Low-carbohydrate diets in type 1 diabetes: balancing benefits and risks.

PURPOSE OF REVIEW: Interest in the use of calorie restriction with low-carbohydrate diets for patients with type 1 diabetes appears to be increasing despite physicians' discomfort about its longer term outcomes. A divergence in opinion regarding the balance of benefits and safety may lead to patient disengagement from conventional medical supervision. This review describes the current evidence regarding the benefits and risks of these diets and suggests a way forward to addressing this potential misalignment between the aims of patients and their physicians. RECENT FINDINGS: Benefits on glycaemia are observed in many studies, with improved HbA1c, time within target range and reduced glycaemic variability. A characteristic lipid profile with high LDL cholesterol is observed in many patients, but association with future cardiovascular events is undefined. A negative impact on growth has been identified in the paediatric population, and impact on mental health and disordered eating is of theoretical concern, without measurement in clinical studies. SUMMARY: Patients will continue to trial and, with immediate glycaemic benefits, potentially remain on lower carbohydrate diets irrespective of concern by treating physicians about potential longer term risks. A supportive multidisciplinary approach with greater nutritional supervision and more research is required, to allow these patients to achieve their desired glycaemic outcomes without compromising longer term safety.

Clinicians' perceptions of medical student teaching in a tertiary hospital.

Background: Medical student placements in teaching hospitals are a cornerstone for gaining clinical experience. However, the ever-evolving nature of health care has also changed the delivery of student education. Few studies have examined clinicians' perspectives toward teaching students in this setting. We sought to explore the attitudes of clinicians involved in teaching medical students at an Australian tertiary hospital. Methods: Clinicians were invited by email to complete an anonymous online survey developed using a combination of questions from previously validated surveys. The questions utilized 5-point Likert scale statements and were based around the themes of "personal purpose and enjoyment of teaching" and "barriers and challenges to teaching." Results for each question are presented as frequency and percentage. Results: Of 490 invited, 67 (13.7%) consultant clinicians from various specialties responded. The majority (>92%) enjoy teaching and see it as part of their work. However, approximately half thought that medical student teaching was under-recognized and half did not have adequate time to teach due to workload. Approximately 60% responded that there was insufficient time to get to know students to provide feedback and approximately 40% indicated that the scope of student knowledge and desired outcomes are not clearly defined by medical schools. Discussion: Our contemporary survey identifies modifiable factors which should be targeted. If these factors are addressed successfully, it may allow the hospital and university medical school to harness the valuable resource of clinical teachers. This could enhance the medical student experience and promote a culture of teaching and learning in hospitals.

Steroid Therapy and Outcome of Parapneumonic Pleural Effusions (STOPPE): A Pilot Randomized Clinical Trial.

Rationale: Pleural effusion commonly complicates community-acquired pneumonia and is associated with intense pleural inflammation. Whether antiinflammatory treatment with corticosteroids improves outcomes is unknown. Objectives: To assess the effects of corticosteroids in an adult population with pneumonia-related pleural effusion. Methods: The STOPPE (Steroid Therapy and Outcome of Parapneumonic Pleural Effusions) trial was a pilot, multicenter, double-blinded, placebo-controlled, randomized trial involving six Australian centers. Patients with community-acquired pneumonia and pleural effusion were randomized (2:1) to intravenous dexamethasone (4 mg twice daily for 48 h) or placebo and followed for 30 days. Given the diverse effects of corticosteroids, a comprehensive range of clinical, serological, and imaging outcomes were assessed in this pilot trial (ACTRN12618000947202). Measurements and Main Results: Eighty patients were randomized (one withdrawn before treatment) and received dexamethasone (n = 51) or placebo (n = 28). This pilot trial found no preliminary evidence of benefits of dexamethasone in improving time to sustained (>12 h) normalization of vital signs (temperature, oxygen saturations, blood pressure, heart, and respiratory rates): median, 41.0 (95% confidence interval, 32.3-54.5) versus 27.8 (15.4-49.5) hours in the placebo arm (hazard ratio, 0.729 [95% confidence interval, 0.453-1.173]; P = 0.193). Similarly, no differences in C-reactive protein or leukocyte counts were observed, except for a higher leukocyte count in the dexamethasone group at Day 3. Pleural drainage procedures were performed in 49.0% of dexamethasone-treated and 42.9% of placebo-treated patients (P = 0.60). Radiographic pleural opacification decreased over time with no consistent intergroup differences. Mean duration of antibiotic therapy (22.4 [SD, 15.4] vs. 20.4 [SD, 13.8] d) and median hospitalization (6.0 [interquartile range, 5.0-10.0] vs. 5.5 [interquartile range, 5.0-8.0] d) were similar between the dexamethasone and placebo groups. Serious adverse events occurred in 25.5% of dexamethasone-treated and 21.4% of placebo-treated patients. Transient hyperglycemia more commonly affected the dexamethasone group (15.6% vs. 7.1%). Conclusions: Systemic corticosteroids showed no preliminary benefits in adults with parapneumonic effusions. Clinical trial registered with www.anzctr.org.au (ACTRN12618000947202).

