Caloric restriction in leptin deficiency does not correct myocardial steatosis: failure to normalize PPAR{alpha}/PGC1{alpha} and thermogenic glycerolipid/fatty acid cycling

Therapeutic mechanism of Curcuma aromatica Salisb. rhizome against coronary heart disease based on integrated network pharmacology, pharmacological evaluation and lipidomics

Curcuma aromatica Salisb. rhizome (CASR) has multifunctional characteristics worldwide and a long history of use as a botanical drug with. Currently, it is often used clinically to treat coronary heart disease (CHD) caused by blood stasis syndrome. However, the therapeutic mechanism of CASR in the treatment of CHD remains poorly understood. In study, the main chemical constituents of CASR were analyzed using UPLC-Q-TOF-MS/MS. Then, its potential therapeutic mechanism against CHD was predicted. Subsequently, pharmacological evaluation was performed using CHD rat model. Finally, a lipidomics approach was applied to explore the different lipid metabolites to verify the regulation of CASR on lipid metabolism disorders in CHD. A total of 35 compounds was identified from CASR. Seventeen active components and 51 potential targets related to CHD were screened by network pharmacology, involving 13 key pathways. In vivo experiments showed that CASR could significantly improve myocardial infarction, blood stasis, and blood lipid levels and regulate the PI3K/AKT/mTOR signaling pathway in CHD rats. Lipidomics further showed that CASR could regulate abnormal sphingolipid, glycerophospholipid, and glycerolipid metabolism in CHD rats. The therapeutic mechanism of CASR against CHD was initially elucidated and included the regulation of lipid metabolism. Its effects may be attributed to active ingredients, such as curzerene, isoprocurcumenol, and (+)-curcumenol. This study reveals the characteristics of multi-component and multi-pathway of CASR in the treatment of CHD, which provides a basis for the follow-up development and utilization of CASR.

A comparative pharmacogenomic analysis of three classic TCM prescriptions for coronary heart disease based on molecular network modeling

Traditional Chinese medicine (TCM) has evolved over several thousands of years, which has been shown to be efficacious in the treatment of ischemic heart disease. Three classical TCM prescriptions, namely Xuefu Zhuyu Decoction, Zhishi Xiebai Guizhi Decoction, and Gualou Xiebai Banxia Decoction, have been extensively used in the treatment of coronary heart disease (CHD). Based on molecular network modeling, we performed a comparative pharmacogenomic analysis to systematically determine the drug-targeting spectrum of the three prescriptions at molecular level. Wide-area target molecules of CHD were covered, which was a common feature of the three decoctions, demonstrating their therapeutic functions. Meanwhile, collective signaling involved metabolic/pro-metabolic pathways, driving and transferring pathways, neuropsychiatric pathways, and exocrine or endocrine pathways. These organized pharmacological disturbance was mainly focused on almost all stages of CHD intervention, such as anti-atherosclerosis, lipid metabolism, inflammation, vascular wall function, foam cells formation, platelets aggregation, thrombosis, arrhythmia, and ischemia-reperfusion injury. In addition, heterogeneity analysis of the global pharmacological molecular spectrum revealed that signaling crosstalk, cascade convergence, and key targets were tendentious among the three decoctions. After all, it is unadvisable to rank the findings on targeting advantages of the three decoctions. Comparative pharmacological evidence may provide an appropriate decoction scheme for individualized intervention of CHD.

Transcriptomics Curation of SARS-CoV-2 Related Host Genes in Mice With COVID-19 Comorbidity: A Pilot Study

The pandemic of coronavirus disease 2019 (COVID-19), a respiratory disease caused by a novel severe acute respiratory syndrome coronavirus-2, is causing substantial morbidity and mortality. Along with the respiratory symptoms, underlying diseases in senior patients, such as diabetes, hypertension, and coronary heart disease, are the most common comorbidities, which cause more severe outcomes and even death. During cellular attachment and entry of severe acute respiratory syndrome coronavirus-2, the key protein involved is the angiotensin I converting enzyme 2 (ACE2), which is located on the membrane of host cells. Here, we aim to curate an expression profile of Ace2 and other COVID-19 related genes across the available diabetes murine strains. Based on strictly manual curation and bioinformatics analysis of the publicly deposited expression datasets, Ace2 and other potentially involved genes such as Furin, Tmprss2, Ang, and Ang2 were examined. We found that Ace2 expression is rather ubiquitous in three selected diabetes prone strains (db/db, ob/ob and diet-induced obese). With the most abundant datasets present, the liver shows a medium Ace2 expression level compared with the lungs, pancreatic islets, brain and even T cells. Age is a more critical factor for Ace2 expression in db/db compared with the other two strains. Besides Ace2, the other four host genes showed varied levels of correlation to each other. To accelerate research on the interaction between COVID-19 and underlying diseases, the Murine4Covid transcriptomics database (www.geneureka.org/Murine4Covid) will facilitate the design of research on COVID-19 and comorbidities.

