The long-term objective of this research program is to identify potential targets for obesity drugs that act on WAT to reduce body fat. Obesity is increasingly becoming a leading health problem in developed countries, especially the U.S. Epidemiological data point to increased body fat (white adipose tissue, WAT) mass as a chief contributor to obesity, which occurs both by increases in fat cell size and number. The effects of current dietary therapies are mostly reversible, and less than 10 % of those who lose weight are able to maintain the weight loss. Recent evidence paints an increasingly complex picture of metabolic regulation within the adipose tissue, which secretes autocrine, paracrine, and endocrine factors that regulate adipose cellular and whole body energy metabolism. In light of this picture, a promising alternative to reducing food intake or inhibiting digestive fat absorption is to reduce WAT mass by directly influencing adipose cellular metabolism. Recognizing the complexity of cellular metabolic regulation, this research takes a novel, systems oriented approach. Addressing the knowledge gap left by gene and protein expression profiling studies, this proposal focuses on obtaining comprehensive metabolic information on obese and non-obese adipose cellular growth. The project develops by: 1) developing tissue-engineered model systems for obese and normal adipose cellular growth, 2) profiling associated changes to extracellular metabolite concentrations and intracellular metabolic fluxes, and 3) identifying discriminatory markers characteristic of the various stages (pre- vs. mature adipocyte) and/or types (obese vs. normal) of adipose cellular growth.
These specific aims will be achieved by performing the following tasks: a) Compare the differentiation and growth of obese (Ob17) and non-obese (3T3-L1) adipocyte precursor cells, first in static, then bioreactor cultures. Comparisons will be made, among others, on the basis of morphology, biochemical function (including insulin sensitivity), and growth rate. Micro-fluidic bioreactor experiments will perform comparisons of Ob17 and 3T3-L1 cells in co-culture, b) Generate metabolic profile libraries encompassing concentration changes for all major primary carbohydrate, amino acid, and lipid metabolites in culture media. The primary analytical method will be liquid chromatography, c) Generate parallel metabolic flux libraries using established modeling methodologies, d) Perform multivariate discriminant analysis on the metabolite and flux libraries to identify significant markers for each of the growth conditions. The expected outcome of these procedures is a comprehensive library of metabolic profiles and markers that capture both broad and unique features of obese and normal adipose growth. This knowledge output marks a significant first step, at the functional level, in the global study of adipose energy metabolism, and should serve as a necessary information platform for further studies that investigate major driving reactions in adipose growth as obesity drug targets.
