Critical Thinking

DISCUSSION have studied several genes that may induce


Diabetes mellitus is a common and serious public health problem all
over the world involving Saudi Arabia. It has been reported by the World Health
Organization (WHO) that Saudi Arabia has the second highest rate of diabetes
among the countries of the Middle East and the seventh in the world2.
 It is likely that both environmental and
genetic factors play important role in the pathogenesis of diabetes26.
Various research groups have studied several genes that may induce the
susceptibility to T2DM in different ethnicities. However, relatively fewer
studies have been conducted in Saudi Arabia to study the relationship between
VDR gene polymorphism and the susceptibility to T2DM.  VDR
gene mediates transcription function, and the interaction with its
ligand (vitamin D) is known to affect insulin secretion and insulin function34.
 We have investigated VDR FokI and
BsmI gene polymorphisms in a group of Saudi people with T2DM, and
matched control subjects for gender and age in Makkah (aka: Mecca) region in
western Saudi Arabia.

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The result of this study found no significant difference in the genotype
distribution and allele frequencies of both FokI and BsmI polymorphisms
in VDR gene between the control and the patients with T2DM.  An important factor for consideration in our
results on VDR polymorphisms is that, this study has been made in Makkah
environs of Saudi Arabia, a   region that
is known to have two seasonal variations, hot and very hot (Table 3).  The available sunshine through the whole year
is fairly high and thus Makkah region can be considered a special reference
region for the possible bio-availability of vitamin D throughout the year,
unlike many European, North American and even areas in Asian countries that are
located in the northern hemisphere such as Hokkaido area of Japan.


Several researchers have investigated VDR polymorphism in different
populations. In Polish subjects, Malecki et al have studied BsmI,
TaqI, FokI and ApaI gene polymorphisms of VDR gene and
they found that the genotype and allele distribution is the same in both controls
and T2DM35.  Also, in French
Caucasian population, Ye et al studied the same SNPs of VDR gene (FokI,
BsmI, TaqI, and ApaI) and they observed that both the
genotype and allele distribution is the same in both controls and T2DM in36.   Furthermore,
in Turkish population, Dilmec et al found no significant difference in
genotype and allele frequencies of the same four SNPs (BsmI, TaqI,
FokI and ApaI) of the VDR gene between both controls and T2DM37.
Among European Caucasians, Bertoccini
 et al studied the VDR
FokI polymorphism in T2DM and found no difference of the genotype distributions
and allele frequencies between T2DM subjects and controls in Italians38.
 Similarly, in Chinese Han population, Fei
Yu et al studied four VDR SNPs and found that VDR FokI and BsmI
polymorphism is not related to T2DM risk in Chinese39. In the African
continent, for Tunisian subjects, no significant association between VDR FokI
polymorphism and T2DM was observed, Mahjoubi et al 40. Thus, all
of the above previously reported observations concur and support our results that
the reported polymorphisms of VDR gene have no bearing on the diabetes

Interestingly, quite the opposite results were obtained by other
investigators studying VDR variants and diabetes in different geographical and
environmental regions.  For example, in North
Indians (Kashmiri population), Malik et al reported VDR TaqI and BsmI
polymorphism and they also found that BsmI G allele is associated with
T2DM risk41. Similarly in United Arab Emirates population, Safar et
al found that the G allele and GG genotype of FokI and T allele and
TT genotype of BsmI are associated with T2DM risk in Emirati population42.  Among the Chinese Han population


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