Why Syndrome X? From Harold Himsworth to the insulin resistance syndrome

Microvascular vasoregulatory dysfunction in African Americans - An enhanced opportunity for early prevention and treatment of atherosclerotic cardiovascular disease

Atherosclerotic cardiovascular disease and its risk factors and precursors are a major driver of disparities in cardiovascular health. This review examines reported evidence that vascular endothelial dysfunction, and its manifestation as coronary microvascular dysfunction, underlies observed excess morbidity and mortality in African Americans. Advanced imaging insights that reveal patho-mechanisms, along with population evidence from the Jackson Heart Study, and the growing evidence emanating from national and international clinical trials and registries are presented. We examine a physiological framework that recognizes insulin-resistant cardiometabolic underpinnings of the conditions of the American Heart Associations' Life's Essential Eight construct of cardiovascular health as a unifying basis that affords early prevention. Mechanistic-based therapeutic approaches, can subsequently be implemented to interrupt progression to adverse outcomes employing layered, or personalized, treatment strategies of a well-defined set of conditions or diseases. Remaining knowledge gaps are acknowledged.

Detection of Metabolic Syndrome Using Insulin Resistance Indexes: A Cross-Sectional Observational Cohort Study

Insulin resistance (IR) is considered cardinal to the pathophysiology of metabolic syndrome (MetS). Previously, several simple indexes of IR calculated from biochemical and anthropometric variables have been proposed. However, these indexes are population-dependent; therefore, further studies on a global scale are necessary. The present study assessed the diagnostic accuracy of eight IR indicators, namely, METS-IR, TG-HDL-c, TyG, TyG-BMI, TyG-NC, TyG-NHtR, TyG-WC, and TyG-WHtR, in indicating MetS among a Brazilian population. For this, 268 patients (152 men and 116 women, 53–59 years of age) were included in the study, out of which 111 were diagnosed with MetS according to the National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III). All indexes achieved significant accuracy, with TyG-WC (0.849 (0.800–0.889)), TyG (0.837 (0.787–0.879)), and TG-HDL-c (0.817 (0.765–0.861)) having the highest area under the curve (AUC). Further, the most heightened diagnostic sensitivities were observed for TG-HDL-c (90.99%), TyG-WC (89.19%), and TyG-NC (84.68%), whereas the highest diagnostic specificities were noted for TyG (73.89%), TyG-WHtR (72.61%), and TyG-WC (66.88%). Thus, TyG-WC, TyG, and TG-HDL-c reached the greatest AUC values in our analyses, making them useful diagnostic indicators of MetS, and crucial for patients’ clinical management.

Role of the Endocannabinoid System in Metabolic Control Processes and in the Pathogenesis of Metabolic Syndrome: An Update

Metabolic syndrome is a complex disease state, which appears mostly as a consequence of an unhealthy, sedentary lifestyle. Metabolic complications include insulin resistance (IR), diabetes, dyslipidemia, hypertension, and atherosclerosis, impairing life standards and reducing life expectancy. The endocannabinoid system (ECS) has an important role in signalization processes, not only in the central nervous system, but also in the peripheral tissues. Several physiological functions are affected, and overexpression or downregulation contributes to several diseases. A better understanding of the functions of cannabinoid (CB) receptors may propose potential therapeutic effects by influencing receptor signaling and enzymes involved in downstream pathways. In this review, we summarize recent information regarding the roles of the ECS and the CB₁ receptor signaling in the physiology and pathophysiology of energy and metabolic homeostasis, in the development of obesity by enhancing food intake, upregulating energy balance and fat accumulation, increasing lipogenesis and glucose production, and impairing insulin sensitivity and secretion. By analyzing the roles of the ECS in physiological and pathophysiological mechanisms, we introduce some recently identified signaling pathways in the mechanism of the pathogenesis of metabolic syndrome. Our review emphasizes that the presence of such recently identified ECS signaling steps raises new therapeutic potential in the treatment of complex metabolic diseases such as diabetes, insulin resistance, obesity, and hypertension.

Cranberry Proanthocyanidins as a Therapeutic Strategy to Curb Metabolic Syndrome and Fatty Liver-Associated Disorders

While the prevalence of metabolic syndrome (MetS) is steadily increasing worldwide, no optimal pharmacotherapy is readily available to address its multifaceted risk factors and halt its complications. This growing challenge mandates the development of other future curative directions. The purpose of the present study is to investigate the efficacy of cranberry proanthocyanidins (PACs) in improving MetS pathological conditions and liver complications; C57BL/6J mice were fed either a standard chow or a high fat/high sucrose (HFHS) diet with and without PACs (200 mg/kg), delivered by daily gavage for 12 weeks. Our results show that PACs lowered HFHS-induced obesity, insulin resistance, and hyperlipidemia. In conjunction, PACs lessened circulatory markers of oxidative stress (OxS) and inflammation. Similarly, the anti-oxidative and anti-inflammatory capacities of PACs were noted in the liver in association with improved hepatic steatosis. Inhibition of lipogenesis and stimulation of beta-oxidation could account for PACs-mediated decline of fatty liver as evidenced not only by the expression of rate-limiting enzymes but also by the status of AMPKα (the key sensor of cellular energy) and the powerful transcription factors (PPARα, PGC1α, SREBP1c, ChREBP). Likewise, treatment with PACs resulted in the downregulation of critical enzymes of liver gluconeogenesis, a process contributing to increased rates of glucose production in type 2 diabetes. Our findings demonstrate that PACs prevented obesity and improved insulin resistance likely via suppression of OxS and inflammation while diminishing hyperlipidemia and fatty liver disease, as clear evidence for their strength of fighting the cluster of MetS abnormalities.

The relationship between insulin resistance and ion mobility lipoprotein fractions

Objective

Insulin resistance (IR) increases risk of type 2 diabetes and atherosclerotic cardiovascular disease and is associated with lipid and lipoprotein abnormalities including high triglycerides (TG) and low high-density lipoprotein cholesterol (HDL-C). Lipoprotein size and lipoprotein subfractions (LS) have also been used to assist in identifying persons with IR. Associations of LS and IR have not been validated using both direct measures of IR and direct measures of LS. We assessed the usefulness of fasting lipoprotein subfractions (LS) by ion mobility to identify individuals with IR.

Methods

Lipid panel, LS by ion mobility (LS-IM), and IR by steady-state plasma glucose (SSPG) concentration were assessed in 526 adult volunteers without diabetes. IR was defined as being in the highest tertile of SSPG concentration. LS-IM score was calculated by linear combination of regression coefficients from a stepwise regression analysis with SSPG concentration as the dependent variable. Improvement in prediction of IR was evaluated after combining LS-IM score with TG/HDL-C, TG/HDL-C and BMI as well as with TG/HDL-C, BMI, sex, race and ethnicity. IR prediction was evaluated by area under the receiver operating characteristic curve (AUC) and positive predictive value (PPV) considering the highest 5% of scores as positive test.

Results

Prediction of IR was similar by LS-IM score and TG/HDL-C (AUC=0.68; PPV=0.59 and AUC=0.70; PPV=0.59, respectively) and prediction was improved when LS-IM was combined with TG/HDL-C (AUC=0.73; PPV=0.70), TG/HDL-C and BMI (AUC=0.82; PPV=0.81) and with TG/HDL-C, BMI, sex, race and ethnicity (AUC=0.84; PPV=0.89).

