Decreased plasma fibronectin during starvation in man

Nutrition, ageing and ill health

There are physical, mental, social and environmental changes which take place with ageing; for example, decreased physical activity, increase in body fat, decrease in lean body mass and consequently decreased energy intake may be associated with physiological functions that affect metabolism, nutrient intake, physical activity and risk of disease. There are now many studies which have found that undernutrition is prevalent and often unrecognized in patients admitted to hospitals and institutions. There is also evidence which links protein-energy undernutrition or its markers with clinical outcomes in acute and non-acute hospital settings and that nutritional supplements can improve outcomes in some of these settings. However, most clinically-available nutrition screening instruments lack sensitivity and specificity, and abnormal nutritional indicators may simply reflect effects of age, functional disability, or severe underlying disease. Thus, causal relationship cannot be assumed without a sufficiently powerful intervention study which adequately adjusts for the effects of non-nutritional factors, such as the number and severity of co-morbid conditions on clinical outcome.

Effects of small-peptide and whole-protein enteral feedings on serum proteins and diarrhea in critically ill patients: a randomized trial

BACKGROUND

It has been proposed that enteral feeding formulas containing small peptides are more efficacious and better tolerated than whole-protein formulas in critically ill patients.

METHODS

Intensive care unit patients were stratified with regard to treatment with antibiotics and serum albumin and randomized to treatment with a small-peptide enteral diet or an isoenergetic, isonitrogenous whole-protein diet for 10 days. To assess efficacy, we measured serum prealbumin and fibronectin, and to assess tolerance, we monitored the incidence of diarrhea. A protocol was followed to ascertain all causes of diarrhea (defined as > 200 g stool or > or = 3 liquid stools on 2 consecutive days).

RESULTS

Fifty subjects completed the trial. Serum prealbumin and fibronectin increased between 21% and 36% in both groups, but the increase was significant only in the small-peptide group. The change in fibronectin between days 5 and 10 was significantly greater in the small-peptide group (p = .02). Diarrhea occurred in 10 subjects (17.8% of days) receiving small-peptide feeding and 4 subjects (7.5% of days) receiving whole-protein feeding (P = .07 for incidence and 0.03 for prevalence), but the difference was explained by the coincidental use of more diarrhea-causing medications in the former. Only one case of diarrhea could be attributed to tube feeding.

CONCLUSIONS

During 10 days of feeding, the small-peptide diet produced slightly greater increases in serum rapid-synthesis proteins than did the whole-protein diet, especially between days 5 and 10. The clinical implications of this difference between the diets are unknown. Both small-peptide and whole-protein diets were well tolerated.

Responses of plasma fibronectin to the changes of dietary protein levels in rats

In this study, the plasma fibronectin was evaluated as a nutritional marker in protein- and protein-energy malnourished rats in comparison with plasma prealbumin, albumin, and total protein. The plasma fibronectin was determined by nephelometric assay based on the interaction of an antigen and antibody. The rats were subjected to three diets, containing 20, 5, and 0% casein, respectively, for 5 wk except in the last 2 wk, the rats on the 0% casein diet were re-fed on a 20% casein diet. The results showed that in the rats on a 5% casein diet (protein malnourished), the plasma fibronectin concentration rose significantly in the early stage and normalized thereafter. In the rats subjected to a 0% casein diet (protein-energy malnourished), the plasma fibronectin concentration did not decline quickly in response to protein depletion, compared with the plasma prealbumin, albumin, and total protein concentrations. Following the re-feeding of a 20% casein diet in the last 2 wk, the plasma fibronectin concentration was restored earlier than other plasma protein concentrations. No significant change in plasma fibronectin concentration was found in the rats receiving a 20% casein diet (control) over the 5 wk feeding period. It is concluded that plasma fibronectin may not be a suitable marker for protein or protein-energy malnutrition, though it is a sensitive index for nutritional rehabilitation.

