Postabsorptive and postprandial myofibrillar protein synthesis rates at rest and after resistance exercise in women with postmenopause

Feeding and resistance exercise stimulate myofibrillar protein synthesis (MPS) rates in healthy adults. This anabolic characterization of "healthy adults" has been namely focused on males. Therefore, the purpose of this study was to examine the temporal responses of MPS and anabolic signaling to resistance exercise alone or combined with the ingestion of protein in postmenopausal females and compare postabsorptive rates with young females. Sixteen females [60 ± 7 yr; body mass index (BMI) = 26 ± 12 kg·m-2] completed an acute bout of unilateral resistance exercise before consuming either: a fortified whey protein supplement (WHEY) or water. Participants received primed continuous infusions of L-[ring-13C6]phenylalanine with bilateral muscle biopsies before and after treatment ingestion at 2 h and 4 h in nonexercised and exercised legs. Resistance exercise transiently increased MPS above baseline at 0-2 h in the water condition (P = 0.007). Feeding after resistance exercise resulted in a late phase (2-4 h) increase in MPS in the WHEY condition (P = 0.005). In both conditions, resistance exercise did not enhance the cumulative (0-4 h) MPS response. In the nonexercised leg, MPS did not differ at 0-2 h, 2-4 h, or 0-4 h of the measurement periods (all, P > 0.05). Likewise, there were no changes in the phosphorylation of p70S6K, AMPKα, or total and phosphorylated yes-associated protein on Ser127. Finally, postabsorptive MPS was lower in premenopausal versus postmenopausal females (P = 0.023). Our results demonstrate that resistance exercise-induced changes in MPS are temporally regulated, but do not result in greater cumulative (0-4 h) MPS in postmenopausal women.NEW & NOTEWORTHY An adequate quality and quantity of skeletal muscle is relevant to support physical performance and metabolic health. Muscle protein synthesis (MPS) is an established remodeling marker, which can be hypertrophic or nonhypertrophic. Importantly, protein ingestion and resistance exercise are two strategies that support healthy muscle by stimulating MPS. Our study shows postmenopause modulates baseline MPS that may diminish the MPS response to the fundamental anabolic stimuli of protein ingestion and resistance exercise in older females.

Acute Microbial Protease Supplementation Increases Net Postprandial Plasma Amino Acid Concentrations After Pea Protein Ingestion in Healthy Adults: A Randomized, Double-Blind, Placebo-Controlled Trial

BACKGROUND

Digestibility is a primary factor in determining the quality of dietary protein. Microbial protease supplementation may be a strategy for improving protein digestion and subsequent postprandial plasma amino acid availability.

OBJECTIVES

To assess the effect of co-ingesting a microbial protease mixture with pea protein on postprandial plasma amino acid concentrations.

DESIGN

A mixture of 3 microbial protease preparations (P3) was tested for proteolytic efficacy in an in vitro static simulation of gastrointestinal digestion. Subsequently, in a randomized, double-blind, placebo-controlled crossover trial, 24 healthy adults (27 ± 4 y; 12 females, 12 males) ingested 25 g pea protein isolate (20 g protein, 2.2 g fat) with either P3 or maltodextrin placebo (PLA). Blood samples were collected at baseline and throughout a 0‒5 h postprandial period and both the early (0-2 h) iAUC and total (0-5 h) iAUC were examined.

RESULTS

Plasma glucose concentrations decreased in both conditions (P < 0.001), with higher concentrations after P3 ingestion compared with PLA (P < 0.001). Plasma insulin concentrations increased for both conditions (P < 0.001) with no difference between conditions (P = 0.331). Plasma total amino acid (TAA) concentrations increased over time (P < 0.001) with higher concentrations observed for P3 compared with PLA (P = 0.010) during the 0‒5 h period. There was a trend for elevated essential amino acid (EAA) concentrations for P3 compared with PLA (P = 0.099) during the 0‒5 h postprandial period but not for leucine (P = 0.282) or branched-chain amino acids (BCAA, P = 0.410). The early net exposure (0‒2 h iAUC) to amino acids (leucine, BCAA, EAA, and TAA) was higher for P3 compared with PLA (all, P < 0.05).

CONCLUSIONS

Microbial protease co-ingestion increases plasma TAA concentrations (0-5 h) and leucine, BCAA, EAA, and TAA availability in the early postprandial period (0‒2 h) compared with ingesting pea protein with placebo in healthy adults.

Ovarian antral follicles metabolize imidacloprid in vitro

Neonicotinoid insecticides are synthetic nicotine derivatives that have high affinity for invertebrate nicotine receptors and low affinity for mammalian nicotine receptors. However, imidacloprid (IMI), the most commonly used neonicotinoid, can be bioactivated by the liver in mammals to desnitro-imidacloprid, an intermediate metabolite that effectively binds and activates mammalian receptors. However, it is not known if other tissues such as the ovaries can metabolize IMI. Thus, the present study tested the hypothesis that ovarian antral follicles metabolize and bioactivate IMI. Antral follicles were dissected from the ovaries of CD-1 mice and cultured in media containing dimethyl sulfoxide or IMI (0.2-200 µg/ml) for 48 and 96 h. Media were subjected to liquid chromatography-mass spectrometry for detection of phase I IMI metabolites. Follicles from the cultures were used for gene expression analysis of metabolic enzymes associated with IMI metabolism. All IMI metabolites were detected at 48 and 96 h. Oxidized IMI intermediates were detected in media from cultured follicles, but not environmental controls. Reduced IMI intermediates were detected in media from cultured follicles and the environmental controls. At 48 h, IMI did not affect expression of any metabolic enzymes compared with control. At 96 h, IMI induced Cyp2e1 and Cyp4f18 compared with control. These data indicate that mouse ovarian follicles metabolize IMI and that IMI induces ovarian Cyp expression over time.

Underpinning the Food Matrix Regulation of Postexercise Myofibrillar Protein Synthesis by Comparing Salmon Ingestion With the Sum of Its Isolated Nutrients in Healthy Young Adults

BACKGROUND

Protein is most commonly consumed as whole foods as opposed to single nutrients. However, the food matrix regulation of the postprandial muscle protein synthetic response has received little attention.

OBJECTIVES

The purpose of this study was to assess the effects of eating salmon (SAL) and of ingesting the same nutrients as an isolated mixture of crystalline amino acids and fish oil (ISO) on the stimulation of postexercise myofibrillar protein synthesis (MPS) and whole-body leucine oxidation rates in healthy young adults.

METHODS

Ten recreationally active adults (24 ± 4 y; 5 men, 5 women) performed an acute bout of resistance exercise, followed by the ingestion of SAL or ISO in a crossover fashion. Blood, breath, and muscle biopsies were collected at rest and after exercise during primed continuous infusions of L-[ring-2H5]phenylalanine and L-[1-13C]leucine. All data are presented as means ± SD and/or mean differences (95% CIs).

