Long-term maintenance of efficacy of dapagliflozin in patients with type 2 diabetes mellitus and cardiovascular disease

AIM

To evaluate the long-term efficacy, safety and tolerability of dapagliflozin versus placebo added to usual care in patients with type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD).

METHODS

Data were pooled from two phase III studies (NCT01031680 and NCT01042977) in high-risk patients (N = 1887) with T2DM and CVD treated with dapagliflozin (10 mg/day) or placebo. Patients completing the double-blind treatment studies (24 weeks) entered one or two sequential double-blind, long-term (LT) extensions of 28 (LT1; n = 1649) and 52 (LT2; n = 568) weeks.

RESULTS

Baseline and CVD characteristics were similar in the two groups. Patients entering LT1 and LT2 on dapagliflozin maintained a greater mean reduction in glycated haemoglobin (HbA1c) versus placebo at 52 weeks [LT1, -0.58% (95% confidence interval -0.68, -0.49)] and 104 weeks [LT2, -0.35% (95% confidence interval -0.59, -0.12)]. Mean body weight and systolic blood pressure (SBP) reductions versus placebo were maintained in patients entering LT1 (52 weeks; -2.23 kg and -3.25 mmHg, respectively) and LT2 (104 weeks; -3.16 kg and -2.03 mmHg, respectively). Patients on dapagliflozin had a better three-item composite endpoint of clinical benefit (glycaemia, weight and SBP) compared with placebo at week 24 (LT1, 10.1% vs. 1.1%) and week 104 (LT2, 6.7% vs. 1.4%). Genital and urinary tract infections were more frequent with dapagliflozin than with placebo. Events of hypoglycaemia, renal impairment/failure and volume depletion were similar between groups.

CONCLUSIONS

The long-term efficacy of dapagliflozin to maintain reductions in HbA1c, SBP and body weight over 2 years, together with its tolerability profile, make dapagliflozin an appropriate option in high-risk patients with T2DM and CVD.

In vivo effects of dietary quercetin and quercetin-rich red onion extract on skeletal muscle mitochondria, metabolism, and insulin sensitivity

Red onions and low doses of the flavonoid, quercetin, increase insulin sensitivity and improve glucose tolerance. We hypothesized that dietary supplementation with red onion extract (RO) would attenuate high fat diet (HFD)-induced obesity and insulin resistance similar to quercetin supplementation by increasing energy expenditure through a mechanism involving skeletal muscle mitochondrial adaptations. To test this hypothesis, C57BL/6J mice were randomized into four groups and fed either a low fat diet (LF), HFD (HF), HFD + quercetin (HF + Q), or HFD + RO (HF + RO) for 9 weeks. Food consumption and body weight and composition were measured weekly. Insulin sensitivity was assessed by insulin and glucose tolerance tests. Energy expenditure and physical activity were measured by indirect calorimetry. Skeletal muscle incomplete beta oxidation, mitochondrial number, and mtDNA-encoded gene expression were measured. Quercetin and RO supplementation decreased HFD-induced fat mass accumulation and insulin resistance (measured by insulin tolerance test) and increased energy expenditure; however, only HF + Q showed an increase in physical activity levels. Although quercetin and RO similarly increased skeletal muscle mitochondrial number and decreased incomplete beta oxidation, establishing mitochondrial function similar to that seen in LF, only HF + Q exhibited consistently lower mRNA levels of mtDNA-encoded genes necessary for complexes IV and V compared to LF. Quercetin- and RO-induced improvements in adiposity, insulin resistance, and energy expenditure occur through differential mechanisms, with quercetin-but not RO-induced energy expenditure being related to increases in physical activity. While both treatments improved skeletal muscle mitochondrial number and function, mtDNA-encoded transcript levels suggest that the antiobesogenic, insulin-sensitizing effects of purified quercetin aglycone, and RO may occur through differential mechanisms.

Efficacy and safety of canagliflozin monotherapy in subjects with type 2 diabetes mellitus inadequately controlled with diet and exercise

AIMS

Canagliflozin is a sodium glucose co-transporter 2 inhibitor in development for type 2 diabetes mellitus (T2DM). The efficacy and safety of canagliflozin were evaluated in subjects with T2DM inadequately controlled with diet and exercise.

METHODS

In this 26-week, randomized, double-blind, placebo-controlled, phase 3 trial, subjects (N = 584) received canagliflozin 100 or 300 mg or placebo once daily. Primary endpoint was the change from baseline in haemoglobin A1c (HbA1c) at week 26. Secondary endpoints included the proportion of subjects achieving HbA1c < 7.0%; change from baseline in fasting plasma glucose (FPG), 2-h postprandial glucose (PPG) and systolic blood pressure (BP); and percent change in body weight, high-density lipoprotein cholesterol (HDL-C) and triglycerides. Adverse events (AEs) were recorded throughout the study.

RESULTS

At week 26, HbA1c was significantly reduced from baseline with canagliflozin 100 and 300 mg compared with placebo (-0.77, -1.03 and 0.14%, respectively; p < 0.001 for both). Both canagliflozin doses significantly decreased FPG, 2-h PPG, body weight and systolic BP (p < 0.001 for all), and increased HDL-C compared with placebo (p < 0.01 for both). Overall incidences of AEs were modestly higher with canagliflozin versus placebo; rates of serious AEs and AE-related discontinuations were low and similar across groups. Incidences of genital mycotic infections, urinary tract infections and osmotic diuresis-related AEs were higher with canagliflozin; these led to few discontinuations. The incidence of hypoglycaemia was low across groups.

CONCLUSION

Canagliflozin treatment improved glycaemic control, reduced body weight and was generally well tolerated in subjects with T2DM inadequately controlled with diet and exercise.

Template to improve glycemic control without reducing adiposity or dietary fat

Drugs that improve chronic hyperglycemia independently of insulin signaling or reduction of adiposity or dietary fat intake may be highly desirable. Ad36, a human adenovirus, promotes glucose uptake in vitro independently of adiposity or proximal insulin signaling. We tested the ability of Ad36 to improve glycemic control in vivo and determined if the natural Ad36 infection in humans is associated with better glycemic control. C57BL/6J mice fed a chow diet or made diabetic with a high-fat (HF) diet were mock infected or infected with Ad36 or adenovirus Ad2 as a control for infection. Postinfection (pi), systemic glycemic control, hepatic lipid content, and cell signaling in tissues pertinent to glucose metabolism were determined. Next, sera of 1,507 adults and children were screened for Ad36 antibodies as an indicator of past natural infection. In chow-fed mice, Ad36 significantly improved glycemic control for 12 wk pi. In HF-fed mice, Ad36 improved glycemic control and hepatic steatosis up to 20 wk pi. In adipose tissue (AT), skeletal muscle (SM), and liver, Ad36 upregulated distal insulin signaling without recruiting the proximal insulin signaling. Cell signaling suggested that Ad36 increases AT and SM glucose uptake and reduces hepatic glucose release. In humans, Ad36 infection predicted better glycemic control and lower hepatic lipid content independently of age, sex, or adiposity. We conclude that Ad36 offers a novel tool to understand the pathways to improve hyperglycemia and hepatic steatosis independently of proximal insulin signaling, and despite a HF diet. This metabolic engineering by Ad36 appears relevant to humans for developing more practical and effective antidiabetic approaches.

Intrahepatic and intramyocellular lipids are determinants of insulin resistance in prepubertal children

AIMS/HYPOTHESIS

We hypothesised that ectopic fat deposition is present in liver and skeletal muscle before puberty and that both are potentially important factors in the early pathogenesis of insulin resistance.

METHODS

Proton magnetic resonance spectroscopy was used to evaluate intramyocellular and intrahepatic lipids in 50 male and 42 female multi-ethnic, prepubertal (Tanner < 2) children (8.1 ± 0.8 years; 35.4 ± 10.7 kg; 27.9 ± 8.3% body fat; means ± SD). Intramyocellular lipid was measured in soleus muscle and intrahepatic lipid in the middle right lobe. Abdominal fat was measured by magnetic resonance imaging, body fat by dual energy X-ray absorptiometry, and insulin resistance using homeostatic model assessment.

