Showing papers on "Insulin resistance published in 2011"
TL;DR: The discovery that obesity itself results in an inflammatory state in metabolic tissues ushered in a research field that examines the inflammatory mechanisms in obesity, and metaflammation is summarized, defined as low-grade, chronic inflammation orchestrated by metabolic cells in response to excess nutrients and energy.
Abstract: The modern rise in obesity and its strong association with insulin resistance and type 2 diabetes have elicited interest in the underlying mechanisms of these pathologies. The discovery that obesity itself results in an inflammatory state in metabolic tissues ushered in a research field that examines the inflammatory mechanisms in obesity. Here, we summarize the unique features of this metabolic inflammatory state, termed metaflammation and defined as low-grade, chronic inflammation orchestrated by metabolic cells in response to excess nutrients and energy. We explore the effects of such inflammation in metabolic tissues including adipose, liver, muscle, pancreas, and brain and its contribution to insulin resistance and metabolic dysfunction. Another area in which many unknowns still exist is the origin or mechanism of initiation of inflammatory signaling in obesity. We discuss signals or triggers to the inflammatory response, including the possibility of endoplasmic reticulum stress as an important contributor to metaflammation. Finally, we examine anti-inflammatory therapies for their potential in the treatment of obesity-related insulin resistance and glucose intolerance.
3,045 citations
TL;DR: It is established that calorie restriction and exercise-mediated weight loss in obese individuals with type 2 diabetes is associated with a reduction in adipose tissue expression of Nlrp3 as well as with decreased inflammation and improved insulin sensitivity, and that the NlrP3 inflammasome senses obesity-associated danger signals and contributes to obesity-induced inflammation and insulin resistance.
Abstract: Obesity is generally considered an inflammatory state. Vishwa Dixit and his colleagues have now shown that excess dietary lipids leads to the activation of the Nlrp3 inflammasome, a sensor of the innate immune system, and that its genetic deficiency results in decreased inflammation and improved insulin sensitivity. These results suggest a possible new therapeutic avenue to treat the effects of obesity.
2,000 citations
TL;DR: Recent mechanistic insights into nonalcoholic fatty liver disease are discussed, focusing primarily on those that have emerged from human genetic and metabolic studies.
Abstract: Nonalcoholic fatty liver disease (NAFLD) is a burgeoning health problem that affects one-third of adults and an increasing number of children in developed countries. The disease begins with the aberrant accumulation of triglyceride in the liver, which in some individuals elicits an inflammatory response that can progress to cirrhosis and liver cancer. Although NAFLD is strongly associated with obesity and insulin resistance, its pathogenesis remains poorly understood, and therapeutic options are limited. Here, we discuss recent mechanistic insights into NAFLD, focusing primarily on those that have emerged from human genetic and metabolic studies.
1,831 citations
TL;DR: It is shown that the saturated fatty acid palmitate, but not unsaturated oleate, induces the activation of the NLRP3-ASC inflammasome, causing caspase-1, IL-1β and IL-18 production, which affects insulin sensitivity through tumor necrosis factor–independent and dependent pathways.
Abstract: High-fat diet (HFD) and inflammation are key contributors to insulin resistance and type 2 diabetes (T2D). Interleukin (IL)-1b plays a role in insulin resistance, yet how IL-1b is induced by the fatty acids in an HFD, and how this alters insulin signaling, is unclear. We show that the saturated fatty acid palmitate, but not unsaturated oleate, induces the activation of the NLRP3-ASC inflammasome, causing caspase-1, IL-1b and IL-18 production. This pathway involves mitochondrial reactive oxygen species and the AMP-activated protein kinase and unc-51–like kinase-1 (ULK1) autophagy signaling cascade. Inflammasome activation in hematopoietic cells impairs insulin signaling in several target tissues to reduce glucose tolerance and insulin sensitivity. Furthermore, IL-1b affects insulin sensitivity through tumor necrosis factor–independent and dependent pathways. These findings provide insights into the association of inflammation, diet and T2D.
1,456 citations
TL;DR: It is shown that increased BAT activity induced by short-term cold exposure controls TRL metabolism in mice, and Activation of BAT might be a therapeutic approach to reduce elevated triglyceride concentrations and combat obesity in humans.
