Dietary Nitrate and Corresponding Gut Microbiota Prevent Cardiac Dysfunction in Obese Mice.

Impaired heart function can develop in individuals with diabetes in the absence of coronary artery disease or hypertension, suggesting mechanisms beyond hypertension/increased afterload contribute to diabetic cardiomyopathy. Identifying therapeutic approaches that improve glycemia and prevent cardiovascular disease are clearly required for clinical management of diabetes-related comorbidities. Since intestinal bacteria are important for metabolism of nitrate, we examined whether dietary nitrate and fecal microbial transplantation (FMT) from nitrate-fed mice could prevent high-fat diet (HFD)-induced cardiac abnormalities. Male C57Bl/6N mice were fed a low-fat diet (LFD), HFD, or HFD+Nitrate (4 mmol/L sodium nitrate) for 8 weeks. HFD-fed mice presented with pathological left ventricle (LV) hypertrophy, reduced stroke volume, and increased end-diastolic pressure, in association with increased myocardial fibrosis, glucose intolerance, adipose inflammation, serum lipids, LV mitochondrial reactive oxygen species (ROS), and gut dysbiosis. In contrast, dietary nitrate attenuated these detriments. In HFD-fed mice, FMT from HFD+Nitrate donors did not influence serum nitrate, blood pressure, adipose inflammation, or myocardial fibrosis. However, microbiota from HFD+Nitrate mice decreased serum lipids, LV ROS, and similar to FMT from LFD donors, prevented glucose intolerance and cardiac morphology changes. Therefore, the cardioprotective effects of nitrate are not dependent on reducing blood pressure, but rather mitigating gut dysbiosis, highlighting a nitrate-gut-heart axis. ARTICLE HIGHLIGHTS: Identifying therapeutic approaches that prevent cardiometabolic diseases are clearly important, and nitrate represents one such potential compound given its multifactorial metabolic effects. We aimed to determine whether nitrate could prevent high-fat diet (HFD)-induced cardiac abnormalities and whether this was dependent on the gut microbiome. Dietary nitrate attenuated HFD-induced pathological changes in cardiac remodelling, left ventricle reactive oxygen species, adipose inflammation, lipid homeostasis, glucose intolerance, and gut dysbiosis. Fecal microbial transplantation from nitrate-fed mice also prevented serum dyslipidemia, left ventricle reactive oxygen species, glucose intolerance, and cardiac dysfunction. Therefore, the cardioprotective effects of nitrate are related to mitigating gut dysbiosis, highlighting a nitrate-gut-heart axis.

Dietary nitrate increases submaximal SERCA activity and ADP transfer to mitochondria in slow-twitch muscle of female mice.

Rapid oscillations in cytosolic calcium (Ca2+) coordinate muscle contraction, relaxation, and physical movement. Intriguingly, dietary nitrate decreases ATP cost of contraction, increases force production, and increases cytosolic Ca2+, which would seemingly necessitate a greater demand for sarcoplasmic reticulum Ca2+ ATPase (SERCA) to sequester Ca2+ within the sarcoplasmic reticulum (SR) during relaxation. As SERCA is highly regulated, we aimed to determine the effect of 7-day nitrate supplementation (1 mM via drinking water) on SERCA enzymatic properties and the functional interaction between SERCA and mitochondrial oxidative phosphorylation. In soleus, we report that dietary nitrate increased force production across all stimulation frequencies tested, and throughout a 25 min fatigue protocol. Mice supplemented with nitrate also displayed an ∼25% increase in submaximal SERCA activity and SERCA efficiency (P = 0.053) in the soleus. To examine a possible link between ATP consumption and production, we established a methodology coupling SERCA and mitochondria in permeabilized muscle fibers. The premise of this experiment is that the addition of Ca2+ in the presence of ATP generates ADP from SERCA to support mitochondrial respiration. Similar to submaximal SERCA activity, mitochondrial respiration supported by SERCA-derived ADP was increased by ∼20% following nitrate in red gastrocnemius. This effect was fully attenuated by the SERCA inhibitor cyclopiazonic acid and was not attributed to differences in mitochondrial oxidative capacity, ADP sensitivity, protein content, or reactive oxygen species emission. Overall, these findings suggest that improvements in submaximal SERCA kinetics may contribute to the effects of nitrate on force production during fatigue.NEW & NOTEWORTHY We show that nitrate supplementation increased force production during fatigue and increased submaximal SERCA activity. This was also evident regarding the high-energy phosphate transfer from SERCA to mitochondria, as nitrate increased mitochondrial respiration supported by SERCA-derived ADP. Surprisingly, these observations were only apparent in muscle primarily expressing type I (soleus) but not type II fibers (EDL). These findings suggest that alterations in SERCA properties are a possible mechanism in which nitrate increases force during fatiguing contractions.

