Prenatal choline supplementation improves biomarkers of maternal docosahexaenoic acid (DHA) status among pregnant participants consuming supplemental DHA: a randomized controlled trial.

BACKGROUND: Dietary methyl donors (e.g., choline) support the activity of the phosphatidylethanolamine N-methyltransferase (PEMT) pathway, which generates phosphatidylcholine (PC) molecules enriched in DHA that are exported from the liver and made available to extrahepatic tissues. OBJECTIVES: This study investigated the effect of prenatal choline supplementation on biomarkers of DHA status among pregnant participants consuming supplemental DHA. METHODS: Pregnant participants (n = 30) were randomly assigned to receive supplemental choline intakes of 550 mg/d [500 mg/d d0-choline + 50 mg/d deuterium-labeled choline (d9-choline); intervention] or 25 mg/d (25 mg/d d9-choline; control) from gestational week (GW) 12-16 until delivery. All participants received a daily 200-mg DHA supplement and consumed self-selected diets. Fasting blood samples were obtained at baseline, GW 20-24, and GW 28-32; maternal/cord blood was obtained at delivery. Mixed-effects linear models were used to assess the impact of prenatal choline supplementation on maternal and newborn DHA status. RESULTS: Choline supplementation (550 vs. 25 mg/d) did not achieve a statistically significant intervention × time interaction for RBC PC-DHA (P = 0.11); a significant interaction was observed for plasma PC-DHA and RBC total DHA, with choline supplementation yielding higher levels (+32-38% and +8-11%, respectively) at GW 28-32 (P < 0.05) and delivery (P < 0.005). A main effect of choline supplementation on plasma total DHA was also observed (P = 0.018); its interaction with time was not significant (P = 0.068). Compared with controls, the intervention group exhibited higher (P = 0.007; main effect) plasma enrichment of d3-PC (d3-PC/total PC). Moreover, the ratio of d3-PC to d9-PC was higher (+50-67%; P < 0.001) in the choline intervention arm (vs. control) at GW 20-24, GW 28-32, and delivery. CONCLUSIONS: Prenatal choline supplementation improves hepatic DHA export and biomarkers of DHA status by bolstering methyl group supply for PEMT activity among pregnant participants consuming supplemental DHA. This trial is registered at www.clinicaltrials.gov as NCT03194659.

Choline metabolome response to prenatal choline supplementation across pregnancy: A randomized controlled trial.

Pregnancy places a unique stress upon choline metabolism, requiring adaptations to support both maternal and fetal requirements. The impact of pregnancy and prenatal choline supplementation on choline and its metabolome in free-living, healthy adults is relatively uncharacterized. This study investigated the effect of prenatal choline supplementation on maternal and fetal biomarkers of choline metabolism among free-living pregnant persons consuming self-selected diets. Participants were randomized to supplemental choline (as choline chloride) intakes of 550 mg/d (500 mg/d d0-choline + 50 mg/d methyl-d9-choline; intervention) or 25 mg/d d9-choline (control) from gestational week (GW) 12-16 until Delivery. Fasting blood and 24-h urine samples were obtained at study Visit 1 (GW 12-16), Visit 2 (GW 20-24), and Visit 3 (GW 28-32). At Delivery, maternal and cord blood and placental tissue samples were collected. Participants randomized to 550 (vs. 25) mg supplemental choline/d achieved higher (p < .05) plasma concentrations of free choline, betaine, dimethylglycine, phosphatidylcholine (PC), and sphingomyelin at one or more study timepoint. Betaine was most responsive to prenatal choline supplementation with increases (p ≤ .001) in maternal plasma observed at Visit 2-Delivery (relative to Visit 1 and control), as well as in the placenta and cord plasma. Notably, greater plasma enrichments of d3-PC and LDL-C were observed in the intervention (vs. control) group, indicating enhanced PC synthesis through the de novo phosphatidylethanolamine N-methyltransferase pathway and lipid export. Overall, these data show that prenatal choline supplementation profoundly alters the choline metabolome, supporting pregnancy-related metabolic adaptations and revealing biomarkers for use in nutritional assessment and monitoring during pregnancy.

Extracellular serine and glycine are required for mouse and human skeletal muscle stem and progenitor cell function.

