Glucagon in type 2 diabetes: Friend or foe?

Hyperglucagonemia is one of the 'ominous' eight factors underlying the pathogenesis of type 2 diabetes (T2D). Glucagon is a peptide hormone involved in maintaining glucose homoeostasis by increasing hepatic glucose output to counterbalance insulin action. Long neglected, the introduction of dual and triple agonists exploiting glucagon signalling pathways has rekindled the interest in this hormone beyond its classic effect on glycaemia. Glucagon can promote weight loss by regulating food intake, energy expenditure, and brown and white adipose tissue functions through mechanisms still to be fully elucidated, thus its role in T2D pathogenesis should be further investigated. Moreover, the role of glucagon in the development of T2D micro- and macro-vascular complications is elusive. Mounting evidence suggests its beneficial effect in non-alcoholic fatty liver disease, while few studies postulated its favourable role in peripheral neuropathy and retinopathy. Contrarily, glucagon receptor agonism might induce renal changes resembling diabetic nephropathy, and data concerning glucagon actions on the cardiovascular system are conflicting. This review aims to summarise the available findings on the role of glucagon in the pathogenesis of T2D and its complications. Further experimental and clinical data are warranted to better understand the implications of glucagon signalling modulation with new antidiabetic drugs.

Professional continuous glucose monitoring in patients with diabetes mellitus: A systematic review and meta-analysis.

AIM: To evaluate the effect on glucose control of professional continuous glucose monitoring (p-CGM)-based care as compared with standard care in the management of patients with type 1 and type 2 diabetes. MATERIALS AND METHODS: The PubMed database was searched comprehensively to identify prospective or retrospective studies evaluating p-CGM as a diagnostic tool for subsequent implementation of lifestyle and/or medication changes and reporting glycated haemoglobin (HbA1c) as an outcome measure. RESULTS: We found 872 articles, 22 of which were included in the meta-analysis. Overall, the use of p-CGM was associated with greater HbA1c reduction from baseline (-0.28%, 95% confidence interval [CI] -0.36% to -0.21%, I2  = 0%, P < 0.00001) than usual care, irrespective of type of diabetes, length of follow-up, frequency of continuous glucose monitoring (CGM) use and duration of CGM recording. In the few studies describing CGM-derived glucose metrics, p-CGM showed a beneficial effect on change in time in range from baseline (5.59%, 95% CI 0.12 to 11.06, I2  = 0%, P = 0.05) and a neutral effect on change in time below the target range from baseline (-0.11%, 95% CI -1.76% to 1.55%, I2  = 33%, P = 0.90). CONCLUSIONS: In patients with type 1 and type 2 diabetes, p-CGM-driven care is superior to usual care in improving glucose control without increasing hypoglycaemia.

The p66Shc Redox Protein and the Emerging Complications of Diabetes.

Diabetes mellitus is a chronic metabolic disease, the prevalence of which is constantly increasing worldwide. It is often burdened by disabling comorbidities that reduce the quality and expectancy of life of the affected individuals. The traditional complications of diabetes are generally described as macrovascular complications (e.g., coronary heart disease, peripheral arterial disease, and stroke), and microvascular complications (e.g., diabetic kidney disease, retinopathy, and neuropathy). Recently, due to advances in diabetes management and the increased life expectancy of diabetic patients, a strong correlation between diabetes and other pathological conditions (such as liver diseases, cancer, neurodegenerative diseases, cognitive impairments, and sleep disorders) has emerged. Therefore, these comorbidities have been proposed as emerging complications of diabetes. P66Shc is a redox protein that plays a role in oxidative stress, apoptosis, glucose metabolism, and cellular aging. It can be regulated by various stressful stimuli typical of the diabetic milieu and is involved in various types of organ and tissue damage under diabetic conditions. Although its role in the pathogenesis of diabetes remains controversial, there is strong evidence regarding the involvement of p66Shc in the traditional complications of diabetes. In this review, we will summarize the evidence supporting the role of p66Shc in the pathogenesis of diabetes and its complications, focusing for the first time on the emerging complications of diabetes.

Adipose Tissue Inflammation and Pulmonary Dysfunction in Obesity.

