James Thomas Brenna

Dietary zinc deficiency affects blood linoleic acid: dihomo-γ-linolenic acid (LA:DGLA) ratio; a sensitive physiological marker of zinc status in vivo (Gallus gallus).

Zinc is a vital micronutrient used for over 300 enzymatic reactions and multiple biochemical and structural processes in the body. To date, sensitive and specific biological markers of zinc status are still needed. The aim of this study was to evaluate Gallus gallus as an in vivo model in the context of assessing the sensitivity of a previously unexplored potential zinc biomarker, the erythrocyte linoleic acid: dihomo-γ-linolenic acid (LA:DGLA) ratio. Diets identical in composition were formulated and two groups of birds (n = 12) were randomly separated upon hatching into two diets, Zn(+) (zinc adequate control, 42.3 μg/g zinc), and Zn(−) (zinc deficient, 2.5 μg/g zinc). Dietary zinc intake, body weight, serum zinc, and the erythrocyte fatty acid profile were measured weekly. At the conclusion of the study, tissues were collected for gene expression analysis. Body weight, feed consumption, zinc intake, and serum zinc were higher in the Zn(+) control versus Zn(−) group (p < 0.05). Hepatic TNF-α, IL-1β, and IL-6 gene expression were higher in the Zn(+) control group (p < 0.05), and hepatic Δ6 desaturase was significantly higher in the Zn(+) group (p < 0.001). The LA:DGLA ratio was significantly elevated in the Zn(−) group compared to the Zn(+) group (22.6 ± 0.5 and 18.5 ± 0.5, % w/w, respectively, p < 0.001). This study suggests erythrocyte LA:DGLA is able to differentiate zinc status between zinc adequate and zinc deficient birds, and may be a sensitive biomarker to assess dietary zinc manipulation.

Metabolic fate of docosahexaenoic acid (DHA; 22:6n‐3) in human cells: direct retroconversion of DHA to eicosapentaenoic acid (20:5n‐3) dominates over elongation to tetracosahexaenoic acid (24:6n‐3)

Docosahexaenoic acid (22:6n‐3) supplementation in humans causes eicosapentaenoic acid (20:5n‐3) levels to rise in plasma, but not in neural tissue where 22:6n‐3 is the major omega‐3 in phospholipids. We determined whether neuronal cells (Y79 and SK‐N‐SH) metabolize 22:6n‐3 differently from non‐neuronal cells (MCF7 and HepG2). We observed that 13C‐labeled 22:6n‐3 was primarily esterified into cell lipids. We also observed that retroconversion of 22:6n‐3 to 20:5n‐3 was 5‐ to 6‐fold greater in non‐neural compared to neural cells and that retroconversion predominated over elongation to tetracosahexaenoic acid (24:6n‐3) by 2–5‐fold. The putative metabolic intermediates, 13C‐labeled 22:5n‐3 and 13C‐labeled 24:5n‐3, were not detected in our assays. Analysis of the expression of enzymes involved in fatty acid beta‐oxidation revealed that MCF7 cells abundantly expressed the mitochondrial enzymes CPT1A, ECI1, and DECR1, whereas the peroxisomal enzyme ACOX1 was abundant in HepG2 cells, thus suggesting that the initial site of 22:6n‐3 oxidation depends on the cell type. Our data reveal that non‐neural cells more actively metabolize 22:6n‐3 to 20:5n‐3 via channeled retroconversion, while neural cells retain 22:6n‐3.

Micronutrient Gaps in Three Commercial Weight-Loss Diet Plans

Weight-loss diets restrict intakes of energy and macronutrients but overlook micronutrient profiles. Commercial diet plans may provide insufficient micronutrients. We analyzed nutrient profiles of three plans and compared their micronutrient sufficiency to Dietary Reference Intakes (DRIs) for male U.S. adults. Hypocaloric vegan (Eat to Live-Vegan, Aggressive Weight Loss; ETL-VAWL), high-animal-protein low-carbohydrate (Fast Metabolism Diet; FMD) and weight maintenance (Eat, Drink and Be Healthy; EDH) diets were evaluated. Seven single-day menus were sampled per diet (n = 21 menus, 7 menus/diet) and analyzed for 20 micronutrients with the online nutrient tracker CRON-O-Meter. Without adjustment for energy intake, the ETL-VAWL diet failed to provide 90% of recommended amounts for B12, B3, D, E, calcium, selenium and zinc. The FMD diet was low (<90% DRI) in B1, D, E, calcium, magnesium and potassium. The EDH diet met >90% DRIs for all but vitamin D, calcium and potassium. Several micronutrients remained inadequate after adjustment to 2000 kcal/day: vitamin B12 in ETL-VAWL, calcium in FMD and EDH and vitamin D in all diets. Consistent with previous work, micronutrient deficits are prevalent in weight-loss diet plans. Special attention to micronutrient rich foods is required to reduce risk of micronutrient deficiency in design of commercial diets.