Alterations In Substrate Metabolism Research Articles

High Salt Induced Alterations in Substrate Metabolism, Respiratory Activity, and Acidification in Isolated Proximal Tubules from Dahl Salt-Sensitive Rats

Rationale: The renal nephron actively reabsorbs nearly 99% of Na+ from the glomerular filtrate to maintain fluid and solute homeostasis, roughly 70% of which occurs in the proximal tubules (PT), where mitochondria consume a great amount of O2 for ATP production to meet the energy demand. However, the effect of a high salt diet upon the PT substrate metabolism and respiratory activity towards energy production and associated cellular acidification is not well-known. Method: To determine alterations in the PT substrate metabolism, respiratory activity, and acidification with a high salt diet, the PT of adult Dahl salt-sensitive (SS) rats were isolated by collagenase digestion and sieving with the rats fed either a 0.4% (LS) or a 4.0% (HS) NaCl diet for 7, 14 and 21 days (age-matched). Responses of the PT O2 consumption rate (OCR) and extracellular acidification rate (ECAR) were determined using a high-throughput Agilent Seahorse XF96 Extracellular Flux Analyzer and a modified mitochondrial stress test protocol, which combined a substrate addition step to the mitochondrial stress reagent addition steps. Basal OCR and ECAR were assessed with only amino acids (basic Seahorse medium) used as fuel for respiration. Subsequently, OCR and ECAR responses were determined by adding different circulating substrates followed by perturbations to the electron transport chain (ETC) in sequential order with oligomycin to inhibit ATP synthase, FCCP to uncouple oxidative phosphorylation, and rotenone + antimycin A to inhibit complexes I and III of the ETC. From these measurements, different OCR and ECAR parameters were derived for each substrate and each salt load condition. Results: The OCR data show that the PT of SS rats preferred to use lactate, glutamine, and palmitate for ATP production under the LS diet. However, the HS diet resulted in significantly reduced OCR when supplied with the same substrates. Interestingly, the basal OCR which occurred with amino acids as metabolic substrates was increased in the PT obtained from HS fed SS rats starting on day 7. These alterations in substrate metabolism were also apparent from the same parametric analysis of the ECAR data. An increased mitochondrial proton leak induced respiration was also deduced form both OCR and ECAR data under the HS diet. Since it is known that uncoupling proteins (UCP) and ADP/ATP translocase (ANT) enhance proton leak, gene expression was quantified from the isolated PT segments. Increased Ucp2 gene expression was found in response to the HS diet (days 7, 14, 21) compared to the LS fed SS rats but no changes were observed in the expression of Slc25A4 (ANT1) or Slc25A5 (ANT2). Summary: HS diet resulted in significant metabolic changes in the PT segments, including substrate metabolism, respiratory activity, and cellular acidification. HS diet also increased PT basal respiration and proton leak, which was associated with an increase of Ucp2 gene expression. Considering the increased ATP demand in the PT segments with a HS diet, these changes would result in increased O2 consumption and increased reactive oxygen species production. Together with the physiological changes on renal hemodynamics that we have observed, we propose that the observed metabolomic changes on the PT upon HS diet contribute to the onset of associated regional ischemia, tissue inflammation, and renal injury observed in hypertensive SS rats. NIH R01-HL151587. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Impaired cardiac glycolysis and glycogen depletion are linked to poor myocardial outcomes in juvenile male swine with metabolic syndrome and ischemia.

