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Dirkes RK, Ortinau LC, Rector RS, Olver TD, Hinton PS. Insulin-Stimulated Bone Blood Flow and Bone Biomechanical Properties Are Compromised in Obese, Type 2 Diabetic OLETF Rats. JBMR Plus 2017; 1:116-126. [PMID: 30283885 PMCID: PMC6124191 DOI: 10.1002/jbm4.10007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 05/08/2017] [Accepted: 05/10/2017] [Indexed: 01/20/2023] Open
Abstract
Type 2 diabetes (T2D) increases skeletal fragility and fracture risk; however, the underlying mechanisms remain to be identified. Impaired bone vascular function, in particular insulin‐stimulated vasodilation and blood flow is a potential, yet unexplored mechanism. The purpose of this study was to determine the effects of T2D on femoral biomechanical properties, trabecular microarchitecture, and insulin‐stimulated bone vasodilation by comparison of hyperphagic Otsuka Long‐Evans Tokushima Fatty (OLETF) rats with normoglycemic control OLETF rats. Four‐week old, male OLETF rats were randomized to two groups: type 2 diabetes (O‐T2D) or normoglycemic control (O‐CON). O‐T2D were allowed ad libitum access to a rodent chow diet and O‐CON underwent moderate caloric restriction (30% restriction relative to intake of O‐T2D) to maintain normal body weight (BW) and glycemia until 40 weeks of age. Hyperphagic O‐T2D rats had significantly greater BW, body fat, and blood glucose than O‐CON. Total cross‐sectional area (Tt.Ar), cortical area (Ct.Ar), Ct.Ar/Tt.Ar, and polar moment of inertia of the mid‐diaphyseal femur adjusted for BW were greater in O‐T2D rats versus O‐CON. Whole‐bone biomechanical properties of the femur assessed by torsional loading to failure did not differ between O‐T2D and O‐CON, but tissue‐level strength and stiffness adjusted for BW were reduced in O‐T2D relative to O‐CON. Micro–computed tomography (μCT) of the distal epiphysis showed that O‐T2D rats had reduced percent bone volume, trabecular number, and connectivity density, and greater trabecular spacing compared with O‐CON. Basal tibial blood flow assessed by microsphere infusion was similar in O‐T2D and O‐CON, but the blood flow response to insulin stimulation in both the proximal epiphysis and diaphyseal marrow was lesser in O‐T2D compared to O‐CON. In summary, impaired insulin‐stimulated bone blood flow is associated with deleterious changes in bone trabecular microarchitecture and cortical biomechanical properties in T2D, suggesting that vascular dysfunction might play a causal role in diabetic bone fragility. © 2017 The Authors. JBMR Plus Published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.
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Affiliation(s)
- Rebecca K Dirkes
- Department of Nutrition and Exercise Physiology University of Missouri-Columbia Columbia MO USA
| | - Laura C Ortinau
- Department of Nutrition and Exercise Physiology University of Missouri-Columbia Columbia MO USA
| | - R Scott Rector
- Department of Nutrition and Exercise Physiology University of Missouri-Columbia Columbia MO USA.,Division of Gastroenterology and Hepatology Department of Medicine University of Missouri-Columbia Columbia MO USA.,Research Service Harry S Truman Memorial VA Hospital Columbia MO USA
| | - T Dylan Olver
- Department of Biomedical Sciences University of Missouri-Columbia Columbia MO USA
| | - Pamela S Hinton
- Department of Nutrition and Exercise Physiology University of Missouri-Columbia Columbia MO USA
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153
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Targeting Select Cellular Stress Pathways to Prevent Hyperglycemia-Related Complications: Shifting the Paradigm. Drugs 2017; 76:1081-91. [PMID: 27364752 DOI: 10.1007/s40265-016-0609-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Despite the advances made in preventing complications of diabetes, there is still substantial residual risk. Hence the need for developing new therapeutic agents that target the various facets of the pathogenesis of complications in people with diabetes. Traditionally four general biochemical pathways had been recognized as major contributors to glucotoxicity. These include the polyol pathway, the protein kinase C (PKC) pathway, glycosylation pathway, and oxidative stress. The latter has been proposed as a common impetus of the other pathways of glucotoxicity. More recently, the cross talk between oxidative stress and other recognized cellular stresses such as endoplasmic reticulum (ER), inflammatory, and mitochondrial stresses has emerged as an important additional mechanism of glucotoxicity. The observation that targeting oxidative stress with antioxidants has been associated with unfavorable clinical outcomes and the recognition that in cell cultures antioxidants may aggravate ER stress, suggests that selective targeting of individual cellular stresses may not be sufficient for preventing glucotoxicity. Future efforts should focus on developing therapeutic agents that can ameliorate cellular stress globally by simultaneously targeting the oxidative, ER, mitochondrial, and inflammatory stresses.
