Calorie restriction (CR) extends lifespan and elicits numerous effects beneficial to health and metabolism in various model organisms, but the underlying mechanisms are not completely understood. Gut microbiota has been reported to be associated with the beneficial effects of CR; however, it is unknown whether these effects of CR are causally mediated by gut microbiota. In this study, we employed an antibiotic-induced microbiota-depleted mouse model to investigate the functional role of gut microbiota in CR. Depletion of gut microbiota rendered mice resistant to CR-induced loss of body weight, accompanied by the increase in fat mass, the reduction in lean mass and the decline in metabolic rate. Depletion of gut microbiota led to increases in fasting blood glucose and cholesterol levels independent of CR. A few metabolism-modulating hormones including leptin and insulin were altered by CR and/or gut microbiota depletion. In addition, CR altered the composition of gut microbiota with significant increases in major probiotic genera such as Lactobacillus and Bifidobacterium, together with the decrease of Helicobacter. In addition, we performed fecal microbiota transplantation in mice fed with high-fat diet. Mice with transferred microbiota from calorie-restricted mice resisted high fat diet-induced obesity and exhibited metabolic improvement such as alleviated hepatic lipid accumulation. Collectively, these data indicate that CR-induced metabolic improvement especially in body weight reduction is mediated by intestinal microbiota to a certain extent.

Cartilage dyshomeostasis contributes to osteoarthritis (OA) pathogenesis, and tumor necrosis factor (TNF)-α has critical role in this process by driving inflammatory cascades and cartilage degradation. However, the negative regulation of TNF-α-mediated signaling remains undefined. Here we demonstrate the crucial role of miR-145 in the modulation of TNF-α-mediated signaling and cartilage matrix degradation. MicroRNA (miRNA) expression profiles of TNF-α-stimulated chondrocytes showed that miR-145 expression was rapidly downregulated by TNF-α. Moreover, miR-145 was directly repressed by p65 and was negatively correlated with TNF-α secretion during OA progression. Further, we found that miR-145 directly targeted mitogen-activated protein kinase kinase 4 (MKK4) and broadly restrained the production of several TNF-α-triggered matrix-degrading enzymes (MMP-3, MMP-13, and Adamts-5). Mechanistic studies unveiled that miR-145 negatively regulated TNF-α-mediated JNK and p38 activation, as well as the nuclear accumulation of p-c-Jun and p-ATF2, by inhibiting MKK4 phosphorylation, eventually resulting in the alteration of catabolic genes transcription. Indeed, p-ATF2 interacted with the promoter of Mmp-13, whereas p-c-Jun bound to promoters of Mmp-3 and Adamts-5. MKK4 was significantly elevated in OA cartilage. Eliminating MKK4 by short hairpin RNA resulted in obviously decreased matrix-degrading enzymes production, JNK and p38 inactivation, and an inhibition of cartilage degradation. On the contrary, MKK4 overexpression enhanced TNF-α-mediated signaling activation and transcription of downstream catabolic genes, and consequently worsened cartilage degradation. Moreover, intra-articular (IA) injection of miR-145 agonist to rat with surgery-induced OA alleviated cartilage destruction. Altogether, we elucidate a novel regulatory mechanism underlying TNF-α-triggered cartilage degradation and demonstrate the potential utility of miR-145 and MKK4 as therapy targets for OA.

Fasting and especially intermittent fasting have been shown to be an effective intervention in many diseases, such as obesity and diabetes. The fasting-mimicking diet (FMD) has recently been found to ameliorate metabolic disorders. To investigate the effect of a new type of low-protein low-carbohydrate FMD on diabetes, we tested an FMD in db/db mice, a genetic model of type 2 diabetes. The diet was administered every other week for a total of 8 weeks. The intermittent FMD normalized blood glucose levels in db/db mice, with significant improvements in insulin sensitivity and β cell function. The FMD also reduced hepatic steatosis in the mice. Deterioration of pancreatic islets and the loss of β cells in the diabetic mice were prevented by the FMD. The expression of β cell progenitor marker Ngn3 was increased by the FMD. In addition, the FMD led to the reconstruction of gut microbiota. Intermittent application of the FMD increased the genera of Parabacteroides and Blautia while reducing Prevotellaceae, Alistipes and Ruminococcaceae. The changes in these bacteria were also correlated with the fasting blood glucose levels of the mice. Furthermore, intermittent FMD was able to reduce fasting blood glucose level and increase β cells in STZ-induced type 1 diabetic mouse model. In conclusion, our study provides evidence that the intermittent application of an FMD is able to effectively intervene in the progression of diabetes in mice.Electronic supplementary materialThe online version of this article (10.1186/s12986-018-0318-3) contains supplementary material, which is available to authorized users.

Osteoarthritis (OA), characterized by insufficient extracellular matrix synthesis and cartilage degeneration, is known as an incurable disease because its pathogenesis is poorly elucidated. Thus far, limited information is available regarding the pathophysiological role of microRNAs (miRNAs) in OA. In this study, we investigated the specific function of miR-146a in OA pathophysiology using mouse OA models. We found that the articular cartilage degeneration of miR-146a knockout (KO) mice was alleviated compared with that of the wild-type (WT) mice in spontaneous and instability-induced OA models. We demonstrate that miR-146a aggravated pro-inflammatory cytokines induced suppressing the expression of cartilage matrix-associated genes. We further identified calcium/calmodulin-dependent protein kinase II delta (Camk2d) and protein phosphatase 3, regulatory subunit B, beta isoform (Ppp3r2, also known as calcineurin B, type II) were essential targets of miR-146a in regulating cartilage homeostasis. Moreover, we found that surgical-induced OA mice treated with a miR-146a inhibitor significantly alleviated the destruction of articular cartilage via targeting Camk2d and Ppp3r2. These results suggested that miR-146a has a crucial role in maintaining cartilage homeostasis. MiR-146a inhibition in chondrocytes can be a potential therapeutic strategy to ameliorate OA.