Obesity continues to rise in the juveniles and obese children are more likely to develop metabolic syndrome (MetS) and related cardiovascular disease. Unfortunately, effective prevention and long-term treatment options remain limited. We determined the juvenile cardiac response to MetS in a swine model. Juvenile male swine were fed either an obesogenic diet, to induce MetS, or a lean diet, as a control (LD). Myocardial ischemia was induced with surgically placed ameroid constrictor on the left circumflex artery. Physiological data were recorded and at 22 weeks of age the animals underwent a terminal harvest procedure and myocardial tissue was extracted for total metabolic and proteomic LC/MS-MS, RNA-seq analysis, and data underwent nonnegative matrix factorization for metabolic signatures. Significantly altered in MetS versus. LD were the glycolysis-related metabolites and enzymes. In MetS compared with LD Glycogen synthase 1 (GYS1)-glycogen phosphorylases (PYGM/PYGL) expression disbalance resulted in a loss of myocardial glycogen. Our findings are consistent with the concept that transcriptionally driven myocardial changes in glycogen and glucose metabolism-related enzymes lead to a deficiency of their metabolite products in MetS. This abnormal energy metabolism provides insight into the pathogenesis of the juvenile heart in MetS. This study reveals that MetS and ischemia diminishes ATP availability in the myocardium via altering the glucose-G6P-pyruvate axis at the level of metabolites and gene expression of related enzymes. The observed severe glycogen depletion in MetS coincides with disbalance in expression of GYS1 and both PYGM and PYGL. This altered energy substrate metabolism is a potential target of pharmacological agents for improving juvenile myocardial function in MetS and ischemia.

Extracellular flux analysis in intact cardiac tissue slices-A novel tool to investigate cardiac substrate metabolism in mouse myocardium.

Cardiac pathologies are accompanied by alterations in substrate metabolism, and extracellular flux analysis is a standard tool to investigate metabolic disturbances, especially in immortalized cell lines. However, preparations of primary cells, such as adult cardiomyocytes require enzymatic dissociation and cultivation affecting metabolism. Therefore, we developed a flux analyzer-based method for the assessment of substrate metabolism in intact vibratome-sliced mouse heart tissue. Oxygen consumption rates were determined using a Seahorse XFe24-analyzer and "islet capture plates." We demonstrate that tissue slices are suitable for extracellular flux analysis and metabolize both free fatty acids (FFA) and glucose/glutamine. Functional integrity of tissue slices was proven by optical mapping-based assessment of action potentials. In a proof-of-principle approach, the sensitivity of the method was tested by analyzing substrate metabolism in the remote myocardium after myocardial infarction (I/R). Here, I/R increased uncoupled OCR compared with sham animals indicating a stimulated metabolic capacity. This increase was caused by a higher glucose/glutamine metabolism, whereas FFA oxidation was unchanged. In conclusion, we describe a novel method to analyze cardiac substrate metabolism in intact cardiac tissue slices by extracellular flux analysis. The proof-of-principle experiment demonstrated that this approach has a sensitivity allowing the investigation of pathophysiologically relevant disturbances in cardiac substrate metabolism.

The effects of caloric restriction on adipose tissue and metabolic health are sex- and age-dependent.

Caloric restriction (CR) reduces the risk of age-related diseases in numerous species, including humans. CR's metabolic effects, including decreased adiposity and improved insulin sensitivity, are important for its broader health benefits; however, the extent and basis of sex differences in CR's health benefits are unknown. We found that 30% CR in young (3-month-old) male mice decreased fat mass and improved glucose tolerance and insulin sensitivity, whereas these effects were blunted or absent in young females. Females' resistance to fat loss was associated with decreased lipolysis, energy expenditure and fatty acid oxidation, and increased postprandial lipogenesis, compared to males. The sex differences in glucose homeostasis were not associated with differential glucose uptake but with altered hepatic ceramide content and substrate metabolism: compared to CR males, CR females had lower TCA cycle activity and higher blood ketone concentrations, a marker of hepatic acetyl-CoA content. This suggests that males use hepatic acetyl-CoA for the TCA cycle whereas in females it accumulates, stimulating gluconeogenesis and limiting hypoglycaemia during CR. In aged mice (18-months old), when females are anoestrus, CR decreased fat mass and improved glucose homeostasis similarly in both sexes. Finally, in a cohort of overweight and obese humans, CR-induced fat loss was also sex- and age-dependent: younger females (<45 years) resisted fat loss compared to younger males while in older subjects (>45 years) this sex difference was absent. Collectively, these studies identify age-dependent sex differences in the metabolic effects of CR and highlight adipose tissue, the liver and oestrogen as key determinants of CR's metabolic benefits. These findings have important implications for understanding the interplay between diet and health, and for maximising the benefits of CR in humans.