RESULTS

Postprandial essential amino acid (EAA) concentrations peaked earlier (P = 0.024) in the ISO group than those in the SAL group. Postprandial leucine oxidation rates increased over time (P < 0.001) and peaked earlier in the ISO group (1.239 ± 0.321 nmol/kg/min; 63 ± 25 min) than those in the SAL group (1.230 ± 0.561 nmol/kg/min; 105 ± 20 min; P = 0.003). MPS rates for SAL (0.056 ± 0.022 %/h; P = 0.001) and ISO (0.046 ± 0.025 %/h; P = 0.025) were greater than the basal rates (0.020 ± 0.011 %/h) during the 0- to 5-h recovery period, with no differences between conditions (P = 0.308).

CONCLUSION

We showed that the postexercise ingestion of SAL or ISO stimulate postexercise MPS rates with no differences between the conditions. Thus, our results indicate that ingesting protein from SAL as a whole-food matrix is similarly anabolic to ISO in healthy young adults. This trial was registered at www.

CLINICALTRIALS

gov as NCT03870165.

Canine urinary lactate and cortisol metabolites in hypercortisolism, nonadrenal disease, congestive heart failure, and health

Spontaneous hypercortisolism (HC) is a common endocrine disease of senior dogs, often overlapping in selected clinical signs and hematologic and blood biochemical abnormalities with nonadrenal diseases (NADs). HC and NAD could differentially affect cortisol metabolism, which is a complex 10-enzymatic pathway process. HC might also affect blood and urine lactate levels through its effects on mitochondrial function. We aimed to differentiate between HC and NAD via a urinary cortisol metabolites and lactate panel. We prospectively recruited 7 healthy dogs and 18 dogs with HC, 15 with congestive heart failure (CHF), and 9 with NAD. We analyzed urine by gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry. We normalized urinary lactate and cortisol metabolites to urine creatinine concentration, and then compared groups using a linear-mixed model and principal component (PC) analysis. A machine-learning classification algorithm generated a decision tree (DT) model for predicting HC. The least-squares means of normalized urinary 6β-hydroxycortisol and PC1 of the HC and CHF groups were higher than those of the healthy and NAD groups (p = 0.05). Creatinine-normalized urinary 6β-hydroxycortisol had better sensitivity (Se, 0.78; 95% CI: 0.55-0.91), specificity (Sp, 0.89; 95% CI: 0.57-0.99), and a likelihood ratio (LR; 7), than the Se (0.72; 95% CI: 0.49-0.88), Sp (0.89; 95% CI: 0.57-0.99), and LR (6.5) of PC1 for distinguishing HC from NAD. Lactate and dihydrocortisone had the highest decreasing node-weighted impurity value and were considered the most important features in the DT model; dihydrocortisol had no role in determining whether a dog had HC.

Pharmacokinetic profiles of three dose rates of morphine sulfate following single intravenous, intramuscular, and subcutaneous administration in the goat

This study aimed to evaluate pharmacokinetic profiles of morphine in goats following a single dose administered intravenously, intramuscularly, or subcutaneously at 0.1 mg/kg, 0.25 mg/kg, and 0.4 mg/kg. Study population included eight healthy adult goats in a randomized cross-over study. Serial plasma samples were collected and morphine was quantified using high-performance liquid chromatography/mass spectrometry. Data fit a two-compartment model following intravenous administration and a non-compartmental model following both intramuscular and subcutaneous administration. Plasma elimination half-life was 2.88 ± 1.13 h (0.1 mg/kg), 2.30 ± 0.49 h (0.25 mg/kg), and 2.67 ± 0.82 h (0.4 mg/kg) following IV morphine. Intramuscular Cmax values were 13.4 ± 2.77 ng/ml (0.1 mg/kg), 34 ± 11.50 ng/ml (0.25 mg/kg), and 68.9 ± 24.5 ng/ml (0.4 mg/kg). Intramuscular Tmax f(h) or IM dosing (in hrs) was 0.19 ± 0.14 (0.1 mg/kg), 0.24 ± 0.24 (0.25 mg/kg), and 0.21 ± 0.24 (0.4 mg/kg). Subcutaneous Cmax values were 9.88 ± 3.31 ng/ml (0.1 mg/kg), 28.5 ± 11.6 ng/ml (0.25 mg/kg), and 39.4 ± 14.3 ng/ml (0.4 mg/kg). Subcutaneous Tmax (h) values for SC dosing were 0.36 ± 0.21 (0.1 mg/kg), 0.31 ± 0.17 (0.25 mg/kg), and 0.4 ± 0.13 (0.4 mg/kg). Intramuscular bioavailability values were 153.77 ± 12.60% (0.4 mg/kg), 104.8 ± 25.12% (0.25 mg/kg), and 100.7 ± 29.57% (0.1 mg/kg). Subcutaneous bioavailability values were 130.58 ± 19.07% (0.4 mg/kg), 116.6 ± 27.03% (0.25 mg/kg), and 111.6 ± 23.24% (0.1 mg/kg). No adverse effects were observed. Assuming plasma concentration required to induce analgesia is 16 ± 9 ng/ml in goats, as demonstrated in humans, it is suggested to administer morphine intramuscularly at 0.4 mg/kg every 3-4 h or SC every 2-3 h. This is a speculative conclusion therefore further studies evaluating pharmacodynamics and plasma analgesic threshold in goats is recommended.

Why the Stall? Using metabolomics to define the lack of upstream movement of invasive bigheaded carp in the Illinois River

Bigheaded Carp have spread throughout the Mississippi River basin since the 1970s. Little has stopped the spread as carp have the ability to pass through locks and dams, and they are currently approaching the Great Lakes. However, the location of the leading edge in the Illinois River has stalled for over a decade, even though there is no barrier preventing further advancement towards the Great Lakes. Defining why carp are not moving towards the Great Lakes is important for predicting why they might advance in the future. The aim of this study was to test the hypothesis that anthropogenic contaminants in the Illinois River may be playing a role in preventing further upstream movement of Bigheaded Carp. Ninety three livers were collected from carp at several locations between May and October of 2018. Liver samples were analyzed using gas chromatography-mass spectrometry in a targeted metabolite profiling approach. Livers from carp at the leading edge had differences in energy use and metabolism, and suppression of protective mechanisms relative to downstream fish; differences were consistent across time. This body of work provides evidence that water quality is linked to carp movement in the Illinois River. As water quality in this region continues to improve, consideration of this impact on carp spread is essential to protect the Great Lakes.

