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Biomedical subjects

William T Cefalu

Publications and source records attributed to William T Cefalu.

At least 19 recordsLinked to original sources
PubMed2006

Increased hypothalamic protein tyrosine phosphatase 1B contributes to leptin resistance with age.

Animals at advanced ages exhibit a reduction in central leptin sensitivity. However, changes in growth, metabolism, and obesity risk occur much earlier in life, particularly during the transition from youth to middle age. To determine when initial decreases in central leptin sensitivity occur, leptin-dependent suppression of food intake was tested in 8-, 12-, and 20-wk-old male, chow-fed Sprague Dawley rats. Intracerebroventricular leptin injection (3 microg) suppressed 24-h food intake in 8- and 12-wk-old rats (P < 0.05) but not 20-wk-old rats. To identify potential cellular mediators of this resistance, we focused on protein tyrosine phosphatase 1B (PTP1B), a recently described inhibitor of leptin signaling. PTP1B protein levels, as determined by Western blot, were significantly higher in mediobasal hypothalamic punches collected from 20-wk-old rats, compared with 8-wk-old rats (P < 0.05). When 20-wk-old rats were fasted for 24 h, levels of hypothalamic PTP1B decreased (P < 0.05), coincident with a restoration of leptin sensitivity. To directly test whether inhibition of PTP1B restores leptin sensitivity, 20-wk-old chow-fed rats were pretreated with a pharmacological PTP1B inhibitor 1 h before leptin, and 24-h food intake was recorded. As expected, leptin alone produced a small but nonsignificant reduction in food intake. However, pretreatment with the PTP1B inhibitor resulted in a marked improvement in leptin-dependent suppression of food intake (P < 0.05). These data are consistent with the hypothesis that increases in PTP1B contribute to hypothalamic leptin resistance as rats transition into middle age.

Aging↗
PubMed2006

Inactivation of PKCtheta leads to increased susceptibility to obesity and dietary insulin resistance in mice.

In this study, we investigated the metabolic phenotype of PKCtheta knockout mice (C57BL/6J) on chow diet and high-fat diet (HFD). The knockout (KO) mice are normal in growth and reproduction. On the chow diet, body weight and food intake were not changed in the KO mice; however, body fat content was increased with a corresponding decrease in body lean mass. Energy expenditure and spontaneous physical activity were decreased in the KO mice. On HFD, energy expenditure and physical activity remained low in the KO mice. The body weight and fat content were increased rapidly in the KO mice. At 8 wk on HFD, severe insulin resistance was detected in the KO mice with hyperinsulinemic euglycemic clamp and insulin tolerance test. Insulin action in both hepatic and peripheral tissues was reduced in the KO mice. Plamsa free fatty acid was increased, and expression of adiponectin in the adipose tissue was decreased, in the KO mice on HFD. This study suggests that loss of PKCtheta reduces energy expenditure and increases the risk of dietary obesity and insulin resistance in mice.

Adiponectin↗
PubMed2006

Animal models of type 2 diabetes: clinical presentation and pathophysiological relevance to the human condition.

The prevalence of diabetes throughout the world has increased dramatically over the recent past, and the trend will continue for the foreseeable future. One of the major concerns associated with diabetes relates to the development of micro- and macrovascular complications, which contribute greatly to the morbidity and mortality associated with the disease. Progression of the disease from prediabetic state to overt diabetes and the development of complications occur over many years. Assessment of interventions designed to delay or prevent disease progression or complications in humans also takes years and requires tremendous resources. To better study both the pathogenesis and potential therapeutic agents, appropriate animal models of type 2 diabetes (T2D) mellitus are needed. However, for an animal model to have relevance to the study of diabetes, either the characteristics of the animal model should mirror the pathophysiology and natural history of diabetes or the model should develop complications of diabetes with an etiology similar to that of the human condition. There appears to be no single animal model that encompasses all of these characteristics, but there are many that provide very similar characteristics in one or more aspects of T2D in humans. Use of the appropriate animal model based on these similarities can provide much needed data on pathophysiological mechanisms operative in human T2D.

Animals↗
PubMed2006

Chromium picolinate enhances skeletal muscle cellular insulin signaling in vivo in obese, insulin-resistant JCR:LA-cp rats.

