Virtual Patient Simulation Offers an Objective Assessment of CME Activity by Improving Clinical Knowledge and the Levels of Competency of Healthcare Providers

The main goal of continuing medical education (CME) is to help healthcare providers (HCP) improve their knowledge and levels of competency with an ultimate enhancement of their performance in practice. Despite the long and well-intentional history of CME, the proof of success (based on improved clinical outcomes) is difficult to obtain objectively. In the past several years, the traditional CME world has been disrupted by replacing multiple-choice questions with virtual simulation. We utilised an innovative, next-generation virtual patient simulation (VPS) platform to develop objective measures to assess the success of educational activities that can be applied to the CME. This VPS platform was used at five distinct educational events designed to assess learners' knowledge and competency in the guideline-driven management of Type 2 diabetes, hyperlipidaemia, and hypertension. A total of 432 learners (medical doctors, nurse practitioners, and clinical pharmacists) participated in these educational events of whom 149 went through two consecutive cases with a similar clinical picture and educational goals. Their ability to achieve glycaemic, lipid, and blood pressure control improved significantly as they moved from the first to the second case. The participants improved their test performance in all categories - between 5 and 38%, achieving statistically significant increases in the many goals examined. In conclusion, this study employed the pioneering application of technology to produce, collect and analyse the VPS data to evaluate objectively educational activities. This VPS platform allows not only an objective assessment of the effectiveness of the CME activity but also provides timely and helpful feedback to both learners and providers of a given educational event.

Virtual patient simulation platforms challenging traditional CME: Identification of gaps in knowledge in the management of Type 2 diabetes and Hyperlipidaemia

As any other aspect of contemporary life, an old and established field of CME undergoes a transformation into a "digital age." Virtual patient simulation (VPS) has shown to be an interactive and efficient way of engaging healthcare professionals (HCP) in continuing medical education. VPS can identify gaps in knowledge and improve competence, using engaging, online tools. The Edocate VPS Platform has been developed by a group of physicians, education experts, and computer specialists. In this communication, we report the experience of several hundreds of HCP using the Edocate VPS application in the fields of type 2 diabetes (T2DM) and hyperlipidemia. The Edocate VPS application, displaying both simple and complex clinical situations, was presented to an international group of HCPs who had the task to perform physical exams, order lab and imaging tests, update the medical record with the right diagnoses, prescribe medications, and perform long-term follow-up through multiple visits. The HCPs received personalized, guideline-based, feedback on their actions. The analytical capabilities of the Edocate VPS platform run very deep and allow in-depth analysis of learners' competence in achieving the best outcomes, while teaching to apply a personalized approach, avoiding side effects of medications, and providing instantaneous access to the most current references in the field. The data collected from the program has shown significant gaps in knowledge and adherence to guidelines in the areas of management of T2DM and hyperlipidemia. Only about 50% of all participants achieved guideline-compatible glycemic control - namely HbA1c below 7%. Furthermore, only 41% of practicing physicians and 23% of family medicine residents achieved levels of LDL below 70 mg/dl in their virtual patients. In conclusion, the data presented in this communication strongly suggests that this novel simulation platform can enable medical organizations to create immersive VPS cases for their primary educational and CME efforts.

Transition of Patients to and from Insulin Degludec: A Clinical Challenge

With appearance of new insulins on the market, new clinical challenges, much like unintended consequences, came into light in our daily practice. One of the most pressing issues has become an issue of switching patients to and from newer insulins in various clinical situations. A proper switch from 1 medication to another requires understanding of pharmacokinetics (PK) and pharmacodynamics (PD) of both drugs. Unfortunately, there is no research in this area and, as a result, there are no guidelines nor is there even a consensus. We present 5 clinical scenarios in which the patients were transitioned to or from insulin degludec. Because there are no data and no current consensus, we have polled 200 diabetes care providers soliciting their opinion as to how they would handle these clinical situations. Our poll of endocrinologists revealed multiple approaches as well as elements of confusion among providers. Even though all answers, summarized following each case, might be reasonable, and there might not be a single correct answer, we wish to express our opinion that is based on PK and PD of these insulins. Because there is more than 1 correct way of implementing these transitions, we urge our colleagues to institute a very close follow-up of these patients with frequent adjustments of insulin dose to avoid stacking with potential hypoglycemia.

Treatment of Diabetes in Older Adults: An Endocrine Society* Clinical Practice Guideline

OBJECTIVE

The objective is to formulate clinical practice guidelines for the treatment of diabetes in older adults.

CONCLUSIONS

Diabetes, particularly type 2, is becoming more prevalent in the general population, especially in individuals over the age of 65 years. The underlying pathophysiology of the disease in these patients is exacerbated by the direct effects of aging on metabolic regulation. Similarly, aging effects interact with diabetes to accelerate the progression of many common diabetes complications. Each section in this guideline covers all aspects of the etiology and available evidence, primarily from controlled trials, on therapeutic options and outcomes in this population. The goal is to give guidance to practicing health care providers that will benefit patients with diabetes (both type 1 and type 2), paying particular attention to avoiding unnecessary and/or harmful adverse effects.

Clinical Diabetes Centers of Excellence: A Model for Future Adult Diabetes Care

Although diabetes research centers are well defined by National Institutes of Health, there is no clear definition for clinical Diabetes Centers of Excellence (DCOEs). There are multiple clinical diabetes centers across the United States, some established with philanthropic funding; however, it is not clear what defines a DCOE from a clinical perspective and what the future will be for these centers. In this Perspective we propose a framework to guide advancement for DCOEs. With the shift toward value-based purchasing and reimbursement and away from fee for service, defining the procedures for broader implementation of DCOEs as a way to improve population health and patient care experience (including quality and satisfaction) and reduce health care costs becomes critically important. It is prudent to implement new financial systems for compensating diabetes care that may not be provided by fiscally constrained private and academic medical centers. We envision that future clinical DCOEs would be composed of a well-defined infrastructure and six domains or pillars serving as the general guiding principles for developing expertise in diabetes care that can be readily demonstrated to stakeholders, including health care providers, patients, payers, and government agencies.

THE IMPACT OF CARDIOVASCULAR DRUGS ON GLYCEMIC CONTROL: A REVIEW

OBJECTIVE

The prevalence of diabetes mellitus (DM) is steadily rising in the U.S., both in the general population and among those with cardiovascular disease (CVD). Understanding how to treat a patient with both conditions is becoming increasingly important. With multiple therapeutic options for CVD management, some medications will invariably impact glycemia in this group of patients. The concept of "DM-friendly" management of CVD is based on a treatment approach of selecting medications that do not impair glycemic control and provide equivalent cardioprotective effects. This article reviews the glycemic effects of various classes of medications commonly used to treat CVD.

METHODS

Data sources were all PubMed- and Google Scholar-referenced articles in English-language peer-reviewed journals from 1980 through April 2016. Studies selected could include observational studies or prospective clinical trials. Prospective clinical trials included in this review focused on investigating the association of the medication of interest with glycemic outcomes. Meta-analyses and systematic reviews were also included.

