Thyroid transcription factor-1, thyroglobulin, cytokeratin 7, and cytokeratin 20 in thyroid neoplasms.

Thyroid transcription factor-1 (TTF-1), a member of the NKx2 family of homeodomain transcription factors, is a mediator of thyroid-specific transcription of the thyroglobulin (TG) gene. The combined immunohistochemical profile of TTF-1, TG, cytokeratin 7 (CK7), and cytokeratin 20 (CK20) in neoplasms of the thyroid gland and their metastases to other sites has not been defined previously. Formalin-fixed tissue of 43 thyroid tumors, including 31 carcinomas and 12 adenomas, and 16 metastasic lesions were immunostained using monoclonal antibodies to TTF-1, TG, CK7, and CK20. Immunoreactivity of the primary tumors (adenomas and carcinomas) for TTF-1 was seen in 32 cases (74%), TG 32 (74%), and CK7 34 (79%), whereas none (0%) showed positivity for CK20. The distribution of reactivity in the 31 carcinomas for TTF-1, TG, and CK7, respectively was papillary (8/8), (8/8), and (8/8); poorly differentiated (6/7), (4/7), and (6/7); oncocytic (Hürthle) cell (2/6), (6/6), and (4/6); follicular (4/4), (3/4), and (3/4); medullary (1/2), (0/2), and (1/2). One of four anaplastic carcinomas was focally immunoreactive showing positivity for TTF-1 only. Of the six follicular adenomas, five were positive for TTF-1, six for TG, and six for CK7. Among the six oncocytic cell adenomas, five were reactive for TTF-1, five for TG, and all six for CK7. Twelve (75%) of the 16 metastatic tumors were positive for TTF-1, 10 (63%) for TG, 15 (94%) for CK7, and none (0%) for CK20. In summary, TTF-1 and TG are demonstrable by immunohistochemistry in the majority of thyroid neoplasms. Compared with TG, an antibody to TTF-I is a similarly sensitive marker for thyroid tumors. Moreover, TTF-1 is a more sensitive marker for poorly differentiated carcinomas and metastasis. In most cases, its nuclear pattern of immunoreactivity facilitates interpretation. Thyroid tumors are CK7+/CK20-. The panel of antibodies for TG, TTF-1, CK7, and CK20 is useful when the thyroid origin of a metastatic tumor is a consideration.

Hepatocyte nuclear factor-4 regulates intestinal expression of the guanylin/heat-stable toxin receptor.

We have investigated the regulation of gene transcription in the intestine using the guanylyl cyclase C (GCC) gene as a model. GCC is expressed in crypts and villi in the small intestine and in crypts and surface epithelium of the colon. DNase I footprint, electrophoretic mobility shift assay (EMSA), transient transfection assays, and mutagenesis experiments demonstrated that GCC transcription is regulated by a critical hepatocyte nuclear factor-4 (HNF-4) binding site between bp -46 and -29 and that bp -38 to -36 were essential for binding. Binding of HNF-4 to the GCC promoter was confirmed by competition EMSA and by supershift EMSA. In Caco-2 and T84 cells, which express both GCC and HNF-4, the activity of GCC promoter and/or luciferase reporter plasmids containing 128 or 1973 bp of 5'-flanking sequence was dependent on the HNF-4 binding site in the proximal promoter. In COLO-DM cells, which express neither GCC nor HNF-4, cotransfection of GCC promoter/luciferase reporter plasmids with an HNF-4 expression vector resulted in 23-fold stimulation of the GCC promoter. Mutation of the HNF-4 binding site abolished this transactivation. Transfection of COLO-DM cells with the HNF-4 expression vector stimulated transcription of the endogenous GCC gene as well. These results indicate that HNF-4 is a key regulator of GCC expression in the intestine.

The guanylin/STa receptor is expressed in crypts and apical epithelium throughout the mouse intestine.

Guanylyl cyclase C (GC-C), a transmembrane receptor for E. coli heat-stable enterotoxin (STa) and for the endogenous peptides guanylin and uroguanylin, catalyzes formation of cGMP and influences fluid and electrolyte flux in the gut. We characterized the expression of GC-C in the mouse by Northern blot, in situ hybridization, and ligand binding studies. GC-C mRNA was present in mouse intestine by embryonic day 12, and was expressed at high levels in both crypts and villus or surface epithelium of adult small intestine and colon, respectively. Radiolabeled STa binding to membranes from several tissues correlated with the presence of GC-C mRNA. Extraintestinal GC-C expression was detected only in neonatal mouse liver. The presence of GC-C in mouse intestinal crypts supports the putative role of GC-C in fluid and electrolyte homeostasis and resembles the pattern in human tissues.