OBJECTIVE: Skeletal muscle regeneration relies on muscle-specific adult stem cells (MuSCs), MuSC progeny, muscle progenitor cells (MPCs), and a coordinated myogenic program that is influenced by the extracellular environment. Following injury, MPCs undergo a transient and rapid period of population expansion, which is necessary to repair damaged myofibers and restore muscle homeostasis. Certain pathologies (e.g., metabolic diseases and muscle dystrophies) and advanced age are associated with dysregulated muscle regeneration. The availability of serine and glycine, two nutritionally non-essential amino acids, is altered in humans with these pathologies, and these amino acids have been shown to influence the proliferative state of non-muscle cells. Our objective was to determine the role of serine/glycine in MuSC/MPC function. METHODS: Primary human MPCs (hMPCs) were used for in vitro experiments, and young (4-6 mo) and old (>20 mo) mice were used for in vivo experiments. Serine/glycine availability was manipulated using specially formulated media in vitro or dietary restriction in vivo followed by downstream metabolic and cell proliferation analyses. RESULTS: We identified that serine/glycine are essential for hMPC proliferation. Dietary restriction of serine/glycine in a mouse model of skeletal muscle regeneration lowered the abundance of MuSCs 3 days post-injury. Stable isotope-tracing studies showed that hMPCs rely on extracellular serine/glycine for population expansion because they exhibit a limited capacity for de novo serine/glycine biosynthesis. Restriction of serine/glycine to hMPCs resulted in cell cycle arrest in G0/G1. Extracellular serine/glycine was necessary to support glutathione and global protein synthesis in hMPCs. Using an aged mouse model, we found that reduced serine/glycine availability augmented intermyocellular adipocytes 28 days post-injury. CONCLUSIONS: These studies demonstrated that despite an absolute serine/glycine requirement for MuSC/MPC proliferation, de novo synthesis was inadequate to support these demands, making extracellular serine and glycine conditionally essential for efficient skeletal muscle regeneration.

Tolerance to graded dosages of histidine supplementation in healthy human adults.

BACKGROUND: Histidine is an essential amino acid with health benefits that may warrant histidine supplementation; however, the clinical safety of histidine intake above the average dietary intake (1.52-5.20 g/d) needs to be vetted. OBJECTIVES: We aimed to determine the tolerance to graded dosages of histidine in a healthy adult population. METHODS: Healthy adults aged 21-50 y completed graded dosages of histidine supplement (4, 8, and 12 g/d, Study 1) (n = 20 men and n = 20 women) and/or a 16-g/d dosage of histidine (Study 2, n = 21 men and n = 19 women); 27 participants (n = 12 men and n = 15 women) completed both studies. After study enrollment and baseline measures, participants consumed encapsulated histidine for 4 wk followed by a 3-wk recovery period. Primary outcomes included vitals, select biochemical analytes, anthropometry, serum zinc, and body composition (via DXA). RESULTS: No changes in vitals or body composition occurred with histidine supplementation in either study. Plasma histidine (measured in subjects who completed all dosages for Studies 1 and 2) was elevated at the 12- and 16-g/d dosages (compared with 0-8 g/d, P < 0.05) and blood urea nitrogen increased with dosage (P = 0.013) and time (P < 0.001) in Study 1 and with time in Study 2 (P < 0.001). In Study 1, mean ferritin concentrations were lower in 12 g/d (46.0 ng/mL; 95% CI: 34.8, 60.9 ng/mL) than in 4 g/d (51.6 ng/mL; 95% CI: 39.0, 68.4 ng/mL; P = 0.038). In Study 2, 16 g/d increased mean aspartate aminotransferase from baseline (19 U/L; 95% CI: 17, 22 U/L) to week 4 (24 U/L; 95% CI: 21, 27 U/L; P < 0.001) and mean serum zinc decreased from baseline (0.75 µg/dL; 95% CI: 0.71, 0.80 µg/dL) to week 4 (0.70 µg/dL; 95% CI: 0.66, 0.74 µg/dL; P = 0.011). CONCLUSIONS: Although values remained within the normal reference ranges for all analytes measured, in all dosages tested, the human no-observed adverse effect level was determined to be 8 g/d owing to changes in blood parameters at the 12-g/d dosage.This trial was registered at clinicaltrials.gov as NCT04142294.

Consumption of a Blueberry-Enriched Diet by Women for 6 Weeks Alters Determinants of Human Muscle Progenitor Cell Function.

BACKGROUND: Human muscle progenitor cell (hMPC) function facilitates skeletal muscle regeneration and is influenced by circulating factors. Yet it is unknown whether dietary interventions impact hMPC function. Blueberry consumption was examined due to the pro-proliferative and antioxidant effects of blueberries and blueberry-derived compounds. OBJECTIVES: This study measured indicators of hMPC function in young and old cultures treated with serum collected from a blueberry-enriched diet (BED) intervention. METHODS: Younger (21-40 y, n = 12) and older (60-79 y, n = 10) women consumed a 6-wk BED (38 g of freeze-dried blueberries daily). Fasting serum was collected at 0, 4, and 6 wk, and a fed serum sample at 1.5 h (acute) after starting the BED intervention. Young and old hMPCs, derived from 3-5 distinct donors (biological replicates), were individually cultured in media containing pooled, age-group-matched serum from each time point. Determinants of hMPC function (e.g., hMPC number, oxidative stress resistance, and upregulation of metabolic pathways) were measured and compared within age groups. RESULTS: Culturing young hMPCs in acute (compared with 0 wk) BED serum did not alter hMPC number or oxidative stress-induced cell death, but increased cellular oxygen consumption (29%, P = 0.026). Culturing young hMPCs in 6-wk (compared with 0-wk) BED serum increased hMPC number (40%, P = 0.0024), conferred minor resistance to oxidative stress-induced cell death (12.6 percentage point decrease, P = 0.10), and modestly increased oxygen consumption (36%, P = 0.09). No beneficial effect of the acute or long-term BED serum was observed in old hMPCs. CONCLUSIONS: In younger women, dietary interventions could be a feasible strategy to improve hMPC function and thus muscle regeneration, through altering the serum environment.This study was registered at clinicaltrials.gov (NCT04262258).

