Differential display of intestinal mRNAs regulated by dietary zinc

Dietary zinc levels affect growth, appetite, and lipid metabolism of Chinese perch (Siniperca chuatsi)

An 84-day feeding experiment was conducted to investigate the effects of dietary Zn (zinc) on growth performance, food intake, and lipid metabolism of Chinese perch (Siniperca chuatsi). Five isonitrogenous and isolipidic diets with differential Zn contents (67, 100, 149, 230, and 410 mg/kg) were fed to 270 fish (35.47 ± 0.49 g). Results showed that fish growth and food intake increased markedly with the dietary 149 mg/kg Zn levels. Meanwhile, the food intake of 149 mg/kg group was significantly higher than that of other treatment groups after feeding for 8 weeks (P < 0.05). The qRT-PCR results showed that the expression of center appetite regulation factors in the hypothalamus was significantly regulated, and 149 mg/kg significantly increased mRNA expression of npy (neuropeptide Y) and decreased pomc (anorexigenic proopiomelanocortin) and cart (cocaine- and amphetamine-regulated transcript) gene expression. Meanwhile, the expressions of the main genes (such as leptin A and ghrelin) involved in peripheral appetite regulation factors were significantly up-regulated firstly and then reduced with the dietary Zn level increased, whereas the expression of cck (cholecystokinin) was significantly up-regulated. Serum AST (aspartate transaminase) and ALT (alanine transaminase) activities in fish fed the diets containing 230 and 410 mg/kg were significantly higher than that in other groups (P < 0.05). The lipid content of liver in 67 and 100 mg/kg groups was significantly higher than other groups (P < 0.05). Furthermore, dietary Zn significantly elevated the serum TG (triglyceride) and TCHO (total cholesterol) content levels (P < 0.05). Fish fed a high Zn diet (149, 230, and 410 mg/kg) dramatically down-regulated expression of srebp1 (sterol regulatory element binding proteins1c) and fas (fatty acid synthetase), but up-regulated expression of pparα (peroxisome proliferators-activated receptor-α) and cpt1 (carnitine palmitoyl transferase I) in the liver. The optimal dietary Zn inclusion level ranged from 146.69 to 152.86 mg/kg diet, based on two-slope broken-line regression analysis of WGR (weight gain rate) and FCR (feed conversion rate) for Chinese perch.

Effects of Zinc Lactate Supplementation on Growth Performance, Intestinal Morphology, Serum Parameters, and Hepatic Metallothionein of Chinese Yellow-Feathered Broilers

In poultry, organic zinc compounds have higher bioavailability than inorganic zinc sources. However, as an organic zinc source, the application of zinc lactate (ZL) on Chinese yellow-feathered broilers has been rarely reported. Hence, the present study aimed to investigate the effects of ZL supplementation on growth performance, small intestinal morphology, serum biochemical parameters, immune organ index, as well as hepatic metallothionein of Chinese yellow-feathered broilers. A total of 2100 broilers (19 days old) were randomly assigned to 5 treatment groups, including the control (fed basal diet), ZL40 (basal diet plus 40 mg/kg ZL), ZL60 (basal diet plus 60 mg/kg ZL), ZL80 (basal diet plus 80 mg/kg ZL), and ZS80 (basal diet plus 80 mg/kg ZS. Each treatment group had 6 replicates with 70 chickens per replicate. Compared to the control group, the ZL40 and the ZS80 groups had a lower feed to gain ratio (P < 0.05), ZL40 group had higher duodenum and ileum villus heights (P < 0.05), and ZS80 and ZL80 groups had a lower ratio of villus height to crypt depth in the jejunum (P < 0.01). In addition, the ZL60 group had a higher concentration of total protein (P < 0.05) and activity of glutathione peroxidase (GSH-Px) (P < 0.01) compared with the ZS80 and the control groups. Interestingly, the ZL40, ZL60, and ZL80 groups all had higher levels of hepatic metallothionein than the other groups (P < 0.01). In conclusion, zinc lactate had a higher bioavailability and could be used as an alternative to zinc sulfate.

Receptor Guanylyl Cyclase C and Cyclic GMP in Health and Disease: Perspectives and Therapeutic Opportunities

Receptor Guanylyl Cyclase C (GC-C) was initially characterized as an important regulator of intestinal fluid and ion homeostasis. Recent findings demonstrate that GC-C is also causally linked to intestinal inflammation, dysbiosis, and tumorigenesis. These advances have been fueled in part by identifying mutations or changes in gene expression in GC-C or its ligands, that disrupt the delicate balance of intracellular cGMP levels and are associated with a wide range of clinical phenotypes. In this review, we highlight aspects of the current knowledge of the GC-C signaling pathway in homeostasis and disease, emphasizing recent advances in the field. The review summarizes extra gastrointestinal functions for GC-C signaling, such as appetite control, energy expenditure, visceral nociception, and behavioral processes. Recent research has expanded the homeostatic role of GC-C and implicated it in regulating the ion-microbiome-immune axis, which acts as a mechanistic driver in inflammatory bowel disease. The development of transgenic and knockout mouse models allowed for in-depth studies of GC-C and its relationship to whole-animal physiology. A deeper understanding of the various aspects of GC-C biology and their relationships with pathologies such as inflammatory bowel disease, colorectal cancer, and obesity can be leveraged to devise novel therapeutics.

Slc39a4 in the small intestine predicts zinc absorption and utilization: a comprehensive analysis of zinc transporter expression in response to diets of varied zinc content in young mice

Zinc homeostasis is primarily maintained by zinc transporters that regulate zinc uptake and efflux in the small intestine; however, the relative contribution of the many zinc transporters identified (Slc39a1-14, Slc30a1-10) to dietary zinc absorption and utilization remains unknown. The objective of this study was to determine the expression of Slc39a1-14 and Slc30a1-10 in the small intestine and their relative contribution to dietary zinc absorption in mice. Five-week-old male C57BL/6J mice were fed modified AIN-93G diets containing <1, 30, or 100ppm zinc (n=15 mice/diet). Following 1 week of feeding, mice were given an oral gavage containing ⁶⁷Zn and liver and plasma isotope appearance was determined 6-h later by ICP-MS. Expression of Slc39a1-14 and Slc30a1-10 was determined in mucosa from duodenum, jejunum, and ileum. Plasma and liver total zinc concentrations were not different after one week of feeding (P>.05). Liver and plasma appearance of ⁶⁷Zn was greater in mice fed <1ppm compared to the 30ppm (P<.0001) and 100ppm (P<.0001) zinc diets. With the exception of Slc39a2, Slc39a12, Slc30a3, and Slc30a8, the remaining zinc transporters were expressed across all diets and intestinal segments. Expression of Slc39a4, Slc39a11, and Slc30a6 changed with diet (P_diet<.05 for all); expression of Slc39a5, Slc39a7, Slc39a11, Slc39a14, Slc30a1, Slc30a2, Slc30a4, Slc30a5, Slc30a7, and Slc30a10 changed by intestinal segment (P_segment<.05 for all). Slc39a4 was the only transporter positively associated with liver (r²=0.316, P<.001) and plasma (r²=0.189, P<.01) ⁶⁷Zn appearance. Although most zinc transporters are expressed in the small intestine, intestinal Slc39a4 predicts fractional zinc absorption and utilization in young mice.

Single or Combined Applications of Zinc and Multi-strain Probiotic on Intestinal Histomorphology of Broilers Under Cyclic Heat Stress

Two-hundred-eighty-day-old broiler chicks were divided into seven groups. The groups were designated as T1, thermoneutral zone; T2, heat stressed (HS); T3, HS + zinc (Zn) supplementation (30 mg/kg); T4, HS + Zn (60 mg/kg); T5, HS + probiotic (0.1 g/kg); T6, HS + probiotic (0.1 g/kg) + Zn (30 mg/kg); and T7, HS + Zn (60 mg/kg) + probiotic (0.1 g/kg). Significant decrease (p < 0.05) was observed in villus height (VH), VH to crypt depth ratio, and villus surface area of all intestinal segments in the T2 group when compared with the T1 group. The same parameters had significantly higher (p < 0.05) values in the jejunum and ileum of the Zn- and probiotic-supplemented groups (alone + combination) when compared with the T2 group. The birds exposed to HS showed fewer (p < 0.05) intraepithelial lymphocytes (IELs) in the jejunum and ileum than the T1 group, while their count increased in the jejunum and ileum with dietary treatments. In conclusion, Zn and probiotic positively modulated the intestinal microstructures of broilers kept under high environmental temperature.

