ABSTRACT
Drug-induced weight loss in humans has been associated with undesirable side effects not present in weight loss from lifestyle interventions (caloric restriction or exercise). To investigate the mechanistic differences of weight loss by drug-induced and lifestyle interventions, we examined the gene expression (mRNA) in brown adipose tissue (BAT) and conducted histopathologic assessments in diet-induced obese (DIO) mice given ephedrine (18 mg/kg/day orally), treadmill exercise (10 m/min, 1-h/day), and dietary restriction (DR: 26% dietary restriction) for 7 days. Exercise and DR mice lost more body weight than controls and both ephedrine and exercise reduced percent body fat. All treatments reduced BAT and liver lipid accumulation (i.e., cytoplasmic lipids in brown adipocytes and hepatocytes) and increased oxygen consumption (VO2 ml/kg/h) compared with controls. Mitochondrial biogenesis/function-related genes (TFAM, NRF1 and GABPA) were up-regulated in the BAT of all groups. UCP-1 was up-regulated in exercise and ephedrine groups, whereas MFSD2A was up-regulated in ephedrine and DR groups. PGC-1α up-regulation was observed in exercise and DR groups but not in ephedrine group. In all experimental groups, except for ephedrine, fatty acid transport and metabolism genes were up-regulated, but the magnitude of change was higher in the DR group. PRKAA1 was up-regulated in all groups but not significantly in the ephedrine group. ADRß3 was slightly up-regulated in the DR group only, whereas ESRRA remained unchanged in all groups. Although our data suggest a common pathway of BAT activation elicited by ephedrine treatment, exercise or DR, mRNA changes were indicative of additional nutrient-sensing pathways in exercise and DR.
Subject(s)
Adipose Tissue, Brown , Caloric Restriction , Dietary Fats/administration & dosage , Ephedrine/therapeutic use , Motor Activity/drug effects , Obesity/prevention & control , Sympathomimetics/therapeutic use , Adipose Tissue, Brown/drug effects , Adipose Tissue, Brown/metabolism , Adipose Tissue, Brown/pathology , Animals , Body Composition/drug effects , Body Weight/drug effects , Energy Metabolism/drug effects , Ephedrine/administration & dosage , Ephedrine/adverse effects , Gene Expression/drug effects , Liver/drug effects , Liver/metabolism , Male , Mice , Mice, Inbred Strains , Mitochondria, Liver/drug effects , Mitochondria, Liver/metabolism , Mitochondrial Proteins/biosynthesis , Mitochondrial Proteins/genetics , Motor Activity/physiology , Obesity/etiology , Obesity/metabolism , Obesity/pathology , Oxygen Consumption/drug effects , Sympathomimetics/administration & dosage , Sympathomimetics/adverse effectsABSTRACT
Several drugs have been linked to valvulopathy in humans, including therapeutic agents for obesity, Parkinson's disease and migraine. There is increasing evidence that the 5-hydroxytryptamine 2B receptor (5HT2BR) activation and/or increased circulating 5HT (5-hydroxytryptamine) may play a significant role in the pathogenesis of drug-induced valvulopathy. In the present study, we investigated whether 7-day 5HT subcutaneous injections led to structural and compositional abnormalities in conjunction with transcriptomic modulation of 5HT2BR and 5HT transporter (5HTT) genes in the aortic and mitral valves of Sprague-Dawley (SD) rats. Subcutaneous injections of 5HT for 7 days resulted in thickening and compositional alteration of aortic and mitral valves in SD rats. More specifically, valve-leaflets from 5HT-treated rats had greater valve thickness, a higher amount of glycosaminoglycans (GAGs) and a lower amount of collagen. The compositional alteration was associated with up-regulation and down-regulation of 5HT2BR and 5HTT genes, respectively. The present study strongly suggests that the activation of 5HT2BR and inhibition of 5HTT played a significant role in the pathogenesis of 5HT-induced valvulopathy in SD rats. Thus, these findings further highlight the necessity and/or utilization of animal models to screen potential valvular effects of serotonergic compounds.
