Hyperketonemia increases tumor necrosis factor-alpha secretion in cultured U937 monocytes and Type 1 diabetic patients and is apparently mediated by oxidative stress and cAMP deficiency

Underlying mechanisms of ketotherapy in heart failure: current evidence for clinical implementations

Heart failure (HF) is a life-threatening cardiac syndrome characterized by high morbidity and mortality, but current anti-heart failure therapies have limited efficacy, necessitating the urgent development of new treatment drugs. Exogenous ketone supplementation helps prevent heart failure development in HF models, but therapeutic ketosis in failing hearts has not been systematically elucidated, limiting the use of ketones to treat HF. Here, we summarize current evidence supporting ketotherapy in HF, emphasizing ketone metabolism in the failing heart, metabolic and non-metabolic therapeutic effects, and mechanisms of ketotherapy in HF, involving the dynamics within the mitochondria. We also discuss clinical strategies for therapeutic ketosis, aiming to deepen the understanding of the characteristics of ketone metabolism, including mitochondrial involvement, and its clinical therapeutic potential in HF.

Macrophage energy metabolism in cardiometabolic disease

In a rapidly expanding body of literature, the major role of energy metabolism in determining the response and polarization status of macrophages has been examined, and it is currently a very active area of research. The metabolic flux through different metabolic pathways in the macrophage is interconnected and complex and could influence the polarization of macrophages. Earlier studies suggested glucose flux through cytosolic glycolysis is a prerequisite to trigger the pro-inflammatory phenotypes of macrophages while proposing that fatty acid oxidation is essential to support anti-inflammatory responses by macrophages. However, recent studies have shown that this understanding is oversimplified and that the metabolic control of macrophage polarization is highly complex and not fully defined yet. In this review, we systematically reviewed and summarized the literature regarding the role of energy metabolism in controlling macrophage activity and how that might be altered in cardiometabolic diseases, namely heart failure, obesity, and diabetes. We critically appraised the experimental studies and methodologies in the published studies. We also highlighted the challenging concepts in macrophage metabolism and identified several research questions yet to be addressed in future investigations.

Metabolic flux in macrophages in obesity and type-2 diabetes

Recent literature extensively investigates the crucial role of energy metabolism in determining the inflammatory response and polarization status of macrophages. This rapidly expanding area of research highlights the importance of understanding the link between energy metabolism and macrophage function. The metabolic pathways in macrophages are intricate and interdependent, and they can affect the polarization of macrophages. Previous studies suggested that glucose flux through cytosolic glycolysis is necessary to trigger pro-inflammatory phenotypes of macrophages, and fatty acid oxidation is crucial to support anti-inflammatory responses. However, recent studies demonstrated that this understanding is oversimplified and that the metabolic control of macrophage polarization is highly complex and not fully understood yet. How the metabolic flux through different metabolic pathways (glycolysis, glucose oxidation, fatty acid oxidation, ketone oxidation, and amino acid oxidation) is altered by obesity- and type 2 diabetes (T2D)-associated insulin resistance is also not fully defined. This mini-review focuses on the impact of insulin resistance in obesity and T2D on the metabolic flux through the main metabolic pathways in macrophages, which might be linked to changes in their inflammatory responses. We closely evaluated the experimental studies and methodologies used in the published research and highlighted priority research areas for future investigations.

Ketone Bodies after Cardiac Arrest: A Narrative Review and the Rationale for Use

Cardiac arrest survivors suffer the repercussions of anoxic brain injury, a critical factor influencing long-term prognosis. This injury is characterised by profound and enduring metabolic impairment. Ketone bodies, an alternative energetic resource in physiological states such as exercise, fasting, and extended starvation, are avidly taken up and used by the brain. Both the ketogenic diet and exogenous ketone supplementation have been associated with neuroprotective effects across a spectrum of conditions. These include refractory epilepsy, neurodegenerative disorders, cognitive impairment, focal cerebral ischemia, and traumatic brain injuries. Beyond this, ketone bodies possess a plethora of attributes that appear to be particularly favourable after cardiac arrest. These encompass anti-inflammatory effects, the attenuation of oxidative stress, the improvement of mitochondrial function, a glucose-sparing effect, and the enhancement of cardiac function. The aim of this manuscript is to appraise pertinent scientific literature on the topic through a narrative review. We aim to encapsulate the existing evidence and underscore the potential therapeutic value of ketone bodies in the context of cardiac arrest to provide a rationale for their use in forthcoming translational research efforts.

Emerging Pathophysiological Roles of Ketone Bodies

The discovery of insulin approximately a century ago greatly improved the management of diabetes, including many of its life-threatening acute complications like ketoacidosis. This breakthrough saved many lives and extended the healthy lifespan of many patients with diabetes. However, there is still a negative perception of ketone bodies stemming from ketoacidosis. Originally, ketone bodies were thought of as a vital source of energy during fasting and exercise. Furthermore, in recent years, research on calorie restriction and its potential impact on extending healthy lifespans, as well as studies on ketone bodies, have gradually led to a reevaluation of the significance of ketone bodies in promoting longevity. Thus, in this review, we discuss the emerging and hidden roles of ketone bodies in various organs, including the heart, kidneys, skeletal muscles, and brain, as well as their potential impact on malignancies and lifespan.

Ketogenic diet: a potential adjunctive treatment for substance use disorders

Substance use disorders (SUD) can lead to serious health problems, and there is a great interest in developing new treatment methods to alleviate the impact of substance abuse. In recent years, the ketogenic diet (KD) has shown therapeutic benefits as a dietary therapy in a variety of neurological disorders. Recent studies suggest that KD can compensate for the glucose metabolism disorders caused by alcohol use disorder by increasing ketone metabolism, thereby reducing withdrawal symptoms and indicating the therapeutic potential of KD in SUD. Additionally, SUD often accompanies increased sugar intake, involving neural circuits and altered neuroplasticity similar to substance addiction, which may induce cross-sensitization and increased use of other abused substances. Reducing carbohydrate intake through KD may have a positive effect on this. Finally, SUD is often associated with mitochondrial damage, oxidative stress, inflammation, glia dysfunction, and gut microbial disorders, while KD may potentially reverse these abnormalities and serve a therapeutic role. Although there is much indirect evidence that KD has a positive effect on SUD, the small number of relevant studies and the fact that KD leads to side effects such as metabolic abnormalities, increased risk of malnutrition and gastrointestinal symptoms have led to the limitation of KD in the treatment of SUD. Here, we described the organismal disorders caused by SUD and the possible positive effects of KD, aiming to provide potential therapeutic directions for SUD.

Cardiac metabolism in HFpEF: from fuel to signalling

Heart failure (HF) is marked by distinctive changes in myocardial uptake and utilization of energy substrates. Among the different types of HF, HF with preserved ejection fraction (HFpEF) is a highly prevalent, complex, and heterogeneous condition for which metabolic derangements seem to dictate disease progression. Changes in intermediate metabolism in cardiometabolic HFpEF-among the most prevalent forms of HFpEF-have a large impact both on energy provision and on a number of signalling pathways in the heart. This dual, metabolic vs. signalling, role is played in particular by long-chain fatty acids (LCFAs) and short-chain carbon sources [namely, short-chain fatty acids (SCFAs) and ketone bodies (KBs)]. LCFAs are key fuels for the heart, but their excess can be harmful, as in the case of toxic accumulation of lipid by-products (i.e. lipotoxicity). SCFAs and KBs have been proposed as a potential major, alternative source of energy in HFpEF. At the same time, both LCFAs and short-chain carbon sources are substrate for protein post-translational modifications and other forms of direct and indirect signalling of pivotal importance in HFpEF pathogenesis. An in-depth molecular understanding of the biological functions of energy substrates and their signalling role will be instrumental in the development of novel therapeutic approaches to HFpEF. Here, we summarize the current evidence on changes in energy metabolism in HFpEF, discuss the signalling role of intermediate metabolites through, at least in part, their fate as substrates for post-translational modifications, and highlight clinical and translational challenges around metabolic therapy in HFpEF.