RESULTS

Intrahepatic lipid ranged from 0.11% to 4.6% relative to the liver water signal (mean 0.79 ± 0.79%) whereas intramyocellular lipid ranged from 0.13% to 1.86% relative to the muscle water signal (mean 0.51 ± 0.28%). Intramyocellular and intrahepatic lipids were significantly correlated with total adiposity (r = 0.49 and 0.59), abdominal adiposity (r = 0.44 and 0.54), and each other (r = 0.39, p < 0.05, Spearman). Both intramyocellular and intrahepatic lipid were positively correlated with fasting insulin (r = 0.37 and 0.38 respectively) and insulin resistance (r = 0.37 and 0.37; p < 0.01). After adjustment for race and sex, the relations between ectopic fat and insulin resistance remained, whereas both disappeared when further adjusted for body fat or BMI z scores.

CONCLUSIONS/INTERPRETATIONS

These results suggest that typical relations between body composition, ectopic fat and insulin resistance are present in children before puberty. Thus, interventions aimed at reducing adiposity have the potential to decrease ectopic fat accumulation, delay the onset of insulin resistance and decrease the risk for development of type 2 diabetes in children.

Efficacy and safety of sitagliptin when added to insulin therapy in patients with type 2 diabetes

OBJECTIVE

To evaluate the efficacy and tolerability of sitagliptin when added to insulin therapy alone or in combination with metformin in patients with type 2 diabetes.

METHODS

After a 2 week placebo run-in period, eligible patients inadequately controlled on long-acting, intermediate-acting or premixed insulin (HbA1c > or = 7.5% and < or = 11%), were randomised 1:1 to the addition of once-daily sitagliptin 100 mg or matching placebo over a 24-week study period. The study capped the proportion of randomised patients on insulin plus metformin at 75%. Further, the study capped the proportion of randomised patients on premixed insulin at 25%. The metformin dose and the insulin dose were to remain stable throughout the study. The primary endpoint was HbA1c change from baseline at week 24.

RESULTS

Mean baseline characteristics were similar between the sitagliptin (n = 322) and placebo (n = 319) groups, including HbA1c (8.7 vs. 8.6%), diabetes duration (13 vs. 12 years), body mass index (31.4 vs. 31.4 kg/m(2)), and total daily insulin dose (51 vs. 52 IU), respectively. At 24 weeks, the addition of sitagliptin significantly (p < 0.001) reduced HbA1c by 0.6% compared with placebo (0.0%). A greater proportion of patients achieved an HbA1c level < 7% while randomised to sitagliptin as compared with placebo (13 vs. 5% respectively; p < 0.001). Similar HbA1c reductions were observed in the patient strata defined by insulin type (long-acting and intermediate-acting insulins or premixed insulins) and by baseline metformin treatment. The addition of sitagliptin significantly (p < 0.001) reduced fasting plasma glucose by 15.0 mg/dl (0.8 mmol/l) and 2-h postmeal glucose by 36.1 mg/dl (2.0 mmol/l) relative to placebo. A higher incidence of adverse experiences was reported with sitagliptin (52%) compared with placebo (43%), due mainly to the increased incidence of hypoglycaemia (sitagliptin, 16% vs. placebo, 8%). The number of hypoglycaemic events meeting the protocol-specified criteria for severity was low with sitagliptin (n = 2) and placebo (n = 1). No significant change from baseline in body weight was observed in either group.

CONCLUSION

In this 24-week study, the addition of sitagliptin to ongoing, stable-dose insulin therapy with or without concomitant metformin improved glycaemic control and was generally well tolerated in patients with type 2 diabetes.

Failure of dietary quercetin to alter the temporal progression of insulin resistance among tissues of C57BL/6J mice during the development of diet-induced obesity

AIMS/HYPOTHESES

High-fat diets produce obesity and glucose intolerance by promoting the development of insulin resistance in peripheral tissues and liver. The present studies sought to identify the initial site(s) where insulin resistance develops using a moderately high-fat diet and to assess whether the bioflavonoid, quercetin, ameliorates progression of this sequence.

METHODS

Four cohorts of male C57BL/6J mice were placed on diets formulated to be low-fat (10% of energy from fat), high-fat (45% of energy from fat) or high-fat plus 1.2% quercetin (wt/wt). After 3 and 8 weeks, cohorts were evaluated using euglycaemic-hyperinsulinaemic clamps, metabolomic analysis of fatty acylcarnitines and acute in vitro assessments of insulin signalling among tissues.

RESULTS

After 3 and 8 weeks, the high-fat diet produced whole-body insulin resistance without altering insulin-dependent glucose uptake in peripheral tissues. The primary defect was impaired suppression of hepatic glucose production by insulin at both times. Quercetin initially exacerbated the effect of high-fat diet by further increasing hepatic insulin resistance, but by 8 weeks insulin resistance and hepatic responsiveness to insulin were similarly compromised in both high-fat groups. The high-fat diet, irrespective of quercetin, increased short-chain fatty acylcarnitines in liver but not in muscle, while reciprocally reducing hepatic long-chain fatty acylcarnitines and increasing them in muscle.

CONCLUSIONS/INTERPRETATION

Failure of insulin to suppress hepatic glucose output is the initial defect that accounts for the insulin resistance that develops after short-term consumption of a high-fat (45% of energy) diet. Hepatic insulin resistance is associated with accumulation of short- and medium-, but not long-chain fatty acylcarnitines. Dietary quercetin does not ameliorate the progression of this sequence.

Pharmacotherapy for the treatment of patients with type 2 diabetes mellitus: rationale and specific agents

Type 2 diabetes, the most common form of diabetes, is characterized by abnormalities in hepatic glucose production, insulin resistance, and a progressive decline in beta-cell function over time. To treat effectively the individual with type 2 diabetes, the provider must have a thorough understanding of the underlying pathophysiology to provide treatment that precisely addresses the metabolic abnormalities. Currently, the provider who cares for subjects with type 2 diabetes can choose an antidiabetic agent from no less than eight pharmacologic classes. These classes include agents that increase insulin secretion, improve insulin action, and delay absorption of carbohydrates. The newer treatments available, specifically incretin therapy, address a previously unmet need in diabetes by modulating glucose supply. The currently available agents can be combined and combination therapy markedly improves glycemic control. This allows the provider to design regimens to specifically address underlying abnormalities. A review of all currently available agents is provided.

Antihyperglycemic activity of Tarralin, an ethanolic extract of Artemisia dracunculus L

The studies reported here were undertaken to examine the antihyperglycemic activity of an ethanolic extract of Artemisia dracunculus L., called Tarralin in diabetic and non-diabetic animals. In genetically diabetic KK-A(gamma) mice, Tarralin treatment by gavage (500 mg/kg body wt./day for 7 days) lowered elevated blood glucose levels by 24% from 479+/-25 to 352+/-16 mg/dl relative to control animals. In comparison, treatment with the known antidiabetic drugs, troglitazone (30 mg/kg body wt./day) and metformin (300 mg/kg body wt./day), decreased blood glucose concentrations by 28% and 41%, respectively. Blood insulin concentrations were reduced in the KK-A(gamma) mice by 33% with Tarralin, 48% with troglitazone and 52% with metformin. In (STZ)-induced diabetic mice, Tarralin treatment, (500 mg/kg body wt./day for 7 days), also significantly lowered blood glucose concentrations, by 20%, from 429+/-41 to 376+/-58 mg/dl relative to control. As a possible mechanism, Tarralin was shown to significantly decrease phosphoenolpyruvate carboxykinase (PEPCK) mRNA expression by 28% in STZ-induced diabetic rats. In non-diabetic animals, treatment with Tarralin did not significantly alter PEPCK expression, blood glucose or insulin concentrations. The extract was also shown to increase the binding of glucagon-like peptide (GLP-1) to its receptor in vitro. These results indicate that Tarralin has antihyperglycemic activity and a potential role in the management of diabetic states.

Effects of insulin sensitizers on plaque vulnerability associated with elevated lipid content in atheroma in ApoE-knockout mice

Acute coronary syndromes are generally precipitated by rupture of lipid-laden, relatively acellular, vulnerable atherosclerotic plaques with thin fibrous caps. We investigated whether a high-fat diet alters insulin sensitivity and whether insulin sensitizers (troglitazone and rosiglitazone) alter the composition of otherwise lipidladen atherosclerotic plaques in mice deficient in apolipoprotein E (ApoE). ApoE-knockout mice were fed a high-fat (n=30) or standard chow (n=10) diet for two weeks. Thereafter, those fed the high-fat diet were treated with troglitazone (n=10), rosiglitazone (n=10) or no drug (n=10) for 16 weeks beginning at 8 weeks of age. Carbohydrate metabolism was assessed with intraperitoneal glucose tolerance tests and insulin tolerance tests. Plaque composition was characterised with confocal laser scanning microscopy. The high-fat diet induced insulin resistance in the absence of weight gain. Compared with control animals on the high-fat diet, animals given troglitazone (400 mg/kg/day) or rosiglitazone (4 mg/kg/day) had significantly less area under the curve (AUC) for insulin ( p<0.05) and glucose disposal ( p<0.05). Despite significant increases in insulin sensitivity with drug treatment, no change in HDL-cholesterol and triglyceride levels, nor reduction in atheroma size or lipid content was noted. Thus, improvement in insulin resistance induced by a high-fat diet in this animal model of vasculopathy did not alter plaque composition.

