Correlation between the glucose clamp technique and the homeostasis model assessment in hypertension

Feeding High-Fat Diet Accelerates Development of Peripheral and Central Insulin Resistance and Inflammation and Worsens AD-like Pathology in APP/PS1 Mice

Alzheimer's disease (AD) is a progressive brain disorder characterized by extracellular amyloid-β (Aβ) plaques, intracellular neurofibrillary tangles formed by hyperphosphorylated Tau protein and neuroinflammation. Previous research has shown that obesity and type 2 diabetes mellitus, underlined by insulin resistance (IR), are risk factors for neurodegenerative disorders. In this study, obesity-induced peripheral and central IR and inflammation were studied in relation to AD-like pathology in the brains and periphery of APP/PS1 mice, a model of Aβ pathology, fed a high-fat diet (HFD). APP/PS1 mice and their wild-type controls fed either a standard diet or HFD were characterized at the ages of 3, 6 and 10 months by metabolic parameters related to obesity via mass spectroscopy, nuclear magnetic resonance, immunoblotting and immunohistochemistry to quantify how obesity affected AD pathology. The HFD induced substantial peripheral IR leading to central IR. APP/PS1-fed HFD mice had more pronounced IR, glucose intolerance and liver steatosis than their WT controls. The HFD worsened Aβ pathology in the hippocampi of APP/PS1 mice and significantly supported both peripheral and central inflammation. This study reveals a deleterious effect of obesity-related mild peripheral inflammation and prediabetes on the development of Aβ and Tau pathology and neuroinflammation in APP/PS1 mice.

Lipidized PrRP Analog Exhibits Strong Anti-Obesity and Antidiabetic Properties in Old WKY Rats with Obesity and Glucose Intolerance

Prolactin-releasing peptide (PrRP) is an anorexigenic neuropeptide that has potential for the treatment of obesity and its complications. Recently, we designed a palmitoylated PrRP31 analog (palm¹¹-PrRP31) that is more stable than the natural peptide and able to act centrally after peripheral administration. This analog acted as an anti-obesity and glucose-lowering agent, attenuating lipogenesis in rats and mice with high-fat (HF) diet-induced obesity. In Wistar Kyoto (WKY) rats fed a HF diet for 52 weeks, we explored glucose intolerance, but also prediabetes, liver steatosis and insulin resistance-related changes, as well as neuroinflammation in the brain. A potential beneficial effect of 6 weeks of treatment with palm¹¹-PrRP31 and liraglutide as comparator was investigated. Liver lipid profiles, as well as urinary and plasma metabolomic profiles, were measured by lipidomics and metabolomics, respectively. Old obese WKY rats showed robust glucose intolerance that was attenuated by palm¹¹-PrRP31, but not by liraglutide treatment. On the contrary, liraglutide had a beneficial effect on insulin resistance parameters. Despite obesity and prediabetes, WKY rats did not develop steatosis owing to HF diet feeding, even though liver lipogenesis was enhanced. Plasma triglycerides and cholesterol were not increased by HFD feeding, which points to unincreased lipid transport from the liver. The liver lipid profile was significantly altered by a HF diet that remained unaffected by palm¹¹-PrRP31 or liraglutide treatment. The HF-diet-fed WKY rats revealed astrogliosis in the brain cortex and hippocampus, which was attenuated by treatment. In conclusion, this study suggested multiple beneficial anti-obesity-related effects of palm¹¹-PrRP31 and liraglutide in both the periphery and brain.

IS HOMEOSTASIS MODEL ASSESSMENT FOR INSULIN RESISTANCE >2.5 A DISTINGUISHED CRITERIA FOR METABOLIC DYSFUNCTION-ASSOCIATED FATTY LIVER DISEASE IDENTIFICATION?

BACKGROUND

Insulin resistance (IR), assessed by different criteria, is an important factor in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). More recently with the characterization of this metabolic dysfunction-associated fatty liver disease (MAFLD), one of the proposed criteria for this diagnosis has been the determination of the homeostasis model assessment-insulin resistance (HOMA-IR).

OBJECTIVE

The purpose of this study was to evaluate the relationship of HOMA-IR>2.5 with clinical, metabolic, biochemical and histological data obtained in non-diabetic patients diagnosed with NAFLD by liver biopsy.

METHODS

Cross-sectional, retrospective study was carried out with data from 174 adult individuals of both genders with non-diabetics NAFLD, without obvious signs of portal hypertension. The body mass index (BMI) was classified according to the World Health Organization (1998), and the metabolic syndrome by the criteria of NCEP-ATP-III. Biochemical tests were evaluated using an automated method and insulinemia through immunofluorometric assay. Histological findings were classified according to Kleiner et al. (2005).

RESULTS

The mean age of the studied population was 53.6±11.2 years, with 60.3% being female. The average BMI was 30.3 kg/m2 and 75.9% of the patients had increased waist circumference. Among evaluated metabolic parameters, there was a higher prevalence of metabolic syndrome (MS) in patients with HOMA-IR>2.5, with no statistical difference in relation to BMI between studied groups. Values of liver enzymes and serum ferritin were significantly higher in patients with this marker of IR, who had a higher prevalence of non-alcoholic steatohepatitis (NASH) and advanced liver fibrosis. In the multivariate analysis, the clinical diagnosis of MS, hyperferritinemia and the presence of NASH in the liver biopsy were the factors independently associated with the presence of altered HOMA-IR.

CONCLUSION

HOMA-IR values >2.5 identify patients with NAFLD with distinct clinical and metabolic characteristics and with a greater potential for disease progression, which validates this parameter in the identification of patients with MAFLD.

Disruption of Pituitary Gonadotrope Activity in Male Rats After Short- or Long-Term High-Fat Diets Is Not Associated With Pituitary Inflammation

Overnutrition is associated with the activation of inflammatory pathways in metabolically linked organs and an early hypothalamic inflammation is now known to disrupt the central control of metabolic function. Because we demonstrated that fatty acids (FA) target the pituitary and affect gonadotropin synthesis, we asked whether overnutrition induces pituitary inflammation that may contribute to obesity-associated disorders in the control of reproduction. We analyzed pituitary inflammation and hypothalamic-pituitary-testicular axis in male rats fed a short- (4 weeks) or long-term (20 weeks) high-fat diet. The effect of diet enrichment with the ω3 polyunsaturated FA, DHA, was also analyzed. After only 4 weeks and before weight gain of rats, high-fat diet caused a significant decrease in pituitary gonadotropin and hypothalamic GnRH transcript levels despite unchanged testosterone and inhibin B levels. Contrasting with the hypothalamus, there was no concomitant increases in gene expression of pituitary inflammatory mediators and even a reduction of prototypical cytokines such as interleukin-1β and TNF-α. No inflammation was still detected in the pituitary after 20 weeks although gonadotropin transcripts and circulating levels were still altered. Gonadotropins were the only pituitary hormones remaining affected at this stage of the regimen, underlying a differential susceptibility of pituitary lineages to metabolic disorders. DHA enrichment of the diet did not prevent alterations of gonadotrope activity due to either a long- or a short-term high-fat diet although it blocked early hypothalamic inflammation and attenuated several metabolic effects. Taken together, our findings suggest that high-fat diet-induced defects in gonadotrope activity in male rats occurred despite a lack of pituitary inflammation.

Insulin resistance in children with juvenile systemic lupus erythematosus and ınvestigation of the possibly responsible factors

OBJECTIVE

Insulin resistance (IR) has been described in adults with systemic lupus erythematosus (SLE), though its mechanism has not been fully clarified. In this study, it was aimed to investigate insulin sensitivity for the first time in children with juvenile SLE (jSLE) by considering the effect of the already known contributing factors of IR.

METHOD

This is a cross-sectional study including 43 patients with jSLE and the same number of healthy controls matched for age, gender, pubertal stage, body mass index, and physical activity level. IR, as calculated by both homeostatic model assessment for insulin resistance (HOMA-IR) and a relatively new method, triglyceride glucose (TyG) index, was compared between the patients and their matched controls, also among the patients stratified by disease duration, corticosteroid use, and disease activity.

RESULTS

Insulin resistance in the patient group was higher than the controls according to both HOMA-IR and TyG index (p < 0.001 for both). In the patient group, no significant effect of disease duration, corticosteroid use, disease activity, and levels of anti-dsDNA, anti-cardiolipin IgM, anti-cardiolipin IgG, C3, and C4 on IR was demonstrated.

CONCLUSION

Children with jSLE were found to have higher IR even after neutralizing the effects of the contributing factors which are expected to aggravate IR. This elevation in IR in jSLE seems not to be associated with corticosteroid use, disease duration, disease activity, or autoantibody levels. Thus, the presence of IR in jSLE cannot be explained solely with neither the already known contributing factors nor the increased inflammation of the disease. Key Points • In this study, insulin sensitivity was investigated for the first time in children with jSLE. • Children with jSLE have higher insulin resistance than healthy ones. • Insulin resistance in children with jSLE is independent of corticosteroid use, disease duration, disease activity or autoantibody, and complement levels.