Nitrate consumption preserves HFD-induced skeletal muscle mitochondrial ADP sensitivity and lysine acetylation: A potential role for SIRT1.

Dietary nitrate supplementation, and the subsequent serial reduction to nitric oxide, has been shown to improve glucose homeostasis in several pre-clinical models of obesity and insulin resistance. While the mechanisms remain poorly defined, the beneficial effects of nitrate appear to be partially dependent on AMPK-mediated signaling events, a central regulator of metabolism and mitochondrial bioenergetics. Since AMPK can activate SIRT1, we aimed to determine if nitrate supplementation (4 mM sodium nitrate via drinking water) improved skeletal muscle mitochondrial bioenergetics and acetylation status in mice fed a high-fat diet (HFD: 60% fat). Consumption of HFD induced whole-body glucose intolerance, and within muscle attenuated insulin-induced Akt phosphorylation, mitochondrial ADP sensitivity (higher apparent Km), submaximal ADP-supported respiration, mitochondrial hydrogen peroxide (mtH2O2) production in the presence of ADP and increased cellular protein carbonylation alongside mitochondrial-specific acetylation. Consumption of nitrate partially preserved glucose tolerance and, within skeletal muscle, normalized insulin-induced Akt phosphorylation, mitochondrial ADP sensitivity, mtH2O2, protein carbonylation and global mitochondrial acetylation status. Nitrate also prevented the HFD-mediated reduction in SIRT1 protein, and interestingly, the positive effects of nitrate ingestion on glucose homeostasis and mitochondrial acetylation levels were abolished in SIRT1 inducible knock-out mice, suggesting SIRT1 is required for the beneficial effects of dietary nitrate. Altogether, dietary nitrate preserves mitochondrial ADP sensitivity and global lysine acetylation in HFD-fed mice, while in the absence of SIRT1, the effects of nitrate on glucose tolerance and mitochondrial acetylation were abrogated.

Ckmt1 is Dispensable for Mitochondrial Bioenergetics Within White/Beige Adipose Tissue.

Within brown adipose tissue (BAT), the brain isoform of creatine kinase (CKB) has been proposed to regulate the regeneration of ADP and phosphocreatine in a futile creatine cycle (FCC) that stimulates energy expenditure. However, the presence of FCC, and the specific creatine kinase isoforms regulating this theoretical model within white adipose tissue (WAT), remains to be fully elucidated. In the present study, creatine did not stimulate respiration in cultured adipocytes, isolated mitochondria or mouse permeabilized WAT. Additionally, while creatine kinase ubiquitous-type, mitochondrial (CKMT1) mRNA and protein were detected in human WAT, shRNA-mediated reductions in Ckmt1 did not decrease submaximal respiration in cultured adipocytes, and ablation of CKMT1 in mice did not alter energy expenditure, mitochondrial responses to pharmacological ß3-adrenergic activation (CL 316, 243) or exacerbate the detrimental metabolic effects of consuming a high-fat diet. Taken together, these findings solidify CKMT1 as dispensable in the regulation of energy expenditure, and unlike in BAT, they do not support the presence of FCC within WAT.

Hippocampal Function Is Impaired by a Short-Term High-Fat Diet in Mice: Increased Blood-Brain Barrier Permeability and Neuroinflammation as Triggering Events.