RESULTS

The data on glycemic effects were lacking for many of the medication classes and individual medications examined. However, in our review, certain beta-blockers and renin angiotensin aldosterone system inhibitors, and select calcium channel blockers were consistently shown to have favorable glycometabolic profiles when compared with other commonly used cardiovascular therapies.

CONCLUSION

Several commonly prescribed medications for the treatment of CVD, such as certain beta-blockers and renin angiotensin aldosterone system inhibiting agents, are associated with favorable glycometabolic effects. As clinicians are more often faced with the challenge of treating patients with DM and concomitant CVD, consideration of how common cardiovascular medications may affect glycemia should be incorporated into the clinical decision making process.

ABBREVIATIONS

A1C = hemoglobin A1C ACE = angiotensin-converting enzyme ARB = angiotensin II receptor blocker CCB = calcium channel blocker CI = confidence interval CVD = cardiovascular disease DM = diabetes mellitus MI = myocardial infarction RR = relative risk.

IMPACT OF GLUCOSE MANAGEMENT TEAM ON OUTCOMES OF HOSPITALIZARON IN PATIENTS WITH TYPE 2 DIABETES ADMITTED TO THE MEDICAL SERVICE

OBJECTIVE

To improve glycemic control of hospitalized patients with diabetes and hyperglycemia, many medical centers have established dedicated glucose management teams (GMTs). However, the impact of these specialized teams on clinical outcomes has not been evaluated.

METHODS

We conducted a retrospective study of 440 patients with type 2 diabetes admitted to the medical service for cardiac or infection-related diagnosis. The primary endpoint was a composite outcome of several well-recognized markers of morbidity, consisting of: death during hospitalization, transfer to intensive care unit, initiation of enteral or parenteral nutrition, line infection, new in-hospital infection or infection lasting more than 20 days of hospitalization, deep venous thrombosis or pulmonary embolism, rise in plasma creatinine, and hospital re-admissions.

RESULTS

Medical housestaff managed the glycemia in 79% of patients (usual care group), while the GMT managed the glycemia in 21% of patients (GMT group). The primary outcome was similar between cohorts (0.95 events per patient versus 0.99 events per patient in the GMT and usual care cohorts, respectively). For subanalysis, the subjects in both groups were stratified into those with average glycemia of <180 mg/dL versus those with glycemia >180 mg/dL. We found a significant beneficial impact of glycemic management by the GMT on the composite outcome in patients with average glycemia >180 mg/dL during their hospital stay. The number of patients who met primary outcome was significantly higher in the usual care group (40 of 83 patients, 48%) than in the GMT-treated cohort (8 of 33 patients, 25.7%) (P<.02).

CONCLUSION

Our data suggest that GMTs may have an important role in managing difficult-to-control hyperglycemia in the inpatient setting.

ABBREVIATIONS

BG = blood glucose GMT = glucose management team HbA1c = hemoglobin A1c ICU = intensive care unit POC = point of care T2D = type 2 diabetes.

Effect of glargine insulin delivery method (pen device versus vial/syringe) on glycemic control and patient preferences in patients with type 1 and type 2 diabetes

OBJECTIVE

To evaluate the effects of two different glargine insulin delivery methods (pen device vs. vial/syringe) on glycemic control and patient preferences in a randomized, open-label, crossover, comparative effectiveness study.

METHODS

Thirty-one patients discharged from the hospital were recruited for this study. In the hospital, all patients were treated with a basal-bolus insulin regimen. Upon discharge, 21 patients received glargine by pen device for 3 months and were then switched to vial/syringe for the next 3 months (group 1). Group 2 consisted of 10 patients discharged on vial/syringe and converted to pen device after 3 months. Hemoglobin A1c (HbA1c) was measured at enrollment and at 3 and 6 months. A questionnaire assessing patient preference was administered at 3 and 6 months.

RESULTS

Groups 1 and 2 had similar baseline HbA1c (10.7 ± 2.2% and 11.2 ± 2.5%, respectively) and similar reduction in HbA1c at 3 months (7.8 ± 1.7% and 7.3 ± 1.4%, respectively; P<.001 vs. baseline). However, after crossover, the changes in HbA1c from 3 to 6 months were significantly different between groups. HbA1c increased to 8.5 ± 2.0% at 6 months in group 1 after switching to the vial/syringe but remained unchanged (7.1 ± 1.6%) in group 2 after switching to a pen device (P<.01, group 1 vs. group 2). Patient questionnaires after each phase of the trial revealed that patients found the pen device more convenient and were more likely to recommend this insulin delivery method to someone else.

CONCLUSION

Patients switching to a glargine pen device achieved lower HbA1c at the 6-month follow-up. Patients in both groups overwhelmingly preferred glargine pens over vials/syringes.

PRIDE Statement on the Need for a Moratorium on the CMS Plan to Cite Hospitals for Performing Point-of-Care Capillary Blood Glucose Monitoring on Critically Ill Patients

OBJECTIVE

A writing committee of the Planning Research in Inpatient Diabetes (PRIDE) group has written this consensus article on behalf of the group in response to a specific request for input from the Centers for Medicare and Medicaid Services (CMS). The purpose of this article is to respond to the March 13, 2015 statement from that agency regarding plans to enforce prohibition of the off-label use of point of care (POC) capillary blood glucose monitor (BGM) testing in most critically ill patients. The article discusses: 1) how POC BGM testing is currently regulated; 2) how POC BGM testing is currently used in the United States; and 3) how POC BGM testing can be safely and effectively regulated in the future through cooperation between the clinician, laboratory, regulatory, industry, and patient communities.

PARTICIPANTS

Nine members of PRIDE volunteered to write the statement on behalf of the entire group.

EVIDENCE

Descriptions of current medical practice for critically ill patients were derived from the experience of the authors. Descriptions of the performance of various methods for measuring glucose levels for intensive insulin therapy came from a literature review.

CONSENSUS PROCESS

Eleven questions were developed by the PRIDE writing group. After extensive electronic and telephone discussion, the article was written and reviewed by all nine authors and then reviewed by two outside experts in the care of critically ill patients. All suggestions by the authors and the outside experts were incorporated.

CONCLUSIONS

Although the CMS is attempting to protect patients with abnormal glycemic control from harm due to inaccurate POC fingerstick capillary BGM testing, their plan will result in more harm than good. A moratorium on enforcement of the prohibition of off-label use of POC capillary BGM testing is needed.

