As the obesity epidemic continues, more Americans are getting fatter, having more weight-related problems such as cardiovascular disease, and are experiencing new metabolic dysfunctions. For over 50 years, the adipose tissue (AT), commonly referred to as fat, has been of interest to academic and clinical scientists, public health officials and individuals interested in body composition and image including much of the average public, athletes, parents, etc. On one hand, efforts to alter body shape, weight and body fat percentage still include bizarre and scientifically unfounded methods. On the other hand, significant new scientific strides have been made in understanding the growth, function and regulation of anatomical and systemic AT. Markers of transition/conversion of precursor cells that mature to form lipid assimilating adipocytes have been identified. Molecular master regulators such as peroxisome proliferator-activated receptor gamma and CCAAT-enhancer-binding proteins were uncovered and regulatory mechanisms behind variables of adiposity defined and refined. Interventions including pharmaceutical compounds, surgical, psychosocial interventions have also been tested. Has all of the preceding research helped alleviate the adverse physiologies of overweight and/or obese people? Does research to date point to new modalities that should be the focus of efforts to rid the world of obesity-related problems in the 21st century? This review provides a general overview of scientific efforts to date and a provocative view of the future for adiposity.
Meat animals are unique as experimental models for both lipid metabolism and adipocyte studies because of their direct economic value for animal production. This paper discusses the principles that regulate adipogenesis in major meat animals (beef cattle, dairy cattle, and pigs), the definition of adipose depot-specific regulation of lipid metabolism or adipogenesis, and introduces the potential value of these animals as models for metabolic research including mammary biology and the ontogeny of fatty livers.
In vitro models have been invaluable in determining the mechanisms involved in adipocyte proliferation, differentiation, adipokine secretion and gene/protein expression. The cells presently available for research purposes all have unique advantages and disadvantages that one should be aware of when selecting cells. Established cell lines, such as 3T3-L1 cells, are easier and less costly to use than freshly isolated cells, even though freshly isolated cells allow for various comparisons such as the in vitro evaluation of different in vivo conditions that may not be possible using cell lines. Moreover, stem cells, transdifferentiated cells or dedifferentiated cells are relatively new cell models being evaluated for the study of adipocyte regulation and physiology. The focus of this brief review is to highlight similarities and differences in adipocyte models to aid in appropriate model selection and data interpretation for successful advancement of our understanding of adipocyte biology.
Skeletal muscle stem cells from food-producing animals are of interest to agricultural life scientists seeking to develop a better understanding of the molecular regulation of lean tissue (skeletal muscle protein hypertrophy) and intramuscular fat (marbling) development. Enhanced understanding of muscle stem cell biology and function is essential for developing technologies and strategies to augment the metabolic efficiency and muscle hypertrophy of growing animals potentially leading to greater efficiency and reduced environmental impacts of animal production, while concomitantly improving product uniformity and consumer acceptance and enjoyment of muscle foods.
White adipose tissue is a mesenchymal tissue that begins developing in the fetus. Classically known for storing the bodys fuel reserves, adipose tissue is now recognized as an endocrine organ. As such, the secretions from adipose tissue are known to affect several systems such as the vascular and immune systems and play major roles in metabolism. Numerous studies have shown nutrient or hormonal manipulations can greatly influence adipose tissue development. In addition, the associations between various disease states, such as insulin resistance and cardiovascular disease, and disregulation of adipose tissue seen in epidemiological and intervention studies are great. Evaluation of known adipokines suggests these factors secreted from adipose tissue play roles in several pathologies. As the identification of more adipokines and determination of their role in biological systems, and the interactions between adipocytes and other cells types continues, there is little doubt that we will gain a greater appreciation for a tissue once thought to simply store excess energy.
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