Dileucine ingestion is more effective than leucine in stimulating muscle protein turnover in young males: a double blind randomized controlled trial

Leucine is regarded as an anabolic trigger for the mTORC1 pathway and the stimulation muscle protein synthesis rates. More recently, there has been an interest in underpinning the relevance of BCAA-containing dipeptides and their intact absorption into circulation to regulate muscle anabolic responses. We investigated the effects of dileucine and leucine ingestion on postprandial muscle protein turnover. Ten healthy young men (age: 23±3 y) consumed either 2 g of leucine (LEU) or 2 g of dileucine (DILEU) in a randomized crossover design. The participants underwent repeated blood and muscle biopsy sampling during primed continuous infusions of L-[ring-¹³C₆]phenylalanine and L-[¹⁵N]phenylalanine to determine myofibrillar protein synthesis (MPS) and mixed muscle protein breakdown rates (MPB), respectively. LEU and DILEU similarly increased plasma leucine net area under the curve (AUC; P = 0.396). DILEU increased plasma dileucine AUC to a greater extent than LEU (P = 0.013). Phosphorylation of Akt (P = 0.002), rpS6 (P <0.001) and p70S6K (P < 0.001) increased over time in both LEU and DILEU conditions. Phosphorylation of 4E-BP1 (P = 0.229) and eEF2 (P = 0.999) did not change over time irrespective of condition. Cumulative (0-180 min) MPS increased in DILEU (0.075±0.032 %⋅hour^-1), but not in LEU (0.047±0.029 %⋅hour^-1; P=0.023). MPB did not differ between LEU (0.043±0.030 %⋅h^-1) and DILEU conditions (0.051±0.027 %⋅hour^-1; P = 0.659). Our results showed that dileucine ingestion elevated plasma dileucine concentrations and muscle protein turnover by stimulating MPS in young men.

Early resistance training-mediated stimulation of daily muscle protein synthetic responses to higher habitual protein intake in middle-aged adults

KEY POINTS

The ingestion of protein potentiates the stimulation of myofibrillar protein synthesis rates after an acute bout of resistance exercise. Protein supplementation (eating above the protein Recommended Dietary Allowance) during resistance training has been shown to maximize lean mass and strength gains in healthy young and older adults. Here, contractile, oxidative, and structural protein synthesis were assessed in skeletal muscle in response to a moderate or higher protein diet during the early adaptive phase of resistance training in middle-aged adults. The stimulation of myofibrillar, mitochondrial or collagen protein synthesis rates during 0-3 weeks of resistance training is not further enhanced by a higher protein diet. These results show that moderate protein diets are sufficient to support the skeletal muscle adaptive response during the early phase of a resistance training programme.

ABSTRACT

Protein ingestion augments muscle protein synthesis (MPS) rates acutely after resistance exercise and can offset age-related loss in muscle mass. Skeletal muscle contains a variety of protein pools, such as myofibrillar (contractile), mitochondrial (substrate oxidation), and collagen (structural support) proteins, and the sensitivity to nutrition and exercise seems to be dependent on the major protein fraction studied. However, it is unknown how free-living conditions with high dietary protein density and habitual resistance exercise mediates muscle protein subfraction synthesis. Therefore, we investigated the effect of moderate (MOD: 1.06 ± 0.22 g kg^-1  day^-1 ) or high (HIGH: 1.55 ± 0.25 g kg^-1  day^-1 ) protein intake on daily MPS rates within the myofibrillar (MyoPS), mitochondrial (MitoPS) and collagen (CPS) protein fractions in middle-aged men and women (n = 20, 47 ± 1 years, BMI 28 ± 1 kg m^-2 ) during the early phase (0-3 weeks) of a dietary counselling-controlled resistance training programme. Participants were loaded with deuterated water, followed by daily maintenance doses throughout the intervention. Muscle biopsies were collected at baseline and after weeks 1, 2 and 3. MyoPS in the HIGH condition remained constant (P = 1.000), but MOD decreased over time (P = 0.023). MitoPS decreased after 0-3 weeks when compared to 0-1 week (P = 0.010) with no effects of protein intake (P = 0.827). A similar decline with no difference between groups (P = 0.323) was also observed for CPS (P = 0.007). Our results demonstrated that additional protein intake above moderate amounts does not potentiate the stimulation of longer-term MPS responses during the early stage of resistance training adaptations in middle-aged adults.

Impact of Weaning and Maternal Immune Activation on the Metabolism of Pigs

Weaning wields environmental, social, and nutritional stresses that are detectable in the blood metabolite levels of the offspring. Prenatal stress in the form of maternal immune activation (MIA) in response to infection, which is associated with health and behavior disorders, also elicits prolonged changes in blood and brain cytokine and metabolite levels of the offspring. The goal of this study was to investigate the effects of weaning and MIA on the offspring’s liver function to advance the understanding of the impact of stressors on peripheral and central nervous systems, physiology, and health. Gas chromatography–mass spectrometry analysis was used to compare the level of hepatic metabolites from 22-day-old pigs (n = 48) evenly distributed among weaning (nursed or weaned), viral MIA exposure (yes or no), and sexes. Weaning effects were detected on 38 metabolites at p-value < 0.05 (28 metabolites at FDR p-value < 0.05), and sex-dependent MIA effects were detected on 11 metabolites. Multiple intermediate and final products of the enriched (FDR p-value < 0.05) glycolysis and gluconeogenesis and pentose phosphate pathways were over-abundant in nursed relative to weaned pigs. The enriched pathways confirm the impact of weaning on hepatic metabolic shift, oxidative stress, and inflammation. Higher levels of the glucogenic amino acid histidine are observed in pigs exposed to MIA relative to controls, suggesting that the role of this metabolite in modulating inflammation may supersede the role of this amino acid as an energy source. The lower levels of cholesterol detected in MIA pigs are consistent with hypocholesterolemia profiles detected in individuals with MIA-related behavior disorders. Our findings underline the impact of weaning and MIA stressors on hepatic metabolites that can influence peripheral and central nervous system metabolic products associated with health and behavior disorders.

The association of Chlamydia trachomatis and Mycoplasma genitalium infection with the vaginal metabolome

Chlamydia trachomatis (CT) and Mycoplasma genitalium (MG) are two highly prevalent bacterial sexually transmitted infections (STIs) with a significant rate of co-infection in some populations. Vaginal metabolites are influenced by resident vaginal microbiota, affect susceptibility to sexually transmitted infections (STIs), and may impact local inflammation and patient symptoms. Examining the vaginal metabolome in the context of CT mono (CT+) and CT/MG co-infection (CT+/MG+) may identify biomarkers for infection or provide new insights into disease etiology and pathogenesis. Yet, the vaginal metabolome in the setting of CT infection is understudied and the composition of the vaginal metabolome in CT/MG co-infected women is unknown. Therefore, in this analysis, we used an untargeted metabolomic approach combined with 16S rRNA gene amplicon sequencing to characterize the vaginal microbiota and metabolomes of CT+, CT+/MG+, and uninfected women. We found that CT+ and CT+/MG+ women had distinct vaginal metabolomic profiles as compared to uninfected women both before and after adjustment for the vaginal microbiota. This study provides important foundational data documenting differences in the vaginal metabolome between CT+, CT+/MG+ and uninfected women. These data may guide future mechanistic studies that seek to provide insight into the pathogenesis of CT and CT/MG infections.