Intestinal permeability enhancement: efficacy, acute local toxicity, and reversibility.

The absorption of the polar drug phenol red was assessed in a rat intestinal perfusion model, in the presence of a variety of potential intestinal permeability enhancers. Both the absorption rate constant KA and the plasma phenol red concentration were measured. Perfusates were also assayed for the presence of lactate dehydrogenase (LDH) and lipid phosphate, as biochemical markers of intestinal wall damage. Histological evaluation of surfactant-perfused intestines was also carried out. The potential permeability enhancers studied were the surfactants sodium dodecyl sulfate (SDS), sodium taurocholate (TC), sodium taurodeoxycholate (TDC), polysorbate-80 (PS-80), and nonylphenoxypolyoxyethylene (NP-POE) with an average polar group size of 10.5 POE units. Among these, SDS and NP-POE-10.5 were the most potent permeability enhancers. The bile salt TDC was a more effective enhancer than the more polar TC. The polar non-ionic surfactant PS-80 was an ineffective enhancer. Phenol red KA and plasma level were generally correlated with biochemical and histological measures of intestinal damage. These observations indicate that permeability enhancement and local damage are closely related sequelae of the interaction of surfactants with the intestinal wall, and suggest that local wall damage may be involved in the mechanism of permeability enhancement. The reversibility of permeability enhancement and acute local damage was assessed for the surfactants TDC and NP-POE-10.5. Enhancement of phenol red permeability was reversed within 1-2 hr of the cessation of enhancer treatment. Biochemical markers of local damage also fell to control values within 1-2 hr of removal of enhancer from the perfusate. Histological evaluation of perfused intestines revealed that morphological damage was reversed within 3 hr. These results demonstrate that surfactant-induced acute intestinal wall damage is rapidly repaired.

Dietary fat level as determinant of protein-sparing actions of structured triglycerides.

This study assessed the effects of total parenteral nutrition (TPN) containing long-chain triglycerides (LCTs), an equimolar physical mixture of LCT and medium-chain triglycerides (MCTs), and a structured triglyceride synthesized from equimolar amounts of MCT and LCT on energy and protein metabolism after thermal injury (25% body surface area full-thickness scald burn). Male Sprague-Dawley rats (245-271 g) received isovolemic diets intravenously that supplied 250 kcal.kg-1.day-1, 2 g amino acid nitrogen.kg-1.day-1, and 50% of nonprotein calories as lipid and 50% as dextrose for 3 days. Whole-body and tissue leucine kinetics were estimated by a 4-h continuous infusion of L-[1-14C]leucine on day 3. Nitrogen balance, plasma albumin, plasma glucose, energy expenditure, and whole-body and liver and rectus muscle protein kinetic parameters were determined. No significant differences were noted in any of the parameters measured. This study suggests that the unique protein-sparing actions usually associated with structured triglyceride administration are not seen when they are provided as 50% of nonprotein calories. In addition, the ratio of MCT to LCT in the starting mixture from which the structured triglycerides are synthesized may be an important determinant of the protein-sparing actions attributed to these lipids.

Persistence of metabolic effects after long-term oral feeding of a structured triglyceride derived from medium-chain triglyceride and fish oil in burned and normal rats.

The persistence of metabolic effects following long-term oral feeding of a structured triglyceride rich in omega-3 fatty acids was studied in burned and normal rats, and compared with controls fed safflower oil, a long-chain triglyceride high in omega-6 fatty acid content. Male Sprague-Dawley rats were pair-fed a high fat diet as either structured triglyceride or safflower oil for 42 days. On day 43, a jugular catheter was placed, and rats received either a dorsal surface scald or sham injury. Following a 48-hour fast, body weight, nitrogen loss, energy metabolism, and liver weight were measured, and whole-body and tissue-specific protein kinetics were studied by constant intravenous infusion of [1-14C]leucine. Plasma albumin, free fatty acids, glucose, insulin, and triglyceride fatty acid composition were determined. Urinary nitrogen loss, energy expenditure, and plasma leucine concentration were elevated in burned rats, confirming the presence of an injury response. Rats previously fed structured triglyceride had greater liver weight, total liver protein, and percentage of leucine flux oxidized, and plasma levels of glucose and insulin were increased. Plasma leucine concentration was decreased in rats previously fed structured triglyceride. Plasma triglyceride and phospholipid fatty acid analysis showed a reduction in arachidonic acid and an increase in omega-3 fatty acids in rats previously fed structured triglyceride. Long-term feeding of structured triglyceride induced major systemic metabolic changes related to the dietary fatty acid composition that persist after the diet is discontinued.