The effect of Vitamin-K1 and Colchicine on Vascular Calcification Activity in subjects with Diabetes Mellitus (ViKCoVaC): A double-blind 2x2 factorial randomized controlled trial.

BACKGROUND: There is currently no treatment for attenuating progression of arterial calcification. 18F-sodium fluoride positron emission tomography (18F-NaF PET) locates regions of calcification activity. We tested whether vitamin-K1 or colchicine affected arterial calcification activity. METHODS: 154 patients with diabetes mellitus and coronary calcification, as detected using computed tomography (CT), were randomized to one of four treatment groups (placebo/placebo, vitamin-K1 [10 mg/day]/placebo, colchicine [0.5 mg/day]/placebo, vitamin-K1 [10 mg/day]/ colchicine [0.5 mg/day]) in a double-blind, placebo-controlled 2x2 factorial trial of three months duration. Change in coronary calcification activity was estimated as a change in coronary maximum tissue-to-background ratio (TBRmax) on 18F-NaF PET. RESULTS: 149 subjects completed follow-up (vitamin-K1: placebo = 73:76 and colchicine: placebo = 73:76). Neither vitamin-K1 nor colchicine had a statistically significant effect on the coronary TBRmax compared with placebo (mean difference for treatment groups 0·00 ± 0·16 and 0·01 ± 0·17, respectively, p > 0.05). There were no serious adverse effects reported with colchicine or vitamin-K1. CONCLUSIONS: In patients with type 2 diabetes, neither vitamin-K1 nor colchicine significantly decreases coronary calcification activity, as estimated by 18F-NaF PET, over a period of 3 months. CLINICAL TRIAL REGISTRATION: ACTRN12616000024448.

A randomised controlled crossover trial investigating the short-term effects of different types of vegetables on vascular and metabolic function in middle-aged and older adults with mildly elevated blood pressure: the VEgetableS for vaScular hEaLth (VESSEL) study protocol.

BACKGROUND: A diet rich in fruits and vegetables is recommended for cardiovascular health. However, the majority of Australians do not consume the recommended number of vegetable servings each day. Furthermore, intakes of vegetables considered to have the greatest cardiovascular benefit are often very low. Results from prospective observational studies indicate that a higher consumption of cruciferous vegetables (e.g. broccoli, cabbage, cauliflower) is associated with lower cardiovascular disease risk. This may be due to the presence of specific nutrients and bioactive compounds found almost exclusively, or at relatively high levels, in cruciferous vegetables. Therefore, the aim of this randomised controlled crossover trial is to determine whether regular consumption of cruciferous vegetables results in short-term improvement in measures related to cardiovascular disease risk, including ambulatory blood pressure, arterial stiffness, glycaemic control, and circulating biomarkers of oxidative stress and inflammation. METHODS: Twenty-five participants (50-75 years) with mildly elevated blood pressure (systolic blood pressure 120-160 mmHg) will complete two 2-week intervention periods in random order, separated by a 2-week washout period. During the intervention period, participants will consume 4 servings (~ 300 g) of cruciferous vegetables per day as a soup (~ 500-600 mL/day). The 'control' soup will consist of other commonly consumed vegetables (potato, sweet potato, carrot, pumpkin). Both soups will be approximately matched for energy, protein, fat, and carbohydrate content. All measurements will be performed at the beginning and end of each intervention period. DISCUSSION: The findings of this study will provide evidence regarding the potential cardiometabolic health benefits of cruciferous vegetables, which may contribute to the revision of dietary and clinical guidelines. TRIAL REGISTRATION: The trial was registered with the Australian New Zealand Clinical Trial Registry on 19th September 2019 (ACTRN12619001294145).

