Moderate Protein Restriction Research Articles

Isocaloric maternal low-protein diet alters IGF-I, IGFBPs, and hepatocyte proliferation in the fetal rat.

We investigated the effect of an isocaloric maternal low-protein diet during pregnancy in rats on the proliferative capacity of cultured fetal hepatocytes. The potential roles of these changes on the IGF-IGF-binding protein (IGFBP) axis, and the role of insulin and glucocorticoids in liver growth retardation, were also evaluated. Pregnant Wistar rats were fed a control (C) diet (20% protein) or a low-protein (LP) diet (8%) throughout gestation. In primary culture, the DNA synthesis of hepatocytes derived from LP fetuses was decreased by approximately 30% compared with control hepatocytes (P < 0.05). In parallel, in vivo moderate protein restriction in the dam reduced the fetal liver weight and IGF-I level in fetal plasma (P < 0.01) and augmented the abundance of 29- to 32-kDa IGFBPs in fetal plasma (P < 0.01) and fetal liver (P < 0.01). By contrast, the abundance of IGF-II mRNA in liver of LP fetuses was unaffected by the LP diet. In vitro, the LP-derived hepatocytes produced less IGF-I (P < 0.01) and more 29- to 32-kDa IGFBPs (P < 0.01) than hepatocytes derived from control fetuses. These alterations still appeared after 3-4 days of culture, indicating some persistence in programming. Dexamethasone treatment of control-derived hepatocytes decreased cell proliferation (54 +/- 2.3%, P < 0.01) and stimulated 29- to 32-kDa IGFBPs, whereas insulin promoted fetal hepatocyte growth (127 +/- 5.5%, P < 0.01) and inhibited 29- to 32-kDa IGFBPs. These results show that liver growth and cell proliferation in association with IGF-I and IGFBP levels are affected in utero by fetal undernutrition. It also suggests that glucocorticoids and insulin may modulate these effects.

Elevated plasma phenylalanine concentrations may adversely affect bone status of phenylketonuric mice.

Children with phenylketonuric (PKU) are at risk for fractures. This study used a PKU murine model (PAH(enu-2)) to evaluate effects of moderate dietary protein restriction and elevated plasma phenylalanine concentration impact upon bone status. Fifty-four male weanling PKU and control mice were assigned to either an elemental phenylalanine (Phe)-restricted diet (treated) or Phe-unrestricted diet (untreated) with low or normal protein levels for 56 days. Untreated mice and control mice received equal amounts of dietary Phe; treated mice consumed prescribed dietary Phe to maintain plasma Phe concentrations between 120 and 480micromol/L. Plasma Phe, osteocalcin, and urine deoxypyridinoline (DPD)/creatinine were analysed at baseline and at days 28 and 56. Femur strength, bone mineral density (BMD) and bone mineral content (BMC) were analysed at day 56. Moderate protein restriction did not significantly affect bone status. Mean plasma Phe concentrations were significantly greater in untreated vs treated and control mice (p < 0.0001). Total body weight was significantly less in untreated vs control mice (p < 0.01). Mean femur weight was reduced in untreated mice vs both treated and control mice (p < 0.03). Untreated mice had smaller mean femur length than control mice (p < 0.002). Femur strength was greater in treated mice compared to control mice (p < 0.01) but not compared to untreated mice. No significant difference among groups was found in BMD and BMC. At day 56 there was a statistical trend (p < 0.056) towards higher urine DPD/creatinine excretion in untreated mice than in treated mice. Plasma Phe concentration was positively correlated with urine DPD/creatinine. These data suggested that hyperphenylalaninaemia may adversely affect bone status in PKU mice.

