Effect of Thunbergia laurifolia water extracts on hepatic insulin resistance in high-fat diet-induced obese mice

Objective: To examine the effect of water extract of Thunbergia laurifolia on hepatic insulin resistance in high-fat diet-induced obese mice. Methods: High-fat diet with 45 kcal％ lard fat was used for obesity induction in ICR mice. The mice were fed with high-fat diet for 16 weeks, and during the last 8 weeks, they were treated with 200 mg/kg/day of water extracts from Thunbergia laurifolia leaf, stem and flower. Serum biochemistry, liver histology, and protein expression were examined after the treatment. Results: Extracts from all of the three parts of Thunbergia laurifolia significantly alleviated hyperglycemia, hyperlipidemia, hyperinsulinemia, and hyperleptinemia. The stem and flower extracts improved glucose tolerance. All of the extracts significantly reduced serum TNFα and monocyte chemoattractant protein-1 levels. Liver weight, triglyceride levels, and lipid accumulation were also decreased. Moreover, hepatic glucose-6-phosphatase level was significantly decreased, while the levels of PPARα, phosphorylated AMPK, and phosphorylated Akt were significantly increased with treatment of Thunbergia laurifolia extracts. Conclusions: Thunbergia laurifolia extracts can ameliorate hepatic insulin resistance in high-fat diet-induced obese mice by improving glucose and lipid homeostasis, which may be associated with stimulating phosphorylation of AMPK and Akt pathways.

Renoprotective effect of umbelliferone in high-fat diet/streptozotocin-induced type 2 diabetic rats

Objective: To evaluate the renoprotective effect of umbelliferone in high-fat diet/streptozotocin-induced type 2 diabetic rats. Methods: We established a streptozotocin-induced type 2 diabetic model in male Wistar rats. The rats were fed with high-fat diet (45 kcal％ lard fat) and injected with 35 mg/kg streptozotocin. Diabetic rats were treated with umbelliferone for 8 weeks. At the end of the experimental period, the serum and kidney were used for measuring biochemical parameters, protein expression and histological analysis. Results: After 8-week treatment, umbelliferone decreased fasting plasma glucose, concentrations of malondialdehyde and monocyte chemoattractant protein-1 in the plasma and tissues. It also significantly reduced serum creatinine, blood urea nitrogen, serum advanced glycation end products, as well as kidney weight in type 2 diabetic rats (P<0.05). Moreover, umbelliferone reduced the 24-h urine albumin, but increased 24-h urine creatinine excretion (P<0.05). In renal protein expression, umbelliferone decreased the levels of transforming growth factor-β1 and fibronectin while increasing the levels of superoxide dismutase and catalase (P<0.05). Renal histological examination revealed an enlarged glomerular size in diabetic rats, which was smaller in umbelliferone-treated diabetic rats. Conclusions: Umbelliferone alleviates renal dysfunction in diabetes via decreasing hyperglycemia, oxidative stress, inflammation and glycation.

Effects of Brassica oleracea extract on impaired glucose and lipid homeostasis in high-fat diet-induced obese mice

Objective: To examine the effect of Brassica oleracea extract (BO) on impaired glucose and lipid homeostasis in high-fat diet (HFD)-induced obese mice. Methods: Obesity of ICR mice was induced by feeding a HFD (45 kcal％ lard fat) for 16 weeks. During the last 8 weeks of study period, obese mice were additionally administered with BO (100 and 200 mg/kg/day). The metabolic parameters were determined. The gene expressions of hepatic lipogenesis were also studied. Results: After 8 weeks of treatment, BO (100 and 200 mg/kg) significantly reduced hyperglycemia and improved insulin sensitivity (P < 0.05). The serum lipid (total cholesterol, triglyceride, and non-esterified fatty acid) and hepatic triglyceride and non-esterified fatty acid were decreased (P < 0.05). The levels of insulin and leptin in serum were also decreased (P < 0.05). Moreover, the expressions of hepatic lipogenic genes including sterol regulatory element-binding protein 1c, fatty acid synthase, and acetyl-CoA carboxylase were decreased by BO treatment (P < 0.05). Conclusions: These results suggest that BO is a new therapeutic agent for improving the homeostasis of glucose and lipid in HFD-induced obese mice probably by suppression of lipogenic genes in liver tissue.

