J Obes Metab Syndr 2021; 30(1): 63-71
Published online March 30, 2021 https://doi.org/10.7570/jomes20086
Copyright © Korean Society for the Study of Obesity.
Department of Clinical Laboratory Sciences, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
Imran Ali Khan
Department of Clinical Laboratory Sciences, College of Applied Medical Sciences, King Saud University, Riyadh 11433, Saudi Arabia
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background: Consanguinity, defined as a blood relation between couples, is associated with genetic diseases in their offspring. In Saudi Arabia, obesity is considered a major health problem associated with increased risks of cardiovascular disease, insulin resistance, and type 2 diabetes mellitus. Angiotensin-converting enzyme (ACE) with insertion (I) and deletion (D) polymorphisms of an Alu-287 bp sequence has been implicated in multiple metabolic disorders, including obesity. To date, no studies have been conducted in the Saudi population regarding the ACE gene in consanguineous offspring with obesity. Therefore, the present study aimed to investigate genetic associations in offspring of first cousins, and specifically the relationship between obesity and ACE (Alu-287 bp) was evaluated in the Saudi population.
Methods: In total, 91 cases of obesity in the offspring of first-cousin couples and 100 control subjects without obesity but with a family history of consanguinity were included. Using genomic DNA, ACE ID polymorphisms between the cases and controls were evaluated by polymerase chain reaction.
Results: There were strong differences in the height, weight, and body mass index between the cases and controls (P<0.001). A genotype analysis confirmed the strong association with allele frequencies (P<0.001; odds ratio, 4.902; 95% confidence interval, 2.867–8.379) when compared between the cases and controls. One-way analysis of variance showed a positive correlation with height and logistic regression (covariance) that could not be strongly correlated (P>0.05).
Conclusion: In conclusion, the ACE gene polymorphism was found, through allele frequencies, to be associated with obesity in the offspring of consanguineous first cousins in the Saudi population.
Keywords: Consanguinity, Obesity, Offspring, First cousin, Consanguineous couples, Angiotensin-converting enzyme-insertion/deletion, Alu-287 bp
Clinical genetics defines consanguineous marriages as the union between blood-related couples, e.g., first cousins, double first cousins, second cousins, or even more closely related individuals, leading to a coefficient of inbreeding (F) in their progeny of >0.01.1 Consanguineous marriages, also termed consanguineous unions, refer to weddings between two individuals with at least one traceable common ancestor, and their offspring are considered offspring of consanguineous couples.2 First cousins are the most frequent cases; accounting for 10.4% of consanguineous couples worldwide.3 In medical genetics, the effects of consanguinity and inbreeding on human health are major focuses of research.4 Consanguineous marriages account for ~20% of marriages worldwide (i.e., ~1.2 billion), but that prevalence varies according to ethnicity, religion, and culture, with rates of 0.5% in Europe, 0.2% in the United States, and 67.6% in the Middle East.5 In the offspring of consanguineous couples, autozygosity mapping is used to identify causal mutations in autosomal recessive disorders.6 These analyses have indicated that children of first consanguineous cousins have an elevated risk for genetic disorders and congenital anomalies compared with children in the normal population.7 Recessive genes do not result in the expression of genetic diseases owing to low visibility relative to dominant genes. However, the inheritance of two identical copies of similar sporadic recessive gene variants results in the expression of genetic diseases.8
Genome-wide association studies, meta-analyses, single nucleotide polymorphisms, exome sequencing, next-generation sequencing, and cohort studies have identified multiple variants in complex and multifactorial human diseases. Angiotensin-converting enzyme (
This case-control study was performed at the College of Applied Medical Sciences (CAMS), King Saud University (KSU), in the capital city of Saudi Arabia. The study protocol was approved by the Ethics Committee of CAMS-KSU, with the approval number 01/1435-1436, and signed informed consent was obtained from all participants. The STROBE statement (guidelines for reporting observational studies in epidemiology, accessible via the EQUATOR network and used to improve the consistency and transparency of health research) was implemented throughout the design, review, interpretation, planning, and revisions of the study. In total, 91 saliva samples from the obese offspring of first cousins were collected from various locations in Riyadh, such as the Sahara Mall, Saudi boys’ school, King Khalid University Hospitals, and KSU Medical College. Blood samples from 100 control subjects were obtained from the KSU premises. The inclusion criterion for the cases was offspring of first cousins with obesity, as defined by the World Health Organization.21 The exclusion criteria were non-obese first cousin offspring, first cousin siblings, non-offspring of first cousins, and offspring of second cousins. Controls were mainly non-obese subjects (BMI <25 kg/m2) without any metabolic, renal, or complex disorders, and whose parents did not belong to a similar family pedigree, i.e., parents were not involved in any degree of consanguineous marriages.
Using ethylenediaminetetraacetic acid (EDTA) vacutainers, 2 mL of whole blood leukocytes was collected from all control subjects. For the cases, 1–2 mL samples of saliva were collected using Oragene DNA Collection Tubes (Norgen Biotek, Thorold, ON, Canada). The saliva tubes were stored at room temperature. The Prep- IT-L2P Kit (Norgen Biotek) was used to extract genomic DNA from the saliva, and the Norgen DNA Extraction Kit was used for extraction from blood. EDTA samples were separated as per the protocol provided by the company. Then, 100 μL of Tris EDTA buffer was added to each sample, and the NanoDrop was used to evaluate DNA purity at 260/280 nm (NanoDrop 2000 Spectrophotometer; Thermo Scientific, Waltham, MA, USA).
