Are insulin sensitizers the new strategy to treat Type 1 diabetes? A long-acting dual amylin and calcitonin receptor agonist improves insulin-mediated glycaemic control and controls body weight

BACKGROUND AND PURPOSE

Insulin therapies for Type 1 diabetes (T1D) have limitations, such as glucose fluctuations, hypoglycaemia, and weight gain. Only pramlintide is approved with insulin. However, its short half-life limits efficacy, requiring multiple daily injections and increasing hypoglycaemia risk. New strategies are needed to improve glycaemic control. Dual amylin and calcitonin receptor agonists are potent insulin sensitizers developed for Type 2 diabetes (T2D) as they improve glucose control, reduce body weight, and attenuate hyperglucagonemia. However, it is uncertain if they could be used to treat T1D.

EXPERIMENTAL APPROACH

Sprague Dawley rats received a single intravenous injection of streptozotocin (STZ) (50 mg·kg-1) to induce T1D. Humulin (1 U/200 g·day-1 or 2 U/200 g·day-1) was continuously infused, while half of the rats received additional KBP-336 (4.5 nmol·kg-1 Q3D) treatment. Bodyweight, food intake, and blood glucose were monitored throughout the study. An oral glucose tolerance test was performed during the study.

KEY RESULTS

Treatment with Humulin or Humulin + KBP-336 improved the health of STZ rats. Humulin increased body weight in STZ rats, but KBP-336 attenuated these increases and maintained a significant weight loss. The combination exhibited greater blood glucose reductions than Humulin-treated rats alone, reflected by improved HbA1c levels and glucose control. The combination prevented hyperglucagonemia, reduced amylin levels, and increased pancreatic insulin content, indicating improved insulin sensitivity and beta-cell preservation.

CONCLUSION AND IMPLICATIONS

The insulin sensitizer KBP-336 lowered glucagon secretion while attenuating insulin-induced weight gain. Additionally, KBP-336 may prevent hypoglycaemia and improve insulin resistance, which could be a significant advantage for individuals with T1D seeking therapeutic benefits.

FAM3D: A gut secreted protein and its potential in the regulation of glucose metabolism

The number of diabetic patients is rising globally and concomitantly so do the diabetes associated complications. The gut secretes a variety of proteins to control blood glucose levels and/or food intake. As the drug class of GLP-1 agonists is based on a gut secreted peptide and the positive metabolic effects of bariatric surgery are at least partially mediated by gut peptides, we were interested in other gut secreted proteins which have yet to be explored. In this respect we identified the gut secreted protein FAM3D by analyzing sequencing data from L- and epithelial cells of VSG and sham operated as well as chow and HFD fed mice. FAM3D was overexpressed in diet induced obese mice via an adeno-associated virus (AAV), which resulted in a significant improvement of fasting blood glucose levels, glucose tolerance and insulin sensitivity. The liver lipid deposition was reduced, and the steatosis morphology was improved. Hyperinsulinemic clamps indicated that FAM3D is a global insulin sensitizer and increases glucose uptake into various tissues. In conclusion, the current study demonstrated that FAM3D controls blood glucose levels by acting as an insulin sensitizing protein and improves hepatic lipid deposition.

Guava Leaf Extract Suppresses Fructose Mediated Non-Alcoholic Fatty Liver Disease in Growing Rats

Purpose

Fructose is highly lipogenic, and its unhindered ingestion by children and adolescents is understood to induce hypertriglyceridemia and non-alcoholic fatty liver disease (ped-NAFLD) that is till date managed symptomatically or surgically. The aim of the present study was to investigate the potential of hydroethanolic extract of leaves of Guava (PG-HM) to suppress the alterations in the hepatic molecular signals due to unrestricted fructose (15%) drinking by growing rats.

Methods

Weaned rats (4 weeks old) in control groups had ad libitum access to fructose drinking solution (15%) for four (4FDR) or eight (8FDR) weeks, ie, till puberty or early adulthood, respectively, while treatment groups (4PGR, 8PGR) additionally received PG-HM (500 mg/kg, po).

Results

The PG-HM suppressed ped-NAFLD through hepatic signalling pathways of 1) leptin-insulin (Akt/FOX-O1/SREBP-1c), 2) hypoxia-inflammation (HIF-1ɑ/VEGF, TNF-ɑ), 3) mitochondrial function (complexes I–V), 4) oxidative stress (MDA, GSH, SOD) and 5) glycolysis/gluconeogenesis/de novo lipogenesis (hexokinase, phosphofructokinase, ketohexokinase, aldehyde dehydrogenase). Parri passu, the insulin sensitizing effect of PG-HM and its ethyl acetate fraction (PG-EA) was elucidated using HepG2 cells grown in media enhanced with fructose. Further, in murine hepatocytes cultured in fructose-rich media, PG-HM (35 µg mL-1) outperformed Pioglitazone (15 µM) and Metformin (5 mM), to suppress hepatic insulin resistance.

Conclusion

This study established that hydroethanolic extract of leaves of Guava (PG-HM) has potential to suppress hepatic metabolic alteration for the management of the pediatric NAFLD.

Dietary Soy Prevents Alcohol-Mediated Neurocognitive Dysfunction and Associated Impairments in Brain Insulin Pathway Signaling in an Adolescent Rat Model

BACKGROUND

Alcohol-related brain degeneration is linked to cognitive-motor deficits and impaired signaling through insulin/insulin-like growth factor type 1 (IGF-1)-Akt pathways that regulate cell survival, plasticity, metabolism, and homeostasis. In addition, ethanol inhibits Aspartyl-asparaginyl-β-hydroxylase (ASPH), a downstream target of insulin/IGF-1-Akt signaling and an activator of Notch networks. Previous studies have suggested that early treatment with insulin sensitizers or dietary soy could reduce or prevent the long-term adverse effects of chronic ethanol feeding.

