The effect of pioglitazone on the liver: role of adiponectin

Exploring the potential of drug repurposing for liver diseases: A comprehensive study

Drug repurposing involves the investigation of existing drugs for new indications. It offers a great opportunity to quickly identify a new drug candidate at a lower cost than novel discovery and development. Despite the importance and potential role of drug repurposing, there is no specific definition that healthcare providers and the World Health Organization credit. Unfortunately, many similar and interchangeable concepts are being used in the literature, making it difficult to collect and analyze uniform data on repurposed drugs. This research was conducted based on understanding general criteria for drug repurposing, concentrating on liver diseases. Many drugs have been investigated for their effect on liver diseases even though they were originally approved (or on their way to being approved) for other diseases. Some of the hypotheses for drug repurposing were first captured from the literature and then processed further to test the hypothesis. Recently, with the revolution in bioinformatics techniques, scientists have started to use drug libraries and computer systems that can analyze hundreds of drugs to give a short list of candidates to be analyzed pharmacologically. However, this study revealed that drug repurposing is a potential aid that may help deal with liver diseases. It provides available or under-investigated drugs that could help treat hepatitis, liver cirrhosis, Wilson disease, liver cancer, and fatty liver. However, many further studies are needed to ensure the efficacy of these drugs on a large scale.

The Role of Organokines in Obesity and Type 2 Diabetes and Their Functions as Molecular Transducers of Nutrition and Exercise

Maintaining systemic homeostasis requires the coordination of different organs and tissues in the body. Our bodies rely on complex inter-organ communications to adapt to perturbations or changes in metabolic homeostasis. Consequently, the liver, muscle, and adipose tissues produce and secrete specific organokines such as hepatokines, myokines, and adipokines in response to nutritional and environmental stimuli. Emerging evidence suggests that dysregulation of the interplay of organokines between organs is associated with the pathophysiology of obesity and type 2 diabetes (T2D). Strategies aimed at remodeling organokines may be effective therapeutic interventions. Diet modification and exercise have been established as the first-line therapeutic intervention to prevent or treat metabolic diseases. This review summarizes the current knowledge on organokines secreted by the liver, muscle, and adipose tissues in obesity and T2D. Additionally, we highlighted the effects of diet/nutrition and exercise on the remodeling of organokines in obesity and T2D. Specifically, we investigated the ameliorative effects of caloric restriction, selective nutrients including ω3 PUFAs, selenium, vitamins, and metabolites of vitamins, and acute/chronic exercise on the dysregulation of organokines in obesity and T2D. Finally, this study dissected the underlying molecular mechanisms by which nutrition and exercise regulate the expression and secretion of organokines in specific tissues.

Pioglitazone reduces epicardial fat and improves diastolic function in patients with type 2 diabetes

AIMS

To examine the effect of pioglitazone on epicardial (EAT) and paracardial adipose tissue (PAT) and measures of diastolic function and insulin sensitivity in patients with type 2 diabetes mellitus (T2DM).

METHODS

Twelve patients with T2DM without clinically manifest cardiovascular disease and 12 subjects with normal glucose tolerance (NGT) underwent cardiac magnetic resonance imaging to quantitate EAT and PAT and diastolic function before and after pioglitazone treatment for 24 weeks. Whole-body insulin sensitivity was measured with a euglycaemic insulin clamp and the Matsuda Index (oral glucose tolerance test).

RESULTS

Pioglitazone reduced glycated haemoglobin by 0.9% (P < 0.05), increased HDL cholesterol by 7% (P < 0.05), reduced triacylglycerol by 42% (P < 0.01) and increased whole-body insulin-stimulated glucose uptake by 71% (P < 0.01) and Matsuda Index by 100% (P < 0.01). In patients with T2DM, EAT (P < 0.01) and PAT (P < 0.01) areas were greater compared with subjects with NGT, and decreased by 9% (P = 0.03) and 9% (P = 0.09), respectively, after pioglitazone treatment. Transmitral E/A flow rate and peak left ventricular flow rate (PLVFR) were reduced in T2DM versus NGT (P < 0.01) and increased following pioglitazone treatment (P < 0.01-0.05). At baseline normalized PLVFR inversely correlated with EAT (r = -0.45, P = 0.03) but not PAT (r = -0.29, P = 0.16). E/A was significantly and inversely correlated with EAT (r = -0.55, P = 0.006) and PAT (r = -0.40, P = 0.05). EAT and PAT were inversely correlated with whole-body insulin-stimulated glucose uptake (r = -0.68, P < 0.001) and with Matsuda Index (r = 0.99, P < 0.002).

CONCLUSION

Pioglitazone reduced EAT and PAT areas and improved left ventricular (LV) diastolic function in T2DM. EAT and PAT are inversely correlated (PAT less strongly) with LV diastolic function and both EAT and PAT are inversely correlated with measures of insulin sensitivity.

Targeting the liver in dementia and cognitive impairment: Dietary macronutrients and diabetic therapeutics

Many people living with dementia and cognitive impairment have dysfunctional mitochondrial and insulin-glucose metabolism resembling type 2 diabetes mellitus and old age. Evidence from human trials shows that nutritional interventions and anti-diabetic medicines that target nutrient-sensing pathways overcome these deficits in glucose and energy metabolism and can improve cognition and/or reduce symptoms of dementia. The liver is the main organ that mediates the systemic effects of diets and many diabetic medicines; therefore, it is an intermediate target for such dementia interventions. A challenge is the efficacy of these treatments in older age. Solutions include the targeted hepatic delivery of diabetic medicines using nanotechnologies and titration of macronutrients to optimize hepatic energy metabolism.

Measuring and estimating insulin resistance in clinical and research settings

The article discusses how to measure insulin resistance in muscle, liver, and adipose tissue in human participants. The most frequently used methodologies to evaluate insulin resistance are described in detail starting from the gold standard, that is, the euglycemic hyperinsulinemic clamp, to the intravenous glucose tolerance test, surrogate indices based on fasting measurements, or dynamic tests (such as oral glucose or mixed meal tolerance tests). The accuracy, precision, and reproducibility of the tests as well as cutoff values are reported.

Liver Protective Effect of Fenofibrate in NASH/NAFLD Animal Models

Nonalcoholic fatty liver disease (NAFLD) is initiated by excessive fat buildup in the liver, affecting around 35% of the world population. Various circumstances contribute to the initiation and progression of NAFLD, and it encompasses a wide range of disorders, from simple steatosis to nonalcoholic steatohepatitis (NASH), cirrhosis, and liver cancer. Although several treatments have been proposed, there is no definitive cure for NAFLD. In recent decades, several medications related to other metabolic disorders have been evaluated in preclinical studies and in clinical trials due to the correlation of NAFLD with other metabolic diseases. Fenofibrate is a fibrate drug approved for dyslipidemia that could be used for modulation of hepatic fat accumulation, targeting peroxisome proliferator-activator receptors, and de novo lipogenesis. This drug offers potential therapeutic efficacy for NAFLD due to its capacity to decrease the accumulation of hepatic lipids, as well as its antioxidant, anti-inflammatory, and antifibrotic properties. To better elucidate the pathophysiological processes underlying NAFLD, as well as to test therapeutic agents/interventions, experimental animal models have been extensively used. In this article, we first reviewed experimental animal models that have been used to evaluate the protective effects of fenofibrate on NAFLD/NASH. Next, we investigated the impact of fenofibrate on the hepatic microcirculation in NAFLD and then summarized the beneficial effects of fenofibrate, as compared to other drugs, for the treatment of NAFLD. Lastly, we discuss possible adverse side effects of fenofibrate on the liver.

Walnut Meal Extracts Rich In Polyphenols Mitigate Insulin Resistance and Modulate Gut Microbiota in High Fat Diet-Fed Rats

Walnut kernel is a traditional Chinese herb recorded in the Chinese Pharmacopoeia with the efficacies of invigorating kidney, tonifying lung, and relaxing bowel. However, the potential mechanisms were unclear. This article aims to uncover the interdict mechanisms of walnut meal extracts (WMP) on high-fat diet (HFD) induced metabolic disorders in rats and reveal how the WMP benefits are associated with changes in the intestinal flora. Sprague-Dawley (SD) rats were fed a standard chow diet or an HFD for 18 weeks. After 6 weeks, the HFD rats were supplemented with 750 mg WMP/kg body weight or the vehicle for 12 weeks. The structure of gut microbiota was assessed by analyzing 16S rDNA sequences. WMP suppressed the weight gain and visceral obesity. WMP treatment also improved lipid profiles and increased antioxidative activities. WMP fully reversed hepatic steatosis with the upregulation of adipocytokines involved in lipid catabolism (e.g., adiponectin, PPAR-γ, visfatin, CEBPα) and the increased activities of lipoprotein lipase and hormone-sensitive lipase, which were associated with glucose tolerance improvement and insulin resistance (IR) mitigation. As revealed by 16S rDNA sequencing, WMP restored the diversity of intestinal flora reduced by HFD. WMP dramatically reduced the abundance of Gram-negative bacteria, especially Fusobacterium varium and Bacteroides vulgatus, and sharply increased the abundance of Lactobacillus animalis decreased by HFD. Our findings demonstrated that WMP suppressed the weight gain and adiposity in HFD-fed rats and fully reversed HFD induced IR and hepatic steatosis while dramatically reducing the abundance of Fusobacteriaceae and Enterobacteriaceae, underscoring the gut-liver axis as a primary target of walnut polyphenols.