Chromium is one of the few trace minerals for which a specific cellular mechanism of action has not been identified. Recent in vitro studies suggest that chromium supplementation may improve insulin sensitivity by enhancing insulin receptor signaling, but this has not been demonstrated in vivo. We investigated the effect of chromium supplementation on insulin receptor signaling in an insulin-resistant rat model, the JCR:LA-corpulent rat. Male JCR:LA-cp rats (4 mo of age) were randomly assigned to receive chromium picolinate (CrPic) (obese n=6, lean n=5) or vehicle (obese n=5, lean n=5) for 3 mo. The CrPic was provided in the water, and based on calculated water intake, rats randomized to CrPic received 80 microg/(kg.d). At the end of the study, skeletal muscle (vastus lateralis) biopsies were obtained at baseline and at 5, 15, and 30 min postinsulin stimulation to assess insulin signaling. Obese rats treated with CrPic had significantly improved glucose disposal rates and demonstrated a significant increase in insulin-stimulated phosphorylation of insulin receptor substrate (IRS)-1 and phosphatidylinositol (PI)-3 kinase activity in skeletal muscle compared with obese controls. The increase in cellular signaling was not associated with increased protein levels of the IRS proteins, PI-3 kinase or Akt. However, protein tyrosine phosphatase 1B (PTP1B) levels were significantly lower in obese rats administered CrPic than obese controls. When corrected for protein content, PTP1B activity was also significantly lower in obese rats administered CrPic than obese controls. Our data suggest that chromium supplementation of obese, insulin-resistant rats may improve insulin action by enhancing intracellular signaling.

Animals↗
PubMed2006

Chromium picolinate supplementation attenuates body weight gain and increases insulin sensitivity in subjects with type 2 diabetes.

OBJECTIVE: Chromium picolinate (CrPic) supplementation has been suggested to improve glycemia, but there are conflicting reports on efficacy. We sought to determine the effect of CrPic on insulin sensitivity, glycemic control, and body composition in subjects with type 2 diabetes. RESEARCH DESIGN AND METHODS: Thirty-seven subjects with type 2 diabetes were evaluated. After baseline, subjects were placed on a sulfonylurea (glipizide gastrointestinal therapeutic system 5 mg/day) with placebo for 3 months. Subjects were then randomized in a double-blind fashion to receive either the sulfonylurea plus placebo (n = 12) or the sulfonylurea plus 1,000 microg Cr as CrPic (n = 17) for 6 months. Body composition, insulin sensitivity, and glycemic control were determined at baseline, end of the 3-month single-blind placebo phase, and end of study. RESULTS: Subjects randomized to sulfonylurea/placebo, as opposed to those randomized to sulfonylurea/CrPic, had a significant increase in body weight (2.2 kg, P < 0.001 vs. 0.9 kg, P = 0.11), percent body fat (1.17%, P < 0.001 vs. 0.12%, P = 0.7), and total abdominal fat (32.5 cm(2), P < 0.05 vs. 12.2 cm(2), P < 0.10) from baseline. Subjects randomized to sulfonylurea/CrPic had significant improvements in insulin sensitivity corrected for fat-free mass (28.8, P < 0.05 vs. 15.9, P = 0.4), GHb (-1.16%, P < 0.005 vs. -0.4%, P = 0.3), and free fatty acids (-0.2 mmol/l, P < 0.001 vs. -0.12 mmol/l, P < 0.03) as opposed to sulfonylurea/placebo. CONCLUSIONS: This study demonstrates that CrPic supplementation in subjects with type 2 diabetes who are taking sulfonylurea agents significantly improves insulin sensitivity and glucose control. Further, CrPic supplementation significantly attenuated body weight gain and visceral fat accumulation compared with the placebo group.

Adipose Tissue↗
PubMed2005

Diabetes, the metabolic syndrome, and angiographic progression of coronary arterial disease in postmenopausal women.

