Quantitative measurements of dietary and [1-14C]linoleate metabolism in pregnant rats: specific influence of moderate zinc depletion independent of food intake

Zinc and DHA have opposing effects on the expression levels of histones H3 and H4 in human neuronal cells

Zn and DHA have putative neuroprotective effects and these two essential nutrients are known to interact biochemically. We aimed to identify novel protein candidates that are differentially expressed in human neuronal cell line M17 in response to Zn and DHA that would explain the molecular basis of this interaction. Two-dimensional gel electrophoresis and MS were applied to identify major protein expression changes in the protein lysates of human Ml7 neuronal cells that had been grown in the presence and absence of Zn and DHA. Proteomic findings were further investigated using Western immunoblot and real-time PCR analyses. Four protein spots, which had significant differential expression, were identified and selected for in-gel trypsin digestion followed by matrix-assisted laser desorption ionisation MS analysis. The resultant peptide mass fingerprint for each spot allowed their respective identities to be deduced. Two human histone variants H3 and H4 were identified. Both H3 and H4 were downregulated by Zn in the absence of DHA (Zn effect) and upregulated by DHA (DHA effect) in the presence of Zn (physiological condition). These proteomic findings were further supported by Western immunoblot and real-time PCR analyses using H3- and H4-specific monoclonal antibodies and oligonucleotide primers, respectively. We propose that dietary Zn and DHA cause a global effect on gene expression, which is mediated by histones. Such novel information provides possible clues to the molecular basis of neuroprotection by Zn and DHA that may contribute to the future treatment, prevention and management of neurodegenerative diseases such as Alzheimer's disease.

Growth of zinc-deficient rats during intra-gastric tube feeding

This study aimed to examine the reasons for the lack of growth in rats fed a zinc-deficient (ZnD) diet via gastric tube. Four days after rats were given free access to the ZnD diet (0.3 mg/kg Zn), their food intake had decreased, and their growth had stopped. Rats were then fed via gastric tube; growth was restored in rats fed a control diet (25 mg/kg Zn; restored group) but not in those fed the ZnD diet (ZnD group). In the ZnD group, there was no reduction in the apparent absorption of dry matter, protein, or ash during 3 days of tube feeding. Dry matter in urine was markedly higher on day 3 and mainly consisted of glucose. Urinary nitrogen was also elevated in the ZnD group, but nitrogen balance remained positive; i.e., bodily protein continued to increase during the 3 days of tube feeding. Drinking water consumption in the ZnD group was markedly reduced from the second day of tube feeding. On the other hand, urine volume in the ZnD group was comparable to that in the restored group. Water content in the bodies of the ZnD group was reduced. These observations demonstrate that the ZnD group was dehydrated. In conclusion, rats fed a ZnD diet via gastric tube did not grow because their drinking water consumption decreased with progression of zinc deficiency, thereby, decreasing bodily water content. Administration of water led to growth in the ZnD group.

Double-blind, placebo-controlled trial comparing effects of supplementation of two micronutrient sprinkles on fatty acid status in Cambodian infants

BACKGROUND

Infants in developing countries require early dietary interventions to prevent nutritional deficiencies, above all protein, energy, iron and zinc. To what extent these interventions may affect the fatty acid (FA) status is still unknown.

OBJECTIVES

To examine and compare the effects of 2 micronutrient "sprinkles" supplementations (iron 12.5 mg + folic acid 150 microg, iron/folate and iron 12.5 mg + folic acid 150 microg + zinc 5 mg + vitamins A, C and D3, mineral/micronutrient [MMN]) versus placebo on the FA status of Cambodian infants.

METHODS

A total of 204 infants age 6 mo and living in Kompong Chhnang Province, Cambodia, were randomly assigned to receive daily supplementation of MMN (n = 68) and iron/folate (n = 68) or placebo (n = 68) for a 12-mo period in powder form as sprinkles. At the end of the intervention period, FAs in the range of 16 to 24 C were determined in blood drops absorbed on a strip collected from 182 subjects, and values among the 3 intervention subgroups and those of 21 Italian 18-mo-old, normal-growing infants as the reference group were compared.

