A metabolomics comparison of plant-based meat and grass-fed meat indicates large nutritional differences despite comparable Nutrition Facts panels.

A new generation of plant-based meat alternatives-formulated to mimic the taste and nutritional composition of red meat-have attracted considerable consumer interest, research attention, and media coverage. This has raised questions of whether plant-based meat alternatives represent proper nutritional replacements to animal meat. The goal of our study was to use untargeted metabolomics to provide an in-depth comparison of the metabolite profiles a popular plant-based meat alternative (n = 18) and grass-fed ground beef (n = 18) matched for serving size (113 g) and fat content (14 g). Despite apparent similarities based on Nutrition Facts panels, our metabolomics analysis found that metabolite abundances between the plant-based meat alternative and grass-fed ground beef differed by 90% (171 out of 190 profiled metabolites; false discovery rate adjusted p < 0.05). Several metabolites were found either exclusively (22 metabolites) or in greater quantities in beef (51 metabolites) (all, p < 0.05). Nutrients such as docosahexaenoic acid (ω-3), niacinamide (vitamin B3), glucosamine, hydroxyproline and the anti-oxidants allantoin, anserine, cysteamine, spermine, and squalene were amongst those only found in beef. Several other metabolites were found exclusively (31 metabolites) or in greater quantities (67 metabolites) in the plant-based meat alternative (all, p < 0.05). Ascorbate (vitamin C), phytosterols, and several phenolic anti-oxidants such as loganin, sulfurol, syringic acid, tyrosol, and vanillic acid were amongst those only found in the plant-based meat alternative. Large differences in metabolites within various nutrient classes (e.g., amino acids, dipeptides, vitamins, phenols, tocopherols, and fatty acids) with physiological, anti-inflammatory, and/or immunomodulatory roles indicate that these products should not be viewed as truly nutritionally interchangeable, but could be viewed as complementary in terms of provided nutrients. The new information we provide is important for making informed decisions by consumers and health professionals. It cannot be determined from our data if either source is healthier to consume.

Muscle-Liver Trafficking of BCAA-Derived Nitrogen Underlies Obesity-Related Glycine Depletion.

Glycine levels are inversely associated with branched-chain amino acids (BCAAs) and cardiometabolic disease phenotypes, but biochemical mechanisms that explain these relationships remain uncharted. Metabolites and genes related to BCAA metabolism and nitrogen handling were strongly associated with glycine in correlation analyses. Stable isotope labeling in Zucker fatty rats (ZFRs) shows that glycine acts as a carbon donor for the pyruvate-alanine cycle in a BCAA-regulated manner. Inhibition of the BCAA transaminase (BCAT) enzymes depletes plasma pools of alanine and raises glycine levels. In high-fat-fed ZFRs, dietary glycine supplementation raises urinary acyl-glycine content and lowers circulating triglycerides but also results in accumulation of long-chain acyl-coenzyme As (acyl-CoAs), lower 5' adenosine monophosphate-activated protein kinase (AMPK) phosphorylation in muscle, and no improvement in glucose tolerance. Collectively, these studies frame a mechanism for explaining obesity-related glycine depletion and also provide insight into the impact of glycine supplementation on systemic glucose, lipid, and amino acid metabolism.

Effects of the kinase inhibitor sorafenib on heart, muscle, liver and plasma metabolism in vivo using non-targeted metabolomics analysis.

BACKGROUND AND PURPOSE: The human kinome consists of roughly 500 kinases, including 150 that have been proposed as therapeutic targets. Protein kinases regulate an array of signalling pathways that control metabolism, cell cycle progression, cell death, differentiation and survival. It is not surprising, then, that new kinase inhibitors developed to treat cancer, including sorafenib, also exhibit cardiotoxicity. We hypothesized that sorafenib cardiotoxicity is related to its deleterious effects on specific cardiac metabolic pathways given the critical roles of protein kinases in cardiac metabolism. EXPERIMENTAL APPROACH: FVB/N mice (10 per group) were challenged with sorafenib or vehicle control daily for 2 weeks. Echocardiographic assessment of the heart identified systolic dysfunction consistent with cardiotoxicity in sorafenib-treated mice compared to vehicle-treated controls. Heart, skeletal muscle, liver and plasma were flash frozen and prepped for non-targeted GC-MS metabolomics analysis. KEY RESULTS: Compared to vehicle-treated controls, sorafenib-treated hearts exhibited significant alterations in 11 metabolites, including markedly altered taurine/hypotaurine metabolism (25-fold enrichment), identified by pathway enrichment analysis. CONCLUSIONS AND IMPLICATIONS: These studies identified alterations in taurine/hypotaurine metabolism in the hearts and skeletal muscles of mice treated with sorafenib. Interventions that rescue or prevent these sorafenib-induced changes, such as taurine supplementation, may be helpful in attenuating sorafenib-induced cardiac injury.