Transitional care clinic for uninsured and medicaid-covered patients with diabetes mellitus discharged from the hospital: a pilot quality improvement study

Transitioning from the inpatient to outpatient setting is often a problematic aspect of diabetes mellitus (DM) care. Different factors during hospitalization may adversely affect glycemic control in patients, who are frequently discharged on regimens that differ markedly from prehospitalization outpatient regimens. Moreover, the discharge recommendations may not have been tested adequately during a relatively short hospital length of stay and pose a significant threat to patient safety upon discharge. Our pilot study evaluated the effect on hospital utilization of the transitional care clinic (TCC), where patients with DM are seen within 2 to 5 days of hospital discharge. One hundred patients with DM, who were either medically indigent (no insurance or Medicaid and no primary care providers) or covered by Medicaid, and who did not have a primary care provider, were randomized into either a control or an intervention group upon discharge from the hospital. Subjects from the intervention group (n = 50) were seen in the TCC. All subjects were contacted 90 days after discharge to collect information about emergency department visits and readmissions. Thirteen subjects from the control group and 13 from the intervention group visited the emergency department within 90 days of discharge. Fourteen control subjects (28%) and 10 intervention patients (20%) were rehospitalized for various medical conditions during the follow-up period (P = not significant). Among patients originally admitted for DM-related issues, 6 of 14 in the control group (42.9%) and 2 out of 16 in the intervention group (12.5%) were readmitted during follow-up (P < 0.05). We conclude that the TCC may be effective for the prevention of rehospitalizations in indigent patients admitted for DM-related problems and who did not have primary care providers. The benefit of the TCC was not seen when patients with DM were admitted for other medical problems. Larger randomized controlled trials are needed to confirm this preliminary finding.

Pathways to quality inpatient management of hyperglycemia and diabetes: a call to action

Currently patients with diabetes comprise up to 25-30% of the census of adult wards and critical care units in our hospitals. Although evidence suggests that avoidance of hyperglycemia (>180 mg/dL) and hypoglycemia (<70 mg/dL) is beneficial for positive outcomes in the hospitalized patient, much of this evidence remains controversial and at times somewhat contradictory. We have recently formed a consortium for Planning Research in Inpatient Diabetes (PRIDE) with the goal of promoting clinical research in the area of management of hyperglycemia and diabetes in the hospital. In this article, we outline eight aspects of inpatient glucose management in which randomized clinical trials are needed. We refer to four as system-based issues and four as patient-based issues. We urge further progress in the science of inpatient diabetes management. We hope this call to action is supported by the American Diabetes Association, The Endocrine Society, the American Association of Clinical Endocrinologists, the American Heart Association, the European Association for the Study of Diabetes, the International Diabetes Federation, and the Society of Hospital Medicine. Appropriate federal research funding in this area will help ensure high-quality investigations, the results of which will advance the field. Future clinical trials will allow practitioners to develop optimal approaches for the management of hyperglycemia in the hospitalized patient and lessen the economic and human burden of poor glycemic control and its associated complications and comorbidities in the inpatient setting.

Arterial insulin resistance in Yucatan micropigs with diet-induced obesity and metabolic syndrome

AIM

Metabolic syndrome affects a large proportion of the population and increases cardiovascular disease risk. Because metabolic syndrome often co-exists clinically with atherosclerosis, it is difficult to distinguish the respective contributions of the components to vascular abnormalities. Accordingly, we utilized a porcine dietary model of metabolic syndrome without atherosclerosis to investigate early abnormalities of vascular function and signaling.

METHODS

Thirty-two Yucatan micropigs were fed either a high-fat, high-simple-sugar, high-calorie (HFHS) or standard chow diet (STD) for 6 months. Neither diet contained added cholesterol. Blood pressure and flow-mediated vasodilatation were assessed at baseline and 6 months. Aortas were harvested at 6 months to assess histology, insulin signaling, and endothelial nitric oxide (eNOS) phosphorylation.

RESULTS

HFHS pigs developed characteristics of metabolic syndrome including obesity, dyslipidemia, and insulin resistance, but without histologic evidence of atherosclerosis. Although arterial intima-media thickness did not differ between groups, vascular dysfunction in HFHS was manifest by increased blood pressure and impaired flow-mediated vasodilation of the femoral artery. Compared with STD, aortas from HFHS exhibited increased p85α expression and Ser307 IRS-1 phosphorylation, and blunted insulin-stimulated IRS-1-associated phosphatidylinositol (PI) 3-kinase activity. In the absence of insulin stimulation, aortic Akt Ser473-phosphorylation was greater in HFHS than in STD. With insulin stimulation, Akt phosphorylation increased in STD, but not HFHS. Insulin-induced Ser1177-phosphorylation of eNOS was decreased in HFHS, compared with STD.

CONCLUSIONS

Pigs with metabolic syndrome develop early vascular dysfunction and aortic insulin signaling abnormalities, and could be a useful model for early human vascular abnormalities in this condition.

Practical approach to management of inpatient hyperglycemia in select patient populations

Hospitalized patients frequently transition between various levels of care and changing clinical situations. Optimal management of hospitalized patients with hyperglycemia includes awareness of situations that may significantly affect glucose and/or insulin metabolism. A review of published clinical trials reveals practical approaches to the management of hyperglycemia in select patient populations that may prove useful for the hospital clinician. We outline approaches to the management of hyperglycemia in hospitalized patients receiving glucocorticoids, patients with severe or end-stage renal disease undergoing hemo- or peritoneal dialysis, and patients receiving total parenteral or enteral feeding, in addition to patients transitioning from intravenous insulin infusion to subcutaneously administered insulin. Key considerations underlying these management methods include a proactive approach, frequent blood glucose monitoring, daily review of blood glucose patterns, and daily reassessment of the insulin regimen and associated orders.

Acute effects of different diet compositions on skeletal muscle insulin signalling in obese individuals during caloric restriction

OBJECTIVE

The cellular effects of restricting fat versus carbohydrate during a low-calorie diet are unclear. The aim of this study was to examine acute effects of energy and macronutrient restriction on skeletal muscle insulin signalling in obesity.

MATERIALS/METHODS

Eighteen obese individuals without diabetes underwent euglycemic-hyperinsulinemic clamp and skeletal muscle biopsy after: (a) 5days of eucaloric diet (30% fat, 50% carbohydrate), and (b) 5days of a 30% calorie-restricted diet, either low fat/high carbohydrate (LF/HC: 20% fat, 60% carbohydrate) or high-fat/low carbohydrate (HF/LC: 50% fat, 30% carbohydrate).

RESULTS

Weight, body composition, and insulin sensitivity were similar between groups after eucaloric diet. Weight loss was similar between groups after hypocaloric diet, 1.3±1.3kg (p<0.0001 compared with eucaloric). Whole-body insulin sensitivity was unchanged after calorie restriction and similar between groups. However, ex vivo skeletal muscle insulin signalling differed depending on macronutrient composition of calorie-restricted diet. Skeletal muscle of the LF/HC group had increased insulin-stimulated tyrosine phosphorylation of IRS-1, decreased insulin-stimulated Ser307 phosphorylation of IRS-1, and increased IRS-1-associated phosphatidylinositol (PI)3-kinase activity. Conversely, insulin stimulation of tyrosine phosphorylated IRS-1 was absent and serine 307 phosphorylation of IRS-1 was increased on HF/LC, with blunting of IRS-1-associated PI3-kinase activity.

CONCLUSION

Acute caloric restriction with an LF/HC diet alters skeletal muscle insulin signalling in a way that improves insulin sensitivity, while acute caloric restriction with an HF/LC diet induces changes compatible with insulin resistance. In both cases, ex vivo changes in skeletal muscle insulin signalling appear prior to changes in whole body insulin sensitivity.

