*4.2.1 rs247616, rs1968905 and rs1270922 polymorphisms (CETP)*

The CETP polymorphisms (rs247616, rs1968905 and rs1270922) are SNPs that occur as a result of substitutions in their nucleotide bases [89, 133]. These polymorphisms have previously been used to determine the CETP levels in a CVD population [133]. Mutations in the CETP gene have been found to cause hyperalphalipoproteinaemia 1 (HALP1). Furthermore, it's also been shown that different variants code for distinct isoforms within this gene. This eventually influences the metabolism of HDL-C [89]. Reports on the link between the CETP polymorphisms, CVR and the concentrations of CETP through LDL-C are inconsistent [89, 132, 133].

#### **4.3 Metabolic biomarkers**

## *4.3.1 Gly972Arg polymorphism*

The Gly972Arg polymorphism occurs as a result of a substitution between glycine and arginine (GGG ↔ AGG substitutions) in codon 972 (G972R). It has been demonstrated that this mutation is involved in the development of type 2 diabetes mellitus (type 2 DM) [141]. This is due to the fact that it's been described to influence tyrosine phosphorylation at a specific site of IRS-1 which may lead to the development of insulin resistance (IR) and impair insulin secretion [142]. The Gly972Arg polymorphism has been investigated in a number of studies and found to have a high prevalence in type 2 diabetic subjects and other conditions like obesity [143, 144].

#### **4.4 Oxidative stress**

## *4.4.1 C677T and A1298C polymorphisms (MTHFR)*

The *MTHFR* C677T polymorphism is a SNP where cytosine (C) is replaced with thymine (T) at position 677 resulting in the gene to code for valine as opposed to

alanine at exon 4. The change between alanine and valine nucleotide bases happens on codon 222 resulting in this polymorphism sometimes being described as Ala222Val polymorphism. It has been reported to have the alleles heterozygous *C677T and* homozygous *T667T* which are mutant, whereas the homozygous *C677C* is a wild type allele [145–149].

The A1298C polymorphism causes a change where glutamate is substituted with an alanine at position 429. Each of these genotypes have been shown to reduce the MTHFR enzymatic activity resulting in the methyl group to be unavailable for attachment to homocysteine in order to generate methionine. Hyperhomocysteinaemia has been reported in the development of a number of conditions, for example, CVR, chronic myeloid leukaemia (CML), multiple abortions, autism, osteoporosis, multiple sclerosis, psoriasis, and Alzheimer's disease [106, 108, 135, 145, 146].

### **4.5 Haemostasis**

#### *4.5.1 R353Q polymorphism (factor VII)*

In the R353Q polymorphism, guanine is substituted with adenine at the 353rd codon of the *FVII* gene. This missense replacement of arginine (R) by glutamine (Q) in this polymorphism has been reported to influence the factor VII levels [150]. Individuals who carry the Q allele carriers have been shown to have lower levels of Factor VII than those who carry the R allele. Nonetheless, the findings on the association between the R353 Q polymorphisms and CVR (thrombosis) are inconclusive [151]. Increased levels of factor VII are linked to thromboembolic disorders risk. A relationship between defects in the factor VII gene and CVD has been reported [114, 150, 151].
