title: Metabolic adaptations in the adipose tissue that underlie the body fat mass gain in middle-aged rats.
abstract: Little is known about adipocyte metabolism during aging process and whether this can influence body fat redistribution and systemic metabolism. To better understand this phenomenon, two animal groups were studied: young-14 weeks old-and middle-aged-16 months old. Periepididymal (PE) and subcutaneous (SC) adipocytes were isolated and tested for their capacities to perform lipolysis and to incorporate D-[U-(14)C]-glucose, D-[U-(14)C]-lactate, and [9,10(n)-(3)H]-oleic acid into lipids. Additionally, the morphometric characteristics of the adipose tissues, glucose tolerance tests, and biochemical determinations (fasting glucose, triglycerides, insulin) in blood were performed. The middle-aged rats showed adipocyte (PE and SC) hypertrophy and glucose intolerance, although there were no significant changes in fasting glycemia and insulin. Furthermore, PE tissue revealed elevated rates (+50 %) of lipolysis during beta-adrenergic-stimulation. There was also an increase (+62 %) in the baseline rate of glucose incorporation into lipids in the PE adipocytes, while these PE cells were almost unresponsive to insulin stimulation and less responsive (a 34 % decrease) in the SC tissue. Also, the capacity of oleic acid esterification was elevated in baseline state and with insulin stimulus in the PE tissue (+90 and 82 %, respectively). Likewise, spontaneous incorporation of lactate into lipids in the PE and SC tissues was higher (+100 and 11 %, respectively) in middle-aged rats. We concluded that adipocyte metabolism of middle-aged animals seems to strongly favor cellular hypertrophy and increased adipose mass, particularly the intra-abdominal PE fat pad. In discussion, we have interpreted all these results as a metabolic adaptations to avoid the spreading of fat that can reach tissues beyond adipose protecting them against ectopic fat accumulation. However, these adaptations may have the potential to lead to future metabolic dysfunctions seen in the senescence.
authors: Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil, rsertie@yahoo.com.br.
authors: Rogério Antonio Laurato
authors: RA
authors: Sertié
authors: Rennan de Oliveira
authors: Rde O
authors: Caminhotto
authors: Sandra
authors: S
authors: Andreotti
authors: Amanda Baron
authors: AB
authors: Campaña
authors: André Ricardo Gomes
authors: AR
authors: de Proença
authors: Natalie Carolina
authors: NC
authors: de Castro
authors: Fábio Bessa
authors: FB
authors: Lima
mesh_terms: D000222:Adaptation, Physiological; D017667:Adipocytes / Q000378:metabolism / Q000473:pathology; D000273:Adipose Tissue / Q000378:metabolism* / Q000473:pathology; D050154:Adiposity / Q000502:physiology*; D000375:Aging / Q000378:metabolism*; D000818:Animals; D004195:Disease Models, Animal; D008066:Lipolysis / Q000502:physiology*; D008297:Male; D009765:Obesity / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar