The human gut microbiota plays a significant role in the pathophysiology of central nervous system related diseases. Recent studies suggest correlations between the altered gut microbiota and major depressive disorder (MDD). It is proposed that normalization of the gut microbiota alleviates MDD. The imbalance of brain-gut-microbiota axis also results in dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis. This imbalance has a crucial role in the pathogenesis of depression. Treatment strategies with certain antibiotics lead to the depletion of useful microbes and thereby induce depression like effects in subjects. Microbiota is also involved in the synthesis of various neurotransmitters (NTs) like 5-hydroxy tryptamine (5-HT; serotonin), norepinephrine (NE) and dopamine (DA). In addition to NTs, the gut microbiota also has influence on brain derived neurotrophic factor (BDNF) levels. Recent research findings have exhibited that transfer of stress prone microbiota in mice is also responsible for depression and anxiety-like behaviour in animals. The use of probiotics, prebiotics, synbiotics and proper diet have shown the beneficial effects in the regulation of depression pathogenesis. Moreover, transplantation of fecal microbiota from depressed individuals to the normal subjects also induces depression like symptoms. With the precedence of limited therapeutic benefits from monoamine targeting drugs, the regulation of brain-gut microbiota is emerging as a new treatment modality for MDDs. In this review, we elaborate the significance of brain-gut-microbiota axis in the progression of MDD, particularly focusing on the modulation of the gut microbiota as a mode of treating MDD.
Gemfibrozil is a well-known potent antihyperlipidemic drug with the capacity to lower triglyceride and cholesterol levels, which are responsible for most cardiovascular and cerebrovascular diseases. In addition, gemfibrozil has a potent activity at elevating the high density lipoprotein levels. However, this drug has a very short half-life of about 2 h and toxicity is observed in the liver as the dose increases. The drug piperine has the capacity to enhance the bioavailability of other drugs without altering their basic properties as well as improving their activity. In this study, we aimed to enhance the bioavailability of gemfibrozil as well as making it more potent and less toxic by applying piperine as a bio-enhancer. Thus, piperine was co-administered to rats with gemfibrozil and the antihyperlipidemic activity was tested when fed on a high fat diet. The results showed that co-administration of gemfibrozil with piperine decreased the elevated triglyceride and cholesterol levels to normal, and they performed significantly better than the individual drugs. Weight gain was controlled effectively by drug administration together with piperine compared with other groups. Hepatic function analyses demonstrated that the potentiation of gemfibrozil did not alter the hepatic function but instead it improved significantly by normalizing the elevated serum glutamic oxaloacetic transaminase, serum glutamic pyruvic transaminase, and alkaline phosphatase levels. The plasma drug concentration of gemfibrozil was studied over time, where the enhanced activity of the drug reached its C
max
within 1 h of administration and the activated drug level was observed in the blood for 4 h.
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