Structural Analysis and Novel Mechanism of Enteromorpha prolifera Sulfated Polysaccharide in Preventing Type 2 Diabetes Mellitus

A water-soluble polysaccharide (EP) was purified from edible algae Enteromorpha prolifera. Gel permeation chromatography (GPC), ion chromatography (IC), and fourier transform infrared (FT-IR) were performed to characterize its structure. EP was defined as a low molecular weight (6625 Da) composed of rhamnose, glucose, glucuronic acid, xylose, galactose, arabinose, and mannose. Moreover, it was a sulfated polysaccharide with a degree of substitution (DS) of 1.48. Then, the high-fat diet/streptozotocin (HFD/STZ) induced diabetic mouse model was established to support evidence for a novel hypoglycemic mechanism. Results showed that blood glucose (47.32%), liver index (7.65%), epididymal fat index (16.86%), serum total cholesterol (26.78%) and triglyceride (37.61%) in the high-dose EP (HEP) group were significantly lower than those in the HFD group. Noticeably, the content of liver glycogen in the HEP group was significantly higher (62.62%) than that in the HFD group, indicating the promotion of glycogen synthesis. These beneficial effects were attributed to significantly increased protein kinase B (AKT) phosphorylation and its downstream signaling response. Further studies showed that diabetic mice exhibited excessive O-GlcNAcylation level and high expression of O-linked β-D-N-acetylglucosamine transferase (OGT), which were decreased by 62.21 and 30.43% in the HEP group. This result suggested that EP had a similar effect to OGT inhibitors, which restored AKT phosphorylation and prevented pathoglycemia. This work reveals a novel hypoglycemic mechanism of EP, providing a theoretical basis for further studies on its pharmacological properties in improvement of T2DM.

[Electroacupuncture regulates glucose metabolism disorder through PI3K/Akt/GSK3β signaling pathway in rats with depression]

OBJECTIVE

To explore the mechanism of electroacupuncture (EA) at "Zusanli" (ST36) on improving glucose metabolism disorder in chronic restraint induced depressed rats.

METHODS

A total of 30 male SD rats were randomly divided into control, model and EA groups, with 10 rats in each group. The depression model was established by chronic restraint 2.5 h each day for 4 weeks. For rats in the EA group, EA stimulation (1 mA, 2 Hz, 30 min) was applied to bilateral ST36 during the modeling period, once a day for 4 weeks. The body weight of the rats was recorded before and after modeling. The behavior of rats was observed by sugar-water preference and forced swimming after modeling. The contents of glucose and glycosylated albumin in serum were determined by biochemical method. The histopathological morphology and liver glycogen content were observed by HE and PAS staining. The expression levels of phosphatidylinositol 3-kinase (PI3K), phosphorylated (p)-PI3K (p-PI3K), protein kinase B (Akt), p-Akt, glycogen synthase kinase-3β (GSK3β) and p-GSK3β proteins in liver were determined by Western blot.

RESULTS

Compared with the control group, the weight increment and sugar-water preference index decreased (P<0.01), the immobile swimming time was prolonged (P<0.01), the glucose and glycosylated albumin contents in serum increased (P<0.05), the expression of p-Akt protein and the ratio of p-Akt/Akt in liver tissues decreased (P<0.001), the expression of p-GSK3β protein and the ratio of p-GSK3β/GSK3β in liver tissues increased (P<0.01,P<0.001) in the model group. Compared with the model group, the weight increment and sugar-water preference index increased (P<0.05), the immobile swimming time was shortened (P<0.05), the glucose and glycosylated albumin contents in serum decreased (P<0.05), the expressions of p-PI3K and p-Akt proteins and the ratio of p-PI3K/PI3K and p-Akt/Akt in liver tissues increased (P<0.05), the expression of p-GSK3β protein and the ratio of p-GSK3β/GSK3β in liver tissues decreased (P<0.01) in the EA group. HE staining showed that the structure of the hepatic lobule was intact, no obvious inflammatory cell infiltration or fibrosis was observed in the lobule and interstitium, and no abnormalities were observed in the small bile duct, portal vein and artery in the portal area. PAS staining showed that the intensity of staining from the center of the hepatic lobule to the periphery of the hepatic lobule was gradually enhanced in the blank group, that is, the glycogen-rich granules in the hepatic cells were gradually increased; most of the hepatocytes were light colored and glycogen was lost significantly in the model group; while the intensity of hepatocyte staining increased, the staining intensity of the perilobular zone was weaker than that in the blank group, and the glycogen particles partially recovered in the EA group.