Combination therapy with pioglitazone/exenatide/metformin reduces the prevalence of hepatic fibrosis and steatosis: The efficacy and durability of initial combination therapy for type 2 diabetes (EDICT)

AIM

To compare the efficacy of triple therapy (metformin/exenatide/pioglitazone) versus stepwise conventional therapy (metformin → glipizide → glargine insulin) on liver fat content and hepatic fibrosis in newly diagnosed, drug-naïve patients with type 2 diabetes.

METHODS

Sixty-eight patients completed the 6-year follow-up and had an end-of-study (EOS) FibroScan to provide measures of steatosis (controlled attenuation parameter [CAP] in dB/m) and fibrosis (liver stiffness measurement [LSM] in kPa); 59 had magnetic resonance imaging-proton density fat fraction (MRI-PDFF) to measure liver fat.

RESULTS

At EOS, HbA1c was 6.8% and 6.0% in triple and conventional therapy groups, respectively (P = .0006). Twenty-seven of 39 subjects (69%) receiving conventional therapy had grade 2/3 steatosis (CAP, FibroScan) versus nine of 29 (31%) in triple therapy (P = .0003). Ten of 39 (26%) subjects receiving conventional therapy had stage 3/4 fibrosis (LSM) versus two of 29 (7%) in triple therapy (P = .04). Conventional therapy subjects had more liver fat (MRI-PDFF) than triple therapy (12.9% vs. 8.8%, P = .03). The severity of steatosis (CAP) (r = 0.42, P < .001) and fibrosis (LSM) (r = -0.48, P < .001) correlated inversely with the Matsuda Index of insulin sensitivity, but not with percentage body fat. Aspartate aminotransferase (AST) to Platelet Ratio Index (APRI), non-alcoholic fatty liver disease fibrosis score (NFS), plasma AST, and alanine aminotransferase (ALT) all decreased significantly with triple therapy, but only the decrease in plasma AST and ALT correlated with the severity of steatosis and fibrosis at EOS.

CONCLUSIONS

At EOS, subjects with type 2 diabetes treated with triple therapy had less hepatic steatosis and fibrosis versus conventional therapy; the severity of hepatic steatosis and fibrosis were both strongly and inversely correlated with insulin resistance; and changes in liver fibrosis scores (APRI, NFS, Fibrosis-4, and AST/ALT ratio) have limited value in predicting response to therapy.

PPAR-Targeted Therapies in the Treatment of Non-Alcoholic Fatty Liver Disease in Diabetic Patients

Peroxisome proliferator-activated receptors (PPAR), ligand-activated transcription factors of the nuclear hormone receptor superfamily, have been identified as key metabolic regulators in the liver, skeletal muscle, and adipose tissue, among others. As a leading cause of liver disease worldwide, non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) cause a significant burden worldwide and therapeutic strategies are needed. This review provides an overview of the evidence on PPAR-targeted treatment of NAFLD and NASH in individuals with type 2 diabetes mellitus. We considered current evidence from clinical trials and observational studies as well as the impact of treatment on comorbid metabolic conditions such as obesity, dyslipidemia, and cardiovascular disease. Future areas of research, such as possible sexually dimorphic effects of PPAR-targeted therapies, are briefly reviewed.

A global view of the interplay between non-alcoholic fatty liver disease and diabetes

Non-alcoholic fatty liver disease (NAFLD) has become an epidemic, much like other non-communicable diseases (NCDs), such as cancer, obesity, diabetes, and cardiovascular disease. The pathophysiology of NAFLD, particularly involving insulin resistance and subclinical inflammation, is not only closely linked to that of those NCDs but also to a severe course of the communicable disease COVID-19. Genetics alone cannot explain the large increase in the prevalence of NAFLD during the past 2 decades and the increase that is projected for the next decades. Impairment of glucose and lipid metabolic pathways, which has been propelled by the worldwide increase in the prevalence of obesity and type 2 diabetes, is most likely behind the increase in people with NAFLD. As the prevalence of NAFLD varies among subgroups of patients with diabetes and prediabetes identified by cluster analyses, stratification of people with diabetes and prediabetes by major pathological mechanistic pathways might improve the diagnosis of NAFLD and prediction of its progression. In this Review, we aim to understand how diabetes can affect the development of hepatic steatosis and its progression to advanced liver damage. First, we emphasise the extent to which NAFLD and diabetes jointly occur worldwide. Second, we address the major mechanisms that are involved in the pathogenesis of NAFLD and type 2 diabetes, and we discuss whether these mechanisms place NAFLD in an important position to better understand the pathogenesis of NCDs and communicable diseases, such as COVID-19. Third, we address whether this knowledge can be used for personalised treatment of NAFLD in the future. Finally, we discuss the current treatment strategies for people with type 2 diabetes and their effectiveness in treating the spectrum of hepatic diseases from simple steatosis to non-alcoholic steatohepatitis and hepatic fibrosis.

PPAR-γ-induced changes in visceral fat and adiponectin levels are associated with improvement of steatohepatitis in patients with NASH

BACKGROUND AND AIMS

Peroxisome proliferator-activated receptor (PPAR)-γ agonists decrease hepatic/visceral fat (VF) and improve necroinflammation despite subcutaneous (SC) fat weight-gain. Understanding the impact of changes in VF, VF-to-SC fat distribution (VF/SC) and adiponectin (ADPN) levels in relation to histological improvement after weight-loss or pioglitazone is relevant as novel PPAR-γ agonists are being developed for treating non-alcoholic steatohepatitis (NASH).

METHODS

Fifty-five patients with NASH received a -500 kcal/d hypocaloric diet and were randomized (double-blind) to pioglitazone (45 mg/d) or placebo for 6-months. Before and after treatment patients underwent a liver biopsy and measurement of hepatic/peripheral glucose fluxes, hepatic/adipose tissue-IR and, in 35 patients, hepatic and VF/SC-fat was measured by magnetic resonance spectroscopy/imaging. Data were examined by multivariable statistical analyses combined with machine-learning techniques (partial least square discriminant analysis [PLS-DA]).

RESULTS

Both pioglitazone (despite weight-gain) and placebo (if weight-loss) reduced steatosis but only pioglitazone ameliorated necroinflammation. Using machine-learning PLS-DA showed that the treatment differences induced by a PPAR-γ agonist vs placebo on metabolic variables and liver histology could be best explained by the increase in ADPN and a decrease in VF/SC, and to a lesser degree, improvement in oral glucose tolerance test-glucose concentrations and ALT. Decrease in steatosis and disease activity score (ballooning plus lobular inflammation) kept a close relationship with an increase in ADPN (r = -.71 and r = -.44, P < .007, respectively) and reduction in VF/SC fat (r = .41 and r = .37, P < .03 respectively).

CONCLUSIONS

Reduction in VF and improved VF/SC-distribution, combined with an increase in ADPN, mediate the histological benefits of PPAR-γ action, highlighting the central role of fat metabolism and its distribution on steatohepatitis disease activity in patients with NASH.

PPARs as Metabolic Sensors and Therapeutic Targets in Liver Diseases

Carbohydrates and lipids are two components of the diet that provide the necessary energy to carry out various physiological processes to help maintain homeostasis in the body. However, when the metabolism of both biomolecules is altered, development of various liver diseases takes place; such as metabolic-associated fatty liver diseases (MAFLD), hepatitis B and C virus infections, alcoholic liver disease (ALD), and in more severe cases, hepatocelular carcinoma (HCC). On the other hand, PPARs are a family of ligand-dependent transcription factors with an important role in the regulation of metabolic processes to hepatic level as well as in other organs. After interaction with specific ligands, PPARs are translocated to the nucleus, undergoing structural changes to regulate gene transcription involved in lipid metabolism, adipogenesis, inflammation and metabolic homeostasis. This review aims to provide updated data about PPARs’ critical role in liver metabolic regulation, and their involvement triggering the genesis of several liver diseases. Information is provided about their molecular characteristics, cell signal pathways, and the main pharmacological therapies that modulate their function, currently engaged in the clinic scenario, or in pharmacological development.