Association of [1H]-MRS quantified liver fat content with glucose metabolism status

BACKGROUND

Previous literatures have implied that the liver fat deposition plays a crucial role in the development and progression of insulin resistance. In the present study, we aimed to investigate the association of liver fat content (LFC) with glucose metabolism status in the population of newly diagnosed type 2 diabetes mellitus (nT2DM), prediabetes mellitus (PDM) and normal controls (NC), and assessing if the LFC could as an indicator for the prediction of T2DM.

METHODS

A total of 242 subjects (including 141 nT2DM patients, 48 PDM subjects and 53 NC) were enrolled. The levels of LFC were quantified by using the proton magnetic resonance spectroscopy ([¹H]-MRS) technique. Clinical and laboratory parameters of study subjects were collected by medical records and biochemical detection. One-way ANOVA or nonparametric test (Kruskal-Wallis) was applied for intergroup comparisons; intergroup comparison was performed in using of Bonferroni multiple-significance-test correction.

RESULTS

There were significantly increased LFC levels in nT2DM (14.72% ± 6.37%) than in PDM (9.62% ± 4.41%) and that of NC groups (5.11% ± 3.66%) (all p < 0.001). The prevalence of nonalcoholic fatty liver disease (NAFLD) was also found to be increased in nT2DM (91.48%) than in PDM (85.41%) and that of NC (32.07%) groups. Correlation analysis revealed that the increase of LFC positively associated with fast plasma glucose (FPG), 2 h plasma glucose (PG), Delta G30 and homeostatic model assessment of insulin resistance (HOMA-IR), negatively associated with Delta Ins30, Delta C30, Ins30/G30 _AUC, CP30/G30 _AUC, Ins _AUC/G _AUC, CP _AUC/G _AUC, homeostatic model assessment for β-cell function index (HOMA-β) and matsuda insulin sensitivity index (Matsuda ISI). Multilinear regression analysis showed that LFC, body mass index (BMI) and diastolic blood pressure (DBP) contributed for the prediction of HOMA-IR, and total cholesterol (TC), age, waist circumference (WC) and low-density lipoprotein cholesterol (LDL-C) were the significant contributors for HOMA-β.

CONCLUSIONS

Our study revealed an increased LFC level and prevalence of NAFLD in nT2DM than in PDM and that of NC groups, the increase of LFC was closely associated with insulin resistance and impaired glucose metabolism status, may be regarded as potential indicator contributing to the development and progression of T2DM.

Beyond the metabolic syndrome: Visceral and marrow adipose tissues impair bone quantity and quality in Cushing's disease

The present study was designed to evaluate the relationship between bone traits [bone mineral density (BMD) and trabecular bone score (TBS)] and the accumulation of fat in adipose tissues [abdominal subcutaneous (SAT), visceral (VAT), marrow (MAT) and intrahepatic lipids (IHL)], as well as insulin resistance, in subjects with Cushing’s disease (CD). The study included control (C = 27), paired (P = 16) and Cushing’s disease (CD = 10) groups, which underwent biochemical assessment, dual X-ray absorptiometry, TBS, and magnetic resonance imaging to determine fat deposits. The CD group showed higher serum levels of glucose and insulin, as well as HOMA-IR values, but lower circulatory levels of osteocalcin, in comparison to C and P. The CD group exhibited lower L1-L4 BMD than P (P = 1.059 ± 0.141 vs CD = 0.935 ± 0.093 g/cm², p < 0.05) (Fig 1A). The lumbar spine BMD from the C group was similar to the other groups. TBS was lower in CD than in P and C (C = 1.512±0.077 vs P = 1.405±0.150 vs CD = 1.135±0.136; p<0.05); there was also significant difference between C and P (p<0.05). MAT, VAT, and IHL were higher in CD than in C and P (p<0.05). Considering all subjects, there was a positive association between TBS with both lumbar spine BMD (R² = 0.45; p<0.0001) and osteocalcin (R² = 0.44; p = 0.05). TBS was negatively associated with MAT (R² = 0.49; p = 0.01), VAT (R² = 0.55; p<0.05), and HOMA-IR (R² = 0.44; p<0.01). MAT was positively related with VAT (R² = 0.44; p<0.01) and IHL (R² = 0.41; p<0.05). In CD, insulin resistance and adipose tissue dysfunction, including high MAT, are active players in bone deterioration, as confirmed by lower lumbar spine BMD and lower TBS. Thus, our findings point to an additional component of the already well-known complex mechanisms of osteoporosis associated with hypercortisolism.

Association of retinol binding protein-4, cystatin C, homocysteine and high-sensitivity C-reactive protein levels in patients with newly diagnosed type 2 diabetes mellitus

INTRODUCTION

To investigate the serum retinol binding protein (RBP)-4, cystatin C (Cys C), homocysteine (HCY) and high-sensitivity C-reactive protein (hs-CRP) levels in newly diagnosed type 2 diabetes mellitus (NT2DM) patients, prediabetes mellitus (PDM) subjects and normal controls, as well as their correlation with clinical and laboratory indexes, such as blood pressure and lipoprotein.

MATERIAL AND METHODS

A total of 242 subjects, including 141 NT2DM patients, 48 PDM subjects and 53 healthy controls, were recruited in the present study. Serum RBP-4, Cys C and hs-CRP concentrations were measured by enzyme-linked immunosorbent assay (ELISA). HCY concentration was determined by the chemical luminescence method.

RESULTS

There were significant differences in Cys C and hs-CRP among NT2DM patients, PDM subjects and normal controls. In comparison to controls, there were significantly elevated Cys C and hs-CRP levels in PDM (both p < 0.001), and a significantly increased Cys C level in NT2DM (p < 0.001); however, there were no significant differences in Cys C and hs-CRP levels between NT2DM and PDM, and no significant differences of hs-CRP levels between NT2DM and normal controls. No significant differences of RBP-4 and HCY levels among NT2DM, PDM and normal control groups were observed.

CONCLUSIONS

Aberrant Cys C expression and its clinical associations in NT2DM suggest their important role in this disease.

Low intakes of dietary fiber and magnesium are associated with insulin resistance and hyperandrogenism in polycystic ovary syndrome: A cohort study

BACKGROUND

Women with polycystic ovary syndrome (PCOS) often have insulin resistance (IR) which may be worsened by obesity. The roles of dietary intake and activity are unclear. Our objectives were to determine whether (a) high caloric intake or inactivity explains obesity in PCOS, and (b) dietary composition is associated with PCOS phenotypes.

METHODS

Eighty-seven women with PCOS and 50 women without PCOS participated in this cohort study at a reproductive medicine center. Data collected included 3-day food and physical activity records, anthropometrics, and metabolic and hormonal assays.

RESULTS

Women with PCOS had increased body mass index (BMI) but similar caloric intake and activity to women without PCOS. There were no differences in protein, carbohydrates, fat, or glycemic load consumption, but women with PCOS consumed less fiber (medians: 19.6 vs. 24.7 g) and less magnesium (medians: 238.9 vs. 273.9 mg). In women with PCOS, those with IR consumed less fiber, less magnesium, and greater glycemic load than those without IR (medians: 18.2 vs. 22.1 g, 208.4 vs. 264.5 mg, 89.6 vs. 83.5). Fiber intake of women with PCOS was negatively correlated with IR, fasting insulin, glucose tolerance, testosterone, and dehydroepiandrosterone sulfate. Magnesium intake was negatively correlated with IR, C-reactive protein, and testosterone, but positively correlated with HDL cholesterol. Fiber intake and BMI accounted for 54.0% of the variance observed in IR.

CONCLUSIONS

Obesity in women with PCOS could not be explained by overeating or inactivity. Increasing dietary fiber and magnesium intakes may assist in reducing IR and hyperandrogenemia in women with PCOS.

Assessment of insulin sensitivity and secretion in patients with fibrocalculous pancreatic diabetes

Background: Fibrocalculous pancreatic diabetes (FCPD) is a secondary form of diabetes seen in patients with tropical chronic pancreatitis. Insulin deficiency plays a major role in the etiopathogenesis of FCPD. Limited data suggest a possible role of insulin resistance (IR) in the pathogenesis of FCPD. Sparse data exist on measures of insulin sensitivity (IS) and secretion in patients with FCPD and its comparison to type 2 diabetes mellitus (T2D) patients. Method: Eighty patients with FCPD, 36 patients with T2D and 36 healthy subjects were included. A 75 g oral glucose tolerance test (OGTT) was performed in the morning after an overnight fast. We evaluated IS and secretion using indices derived from fasting (homeostasis model assessment of insulin resistance [HOMA-IR], quantitative insulin sensitivity check index [QUICKI] and homeostasis model assessment of beta-cell function [HOMA-ß]) and OGTT (Matsuda, insulin sensitivity index by Kanauchi [ISI-K], oral glucose insulin sensitivity index [OGIS], Stumvoll, insulinogenic index and oral disposition index [ODI]) measurements of glucose and insulin. Results: HOMA-IR was significantly higher and QUICKI significantly lower in patients with FCPD and T2D than in healthy controls (P<0.001). Matsuda, ISI-K, OGIS and Stumvoll were significantly lower in patients with FCPD and T2D than in healthy controls (P<0.001), indicating reduced IS in both FCPD and T2D patients. HOMA-ß, insulinogenic index and ODI were significantly lower in patients with FCPD and T2D compared to healthy controls (P<0.001). Conclusion: FCPD is associated with reduced IS as assessed by fasting and OGTT-based indices. FCPD is also associated with a greater degree of impairment in insulin secretion than in T2D. IR may play a role in the pathogenesis of FCPD.