OBJECTIVE

The goal of this study was to assess the effects of substituting soy isolate for casein to prevent or reduce ethanol's adverse effects on brain structure and function.

METHODS

Young adolescent male and female Long Evans were used in a 4-way model as follows: Control + Casein; Ethanol + Casein; Control + Soy; Ethanol + Soy; Control = 0% ethanol; Ethanol = 26% ethanol (caloric). Rats were fed isocaloric diets from 4 to 11 weeks of age. During the final experimental week, the Morris Water maze test was used to assess spatial learning (4 consecutive days), after which the brains were harvested to measure the temporal lobe expression of the total phospho-Akt pathway and downstream target proteins using multiplex bead-based enzyme-linked immunosorbent assays (ELISAs) and duplex ELISAs.

RESULTS

Ethanol inhibited spatial learning and reduced brain weight, insulin signaling through Akt, and the expression of ASPH when standard casein was provided as the protein source. The substitution of soy isolate for casein largely abrogated the adverse effects of chronic ethanol feeding. In contrast, Notch signaling protein expression was minimally altered by ethanol or soy isolate.

CONCLUSIONS

These novel findings suggest that the insulin sensitizer properties of soy isolate may prevent some of the adverse effects that chronic ethanol exposure has on neurobehavioral function and insulin-regulated metabolic pathways in adolescent brains.

A Novel Angiotensin Converting Enzyme 2 (ACE2) Activating Peptide: A Reflection of 10 Years of Research on a Small Peptide Ile-Arg-Trp (IRW)

IRW (Ile-Arg-Trp) was identified as an inhibitor of angiotensin converting enzyme (ACE) from egg white protein ovotransferrin through an integrated in silico digestion and quantitative structure and activity relationship prediction in 2011. Oral administration of IRW to spontaneously hypertensive rats (SHRs) can significantly reduce blood pressure, via upregulation of ACE2, but not through the inhibition of ACE. ACE2 converts Ang II into Ang (1-7), thus lowering blood pressure via Mas receptor (MasR); coinfusion of Mas receptor antagonist A779 and IRW in SHRs abolished blood pressure-lowering effect of IRW, supporting a key role of ACE2/Ang (1-7)/MasR axis. Our ongoing study further established new roles of IRW as an antioxidant, an anti-inflammatory agent, an insulin sensitizer, and a bone cell anabolic. Future studies are warranted to understand the unique structure features of this peptide, its mechanisms of action at various targets, its bioavailability and metabolism, and its possible roles toward COVID-19.

Molecules Isolated from Mexican Hypoglycemic Plants: A Review

Like in many developing countries, in Mexico, the use of medicinal plants is a common practice. Based on our own field experience, there are at least 800 plants used for treating diabetes nowadays. Thus, their investigation is essential. In this context, this work aims to provide a comprehensive and critical review of the molecules isolated from Mexican hypoglycemic plants, including their source and target tested. In the last few years, some researchers have focused on the study of Mexican hypoglycemic plants. Most works describe the hypoglycemic effect or the mechanism of action of the whole extract, as well as the phytochemical profile of the tested extract. Herein, we analyzed 85 studies encompassing 40 hypoglycemic plants and 86 active compounds belonging to different classes of natural products: 28 flavonoids, 25 aromatic compounds, other than flavonoids, four steroids, 23 terpenoids, 4 oligosaccharides, and 1 polyalcohol. These compounds have shown to inhibit α-glucosidases, increase insulin secretion levels, increase insulin sensitivity, and block hepatic glucose output. Almost half of these molecules are not common metabolites, with a narrow taxonomic distribution, which makes them more interesting as lead molecules. Altogether, this analysis provides a necessary inventory useful for future testing of these active molecules against different hypoglycemic targets, to get a better insight into the already described mechanisms, and overall, to contribute to the knowledge of Mexican medicinal plants.

GPR120 agonists for the treatment of diabetes: a patent review (2014 present)

INTRODUCTION

G protein-coupled receptor 120 (GPR120) is a G_αq coupled GPCR specifically activated by long-chain fatty acids (LCFAs). Functionally, it has been identified as a member of a family of lipid-binding free fatty acid receptors including GPR40, GPR41, and GPR43. Upon stimulation by LCFAs, GPR120 can directly or indirectly modulate hormone secretion from the gastrointestinal tract and pancreas, and regulate lipid and/or glucose metabolism in adipose, liver, and muscle tissues. Additionally, GPR120 is postulated to mediate anti-inflammatory and insulin-sensitizing effects in adipose and macrophages. These benefits suggest that GPR120 agonists have the potential to be an effective treatment for obesity, type 2 diabetes mellitus (T2DM), and other metabolic syndromes.

AREA COVERED

This article highlights and reviews research advances in this field that have been published in patent literature and peer-reviewed journals since 2014.

EXPERT OPINION

Current development has been hindered by species differences in GPR120 distribution, differences in GPR120-mediated signaling in distinct tissue types, and lack of available ligands with suitable selectivity for GPR120 over GPR40 in both human and rodents. The discovery of β-arrestin biased GPR120 agonists will help elucidate the potential of selective therapeutics that may discriminate between desirable and undesirable pharmacological effects.