Obesity is a chronic disease caused by an excess of adipose tissue that may impair health by altering the functionality of various organs, including the lungs. Excessive deposition of fat in the abdominal area can lead to abnormal positioning of the diaphragm and consequent reduction in lung volume, leading to a heightened demand for ventilation and increased exposure to respiratory diseases, such as chronic obstructive pulmonary disease, asthma, and obstructive sleep apnoea. In addition to mechanical ventilatory constraints, excess fat and ectopic deposition in visceral depots can lead to adipose tissue dysfunction, which promotes metabolic disorders. An altered adipokine-secretion profile from dysfunctional adipose tissue in morbid obesity fosters systemic, low-grade inflammation, impairing pulmonary immune response and promoting airway hyperresponsiveness. A potential target of these adipokines could be the NLRP3 inflammasome, a critical component of the innate immune system, the harmful pro-inflammatory effect of which affects both adipose and lung tissue in obesity. In this review, we will investigate the crosstalk between adipose tissue and the lung in obesity, highlighting the main inflammatory mediators and novel therapeutic targets in preventing pulmonary dysfunction.

Reduction of hypoglycaemia, lifestyle modifications and psychological distress during lockdown following SARS-CoV-2 outbreak in type 1 diabetes.

AIMS: To assess changes in glucose metrics and their association with psychological distress and lifestyle changes in patients with type 1 diabetes (T1D) using flash glucose monitoring (FGM) during lockdown following severe acute respiratory syndrome coronavirus 2 outbreak. MATERIALS AND METHODS: Single-centre, observational, retrospective study enrolling T1D patients who attended a remote visit on April 2020 at the Endocrinology division of the University Hospital Policlinico Consorziale, Bari, Italy. Lockdown-related changes in physical activity level and dietary habits were assessed on a semi-quantitative basis. Changes in general well-being were assessed by the General Health Questionnaire-12 items with a binary scoring system. Glucose metrics were obtained from the Libreview platform for the first 2 weeks of February 2020 (T0) and the last 2 weeks before the phone visit (T1). RESULTS: Out of 84 patients assessed for eligibility, 48 had sufficient FGM data to be included in the analysis. FGM data analysis revealed significant reductions in coefficient of variation, number of hypoglycaemic events, and time below range, while no changes were found in time in range, time above range, mean sensor glucose, and glucose management indicator. Moreover, the frequency of sweets consumption was inversely related to the occurrence of hypoglycaemic events during lockdown. CONCLUSIONS: Lockdown-related lifestyle changes, albeit unhealthy, may lead to reduction in FGM-derived measures of hypoglycaemia and glycaemic variability in patients with T1D.

Impaired Leptin Signalling in Obesity: Is Leptin a New Thermolipokine?

Leptin is a principal adipose-derived hormone mostly implicated in the regulation of energy balance through the activation of anorexigenic neuronal pathways. Comprehensive studies have established that the maintenance of certain concentrations of circulating leptin is essential to avoid an imbalance in nutrient intake. Indeed, genetic modifications of the leptin/leptin receptor axis and the obesogenic environment may induce changes in leptin levels or action in a manner that accelerates metabolic dysfunctions, resulting in a hyperphagic status and adipose tissue expansion. As a result, a vicious cycle begins wherein hyperleptinaemia and leptin resistance occur, in turn leading to increased food intake and fat enlargement, which is followed by leptin overproduction. In addition, in the context of obesity, a defective thermoregulatory response is associated with impaired leptin signalling overall within the ventromedial nucleus of the hypothalamus. These recent findings highlight the role of leptin in the regulation of adaptive thermogenesis, thus suggesting leptin to be potentially considered as a new thermolipokine. This review provides new insight into the link between obesity, hyperleptinaemia, leptin resistance and leptin deficiency, focusing on the ability to restore leptin sensitiveness by way of enhanced thermogenic responses and highlighting novel anti-obesity therapeutic strategies.

Reduced SIRT1 and SIRT2 expression promotes adipogenesis of human visceral adipose stem cells and associates with accumulation of visceral fat in human obesity.

