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Insulin resistance (IR) is a putative risk factor for cognitive decline and dementia, and has been shown to impede neuronal glucose metabolism in animal models. This post hoc study focused on metabolic changes in the medial prefrontal region, a brain region exhibiting decline years before documented cognitive changes, relative to high or low IR status in a cohort of postmenopausal women at risk for dementia who were randomized to continue or discontinue existing stable hormone therapy (HT) for 2 years. Subjects were dichotomized into high and low IR groups based on the homeostatic model assessment of insulin resistance, which was within clinically normal limits for the group as a whole at both baseline and 2-year follow-up. Results showed that high and low IR groups showed significant differences in metabolic decline of the medial prefrontal gyrus, regardless of HT randomization group. However, HT randomization was predictive of metabolic decline only in women with low HOMA (homeostatic assessment of insulin resistance). Performance in working memory was consistent with observed metabolic changes. These results suggest IR may be an independent moderator of regional metabolic changes, while protective metabolic effects of HT are most apparent in those at low-end range of IR. If replicated in future studies, these findings will help to better understand the interaction between putative risk and protective factors, and further delineate cohort postmenopausal women who may benefit from HT., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

Insulin resistance (IR) is the main pathological condition underlying vascular disorders, such as diabetes and cardiovascular disease, which are well established risk factors for cognitive decline and Alzheimer disease (AD). Hippocampal atrophy has been associated with cognitive decline, but little is known about the influence of IR on hippocampus integrity in non-diabetic, cognitively intact individuals. Herein, 50 women ages 50-65, current users of hormone therapy, underwent magnetic resonance imaging, cognitive testing, and homeostatic assessment of insulin resistance (HOMA-IR), as part of a longitudinal study examining brain structure and function in postmenopausal women at risk for AD. Results demonstrated a significant negative relationship between HOMA-IR and right and total hippocampal volume, overall cognitive performance, and selective tests of verbal and non-verbal memory. The main effect of HOMA-IR on brain structure and cognition was not altered by the presence of APOE-ε4 allele or by reproductive history, such as duration of endogenous and exogenous estrogen exposure. These results suggest that IR in middle-aged individuals at risk for AD may be biomarker for dementia risk., (Copyright © 2009 Elsevier Inc. All rights reserved.)

A number of cross-sectional studies have suggested an association between insulin resistance (IR) and affective disorders. However, limited data exist on potential changes in IR in a prospective treatment of depression. The present pilot study tested the hypothesis that improvement of IR with the addition of an insulin-sensitizing agent would improve mood in nondiabetic patients with unipolar or bipolar depression, who had surrogate blood markers suggestive of IR. Surrogate IR-criteria blood markers were fasting plasma glucose >100 mg/dl or triglyceride (TG) to high density lipoprotein (HDL) ratio >3.0. Open-label rosiglitazone, titrated to a dose of 8 mg/day, was administered for 12 weeks to 12 patients with depressive disorder receiving treatment as usual (TAU). Eight patients who completed the 12-week study exhibited significant declines in both depression severity by the Hamilton Depression Rating Scale and the Clinical Global Impression scale, with moderate effect sizes noted. Modest improvement in Matsuda Index scores was also noted at 12 weeks, yet declines in depression severity scores were not associated with improvements in the endocrine markers (Matsuda Index, TG/HDL ratio, and body mass index). These results suggest the potential novel use for an insulin-sensitizing agent in the treatment of depressive disorders. Larger placebo-controlled studies are warranted.

