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SA JOURNAL OF DIABETES & VASCULAR DISEASE
RESEARCH ARTICLE
VOLUME 16 NUMBER 2 • NOVEMBER 2019
63
Studies investigating circulating FAs have also reported some
conflicting results. A recent study examined the relationship between
body mass index (BMI) and plasma phospholipid FA composition in
men aged between 48 and 65 years and reported higher plasma
phospholipid levels of palmitic (C16:0) and stearic acid (C18:0) in
obese individuals.
13
Furthermore, plasma concentrations of C16:0
were positively associated with risk for total mortality in men and
women in a prospective study in the USA.
14
SFAs, myristic acid
(C14:0), C16:0 and C18:0 in plasma were positively associated with
the MetS, while longer-chain SFAs, and arachidic (C20:0), behenic
(C22:0) and lignoceric acid (C24:0) were inversely associated in
men and women from Taiwan.15 Another study also reported
lower levels of plasma C22:0 and C24:0 in the MetS participants.
16
Palmitoleic acid (C16:1
n-
7) level in plasma phospholipids was
positively associated with BMI in men and women,
13,17
and higher
levels of plasma C16:1
n-
7 were associated with multiple metabolic
risk factors in men and women.
18,19
In different populations, total
n-
3 FAs in plasma were associated
with lower BMI, waist circumference (WC) and hip circumference
20
and inversely associated with the MetS,
21
while omega-6 PUFA have
been associated with obesity and the MetS. Pickens and associates
reported higher plasma phospholipid levels of dihomo-
γ
-linolenic
acid (C20:3
n-
6) in overweight and obese individuals.
13
Positive
associations of serum phospholipid C20:3
n-
6 with BMI, as well as
total
n-
6 PUFAs with waist:hip ratio were also documented in a study
of Mexican women.
17
Some studies also report positive associations
of specific plasma phospholipids
n-
6 PUFAs with metabolic risk,
18,22
while other studies report inverse associations of total
n-
6 PUFAs
in erythrocytes and serum, respectively, with the MetS.
23,24
Due to
inconsistent results in different studies relating to circulating
n-
6
PUFAs, further research to understand their role in association with
obesity and the MetS is highly recommended.
25
Since people consume food rather than individual nutrients, it
is difficult to isolate the individual nutrients in the diet and link
them to disease and health.
26
Therefore, the analysis of food intakes
into patterns derived from various combinations of nutrients or
foods has developed as a preferred alternative to investigating
associations between nutrients and diseases.
27
Several studies have
applied factor and cluster analysis to derive patterns from food and
tissues in investigating the association of these patterns with health
and diseases.
28
FA patterns from adipose tissue and plasma have been employed
to describe associations of FAs with obesity
29
and the MetS.
22,30
Despite the extensive use of plasma FAs in research, there is limited
epidemiological research on the use of both dietary and circulating FA
patterns in association with obesity and the MetS in black populations
in Africa. To address the key gaps in the current knowledge, the
aim of this study was to investigate the associations of dietary and
plasma phospholipid FA patterns with adiposity measures [BMI, waist
circumference (WC) and waist-to-height ratio (WHtR)] and the MetS
in a selected group of black South African adults. This study was
based on a random sub-sample of 711 participants selected from
the South African site (North West Province) of the multicountry
Prospective Urban and Rural Epidemiological (PURE) study. This study
made use of cross-sectional data collected at baseline during the
months of August to November 2005.
Methods
A sub-sample of 711 black South African participants were
randomly selected from 2 010 adults recruited at baseline (in 2005)
from urban (1 004) and rural (1 006) households in the North
West Province to assess dietary FA intake and plasma phospholipid
FA status. Those included were apparently healthy subjects older
than 30 years at baseline, with no reported diseases of lifestyle,
tuberculosis or HIV, and used chronic medication for diabetes and
hypertension only.
Ethical approval for the South African PURE study was obtained
from the Ethics Committee of North-West University (Ethics
number 04M
10
). Participants provided written informed consent
and participation was voluntarily.
Transportation was provided for the study subjects to reach
the data-collection centres in both rural and urban areas. During
face-to-face interviews by trained fieldworkers, each participant
completed questionnaires in his or her preferred language
(Afrikaans, Setswana or English). The questionnaires included
demographic,
31
physical activity
32
and quantitative food-frequency
questions (QFFQ),
33,34
and made use of, among others, validated
food photo-books to estimate portion sizes.
35
Reproducibility
33
and
details of dietary assessments have been published elsewhere.
10
Dietary macronutrients and FAs were calculated using the
South African Medical Research Council food composition tables.
36
Twenty-eight dietary FAs were included initially, but FAs that had a
daily median intake of less than 0.10 mg were excluded. A total of
11 dietary FAs were used to derive FA patterns for investigation in
this study.
Anthropometric measurements were performed by trained
research assistants according to standards prescribed by the
International Society for the Advancement of Kinanthropometry.
37
A portable electronic scale (Precision Health Scale, A&D Company,
Tokyo, Japan) was used to measure weight. Height was measured
using a calibrated stadiometer (Seca, Hamburg, Germany). Waist
and hip circumferences were recorded using steel tapes (Lufkin,
Apex, NC, USA). BMI and WHtR were calculated using weight (kg)/
height (m
2
) and waist (cm)/height (cm) formulas, respectively. Blood
pressure (mmHg) was measured in duplicate (five minutes apart)
on the right upper arm. Appropriately sized cuffs were used for
obese subjects.
Fasting blood samples were collected from the antecubital vein
with a sterile winged infusion set with minimal stasis. The samples
were collected and plasma and serum were prepared and aliquoted
by a registered nurse and then stored at –80°C in the urban areas.
In rural areas, the samples were stored at –18°C for up to five days,
where after it was transported to the laboratory facility and stored
at –80°C until analysed.
Fasting plasma glucose concentration was determined by the
hexokinase method using the Synchron
®
system (Beckman Coulter
Co, Fullerton, CA, USA). The sequential multiple analyser computer
(SMAC) using the Konelab™ auto-analyser (Thermo Fisher Scientific
Oy, Vantaa, Finland) performed quantitative determinations of
high-density lipoprotein cholesterol (HDL-C), triglycerides and total
cholesterol (TC). Low-density lipoprotein cholesterol (LDL-C) was
calculated using the Friedewald equation.
38
EDTA plasma samples were thawed and extracted with
chloroform:methanol (2:1 v/v) according to the modified Folch
method.
39
The plasma phospholipid FA fraction was isolated by thi
n-
layer chromatography from the extracted lipids.
40
Subsequently,
the phospholipid FA fraction was transmethylated to FA methyl
esters and analysed by quadrupole gas chromatography electron
ionisation mass spectrometry by means of an Agilent Technologies
7890 A GC system, as described by Baumgartner
et al
.
40