Compromised bioavailable IGF-1 of black men relates favourably to ambulatory blood pressure: The SABPA study

Insulin-Like Growth Factor 1 in the Cardiovascular System

Non-communicable diseases, such as cardiovascular diseases, are the leading cause of mortality worldwide. For this reason, a tremendous effort is being made worldwide to effectively circumvent these afflictions, where insulin-like growth factor 1 (IGF1) is being proposed both as a marker and as a central cornerstone in these diseases, making it an interesting molecule to focus on. Firstly, at the initiation of metabolic deregulation by overfeeding, IGF1 is decreased/inhibited. Secondly, such deficiency seems to be intimately related to the onset of MetS and establishment of vascular derangements leading to atherosclerosis and finally playing a definitive part in cerebrovascular and myocardial accidents, where IGF1 deficiency seems to render these organs vulnerable to oxidative and apoptotic/necrotic damage. Several human cohort correlations together with basic/translational experimental data seem to confirm deep IGF1 implication, albeit with controversy, which might, in part, be given by experimental design leading to blurred result interpretation.

Sodium Reduction, Metabolomic Profiling, and Cardiovascular Disease Risk in Untreated Black Hypertensives

Dietary sodium restriction has multiple beneficial effects on cardiovascular health. The underlying mechanisms are not fully understood, and the roles of metabolomics have been rarely studied. We aimed to test the hypothesis that the reduction in dietary sodium intake would induce changes in metabolomic profiling among black hypertensives, and the changes would be associated with reduced blood pressure (BP) and improved skin capillary density. A total of 64 untreated black hypertensives were included from a randomized, double-blind, placebo-controlled cross-over trial of sodium reduction. The participants were given either 9 slow sodium tablets (10 mmol sodium per tablet) or placebo tablets daily for 6 weeks, they then crossed over to receive the other tablets for another 6 weeks, while on reduced sodium diet aiming at achieving daily sodium intake around 2.0 g. Untargeted metabolomic profiling was performed in paired serum samples, which were collected at the end of each period, so were BP and capillary density. Mixed-effects models were used. There were 34 metabolites identified with raw P's<0.05. Among those, 2 metabolites including β-hydroxyisovalerate and methionine sulfone were significantly increased with sodium reduction (false discovery rate =0.006 and 0.099, respectively). Increased β-hydroxyisovalerate was associated with reduced office systolic BP and ambulatory daytime systolic BP, whereas increased methionine sulfone was associated with reduced 24-hour diastolic BP, ambulatory nighttime diastolic BP, and increased skin capillary density. Our results suggest that dietary sodium reduction increases the circulating levels of β-hydroxyisovalerate and methionine sulfone. Further studies are warranted. Clinical Trial Registration- URL: http://www.clinicaltrials.gov . Unique identifier: NCT00152074.

Bioavailable IGF-1 is beneficially associated with biomarkers of endothelial function in young healthy adults: The African-PREDICT study

INTRODUCTION

Low circulating levels of insulin-like growth factor-1 (IGF-1) are associated with endothelial dysfunction, subsequently leading to the development of cardiovascular disease.

OBJECTIVE

To better understand the early phases of vascular deterioration in a young, healthy population, we investigated, cross-sectionally, whether biomarkers of endothelial function (intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and von Willebrand factor antigen (vWF_ag)) are associated with IGF-1 in a healthy study population forming part of the larger African Prospective study on the Early Detection and Identification of Cardiovascular diseases and Hypertension (African-PREDICT).

METHOD

We included 825 black and white men and women (aged 20-30 years) and determined IGF-1, IGF binding protein-3 (IGFBP-3), ICAM-1, VCAM-1 and vWF_ag from blood samples. We also measured 24-h blood pressure and health behaviours namely waist circumference, accelerometery, cotinine and gamma glutamyl transferase. We used the IGF-1/IGFBP-3 M ratio as an estimate of bioavailable IGF-1.

RESULTS

In multivariable-adjusted regression analyses performed in the total group, VCAM-1 associated positively with IGFBP-3 (β = 0.21; p < .001) and negatively with IGF-1/IGFBP-3 (β = -0.18; p < .001). ICAM-1 showed a borderline negative association with IGF-1 (β = -0.09; p = .054) and IGF-1/IGFBP-3 (β = -0.08; p = .057). vWF_ag was not associated with IGF-1, IGFBP-3 or bioavailable IGF-1.

CONCLUSION

VCAM-1 is beneficially associated with IGF-1 in a young healthy cohort, independent of sex, ethnicity, blood pressure and health behaviours - thereby confirming the potential importance of bioavailable IGF-1 in early vascular endothelial protection.