Conclusion

For identifying individuals with IR, LS-IM score and TG/HDL-C are comparable and their combination further improves IR prediction by TG/HDL-C alone. Among patients who have undergone IM testing, the LS-IM score may assist prioritization of subjects for further evaluation and interventions to reduce IR.

Insulin Resistance and Urolithiasis as a Challenge for a Dietitian

Many obesity and diet-related diseases have been observed in recent years. Insulin resistance (IR), a state of tissue resistance to insulin due to its impaired function, is a common coexisting condition. The most important predisposing factors are excessive visceral fat and chronic low-grade inflammatory response. However, IR’s pathogenesis is not fully understood. Hence, the diagnosis of IR should be carried out carefully because many different diagnostic paths do not always give equivalent results. An additional disease that is often associated with IR is urolithiasis. The common feature of these two conditions is metabolic acidosis and mild inflammation. A patient diagnosed with IR and urolithiasis is a big challenge for a dietitian. It is necessary to check a thorough dietary history, make an appropriate anthropometric measurement, plan a full-fledged diet, and carry out the correct nutritional treatment. It is also essential to conduct proper laboratory diagnostics to plan nutritional treatment, which is often a big challenge for dietitians. The diet’s basic assumptions are based on the appropriate selection of carbohydrates, healthy fats, and wholesome protein sources. It is also essential to properly compose meals, prepare them, and plan physical activities tailored to the abilities. The study aims to summarise the necessary information on IR with concomitant urolithiasis, which may be helpful in dietary practice.

Preclinical and clinical evaluation of a new method to assess cardiac insulin resistance using nuclear imaging

BACKGROUND

Myocardial insulin resistance (IR) could be a predictive factor of cardiovascular events. This study aimed to introduce a new method using 123I-6-deoxy-6-iodo-D-glucose (6DIG), a pure tracer of glucose transport, for the assessment of IR using cardiac dynamic nuclear imaging.

METHODS

The protocol evaluated first in rat-models consisted in two 6DIG injections and one of insulin associated with planar imaging and blood sampling. Compartmental modeling was used to analyze 6DIG kinetics in basal and insulin conditions and to obtain an index of IR. As a part of a translational approach, a clinical study was then performed in 5 healthy and 6 diabetic volunteers.

RESULTS

In rodent models, the method revealed reproducible when performed twice at 7 days apart in the same animal. Rosiglitazone, an insulin-sensitizing drug, induced a significant increase of myocardial IR index in obese Zucker rats from 0.96 ± 0.18 to 2.26 ± 0.44 (P<.05) after 7 days of an oral treatment, and 6DIG IR indexes correlated with the gold standard IR index obtained through the hyperinsulinemic-euglycemic clamp (r=.68, P<.02). In human, a factorial analysis was applied on images to obtain vascular and myocardial kinetics before compartmental modeling. 1.5-fold to 2.2-fold decreases in mean cardiac IR indexes from healthy to diabetic volunteers were observed without reaching statistical significance.

CONCLUSIONS

These preclinical results demonstrate the reproducibility and sensibility of this novel imaging methodology. Although this first in-human study showed that this new method could be rapidly performed, larger studies need to be planned in order to confirm its performance.

Acne Vulgaris and Metabolic Syndrome: A Possible Association

Introduction

Acne vulgaris is an androgen-dependent disorder with excessive sebum production and proliferation of Propionibacterium acnes. Metabolic syndrome (MetS) is a multisystem disorder that increases the risk of diabetes mellitus, stroke, and cardiovascular diseases. ​This study aims to analyze the association of MetS with acne vulgaris.

Methods

A cross-sectional study was conducted with 65 cases of acne vulgaris and 65 age and sex-matched controls. We used the system provided by the Indian authors for grading acne according to the clinical severity. In addition, the criteria updated according to the joint consensus of 2009 were employed for the diagnosis of MetS.

Results

On clinical examination, grade 2 was the most prevalent grade of acne. We observed an increased incidence of abnormal waist circumference, triglyceride, HDL, and fasting blood glucose among the cases (p<0.05). Consequently, an increased occurrence of MetS was observed in the case group (p=0.011). While comparing the mean values of the parameters, we noted a significant difference in terms of waist circumference and HDL values. An increased mean value of waist circumference was noted in the case group while an increased mean value of HDL was reported from the control group (p<0.05). 

Conclusion

Patients with acne vulgaris have a greater chance of developing MetS. Hence, an in-depth examination of clinical, anthropometric, and biochemical parameters that may lead to the development of MetS is necessary.

Structure and activity study of tripeptide IRW in TNF-α induced insulin resistant skeletal muscle cells

Egg white protein ovotransferrin derived peptide IRW (Ile-Arg-Trp) was found to improve tumor necrosis factor alpha (TNF-α) or angiotensin II induced insulin resistance in L6 cells. Our recent study further showed that this peptide can improve glucose tolerance in high fat diet fed C57BL/6 mice. However, the structural requirements of IRW, especially the significance of each amino acid residue of IRW, is unknown. The study was aimed to investigate the structure and activity relationships of IRW in TNF-α induced insulin resistance L6 cells. The peptides were designed to determine the significance of individual amino acids in IRW using alanine scanning (replacing one amino acid at one time), the order of the peptide sequence and the constituting elements of IRW. Among the tested peptides and amino acids, only IRA and IR showed the same effects as that of IRW: enhanced glucose uptake, improvement in the impaired insulin signaling pathway and increased glucose transporter protein 4 (GLUT4) translocation in TNF-α treated L6 myotubes. This study demonstrated that C-terminal W is not essential to the activity of IRW. Further study is necessary to establish if IR and IRA show similar effects to that of IRW in vivo.

Djulis Hull Improves Insulin Resistance and Modulates the Gut Microbiota in High-Fat Diet (HFD)-Induced Hyperglycaemia

In this study, we annotated the major flavonoid glycoside, rutin, of djulis hull crude extract using a Global Natural Products Social Molecular Networking (GNPS) library and its MS/MS spectra. To evaluate the protective effect of djulis hull crude extract and rutin on glucose tolerance, we fed mice a high-fat diet (HFD) for 16 weeks to induce hyperglycaemia. These results showed that crude extract significantly decreased HFD-induced elevation in the area under the curve (AUC) of weekly random blood glucose and oral glucose tolerance tests (OGTT), homeostasis model assessment (HOMA-IR), and advanced glycation end product (AGE) levels, and significantly increased pIRS1 and Glut4 protein expression in epididymal white adipose tissue (eWAT) and liver. Furthermore, the HFD-induced reduction in the activity of glutathione peroxidase (GPx) and catalase (CAT) was reversed by crude extract. In addition, ZO-1 and occludin protein expression in the colon was markedly downregulated in HFD-fed mice, resulting in decreased intestinal permeability and lipopolysaccharide (LPS) translocation, but were restored following crude extract. Moreover, the crude extract intervention had a profound effect on the alpha diversity and microbial community in the gut microbiota. Therefore, djulis hull crude extract could improve blood glucose and increase insulin receptor sensitivity in HFD-induced hyperglycaemia, which is likely due to its modulation of the gut microbiota, preservation of the integrity of the intestinal barrier to reduce body inflammation, increased antioxidant activity, and modulation of insulin signalling.