Isolation, Culture, Characterization, and Differentiation of Human Muscle Progenitor Cells from the Skeletal Muscle Biopsy Procedure.

The use of primary human tissue and cells is ideal for the investigation of biological and physiological processes such as the skeletal muscle regenerative process. There are recognized challenges to working with human primary adult stem cells, particularly human muscle progenitor cells (hMPCs) derived from skeletal muscle biopsies, including low cell yield from collected tissue and a large degree of donor heterogeneity of growth and death parameters among cultures. While incorporating heterogeneity into experimental design requires a larger sample size to detect significant effects, it also allows us to identify mechanisms that underlie variability in hMPC expansion capacity, and thus allows us to better understand heterogeneity in skeletal muscle regeneration. Novel mechanisms that distinguish the expansion capacity of cultures have the potential to lead to the development of therapies to improve skeletal muscle regeneration.

Expansion capacity of human muscle progenitor cells differs by age, sex, and metabolic fuel preference.

Activation of satellite cells and expansion of the muscle progenitor cell (MPC) population are essential to generate a sufficient number of cells to repair damaged skeletal muscle. Proliferating MPCs have high energetic and biosynthetic material requirements, and the ability to utilize oxidative phosphorylation (OXPHOS) and/or glycolysis may affect expansion capacity of MPCs. In the present study, we investigated the effect of donor age and sex on human (h)MPC expansion capacity and metabolic fuel preference. hMPCs from young and old male and female donors were grown for 408 h (17 days). Percent confluence, live nuclei count, and dead cell count were measured every 24 h. Metabolic phenotype was assessed by glucose uptake, expression of genes related to glycolysis and OXPHOS, and the Seahorse XF24 Phenotype Test Kit during the exponential phase of growth. hMPCs from old male donors had impaired expansion capacity secondary to heightened cell death early in expansion compared with hMPCs from young male donors, an effect not observed in female hMPCs. Age-related differences in metabolism were also sex dependent; markers of OXPHOS were altered in old (vs. young) male hMPCs, whereas markers of metabolism were largely unaffected by age in female hMPCs. For the first time, we identify sex-specific differences in cell death and OXPHOS that contribute to impaired expansion capacity of hMPC cell populations with age.

Transcript profile distinguishes variability in human myogenic progenitor cell expansion capacity.

Primary human muscle progenitor cells (hMPCs) are commonly used to understand skeletal muscle biology, including the regenerative process. Variability from unknown origin in hMPC expansion capacity occurs independently of disease, age, or sex of the donor. We sought to determine the transcript profile that distinguishes hMPC cultures with greater expansion capacity and to identify biological underpinnings of these transcriptome profile differences. Sorted (CD56+/CD29+) hMPC cultures were clustered by unbiased, K-means cluster analysis into FAST and SLOW based on growth parameters (saturation density and population doubling time). FAST had greater expansion capacity indicated by significantly reduced population doubling time (-60%) and greater saturation density (+200%), nuclei area under the curve (AUC, +250%), and confluence AUC (+120%). Additionally, FAST had fewer % dead cells AUC (-44%, P < 0.05). RNA sequencing was conducted on RNA extracted during the expansion phase. Principal component analysis distinguished FAST and SLOW based on the transcript profiles. There were 2,205 differentially expressed genes (DEgenes) between FAST and SLOW (q value ≤ 0.05); 362 DEgenes met a more stringent cut-off (q value ≤ 0.001 and 2.0 fold-change). DEgene enrichment suggested FAST (vs. SLOW) had promotion of the cell cycle, reduced apoptosis and cellular senescence, and enhanced DNA replication. Novel (RABL6, IRGM1, and AREG) and known (FOXM1, CDKN1A, Rb) genes emerged as regulators of identified functional pathways. Collectively the data suggest that variation in hMPC expansion capacity occurs independently of age and sex and is driven, in part, by intrinsic mechanisms that support the cell cycle.

The metabolic fate of isotopically labeled trimethylamine-N-oxide (TMAO) in humans.

