INFLUENCE OF GENDER ON TOTAL SERUM CREATINE KINASE AND CREATINE KINASE-MB LEVELS OF NIGERIAN

1 2* Henry Afamuefuna Efobi , Iya Eze Bassey 1436 ISSN: 2542-2758 (Print) 2542-2804 (Online) Birat Journal of Health Sciences Vol.6/No.2/Issue 15/May-Aug., 2021 Received : 23 September, 2020 Accepted : 09 August, 2021 Published : 04 November, 2021 Original Research Ar cle


Introduc on
Hypertension is a long-term medical condi on which when not detected and managed properly and on me o en results to complica ons leading to disabili es and mortality. Gender has been known to affect the interpreta on of some variables necessita ng the need for gender-specific ranges.

Objec ves
This study evaluated total crea ne kinase (CK) and crea ne kinase-MB (CK-MB) isoenzyme ac vi es of hypertensive subjects in Calabar, Nigeria and to assess if gender has influence on the ac vi es of these enzymes.

Methodology
One hundred and two par cipants were consecu vely enrolled in this case control study. Serum total serum CK and CK-MB ac vity were evaluated in fi y one hypertensive and 51 normotensive subjects. The total CK levels were assessed using a spectrophotometric method while immunoinhibi on method was used to determine the ac vity of CK-MB. Data was analyzed using Student's t-test and Pearson's correla on. Sta s cal significance was set at p<0.05.

Result
The total crea ne kinase ac vi es of the hypertensives did not differ significantly from those of the normotensive controls (p = 0.428) while the serum CK-MB ac vi es of the hypertensive subjects were significantly higher than those of the normotensive controls (p=0.000). The body mass index of the hypertensives was significantly higher than those of the normotensive subjects (p=0.030). Gender had no effect on the blood pressure, body mass index and levels of CK and CK-MB (p>0.05). There was also no significant correla on (p>0.05) between blood pressure, body mass index and the levels of CK and CK-MB.

Conclusion
CK-MB ac vi es were significantly higher in hypertensive subjects compared to normotensive controls. There were no gender specific differences in the CK-MB levels of male and female hypertensives. This cardiac marker should be included in the rou ne assessment of hypertensives and gender-specific considera ons may not be necessary in the interpreta on of the data.

KEY WORDS
Blood pressure, crea ne kinase, crea ne kinase -MB, gender, hypertension.

INTRODUCTION
Hypertension is a chronic non-communicable disease and a 1 major global public health problem. Usually defined as systolic blood pressure ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg, it accounts for up to half of both stroke and ischemic heart disease cases, and about a sixth of the 2 total deaths globally. Hypertension affects about 22% of adults above 18 years, with developing na ons bearing the bulk of the burden. It has been projected that by 2020, the low and middle-income countries (LMIC) will bear 80% of the cardiovascular disease burden and three quarters of all 2 deaths in Africa may be caused by it. It o en remains asymptoma c un l late in its course. Since it has been iden fied as a silent killer, it is thus important to iden fy its risk factors and efforts made early enough to prevent its 3 progression, a endant complica ons and final outcome. Crea ne kinase is an intracellular enzyme present in cells of the heart, brain and skeletal muscle. Disrup on of cell membrane of the heart due to hypoxia release crea ne kinase MB, an isoenzyme of crea ne kinase, from the cellular 4 cytosol in to the systemic circula on. CK-MB is bound lightly to the contrac ve apparatus and their plasma level is dependent on how severe myocardial injury is as its entry into circula on 5 is passive. On this basis elevated serum level of CK-MB has been used as a sensi ve marker for myocardial infarc on. Some studies have reported both racial and gender differences for CK ac vity in normal popula ons and some [6][7][8] other diseases. It has also been documented that nonconsidera on of gender-related differences could lead to the wrong classifica on of subjects in both epidemiological and/ or clinical studies. However, literature on gender differences in crea ne kinase-MB levels among Nigerian subjects with hypertension is scarce. Therefore, this study evaluated total crea ne kinase and crea ne kinase-MB isoenzyme ac vi es of hypertensive subjects in Calabar, Nigeria to assess if gender, body weight and blood pressure have influence on the ac vi es of these enzymes.

METHODOLOGY Pa ents and Methods
A total of 102 par cipants of Nigerian origin were consecu vely recruited into this case control study. Fi y-one hypertensive pa ents (33 males and 18 females) were recruited from the Medical Out-pa ent Department of University of Calabar Teaching Hospital (UCTH) Calabar. Fi y-one apparently healthy non-hypertensive subjects (29 males and 22 females) were recruited from the environs of the Calabar metropolis. Subjects were between the ages of 40 and 65 years. This study was done in accordance with the ethical 9 requirements of the World Medical Associa on. Ethical approval was obtained from the Cross River state ministry of Health Research ethics commi ee with approval number CRS/MH/CGS/BH/018/VOLII/109. The nature and purpose of the study was explained to each par cipant a er which wri en informed consent was obtained. Informa on on the subjects' age, family history, dietary and physical lifestyle was obtained using a standard ques onnaire. Blood pressure, 10 weight and height were measured as described elsewhere.

