Breast cancer (BC) is an important health concern in women worldwide (Coughlin and Ekwueme, 2009[11]). Due to advances in cancer treatment and early detection, the five-year relative survival rate for females diagnosed with BC has increased to 89.7 % (American Cancer Society, 2018[3]). However, many of these patients face chronic complications of BC treatments, such as lymphedema (Erickson et al., 2001[16]). Lymphedema is the most prevalent and distressing symptom for patients with breast cancer after surgery and/or radiation (Wanchai et al., 2016[55]).

Breast cancer survivors may experience lymphedema complications for months or years after cancer treatment (Norman et al., 2009[33]). Breast cancer-related lymphedema (BCRL) incidence has been reported to be 21.4 % (DiSipio et al., 2013[14]) and is characterized by swelling, heaviness, pain, limb use limitation, and decreased quality of life (Hormes et al., 2010[20]; Dayan et al., 2018[12]). The lymphatic system is critically important in maintaining tissue fluid homeostasis and regulating the inflammatory response by improving drainage of extravasated fluid, thus reducing edema formation and levels of pro-inflammatory mediators include tumor necrosis factor-α (TNF-α) (Schwager and Detmar, 2019[42]).

Lymphatic injury due to cancer treatments leads to the disruption of lymph flow. Lymphatic fluid stasis may cause increased inflammatory mediators such as TNF-α, fat deposition and progressive fibrosis (Gousopoulos et al., 2016[17], Tashiro et al., 2017[49]). Beside, TNF-α plays the main role in inflammation-induced lymphatic contractile dysfunction (Chen et al., 2017[10]). Studies have implicated that chronic inflammation is a hallmark in the pathophysiology of lymphedema (Ly et al., 2017[25]; Rockson et al., 2018[37]).

Many studies indicated that obesity and also overweight may predispose women to lymphedema and may affect the response to treatment (DiSipio et al., 2013[14]; Ly et al., 2017[25]; Helyer et al., 2010[18]; Hespe et al., 2017[19]; Rockson et al., 2018[37]). Moreover, obesity has a positive correlation with lymphedema severity (Ridner et al., 2011[35]; Helyer et al., 2010[18]). In contrast, weight loss programs have effectively improved the treatment of BCRL (Shaw et al., 2007[44][45]). An increase in serum leptin concentration has been reported in obese patients (Minocci et al., 2000[29]; Van Dielen et al., 2001[51]). Leptin enhances the expression of pro-inflammatory cytokines, such as TNF-α (Bulló et al., 2003[9]). Since obesity is a major risk factor for lymphedema (Vignes et al., 2007[54]; Mehrara and Greene, 2014[28]), the increased level of leptin in overweight and obese patients, can exacerbate inflammation and increase the edema severity (Ly et al., 2017[25]). Anti-inflammatory and anti-fibrotic agents seem to be two key factors in preventing the progression of this disorder (Schaverien and Aldrich, 2018[41]; Hespe et al., 2017[19]; Rockson et al., 2018[37]).

Dysbiosis or gut microflora alteration is not uncommon among overweight and obese individuals (Brown et al., 2012[8]), which may cause systemic inflammation (Le Chatelier et al., 2013[24]; Verdam et al., 2013[53]). Probiotics are living and non-pathogenic bacteria with helpful effects for improving or maintaining the microbiome which can modify the microflora (Alard et al., 2016[1]; Wischmeyer et al., 2016[56]). Synbiotics refer to food ingredients or dietary supplements combining probiotics and prebiotics, non-digestible fiber compounds that stimulate the growth of beneficial bacteria, in the form of synergism (Pandey et al., 2015[34]). Further, probiotics may contribute to improved homeostasis and decreased side effects related to anti-cancer therapies (Mego et al., 2013[27]). Moreover, it has been shown that decreased inflammation may occur by reducing the production of pro-inflammatory cytokines, including interleukin‐1 (IL-1) and TNF-α (McLoughlin et al., 2017[26]). On the other hand, the intestinal microbiome dysbiosis has been shown to affect the development of lymphedema through complicated biological mechanisms including downregulation of pro-inflammatory cytokines such as TNF-α (Amdekar et al., 2012[2]; Archer et al., 2015[4]; Solanki et al., 2015[46]).

