Role of melatonin receptor 1B gene polymorphism and its effect on the regulation of glucose transport in gestational diabetes mellitus / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Melatonin receptor 1B (MT2, encoded by the MTNR1B gene), a high-affinity receptor for melatonin, is associated with glucose homeostasis including glucose uptake and transport. The rs10830963 variant in the MTNR1B gene is linked to glucose metabolism disorders including gestational diabetes mellitus (GDM); however, the relationship between MT2-mediated melatonin signaling and a high birth weight of GDM infants from maternal glucose abnormality remains poorly understood. This article aims to investigate the relationship between rs10830963 variants and GDM development, as well as the effects of MT2 receptor on glucose uptake and transport in trophoblasts. TaqMan-MGB (minor groove binder) probe quantitative real-time polymerase chain reaction (qPCR) assays were used for rs10930963 genotyping. MT2 expression in the placenta of GDM and normal pregnant women was detected by immunofluorescence, western blot, and qPCR. The relationship between MT2 and glucose transporters (GLUTs) or peroxisome proliferator-activated receptor γ (PPARγ) was established by western blot, and glucose consumption of trophoblasts was measured by a glucose assay kit. The results showed that the genotype and allele frequencies of rs10830963 were significantly different between GDM and normal pregnant women (P<0.05). The fasting, 1-h and 2-h plasma glucose levels of G-allele carriers were significantly higher than those of C-allele carriers (P<0.05). Besides, the protein and messenger RNA (mRNA) expression of MT2 in the placenta of GDM was significantly higher than that of normal pregnant women (P<0.05). Melatonin could stimulate glucose uptake and GLUT4 and PPARγ protein expression in trophoblasts, which could be attenuated by MT2 receptor knockdown. In conclusion, the rs10830963 variant was associated with an increased risk of GDM. The MT2 receptor is essential for melatonin to raise glucose uptake and transport, which may be mediated by PPARγ.

Differentiated hypoglycemic effects of baicalin, berberine and puerarin on insulin-resistance HepG2 cells / 中国中药杂志

To investigate the hypoglycemic effects of baicalin, berberine, puerarin and liquiritin on the insulin resistance (IR) cells. The IR model of HepG2 cells was established by treatment with insulin and dexamethasone for 48 h. Glucose uptake, glycogen content and cell viability were detected with different concentrations of baicalin, berberine, puerarin, liquiritin in IR-HepG2 cells. Compared with IR model group, all of intervened groups significantly increased the glucose consumption, except for liquiritin groups and 1 μmol·L⁻¹ baicalin group. Moreover, 10, 20, 50 μmol·L⁻¹ baicalin, 5, 10, 20, 50 μmol·L⁻¹ berberine and 40, 80, 160 μmol·L⁻¹ puerarin significantly elevated glycogen content in IR-HepG2 cells. Liquiritin did not show obvious hypoglycemic effect. Compared with normal group, the mRNA expression levels of GLUT1 and GLUT4 were decreased in IR-HepG2 cells according to qPCR results. 5, 20 μmol·L⁻¹ berberine decreased the mRNA expression level of GLUT1 in IR-HepG2 cells, whereas 20, 40, 80 μmol·L⁻¹ puerarin significantly elevated the mRNA expression level of GLUT1. Moreover, 10, 20, 50 μmol·L⁻¹ baicalin and 20 μmol·L⁻¹ berberine increased the mRNA expression level of GLUT4. Whereas, 40, 80 μmol·L⁻¹ puerarin decreased the mRNA expression level of GLUT4. Western blot results suggested that 10, 20, 50 μmol·L⁻¹ baicalin significantly increased the protein expressions of GLUT2 and GLUT4, whereas 20, 40, 80 μmol·L⁻¹ puerarin significantly up-regulated GLUT1 and GLUT2 proteins. In addition, 20 μmol·L⁻¹ berberine increased the protein expressions of GLUT2 and GLUT4, whereas 10 μmol·L⁻¹ berberine up-regulated GLUT4 expression. The results preliminarily suggested that baicalin, berberine and puerarin have differentiated hypoglycemic effects, which accelerate glucose transport, increase glycogen synthesis, regulate glucose metabolism and improve hepatic IR.