Worldwide, and especially in Western civilizations, most of the staple diets contain high amounts of fat and refined carbohydrates, leading to an increasing number of obese individuals. In addition to inducing metabolic disorders, energy dense food intake has been suggested to impair brain functions such as cognition and mood control. Here we demonstrate an impaired memory function already 3 days after the start of a high-fat diet (HFD) exposure, and depressive-like behavior, in the tail suspension test, after 5 days. These changes were followed by reduced synaptic density, changes in mitochondrial function and astrocyte activation in the hippocampus. Preceding or coinciding with the behavioral changes, we found an induction of the proinflammatory cytokines TNF-α and IL-6 and an increased permeability of the blood-brain barrier (BBB), in the hippocampus. Finally, in mice treated with a TNF-α inhibitor, the behavioral and BBB alterations caused by HFD-feeding were mitigated suggesting that inflammatory signaling was critical for the changes. In summary, our findings suggest that HFD rapidly triggers hippocampal dysfunction associated with BBB disruption and neuroinflammation, promoting a progressive breakdown of synaptic and metabolic function. In addition to elucidating the link between diet and cognitive function, our results might be relevant for the comprehension of the neurodegenerative process.

Independent of mitochondrial respiratory function, dietary nitrate attenuates HFD-induced lipid accumulation and mitochondrial ROS emission within the liver.

The liver is particularly susceptible to the detrimental effects of a high-fat diet (HFD), rapidly developing lipid accumulation and impaired cellular homeostasis. Recently, dietary nitrate has been shown to attenuate HFD-induced whole body glucose intolerance and liver steatosis, however, the underlying mechanism(s) remain poorly defined. In the current study, we investigated the ability of dietary nitrate to minimize possible impairments in liver mitochondrial bioenergetics following 8 wk of HFD (60% fat) in male C57BL/6J mice. Consumption of a HFD caused whole body glucose intolerance (P < 0.0001), and within the liver, increased lipid accumulation (P < 0.0001), mitochondrial-specific reactive oxygen species emission (P = 0.007), and markers of oxidative stress. Remarkably, dietary nitrate attenuated almost all of these pathological responses. Despite the reduction in lipid accumulation and redox stress (reduced TBARS and nitrotyrosine), nitrate did not improve insulin signaling within the liver or whole body pyruvate tolerance (P = 0.313 HFD vs. HFD + nitrate). Moreover, the beneficial effects of nitrate were independent of changes in weight gain, 5' AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC) signaling, mitochondrial content, mitochondrial respiratory capacity and ADP sensitivity or antioxidant protein content. Combined, these data suggest nitrate supplementation represents a potential therapeutic strategy to attenuate hepatic lipid accumulation and decrease mitochondrial ROS emission following HFD, processes linked to improvements in whole body glucose tolerance. However, the beneficial effects of nitrate within the liver do not appear to be a result of increased oxidative capacity or mitochondrial substrate sensitivity.NEW & NOTEWORTHY The mechanism(s) for how dietary nitrate prevents high-fat diet (HFD)-induced glucose intolerance remain poorly defined. We show that dietary nitrate attenuates HFD-induced increases in lipid accumulation, mitochondrial-specific reactive oxygen species (ROS) emission, and markers of oxidative stress within the liver. The beneficial effects of nitrate were independent of changes 5' AMP-activated protein kinase signaling, mitochondrial content/respiratory capacity, or lipid-supported respiratory sensitivity. Combined, these data provide potential mechanisms underlying the therapeutic potential of dietary nitrate.

Insulin rapidly increases skeletal muscle mitochondrial ADP sensitivity in the absence of a high lipid environment.

