Insulin resistance and exaggerated insulin sensitivity triggered by single-gene mutations in the insulin signaling pathway

The interplay of factors in metabolic syndrome: understanding its roots and complexity

Metabolic syndrome (MetS) is an indicator and diverse endocrine syndrome that combines different metabolic defects with clinical, physiological, biochemical, and metabolic factors. Obesity, visceral adiposity and abdominal obesity, dyslipidemia, insulin resistance (IR), elevated blood pressure, endothelial dysfunction, and acute or chronic inflammation are the risk factors associated with MetS. Abdominal obesity, a hallmark of MetS, highlights dysfunctional fat tissue and increased risk for cardiovascular disease and diabetes. Insulin, a vital peptide hormone, regulates glucose metabolism throughout the body. When cells become resistant to insulin's effects, it disrupts various molecular pathways, leading to IR. This condition is linked to a range of disorders, including obesity, diabetes, fatty liver disease, cardiovascular disease, and polycystic ovary syndrome. Atherogenic dyslipidemia is characterized by three key factors: high levels of small, low-dense lipoprotein (LDL) particles and triglycerides, alongside low levels of high-density lipoprotein (HDL), the "good" cholesterol. Such a combination is a major player in MetS, where IR is a driving force. Atherogenic dyslipidemia contributes significantly to the development of atherosclerosis, which can lead to cardiovascular disease. On top of that, genetic alteration and lifestyle factors such as diet and exercise influence the complexity and progression of MetS. To enhance our understanding and consciousness, it is essential to understand the fundamental pathogenesis of MetS. This review highlights current advancements in MetS research including the involvement of gut microbiome, epigenetic regulation, and metabolomic profiling for early detection of Mets. In addition, this review emphasized the epidemiology and fundamental pathogenesis of MetS, various risk factors, and their preventive measures. The goal of this effort is to deepen understanding of MetS and encourage further research to develop effective strategies for preventing and managing complex metabolic diseases.

PTPN11 is a potential biomarker for type 2 diabetes mellitus complicated with colorectal cancer

Epidemiological surveys have shown that the incidence of type 2 diabetes mellitus (T2DM) and malignancies is rapidly increasing worldwide and has become a major disease that threatens human life. In this study, we quantitatively analyzed the proteome of tumor tissues and adjacent normal tissues from six patients withT2DM combined with colorectal cancer (CRC) and eight non-diabetic CRC, focusing on the effect of T2DM on tumor tissues. We analyzed the functional enrichment of differentially expressed proteins (DEPs) using clusterProfiler in R and the expression level of protein tyrosine phosphatase non-receptor type 11 (PTPN11) and other key proteins in the TIMER and GEPIA2 databases. The HPA database was used to validate PTPN11 protein expression. The correlation between PTPN11 expression and clinicopathological features was analyzed by UALCAN database. The impact of PTPN11 on clinical prognosis was evaluated utilizing Kaplan-Meier Plotter. The correlation between PTPN11 expression and tumor-infiltrated immune cells was investigated via TIMER and TISIDB databases. Gene set enrichment analysis (GSEA) was performed to examined the pathway of PTPN11 enrichment in CRC using data from The Cancer Genome Atlas (TCGA) database. Furthermore, small interfering (si) RNA was used to knock down PTPN11 in CRC cell line SW480. Western blot analysis was used to detect PTPN11 expression in tissue samples or cells and the effect of PTPN11 knockdown on key proteins related to PI3K/AKT and cell cycle pathway in SW480 cells. Cell proliferation and wound healing assays were used to detect the effects of cell proliferation and migration after knockdown of PTPN11 or treatment with high glucose. We found that metabolic pathways such as oxidative phosphorylation, glycolysis/gluconeogenesis, and insulin secretion were significantly enriched in tumor tissues from diabetic patients compared to non-diabetic patients. In addition, PTPN11, a marker gene associated with T2DM and CRC, were mined in diabetic tumor tissues. PTPN11 showed high expression in diabetic tumor tissues compared to normal tissues. High PTPN11 expression predicted poor prognosis in CRC. PTPN11 expression was strongly associated with immune infiltrating cells in CRC. GSEA analysis revealed that PTPN11 was enriched in cancer-related pathways. Western blotting analysis indicated that PTPN11 knockdown reduced the protein levels of p-PI3K, p-AKT, CDK1 and CYCLIN D, without altering PI3K and AKT protein levels. Cell proliferation and wound healing data showed that PTPN11 and high glucose could increase the proliferation and migration ability. These findings showed that PTPN11 may be a potential key biomarker for CRC in patients with diabetes, which will provide new potential targets for future intervention of T2DM complicated with CRC.