OBJECTIVE: Although the metabolic syndrome (MS) is associated with increased cardiovascular risk, its relationship with atherosclerotic progression is less well defined. We sought to determine whether the MS predicts angiographic progression of coronary heart disease in a cohort of postmenopausal women. METHODS AND RESULTS: A total of 309 postmenopausal women entered the Estrogen Replacement and Atherosclerosis trial, of whom 248 underwent baseline angiography and completed follow-up angiography after an average of 3.2 years. Women were identified as having type 2 diabetes mellitus (T2DM) or the MS (National Cholesterol Education Panel diagnostic criteria). In adjusted models, participants with T2DM and the MS had greater angiographic progression [change in minimal diameter (DeltaMD): -0.15] than women without T2DM or the MS (DeltaMD: -0.08; P<0.05) or with MS alone (DeltaMD: -0.07; P<0.005); there was no difference in progression by MS status in women without T2DM (P=0.54)]. In adjusted logistic regression models, T2DM predicted coronary heart disease events [odds ratio, 2.79 (95% CI, 1.29 to 6.02)], and the MS demonstrated a similar trend [odds ratio, 1.98 (95% CI, 0.90 to 4.33)]. CONCLUSIONS: Among postmenopausal women with coronary heart disease, the presence of diabetes predicted disease progression, but the MS did not.

Aged↗
PubMed2005

Inhaled insulin improves glycemic control when substituted for or added to oral combination therapy in type 2 diabetes: a randomized, controlled trial.

BACKGROUND: Patients with type 2 diabetes who do not achieve glycemic control with oral agent therapy eventually require insulin. OBJECTIVE: To determine the effect on glycemic control of inhaled insulin alone or added to dual oral therapy (insulin secretagogue and sensitizer) after failure of dual oral therapy. DESIGN: Open-label, randomized, controlled trial. SETTING: 48 outpatient centers in the United States and Canada. PATIENTS: 309 patients with type 2 diabetes, no clinically significant respiratory disease, and hemoglobin A(1c) level of 8% to 11% who were receiving dual oral therapy. MEASUREMENTS: Primary end point was change in hemoglobin A(1c) level from baseline to 12 weeks. Secondary outcomes included hemoglobin A(1c) level less than 8% and less than 7%, hypoglycemia, weight, lipid levels, pulmonary function, insulin antibody binding, and adverse events. INTERVENTION: Inhaled insulin (Exubera; Pfizer Inc. [New York, New York], sanofi-aventis Group [Paris, France], and Nektar Therapeutics [San Carlos, California]), titrated to blood glucose, administered alone (n = 104) or added to dual oral agents (n = 103) versus oral therapy alone (n = 99). RESULTS: Reductions in hemoglobin A(1c) level were greater with inhaled insulin. Adjusted treatment group differences for inhaled insulin plus oral agents and inhaled insulin alone compared with continued oral agent therapy were -1.67 percentage points (95% CI, -1.90 to -1.44 percentage points; P < 0.001) and -1.18 percentage points (CI, -1.41 to -0.95 percentage point; P < 0.001), respectively. Hemoglobin A(1c) level less than 7% was achieved by 32% (inhaled insulin plus oral agents) and by 1% (oral agent therapy) of patients (adjusted odds ratio, 44.7 [CI, 6.0 to 335.2]). Hypoglycemia, mild weight gain, mild cough, and insulin antibodies were more frequent with inhaled insulin than with oral agent therapy alone. Pulmonary function was similar in all groups. LIMITATIONS: This study evaluated only patients with hemoglobin A1c levels of 8% to 11%, did not compare inhaled insulin with other insulins or oral therapy except a dual regimen of secretagogue and sensitizer, and lasted only 12 weeks. CONCLUSIONS: Inhaled insulin improved overall glycemic control and hemoglobin A1c level when added to or substituted for dual oral agent therapy with an insulin secretagogue and sensitizer. Consistent with other insulin therapies, hypoglycemia and mild weight gain occurred. Pulmonary function showed no between-group differences.

Administration, Inhalation↗
PubMed2005

Elevated pregnancy losses at high and low extremes of maternal glucose in early normal and diabetic pregnancy: evidence for a protective adaptation in diabetes.