BACKGROUND/OBJECTIVES: The histone deacetylases SIRT1 and SIRT2 have been shown to be involved in the differentiation of rodent adipocyte precursors. In light of the differences in gene expression and metabolic function of visceral (V) and subcutaneous (S) adipose tissue (AT) and their resident cells, the aim of this study was to investigate the role of SIRT1 and SIRT2 in the differentiation of adipose stem cells (ASCs) isolated from SAT and VAT biopsies of nondiabetic obese and nonobese individuals. METHODS: Human ASCs were isolated from paired SAT and VAT biopsies obtained from 83 nonobese and 92 obese subjects and were differentiated in vitro. Adipogenesis was evaluated by analyzing the lipid deposition using an image processing software, and gene expression by RT-qPCR. SIRT1 and SIRT2 protein expression was modified by using recombinant adenoviral vectors. RESULTS: Visceral but not subcutaneous ASCs from obese subjects showed an intrinsic increase in both adipogenesis and lipid accumulation when compared with ASCs from nonobese subjects, and this was associated with reduced SIRT1 and SIRT2 mRNA and protein levels. Moreover, adipose tissue mRNA levels of SIRT1 and SIRT2 showed an inverse correlation with BMI in the visceral but not subcutaneous depot. Overexpression of SIRT1 or SIRT2 in visceral ASCs from obese subjects resulted in inhibition of adipocyte differentiation, whereas knockdown of SIRT1 or SIRT2 in visceral ASCs from nonobese subjects enhanced this process. Changes in SIRT1 or SIRT2 expression and adipocyte differentiation were paralleled by corresponding changes in PPARG, CEBPA, and other genes marking terminal adipocyte differentiation. CONCLUSIONS: SIRT1 and SIRT2 modulate the differentiation of human ASC. Reduced expression of SIRT1 and SIRT2 may enhance the differentiation capacity of visceral ASC in human obesity, fostering visceral adipose tissue expansion.

Irisin increases the expression of anorexigenic and neurotrophic genes in mouse brain.

BACKGROUND: Irisin, a newly discovered muscle-derived hormone, acts in different organs and tissues, improving energy homeostasis. In this study, we assessed, for the first time, the effects of intraperitoneal irisin injections on circulating levels of leptin and ghrelin, mRNA expression of the major hypothalamic appetite regulators and brain neurotrophic factors, as well as feeding behaviour in healthy mice. METHODS: Twelve male 6-week-old C57BL/6 mice were randomized into two groups and intraperitoneally injected daily with irisin (0.5 µg/g body weight) or vehicle (phosphate-buffered saline [PBS]) for 14 days. On the last day of observation, leptin and ghrelin levels were measured with an enzyme-linked immunosorbent assay (ELISA). mRNA levels of genes of interest were analysed by quantitative reverse transcription polymerase chain reaction (qRT-PCR) in brain extracts. RESULTS: Irisin administration did not change leptin or ghrelin serum concentrations. However, irisin injection increased CART, POMC, NPY, and BDNF mRNA levels, without affecting the mRNA expression of AgRP, orexin, PMCH, and UCP2. Finally, over the time frame of irisin treatment, body weight and feeding behaviour were unaltered. CONCLUSIONS: These results suggest that intraperitoneal injection of irisin, although without effects on feeding behaviour and body weight, can increase the expression of anorexigenic and neurotrophic genes in mouse brain.

Efficacy and safety of very low calorie ketogenic diet (VLCKD) in patients with overweight and obesity: A systematic review and meta-analysis.