Effect of dietary protein restriction on prognosis in patients with diabetic nephropathy

Recent data suggest that dietary protein restriction improves survival and delays the progression to end-stage renal disease (ESRD) in non-diabetic nephropathies. The purpose of our study was to determine the effect of dietary protein restriction on survival and progression to ESRD in diabetic nephropathy. A four-year prospective, controlled trial with concealed randomization was performed comparing the effects of a low-protein diet (0.6 g/kg/day) with a usual-protein diet. The study included 82 type 1 diabetic patients with progressive diabetic nephropathy [pre-study mean decline in glomerular filtration rate (GFR) 7.1 mL/min/year (95% CI, 5.8 to 8.5)]. The main outcome measures were decline in GFR and development of ESRD or death. During the follow-up period the usual-protein diet group consumed 1.02 g/kg/day (95% CI; 0.95 to 1.10) as compared with 0.89 (0.83 to 0.95) in the low-protein diet group (P = 0.005). The mean declines in GFR were 3.9 mL/min/year (2.7 to 5.2) in the usual-protein diet group and 3.8 (2.8 to 4.8) in the low-protein diet group. ESRD or death occurred in 27% of patients on a usual-protein diet as compared with 10% on a low-protein diet (log-rank test; P = 0.042). The relative risk of ESRD or death was 0.23 (0.07 to 0.72) for patients assigned to a low-protein diet, after an adjustment at baseline for the presence of cardiovascular disease (P = 0.01). Blood pressure and glycemic control were comparable in the two diet groups during the follow-up period. Moderate dietary protein restriction improves prognosis in type 1 diabetic patients with progressive diabetic nephropathy in addition to the beneficial effect of antihypertensive treatment.

Nutrition interventions in early diabetic renal disease.

Education and nutritional intervention play an important role in preventing and delaying the progression of renal disease in persons with diabetes. We need to identify those patients at risk or who have renal disease early, when interventions are most effective. Patients should visit a dietitian with expertise in diabetes to obtain an individual meal plan that focuses on those aspects that have the greatest impact on the disease: blood pressure control, blood glucose control, and moderate protein restriction.

Changes of protein kinetics in nephrotic patients.

Nephrotic patients show various abnormalities in protein kinetics. Plasma albumin levels and the total plasma albumin pool are reduced. The rate of hepatic absolute and fractional albumin synthesis are increased. Transferrin synthesis is also increased. Fibrinogen levels are elevated in nephrotic syndrome because of an increase in the hepatic synthesis. Regulation of albumin and fibrinogen synthesis seems to be coordinated. A low protein diet has been proposed as a therapeutic tool in nephrotic patients--clinical studies have shown that such a diet reduces proteinuria and increases renal survival. Nephrotic patients can adapt to moderate protein restriction with no sign of malnutrition and maintenance of a neutral nitrogen balance. Albumin and fibrinogen synthesis are ameliorated by dietary protein restriction and these changes are correlated with the beneficial effect of the diet on proteinuria.

Enhanced glucose uptake into adipose tissue induced by early growth restriction augments excursions in plasma leptin response evoked by changes in insulin status.

The study used a rat model of moderate protein restriction exclusively during fetal and early neonatal life, which has been established to cause intrauterine early growth retardation, to investigate possible association between adipocyte glucose utilisation and leptin secretion in vivo. These rats, termed early protein restricted, were transferred to a diet containing the standard amount of protein at weaning and remained on this diet til adulthood, at which time adipocyte glucose utilisation and leptin secretion was compared with that of age-matched controls. Insulin status was modulated by acute (2 h) insulin infusion at a constant rate (4.2 mU/min per kg) to elevate insulin to the high physiological range. Euglycaemia was maintained by variable glucose infusion. Glucose utilisation was measured in vivo in conscious unrestrained rats using 2-deoxy[1-3H] glucose. Leptin concentrations (measured by radioimmunoassay) and whole-body glucose kinetics (measured using [3-3H] glucose) were studied in the postabsorptive state and after acute insulin stimulation. Adipose-tissue glucose utilisation rates in vivo tended to be higher in the post-absorptive state and were consistently 1.8-3.0-fold higher after insulin stimulation in the early-protein-restricted group compared with the control group. Both the absolute increase in leptin concentration elicited by hyperinsulinaemia and the magnitude of the effect of insulin to elevate plasma leptin levels were greater in the early-protein-restricted group compared with the control group (by 2.2-fold and 1.6-fold, respectively). The effect of insulin to stimulate R(d) was much greater in the early-protein-restricted group (4.1-fold) than in the control group (2.2-fold) and the absolute increase in R(d) elicited by insulin was 43% higher in the early-protein-restricted group than in the control group. It is concluded that poor early growth enhances the acute leptin response to changes in insulin status through programmed changes in adipocyte glucose handling.

