Jeffrey F. Horowitz

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Dysregulated lipid metabolism and inflammation are linked to the development of insulin resistance in obesity, and the intracellular accumulation of the sphingolipid ceramide has been implicated in these processes. Here, we explored the role of circulating ceramide on the pathogenesis of insulin resistance. Ceramide transported in LDL is elevated in the(More)
BACKGROUND This study examined the independent association of objectively measured physical activity on insulin resistance while controlling for confounding variables including: cardiorespiratory fitness, adiposity, sex, age, and smoking status. METHODS Data were obtained from National Health and Nutrition Examination Survey 2003-2004, a cross-sectional(More)
OBJECTIVE Leptin therapy improves insulin sensitivity in people with leptin deficiency, but it is not known whether it improves insulin action in people who are not leptin deficient. The purpose of the current study was to determine whether leptin treatment has weight loss-independent effects on insulin action in obese subjects with type 2 diabetes. (More)
By far the largest energy reserve in the human body is adipose tissue triglycerides, and these reserves are an important source of fuel during prolonged endurance exercise. To use this rich source of potential energy during exercise, adipose tissue triglycerides must first be hydrolyzed and the resultant fatty acids delivered to the working muscles. The(More)
Insulin receptor substrate 1 (IRS1) is a key mediator of insulin signal transduction. Perturbations involving IRS1 complexes may lead to the development of insulin resistance and type 2 diabetes (T2D). Surprisingly little is known about the proteins that interact with IRS1 in humans under health and disease conditions. We used a proteomic approach to assess(More)
OBJECTIVE The purpose of this study was to determine the effect of a relatively modest session of exercise on insulin sensitivity and fatty acid uptake the next day in obese adults. RESEARCH DESIGN AND METHODS Eleven sedentary obese adults (male/female: 3/8; BMI 37 ± 1 kg/m(2); peak oxygen uptake [VO2peak] 20 ± 1 mL/kg/min) completed three experimental(More)
In vitro examinations of the effect of saturated fatty acids on skeletal muscle insulin action often use only one or two different fatty acid species, which does not resemble the human plasma fatty acid profile. We compared graded concentrations (0.1-0.8 mM) of 3 different lipid mixtures: 1) a physiologic fatty acid mixture (NORM; 40% saturated fatty(More)
Reduced carbohydrate (CHO) availability after exercise has a potent influence on the regulation of substrate metabolism, but little is known about the impact of fat availability and/or energy deficit on fuel metabolism when dietary CHO availability is not reduced. The purpose of this study was to determine the influence of a postexercise energy deficit,(More)
BACKGROUND Although obesity is commonly linked with metabolic disease risk, some obese adults do not develop metabolic abnormalities, such as insulin resistance. OBJECTIVES The primary aim of this study was to determine whether alterations in fatty acid mobilization and uptake underlie differences in insulin sensitivity (Si) among a seemingly homogeneous(More)
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