Ketogenic Diet for Neonatal Hypoxic-Ischemic Encephalopathy

The prevalence of neonatal hypoxic-ischemic encephalopathy (HIE), a devastating neurological injury, is increasing; thus, effective treatments and preventions are urgently needed. The underlying pathology of HIE remains unclear; recent research has focused on elucidating key features of the disease. A variety of diseases can be alleviated by consuming a ketogenic diet (KD) despite differences in pathogenesis and features, given the common mechanisms of KD-induced effects. Dietary modification is the most translatable, cost-efficient, and safest approach to treat acute or chronic neurological disorders and reduces reliance on pharmaceutical treatments. Evidence suggests that the KD can exert beneficial effects in animal models and in humans with brain injuries. The efficacy of the KD in preventing neuronal damage, motor alterations, and cognitive decline varies. Moreover, the KD may provide an alternative source of energy, enhance mitochondrial function, and reduce the expression of inflammatory and apoptotic mediators. Thus, this diet has attracted interest as a potential therapy for HIE. This review examined the role of the KD in HIE treatment and described the mechanisms by which ketone bodies (KBs) exert effects under pathological conditions and protect against brain damage; the evidence supports the implementation of dietary interventions as a therapeutic strategy for HIE. Future research should aim to elucidate the underlying mechanisms of the KD in patients with HIE and determine whether the effect of the KD on clinical outcomes can be reproduced in humans.

Molecular Mechanisms for Ketone Body Metabolism, Signaling Functions, and Therapeutic Potential in Cancer

The ketone bodies (KBs) β-hydroxybutyrate and acetoacetate are important alternative energy sources for glucose during nutrient deprivation. KBs synthesized by hepatic ketogenesis are catabolized to acetyl-CoA through ketolysis in extrahepatic tissues, followed by the tricarboxylic acid cycle and electron transport chain for ATP production. Ketogenesis and ketolysis are regulated by the key rate-limiting enzymes, 3-hydroxy-3-methylglutaryl-CoA synthase 2 and succinyl-CoA:3-oxoacid-CoA transferase, respectively. KBs participate in various cellular processes as signaling molecules. KBs bind to G protein-coupled receptors. The most abundant KB, β-hydroxybutyrate, regulates gene expression and other cellular functions by inducing post-translational modifications. KBs protect tissues by regulating inflammation and oxidative stress. Recently, interest in KBs has been increasing due to their potential for treatment of various diseases such as neurological and cardiovascular diseases and cancer. Cancer cells reprogram their metabolism to maintain rapid cell growth and proliferation. Dysregulation of KB metabolism also plays a role in tumorigenesis in various types of cancer. Targeting metabolic changes through dietary interventions, including fasting and ketogenic diets, has shown beneficial effects in cancer therapy. Here, we review current knowledge of the molecular mechanisms involved in the regulation of KB metabolism and cellular signaling functions, and the therapeutic potential of KBs and ketogenic diets in cancer.

Association of Serum β-Hydroxybutyrate and Coronary Artery Disease in an Urban Chinese Population

Ketone bodies, including β-hydroxybutyrate (BHB), acetoacetate (AA), and acetone, can substitute and alternate with glucose under conditions of fuel/food deficiency. Ketone-body metabolism is increased in a myriad of tissue-metabolism disorders. Perturbations in metabolism are major contributors to coronary artery disease (CAD). We investigated the association of BHB with CAD. A total of 2,970 people of Chinese Han ethnicity were enrolled. The Gensini score was calculated for all patients who had positive findings. The serum level of BHB and other laboratory parameters were measured. The association of serum levels of metabolites with traditionally risk factors and CAD severity was analyzed. The BHB was found to be associated with some traditional risk factors of CAD and CAD severity, as determined by the Gensini score or the number of diseased regions. Moreover, BHB was associated with the T3/T1 tertiles of the Gensini score after the adjustment for traditional risk factors by multivariable logistic regression analysis. The association of BHB with CAD severity was more obvious in women. Taken together, these data suggest that the circulating BHB level is independently associated with CAD severity, and that this association is more pronounced in women.

Neuroprotection by the Ketogenic Diet: Evidence and Controversies

The ketogenic diet (KD) is a high-fat low-carbohydrate diet that has been used for decades as a non-pharmacologic approach to treat metabolic disorders and refractory pediatric epilepsy. In recent years, enthusiasm for the KD has increased in the scientific community due to evidence that the diet reduces pathology and improves various outcome measures in animal models of neurodegenerative disorders, including multiple sclerosis, stroke, glaucoma, spinal cord injury, retinal degenerations, Parkinson's disease and Alzheimer's disease. Clinical trials also suggest that the KD improved quality of life in patients with multiple sclerosis and Alzheimer's disease. Furthermore, the major ketone bodies BHB and ACA have potential neuroprotective properties and are now known to have direct effects on specific inflammatory proteins, transcription factors, reactive oxygen species, mitochondria, epigenetic modifications and the composition of the gut microbiome. Neuroprotective benefits of the KD are likely due to a combination of these cellular processes and other potential mechanisms that are yet to be confirmed experimentally. This review provides a comprehensive summary of current evidence for the effectiveness of the KD in humans and preclinical models of various neurological disorders, describes molecular mechanisms that may contribute to its beneficial effects, and highlights key controversies and current gaps in knowledge.

Acetoacetate protects macrophages from lactic acidosis-induced mitochondrial dysfunction by metabolic reprograming

Lactic acidosis, the extracellular accumulation of lactate and protons, is a consequence of increased glycolysis triggered by insufficient oxygen supply to tissues. Macrophages are able to differentiate from monocytes under such acidotic conditions, and remain active in order to resolve the underlying injury. Here we show that, in lactic acidosis, human monocytes differentiating into macrophages are characterized by depolarized mitochondria, transient reduction of mitochondrial mass due to mitophagy, and a significant decrease in nutrient absorption. These metabolic changes, resembling pseudostarvation, result from the low extracellular pH rather than from the lactosis component, and render these cells dependent on autophagy for survival. Meanwhile, acetoacetate, a natural metabolite produced by the liver, is utilized by monocytes/macrophages as an alternative fuel to mitigate lactic acidosis-induced pseudostarvation, as evidenced by retained mitochondrial integrity and function, retained nutrient uptake, and survival without the need of autophagy. Our results thus show that acetoacetate may increase tissue tolerance to sustained lactic acidosis.

Lactic acidosis is a metabolic state that occurs in injured tissues. Here the authors show that macrophages, in order to remain functional in acidosis, reduce their mitochondrial mass by mitophagy and rely on autophagy for survival, with mitochondrial integrity retained using acetoacetate as alternative fuel.

Sult2b1 deficiency exacerbates ischemic stroke by promoting pro-inflammatory macrophage polarization in mice

Rationale: Stroke is a leading causes of human death worldwide. Ischemic damage induces the sterile neuroinflammation, which directly determines the recovery of patients. Lipids, a major component of the brain, significantly altered after stroke. Cholesterol sulfate, a naturally occurring analog of cholesterol, can directly regulate immune cell activation, indicating the possible involvement of cholesterol metabolites in neuroinflammation. Sulfotransferase family 2b member 1 (Sult2b1) is the key enzyme that catalyzes the synthesis of cholesterol sulfate. This study aimed to investigate the function of Sult2b1 and cholesterol sulfate in the neuroinflammation after ischemic stroke.