Pioglitazone even at low dosage improves NAFLD in type 2 diabetes: clinical and pathophysiological insights from a subgroup of the TOSCA.IT randomised trial

AIMS

Non-Alcoholic Fatty Liver Disease (NAFLD) and type 2 diabetes (T2D) share pathophysiological mechanisms and possible therapeutic strategies. We evaluated the effects of 1-year treatment with pioglitazone or sulphonylureas on indirect indices of NAFLD in people with T2D and the role of insulin-resistance and glucotoxicity in determining these effects.

METHODS

Patients with T2D (n = 195) aged 50-75 years, poorly controlled with metformin 2 g/day, were randomly allocated to add-on pioglitazone (n = 98) or sulphonylureas (n = 97) within the TOSCA.IT trial. Plasma insulin, glucose, and liver enzymes were measured at baseline and after 1-year. Indirect indices of NAFLD (Liver Fat Equation [LFE], Hepatic Steatosis Index [HSI], and Index of NASH [ION]), and insulin resistance (HOMA-IR, Visceral Adiposity Index [VAI] and adipose tissue Insulin Resistance [ADIPO-IR]) were calculated.

RESULTS

Indices of NAFLD improved after pioglitazone, but not after sulphonylureas; differences between changes (1-year minus baseline) were respectively: -1.76 ± 3.84 vs. 0.28 ± 3.75 for LFE; -1.35 ± 2.78 vs. -0.27 ± 2.63 for HSI; -9.75 ± 43 vs. 3.24 ± 31 for ION; p < 0.05 for all. Indices of insulin resistance decreased after pioglitazone, but not after sulphonylureas: -0.95 ± 4.57 vs. 0.37 ± 3.34 for HOMA-IR, p = 0.032; -1.25 ± 4.11 vs. 1.36 ± 5.43 for ADIPO-IR, p = 0.001; -0.53 ± 1.88 vs. 0.03 ± 2.36 for VAI, p = 0.074. Changes in NAFLD indices were similar with different doses of pioglitazone (15, 30, or 45 mg/day), and were independent of blood glucose control.

CONCLUSIONS

One-year treatment with pioglitazone even at low dosage significantly improved liver steatosis and inflammation, systemic and adipose tissue insulin resistance in patients with T2D. The beneficial effects of pioglitazone on NAFLD were independent of blood glucose control.

Liver-targeting drugs and their effect on blood glucose and hepatic lipids

The global epidemic of non-alcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH) and the high prevalence among individuals with type 2 diabetes has attracted the attention of clinicians specialising in liver disorders. Many drugs are in the pipeline for the treatment of NAFLD/NASH, and several glucose-lowering drugs are now being tested specifically for the treatment of liver disease. Among these are nuclear hormone receptor agonists (e.g. peroxisome proliferator-activated receptor agonists, farnesoid X receptor agonists and liver X receptor agonists), fibroblast growth factor-19 and -21, single, dual or triple incretins, sodium-glucose cotransporter inhibitors, drugs that modulate lipid or other metabolic pathways (e.g. inhibitors of fatty acid synthase, diacylglycerol acyltransferase-1, acetyl-CoA carboxylase and 11β-hydroxysteroid dehydrogenase type-1) or drugs that target the mitochondrial pyruvate carrier. We have reviewed the metabolic effects of these drugs in relation to improvement of diabetic hyperglycaemia and fatty liver disease, as well as peripheral metabolism and insulin resistance.

A role for sodium glucose cotransporter 2 inhibitors (SGLT2is) in the treatment of Alzheimer's disease?

With the lack of success and increasing urgency for therapies capable of impacting Alzheimer's disease (AD) and its progression, there are increasing efforts to expand testing of new mechanistic hypotheses to attack the disease from different angles. Three such hypotheses are the "Mitochondrial Cascade (MC)" hypothesis, the "Endo-Lysosomal Dysfunction (ELD)" hypothesis and the "Type 3 Diabetes (T3D)" hypothesis. These hypotheses provide a rationale for new pharmacological approaches to address the mitochondrial, endo-lysosomal and metabolic dysfunction associated with AD. It is increasingly evident that there is critical interplay between the metabolic dysfunction associated with obesity/metabolic syndrome/type 2 diabetes mellitus (T2DM) and patient susceptibility to AD development. A candidate for a common mechanism linking these metabolically-driven disease states is chronically-activated mechanistic target of rapamycin (mTOR) signaling. Unrestrained chronic mTOR activation may be responsible for sustaining metabolic, lysosomal and mitochondrial dysfunction in AD, driving both the breakdown of the blood-brain barrier via endothelial cell dysfunction and hyperphosphorylation of tau and formation of amyloid plaques in the brain. It is hypothesized that sodium glucose cotransporter 2 (SGLT2) inhibition, mediated by sustained glucose loss, restores mTOR cycling through nutrient-driven, nightly periods of transient mTOR inhibition (and restoration of catabolic cellular housekeeping processes) interspersed by daily periods of transient mTOR activation (and anabolism) accompanying eating. In this way, a flexible mTOR dynamic is restored, thereby preventing or even reducing the progress of AD pathology. The first study to investigate the effect of SGLT2 inhibition in patients with AD is ongoing and focuses on the impact on energy metabolism in the brain following treatment with the SGLT2 inhibitor dapagliflozin.

Insulin sensitivity depends on the route of glucose administration

AIMS/HYPOTHESIS

The small intestine plays an important role in hepatic and whole-body insulin sensitivity, as shown by bariatric surgery. Our goal was to study whether routes and dose of glucose administration have an acute impact on insulin sensitivity. The primary endpoint of this proof-of-concept study was the difference in insulin-mediated metabolic clearance rate (MCR/I) of glucose between the oral and intravenous routes of glucose administration. Secondary endpoints were differences in insulin effect on proteolysis, ketogenesis, lipolysis and glucagon levels.

METHODS

In this parallel cohort study, we administered multiple oral glucose loads to 23 participants (aged between 18 and 65 years) with morbid obesity and with normal or impaired glucose tolerance or type 2 diabetes. In a different session, we administered isoglycaemic intravenous glucose infusions (IGIVI) to match the plasma glucose levels observed during the oral challenges. Glucose rate of appearance (R_a) and disappearance (R_d) and endogenous glucose production (EGP) were calculated by infusing [6,6-²H₂]glucose with or without oral [U-¹³C₆]glucose. Plasma small polar metabolites were measured by gas chromatography and time-of-flight mass spectrometry. Lipids were measured by ultra-HPLC and quadrupole mass spectrometry. Glucagon-like peptide-1, insulin, C-peptide and glucagon were also measured. Participants, caregivers, people doing measurements or examinations, and people assessing the outcomes were unblinded to group assignment.

RESULTS

Glucose MCR/I was significantly higher during IGIVI than during oral glucose administration, independently of glycaemic status (12 ± 6 for IGIVI vs 7.4 ± 3 ml min^-1 kg^-1 per nmol/l for oral, p< 0.001 from paired t test). Insulin secretion was higher during oral administration than during IGIVI (p< 0.001). The disposition index was significantly lower during the oral procedure: 4260 ± 1820 vs 5000 ± 2360 (ml min^-1 kg^-1 (nmol/l)^-1 pmol/min; p = 0.005). Insulin clearance was significantly higher when glucose was infused rather than ingested (2.53 ± 0.82 vs 2.16 ± 0.49 l/min in intravenous and oral procedure, respectively, p = 0.006). The efficacy of insulin in inhibiting lipolysis and proteolysis was decreased after oral glucose loads. A heat map diagram showed a different pattern for the metabolites between the two routes of glucose administration.

CONCLUSIONS/INTERPRETATION

Our study shows that insulin sensitivity depends on the route of glucose administration, the oral route leading to increased insulin secretion and compensatory insulin resistance compared with the intravenous route. The efficacy of insulin in blocking lipolysis and protein breakdown is lower after oral glucose loads vs the intravenous route. Our findings suggest that, while the glucose-mediated incretin release is followed by an increase in insulin release, the effect of the released insulin is limited by an increase in insulin resistance.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03223129. Graphical abstract.

Participation of white adipose tissue dysfunction on circulating HDL cholesterol and HDL particle size in apparently healthy humans

OBJECTIVE

To use the combined presence of the elevated insulin resistance index in adipose tissue (Adipo-IR) and low values of adiponectin as a marker of dysfunctional adipose tissue, and to analyze its possible association with low values of high-density lipoprotein cholesterol (HDL-C) and small size of HDL particles.

RESEARCH DESIGN AND METHODS

The analysis included 253 subjects with functional adipose tissue and 253 with dysfunctional adipose tissue, considering similar gender, age, and body mass index (BMI). Adipo-IR was considered when index values (free fatty acids × insulin concentrations) were ≥75th percentile. Low levels of adiponectin were considered when concentration in serum was <25th percentile (determined by ELISA). HDL size was estimated by a quantitative validated equation. Small HDL size was considered when values were <25th percentile.

