ABSTRACT
Changes in the biological efficacy of leptin were evaluated in obesity-resistant (A/J) and obesity-prone (C57BL/6J) mice at weaning and after consuming a high-fat (HF) diet for 4 and 8 wk. There was no evidence of leptin resistance in either strain at the start of the study, but after 4 and 8 wk on the HF diet, C57BL/6J mice became unresponsive to ip leptin. C57BL/6J mice responded to intracerebroventricular leptin at these time points but developed peripheral resistance to sympathetic stimulation of retroperitoneal white adipose tissue. In contrast, intracerebroventricular leptin was fully effective in A/J mice, reproducing the complete profile of responses observed in weanling mice. A/J mice were also partially responsive to ip leptin at both time points, increasing uncoupling protein 1 mRNA expression in brown adipose tissue and decreasing leptin mRNA in white adipose tissue. The findings indicate that retention of leptin responsiveness is an important component of the ability of A/J mice to mount a robust adaptive thermogenic response and resist diet-induced obesity.
Subject(s)
Dietary Fats/pharmacology , Leptin/metabolism , Obesity/metabolism , Adipose Tissue/drug effects , Adipose Tissue/metabolism , Animals , Carrier Proteins/genetics , DNA-Binding Proteins/metabolism , Energy Intake , Gene Expression/drug effects , Gene Expression/physiology , Hypothalamus/drug effects , Hypothalamus/metabolism , Ion Channels , Leptin/pharmacology , Membrane Proteins/genetics , Mice , Mice, Inbred A , Mice, Inbred C57BL , Mitochondrial Proteins , STAT3 Transcription Factor , Species Specificity , Trans-Activators/metabolism , Uncoupling Protein 1ABSTRACT
Obesity-prone (AKR/J) and obesity-resistant (SWR/J) mice were weaned onto low (LF) or high fat (HF) diets to identify adaptive changes in adipocyte gene expression that are associated with differences between the strains in fat deposition. Food consumption was monitored at weekly intervals and all mice were evaluated after consuming their respective diets for 4 wk for analysis of mRNA levels of selected metabolic genes. Despite similar food consumption, body weight and fat deposition were significantly greater in AKR/J than in SWR/J mice, and this difference was greatly accentuated by the HF diet. The HF diet produced distinct differences between strains in gene expression patterns among fat depots. In AKR/J mice, UCP1 mRNA was decreased 10-fold in interscapular brown adipose tissue (BAT) and four- to fivefold in retroperitoneal and inguinal white adipose tissue (WAT). The HF diet also decreased PGC-1 and beta(3)-adrenergic receptor mRNA by two- and ninefold in BAT from AKR/J mice. In contrast, the HF diet either increased uncoupling protein (UCP)1 in BAT or had no effect on expression of these genes in adipose tissues from SWR/J mice. UCP2 mRNA was fourfold higher in WAT from AKR/J compared with SWR/J mice and increased by an additional twofold in WAT from AKR/J mice fed the HF diet. UCP2 was unaffected by diet in SWR/J mice. These studies show that the diet-induced obesity of AKR/J mice is characterized by increased metabolic efficiency and is associated with changes in adipocyte gene expression that limit the adaptive thermogenic response to increased energy density.
