Low testosterone level is associated with increased risks of cardiovascular diseases. As obese-insulin-resistant condition could impair cardiac function and that the incidence of obesity is increased in aging men, a condition of testosterone deprivation could aggravate the cardiac dysfunction in obese-insulin-resistant subjects. However, the mechanism underlying this adverse effect is unclear. This study investigated the effects of obesity on metabolic parameters, heart rate variability (HRV), left ventricular (LV) function, and cardiac mitochondrial function in testosterone-deprived rats. Orchiectomized or sham-operated male Wistar rats (n=36per group) were randomly divided into groups and were given either a normal diet (ND, 19.77% of energy fat) or a high-fat diet (HFD, 57.60% of energy fat) for 12weeks. Metabolic parameters, HRV, LV function, and cardiac mitochondrial function were determined at 4, 8, and 12weeks after starting each feeding program. We found that insulin resistance was observed after 8weeks of the consumption of a HFD in both sham (HFS) and orchiectomized (HFO) rats. Neither the ND sham (NDS) group nor ND orchiectomized (NDO) rats developed insulin resistance. The development of depressed HRV, LV contractile dysfunction, and increased cardiac mitochondrial reactive oxygen species production was observed earlier in orchiectomized (NDO and HFO) rats at week 4, whereas HFS rats exhibited these impairments later at week 8. These findings suggest that testosterone deprivation accelerates the impairment of cardiac autonomic regulation and LV function via increased oxidative stress and impaired cardiac mitochondrial function in obese-orchiectomized male rats.
Wanpitak Pongkan, Hiranya Pintana, Sivaporn Sivasinprasasn, Thidarat Jaiwongkam, Siriporn C Chattipakorn and Nipon Chattipakorn
Wanpitak Pongkan, Hiranya Pintana, Thidarat Jaiwongkam, Sasiwan Kredphoo, Sivaporn Sivasinprasasn, Siriporn C Chattipakorn and Nipon Chattipakorn
Obesity and testosterone deprivation are associated with coronary artery disease. Testosterone and vildagliptin (dipeptidyl peptidase-4 inhibitors) exert cardioprotection during ischemic-reperfusion (I/R) injury. However, the effect of these drugs on I/R heart in a testosterone-deprived, obese, insulin-resistant model is unclear. This study investigated the effects of testosterone and vildagliptin on cardiac function, arrhythmias and the infarct size in I/R heart of testosterone-deprived rats with obese insulin resistance. Orchiectomized (O) or sham operated (S) male Wistar rats were divided into 2 groups to receive normal diet (ND) or high-fat diet (HFD) for 12 weeks. Orchiectomized rats in each diet were divided to receive testosterone (2 mg/kg), vildagliptin (3 mg/kg) or the vehicle daily for 4 weeks. Then, I/R was performed by a 30-min left anterior descending coronary artery ligation, followed by a 120-min reperfusion. LV function, arrhythmia scores, infarct size and cardiac mitochondrial function were determined. HFD groups developed insulin resistance at week 12. At week 16, cardiac function was impaired in NDO, HFO and HFS rats, but was restored in all testosterone- and vildagliptin-treated rats. During I/R injury, arrhythmia scores, infarct size and cardiac mitochondrial dysfunction were prominently increased in NDO, HFO and HFS rats, compared with those in NDS rats. Treatment with either testosterone or vildagliptin similarly attenuated these impairments during I/R injury. These finding suggest that both testosterone replacement and vildagliptin share similar efficacy for cardioprotection during I/R injury by decreasing the infarct size and attenuating cardiac mitochondrial dysfunction caused by I/R injury in testosterone-deprived rats with obese insulin resistance.
Apiwan Arinno, Nattayaporn Apaijai, Puntarik Kaewthep, Wasana Pratchayasakul, Thidarat Jaiwongkam, Sasiwan Kerdphoo, Siriporn C Chattipakorn and Nipon Chattipakorn
Although a physiological dose of testosterone replacement therapy (p-TRT) has been shown to improve left ventricular (LV) function, some studies reported that it increased the risk of myocardial infarction in testosterone-deprived men. We previously reported that vildagliptin might be used as an alternative to p-TRT. In this study, we hypothesized that a combined low-dose TRT with vildagliptin exerts greater efficacy than single regimen in improving cardiometabolic function in obese, insulin-resistant rats with testosterone deprivation. Male rats were fed on a normal diet or high-fat diet for 12 weeks. Then, they were divided into two subgroups, sham operation and orchiectomy (normal diet rats with orchiectomy (NDO), high-fat diet rats with orchiectomy (HFO)) and fed their diets for another 12 weeks. At week 25, orchiectomized rats were subdivided into four groups: vehicle, p-TRT, vildagliptin and combined drugs. At week 29, cardiometabolic and biochemical parameters were determined. HFO rats had obese insulin resistance with a worse LV dysfunction, compared with sham. Vildagliptin and combined drugs effectively reduced insulin resistance. All treatments reduced blood pressure, cardiac autonomic imbalance, LV dysfunction, mitochondrial dysfunction, apoptosis and increased mitochondrial fusion in NDO and HFO rats. However, p-TRT and combined drugs, but not vildagliptin, reduced mitochondrial fission in NDO and HFO rats. We concluded that combined low-dose TRT with vildagliptin mitigated LV function at a similar level to the p-TRT alone and vildagliptin via improving mitochondrial fusion, reducing mitochondrial dysfunction and apoptosis in testosterone-deprived rats. Our findings suggest that low-dose TRT combined with vildagliptin may be an alternative for p-TRT in conditions of obese insulin resistance with testosterone deprivation.