Alterations in endothelium-associated proteins and serum thyroid hormone concentrations in anorexia nervosa

Plasma concentrations of endothelium-associated proteins (EAP) (plasma fibronectin (PFN), angiotensin-converting enzyme, factor VIII-related antigen (F VIII-R:Ag)) and tissue plasminogen activator and serum thyroid hormone concentrations were studied in nine patients with anorexia nervosa (AN), before and after weight gain. Before weight gain (-35.9 (SE 2.3)% of standard body-weight) PFN was significantly reduced and F VIII-R:Ag was significantly increased in AN patients compared with the concentrations in control subjects (211.5 (SE 14.9) v. 274.7 (SE 16.6) micrograms/ml, P < 0.05; 129.2 (SE 14.1) v. 88.2 (SE 9.7) %, P < 0.05 respectively). Serum triiodothyronine (T3) and free T3 levels were also significantly lower before weight gain in AN patients (0.85 (SE 0.07) v. 1.53 (SE 0.08) nmol/l, P < 0.001; 2.57 (SE 0.23) v. 5.31 (SE 0.34) pmol/l, P < 0.001 respectively), although serum thyroxine (T4), free T4, and thyrotropin concentrations were within the normal range throughout the study periods. Following weight gain, PFN and F VIII-R:Ag concentrations normalized as did the thyroid hormone levels. The incremental changes in PFN levels correlated significantly with those in serum thyroid hormone concentrations (T3, r 0.79, P < 0.01; free T3, r 0.84, P < 0.01). These findings suggest that PFN levels may be directly related to serum T3 concentrations in AN patients.

Effect of serum components on syncytium formation and virus production by cells infected with human immunodeficiency virus in vitro

Previously it has been reported that cocultivation of human immunodeficiency virus type 1 (HIV-1)-infected cells with uninfected cells results in formation of multinuclear giant cells, generated via an interaction of gp120 on the surface of infected cells with CD4 on the uninfected cells. Formation of multinuclear giant cells as occurring in the presence of normal fetal calf serum was not observed when HIV-infected MOLT-4 or MOLT-3 cells (chronically infected with HTLV-IIIB) and uninfected cells were cocultured in both serum-free medium and fibrinogen-depleted serum. Addition of sera (human and rabbit) as well as of fibrinogen (human and bovine), fibronectin (human), and alpha-globulin (human), but not of albumin, transferrin or gamma-globulin to serum-free medium caused formation of multinuclear giant cells. In contrast, HIV production from MOLT-3 cells proceeds also in the absence of serum. In control experiments it was established that the cells maintained at reduced serum concentration, or in serum-free medium without or with fibrinogen are viable even though displaying a lower metabolic rate (ATP formation and DNA synthesis). From these findings we conclude that serum components (e.g., fibrinogen, fibronectin, and alpha-globulin) are absolutely required for syncytium formation but are not essential for virus release.

Polymorphonuclear leukocyte function and serum opsonic activity in surgical patients

Thirty-six patients who underwent major surgery were studied in order to clarify the perioperative changes in polymorpho - nuclear leukocyte (PMNL) function and serum opsonic activity. In patients without postoperative infection, the PMNL phagocytic-bactericidal capacity and plasma elastase levels significantly increased, while the serum opsonic index remarkably decreased just after surgery, however, all returned to the preoperative levels within 1 or 2 weeks. Conversely, in patients with postoperative infection, the PMNL bactericidal capacity and plasma elastase levels remained at high levels even after 1 or 2 weeks, while the PMNL phagocytic capacity and serum opsonic index substantially decreased after 2 weeks compared with the patients without postoperative infection. Plasma leukotriene B4, which is a potent chemo-attractant for PMNL, noticeably decreased in the patients with postoperative infection on the first postoperative day compared with that in the patients without postoperative infection. Our data suggests that the most important predisposing factors to postoperative infection may be a depressed PMNL phagocytic capacity and a lower serum opsonic activity after surgery, and that the increased PMNL bactericidal capacity and high plasma elastase levels during postoperative infection may contribute to the susceptibility to multiple organ failure.

Modern approaches to the therapy of septic shock

Bacteremia from gram-negative rods is a great cause of concern for hospital physicians today. Shock-complicating gram-negative sepsis has a mortality rate of 60% and above, despite early diagnosis and treatment. Intensive research efforts have shown new pathophysiological mechanisms and mediators involved in septic shock, with changes in recommended treatment protocols. In this report, the authors review the use of corticosteroids, fibronectin, naloxone hydrochloride, and immunotherapy, with emphasis on theoretical considerations and relevant clinical experience. Although these treatment methods may have been promising initially, data from large double-blind human trials are either lacking or unencouraging. While continued research and modern therapeutic approaches should improve future survival rates from septic shock, use of the therapies reviewed should be considered experimental at this time.

