Weight Loss Improves Renal Hemodynamics

Overview

Metabolic syndrome (MS) is a clustering of risk factors for cardiovascular disease (CVD) such as hypertension, hypertriglyceridemia, low HDL-cholesterol levels, disorders of glucose metabolism, and insulin resistance. A number of associated conditions are included in the MS spectrum such as abdominal obesity, systemic inflammatory activation, endothelial dysfunction, non-alcoholic fatty liver disease, hyperuricemia, polycystic ovarian syndrome, and microalbuminuria. As a consequence, the diagnosis of MS identifies patients who are at increased risk for type 2 diabetes mellitus and CVD. In the last few years, the potential for MS to trigger renal damage and accelerate the progression of pre-existing nephropathy has become a focus of research. Some studies have suggested that MS can influence the development of CKD, although the underlying mechanisms are not well understood. In this study, the investigators hypothesized that modifying a key component of the MS, namely obesity, could attenuate renal damage. The investigators examined the impact of weight loss on creatinine clearance and urinary albumin excretion in non-diabetic obese patients with MS.

Non-diabetic patients with MS were recruited from an outpatient clinic at the Division of Nephrology of the Federal University of Juiz de Fora, Brazil. MS was defined according to the criteria of the National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATPIII). The study was divided into two phases: phase 1 (baseline) and phase 2 (intervention). At the first study visit, a full medical history was taken and a clinical examination was performed. Blood samples were taken to determine plasma glucose levels, both after fasting and 2 h after a 75-g oral glucose overload (oral glucose tolerance test; OGTT), as well as levels of plasma insulin, creatinine, total cholesterol, HDL-cholesterol, triglycerides, and uric acid. At visit 2, the preliminary results were evaluated and urine samples were collected in duplicate for measurement of microalbuminuria. Creatinine clearance was estimated using the Cockcroft-Gault formula, corrected for body surface area. The subjects were kept free of any medication (statins, antihypertensive, and anti-inflammatory drugs) over the entire study period. The only medications allowed during the study were analgesics such as dipyrone and hioscin. At visit 3, each patient was evaluated by a registered dietitian with expertise in medical nutrition therapy with the aim of achieving a weight loss of at least 5% from baseline. Patients were commenced on a 12-week calorie-restricted diet consisting of 50% carbohydrate, 20-25% protein, and 25-30% fat. The patients were evaluated by the dietitian every 2 weeks. At the final visit all laboratory tests were repeated. At the end of phase 2, patients were divided into two groups: responders, who had achieved at least a 5% reduction in body weight and non-responders, who had not achieved the target weight reduction.