Oleate-enriched diet improves insulin sensitivity and restores muscle protein synthesis in old rats.

BACKGROUND & AIMS: Age-related inflammation and insulin resistance (IR) have been implicated in the inability of old muscles to properly respond to anabolic stimuli such as amino acids (AA) or insulin. Since fatty acids can modulate inflammation and IR in muscle cells, we investigated the effect of palmitate-enriched diet and oleate-enriched diet on inflammation, IR and muscle protein synthesis (MPS) rate in old rats. METHODS: Twenty-four 25-month-old rats were fed either a control diet (OC), an oleate-enriched diet (HFO) or a palmitate-enriched diet (HFP) for 16 weeks. MPS using labeled amino acids and mTOR activation were assessed after AA and insulin anabolic stimulation to mimic postprandial state. RESULTS: IR and systemic and adipose tissue inflammation (TNFα and IL1ß) were improved in the HFO group. Muscle genes controlling mitochondrial ß-oxidation (PPARs, MCAD and CPT-1b) were up-regulated in the HFO group. AA and insulin-stimulated MPS in the HFO group only, and this stimulation was related to activation of the Akt/mTOR pathway. CONCLUSIONS: The age-related MPS response to anabolic signals was improved in rats fed an oleate-enriched diet. This effect was related to activation of muscle oxidative pathways, lower IR, and a decrease in inflammation.

Suppression of estrogen-related receptor alpha and medium-chain acyl-coenzyme A dehydrogenase in the acute-phase response.

Fatty acid oxidation provides energy in tissues with high metabolic demands. During the acute-phase response (APR) induced by infection and inflammation, fatty acid oxidation is decreased associated with hypertriglyceridemia. Little is known about the mechanism by which the APR decreases fatty acid oxidation. Therefore, we investigated whether the APR affects the expression of medium-chain acyl-coenzyme A dehydrogenase (MCAD), its regulator the estrogen-related receptor alpha (ERRalpha), and a key coactivator of ERRalpha, the peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha). mRNA levels of PGC-1alpha, ERRalpha, and MCAD are markedly reduced in the liver, heart, and kidney of mice during the lipopolysaccharide (LPS)-induced APR. The decreases were rapid and occurred at very low doses of LPS. MCAD activity in liver was also reduced. Furthermore, binding of hepatic nuclear extracts to the ERRalpha response element found in the promoter region of MCAD was significantly decreased during the APR, suggesting the decreased transcription of the MCAD gene. The binding activity was identified as ERRalpha by supershift with antibody to ERRalpha. Similar decreases in mRNA levels of these genes occur during zymosan- and turpentine-induced inflammation, indicating that suppression of the PGC-1alpha, ERRalpha, and MCAD pathway is a general response during infection and inflammation. Our study provides a potential mechanism by which the APR decreases fatty acid oxidation.

In vitro correction of medium chain acyl CoA dehydrogenase deficiency with a recombinant adenoviral vector.

Defects of mitochondrial beta-oxidation are a growing group of disorders with variable clinical presentations ranging from mild hypotonia to sudden infant death. Current therapy involves avoidance of fasting, dietary restrictions, and cofactor supplementation. Unfortunately, times of acute illness and noncompliance can interfere with these therapies and result in a rapid clinical decline. The development of a safe, durable, and effective gene delivery system remains an attractive alternative therapy for individuals with these disorders. To this end, a recombinant first-generation adenovirus vector (Ad/cmv-hMCAD) has been prepared that constitutively expresses the human medium chain acyl CoA dehydrogenase (MCAD) protein under the control of the CMV promoter and bovine polyadenylation signal. Characterization of human fibroblasts deficient in MCAD infected with Ad/cmv-hMCAD including Western analysis, immunohistological staining visualized with confocal microscopy, electron transfer protein (ETF) reduction assay, and palmitate loading studies was performed. Infection of MCAD deficient fibroblast with Ad/cmv-hmcad resulted in the production of a 55kDa protein that co-localized in cells with a mitochondrial marker. Extracts prepared from Ad/cmv-hMCAD infected deficient fibroblasts demonstrated correction of the block seen in the MCAD catalyzed reduction of ETF in the presence of octanoyl CoA. Finally, MCAD deficient fibroblasts infected with increasing amounts of Ad/cmv-hMCAD showed a stepwise improvement of the abnormal acylcarnitine profile exhibited by the deficient cells. Together these studies demonstrate our ability to express and monitor the expression of MCAD in treated cells and support further in vivo murine studies to assess toxicity and duration of correction with this and other MCAD recombinant vectors.