Novel routes of insulin delivery for patients with type 1 or type 2 diabetes

Subcutaneous insulin has been used to treat diabetes since the 1920s; however, despite a number of different formulations, intensive insulin therapy with multiple daily injections has not gained widespread clinical acceptance. Attempts to find effective, well-tolerated, nonenteral routes for delivering insulin began in the 1920s, and, over the years, have included ocular, buccal, rectal, vaginal, oral, nasal and uterine delivery systems. Until recently, many researchers believed that insulin delivered noninvasively was associated with too low a bioavailability to offer a realistic clinical approach. However, a growing body of evidence suggests that inhaled insulin is an effective, well-tolerated, noninvasive alternative to subcutaneous regular insulin. Critically, inhaled insulin shows a more physiological insulin profile than that seen with conventional insulin. Further studies are needed to confirm long-term efficacy and pulmonary safety, to compare the different approaches, and to characterize better their relative places in practice. As a result of the recognition of the importance of tighter control of glycaemia and the growing number of patients with type 2 diabetes who receive insulin, inhaled insulin could become an increasingly integral part of managing diabetes.

Caloric restriction lowers plasma lipoprotein (a) in male but not female rhesus monkeys

Many age-associated pathophysiological changes are retarded by caloric restriction (CR). The present study has investigated the effect of CR on plasma lipoprotein (a) [Lp(a)], an independent risk factor for the age-associated process of atherosclerosis. Rhesus monkeys were fed a control diet (n=19 males, 12 females) or subjected to CR (n=20 males, 11 females fed 30% less calories) for >2 years. All female animals were premenopausal. Plasma Lp(a) levels in control animals were almost two fold higher for males than females (47+/-9 vs 25+/-5mg/dl mean+/-SEM, p=0.05). CR resulted in a reduction in circulating Lp(a) in males to levels similar to those measured in calorie-restricted females, (27+/-5 vs 24+/-4 mg/dl mean+/-SEM). For all animals, plasma Lp(a) was correlated with total cholesterol (r=0.27, p=0.03) and LDL cholesterol (r=0.50, p=0.0001) whether unadjusted or after adjustment for treatment, gender or group. These studies introduce a new mechanism whereby CR may have a beneficial effect on risk factors for the development of atherosclerosis in primates.

Determinants of insulin-stimulated glucose disposal in middle-aged, premenopausal women

Controversy exists regarding the relative importance of adiposity, physical fitness, and physical activity in the regulation of insulin-stimulated glucose disposal. To address this issue, we measured insulin-stimulated glucose disposal [mg. kg fat-free mass (FFM)(-1). min(-1); oxidative and nonoxidative components] in 45 nondiabetic, nonobese, premenopausal women (mean +/- SD; 47 +/- 3 yr) by use of hyperinsulinemic euglycemic clamp (40 mU. m(-2). min(-1)) and [6,6-2H2]glucose dilution techniques. We also measured body composition, abdominal fat distribution, thigh muscle fat content, maximal oxygen consumption (VO2 max), and physical activity energy expenditure ((2)H(2)(18)O kinetics) as possible correlates of glucose disposal. VO2 max was the strongest correlate of glucose disposal (r = 0.63, P < 0.01), whereas whole body and abdominal adiposity showed modest associations (range of r values from -0.32 to -0.46, P < 0.05 to P < 0.01). A similar pattern of correlations was observed for nonoxidative glucose disposal. None of the variables measured correlated with oxidative glucose disposal. The relationship of VO2 max to glucose disposal persisted after statistical control for FFM, percent body fat, and intra-abdominal fat (r = 0.40, P < 0.01). In contrast, correlations of total and regional adiposity measures to insulin sensitivity were no longer significant after statistical adjustment for VO2 max. VO2 max was the only variable to enter stepwise regression models as a significant predictor of total and nonoxidative glucose disposal. Our results highlight the importance of VO2 max as a determinant of glucose disposal and suggest that it may be a stronger determinant of variation in glucose disposal than total and regional adiposity in nonobese, nondiabetic, premenopausal women.

Insulin resistance: cellular and clinical concepts

Insulin resistance is defined as a clinical state in which a normal or elevated insulin level produces an attenuated biologic response. Specifically, the biologic response most studied is insulin-stimulated glucose disposal, yet the precise cellular mechanism responsible is not yet known. However, the presence of insulin resistance is observed many years before the onset of clinical hyperglycemia and the diagnosis of Type 2 diabetes. Insulin resistance at this stage appears to be significantly associated with a clustering of cardiovascular risk factors predisposing the individual to accelerated cardiovascular disease. An overview of insulin resistance and the associated clinical insulin resistant state will be discussed.

The use of hormone replacement therapy in postmenopausal women with type 2 diabetes

In healthy postmenopausal women, estrogen or hormone replacement therapy (ERT or HRT) can alleviate menopausal symptoms and prevent osteoporosis and may also protect against cardiovascular disease (CVD). In addition to improving lipid metabolism, there are reports that estrogen also improves parameters regulating carbohydrate metabolism, including insulin resistance, in healthy women. Therefore, it is likely that ERT or HRT would also benefit women with type 2 diabetes, not only in relieving menopausal symptoms but also in improving the metabolic abnormalities associated with diabetes and in preventing cardiovascular disease.

Inhaled human insulin treatment in patients with type 2 diabetes mellitus

BACKGROUND

Despite demonstrated benefits, intensive insulin therapy has not gained widespread clinical acceptance for several reasons: Multiple daily injections are inconvenient, adherence is a concern, and the time-activity profile may not mimic normal insulin secretion. As such, alternate means of administering insulin are being evaluated.

OBJECTIVE

To assess the efficacy and safety of pulmonary delivery of insulin in type 2 diabetic patients who require insulin.

DESIGN

Randomized, open-label, 3-month study consisting of a screening visit, a 4-week baseline lead-in phase, and a 12-week treatment phase.

SETTING

General clinical research center and outpatient research clinics.

PATIENTS

26 patients (16 men, 10 women) with type 2 diabetes (average age, 51.1 years; average duration of diabetes, 11.2 years).

INTERVENTION

Patients received inhaled insulin before each meal plus a bedtime injection of ultralente insulin, performed home glucose monitoring, and had weekly adjustment of insulin dose; target level for preprandial plasma glucose was 5.55 to 8.88 mmol/L (100 to 160 mg/dL).

MEASUREMENTS

Glycemic control (hemoglobin A(1c) level) obtained at baseline and monthly for 3 months. Pulmonary function tests were done at baseline and at the end of the study.

RESULTS

Inhaled insulin treatment for 3 months significantly improved glycemic control compared with baseline: Mean hemoglobin A(1c) levels decreased by 0.0071 +/- 0.0072 (0.71% +/- 0.72%). Patients experienced an average of 0.83 mild to moderate hypoglycemic event per month; no severe events were recorded. Patients showed no significant weight gain or change in pulmonary function compared with baseline.

CONCLUSIONS

Pulmonary delivery of insulin in type 2 diabetic patients who require insulin improved glycemic control, was well tolerated, and demonstrated no adverse pulmonary effects. Larger-scale studies are ongoing to provide long-term efficacy and safety data.

Efficacy of inhaled human insulin in type 1 diabetes mellitus: a randomised proof-of-concept study

BACKGROUND

Effective glycaemic control in type 1 diabetes mellitus usually requires two or more insulin injections daily. Inhaled intrapulmonary delivery of insulin offers a potential new way to deliver meal-related insulin, eliminating the need for preprandial injections.

METHODS

73 patients with type 1 diabetes mellitus were studied in an open-label, proof-of-concept, parallel-group randomised trial. Patients in the experimental group received preprandial inhaled insulin plus a bedtime subcutaneous ultralente insulin injection. Patients in the control group received their usual insulin regimen of two to three injections per day. Participants monitored their blood glucose four times daily, and adjusted insulin doses weekly to achieve preprandial glucose targets of 5.6-8.9 mmol/L. The primary outcome measure was change in glycosylated haemoglobin (HbA1c) after 12 weeks. Secondary outcomes were fasting and postprandial glucose response to a mixed meal; hypoglycaemia frequency and severity; pulmonary function; and patients' satisfaction.

