Lack of skeletal muscle liver kinase B1 alters gene expression, mitochondrial content, inflammation and oxidative stress without affecting high-fat diet-induced obesity or insulin resistance

SIRT1/AMPK-mediated pathway: Ferulic acid from sugar beet pulp mitigating obesity-induced diabetes-linked complications and improving metabolic health

Obesity-induced type 2 diabetes (T2D) increases the risk of metabolic syndrome due to the high calorie intake. The role of sugar beet pulp (SBP) in T2D and the mechanism of its action remain unclear, though it is abundant in phenolics and has antioxidant activity. In this study, we isolated and purified ferulic acid from SBP, referred to as SBP-E, and studied the underlying molecular mechanisms in the regulation of glucose and lipid metabolism developing high glucose/high fat diet-induced diabetic models in vitro and in vivo. SBP-E showed no cytotoxicity and reduced the oxidative stress by increasing glutathione (GSH) in human liver (HepG2) and rat skeletal muscle (L6) cells. It also decreased body weight gain, food intake, fasting blood glucose levels (FBGL), glucose intolerance, hepatic steatosis, and lipid accumulation. Additionally, SBP-E decreased the oxidative stress and improved the antioxidant enzyme levels in high-fat diet (HFD)-induced T2D mice. Further, SBP-E reduced plasma and liver advanced glycation end products (AGEs), malondialdehyde (MDA), and pro-inflammatory cytokines, and increased anti-inflammatory cytokines in HFD-fed mice. Importantly, SBP-E significantly elevated AMPK, glucose transporter, SIRT1 activity, and Nrf2 expression and decreased ACC expression and SREBP1 levels in diabetic models. Collectively, our study results suggest that SBP-E treatment can improve obesity-induced T2D by regulating glucose and lipid metabolism via SIRT1/AMPK signalling and the AMPK/SREBP1/ACC1 pathway.

Heme oxygenase-1: A potential therapeutic target for improving skeletal muscle atrophy

Skeletal muscle atrophy is a common muscle disease that is directly caused by an imbalance in protein synthesis and degradation. At the histological level, it is mainly characterized by a reduction in muscle mass and fiber cross-sectional area (CSA). Patients with skeletal muscle atrophy present with reduced motor ability, easy fatigue, and poor life quality. Heme oxygenase-1 (HO-1) is an inducible enzyme that catalyzes the degradation of heme and has attracted much attention for its anti-oxidation effects. In addition, there is growing evidence that HO-1 plays an important role in anti-inflammatory, anti-apoptosis, pro-angiogenesis, and maintaining skeletal muscle homeostasis, making it a potential therapeutic target for improving skeletal muscle atrophy. Here, we review the pathogenesis of skeletal muscle atrophy, the biology of HO-1 and its regulation, and the biological function of HO-1 in skeletal muscle homeostasis, with a specific focus on the role of HO-1 in skeletal muscle atrophy, aiming to observe the therapeutic potential of HO-1 for skeletal muscle atrophy.

LKB1 alleviates high glucose‑ and high fat‑induced inflammation and the expression of GnRH and sexual precocity‑related genes, in mouse hypothalamic cells by activating the AMPK/FOXO1 signaling pathway