Lipidized prolactin-releasing peptide improved glucose tolerance in metabolic syndrome: Koletsky and spontaneously hypertensive rat study

Background/Objectives

Prolactin-releasing peptide (PrRP) has a potential to decrease food intake and ameliorate obesity, but is ineffective after peripheral administration. We have previously shown that our novel lipidized analogs PrRP enhances its stability in the circulation and enables its central effect after peripheral application. The purpose of this study was to explore if sub-chronic administration of novel PrRP analog palmitoylated in position 11 (palm¹¹-PrRP31) to Koletsky-spontaneously hypertensive obese rats (SHROB) could lower body weight and glucose intolerance as well as other metabolic parameters.

Subjects/Methods

The SHROB rats (n = 16) were used for this study and age-matched hypertensive lean SHR littermates (n = 16) served as controls. Palm¹¹-PrRP31 was administered intraperitoneally to SHR and SHROB (n = 8) at a dose of 5 mg/kg once-daily for 3 weeks. During the dosing period food intake and body weight were monitored. At the end of the experiment the oral glucose tolerance test was performed; plasma and tissue samples were collected. Thereafter, arterial blood pressure was measured.

Results

At the end of the experiment, vehicle-treated SHROB rats showed typical metabolic syndrome parameters, including obesity, glucose intolerance, dyslipidemia, and hypertension. Peripheral treatment with palm¹¹-PrRP31 progressively decreased the body weight of SHR rats but not SHROB rats, though glucose tolerance was markedly improved in both strains. Moreover, in SHROB palm¹¹-PrRP31 ameliorated the HOMA index, insulin/glucagon ratio, and increased insulin receptor substrate 1 and 2 expression in fat and insulin signaling in the hypothalamus, while it had no effect on blood pressure.

Conclusions

We demonstrated that our new lipidized PrRP analog is capable of improving glucose tolerance in obese SHROB rats after peripheral application, suggesting that its effect on glucose metabolism is independent of leptin signaling and body weight lowering. These data suggest that this analog has the potential to be a compound with both anti-obesity and glucose-lowering properties.

Impact of novel palmitoylated prolactin-releasing peptide analogs on metabolic changes in mice with diet-induced obesity

Analogs of anorexigenic neuropeptides, such as prolactin-releasing peptide (PrRP), have a potential as new anti-obesity drugs. In our previous study, palmitic acid attached to the N-terminus of PrRP enabled its central anorexigenic effects after peripheral administration. In this study, two linkers, γ-glutamic acid at Lys¹¹ and a short, modified polyethylene glycol at the N-terminal Ser and/or Lys¹¹, were applied for the palmitoylation of PrRP31 to improve its bioavailability. These analogs had a high affinity and activation ability to the PrRP receptor GPR10 and the neuropeptide FF2 receptor, as well as short-term anorexigenic effect similar to PrRP palmitoylated at the N-terminus. Two-week treatment with analogs that were palmitoylated through linkers to Lys¹¹ (analogs 1 and 2), but not with analog modified both at the N-terminus and Lys¹¹ (analog 3) decreased body and liver weights, insulin, leptin, triglyceride, cholesterol and free fatty acid plasma levels in a mouse model of diet-induced obesity. Moreover, the expression of uncoupling protein-1 was increased in brown fat suggesting an increase in energy expenditure. In addition, treatment with analogs 1 and 2 but not analog 3 significantly decreased urinary concentrations of 1-methylnicotinamide and its oxidation products N-methyl-2-pyridone-5-carboxamide and N-methyl-4-pyridone-3-carboxamide, as shown by NMR-based metabolomics. This observation confirmed the previously reported increase in nicotinamide derivatives in obesity and type 2 diabetes mellitus and the effectiveness of analogs 1 and 2 in the treatment of these disorders.

Methods of Measuring Insulin Sensitivity

Insulin resistance is a component of several health disorders, most notably impaired glucose tolerance and type 2 diabetes mellitus. Insulin-resistant individuals have an impaired biological response to the usual action of insulin; that is, they have reduced insulin sensitivity. Various methods are used to assess insulin sensitivity both in individuals and in study populations. Validity, reproducibility, cost, and degree of subject burden are important factors for both clinicians and researchers to consider when weighing the merits of a particular method. This article describes several in vivo methods used to assess insulin sensitivity and presents the advantages and disadvantages of each.

Skeletal muscle mitochondrial uncoupling prevents diabetes but not obesity in NZO mice, a model for polygenic diabesity

Induction of skeletal muscle (SM) mitochondrial stress by expression of uncoupling protein 1 (UCP1) in mice results in a healthy metabolic phenotype associated with increased secretion of FGF21 from SM. Here, we investigated whether SM mitochondrial uncoupling can compensate obesity and insulin resistance in the NZO mouse, a polygenic diabesity model. Male NZO mice were crossed with heterozygous UCP1 transgenic (tg) mice (mixed C57BL/6/CBA background) and further backcrossed to obtain F1 and N2 offspring with 50 and 75 % NZO background, respectively. Male F1 and N2 progeny were fed a high-fat diet ad libitum for 20 weeks from weaning. Blood glucose was reduced, and diabetes (severe hyperglycemia >300 mg/dl) was fully prevented in both F1- and N2-tg progeny compared to a diabetes prevalence of 15 % in F1 and 42 % in N2 wild type. In contrast, relative body fat content and plasma insulin were decreased, and glucose tolerance was improved, in F1-tg only. Both F1 and N2-tg showed decreased lean body mass. Accordingly, induction of SM stress response including FGF21 expression and secretion was similar in both F1 and N2-tg mice. In white adipose tissue, expression of FGF21 target genes was enhanced in F1 and N2-tg mice, whereas lipid metabolism genes were induced in F1-tg only. There was no evidence for induction of browning in either UCP1 backcross. We conclude that SM mitochondrial uncoupling induces FGF21 expression and prevents diabetes in mice with a 50-75 % NZO background independent of its effects on adipose tissue.

Insulin resistance in moderate to severe obstructive sleep apnea in nondiabetics and its response to continuous positive airway pressure treatment

Background:

The effects of nasal continuous positive airway pressure (CPAP) on insulin resistance (IR) in obstructive sleep apnea (OSA) are still under discussion especially in nondiabetics. Trials have found conflicting results in this regard.

Aims:

The study was to measure IR in nondiabetic patients with moderate to severe OSA and to evaluate the effect of nasal CPAP on IR in these patients.

Materials and Methods:

A total of 30 consecutively newly diagnosed patients with moderate to severe OSA was enrolled in the study. OSA was diagnosed by doing an overnight polysomnography. Plasma glucose and insulin levels were measured at baseline and after 1 month of CPAP treatment. IR was calculated by homeostasis model assessment (HOMA) method.

Results:

Of 30 OSA patients, 21 were males, and 9 were females. The mean age of the subjects was 49.9 years, and mean body mass index (BMI) was 29.33. All 30 patients had moderate to severe OSA with a mean apnea and hypopnea index (AHI) of 80.46/h. The Epworth sleepiness score (ESS) showed a significant change with 1 month of treatment with CPAP from baseline of 13 to 9.7 (P ≤ 0.0001). There was a significant reduction in fasting insulin levels from 21.75 to 19.39 (P = 0.009). There was a small fall in fasting glucose, but it was not significant. The HOMA IR also reduced from 5.78 to 4.82 which was significant (P = 0.024) without any significant change in BMI (P = 0.916). The HOMA IR did not showed any positive correlation with different variables of OSA severity, ESS (r = 0.156) (P = 0.410), AHI (r = 0.177) (P = 0.349), and percentage of test time <90% saturation (r = −0.296) (P = 0.112).

Conclusion:

Moderate to severe OSA is associated with an increase in IR and effective treatment with CPAP rapidly improves the insulin sensitivity in nondiabetic patients with OSA without any change in BMI.

Lifetime, untreated isolated GH deficiency due to a GH-releasing hormone receptor mutation has beneficial consequences on bone status in older individuals, and does not influence their abdominal aorta calcification

The GH/IGF-I axis has essential roles in regulating bone and vascular status. The age-related decrease in GH secretion ("somatopause") may contribute to osteoporosis and atherosclerosis, commonly observed in the elderly. Adult-onset GH deficiency (GHD) has been reported to be associated with reduced bone mineral density (BMD), increased risk of fractures, and premature atherosclerosis. We have shown the young adult individuals with isolated GHD (IGHD) due to a homozygous for the c.57+1G>A GHRH receptor gene mutation have normal volumetric BMD (vBMD), and not develop premature atherosclerosis, despite adverse risk factor profile. However, the bone and vascular impact of lifetime GHD on the aging process remains unknown. We studied a group of ten older IGHD subjects (≥60 years) homozygous for the mutation, comparing them with 20 age- and gender-matched controls (CO). Areal BMD was measured, and vBMD was calculated at the lumbar spine and total hip. Vertebral fractures and abdominal aortic calcifications (expressed as calcium score) were also assessed. Areal BMD was lower in IGHD, but vBMD was similar in the two groups. The percent of fractured individuals was similar, but the mean number of fractures per individual was lower in IGHD than CO. Calcium score was similar in the two groups. A positive correlation was found between calcium score and number of fractures. Untreated lifetime IGHD has beneficial consequences on bone status and does not have a deleterious effect on abdominal aorta calcification.

