visfatin , also known as nicotinamide phosphoribosyltransferase ( nampt ) as well as pre - b - cell colony - enhancing factor , is a multifaceted protein with suggested enzymatic , immunological , and metabolic properties .
visfatin has been analyzed in hypo- and hyperthyroidism in in vitro and in vivo studies , but results are inconclusive .
in addition , nampt level was found to be elevated in many autoimmune diseases , that is , rheumatoid arthritis , systemic lupus erythematosus , inflammatory bowel diseases , and psoriasis [ 25 ] .
visfatin also positively correlates with activity and severity of rheumatoid arthritis and psoriasis [ 2 , 5 ] .
we have recently found an overexpression of nampt in leukocytes of patients with graves ' ophthalmopathy with corresponding increased serum concentration ( accepted manuscript ) .
our findings suggest that visfatin might be involved in autoimmune processes in thyroid diseases . in our opinion
, the controversial findings of visfatin in thyroid hormone deficiency may arise from the heterogeneity of thyroid dysfunction .
we hypothesized that regulation of visfatin in hypothyroidism might be altered by coexisting chronic autoimmune thyroiditis , since high visfatin levels were observed in other autoimmune diseases . to answer the question about the influence of coexisting chronic autoimmune inflammation on visfatin level
, we analyzed its serum concentration among hypothyroid patients with chronic autoimmune thyroiditis and in patients after thyroidectomy , who were negative for thyroid antibodies .
this is a prospective case - control study of 118 subjects . the autoimmune study group ( ait ) consisted of 39 patients newly diagnosed with hypothyroidism in a course of chronic autoimmune thyroiditis .
the nonautoimmune study group ( tt ) consisted of 40 patients thyroidectomized due to the differentiated thyroid cancer staged pt1 .
tt patients were evaluated five years after radioiodine remnant ablation and were negative for thyroglobulin and radioiodine uptake in a whole body scintigraphy ( wbs ) .
they achieved endogenous tsh stimulation and became hypothyroid after l - t4 withdrawal for at least 4 weeks .
the control group comprised 39 healthy volunteers adjusted for age , sex , and bmi with normal thyroid function and negative thyroid antibodies .
exclusion criteria consisted of other autoimmune diseases , active neoplastic disease , diabetes mellitus , and infection , which were reported to alter visfatin level .
fasting blood samples were taken for visfatin , tsh , free thyroxine ( ft4 ) , free triiodothyronine ( ft3 ) , antithyroperoxidase antibodies ( tpoab ) , antithyroglobulin antibodies ( tgab ) , glucose , and insulin levels . in tt group
tsh , ft4 , and ft3 were measured using the electrochemiluminescence technique in cobas e 601 ( norm ranges : tsh 0.274.2 
tpoab and tgab were measured by radioimmunoassay ( norm range : < 34  iu / ml and < 115  iu / ml , resp . ) .
glucose level was assessed with the use of hitachi cobas e601 chemiluminescent analyzer ( roche diagnostics ) and insulin concentration was assessed using elisa kit from phoenix pharmaceuticals .
the estimate of insulin resistance by homeostasis model assessment ( homa - ir ) was calculated .
the study was approved by the local ethics committee , and informed consent was signed by every subject .
statistical analysis was performed with medcalc version 12.1.3.0 ( medcalc software , mariakerke , belgium ) .
variables with normal distribution were compared between three groups with one - way analysis of variance .
if data did not follow normal distribution , comparison of the analyzed parameters between three groups was performed with the kruskal - wallis test .
simple regression analysis was used to test for the relationships between them . before inclusion to this statistical analysis ,
furthermore , stepwise multiple regression analysis was employed to investigate the influence of various parameters on visfatin serum concentration [ age , bmi , ft3 , autoimmunity ( yes / no ) , homa - ir ] .
variables were entered into the model if their associated p - values were less than 0.05 and then sequentially removed if their associated p - values became greater than 0.2 .
