Dietary management of canine and feline chronic renal failure

Nutritional therapy is the mainstay of management of chronic renal failure in dogs and cats. Diets designed for use in renal failure are typically reduced in protein, phosphorus, and sodium content. These and other dietary modifications are designed to prevent or ameliorate clinical signs of uremia, minimize disturbances associated with excesses or losses of electrolytes and minerals, arrest or retard progression of renal failure, and maintain adequate nutrition.     

Extracellular matrix proteoglycan decorin-mediated myogenic satellite cell responsiveness to transforming growth factor-beta1 during cell proliferation and differentiation Decorin and transforming growth factor-beta1 in satellite cells

Transforming growth factor-beta1 (TGF-beta1) is a potent inhibitor of muscle cell proliferation and differentiation. Decorin, a small proteoglycan in the extracellular matrix, binds to TGF-beta1 and modulates the activity of TGF-beta1 during muscle cell growth and development. However, its interaction with TGF-beta1 and involvement in myogenesis is not well characterized. In the present study, chicken myogenic satellite cells, myogenic precursors for muscle growth and repair, were isolated from the pectoralis major muscle and used to investigate the biological function of TGF-beta1 and decorin during myogenesis. The over-expression of decorin in satellite cells significantly increased cell proliferation, compared to the control cells. Consistent with this result, reducing decorin expression decreased cell proliferation, which suggests a decorin-mediated mechanism is involved in the regulation of myogenic satellite cell proliferation. Satellite cells over-expressing decorin were less sensitive to TGF-beta1 during proliferation, which indicates that decorin may sequester TGF-beta1 leading to increased proliferation. During satellite cell differentiation, the over-expression of decorin induced differentiation by increasing the muscle specific creatine kinase concentration. However, the addition of TGF-beta1 diminished decorin-mediated cell responsiveness to TGF-beta1 during differentiation. Taken together, these results suggest that decorin induces myogenic satellite cell proliferation and differentiation by regulating cellular responsiveness to TGF-beta1. An alternative TGF-beta1-independent pathway may be involved in the regulation of satellite cells by decorin.     

Effect of transforming growth factor-beta1 on bone regeneration in critical-sized bone defects after irradiation of host tissues

OBJECTIVE: To determine whether sustained release of transforming growth factor (TGF)-beta1 from a gelatin hydrogel would enhance bone regeneration in critical-sized long-bone defects and overcome inhibitory effects of preoperative irradiation. ANIMALS: 24 adult New Zealand White rabbits. PROCEDURE: Rabbits were allocated to 2 groups. Twelve rabbits received localized megavoltage radiation to the right ulna by use of a cobalt 60 teletherapy unit, and 12 rabbits received no irradiation. Then, a 1.5-cm defect was aseptically created in the right ulna of each rabbit. Gelatin hydrogel that contained 5 microg of adsorbed recombinant-human (rh)TGF-beta1 was placed in the defect of 12 rabbits (6 irradiated and 6 nonirradiated), and the other 12 rabbits received hydrogel without rhTGF-beta1. Rabbits were euthanatized 10 weeks after surgery. New bone formation within the defect was analyzed by use of nondecalcified histomorphometric methods. A 1-way ANOVA was used to compare differences among groups. RESULTS: New bone formation within the defect was significantly greater in TGF-beta1-treated rabbits than in rabbits treated with hydrogel carrier alone. Local delivery of rhTGF-beta1 via a hydrogel carrier in irradiated defects resulted in amounts of bone formation similar to those for nonirradiated defects treated by use of rhTGF-beta1. CONCLUSIONS AND CLINICAL RELEVANCE: Local delivery of TGF-beta1 by use of a hydrogel carrier appears to have therapeutic potential for enhancing bone formation in animals after radiation treatments. IMPACT FOR HUMAN MEDICINE: This technique may be of value for treating human patients at risk for delayed bone healing because of prior radiation therapy.     