Effects of zinc source and dietary concentration on serum zinc concentrations, growth performance, wool and reproductive characteristics in developing rams

Dietary Zn has significant impacts on the growth and development of breeding rams. The objectives of this study were to evaluate the effects of dietary Zn source and concentration on serum Zn concentration, growth performance, wool traits and reproductive performance in rams. Forty-four Targhee rams (14 months; 68 ± 18 kg BW) were used in an 84-day completely randomized design and were fed one of three pelleted dietary treatments: (1) a control without fortified Zn (CON; n = 15; ~1 × NRC); (2) a diet fortified with a Zn amino acid complex (ZnAA; n = 14; ~2 × NRC) and (3) a diet fortified with ZnSO4 (ZnSO4; n = 15; ~2 × NRC). Growth and wool characteristics measured throughout the course of the study were BW, average daily gain (ADG), dry matter intake (DMI), feed efficiency (G : F), longissimus dorsi muscle depth (LMD), back fat (BF), wool staple length (SL) and average fibre diameter (AFD). Blood was collected from each ram at four time periods to quantify serum Zn and testosterone concentrations. Semen was collected 1 to 2 days after the trial was completed. There were no differences in BW (P = 0.45), DMI (P = 0.18), LMD (P = 0.48), BF (P = 0.47) and AFD (P = 0.9) among treatment groups. ZnSO4 had greater (P ≤ 0.03) serum Zn concentrations compared with ZnAA and CON treatments. Rams consuming ZnAA had greater (P ≤ 0.03) ADG than ZnSO4 and CON. There tended to be differences among groups for G : F (P = 0.06), with ZnAA being numerically greater than ZnSO4 and CON. Wool staple length regrowth was greater (P < 0.001) in ZnSO4 and tended to be longer (P = 0.06) in ZnAA treatment group compared with CON. No differences were observed among treatments in scrotal circumference, testosterone, spermatozoa concentration within ram semen, % motility, % live sperm and % sperm abnormalities (P ≥ 0.23). Results indicated beneficial effects of feeding increased Zn concentrations to developing Targhee rams, although Zn source elicited differential responses in performance characteristics measured.

Current understanding of guanylin peptides actions

Guanylin peptides (GPs) family includes guanylin (GN), uroguanylin (UGN), lymphoguanylin, and recently discovered renoguanylin. This growing family is proposed to be intestinal natriuretic peptides. After ingestion of a salty meal, GN and UGN are secreted into the intestinal lumen, where they inhibit sodium absorption and induce anion and water secretion. At the same conditions, those hormones stimulate renal electrolyte excretion by inducing natriuresis, kaliuresis, and diuresis and therefore prevent hypernatremia and hypervolemia after salty meals. In the intestine, a well-known receptor for GPs is guanylate cyclase C (GC-C) whose activation increases intracellular concentration of cGMP. However, in the kidney of GC-C-deficient mice, effects of GPs are unaltered, which could be by new cGMP-independent signaling pathway (G-protein-coupled receptor). This is not unusual as atrial natriuretic peptide also activates two different types of receptors: guanylate cylcase A and clearance receptor which is also G-protein coupled receptor. Physiological role of GPs in other organs (liver, pancreas, lung, sweat glands, and male reproductive system) needs to be discovered. However, it is known that they are involved in pathological conditions like cystic fibrosis, asthma, intestinal tumors, kidney and heart failure, obesity, and metabolic syndrome.

Trace elements analysis of urine and hair in tuberculous pleurisy

In this study, copper, zinc, magnesium, manganese, selenium, and iron of urine and hair were measured in the patients with tuberculous (TB) pleurisy (n = 24) and in the control group (n = 20). Selenium, magnesium, and zinc of hair were found to be significantly lower in TB pleurisy cases than those in the control group (p < 0.05, p < 0.001, and p < 0.01, respectively). On the contrary, selenium and magnesium of urine were found to be significantly elevated in TB pleurisy cases than those in the control group (p < 0.05 and p < 0.001, respectively). There was no significant difference in the value of manganese and iron between TB pleurisy and the control group (p > 0.05). Copper level were significantly increased in hair and decreased in urine of the patients (p < 0.01). The occurrence of these abnormalities constitutes new information regarding trace elements in TB pleurisy patients. These results may provide an additional disease correlate for assessing TB pleurisy risk.

Serum trace element levels in tuberculous pleurisy

In this study, copper, zinc, magnesium, manganese, selenium, and iron were measured by inductively coupled plasma atomic emission spectrophotometry in patients with tuberculous (TB) pleurisy (n = 24) and in the control group (n = 20). Selenium, magnesium, and zinc were found to be significantly lower in TB pleurisy cases than those in the control group (p < 0.01, p < 0.001, and p < 0.001, respectively). There was no significant difference in the value of manganese and iron between TB pleurisy and the control group (p > 0.05). Copper levels were significantly increased in the serum of the patients (p < 0.0001). These results may provide an additional disease correlate for assessing TB pleurisy risk.

Comparative analysis of serum manganese, zinc, calcium, copper and magnesium level in panic disorder patients

The purpose of the study was to determine the serum concentration of trace elements of panic disorder patients and to find out the relationship between trace element levels and nutritional status or socio-economic factors. The study was conducted among 54 panic disorder patients and 52 healthy volunteers. Patients were recruited from Bangabandhu Sheikh Mujib Medical University by random sampling. Serum trace element concentrations were determined by flame atomic absorption spectroscopy (for Mg, Zn, Ca, and Cu) as well as graphite furnace (for Mn). Data were analyzed by independent t test, Pearson's correlation analysis, regression analysis, and ANOVA. The serum concentration of Mn, Zn, Ca, Cu, and Mg in panic disorder patients were 0.37 +/- 0.30, 0.67 +/- 0.20, 99.91 +/- 15.15, 0.83 +/- 0.23, and 21.14 +/- 3.72 mg/L, while those were 0.4163 +/- 0.2527, 0.86 +/- 0.3, 106.6073 +/- 18.6531, 0.8514 +/- 0.3646, and 21.37 +/- 2.03 mg/L in control subjects, respectively. The serum concentration of Zn decreased significantly (p = 0.001) in patient group. But the differences of the concentration of Mn, Ca, Cu, and Mg between patient and control group were not significant (p = 0.522, p = 0.065, p = 0.800, and p = 0.712, respectively). Socio-economic data reveal that most of the patients were very poor and middle aged. Mean BMIs of the control group (23.74 +/- 2.71 kg/m(2)) and the patient group (22.62 +/- 3.74 kg/m(2)) were within the normal range (18.5-25.0 kg/m(2)). There was no significant relationship between serum zinc level and BMI of patients (r = 0.038; p = 0.809). So the decreased level of serum zinc in panic disorder patients was not because of other reasons, but rather it may provide a prognostic tool for the diagnosis and treatment of this disease.

Supplementation of diets for lactating sows with zinc amino acid complex and gastric nutriment-intubation of suckling pigs with zinc methionine on mineral status, intestinal morphology and bacterial translocation in lipopolysaccharide-challenged weaned pigs

Sixty-four pigs from 16 sows were used to evaluate addition of zinc amino acid complex (ZnAA) to lactating sows and gastric nutriment-intubation of zinc methionine (ZnMet) to suckling pigs on mineral status, intestinal morphology and bacterial translocation after weaning. Sows were fed a barley-based diet supplying 120 ppm zinc (Zn; control) or the control diet supplemented with 240 ppm Zn from ZnAA. At birth, day-10 and day-21 (weaning) of age, pigs from each litter were nutriment-intubated with 5 ml of an electrolyte solution without or with 40 mg Zn from ZnMet. At weaning, 24 h prior to the collection of small and large intestinal lymph nodes and sections of the duodenum, jejunum and ileum, the pigs received an intramuscular injection of saline without or with 150 microg/kg body weight of Escherichia coli O26:B6 lipopolysaccharide (LPS). With the exception of a tendency (p = 0.09) for lower serum concentration of copper in pigs at weaning from ZnAA-supplemented sows, there were no differences (p > 0.1) than for pigs from control-fed sows for mineral status or intestinal morphology. Nutriment-intubation of ZnMet increased serum (p = 0.001) and liver (p = 0.003) Zn concentrations, number of goblet cells per 250 microm length of jejunal villous epithelium (p = 0.001) and tended (p = 0.06) to enhance jejunum mucosa thickness. Interactive effects (p < 0.05) for higher jejunal villi height and villi:crypt ratio and increased ileal goblet cell counts were apparent for pigs from ZnAA-supplemented sows that also received nutriment-intubation of ZnMet. Challenge with LPS increased (p = 0.05) ileal villous width. Nutriment-intubation of ZnMet decreased (p = 0.05) anaerobic bacteria colony forming unit counts in the large intestinal mesenteric lymph nodes. In conclusion, nutriment-intubation of ZnMet increased serum and liver tissue concentrations of Zn and resulted in limited improvement to intestinal morphology of weaned pigs.