Is type 2 diabetes an adiposity-based metabolic disease? From the origin of insulin resistance to the concept of dysfunctional adipose tissue

In the last decades of the past century, a remarkable amount of research efforts, money and hopes was generated to unveil the basis of insulin resistance that was believed to be the primary etiological factor in the development of type 2 diabetes. From the Reaven's insulin resistance syndrome to the DeFronzo's triumvirate (skeletal muscle, liver and beta-cell) and to Kahn's discovery (among many others) of insulin receptor downregulation and autophosphorylation, an enthusiastic age of metabolic in vivo and in vitro research took place, making the promise of a resolutory ending. However, from many published data (those of insulin receptoropathies and lipodystrophies, the genome-wide association studies results, the data on reversibility of type 2 diabetes after bariatric surgery or very-low-calorie diets, and many others) it appears that insulin resistance is not a primary defect but it develops secondarily to increased fat mass. In particular, it develops from a mismatch between the surplus caloric intake and the storage capacity of adipose tissue. On this basis, we propose to change the today's definition of type 2 diabetes in adiposity-based diabetes.Level of Evidence as a narrative review a vast array of studies have been included in the analysis, ranging from properly designed randomized controlled trials to case studies; however, the overall conclusion may be regarded as level IV.

Beta cell functionality and hepatic insulin resistance are major contributors to type 2 diabetes remission and starting pharmacological therapy: from CORDIOPREV randomized controlled trial

In order to assess whether previous hepatic IR (Hepatic-IR_fasting) and beta-cell functionality could modulate type 2 diabetes remission and the need for starting glucose-lowering treatment, newly-diagnosed type 2 diabetes participants who had never received glucose-lowering treatment (190 out of 1002) from the CORonary Diet Intervention with Olive oil and cardiovascular PREVention study (a prospective, randomized and controlled clinical trial), were randomized to consume a Mediterranean or a low-fat diet. Type 2 diabetes remission was defined according to the American Diabetes Association recommendation for levels of HbA1c, fasting plasma glucose and 2h plasma glucose after oral glucose tolerance test, and having maintained them for at least 2 consecutive years. Patients were classified according to the median of Hepatic-IR_fasting and beta-cell functionality, measured as the disposition index (DI) at baseline. Cox proportional hazards regression determined the potential for Hepatic-IR_fasting and DI indexes as predictors of diabetes remission and the probability of starting pharmacological treatment after a 5-year follow-up. Low-Hepatic-IR_fasting or high-DI patients had a higher probability of diabetes remission than high-Hepatic-IR_fasting or low-DI subjects (HR:1.79; 95% CI 1.06-3.05; and HR:2.66; 95% CI 1.60-4.43, respectively) after a dietary intervention with no pharmacological treatment and no weight loss. The combination of low-Hepatic-IR_fasting and high-DI presented the highest probability of remission (HR:4.63; 95% CI 2.00-10.70). Among patients maintaining diabetes, those with high- Hepatic-IR_fasting and low-DI showed the highest risk of starting glucose-lowering therapy (HR:3.24;95% CI 1.50-7.02). Newly-diagnosed type 2 diabetes patients with better beta-cell functionality and lower Hepatic-IR_fasting had a higher probability of type 2 diabetes remission in a dietary intervention without pharmacological treatment or weight loss, whereas among patients not achieving remission, those with worse beta-cell functionality and higher Hepatic-IR_fasting index had the highest risk of starting glucose-lowering treatment after 5 years of follow-up.

Poor adherence to the Mediterranean diet is associated with increased likelihood of metabolic syndrome components in children: the Healthy Growth Study

OBJECTIVE

To examine the associations between the level of adherence to the Mediterranean diet (MedDiet) with obesity, insulin resistance (IR), metabolic syndrome (MetS) and its components in schoolchildren.

DESIGN

The Healthy Growth Study was a large epidemiological cross-sectional study.

SETTING

School children who were enrolled in primary schools in four counties covering the northern, southern, western and central part of Greece were invited to participate.

PARTICIPANTS

The study was conducted with a representative sample of 9-13-year-old schoolchildren (n 1972) with complete data. This study applied the KIDMed score to determine 'poor' (≤3), 'medium' (4-7) and 'high' (≥8) adherence of children to the MedDiet. The research hypothesis was examined using multivariate logistic regression models, controlling for potential confounders.

RESULTS

The percentage of children with 'poor', 'medium' and 'high' adherence to the MedDiet was 64·8 %, 34·2 % and 1 %, respectively. Furthermore, the prevalence of obesity, IR and MetS was 11·6 %, 28·8 % and 3·4 %, respectively. Logistic regression analyses revealed that 'poor' adherence to the MedDiet was associated with an increased likelihood for central obesity (OR 1·31; 95 % CI 1·01, 1·73), hypertriglyceridaemia (OR 2·80; 95 % CI 1·05, 7·46) and IR (OR 1·31; 95 % CI 1·05, 1·64), even after adjusting for several potential confounders.

CONCLUSIONS

The present study showed that approximately two-thirds of the examined sample of schoolchildren in Greece have 'poor' adherence to the MedDiet, which also increases the likelihood for central obesity, hypertriglyceridaemia and IR. Prospective studies are needed to confirm whether these are cause-effect associations.

Metabolic Syndrome: Is It Time to Add the Central Nervous System?

Metabolic syndrome (MS) is a set of cardio-metabolic risk factors that includes central obesity, hyperglycemia, hypertension, and dyslipidemias. The syndrome affects 25% of adults worldwide. The definition of MS has evolved over the last 80 years, with various classification systems and criteria, whose limitations and benefits are currently the subject of some controversy. Likewise, hypotheses regarding the etiology of MS add more confusion from clinical and epidemiological points of view. The leading suggestion for the pathophysiology of MS is insulin resistance (IR). IR can affect multiple tissues and organs, from the classic “triumvirate” (myocyte, adipocyte, and hepatocyte) to possible effects on organs considered more recently, such as the central nervous system (CNS). Mild cognitive impairment (MCI) and Alzheimer’s disease (AD) may be clinical expressions of CNS involvement. However, the association between MCI and MS is not understood. The bidirectional relationship that seems to exist between these factors raises the questions of which phenomenon occurs first and whether MCI can be a precursor of MS. This review explores shared pathophysiological mechanisms between MCI and MS and establishes a hypothesis of a possible MCI role in the development of IR and the appearance of MS.

A Bittersweet Response to Infection in Diabetes; Targeting Neutrophils to Modify Inflammation and Improve Host Immunity

Chronic and recurrent infections occur commonly in both type 1 and type 2 diabetes (T1D, T2D) and increase patient morbidity and mortality. Neutrophils are professional phagocytes of the innate immune system that are critical in pathogen handling. Neutrophil responses to infection are dysregulated in diabetes, predominantly mediated by persistent hyperglycaemia; the chief biochemical abnormality in T1D and T2D. Therapeutically enhancing host immunity in diabetes to improve infection resolution is an expanding area of research. Individuals with diabetes are also at an increased risk of severe coronavirus disease 2019 (COVID-19), highlighting the need for re-invigorated and urgent focus on this field. The aim of this review is to explore the breadth of previous literature investigating neutrophil function in both T1D and T2D, in order to understand the complex neutrophil phenotype present in this disease and also to focus on the development of new therapies to improve aberrant neutrophil function in diabetes. Existing literature illustrates a dual neutrophil dysfunction in diabetes. Key pathogen handling mechanisms of neutrophil recruitment, chemotaxis, phagocytosis and intracellular reactive oxygen species (ROS) production are decreased in diabetes, weakening the immune response to infection. However, pro-inflammatory neutrophil pathways, mainly neutrophil extracellular trap (NET) formation, extracellular ROS generation and pro-inflammatory cytokine generation, are significantly upregulated, causing damage to the host and perpetuating inflammation. Reducing these proinflammatory outputs therapeutically is emerging as a credible strategy to improve infection resolution in diabetes, and also more recently COVID-19. Future research needs to drive forward the exploration of novel treatments to improve infection resolution in T1D and T2D to improve patient morbidity and mortality.