Reductions in mitochondrial function have been proposed to cause insulin resistance, however the possibility that impairments in insulin signaling negatively affects mitochondrial bioenergetics has received little attention. Therefore, we tested the hypothesis that insulin could rapidly improve mitochondrial ADP sensitivity, a key process linked to oxidative phosphorylation and redox balance, and if this phenomenon would be lost following high-fat diet (HFD)-induced insulin resistance. Insulin acutely (60 min post I.P.) increased submaximal (100-1000 µM ADP) mitochondrial respiration ∼2-fold without altering maximal (>1000 µM ADP) respiration, suggesting insulin rapidly improves mitochondrial bioenergetics. The consumption of HFD impaired submaximal ADP-supported respiration ∼50%, however, despite the induction of insulin resistance, the ability of acute insulin to stimulate ADP sensitivity and increase submaximal respiration persisted. While these data suggest that insulin mitigates HFD-induced impairments in mitochondrial bioenergetics, the presence of a high intracellular lipid environment reflective of an HFD (i.e. presence of palmitoyl-CoA) completely prevented the beneficial effects of insulin. Altogether, these data show that while insulin rapidly stimulates mitochondrial bioenergetics through an improvement in ADP sensitivity, this phenomenon is possibly lost following HFD due to the presence of intracellular lipids.

Mitochondria-associated ER membranes in glucose homeostasis and insulin resistance.

Obesity and insulin resistance (IR) are associated with endoplasmic reticulum (ER) stress and mitochondrial dysfunction in several tissues. Although for many years mitochondrial and ER function were studied separately, these organelles also connect to produce interdependent functions. Communication occurs at mitochondria-associated ER membranes (MAMs) and regulates lipid and calcium homeostasis, apoptosis, and the exchange of adenine nucleotides, among other things. Recent evidence suggests that MAMs contribute to organelle, cellular, and systemic metabolism. In obesity and IR models, metabolic tissues such as the liver, skeletal muscle, pancreas, and adipose tissue present alterations in MAM structure or function. The purpose of this mini review is to highlight the MAM disruptions that occur in each tissue during obesity and IR and its relationship with glucose homeostasis and IR. We also discuss the current controversy that surrounds MAMs' role in the development of IR.

In vitro ketone-supported mitochondrial respiration is minimal when other substrates are readily available in cardiac and skeletal muscle.

KEY POINTS: Ketone bodies are proposed to represent an alternative fuel source driving energy production, particularly during exercise. Biologically, the extent to which mitochondria utilize ketone bodies compared to other substrates remains unknown. We demonstrate in vitro that maximal mitochondrial respiration supported by ketone bodies is low when compared to carbohydrate-derived substrates in the left ventricle and red gastrocnemius muscle from rodents, and in human skeletal muscle. When considering intramuscular concentrations of ketone bodies and the presence of other carbohydrate and lipid substrates, biological rates of mitochondrial respiration supported by ketone bodies are predicted to be minimal. At the mitochondrial level, it is therefore unlikely that ketone bodies are an important source for energy production in cardiac and skeletal muscle, particularly when other substrates are readily available. ABSTRACT: Ketone bodies (KB) have recently gained popularity as an alternative fuel source to support mitochondrial oxidative phosphorylation and enhance exercise performance. However, given the low activity of ketolytic enzymes and potential inhibition from carbohydrate oxidation, it remains unknown if KBs can contribute to energy production. We therefore determined the ability of KBs (sodium dl-ß-hydroxybutyrate, ß-HB; lithium acetoacetate, AcAc) to stimulate in vitro mitochondrial respiration in the left ventricle (LV) and red gastrocnemius (RG) of rats, and in human vastus lateralis. Compared to pyruvate, the ability of KBs to maximally drive respiration was low in isolated mitochondria and permeabilized fibres (PmFb) from the LV (∼30-35% of pyruvate), RG (∼10-30%), and human vastus lateralis (∼2-10%). In PmFb, the concentration of KBs required to half-maximally drive respiration (LV: 889 µm ß-HB, 801 µm AcAc; RG: 782 µm ß-HB, 267 µm AcAc) were greater than KB content representative of the muscle microenvironment (∼100 µm). This would predict low rates (∼1-4% of pyruvate) of biological KB-supported respiration in the LV (8-14 pmol s-1 mg-1 ) and RG (3-6 pmol s-1 mg-1 ) at rest and following exercise. Moreover, KBs did not increase respiration in the presence of saturating pyruvate, submaximal pyruvate (100 µm) reduced the ability of physiological ß-HB to drive respiration, and addition of other intracellular substrates (succinate + palmitoylcarnitine) decreased maximal KB-supported respiration. As a result, product inhibition is likely to limit KB oxidation. Altogether, the ability of KBs to drive mitochondrial respiration is minimal and they are likely to be outcompeted by other substrates, compromising their use as an important energy source.

