Antibodies in research of thymosin β4: investigation of cross-reactivity and influence of fixatives

Association of serum thymosin β4 with malnutrition-inflammation-atherosclerosis syndrome in peritoneal dialysis patients: a cross-sectional study

BACKGROUND

Malnutrition-inflammation-atherosclerosis (MIA) syndrome may worsen the prognosis of peritoneal dialysis (PD) patients. Serum thymosin β4 (sTβ4) protects against inflammation, fibrosis and cardiac dysfunction.

OBJECTIVES

The present study aimed to characterize the association between sTβ4 and MIA syndrome as well as to investigate the potential of regulating sTβ4 to improve the prognosis of PD patients.

METHODS

We performed a cross-sectional, single-center pilot study involving 76 PD patients. Demographic characteristics, clinical characteristics, nutritional profiles, inflammatory mediators, atherosclerosis-related factors and sTβ4 levels were collected and subjected to association analysis for sTβ4 and MIA syndrome.

RESULTS

sTβ4 levels did not significantly vary with sex or primary disease in PD patients. Ages and PD features did not vary between patients with different levels of sTβ4. PD patients with higher levels of sTβ4 had significantly higher levels of nutritional indicators, including subjective global nutritional assessment (SGA) (p < 0.001) and serum albumin (ALB) (p < 0.001) but lower levels of inflammatory and atherosclerotic indicators, including serum C reaction protein (CRP) (p = 0.009), the right common carotid artery (RCCA) intimal thickness (p < 0.001) and the left common carotid artery (LCCA) intimal thickness (p = 0.02). Correlation analysis showed that sTβ4 was positively associated with SGA (p < 0.001) and serum ALB (p < 0.001) but negatively associated with CRP (p = 0.020), RCCA intimal thickness (p < 0.001) and LCCA intimal thickness (p = 0.033). In multiple adjusted models, the prevalence of MIA syndrome was significantly decreased in PD patients with increased levels of sTβ4 when patients without MIA syndrome were compared to those with all indicators of MIA syndrome (OR = 0.996, 95% CI 0.993-0.999, p = 0.003) or those with at least one indicator of MIA syndrome (OR = 0.997, 95% CI 0.995-0.998, p < 0.001).

CONCLUSIONS

The sTβ4 level decreases in PD patients with MIA syndrome. The prevalence of MIA syndrome decreases significantly as the level of sTβ4 increases in PD patients.

Loss of endogenous thymosin β4 accelerates glomerular disease

Glomerular disease is characterized by morphologic changes in podocyte cells accompanied by inflammation and fibrosis. Thymosin β₄ regulates cell morphology, inflammation, and fibrosis in several organs and administration of exogenous thymosin β₄ improves animal models of unilateral ureteral obstruction and diabetic nephropathy. However, the role of endogenous thymosin β₄ in the kidney is unknown. We demonstrate that thymosin β₄ is expressed prominently in podocytes of developing and adult mouse glomeruli. Global loss of thymosin β₄ did not affect healthy glomeruli, but accelerated the severity of immune-mediated nephrotoxic nephritis with worse renal function, periglomerular inflammation, and fibrosis. Lack of thymosin β₄ in nephrotoxic nephritis led to the redistribution of podocytes from the glomerular tuft toward the Bowman capsule suggesting a role for thymosin β₄ in the migration of these cells. Thymosin β₄ knockdown in cultured podocytes also increased migration in a wound-healing assay, accompanied by F-actin rearrangement and increased RhoA activity. We propose that endogenous thymosin β₄ is a modifier of glomerular injury, likely having a protective role acting as a brake to slow disease progression.