Exercise-Induced Alterations in Skeletal Muscle, Heart, Liver, and Serum Metabolome Identified by Non-Targeted Metabolomics Analysis.

BACKGROUND: The metabolic and physiologic responses to exercise are increasingly interesting, given that regular physical activity enhances antioxidant capacity, improves cardiac function, and protects against type 2 diabetes. The metabolic interactions between tissues and the heart illustrate a critical cross-talk we know little about. METHODS: To better understand the metabolic changes induced by exercise, we investigated skeletal muscle (plantaris, soleus), liver, serum, and heart from exercise trained (or sedentary control) animals in an established rat model of exercise-induced aerobic training via non-targeted GC-MS metabolomics. RESULTS: Exercise-induced alterations in metabolites varied across tissues, with the soleus and serum affected the least. The alterations in the plantaris muscle and liver were most alike, with two metabolites increased in each (citric acid/isocitric acid and linoleic acid). Exercise training additionally altered nine other metabolites in the plantaris (C13 hydrocarbon, inosine/adenosine, fructose-6-phosphate, glucose-6-phosphate, 2-aminoadipic acid, heptadecanoic acid, stearic acid, alpha-tocopherol, and oleic acid). In the serum, we identified significantly decreased alpha-tocopherol levels, paralleling the increases identified in plantaris muscle. Eleven unique metabolites were increased in the heart, which were not affected in the other compartments (malic acid, serine, aspartic acid, myoinositol, glutamine, gluconic acid-6-phosphate, glutamic acid, pyrophosphate, campesterol, phosphoric acid, creatinine). These findings complement prior studies using targeted metabolomics approaches to determine the metabolic changes in exercise-trained human skeletal muscle. Specifically, exercise trained vastus lateralus biopsies had significantly increased linoleic acid, oleic acid, and stearic acid compared to the inactive groups, which were significantly increased in plantaris muscle in the present study. CONCLUSIONS: While increases in alpha-tocopherol have not been identified in muscle after exercise to our knowledge, the benefits of vitamin E (alpha-tocopherol) supplementation in attenuating exercise-induced muscle damage has been studied extensively. Skeletal muscle, liver, and the heart have primarily different metabolic changes, with few similar alterations and rare complementary alterations (alpha-tocopherol), which may illustrate the complexity of understanding exercise at the organismal level.

Nicotinamide mononucleotide requires SIRT3 to improve cardiac function and bioenergetics in a Friedreich's ataxia cardiomyopathy model.

Increasing NAD+ levels by supplementing with the precursor nicotinamide mononucleotide (NMN) improves cardiac function in multiple mouse models of disease. While NMN influences several aspects of mitochondrial metabolism, the molecular mechanisms by which increased NAD+ enhances cardiac function are poorly understood. A putative mechanism of NAD+ therapeutic action exists via activation of the mitochondrial NAD+-dependent protein deacetylase sirtuin 3 (SIRT3). We assessed the therapeutic efficacy of NMN and the role of SIRT3 in the Friedreich's ataxia cardiomyopathy mouse model (FXN-KO). At baseline, the FXN-KO heart has mitochondrial protein hyperacetylation, reduced Sirt3 mRNA expression, and evidence of increased NAD+ salvage. Remarkably, NMN administered to FXN-KO mice restores cardiac function to near-normal levels. To determine whether SIRT3 is required for NMN therapeutic efficacy, we generated SIRT3-KO and SIRT3-KO/FXN-KO (double KO [dKO]) models. The improvement in cardiac function upon NMN treatment in the FXN-KO is lost in the dKO model, demonstrating that the effects of NMN are dependent upon cardiac SIRT3. Coupled with cardio-protection, SIRT3 mediates NMN-induced improvements in both cardiac and extracardiac metabolic function and energy metabolism. Taken together, these results serve as important preclinical data for NMN supplementation or SIRT3 activator therapy in Friedreich's ataxia patients.