Long-term, high-fat feeding exacerbates short-term increases in adipose mitochondrial reactive oxygen species, without impairing mitochondrial respiration.

White adipose tissue (WAT) dysfunction in obesity is implicated in the onset of whole body insulin resistance. Alterations in mitochondrial bioenergetics, namely impaired mitochondrial respiration and increased mitochondrial reactive oxygen species (mtROS) production, have been suggested to contribute to this metabolic dysregulation. However, techniques investigating mitochondrial function are classically normalized to tissue weight, which may be confounding when considering obesity-related adipocyte hypertrophy. Furthermore, the effect of long-term high-fat diet (HFD) on mtROS in WAT has yet to be elucidated. Therefore, we sought to determine the HFD-mediated temporal changes in mitochondrial respiration and mtROS emission in WAT. C57BL/6N mice received low-fat diet or HFD for 1 or 8 wk and changes in inguinal WAT (iWAT) and epididymal WAT (eWAT) were assessed. While tissue weight-normalized mitochondrial respiration was reduced in iWAT following 8-wk HFD-feeding, this effect was mitigated when adipocyte cell size and/or number were considered. These data suggest HFD does not impair mitochondrial respiratory capacity per adipocyte within WAT. In support of this assertion, within eWAT compensatory increases in lipid-supported and maximal succinate-supported respiration occurred at 8 wk despite cell hypertrophy and increases in WAT inflammation. Although these data suggest impairments in mitochondrial respiration do not contribute to HFD-mediated WAT phenotype, lipid-supported mtROS emission increased following 1-wk HFD in eWAT, while both lipid and carbohydrate-supported mtROS were increased at 8 wk in both depots. Combined, these data establish that while HFD does not impair adipocyte mitochondrial respiratory capacity, increased mtROS is an enduring physiological occurrence within WAT in HFD-induced obesity.

Behavioral, cardiovascular and endocrine alterations induced by chronic stress in rats fed a high-fat diet.

Chronic stress is a risk factor for cardiovascular diseases (CVD) and anxiety disorders (AD). Obesity also increases the risk of CVD and AD. The modern lifestyle commonly includes high-fat diet (HFD) intake and daily exposure to stressful events. However, it is not completely understood whether chronic stress exacerbates HFD-induced behavioral and physiological changes. Thus, this study aimed to evaluate the effects of the exposure to chronic variable stress (CVS) on behavioral, cardiovascular, and endocrine parameters in rats fed an HFD. Male Wistar rats were divided into four groups: control-standard chow diet (control-SD), control-HFD, CVS-SD, and CVS-HFD. The control-HFD and CVS-HFD groups were fed with HFD for six weeks. The CVS-HFD and CVS-SD groups were exposed to a CVS protocol in the last ten days of the six weeks. The behavioral analysis revealed that CVS decreased the open-arm exploration time during the elevated plus-maze test (p < 0.05). HFD promoted metabolic disorders and increased angiotensin II and leptin blood levels (p < 0.05). CVS or HFD increased blood pressure and the sympathetic nervous system (SNS) modulation of the heart and vessels and decreased baroreflex activity (p < 0.05). Combining CVS and HFD exacerbated the cardiac SNS response and increased basal heart rate (HR) (p < 0.05). CVS or HFD did not affect vascular function and aorta nitrate (p > 0.05). Taken together, these data indicate a synergism between HFD and CVS on the HR and cardiac SNS responses, suggesting an increased cardiovascular risk. Besides, neuroendocrine and anxiogenic disturbers may contribute to the cardiovascular changes induced by HFD and CVS, respectively.

Nitrate attenuates high fat diet-induced glucose intolerance in association with reduced epididymal adipose tissue inflammation and mitochondrial reactive oxygen species emission.

