The gut microbiota, HPA axis, and brain in adolescent-onset depression: Probiotics as a novel treatment

Anxiety and Depression in Patients with Diabetic Retinopathy

“…The number of Bacteroides, Lactobacillus, and Bifidobacteria was negatively correlated with IL-6 and TNF-a, whereas the number of Enterobacteriaceae and IL-6, IL-22, and TNF-α were positively correlated, and there is a correlation between the number of intestinal flora and inflammatory factors in elderly patients with type 2 diabetes (38). At the same time, probiotic intervention can alter the HPA axis' excitability and lessen animals' depressive-like behavior (39). Moreover, intestinal flora can influence nerve cell regeneration and differentiation, decrease BDNF secretion, and cause symptoms of anxiety and depression (40).…”

A Microbial-Based Approach to Mental Health: The Potential of Probiotics in the Treatment of Depression

“…Nevertheless, its neurobiological underpinnings have been understood to primarily involve altered neurochemicals, impaired stress response systems implicating neuroendocrine components, and neuroinflammation [ 78 , 116 ]. These neurobiological occurrences could be possibly ameliorated through the use of probiotics in depression [ 117 ]. Probiotics’ strain-specific and epigenetic potential counters the possible genetic elements involved in the development of depression.…”

“…Chronic stress exposure leading to persistent elevation of stress hormones, mainly cortisol, has a culpable role in the dysregulation of the HPA axis. It has been elucidated that the MGBA is one of the pathways through which prolonged stress exerts such a consequential effect on the HPA axis, resulting in depressive symptoms [ 117 , 122 , 123 ]. One of the theoretical frameworks to explain this mechanism is by relating the internalized disruptive impact of stress on the gut microbial ecosystem, which augments an increased permeability of the intestinal barrier and subsequent activation of immune responses.…”

“…Conversely, the hyperactivation of the HPA axis exerts harmful effects on the gut microbial ecosystem [ 117 , 124 , 125 , 126 ]. The stress-induced intestinal dysbiosis has also been linked to an altered intestinal fatty acid metabolism, which has consequential effects on adult hippocampal neurogenesis and neuroplasticity, exacerbating HPA axis hyperactivity [ 82 ].…”

“…Chronic stress imposes vicious consequences on the neuronal structure and functionality through its disruptive effects on the integrity of the intestinal barrier, escalation of inflammatory responses, and a maladaptive stress-response system involving the HPA axis. It reduces hippocampal and hypothalamic expression of glucocorticoid receptors and suppresses hippocampal neurogenesis, which ultimately contribute to the pathogenic occurrence of depressive disorder [ 111 , 117 , 141 , 194 ]. Persistently elevated levels of glucocorticoids, particularly cortisol, impose detrimental alterations to the critical frontolimbic structures and neurocircuits, which are instrumental in regulating emotions and rewarding behaviors [ 195 ].…”