ABBREVIATIONS

ALA: α-linolenic acid; AUC: area under the curve; BRET: bioluminescence resonance energy transfer; CCK: cholecystokinin; CHO-K1 cell: Chinese hamster ovary-K1 cell; db/db mouse: diabetic mouse; DHA: docosahexaenoic acid; DIO: diet-induced obesity; DMSO: dimethyl sulfoxide; DPP-4: dipeptidyl peptidase 4; EPA: eicosapentaenoic acid; FA(s): fatty acid(s); FFA(s): free fatty acid(s); FFAR: free fatty acid receptor; FLIPR: fluorescent imaging plate reader; GIR: glucose infusion rate; GLP-1: glucagon-like peptide 1; GP(C)R: G protein-coupled receptor; GSIS: glucose-stimulated insulin secretion; HEK293 cell: human embryonic kidney 293 cell; HOMA-IR: homeostatic measurement assessment of insulin resistance; IP1: inositol phosphate turnover; IPGTT: intraperitoneal glucose tolerance test; LCFA(s): long-chain fatty acid(s); MED_max: maximal efficacy; MIN6 cell: mouse insulin-secreting cell; NPY: neuropeptide Y; OGTT: oral glucose tolerance test; pERK: phosphorylated ERK; PPAR: peroxisome proliferator-activated receptor; QD: once daily; SAR: structure-activity relationship; siRNA: small interfering ribonucleic acid; STC-1: intestinal secretin tumor cell; T2DM: type 2 diabetes mellitus; U2OS cell: human bone osteosarcoma epithelial cell; uHTS: ultrahigh-throughput screening; ZDF: zucker diabetic fatty.

Developmental programming of insulin resistance: are androgens the culprits?

Insulin resistance is a common feature of many metabolic disorders. The dramatic rise in the incidence of insulin resistance over the past decade has enhanced focus on its developmental origins. Since various developmental insults ranging from maternal disease, stress, over/undernutrition, and exposure to environmental chemicals can all program the development of insulin resistance, common mechanisms may be involved. This review discusses the possibility that increases in maternal androgens associated with these various insults are key mediators in programming insulin resistance. Additionally, the intermediaries through which androgens misprogram tissue insulin sensitivity, such as changes in inflammatory, oxidative, and lipotoxic states, epigenetic, gut microbiome and insulin, as well as data gaps to be filled are also discussed.

What is new in the landscape of insulin-sensitizing agents for polycystic ovary syndrome treatment

Polycystic ovary syndrome, the most common gynecological endocrinopathy, is burdened with a state of hyperinsulinemia and insulin resistance in 50–80% of affected women. Wherever the origin of these metabolic abnormalities lies, their pathogenetic role in determining, perpetuating, and worsening the clinical traits of the syndrome is ascertained. Many studies have already highlighted possible mechanisms: hyperinsulinemia and insulin resistance may contribute to hyperandrogenemia, chronic anovulation, and other comorbidities of the syndrome by differentially affecting the endocrine glands (ovaries, adrenals, and pituitary) and peripheral tissues (fat mass and skeletal muscle). Based on these evidences, in the past years, thorough research has been focused on the possible role of insulin-sensitizing agents in the treatment of polycystic ovary syndrome. Many compounds were tested to verify their efficacy against polycystic ovary syndrome–related metabolic dysfunction, both relying on previous acquired experiences in the field of diabetes mellitus and experimenting new agents, in particular, those belonging to the class of nutraceuticals. We sought to summarize the most relevant aspects of insulin-sensitizing treatments in polycystic ovary syndrome, by reporting the relevant literature on this topic and by keeping an attentive eye on the newly published international guidelines on polycystic ovary syndrome 2018. This overview encompasses metformin, thiazolidinediones, inositols, alpha-lipoic acid, and GLP1-R analogues. Starting from the analysis of the mechanisms of action, we anchored to the state of the art of the use of these drugs in polycystic ovary syndrome, to the most recent evidences for clinical practice and to the remaining open questions around indications, dose, treatment schedules, and side effects.

Pharmacological Overview of the BGP-15 Chemical Agent as a New Drug Candidate for the Treatment of Symptoms of Metabolic Syndrome

BGP-15 is a new insulin sensitizer drug candidate, which was developed by Hungarian researchers. In recent years, numerous research groups have studied its beneficial effects. It is effective in the treatment of insulin resistance and it has protective effects in Duchenne muscular dystrophy, diastolic dysfunction, tachycardia, heart failure, and atrial fibrillation, and it can alleviate cardiotoxicity. BGP-15 exhibits chemoprotective properties in different cytostatic therapies, and has also proven to be photoprotective. It can additionally have advantageous effects in mitochondrial-stress-related diseases. Although the precise mechanism of the effect is still unknown to us, we know that the molecule is a PARP inhibitor, chaperone co-inducer, reduces ROS production, and is able to remodel the organization of cholesterol-rich membrane domains. In the following review, our aim was to summarize the investigated molecular mechanisms and pharmacological effects of this potential API. The main objective was to present the wide pharmacological potentials of this chemical agent.

Acute and Repeated Treatment with 5-PAHSA or 9-PAHSA Isomers Does Not Improve Glucose Control in Mice

Fatty acid esters of hydroxylated fatty acids (FAHFAs) were discovered as a novel class of endogenous mammalian lipids whose profound effects on metabolism have been shown. In the current study, in vitro and in vivo the metabolic effects of two of these FAHFAs, namely palmitic acid-5- (or -9) -hydroxy-stearic acid (5- or 9-PAHSA, respectively) were profiled. In DIO mice fed with differentially composed low- or high-fat diets, acute and subchronic treatment with 5-PAHSA and 9-PAHSA alone, or in combination, did not significantly improve the deranged metabolic status. Neither racemic 5- or 9-PAHSA, nor the enantiomers were able to: (1) increase basal or insulin-stimulated glucose uptake in vitro, (2) stimulate GLP-1 release from GLUTag cells, or (3) induce GSIS in rat, mouse, or human islets or in a human pancreatic β cell line. Therefore, our data do not support the further development of PAHSAs or their derivatives for the control of insulin resistance and hyperglycemia.

