Insulin secretion in metabolically obese, but normal weight, and in metabolically healthy but obese individuals

Metabolomics Reveals Metabolically Healthy and Unhealthy Obese Individuals Differ in their Response to a Caloric Challenge

OBJECTIVE

To determine if metabolically healthy obese (MHO) individuals have a different metabolic response to a standardized diet compared to lean healthy (LH) and metabolically unhealthy obese (MUO) individuals.

METHODS

Thirty adults (35-70 yrs) were classified as LH, MHO, and MUO according to anthropometric and clinical measurements. Participants consumed a standardized high calorie meal (~1330 kcal). Blood glucose and insulin were measured at fasting, and 15, 30, 60, 90 and 120 min postprandially. Additional blood samples were collected for the targeted analysis of amino acids (AAs) and derivatives, and fatty acids (FAs).

RESULTS

The postprandial response (i.e., area under the curve, AUC) for serum glucose and insulin were similar between MHO and LH individuals, and significantly lower than MUO individuals (p < 0.05). Minor differences were found in postprandial responses for AAs between MHO and MUO individuals, while three polyunsaturated FAs (linoleic acid, γ-linolenic acid, arachidonic acid) showed smaller changes in serum after the meal in MHO individuals compared to MUO. Fasting levels for various AAs (notably branched-chain AA) and FAs (e.g., saturated myristic and palmitic acids) were found to correlate with glucose and insulin AUC.

CONCLUSION

MHO individuals show preserved insulin sensitivity and a greater ability to adapt to a caloric challenge compared to MUO individuals.

Prevalence of Insulin Resistance in Subjects with Nonalcoholic Fatty Liver Disease and Its Predictors in a Chinese Population

OBJECTIVE

Insulin resistance (IR) is a key factor involved in the development and progression of nonalcoholic fatty liver disease (NAFLD). However, the prevalence of IR in NAFLD patients and its risk factors have been rarely reported, especially in China. This prospective study was undertaken to clarify these issues in the Chinese population.

METHODS

A total of 600 NAFLD patients and 300 age- and sex-matched healthy controls were recruited between January 1, 2011, and December 31, 2013. Demographic information and clinical characteristics were collected, and the presence of IR was evaluated using the homeostasis model. Uni- and multivariate analyses were conducted, and receiver operating characteristic (ROC) curves were generated to identify IR predictors.

RESULTS

NAFLD patients had a much higher prevalence of IR than healthy controls (37.8 vs. 2.3 %, P < 0.001). The rates of elevated alanine transferase (ALT) and aspartate transferase (AST) levels were much higher in NAFLD patients with IR than those without (53.7 vs. 41.6 % and 28.6 vs. 18.2 %, respectively, P < 0.001). Uni- and multivariate analyses revealed that female sex, general obesity, abdominal obesity, and hypertension were independent predictors for IR. The area under the ROC curve for fasting plasma insulin (FPI) detecting IR was 0.93 (P < 0.001), and the optimal cutoff was 11.3 μU/ml (sensitivity = 0.86, specificity = 0.92).

CONCLUSION

Chinese NAFLD patients are susceptible to IR. Female sex, general and abdominal obesity, and hypertension were independent predictors for IR in NAFLD patients. FPI is an optimal predictor for IR.

Normal-weight obesity: implications for cardiovascular health

We sought to review the epidemiological features and clinical implications of normal-weight obesity. The concept of normal-weight obesity has been recently reported as an important risk factor for cardiovascular disease, metabolic dysregulation, and poor functional outcomes. However, in clinical practice, normal-weight obesity is not commonly recognized. In this review, we examine the clinical significance and important epidemiological outcomes of normal-weight obesity and describe other variants of adiposity and adiposity-related metabolic status. The incorporation of measures of body fat content and distribution in the clinical setting could allow more accurate identification of adiposity-related long-term risk. This could in turn lead to early lifestyle changes and behavioral modifications that are essential to the treatment of obesity.

TonEBP suppresses adipogenesis and insulin sensitivity by blocking epigenetic transition of PPARγ2

TonEBP is a key transcription factor in cellular adaptation to hypertonic stress, and also in macrophage activation. Since TonEBP is involved in inflammatory diseases such as rheumatoid arthritis and atherosclerosis, we asked whether TonEBP played a role in adipogenesis and insulin resistance. Here we report that TonEBP suppresses adipogenesis and insulin signaling by inhibiting expression of the key transcription factor PPARγ2. TonEBP binds to the PPARγ2 promoter and blocks the epigenetic transition of the locus which is required for the activation of the promoter. When TonEBP expression is reduced, the epigenetic transition and PPARγ2 expression are markedly increased leading to enhanced adipogenesis and insulin response while inflammation is reduced. Thus, TonEBP is an independent determinant of adipose insulin sensitivity and inflammation. TonEBP is an attractive therapeutic target for insulin resistance in lieu of PPARγ agonists.

Comparison of Serum Adipocytokine Levels according to Metabolic Health and Obesity Status

BACKGROUND

Metabolic health is an emerging concept that is highly correlated with various metabolic complications, and adipocytokines have been causally linked to a wide range of metabolic diseases. Thus, this study compared serum adipocytokine levels according to metabolic health and obesity status.

METHODS

Four hundred and fifty-six nondiabetic subjects (mean age, 40.5 years) were categorized into four groups according to metabolic health and obesity status: metabolically healthy nonobese (MHNO), metabolically healthy obese (MHO), metabolically unhealthy nonobese (MUHNO), and metabolically unhealthy obese (MUHO). Being metabolically healthy was defined as the presence of fewer than two of the following five metabolic abnormalities: high blood pressure, high fasting blood glucose, high triglyceride, low high density lipoprotein cholesterol, and being in the highest decile of the homeostatic model assessment of insulin resistance index. Obesity status was assessed using body mass index (BMI), with obesity defined as a BMI higher than 25 kg/m². Levels of serum interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor α (TNF-α), and adipocyte fatty acid binding protein (A-FABP) were also evaluated.

RESULTS

Of the 456 subjects, 247 (54.2%) were in the MHNO group, 66 (14.5%) were in the MHO group, 66 (14.5%) were in the MUHNO group, and 77 (16.9%) were in the MUHO group. There were no significant differences in IL-6 or MCP-1 levels among the groups, but levels of TNF-α and A-FABP were significantly higher in the MUHNO group compared to the MHNO group.

CONCLUSION

High TNF-α and A-FABP levels are significantly associated with metabolically unhealthiness in nonobese Korean individuals.

Obesity, insulin resistance and comorbidities? Mechanisms of association

Overall excess of fat, usually defined by the body mass index, is associated with metabolic (e.g. glucose intolerance, type 2 diabetes mellitus (T2DM), dyslipidemia) and non-metabolic disorders (e.g. neoplasias, polycystic ovary syndrome, non-alcoholic fat liver disease, glomerulopathy, bone fragility etc.). However, more than its total amount, the distribution of adipose tissue throughout the body is a better predictor of the risk to the development of those disorders. Fat accumulation in the abdominal area and in non-adipose tissue (ectopic fat), for example, is associated with increased risk to develop metabolic and non-metabolic derangements. On the other hand, observations suggest that individuals who present peripheral adiposity, characterized by large hip and thigh circumferences, have better glucose tolerance, reduced incidence of T2DM and of metabolic syndrome. Insulin resistance (IR) is one of the main culprits in the association between obesity, particularly visceral, and metabolic as well as non-metabolic diseases. In this review we will highlight the current pathophysiological and molecular mechanisms possibly involved in the link between increased VAT, ectopic fat, IR and comorbidities. We will also provide some insights in the identification of these abnormalities.

Metabolically healthy obesity--does it exist?

The prevalence of obesity has been increasing worldwide over the past 30 years and is a major public health concern. Obesity is known to be associated with metabolic disturbances including insulin resistance and inflammation; however, there is a subset of obese subjects who have normal metabolic profiles, and they have been identified as the metabolically healthy obese (MHO). Several studies have described MHO as obese individuals who have high levels of insulin sensitivity and the absence of diabetes, dyslipidemia, or hypertension. The prevalence of MHO varies from 20 to 30% among obese individuals. This review will discuss the MHO phenotype; the differences between MHO and metabolically unhealthy obese (MUO) individuals; and the possible underlying mechanisms including adipocyte differentiation, immune regulation, and cellular energy metabolism.

