Effects of vildagliptin versus sitagliptin, on cardiac function, heart rate variability and mitochondrial function in obese insulin-resistant rats

Sitagliptin alleviates renal steatosis and endoplasmic reticulum stress in high fat diet-induced obese rats by targeting SREBP-1/CD36 signaling pathway

High fat diet (HFD) consumption can cause dysregulation of glucose and lipid metabolism, coupled with increased ectopic lipid deposition in renal tissue leading to steatosis and dysfunction. Sitagliptin is a dipeptidyl peptidase-4 (DPP-4) inhibitor clinically used for type II diabetes therapy; however its effect on renal steatosis in obese state is still uncertain. Herein, obesity was induced by feeding male Wistar rats HFD for 18 weeks, thereafter received either drug vehicle, or sitagliptin (10 mg/kg, PO) along with HFD for further 6 weeks and compared with age-matched rats receiving normal chow diet (NCD). After 24 weeks, serum and kidneys were collected for histological and biochemical assessments. Compared to NCD-fed group, HFD-fed rats displayed marked weight gain, increased fat mass, insulin resistance, dyslipidemia, impaired kidney functions and renal histological alterations. Sitagliptin effectively ameliorated obesity and related metabolic perturbations and improved kidney architecture and function. There were increased levels of triglycerides and cluster of differentiation 36 (CD36) in kidneys of obese rats, that were lowered by sitagliptin therapy. Sitagliptin significantly repressed the expression of lipogenesis genes, while up-regulated genes involved in mitochondrial biogenesis and fatty acid oxidation in kidneys of HFD-fed rats. Sitagliptin was found to induce down-regulation of endoplasmic reticulum (ER) stress and apoptotic markers in kidneys of obese rats. These findings together may emphasize a novel concept that sitagliptin can be an effective therapeutic approach for halting obesity-related renal steatosis and CKD.

Cyclosporine-induced kidney damage was halted by sitagliptin and hesperidin via increasing Nrf2 and suppressing TNF-α, NF-κB, and Bax

Cyclosporine A (CsA) is employed for organ transplantation and autoimmune disorders. Nephrotoxicity is a serious side effect that hampers the therapeutic use of CsA. Hesperidin and sitagliptin were investigated for their antioxidant, anti-inflammatory, and tissue-protective properties. We aimed to investigate and compare the possible nephroprotective effects of hesperidin and sitagliptin. Male Wistar rats were utilized for induction of CsA nephrotoxicity (20 mg/kg/day, intraperitoneally for 7 days). Animals were treated with sitagliptin (10 mg/kg/day, orally for 14 days) or hesperidin (200 mg/kg/day, orally for 14 days). Blood urea, serum creatinine, albumin, cystatin-C (CYS-C), myeloperoxidase (MPO), and glucose were measured. The renal malondialdehyde (MDA), glutathione (GSH), catalase, and SOD were estimated. Renal TNF-α protein expression was evaluated. Histopathological examination and immunostaining study of Bax, Nrf-2, and NF-κB were performed. Sitagliptin or hesperidin attenuated CsA-mediated elevations of blood urea, serum creatinine, CYS-C, glucose, renal MDA, and MPO, and preserved the serum albumin, renal catalase, SOD, and GSH. They reduced the expressions of TNF-α, Bax, NF-κB, and pathological kidney damage. Nrf2 expression in the kidney was raised. Hesperidin or sitagliptin could protect the kidney against CsA through the mitigation of oxidative stress, apoptosis, and inflammation. Sitagliptin proved to be more beneficial than hesperidin.

Targeting mitochondrial quality control for diabetic cardiomyopathy: Therapeutic potential of hypoglycemic drugs

Diabetic cardiomyopathy is a chronic cardiovascular complication caused by diabetes that is characterized by changes in myocardial structure and function, ultimately leading to heart failure and even death. Mitochondria serve as the provider of energy to cardiomyocytes, and mitochondrial dysfunction plays a central role in the development of diabetic cardiomyopathy. In response to a series of pathological changes caused by mitochondrial dysfunction, the mitochondrial quality control system is activated. The mitochondrial quality control system (including mitochondrial biogenesis, fusion and fission, and mitophagy) is core to maintaining the normal structure of mitochondria and performing their normal physiological functions. However, mitochondrial quality control is abnormal in diabetic cardiomyopathy, resulting in insufficient mitochondrial fusion and excessive fission within the cardiomyocyte, and fragmented mitochondria are not phagocytosed in a timely manner, accumulating within the cardiomyocyte resulting in cardiomyocyte injury. Currently, there is no specific therapy or prevention for diabetic cardiomyopathy, and glycemic control remains the mainstay. In this review, we first elucidate the pathogenesis of diabetic cardiomyopathy and explore the link between pathological mitochondrial quality control and the development of diabetic cardiomyopathy. Then, we summarize how clinically used hypoglycemic agents (including sodium-glucose cotransport protein 2 inhibitions, glucagon-like peptide-1 receptor agonists, dipeptidyl peptidase-4 inhibitors, thiazolidinediones, metformin, and α-glucosidase inhibitors) exert cardioprotective effects to treat and prevent diabetic cardiomyopathy by targeting the mitochondrial quality control system. In addition, the mechanisms of complementary alternative therapies, such as active ingredients of traditional Chinese medicine, exercise, and lifestyle, targeting mitochondrial quality control for the treatment of diabetic cardiomyopathy are also added, which lays the foundation for the excavation of new diabetic cardioprotective drugs.

Roles of mitochondrial dynamics and mitophagy in diabetic myocardial microvascular injury

Myocardial microvessels are composed of a monolayer of endothelial cells, which play a crucial role in maintaining vascular barrier function, luminal latency, vascular tone, and myocardial perfusion. Endothelial dysfunction is a key factor in the development of cardiac microvascular injury and diabetic cardiomyopathy. In addition to their role in glucose oxidation and energy metabolism, mitochondria also participate in non-metabolic processes such as apoptosis, intracellular ion handling, and redox balancing. Mitochondrial dynamics and mitophagy are responsible for regulating the quality and quantity of mitochondria in response to hyperglycemia. However, these endogenous homeostatic mechanisms can both preserve and/or disrupt non-metabolic mitochondrial functions during diabetic endothelial damage and cardiac microvascular injury. This review provides an overview of the molecular features and regulatory mechanisms of mitochondrial dynamics and mitophagy. Furthermore, we summarize findings from various investigations that suggest abnormal mitochondrial dynamics and defective mitophagy contribute to the development of diabetic endothelial dysfunction and myocardial microvascular injury. Finally, we discuss different therapeutic strategies aimed at improving endothelial homeostasis and cardiac microvascular function through the enhancement of mitochondrial dynamics and mitophagy.

Vagus nerve stimulation and acetylcholinesterase inhibitor donepezil provide cardioprotection against trastuzumab-induced cardiotoxicity in rats by attenuating mitochondrial dysfunction

Trastuzumab (Trz) is a targeted anticancer drug for human epidermal growth factor receptor 2 (HER2)-positive tumors, as Trz-induced cardiotoxicity (TIC) is commonly observed in Trz-treated patients. Since cardiac autonomic modulation with electrical vagus nerve stimulation (VNS) and acetylcholinesterase (AChE) inhibitors exerts cardioprotection against various heart diseases, the comparative effects of electrical VNS and an AChE inhibitor (donepezil) on cardiac and mitochondrial functions and programmed cell death pathways in TIC are not known. VNS devices were implanted in thirty-two male Wistar rats and were divided into 4 groups: (i) Control-Sham (CSham), (ii) Trz-Sham (TSham), (iii) Trz-VNS (TVNS), and (iv) Trz-donepezil (TDPZ). Rats in the Trz-treated groups were intraperitoneally injected with Trz (4 mg/kg/day) for 7 days, while CSham rats were injected with NSS. VNS devices were activated in the TVNS rats during the 7-day Trz treatment, but not in the sham rats. Rats in the TDPZ group received donepezil orally (5 mg/kg/day) for 7 days. At the end, left ventricular (LV) function and heart rate variability were evaluated, and heart tissue was collected for biochemical and histological analysis. Trz rats showed LV dysfunction and cardiac sympathovagal imbalance. In addition, mitochondrial function and dynamics were impaired in TIC rats. Trz also increased cardiomyocyte death by inducing apoptosis, pyroptosis, and ferroptosis. Electrical VNS and donepezil had similar efficacy in alleviating cardiac mitochondrial dysfunction, dynamic imbalances, and cardiomyocyte death, leading to improved LV function. These findings suggested that parasympathetic activation via either VNS or an AChE inhibitor could be a promising therapeutic intervention against TIC.

Acetylcholine receptor agonists effectively attenuated multiple program cell death pathways and improved left ventricular function in trastuzumab-induced cardiotoxicity in rats

AIMS

Cardiotoxicity is a seriously debilitating complication of trastuzumab (TRZ) therapy in patients with cancer as a consequence of overexpression of the human epidermal growth factor receptor 2. Although most TRZ-induced cardiotoxicity (TIC) cases are reversible, some patients experience chronic cardiac dysfunction, and these irreversible concepts may be associated with cardiomyocyte death. Acetylcholine receptor (AChR) activation has been shown to exert cardioprotection in several heart diseases, but the effects of AChR agonists against TIC have not been investigated.

MAIN METHOD

Forty adult male Wistar rats were randomized into 5 groups: (i) CON (0.9 % normal saline), (ii) TRZ (4 mg/kg/day), (iii) TRZ + α7nAChR agonist (PNU-282987: 3 mg/kg/day), (iv) TRZ + mAChR agonists (bethanechol: 12 mg/kg/day), and (v) TRZ + combined treatment (Combined PNU-282987 and bethanechol).

