Childhood obesity signals: Protein family abundances altered

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  • Published: Jun 1, 2011
  • Author: Steve Down
  • Channels: Proteomics
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Childhood obesity is a growing problem, literally, with more young people affected in the western world than ever before. In the US, the CDC reports a 17% obesity rate for children and adolescents aged 2-19, representing 12.5 million cases. This is triple the rate reported from last generation figures from 1980.

It is a similar picture in the UK, where about 16 and 14% of boys and girls, respectively, aged 2-15 were obese in 2008. Not surprisingly, a scientific report commissioned by the government predicted that nearly half of men and over a third of women will be obese by 2025.

And it's not simply a case of appearance. Obesity brings with it a glut of health problems. Obese children are more likely to suffer from high blood pressure and high cholesterol, which are risk factors for cardiovascular disease. There is also a high risk of impaired glucose tolerance, insulin resistance and type 2 diabetes.

Other problems might arise from fatty liver disease, gallstones, and heartburn. There are also the potential psychological effects of being overweight for children, including low self-esteem, bullying and discrimination.

Obese children are more likely to become obese adults too, with an increased risk of heart disease and some cancers.

The onset of obesity is marked by reduced levels of high density lipoprotein cholesterol (HDL-cholesterol), which are maintained during obesity, but a team of Greek researchers decided to explore the possibility of other indications.

They examined the protein profiles, using plasma proteomics for the first time in a study of childhood obesity to see if the proteins are affected by obesity.

Plasma proteins compared

Evangelia Charmandari and colleagues from the Biomedical Research Foundation of the Academy of Athens, the Harokopio University of Athens and the Aghia Sophia Children's Hospital, Athens, compared the plasma profiles of 10 obese, 10 overweight and 10 normal-weight prepubertal boys with average ages of 10-11.

The status of each individual was assessed by the body mass index, which is a recognised measure of healthy weight based on the height and weight of an individual.

Each plasma sample was treated with a peptide ligand library to remove the majority of the abundant proteins such as albumin and immunoglobulins, which can mask the presence of less abundant proteins. The proteins in the depleted plasma samples were then separated by two-dimensional gel electrophoresis and the protein spots were stained and analysed by image processing software.

Proteins with different abundances between the three groups of boys were selected for identification by mass spectrometry, matching against the SWISS-PROT human database.

Protein family affected by obesity

The most striking observation was major differences between the levels of the apolipoproteins of obese and overweight children compared with those of normal weight.

Apolipoprotein A-I was about half as abundant in plasma from obese and overweight children than in normal children and apolipoprotein E was also less abundant in overweight children.

Conversely, apolipoprotein A-IV was notably higher in obese children than in their normal counterparts.

The serum levels of the apolipoproteins were measured by biochemical methods (an immunonephelometric assay), confirming that apolipoprotein A-I was less abundant in obese and overweight boys.

However, measurements of serum total, high-density and low-density cholesterol by enzymatic colorimetric assays revealed that there were no significant differences between the three childhood groups. So, the altered expressions of apolipoproteins manifest themselves before the well-documented changes in HDL-cholesterol become evident.

The researchers noted that altered level of apolipoprotein E in plasma was not mirrored by that in serum. It might be a false positive or the serum and plasma proteins might be different isoforms. Either way, they could not place any importance on this protein.

Another protein at raised levels in obese and overweight children was fibrinogen beta-chain, which correlated with higher concentrations of high-sensitivity C-reactive protein. The increases are consistent with the predisposition of obese children towards atherosclerotic cardiovascular disease.

This study was conducted with a relatively small sample set but the results are promising. It appears that reduced levels of apolipoprotein A-I might be present in the plasma of obese and overweight children before alterations in the abundance of HDL-cholesterol take place.

With the corresponding changes in serum apolipoprotein A-I able to be measured by a biochemical method, the research team recommended that this should be undertaken for all overweight and obese children.

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

Obesity and overweight in children is associated with changes in the expression profiles of plasma apolipoproteins, which might manifest themselves before the well-documented alterations in cholesterol levels, say Greek researchers

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