RESULTS

At the end of the supplementation trial, higher levels of the 2 essential FAs (EFAs) (linoleic acid, 18:2n-6, and alpha-linolenic acid, 18:3n-3) were found in the MMN group. No differences occurred for the major longer chain derivatives of both EFAs arachidonic acid (20:4n-6) and docosahexaenoic acid (22:6n-3). In MMN supplemented Cambodians, blood levels of linoleic acid approached those of Italian infants, and in addition their alpha-linolenic acid levels were improved. Cambodian infants, mostly still breast-fed through the second year of life, showed significantly higher levels of long-chain derivatives of both the n-6 and the n-3 series compared with Italians.

CONCLUSIONS

Supplementation with iron, folic acid, zinc and vitamins was associated with an increase of linoleic acid and alpha-linolenic acid levels in Cambodian infants versus placebo, without significant changes in the concentrations of their longer chain derivatives, resulting in a FA status closer to Italian counterparts for the essential polyunsaturated FA levels. The iron/folate-treated infants showed no differences compared with the other 2 groups. Studies are needed to differentiate the potential effects of the supplemented micronutrients on the FA status.

α-Linolenic acid does not contribute appreciably to docosahexaenoic acid within brain phospholipids of adult rats fed a diet enriched in docosahexaenoic acid

Adult male unanesthetized rats, reared on a diet enriched in both alpha-linolenic acid (alpha-LNA) and docosahexaenoic acid (DHA), were infused intravenously for 5 min with [1-(14)C]alpha-LNA. Timed arterial samples were collected until the animals were killed at 5 min and the brain was removed after microwaving. Plasma and brain lipid concentrations and radioactivities were measured. Within plasma lipids, > 99% of radioactivity was in the form of unchanged [1-(14)C]alpha-LNA. Eighty-six per cent of brain radioactivity at 5 min was present as beta-oxidation products, whereas the remainder was mainly in 'stable' phospholipid or triglyceride as alpha-LNA or DHA. Equations derived from kinetic modeling demonstrated that unesterified unlabeled alpha-LNA rapidly enters brain from plasma, but that its incorporation into brain phospholipid and triglyceride, as in the form of synthesized DHA, is < or = 0.2% of the amount that enters the brain. Thus, in rats fed a diet containing large amounts of both alpha-LNA and DHA, the alpha-LNA that enters brain from plasma largely undergoes beta-oxidation, and is not an appreciable source of DHA within brain phospholipids.

Effects of dietary fat and zinc on adiposity, serum leptin and adipose fatty acid composition in C57BL/6J mice

Zinc (Zn) has been implicated in altered adipose metabolism, insulin resistance and obesity. The objective of this study was to investigate the effects dietary Zn deficiency and supplementation on adiposity, serum leptin and fatty acid composition of adipose triglycerides and phospholipid in C57BL/6J mice fed low-fat (LF) or high-fat (HF) diets for a 16 week period. Weanling C57BL/6J mice were fed LF (16% kcal from soybean oil) or HF (39% kcal from lard and 16% kcal from soybean oil) diets containing 3, 30 or 150 mg Zn/kg diet (ZD = Zn-deficient, ZC = Zn control and ZS = Zn-supplemented, respectively). HF-fed mice had higher fat pad weights and lower adipose Zn concentrations than the LF-fed mice. The ZD and ZS groups had a reduced content of fatty acids in adipose triglycerides compared to the ZC group, suggesting that zinc status may influence fatty acid accumulation in adipose tissue. Serum leptin concentration was positively correlated with body weight and body fat, and negatively correlated with adipose Zn concentration. Dietary fat, but not dietary Zn, altered the fatty acid composition of adipose tissue phospholipid and triglyceride despite differences in Zn status assessed by femur Zn concentrations. The fatty acid profile of adipose triglycerides generally reflected the diets. HF-fed mice had a higher percentage of C20:4 n-6, elevated ratio of n-6/n-3, lower ratio of PUFA/SAT and reduced percentage of total n-3 fatty acids in adipose phospholipid, a fatty acid profile associated with obesity-induced risks for insulin resistance and impaired glucose transport. In summary, the reduced adipose Zn concentrations in HF-fed mice and the negative correlation between serum leptin and adipose Zn concentrations support an interrelationship among obesity, leptin and Zn metabolism.