The effect of regular consumption of lupin-containing foods on glycaemic control and blood pressure in people with type 2 diabetes mellitus.

BACKGROUND: Type 2 diabetes mellitus is a metabolic disorder characterized by high glucose and insulin resistance. It is strongly linked to lifestyle, including poor diet and physical inactivity. Lupin is a novel food ingredient, rich in protein and fibre with negligible sugar and starch, which can be incorporated into various foods to reduce glycaemic load. Regular consumption of lupin-enriched foods may be a novel and easily achievable means of reducing overall glycaemic load and improving glycaemic control in diabetes. OBJECTIVE: To determine whether regular consumption of lupin-enriched foods can improve glycaemic control and lower blood pressure in people with type 2 diabetes mellitus. DESIGN: Fourteen men and 8 women (mean age 58.0 ± 6.6 years and BMI 29.0 ± 3.5 kg m-2) with type 2 diabetes mellitus were recruited from the general population to take part in a double-blind, randomised, controlled cross-over study. Participants consumed lupin or control foods for breakfast and lunch every day, and for dinner at least 3 days per week during the 8-week treatment periods. Lupin-enriched foods consisted of bread, pasta, Weetbix™ cereal and crumbs, with energy-matched control products. Treatments were completed in random order with an 8-week washout period. All participants monitored their blood glucose levels pre- and post-breakfast and lunch, and their blood pressure in the morning and evening, 3 days per week for the duration of each treatment period. RESULTS: Seventeen participants completed both treatment arms, with all 22 participants (14 males, 8 females) analysed on an intention-to-treat basis. Eight weeks consumption of lupin-enriched food had no significant effect on mean blood glucose levels (mean difference: -0.08 ± 0.06 mmol L-1, p = 0.214) or post-prandial blood glucose levels (-0.13 ± 0.10 mmol L-1, p = 0.196). There was no effect on home systolic (-0.4 ± 0.4 mmHg, p = 0.33) or diastolic (0.3 ± 0.3 mmHg, p = 0.321) blood pressure and heart rate (0.5 ± 0.3 bpm, p = 0.152), and no effect on body weight throughout the treatment periods. CONCLUSION: Regular consumption of lupin-enriched foods had no significant effect on glycaemic control or blood pressure in people with type 2 diabetes mellitus.

Steroid therapy and outcome of parapneumonic pleural effusions (STOPPE): Study protocol for a multicenter, double-blinded, placebo-controlled randomized clinical trial.

BACKGROUND: Community-acquired pneumonia (CAP) is a major global disease. Parapneumonic effusions often complicate CAP and range from uninfected (simple) to infected (complicated) parapneumonic effusions and empyema (pus). CAP patients who have a pleural effusion at presentation are more likely to require hospitalization, have a longer length of stay and higher mortality than those without an effusion. Conventional management of pleural infection, with antibiotics and chest tube drainage, fails in about 30% of cases. Several randomized controlled trials (RCT) have evaluated the use of corticosteroids in CAP and demonstrated some potential benefits. Importantly, steroid use in pneumonia has an acceptable safety profile with no adverse impact on mortality. A RCT focused on pediatric patients with pneumonia and a parapneumonic effusion demonstrated shorter time to recovery. The effects of corticosteroid use on clinical outcomes in adults with parapneumonic effusions have not been tested. We hypothesize that parapneumonic effusions develop from an exaggerated pleural inflammatory response. Treatment with systemic steroids may dampen the inflammation and lead to improved clinical outcomes. The steroid therapy and outcome of parapneumonic pleural effusions (STOPPE) trial will assess the efficacy and safety of systemic corticosteroid as an adjunct therapy in adult patients with CAP and pleural effusions. METHODS: STOPPE is a pilot multicenter, double-blinded, placebo-controlled RCT that will randomize 80 patients with parapneumonic effusions (2:1) to intravenous dexamethasone or placebo, administered twice daily for 48 hours. This exploratory study will capture a wide range of clinically relevant endpoints which have been used in clinical trials of pneumonia and/or pleural infection; including, but not limited to: time to clinical stability, inflammatory markers, quality of life, length of hospital stay, proportion of patients requiring escalation of care (thoracostomy or thoracoscopy), and mortality. Safety will be assessed by monitoring for the incidence of adverse events during the study. DISCUSSION: STOPPE is the first trial to assess the efficacy and safety profile of systemic corticosteroids in adults with CAP and pleural effusions. This will inform future studies on feasibility and appropriate trial endpoints. TRIAL REGISTRATION: ACTRN12618000947202 PROTOCOL VERSION:: version 3.00/26.07.18.

