How is prealbumin related to albumin?

Aside from being synthesized in the liver and serving as a transport protein in the blood, prealbumin (PA) doesn’t really have much in common with albumin. More specifically, PA is not derived from albumin and, in fact, the two proteins are structurally distinct from each other!

So where does PA get its name? PA is the original name for transthyretin (TTR), a transport protein that primarily carries thyroxine (T4) and a protein bound to retinol (vitamin A). The name arose because TTR migrated faster than albumin on gel electrophoresis of human serum.1

Because of its much shorter serum half-life compared to that of albumin ( ~2 days vs ~20 days),2 PA is more sensitive to recent changes in protein synthesis and more accurately reflects recent dietary intake (not necessarily overall nutritional status) than albumin. 3

But, just like albumin, PA may represent a negative acute phase reactant, as its synthesis drops during inflammatory states in favor of acute phase reactants such as C-reactive protein. 4 So be cautious about interpreting low PA levels in patients with active infection, inflammation or trauma.

 

Reference

  1. Socolow EL, Woeber KA, Purdy RH, et al. Preparation of I-131-labeled human serum prealbumin and its metabolism in normal and sick patients. J. Clin Invest 1965; 44: 1600-1609. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC292644/
  2. Oppenheimer JH, Surks MI, Bernstein G, and Smith JC. Metabolism of Iodine-131-labeled Thyroxine-Binding Prealbumin in Man. Science 1965; 149: 748-750. https://www.ncbi.nlm.nih.gov/pubmed/14330531
  3. Ingenbleek Y, Young VR. Significance of prealbumin in protein metabolism. Clin Chem Lab Med 2002; 40: 1281-1291. https://www.ncbi.nlm.nih.gov/pubmed/12553432
  4. Shenkin A. Serum prealbumin: is it a marker of nutritional status or of risk of malnutrition? Clin Chem 2006;52:2177 – 2179. http://clinchem.aaccjnls.org/content/52/12/2177

 

Contributed by Colin Fadzen, Medical Student, Harvard Medical School, Boston, MA.

 

If you liked this post, sign up under Menu and received future pearls right into your mailbox!

How is prealbumin related to albumin?

My patient with spontaneous bacterial peritonitis (SBP) is requiring IV albumin. Does IV albumin do anything other than expand the plasma volume?

Yes! Besides expanding the circulatory plasma volume by raising the oncotic pressure, albumin appears to have a vasoconstricting effects by binding to endotoxins, nitric oxide (NO), bilirubin and fatty acids1,2.

Splanchnic vasodilatation, a feature of decompensated cirrhosis (eg ascites, bleeding varices, hepatorenal syndrome, and hepatic encephalopathy), is accentuated by superimposed infections through cytokine-mediated release of endothelial vasodilators3.  By binding to potential vasodilators such as bile acids, endotoxins and NO, albumin may also help restore endothelial function and act as a vasoconstrictor.  

In a cool study involving patients with SBP randomized to either albumin or hydroxyethyl starch (HS, a synthetic volume expander), the albumin (not HS) group had a significant increase in mean arterial pressure, right atrial pressure, pulmonary artery pressure,  systolic volume, left ventricular stroke work, and systemic vascular resistance3.

Albumin may also have an immune-modulating activity in patients with cirrhosis or acute liver decompensation by binding to prostaglandin E-2 (PGE-2), generated as a result of inflammatory reaction in the liver and bacterial translocation4.  PGE-2 is a suppressor of macrophage cytokine secretion and bacterial killing.  By binding to PGE-2, albumin can reverse this immunosuppression by reducing the availability of serum PGE-2.

References

  1. Baraldi O, Valenini C, Donati G, et al. Hepatorenal syndrome: update on diagnosis and treatment 2015;4:511-20. https://www.ncbi.nlm.nih.gov/pubmed/26558188
  2. Angeli P, Volpin R, Piovan D, et al. Acute effects of the oral administration of midodrine, an α-adrenergic agonist, on renal hemodynamics and renal function in cirrhotic patients with ascites. Hepatology 1998;28:937-43. https://www.ncbi.nlm.nih.gov/pubmed/9755229
  3. Fernandez J, Monteagudo J, Bargallo X, et al. A randomized unblended pilot study comparing albumin versus hydroxyethyl starch in spontaneous bacterial peritonitis. Hepatology 2005;42:627-634. https://www.ncbi.nlm.nih.gov/pubmed/16108036
  4. Gleeson, MW, Dickson RC. Albumin gains immune boosting credibility. Clin Transl 2015;6:e86;doi:10.1038/ctg.2015.11. http://www.nature.com/ctg/journal/v6/n4/full/ctg201511a.html
My patient with spontaneous bacterial peritonitis (SBP) is requiring IV albumin. Does IV albumin do anything other than expand the plasma volume?

The serum creatinine of my patient originally admitted for management of tense ascites is slowly rising. How concerned should I be?