Zinc, manganese, calcium, copper, and cadmium level in scalp hair samples of schizophrenic patients

The purpose of the study was to determine the concentration of trace elements present in scalp hair sample of schizophrenic patients and to find out the relationship between trace elements level and nutritional status or socioeconomic factors. The study was conducted among 30 schizophrenic male patients and 30 healthy male volunteers. Patients were recruited from Bangabandhu Sheikh Mujib Medical University by random sampling. Hair trace element concentrations were determined by flame atomic absorption spectroscopy and analyzed by independent t test, Pearson's correlation analysis, regression analysis, and analysis of variance (ANOVA). Mn, Zn, Ca, Cu, and Cd concentrations of schizophrenic patients were 3.8 +/- 2.31 microg/gm, 171.6 +/- 59.04 microg/gm, 396.23 +/- 157.83 microg/gm, 15.40 +/- 5.68 microg/gm, and 1.14 +/- 0.89 microg/gm of hair sample, while those of control subjects were 4.4 +/- 2.32 microg/gm, 199.16 +/- 27.85 microg/gm, 620.9 +/- 181.55 microg/gm, 12.23 +/- 4.56 microg/gm, and 0.47 +/- 0.32 microg/gm of hair sample, respectively. The hair concentration of Zn and Ca decreased significantly (p = 0.024; p = 0.000, respectively) and the concentration of Cu and Cd increased significantly (p = 0.021; p = 0.000, respectively) in schizophrenic patients while the concentration of Mn (p = 0.321) remain unchanged. Socioeconomic data reveals that most of the patients were poor, middle-aged and divorced. Mean body mass indices (BMIs) of the control group (22.26 +/- 1.91 kg/m(2)) and the patient group (20.42 +/- 3.16 kg/m(2)) were within the normal range (18.5-25.0 kg/m(2)). Pearson's correlation analysis suggested that only Ca concentration of patients had a significant positive correlation with the BMI (r = 0.597; p = 0.000) which was further justified from the regression analysis (R (2) = 44%; t = 3.59; p = 0.002) and one-way ANOVA test (F = 3.62; p = 0.015). A significant decrease in the hair concentration of Zn and Ca as well as a significant increase in the hair concentration of Cu and Cd in schizophrenic patients than that of its control group was observed which may provide prognostic tool for the diagnosis and treatment of this disease. However, further work with larger population is suggested to examine the exact correlation between trace element level and the degree of disorder.

Supplementation of diets for gestating sows with zinc amino acid complex and gastric intubation of suckling pigs with zinc-methionine on mineral status, intestinal morphology and bacterial translocation in lipopolysaccharide-challenged early-weaned pigs

Eighty male pigs from 20 litters were used to evaluate dietary addition of 250mg/kg of Zn from zinc amino acid complex (ZnAA) to sows during the last trimester of gestation and gastric intubation of 40mg Zn from soluble zinc methionine (ZnMet) to suckling pigs at birth and on day 7 and 14 (weaning) on small intestinal morphology, Zn status and bacterial translocation in early-weaned pigs. At weaning, pigs were challenged with an intramuscular injection of saline without or with 120microg/kg BW of lipopolysaccharide (LPS; from Escherichia coli O26:B6) and were euthanized 24h later prior to collection of intestinal lymph nodes and small intestinal sections. Zinc concentration in serum 7 days after birth and at weaning were higher in pigs from ZnAA-supplemented sows and those receiving gastric intubation with ZnMet (P=0.05 and P<0.0001, respectively). Post-weaning liver tissue concentrations for Zn (P<0.0001) and Fe (P=0.04) were higher and for Cu lower (P<0.0001) in pigs intubated with ZnMet. Pigs from ZnAA-supplemented compared with control-fed sows tended (P<0.1) to have increased villi height and villus:crypt ratio in the jejunum and higher (P=0.1) goblet cell counts in the ileum. Goblet cell counts of ZnMet-intubated (P=0.03) and LPS-challenged pigs (P=0.05) were also higher in the jejunum. Supplementation of ZnAA to gestating sows increased (P=0.04) E. coli colony forming unit counts in the small intestinal mesenteric lymph nodes of early-weaned pigs. In conclusion, dietary addition of ZnAA to gestating sows and gastric intubation of ZnMet improved Zn status of suckling pigs.

Gene expression profile in human cells exposed to zinc

Although Zn is an essential trace metal for humans, a comprehensive view of its effects on cellular functions has not been obtained. We used a DNA microarray to assess transcriptional alterations in human HeLa cells after exposure to a moderate concentration of Zn (100 muM ZnSO(4)). Out of 9,182 human genes, expression was increased in 7 genes and decreased in 4 genes twofold or greater. Four of the 7 upregulated genes were those coding for metallothionein isoforms or related proteins. An unexpectedly small extent of changes in gene expression might reflect rapid sequestration of Zn ions by metallothioneins, and the absence of most of the other protective responses indicated the non-toxic nature of Zn at this concentration. Comparison with our previous DNA microarray results for 5 muM CdSO(4)-exposed HeLa cells revealed several genes that are regulated by both metals in parallel, and a gene reciprocally regulated by them.

Insights on zinc regulation of food intake and macronutrient selection

Zinc (Zn) is an essential trace element required for human beings and animals. This divalent cation is involved in many physiological functions, including immune and antioxidant function, growth, and reproduction. Deficiency of Zn produces several pathological disorders and abnormalities in its metabolism, such as anorexia, weight loss, poor efficiency, and growth retardation. Although it has been known for more than 50 yr that Zn deficiency regularly and consistently causes anorexia in many animal species, the mechanism that causes this phenomenon still remains an enigma. The present review describes recent research investigating the relationship between Zn deficiency and the regulation of food intake, as well as macronutrient selection.

Influence of dietary zinc and copper on digestive enzyme activity and intestinal morphology in weaned pigs1

The current study was conducted to investigate the effects of high dietary concentrations of Zn as zinc oxide and Cu as copper sulfate on the activity of digestive enzymes in the pancreas and the intestinal mucosa, intestinal morphology, and mucin histochemistry in pigs after weaning. Thirty-two pigs were weaned at 4 wk of age. The pigs were fed standard weaning diets supplemented with Zn (100 or 2,500 ppm) and Cu (0 or 175 ppm) in a 2 x 2 factorial arrangement of treatments for a 14-d period. In pancreatic tissue, the activity of amylase, carboxypeptidase A, chymotrypsin, trypsin, and lipase increased (P < 0.01) in pigs fed 2,500 ppm of Zn, whereas the activity of carboxypeptidase B and carboxylester hydrolase was unaffected. Copper had no effect on the activity of pancreatic enzymes. In small intestinal contents, the total activity of amylase and carboxypeptidase A was greater in pigs fed 100 ppm of Zn (P < 0.05), whereas feeding 2,500 ppm of Zn increased the chymotrypsin activity (P < 0.001). The remaining enzymes were unaffected by dietary Zn concentration. The villi were longer in the cranial small intestine (P < 0.001) in pigs fed 100 ppm of Zn than in pigs fed 2,500 ppm of Zn, but otherwise there were no clear effects of Zn and Cu supplementation on intestinal morphology. In the cranial small intestine, the activity of maltase (P < 0.001), sucrase (P < 0.001), and lactase was greater in pigs fed 100 ppm of Zn, even though there was a Zn x Cu interaction (P < 0.05) in lactase activity. In the middle and caudal small intestine, no clear differences between dietary treatments were observed. The activity of gamma-glutamyl transpeptidase in the intestinal mucosa was not affected by dietary Zn or Cu. In pigs fed 100 ppm of Zn, the activity of aminopeptidase N was greater in the caudal small intestine, but dietary Zn or Cu had no effect on aminopeptidase N in the cranial and middle small intestine. No effect of dietary Zn or Cu supplementation was found on carbohydrate histochemistry in the caudal small intestine, whereas high dietary Zn increased the area of neutral, acidic, and sulfomucins in the cecum (P < 0.01) and in the colon (P < 0.001). In summary, high dietary Zn increased the activity of several enzymes in the pancreatic tissue and increased the mucin staining area in the large intestine, whereas Cu had no clear effect on these variables. However, no definite answers were found as to how the growth promoting and diarrhea reducing effects of excess dietary Zn are exerted.

