Integrated Remodeling of Gut-Liver Metabolism Induced by Moderate Protein Restriction Contributes to Improvement of Insulin Sensitivity

Total Sesquiterpenoids of Loquat Leaves Alleviated High-Fat Diet-Induced Obesity by Targeting Fecal Metabolic Profiling and Gut Microbiota Composition

In the present study, we demonstrated that whether the gut microbiota and related metabolites contribute to the therapeutic effect of total sesquiterpenoids (TSs) from loquat leaves on obesity. A 4-week high fat diet was used to induce obesity which was then treated with TSs for another 4 weeks. TSs remarkedly reduced the weight of body and white adipose and the levels of total cholesterol (TC) and triglyceride (TG) in serum. We also found that TSs restored the diversity and richness of gut microbiota. In addition, TSs administration affected the relative abundance of seven key genera. Meanwhile, TSs were determined to affect the metabolism of the host through detecting the metabolites in feces. By applying KEGG and the correlation analysis with gut microbiota, 10 differential metabolites were identified to be the key. The results in this work proved that TSs inhibited obesity by remodeling gut microbiota and related metabolites.

DPHC From Alpinia officinarum Ameliorates Oxidative Stress and Insulin Resistance via Activation of Nrf2/ARE Pathway in db/db Mice and High Glucose-Treated HepG2 Cells

(R)-5-hydroxy-1,7-diphenyl-3-heptanone (DPHC) from the natural plant Alpinia officinarum has been reported to have antioxidation and antidiabetic effects. In this study, the therapeutic effect and molecular mechanism of DPHC on type 2 diabetes mellitus (T2DM) were investigated based on the regulation of oxidative stress and insulin resistance (IR) in vivo and in vitro. In vivo, the fasting blood glucose (FBG) level of db/db mice was significantly reduced with improved glucose tolerance and insulin sensitivity after 8 weeks of treatment with DPHC. In vitro, DPHC ameliorated IR because of its increasing glucose consumption and glucose uptake of IR-HepG2 cells induced by high glucose. In addition, in vitro and in vivo experiments showed that DPHC could regulate the antioxidant enzyme levels including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px), thereby reducing the occurrence of oxidative stress and improving insulin resistance. Western blotting and polymerase chain reaction results showed that DPHC could promote the expressions of nuclear factor erythroid 2-related factor 2 (Nrf2), the heme oxygenase-1 (HO-1), protein kinase B (AKT), and glucose transporter type 4 (GLUT4), and reduced the phosphorylation levels of c-Jun N-terminal kinase (JNK) and insulin receptor substrate-1 (IRS-1) on Ser307 both in vivo and in vitro. These findings verified that DPHC has the potential to relieve oxidative stress and IR to cure T2DM by activating Nrf2/ARE signaling pathway in db/db mice and IR-HepG2 cells.

Fermented noni (Morinda citrifolia L.) fruit juice improved oxidative stress and insulin resistance under the synergistic effect of Nrf2/ARE pathway and gut flora in db/db mice and HepG2 cells

Oxidative stress interferes with blood glucose homeostasis, leading to insulin resistance (IR) and hyperglycemia, which eventually induces type 2 diabetes (T2DM). Fermented noni (Morinda citrifolia L.) fruit juice (FNJ) is...

Uterine Insulin Sensitivity Defects Induced Embryo Implantation Loss Associated with Mitochondrial Dysfunction-Triggered Oxidative Stress

Methods and Results

Herein, a comprehensive proteomic analysis was conducted on proliferative endometria from sows with low and normal reproductive performance (LRP and NRP, respectively). Enrichment analysis of differentially expressed proteins revealed alterations in endometrial remodeling, substance metabolism (mainly lipid, nitrogen, and retinol metabolism), immunological modulation, and insulin signaling in LRP sows. Importantly, aberrant lipid metabolite accumulation and dysregulation of insulin signaling were coincidently confirmed in endometria of LPR sows, proving an impaired insulin sensitivity. Furthermore, established high-fat diet- (HFD-) induced insulin-resistant mouse models revealed that uterine insulin resistance beginning before pregnancy deteriorated uterine receptivity and decreased implantation sites and fetal numbers. Mitochondrial biogenesis and fusion were decreased, and reactive oxygen species was overproduced in uteri from the HFD group during the implantation period. Ishikawa and JAR cells directly demonstrated that oxidative stress compromised implantation in vitro.

