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ARS Home Pacific West Area Davis, California Western Human Nutrition Research Center Obesity and Metabolism Research Research





- Allen, Lindsay - A
- Human Nutrition (107)

Research Project: **Location:
                            Obesity and Metabolism Research** Project Number: 2032-51530-025-046-A
                        
                        Project Type: Cooperative Agreement Start Date: Jun 1, 2019
                        
                        End Date: Sep 1, 2021 **Objective:**
                        
                        The purpose of the proposed research is to establish Reference Values (RVs) for micronutrients (MN) and macronutrients in human milk. We propose to conduct a longitudinal project on well-nourished women and infants in four countries in which milk will be collected in a systematic, consistent way as informed by our review. With the samples obtained we will perform (a) laboratory analyses of milk, plasma and urine macronutrients and micronutrients (including iodine) to construct RVs for global application, (b) analyses of HMOs and proteins in milk, and (c) metabolomic analysis of FAA and other metabolites in infant serum. The project is funded by Bill and Melinda Gates Foundation (B&MGF). 

Iodine concentration in mature human milk is highly variable and sensitive to maternal iodine intake. More data on milk concentrations are needed in combination with measures of maternal and infant iodine intake to resolve disparities in recommended iodine intakes for infants and to discourage excessively high fortification levels in formula and complementary foods. As part of the planned micronutrient analyses the iodine status of the mothers, infants and milk will be assessed. **Approach:**
                        
                        Dried blood spot ( ̃ 5000), milk ( ̃ 3000), and urine samples ( ̃ 6000) along with salt samples ( ̃ 400) from the 4 sites will be used to assess the iodine status of mothers and infants as well as local salt iodization levels in this study. In dried blood spot collected from mothers and infants, thyroglobulin (Tg), thyroid stimulating hormone (TSH) and thyroxine (T4) in the infant should be measured to confirm adequate maternal and infant iodine status ( ̃ 5000 x 3 analyses). Milk ( ̃ 3000 analyses) and maternal and infant urine iodine concentrations (UIC,  ̃ 6000 analyses) will provide further information on the iodine economy during breastfeeding and lactation. Salt samples from the households and markets will be used to assess the level of local salt iodization ( ̃ 400 analyses).

Dried blood spots (DBS)
Tg will be measured with a DBS-Tg enzyme-linked immunosorbent assay (ELISA) (1). Serum control samples (Liquicheck Tumor Marker Control; Bio-Rad, Hercules, CA, USA) will be used as standards for the DBS Tg assays and in-house DBS samples will be used for quality control.

TSH and total T4 will be measured with the use of an automated time-resolved fluoroimmunoassay method (GSP 2021-0010; PerkinElmer, Turku, Finland) and related GSP Neonatal TSH/T4 kit (PerkinElmer, Turku, Finland). Kit-specific DBS controls will be used for the analysis. 

Urine and salt samples 
Urinary iodine concentration (UIC) and salt iodine concentration will be analyzed with the use of the Sandell-Kolthoff method (2). The laboratory at ETH Zurich participates in the program to ensure the quality of UIC procedures (EQUIP, U.S. Centers for Disease Control and Prevention, Atlanta GA, USA). External quality control will be ensured by measuring two control urine samples that will be added to the daily sample measurements. 

Breast milk samples
Breast milk iodine concentration will be analyzed by multi collector inductively coupled plasma mass spectrometry (MC-ICP-MS) with the use of isotope dilution analysis with 129I and Tellurium for mass bias correction (3). Samples will be prepared with the use of tetramethylammonium hydroxide (Tama, Kawasaki, Japan) for iodine extraction at 90°C for 180 min. Whole-milk powder standard reference material (NIST SRM1549a Whole Milk Powder; National Institute of Standards and Technology, Gaithersburg, MD) will be used as an external control.


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