Chromogranins from Cell Biology to Physiology and Biomedicine

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~2.4-fold, and decreased sympathetic index by ~26%. Increased pulse interval
variability (by ~96%) and increased baroreflex coupling were noted in Gly364Ser
heterozygotes in the parasympathetic high frequency band (0.15–0.4  Hz) (Rao
et al. 2007 ) (Fig. 6b). Although the baroreceptor slope in Gly364Ser heterozygotes
increased significantly in the mixed parasympathetic/sympathetic low frequency
band (0.05–0.15 Hz), no difference was detected in pulse interval power. The pulse
interval power and baroreceptor coupling were comparable between cases and con-
trols in the sympathetic very low frequency band (0.01–0.05 Hz) (Rao et al. 2007 )
(Fig. 6b). Interestingly, the BP changes associated with this Gly364Ser variant
were restricted to men only (Rao et  al. 2007 ). Thus, the Gly364Ser variant dis-
played the most robust phenotype in human autonomic activity, both parasympa-
thetic and sympathetic. In contrast, the Japanese study showed an association of
Gly364Ser variant with high SBP and pulse pressure compared to Gly 364 Gly
homozygote (controls), thereby increasing the risk for cardiovascular diseases in
Japanese population (Choi et al. 2015 ). This directionally opposite association of
the CST Gly364Ser SNP with blood pressure in two different studies suggests that
the association may be specific to the particular ethnic population and points
towards the genetic heterogeneity in different human populations.

5 Conclusions and Perspectives

In USA, the prevalence of hypertension and uncontrolled hypertension is highest
among African Americans, where reconciliation of differences between patient and
provider expectations for management of hypertension improves adherence to and
acceptance of medical treatments. In addition, African Americans are more

60

65

70

75

80

DBP

(mmHg)

p=0.023

p=0.009

UCSD

(initial)

Kaiser

(replication)

(435)

(54)

(1274)

(73)

Gly/Gly (n=1709)

Gly/Ser (n=127)

0

5

10

15

20

25

p<0.0036 p<0.044

p<0.016

Upward

deflection

Downward

deflection

LFB coupling

(0.05-0.15 Hz

Gly/Gly (n=48)

Gly/Ser (n=17)

Time domain (slope) Frequency domain

a b

Baroreceptor slope

or coupling (msec/mmHg)

Fig. 6 (a) Association of Gly364Ser variant with DBP. (b) Effects of Gly364Ser variants on
changes in baroreceptor function as evaluated by time and frequency domains

N.R. Mahapatra et al.