RESULTS

When comparing subjects with functional adipose tissue with those of dysfunctional adipose tissue, the latter had a higher prevalence of low HDL-C (51.4% vs. 64.0%; p = 0.004) and small HDL (56.9% vs. 67.6%; p = 0.009). Multivariate analysis indicated that independently from other metabolic risk factors, dysfunction of adipose tissue is significantly associated with low HDL-C (OR: 1.624 [CI 95%: 1.100-2.397]) and small HDL (OR: 1.462 [CI 95%: 1.000-2.139]). Adding BMI, waist circumference, and subcutaneous or visceral adipose tissue did not modify the association.

CONCLUSIONS

Dysfunction of adipose tissue is associated with a 65 and 50% higher probability of having low HDL-C and small HDL. Identification of dysfunctional adipose tissue could be a useful tool in the clinical setting to prevent the cardiometabolic risk independently from adiposity.

Individuals With Prediabetes Display Different Age-Related Pathophysiological Characteristics

CONTEXT

Impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) are highly pathophysiologic heterogeneous prediabetes conditions that can occur in all age groups, from youth to elderly people.

OBJECTIVE

We evaluated whether distinct age-related phenotypes exist among individuals with IFG or IGT.

RESEARCH DESIGN

479 young (aged 18 to 35 years), 699 adult (45 to 55 years) and 240 older (≥65 years) subjects underwent an oral glucose tolerance test (OGTT). From the OGTT results, the participants were grouped as follows: young age and normal glucose tolerance (NGT), adult age and NGT, older age and NGT, IFG young subjects, IFG adult subjects, IFG older subjects, IGT young (Y-IGT) subjects, IGT adult (A-IGT) subjects, and IGT older (O-IGT) subjects.

MAIN OUTCOME MEASURES

Insulin sensitivity and secretion, insulin clearance, and β-cell function.

RESULTS

Peripheral insulin sensitivity assessed using the Matsuda index, basal and glucose-stimulated insulin secretion, and β-cell function estimated using the disposition index were decreased in IFG adult subjects and IFG older subjects compared with IFG young subjects. A-IGT and Y-IGT subjects exhibited a progressively greater degree of hepatic insulin resistance assessed using the liver insulin resistance index, and reduced insulin clearance compared with O-IGT subjects. In contrast, the Matsuda index did not differ among Y-IGT, A-IGT, and O-IGT subjects. Basal and glucose-stimulated insulin secretion and β-cell function were lower in A-IGT and O-IGT subjects compared with Y-IGT individuals.

CONCLUSIONS

Subjects with IFG or IGT exhibited different age-related pathophysiologic characteristics. A more precise phenotyping of subjects with IGT or IFG could help to better design individualized preventive approaches to counteract diabetes progression.

Pioglitazone: The forgotten, cost-effective cardioprotective drug for type 2 diabetes

Type 2 diabetes individuals are at high risk for macrovascular complications: myocardial infarction, stroke and cardiovascular mortality. Recent cardiovascular outcome trials have demonstrated that agents in two antidiabetic classes (SGLT2 inhibitors and GLP-1 receptor agonists) reduce major adverse cardiovascular events. However, there is strong evidence that an older and now generically available medication, the thiazolidinedione, pioglitazone, can retard the atherosclerotic process (PERISCOPE and Chicago) and reduce cardiovascular events in large randomized prospective cardiovascular outcome trials (IRIS and PROactive). Pioglitazone is a potent insulin sensitizer, preserves beta-cell function, causes durable reduction in HbA1c, corrects multiple components of metabolic syndrome and improves nonalcoholic fatty liver disease/nonalcoholic steatohepatitis. Adverse effects (weight gain, fluid retention, fractures) must be considered, but are diminished with lower doses and are arguably outweighed by these multiple benefits. With healthcare expenses attributable to diabetes increasing rapidly, this cost-effective drug requires reconsideration in the therapeutic armamentarium for the disease.

Pioglitazone improves hepatic mitochondrial function in a mouse model of nonalcoholic steatohepatitis

Pioglitazone is effective in improving insulin resistance and liver histology in patients with nonalcoholic steatohepatitis (NASH). Because dysfunctional mitochondrial metabolism is a central feature of NASH, we hypothesized that an important target of pioglitazone would be alleviating mitochondrial oxidative dysfunction. To this end, we studied hepatic mitochondrial metabolism in mice fed high-fructose high-transfat diet (TFD) supplemented with pioglitazone for 20 wk, using nuclear magnetic resonance-based ¹³C isotopomer analysis. Pioglitazone improved whole body and adipose insulin sensitivity in TFD-fed mice. Furthermore, pioglitazone reduced intrahepatic triglyceride content and fed plasma ketones and hepatic TCA cycle flux, anaplerosis, and pyruvate cycling in mice with NASH. This was associated with a marked reduction in most intrahepatic diacylglycerol classes and, to a lesser extent, some ceramide species (C22:1, C23:0). Considering the cross-talk between mitochondrial function and branched-chain amino acid (BCAA) metabolism, pioglitazone's impact on plasma BCAA profile was determined in a cohort of human subjects. Pioglitazone improved the plasma BCAA concentration profile in patients with NASH. This appeared to be related to an improvement in BCAA degradation in multiple tissues. These results provide evidence that pioglitazone-induced changes in NASH are related to improvements in hepatic mitochondrial oxidative dysfunction and changes in whole body BCAA metabolism.

Targeting Sirt1 in a rat model of high-fat diet-induced non-alcoholic fatty liver disease: Comparison of Gegen Qinlian decoction and resveratrol

The present study aimed to explore the mechanism of action of Gegen Qinlian decoction (GGQLD) in experimental non-alcoholic fatty liver disease (NAFLD). A total of 30 rats were randomly divided into five groups: The chow, model, high- and low-dose GGQLD (GGQLD-H and GGQLD-L, respectively) and resveratrol (Resl) groups, and were treated with saline, GGQLD and Resl when a model of high-fat diet (HFD)-induced NAFLD was established. Blood lipid and liver enzymes were detected following treatment for 8 weeks and liver tissue pathology was observed using Oil Red O and haematoxylin and eosin staining. Furthermore, the liver protein and mRNA expression of sirtuin (Sirt)1, peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α and nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) were measured using western blotting and reverse transcription-quantitative polymerase chain reaction. Compared with the chow group, the model group demonstrated significantly increased serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels (P<0.01). GGQLD doses and Resl attenuated the elevated serum ALT and AST levels. GGQLD-H and Resl significantly increased the serum high-density lipoprotein cholesterol level compared with that in the model group (P<0.01), while GGQLD-L and Resl significantly decreased serum low-density lipoprotein cholesterol levels (P<0.01). The GGQLDs and Resl groups revealed an evident improvement in Sirt1 protein and mRNA expression. Although GGQLD and Resl significantly decreased NF-κB gene expression compared with the model group (P<0.01), the effect on NF-κB protein expression was not significant. Furthermore, the PGC-1α gene and protein expression in the HFD rat group slightly decreased compared to the levels in the chow group, but the decrease was insignificant. However, an evident increase in PGC-1α mRNA expression was observed in the GGQLD-H group compared with the model group (P<0.01). Histological staining revealed that GGQLD and Resl decreased the lipid droplets in hepatocytes and normalized steatosis in rats fed with a HFD. The results indicated that GGQLD treatment may be a potent strategy for managing NAFLD by managing lipid metabolism and inflammatory and histological abnormalities by triggering the Sirt1 pathway.

Pioglitazone inhibits mitochondrial pyruvate metabolism and glucose production in hepatocytes

Pioglitazone is used globally for the treatment of type 2 diabetes mellitus (T2DM) and is one of the most effective therapies for improving glucose homeostasis and insulin resistance in T2DM patients. However, its mechanism of action in the tissues and pathways that regulate glucose metabolism are incompletely defined. Here we investigated the direct effects of pioglitazone on hepatocellular pyruvate metabolism and the dependency of these observations on the purported regulators of mitochondrial pyruvate transport, MPC1 and MPC2. In cultured H4IIE hepatocytes, pioglitazone inhibited [2-¹⁴ C]-pyruvate oxidation and pyruvate-driven oxygen consumption and, in mitochondria isolated from both hepatocytes and human skeletal muscle, pioglitazone selectively and dose-dependently inhibited pyruvate-driven ATP synthesis. Pioglitazone also suppressed hepatocellular glucose production (HGP), without influencing the mRNA expression of key HGP regulatory genes. Targeted siRNA silencing of MPC1 and 2 caused a modest inhibition of pyruvate oxidation and pyruvate-driven ATP synthesis, but did not alter pyruvate-driven HGP and, importantly, it did not influence the actions of pioglitazone on either pathway. In summary, these findings outline a novel mode of action of pioglitazone relevant to the pathogenesis of T2DM and suggest that targeting pyruvate metabolism may lead to the development of effective new T2DM therapies.