Very low calorie ketogenic diet (VLCKD) has been proposed as a promising option to achieve a significant weight loss in a short time period. We conducted a systematic review and meta-analysis to evaluate its efficacy and safety in patients with overweight and obesity. Four databases were searched on May 2019. Studies reporting data on body weight, body mass index (BMI), waist circumference, body composition, blood pressure, HbA1c, lipids, and markers of liver and kidney function were selected. Discontinuation was also assessed. Twelve studies were included. VLCKD was associated with weight losses of -10.0 kg (I2 = 6%) and - 15.6 kg (I2 = 37%) in studies with a ketogenic phase up to and of at least four weeks, respectively. The weight lost during the ketogenic phase was stable in the subsequent follow-up up to two years (p = 0.12). Also, VLCKD was associated with reductions of BMI (-5.3 kg/m2), waist circumference (-12.6 cm), HbA1c (-0.7%), total cholesterol (-28 mg/dl), triglycerides (-30 mg/dl), AST (-7 U/l), ALT (-8 U/l), GGT (-8 U/l), systolic and diastolic blood pressure (-8 and - 7 mmHg, respectively). No changes in LDL cholesterol, HDL cholesterol, serum creatinine, serum uric acid and serum potassium were found. Serum sodium increased during VLCKD (+1.6 mEq/l). The overall prevalence of patients discontinuing VLCKD was 7.5% and this was similar to patients undergoing a low calorie diet (p = 0.83). The present review supports the use of VLCKD as an effective strategy for the management of overweight and obesity. Future guidelines should include a specific recommendation for this intervention.

Insulin and Insulin Receptors in Adipose Tissue Development.

Insulin is a major endocrine hormone also involved in the regulation of energy and lipid metabolism via the activation of an intracellular signaling cascade involving the insulin receptor (INSR), insulin receptor substrate (IRS) proteins, phosphoinositol 3-kinase (PI3K) and protein kinase B (AKT). Specifically, insulin regulates several aspects of the development and function of adipose tissue and stimulates the differentiation program of adipose cells. Insulin can activate its responses in adipose tissue through two INSR splicing variants: INSR-A, which is predominantly expressed in mesenchymal and less-differentiated cells and mainly linked to cell proliferation, and INSR-B, which is more expressed in terminally differentiated cells and coupled to metabolic effects. Recent findings have revealed that different distributions of INSR and an altered INSR-A:INSR-B ratio may contribute to metabolic abnormalities during the onset of insulin resistance and the progression to type 2 diabetes. In this review, we discuss the role of insulin and the INSR in the development and endocrine activity of adipose tissue and the pharmacological implications for the management of obesity and type 2 diabetes.

NANOG Plays a Hierarchical Role in the Transcription Network Regulating the Pluripotency and Plasticity of Adipose Tissue-Derived Stem Cells.

The stromal vascular cell fraction (SVF) of visceral and subcutaneous adipose tissue (VAT and SAT) has increasingly come into focus in stem cell research, since these compartments represent a rich source of multipotent adipose-derived stem cells (ASCs). ASCs exhibit a self-renewal potential and differentiation capacity. Our aim was to study the different expression of the embryonic stem cell markers NANOG (homeobox protein NANOG), SOX2 (SRY (sex determining region Y)-box 2) and OCT4 (octamer-binding transcription factor 4) and to evaluate if there exists a hierarchal role in this network in ASCs derived from both SAT and VAT. ASCs were isolated from SAT and VAT biopsies of 72 consenting patients (23 men, 47 women; age 45 ± 10; BMI between 25 ± 5 and 30 ± 5 range) undergoing elective open-abdominal surgery. Sphere-forming capability was evaluated by plating cells in low adhesion plastic. Stem cell markers CD90, CD105, CD29, CD31, CD45 and CD146 were analyzed by flow cytometry, and the stem cell transcription factors NANOG, SOX2 and OCT4 were detected by immunoblotting and real-time PCR. NANOG, SOX2 and OCT4 interplay was explored by gene silencing. ASCs from VAT and SAT confirmed their mesenchymal stem cell (MSC) phenotype expressing the specific MSC markers CD90, CD105, NANOG, SOX2 and OCT4. NANOG silencing induced a significant OCT4 (70 ± 0.05%) and SOX2 (75 ± 0.03%) downregulation, whereas SOX2 silencing did not affect NANOG gene expression. Adipose tissue is an important source of MSC, and siRNA experiments endorse a hierarchical role of NANOG in the complex transcription network that regulates pluripotency.

The p66(Shc) redox adaptor protein is induced by saturated fatty acids and mediates lipotoxicity-induced apoptosis in pancreatic beta cells.