PHOSPHORYLATION OF ULK1 AT S555 IS REQUIRED FOR METABOLIC ADAPTATIONS TO CALORIC RESTRICTION

Abstract Unc-51 Like Autophagy Activating Kinase 1 (Ulk1) is responsible for initiating selective degradation of damaged/dysfunctional mitochondria (mitophagy) once phosphorylated at S555 in response to energetic stress. Mitophagy is integral for mitochondrial health and Ulk1 has been implicated to be important for metabolic adaptation to exercise. Caloric restriction (CR), which extends lifespan and healthspan, has profound metabolic benefits, including improved mitochondrial health. However, the contribution of Ulk1 in adaptation to CR is unknown. To decipher a functional role of Ulk1(S555) in adaptations to CR we used CRISPR-Cas9 generated, loss-of-function Ulk1(S555A) mice, in which Ulk1 cannot be phosphorylated at S555. 6-month-old, male and female homozygous Ulk1(S555A) mice and C57BL6/J (wild type, WT) mice were placed on a 40% CR diet for 8 weeks. Body mass in both male and female Ulk1(S555A) and WT mice was reduced with CR (p &amp;lt; 0.001), however female Ulk1(S555A) were heavier than their WT counterparts (p=0.02). Via nuclear magnetic resonance (NMR), male and female Ulk1(S555A) mice did not lose fat mass during CR. In addition, periovarian (female) and epididymal (male) fat mass was greater in Ulk1(S555A) compared to WT mice post-CR (p &amp;lt; 0.001). Furthermore, fasting blood glucose increased in male and female Ulk1(S555A) post-CR (p &amp;lt; 0.0001), suggesting altered substrate metabolism. In support of this notion, glucose oxidation in both quadriceps muscle and liver of male mice increased in WT following CR but not in Ulk1(S555A) mice (interaction effect p&amp;lt; 0.002). In sum, these data suggest that phosphorylation of Ulk1 at S555 is required for metabolic adaptations to CR.

Single amino acid variations drive functional divergence of cytochrome P450s in Helicoverpa species

Divergence of gene function is a hallmark of evolution, but assessing such divergence in one species or between species requires information on functional alterations of the alleles and homologs. Here, we explore the functional divergence of two paralogs, CYP6AE19 and CYP6AE20, from Helicoverpa armigera, and two close orthologs, CYP6B8 and CYP6B7, from two related species (Helicoverpa zea and H. armigera); although there is high sequence identity within each pair of enzymes, the latter P450 of each pair has lost metabolic competence towards the plant allelochemical xanthotoxin. Multiple chimeric and single/double site mutants were created by exchanging the diverse substrate recognition sites (SRSs) and amino acids within each pair of P450s. Heterologous expression in Sf9 cells and in vitro metabolism studies showed that the exchange of SRS4 swapped the activity of CYP6AE19 and CYP6AE20, and subsequent site-directed mutagenesis demonstrated that the CYP6AE20 V318M substitution causes a gain-of-function towards xanthotoxin. Meanwhile, a single amino acid substitution (L489P) in SRS6 was found to swap activity between the CYP6B orthologs. Sequence alignments of CYP6AE paralogs and all reported insect xanthotoxin-metabolizing P450s suggest M318 and P489 are essential for the catalytic activities of CYP6AE paralogs and CYP6B orthologs, respectively, but P450s in different subfamilies may have different mechanisms towards the same substrate. Our findings demonstrate that a single amino acid substitution can suffice to alter substrate metabolism and this functional divergence resulting from natural mutations will help to further our understanding of the process of natural selection of P450 genes and their role in insect-host plant interactions.

Acute Ingestion of Ketone Monoesters and Precursors Do Not Enhance Endurance Exercise Performance: A Systematic Review and Meta-Analysis.