Identification of subgroups with differential treatment effects for longitudinal and multiresponse variables

We describe and evaluate a regression tree algorithm for finding subgroups with differential treatments effects in randomized trials with multivariate outcomes. The data may contain missing values in the outcomes and covariates, and the treatment variable is not limited to two levels. Simulation results show that the regression tree models have unbiased variable selection and the estimates of subgroup treatment effects are approximately unbiased. A bootstrap calibration technique is proposed for constructing confidence intervals for the treatment effects. The method is illustrated with data from a longitudinal study comparing two diabetes drugs and a mammography screening trial comparing two treatments and a control. Copyright © 2016 John Wiley & Sons, Ltd.

Mechanisms by which the thiazolidinedione troglitazone protects against sucrose-induced hepatic fat accumulation and hyperinsulinaemia

BACKGROUND AND PURPOSE

Thiazolidinediones (TZD) are known to ameliorate fatty liver in type 2 diabetes. To date, the underlying mechanisms of their hepatic actions remain unclear.

EXPERIMENTAL APPROACH

Hepatic triglyceride content and export rates were assessed in 2 week high-sucrose-fed Wistar rats treated with troglitazone and compared with untreated high-sucrose rodent controls. Fractional de novo lipogenesis (DNL) contributions to hepatic triglyceride were quantified by analysis of triglyceride enrichment from deuterated water. Hepatic insulin clearance and NO status during a meal tolerance test were also evaluated.

KEY RESULTS

TZD significantly reduced hepatic triglyceride (P < 0.01) by 48%, decreased DNL contribution to hepatic triglyceride (P < 0.01) and increased postprandial non-esterified fatty acids clearance rates (P < 0.01) in comparison with the high-sucrose rodent control group. During a meal tolerance test, plasma insulin AUC was significantly lower (P < 0.01), while blood glucose and plasma C-peptide levels were not different. Insulin clearance was increased (P < 0.001) by 24% and was associated with a 22% augmentation of hepatic insulin-degrading enzyme activity (P < 0.05). Finally, hepatic NO was decreased by 24% (P < 0.05).

CONCLUSIONS

Overall, TZD show direct actions on liver by reducing hepatic DNL and increasing hepatic insulin clearance. The alterations in hepatic insulin clearance were associated with changes in insulin-degrading enzyme activity, with possible modulation of NO levels.

Revitalization of pioglitazone: the optimum agent to be combined with a sodium-glucose co-transporter-2 inhibitor

The recently completed EMPA-REG study showed that empagliflozin significantly decreased the major adverse cardiac events (MACE) endpoint, which comprised cardiovascular death, non-fatal myocardial infarction (MI) and stroke, in patients with high-risk type 2 diabetes (T2DM), primarily through a reduction in cardiovascular death, without a significant decrease in either MI or stroke. In the PROactive study, pioglitazone decreased the MACE endpoint by a similar degree to that observed in the EMPA-REG study, through a marked reduction in both recurrent MI and stroke and a modest reduction in cardiovascular death. These observations suggest that pioglitazone might be an ideal agent to combine with empagliflozin to further reduce cardiovascular events in patients with high-risk diabetes as empagliflozin also promotes salt/water loss and would be expected to offset any fluid retention associated with pioglitazone therapy. In the present paper, we provide an overview of the potential benefits of combined pioglitazone/empagliflozin therapy to prevent cardiovascular events in patients with T2DM.

Early Clinical Detection of Pharmacologic Response in Insulin Action in a Nondiabetic Insulin-Resistant Population

Background

Insulin resistance heightens the risk for type 2 diabetes mellitus and cardiovascular disease. Amelioration of insulin resistance may reduce this risk. The thiazolidinedone class of insulin sensitizers improves insulin action in individuals with insulin-resistant diabetes and nondiabetic individuals. However, there are few reports on the time of onset of such effects independent of reversal of glucotoxicity.

Objective

The goal of our study was to test whether the thiazolidinedione pioglitazone has prominent early metabolic effects that can be detected in an obese, nondiabetic, insulin-resistant population.

Methods

We conducted a randomized, double-blind, placebo-controlled, parallel-group trial in men with nondiabetic insulin resistance using a hyperinsulinemic euglycemic clamp technique (at low and high doses of insulin at 10 and 40 mU/m²/min, respectively). The patients were given 30 mg daily oral pioglitazone or placebo for 28 days. Patients underwent a baseline clamp before initiation of treatment, and again at 14 and 28 days of treatment.

Results

Compared with placebo, under high-dose hyperinsulinemia, pioglitazone led to significant increases in glucose disposal rates (GDR) of 1.29 mg/kg/min (90% CI, 0.43–2.15; 39%; P=0.008) that were detectable at 2 weeks of treatment and persisted at 4 weeks of treatment. Under low-dose hyperinsulinemia, significant increases in GDR of 0.40 mg/kg/min (90% CI, 0.17–0.62; 95%; P=0.003) were observed at 4 weeks of treatment. These responses were accompanied by robust suppression of free fatty acids under hyperinsulinemic conditions, and by significant increases in circulating basal total adiponectin at 2 and 4 weeks of treatment.

Conclusions

Significant changes in insulin action across multiple insulin-sensitive tissues can be detected within 2 weeks of initiation of insulin-sensitizing therapy with pioglitazone in obese patients with nondiabetic insulin resistance. ClinicalTrials.gov identifier: NCT01115712.

Intervening TNF-α via PPARγ with Gegenqinlian Decoction in Experimental Nonalcoholic Fatty Liver Disease

This paper is to explore the effect and mechanism of Gegenqinlian decoction on experimental nonalcoholic fatty liver disease (NAFLD) in vivo and in vitro. The final aim is to make clear whether Gegenqinlian decoction would impact NAFLD through improving PPARγ to suppress inflammation and regulate lipid. The data in this research suggested that Gegenqinlian decoction is a potent way to manage NAFLD through improving PPARγ to regulate lipid and suppress inflammation.

Impact of glucose-lowering drugs on cardiovascular disease in type 2 diabetes

Type 2 diabetes mellitus (T2DM) is characterized by multiple pathophysiologic abnormalities. With time, multiple glucose-lowering medications are commonly required to reduce and maintain plasma glucose concentrations within the normal range. Type 2 diabetes mellitus individuals also are at a very high risk for microvascular complications and the incidence of heart attack and stroke is increased two- to three-fold compared with non-diabetic individuals. Therefore, when selecting medications to normalize glucose levels in T2DM patients, it is important that the agent not aggravate, and ideally even improve, cardiovascular risk factors (CVRFs) and reduce cardiovascular morbidity and mortality. In this review, we examine the effect of oral (metformin, sulfonylureas, meglitinides, thiazolidinediones, DPP4 inhibitors, SGLT2 inhibitors, and α-glucosidase inhibitors) and injectable (glucagon-like peptide-1 receptor agonists and insulin) glucose-lowering drugs on established CVRFs and long-term studies of cardiovascular outcomes. Firm evidence that in T2DM cardiovascular disease can be reversed or prevented by improving glycaemic control is still incomplete and must await large, long-term clinical trials in patients at low risk using modern treatment strategies, i.e., drug combinations designed to maximize HbA1c reduction while minimizing hypoglycaemia and excessive weight gain.

Thiazolidinediones and Edema: Recent Advances in the Pathogenesis of Thiazolidinediones-Induced Renal Sodium Retention

Thiazolidinediones (TZDs) are one of the major classes of antidiabetic drugs that are used widely. TZDs improve insulin resistance by activating peroxisome proliferator-activated receptor gamma (PPARγ) and ameliorate diabetic and other nephropathies, at least, in experimental animals. However, TZDs have side effects, such as edema, congestive heart failure, and bone fracture, and may increase bladder cancer risk. Edema and heart failure, which both probably originate from renal sodium retention, are of great importance because these side effects make it difficult to continue the use of TZDs. However, the pathogenesis of edema remains a matter of controversy. Initially, upregulation of the epithelial sodium channel (ENaC) in the collecting ducts by TZDs was thought to be the primary cause of edema. However, the results of other studies do not support this view. Recent data suggest the involvement of transporters in the proximal tubule, such as sodium-bicarbonate cotransporter and sodium-proton exchanger. Other studies have suggested that sodium-potassium-chloride cotransporter 2 in the thick ascending limb of Henle and aquaporins are also possible targets for TZDs. This paper will discuss the recent advances in the pathogenesis of TZD-induced sodium reabsorption in the renal tubules and edema.