Body shape index versus body mass index as correlates of health risk in young healthy sedentary men

Recently a new simply calculated index of body composition -a body shape index (ABSI) has been introduced as an index more reliable than BMI of association between body composition and all-cause mortality. However, until now associations between ABSI and metabolic risk factors have not been evaluated. A total of 114 male university students not engaged in any planned physical activity participated in the present study. Anthropometric measurements (weight, height, waist circumference) were recorded. Body mass index (BMI) was calculated from weight and height, body shape index (ABSI) was calculated from waist circumference, weight, height and BMI. Blood was withdrawn after an overnight fast from the antecubital vein. Triacylglycerols, total cholesterol and HDL-cholesterol levels in plasma were determined using colorimetric methods and Randox commercial kits. Plasma LDL-cholesterol concentrations were calculated according to the Friedewald formula. Circulating insulin was assayed using a standard radioimmunological method with monoclonal antibodies against insulin and BioSource commercial kits. BMI was slightly, but significantly correlated only with circulating TG (r=0.330, p < 0.001) In contrast, ABSI was slightly, but significantly correlated with plasma levels of insulin (r=0.360, p<0.001), TC (r=0.270, p<0.002), LDL-C and non-HDL-C (r=0.300, p<0.001). In participants at the upper quartile of BMI circulating TG was higher (by 50%, p<0.05) than in their counterparts at the lower BMI quartile. Subjects representing the upper quartile of ABSI were characterized by higher plasma levels of insulin, TC, LDL-C and non-HDL in comparison with subjects at the lower ABSI quartile. (by 92 %, 11. %, 29 % and 21 % respectively, p<0.001). ABSI, a new simply calculated index of body fat seems to more accurately depict the variability in circulating insulin and lipoproteins than BMI at least in young, healthy male subjects.

Main characteristics of metabolically obese normal weight and metabolically healthy obese phenotypes

In this review, the influence of fat depots on insulin resistance and the main characteristics of metabolically obese normal-weight and metabolically healthy obese phenotypes are discussed. Medline/PubMed and Science Direct were searched for articles related to the terms metabolically healthy obesity, metabolically obese normal weight, adipose tissue, and insulin resistance. Normal weight and obesity might be heterogeneous in regard to their effects. Fat distribution and lower insulin sensitivity are the main factors defining phenotypes within the same body mass index. Although these terms are interesting, controversies about them remain. Future studies exploring these phenotypes will help elucidate the roles of adiposity and/or insulin resistance in the development of metabolic alterations.

Lower body adipose tissue removal decreases glucose tolerance and insulin sensitivity in mice with exposure to high fat diet

It has been postulated that the protective effects of lower body subcutaneous adipose tissue (LBSAT) occur via its ability to sequester surplus lipid and thus serve as a "metabolic sink." However, the mechanisms that mediate this protective function are unknown thus this study addresses this postulate. Ad libitum, chow-fed mice underwent Sham-surgery or LBSAT removal (IngX, inguinal depot removal) and were subsequently provided chow (Chow; typical adipocyte expansion) or high fat diet (HFD; enhanced adipocyte expansion) for 5 weeks. Primary outcome measures included glucose tolerance and subsequent insulin response, muscle insulin sensitivity, liver and muscle triglycerides, adipose tissue gene expression, and circulating lipids and adipokines. In a follow up study the consequences of extended experiment length post-surgery (13 wks) or pre-existing glucose intolerance were examined. At 5 wks post-surgery IngX in HFD-fed mice reduced glucose tolerance and muscle insulin sensitivity and increased circulating insulin compared with HFD Sham. In Chow-fed mice, muscle insulin sensitivity was the only measurement reduced following IngX. At 13 wks circulating insulin concentration of HFD IngX mice continued to be higher than HFD Sham. Surgery did not induce changes in mice with pre-existing glucose intolerance. IngX also increased muscle, but not liver, triglyceride concentration in Chow- and HFD-fed mice 5 wks post-surgery, but chow group only at 13 wks. These data suggest that the presence of LBSAT protects against triglyceride accumulation in the muscle and HFD-induced glucose intolerance and muscle insulin resistance. These data suggest that lower body subcutaneous adipose tissue can function as a "metabolic sink."

Is there a paradox in obesity?

In an industrialized society, the increase in obesity incidence has led to an increase in premature morbidity and mortality rates. There is a relationship between body mass index (BMI) and the increased incidence of hypertension, dyslipidemia, type 2 diabetes mellitus, and cardiovascular disease, an increase in mortality. However, obese individuals with these conditions may have better outcomes than their lean counterparts, thus the term "obesity paradox." Most studies supporting this paradox are cross-sectional and do not take into account the quantity or type of adiposity, the disease severity, and comorbidities. Although BMI is an indicator of the amount of body fat, it does not differentiate between adiposity types. Adipocytes that are highly functional have good fuel storage capacity are different from adipocytes found in visceral obesity, which are poorly functioning, laden with macrophages, and causing low-grade inflammation. Individuals with high BMI may be physically fit and have a lower mortality risk when compared with individuals with a lower BMI and poorly functioning adiposity. We review the complexity of adipose tissue and its location, function, metabolic implications, and role in cardiovascular morbidity and mortality. The terminology "obesity paradox" may reflect a lack of understanding of the complex pathophysiology of obesity and the association between adiposity and cardiovascular disease.

Phenotypic characteristics in metabolically healthy but obese patients with schizophrenia

The purpose of this study was to characterize phenotypic characteristics of metabolically healthy but obese individuals with schizophrenia. Participants were non-diabetic outpatients 19 to 75 years old diagnosed with schizophrenia or schizoaffective disorder. Obese patients (body mass index (BMI)>30 kg/m(2)) were included in the present analysis. Patients were further defined as metabolically healthy but obese or obese individuals with metabolic abnormalities based on a cut-off value of 2.5 using the homeostasis model assessment of insulin resistance (HOMA-IR). Fasting blood samples were collected to determine levels of various metabolic parameters. Lipoprotein subclass concentrations and sizes were analyzed using nuclear magnetic resonance (NMR) spectroscopy. Fourteen metabolically healthy but obese patients and 62 obese patients with metabolic abnormalities were identified from 206 patients with schizophrenia. After controlling for age, there were no significant differences between the two groups on anthropometric measures. However, the metabolically healthy but obese group had significantly lower levels of large VLDL particle, significantly higher levels of intermediate VLDL particle, and significantly smaller mean particle size in VLDL compared with the obese group with metabolic abnormalities (metabolically obese). A metabolically healthy but obese phenotype characterized by high levels of intermediate VLDL particle and low levels of large VLDL particle exists in obese, non-diabetic patients with schizophrenia.

Serum 25-hydroxyvitamin D levels and metabolic health status in extremely obese individuals

OBJECTIVE

Vitamin D deficiency is prevalent in obese individuals. 25-hydroxyvitamin D [25(OH)D] levels in metabolically healthy obese (MHO) and metabolically unhealthy obese (MUO) adult individuals were examined and the relationship between 25(OH)D levels and other clinical parameters was evaluated.

METHODS

This is a retrospective chart review of outpatient medical records from the Nutrition and Weight Management Center at Boston Medical Center. Subjects were divided into two groups, MHO and MUO, using the homeostasis model assessment of insulin resistance criteria.

RESULTS

A total of 191 obese subjects were included in this analysis. The average body mass index (BMI) was 43.0 ± 9.2 kg/m(2) . Sixty-three subjects (33%) met criteria for MHO. MHO subjects had lower BMI and waist circumferences compared to MUO subjects. 25(OH)D levels were not significantly different between the two groups (P = 0.242). Overall, there were high prevalences of vitamin D deficiency (48.7%) and vitamin D insufficiency (33.0%). 25(OH)D levels were inversely correlated with BMI, body weight, waist circumferences, and HbA1c levels but not with blood pressure, total cholesterol, HDL, triglycerides, or LDL.

CONCLUSIONS

In extremely obese individuals, 25(OH)D levels were not related to metabolic health status or insulin resistance but correlated with the degree of adiposity.

Clinical, anthropometric, biochemical, and histological characteristics of nonobese nonalcoholic fatty liver disease patients of Bangladesh

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is considered to be a disease of obese individuals, yet lean patients are increasingly susceptible to have NAFLD. The aim of this study was to evaluate the profile of nonobese patients by comparing with obese NAFLD patients.

METHODS

We have included 465 patients of NAFLD after exclusion of other diseases, and 220 with elevated alanine aminotransferase (ALT) were biopsied. Patients were biochemically and clinically evaluated: blood pressure, body mass index (BMI), and waist circumference (WC) were recorded for every patient. A BMI  ≥ 25 kg/m(2) was defined as obese, and those with a BMI of <25 kg/m(2) were labeled as nonobese. Histological activity was expressed with NAFLD activity score (NAS).

