Down-regulation of rat mitochondrial branched-chain 2-oxoacid dehydrogenase kinase gene expression by glucocorticoids.
The mammalian mitochondrial branched-chain 2-oxoacid dehydrogenase (BCOD) complex is regulated by a reversible phosphorylation (inactivation)/dephosphorylation (activation) cycle. In the present study, the effects of glucocorticoids on the level of BCOD kinase mRNA were investigated in rat hepatoma cell lines (H4IIE and FTO-2B), as well as in the rat. In H4IIE cells, dexamethasone was found to significantly reduce steady-state concentrations of BCOD kinase mRNA after a 48 h culture, and this was correlated with a 2-fold increase in the dephosphorylated form of the BCOD complex. The half-life of the kinase mRNA in H4IIE cells was not affected by dexamethasone treatment. Therefore, the decrease in the steady-state kinase mRNA level resulting from dexamethasone treatment was not caused by changes in mRNA stability, which raised the possibility of regulation at the level of gene transcription. To identify the negative glucocorticoid-responsive element in the kinase promoter, nested deletion constucts in the 3.0 kb promoter region were examined in H4IIE cells cultured in the presence or absence of dexamethasone. No significant differences in promoter activity were observed on either transient or stable transfection. The data showed that the glucocorticoid-responsive element was located outside the 3. 0 kb promoter region. At the physiological level, hepatic BCOD kinase mRNA levels were reduced in rats injected intraperitoneally with dexamethasone. This effect was liver-specific, and was not detected in other tissues. These results suggest that the down-regulation of kinase gene expression by glucocorticoids is mediated through a liver-specific or -enriched transcription factor(s). (+info)
Dissection of the metabolic actions of insulin in adipocytes from early growth-retarded male rats.
Numerous studies have shown a relationship between early growth restriction and Type 2 diabetes. Studies have shown that offspring of rats fed a low protein (LP) diet during pregnancy and lactation have a worse glucose tolerance in late adult life compared with controls. In contrast, in young adult life LP offspring have a better glucose tolerance which is associated with increased insulin-stimulated glucose uptake into skeletal muscle. The aim of the present study was to compare the regulation of glucose uptake and lipolysis in adipocytes by insulin in control and LP offspring. LP adipocytes had increased basal and insulin-stimulated glucose uptake compared with controls. There was no difference in basal rates of lipolysis. Isoproterenol stimulated lipolysis in both groups, but it was more effective on LP adipocytes. Insulin reduced lipolytic rates in controls to basal levels but had a reduced effect in LP adipocytes. Protein kinase B activity matched glucose uptake, with LP adipocytes having elevated activities. These results suggest that early growth retardation has long-term effects on adipocyte metabolism. In addition, they show selective resistance to different metabolic actions of insulin and provide insight into the mechanisms by which insulin regulates glucose uptake and lipolysis. (+info)
Hypergastrinemia and enterochromaffin-like cell hyperplasia.
The enterochromaffin-like (ECL) cells, the most frequent endocrine cells of the oxyntic mucosa of the stomach, are under the trophic stimulus of gastrin. These cells undergo a hyperplastic increase in variety of hypergastrinemic diseases. The most widely accepted nomenclature for the description of hyperplastic proliferation has been retrospectively arranged in a sequence presumed to reflect a temporal evolution of the proliferative process. A comparative, prospective study aimed to verify, in human hypergastrinemic diseases such as atrophic body gastritis (ABG), Zollinger-Ellison syndrome (ZES) and antral gastrin cell hyperfunction (AGCH), the effect of exposure of ECL cells to different pattern of gastrin hypersecretion, is lacking. To this purpose, we studied a series of consecutive patients with ABG, ZES and AGCH at the time of first diagnosis. MATERIAL AND METHODS: The patients included in this study (124 ABG, 18 ZES and 10 AGCH) were selected on the basis of two previously performed screening studies aimed to diagnose these diseases. All patients at the time of diagnosis underwent gastroscopy, with multiple biopsies of the gastric body mucosa for the evaluation of qualitative pattern of ECL cells hyperplasia, and basal fasting gastrin determination. A sample of hypergastrinemic patients from each group was further investigated by meal-stimulation of gastrin secretion and quantitative morphometry for CgA positive gastric body endocrine cells. RESULTS: AGCH patients showed only the normal or simple hyperplasia pattern. In the ZES group, simple and linear grades accounted for 38.4 percent and 46.1 percent, respectively. MEN-I patients showed only these two patterns. The majority of ABG patients showed the presence of micronodular pattern (59.7 percent). A correlation analysis between fasting gastrin levels and grade of hyperplasia (r = 0.5580, p < 0.0001), indicates that the greater the gastrin levels, the higher is the degree of severity of ECL hyperplasia pattern. In conclusion, our data support the role of gastrin as the selective contributor to the progression of ECL cell hyperplasia in humans. (+info)
A tracer investigation of obligatory oxidative amino acid losses in healthy, young adults.