Fermentable carbohydrate and digestive nitrogen excretion

Background: Interventions that restrict protein intake lower plasma urea concentration and may slow the progression of renal failure. The question arises whether the effect of a dietary protein restriction could be reinforced by enrichment of the diet with fermentable carbohydrate because these carbohydrates may stimulate the extra-renal route of nitrogen (N) excretion through the digestive route. Methods: The influence of fermentable carbohydrate and moderate protein restriction on N metabolism was investigated in a rat model of renal failure with ablation of 70% of renal mass compared with control rats with intact kidneys. Animals were adapted to diets varying with respect to nondigestible fermentable carbohydrate (0% or 10% fructooligosaccharide [FOS]) and with respect to protein content (10% or 18% casein). Results: Feeding FOS led to a considerable enlargement of the cecum (increase in contents, wall thickness, and blood flow). These changes resulted in a concomitant enhancement of urea N uptake into the cecum and a decrease in plasma urea concentration (−30%). The extent of urea uptake by the cecum was influenced by plasma urea level that was determined by the dietary protein level and by the renal function. Thus, compared with control rats, the rate of urea uptake by the cecum and the total N excreted by the uremic rats was greater under all nutritional conditions. It is noteworthy that, when expressed as a percentage of total N excretion, fecal N excretion nearly doubled in rats adapted to the low-protein diets containing FOS. These effects occurred in both control rats and in uremic rats, in which a 22% decrease in urinary N was recorded as a result of FOS in addition to the low-protein diet. Globally, decreasing the amount of protein in the diet and adding a fermentable carbohydrate led to a decrease in urinary N excretion of more than 65% in uremic rats. Conclusion: These results suggest a possible usefulness for combining fermentable carbohydrate, such as FOS, with a low-protein diet to increase N excretion through the digestive route in detriment of the renal route. This may represent an efficient preventive measure to relieve the renal function in case of renal failure. © 2001 by the National Kidney Foundation, Inc.

Antecedent protein restriction and high-fat feeding interactively sensitise the leptin response to elevated insulin

Using a rat model of moderate (8 vs. 20% protein) isocaloric protein restriction initiated in early life (low protein, LP), we examined the possible basis for the association between impaired early growth and elevated leptin levels in later life in man by examining the acute leptin response to insulin and its relationship with glucose utilisation. We placed subsets of LP rats on a high-saturated-fat (HF) diet containing 20% protein for 4 weeks (LP-4HF) or 8 weeks (LP-8HF), making comparison with age-matched control (C) groups (C, C-4HF, C-8HF). At ambient insulin concentrations, LP was not associated with altered leptinaemia compared with C, despite a more active lipolytic programme as inferred from increased adipocyte sensitivity to norepinephrine. HF feeding led to insulin resistance with respect to whole-body glucose disposal ( R d) (measured using [3- 3H] glucose at steady state) in both LP and C in vivo and impaired suppression of agonist-stimulated lipolysis by insulin in LP but not C in vitro. Whereas insulin infusion for 2 h (while maintaining euglycaemia) only modestly increased plasma leptin levels in vivo in C, C–4HF, C–8HF and LP groups, the leptin response to insulin was greatly enhanced in the HF-fed LP groups. A close positive correlation (r=0.96) existed between plasma leptin levels and R d in the C groups (viz. C, C–4HF, C–8HF) whereas a close inverse correlation (r=0.95) existed between plasma leptin levels and insulin-stimulated R d in the LP groups (viz. LP, LP–4HF, LP–8HF). Glucose utilisation (estimated from 2-deoxy- d-[1- 3H] glucose 6-phosphate accumulation) in vivo in two intra-abdominal and two superficial adipose-tissue depots was consistently higher in the LP group. After HF feeding, glucose utilisation by the superficial adipose-tissue depots was threefold higher in the LP than in the C group. We conclude that protein restriction from conception to adulthood followed by high-fat feeding sensitises the acute leptin response to insulin, an adaptation associated with enhanced glucose utilisation by adipose tissue. This effect is observed despite impaired insulin sensitivity, both at the level of whole-body glucose disposal and adipocyte anti-lipolysis, and increased lipolytic activity (although the latter is not in itself sufficient to influence the leptin response). We propose that associations between a low birthweight and elevated leptin concentrations in later life may reflect long-term modulation of adipocyte glucose handling.

