Cardiovascular Journal of Africa: Vol 27 No 1 (January/February 2016)

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 27, No 1, January/February 2016

AFRICA

Combined effects of

FTO

rs9939609 and

MC4R

rs17782313

on elevated nocturnal blood pressure in the Chinese Han

population

Yanlei Sun, Jiazhong Sun, Jun Wu, Mei Yang

Abstract

Aim:

In this study we investigated the association of

FTO

rs9939609 and

MC4R

rs17782313 with elevated blood pres-

sure in the Chinese Han population, and analysed the rela-

tionship between the rs9939609 and rs17782313 variants.

Methods:

We tested the rs9939609 and rs17782313 variants

with the sequence-retrieval method.

Results:

The increase in odds ratios of the A allele of

rs9939609 and the C allele of rs17782313 for nocturnal blood

pressure were 1.37 and 1.69. The nocturnal blood pressure of

participants simultaneously carrying the A and C alleles was

significantly higher than the blood pressure of those carrying

neither

FTO

nor

MC4R

risk alleles (

0.05), and that of

the controls carrying only the A or C alleles (

0.05). No

association between the

FTO

MC4R

genes with daytime

hypertension was found in this Chinese population (

0.05).

Conclusion:

Our data suggest that the rs9939609 and

rs17782313 variants may be significantly associated with

nocturnal but not daytime blood pressure levels and their

combined effects were significant in this Chinese Han popu-

lation.

Keywords:

gene polymorphism, daytime blood pressure, noctur-

nal blood pressure, Chinese Han population

Submitted 6/9/14, accepted 11/8/15

Published online 31/8/15

Cardiovasc J Afr

2016;

: 21–24

www.cvja.co.za

DOI: 10.5830/CVJA-2015-064

Elevated blood pressure increases the risk of experiencing

cardiovascular events such as myocardial infarction and stroke.

Current observational data suggest that body mass index (BMI)

may have a causal role in the aetiology of hypertension, but this

may be influenced by confounding and reverse causation.

Genetic factors play an important role in the development of

hypertension. Recent studies have revealed a strong association

between common variants in introductory studies on the

FTO

gene and obesity in children and adults.

2-4

Frayling and

co-workers found that each rs9939609 allele (chr16:52,378,028;

dbSNP build 129) increased body weight by 1.2 kg in the general

adult population and conferred a 31% higher risk of developing

obesity.

FTO

protein is a key link between the central nervous system

and energy balance. It was found to be ubiquitously expressed in

the hypothalamus and is thought to mediate this effect through

its influence on energy homeostasis. The hypothalamus, however,

also regulates blood pressure.

Masked (nocturnal) hypertension

is common in patients with type 2 diabetes mellitus.

Masked

hypertension (normal blood pressure in the clinic but elevated

levels when measured outside the clinic) is associated with

an increased risk of cardiovascular disease. Therefore, we

investigated whether the

FTO

risk variant may not be associated

only with obesity and BMI, but also with elevated nocturnal

blood pressure.

The

MC4R

gene, encoding for the melanocortin 4 receptor,

was the first locus at which mutations were associated with

dominantly inherited morbid human obesity, and was the

commonest genetic cause of human obesity.

The rs17782313

C allele (chr18:56,002,077; dbSNP build 129), located 188 kb

downstream of

MC4R

, was similarly associated with obesity

[OR

1.30 (1.20–1.41)] in populations of European origin.

Cardiovascular risk factors such as type 2 diabetes mellitus,

9,10

insulin resistance,

and hypertension

were associated with the

risk allele A for

FTO

rs9939609 and the risk allele C for

MC4R

rs17782313, regardless of BMI.

9,10

In Marcadenti and colleagues’

study, however, common genetic variants of

FTO

rs9939609

had a positive association with BMI and neck circumference,

and

MC4R

rs17782313 in women, but a negative association

with diastolic and mean blood pressure in hypertensive men in

southern Brazil.

In the present study, we investigated the association of

FTO

and

MC4R

gene polymorphisms with hypertension in the

Chinese Han population and analysed the relationship between

FTO

rs9939609 and

MC4R

rs17782313 variants.

Methods

The subjects were divided into two groups comprising a daytime

hypertension group (575 patients) and a night-time hypertension

group (583 patients). The number of control subjects was

1 200. We recruited by physical examination 2 358 non-related

individuals, aged 50 to 70 years (1 175 men and 1 183 women),

who all belong to the Han nationality from the Hubei province

of China.

The study was carried out in the examination centre at

the ZhongNan Hospital of Wuhan University. Daytime

Department of Endocrinology, the Third Hospital of Wuhan,

Wuhan, China, 430060

Yanlei Sun, PhD,

syleilei2008@qq.com

Jun Wu, PhD

Department of Endocrinology, Zhongnan Hospital, Wuhan

University, Wuhan, China, 430071

Jiazhong Sun, MD

Mei Yang, PhD