Relationship of diastolic blood pressure with cyclic GMP excretion among young adults (the CARDIA Study): influence of a family history of hypertension. Coronary Artery Risk Development in Young Adults

cGMP-dependent protein kinase-2 regulates bone mass and prevents diabetic bone loss

NO/cGMP signaling is important for bone remodeling in response to mechanical and hormonal stimuli, but the downstream mediator(s) regulating skeletal homeostasis are incompletely defined. We generated transgenic mice expressing a partly-activated, mutant cGMP-dependent protein kinase type 2 (PKG2R242Q) under control of the osteoblast-specific Col1a1 promoter to characterize the role of PKG2 in post-natal bone formation. Primary osteoblasts from these mice showed a two- to three-fold increase in basal and total PKG2 activity; they proliferated faster and were resistant to apoptosis compared to cells from WT mice. Male Col1a1-Prkg2R242Q transgenic mice had increased osteoblast numbers, bone formation rates and Wnt/β-catenin-related gene expression in bone and a higher trabecular bone mass compared to their WT littermates. Streptozotocin-induced type 1 diabetes suppressed bone formation and caused rapid bone loss in WT mice, but male transgenic mice were protected from these effects. Surprisingly, we found no significant difference in bone micro-architecture or Wnt/β-catenin-related gene expression between female WT and transgenic mice; female mice of both genotypes showed higher systemic and osteoblastic NO/cGMP generation compared to their male counterparts, and a higher level of endogenous PKG2 activity may be responsible for masking effects of the PKG2R242Q transgene in females. Our data support sexual dimorphism in Wnt/β-catenin signaling and PKG2 regulation of this crucial pathway in bone homeostasis. This work establishes PKG2 as a key regulator of osteoblast proliferation and post-natal bone formation.

Influence of the endothelial nitric oxide synthase gene on conventional and ambulatory blood pressure: sib-pair analysis and haplotype study

BACKGROUND

Nitric oxide is involved in the regulation of vascular basal tone and blood pressure. Polymorphisms of NOS3, the gene that codes for endothelial nitric oxide synthase, have been associated with essential hypertension.

OBJECTIVE

To look for linkage and association of three di-allelic polymorphisms (Glu298Asp, intron 4 VNTR and T-786C) and the intron 13 CA-repeat of NOS3 with blood pressure as a continuous trait.

METHODS

Genotyping was performed in 110 dizygotic white twin pairs from Flanders, Belgium. The influence of NOS3 polymorphisms on conventional and ambulatory blood pressure was assessed by sib-pair analysis and haplotype association analysis.

RESULTS

Genotype frequencies were similar to those previously reported in white populations. Sib-pair analysis did not show a significant influence of either polymorphism on blood pressure. Haplotype analysis disclosed a significant association between NOS3 haplotypes and daytime ambulatory diastolic (P = 0.02) and systolic (P < 0.0001) blood pressure, the latter remaining significant after multiple testing was taken into account (P = 0.032). The association between daytime ambulatory systolic blood pressure and NOS3 haplotypes was mainly attributable to four haplotypes accounting for 11.9% of all represented haplotypes.

CONCLUSION

We show for the first time a highly significant association of ambulatory blood pressure with NOS3 haplotypes in well-characterized white individuals from Flanders. These results pave the way for studies looking for the influence of NOS3 on blood pressure in high-risk subsets such as diabetic or hypertensive patients. They indicate the importance of ambulatory blood pressure and haplotype analysis in revealing the moderate effect of polymorphisms on blood pressure.