RESULTS

Of 465 cases, 119 (25.6 %) were nonobese. Diabetes was noted in 122 (26.2 %) and hypertension in 122 (26.2 %). Metabolic syndrome was present in 253 (59.7 %), low HDL cholesterol in 228 (64.8 %), hypertriglyceridemia in 297 (73.2 %), and WC above normal in 308 (70.2 %). Males were predominating in the nonobese compared to females in the obese (p = 0.001). Hypertriglyceridemia and low high-density lipoprotein was similar in the obese and nonobese (76.2 % vs. 72.3 %, p = 0.5 and 65.2 % vs. 64.6 %, p = 1.0, respectively). The grades of steatosis, lobular inflammation, ballooning, NAS, and the stage of fibrosis did not also significantly differ between obese and nonobese patients. Nonalcoholic steatohepatitis (NASH) was 53.1 % in nonobese.

CONCLUSION

Nonobese was 25.6 % among NAFLD patients of Bangladesh, and 53.1 % of nonobese NAFLD cases were NASH. Though they were nonobese by BMI grade, they were metabolically similar to obese. Males were predominant in the nonobese, whereas females in the obese. NASH and fibrosis were similar in the obese and nonobese.

Hypothalamic-pituitary-adrenal axis activity, personality traits, and BCL1 and N363S polymorphisms of the glucocorticoid receptor gene in metabolically obese normal-weight women

We sought associations among metabolic profiles, copeptin levels, emotional control, personality traits, and hypothalamic-pituitary-adrenal axis activity in metabolically obese normal-weight young women (MONW). We assessed body composition, including fat-free mass; body fat (BF) and android and gynoid fat depots; fasting blood glucose, insulin, copeptin, cortisol (baseline and after dexamethasone), adrenocorticotropin (ACTH), triglycerides, total cholesterol, low- (LDL) and high-density (HDL) lipoproteins; and the BCL1 and N363S polymorphisms of the glucocorticoid receptor gene in 59 MONW and 71 healthy women aged 20-40 years. We also evaluated personality traits using the NEO-Five Factor Inventory and the subjective extent of emotional suppression by the Courtauld Emotional Control Scale. Compared to the controls, MONW had significantly higher insulin, cholesterol, LDL, triglycerides, and waist circumference, but lower HDL. MONW also had increased BF (>30 % of weight) and unfavorable regional fat distribution with excess android fat. The android/BF ratio was 8.29 % (MONW) versus 7.89 % (controls) (p = 0.005), while the gynoid/BF ratio was 31.99 versus 34.1 %, respectively (p = 0.008). Despite similar ACTH levels in both groups, MONW had higher cortisol levels both at the baseline (p < 0.001) and in the dexamethasone suppression test (p = 0.003). Copeptin levels and the distribution of glucocorticoid receptor polymorphisms were similar in both groups. There were also no significant differences in psychological features between MONW and controls. In conclusion, the MONW phenotype was associated with hypothalamic-pituitary-adrenal axis dysregulation, unfavorable metabolic profiles, and fat accumulation, but normal distribution of glucocorticoid receptor gene polymorphisms and copeptin levels, and no significant differences in psychological features between MONW and controls.

A new predictive equation for evaluating women body fat percentage and obesity-related cardiovascular disease risk

BACKGROUND

Obesity represents a global public health problem due to its association with cardiovascular diseases and reduced lifespan. The most widely used classification of obesity is expressed as Body Mass Index (BMI); however, this formula is an imprecise adiposity measurement that ignores several important factors involved. Body Adiposity Index (BAI) was more recently proposed as an indirect evaluation of percentage body fat (PBF). PBF is a direct measure of person's relative body fat and a better predictor of obesity-related risk diseases than BMI and BAI. Since obesity and consequent diseases are considered epidemic, new accurate formulas for epidemiological studies are of interest to the scientific community. Because direct measurement of body composition could be quite expensive, the aims of our work were to analyse the distributions of PBF by Dual X-ray absorptiometry, and the creation of new predictive equation using only anthropometric measures that could be helpful to clinicians to assess easily body fat of female patients.

METHODS/RESULTS

A sample of 1,031 Caucasian Italian women was recruited and BMI, BAI and PBF were evaluated. With the aim of developing a predictive model of PBF a multivariate regression model was fitted to observed data.

CONCLUSIONS

The definition of universally recognized PBF by gender and age could have public health implications. In this study, we developed a new predictive PBF equation that does not require the use of medical instruments or skilled measurement techniques and that may be easily applicable to Italian women.

Differences in insulin clearance between metabolically healthy and unhealthy obese subjects

Metabolically healthy obese (MHO) are relatively insulin sensitive and have a favorable cardio-metabolic risk profile compared with metabolically abnormal obese (MAO). To evaluate whether MAO individuals have a decreased insulin clearance compared with MHO individuals, 49 MHO, 147 MAO, and 172 non-obese individuals were analyzed in this cross-sectional study. Insulin clearance and insulin sensitivity were assessed through euglycemic hyperinsulinemic clamp. MHO subjects exhibited significant lower triglycerides, total cholesterol, 2-h post-challenge glucose, fasting and 2-h post-challenge insulin, steady-state plasma insulin, alanine aminotransferase, aspartate aminotransferase, and gamma-glutamyltransferase as compared with MAO individuals. Disposition index was higher in MHO subjects as compared with MAO individuals after adjusting for gender and age (P = 0.04). Insulin clearance was significantly lower in MAO individuals as compared with MHO and non-obese individuals. The difference between the two obese subgroups remained significant after adjusting for gender, age, waist circumference, fat mass, and insulin-stimulated glucose disposal (P = 0.03). The hepatic insulin extraction (C-peptide/insulin) in the fasting state was significantly higher in MHO subjects as compared with MAO individuals (P < 0.0001). In univariate analysis adjusted for gender and age, insulin clearance was correlated with hepatic insulin extraction (P = 0.01). In conclusion, insulin clearance differs among obese subjects with different metabolic phenotypes. Impaired insulin clearance may contribute to sustained fasting and post-meal hyperinsulinemia observed in MAO individuals.

A distinct fatty acid profile underlies the reduced inflammatory state of metabolically healthy obese individuals

BACKGROUND

Obesity is associated with numerous health complications; however, a subgroup of obese individuals (termed the metabolically healthy obese or MHO) appear to have lower risk for complications such as type 2 diabetes and cardiovascular disease. Emerging evidence suggests that MHO individuals have reduced inflammation compared to their metabolically unhealthy obese (MUO) counterparts. As it is recognized that fatty acids (FAs) have a strong relationship with inflammation, the current study aimed to uncover if the reduced inflammation observed in MHO individuals is mirrored by a more favourable FA profile.

METHODS

Fasted serum samples were collected from lean healthy (LH), MHO, and MUO participants (n = 10/group) recruited from the Diabetes Risk Assessment study. A panel of pro- and anti-inflammatory markers were measured by immunoassay. Total serum FA profiling, as well as the FA composition of circulating phospholipids (PL) and triglycerides (TG), was measured by gas chromatography. ANOVA and Mann-Whitney-Wilcoxon tests were used to assess statistical significance between the groups (P<0.05).

RESULTS

MHO and MUO individuals had similar BMI and body fat %; however, lipid parameters in MHO individuals more closely resembled that of LH individuals. MHO individuals had circulating levels of high sensitivity C-reactive protein (hsCRP) and interleukin-6 (IL-6) similar to LH individuals, while levels of platelet derived growth factor-ββ (PDGF-ββ) were intermediate to that of LH and MUO individuals. FA profiling analysis combined with discriminant analysis modelling highlighted a panel of nine FAs (consisting of three saturated, three monounsaturated, and three polyunsaturated FAs) in PL and TG fractions that distinguished the three groups. Specifically, saturated FA (myristic and stearic acids) levels in MHO individuals resembled that of LH individuals.

CONCLUSION

Our results suggest that the reduced inflammatory state of MHO individuals compared to MUO individuals may stem, in part, from a more favourable underlying FA profile.

Risk of developing diabetes and cardiovascular disease in metabolically unhealthy normal-weight and metabolically healthy obese individuals

CONTEXT

The risk of cardiovascular disease (CVD) and type 2 diabetes mellitus (DM) associated with obesity appears to be influenced by the coexistence of other metabolic abnormalities.

OBJECTIVE

We examined the risk of developing CVD and DM in metabolically healthy obese (MHO) and metabolically unhealthy normal weight (MUH-NW) individuals.

DESIGN AND SETTING

We analyzed prospective data of the San Antonio Heart Study, a population-based study among Mexican Americans and non-Hispanic whites (median follow-up, 7.4 y).

PARTICIPANTS

Incident DM and CVD were assessed in 2814 and 3700 participants aged 25 to 64 years, respectively.