BACKGROUND: Estimation of the minimum requirement for indispensable amino acids (IAAs) has been attempted by assuming that obligatory oxidative losses (OOLs) of IAAs can be approximated from nitrogen losses and that the efficiency of utilization of IAAs at requirement intakes is approximately 70%. OBJECTIVE: We wished to determine the rates of OOLs in healthy adults, using L-[1-(13)C]leucine and L-[1-(13)C, methyl-(2)H(3)]methio-nine as tracers, after adjustment to a protein-free diet and how these rates compare with those when either sulfur amino acids (SAAs: methionine and cyst(e)ine) or leucine were removed from an otherwise adequate diet. DESIGN: Eleven subjects were randomly assigned to a 5-d protein-free diet or a 5-d diet providing adequate nitrogen and amino acids except for the SAAs or leucine. A 24-h constant intravenous infusion of [(15)N, (15)N]urea and L-[1-(13)C]leucine (Leu group; n = 5) or L-[1-(13)C, methyl-(2)H(3)]methionine (Met group; n = 6 ) began at 1800 on day 5 and rates of amino acid oxidation were determined. RESULTS: Mean (+/-SD) oxidation rates (mg kg(-)(1) d(-)(1)) of methionine and leucine were 6.4 +/- 1.4 and 24.7 +/- 3.6, respectively, with the protein-free diet; rates were significantly lower (3.9 +/- 2.2 and 7. 2 +/- 3.4, respectively) after the SAA- and leucine-free diets. Urea production was significantly lower (P < 0.01) with the protein-free than with the SAA- or leucine-free diet. CONCLUSIONS: Isotopically determined OOLs for methionine and leucine are consistent with losses predicted from nitrogen excretion, and consistent with our previous measurements of cysteine oxidation as an index of total SAA losses. The data further support our earlier conclusions regarding methionine sparing by cysteine and tentative recommended SAA requirements in adults. (+info)
Differential hepatic lobar gene expression in offspring exposed to altered maternal dietary protein intake.
Increased plasma fibrinogen concentrations are a recognized risk factor for coronary heart disease, and increased fibrinogen levels in adults are associated with parameters of reduced early growth. We studied fibrinogen gene expression in adult offspring of dams fed either a 20% (control) or an 8% protein diet [maternal low-protein (MLP) rats] during pregnancy and lactation and determined whether any effects were consistent between left and right liver lobes, since the fetal liver has a unique blood supply that produces differential stimuli to the left and right lobes. In MLP offspring, there was a reduction in all three fibrinogen mRNA copy numbers in the left liver lobe [left vs. right lobes for alpha-, beta-, and gamma-fibrinogen (x10(6) copies/ng total RNA): 8.04 vs. 23.16, P<0.001; 4.74 vs. 13.07, P<0.001; and 4.61 vs. 16.38, P = 0.007, respectively], with a parallel reduction in fibrinogen concentration in the left liver lobe (8.53+/-0.33 vs. 10.41 +/-0.65 arbitrary units, P = 0.014, left and right lobes, respectively). No such effect was observed in offspring of control dams. To investigate the underlying mechanism, glucocorticoid receptor function and mRNA levels were studied, since expression of fibrinogen genes is regulated by glucocorticoid hormones. The binding affinity of the high-affinity glucocorticoid receptor was reduced only in the left liver lobe of the MLP offspring (P = 0.02, left. vs. right), with a parallel reduction in this lobe in glucocorticoid receptor mRNA level (P = 0.006, left vs. right). In conclusion, maternal dietary protein restriction reduces fibrinogen gene expression, fibrinogen protein, and mRNA level and binding affinity of glucocorticoid receptors only in the left liver lobe of the adult offspring. (+info)
Cysteine kinetics and oxidation at different intakes of methionine and cystine in young adults.