A branched-chain amino acid-related metabolic signature that differentiates obese and lean humans and contributes to insulin resistance.

Metabolomic profiling of obese versus lean humans reveals a branched-chain amino acid (BCAA)-related metabolite signature that is suggestive of increased catabolism of BCAA and correlated with insulin resistance. To test its impact on metabolic homeostasis, we fed rats on high-fat (HF), HF with supplemented BCAA (HF/BCAA), or standard chow (SC) diets. Despite having reduced food intake and a low rate of weight gain equivalent to the SC group, HF/BCAA rats were as insulin resistant as HF rats. Pair-feeding of HF diet to match the HF/BCAA animals or BCAA addition to SC diet did not cause insulin resistance. Insulin resistance induced by HF/BCAA feeding was accompanied by chronic phosphorylation of mTOR, JNK, and IRS1Ser307 and by accumulation of multiple acylcarnitines in muscle, and it was reversed by the mTOR inhibitor, rapamycin. Our findings show that in the context of a dietary pattern that includes high fat consumption, BCAA contributes to development of obesity-associated insulin resistance.

Metabolic profiling of PPARalpha-/- mice reveals defects in carnitine and amino acid homeostasis that are partially reversed by oral carnitine supplementation.

Peroxisome proliferator-activated receptor-alpha (PPARalpha) is a master transcriptional regulator of beta-oxidation and a prominent target of hypolipidemic drugs. To gain deeper insights into the systemic consequences of impaired fat catabolism, we used quantitative, mass spectrometry-based metabolic profiling to investigate the fed-to-fasted transition in PPARalpha(+/+) and PPARalpha(-/-) mice. Compared to PPARalpha(+/+) animals, acylcarnitine profiles of PPARalpha(-/-) mice revealed 2- to 4-fold accumulation of long-chain species in the plasma, whereas short-chain species were reduced by as much as 69% in plasma, liver, and skeletal muscle. These results reflect a metabolic bottleneck downstream of carnitine palmitoyltransferase-1, a mitochondrial enzyme that catalyzes the first step in beta-oxidation. Organic and amino acid profiles of starved PPARalpha(-/-) mice suggested compromised citric acid cycle flux, enhanced urea cycle activity, and increased amino acid catabolism. PPARalpha(-/-) mice had 40-50% lower plasma and tissue levels of free carnitine, corresponding with diminished hepatic expression of genes involved in carnitine biosynthesis and transport. One week of oral carnitine supplementation conferred partial metabolic recovery in the PPARalpha(-/-) mice. In summary, comprehensive metabolic profiling revealed novel biomarkers of defective fat oxidation, while also highlighting the potential value of supplemental carnitine as a therapy and diagnostic tool for metabolic disorders.

Hypothalamic CaMKK2 contributes to the regulation of energy balance.

Detailed knowledge of the pathways by which ghrelin and leptin signal to AMPK in hypothalamic neurons and lead to regulation of appetite and glucose homeostasis is central to the development of effective means to combat obesity. Here we identify CaMKK2 as a component of one of these pathways, show that it regulates hypothalamic production of the orexigenic hormone NPY, provide evidence that it functions as an AMPKalpha kinase in the hypothalamus, and demonstrate that it forms a unique signaling complex with AMPKalpha and beta. Acute pharmacologic inhibition of CaMKK2 in wild-type mice, but not CaMKK2 null mice, inhibits appetite and promotes weight loss consistent with decreased NPY and AgRP mRNAs. Moreover, the loss of CaMKK2 protects mice from high-fat diet-induced obesity, insulin resistance, and glucose intolerance. These data underscore the potential of targeting CaMKK2 as a therapeutic intervention.