MAIN MEASURES

MHO was defined as obesity (body mass index ≥ 30 kg/m(2)) with no more than one metabolic abnormality, and MUH-NW was defined as body mass index <25 kg/m(2) with two or more abnormalities.

RESULTS

In logistic regression models, BMI was associated with incident DM after controlling for demographics, family history of DM, and fasting glucose (odds ratio × 1 SD, 1.7 [95% CI, 1.5-2.0]). Both MUH-NW and MHO individuals had an increased DM risk (2.5 [1.1-5.6] and 3.9 [2.0-7.4], respectively). Similarly, BMI was related to incident CVD after adjusting for demographics and Framingham risk score (1.3 [1.1-1.6]). Incident CVD was also increased in MUH-NW and MHO individuals (2.9 [1.3-6.4] and 3.9 [1.9-7.8], respectively). Results were consistent across gender and ethnic categories.

CONCLUSION

The risk of developing DM and CVD is increased in MUH-NW and MHO individuals. Screening for obesity and other metabolic abnormalities should be routinely performed in clinical practice to institute appropriate preventive measures.

A community-based exercise intervention transitions metabolically abnormal obese adults to a metabolically healthy obese phenotype

BACKGROUND

Lower habitual physical activity and poor cardiorespiratory fitness are common features of the metabolically abnormal obese (MAO) phenotype that contribute to increased cardiovascular disease risk. The aims of the present study were to determine 1) whether community-based exercise training transitions MAO adults to metabolically healthy, and 2) whether the odds of transition to metabolically healthy were larger for obese individuals who performed higher volumes of exercise and/or experienced greater increases in fitness.

METHODS AND RESULTS

Metabolic syndrome components were measured in 332 adults (190 women, 142 men) before and after a supervised 14-week community-based exercise program designed to reduce cardiometabolic risk factors. Obese (body mass index ≥30 kg · m(2)) adults with two to four metabolic syndrome components were classified as MAO, whereas those with no or one component were classified as metabolically healthy but obese (MHO). After community exercise, 27/68 (40%) MAO individuals (P<0.05) transitioned to metabolically healthy, increasing the total number of MHO persons by 73% (from 37 to 64). Compared with the lowest quartiles of relative energy expenditure and change in fitness, participants in the highest quartiles were 11.6 (95% confidence interval: 2.1-65.4; P<0.05) and 7.5 (95% confidence interval: 1.5-37.5; P<0.05) times more likely to transition from MAO to MHO, respectively.

CONCLUSION

Community-based exercise transitions MAO adults to metabolically healthy. MAO adults who engaged in higher volumes of exercise and experienced the greatest increase in fitness were significantly more likely to become metabolically healthy. Community exercise may be an effective model for primary prevention of cardiovascular disease.

Association between Lower Normal Free Thyroxine Concentrations and Obesity Phenotype in Healthy Euthyroid Subjects

We investigated whether thyroid function could identify obesity phenotype in euthyroid subjects. A cross-sectional analysis was performed among nondiabetic, euthyroid subjects. We stratified subjects into four groups by BMI and insulin resistance (IR). Of 6241 subjects, 33.8% were overweight or obese (OW/OB) and 66.2% were normal weight (NW). Free thyroxine (FT4) levels were negatively associated with body mass index, waist circumference, triglyceride, c-reactive protein, and HOMA-IR and positively with high-density lipoprotein cholesterol in both genders. In multivariate regression analysis, FT4 level, a continuous measurement, was negatively correlated with HOMA-IR (β = -0.155, P < 0.001 in men; β = -0.175, P < 0.001 in women). After adjustment for age, sex, metabolic, and life style factors, subjects in the lowest FT4 quartile had an odds ratio (OR) for IR of 1.99 (95% confidence interval 1.61-2.46), as compared to those in the highest quartile. The association between low FT4 and IR remained significant in both NW and OW/OB subgroups. In conclusion, low normal FT4 levels were independently related to IR in NW and OW/OB euthyroid subjects. Further studies are needed to investigate the mechanisms by which low FT4 levels are linked to high IR in euthyroid ranges.

Differences in body composition between metabolically healthy obese and metabolically abnormal obese adults

Potential differences in body composition between metabolically healthy obese (MHO) and metabolically abnormal obese (OA) adults were explored with 395 obese adults from the Pennington Center Longitudinal Study (18-68 years). Adults were classified as OA (≥2 risk factors: blood pressure ≥130/85 mmHg; triglycerides ≥150 mg dl(-1); high-density lipoprotein cholesterol: men <40, women <50 mg dl(-1); fasting glucose ≥100 mg dl(-1); waist circumference: ≥102 cm men, women ≥88 cm) or MHO (<2 risk factors). Whole-body bone mineral density and content, percent body fat, fat mass, lean mass and trunk adipose tissue mass were measured with dual-energy X-ray absorptiometry. Visceral (VAT), subcutaneous (SAT) and total abdominal adipose tissue (TAT) were measured with computed tomography. Gender-specific general linear regression models were used to determine differences in body composition between MHO and OA controlling for age, race, smoking status and menopause status. In men, MHO had lower fat mass (kg and %), trunk adipose tissue, VAT, SAT, TAT and lean mass compared with OA. MHO women had lower fat mass (kg), lean mass, trunk adipose tissue, VAT and TAT when compared with OA women. In conclusion, OA and MHO cardiometabolic profiles are characterized by differences in body composition consistent between genders.

The concept of normal weight obesity

Individuals with normal body weight by body mass index (BMI) and high body fat percentage show a high degree of metabolic dysregulation. This phenomenon, defined as normal weight obesity, is associated with a significantly higher risk of developing metabolic syndrome, cardiometabolic dysfunction and with higher mortality. Recently, we have also shown that coronary artery disease patients with normal BMI and central obesity have the highest mortality risk as compared to other adiposity patterns. Therefore, it is important to recognize these high-risk groups for better adiposity-based risk stratification. There is a need for an updated definition of obesity based on adiposity, not on body weight.

Diabetes and cardiovascular disease outcomes in the metabolically healthy obese phenotype: a cohort study

OBJECTIVE

To determine the correlates of the "metabolically healthy obese" (MHO) phenotype and the longitudinal risks of diabetes and cardiovascular disease (CVD)/stroke associated with this phenotype.

RESEARCH DESIGN AND METHODS

The North West Adelaide Health Study is a prospective cohort study of 4,056 randomly selected adults aged ≥ 18 years. Participants free of CVD/stroke and not underweight (n = 3,743) were stratified by BMI categories and metabolic risk, defined as having two or more International Diabetes Federation metabolic syndrome criteria, excluding waist circumference.

RESULTS

Correlates of the MHO (n = 454 [12.1%]) included smoking, socioeconomic disadvantage, and physical inactivity. Compared with metabolically healthy normal-weight subjects (n = 1,172 [31.3%]), the MHO were more likely to develop metabolic risk (15.5 vs. 33.1%, P < 0.001) and incident diabetes (odds ratio 2.09 [95% CI 0.87-5.03]) but not CVD/stroke (1.16 [0.58-2.29]) during 5.5-10.3 years of follow-up. These risks were not seen in MHO subjects maintaining metabolic health (n = 188 [67%]). Sustained metabolic health in obese participants was associated with age ≤ 40 years and lower waist circumference. Compared with the metabolically at-risk obese, MHO women demonstrated a significantly higher (mean [SE]) percentage of leg fat (49.9 [0.5] vs. 53.2 [0.7]) and lower waist circumference (104 [0.6] vs. 101 cm [0.8]), despite no significant differences in overall adiposity.

CONCLUSIONS

"Healthy" obesity was a transient state for one-third of subjects. Persistence of a MHO phenotype, which was associated with favorable outcomes, was related to younger age and a more peripheral fat distribution. The MHO phenotype may be sustained by promoting lower waist circumferences.

Clinicopathological characteristics and metabolic profiles of non-alcoholic fatty liver disease in Indian patients with normal body mass index: Do they differ from obese or overweight non-alcoholic fatty liver disease?

BACKGROUND

Obesity is an important risk factor for non-alcoholic fatty liver disease (NAFLD); however, NAFLD does occur in lean subjects. This study was aimed to evaluate the magnitude, clinical, pathological, and metabolic profiles of NAFLD in normal body mass index (BMI) subjects (defined as lean NAFLD) in comparison to overweight or obese NAFLD and lean healthy control.

MATERIALS AND METHODS

336 subjects (205 consecutive NAFLD, and 131 healthy controls) were studied.