Abstract: Elevated triglyceride levels often occur in obesity and can contribute to cardiovascular disease. Brown adipose tissue (BAT) is known to burn fat, and now Joerg Heeren and his colleagues show that BAT actively takes up triglycerides in cold conditions, suggesting a possible therapy to lower triglyceride levels in states of obesity. Brown adipose tissue (BAT) burns fatty acids for heat production to defend the body against cold1,2 and has recently been shown to be present in humans3,4,5. Triglyceride-rich lipoproteins (TRLs) transport lipids in the bloodstream, where the fatty acid moieties are liberated by the action of lipoprotein lipase (LPL)6. Peripheral organs such as muscle and adipose tissue take up the fatty acids, whereas the remaining cholesterol-rich remnant particles are cleared by the liver6. Elevated plasma triglyceride concentrations and prolonged circulation of cholesterol-rich remnants, especially in diabetic dyslipidemia, are risk factors for cardiovascular disease7,8,9,10,11. However, the precise biological role of BAT for TRL clearance remains unclear. Here we show that increased BAT activity induced by short-term cold exposure controls TRL metabolism in mice. Cold exposure drastically accelerated plasma clearance of triglycerides as a result of increased uptake into BAT, a process crucially dependent on local LPL activity and transmembrane receptor CD36. In pathophysiological settings, cold exposure corrected hyperlipidemia and improved deleterious effects of insulin resistance. In conclusion, BAT activity controls vascular lipoprotein homeostasis by inducing a metabolic program that boosts TRL turnover and channels lipids into BAT. Activation of BAT might be a therapeutic approach to reduce elevated triglyceride concentrations and combat obesity in humans.
1,369 citations
TL;DR: It is demonstrated that AMPK interacts with and directly phosphorylates sterol regulatory element binding proteins (SREBP-1c and -2) and AMPK-dependent phosphorylation of SREBP may offer therapeutic strategies to combat insulin resistance, dyslipidemia, and atherosclerosis.
1,335 citations
TL;DR: A greater understanding is required of the mechanisms by which glucocorticoids exert their anti-inflammatory and immunosuppressive actions, and recent research is shedding new light on some of these mechanisms and has produced some surprising new findings.
1,206 citations
TL;DR: It is shown that eosinophils are the major IL-4–expressing cells in white adipose tissues of mice, and, in their absence, AAMs are greatly attenuated.
Abstract: Eosinophils are associated with helminth immunity and allergy, often in conjunction with alternatively activated macrophages (AAMs). Adipose tissue AAMs are necessary to maintain glucose homeostasis and are induced by the cytokine interleukin-4 (IL-4). Here, we show that eosinophils are the major IL-4-expressing cells in white adipose tissues of mice, and, in their absence, AAMs are greatly attenuated. Eosinophils migrate into adipose tissue by an integrin-dependent process and reconstitute AAMs through an IL-4- or IL-13-dependent process. Mice fed a high-fat diet develop increased body fat, impaired glucose tolerance, and insulin resistance in the absence of eosinophils, and helminth-induced adipose tissue eosinophilia enhances glucose tolerance. Our results suggest that eosinophils play an unexpected role in metabolic homeostasis through maintenance of adipose AAMs.
1,198 citations
TL;DR: Overall, this review outlines various mechanisms that lead to the development of oxidative stress and intervention and therapy that alter or disrupt these mechanisms may serve to reduce the risk of insulin resistance and theDevelopment of diabetes.
1,125 citations
TL;DR: Treatment of PCOS is focused on the goals of ameliorating hyperandrogenic symptoms, inducing ovulation and preventing cardiometabolic complications, and ruling out other hyper androgenic or oligo-ovulatory disorders.
Abstract: Polycystic ovary syndrome (PCOS) is the most common endocrinopathy in women of reproductive age, with a prevalence of up to 10%. Various diagnostic criteria have been proposed, generally centered around the features of hyperandrogenism and/or hyperandrogenemia, oligo-ovulation and polycystic ovarian morphology. Insulin resistance is present in a majority of cases, with compensatory hyperinsulinemia contributing to hyperandrogenism via stimulation of ovarian androgen secretion and inhibition of hepatic sex hormone-binding globulin production. Adipose tissue dysfunction has been implicated as a contributor to the insulin resistance observed in PCOS. Environmental and genetic factors also have a role in the development of PCOS. The syndrome is associated with numerous morbidities, including infertility, obstetrical complications, type 2 diabetes mellitus, cardiovascular disease, and mood and eating disorders. Despite these morbidities, PCOS may be common in our society owing to evolutionary advantages of the syndrome in ancient times, including smaller family sizes, reduced exposure to childbirth-related mortality, increased muscle mass and greater capacity to store energy. The diagnosis of PCOS hinges on establishing key features while ruling out other hyperandrogenic or oligo-ovulatory disorders. Treatment is focused on the goals of ameliorating hyperandrogenic symptoms, inducing ovulation and preventing cardiometabolic complications.