AIMS/HYPOTHESIS: The role of the redox adaptor protein p66(Shc) as a potential mediator of saturated fatty acid (FA)-induced beta cell death was investigated. METHODS: The effects of the FA palmitate on p66(Shc) expression were evaluated in human and murine islets and in rat insulin-secreting INS-1E cells. p66(Shc) expression was also measured in islets from mice fed a high-fat diet (HFD) and from human donors with different BMIs. Cell apoptosis was quantified by two independent assays. The role of p66(Shc) was investigated using pancreatic islets from p66 (Shc-/-) mice and in INS-1E cells with knockdown of p66(Shc) or overexpression of wild-type and phosphorylation-defective p66(Shc). Production of reactive oxygen species (ROS) was evaluated by the dihydroethidium oxidation method. RESULTS: Palmitate induced a selective increase in p66(Shc) protein expression and phosphorylation on Ser(36) and augmented apoptosis in human and mouse islets and in INS-1E cells. Inhibiting the tumour suppressor protein p53 prevented both the palmitate-induced increase in p66(Shc) expression and beta cell apoptosis. Palmitate-induced apoptosis was abrogated in islets from p66 (Shc-/-) mice and following p66 (Shc) knockdown in INS-1E cells; by contrast, overexpression of p66(Shc), but not that of the phosphorylation-defective p66(Shc) mutant, enhanced palmitate-induced apoptosis. The pro-apoptotic effects of p66(Shc) were dependent upon its c-Jun N-terminal kinase-mediated phosphorylation on Ser(36) and associated with generation of ROS. p66(Shc) protein expression and function were also elevated in islets from HFD-fed mice and from obese/overweight cadaveric human donors. CONCLUSIONS/INTERPRETATION: p53-dependent augmentation of p66(Shc) expression and function represents a key signalling response contributing to beta cell apoptosis under conditions of lipotoxicity.

The p66Shc protein controls redox signaling and oxidation-dependent DNA damage in human liver cells.

The p66Shc protein mediates oxidative stress-related injury in multiple tissues. Steatohepatitis is characterized by enhanced oxidative stress-mediated cell damage. The role of p66Shc in redox signaling was investigated in human liver cells and alcoholic steatohepatitis. HepG2 cells with overexpression of wild-type or mutant p66Shc, with Ser36 replacement by Ala, were obtained through infection with recombinant adenoviruses. Reactive oxygen species and oxidation-dependent DNA damage were assessed by measuring dihydroethidium oxidation and 8-hydroxy-2'-deoxyguanosine accumulation into DNA, respectively. mRNA and protein levels of signaling intermediates were evaluated in HepG2 cells and liver biopsies from control and alcoholic steatohepatitis subjects. Exposure to H2O2 increased reactive oxygen species and phosphorylation of p66Shc on Ser36 in HepG2 cells. Overexpression of p66Shc promoted reactive oxygen species synthesis and oxidation-dependent DNA damage, which were further enhanced by H2O2. p66Shc activation also resulted in increased Erk-1/2, Akt, and FoxO3a phosphorylation. Blocking of Erk-1/2 activation inhibited p66Shc phosphorylation on Ser36. Increased p66Shc expression was associated with reduced mRNA levels of antioxidant molecules, such as NF-E2-related factor 2 and its target genes. In contrast, overexpression of the phosphorylation defective p66Shc Ala36 mutant inhibited p66Shc signaling, enhanced antioxidant genes, and suppressed reactive oxygen species and oxidation-dependent DNA damage. Increased p66Shc protein levels and Akt phosphorylation were observed in liver biopsies from alcoholic steatohepatitis compared with control subjects. In human alcoholic steatohepatitis, increased hepatocyte p66Shc protein levels may enhance susceptibility to DNA damage by oxidative stress by promoting reactive oxygen species synthesis and repressing antioxidant pathways.

Remission of type 2 diabetes: position statement of the Italian society of diabetes (SID).

