INTRODUCTION
Insulin resistance (IR) is a metabolic condition in which insulin dependent
tissues become less sensitive to insulin action, leading to an imbalance in the
metabolism of carbohydrates, lipids and proteins1. This condition is
caused by the influence of different risk factors in the population, such as
aging, alcohol consumption, smoking, hypercaloric
diets, sedentary lifestyle and obesity2.The role of insulin
resistance in the development of different pathologies, as CVD3is
now recognized, as well as, in the pathogenesis and clinical outcomes of type
2diabetes mellitus (DM2)4.
Many mathematical models have been proposed in recent years with
the objective of simplifying the measurement of IR, highlighting the HOMA-IR, a
validated method to measure IR from serum glucose and fasting serum insulin5.
IR, characterized by a decrease in cell sensitivity to
insulin, is one of the leading causes of metabolic abnormalities. Considering
that metabolic abnormalities at childhood may increase the risk of
cardiovascular diseases during adulthood, it is critical to diagnose insulin
resistance in adolescents6.
Insulin resistance (IR)
is characterized by inappropriate physiologic response in which insensitivity
to insulin results in compensatory hyperinsulinemia7. It is regarded
a major risk factor for type 2 diabetes8,9,10.
Increased human population with chronic diseases associated with IR are
reported globally11,12. Thus, early
detection of IR is crucial to prevent the manifestation of clinical diseases.
Many
studies have demonstrated that IR is one of the most important contributing
factors to CVD13,14. Furthermore,
given that insulin resistance is an important risk factor for development of
type 2 diabetes and incident cardiovascular diseases, identification of
subjects with insulin resistance is a strategy for identifying high-risk people
for targeted preventive interventions13,15.
HOMA-IR,
derived from the product of the fasting levels of insulin and glucose, is a
robust tool used as a surrogate measure for insulin resistance16,17. Several population-based studies were conducted
to establish cut-off values of HOMA-IR using receiver operating characteristic
(ROC) curves for metabolic syndrome for the clinical usefulness17,18,19,20,21,22.
The HOMA-IR was
developed in 1985 and has been widely used for IR quantification. However,
insulin measurement is still not readily available in many routine laboratories
and this is due to standardization issues23. IR
predisposes to several metabolic disorders including hyperglycemia, high blood
pressure, and dyslipidemia, all of them strongly associated with diabetes,
atherosclerosis, and cardiovascular disease. The evaluation of IR requires sophisticated
methods which are not available for use in daily clinical practice24.
Hyperinsulinemic-euglycemic
clamp is the direct method to measure IR and is considered the ‘‘gold
standard’’ procedure, but it is difficult to perform in daily practice. Several
surrogate markers have therefore been proposed, including the homeostatic model
assessment of IR (HOMA-IR), one of the most widely used. HOMA-IR is calculated
based on the measurement of fasting blood glucose and insulin levels5.Thereare
two issues to be considered with regard to insulin. On one hand, insulin has a
high biological variability(within- and
between-subject variability of 21.1% and 58.3%respectively)25and on
the other hand, its measurement is yet to be standardized26,27. These
two aspects have direct impact on the estimation of IR using the HOMA-IR index28.
Having in mind the
association between insulin and diabetes, and other metabolic conditions, and
the importance of determining the level of insulin, this study investigated the
effect of insulin resistance on platelet counts in normal, pre-diabetic and
diabetic human subjects. The study was done on the premise that base-line data could be provided for physicians in the assessment of insulin resistance on platelet counts. This is by proffering some scientific information on
insulin resistance, PLT counts, HbA1c, FBS, and HOMA-IR index of normal,
pre-diabetic and diabetic human subjects. The study was limited to enrolling
normal individuals, pre-diabetic and diabetic human subjects for the purpose of
investigation
IR and/or PLT counts, and FBS, HbA1c, and HOMA-IR.
METHODOLOGY
This
study was conducted in the University of Port Harcourt
Teaching Hospital (UPTH) in Obio/Akpor
Local Government Area of Rivers State, Nigeria. The study area is located in
the Niger Delta region, bordering the Atlantic Ocean. It was a cross-sectional
study involving subjects that routinely visited the healthcare facility for
their medical needs at the Out-Patient unit. They were grouped into three:
control GROUP A, and test Groups B and C.
GROUP A: The
control group consists of forty (40) normal (non-diabetic) subjects.
GROUP B: The
test group consists of 40 pre-diabetic subjects.
GROUP C: The
test group consists of 40 diabetic subjects.
Individuals
aged between thirty six (36) to seventy six (76) years who agreed to
participate in the study were included, while those with co-infection and other
metabolic disorders were excluded. The minimum sample size was calculated by employing
the formula below:
N =
Z2(pq) / e2
29.
