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Background There is growing interest in the supplementation of arginine (Arg) and citrulline (Cit) in obesity due to their potential anti-obesogenic and anti-inflammatory properties. However, there is no consensus on the metabolic changes in Arg kinetics in obesity. Objectives This exploratory cross-sectional study aimed to investigate the association between obesity, sex, and sex-by-obesity interaction on whole-body Arg kinetics in a large group of human subjects. Methods We studied 83 nonobese [BMI (kg/m2) <30] and 80 morbidly obese (BMI >30) middle-aged individuals (40% males) enrolled in the MEDIT (Metabolism of Disease with Isotope Tracers) trial. After body-composition measurement by DXA, we collected arterial(ized) blood samples for amino acid (AA) concentrations, markers of inflammation [high-sensitivity C-reactive protein (hs-CRP)], liver function, and glucose in a postabsorptive state. We administered a pulse of AA stable tracers and measured whole-body production (WBP) of Arg, Cit, ornithine (Orn), phenylalanine, and tyrosine, and calculated their clearance (disposal capacity) and metabolite interconversions [markers for NO and de novo Arg production, systemic Arg hydrolysis, and whole-body protein breakdown (wbPB)]. We measured plasma enrichments by LC-MS/MS and statistics by Fisher's exact test or analysis of (co)variance. Significance was set at P  < 0.05. Results Obese individuals were normoglycemic and characterized by low-grade inflammation (P  < 0.0001) and greater wbPB (P  = 0.0298). We found lower plasma Cit concentration (P  < 0.0001) in the obese group but no differences in the WBP of Arg, Cit, and Orn. Furthermore, we observed overproduction of NO (P  < 0.0001) in obesity but lower de novo Arg production (P  = 0.0007). The WBP of Arg was lower in females for almost all Arg-related AAs, except for plasma Cit and NO production. Conclusions Alterations in Arg metabolism are present in morbid obesity. Further studies are needed to investigate if these changes could be related to factors such as increased Arg requirement in obesity or metabolic adaptation. [ABSTRACT FROM AUTHOR]

Background There has been growing interest in studying postprandial glucose responses using continuous glucose monitoring (CGM) in nondiabetic individuals. Accurate measurement of glucose responses to meals can facilitate applications such as precision nutrition and early detection of diabetes. Objectives We aimed to quantify the discordance between simultaneous postprandial glucose measurements made using plasma and CGM. Methods We studied 10 nondiabetic older adults who randomly consumed 9 predefined meals of varying macronutrient compositions. Glucose was measured for 8 h after the meal by the CGM, blood samples for plasma collection were taken regularly, and plasma glucose was quantified using gold-standard laboratory measurement and a fingerstick blood glucose meter. The primary outcome measured was the mean absolute relative difference (MARD) of CGM and fingerstick measurements relative to the gold standard. Secondary outcomes were Bland–Altman statistics, Clarke Error Grid, and time in range metrics. Additional subgroup analyses were performed by stratifying the postprandial glucose measurements based on the macronutrient composition of the meals. Results When compared against the gold-standard postprandial glucose measurements, the fingerstick meter was more accurate (MARD: 8.0%; 95% CI: 7.6%, 8.6%) than the CGM (MARD: 13.7%; 95% CI: 13.1%, 14.3%; P  < 0.0001). After the meals, Bland–Altman analysis demonstrated that the CGM underestimated the 8-h gold-standard glucose rise by 12.8 mg/dL on average (P  < 0.0001), whereas the fingerstick meter did so by 5.5 mg/dL on average (P  < 0.0001). The CGM underestimated the time spent in the 70–180 mg/dL range (P  = 0.002) and overestimated the time spent <70 mg/dL (P  < 0.0001) compared with the other 2 methods. Conclusions We discovered discordance between gold standard, fingerstick, and CGM in measuring plasma glucose concentrations after a meal. Consequently, emerging applications of CGM in healthy individuals, such as precision nutrition and diabetes onset prediction, may need to account for these discordances. This trial was registered at clinicaltrials.gov as NCT04928872. [ABSTRACT FROM AUTHOR]