Pegmatites commonly form in the waning stage of magma evolution by fractional crystallization of volatile-rich magmas and may be important host rocks of strategic metals (e.g., Li, Be, Cs, Ta, and Nb) and high-quality gem minerals. This study reports new zircon U-Pb dating results and Hf isotopic compositions of the KLA803 pegmatite, the AZB-01 pegmatite, the JMK-09 pegmatite (abbreviated as the K-A-J pegmatites) and the Halong granite from the Chinese Altay to determine the potential petrogenetic relationships between them. The geochronological data document that the K-A-J pegmatites were emplaced at 224.6 ± 2.3 Ma, 191.6 ± 2.0 Ma and 192.0 ± 2.3 Ma, respectively, and they are characterized by negative to low positive εHf(t) values (from-1.0 to +6.3) and old model ages (T DM) (with the T DM1 from 874 to 597 Ma and T DM2 from 1,298 to 833 Ma). In contrast, the Halong granite has an emplacement age of 398.3 ± 2.4 Ma and is characterized by higher positive εHf(t) values (from +9.9 to +15.2) and younger model ages (T DM) (with the T DM1 from 626 to 414 Ma and T DM2 from 760 to 423 Ma). They all have intruded into the Kulumuti group stratum, which has negative initial εNd(t) values (from-4.3 to-0.2) and old T DM model ages (between 1.22 and 1.56 Ga). Based on the calculated results of the mixing ratios (f) of the initial magmas and the prevailing Paleozoic tectonic framework of the Chinese Altay, we establish two petrogenetic models for the K-A-J pegmatites: Model 1 refers to that these pegmatites originated from a mixed magma that was composed of 72 wt.% to 91 wt.% depleted mantle components and 9 wt.% to 28 wt.% lower crust components; and Model 2 refers to that they were derived from the partial melting of 38 wt.% to 83 wt.% Halong granite and 17 wt.% to 62 wt.% sedimentary rocks from the Kulumuti group. We also suggest that the initial magma of the Halong granite was significantly contributed by juvenile materials with a slight involvement of crustal materials. In Model 1, because LCT-type pegmatites (classified as Li-Cs-Ta enriched pegmatites associated with S-type granite that was produced by the partial melting of preexisting sedimentary rocks) have close geochemical affinities with crustal materials, the excessively high weight percentages (72 wt.% to 91 wt.%) of the depleted mantle components in the initial magma of the K-A-J pegmatites indicate that this model is unrealistic. Therefore, we consider that Model 2 is more reasonable at present for interpreting the petrogenesis of the K-A-J pegmatites, and it needs to be verified in other pegmatite fields of the Chinese Altay.

Transforming growth factor‐β1 (TGF‐β1) is a key factor in bone reconstruction. However, its pathophysiological role in non‐union and bone repair remains unclear. Here we demonstrated that TGF‐β1 was highly expressed in both C57BL/6 mice where new bone formation was impaired after autologous bone marrow mesenchymal stem cell (BMMSC) implantation in non‐union patients. High doses of TGF‐β1 inhibited BMMSC osteogenesis and attenuated bone regeneration in vivo. Furthermore, different TGF‐β1 levels exhibited opposite effects on osteogenic differentiation and bone healing. Mechanistically, low TGF‐β1 doses activated smad3, promoted their binding to bone morphogenetic protein 2 (Bmp2) promoter, and upregulated Bmp2 expression in BMMSCs. By contrast, Bmp2 transcription was inhibited by changing smad3 binding sites on its promoter at high TGF‐β1 levels. In addition, high TGF‐β1 doses increased tomoregulin‐1 (Tmeff1) levels, resulting in the repression of Bmp2 and bone formation in mice. Treatment with the TGF‐β1 inhibitor SB431542 significantly rescued BMMSC osteogenesis and accelerated bone regeneration. Our study suggests that high‐dose TGF‐β1 dampens BMMSC‐mediated bone regeneration by activating canonical TGF‐β/smad3 signaling and inhibiting Bmp2 via direct and indirect mechanisms. These data collectively show a previously unrecognized mechanism of TGF‐β1 in bone repair, and TGF‐β1 is an effective therapeutic target for treating bone regeneration disability. © 2019 American Society for Bone and Mineral Research.

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MicroRNAs play important roles in osteoporosis and show great potential for diagnosis and therapy of osteoporosis. Previous studies have demonstrated that miR‐146a affects osteoblast (OB) and osteoclast (OC) formation. However, these findings have yet to be identified in vivo, and it is unclear whether miR‐146a is related to postmenopausal osteoporosis. Here, we demonstrated that miR‐146a knockout protects bone loss in mouse model of estrogen‐deficient osteoporosis, and miR‐146a inhibits OB and OC activities in vitro and in vivo. MiR‐146a−/− mice displayed the same bone mass as the wild type (WT) but exhibited a stronger bone turnover than the WT did under normal conditions. Nevertheless, miR‐146a−/− mice showed an increase in bone mass after undergoing ovariectomy (OVX) compared with those subjected to sham operation. OC activities were impaired in the miR‐146a−/− mice exposed to estrogen deficiency, which was diametrically opposite to the enhanced bone resorption ability of WT. Macrophage colony‐stimulating factor (M‐CSF) and receptor activator of NF‐κB ligand (RANKL)/osteoprotegerin (OPG) from a bone microenvironment affect this extraordinary phenomenon. Therefore, our results implicate that miR‐146a plays a key role in estrogen deficiency–induced osteoporosis, and the inhibition of this molecule provides skeleton protection. © 2019 American Society for Bone and Mineral Research.