A multicenter, open-label, single-arm trial of the long-term safety of empagliflozin treatment for refractory diabetes mellitus with insulin resistance (EMPIRE-02)

AIMS/INTRODUCTION

Insulin resistance syndrome and lipoatrophic diabetes are rare conditions characterized by the development of treatment-refractory diabetes with severe insulin resistance. We recently conducted a 24 week, multicenter, single-arm trial (EMPIRE-01) that demonstrated a certain level of effectiveness and safety of empagliflozin for these conditions. To evaluate treatment safety over a longer period, we have now performed an additional 28 week trial (EMPIRE-02) that followed on from EMPIRE-01.

MATERIALS AND METHODS

The primary and secondary outcomes were safety and efficacy evaluations, respectively. All eight subjects of the EMPIRE-01 trial participated in EMPIRE-02.

RESULTS

Twenty adverse events (AEs) were recorded among five individuals during the combined 52 week treatment period of both trials. Whereas one case of chronic hepatitis B was moderate in severity, all other AEs were mild. There were thus no serious AEs or events necessitating discontinuation or suspension of treatment or a reduction in drug dose. Whereas ketoacidosis or marked increases in serum ketone body levels were not observed, the mean body mass of the subjects was decreased slightly after completion of EMPIRE-02. The improvement in mean values of glycemic parameters observed in EMPIRE-01 was not sustained in EMPIRE-02, mostly because of one individual whose parameters deteriorated markedly, likely as a result of nonadherence to diet therapy. The improvement in glycemic parameters was sustained during EMPIRE-02 after exclusion of this subject from analysis.

CONCLUSIONS

Empagliflozin demonstrated a certain level of safety and efficacy for the treatment of insulin resistance syndrome and lipoatrophic diabetes over 52 weeks, confirming its potential as a therapeutic option.

Genetic and inflammatory factors underlying gestational diabetes mellitus: a review

Gestational diabetes mellitus (GDM) poses a significant global health concern, impacting both maternal and fetal well-being. Early detection and treatment are imperative to mitigate adverse outcomes during pregnancy. This review delves into the pivotal role of insulin function and the influence of genetic variants, including SLC30A8, CDKAL1, TCF7L2, IRS1, and GCK, in GDM development. These genetic variations affect beta-cell function and insulin activity in crucial tissues, such as muscle, disrupting glucose regulation during pregnancy. We propose a hypothesis that this variation may disrupt zinc transport, consequently impairing insulin production and secretion, thereby contributing to GDM onset. Furthermore, we discussed the involvement of inflammatory pathways, such as TNF-alpha and IL-6, in predisposing individuals to GDM. Genetic modulation of these pathways may exacerbate glucose metabolism dysregulation observed in GDM patients. We also discussed how GDM affects cardiovascular disease (CVD) through a direct correlation between pregnancy and cardiometabolic function, increasing atherosclerosis, decreased vascular function, dyslipidemia, and hypertension in women with GDM history. However, further research is imperative to unravel the intricate interplay between inflammatory pathways, genetics, and GDM. This understanding is pivotal for devising targeted gene therapies and pharmacological interventions to rectify genetic variations in SLC30A8, CDKAL1, TCF7L2, IRS1, GCK, and other pertinent genes. Ultimately, this review offers insights into the pathophysiological mechanisms of GDM, providing a foundation for developing strategies to mitigate its impact.

