A new insulin-sensitive enhancer from Silene viscidula, WPTS, treats type 2 diabetes by ameliorating insulin resistance, reducing dyslipidemia, and promoting proliferation of islet β cells

Phlorizin from Lithocarpus litseifolius [Hance] Chun ameliorates FFA-induced insulin resistance by regulating AMPK/PI3K/AKT signaling pathway

BACKGROUND

Insulin resistance (IR) is the central pathophysiological feature in the pathogenesis of metabolic syndrome, obesity, type 2 diabetes mellitus (T2DM), hypertension, and dyslipidemia. As the main active ingredient in Lithocarpus litseifolius [Hance] Chun, previous studies have shown that phlorizin (PHZ) can reduce insulin resistance in the liver. However, the effect of phlorizin on attenuating hepatic insulin resistance has not been fully investigated, and whether this effect is related to AMPK remains unclear.

PURPOSE

The present study aimed to further investigate the effect of phlorizin on attenuating insulin resistance and the potential action mechanism.

METHODS

Free fatty acids (FFA) were used to induce insulin resistance in HepG2 cells. The effects of phlorizin and FFA on cell viability were detected by MTT analysis. Glucose consumption, glycogen synthesis, intracellular malondialdehyde (MDA), superoxide dismutase (SOD), total cholesterol (TC), and triglyceride (TG) contents were quantified after phlorizin treatment. Glucose uptake and reactive oxygen species (ROS) levels in HepG2 cells were assayed by flow cytometry. Potential targets and signaling pathways for attenuating insulin resistance by phlorizin were predicted by network pharmacological analysis. Moreover, the expression levels of proteins related to the AMPK/PI3K/AKT signaling pathway were detected by western blot.

RESULTS

Insulin resistance was successfully induced in HepG2 cells by co-treatment of 1 mM sodium oleate (OA) and 0.5 mM sodium palmitate (PA) for 24 h. Treatment with phlorizin promoted glucose consumption, glucose uptake, and glycogen synthesis and inhibited gluconeogenesis in IR-HepG2 cells. In addition, phlorizin inhibited oxidative stress and lipid accumulation in IR-HepG2 cells. Network pharmacological analysis showed that AKT1 was the active target of phlorizin, and the PI3K/AKT signaling pathway may be the potential action mechanism of phlorizin. Furthermore, western blot results showed that phlorizin ameliorated FFA-induced insulin resistance by activating the AMPK/PI3K/AKT signaling pathway.

CONCLUSION

Phlorizin inhibited oxidative stress and lipid accumulation in IR-HepG2 cells and ameliorated hepatic insulin resistance by activating the AMPK/PI3K/AKT signaling pathway. Our study proved that phlorizin played a role in alleviating hepatic insulin resistance by activating AMPK, which provided experimental evidence for the use of phlorizin as a potential drug to improve insulin resistance.

Developments in the study of Chinese herbal medicine's assessment index and action mechanism for diabetes mellitus

In traditional Chinese medicine (TCM), based on various pathogenic symptoms and the 'golden chamber' medical text, Huangdi Neijing, diabetes mellitus falls under the category 'collateral disease'. TCM, with its wealth of experience, has been treating diabetes for over two millennia. Different antidiabetic Chinese herbal medicines reduce blood sugar, with their effective ingredients exerting unique advantages. As well as a glucose lowering effect, TCM also regulates bodily functions to prevent diabetes associated complications, with reduced side effects compared to western synthetic drugs. Chinese herbal medicine is usually composed of polysaccharides, saponins, alkaloids, flavonoids, and terpenoids. These active ingredients reduce blood sugar via various mechanism of actions that include boosting endogenous insulin secretion, enhancing insulin sensitivity and adjusting key enzyme activity and scavenging free radicals. These actions regulate glycolipid metabolism in the body, eventually achieving the goal of normalizing blood glucose. Using different animal models, a number of molecular markers are available for the detection of diabetes induction and the molecular pathology of the disease is becoming clearer. Nonetheless, there is a dearth of scientific data about the pharmacology, dose-effect relationship, and structure-activity relationship of TCM and its constituents. Further research into the efficacy, toxicity and mode of action of TCM, using different metabolic and molecular markers, is key to developing novel TCM antidiabetic formulations.

Carboxymethyl chitosan and octadecylamine-coated liposome-containing WPTS: design, optimization, and evaluation

Liposomes (LPs) are a delivery system for stabilizing pharmaceuticals with limited use due to their propensity to congregate and fuse. A proposed method of addressing these problems is polymer coating. In this study, the potential of octadecylamine (ODA)-coated liposomes and carboxymethyl chitosan (CMCS/ODA-LPs) for enhancing Wacao pentacyclic triterpene saponin (WPTS) transport capacity was investigated. CMCS/ODA-LPs were produced by electrostatic adsorption and thin-film hydration. Response surface methodology (RSM) was employed to enhance the process and encapsulation efficiency (EE) for optimum drug encapsulation efficiency. The synthesized WPTS-CMCS/ODA-LPs were uniformly dispersed in a circular shape, and during 14 days of storage at 4 °C, the particle size and morphology did not significantly change. Vesicle size, zeta potential, polydispersity index (PDI), and entrapment efficiency (%) were 179.1 ± 7.31 nm, -29.6 ± 1.35 mV, 0.188 ± 0.052, and 75.62 ± 0.43, respectively. The hemolysis test revealed that WPTS-CMCS/ODA-LPs were sufficiently biocompatible. Compared to WPTS-LPs, WPTS-CMCS/ODA-LPs consistently showed a much more significant cytotoxic effect on cancer cells. Early and WPTS-CMCS/ODA-LPs-induced apoptosis resulted in almost seven times more cell death than the control. Compared to physiological pH 7.3, the pH-sensitive CMCS coupled LPs increased drug release at acidic pH 6.5. These findings suggest the efficacy of pH-sensitive CMCS/ODA-LPs as a medication delivery method for WPTS.

