The effect of dietary zinc deficiency on the lipid composition of the rat erythrocyte membrane

Paternal Zn-deficiency abolishes metabolic effects in offspring induced by diet type

Accumulating evidence implicates that offspring are susceptible to paternal alterations in numerous fetal disorders, such as growth and metabolic defects. However, less study has been conducted to define the relationship between paternal zinc deficiency (ZnD) and energy metabolism of offspring. In the present study, we used a paternal ZnD exposure (Zn at 0.3 μg/g) model to test energy metabolism of male and female offspring with the intervention of diet type (high-fat diet and low-fat diet). Our results demonstrated that paternal ZnD decreased body weight (BW) gain per week (P < 0.01) and ME intake per week (P < 0.05) at 11 weeks in male offspring with high-fat diet intervention but not in female offspring. Further, anabolism and catabolism of hepatic energy products also exhibited alterations. ZnD attenuated liver glucose but increased lipids content accompanied with elevated adiponectin and reduction in leptin level in serum, which exhibited lipid metabolic disturbance and smaller ratio of liver weight to BW in male but not female offspring. The qRT-PCR and liver energy metabolites analysis revealed that paternal ZnD mainly induced reduction in glucose tolerance and lowered glucose uptaking ability in male offspring and thereby alleviated glycolysis and the tricarboxylic acid cycle (TCA) cycle, which displayed a male gender-dependency. Therefore, we propose that paternal ZnD abolishes metabolic effects in male offspring induced by diet type intervention. Our findings reveal a novel link between paternal Zn-D and offspring energy metabolism.

Effects of high zinc levels on the lipid synthesis in rat hepatocytes

Zinc deficiency impairs the hepatic lipid metabolism. Previous studies were focused on the negative effects of zinc deficiency on the hepatic lipid metabolism. A few studies investigated the effects of high zinc levels on the lipid metabolism in hepatocytes. In this study, rat hepatocytes were cultured and treated with different and high concentrations of zinc to investigate the effects of high zinc levels on the lipid synthesis in hepatocytes in vitro. The levels of hepatocytes functional markers, including alkaline phosphatase, lactate dehydrogenase, and albumin, were significantly higher in the zinc treatment groups than in the control group (p < 0.05, p < 0.01). The mRNA and protein levels of sterol regulatory element-binding protein 1c (SREBP-1c) were significantly higher in the zinc treatment groups than in the control group (p < 0.05, p < 0.01). Furthermore, the mRNA expression levels of acetyl-CoA carboxylase 1 (ACC1) and fatty acid synthase (FAS) were significantly higher in the medium- and high-dose zinc treatment groups than in the control group (p < 0.01). The mRNA levels of stearoyl-CoA desaturase-1 (SCD-1) were significantly higher in the high-dose group (p < 0.01). These results indicate that high levels of zinc increase hepatocytes activity and SREBP-1c expression, which upregulate the expression of ACC1, FAS, and SCD-1, thereby improving the lipid metabolism in the hepatocytes.

Influence of zinc deficiency on cell-membrane fluidity in Jurkat, 3T3 and IMR-32 cells

We investigated whether zinc deficiency can affect plasma membrane rheology. Three cell lines, human leukaemia T-cells (Jurkat), rat fibroblasts (3T3) and human neuroblastoma cells (IMR-32), were cultured for 48 h in control medium, in zinc-deficient medium (1.5 microM zinc; 1.5 Zn), or in the zinc-deficient medium supplemented with 15 microM zinc (15 Zn). The number of viable cells was lower in the 1.5 Zn group than in the control and 15 Zn groups. The frequency of apoptosis was higher in the 1.5 Zn group than in the control and 15 Zn groups. Membrane fluidity was evaluated using the 6-(9-anthroyloxy)stearic acid and 16-(9-anthroyloxy)palmitic acid probes. Membrane fluidity was higher in 1.5 Zn cells than in the control cells; no differences were observed between control cells and 15 Zn cells. The effect of zinc deficiency on membrane fluidity at the water/lipid interface was associated with a higher phosphatidylserine externalization. The higher membrane fluidity in the hydrophobic region of the bilayer was correlated with a lower content of arachidonic acid. We suggest that the increased fluidity of the membrane secondary to zinc deficiency is in part due to a decrease in arachidonic acid content and the apoptosis-related changes in phosphatidylserine distribution.