CONCLUSION

EA intervention can regulate glucose metabolism disorder in chronic restraint induced depressed rats through PI3K/Akt/GSK3β signaling pathway.

Three weeks of time-restricted eating improves glucose homeostasis in adults with type 2 diabetes but does not improve insulin sensitivity: a randomised crossover trial

AIMS/HYPOTHESIS

Time-restricted eating (TRE) is suggested to improve metabolic health by limiting food intake to a defined time window, thereby prolonging the overnight fast. This prolonged fast is expected to lead to a more pronounced depletion of hepatic glycogen stores overnight and might improve insulin sensitivity due to an increased need to replenish nutrient storage. Previous studies showed beneficial metabolic effects of 6-8 h TRE regimens in healthy, overweight adults under controlled conditions. However, the effects of TRE on glucose homeostasis in individuals with type 2 diabetes are unclear. Here, we extensively investigated the effects of TRE on hepatic glycogen levels and insulin sensitivity in individuals with type 2 diabetes.

METHODS

Fourteen adults with type 2 diabetes (BMI 30.5±4.2 kg/m², HbA_1c 46.1±7.2 mmol/mol [6.4±0.7%]) participated in a 3 week TRE (daily food intake within 10 h) vs control (spreading food intake over ≥14 h) regimen in a randomised, crossover trial design. The study was performed at Maastricht University, the Netherlands. Eligibility criteria included diagnosis of type 2 diabetes, intermediate chronotype and absence of medical conditions that could interfere with the study execution and/or outcome. Randomisation was performed by a study-independent investigator, ensuring that an equal amount of participants started with TRE and CON. Due to the nature of the study, neither volunteers nor investigators were blinded to the study interventions. The quality of the data was checked without knowledge on intervention allocation. Hepatic glycogen levels were assessed with ¹³C-MRS and insulin sensitivity was assessed using a hyperinsulinaemic-euglycaemic two-step clamp. Furthermore, glucose homeostasis was assessed with 24 h continuous glucose monitoring devices. Secondary outcomes included 24 h energy expenditure and substrate oxidation, hepatic lipid content and skeletal muscle mitochondrial capacity.

RESULTS

Results are depicted as mean ± SEM. Hepatic glycogen content was similar between TRE and control condition (0.15±0.01 vs 0.15±0.01 AU, p=0.88). M value was not significantly affected by TRE (19.6±1.8 vs 17.7±1.8 μmol kg^-1 min^-1 in TRE vs control, respectively, p=0.10). Hepatic and peripheral insulin sensitivity also remained unaffected by TRE (p=0.67 and p=0.25, respectively). Yet, insulin-induced non-oxidative glucose disposal was increased with TRE (non-oxidative glucose disposal 4.3±1.1 vs 1.5±1.7 μmol kg^-1 min^-1, p=0.04). TRE increased the time spent in the normoglycaemic range (15.1±0.8 vs 12.2±1.1 h per day, p=0.01), and decreased fasting glucose (7.6±0.4 vs 8.6±0.4 mmol/l, p=0.03) and 24 h glucose levels (6.8±0.2 vs 7.6±0.3 mmol/l, p<0.01). Energy expenditure over 24 h was unaffected; nevertheless, TRE decreased 24 h glucose oxidation (260.2±7.6 vs 277.8±10.7 g/day, p=0.04). No adverse events were reported that were related to the interventions.

CONCLUSIONS/INTERPRETATION

We show that a 10 h TRE regimen is a feasible, safe and effective means to improve 24 h glucose homeostasis in free-living adults with type 2 diabetes. However, these changes were not accompanied by changes in insulin sensitivity or hepatic glycogen.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03992248 FUNDING: ZonMW, 459001013.