FINDINGS

Changes in HbA1c were indistinguishable between groups (difference 0.2% [95% CI -0.2 to 0.5]). Changes in fasting and postprandial glucose concentrations, and occurrence and severity of hypoglycaemia were also similar between groups. Inhaled insulin was well tolerated and had no effect on pulmonary function (ie, spirometry, lung volumes, diffusion capacity, and oxygen saturation).

INTERPRETATION

This proof-of-concept study shows that preprandial insulin can be given by inhalation in individuals with insulin-deficient type 1 diabetes as a less invasive alternative to conventional preprandial insulin injections.

Naturally occurring and experimental diabetes in cynomolgus monkeys: a comparison of carbohydrate and lipid metabolism and islet pathology

Diabetes is a major health problem of increasing incidence in the United States. Diabetes research has been limited by lack of availability of good animal models, particularly for the study of comorbidities associated with diabetes. We investigated the use of cynomolgus monkeys as an animal model of both type 1 and type 2 diabetes and compared these naturally occurring diseases with streptozotocin-induced diabetes. Both type 1 diabetics and streptozotocin-induced diabetics present with sudden onset of hyperglycemia and are ketosis prone without exogenous insulin. Type 2 diabetics can have a very long period of moderate hyperglycemia and hypertriglyceridemia and only require exogenous insulin therapy if pancreatic islet reserves are depleted. Type 2 diabetes is preceded by a relatively long period of insulin resistance that is associated with obesity and dyslipidemia. As insulin resistance progresses, islet size and insulin content increases initially. However, with sustained periods of insulin resistance, islet amyloid polypeptide (IAPP) is deposited in islets and can replace normal islet architecture, resulting in an insulin-deficient state. Appearance of IAPP also occurs in human type 2 diabetics but not in conventional rodent models. Unlike type 2 diabetes, neither type 1 nor streptozotocin-induced diabetes is associated with IAPP. Rather, islets can appear normal histologically, but have decreased insulin secretion and immunostaining. Further, the amount of insulin present in the islet is correlated with plasma insulin levels following glucose challenge. Studies are ongoing to determine the pathogenic changes associated with the progression of diabetes and to find novel drug treatments for diabetics.

In vitro oxidation of low-density lipoprotein in two species of nonhuman primates subjected to caloric restriction

Caloric restriction (CR), which increases longevity and retards age-associated diseases in laboratory rodents, is being evaluated in nonhuman primate trials. CR reduces oxidative stress in rodents and appears to improve risk factors for cardiovascular disease in nonhuman primates. We tested the hypothesis that low-density lipoprotein (LDL) oxidizability is reduced in two monkey species (rhesus and cynomolgus) subjected to chronic CR. In both species, no significant differences occurred between CR and control animals on total, LDL, or high-density lipoprotein (HDL) cholesterol. In rhesus monkeys, triglycerides were higher in controls than CR (139 +/- 23 vs 66 +/- 8 mg/dl,p < .01, respectively). LDL from CR rhesus monkeys was reduced in triglyceride content and molecular weight compared to controls, whereas LDL composition in cynomolgus monkeys was similar in CR and control animals. In keeping with minor deviations in lipids, antioxidants, and LDL composition, no consistent differences in in vitro LDL oxidizability were apparent between CR and controls in either species.

Chronic caloric restriction alters muscle membrane fatty acid content

Chronic caloric restriction (CR) has been demonstrated to increase longevity in lower species and studies are ongoing to evaluate its effect in higher species. A consistent metabolic feature of CR is improved insulin sensitivity and lowered lifetime glycemia, yet the mechanism responsible is currently unknown. However, the membrane's physiochemical properties, as determined by phospholipid composition, have been related to insulin action in animal and human studies and CR has been reported to alter membrane lipid content. We evaluated muscle membrane fatty acid content in rodents randomized to CR versus control diets for up to 29 months. CR was observed to increase the membrane content of C22:6 (docosahexaenoate) and to decrease C18:2 content. The membrane lipid content was related to insulin levels but not to parameters assessing glycemic control. This study suggests that membrane lipids, in particular 22:6, may contribute to the variation in insulin sensitivity seen with age.

Pleiotropic effects of growth hormone and insulin-like growth factor (IGF)-1 on biological aging: inferences from moderate caloric-restricted animals

Moderate caloric restriction (60% of ad libitum intake) is an important model to investigate potential mechanisms of biological aging. This regimen has been reported to decrease the number of pathologies and increase life span in all species tested to date. Although moderate caloric restriction induces a wide range of physiological changes within the organism, adaptive changes within the endocrine system are evident and serve to maintain blood levels of glucose. These alterations include an increase in growth hormone secretory dynamics and a decline in plasma levels of IGF-1. These endocrine compensatory mechanisms can be induced at any age, and we have proposed that these alterations mediate some of the beneficial aspects of moderate caloric restriction. Numerous studies indicate that growth hormone and IGF-1 decrease with age and that administration of these hormones ameliorates the deterioration of tissue function evident in aged ad libitum-fed animals, suggesting that the absence of these hormones contributes to the phenotype of aging. Nevertheless, IGF-1 is an important risk factor in age-related pathologies including lung, breast, and prostate cancer. From these studies, we propose that endocrine compensatory mechanisms induced by moderate caloric restriction (including increased growth hormone and decreased IGF-1) decrease the stimulus for cellular replication, resulting in a decline in pathologies and increased life span observed in these animals. These findings have important implications for potential mechanisms of moderate caloric restriction and suggest that neuroendocrine compensatory mechanisms exert a key role on the actions of moderate caloric restriction on life span.

Influence of caloric restriction on the development of atherosclerosis in nonhuman primates: progress to date

Caloric restriction (CR) has been observed to retard aging processes and extend the maximum life span in rodents. In an effort to evaluate the effect of this nutritional intervention on physiologic variables in higher species, several nonhuman primate trials are ongoing. In particular, a study evaluating the independent effect of CR on the extent of atherosclerosis was initiated in 1993 in 32 adult cynomolgus monkeys. Therefore, the trial was designed to achieve identical cholesterol intake after animals were randomized to a control group or a calorie-restricted group (30% reduction from baseline caloric intake). The animals were routinely evaluated for glycated proteins, plasma insulin and glucose levels, insulin sensitivity, and specific measures for abdominal fat distribution by CT scans over a 4-year interval. The results from 4 years of intervention demonstrate that CR improves cardiovascular risk factors (such as visceral fat accumulation) and improves insulin sensitivity. In contrast to other primate studies with normolipidemic animals, CR had no independent effects on plasma lipid levels and composition in the presence of equivalent amounts of dietary cholesterol intake. Preliminary analysis of atherosclerotic lesion extent in the abdominal aorta has failed to demonstrate differences between control animals and CR animals. Follow-up studies are being conducted to determine the effect of CR on atherosclerosis extent in coronary and carotid arteries.

Glycation of plasma low density lipoproteins increases interaction with arterial proteoglycans

The increased susceptibility to atherosclerosis of diabetic individuals, may result from diabetes-associated modification in plasma low density lipoproteins (LDL) which enhance their interaction with arterial extracellular matrix proteoglycans. Using a nonhuman primate model for human diabetes, studies were conducted to examine diabetes-induced changes in LDL. Plasma LDL were isolated from control (n = 4) and streptozotocin-induced diabetic (n = 3) cynomolgus macaques by differential ultracentrifugation. An in vitro binding assay was used to measure LDL interaction with arterial proteoglycans. Significantly more diabetic LDL bound to proteoglycans than control LDL (12.9+/-0.7 microg LDL cholesterol/microg proteoglycan versus 8.9+/-0.5 microg LDL cholesterol/microg proteoglycan (mean +/- S.E.M.), P < 0.005). Glycation of LDL, determined by fructosamine content, was significantly enhanced in diabetic versus control animals (37+/-3.1 versus 20+/-1.5 micromol/l (mean +/- S.E.M.) P < 0.005). The correlation coefficient between fructosamine content of LDL and its binding to arterial proteoglycans was 0.95. No LDL compositional variables other than glycation correlated with proteoglycan binding. Removal of the glycated portion of LDL from diabetic animals returned LDL proteoglycan binding to normal. These data demonstrate that the diabetes induced glycation of LDL increases its proteoglycan binding properties: thus, a critical mechanism in atherosclerosis, enhanced LDL interaction with arterial proteoglycans, may be accelerated by the diabetic state.