Utilization of continuous renal replacement therapy in a case of feline acute renal failure

Objective: To introduce and investigate the application, efficacy, and potential clinical complications of a continuous renal replacement therapy (CRRT) in a feline acute renal failure (ARF) patient. Case summary: A domestic short‐haired cat presented for continued management of ARF of a presumed toxic etiology. Severe azotemia and uremic complications had been identified on initial presentation to a local urgent care facility, and the cat had been referred for renal replacement therapy following approximately 9 hours of conservative management. Continuous venovenous hemodiafiltration was performed over an approximately 25‐hour period, and a significant resolution of the cat's uremic derangements was obtained. Major complications included significant hypothermia and a single episode of hypocalcemia associated with utilization of citrate anticoagulation. All complications identified were readily managed. Following hospital discharge, long‐term medical support was not required, and no evidence of significant illness was noted 6 months following therapy. New or unique information provided: CRRT represents a collection of extracorporeal blood purification techniques that utilize extended treatment periods for gradual, physiologically balanced correction of uremic toxicity. These therapies demonstrate significant promise in the treatment of ARF cats with actual or potential hemodynamic compromise, and prior advances in therapeutic administration have made these techniques readily accessible within the intensive care unit setting.     

Expression of transforming growth factor-beta 1 (TGF-beta1) in different types of granulomatous lesions in bovine and ovine paratuberculosis

Paratuberculosis, caused by Mycobacterium avium subsp. paratuberculosis (Map), is manifested by a broad spectrum of clinical and lesional presentations. We have evaluated the expression of transforming growth factor-beta1 (TGF-beta1), a cytokine known to have immunosuppressor effects, by immunohistochemistry, in different paratuberculosis lesions in the intestine and lymph nodes from 20 sheep and 25 cattle. Peripheral immune responses were assessed by interferon-gamma (IFN-gamma) test and the presence of antibodies. Expression of TGF-beta1, observed in macrophages and giant cells forming the lesions, was closely related to the amount of Map. In focal and multifocal forms, usually positive to IFN-gamma test, bacilli were difficult to detect and TGF-beta1 expression was low or absent. Diffuse multibacillary lesions, negative to IFN-gamma, show large numbers of Map and the highest percentage of immunolabelled cells. Diffuse paucibacillary forms, positive to IFN-gamma, have low numbers of AFB and scant or no cells positive to TGF-beta1. The high expression of TGF-beta1 would be related to the inability of macrophages to limit the multiplication of Map.     

Relationship among growth, steroid production and immunolocalization of transforming growth factor-beta 1 in the normally developing mouse follicles cultured in vitro

This study examined the relationship among growth, steroid production and transforming growth factor-beta 1 (TGF-beta 1) immunolocalization in the mouse follicles cultured in vitro to evaluate the hypothesis that normally developing follicles should express TGF-beta 1 in the granulosa cells around the time of antrum formation. Preantral follicles with 151-175 microns (large category) and 125-150 microns (small category) of initial diameters were used as models for normal and retarded follicles, respectively. Growth rate and timing of antrum formation in both categories were comparable to those of in-vivo grown follicles. At the time of antrum formation, follicular diameters were similar between the two follicle categories; however, antral follicles from the large category showed larger number of granulosa cells, higher estradiol production and proportion of follicles with TGF-beta 1 positive granulosa cells. Two days after antrum formation, there were no differences in the number of granulosa cells and the proportions of follicles with TGF-beta 1 positive granulosa or theca cells between the two categories. Temporal association in large follicles between the increase in estradiol production and proportion of follicles with TGF-beta 1 positive granulosa cells at the time of antrum formation supports our hypothesis. Furthermore, this study demonstrated the usefulness of the follicle culture system in the investigations of follicular physiology.     

Upregulation of transforming growth factor-beta and interleukin-10 in cows with clinical Johne's disease

Johne's disease progresses through distinct stages including a protracted subclinical stage in which the infection appears to be controlled; followed by a more acute stage in which the host animal demonstrates clinical signs such as diarrhea and weight loss. Little is known about the dynamics of the host immune response during these two phases of disease, however, it is possible that immune modulation in the early stages of disease may play an important role in disease progression. We hypothesized that the clinical stage of Johne's disease is mediated by the expression of cytokines such as transforming growth factor-beta (TGF-beta) and interleukin-10 (IL-10) that may be accompanied by the downregulation of IFN-gamma gene expression. In the present study, tissue samples were collected from the ileum, ileocecal junction, ileocecal lymph node, and mesenteric lymph nodes of healthy, subclinically or clinically infected cows. The expression of TGF-beta, IL-10, and IFN-gamma genes in these tissues was determined by quantitative competitive RT-PCR. The results demonstrate that TGF-beta and IL-10 mRNA levels are higher in cows that have progressed to the clinical stage of disease compared to subclinically infected or healthy cows. In contrast, IFN-gamma gene expression was significantly higher in subclinically infected cows. These results suggest that a change in the balance of cytokines at the site of infection may contribute to the ability of the host to control Mycobacterium avium subsp. paratuberculosis infection.     