Insulin Resistance: The Increased Risk of Cancers

Insulin resistance, also known as impaired insulin sensitivity, is the result of a decreased reaction of insulin signaling to blood glucose levels. This state is observed when muscle cells, adipose tissue, and liver cells, improperly respond to a particular concentration of insulin. Insulin resistance and related increased plasma insulin levels (hyperinsulinemia) may cause metabolic impairments, which are pathological states observed in obesity and type 2 diabetes mellitus. Observations of cancer patients confirm that hyperinsulinemia is a major factor influencing obesity, type 2 diabetes, and cancer. Obesity and diabetes have been reported as risks of the initiation, progression, and metastasis of several cancers. However, both of the aforementioned pathologies may independently and additionally increase the cancer risk. The state of metabolic disorders observed in cancer patients is associated with poor outcomes of cancer treatment. For example, patients suffering from metabolic disorders have higher cancer recurrence rates and their overall survival is reduced. In these associations between insulin resistance and cancer risk, an overview of the various pathogenic mechanisms that play a role in the development of cancer is discussed.

A Multicenter, Open-Label, Single-Arm Trial of the Efficacy and Safety of Empagliflozin Treatment for Refractory Diabetes Mellitus with Insulin Resistance (EMPIRE-01)

INTRODUCTION

Insulin resistance syndrome and lipoatrophic diabetes are characterized by severe insulin resistance and are often refractory to treatment. Trials assessing the efficacy of antidiabetes drugs for these rare conditions have been limited, however. Sodium-glucose cotransporter 2 (SGLT2) inhibitors, which lower glycemia independently of insulin action, have shown efficacy for type 2 diabetes with insulin resistance. We here investigated the efficacy and safety of the SGLT2 inhibitor empagliflozin for treatment of insulin resistance syndrome and lipoatrophic diabetes.

METHODS

The trial was conducted at five academic centers in Japan and included seven patients with insulin resistance syndrome and one patient with lipoatrophic diabetes. Participants received 10 mg of empagliflozin daily. If the hemoglobin A1c (HbA1c) level was ≥ 7.0% (52 mmol/mol) after 12 weeks, the dose was adjusted to 25 mg. The study duration was 24 weeks, and the primary outcome was the change in HbA1c level by the end of the treatment period. Safety evaluations were performed for all participants.

RESULTS

By the end of the 24-week treatment period, the mean HbA1c level for all eight patients had decreased by 0.99 percentage points (10.8 mmol/mol) (95% confidence interval [CI], 0.59 to 1.38 percentage points, 6.6 to 14.9 mmol/mol) and the mean fasting plasma glucose concentration had declined by 63.9 mg/dL (3.55 mmol/L) (95% CI 25.5 to 102.3 mg/dL, 1.42 to 5.68 mmol/L). Continuous glucose monitoring revealed a reduction in mean glucose levels from 164.3 ± 76.1 to 137.6 ± 46.6 mg/dL (9.13 ± 4.23 to 7.65 ± 2.59 mmol/L) as well as an increase in the time in range (70-180 mg/dL) from 58.9 ± 36.1% to 70.8 ± 18.3%. Seventeen mild adverse events were recorded in five individuals throughout the study period. No severe events were reported. The mean body mass showed a slight decrease and the mean serum ketone body concentration showed a slight increase during treatment.

CONCLUSION

Our results demonstrate that empagliflozin shows a certain level of efficacy and safety for treatment of insulin resistance syndrome and lipoatrophic diabetes.

TRIAL REGISTRATION

jRCTs2051190029 and NCT04018365.