Anti-insulin resistant effect of ferulic acid on high fat diet-induced obese mice

To evaluate the insulin sensitivity action of ferulic acid (FA) in skeletal muscle and hypothalamus of high-fat diet (HFD)-induced obese mice.Methods: Obese mouse model was induced by HFD (45 kcal％ lard fat) for 16 weeks. After 8 weeks of HFD feeding, these obese mice were orally treated with FA at doses of 25 and 50 mg/kg/day for 8 weeks. At the end of all treatments, the epididymal fat, pancreas, skeletal muscle and hypothalamus were removed for biochemical parameter and protein expression examinations.Results: FA treatment significantly decreased leptin level in fat tissue and insulin level in pancreas (P < 0.05). Interestingly, obese mice treated with FA increased the protein expressions of insulin receptor substrate-1, phosphatidylinositol 3-kinase, and phosphorylated-protein kinase B in both muscle and brain (P < 0.05). The phosphorylations of adenosine monophosphate-activated protein kinase and acetyl-CoA carboxylase in muscle, and leptin receptor protein in hypothalamus were also increased (P < 0.05). The pancreatic islets histology showed smaller size in obese mice treated with FA compared to untreated obese mice.Conclusions: These findings indicate the beneficial effect of FA in improving insulin resistance in HFD-induced obese mice. These effects are probably mediatedvia modulating the insulin receptor substrate/phosphatidylinositol 3-kinase/protein kinase B or adenosine monophosphate-activated protein kinase pathways.

Rhinacanthus nasutus leaf improves metabolic abnormalities in high-fat diet-induced obese mice

Objective: To investigate the effect of Rhinacanthus nasutus (R. nasutus) leaf extract on impaired glucose and lipid metabolism in obese ICR mice. Methods: Obesity was induced in the male ICR mice by feeding them a high-fat diet (60 kcal% fat) for 12 weeks. After the first six weeks of the diet, the obese mice were administered with the water extract of R. nasutus leaves at 250 and 500 mg/kg per day for the next six weeks. Subsequently, the blood glucose, lipid profiles, insulin, leptin, and adiponectin levels were measured. The liver and adipose tissues were excised for his-topathological examination and protein expression study. Results: After six weeks of the treatment, R. nasutus extract (at 250 and 500 mg/kg per day) was found to reduce the elevated blood glucose level, improve the insulin sensitivity, decrease the serum leptin, and increase the serum adiponectin levels. The obese mice treated with R. nasutus were found to have a reduction in the increased lipid concen-trations in their serum and liver tissues. Moreover, treatment with R. nasutus reduced the fat accumulation in the liver and the large adipocyte size in the fat tissues. Interestingly, the administration with R. nasutus extract was marked by an increase in the hepatic peroxisome proliferators-activated receptor alpha, fat cell adiponectin, and glucose transporter 4 proteins. Conclusions: To the best of our knowledge, the present study is the first report on the impact of R. nasutus extract in improving the impaired glucose and lipid metabolism in high-fat diet-induced obesity in mice via stimulating the insulin sensitivity in the liver and adipose tissues.

Pandanus amaryllifolius leaf extract increases insulin sensitivity in high-fat diet-induced obese mice

Objective: To examine the effect of Pandanus amaryllifolius (P. amaryllifolius) leaf extract on the insulin resistance state in obese ICR mice. Methods: Obesity was induced in mice fed with high-fat diet (45%fat) for 12 weeks. After the first six weeks on the diet, the obese mice were administered with the water extract of P. amaryllifolius leaf at 125 and 250 mg/kg/day, respectively for another six weeks. At the 5th week of treatment, oral glucose tolerance test was conducted. After six weeks of treat-ment, the levels of blood glucose, serum insulin, leptin, adiponectin, and lipid profiles were determined. The liver, muscle and epididymal fat tissues were removed for measuring the biochemical parameters and protein expression, as well as histological examination. Results: Six weeks of treatment with P. amaryllifolius led to a significant reduction in the blood glucose level as well as improvement in the insulin resistance. P. amaryllifolius also increased the liver glycogen storage and serum adiponectin and decreased the serum leptin levels. A reduction in the serum and hepatic triglyceride, and non-esterified fatty acid levels was also observed. The histological examination showed that the obese mice treated with P. amaryllifolius reduced the lipid droplet in liver tissue and adipocyte size in epididymal fat tissue. The treatment also increased the protein expression of glucose transporter 4 in the muscle and fat tissues. Conclusions: The treatment with P. amaryllifolius could decrease several parameters of impaired glucose and lipid metabolism. To the best of our knowledge, this is the first report on the role of P. amaryllifolius leaf extract in alleviating the insulin dysfunction in obesity state.