Methods and Results: Sult2b1^-/- and wild-type mice were subjected to transient middle cerebral artery occlusion. Our data showed that Sult2b1^-/- mice had larger infarction and worse neurological scores. To determine whether immune cells were involved in the worsening stroke outcome in Sult2b1^-/- mice, bone marrow transplantation, immune cell depletion, and adoptive monocyte transfer were performed. Combined with CyTOF and immunofluorescence techniques, we demonstrated that after stroke, the peripheral monocyte-derived macrophages were the dominant cell type promoting the pro-inflammatory status in Sult2b1^-/-mice. Using primary bone marrow-derived macrophages, we showed that cholesterol sulfate could attenuate the pro-inflammatory polarization of macrophages under both normal and oxygen-glucose deprivation conditions by regulating the levels of nicotinamide adenine dinucleotide phosphate (NADPH), reactive oxygen species (ROS), and activating the AMP-activated protein kinase (AMPK) - cAMP responsive element-binding protein (CREB) signaling pathway.

Conclusions:Sult2b1^-/- promoted the polarization of macrophages into pro-inflammatory status. This trend could be attenuated by adding cholesterol sulfate, which promotes the polarization of macrophages into anti-inflammatory status by metabolic regulation. In this study, we established an inflammation-metabolism axis during the macrophage polarization after ischemic stroke.

Urinary metabolites of type 2 diabetes rats fed with palm oil-enriched high fat diet

High fat diet (HFD) is one of the risk factors of obesity and diabetes. Recommended diet regimen for diabetes is difficult to abide by especially for HFD as it adds flavour to the taste buds. In this study, palm oil-enriched HFD and normal diet were fed to nicotinamide-induced type 2 diabetes rats, respectively for six weeks. Additionally, metformin, a common drug used to treat diabetes was given to rats under treatment groups. We evaluated the change of urinary metabolites of diabetes rats fed with palm oil-enriched HFD, and also after metformin treatment. Rats were divided into six-groups with different feeding diets, disease condition and with or without metformin treatment. Rats’ urine were collected at the end of six weeks feeding program and subjected to 1H-NMR and multivariate data analysis to evaluate their metabolite profiles. At the early phase of diabetes, metabolites changes in diabetic rats were associated with the disease itself. Our data showed that continuous consumption of HFD altered various metabolic pathways of diabetic rats and caused detrimental effects to the rats. On the other hand, metformin treatment combined with normal diet lessened the physiological impacts caused by diabetes condition.

Hesperetin suppresses LPS/high glucose-induced inflammatory responses via TLR/MyD88/NF-κB signaling pathways in THP-1 cells

BACKGROUND/OBJECTIVES

Unregulated inflammatory responses caused by hyperglycemia may induce diabetes complications. Hesperetin, a bioflavonoid, is a glycoside in citrus fruits and is known to have antioxidant and anticarcinogenic properties. However, the effect of inflammation on the diabetic environment has not been reported to date. In this study, we investigated the effect of hesperetin on proinflammatory cytokine secretion and its underlying mechanistic regulation in THP-1 macrophages with co-treatment LPS and hyperglycemic conditions.

MATERIALS/METHODS

THP-1 cells differentiated by PMA (1 μM) were cultured for 48 h in the presence or absence of hesperetin under normoglycemic (5.5 mM/L glucose) or hyperglycemic (25 mM/L glucose) conditions and then treated with LPS (100 ng/mL) for 6 h before harvesting. Inflammation-related proteins and mRNA levels were evaluated by enzyme-linked immunosorbent assay, western blot, and quantitative polymerase chain reaction analyses.

RESULTS

Hesperetin (0-100 μM, 48 h) treatment did not affect cell viability. The tumor necrosis factor-α and interleukin-6 levels increased in cells co-treated with LPS under hyperglycemic conditions compared to normoglycemic conditions, and these increases were decreased by hesperetin treatment. The TLR2/4 and MyD88 activity levels increased in cells co-treated with LPS under hyperglycemic conditions compared to normoglycemic conditions; however, hesperetin treatment inhibited the TLR2/4 and MyD88 activity increases. In addition, nuclear factor-κB (NF-κB) and Acetyl-NF-κB levels increased in response to treatment with LPS under hyperglycemic conditions compared to normoglycemic conditions, but those levels were decreased when treated with hesperetin. SIRT3 and SIRT6 expressions were increased by hesperetin treatment.

CONCLUSIONS

Our results suggest that hesperetin may be a potential agent for suppressing inflammation in diabetes.

SGLT2 Inhibition by Dapagliflozin Attenuates Diabetic Ketoacidosis in Mice with Type-1 Diabetes

BACKGROUND

SGLT2 inhibitors increase plasma ketone concentrations. It has been suggested that insulinopenia, along with an increase in the counter-regulatory hormones epinephrine, corticosterone, glucagon and growth hormone, can induce ketoacidosis, especially in type-1 diabetes (T1DM). Dehydration precipitates SGLT2 inhibitor-induced ketoacidosis in type-2 diabetes. We studied the effects of dapagliflozin and water deprivation on the development of ketoacidosis and the associated signaling pathways in T1DM mice.

METHODS

C57BL/6 mice were fed a high-fat diet. After 7 days, some mice received intraperitoneal injection of streptozocin + alloxan (STZ/ALX). The treatment groups were control + water at lib; control + dapagloflozin + water at lib; control + dapagloflozin + water deprivation; STZ/ALX + water at lib; STZ/ALX + water deprivation; STZ/ALX + dapagloflozin + water at lib; STZ/ALX + dapagloflozin + water deprivation. Dapagliflozin was given for 7 days. In the morning of day 18, food was removed, and water was removed in the water deprivation groups. ELISA, rt-PCR, and immunoblotting were used to assess blood, heart, liver, white and brown adipose tissues.

RESULTS

The T1DM mice had ketoacidosis even without water deprivation. Water deprivation increased plasma levels of β-hydroxybutyrate, acetoacetate, corticosterone, and epinephrine and reduced the levels of adiponectin in T1DM mice. Interleukin (IL) 1β, IL-6, IL-8, and TNFα were also increased in the T1DM mice with water deprivation. Dapagliflozin attenuated the changes in the T1DM mice without and with water deprivation. Likewise, water deprivation increased the activation of the inflammasome in the heart, liver, and white fat of the T1DM mice and dapagliflozin attenuated these changes. Dapagliflozin reduced the mRNA levels of glucagon receptors in the liver and the increase in GPR109a in white and brown fat. In the liver, dapagliflozin increased AMPK phosphorylation, and attenuated the phosphorylation of TBK1 and the activation of NFκB.

CONCLUSIONS

Dapagliflozin reduced ketone body levels and attenuated the activation of NFκB and the activation of the inflammasome in T1DM mice with ketoacidosis.

Immunoglobulins reduced oxidative stress in human microglial cells induced by high dose of acetoacetate

Diabetic ketoacidosis (DKA) has been associated with cognitive impairment and structural alterations in the brain. There is increased evidence supporting the role of neuroinflammation in causing these alterations. In the present study, using human microglial cell line (CHME-5), we aimed to investigate the effect of immunoglobulins (IG) on survival, activation, reactive oxygen species (ROS) and cytokine production of microglia exposed to ketone bodies. We demonstrated that high and low dose of ketone bodies induced a significant increase in ROS within 1 h after exposure to CHME-5 cells with upregulation in mitochondrial superoxide level 5 min after exposure suggestive of early and selective impairment of mitochondrial function. A significant and delayed increase of apoptosis of CHME-5 cells was observed 4 days after ketone bodies exposure. Cytokine expression reached a peak within 1 h and persisted for 3 days after exposure to ketone bodies. IG significantly reduced ROS and transiently suppressed cytokine expression of CHME-5 cells after exposure to ketone bodies. However, no effect of IG on apoptosis was observed. Overall, these results supported that ketone bodies induced microglia activation with early and selective impairment of mitochondrial function, increased cytokines expression and delayed increase in apoptosis. IG suppressed microglia activation and transiently inhibited cytokines expression without affecting apoptosis. These results warrant further experimental work on the role of microglia and potential benefit of IG in brain structural changes induced by DKA.

