Correlations between mercury concentration, and stable isotope ratios of carbon and nitrogen of amino acids in scalp hair from whale meat eaters and heavy fish eaters

Amino Acid Nitrogen Isotope Ratios Respond to Fish and Meat Intake in a 12-Week Inpatient Feeding Study of Men

BACKGROUND

The natural abundance nitrogen stable isotope ratio (NIR) of whole tissue correlates with animal protein intakes, including meat and fish. Amino acid (AA) NIRs (NIRAAs) are more variable than the whole-tissue NIRs and may thus better differentiate among foods.

OBJECTIVES

We evaluated whether NIRAAs were associated with intakes of fish and meat and whether these dietary associations were larger than with whole-tissue NIRs.

METHODS

Men were recruited at the National Institute of Diabetes and Digestive and Kidney Diseases in Phoenix, Arizona, and randomly assigned to one of eight 12-wk inpatient dietary interventions, which varied the presence/absence of fish, meat, and sugar-sweetened beverages (SSBs) in all possible combinations. Fasting blood was drawn pre- and postintervention and plasma and RBC NIRAAs (free and protein-bound) were measured as secondary outcomes in 32 participants. Multivariable regression was used to determine responses of postintervention NIRAAs to dietary variables, and logistic regression was used to calculate receiver operating characteristic AUCs.

RESULTS

Most plasma NIRAAs increased with fish and meat intakes, but to a greater extent with fish intake. The largest increase in response to fish intake was plasma NIRLeucine (β = 2.19, SE = 0.26). The NIRThreonine decreased with both fish and meat intakes. Fewer RBC NIRAAs increased with fish intake, and only RBC NIRProline increased with meat intake. No plasma or RBC NIRAA responded to SSB intake. We identified fish intake with a high degree of accuracy using plasma NIRLeucine (corrected AUC, cAUC = 0.96) and NIRGlutamic acid/glutamine (cAUC = 0.93), and meat intake to a lower degree using plasma NIRProline (cAUC = 0.80) and RBC NIRProline (cAUC = 0.85).

CONCLUSIONS

Plasma and RBC NIRAAs were associated with fish and meat intakes but were not superior to whole-tissue stable isotope biomarkers in identifying these intakes in a US diet. This trial is registered at www.clinicaltrials.gov as NCT01237093.

Stable isotope ratios of carbon, nitrogen and selenium concentration in the scalp hair of Crohn's disease patients who ingested the elemental diet Elental®

RATIONALE

Elental^® is an elemental diet widely used as a nutritional supplement for Crohn's disease (CD) patients in Japan. Elental^® contains amino acids as nitrogen sources and does not contain selenium (Se), and the δ¹³ C and δ¹⁵ N values of Elental^® are markedly higher and lower, respectively, than those of a normal diet.

METHODS

We compared the δ¹³ C and δ¹⁵ N values and Se concentration in the scalp hair of CD patients with those of control subjects who ate a regular diet, and estimated the amount of Elental^® ingested as a supplement. The δ¹³ C and δ¹⁵ N values and the Se concentrations were quantified using isotope ratio mass spectrometry (IRMS) and inductively coupled plasma mass spectrometry (ICP-MS), respectively.

RESULTS

An increase in Elental^® ingestion increased the δ¹³ C value in the hair of CD patients (p <0.05), while it reduced the δ¹⁵ N value (p <0.05) and tended to reduce the Se concentration in female patients.

CONCLUSIONS

The amount of Elental^® ingested could be estimated by the δ¹³ C and δ¹⁵ N values in the hair of CD patients. Furthermore, the Se deficiency in female patients may be predicted from the δ¹³ C and δ¹⁵ N values.

Essential and Non-essential Elements in Scalp Hair of Diabetics: Correlations with Glycated Hemoglobin (HbA1c)

Essential elements (Ca, Mg, Zn, Cu, Fe, Cr, Mn and V) and non-essential elements (As, Cd, Hg and Pb) were measured in scalp hair samples of 45 diabetic subjects and 59 control subjects in Japan using inductively coupled plasma mass spectrometry. All diabetic subjects took insulin and/or antidiabetic agents, with glycated hemoglobin (HbA1c) ranging between 6.2 and 14.4%. The levels of Zn, Cu and Cr in the diabetic subjects (HbA1c>7) were significantly lower than those in the control subjects (p<0.05), and these concentrations decreased significantly with increases in HbA1c (p<0.01). The levels of Fe and Mg in the diabetic subjects were insignificantly lower, and the concentration of Fe decreased significantly with increases in HbA1c (p<0.05) and the concentration of Mn tended to decrease (p<0.10). In contrast, the concentration of As tended to increase with increases in HbA1c (p<0.10). The concentrations of other elements, such as Ca, Mn, V, Pb, Cd and Hg, in the diabetic subjects were similar to those of control subjects, and did not correlate with HbA1c. The average of estimated glomerular filtration rate (eGFR) in the diabetic subjects was 77.7±29.7 mL/min/1.73 m² with large variation (12.7-148 mL/min/1.73 m²), and previous study reported the increase of urinary excretion of Zn, Cr, Mn and Mg in diabetic subjects. The decreases of Zn, Cu, Cr, Fe and Mg concentrations in hair may reflect increased urinary excretion of these elements due to diabetic nephropathy.