tests were considered to be statistically significant if p - value was lower than 0.05 .
clinical and laboratory data of the study groups and the control group are shown in table 1 .
the highest visfatin serum concentration was in ait group , and healthy controls had visfatin level higher than tt ( p = 0.0001 ) ( figure 1 ) .
three groups did not differ in age , sex , bmi , fasting glucose , and insulin levels , homa - ir .
they had statistically different tsh , ft4 , ft3 , and tgab levels ( table 1 ) .
simple linear regression analysis revealed that visfatin serum concentration was significantly associated with autoimmunity (  = 0.1014 ; p = 0.003 ) , ft4 (  = 0.05412 ; p = 0.048 ) , ft3 (  = 0.05242 ; p = 0.038 ) , and tpoab (  = 0.0002 ; p = 0.0025 ) ( figure 2 ) .
there was no association between visfatin and age , sex , bmi , tsh , tgab , fasting insulin and glucose levels , and homa - ir ( table 2 ) .
in the stepwise multiple regression analysis we confirmed the association between serum visfatin level and autoimmunity ( coefficient = 3.8461 ; p = 0.0001 ) , and ft3 ( coefficient = 0.4198 ; p = 0.0441 ) , whereas age , bmi , and homa - ir did not contribute significantly .
in separate stepwise multiple regression analysis we confirmed the association of serum visfatin concentration with autoimmunity ( coefficient = 4.1105 ; p = 0.0001 ) and ft4 ( coefficient = 0.1397 ; p = 0.038 ) , whereas age , bmi , and homa - ir did not enter the model .
similarly , association of visfatin with tpoab ( coefficient = 0.0057 ; p = 0.0163 ) was observed with adjustment for age , bmi , ft3 , and homa - ir in multivariate regression analysis .
to date , visfatin serum concentration in hypothyroidism has been analyzed in a few studies .
reported elevated level of this adipocytokine in hypothyroidism with further increase after restoration of thyroid function .
ozkaya et al . observed that visfatin level decreased after recovery . in those articles the etiology of hypothyroidism varied from chronic autoimmune thyroiditis , postpartum thyroiditis to thyroid function insufficiency after radioiodine treatment or after thyroidectomy .
hence , to date autoimmune status of studied patients has not been taken into consideration .
we hypothesized that these controversial findings might result from heterogeneity of study groups . to answer the question ,
whether coexisting autoimmune inflammation influences visfatin level in hypothyroid patients , we analyzed its serum concentration in chronic autoimmune thyroiditis and thyroidectomized patients negative for thyroid antibodies . since we have previously proved that visfatin mrna expression is increased in thyroid malignancies and is correlated with tumor stage , we recruited only those patients who did not have any features of active neoplastic disease .
we also recruited the control group adjusted for age , sex , and bmi . to the best of our knowledge ,
this is the first study addressing the changes in the release of visfatin in thyroid autoimmunity .
we came to interesting results indicating that visfatin serum concentration in hypothyroid patients is associated with both autoimmunity and free thyroid hormones level ( ft4 , ft3 ) .
visfatin has been recognized as a cytokine with a broad range of immune and inflammatory activities , including induction of inflammatory cytokines , and regulation of macrophage and lymphocyte proliferation .
visfatin stimulates the production of proinflammatory cytokines ( il-6 , tnf- , and il-1 ) and potentially acts as a chemotactic factor for monocytes .
furthermore , its expression is upregulated by il-6 , tnf- , and il-1 [ 1012 ] .
enhanced mrna expression of visfatin was observed in inflamed mucosa of patients with inflammatory bowel disease ( ibd ) .
further analysis identified that antigen presenting cells ( i.e. , macrophages , dendritic cells ) might be a main source of this protein in ibd .
visfatin has also potency for activation of t cells by upregulation of costimulatory molecules ( cd40 , cd54 , and cd80 ) on monocytes .