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154
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ERK1 and ERK2 activation modulates diet-induced obesity in mice. Biochimie 2017; 137:78-87. [PMID: 28302472 DOI: 10.1016/j.biochi.2017.03.004] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Accepted: 03/10/2017] [Indexed: 01/13/2023]
Abstract
Obesity is a worldwide problem, and dietary lipids play an important role in its pathogenesis. Recently, Erk1 knock-out (ERK1-/-) mice have been shown to exhibit low preference for dietary fatty acids. Hence, we maintained Erk1-/- mice on a high-fat diet (HFD) to assess the implication of this mitogen-activated protein (MAP) kinase in obesity. The Erk1-/- mice, fed the HFD, were more obese than wild-type (WT) animals, fed the same diet. Erk1-/- obese mice gained more fat and liver mass than WT obese animals. No difference was observed in daily food and energy intake in HFD-fed both group of animals. However, feed efficiency was higher in Erk1-/- than WT animals. Blood cholesterol, triglyceride and insulin concentrations were higher in Erk1-/- obese mice compared to WT obese animals. Accordingly, homeostatic model assessment of insulin resistance (HOMA-IR) value was higher in Erk1-/- obese mice compared to WT obese animals. Interestingly, only Erk1-/- obese mice, but not WT-obese animals, exhibited high degree of phosphorylation of liver MEK, the upstream regulator of ERK1/2. This phenomenon was associated with high liver ERK2 phosphorylation in Erk1-/- obese mice which also had high liver acetyl-CoA carboxylase 1 (ACC1) and fatty acid synthase (FAS) mRNA expression, suggesting high lipogenesis in these animals. The Erk1-/- obese mice also had low PPAR-α and CPT1β mRNA, indicating low fatty acid oxidation. Our observations suggest that ERK1 and ERK2 might play key roles in the regulation of obesity.
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155
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Rask-Madsen C, Park K, Li Q, King GL. Letter by Rask-Madsen et al Regarding Article, “Selective Enhancement of Insulin Sensitivity in the Endothelium In Vivo Reveals a Novel Proatherosclerotic Signaling Loop”. Circ Res 2017; 120:e2-e3. [DOI: 10.1161/circresaha.116.310491] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
| | - Kyoungmin Park
- Joslin Diabetes Center and Harvard Medical School, Boston, MA
| | - Qian Li
- Joslin Diabetes Center and Harvard Medical School, Boston, MA
| | - George L. King
- Joslin Diabetes Center and Harvard Medical School, Boston, MA
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156
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Viswambharan H, Kearney MT. Response by Viswambharan and Kearney to Letter Regarding Article, "Selective Enhancement of Insulin Sensitivity in the Endothelium In Vivo Reveals a Novel Proatherosclerotic Signaling Loop". Circ Res 2017; 120:e4-e5. [PMID: 28209800 DOI: 10.1161/circresaha.117.310510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Hema Viswambharan
- Leeds Institute for Cardiovascular and Metabolic Medicine, University of Leeds School of Medicine, University of Leeds, Leeds, United Kingdom
| | - Mark T Kearney
- Leeds Institute for Cardiovascular and Metabolic Medicine, University of Leeds School of Medicine, University of Leeds, Leeds, United Kingdom
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157
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Olver TD, McDonald MW, Klakotskaia D, Richardson RA, Jasperse JL, Melling CWJ, Schachtman TR, Yang HT, Emter CA, Laughlin MH. A chronic physical activity treatment in obese rats normalizes the contributions of ET-1 and NO to insulin-mediated posterior cerebral artery vasodilation. J Appl Physiol (1985) 2017; 122:1040-1050. [PMID: 28183819 DOI: 10.1152/japplphysiol.00811.2016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 01/11/2017] [Accepted: 02/02/2017] [Indexed: 12/31/2022] Open
Abstract