KEY POINTS: Dietary nitrate is a prominent therapeutic strategy to mitigate some metabolic deleterious effects related to obesity. Mitochondrial dysfunction is causally linked to adipose tissue inflammation and insulin resistance. Whole-body glucose tolerance is prevented by nitrate independent of body weight and energy expenditure. Dietary nitrate reduces epididymal adipose tissue inflammation and mitochondrial reactive oxygen species emission while preserving insulin signalling. Metabolic beneficial effects of nitrate consumption are associated with improvements in mitochondrial redox balance in hypertrophic adipose tissue. ABSTRACT: Evidence has accumulated to indicate that dietary nitrate alters energy expenditure and the metabolic derangements associated with a high fat diet (HFD), but the mechanism(s) of action remain incompletely elucidated. Therefore, we aimed to determine if dietary nitrate (4 mm sodium nitrate via drinking water) could prevent HFD-mediated glucose intolerance in association with improved mitochondrial bioenergetics within both white (WAT) and brown (BAT) adipose tissue in mice. HFD feeding caused glucose intolerance (P < 0.05) and increased body weight. As a result of higher body weight, energy expenditure increased proportionally. HFD-fed mice displayed greater mitochondrial uncoupling and a twofold increase in uncoupling protein 1 content within BAT. Within epididymal white adipose tissue (eWAT), HFD increased cell size (i.e. hypertrophy), mitochondrial H2 O2 emission, oxidative stress, c-Jun N-terminal kinase phosphorylation and leucocyte infiltration, and induced insulin resistance. Remarkably, dietary nitrate consumption attenuated and/or mitigated all these responses, including rendering mitochondria more coupled within BAT, and normalizing mitochondrial H2 O2 emission and insulin-mediated Akt-Thr308 phosphorylation within eWAT. Intriguingly, the positive effects of dietary nitrate appear to be independent of eWAT mitochondrial respiratory capacity and content. Altogether, these data suggest that dietary nitrate attenuates the development of HFD-induced insulin resistance in association with attenuating WAT inflammation and redox balance, independent of changes in either WAT or BAT mitochondrial respiratory capacity/content.

Adipose Tissue Inflammation Is Directly Linked to Obesity-Induced Insulin Resistance, while Gut Dysbiosis and Mitochondrial Dysfunction Are Not Required.

Obesity is associated with adipose tissue hypertrophy, systemic inflammation, mitochondrial dysfunction, and intestinal dysbiosis. Rodent models of high-fat diet (HFD)-feeding or genetic deletion of multifunctional proteins involved in immunity and metabolism are often used to probe the etiology of obesity; however, these models make it difficult to divorce the effects of obesity, diet composition, or immunity on endocrine regulation of blood glucose. We, therefore, investigated the importance of adipose inflammation, mitochondrial dysfunction, and gut dysbiosis for obesity-induced insulin resistance using a spontaneously obese mouse model. We examined metabolic changes in skeletal muscle, adipose tissue, liver, the intestinal microbiome, and whole-body glucose control in spontaneously hyperphagic C57Bl/6J mice compared to lean littermates. A separate subset of lean and obese mice was subject to 8 weeks of obesogenic HFD feeding, or to pair feeding of a standard rodent diet. Hyperphagia, obesity, adipose inflammation, and insulin resistance were present in obese mice despite consuming a standard rodent diet, and these effects were blunted with caloric restriction. However, hyperphagic obese mice had normal mitochondrial respiratory function in all tissues tested and no discernable intestinal dysbiosis relative to lean littermates. In contrast, feeding mice an obesogenic HFD altered the composition of the gut microbiome, impaired skeletal muscle mitochondrial bioenergetics, and promoted poor glucose control. These data show that adipose inflammation and redox stress occurred in all models of obesity, but gut dysbiosis and mitochondrial respiratory dysfunction are not always required for obesity-induced insulin resistance. Rather, changes in the intestinal microbiome and mitochondrial bioenergetics may reflect physiological consequences of HFD feeding.

New tools for an old question: dependence of ATP and bicarbonate for branched-chain keto acids oxidation.

