Among the 22 fibroblast growth factors (FGFs), FGF21 has now emerged as a key metabolic regulator. However, the mechanism whereby FGF21 mediates its metabolic actions per se remains largely unknown. Here, we show that FGF21 represses mammalian target of rapamycin complex 1 (mTORC1) and improves insulin sensitivity and glycogen storage in a hepatocyte-autonomous manner. Administration of FGF21 in mice inhibits mTORC1 in the liver, whereas FGF21-deficient mice display pronounced insulin-stimulated mTORC1 activation and exacerbated hepatic insulin resistance (IR). FGF21 inhibits insulin- or nutrient-stimulated activation of mTORC1 to enhance phosphorylation of Akt in HepG2 cells at both normal and IR condition. TSC1 deficiency abrogates FGF21-mediated inhibition of mTORC1 and augmentation of insulin signaling and glycogen synthesis. Strikingly, hepatic βKlotho knockdown or hepatic hyperactivation of mTORC1/ribosomal protein S6 kinase 1 abrogates hepatic insulin-sensitizing and glycemic-control effects of FGF21 in diet-induced insulin-resistant mice. Moreover, FGF21 improves methionine- and choline-deficient diet-induced steatohepatitis. Conclusions: FGF21 acts as an inhibitor of mTORC1 to control hepatic insulin action and maintain glucose homeostasis, and mTORC1 inhibition by FGF21 has the therapeutic potential for treating IR and type 2 diabetes.

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BackgroundThe purpose of this study was to assess the relationship of smoking duration with respiratory symptoms and history of chronic obstructive pulmonary disease (COPD) in the South Carolina Behavioral Risk Factor Surveillance System survey in 2012.MethodsData from 4,135 adults aged ≥45 years with a smoking history were analyzed using multivariable logistic regression that accounted for sex, age, race/ethnicity, education, and current smoking status, as well as the complex sampling design.ResultsThe distribution of smoking duration ranged from 19.2% (1–9 years) to 36.2% (≥30 years). Among 1,454 respondents who had smoked for ≥30 years, 58.3% were current smokers, 25.0% had frequent productive cough, 11.2% had frequent shortness of breath, 16.7% strongly agreed that shortness of breath affected physical activity, and 25.6% had been diagnosed with COPD. Prevalence of COPD and each respiratory symptom was lower among former smokers who quit ≥10 years earlier compared with current smokers. Smoking duration had a linear relationship with COPD (P<0.001) and all three respiratory symptoms (P<0.001) after adjusting for smoking status and other covariates. While COPD prevalence increased with prolonged smoking duration in both men and women, women had a higher age-adjusted prevalence of COPD in the 1–9 years, 20–29 years, and ≥30 years duration periods.ConclusionThese state population data confirm that prolonged tobacco use is associated with respiratory symptoms and COPD after controlling for current smoking behavior.

Recent reports have shown that preconditioning with the TLR3 ligand polyinosinic-polycytidylic acid (poly(I:C)) protects against cerebral ischemia/reperfusion (I/R) injury. However, it is unclear whether poly(I:C) treatment after cerebral I/R injury is also effective. We used mouse/rat middle cerebral artery occlusion and cell oxygen-glucose deprivation models to evaluate the therapeutic effects and mechanisms of poly(I:C) treatment. Poly(I:C) was i.p. injected 3 h after ischemia (treatment group). Cerebral infarct volumes and brain edemas were significantly reduced, and neurologic scores were significantly increased. TNF-α and IL-1β levels were markedly decreased, whereas IFN-β levels were greatly increased, in the ischemic brain tissues, cerebral spinal fluid, and serum. Injuries to hippocampal neurons and mitochondria were greatly reduced. The numbers of TUNEL-positive and Fluoro-Jade B+ cells also decreased significantly in the ischemic brain tissues. Poly(I:C) treatment increased the levels of Hsp27, Hsp70, and Bcl2 and decreased the level of Bax in the ischemic brain tissues. Moreover, poly(I:C) treatment attenuated the levels of TNF-α and IL-1β in serum and cerebral spinal fluid of mice stimulated by LPS. However, the protective effects of poly(I:C) against cerebral ischemia were abolished in TLR3−/− and TLR4−/−mice. Poly(I:C) downregulated TLR4 signaling via TLR3. Poly(I:C) treatment exhibited obvious protective effects 14 d after ischemia and was also effective in the rat permanent middle cerebral artery occlusion model. The results suggest that poly(I:C) exerts therapeutic effects against cerebral I/R injury through the downregulation of TLR4 signaling via TLR3. Poly(I:C) is a promising new drug candidate for the treatment of cerebral infarcts.