KEY FINDINGS

The progression of TIC was driven by mitochondrial dysfunction, autophagic deficiency, and excessive myocyte death including by pyroptosis, ferroptosis, and apoptosis, which were significantly alleviated by α7nAChR and mAChR agonists. Interestingly, necroptosis was not associated with development of TIC. More importantly, the in vitro study validated the cytoprotective effects of AChR activation in TRZ-treated H9c2 cells, while not interfering with the anticancer properties of TRZ. All of these findings indicated that TRZ induced mitochondrial dysfunction, autophagic deficiency, and excessive myocyte death including pyroptosis, ferroptosis, and apoptosis, leading to impaired cardiac function. These pathological alterations were attenuated by α7nAChR and mAChR agonists.

SIGNIFICANCE

α7nAChR and mAChR agonists might be used as a future therapeutic target in the mitigation of TIC.

Acetylcholinesterase inhibition protects against trastuzumab-induced cardiotoxicity through reducing multiple programmed cell death pathways

BACKGROUND

Trastuzumab (Trz)-induced cardiotoxicity (TIC) is one of the most common adverse effects of targeted anticancer agents. Although oxidative stress, inflammation, mitochondrial dysfunction, apoptosis, and ferroptosis have been identified as potential mechanisms underlying TIC, the roles of pyroptosis and necroptosis under TIC have never been investigated. It has been shown that inhibition of acetylcholinesterase function by using donepezil exerts protective effects in various heart diseases. However, it remains unknown whether donepezil exerts anti-cardiotoxic effects in rats with TIC. We hypothesized that donepezil reduces mitochondrial dysfunction, inflammation, oxidative stress, and cardiomyocyte death, leading to improved left ventricular (LV) function in rats with TIC.

METHODS

Male Wistar rats were randomly assigned to be Control or Trz groups (Trz 4 mg/kg/day, 7 days, I.P.). Rats in Trz groups were assigned to be co-treated with either drinking water (Trz group) or donepezil 5 mg/kg/day (Trz + DPZ group) via oral gavage for 7 days. Cardiac function, heart rate variability (HRV), and biochemical parameters were evaluated.

RESULTS

Trz-treated rats had impaired LV function, HRV, mitochondrial function, and increased inflammation and oxidative stress, leading to apoptosis, ferroptosis, and pyroptosis. Donepezil co-treatment effectively decreased those adverse effects of TIC, resulting in improved LV function. An in vitro study revealed that the cytoprotective effects of donepezil were abolished by a muscarinic acetylcholine receptor (mAChR) antagonist.

CONCLUSIONS

Donepezil exerted cardioprotection against TIC via attenuating mitochondrial dysfunction, oxidative stress, inflammation, and cardiomyocyte death, leading to improved LV function through mAChR activation. This suggests that donepezil could be a novel intervention strategy in TIC.

Mitochondrial quality control in cardiac fibrosis: Epigenetic mechanisms and therapeutic strategies

Cardiac fibrosis (CF) is considered an ultimate common pathway of a wide variety of heart diseases in response to diverse pathological and pathophysiological stimuli. Mitochondria are characterized as isolated organelles with a double-membrane structure, and they primarily contribute to and maintain highly dynamic energy and metabolic networks whose distribution and structure exert potent support for cellular properties and performance. Because the myocardium is a highly oxidative tissue with high energy demands to continuously pump blood, mitochondria are the most abundant organelles within mature cardiomyocytes, accounting for up to one-third of the total cell volume, and play an essential role in maintaining optimal performance of the heart. Mitochondrial quality control (MQC), including mitochondrial fusion, fission, mitophagy, mitochondrial biogenesis, and mitochondrial metabolism and biosynthesis, is crucial machinery that modulates cardiac cells and heart function by maintaining and regulating the morphological structure, function and lifespan of mitochondria. Certain investigations have focused on mitochondrial dynamics, including manipulating and maintaining the dynamic balance of energy demand and nutrient supply, and the resultant findings suggest that changes in mitochondrial morphology and function may contribute to bioenergetic adaptation during cardiac fibrosis and pathological remodeling. In this review, we discuss the function of epigenetic regulation and molecular mechanisms of MQC in the pathogenesis of CF and provide evidence for targeting MQC for CF. Finally, we discuss how these findings can be applied to improve the treatment and prevention of CF.

An Overview of the Cardioprotective Effects of Novel Antidiabetic Classes: Focus on Inflammation, Oxidative Stress, and Fibrosis

Metabolic diseases, particularly diabetes mellitus (DM), are significant global public health concerns. Despite the widespread use of standard-of-care therapies, cardiovascular disease (CVD) remains the leading cause of death among diabetic patients. Early and evidence-based interventions to reduce CVD are urgently needed. Large clinical trials have recently shown that sodium-glucose cotransporter-2 inhibitors (SGLT2i) and glucagon-like peptide-1 receptor agonists (GLP-1RA) ameliorate adverse cardiorenal outcomes in patients with type 2 DM. These quite unexpected positive results represent a paradigm shift in type 2 DM management, from the sole importance of glycemic control to the simultaneous improvement of cardiovascular outcomes. Moreover, SGLT2i is also found to be cardio- and nephroprotective in non-diabetic patients. Several mechanisms, which may be potentially independent or at least separate from the reduction in blood glucose levels, have already been identified behind the beneficial effect of these drugs. However, there is still much to be understood regarding the exact pathomechanisms. This review provides an overview of the current literature and sheds light on the modes of action of novel antidiabetic drugs, focusing on inflammation, oxidative stress, and fibrosis.

Melatonin and metformin ameliorated trastuzumab-induced cardiotoxicity through the modulation of mitochondrial function and dynamics without reducing its anticancer efficacy

Trastuzumab has an impressive level of efficacy as regards antineoplasticity, however it can cause serious cardiotoxic side effects manifested by impaired cardiac contractile function. Although several pharmacological interventions, including melatonin and metformin, have been reported to protect against various cardiovascular diseases, their potential roles in trastuzumab-induced cardiotoxicity remain elusive. We hypothesized that either melatonin or metformin co-treatment effectively attenuates trastuzumab-mediated cardiotoxicity through attenuating the impaired mitochondrial function and mitochondrial dynamics. Male Wistar rats were divided into control (normal saline, n = 8) and trastuzumab group (4 mg/kg/day for 7 days, n = 24). Rats in the trastuzumab group were subdivided into 3 interventional groups (n = 8/group), and normal saline, or melatonin (10 mg/kg/day), or metformin (250 mg/kg/day) were orally administered for 7 consecutive days. Cardiac parameters were determined, and biochemical investigations were carried out on blood and heart tissues. Trastuzumab induced left ventricular (LV) dysfunction by increasing oxidative stress, inflammation, and apoptosis. It also impaired cardiac mitochondrial function, dynamics, and autophagy. Treatment with either melatonin or metformin equally attenuated trastuzumab-induced cardiac injury, indicated by a marked reduction in inflammation, oxidative damage, cardiac mitochondrial injury, mitochondrial dynamic imbalance, autophagy dysregulation, and apoptosis, leading to improved LV function, as demonstrated by increased LV ejection fraction. Melatonin and metformin conferred equal levels of cardioprotection against trastuzumab-induced cardiotoxicity, which may provide novel and promising approaches for management of cardiotoxicity induced by trastuzumab.

A novel combination of sitagliptin and melatonin ameliorates T2D manifestations: studies on experimental diabetic models

INTRODUCTION

Type 2 diabetes (T2D) is an endocrine disorder characterized by hyperglycemia, insulin resistance, dysregulated glucose and lipid metabolism, reduced pancreatic β-cell function and mass, and a reduced incretin effect. Circadian rhythm disruption is associated with increased T2D risk. We have investigated the therapeutic potential of a combination of melatonin (M) and sitagliptin (S), a dipeptidyl peptidase IV (DPP-IV) inhibitor, in the amelioration of T2D manifestations in high-fat diet (HFD) induced T2D mouse model and also on β-cell proliferation under gluco-lipotoxicity stress in vitro.

METHODS

For in vivo study, mice were fed with HFD for 25 weeks to induce T2D and were treated with monotherapies and S + M for four weeks. For the in vitro study, primary mouse islets were exposed to normal glucose and high glucose + palmitate to induce gluco-lipotoxic stress.

RESULTS

Our results suggest that monotherapies and S + M improve metabolic parameters and glyco-lipid metabolism in the liver and adipose tissue, respectively, and improve mitochondrial function in the skeletal muscle. Moreover, it increases peripheral insulin sensitivity. Our in vitro and in vivo studies suggest that β-cell mass was preserved in all the drug-treated groups.

CONCLUSION

The combination treatment is superior to monotherapies in the management of T2D.

GSDMD-mediated pyroptosis dominantly promotes left ventricular remodeling and dysfunction in post-myocardial infarction: a comparison across modes of programmed cell death and mitochondrial involvement

BACKGROUND

Myocardial infarction (MI) has recently accounted for more than one-third of global mortality. Multiple molecular pathological pathways, such as oxidative stress, inflammation, and mitochondrial dysfunction, have been recognized as possible mechanisms in the development of MI. Furthermore, different phases of ischemic injury following the progression of MI were also associated with multiple types of programmed cell death (PCDs), including apoptosis, necroptosis, ferroptosis, and pyroptosis. However, it remains unknown whether which types of PCDs play the most dominant role in post-myocardial infarction (post-MI).

METHOD

In this study, we used a preclinical rat model of MI induced by permanent left anterior descending coronary artery (LAD) ligation (n = 6) or a sham operated rat model (n = 6). After a 5-week experiment, cardiac function and morphology, mitochondrial studies, and molecular signaling analysis of PCDs were determined.