Where
N = minimum sample size, Z = 1.96 at 95% confidence limits, so that z2
= 3.8416, p = prevalence of increased normal and diabetic subjects’ percentage
average, q = 1-p and e = error margin tolerated at 5% = 0.05 (e2 =
0.0025).
6.80%
was the prevalence of increased normal subjects and 10.20% the prevalence of
increased diabetic subjects.
((6.80
+ 10.20)/2)% = (17.00/2)% = 8.50% (8.50% as the
prevalence of increased mean of normal and diabetic subjects), p = 8.50% =
0.0850, q = 1-p = 1-0.0850 = 0.9150
N =
((3.8416(0.0850 x 0.9150))/0.0025 = 119.51 = approximately 120.
Subjects were issued or given the informed consent form to
complete or fill out after listening to a detailed explanation from the
researcher. This is followed by obtaining five (5) ml of blood samples was
collected from the phlebotomy department of UPTH using 5 ml syringe from each
subject. Two (2) ml was put into Lithium heparin bottle, 2 ml into plain
bottle, and one (1) ml into Fluoride oxalate bottle. The samples were placed in
sample racks and left to stand for at least thirty (30) minutes at room
temperature. The sample was centrifuged for 5 minutes using the centrifuge (Hettich Universal 320) at room temperature and a completely
cell free non-haemolysed sample was obtained. The
samples were then separated into a 1 ml sample container which was labeled with
the serial number of the subject, and left to refrigerate before use.
Whole blood sample collection from subjects was by intravenous means
(collected intravenously) and the samples were collected into plain and
heparinized bottles respectively, which were allowed to stand for 30 minutes to
clot, centrifuged at 3,000 rpm for 10min for proper separation, separated into
plain bottles and labeled accordingly. This was stored frozen, until when
needed for biochemical and haematological analysis.
Sources of information was from published studies that
assess insulin resistance on platelet counts in normal, pre-diabetic and
diabetic human subjects were searched in MEDLINE, EMBASE and PubMed databases
covering the period from year 2000 to 2018. Literature search was then carried
out using the combination of terms “insulin”, “insulin resistance”, ‘PLT’, ‘PLT
counts’, “HOMA-IR”, “HbA1c”, "Blood Sugar", “FBS”,
"diabetes", "diabetes mellitus", "type 2diabetes","T2DM",
"type 2 DM", "epidemiology", and "review". The
reference lists of the retrieved articles and reviews of this field30,31,32 were also searched. The search was limited to
human studies and English publications.
Fasting Blood Sugar (FBS) was analyzed using Randox Kits (RANDOX, USA). HbA1c test was analyzed using Wondfo Finecare System (WONDFO,
CHINA). Insulin was analyzed using Calbiotech Inc.,
enzyme-linked immunosorbent assay (ELISA) Kit while
HOMA-IR was also analyzed. Full blood count (FBC) which involves Platelet
counts level was also analyzed.HbA1c was determined using the FinecareTM HbA1c Rapid Quantitative Test which
is a fluorescence immunoassay used for quantitative determination of HbA1c in
human blood (Jeppsson et al., 2002).The quantitative in
vitro determination of FBS in serum and/or plasma was done on the Randox (Rx) Monza analyzer,
In
determining the HOMA-IR, the IR
Calculation: Insulin × Glucose÷405
Optimal Range: 1.0 (0.5 – 1.4). Less than 1.0 means one is
insulin-sensitive which is optimal, above 1.9 indicates early insulin
resistance and above 2.9 indicates significant insulin resistance. This
calculation marks for both the presence and extent of any insulin resistance
that one might currently express.
All data were subjected to statistical analyses. Statistical
analysis was performed using SPSS version 21 (IBM, U.S.A). The data was
analyzed using one-way analysis of variance (ANOVA) and significant differences
were determined using post Hoc Duncan multiple comparison test (p<0.05). The
results were considered significant at 95% confidence level. The values were
represented as mean ± standard deviation (SD) and data obtained was analyzed
using the SPSS. Data was shown as mean + SD and displayed in figures.
Qualitative variables of gender categories were summarized as proportions.
Quantitative variables such as age were summarized as mean. Difference in mean
of parameters was compared using ANOVA.
RESULTS
Glycemic indices, HOMA-IR and platelet counts level of
subjects
The
results obtained for the glycemic indices comprising the HOMA-IR and PLT counts
level are shown in Tables 1-3.
FBS and HbA1c
(Glycemic indices), and insulin of the subjects are shown in Table 1.