Central leptin regulates heart lipid content by selectively increasing PPAR β/δ expression

The role of central leptin in regulating the heart from lipid accumulation in lean leptin-sensitive animals has not been fully elucidated. Herein, we investigated the effects of central leptin infusion on the expression of genes involved in cardiac metabolism and its role in the control of myocardial triacylglyceride (TAG) accumulation in adult Wistar rats. Intracerebroventricular (icv) leptin infusion (0.2 µg/day) for 7 days markedly decreased TAG levels in cardiac tissue. Remarkably, the cardiac anti-steatotic effects of central leptin were associated with the selective upregulation of gene and protein expression of peroxisome proliferator-activated receptor β/δ (PPARβ/δ, encoded by Pparb/d) and their target genes, adipose triglyceride lipase (encoded by Pnpla2, herefater referred to as Atgl), hormone sensitive lipase (encoded by Lipe, herefater referred to as Hsl), pyruvate dehydrogenase kinase 4 (Pdk4) and acyl CoA oxidase 1 (Acox1), involved in myocardial intracellular lipolysis and mitochondrial/peroxisomal fatty acid utilization. Besides, central leptin decreased the expression of stearoyl-CoA deaturase 1 (Scd1) and diacylglycerol acyltransferase 1 (Dgat1) involved in TAG synthesis and increased the CPT-1 independent palmitate oxidation, as an index of peroxisomal β-oxidation. Finally, the pharmacological inhibition of PPARβ/δ decreased the effects on gene expression and cardiac TAG content induced by leptin. These results indicate that leptin, acting at central level, regulates selectively the cardiac expression of PPARβ/δ, contributing in this way to regulate the cardiac TAG accumulation in rats, independently of its effects on body weight.

Metabolic reprogramming via PPARα signaling in cardiac hypertrophy and failure: From metabolomics to epigenetics

Studies using omics-based approaches have advanced our knowledge of metabolic remodeling in cardiac hypertrophy and failure. Metabolomic analysis of the failing heart has revealed global changes in mitochondrial substrate metabolism. Peroxisome proliferator-activated receptor-α (PPARα) plays a critical role in synergistic regulation of cardiac metabolism through transcriptional control. Metabolic reprogramming via PPARα signaling in heart failure ultimately propagates into myocardial energetics. However, emerging evidence suggests that the expression level of PPARα per se does not always explain the energetic state in the heart. The transcriptional activities of PPARα are dynamic, yet highly coordinated. An additional level of complexity in the PPARα regulatory mechanism arises from its ability to interact with various partners, which ultimately determines the metabolic phenotype of the diseased heart. This review summarizes our current knowledge of the PPARα regulatory mechanisms in cardiac metabolism and the possible role of PPARα in epigenetic modifications in the diseased heart. In addition, we discuss how metabolomics can contribute to a better understanding of the role of PPARα in the progression of cardiac hypertrophy and failure.

Peroxisome proliferator-activated receptors (PPARs) as therapeutic target in neurodegenerative disorders

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors and they serve to be a promising therapeutic target for several neurodegenerative disorders, which includes Parkinson disease, Alzheimer's disease, Huntington disease and Amyotrophic Lateral Sclerosis. PPARs play an important role in the downregulation of mitochondrial dysfunction, proteasomal dysfunction, oxidative stress, and neuroinflammation, which are the major causes of the pathogenesis of neurodegenerative disorders. In this review, we discuss about the role of PPARs as therapeutic targets in neurodegenerative disorders. Several experimental approaches suggest potential application of PPAR agonist as well as antagonist in the treatment of neurodegenerative disorders. Several epidemiological studies found that the regular usage of PPAR activating non-steroidal anti-inflammatory drugs is effective in decreasing the progression of neurodegenerative diseases including PD and AD. We also reviewed the neuroprotective effects of PPAR agonists and associated mechanism of action in several neurodegenerative disorders both in vitro as well as in vivo animal models.

HDAC Inhibition Modulates Cardiac PPARs and Fatty Acid Metabolism in Diabetic Cardiomyopathy