Effect of ezetimibe on hepatic fat, inflammatory markers, and apolipoprotein B-100 kinetics in insulin-resistant obese subjects on a weight loss diet.

OBJECTIVE: Nonalcoholic fatty liver disease is highly prevalent in obese and type 2 diabetic individuals and is strongly associated with dyslipidemia and inflammation. Weight loss and/or pharmacotherapy are commonly used to correct these abnormalities. RESEARCH DESIGN AND METHODS: We performed a 16-week intervention trial of a hypocaloric, low-fat diet plus 10 mg/day ezetimibe (n = 15) versus a hypocaloric, low-fat diet alone (n = 10) on intrahepatic triglyceride (IHTG) content, plasma high sensitivity-C-reactive protein (hs-CRP), adipocytokines, and fetuin-A concentrations and apolipoprotein (apo)B-100 kinetics in obese subjects. ApoB-100 metabolism was assessed using stable isotope tracer kinetics and compartmental modeling; liver and abdominal fat contents were determined by magnetic resonance techniques. RESULTS: Both weight loss and ezetimibe plus weight loss significantly (all P < 0.05) reduced body weight, visceral and subcutaneous adipose tissues, insulin resistance and plasma triglycerides, VLDL-apoB-100, apoC-III, fetuin-A, and retinol-binding protein-4 and increased plasma adiponectin concentrations. Compared with weight loss alone, ezetimibe plus weight loss significantly (all P < 0.05) decreased IHTG content (-18%), plasma hs-CRP (-53%), interleukin-6 (-24%), LDL cholesterol (-18%), campesterol (-59%), and apoB-100 (-14%) levels, with a significant increase in plasma lathosterol concentrations (+43%). The LDL-apoB-100 concentration also significantly fell with ezetimibe plus weight loss (-12%), chiefly owing to an increase in the corresponding fractional catabolic rate (+29%). The VLDL-apoB-100 secretion rate fell with both interventions, with no significant independent effect of ezetimibe. CONCLUSIONS: Addition of ezetimibe to a moderate weight loss diet in obese subjects can significantly improve hepatic steatosis, inflammation, and LDL-apoB-100 metabolism.

The trials and tribulations of the treatment of nonalcoholic fatty-liver disease.

PURPOSE OF REVIEW: To review published clinical trials, with a focus on those of randomized design, of the management of nonalcoholic fatty-liver disease (NAFLD), an increasing complication of the obesity epidemic. RECENT FINDINGS: There is increasing recognition that cardiovascular risk issues are associated with NAFLD. Clinical trials of management of NAFLD have focused mainly on hepatic complications. The weight of data point to greatest biochemical and histological benefit with weight-loss measures and thiazolidinediones, but further trials are needed to characterize the benefits and risks of the latter agents. There is currently insufficient trial data to recommend other strategies for treating NAFLD. There is an emerging need for early multiple factor risk intervention, emphasizing cardiometabolic risk and weight management, in addition to minimizing risk of hepatic complications. SUMMARY: Given the strong association of NAFLD with the metabolic syndrome, early recognition, assessment and management of NAFLD is essential. The management emphasizes weight reduction and attention to cardiometabolic risk factors, similar to recommendations for management of the metabolic syndrome. Future research, guided by increasing knowledge of the pathogenetic factors driving the condition, should clarify the role of other therapies for reducing hepatic and cardiovascular morbidity associated with NAFLD.

Is adipose tissue lipolysis always an adaptive response to starvation?: implications for non-alcoholic fatty liver disease.