Dynamic molecular architecture and substrate recruitment of cullin3-RING E3 ligase CRL3KBTBD2

Phosphatidylinositol 3-kinase α, a heterodimer of catalytic p110α and one of five regulatory subunits, mediates insulin- and insulin like growth factor-signaling and, frequently, oncogenesis. Cellular levels of the regulatory p85α subunit are tightly controlled by regulated proteasomal degradation. In adipose tissue and growth plates, failure of K48-linked p85α ubiquitination causes diabetes, lipodystrophy and dwarfism in mice, as in humans with SHORT syndrome. Here we elucidated the structures of the key ubiquitin ligase complexes regulating p85α availability. Specificity is provided by the substrate receptor KBTBD2, which recruits p85α to the cullin3-RING E3 ubiquitin ligase (CRL3). CRL3KBTBD2 forms multimers, which disassemble into dimers upon substrate binding (CRL3KBTBD2-p85α) and/or neddylation by the activator NEDD8 (CRL3KBTBD2~N8), leading to p85α ubiquitination and degradation. Deactivation involves dissociation of NEDD8 mediated by the COP9 signalosome and displacement of KBTBD2 by the inhibitor CAND1. The hereby identified structural basis of p85α regulation opens the way to better understanding disturbances of glucose regulation, growth and cancer.

Microglial NF-κB Signaling Deficiency Protects Against Metabolic Disruptions Caused by Volatile Organic Compound via Modulating the Hypothalamic Transcriptome

Prolonged exposure to benzene, a prevalent volatile organic compound (VOC), at concentrations found in smoke, triggers hyperglycemia, and inflammation in mice. Corroborating this with existing epidemiological data, we show a strong correlation between environmental benzene exposure and metabolic impairments in humans. To uncover the underlying mechanisms, we employed a controlled exposure system and continuous glucose monitoring (CGM), revealing rapid blood glucose surges and disturbances in energy homeostasis in mice. These effects were attributed to alterations in the hypothalamic transcriptome, specifically impacting insulin and immune response genes, leading to hypothalamic insulin resistance and neuroinflammation. Moreover, benzene exposure activated microglial transcription characterized by heightened expression of IKKβ/NF-κB-related genes. Remarkably, selective removal of IKKβ in immune cells or adult microglia in mice alleviated benzene-induced hypothalamic gliosis, and protected against hyperglycemia. In summary, our study uncovers a crucial pathophysiological mechanism, establishing a clear link between airborne toxicant exposure and the onset of metabolic diseases.

Insulin signaling and its application

The discovery of insulin in 1921 introduced a new branch of research into insulin activity and insulin resistance. Many discoveries in this field have been applied to diagnosing and treating diseases related to insulin resistance. In this mini-review, the authors attempt to synthesize the updated discoveries to unravel the related mechanisms and inform the development of novel applications. Firstly, we depict the insulin signaling pathway to explain the physiology of insulin action starting at the receptor sites of insulin and downstream the signaling of the insulin signaling pathway. Based on this, the next part will analyze the mechanisms of insulin resistance with two major provenances: the defects caused by receptors and the defects due to extra-receptor causes, but in this study, we focus on post-receptor causes. Finally, we discuss the recent applications including the diseases related to insulin resistance (obesity, cardiovascular disease, Alzheimer's disease, and cancer) and the potential treatment of those based on insulin resistance mechanisms.

Altered macronutrient composition and genetics influence the complex transcriptional network associated with adiposity in the Collaborative Cross

Background

Obesity is a serious disease with a complex etiology characterized by overaccumulation of adiposity resulting in detrimental health outcomes. Given the liver’s critical role in the biological processes that attenuate adiposity accumulation, elucidating the influence of genetics and dietary patterns on hepatic gene expression is fundamental for improving methods of obesity prevention and treatment. To determine how genetics and diet impact obesity development, mice from 22 strains of the genetically diverse recombinant inbred Collaborative Cross (CC) mouse panel were challenged to either a high-protein or high-fat high-sucrose diet, followed by extensive phenotyping and analysis of hepatic gene expression.

Results

Over 1000 genes differentially expressed by perturbed dietary macronutrient composition were enriched for biological processes related to metabolic pathways. Additionally, over 9000 genes were differentially expressed by strain and enriched for biological process involved in cell adhesion and signaling. Weighted gene co-expression network analysis identified multiple gene clusters (modules) associated with body fat % whose average expression levels were influenced by both dietary macronutrient composition and genetics. Each module was enriched for distinct types of biological functions.