Influence of a ketogenic diet, fish-oil, and calorie restriction on plasma metabolites and lipids in C57BL/6J mice

BACKGROUND

Diet therapies including calorie restriction, ketogenic diets, and fish-oil supplementation have been used to improve health and to treat a variety of neurological and non-neurological diseases.

METHODS

We investigated the effects of three diets on circulating plasma metabolites (glucose and β-hydroxybutyrate), hormones (insulin and adiponectin), and lipids over a 32-day period in C57BL/6J mice. The diets evaluated included a standard rodent diet (SD), a ketogenic diet (KD), and a standard rodent diet supplemented with fish-oil (FO). Each diet was administered in either unrestricted (UR) or restricted (R) amounts to reduce body weight by 20%.

RESULTS

The KD-UR increased body weight and glucose levels and promoted a hyperlipidemic profile, whereas the FO-UR decreased body weight and glucose levels and promoted a normolipidemic profile, compared to the SD-UR. When administered in restricted amounts, all three diets produced a similar plasma metabolite profile, which included decreased glucose levels and a normolipidemic profile. Linear regression analysis showed that circulating glucose most strongly predicted body weight and triglyceride levels, whereas calorie intake moderately predicted glucose levels and strongly predicted ketone body levels.

CONCLUSIONS

These results suggest that biomarkers of health can be improved when diets are consumed in restricted amounts, regardless of macronutrient composition.

Evaluation of fasting plasma insulin concentration as an estimate of insulin action in nondiabetic individuals: comparison with the homeostasis model assessment of insulin resistance (HOMA-IR)

Insulin-mediated glucose disposal varies severalfold in apparently healthy individuals, and approximately one-third of the most insulin resistant of these individuals is at increased risk to develop various adverse clinical syndromes. Since direct measurements of insulin sensitivity are not practical in a clinical setting, several surrogate estimates of insulin action have been proposed, including fasting plasma insulin (FPI) concentration and the homeostasis model assessment of insulin resistance (HOMA-IR) calculated by a formula employing fasting plasma glucose (FPG) and FPI concentrations. The objective of this study was to compare FPI as an estimate of insulin-mediated glucose disposal with values generated by HOMA-IR in 758 apparently healthy nondiabetic individuals. Measurements were made of FPG, FPI, triglyceride (TG), and high-density lipoprotein cholesterol (HDL-C) concentrations, and insulin-mediated glucose uptake was quantified by determining steady-state plasma glucose (SSPG) concentration during the insulin suppression test. FPI and HOMA-IR were highly correlated (r = 0.98, P < 0.001). The SSPG concentration also correlated to a similar degree (P < 0.001) with FPI (r = 0.60) and HOMA-IR (r = 0.64). Furthermore, the relationship between FPI and TG (r = 0.35) and HDL-C (r = -0.40) was comparable to that between HOMA-IR and TG (r = 0.39) and HDL-C (r = -0.41). In conclusion, FPI and HOMA-IR are highly correlated in nondiabetic individuals, with each estimate accounting for ~40% of the variability (variance) in a direct measure of insulin-mediated glucose disposal. Calculation of HOMA-IR does not provide a better surrogate estimate of insulin action, or of its associated dyslipidemia, than measurement of FPI.

Pilot study of pioglitazone and exercise training effects on basal myocardial substrate metabolism and left ventricular function in HIV-positive individuals with metabolic complications

BACKGROUND

Individuals with HIV infection and peripheral metabolic complications have impaired basal myocardial insulin sensitivity that is related to left ventricular (LV) diastolic dysfunction. It is unknown whether interventions shown to be effective in improving peripheral insulin sensitivity can improve basal myocardial insulin sensitivity and diastolic function in people with HIV and peripheral metabolic complications.

OBJECTIVE

In a pilot study, we evaluated whether the peroxisome proliferator-activated receptor-gamma (PPAR-γ) agonist pioglitazone or combined endurance and resistance exercise training improves basal myocardial insulin sensitivity and diastolic function in HIV+ adults with peripheral metabolic complications.

DESIGN

Twenty-four HIV+ adults with metabolic complications including peripheral insulin resistance were randomly assigned to 4 months of pioglitazone (PIO; 30 mg/d) or supervised, progressive endurance and resistance exercise training (EXS; 90-120 min/d, 3 d/wk). Basal myocardial substrate metabolism was quantified by radioisotope tracer methodology and positron emission tomography (PET) imaging, and LV function was measured by echocardiography.

RESULTS

Twenty participants completed the study. Neither PIO nor EXS resulted in a detectable improvement in basal myocardial insulin sensitivity or diastolic function. Post hoc analyses revealed sample sizes of more than 100 participants are needed to detect significant effects of these interventions on basal myocardial insulin sensitivity and function.

CONCLUSIONS

PIO or EXS alone did not significantly increase basal myocardial insulin sensitivity or LV diastolic function in HIV+ individuals with peripheral metabolic complications.

Aldosterone excess impairs first phase insulin secretion in primary aldosteronism

CONTEXT

Primary aldosteronism (PA) represents the most frequent cause of secondary arterial hypertension. Conflicting data have been published regarding the effect of aldosterone excess on glucose metabolism.

OBJECTIVE

Our aim was to analyze insulin sensitivity and β-cell function in a cohort of PA patients. Prospective follow-up investigations were performed in a subgroup of patients before and after adrenalectomy to assess the metabolic outcome.

DESIGN

Oral glucose tolerance test, combined intravenous glucose tolerance test, hyperinsulinemic-euglycemic glucose clamp test, and arginine test were carried out after a 12-hour fasting period.

PATIENTS

Twenty-two consecutive patients with both unilateral aldosterone-producing adenoma and bilateral idiopathic adrenal hyperplasia were recruited through the Munich center of the German Conn's Registry. The control group of patients with essential hypertension (n = 11) of corresponding age and body mass index was recruited from our hypertension unit. A normotensive cohort (n = 11) served as a further control group.

RESULTS

At baseline, first-phase insulin reaction in intravenous glucose tolerance test was significantly reduced in patients with PA as compared to normal controls (36.0 [24.0; 58.7] vs 90.1 [52.6; 143.8] μU/mL, P = .031) and lower in comparison to essential hypertension without reaching statistical significance (53.2 [30.8; 73.3] μU/mL, P = .123). The study was repeated 6 months after unilateral adrenalectomy in 9 consecutive patients with aldosterone-producing adenoma. At this time point, blood pressure had been normalized in most of the patients while body mass index remained unchanged (26.9 [25.5; 37.6] vs 27.5 [25.1; 35.6] kg/m(2), P = .401). First-phase insulin reaction in response to glucose significantly increased at follow-up (from 36.0 [25.5; 58.7] to 48.5 [40.4; 95.2] μU/mL, P = .038, n = 9). In contrast, insulin sensitivity and response to iv arginine did not differ before and after adrenalectomy.

CONCLUSION

Aldosterone excess has a direct negative effect on β-cell function in patients with PA. After adrenalectomy, glucose-induced first-phase insulin secretion improves significantly in the patients.

The consequences of growth hormone-releasing hormone receptor haploinsufficiency for bone quality and insulin resistance

OBJECTIVE

Growth hormone (GH)/insulin-like growth factor (IGF) axis and insulin are key determinants of bone remodelling. Homozygous mutations in the GH-releasing hormone receptor (GHRHR) gene (GHRHR) are a frequent cause of genetic isolated GH deficiency (IGHD). Heterozygosity for GHRHR mutation causes changes in body composition and possibly an increase in insulin sensitivity, but its effects on bone quality are still unknown. The objective of this study was to assess the bone quality and metabolism and its correlation with insulin sensitivity in subjects heterozygous for a null mutation in the GHRHR.

PATIENTS AND METHODS

A cross-sectional study was performed on 76 normal subjects (68·4% females) (N/N) and 64 individuals (64·1% females) heterozygous for a mutation in the GHRHR (MUT/N). Anthropometric features, quantitative ultrasound (QUS) of the heel, bone markers [osteocalcin (OC) and CrossLaps], IGF-I, glucose and insulin were measured, and homeostasis model assessment of insulin resistance (HOMA(IR) ) was calculated.

RESULTS

There were no differences in age or height between the two groups, but weight (P = 0·007) and BMI (P = 0·001) were lower in MUT/N. There were no differences in serum levels of IGF-I, glucose, T-score or absolute values of stiffness and OC, but insulin (P = 0·01), HOMA(IR) (P = 0·01) and CrossLaps (P = 0·01) were lower in MUT/N. There was no correlation between OC and glucose, OC and HOMA(IR) in the 140 individuals as a whole or in the separate MUT/N or N/N groups.

CONCLUSIONS

This study suggests that one allele mutation in the GHRHR gene has a greater impact on energy metabolism than on bone quality.