BACKGROUND: We previously studied methionine kinetics and oxidation with the tracer L-[1-(13)C, methyl-(2)H(3)]methionine. OBJECTIVES: We sought to explore methionine-cysteine interrelations in adults by using L-[1-(13)C]cysteine under different dietary conditions. DESIGN: In experiment 1, 12 adults consumed a protein-free diet for 6 d. On day 7, methionine (n = 6) or cysteine (n = 6) oxidation rates were measured during an 8-h continuous infusion of L-[1-(13)C, methyl-(2)H(3)]methionine or L-[1-(13)C]cysteine, respectively. In experiment 2, 6 young men consumed 3 diets for 6 d each before a tracer study on day 7 with L-[1-(13)C]cysteine. The amounts (in mg*kg(-)(1)*d(-)(1)) of methionine and cysteine, respectively, were: high-methionine (HM) diet, 13 and 0; low-methionine (LM) diet, 6.5 and 0; and methionine-plus-cystine (MC) diet, 6.5 and 5.6. Cysteine flux and oxidation rates were determined and sulfur amino acid (SAA, methionine plus cysteine) balances were estimated. RESULTS: In experiment 1, rates of methionine and cysteine oxidation were similar to losses predicted from obligatory nitrogen losses. In experiment 2, SAA balance was less negative when subjects consumed the HM diet than the LM and MC diets (interaction, P = 0.034), largely because of a difference in fed-state balance (HM compared with LM, P < 0.01; HM compared with MC, P < 0.05). There was no evidence of a sparing effect of dietary cystine on the methionine requirement. CONCLUSION: These studies support use of [1-(13)C]cysteine for studying whole-body SAA oxidation and conclusions that maintenance of SAA balance is best achieved by supplying methionine at approximately the FAO/WHO/UNU recommendations for total SAA intake (13 mg*kg(-)(1)*d(-)(1)). (+info)
Antihypertensive treatment in early postnatal life modulates prenatal dietary influences upon blood pressure in the rat.
Epidemiological evidence from diverse human populations, supported by experimental evidence from animal models, suggests that maternal nutrition during pregnancy is an important fetal programming influence upon cardiovascular disease. Experiments with a low-protein-diet model of rat pregnancy suggest a role for the renin-angiotensin system in the programming mechanism, since fetal undernutrition permanently elevates pulmonary and plasma angiotensin-converting enzyme activity. Long-term beneficial effects of captopril on blood pressure in this model require further investigation in order to clarify the role of angiotensin II. Pregnant rats were fed a control diet containing 18% (w/w) casein as the protein source or a low-protein diet containing 9% (w/w) casein. Between the ages of 2 and 4 weeks postnatally, mothers and their pups were treated with losartan or nifedipine. All pups in the study had blood pressure determined at 4 and 12 weeks of age using a tail cuff. Animals exposed to the low-protein diet in utero and not subjected to drug treatment had elevated blood pressure relative to control rats (mean increase of 27 mmHg; P<0.001). Treatment of rats exposed to the control diet in utero with either nifedipine or losartan between 2 and 4 weeks of age did not alter their blood pressure. Nifedipine had no effect upon the blood pressure of low-protein-exposed pups, but losartan prevented the blood pressure elevation in these animals. Between 4 and 12 weeks of age, blood pressure increased significantly in all groups (P<0.001). The pattern of blood pressure among the groups was identical to that observed at 4 weeks, suggesting that the observed early effects of losartan would be maintained into adult life. The data are consistent with the hypothesis that angiotensin II plays a major role in the prenatal programming of hypertension. The action of angiotensin II at the AT(1) receptor between 2 and 4 weeks of age may be critically up-regulated by fetal factors, including exposure to glucocorticoids of maternal origin. (+info)
Nutrition and outcome on renal replacement therapy of patients with chronic renal failure treated by a supplemented very low protein diet.
Protein-restricted diets are prescribed in patients with chronic renal failure (CRF) to alleviate uremic symptoms and to slow the progression of CRF. The potential deleterious effects of protein restriction on nutritional status and clinical outcome of patients with CRF have raised concern. In this study, data were collected from 1985 to 1998 on 239 consecutive patients (age 50.2 +/- 15.6 yr) with advanced CRF (GFR 13.1 +/- 4.8 ml/min) to whom a supplemented very low protein diet (SVLPD) providing 0.3 g protein, 35 kcal, and 5 to 7 mg of inorganic phosphorus per kg per day was administered for a mean duration of 29.6 +/- 25.1 mo. The diet was supplemented with essential amino acids and ketoanalogs, calcium carbonate, iron, and multivitamins. During SVLPD, protein intake decreased from 0.85 +/- 0.23 to 0.43 +/- 0.11 g/kg per d, and body mass index and serum albumin concentration remained unchanged overall. Fourteen patients died during SVLPD; death was unrelated to nutritional parameters. Hemodialysis was initiated after SVLPD in 165 patients at a mean GFR of 5.8 +/-1.5 ml/min. During an average of 54 mo on hemodialysis, mortality was low (2.4% after 1 yr) and correlated to age only, not to nutritional parameters observed at the end of SVLPD. Similar results were obtained in 66 transplanted patients (12 were not dialyzed before transplantation). SVLPD can be safely used in patients with CRF without adverse effects on the clinical and nutritional status of the patients. Due to the preservation of nutritional status and the correction of uremic symptoms, the initiation of dialysis was deferred in these patients. The outcome of patients on renal replacement therapy is not affected by prior treatment with SVLPD during the predialysis phase of CRF. (+info)