OBJECTIVE: Early pregnancy losses increase with marked hyperglycemia in diabetic pregnancy. However, mean loss rates do not differ from those of nondiabetic pregnancy. This observation might be explained by increased fetal losses at the extremes of glycemia in diabetic and nondiabetic pregnancy. To test this hypothesis, we examined relationships of proximate measures of prior glycemia, glycated protein and fructosamine, to pregnancy loss. RESEARCH DESIGN AND METHODS: A total of 389 diabetic and 429 nondiabetic pregnant subjects participated in the Diabetes In Early Pregnancy study. Glycated protein and fructosamine measurements were standardized as multiples of control values for each center (Z score). The logarithm of odds of pregnancy loss were plotted against Z scores and tested by logistic models. RESULTS: Mean pregnancy loss rates were 12% in diabetic and 13% in normal pregnancies. However, over six intervals of glycated protein in diabetic pregnancy, fetal loss rates at the upper and lower extremes (24 and 33%, respectively) were approximately threefold higher than the four intervening rates (8-14%). The odds ratio of pregnancy loss for these extreme intervals to the intervening intervals is 3.0 (P = 0.01). Nondiabetic losses showed a similar pattern. In confirmation, logit pregnancy losses were increased in a J-shaped curve at the glycemic extremes in normal (P < 0.019) and diabetic (P < 0.015) pregnancy. The upper glycemic extreme in diabetic pregnancy was two- to fivefold higher than in control pregnancy. CONCLUSIONS: Pregnancy losses are increased at the extremes of glycemia in both normal and diabetic pregnancy but at higher levels in diabetic pregnancy. The data suggest defensive adaptations against hyperglycemia in diabetic pregnancy.

Abortion, Spontaneous↗
PubMed2005

Efficacy of inhaled insulin in patients with type 2 diabetes not controlled with diet and exercise: a 12-week, randomized, comparative trial.

OBJECTIVE: Effective type 2 diabetes management requires prompt intervention if glycemic control is not achieved by nonpharmacological means. This study investigates whether inhaled insulin (INH; Exubera) can achieve target glycemic control in patients failing on diet and exercise. RESEARCH DESIGN AND METHODS: Patients with suboptimal control on diet and exercise (HbA(1c) [A1C] 8-11%) were randomized to 3 months' treatment with either INH before meals (n = 76) or rosiglitazone 4 mg twice a day (n = 69), in conjunction with a diet and exercise regimen. The primary end point was percentage of patients achieving A1C <8.0%. RESULTS: The INH and rosiglitazone groups had comparable baseline A1C values (9.5 vs. 9.4%, respectively). Significantly more patients achieved A1C <8.0% (83 vs. 58%, adjusted odds ratio 7.14 [95% CI 2.48-20.58], P = 0.0003), A1C <7.0% (44 vs. 18%, 4.43 [1.94-10.12]), and A1C < or = 6.5% (28 vs. 7.5% 5.34 [1.83-15.57]) with INH. A1C decrease was greater with INH (-2.3% vs. -1.4%, adjusted treatment group difference: -0.89% [95% CI -1.23 to -0.55]) with final mean A1C values of 7.2 and 8.0% for INH and rosiglitazone, respectively. Hypoglycemia (episodes per subject-month) was higher with INH (0.7 vs. 0.05, risk ratio 14.72 [95% CI 7.51-28.83]), with no severe hypoglycemic episodes. Pulmonary function changes were small and comparable between groups. CONCLUSIONS: INH could be an effective therapy for people with type 2 diabetes early in the course of their disease.

Administration, Inhalation↗
PubMed2004

Arterial heparan sulfate is negatively associated with hyperglycemia and atherosclerosis in diabetic monkeys.

BACKGROUND: Arterial proteoglycans are implicated in the pathogenesis of atherosclerosis by their ability to trap plasma lipoproteins in the arterial wall and by their influence on cellular migration, adhesion and proliferation. In addition, data have suggested an anti-atherogenic role for heparan sulfate proteoglycans and a pro-atherogenic role for dermatan sulfate proteoglycans. Using a non-human primate model for human diabetes, studies examined diabetes-induced changes in arterial proteoglycans that may increase susceptibility to atherosclerosis. METHODS: Control (n = 7) and streptozotocin-induced diabetic (n = 8) cynomolgous monkeys were assessed for hyperglycemia by measurement of plasma glycated hemoglobin (GHb). Thoracic aortas obtained at necropsy, were extracted with 4 M guanidine HCL and proteoglycans were measured as hexuronic acid. Atherosclerosis was measured by enzymatic analysis of extracted tissue cholesterol. Glycosaminoglycan chains of arterial proteoglycans were released with papain, separated by agarose electrophoresis and analysed by scanning densitometry. RESULTS: Tissue cholesterol was positively associated with hexuronic acid content in diabetic arteries (r = .82, p < .025) but not in control arteries. Glycosaminoglycan chain analysis demonstrated that dermatan sulfate was associated with increased tissue cholesterol in both control (r = .8, p < 0.05) and diabetic (r = .8, p < .025) arteries, whereas a negative relationship was observed between heparan sulfate and tissue cholesterol in diabetic arteries only (r = -.7, p < .05). GHb, which was significantly higher in diabetic animals (8.2 +/- 0.9 vs 3.8 +/- 0.2%, p < .0005) was negatively associated with heparan sulfate in diabetic arteries (r = -.7, p < .05). CONCLUSIONS: These data implicate hyperglycemia induced modifications in arterial proteoglycans that may promote atherosclerosis.