Beta-cell function during insulin-modified intravenous glucose tolerance test successfully assessed by the C-peptide minimal model

The insulin-modified intravenous glucose tolerance test (IM-IVGTT) is increasingly used to measure insulin sensitivity. However, the assessment of beta-cell secretion is usually made using rough indices. The aim here is to evaluate the ability of the minimal model of C-peptide secretion and kinetics recently proposed for the standard IVGTT (S-IVGTT) to also assess beta-cell function during the IM-IVGTT. C-peptide and glucose data from the IM-IVGTT in 15 normal humans were analyzed. The results show that the same rich beta-cell picture from the S-IVGTT can be obtained during an IM-IVGTT. In particular, in each individual, the time course of beta-cell secretion can be reconstructed and the functional indices of glucose control on first-phase (phi1), second-phase (phi2), and basal (phi(b)) insulin secretion can be estimated (phi1 = 191 +/- 29, phi2 = 10.9 +/- 1.4 x 10(-9) x min(-1), and phi(b) = 5.7 +/- 1.0 x 10(-9) x min(-1), mean +/- SE). Finally, the comparison between IM-IVGTT and S-IVGTT phi1, phi2, and phi(b) values suggest they are not affected by insulin administration.

Increased nonenzymatically glycosylated proteins in the vitreous humor of diabetic animals

One of the earliest pathologic changes of diabetes mellitus is increased nonenzymatic glycosylation (i.e., glycation) of proteins, which results in abnormal aggregation of collagen fibrils and production of superoxide radicals. These abnormalities may be responsible for the precocious senescence of connective tissue associated with the disease. We sought to determine whether glycation is increased in the vitreous humor of short-term diabetic cats (6 months' duration) and rabbits (2 months' duration), using a nitroblue tetrazolium colorimetric assay for fructosamine. Vitreous protein fructosamine concentration was significantly higher in diabetic cats and rabbits, compared with that in control (nondiabetic) animals. These results indicate that glycation is increased in the vitreous humor of short-term diabetic animals, and therefore may be one of the initial triggers for clinically apparent diabetic retinopathy.

Clinical validity of a self-test fructosamine in outpatient diabetic management

BACKGROUND

Measurement of glycated hemoglobin and hemoglobin A1c (HbA1c) is now well established as the best means of measuring overall glucose control in managing diabetes. Other glycated serum protein assays reflecting recent glycemic control, e.g., glycated albumin and glycated protein (fructosamine), have also been validated in clinical studies. Regardless of the method, the expense and inconvenience of laboratory testing of blood samples may contribute to the well-documented underutilization of clinical glycated protein assessment. Accordingly, a rapid, inexpensive fingerstick test of fructosamine has been developed. This study cross-sectionally and prospectively assesses the clinical validity of fingerstick fructosamine versus laboratory determination.

METHODS

Fifty-one subjects (18 control, 33 with diabetes) participated in a cross-sectional study and 20 subjects with type 2 diabetes participated in a prospective, 6-week study with clinical intervention consisting of glipizide gits or metformin in mono- and combination therapy. Subjects had weekly laboratory determination of serum fructosamine, glycated hemoglobin, and fasting glucose; fingerstick fructosamine was obtained at each clinic visit.

RESULTS

Fingerstick fructosamine was shown to correlate highly to laboratory fructosamine (r = 0.80, p < 0.001) and glycated hemoglobin (r = 0.81, p < 0.001). In the clinical intervention study subjects, significant decreases in fasting glucose (p < 0.001), laboratory fructosamine (p < 0.001), and fingerstick fructosamine (p < 0.001) were noted compared to baseline. The subject's self-test fingerstick fructosamine mirrored laboratory testing of fructosamine in detection of changes in clinical glucose control.

CONCLUSIONS

This study demonstrates that fingerstick fructosamine correlates well to laboratory assessment of fructosamine and glycated hemoglobin. The patient self-test fructosamine provides the same clinical information as laboratory assessment.

Caloric restriction in rhesus monkeys reduces low density lipoprotein interaction with arterial proteoglycans

Caloric restriction (CR) has been shown to retard aging processes in many species. We investigated effects of CR on plasma low density lipoproteins (LDL), a major risk factor for the age-associated process of atherosclerosis. Studies emphasized effects of CR on LDL composition and their interaction with arterial proteoglycans (PG). Rhesus monkeys were fed a control diet (n=13) or subjected to CR (n=12 fed 30% less calories) for > 5 years. Plasma LDL cholesterol concentrations were similar for control and CR groups (82+/-8 vs 72+/-6 mg/dL, mean+/-SEM). LDL was isolated by ultracentrifugation and HPLC. LDL particles from CR animals had a lower molecular weight (2.9+/-0.1 vs 3.2+/-0.1 g/micromol, p < .05) and were depleted in triglyceride (249+/-16 vs 433+/-49 mol/particle, p < .005) and phospholipid (686+/-20 vs 837+/-33 mol/particle, p <.001). Lower PG binding was measured for LDL from CR animals (10.1+/-0.8 vs 15.6+/-1.1 microg LDL cholesterol/microg PG, p <.005). This was associated with the lower triglycerides (r=.76, p < .0005) and phospholipids (r=.48, p < .01). Thus, a dietary intervention which may retard aging inhibits a proposed mechanism of atherogenesis.

Chronic hyperglycemia increases arterial low-density lipoprotein metabolism and atherosclerosis in cynomolgus monkeys

Diabetes mellitus confers a threefold to fivefold increased risk of mortality from vascular disease. The primary cause of this increased incidence of vascular disease is atherosclerosis, but the mechanisms accounting for the increase are unclear. Chronic hyperglycemia is a common feature of all forms of diabetes mellitus and may contribute greatly to the increased incidence of atherosclerosis, via promotion of both lipoprotein and tissue glycation, which may have atherogenic effects. The present study investigated the effect of chronic hyperglycemia on measures of low-density lipoprotein (LDL) metabolism and atherosclerosis in streptozotocin-induced diabetic (STZ-DM) and control cynomolgus monkeys after 6 months of study. Consistent with a chronic hyperglycemic state, diabetic monkeys had significant increases in glycated hemoglobin (GHb) and glycated plasma LDL concentrations, but had minimal changes in total plasma cholesterol (TPC) or triglyceride (TG) concentrations during the study. Forty-eight hours before necropsy, control and in vitro-glycated LDL were differentially radiolabeled and coinjected into diabetic and control monkeys. There was a significant increase in arterial LDL accumulation in femoral arteries from diabetic monkeys compared with controls, with similar trends in other arterial sites. The effect of LDL glycation on arterial LDL accumulation was minimal in both groups. Arterial segments from diabetic monkeys also had greater amounts of arterial cholesterol content compared with controls. Histomorphometric analyses showed that diabetic monkeys had significantly greater intimal areas in the femoral artery and abdominal aorta compared with controls. Diabetic monkeys also had reduced arterial remodeling, or compensation, in the femoral artery and abdominal aorta. However, there was no difference in advanced glycation end products (AGE) in arterial collagen between groups. In conclusion, experimentally induced diabetes mellitus increases arterial LDL accumulation and atherosclerosis extent in cynomolgus monkeys before changes in AGE formation. The increased atherogenesis may be due to changes in lipoproteins or direct effects of hyperglycemia on the artery wall.