The physiological response to starvation involves increased muscle proteolysis and adipose tissue lipolysis that supply amino acids and non-esterified fatty acids ('free fatty acids') for gluconeogenesis, oxidation and ketogenesis. In the present issue of Clinical Science, Moller and co-workers show that, in humans, IHL (intrahepatic lipid) content, measured using (1)H-magnetic resonance spectroscopy, increases following 36 h of fasting, with a direct association with plasma levels of 3-hydroxybutyrate. The observation raises interesting questions as to how IHL levels increase in a situation of increased mitochondrial fatty acid oxidation and ketogenesis. Possible mechanisms for increased IHLs include reduced apoB-100 (apolipoprotein B-100) production and hepatic lipid export, and/or impaired mitochondrial function resulting from increased oxidative stress, with diversion of fatty acids for esterification. The accumulation of IHL during prolonged fasting may, therefore, reflect a maladaptive response to increased non-esterified fatty acid delivery to the liver that unmasks a subtle defect in mitochondrial function. This could have implications for the pathogenesis of the common human disorder of non-alcoholic fatty liver disease. The accumulation of IHLs observed with prolonged fasting may also explain exacerbations of steatohepatitis seen sometimes with rapid weight loss, anorexia nervosa and parenteral nutrition. The findings also suggest caution against promoting excessive ketogenesis with weight-loss regimens.

Markers of mitochondrial biogenesis and metabolism are lower in overweight and obese insulin-resistant subjects.

BACKGROUND: Impaired mitochondrial function in skeletal muscle is implicated in the development of insulin resistance. However, potential differences in fatness and fitness may influence previous results. METHODS: Subjects (n=18) were divided into insulin-sensitive (IS) and insulin-resistant (IR) groups by median glucose infusion rate during a hyperinsulinemic euglycemic clamp. Weight, VO2max (maximal aerobic capacity), and percentage body fat were measured before and after 6 continuous weeks of aerobic exercise training at 55-70% VO2max (40 min/session, 4 d/wk). RESULTS: Age, percentage fat, and VO2max were not different between IS and IR groups at baseline. Expression of the nuclear encoded PGC1alpha and mitochondrial encoded gene COX1 were significantly lower in the IR group (P<0.05). Citrate synthase activity and protein levels of subunits from complexes I and III of the respiratory chain were also lower in the IR group (P<0.05). Insulin sensitivity and aerobic fitness were increased after exercise training in both groups (P<0.001), and the expression of mitochondrial encoded genes CYTB and COX1 was also increased (P<0.01). However, there was no change in PGC1alpha expression, mitochondrial enzyme activity, or protein levels of complexes of the respiratory chain in response to exercise in either group. CONCLUSION: This study confirms that IR men have reduced markers of mitochondrial metabolism, independent of fatness and fitness. Moderate exercise training did not alter these markers despite improving fitness and whole body insulin sensitivity. This study suggests that additional mechanisms may be involved in improving insulin resistance after exercise training in obese men.

Revisiting the metabolic syndrome.

Metabolic syndrome (MS) refers to the clustering of cardiometabolic risk factors - including abdominal obesity, hyperglycaemia, dyslipidaemia and elevated blood pressure - that are thought to be linked to insulin resistance. MS is associated with increased risk of cardiovascular disease and type 2 diabetes. MS is common, affecting a quarter to a third of adults, and its prevalence is rising, in parallel with increasing obesity and population ageing. Operational definitions of MS have been proposed by the World Health Organization and the National Cholesterol Education Program. Recently, the International Diabetes Federation proposed a global definition that emphasised the importance of central adiposity. In cardiovascular risk assessment, MS encapsulates the contribution of non-traditional risk factors and provides a clinically useful framework for early identification of people at increased long-term risk. It should be used in conjunction with standard algorithms based on conventional risk factors, which better predict short-term risk. Management of MS should emphasise lifestyle interventions (eg, physical activity, healthy diet and weight reduction) to reduce long-term risk of cardiovascular disease and diabetes. Those at increased short-term risk should also have individual risk factors treated according to established guidelines.

Relationship of adiponectin with insulin sensitivity in humans, independent of lipid availability.

