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Is obesity bad for the heart?
By WenJun Fan, Barbara Huisamen, Amanda Lochner*
We all know that obesity is a major health risk, responsible for diseases such as insulin
resistance, type 2-diabetes and heart disease.
But while it is true that obesity radically increases your chances of developing these
conditions, scientists have recently been baffled by a so-called ‘obesity paradox.’ Numerous
studies over the past 10 years have shown that obese patients with heart disease have a
significantly better recovery rate than their lean counterparts.
The aim of our study was to investigate how the hearts of obese laboratory rats responded to
a heart attack. How would it differ from the responses of the hearts of normal weight rats?
We also wanted to investigate the respective roles of 3 enzymes, PKB, ERK and JNK, known
to be associated with protection against a heart attack.
We divided Male Wistar rats into two groups. One group was fed a high-energy diet for 16
weeks to induce obesity and insulin resistance. The control group was fed a normal diet,
roughly two thirds of the kilojoule content of the first.
The hearts were removed from these rats, then subjected to a simulated heart attack through
radically reducing coronary flow to the heart.
The experiments showed that after a heart attack, the hearts from the obese rats functionally
recovered better than the control group and had significantly less damage.
These changes were associated with increased activation of the enzymes PKB, ERK and
JNK within the cell, suggesting a role for these enzymes in the recovery of hearts after a
heart attack.
The enzyme JNK appeared to be of particular importance since when this enzyme was
artificially inhibited, recovery was especially poor.
The results obtained in this study confirm data obtained in recent clinical trials. While further
investigation is clearly needed, this study has highlighted the possible positive role played by
the 3 enzymes, in particular the enzyme JNK, in the beneficial effects of obesity on the heart
responded to a heart attack.
*The athors are attached to the Dept of Biomedical Sciences (Medical Physiology)
Faculty of Health Sciences Stellenbosch University