RESULTS

Among 205 NAFLD patients, 27 (13.2%) were lean, while 141 (68.8%) and 37 (18%) patients were obese and overweight, respectively. The lean NAFLD compared to obese NAFLD had significantly lesser degree of fasting hyperinsulinemia (P < 0.001), homeostasis model assessment insulin resistance (HOMA-IR, P < 0.001), and lower prevalence of diabetes mellitus (P = 0.01) and metabolic syndrome (P < 0.001). The profiles of serum lipids were similar between all 3 BMI categories, and 89% of lean NAFLD were dyslipidemic. Compared to obese subjects, patients with lean NAFLD had less hepatic necro-inflammation (P = 0.05) and fibrosis (P < 0.001). However, the proportion of steatohepatitis and advanced fibrosis were similar between all BMI categories. The profiles of overweight NAFLD were similar to those of lean NAFLD, except for higher HOMA-IR, uric acids and male gender in overweight group. Despite being lean, the mean BMI of lean NAFLD were still higher than unselected lean healthy controls (P = 0.02).

CONCLUSIONS

Lean NAFLD patients have less severe disease, minor, or no insulin resistance, but are frequently dyslipidemic and have BMI higher than lean healthy control.

Characterization of β-cell function and insulin resistance in overweight Chinese adolescents with normal glucose tolerance

This study aimed to investigate the characteristics of insulin resistance and β-cell secretion in healthy adolescents. A total of 124 adolescents with normal glucose tolerance (NGT) were divided according to BMI into normal weight (n=31; control), overweight (n=52) and obese (n=41) groups. Oral glucose tolerance tests were performed, and blood glucose (G₀, G₃₀ and G₁₂₀) and insulin (I₀, I₃₀ and I₁₂₀) levels at 0, 30 and 120 min, respectively, were measured. The homeostasis model assessment estimate of insulin resistance (HOMA-IR) and early insulin release index (IRI) were calculated to evaluate insulin sensitivity and early β-cell secretion. The G₀, G₁₂₀ levels and the natural logarithm (Ln) of I₃₀ and ΔI₃₀/ΔG₃₀ were similar in the overweight and obese groups, but significantly higher compared with those of the normal weight group (P<0.05). LnI₀ and LnHOMA-IR progressively increased (P<0.01) in correlation with the degree of obesity among the three groups. LnΔI₃₀/ΔG₃₀ and LnHOMA-IR were significantly positively correlated with the indices of obesity (P<0.001 and P<0.05, respectively). LnHOMA-IR was also positively correlated with the insulin levels at 30 and 120 min (r=0.454 and 0.314, respectively; P<0.001). In healthy adolescents, insulin resistance progressively increased with increased body mass index (BMI), but the compensatory increase in early insulin secretion was limited.

The role of chronic inflammation in obesity-associated cancers

There is a strong relationship between metabolism and immunity, which can become deleterious under conditions of metabolic stress. Obesity, considered a chronic inflammatory disease, is one example of this link. Chronic inflammation is increasingly being recognized as an etiology in several cancers, particularly those of epithelial origin, and therefore a potential link between obesity and cancer. In this review, the connection between the different factors that can lead to the chronic inflammatory state in the obese individual, as well as their effect in tumorigenesis, is addressed. Furthermore, the association between obesity, inflammation, and esophageal, liver, colon, postmenopausal breast, and endometrial cancers is discussed.

Age-Related Differences in Response to High-Fat Feeding on Adipose Tissue and Metabolic Profile in ZDSD Rats

The recruitment of new fat cells through adipogenesis may prevent the development of obesity-related comorbidities. However, adipogenic capacity is markedly reduced in mature adults. This study examined how initiation of high-fat feeding at different phases of adulthood modified adipose tissue (AT) morphology and obesity phenotype in obese and diabetic Zucker Diabetic Sprague Dawley (ZDSD) rats. For this, rodents were provided high-fat diet (HFD) beginning at 63, 84, or 112 d after parturition until termination (n = 6). At termination, ZDSD rats fed HFD beginning at 63 d after parturition (early adulthood) exhibited greater body fat and lower lean mass without significant changes to energy intake or body weight. Moreover, early high fat feeding increased adipocyte size and number, whereas these effects were absent at 84 or 112 d after parturition. At 126 d after parturition, there were no detectable transcript differences in PPARγ or C/EBPα. However, rodents provided HFD in early adolescence exhibited lower expression of canonical Wnt signaling intermediates. Corresponding with these changes was a marked reduction in AT-specific inflammation, as well as overall improvement in systemic glucose, lipid, and inflammatory homeostasis. Taken together, these data indicate that dietary regulation of adipocyte recruitment in adolescence may represent a major determinant of obesity phenotype.

Mechanisms of obesity-induced inflammation and insulin resistance: insights into the emerging role of nutritional strategies

Obesity and associated chronic inflammation initiate a state of insulin resistance (IR). The secretion of chemoattractants such as MCP-1 and MIF and of cytokines IL-6, TNF-α, and IL-1β, draw immune cells including dendritic cells, T cells, and macrophages into adipose tissue (AT). Dysfunctional AT lipid metabolism leads to increased circulating free fatty acids, initiating inflammatory signaling cascades in the population of infiltrating cells. A feedback loop of pro-inflammatory cytokines exacerbates this pathological state, driving further immune cell infiltration and cytokine secretion and disrupts the insulin signaling cascade. Disruption of normal AT function is causative of defects in hepatic and skeletal muscle glucose homeostasis, resulting in systemic IR and ultimately the development of type 2 diabetes. Pharmaceutical strategies that target the inflammatory milieu may have some potential; however there are a number of safety concerns surrounding such pharmaceutical approaches. Nutritional anti-inflammatory interventions could offer a more suitable long-term alternative; whilst they may be less potent than some pharmaceutical anti-inflammatory agents, this may be advantageous for long-term therapy. This review will investigate obese AT biology, initiation of the inflammatory, and insulin resistant environment; and the mechanisms through which dietary anti-inflammatory components/functional nutrients may be beneficial.

Association of serum angiopoietin-like protein 2 and epinephrine levels in metabolically healthy but obese individuals: In vitro and in vivo evidence

In the present study, we explored the association of serum angiopoietin-like protein 2 (ANGPTL2) levels with insulin sensitivity and serum epinephrine levels in metabolically healthy but obese (MHO) subjects. We also investigated the effects of epinephrine on ANGPTL2 expression in adipocytes in vitro. We examined the metabolic characteristics and serum ANGPTL2 and epinephrine levels in 100 non-diabetic obese postmenopausal women. Subjects were classified as MHO (n=25) or at-risk (n=25) based on the upper and lower quartiles of insulin sensitivity, respectively. Differentiated 3T3-L1 adipocytes were treated with increasing doses of epinephrine (10, 30 and 50 nM) in the presence or absence of phentolamine (10 μM), propranolol (0.3 μM), LY294002 (50 μM) or protein kinase A inhibitor fragment 6-22 amide (PKAI, 1 mM) for 24 h. We observed that serum ANGPTL2 levels were negatively correlated with insulin sensitivity (r=-0.23, P=0.021) and serum epinephrine level (r=-0.62, P<0.001) in the study subjects, with the MHO subjects displaying significantly lower serum ANGPTL2 and higher serum epinephrine levels than the at-risk subjects. Epinephrine reduced the ANGPTL2 mRNA and protein levels in differentiated 3T3-L1 adipocytes in a dose-dependent manner. Propranolol and PKAI were able to eliminate this reduction in ANGPTL2 levels whereas phentolamine and LY294002 were not. The in vitro findings indicated that epinephrine decreased ANGPTL expression at the mRNA and protein levels via the β-adrenoceptors and the PKA signaling pathway. This study suggests that β-receptor activation helps to maintain the metabolic profile of MHO individuals and prevent type 2 diabetes mellitus (T2DM) by decreasing serum ANGPTL2 levels.

Biochemical characteristics and risk factors for insulin resistance at different levels of obesity

OBJECTIVE

To establish the biochemical characteristics of nonobese, overweight, and obese children as well as to determine the risk factors associated with insulin resistance in nonobese children and with non-insulin resistance in obese children in the age strata of 6 to 11 years.

METHODS

A total of 3512 healthy children were enrolled in a cross-sectional study. In the absence of obesity, fasting hyperinsulinemia and hypertriglyceridemia defined nonobese, insulin-resistant (NO-IR) children. In the absence of metabolic abnormalities of fasting insulin and triglycerides levels, obese children were defined as obese, not insulin-resistant (O-NIR) children.