Branched chain amino acids and carbohydrate restriction exacerbate ketogenesis and hepatic mitochondrial oxidative dysfunction during NAFLD

Mitochondrial adaptation during non-alcoholic fatty liver disease (NAFLD) include remodeling of ketogenic flux and sustained tricarboxylic acid (TCA) cycle activity, which are concurrent to onset of oxidative stress. Over 70% of obese humans have NAFLD and ketogenic diets are common weight loss strategies. However, the effectiveness of ketogenic diets toward alleviating NAFLD remains unclear. We hypothesized that chronic ketogenesis will worsen metabolic dysfunction and oxidative stress during NAFLD. Mice (C57BL/6) were kept (for 16-wks) on either a low-fat, high-fat, or high-fat diet supplemented with 1.5X branched chain amino acids (BCAAs) by replacing carbohydrate calories (ketogenic). The ketogenic diet induced hepatic lipid oxidation and ketogenesis, and produced multifaceted changes in flux through the individual steps of the TCA cycle. Higher rates of hepatic oxidative fluxes fueled by the ketogenic diet paralleled lower rates of de novo lipogenesis. Interestingly, this metabolic remodeling did not improve insulin resistance, but induced fibrogenic genes and inflammation in the liver. Under a chronic "ketogenic environment," the hepatocyte diverted more acetyl-CoA away from lipogenesis toward ketogenesis and TCA cycle, a milieu which can hasten oxidative stress and inflammation. In summary, chronic exposure to ketogenic environment during obesity and NAFLD has the potential to aggravate hepatic mitochondrial dysfunction.

Ketone metabolism in the failing heart

The high energy demands of the heart are met primarily by the mitochondrial oxidation of fatty acids and glucose. However, in heart failure there is a decrease in cardiac mitochondrial oxidative metabolism and glucose oxidation that can lead to an energy starved heart. Ketone bodies are readily oxidized by the heart, and can provide an additional source of energy for the failing heart. Ketone oxidation is increased in the failing heart, which may be an adaptive response to lessen the severity of heart failure. While ketone have been widely touted as a "thrifty fuel", increasing ketone oxidation in the heart does not increase cardiac efficiency (cardiac work/oxygen consumed), but rather does provide an additional fuel source for the failing heart. Increasing ketone supply to the heart and increasing mitochondrial ketone oxidation increases mitochondrial tricarboxylic acid cycle activity. In support of this, increasing circulating ketone by iv infusion of ketone bodies acutely improves heart function in heart failure patients. Chronically, treatment with sodium glucose co-transporter 2 inhibitors, which decreases the severity of heart failure, also increases ketone body supply to the heart. While ketogenic diets increase circulating ketone levels, minimal benefit on cardiac function in heart failure has been observed, possibly due to the fact that these dietary regimens also markedly increase circulating fatty acids. Recent studies, however, have suggested that administration of ketone ester cocktails may improve cardiac function in heart failure. Combined, emerging data suggests that increasing cardiac ketone oxidation may be a therapeutic strategy to treat heart failure.

Implications of Altered Ketone Metabolism and Therapeutic Ketosis in Heart Failure

Despite existing therapy, patients with heart failure (HF) experience substantial morbidity and mortality, highlighting the urgent need to identify novel pathophysiological mechanisms and therapies, as well. Traditional models for pharmacological intervention have targeted neurohormonal axes and hemodynamic disturbances in HF. However, several studies have now highlighted the potential for ketone metabolic modulation as a promising treatment paradigm. During the pathophysiological progression of HF, the failing heart reduces fatty acid and glucose oxidation, with associated increases in ketone metabolism. Recent studies indicate that enhanced myocardial ketone use is adaptive in HF, and limited data demonstrate beneficial effects of exogenous ketone therapy in studies of animal models and humans with HF. This review will summarize current evidence supporting a salutary role for ketones in HF including (1) normal myocardial ketone use, (2) alterations in ketone metabolism in the failing heart, (3) effects of therapeutic ketosis in animals and humans with HF, and (4) the potential significance of ketosis associated with sodium-glucose cotransporter 2 inhibitors. Although a number of important questions remain regarding the use of therapeutic ketosis and mechanism of action in HF, current evidence suggests potential benefit, in particular, in HF with reduced ejection fraction, with theoretical rationale for its use in HF with preserved ejection fraction. Although it is early in its study and development, therapeutic ketosis across the spectrum of HF holds significant promise.

An overlooked danger of ketogenic diets: Making the case that ketone bodies induce vascular damage by the same mechanisms as glucose

Intense debate surrounds the use of low-carbohydrate, ketogenic diets for the promotion of weight loss and avoidance of cardiovascular disease. The rationale behind these diets is that they promote fat oxidation and minimize the addition of glucose to proteins in the formation of adducts that trigger inflammation. Although nutritional ketosis is widely assumed to be a safe metabolic condition, proper consideration has not been given to the fact that ketones are reactive toward proteins through the same mechanisms as glucose. Here, the case is made that ketone bodies are more potent than glucose in bringing about the protein modifications to which the harmful effects of glucose have been attributed. It is suggested, therefore, that attempts to minimize such protein modifications through nutritional ketosis are futile and may lead to adverse health outcomes.

Melanoma-Time to fast or time to feast? An interplay between PPARs, metabolism and immunity

Development and progression of melanoma can be accelerated by intensification of particular metabolic pathways, such as aerobic glycolysis and avid amino acid catabolism, and is accompanied by aberrant immune responses within the tumor microenvironment. Contrary to other cancer types, melanoma reveals some unique tissue-specific features, such as melanogenesis, which is intertwined with metabolism. Nuclear peroxisome proliferator-activated receptors (PPARs) take part in regulation of systemic and cellular metabolism, inflammation and melanogenesis. They appear as a focal regulatory point for these three distinct processes by occupying the intersection among AMP-dependent protein kinase (AMPK), mammalian target of rapamycin (mTOR) and PPAR gamma coactivator 1-alpha (PGC-1α) signalling pathways. When deregulated, they may accelerate melanoma malignant growth. Presenting the contribution of PPARα and PPARγ in melanoma biology, we attempt to ask how two contrasting metabolic states: obesity and fasting, can change progression of the disease and possible outcome of the treatment. This short essay is aimed to provoke a discussion about some practical implications for melanoma prevention and treatment, especially: how metabolic manipulation may be exploited to overcome immunosuppression and support immune checkpoint blockade efficacy.

Ketone Bodies Promote Amyloid-β1-40 Clearance in a Human in Vitro Blood-Brain Barrier Model

Alzheimer's disease (AD) is characterized by the abnormal accumulation of amyloid-β (Aβ) peptides in the brain. The pathological process has not yet been clarified, although dysfunctional transport of Aβ across the blood-brain barrier (BBB) appears to be integral to disease development. At present, no effective therapeutic treatment against AD exists, and the adoption of a ketogenic diet (KD) or ketone body (KB) supplements have been investigated as potential new therapeutic approaches. Despite experimental evidence supporting the hypothesis that KBs reduce the Aβ load in the AD brain, little information is available about the effect of KBs on BBB and their effect on Aβ transport. Therefore, we used a human in vitro BBB model, brain-like endothelial cells (BLECs), to investigate the effect of KBs on the BBB and on Aβ transport. Our results show that KBs do not modify BBB integrity and do not cause toxicity to BLECs. Furthermore, the presence of KBs in the culture media was combined with higher MCT1 and GLUT1 protein levels in BLECs. In addition, KBs significantly enhanced the protein levels of LRP1, P-gp, and PICALM, described to be involved in Aβ clearance. Finally, the combined use of KBs promotes Aβ efflux across the BBB. Inhibition experiments demonstrated the involvement of LRP1 and P-gp in the efflux. This work provides evidence that KBs promote Aβ clearance from the brain to blood in addition to exciting perspectives for studying the use of KBs in therapeutic approaches.