1,060 citations
TL;DR: Normalisation of both beta cell function and hepatic insulin sensitivity in type 2 diabetes was achieved by dietary energy restriction alone, and was associated with decreased pancreatic and liver triacylglycerol stores.
Abstract: Aims/hypothesis Type 2 diabetes is regarded as inevitably progressive, with irreversible beta cell failure. The hypothesis was tested that both beta cell failure and insulin resistance can be reversed by dietary restriction of energy intake. Methods Eleven people with type 2 diabetes (49.5± 2.5 years, BMI 33.6±1.2 kg/m 2 , nine male and two female) were studied before and after 1, 4 and 8 weeks of a 2.5 MJ (600 kcal)/day diet. Basal hepatic glucose output, hepatic and peripheral insulin sensitivity and beta cell function were measured. Pancreas and liver triacylglycerol content was measured using three-point Dixon magnetic resonance imaging. An age-, sex- and weight-matched group of eight non-diabetic participants was studied. Results After 1 week of restricted energy intake, fasting plasma glucose normalised in the diabetic group (from 9.2± 0.4 to 5.9±0.4 mmol/l; p=0.003). Insulin suppression of hepatic glucose output improved from 43±4% to 74±5% (p= 0.003 vs baseline; controls 68±5%). Hepatic triacylglycerol content fell from 12.8±2.4% in the diabetic group to 2.9± 0.2% by week 8 (p=0.003). The first-phase insulin response increased during the study period (0.19±0.02 to 0.46± 0.07 nmol min �1 m �2 ; p<0.001) and approached control
TL;DR: It is concluded that specific gut microbiota modulation improves glucose homeostasis, leptin sensitivity, and target enteroendocrine cell activity in obese and diabetic mice.
Abstract: OBJECTIVE To investigate deep and comprehensive analysis of gut microbial communities and biological parameters after prebiotic administration in obese and diabetic mice. RESEARCH DESIGN AND METHODS Genetic ( ob/ob ) or diet-induced obese and diabetic mice were chronically fed with prebiotic-enriched diet or with a control diet. Extensive gut microbiota analyses, including quantitative PCR, pyrosequencing of the 16S rRNA, and phylogenetic microarrays, were performed in ob/ob mice. The impact of gut microbiota modulation on leptin sensitivity was investigated in diet-induced leptin-resistant mice. Metabolic parameters, gene expression, glucose homeostasis, and enteroendocrine-related L-cell function were documented in both models. RESULTS In ob/ob mice, prebiotic feeding decreased Firmicutes and increased Bacteroidetes phyla, but also changed 102 distinct taxa, 16 of which displayed a >10-fold change in abundance. In addition, prebiotics improved glucose tolerance, increased L-cell number and associated parameters (intestinal proglucagon mRNA expression and plasma glucagon-like peptide-1 levels), and reduced fat-mass development, oxidative stress, and low-grade inflammation. In high fat–fed mice, prebiotic treatment improved leptin sensitivity as well as metabolic parameters. CONCLUSIONS We conclude that specific gut microbiota modulation improves glucose homeostasis, leptin sensitivity, and target enteroendocrine cell activity in obese and diabetic mice. By profiling the gut microbiota, we identified a catalog of putative bacterial targets that may affect host metabolism in obesity and diabetes.
TL;DR: The results establish the importance of B cells and adaptive immunity in insulin resistance and suggest new diagnostic and therapeutic modalities for managing the disease.
Abstract: Chronic inflammation characterized by T cell and macrophage infiltration of visceral adipose tissue (VAT) is a hallmark of obesity-associated insulin resistance and glucose intolerance. Here we show a fundamental pathogenic role for B cells in the development of these metabolic abnormalities. B cells accumulate in VAT in diet-induced obese (DIO) mice, and DIO mice lacking B cells are protected from disease despite weight gain. B cell effects on glucose metabolism are mechanistically linked to the activation of proinflammatory macrophages and T cells and to the production of pathogenic IgG antibodies. Treatment with a B cell-depleting CD20 antibody attenuates disease, whereas transfer of IgG from DIO mice rapidly induces insulin resistance and glucose intolerance. Moreover, insulin resistance in obese humans is associated with a unique profile of IgG autoantibodies. These results establish the importance of B cells and adaptive immunity in insulin resistance and suggest new diagnostic and therapeutic modalities for managing the disease.
