title: Methionine restriction decreases visceral fat mass and preserves insulin action in aging male Fischer 344 rats independent of energy restriction.
abstract: Reduced dietary methionine intake (0.17% methionine, MR) and calorie restriction (CR) prolong lifespan in male Fischer 344 rats. Although the mechanisms are unclear, both regimens feature lower body weight and reductions in adiposity. Reduced fat deposition in CR is linked to preservation of insulin responsiveness in older animals. These studies examine the relationship between insulin responsiveness and visceral fat in MR and test whether, despite lower food intake observed in MR animals, decreased visceral fat accretion and preservation of insulin sensitivity is not secondary to CR. Accordingly, rats pair fed (pf) control diet (0.86% methinone, CF) to match the food intake of MR for 80 weeks exhibit insulin, glucose, and leptin levels similar to control-fed animals and comparable amounts of visceral fat. Conversely, MR rats show significantly reduced visceral fat compared to CF and PF with concomitant decreases in basal insulin, glucose, and leptin, and increased adiponectin and triiodothyronine. Daily energy expenditure in MR animals significantly exceeds that of both PF and CF. In a separate cohort, insulin responses of older MR animals as measured by oral glucose challenge are similar to young animals. Longitudinal assessments of MR and CF through 112 weeks of age reveal that MR prevents age-associated increases in serum lipids. By 16 weeks, MR animals show a 40% reduction in insulin-like growth factor-1 (IGF-1) that is sustained throughout life; CF IGF-1 levels decline much later, beginning at 112 weeks. Collectively, the results indicate that MR reduces visceral fat and preserves insulin activity in aging rats independent of energy restriction.
authors.affiliation: Orentreich Foundation for the Advancement of Science, Inc., Cold Spring-on-Hudson, NY 10516, USA. vmalloy@orentreich.org
authors.forename: Virginia L
authors.initials: VL
authors.lastname: Malloy
authors.forename: Rozlyn A
authors.initials: RA
authors.lastname: Krajcik
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Bailey
authors.forename: George
authors.initials: G
authors.lastname: Hristopoulos
authors.forename: Jason D
authors.initials: JD
authors.lastname: Plummer
authors.forename: Norman
authors.initials: N
authors.lastname: Orentreich
mesh_terms: D000273:Adipose Tissue / Q000187:drug effects; D050154:Adiposity; D000375:Aging; D000818:Animals; D001823:Body Composition / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects*; D002784:Cholesterol / Q000378:metabolism; D002149:Energy Intake; D004734:Energy Metabolism / Q000187:drug effects*; D005951:Glucose Tolerance Test; D007328:Insulin / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D008715:Methionine / Q000172:deficiency*; D051381:Rats; D011916:Rats, Inbred F344; D013997:Time Factors; D014280:Triglycerides / Q000378:metabolism
chemical_list: D007328:Insulin; D014280:Triglycerides; D007334:Insulin-Like Growth Factor I; D002784:Cholesterol; D008715:Methionine