Clinical data are presented as mean±standard deviation. Pearson chi-square experiments evaluated the Hardy-Weinberg Equilibrium (HWE) for
The anthropometric characteristics of the cases and controls are documented in Table 1. Obesity cases (mean age, 29.4±12.45 years) were younger than the controls (mean age, 48.05±10.69 years), and sex ratio differed between groups. Obese offspring showed significantly higher values for anthropometric parameters, such as weight and BMI, than those of the controls (
Genotype frequencies for
Genotype and allele frequencies for the
One-way ANOVA with genotypes II, ID, and DD and anthropometric measurements such as age (
This case-control study of 91 cases and 100 controls provides the first analysis of the
The relationship between consanguinity and genetic disorders is now recognized, and it is predicted that one billion people worldwide from different cultural communities are in consanguineous marriages, particularly in the Middle East, Asia, and North Africa, where these marriages represent 20%–50% of total marriages. In Saudi Arabia, a nearly 50% rate of consanguinity has been reported, with rates as high as 80% in some specific regions; marriages between first cousins are particularly frequent, ranging between 28% and 40%.25 The risks associated with consanguinity for first-cousin parents have been confirmed by analyses of birth defects in newborns.26 These risks are passed to offspring through autosomal recessive gene mutations inherited from a common ancestor.27 Loss of function (missense) variants are expected to disrupt the functions of protein-coding genes.28 Among 22 countries in the Arab world totaling a population of 500 million, Saudi Arabia is one of the highest income countries in the Arabian Peninsula. In total, 955 genetic diseases have been acknowledged in the Arab population,29 whereas 7,500 disorders are documented in the global population.6 Bosdou et al.30 confirmed the connection between obesity and infertility in consanguineous women; an elevated BMI increases the risk of infertility due to hormonal abnormalities and ovulation dysfunction. However, genetic studies of the correlation between consanguinity and obesity are lacking. The lifestyle in Saudi Arabia has changed drastically since the discovery of oil and subsequent increases in wealth. Obesity in Saudi Arabia has become a serious health complication, resulting in preventable deaths, and is connected with an increase in chronic non-communicable diseases; 68% of citizens are classified as overweight or obese.31
The rs4646994 is one of the functional polymorphisms that appears on the
The heterozygous genotypes (ID) vary from our study (1.1%) when compared with other obesity studies with non-consanguineous subjects.40 There is the possibility that offspring might receive the dominant alleles (deletion) from both parents because of consanguinity. However, from this single and low-sample-sized study, this is difficult to conclude. Apart from this, the control subjects in the present study, i.e., non-obese offspring in non-consanguineous parents, differed in the heterozygous genotypes (ID) of the
Finally, some important limitations of this study need to be considered. Only one single nucleotide polymorphism was evaluated, which may be inadequate for assessing the risk levels associated with consanguinity. In addition, serum assays were not performed. Furthermore, these genotype data must be interpreted with caution because our population data were not consistent with those of other Saudi studies, and the sample size was not large enough. The final limitation of this study is that it was performed with the obese offspring of first cousins only, instead of also including non-obese offspring of non-consanguineous couples. Additional subject groups were not involved in this study.
In conclusion, this analysis of the
The authors declare no conflict of interest.
Study concept and design, acquisition of data, analysis and interpretation of data, drafting of the manuscript, critical revision of the manuscript, statistical analysis, obtained funding, administrative, technical, or material support, and study supervision: all authors.
Anthropometric details of first cousin siblings and control subjects
|Variable||Case (n = 91)||Control (n = 100)|
|Age (yr)||29.40 ± 12.45||48.05 ± 10.69||0.130|
|Weight (kg)||98.19 ± 31.58||67.23 ± 11.48||< 0.001*|
|Height (cm)||156.28 ± 20.31||163.68 ± 8.84||0.160|
|BMI (kg/m2)||38.10 ± 11.07||24.83 ± 3.52||< 0.001*|
|First cousin siblings||91 (100)||0||< 0.001*|
Values are presented as mean± standard error or number (%).
BMI, body mass index.
Genotype and allele frequency distributions of the
|Genotype/allele||Case (n = 91)||Control (n = 100)||OR (95% CI)||OR (95% CI)*|
|II||10 (11.0)||10 (10)||Reference||Reference||Reference||Reference|
|ID||1 (1.1)||58 (58)||0.017 (0.002–0.149)||< 0.001||0.019 (0.002–0.148)||< 0.001|
|DD||80 (87.9)||32 (32)||2.500 (0.095–6.579)||0.058||2.200 (0.099–6.582)||0.036|
|Dominant (II vs. ID+DD)||10 (11)||10 (10)||1.110 (0.440–2.806)||0.820||1.130 (0.480–2.824)||0.680|
|Co-dominant (ID vs. II+ID)||1 (1.1)||58 (58)||0.008 (0.001–0.060)||< 0.001||0.009 (0.002–0.090)||< 0.001|
|Recessive (II+ID vs. DD)||11 (12.1)||68 (68)||0.064 (0.030–0.130)||< 0.001||0.066 (0.032–0.140)||< 0.001|
|I allele||21 ± 12||78 ± 39||Reference||Reference||Reference||Reference|
|D allele||161 ± 89||122 ± 61||4.902 (2.867–8.379)||< 0.001||4.905 (2.871–8.382)||< 0.001|
Values are presented as number (%) or mean± standard error. Reference indicates the II genotypes and I allele.
*The correlation between age/sex and the genotypes; †
Multinomial logistic regression analysis
|Characteristics||OR (95% CI)|
|Age (yr)||0.692 (0.547–0.874)||0.002|
|Sex (male:female)||0.008 (0.000–11.587)||0.193|
|Weight (kg)||1.073 (0.929–1.238)||0.338|
|Height (cm)||0.966 (0.817–1.142)||0.684|
|BMI (kg/m2)||1.860 (1.081–3.201)||0.025|
Cox & Snell R2: 0.707.
OR, odds ratio; CI, confidence interval; BMI, body mass index;