Urinary cyclic GMP excretion and blood pressure levels in a general population

Dysfunction of the nitric oxide (NO) system is potentially involved in the development of hypertension, but only limited data are currently available from experimental or clinical studies. We investigated cross-sectionally the relation between urinary excretion of cyclic guanosine 3',5'-monophosphate (cyclic GMP), a second messenger of NO, and hypertension in a general population sample of Japanese men and women. The samples comprised 1541 subjects (788 men and 753 women) aged 40-79 years who participated in cardiovascular risk surveys between 1997 and 2002 and underwent a 24h urine collection. Urinary excretion of cyclic GMP was measured using a 125I-labeled cyclic GMP radioimmunoassay, and was adjusted for urinary creatinine excretion (nmol/mmol creatinine). Urinary cyclic GMP excretion was 66.0+/-62.0nmol/mmol creatinine (mean+/-S.D.). Compared with normal blood pressure individuals, the multivariate-adjusted mean value of urinary cyclic GMP excretion was significantly higher in people with moderate hypertension, but not higher in severe hypertension. Among subjects with hypertensive end-organ damage, we observed reduced urinary cyclic GMP excretion in severe hypertension and no increased excretion in moderate hypertension, compared with normal blood pressure. Although we had the limited number of subjects with severe hypertension (n=15), our data suggest that NO bioactivity may be increase in the early stage of hypertension but decreased in severe hypertension with end-organ damage.

Fluvastatin reduces atherogenic lipids without any effect on native endothelial function early after kidney transplantation

BACKGROUND

Cardiovascular risk is greatly increased in renal transplant recipients. 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor (statin) therapy may reduce cardiovascular risk by improving both dyslipidemia and endothelial function. We therefore performed this study to assess the effect of fluvastatin on endothelial function in renal transplant recipients.

METHODS

This randomized, placebo-controlled, double-blind designed study investigated the effect of fluvastatin on endothelial function. Thirty-seven recipients received fluvastatin 40 mg/d and 35 received placebo during the first 12 wk following transplantation. All patients initially received cyclosporin A, prednisolone and azathioprine. At the end of treatment, endothelial function was assessed in the forearm skin microvasculature by laser Doppler flowmetry following acetylcholine stimulation. Samples were taken for measurements of serum lipids and vasoactive markers.

RESULTS

There were no differences in endothelial function between fluvastatin recipients and controls, AUCACh was 656 +/- 479 and 627 +/- 518 AU min, respectively (fluv vs. control, p > 0.65). In the placebo limb, total cholesterol and LDL cholesterol increased 22 +/- 12% and 22 +/- 18%, respectively in the first 12 wk following transplantation. The respective values were 18 +/- 13% (p = 0.010) and 34 +/- 19% (p = 0.0013) lower at 12 wk in the fluvastatin treated patients. Plasma ET-1, BigET-1 and urinary excretion of cGMP were not significantly different between treatment groups (p > 0.55).

CONCLUSION

Although fluvastatin 40 mg/d significantly lowers cholesterol it does not affect endothelial function the first 3 months after renal transplantation. The lack of effect on endothelial function is consistent with a lack of effect on vasoactive substances.

Inverse relationship of urinary cyclic GMP to blood pressure reactivity in the CARDIA study: vasodilatory regulation of sympathetic vasoconstriction. Coronary Artery Risk Development in Young Adults

OBJECTIVE

To determine whether urinary cyclic GMP (cGMP), which mediates the actions of the vasodilators nitric oxide and atrial natriuretic factor, is inversely related to blood pressure (BP) reactivity. In previous work, we found that urinary cGMP was inversely related to diastolic BP, but cGMP levels were higher among individuals presumed to have increased adrenergic activity, increased reactivity, and increased risk of hypertension (blacks, individuals with a family history of hypertension).

METHOD

We measured 24-hour urinary cGMP levels in a substudy of 529 individuals in the Coronary Artery Risk Development in Young Adults (CARDIA) study; the sample was 23 to 35 years of age and approximately balanced for race (black/white) and gender. BP reactivity to stressors (video game, star-tracing, cold pressor) was tested 3 years earlier. Baseline BP was included as a covariate in all analyses.

RESULTS

Diastolic BP reactivity to cold pressor was inversely related to cGMP excretion (p < .05); the relationship was strongest among black women with a family history of hypertension (partial r = -.33, p < .01). Systolic BP reactivity to star-tracing was also inversely related to cGMP (p < .01); the relationship for both star-tracing and video game stressors was strongest among black men (partial r values = -.25 and -.24, respectively; p values < .01).

CONCLUSIONS

The results indicate that vasodilatory activity may impact the BP response to stress through modulation of adrenergic activation, particularly among blacks.