrations in causing stress fractures, and hence prophylactic vitamin D supplementation as an injury risk mitigation strategy.

Association between plasma levels of heat shock protein 60 and cardiovascular disease in patients with diabetes mellitus.

AIMS: Evidence is accumulating to support the hypothesis that the release of heat shock protein (Hsp)60 into the circulation is associated with the development of coronary heart disease (CHD). As diabetes is a risk factor for CHD, it was of interest to determine Hsp60 blood levels in a cross-sectional cohort of diabetic patients, some of whom had cardiovascular disease, and relate levels to relevant biochemical markers. METHODS AND RESULTS: A total of 855 patients with T1DM or T2DM, recruited as part of the UCL Diabetes and Cardiovascular disease Study (UDACS), were assayed for plasma levels of Hsp60. Immunoreactive Hsp60 was detected in 54% of the samples, with 26% having plasma levels > 1 microg/mL. Levels of Hsp60 were higher in Caucasians than in other ethnic groupings, with 56.5% of Caucasian subjects, 37.5% of African-Caribbean subjects, and 47.1% of Indian subjects having detectable levels (P = 0.007), and with a higher proportion of non-smokers having detectable Hsp60 levels than smokers (54.9 vs. 43.5%, P = 0.01). Of note was the finding of an association between higher mean plasma levels of Hsp60 in subjects with clinically manifest cardiovascular disease and those with a history of myocardial infarction having an adjusted odds ratio of having detectable Hsp60 of 2.17 (CI 1.26-3.73). CONCLUSION: This is the first report of circulating Hsp60 levels in diabetic patients, which suggests that this secreted mitochondrial cell stress protein may be playing an unexpected role in the cardiovascular pathology associated with diabetes.

A common functional variant in the interleukin-6 gene is associated with increased body mass index in subjects with type 2 diabetes mellitus.

Circulating levels of interleukin-6 (IL-6) are raised in insulin resistant states such as obesity, impaired glucose tolerance (IGT), and type 2 diabetes mellitus (T2DM). Growing evidence suggests that IL-6 is not only produced by fat cells but is also capable of inducing insulin resistance in these cells. The expected result of this in vivo, would be to increase adipose mass and subsequently body mass index (BMI). The IL-6 -174G > C common functional gene variant has consistently been associated with increased plasma IL-6, insulin resistance, and increased cardiovascular risk. We looked at the association between genotype and BMI in 571 Caucasian subjects with T2DM. There was a significant linear association between genotype and BMI: Median (interquartile range) GG 28.8 kg/m2 (26.0-31.6) vs GC; 29.4 kg/m2 (26.3-32.5) vs CC; 30.4 kg/m2 (26.1-33.0), p=0.05. When the group was divided by the median BMI (29.1 kg/m2), 62% of -174CC subjects were in the higher group compared to 38% in the lower group (p=0.008). By contrast, in 2,652 non-diabetic Caucasian men with a median BMI of 26.1 kg/m2, there was no difference in genotype distribution (p=0.288). The frequency of the -174C allele was lower in type 2 diabetes compared to the non-diabetic men (-174C allele frequency: 0.35[0.33-0.38] vs 0.43[0.42-0.45], p <0.00001; -174CC homozygotes: 12.3 vs 18.3%, respectively). The -174C allele is associated with higher BMI in type 2 diabetes, but not amongst healthy subjects. The increased cardiovascular risk associated with the -174C allele may account for the lower frequency of this allele in those with type 2 diabetes.

Cardiovascular risk in healthy men and markers of oxidative stress in diabetic men are associated with common variation in the gene for uncoupling protein 2.

BACKGROUND: Oxidative stress reduces total antioxidant status (TAOS) and is implicated in atherogenesis. Mitochondrial uncoupling protein 2 (UCP2) negatively regulates reactive oxygen species generation. The UCP2 gene demonstrates a common functional promoter variant (-866G>A). METHODS AND RESULTS: Amongst 465 diabetic men (age 61.7 +/- 13.3 years), an association of the UCP2-866A allele with significantly lower TAOS in those without CHD was even more pronounced in those with CHD (TAOS 30.1 +/- 16.1% vs. 41.6 +/- 12.4% for AA vs. GG; P=0.016). In a sample of 20 diabetic men selected for homozygosity for the UCP2-866G>A variant, matched for baseline characteristics, plasma markers of oxidative stress in those with CHD were significantly higher in AA genotype men (TAOS 31.7 +/- 7.3% vs. 52.6 +/- 6.3%; P=0.001 and F2-isoprostanes 220.6 +/- 37.2 pg ml(-1) vs. 109.9 +/- 51.1 pg ml(-1); P=0.005 for AA vs. GG). Amongst 2695 healthy men (age 56.1 +/- 3.5 years) prospectively studied for a median 10.2 years, AA homozygotes had a highly significant doubling in CHD risk after adjustment for established risk factors (HR 1.99 [1.37-2.90]; P=0.002). Risk associated with this genotype was substantially increased by the presence of other risk factors (obesity, hypertension and diabetes). CONCLUSIONS: This study provides the first in vivo evidence of a role for UCP2 in modifying oxidative stress and CHD risk in humans.

Variation in bradykinin receptor genes increases the cardiovascular risk associated with hypertension.

AIMS: The contribution of kinins to the beneficial effects of angiotensin I converting enzyme (ACE) inhibition in cardiovascular risk reduction remains unclear. The genes for the kinin inducible B1 receptor (B(1)R) and constitutive B2 receptor (B(2)R) contain functional variants: the B(1)R-699C (rather than G) and the B(2)R(-9) (rather than +9) alleles are associated with greater mRNA expression and the B(2)R(-9) allele with reduced left ventricular hypertrophic responses. We tested whether these gene variants influenced hypertensive coronary risk in a large prospective study. METHODS AND RESULTS: Two thousand, seven hundred and six previously healthy UK men (mean age at recruitment 56 years; median follow-up 10.8 years) were genotyped for the kinin receptor variants. The coronary risk attributable to systolic hypertension (SBP>/=160 mmHg) was significantly higher only in B(1)R-699GG homozygotes (HR 2.14 [1.42-3.22]; P<0.0001) and B(2)R(+9,+9) individuals (HR 3.51 [1.69-7.28]; P=0.001) but not in B(1)R-699C allele carriers (HR 0.82 [0.28-2.42]; P=0.76) or in B(2)R(-9,-9) homozygotes (HR 1.25 [0.51-3.04]; P=0.63). CONCLUSIONS: Common variation in the genes for the kinin B(1)and B(2)receptors influences prospective hypertensive coronary risk. These are the first reported human data to suggest a role for the B(1)R in human coronary vascular disease, and the first prospective study to demonstrate a similar role for the B(2)R.