The Effect of Zinc Supplementation in Humans on Plasma Lipids, Antioxidant Status and Thrombogenesis

The potential exists for zinc to influence numerous metabolic functions and to impact a range of diseases. In the present review we examine the reported relationships between zinc and plasma lipids, haemostasis and other factors postulated to play a role in atherogenesis. Ecological studies that investigated zinc intake or status, and incidence of coronary heart disease (CHD) reveal no consistent pattern. The conflicting observations may be explained by differences in the extent of CHD, site of atherosclerosis, or confounding factors. In most studies the diurnal variation in serum zinc concentrations, and the lifestyle factors that affect cholesterol metabolism were not explicitly considered. Results of randomised controlled trials show that low-density lipoprotein (LDL) oxidation and the concentrations of LDL-cholesterol (c), total cholesterol and triglycerides in plasma are unaffected by supplementation with up to 150 mg Zn/d. In contrast, plasma high-density lipoprotein (HDL)-c concentrations decline when zinc supplements provide a dose >50 mg/d. Limited data suggest that sustained hyperzincaemia predisposes individuals to thrombogenesis, whereas acute zinc depletion impairs platelet aggregation and prolongs bleeding time. In addition, Zinc supplements have been shown in some studies to decrease Cu/Zn-superoxide dismutase activity, primarily due to the antagonistic relationship between high zinc intakes and copper absorption. Besides the demonstrated adverse effect of zinc supplementation on plasma HDL-c concentrations in apparently healthy men, there is insufficient evidence to determine the role of zinc supplementation in influencing other risk factors for CHD such as antioxidant status and thrombogenesis.

Transcrição reversa na determinação da expressão do mRNA para a enzima conversora de angiotensina testicular em animais tratados com zinco

OBJETIVO: O objetivo deste trabalho foi otimizar as condições reacionais capazes de ocasionar variabilidade e de introduzir erros sistemáticos na reação em cadeia pela polimerase aplicada à análise da expressão gênica da isoforma testicular da enzima conversora de angiotensina. MÉTODOS: Avaliaram-se a concentração de cDNA, a concentração dos iniciadores, a temperatura de hibridização e o número de ciclos de desnaturação, hibridização e extensão. Para tanto, extraiu-se o RNA total por meio da reação com fenol-clorofórmio e isotiocianato de guanidina de amostras de testículos de ratos Wistar alimentados com uma ração contendo zinco. Em seguida, gerou-se o cDNA por transcrição reversa. Utilizando-se iniciadores específicos, amplificaram-se o gene de interesse (isoforma testicular da enzima conversora de angiotensina) e o gene controle Gliceraldeído-3-Fosfato-Desidrogenase. As amostras foram então aplicadas em gel de agarose e submetidas à eletroforese, coradas em brometo de etídio e visualizadas sob luz ultravioleta. RESULTADOS: Demonstrou-se que a melhor condição reacional para a reação em cadeia pela polimerase da isoforma testicular da enzima conversora de angiotensina e do Gliceraldeído-3-Fosfato-Desidrogenase foi: (1) concentração inicial de cDNA de 2µg, (2) concentração de iniciadores de 200nM, (3) temperatura de hibridização entre 57,5ºC e 60,1ºC e (4) 33 ciclos. CONCLUSÃO: Com essa otimização pôde-se minimizar as interferências sobre a técnica, contribuindo-se para a obtenção de dados comparativos a respeito da expressão gênica da enzima conversora de angiotensina testicular.

Zinc protection of HepG2 cells from sporidesmin toxicity does not require de novo gene transcription

Sporidesmin is an epidithiodioxopiperazine mycotoxin secreted by the saprophytic fungus Pithomyces chartarum. Ingestion of sporidesmin by ruminants grazing on the saprophyte infested pasture causes severe liver and bile duct damage leading to secondary photosensitisation. Zinc supplementation is used as an effective prophylaxis against sporidesmin toxicity in ruminants, however, the mechanism by which zinc protects is unknown. This study used the human hepatoma cell line, HepG2, as a model to examine the mechanism of zinc protection against sporidesmin toxicity. Treatment of cells with various concentrations of sporidesmin (0-10 microg/ml) resulted in a sigmoidal dose response curve with an LC50 of 5 microg/ml. Cells were protected from sporidesmin toxicity by pre-treatment for 2h or 16 h with zinc sulphate in a concentration dependent manner, with significant protection at 50 microM zinc and maximal protection at 200 microM zinc. To determine whether zinc protection required de novo gene transcription, cells were treated with the transcriptional inhibitor actinomycin D for one hour prior to and throughout the zinc pre-treatment. The presence of actinomycin D did not significantly reduce the zinc protection against sporidesmin cytotoxicity (80% protection without actinomycin D versus 71% protection with actinomycin D). Therefore, de novo gene transcription does not play a major role in the mechanism of zinc protection against sporidesmin toxicity in HepG2 cells.

Molecular cloning of rat Spergen-3, a spermatogenic cell-specific gene-3, encoding a novel 75-kDa protein bearing EF-hand motifs

By use of differential display in combination with cDNA cloning approach, we isolated a novel rat gene designated as Spergen-3, which has an open reading frame of 2055-length nucleotides encoding a protein of 685 amino acids. Spergen-3 gene is composed of 15 exons and mapped on chromosome 5q36, and its mouse counterpart, which shares 85.5% identity to rat Spergen-3 at the amino acid level, is mapped on chromosome 4E1. Spergen-3 encodes a 75-kDa soluble protein bearing putative 2 EF-hand motifs, proline-repeat, and a putative nuclear localization signal. Of the 2 EF-hand motifs in Spergen-3, the second one seems to match the consensus sequence. Reverse transcription-polymerase chain reaction analysis showed that the expression of Spergen-3 is developmentally up-regulated and that it is exclusively expressed in testis. In situ hybridization revealed that Spergen-3 mRNA was exclusively expressed in haploid spermatids, but its signal was weak or undetectable in spermatogonia, spermatocytes, and Sertoli cells as well as in interstitial cells. We interpreted these data as a potential role of Spergen-3, a new member of EF-hand family, in differentiation of haploid spermatids in testis.

Complementary DNA cloning of rat spetex-1, a spermatid-expressing gene-1, encoding a 63 kDa cytoplasmic protein of elongate spermatids

We used differential display in combination with complementary DNA (cDNA) cloning approach to isolate a novel rat gene designated as spetex-1, which had an open reading frame of 1,668-length nucleotides encoding a protein of 556 amino acids. Spetex-1 mRNA was highly expressed in testis, and weekly expressed in lung, intestine, and spleen. Spetex-1 expression in the rat testes was detected first at 3 weeks in postnatal development and continued to be detected up to adulthood. A search in the databases showed that the amino acid sequence of spetex-1 was 82% identical to that of its mouse homologue found in the databases. Both rat spetex-1 and the mouse homologue contained Ser-X (X = His, Arg, or Asn) repeats in the middle portion of the proteins. In situ hybridization revealed that spetex-1 mRNA was expressed in haploid spermatids of step 7-18 within the seminiferous epithelium. Immunohistochemical analysis with confocal laser-scanning microscopy demonstrated that spetex-1 protein was not expressed in spermatogonia, spermatocytes, and round spermatids in adult rat testis, but was specifically detected in the residual cytoplasm of elongate spermatids of step 15-18 as well as in residual bodies engulfed by Sertoli cells. We interpreted these data as a potential role of spetex-1 in spermatogenesis, especially in cell differentiation from late elongate spermatids to mature spermatozoa.

Transcriptome and proteome analysis identifies the pathways that increase hepatic lipid accumulation in zinc-deficient rats

For identification of the underlying molecular changes in hepatic lipid metabolism in zinc deficiency, rats were force-fed a zinc-deficient diet. Subsequently DNA-microarray and proteome profiling was performed in combination with hepatic lipid analysis. Of 6200 target sequences analyzed, 268 transcripts showed altered expression levels in livers of zinc-deficient rats, with 43 genes thereof related to hepatic lipid metabolism. Northern blot analysis and quantitative real-time RT-PCR were employed to confirm changes in mRNA levels. Proteins involved in lipid metabolism were identified by proteome analysis. Functional gene clusters with uniform changes in transcript levels suggested that the pathways required for lipolysis and mitochondrial as well as peroxisomal fatty acid degradation were downregulated, whereas those needed for de novo fatty acid synthesis and triglyceride assembly were increased. Subsequent enzymatic analysis of liver tissues confirmed an almost 40% greater triacylglycerol concentration in zinc-depleted rats, as well as an altered fatty acid composition of the lipid fraction as determined by gas chromatography. Liver lipids of zinc-deficient rats had significantly greater proportions of cis-9-oleic acid, cis-11-vaccenic acid, caprylic acid, myristic acid, alpha-linolenic acid, and eicosapentaenoic acid, and significantly less stearic and arachidonic acids. These alterations in hepatic metabolism are discussed in the context of changes in mRNA and protein levels of enzymes and transporters responsible for fatty acid metabolism, sequestration, and their transcriptional control.