There has been much consideration over whether exogenous ketone bodies have the capacity to enhance exercise performance through mechanisms such as altered substrate metabolism, accelerated recovery, or neurocognitive improvements. This systematic review aimed to determine the effects of both ketone precursors and monoesters on endurance exercise performance. A systematic search was conducted in PubMed, SPORTDiscus, and CINAHL for randomized controlled trials investigating endurance performance outcomes in response to ingestion of a ketone supplement compared to a nutritive or nonnutritive control in humans. A meta-analysis was performed to determine the standardized mean difference between interventions using a random-effects model. Hedge's g and 95% confidence intervals (CI) were reported. The search yielded 569 articles, of which eight were included in this review (80 participants; 77 men and three women). When comparing endurance performance among all studies, no significant differences were found between ketone and control trials (Hedges g = 0.136; 95% CI [-0.195, 0.467]; p = .419). Subanalyses based on type of endurance tests showed no significant differences in time to exhaustion (Hedge's g = -0.002; 95% CI [-0.312, 0.308]; p = .989) or time trial (Hedge's g = 0.057; 95% CI [-0.282, 0.395]; p = .744) values. Based on these findings, exogenous ketone precursors and monoesters do not exert significant improvements on endurance exercise performance. While all studies reported an increase in blood ketone concentrations after ingestion, ketone monoesters appear to be more effective at raising concentrations than precursors.

Human Induced Pluripotent Stem Cell Modelling for Diabetic Cardiomyopathy and its Susceptibility to SARS-CoV2 myocardial damage

For decades, it has been well known that patients with diabetes mellitus can develop ventricular dysfunction, even in the absence of coronary artery disease. The condition is commonly referred to as diabetic cardiomyopathy and is considered a cardiac muscle disorder due to the metabolic consequences of diabetes mellitus. It is characterized in the early stages by ventricular hypertrophy and diastolic dysfunction, and in later stages by systolic dysfunction that progresses to decompensated heart failure, resulting in morbidities and mortality. The pathogenesis of diabetic cardiomyopathy is complex and multifactorial. Mechanisms that include impaired calcium handling, up-regulated renin-angiotensin system, increased oxidative stress, altered substrate metabolism, and mitochondrial dysfunction have been implicated. In the COVID-19 pandemic, patients with diabetes mellitus infected with SARS-CoV-2 have a poorer prognosis including mortality. In this talk, I shall share our recent research findings using human induced pluripotent stem cell technology to identify potential mechanistic pathway related diabetic cardiomyopathy, and the direct therapeutic effects of SGLT inhibitors in diabetic cardiomyopathy, and the pathogenic link between SARS-CoV-2 infection and direct myocardial damage. Furthermore, our cardiac magnetic resonance imaging data has shown that patients with diabetes and impaired left ventricular ejection fraction, dapagliflozin alleviates cardiomyopathic changes.

Modelling Metabolic Shifts during Cardiomyocyte Differentiation, Iron Deficiency and Transferrin Rescue Using Human Pluripotent Stem Cells.

Cardiomyocytes rely on specialised metabolism to meet the high energy demand of the heart. During heart development, metabolism matures and shifts from the predominant utilisation of glycolysis and glutamine oxidation towards lactate and fatty acid oxidation. Iron deficiency (ID) leads to cellular metabolism perturbations. However, the exact alterations in substrate metabolism during ID are poorly defined. Using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM), the present study investigated changes in major metabolic substrate utilisation in the context of ID or upon transferrin rescue. Typically, during hiPSC-CM differentiation, the greatest increase in total metabolic output and rate was seen in fatty acid metabolism. When ID was induced, hiPSC-CMs displayed increased reliance on glycolytic metabolism, and six TCA cycle, five amino acid, and four fatty acid substrates were significantly impaired. Transferrin rescue was able to improve TCA cycle substrate metabolism, but the amino acid and fatty acid metabolism remained perturbed. Replenishing iron stores partially reverses the adverse metabolic changes that occur during ID. Understanding the changes in metabolic substrate utilisation and their modification may provide potential for discovery of new biomarkers and therapeutic targets in cardiovascular diseases.

Physiological responses to acute fasting: implications for intermittent fasting programs.

Intermittent fasting (IF) is a dietary strategy that involves alternating periods of abstention from calorie consumption with periods of ad libitum food intake. There is significant interest in the body of literature describing longitudinal adaptations to IF. Less attention has been given to the acute physiological responses that occur during the fasting durations that are commonly employed by IF practitioners. Thus, the purpose of this review was to examine the physiological responses - including alterations in substrate metabolism, systemic hormones, and autophagy - that occur throughout an acute fast. Literature searches were performed to locate relevant research describing physiological responses to acute fasting and short-term starvation. A single fast demonstrated the ability to alter glucose and lipid metabolism within the initial 24 hours, but variations in protein metabolism appeared to be minimal within this time frame. The ability of an acute fast to elicit significant increases in autophagy is still unknown. The information summarized in this review can be used to help contextualize existing research and better inform development of future IF interventions.