Effect of dietary macronutrient composition on AMPK and SIRT1 expression and activity in human skeletal muscle

Adenosine monophosphate-activated protein kinase (AMPK), silent mating type information regulation 2 homologue 1 (SIRT 1), and peroxisome proliferator-activated receptor γ co-activator α (PGC1α) constitute an energy sensing cellular network that controls mitochondrial biogenesis. Caloric restriction activates both AMPK and SIRT-1 to increase ATP production from fat oxidation. We characterized AMPK and SIRT 1 expression and activity in human skeletal muscle in response to dietary fat or carbohydrate intake on the background of either overfeeding or caloric restriction. AMPK phosphorylation and acetylation of PGC1α (as a measure of SIRT activity) were determined. Euglycemic-hyperinsulinemic clamp and muscle biopsies were performed in human subjects participating in 2 separate studies. In study 1, 21 lean healthy individuals were overfed for 5 days, while in study 2, 18 obese otherwise healthy individuals consumed a calorie-restricted diet for 5 days. Under both conditions - overfeeding and caloric restriction - high fat/low carbohydrate (HF/LC) diet significantly increased phosphorylation of AMPK and deacetylation of PGC1α in skeletal muscle without affecting total amounts of AMPK, PGC1α, or SIRT 1. In contrast, low fat/high carbohydrate (LF/HC) hypocaloric diet reduced phosphorylation of AMPK and deacetylation of PGC1α. Our data indicate that a relative deficiency in carbohydrate intake or, albeit less likely, a relative excess of fat intake even in the absence of caloric deprivation is sufficient to activate the AMPK-SIRT 1-PGC1α energy-sensing cellular network in human skeletal muscle.

Cystic fibrosis-related diabetes in adults: inpatient management of 121 patients during 410 admissions

BACKGROUND

With improved longevity, cystic fibrosis (CF)-related diabetes (CFRD) has emerged as the most common nonpulmonary complication of CF. Patients with CFRD are frequently admitted to the hospital with infections and deterioration of pulmonary function, during which time glycemic control might have an impact on pulmonary function, recovery from infection, and survival.

METHODS AND RESULTS

In an attempt to share our insight into inpatient management of CFRD, this article summarizes the experience of our inpatient glucose management team with hospital management of 121 adult CFRD patients who were hospitalized on 410 occasions at the University of Colorado Hospital between January 2009 and September 2011. This is a retrospective chart review descriptive study of inpatient management of CFRD in our center. Our cohort includes CFRD patients treated with basal and mealtime insulin through multiple daily injections or continuous subcutaneous insulin infusion (CSII), as well as patients receiving steroids or enteral nutrition, which adds complexity to the management of CFRD during hospitalization.

CONCLUSIONS

Multiple hospitalizations and intensive inpatient management of CF are integral elements of treatment. Inpatient therapy for CFRD requires a customized approach that is uniquely different from that of type 1 or type 2 diabetes. Our experience highlights clinical circumstances such as irregular food intake, high dose steroid therapy, and supplemental tube feeding. For many patients, it is possible to continue CSII therapy during hospitalization through a combination of mutual trust between the patient and hospital staff and oversight provided by the glucose management team.

Subcutaneous administration of glargine to diabetic patients receiving insulin infusion prevents rebound hyperglycemia

CONTEXT

Transition of diabetic patients from iv insulin infusion to s.c. insulin frequently results in rebound hyperglycemia.

OBJECTIVES

We hypothesized that initiation of a long-acting insulin therapy concurrently with i.v. insulin infusion would decrease the rate of rebound hyperglycemia after discontinuation of the insulin infusion.

DESIGN AND INTERVENTION

Sixty-one diabetic patients receiving i.v. insulin therapy participated in this prospective randomized study. Subjects in the intervention group received daily injections of glargine s.c. (0.25 U/kg body weight) starting within 12 h of initiation of i.v. insulin infusion. Capillary blood glucose measurements were obtained up to 12 h after discontinuation of insulin infusion. Rebound hyperglycemia was defined as a blood glucose level greater than 180 mg/dl.

SETTING

The study was conducted at the University of Colorado Hospital.

PATIENTS

Sixty-one hospitalized patients with known type 1 or type 2 diabetes receiving i.v. insulin infusion participated in the study.

MAIN OUTCOME

The primary outcome of this study was to compare the rates of rebound hyperglycemia between the control and the intervention groups after i.v. insulin infusion is discontinued.

RESULTS

Overall, 29 subjects in the control group (93.5%) had at least one glucose value above 180 mg/dl during the 12-h follow-up period. This was significantly greater than the rate of rebound hyperglycemia in the intervention group (10 subjects or 33.3%, P < 0.001). The effect of the intervention was apparent in subjects who presented with diabetic ketoacidosis, after solid organ transplantation, and in patients with other surgical and medical diagnoses. There were three hypoglycemic measurements in two control subjects (68, 62, and 58 mg/dl) and none in the intervention group.

CONCLUSIONS

Once-daily s.c. insulin glargine administered during i.v. insulin infusion is a safe method for preventing future rebound hyperglycemia, without increased risk of hypoglycemia.

Comparison of 70/30 biphasic insulin with glargine/lispro regimen in non-critically ill diabetic patients on continuous enteral nutrition therapy

Despite significant advances in inpatient diabetes management, it is still a challenge to choose the safest and most efficacious subcutaneous insulin regimen for diabetic patients on continuous enteral nutrition (EN) therapy. The authors conducted a retrospective analysis of glycemic control in 22 non-critically ill diabetic patients, receiving at least 3 days of continuous EN. Patients received different insulin regimens while on continuous EN, including a basal/bolus glargine/lispro regimen (group 1, n = 8), 70/30 biphasic insulin twice daily (group 2, n = 8), and 70/30 biphasic insulin 3 times a day (group 3, n = 6). The glucose data from 72 hours from the initiation of EN were analyzed (12 point-of-contact glucose measurements per patient). Overall, the degree of control was comparable in all groups, with target range maintained more consistently in group 3 (70/30 insulin administered 3 times daily). In this group, 69% of values were in the target range (140-180 mg/dL) as compared with 24% in glargine/lispro group and 22% in the 70/30 insulin bid group. Eight hypoglycemic episodes occurred among the 3 groups: 5 episodes in group 1 (5.4%), 2 episodes in group 2 (2.1%), and 1 episode in group 3 (1.4%) (P = .05, groups 2 and 3 vs group 1). Administration of 70/30 biphasic insulin 3 times daily is a safe therapeutic regimen in diabetic patients on continuous EN as it maintains glycemia in the target range and might produce fewer episodes of hypoglycemia.