University of Southampton1, University of Paris2, Nestlé3, French Institute of Health and Medical Research4, The Coca-Cola Company5, University of Naples Federico II6, University of Düsseldorf7, Spanish National Research Council8, University of Crete9, Kraft Foods10, Sapienza University of Rome11, Maastricht University12, University of Helsinki13, University of Graz14
TL;DR: Potential mechanisms are described and research gaps, which limit the understanding of the interaction between diet and postprandial and chronic low-grade inflammation, are identified.
Abstract: Low-grade inflammation is a characteristic of the obese state, and adipose tissue releases many inflammatory mediators. The source of these mediators within adipose tissue is not clear, but infiltrating macrophages seem to be especially important, although adipocytes themselves play a role. Obese people have higher circulating concentrations of many inflammatory markers than lean people do, and these are believed to play a role in causing insulin resistance and other metabolic disturbances. Blood concentrations of inflammatory markers are lowered following weight loss. In the hours following the consumption of a meal, there is an elevation in the concentrations of inflammatory mediators in the bloodstream, which is exaggerated in obese subjects and in type 2 diabetics. Both high-glucose and high-fat meals may induce postprandial inflammation, and this is exaggerated by a high meal content of advanced glycation end products (AGE) and partly ablated by inclusion of certain antioxidants or antioxidant-containing foods within the meal. Healthy eating patterns are associated with lower circulating concentrations of inflammatory markers. Among the components of a healthy diet, whole grains, vegetables and fruits, and fish are all associated with lower inflammation. AGE are associated with enhanced oxidative stress and inflammation. SFA and trans-MUFA are pro-inflammatory, while PUFA, especially long-chain n-3 PUFA, are anti-inflammatory. Hyperglycaemia induces both postprandial and chronic low-grade inflammation. Vitamin C, vitamin E and carotenoids decrease the circulating concentrations of inflammatory markers. Potential mechanisms are described and research gaps, which limit our understanding of the interaction between diet and postprandial and chronic low-grade inflammation, are identified.
TL;DR: Evidence is emerging that a substantial part of diabetes susceptibility is acquired early in life, probably owing to fetal or neonatal programming via epigenetic phenomena, and maternal and early childhood health might, therefore, be crucial to the development of effective prevention strategies.
TL;DR: The relationship between systemic concentrations of NEFA and obesity/insulin resistance is examined and the vehicle by which triacylglycerol stored in adipose tissue is transported to its sites of utilization is recognized.
Abstract: There is a widespread acceptance in the literature that plasma nonesterified fatty acids (NEFA), also called free fatty acids (FFA), can mediate many adverse metabolic effects, most notably insulin resistance. Elevated NEFA concentrations in obesity are thought to arise from an increased adipose tissue mass. It is also argued that the process of fatty acid mobilization from adipose tissue, normally suppressed by insulin, itself becomes insulin resistant—thus, lipolysis is further increased, potentially leading to a vicious cycle. Although we have also accepted this model for many years (1,2), recently there has been a steady accumulation of data, both in the literature and from our own research, that has forced us to realize that this simple story is not always true. Here we review the background to the idea of “fatty acids as metabolic villains,” together with data from the literature and from our own studies, which tend to show another side to the fatty acids/insulin resistance story.
We will first examine the relationship between systemic concentrations of NEFA and obesity/insulin resistance and then study adipose tissue in the obese state with regard to its adaptation for NEFA release.
NEFA circulate in the plasma bound to plasma albumin. Their function was largely elucidated in the 1950s through the work of Vincent Dole (3) at the Rockefeller Institute in New York and Robert Gordon (4,5) at the National Institutes of Health. Gordon demonstrated the origin of plasma NEFA from adipose tissue and their use by tissues such as the liver and myocardium, but not the brain.
We now recognize that NEFA are the vehicle by which triacylglycerol (TG) stored in adipose tissue is transported to its sites of utilization. NEFA turnover is rapid, with a plasma half-life around 2–4 min (6). The only significant site of NEFA liberation …
TL;DR: In this paper, the Lin28/let-7 pathway was shown to be a central regulator of mammalian glucose metabolism, including insulin-PI3K-mTOR and IRS2.