Nervonic acid is transferred from the maternal diet to milk and tissues of suckling rat pups

Three experiments were designed to investigate the metabolism of dietary nervonic acid (24:1n-9, NA) during reproduction in the rat. The first experiment determined the effect of early development on the sphingomyelin (SM) composition of rat heart and liver tissues. Rats were fed a standard chow diet and the SM fatty acid composition of the hearts and livers were analyzed of 18-20 day old fetuses, 14 day old sucklings and adult rats. The 18:0 content of SM decreases with age, while 23:0 and iso 24:0 increase with age. In the second experiment pregnant rats were fed diets supplemented with either canola, corn or peanut oil to determine the effect of diets high in 24:1n-9 and 24:0 on liver and heart SM at birth and after 14 days of suckling. Pups from the dams fed the corn oil diet had elevated 24:2n-6 in SM from heart and liver at birth, but the content of NA was not altered by dietary fat type. In the third experiment oil mixtures were designed to provide elevated levels of 22:1 and 24:1 (canola-N25), 22:0 and 24:0 (peanut-flax) or <0.01% of these fatty acids (olive-flax) and were supplemented to the diets of lactating rats. Canola-N25 oil supplemented to lactating rats resulted in increased 24:1n-9 and 24:1/24:0 with decreased 22:0 and 24:0 in milk SM relative to the other groups. The SM composition of livers of the suckling rats showed significant changes reflecting the changes in milk SM composition after 6 days of milk consumption. These experiments suggest that dietary NA and is not readily transferred across the placental barrier but does readily cross the mammary epithelium and is incorporated into milk SM. In addition, NA in milk appears to cross the intestinal epithelium where it is incorporated into the SM of heart and liver of suckling rats.

The effect of a Tropaeolum speciosum oil supplement on the nervonic acid content of sphingomyelin in rat tissues

The lipids of Tropaeolum speciosum (T. speciosum) are a rich source of naturally occurring nervonic acid (24:1n-9). We report that adding a T. speciosum oil supplement to a semi-purified diet significantly increased the amount of 24:1n-9 in liver and heart, but not brain, sphingomyelin (SM) of young rats. The bioavailability of 24:1n-9 from the lipids of T. speciosum was similar to that of 24:1n-9 ethyl ester in this rat bioassay.

Supplementation with vitamin C, vitamin E or beta-carotene influences osmotic fragility and oxidative damage of erythrocytes of zinc-deficient rats

Dietary zinc deficiency in rats causes increased osmotic fragility of their erythrocytes. In this study, the influence of supplementary antioxidants (vitamin C, vitamin E or beta-carotene) on osmotic fragility, oxidative damage and components of the primary defense system of erythrocytes of zinc-deficient rats was investigated. Indicators of hemolysis in vivo were also examined. Five groups of 12 male rats were force-fed a zinc-adequate diet (control rats), a zinc-deficient diet or a zinc-deficient diet enriched with vitamin C, vitamin E or beta-carotene. Compared with the control rats, the rats fed the zinc-deficient diet without supplementary antioxidants had greater red blood cell osmotic fragility, higher concentrations of thiobarbituric acid-reactive substances and alanine, higher glutathione S-transferase activity, lower concentration of glutathione and activity of glutathione peroxidase as well as lower activity of superoxide dismutase in plasma (P < 0.05). Supplementation with antioxidants generally improved osmotic fragility in zinc-deficient rats without influencing zinc concentration or alkaline phosphatase activity in plasma, indicators of zinc status. At some of the hypotonic saline concentrations tested, vitamin C and beta-carotene significantly affected osmotic fragility. The zinc-deficient rats fed a diet without supplementary antioxidants had significantly higher concentrations of alanine in erythrocytes than the zinc-deficient rats supplemented with vitamin C, vitamin E or beta-carotene and had significantly higher levels of thiobarbituric acid-reactive substances in erythrocytes than the rats supplemented with beta-carotene. There was no indication of hemolysis in vivo in rats fed zinc-deficient diets. The results show that supplementary antioxidants decrease osmotic fragility and oxidative damage of erythrocytes in zinc-deficient rats.