Molecular cloning of rat Spetex2 family genes mapped on chromosome 15p16, encoding a 23-kilodalton protein associated with the plasma membranes of haploid spermatids

We used differential display in combination with cDNA cloning to isolate a novel rat gene, designated as Spetex2, that has an open reading frame of 582 nucleotides, encoding a protein of 194 amino acids. Spetex2 mRNA was highly expressed in testis and spleen, and its expression in rat testis was developmentally up-regulated. In situ hybridization revealed that Spetex2 mRNA was predominantly expressed in haploid spermatids at steps 1-13 within the seminiferous epithelium. A BLAST search against rat genome databases at the National Center for Biotechnology Information revealed that the Spetex2 gene is composed of four exons and is mapped to at least 18 loci in a cluster on rat chromosome 15p16, indicating that the genes occur as a repeated tandem array over a long stretch of genomic DNA. By immunocytochemical analysis with confocal laser-scanning microscopy, SPETEX2 protein was detected as a dot-like distribution on the cell periphery of haploid spermatids (steps 1-13) but was not observed in other spermatogenic cells. On the basis of these data, we hypothesize that SPETEX2 might be correlated with cell differentiation of spermaytids in rat testis.

Effect of zinc deficiency on the mRNA expression pattern in liver and jejunum of adult rats: monitoring gene expression using cDNA microarrays combined with real-time RT-PCR

In the study presented here, the effect of zinc deficiency on mRNA expression levels in liver and jejunum of adult rats was analyzed. Feed intake was restricted to 8 g/day. The semi-synthetic diet was fortified with pure phytate and contained either 2 microg Zn/g (Zn deficiency, n = 6) or 58 microg Zn/g (control, n = 7). After 29 days of Zn depletion feeding, entire jejunum and liver were retrieved and total RNA was extracted. Tissue specific expression pattern were screened and quantified by microarray analysis and verified individually via real-time RT-PCR. A relative quantification was performed with the newly developed Relative Expression Software Tool Copyright on numerous candidate genes which showed a differential expression. This study provides the first comparative view of gene expression regulation and fully quantitative expression analysis of 35 candidate genes in a non-growing Zn deficient adult rat model. The expression results indicate the existence of individual expression pattern in liver and jejunum and their tissue specific regulation under Zn deficiency. In addition, in jejunum a number of B-cell related genes could be demonstrated to be suppressed at Zn deficiency. In liver, metallothionein subtype 1 and 2 (MT-1 and MT-2) genes could be shown to be dramatically repressed and therefore represent putative markers for Zn deficiency. Expression results imply that some genes are expressed constitutively, whereas others are highly regulated in tissues responsible for Zn homeostasis.

Regulation of the mammalian selenoprotein thioredoxin reductase 1 in relation to cellular phenotype, growth, and signaling events

Reactive oxygen species (ROS) are generated as toxic by-products of aerobic metabolism, but are also essential biomolecules in cell signaling. The thioredoxin (Trx) system is a major enzymatic system modulating ROS levels and is important for redox regulation of cellular function. It consists of Trx and thioredoxin reductase (TrxR), which reduces Trx using NADPH. Most, if not all, of the functions of Trx depend on the activity of TrxR. Mammalian TrxR enzymes are selenoproteins with broad substrate specificities, and alteration of cytosolic TrxR1 expression and activity is likely to be an important determinant for the control of cellular redox regulation. TrxR1 activity in cells seems to be modulated by an intricate interplay, involving a housekeeping type promoter in combination with alternative splice variants and transcriptional start sites, posttranscriptional regulation through AU-rich elements, inactivation by electrophilic agents and by itself modulating the effects of several key signaling molecules. TrxR1 activity is also intimately linked with several aspects of selenium metabolism, and hence selenoprotein function in general. Here, we summarize the current knowledge of these different levels of TrxR1 regulation in diverse cell types and in response to growth and signaling events.

Identification of genes responsive to intracellular zinc depletion in the human colon adenocarcinoma cell line HT-29

Zinc is essential for the structural and functional integrity of cells and plays a pivotal role in the control of gene expression. To identify genes with altered mRNA expression level after zinc depletion, we employed oligonucleotide arrays with approximately 10,000 targets and used the human colon adenocarcinoma epithelial cell line HT-29 as a model. A low intracellular zinc concentration caused alterations in the steady-state mRNA levels of 309 genes at a threshold factor of 2.0. Northern blot analysis and/or real-time RT-PCR confirmed the array results for 12 of 14 selected targets. Genes identified as regulated based on microarray data encode mainly proteins involved in central pathways of intermediary metabolism (79 genes) including protein metabolism (21). We also identified five groups of genes important for basic cellular functions such as signaling (30), cell cycle control and growth (15), vesicular trafficking (15), cell-cell interaction (13), cytoskeleton (10) and transcription control (19). The latter group comprises several zinc finger-containing transcription factors of which the Kruppel-like factor 4 showed the most pronounced changes. Western blot analysis confirmed the increased expression level of this protein in cells grown under low zinc conditions. Our findings in a homogeneous cell population demonstrate that the molecular mechanisms by which cellular functions are altered at a low zinc status, occur via pleiotropic effects on gene expression. In conclusion, the pattern of zinc-affected genes may represent a reference for further studies to define the zinc regulon in mammalian cells.

Aspectos recentes da absorção e biodisponibilidade do zinco e suas correlações com a fisiologia da isoforma testicular da Enzima Conversora de Angiotensina

A associação estável a macromoléculas e a flexibilidade da esfera de coordenação são propriedades intrínsecas do zinco e sua essencialidade encontra-se intimamente relacionada ao seu papel biológico, seja na ativação da função catalítica de enzimas, seja na estabilização das estruturas conformacionais de proteínas e ácidos nucléicos. O zinco é o segundo elemento traço essencial mais abundante no organismo humano e é necessário à atividade de mais de 300 enzimas dos 6 tipos de classes existentes. Estas características tornaram o metal e seus ligantes fontes de grande interesse para a nutrição experimental, já que o seu estudo converge para a determinação da biodisponibilidade do metal. Dentre esses ligantes, a isoforma testicular da Enzima Conversora de Angiotensina, sintetizada pelas células germinais masculinas, pode ser considerada um exemplo marcante de regulação molecular a partir da ligação do zinco, influenciando tanto a atividade quanto a concentração desta enzima e conseqüentemente a função testicular.

Complementary DNA cloning and characterization of rat spergen-2, a spermatogenic cell-specific gene 2 encoding a 56-kilodalton nuclear protein bearing ankyrin repeat motifs

Differential display in combination with a cDNA cloning approach were used to isolate a novel gene, spergen-2, which has an open reading frame of 1500 nucleotides and encodes a protein of 500 amino acids that contains ankyrin repeat motifs and a putative nuclear localization signal. Expression of spergen-2 is developmentally upregulated in testis. In situ hybridization revealed that spergen-2 mRNA is expressed in spermatocytes and round spermatids (steps 1-6). Immunohistochemical analysis with confocal laser-scanning microscopy demonstrated that spergen-2 protein is predominantly expressed in nuclei of late spermatocytes (stages IX-XIV) and spermatids (steps 1-11), indicating the restricted expression of spergen-2 during spermatogenesis. In nucleoplasm of spermatogenic cell nuclei, spergen-2 tends to localize in the interchromosome space with relatively low DNA density. These findings indicate a potential role of spergen-2 in spermatogenesis, especially in cell differentiation from late pachytene spermatocytes to spermatids or in early spermatid differentiation.