Synergizing Mouse and Human Studies to Understand the Heterogeneity of Obesity

Obesity is routinely considered as a single disease state, which drives a "one-size-fits-all" approach to treatment. We recently convened the first annual University of North Carolina Interdisciplinary Nutrition Sciences Symposium to discuss the heterogeneity of obesity and the need for translational science to advance understanding of this heterogeneity. The symposium aimed to advance scientific rigor in translational studies from animal to human models with the goal of identifying underlying mechanisms and treatments. In this review, we discuss fundamental gaps in knowledge of the heterogeneity of obesity ranging from cellular to population perspectives. We also advocate approaches to overcoming limitations in the field. Examples include the use of contemporary mouse genetic reference population models such as the Collaborative Cross and Diversity Outbred mice that effectively model human genetic diversity and the use of translational models that integrate -omics and computational approaches from pre-clinical to clinical models of obesity. Finally, we suggest best scientific practices to ensure strong rigor that will allow investigators to delineate the sources of heterogeneity in the population with obesity. Collectively, we propose that it is critical to think of obesity as a heterogeneous disease with complex mechanisms and etiologies, requiring unique prevention and treatment strategies tailored to the individual.

Curcumin anti-diabetic effect mainly correlates with its anti-apoptotic actions and PI3K/Akt signal pathway regulation in the liver

This study aimed to investigate the therapeutic effect of curcumin on type 2 diabetes and its underlying mechanisms. A type 2 diabetes mellitus rat model was established by providing high-fat diet and low doses of streptozotocin. Type 2 diabetes mellitus rats were treated with low dose and high dose of curcumin for 8 weeks. The results showed that high-dose curcumin significantly reduced fasting blood glucose, total cholesterol, triglyceride, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, alanine aminotransferase, and aspartate transaminase, liver coefficient, and malondialdehyde levels, and BCL2-Associated X expression in the type 2 diabetes mellitus rats. High-dose curcumin increased the levels of liver superoxide dismutase, catalase, and glutathione; as well as the expression of liver B-cell lymphoma-2, phosphatidylinositol 3-kinase, phosphorylated phosphatidylinositol 3-kinase, protein kinase B, and phosphorylated protein kinase B in type 2 diabetes mellitus rats. Furthermore, it ameliorated the histological structure of the liver and pancreas in diabetes mellitus model rats. However, low-dose curcumin had no significant effect on diabetes mellitus model rats. The results suggest that adequate doses of curcumin controls type 2 diabetes mellitus development as well as the mechanism involved in its anti-apoptotic actions and phosphatidylinositol 3-hydroxy kinase/protein kinase B signal pathway regulation in the liver.

Enhanced peripheral blood miR-324-5p is associated with the risk of metabolic syndrome by suppressing ROCK1

The current study aims to evaluate whether peripheral blood miR-324-5p could be used to differentiate patients with metabolic disorders and healthy controls. Our data showed that miR-324-5p levels were elevated in the peripheral blood of patients with hyperglycemia or hyperlipidemia. In addition, the expression of miR-324-5p was enhanced in the peripheral blood and liver of db/db mice. Further study indicated that overexpression of miR-324-5p reduced the activation of the AKT/GSK pathway and increased lipid accumulation, while the inhibition of miR-324-5p activated the AKT/GSK pathway and decreased lipid accumulation. A dual luciferase assay revealed that Rho-associated coiled-coil containing protein kinase 1 (ROCK1) was a target gene of miR-324-5p. In addition, silencing ROCK1 deteriorated lipid and glucose metabolism. More importantly, knockdown of ROCK1 reversed the miR-324-5p inhibitor-induced improvement of glucose and lipid metabolism. In summary, miR-324-5p plays a regulatory role in glucose and lipid metabolism by targeting ROCK1, which is involved in metabolic disorders. The use of miR-324-5p in diagnosing metabolic syndrome is worth investigating and may benefit patients.

Race affects the association of obesity measures with insulin sensitivity

BACKGROUND

Race differences in body composition and fat distribution may in part explain the differences in insulin sensitivity and the disproportionate burden of type 2 diabetes in African Americans.

OBJECTIVE

To determine if differences in body composition and fat distribution explain race differences in insulin sensitivity and identify obesity measures that were independently associated with insulin sensitivity.

METHODS

Participants were 113 lean, overweight, and obese African-American and Caucasian-American adults without diabetes. Skeletal muscle insulin sensitivity was determined using a hyperinsulinemic-euglycemic clamp (SIClamp, insulin rate:120 mU/m2/min). Subcutaneous abdominal adipose tissue (SAAT), intra-abdominal adipose tissue (IAAT), and liver fat were measured by MRI; leg fat, total fat, and lean mass were measured by DXA.

RESULTS

Race-by-adiposity interactions were significant in cross-sectional analyses utilizing multiple linear regression models for SIClamp (P < 0.05); higher BMI, fat mass, SAAT, leg fat, and liver fat were associated with lower SIClamp in Caucasian Americans but not African Americans. Race-by-IAAT interaction was not significant (P = 0.65). A central fat distribution (SAAT adjusted for leg fat) was associated with lower SIClamp in African Americans (β = -0.45, SE = 0.11, P < 0.001) but not Caucasian Americans (β = -0.42, SE = 0.30, P = 0.17). A peripheral fat distribution (leg fat adjusted for IAAT/SAAT) was associated with a higher SIClamp in African Americans (β = 0.11, SE = 0.05, P = 0.02) but lower SIClamp in Caucasian Americans (β = -0.28, SE = 0.14, P = 0.049). Lean mass was inversely associated with SIClamp in African Americans (β = -0.05, SE = 0.03, P = 0.04) but not Caucasian Americans (β = 0.08, SE = 0.05, P = 0.10) in the model for leg fat.

CONCLUSIONS

Measures of overall adiposity were more strongly associated with SIClamp in Caucasian Americans, whereas body fat distribution and lean mass showed stronger correlations with SIClamp in African Americans. Insulin sensitivity may have a genetic basis in African Americans that is reflected in the pattern of body fat distribution. These findings suggest a race-specific pathophysiology of insulin resistance, which has implications for the prevention of diabetes and related cardiometabolic diseases.

Lower limb muscle mass is associated with insulin resistance more than lower limb muscle strength in non-diabetic older adults

AIM

We examined the association of muscle mass and muscle strength with insulin resistance, focusing on lower limb muscles.

METHODS

This was a cross-sectional study, and participants were registered in 2017 from the Tanno-Sobetsu Study, a population-based cohort study. After excluding individuals aged <64 years or with a history of diabetes mellitus, 272 non-diabetic older adults (116 men, 156 women) met the inclusion criteria. According to the homeostasis model assessment of insulin resistance, the participants were divided into two groups; that is, the insulin resistance group (homeostasis model assessment of insulin resistance ≥1.73) and non-insulin resistance group (homeostasis model assessment of insulin resistance <1.73). Muscle mass (lower limb, upper limb, appendicular and trunk) and muscle strength (grip strength and knee extension torque) were measured and divided by the weight, and then multiplied by 100 to calculate the weight ratio (%). The adjusted odds ratio (OR) of each muscle index for risk of insulin resistance was calculated separately for both men and women.