High sensitivity C-reactive protein and its relationship with impaired glucose regulation in lean patients with polycystic ovary syndrome

The polycystic ovary syndrome (PCOS) is the most common endocrine-metabolic disorder, also associated with the metabolic syndrome. Serum high sensitivity C-reactive protein (hs-CRP), a marker of low-grade chronic inflammation is a potent predictor of cardiovascular events, closely linked to metabolic syndrome features and higher in patients with PCOS. However, hs-CRP in lean patients with PCOS has not been fully evaluated and few data are available. We aimed to investigate the relation between glucose intolerance and hs-CRP levels in lean patients with PCOS, and to evaluate the possible relationship between hs-CRP and PCOS by evaluating PCOS-related metabolic abnormalities in Korean women. We consecutively recruited 115 lean (BMI < 25kg/m(2)) patients diagnosed with PCOS and 103 lean healthy controls. The PCOS group was divided two groups: impaired glucose regulation (IGR) and normal glucose tolerance group (NGT). In lean patients with PCOS, hs-CRP level was higher in the IGR group than in the NGT group (0.60 ± 1.37 versus 0.18 ± 0.46, p(Bonf) = 0.023) and other metabolic risk factors were also higher in the IGR group than in the NGT group. And there were close relationships between hs-CRP level and metabolic risk factor, such as 2 h postprandial insulin level in the lean patients with PCOS.

Interaction between physical activity and sleep duration in relation to insulin resistance among non-diabetic Chinese adults

BACKGROUND

It is of a public health interest to explore the relationship between different types of physical activity, sleep duration and diabetes/insulin resistance. However, little is known about such relationship. This study examines the single and joint associations of different types of physical activity, and sleep duration on insulin resistance among non-diabetic Chinese adults.

METHODS

Data was collected from 1124 non-diabetic adults in Jiangsu Province from the China Health and Nutrition Survey (CHNS). Domestic, occupational, transportation and leisure physical activity were assessed in terms of metabolic equivalent (MET)-hours-per-week to account for both intensity and time spent. Sleep duration was categorized into three groups: ≤ 7 hours, 7-9 hours, and ≥ 9 hours. Insulin resistance was evaluated by the homeostasis model of assessment (HOMA) and defined as the highest quartile of HOMA.

RESULTS

Total physical activity was mainly composed of occupational activity (75.1%), followed orderly by domestic, transportation and leisure time activity in both men and women. Total physical activity level was strongly negatively associated with fasting insulin and HOMA (p < 0.001). Among four types of physical activity, occupational activity was significantly negatively associated with HOMA after full adjustment (p < 0.05). Transportation activity was also negatively associated with HOMA when adjusted for age and gender (p = 0.028). Moreover, the combination of low physical activity and short sleep duration was associated with the highest odds of insulin resistance (adjusted OR = 3.26, 95% CI: 1.57-6.78), compared to those with high physical activity and adequate sleep duration.

CONCLUSIONS

Physical activity, mainly occupational physical activity, was negatively associated with insulin resistance in non-diabetic Chinese population, independently of potential confounders. There was a synergic effect of low physical activity and short sleep duration on insulin resistance.

Effects of human immunodeficiency virus and metabolic complications on myocardial nutrient metabolism, blood flow, and oxygen consumption: a cross-sectional analysis

BACKGROUND

In the general population, peripheral metabolic complications (MC) increase the risk for left ventricular dysfunction. Human immunodeficiency virus infection (HIV) and combination anti-retroviral therapy (cART) are associated with MC, left ventricular dysfunction, and a higher incidence of cardiovascular events than the general population. We examined whether myocardial nutrient metabolism and left ventricular dysfunction are related to one another and worse in HIV infected men treated with cART vs. HIV-negative men with or without MC.

METHODS

Prospective, cross-sectional study of myocardial glucose and fatty acid metabolism and left ventricular function in HIV+ and HIV-negative men with and without MC. Myocardial glucose utilization (GLUT), and fatty acid oxidation and utilization rates were quantified using 11C-glucose and 11C-palmitate and myocardial positron emission tomography (PET) imaging in four groups of men: 23 HIV+ men with MC+ (HIV+/MC+, 42 ± 6 yrs), 15 HIV+ men without MC (HIV+/MC-, 41 ± 6 yrs), 9 HIV-negative men with MC (HIV-/MC+, 33 ± 5 yrs), and 22 HIV-negative men without MC (HIV-/MC-, 25 ± 6 yrs). Left ventricular function parameters were quantified using echocardiography.

RESULTS

Myocardial glucose utilization was similar among groups, however when normalized to fasting plasma insulin concentration (GLUT/INS) was lower (p < 0.01) in men with metabolic complications (HIV+: 9.2 ± 6.2 vs. HIV-: 10.4 ± 8.1 nmol/g/min/μU/mL) than men without metabolic complications (HIV+: 45.0 ± 33.3 vs. HIV-: 60.3 ± 53.0 nmol/g/min/μU/mL). Lower GLUT/INS was associated with lower myocardial relaxation velocity during early diastole (r = 0.39, p < 0.001).

CONCLUSION

Men with metabolic complications, irrespective of HIV infection, had lower basal myocardial glucose utilization rates per unit insulin that were related to left ventricular diastolic impairments, indicating that well-controlled HIV infection is not an independent risk factor for blunted myocardial glucose utilization per unit of insulin.

TRIAL REGISTRATION

NIH Clinical Trials NCT00656851.

Whole-body and muscle protein metabolism are not affected by acute deviations from habitual protein intake in older men: the Hormonal Regulators of Muscle and Metabolism in Aging (HORMA) Study

BACKGROUND

Acute deviations in protein intake before the quantification of protein kinetics in older humans may explain the controversy over the effects of older age on muscle protein synthesis and proteolysis rates.

OBJECTIVE

We hypothesized that an acute decrease in protein intake from the habitual intake is associated with lower muscle protein synthesis and higher proteolysis rates, whereas an acute increase in protein intake from the habitual intake is associated with higher muscle protein synthesis and lower proteolysis rates.

DESIGN

In 112 community-dwelling healthy men aged 65-90 y, we quantified resting whole-body [1,2-(13)C(2)]leucine kinetics, muscle mixed protein fractional synthesis rates (FSRs), and muscle proteasome proteolytic enzyme activities after participants consumed for 3 d controlled research meals (0.9-1.1 g protein · kg(-1) · d(-1)) that contained more or less protein than that habitually consumed and that induced alterations in nitrogen balance.

RESULTS

Protein kinetic parameters were not significantly different between the groups, despite controlled research protein intakes that were lower (-0.2 to -0.3 g · kg(-1) · d(-1)) or higher (+0.2 g · kg(-1) · d(-1)) than habitual intakes and that induced negative (-22 to -25 mg · kg(-1) · d(-1)) or positive (22-25 mg · kg(-1) · d(-1)) nitrogen balance. Within these acutely altered protein intake and nitrogen balance boundaries, a reduction in protein intake from habitual intake and induction of negative nitrogen balance were not associated with higher proteolysis or lower muscle FSR, and an acute increase in protein intake from habitual intake and induction of positive nitrogen balance were not associated with lower proteolysis or higher muscle FSR. A higher quantitative insulin sensitivity check index was associated with lower whole-body proteolysis rates.

CONCLUSIONS

The practice of acutely controlling protein intake, even at intakes lower than habitual intakes that induce negative nitrogen balance, before quantifying human protein kinetics does not significantly reduce muscle protein synthesis or increase proteolysis. Factors other than protein intake explain lower muscle protein synthesis rates with advanced age. This trial is registered at clinicaltrials.gov as NCT00183040.

Dietary effects on body composition, glucose metabolism, and longevity are modulated by skeletal muscle mitochondrial uncoupling in mice

Little is known about how diet and energy metabolism interact in determination of lifespan under ad libitum feeding. From 12 weeks of age until death, male and female wild-type (WT) and transgenic (TG) mice with increased skeletal muscle mitochondrial uncoupling (HSA-mUCP1 mice) were fed one of three different semisynthetic diets differing in macronutrient ratio: control (high-carbohydrate/low-fat-HCLF) and two high-fat diets: high-carbohydrate/high-fat (HCHF), and low-carbohydrate/high-fat (LCHF). Compared to control and LCHF, HCHF feeding rapidly and significantly increased body fat content in WT. Median lifespan of WT was decreased by 33% (HCHF) and 7% (LCHF) compared to HCLF. HCHF significantly increased insulin resistance (HOMA) of WT from 24 weeks on compared to control. TG mice had lower lean body mass and increased energy expenditure, insulin sensitivity, and maximum lifespan (+10%) compared to WT. They showed a delayed development of obesity on HCHF but reached similar maximum adiposity as WT. TG median lifespan was only slightly reduced by HCHF (−7%) and unaffected by LCHF compared to control. Correlation analyses showed that decreased longevity was more strongly linked to a high rate of fat gain than to adiposity itself. Furthermore, insulin resistance was negatively and weight-specific energy expenditure was positively correlated with longevity. We conclude that (i) dietary macronutrient ratios strongly affected obesity development, glucose homeostasis, and longevity, (ii) that skeletal muscle mitochondrial uncoupling alleviated the detrimental effects of high-fat diets, and (iii) that early imbalances in energy homeostasis leading to increased insulin resistance are predictive for a decreased lifespan.

