Inclusion Criteria:

• Previous enrollment in protocol OH95-DK-N037 or a first-degree relative of an enrollee who is aged ≥18 years and has type 2 diabetes.
• Willingness, after receiving a thorough explanation of the study, to participate.

Exclusion Criteria:

• Clinically significant disorders of the liver [cirrhosis, portal hypertension, hepatitis, increased bilirubin (≥1.5 mg/dl), cardiovascular disease (angina pectoris, history of myocardial infarction, left ventricular ejection fraction <40%, congestive heart failure of New York Heart Association Class I to IV), cerebrovascular disease, peripheral vascular disease, pulmonary diseases (asthma and restrictive or obstructive lung disease requiring therapy), renal-urinary disorders (calculi, urinary tract obstruction, glomerulonephritis, chronic infection), gastrointestinal disorders (nausea, vomiting, diarrhea or anorexia sufficient to cause weight loss or wasting), or hematocrit levels ≤30 percent in women or ≤35 percent in men.
• Renovascular or malignant hypertension; uncontrolled hypertension (systolic blood pressure ≥160 or diastolic ≥95 mm Hg) despite treatment with three antihypertensive drugs; or hypertension that is being treated with antihypertensive medicines and the primary care physician or the patient refuses to adopt the blood pressure treatment regimen outlined in the study protocol.
• Hematuria of unknown etiology. Prior to entry into the study, any subject with hematuria should be evaluated, the etiology established and documented, and treatment rendered as appropriate.
• Chronic debilitating disorders with or without treatment (e.g., systemic lupus erythematosus (SLE), cancer, amyloidosis, and chronic infection) that would interfere with the assessment of kidney function. Participants who develop these disorders after their original enrollment into one of our kidney studies will continue to be followed in the protocol.
• Currently receiving a drug regimen that includes: steroids, immunosuppressants, or investigational new drugs. Participants who receive these drugs following original enrollment into one of our kidney studies will continue to be followed in the protocol, unless they have known chronic significant effects on kidney morphology or a high incidence of adverse effects on kidney function, in which case they will be withdrawn from the study (see Section D-7.2).
• Pregnancy. Women of childbearing potential must have a negative pregnancy test prior to entry and prior to each renal clearance study. Women who are pregnant will be offered the opportunity to participate following the conclusion of the pregnancy and those who become pregnant during the study will be able to resume the study following the conclusion of the pregnancy.
• Hypersensitivity to iodine.
• Bleeding disorders, since kidney biopsies could not be performed safely in these individuals.
• Massive obesity with body mass index ≥45 kg/m². Kidney biopsies are more difficult and present greater hazards to persons with massive obesity.
• Conditions likely to interfere with informed consent or compliance with the protocol.