RESULTS

Lower limb muscle mass (OR 0.72, 95% CI 0.55-0.92 in men; OR 0.69, 95% CI 0.51-0.96 in women, respectively) and appendicular muscle mass (OR 0.75, 95% CI 0.61-0.94 in men; OR 0.72, 95% CI 0.54-0.95 in women, respectively), but not other muscle indexes, were associated with risk of insulin resistance, after adjusting for age, body mass index, highly sensitive C-reacting protein and smoking habits.

CONCLUSIONS

Lower limb muscle mass of non-diabetic older adults is independently related to insulin resistance. Geriatr Gerontol Int 2019; 19: 1254-1259.

Safety, Biodistribution, and Dosimetry of 123I-6-Deoxy-6-Iodo-D-Glucose, a Tracer of Glucose Transport, in Healthy and Diabetic Volunteers

PURPOSE

Insulin resistance is a key feature of the metabolic syndrome and type 2 diabetes, in which noninvasive assessment is not currently allowed by any methodology. We previously validated an iodinated tracer of glucose transport (6DIG) and a new methodology for the in vivo quantification of cardiac insulin resistance in rodents. The aim of this study was to investigate the safety, biodistribution, and radiation dosimetry of this method using I-6DIG in 5 healthy and 6 diabetic volunteers.

METHODS

The collection of adverse effects (AEs) and medical supervision of vital parameters and biological variables allowed the safety evaluation. Biodistribution was studied by sequentially acquiring whole-body images at 1, 2, 4, 8, and 24 hours postinjection. The total number of disintegrations in each organ normalized to the injected activity was calculated as the area under the time-activity curves. Dosimetry calculations were performed using OLINDA/EXM.

RESULTS

No major adverse events were observed. The average dose corresponding to the 2 injections of I-6DIG used in the protocol was 182.1 ± 7.5 MBq. A fast blood clearance of I-6DIG was observed. The main route of elimination was urinary, with greater than 50% of urine activity over 24 hours. No blood or urine metabolite was detected. I-6DIG accumulation mostly occurred in elimination organs such as kidneys and liver. Mean radiation dosimetry calculations indicated an effective whole-body absorbed dose of 3.35 ± 0.57 mSv for the whole procedure.

CONCLUSIONS

I-6DIG was well tolerated in human with a dosimetry profile comparable to that of other commonly used iodinated tracers, thereby allowing further clinical development of the tracer.

Effects of magnitude of visceral adipose tissue reduction: Impact on insulin resistance, hyperleptinemia and cardiometabolic risk in adolescents with obesity after long-term weight-loss therapy

AIM

To investigate the association between visceral adipose tissue loss and insulin resistance and hyperleptinemia in adolescents with obesity submitted to interdisciplinary weight-loss therapy.

METHODS

A total of 172 post-pubertal adolescents (body mass index greater than the 95th percentile of the Centers for Disease Control and Prevention reference growth charts) were recruited for the study. The adolescents were assigned to long-term weight-loss therapy. Body composition, visceral and subcutaneous fat, glucose metabolism, lipid profile, hepatic enzymes and leptin concentration were measured. After the therapy, the adolescents were allocated to three different groups according to the tertile of visceral fat reduction.

RESULTS

Positive effects on body composition were observed in all analysed groups independent of visceral fat reduction. It was found that visceral fat was an independent predictor of insulin resistance in the investigated population. Obese adolescents who lost a higher proportion of visceral adipose tissue (>1.8 cm) demonstrated improved metabolic and inflammatory parameters twice as much than those who presented smaller losses. Positive correlations between visceral fat reduction and glucose metabolism, lipid profile, hepatic enzymes and homeostasis model assessment of insulin resistance index were demonstrated.

CONCLUSION

The magnitude of the reduction in visceral fat was an independent predictor of insulin resistance, hyperleptinemia and metabolic disorders related to obese adolescents.

Insulin resistance: Impact on therapeutic developments in diabetes

Insulin resistance has a broad pathogenic impact affecting metabolic, cardio-renal and other disease areas. Extensive studies to dissect the mechanisms of insulin resistance have provided valuable insights to shape current clinical awareness and advance therapeutic practice. However, the development of direct interventions against insulin resistance has been hindered by its complex and highly variable presentations, especially in type 2 diabetes. Among glucose-lowering agents, metformin and thiazolidinediones provide cellular actions that counter some effects of insulin resistance: reduced glucotoxicity and weight-lowering with antidiabetic therapies also improve insulin action, except that endogenously- or exogenously-created hyperinsulinaemia may partially compromise these benefits. Increasing awareness of the pervasiveness and damaging ramifications of insulin resistance heightens the need for more specifically targeted and more effective therapies.

Egg white hydrolysate and peptide reverse insulin resistance associated with tumor necrosis factor-α (TNF-α) stimulated mitogen-activated protein kinase (MAPK) pathway in skeletal muscle cells

Purpose

Excessive formation of tumor necrosis factor-α (TNF-α), a pro-inflammatory cytokine, has been implicated in the development of insulin resistance in obesity and type-2 diabetes. In skeletal muscle, chronic exposure to TNF-α impairs insulin-stimulated glucose uptake and insulin signaling. The aim of this study is to investigate the effects of enzymatic egg white hydrolysate (EWH) and its responsible peptide, IRW, on TNF-α-induced insulin resistance and the underlying molecular mechanisms using rat skeletal muscle cells (L6 cells).

Methods

Insulin resistance was induced by treating L6 cells with 5 ng/ml TNF-α for 24 h. Effects of EWH and IRW on glucose uptake were detected by glucose uptake assay, glucose transporter 4 (GLUT4) translocation by immunofluorescence, and western blot, while insulin-signaling pathway and mitogen-activated protein kinase (MAPK) pathway were investigated using western blot.

Results

Adding both EWH and IRW significantly improved glucose uptake in TNF-α-treated cells, increased activation of insulin receptor substrate (IRS-1) tyrosine residue and protein kinase B (Akt), whereas decreased activation of IRS-1 serine residue. In addition, TNF-α-induced activation of p38-mitogen-activated protein kinase (p38) and c-Jun N-terminal kinases (JNK) 1/2 were decreased by either EWH or IRW treatment.

Conclusion

EWH and IRW improve impaired insulin sensitivity by down-regulating the activation of p38 and JNK1/2 in TNF-α-treated skeletal muscle cells.

Relationship between several surrogate estimates of insulin resistance and a direct measure of insulin-mediated glucose disposal: Comparison of fasting versus post-glucose load measurements

AIMS

The study aim was to determine the correlation of several surrogate estimates of insulin resistance with a direct measure of insulin action and the ability of these estimates to identify insulin resistant persons.

METHODS

Retrospective analysis of 454 apparently healthy individuals studied in a clinical research center. The correlations between 11 surrogate estimates of insulin resistance, using either fasting or post-oral glucose challenge values, and a direct measure of insulin-mediated glucose uptake (SSPG concentration during the Insulin Suppression Test) were determined as well as the ability of the surrogate estimates to identify insulin resistant individuals.

RESULTS

All surrogate estimates were significantly (P < .001) correlated with SSPG concentrations and successfully identified insulin resistant persons. These relationships were of lesser magnitude when estimates were based on fasting data, with the exception of the McAuley index-derived from fasting data, but resembling post-glucose challenge estimates. Moreover, correlation with SSPG concentration, and positive identification of insulin resistance, varied considerably among estimates.