Perinatal development and adult blood pressure.

A growing body of evidence supports the concept of fetal programming in cardiovascular disease in man, which asserts that an insult experienced in utero exerts a long-term influence on cardiovascular function, leading to disease in adulthood. However, this hypothesis is not universally accepted, hence animal models may be of value in determining potential physiological mechanisms which could explain how fetal undernutrition results in cardiovascular disease in later life. This review describes two major animal models of cardiovascular programming, the in utero protein-restricted rat and the cross-fostered spontaneously hypertensive rat. In the former model, moderate maternal protein restriction during pregnancy induces an increase in offspring blood pressure of 20-30 mmHg. This hypertensive effect is mediated, in part, by fetal exposure to excess maternal glucocorticoids as a result of a deficiency in placental 11-ss hydroxysteroid dehydrogenase type 2. Furthermore, nephrogenesis is impaired in this model which, coupled with increased activity of the renin-angiotensin system, could also contribute to the greater blood pressure displayed by these animals. The second model discussed is the cross-fostered spontaneously hypertensive rat. Spontaneously hypertensive rats develop severe hypertension without external intervention; however, their adult blood pressure may be lowered by 20-30 mmHg by cross-fostering pups to a normotensive dam within the first two weeks of lactation. The mechanisms responsible for this antihypertensive effect are less clear, but may also involve altered renal function and down-regulation of the renin-angiotensin system. These two models clearly show that adult blood pressure is influenced by exposure to one of a number of stimuli during critical stages of perinatal development.

Effects of Severe Protein Restriction with Ketoanalogues in Advanced Renal Failure

Objective: To compare a severe protein restriction diet supplemented with ketoanalogues to a moderate protein restriction diet in order to limit glomerular filtration rate (GFR) decrease in an advanced renal insufficiency stage.Design: Prospective randomised study conducted to compare a severe protein restriction diet (0.30 g/kg/day) supplemented with a preparation of ketoanalogues, hydroxyanalogues of aminoacids and aminoacids (Group A) to a moderate protein restriction diet (0.65 g/kg/day) (Group B).Patients: 50 uremic patients included (25 in each group) with GFR is <20 mL/min/1.73m2.Results: There were no statistically significant differences between the two dietary regimens for the renal survival. But uremia decreased significantly in Group A (22.7±5.2 to 18.5±6.7 mmol/L) and increased in Group B (26.8±9.0 to 34.9±9.9 mmol/L). Calcemia increased in Group A from 2.28±0.18 to 2.42±0.17 mmol/L, p<0.01 with a stable phosphoremia while calcemia decreased in Group B (2.33±0.18 to 2.25±0.17 mmol/L, p<0.05). At the end of the study, Group A was different from Group B for calcemia (2.42±0.17 vs. 2.25±0.17 mmol/L, p<0.01), phosphoremia (1.39±0.30 vs. 1.80±0.65 mmol/L, p<0.02), alkaline phosphatase (61.42±22.93 vs. 78.8±27.0, p<0.05) and parathormone plasma levels (2.71±1.55 vs. 5.91±1.41 ng/mL, p<0.001).Comments: Compared to a moderate protein restriction (0.65 g/kg/day), a severe protein restriction (0.3 g/kg/day) supplemented by ketoanologues does not limit GFR decrease when GFR is below 20 mL/min/1.73m2, but improves phosphocalcic plasma parameters.