The Molecular Targets of Swertiamarin and its Derivatives Confer Anti- Diabetic and Anti-Hyperlipidemic Effects

The herbal plant extract of Enicostemma littorale is widely used to medicate and treat type II Diabetes. This extract in medicine has shown its value in reducing blood glucose & lipid levels, and improving the kidney functioning, lipid profile, controlling blood pressure and heart rate. The well characterized chemical components such as iridoid and secoiridoid glycosides are present in aqueous and ethanolic extracts of the plant. Swertiamarin, a secoiridoid glycoside, is identified as the lead compound that confers anti-hyperglycemic & anti-hyperlipidemic effects. The swertiamarin binds with one or more molecular targets to alter their expression and/or activity. The in silico, in vivo and in vitro studies have been carried out to uncover the underlying molecular mechanism of action of swertiamarin and its derivatives for showing the better anti-diabetic & anti-hyperlipidemic activities. In brief, the present review focuses on unraveling the information about molecular targets of swertiamarin. Our review will open new avenues to develop therapeutic approaches and drugs to treat diabetes and other inflammatory diseases.

Developmental Programming: Impact of Prenatal Testosterone Excess on Steroidal Machinery and Cell Differentiation Markers in Visceral Adipocytes of Female Sheep

Prenatal testosterone (T)-treated female sheep manifest reduced adipocyte size and peripheral insulin resistance. The small adipocyte phenotype may reflect defects in adipogenesis and its steroidal machinery. To test whether prenatal T treatment from gestational days 30 to 90 alters the visceral adipose tissue (VAT) steroidal machinery and reduces adipocyte differentiation, we examined expression of the steroidogenic enzymes, steroid receptors, and adipocyte differentiation markers at fetal day 90 and postnatal ages 10 and 21 months. Because gestational T treatment increases fetal T and maternal insulin, the contributions of these were assessed by androgen receptor antagonist or insulin sensitizer cotreatment, either separately (at fetal day 90 and 21 months of age time points) or together (10 months of age). The effects on adipogenesis were assessed in the VAT-derived mesenchymal stem cells (AT-MSCs) from pre- and postpubertal time points to evaluate the effects of pubertal steroidal changes on adipogenesis. Our results show that VAT manifests potentially a predominant estrogenic intracrine milieu (increased aromatase and estrogen receptor α) and reduced differentiation markers at fetal day 90 and postnatal 21 months of age. These changes appear to involve both androgenic and metabolic pathways. Preliminary findings suggest that prenatal T treatment reduces adipogenesis, decreases expression of differentiation, and increases expression of commitment markers at both pre- and postpubertal time points. Together, these findings suggest that (1) increased commitment of AT-MSCs to adipocyte lineage and decreased differentiation to adipocytes may underlie the small adipocyte phenotype of prenatal T-treated females and (2) excess T-induced changes in steroidal machinery in the VAT likely participate in the programming/maintenance of this defect.

FGF19, FGF21, and an FGFR1/β-Klotho-Activating Antibody Act on the Nervous System to Regulate Body Weight and Glycemia

Despite the different physiologic functions of FGF19 and FGF21 as hormonal regulators of fed and fasted metabolism, their pharmacologic administration causes similar increases in energy expenditure, weight loss, and enhanced insulin sensitivity in obese animals. Here, in genetic loss-of-function studies of the shared co-receptor β-Klotho, we show that these pharmacologic effects are mediated through a common, tissue-specific pathway. Surprisingly, FGF19 and FGF21 actions in liver and adipose tissue are not required for their longer-term weight loss and glycemic effects. In contrast, β-Klotho in neurons is essential for both FGF19 and FGF21 to cause weight loss and lower glucose and insulin levels. We further show an FGF21 mimetic antibody that activates the FGF receptor 1/β-Klotho complex also requires neuronal β-Klotho for its metabolic effects. These studies highlight the importance of the nervous system in mediating the beneficial weight loss and glycemic effects of endocrine FGF drugs.

Myo-inositol administration positively effects ovulation induction and intrauterine insemination in patients with polycystic ovary syndrome: a prospective, controlled, randomized trial

Objectıve: The aim of the study is to investigate the effect of myo-inositol (MYO) on pregnancy rates of patients diagnosed with polycystic ovary syndrome (PCOS) who undergone controlled ovulation induction and intrauterine insemination (IUI).

METHODS

A total of 196 infertile patients diagnosed with PCOS and admitted to Dokuz Eylul University Faculty of Medicine were included in the study between March 2013 and May 2016. The patients in group 1 (n = 98) were given 4 g MYO and 400 μg folic acid before and during ovulation induction. The patients undergone controlled ovarian hyperstimulation (COH) with recombinant FSH and IUI. The patients in group 2 (n = 98), were given recombinant FSH directly and 400 μg folic acid. The primary outcome measure of this study was the clinical pregnancy rate.

RESULTS

In group 1, 9 patients conceived spontaneous pregnancy. During COH + IUI treatment three cycles were canceled in group 1 and 8 cycles in group 2. Total rFSH dose and cycle duration were significantly lower and clinical pregnancy rates were higher in group 1. The pregnancy rate for group 1 was %18.6 and for group 2 was %12.2. Conclusıons: This study shows that MYO should be considered in the treatment of infertile PCOS patients. MYO administration increases clinical pregnancy rates, lowers total rFSH dose and the duration of the ovulation induction.

Comparison of two insulin sensitizers, metformin and myo-inositol, in women with polycystic ovary syndrome (PCOS)

Insulin resistance (IR) plays a pivotal role in PCOS. Insulin-sensitizer agents such as metformin and inositols have been shown to improve the endocrine and metabolic aspects of PCOS. The purpose of this study is to compare their effects on the clinical and metabolic features of the women with PCOS. Fifty PCOS women with IR and/or hyperinsulinemia were randomized to treatment with metformin (1500 mg/day) or myo-inositol (4 g/day). IR was defined as HOMA-IR >2.5, while hyperinsulinemia was defined as a value of AUC for insulin after a glucose load over the cutoff of our laboratory obtained in normal women. The Matsusa Index has been calculated. The women have been evaluated for insulin secretion, BMI, menstrual cycle length, acne and hirsutism, at baseline and after 6 months of therapy. The results obtained in both groups were similar. The insulin sensitivity improved in both treatment groups. The BMI significantly decreased and the menstrual cycle was normalized in about 50% of the women. No significant changes in acne and hirsutism were observed. The two insulin-sensitizers, metformin and myo-inositol, show to be useful in PCOS women in lowering BMI and ameliorating insulin sensitivity, and improving menstrual cycle without significant differences between the two treatments.