Hepatic glycogen participates in the regulation of hypothalamic pAkt/Akt ratio in high-sugar/high-fat diet-induced obesity

The hypothalamus is a major integrating centre that controls energy homeostasis and plays a major role in hepatic glycogen (HGlyc) turnover. Not only do hypothalamic and hepatic Akt levels influence glucose homeostasis and glycogen synthesis, but exposure to high-sugar/high-fat diets (HSHF) can also lead to hypothalamic inflammation and HGlyc accumulation. HSHF withdrawal overall restores energy and glucose homeostasis, but the actual relationship between hypothalamic inflammation and HGlyc after short-term HSHF withdrawal has not yet been fully elucidated. Here we investigated the short-term effects of HSHF withdrawal preceded by a 30-day HSHF intake on the liver-hypothalamus crosstalk and glucose homeostasis. Sixty-day old male Wistar rats were fed for 30 days a control chow (n = 10) (Ct), or an HSHF diet (n = 20). On the 30th day of dietary intervention, a random HSHF subset (n = 10) had their diets switched to control chow for 48 h (Hw) whilst the remaining HSHF rats remained in the HSHF diet (n = 10) (Hd). All rats were anaesthetized and euthanized at the end of the protocol. We quantified HGlyc, Akt phosphorylation, inflammation and glucose homeostasis biomarkers. We also assessed the effect of propensity to obesity on those biomarkers, as detailed previously. Hd rats showed impaired glucose homeostasis, higher HGlyc and hypothalamic inflammation, and lower pAkt/Akt. Increased HGlyc was significantly associated with HSHF intake on pAkt/Akt lowered levels. We also found that HGlyc breakdown may have prevented a further pAkt/Akt drop after HSHF withdrawal. Propensity to obesity showed no apparent effect on hypothalamic inflammation or glucose homeostasis. Our findings suggest a comprehensive role of HGlyc as a structural and functional modulator of energy metabolism, and such roles may come into play relatively rapidly.

Age-dependent hepatic alterations induced by a high-fat high-fructose diet

OBJECTIVE

The present study aimed to evaluate and clarify how the age at which the intake of a high-fat and high-fructose diet begins can affect animals' livers.

METHODS

Thirty-eight male wistar rats aged 6 and 12 weeks were fed a high-fat and high-fructose diet for 13 weeks. Inflammatory cytokines, hepatic glycogen, serum and hepatic triacylglycerol and pAkt protein content in the liver were assessed. Percentage of weight gained, and visceral adiposity were also evaluated.

RESULTS

Young animal presented increased hepatic triacylglycerol and decreased glycogen, while adult animals had no significant alterations regarding its contents. IL6 and IL10 to IL6 ratio were also altered in young animals exposed to HFHF, while adult animals fed with HFHF had only increases in TNF-α. Both groups which received HFHF had increased serum triacylglycerol and visceral adiposity. However, only young animals gained more relative weight and had greater final body weight, gains which were related to alterations found in hepatic triacylglycerol and glycogen.

CONCLUSION

Age of which consumption begins interferes in how the liver deals with an excess of nutrient and subsequent proinflammatory stimulation, leading to different phenotypes.

Behavior and histopathology as biomarkers for evaluation of the effects of paracetamol and propranolol in the neotropical fish species Phalloceros harpagos

Pharmaceutical drugs in the aquatic environment can induce adverse effects on nontarget organisms. This study aimed to assess the short-term effects of sublethal concentrations of both paracetamol and propranolol on the fish Phalloceros harpagos, specifically light/dark preference, swimming patterns, skin pigmentation, histopathology, and liver glycogen levels. Fish were acutely exposed to sublethal concentrations of both paracetamol (0.008, 0.08, 0.8, 8, 80 mg L^-1) and propranolol (0.0001, 0.001, 0.01, 0.1, 1 mg L^-1) under controlled conditions. For scototaxis, a significant preference for the dark compartment was observed for the group exposed to the highest concentration of paracetamol (80 mg L^-1). Propranolol exposure significantly altered the swimming pattern, especially in fish exposed to the 0.001 mg L^-1 concentration. Pigmentation was reduced in propranolol-exposed fish (0.1, 1 mg L^-1). The lowest concentration of propranolol (0.0001 mg L^-1) induced a decrease of histochemical reaction for hepatic glycogen. These data demonstrate that pharmaceuticals can induce sublethal effects in nontarget organisms, even at low concentrations, compromising specific functions of the individual with ecological relevance, such as energy balance and behavior.