The primary cause of the pandemic scale of type 2 diabetes (T2D) is the excessive and/or abnormal accumulation of adiposity resulting from a chronic positive energy balance. Any form of weight loss dramatically affects the natural history of T2D, favoring prevention, treatment, and even remission in the case of significant weight loss. However, weight regain, which is often accompanied by the recurrence or worsening of obesity complications such as T2D, is an inevitable biological phenomenon that is an integral part of the pathophysiology of obesity. This can occur not only after weight loss, but also during obesity treatment if it is not effective enough to counteract the physiological responses aimed at restoring adiposity to its pre-weight-loss equilibrium state. Over the past few years, many controlled and randomized studies have suggested a superior efficacy of bariatric surgery compared to conventional therapy in terms of weight loss, glycemic control, and rates of T2D remission. Recently, the therapeutic armamentarium in the field of diabetology has been enriched with new antihyperglycemic drugs with considerable efficacy in reducing body weight, which could play a pathogenetic role in the remission of T2D, not through the classical incretin effect, but by improving adipose tissue functions. All these concepts are discussed in this position statement, which aims to deepen the pathogenetic links between obesity and T2D, shift the paradigm from a "simple" interaction between insulin resistance and insulin deficiency, and evaluate the efficacy of different therapeutic interventions to improve T2D management and induce diabetes remission whenever still possible.

Exendin-4 protects pancreatic beta cells from palmitate-induced apoptosis by interfering with GPR40 and the MKK4/7 stress kinase signalling pathway.

AIMS/HYPOTHESIS: The mechanisms of the protective effects of exendin-4 on NEFA-induced beta cell apoptosis were investigated. METHODS: The effects of exendin-4 and palmitate were evaluated in human and murine islets, rat insulin-secreting INS-1E cells and murine glucagon-secreting alpha-TC1-6 cells. mRNA and protein expression/phosphorylation were measured by real-time RT-PCR and immunoblotting or immunofluorescence, respectively. Small interfering (si)RNAs for Ib1 and Gpr40 were used. Cell apoptosis was quantified by two independent assays. Insulin release was assessed with an insulin ELISA. RESULTS: Exposure of human and murine primary islets and INS-1E cells, but not alpha-TC1-6 cells, to exendin-4 inhibited phosphorylation of the stress kinases, c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK), and prevented apoptosis in response to palmitate. Exendin-4 increased the protein content of islet-brain 1 (IB1), an endogenous JNK blocker; however, siRNA-mediated reduction of IB1 did not impair the ability of exendin-4 to inhibit JNK and prevent apoptosis. Exendin-4 reduced G-protein-coupled receptor 40 (GPR40) expression and inhibited palmitate-induced phosphorylation of mitogen-activated kinase kinase (MKK)4 and MKK7. The effects of exendin-4 were abrogated in the presence of the protein kinase A (PKA) inhibitors, H89 and KT5720. Knockdown of GPR40, as well as use of a specific GPR40 antagonist, resulted in diminished palmitate-induced JNK and p38 MAPK phosphorylation and apoptosis. Furthermore, inhibition of JNK and p38 MAPK activity prevented palmitate-induced apoptosis. CONCLUSIONS/INTERPRETATION: Exendin-4 counteracts the proapoptotic effects of palmitate in beta cells by reducing GPR40 expression and inhibiting MKK7- and MKK4-dependent phosphorylation of the stress kinases, JNK and p38 MAPK, in a PKA-dependent manner.

Hepatokines, bile acids and ketone bodies are novel Hormones regulating energy homeostasis.

Current views show that an impaired balance partly explains the fat accumulation leading to obesity. Fetal malnutrition and early exposure to endocrine-disrupting compounds also contribute to obesity and impaired insulin secretion and/or sensitivity. The liver plays a major role in systemic glucose homeostasis through hepatokines secreted by hepatocytes. Hepatokines influence metabolism through autocrine, paracrine, and endocrine signaling and mediate the crosstalk between the liver, non-hepatic target tissues, and the brain. The liver also synthetizes bile acids (BAs) from cholesterol and secretes them into the bile. After food consumption, BAs mediate the digestion and absorption of fat-soluble vitamins and lipids in the duodenum. In recent studies, BAs act not simply as fat emulsifiers but represent endocrine molecules regulating key metabolic pathways. The liver is also the main site of the production of ketone bodies (KBs). In prolonged fasting, the brain utilizes KBs as an alternative to CHO. In the last few years, the ketogenic diet (KD) became a promising dietary intervention. Studies on subjects undergoing KD show that KBs are important mediators of inflammation and oxidative stress. The present review will focus on the role played by hepatokines, BAs, and KBs in obesity, and diabetes prevention and management and analyze the positive effects of BAs, KD, and hepatokine receptor analogs, which might justify their use as new therapeutic approaches for metabolic and aging-related diseases.