Ingestion of lean meat elevates muscle inositol hexakisphosphate kinase 1 protein content independent of a distinct post-prandial circulating proteome in young adults with obesity

BACKGROUND

We have recently shown that a novel signalling kinase, inositol hexakisphosphate kinase 1 (IP6K1), is implicated in whole-body insulin resistance via its inhibitory action on Akt. Insulin and insulin like growth factor 1 (IGF-1) share many intracellular processes with both known to play a key role in glucose and protein metabolism in skeletal muscle.

AIMS

We aimed to compare IGF/IP6K1/Akt signalling and the plasma proteomic signature in individuals with a range of BMIs after ingestion of lean meat.

METHODS

Ten lean [Body mass index (BMI) (in kg/m²): 22.7 ± 0.4; Homeostatic model assessment of insulin resistance (HOMA_IR): 1.36 ± 0.17], 10 overweight (BMI: 27.1 ± 0.5; HOMA_IR: 1.25 ± 0.11), and 10 obese (BMI: 35.9 ± 1.3; HOMA_IR: 5.82 ± 0.81) adults received primed continuous L-[ring-¹³C₆]phenylalanine infusions. Blood and muscle biopsy samples were collected at 0 min (post-absorptive), 120 min and 300 min relative to the ingestion of 170 g pork loin (36 g protein and 5 g fat) to examine skeletal muscle protein signalling, plasma proteomic signatures, and whole-body phenylalanine disappearance rates (R_d).

RESULTS

Phenylalanine R_d was not different in obese compared to lean individuals at all time points and was not responsive to a pork ingestion (basal, P = 0.056; 120 & 300 min, P > 0.05). IP6K1 was elevated in obese individuals at 120 min post-prandial vs basal (P < 0.05). There were no acute differences plasma proteomic profiles between groups in the post-prandial state (P > 0.05).

CONCLUSIONS

These data demonstrate, for the first time that muscle IP6K1 protein content is elevated after lean meat ingestion in obese adults, suggesting that IP6K1 may be contributing to the dysregulation of nutrient uptake in skeletal muscle. In addition, proteomic analysis showed no differences in proteomic signatures between obese, overweight or lean individuals.

Potato ingestion is as effective as carbohydrate gels to support prolonged cycling performance

Carbohydrate (CHO) ingestion is an established strategy to improve endurance performance. Race fuels should not only sustain performance but also be readily digested and absorbed. Potatoes are a whole-food-based option that fulfills these criteria, yet their impact on performance remains unexamined. We investigated the effects of potato purée ingestion during prolonged cycling on subsequent performance vs. commercial CHO gel or a water-only condition. Twelve cyclists (70.7 ± 7.7 kg, 173 ± 8 cm, 31 ± 9 yr, 22 ± 5.1% body fat; means ± SD) with average peak oxygen consumption (V̇o_2peak) of 60.7 ± 9.0 mL·kg⁻¹·min⁻¹ performed a 2-h cycling challenge (60–85% V̇o_2peak) followed by a time trial (TT; 6 kJ/kg body mass) while consuming potato, gel, or water in a randomized-crossover design. The race fuels were administered with [U-¹³C₆]glucose for an indirect estimate of gastric emptying rate. Blood samples were collected throughout the trials. Blood glucose concentrations were higher (P < 0.001) in potato and gel conditions compared with water condition. Blood lactate concentrations were higher (P = 0.001) after the TT completion in both CHO conditions compared with water condition. TT performance was improved (P = 0.032) in both potato (33.0 ± 4.5 min) and gel (33.0 ± 4.2 min) conditions compared with water condition (39.5 ± 7.9 min). Moreover, no difference was observed in TT performance between CHO conditions (P = 1.00). In conclusion, potato and gel ingestion equally sustained blood glucose concentrations and TT performance. Our results support the effective use of potatoes to support race performance for trained cyclists.

NEW & NOTEWORTHY The ingestion of concentrated carbohydrate gels during prolonged exercise has been shown to promote carbohydrate availability and improve exercise performance. Our study aim was to expand and diversify race fueling menus for athletes by providing an evidence-based whole-food alternative to the routine ingestion of gels during training and competition. Our work shows that russet potato ingestion during prolonged cycling is as effective as carbohydrate gels to support exercise performance in trained athletes.

Altered anabolic signalling and reduced stimulation of myofibrillar protein synthesis after feeding and resistance exercise in people with obesity

KEY POINTS

Lifestyle modifications that include the regular performance of exercise are probably important for counteracting the negative consequences of obesity on postprandial myofibrillar protein synthetic responses to protein dense food ingestion. We show that the interactive effect of resistance exercise and feeding on the stimulation of myofibrillar protein synthesis rates is diminished with obesity compared to normal weight adults. The blunted myofibrillar protein synthetic response with resistance exercise in people with obesity may be underpinned by alterations in muscle anabolic signalling phosphorylation (p70S6K and 4E-BP1). The results obtained in the present study suggest that further exercise prescription manipulation may be necessary to optimize post-exercise myofibrillar protein synthesis rates in adults with obesity.

ABSTRACT

We aimed to determine whether obesity alters muscle anabolic and inflammatory signalling phosphorylation and also muscle protein synthesis within the myofibrillar (MYO) and sarcoplasmic (SARC) protein fractions after resistance exercise. Nine normal weight (NW) (21 ± 1 years, body mass index 22 ± 1 kg m^-2 ) and nine obese (OB) (22 ± 1 years, body mass index 36 ± 2 kg m^-2 ) adults received l-[ring-¹³ C₆ ]phenylalanine infusions with blood and muscle sampling at basal and fed-state of the exercise (EX) and non-exercise (CON) legs. Participants performed unilateral leg extensions and consumed pork (36 g of protein) immediately after exercise. Basal muscle Toll-like receptor 4 (TLR4) protein was similar between OB and NW groups (P > 0.05) but increased at 300 min after pork ingestion only in the OB group (P = 0.03). Resistance exercise reduced TLR4 protein in the OB group at 300 min (EX vs. CON leg in OB: P = 0.04). Pork ingestion increased p70S6K phosphorylation at 300 min in CON and EX of the OB and NW groups (P > 0.05), although the response was lower in the EX leg of OB vs. NW at 300 min (P = 0.05). Basal MYO was similar between the NW and OB groups (P > 0.05) and was stimulated by pork ingestion in the EX and CON legs in both groups (Δ from basal NW: CON 0.04 ± 0.01% h^-1 ; EX 0.10 ± 0.02% h^-1 ; OB: CON 0.06 ± 0.01% h^-1 ; EX 0.06 ± 0.01% h^-1 ; P < 0.05). MYO was more strongly stimulated in the EX vs. CON legs in NW (P = 0.02) but not OB (P = 0.26). SARC was feeding sensitive but not further potentiated by resistance exercise in both groups. Our results suggest that obesity may attenuate the effectiveness of resistance exercise to augment fed-state MYO.

