Src homology 3 domain binding kinase 1 protects against hepatic steatosis and insulin resistance through the Nur77-FGF21 pathway.

BACKGROUND AND AIMS: Metabolism in the liver is dysregulated in obesity, contributing to various health problems including steatosis and insulin resistance. While the pathogenesis of lipid accumulation has been extensively studied, the protective mechanism against lipid challenge in the liver remains unclear. Here, we report that Src homology 3 domain binding kinase 1 (SBK1) is a regulator of hepatic lipid metabolism and systemic insulin sensitivity in response to obesity. APPROACH AND RESULTS: Enhanced Sbk1 expression was found in the liver of high-fat diet (HFD)-induced obese mice and fatty acid (FA)-challenged hepatocytes. SBK1 knockdown in mouse liver cells augmented FA uptake and lipid accumulation. Similarly, liver-specific SBK1 knockout ( Lsko ) mice displayed more severe hepatosteatosis and higher expression of genes in FA uptake and lipogenesis than the Flox/Flox ( Fl/Fl ) control mice when fed the HFD. The HFD-fed Lsko mice also showed symptoms of hyperglycemia, poor systemic glucose tolerance, and lower insulin sensitivity than the Fl/Fl mice. On the other hand, hepatic Sbk1 overexpression alleviated the high-fructose diet-induced hepatosteatosis, hyperlipidemia, and hyperglycemia in mice. White adipose tissue browning was also observed in hepatic SBK1 -overexpressed mice. Moreover, we found that SBK1 was a positive regulator of FGF21 in the liver during energy surplus conditions. Mechanistically, SBK1 phosphorylates the orphan nuclear receptor 4A1 (Nur77) on serine 344 to promote hepatic FGF21 expression and inhibit the transcription of genes involved in lipid anabolism. CONCLUSIONS: Collectively, our data suggest that SBK1 is a regulator of the metabolic adaption against obesity through the Nur77-FGF21 pathway.

Differential regulation of hepatic SH3 domain binding kinase 1 (SBK1) expression in mouse and goldfish.

SH3 domain binding kinase 1 (SBK1) is a serine/threonine kinase that belongs to the new kinase family (NFK) with limited information on its function. Previous studies reported that SBK1 plays a role in memory formation, lipid metabolism, and cancer cell progression. Nevertheless, the regulatory mechanism of Sbk1 expression in various tissues remains unknown. We report here that Sbk1 expression in mouse hepatocytes was downregulated by glucocorticoid, whereas saturated and unsaturated fatty acids were stimulators of Sbk1 expression. The regulatory role of glucocorticoid and fatty acid was further confirmed by the Sbk1 promoter assay, which aligned with the presence of several glucocorticoid-response elements (GRE) and peroxisome proliferator responsive elements (PPRE) in the mouse Sbk1 promoter. The inhibitory effect of glucocorticoids on hepatic Sbk1 expression and protein content could also be demonstrated in vivo after prednisolone injection. Moreover, the expression of SBK1 in goldfish (gfSBK1) was also sensitive to glucocorticoid suppression as their mouse orthologues. In contrast, insulin had a differential action on SBK1 expression that it promoted the expression of all SBK1 isoforms in the goldfish hepatocytes but inhibited Sbk1 expression in the mouse hepatocytes. Together, our findings indicate that SBK1 expression is hormone- and nutrient-sensitive with a species-specific response.

Exercise-induced BDNF promotes PPARδ-dependent reprogramming of lipid metabolism in skeletal muscle during exercise recovery.

Post-exercise recovery is essential to resolve metabolic perturbations and promote long-term cellular remodeling in response to exercise. Here, we report that muscle-generated brain-derived neurotrophic factor (BDNF) elicits post-exercise recovery and metabolic reprogramming in skeletal muscle. BDNF increased the post-exercise expression of the gene encoding PPARδ (peroxisome proliferator-activated receptor δ), a transcription factor that is a master regulator of lipid metabolism. After exercise, mice with muscle-specific Bdnf knockout (MBKO) exhibited impairments in PPARδ-regulated metabolic gene expression, decreased intramuscular lipid content, reduced ß-oxidation, and dysregulated mitochondrial dynamics. Moreover, MBKO mice required a longer period to recover from a bout of exercise and did not show increases in exercise-induced endurance capacity. Feeding naïve mice with the bioavailable BDNF mimetic 7,8-dihydroxyflavone resulted in effects that mimicked exercise-induced adaptations, including improved exercise capacity. Together, our findings reveal that BDNF is an essential myokine for exercise-induced metabolic recovery and remodeling in skeletal muscle.

Ultrasound-assisted thawing of mango pulp: Effect on thawing rate, sensory, and nutritional properties.

Sensory and nutritional properties of mango pulp thawed by different ultrasound intensities and temperatures were studied. Compared to water immersion thawing, a thawing time reduction of 16-64% (p < 0.05) and more phenolic acids contents (gallic, hydroxybenzoic, and caffeic acid) were observed after ultrasonic thawing. The sensory evaluation revealed texture and aroma deterioration at higher ultrasonic intensities (4 °C:0.074 W/mL; 25 °C:0.123 W/mL) due to increase in viscosity and some volatile compounds in the mango pulp. Ultrasonic thawing treatment at 25 °C reduced thawing time by 51-73% compared to that at 4 °C. Mango pulp processed at 25 °C exhibited better sensory quality and retained 26.5-58.5% more total phenol and 8.7-11.0% more total carotenoid contents. In short, higher ultrasonic intensities (0.074-0.123 W/mL) at a temperature of 25 °C contributed to better thawing efficiency and nutritional quality. The results demonstrated that ultrasound processing at optimized conditions could serve as a potential alternative to conventional thawing processing of mango pulp.

Apios americana Medik flowers extract protects PC12 cells against H2O2 induced neurotoxicity via regulating autophagy.

Since flavonoids are antioxidant compounds, they could beneficially affect neurodegenerative diseases where reactive oxygen species are involved. In this study, we firstly isolated and identified fourteen compounds from the flowers of Apios americana Medik. Then, we tested whether Apios americana Medik flowers water extract (AFWE) exerts a protective effect on H2O2 induced PC12 cells injure. As expected, pretreatment with AFWE inhibited cytotoxicity and DNA condensation in H2O2induced PC12 cells. Exposure of PC12 cells to H2O2 resulted in reactive oxygen species accumulation and mitochondrial dysfunction, while AFWE alleviated these damages. AFWE obviously reversed the alternations as H2O2 increased Caspase-3 and decreased the ratio of Bcl-2/Bax expressions. Furthermore, autophagy in PC12 cells was further activated by AFWE, which was beneficial to resisting adversity. These results manifest that AFWE prevents H2O2 induced damage via regulating autophagy.