Regulation of glucose metabolism in nondiabetic, metabolically obese normal-weight Asians

Type 2 diabetes in Asia occurs largely in the absence of obesity. The metabolically obese normal-weight (MONW) phenotype refers to lean subjects with metabolic dysfunction that is typically observed in people with obesity and is associated with increased risk for diabetes. Previous studies evaluated MONW subjects who had greater body mass index (BMI) or total body fat than respective control groups, making interpretation of the results difficult. We evaluated insulin sensitivity (hyperinsulinemic-euglycemic clamp); insulin secretion (mixed meal with oral minimal modeling); intra-abdominal, muscle, and liver fat contents (magnetic resonance); and fasting and postprandial glucose and insulin concentrations in 18 MONW subjects and 18 metabolically healthy controls matched for age (43 ± 3 and 40 ± 3 yr; P = 0.52), BMI (both 22 ± 1 kg/m²; P = 0.69), total body fat (17 ± 1 and 16 ± 1 kg; P = 0.33), and sex (9 men and 9 women in each group). Compared with controls, MONW subjects had an approximately twofold greater visceral adipose tissue volume and an approximately fourfold greater intrahepatic fat content (but similar muscle fat), 20-30% lower glucose disposal rates and insulin sensitivity, and 30-40% greater insulin secretion rates (all P < 0.05). The disposition index, fasting glucose, and HbA1c concentrations were not different between groups, whereas postprandial glucose and insulin concentrations were ~15% and ~65% greater, respectively, in MONW than control subjects (both P < 0.05). We conclude that the MONW phenotype is associated with accumulation of fat in the intra-abdominal area and the liver, profound insulin resistance, but also a robust β-cell insulin secretion response that compensates for insulin resistance and helps maintain glucose homeostasis.

Evidence of genetic predisposition for metabolically healthy obesity and metabolically obese normal weight

Obesity has evolved into a global pandemic that constitutes a major threat to public health. The majority of obesity-related health care costs are due to cardiometabolic complications, such as insulin resistance, dyslipidemia, and hypertension, which are risk factors for Type 2 diabetes and cardiovascular disease. However, many obese individuals, often called metabolically healthy obese (MHO), seem to be protected from these cardiometabolic complications. Conversely, there is a group of individuals who suffer from cardiometabolic complications despite being of normal weight; a condition termed metabolically obese normal weight (MONW). Recent large-scale genomic studies have provided evidence that a number of genetic variants show an association with increased adiposity but a favorable cardiometabolic profile, an indicator for the genetic basis of the MHO and MONW phenotypes. Many of these loci are located in or near genes that implicate pathways involved in adipogenesis, fat distribution, insulin signaling, and insulin resistance. It has been suggested that a threshold for subcutaneous adipose tissue expandability may be at play in the manifestation of MHO and MONW, where expiry of adipose tissue storage capacity could lead to ectopic lipid accumulation in non-adipose tissues such as liver, muscle, heart, and pancreatic beta cells. Understanding the genetic aspects of the mechanisms that underpin MHO and MONW is crucial to define appropriate public health action points and to develop effective intervention measures.

Lipid accumulation product and incident cardiovascular events in a normal weight population: Tehran Lipid and Glucose Study

BACKGROUND

The lipid accumulation product (LAP) is a relatively new marker for measuring cardiovascular disease (CVD) risk factors. We investigated predictability of LAP value for incident CVD among Tehranian adults with normal BMI.

METHODS

A population based cohort of subjects without history of prevalent cardiovascular disease, aged ≥30 years who had BMI <25 were followed for a median (interquartile range 25-75) of 10.1 (7.25-10.57) years. Subjects were stratified according to LAP tertiles. LAP was defined as WC-58 × TG for women and WC-65 × TG for men (where WC is waist circumference and TG is triglycerides). Cox regression analyses were used to estimate the hazard ratio (HR) of CVD events; c-statistics test was also calculated to compare LAP with other anthropometric indices.

RESULT

In this prospective study of 2378 subjects (57.0% men) with mean age of 46.1 ± 13.5 years, and mean BMI 22.59 ± 1.9 kg/m(2) an increasing trend of cardiovascular risk factors along LAP tertiles (except for smoking and history of premature CVD events) was observed. During follow-up 160 CVD cases occurred (incidence rates (per 1000 person-years) of CVD across LAP tertiles were 4.14 (2.88-5.96), 6.82 (5.13-9.04) and 12.37 (9.97-15.34), respectively). Adjusted HRs for development of cardiovascular disease across LAP tertiles were 1.56 (95% confidence interval (CI) =0.91-2.69) and 2.17 (95% CI = 1.22-3.86) respectively. C-statistics of LAP were not significantly higher than other anthropometric measures for predicting incident CVD.

CONCLUSION

LAP is an independent predictor of cardiovascular events in normal BMI subjects, but is not superior over other anthropometrics indices.

Dark and light side of obesity: mortality of metabolically healthy obese people

Evaluation of: Hamer M, Stamatakis E. Metabolically healthy obesity and risk of all-cause and cardiovascular disease mortality. J. Clin. Endocrinol. Metab. 97(7), 2482-2488 (2012). The health effects of different obesity phenotypes remain unclear. In this observational voluminous study with prospective linkage to mortality records, participants were classified as metabolically healthy (zero or one metabolic abnormality) or unhealthy (two or more metabolic abnormalities) based on blood pressure, HDL-cholesterol, diabetes, waist circumference and low-grade inflammation signs. Obesity was defined as a BMI of 30 kg/m² or greater. The association between metabolically healthy obesity and risk of cardiovascular disease and all-cause mortality was examined after follow-up, on average, of more than 7.0 ± 3.0 years. Participants with 'standard' (metabolically unhealthy) obesity were at elevated risk of cardiovascular disease and all-cause mortality compared with their metabolically healthy obese counterparts. No significant difference in mortality has been found between metabolically healthy obese and referent group (metabolically healthy nonobese participants). By adding new information to the data collected previously, this important paper calls for further clarifications, including an analysis of mortality in cancer and diabetic patients with various obesity types.