Raj S. Kasthuri

O-glycoside biomarker of apolipoprotein C3: responsiveness to obesity, bariatric surgery, and therapy with metformin, to chronic or severe liver disease and to mortality in severe sepsis and graft vs host disease.

The glyco-isoforms of intact apolipoprotein C3 (ApoC3) were used to probe glycomic changes associated with obesity and recovery following bariatric surgery, liver diseases such as chronic hepatitis C (CHC) and alcoholic liver cirrhosis, as well as severe, multiorgan diseases such as sepsis and graft vs host disease (GVHD). ApoC3 glyco-isoform ratios responded to unique stimuli that did not correlate with serum lipids or with other blood components measured in either a control population or a group of extremely obese individuals. However, glyco-isoform ratios correlated with obesity with a 1.8-fold change among subjects eligible for bariatric surgery relative to a nonobese control population. Bariatric surgery resulted in rapid change of isoform distribution to that of nonobese individuals, after which the distribution was stable in each individual. Although multiple simultaneous factors complicated effector attribution, the isoform ratios of very obese individuals were nearly normal for diabetic individuals on metformin therapy. Glyco-isoform ratios were sensitive to liver diseases such as chronic hepatitis C and alcoholic liver cirrhosis. The correlation coefficient with fibrosis was superior to that of current assays of serum enzyme levels. Diseases of pregnancy that can result in liver damage, HELLP syndrome and pre-eclampsia, did not alter ApoC3 glyco-isoform ratios. Early after umbilical cord blood transplantation the isoform ratios changed and returned to normal in long-term survivors. Larger changes were observed in persons who died. GVHD had little effect. Persons with severe sepsis showed altered ratios. Similar cut-points for mortality (3.5-fold difference from controls) were found for UCBT and sepsis. Similar values characterized liver cirrhosis. Overall, while changes of glyco-isoform ratios occurred in many situations, individual stability of isoform distribution was evident and large changes were limited to high-level disease. If ratio changes associated with obesity are found to document a risk factor for long-term outcomes, the information provided by glyco-isoform ratio changes may provide important, novel information for diagnostic, prognostic and therapy response to metabolic conditions.

A functional polymorphism of apolipoprotein C1 detected by mass spectrometry

A survey of plasma proteins in approximately 1300 individuals by MALDI‐TOF MS resulted in identification of a structural polymorphism of apolipoprotein C1 (ApoC1) that was found only in persons of American Indian or Mexican ancestry. MS/MS analysis revealed that the alteration consisted of a T45S variation. The methyl group of T45 forms part of the lipid‐interacting surface of ApoC1. In agreement with an impact on lipid contact, the S45 variant was more susceptible to N‐terminal truncation by dipeptidylpeptidase IV in vitro than was the T45 variant. The S45 protein also displayed greater N‐terminal truncation (loss of Thr‐Pro) in vivo than the T45 variant. The S45 variant also showed preferential distribution to the very‐low‐density lipoprotein fraction than the T45 protein. These properties indicate a functional effect of the S45 variant and support a role for residue 45 in lipid contact and lipid specificity. Further studies are needed to determine the effects of the variant and its altered N‐terminal truncation on the metabolic functions of ApoC1.

Studying multiple protein profiles over time to assess biomarker validity

Protein profile analysis is increasingly used for identification of disease biomarkers. The approaches vary from surface-enhanced laser desorption/ionization to protein arrays. Newer platforms are constantly being developed. Almost all are based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and are often coupled with sophisticated software tools. Protein profiling has been applied to a variety of samples including plasma, urine, cerebrospinal fluid, saliva and solid tissue. This article focuses on those instances where it is possible to obtain sequential samples from the same individual. In the authors use of a profile method, many protein changes with highly significant correlations to disease have been found. The main challenge lies in the validation of the marker to demonstrate its adequacy for use in the clinical setting. The latter requires a methodology that is robust and amenable to high-throughput. One problem is that interindividual variability among the healthy population can mask major changes that occur on an intraindividual basis. Often, a large change for an individual may remain within the range of healthy individuals. Thus, one strategy to optimize biomarker discovery is to examine serial samples from a given individual, where a disease biomarker is established by comparison with the individual’s own baseline sample. The focus of this review is to illustrate the principle and value of serial protein profiling using a rapid protein extraction method.