Dysregulated Handling of Dietary Protein and Muscle Protein Synthesis After Mixed-Meal Ingestion in Maintenance Hemodialysis Patients

Introduction

Skeletal muscle loss is common in patients with renal failure who receive maintenance hemodialysis (MHD) therapy. Regular ingestion of protein-rich meals are recommended to help offset muscle protein loss in MHD patients, but little is known about the anabolic potential of this strategy.

Methods

Eight MHD patients (age: 56 ± 5 years; body mass index [BMI]: 32 ± 2 kg/m²) and 8 nonuremic control subjects (age: 50 ± 2 years: BMI: 31 ± 1 kg/m²) received primed continuous L-[ring-²H₅]phenylalanine and L-[1-¹³C]leucine infusions with blood and muscle biopsy sampling on a nondialysis day. Participants consumed a mixed meal (546 kcal; 20-g protein, 59-g carbohydrates, 26-g fat) with protein provided as L-[5,5,5-²H₃]leucine-labeled eggs.

Results

Circulating dietary amino acid availability was reduced in MHD patients (41 ± 5%) versus control subjects (61 ± 4%; P = 0.03). Basal muscle caspase-3 protein content was elevated (P = 0.03) and large neutral amino acid transporter 1 (LAT1) protein content was reduced (P = 0.02) in MHD patients versus control subjects. Basal muscle protein synthesis (MPS) was ∼2-fold higher in MHD patients (0.030 ± 0.005%/h) versus control subjects (0.014 ± 0.003%/h) (P = 0.01). Meal ingestion failed to increase MPS in MHD patients (absolute change from basal: 0.0003 ± 0.007%/h), but stimulated MPS in control subjects (0.009 ± 0.002%/h; P = 0.004).

Conclusions

MHD patients demonstrated muscle anabolic resistance to meal ingestion. This blunted postprandial MPS response in MHD patients might be related to high basal MPS, which results in a stimulatory ceiling effect and/or reduced plasma dietary amino acid availability after mixed-meal ingestion.

Endurance Exercise Attenuates Postprandial Whole-Body Leucine Balance in Trained Men

PURPOSE

Endurance exercise increases indices of small intestinal damage and leucine oxidation, which may attenuate dietary amino acid appearance and postprandial leucine balance during postexercise recovery. Therefore, the purpose of this study was to examine the effect of an acute bout of endurance exercise on postprandial leucine kinetics and net leucine balance.

METHODS

In a crossover design, seven trained young men (age = 25.6 ± 2.3 yr; V˙O2peak = 61.4 ± 2.9 mL·kg·min; mean ± SEM) received a primed constant infusion of L-[1-C]leucine before and after ingesting a mixed macronutrient meal containing 18 g whole egg protein intrinsically labeled with L-[5,5,5-H3]leucine, 17 g fat, and 60 g carbohydrate at rest and after 60 min of treadmill running at 70% V˙O2peak.

RESULTS

Plasma intestinal fatty acid binding protein concentrations and leucine oxidation both increased (P < 0.01) to peaks that were ~2.5-fold above baseline values during exercise with a concomitant decrease (P < 0.01) in nonoxidative leucine disposal. Meal ingestion attenuated (P < 0.01) endogenous leucine rates of appearance at rest and after exercise. There were no differences (both, P > 0.05) in dietary leucine appearance rates or in the amount of dietary protein-derived leucine that appeared into circulation over the 5-h postprandial period at rest and after exercise (62% ± 2% and 63% ± 2%, respectively). Leucine balance over the 5-h postprandial period was positive (P < 0.01) in both conditions but was negative (P < 0.01) during the exercise trial after accounting for exercise-induced leucine oxidation.

CONCLUSIONS

We demonstrate that endurance exercise does not modulate dietary leucine availability from a mixed meal but attenuates postprandial whole-body leucine balance in trained young men.

Enhancement of gama-aminobutyric acid (GABA) and other health-related metabolites in germinated red rice (Oryza sativa L.) by ultrasonication

Red rice (Oryza sativa L.) that has a red (reddish brown) bran layer in de-hulled rice is known to contain rich biofunctional components. Germination is an effective technique to improve the nutritional quality, digestibility, and flavor of de-hulled rice. Ultrasonication, a form of physical stimulation, has been documented as a novel approach to improve the nutritional quality of plant-based food. This study was undertaken to test the use of ultrasound to enhance the nutritional value of red rice. Ultrasonication (5min, 16W/L) was applied to rice during soaking or after 66h germination. Changes of metabolites (amino acids, sugars, and organic acids) in red rice treated by ultrasonication were determined using a GC/MS plant primary metabolomics analysis platform. Differential expressed metabolites were identified through multivariate statistical analysis. Results showed that γ-aminobutyric acid (GABA) and riboflavin (vitamin B₂) in red rice significantly increased after germination for 72h, and then experienced a further increase after treatment by ultrasound at different stages during germination. The metabolomics analysis showed that some plant metabolites, i.e. GABA, O-phosphoethanolamine, and glucose-6-phosphate were significantly increased after the ultrasonic treatment (VIP>1.5) in comparison with the untreated germinated rice. The findings of this study showed that controlled germination with ultrasonic stress is an effective method to enhance GABA and other health-promoted components in de-hulled rice.

Consumption of whole eggs promotes greater stimulation of postexercise muscle protein synthesis than consumption of isonitrogenous amounts of egg whites in young men

Background: Protein in the diet is commonly ingested from whole foods that contain various macro- and micronutrients. However, the effect of consuming protein within its natural whole-food matrix on postprandial protein metabolism remains understudied in humans.Objective: We aimed to compare the whole-body and muscle protein metabolic responses after the consumption of whole eggs with egg whites during exercise recovery in young men.Design: In crossover trials, 10 resistance-trained men [aged 21 ± 1 y; 88 ± 3 kg; body fat: 16% ± 1% (means ± SEMs)] received primed continuous l-[ring-²H₅]phenylalanine and l-[1-¹³C]leucine infusions and performed a single bout of resistance exercise. After exercise, participants consumed intrinsically l-[5,5,5-²H₃]leucine-labeled whole eggs (18 g protein, 17 g fat) or egg whites (18 g protein, 0 g fat). Repeated blood and muscle biopsy samples were collected to assess whole-body leucine kinetics, intramuscular signaling, and myofibrillar protein synthesis.Results: Plasma appearance rates of protein-derived leucine were more rapid after the consumption of egg whites than after whole eggs (P = 0.01). Total plasma availability of leucine over the 300-min postprandial period was similar (P= 0.75) between the ingestion of whole eggs (68% ± 1%) and egg whites (66% ± 2%), with no difference in whole-body net leucine balance (P = 0.27). Both whole-egg and egg white conditions increased the phosphorylation of mammalian target of rapamycin complex 1, ribosomal protein S6 kinase 1, and eukaryotic translation initiation factor 4E-binding protein 1 during postexercise recovery (all P < 0.05). However, whole-egg ingestion increased the postexercise myofibrillar protein synthetic response to a greater extent than did the ingestion of egg whites (P= 0.04).Conclusions: We show that the ingestion of whole eggs immediately after resistance exercise resulted in greater stimulation of myofibrillar protein synthesis than did the ingestion of egg whites, despite being matched for protein content in young men. Our data indicate that the ingestion of nutrient- and protein-dense foods differentially stimulates muscle anabolism compared with protein-dense foods. This trial was registered at clinicaltrials.gov as NCT03117127.