Type 2 Diabetes and Alzheimer's Disease: The Emerging Role of Cellular Lipotoxicity.

Type 2 diabetes (T2D) and Alzheimer's diseases (AD) represent major health issues that have reached alarming levels in the last decades. Although growing evidence demonstrates that AD is a significant comorbidity of T2D, and there is a ~1.4-2-fold increase in the risk of developing AD among T2D patients, the involvement of possible common triggers in the pathogenesis of these two diseases remains largely unknown. Of note, recent mechanistic insights suggest that lipotoxicity could represent the missing ring in the pathogenetic mechanisms linking T2D to AD. Indeed, obesity, which represents the main cause of lipotoxicity, has been recognized as a major risk factor for both pathological conditions. Lipotoxicity can lead to inflammation, insulin resistance, oxidative stress, ceramide and amyloid accumulation, endoplasmic reticulum stress, ferroptosis, and autophagy, which are shared biological events in the pathogenesis of T2D and AD. In the current review, we try to provide a critical and comprehensive view of the common molecular pathways activated by lipotoxicity in T2D and AD, attempting to summarize how these mechanisms can drive future research and open the way to new therapeutic perspectives.

Very low-calorie ketogenic diet rapidly augments testosterone levels in non-diabetic obese subjects.

BACKGROUND: The very low-calorie ketogenic diet (VLCKD) represents an opportunity to attain clinically relevant weight loss in obese patients. Functional hypogonadism represents a frequent hormonal disorder associated with obesity and visceral fat accumulation characterised by low testosterone levels and subnormal luteinising hormone (LH) levels. AIM: To evaluate the early effects of VLCKD on serum total testosterone (TT) levels in non-diabetic obese patients. METHODS: Twenty-two obese male patients (mean age 39.3 ± 11.7 years, mean body mass index (BMI) 38.2 ± 6.4 kg/m2 ) were enrolled and treated for 28 days with VLCKD. Anthropometric and hormonal variables were assessed before, during and after diet intervention. RESULTS: After 7 and 28 days on a VLCKD, a significant and persistent reduction in body weight, BMI, fat mass, blood glucose, insulin and homeostasis model assessment index was observed compared with baseline. TT significantly increased after 7 days (+35 ± 64 ng/dl) and 28 days (+74 ± 97 ng/dl) on a VLCKD. In addition to TT, a significant increase in serum sex hormone-binding globulin levels was observed after 7 (+2.1 ± 4.1) and 28 days (+7.7 ± 10.0). However, both calculated free testosterone and LH did not change after 7 or 28 days of VLCKD. Following cessation of VLCKD, hypogonadal subjects achieved a higher percentage of total weight loss (8.5% ± 1.5%), a greater reduction in weight (-9.94 ± 1.66 kg), fat mass (-7 ± 2.1 kg) and waist circumference (-6.31 ± 2.65 cm) and a greater improvement in glycaemia (-8.75 ± 10.92 mg/dl) as compared with eugonadal subjects. Furthermore, hypogonadal subjects exhibited a trend of higher TT increase (+98.12 ± 71.51 ng/dl) as compared with eugonadal subjects. CONCLUSIONS: VLCKD results in rapid improvements in TT levels associated with weight loss in male obese non-diabetic subjects, particularly in the presence of obesity-related hypogonadism.

Glucometabolic outcomes of GLP-1 receptor agonist-based therapies in patients with type 2 diabetes: a systematic review and network meta-analysis.