Conclusions

Genetic background affected hepatic gene expression in the CC overall, but diet macronutrient differences also altered expression of a specific subset of genes. Changes in macronutrient composition altered gene expression related to metabolic processes, while genetic background heavily influenced a broad range of cellular functions and processes irrespective of adiposity. Understanding the individual role of macronutrient composition, genetics, and their interaction is critical to developing therapeutic strategies and policy recommendations for precision nutrition.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12263-022-00714-x.

SHORT Syndrome: an Update on Pathogenesis and Clinical Spectrum

PURPOSE OF REVIEW

This review describes the unique pathogenesis of SHORT syndrome, a rare genetic form of insulin resistance syndrome, and recent advances in understanding the underlying mechanisms. SHORT syndrome results from dysfunction of PI3K, but the mechanisms behind the clinical manifestations are not entirely understood. Elucidating these mechanisms may contribute to the understanding of the roles of insulin signaling and PI3K signaling in humans. There are paucity of data on treatment and outcomes.

RECENT FINDINGS

The clinical spectrum of the disorder appears wider than previously understood, and overlaps with other clinical syndromes. PI3K malfunction is associated with insulin resistance, decreased lipogenesis, increased energy expenditure, and possible IGF1 resistance. SHORT syndrome may be underdiagnosed, and should be considered in individuals with growth failure, craniofacial dysmorphism, and lipodystrophy. Much is still unknown about the optimal management and long-term outcomes.

Mulberry-Derived 1-Deoxynojirimycin Prevents Type 2 Diabetes Mellitus Progression via Modulation of Retinol-Binding Protein 4 and Haptoglobin

Pre-diabetic or early-stage type 2 diabetes patients may develop an adverse diabetic progression, leading to several complications and increasing hospitalization rates. Mulberry leaves, which contain 1-deoxynojirimycin (DNJ), have been used as a complementary medicine for diabetes prevention and treatment. Our recent study demonstrated that mulberry leaf powder with 12 mg of DNJ improves postprandial hyperglycemia, fasting plasma glucose, and glycated hemoglobin. However, the detailed mechanisms are still unknown. This study investigates the effect of long-term (12-week) supplementation of mulberry leaves in obese people with prediabetes and patients with early-stage type 2 diabetes. Participants’ blood was collected before and after supplementation. The protein profile of the plasma was examined by proteomics. In addition, the mitochondrial function was evaluated by energetic and homeostatic markers using immunoelectron microscopy. The proteomics results showed that, from a total of 1291 proteins, 32 proteins were related to diabetes pathogenesis. Retinol-binding protein 4 and haptoglobin protein were downregulated, which are associated with insulin resistance and inflammation, respectively. For mitochondrial function, the haloacid dehalogenase-like hydrolase domain-containing protein 3 (HDHD-3) and dynamin-related protein 1 (Drp-1) displayed a significant increment in the after treatment group. In summary, administration of mulberry leaf powder extract in prediabetes and the early stage of diabetes can alleviate insulin resistance and inflammation and promote mitochondrial function in terms of energy production and fission.

New insights into the role and therapeutic potential of HSP70 in diabetes

Emerging evidence indicates that HSP70 represents a key mechanism in the pathophysiology of β-cell dysfunction, insulin resistance, and various diabetic complications, including micro- and macro-vascular alterations, as well as impaired hemostasis. Hyperglycemia, a hallmark of both types of diabetes, increases the circulating levels of HSP70 (eHSP70), but there is still divergence about whether diabetes up- or down-regulates the intracellular fraction of this protein (iHSP70). Here, we consider that iHSP70 levels reduce in diabetic arterial structures and that the vascular system is in direct contact with all other systems in the body suggesting that a systemic response might also be happening for iHSP70, which is characterized by decreased levels of HSP70 in the vasculature. Furthermore, although many pathways have been proposed to explain HSP70's functions in diabetes, and organs/tissues/cells-specific variations occur, the membrane-bound receptor of the innate immune system, Toll-like receptor 4, and its downstream signal transduction pathways appear to be a constant, not only when we explore the actions of eHSP70, but also when we assess the contributions of iHSP70. In this review, we focus on discussing the multiple roles of HSP70 across organs/tissues/cells affected by hyperglycemia to further explore the possibility of targeting this protein with pharmacological and non-pharmacological approaches in the context of diabetes.