Background Disturbances in protein metabolism and impaired muscle health have been observed in chronic obstructive pulmonary disease (COPD). The ω-3 (n–3) PUFAs EPA and DHA are known for their anti-inflammatory and muscle health-enhancing properties. Objectives We examined whether daily EPA + DHA supplementation can improve daily protein homeostasis in patients with COPD by reducing postabsorptive whole-body protein breakdown (PB) and enhancing the anabolic response to feeding in a dose-dependent way. Methods Normal-weight participants with moderate to severe COPD (n  = 32) received daily for 4 wk, according to a randomized double-blind placebo controlled 3-group design, a high dose (3.5 g, n  = 10) of EPA + DHA, a low dose (2.0 g, n  = 10) of EPA + DHA, or placebo (olive oil, n  = 12) via gel capsules. At pre- and postintervention, stable isotope tracers were infused to assess postabsorptive netPB [postabsorptive PB – protein synthesis (PS)] and the anabolic response (prandial netPS = prandial PS-PB) to a protein meal. In addition, muscle mass and function were measured. Results Plasma phosphatidylcholine EPA and DHA concentrations were higher after 4 wk of supplementation in both EPA + DHA groups (P  < 0.004), and there was a trend toward higher values for plasma EPA after the high compared with the low dose of EPA + DHA (P  = 0.065). Postabsorptive PB was lower after 4 wk of the high dose of EPA + DHA, whereas netPB was lower independent of the dose of EPA + DHA (low dose, P  = 0.037; high dose, P  = 0.026). Prandial netPS was increased only after the high dose of EPA + DHA (P  = 0.03). Extremity lean mass but not muscle function was increased, independent of the EPA + DHA dose (P  < 0.05). Conclusions Daily n–3 PUFA supplementation for 4 wk induces a shift toward a positive daily protein homeostasis in patients with COPD in part in a dose-dependent way. Daily doses up to 3.5 g EPA and DHA are still well tolerated and lead to protein gain in these patients. This trial was registered at clinicaltrials.gov as NCT01624792. [ABSTRACT FROM AUTHOR]

Background Milk is an important high-quality animal protein source in low- and middle-income countries (LMICs). Although the true ileal digestibility and absorption of milk has been shown to be high in French adults, this may be lower in individuals from LMICs who are at risk of environmental enteropathy. Objective To determine the true ileal indispensable amino acid (IAA) digestibility of intrinsically labeled goat milk protein in South Indian women of reproductive age (WRA), using the dual-isotope tracer technique, and to measure intestinal absorption of amino acid and inert sugar in the same participants using L-allo-isoleucine and a dual-sugar assay. Methods Milk with 2H-labeled protein collected from a lactating goat fed intrinsically 2H-labeled fodder (maize and cowpea) was spray dried. Labeled milk protein was administered in a plateau feeding protocol to WRA with normal BMI, in whom urinary lactulose and mannitol recovery and the lactulose/mannitol ratio (LMR) were measured, to determine its true ileal IAA digestibility by the dual-isotope tracer technique with a reference U-13C–amino acid mixture. A phenylalanine absorption index was calculated from the plasma to meal ratio of 13C9 phenylalanine within the digestibility protocol. On a separate day, the allo-isoleucine absorption index was estimated from the ratio of plasma allo-isoleucine enrichments after oral 13C6-15N-L- and intravenous 2H10-L-allo-isoleucine administration. Results The means ± SDs of true ileal IAA digestibility of goat milk protein, lactulose and mannitol recovery, LMR, allo-isoleucine and phenylalanine absorption index were 94.0 ± 2.9%, 0.09 ± 0.03%, 7.9 ± 2.3%, 0.012 ± 0.004, 88.4 ± 3.8% and 24.5 ± 1.6%, respectively. The LMR correlated with the allo-isoleucine absorption index (r s = –0.93, P  = 0.008). Conclusion The true ileal digestibility of goat milk protein in South Indian WRA with normal intestinal absorptive function and integrity was comparable to earlier estimates in healthy French adults. [ABSTRACT FROM AUTHOR]

Researchers have found that decreased levels of circulating citrulline could be an indicator of intestinal failure. Typically, this amino acid, which is produced by the intestinal mucosa cells, circulates in the blood at a physiological level of ~40 µM. The current methodology for measuring this level involves the use of bulky equipment, such as mass spectroscopy and analysis at a central laboratory, which can delay diagnosis. Therefore, the current detection method is unsuited for routine monitoring at a doctor's office. Our research group proposes the development of a point-of-care (POC) device to overcome this issue. The proposed device utilizes surface-enhanced Raman spectroscopy (SERS) coupled with a specifically designed aptamer, capable of binding to citrulline, conjugated to colloidal gold nanoparticles. The assay is then embedded within a vertical flow paper-fluidic platform as a deliverable at the POC, and a handheld Raman spectrometer (638-nm excitation) was used to interrogate the sample. Results showed good dynamic range and specificity with an average 73% decrease in SERS signal intensity with increasing concentrations of citrulline (0 to 50 µM) in phosphate- buffered saline compared to its controls: glycine, glutamine, histidine, and valine, which showed less than 10% average decrease in the presence of 200 µM of each analyte. Further, the limit of detection (LOD) within a chip was determined to be 0.56 µM, whereas the LOD across chips was below 10 µM. [ABSTRACT FROM AUTHOR]