Abstract
Diabetes mellitus type-2 (T2D) is a metabolic disease characterised by chronic hyperglycaemia.
Much of the burden of T2D placed on healthcare is due to diabetes-induced complications, such
as cardiovascular disease (CVD). T2D is an independent risk factor for total CVD, which is
presently the leading cause of morbidity and mortality globally. Diabetic cardiomyopathy (DCM)
is one such complication. DCM is characterised by hypertrophy, cardiac fibrosis (CF) and left
ventricle (LV) diastolic dysfunction in the absence of other CVD. Research suggests that diabetic
females demonstrate a more severe DCM phenotype, presenting clinically with greater LV mass
and worse diastolic dysfunction compared to males, independent of age. The reasons for this are
yet to be fully understood, but a sexually dimorphic pattern of CF remodelling is a potential cause.
Our research investigates whether sex differences in the progression of fibrotic remodelling are
accountable for the female diabetic heart’s greater propensity for developing a pathological
phenotype. The anti-fibrotic drug pirfenidone has been demonstrated to have a cardioprotective
effect, however, whether this effect is sex-dependent has not been investigated.
The study used male and female obese db/db mice (a T2D model) and lean controls. A subset of
db/db mice were randomly selected to receive pirfenidone to assess whether its cardioprotective
effects occur independently of sex. Cardiac function and the degree of ventricular remodelling
were assessed, in vivo, using m-mode and pulse wave Doppler echocardiography. Ex vivo,
ventricular tissue was stained and imaged using immunofluorescence and confocal microscopy.
Using this, hypertrophy and the extent of fibrosis was measured. Additionally, we quantified
the proportions of fibrotic substrates, collagen-I and -IV, as well as derived an index of
myofibroblast activation from within the tissue. We identified that cellular hypertrophy was
significantly increased in female db/db mice treated with pirfenidone compared to same-sex
control and untreated db/db mice (p = 0.0076, p = 0.0323). Interestingly, collagen-IV deposition
was also found to be significantly higher in treated female db/db mice compared to their treated
male counterparts (p = 0.0205). The same was found in the myofibroblast activation, being
significantly higher in the pirfenidone-treated females than their male counterparts (p = 0.0470).
The exact mechanisms of pirfenidone are unknown; however, our results suggest that a component
of pirfenidone’s action is influenced by sex. Our research underscores the critical need to further
characterize pirfenidone's mechanisms, as its therapeutic efficacy may be significantly influenced
by biological sex.