OBJECTIVE: To test in humans the hypothesis that part of the association of adiponectin with insulin sensitivity is independent of lipid availability. RESEARCH METHODS AND PROCEDURES: We studied relationships among plasma adiponectin, insulin sensitivity (by hyperinsulinemic-euglycemic clamp), total adiposity (by DXA), visceral adiposity (VAT; by magnetic resonance imaging), and indices of lipid available to muscle, including circulating and intramyocellular lipid (IMCL; by 1H-magnetic resonance spectroscopy). Our cohort included normal weight to obese men (n = 36). RESULTS: Plasma adiponectin was directly associated with insulin sensitivity and high-density lipoprotein-cholesterol and inversely with plasma triglycerides but not IMCL. These findings are consistent with adiponectin promoting lipid uptake and subsequent oxidation in muscle and inhibiting TG synthesis in the liver. In multiple regression models that also included visceral and total fat, free fatty acids, TGs, and IMCL, either alone or in combination, adiponectin independently predicted insulin sensitivity, consistent with some of its insulin-sensitizing effects being mediated through mechanisms other than modulation of lipid metabolism. Because VAT directly correlated with total fat and all three indices of local lipid availability, free fatty acids, and IMCL, an efficient regression model of insulin sensitivity (R2 = 0.69, p < 0.0001) contained only VAT (part R2 = 0.12, p < 0.002) and adiponectin (part R2 = 0.41, p < 0.0001) as independent variables. DISCUSSION: Given the broad range of total adiposity and body fat distribution in our cohort, we suggest that insulin sensitivity is robustly associated with adiponectin and VAT.

Insulin action, regional fat, and myocyte lipid: altered relationships with increased adiposity.

OBJECTIVE: Abdominal fat and myocyte triglyceride levels relate negatively to insulin sensitivity, but their interrelationships are inadequately characterized in the overweight. Using recent methods for measuring intramyocyte triglyceride, these relationships were studied in men with a broad range of adiposity. RESEARCH METHODS AND PROCEDURES: Myocyte triglyceride content ((1)H-magnetic resonance spectroscopy of soleus and tibialis anterior muscles and biochemical assessment of vastus lateralis biopsies), regional fat distribution (DXA and abdominal magnetic resonance imaging), serum lipids, insulin action (euglycemic hyperinsulinemic clamp), and substrate oxidation rates (indirect calorimetry) were measured in 39 nondiabetic men (35.1 +/- 7.8 years) with a broad range of adiposity (BMI 28.6 +/- 4.1 kg/m(2), range 20.1 to 37.6 kg/m(2)). RESULTS: Relationships between insulin-stimulated glucose disposal and regional body fat depots appeared more appropriately described by nonlinear than linear models. When the group was subdivided using median total body fat as the cut-point, insulin-stimulated glucose disposal correlated negatively to all regional body fat measures (all p < or = 0.004), serum triglycerides and free fatty acids (p < 0.02), and both soleus intramyocellular lipid (p = 0.003) and vastus lateralis triglyceride (p = 0.04) in the normal/less overweight group. In contrast, only visceral abdominal fat showed significant negative correlation with insulin-stimulated glucose disposal in more overweight men (r = -0.576, p = 0.01), some of whom surprisingly had lower than expected myocyte lipid levels. These findings persisted when the group was subdivided using different cut-points or measures of adiposity. DISCUSSION: Interrelationships among body fat depots, myocyte triglyceride, serum lipids, and insulin action are generally absent with increased adiposity. However, visceral abdominal fat, which corresponds less closely to total adiposity, remains an important predictor of insulin resistance in men with both normal and increased adiposity.

Nicotinic acid-induced insulin resistance is related to increased circulating fatty acids and fat oxidation but not muscle lipid content.