Insulin resistance index (HOMA-IR) in the differentiation of patients with non-alcoholic fatty liver disease and healthy individuals

CONTEXT

Due to its good correlation to glycemic clamp, HOMA-IR has been widely utilized as insulin resistance index in clinical and epidemiological studies involving non-alcoholic fatty liver disease carriers. However, values used for this parameter have shown large variability.

OBJECTIVE

To identify the HOMA-IR cut value that best distinguishes non-diabetic non-alcoholic fatty liver disease patients from a control group.

METHODS

One hundred sixteen non-alcoholic fatty liver disease patients were studied, diagnosed by clinical, biochemical, and liver image or biopsy criteria, and 88 healthy individuals, without any liver disease and testing for oral glucose tolerance within normality. These groups did not differ in age and gender. All were submitted to oral glucose tolerance test and blood samples were collected for glucose and insulin measurements by immunofluorometric method. HOMA-IR was calculated according to the formula: fasting insulin (microU/L) x fasting glucose (nmol/L)/22.5.

RESULTS

NAFLD patients showed higher insulin, glycemia, and HOMA-IR values than control group, even when excluding glucose intolerant and diabetes mellitus patients by their glycemic curves. HOMA-IR 75th percentile for control group was 1.78 and the best area under the curve index was obtained for HOMA-IR values of 2.0 [AUC= 0.840 (0.781-0.899 CI 95%), sensitivity (Se): 85%, specificity (Sp): 83%] while value 2.5 showed best specificity without important loss in sensitivity [AUC=0,831 (0.773-0.888) Se = 72%, Sp = 94%].

CONCLUSION

HOMA-IR values above or equal to 2.0 or 2.5 show enhanced diagnostic value in distinguishing non-alcoholic fatty liver disease carriers from control group individuals.

Major depressive disorder and insulin resistance in nondiabetic young adults in the United States: the National Health and Nutrition Examination Survey, 1999-2002

OBJECTIVE

The association between depression and insulin resistance has been evaluated in previous studies with conflicting results. This study aimed to explore the relationship between major depressive disorder (MDD) and insulin resistance among nondiabetic young adult men and women in the United States.

METHOD

Analyses of cross-sectional data from the National Health and Nutrition Examination Survey (NHANES), 1999-2002, were conducted. The nationally representative sample consisted of 279 men and 358 women aged 20-39 years. MDD was determined by the WHO Composite International Diagnostic Interview (CIDI). Insulin resistance was measured by the homeostasis model assessment for insulin resistance.

RESULTS

Of 637 subjects, 16 men and 18 women had MDD (weighted percentage = 6.6%, SE = 1.2). Using logistic regression, no significant association was found between MDD and insulin resistance among the nondiabetic young adults in bivariate analysis (β = -0.01, OR = 0.99, 95% CI = [0.38, 2.57], p = .98). A significant interaction effect between gender and MDD was observed. For men, MDD was negatively associated with insulin resistance after adjusting for age, race/ethnicity, waist circumference, smoking status, systolic blood pressure and triglyceride level (β = -2.12, OR = 0.12, 95% CI = [0.02, 0.62], p = .01). No significant association between MDD and insulin resistance among women was found (β = 0.61, OR = 1.84, 95% CI = [0.47, 7.14], p = .38).

CONCLUSIONS

Overall findings suggest there is no significant association between MDD and insulin resistance among nondiabetic young adults aged 20-39 years. However, gender differences in this relationship were noted.

Statin users without an APOE-epsilon4 allele have increased insulin resistance

The present study examined the relationships among statin use, APOE genotype, and insulin resistance as measured by the homeostasis model assessment of insulin resistance (HOMA-IR) in healthy older adults. APOE epsilon4- (i.e., not having an epsilon4 allele) statin users had higher HOMA-IR values compared with epsilon4+/statin users (p=0.0169), and with non-users who were epsilon4- (p=0.0003) or epsilon4+ (p=0.0006). These results suggest that statin use may modulate insulin levels for individuals without an APOE epsilon4 allele.

Impaired glucose metabolism and the exaggerated blood pressure response to exercise treadmill testing in normotensive patients

The authors aimed to investigate the association between glucose metabolism measures and the exaggerated blood pressure response (EXBPR) to exercise testing in normotensive nondiabetic patients. One hundred and forty-two consecutive patients underwent office blood pressure (BP) measurements, 24-hour BP monitoring, echocardiography, and treadmill exercise test according to the Bruce protocol. The population was divided into 2 groups according to EXBPR at a submaximal workload level. Furthermore, blood samples were obtained for fasting glucose (FG), fasting insulin (FI), and lipid profile assessment. Measures of insulin resistance (homeostasis model assessment of insulin resistance [HOMA-IR], quantitative insulin sensitivity check index [QUICKI], and McAuley index) were also estimated, and a standardized oral glucose tolerance test was performed to evaluate glucose levels at 120 minutes (G120). Patients with EXBPR (n=40; 27 men) compared with those without EXBPR (n=102; 66 men) were older by 4+/-6 years (P<.001). FG, FI, G120, HOMA-IR, QUICKI, and McAuley index differed in patients with EXBPR compared with those without EXBPR (P<.001 for all). Logistic multivariable regression models revealed that the studied glucose metabolism measures, duration of exercise, and 24-hour systolic BP remained determinants of EXBPR (P<.05 for all) after adjustment. Impaired glucose measures are significant determinants of EXBPR to exercise testing in normotensive nondiabetic patients, suggesting that impaired glucose metabolism may contribute to adverse cardiovascular prognosis including new-onset hypertension.

Prognostic role of insulin resistance as assessed by homeostatic model assessment index in the acute phase of myocardial infarction in nondiabetic patients submitted to percutaneous coronary intervention

BACKGROUND AND OBJECTIVES

Little information is available on the relation between insulin resistance and acute myocardial infarction.

METHODS

In 253 consecutive nondiabetic patients with ST elevation myocardial infarction (STEMI) submitted to percutaneous coronary intervention, we assessed the prevalence of insulin resistance by homeostatic model assessment (HOMA) index and its prognostic role in early and late mortality.

RESULTS

Insulin resistance was detectable in 52.9% of patients. Anterior STEMI was more frequent in insulin-resistant patients (P = 0.040), who showed higher values of probrain natriuretic peptide (P = 0.010), creatinine (P < 0.001), creatinine phosphokinase and creatinine phosphokinase-MB (MB, isoenzyme present in the myocardium; P = 0.016 and P = 0.003, respectively). At backward stepwise logistic regression analysis, the following variables were independent predictors for intra-intensive cardiac care unit mortality: HOMA index [hazard ratio 1.40; 95% confidence interval (CI) 1.02-1.95; P = 0.049]; C-peptide (hazard ratio 3.14; 95% CI 1.40-24.80; P = 0.001) and lactic acid (hazard ratio 2.50; 95% CI 1.41-4.44; P = 0.002). At long-term follow-up (Cox regression analysis), neither fasting glycaemia nor HOMA index resulted in predictors for mortality.

CONCLUSION

In nondiabetic STEMI patients submitted to percutaneous coronary intervention, insulin resistance, as assessed by HOMA index, is quite common and helps in the early prognostic stratification, as it represents an independent predictor of in-hospital mortality.

Non-alcoholic fatty liver disease is associated with left ventricular diastolic dysfunction in essential hypertension

BACKGROUND AND AIM

Insulin resistance is recognized as the pathophysiological hallmark of non-alcoholic fatty liver disease (NAFLD). A relation between insulin sensitivity and left ventricular morphology and function has been reported in essential hypertension, where a high prevalence of NAFLD has been recently found. We investigated the inter-relationship between left ventricular morphology/function, metabolic parameters and NAFLD in 86 never-treated essential hypertensive patients subdivided in two subgroups according to the presence (n = 48) or absence (n = 38) of NAFLD at ultrasonography.

METHODS AND RESULTS

The two groups were similar as to sex, age and blood pressure levels. No patient had diabetes mellitus, obesity, hyperlipidemia, or other risk factors for liver disease. Body mass index, waist circumference, triglycerides, glucose, insulin, homeostasis model of assessment index for insulin resistance (HOMA-IR), aspartate aminotransferase and alanine aminotransferase were higher and adiponectin levels were lower in patients with NAFLD than in patients without NAFLD, and were associated with NAFLD at univariate analysis. Patients with NAFLD had similar prevalence of left ventricular hypertrophy compared to patients without NAFLD, but a higher prevalence of diastolic dysfunction (62.5 vs 21.1%, P < 0.001), as defined by E/A ratio <1 and E-wave deceleration time >220 ms. Diastolic dysfunction (P = 0.040) and HOMA-IR (P = 0.012) remained independently associated with NAFLD at backward multivariate analysis.

CONCLUSIONS

Non-alcoholic fatty liver disease was associated with insulin resistance and abnormalities of left ventricular diastolic function in a cohort of patients with essential hypertension, suggesting a concomitant increase of metabolic and cardiac risk in this condition.

Testosterone and growth hormone improve body composition and muscle performance in older men

CONTEXT

Impairments in the pituitary-gonadal axis with aging are associated with loss of muscle mass and function and accumulation of upper body fat.

OBJECTIVES

We tested the hypothesis that physiological supplementation with testosterone and GH together improves body composition and muscle performance in older men.

