PLIN2
Perilipin-2 (Adipophilin) (Adipose differentiation-related protein) (ADRP) [ADFP]
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Atrial fibrillation (AF) is prevalent in patients with obesity and diabetes, and such patients often exhibit cardiac steatosis. Since the role of cardiac steatosis per se in the induction of AF has not been elucidated, the present study was designed to explore the relation between cardiac steatosis and AF. Transgenic (Tg) mice with cardiac-specific overexpression of perilipin 2 (PLIN2) were housed in the laboratory for more than 12 mo before the study. Electron microscopy of the atria of PLIN2-Tg mice showed accumulation of small lipid droplets around mitochondrial chains, and five- to ninefold greater atrial triacylglycerol (TAG) content compared with wild-type (WT) mice. Electrocardiography showed significantly longer RR intervals in PLIN2-Tg mice than in WT mice. Transesophageal electrical burst pacing resulted in significantly higher prevalence of sustained (>5 min) AF (69%) in PLIN2-Tg mice than in WT mice (24%), although it was comparable in younger (4-mo-old) mice. Connexin 43 (Cx43), a gap junction protein, was localized at the intercalated disks in WT atria but was heterogeneously distributed on the lateral side of cardiomyocytes in PLIN2-Tg atria. Langendorff-perfused hearts using the optical mapping technique showed slower and heterogeneous impulse propagation in PLIN2-Tg atria compared with WT atria. Cardiac overexpression of hormone-sensitive lipase in PLIN2-Tg mice resulted in atrial TAG depletion and amelioration of AF susceptibility. The results suggest that PLIN2-induced steatosis is associated with Cx43 remodeling, impaired conduction propagation, and higher incidence of AF in aged mice. Therapies targeting cardiac steatosis could be potentially beneficial against AF in patients with obesity or diabetes.
MeSH Terms
- Animals
- Atrial Fibrillation
- Connexin 43
- Gene Knock-In Techniques
- Heart Atria
- Isolated Heart Preparation
- Lipid Droplets
- Mice
- Mice, Transgenic
- Microscopy, Electron
- Myocytes, Cardiac
- Perilipin-2
- Sterol Esterase
- Triglycerides
- Voltage-Sensitive Dye Imaging
Keywords
- aging
- cardiac steatosis
- gap junction
- lipid droplets
- lipotoxic arrhythmia
Age-dependent ectopic fat accumulation (EFA) in animals contributes to the progression of tissue aging and diseases such as obesity, diabetes, and cancer. However, the primary causes of age-dependent EFA remain largely elusive. Here, we characterize the occurrence of age-dependent EFA in Drosophila and identify HDAC6, a cytosolic histone deacetylase, as a suppressor of EFA. Loss of HDAC6 leads to significant age-dependent EFA, lipid composition imbalance, and reduced animal longevity on a high-fat diet. The EFA and longevity phenotypes are ameliorated by a reduction of the lipid-droplet-resident protein PLIN2. We show that HDAC6 is associated physically with the chaperone protein dHsc4/Hsc70 to maintain the proteostasis of PLIN2. These findings indicate that proteostasis collapse serves as an intrinsic cue to cause age-dependent EFA. Our study suggests that manipulation of proteostasis could be an alternative approach to the treatment of age-related metabolic diseases such as obesity and diabetes.
MeSH Terms
- Aging
- Animals
- Autophagy
- Cytosol
- Diet, High-Fat
- Drosophila Proteins
- Drosophila melanogaster
- Fats
- Histone Deacetylase 6
- Histone Deacetylases
- Lipid Droplets
- Longevity
- Perilipin-2
Keywords
- Drosophila
- HDAC6
- Hsc70/dHsc4
- PLIN2
- acetylation
- aging
- autophagy
- chaperone
- fat metabolism
- proteostasis
Aging and inactivity lead to skeletal muscle metabolic inflexibility, but the underlying molecular mechanisms are not entirely elucidated. Therefore, we investigated how muscle lipid and glycogen stores and major regulatory proteins were affected by short-term immobilization followed by aerobic training in young and older men. 17 young (23 ± 1 years, 24 ± 1 kg m(-2), and 20 ± 2% body fat) and 15 older men (68 ± 1 years; 27 ± 1 kg m(-2), and 29 ± 2% body fat) underwent 2 weeks' one leg immobilization followed by 6 weeks' cycle training. Biopsies were obtained from m. vastus lateralis just before immobilization (at inclusion), after immobilization, and the after 6 weeks' training. The biopsies were analyzed for muscle substrates; muscle perilipin protein (PLIN), glycogen synthase (GS), synaptosomal-associated protein of 23 kDa (SNAP23) protein content, and muscle 3-hydroxyacyl-CoA dehydrogenase (HAD) activity The older men had higher intramuscular triglyceride (IMTG) (73 %) and Glycogen (16%) levels compared to the young men, and IMTG tended to increase with immobilization. PLIN2 and 3 protein content increased with immobilization in the older men only. The young men had higher GS (74%) protein compared to the older men. Immobilization decreased and training restored HAD activity, GS and SNAP23 protein content in young and older men. Evidence of age-related metabolic inflexibility is presented, seen as body fat and IMTG accumulation. The question arises as to whether IMTG accumulation in the older men is caused by or leading to the increase in PLIN2 and 3 protein content. Training decreased body fat and IMTG levels in both young and older men; hence, training should be prioritized to reduce the detrimental effect of aging on metabolism.
MeSH Terms
- 3-Hydroxyacyl-CoA Dehydrogenase
- Aged
- Carrier Proteins
- Exercise
- Glycogen
- Glycogen Synthase
- Humans
- Immobilization
- Lipid Metabolism
- Male
- Muscle Proteins
- Muscle, Skeletal
- Perilipin-1
- Phosphoproteins
- Qb-SNARE Proteins
- Qc-SNARE Proteins
- Young Adult
Keywords
- Aerobic training
- Aging
- Immobilization
- Intramuscular triglycerides
- Muscle metabolism
- Perilipin protein