Sample size calcula on
Power and sample size calcula ons for Unmatched Case-Control study were carried out using the Stat Calc func on of Epi Info so ware (Centre for Disease control and Preven on -CDC). A two-sided confidence level of 95%, desired Power of 80%, the ra o of controls to cases as 1 and 8 odds ra o of 3.19 from a study by Ciruzziet al., was u lized. The percentage outcome in the unexposed group was 55.4%. The Kelsey formula 16 gave a sample size of 51 for cases and 51 for controls (i.e. a total of 102 par cipants).

Inclusion and Exclusion Criteria
All the subjects were known hypertensives receiving treatment for hypertension. Those with history of diabetes mellitus were excluded from this study. The controls were apparently healthy with no history of hypertension, diabetes mellitusor chronic illness and smoking. Pregnant and lacta ng women were also excluded.

Specimen Collec on
A er an overnight fast, blood samples (5mls)were asep cally collected from the antecubital vein into plain bo les, allowed to clot and sera extracted and frozen. The samples were thawed and used (within two hours) for total CK and CK-MB determina on.

Analysis of total Crea ne kinase and CK-MB
To t a l c r e a n i n e k i n a s e w a s m e a s u r e d u s i n g spectrophotometric method, while immune-inhibi on method was used to determine the ac vity of CK-MB. Both kits were obtained from Randox Laboratories Ltd, Antrim -United Kingdom.

Sta s cal Analysis
Sta s cal analysis was done using the PAW sta s c 18, a sta s cal package from SPSS Inc, California, USA. The results were expressed as Mean ± SD. Student's t-test and Pearson's correla on was used to analyze the data. The level of significance was set at 95% confidence interval, where a probability value (p<0.05) was regarded as sta s cally significant. Table 1 the mean systolic and diastolic blood pressures as well as the CK-MB ac vity of the hypertensive subjects were significantly higher than those of normotensives ( =0.0001). However, the body mass index of the hypertensives p was significantly lower than of those thenormotensive group (p= 0.030). There was no significant difference in the age and total crea ne kinase of both groups. The age, body mass index, blood pressures, total crea ne kinase and crea ne kinase-MB of the male hypertensives did not differ significantly from those of female hypertensives (p >0.05) (Table2). Similar findings were observed among the male and female normotensives except for the body mass index which was significantly higher in the female normotensives. Among the normotensives: the female subjects had significantly higher BMI compare to the male subjects (p =0.002). This is shown in table 3.

Original Research Ar cle
The Pearson's correla on analyses were carried out to determine the level of associa on between assayed variables for both the hypertensive and normotensive subjects. Table 4 and 5 contain the correla on coefficients for each of the pairing. Inspec on of these tables revealed that there was no correla on between CK-MB and Body mass index; CKMB and blood pressure (p >0.05) Table 1: Age, body mass index, blood pressures, total crea ne kinase and crea ne kinase-MB in hypertensive and normotensive subjects

DISCUSSION
In this study the ac vi es of serum Crea ne kinase and its MB isoenzyme were evaluated in both hypertensive and normotensive subjects. Total crea ne kinase ac vi es of the hypertensive subjects did not differ significantly from that of the normotensives, though their levels were higher. It has been shown in animal models that an hypertensive 11 therapy lowers high ssue CK in animal models. All the hypertensive pa ents in our study were on an hypertensive therapy, this may be the reason for this observa on. We also observed no gender differences in the levels of total CK.  15 mass index and ethnicity. However, the hypertensive subjects had higher CK-MB compared to the normotensive group. The severity of myocardial injury determines the plasma CKMB level. The enzyme enters the circula on by passive diffusion from 5 infarct myocardium cells. Hypoxia causes a decrease in oxygen tension consequently resul ng in a decrease in 16 oxida ve phosphoryla on and genera on of ATP. The drop in ATP genera on affects the plasma membrane of the myocardium causing it to lose its integrity and resul ng in a 17 leaky membrane and an increase in CKMB levels. Even slight rises in CK-MB levels are significant prognos cally. This is due to reports sta ng that pa ents with suspected infarc on that had even slightly raised CK-MB levels have 18 been linked with worse outcomes clinically. Our finding is in 5 agreement with that of Emokpae and Nwagbara. It was observed in this study that there were no significant differences in the mean CK-MB ac vi es between male and female hypertensivesor normotensives. Gender-related differences in CK-MB mass have been previously reported [19][20] only in healthy subjects.
Both studies reported that females had significantly lower levels of CK-MB mass than males among healthy subjects. They suggested that the observed differences were due to greater body muscle mass in men there by indica ng a need for different gender-based decision limit values in clinical se ngs. However, in a study on Nigerian hypertensives, Emokpae and Nwagbara reported that serum CK-MB ac vity was lower in male than 5 female hypertensives. Though the reason for their observa on was unclear, they suggested that this may be an underlying reason for the worse clinical outcome and prognosis in women with respect to cardiovascular complica ons. The lack of genderspecific differences in our study implies that gender-specific considera ons may not be necessary in the interpreta on of the data and management of these pa ents.

CONCLUSION
CK-MB ac vi es were significantly higher in hypertensive subjects compared to normotensive controls. There were no gender specific differences in the CK-MB levels of male and female hypertensives.

RECOMMENDATION
This cardiac marker should be rou nely included in the evalua on of hypertensive subjects and gender-specific considera on may not be necessary in the interpreta on of the data and management of these pa ents.

LIMITATIONS OF THE STUDY
A limita on of this study was the small size of the study popula on, being restricted to only one hospital.

ACKNOWLEDGMENTS
I acknowledge all the par cipants who agreed to take part in this study.