Ketone Bodies in Neurological Diseases: Focus on Neuroprotection and Underlying Mechanisms

There is growing evidence that ketone bodies, which are derived from fatty acid oxidation and usually produced in fasting state or on high-fat diets have broad neuroprotective effects. Although the mechanisms underlying the neuroprotective effects of ketone bodies have not yet been fully elucidated, studies in recent years provided abundant shreds of evidence that ketone bodies exert neuroprotective effects through possible mechanisms of anti-oxidative stress, maintaining energy supply, modulating the activity of deacetylation and inflammatory responses. Based on the neuroprotective effects, the ketogenic diet has been used in the treatment of several neurological diseases such as refractory epilepsy, Parkinson's disease, Alzheimer's disease, and traumatic brain injury. The ketogenic diet has great potential clinically, which should be further explored in future studies. It is necessary to specify the roles of components in ketone bodies and their therapeutic targets and related pathways to optimize the strategy and efficacy of ketogenic diet therapy in the future.

Hepatocyte-Macrophage Acetoacetate Shuttle Protects against Tissue Fibrosis

Metabolic plasticity has been linked to polarized macrophage function, but mechanisms connecting specific fuels to tissue macrophage function remain unresolved. Here we apply a stable isotope tracing, mass spectrometry-based untargeted metabolomics approach to reveal the metabolome penetrated by hepatocyte-derived glucose and ketone bodies. In both classically and alternatively polarized macrophages, [¹³C]acetoacetate (AcAc) labeled ∼200 chemical features, but its reduced form D-[¹³C]β-hydroxybutyrate (D-βOHB) labeled almost none. [¹³C]glucose labeled ∼500 features, and while unlabeled AcAc competed with only ∼15% of them, the vast majority required the mitochondrial enzyme succinyl-coenzyme A-oxoacid transferase (SCOT). AcAc carbon labeled metabolites within the cytoplasmic glycosaminoglycan pathway, which regulates tissue fibrogenesis. Accordingly, livers of mice lacking SCOT in macrophages were predisposed to accelerated fibrogenesis. Exogenous AcAc, but not D-βOHB, ameliorated diet-induced hepatic fibrosis. These data support a hepatocyte-macrophage ketone shuttle that segregates AcAc from D-βOHB, coordinating the fibrogenic response to hepatic injury via mitochondrial metabolism in tissue macrophages.

The Significance of an Increased Beta-Hydroxybutyrate at Presentation to the Emergency Department in Patients with Diabetes in the Absence of a Hyperglycemic Emergency

The significance of hyperketonemia in adults with diabetes presenting to the emergency department with acute illness, not due to a diabetic hyperglycemic emergency, has not been well characterized. Adult patients with diabetes presenting to the emergency department who had venous blood gas and beta-hydroxybutyrate levels measured whilst in the emergency department were retrospectively evaluated for the relationship between BHB and clinical outcomes. Over 6 months, 404 patients with diabetes had at least one beta-hydroxybutyrate level measured in the emergency department. There were 23 admissions for diabetic ketoacidosis (DKA) or hyperosmolar state. Of the remainder, 58 patients had a beta-hydroxybutyrate ≥ 1 mmol/L; this group had a higher glucose at presentation (19.0 (8.8) versus 10.4 (9.9) mmol/L), higher HbA1c (8.8 (5.4) versus 8.0 (3.3)%), lower bicarbonate (22.6 (6.2) versus 24.8 (4.7) mmol/L), and higher anion gap (14.8 (6.1) versus 12.6 (4.2)) than had those with BHB < 1 mmol/L. There was no association between the presence of ketosis and the length of stay (4.2 (7.3) versus (3.0) (7.2) days). Acute illness in those with diabetes associated with ketosis in the absence of DKA is associated with worse glycaemic control than in those without ketosis. Ketosis may represent an intermediate state of metabolic dysregulation rather than being associated with a more severe acute illness, as suggested by no relationship between BHB and length of stay.

P66Shc expression in diabetic rat retina

Background

P66Shc is partially localised within the mitochondrial fraction. It is primarily related to the generation of mitochondrial reactive oxygen species and apoptosis. Based on previous studies, we hypothesize that in the retina, p66Shc may exist and affect the development of diabetic retinopathy. The purpose of this study was to investigate p66Shc expression in retinal in streptozotocin-induced diabetic (SD) rats, which may provide a pathway to study the pathogenesis of diabetic retinopathy.

Methods

Reverse transcription-polymerase chain reaction (RT-PCR) and western blot were used to detect retinal p66Shc mRNA and protein expression in SD rats, respectively. Immunohistochemical staining was applied to detect the location of rat retinal p66Shc expression. TUNEL assay was applied to detect the number of apoptotic cells.

Results

P66Shc expression was found in the retina of normal and diabetic rats, and the level of mRNA and protein expression increased with the progression of diabetes mellitus (DM). P66Shc expression was mainly located in the retinal ganglion cell layer and inner nuclear layer. Compared with the normal group, retinal cell tissue apoptosis rate in the D12w group was significantly increased.

Conclusion

Rat retinal p66Shc expression was mainly in the ganglion cell layer and inner nuclear layer. As the degree of DM progressed, p66Shc expression gradually increased, and the number of apoptotic cells also increased.

Evaluation of 4-methyl-2-[(2-methylbenzyl) amino]-1,3-thiazole-5-carboxylic acid against hyperglycemia, insulin sensitivity, and oxidative stress-induced inflammatory responses and β-cell damage in the pancreas of streptozotocin-induced diabetic rats

4-Methyl-2-[(2-methylbenzyl) amino]-1,3-thiazole-5-carboxylic acid (bioactive compound (BAC)), a novel thiazole derivative, is a xanthine oxidase inhibitor and free radical scavenging agent. Effects of BAC on hyperglycemia, insulin sensitivity, oxidative stress, and inflammatory mediators were evaluated in streptozotocin (STZ)-induced neonatal models of non-insulin-dependent diabetes mellitus (NIDDM) rats where NIDDM was induced in neonatal pups with single intraperitoneal injection of STZ (100 mg/kg). The effect of BAC (10 and 20 mg/kg, p.o.) for 3 weeks was evaluated by the determination of blood glucose, oral glucose tolerance test (OGTT), HbA1c level, insulin level, insulin sensitivity, and insulin resistance (IR). Furthermore, inflammatory mediators (tumor necrosis factor-alpha and interleukin-6) and oxidative stress were estimated in serum and pancreatic tissue, respectively. Significant alteration in the level of blood glucose, OGTT, HbA1c, insulin level, insulin sensitivity, in addition variation in the antioxidant status and inflammatory mediators, and alteration in histoarchitecture of pancreatic tissue confirmed the potential of BAC in STZ-induced neonatal models of NIDDM rats. Pretreatment with BAC restored the level of glucose by decreasing the IR and increasing the insulin sensitivity. Furthermore, BAC balanced the antioxidant status and preserved the inflammatory mediators. Histological studies of pancreatic tissues showed normal architecture after BAC administration to diabetic rats. Altogether, our results suggest that BAC successfully reduces the blood glucose level and possesses antioxidant as well as anti-inflammatory activities. This leads to decreased histological damage in diabetic pancreatic tissues, suggesting the possibility of future diabetes treatments.

D-β-Hydroxybutyrate and melatonin for treatment of porcine hemorrhagic shock and injury: a melatonin dose-ranging study

OBJECTIVE

Treatment with a combination of D-β-hydroxybutyrate (BHB) and melatonin (M) improves survival in hemorrhagic shock models. Our objective was to find the most effective melatonin concentration in combination with 4 molar BHB (4 M BHB). Survival and markers of organ injury were analyzed in pigs exposed to pulmonary contusion, liver crush injury, and hemorrhagic shock and treated with lactated Ringer's solution; 4 M BHB/43 mM M; 4 M BHB/20 mM M; 4 M BHB/10 mM M; 4 M BHB/4.3 mM M; or 4 M BHB/0.43 mM M. This work is an extension of a previously published research study.