RESULTS

The gender- and age-adjusted prevalence of NO-IR and O-NIR was 6.6% and 21.3%, respectively. In the age-, gender-, and birth weight-adjusted analysis, family history of hypertension (FHH) in both maternal and paternal branches (odds ratio [OR]: 1.514; 95% confidence interval [CI]: 1.2-3.9; P = .04) was associated with NO-IR children. In the analysis adjusted by gender, age, waist circumference (WC), BMI, FHH, and family history of diabetes, high birth weight was associated with NO-IR children (OR: 1.319; 95% CI: 1.2-2.1; P = .04). Finally, in the gender-, age-, family history-, and birth weight-adjusted analysis, a WC lower than the 95th percentile was associated with a lower odds of insulin resistance among obese children (OR: 0.96; 95% CI: 0.91-0.98; P < .0005).

CONCLUSIONS

FHH and high birth weight are associated with NO-IR children, and a low WC is associated with lower odds of O-IR children.

Diet composition and activity level of at risk and metabolically healthy obese American adults

OBJECTIVE

Obesity often clusters with other major cardiovascular disease risk factors, yet a subset of the obese appears to be protected from these risks. Two obesity phenotypes are described, (i) "metabolically healthy" obese, broadly defined as body mass index (BMI) ≥ 30 kg/m(2) and favorable levels of blood pressure, lipids, and glucose; and (ii) "at risk" obese, BMI ≥ 30 with unfavorable levels of these risk factors. More than 30% of obese American adults are metabolically healthy. Diet and activity determinants of obesity phenotypes are unclear. We hypothesized that metabolically healthy obese have more favorable behavioral factors, including less adverse diet composition and higher activity levels than at risk obese in the multi-ethnic group of 775 obese American adults ages 40-59 years from the International Population Study on Macro/Micronutrients and Blood Pressure (INTERMAP) cohort.

DESIGN AND METHODS

In gender-stratified analyses, mean values for diet composition and activity behavior variables, adjusted for age, race, and education, were compared between metabolically healthy and at risk obese.

RESULTS

Nearly one in five (149/775 or 19%) of obese American INTERMAP participants were classified as metabolically healthy obese. Diet composition and most activity behaviors were similar between obesity phenotypes, although metabolically healthy obese women reported higher sleep duration than at risk obese women.

CONCLUSIONS

These results do not support hypotheses that diet composition and/or physical activity account for the absence of cardiometabolic abnormalities in metabolically healthy obese.

Physical activity and screen time in metabolically healthy obese phenotypes in adolescents and adults

INTRODUCTION

The purpose of this study was to examine levels of physical activity (PA) and screen time (ST) in metabolically healthy obese (MHO) and metabolically unhealthy obese (MUO) adolescents and adults.

METHODS

NHANES data from obese adolescents (12-18 years, BMI z-score ≥ 95th percentile) and adults (19-85 years, BMI ≥ 30 kg/m(2)) were pooled from 2003-2005 cycles. Metabolic phenotypes were categorized as MHO (0 or 1 cardiometabolic risk factor; triglycerides, HDL-C, blood pressure, or glucose) or MUO (≥2 cardiometabolic risk factors). Logistic regression models estimated associations between phenotype and PA/ST adjusted for age, gender, BMI, race/ethnicity, menopausal status, and NHANES cycle.

RESULTS

Among adolescents, PA was not associated with MHO. In contrast, MHO adults 19-44 years were 85% more likely to engage in active transportation and 2.7 times more likely to be involved in light intensity usual daily activity versus sitting. For each minute per day, adults 45-85 years were 36% more likely to have the MHO phenotype with higher levels of moderate PA. ST was not associated with metabolic phenotypes in adolescents or adults.

CONCLUSION

The current study provides evidence that PA, but not ST, differs between MHO and MUO in adults, but not in adolescents. Future studies are needed to confirm results.

Brd2 gene disruption causes "metabolically healthy" obesity: epigenetic and chromatin-based mechanisms that uncouple obesity from type 2 diabetes

Disturbed body energy balance can lead to obesity and obesity-driven diseases such as Type 2 diabetes, which have reached an epidemic level. Evidence indicates that obesity-induced inflammation is a major cause of insulin resistance and Type 2 diabetes. Environmental factors, such as nutrients, affect body energy balance through epigenetic or chromatin-based mechanisms. As a bromodomain and external domain family transcription regulator, Brd2 regulates expression of many genes through interpretation of chromatin codes and participates in the regulation of body energy balance and immune function. In the severely obese state, Brd2 knockdown in mice prevented obesity-induced inflammatory responses, protected animals from insulin resistance, glucose intolerance and pancreatic beta cell dysfunction, and thus uncoupled obesity from diabetes. Brd2 provides an important model for investigation of the function of transcription regulators and the development of obesity and diabetes; it also provides a possible, innovative target to treat obesity and diabetes through modulation of the function of a chromatin code reader.

Prognostic implications for insulin-sensitive and insulin-resistant normal-weight and obese individuals from a population-based cohort

BACKGROUND

There are few prospective data on the prognosis of insulin-sensitive and insulin-resistant normal-weight (NW) or obese individuals.

OBJECTIVES

The estimated liver fat content, incidences of hyperglycemia and cardiovascular disease, and all-cause and cardiovascular mortality rates were investigated in a population-based cohort of 1658 individuals who were categorized according to BMI and insulin resistance as defined by HOMA-IR values ≥2.5 and the presence of metabolic syndrome.

DESIGN

This was a prospective cohort study with a 9-y follow-up. Anthropometric values, blood pressure, and blood metabolic variables were measured, and information on vital status was collected from demographic files at follow-up.

RESULTS

A total of 137 of 677 NW individuals (20%) were classified as insulin resistant and normal weight (IR-NW), and 72 of 330 obese individuals (22%) were classified as insulin sensitive and obese (IS-obese). Incidences of diabetes, impaired fasting glucose, and cardiovascular events were 0.4%, 6.3%, and 3.3%, respectively, in insulin-sensitive and normal-weight (IS-NW) individuals (reference category); 5.8%, 10.2%, and 6.6%, respectively, in IR-NW individuals; and 5.6%, 8.3%, and 8.3%, respectively, in IS-obese individuals. In a multiple logistic regression model, risks of incident hyperglycemia and cardiovascular events increased in both groups compared with in the reference category [HR (95% CI): 2.54 (1.42, 4.55) and 1.98 (0.86, 4.54) in IR-NW subjects; 2.16 (1.01, 4.63) and 2.76 (1.05, 7.28) in IS-obese subjects]. The estimated liver fat content significantly increased during follow-up only in the IR-NW group in the same model. Cardiovascular mortality was 2-3-fold higher in IR-NW and IS-obese than in IS-NW individuals in a Cox regression model.

CONCLUSIONS

Our data refute the existence of healthy obese phenotypes because IS-obese individuals showed increased cardiometabolic risk. The existence of unhealthy NW phenotypes is supported by their increased risk of incident hyperglycemia, fatty liver, cardiovascular events, and death.

'Metabolically healthy obesity': origins and implications

When humans eat more and exercise less, they tend to become obese and unhealthy. The molecular pathways that link obesity to serious diseases like Type 2 diabetes and cardiovascular disease have become a subject of intensive scientific investigation because the exploding prevalence of obesity worldwide represents a grave new threat to the health of hundreds of millions of people. However, obesity is not always destiny. Two important clinical populations have been valuable to understand the mechanisms behind this conundrum: individuals who exhibit metabolic dysfunction, diabetes and elevated cardiovascular disease risk despite a lean body type, and individuals who are relatively protected from these dangers despite significant obesity. Study of this second group of 'metabolically healthy obese' people in particular has been revealing because such individuals exhibit specific, identifiable, anatomic, cellular and molecular features that set them apart from the rest of us who suffer declining health with increasing weight. Here, we examine some of these features, including some mouse models that are informative of mechanism, and suggest hypotheses for further study, including the possibility that genes and pathways of the immune system might offer new diagnostic or therapeutic targets.

Does inflammation determine whether obesity is metabolically healthy or unhealthy? The aging perspective

Obesity is a major health issue in developed as well as developing countries. While obesity is associated with relatively good health status in some individuals, it may become a health issue for others. Obesity in the context of inflammation has been studied extensively. However, whether obesity in its various forms has the same adverse effects is a matter of debate and requires further research. During its natural history, metabolically healthy obesity (MHO) converts into metabolically unhealthy obesity (MUHO). What causes this transition to occur and what is the role of obesity-related mediators of inflammation during this transition is discussed in this paper.