Neonatal dietary zinc deficiency in artificially reared rat pups retards behavioral development and interacts with essential fatty acid deficiency to alter liver and brain fatty acid composition

The objective of this study was to investigate whether short-term zinc deficiency in the early neonatal period would exacerbate the effects of essential fatty acid (EFA) deficiency on liver and brain long-chain polyunsaturated fatty acid (LCPUFA) composition, as well as on behavioral development in artificially reared rat pups. Using a 2 x 2 factorial design, male Long-Evans rat pups were reared artificially from postnatal d 5 to 16; pups were fed through gastrostomy tubes with rat formula deficient in zinc and/or EFA. As expected, EFA deficiency significantly reduced levels of arachidonic acid [AA, 20:4(n-6)] and docosahexanoic acid [DHA, 22:6(n-3)] in liver phosphatidylcholine (PC) and brain phosphaditylethanolamine (PE), and increased 22:5(n-6) levels in liver and brain PC and PE. There were significant interactions between zinc and EFA in liver such that zinc deficiency reduced AA and DHA in the EFA-adequate groups, but significantly increased AA in the EFA-deficient groups. Contrary to the hypothesis, short-term zinc deficiency did not exacerbate the effects of EFA deficiency in liver phospholipids. In brain PE, a significant interaction between EFA and zinc was observed such that zinc deficiency increased 22:5(n-6) concentrations in EFA-adequate but not in EFA-deficient groups. Regardless of their EFA status, zinc-deficient rats were growth retarded and demonstrated deficits in locomotor skills. Possible effects of long-term zinc and EFA deficiency on brain function should be investigated in future studies.

The influence of neonatal nutrition on behavioral development: a critical appraisal

Specific nutrients appear to modify the metabolism of neurotransmitters, which are endogenous regulators of neurogenesis, neural migration, and synaptogenesis during both embryonic and early postnatal life. This has led to the question of whether, by affecting neurotransmission, malnutrition during the early neonatal period affects behavioral development. The literature based on animal models suggests that nutrient deficiencies during early life influence neurotransmission and, in some instances, also affect behavioral outcomes. A clear answer to the question, however, remains elusive. This can be attributed to the complexity of the process of brain development, where changes at a cellular level may not necessarily translate into changes at a behavioral level. Future investigations in this important area of research should work toward refinement of the design of behavioral experiments so that these studies can contribute to the understanding of the putative mechanisms involved.

Zinc deficiency impairs whole-body accumulation of polyunsaturates and increases the utilization of [1-14C]linoleate for de novo lipid synthesis in pregnant rats

Zinc deficiency impairs the metabolism of polyunsaturates, but the degree to which its effects are independent of food intake are still in question. Identical amounts of a semiliquid control diet (26.4 mg zinc/kg) or moderately zinc deficient diet (3.2 mg zinc/kg) were tube fed to rats for 11 days during the second half of pregnancy to evaluate the specific effects of zinc deficiency on maternal utilization and fetal accumulation of polyunsaturates. The whole body fatty acid balance method was used to determine net accumulation of polyunsaturates and their whole-body disappearance. Incorporation of 14C from [1-14C]linoleate into maternal and fetal lipid classes was also studied on days 20-21. At term, zinc-deficient rats had significantly higher whole-body disappearance of linoleate and alpha-linolenate and lower accumulation of n-6 and n-3 long-chain polyunsaturates. Zinc-deficient rats had higher 14C activity in free cholesterol, saturates, and monounsaturates in several maternal organs but not in the fetuses. We conclude that during pregnancy, moderate zinc deficiency not affecting food intake or weight gain still alters whole-body metabolism of linoleate and alpha-linolenate towards increased beta-oxidation and also increases the utilization of carbon from linoleate for de novo lipid synthesis.