Inositol's and other nutraceuticals' synergistic actions counteract insulin resistance in polycystic ovarian syndrome and metabolic syndrome: state-of-the-art and future perspectives

The incidence of metabolic syndrome (MetS), type II diabetes (T2D) and polycystic ovarian syndrome (PCOS) has been progressively increasing. Insulin resistance (InsR) seems to play a key role in a majority of phenotypes of these conditions, altering metabolic homeostasis, within muscle, liver, adipose and other tissues. Hyperinsulinemia is often associated with InsR and causes hormonal imbalances especially within ovaries and adrenals. Inositol is a polyalcohol, naturally occurring as nine stereoisomers, including D-chiro-inositol (DCI) and myo-inositol (MI), which have prominent roles in the metabolism of glucose and free fatty acids. MI and DCI have been classified as insulin-sensitizers and seem to adequately counteract several InsR-related metabolic alterations with a safe nutraceutical profile. Based on our analysis of selected studies that investigated MI and/or DCI, we conclude that supplementation with MI and/or DCI complement each other in their metabolic actions and act in synergy with other insulin sensitizing drugs and/or nutraceuticals. Nevertheless, considering the possible severe bias due to different methodologies across published studies, we conclude that there is a need for further studies on larger cohorts and with greater statistical power. These should further clarify outcomes and suitable therapeutic dosages of MI and DCI, possibly based on each patient's clinical status.

Developmental Programming: Prenatal Testosterone Excess and Insulin Signaling Disruptions in Female Sheep

Women with polycystic ovary syndrome often manifest insulin resistance. Using a sheep model of polycystic ovary syndrome-like phenotype, we explored the contribution of androgen and insulin in programming and maintaining disruptions in insulin signaling in metabolic tissues. Phosphorylation of AKT, ERK, GSK3beta, mTOR, and p70S6K was examined in the liver, muscle, and adipose tissue of control and prenatal testosterone (T)-, prenatal T plus androgen antagonist (flutamide)-, and prenatal T plus insulin sensitizer (rosiglitazone)-treated fetuses as well as 2-yr-old females. Insulin-stimulated phospho (p)-AKT was evaluated in control and prenatal T-, prenatal T plus postnatal flutamide-, and prenatal T plus postnatal rosiglitazone-treated females at 3 yr of age. GLUT4 expression was evaluated in the muscle at all time points. Prenatal T treatment increased mTOR, p-p70S6K, and p-GSK3beta levels in the fetal liver with both androgen antagonist and insulin sensitizer preventing the mTOR increase. Both interventions had partial effect in preventing the increase in p-GSK3beta. In the fetal muscle, prenatal T excess decreased p-GSK3beta and GLUT4. The decrease in muscle p-GSK3beta was partially prevented by insulin sensitizer cotreatment. Both interventions partially prevented the decrease in GLUT4. Prenatal T treatment had no effect on basal expression of any of the markers in 2-yr-old females. At 3 yr of age, prenatal T treatment prevented the insulin-stimulated increase in p-AKT in liver and muscle, but not in adipose tissue, and neither postnatal intervention restored p-AKT response to insulin stimulation. Our findings provide evidence that prenatal T excess changes insulin sensitivity in a tissue- and development-specific manner and that both androgens and insulin may be involved in the programming of these metabolic disruptions.

Hypoglycemic effect and mechanism of honokiol on type 2 diabetic mice

BACKGROUND

Honokiol is one of the main bioactive constituents of the traditional Chinese herbal drug Magnolia bark (Cortex Magnoliae officinalis, Hou Po). The aim of this study was to probe its anti-type 2 diabetes mellitus effects and the underlying mechanism.

METHODS

Type 2 diabetic mouse model was established by intraperitoneally injecting with streptozotocin. Fasting blood glucose, body weight, and lipid profile were measured. The subcutaneous adipose tissue, skeletal muscle, and liver were isolated as well as homogenized. The phospho-insulin receptor β-subunit (IRβ), IRβ, phospho-AKT, AKT, phospho-ERK1/2, ERK1/2, phosphotyrosine, and actin were examined by Western blot assay. Cell viability or cytotoxicity was analyzed by using MTT method. The inhibitory potencies of honokiol on the protein tyrosine phosphatase 1B (PTP1B) activity were performed in reaction buffer. Molecular docking and dynamic simulation were also analyzed.

RESULTS

In in vivo studies, oral treatment with 200 mg/kg honokiol for 8 weeks significantly decreases the fasting blood glucose in type 2 diabetes mellitus mice. The phosphorylations of the IRβ and the downstream insulin signaling factors including AKT and ERK1/2 significantly increase in adipose, skeletal muscle, and liver tissue of the honokiol-treated mice. Moreover, honokiol enhanced the insulin-stimulated phosphorylations of IRβ, AKT, and ERK1/2 in a dose-dependent manner in C2C12 myotube cells. Meanwhile, honokiol enhanced insulin-stimulated GLUT4 translocation. Importantly, honokiol exhibited reversible competitive inhibitory activity against PTP1B with good selectivity in vitro and in vivo. Furthermore, using molecular docking and dynamic simulation approaches, we determined the potential binding mode of honokiol to PTP1B at an atomic level.

CONCLUSION

These findings indicated the hypoglycemic effects of honokiol and its mechanism that honokiol improved the insulin sensitivity by targeting PTP1B. Therefore, our study may highlight honokiol as a promising insulin sensitizer for the therapy of type 2 diabetes.