Insulin resistance is associated with increased circulating lipids and skeletal muscle lipid content. Chronic nicotinic acid (NA) treatment reduces insulin sensitivity and provides a model of insulin resistance. We hypothesized that the reduction in insulin sensitivity occurs via elevation of circulating nonesterified fatty acids (NEFAs) and an increase in intramyocellular lipid (IMCL). A total of 15 nondiabetic males (mean age 27.4 +/- 1.6 years) were treated with NA (500 mg daily for 1 week, 1 g daily for 1 week). Insulin sensitivity (glucose infusion rate [GIR]) was determined pre- and post-NA by euglycemic-hyperinsulinemic clamp. Substrate oxidation was determined by indirect calorimetry. Skeletal muscle lipid was assessed by estimation of long-chain acyl-CoA (LCACoA) and triglyceride (TG) content and by (1)H-magnetic resonance spectroscopy quantification of IMCL (n = 11). NA reduced GIR (P =.03) and nonoxidative glucose disposal (P <.01) and increased fasting NEFAs (P =.01). The decrease in GIR related significantly to the increase in fasting NEFAs (r(2) =.30, P =.03). The intrasubject increase in basal and clamp fat oxidation correlated with the decrease in GIR (r(2) =.45, P <.01 and r(2) =.63, P <.01). There were no significant changes in muscle LCACoA, TG, or IMCL content. Therefore, induction of insulin resistance by NA occurs with increased availability of circulating fatty acids to muscle rather than with increased muscle lipid content.

Changes in aerobic capacity and visceral fat but not myocyte lipid levels predict increased insulin action after exercise in overweight and obese men.

OBJECTIVE: To examine the effect of moderate intensity physical activity on the interactions between central abdominal adiposity, myocyte lipid content, and insulin action in overweight and obese, sedentary men. RESEARCH DESIGN AND METHODS: Myocyte lipid (biochemical triglyceride and long-chain acyl CoA [LCAC] from vastus lateralis biopsy and soleus and tibialis anterior intramyocellular lipid by (1)H-magnetic resonance spectroscopy), regional body and abdominal fat (dual-energy X-ray absorptiometry and magnetic resonance imaging), serum lipids, insulin action (hyperinsulinemic-euglycemic clamp), and substrate oxidation were measured in 18 nondiabetic, sedentary, and overweight to obese men (aged 37.4 +/- 1.3 years and BMI 30.9 +/- 0.7 kg/m(2), range 26.4-37.6) at baseline, after the first two to four bouts of aerobic exercise (55-70% of VO(2max) for 40 min/session), and at completion of 4.1 +/- 0.2 exercise sessions/week for 9.7 +/- 0.5 weeks (postexercise measurements performed 24-36 h after the last exercise bout). RESULTS: Mean whole body insulin-stimulated glucose uptake and basal fat oxidation rate increased 16 and 41%, respectively, after two to four bouts of exercise, without further increase at program end. Mean aerobic capacity increased 11%, and central abdominal fat decreased 5% at program end, but myocyte lipid levels were not significantly changed. Posttraining increases in insulin-stimulated glucose uptake were predicted by increase in aerobic capacity (r = 0.726, P = 0.001) and magnitude of reduction in visceral fat (r = -0.544, P = 0.02) and not by changes in myocyte lipid or LCAC levels. CONCLUSIONS: These results suggest that in overweight and obese sedentary men, increase in insulin sensitivity with moderate intensity exercise is predicted by improvement in aerobic capacity and reduction in visceral fat but is independent of myocyte triglyceride or LCAC levels.

Multiple indexes of lipid availability are independently related to whole body insulin action in healthy humans.

An increase in muscle lipid content has been postulated to relate closely to the evolution of insulin resistance. We aimed to test whether the multiple indexes of lipid supply within man [namely, circulating triglycerides, skeletal muscle triglycerides (SMT), total and central fat mass, and circulating leptin] were independent predictors of insulin resistance, or whether triglycerides from different sources are additive in their influence on whole body insulin sensitivity. Whole body insulin sensitivity, body composition, and SMT content were determined in 49 sedentary, nondiabetic males (age, 20-74 yr; body mass index, 20-38 kg/m(2)). Insulin sensitivity was inversely associated with central abdominal fat (r(2) = 0.38; P < 0.0001), total body fat (r(2) = 0.21; P = 0.0003), SMT content (r(2) = 0.16; P = 0.005), and fasting triglycerides (r(2) = 0.24; P = 0.0003), nonesterified free fatty acid (r(2) = 0.19; P = 0.002), and leptin (r(2) = 0.35; P < 0.0001) levels. However, only central abdominal fat was significantly related to SMT content (r(2) = 0.10; P = 0.03). SMT content, circulating triglycerides, and measurements of total or central adiposity were independent predictors of whole body insulin sensitivity.