This study tested the hypotheses that obesity-induced decrements in insulin-stimulated cerebrovascular vasodilation would be normalized with acute endothelin-1a receptor antagonism and that treatment with a physical activity intervention restores vasoreactivity to insulin through augmented nitric oxide synthase (NOS)-dependent dilation. Otsuka Long-Evans Tokushima Fatty rats were divided into the following groups: 20 wk old food controlled (CON-20); 20 wk old free food access (model of obesity, OB-20); 40 wk old food controlled (CON-40); 40 wk old free food access (OB-40); and 40 wk old free food access+RUN (RUN-40; wheel-running access from 20 to 40 wk). Rats underwent Barnes maze testing and a euglycemic hyperinsulinemic clamp (EHC). In the 40-wk cohort, cerebellum and hippocampus blood flow (BF) were examined (microsphere infusion). Vasomotor responses (pressurized myography) to insulin were assessed in untreated, endothelin-1a receptor antagonism, and NOS inhibition conditions in posterior cerebral arteries. Insulin-stimulated vasodilation was attenuated in the OB vs. CON and RUN groups (P ≤ 0.04). Dilation to insulin was normalized with endothelin-1a receptor antagonism in the OB groups (between groups, P ≥ 0.56), and insulin-stimulated NOS-mediated dilation was greater in the RUN-40 vs. OB-40 group (P < 0.01). At 40 wk of age, cerebellum BF decreased during EHC in the OB-40 group (P = 0.02) but not CON or RUN groups (P ≥ 0.36). Barnes maze testing revealed increased entry errors and latencies in the RUN-40 vs. CON and OB groups (P < 0.01). These findings indicate that obesity-induced impairments in vasoreactivity to insulin involve increased endothelin-1 and decreased nitric oxide signaling. Chronic spontaneous physical activity, initiated after disease onset, reversed impaired vasodilation to insulin and decreased Barnes maze performance, possibly because of increased exploratory behavior.NEW & NOTEWORTHY The new and noteworthy findings are that 1) in rodents, obesity-related deficits in insulin-mediated vasodilation are associated with increased influence of insulin-stimulated ET-1 and depressed influence of insulin-stimulated NOS and 2) a physical activity intervention, initiated after the onset of disease, restores insulin-mediated vasodilation, likely by normalizing insulin-stimulated ET-1 and NOS balance. These data demonstrate that the treatment effects of chronic exercise on insulin-mediated vasodilation extend beyond active skeletal muscle vasculature and include the cerebrovasculature.
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Affiliation(s)
- T Dylan Olver
- Department of Biomedical Sciences, University of Missouri-Columbia, Columbia, Missouri;
| | - Matthew W McDonald
- Department of Kinesiology, University of Western Ontario, London, Ontario, Canada
| | - Diana Klakotskaia
- Department of Psychological Sciences, University of Missouri-Columbia, Columbia, Missouri; and
| | - Rachel A Richardson
- Department of Psychological Sciences, University of Missouri-Columbia, Columbia, Missouri; and
| | | | - C W James Melling
- Department of Kinesiology, University of Western Ontario, London, Ontario, Canada
| | - Todd R Schachtman
- Department of Psychological Sciences, University of Missouri-Columbia, Columbia, Missouri; and
| | - Hsiao T Yang
- Department of Biomedical Sciences, University of Missouri-Columbia, Columbia, Missouri
| | - Craig A Emter
- Department of Biomedical Sciences, University of Missouri-Columbia, Columbia, Missouri
| | - M Harold Laughlin
- Department of Biomedical Sciences, University of Missouri-Columbia, Columbia, Missouri
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158
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Abstract
IRS proteins are cellular adaptor molecules that mediate many of the key metabolic actions of insulin. When tyrosine is phosphorylated by the activated insulin receptor, IRS proteins recruit downstream effectors, such as phosphoinositide 3-kinase and mitogen-activated protein kinase, in order to elicit cellular responses such as glucose uptake, lipid metabolism and cell proliferation. There are two main IRS proteins in humans (IRS1 and IRS2), both of which are widely expressed. Given their central role in the insulin signalling pathway, it is not surprising that male mice lacking Irs1 or Irs2 present with elevated blood glucose or type 2 diabetes, respectively. For reasons yet to be identified, female Irs2 (-/-) mice do not develop type 2 diabetes. A number of organs are affected by complications of diabetes; macrovascular complications include stroke and coronary artery disease, while nephropathy, neuropathy and retinopathy fall into the category of microvascular complications. Given the serious consequences of these complications on patient morbidity and mortality, it is essential to identify the molecular pathogenesis underlying diabetic complications, with a view to improving therapeutic intervention and patient outcomes. A number of recently published papers have converged on the hypothesis that the loss of insulin signalling and IRS proteins is instrumental to the development and/or progression of diabetic complications. This review will summarise some highlights from the published work in which this hypothesis is discussed.
