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.

Low‐Intensity Exercise Routine for a Long Period of Time Prevents Osteosarcopenic Obesity in Sedentary Old Female Rats, by Decreasing Inflammation and Oxidative Stress and Increasing GDF‐11

“…Age-related fat gain is known to correlate with muscle and bone deterioration during OSO [35,46]. Moreover, it has been observed that body fat increases in Wistar rats throughout life, which has been related to a decrease in muscle mass, BMC, and life expectancy [57][58][59][60]. As mentioned before, one of the main benefits observed in the LIERLT routine was that reducing body fat increased the survival of Wistar female rats by 66%.…”

Age-related changes in central effects of corticotropin-releasing factor (CRF) suggest a role for this mediator in aging anorexia and cachexia

“…During the course of aging, long-term trends emerge in the regulation of energy balance resulting in middleaged obesity and aging anorexia leading to loss of active tissues and cachexia and sarcopenia in old age (Scarpace et al 2000;Morley 2001;Di Francesco et al 2007;Pétervári et al 2011b;Sertié et al 2015;Tay et al 2015;Wysokiński et al 2015;Jura and Kozak 2016;Loenneke and Loprinzi 2016). Both abnormalities represent serious public health challenges (Morley 2001;Sertié et al 2015;Sivasinprasasn et al 2015;Wysokiński et al 2015;Jura and Kozak 2016). The question arises whether production or efficacy of catabolic CRF show changes in the course of aging that may potentially contribute to the above-mentioned ageassociated obesity and/or to the development of sarcopenia.…”

Participación del GDF11 como factor de regeneración muscular en ratas con obesidad sarcopénica asociada al envejecimiento bajo un régimen de ejercicio

“…El aumento de grasa relacionado con la edad correlaciona con el deterioro muscular y óseo durante la OSO (Lin et al, 2018;Ezzat et al, 2017). Además, se ha observado que la grasa corporal aumenta en las ratas Wistar a lo largo de la vida, lo que se ha relacionado con una disminución de la masa muscular, la BMD y la esperanza de vida (Fernández et al, 2019;Sertié et al, 2015;Ahima et al, 2019;Duque et al, 2009). Nuestros resultados, demuestran que la rutina LIERLT reduce la grasa corporal y aumenta la supervivencia de las ratas hasta en un 66% (Figura 22).…”