Increasing dietary fat elicits similar changes in fat oxidation and markers of muscle oxidative capacity in lean and obese humans

In lean humans, increasing dietary fat intake causes an increase in whole-body fat oxidation and changes in genes that regulate fat oxidation in skeletal muscle, but whether this occurs in obese humans is not known. We compared changes in whole-body fat oxidation and markers of muscle oxidative capacity differ in lean (LN) and obese (OB) adults exposed to a 2-day high-fat (HF) diet. Ten LN (BMI = 22.5±2.5 kg/m², age = 30±8 yrs) and nine OB (BMI = 35.9±4.93 kg/m², 38±5 yrs, Mean±SD) were studied in a room calorimeter for 24hr while consuming isocaloric low-fat (LF, 20% of energy) and HF (50% of energy) diets. A muscle biopsy was obtained the next morning following an overnight fast. 24h respiratory quotient (RQ) did not significantly differ between groups (LN: 0.91±0.01; OB: 0.92±0.01) during LF, and similarly decreased during HF in LN (0.86±0.01) and OB (0.85±0.01). The expression of pyruvate dehydrogenase kinase 4 (PDK4) and the fatty acid transporter CD36 increased in both LN and OB during HF. No other changes in mRNA or protein were observed. However, in both LN and OB, the amounts of acetylated peroxisome proliferator-activated receptor γ coactivator-1-α (PGC1-α) significantly decreased and phosphorylated 5-AMP-activated protein kinase (AMPK) significantly increased. In response to an isoenergetic increase in dietary fat, whole-body fat oxidation similarly increases in LN and OB, in association with a shift towards oxidative metabolism in skeletal muscle, suggesting that the ability to adapt to an acute increase in dietary fat is not impaired in obesity.

Intensive control of diabetes in the hospital: why, how, and what is in the future?

Intensive management of diabetes is identified as a critical component of inpatient care. However, the fundamental question that remains is whether controlling glycemia in noncritically ill diabetes patients at the lower end of the current guidelines improves outcomes of hospitalization, long-term outcomes of the primary condition, and long-term outcomes of diabetes compared with average glycemia greater than 180 mg/dl. A group of clinical investigators--Planning Research in Inpatient Diabetes (PRIDE)--is preparing randomized controlled trials with the hope of defining optimal glycemic targets for hospitalized patients with diabetes. Given the variety of clinical situations that can occur in the inpatient setting, many medical centers have established dedicated inpatient diabetes teams. There is ample evidence, albeit retrospective, that these teams improve inpatient glucose control and reduce lengths of hospital stays. Using hospitalization as an opportunity to educate patients about diabetes and to optimize their treatment regimen may improve long-term outpatient glycemic control.

Mechanism of the mitogenic influence of hyperinsulinemia

Either endogenous or exogenous hyperinsulinemia in the setting of insulin resistance promotes phosphorylation and activation of farnesyltransferase, a ubiquitous enzyme that farnesylates Ras protein. Increased availability of farnesylated Ras at the plasma membrane enhances mitogenic responsiveness of cells to various growth factors, thus contributing to progression of cancer and atherosclerosis. This effect is specific to insulin, but is not related to the type of insulin used. Stimulatory effect of hyperinsulinemia on farnesyltransferase in the presence of insulin resistance represents one potential mechanism responsible for mitogenicity and atherogenicity of insulin.

Insulin resistance in adolescents with type 1 diabetes and its relationship to cardiovascular function

CONTEXT

Cardiovascular disease is the major cause of death in adults with diabetes, yet little is specifically known about the effects of type 1 diabetes (T1D) on cardiovascular outcomes in youth. Although insulin resistance (IR) likely contributes to exercise and cardiovascular dysfunction in T2D, IR is not typically considered a contributor in T1D.

OBJECTIVE

We hypothesized that cardiopulmonary fitness would be reduced in T1D youth in association with IR and cardiovascular dysfunction.

DESIGN AND PARTICIPANTS

This cross-sectional study at an academic hospital included 12 T1D adolescents compared with 12 nondiabetic controls, similar in age, pubertal stage, activity level, and body mass index.

OUTCOME MEASURES

Cardiopulmonary fitness was measured by peak oxygen consumption (VO(2)peak) and oxygen uptake kinetics (VO(2)kinetics), IR by hyperinsulinemic clamp, cardiac function by echocardiography, vascular function by venous occlusion plethysmography, intramyocellular lipid by magnetic resonance spectroscopy, and body composition by dual-energy x-ray absorptiometry.

RESULTS

T1D adolescents had significantly decreased VO(2)peak, peak work rate, and insulin sensitivity compared with nondiabetic adolescents. T1D youth also had reduced vascular reactivity and evidence of diastolic dysfunction and left ventricular hypertrophy. Despite their IR and reduced cardiovascular fitness, T1D youth had paradoxically normal intramyocellular lipid, waist to hip ratio, and serum lipids and high adiponectin levels. In multivariate analysis, IR primarily, and forearm blood flow secondarily, independently predicted VO(2)peak.

CONCLUSIONS

T1D youth demonstrated IR, impaired functional exercise capacity and cardiovascular dysfunction. The phenotype of IR in T1D youth was unique, suggesting a pathophysiology that is different from T2D, yet may adversely affect long-term cardiovascular outcomes.

Mitogenic action of insulin: friend, foe or 'frenemy'?

Either endogenous or exogenous hyperinsulinaemia in the setting of insulin resistance promotes phosphorylation and activation of farnesyltransferase, a ubiquitous enzyme that farnesylates Ras proteins. Increased availability of farnesylated Ras at the plasma membrane enhances mitogenic responsiveness of cells to various growth factors, thus contributing to progression of cancer and atherosclerosis. This effect is specific to insulin, but is not related to the type of insulin used. The stimulatory effect of hyperinsulinaemia on farnesyltransferase in the presence of insulin resistance represents one potential mechanism responsible for mitogenicity and atherogenicity of insulin.

Multiple abnormalities of myocardial insulin signaling in a porcine model of diet-induced obesity

Heightened cardiovascular risk among patients with systemic insulin resistance is not fully explained by the extent of atherosclerosis. It is unknown whether myocardial insulin resistance accompanies systemic insulin resistance and contributes to increased cardiovascular risk. This study utilized a porcine model of diet-induced obesity to determine if myocardial insulin resistance develops in parallel with systemic insulin resistance and investigated potential mechanisms for such changes. Micropigs (n = 16) were assigned to control (low fat, no added sugars) or intervention (25% wt/wt coconut oil and 20% high-fructose corn syrup) diet for 7 mo. Intervention diet resulted in obesity, hypertension, and dyslipidemia. Systemic insulin resistance was manifest by elevated fasting glucose and insulin, abnormal response to intravenous glucose tolerance testing, and blunted skeletal muscle phosphatidylinositol-3-kinase (PI 3-kinase) activation and protein kinase B (Akt) phosphorylation in response to insulin. In myocardium, insulin-stimulated glucose uptake, PI 3-kinase activation, and Akt phosphorylation were also blunted in the intervention diet group. These findings were explained by increased myocardial content of p85alpha (regulatory subunit of PI 3-kinase), diminished association of PI 3-kinase with insulin receptor substrate (IRS)-1 in response to insulin, and increased serine-307 phosphorylation of IRS-1. Thus, in a porcine model of diet-induced obesity that recapitulates many characteristics of insulin-resistant patients, myocardial insulin resistance develops along with systemic insulin resistance and is associated with multiple abnormalities of insulin signaling.

