Discussion
obesity, weight loss, TG
OBESITY, INSULIN RESISTANCE, INSULIN SENSITIVITY
The present study evaluated the impacts of co-supplementing L-carnitine with multistrain/multispecies synbiotic vs. L-carnitine concomitant with placebo on anthropometric and metabolic profiles in women with obesity. Both “L-carnitine + synbiotic” and “L-carnitine + placebo” supplementation significantly ameliorated the anthropometric indices, lipid profile, and glucose homeostasis parameters, except for the reduction of TG and FBS in the L-carnitine + placebo group. Importantly, L-carnitine + synbiotic co-supplementation significantly alleviated the anthropometric and glycemic indices, compared with the L-carnitine + placebo; nonetheless, no significant intergroup disparities were detected for the lipid indices, except for HDL-C. Overall, the intragroup findings of this study indicate that both L-carnitine + synbiotic and L-carnitine + placebo supplementation might have beneficial effects on obesity and related cardiometabolic biomarkers. Nevertheless, according to the statistically significant intergroup disparities revealed for the anthropometric (BMI, weight, NC, WC, and HC) and glycemic indices (FBS, insulin, HOMA-IR, QUICKI) and HDL-C, co-supplementation of L-carnitine with synbiotic was more advantageous to improve these parameters. Based on our in-depth search, there were no reports on the L-carnitine + synbiotic joint supplementation effects on the stated factors in individuals with obesity; therefore, we discussed our findings based on the literature indicating the impacts of either supplement separately. The conceivable mechanisms for the ameliorating impacts of either synbiotics or L-carnitine on obesity and glycemic/lipid indices are illustrated in Potential mechanisms for the improving effects of L-carnitine/synbiotics on obesity, lipid profile, and glycemic indices Although preclinical investigations have implied the efficiency of L-carnitine in weight reduction (Multiple plausible mechanisms are suggested for the beneficial effects of carnitine on increasing energy expenditure and subsequent weight loss. Carnitine plays a pivotal role in fatty acid ß-oxidation, through facilitating the translocation of long-chain fatty acids across the mitochondrial membrane (According to the evidence demonstrating altered gut microbiota diversity or composition in obesity (Several possible mechanisms have been conceived for the favorable impacts of synbiotics supplementation on anthropometric indices, mediated through the complementary/synergistic effects of their pro- and prebiotic compartments (Evidence has intimated that synbiotics might reverse the detrimental effects of microbiota dysbiosis, promoting weight loss and maintenance via restoring healthy gut microbiota composition and/or function (Growing evidence has depicted that gut microbiota modification leads to augmented SCFA production, which underlies most of the aforementioned beneficial impacts (Regarding the lipid profile, despite the significant intragroup amelioration in lipid indices, except for TG in the L-carnitine + placebo group, no significant disparities were found for the lipid parameters among the groups, except for HDL-C. Our failure to find significant intergroup differences in lipid profile could be due to the fact that both carnitine and synbiotics might induce beneficial effects on lipid profile (Our results regarding the hypolipidemic properties of L-carnitine were in accordance with the findings of recent meta-analyses, addressing the ameliorating effects of L-carnitine on TG, TC, LDL-C, and HDL-C (A very recent meta-analysis concluded that synbiotic supplementation could significantly amend TG, TC, LDL-C, and HDL-C (The present study showed that L-carnitine + synbiotic co-supplementation resulted in a significant amelioration in all glycemic parameters including FBS, insulin, HOMA-IR, and QUICKI, compared with L-carnitine + placebo monotherapy, even when adjusted for possible confounding factors. Additionally, either L-carnitine + synbiotic or L-carnitine + placebo supplementation led to a remarkable intragroup amendment in glycemic parameters, except for FBS in the L-carnitine + placebo group. Considering that both carnitine and synbiotics are perceived to induce beneficial effects on glycemic indices (Various clinical trials have demonstrated the promising effects of L-carnitine on insulin sensitivity and/or glucose tolerance (Several mechanisms are suggested for the beneficial impacts of L-carnitine on glucose homeostasis, including improving insulin sensitivity, enhancing glucose utilization, modulating the gluconeogenic and glycolytic enzymes expression, altering the insulin signaling cascade gene expression, and stimulating the insulin-like growth factor 1 (IGF-1) axis and IGF-1 signaling cascade (It has been clarified in several clinical trials that pro/pre/synbiotics might improve glucose homeostasis features (The putative mechanisms for the ameliorating effects of synbiotics on glycemic status principally mediated through amplifying SCFA production could be considered as four principal issues, namely, ameliorating glucose homeostasis, attenuating insulin resistance, amending gut integrity, and hindering proinflammatory signaling pathways (Collectively, mounting data support the ameliorating impacts of either synbiotics or L-carnitine on obesity, lipid profile, or glycemic markers although distinctions in metabolic modifying agents, such as the participants’ ethnic group, genotype, health condition, dietary intake, physical activity, and baseline values of biological markers, along with formulation, dose, and supplementation length, might have resulted in diverse reports. Furthermore, given the aforementioned purported mechanisms for the improving effects of L-carnitine/synbiotics on weight or metabolic parameters, it could be conceived that concomitant supplementation of L-carnitine and synbiotics may confer more pronounced impacts on these indicators, potentially through simultaneous modulation of energy homeostasis (