Protein-Rich Food Ingestion Stimulates Mitochondrial Protein Synthesis in Sedentary Young Adults of Different BMIs

CONTEXT

Excess fat mass may diminish the anabolic potency of protein-rich food ingestion to stimulate muscle protein subfractional synthetic responses. However, the impact of adiposity on mitochondrial protein synthesis (MPS) rates after protein-rich food ingestion has not been thoroughly examined in vivo in humans.

OBJECTIVE

We compared basal and postprandial MPS and markers of muscle inflammation [toll-like receptor 4 (TLR4) and myeloid differentiation primary response protein 88 (MyD88) protein content] in young adults with different body mass indices (BMIs).

METHODS

Ten normal-weight (NW; BMI = 22.7 ± 0.4 kg/m2), 10 overweight (OW; BMI = 27.1 ± 0.5 kg/m2), and 10 obese (OB; BMI = 35.9 ± 1.3 kg/m2) adults received primed continuous L-[ring-13C6]phenylalanine infusions, blood sampling, and skeletal muscle biopsies before and after the ingestion of 170 g of pork.

RESULTS

Pork ingestion increased muscle TLR4 and MyD88 protein content in the OB group (P < 0.05), but not in the NW or OW groups. Basal MPS was similar between groups (P > 0.05). Pork ingestion stimulated MPS (P < 0.001; 0 to 300 minutes) in the NW (2.5- ± 0.6-fold above baseline values), OW (1.7- ± 0.3-fold), and OB groups (2.4- ± 0.5-fold) with no group differences (P > 0.05).

CONCLUSIONS

Protein-dense food ingestion promotes muscle inflammatory signaling only in OB adults. However, the consumption of a dinner-sized amount of protein strongly stimulated a postprandial MPS response irrespective of BMI. Our data suggest that alterations in postprandial MPS are unlikely to contribute to compromised muscle macronutrient metabolism witnessed with obesity.

Anabolic sensitivity of postprandial muscle protein synthesis to the ingestion of a protein-dense food is reduced in overweight and obese young adults

BACKGROUND

Excess body fat diminishes muscle protein synthesis rates in response to hyperinsulinemic-hyperaminoacidemic clamps. However, muscle protein synthetic responses after the ingestion of a protein-dense food source across a range of body mass indexes (BMIs) have not been compared.

OBJECTIVE

We compared the myofibrillar protein synthetic response and underlying nutrient-sensing mechanisms after the ingestion of lean pork between obese, overweight, and healthy-weight adults.

DESIGN

Ten healthy-weight [HW; BMI (in kg/m²): 22.7 ± 0.4], 10 overweight (OW; BMI: 27.1 ± 0.5), and 10 obese (OB; BMI: 35.9 ± 1.3) adults received primed continuous l-[ring-¹³C₆]phenylalanine infusions. Blood and muscle biopsy samples were collected before and after the ingestion of 170 g pork (36 g protein and 3 g fat) to assess skeletal muscle anabolic signaling, amino acid transporters [large neutral and small neutral amino acid transporters (LAT1, SNAT2) and CD98], and myofibrillar protein synthesis.

RESULTS

At baseline, OW and OB groups showed greater relative amounts of mammalian target of rapamycin complex 1 (mTORC1) protein than the HW group. Pork ingestion increased mTORC1 phosphorylation only in the HW group (P = 0.001). LAT1 and SNAT2 protein content increased during the postprandial period in all groups (time effect, P < 0.05). Basal myofibrillar protein synthetic responses were similar between groups (P = 0.43). However, myofibrillar protein synthetic responses (0-300 min) were greater in the HW group (1.6-fold; P = 0.005) after pork ingestion than in the OW and OB groups.

CONCLUSIONS

There is a diminished myofibrillar protein synthetic response to the ingestion of protein-dense food in overweight and obese adults compared with healthy-weight controls. These data indicate that impaired postprandial myofibrillar protein synthetic response may be an early defect with increasing fat mass, potentially dependent on altered anabolic signals, that reduces muscle sensitivity to food ingestion. This trial was registered at clinicaltrials.gov as NCT02613767.

Development of Intrinsically Labeled Eggs and Poultry Meat for Use in Human Metabolic Research

BACKGROUND

Stable isotope amino acids are regularly used as tracers to examine whole-body and muscle protein metabolism in humans. To accurately assess in vivo dietary protein digestion and absorption kinetics, the amino acid tracer is required to be incorporated within the dietary protein food source (i.e., intrinsically labeled protein).

OBJECTIVE

We assessed the practicality of producing eggs and poultry meat intrinsically labeled with l-[5,5,5-(2)H3]leucine through noninvasive oral tracer administration.

METHODS

A specifically formulated diet containing 0.52% leucine was supplemented with 0.3% l-[5,5,5-(2)H3]leucine and subsequently fed to 3 laying hens (Lohmann LSL Whites) for 55 d. On day 55, the hens were slaughtered and their meat, bones, and organs were harvested to determine tissue labeling. In Expt. 1, 2 healthy young men [mean ± SEM age: 22 ± 1.5 y; mean ± SEM body mass index (BMI; in kg/m(2)): 23.7 ± 0.5] ingested 18 g l-[5,5,5-(2)H3]leucine-labeled egg protein. In Expt. 2, 2 healthy young men (mean ± SEM age: 20.0 ± 0.0 y; mean ± SEM BMI: 26.4 ± 3.1) ingested 28 g l-[5,5,5-(2)H3]leucine-labeled poultry meat protein. Plasma samples (Expts. 1 and 2) and muscle biopsies (Expt. 1) were collected before and after labeled-food ingestion.

