The effects of taurine supplementation on obesity, blood pressure and lipid profile: A meta-analysis of randomized controlled trials
Introduction
Chronic inflammation is a cornerstone for the development of cardiovascular diseases and non-alcohol fatty liver diseases (Abdallah et al., 2020; Lopez-Candales et al., 2017). Potential mechanisms for the activation of inflammation include chronic exposure to environmental stresses such as air pollutant inhalation, drugs, excess food consumption, among others (Zappulla, 2008). Regarding the excessive calorie intake, in a long-term fashion, this is a triggering factor for obesity, in which abdominal obesity is linked to the release of pro-inflammatory cytokines from visceral adipose tissue and the overabundance of oxidative stress (Ellulu et al., 2017; Nishida et al., 2007).
Chronic exposure to these environmental stresses may lead to endogenous carbon dioxide increase that, in turn, may cause eryptosis, i.e., the suicidal death of erythrocytes (Lang et al., 2010; Lang and Qadri, 2012; Zappulla, 2008). This may activate factor nuclear kappa B and stimulate the release of pro-inflammatory cytokines in the systemic circulation, followed by the activation of the hormonal stress response, with consequent sustained glucocorticoids increase and clustering of cardiovascular risk factors of the metabolic syndrome, namely, abdominal obesity, hypertension, non-alcohol fatty liver diseases, higher fasting blood glucose (FBG) values, lower high-density lipoprotein cholesterol (HDL-C), and higher triglyceride (TG) levels (Huang, 2009).
The β-amino acid, L-taurine (Tau; 2-aminoethanesulfonic acid), is a zwitterion compound and a sulfur-containing semi-essential amino acid produced by the endogenous metabolism of cysteine or methionine, or exogenously derived dietary sources and is vital to preserving cellular integrity in cardiac, ocular (particularly retinal), hepatic, renal, skeletal muscle, central nervous system tissues, and white blood cells (Schaffer et al., 2010; Schuller-Levis and Park, 2003). Taurine’s diverse physiological and pharmacological functions are well documented including conjugation of bile acids, modulation of endoplasmic reticulum stress, osmoregulation, cell membrane stabilization, energy metabolism, neuromodulation, anti-oxidation, anti-inflammation, and calcium homeostasis (Salze and Davis, 2015), however, the cytoprotective properties of taurine have drawn the most attention (Schaffer and Kim, 2018).
Taurine supplementation has exhibited efficacy in hypertension (Katakawa et al., 2016; Sun et al., 2016; Waldron et al., 2018). Nevertheless, taurine consumption by obese individuals provided no substantial effect on weight reduction measures (Rosa et al., 2014; Zhang et al., 2004), nor any significant anti-diabetogenic effects or potentiation of insulin release in participants with dysglycemia, including diabetes, and non-alcohol fatty liver diseases through randomized clinical trials (RCTs) (Brons et al., 2004; Chauncey et al., 2003). Conversely, some smaller-sized trials have displayed some favorable results from taurine in augmenting insulin sensitivity in patients with type 1 diabetes and obesity (Elizarova and Nedosugova, 1996; Xiao et al., 2008). Furthermore, a reduction in TG with taurine supplementation has been noted previously (Ishikawa et al., 2010; Zhang et al., 2004).
Notwithstanding the numerous clinical studies evaluating the diverse health benefits of taurine (Lourenco and Camilo, 2002; Murakami, 2015; Sirdah, 2015), some inconsistencies and shortcomings remain to determine whether or not taurine is a promising supplement for the management of liver markers. Cooking has no negative effect in destroying the taurine across foods and its dietary sources include meat and fish, specifically shellfish, chicken, turkey, while dairy products are considered low in taurine levels (Wojcik et al., 2010). The average daily consumption of taurine in a non-vegetarian adult has been reported to be between 40-400 mg (Finnegan, 2003) and, therefore, taurine supplementation may be conceivable as a means of providing a therapeutic effect.
Herein, we carried out a systematic review and meta-analysis of RCTs, whose aim was to analyze the effects of taurine supplementation on liver markers, such as biomarkers of glycemic and lipid control, as well as blood pressure (BP). Secondarily, we investigated the impact of taurine supplementation on anthropometric measures related to obesity, since they can be considered liver markers as well, at least in a population terms.
Section snippets
Material and methods
This systematic review and meta-analysis was executed in agreement with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement guidelines, with a pre-determined search strategy (Moher et al., 2009).
Study selection
The PRISMA flow diagram of the literature search and study selection approach is outlined in Fig. 1. Out of 1609 pertinent articles that were originally retrieved in the literature search, 961 deduplications were performed. The residual 648 articles were screened, of which 570 articles were eliminated based on title and abstract screening. Subsequently, 78 relevant articles were chosen for further exploration of full texts. Of these publications, 66 studies were rejected. Ultimately, a total of
Discussion
Overall, taurine supplementation reduced SBP, DBP, TC, and TG; however, it had no substantial effect on FBG, HDL-C, and LDL-C, as well as on anthropometric measures BMI and BW. Taurine dosage was comprised of 0.5–6 g/d for 15 days to 6 months. Patients had diseases associated with cardiometabolic dysregulation, such as type 2 diabetes mellitus (Shari et al., 2019; Spohr et al., 2005), type 1 diabetes mellitus (Moloney et al., 2010), chronic hepatitis (Hu et al., 2008), cystic fibrosis (Merli et
Strengths and limitations
To date, this is the first comprehensive systematic review and meta-analysis on the effectiveness of taurine supplementation on a variety of biochemical and anthropometric indices. Most importantly, the parameters investigated are closely intertwined with metabolic syndrome and obesity-related comorbidities, and are traditional risk markers for cardiovascular events. Nevertheless, specific limitations of the meta-analysis should be acknowledged including the: (i) varied age and comorbidity
Conclusion
Overall, this updated meta-analysis of RCTs demonstrated that, in patients with cardiometabolic dysregulation (diabetes, hepatitis, obesity, cystic fibrosis, chronic alcoholism, and cardiac surgery), taurine supplementation reduced SBP, DBP, TC, and TG, but had no substantial effect on FBG, HDL-C, LDL-C, as well as on anthropometric measures BMI and BW. Therefore, taurine supplementation may improve some cardiometabolic markers, mainly BP and circulating lipids. However, long-term prospective
Funding
No Funding.
Declaration of competing interest
There was no conflict of interest declared by the authors.
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