RESULTS

Survival was highest in pigs receiving 4 M BHB/43 mM M (13/14), followed by lactated Ringer's solution (11/16) and BHB/M with decreased melatonin concentrations (4 M BHB/20 mM M 3/6, 4 M BHB/10 mM M 2/6, 4 M BHB/4.3 mM M 3/6, 4 M BHB/0.43 mM M 1/6, p = 0.011). High mortality was associated with increases in serum lactate, higher liver and muscle injury markers and decreases in PaO2:FiO2 ratios. Our study indicates that treatment with 4 M BHB and melatonin concentrations below 43 mM lack the survival benefit observed from 4 M BHB/43 mM melatonin in pigs experiencing hemorrhagic shock and polytrauma.

Comparative study of cardio-protective effects of zinc oxide nanoparticles and zinc sulfate in streptozotocin-induced diabetic rats

The cardio-protective effects of zinc oxide nanoparticles (Zn NPs) against diabetes-induced cardiopathy were evaluated and compared with zinc sulfate (ZnSO₄). A total of 120 Wistar rats were randomly categorized as healthy and diabetic groups. Then, the 2 groups were classified in 5 subgroups. The animals received oral supplementations containing different Zn NP (ie, doses of 1, 3, and 10mg/kg) and ZnSO₄ (30mg/kg) concentrations over 8 weeks. Blood and cardiac tissue samples were collected in the different time intervals and subjected to biochemical and histopathological analysis. Zn NPs showed dual effects, as its middle dose played protective role and recovered cardiac damages evidenced by significant reduction of serum cholesterol, HDL-cholesterol, lipoprotein (a), atherogenic index, TNF-α, cardiac MDA, B-type natriuretic peptide and caspase-3 activity. Apoptosis indices and histopathological features also were improved. However, the highest dose was found to be toxic and resulted in aggravation of the injuries. Another interesting finding is the ability of the higher doses of Zn-NPs (3 and 10mg/kg) to elevate cardiac zinc levels above the normal range in healthy animal. ZnSO₄ also helped to recuperation of the damages, but the middle dose of Zn NPs was more efficient as compared to ZnSO₄. Conclusively, Zn NPs have the potential for Zn delivery in diabetic patients.

Multi-dimensional Roles of Ketone Bodies in Fuel Metabolism, Signaling, and Therapeutics

Ketone body metabolism is a central node in physiological homeostasis. In this review, we discuss how ketones serve discrete fine-tuning metabolic roles that optimize organ and organism performance in varying nutrient states and protect from inflammation and injury in multiple organ systems. Traditionally viewed as metabolic substrates enlisted only in carbohydrate restriction, observations underscore the importance of ketone bodies as vital metabolic and signaling mediators when carbohydrates are abundant. Complementing a repertoire of known therapeutic options for diseases of the nervous system, prospective roles for ketone bodies in cancer have arisen, as have intriguing protective roles in heart and liver, opening therapeutic options in obesity-related and cardiovascular disease. Controversies in ketone metabolism and signaling are discussed to reconcile classical dogma with contemporary observations.

Hyperketonemia and ketosis increase the risk of complications in type 1 diabetes

Diets that boost ketone production are increasingly used for treating several neurological disorders. Elevation in ketones in most cases is considered favorable, as they provide energy and are efficient in fueling the body's energy needs. Despite all the benefits from ketones, the above normal elevation in the concentration of ketones in the circulation tend to illicit various pathological complications by activating injurious pathways leading to cellular damage. Recent literature demonstrates a plausible link between elevated levels of circulating ketones and oxidative stress, linking hyperketonemia to innumerable morbid conditions. Ketone bodies are produced by the oxidation of fatty acids in the liver as a source of alternative energy that generally occurs in glucose limiting conditions. Regulation of ketogenesis and ketolysis plays an important role in dictating ketone concentrations in the blood. Hyperketonemia is a condition with elevated blood levels of acetoacetate, 3-β-hydroxybutyrate, and acetone. Several physiological and pathological triggers, such as fasting, ketogenic diet, and diabetes cause an accumulation and elevation of circulating ketones. Complications of the brain, kidney, liver, and microvasculature were found to be elevated in diabetic patients who had elevated ketones compared to those diabetics with normal ketone levels. This review summarizes the mechanisms by which hyperketonemia and ketoacidosis cause an increase in redox imbalance and thereby increase the risk of morbidity and mortality in patients.

1,25(OH)2D3 inhibits oxidative stress and monocyte adhesion by mediating the upregulation of GCLC and GSH in endothelial cells treated with acetoacetate (ketosis)

BACKGROUND

There is a significantly higher incidence of cardiovascular disease (CVD) among type 1 diabetic (T1D) patients than among non-diabetic subjects. T1D is associated with hyperketonemia, a condition with elevated blood levels of ketones, in addition to hyperglycemia. The biochemical mechanism by which vitamin D (VD) may reduce the risk of CVD is not known. This study examines whether VD can be beneficial in reducing hyperketonemia (acetoacetate, AA) induced oxidative stress in endothelial cells.

METHODS

HUVEC were pretreated with 1,25(OH)2D3, and later exposed to the ketone body acetoacetate.

RESULTS

The increases in ROS production, ICAM-1 expression, MCP-1 secretion, and monocyte adhesion in HUVEC treated with AA were significantly reduced following treatment with 1,25(OH)2D3. Interestingly, an increase in glutathione (GSH) levels was also observed with 1,25(OH)2D3 in ketone treated cells. The effects of 1,25(OH)2D3 on GSH, ROS, and monocyte-endothelial adhesion were prevented in GCLC knockdown HUVEC. This suggests that 1,25(OH)2D3 inhibits ROS, MCP-1, ICAM-1, and adherence of monocytes mediated by the upregulation of GCLC and GSH.

CONCLUSION

This study provides evidence for the biochemical mechanism through which VD supplementation may reduce the excess monocyte adhesion to endothelium and inflammation associated with T1D.

Rehmannia glutinosa (Gaertn.) DC. polysaccharide ameliorates hyperglycemia, hyperlipemia and vascular inflammation in streptozotocin-induced diabetic mice

ETHNOPHARMACOLOGICAL RELEVANCE

Rehmannia glutinosa (Gaertn.) DC. (RG) has been widely used as traditional Chinese herbal medicine for treatment of diabetes and its complications. The polysaccharide fraction of RG has been proposed to possess hypoglycemic effect by intraperitoneal administration, however, the mechanisms responsible for the hypoglycemic effect of RG polysaccharide (RGP) remain poorly understood. Here we studied the anti-hyperglycemic and anti-hyperlipidemic effect of oral administration of a purified RGP and its underlying mechanisms in streptozotocin (STZ)-induced diabetic mice.

MATERIALS AND METHODS

The preliminary structure of RGP was determined by GC and FT-IR. Mice were injected with STZ to induce type 1 diabetes. RGP at doses of 20, 40 and 80 mg/kg/day was orally administered to mice for 4 weeks, and metformin was used as positive control. After 4 weeks, the blood biochemical parameters, the pancreatic insulin contents, in vitro insulin secretion, the hepatic glycogen contents and mRNA expression of phosphoenolpyruvate carboxyl kinase (PEPCK) were assayed.