In vivo knockdown of p85alpha with an antisense oligonucleotide improves insulin sensitivity in Lep(ob/ob) and diet-induced obese mice

Phosphoinositide 3-kinase is a key signaling intermediate necessary for the metabolic actions of insulin. In this study, we assessed the effects of in vivo knockdown of the p85alpha subunit of phosphoinositide 3-kinase on insulin sensitivity, using an antisense oligonucleotide, in lean mice, diet-induced obese mice, and obese leptin-deficient Lep (ob/ob) mice. Mice were injected with either p85alpha-targeted antisense oligonucleotide or saline twice weekly for 4 weeks. Fasting levels of glycemia and insulinemia and insulin and glucose tolerance tests were used to determine insulin sensitivity. Western blot analysis and real-time polyacrylamide chain reaction were used to assess p85alpha protein and mRNA expression. IN VIVO administration of antisense oligonucleotide resulted in 50 and 60% knockdown of liver p85alpha protein and mRNA, respectively, in the lean, diet-induced obese and Lep (ob/ob) mice. This was associated with increased phosphoinositide 3-kinase activity and improved insulin sensitivity in diet-induced obese and Lep (ob/ob) mice. Thus, p85alpha could be an important therapeutic target to ameliorate insulin resistance.

Insulin resistance in adolescents with type 2 diabetes is associated with impaired exercise capacity

CONTEXT

The incidence of pediatric type 2 diabetes (T2D) is rising, with unclear effects on the cardiovascular system. Cardiopulmonary fitness, a marker of morbidity and mortality, is abnormal in adults with T2D, yet the mechanisms are incompletely understood.

OBJECTIVE

We hypothesized that cardiopulmonary fitness would be reduced in youth with T2D in association with insulin resistance (IR) and cardiovascular dysfunction.

DESIGN, SETTING, AND PARTICIPANTS

We conducted a cross-sectional study at an academic hospital that included 14 adolescents (age range, 12-19 yr) with T2D, 13 equally obese adolescents and 12 lean adolescents similar in age, pubertal stage, and activity level.

MAIN OUTCOME MEASURES

Cardiopulmonary fitness was measured by peak oxygen consumption (VO(2)peak) and oxygen uptake kinetics (VO(2)kinetics), IR by hyperinsulinemic clamp, cardiac function by echocardiography, vascular function by venous occlusion plethysmography, body composition by dual-energy x-ray absorptiometry, intramyocellular lipid by magnetic resonance spectroscopy, and inflammation by serum markers.

RESULTS

Adolescents with T2D had significantly decreased VO(2)peak and insulin sensitivity, and increased soleus intramyocellular lipid, C-reactive protein, and IL-6 compared to obese or lean adolescents. Adolescents with T2D also had significantly prolonged VO(2)kinetics, decreased work rate, vascular reactivity, and adiponectin, and increased left ventricular mass and fatty acids compared to lean adolescents. In multivariate linear regression analysis, IR primarily, and fasting free fatty acids and forearm blood flow secondarily, were significant independent predictors of VO(2)peak.

CONCLUSIONS

Given the strong relationship between decreased cardiopulmonary fitness and increased mortality, these findings in children are especially concerning and represent early signs of impaired cardiac function.

Early responses of insulin signaling to high-carbohydrate and high-fat overfeeding

Background

Early molecular changes of nutritionally-induced insulin resistance are still enigmatic. It is also unclear if acute overnutrition alone can alter insulin signaling in humans or if the macronutrient composition of the diet can modulate such effects.

Methods

To investigate the molecular correlates of metabolic adaptation to either high-carbohydrate (HC) or high-fat (HF) overfeeding, we conducted overfeeding studies in 21 healthy lean (BMI < 25) individuals (10 women, 11 men), age 20-45, with normal glucose metabolism and no family history of diabetes. Subjects were studied first following a 5-day eucaloric (EC) diet (30% fat, 50% CHO, 20% protein) and then in a counter balanced manner after 5 days of 40% overfeeding of both a HC (20% fat, 60% CHO) diet and a HF (50% fat, 30% CHO) diet. At the end of each diet phase, in vivo insulin sensitivity was assessed using the hyperinsulinemic-euglycemic clamp technique. Ex vivo insulin action was measured from skeletal muscle tissue samples obtained 15 minutes after insulin infusion was initiated.

Results

Overall there was no change in whole-body insulin sensitivity as measured by glucose disposal rate (GDR, EC: 12.1 ± 4.7; HC: 10.9 ± 2.7; HF: 10.8 ± 3.4). Assessment of skeletal muscle insulin signaling demonstrated increased tyrosine phosphorylation of IRS-1 (p < 0.001) and increased IRS-1-associated phosphatidylinositol 3 (PI 3)-kinase activity (p < 0.001) following HC overfeeding. In contrast, HF overfeeding increased skeletal muscle serine phosophorylation of IRS-1 (p < 0.001) and increased total expression of p85α (P < 0.001).

Conclusion

We conclude that acute bouts of overnutrition lead to changes at the cellular level before whole-body insulin sensitivity is altered. On a signaling level, HC overfeeding resulted in changes compatible with increased insulin sensitivity. In contrast, molecular changes in HF overfeeding were compatible with a reduced insulin sensitivity.

Rescuing 3T3-L1 adipocytes from insulin resistance induced by stimulation of Akt-mammalian target of rapamycin/p70 S6 kinase (S6K1) pathway and serine phosphorylation of insulin receptor substrate-1: effect of reduced expression of p85alpha subunit of phosphatidylinositol 3-kinase and S6K1 kinase

Phosphorylation of insulin receptor substrate-1 (IRS-1) on serine residues has been recognized as a mechanism responsible for a diminution of insulin action and insulin resistance. Potential approaches to improve insulin sensitivity may include interference with and/or reduction in expression of certain signaling intermediates that participate in the pathogenesis of insulin resistance. In this study, we transduced fully differentiated 3T3-L1 adipocytes with a constitutively active myristoylated Akt that led to hyperactivation of mammalian target of rapamycin and p70 S6 kinase (S6K1), increased serine phosphorylation of IRS-1, and reduction in insulin-stimulated phosphatidylinositol (PI) 3-kinase activity and glucose transport. We then reduced expression of the PI 3-kinase regulatory subunit, p85alpha, or expression of S6K1 kinase using small interfering RNA transfections, which led to a reduction in p85alpha expression of 70% at 48 h (P < 0.05) and S6K1 of 49% (P < 0.05). Reduction in expression of either p85alpha or S6K1 achieved with small interfering RNA in the presence of myristoylated Akt rescued 3T3-L1 adipocytes from the insulin resistance induced by serine phosphorylation of IRS-1 and completely restored insulin-stimulated activation of PI 3-kinase and glucose uptake. We conclude that reduction in expression of p85alpha or S6K1 could represent therapeutic targets to mitigate insulin resistance.