Effect of acute starvation on plasma fibronectin response to sepsis

There is evidence that undernutrition may contribute to the reduction in plasma fibronectin concentration and the depression of the reticuloendothelial (RE) system associated with severe sepsis. We have investigated the effects of fasting, surgical trauma and sepsis on plasma fibronectin concentrations and RE function. In experiment 1, plasma fibronectin was measured in rabbits (n = 14) before and 48 h after fasting. In experiment 2, sepsis was induced by devascularization of the appendix in animals on a normal diet (sepsis group, n = 7). A third group of animals underwent only a laparotomy (laparotomy only group, n = 7). Plasma fibronectin concentrations and the blood clearance and organ distribution of 99mtechnetium tin colloid (TTC) were measured 24 h after operation. Compared with pooled reference plasma, fasting in experiment 1 resulted in a reduction in mean(s.e.m.) plasma fibronectin concentration from 98(1.5) per cent to 86(3.7) per cent (T = 2, P less than 0.005). Mean(s.e.m.) plasma fibronectin concentration was raised in the sepsis group to 117(4.6) per cent, compared with 97(2.5) per cent in the laparotomy only group (U = 5, P less than 0.02), but there was no such increase in the fasting and sepsis group. There was a delay in the blood clearance and reduced hepatic uptake of TTC in both sepsis groups. The dissociation between fibronectin concentrations and RE function in animal models of sepsis casts doubt on the importance of fibronectin in RE function.

Influence of preoperative intravenous nutrition upon hepatic protein synthesis and plasma proteins and amino acids

The influence of 3 and 7 days of preoperative intravenous nutrition (IVN) on the capacity for protein synthesis in liver and on concentrations of plasma proteins and amino acids were investigated in patients with gastrointestinal malignancy. Thirty patients with gastrointestinal neoplasms who had lost more than 5 kg of weight over 3 months were randomized into three groups to receive preoperatively: (a) no IVN, (b) IVN for 3 days (0.18 gN/kg/day as amino acid; 30 kcal/kg/day as glucose), or (c) IVN for 7 days. Free access to a hospital diet was available to all patients including 10 patients who had not lost weight who served as controls. In the three groups of patients who had lost weight, median transferrin and fibronectin were lower than for controls, whereas other proteins and amino acids were comparable. After feeding, samples of liver were obtained peroperatively and the potential rates of protein synthesis were calculated from the in vitro incorporation of (14C)-leucine, into protein. Preoperative IVN significantly increased the potential rate of protein synthesis in liver after 3 days. Plasma amino acids were comparable with controls whereas in the unfed-group concentrations suggested utilization of alanine and breakdown of muscle. Three days of IVN also increased plasma fibronectin and IgA but increases of prealbumin, IgM, and complement C3 were only significant in the group fed for 7 days. On the 7th postoperative day plasma proteins were decreased similarly in each group. This study shows that concentrations of several plasma proteins, in preoperative patients reflect net rates of hepatic protein synthesis and are susceptible to depletion during starvation and repletion by 3 or 7 days of IVN.

Plasma fibronectin synthesis in normal and injured humans as determined by stable isotope incorporation

In humans, plasma fibronectin decreases early after operative injury, burn, or trauma, followed by a rapid restoration with a secondary decline typically observed if such patients become septic. We determined the rate of plasma fibronectin and plasma fibrinogen synthesis in normal subjects and injured patients using a stable isotope incorporation technique with [15N]glycine. During a constant 14-h infusion of [15N]glycine, the enrichment of [15N]glycine in both the free plasma glycine precursor pool as well as the urinary hippurate pool was determined; the latter used as an estimate of intracellular hepatic precursor enrichment. [15N]Glycine enrichment in both plasma fibronectin and fibrinogen was also quantified. The synthesis rate (Js/V) expressed in micrograms per milliliter of plasma per hour and the fractional synthesis rate (FSR) expressed as percentage of the plasma pool produced per day were determined. In normal subjects, the FSR for plasma fibronectin using 15N enrichment into urinary hippurate was 35.35 +/- 1.46%/d, whereas the Js/V was 4.45 +/- 0.19 micrograms/ml plasma per h. In normal subjects, the FSR for plasma fibronectin using 15N enrichment into free plasma glycine was 14.73 +/- 0.63%/d, whereas the Js/V was 1.98 +/- 0.09 micrograms/ml plasma per h. Early (2-3 d) after burn injury, fibronectin synthesis was increased (Js/V = 5.74 +/- 0.36; P less than 0.05), whereas later after injury, fibronectin synthesis began to decline (Js/V = 3.52 +/- 0.24; P less than 0.05) based on 15N enrichment of urinary hippurate. In contrast, the Js/V and FSR of plasma fibrinogen, a well-documented acute-phase plasma protein, revealed a sustained elevation (P less than 0.05) after injury in both the trauma and burn patients. Thus, plasma fibronectin synthesis is elevated early postinjury, which may contribute to the rapid restoration of its blood level. However, once fibronectin levels have normalized, the synthesis of plasma fibronectin appears to decline.