A global view of the selectivity of zinc deprivation and excess on genes expressed in human THP-1 mononuclear cells

Among the micronutrients required by humans, zinc has particularly divergent modes of action. cDNA microarray and quantitative PCR technologies were used to investigate the zinc responsiveness of known genes that influence zinc homeostasis and to identify, through global screening, genes that may relate to phenotypic outcomes of altered dietary zinc intake. Human monocytic/macrophage THP-1 cells were either acutely zinc depleted, using a cell-permeable zinc-specific chelator, or were supplemented with zinc to alter intracellular zinc concentrations. Initially, genes associated with zinc homeostasis were evaluated by quantitative PCR to establish ranges for fold changes in transcript abundance that might be expected with global screening. Zinc transporter-1 and zinc transporter-7 expression increased when cellular zinc increased, whereas Zip-2 expression, the most zinc-responsive gene examined, was markedly increased by zinc depletion. Microarrays composed of approximately 22,000 elements were used to identify those genes responsive to either zinc depletion, zinc supplementation, or both conditions. Hierarchal clustering and ANOVA revealed that approximately 5% or 1,045 genes were zinc responsive. Further sorting based on this pattern of the zinc responsiveness of these genes into seven groups revealed that 104 genes were linearly zinc responsive in a positive mode (i.e., increased expression as cellular zinc increases) and 86 genes that were linearly zinc responsive in a negative mode (i.e., decreased expression as cellular zinc increases). Expression of some genes was responsive to only zinc depletion or supplementation. Categorization by function revealed numerous genes needed for host defense were among those identified as zinc responsive, including cytokine receptors and genes associated with amplification of the Th1 immune response.

Regulation of zinc metabolism and genomic outcomes

Differential mRNA display and cDNA array analysis have identified zinc-regulated genes in small intestine, thymus and monocytes. The vast majority of the transcriptome is not influenced by dietary zinc intake, high or low. Of the genes that are zinc regulated, most are involved in signal transduction (particularly influencing the immune response), responses to stress and redox, growth and energy utilization. Among the genes identified are uroguanylin (UG), cholecystokinin, lymphocyte-specific protein tyrosine kinase (LCK), T-cell cytokine receptor, heat shock proteins and the DNA damage repair and recombination protein-23B. Zinc transporters (ZnT) help regulate the supply of this micronutrient to maintain cellular functions. Expression of ZnT-1 and -2 is regulated by dietary zinc in many organs including small intestine and kidney. ZnT-4 is ubiquitously expressed but is refractory to zinc intake. Expression of ZnT-1, -2 and -4 changes markedly during gestation and lactation from highly abundant to undetectable. Each ZnT has an endosomal-like appearance in the tissues examined. Upregulation of ZnT-1 and ZnT-2 by dietary zinc strongly implicates these transporters in zinc acquisition and/or storage for subsequent systemic needs. THP-1 cells were used as a model to examine the response of human cells to changes in zinc status. Based on mRNA quantities, Zip1 and ZnT-5 were the most highly expressed. Zinc depletion of these cells decreased expression of all transporters except Zip2, where expression increased markedly. Collectively, these findings provide a genomic footprint upon which to address the biological and clinical significance of zinc and new avenues for status assessment.

Dietary zinc modulates gene expression in murine thymus: results from a comprehensive differential display screening

Differential mRNA display was used to comprehensively screen the murine thymic transcriptome for genes modulated in vivo by dietary zinc. A moderate feeding protocol rendered young adult, outbred mice zinc-deficient and zinc-supplemented without alterations in feeding behavior or growth. However, these levels of deficiency and supplementation altered specific mRNA abundances in a manner detectable by differential display. In total, 240 primer-pair combinations were used to generate >48,000 interpretable cDNA bands derived from thymic total RNA, of which only 265 or 0.55% were identified as zinc-modulated under these moderate dietary conditions. The most strongly zinc-modulated cDNAs identified by display were reamplified and sequenced. No cDNAs encoding zinc-metalloenzymes or zinc-finger transcription factors were identified as zinc-modulated in this global screening. Those zinc-regulated genes independently confirmed by quantitative PCR included: heat shock proteins 40 and 60; heat shock cognate 70; histocompatibility 2, class II antigen A, alpha; and the T cell cytokine receptor. In addition, a variety of transcription- and translation-related factors (such as ribosomal proteins L3, L5, and L28; nuclear matrix protein 84; matrin cyclophilin; the H3 histone family 3A protein; beta(2) microglobulin; and a cleavage and polyadenylation factor) were identified as zinc-modulated. These profiling data show that differential expression of genes in the thymus in response to the dietary zinc supply precedes many of the phenotypic effects on thymic function associated with severe zinc restriction or supplementation. Several genes involved in T cell development were identified as regulated by zinc and will be targets to evaluate the effects of zinc on immune function.

Changes in rat hepatic gene expression in response to zinc deficiency as assessed by DNA arrays

Zinc deficiency affects hepatic functions and due to the central role of the liver in metabolism, this may contribute to metabolic alterations in other tissues in zinc deficiency. In addition to clinical manifestations of zinc deficiency, we used cDNA- and oligonucleotide-arrays to compare the expression of > 2500 different genes in liver of rats force-fed a zinc-adequate or a zinc-deficient diet for 11 d. Radio- or fluorescence-labeled cDNAs from liver of control and zinc-deficient rats were hybridized to arrays. Approximately 1550 mRNAs were detected above background levels; by comparing expression profiles of the two groups, the mRNA levels of 66 genes were found to be altered by zinc deficiency. Steady-state expression levels of 35 genes were reduced, whereas the mRNA-levels of 31 genes were elevated. Array data were verified by Northern blot analysis for 24 selected genes and 19 were confirmed to be up- or down-regulated. Among those, predominantly gene products that participate in growth (i.e., insulin-like growth factor binding proteins), lipid metabolism (long-chain acyl-CoA synthetase), xenobiotic metabolism (cytochrome P(450) isoenzymes), the stress response (glutathione transferase), nitrogen metabolism (cytosolic aspartate aminotransferase), intracellular trafficking (syntaxin isoforms) and signal transduction (G-protein-coupled receptors) were identified. Additionally, regulation of mRNA levels of genes important for porphyrin synthesis and collagen metabolism was observed. In conclusion, we have identified in vivo a number of mammalian genes from different cellular pathways whose expression changes in response to zinc depletion. The characterization of the identified genes and their products will allow a more comprehensive analysis of the role of zinc in metabolism; moreover, the mRNAs identified could be useful in establishing biomarkers for the determination of zinc status in mammals.

The permissive effect of zinc deficiency on uroguanylin and inducible nitric oxide synthase gene upregulation in rat intestine induced by interleukin 1alpha is rapidly reversed by zinc repletion

Deficient intake of zinc from the diet upregulates both uroguanylin (UG) and inducible nitric oxide synthase (iNOS) expression in rats. Because these changes influence intestinal fluid secretion and intestinal cell pathophysiology, they relate to the incidence of diarrheal disease and its reversal by zinc as well as intestinal inflammation in general. A model of moderate zinc deficiency in rats, which changes molecular indices of zinc deficiency, was used to further explore the effects of the proinflammatory cytokine interleukin (IL)-1alpha and zinc repletion on these changes. IL-1alpha has been shown to have a role in the intestinal inflammation that occurs with bacterial infection. Our results showed a permissive effect of zinc deficiency on both UG and iNOS expression. Specifically, UG expression was responsive to zinc deficiency and IL-1alpha challenge, which were additive when combined, whereas iNOS expression was upregulated by IL-1alpha only during the deficiency. Immunohistochemistry showed that the increase in UG was limited to enterocytes of the upper villus but, in contrast, the increase in iNOS was principally in cells of the lamina propria of IL-1alpha-treated rats. Cells exhibiting UG upregulation did not co-express serotonin. Repletion with zinc reversed upregulation of the iNOS gene within 1 d, whereas UG upregulation required 3-4 d to return to normal. This differential response to repletion suggests that mechanisms of UG and iNOS dysregulation are different. Dysregulation of both genes may contribute to the severity of zinc-responsive diarrheal disease and intestinal inflammatory disease.

Application of genomics and proteomics for study of the integrated response to zinc exposure in a non-model fish species, the rainbow trout

The advent of DNA array technology and proteomics has revolutionised biology by allowing global analysis of cellular events. So far, the benefits from these new techniques have primarily been realised for well-characterised species. These organisms are rarely the most relevant for environmental biology and ecotoxicology. Thus, there is a need to explore new ways to exploit transcriptomics and proteomics for non-model species. In the present study, rainbow trout (Oncorhynchus mykiss) were exposed to a sublethal concentration of waterborne zinc for up to 6 days. The response in gill tissue was investigated by differential screening of a heterologous cDNA array and by protein profiling using Surface Enhanced Laser Desorption/Ionisation (SELDI). The cDNA array, which was a high-density spotted library of cDNA from Fugu rubripes gill, revealed differentially expressed genes related to energy production, protein synthesis, paracellular integrity, and inflammatory response. SELDI analysis yielded seven proteins that were consistently present only in zinc-exposed gills, and four proteins unique to gills from control fish. A further 11 proteins were differentially regulated. Identification of these proteins by bioinformatics proved difficult in spite of detailed information on molecular mass, charge and zinc-binding affinity. It is concluded that these approaches are viable to non-model species although both have clear limitations.