Mass recovery following caloric restriction reverses lipolysis and proteolysis, but not gluconeogenesis, in insulin resistant OLETF rats

Caloric restriction (CR) is one of the most important behavioral interventions to reduce excessive abdominal adiposity, which is a risk factor for the development of insulin resistance. Previous metabolomics studies have characterized substrate metabolism during healthy conditions; however, the effects of CR and subsequent mass recovery on shifts in substrate metabolism during insulin resistance (IR) have not been widely investigated. To assess the effects of acute CR and the subsequent mass recovery on shifts in substrate metabolism, a cohort of 15-week old Long Evans Tokushima Otsuka (LETO) and Otsuka Long Evans Tokushima Fatty (OLETF) rats were calorie restricted (CR: 50% × 10 days) with or without partial body mass recovery (PR; 73% x 7 days), along with their respective ad libitum controls. End-of-study plasma samples were analyzed for primary carbon metabolites by gas chromatography (GC) time-of-flight (TOF) mass spectrometry (MS) data acquisition. Data analysis included PCA, Pearson correlation vs previously reported variables (adipose and body masses, and insulin resistance index, IRI), and metabolomics maps (MetaMapp) generated for the most significant group comparisons. All treatments elicited a significant group differentiation in at least one principal component. CR improved TCA cycle in OLETF, and increased lipolysis and proteolysis. These changes were reversed after PR except for gluconeogenesis. Plasma lipid concentrations were inversely correlated to IRI in LETO, but not OLETF. These shifts in substrate metabolism suggest that the CR-induced decreases in adipose may not be sufficient to more permanently alter substrate metabolism to improve IR status during metabolic syndrome.

Effect of elevated plasma ketones on cardiac efficiency

BackgroundThe mechanism(s) responsible for the cardiac benefits of SGLT2 inhibitors remain unknown. Specific AimTo examine the effect of increased plasma ketone concentration (with infusion of beta-hydroxybutyrate [BOHB]) on LV function and myocardial glucose uptake. MethodsTwo groups (6 per group) of T2DM with HFrEF (<45%) were studied. Group I (Age=59; BMI=31 kg/m2; A1c = 7.2%; EF=41%) received in random order a 6-hour BOHB infusion (Prime =1.5 mg/kg.min, then 0.75 mg/kg.min) or 6-hour HCO3 infusion with matching volume (control). Group II (Age=56; BMI=34 kg/m2; A1c=7.2%; EF=38%) received a 3-hour BOHB infusion at a higher rate (Prime=4.0 mg/kg.min, then 2.0 mg/kg.min). A cardiac MRI was performed before and after each infusion. Additionally, Group I underwent a PET study with 18F-2-DOG and 15O. ResultsGroups I and II achieved plasma ketone levels of 1.4 and 2.5 mmol/L, respectively. In Group II, BOHB infusion significantly (P<0.01) increased CO and EF, whereas in Group I the increase in CO and EF tend toward significance (p=0.06), suggesting a dose-dependent response to the increase in plasma ketone concentration. NaHCO3 infusion had no effect on any cardiac indices (Fig.1). Myocardial blood flow increased significantly (P<0.01) in both Group I and II. Myocardial glucose uptake was not altered by BOHB infusion. ConclusionIn patients with T2DM and HFrEF, a physiologic increase in plasma ketone concentration significantly increased LV function and myocardial blood flow without affecting cardiac glucose metabolism. These results suggest that altered myocardial substrate metabolism can be employed therapeutically to improve cardiac function in HFrEF.

