Glucagon‐like peptide‐1 receptor activation stimulates hepatic lipid oxidation and restores hepatic signalling alteration induced by a high‐fat diet in nonalcoholic steatohepatitis

Background/Aims: High‐fat dietary intake and low physical activity lead to insulin resistance, nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). Recent studies have shown an effect of glucagon‐like peptide‐1 (GLP‐1) on hepatic glucose metabolism, although GLP‐1 receptors (GLP‐1r) have not been found in human livers. The aim of this study was to investigate the presence of hepatic GLP‐1r and the effect of exenatide, a GLP‐1 analogue, on hepatic signalling. Methods: The expression of GLP‐1r was evaluated in human liver biopsies and in the livers of high‐fat diet‐treated rats. The effect of exenatide (100 nM) was evaluated in hepatic cells of rats fed 3 months with the high‐fat diet. Results: GLP‐1r is expressed in human hepatocytes, although reduced in patients with NASH. Similarly, in rats with NASH resulted from 3 months of the high‐fat diet, we found a decreased expression of GLP‐1r and peroxisome proliferator‐activated receptor γ (PPARγ), and reduced peroxisome proliferator‐activated receptor α (PPARα) activity. Incubation of hepatocytes with exenatide increased PPARγ expression, which also exerted an insulin‐sensitizing action by reducing JNK phosphorylation. Moreover, exenatide increased protein kinase A (PKA) activity, Akt and AMPK phosphorylation and determined a PKA‐dependent increase of PPARα activity. Conclusions: GLP‐1 has a direct effect on hepatocytes, by activating genes involved in fatty acid β‐oxidation and insulin sensitivity. GLP‐1 analogues could be a promising treatment approach to improve hepatic insulin resistance in patients with NAFLD/NASH.     

Evidence for a gut-brain axis used by glucagon-like peptide-1 to elicit hyperglycaemia in fish

In mammals, glucagon-like peptide-1 (GLP-1) produces changes in glucose and energy homeostasis through a gut-pancreas-brain axis. In fish, the effects of GLP-1 are opposed to those described in other vertebrates, such as stimulation of hyperglycaemia and the lack of an effect of incretin. In the present study conducted in a teleost fish such as the rainbow trout, we present evidence of a gut-brain axis used by GLP-1 to exert its actions on glucose and energy homeostasis. We have assessed the effects of GLP-1 on glucose metabolism in the liver as well as the glucose-sensing potential in the hypothalamus and hindbrain. We confirm that peripheral GLP-1 administration elicits sustained hyperglycaemia, whereas, for the first time in a vertebrate species, we report that central GLP-1 treatment increases plasma glucose levels. We have observed (using capsaicin) that at least part of the action of GLP-1 on glucose homeostasis was mediated by vagal and splanchnic afferents. GLP-1 has a direct effect in parameters involved in glucose sensing in the hindbrain, whereas, in the hypothalamus, changes occurred indirectly through hyperglycaemia. Moreover, in the hindbrain, GLP-1 altered the expression of peptides involved in the control of food intake. We have elaborated a model for the actions of GLP-1 in fish in which this peptide uses a mammalian-like ancestral gut-brain axis to elicit the regulation of glucose homeostasis in different manner than the model described in mammals. Finally, it is worth noting that the hyperglycaemia induced by this peptide and the lack of incretin function could be related to the glucose intolerance observed in carnivorous teleost fish species such as the rainbow trout.     

Combination treatment of db/db mice with exendin‐4 and gastrin preserves β‐cell mass by stimulating β‐cell growth and differentiation

Aim/Introduction: Preservation of β‐cell mass is crucial for maintaining long‐term glucose homeostasis. Therapies based on incretin and its mimetics are expected to achieve this goal through various biological functions, particularly the restoration of β‐cell mass. Here we tested the effects of gastrin and exendin‐4 in type 2 diabetic animals. Materials and Methods: The effects of exendin‐4 and gastrin on β‐cell function and mass were examined in 8‐week‐old db/db mice. INS‐1 beta cells and AR42J cells were used to determine the molecular mechanism underlying the effects of the two agents. Immunohistochemistry, western blotting and RT‐PCR assays were used to assess the biological effects of the two agents. Results: Two weeks of combination administration of exendin‐4 plus gastrin resulted in a significant improvement of glucose tolerance associated with a marked preservation of β‐cell mass in db/db mice. Immunohistochemical analysis showed that such treatment resulted in the appearance of numerous irregularly‐shaped small islets and single insulin‐positive cells. While gastrin had little biological effect on INS‐1 β‐cells consistent with low expression of its intrinsic receptor on these cells, it caused differentiation of AR42J cells into insulin‐producing cells. Co‐stimulation with exendin‐4 significantly enhanced gastrin‐induced endocrine differentiation of AR42J precursor cells. These findings were further supported by enhanced expression of key genes involved in β‐cell differentiation and maturation, such as neurogenin3 (Ngn3) and MafA. Conclusions: These results suggest that combination treatment of db/db mice with exendin‐4 and gastrin preserves β‐cell mass by stimulating β‐cell growth and differentiation. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.00044.x, 2010)     

