SMP30-mediated synthesis of vitamin C activates the liver PPARα/FGF21 axis to regulate thermogenesis in mice.

The vitamin-C-synthesizing enzyme senescent marker protein 30 (SMP30) is a cold resistance gene in Drosophila, and vitamin C concentration increases in brown adipose tissue post-cold exposure. However, the roles of SMP30 in thermogenesis are unknown. Here, we tested the molecular mechanism of thermogenesis using wild-type (WT) and vitamin C-deficient SMP30-knockout (KO) mice. SMP30-KO mice gained more weight than WT mice without a change in food intake in response to short-term high-fat diet feeding. Indirect calorimetry and cold-challenge experiments indicated that energy expenditure is lower in SMP30-KO mice, which is associated with decreased thermogenesis in adipose tissues. Therefore, SMP30-KO mice do not lose weight during cold exposure, whereas WT mice lose weight markedly. Mechanistically, the levels of serum FGF21 were notably lower in SMP30-KO mice, and vitamin C supplementation in SMP30-KO mice recovered FGF21 expression and thermogenesis, with a marked reduction in body weight during cold exposure. Further experiments revealed that vitamin C activates PPARα to upregulate FGF21. Our findings demonstrate that SMP30-mediated synthesis of vitamin C activates the PPARα/FGF21 axis, contributing to the maintenance of thermogenesis in mice.

Role of hypothalamic autophagy in the control of whole body energy balance.

Autophagy is a catabolic process involving the rearrangement of subcellular membranes to sequester cytoplasm and organelles for delivery to lysosomes, where the sequestered material is degraded and recycled. Autophagy is important for maintenance of intracellular energy homeostasis and the quality control of organelles such as the endoplasmic reticulum (ER) and mitochondria, which suggests that dysregulated autophagy might play a role in the pathogenesis of metabolic disorders and diabetes. In an attempt to elucidate the role of autophagy in metabolic disorders, diverse in vivo and in vitro models have been employed. Site-specific autophagy knockout models that are autophagy-deficient specifically in pancreatic ß-cells, skeletal muscle, adipose tissues or liver have been produced. These models have generated valuable information regarding the role of autophagy in body metabolism. The role of autophagy in the hypothalamus, which controls whole body energy balance, appetite and energy expenditure, has also been investigated. Thus, mice with autophagy deficiency in the hypothalamus have shown diverse phenotypes (lean vs. obese) depending on the site of autophagy deficiency or the method of autophagy abrogation.

Role of hypothalamic proopiomelanocortin neuron autophagy in the control of appetite and leptin response.

Autophagy is a catabolic cellular process involving the degradation of the cell's own components. Although the role of autophagy of diverse tissues in body metabolism has been investigated, the importance of autophagy in hypothalamic proopiomelanocortin (POMC) neurons, key regulators of energy balance, has not been addressed. The role of autophagy in leptin sensitivity that is critical for the control of body weight and appetite has also not been investigated. We produced mice with specific deletion of autophagy-related 7 (Atg7), an essential autophagy gene, in hypothalamic POMC neurons (Atg7(ΔPOMC) mice). Atg7 expression was deficient in the arcuate nucleus of the hypothalamus of Atg7(ΔPOMC) mice. p62, a specific substrate of autophagy, accumulated in the hypothalamus of Atg7(ΔPOMC) mice, which colocalized with ubiquitin. Atg7(ΔPOMC) mice had increased body weight due to increased food intake and decreased energy expenditure. Atg7(ΔPOMC) mice were not more prone to diet-induced obesity compared with control mice but more susceptible to hyperglycemia after high-fat diet. The ability of leptin to suppress fasting-elicited hyperphagia and weight gain during refeeding was attenuated in Atg7(ΔPOMC) mice. Deficient autophagy did not significantly affect POMC neuron number but impaired leptin-induced signal transducer and activation of transcription 3 activation. Our findings indicate a critical role for autophagy of POMC neurons in the control of energy homeostasis and leptin signaling.

2'-Hydroxycinnamaldehyde targets low-density lipoprotein receptor-related protein-1 to inhibit lipopolysaccharide-induced microglial activation.

2'-Hydroxycinnamaldehyde (HCA) isolated from the stem bark of Cinnamomum cassia and its derivative 2'-benzoyloxycinnamaldehyde (BCA) were reported to have anti-angiogenic, anti-proliferative, and anti-inflammatory effects in several human cancer cells and RAW 264.7 macrophage cells. However, effects of HCA/BCA on the neuroinflammation have not been investigated. In the present study, a potential anti-neuroinflammatory effect of HCA/BCA was assessed in lipopolysaccharide (LPS)-stimulated microglial cultures and microglia/neuroblastoma cocultures. Nitric oxide production, inflammatory gene expression, and signaling pathways were investigated. HCA/BCA significantly decreased the production of nitric oxide and tumor necrosis factor-alpha (TNF-α) in microglial cells. HCA/BCA also attenuated the expression of inducible nitric oxide synthase (iNOS) and pro-inflammatory cytokines such as interleukin-1ß (IL-1ß) and TNF-α at mRNA level via blockade of ERK, JNK, p38 MAPK, and NF-κB activation. Moreover, HCA/BCA was neuroprotective by reducing microglia-mediated neuroblastoma cell death in a microglia-neuroblastoma co-culture. Affinity chromatography and LC-MS/MS analysis identified low-density lipoprotein receptor-related protein 1 (LRP1) as a potential molecular target of HCA in microglial cells. Based on the studies using the receptor-associated protein (RAP) that blocks a ligand binding to LRP1 and the siRNA-mediated LRP1 gene silencing, we were able to conclude that HCA inhibited LPS-induced microglial activation via LRP1. Our results suggest that HCA/BCA be anti-inflammatory and neuroprotective in the CNS by targeting LRP1, and may have a therapeutic potential against neuroinflammatory diseases.