New classification and diagnostic criteria for insulin resistance syndrome

This report of a working group established by the Japan Diabetes Society proposes a new classification and diagnostic criteria for insulin resistance syndrome. Insulin resistance syndrome is defined as a condition characterized by severe attenuation of insulin action due to functional impairment of the insulin receptor or its downstream signaling molecules. This syndrome is classified into two types: genetic insulin resistance syndrome, caused by gene abnormalities, and type B insulin resistance syndrome, caused by autoantibodies to the insulin receptor. Genetic insulin resistance syndrome includes type A insulin resistance as well as Donohue and Rabson-Mendenhall syndromes, all of which are caused by abnormalities of the insulin receptor gene; conditions such as SHORT syndrome caused by abnormalities of PIK3R1, which encodes a regulatory subunit of phosphatidylinositol 3-kinase; conditions caused by abnormalities of AKT2, TBC1D4, or PRKCE; and conditions in which a causative gene has not yet been identified. Type B insulin resistance syndrome is characterized by severe impairment of insulin action due to the presence of insulin receptor autoantibodies. Cases in which hypoglycemia alone is induced by autoantibodies that stimulate insulin receptor were not included in Type B insulin resistance syndrome.

New classification and diagnostic criteria for insulin resistance syndrome

This report of a working group established by the Japan Diabetes Society proposes a new classification and diagnostic criteria for insulin resistance syndrome. Insulin resistance syndrome is defined as a condition characterized by severe attenuation of insulin action due to functional impairment of the insulin receptor or its downstream signaling molecules. This syndrome is classified into two types: genetic insulin resistance syndrome, caused by gene abnormalities, and type B insulin resistance syndrome, caused by autoantibodies to the insulin receptor. Genetic insulin resistance syndrome includes type A insulin resistance as well as Donohue and Rabson-Mendenhall syndromes, all of which are caused by abnormalities of the insulin receptor gene; conditions such as SHORT syndrome caused by abnormalities of PIK3R1, which encodes a regulatory subunit of phosphatidylinositol 3-kinase; conditions caused by abnormalities of AKT2, TBC1D4, or PRKCE; and conditions in which a causative gene has not yet been identified. Type B insulin resistance syndrome is characterized by severe impairment of insulin action due to the presence of insulin receptor autoantibodies. Cases in which hypoglycemia alone is induced by autoantibodies that stimulate insulin receptor were not included in Type B insulin resistance syndrome.

Efficacy and safety of sirolimus therapy in familial hypoinsulinemic hypoglycemia caused by AKT2 mutation inherited from the mosaic father

Activating mutation in the insulin signal-transducing kinase AKT2 results in severe hypoinsulinemic hypoketotic hypoglycemia and a characteristic phenotype of possible overgrowth and, sometimes, acanthosis nigricans. Herein, we describe a metabolic and hormonal profile before and during treatment with sirolimus in two brothers with AKT2 mutation inherited from the mosaic father, who showed low-level mosaicism in sperm. The boys, aged 1 and 14, who had severe non-insulin-dependent hypoketotic hypoglycemia and a typical dysmorphism, were admitted to endocrinology department for the analysis of their metabolic parameters: lipids, lactate, ammonia, glucose, insulin, c-peptide, and hormones (GH, IGF1, IGFBP3, TSH, fT4, cortisol, ACTH) before and during treatment with sirolimus. Previously, they had been treated with high-carbohydrate diet. The brothers were started on sirolimus with subsequent normalization of glycemia and reduced carbohydrate feedings overnight. The lowest fasting glucose levels improved from 20 mg/dl to 45 mg/dl in both sibs. The BMI of both brothers significantly dropped. After 6 months of sirolimus therapy we did not observe any laboratory or clinical side effects of the treatment.