Journal Article↗
PubMed2004

Caloric restriction and cardiovascular aging in cynomolgus monkeys (Macaca fascicularis): metabolic, physiologic, and atherosclerotic measures from a 4-year intervention trial.

Caloric restriction (CR) retards aging processes, extends maximal life span, and consistently improves insulin resistance in lower species. Insulin resistance is associated with cardiovascular disease, but data is lacking demonstrating that increased insulin sensitivity reduces atherosclerosis progression. We initiated a study in 32 adult cynomolgus monkeys to evaluate increased insulin sensitivity secondary to CR on atherosclerosis extent. Following pretrial determinations, animals were randomized to a moderately atherogenic (0.25 mg cholesterol/Cal containing 30% of calories from fat)-fed control group or CR group (30% reduction) with equivalent dietary cholesterol intake. CR significantly improved insulin sensitivity and reduced intraabdominal fat over the 4-year intervention, while no significant differences were seen for the lipid profile between groups. Despite improved insulin sensitivity with CR, atherosclerosis extent did not differ between the ad libitum-fed or CR groups. These studies demonstrate that CR significantly improves insulin sensitivity, but when elevated plasma cholesterol concentrations were held similar, there was no effect on atherosclerosis extent. However, the composition of these lesions and changes in endothelial function may have been improved but were not evaluated in this study. Thus, further studies are needed to determine if improved insulin sensitivity might decrease arterial inflammation and improve endothelial function, despite no changes in atherosclerosis extent.

Abdomen↗
PubMed2004

Evolving strategies for insulin delivery and therapy.

It has now been conclusively proven that adequate control of blood glucose delays or prevents the progression of diabetic complications. In order to achieve the suggested targets for glycaemic control necessary to reduce the incidence of diabetic complications, it has been established that a more intensive insulin regimen requiring multiple insulin injections is required for patients with type 1 diabetes mellitus. For patients with type 2 diabetes, oral antidiabetic therapy is generally used initially, but given the natural history of type 2 diabetes and the need to achieve improved glycaemic control, earlier use of insulin has been promoted. However, the use of insulin in more intensive regimens for the patient with type 1 diabetes or for earlier treatment of the patient with type 2 diabetes is not routine. Many factors are responsible for this observation. Nevertheless, available device options such as insulin pens or insulin pumps are routinely available for implementation of intensive insulin therapy. However, a major limitation for advancing to intensive insulin therapy is that the only viable way to administer insulin is through injection. Delivery options that use dermal, nasal and oral approaches have been explored. The oral approach may include gastrointestinal, buccal or pulmonary uptake. Recent evidence shows that delivery of insulin via the oral cavity with uptake occurring in the pulmonary alveoli may be the most viable clinical option in the future.

Administration, Oral↗
PubMed2004

Concept, strategies, and feasibility of noninvasive insulin delivery.

OBJECTIVE: To comprehensively review the progress to date on the development of alternative routes for insulin delivery. RESEARCH DESIGN AND METHODS: Study data were collected through a Medline review. RESULTS: Proof of principle has been established for many routes of administration including dermal, nasal, oral, buccal, and pulmonary insulin delivery. CONCLUSIONS: Of all the approaches to date, pulmonary delivery appears to be most feasible. Ongoing phase III studies will ultimately determine safety, tolerability, and efficacy before approval for clinical use.

Administration, Inhalation↗