Metabolic profile of Diane-35 versus Diane-35 plus metformin in Chinese PCOS women under standardized life-style changes

OBJECTIVE

The aim of this study was to compare the effect of Diane-35 versus Diane-35 + metformin on metabolic parameters in Chinese PCOS patients.

METHODS

Patients getting individualized life-style modification were treated with Diane-35. Metformin was added according to its indication. Within a 3-month prospective study, metabolic parameters were assessed.

RESULTS

Eighty-three patients were recruited, 45 using Diane-35 and 38 Diane-35 plus metformin. Using Diane-35, triglycerides (TG) (p < 0.05) and tendencially (p < 0.1) total cholesterol (TC) increased, but significant positive effects on BMI, high-density lipoprotein cholesterol (HDL-C), and HDL-C/TC ratio were observed. Other lipids and the parameters for glucose metabolism remained unchanged. In the combination group, no negative effect on TG and TC was seen, other lipid fractions improved, as well as BMI, % body fat, and all parameters for glucose metabolism like fasting plasma glucose (FPG), fasting insulin, HOMA-insulin-resistance index, and insulin sensitivity index (ISI), whereby the beneficial effect of metformin got significance compared with Diane-35 for BMI, FPG, and ISI.

CONCLUSION

With the exception of increasing triglycerides, Diane-35 had no relevant negative effects in the metabolic system. It does not negatively impact the beneficial effects of metformin in lipids and glucose metabolism. Diane-35 plus metformin is effective in improving the metabolic profile of Chinese PCOS patients.

Saroglitazar, a novel PPARα/γ agonist with predominant PPARα activity, shows lipid-lowering and insulin-sensitizing effects in preclinical models

Saroglitazar is a novel nonthiazolidinediones (TZD) and nonfibric acid derivative designed to act as dual regulator of lipids and glucose metabolism by activating peroxisome proliferator-activated receptors (PPAR). These studies evaluate the efficacy and safety profile of Saroglitazar in preclinical in vitro and in vivo models. The EC₅₀ values of Saroglitazar assessed in HepG2 cells using PPAR transactivation assay for hPPARα and hPPARγ were 0.65 pmol/L and 3 nmol/L, respectively. In db/db mice, 12-day treatment with Saroglitazar (0.01–3 mg/kg per day, orally) caused dose-dependent reductions in serum triglycerides (TG), free fatty acids (FFA), and glucose. The ED₅₀ for these effects was found to be 0.05, 0.19, and 0.19 mg/kg, respectively with highly significant (91%) reduction in serum insulin and AUC-glucose following oral glucose administration (59%) at 1 mg/kg dose. Significant reduction in serum TG (upto 90%) was also observed in Zucker fa/fa rats, Swiss albino mice, and in high fat -high cholesterol (HF-HC)-fed Golden Syrian hamsters. LDL cholesterol was significantly lowered in hApoB100/hCETP double transgenic mice and HF-HC diet fed Golden Syrian Hamsters. Hyperinsulinemic-Euglycemic clamp study in Zucker fa/fa rats demonstrated potent insulin-sensitizing activity. Saroglitazar also showed a significant decrease in SBP (22 mmHg) and increase (62.1%) in serum adiponectin levels in Zucker fa/fa rats. A 90-day repeated dose comparative study in Wistar rats and marmosets confirmed efficacy (TG lowering) potential of Saroglitazar and has indicated low risk of PPAR-associated side effects in humans. Based on efficacy and safety profile, Saroglitazar appears to have good potential as novel therapeutic agent for treatment of dyslipidemia and diabetes.

Thiazolidinediones and the promise of insulin sensitization in type 2 diabetes

Type 2 diabetes is caused by insulin resistance coupled with an inability to produce enough insulin to control blood glucose, and thiazolidinediones (TZDs) are the only current antidiabetic agents that function primarily by increasing insulin sensitivity. However, despite clear benefits in glycemic control, this class of drugs has recently fallen into disuse due to concerns over side effects and adverse events. Here we review the clinical data and attempt to balance the benefits and risks of TZD therapy. We also examine potential mechanisms of action for the beneficial and harmful effects of TZDs, mainly via agonism of the nuclear receptor PPARγ. Based on critical appraisal of both preclinical and clinical studies, we discuss the prospect of harnessing the insulin sensitizing effects of PPARγ for more effective, safe, and potentially personalized treatments of type 2 diabetes.

Non-alcoholic fatty liver disease in patients with diabetes mellitus

Non-alcoholic fatty liver disease (NAFLD), including the disease stages steatosis and non-alcoholic steatohepatitis, is the most common cause of chronic liver disease worldwide and linked to the epidemic of diabetes mellitus and obesity. It is characterized by a high cardiovascular and liver-related mortality and expected to be the leading cause for liver transplantation in the near future. This review summarizes recent progress made in our understanding of the disease pathogenesis and the clinical management of patients with NAFLD. Strategies to manage diabetes mellitus will be evaluated in terms of their effectiveness in treating patients with NAFLD and novel pharmacological targets capable to treat diabetes mellitus and NAFLD will be highlighted.

Modulatory role of D-chiro-inositol (DCI) on LH and insulin secretion in obese PCOS patients

Polycystic ovary syndrome (PCOS) is a common endocrine condition that affects fertility through oligo-ovulation, hyperandrogenism and polycystic morphology of the ovaries. Since it has been demonstrated a high incidence of insulin resistance in PCOS patients, our study aimed to evaluate the efficacy of the integrative treatment with D-chiro-inositol (DCI) (500 mg die, per os, for 12 weeks) on hormonal parameters and insulin sensitivity in a group of overweight/obese PCOS patients (body mass index; BMI > 26). After the treatment, interval several endocrine parameters improved (luteinizing hormone [LH], LH/follicle stimulating hormone [FSH], androstenedione and insulin), insulin response to oral glucose tolerance test reported the significant improvement of insulin sensitivity as well as the gonadotropin-releasing hormone (GnRH)-induced (10 µg, in bolus) LH response. BMI decreased, though no lifestyle modification was requested. When data were analyzed according to the presence or absence of first-grade diabetic relatives, PCOS patients with diabetic relatives showed greater improvement after DCI administration. In conclusion DCI administration is effective in restoring better insulin sensitivity and an improved hormonal pattern in obese hyperinsulinemic PCOS patients, in particular, in hyperinsulinemic PCOS patients who have diabetic relatives.