Old formula, new Rx: the journey of PHY906 as cancer adjuvant therapy

Ethnopharmacological relevance

PHY906, is a decoction of a mixture of the four herbs Scutellaria baicalensis Geori, Glycyrrhiza uralensis Fisch, Paeonia lactiflora Pall, and Ziziphus jujuba Mill. A combination of these four herbs has been in continuous use in traditional Chinese medicine for over 1800 years for treating a variety of gastrointestinal distress such as diarrhea, cramps, nausea, vomiting etc.

Aim of the study

Preclinical and clinical studies to find PHY906 enhances the therapeutic indices of a broad spectrum of anticancer agents.

Materials and methods

Using various mouse tumor xenograft and allograft models, PHY906 has been shown to enhance the chemotherapeutic efficacy of a variety of anticancer agents in various cancers. The PHY906 clinical program consists of five trials in three different types of cancers in both the United States and Taiwan. To date, approximately 150 subjects have received PHY906 in combination with chemotherapy in these five clinical studies.

Results

Preclinical studies have shown that PHY906 enhances the therapeutic indices of a broad spectrum of anticancer agents. These findings have been examined in clinical studies for colorectal, liver, and pancreatic cancers when PHY906 is used as an adjuvant to chemotherapy and the results were promising; i.e. PHY906 could reduce chemotherapy-induced toxicities and/or increase chemotherapeutic efficacy. Furthermore, PHY906 did not affect the pharmacokinetics of the chemotherapeutic agents used. Some information has been obtained regarding the mechanism of action of PHY906 in preclinical studies. A comprehensive platform, PhytomicsQC that integrates chemical and biological fingerprints together with a novel biostatistical methodology has been developed to assess the quality of different batches of PHY906.

Conclusions

Over a ten-year period, the multiplex technology “PhytomicsQC” has been used to show batch-to-batch consistency of PHY906 production. Advanced clinical trials are ongoing to demonstrate the effectiveness of PHY906 as adjuvant therapy for cancer patients undergoing chemotherapy.     

Future challenges and therapeutic opportunities in type 2 diabetes: Changing the paradigm of current therapy

Most algorithms for type 2 diabetes mellitus (T2DM) do not recommend treatment escalation until glycated haemoglobin (HbA1c) fails to reach the recommended target of 7% (53 mmol/mol) within approximately 3 months on any treatment regimen (“treat to failure”). Clinical inertia and/or poor adherence to therapy contribute to patients not reaching glycaemic targets when managed according to this paradigm. Clinical inertia exists across the entire spectrum of anti‐diabetes therapies, although it is most pronounced when initiating and optimizing insulin therapy. Possible reasons include needle aversion, fear of hypoglycaemia, excessive weight gain and/or the need for increased self‐monitoring of blood glucose. Studies have suggested, however, that early intensive insulin therapy in newly diagnosed, symptomatic patients with T2DM with HbA1c >9% (75 mmol/mol) can preserve beta‐cell function, thereby modulating the disease process. Furthermore, postprandial plasma glucose is a key component of residual dysglycaemia, evident especially when HbA1c remains above target despite fasting normoglycaemia. Therefore, to achieve near normoglycaemia, additional treatment with prandial insulin or a glucagon‐like peptide‐1 receptor agonist (GLP‐1 RA) is often required. Long‐ or short‐acting GLP‐1 RAs offer effective alternatives to basal or prandial insulin in patients inadequately controlled with other therapies or basal insulin alone, respectively. This review highlights the limitations of current algorithms, and proposes an alternative based on the early introduction of insulin therapy and the rationale for the sequential or fixed combination of GLP‐1 RAs with insulin (“treat‐to‐success” paradigm).     