Dietary zinc deficiency induced-changes in the activity of enzymes and the levels of free radicals, lipids and protein electrophoretic behavior in growing rats

Zinc (Zn) is an essential nutrient that is required in humans and animals for many physiological functions, including immune and antioxidant function, growth and reproduction. The present study was conducted to investigate the effects of adequate Zn level (38 mg/kg diet, as a control) and two low levels that create Zn deficiencies (19 mg/kg diet, 1/2 of the control and 3.8 mg/kg diet, 1/10 of the control) in growing male and female rats for 10 weeks. To evaluate the effects of these levels, the concentrations of thiobarbituric acid-reactive substances (TBARS), biochemical parameters and protein pattern were studied. Lipid peroxidation in liver, brain and testes of rats fed Zn-deficient diet was indicated by increased TBARS. Serum, liver, brain and testes glutathione S-transferase (GST) activities were significantly (P<0.05) increased in Zn-deficient rats, the effect was pronounced in rats fed the lowest level of Zn (1/10 of control). The activity of lactate dehydrogenase (LDH) was significantly (P<0.05) increased in liver, brain and testes, but decreased in serum in a dose-dependent manner. Zinc deficiency increased (P<0.05) liver aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities in a dose-dependent manner, while there was no effect on the activity of these enzymes in testes. Zinc deficiency resulted in a significant (P<0.05) decrease in the activity of alkaline phosphatase (AlP) in serum and liver in a dose-dependent manner, but no effect in testes was found. The activity of acid phosphatase (AcP) was not affected in serum, liver and testes. Zn-deficient rats had higher liver concentrations of total lipids (TL), cholesterol, triglyceride (TG), and low density lipoprotein (LDL), while high density lipoprotein (HDL) was significantly (P<0.05) declined in a dose-dependent manner. Brain and serum acetylcholinesterase (AChE) activities were, however, not affected (P<0.05) by Zn deficiency. Protein content in liver, brain and testes showed a significant (P<0.05) decrease in rats fed the lowest level of Zn (1/10 of control). Polyacrylamide gel electrophoresis (native-PAGE) of serum proteins revealed that the intensity of immunoglobulins, serum albumin as well as several peptide bands were decreased in rats fed 1/2 or 1/10 of Zn adequate, i.e. their synthesis was affected and it was pronounced with the lowest level of Zn deficiency (1/10 of control). However, no clear effect on the transferrin was observed in both cases compared to controls. From the results of this study it can be concluded that Zn deficiency exerts numerous alterations in the studied biochemical parameters, protein pattern, and increased lipid peroxidation.

Overexpression of CRIP in transgenic mice alters cytokine patterns and the immune response

Cysteine-rich intestinal protein (CRIP), which contains a double zinc finger motif, is a member of the Group 2 LIM protein family. Our results showed that the developmental regulation of CRIP in neonates was not influenced by conventional vs. specific pathogen-free housing conditions. Thymic and splenic CRIP expression was not developmentally regulated. A line of transgenic (Tg) mice that overexpress the rat CRIP gene was created. When challenged with lipopolysaccharide, the Tg mice lost more weight, exhibited increased mortality, experienced greater diarrhea incidence, and had less serum interferon-gamma (IFN-gamma) and more interleukin (IL)-6 and IL-10. Similarly, splenocytes from the Tg mice produced less IFN-gamma and IL-2 and more IL-10 and IL-6 upon mitogen stimulation. Delayed-type hypersensitivity response was less in the Tg mice. Influenza virus infection produced greater weight loss in the Tg mice, which also showed delayed viral clearance. The observed responses to overexpression of the CRIP gene are consistent with a role for this LIM protein in a cellular pathway that produces an imbalance in cytokine pattern favoring Th2 cytokines.

Complementary DNA cloning and characterization of rat spergen-1, a spermatogenic cell-specific gene-1, containing a mitochondria-targeting signal

To elucidate the molecular mechanisms involved with spermiogenesis in testis, we performed differential display screening to isolate genes that are developmentally up-regulated during rat testis development. One of the cDNAs isolated by differential display was highly expressed in testis. Both reverse transcription-polymerase chain reaction and Northern blot analysis showed that the expression level of the gene developmentally increased. By screening the rat testis cDNA library, we successfully isolated rat cDNA clones encoding the entire open-reading frame of 462 base pairs coding a small protein of 154 amino acids. Because in situ hybridization revealed that the gene was specifically expressed in haploid spermatids in the rat seminiferous tubules, it was designated as spergen-1 (spermatogenic cell-specific gene-1). The recently opened database of the full-length mouse cDNA collection contains a mouse gene that is homologous to rat spergen-1. Subcellular fractionation followed by immunoblot analysis revealed that spergen-1 protein was associated with mitochondria. The transfection experiments performed in COS-7 cells suggested that spergen-1 has a N-terminal mitochondria-targeting signal. We suggest that spergen-1 might be involved in spermiogenesis by transiently associating with spermatid mitochondria.

Protective nutrients and functional foods for the gastrointestinal tract

Epithelial and other cells of the gastrointestinal mucosa rely on both luminal and bloodstream sources for their nutrition. The term functional food is used to describe nutrients that have an effect on physiologic processes that is separate from their established nutritional function, and some of these nutrients are proposed to promote gastrointestinal mucosal integrity. We review the recent in vitro, animal, and clinical experiments that evaluated the role of several types of gastrointestinal functional foods, including the amino acids glutamine and arginine, the essential micronutrients vitamin A and zinc, and 2 classes of food additives, prebiotics and probiotics. Many of the data from preclinical studies support a strong role for enteral nutrients in gastrointestinal health; in comparison, the data from human studies are limited. In some cases, impressive data from in vitro and animal studies have not been replicated in human trials. Other clinical trials have shown positive health benefits, but some of those studies were plagued by flaws in study design or analysis. The methods available to detect important changes in human gastrointestinal function and structure are still limited, but with the development of more sensitive measures of gastrointestinal function, the effects of specific nutrients may be more easily detected. This may facilitate the development of phase 3 clinical trials designed to more rigorously evaluate the effects of a particular nutrient by focusing on valid and reliable outcome measures. Regulatory changes in the way in which health claims can be made for dietary supplements should also be encouraged.

cDNA array analysis identifies thymic LCK as upregulated in moderate murine zinc deficiency before T-lymphocyte population changes

The detrimental sequelae of severe zinc deficiency on the thymus and T-lymphocyte compartment of the mammalian immune system have been established, but underlying mechanisms remain unknown. Hypothesizing that the alterations in T-lymphocyte number and function observed during zinc deficiency may result from changes in gene expression, we sought to compare thymic mRNA expression profiles of zinc-deficient and zinc-normal mice utilizing cDNA arrays. For our murine model described herein, 3 wk of dietary zinc deficiency did not perturb food intake or growth rate in young adult, outbred mice, but significantly depressed multiple parameters of zinc status. Furthermore, fluorescence-activated cell sorting (FACS) analysis demonstrated no changes in thymocyte populations expressing the cell surface markers CD3, CD4 or CD8, establishing that observed changes in mRNA abundances were not attributable to different thymocyte populations. Yet notably, at this moderate level of zinc deficiency, cDNA array analysis identified four potentially zinc-regulated mRNAs whose modulation was confirmed independently, twice, using both semiquantitative and real-time quantitative reverse transcription-polymerase chain reaction. Expression of one of these genes (myeloid cell leukemia sequence-1) was depressed, whereas the others [DNA damage repair and recombination protein 23B, the mouse laminin receptor and the lymphocyte-specific protein tyrosine kinase (LCK)] were elevated in the zinc-deficient mice. Further Western analysis demonstrated that the zinc binding protein LCK was elevated in these zinc-deficient mice. Results demonstrate that 3 wk of dietary zinc insufficiency can alter specific thymic mRNA and protein abundances before alterations occur in thymocyte development as detectable by FACS analysis.

Modulation of intestinal gene expression by dietary zinc status: effectiveness of cDNA arrays for expression profiling of a single nutrient deficiency

Mammalian nutritional status affects the homeostatic balance of multiple physiological processes and their associated gene expression. Although DNA array analysis can monitor large numbers of genes, there are no reports of expression profiling of a micronutrient deficiency in an intact animal system. In this report, we have tested the feasibility of using cDNA arrays to compare the global changes in expression of genes of known function that occur in the early stages of rodent zinc deficiency. The gene-modulating effects of this deficiency were demonstrated by real-time quantitative PCR measurements of altered mRNA levels for metallothionein 1, zinc transporter 2, and uroguanylin, all of which have been previously documented as zinc-regulated genes. As a result of the low level of inherent noise within this model system and application of a recently reported statistical tool for statistical analysis of microarrays [Tusher, V.G., Tibshirani, R. & Chu, G. (2001) Proc. Natl. Acad. Sci. USA 98, 5116-5121], we demonstrate the ability to reproducibly identify the modest changes in mRNA abundance produced by this single micronutrient deficiency. Among the genes identified by this array profile are intestinal genes that influence signaling pathways, growth, transcription, redox, and energy utilization. Additionally, the influence of dietary zinc supply on the expression of some of these genes was confirmed by real-time quantitative PCR. Overall, these data support the effectiveness of cDNA array expression profiling to investigate the pleiotropic effects of specific nutrients and may provide an approach to establishing markers for assessment of nutritional status.

