MANF in POMC Neurons Promotes Brown Adipose Tissue Thermogenesis and Protects Against Diet-Induced Obesity

Cerebrospinal fluid mesencephalic astrocyte-derived neurotrophic factor: A moderating effect on sleep time and cognitive function

BACKGROUND

Sleeping late has been associated with cognitive impairment, and insufficient sleep can affect the secretion of feeding-related cytokines. Feeding-related cytokines may contribute to cognitive deficits resulting from delayed bedtime. Glial cell line-derived neurotrophic factor (GDNF) and mesencephalic astrocyte-derived neurotrophic factor (MANF), which are feeding-related neurotrophic factors, have been associated with improved cognitive function and neuroprotective abilities. Enhanced expression of GDNF and MANF is linked to increased energy expenditure and hyperphagia, respectively.

AIMS

This study aimed to investigate the association between cerebrospinal fluid (CSF) GDNF, MANF, cognition, and sleep time and to explore the moderating effects of GDNF and MANF on cognitive impairment in individuals who sleep late.

METHOD

This cross-sectional study included participants (mean age 31.76 ± 10.22 years) who were categorized as ≤23 o'clock sleepers (n = 66) and >23 o'clock sleepers (n = 125) based on sleep time. Cognition was assessed using Montreal Cognitive Assessment (MoCA), and GDNF and MANF levels in CSF were measured.

RESULTS

MANF may play a moderating role in the relationship between sleep time and cognition (R2 = 0.06, β = 0.59, p = 0.031). Age showed a negative correlation with MoCA scores (R2 = 0.08, β = -0.18), while education exhibited a positive correlation (β = 0.17, both p < 0.05). Only ≤23 o'clock sleepers exhibited a negative correlation between MANF levels and BMI (r = -0.35, p = 0.005).

CONCLUSIONS

This study provides hitherto undocumented evidence of the potential protective effect of CSF MANF on cognitive impairment of late sleepers, which suggests that maintaining a regular sleep schedule may contribute to cognition and overall health, with MANF playing a role in this process.

Mesencephalic astrocyte-derived neurotrophic factor ameliorates inflammatory response in polycystic ovary syndrome via inhibiting TLR4-NF-κB-NLRP3 pathway

Polycystic ovary syndrome (PCOS) is a common reproductive endocrine disorder in women of reproductive age, which often leads to female infertility. Chronic inflammation is a significant factor in the development of PCOS. Our study aimed to explore the impact of mesencephalic astrocyte-derived neurotrophic factor (MANF), a scientifically validated anti-inflammatory factor, on 99 diagnosed PCOS patients. We also investigated its effects on PCOS mice induced with dehydroepiandrosterone (DHEA) and KGN cells induced with dihydrotestosterone (DHT). Our findings revealed a decrease in serum MANF levels in PCOS patients, which were negatively associated with serum tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) levels. The administration of recombinant human MANF (rhMANF) in PCOS mice demonstrated a decrease in pro-inflammatory cytokines and monocytes/macrophages in both peripheral blood and ovarian tissues. Furthermore, the inclusion of rhMANF notably ameliorated DHEA-induced ovarian dysfunction and fibrosis by negatively regulating the toll-like receptor 4 (TLR4)-nuclear factor kappa B (NF-κB)-NLR family, pyrin domain containing protein 3 (NLRP3) pathway. Additionally, in vitro experiments showed that the up-regulation of MANF offset DHT-induced inhibition of viability and apoptosis in KGN cells. Collectively, this study highlights the anti-inflammatory properties of MANF in PCOS and suggests its potential as a therapeutic approach for the management of PCOS.

AZGP1 in POMC neurons modulates energy homeostasis and metabolism through leptin-mediated STAT3 phosphorylation

Zinc-alpha2-glycoprotein (AZGP1) has been implicated in peripheral metabolism; however, its role in regulating energy metabolism in the brain, particularly in POMC neurons, remains unknown. Here, we show that AZGP1 in POMC neurons plays a crucial role in controlling whole-body metabolism. POMC neuron-specific overexpression of Azgp1 under high-fat diet conditions reduces energy intake, raises energy expenditure, elevates peripheral tissue leptin and insulin sensitivity, alleviates liver steatosis, and promotes adipose tissue browning. Conversely, mice with inducible deletion of Azgp1 in POMC neurons exhibit the opposite metabolic phenotypes, showing increased susceptibility to diet-induced obesity. Notably, an increase in AZGP1 signaling in the hypothalamus elevates STAT3 phosphorylation and increases POMC neuron excitability. Mechanistically, AZGP1 enhances leptin-JAK2-STAT3 signaling by interacting with acylglycerol kinase (AGK) to block its ubiquitination degradation. Collectively, these results suggest that AZGP1 plays a crucial role in regulating energy homeostasis and glucose/lipid metabolism by acting on hypothalamic POMC neurons.