Protein restriction during early development enhances insulin responsiveness but selectively impairs sensitivity to insulin at low concentrations in white adipose tissue during a later pregnancy

Poor early nutrition may elicit long-term detrimental effects on adult health, including susceptibility to non-insulin-dependent diabetes mellitus. We investigated the impact of moderate maternal protein restriction during pregnancy and lactation on the action of insulin on adipocyte glucose uptake in female offspring during their own pregnancies. Offspring of dams provided with diets containing either 200 g protein/kg or 80 g protein/kg during pregnancy and lactation (termed C and EPR groups respectively) were weaned on to 200 g protein/kg diet at 24 d of age. At 9-12 weeks of age both groups were time-mated and studied at day 19 of gestation. Rates of glucose utilization (assessed using the 2-deoxy-D-[1-3H]glucose technique) measured in five distinct adipose tissue depots (parametrial (PM), mesenteric (MES), perirenal (PR), subcutaneous (s.c.), interscapular (IS)) in vivo in the post-absorptive state were consistently lower in early-protein-restricted (EPR) pregnant rats compared with control (C) pregnant rats. In C pregnant rats, insulin significantly increased glucose utilization only in the IS depot. In contrast, significantly increased glucose utilization rates in response to hyperinsulinaemia were evident in all five adipose-tissue depots of the EPR pregnant group. Consequently, glucose utilization rates in PM and s.c. depots during hyperinsulinaemia were significantly higher in EPR pregnant rats compared with C pregnant rats. Adipocytes were isolated from PM and MES depots to determine whether altered responses to insulin in vivo were retained in vitro. Rates of insulin-stimulated glucose uptake at sub-maximal (15 microU/ml) and maximal (15 mU/ml) insulin concentrations were significantly higher in both MES and PM adipocytes from EPR pregnant rats, but the sensitivity of glucose uptake to insulin at low concentrations was blunted compared with adipocytes from C pregnant rats. The results demonstrate that early protein restriction enhances the capacity for adipocyte glucose uptake at high insulin concentrations, but dampens the response to insulin at low physiological concentrations.

Role of fermentable carbohydrate supplements with a low-protein diet in the course of chronic renal failure: experimental bases.

During the past few years, considerable attention has been given to the impact of nutrition on kidney disease. The question arises of whether the effect of a moderate dietary protein restriction could be reinforced by enrichment of the diet with fermentable carbohydrates. Feeding fermentable carbohydrates may stimulate the extrarenal route of nitrogen (N) excretion through the fecal route. Such an effect has been reported in several species, including healthy humans and patients with chronic renal failure (CRF). Furthermore, studies of these subjects show that the greater fecal N excretion during the fermentable carbohydrate supplementation period was accompanied by a significant decrease in plasma urea concentration. In animal models of experimental renal failure, the consumption of diets containing fermentable carbohydrates results in a greater rate of urea N transfer from blood to the cecal lumen, where it is hydrolyzed by bacterial urease before subsequent microflora metabolism and proliferation. Therefore, this results in a greater fecal N excretion, coupled with a reduction in urinary N excretion and plasma urea concentration. Because elevated concentrations of serum urea N have been associated with adverse clinical symptoms of CRF, these results suggest a possible usefulness of combining fermentable carbohydrates with a low-protein diet to increase N excretion through the fecal route. Further investigations in this population of patients of whether fermentable carbohydrates in the diet may be beneficial in delaying or treating the symptoms and chronic complications of CRF will certainly emerge in the future. This should be realized without adversely affecting nutritional status and, as far as possible, by optimizing protein intake for the patients without being detrimental to renal function.