01 Sep 2011
TL;DR: The Lin28/let-7 pathway is established as a central regulator of mammalian glucose metabolism and enriched for genes containing SNPs associated with type 2 diabetes and control of fasting glucose in human genome-wide association studies.
Abstract: The let-7 tumor suppressor microRNAs are known for their regulation of oncogenes, while the RNA-binding proteins Lin28a/b promote malignancy by inhibiting let-7 biogenesis. We have uncovered unexpected roles for the Lin28/let-7 pathway in regulating metabolism. When overexpressed in mice, both Lin28a and LIN28B promote an insulin-sensitized state that resists high-fat-diet induced diabetes. Conversely, muscle-specific loss of Lin28a or overexpression of let-7 results in insulin resistance and impaired glucose tolerance. These phenomena occur, in part, through the let-7-mediated repression of multiple components of the insulin-PI3K-mTOR pathway, including IGF1R, INSR, and IRS2. In addition, the mTOR inhibitor, rapamycin, abrogates Lin28a-mediated insulin sensitivity and enhanced glucose uptake. Moreover, let-7 targets are enriched for genes containing SNPs associated with type 2 diabetes and control of fasting glucose in human genome-wide association studies. These data establish the Lin28/let-7 pathway as a central regulator of mammalian glucose metabolism.
TL;DR: Meta-analyses conclude that periodontal therapy in individuals with diabetes mellitus can result in a modest improvement of glycemic control and increased patient awareness of the link between Diabetes mellitus and oral health and collaboration among medical and dental professionals for the management of affected individuals become increasingly important.
Abstract: Diabetes mellitus (a group of metabolic disorders characterized by hyperglycemia) and periodontitis (a microbially induced inflammatory disorder that affects the supporting structures of teeth) are both common, chronic conditions. Multiple studies have demonstrated that diabetes mellitus (type 1 and type 2) is an established risk factor for periodontitis. Findings from mechanistic studies indicate that diabetes mellitus leads to a hyperinflammatory response to the periodontal microbiota and also impairs resolution of inflammation and repair, which leads to accelerated periodontal destruction. The cell surface receptor for advanced glycation end products and its ligands are expressed in the periodontium of individuals with diabetes mellitus and seem to mediate these processes. The association between the two diseases is bidirectional, as periodontitis has been reported to adversely affect glycemic control in patients with diabetes mellitus and to contribute to the development of diabetic complications. In addition, meta-analyses conclude that periodontal therapy in individuals with diabetes mellitus can result in a modest improvement of glycemic control. The effect of periodontal infections on diabetes mellitus is potentially explained by the resulting increase in levels of systemic proinflammatory mediators, which exacerbates insulin resistance. As our understanding of the relationship between diabetes mellitus and periodontitis deepens, increased patient awareness of the link between diabetes mellitus and oral health and collaboration among medical and dental professionals for the management of affected individuals become increasingly important.
TL;DR: It is found that high-fat diet (HFD) feeding induces hepatic mitochondrial protein hyperacetylation in mice and downregulation of the major mitochondrial protein deacetylase SIRT3, which contributes to the metabolic syndrome.
TL;DR: Although it is difficult to prove that alterations in IGF-1 amounts are responsible for the cancer- and diabetes-free lives of these Ecuadorian people, genetic work from several model organisms suggests that this is so, and mutations in growth signaling pathways extend life span and reduce abnormal cellular proliferation in worms.
Abstract: Mutations in growth signaling pathways extend life span, as well as protect against age-dependent DNA damage in yeast and decrease insulin resistance and cancer in mice. To test their effect in humans, we monitored for 22 years Ecuadorian individuals who carry mutations in the growth hormone receptor (GHR) gene that lead to severe GHR and IGF-1 (insulin-like growth factor-1) deficiencies. We combined this information with surveys to identify the cause and age of death for individuals in this community who died before this period. The individuals with GHR deficiency exhibited only one nonlethal malignancy and no cases of diabetes, in contrast to a prevalence of 17% for cancer and 5% for diabetes in control subjects. A possible explanation for the very low incidence of cancer was suggested by in vitro studies: Serum from subjects with GHR deficiency reduced DNA breaks but increased apoptosis in human mammary epithelial cells treated with hydrogen peroxide. Serum from GHR-deficient subjects also caused reduced expression of RAS, PKA (protein kinase A), and TOR (target of rapamycin) and up-regulation of SOD2 (superoxide dismutase 2) in treated cells, changes that promote cellular protection and life-span extension in model organisms. We also observed reduced insulin concentrations (1.4 μU/ml versus 4.4 μU/ml in unaffected relatives) and a very low HOMA-IR (homeostatic model assessment-insulin resistance) index (0.34 versus 0.96 in unaffected relatives) in individuals with GHR deficiency, indicating higher insulin sensitivity, which could explain the absence of diabetes in these subjects. These results provide evidence for a role of evolutionarily conserved pathways in the control of aging and disease burden in humans.