Trimethylamine-N-oxide (TMAO) is associated with chronic disease risk. However, little is known about the metabolic fate of dietary TMAO. This study sought to quantitatively elucidate the metabolic fate of orally consumed TMAO in humans. As part of a crossover feeding study, healthy young men (n=40) consumed 50-mg deuterium-labeled methyl d9-TMAO (d9-TMAO), and enrichments of TMAO and its derivatives were measured in blood for 6 h, urine and stool, as well as skeletal muscle in a subset of men (n=6). Plasma d9-TMAO was detected as early as 15 min, increased until 1 h and remained elevated through the 6-h period. TMAO exhibited an estimated turnover time of 5.3 h, and ~96% of the dose was eliminated in urine by 24 h, mainly as d9-TMAO. No d9-TMAO was detected in feces. Notably, d9-TMAO and d9-trimethylamine were detected in skeletal muscle (n=6) at 6 h, and the enrichment ratio of d9-TMAO to d9-trimethylamine was influenced by a genetic variant in flavin-containing monooxygenase isoform 3 (FMO3 G472A). These results suggest that the absorption of orally consumed TMAO is near complete and does not require processing by gut microbes. TMAO exhibits fast turnover in the circulation with the majority being eliminated in urine within 24 h. A small portion of the dose, however, is taken up by extrahepatic tissue in a manner that appears to be under the influence of FMO3 G472A polymorphism. This trial was registered at clinicaltrials.gov as NCT02558673.

Trimethylamine-N-oxide (TMAO) response to animal source foods varies among healthy young men and is influenced by their gut microbiota composition: A randomized controlled trial.

SCOPE: Trimethylamine-N-oxide (TMAO), a metabolite linked to the gut microbiota, is associated with excess risk of heart disease. We hypothesized that (i) TMAO response to animal source foods would vary among healthy men and (ii) this response would be modified by their gut microbiome. METHODS AND RESULTS: A crossover feeding trial in healthy young men (n = 40) was conducted with meals containing TMAO (fish), its dietary precursors, choline (eggs) and carnitine (beef), and a fruit control. Fish yielded higher circulating and urinary concentrations of TMAO (46-62 times; p < 0.0001), trimethylamine (8-14 times; p < 0.0001), and dimethylamine (4-6-times; P<0.0001) than eggs, beef, or the fruit control. Circulating TMAO concentrations were increased within 15 min of fish consumption, suggesting that dietary TMAO can be absorbed without processing by gut microbes. Analysis of 16S rRNA genes indicated that high-TMAO producers (≥20% increase in urinary TMAO in response to eggs and beef) had more Firmicutes than Bacteroidetes (p = 0.04) and less gut microbiota diversity (p = 0.03). CONCLUSION: Consumption of fish yielded substantially greater increases in circulating TMAO than eggs or beef. The higher Firmicutes to Bacteroidetes enrichment among men exhibiting a greater response to dietary TMAO precursor intake indicates that TMAO production is a function of individual differences in the gut microbiome.

Sonographic markers of ovarian morphology, but not hirsutism indices, predict serum total testosterone in women with regular menstrual cycles.

OBJECTIVE: To determine whether sonographic markers of ovarian morphology or male pattern hair growth scores predict androgen levels in women with regular or irregular menstrual cycles. DESIGN: Cross-sectional observational study. SETTING: Clinical research unit. PATIENT(S): Seventy-six women of reproductive age (18-39 years) were evaluated for male-pattern hair growth (using a modified Ferriman-Gallwey scoring system), ovarian morphology (by transvaginal ultrasonography), and total serum testosterone (T) (by liquid chromatography tandem mass spectrometry). INTERVENTION(S): Not applicable. MAIN OUTCOME MEASURE(S): Regional and total modified Ferriman-Gallwey scores, number of follicles per follicle size category, follicle number per ovary, ovarian volume, ovarian area, stromal to ovarian area ratio, stromal echogenicity index, total testosterone (total T), and menstrual cycle length. RESULT(S): Neither regional nor total modified Ferriman-Gallwey scores correlated with total T concentrations in women with regular or irregular menstrual cycles, as judged by the Least Absolute Shrinkage and Selection Operator technique. By contrast, a sonographic marker (follicle number per ovary 6-9 mm) significantly predicted total T concentrations in women with regular menstrual cycles but not in women with irregular menstrual cycles. CONCLUSION(S): Sonographic markers of ovarian morphology, but not hirsutism scores, predicted total T levels. However, the predictive value of ovarian morphology for total T differed by menstrual cycle status. That sonographic markers did not predict androgen levels in a diverse cohort of women with cycle irregularity suggests the potential for distinct variations in ovarian morphology for androgenic and nonandrogenic types of cycle irregularity. Overall, our findings support that an assessment of ovarian morphology may be helpful in reflecting total T levels.