We are aware of no study that has examined the effect of synbiotic supplementation on inflammatory profiles and edema volume in BCRL. The current study was therefore performed to investigate the effects of synbiotics on the inflammation status and edema volume of breast cancer survivors with lymphedema following a low-calorie diet. The result of this research may provide new strategies for lymphedema management.

This is the first interventional trial that investigates the possible beneficial role of synbiotic supplementation on inflammatory markers (TNF-α, IL-1β, hs-CRP), serum leptin concentration, anthropometric parameters, and edema volume in BCRL patients.

Our results revealed that synbiotic supplementation for 10 weeks reduced edema volume, the serum concentration of hs-CRP, IL-1β and leptin in overweight and obese patients with BCRL. Furthermore, the synbiotics group had significantly lower levels of serum leptin and TNF-α concentration compared to placebo after the intervention.

A significant improvement was seen in anthropometric indices including body weight, BMI, fat percent and waist circumference within groups at the end of the intervention which is the predictable consequence of the low-calorie diet prescribed to all patients. The anthropometric changes were not significant between the study groups because the simultaneous occurrence of cancer, lymphedema and obesity increased the patient's inflammation (Kolb et al., 2016[23], Zahid et al., 2016[58]) to the level that we could not observe any significant effects for synbiotics in these cases. Also, in a meta-analysis study was shown that probiotic supplementation (3 to 12 weeks) has a small size effect on the reduction of anthropometric factors (Borgeraas et al., 2018[7]).

Reduction in excess edema volume after synbiotic supplementation is a new finding that has not been reported elsewhere. The percentage of edema reduction was 37.36 % and 20.75 % in the synbiotic and placebo groups, respectively. The lack of significant differences between the study groups after the intervention could indicate the positive effects of the weight-loss diet on this marker. In the study by Shaw et al. 12 weeks prescription of a weight-loss diet, led to a significant reduction in weight, BMI, and edema volume in BCRL patients (Shaw et al., 2007[44]) Probiotics with their weight-lowering characteristics can promote this positive effect. Obesity is one of the well-known factors in the onset and progression of lymphedema and obese individuals have a decreased lymphatic transport capacity (Yoon et al., 2018[57]; Savetsky et al., 2014[39]).

In different studies, the prognostic effect of high BMI in lymphedema incidence (Yoon et al., 2018[57]; Iyigun et al., 2018[21]; Helyer et al., 2010[18]) and the predictive effect of weight loss accompanied by complete decongestive therapy in edema reduction (Shaw et al., 2007[44][45]; Duyur Cakit et al., 2019[15]) have been confirmed.

Alleviated hs-CRP serum levels in the synbiotic group was another finding of this study. This beneficial effect was also seen in another study performed on diabetic hemodialysis patients. After 12 weeks of intervention, serum hs-CRP was significantly lower in the synbiotics group (Soleimani et al., 2017[47]). Obesity by activation of the c-Jun N-terminal kinase, nuclear factor-kappa B, and protein kinase R pathways induce the inflammatory response (Solinas et al., 2010[48]; Nakamura et al., 2010[31]). Lack of significant differences in hs-CRP serum levels between the study groups after the intervention may be because of the synergistic effects of cancer/chemotherapy and obesity on inflammation in our study (Kolb et al., 2016[23]; Zahid et al., 2016[58]).

The results of the current study showed a significant reduction in serum IL-1β in both groups after the intervention (-8.37 %; control = -5.01 %), but the non-significant differences of this variable between groups are probably due to the beneficial effects of the weight loss program on this cytokine, owing to the fact that a decrease in body fat during weight loss reduces the production of IL-1β (Kirchner et al., 2014[22]). Shadnoush et al. reported that 8 weeks of consumption of bifidobacterium and lactobacillus in the form of probiotic yogurt, decreased serum IL-1β concentration in inflammatory bowel disease patients compared to control (Shadnoush et al., 2013[43]). No weight loss program was performed in their study that could explain why the differences in serum IL-1β were significant after probiotic intake.