Pioglitazone increases whole body insulin sensitivity in obese, insulin-resistant rhesus monkeys

Hyperinsulinemic-euglycemic clamps are considered the "gold standard" for assessing whole body insulin sensitivity. When used in combination with tracer dilution techniques and physiological insulin concentrations, insulin sensitization can be dissected and attributed to hepatic and peripheral (primarily muscle) effects. Non-human primates (NHPs), such as rhesus monkeys, are the closest pre-clinical species to humans, and thus serve as an ideal model for testing of compound efficacy to support translation to human efficacy. We determined insulin infusion rates that resulted in high physiological insulin concentrations that elicited maximal pharmacodynamic responses during hyperinsulinemic-euglycemic clamps. These rates were then used with [U-¹³C]-D-glucose, to assess and document the degrees of hepatic and peripheral insulin resistance between healthy and insulin-resistant, dysmetabolic NHPs. Next, dysmetabolic NHPs were treated for 28 days with pioglitazone (3 mg/kg) and again had their insulin sensitivity assessed, illustrating a significant improvement in hepatic and peripheral insulin sensitivity. This coincided with a significant increase in insulin clearance, and normalization of circulating adiponectin. In conclusion, we have determined a physiological clamp paradigm (similar to humans) for assessing glucose turnover in NHPs. We have also demonstrated that insulin-resistant, dysmetabolic NHPs respond to the established insulin sensitizer, pioglitazone, thus confirming their use as an ideal pre-clinical translational model to assess insulin sensitizing compounds.

The effect of muraglitazar on adiponectin signalling, mitochondrial function and fat oxidation genes in human skeletal muscle in vivo

AIMS

The molecular mechanisms by which muraglitazar (peroxisome proliferator-activated receptor γ/α agonist) improves insulin sensitivity in Type 2 diabetes mellitus are not fully understood. We hypothesized that muraglitazar would increase expression of 5'-monophosphate-activated protein kinase and genes involved in adiponectin signalling, free fatty acid oxidation and mitochondrial function in skeletal muscle.

METHODS

Sixteen participants with Type 2 diabetes received muraglitazar, 5 mg/day (n = 12) or placebo (n = 4). Before and after 16 weeks, participants had vastus lateralis muscle biopsy followed by 180 min euglycaemic hyperinsulinaemic clamp.

RESULTS

Muraglitazar increased plasma adiponectin (9.0 ± 1.1 to 17.8 ± 1.5 μg/ml, P < 0.05), while no significant change was observed with placebo. After 16 weeks with muraglitazar, fasting plasma glucose declined by 31%, fasting plasma insulin decreased by 44%, insulin-stimulated glucose disposal increased by 81%, HbA1c decreased by 21% and plasma triglyceride decreased by 39% (all P < 0.05). Muraglitazar increased mRNA levels of 5'-monophosphate-activated protein kinase, adiponectin receptor 1, adiponectin receptor 2, peroxisome proliferator-activated receptor gamma coactivator-1 alpha and multiple genes involved in mitochondrial function and fat oxidation. In the placebo group, there were no significant changes in expression of these genes.

CONCLUSIONS

Muraglitazar increases plasma adiponectin, stimulates muscle 5'-monophosphate-activated protein kinase expression and increases expression of genes involved in adiponectin signalling, mitochondrial function and fat oxidation. These changes represent important cellular mechanisms by which dual peroxisome proliferator-activated receptor agonists improve skeletal muscle insulin sensitivity.

PPAR gamma gene--a review

Peroxisome proliferator-activated receptor gamma (PPARγ) has been the focus of intense research because ligands for this receptor have emerged as potent insulin sensitizers used in the treatment of type 2 diabetes. There have been described three PPAR isotypes α, δ and γ which have an integrated role in controlling the expression of genes playing key roles in the storage and mobilization of lipids, in glucose metabolism, in morphogenesis and inflammatory response. Recent advances include the discovery of novel genes that are regulated by PPARγ, which helps to explain how activation of this adipocyte predominant transcription factor regulates glucose and lipid homeostasis. Increased levels of circulating free fatty acids and lipid accumulation in non-adipose tissue have been implicated in the development of insulin resistance. This situation is improved by PPARγ ligands, which promotes fatty acid storage in fat deposits and regulates the expression of adipocyte-secreted hormones that impacts on glucose homeostasis. So the net result of the pleiotropic effects of PPARγ ligands is improvement of insulin sensitivity. This review highlights the roles that PPAR gamma play in the regulation of gene expression of multiple diseases including obesity, diabetes and cancer and highlights the gene isolation transformation role. Further studies are needed for the transformation of PPAR gamma gene in plants and evaluate in animals for the treatment of type 2 diabetes.

Regulation of glucose and lipid homeostasis by adiponectin: effects on hepatocytes, pancreatic β cells and adipocytes

Adiponectin has received considerable attention for its potential anti-diabetic actions. The adipokine exerts control of glucose and lipid homeostasis via critical effects within the liver, adipose, and pancreas. By stimulating adipogenesis, opposing inflammation, and influencing rates of lipid oxidation and lipolysis, adiponectin critically governs lipid spillover into non-adipose tissues. Ceramide, a cytotoxic and insulin desensitizing lipid metabolite formed when peripheral tissues are exposed to excessive lipid deposition, is potently opposed by adiponectin. Via adiponectin receptors, AdipoR1 and AdipoR2, adiponectin stimulates the deacylation of ceramide- yielding sphingosine for conversion to sphingosine 1-phosphate (S1P) by sphingosine kinase. The resulting conversion from ceramide to S1P promotes survival of functional beta cell mass, allowing for insulin production to meet insulin demands. Alleviation of ceramide burden on the liver allows for improvements in hepatic insulin action. Here, we summarize how adiponectin-induced changes in these tissues lead to improvements in glucose metabolism, highlighting the sphingolipid signaling mechanisms linking adiponectin to each action. ONE SENTENCE SUMMARY: We review the anti-diabetic actions of adiponectin.

Expansion of the homeostasis model assessment of β-cell function and insulin resistance to enable clinical trial outcome modeling through the interactive adjustment of physiology and treatment effects: iHOMA2

OBJECTIVE

To describe and make available an interactive, 24-variable homeostasis model assessment (iHOMA2) that extends the HOMA2 model, enabling the modeling of physiology and treatment effects, to present equations of the HOMA2 and iHOMA2 models, and to exemplify iHOMA2 in two widely differing scenarios: changes in insulin sensitivity with thiazolidinediones and changes in renal threshold with sodium glucose transporter 2 (SGLT2) inhibition.

RESEARCH DESIGN AND METHODS

iHOMA2 enables a user of the available software to examine and modify the mathematical functions describing the organs and tissues involved in the glucose and hormonal compartments. We exemplify this with SGLT2 inhibition modeling (by changing the renal threshold parameters) using published data of renal effect, showing that the modeled effect is concordant with the effects on fasting glucose from independent data.

RESULTS

iHOMA2 modeling of thiazolidinediones effect suggested that changes in insulin sensitivity in the fasting state are predominantly hepatic. SGLT2 inhibition modeled by iHOMA2 resulted in a decrease in mean glucose of 1.1 mmol/L. Observed data showed a decrease in glucose of 0.9 mmol/L. There was no significant difference between the model and the independent data. Manipulation of iHOMA2's renal excretion threshold variable suggested that a decrease of 17% was required to obtain a 0.9 mmol/L decrease in mean glucose.

CONCLUSIONS

iHOMA2 is an extended mathematical model for the assessment of insulin resistance and β-cell function. The model can be used to evaluate therapeutic agents and predict effects on fasting glucose and insulin and on β-cell function and insulin sensitivity.

Ectopic fat: the true culprit linking obesity and cardiovascular disease?

Obesity is a major risk factor for cardiovascular disease and its complications. However, not all fat depots share the same characteristics. Recent studies have found that ectopic rather than subcutaneous fat accumulation is associated with increased cardiometabolic risk. However, ectopic fat accumulation can be seen initially as a protective mechanism against lipotoxicity. Subsequently the adipose tissue becomes dysfunctional, thus inducing systemic metabolic alterations (through release of cytokines) or specific organ dysfunctions. The purpose of this review is to summarise the current available data on the impact of excess adiposity vs ectopic fat in the development of cardio-metabolic diseases.

Personalized management of hyperglycemia in type 2 diabetes: reflections from a Diabetes Care Editors' Expert Forum

In June 2012, 13 thought leaders convened in a Diabetes Care Editors' Expert Forum to discuss the concept of personalized medicine in the wake of a recently published American Diabetes Association/European Association for the Study of Diabetes position statement calling for a patient-centered approach to hyperglycemia management in type 2 diabetes. This article, an outgrowth of that forum, offers a clinical translation of the underlying issues that need to be considered for effectively personalizing diabetes care. The medical management of type 2 diabetes has become increasingly complex, and its complications remain a great burden to individual patients and the larger society. The burgeoning armamentarium of pharmacological agents for hyperglycemia management should aid clinicians in providing early treatment to delay or prevent these complications. However, trial evidence is limited for the optimal use of these agents, especially in dual or triple combinations. In the distant future, genotyping and testing for metabolomic markers may help us to better phenotype patients and predict their responses to antihyperglycemic drugs. For now, a personalized ("n of 1") approach in which drugs are tested in a trial-and-error manner in each patient may be the most practical strategy for achieving therapeutic targets. Patient-centered care and standardized algorithmic management are conflicting approaches, but they can be made more compatible by recognizing instances in which personalized A1C targets are warranted and clinical circumstances that may call for comanagement by primary care and specialty clinicians.