Peroxisome proliferator-activated receptors (PPARs) regulate cardiac glucose and lipid homeostasis. Histone deacetylase (HDAC) inhibitor has anti-inflammatory effects which may play a key role in modulating PPARs and fatty acid metabolism. The aim of this study was to investigate whether HDAC inhibitor, MPT0E014, can modulate myocardial PPARs, inflammation, and fatty acid metabolism in diabetes mellitus (DM) cardiomyopathy. Electrocardiography, echocardiography, and western blotting were used to evaluate the electrophysiological activity, cardiac structure, fatty acid metabolism, inflammation, and PPAR isoform expressions in the control and streptozotocin-nicotinamide-induced DM rats with or without MPT0E014. Compared to control, DM and MPT0E014-treated DM rats had elevated blood glucose levels and lower body weights. However, MPT0E014-treated DM and control rats had smaller left ventricular end-diastolic diameter and shorter QT interval than DM rats. The control and MPT0E014-treated DM rats had greater cardiac PPAR-α and PPAR-δ protein expressions, but less cardiac PPAR-γ than DM rats. Moreover, control and MPT0E014-treated DM rats had lower concentrations of 5′ adenosine monophosphate-activated protein kinase 2α, PPAR-γ coactivator 1α, phosphorylated acetyl CoA carboxylase, cluster of differentiation 36, diacylglycerol acyltransferase 1 (DGAT1), DGAT2, tumor necrosis factor-α, and interleukin-6 protein than DM rats. HDAC inhibition significantly attenuated DM cardiomyopathy through modulation of cardiac PPARS, fatty acid metabolism, and proinflammatory cytokines.

Cardiac Myocyte KLF5 Regulates Ppara Expression and Cardiac Function

RATIONALE

Fatty acid oxidation is transcriptionally regulated by peroxisome proliferator-activated receptor (PPAR)α and under normal conditions accounts for 70% of cardiac ATP content. Reduced Ppara expression during sepsis and heart failure leads to reduced fatty acid oxidation and myocardial energy deficiency. Many of the transcriptional regulators of Ppara are unknown.

OBJECTIVE

To determine the role of Krüppel-like factor 5 (KLF5) in transcriptional regulation of Ppara.

METHODS AND RESULTS

We discovered that KLF5 activates Ppara gene expression via direct promoter binding. This is blocked in hearts of septic mice by c-Jun, which binds an overlapping site on the Ppara promoter and reduces transcription. We generated cardiac myocyte-specific Klf5 knockout mice that showed reduced expression of cardiac Ppara and its downstream fatty acid metabolism-related targets. These changes were associated with reduced cardiac fatty acid oxidation, ATP levels, increased triglyceride accumulation, and cardiac dysfunction. Diabetic mice showed parallel changes in cardiac Klf5 and Ppara expression levels.

CONCLUSIONS

Cardiac myocyte KLF5 is a transcriptional regulator of Ppara and cardiac energetics.

Nutrient sensing and utilization: Getting to the heart of metabolic flexibility

A central feature of obesity-related cardiometabolic diseases is the impaired ability to transition between fatty acid and glucose metabolism. This impairment, referred to as "metabolic inflexibility", occurs in a number of tissues, including the heart. Although the heart normally prefers to metabolize fatty acids over glucose, the inability to upregulate glucose metabolism under energetically demanding conditions contributes to a pathological state involving energy imbalance, impaired contractility, and post-translational protein modifications. This review discusses pathophysiologic processes that contribute to cardiac metabolic inflexibility and speculates on the potential physiologic origins that lead to the current state of cardiometabolic disease in an obesogenic environment.

Obesity-induced oxidative stress, accelerated functional decline with age and increased mortality in mice

Obesity is a serious chronic disease that increases the risk of numerous co-morbidities including metabolic syndrome, cardiovascular disease and cancer as well as increases risk of mortality, leading some to suggest this condition represents accelerated aging. Obesity is associated with significant increases in oxidative stress in vivo and, despite the well-explored relationship between oxidative stress and aging, the role this plays in the increased mortality of obese subjects remains an unanswered question. Here, we addressed this by undertaking a comprehensive, longitudinal study of a group of high fat-fed obese mice and assessed both their changes in oxidative stress and in their performance in physiological assays known to decline with aging. In female C57BL/6J mice fed a high-fat diet starting in adulthood, mortality was significantly increased as was oxidative damage in vivo. High fat-feeding significantly accelerated the decline in performance in several assays, including activity, gait, and rotarod. However, we also found that obesity had little effect on other markers of function and actually improved performance in grip strength, a marker of muscular function. Together, this first comprehensive assessment of longitudinal, functional changes in high fat-fed mice suggests that obesity may induce segmental acceleration of some of the aging process.

Impaired cytosolic NADH shuttling and elevated UCP3 contribute to inefficient citric acid cycle flux support of postischemic cardiac work in diabetic hearts