DESIGN, SETTING, AND PARTICIPANTS

One hundred twenty-two community-dwelling men 70.8 +/- 4.2 yr of age with body mass index of 27.4 +/- 3.4 kg/m2, testosterone of 550 ng/dl or less, and IGF-I in lower adult tertile (< or =167 ng/dl) were randomized to receive transdermal testosterone (5 or 10 g/d) during a Leydig cell clamp plus GH (0, 3, or 5 microg/kg . d) for 16 wk.

MAIN OUTCOME MEASURES

Body composition by dual-energy x-ray absorptiometry, muscle performance, and safety tests were conducted.

RESULTS

Total lean body mass increased (1.0 +/- 1.7 to 3.0 +/- 2.2 kg) as did appendicular lean tissue (0.4 +/- 1.4 to 1.5 +/- 1.3 kg), whereas total fat mass decreased by 0.4 +/- 0.9 to 2.3 +/- 1.7 kg as did trunk fat (0.5 +/- 0.9 to 1.5 +/- 1.0 kg) across the six treatment groups and by dose levels for each parameter (P < or = 0.0004 for linear trend). Composite maximum voluntary strength of upper and lower body muscles increased by 14 +/- 34 to 35 +/- 31% (P < 0.003 in the three highest dose groups) that correlated with changes in appendicular lean mass. Aerobic endurance increased in all six groups (average 96 +/- 137 sec longer). Systolic and diastolic blood pressure increased similarly in each group with mean increases of 12 +/- 14 and 8 +/- 8 mm Hg, respectively. Other predictable adverse events were modest and reversible.

CONCLUSIONS

Supplemental testosterone produced significant gains in total and appendicular lean mass, muscle strength, and aerobic endurance with significant reductions in whole-body and trunk fat. Outcomes appeared to be further enhanced with GH supplementation.

Prognostic value of exercise echocardiography in diabetic patients

BACKGROUND

Coronary artery disease (CAD) is the leading cause of death in diabetic patients. Although exercise echocardiography (EE) is established as a useful method for diagnosis and stratification of risk for CAD in the general population, there are few studies on its value as a prognostic tool in diabetic patients. The purpose of this investigation was to evaluate the value of EE in predicting cardiac events in diabetics.

METHODS

193 diabetic patients, 97 males, 59.8 +/- 9.3 yrs (mean +/- SD) were submitted to EE between 2001 and 2006 and followed from 7 to 65 months with median of 29 months by phone calls and personal interviews with patients and their primary physician, and reviewing medical records and death certificates. The end points were cardiac events, defined as non-fatal myocardial infarction, late myocardial revascularization and cardiac death. Sudden death without another explanation was considered cardiac death. Survival free of end points was estimated by the Kaplan-Meier method.

RESULTS

Twenty-six cardiac events were registered in 24 individuals during the follow-up. The rates of cardiac events were 20.6 and 7% in patients with positive and negative EE, respectively (p < 0.001). Predictors of cardiac events included sedentary lifestyle, with RR of 2.57 95%CI [1.09 to 6.02] (P = 0.03) and positive EE, with RR 3.63, 95%CI [1.44 to 9.16] (P = 0.01). Patients with positive EE presented higher rates of cardiac events at 12 months (6.8% vs. 2.2%), p = 0.004.

CONCLUSION

EE is a useful method to predict cardiac events in diabetic patients with suspected or known CAD.

[Critical analysis on the use of the homeostasis model assessment (HOMA) indexes in the evaluation of the insulin resistance and the pancreatic beta cells functional capacity]

Beta-cell dysfunction and insulin resistance are interrelated metabolic abnormalities in the aetiology of Type 2 Diabetes. In several countries, increases in the prevalence of obesity and diabetes have been observed in association with the presence of insulin resistance. In this context, measurement of insulin resistance and beta-cell function is useful. The HOMA indexes (Homeostasis Model Assessment) have been widely used, representing an alternative for the evaluation of these parameters, particularly as a fast, easy and cheap method. This review discusses the origin and evolution of the HOMA index, as well as details of the method, analyzing features related to its validation and the cutoff limits for its interpretation.

Evaluation of high-protein supplementation in weight-stable HIV-positive subjects with a history of weight loss: a randomized, double-blind, multicenter trial

BACKGROUND

HIV patients with wasting are at increased risk of opportunistic complications and fatality.

OBJECTIVE

We hypothesized that augmenting dietary intake with high-biologic-value protein would enhance weight and lean tissue in weight-stable subjects with a prior unintentional weight loss of >3%.

DESIGN

Fifty-nine subjects with HIV RNA concentrations <5000 copies/mL were randomly assigned to receive a 280-kcal supplement containing 40 g whey protein or a matched isocaloric control supplement without added protein twice daily for 12 wk.

RESULTS

Before the study, intake of total energy and protein exceeded estimated requirements (44.3 +/- 12.6 kcal x kg(-1) x d(-1) and 1.69 +/- 0.55 g x kg(-1) x d(-1), respectively). Both supplements failed to increase total energy intake because of decreases in self-selected food intake. Changes in weight (0.8 +/- 2.4 and 0.7 +/- 2.4 kg) and lean body mass (0.3 +/- 1.4 and 0.3 +/- 1.5 kg) did not differ significantly between the whey protein and control groups, respectively. Waist-to-hip ratio improved more with whey protein (-0.02 +/- 0.05) than with the control (0.01 +/- 0.03; P = 0.025) at week 6 but not at week 12. Fasting triacylglycerol increased by 39 +/- 98 mg/dL with the control supplement and decreased by 16 +/- 62 mg/dL with whey protein at week 12 (P = 0.03). CD4 lymphocytes increased by 31 +/- 84 cells/mm(3) with whey protein and decreased by 5 +/- 124 cells/mm(3) with the control supplement at 12 wk (P = 0.03). Gastrointestinal symptoms occurred more often with whey protein.

CONCLUSIONS

A whey protein supplement did not increase weight or lean body mass in HIV-positive subjects who were eating adequately, but it did increase CD4 cell counts. The control supplement with rapidly assimilable carbohydrate substituted for protein increased cardiovascular disease risk factors. Careful dietary and weight history should be obtained before starting nutritional supplements in subjects with stable weight loss and good viral control.

An international matched cohort study of the contribution of metabolic impairments to subclinical atherosclerosis in United Kingdom and Jamaican African-Caribbeans

BACKGROUND

A gradient of increased vascular risk exists across the African diaspora. We hypothesised that increased insulin resistance with environmental transition contributes to this risk.

METHODS

The study was undertaken in 73 healthy African-Caribbeans in the UK and 151 age and sex matched African-Caribbeans in Jamaica. Body mass index (BMI), fasting insulin, insulin resistance, carotid intima media thickness (CIMT) and endothelium dependent vasodilatation (EDV) were compared. CIMT was measured ultrasonographically in the distal 1cm of both common carotid arteries. EDV was measured the absolute change from baseline in the Reflection index (RI) of the digital volume pulse during intravenous infusion of albuterol (DeltaRI(ALB)).

RESULTS

UK African-Caribbeans had greater CIMT (mean difference 0.124 [95% C.I. 0.075-0.173] mm, p<0.0001) and decreased EDV (mean difference in DeltaRI(ALB) 5.1 [95% C.I. 2.5-7.6] percentage points, p<0.0001). This was associated with higher insulin concentrations (mean difference 1.6 [95% C.I. 1.3-4.1] microU/mL, p=0.038) and greater HOMA score (2.8 versus 2.0; p=0.035) despite no significant differences in BMI (28.8 versus 27.6; p=0.168) or the waist to hip ratio (0.86 versus 0.85; p=0.188). HOMA scores correlated positively with CIMT (r=0.35, p=0.01) and negatively with DeltaRI(ALB) (r=-0.17; p=0.02) in UK, but not in Jamaican, African-Caribbeans. A significant interaction was seen between HOMA and UK domicile for CIMT (p<0.0001) and between fasting insulin and UK domicile for DeltaRI(ALB) (p<0.0001).

CONCLUSIONS

Increased insulin resistance, associated with living in a nutritionally enriched environment, may contribute to early subclinical atherosclerosis in UK African-Caribbeans.

Congenital growth hormone (GH) deficiency and atherosclerosis: effects of GH replacement in GH-naive adults

BACKGROUND

GH deficiency (GHD) in adults is associated with increased abdominal adiposity and systolic blood pressure, total and low-density lipoprotein cholesterol, and C-reactive protein.

METHODS

We have studied the effects of 6-month GH replacement therapy in 20 adult members of a large Brazilian kindred with lifelong severe and isolated GHD due to a homozygous mutation in GHRH receptor gene (46 +/- 14.5 yr; 122 +/- 7.7 cm; 36.7 +/- 5.4 kg; 10 men). Subjects were studied at baseline, after 6-month bimonthly depot GH injections (Nutropin Depot; Genentech, Inc., South San Francisco, CA) [post GH (pGH)], and after 6- and 12-month washout.

RESULTS

Despite modest trough serum IGF-I increase, GH replacement therapy caused a decrease in skinfolds and in waist-hip ratio, with a rebound increase at 12 months. Total and low-density lipoprotein cholesterol were reduced pGH and returned to baseline at 6 months. High-density lipoprotein cholesterol increased pGH, but at 12 months was lower than baseline. A progressive increase in left ventricular mass index, posterior wall, and septum thickness occurred from pGH to 12 months, and of carotid intima-media thickness, from 6 to 12 months. Individuals were 6, 16, and 52 times more likely to have an atherosclerotic carotid plaque at pGH, 6 and 12 months, respectively, when compared with baseline.

