ABSTRACT
Cardiac markers are biomarkers measured to evaluate heart function. They can be useful in the early prediction or diagnosis of disease. Until other biomarkers became available, total creatine kinase (CK) was the most widely used biomarker for the diagnosis of myocardial and musculoskeletal disorders. Brain derived neurotrophic factor (BDNF) is a member of the neurotrophin family of growth factors, which also includes nerve growth factor (NGF), neurotrophin 3 (NT-3), and neurotrophin 4 (NT-4).BDNF is widely expressed in the CNS, particularly in the hippocampus where it is essential for long-term potentiation underlying hippocampus-related memory. The worldwide heat wave due to climate change formed the basis for this study with the aim of examining the levels of cardiac involvement and BDNF gene expression in heat adapted rats. A total of forty (40) male and female wistar albino rats weighing between 140-300g were used. After two weeks period of acclimatization, the rats were randomly divided into 2 major groups: Group 1 (n = 10): this was subdivided into experimental and non-experimental groups. The experimental group (n=5) served as baseline for the rest while the non-experimental group (n=5) served as the normal control. These groups were caged at room temperature (30 ± 10C) .Group 2 (n = 30): This group were subdivided into acute and chronic heat exposures at 38-420C for 5 hours per day. The acute exposure group (n=15) were animals exposed to heat for 21 days. Sample were collected longitudinally at weekly interval (i.e day 7, 14, and 21). The chronic exposure group (n=15) were exposed to heat for 42 days, and sample were collected longitudinally at weekly interval (i.e day 28, 35 and 42). Blood samples were collected through cardiac puncture and brain tissues was also collected for serum CK and BDNF gene expression respectively using standard analytical methods. The results were presented as Mean ± SEM (Standard Error of Mean) and P-value less than 0.05 were considered statistically significant. The results showed that chronic heat exposure caused a significant increase in BDNF gene expression (P < 0.05). Also, the result showed that heat exposure caused a significant (P < 0.05) increase in serum CK on week 4 but there was no significant differences observed in week 1, week 2, week 3, week 5, and week 6 compared with the control. Negative correlation was observed between CK and BDNF in control and heat adapted rats, between body weight /CK and CK at week 1 and 2 respectively. There were positive correlations observed between body weight/CK and body weight/BDNF at week 3, 4, 5, and 6. All correlations were not statistically significant (P > 0.05). In conclusion, chronic heat exposure causes up-regulation of BDNF gene expression and also increase serum CK level. This could be interpreted to be a negative cardiac effect as well as long-term memory disturbance.