Insulin resistance and fat patterning with aging: relationship to metabolic risk factors for cardiovascular disease

Both insulin resistance and abdominal fat patterning are related to aging, and have been related to cardiovascular disease (CVD) risk factors such as dyslipidemia and hypertension. However, previous studies have not used direct methods to quantify the independent strength of the association of each of these two putative primary factors with metabolic outcomes. We quantified overall obesity by the body mass index (BMI) and used a previously validated magnetic resonance imaging (MRI) method to quantify abdominal fat in 63 healthy nondiabetic individuals aged 22 to 83 years. We also measured the glucose and insulin response to an oral glucose tolerance test and the insulin sensitivity ([SI] by modified minimal model analysis). Body fat patterning was evaluated by the waist to hip ratio (WHR) and by MRI, which allowed direct measurement of subcutaneous (SCF) and intraabdominal (IAF) fat depots at the umbilicus in these subjects. These independent parameters were related to risk factors for CVD (blood pressure, lipids, and lipoproteins) and to plasma concentrations of free fatty acids (FFAs). Measures of overall obesity (BMI), total fat [TF], and/or SCF measured at the abdomen by MRI), glucose/insulin metabolism and SI, and central fat patterning (WHR or IAF measured by MRI) were correlated with mean arterial pressure (MAP), triglyceride (TG), and high-density lipoprotein cholesterol (HDL-C) levels in univariate analysis and after controlling for age and gender. An index of central fat patterning (WHR) added to the informativeness of the insulin area under the curve (IAUC) in explaining 24% of the variability in plasma TG concentration, but measures of overall obesity were not independently related. Both the BMI and TF contributed to the IAUC in explaining 32% to 34% of the variability in MAP, but central fat patterning was not independently related. No index of overall obesity, fat patterning, glucose/insulin metabolism, and/or SI, was independently related to the plasma concentration of HDL-C after controlling for any one of the other two. Direct measurement of glucose/insulin metabolism and SI, as well as fat patterning, provides information on their relative associations with CVD risk factors. The measures of glucose/insulin metabolism and SI were more consistently related to dyslipidemia and hypertension than were the overall obesity and fat patterning in this healthy population.

Streptozotocin-induced diabetes mellitus in cynomolgus monkeys: changes in carbohydrate metabolism, skin glycation, and pancreatic islets

Chronic hyperglycemia has been implicated in a number of diabetes mellitus-related conditions in the human population, including retinopathy, neuropathy, nephropathy, and vasculopathy. However, it has been difficult to evaluate the effect of long-term hyperglycemia in a research setting because of the disease's slow progression. In this study, we used streptozotocin (30 mg/kg of body weight, intravenously) to induce a state of chronic hyperglycemia in eight cynomolgus monkeys, and compared these monkeys with a matched control group (n = 8). Seven of eight monkeys with streptozotocin-induced diabetes required insulin therapy to avoid ketosis. After disease induction, all diabetic monkeys had significantly higher preprandial plasma glucose and glycated hemoglobin values, compared with their baseline values or values for control monkeys. Diabetic monkeys also had abnormal responses to an intravenous glucose tolerance test. Consistent with the chronic hyperglycemic state and formation of advanced glycation end products, diabetic monkeys had a significant increase in skin fluorescence over the course of the 6-month study. Plasma triglyceride and cholesterol concentrations increased, but not significantly so, in the diabetic monkeys after disease induction and were not significantly different from concentrations in control monkeys. Six months after disease induction, monkeys were necropsied, and immunohistochemical staining for insulin in the pancreatic islets indicated that diabetic monkeys had a significantly decreased amount of staining for the hormone. The percentage of islet insulin staining was significantly correlated with physiologic responses to the postinduction intravenous glucose tolerance test in all monkeys. Because cynomolgus monkeys are well-characterized models of atherosclerosis, this model may be useful for determining mechanisms whereby diabetes mellitus increases cardiovascular disease.

Insulin sensitivity and cardiovascular risk factors in ovariectomized monkeys with estradiol alone or combined with nomegestrol acetate

We have previously shown that medroxyprogesterone acetate (MPA), either alone or combined with conjugated equine estrogens (CEE), significantly decreased insulin sensitivity (SI), compared with both untreated controls and those treated with CEE alone. The purpose of this study was to determine the effects of estradiol (E2), with and without nomegestrol acetate (NA; a potent progestin that lacks androgenic activity), on SI and arterial antioxidant activity, as determined by F2-isoprostanes. Thirty-six adult female cynomolgus monkeys (Macaca fascicularis) were ovariectomized and fed a moderately atherogenic diet, with one of the following three treatments added to the diet, for 12 weeks: 1) no treatment (control); 2) E2; or 3) continuous combined E2 + NA (E2+NA). SI and glucose effectiveness were assessed by the frequently sampled i.v. glucose tolerance test using a third-phase insulin infusion after 10 weeks of treatment. Cholesterol content and F2-isoprostanes were measured in the thoracic aorta after 12 weeks of treatment. E2 treatment resulted in a significantly greater SI, compared with control or E2+NA-treated monkeys (10.03 +/- 0.91 vs. 6.35 and 6.49 x 10(-4) min(-1) microU(-1) mL; P < 0.05). In contrast to our studies of CEE and MPA, E2+NA treatment, though reducing the SI below that of the E2 group, did not reduce the SI below that of control monkeys. As expected, the short period of treatment resulted in no significant differences in aortic cholesterol content. There was no treatment effect on total F2-isoprostanes (representing F2-isoprostane formation caused primarily by autooxidation), suggesting minimal antioxidant activity. However, there was a treatment difference in the prostaglandin F2alpha (PGF2alpha) isomer (a prostaglandin (PG) isomer formed by both autooxidation of arachidonate and cyclooxygenase activity). PGF2alpha concentrations were 32% lower with E2 treatment, compared with controls, and 36% lower, compared with E2+NA treatment (0.48 +/- 0.08 vs. 0.71 +/- 0.12 and 0.75 +/- 0.06; P < 0.05), suggesting differences in PG synthesis between hormone treatments. In conclusion, NA, a progestin without androgenic activity, may still affect some cardiovascular risk factors differently than estrogen-only therapy. However, it seems to be less detrimental than MPA.

Effect of age and caloric restriction on insulin receptor binding and glucose transporter levels in aging rats

We report on the effect of age and chronic caloric restriction (CR) on insulin binding and glucose transporter content in both diaphragm and heart muscle membrane of young (11 months), mid-age (17 months), and old (29 month) ad libitum fed and CR Brown-Norway rats. The control animals received rat chow ad lib and CR animals were allowed 60% of ad libitum food. The CR regimen was initiated at four months of age and the animals were maintained on their respective diets until necropsy. There was no effect of age on insulin binding for either ad libitum or CR animals at each age evaluated. Caloric restriction significantly lowered insulin levels at each age studied when compared to the ad libitum-fed rats. However, CR animals were noted to have increased insulin binding (p < 0.001) compared to ad libitum-fed animals at each age for diaphragm muscle. For the heart, there appeared to be a decreased binding, particularly at higher insulin concentrations, in CR-fed animals. There was no net change in Glut-1 or Glut-4 levels for heart muscle membrane, or Glut-4 levels for diaphragm muscle membrane between ad libitum or CR animals. This data indicates that caloric restriction may have tissue-specific effects for insulin receptor binding, and that the improved insulin sensitivity in CR states is not a result of altered glucose transporter protein content.

Dietary soy protein and estrogen replacement therapy improve cardiovascular risk factors and decrease aortic cholesteryl ester content in ovariectomized cynomolgus monkeys

Estrogen replacement therapy (ERT) decreases the progression of coronary artery atherosclerosis in monkeys. Dietary soy protein also retards the progression of atherosclerosis relative to animal proteins such as casein. Soy protein contains weakly estrogenic compounds called isoflavones or phytoestrogens that may be responsible for the cardioprotective effects. This study was designed as a 2 x 2 factorial to determine the magnitude of soy protein's effects on cardiovascular risk factors relative to casein and lactalbumin, with or without estradiol treatment. Ovariectomized female monkeys were randomized to four treatment groups based on past dietary cholesterol consumption, their origin, and past reproductive history, and studied for 7 months. The animals were divided into (1) a group fed casein and lactalbumin as the protein source (n = 14), (2) a group fed casein and lactalbumin as the protein source plus 17 beta-estradiol (E2) (n = 13), (3) a group fed soybean protein isolate as the protein source (n = 11), and (4) a group fed soybean protein isolate as the protein source plus E2 (n = 10). Soy protein compared with casein consumption resulted in a significant improvement in plasma lipid and lipoprotein concentrations, a significant improvement in insulin sensitivity and glucose effectiveness as determined by minimal-model analyses, and a decrease in arterial lipid peroxidation. E2-treated monkeys had a significant reduction in fasting insulin levels and insulin to glucose ratios, total body weight, and amounts of abdominal fat, and had smaller low-density lipoprotein (LDL) particles. In addition, E2 treatment resulted in a significant reduction (P = .001) in aortic cholesteryl ester content. A similar trend (P = .14) was found for soy protein compared with casein. There also was a significant interaction (P = .02) with soy and E2, such that animals consuming soy protein +E2 had the least arterial cholesteryl ester content. These results suggest that both ERT and dietary soybean protein have beneficial effects on cardiovascular risk factors. Interestingly, the two treatments affected different risk factors and together resulted in the greatest reduction in arterial cholesterol content. Further studies are needed to determine the active component of the soy protein and to assess its long-term effects on the cardiovascular system and other organ systems (such as the bones and reproductive system).