RESULTS

Herein, we demonstrated that post-MI rats had considerably impaired cardiac geometry, increased oxidative stress, myocardial injuries, and subsequently contractile dysfunction. They also exhibited worsened cardiac mitochondrial function and dynamic imbalance. More importantly, we found that post-MI mediated abundant myocardial cell death through multiple PCDs, including apoptosis, necroptosis, and pyroptosis, but not ferroptosis.

CONCLUSION

In this study, we provide the first insights into the mechanism of PCDs by pyroptosis, which is leveraged as the most dominant mode of cell death after MI.

Combined caloric restriction and exercise provides greater metabolic and neurocognitive benefits than either as a monotherapy in obesity with or without estrogen deprivation

Neurodegeneration, as indicated by brain dysfunction and cognitive decline, is one of the complications associated with obesity and estrogen deprivation. Calorie restriction and exercise regimes improved brain function in neurodegenerative diseases. However, the comparative effects of a combination of calorie restriction with exercise, calorie restriction, and an exercise regime alone on brain/cognitive function in obesity with or without estrogen deprivation have not been investigated. Sixty female rats were fed a normal diet (ND) or a high-fat diet (HFD) for 27 weeks. At week 13, the ND-fed rats underwent a sham operation with sedentary lifestyle, HFD-fed rats were divided into two groups: each having either a sham operation (HFS) or ovariectomy (HFO). At week 20, HFD-fed rats in each group were divided into four subgroups undergoing either a sedentary lifestyle, calorie restriction, exercise regime or a combination of calorie restriction and exercise for 7 weeks. Insulin resistance, cognitive decline and hippocampal pathologies were found in both HFS and HFO rats. HFO rats had higher levels of insulin resistance and hippocampal reactive oxygen species levels than HFS rats. Calorie restriction decreased metabolic disturbance and hippocampal oxidative stress but failed to attenuate cognitive decline in HFS and HFO rats. Exercise attenuated metabolic/hippocampal dysfunctions, resulting in improved cognition only in HFS rats. Combined therapies restored brain function, and cognitive function in HFS and HFO rats. Therefore, a combination of calorie restriction with exercise is probably the greatest lifestyle modification to diminish the brain pathologies and cognitive decline in obesity with or without estrogen deprivation.

Ranolazine alleviated cardiac/brain dysfunction in doxorubicin-treated rats

Doxorubicin (Dox), a powerful chemotherapeutic agent, has been shown to cause cardiotoxicity and neurotoxicity. Ranolazine, a drug that is commonly used to treat patients with chronic angina, has been shown to reduce toxicity from Dox therapy. Therefore, the present study aims to investigate the mechanisms behind the protective effects of ranolazine on the heart and brain in Dox-treatment. Twenty-four male Wistar rats received 6 doses of either 0.9% normal saline (0.9% NSS, i.p., n = 8) or Dox (3 mg/kg, i.p., n = 16). All Dox-treated rats were assigned into 2 groups to receive vehicle (0.9% NSS, orally; n = 8) or ranolazine (305 mg/kg/day, orally; n = 8) for 30 consecutive days. Following the treatments, left ventricular (LV) function and cognition were determined. Animals were euthanized, then the heart and brain were collected for further analysis. Dox induced systemic oxidative stress/inflammation, and cardiac injury evidenced by mitochondrial dysfunction, mitochondrial dynamic imbalance, and apoptosis, resulting in LV dysfunction. Ranolazine significantly improved LV function via attenuating cardiac injury. Dox also caused brain pathologies as indicated by increased brain inflammation, impaired blood-brain barrier integrity, brain mitochondrial dysfunction, microglial dysmorphology, hippocampal dysplasticity, and increased apoptosis, resulting in cognitive decline. Ranolazine exerted neuroprotective effects by suppressing brain pathologies and restoring cognitive function. These findings suggest that ranolazine has a potential role in cardio- and neuro-protection against chemotherapy.

Modulation of Reactive Oxygen Species Homeostasis as a Pleiotropic Effect of Commonly Used Drugs

Age-associated diseases represent a growing burden for global health systems in our aging society. Consequently, we urgently need innovative strategies to counteract these pathological disturbances. Overwhelming generation of reactive oxygen species (ROS) is associated with age-related damage, leading to cellular dysfunction and, ultimately, diseases. However, low-dose ROS act as crucial signaling molecules and inducers of a vaccination-like response to boost antioxidant defense mechanisms, known as mitohormesis. Consequently, modulation of ROS homeostasis by nutrition, exercise, or pharmacological interventions is critical in aging. Numerous nutrients and approved drugs exhibit pleiotropic effects on ROS homeostasis. In the current review, we provide an overview of drugs affecting ROS generation and ROS detoxification and evaluate the potential of these effects to counteract the development and progression of age-related diseases. In case of inflammation-related dysfunctions, cardiovascular- and neurodegenerative diseases, it might be essential to strengthen antioxidant defense mechanisms in advance by low ROS level rises to boost the individual ROS defense mechanisms. In contrast, induction of overwhelming ROS production might be helpful to fight pathogens and kill cancer cells. While we outline the potential of ROS manipulation to counteract age-related dysfunction and diseases, we also raise the question about the proper intervention time and dosage.

Therapeutic potential of a single-dose melatonin in the attenuation of cardiac ischemia/reperfusion injury in prediabetic obese rats

Although acute melatonin treatment effectively reduces cardiac ischemia/reperfusion (I/R) injury in lean rats by modulating melatonin receptor 2 (MT2), there is no information regarding the temporal effects of melatonin administration during cardiac I/R injury in prediabetic obese rats. Prediabetic obese rats induced by chronic consumption of a high-fat diet (HFD) were used. The rats underwent a cardiac I/R surgical procedure (30-min of ischemia, followed by 120-min of reperfusion) and were randomly assigned to receive either vehicle or melatonin treatment. In the melatonin group, rats were divided into 3 different subgroups: (1) pretreatment, (2) treatment during ischemic period, (3) treatment at the reperfusion onset. In the pretreatment subgroup either a nonspecific MT blocker (Luzindole) or specific MT2 blocker (4-PPDOT) was also given to the rats prior to melatonin treatment. Pretreatment with melatonin (10 mg/kg) effectively reduced cardiac I/R injury by reducing infarct size, arrhythmia, and LV dysfunction. Reduction in impaired mitochondrial function, mitochondrial dynamic balance, oxidative stress, defective autophagy, and apoptosis were observed in rats pretreated with melatonin. Unfortunately, the cardioprotective benefits were not observed when 10-mg/kg of melatonin was acutely administered to the rats after cardiac ischemia. Thus, we increased the dose of melatonin to 20 mg/kg, and it was administered to the rats during ischemia or at the onset of reperfusion. The results showed that 20-mg/kg of melatonin effectively reduced cardiac I/R injury to a similar extent to the 10-mg/kg pretreatment regimen. The MT2 blocker inhibited the protective effects of melatonin. Acute melatonin treatment during cardiac I/R injury exerted protective effects in prediabetic obese rats. However, a higher dose of melatonin is required when given after the onset of cardiac ischemia. These effects of melatonin were mainly mediated through activation of MT2.

Promoting mitochondrial fusion in doxorubicin-induced cardiotoxicity: a novel therapeutic target for cardioprotection

Changes in mitochondrial dynamics have been recognized as being one of the mechanisms related to cardiotoxicity following a high cumulative dose of doxorubicin (DOX).  A mitochondrial division inhibitor (Mdivi-1) and fusion promoter (M1) have been shown to be cardioprotective in a variety of cardiovascular settings, however their anti-cardiotoxic efficacy against DOX therapy remains unclear.  We therefore investigated whether treatment with Mdivi-1 and M1 protect the heart against DOX-induced cardiotoxicity via mitochondria-targeted pathways.  Male Wistar rats (n=40) received DOX (3 mg/kg, 6 doses, n=32) or 3% DMSO in the normal saline solution (NSS) (n=8) as a control.  DOX-injected rats were given one of four treatments beginning with the first DOX injection via intraperitoneal injection: 1) 3% DMSO in NSS (n=8), 2) Mdivi-1 (1.2 mg/kg/day, n=8), 3) M1 (2 mg/kg/day, n=8), and 4) Mdivi-1+M1 (n=8) for 30 days.  Cardiac function, mitochondrial function, oxidative stress, myocardial injury, and protein expression associated with inflammation, autophagy, mitophagy, apoptosis and mitochondrial dynamics were determined.  DOX caused a significant deterioration in mitochondrial function and dynamic regulation, and an increase in markers of oxidative stress, inflammation, myocardial injury, apoptosis, autophagy, and mitophagy, resulting in impaired cardiac function.  Co-treatment of DOX with Mdivi-1, M1, or a combination of the two mitigated these detrimental effects of DOX.  These findings imply that either inhibiting fission or promoting fusion of mitochondria protects the heart from DOX-induced myocardial damage.  Modulation of mitochondrial dynamics could be a novel therapeutic target in alleviating DOX-induced cytotoxic effects without compromising its anti-cancer efficacy.

Sexual dimorphism in cardiometabolic and cardiac mitochondrial function in obese rats following sex hormone deprivation

OBJECTIVE

Our study aims to test the hypothesis that poorer function of cardiac mitochondria in males, under sex hormone-deprived and obese-insulin-resistant conditions, is responsible for a worse cardiometabolic function than females.

METHODS

One hundred and forty-four rats were subjected to receive either 12 weeks of normal diet (ND) or a high-fat diet (HFD) consumption following the induction of sex hormone deprivation. Temporal evaluations of metabolic parameters, cardiac autonomic modulation, left ventricular (LV) contractile, and mitochondrial functions were measured after starting each feeding protocol for 4, 8, and 12 weeks.