Metabolic effects of late dinner in healthy volunteers – a randomized crossover clinical trial

Context Consuming calories later in the day is associated with obesity and metabolic syndrome. We hypothesized that eating a late dinner alters substrate metabolism during sleep in a manner that promotes obesity. Objective The objective of this work is to examine the impact of late dinner on nocturnal metabolism in healthy volunteers. Design and setting This is a randomized crossover trial of late dinner (LD, 22:00) vs routine dinner (RD, 18:00), with a fixed sleep period (23:00-07:00) in a laboratory setting. Participants Participants comprised 20 healthy volunteers (10 male, 10 female), age 26.0 ± 0.6 years, body mass index 23.2 ± 0.7 kg/m2, accustomed to a bedtime between 22:00 and 01:00. Interventions An isocaloric macronutrient diet was administered on both visits. Dinner (35% daily kcal, 50% carbohydrate, 35% fat) with an oral lipid tracer ([2H31] palmitate, 15 mg/kg) was given at 18:00 with RD and 22:00 with LD. Main outcome measures Measurements included nocturnal and next-morning hourly plasma glucose, insulin, triglycerides, free fatty acids (FFAs), cortisol, dietary fatty acid oxidation, and overnight polysomnography. Results LD caused a 4-hour shift in the postprandial period, overlapping with the sleep phase. Independent of this shift, the postprandial period following LD was characterized by higher glucose, a triglyceride peak delay, and lower FFA and dietary fatty acid oxidation. LD did not affect sleep architecture, but increased plasma cortisol. These metabolic changes were most pronounced in habitual earlier sleepers determined by actigraphy monitoring. Conclusion LD induces nocturnal glucose intolerance, and reduces fatty acid oxidation and mobilization, particularly in earlier sleepers. These effects might promote obesity if they recur chronically.

Erythrocyte Long-Chain ω-3 Fatty Acids Are Positively Associated with Lean Mass and Grip Strength in Women with Recent Diagnoses of Breast Cancer.

Sarcopenia may hasten the risk of mortality in women with breast cancer. Long-chain omega-3 (n-3) polyunsaturated fatty acids (LCn-3PUFAs) may favor muscle mass which, in turn, could enhance resilience of cancer patients toward cancer treatment. The objective of this study was to measure the relation of erythrocyte LCn-3PUFA concentrations with lean mass, grip strength, and postprandial energy metabolism in women with newly diagnosed breast cancer. This cross-sectional analysis evaluated women (n=150) ages 65 y and younger who were recently diagnosed with breast cancer (stages I-III). Erythrocyte LCn-3PUFA composition was measured using GC. Body composition was measured by DXA. Grip strength was assessed at the same visit. Postprandial energy metabolism was measured for 7.5 h after the consumption of a high-calorie, high-saturated-fat test meal using indirect calorimetry. Associations of fatty acids with outcomes were analyzed using multiple linear regression models and linear mixed-effects models. The ω-3 index, a measurement of LCn-3PUFA status, was positively associated with appendicular lean mass (ALM)/BMI (β = 0.015, P=0.01) and grip strength (β = 0.757, P=0.04) after adjusting data for age and cancer stage. However, when cardiorespiratory fitness was also included in the analyses, these relations were no longer significant (P>0.08). After a test meal, a higher ω-3 index was associated with a less steep rise in fat oxidation (P=0.02) and a steeper decline in glucose (P=0.01) when adjusting for age, BMI, cancer stage, and cardiorespiratory fitness. The ω-3 index was positively associated with ALM/BMI and grip strength in women newly diagnosed with breast cancer and was associated with altered postprandial substrate metabolism. These findings warrant further studies to determine whether enriching the diet with LCn-3PUFAs during and after cancer treatments is causally linked with better muscle health and metabolic outcomes in breast cancer survivors.

Nicotinamide riboside supplementation does not alter whole-body or skeletal muscle metabolic responses to a single bout of endurance exercise.