Metabolic effects of medium chain triglyceride-enriched total parenteral nutrition in rats bearing Yoshida sarcoma.

The ability of medium chain triglyceride-enriched total parenteral nutrition to support host tissue in a model of cancer cachexia was assessed by measuring tumor growth, body weight, nitrogen balance, energy expenditure, leucine kinetics, fractional protein synthetic rate of tumor, liver, and abdominis rectus muscle, and plasma levels of glucose and albumin. Male Sprague-Dawley rats (85-90 gm) received 10(7) cells of viable Yoshida sarcoma subcutaneously on day 0. Control rats received injections of sterile saline. On day 10 rats underwent central venous cannulation and were randomized to one of three isocaloric diets. One group received amino acids and dextrose, while the other two groups were infused with amino acids, dextrose, and fat as either long chain triglyceride or a physical mixture of medium chain triglyceride: long chain triglyceride (3:1). On day 14 L-1-(14)C-leucine was added to the diet to study protein kinetics, and energy metabolism was measured by indirect calorimetry. Both tumor-bearing and nontumor-bearing rats demonstrated improved nitrogen balance when given medium chain triglyceride-enriched total parenteral nutrition. Tumor-bearing rats had reduced resting energy expenditure vs. nontumor-bearing, while rats receiving total parenteral nutrition without fat had significantly greater respiratory quotients. Tumor-bearing rats had lower total body weight vs. nontumor-bearing on day 10, but body weight of tumor-bearing and nontumor-bearing did not differ on day 14. Whole body protein breakdown decreased and leucine balance increased in tumor-bearing rats as compared to nontumor-bearing. Total liver mass was greater in tumor-bearing rats, but liver protein fractional protein synthetic rate decreased in tumor-bearing rats vs. nontumor-bearing. Tumor growth rate and fractional protein synthetic rate were not altered by the parenteral diet. The data confirm an altered metabolism in the tumor-bearing host, and suggest that medium chain triglyceride can better support host tissue.

Effect of structured lipid-enriched total parenteral nutrition in rats bearing yoshida sarcoma.

The efficacy of structured lipid, a triacylglycerol of medium and long chain fatty acids, as an element of nutritional support therapies in cancer cachexia was investigated. Using the Yoshida sarcoma to induce cachexia, male Sprague Dawley rats (90 g) were injected subcutaneously with tumor cells (n = 17) or sterile saline (n = 16). Seven days later, rats were randomized to two intravenous diets for 3 days at 220 kcal/kg body weight/d, including 2 g nitrogen/kg body weight/d and 39% of total calories as either structured lipid or long chain triglyceride. Nitrogen balance, tumor growth rate, energy metabolism, and plasma albumin and free fatty acid levels were measured, and whole-body protein kinetics and liver, muscle, and tumor fractional protein synthetic rates were evaluated by adding (14)C-leucine to the diet during the last 4 hours of feeding. Nitrogen balance improved (P < .05) in both tumor and control rats receiving structured lipid-enriched total parenteral nutrition, and was also greater in tumor rats compared with controls. There were no differences in tumor growth or protein kinetics between diet groups. Albumin was lower (P < .05) in tumor rats, but significantly higher in both tumor and control rats given structured lipid-enriched total parenteral nutrition. Free fatty acid was significantly higher in tumor rats versus controls. Whole-body protein kinetics were similar among the four groups. Liver weight, liver weight to body weight ratio, and liver protein synthetic rate were higher in tumor rats. Also, liver weight to body weight ratio was lower in tumor and control animals given structured lipid-enriched total parenteral nutrition. Muscle protein synthetic rate was significantly lower in tumor rats, but higher in tumor and control rats given long chain triglyceride-enriched total parenteral nutrition. The nutritional benefits of structured lipid-enriched total parenteral nutrition favor support of host tissue without promoting tumor growth.