Esophageal cancer prevention in zinc-deficient rats: rapid induction of apoptosis by replenishing zinc

BACKGROUND

Nutritional zinc deficiency in rats increases esophageal cell proliferation and the incidence of N-nitrosomethylbenzylamine (NMBA)-induced esophageal tumors. Replenishing zinc with a zinc-sufficient diet reduces these effects in zinc-deficient (ZD) rats. We investigated whether apoptosis was involved in the reduction of NMBA-induced esophageal tumors when ZD rats consumed a zinc-sufficient diet.

METHODS

Weanling rats were fed a ZD diet (zinc at 3-4 ppm) for 5 weeks to establish esophageal cell proliferation, then treated once with NMBA (2 mg/kg body weight), and divided into the following five groups (47-100 per group). One ZD group was fed the ZD diet, and four zinc-replenished (ZR) groups, ZR(1), ZR(24), ZR(72), and ZR(432), were fed a zinc-sufficient diet (zinc at 74-75 ppm) beginning 1, 24, 72, and 432 hours, respectively, after NMBA treatment. From 24 hours to 2 weeks after beginning a zinc-sufficient diet, esophagi from all ZR groups were analyzed for apoptosis and cell proliferation; ZD esophagi were the controls. Tumor incidence was determined 15 weeks after zinc replenishment. All statistical tests were two-sided.

RESULTS

Zinc replenishment initiated shortly after NMBA treatment effectively reduced esophageal tumorigenesis; 8% (three of 37) of ZR(1), 14% (five of 37) of ZR(24), 19% (five of 26) of ZR(72), and 48% (19 of 40) of ZR(432) rats developed esophageal tumors compared with 93% (14 of 15) of ZD animals (all P<.001). Importantly, 24 and 30 hours after zinc replenishment, esophagi had numerous apoptotic cells (% apoptotic cells: 0 hour = 2.9%, 95% confidence interval [CI] = 2.5% to 3.3%; 24 hours = 9.4%, 95% CI = 8.2% to 10.6%), and the expression of the proapoptotic Bax protein doubled. Within 48 hours, the ZR(1) epithelium was three to five cell layers thick compared with 10-20 layers before zinc replenishment.

CONCLUSIONS

Zinc replenishment of NMBA-treated ZD rats rapidly induces apoptosis in esophageal epithelial cells and thereby substantially reduces the development of esophageal cancer.

Dietary zinc deficiency increases uroguanylin accumulation in rat kidney

BACKGROUND

Zinc deficiency in humans produces a secretory diarrhea that is corrected by zinc supplementation. In rats, differential mRNA display analysis has shown that intestinal uroguanylin gene expression is increased in zinc deficiency. An endocrine axis involving intestinal uroguanylin and the kidney may exist. Therefore, we conducted this study to examine whether zinc deficiency would affect uroguanylin expression in the kidney of rats.

METHODS

A purified diet, deficient or adequate in zinc content, was fed to rats. Preprouroguanylin mRNA was localized in kidney by in situ hybridization, and prouroguanylin/uroguanylin peptides were localized in the kidney by immunohistochemistry. Abundance was measured by Western blotting and slot blotting analyses.

RESULTS

In situ hybridization demonstrated that preprouroguanylin mRNA-expressing cells were localized in the proximal tubules, being primarily limited to the cortical-medullary junction. Zinc deficiency did not alter the abundance or distribution of the mRNA. Immunohistochemistry, using a uroguanylin peptide-specific, affinity-purified antibody, demonstrated that immunoreactive uroguanylin peptide was localized to the same cells but that the staining was stronger in zinc-deficient rats. Western blotting analysis of kidney extracts showed that there was no difference in abundance of prouroguanylin between zinc adequate and deficient rats. However, slot blotting analysis demonstrated that the abundance of a low molecular weight immunoreactive peptide, presumably uroguanylin, was higher in extracts of zinc-deficient rats.

CONCLUSION

The results suggest that production of prouroguanylin by the kidney, in contrast to the intestine, is not influenced by dietary zinc intake, but that higher amounts of uroguanylin in kidney extracts may reflect renal processing of the hormone obtained from the systemic circulation.

Spermatid-specific expression of Iba1, an ionized calcium binding adapter molecule-1, in rat testis

Postnatal development of mammalian seminiferous tubules can be divided into three phases: spermatogonial mitosis, spermatocyte meiosis, and a postmeiotic phase in which drastic morphological changes occur in spermatids (spermiogenesis). In an attempt to elucidate the molecular mechanisms involved in spermiogenesis, we have applied a differential display method to identify genes that are developmentally up-regulated during rat testis development. One of the cDNA fragments isolated by differential display turned out to be iba1, an ionized calcium binding adapter molecule-1, that contains two EF hand-like motifs. Expression of iba1 mRNA in the rat testis was detected first at 4 wk in postnatal development and then increased up to adulthood. Using the antibody against a synthetic peptide corresponding to the N-terminal Iba1 protein, we discovered that Iba1 protein was not detectable by immunohistochemistry in spermatogonia, spermatocytes, and round spermatids in adult rat testis but was specifically expressed in the cytoplasm of elongate spermatids (steps 10-19) as well as in residual bodies that are ultimately engulfed by Sertoli cells. In situ hybridization, on the other hand, revealed that iba1 mRNA is present in round spermatids as well as early elongate spermatids (steps 1-12) but not in late spermatids, suggesting that iba1 mRNA undergoes post-transcriptional regulation. Because Iba1 protein is specifically expressed in the cytoplasm of elongate spermatids, which is finally engulfed as residual bodies into Sertoli cells, we suggest that Iba1 may be involved in the final stage of spermiogenesis (i.e., in elimination of the residual cytoplasm from spermatids).

Dietary regulation of intestinal gene expression

We are becoming increasingly aware of inherited genetic abnormalities as causes of disease. However, alterations in gene expression can also contribute to other disease processes. Recently it has been suggested that our environment may alter such genes and thus be a direct influence on disease. Diet is a potent mechanism for altering the environment of cells of most organs, particularly the gastrointestinal tract. This review addresses the influence of nutritional factors on intestinal gene regulation. These influences include insulin, which is not a dietary component but responds to dietary changes, and butyrate, a short chain fatty acid produced by normal intestinal flora. Manipulation of diet may be a means of treating intestinal disorders. Nutritional treatment therefore is also discussed in the light of its effect on gene expression.

Differential regulation of zinc transporter 1, 2, and 4 mRNA expression by dietary zinc in rats

Zinc metabolism is well regulated over a wide range of dietary intakes to help maintain cellular zinc-dependent functions. Expression of transporter molecules, which influence zinc influx and efflux across the plasma and intracellular membranes, contributes to this regulation. We have examined in rats the comparative response of zinc transporters 1, 2, and 4 (ZnT-1, ZnT-2 and ZnT-4) to dietary zinc. ZnT-1 and ZnT-4 are expressed ubiquitously, whereas ZnT-2 is limited to small intestine, kidney, placenta and, in some cases, the liver. When zinc intake was low (<1 mg Zn/kg), ZnT-2 mRNA was extremely low in small intestine and kidney compared with an adequate intake (30 mg Zn/kg). ZnT-1 and ZnT-2 mRNAs were markedly greater in both tissues when a supplemental zinc intake (180 mg Zn/kg) was provided. ZnT-4 was refractory to changes in zinc intake. When zinc was provided as a single oral dose (70 mg/kg body), ZnT-1 and ZnT-2 mRNA levels were increased many fold in small intestine, liver and kidney, whereas ZnT-4 gene expression was not changed. The expression of ZnT-1 and ZnT-2 is comparable to zinc-induced changes in metallothionein mRNA levels, suggesting a similar mode of regulation for these genes. The relative differential in regulation by zinc is ZnT-2 > ZnT-1 > ZnT-4. These data provide evidence that, in an animal model, zinc transporter expression is responsive to zinc under physiologically relevant conditions.