title: Effects of fasting and refeeding on serum leptin, adiponectin and free fatty acid concentrations in young and old male rats.
abstract: BACKGROUND
  Regulatory mechanisms of metabolic homeostasis undergo important alterations during ageing. The age-related changes become often evident only during stimulation of basic functions that occurs, e.g. during fasting and refeeding which represent natural challenge to energy metabolism.
  
  
  OBJECTIVE
  To determine the effect of short-term fasting and subsequent refeeding on serum levels of key hormones and metabolites in young adult 5- and 24-month-old male Wistar rats.
  
  
  METHODS
  Control rats were fed ad libitum. Animals were fasted for 48 h or fasted and refed for 24 h. Metabolite serum concentrations were measured by standard methods. Leptin and insulin were determined by rat-specific RIA, and adiponectin serum levels by mouse/rat-specific ELISA.
  
  
  RESULTS
  (1) Control serum levels of key metabolites and hormones were similar in both age groups except for increased triglycerides (TG) in old fed rats. (2) Fasting caused a significant decrease of leptin, insulin, glucose, and TG serum levels in both age groups, and an increase of free fatty acids (FFA) concentration, however, only in young animals. (3) Upon refeeding serum glucose, TG and insulin reversed to control levels in both age groups, however, FFA concentration decreased to control values only in young rats. (4) In contrast to young animals, refeeding of old rats did not increase serum leptin concentration to control level. (5) Neither fasting nor refeeding changed adiponectin serum levels in both age groups.
  
  
  CONCLUSIONS
  Aging suppresses leptin secretion and metabolism of FFA during refeeding that follows short-term starvation. In old rats serum levels of FFA are refractive to the alterations induced by fasting/refeeding in young ones.
authors.affiliation: Department Histology and Immunology, Medical University of Gdansk, Gdansk, Poland. zkmiec@amg.gda.pl
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Kmiec
authors.forename: Leszek
authors.initials: L
authors.lastname: Pokrywka
authors.forename: Grazyna
authors.initials: G
authors.lastname: Kotlarz
authors.forename: Jolanta
authors.initials: J
authors.lastname: Kubasik
authors.forename: Andrzej
authors.initials: A
authors.lastname: Szutowicz
authors.forename: Andrzej
authors.initials: A
authors.lastname: Mysliwski
mesh_terms: D052242:Adiponectin / Q000097:blood*; D000375:Aging / Q000097:blood*; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight; D004435:Eating / Q000502:physiology; D005215:Fasting / Q000097:blood*; D005230:Fatty Acids, Nonesterified / Q000097:blood*; D006706:Homeostasis; D007328:Insulin / Q000097:blood; D020738:Leptin / Q000097:blood*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D014280:Triglycerides / Q000097:blood
chemical_list: D052242:Adiponectin; D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D020738:Leptin; D014280:Triglycerides