Influence of Different Dialyzer Membranes on Plasma Fibronectin Levels in Hemodialyzed Patients

Plasma fibronectin (FN) was assayed in 30 patients with chronic renal failure under conservative therapy, 60 uremic patients undergoing periodic hemodialysis, and 7 patients treated by hemofiltration.

Plasma FN was significantly lower in uremic patients on conservative therapy and in those who received intermittent hemodialysis than in the control group. No difference was seen between mean FN concentrations using different dialyzer membranes. Nevertheless, plasma FN levels were significantly higher in subjects after intermittent hemofiltration. There was no evidence of activation of the coagulation system or of any correlation between FN and fibrinogen values.

These findings suggest that conventional hemodialysis is not effective in improving the low levels of plasma FN found in uremic patients, whereas intermittent hemofiltration raises FN. These differences may be due to the fact that during hemofiltration, even when using the same dialyzer membranes as in conventional hemodialysis, some “substances” with high molecular weight that could block the synthesis of FN could be removed.

Diagnosing malnutrition

The measurement of selected anthropometric, biochemical and immunological variables, and clinical judgment can be used to assess nutritional state. Nutritional assessment has three main aims: to define the type and severity of malnutrition; to identify high risk patients; to monitor the efficacy of nutritional support. The problems associated with the various methods to assess the nutritional state and the applications of nutritional assessment in clinical practice are presented and discussed.

Fibronectin and the critically ill patient: current status

In summary, deficiency of plasma fibronectin has now been documented in a variety of clinical entities. Persistently low fibronectin may have prognostic value, and in certain patients may provide a clue to occult sepsis and potential organ failure. The clinical benefit of infusion of fibronectin-rich cryoprecipitate or purified human plasma fibronectin has yet to be determined in well-controlled randomized clinical trials. However, if such results become available then infusion of plasma fibronectin may provide a valuable therapeutic modality in the care of the critically-ill patient.

Fibronectin levels in stressed and septic patients fed with total parenteral nutrition

Plasma fibronectin concentrations were measured in healthy persons as well as in septic and stressed patients. A decrease in plasma fibronectin concentration was shown in volunteers receiving a low energy (600 kcal), amino acids- and lipid-deficient diet. Increased fibronectin levels were measured in stressed and septic patients, not receiving enteral nutrition, after adequate total parenteral nutrition (TPN during 1 week). It is concluded that total parenteral nutrition facilitates improved fibronectin synthesis in stressed and septic patients. Total parenteral nutrition containing an amino acid mixture rich in branched amino acids (50.2% BCAA) is not superior to TPN containing a standard amino acid mixture (15.6% BCAA) in this respect.

Reversal of opsonic deficiency in surgical, trauma, and burn patients by infusion of purified human plasma fibronectin. Correlation with experimental observations