RESULTS

RGP was composed of rhamnose, arabinose, mannose, glucose and galactose in the molar ratio of 1.00:1.26:0.73:16.45:30.40 with the average molecular weight of 63.5 kDa. RGP administration significantly decreased the blood levels of glucose, total cholesterol, triglycerides, low density lipoprotein-cholesterol, and increased the blood levels of high density lipoprotein-cholesterol and insulin in diabetic mice, concurrent with increases in body weights and pancreatic insulin contents. The in vitro study revealed that RGP significantly enhanced both basal and glucose-stimulated insulin secretions, as well as islet insulin contents in the pancreatic islets of diabetic mice. Moreover, RGP reversed the increased mRNA expression of PEPCK and the reduced glycogen contents in the liver of diabetic mice. Furthermore, RGP exhibited potent anti-inflammatory and anti-oxidative activities, as evidenced by the decreased blood levels of TNF-α, IL-6, monocyte chemoattractant protein-1, MDA, and also the elevated blood levels of SOD and GPx activities in diabetic mice.

CONCLUSIONS

Taken together, RGP can effectively ameliorate hyperglycemia, hyperlipemia, vascular inflammation and oxidative stress in STZ-induced diabetic mice, and thus may be a potential therapeutic option for type 1 diabetes.

Hyperketonemia (acetoacetate) upregulates NADPH oxidase 4 and elevates oxidative stress, ICAM-1, and monocyte adhesivity in endothelial cells

BACKGROUND/AIMS

The incidence of developing microvascular dysfunction is significantly higher in type 1 diabetic (T1D) patients. Hyperketonemia (acetoacetate, β-hydroxybutyrate) is frequently found along with hyperglycemia in T1D. Whether hyperketonemia per se contributes to the excess oxidative stress and cellular injury observed in T1D is not known.

METHODS

HUVEC were treated with ketones in the presence or absence of high glucose for 24 h. NOX4 siRNA was used to specifically knockdown NOX4 expression in HUVEC.

RESULTS

Ketones alone or in combination with high glucose treatment cause a significant increase in oxidative stress, ICAM-1, and monocyte adhesivity to HUVEC. Using an antisense approach, we show that ketone induced increases in ROS, ICAM-1 expression, and monocyte adhesion in endothelial cells were prevented in NOX4 knockdown cells.

CONCLUSION

This study reports that elevated levels of ketones upregulate NOX, contributing to increased oxidative stress, ICAM-1 levels, and cellular dysfunction. This provides a novel biochemical mechanism that elucidates the role of hyperketonemia in the excess cellular injury in T1D. New drugs targeting inhibition of NOX seems promising in preventing higher risk of complications associated with T1D.

Effect of hyperketonemia (Acetoacetate) on nuclear factor-κB and p38 mitogen-activated protein kinase activation mediated intercellular adhesion molecule 1 upregulation in endothelial cells

BACKGROUND

Hyperketonemia is a pathological condition observed in patients with type 1 diabetes and ketosis-prone diabetes (KPD), which results in increased blood levels of acetoacetate (AA) and β-hydroxybutyrate (BHB). Frequent episodes of hyperketonemia are associated with a higher incidence of vascular disease. We examined the hypothesis that hyperketonemia activates the nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways that regulate intercellular adhesion molecule 1 (ICAM-1) expression in endothelial cells.

METHODS

Human umbilical vein endothelial cells (HUVECs) were cultured with AA (0-8 mM) or BHB (0-10 mM) for 0-24 hr. Western blotting was used to determine NF-κB activation in whole-cell lysates. ICAM-1 expression was measured using flow cytometry.

RESULTS

RESULTS show a 2.4-fold increase in NF-κB activation in cells treated with 8 mM AA compared to the control. BHB had little or no effect on NF-κB activation. Pretreatment with a reactive oxygen species (ROS) inhibitor [N-acetyl-l-cysteine (NAC)] reduced NF-κB to near-control levels. The expression of AA-induced ICAM-1 was significantly reduced when cells were pretreated with either NAC or p38 MAPK inhibitor.

CONCLUSIONS

These results suggest that NF-κB and p38 MAPK mediate upregulation of ICAM-1 expression in endothelial cells exposed to elevated levels of AA, which may contribute to the development of vascular disease in diabetes.

Vitamin D and L-cysteine levels correlate positively with GSH and negatively with insulin resistance levels in the blood of type 2 diabetic patients

Background/Objectives:

Vitamin D, L-cysteine (LC) and glutathione (GSH) levels are lower in the blood of diabetic patients. This study examined the hypothesis that the levels of vitamin D and LC correlate with those of GSH in the blood of type 2 diabetic patients (T2D), and that vitamin D and LC upregulate glutamate–cysteine ligase (GCLC), which catalyzes GSH biosynthesis, in cultured monocytes.

Subjects/Methods:

Fasting blood was obtained after written informed consent from T2D (n=79) and healthy controls (n=22). U937 monocytes were pretreated with 1,25 (OH)₂ vitamin D (0–25 nM) or LC (0–500 μM) for 24 h and then exposed to control or high glucose (25 mM) for 4 h.

Results:

Plasma levels of vitamin D, LC, GSH and GCLC protein were significantly lower in T2D versus those in age-matched healthy controls. Multiple linear regression analyses and adjustment for body weight showed a significant positive correlation between plasma levels of vitamin D (r=0.26, P=0.05) and LC (r=0.81, P=0.001) and that of GSH, and between LC and vitamin D (r=0.27, P=0.045) levels. Plasma levels of GSH (r=−0.34, P=0.01) and LC (r=−0.33, r=0.01) showed a negative correlation with triglyceride levels. Vitamin D correlated inversely with HbA_1C (−0.30, P=0.01) and homeostatic model assessment insulin resistance (r=−0.31, P=0.03), which showed a significant positive correlation with triglycerides (r=0.44, P=0.001) in T2D. Cell culture studies demonstrate that supplementation with vitamin D and LC significantly increased GCLC expression and GSH formation in control and high-glucose-treated monocytes.

Conclusions:

This study suggests a positive relationship between the concentrations of the micronutrients vitamin D and LC and that of GSH. Some of the beneficial effects of vitamin D and LC supplementation may be mediated by an increase in the levels of GSH and a decrease in triglyceride levels in T2D patients.

Expression of interleukin-15 and inflammatory cytokines in skeletal muscles of STZ-induced diabetic rats: effect of resistance exercise training

Skeletal muscle atrophy is associated with type-1 diabetes. Skeletal muscle is the source of pro- and anti-inflammatory cytokines that can mediate muscle hypertrophy and atrophy, while resistance exercise can modulate both muscle mass and muscle cytokine expression. This study determined the effects of a 5-week resistance exercise training regimen on the expression of muscle cytokines in healthy and streptozotocin-induced diabetic rats, with special emphasis on interleukin-15 (IL-15), a muscle-derived cytokine proposed to be involved in muscle hypertrophy or responses to stress. Induction of diabetes reduced muscle weight in both the fast flexor hallucis longus (FHL) and slow soleus muscles, while resistance training preserved FHL muscle weight in diabetic rats. IL-15 protein content was increased by training in both FHL and soleus muscles, as well as serum, in normal and diabetic rats. With regard to proinflammatory cytokines, muscle IL-6 levels were increased in diabetic rats, while training decreased muscle IL-6 levels in diabetic rats; training had no effect on FHL muscle IL-6 levels in healthy rats. Also, tumor necrosis factor-alpha (TNF-α) and IL-1β levels were increased by diabetes, but not changed by training. In conclusion, we found that in diabetic rats, resistance training increased muscle and serum IL-15 levels, decreased muscle IL-6 levels, and preserved FHL muscle mass.