Branched-chain keto acids (BCKA) metabolism involves several well-regulated steps within mitochondria, requires cofactors, and is modulated according to the metabolic status of the cells. This regulation has made it challenging to utilize in vitro approaches to determine the contribution of branched-chain amino acid oxidation to energy production. These methodological issues were elegantly addressed in a recent publication within the Biochemical Journal. In this issue, Goldberg et al. [Biochem. J. (2019) 476, 1521-1537] demonstrated in a well-designed system the dependence of ATP and bicarbonate for BCKA full oxidation. In addition, the utilized system allowed the authors to characterize specific biochemical routes within mitochondria for each BCKA. Among them, a quantitative analysis of the participation of BCKA on mitochondrial flux was estimated between tissues. These findings are milestones with meaningful impact in several fields of metabolism.

Does L-leucine supplementation cause any effect on glucose homeostasis in rodent models of glucose intolerance? A systematic review.

L-Leucine has been used to improve metabolic outcomes in glucose-intolerant rodent models. However, because studies have used different experimental models and conditions it is difficult to establish the best approach for new clinical trials evaluating the potential effects of L-leucine on glucose homeostasis. We performed a systematic review to report the effect of L-leucine supplementation on glucose homeostasis in rodents with glucose intolerance. The search engines MEDLINE and ScienceDirect were applied using MeSH terms. Thirty-four studies were included in this systematic review. Based on the current data, ingestion of 90-140 mg day-1 of isolated L-leucine in diet-induced obesity (DIO) models shows improvement in metabolic markers if offered during the development of the metabolic disorder in almost all the studies, but not after. Branched-chain amino acid supplementation was effective in streptozotocin-induced ß-cells death but not in DIO models. L-Leucine supplementation seems to have an optimal dose and timing for supplementation to improve glucose homeostasis in DIO.

Effects of cotreatment with omega-3 polyunsaturated fatty acids and anticancer agents on oxidative stress parameters: a systematic review of in vitro, animal, and human studies.

Context: Omega-3 (n-3) polyunsaturated fatty acids (PUFAs), especially docosahexaenoic acid and eicosapentaenoic acid, demonstrate possible beneficial effects as adjuvants in cancer treatment. One mechanism seems to be related to alterations in the redox status of cancer cells. Such alterations are thought to act in synergy with conventional anticancer agents. Objective: This review examines published data on the effects of cotreatment with anticancer agents and n-3 PUFAS on oxidative stress parameters to determine whether any patterns of oxidative stress alterations can be identified. Data Sources: A systematic search of MEDLINE (via PubMed) was conducted to identify articles published in English, Spanish, or Portuguese until November 2017. Study Selection: The following inclusion criteria were applied: (1) individuals or animals with cancer or malignant cell lines supplemented with some source of n-3 PUFAs; (2) concomitant use of anticancer treatment; and (3) evaluation of oxidative stress-related variables. Data Extraction: A standardized outline was used to extract the following data: study type, supplement used, type of cells, tumor or patient characteristics, study design, anticancer treatment used, and oxidative stress-related outcomes. Results: After the literature search and screening of 1563 citations, 28 studies were included for data extraction and evaluation: 16 in vitro studies (2 of which also used in vivo studies), 8 animal studies, and 4 human studies (3 clinical trials and 1 case series). In most in vitro and animal studies, intervention groups receiving cotreatment with n-3 PUFAs showed enhanced lipid peroxidation and cytotoxicity compared with groups receiving anticancer treatment alone. Eleven of the 12 studies that investigated the effect of vitamin E on the sensitivity of cancer cells to the oxidative stress caused by n-3 PUFAs showed that vitamin E abolished the positive effects of cotreatment. Conclusions: Alterations in oxidative stress caused by cotreatment with anticancer agents and n-3 PUFAs can exert positive effects on the efficacy of conventional treatment. This seems to occur in most cells and tumors tested thus far, but not all. Identifying tumors that are sensitive to these oxidative effects may provide support for the rational use of n-3 PUFAs as an adjuvant treatment in specific types of cancer.