The FBS and HbA1c
showed a significantly increasing trend with values of 4.49±0.08 mmol/l, 6.00±0.11 mmol/l, and
10.84±0.96 mmol/l for FBS; and 4.75±0.05 mmol/l, 5.73±0.08 mmol/l, and
9.74±0.47 mmol/l for HbA1c, for the non-diabetics,
pre-diabetics, and diabetics respectively. All values were significantly higher
(p<0.05) across the groups for
both FBS and HbA1c.
Table
1 Fasting Blood Sugar and HbA1c (Glycemic indices), and Insulin of the
subjects.
|
GROUP
|
FBSmmol/l
|
HbA1c mmol/l
|
|
NON-DIABETIC
|
4.49±0.08bc
|
4.75±0.05bc
|
|
PRE-DIABETIC
|
6.80±0.11ac
|
5.73±0.08ac
|
|
DIABETIC
|
10.84±0.96a
|
9.74±0.47a
|
Data are expressed as
Mean ± Standard deviation (SD), n=120 where n represents the number of
subjects. Values in the same column with similar
superscript letter a, were significantly higher (p<0.05) than that of the
non-diabetic. Values with the superscript b, were significantly lower
(p<0.05) than that of the pre-diabetic. Values with the superscript c, were
significantly lower (p<0.05) than that of the diabetic group. FBS –
Fasting Blood Sugar, HbA1c – Glycated Haemoglobin, INS – Insulin
The HOMA-IR index of
the non-diabetic, pre-diabetic and diabetic human subjects is shown in Table 2.
The table reveals an
increasing trend in the HOMA-IR index across the groups. HOMA-IR values were
0.94±0.04 for the non-diabetics, 2.28±0.17 for the pre-diabetics, and 3.25±0.44
for the diabetics. HOMA-IR index values of the diabetics and pre-diabetics were
significantly higher than that of the non-diabetics as shown in Table 2 below.
Table 2 Homeostatic
model index (HOMA-IR) of human subjects for the non-diabetic control,
pre-diabetic, and diabetic groups
|
GROUP
|
HOMA-IR
|
|
NON- DIABETIC
|
0.94±0.04c
|
|
PRE-DIABETIC
|
2.28±0.17ac
|
|
DIABETIC
|
3.25±0.44ab
|
Data are expressed as Mean ± Standard
deviation (SD), n=120 where n represents the number of human subjects. Value with similar superscript letter a, was significantly higher
(p<0.05) than that of the non-diabetic. Value with the superscript b, was
significantly higher (p<0.05) than that of the pre-diabetic. Value with the
superscript c, was significantly lower (p<0.05) than that of the diabetic
group. HOMA-IR
– Homeostatic Model Assessment of Insulin Resistance
Table 3 below shows the platelets counts
levels of the human subjects used in this study. Platelet (PLT) counts were
significantly increased (p<0.05) in the pre-diabetic and diabetic groups
showing values of 186.95±6.04 mL, 206.70±8.72 mL, and 229.97±11.21 mL
respectively for the non-diabetics, pre-diabetics and diabetics.
Table 3 Platelet
(PLT) count in Human subjects
|
GROUP
|
PLT (×109/L)
|
|
NON-DIABETIC
|
186.95±6.04c
|
|
PRE-DIABETIC
|
206.70±8.72ac
|
|
DIABETIC
|
229.97±11.21ab
|
Data are expressed as Mean ± Standard
deviation (SD), n=120 where n represents the number of human subjects. Value with similar superscript letter a, was significantly higher
(p<0.05) than that of the non-diabetic. Value with the superscript b, was
significantly higher (p<0.05) than that of the pre-diabetic. Value with the
superscript c, was significantly lower (p<0.05) than that of the diabetic
group. PLT
– Platelet
DISCUSSION
The hall-mark of Type 2 diabetes is an
abnormally high glucose that is unresponsive or only slightly responsive to
insulin regulation.
Analysis of the platelet counts in the human
subjects in this study showed that there were alterations in the platelet
levels in the diabetic state. Platelet counts were also found to be elevated in
the pre-diabetic and diabetic subjects relative to the normal control group.
This is in agreement with findings reported by several previous studies and
might be the indirect features of insulin resistance syndrome33.
CONCLUSION
The
study investigated the effect of insulin resistance on platelets counts and the
findings largely corroborated previous studies. This
study revealed that insulin resistance has a significant effect
on platelet counts in normal, pre-diabetic and diabetic human subjects.
RECOMMENDATIONS
It is recommended that platelets counts
should be checked routinely as it is significantly in diabetes. The research
should also be conducted in various geographical locations as variations in
different locations affect the genetic factor and limit the generalization of
the research findings.
CONTRIBUTION
TO KNOWLEDGE
Improvement in insulin resistance will help
in ameliorating its effect on platelet counts and reduce the effect of diabetes
on the subjects.
CONFLICT
OF INTEREST
There was no conflict of interest
FUNDING
There was no funding for the research
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