Mogher Khamaisi

Preserved DNA Damage Checkpoint Pathway Protects against Complications in Long-Standing Type 1 Diabetes

The mechanisms underlying the development of complications in type 1 diabetes (T1D) are poorly understood. Disease modeling of induced pluripotent stem cells (iPSCs) from patients with longstanding T1D (disease duration ≥ 50 years) with severe (Medalistxa0+C) or absent to mild complications (Medalist -C) revealed impaired growth, reprogramming, and differentiation in Medalistxa0+C. Genomics and proteomics analyses suggested differential regulation of DNA damage checkpoint proteins favoring protection from cellular apoptosis in Medalist -C. In silico analyses showed altered expression patterns of DNA damage checkpoint factors among the Medalist groups to be targets of miR200, whose expression was significantly elevated in Medalistxa0+C serum. Notably, neurons differentiated from Medalistxa0+C iPSCs exhibited enhanced susceptibility to genotoxic stress that worsened upon miR200 overexpression. Furthermore, knockdown of miR200 in Medalistxa0+C fibroblasts and iPSCs rescued checkpoint protein expression and reduced DNA damage. We propose miR200-regulated DNA damage checkpoint pathway as a potential therapeutic target for treating complications of diabetes.

PKCδ inhibition normalizes the wound-healing capacity of diabetic human fibroblasts

Abnormal fibroblast function underlies poor wound healing in patients with diabetes; however, the mechanisms that impair wound healing are poorly defined. Here, we evaluated fibroblasts from individuals who had type 1 diabetes (T1D) for 50 years or more (Medalists, n = 26) and from age-matched controls (n = 7). Compared with those from controls, Medalist fibroblasts demonstrated a reduced migration response to insulin, lower VEGF expression, and less phosphorylated AKT (p-AKT), but not p-ERK, activation. Medalist fibroblasts were also functionally less effective at wound closure in nude mice. Activation of the δ isoform of protein kinase C (PKCδ) was increased in postmortem fibroblasts from Medalists, fibroblasts from living T1D subjects, biopsies of active wounds of living T1D subjects, and granulation tissues from mice with streptozotocin-induced diabetes. Diabetes-induced PKCD mRNA expression was related to a 2-fold increase in the mRNA half-life. Pharmacologic inhibition and siRNA-mediated knockdown of PKCδ or expression of a dominant-negative isoform restored insulin signaling of p-AKT and VEGF expression in vitro and improved wound healing in vivo. Additionally, increasing PKCδ expression in control fibroblasts produced the same abnormalities as those seen in Medalist fibroblasts. Our results indicate that persistent PKCδ elevation in fibroblasts from diabetic patients inhibits insulin signaling and function to impair wound healing and suggest PKCδ inhibition as a potential therapy to improve wound healing in diabetic patients.

Diabetic Microvascular Disease: An Endocrine Society Scientific Statement

Both type 1 and type 2 diabetes adversely affect the microvasculature in multiple organs. Our understanding of the genesis of this injury and of potential interventions to prevent, limit, or reverse injury/dysfunction is continuously evolving. This statement reviews biochemical/cellular pathways involved in facilitating and abrogating microvascular injury. The statement summarizes the types of injury/dysfunction that occur in the three classical diabetes microvascular target tissues, the eye, the kidney, and the peripheral nervous system; the statement also reviews information on the effects of diabetes and insulin resistance on the microvasculature of skin, brain, adipose tissue, and cardiac and skeletal muscle. Despite extensive and intensive research, it is disappointing that microvascular complications of diabetes continue to compromise the quantity and quality of life for patients with diabetes. Hopefully, by understanding and building on current research findings, we will discover new approaches for prevention and treatment that will be effective for future generations.

Cardiovascular Disease Protection in Long-Duration Type 1 Diabetes and Sex Differences

Two recent articles describe higher morbidity and mortality from cardiovascular disease (CVD) at younger ages for women with type 1 diabetes compared with men in cohorts with average duration of approximately 30 years (1,2). Women in the Joslin 50-Year Medalist Study (total n = 680) have a significantly lower CVD prevalence than men (women 35.3% vs. men 51.6%, P < 0.001), suggesting a protective factor. The objective of this analysis was to investigate protective factors associated with CVD and sex-associated differences in rates in those with long-term type 1 diabetes.nnThe Joslin 50-Year Medalist Study is a cross-sectional study of individuals with 50 or more years of type 1 diabetes ( n = 651). To be awarded the Joslin 50-Year Medal, individuals provide an original medical record from time of diagnosis, or three other forms of documentation of insulin dependence since the time of diagnosis 50 or more …