A study of caloric restriction and cardiovascular aging in cynomolgus monkeys (Macaca fascicularis): a potential model for aging research

Caloric restriction has been demonstrated to retard aging processes and extend maximal life span in rodents, and is currently being evaluated in several nonhuman primate trials. We initiated a study in 32 adult cynomolgus monkeys to evaluate the effect of caloric restriction on parameters contributing to atherosclerosis extent. Following pretrial determinations, at which time a baseline measure of ad libitum (ad lib) dietary intake was assessed, animals were randomized to an ad lib fed group (control) or a caloric restriction group (30% reduction from baseline intake). The animals are being evaluated for glycated proteins, insulin, glucose, insulin sensitivity measures, and specific measures of body fat composition by CT scans (e.g., intra-abdominal fat) over specified intervals. The results from the first year of observation demonstrate a significant diet effect on body weight, and specifically intra-abdominal fat. Further, insulin sensitivity has been significantly increased after 1 year of caloric restriction compared to the ad lib fed group. These studies indicate that caloric restriction has a marked effect on a pathologic fat depot, and this change is associated significantly with an improvement in peripheral tissue insulin sensitivity.

Aging and atherosclerosis in human and nonhuman primates

Atherosclerosis is a major age-related process and public health problem and its clinical manifestations (coronary heart disease [CHD] and cerebrovascular disease) continue to be responsible for approximately 50% of all deaths occurring annually. In addition, CHD is responsible for over 70 to 80% of deaths among men and women over 65 years old. As our population ages (35 million people over the age of 65 in the U.S. by the year 2030) and because of the increased morbidity and mortality associated with atherosclerosis, an understanding of the role of aging in the development of atherosclerosis is needed. Multiple risk factors such as smoking, gender, hypertension, and lipids contribute to the development of atherosclerosis. However, these risk factors in combination explain only about half of the individual variability in incidence of CHD, and it has been hypothesized that age-related conditions may play a role. To propectively evaluate the effects of age per se on atherosclerosis progression in humans would require observation over many years. Thus, animal models that are representative of both aging processes and atherosclerosis would be extremely valuable. As such, nonhuman primates have been used extensively in atherosclerosis research. However, studies that will specifically evaluate the role of aging per se in contributing to development of atherosclerosis in nonhuman primates have only recently been initiated. In this review, the contribution of nonhuman primates to atherosclerosis research will be discussed, as will the development of atherosclerosis in both human and nonhuman primates. In addition, a role for age-related conditions in atherosclerosis development in both human and nonhuman primates will be outlined.

The effects of hormone replacement therapy on carbohydrate metabolism and cardiovascular risk factors in surgically postmenopausal cynomolgus monkeys

Controversy exists regarding the effects of estrogen and estrogen/progestin replacement therapies on glucose tolerance and insulin resistance. Also unknown are whether changes in glucose tolerance and insulin resistance with hormone therapy affect arterial glycation and atherosclerosis. We studied ovariectomized female monkeys fed a lipid-lowering diet and given either no hormone replacement therapy (n = 25) or conjugated equine estrogens (CEE) alone (n = 22) or combined with medroxyprogesterone acetate ([MPA] n = 21) for 30 months. Monkeys receiving combined hormone replacement had significantly higher fasting glucose and insulin levels and higher insulin responses to a glucose challenge compared with controls or those given estrogen alone. Monkeys given estrogen-only therapy had lower body weights, lower measures of abdominal adiposity, and decreased serum androgen concentrations. However, due to the effective dietary lipid decrease, there was no additional effect of hormone treatment on atherosclerosis. Also, there was no correlation between either arterial glycation or insulin levels and atherosclerosis extent. Thus, although there were adverse effects of combined hormone replacement therapy on carbohydrate metabolism, we were unable to determine whether these effects altered the extent of atherosclerosis.

Islet amyloid and islet amyloid polypeptide in cynomolgus macaques (Macaca fascicularis): an animal model of human non-insulin-dependent diabetes mellitus

To further characterize spontaneous diabetes mellitus in cynomolgus macaques (Macaca fascicularis) as a model for human non-insulin-dependent diabetes mellitus (NIDDM), we evaluated the morphologic characteristics of the endocrine pancreas of 4 diabetic and 12 age-matched nondiabetic cynomolgus macaques. In addition, the cDNA-predicted amino acid sequence for islet amyloid polypeptide (IAPP) of this species was determined. Islet amyloid deposits exhibiting typical congophilia and green birefringence were found in 4/4 diabetic animals and in 8/12 nondiabetics. Islet amyloid deposits were significantly more extensive in the diabetic macaques (P = 0.001), in which they occupied a mean of 60% of the islet area. In contrast, in the nondiabetic group the maximum islet area occupied by amyloid was 24% (group mean = 6.8%), with four animals having no detectable islet amyloid. Amyloid deposits consistently showed immunoreactivity for IAPP but not for insulin. Comparisons between group means for diabetic versus nondiabetic macaques showed significantly greater islet area (P = 0.01, 85,390 versus 36,540 microns 2) and significantly greater islet area fraction (P = 0.02, 0.065 versus 0.032) for the diabetic group. The cDNA-predicted amino acid sequence for cynomolgus IAPP was identical to that previously reported for pig-tail macaques (M. nemestrina) and had 92%, 86%, and 84% amino acid sequence identity with human, domestic cat, and murine IAPPs, respectively. These findings support the use of cynomolgus macaques as an animal model of human NIDDM.

Treatment of type II diabetes: what options have been added to traditional methods?

Clinical goals in patients with non-insulin-dependent (type II) diabetes are to control glucose levels and prevent microvascular complications (eye, kidney, and nerve damage) while improving risk factors associated with cardiovascular disease (obesity, smoking, hyperlipidemia, hypertension, and hyperinsulinemia or insulin resistance). A wide array of medications and approaches is available to treat type II diabetes. Still, establishing an effective treatment regimen can be difficult, because patients have varying degrees of insulin secretory defects and insulin resistance and different conditions that must be factored in. Therefore, an individualized plan centered on self-management is the key to successful therapy in type II diabetes.

Increased glycation of plasma lipoproteins in diabetic cynomolgus monkeys

Hyperglycemia associated with diabetes mellitus increases glycation of hemoglobin and serum proteins in human and nonhuman primates. It also has been documented that numerous other circulating proteins may be glycated. In this study we found that most of the major subclasses of lipoproteins (low-density, very low-density, and high-density) from diabetic cynomolgus monkeys were significantly more glycated than were lipoproteins from age- and sex-matched controls. Correlations between levels of glycemic control and glycation of lipoproteins also were significant. Because glycation of lipoproteins has been shown to affect their normal metabolism, this animal model may be useful in determining the interaction between lipoproteins, diabetes mellitus, and the increased risk of atherosclerosis.

Diabetes mellitus and islet amyloidosis in cynomolgus monkeys

Six 15- to 20-year-old obese cynomolgus monkeys were determined to have diabetes mellitus. These monkeys were hyperglycemic and hypertriglyceridemic, yet remained nonketotic for several years before requiring clinical intervention. A significant decrease in glucose disappearance and an increased area under the glucose disappearance curve were found in response to intravenous glucose tolerance testing. Basal hyperinsulinemia was found in three animals that, in response to glucose stimulation, had a blunted insulin response, resulting in an overall decrease in the area under the insulin curve. Two animals died during the study and had extensive amyloid infiltration of pancreatic islets. The combined findings of old age, obesity, hyperinsulinemia, improvement in response to caloric restriction, and islet amyloidosis are consistent with type 2 diabetes mellitus.