Neural circuits of long-term thermoregulatory adaptations to cold temperatures and metabolic demands

The mammalian brain controls heat generation and heat loss mechanisms that regulate body temperature and energy metabolism. Thermoeffectors include brown adipose tissue, cutaneous blood flow and skeletal muscle, and metabolic energy sources include white adipose tissue. Neural and metabolic pathways modulating the activity and functional plasticity of these mechanisms contribute not only to the optimization of function during acute challenges, such as ambient temperature changes, infection and stress, but also to longitudinal adaptations to environmental and internal changes. Exposure of humans to repeated and seasonal cold ambient conditions leads to adaptations in thermoeffectors such as habituation of cutaneous vasoconstriction and shivering. In animals that undergo hibernation and torpor, neurally regulated metabolic and thermoregulatory adaptations enable survival during periods of significant reduction in metabolic rate. In addition, changes in diet can activate accessory neural pathways that alter thermoeffector activity. This knowledge may be harnessed for therapeutic purposes, including treatments for obesity and improved means of therapeutic hypothermia.

GPSM1 in POMC neurons impairs brown adipose tissue thermogenesis and provokes diet-induced obesity

OBJECTIVE

G-protein-signaling modulator 1 (GPSM1) has been proved the potential role in brain tissues, however, whether GPSM1 in hypothalamic nuclei, especially in POMC neurons is essential for the proper regulation of whole-body energy balance remains unknown. The aim of our current study was to explore the role of GPSM1 in POMC neurons in metabolic homeostasis.

METHODS

We generated POMC neuron specific GPSM1 deficiency mice and subjected them to a High Fat Diet to monitor metabolic phenotypes in vivo. By using various molecular, biochemical, immunofluorescent, immunohistochemical analyses, and cell culture studies to reveal the pathophysiological role of GPSM1 in POMC neurons and elucidate the underlying mechanisms of GPSM1 regulating POMC neurons activity.

RESULTS

We demonstrated that mice lacking GPSM1 in POMC neurons were protected against diet-induced obesity, glucose dysregulation, insulin resistance, and hepatic steatosis. Mechanistically, GPSM1 deficiency in POMC neurons induced enhanced autophagy and improved leptin sensitivity through PI3K/AKT/mTOR signaling, thereby increasing POMC expression and α-MSH production, and concurrently enhancing sympathetic innervation and activity, thus resulting in decreased food intake and increased brown adipose tissue thermogenesis.

CONCLUSIONS

Our findings identify a novel function of GPSM1 expressed in POMC neurons in the regulation of whole-body energy balance and metabolic homeostasis by regulating autophagy and leptin sensitivity, which suggests that GPSM1 in the POMC neurons could be a promising therapeutic target to combat obesity and obesity-related metabolic disorders.

TLR4 in POMC neurons regulates thermogenesis in a sex-dependent manner

The rising prevalence of obesity has become a worldwide health concern. Obesity usually occurs when there is an imbalance between energy intake and energy expenditure. However, energy expenditure consists of several components, including metabolism, physical activity, and thermogenesis. Toll-like receptor 4 (TLR4) is a transmembrane pattern recognition receptor, and it is abundantly expressed in the brain. Here, we showed that pro-opiomelanocortin (POMC)-specific deficiency of TLR4 directly modulates brown adipose tissue thermogenesis and lipid homeostasis in a sex-dependent manner. Deleting TLR4 in POMC neurons is sufficient to increase energy expenditure and thermogenesis resulting in reduced body weight in male mice. POMC neuron is a subpopulation of tyrosine hydroxylase neurons and projects into brown adipose tissue, which regulates the activity of sympathetic nervous system and contributes to thermogenesis in POMC-TLR4-KO male mice. By contrast, deleting TLR4 in POMC neurons decreases energy expenditure and increases body weight in female mice, which affects lipolysis of white adipose tissue (WAT). Mechanistically, TLR4 KO decreases the expression of the adipose triglyceride lipase and lipolytic enzyme hormone-sensitive lipase in WAT in female mice. Furthermore, the function of immune-related signaling pathway in WAT is inhibited because of obesity, which exacerbates the development of obesity reversely. Together, these results demonstrate that TLR4 in POMC neurons regulates thermogenesis and lipid balance in a sex-dependent manner.

Feeding-induced hepatokines and crosstalk with multi-organ: A novel therapeutic target for Type 2 diabetes

Hyperglycemia, which can be caused by either an insulin deficit and/or insulin resistance, is the main symptom of Type 2 diabetes, a significant endocrine metabolic illness. Conventional medications, including insulin and oral antidiabetic medicines, can alleviate the signs of diabetes but cannot restore insulin release in a physiologically normal amount. The liver detects and reacts to shifts in the nutritional condition that occur under a wide variety of metabolic situations, making it an essential organ for maintaining energy homeostasis. It also performs a crucial function in glucolipid metabolism through the secretion of hepatokines. Emerging research shows that feeding induces hepatokines release, which regulates glucose and lipid metabolism. Notably, these feeding-induced hepatokines act on multiple organs to regulate glucolipotoxicity and thus influence the development of T2DM. In this review, we focus on describing how feeding-induced cross-talk between hepatokines, including Adropin, Manf, Leap2 and Pcsk9, and metabolic organs (e.g.brain, heart, pancreas, and adipose tissue) affects metabolic disorders, thus revealing a novel approach for both controlling and managing of Type 2 diabetes as a promising medication.