The Genetics of Diabetes: What We Can Learn from Drosophila

Diabetes mellitus is a heterogeneous disease characterized by hyperglycemia due to impaired insulin secretion and/or action. All diabetes types have a strong genetic component. The most frequent forms, type 1 diabetes (T1D), type 2 diabetes (T2D) and gestational diabetes mellitus (GDM), are multifactorial syndromes associated with several genes’ effects together with environmental factors. Conversely, rare forms, neonatal diabetes mellitus (NDM) and maturity onset diabetes of the young (MODY), are caused by mutations in single genes. Large scale genome screenings led to the identification of hundreds of putative causative genes for multigenic diabetes, but all the loci identified so far explain only a small proportion of heritability. Nevertheless, several recent studies allowed not only the identification of some genes as causative, but also as putative targets of new drugs. Although monogenic forms of diabetes are the most suited to perform a precision approach and allow an accurate diagnosis, at least 80% of all monogenic cases remain still undiagnosed. The knowledge acquired so far addresses the future work towards a study more focused on the identification of diabetes causal variants; this aim will be reached only by combining expertise from different areas. In this perspective, model organism research is crucial. This review traces an overview of the genetics of diabetes and mainly focuses on Drosophila as a model system, describing how flies can contribute to diabetes knowledge advancement.

Pathophysiology of Physical Inactivity-Dependent Insulin Resistance: A Theoretical Mechanistic Review Emphasizing Clinical Evidence

The modern lifestyle has a negative impact on health. It is usually accompanied by increased stress levels and lower physical activity, which interferes with body homeostasis. Diabetes mellitus is a relatively common metabolic disorder with increasing prevalence globally, associated with various risk factors, including lower physical activity and a sedentary lifestyle. It has been shown that sedentary behavior increases the risk of insulin resistance, but the intermediate molecular mechanisms are not fully understood. In this mechanistic review, we explore the possible interactions between physical inactivity and insulin resistance to help better understand the pathophysiology of physical inactivity-dependent insulin resistance and finding novel interventions against these deleterious pathways.

High serum miR-421 is associated with metabolic dysregulation and inflammation in patients with metabolic syndrome

Aim: To explore the association of circulating miRNAs with adiposity, metabolic status and inflammatory biomarkers in patients with metabolic syndrome (MetS). Methods: Serum levels of 372 miRNAs were measured in patients with (n = 6) and without MetS (n = 6) by quantitative PCR array, and dysregulated miRNAs were validated in a larger cohort (MetS, n = 89; non-MetS, n = 144). Results: In the screening study, seven miRNAs were dysregulated in patients with MetS, and miR-421 remained increased in the validation study. miR-421 was associated with a high risk of MetS and insulin resistance and hypertension and correlated with glycated hemoglobin, triacylglycerols, high-sensitivity CRP, IL-6, resistin and adiponectin (p < 0.05). Conclusion: Circulating miR-421 is a potential biomarker for insulin resistance, metabolic dysregulation and inflammatory status in patients with MetS.

Role of Phosphodiesterase in the Biology and Pathology of Diabetes

Glucose metabolism is the initiator of a large number of molecular secretory processes in β cells. Cyclic nucleotides as a second messenger are the main physiological regulators of these processes and are functionally divided into compartments in pancreatic cells. Their intracellular concentration is limited by hydrolysis led by one or more phosphodiesterase (PDE) isoenzymes. Literature data confirmed multiple expressions of PDEs subtypes, but the specific roles of each in pancreatic β-cell function, particularly in humans, are still unclear. Isoforms present in the pancreas are also found in various tissues of the body. Normoglycemia and its strict control are supported by the appropriate release of insulin from the pancreas and the action of insulin in peripheral tissues, including processes related to homeostasis, the regulation of which is based on the PDE- cyclic AMP (cAMP) signaling pathway. The challenge in developing a therapeutic solution based on GSIS (glucose-stimulated insulin secretion) enhancers targeted at PDEs is the selective inhibition of their activity only within β cells. Undeniably, PDEs inhibitors have therapeutic potential, but some of them are burdened with certain adverse effects. Therefore, the chance to use knowledge in this field for diabetes treatment has been postulated for a long time.