Caloric restriction decreases age-dependent accumulation of the glycoxidation products, N epsilon-(carboxymethyl)lysine and pentosidine, in rat skin collagen

Nonenzymatic glycation of body proteins and subsequent advanced glycation reactions have been implicated in the aging process, while caloric restriction (CR) in rodents results in an increase in both mean and maximum life span. We have evaluated the effect of chronic (25 months) CR on glycation of blood proteins and accumulation of advanced glycation and oxidation (glycoxidation) products, N epsilon-(carboxymethyl)lysine (CML), and pentosidine, in skin collagen. Brown-Norway rats, fed ad libitum (AL) from birth, were divided into two equal groups at 4 months of age and placed on AL or CR diets (CR = 60% of AL diet). Cohorts of animals were sacrificed at 7, 13, and 25 months after the initiation of CR. At necropsy glycated hemoglobin was measured by affinity HPLC and glycated plasma protein by the fructosamine assay; extracts of skin collagen were analyzed by gas chromatography-mass spectrometry for CML and by reversed-phase HPLC for pentosidine. Glycation of hemoglobin, plasma proteins, and skin collagen was decreased significantly (18-33%) by CR. Concentrations of CML and pentosidine increased significantly with age in skin collagen in both AL and CR animals; however, CR significantly reduced levels of CML (25%), pentosidine (50%), and fluorescence (15%) in collagen in the oldest rats. We conclude that CR reduces the extent of glycation of blood and tissue proteins and the age-related accumulation of glycoxidation products in skin collagen.

Contribution of visceral fat mass to the insulin resistance of aging

Recent studies have shown that central obesity (increased waist to hip ratio [WHR]) is related to insulin resistance and aging. Furthermore, in central-obesity states, the intraabdominal fat (IAF) depot has been postulated to contribute most to the development of insulin resistance. Therefore, the observed insulin resistance of aging may be related more to changes in body composition than to aging per se. The purpose of this study was to explore the association of IAF with age and insulin sensitivity (SI) after controlling for obesity. We examined 60 healthy nondiabetic subjects (normal 75-g oral glucose tolerance test, aged 23 to 83, 15 men and 45 women). We chose subjects so that those < or = 125% and greater than 125% of ideal body weight were equally represented in each age decade. We quantified total and subcutaneous abdominal fat and IAF at the umbilicus using a validated magnetic resonance imaging (MRI) scanning technique and determined SI using a modified minimal model. IAF correlated significantly with age (r = .49, P = .0001) in the group as a whole, as well as in men (r = .58, P = .022) and women (r = .48, P = .0008) separately. In all subjects, SI was significantly related to IAF (r = -.50, P < .0001) but was not related to age (r = .00, P = .98). In multivariate analysis for various combinations of age, sex, and measures of fat distribution, WHR accounted for 28% and IAF for 51% of the variance in SI, whereas age, sex, and interactions of age and sex accounted for only 1%.(ABSTRACT TRUNCATED AT 250 WORDS)

Doxazosin lowers blood pressure and improves insulin responses to a glucose load with no changes in tyrosine kinase activity or insulin binding

alpha-Adrenergic blockers have shown favorable metabolic effects. We evaluated the glucose and insulin responses to a glucose load and lipid profiles in 36 diabetic hypertensive patients before and after 8 weeks of doxazosin administration. To evaluate insulin action at the cellular level, erythrocyte insulin binding and tyrosine kinase (TK) activity were measured in 12 of these patients. Systolic and diastolic blood pressures decreased significantly (P < .0001) after 8 weeks of doxazosin therapy. Doxazosin administration significantly reduced the integrated insulin response (area under the curve [AUC]-insulin: 6093 +/- 894 to 5260 +/- 807; P = .04) and the insulin/glucose index (I/G) at 90 and 120 min after a glucose load (at 90 min, 0.230 +/- 0.055 v 0.180 +/- 0.04, P < .05; at 120 min, 0.275 +/- 0.071 v 0.173 +/- 0.036, P < .05). HDL3 level increased from 31.1 +/- 1.5 mg% to 34 +/- 1.6 mg% (P < .05) after doxazosin. Erythrocyte insulin binding and tyrosine kinase activity were not significantly altered after doxazosin. No significant correlation was found between the insulin or glucose responses and the insulin receptor binding or tyrosine kinase activity before and after treatment.

The effects of hormonal replacement therapy on insulin sensitivity in surgically postmenopausal cynomolgus monkeys (Macaca fascicularis)

OBJECTIVE

Our purpose was to evaluate the effect of hormone replacement therapy on insulin resistance in postmenopausal cynomolgus monkeys (Macaca fascicularis).

STUDY DESIGN

We studied 37 surgically postmenopausal cynomolgus monkeys that were fed a moderately atherogenic diet for 12 weeks with either no treatment (control), conjugated equine estrogens, medroxyprogesterone acetate, combination conjugated equine estrogens and medroxyprogesterone acetate, or tamoxifen. Insulin sensitivity and glucose effectiveness were determined by the frequent-sampling intravenous tolerance test by means of the minimal model analysis.

RESULTS

There were no differences in body weight, total plasma cholesterol, or body fat distribution between control and conjugated equine estrogens, medroxyprogesterone acetate, or combination treatment groups. However, compared with control animals (insulin sensitivity = 5.9 +2- 1.2 x 10(-4) min-1 microU-1 ml) or conjugated equine estrogens treatment (6.3 +/- 1.1 x 10(-4) min-1 microU-1 ml) insulin sensitivity was significantly decreased in animals treated with medroxyprogesterone acetate (2.9 +/- 0.4 x 10(-4) min-1 microU-1 ml, p < 0.001) or conjugated equine estrogens and medroxyprogesterone acetate (2.8 +/- 0.6 x 10(-4) min-1 microU-1 ml, p < 0.001). Although insulin sensitivity was shown to be decreased in the tamoxifen-treated animals (insulin sensitivity = 4.6 +/- 0.6 x 10(-4) min-1 microU -1 ml), the difference was not statistically significant compared with the control or conjugated equine estrogens-treated animals. No significant differences were seen for glucose effectiveness comparing control animals (glucose effectiveness = 0.043 +/- 0.006 min-1) to animals treated with medroxyprogesterone acetate (glucose effectiveness = 0.046 +/- 0.009 min-1), conjugated equine estrogens and medroxyprogesterone acetate (0.048 +/- 0.008 min-1) or tamoxifen (0.039 +/- 0.006 min-1).

CONCLUSION

These results suggest that progestins alone or in combination with estrogens can induce insulin resistance in postmenopausal monkeys while having no effect on plasma lipid concentrations or glucose effectiveness.

Glycohemoglobin measured by automated affinity HPLC correlates with both short-term and long-term antecedent glycemia

We evaluated glycohemoglobin (GHb) and glycated plasma protein (GPP) by automated affinity HPLC for their ability to monitor both short-term and long-term antecedent glycemia in 70 diabetic subjects. We placed 30 subjects on an intervention protocol in which insulin and (or) dietary changes were made twice weekly to acutely decrease glycemia. We monitored 40 subjects at 6-week intervals; changes in the clinical regimen were made at that time only. Despite weekly changes in mean blood glucose in the subjects who received more intensive intervention. GHb concentrations correlated significantly with the weekly (r = 0.66, P < 0.001), 2-week (r = 0.70, P < 0.001), 3-week (r = 0.72, P < 0.001), and 6-week (r = 0.83, P < 0.001) mean glucose concentrations. GPP correlated significantly with measured glycated albumin determined by boronate affinity columns (r = 0.83, P < .001) and correlated best with the 1-week (r = 0.66, P < 0.001), 2-week (r = 0.64, P < .001) and 3-week (r = 0.60, P < 0.001) mean antecedent glucose concentration. Thus, GHb, traditionally considered a marker for only long-term diabetic control, correlated significantly with both short-term and long-term antecedent glycemia.

Glycohemoglobin measured by automated affinity HPLC correlates with both short-term and long-term antecedent glycemia

We evaluated glycohemoglobin (GHb) and glycated plasma protein (GPP) by automated affinity HPLC for their ability to monitor both short-term and long-term antecedent glycemia in 70 diabetic subjects. We placed 30 subjects on an intervention protocol in which insulin and (or) dietary changes were made twice weekly to acutely decrease glycemia. We monitored 40 subjects at 6-week intervals; changes in the clinical regimen were made at that time only. Despite weekly changes in mean blood glucose in the subjects who received more intensive intervention. GHb concentrations correlated significantly with the weekly (r = 0.66, P &lt; 0.001), 2-week (r = 0.70, P &lt; 0.001), 3-week (r = 0.72, P &lt; 0.001), and 6-week (r = 0.83, P &lt; 0.001) mean glucose concentrations. GPP correlated significantly with measured glycated albumin determined by boronate affinity columns (r = 0.83, P &lt; .001) and correlated best with the 1-week (r = 0.66, P &lt; 0.001), 2-week (r = 0.64, P &lt; .001) and 3-week (r = 0.60, P &lt; 0.001) mean antecedent glucose concentration. Thus, GHb, traditionally considered a marker for only long-term diabetic control, correlated significantly with both short-term and long-term antecedent glycemia.