RESULTS

High tracer labeling [>20 mole percent excess (MPE)] in the eggs was obtained after 7 d and maintained throughout the feeding protocol (P < 0.05). Over a 55-d period, ∼850 g egg protein (145 eggs) was produced, with a mean ± SEM tracer enrichment of 22.0 ± 0.8 MPE. Mean ± SEM l-[5,5,5-(2)H3]leucine enrichment in the meat was 9.6 ± 0.1 MPE. In Expts. 1 and 2, the consumption of labeled eggs and poultry meat protein increased plasma l-[5,5,5-(2)H3]leucine enrichment, with mean ± SEM peak values of 6.7 ± 0.1 MPE and 4.0 ± 0.9 MPE, respectively. The mean ± SEM 5-h postprandial increase in myofibrillar l-[5,5,5-(2)H3]leucine enrichment after egg ingestion in healthy young men was 0.051 ± 0.008 MPE (Expt. 1).

CONCLUSION

We demonstrated the feasibility of producing intrinsically labeled eggs and poultry meat for use in human metabolic research.

Metabolite Profiles of Male and Female Humboldt Penguins

We examined 185 metabolites in 30 adult Humboldt Penguins (Spheniscus humboldti) nesting at the Punta San Juan Marine Protected Area, Peru, in order to examine gender differences in metabolome profiles, particularly those involved in metabolism and energetics. The majority of the compounds identified were fatty (26% of total identified compounds), organic (19%), and amino (16%) acids. We were able to differentiate male and female penguins with 96.6% accuracy on the basis of 12 metabolites, most of which are involved in lipid and carbohydrate metabolism. These included 2-oxoglutarate, erythronic acid, GABA, mannitol, sedoheptulose 7-phosphate, and serine and six metabolites present in higher concentrations in females compared to males (2-aminoadipic acid, O-phosphorylethanolamine, glycerol 2-phosphate, glycerol 3-phosphate, pantothenic acid, and creatinine). Of these, 2-oxoglutarate and glycerol 3-phosphate were key metabolites distinguishing gender. Our results indicated that male and female Humboldt Penguins were characterized by differing metabolic states. Such differences could be important to individual and brood survival in times of environmental stress.

Genomic, Transcriptomic and Metabolomic Studies of Two Well-Characterized, Laboratory-Derived Vancomycin-Intermediate Staphylococcus aureus Strains Derived from the Same Parent Strain

Complete genome comparisons, transcriptomic and metabolomic studies were performed on two laboratory-selected, well-characterized vancomycin-intermediate Staphylococcus aureus (VISA) derived from the same parent MRSA that have changes in cell wall composition and decreased autolysis. A variety of mutations were found in the VISA, with more in strain 13136p(-)m⁺V20 (vancomycin MIC = 16 µg/mL) than strain 13136p(-)m⁺V5 (MIC = 8 µg/mL). Most of the mutations have not previously been associated with the VISA phenotype; some were associated with cell wall metabolism and many with stress responses, notably relating to DNA damage. The genomes and transcriptomes of the two VISA support the importance of gene expression regulation to the VISA phenotype. Similarities in overall transcriptomic and metabolomic data indicated that the VISA physiologic state includes elements of the stringent response, such as downregulation of protein and nucleotide synthesis, the pentose phosphate pathway and nutrient transport systems. Gene expression for secreted virulence determinants was generally downregulated, but was more variable for surface-associated virulence determinants, although capsule formation was clearly inhibited. The importance of activated stress response elements could be seen across all three analyses, as in the accumulation of osmoprotectant metabolites such as proline and glutamate. Concentrations of potential cell wall precursor amino acids and glucosamine were increased in the VISA strains. Polyamines were decreased in the VISA, which may facilitate the accrual of mutations. Overall, the studies confirm the wide variability in mutations and gene expression patterns that can lead to the VISA phenotype.

A multi-omic systems-based approach reveals metabolic markers of bacterial vaginosis and insight into the disease

BACKGROUND

Bacterial vaginosis (BV) is the most common vaginal disorder of reproductive-age women. Yet the cause of BV has not been established. To uncover key determinants of BV, we employed a multi-omic, systems-biology approach, including both deep 16S rRNA gene-based sequencing and metabolomics of lavage samples from 36 women. These women varied demographically, behaviorally, and in terms of health status and symptoms.

PRINCIPAL FINDINGS

16S rRNA gene-based community composition profiles reflected Nugent scores, but not Amsel criteria. In contrast, metabolomic profiles were markedly more concordant with Amsel criteria. Metabolomic profiles revealed two distinct symptomatic BV types (SBVI and SBVII) with similar characteristics that indicated disruption of epithelial integrity, but each type was correlated to the presence of different microbial taxa and metabolites, as well as to different host behaviors. The characteristic odor associated with BV was linked to increases in putrescine and cadaverine, which were both linked to Dialister spp. Additional correlations were seen with the presence of discharge, 2-methyl-2-hydroxybutanoic acid, and Mobiluncus spp., and with pain, diethylene glycol and Gardnerella spp.

CONCLUSIONS

The results not only provide useful diagnostic biomarkers, but also may ultimately provide much needed insight into the determinants of BV.

Polyethylene glycol treatment promotes metabolic events associated with maize callus morphogenic competence

Metabolic changes were studied, which accompanied the conversion of 6month old HiII maize non-regenerable (NR) calli into regenerable (R) calli when cultured for 63days with 10% polyethylene glycol (PEG) (3350MW) in culture medium. The conversion of 6month old NR to R callus morphotype caused by PEG application decreased cell wall contents in callus dry mass and changed cell wall phenolics making their profile similar to that of R callus by reduction of lignin and ester- and ether-bound phenolic concentrations, including p-coumaric acid and ester- and ether-bound diferulates and by increase of the ratios of ester- and ether-bound ferulic acid/coumaric acid and ferulic acid/diferulic acid in cell walls of NR callus. Some similar changes of cell wall phenolics caused by PEG application were also found in 48month old NR callus, that changed the morphology, but did not regenerate plants. However, there were no changes in the old callus in levels of total ester and ether-bound cell wall phenolics and substantially smaller decreases were found in ratios of ester- and ether-bound ferulic acid/coumaric acid and ferulic acid/diferulic acid, as well as in diferulate concentrations compared to young NR callus cultured with PEG. Remarkably, application of PEG also changed the primary metabolism of young NR callus tissues, so that they acquired metabolic features of highly regenerable callus. These data clearly suggest that PEG alters metabolism of NR calli, so they acquire biochemical characteristics of R calli, and that adaptive osmotic adjustments vary in different types of callus tissues.