MONW phenotype is associated with advanced colorectal adenoma in Korean men

The aim of this study was to investigate whether there was a relationship between colorectal adenoma and metabolically obese but normal weight (MONW) among Korean men and women. The MONW phenotype is defined as a BMI <25, but fulfilling the metabolic syndrome (MS) criteria with a modified waist circumference (≥90 cm for men and ≥85 cm for women) appropriate for Korean. A total of 3,430 subjects (2,263 men and 1,167 women; 23-75 years old) were included in the study. Colorectal adenomas were diagnosed in 775 men and 199 women. The rate of advanced adenomas in males was 24.3% and in females 21.1%. A significant association between MONW and advanced colorectal adenoma was found in men (age-adjusted odds ratio (OR) = 1.92, 95% confidence interval (CI): 1.06-3.47) but not in women (age-adjusted OR = 1.80, 95% CI: 0.50-6.45). The findings suggest that men with MONW may have an increased risk of developing advanced colorectal adenoma whereas this does not seem true for females.

Body fat percentage is associated with cardiometabolic dysregulation in BMI-defined normal weight subjects

BACKGROUND AND AIMS

Nearly 25% of normal weight individuals display abnormal metabolic profiles associated with obesity. As a wide range in body fat percentage (%BF) exists for BMI-defined normal weight individuals, we investigated whether elevated %BF (determined using DXA) was associated with cardiometabolic dysregulation among 977 normal weight subjects (192 men, 785 women) from the Canadian province of Newfoundland and Labrador.

METHODS AND RESULTS

BMI and %BF were measured after a 12-h fasting period. Cardiometabolic abnormalities considered included elevated triglyceride, glucose and hsCRP levels, decreased HDL cholesterol, insulin resistance, and hypertension. Subjects were classified as metabolically healthy (0 or 1 cardiometabolic abnormality) or abnormal (≥2 cardiometabolic abnormalities) and divided into sex-specific %BF tertiles as follows: low (≤15.2% men, ≤29.7% women), medium (15.3-20.7%% men, 29.8-34.9%% women) and high (≥20.8% men, ≥35.0% women). The prevalence of the metabolically abnormal phenotype was higher among medium and high %BF subjects (12.0% and 19.5%, respectively) compared to the low group (7.4%; p < 0.05). Furthermore, the odds of being metabolically abnormal were 1.61 (95% CI 0.94-2.77) for medium %BF subjects compared to the low group and nearly tripled for high %BF subjects (OR 2.73, 95% CI 1.63-4.86). ORs remained significant after further adjustment for waist circumference.

CONCLUSION

Our findings indicate that those with elevated %BF are at increased risk of developing cardiometabolic disease despite having a normal BMI. Future development of adequate screening tools to identify these individuals is crucial to the prevention of obesity-associated disease.

BET domain co-regulators in obesity, inflammation and cancer

The bromodomain is a highly conserved motif of 110 amino acids that is bundled into four anti-parallel α-helices and found in proteins that interact with chromatin, such as transcription factors, histone acetylases and nucleosome remodelling complexes. Bromodomain proteins are chromatin 'readers'; they recruit chromatin-regulating enzymes, including 'writers' and 'erasers' of histone modification, to target promoters and to regulate gene expression. Conventional wisdom held that complexes involved in chromatin dynamics are not 'druggable' targets. However, small molecules that inhibit bromodomain and extraterminal (BET) proteins have been described. We examine these developments and discuss the implications for small molecule epigenetic targeting of chromatin networks in cancer.

Effect of adipose tissue insulin resistance on metabolic parameters and liver histology in obese patients with nonalcoholic fatty liver disease

The role of adipose tissue insulin resistance in the pathogenesis of nonalcoholic fatty liver disease (NAFLD) remains unclear. To evaluate this, we measured in 207 patients with NAFLD (age = 51 ± 1, body mass index = 34.1 ± 0.3 kg/m(2) ) and 22 controls without NAFLD (no NAFLD) adipose tissue insulin resistance by means of a validated index (Adipo-IR(i) = plasma free fatty acids [FFA] x insulin [FPI] concentration) and as the suppression of plasma FFA during an oral glucose tolerance test and by a low-dose insulin infusion. We also explored the relationship between adipose tissue insulin resistance with metabolic and histological parameters by dividing them based on quartiles of adipose tissue insulin resistance (Adipo-IR(i) quartiles: Q1 = more sensitive; Q4 = more insulin resistant). Hepatic insulin resistance, measured as an index derived from endogenous glucose production x FPI (HIRi), and muscle insulin sensitivity, were assessed during a euglycemic insulin clamp with 3-[(3) H] glucose. Liver fat was measured by magnetic resonance imaging and spectroscopy, and a liver biopsy was performed to assess liver histology. Compared to patients without steatosis, patients with NAFLD were insulin resistant at the level of adipose tissue, liver, and skeletal muscle and had higher plasma aspartate aminotransferase and alanine aminotransferase, triglycerides, and lower high-density lipoprotein cholesterol and adiponectin levels (all P < 0.01). Metabolic parameters, hepatic insulin resistance, and liver fibrosis (but not necroinflammation) deteriorated as quartiles of adipose tissue insulin resistance worsened (all P < 0.01).

CONCLUSION

Adipose tissue insulin resistance plays a key role in the development of metabolic and histological abnormalities of obese patients with NAFLD. Treatment strategies targeting adipose tissue insulin resistance (e.g., weight loss and thiazolidinediones) may be of value in this population.

Different response of body weight change according to ketonuria after fasting in the healthy obese

The relationship between obesity and ketonuria is not well-established. We conducted a retrospective observational study to evaluate whether their body weight reduction response differed by the presence of ketonuria after fasting in the healthy obese. We used the data of 42 subjects, who had medical records of initial urinalysis at routine health check-up and follow-up urinalysis in the out-patient clinic, one week later. All subjects in the initial urinalysis showed no ketonuria. However, according to the follow-up urinalysis after three subsequent meals fasts, the patients were divided into a non-ketonuria group and ketonuria group. We compared the data of conventional low-calorie diet programs for 3 months for both groups. Significantly greater reduction of body weight (-8.6 ± 3.6 kg vs -1.1 ± 2.2 kg, P < 0.001), body mass index (-3.16 ± 1.25 kg/m(2) vs -0.43 ± 0.86 kg/m(2), P < 0.001) and waist circumference (-6.92 ± 1.22 vs -2.32 ± 1.01, P < 0.001) was observed in the ketonuria group compared to the non-ketonuria group. Fat mass and lean body mass were also more reduced in the ketonuria group. In addition, serum free fatty acid concentration after intervention in the ketonuria group showed significant more increment than in the non-ketonuria group. The presence of ketonuria after fasting may be a predicting factor of further body weight reduction.

All-cause mortality risk of metabolically healthy obese individuals in NHANES III

Mortality risk across metabolic health-by-BMI categories in NHANES-III was examined. Metabolic health was defined as: (1) homeostasis model assessment-insulin resistance (HOMA-IR) <2.5; (2) ≤2 Adult Treatment Panel (ATP) III metabolic syndrome criteria; (3) combined definition using ≤1 of the following: HOMA-IR ≥1.95 (or diabetes medications), triglycerides ≥1.7 mmol/L, HDL-C <1.04 mmol/L (males) or <1.30 mmol/L (females), LDL-C ≥2.6 mmol/L, and total cholesterol ≥5.2 mmol/L (or cholesterol-lowering medications). Hazard ratios (HR) for all-cause mortality were estimated with Cox regression models. Nonpregnant women and men were included (n = 4373, mean ± SD, age 37.1 ± 10.9 years, BMI 27.3 ± 5.8 kg/m², 49.4% female). Only 40 of 1160 obese individuals were identified as MHO by all definitions. MHO groups had superior levels of clinical risk factors compared to unhealthy individuals but inferior levels compared to healthy lean groups. There was increased risk of all-cause mortality in metabolically unhealthy obese participants regardless of definition (HOMA-IR HR 2.07 (CI 1.3-3.4), P < 0.01; ATP-III HR 1.98 (CI 1.4-2.9), P < 0.001; combined definition HR 2.19 (CI 1.3-3.8), P < 0.01). MHO participants were not significantly different from healthy lean individuals by any definition. While MHO individuals are not at significantly increased risk of all-cause mortality, their clinical risk profile is worse than that of metabolically healthy lean individuals.

IGF-1 levels link estimated glomerular filtration rate to insulin resistance in obesity: a study in obese, but metabolically healthy, subjects and obese, insulin-resistant subjects

BACKGROUND AND AIMS

Metabolically healthy but obese (MHO) subjects have a favourable cardio-metabolic risk profile, but whether they are also at lower risk for kidney dysfunction is still questionable.