Jatrorrhizine regulates GLUTs with multiple manners for hypoglycemic effect in insulin-resistance 3T3-L1 adipocytes / 中国中药杂志

This paper aimed to investigate the hypoglycemic effect and relative mechanism of jatrorrhizine in insulin-resistance (IR)-3T3-L1 adipocytes. The 3T3-L1 preadipocytes were used to induce mature adipocytes, then the stable IR model was established with 1 μmol·L⁻¹ dexamethasone. The adipocytes were divided into normal group, IR model group, rosiglitazone positive group and jatrorrhizine group (0.5, 1, 5, 10, 20 μmol·L⁻¹). After different time points (12, 24, 30, 36, 48 h) treatment, glucose content of 3T3-L1 adipocytes was detected by the glucose oxidase peroxidase method and TG content was measured by glycerol phosphate oxidase method, whereas cell viability was detected by CCK-8 assay. Furthermore, the protein expression levels of insulin receptor substrate 2 (IRS2), phosphinositide-3-kinase regulatory subunit 1(PI3KR1), phosphorylated protein B [p-AKT (Ser473)], phosph-AMP-activated protein [p-AMPK (Thr172)], and glucose transporter type 4/1/2 (GLUT4/1/2) were detected by Western blot assay. The results showed that as compared with the normal group, the glucose consumptionwas significantly decreased in IR model group(<0.01); whereas 0.5, 1, 5, 10, 20 μmol·L⁻¹ jatrorrhizine and rosiglitazone group elevated IR-3T3-L1 cells glucose consumption (<0.01) at 36 h and 48 h administration as compared with IR group. The optimal administration time was 48 h for jatrorrhizine. 1, 5, 10, 20 μmol·L⁻¹ of jatrorrhizine decreased the TG content in 3T3-L1 adipocytes for 48 h administration (<0.05). The protein expression levels of IRS2, PI3KR1, p-AKT (Ser473), p-AMPK (Thr172), GLUT4/1/2 were significantly up-regulated by different concentrations of jatrorrhizine and rosiglitazone (<0.01). The results showed that jatrorrhizine increased glucose uptake with elevated glucose consumption, whereas reduced intracellular TG content in IR-3T3-L1 adipocytes. Moreover, it intervened classic insulin signal pathway IRS2/PI3KR1/p-AKT/GLUT4 and increase AMPK protein phosphorylation level for the activation of GLUT1/4 for insulin sensibility. Thus, jatrorrhizine could effectively regulate the GLUTs with multiple manners for hypoglycemic effect.

A glucose-centric perspective of hyperglycemia.

Digestion of food in the intestines converts the compacted storage carbohydrates, starch and glycogen, to glucose. After each meal, a flux of glucose (>200 g) passes through the blood pool (4-6 g) in a short period of 2 h, keeping its concentration ideally in the range of 80-120 mg/100 mL. Tissue-specific glucose transporters (GLUTs) aid in the distribution of glucose to all tissues. The balance glucose after meeting the immediate energy needs is converted into glycogen and stored in liver (up to 100 g) and skeletal muscle (up to 300 g) for later use. High blood glucose gives the signal for increased release of insulin from pancreas. Insulin binds to insulin receptor on the plasma membrane and activates its autophosphorylation. This initiates the post-insulin-receptor signal cascade that accelerates synthesis of glycogen and triglyceride. Parallel control by phos-dephos and redox regulation of proteins exists for some of these steps. A major action of insulin is to inhibit gluconeogensis in the liver decreasing glucose output into blood. Cases with failed control of blood glucose have alarmingly increased since 1960 coinciding with changed life-styles and large scale food processing. Many of these turned out to be resistant to insulin, usually accompanied by dysfunctional glycogen storage. Glucose has an extended stay in blood at 8 mM and above and then indiscriminately adds on to surface protein-amino groups. Fructose in common sugar is 10-fold more active. This random glycation process interferes with the functions of many proteins (e.g., hemoglobin, eye lens proteins) and causes progressive damage to heart, kidneys, eyes and nerves. Some compounds are known to act as insulin mimics. Vanadium-peroxide complexes act at post-receptor level but are toxic. The fungus-derived 2,5-dihydroxybenzoquinone derivative is the first one known to act on the insulin receptor. The safe herbal products in use for centuries for glucose control have multiple active principles and targets. Some are effective in slowing formation of glucose in intestines by inhibiting α–glucosidases (e.g., salacia/saptarangi). Knowledge gained from French lilac on active guanidine group helped developing Metformin (1,1-dimethylbiguanide) one of the popular drugs in use. One strategy of keeping sugar content in diets in check is to use artificial sweeteners with no calories, no glucose or fructose and no effect on blood glucose (e.g., steviol, erythrytol). However, the three commonly used non-caloric artificial sweeteners, saccharin, sucralose and aspartame later developed glucose intolerance, the very condition they are expected to evade. Ideal way of keeping blood glucose under 6 mM and HbA1c, the glycation marker of hemoglobin, under 7% in blood is to correct the defects in signals that allow glucose flow into glycogen, still a difficult task with drugs and diets.