Acute effects of moderate dietary protein restriction in patients with idiopathic hypercalciuria and calcium nephrolithiasis

High dietary protein intake is a potential risk factor for nephrolithiasis because of its capacity to increase urinary calcium and to facilitate lithogenesis through many other mechanisms. Our aim was to verify the effects of moderate protein restriction in hypercalciuric patients. We studied 18 patients (10 men and 8 women aged 45.6+/-12.3 y) with idiopathic hypercalciuria and renal calculi. Before and after 15 d of a diet with 0.8 g protein x kg(-1) x d(-1) and 955 mg Ca, all patients were evaluated for the main serum and urinary measures of calcium metabolism as well as for urinary uric acid, oxalate, citrate, and prostaglandin E2. Urinary excretion of urea fell after the diet (P < 0.001). Urinary calcium (P < 0.001), uric acid (P < 0.005), oxalate (P < 0.01), and hydroxyproline (P < 0.01) decreased after protein restriction, whereas urinary citrate increased (P < 0.025). Blood pH increased after the hypoproteic diet (P < 0.05). 1,25-Dihydroxycholecalciferol (calcitriol) concentration fell significantly (P < 0.025) and parathyroid hormone increased (P < 0.001). Creatinine clearance tended to decrease (106.4+/-4.8 compared with 97.5+/-5.7 mL/min) after the diet. The decrease in urinary uric acid after the diet correlated with calcitriol concentration (r = 0.57, P < 0.05) and the decrease in urinary urea correlated positively with that in hydroxyproline excretion (r = 0.58, P < 0.01). In hypercalciuric patients, moderate protein restriction decreases calcium excretion, mainly through a reduction in bone resorption and renal calcium loss; both are likely due to a decreased exogenous acid load. Moreover, dietary protein restriction ameliorates the entire lithogenic profile in these patients.

Beverages, diet, and prevention of kidney stones.

Beverages, diet, and prevention of kidney stones.

Moderate protein restriction during pregnancy modifies the regulation of triacylglycerol turnover and leads to dysregulation of insulin’s anti-lipolytic action

Moderate protein restriction throughout pregnancy in the rat leads to relative hyperlipidaemia and blunted insulin responsiveness of lipid fuel supply, and impairs foetal growth. The present study examined the basis for these changes. Isocaloric 8% (vs 20%) protein diets were provided throughout pregnancy. Rats were sampled at 19–20 days of gestation. Protein restriction enhanced triacylglycerol (TAG) secretion rates (estimated using Triton WR 1339) 1.6-fold ( P<0.05) in the post-absorptive state. Insulin infusion (4.2 mU/kg per min) decreased plasma TAG concentrations by 33% ( P<0.05) and 48% ( P<0.05) in control (C) and protein-restricted (PR) pregnant groups, an effect associated with suppression of TAG secretion by 42% ( P<0.05) and 51% ( P<0.01) respectively, in the C and PR groups. Since TAG concentrations decline more rapidly, while TAG secretion is enhanced, TAG utilisation during hyperinsulinaemia is enhanced in the PR group. We evaluated whether these changes were associated with dysregulation of lipolysis using adipocytes from two abdominal depots (mesenteric and parametrial). Noradrenaline-stimulated glycerol release was enhanced in parametrial adipocytes (by 40%; P<0.05) from PR pregnant rats. The anti-lipolytic action of insulin at low concentrations (≤15 μU/ml) was impaired by protein restriction (adipocytes from both depots). There was no evidence for altered intra-hepatic regulation of fatty acid (FA) disposal at the level of carnitine palmitoyltransferase. Our results demonstrate increased post-absorptive production of non-carbohydrate energy substrates (TAG and FA) as a consequence of mild protein restriction during pregnancy. These adaptations contribute to a homeostatic strategy to reduce the maternal requirement for gluconeogenesis from available amino acids, optimising the foetal protein supply. Protein restriction also enhances TAG turnover during hyperinsulinaemia. This effect is not a consequence of abnormal regulation of hepatic lipid metabolism by insulin.