RESULTS

After HFD feeding for 8 weeks, increased plasma insulin and HOMA index were initially observed in male HFD-fed sham-operated rats (M-HFS), male HFD-fed orchiectomized rats (M-HFO), female ND-fed ovariectomized rats (F-OVX), female HFD-fed sham-operated rats (F-HFS), and female HFD-fed ovariectomized rats (F-HFO) groups. In addition, as early as week 4, male ND-fed orchiectomized rats (M-ORX) and M-HFO exhibited impaired cardiac autonomic balance, LV contractile and mitochondrial functions, whereas M-HFS and F-HFO developed these impairments at week 8 and F-OVX and F-HFS exhibited them at week 12.

CONCLUSION

We concluded that sex hormone-deprived females are prone to develop metabolic impairments, whereas males are more likely to have cardiac autonomic impairment, LV contractile and mitochondrial dysfunction even in the absence of obese-insulin-resistant condition. However, under estrogen-deprived condition, these impairments were further accelerated and aggravated by obese-insulin resistance.

Inhibition of myeloid differentiation factor 2 attenuates cardiometabolic impairments via reducing cardiac mitochondrial dysfunction, inflammation, apoptosis and ferroptosis in prediabetic rats

Systemic inflammation is a key mediator of left ventricular dysfunction (LV) in prediabetes via the activation of myeloid differentiation factor 2 (MD2)/toll-like receptor 4 complex. The MD2 inhibitor L6H21 effectively reduced systemic and cardiac inflammation in obese mice. However, its effects on cardiac function and regulated cell death pathways in the heart in prediabetes are still unknown. The prediabetic rats were divided into 3 subgroups to receive vehicle, L6H21 (10, 20, 40 mg/kg) or metformin (300 mg/kg) for 1, 2 and 4 weeks. Then, metabolic parameters, cardiac sympathovagal balance, LV function, cardiac mitochondrial function, oxidative stress, inflammation, apoptosis, necroptosis, and ferroptosis were determined. All prediabetic rats exhibited cardiac sympathovagal imbalance, LV dysfunction, and cardiac mitochondrial dysfunction. All doses of L6H21 treatment for 2- and 4-weeks attenuated insulin resistance. L6H21 at 40 mg/kg attenuated cardiac autonomic imbalance and LV dysfunction after 1 week of treatment. Both 10 and 20 mg/kg of L6H21 required longer treatment duration to show these benefits. Mechanistically, all doses of L6H21 reduced cardiac mitochondrial dysfunction after 1 week of treatment, resulting in alleviated oxidative stress and inflammation. L6H21 also effectively suppressed cardiac apoptosis and ferroptosis, but it did not affect necroptosis in prediabetic rats. L6H21 provided the cardioprotective efficacy in dose- and time-dependent manners in prediabetic rats via reduction in apoptosis and ferroptosis.

Acetylcholinesterase inhibitor ameliorates doxorubicin-induced cardiotoxicity through reducing RIP1-mediated necroptosis

Doxorubicin is an effective chemotherapeutic drug, but causes cardiotoxicity which limits its use. Oxidative stress, mitochondrial dysfunction, and inflammation are closely implicated in doxorubicin-induced cardiotoxicity (DIC). Necroptosis, a new form of programmed cell death, was also upregulated by doxorubicin, leading to cardiomyocyte death and cardiac dysfunction. Donepezil, an acetylcholinesterase inhibitor, exerted cardioprotection against various heart diseases. However, its cardioprotective effects in DIC are still unknown. We hypothesized that donepezil reduces reactive oxygen species (ROS) production, mitochondrial dysfunction, mitochondrial dynamics imbalance, necroptosis, and apoptosis in DIC rats. Male Wistar rats were assigned to receive either normal saline solution (n = 8) or doxorubicin (3 mg/kg, 6 doses, n = 16) via intraperitoneal injection. The doxorubicin-treated rats were further subdivided to receive either sterile drinking water (n = 8) or donepezil (5 mg/kg/day, p.o., n = 8) for 30 days. At the end of the experiment, the left ventricular (LV) function was determined. Serum and heart tissue were collected to evaluate histological and biochemical parameters. Doxorubicin-treated rats exhibited higher levels of inflammatory cytokines and ROS production. Doxorubicin also impaired mitochondrial function, mitochondrial dynamics balance, mitophagy, and autophagy, which culminated in apoptosis. Furthermore, doxorubicin increased necroptosis as evidenced by increased phosphorylation of receptor-interacting protein kinase 1, receptor-interacting protein kinase 3, and mixed-lineage kinase domain-like. All of these mechanisms led to LV dysfunction. Interestingly, donepezil alleviated mitochondrial injury, mitophagy, autophagy, and cardiomyocyte death, leading to improved LV function in DIC. In conclusion, donepezil attenuated DIC-induced LV dysfunction by reducing mitochondrial damage, mitophagy, autophagy, apoptosis, and necroptosis.

Cardioprotective effects of melatonin and metformin against doxorubicin-induced cardiotoxicity in rats are through preserving mitochondrial function and dynamics

Doxorubicin (Dox) is widely used in chemotherapy regimens for several malignant conditions. Unfortunately, cumulative and irreversible cardiotoxicity of Dox is the most prominent adverse effect which limits its use. Several pharmacological interventions which exert antioxidant properties, including melatonin and metformin, have demonstrated beneficial effects against various cardiac pathological conditions. However, the exact molecular mechanisms underlying their cardioprotective effects are not completely understood. We hypothesized that treatment with either melatonin or metformin provides cardioprotection against Dox-induced cardiotoxicity through mitochondrial protection. Thirty-two male Wistar rats received 6 doses of either 0.9% normal saline solution (0.9% NSS, n = 8) or Dox (3 mg/kg, i.p., n = 24). The Dox-treated rats (n = 8/group) were co-treated with: 1) Vehicle (0.9% NSS), 2) Melatonin (10 mg/kg/day), and 3) Metformin (250 mg/kg/day) for 30 consecutive days via oral gavage. Following the treatment, left ventricular (LV) function, oxidative stress, inflammation, mitochondrial function, dynamics, biogenesis and bioenergetics, mitophagy, autophagy, and apoptosis were determined. Dox induced excessive oxidative stress, inflammation, autophagy, apoptosis, reduced mitochondrial function, dynamics balance, biogenesis, and bioenergetics leading to LV dysfunction. Treatment with either melatonin or metformin exerted equal measures of cardioprotection via reducing oxidative stress, inflammation, autophagy, apoptosis, and improved mitochondrial function, dynamics balance, biogenesis, and bioenergetics in the Dox-treated rats. Melatonin and metformin exerted both anti-cancer and cardioprotective properties, suggesting they have potential roles in concomitant therapy in cancer patients receiving Dox treatment.

A molecular link between diabetes and breast cancer: Therapeutic potential of repurposing incretin-based therapies for breast cancer

Female breast cancer recently surpassed lung cancer and became the most commonly diagnosed cancer worldwide. As per the recent data from WHO, breast cancer accounts for one out of every 8 cancer cases diagnosed among an estimated 2.3 million new cancer cases. Breast cancer is the most prevailing cancer type among women causing the highest number of cancer-related mortality. It has been estimated that in 2020, 68,5000 women died due to this disease. Breast cancers have varying degrees of molecular heterogeneity; therefore, they are divided into various molecular clinical sub types. Recent reports suggest that type 2 diabetes (one of the common chronic diseases worldwide) is linked to the higher incidence, accelerated progression, and aggressiveness of different cancers; especially breast cancer. Breast cancer is hormone-dependent in nature and has a cross-talk with metabolism. A number of antidiabetic therapies are known to exert beneficial effects on various types of cancers, including breast cancer. However, only a few reports are available on the role of incretin-based antidiabetic therapies in cancer as a whole and in breast cancer in particular. The present review sheds light on the potential of incretin based therapies on breast cancer and explores the plausible underlying mechanisms. Additionally, we have also discussed the sub types of breast cancer as well as the intricate relationship between diabetes and breast cancer.

Donepezil Protects Against Doxorubicin-Induced Chemobrain in Rats via Attenuation of Inflammation and Oxidative Stress Without Interfering With Doxorubicin Efficacy

Although doxorubicin (Dox) is an effective chemotherapy medication used extensively in the treatment of breast cancer, it frequently causes debilitating neurological deficits known as chemobrain. Donepezil (DPZ), an acetylcholinesterase inhibitor, provides therapeutic benefits in various neuropathological conditions. However, comprehensive mechanistic insights regarding the neuroprotection of DPZ on cognition and brain pathologies in a Dox-induced chemobrain model remain obscure. Here, we demonstrated that Dox-treated rats manifested conspicuous cognitive deficits and developed chemobrain pathologies as indicated by brain inflammatory and oxidative insults, glial activation, defective mitochondrial homeostasis, increased potential lesions associated with Alzheimer's disease, disrupted neurogenesis, loss of dendritic spines, and ultimately neuronal death through both apoptosis and necroptosis. Intervention with DPZ co-treatment completely restored cognitive function by attenuating these pathological conditions induced by DOX. We also confirmed that DPZ treatment does not affect the anti-cancer efficacy of Dox in breast cancer cells. Together, our findings suggest that DPZ treatment confers potential neuroprotection against Dox-induced chemobrain.

The differences in mitochondrial function, mitochondrial dynamics, and cell death between odontogenic cysts/tumors and normal dental follicles

We aimed to compare mitochondrial function, mitochondrial dynamics, apoptosis, and necroptosis between odontogenic cysts/tumors, including radicular cysts, dentigerous cysts, ameloblastoma, vs. dental follicles as control. We demonstrated that mitochondrial dysregulation and imbalanced mitochondrial dynamics were observed in ameloblastoma. Apoptosis was increased in dentigerous cysts, and ameloblastoma, while necroptosis was suppressed in ameloblastoma. Necroptosis in radicular cysts was higher than that of control, suggesting that the inflammation-associated cell death occurred in radicular cysts. Our findings suggest ameloblastoma exhibited mitochondrial dysfunction, decreased mitochondrial fusion, and potential apoptosis. Therefore, alleviating mitochondrial dysregulation and apoptosis may be novel-targeted therapy for odontogenic cysts and tumors.

