Ghrelin ameliorates diabetes-associated behavioral deficits and NLRP3 inflammasome activation via autophagic flux enhancement

Potential role of ghrelin in neuroprotection and cognitive function: implications for diabetic cognitive impairment

Ghrelin is a class of brain and intestinal peptides. It regulates food intake and body glucose levels and maintains cellular homeostasis. In recent years, research has revealed that ghrelin may positively impact learning and memory. Despite ghrelin's multiple functions in the central nervous system, its use as a therapeutic agent for neurologic dysfunction remains unclear. Diabetic cognitive impairment (DCI) is a severe neurological complication of diabetes mellitus. Its incidence is increasing as a comorbidity in endocrinology and neurology. Additionally, it is a risk factor for Alzheimer' s disease (AD). Ghrelin levels are altered in patients with diabetes mellitus combined with cognitive impairment. Furthermore, modulation of ghrelin levels improved cognitive function in rats with DCI. These findings suggest the potential therapeutic importance of ghrelin in the pathogenesis of DCI. This article presents a comprehensive review of the pathogenesis of DCI and its potential modulation by ghrelin and its mimics. Furthermore, this study elucidates the therapeutic prospects of ghrelin and its mimics for DCI, aiming to identify novel therapeutic targets and research avenues for the prevention and management of DCI in the future.

Ghrelin Inhibits Inflammasomes Activation in Astrocytes, Alleviates Pyroptosis, and Prevents Lipopolysaccharide-induced Depression-like Behavior in Mice

Depression is the leading cause of disability worldwide and places a significant burden on society. Neuroinflammation is closely associated with the pathophysiology of depression. Increasing evidence suggests that astrocytes, as the most abundant glial cells in the brain, are involved in the occurrence and development of depression due to morphological abnormalities and dysfunction. Astrocytes express the NOD-like receptor protein 2 (NLRP2) and NLRP3 inflammasomes, and the activation of inflammasomes induces pyroptosis. Ghrelin, a gastrointestinal peptide, plays vital role in regulating inflammation and alleviating stress. Therefore, we proposed a hypothesis that ghrelin inhibits the activation of inflammasomes on astrocytes, reduces pyroptosis, and consequently prevents depression. We used lipopolysaccharide (LPS)-induced mouse depression model and cultured primary astrocytes in vitro to explore the mechanism of the antidepressant effect of ghrelin. Our results showed that ghrelin effectively inhibited acute inflammatory responses and damage in the hippocampus and prefrontal cortex. The activation of NLRP2 and NLRP3 in astrocytes induced by LPS was significantly inhibited by ghrelin. Pretreatment with ghrelin effectively suppressed LPS-induced upregulation of pyroptosis-related proteins and mRNA. Ghrelin alleviated cell membrane pore formation and cell swelling, ultimately improved LPS-induced depression-like behavior. In vitro, ghrelin prevented the LPS-induced upregulation of pyroptosis-related proteins and mRNA expression in astrocytes, and inhibited the initiation and assembly of NLRP2 and NLRP3. Ghrelin exhibits antidepressant effects, inhibits inflammasomes activation in astrocytes, and prevents pyroptosis, suggesting a novel strategy for treating depression. This groundbreaking study reveals new avenues for targeting potential therapeutic interventions to alleviate depression.

The Pathologic Roles and Therapeutic Implications of Ghrelin/GHSR System in Mental Disorders

Ghrelin is a hormone consisting of 28 amino acids. Growth hormone secretagogue receptor (GHSR) is a receptor for ghrelin, which is expressed in the brain, pituitary gland, and adrenal glands, especially in the hypothalamus. The binding of ghrelin to the receptor 1a subtype mediates most of the biological effects of ghrelin. Ghrelin has a close relationship with the onset of psychosis. Ghrelin can affect the onset of psychosis by regulating neurotransmitters such as dopamine, γ-aminobutyric acid (GABA), and 5-hydroxytryptamine (5-HT) through the hypothalamus-pituitary-adrenal (HPA) axis, brain-gut axis, the mesolimbic dopamine system, and other ways. Ghrelin activates neuropeptide Y (NPY) in the hypothalamic arcuate nucleus (ARC) through the GHSR. Ghrelin binds to neurons in the ventral tegmental area (VTA), where it promotes the activity of dopamine neurons in the nucleus accumbens (NAcs) in a GHSR-dependent way, increasing dopamine levels and the reward system. This article summarized the recent research progress of ghrelin in depression, anxiety, schizophrenia, anorexia nervosa (AN), and bulimia nervosa (BN), and emphasized its potential application for psychiatric disorders treatment.