Moderate Dietary Protein and Energy Restriction Modulate cAMP-Dependent Protein Kinase Activity in Rat Liver

Very low protein diets result in a desensitization of hepatic cAMP signaling in rats, which is characterized by a loss of cAMP-dependent protein kinase (PKA) activity and type I regulatory subunit (RI). Here we have tested whether more moderate protein restriction (Trial 1) or energy restriction (Trial 2) also modulates hepatic PKA quantity and activity. In trial 1, weanling rats were allowed free access to diets containing normal protein (15%, AL-NP), moderately restricted protein (12.5%, AL-MP) and low protein (7.5%, AL-LP); in trial 2, rats were allowed free access to diet containing 15% (AL-NP) or 0.5% protein (very low protein, AL-VLP) or were energy restricted by pair-feeding a diet isonitrogenous to AL-NP but at 65% of the energy intake (ER-IN) for 14 d. Body weights were lower (P < 0.05) by d 14 in all restricted groups compared with the AL-NP group. The quantity of cytosolic RI was lower (P < 0.05) in AL-LP and AL-VLP, but not in AL-MP or ER-IN, compared with AL-NP. In contrast, there was no effect of diet on RI in the particulate fraction. RII was not changed by moderate and low protein diets in either the cytosol or particulate fraction. However, type II regulatory subunit (RII) was greater in the cytosol of ER-IN and in the particulate fraction of AL-VLP (P < 0.05) compared with AL-NP. Specific activity of PKA was lower in the cytosol and particulate fraction (P < 0.05) in the AL-VLP and ER-IN groups compared with the AL-NP group. In contrast, specific activity of PKA was maintained in cytosol from AL-LP, but lower in the particulate fraction (P < 0.05) compared with AL-NP. In summary, protein restricted-diets lower RI subunit in the cytosol; however, only in rats fed very low protein diets is this loss of RI associated with lower cytosolic PKA activity. In contrast, energy restriction lowers PKA activity in the cytosol and particulate fractions, independent of signficant reduction in RI or RII subunits. Taken together, these data indicate that moderate protein and energy restrictions have differential effects on activity and quantity of PKA.

Growth sensitive genes expressed in the placenta.

The placenta has a central role in regulating fetal growth. Placental growth, transport activity and endocrine function all change in response to the maternal diet. The changes depend on the degree of metabolic stress. Moderate protein restriction increases the relative growth of the placenta whereas a more severe depletion reduces it [l]. The placenta also acts as the interface between the fetal and maternal circulation and regulates nutrient uptake by the fetus [2]. There is little information on the mechanisms controlling these processes. In cell culture systems, imposing a nutritional stress (for example reducing the concentration of an essential amino acid) arrests cell growth and increases the expression of a range of genes by twoto ten-fold [3]. These include the growth arrest specific (gas) [4], rhe growth arrest and DNA damage (gadd) [5] and the CCAAT enhancer binding protein (CEBP) [6] gene families. These code for a diverse group of proteins implicated in the control of growth, differentiation, celVcell interactions and apoptosis. Gestation in the rat takes 22 days with the growth and development of the placenta being completed by about d18. These experiments were carried out to inleasure the expression of the gas gadd and CEBP genes during the different stages of placental development. Female hooded Lister rats (230g) were mated with normal males. The day vaginal plugs were observed was taken as day 0.5 of gestation. Animals were killed at intervals during gestation, placentae were rapidly removed and frozen in liquid nitrogen. Total RNA was prepared from the frozen samples by disrupting them in Tri-reagent (Sigma). Northern blotting was carried out as previously described [3]. Blots were imaged on a proportional wire counter (Packard Instant Imager). Probes for the gas6, gadd153 (CHOP-lo), CEBP-a, CEBP-B and CEBP-6 genes hybridised strongly to RNA from the placenta (Fig. 1). All of the transcripts were of the anticipated sizes. The gas3 gene was expressed at a low level which was only just detectable by Northern blotting. No gas2 expression could be detected. The expression of gas6 was high during early stages of placental development but then decreased by about three-fold after d12. The expression of gadd153 (CHOP-10) increased by four-fold between d18 and d19 following the drop in gas6 expression. Expression remained elevated until just prior to parturition when the levels fell by about 50%. CIEBP-a and CEBP-I3 expression increased by three-fold between d18 and d19 at the sime time as gadd153 (CHOP-10). There were twn periods of C.EBP-6 expression, one during the early stages of placental development and then a second on the final day which may be related to the parturition process. The expression of gas6 is first detectable by RT-PCR at the blastocyst stage [7] and remains high until d12. The product of the gas6 gene has been shown to be a ligand for the Axl (tyro3) receptor tyrosine kinase [8]. It is probable that gas6 is involved in the celVcell interactions occurring during the development of the placenta. Gas6 has been shown to be a growth factor for endothelial cells [9] and may also have a role in vascularisation. The CEBP family of genes are associated with the differentiation of adipocytes and hepatocytes. CEBP-6 induces the expression of CEBP-R, this then stimulates CEBP-a which maintains the differentiated phenotype [6]. CIEBP-a expression in the placenta is similar to other tissues, increasing when development is complete and the mature placenta has formed. However, unlike adipocytes and hepatocytes, maximum expression of the gadd 153 (CHOP-I 0) and CEBP-B genes occurs after differentiation is complete. In I ,