Obesity leads to impairment and imbalance in gut microbiota called dysbiosis which weakens intestinal integrity accompanied by lipopolysaccharide (LPS)-related endotoxemia. LPS is a large molecule that exists in the cell wall of gram-negative bacteria. LPS stimulates the activation of the transcription nuclear factor-kappa B (NF-κB) by binding to toll-like receptor 4 (TLR4) in intestinal epithelial cells. NF-κB upregulates gene expression of pro-inflammatory cytokines such as TNF-α, IL-1β, and IL-6 which mediate a rise in hs-CRP, inflammation, and consequently edema (Neyrinck et al., 2016[32]; Torres et al., 2018[50]; Dinarello, 2009[13]). Also, producing short-chain fatty acids by probiotics prevents the synthesis of hepatic CRP that results in a reduction in its serum levels (Badehnoosh et al., 2018[5]).

We demonstrated that synbiotic supplementation for 10 weeks in BCRL patients led to a significant reduction in serum leptin levels compared to baseline and control group. This effect was also seen in studies on overweight and obese individuals (Sanchez et al., 2014[38]; Zarrati et al., 2014[59]), but it was not in line with the study by Mobini et al. Supplementation with Lactobacillus reuteri in diabetic patients for 12 weeks, could not change leptin (Mobini et al., 2017[30]). Our supplements contain diverse strains of probiotics compared to that study. Each strain of probiotics may exert a special function (Pandey et al., 2015[34]), which may be responsible for the inconsistency of the results. Several mechanisms can explain the beneficial effects of probiotics serum leptin levels. Probiotics have a critical role in leptin secretion regulation (Behrouz et al., 2017[6]). Leptin increases the production of TNF-α in monocytes (Scarpellini and Tack, 2012[40]; Zhou et al., 2011[60]). Any factor that reduces the leptin level can also reduce the levels of TNF-α. Therefore, in our study, a decrease in the leptin serum level consequently reduced the TNF-α serum level in the synbiotic group compared with the placebo. Despite a significant decrease in TNF-α serum level, because of multiple outcomes and the possibility of significant correlation due to multiple testing, this factor should be interpreted with caution. An adjusted significant level can be confirmed in the next and larger studies.

In spite of the potential strengths of our study, such as using a probiotic intervention for the first time among BCRL patients, this study has some limitations. Although the synbiotics supplementation may affect fecal bacterial load, we could not assess this correlation because of budget limitations. Also, we did not consider a control group receiving placebo capsules without any low-calorie diet. So, we can not conclude if the weight reduction program had a synergistic effect along with the synbiotic capsules or not. Evaluation of the gene expression of inflammatory cytokines in future researches may provide valuable evidence in this field.

In conclusion, 10 weeks of synbiotic supplementation along with an LCD program among BCRL patients resulted in a significant reduction in serum levels of TNF-α and leptin compared with the control group. Also, edema volume was significantly reduced within the synbiotic group after intervention. However, no significant differences were found in either of the anthropometric variables, IL-1β, and hs-CRP between the study groups. Weight reduction and synbiotic product consumption in the daily diet of lymphedema patients may be suggested as effective and safe interventions in lymphedema management.

Shahpar Haghighat and Mitra Zarrati (Faculty of Nutrition, School of Public, Iran University of Medical Sciences, Tehran, Iran; Tel: +982186704814, Fax: +982186704814, E-mail: Zarrati_ms@yahoo.com, zarrati.m@iums.ac.ir) contributed equally as corresponding authors.

We would like to gratefully thank the participants for their support in the study. We are also thankful to Namdar laboratory and Zist Takhmir Company and all patients that participated in this study.

This study was supported by Iran University of Medical Sciences (IUMS) with a 96-02-27-31433 grant number.

The authors declare that they have no conflict of interest.