TL;DR: The role of free fatty acid (FFA) as a cause for insulin resistance in obese people is described and increased plasma FFA levels are an important cause of obesity-associated insulin resistance and cardiovascular disease.
Abstract: Purpose of reviewTo describe the role of free fatty acid (FFA) as a cause for insulin resistance in obese people.Recent findingsElevated plasma FFA levels can account for a large part of insulin resistance in obese patients with type 2 diabetes. Insulin resistance is clinically important because it
TL;DR: Understanding the mechanisms whereby type 2 diabetes exacerbates CAD offers hope for new therapeutic strategies to prevent and treat atherosclerotic vascular disease.
TL;DR: It is demonstrated that mice deficient in Nlrp3, apoptosis-associated speck-like protein, and caspase-1 were resistant to the development of high-fat diet-induced obesity, which correlated with protection from obesity-induced insulin resistance, and inhibition of the inflammasome is suggested as a potential therapeutic strategy.
Abstract: Inflammation plays a key role in the pathogenesis of obesity. Chronic overfeeding leads to macrophage infiltration in the adipose tissue, resulting in proinflammatory cytokine production. Both microbial and endogenous danger signals trigger assembly of the intracellular innate immune sensor Nlrp3, resulting in caspase-1 activation and production of proinflammatory cytokines IL-1β and IL-18. Here, we showed that mice deficient in Nlrp3, apoptosis-associated speck-like protein, and caspase-1 were resistant to the development of high-fat diet-induced obesity, which correlated with protection from obesity-induced insulin resistance. Furthermore, hepatic triglyceride content, adipocyte size, and macrophage infiltration in adipose tissue were all reduced in mice deficient in inflammasome components. Monocyte chemoattractant protein (MCP)-1 is a key molecule that mediates macrophage infiltration. Indeed, defective inflammasome activation was associated with reduced MCP-1 production in adipose tissue. Furthermore, plasma leptin and resistin that affect energy use and insulin sensitivity were also changed by inflammasome-deficiency. Detailed metabolic and molecular phenotyping demonstrated that the inflammasome controls energy expenditure and adipogenic gene expression during chronic overfeeding. These findings reveal a critical function of the inflammasome in obesity and insulin resistance, and suggest inhibition of the inflammasome as a potential therapeutic strategy.
TL;DR: IER is as effective as CER with regard to weight loss, insulin sensitivity and other health biomarkers, and may be offered as an alternative equivalent to CER for weight loss and reducing disease risk.
Abstract: The problems of adherence to energy restriction in humans are well known. To compare the feasibility and effectiveness of intermittent continuous energy (IER) with continuous energy restriction (CER) for weight loss, insulin sensitivity and other metabolic disease risk markers. Randomized comparison of a 25% energy restriction as IER (∼2710 kJ/day for 2 days/week) or CER (∼6276 kJ/day for 7 days/week) in 107 overweight or obese (mean (±s.d.) body mass index 30.6 (±5.1) kg m−2) premenopausal women observed over a period of 6 months. Weight, anthropometry, biomarkers for breast cancer, diabetes, cardiovascular disease and dementia risk; insulin resistance (HOMA), oxidative stress markers, leptin, adiponectin, insulin-like growth factor (IGF)-1 and IGF binding proteins 1 and 2, androgens, prolactin, inflammatory markers (high sensitivity C-reactive protein and sialic acid), lipids, blood pressure and brain-derived neurotrophic factor were assessed at baseline and after 1, 3 and 6 months. Last observation carried forward analysis showed that IER and CER are equally effective for weight loss: mean (95% confidence interval ) weight change for IER was −6.4 (−7.9 to −4.8) kg vs −5.6 (−6.9 to −4.4) kg for CER (P-value for difference between groups=0.4). Both groups experienced comparable reductions in leptin, free androgen index, high-sensitivity C-reactive protein, total and LDL cholesterol, triglycerides, blood pressure and increases in sex hormone binding globulin, IGF binding proteins 1 and 2. Reductions in fasting insulin and insulin resistance were modest in both groups, but greater with IER than with CER; difference between groups for fasting insulin was −1.2 (−1.4 to −1.0) μU ml−1 and for insulin resistance was −1.2 (−1.5 to −1.0) μU mmol−1 l−1 (both P=0.04). IER is as effective as CER with regard to weight loss, insulin sensitivity and other health biomarkers, and may be offered as an alternative equivalent to CER for weight loss and reducing disease risk.