Changes in physical performance in older women according to presence and treatment of diabetes mellitus

OBJECTIVES

To determine whether older women with diabetes mellitus have a greater longitudinal decline in physical performance than those without and whether any decline differs according to insulin sensitizer use.

DESIGN

Prospective cohort study.

SETTING

Baltimore, Maryland; Minneapolis, Minnesota; Portland, Oregon; and the Monongahela, Pennsylvania.

PARTICIPANTS

Community-dwelling women (mean age 78.5 ± 3.6) enrolled in the Study of Osteoporotic Fractures in 1997-98 and restudied 4.9 ± 0.6 years later (N = 2,864).

MEASUREMENTS

Women were categorized as having no diabetes mellitus (n = 2,680) or having diabetes mellitus (n = 184). A prescription medication inventory was used to determine use of insulin sensitizers (metformin and thiazolidinedione). The outcomes were longitudinal changes in physical performance measures, including grip strength, usual walk speed, and rapid walk speed.

RESULTS

Estimates from fully adjusted models showed that women with diabetes mellitus had greater declines in usual walk speed (-0.16 m/s, 95% confidence interval (CI) = -0.19 to -0.14) and rapid walk speed (-0.21 m/s, 95% CI = -0.24 to -0.17) than those without (usual walk speed -0.11 m/s, 95% CI = -0.12 to -0.11, P < .001; rapid walk speed -0.15 m/s, 95% CI = -0.16 to -0.14; P = .005). Women with diabetes mellitus taking insulin sensitizers had less decline in usual walk speed than those not taking insulin sensitizers (P < .001). Declines in grip strength did not differ significantly by diabetes mellitus status or insulin sensitizer use.

CONCLUSION

Older women with diabetes mellitus have a greater decline in walk speed, but not grip strength, than older women without diabetes mellitus. Clinical studies in older adults to determine whether diabetes mellitus treatments such as insulin sensitizers can prevent loss in walk speed and mobility are needed.

Why do anti-inflammatory therapies fail to improve insulin sensitivity?

Chronic inflammation occurs in obese conditions in both humans and animals. It also contributes to the pathogenesis of type 2 diabetes (T2D) through insulin resistance, a status in which the body loses its ability to respond to insulin. Inflammation impairs insulin signaling through the functional inhibition of IRS-1 and PPARγ. Insulin sensitizers (such as rosiglitazone and pioglitazone) inhibit inflammation while improving insulin sensitivity. Therefore, anti-inflammatory agents have been suggested as a treatment strategy for insulin resistance. This strategy has been tested in laboratory studies and clinical trials for more than 10 years; however, no significant progress has been made in any of the model systems. This status has led us to re-evaluate the biological significance of chronic inflammation in obesity. Recent studies have consistently asserted that obesity-associated inflammation helps to maintain insulin sensitivity. Inflammation stimulates local adipose tissue remodeling and promotes systemic energy expenditure. We propose that these beneficial activities of inflammation provide an underlying mechanism for the failure of anti-inflammatory therapy in the treatment of insulin resistance. Current literature will be reviewed in this article to present evidence that supports this viewpoint.

Insulin tolerance test predicts the effectiveness of insulin sensitizers in japanese type 2 diabetic patients

INTRODUCTION

The purpose of this study was to assess the efficacy of the insulin tolerance test (ITT) in predicting the effectiveness of insulin sensitizers in type 2 diabetic patients.

METHODS

We retrospectively reviewed 360 consecutive patients with type 2 diabetes admitted to Osaka University Hospital, Japan. In 163 of these hospitalized patients, insulin resistance was evaluated by the ITT after their blood glucose level was ameliorated. We then analyzed the association between their clinical characteristics and their glycemic control 6 months after discharge.

RESULTS

The rate constant for plasma glucose disappearance, K (ITT), was negatively correlated with body mass index (BMI), waist circumference (WC), and visceral fat area (VFA). The median value of K (ITT) was 1.56 (%/min). In the K (ITT) > 1.56 group (n=81), hemoglobin A(1c) (HbA(1c)) significantly increased in both patients treated with insulin sensitizers (n=10) and patients not treated with insulin sensitizers (n=71). In the K (ITT) ≤1.56 group (n=82), HbA(1c) significantly increased in patients not treated with insulin sensitizers (n=60); however, it was maintained well in the patients treated with insulin sensitizers (n=22). When the patients were divided and analyzed according to the median values of BMI, WC, or VFA, the glycemic control change was not different between the two groups with insulin sensitizers for each parameter.

CONCLUSION

Insulin sensitizers were effective in type 2 diabetic patients with high insulin resistance estimated by the ITT. The ITT could be useful to predict the effectiveness of insulin sensitizers.