Diabetic hearts are subject to more extensive ischemia/reperfusion (ISC/REP) damage. This study examined the efficiency of citric acid cycle (CAC) flux and the transfer of cytosolic reducing equivalents into the mitochondria for oxidative support of cardiac work following ISC/REP in hearts of c57bl/6 (NORM) and type 2 diabetic, db/db mouse hearts. Flux through the CAC and malate-aspartate shuttle (MA) were monitored via dynamic (13)C NMR of isolated hearts perfused with (13)C palmitate+glucose. MA flux was lower in db/db than NORM. Oxoglutarate malate carrier (OMC) was elevated in the db/db heart, suggesting a compensatory response to low NADHc. Baseline CAC flux per unit work (rate-pressure-product, RPP) was similar between NORM and db/db, but ISC/REP reduced the efficiency of CAC flux/RPP by 20% in db/db. ISC/REP also increased UCP3 transcription, indicating potential for greater uncoupling. Therefore, ISC/REP induces inefficient carbon utilization through the CAC in hearts of diabetic mice due to the combined inefficiencies in NADHc transfer per OMC content and increased uncoupling via UCP3. Ischemia and reperfusion exacerbated pre-existing mitochondrial defects and metabolic limitations in the cytosol of diabetic hearts. These limitations and defects render diabetic hearts more susceptible to inefficient carbon fuel utilization for oxidative energy metabolism.

Mechanisms of lipotoxicity in the cardiovascular system

Cardiovascular diseases account for approximately one third of all deaths globally. Obese and diabetic patients have a high likelihood of dying from complications associated with cardiovascular dysfunction. Obesity and diabetes increase circulating lipids that upon tissue uptake, may be stored as triglyceride, or may be metabolized in other pathways, leading to the generation of toxic intermediates. Excess lipid utilization or activation of signaling pathways by lipid metabolites may disrupt cellular homeostasis and contribute to cell death, defining the concept of lipotoxicity. Lipotoxicity occurs in multiple organs, including cardiac and vascular tissues, and a number of specific mechanisms have been proposed to explain lipotoxic tissue injury. In addition, recent data suggests that increased tissue lipids may also be protective in certain contexts. This review will highlight recent progress toward elucidating the relationship between nutrient oversupply, lipotoxicity, and cardiovascular dysfunction. The review will focus in two sections on the vasculature and cardiomyocytes respectively.

Beneficial cardiac effects of caloric restriction are lost with age in a murine model of obesity

Obesity is associated with increased diastolic stiffness and myocardial steatosis and dysfunction. The impact of aging on the protective effects of caloric restriction (CR) is not clear. We studied 2-month (younger) and 6-7-month (older)-old ob/ob mice and age-matched C57BL/6J controls (WT). Ob/ob mice were assigned to diet ad libitum or CR for 4 weeks. We performed echocardiograms, myocardial triglyceride assays, Oil Red O staining, and measured free fatty acids, superoxide, NOS activity, ceramide levels, and Western blots. In younger mice, CR restored diastolic function, reversed myocardial steatosis, and upregulated Akt phosphorylation. None of these changes was observed in the older mice; however, CR decreased oxidative stress and normalized NOS activity in these animals. Interestingly, myocardial steatosis was not associated with increased ceramide, but CR altered the composition of ceramides. In this model of obesity, aging attenuates the benefits of CR on myocardial structure and function.

UCP3 regulates cardiac efficiency and mitochondrial coupling in high fat-fed mice but not in leptin-deficient mice

These studies investigate the role of uncoupling protein 3 (UCP3) in cardiac energy metabolism, cardiac O(2) consumption (MVO(2)), cardiac efficiency (CE), and mitochondrial uncoupling in high fat (HF)-fed or leptin-deficient mice. UCP3KO and wild-type (WT) mice were fed normal chow or HF diets for 10 weeks. Substrate utilization rates, MVO(2), CE, and mitochondrial uncoupling were measured in perfused working hearts and saponin-permeabilized cardiac fibers, respectively. Similar analyses were performed in hearts of ob/ob mice lacking UCP3 (U3OB mice). HF increased cardiac UCP3 protein. However, fatty acid (FA) oxidation rates were similarly increased by HF diet in WT and UCP3KO mice. By contrast, MVO(2) increased in WT, but not in UCP3KO with HF, leading to increased CE in UCP3KO mice. Consistent with increased CE, mitochondrial coupling was increased in the hearts of HF-fed UCP3KO mice. Unexpectedly, UCP3 deletion in ob/ob mice reduced FA oxidation but had no effect on MVO(2) or CE. In addition, FA-induced mitochondrial uncoupling was similarly enhanced in U3OB compared with ob/ob hearts and was associated with elevated mitochondrial thioesterase-1 protein content. These studies show that although UCP3 may mediate mitochondrial uncoupling and reduced CE after HF feeding, it does not mediate uncoupling in leptin-deficient states.

Modulation of the cardiovascular system by leptin

It is well established that individuals with the metabolic syndrome have a significantly increased risk of cardiovascular disease and much effort has been expended to elicit the underlying mechanisms. Various studies have proposed that excessive or deficient physiological effects mediated by leptin make an important contribution, yet many paradoxical observations often preclude a clear definition of the role of leptin. This review article will briefly discuss principal and most recent evidence on direct and indirect regulation of the cardiovascular system by leptin, focusing on cardiac structural and functional as well as vascular effects.