GLUT2 proteins and PPARγ transcripts levels are increased in liver of ovariectomized rats: reversal effects of resistance training

[Purpose]

This study investigated the effects of ovariectomy (Ovx) and 12 weeks of resistance training (RT) on gene expression of GLUT2, the main glucose transporter in the liver, and on PPARγ, a transcription factor known to target GLUT2 expression.

[Methods]

Forty Holtzman rats were divided into 5 groups: Sham-sedentary (Sed), Sham- RT, Ovx-Sed, Ovx-RT, and Ovx-Sed with hormone replacement (E2). The RT protocol consisted of sessions held every 72 h for 12 weeks, during which the animals performed 4 to 9 vertical climbs (1.1 m) at 2 min intervals with progressively heavier weights (30 g after the fourth climb) tied to the tail. The E2 silastic capsule was inserted into the rats’ backs 48 hours before the first RT session.

[Results]

In addition to liver fat, GLUT2 protein levels and PPARγ transcripts were increased (P < 0.05) in Ovx compared to Sham-Sed animals, suggesting increased hepatic glucose uptake under estrogen deficient conditions. RT and E2 in Ovx rats decreased liver fat accumulation as well as GLUT2 and PPARγ gene expression to the level of Sham-Sed animals.

[Conclusion]

The results of this study suggest that liver GLUT2 as well as PPARγ expression in Ovx rats are accompanied by increased fat accumulation and glucose uptake, thus providing a substrate for increased de novo lipogenesis. RT appears to be an appropriate exercise model to circumvent these effects.

Hepatic and intramyocellular glycogen stores in adults with type 1 diabetes and healthy controls

Glycogen levels in liver and skeletal muscle assessed non-invasively using magnetic resonance spectroscopy after a 48-h pre-study period including a standardized diet and withdrawal from exercise did not differ between individuals with well-controlled Type 1 DM and matched healthy controls.

Cordycepin from Cordyceps militaris prevents hyperglycemia in alloxan-induced diabetic mice

Cordyceps militaris has long been used in prescriptions of traditional Chinese medicine as a tonic for the treatment of metabolic syndrome. Cordycepin with proven immunomodulatory, antitumor, and hepatoprotective properties is the main active metabolite of C militaris. Diabetes mellitus is a group of metabolic diseases in which the body is unable to regulate blood sugar levels. Hence, we hypothesized that cordycepin can normalize blood sugar levels and improve the indicators of diabetes. The aim of this study was to investigate the possible effects of cordycepin from C militaris on diabetes in an alloxan-induced diabetic mouse model. Diabetic mice were intraperitoneally administered different doses of cordycepin (8, 24, and 72 mg/kg body weight) daily for 21 days. Acute toxicity test on normal mice was carried out by giving them maximum tolerance dose of cordycepin (3600 mg/kg) daily. A 47% reduction of the blood glucose level, 214% increase of hepatic glycogen content, and significant improvement of oral glucose tolerance were noticed after the effective dose of cordycepin was administered. Polyphagia and polydipsia, the typical symptoms of diabetes, were partly alleviated. Moreover, cordycepin offered protective effects against diabetes-related kidney and spleen injury. Maximum tolerance dose test indicated that cordycepin at the large dose of 3600 mg/kg did not show significant effect on body weight and major organ in normal mice after intraperitoneal administration for 14 days. The results showed that cordycepin from C militaris that elicited hypoglycemic activity contributes to the regulation of glucose metabolism in liver in alloxan-induced diabetic mice. Therefore, a cordycepin treatment during diabetes can improve some of the metabolic syndrome symptoms by regulation of glucose absorption in vivo. Cordycepin may serve as a therapeutic agent in the treatment of diabetes and its related complications.