CONCLUSION

In patients with lifetime isolated GHD, 6-month treatment with GH has reversible beneficial effects on body composition and metabolic profile, but it causes a progressive increase in intima-media thickness and in the number of atherosclerotic carotid plaques.

Correlation of calculated indices of insulin resistance (QUICKI and HOMA) with the euglycaemic hyperinsulinaemic clamp technique for evaluating insulin resistance in critically ill patients

BACKGROUND AND OBJECTIVE

Insulin resistance is frequently observed in critical illness. It can be quantified by the expensive and time-consuming euglycaemic hyperinsulinaemic clamp technique (M-value) and calculated indices of insulin resistance (Quantitative Insulin Sensitivity Check Index; QUICKI and Homeostasis Model Assessment; HOMA) with lower costs and efforts. We performed an observational study to assess the reliability of QUICKI and HOMA to evaluate insulin resistance in critically ill patients compared with the current gold standard method, the euglycaemic hyperinsulinaemic clamp technique.

METHODS

Insulin resistance was measured in 30 critically ill medical patients by the euglycaemic hyperinsulinaemic clamp technique (M-value) as well as calculated using QUICKI and HOMA. Correlations between the M-values as well as QUICKI and HOMA were assessed by means of the Pearson's correlation coefficient.

RESULTS

M-value, QUICKI and HOMA indicated insulin resistance in all 30 patients. However, both indices QUICKI and HOMA did not correlate with the M-values in our patients (r2 = 0.008 and 0.0005, respectively). A significant negative correlation was found between the M-value and the severity of illness assessed by the APACHE (Acute Physiology and Chronic Health Evaluation) III score (r2 = 0.16; P < 0.05). In contrast, neither HOMA nor QUICKI correlated with the APACHE III score (r2 = 0.034 and 0.033, respectively).

CONCLUSIONS

Although QUICKI and HOMA indicated insulin resistance in the critically ill medical patients, both indices did not correlate with the M-value. Therefore, the euglycaemic hyperinsulinaemic clamp technique remains the gold standard for estimating insulin resistance in critically ill patients.

Heterozygosity for a mutation in the growth hormone-releasing hormone receptor gene does not influence adult stature, but affects body composition

CONTEXT

Biallelic mutations in the GHRH receptor (GHRHR) gene (GHRHR) are a frequent cause of isolated GH deficiency (IGHD). Although heterozygous carriers of these mutations appear normal, we hypothesized that heterozygosity for a GHRHR mutation might be associated with a subclinical phenotype.

METHODS

We studied members of a large Brazilian kindred with IGHD (Itabaianinha cohort) caused by a homozygous null GHRHR mutation. We compared 76 adult subjects (age, 25-75 yr) heterozygous for the mutation (WT/MT) with 77 sex-matched controls from the same population who are homozygous for the wild-type GHRHR allele (WT/WT).

RESULTS

We found no difference in adult height and sd score for serum IGF-I between the two groups. Body weight, body mass index, skin folds, waist and hip circumferences, and lean mass were all reduced in WT/MT subjects. Percentage fat mass and waist/hip ratio were similar in the two groups. Fasting insulin and homeostasis model assessment of insulin resistance were lower in WT/MT. The other biochemical parameters [total and fractionated cholesterol, triglycerides, lipoprotein (a), and C-reactive protein] were not different between the two groups.

CONCLUSIONS

Heterozygosity for a null GHRHR mutation is not associated with reduction in adult stature or in serum IGF-I but is associated with changes in body composition and possibly an increase in insulin sensitivity. These effects do not seem to be modulated by changes in circulating IGF-I.

Validity and reproducibility of HOMA-IR, 1/HOMA-IR, QUICKI and McAuley's indices in patients with hypertension and type II diabetes

The aim of this study was to evaluate the validity and reliability of homeostasis model assessment-insulin resistance (HOMA-IR) index, its reciprocal (1/HOMA-IR), quantitative insulin sensitivity check index (QUICKI) and McAuley's index in hypertensive diabetic patients. In 78 patients with hypertension and type II diabetes glucose, insulin and triglyceride levels were determined after a 12-h fast to calculate these indices, and insulin sensitivity (IS) was measured with the hyperinsulinemic euglycemic clamp technique. Two weeks later, subjects had again their glucose, insulin and triglycerides measured. Simple and multiple linear regression analysis were applied to assess the validity of these indices compared to clamp IS and coefficients of variation between the two visits were estimated to assess their reproducibility. HOMA-IR index was strongly and inversely correlated with the basic IS clamp index, the M-value (r=-0.572, P<0.001), M-value normalized with subjects' body weight or fat-free mass and every other clamp-derived index. 1/HOMA-IR and QUICKI indices were positively correlated with the M-value (r=0.342, P<0.05 and r=0.456, P<0.01, respectively) and the rest clamp indices. McAuley's index generally presented less strong correlations (r=0.317, P<0.05 with M-value). In multivariate analysis, HOMA-IR was the best fit of clamp-derived IS. Coefficients of variation between the two visits were 23.5% for HOMA-IR, 19.2% for 1/HOMA-IR, 7.8% for QUICKI and 15.1% for McAuley's index. In conclusion, HOMA-IR, 1/HOMA-IR and QUICKI are valid estimates of clamp-derived IS in patients with hypertension and type II diabetes, whereas the validity of McAuley's index needs further evaluation. QUICKI displayed better reproducibility than the other indices.

Association of Adrenal Steroids With Hypertension and the Metabolic Syndrome in Blacks

Blacks have a high prevalence of hypertension and adrenal cortical adenomas/hyperplasia. We evaluated the hypothesis that adrenal steroids are associated with hypertension and the metabolic syndrome in blacks. Ambulatory blood pressures, anthropometric measurements, and measurements of plasma renin activity (PRA), aldosterone, fasting lipids, glucose, and insulin were obtained in 397 subjects (46% hypertensive and 50% female) after discontinuing antihypertensive and lipid-lowering medications. Hypertension was defined as average ambulatory blood pressure >130/85 mm Hg. Late-night and early morning salivary cortisol, 24-hour urine-free cortisol, and cortisone excretion were measured in a consecutive subsample of 97 subjects (40% hypertensive and 52% female). Compared with normotensive subjects, hypertensive subjects had greater waist circumference and unfavorable lipid profiles, were more insulin resistant, and had lower PRA and higher plasma aldosterone and both late-night and early morning salivary cortisol concentrations. Twenty-four-hour urine-free cortisol and cortisone did not differ. Overall, ambulatory blood pressure was positively correlated with plasma aldosterone (r=0.22; P<0.0001) and late-night salivary cortisol (r=0.23; P=0.03) and inversely correlated with PRA (r=-0.21; P<0.001). Plasma aldosterone correlated significantly with waist circumference, total cholesterol, triglycerides, insulin, and the insulin-resistance index. Based on Adult Treatment Panel III criteria, 17% of all of the subjects were classified as having the metabolic syndrome. Plasma aldosterone levels, but not PRA, were elevated in subjects with the metabolic syndrome (P=0.0002). The association of aldosterone with blood pressure, waist circumference, and insulin resistance suggests that aldosterone may contribute to obesity-related hypertension in blacks. In addition, we speculate that relatively high aldosterone and low PRA in these hypertensive individuals may reflect a mild variant of primary aldosteronism.

Surrogate estimates of insulin sensitivity in subjects with hypertension

The purpose of the study is to compare surrogate estimates of insulin sensitivity with a directly measured insulin sensitivity index, steady-state plasma glucose (SSPG) from insulin suppression test (IST), in subjects with hypertension. Two hundred and twenty-eight hypertensive patients who received IST for SSPG were included for analysis. Estimates from fasting measurements alone, homeostasis model assessment for insulin resistance (HOMA-IR) and quantitative insulin sensitivity check index (QUICKI)), and indices from fasting and/or 2 h samples (ISI(0,120) and ISI(TX)) were calculated. In addition to Pearson and partial correlations, variance-component models were used to test the relationship between surrogate estimates of insulin sensitivity and SSPG. A large proportion of variance owing to covariates in the variance-component models indicated the goodness of model fit, irrespective of the independence among variables. SSPG was positively correlated with logarithmic transformation (Log) (HOMA-IR) and negatively correlated with QUICKI, Log (ISI(0,120)) and ISI(TX) (all P<0.0001). Log (ISI(0,120)) seemed to have a better correlation with SSPG (r=-0.72) than other measures in partial correlation. The proportion of variance owing to all covariates of Log (ISI(0,120)) and ISI(TX) were larger than those of Log (HOMA-IR) and QUICKI in the variance-component models. After adjustments for demographic and obesity covariates, the proportion of variance explained by Log (ISI(0,120)) were largest among the surrogate measures in the variance-component models. Our results showed that ISI(0,120) and ISI(TX) correlated better with SSPG than those used fasting measures alone (HOMA-IR and QUICKI). Log (ISI(0,120)) currently showing the strongest association with SSPG than other estimates is adaptable for use in large studies of hypertension.