Role of central nervous system insulin resistance in fetal alcohol spectrum disorders

Fetal alcohol spectrum disorder (FASD) is the most common preventable cause of mental retardation in the USA. Ethanol impairs neuronal survival and function by two major mechanisms: 1) it inhibits insulin signaling required for viability, metabolism, synapse formation, and acetylcholine production; and 2) it functions as a neurotoxicant, causing oxidative stress, DNA damage and mitochondrial dysfunction. Ethanol inhibition of insulin signaling is mediated at the insulin receptor (IR) level and caused by both impaired receptor binding and increased activation of phosphatases that reverse IR tyrosine kinase activity. As a result, insulin activation of PI3K-Akt, which mediates neuronal survival, motility, energy metabolism, and plasticity, is impaired. The neurotoxicant effects of ethanol promote DNA damage, which could contribute to mitochondrial dysfunction and oxidative stress. Therefore, chronic in utero ethanol exposure produces a dual state of CNS insulin resistance and oxidative stress, which we postulate plays a major role in ethanol neurobehavioral teratogenesis. We propose that many of the prominent adverse effects of chronic prenatal exposure to ethanol on CNS development and function may be prevented or reduced by treatment with peroxisome-proliferated activated receptor (PPAR) agonists which enhance insulin sensitivity by increasing expression and function of insulin-responsive genes, and reducing cellular oxidative stress.

Insulin sensitizers for women with polycystic ovarian syndrome

Polycystic ovarian syndrome (PCOS) is the most frequent endocrine disorder and most common cause of anovulation in women of reproductive age. It is a heterogeneous disorder, characterized by excess androgen, ovulatory dysfunction and/or polycystic ovaries. The syndrome is known for its association with several reproductive problems, including infertility and obstetric adverse effects. In addition, significant long-term health problems have been strongly linked to PCOS, with women suffering from the disorder having a significantly higher risk of diabetes, cardiovascular risk and some types of cancer, such as endometrial cancer. Although its etiology is unknown, insulin resistance is believed to play a pivotal role in its pathophysiology, with insulin sensitizers found to provide an exciting option in managing health problems associated with PCOS. Almost a decade ago, we proposed a non-insulin-sensitizing mechanism of action for insulin sensitizers through their effect on steroidogenesis. Accumulating evidence supported such an assumption, with solid evidence for a modulating effect on steroidogenesis by metformin and glitazones in the ovaries, adrenal glands and fat cells. Furthermore, other exciting positive roles for insulin sensitizers, in particular glitazones, have been reported at the level of endothelial function. Studying the value of insulin sensitizers in preventing long-term health problems in women with PCOS is still in the stage of infancy.

Insulin sensitizing pharmacology of thiazolidinediones correlates with mitochondrial gene expression rather than activation of PPAR gamma

Insulin sensitizing thiazolidinediones (TZDs) are generally considered to work as agonists for the nuclear receptor peroxisome proliferative activated receptor-gamma (PPAR gamma). However, TZDs also have acute, non-genomic metabolic effects and it is unclear which actions are responsible for the beneficial pharmacology of these compounds. We have taken advantage of an analog, based on the metabolism of pioglitazone, which has much reduced ability to activate PPAR gamma. This analog (PNU-91325) was compared to rosiglitazone, the most potent PPAR gamma activator approved for human use, in a variety of studies both in vitro and in vivo. The data demonstrate that PNU-91325 is indeed much less effective than rosiglitazone at activating PPAR gamma both in vitro and in vivo. In contrast, both compounds bound similarly to a mitochondrial binding site and acutely activated PI-3 kinase-directed phosphorylation of AKT, an action that was not affected by elimination of PPAR gamma activation. The two compounds were then compared in vivo in both normal C57 mice and diabetic KKAy mice to determine whether their pharmacology correlated with biomarkers of PPAR gamma activation or with the expression of other gene transcripts. As expected from previous studies, both compounds improved insulin sensitivity in the diabetic mice, and this occurred in spite of the fact that there was little increase in expression of the classic PPAR gamma target biomarker adipocyte binding protein-2 (aP2) with PNU-91325 under these conditions. An examination of transcriptional profiling of key target tissues from mice treated for one week with both compounds demonstrated that the relative pharmacology of the two thiazolidinediones correlated best with an increased expression of an array of mitochondrial proteins and with expression of PPAR gamma coactivator 1-alpha (PGC1 alpha), the master regulator of mitochondrial biogenesis. Thus, important pharmacology of the insulin sensitizing TZDs may involve acute actions, perhaps on the mitochondria, that are independent of direct activation of the nuclear receptor PPAR gamma. These findings suggest a potential alternative route to the discovery of novel insulin sensitizing drugs.

Ragaglitazar: a novel PPAR alpha PPAR gamma agonist with potent lipid-lowering and insulin-sensitizing efficacy in animal models

Ragaglitazar [(-) DRF 2725; NNC 61-0029] is a coligand of PPARalpha and PPARgamma. In ob/ob mice, ragaglitazar showed significant reduction in plasma glucose, triglyceride and insulin (ED50 values <0.03, 6.1 and <0.1 mg kg-1). These effects are three-fold better than rosiglitazone and KRP-297. In Zucker fa/fa rats, ragaglitazar showed dose-dependent reduction in triglyceride and insulin, hepatic triglyceride secretion and triglyceride clearance kinetics (maximum of 74, 53, 32 and 50% at 3 mg kg-1), which are better than rosiglitazone and KRP-297. In a high-fat-fed hyperlipidaemic rat model, the compound showed an ED50 of 3.95, 3.78 mg kg-1 for triglyceride and cholesterol lowering, and 0.29 mg kg-1 for HDL-C increase. It also showed improvement in clearance of plasma triglyceride and hepatic triglyceride secretion rate. All these effects are 3-10-fold better than fenofibrate and KRP-297. Ragaglitazar treatment showed significant reduction in plasma Apo B and Apo CIII levels, and increase in liver CPT1 and CAT activity and ACO mRNA. Significant increase of both liver and fat LPL activity and fat aP2 mRNA was also observed. In a high-fat-fed hamster model, ragaglitazar at 1 mg kg-1 showed 83 and 61% reduction in triglyceride and total cholesterol, and also 17% reduction in fat feed-induced body weight increase. In these hyperlipidaemic animal models, PPARgamma ligands failed to show any significant efficacy. Taken together, ragaglitazar shows better insulin-sensitizing and lipid-lowering potential, as compared to the standard compounds.