PF Mice Research Articles

Suppression of PI3K by Weight Loss via Dietary Calorie Restriction and/or Treadmill Exercise in TPA‐induced Mouse Skin

Obesity or overweight by excessive calorie intake and/or sedentary lifestyle has been associated with increased cancer risks. Our previous study demonstrated that the inhibition of IGF-1 signaling such as PI3K pathway might account for the mechanisms of cancer prevention by weight control in a skin cancer mouse model. This study was designed to further investigate PI3K expression by using immunohistochemical analysis in response to weight loss by decreasing calorie intake or increasing physical activity in TPA-promoted mouse skin samples. SENCAR mice were randomly divided into three groups: ad-libitum-fed sedentary control (control), exercise with pair-feeding at a same amount as control (Ex+PF), and 20% dietary calorie restriction (DCR). After 10 weeks, body weight and percent fat composition were significantly decreased in the groups of Ex+PF and DCR when compared with the control. Western blotting showed PI3K protein levels in TPA-induced skin samples were decreased significantly in both Ex+PF and DCR groups. The distribution of PI3K protein in epidermis as measured by immunohistochemistry demonstrated a significant decrease in DCR-fed mice but not Ex+PF mice. These results present more evidence that PI3K is an important target of weight loss for potential cancer prevention (supported by NIH R01CA106397).

Leptin treatment markedly increased plasma adiponectin but barely decreased plasma resistin of ob/ob mice.

Adiponectin (ApN) and leptin are two adipocytokines that control fuel homeostasis, body weight, and insulin sensitivity. Their interplay is still poorly studied. These hormones are either undetectable or decreased in obese, diabetic ob/ob mice. We examined the effects of leptin treatment on ApN gene expression, protein production, secretion, and circulating levels of ob/ob mice. We also briefly tackled the influence of this treatment on resistin, another adipocytokine involved in obesity-related insulin resistance. Leptin-treated (T) obese mice (continuous sc infusion for 6 days) were compared with untreated lean (L), untreated obese (O), and untreated pair-fed obese (PF) mice. Blood was collected throughout the study. At day 3 or day 6, fat pads were either directly analyzed (mRNA, ApN content) or cultured for up to 24 h (ApN secretion). The direct effect of leptin was also studied in 3T3-F442A adipocytes. Compared with L mice, ApN content of visceral or subcutaneous fat and ApN secretion by adipose explants were blunted in obese mice. Accordingly, plasma ApN levels of O mice were decreased by 50%. Leptin treatment of ob/ob mice increased ApN mRNAs, ApN content, and secretion from the visceral depot by 50-80%. Leptin also directly stimulated ApN mRNAs and secretion from 3T3-F442A adipocytes. After 6 days of treatment, plasma ApN of ob/ob mice increased 2.5-fold, a rise that did not occur in PF mice. Plasma resistin of T mice was barely decreased. Leptin treatment, but not mere calorie restriction, corrects plasma ApN in obese mice by restoring adipose tissue ApN concentrations and secretion, at least in part, via a direct stimulation of ApN gene expression. Such a treatment only minimally affects circulating resistin. ApN restoration could, in concert with leptin, contribute to the metabolic effects classically observed during leptin administration.

Iron deficiency and in vitro iron chelation reduce the expression of cluster of differentiation molecule (CD)28 but not CD3 receptors on murine thymocytes and spleen cells.

Cluster of differentiation molecule (CD)3 and CD28 receptors play crucial roles in T-lymphocyte proliferation. Fe deficiency in man and animals impairs T-lymphocyte proliferation by unknown mechanisms. To test the hypothesis that reduced CD3 and CD28 expression is one of them, thymocytes and splenocytes from control (C; n 24), Fe-deficient (ID; n 24), pair-fed (PF; n 24), and ID mice that were Fe-repleted for 3 (R3; n 24) or 14 d (R14; n 12) were labelled with anti-CD3-fluorescein isothiocyanate and anti-CD28-phycoerythrin antibodies. Positive cells were analysed by flow cytometry. Significant differences were observed among groups in the mean levels of haemoglobin and liver Fe stores (C=PF=R14>R3>ID; P<0.005). While Fe deficiency slightly increased the percentage of CD3+ splenocytes, it reduced that of CD28+ thymocytes in mice with thymus atrophy and splenomegaly (P<0.05). These changes were corrected by Fe repletion. CD28 mean fluorescence intensity (FI) was lower and CD3 FI was higher in lymphocytes from R3 and ID, especially those with splenomegaly, than in those from R14 and PF mice (P<0.05). In vitro Fe chelation by deferoxamine (60 min) significantly decreased CD28 expression (P<0.05), and slightly increased that of CD3 (P>0.05). Spleen cell proliferative responses to concanavalin A and anti-CD3+/-anti-CD28 were reduced by Fe deficiency (ID</=R3<C=PF<R14; P<0.05); and they correlated with FI and percentages of CD3+ and CD28+ cells (r< or =0.69; P<0.05). Indicators of Fe status negatively correlated with CD3 FI (r-0.23), but positively correlated with CD28 FI (r< or =0.44; P<0.05). Data suggest that altered CD28 expression may contribute to reduced T-cell proliferation during Fe deficiency.