Plasma fibronectin deficiency has been documented in critically ill surgical, trauma, and burn patients. Human plasma fibronectin was isolated by gelatin-Sepharose affinity chromatography and evaluated with respect to its opsonic activity following pasteurization, its in vivo clearance kinetics, and its short-term influence on cardiovascular hemodynamics in postoperative septic sheep. Six patients with low plasma fibronectin levels were also evaluated with respect to temporal changes of immunoreactive fibronectin and opsonic activity following infusion of fibronectin at a dose calculated to elevate the plasma fibronectin level to 400 micrograms/ml. With utilization of three different in vitro radioisotopic phagocytic assays, i.e., liver slice assay, peritoneal macrophage monolayer assay, and Kupffer cell monolayer assay, retention of opsonic activity by fibronectin following pasteurization was documented. The normal biphasic kinetics associated with plasma clearance of fibronectin were also not altered by pasteurization. In postoperative septic sheep with hemodynamic instability, intravenous infusion of 500 mg of purified human fibronectin initiated no abnormal hemodynamic response. Indeed, as compared with placebo, the infusion of fibronectin into the postoperative septic sheep resulted in a more stable systemic vascular resistance and pulmonary vascular resistance with a higher arterial pressure. It also elevated immunoreactive fibronectin levels (p less than 0.05) and increased opsonic activity (p less than 0.05). Surgical, trauma, and burn patients (ages 18 to 80 years) with low plasma fibronectin levels (160 to 236 micrograms/ml) manifested no disturbance in cardiovascular, respiratory, or hematologic parameters following fibronectin infusion (590 to 988 mg per patient), but did display an early increase of opsonic activity. This standardized, pasteurized, and opsonically active preparation of purified human plasma fibronectin (5.0 mg/ml after reconstitution) has utility for future randomized clinical trials in injured patients with sepsis.

Changes in plasma fibronectin during acute nutritional deprivation in healthy human subjects

1. Plasma fibronectin, a glycoprotein, is an opsonin of the reticuloendothelial system. 2. In ten healthy volunteers starved for 4.5 d, daily measurements showed a rapid reduction in plasma fibronectin, no alteration in either C3 or plasma transferrin and, at the end of the starvation period, an elevated serum albumin. 3. On refeeding, plasma fibronectin rapidly returned to its prestarvation level but plasma transferrin was significantly reduced and did not recover by the end of the study. 4. Changes in plasma fibronectin may be a sensitive index of nutritional status. The reduction of plasma fibronectin in short-term starvation may compromise host defence tolerance of injury and sepsis.

The clinical evaluation of plasma fibronectin as a marker for nutritional depletion and repletion and as a measure of nitrogen balance

Plasma fibronectin has been suggested as a possible marker for nutritional repletion or depletion. This study was undertaken to evaluate the usefulness of plasma fibronectin in patients who received intense nutritional support. Twenty-seven patients referred to our Nutritional Support Services were followed for 3 to 5 wk; 22 received parenteral hyperalimentation alone, two received enteral alone, and three received a combination of both. Plasma fibronectin, serum albumin, serum transferrin, total lymphocyte counts, and 24-hr urine nitrogen balance studies were performed weekly; anthropometric measurements were performed every other week. Plasma fibronectin concentration, measured by laser nephelometry, showed a significant rise (p less than 0.005) in all patients after 1 wk of nutritional therapy; however, there was no significant difference among the subsequent weeks. Plasma fibronectin did not correlate with nitrogen balance studies, serum albumin, or total lymphocyte counts. A correlation between serum transferrin and plasma fibronectin was found not to be clinically useful. Thus, plasma fibronectin is sensitive to nutritional repletion after 1 wk of therapy, but is not useful thereafter. The relationship among nutritional status, immunologic function, plasma fibronectin, and other serum proteins are discussed.

The response of fibronectin to differing parenteral caloric sources in normal man

The relationship between circulating fibronectin concentration and nutritional status was examined in eight healthy male (31 +/- 1 yr old) volunteers in three nutritional states: the postabsorptive state, after 10 days of protein-caloric starvation, and during the 10th day of refeeding by total parenteral nutrition. Plasma fibronectin was significantly decreased from 330 +/- 22 to 154 +/- 11 micrograms/ml (p less than 0.001) from the postabsorptive to starved state which was accompanied by appropriate changes in body weight, anthropometric measurements, and nitrogen balance. Plasma fibronectin levels were restored to 402 +/- 39 micrograms/ml following 10 days of total parenteral nutrition. The plasma fibronectin response was greater (p less than 0.05) during total parenteral nutrition with dextrose as the nonprotein calorie source as compared to a 50% dextrose/50% lipid regimen. These results suggest that the calorie source must be considered during interpretation of plasma fibronectin levels in patients undergoing parenteral nutrition.