TL;DR: In this article, the effect of catheter-based renal sympathetic denervation on glucose metabolism and blood pressure control in patients with resistant hypertension was investigated, and the results showed that renal denervation significantly improved glucose metabolism in addition to reducing blood pressure.
Abstract: Background—Hypertension is associated with impaired glucose metabolism and insulin resistance. Chronic activation of the sympathetic nervous system may contribute to either condition. We investigated the effect of catheter-based renal sympathetic denervation on glucose metabolism and blood pressure control in patients with resistant hypertension. Methods and Results—We enrolled 50 patients with therapy-resistant hypertension. Thirty-seven patients underwent bilateral catheter-based renal denervation, and 13 patients were assigned to a control group. Systolic and diastolic blood pressures, fasting glucose, insulin, C peptide, hemoglobin A1c, calculated insulin sensitivity (homeostasis model assessment–insulin resistance), and glucose levels during oral glucose tolerance test were measured before and 1 and 3 months after treatment. Mean office blood pressure at baseline was 178/963/2 mm Hg. At 1 and 3 months, office blood pressure was reduced by 28/10 mm Hg (P0.001) and 32/12 mm Hg (P0.001), respectively, in the treatment group, without changes in concurrent antihypertensive treatment. Three months after renal denervation, fasting glucose was reduced from 1183.4 to 1083.8 mg/dL (P0.039). Insulin levels were decreased from 20.83.0 to 9.32.5 IU/mL (P0.006) and C-peptide levels from 5.30.6 to 3.00.9 ng/mL (P0.002). After 3 months, homeostasis model assessment–insulin resistance decreased from 6.00.9 to 2.40.8 (P0.001). Additionally, mean 2-hour glucose levels during oral glucose tolerance test were reduced significantly by 27 mg/dL (P0.012). There were no significant changes in blood pressure or metabolic markers in the control group. Conclusions—Renal denervation improves glucose metabolism and insulin sensitivity in addition to a significantly reducing blood pressure. However, this improvement appeared to be unrelated to changes in drug treatment. This novel procedure may therefore provide protection in patients with resistant hypertension and metabolic disorders at high cardiovascular risk. Clinical Trial Registration—URL: http://www.ClinicalTrials.gov. Unique identifiers: NCT00664638 and NCT00888433. (Circulation. 2011;123:1940-1946.)
TL;DR: It is shown here that TLR4 is an upstream signaling component required for saturated fatty acid-induced ceramide biosynthesis, and that sphingolipids such as ceramide might be key components of the signaling networks that link lipid-induced inflammatory pathways to the antagonism of insulin action that contributes to diabetes.
Abstract: Obesity is associated with an enhanced inflammatory response that exacerbates insulin resistance and contributes to diabetes, atherosclerosis, and cardiovascular disease. One mechanism accounting for the increased inflammation associated with obesity is activation of the innate immune signaling pathway triggered by TLR4 recognition of saturated fatty acids, an event that is essential for lipid-induced insulin resistance. Using in vitro and in vivo systems to model lipid induction of TLR4-dependent inflammatory events in rodents, we show here that TLR4 is an upstream signaling component required for saturated fatty acid–induced ceramide biosynthesis. This increase in ceramide production was associated with the upregulation of genes driving ceramide biosynthesis, an event dependent of the activity of the proinflammatory kinase IKKβ. Importantly, increased ceramide production was not required for TLR4-dependent induction of inflammatory cytokines, but it was essential for TLR4-dependent insulin resistance. These findings suggest that sphingolipids such as ceramide might be key components of the signaling networks that link lipid-induced inflammatory pathways to the antagonism of insulin action that contributes to diabetes.
TL;DR: It is shown for the first time that resveratrol improves insulin sensitivity in humans, which might be due to a resver atrol-induced decrease in oxidative stress that leads to a more efficient insulin signalling via the Akt pathway.