Two novel cases of biallelic SMPD4 variants with brain structural abnormalities

Sphingomyelin phosphodiesterase 4 (SMPD4) encodes a member of the Mg2+-dependent, neutral sphingomyelinase family that catalyzes the hydrolysis of the phosphodiester bond of sphingomyelin to form phosphorylcholine and ceramide. Recent studies have revealed that biallelic loss-of-function variants of SMPD4 cause syndromic neurodevelopmental disorders characterized by microcephaly, congenital arthrogryposis, and structural brain anomalies. In this study, three novel loss-of-function SMPD4 variants were identified using exome sequencing (ES) in two independent patients with developmental delays, microcephaly, seizures, and brain structural abnormalities. Patient 1 had a homozygous c.740_741del, p.(Val247Glufs*21) variant and showed profound intellectual disability, hepatomegaly, a simplified gyral pattern, and a thin corpus callosum without congenital dysmorphic features. Patient 2 had a compound heterozygous nonsense c.2124_2125del, p.(Phe709*) variant and splice site c.1188+2dup variant. RNA analysis revealed that the c.1188+2dup variant caused exon 13 skipping, leading to a frameshift (p.Ala406Ser*6). In vitro transcription analysis using minigene system suggested that mRNA transcribed from mutant allele may be degraded by nonsense-mediated mRNA decay system. He exhibited diverse manifestations, including growth defects, muscle hypotonia, respiratory distress, arthrogryposis, insulin-dependent diabetes mellitus, sensorineural hearing loss, facial dysmorphism, and various brain abnormalities, including cerebral atrophy, hypomyelination, and cerebellar hypoplasia. Here, we review previous literatures and discuss the phenotypic diversity of SMPD4-related disorders.

Effects of two triterpenoids from Nigella sativa seeds on insulin resistance of 3T3-L1 adipocytes

Insulin resistance (IR) is a physiological abnormality that occurs when insulin fails to activate the signal transduction pathway in target organs. It was found that supplementation of Nigella sativa seeds with oral antidiabetic medicines helps improve blood glucose control by enhanced β cells activity and alleviation of IR. However, the activities and related mechanisms of phytochemicals from N. sativa seeds have not been thoroughly explored. In this study, the effects of two triterpenoids, 3-O-[β-D-xylopyranose-(1→3)-α-L-rhamnose-(1→2)-α-L-arabinose]-28-O-[α-L-rhamnose-(1→4)-β-D-glucopyranose-L-(1→6)-β-D-glucopyranose]-hederagenin (Hxrarg) and 3-O-[β-D-xylopyranose-(1→3)-α-L-rhamnose-(1→2)-α-L-arabinose]-hederagenin (Hxra), on IR were studied by 3T3-L1 adipocytes model. The results demonstrated that Hxrarg and Hxra inhibited maturation of 3T3-L1 preadipocytes, dramatically stimulated glucose uptake of IR-3T3-L1 adipocytes, promoted transcription of IRS, AKT, PI-3K, and GLUT4 mRNA. Western Blot results suggested that Hxrarg and Hxra were able to markedly up-regulate expression of p-IRS, p-AKT, PI-3K, and GLUT4 proteins. These findings could provide a basic foundation for the continued development and application of N. sativa in medicine and functional foods.

Baicalin Alleviates Oxidative Stress and Inflammation in Diabetic Nephropathy via Nrf2 and MAPK Signaling Pathway

Background

Oxidative stress and inflammation play essential roles in the development and progression of diabetic nephropathy (DN). Baicalin (BAI), a natural flavonoid, has been showed to have a renoprotective effect in various renal diseases. However, its underlying mechanisms in DN remain unclear. In this study, we explored the potential effects and underlying mechanisms of BAI on DN using a spontaneous DN model.

Methods

The protective effects of BAI on DN have been evaluated by detecting DN-related biochemical indicators, kidney histopathology and cell apoptosis. After that, we examined the level of renal oxidative stress and inflammation to explain BAI’s renoprotective effects. Then, Nrf2 pathway was tested to clarify its antioxidant activity, and kidney transcriptomics was conducted to elucidate its anti-inflammatory activity. Finally, Western blot was applied for final mechanism verification.

Results

Our results found that BAI effectively ameliorated diabetic conditions, proteinuria, renal histopathological changes and cell apoptosis in DN. BAI significantly improved the kidney levels of glutathione peroxidase (GSH-PX), superoxide dismutase (SOD) and catalase (CAT), and reduced malondialdehyde (MDA) level. Meanwhile, the infiltration of inflammatory cells including T-lymphocytes, T-helper cells, neutrophils and macrophages, and the mRNA levels of pro-inflammatory cytokines (IL-1β, IL-6, MCP-1 and TNFα) were also obviously inhibited by BAI. Afterward, Western blot found that BAI significantly activated Nrf2 signaling and increased the expression of downstream antioxidant enzymes (HO-1, NQO-1). Kidney transcriptomics revealed that the inhibition of MAPK signaling pathway may contribute to BAI’s anti-inflammatory activity, which has also been verified in later experiment. BAI treatment did obviously inhibit the activation of canonical pro-inflammatory signaling pathway MAPK family, such as Erk1/2, JNK and P38.

Conclusion

In summary, our data demonstrated that BAI can treat DN by alleviating oxidative stress and inflammation, and its underlying mechanisms were associated with the activation of Nrf2-mediated antioxidant signaling pathway and the inhibition of MAPK-mediated inflammatory signaling pathway.