Influence of vitamin C, vitamin E and beta-carotene on the osmotic fragility and the primary antioxidant system of erythrocytes in zinc-deficient rats

The present study was designed to investigate the effect of antioxidant supplementation on the in vitro osmotic fragility of erythrocytes from zinc-deficient rats. Rats were fed either a zinc-adequate diet, zinc-deficient diet or a zinc-deficient diet enriched either with vitamin C or vitamin E or beta-carotene. Components of the primary antioxidant system of erythrocytes, parameters of hemolysis in vivo and indicators of liver injuries were also examined. In order to ensure adequate and identical food intake rats were force-fed by intragastric tube. The supplementation with antioxidants led to a marked improvement of the osmotic fragility without having influenced zinc status of the animals and components of the antioxidant system. The strongest effect was exerted by vitamin E. The rats fed the zinc-adequate diet (control group) showed unusually high values of erythrocytes osmotic fragility. Therefore there was no difference between control group and zinc-deficient group. A possible reason for this is discussed. Zinc deficiency led to a reduction of serum zinc concentration and alkaline phosphatase activity as well as to changes in the antioxidant system of erythrocytes characterized by a decrease of glutathione and an increase of glutathione S-transferase activity. Superoxide dismutase activity in serum decreased. There was no indication for hemolysis in vivo and for liver injuries.

Dietary very long chain fatty acids directly influence the ratio of tetracosenoic (24:1) to tetracosanoic (24:0) acids of sphingomyelin in rat liver

Twenty-one groups of weanling male Wistar rats were fed semipurified diets containing 5% (w/w) of different dietary fats. After 2 wk, liver sphingomyelin (SM) fatty acid composition was determined. The ratio of 24:1 to 24:0 in liver SM varied over a tenfold range in response to dietary fat type. Step-wise multiple regression analysis indicated that dietary 24:1, 24:0, and 22:1 were the most significant factors in predicting the 24:1/24:0 ratio of liver SM. The mathematical relation between the dietary fatty acid composition and liver SM 24:1/24:0 was y = 1.88 (24:1) -1.49 (24:0) +0.21 (22:1) +0.01 (18:1) +0.26, r2 = 0.95, P < 0.0001. These results were confirmed by a second experiment in which the rats were fed olive oil-based diets supplemented with various fatty acid ethyl esters.

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.

[The effect of zinc depletion on the fat content and fatty acid composition of the liver and brain in forcibly fed rats]

In the present work the influence of zinc deficiency on fat content and fatty acid composition of liver and fatty acid composition of brain of rats with a high food intake was investigated. Using the force-feeding technique the rats were fed 14.5 g food daily at days 1 to 4, and then 11.6 g food for later days. After 7 days the zinc-deficient animals had a fatty liver which was characterized by an increase in fat content (68%) and dry matter (23%). The amounts of lauric acid, myristic acid, myristoleic acid, palmitic acid, palmitoleic acid, and oleic acid were also increased by 100 to 200% in the liver of zinc-deficient animals, whereas the amount of arachidonic acid was decreased by 29%. The amounts of phosphatidylcholine and phosphatidylethanolamine in the liver were not changed by zinc deficiency, but the fatty acid composition of these phospholipids was changed. The liver phospholipids of zinc-deficient animals had a decreased proportion of arachidonic acid, but an increased proportion of docosahexaenoic acid. In the zinc-deficient animals there also existed a positive correlation between the fat content in the liver and the ratio between linoleic and arachidonic acid in the liver and a negative correlation between the fat content in the liver and the amount of arachidonic acid in the liver. These correlations as well as the changes in liver fatty acid composition of zinc-deficient animals suggest that the fatty liver might be the result of a disturbed metabolism of linoleic acid. In contrast, zinc deficiency did not influence the fatty acid composition of brain. This means that brain is protected against the effects of short-term zinc deficiency.

Zinc deficiency in the rat alters the lipid composition of the erythrocyte membrane Triton shell

The effect of dietary zinc deficiency on the lipid composition of the erythrocyte membrane Triton shell was determined. Weanling male Wistar rats were fed an egg white-based diet containing < 1.0 mg Zn/kg diet ad libitum. Control rats were either pair-fed or ad libitum-fed the basal diet supplemented with 100 mg Zn/kg diet. A Zn refed group was fed the -Zn diet until day 18 and then pair-fed the +Zn diet until day 21. Dietary Zn deficiency caused an increased cholesterol/phospholipid ratio in Triton shells compared to those from pair-fed controls. Zn deficiency caused a decreased double bond index of fatty acids in phosphatidylinositol (PI) and phosphatidylcholine (PC); there was a decreased proportion of 18:2n-6 and 22:4n-6 in PC and 20:4n-6 in PI as compared to that found in pair-fed controls. All glycerophospholipids that were retained in the shell had a lower double bond index and increased content of 16:0 and/or 18:0 relative to the phospholipid in the intact membrane.