Nutritional Effects of Dietary Protein Restriction in Insulin-Dependent Diabetes Mellitus

The effects of dietary protein deprivation in insulin-dependent diabetes mellitus (IDDM) have been investigated in a merely rudimentary fashion in human subjects. Moderate dietary protein restriction of 0.6 g/(kg ideal body weight⋅d) over 3 mo in free-living IDDM patients produces increased adiposity during weight maintenance and decreased muscle strength. These effects might have been predicted from studies of protein deprivation in diabetic subjects, indicating impairment of nitrogen retention. The clinical consequences of dietary protein restriction in IDDM may be more complex than described to date. This is suggested by the overriding paradox that the actions of insulin on protein synthesis are inconsistent among in vitro, animal and human in vivo models. The inconsistency and the observation that insulin deficiency in humans accelerates both proteolysis and protein synthesis imply that knowledge about insulin, diabetes and protein metabolism in humans is inadequate and should be studied in increasing detail. Better understanding of the clinical consequences of dietary protein restriction in diabetes, both beneficial and adverse, is likely to come from future studies incorporating clinically relevant levels of insulin deficiency and protein deprivation into studies of bodily function, clinical outcomes and specific examination of the metabolism of individual proteins.

DIABETIC NEPHROPATHY

Diabetic nephropathy accounts for almost a third of all causes of ESRD. Microalbuminuria screening among diabetics can offer early detection of incipient nephropathy. Aggressive treatment with ACE inhibitors may delay the onset of overt renal failure or delay its progression. Furthermore, intensive control of blood glucose has also been proven to prevent the microvascular complications of diabetes and should be pursued in both IDDM and NIDDM. The high association of diabetes mellitus with hypertension presents another problem to the clinician. It is necessary to control blood pressure to prevent further progression of renal failure. The choice of antihypertensive medications, however, becomes a therapeutic dilemma because of the metabolic and lipid disturbances that some drugs can cause. ACE inhibitors, CCBs, alpha-agonists, and low-dose diuretics, alone or in combination, may be tried to normalize blood pressures. Although beta-blockers are widely used and effective in nondiabetics, these agents should be considered the drugs of last resort because of their adverse effects, which are particularly troublesome for diabetics. Moderate protein restriction should also be advocated as a helpful adjunct to therapy.

Role of Medical Approach in the Management of Stone Disease

In the management of stone disease, the medical approach concerned with the prevention of stone recurrence is equally as important as the surgical removal of stones. The application of medical approach requires an understanding of the pathophysiology of stone formation. A wide variety of physiological or environmental disturbances have been identified in stone-forming patients. They include hypercalciuria, hypocitraturia, undue urinary acidity and hyperuricosuria. Reliable diagnostic protocols have been developed which are based on the presence of above derangements. The prophylactic treatment programs are directed at the correction or amelioration of underlying environmental disturbances. Conservative measures include a high fluid intake, dietary sodium and oxalate restriction, dietary calcium restriction (in absorptive hypercalciuria and primary hyperparathyroidism), and moderate animal protein restriction. Specific medical treatments chosen for discussion are thiazide, slow-release neutral potassium phosphate, potassium citrate and potassium magnesium citrate.