Abstract: Although resveratrol has widely been studied for its potential health benefits, little is known about its metabolic effects in humans. Our aims were to determine whether the polyphenol resveratrol improves insulin sensitivity in type 2 diabetic patients and to gain some insight into the mechanism of its action. After an initial general examination (including blood chemistry), nineteen patients enrolled in the 4-week-long double-blind study were randomly assigned into two groups: a resveratrol group receiving oral 2 × 5 mg resveratrol and a control group receiving placebo. Before and after the second and fourth weeks of the trial, insulin resistance/sensitivity, creatinine-normalised ortho-tyrosine level in urine samples (as a measure of oxidative stress), incretin levels and phosphorylated protein kinase B (pAkt):protein kinase B (Akt) ratio in platelets were assessed and statistically analysed. After the fourth week, resveratrol significantly decreased insulin resistance (homeostasis model of assessment for insulin resistance) and urinary ortho-tyrosine excretion, while it increased the pAkt:Akt ratio in platelets. On the other hand, it had no effect on parameters that relate to β-cell function (i.e. homeostasis model of assessment of β-cell function). The present study shows for the first time that resveratrol improves insulin sensitivity in humans, which might be due to a resveratrol-induced decrease in oxidative stress that leads to a more efficient insulin signalling via the Akt pathway.
TL;DR: Higher muscle mass is associated with better insulin sensitivity and lower risk of PDM across the full range and the effect of appropriate exercise interventions designed to increase muscle mass on incidence of diabetes is needed.
Abstract: Context: Insulin resistance, the basis of type 2 diabetes, is rapidly increasing in prevalence; very low muscle mass is a risk factor for insulin resistance. Objective: The aim was to determine whether increases in muscle mass at average and above average levels are associated with improved glucose regulation. Design: We conducted a cross-sectional analysis of National Health and Nutrition Examination Survey III data. Participants: Data from 13,644 subjects in a national study were evaluated. Outcome Measurements: We measured homeostasis model assessment of insulin resistance (HOMA-IR), blood glycosylated hemoglobin level, prevalence of transitional/pre- or overt diabetes (PDM), and prevalence of overt diabetes mellitus. Results: All four outcomes decreased from the lowest quartile to the highest quartile of skeletal muscle index (SMI), the ratio of total skeletal muscle mass (estimated by bioelectrical impedance) to total body weight. After adjusting for age, ethnicity, sex, and generalized and central o...
TL;DR: Greater insulin resistance was associated with an AD-like pattern of reduced CMRglu in frontal, parietotemporal, and cingulate regions in adults with PD/T2D.
Abstract: Background—Insulin resistance is a causal factor in pre-diabetes and type 2 diabetes (T2D), and also increases the risk of developing Alzheimer’s disease (AD). Reductions in cerebral glucose metabolic rate (CMRglu) as measured by fluorodeoxyglucose positron emission tomography (FDG PET) in parietotemporal, frontal, and cingulate cortex are also associated with increased AD risk, and can be observed years before dementia onset. Objectives—We examined whether greater insulin resistance as indexed by the homeostasis model assessment (HOMA-IR) would be associated with reduced resting CMRglu in areas known to be vulnerable in AD in a sample of cognitively normal adults with newly diagnosed prediabetes or T2D (P-D/T2D). We also determined whether P-D/T2D adults have abnormal patterns of CMRglu during a memory encoding task. Design—Randomized crossover design of resting and activation [F-18] FDG-PET. Setting—University Imaging Center and VA Clinical Research Unit. Participants—Participants included 23 older adults (mean age±SEM=74.4±1.4) with no prior diagnosis of or treatment for diabetes, but who met American Diabetes Association glycemic criteria for pre-diabetes (n=11) or diabetes (n=12) based on fasting or 2-h oral glucose tolerance test (OGTT) glucose values, and 6 adults (mean age±SEM=74.3±2.8) with normal fasting glucose and glucose tolerance. No participant met Petersen criteria for mild cognitive impairment (MCI). Intervention—Fasting participants rested with eyes open in a dimly lit room and underwent resting and cognitive activation [F-18]FDG PET imaging on separate days, in randomized order, at 9 am. Following a 30-min transmission scan, subjects received an intravenous injection of 5 mCi [F-18]FDG, and the emission scan commenced 40 min post-injection. In the activation condition, a 35-min memory encoding task was initiated at the time of tracer injection. Subjects