CONCLUSION

All 11 surrogate estimates of insulin resistance significantly correlated with insulin-mediated glucose disposal and identified insulin resistant persons with a reasonable degree of sensitivity and specificity. For identification of insulin resistant individuals, indices based on post-glucose challenge measurements performed better than those based on fasting measurements, with the exception of McAuley index. The quantitative information derived from this analysis should help investigators select the surrogate marker of insulin resistance best suited for their study.

Fifty Years of Behavioral/Lifestyle Interventions for Overweight and Obesity: Where Have We Been and Where Are We Going?

OBJECTIVE

This paper reviews the literature pertaining to the structure and content of intensive lifestyle interventions (ILIs) for overweight/obesity since Richard Stuart described this new treatment approach in 1967. A consensus opinion has formed that behavioral/lifestyle treatment of overweight and obesity should be viewed as a mainstream intervention for the treatment and prevention of type 2 diabetes and medical complications associated with obesity.

METHODS

The development of modern ILIs and demonstration of their efficacy are compared by structure, content, and efficacy of four major randomized controlled trials: Diabetes Prevention Program (DPP), Look AHEAD, POUNDS Lost, and CALERIE.

RESULTS

The results of these studies indicated that modification of lifestyle behaviors related to nutrition and physical activity can yield weight loss and prevention or improvement of a variety of medical conditions associated with obesity in a variety of subpopulations.

CONCLUSIONS

Recommendations for the structure and length of behavioral/lifestyle interventions have been recently adopted by agencies and institutions that approve reimbursement for medical services. These recommendations represent a giant step in the effort to recognize ILIs as a mainstream approach for the treatment of obesity and comorbid medical conditions. Nevertheless, they do not adequately represent advances made since the publication of the DPP results.

[Diabetology as an interdisciplinary challenge]

Type 2 diabetes mellitus is a growing chronic disease with a complex pathophysiology and multiple therapeutic options. Clinical prognosis is determined by multimorbidity and cardiovascular complications. For example, the prognosis of patients with diabetes hospitalized for heart failure is very poor with up to 50% mortality rate over the 3 years thereafter. Therefore, three levels have to be addressed in our approach to interdisciplinary diabetes care: screening and prevention, efficient patient-centered drug therapy, and a strategy for care including social environment of the patient suffering from complex diseases. Thus, we need diabetes specialists in out- and in-patient settings. Transsectoral interdisciplinary approaches to clinical care, as exemplary shown for the treatment of the diabetes foot syndrome, should be developed for other comorbidities, like renal and heart failure, respectively. The basis in the therapy of the cardiometabolic high-risk patient is prevention and multimodal treatment of cardiovascular risk factors. In this context, it is interesting to note that new cardiovascular outcome trials with a so-called safety design have shown that the GLP-1 receptor agonist liraglutide and the SGLT-2 inhibitor empagliflozin can reduce cardiovascular event rates. In addition, empagliflozin has significantly reduced the rate of hospitalization for heart failure. The latter has been included in the recent guidelines on heart failure by the European Society of Cardiology.

Hyperinsulinemia and Insulin Resistance: Scope of the Problem

No abstract available.

Relationship Between Two Common Lipoprotein Lipase Variants and the Metabolic Syndrome and Its Individual Components

BACKGROUND

Common lipoprotein lipase (LPL) variants are important determinants of triglycerides (TG) and high-density lipoprotein (HDL) cholesterol (C) concentrations. High TG/low HDL-C tend to cluster with hypertension, glucose intolerance, and abdominal obesity and comprise the metabolic syndrome (MetS). The role of LPL variants as a cause of MetS is unclear. This study investigated the relationship between two common LPL variants and the presence of MetS and its individual components.

METHODS

Cross-sectional study, including 2348 Danish women (50.7%) and men, age 41-72 years, without known cardiovascular disease. Carrier status for the two common LPL variants: 447Ter (low TG/high HDL-C) and 291Ser (high TG/low HDL-C) was determined. The prevalence of MetS according to the National Cholesterol Education Program criteria was 16.6%.

RESULTS

Of the 2348 participants, 19.8% had the 447Ter variant and 4.9% had the 291Ser variant. Compared with the reference variant, the prevalence of MetS was lower in carriers of the 447Ter variant (11.2% vs. 17.9%, P < 0.001) but with no difference in carriers of the 291Ser variant (18.4% vs. 16.5%, P = 0.59). Adjusted for age, sex, smoking, physical activity, alcohol consumption, and highest sex-specific insulin quartile, the relative risk of MetS was 0.63 (95% confidence interval [CI] 0.45-0.89, P < 0.01) for carriers of the 447Ter variant and 1.20 (95% CI 0.70-2.03, P > 0.05) for carriers of the 291Ser variant. Both LPL variants were associated with high TG/low HDL-C (P < 0.01), but not with the MetS components waist circumference, hypertension, and glucose intolerance (P > 0.05).

CONCLUSION

The two common LPL variants were associated with MetS through their effect on high TG/low HDL-C.

Strength Training Prevents Hyperinsulinemia, Insulin Resistance, and Inflammation Independent of Weight Loss in Fructose-Fed Animals

The aim of this study was to compare the effects of aerobic, strength, and combined training on metabolic disorders induced by a fructose-rich diet. Wistar rats (120 days old) were randomized into five groups (n = 8-14): C (control diet and sedentary), F (fed the fructose-rich diet and sedentary), FA (fed the fructose-rich diet and subject to aerobic exercise), FS (fed the fructose-rich diet and subject to strength exercise), and FAS (fed the fructose-rich diet and subject to combined aerobic and strength exercises). After the 8-week experiment, glucose homeostasis, blood biochemistry, tissue triglycerides, and inflammation were evaluated and analyzed. The strength protocol exerted greater effects on glucose homeostasis, insulin sensitivity, and liver lipid contents than other protocols (all P < 0.05). All three exercise protocols induced a remarkable reduction in inflammation, tissue triglyceride content, and inflammatory pathways, which was achieved through c-Jun NH2-terminal kinase (JNK) phosphorylation and factor nuclear kappa B (NFkB) activation in both the liver and the muscle. Our data suggest that strength training reduced the severity of most of the metabolic disorders induced by a fructose-rich diet and could be the most effective strategy to prevent or treat fructose-induced metabolic diseases.

Hypoglycemic Activity through a Novel Combination of Fruiting Body and Mycelia of Cordyceps militaris in High-Fat Diet-Induced Type 2 Diabetes Mellitus Mice

Diabetes mellitus (DM) is currently ranked among leading causes of death worldwide in which type 2 DM is reaching an epidemic proportion. Hypoglycemic medications for type 2 DM have either proven inadequate or posed adverse effects; therefore, the Chinese herbal products are under investigation as an alternative treatment. In this study, a novel combination of fruiting body and mycelia powder of herbal Cordyceps militaris number 1 (CmNo1) was administered to evaluate their potential hypoglycemic effects in high-fat diet- (HFD-) induced type 2 DM in C57BL/6J mice. Body weight, fasting blood glucose (FBG), oral glucose tolerance test (OGTT), and blood biochemistry indexes were measured. Results indicated that CmNo1 lowered the blood glucose level by increasing insulin sensitivity, while no change in body weight was observed. Increased protein expression of IRS-1, pIRS-1, AKT, pAKT, and GLUT-4 in skeletal muscle and adipose tissue was found indicating restoration of insulin signaling. Additionally, PPAR-γ expression in adipose tissue restored the triglyceride and cholesterol levels. Finally, our results suggest that CmNo1 possesses strong hypoglycemic, anticholesterolemic, and antihypertriglyceridemic actions and is more economical alternate for DM treatment.