NF-kappaB activation in hypothalamic pro-opiomelanocortin neurons is essential in illness- and leptin-induced anorexia.

Anorexia and weight loss are prevalent in infectious diseases. To investigate the molecular mechanisms underlying these phenomena, we established animal models of infection-associated anorexia by administrating bacterial and viral products, lipopolysaccharide (LPS) and human immunodeficiency virus-1 transactivator protein (Tat). In these models, we found that the nuclear factor-kappaB (NF-kappaB), a pivotal transcription factor for inflammation-related proteins, was activated in the hypothalamus. In parallel, administration of LPS and Tat increased hypothalamic pro-inflammatory cytokine production, which was abrogated by inhibition of hypothalamic NF-kappaB. In vitro, NF-kappaB activation directly stimulated the transcriptional activity of pro-opiomelanocortin (POMC), a precursor of anorexigenic melanocortin, and mediated the stimulatory effects of LPS, Tat, and pro-inflammatory cytokines on POMC transcription, implying the involvement of NF-kappaB in controlling feeding behavior. Consistently, hypothalamic injection of LPS and Tat caused a significant reduction in food intake and body weight, which was prevented by blockade of NF-kappaB and melanocortin. Furthermore, disruption of I kappaB kinase-beta, an upstream kinase of NF-kappaB, in POMC neurons attenuated LPS- and Tat-induced anorexia. These findings suggest that infection-associated anorexia and weight loss are mediated via NF-kappaB activation in hypothalamic POMC neurons. In addition, hypothalamic NF-kappaB was activated by leptin, an important anorexigenic hormone, and mediates leptin-stimulated POMC transcription, indicating that hypothalamic NF-kappaB also serves as a downstream signaling pathway of leptin.

A patient with primary squamous cell carcinoma of the thyroid intermingled with follicular thyroid carcinoma that remains alive more than 8 years after diagnosis.

Primary squamous cell carcinoma of the thyroid is an extremely rare tumor with a highly aggressive clinical course. We report here on a patient with primary squamous cell carcinoma of the thyroid who remains alive more than 8 years after diagnosis. A 56-year-old man presented with a hoarse voice and a rapidly progressing mass on the right side of the thyroid gland. The patient underwent a total thyroidectomy without neck lymph node dissection. Histopathologic findings revealed primary squamous cell carcinoma combined with follicular carcinoma of the thyroid. The tumors metastasized to the cervical lymph nodes, thoracic spine and lung. He underwent 5000 rads of adjuvant radiotherapy to the neck. TSH suppressive therapy with L-thyroxine was administered alone rather than radioactive iodine therapy or chemotherapy. The patient's clinical course has been remarkable over the first 7 years; he has remained stable except for a transient paraplegia due to nerve compression. The patient underwent colectomy for the diagnosis of a colon cancer. Recent evaluation has revealed a new lesion in the lung; this was diagnosed as metastatic follicular carcinoma originating from the thyroid. High dose radioactive iodine therapy was administered, and he remains alive in stable condition.

Sequential induction of heme oxygenase-1 and manganese superoxide dismutase protects cultured astrocytes against nitric oxide.

Nitric oxide (NO) is a widely recognized mediator of physiological and pathophysiological signal transmission. In an attempt to better understand the molecular actions of NO in astrocytes, stress protein expression in response to NO donor sodium nitroprusside was investigated. Heme oxygenase-1 (HO-1) has been identified as an inducer of manganese superoxide dismutase (MnSOD), playing a cytoprotective role under the condition of nitrosative stress. We present evidence that the sequential induction of HO-1 and MnSOD protects astrocytes from NO toxicity: (1) both HO-1 and MnSOD expression were induced by NO; (2) NO-mediated increase in MnSOD activity was partly abolished by HO-1 inhibitor Zn(II) protoporphyrin IX (ZnPP); (3) pretreatment of astrocytes with a nontoxic dose of NO protected the cells against the later treatment with a toxic dose of NO; (4) inhibition of HO-1 by ZnPP sensitized astrocytes to the nontoxic dose of NO resulting in a marked cytotoxicity; and (5) adenovirus-mediated overexpression of MnSOD protected astrocytes from the NO toxicity. The molecular action of NO in astrocytes appears to be dose-dependent. While a high dose of NO exerts cytotoxicity leading to the tissue damage in the central nervous system, a low dose of NO may act as an important signaling molecule in astrocytes with concurrent induction of cytoprotective proteins such as HO-1 and MnSOD.