ABSTRACT
PURPOSE OF REVIEW: Despite a strong correlation between obesity and insulin resistance, 25% of severely obese (BMI >40) individuals are insulin sensitive. In this review, we will examine the factors in adipose tissue that distinguish the two groups, as well as reasons for believing the insulin-sensitive group will be less disease prone. RECENT FINDINGS: Obesity has been linked to the metabolic syndrome with an increase in visceral (intra-abdominal) compared to subcutaneous fat. Recent studies in which adipose tissue of insulin-sensitive and insulin-resistant patients with severe obesity were compared indicate that the insulin-resistant group is also distinguished by increases in oxidative stress and decreases in AMP-activated protein kinase (AMPK) activity. In contrast, changes in the expression of genes for SIRT1, inflammatory cytokines, mitochondrial biogenesis and function, and the two α-isoforms of AMPK showed more depot variation. Studies of how these and other changes in adipose tissue respond to bariatric surgery are still in their infancy. SUMMARY: Available data suggest that increases in oxidative stress, decreases in AMPK activity and SIRT1 gene expression, depot-specific changes in inflammatory, mitochondrial and other genes distinguish adipose tissue of insulin resistant from insulin-sensitive individuals with severe obesity.
Subject(s)
AMP-Activated Protein Kinases/metabolism , Adipose Tissue/pathology , Insulin Resistance , Obesity, Morbid/pathology , AMP-Activated Protein Kinases/genetics , Adipose Tissue/enzymology , Adipose Tissue/metabolism , Animals , Bariatric Surgery , Body Mass Index , Diabetes Mellitus, Type 2/metabolism , Diabetes Mellitus, Type 2/pathology , Enzyme Activation , Humans , Inflammation/pathology , Insulin/metabolism , Metabolic Syndrome/metabolism , Metabolic Syndrome/pathology , Mitochondria/metabolism , Mitochondria/pathology , Obesity, Morbid/enzymology , Obesity, Morbid/metabolism , Obesity, Morbid/surgery , Oxidative Stress , Sirtuin 1/genetics , Sirtuin 1/metabolismABSTRACT
The application of the BMI of > or =35 as the major prerequisite for access to bariatric surgery is no longer appropriate because the index, now incorporated in the requirements of Medicare, Medicaid and most private carriers, does not reflect the degree or distribution of adiposity, it discriminates unfairly on the basis of gender, race, age, fitness, and body fat composition. Further, with increasing evidence that bariatric surgery can also induce full and durable remission of such comorbidities as type 2 diabetes even in patients with BMIs <30, new guidelines must be pursued.