Antinociceptive effect following dietary-induced thiamine deficiency in mice: Involvement of substance P and somatostatin

We produced thiamine deficiency by treating mice with a thiamine deficient (TD) diet, but not with pyrithiamine, a thiamine antagonist. Twenty days after TD feeding, a significant antinociceptive effect was observed in the formalin test. A single injection of thiamine HCl (50 mg/kg, s.c.) on the 19th day after TD feeding (on the late TD stage) failed to reverse the antinociceptive effect, the muricide effect, and impairment of avoidance learning induced by TD feeding, as compared to pair-fed controls. These results indicate the possibility that the TD-induced antinociceptive effect may result from irreversible changes in the spinal and/or brain neurons. To clarify the involvement of substance P (SP) and somatostatin (SST) systems in the spinal cord, we examined the effect of intrathecal (i.t.) injections of these agonists on TD feeding-inducd elevation of pain threshold. I.t. injection of SP and SST elicited a behavioral response consisting of reciprocal hindlimb scratching, biting and/or licking of hindpaws. There was no significant difference in the behavioral response to SP between TD mice and PF mice on the 5th day after feeding. However, on the 10th and 20th day after TD feeding the response to SP was significantly increased compared with PF mice. This phenomenon was also observed with SST on the 20th day after TD feeding. These results indicate the possibility that TD feeding may produce an increased behavioral response to SP and SST through an enhanced sensitivity of neurokinin-1 and SST receptors in the spinal cord. Taken together, the antinociceptive effect following TD feeding may result from a decrease in spinal SP and SST contents.

Differential effects of iron status on lymphocyte subsets in lupus and non-lupus strains of mice

The MRL/MPJ-lpr/lpr (MRL) mouse is a model of human systemic lupus erythematosus (SLE) and develops autoimmunity accompanied by lymphadenopathy and accumulation of cells bearing CD3+L3T4-Lyt2-markers. Since iron status was previously shown to alter disease manifestation in these mice, the effect of iron status on lymphocyte subsets was studied. Weanling female MRL mice were divided into four groups (n=9–10) and fed purified diets containing varying levels of iron: 4 mg/kg diet-severely deficient (SD); 35 mg/kg diet-iron-adequate controls (C); and 250 mg/kg diet-iron supplemented (IS). A fourth group was fed C diet in amounts eaten by the SD group-pair-fed controls (PF). C3H/Hej (C3H) mice were fed the same diets and served as non-SLE controls. At 18 weeks of age, both MRL and C3H SD mice were anemic; however, MRL SD mice were significantly more anemic as reflected in lower hemoglobin and hematocrit levels. Spleen and lymph node weights were lowest in MRL SD and PF mice, and spleen cell number was significantly reduced in SD mice. Iron deficiency in C3H mice resulted in reduced percentages of total T lymphocytes, T helper/inducer and T suppressor/cytotoxic, and B lymphocytes. The T helper/T suppressor cell ratio was not affected. The percentage of B cells was also reduced in C3H IS mice compared to C mice. In MRL mice, iron status had no effect on the percentages of T cells, T helper cells, or B cells, nor the estimated percentage of cells expressing the double negative (CD3+L3T4-Lyt 2-) phenotype. T supressor/cytotoxic cells were significantly higher in the lymph nodes of SD MRL mice. No statistical differences were found in the T helper/T suppressor ratio. This study has demonstrated differential effects of iron status on lymphocyte subsets of SLE and non-SLE strains of mice. Altered disease manifestation by iron status in MRL-lpr mice is not related to reductions in T and B lymphocytes or the CD3+L3T4- Lyt 2-population

Zinc deficiency impairs T cell function in mice with primary infection of Heligmosomoides polygyrus (Nematoda).