Insulin-Like Growth Factor-1 and Receptor Contribute Genetic Susceptibility to Hypertension in a Han Chinese Population

BACKGROUND

Insulin-like growth factor 1 (IGF-1) and IGF-1 receptor (IGF-1R) have been suggested to mediate the pathophysiological response to elevated blood pressure. This study aims to evaluate the association of IGF-1 and IGF-1R with hypertension.

METHODS

Overall, 2,012 hypertensive cases and 2,210 controls were included in a case-control study, and 10 tagging single nucleotide polymorphisms (tagSNPs) were selected. The association of these SNPs with hypertension was further evaluated in a follow-up analysis and in an adolescent population.

RESULTS

A case-control study indicated that rs1815009 and rs2654981 in IGF-1R were significantly associated with hypertension, with odds ratios of 0.89 (P = 0.009) and 1.19 (P = 0.034), respectively, after adjusting for covariates. Stratification analyses revealed significant associations with hypertension (P < 0.05) for rs35767 in normal weight and obese populations; for rs2229765 in individuals <55 years of age and in overweight and nondrinking populations; and for rs2002880 in overweight and drinking populations. In a follow-up study, rs13379905 in IGF-1R was associated with hypertension incidence (hazard ratio, HR = 1.24, P = 0.042). This association was more significant in individuals with a hypertensive family history (HR = 2.10, P = 0.001). The association of rs13379905 with prehypertension and hypertension was further replicated in adolescent males (P = 0.005). Significant associations with hypertension incidence (P < 0.05) were observed for rs6219 in individuals <55 years of age and among those with obesity and a hypertensive family history as well as rs2002880 in obese individuals.

CONCLUSIONS

Our findings suggest that IGF-1R may contribute to the genetic susceptibility to hypertension, with BMI, age, and family history of hypertension all potentially modulating the genetic effects of IGF-1 on hypertension.

Relationships of insulin-like growth factor-1, its binding proteins, and cardiometabolic risk in hypertensive perimenopausal women

PURPOSE

During the transition from premenopause to postmenopause, many women experience weight gain and central fat deposition; therefore, we hypothesized that circulating growth factors can play a role in the pathogenesis of hypertension, metabolic syndrome, and subclinical organ damage in perimenopausal women.

BASIC PROCEDURES

The study included 192 women aged 40 to 60years; 152 had newly diagnosed essential hypertension that had never been treated, and 40 were normotensive age-matched controls. For all subjects, 24-h ambulatory blood pressure monitoring (ABPM), echocardiographic examination with assessment of left ventricular mass (LVM) and systolic and diastolic functions (GE Vivid 7.0, General Electric Vingmed Ultrasound, Horten, Norway), carotid ultrasound with measurement of intima-media thickness, and carotid-femoral pulse wave velocity (PWV) measurement (SphygmoCor, AtCor Medical, Sydney, Australia) were performed. Serum levels of insulin-like growth factor 1 (IGF-1), insulin-like growth factor-binding protein 2 (IGFBP-2), and insulin-like growth factor-binding protein 3 (IGFBP-3) were measured using an immunochemical assay.

MAIN FINDINGS

Hypertensive women had significantly lower IGFBP-2 levels than did normotensive controls (162.9±83.7 vs. 273.1±103.0μg/L, p<0.001); the groups did not differ regarding IGF and IGFBP-3 concentrations. After adjusting the covariates, multivariate analysis showed that IGFBP2 was significantly negatively correlated with 24-h systolic blood pressure (β=-0.31, p=0.02). The adjusted odds ratio for hypertension per standard deviation decrease in IGFBP-2 was 3.43 (95% confidence interval [CI] 1.65-7.13). IGFBP-2 showed a negative correlation with the number of metabolic syndrome components. Independent of body composition, IGFBP-2 was significantly related to left ventricular relative wall thickness and the ratio of mitral inflow velocities as parameter of diastolic function.

PRINCIPAL CONCLUSIONS

In perimenopausal women, decreased IGFBP-2 levels may play a role in blood pressure regulation and the development of subclinical left ventricular diastolic dysfunction. Whether IGFBP-2 is a marker or a mediator of cardiovascular disease in this population merits further investigation.

IGF-1 and NT-proBNP in a black and white population: The SABPA study

BACKGROUND

Black populations exhibit lower concentrations of the cardioprotective peptide, insulin-like growth factor-1 (IGF-1), and are more prone to develop hypertensive heart disease than whites. We therefore determined whether lower IGF-1 in black individuals relates to a marker of cardiac overload and systolic dysfunction, namely N-terminal prohormone B-type natriuretic peptide (NT-proBNP).