Oral ingestion of colostrum alters intestinal transforming growth factor-beta receptor intensity in newborn pigs

Mammary gland secretion contains numerous bioactive compounds including transforming growth factor-beta (TGF-β). The concentrations of such bioactive compounds are usually much higher in colostrum compared with those in mature milk. To investigate possible effects of colostrum-borne TGF-β on the suckling animal, newborn piglets were naturally suckled or bottle-fed with porcine colostrum, bovine colostrum, porcine milk, infant formula or water for 24 h and intestinal TGF-β receptor intensity was assessed using an immunohistochemical staining technique in combination with computerized image analysis. The intestinal structure was also analyzed by morphometric analysis technique. It was observed that newborn pigs naturally suckled or bottle-fed with porcine or bovine colostrum had significantly greater intestinal villous height and crypt depth when compared with those fed with porcine milk, infant formula or water (p < 0.05). The immunostaining intensity for TGF-β receptors in the intestinal epithelium, particularly on the apical membrane of the villous epithelium, was significantly lower in naturally suckled or colostrum fed piglets compared with that in piglets fed with milk, infant formula or water (p < 0.05). Such decline in receptor intensity is likely the result of receptor internalization and degradation following exposure to colostrum-borne TGF-β. These findings suggest that colostrum-borne TGF-β can modulate intestinal TGF-β signalling pathways and may play a role in postnatal adaptation of the gut in newborn pigs.     

Effect of transforming growth factor-beta1, insulin-like growth factor-I,and hepatocyte growth factor on proteoglycan production and regulation in canine melanoma cell lines

OBJECTIVE:To identify extracellular proteoglycans produced by canine melanoma cell lines and analyze the effect of transforming growth factor-beta1 (TGF-beta1), insulin-like growth factor-I (IGF-I), and hepatocyte growth factor (HGF) on these proteoglycans. SAMPLE POPULATION: 3 canine melanoma cell lines (ie, CML-1, CML-6M, and CML-10c2). PROCEDURE: Extracellular proteoglycans were analyzed by use of metabolic labeling and western immunoblot analysis. The effect of TGF-beta1 on cell proliferation was determined by incorporation of 5-bromo-2'-deoxyuridine. RESULTS: The CML-1 and CML-6M melanoma cell lines produced 2 main extracellular proteoglycans. One of them was identified as versican, a proteoglycan found in undifferentiated human melanoma cell lines. The CML-10c2 cells produced a small amount of extracellular proteoglycans. Addition of TGF-beta1 (1.25 to 6.25 ng/ml) increased the release of sulfated proteoglycans into the medium. The TGF-beta1 had mainly a posttranslational effect, because it increased the molecular mass of the sulfated bands. Addition of IGF-I (50 ng/ml) slightly increased production of proteoglycans in the CML-6M cell line, whereas HGF (50 ng/ml) did not have any effect on proteoglycan production. CONCLUSIONS AND CLINICAL RELEVANCE: The proteoglycan content and response toTGF-beta1 treatment for CML-1 and CML-6M canine melanoma cell lines are similar to that for undifferentiated human melanoma cell lines. In contrast, CML-10c2 cells produced a low amount of proteoglycans with high molecular weight. Because these extracellular proteoglycans are involved in the control of cell adhesion, proliferation, and migration, they may play an important role in the progression of melanomas in dogs.     

Absence of renal cortical anisotropic backscattering artifact in feline chronic kidney disease

Renal cortical anisotropy backscattering artifact (CABA) is a focal hyperechoic region where the tubules are parallel to the incident ultrasound beam, reflecting most of the beams to the transducer. To investigate the association between chronic kidney disease (CKD) and the absence of renal CABA in cats. Ultrasonographic renal images of 40 cats with CKD (stage II-IV) and 36 clinically healthy cats were blindly evaluated by two observers to determine the visibility of renal CABA. Inter- and intraobserver agreements were evaluated using McNemar’s test. The association between the absence of renal CABA and CKD was assessed using Fisher’s exact test. Excellent intraobserver and substantial interobserver agreements were demonstrated. A significant association (P < .0001) between absent renal CABA and CKD stage was revealed in all cats. Cats with CKD had an increased risk of the absence of renal CABA (Odds ratio, 56.0; 95% CI, 13.8–227.0) compared with the clinically healthy cats. The absence of renal CABA revealed 87.5% sensitivity and 88.9% specificity to detect CKD in all cats, and 91.7% sensitivity and 83.3% specificity in aged cats. Our study demonstrated a correlation between feline CKD and the absence of renal CABA, providing a feasible and alternative method for feline CKD evaluation.     