we observed the positive association between visfatin and tpoab , and the latter is considered the best serological marker of chronic autoimmune thyroiditis .
furthermore , tpoab contribute to thyroid destruction through antibody- and complement - dependent cell - cytotoxicity [ 13 , 14 ] . the first mechanism is associated with mononuclear cell infiltration of thyroid stroma .
in addition , th1-derived cytokines ( il-2 , tnf- , and inf ) were found to be elevated in patients with chronic autoimmune thyroiditis .
also , il-1 and tnf- have been recently reported to discriminate chronic autoimmune hypothyroid children from healthy controls .
altogether , association of visfatin with tpoab observed in our study further supports our hypothesis that visfatin might be involved in the pathogenesis of chronic autoimmune thyroiditis .
our findings about the association of visfatin with ft3 levels are in accordance with the results of in vitro and in vivo studies .
however , controversial results whether t3 stimulates or downregulates the production of visfatin were found .
in contrast , caixs et al . did not find any relationship between visfatin and free thyroid hormones . in vitro experiment
showed the nonlinear regulation of visfatin mrna expression in the 3t3-l1 cell culture model affected by t3 .
since our study groups significantly differed with free thyroid hormones levels , we were able to analyze visfatin concentration in a broad spectrum of ft3 and ft4 .
therefore , we might suggest that pattern of visfatin changes varies in different ft3 concentration . according to our observations , as well as other authors
, visfatin did not reflect insulin resistance assessed by homa - ir [ 18 , 19 ] .
our study might then prove that visfatin in hypothyroidism depends on thyroid hormones level and coexisting autoimmunity .
we may assume that these two factors should be taken into consideration to assess visfatin level in patients with thyroid dysfunction .
in addition , the possible involvement of visfatin in pathogenesis of chronic autoimmune thyroiditis needs further research .
the main limitation of our study is its cross - sectional design that does not enable us to reveal the causal pathways of relationship between visfatin and autoimmune thyroiditis .
however , we used very strict criteria of exclusion to limit the possible influence of other known factors such as diabetes mellitus , other autoimmune processes , infection , and active neoplastic disease .
our nonautoimmune group with hypothyroidism had been thyroidectomized at least 5 years earlier and did not have any clinical nor laboratory features of active thyroid cancer .
 we hypothesized that regulation of visfatin in hypothyroidism might be altered by coexisting chronic autoimmune thyroiditis . 
 this is a prospective case - control study of 118 subjects . the autoimmune study group ( ait ) consisted of 39 patients newly diagnosed with hypothyroidism in a course of chronic autoimmune thyroiditis . 
 the nonautoimmune study group ( tt ) consisted of 40 patients thyroidectomized due to the differentiated thyroid cancer staged pt1 . 
 the control group comprised 39 healthy volunteers adjusted for age , sex , and bmi with normal thyroid function and negative thyroid antibodies . 
 exclusion criteria consisted of other autoimmune diseases , active neoplastic disease , diabetes mellitus , and infection , which were reported to alter visfatin level . 
 fasting blood samples were taken for visfatin , tsh , free thyroxine ( ft4 ) , free triiodothyronine ( ft3 ) , antithyroperoxidase antibodies ( tpoab ) , antithyroglobulin antibodies ( tgab ) , glucose , and insulin levels . 
 the highest visfatin serum concentration was in ait group , and healthy controls had visfatin level higher than tt ( p = 0.0001 ) . 
 simple linear regression analysis revealed that visfatin serum concentration was significantly associated with autoimmunity (  = 0.1014 ; p = 0.003 ) , ft4 (  = 0.05412 ; p = 0.048 ) , ft3 (  = 0.05242 ; p = 0.038 ) , and tpoab (  = 0.0002 ; p = 0.0025 ) , and the relationships were further confirmed in the multivariate regression analysis . 
1. Introduction
2. Patients and Methods
3. Results
4. Discussion
Limitation of the Study