We tested the hypothesis that weight loss alleviates insulin resistance in skeletal muscle within the proximal steps of glucose metabolism, namely substrate delivery, glucose transport, and glucose phosphorylation. In obese subjects with and without type 2 diabetes, in vivo skeletal muscle assessments were obtained with dynamic positron emission tomography (PET) imaging performed during euglycemic clamps at moderate hyperinsulinemia (40 mU x min(-1) x m(-2)), using [(15)O]H(2)O and [(18)F]fluoro-deoxyglucose ([(18)F]FDG) to quantify tissue perfusion and glucose metabolism. Dynamic [(18)F]FDG PET data were analyzed using both a novel muscle-specific compartmental model and a compartmental model originally developed for the brain and often used for [(18)F]FDG muscle image quantification. Weight loss in obese subjects with (n = 9) and without (n = 9) type 2 diabetes over a 4-month intervention was substantial (14 +/- 2 kg, P < 0.05). Muscle insulin resistance, assessed by insulin-stimulated [(18)F]FDG uptake, decreased threefold in diabetic subjects and twofold in nondiabetic subjects (P < 0.001). Kinetic parameters for [(18)F]FDG transport and phosphorylation improved substantially in both groups, whereas tissue blood flow did not change. In particular, clinically significant weight loss fully corrected insulin resistance in type 2 diabetes at the step of glucose phosphorylation and largely, but incompletely, corrected insulin resistance at the glucose transport step.

Objective: To determine the independent risk factors for coronary artery disease (CAD) in type 1 diabetes by type of CAD at first presentation., Research Design and Methods: This is a historical prospective cohort study of 603 patients with type 1 diabetes diagnosed before 18 years of age between 1950 and 1980. The mean age and duration of diabetes at baseline were 28 (range 8-47) and 19 years (7-37), respectively, and patients were followed for 10 years. Patients with prevalent CAD were excluded from the study. Electrocardiogram (ECG) ischemia was defined by Minnesota Code (MC) 1.3, 4.1-3, 5.1-3, or 7.1; angina was determined by Pittsburgh Epidemiology of Diabetes Complications (EDC) study physician diagnosis; and hard CAD was determined by angiographic stenosis > or =50%, revascularization procedure, Q waves (MC 1.1-1.2), nonfatal myocardial infarction (MI), or CAD death., Results: A total of 108 incident CAD events occurred during the 10-year follow-up: 17 cases of ECG ischemia, 49 cases of angina, and 42 cases of hard CAD (5 CAD deaths, 25 nonfatal MI or major Q waves, and 12 revascularization or > or =50% stenosis). Blood pressure, lipid levels, inflammatory markers, renal disease, and peripheral vascular disease showed a positive gradient across the groups of no CAD, angina, and hard CAD (P < 0.01, trend analysis, all variables), although estimated glucose disposal rate (eGDR) and physical activity showed inverse associations (P < 0.01, trend analysis, both variables). In addition, depressive symptomatology predicted angina (P = 0.016), whereas HbA(1) showed no association with subsequent CAD., Conclusions: These data suggest that although the standard CAD risk factors are still operative in type 1 diabetes, greater glycemia does not seem to predict future CAD events. In addition, depressive symptomatology predicts angina and insulin resistance (eGDR) predicts hard CAD end points.

A controversial area in understanding the contribution of obesity to skeletal muscle insulin resistance is the distribution of control of glucose metabolism across proximal steps of glucose delivery, trans-membrane transport, and intracellular trapping via phosphorylation. Dynamic positron emission tomography (PET) imaging of skeletal muscle [(18)F]2-deoxy-2-D-glucose ((18)F-FDG) uptake provides an in vivo method for assessment of these steps in humans. In the current study we have examined the application of a four-compartment skeletal muscle-specific model for assessment of (18)F-FDG metabolism that takes interstitial (18)F-FDG kinetics into account and compared this to the classic three-compartment model in lean and obese volunteers. We assessed the effects of insulin infusions at three rates (0, 40, and 120 mU/m(2).min). In comparison with the classic model, the skeletal muscle-specific model reveals more clearly definable effects of insulin on transmembrane glucose transport and an impairment of this response in obesity. Compared with the classic model for assessment of (18)F-FDG metabolism, both the skeletal muscle-specific and the classic model indicate that, with respect to distribution of control, glucose phosphorylation has an important effect at low to moderate levels of insulin stimulation in both lean and obese subjects.