This study was designed to determine whether severe zinc deficiency would prolong the course of a primary Heligmosomoides polygyrus infection in mice, and whether this could be related to impaired T cell function. Female BALB/c mice were fed a zinc-sufficient (Zn+; 60 mg/kg), a zinc-deficient (Zn-; 0.75 mg/kg) or an energy restricted (PF; 60 mg zinc/kg) diet. After four weeks, some mice in each dietary group were given a primary infection with 100 larvae; nutritional, parasitological and immunological parameters were assayed over the following five weeks. Liver zinc concentrations were significantly reduced in Zn- mice compared with Zn+ mice. In certain cases, PF mice also had reduced liver zinc concentrations, showing the negative effects of restricted food intake on zinc status. Zinc deficiency prolonged the course of a primary infection, with the effects being most evident five weeks post-infection when Zn+ mice had only 40% as many worms as Zn- mice. Parasite infection induced strong immunological responses in Zn+ mice in contrast to Zn- mice. The reduced production of IL-4 and IFN-gamma, the reduced peripheral eosinophilia and reduced serum levels of IgE and IgG1 in Zn- mice were attributed to the zinc deficiency, whereas the reduced delayed type hypersensitivity response to parasite antigen and reduced production of IL-5 were in certain instances attributed to reduced energy intake rather than zinc deficiency. These results show that zinc deficiency significantly impairs functions normally attributed to both Th1 and Th2 cell populations, and that these alterations are associated with elevated worm numbers in zinc-deficient mice.

Mitogenic response of lymph nodes and spleen lymphocytes from mice with moderate and severe iron deficiency anemia

To define the effects of moderate and severe iron deficiency (Hb: 4–10.4 g/dl) on mitogenic response of lymph nodes (LN) and splenic (S) lymphocytes, C57BL/6 weanling female mice were fed an iron deficient (<5ppm; ID), an iron adequate diet (30 cpm, C) or restricted amounts of the adequate diet (pairfed:PF) for 45–56 days. 3H-thymidine incorporation into DNA was measured in the presence of Con A, PHA and LPS. In both lymphoid organs and with three mitogens tested, iron deficiency significantly reduced blastogenic response (stimulation indices=SI) by 23% to 93%. However, splenic lymphocytes were more affected than lymph nodes. In the spleen, SI positively correlated with Hb and liver iron stores but negatively with spleen weight. Total cpm in response to Con A and LPS were reduced in both S and LN; but those in response to PHA were reduced only in moderately deficient mice. In S but not LN, underfeeding in the overall population of PF mice significantly reduced SI in response to Con A but not PHA or LPS. In ID mice, thymus weight correlated with body weight, (r=0.88), Hb levels (r=0.50) and liver iron stores (r=0.34). While iron deficiency significantly decreased IgG and IgM levels, underfeeding in PF significantly reduced IgA levels and only slightly IgM levels. We conclude that even moderate iron deficiency anemia (11 g/dl<Hb<8 g/dl) impairs mitogenic response in both S and LN.

Ethanol consumption during pregnancy in mice: effects on hormone concentrations.

Hormonal and metabolic responses to ethanol consumption were studied in pregnant Swiss Webster mice and their fetuses. On day 10 of pregnancy, mice were assigned to one of three liquid diet groups: 36% ethanol-derived calories fed ad libitum (ETOH); control liquid diet fed ad libitum (control); control liquid diet administered in the same amount as that consumed by the ETOH group on the same day of pregnancy [pair-fed controls (PF)]. Dams were killed on days 14-18 of pregnancy, and fetuses were collected on days 16-18. Serum mouse placental lactogen-II (mPL-II), prolactin (mPRL), growth hormone (mGH), insulin, and glucose concentrations were determined for each group. Ethanol consumption resulted in a significant reduction in fetal weight on day 18 of pregnancy. The maternal serum mPRL concentration was reduced in ETOH mice on days 16 and 17 of pregnancy when compared with control mice, but when compared with PF mice, it was significantly reduced only on day 16. Maternal and fetal serum insulin concentrations were reduced in ETOH mice when compared with control mice, but it is unclear whether this was a specific effect of ethanol consumption or due to reduced food intake. Maternal serum glucose concentrations were reduced in the ETOH mice but not as severely as in the PF mice. Ethanol consumption had no effect on maternal or fetal serum mPL-II and mGH concentrations. These data confirm that ethanol consumption during pregnancy results in fetal growth retardation, but they do not indicate any major effects of ethanol on mPL-II, mPRL, mGH, and insulin concentrations in either the mother or fetus.