Although the causes of increasing serum creatinine (SCr) in patients with cirrhosis are legion (eg, sepsis, acute tubular injury, and intravascular volume depletion due to over-diuresis, gastrointestinal bleed, or other causes), the most feared cause is often hepatorenal syndrome (HRS). HRS is a functional renal impairment that reflects the final pathophysiological stages of systemic circulatory impairment1, and significantly contributes to a worsening prognosis in patients with cirrhosis2. For example, without treatment, in patients whose SCr doubles in less than 2 weeks (type I HRS) the median survival is less than 2 weeks , while in those who develop a more gradual renal impairment (type II HRS) the median survival is 6 months3.

Physiologically, HRS is a culmination of significant vasodilation in the splanchnic arteries which, in time, leads to reduced organ perfusion due to a drop in the cardiac output. The associated increase in the activity of the renin-angiotensin-aldosterone and the sympathetic nervous systems contributes to sodium and water retention, and further exacerbates intra-renal vasoconstriction and ascites3.

The primary goal in the medical management of HRS is to increase splanchnic vascular resistance4, often by administering a combination of IV albumin, octreotide and other vasoconstricting agents (eg, midodrine, norepinephrine, or terlipressin [unavailable in US and Canada]).  Of interest, in addition to expanding the circulating plasma volume, albumin may have a vasoconstricting effect by binding to endotoxins, nitric oxide, bilirubin and fatty acids4!

 

References

  1. Arroyo V, Fernandez J, Gines P. Pathogenesis and treatment of hepatorenal syndrome. Semin Liver Dis 2008;28:81-95.
  2. Salerno F, Gerbes A, Ginès P, et al. Diagnosis, prevention and treatment of hepatorenal syndrome in cirrhosis. Gut. 2007 Sep;56(9):1310-8.
  3. Cardenas A, Gines P. A Patient with cirrhosis and increasing creatinine Level: What Is It and what to do? Clin Gatroenterol Hepatol 2009;7:1287–1291. 
  4. Baraldi O, Valentini C, Donati G, et al. Hepatorenal syndrome: Update on diagnosis and treatment. World J Nephrol. 2015;4:511-20.

Contributed by Alireza Sameie, Medical Student, Harvard Medical School

The serum creatinine of my patient originally admitted for management of tense ascites is slowly rising. How concerned should I be?

My elderly patient with acute heart failure with preserved ejection fraction (HFpEF) has a low serum albumin. Can hypoalbuminemia be associated with HFpEF?

Absolutely! As early as 1959, Guyton and Lindsey demonstrated the importance of serum colloid osmotic pressure in the pathogenesis of pulmonary edema1.

Specifically, they found that in dogs with normal plasma protein concentrations fluid began to transudate into the lungs when the left atrial pressure rose above an average of 24 mm Hg vs only 11 mm Hg when plasma protein concentration was reduced by about 50%.

Fast forward to 2003, Arques et al studied serum albumin and pulmonary artery wedge pressures in 4 groups of patients: acute HFpEF, heart failure with reduced ejection fraction (HFrEF), acute dyspnea from pulmonary origin and normal controls2.   Patients with HFpEF were significantly more likely to have hypoalbuminemia , compared to those with HFrEF, pulmonary disease or normal controls.  The main cause of hypoalbuminemia in the HFpEF was malnutrition in 77% and/or sepsis in 41% of patients.   Hypoalbuminemia was inversely related to age and plasma C-reactive protein.

Perhaps, we should pay more attention the nutritional status of our patients with HFpEF!

 

 

References

  1. Guyton AC, Lindsey AW. Effect of elevated left atrial pressure and decreased plasma protein concentration on the development of pulmonary edema. Circ Res 1959;7: 649-657.
  2. Arquès S, Ambrosi P, Gélisse R, Luccioni R, Habib G. Hypoalbuminemia in elderly patients with acute diastolic heart failure. J Am Coll Card 2003;42:712-16. https://wordpress.com/post/pearls4peers.com/762  
My elderly patient with acute heart failure with preserved ejection fraction (HFpEF) has a low serum albumin. Can hypoalbuminemia be associated with HFpEF?

Why does my patient with cirrhosis have a normal serum albumin?

The finding of normal serum albumin in cirrhotic patients is not at all uncommon. In fact, in a meta-analysis involving 8 published articles, the sensitivity of serum albumin (< 3.5 g/dL) in cirrhosis was only 45% (1). It turns out that in many patients with cirrhosis, the synthetic ability of liver with respect to albumin appears well preserved until more advanced stages of liver dysfunction develop (2). So don’t exclude cirrhosis just because serum albumin is normal.

1. Udell JA, Wang CS, Tinmouth J et al. Does this patient with liver disease have cirrhosis? JAMA 2012;307:832-842.

2. Ballmer PE, Washe D. McNurlan M, et al. Albumin synthesis rates in cirrhosis: correlation with Child-Turcotte classification. Hepatology 1993;18:292-297.

Why does my patient with cirrhosis have a normal serum albumin?