Metabolomes of the psychrotolerant bacterium Listeria monocytogenes 10403S grown at 37 °C and 8 °C

Listeria monocytogenes is a food-borne pathogen with the ability to grow at refrigeration temperatures. Knowledge of the mechanisms involved in low temperature growth is incomplete and here we report the results of a metabolomics investigation of this. The small molecule contents of L. monocytogenes 10403S grown at 37 °C and 8 °C were compared by gas chromatography/mass spectrometry (GC/MS). Over 500 peaks were detected in both 37 °C and 8 °C-grown cells, and 103 were identified. Of the identified metabolites, the concentrations of 56 metabolites were increased (P<0.05), while the concentrations of 8 metabolites were decreased at low temperature. Metabolites increasing in concentration at 8 °C included amino acids, sugars, organic acids, urea cycle intermediates, polyamines, and different compatible solutes. A principal component analysis (PCA) was used to visualize and compare the matrix containing the data in 6 samples, and this clearly identified the 37 °C and 8 °C metabolomes as different. The results indicated that an increase in solute concentrations in the cytoplasm was associated with low temperature adaptation, which may be a response to chill stress with the effect of lowering the freezing point of intracellular water and decreasing ice crystal formation.

Major impacts on the primary metabolism of the plant pathogen Cryphonectria parasitica by the virulence-attenuating virus CHV1-EP713

Cryphonectria parasitica, the chestnut blight fungus, can be infected by virulence-attenuating mycoviruses of the family Hypoviridae. Previous studies have led to the hypothesis that the hypovirus-infected phenotype is partly due to metabolic changes induced by the viral infection. To investigate this, we measured the metabolic rate and respiration of C. parasitica colonies grown on solid medium. These experiments supported historical observations of other fungal species done in liquid cultures that the metabolic rate steadily declines with age and differentiation of the mycelium. Hypovirus infection increased metabolic rate in the youngest mycelium, but a subsequent decline was also observed as the mycelium aged. By measuring both CO(2) production and O(2) consumption, we also observed that changes occur in carbohydrate metabolism as a result of ageing in both infected and uninfected mycelium. Mycelium on the periphery of the colony exploited fermentation pathways extensively, before transitioning to aerobic carbohydrate metabolism and finally lipid metabolism in the interior regions, despite abundant remaining glucose. However, the hypovirus affected the extent of these changes, with infected mycelium apparently unable to utilize lipid-related metabolic pathways, leading to an increased depletion of glucose. Finally, we used metabolic profi fi ling to determine the changes in accumulation of primary metabolites in wild-type and hypovirus-infected mycelium and found that approximately one-third of the 164 detected metabolites were affected. These results are consistent with those expected from the physiological measurements, with significant alterations noted for compounds related to lipid and carbohydrate metabolism. Additionally, we observed an increase in the accumulation of the polyamine spermidine in the presence of hypovirus. Polyamines have been implicated in antiviral responses of mammalian systems; therefore this may suggest a novel antiviral response mechanism in fungi.

Physiological and molecular adaptations to drought in Andean potato genotypes

The drought stress tolerance of two Solanum tuberosum subsp. andigena landraces, one hybrid (adgxtbr) and Atlantic (S. tuberosum subsp. tuberosum) has been evaluated. Photosynthesis in the Andigena landraces during prolonged drought was maintained significantly longer than in the Tuberosum (Atlantic) line. Among the Andigena landraces, 'Sullu' (SUL) was more drought resistant than 'Negra Ojosa' (NOJ). Microarray analysis and metabolite data from leaf samples taken at the point of maximum stress suggested higher mitochondrial metabolic activity in SUL than in NOJ. A greater induction of chloroplast-localized antioxidant and chaperone genes in SUL compared with NOJ was evident. ABA-responsive TFs were more induced in NOJ compared with SUL, including WRKY1, mediating a response in SA signalling that may give rise to increased ROS. NOJ may be experiencing higher ROS levels than SUL. Metabolite profiles of NOJ were characterized by compounds indicative of stress, for example, proline, trehalose, and GABA, which accumulated to a higher degree than in SUL. The differences between the Andigena lines were not explained by protective roles of compatible solutes; hexoses and complex sugars were similar in both landraces. Instead, lower levels of ROS accumulation, greater mitochondrial activity and active chloroplast defences contributed to a lower stress load in SUL than in NOJ during drought.

Modification of phenolic metabolism in soybean hairy roots through down regulation of chalcone synthase or isoflavone synthase

Soybean hairy roots, transformed with the soybean chalcone synthase (CHS6) or isoflavone synthase (IFS2) genes, with dramatically decreased capacity to synthesize isoflavones were produced to determine what effects these changes would have on susceptibility to a fungal pathogen. The isoflavone and coumestrol concentrations were decreased by about 90% in most lines apparently due to gene silencing. The IFS2 transformed lines had very low IFS enzyme activity in microsomal fractions as measured by the conversion of naringenin to genistein. The CHS6 lines with decreased isoflavone concentrations had 5 to 20-fold lower CHS enzyme activities than the appropriate controls. Both IFS2 and CHS transformed lines accumulated higher concentrations of both soluble and cell wall bound phenolic acids compared to controls with higher levels found in the CHS6 lines indicating alterations in the lignin biosynthetic branch of the pathway. Induction of the soybean phytoalexin glyceollin, of which the precursor is the isoflavone daidzein, by the fungal pathogen Fusarium solani f. sp. glycines (FSG) that causes soybean sudden death syndrome (SDS) showed that the low isoflavone transformed lines did not accumulate glyceollin while the control lines did. The (iso)liquritigenin content increased upon FSG induction in the IFS2 transformed roots indicating that the pathway reactions before this point can control isoflavonoid synthesis. The lowest fungal growth rate on hairy roots was found on the FSG partially resistant control roots followed by the SDS sensitive control roots and the low isoflavone transformants. The results indicate the importance of phytoalexin synthesis in root resistance to the pathogen.

Genetic and transgenic perturbations of carbon reserve production in Arabidopsis seeds reveal metabolic interactions of biochemical pathways

The biosynthesis of seed oil and starch both depend on the supply of carbon from the maternal plant. The biochemical interactions between these two pathways are not fully understood. In the Arabidopsis mutant shrunken seed 1 (sse1)/pex16, a reduced rate of fatty acid synthesis leads to starch accumulation. To further understand the metabolic impact of the decrease in oil synthesis, we compared soluble metabolites in sse1 and wild type (WT) seeds. Sugars, sugar phosphates, alcohols, pyruvate, and many other organic acids accumulated in sse1 seeds as a likely consequence of the reduced carbon demand for lipid synthesis. The enlarged pool size of hexose-P, the metabolites at the crossroad of sugar metabolism, glycolysis, and starch synthesis, was likely a direct cause of the increased flow into starch. Downstream of glycolysis, more carbon entered the TCA cycle as an alternative to the fatty acid pathway, causing the total amount of TCA cycle intermediates to rise while moving the steady state of the cycle away from fumarate. To convert the excess carbon metabolites into starch, we introduced the Escherichia coli starch synthetic enzyme ADP-glucose pyrophosphorylase (AGPase) into sse1 seeds. Expression of AGPase enhanced net starch biosynthesis in the mutant, resulting in starch levels that reached 37% of seed weight. However, further increases above this level were not achieved and most of the carbon intermediates remained high in comparison with the WT, indicating that additional mechanisms limit starch deposition in Arabidopsis seeds.