Precocious puberty (PP) is a developmental disorder. Hypothalamic cells can produce gonadotropin-releasing hormone (GnRH), the final output of neuroendocrine regulation that occurs during puberty. The aim of the present study was to investigate the role of live kinase B1 (LKB1), also known as serine/threonine kinase, in the progression of PP and identify the underlying mechanisms. First, the levels of LKB1 in peripheral blood and peripheral blood mononuclear cells of children with PP were detected by reverse transcription-quantitative (RT-q) PCR or western blotting. After the GT1-7 mouse hypothalamus cell line was treated with high glucose (HG) and high fat (HF), the expression of LKB1 and GnRH was tested. LKB1 was overexpressed by transfection with a pcDNA3.1 plasmid and the levels of inflammatory factors, GnRH, PP-related factors and proteins in the AMP-activated protein kinase (AMPK)/forkhead box protein O1 (FOXO1) pathway were determined using RT-qPCR or western blot analysis. Subsequently, Compound C, an inhibitor of AMPK/FOXO1 signaling, was used to clarify whether the effects of LKB1 on PP were mediated by the regulation of this pathway. Results indicated that children with PP exhibited a lower LKB1 expression. In addition, HG and HF culture resulted in an enhanced GnRH expression and a reduced LKB1 expression in GT1-7 cells. LKB1 overexpression inhibited the contents of TNF-α, IL-6 and GnRH in in GT1-7 cells exposed to HG and HF and reduced the expression of PP-related proteins, including estrogen receptor-β, cluster of differentiation 36 and G-protein-coupled receptor. In addition, the expression of phosphorylated (p)-AMPK and p-FOXO1 was markedly downregulated following LKBI overexpression. Furthermore, compound C intervention partially diminished the inhibitory effects of LKB1-mediated upregulation on the levels of inflammation and PP-related factors. In conclusion, these results demonstrated that LKB1 alleviated HG- and HF-induced inflammation, as well as the expression of GnRH and sexual precocity-related genes, in GT1-7 cells by activating the AMPK/FOXO1 signaling pathway.

Free fatty acid impairs myogenic differentiation through AMPKα-miR-206 pathway

The activity of AMPKα is reduced in type-2 diabetes, and type-2 diabetes is associated with muscular atrophy. To date, there is little known about the mechanism by which FFA participates in muscular impairment. The purpose of the present study was to explore whether FFA damages myogenesis through AMPKα-HDAC4-miR-206 pathway. The results showed that 1mM FFA produced lipid accumulation, significantly impaired insulin signaling pathway and decreased myogenic differentiation of C2C12 myoblast cells. FFA reduced LKB1-AMPKα pathway; activation of AMPKα rescued the myogenic impairment caused by FFA (P < 0.05). AMPKα promoted myogenesis by regulating the expression of miR-206 through HDAC4 (P < 0.05); AMPKα affected cell cycle and cell proliferation to promote myogenesis by regulating miR-206 and miR-206's target gene - cyclin D1. In addition, AICAR and HDAC4 siRNA promoted myogenic differentiation compared with FFA group; however, this positive effect was significantly down-regulated after transfection of miR-206 inhibitor. In summary, AMPKα plays positive roles in myogenic differentiation and myogenesis, and FFA decreased myogenic differentiation and myotubes formation through AMPKα-HDAC4-miR-206 pathway.

Anti-obesity potentiality of Tapra fish (Opisthopterus tardoore) oil

In this present investigation, we have extracted and characterized the Tapra fish oil as well as applied it to evaluate anti-obesity potentiality. The Tapra fish oil had 1.14 ± 0.10 mg KOH/g of acid value, 129.8 ± 5.09 mg KOH/g of saponification number, 2.67 ± 0.67 mEq/kg of peroxide value, 121.9 ± 2.14 mg of iodine value, and 17.67 ± 1.45 totox value. Gas Chromatography-Mass Spectrometric analysis clearly revealed the presence of nine different fatty acids. When the fish oil was applied to high-fat diet-induced obese mice, it showed significant reduction of body weight, Body Mass Index, and serum lipid profiles compared to the high-fat diet-induced obese mice. The levels of leptin and TNF-α were moderately reduced in fish oil treated high-fat diet-induced obese mice than control obese mice. In conclusion, the Tapra fish oil was enriched with essential fatty acids and it could be used as an antiobese food supplement. PRACTICAL APPLICATIONS: Considering the adverse effects of drugs used for the treatment of obesity, there is always a need to find out the alternatives. While the anti-obesity potentialities of different sea fish oil have been documented, the same for the Tapra fish (Opisthopterus tardoore) oil has not been studied at all. The extracted Tapra fish oil was found good in quality. Administration of fish oil in the mice exhibited anti-obesity effect in terms of lowering body weight, Body Mass Index, and serum lipid profiles, leptin, and TNF-α in mice model. These findings are fostering new therapeutic approaches to obesity treatment.