Knockdown of JNK rescues 3T3-L1 adipocytes from insulin resistance induced by mitochondrial dysfunction

Mitochondrial dysfunction has been linked to etiology of insulin resistance, however the mechanism remains unknown. In this study we investigated whether mitochondrial dysfunction induced by cyanide p-trifluoromethoxyphenyl-hydrazone (FCCP) alters insulin sensitivity in 3T3-L1 adipocytes and which cellular signaling molecules might be involved. Fully differentiated 3T3-L1 adipocytes were treated with 10 microM FCCP for 1h, resulting in increased serine-307 phosphorylation of IRS-1 and decreased insulin-stimulated tyrosine phosphorylation, association of p85alpha subunit of phosphatidylinositol 3-kinase (PI 3-kinase) with IRS-1, decreased insulin-stimulated PI 3-kinase activity and H(3)-2-deoxyglucose (2DOG) uptake. A partial (46%) knockdown of JNK1 blocked FCCP-induced serine phosphorylation of IRS-1 and restored insulin-stimulated tyrosine phosphorylation of IRS-1, association of p85alpha subunit of PI 3-kinase with IRS-1, activation of PI 3-kinase, and stimulation of 2DOG uptake. Thus, FCCP-induced mitochondrial dysfunction may cause insulin resistance that is ameliorated by reduction of JNK1 expression.

Effects of chronic hyperinsulinemia in insulin-resistant patients

Selective insulin resistance influences pathogenesis and treatment of type 2 diabetes and metabolic syndrome. Downregulation of the antiatherogenic pathway and maintained activity of the proatherogenic and cancerogenic pathways lead to atherosclerosis and cancer. Exogenous insulin added to "compensatory" hyperinsulinemia might worsen the primary end points, resulting in potential increase in cardiovascular and cancer events in spite of improvement of surrogate metabolic end points. Conversely, metformin can improve primary and surrogate end points.

Dietary carbohydrate restriction in type 2 diabetes mellitus and metabolic syndrome: time for a critical appraisal

Current nutritional approaches to metabolic syndrome and type 2 diabetes generally rely on reductions in dietary fat. The success of such approaches has been limited and therapy more generally relies on pharmacology. The argument is made that a re-evaluation of the role of carbohydrate restriction, the historical and intuitive approach to the problem, may provide an alternative and possibly superior dietary strategy. The rationale is that carbohydrate restriction improves glycemic control and reduces insulin fluctuations which are primary targets. Experiments are summarized showing that carbohydrate-restricted diets are at least as effective for weight loss as low-fat diets and that substitution of fat for carbohydrate is generally beneficial for risk of cardiovascular disease. These beneficial effects of carbohydrate restriction do not require weight loss. Finally, the point is reiterated that carbohydrate restriction improves all of the features of metabolic syndrome.

Discordance between intramuscular triglyceride and insulin sensitivity in skeletal muscle of Zucker diabetic rats after treatment with fenofibrate and rosiglitazone

AIM

Intramyocellular triglyceride (IMTG) correlates with insulin resistance, but there is no clear causal relationship. Insulin resistance and associated hyperinsulinaemia may increase IMTG, via the insulin-regulated transcription factor, sterol regulatory element-binding protein 1 (SREBP-1). PPAR agonists may also affect IMTG via changes in insulin sensitivity, SREBP-1 or other factors.

METHODS

We examined skeletal muscle IMTG and SREBP-1 expression, and metabolic parameters in Zucker diabetic fatty rats (ZDF) after 25 weeks of PPAR-gamma or PPAR-alpha administration.

RESULTS

Compared with Zucker lean rats (ZL), untreated ZDF had significantly higher weights, serum glucose, insulin, free fatty acids, total cholesterol and triglycerides. IMTG and SREBP-1c messenger RNA (mRNA) were also higher in untreated ZDF; both were decreased by fenofibrate (FF). Rosiglitazone (Rosi), despite marked improvement in glycaemia, hyperinsulinaemia and hyperlipidaemia, failed to affect SREBP-1 expression, and increased body weight and IMTG. Rosi/FF combination caused less weight gain and no IMTG increase, despite metabolic effects similar to Rosi alone.

CONCLUSIONS

IMTG and SREBP-1c mRNA are high in the ZDF. FF and Rosi both improved insulin sensitivity but had opposite effects on IMTG. Thus, there was a clear discordance between insulin sensitivity and IMTG with PPAR agonists, indicating that IMTG and insulin sensitivity do not share a simple relationship.

Growth hormone regulation of p85alpha expression and phosphoinositide 3-kinase activity in adipose tissue: mechanism for growth hormone-mediated insulin resistance

Phosphoinositide (PI) 3-kinase is involved in insulin-mediated effects on glucose uptake, lipid deposition, and adiponectin secretion from adipocytes. Genetic disruption of the p85alpha regulatory subunit of PI 3-kinase increases insulin sensitivity, whereas elevated p85alpha levels are associated with insulin resistance through PI 3-kinase-dependent and -independent mechanisms. Adipose tissue plays a critical role in the antagonistic effects of growth hormone (GH) on insulin actions on carbohydrate and lipid metabolism through changes in gene transcription. The objective of this study was to assess the role of the p85alpha subunit of PI 3-kinase and PI 3-kinase signaling in GH-mediated insulin resistance in adipose tissue. To do this, p85alpha mRNA and protein expression and insulin receptor substrate (IRS)-1-associated PI 3-kinase activity were measured in white adipose tissue (WAT) of mice with GH excess, deficiency, and sufficiency. Additional studies using 3T3-F442A cells were conducted to confirm direct effects of GH on free p85alpha protein abundance. We found that p85alpha expression 1) is decreased in WAT from mice with isolated GH deficiency, 2) is increased in WAT from mice with chronic GH excess, 3) is acutely upregulated in WAT from GH-deficient and -sufficient mice after GH administration, and 4) is directly upregulated by GH in 3T3-F442A adipocytes. The insulin-induced increase in PI 3-kinase activity was robust in mice with GH deficiency, but not in mice with GH excess. In conclusion, GH regulates p85alpha expression and PI 3-kinase activity in WAT and provides a potential explanation for 1) the insulin hypersensitivity and associated obesity and hyperadiponectinemia of GH-deficient mice and 2) the insulin resistance and associated reduced fat mass and hypoadiponectinemia of mice with GH excess.

Insulin attenuates vascular smooth muscle calcification but increases vascular smooth muscle cell phosphate transport

Medial artery vascular smooth muscle cell (VSMC) calcification increases the risk of cardiovascular mortality in type 2 diabetes. However, the influence of insulin on VSMC calcification is unclear. We explored the effects of insulin on rat VSMC calcification in vitro and found that in a dose-dependent fashion, insulin attenuates VSMC calcification induced by high phosphate conditions as quantified by the o-cresolphthalein calcium (OCPC) method. In an in vitro model of insulin resistance in which cells are exposed to elevated insulin concentrations and the PI 3-kinase pathway is selectively inhibited, increased VSMC calcification was observed, suggesting that the PI 3-kinase pathway is involved in this attenuating effect of insulin. We postulated that insulin may also have an effect on phosphate or calcium transport in VSMC. We found that insulin increases phosphate transport at 3 and 24 h. This effect was mediated by increased Vmax for phosphate transport but not Km. Because type III sodium-phosphate co-transporters Pit-1 and Pit-2 are found in VSMC, we examined their expression by Western blot and real-time RT-PCR. Insulin stimulates Pit-1 mRNA modestly (*p<0.01 versus control), an effect inhibited by PD98059 but not by wortmannin. Pit-1 protein expression is induced by insulin, an effect also inhibited by PD98059 (*p<0.001 versus insulin alone). Our results suggest a role for insulin in attenuating VSMC calcification which may be disrupted in selective insulin signaling impairment seen in insulin resistance. This effect of insulin contrasts with its effect to induce phosphate transport in VSMC.