Du-moxibustion ameliorates depression-like behavior and neuroinflammation in chronic unpredictable mild stress-induced mice

BACKGROUND

Neuroinflammation is involved in the advancement of depression. Du-moxibustion can treat depression. Here, we explored whether Du-moxibustion could alleviate neuroglia-associated neuro-inflammatory process in chronic unpredictable mild stress (CUMS) mice.

METHODS

C57BL/6J mice were distributed into five groups. Except for the CON group, other four groups underwent CUMS for four consecutive weeks, and Du-moxibustion was given simultaneously after modeling. Behavioral tests were then carried out. Additionally, Western blot was conducted to measure the relative expression levels of high-mobility group box 1 (HMGB1), toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), and nuclear factor-kappa B (NF-κB). Immunofluorescence was employed to evaluate the positive cells of ionized calcium binding adapter molecule 1 (Iba-1) and glial fibrillary acidic protein (GFAP). Furthermore, interleukin-1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) were analyzed using an ELISA assay.

RESULTS

We found that CUMS induced depression-like behaviors, such as reduced sucrose preference ratio, decreased locomotor and exploratory activity, decreased the time in open arms and prolonged immobility. Furthermore, versus the CON group, the expression of HMGB1, TLR4, MyD88, NF-κB, positive cells of Iba-1, IL-1β and TNF-α were increased but positive cells of GFAP were decreased in CUMS group. However, the detrimental effects were ameliorated by treatment with CUMS+FLU and CUMS+DM.

LIMITATIONS

A shortage of this study is that only CUMS model of depression were used, while other depression model were not included.

CONCLUSIONS

Du-moxibustion alleviates depression-like behaviors in CUMS mice mainly by reducing neuroinflammation, which offers novel insights into the potential treatment of depression.

Emerging Relevance of Ghrelin in Programmed Cell Death and Its Application in Diseases

Ghrelin, comprising 28 amino acids, was initially discovered as a hormone that promotes growth hormones. The original focus was on the effects of ghrelin on controlling hunger and satiation. As the research further develops, the research scope of ghrelin has expanded to a wide range of systems and diseases. Nevertheless, the specific mechanisms remain incompletely understood. In recent years, substantial studies have demonstrated that ghrelin has anti-inflammatory, antioxidant, antiapoptotic, and other effects, which could affect the signaling pathways of various kinds of programmed cell death (PCD) in treating diseases. However, the regulatory mechanisms underlying the function of ghrelin in different kinds of PCD have not been thoroughly illuminated. This review describes the relationship between ghrelin and four kinds of PCD (apoptosis, necroptosis, autophagy, and pyroptosis) and then introduces the clinical applications based on the different features of ghrelin.

Novel insights into the pathogenic impact of diabetes on the gastrointestinal tract

Type 2 and type 1 diabetes are common endocrine disorders with a progressively increasing incidence worldwide. These chronic, systemic diseases have multiorgan implications, and the whole gastrointestinal (GI) tract represents a frequent target in terms of symptom appearance and interdependent pathophysiological mechanisms. Metabolic alterations linked with diabetic complications, neuropathy and disrupted hormone homeostasis can lead to upper and/or lower GI symptoms in up to 75% of diabetic patients, with multifactorial involvement of the oesophagus, stomach, upper and lower intestine, and of the gallbladder. On the other hand, altered gastrointestinal motility and/or secretions are able to affect glucose and lipid homeostasis in the short and long term. Finally, diabetes has been linked with increased cancer risk at different levels of the GI tract. The presence of GI symptoms and a comprehensive assessment of GI function should be carefully considered in the management of diabetic patients to avoid further complications and to ameliorate the quality of life. Additionally, the presence of gastrointestinal dysfunction should be adequately managed to improve metabolic homeostasis, the efficacy of antidiabetic treatments and secondary prevention strategies.