Acute nicotinamide riboside (NR) supplementation does not alter substrate metabolism at rest, during or in recovery from endurance exercise. NR does not alter NAD+ -sensitive signalling pathways in human skeletal muscle. NR supplementation and acute exercise influence the NAD+ metabolome. Oral supplementation of the NAD+ precursor nicotinamide riboside (NR) has been reported to alter metabolism alongside increasing sirtuin (SIRT) signalling and mitochondrial biogenesis in rodent skeletal muscle. However, whether NR supplementation can elicit a similar response in human skeletal muscle is unclear. This study assessed the effect of 7-day NR supplementation on whole-body metabolism and exercise-induced mitochondrial biogenic signalling in skeletal muscle. Eight male participants (age: 23±4years, 46.5±4.4mlkg-1 min-1 ) received 1week of NR or cellulose placebo (PLA) supplementation (1000mgday-1 ). Muscle biopsies were collected from the medial vastus lateralis prior to supplementation and pre-, immediately post- and 3h post-exercise (1h of 60% Wmax cycling) performed following the supplementation period. There was no effect of NR supplementation on substrate utilisation at rest or during exercise or on skeletal muscle mitochondrial respiration. Global acetylation, auto-PARylation of poly ADP-ribose polymerase 1 (PARP1), acetylation of Tumour protein 53 (p53)Lys382 and Manganese superoxide dismutase (MnSOD)Lys122 were also unaffected by NR supplementation or exercise. NR supplementation did not increase skeletal muscle NAD+ concentration, but it did increase the concentration of deaminated NAD+ precursors nicotinic acid riboside (NAR) and nicotinic acid mononucleotide (NAM) and methylated nicotinamide breakdown products (Me2PY and Me4PY), demonstrating the skeletal muscle bioavailability of NR supplementation. In summary, 1week of NR supplementation does not alter whole-body metabolism or skeletal muscle signal transduction pathways implicated in the mitochondrial adaptation to endurance exercise.

Nutritional Requirements for Sustaining Health and Performance During Exposure to Extreme Environments.

Dietary guidelines are formulated to meet minimum nutrient requirements, which prevent deficiencies and maintain health, growth, development, and function. These guidelines can be inadequate and contribute to disrupted homeostasis, lean body mass loss, and deteriorated performance in individuals who are working long, arduous hours with limited access to food in environmentally challenging locations. Environmental extremes can elicit physiological adjustments that alone alter nutrition requirements by upregulating energy expenditure, altering substrate metabolism, and accelerating body water and muscle protein loss. The mechanisms by which the environment, including high-altitude, heat, and cold exposure, alters nutrition requirements have been studied extensively. This contemporary review discusses physiological adjustments to environmental extremes, particularly when those adjustments alter dietary requirements.

Metabolic Effects of Late Dinner in Healthy Volunteers-A Randomized Crossover Clinical Trial.

Consuming calories later in the day is associated with obesity and metabolic syndrome. We hypothesized that eating a late dinner alters substrate metabolism during sleep in a manner that promotes obesity. The objective of this work is to examine the impact of late dinner on nocturnal metabolism in healthy volunteers. This is a randomized crossover trial of late dinner (LD, 22:00) vs routine dinner (RD, 18:00), with a fixed sleep period (23:00-07:00) in a laboratory setting. Participants comprised 20 healthy volunteers (10 male, 10 female), age 26.0 ± 0.6 years, body mass index 23.2 ± 0.7 kg/m2, accustomed to a bedtime between 22:00 and 01:00. An isocaloric macronutrient diet was administered on both visits. Dinner (35% daily kcal, 50% carbohydrate, 35% fat) with an oral lipid tracer ([2H31] palmitate, 15 mg/kg) was given at 18:00 with RD and 22:00 with LD. Measurements included nocturnal and next-morning hourly plasma glucose, insulin, triglycerides, free fatty acids (FFAs), cortisol, dietary fatty acid oxidation, and overnight polysomnography. LD caused a 4-hour shift in the postprandial period, overlapping with the sleep phase. Independent of this shift, the postprandial period following LD was characterized by higher glucose, a triglyceride peak delay, and lower FFA and dietary fatty acid oxidation. LD did not affect sleep architecture, but increased plasma cortisol. These metabolic changes were most pronounced in habitual earlier sleepers determined by actigraphy monitoring. LD induces nocturnal glucose intolerance, and reduces fatty acid oxidation and mobilization, particularly in earlier sleepers. These effects might promote obesity if they recur chronically.