Therapeutic potential of targeting oxidative stress in diabetic cardiomyopathy

Even in the absence of coronary artery disease and hypertension, diabetes mellitus (DM) may increase the risk for heart failure development. This risk evolves from functional and structural alterations induced by diabetes in the heart, a cardiac entity termed diabetic cardiomyopathy (DbCM). Oxidative stress, defined as the imbalance of reactive oxygen species (ROS) has been increasingly proposed to contribute to the development of DbCM. There are several sources of ROS production including the mitochondria, NAD(P)H oxidase, xanthine oxidase, and uncoupled nitric oxide synthase. Overproduction of ROS in DbCM is thought to be counterbalanced by elevated antioxidant defense enzymes such as catalase and superoxide dismutase. Excess ROS in the cardiomyocyte results in further ROS production, mitochondrial DNA damage, lipid peroxidation, post-translational modifications of proteins and ultimately cell death and cardiac dysfunction. Furthermore, ROS modulates transcription factors responsible for expression of antioxidant enzymes. Lastly, evidence exists that several pharmacological agents may convey cardiovascular benefit by antioxidant mechanisms. As such, increasing our understanding of the pathways that lead to increased ROS production and impaired antioxidant defense may enable the development of therapeutic strategies against the progression of DbCM. Herein, we review the current knowledge about causes and consequences of ROS in DbCM, as well as the therapeutic potential and strategies of targeting oxidative stress in the diabetic heart.

DPP4 Activity, Hyperinsulinemia, and Atherosclerosis

CONTEXT

Obesity and type 2 diabetes are associated with chronic hyperinsulinemia, elevated plasma levels of dipeptidyl peptidase-4 (DPP4), and a pro-atherosclerotic milieu.

EVIDENCE ACQUISITION

PubMed search of the term "insulin and atherosclerosis," "hyperinsulinemia," "atherosclerosis," or "cardiovascular outcomes" cross-referenced with "DPP4." Relevant research and review articles were reviewed.

EVIDENCE SYNTHESIS

Hyperinsulinemia in the setting of insulin resistance promotes vascular inflammation, vascular smooth muscle cell growth, pathological cholesterol profile, hypertension, and recruitment of immune cells to the endothelium, all contributing to atherosclerosis. DPP4 has pleiotropic functions and its activity is elevated in obese humans. DPP4 mirrors hyperinsulinemia's atherogenic actions in the insulin resistant state, and genetic deletion of DPP4 protects rodents from developing insulin resistance and improves cardiovascular outcomes. DPP4 inhibition in pro-atherosclerotic preclinical models results in reduced inflammation and oxidative stress, improved endothelial function, and decreased atherosclerosis. Increased incretin levels may have contributed to but do not completely account for these benefits. Small clinical studies with DPP4 inhibitors demonstrate reduced carotid intimal thickening, improved endothelial function, and reduced arterial stiffness. To date, this has not been translated to cardiovascular risk reduction for individuals with type 2 diabetes with prior or exaggerated risk of cardiovascular disease.

CONCLUSION

DPP4 may represent a key link between central obesity, insulin resistance, and atherosclerosis. The gaps in knowledge in DPP4 function and discrepancy in cardiovascular outcomes observed in preclinical and large-scale randomized controlled studies with DPP4 inhibitors warrant additional research.

Vildagliptin Attenuates Myocardial Dysfunction and Restores Autophagy via miR-21/SPRY1/ERK in Diabetic Mice Heart

Aim: Vildagliptin (vild) improves diastolic dysfunction and is associated with a lower relative risk of major adverse cardiovascular events in younger patients. The present study aimed to evaluate whether vild prevents the development of diabetic cardiomyopathy in type 2 diabetic mice and identify its underlying mechanisms. Methods: Type 2 diabetic mouse model was generated using wild-type (WT) (C57BL/6J) and miR-21 knockout mice by treatment with HFD/STZ. Cardiomyocyte-specific miR-21 overexpression was achieved using adeno-associated virus 9. Echocardiography was used to evaluate cardiac function in mice. Morphology, autophagy, and proteins levels in related pathway were analyzed. qRT-PCR was used to detect miR-21. Rat cardiac myoblast cell line (H9c2) cells were transfected with miR-21 mimics and inhibitor to explore the related mechanisms of miR-21 in diabetic cardiomyopathy. Results: Vild restored autophagy and alleviated fibrosis, thereby enhancing cardiac function in DM mice. In addition, miR-21 levels were increased under high glucose conditions. miR-21 knockout DM mice with miR-21 knockout had reduced cardiac hypertrophy and cardiac dysfunction compared to WT DM mice. Overexpression of miR-21 aggravated fibrosis, reduced autophagy, and attenuated the protective effect of vild on cardiac function. In high-glucose-treated H9c2 cells, the downstream effectors of sprouty homolog 1 (SPRY1) including extracellular signal-regulated kinases (ERK) and mammalian target of rapamycin showed significant changes following transfection with miR-21 mimics or inhibitor. Conclusion: The results of our study indicate that vild prevents DCM by restoring autophagy through the miR-21/SPRY1/ERK/mTOR pathway. Therefore, miR-21 is a target in the development of DCM, and vild demonstrates significant potential for clinical application in prevention of DCM.

Vildagliptin, a dipeptidyl peptidase-4 inhibitor, attenuated endothelial dysfunction through miRNAs in diabetic rats

INTRODUCTION

Dipeptidyl peptidase-4 (DPP-4) inhibitors have various cellular effects that are associated with vascular protection. Here, we examined whether vildagliptin protected endothelial function in diabetic rats and explored the involved mechanism.

MATERIAL AND METHODS

Experimental diabetic rats were obtained by feeding a high-fat diet and administering an intraperitoneal injection of streptozotocin. Rats were randomly divided into four groups: controls (CON), diabetes (DM), diabetes + low dose of vildagliptin (Lvil, 10 mg/kg/day), and diabetes + high dose of vildagliptin (Hvil, 20 mg/kg/day). The metabolic parameters, endothelial function, and whole miRNA expression were measured.

RESULTS

After a 12-week treatment, vildagliptin-treated rats showed a significant reduction in blood glucose and blood lipid levels. Moreover, vildagliptin recovered aortic endothelial function in diabetic rats. We identified 31 miRNAs that were differentially expressed in the Hvil group compared with the diabetic group. Importantly, through miRNA target biological function and pathway analysis, we found that vildagliptin activated miR-190-5p to inhibit Ccl2 expression and inhibited miR-134-5p and miR-375-3p to increase Bdnf and Pdk1 expression in the aorta.

CONCLUSIONS

Our present study indicates that vildagliptin can recover endothelial function in diabetic rats. Anti-inflammatory and anti-apoptosis mechanisms and endothelial moderation may be the intervention targets of vildagliptin to protect the cardiovascular system through miRNA regulation.

Obesity-Induced Heart Rate Variability Impairment and Decreased Systolic Function in Obese Male Dogs

Simple Summary

Obesity in dogs can induce many adverse health effects including musculoskeletal problems, respiratory distress, metabolic syndrome, and cardiovascular diseases. In humans with obesity, heart rate variability (HRV) is used to identify and predict the risk of cardiovascular diseases. However, this predictive tool has never been used in veterinary medicine, and the relationship between obesity and HRV has rarely been investigated. In this study, we investigated HRV, plasma oxidative stress (MDA), and cardiac function in obese male dogs. We hypothesized that obese male dogs have decreased cardiac function and impaired HRV compared to non-obese dogs. Our study found that obese dogs have decreased cardiac systolic function and impaired HRV, as indicated by reduced percentages of cardiac contraction and impaired cardiac autonomic activity compared to non-obese dogs. We concluded that obesity can decrease systolic function and cause HRV impairment, which might increase the risk of cardiovascular disease in dogs. In addition, HRV might be used as a predictive or prognostic tool in the prevention of cardiovascular disease in obese dogs.

Abstract

Obesity can induce cardiovascular diseases in both humans and animals. Heart rate variability (HRV) is an indicator of sympathovagal balance and is used to identify cardiovascular diseases in humans. However, HRV and cardiac function have rarely been investigated in obese dogs. This study investigated the effect of obesity on oxidative stress, HRV, and cardiac function in obese and non-obese dogs. The nine-scale body condition score (BCS) system was used to determine obesity. Thirty small breed dogs were divided into a normal weight group (n = 15) and an obese group (n = 15). All dogs underwent physical examination, plasma malondialdehyde (MDA) measurement, electrocardiography, echocardiography, and two hours of Holter monitoring. This study found that obese dogs had increased plasma MDA and sympathovagal imbalance, which was indicated by impaired time and frequency domains compared to normal weight dogs. Although cardiac function was within normal limits, the echocardiographic study found that the obese dogs had reduced cardiac wall thickness and lower systolic function, as indicated by a reduction in %ejection fraction, %fractional shortening, increased left ventricular (LV) internal diameter during systole, and LV end-systolic volume compared to normal weight dogs. This study concluded that obesity in dogs can induce increased plasma oxidative stress, impaired HRV, and reduced cardiac systolic function compared to non-obese dogs.