Increased farnesylation of p21-Ras and neonatal macrosomia in women with gestational diabetes

Six of 22 mothers with gestational diabetes mellitus had infants with macrosomia, cord blood hyperinsulinemia, and increased amounts of a key mitogenic intermediate, farnesylated p21-Ras. The ability of fetal hyperinsulinemia to increase the availability of farnesylated p21-Ras may represent one mechanism of the growth-promoting action of insulin during fetal development.

Molecular mechanisms of insulin resistance: serine phosphorylation of insulin receptor substrate-1 and increased expression of p85alpha: the two sides of a coin

Initial attempts to unravel the molecular mechanism of insulin resistance have strongly suggested that a defect responsible for insulin resistance in the majority of patients lies at the postreceptor level of insulin signaling. Subsequent studies in insulin-resistant animal models and humans have consistently demonstrated a reduced strength of insulin signaling via the insulin receptor substrate (IRS)-1/phosphatidylinositol (PI) 3-kinase pathway, resulting in diminished glucose uptake and utilization in insulin target tissues. However, the nature of the triggering event(s) remains largely enigmatic. Two separate, but likely, complementary mechanisms have recently emerged as a potential explanation. First, it became apparent that serine phosphorylation of IRS proteins can reduce their ability to attract PI 3-kinase, thereby minimizing its activation. A number of serine kinases that phosphorylate serine residues of IRS-1 and weaken insulin signal transduction have been identified. Additionally, mitochondrial dysfunction has been suggested to trigger activation of several serine kinases, leading to a serine phosphorylation of IRS-1. Second, a distinct mechanism involving increased expression of p85alpha has also been found to play an important role in the pathogenesis of insulin resistance. Conceivably, a combination of both increased expression of p85alpha and increased serine phosphorylation of IRS-1 is needed to induce clinically apparent insulin resistance.

Exercise training and calorie restriction increase SREBP-1 expression and intramuscular triglyceride in skeletal muscle

Intramuscular triglyceride (IMTG) deposition in skeletal muscle is associated with obesity and type 2 diabetes (T2DM) and is thought to be related to insulin resistance (IR). Curiously, despite enhanced skeletal muscle insulin sensitivity, highly trained athletes and calorie-restricted (CR) monkeys also have increased IMTG. Sterol regulatory element-binding proteins (SREBPs) are transcription factors that regulate the biosynthesis of cholesterol and fatty acids. SREBP-1 is increased by insulin in skeletal muscle in vitro and in skeletal muscle of IR subjects, but SREBP-1 expression has not been examined in exercise training or calorie restriction. We examined the relationship between IMTG and SREBP-1 expression in animal models of exercise and calorie restriction. Gastrocnemius and soleus muscle biopsies were obtained from 38 Sprague-Dawley rats (18 control and 20 exercise trained). Triglyceride content was higher in the gastrocnemius and soleus muscles of the trained rats. SREBP-1c mRNA, SREBP-1 precursor and mature proteins, and fatty acid synthase (FAS) protein were increased with exercise training. Monkeys (Macaca mulatta) were CR for a mean of 10.4 years, preventing weight gain and IR. Vastus lateralis muscle was obtained from 12 monkeys (6 CR and 6 controls). SREBP-1 precursor and mature proteins and FAS protein were higher in the CR monkeys. In addition, phosphorylation of ERK1/ERK2 was increased in skeletal muscle of CR animals. In summary, SREBP-1 protein and SREBP-1c mRNA are increased in interventions that increase IMTG despite enhanced insulin sensitivity. CR and exercise-induced augmentation of SREBP-1 expression may be responsible for the increased IMTG seen in skeletal muscle of highly conditioned athletes.

Nutritional upregulation of p85alpha expression is an early molecular manifestation of insulin resistance

AIMS/HYPOTHESIS

We sought to define early molecular alterations associated with nutritionally induced insulin resistance in humans.

METHODS

Insulin sensitivity was assessed using a hyperinsulinaemic-euglycaemic clamp in eight healthy women while on an isocaloric diet and after 3 days of overfeeding (50% above eucaloric diet). Expression of phosphatidylinositol (PI) 3-kinase subunits p85alpha and p110 was assessed and measurements were made of IRS-1-associated PI 3-kinase activity, tyrosine and serine phosphorylation of IRS-1, and serine and threonine phosphorylation of p70S6 kinase. Measurements were made in skeletal muscle biopsies obtained before and after overfeeding.

RESULTS

Three days of overfeeding resulted in a reduction of insulin sensitivity accompanied by: (1) increased expression of skeletal muscle p85alpha; (2) an alteration in the ratio of p85alpha to p110; (3) a decrease in the amount of IRS-1-associated p110; and (4) a decrease in PI 3-kinase activity. Increases in expression of p85alpha and in the p85alpha:p110 ratio demonstrated a highly significant inverse correlation with insulin sensitivity, and changes in PI 3-kinase activity correlated with changes in insulin sensitivity. Tyrosine and serine phosphorylation of IRS-1 and serine and threonine phosphorylation of p70S6 kinase were unaffected by 3 days of overfeeding.

CONCLUSIONS/INTERPRETATION

We identified a novel mechanism of nutritionally induced insulin resistance in healthy women of normal weight. We conclude that increased expression of p85alpha may be one of the earliest molecular alterations in the mechanism of the insulin resistance associated with overfeeding.

Early growth response gene-1 expression in vascular smooth muscle cells effects of insulin and oxidant stress

BACKGROUND

Cardiovascular mortality is increased in individuals with insulin resistance, and increased oxidant stress is strongly implicated in atherogenesis. Early growth response gene-1 (Egr-1) may be an important link between insulin resistance and oxidant stress. In this study we examined the effects of insulin and oxidant stress on Egr-1 expression in vascular smooth muscle cells (VSMC), and identified mechanisms for these effects on Egr-1.

METHODS

Rat VSMC were used to obtain time course and dose-response curves for insulin and oxidant stress on Egr-1 protein expression. Intracellular signaling pathway inhibitors and adenoviral vectors with dominant negative effects on specific signaling pathways were used to determine mechanisms for these effects.

RESULTS

Insulin and oxidant stress each significantly stimulate Egr-1 protein expression. Insulin and oxidant stress combined have a greater effect on Egr-1 than either alone. Insulin effects are mediated via the ERK1/2 MAP kinase pathway, whereas oxidant stress effects may be mediated via the ERK5 and p38 MAP kinase pathways.

CONCLUSIONS

We demonstrated that insulin and oxidant stress stimulate Egr-1 expression in VSMC. Insulin effects are mediated via the ERK1/2 MAP kinase pathway, whereas oxidant stress effects may be mediated via the ERK5 and p38 MAP kinase pathways. As insulin resistance is characterized by compensatory hyperinsulinemia and selective impairment of the PI 3-kinase pathway with intact signaling along the ERK1/2 MAP kinase pathway, this may have implications for accelerated atherosclerosis in insulin resistance.