HDLs, diabetes, and metabolic syndrome

The prevalence of type 2 diabetes mellitus and of the metabolic syndrome is rising worldwide and reaching epidemic proportions. These pathologies are associated with significant morbidity and mortality, in particular with an excess of cardiovascular deaths. Type 2 diabetes mellitus and the cluster of pathologies including insulin resistance, central obesity, high blood pressure, and hypertriglyceridemia that constitute the metabolic syndrome are associated with low levels of HDL cholesterol and the presence of dysfunctional HDLs. We here review the epidemiological evidence and the potential underlying mechanisms of this association. We first discuss the well-established association of type 2 diabetes mellitus and insulin resistance with alterations of lipid metabolism and how these alterations may lead to low levels of HDL cholesterol and the occurrence of dysfunctional HDLs. We then present and discuss the evidence showing that HDL modulates insulin sensitivity, insulin-independent glucose uptake, insulin secretion, and beta cell survival. A dysfunction in these actions could play a direct role in the pathogenesis of type 2 diabetes mellitus.

Fenugreek seed extract inhibit fat accumulation and ameliorates dyslipidemia in high fat diet-induced obese rats

This study investigated the inhibitory effect of aqueous extract of Trigonella foenum-graecum seeds (AqE-TFG) on fat accumulation and dyslipidemia in high fat diet- (HFD-) induced obese rats. Female Wistar rats were fed with HFD ad libitum, and the rats on HFD were treated orally with AqE-TFG or orlistat ((HFD for 28 days + AqE-TFG (0.5 and 1.0 g/kg) or orlistat (10 mg/kg) from day 8 to 28), respectively. Treatment with AqE-TFG produced significant reduction in body weight gain, body mass index (BMI), white adipose tissue (WAT) weights, blood glucose, serum insulin, lipids, leptin, lipase, and apolipoprotein-B levels and elevation in adiponectin levels. AqE-TFG improved serum aspartate amino transferase (AST), alanine amino transferase (ALT), and lactate dehydrogenase (LDH) levels. AqE-TFG treatment reduced the hepatic and cardiac thiobarbituric acid reactive substances (TBARS) and elevated the antioxidant enzyme (glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT)) levels. In addition, liver and uterine WAT lipogenic enzyme (fatty acid synthetase (FAS) and glucose-6-phosphate dehydrogenase (G6PD)) activities were restored towards normal levels. These findings demonstrated the preventive effect of AqE-TFG on fat accumulation and dyslipidemia, due to inhibition of impaired lipid digestion and absorption, in addition to improvement in glucose and lipid metabolism, enhancement of insulin sensitivity, increased antioxidant defense, and downregulation of lipogenic enzymes.

Evaluation of fasting plasma insulin concentration as an estimate of insulin action in nondiabetic individuals: comparison with the homeostasis model assessment of insulin resistance (HOMA-IR)

Insulin-mediated glucose disposal varies severalfold in apparently healthy individuals, and approximately one-third of the most insulin resistant of these individuals is at increased risk to develop various adverse clinical syndromes. Since direct measurements of insulin sensitivity are not practical in a clinical setting, several surrogate estimates of insulin action have been proposed, including fasting plasma insulin (FPI) concentration and the homeostasis model assessment of insulin resistance (HOMA-IR) calculated by a formula employing fasting plasma glucose (FPG) and FPI concentrations. The objective of this study was to compare FPI as an estimate of insulin-mediated glucose disposal with values generated by HOMA-IR in 758 apparently healthy nondiabetic individuals. Measurements were made of FPG, FPI, triglyceride (TG), and high-density lipoprotein cholesterol (HDL-C) concentrations, and insulin-mediated glucose uptake was quantified by determining steady-state plasma glucose (SSPG) concentration during the insulin suppression test. FPI and HOMA-IR were highly correlated (r = 0.98, P < 0.001). The SSPG concentration also correlated to a similar degree (P < 0.001) with FPI (r = 0.60) and HOMA-IR (r = 0.64). Furthermore, the relationship between FPI and TG (r = 0.35) and HDL-C (r = -0.40) was comparable to that between HOMA-IR and TG (r = 0.39) and HDL-C (r = -0.41). In conclusion, FPI and HOMA-IR are highly correlated in nondiabetic individuals, with each estimate accounting for ~40% of the variability (variance) in a direct measure of insulin-mediated glucose disposal. Calculation of HOMA-IR does not provide a better surrogate estimate of insulin action, or of its associated dyslipidemia, than measurement of FPI.

Insulin signaling, resistance, and the metabolic syndrome: insights from mouse models into disease mechanisms

Insulin resistance is a major underlying mechanism responsible for the 'metabolic syndrome', which is also known as insulin resistance syndrome. The incidence of the metabolic syndrome is increasing at an alarming rate, becoming a major public and clinical problem worldwide. The metabolic syndrome is represented by a group of interrelated disorders, including obesity, hyperglycemia, hyperlipidemia, and hypertension. It is also a significant risk factor for cardiovascular disease and increased morbidity and mortality. Animal studies have demonstrated that insulin and its signaling cascade normally control cell growth, metabolism, and survival through the activation of MAPKs and activation of phosphatidylinositide-3-kinase (PI3K), in which the activation of PI3K associated with insulin receptor substrate 1 (IRS1) and IRS2 and subsequent Akt→Foxo1 phosphorylation cascade has a central role in the control of nutrient homeostasis and organ survival. The inactivation of Akt and activation of Foxo1, through the suppression IRS1 and IRS2 in different organs following hyperinsulinemia, metabolic inflammation, and overnutrition, may act as the underlying mechanisms for the metabolic syndrome in humans. Targeting the IRS→Akt→Foxo1 signaling cascade will probably provide a strategy for therapeutic intervention in the treatment of type 2 diabetes and its complications. This review discusses the basis of insulin signaling, insulin resistance in different mouse models, and how a deficiency of insulin signaling components in different organs contributes to the features of the metabolic syndrome. Emphasis is placed on the role of IRS1, IRS2, and associated signaling pathways that are coupled to Akt and the forkhead/winged helix transcription factor Foxo1.

11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) inhibitors still improve metabolic phenotype in male 11β-HSD1 knockout mice suggesting off-target mechanisms

The enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) is a target for novel type 2 diabetes and obesity therapies based on the premise that lowering of tissue glucocorticoids will have positive effects on body weight, glycemic control, and insulin sensitivity. An 11β-HSD1 inhibitor (compound C) inhibited liver 11β-HSD1 by >90% but led to only small improvements in metabolic parameters in high-fat diet (HFD)-fed male C57BL/6J mice. A 4-fold higher concentration produced similar enzyme inhibition but, in addition, reduced body weight (17%), food intake (28%), and glucose (22%). We hypothesized that at the higher doses compound C might be accessing the brain. However, when we developed male brain-specific 11β-HSD1 knockout mice and fed them the HFD, they had body weight and fat pad mass and glucose and insulin responses similar to those of HFD-fed Nestin-Cre controls. We then found that administration of compound C to male global 11β-HSD1 knockout mice elicited improvements in metabolic parameters, suggesting "off-target" mechanisms. Based on the patent literature, we synthesized another 11β-HSD1 inhibitor (MK-0916) from a different chemical series and showed that it too had similar off-target body weight and food intake effects at high doses. In summary, a significant component of the beneficial metabolic effects of these 11β-HSD1 inhibitors occurs via 11β-HSD1-independent pathways, and only limited efficacy is achievable from selective 11β-HSD1 inhibition. These data challenge the concept that inhibition of 11β-HSD1 is likely to produce a "step-change" treatment for diabetes and/or obesity.