Pleiotropic effects of thiazolidinediones: implications for the treatment of patients with type 2 diabetes mellitus

Thiazolidinediones (TZDs) are insulin-sensitizing antidiabetes agents that act through the peroxisome proliferator-activated receptor-γ to cause a durable improvement in glycemic control in patients with type 2 diabetes mellitus. Although less well recognized, TZDs also exert a protective effect on β-cell function. In addition to their beneficial effects on glucose homeostasis, TZDs-especially pioglitazone-exert a number of other pleiotropic effects that make them ideal agents as monotherapy or in combination with other oral agents, glucagon-like peptide-1 analogs, or insulin. Pioglitazone improves endothelial dysfunction, reduces blood pressure, corrects diabetic dyslipidemia, and reduces circulating levels of inflammatory cytokines and prothrombotic factors. Pioglitazone also redistributes fat and toxic lipid metabolites in muscle, liver, β cells, and arteries, and deposits the fat in subcutaneous adipocytes where it cannot exert its lipotoxic effects. Consistent with these antiatherogenic effects, pioglitazone reduced major adverse cardiac event endpoints (ie, mortality, myocardial infarction, and stroke) in the Prospective Pioglitazone Clinical Trial in Macrovascular Events and in a meta-analysis of all other published pioglitazone trials. Pioglitazone also mobilizes fat out of the liver, improving liver function and histologic abnormalities in patients with nonalcoholic fatty liver disease and nonalcoholic steatohepatitis. Pioglitazone also reduces proteinuria, all-cause mortality, and cardiovascular events in patients with type 2 diabetes mellitus with a reduced glomerular filtration rate. These benefits must be weighed against the side effects of the drug, including weight gain, fluid retention, atypical fractures, and, possibly, bladder cancer. When low doses of pioglitazone are used (eg, 7.5-30 mg/d) with gradual titration, and physician recognition of the potential side effects are applied, the risk-to-benefit ratio is very favorable. Despite having similar effects on glycemic control, pioglitazone and rosiglitazone appear to have different effects on cardiovascular outcomes. Rosiglitazone has been associated with an increased risk of myocardial infarction, and its use in the United States is restricted because of cardiovascular safety concerns.

Markers in nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD), the most common liver disorder worldwide, encompasses a spectrum of abnormal liver histology ranging from simple steatosis to nonalcoholic steatohepatitis (NASH) and cirrhosis. Population studies show that NAFLD is strongly associated with insulin resistance, obesity, type 2 diabetes mellitus, and lipid abnormalities. In the context of hepatic steatosis, factors that promote cell injury, inflammation, and fibrosis include oxidative stress, early mitochondrial dysfunction, endoplasmic reticulum stress, iron accumulation, apoptosis, adipocytokines, and stellate cell activation. The exact NASH prevalence is unknown because of the absence of simple noninvasive diagnostic tests. Although liver biopsy is the "gold standard" for the diagnosis of NASH, other tests are needed to facilitate the diagnosis and greatly reduce the requirement for invasive liver biopsy. In addition, the development of new fibrosis markers in NASH is needed to facilitate the assessment of its progression and the effectiveness of new therapies. The aim of this chapter, which is overview of biomarkers in NASH, is to establish a systematic approach to laboratory findings of the disease.

Thiazolidinediones improve hepatic fibrosis in rats with non-alcoholic steatohepatitis by activating the adenosine monophosphate-activated protein kinase signalling pathway

Thiazolidinediones (TZDs) markedly reduce hepatic steatosis in both rodents and humans. However, the effects and mechanisms of action of TZDs on hepatic fibrosis remain unclear. The aim of the present study was to determine the effects of TZDs on histological changes in the liver and on the modulation by adiponectin via the AMP-activated protein kinase (AMPK) signalling pathway in rats with non-alcoholic steatohepatitis (NASH). Forty rats were divided into normal control, high-fat diet (HFD), pioglitazone control and pioglitazone intervention groups. After 24 weeks treatment with pioglitazone (10 mg/kg per day by gavage), changes in liver histology, serum aminotransaminase, triglyceride (TG), free fatty acid (FFA), glucose, insulin, adiponectin and transforming growth factor (TGF)-β1 concentrations and hepatic adiponectin, AMPK, α-smooth muscle actin (α-SMA) and collagen I expression were evaluated. The degree of hepatic steatosis and fibrosis was significantly higher in HFD-induced NASH rats compared with normal controls, as were serum concentrations of aminotransaminase, TG, FFA, glucose, insulin and TGF-β1 and hepatic expression of α-SMA and collagen I protein. Serum adiponectin concentrations and hepatic expression of adiponectin mRNA and AMPK protein were significantly lower in the HFD-induced NASH rats compared with the normal control. Pioglitazone significantly reduced the degree of hepatic steatosis and fibrosis, as well as serum concentrations of aminotransaminase, TG, FFA, glucose, insulin and TGF-β1 and hepatic expression of α-SMA and collagen I protein. In addition, pioglitazone significantly increased serum adiponectin concentrations and hepatic expression of adiponectin mRNA and AMPK protein. In conclusion, the TZD pioglitazone improved hepatic fibrosis in rats with NASH by upregulating adiponectin expression and activating AMPK, thus subsequently inhibiting the activation of hepatic stellate cells and the overproduction of extracellular matrix.

Aerobic exercise improves insulin resistance and decreases body fat and serum levels of leptin in patients with hepatitis C virus

AIM

  Hepatitis C virus infection often complicates glucose intolerance, which can be caused by insulin resistance. Aerobic exercise can improve insulin resistance and decrease body fat in patients with diabetes. The aim of the present study is to clarify whether aerobic exercise improves insulin resistance and decreases body fat in patients with chronic hepatitis C (CH-C).

METHODS

  Seventeen patients with CH-C received nutrition education at entry and every two months thereafter. The following were evaluated before and after 6 months of walking at least 8000 steps/day monitored using a pedometer that started 2 months after entry: body composition, fat and muscle weight, visceral and subcutaneous fat areas (VFA and SFA, respectively), liver function tests, the Homeostatic Model of Assessment of Insulin Resistance (HOMA-IR), serum tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, adiponectin, leptin and the Short Form-36.

RESULTS

  Fifteen of the 17 patients completed the study protocol. Bodyweight, body mass index, fat weight, VFA, SFA, alanine aminotransferase level and HOMA-IR were significantly decreased at the end of the study (P = 0.004, =0.004, =0.008, =0.041, =0.001, =0.023 and =0.002, respectively). Serum levels of TNF-α, IL-6 and adiponectin did not change, whereas those of leptin significantly decreased (P = 0.002).

CONCLUSION

  Patients with CH-C could safely walk as aerobic exercise. Furthermore, walking improved insulin resistance and decreased body fat while lowering serum levels of leptin.

The role of metformin and thiazolidinediones in the regulation of hepatic glucose metabolism and its clinical impact

Fasting hyperglycemia in type 2 diabetes mellitus (T2DM) results from elevated endogenous glucose production (EGP), which is mostly due to augmented hepatic gluconeogenesis. Insulin-resistant humans exhibit impaired insulin-dependent suppression of EGP and excessive hepatic lipid storage (steatosis), which relates to abnormal supply of free fatty acids (FFA) and energy metabolism. Only two glucose-lowering drug classes, the biguanide metformin and the thiazolidendiones (TZDs), exert insulin- and glucagon-independent hepatic effects. Preclinical studies suggest that metformin inhibits mitochondrial complex I. TZDs, as peroxisome proliferator-activated receptor (PPAR) γ-agonists, predominantly reduce the flux of FFA and cytokines from adipose tissue to the liver, but could also directly inhibit mitochondrial complex I. Although both metformin and TZDs improve fasting hyperglycemia and EGP in clinical trials, only TZDs decrease steatosis and peripheral insulin resistance. More studies are required to address their effects on hepatocellular energy metabolism with a view to identifying novel targets for the treatment of T2DM.

Inflammation in nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) describes a range of disorders characterized by excess accumulation of triglyceride within the liver. While simple steatosis may be clinically stable, nonalcoholic steatohepatitis (NASH) can be progressive. Inflammation is believed to be the driving force behind NASH and the progression to fibrosis and subsequent cirrhosis. This article will review and interpret the current literature in an attempt to expand our understanding of the environmental and genetic causes of inflammation and its effects in NAFLD.