Acute metformin treatment provides cardioprotection via improved mitochondrial function in cardiac ischemia / reperfusion injury

Cardiac ischemia/reperfusion (I/R) injury following reperfusion therapy in acute myocardial infarction results in mitochondrial dynamic imbalance and cardiomyocyte apoptosis. Although diabetic patients taking metformin have been shown to have a lower risk of myocardial infarction, the efficacy of the cardioprotection conferred by metformin regarding the mitochondrial function and dynamic in cardiac I/R injury are still inconclusive. In addition, the comparative effects between different doses of metformin given acutely prior to cardiac I/R injury have never been investigated. Fifty 8-week-old male Wistar rats weighing 300-350 g were divided into sham-operated (n = 10) and cardiac I/R-operated (n = 40) groups. In the cardiac I/R group, rats underwent 30-min ischemia followed by 120-min reperfusion and were randomly divided into four subgroups (n = 10/group): control (received normal saline), metformin (100, 200, and 400 mg/kg). The arrhythmia score, cardiac function, infarct size, mortality rate, mitochondrial function and apoptosis, were determined. Metformin (200 mg/kg) exerted the highest level of cardioprotection through reduction in arrhythmia, infarct size, mitochondrial fission, and apoptosis, in addition to preservation of mitochondrial function, leading to the attenuation of cardiac dysfunction. Doses of metformin (100 and 400 mg/kg) also improved mitochondrial and cardiac function, but to a lesser extent than metformin (200 mg/kg). In conclusion, metformin exerts cardioprotection by attenuating mitochondrial dysfunction, mitochondrial dynamic imbalance, and apoptosis. These led to decreased infarct size and eventual improvement in cardiac function in rats with acute cardiac I/R injury. These findings indicate the potential clinical benefits of acute metformin treatment in acute myocardial infarction.

PCSK9 inhibitor effectively attenuates cardiometabolic impairment in obese-insulin resistant rats

Long-term high-fat diet consumption causes obese-insulin resistance and cardiac mitochondrial dysfunction, leading to impaired left ventricular (LV) function. Atorvastatin effectively improved lipid profiles in obese patients. However, inadequate reduction in low density lipoprotein cholesterol (LDL-C) level was found. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor effectively reduced LDL-C levels. We hypothesized that this PCSK9 inhibitor has a greater efficacy in attenuating cardiometabolic impairments than atorvastatin in obese-insulin resistant rats. Female rats were fed with either a high fat or normal diet for 12 weeks. High fat diet fed rats (HFD) were then divided into 3 groups and were given vehicle, atorvastatin (40 mg/kg/day; s.c.), or PCSK9 inhibitor (4 mg/kg/day; s.c.) for additional 3 weeks. The metabolic parameters, cardiac and mitochondrial function and [Ca²⁺]_i transients were determined. HFD rats developed obese-insulin resistance as indicated by increased plasma insulin and HOMA index. Although high-fat diet fed rats treated with vehicle (HFV) rats had markedly impaired LV function as indicated by reduced %LVFS, impaired cardiac mitochondrial function, and [Ca²⁺]_i transient regulation, these impairments were attenuated in high-fat diet fed rats treated with atorvastatin (HFA) and high-fat diet fed rats treated with PCSK9 inhibitor (HFP) rats. However, these improvements were greater in HFP rats than HFA rats. Our findings indicated that the PCSK9 inhibitor exerted greater cardioprotection than atorvastatin through improved mitochondrial function in obese-insulin resistant rats.

PCSK9 inhibitor and atorvastatin reduce cardiac impairment in ovariectomized prediabetic rats via improved mitochondrial function and Ca2+ regulation

Post‐menopausal women have a higher risk of developing cardiometabolic dysfunction. Atorvastatin attenuates dyslipidaemia and cardiac dysfunction but it can have undesirable effects including increased risk of diabetes and myalgia. Currently, the proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor efficiently reduces low‐density lipoprotein cholesterol (LDL‐C) levels more effectively than atorvastatin. We have been suggested that PCSK9 inhibitor attenuated cardiometabolic impairment more effectively than atorvastatin in ovariectomized prediabetic rats. Female Wistar rats (n = 48) were fed a normal diet (ND) or high‐fat diet (HFD) for 12 weeks. Then, HFD rats were assigned to a sham‐operated (Sham) or ovariectomized (OVX) group. Six weeks after surgery, the OVX group was subdivided into 4 treatment groups: vehicle (HFOV), atorvastatin (HFOA) (40 mg/kg/day; s.c.), PCSK9 inhibitor (HFOP) (4 mg/kg/day; s.c.) and oestrogen (HFOE₂) (50 µg/kg/day; s.c.) for an additional 3 weeks. Metabolic parameters, cardiac and mitochondrial function, and [Ca²⁺]_i transients were evaluated. All HFD rats became obese‐insulin resistant. HFS rats had significantly impaired left ventricular (LV) function, cardiac mitochondrial function and [Ca²⁺]_i transient dysregulation. Oestrogen deprivation (HFOV) aggravated all of these impairments. Our findings indicated that the atorvastatin, PCSK9 inhibitor and oestrogen shared similar efficacy in the attenuation in cardiometabolic impairment in ovariectomized prediabetic rats.

Treatment with anagliptin, a DPP-4 inhibitor, decreases FABP4 concentration in patients with type 2 diabetes mellitus at a high risk for cardiovascular disease who are receiving statin therapy

Background

Fatty acid-binding protein 4 (FABP4) acts as a novel adipokine, and elevated FABP4 concentration is associated with obesity, insulin resistance and atherosclerosis. Dipeptidyl peptidase-4 (DPP-4) inhibitors, a class of antidiabetic drugs, have distinct structures among the drugs, possibly leading to a drug class effect and each drug effect. Sitagliptin, a DPP-4 inhibitor, has been reported to decrease FABP4 concentration in drug-naïve and sulfonylurea-treated patients with type 2 diabetes mellitus. Anagliptin, another DPP-4 inhibitor, was shown to decrease low-density lipoprotein cholesterol (LDL-C) level to a greater extent than that by sitagliptin in the Randomized Evaluation of Anagliptin vs. Sitagliptin On low-density lipoproteiN cholesterol in diabetes (REASON) trial.

Aim and methods

As a sub-analysis study using data obtained from the REASON trial, we investigated the effects of treatment with anagliptin (n = 148, male/female: 89/59) and treatment with sitagliptin (n = 159, male/female: 93/66) for 52 weeks on FABP4 concentration in patients with type 2 diabetes mellitus at a high risk for cardiovascular events who were receiving statin therapy.

Results

The DPP-4 inhibitor had been administered in 82% of the patients in the anagliptin group and 81% of the patients in sitagliptin group prior to randomization. Serum FABP4 level was significantly decreased by 7.9% by treatment with anagliptin (P = 0.049) and was not significantly decreased by treatment with sitagliptin (P = 0.660). Change in FABP4 level was independently associated with basal FABP4 level and changes in waist circumference and creatinine after adjustment of age, sex and the treatment group.

Conclusion

Anagliptin decreases serum FABP4 concentration independent of change in hemoglobin A1c or LDL-C in patients with type 2 diabetes mellitus and dyslipidemia who are on statin therapy.

Trial registration ClinicalTrials.gov number NCT02330406. Registered January 5, 2015, https://clinicaltrials.gov/ct2/show/NCT02330406

Mitochondrial dynamic modulation exerts cardiometabolic protection in obese insulin-resistant rats

Obese insulin resistance impairs cardiac mitochondrial dynamics by increasing mitochondrial fission and decreasing mitochondrial fusion, leading to mitochondrial damage, myocardial cell death and cardiac dysfunction. Therefore, inhibiting fission and promoting fusion could provide cardioprotection in this pre-diabetic condition. We investigated the combined effects of the mitochondrial fission inhibitor (Mdivi1) and fusion promoter (M1) on cardiac function in obese insulin-resistant rats. We hypothesized that Mdivi1 and M1 protect heart against obese insulin-resistant condition, but also there will be greater improvement using Mdivi1 and M1 as a combined treatment. Wistar rats (n=56, male) were randomly assigned to a high-fat diet (HFD) and normal diet (ND) fed groups. After feeding with either ND or HFD for 12 weeks, rats in each dietary group were divided into groups to receive either the vehicle, Mdivi1 (1.2 mg/kg, i.p.), M1 (2 mg/kg, i.p.) or combined treatment for 14 days. The cardiac function, cardiac mitochondrial function, metabolic and biochemical parameters were monitored before and after the treatment. HFD rats developed obese insulin resistance which led to impaired dynamics balance and function of mitochondria, increased cardiac cell apoptosis and dysfunction. Although Mdivi1, M1 and combined treatment exerted similar cardiometabolic benefits in HFD rats, the combined therapy showed a greater reduction in mitochondrial reactive oxygen species (ROS). Mitochondrial fission inhibitor and fusion promoter exerted similar levels of cardioprotection in a pre-diabetic condition.

Impact of vildagliptin on vascular and fibrotic remodeling of myocardium in experimental diabetic cardiomyopathy

The effect of dipeptidyl peptidase-4 inhibitors (DPP-4is) on myocardium in diabetic cardiomyopathy (DCM) remains a matter of debate. In the current study we investigated the effect of vildagliptin (VILDA, 3 mg/kg/d) on myocardium of DCM focusing on coronary microcirculation as well as on endothelial stress markers (ICAM and VCAM). We divided animals equally into 4 groups; nondiabetic (ND), VILDA per se, DCM and DCM + VILDA and their myocardium was evaluated for the fibro-vascular remodeling immunohistochemically as well as for molecular changes. VILDA had reversed the histological changes occurred in DCM including the disintegration, degeneration, and steatosis of cardiomyocytes with disappearance of the edema fluid. In addition VILDA significantly increased (p < 0.05) density of the coronary microcirculation and relieved endothelial stress. However, it did not prevent the development of fibrotic remodeling including the increased collagen deposition and the significantly upregulated (p < 0.05) corresponding genes. Therefore VILDA may have a positive impact on the microvascular remodeling, but not on fibrotic changes, in DCM.