MATERIALS AND METHODS

We included 160 black and 195 white nondiabetic South African men and women (aged 44·4 ± 9·81 years) and measured ambulatory blood pressure, NT-proBNP, IGF-1 and insulin-like growth factor-binding protein-3 (IGFBP-3).

RESULTS

Although the black group presented elevated ambulatory blood pressure accompanied by lower IGF-1 compared to the white group (all P < 0·001), we found similar NT-proBNP concentrations (P = 0·72). Furthermore, in blacks we found a link between NT-proBNP and systolic blood pressure (SBP) (R(2) = 0·37; β = 0·28; P < 0·001), but not with IGF-1. In the white group, NT-proBNP was inversely associated with IGF-1 (R(2) = 0·39; β = -0·22; P < 0·001) after adjusting for covariates and potential confounders. As IGF-1 is attenuated in diabetes, we added the initially excluded patients with diabetes (n = 38), and the aforementioned associations remained robust.

CONCLUSION

Contrary to the white group, we found no association between NT-proBNP and IGF-1 in black adults. Our findings suggest that SBP and other factors may play a greater contributory role in cardiac pathology in blacks.

Attenuated IGF-1 predicts all-cause and cardiovascular mortality in a Black population: A five-year prospective study

BACKGROUND

Inconsistent findings are reported on whether insulin-like growth factor-1 (IGF-1) is protective or harmful in predicting hypertension, carotid wall thickness and mortality. We determined the five-year prognostic value of IGF-1 for these outcomes in a large Black population prone to hypertension and cardiovascular disease.

DESIGN

A longitudinal study as part of the PURE (Prospective Urban and Rural Epidemiology) study, North West Province, South Africa.

METHODS

We measured IGF-1 and IGF binding protein-3 (IGFBP-3) in 1038 HIV-uninfected participants (age range 32-94 years) and assessed blood pressure, carotid intima-media thickness and mortality.

RESULTS

Over five years 116 deaths occurred. Baseline IGF-1 was similar in survivors and non-survivors (p = 0.50), but tended to be higher in survivors upon adjustment for IGFBP-3 and covariates (p = 0.061). Normotensives and hypertensives (p = 0.072), and those with carotid intima-media thickness < 0.9 mm and ≥ 0.9 mm also displayed similar baseline IGF-1 (p = 0.55). Multivariable-adjusted Cox-regression indicated high IGF-1 predicting lower risk for all-cause mortality (hazard ratio 0.45; 0.23-0.88) and cardiovascular mortality (hazard ratio 0.26; 0.08-0.83) when also adjusting for IGFBP-3. When including normo- and hypertensives at baseline, high IGF-1 was related to normotension at follow-up (hazard ratio 0.68; 0.49-0.95). We found no association with carotid intima-media thickness (hazard ratio 0.59; 0.31-1.14).

CONCLUSION

In a Black South African population with low socio-economic status and harmful health behaviours, we found a protective independent association between IGF-1 and hypertension, cardiovascular and all-cause mortality, with no association with carotid wall thickness.

Cardiovascular function is not associated with creatine kinase activity in a black African population: The SABPA study

Background

Higher creatine kinase (CK) activity is associated with the development of cardiovascular disease in black African populations. We compared CK activity and investigated associations of blood pressure with CK activity in black and white men as well as black and white women.

Methods

Ambulatory blood pressure, total peripheral resistance and pulse wave velocity of 197 black and 208 white participants were determined and serum CK activity was measured.

Results

Blood pressure and pulse wave velocity were higher in black men and women (all p < 0.001) when compared to their white counterparts. CK activity only varied between black and white women (75.9 U/l vs 62.8 U/l, p = 0.009), even after adjusting for age, body mass index and physical activity. Despite the worse cardiovascular profile of black men and women, and the higher CK activity in the black women, we were unable to link blood pressure, pulse wave velocity or total peripheral resistance with CK activity, in the black African population. In white men, total peripheral resistance was associated with CK activity (R² = 0.32; β = 0.25; p = 0.009), whereas systolic blood pressure (R² = 0.46; β = 0.17; p = 0.03) and pulse pressure (R² = 0.31; β = 0.21; p = 0.01) were associated with CK activity in white women.

Conclusions

The lack of associations in the black African population suggests that the link between a worse cardiovascular profile and CK activity may be overshadowed by other contributing factors. Whereas, the established link between cardiovascular function and CK activity in the white groups may be the result of enhanced smooth muscle cell contractility and/or attenuated nitric oxide synthesis capacity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-016-0315-2) contains supplementary material, which is available to authorized users.