METHODS AND RESULTS

A total of 106 MHO, 122 normal-weight and 212 insulin-resistant obese (IRO) subjects were stratified on the basis of their insulin sensitivity and body mass index (BMI). The CKD-EPI equation was used to estimate glomerular filtration rate (eGFR) and ISI index was used to estimate insulin sensitivity. eGFR was significantly lower in IRO as compared to MHO subjects after adjusting for age, gender and BMI (P = 0.008). In a logistic regression model adjusted for age, gender and BMI, IRO subjects showed an increased risk of having eGFR in the lowest quartile (odds ratio (OR) 1.91, 95% confidence interval (CI) 1.01-3.58; P = 0.04) as compared with MHO subjects. This association was maintained when waist, lean body mass, blood pressure, HDL cholesterol, triglyceride, fasting glucose and insulin levels were additionally included into the model (OR 2.49, 95%CI 1.17-5.27; P = 0.01), but its independence was not retained with further inclusion of insulin-like growth factor-1 (IGF-1) levels (OR 2.16, 95%CI 0.93-5.04; P = 0.07) No differences in eGFR were observed between non-obese and MHO individuals.

CONCLUSIONS

These results indicate that heterogeneity in obese phenotypes may account for conflicting evidence regarding the significance of obesity as a risk factor for chronic kidney disease. Our findings suggest that obesity is associated with lower kidney function only when insulin sensitivity is reduced, and that plasma IGF-1 is likely to be an important mechanism linking the IRO phenotype with reduced eGFR.

Association of plasma epinephrine level with insulin sensitivity in metabolically healthy but obese individuals

In the present study, we explored the association of catecholamines with insulin sensitivity in "metabolically healthy but obese" (MHO) individuals, by examining the metabolic characteristics and plasma catecholamine levels in 100 obese, sedentary postmenopausal women. Subjects were classified as MHO (n=25) or at-risk (n=25) based on the upper and lower quartiles of insulin sensitivity as measured by the hyperinsulinemic-euglycemic clamp technique. The MHO group presented a significantly higher range of plasma epinephrine levels (73 ± 21 pg/mL) than the at-risk group (39 ± 20 pg/mL) (P<0.05), though both within the normal basal range of plasma epinephrine (56 ± 30 pg/mL). Multivariate regression analysis showed that high-sensitivity C-reactive protein, plasma epinephrine, triglycerides and lean body mass index were independent predictors of glucose disposal. The plasma epinephrine level was positively correlated with the glucose disposal rate, insulin sensitivity and the HDL-cholesterol level, and negatively correlated with the triglycerides level (P<0.05). In conclusion, this study for the first time demonstrates a positive association between plasma epinephrine level and insulin sensitivity in MHO individuals.

Identifying metabolically obese but normal-weight (MONW) individuals in a nondiabetic Korean population: the Chungju Metabolic disease Cohort (CMC) study

OBJECTIVE

To investigate the prevalence and identify the phenotype of individuals suspected to be metabolically obese but normal weight (MONW).

DESIGN AND SUBJECTS

Eight thousand nine hundred and eighty-seven nondiabetic subjects aged over 40 years were selected from the Chungju Metabolic disease Cohort study performed in 2003-2006 in Korea. Those within the highest quartile in the homeostasis model assessment of insulin resistance (HOMA-IR) with a normal body mass index (BMI) between 18·5 and 23 kg/m(2) were classified as MONW.

MEASUREMENTS

Data on anthropometry, lipid profiles and HOMA-IR values were analysed.

RESULTS

The prevalence of MONW was 14·2% for men and 12·9% for women amongst normal-weight subjects. Multiple logistic regression analysis showed that total cholesterol (TC) levels over 5·17 mm (odds ratio, OR = 1·481; 95% confidence intervals, CI 1·086-2·021), triglyceride (TG) levels over 1·69 mm (OR = 1·507; 95% CI 1·093-2·077) and high-density lipoprotein-cholesterol levels lower than 1·03 mm (OR = 1·580; 95% CI 1·053-2·371) independently had higher odds of diagnosing MONW amongst men. For women, a BMI over 21·5 kg/m(2) (OR = 1·405; 95% CI 1·034-1·909), TC levels over 5·17 mm (OR = 1·524; 95% CI 1·112-2·090) and TG levels over 1·69 mm (OR = 1·799; 95% CI 1·302-2·487) were independently associated with a diagnosis of MONW.

CONCLUSIONS

More than 10% of normal-weight subjects were classed as MONW in this cohort. Identification of these subjects based on lipid profiles could aid in the early detection of a high risk group of developing cardiometabolic diseases.

Type 2 diabetes across generations: from pathophysiology to prevention and management

Type 2 diabetes is now a pandemic and shows no signs of abatement. In this Seminar we review the pathophysiology of this disorder, with particular attention to epidemiology, genetics, epigenetics, and molecular cell biology. Evidence is emerging that a substantial part of diabetes susceptibility is acquired early in life, probably owing to fetal or neonatal programming via epigenetic phenomena. Maternal and early childhood health might, therefore, be crucial to the development of effective prevention strategies. Diabetes develops because of inadequate islet β-cell and adipose-tissue responses to chronic fuel excess, which results in so-called nutrient spillover, insulin resistance, and metabolic stress. The latter damages multiple organs. Insulin resistance, while forcing β cells to work harder, might also have an important defensive role against nutrient-related toxic effects in tissues such as the heart. Reversal of overnutrition, healing of the β cells, and lessening of adipose tissue defects should be treatment priorities.

High leptin/adiponectin ratio and serum triglycerides are associated with an "at-risk" phenotype in young severely obese patients

"At-risk" severely obese subjects are characterized by insulin resistance, and higher visceral fat and plasma lipid levels compared with metabolically healthy obese (MHO) subjects, although both groups have a high BMI and fat mass. The aim of this study was to measure several serum adipokines and gastrointestinal hormones in a young severely obese population from Southern Italy to identify biochemical markers of the "at-risk" insulin-resistant obese profile. We studied 160 unrelated white young adults (mean age = 25.2 years, mean BMI = 44.9 kg/m(2), 65% women) affected by obesity for at least 5 years. Serum concentrations of glucagon, ghrelin, gastric inhibitory peptide, glucagon like peptide-1, interleukin-6, tumor necrosis factor α, leptin, adiponectin, adipsin, and visfatin were measured. The leptin/adiponectin (L/A) ratio and fatty liver index (FLI) were calculated. We found a prevalence of 21.3% of MHO patients in our young severely obese patients. At univariate analysis, the "at-risk" group had higher mean levels of BMI (P < 0.0001), leptin (P = 0.039, men) and the L/A ratio (P = 0.003), and lower mean levels of visfatin (P = 0.026) than the MHO group. The L/A ratio, serum triglycerides, and male sex were significantly associated with "at-risk" obesity and accounted for 19.5% of insulin resistance at multivariate analysis. In conclusion, we demonstrate that a high serum L/A ratio and high levels of serum triglycerides may be markers of "at-risk" obesity, independent of waist circumference (WC) and BMI, in young severely obese population.

"Predictability of body mass index for diabetes: affected by the presence of metabolic syndrome?"

Background

Metabolic syndrome (MetS) and body mass index (BMI, kg.m^-2) are established independent risk factors in the development of diabetes; we prospectively examined their relative contributions and joint relationship with incident diabetes in a Middle Eastern cohort.

Method

participants of the ongoing Tehran lipid and glucose study are followed on a triennial basis. Among non-diabetic participants aged≥ 20 years at baseline (8,121) those with at least one follow-up examination (5,250) were included for the current study. Multivariate logistic regression models were used to estimate sex-specific adjusted odd ratios (ORs) and 95% confidence intervals (CIs) of baseline BMI-MetS categories (normal weight without MetS as reference group) for incident diabetes among 2186 men and 3064 women, aged ≥ 20 years, free of diabetes at baseline.

Result

During follow up (median 6.5 years); there were 369 incident diabetes (147 in men). In women without MetS, the multivariate adjusted ORs (95% CIs) for overweight (BMI 25-30 kg/m2) and obese (BMI≥30) participants were 2.3 (1.2-4.3) and 2.2 (1.0-4.7), respectively. The corresponding ORs for men without MetS were 1.6 (0.9-2.9) and 3.6 (1.5-8.4) respectively. As compared to the normal-weight/without MetS, normal-weight women and men with MetS, had a multivariate-adjusted ORs for incident diabetes of 8.8 (3.7-21.2) and 3.1 (1.3-7.0), respectively. The corresponding ORs for overweight and obese women with MetS reached to 7.7 (4.0-14.9) and 12.6 (6.9-23.2) and for men reached to 3.4(2.0-5.8) and 5.7(3.9-9.9), respectively.

Conclusion

This study highlights the importance of screening for MetS in normal weight individuals. Obesity increases diabetes risk in the absence of MetS, underscores the need for more stringent criteria to define healthy metabolic state among obese individuals. Weight reduction measures, thus, should be encouraged in conjunction with achieving metabolic targets not addressed by current definition of MetS, both in every day encounter and public health setting.