Purpose: To investigate the usefulness of ischemic resting electrocardiogram (ECG), ankle brachial index (ABI) <0.8, ankle brachial difference (ABD) > or = 75 mm Hg (a marker of peripheral medial arterial wall calcification), and estimated glucose disposal rate (eGDR) (a marker for insulin resistance) for predicting mortality risk in the context of standard risk factors., Methods: Data are from participants in the Pittsburgh Epidemiology of Diabetes Complications Study of 658 subjects with childhood onset Type 1 diabetes of mean age 28 years (range 8-48) and duration of diabetes 19 years (range 7-37) at baseline. Deaths were confirmed by death certificates., Results: There were 68 deaths from all causes during 10 years follow-up. In univariate analysis, the mortality hazard ratios and 95% confidence intervals associated with ischemic ECG (6.7, 3.7-12.1), the lowest quintile of eGDR (i.e., the most insulin resistant) (6.7, 4.1-10.9), ABI <0.8 (2.5, 1.1-5.9), and ABD > or = 75 mm Hg (6.7) were only marginally less than those conveyed by pre-existing coronary artery disease (8.4, 4.7-15.2) or overt nephropathy (7.6, 4.5-12.9). Ischemic ECG and eGDR were independent mortality predictors, together with duration of diabetes, coronary artery disease, overt nephropathy, nonhigh density lipoprotein cholesterol, and smoking history. If serum creatinine was available, it entered, and glycosylated hemoglobin replaced eGDR., Conclusions: Estimated GDR and ECG ischemia are strong predictors of mortality in type 1 diabetes and may be useful in the identification of those at risk.

It has been postulated that glucose transport is the principal site of skeletal muscle insulin resistance in obesity and type 2 diabetes, though a distribution of control between glucose transport and phosphorylation has also been proposed. The current study examined whether the respective contributions of transport and phosphorylation to insulin resistance are modulated across a dose range of insulin stimulation. Rate constants for transport and phosphorylation in skeletal muscle were estimated using dynamic positron emission tomography (PET) imaging of 2-deoxy-2[18F]fluoro-D-glucose ([18F]FDG) during insulin infusions at three rates (0, 40, and 120 mU/m2 per min) in lean glucose-tolerant, obese glucose-tolerant, and obese type 2 diabetic subjects. Parallel studies of arteriovenous fractional extraction across the leg of [18F]FDG and [2-3H] glucose were performed to measure the "lumped constant" (LC) (i.e., the analog effect) for [18F]FDG to determine whether this value is affected by insulin dose or insulin resistance. The value of the LC was similar across insulin doses and groups. Leg glucose uptake (LGU) also provided a measure of skeletal muscle glucose metabolism independent of PET. [18F]FDG uptake determined by PET imaging strongly correlated with LGU across groups and across insulin doses (r = 0.81, P < 0.001). Likewise, LGU correlated with PET parameters of glucose transport (r = 0.67, P < 0.001) and glucose phosphorylation (r = 0.86, P < 0.001). Glucose transport increased in response to insulin in the lean and obese groups (P < 0.05), but did not increase significantly in the type 2 diabetic group. A dose-responsive pattern of stimulation of glucose phosphorylation was observed in all groups of subjects (P < 0.05); however, glucose phosphorylation was lower in both the obese and type 2 diabetic groups compared with the lean group at the moderate insulin dose (P < 0.05). These findings indicate an important interaction between transport and phosphorylation in the insulin resistance of obesity and type 2 diabetes. [ABSTRACT FROM AUTHOR]

Investigates whether clinical factors can estimate insulin resistance in type 1 diabetes. Inverse relationship between the insulin resistance syndrome score and insulin sensitivity; Predictors of insulin resistance; Association between clinical factors and insulin resistance in type 1 diabetes.