Distinct sex-specific effects of semaglutide on cardiomyocyte function and mitochondrial respiration in a rat model of HFpEF

Background: Glucagon-like peptide-1 receptor (GLP-1R) agonists, such as semaglutide (SEMA), are widely recognized for their metabolic benefits in obesity and diabetes and have shown promise in treating heart failure with preserved ejection fraction (HFpEF). However, little is known about their direct effects on cardiomyocyte function and mitochondrial respiration, and whether these effects differ by sex.

Methods and Results: Male and female Wistar rats (6-7 weeks old) were fed standard chow (CO) or a high-fat/fructose (HFD) diet combined with L-NAME (0.25 mg/ml for males, 0.15 mg/ml for females due to tolerance differences) via drinking water for 8 weeks to induce HFpEF. HFpEF rats were then randomly assigned to receive SEMA (120 μg/kg/day subcutaneously) or saline for an additional 8 weeks. During this period, HFpEF groups had ad libitum access to either HFD or a low-fat but high-fructose diet. Cardiac echocardiography (n=3–6 per group) was conducted at the end of treatment, and cardiomyocytes (n=3–4 per group, minimum of 33 cells) were isolated to assess sarcomere shortening and mitochondrial redox state (NAD(P)H/FAD ratios) using a customized manual IonOptix setup. Cardiomyocytes were paced at baseline (0.3 Hz) and under stress (3 Hz) with isoprenaline (30 nM) for 3 minutes. Additionally, mitochondria (n=6–8 per group) were isolated from the same and additional hearts for high-resolution respirometry using an Oroboros Oxygraph-2k.

In males, the HFpEF group showed a significantly reduced E/A ratio with preserved ejection fraction, corresponding to shortened diastolic sarcomere length and an oxidized mitochondrial redox state, suggesting an increased metabolic workload. SEMA treatment restored the E/A ratio, diastolic sarcomere length, and shifted the mitochondrial redox balance toward a more reduced state. Mitochondrial respiration, initially impaired in HFpEF, was fully restored by SEMA with pyruvate/malate, fatty acids, or succinate as substrates, respectively. In females, HFpEF also led to a reduced E/A ratio (with preserved EF) and shortened diastolic sarcomere length. However, mitochondrial redox state remained similar to controls, and mitochondrial respiration was paradoxically elevated. SEMA treatment did not restore the E/A ratio, diastolic sarcomere length, or mitochondrial respiration in females, though a modest increase in fractional shortening was observed at baseline. No significant changes in mitochondrial redox state were noted following SEMA treatment in females.

Conclusions: Semaglutide demonstrates clear sex-specific effects in a diet-induced HFpEF model, with significant improvements in mitochondrial function and cardiomyocyte contractility observed in males but not females. These findings underscore the importance of incorporating sex-based analyses in HFpEF research, as physiological responses to SEMA may differ substantially between sexes, potentially influencing treatment strategies.