Short‐acting glucagon‐like peptide‐1 receptor agonists as add‐on to insulin therapy in type 1 diabetes: A review

A large proportion of patients with type 1 diabetes do not reach their glycaemic target of glycated hemoglobin (HbA1c) <7.0% (53 mmol/mol) and, furthermore, an increasing number of patients with type 1 diabetes are overweight and obese. Treatment of type 1 diabetes is based on insulin therapy, which is associated with well‐described and unfortunate adverse effects such as hypoglycaemia and increased body weight. Glucagon‐like peptide‐1 (GLP‐1) receptor agonists (RAs) are the focus of increasing interest as a possible adjunctive treatment to insulin in type 1 diabetes because of their glucagonostatic and extrapancreatic effects. So far, the focus has mainly been on the long‐acting GLP‐1RAs, but the risk–benefit ratio emerging from studies evaluating the effect of long‐acting GLP‐1RAs as adjunctive therapy to insulin therapy in patients with type 1 diabetes has been disappointing. This might be attributable to a lack of glucagonostatic effect of these long‐acting GLP‐1RAs in type 1 diabetes, alongside development of tachyphylaxis to GLP‐1‐induced retardation of gastric emptying. In contrast, the short‐acting GLP‐1RAs seem to have a preserved and sustained effect on glucagon secretion and gastric emptying in patients with type 1 diabetes, which could translate into effective lowering of postprandial glucose excursions; however, these observations regarding short‐acting GLP‐1RAs are all derived from small open‐label trials and should thus be interpreted with caution. In the present paper we review the potential role of GLP‐1RAs, in particular short‐acting GLP‐1RAs, as add‐on to insulin in the treatment of type 1 diabetes.     

Impact of baseline glycated haemoglobin,diabetes duration and body mass index on clinical outcomes in the LixiLan‐O trial testing a titratable fixed‐ratio combination of insulin glargine/lixisenatide (iGlarLixi) vs insulin glargine and lixisenatide monocomponents

To determine whether baseline characteristics had an impact on clinical outcomes in the LixiLan‐O trial (N = 1170), we compared the efficacy and safety of iGlarLixi, a titratable fixed‐ratio combination of insulin glargine 100 U (iGlar) and lixisenatide (Lixi) with iGlar or Lixi alone in patients with uncontrolled type 2 diabetes mellitus (T2DM) on oral therapy. Subgroups according to baseline glycated haemoglobin (HbA1c; <8% or ≥8% [<64 or ≥64 mmol/mol]), T2DM disease duration (<7 or ≥7 years) and body mass index (BMI; <30 or ≥30 kg/m²) were investigated. In all subpopulations, iGlarLixi was consistently statistically superior to iGlar and Lixi alone in reducing HbA1c from baseline to week 30; higher proportions of patients achieved HbA1c <7% (<53 mmol/mol) with iGlarLixi vs iGlar and Lixi alone. Compared with iGlar, iGlarLixi resulted in a substantial decrease in 2‐hour postprandial plasma glucose levels, and mitigation of weight gain, with no differences among subpopulations in incidence of symptomatic hypoglycaemia. iGlarLixi consistently improved glycaemic control compared with iGlar and Lixi alone, without weight gain or increase in hypoglycaemic risk compared with iGlar in the subpopulations tested, regardless of baseline HbA1c, disease duration and BMI.     

Effects of liraglutide on cardiovascular risk factors in patients with type 1 diabetes

We investigated the short‐term effect of adding liraglutide 1.8 mg once daily to insulin treatment on cardiovascular risk factors in patients with type 1 diabetes. In total, 100 overweight (BMI ≥25 kg/m²) adult patients (age ≥18 years) with type 1 diabetes and HbA1c ≥ 8% (64 mmol/mol) were randomized to liraglutide 1.8 mg or placebo added to insulin treatment in a 24‐week double‐blinded, placebo‐controlled trial. At baseline and after 24 weeks of treatment, 24‐hour blood pressure and heart rate, pulse pressure, pulse wave velocity and carotid intima‐media thickness were evaluated. Compared with placebo, liraglutide increased 24‐hour heart rate by 4.6 beats per minute (BPM); P = .0015, daytime heart rate by 3.7; P = .0240 and night‐time heart rate by 7.5 BPM; P < .001 after 24 weeks. Diastolic nocturnal blood pressure increased by 4 mm Hg; P = .0362 in the liraglutide group compared with placebo. In conclusion, in patients with long‐standing type 1 diabetes, liraglutide as add‐on to insulin increased heart rate and did not improve other cardiovascular risk factors after 24 weeks of treatment.