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Affiliation(s)
- Deborah P Lavin
- Centre for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, Northern Ireland, UK
| | - Morris F White
- Division of Endocrinology, Children's Hospital Boston, Harvard Medical School, Boston, MA, USA
| | - Derek P Brazil
- Centre for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, Northern Ireland, UK.
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159
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Scholz GH, Hanefeld M. Metabolic Vascular Syndrome: New Insights into a Multidimensional Network of Risk Factors and Diseases. Visc Med 2016; 32:319-326. [PMID: 27921043 DOI: 10.1159/000450866] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND Since 1981, we have used the term metabolic syndrome to describe an association of a dysregulation in lipid metabolism (high triglycerides, low high-density lipoprotein cholesterol, disturbed glucose homeostasis (enhanced fasting and/or prandial glucose), gout, and hypertension), with android obesity being based on a common soil (overnutrition, reduced physical activity, sociocultural factors, and genetic predisposition). We hypothesized that main traits of the syndrome occur early and are tightly connected with hyperinsulinemia/insulin resistance, procoagulation, and cardiovascular diseases. METHODS To establish a close link between the traits of the metabolic vascular syndrome, we focused our literature search on recent original work and comprehensive reviews dealing with the topics metabolic syndrome, visceral obesity, fatty liver, fat tissue inflammation, insulin resistance, atherogenic dyslipidemia, arterial hypertension, and type 2 diabetes mellitus. RESULTS Recent research supports the concept that the metabolic vascular syndrome is a multidimensional and interactive network of risk factors and diseases based on individual genetic susceptibility and epigenetic changes where metabolic dysregulation/metabolic inflexibility in different organs and vascular dysfunction are early interconnected. CONCLUSION The metabolic vascular syndrome is not only a risk factor constellation but rather a life-long abnormality of a closely connected interactive cluster of developing diseases which escalate each other and should continuously attract the attention of every clinician.
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Affiliation(s)
- Gerhard H Scholz
- Department of Endocrinology, Diabetology, Cardiology and General Medicine, St. Elisabeth-Krankenhaus Leipzig, Leipzig, Germany; Leipziger Institut für Präventivmedizin GmbH, Leipzig, Germany
| | - Markolf Hanefeld
- GWT-TUD GmbH, Dresden Technical University, Dresden, Germany; Medical Clinic III, University Hospital Carl Gustav Carus, Dresden, Dresden, Germany
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160
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Torkamandi S, Bastami M, Ghaedi H, Moghadam F, Mirfakhraie R, Omrani MD. MAP3K1 May be a Promising Susceptibility Gene for Type 2 Diabetes Mellitus in an Iranian Population. INTERNATIONAL JOURNAL OF MOLECULAR AND CELLULAR MEDICINE 2016; 5:134-140. [PMID: 27942499 PMCID: PMC5125365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 07/02/2016] [Indexed: 11/11/2022]
Abstract
Considering that MAPK (mitogen- activated protein kinase) signaling pathway has an important role in the progression of inflammatory cytokine secretion in type 2 diabetes mellitus (T2DM), we have recently investigated the reported genetic polymorphism from genome wide association study in MAP3K1 (mitogen-activated protein kinase kinase kinase 1) in diabetes as an important member of MAPK signaling. This study aimed to investigate the possible association of rs10461617 at the upstream of MAP3K1 gene in an Iranian case-control study with the risk of T2DM. The study population was comprised of 342 unrelated Iranian individuals including 177 patients with T2DM and 165 unrelated healthy control subjects. Genotyping was performed using PCR-RFLP and confirmed with sequencing. In a logistic regression analysis, the rs10461617A allele was associated with a significantly higher risk of T2DM assuming the log- additive model (OR: 1.44, 95% CI: 1.01-2.05, P = 0.039). In conclusion, we provided the first evidence for the association of rs10461617 at the upstream of MAP3K1 with the risk of T2DM in an Iranian population.
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Affiliation(s)
- Shahram Torkamandi
- Department of Medical Genetics, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
| | - Milad Bastami
- Department of Medical Genetics, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.
| | - Hamid Ghaedi
- Department of Medical Genetics, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
| | - Fateme Moghadam
- Imam Hossein Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
| | - Reza Mirfakhraie
- Department of Medical Genetics, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
| | - Mir Davood Omrani
- Department of Medical Genetics, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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