Background: Innovative GLP-1 receptor agonist (GLP-1RA)-based treatment strategies-such as tirzepatide, GLP-1RA plus basal insulin fixed-ratio combinations [FRC], GLP-1RA plus sodium glucose cotransporter-2 inhibitors [SGLT-2i] combinations, and high-dose GLP-1RA-have been listed among the most efficacious options for type 2 diabetes management. However, differences in their glucometabolic effects have not been assessed in dedicated head-to-head trials. In the absence of such trials, we aimed to provide a useful comparison among these treatment strategies to guide clinical practice. Methods: In this network meta-analysis, we searched PubMed, MEDLINE, and Web of Science (from database inception to June 24, 2023) for randomised controlled studies, published in English, that enrolled individuals with type 2 diabetes treated with tirzepatide, iGlarLixi, iDegLira, GLP-1RA plus SGLT-2i combination, or high-dose GLP-1RA (dulaglutide 3 mg and 4.5 mg, semaglutide 2 mg) compared with placebo or active comparators. Eligible studies reported change from baseline in HbA1c as an outcome, which was the primary outcome of this analysis. Secondary outcomes were changes in fasting and post-prandial glucose, bodyweight, LDL-cholesterol, blood pressure and risk of hypoglycaemia. We assessed risk of bias through the Cochrane Collaboration's tool (RoB2 tool), publication bias through visual inspection of funnel plots and Egger's test, and heterogeneity by comparing the magnitude of the common between-study variance (τ2) for each outcome with empirical distributions of heterogeneity variances. This network meta-analysis was registered in PROSPERO (CRD42022329878). Findings: 40 trials were included. Tirzepatide 15 mg ranked first in terms of HbA1c reduction compared to other GLP-1RA-based strategies, even those including insulin (vs. iDegLira MD -0.40%, 95% CI [-0.66; -0.14], low certainty; vs. iGlarLixi MD -0.48%, 95% CI [-0.75; -0.21], low certainty), without increasing the risk of hypoglycaemia (vs. iDegLira OR 0.35, 95% CI [0.16; 0.79], high certainty; vs. iGlarLixi OR 0.31, 95% CI [0.20; 0.48], high certainty). Tirzepatide 15 mg was also the most efficacious on weight lowering, even compared to high-dose GLP-1RA (eg, semaglutide 2 mg MD -6.56 kg, 95% CI [-7.38; -5.73], low certainty) and GLP-1RA plus SGLT-2i combination (MD -4.61 kg, 95% CI [-5.29; -3.93], low certainty). Risk of bias and publication bias were generally low throughout studies, while high levels of heterogeneity were detected for most outcomes. Interpretation: Aiming to support clinicians in tailoring treatment to patients' needs, we suggest that a hierarchy among treatment strategies be devised considering the best options for type 2 diabetes. Tirzepatide, followed by GLP-1RA plus basal insulin FRC and GLP-1RA plus SGLT-2i combination, was associated with greater benefit on HbA1c than high-dose GLP-1RA. Funding: Fondazione per la Ricerca Biomedica "Saverio e Isabella Cianciola" and Next Generation EU, in the context of the National Recovery and Resilience Plan, Investment PE8-Project Age-It: Ageing Well in an Ageing Society.

Human adipose tissue stem cells: relevance in the pathophysiology of obesity and metabolic diseases and therapeutic applications.

Stem cells are unique cells exhibiting self-renewing properties and the potential to differentiate into multiple specialised cell types. Totipotent or pluripotent stem cells are generally abundant in embryonic or fetal tissues, but the use of discarded embryos as sources of these cells raises challenging ethical problems. Adult stem cells can also differentiate into a wide variety of cell types. In particular, adult adipose tissue contains a pool of abundant and accessible multipotent stem cells, designated as adipose-derived stem cells (ASCs), that are able to replicate as undifferentiated cells, to develop as mature adipocytes and to differentiate into multiple other cell types along the mesenchymal lineage, including chondrocytes, myocytes and osteocytes, and also into cells of endodermal and neuroectodermal origin, including beta-cells and neurons, respectively. An impairment in the differentiation potential and biological functions of ASCs may contribute to the development of obesity and related comorbidities. In this review, we summarise different aspects of the ASCs with special reference to the isolation and characterisation of these cell populations, their relation to the biochemical features of the adipose tissue depot of origin and to the metabolic characteristics of the donor subject and discuss some prospective therapeutic applications.