Bone health in subjects with type 1 diabetes for more than 50 years

AimsFew data regarding prevalence of and risk factors for poor bone health in aging individuals with long-standing T1D are available. In this study, we aim to describe the prevalence of bone fragility and to identify factors associated with low bone density in individuals with long-term T1D.MethodsWe examined the prevalence of non-vertebral fractures in 985 subjects enrolled in the Joslin 50-Year Medalist Study and measured bone mineral density (BMD) by dual-energy X-ray absorptiometry at the femoral neck, lumbar spine and radius in a subset (65 subjects, mean age 62.6xa0years, duration 52.5xa0years, HbA1c 7.1%) with no significant clinical or demographic differences from the rest of the cohort.ResultsMedalists have low prevalence of fractures (0.20% hip and 0.91% wrist) and normal Z-score values (spine +1.15, total hip +0.23, femoral neck −0.01, radius +0.26; pxa0>xa00.05 for differences vs. 0 at all sites). A significant relationship was found between lower BMD and higher total cholesterol, triglycerides and LDL levels, but not HbA1c. Low BMD at the femoral neck was associated with cardiovascular disease after adjustment for confounding factors: prevalence risk ratio of CVD [95% CI] 4.6 [1.2–18.1], p = 0.03. No other diabetic vascular complication was found to be associated with low BMD.ConclusionsThese are the first data regarding bone health in aging individuals who have had diabetes for 50 or more years. The low rates of non-vertebral fractures and the normal Z-score suggest the long T1D diabetes duration did not increase the risk of bone fractures in Medalists compared to non-diabetic peers. Additionally, the association with cardiovascular disease demonstrates the BMD differences in groups are likely not due to glycemic control alone.

Overexpressing IRS1 in Endothelial Cells Enhances Angioblast Differentiation and Wound Healing in Diabetes and Insulin Resistance

The effect of enhancing insulin’s actions in endothelial cells (ECs) to improve angiogenesis and wound healing was studied in obesity and diabetes. Insulin receptor substrate 1 (IRS1) was overexpressed in ECs using the VE-cadherin promoter to create ECIRS1 TG mice, which elevated pAkt activation and expressions of vascular endothelial growth factor (VEGF), Flk1, and VE-cadherin in ECs and granulation tissues (GTs) of full-thickness wounds. Open wound and epithelialization rates and angiogenesis significantly improved in normal mice and high fat (HF) diet–induced diabetic mice with hyperinsulinemia in ECIRS1 TG versus wild type (WT), but not in insulin-deficient diabetic mice. Increased angioblasts and EC numbers in GT of ECIRS1 mice were due to proliferation in situ rather than uptake. GT in HF-fed diabetic mice exhibited parallel decreases in insulin and VEGF-induced pAkt and EC numbers by >50% without changes in angioblasts versus WT mice, which were improved in ECIRS1 TG mice on normal chow or HF diet. Thus, HF-induced diabetes impaired angiogenesis by inhibiting insulin signaling in GT to decrease the differentiation of angioblasts to EC, which was normalized by enhancing insulin’s action targeted to EC, a potential target to improve wound healing in diabetes and obesity.

Exogenous Insulin Infusion Can Decrease Atherosclerosis in Diabetic Rodents by Improving Lipids, Inflammation, and Endothelial Function

Objective— The objective of this study is to evaluate whether exogenously induced hyperinsulinemia may increase the development of atherosclerosis. Approach and Results— Hyperinsulinemia, induced by exogenous insulin implantation in high-fat fed (60% fat HFD) apolipoprotein E–deficient mice (ApoE−/−) mice, exhibited insulin resistance, hyperglycemia, and hyperinsulinemia. Atherosclerosis was measured by the accumulation of fat, macrophage, and extracellular matrix in the aorta. After 8 weeks on HFD, ApoE−/− mice were subcutaneously implanted with control (sham) or insulin pellet, and phlorizin, a sodium glucose cotransporters inhibitor (1/2)inhibitor, for additional 8 weeks. Intraperitoneal glucose tolerance test showed that plasma glucose levels were lower and insulin and IGF-1 (insulin-like growth factor-1) levels were 5.3- and 3.3-fold higher, respectively, in insulin-implanted compared with sham-treated ApoE−/− mice. Plasma triglyceride, cholesterol, and lipoprotein levels were decreased in mice with insulin implant, in parallel with increased lipoprotein lipase activities. Atherosclerotic plaque by en face and complexity staining showed significant reductions of fat deposits and expressions of vascular adhesion molecule-1, tumor necrosis factor-&agr;, interleukin 6, and macrophages in arterial wall while exhibiting increased activation of pAKT and endothelial nitric oxide synthase (P<0.05) comparing insulin-implanted versus sham HFD ApoE−/− mice. No differences were observed in atherosclerotic plaques between phlorizin-treated and sham HFD ApoE−/− mice, except phlorizin significantly lowered plasma glucose and glycated hemoglobin levels while increased glucosuria. Endothelial function was improved only by insulin treatment through endothelial nitric oxide synthase/nitric oxide activations and reduced proinflammatory (M1) and increased anti-inflammatory (M2) macrophages, which were inhibited by endothelial nitric oxide synthase inhibitor. Conclusions— Exogenous insulin decreased atherosclerosis by lowering inflammatory cytokines, macrophages, and plasma lipids in HFD-induced hyperlipidemia, insulin resistant and mildly diabetic ApoE−/− mice.