Immunohistochemical expression of p53, fibroblast growth factor-b, and transforming growth factor-alpha in feline vaccine-associated sarcomas

Fifty feline sarcomas associated with vaccine-site injection were evaluated to determine the immunohistochemical expression of p53 protein, basic fibroblast growth factor (FGF-b), and transforming growth factor-alpha (TGF-alpha). Forty-one tumors (82%) were fibrosarcomas (FS), eight (16%) were malignant fibrous histiocytomas (MFH), and one (2%) was a chondrosarcoma (CS). Overexpression of p53 protein was observed in the nuclei of tumor cells in 28 (56%) sarcomas; FGF-b expression was found in the cytoplasm of tumor cells in 40 (80%) feline sarcomas, but the staining was more intense in the spindle-shaped cells of FS than in polygonal or round cells of MFH. The single CS faintly expressed FGF-b. The majority of feline vaccine-associated sarcomas (43 of 50, 86%) expressed moderate or intense staining for TGF-alpha in the cytoplasm of tumor cells. Heterogeneous immunolabeling for p53, FGF-b, and TGF-alpha was present in neoplastic, multinucleated giant cells. Intense expression of FGF-b was statistically associated with younger cats (P < 0.01) and with tumors with nodular growth patterns (P = 0.02). In addition, sarcomas negative for p53 protein expressed FGF-b more frequently than did p53-positive tumors (P = 0.04). The frequency of FGF-b immunostaining was significantly higher in sarcomas with intense expression of TGF-alpha (P = 0.05). Immunohistochemical detection of p53 protein, FGF-b, and TGF-alpha suggests that these growth-regulating proteins may play different roles in the development of sarcomas associated with vaccine sites.     

Temporal expression of transforming growth factor-beta2 and myostatin mRNA during embryonic myogenesis in Indian broilers

TGF-beta2 and myostatin, the members of TGF family, act through both autocrine and paracrine mechanisms to regulate the growth and differentiation at various developmental stages in chicken. The kinetics and expression profile of these two growth factors were investigated by semi-quantitative RT-PCR, during the myogenesis of Indian broiler chickens. Total RNA was isolated from whole embryos on each of embryonic days (E) 0-6 (n=3 per day) and from the biceps femoris muscle at E7-E18 (n=3 per day). The expression of TGF-beta2 was noticed on E2 that remained at the same level until E6. In biceps femoris muscle, higher level of TGF-beta2 expression was observed during E7-E12, which decreased gradually thereafter. These findings suggested that TGF-beta2 might be a regulatory factor participating in the myogenesis of chicken embryos. Initial myostatin expression was noticed on E1, even before the myogenic lineage is established in embryo. This finding suggested an additional role of myostatin in early chicken embryo development, other than myogenesis. Furthermore, myostatin expression was significantly higher on E3 as compared to earlier studies, where initial higher level was observed at E2, suggesting the differential expression of myostatin among breeds. Higher and almost static myostatin expression was noticed in biceps femoris muscle during the entire period of myogenesis (E7-E18). In the present study, the ontogeny of myostatin expression coincided with myogenesis of chicken. Therefore, it may be hypothesized that myostatin is not only a major determinant of muscle mass, but also involved in early embryogenesis in chickens.     

Dietary management of feline chronic renal failure: where are we now? In what direction are we headed?

Dietary modification is of primary importance in managing cats with chronic renal failure. Diets designed for cats with chronic renal failure are typically formulated to be pH neutral and contain reduced quantities of protein, phosphorus and sodium and an increased quantity of potassium. These changes in diet formulation are designed to ameliorate clinical signs of renal failure by adapting dietary intakes to meet the limited ability of failing kidneys to adapt to the normal range of dietary intakes. Important recent clinical trials support the therapeutic value of dietary therapy in cats with chronic renal failure.     

The anemia of chronic renal failure revisited

The mechanisms of the anemia of chronic renal failure are reviewed. Ineffective erythropoiesis is undoubtedly the major cause of this anemia. The contributions of inadequate erythropoietin secretion by the diseased kidneys, suppressive effects of uremic "toxins" on erythropoiesis and red cell survival, excess blood loss, and plasma concentrations of parathyroid hormone, calcium and phosphate are discussed.