Early intervention exercise training does not delay prostate cancer progression in Pten−/− mice

There is convincing evidence that men with advanced prostate cancer experience improved quality of life as a result of exercise therapy, although there is limited preclinical, and no clinical, data to directly support the notion that exercise training improves prostate cancer prognosis or outcome. The aim of this study was to investigate the effect of regular exercise training on the early stages of prostate cancer progression, as well as assessing whether alterations to prostate cancer metabolism are induced by exercise. Mice with prostate-specific deletion of Pten (Pten-/- ) remained sedentary or underwent 6 weeks of endurance exercise training or high-intensity exercise training involving treadmill running. At the conclusion of the training period, the prostate lobes were excised. A portion of fresh tissue was used to assess glucose, glutamine, and fatty acid metabolism by radiometric techniques and a second portion was fixed for histopathology. Despite the implementation of an effective exercise regime, as confirmed by improvements in running capacity, neither prostate mass, cell proliferation or the incidence of high-grade prostate intraepithelial hyperplasia or noninvasive carcinoma in situ were significantly different between groups. Similarly, neither glucose uptake, oxidation and de novo lipogenesis, glutamine oxidation, or fatty acid uptake, oxidation and storage into various lipids were significantly different in prostate tissue obtained from untrained and exercise trained mice. These results show that 6 weeks of moderate or high-intensity exercise training does not alter substrate metabolism in the prostate or slow the progression of Pten-null prostate cancer. These results question whether exercise is a useful therapy to prevent or delay prostate cancer progression.

Hepatic proteome analysis reveals altered mitochondrial metabolism and suppressed acyl-CoA synthetase-1 in colon-26 tumor-induced cachexia.

Cachexia is a life-threatening complication of cancer traditionally characterized by weight loss and muscle dysfunction. Cachexia, however, is a systemic disease that also involves remodeling of nonmuscle organs. The liver exerts major control over systemic metabolism, yet its role in cancer cachexia is not well understood. To advance the understanding of how the liver contributes to cancer cachexia, we used quantitative proteomics and bioinformatics to identify hepatic pathways and cellular processes dysregulated in mice with moderate and severe colon-26 tumor-induced cachexia; ~300 differentially expressed proteins identified during the induction of moderate cachexia were also differentially regulated in the transition to severe cachexia. KEGG pathway enrichment revealed representation by oxidative phosphorylation, indicating altered hepatic mitochondrial function as a common feature across cachexia severity. Glycogen catabolism was also observed in cachexic livers along with decreased pyruvate dehydrogenase protein X component (Pdhx), increased lactate dehydrogenase A chain (Ldha), and increased lactate transporter Mct1. Together this suggests altered lactate metabolism and transport in cachexic livers, which may contribute to energetically inefficient interorgan lactate cycling. Acyl-CoA synthetase-1 (ACSL1), known for activating long-chain fatty acids, was decreased in moderate and severe cachexia based on LC-MS/MS analysis and immunoblotting. ACSL1 showed strong linear relationships with percent body weight change and muscle fiber size (R2 = 0.73-0.76, P < 0.01). Mitochondrial coupling efficiency, which is compromised in cachexic livers to potentially increase energy expenditure and weight loss, also showed a linear relationship with ACSL1. Findings suggest altered mitochondrial and substrate metabolism of the liver in cancer cachexia, and possible hepatic targets for intervention.

Aspalathin, a natural product with the potential to reverse hepatic insulin resistance by improving energy metabolism and mitochondrial respiration.

Aspalathin is a rooibos flavonoid with established blood glucose lowering properties, however, its efficacy to moderate complications associated with hepatic insulin resistance is unknown. To study such effects, C3A liver cells exposed to palmitate were used as a model of hepatic insulin resistance. These hepatocytes displayed impaired substrate metabolism, including reduced glucose transport and free fatty acid uptake. These defects included impaired insulin signaling, evident through reduced phosphatidylinositol-4,5-bisphosphate 3-kinase/ protein kinase B (PI3K/AKT) protein expression, and mitochondrial dysfunction, depicted by a lower mitochondrial respiration rate. Aspalathin was able to ameliorate these defects by correcting altered substrate metabolism, improving insulin signaling and mitochondrial bioenergetics. Activation of 5ʹ-adenosine monophosphate-activated protein kinase (AMPK) may be a plausible mechanism by which aspalathin increases hepatic energy expenditure. Overall, these results encourage further studies assessing the potential use of aspalathin as a nutraceutical to improve hepatocellular energy expenditure, and reverse metabolic disease-associated complications.