Top‐down proteomic analysis by MALDI‐TOF profiling: Concentration‐independent biomarkers

Although numerous protein biomarkers have been correlated with advanced disease states, no new clinical assays have been developed. Goals often anticipate disease‐specific protein changes that exceed values among healthy individuals, a property common to acute phase reactants. This review considers somewhat different approaches. It focuses on intact protein isoform ratios that present a biomarker without change in the total concentration of the protein. These will seldom be detected by peptide level analysis or by most antibody‐based assays. For example, application of an inexpensive method to large sample groups resulted in observation of several polymorphisms, including the first structural polymorphism of apolipoprotein C1. Isoform distribution of this protein was altered and was eventually linked to increased obesity. Numerous other protein isoforms included C‐ and N‐terminal proteolysis, changes of glycoisoform ratios and certain types of sulfhydryl oxidation. While many of these gave excellent statistical correlation with advanced disease, clinical utility was not apparent. More important may be that protein isoform ratios were very stable in each individual. Diagnosis by longitudinal analysis of the same individual might increase sensitivity of protein biomarkers by 20‐fold or more. Protein changes that exceed the range of values found among healthy individuals may be uncommon.

Correlation of a T45S variant of apolipoprotein C1 with elevated BMI in persons of American Indian and Mexican ancestries

Obesity and diabetes are serious health problems for Americans and especially for those with American Indian or Mexican ancestry. A preliminary survey by protein analysis rather than classical nucleic acid sequencing methods has suggested a correlation between a newly discovered T45S variant of apolipoprotein C1 (ApoC1), found only in persons with American Indian or Mexican ancestry, and elevated body mass index (BMI). American Indians with the S45 ApoC1 variant (n=36) had an average of 9% higher BMI than those who had only T45 ApoC1 (n=192, P=0.029). Elevated rates of diabetes were reported for parents of subjects with the S45 protein (P=0.006). In five gender-matched sibling pairs, persons with Mexican ancestry showed a 1.34-fold higher BMI for those with S45 ApoC1 (P=0.022). This protein may contribute to the elevated rates of diabetes in relevant ethnic groups and might be more common in isolated populations.

Potential biomarkers of an exaggerated response to endotoxemia

Abstract Serial plasma protein analysis was used to study the acute plasma proteome response to endotoxemia (presence of toxic bacterial products called endotoxins in the blood stream). Plasma samples from healthy volunteers before and multiple time points up to 24 h following administration of low-dose endotoxin were evaluated. Plasma protein profiles were obtained by rapid extraction of whole plasma followed by analysis with matrix-assisted laser desorption ionisation-time of flight mass spectrometry. The profiles were unique to each individual and stable over the time of the experiment. Administration of low-dose endotoxin caused profound change in six of 18 individuals. At 8 h many proteins showed quantitative oxidation, in addition to the appearance of new components and disappearance of common baseline components. An exceptionally intense new component at 4154 mass units was identified as the activation peptide of C1 esterase inhibitor. While recovery of baseline protein structure was nearly complete by 24 h, serum amyloid A, an acute-phase reactant, was still increasing and minor profile changes persisted. Clinical features did not distinguish these extreme responders from others, suggesting that plasma proteome changes offered unique insights into and potential biomarkers of subclinical events following endotoxin exposure.

Medical management of venous thromboembolism: what the interventional radiologist needs to know.

Deep vein thrombosis and pulmonary embolism are considered manifestations of the same pathophysiological process and are together referred to as venous thromboembolism (VTE). VTE is a common disorder with an incidence of 1 to 3 in 1000 in the general population. It is estimated that the incidence of VTE is likely to increase as the average life expectancy of the U.S. population increases. Treatment of VTE consists of anticoagulation; the duration of anticoagulation is largely determined by the circumstances surrounding development of the thrombotic event. Vitamin K antagonists, the only oral anticoagulants approved for treatment of VTE in the United States, have several drawbacks and therefore new oral anticoagulants are currently in various stages of development. This review focuses on the risk factors for VTE and the approach to determining the duration of anticoagulation in patients with VTE. Results of clinical trials on the new oral anticoagulants that may soon be licensed for the treatment of VTE are also discussed.