Metabolic Characteristics of Lean Diabetes in Rural and Semi-urban India and in the United States

India has the world's highest prevalence of diabetes, expected to rise to 80 million by 2030. This includes many patients with Lean Diabetes, which is a form of diabetes identified clinically by early onset, high insulin requirements, absence of other pancreatic disease, and low body mass index (typically ≤17 kg/m2) at presentation. Despite its prevalence, Lean Diabetes remains a relatively unknown disease that stirs conflicting opinions regarding its classification, diagnostic criteria, and pathogenesis.

In this study, the investigators will study individuals meeting the criteria for Lean Diabetes, Type 1 diabetes, Type 2 diabetes, and two group of participants without diabetes using a procedure called a "pancreatic clamp" study. During the clamp procedure, glucose (a sugar) and insulin (a hormone produced in the pancreas that regulates the amount of glucose in the blood) are infused with an intravenous catheter, and blood samples are collected periodically throughout the procedure to measure blood sugar levels and the levels of several hormones that are found in the body and are related to glucose metabolism. Endogenous glucose production (a measure of the body's production of sugar) will also be measured. Participants will also have a fat biopsy, and will be given a mixed meal challenge which is a test that detects hyperglycemia and glucose intolerance.

The overall goal of this study is to define the metabolic characteristics of individuals with Lean Diabetes and to determine which differences exist compared to individuals with other known forms of diabetes or individuals without diabetes.