Conclusions

This study demonstrated that uterine insulin sensitivity impairment beginning before pregnancy resulted in implantation and fetal loss associated with oxidative stress induced by mitochondrial dysfunction.

Impacts of Selected Dietary Nutrient Intakes on Skeletal Muscle Insulin Sensitivity and Applications to Early Prevention of Type 2 Diabetes

As the largest tissue in the body, skeletal muscle not only plays key roles in movement and glucose uptake and utilization but also mediates insulin sensitivity in the body by myokines. Insulin resistance in the skeletal muscle is a major feature of type 2 diabetes (T2D). A weakened response to insulin could lead to muscle mass loss and dysfunction. Increasing evidence in skeletal muscle cells, rodents, nonhuman primates, and humans has shown that restriction of caloric or protein intake positively mediates insulin sensitivity. Restriction of essential or nonessential amino acids was reported to facilitate glucose utilization and regulate protein turnover in skeletal muscle under certain conditions. Furthermore, some minerals, such as zinc, chromium, vitamins, and some natural phytochemicals such as curcumin, resveratrol, berberine, astragalus polysaccharide, emodin, and genistein, have been shown recently to protect skeletal muscle cells, mice, or humans with or without diabetes from insulin resistance. In this review, we discuss the roles of nutritional interventions in the regulation of skeletal muscle insulin sensitivity. A comprehensive understanding of the nutritional regulation of insulin signaling would contribute to the development of tools and treatment programs for improving skeletal muscle health and for preventing T2D.

The role of liver metabolism in compensatory-growth piglets induced by protein restriction and subsequent protein realimentation

The aim of this work was to study the role of hepatic metabolism of compensatory growth in piglets induced by protein restriction and subsequent protein realimentation. Thirty-six weaned piglets were randomly distributed in a control group and a treatment group. The control group piglets were fed with a normal protein level diet (18.83% CP) for the entire experimental period (day 1-28). The treatment group piglets were fed with a protein-restriction diet (13.05% CP) for day 1 to day 14, and the diet was restored to normal protein level diet for day 15 to day 28. RNA-seq is used to analyze samples of liver metabolism on day 14 and day 28, respectively. Hepatic RNA-sequencing analysis revealed that some KEGG signaling pathways involved in glycolipid metabolism (eg, "AMPK signaling pathway," "insulin signaling pathway," and "glycolysis or gluconeogenesis") were significantly enriched on day 14 and day 28. On day 14, protein restriction promoted hepatic lipogenesis by increasing the genes expression level of ACACA, FASN, GAPM, and SREBP1C, decreasing protein phosphorylation levels of AMPKɑ and ACC in AMPK signaling pathway. In contrast, on day 28, protein realimentation promoted hepatic gluconeogenesis by increasing the concentration of G6Pase and PEPCK, decreasing protein phosphorylation levels of IRS1, Akt, and FoXO1 in insulin signaling pathway. In addition, protein realimentation activated the GH-IGF1 axis between the liver and skeletal muscle. Overall, these findings revealed the importance of liver metabolism in achieving compensatory growth.

Integrated Remodeling of Gut-Liver Metabolism Induced by Moderate Protein Restriction Contributes to Improvement of Insulin Sensitivity

SCOPE

Protein restriction (PR) is beneficial for relieving metabolic disorders and aging-related diseases. However, extreme PR could result in malnutrition due to severe deficiency of essential amino acids. Therefore, the effect of moderate PR on insulin sensitivity is investigated.

METHODS AND RESULTS

The growing and adult pigs are subjected to moderate PR by 15-30%. Plasma insulin concentration and insulin resistance index HOMA-IR are significantly decreased upon moderate PR. Furthermore, IRS1/PI3K/AKT pathway in the basal state is enhanced in both liver and skeletal muscle. The adapted metabolism in the liver upon moderate PR is in support of improving insulin sensitivity. The liver shares a coordinated metabolic adaption in terms of energy metabolism and amino acid metabolism with the small intestine. Particularly, alteration of the metabolic footprint appeared in the portal venous blood, representing metabolites to be absorbed into liver after intestinal metabolism, is also in favor of improvement of insulin sensitivity.

CONCLUSION

In summary, the study proves that moderate PR could improve insulin sensitivity from childhood to adulthood in a pig model, and sheds a new light on the role of integrated remodeling of gut and liver metabolism in the improved insulin sensitivity induced by moderate PR.