Decreased cystathionine-γ-lyase (CSE) activity in livers of type 1 diabetic rats and peripheral blood mononuclear cells (PBMC) of type 1 diabetic patients

The liver plays a major role in the formation of H2S, a novel signaling molecule. Diabetes is associated with lower blood levels of H2S. This study investigated the activities of cystathionine-γ-lyase (CSE, the enzyme that catalyzes H2S formation) in livers of type 1 diabetic (T1D) animals and in peripheral blood mononuclear cells (PBMC) isolated from T1D patients. T1D is associated with both hyperketonemia (acetoacetate and β-hydroxybutyrate) and hyperglycemia. This study also examined the role of hyperglycemia and hyperketonemia per se in decreased CSE activity using U937 monocytes and PBMC isolated from healthy subjects. Livers from streptozotocin-treated T1D rats demonstrated a significantly higher reactive oxygen species production, lower CSE protein expression and activity, and lower H2S formation compared with those of controls. Studies with T1D patients showed a decrease in CSE protein expression and activity in PBMC compared with those of age-matched normal subjects. Cell culture studies demonstrated that high glucose (25 mm) and/or acetoacetate (4 mm) increased reactive oxygen species, decreased CSE mRNA expression, protein expression, and enzymatic activity, and reduced H2S levels; however, β-hydroxybutyrate treatment had no effect. A similar effect, which was also observed in PBMC treated with high glucose alone or along with acetoacetate, was prevented by vitamin D supplementation. Studies with CSE siRNA provide evidence for a relationship between impaired CSE expression and reduced H2S levels. This study demonstrates for the first time that both hyperglycemia and hyperketonemia mediate a reduction in CSE expression and activity, which can contribute to the impaired H2S signaling associated with diabetes.

GABA tea prevents cardiac fibrosis by attenuating TNF-alpha and Fas/FasL-mediated apoptosis in streptozotocin-induced diabetic rats

GABA tea is a tea product that contains a high level of gamma-aminobutyric acid (GABA). This study investigated the effects of GABA tea on the heart in a diabetic rat model. Male Wistar rats were injected with 55mg/kg streptozotocin (STZ) to induce diabetes for 2weeks and then orally given dosages of 4.55 and 45.5mg/kg/day GABA tea extract for 6weeks. The results revealed that fasting blood glucose levels returned to normal levels in GABA tea-treated diabetic rats, but not in the untreated diabetic rats. Additionally, GABA tea effectively inhibited cardiac fibrosis induced by STZ. Further experiments showed that the STZ-induced protein levels of tumor necrosis factor-alpha (TNF-alpha), Fas, activated caspase-8 and caspase-3 were significantly inhibited by the GABA tea treatment. Therefore, our data suggest that the inhibiting effect of GABA tea on STZ-induced cardiac fibrosis in diabetic rats may be mediated by reducing blood glucose and further attenuating TNF-alpha expression and/or Fas/Fas ligand (FasL)-mediated apoptosis. These findings will provide implications for the potential anti-diabetic properties of GABA tea.

Vitamin D upregulates glutamate cysteine ligase and glutathione reductase, and GSH formation, and decreases ROS and MCP-1 and IL-8 secretion in high-glucose exposed U937 monocytes

INTRODUCTION

Glutathione is a major endogenous antioxidant and its deficiency is implicated in the etiology and progression of a number of human diseases. Vitamin D is important for the prevention of osteoporosis, cardiovascular disease, diabetes, autoimmune diseases, and some cancers. Using a monocyte cell model, this study examined the hypothesis that vitamin D upregulate glutamate cysteine ligase (GCLC) and glutathione reductase (GR), which catalyzes GSH biosynthesis.

METHODS

U937 monocytes were pretreated with and without 1,25 (OH)₂ vitamin D (10-25 nM) for 24 h and then exposed to control and high glucose (HG, 25 mM) for 4h. Levels of GSH determined using HPLC; GR activity by oxidation of NADPH; GCLC protein, MCP-1 and IL-8 using ELISA kits.

RESULTS

1,25 (OH)₂ vitamin D supplementation significantly upregulated expression of GCLC and GR, levels of GCLC protein and GR activity, and formation of GSH in control and HG-treated monocytes. 1,25 (OH)₂ vitamin D caused significantly (p<0.05) lower secretion of IL-8 and MCP-1, and lower ROS levels in monocytes exposed to control and HG-treated monocytes.

CONCLUSIONS

This study demonstrates a positive link between vitamin D and GSH levels, and that some beneficial effects of vitamin D supplementation may be mediated by an improvement in the cellular GSH levels and a decrease in ROS and pro-inflammatory cytokines.

Hyperketonemia induces upregulation of LFA-1 in monocytes, which is mediated by ROS and P38 MAPK activation

Type 1 diabetic patients have hyperketonemia, elevated levels of pro-inflammatory and oxidative stress markers, and a higher incidence of vascular disease. This study examines the hypothesis that hyperketonemia increases reactive oxygen species (ROS) and is in part responsible for increased expression of adhesion molecules in monocytes. THP-1 monocytes were treated with acetoacetate (AA) or β-hydroxybutyrate (BHB) (0–10 mmol/L) for 24 h. Results show that AA, but not BHB, increases ROS production in monocytes. Pretreatment of monocytes with N-acetylcysteine (NAC) inhibited AA-induced ROS production. AA treatment induced upregulation of LFA-1 and pretreatment of monocytes with NAC or an inhibitor to p38 MAPK inhibited this upregulation in monocytes. This suggests that physiological concentrations of AA can contribute to increased ROS and activation of p38 MAPK, which may be responsible for AA-induced upregulation of LFA-1 in monocytes. Thus, hyperketonemia contributes to the risk for cardiovascular disease in type 1 diabetes.

Hesperidin and naringin attenuate hyperglycemia-mediated oxidative stress and proinflammatory cytokine production in high fat fed/streptozotocin-induced type 2 diabetic rats

Abnormal regulation of glucose and impaired carbohydrate utilization that result from a defective or deficient insulin are the key pathogenic events in type 2 diabetes mellitus (T2DM). The present study was hypothesized to investigate the beneficial effects of hesperidin and naringin on hyperglycemia-induced oxidative damage in HFD/STZ-induced diabetic rats. Diabetes was induced by feeding rats with an HFD for 2 weeks followed by an intraperitoneal injection of STZ (35 mg/kg body weight). An oral dose of 50mg/kg hesperidin or naringin was daily given for 4 weeks after diabetes induction. At the end of the experimental period, blood was obtained from jugular vein and livers were rapidly excised and homogenized for biochemical assays. In the diabetic control group, levels of glucose, glycosylated hemoglobin (HbA1c%), MDA, NO, TNF-α and IL-6 were significantly increased, while serum insulin, GSH, vitamin C, and vitamin E levels were decreased. Both hesperidin and naringin administration significantly reversed these alterations. Moreover, supplementation with either compound significantly ameliorated serum and liver MDA, NO and glutathione, and liver antioxidant enzymes. Although detailed studies are required for the evaluation of the exact mechanism of the ameliorative effects of hesperidin and naringin against diabetic complications, these preliminary experimental findings demonstrate that both hesperidin and naringin exhibit antidiabetic effects in a rat model of T2DM by potentiating the antioxidant defense system and suppressing proinflammatory cytokine production.

L-cysteine supplementation as an adjuvant therapy for type-2 diabetes

Diabetes remains a major public health issue. According to the American Diabetes Association, 23.5 million, or 10.7% of people in the USA aged 20 years and older, have diabetes. Type-2 diabetes is treated both by controlling the diet and with oral hypoglycemic drugs. However, for many patients, achieving a tight control of glucose is difficult with current regimens. This chapter discusses a relatively low-cost dietary supplement that could be used as an adjuvant therapy for type-2 diabetes. A review of the literature indicates that cysteine-rich whey protein improves glucose metabolism in diabetic animals and type-2 diabetic patients. Similarly, in animal studies, improvement in glucose metabolism is observed after supplementation with L-cysteine, or molecules containing a cysteine moiety. This chapter discusses the biochemical mechanisms by which L-cysteine can upregulate the insulin-dependent signaling cascades of glucose metabolism. Further studies are needed to examine whether clinical interventions using L-cysteine as an adjuvant therapy indeed help to control glycemia and vascular inflammation in the diabetic patient population.