The effects of acetylcholinesterase inhibitors on the heart in acute myocardial infarction and heart failure: From cells to patient reports

Cardiovascular diseases remain a major cause of morbidity and mortality worldwide. Cardiovascular diseases such as acute myocardial infarction, ischaemia/reperfusion injury and heart failure are associated with cardiac autonomic imbalance characterized by sympathetic overactivity and parasympathetic withdrawal from the heart. Increased parasympathetic activity by electrical vagal nerve stimulation has been shown to provide beneficial effects in the case of cardiovascular diseases in both animals and patients by improving autonomic function, cardiac remodelling and mitochondrial function. However, clinical limitations for electrical vagal nerve stimulation exist because of its invasive nature, costly equipment and limited clinical validation. Therefore, novel therapeutic approaches which moderate parasympathetic activities could be beneficial for in the case of cardiovascular disease. Acetylcholinesterase inhibitors inhibit acetylcholinesterase and hence increase cholinergic transmission. Recent studies have reported that acetylcholinesterase inhibitors improve autonomic function and cardiac function in cardiovascular disease models. Despite its potential clinical benefits for cardiovascular disease patients, the role of acetylcholinesterase inhibitors in acute myocardial infarction and heart failure remediation remains unclear. This article comprehensively reviews the effects of acetylcholinesterase inhibitors on the heart in acute myocardial infarction and heart failure scenarios from in vitro and in vivo studies to clinical reports. The mechanisms involved are also discussed in this review.

N-acetylcysteine Restored Heart Rate Variability and Prevented Serious Adverse Events in Transfusion-dependent Thalassemia Patients: a Double-blind Single Center Randomized Controlled Trial

Regular blood transfusions in transfusion-dependent thalassemia (TDT) patients can lead to iron overload, causing oxidative stress and sympathovagal imbalance, resulting in increased cardiac complications. We hypothesized that administrating of N-acetylcysteine (NAC) prevents serious adverse events including cardiac complications in TDT patients by reducing systemic oxidative stress and balancing cardiac sympathovagal control. This study was double-blind, randomized control trial, investigating in 59 Thai TDT patients. After randomization, the participants were divided into two groups. The control group received standard care of TDT patient plus placebo, whereas the intervention group received 600 mg of NAC orally for six months. Serum 8-isoprostane, TNF-alpha, IL-10, 24-hour ECG monitoring, echocardiograms and the incidence of thalassemia-related complications were collected. At baseline, no significant difference in any parameters between the control and the intervention groups. At the end of intervention, the incidence of serious adverse events (i.e. infection, worsening thalassemia) was significantly higher in the control group when compared with the intervention group (24.1% vs. 3.3%, p=0.019) (Chi-square test; absolute risk reduction=20.8%, number needed to treat=4.8). The control group also had significantly lower time-dependent HRV parameters, compared with the intervention group (p=0.025 and 0.030, independent t-test). Treatment with NAC restored HRV and reduced serious adverse event in TDT patients, however, no difference in cardiac complications could be demonstrated. NAC could prevent serious adverse events in TDT patients. The proposed mechanism might be the balancing of sympathovagal control.

Vildagliptin reduces myocardial ischemia-induced arrhythmogenesis via modulating inflammatory responses and promoting expression of genes regulating mitochondrial biogenesis in rats with type-II diabetes

PURPOSE

Fatal arrhythmias are one of the main manifestations of ischemic heart disease in diabetic patients. Here, we investigated the effect of pretreatment with vildagliptin on myocardial arrhythmias, inflammatory responses, and expression of genes regulating mitochondrial biogenesis following cardiac ischemic injury in type II diabetic male Wistar rats.

METHODS

Chronic diabetes was modeled by a high-fat diet and low-dose streptozotocin method and lasted for 12 weeks. Vildagliptin (6 mg/dl) was orally administered during the last 4 weeks of the diabetic period. Then, rats' hearts (n = 8/each group) were immediately isolated and transferred to the Langendorff apparatus, in which left anterior descending coronary artery was tightened for 35 min to induce regional ischemia. Electrocardiography was continuously recorded and myocardial arrhythmias were interpreted according to the Lambeth Convention. Inflammatory cytokines in left ventricular samples were measured using ELISA kits, and gene expression was assayed using real-time PCR.

RESULTS

Diabetic groups showed increased incidence and duration of ventricular fibrillation (VF) than controls (P < 0.05). Pretreatment of diabetic rats with vildagliptin resulted in a significant decrease in number, duration, and severity of premature ventricular complexes (PVC), tachycardia (VT), and VF during ischemia, compared to non-treated diabetic group (P < 0.05). Additionally, vildagliptin significantly increased the expression of genes PGC-1α, SIRT-1, and NRF-2 and reduced the levels of myeloperoxidase, creatine kinase release, and myocardial content of TNF-α and IL-1β in nondiabetic and diabetic rats as compared to corresponding controls (P < 0.01-0.05).

CONCLUSION

Vildagliptin preconditioning reduced the occurrence and severity of fatal ventricular arrhythmias induced by myocardial ischemia in type II diabetic rats through increased activity of mitochondrial biogenesis-regulating genes and reduction of inflammatory reactions.

Protective effect of dipeptidyl peptidase-4 inhibitors in testicular torsion/detorsion in rats: a possible role of HIF-1α and nitric oxide

Spermatic cord torsion is a serious and common urologic emergency. It requires early diagnosis for prevention of subfertility and testicular necrosis. Vildagliptin and sitagliptin are anti-diabetic drugs of the dipeptidyl peptidase-4 (DPP-4) inhibitors that have a protective role against cerebral ischemic stroke and cardiac ischemia reperfusion. This study aimed to investigate the role and mechanism of action of vildagliptin and sitagliptin in a model of testicular ischemia/reperfusion injury by testicular torsion/detorsion (T/D). Testicular T/D was done and vildagliptin and sitagliptin were administered either alone or in combination with nitric oxide synthase (NOS) inhibitor. Serum total cholesterol and testosterone were measured, while in testicular tissue testosterone, malondialdehyde (MDA) level, total antioxidant capacity (TAC), nitric oxide level, caspase-3, superoxide dismutase (SOD), hypoxia-inducible factor-1α (HIF-1α), tumor necrosis factor-α (TNF-α) and endothelial NOS (eNOS), and inducible NOS (iNOS) and neuronal NOS (nNOS) were measured. Histopathology of testicular tissue was done. Vildagliptin and sitagliptin increased serum testosterone, expression, and activity of SOD and testicular TAC. It also reduced total serum cholesterol, testicular MDA, caspase-3, HIF-1α, TNF-α, and expression of eNOS, iNOS, and nNOS. Vildagliptin and sitagliptin also improved histopathological picture of testicular tissue. NOS inhibitor produced similar result to DDP-4 inhibitors; however, its co-administration augmented the effect of vildagliptin and sitagliptin on these parameters. DPP-4 inhibitors, vildagliptin, and sitagliptin were protective against testicular T/D-induced injury mostly by anti-oxidative stress, and anti-apoptotic and anti-inflammatory actions that was augmented by NOS inhibition with a possible role for HIF-1α expression.

Pretreatment with vildagliptin boosts ischemic-postconditioning effects on cardioprotection and expression profile of genes regulating autophagy and mitochondrial fission/fusion in diabetic heart with reperfusion injury

The burden of myocardial ischemia/reperfusion (IR) injury is 2-3-folds higher in diabetic patients, so protecting diabetic hearts is clinically important. Here, we investigated the effect of combinational therapy with vildagliptin and ischemic postconditioning (IPostC) on cardioprotection and the expression of genes regulating autophagy and mitochondrial function in diabetic hearts with IR injury. Type 2 diabetes was induced through high-fat diet and streptozotocin protocol in Wistar rats. Vildagliptin was orally administered to diabetic rats 5 weeks before IR injury. Myocardial-IR injury was modeled by ligation of left the coronary artery for 30 min followed by 60-min reperfusion, on a Langendorff-perfusion system. IPostC was applied at early reperfusion as 6 alternative cycles of 10-s reperfusion/ischemia. Creatine-kinase levels were measured spectrometrically, and infarct size was evaluated by TTC staining method. Left ventricles were harvested for assessing the expression levels of autophagy and mitochondrial-related genes using real-time PCR. Induction of diabetes significantly increased creatine-kinase release in comparison to healthy rats, and all treatments significantly reduced the release of enzyme toward control levels (P < 0.05). Only the combination therapy (IPostC + vildagliptin) could significantly reduce the infarct size of diabetic hearts as compared to untreated diabetic-IR group (P < 0.01). The levels of autophagy genes LC3 and p62 were significantly higher in diabetic groups than healthy ones. Induction of IR injury in diabetic hearts enhanced mitochondrial fission (drp-1) and reduced mitochondrial fusion (mfn1 and mfn2) genes. IPostC alone had no significant effect on the gene expression and vildagliptin alone could only affect LC3-II and mfn2 expressions. Nevertheless, administration of combination therapy significantly reduced the expression of both autophagy genes and increased both LC3-II/I and mfn2/1 ratios as compared with diabetic-IR hearts (P < 0.01-0.05). Application of this combination therapy could overcome the diabetes-induced failure of cardioprotection by individual treatments and improve mitochondrial dynamic and autophagy flux.