Pioglitazone and alogliptin combination therapy in type 2 diabetes: a pathophysiologically sound treatment

Insulin resistance and islet (beta and alpha) cell dysfunction are major pathophysiologic abnormalities in type 2 diabetes mellitus (T2DM). Pioglitazone is a potent insulin sensitizer, improves pancreatic beta cell function and has been shown in several outcome trials to lower the risk of atherosclerotic and cardiovascular events. Glucagon-like peptide-1 deficiency/resistance contributes to islet cell dysfunction by impairing insulin secretion and increasing glucagon secretion. Dipeptidyl peptidase-4 (DPP-4) inhibitors improve pancreatic islet function by augmenting glucose-dependent insulin secretion and decreasing elevated plasma glucagon levels. Alogliptin is a new DPP-4 inhibitor that reduces glycosylated hemoglobin (HbA_1c), is weight neutral, has an excellent safety profile, and can be used in combination with oral agents and insulin. Alogliptin has a low risk of hypoglycemia, and serious adverse events are uncommon. An alogliptin–pioglitazone combination is advantageous because it addresses both insulin resistance and islet dysfunction in T2DM. HbA_1c reductions are significantly greater than with either monotherapy. This once-daily oral combination medication does not increase the risk of hypoglycemia, and tolerability and discontinuation rates do not differ significantly from either monotherapy. Importantly, measures of beta cell function and health are improved beyond that observed with either monotherapy, potentially improving durability of HbA_1c reduction. The alogliptin–pioglitazone combination represents a pathophysiologically sound treatment of T2DM.

Pioglitazone improvement of fasting and postprandial hyperglycaemia in Mexican-American patients with Type 2 diabetes: a double tracer OGTT study

OBJECTIVES

By using tracer techniques, we explored the metabolic mechanisms by which pioglitazone treatment for 16 weeks improves oral glucose tolerance in patients with type 2 diabetes when compared to subjects without diabetes.

METHODS

In all subjects, before and after treatment, we measured rates of tissue glucose clearance (MCR), oral glucose appearance (RaO) and endogenous glucose production (EGP) during a (4-h) double tracer oral glucose tolerance test (OGTT) (1-(14)C-glucose orally and 3-(3)H-glucose intravenously). Basal hepatic insulin resistance index (HepIR) was calculated as EGPxFPI. beta-cell function was assessed as the incremental ratio of insulin to glucose (DeltaI/DeltaG) during the OGTT.

RESULTS

Pioglitazone decreased fasting plasma glucose concentration (10.5 +/- 0.7 to 7.8 +/- 0.6 mM, P < 0.0003) and HbA1c (9.7 +/- 0.7 to 7.5 +/- 0.5%, P < 0.003) despite increased body weight and no change in plasma insulin concentrations. This was determined by a decrease both in fasting EGP (20.0 +/- 1.1 to 17.3 +/- 0.8 micromol/kg(ffm) min, P < 0.005) and HepIR (from 8194 declined by 49% to 3989, P < 0.002). During the OGTT, total glucose Ra during the 0- to 120-min time period following glucose ingestion decreased significantly because of a reduction in EGP. During the 0- to 240-min time period, pioglitazone caused only a modest increase in MCR (P < 0.07) but markedly increased DeltaI/DeltaG (P = 0.003). The decrease in 2h-postprandial hyperglycaemia correlated closely with the increase in DeltaI/DeltaG (r = -0.76, P = 0.004) and tissue clearance (r = -0.74, P = 0.006) and with the decrease in HepIR (r = 0.62, P = 0.006).

CONCLUSIONS

In diabetic subjects with poor glycaemic control, pioglitazone improves oral glucose tolerance mainly by enhancing the suppression of EGP and improving beta-cell function.

Pioglitazone in the treatment of NASH: the role of adiponectin

BACKGROUND

Plasma adiponectin is decreased in NASH patients and the mechanism(s) for histological improvement during thiazolidinedione treatment remain(s) poorly understood.

AIM

To evaluate the relationship between changes in plasma adiponectin following pioglitazone treatment and metabolic/histological improvement.

METHODS

We measured in 47 NASH patients and 20 controls: (i) fasting glucose, insulin, FFA and adiponectin concentrations; (ii) hepatic fat content by magnetic resonance spectroscopy; and (iii) peripheral/hepatic insulin sensitivity (by double-tracer oral glucose tolerance test). Patients were then treated with pioglitazone (45 mg/day) or placebo and all measurements were repeated after 6 months.

RESULTS

Patients with NASH had decreased plasma adiponectin levels independent of the presence of obesity. Pioglitazone increased 2.3-fold plasma adiponectin and improved insulin resistance, glucose tolerance and glucose clearance, steatosis and necroinflammation (all P < 0.01-0.001 vs. placebo). In the pioglitazone group, plasma adiponectin was significantly associated (r = 0.52, P = 0.0001) with hepatic insulin sensitivity and with the change in both variables (r = 0.44, P = 0.03). Increase in adiponectin concentration was related also to histological improvement, in particular, to hepatic steatosis (r = -0.46, P = 0006) and necroinflammation (r = -0.56, P < 0.0001) but importantly also to fibrosis (r = -0.29, P = 0.03).

CONCLUSIONS

Adiponectin exerts an important metabolic role at the level of the liver, and its increase during pioglitazone treatment is critical to reverse insulin resistance and improve liver histology in NASH patients.

Insulin resistance, lipotoxicity, type 2 diabetes and atherosclerosis: the missing links. The Claude Bernard Lecture 2009

Insulin resistance is a hallmark of type 2 diabetes mellitus and is associated with a metabolic and cardiovascular cluster of disorders (dyslipidaemia, hypertension, obesity [especially visceral], glucose intolerance, endothelial dysfunction), each of which is an independent risk factor for cardiovascular disease (CVD). Multiple prospective studies have documented an association between insulin resistance and accelerated CVD in patients with type 2 diabetes, as well as in non-diabetic individuals. The molecular causes of insulin resistance, i.e. impaired insulin signalling through the phosphoinositol-3 kinase pathway with intact signalling through the mitogen-activated protein kinase pathway, are responsible for the impairment in insulin-stimulated glucose metabolism and contribute to the accelerated rate of CVD in type 2 diabetes patients. The current epidemic of diabetes is being driven by the obesity epidemic, which represents a state of tissue fat overload. Accumulation of toxic lipid metabolites (fatty acyl CoA, diacylglycerol, ceramide) in muscle, liver, adipocytes, beta cells and arterial tissues contributes to insulin resistance, beta cell dysfunction and accelerated atherosclerosis, respectively, in type 2 diabetes. Treatment with thiazolidinediones mobilises fat out of tissues, leading to enhanced insulin sensitivity, improved beta cell function and decreased atherogenesis. Insulin resistance and lipotoxicity represent the missing links (beyond the classical cardiovascular risk factors) that help explain the accelerated rate of CVD in type 2 diabetic patients.

Fat mass largely contributes to insulin mediated glucose uptake in morbidly obese subjects

OBJECTIVE

The aim of this study is to investigate the effect of body size on insulin-mediated, whole-body glucose uptake (M-value) in morbidly obese (MO) subjects, who have large amounts of fat mass. Furthermore, we aimed at verifying which surrogate insulin-sensitivity index can better substitute the euglycemic clamp values and whether the insulin secretion/insulin resistance index is meaningful also in MO subjects.

DESIGN

The study design is cross-sectional, case-control study of insulin sensitivity--assessed by different methods--and insulin secretion.

SUBJECTS

One-hundred and sixty-eight subjects ca. 39 years old, with a body mass index (BMI) between 17 and 64 kg m⁻², underwent euglycemic hyperinsulinemic clamp and oral glucose tolerance test (OGTT) with surrogate measures of insulin sensitivity together with body composition by ³H₂O dilution. Insulin secretion rate (ISR) was measured at fast and after OGTT by C-peptide deconvolution.

RESULTS

The population was divided into quartiles of BMI. In the fourth quartile, the best insulin-sensitivity variable between M/I/kg(FFM) and M/I/kg(bw) was the latter, as shown by area under the receiver-operator characteristic (ROC) curve (0.85 vs 0.89). The best index to identify insulin-resistant individuals (lowest distribution quartile: M/I/kg(bw)≤ 29.3 μmol min⁻¹ kg⁻¹ nmol l⁻¹) were Matsuda index and oral glucose insulin sensitivity (OGIS), whereas fasting insulin concentration, QUICKI, and HOMA failed (ROC analysis). M-value declined exponentially as the BMI increased, whereas ISR linearly increased. The insulin secretion/insulin resistance index well applied to MO.

CONCLUSION

In MO subjects, in which the fat mass is highly represented, fat-free mass cannot be considered the only determinant of insulin sensitivity, thus M-value should be normalized by total body weight. The best surrogates of insulin sensitivity measured by euglycemic clamp are Matsuda index and OGIS. BMI directly affects both insulin sensitivity and ISR and the insulin secretion/insulin resistance index is a valid model to correlate ISR with insulin sensitivity also in MO.