27-Hydroxycholesterol promotes cell-autonomous, ER-positive breast cancer growth

To date, estrogen is the only known endogenous estrogen receptor (ER) ligand that promotes ER+ breast tumor growth. We report that the cholesterol metabolite 27-hydroxycholesterol (27HC) stimulates MCF-7 cell xenograft growth in mice. More importantly, in ER+ breast cancer patients, 27HC content in normal breast tissue is increased compared to that in cancer-free controls, and tumor 27HC content is further elevated. Increased tumor 27HC is correlated with diminished expression of CYP7B1, the 27HC metabolizing enzyme, and reduced expression of CYP7B1 in tumors is associated with poorer patient survival. Moreover, 27HC is produced by MCF-7 cells, and it stimulates cell-autonomous, ER-dependent, and GDNF-RET-dependent cell proliferation. Thus, 27HC is a locally modulated, nonaromatized ER ligand that promotes ER+ breast tumor growth.

Selective leptin resistance revisited

In addition to effects on appetite and metabolism, leptin influences many neuroendocrine and physiological systems, including the sympathetic nervous system. Building on my Carl Ludwig Lecture of the American Physiological Society, I review the sympathetic and cardiovascular actions of leptin. The review focuses on a critical analysis of the concept of selective leptin resistance (SLR) and the role of leptin in the pathogenesis of obesity-induced hypertension in both experimental animals and humans. We introduced the concept of SLR in 2002 to explain how leptin might increase blood pressure (BP) in obese states, such as diet-induced obesity (DIO), that are accompanied by partial leptin resistance. This concept, analogous to selective insulin resistance in the metabolic syndrome, holds that in several genetic and acquired models of obesity, there is preservation of the renal sympathetic and pressor actions of leptin despite attenuation of the appetite and weight-reducing actions. Two potential overlapping mechanisms of SLR are reviewed: 1) differential leptin molecular signaling pathways that mediate selective as opposed to universal leptin action and 2) brain site-specific leptin action and resistance. Although the phenomenon of SLR in DIO has so far focused on preservation of sympathetic and BP actions of leptin, consideration should be given to the possibility that this concept may extend to preservation of other actions of leptin. Finally, I review perplexing data on the effects of leptin on sympathetic activity and BP in humans and its role in human obesity-induced hypertension.

Oral administration of Lactobacillus reuteri GMNL-263 improves insulin resistance and ameliorates hepatic steatosis in high fructose-fed rats

BACKGROUND

Type 2 diabetes mellitus (DM), characterized by peripheral insulin resistance, is the most common form of diabetes. Probiotics are live micro-organisms that, when administered in adequate amounts, confer delaying effect on DM development. In this study, the effects Lactobacillus reuteri GMNL-263 (Lr263), a new probiotic strain developed by our laboratory, on insulin resistance and the development of hepatic steatosis in high-fructose fed rats were explored. Furthermore, the relevant regulatory pathways involved were also investigated.

METHOD

Male Sprague-Dawley rats were fed a high-fructose diet with or without Lr263 administration for 14 weeks. The composition of fecal microbiota, oral glucose tolerance, glycated haemoglobin, insulin, leptin, C-peptide, and incretins were measured. The markers of liver injury, serum and hepatic lipids profile, activity of hepatic antioxidant enzyme, and proinflammatory cytokines in adipose tissue were investigated. Additionally, the expression of hepatic lipogenic genes and insulin signaling related genes in adipose tissue were also studied. Liver sections were examined for hepatic steatosis using hematoxylin-eosin staining.

RESULTS

The levels of serum glucose, insulin, leptin, C-peptide, glycated hemoglobin, GLP-1, liver injury markers, lipid profile in serum and liver were significantly increased in high-fructose-fed rats. However, after Lr263 administration, the elevation of these parameters was significantly suppressed. Feeding of Lr263 reversed the decreased number of bifidobacterium species and lactobacillus species and increased number of clostridium species induced by high fructose treatment. The decreased activities of hepatic antioxidant enzymes in HFD rats were dramatically reversed by Lr263 treatment. Concentrations of IL-6 and TNF-α in adipose tissue which were elevated in high fructose treatment were markedly decreased after Lr263 feeding. Decreased levels of PPAR-γ and GLUT4 mRNA after high fructose treatment were significantly enhanced by Lr263 administration. Lr263 consumption normalized the increased lipogenic gene (Srebp-1c, FAS, and Elvol6) expressions stimulated by high fructose. Administration of Lr263 significantly ameliorated hepatic steatosis observed in high fructose treated rats.

CONCLUSION

Our study provided evidences clarifying the effectiveness of Lr263 on reducing insulin resistance as well as hepatic steatosis formation in high-fructose-fed rats and suggested that Lr263 may be a promising therapeutic agent in treating type 2 diabetes.

Measurement of insulin-mediated glucose uptake: direct comparison of the modified insulin suppression test and the euglycemic, hyperinsulinemic clamp

BACKGROUND

Two direct measurements of peripheral insulin sensitivity are the M value derived from the euglycemic, hyperinsulinemic clamp (EC) and the steady-state plasma glucose (SSPG) concentration derived from the insulin suppression test (IST). Prior work suggests that these measures are highly correlated, but the agreement between them is unknown. To determine the agreement between SSPG and M and to develop transformation equations to convert SSPG to M and vice versa, we directly compared these two measurements in the same individuals.

METHODS

A total of 15 nondiabetic subjects (9 women and 6 men) underwent both an EC and a modified version of the IST within a median interval of 5days. We performed standard correlation metrics of the two measures and developed transformation regression equations for the two measures.

RESULTS

The mean±SD age of the subjects was 57±7years and body mass index, 27.7±3.9kg/m(2). The median (interquartile range) SSPG concentration was 6.7 (5.1, 9.8) mmol/L and M value, 49.6 (28.9, 64.2) μmol/min/kg-LBM. There was a highly significant correlation between SSPG and M (r=-0.87, P <0.001). The relationship was best fit by regression models with exponential/logarithmic functions (R(2)=0.85). Bland-Altman plots demonstrated an excellent agreement between these measures of insulin action.

CONCLUSION

The SSPG and M are highly related measures of insulin sensitivity and the results provide the means to directly compare the two measurements.

Adipose tissue-specific PPARγ gene targeting

The nuclear receptor peroxisome proliferator activated receptor gamma (PPARγ) is most abundantly expressed in adipose tissue and has been shown to play imperative roles in controlling adipogenesis and lipogenesis in cultured cell systems in vitro as well as in mice and humans. However, it is unclear how important the role this receptor plays in regulating physiological functions of mature adipocytes in vivo. The Cre-loxP gene targeting strategy is employed to specifically disrupt PPARγ in mature adipocytes in mice. In this chapter, I will describe generation of "floxed" PPARγ mice, which bear loxP sequences in the introns of PPARγ gene locus flanking the coding exons 1 and 2 of PPARγ and creation of the aP2-Cre transgenic mice, which express Cre recombinase under the control of the promoter of adipocyte fatty acid binding protein (aP2). Crossing of the two mouse lines results in deletion of PPARγ gene only in differentiated adipocytes in Cre positive mice.