High density lipoprotein modulates osteocalcin expression in circulating monocytes: a potential protective mechanism for cardiovascular disease in type 1 diabetes

BackgroundCardiovascular disease (CVD) is a major cause of mortality in type 1 diabetes (T1D). A pro-calcific drift of circulating monocytes has been linked to vascular calcification and is marked by the surface expression of osteocalcin (OCN). We studied OCN+ monocytes in a unique population with ≥50xa0years of T1D, the 50-Year Joslin Medalists (J50M).MethodsCD45 bright/CD14+/OCN+ cells in the circulating mononuclear blood cell fraction were quantified by flow cytometry and reported as percentage of CD45 bright cells. Mechanisms were studied by inducing OCN expression in human monocytes in vitro.ResultsSubjects without history of CVD (nxa0=xa016) showed lower levels of OCN+ monocytes than subjects with CVD (nxa0=xa014) (13.1xa0±xa08.4% vs 19.9xa0±xa06.4%, pxa0=xa00.02). OCN+ monocytes level was inversely related to total high density lipoprotein (HDL) cholesterol levels (rxa0=xa0−0.424, pxa0=xa00.02), large (rxa0=xa0−0.413, pxa0=xa00.02) and intermediate (rxa0=xa0−0.445, pxa0=xa00.01) HDL sub-fractions, but not to small HDL. In vitro, incubation with OxLDL significantly increased the number of OCN+ monocytes (pxa0<xa00.01). This action of OxLDL was significantly reduced by the addition of HDL in a concentration dependent manner (pxa0<xa00.001). Inhibition of the scavenger receptor B1 reduced the effects of both OxLDL and HDL (pxa0<xa00.05).ConclusionsLow OCN+ monocytes levels are associated with lack of CVD in people with long duration T1D. A possible mechanism for the increased OCN+ monocytes could be the elevated levels of oxidized lipids due to diabetes which may be inhibited by HDL. These findings suggest that circulating OCN+ monocytes could be a marker for vascular disease in diabetic patients and possibly modified by HDL elevation.

SHP-1 activation inhibits vascular smooth muscle cell proliferation and intimal hyperplasia in a rodent model of insulin resistance and diabetes

Aims/hypothesisAccelerated migration and proliferation of vascular smooth muscle cells (VSMCs) enhances arterial restenosis after angioplasty in insulin resistance and diabetes. Elevation of Src homology 2-containing protein tyrosine phosphatase 1 (SHP-1) induces apoptosis in the microvasculature. However, the role of SHP-1 in intimal hyperplasia and restenosis has not been clarified in insulin resistance and diabetes.MethodsWe used a femoral artery wire injury mouse model, rodent models with insulin resistance and diabetes, and patients with type 2 diabetes. Further, we modulated SHP-1 expression using a transgenic mouse that overexpresses SHP-1 in VSMCs (Shp-1-Tg). SHP-1 agonists were also employed to study the molecular mechanisms underlying the regulation of SHP-1 by oxidised lipids.ResultsMice fed a high-fat diet (HFD) exhibited increased femoral artery intimal hyperplasia and decreased arterial SHP-1 expression compared with mice fed a regular diet. Arterial SHP-1 expression was also decreased in Zucker fatty rats, Zucker diabetic fatty rats and in patients with type 2 diabetes. In primary cultured VSMCs, oxidised LDL suppressed SHP-1 expression by activating Mek-1 (also known as Map2k1) and increased DNA methylation of the Shp-1 promoter. VSMCs from Shp-1-Tg mice exhibited impaired platelet-derived growth factor (PDGF)-stimulated tyrosine phosphorylation with a concomitant decrease in PDGF-stimulated VSMC proliferation and migration. Similarly, HFD-fed Shp-1-Tg mice and mice treated with the SHP-1 inducer, Icariside II, were protected from the development of intimal hyperplasia following wire injury.Conclusions/interpretationSuppression of SHP-1 by oxidised lipids may contribute to the excessive VSMC proliferation, inflammatory cytokine production and intimal hyperplasia observed in arteries from diabetes and insulin resistance. Augmenting SHP-1 levels is a potential therapeutic strategy to maintain stent patency in patients with insulin resistance and diabetes.

Association of Continuous Subcutaneous Insulin Injection Pumps with Lower HbA1c and Mortality in Type 1 Diabetes of Chronic Duration (1728-P)

SamenvattingContinuous subcutaneous insulin infusion pumps (CSII) may improve HbA1c and quality of life relative to the use of multiple daily injections (MDI) in individuals with type 1 diabetes (T1D), yet there is limited information about the relationship of CSII to mortality. The 50-Year Medalist Study provides a unique opportunity to investigate in 944 individuals with more than 50 y of T1D (mean duration = 53 y, HbA1c = 7.1%, age = 65 y, age at onset = 11 y, daily insulin dose = 0.43 u/kg; 59% use CSII, 49% for 10 y or longer).