Ablation of TMEM126B protects against heart injury via improving mitochondrial function in high fat diet (HFD)-induced mice

The mitochondrial dysfunction in the pathogenesis of myocardial damage associated with high fat diet (HFD)-induced obesity remains largely unknown. Transmembrane protein 126B (TMEM126B), as a complex I assembly factor, plays a key role in regulating mitochondrial function. In the present study, the effects of TMEM126B on mitochondrial function were investigated using genetic knockout approach in HFD-induced mouse models with obesity. We found that TMEM126B was significantly increased in HFD-treated cardiac samples. Genetic ablation of TMEM126B alleviated HFD-mediated metabolic disorder and heart injury. TEM results suggested that cardiac mitochondrial integrity was improved in TMEM126B knockout mice compared with the wild type (WT) mice after HFD challenge. Additionally, the mitochondrial dysfunction induced by HFD was alleviated in mice with TMEM126B knockout, as evidenced by the decreased protein expression levels of dynamic-related protein-1 (DRP1) and fission-1 (FIS1) and increased expression of mitofusin-1 (MFN1). The mitochondrial impairments were further confirmed in palmitic acid (PA)-incubated cardiomyocytes, as evidenced by the down-regulated membrane potential and ATP levels, and by the up-regulated mitochondrial reactive oxygen species (ROS) production and DNA damage, which were significantly reversed by TMEM126B knockdown in vitro. Finally, TMEM126B ablation suppressed mitochondrial-dependent apoptotic death in the hearts of HFD mice. Therefore, TMEM126B led to mitochondrial impairments, contributing to the pathogenesis of HFD-induced cardiac injury, and blockage of TMEM126B could inhibit mitochondrial dysfunction, paving the road to new therapeutic modalities for the prevention of obesity-associated heart injury.

Mitochondrial dysfunction in diabetes and the regulatory roles of antidiabetic agents on the mitochondrial function

The prevalence of type 2 diabetes mellitus (T2DM) is increasing rapidly with its associated morbidity and mortality. Many pathophysiological pathways such as oxidative stress, inflammatory responses, adipokines, obesity‐induced insulin resistance, improper insulin signaling, and beta cell apoptosis are associated with the development of T2DM. There is increasing evidence of the role of mitochondrial dysfunction in the onset of T2DM, particularly in relation to the development of diabetic complications. Here, the role of mitochondrial dysfunction in T2DM is reviewed together with its modulation by antidiabetic therapeutic agents, an effect that may be independent of their hypoglycemic effect.

Combination of exercise and calorie restriction exerts greater efficacy on cardioprotection than monotherapy in obese-insulin resistant rats through the improvement of cardiac calcium regulation

BACKGROUND

Long-term high-fat diet (HFD) consumption causes obese-insulin resistance which is known to be a major risk factor for cardiovascular diseases due to its impact on the impairment of left ventricular (LV) contractile function and cardiac mitochondrial function. Intracellular calcium [Ca²⁺]i regulation plays an important role in the maintenance of LV function. Although either caloric restriction (CR) or exercise (Ex) are shown to strongly affect metabolic status and LV function, the combined effects of exercise and calorie restriction on cardiometabolic status, cardiac mitochondrial dynamics and cardiac [Ca²⁺]i transient homeostasis under conditions of obese-insulin resistance have never been investigated.

METHODS

Female rats were fed with either a high-fat diet (HFD: fat, 59.28%; protein, 26.45%; carbohydrate, 14.27%) or a normal diet (fat, 19.77%; protein, 28.24%; carbohydrate, 51.99%) for 13 weeks. HFD rats were then divided into 4 groups: 1) Vehicle (HFD + Veh); 2) Calorie restriction (HFD + CR); 3) Exercise (HFD + Ex) and 4) Combined therapy (HFD + CR + Ex). After 6-week intervention, the metabolic status, heart rate variability (HRV), LV function, cardiac mitochondrial dynamics, and [Ca²⁺]i transients were determined.

RESULTS

Insulin resistance developed in HFD rats as indicated by increased plasma insulin and HOMA index. Although HFD + Veh rats had markedly impaired LV function, indicated by reduced %LVFS and impaired cardiac mitochondrial dynamics and [Ca²⁺]i transients, these impairments were attenuated in the HFD + CR, HFD + Ex and HFD + CR + Ex rats. However, the greatest improvement in cardiometabolic function was observed in HFD + CR + Ex rats.

CONCLUSIONS

Our findings indicated that a combination of calorie restriction and exercise exerted greater cardioprotection than a monotherapy through the improvement of cardiometabolic status, cardiac mitochondrial dynamics and cardiac [Ca²⁺]i homeostasis in obese-insulin resistant rats.

The effect of exenatide (a GLP-1 analog) and sitagliptin (a DPP-4 inhibitor) on plasma platelet-activating factor acetylhydrolase (PAF-AH) activity and concentration in normal and fructose-fed rats

Inflammation and oxidative stress are the two processes crucial in atherogenesis. Platelet-activating factor acetylhydrolase (PAF-AH), a plasma lipoprotein-associated enzyme, degrades pro-inflammatory lipids generated within oxidatively modified lipoproteins. Extensive evidence shows that incretin-based drugs, a new class of anti-diabetic agents, can provide cardiovascular protection that cannot be attributed to their glucose-lowering effects. The present study was undertaken to determine whether the antiatherogenic effects of the GLP-1(glucagon-like peptide-1) receptor agonist (exenatide) and DPP-4(dipeptidyl peptidase-4) inhibitors (sitagliptin) may occur via the regulation of platelet-activating factor acetylhydrolase (PAF-AH) activity/mass and inhibition of low-density lipoprotein (LDL) oxidation in the fructose-fed rats. Normal and fructose-fed rats (8 wk) were treated (4 wk) with sitagliptin (5 and 10 mg/kg p.o.) or with exenatide (5 and 10 µg/kg, s.c.). Plasma PAF-AH activity and phosphatidylcholine (PC) concentration were measured colorimetrically. Plasma PAF-AH concentration, oxidized LDL (oxLDL), hexanoyl-Lys adduct (HEL), lyso-PC, apolipoprotein A-I (apoA-I), apoB, platelet-activating factor (PAF), monocyte chemoattractant protein-1 (MCP-1) and endothelin-1 (ET-1) were measured by ELISA. The four-week exenatide (5 µg/kg, sc.) treatment of fructose fed-rats significantly increased plasma PAF-AH activity (+33%, P < 0.001) and decreased the level of circulating oxLDL (-42%, P < 0.05) and MCP-1 (-23%, P < 0.01). These changes were accompanied by the decrease in plasma PC/lyso-PC (-47%, P < 0.001) and apoB/apoA-I ratio (-75%, P < 0.001). The effect of exenatide on enzyme activity was associated with only a minor effect on metabolic parameters and was independent of weight reduction. Exenatide but not sitagliptin inhibits oxidative modification of LDL probably due to favorable effect on plasma PAF-AH activity.

Combined low-dose testosterone and vildagliptin confers cardioprotection in castrated obese rats

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 the 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 2 subgroups; sham operation and orchiectomy (NDO, HFO) and fed their diets for another 12 weeks. At week 25, orchiectomized rats were subdivided into 4 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.

A closer look at heart failure in patients with concurrent diabetes mellitus using glucose lowering drugs

INTRODUCTION

Type 2 diabetes (T2D) is an independent risk factor for heart failure (HF). With concomitant T2D and HF, recent data suggests an incremental risk of cardiovascular death and hospitalization for HF, as compared to patients with HF without T2D. Areas covered: Management of these two diseases has been a challenge for physicians. The treatment goals for HF patients in T2D are very important. They serve as the endpoint in using a specific treatment for management and treatment of T2D patients hence, decreasing mortality rates. In this review, we examine the effects of oral antidiabetic drugs on HF patients, discussing current evidence-based up-to-date management strategies and guidelines in the general population with HF and T2D. Expert commentary: Future in the management of T2D in HF patients looks bright. Augmenting data on potential cardiovascular side effects of antidiabetic drugs is valuable since millions of people are treated over many years. Newer novel drugs targeting specific signaling pathways are approaching the stages of clinical investigation. They have been a highly attractive concept for the future in the management of these patients. However, while advances in technology elucidated many aspects of these diseases, many mysteries still remain.

Improved glucose homeostasis in male obese Zucker rats coincides with enhanced baroreflexes and activation of the nucleus tractus solitarius

Young adult male obese Zucker rats (OZR) develop insulin resistance and hypertension with impaired baroreflex-mediated bradycardia and activation of nucleus tractus solitarius (NTS). Because type 1 diabetic rats also develop impaired baroreflex-mediated NTS activation, we hypothesized that improving glycemic control in OZR would enhance compromised baroreflexes and NTS activation. Fasting blood glucose measured by telemetry was comparable in OZR and lean Zucker rats (LZR) at 12-17 wk. However, with access to food, OZR were chronically hyperglycemic throughout this age range. By 15-17 wk of age, tail samples yielded higher glucose values than those measured by telemetry in OZR but not LZR, consistent with reports of exaggerated stress responses in OZR. Injection of glucose (1g/kg ip) produced larger rises in glucose and areas under the curve in OZR than LZR. Treatment with metformin (300 mg·kg^-1·day^-1) or pioglitazone (5 mg·kg^-1·day^-1) in drinking water for 2-3 wk normalized fed glucose levels in OZR with no effect in LZR. After metformin treatment, area under the curve for blood glucose after glucose injection was reduced in OZR and comparable to LZR. Hyperinsulinemia was slightly reduced by each treatment in OZR, but insulin was still greatly elevated compared with LZR. Neither treatment reduced hypertension in OZR, but both treatments significantly improved the blunted phenylephrine-induced bradycardia and NTS c-Fos expression in OZR with no effect in LZR. These data suggest that restoring glycemic control in OZR enhances baroreflex control of heart rate by improving the response of the NTS to raising arterial pressure, even in the presence of hyperinsulinemia and hypertension.