Postprandial triglyceride metabolism in elderly men with subnormal testosterone levels

Delayed clearance of triglyceride-rich lipoproteins in young, healthy obese subjects

Obesity is associated with the metabolic syndrome. The aims were, first, to study the postprandial triglyceride clearance in young, healthy obese subjects and, second, to investigate if fasting triglycerides can predict delayed postprandial triglyceride clearance. Eighteen apparently healthy, obese subjects with no clinical signs of metabolic disturbances participated. Controls were age- and sex-matched, healthy, normal weight subjects. Subclinical markers of metabolic disturbances were assessed by measuring postprandial triglycerides in serum and in chylomicrons by oral fat tolerance test. Postprandial triglyceride clearance for 8 h was assessed indirectly as removal of the lipid from serum during the oral fat tolerance test. Insulin resistance was measured by the homeostasis model assessment of insulin resistance (HOMA-IR). Twelve (66%) of the apparently healthy obese individuals had insulin resistance measured by HOMA-IR. There was a delayed clearance of serum triglycerides and chylomicron triglycerides at 6 h when compared with the control group, while, at 8 h, the differences were only detected for the chylomicron triglyceride clearance. Triglyceride response was significantly greater in the obese subjects. Fasting triglycerides in upper normal level predicted a delayed postprandial triglyceride clearance and insulin resistance. In young, apparently healthy obese subjects early metabolic disturbances including insulin resistance and delayed postprandial triglyceride clearance can be detected. Fasting serum triglyceride in upper normal level predicted delayed postprandial triglyceride clearance and insulin resistance.

Proteomic analysis of lipid droplets from Caco-2/TC7 enterocytes identifies novel modulators of lipid secretion

In enterocytes, the dynamic accumulation and depletion of triacylglycerol (TAG) in lipid droplets (LD) during fat absorption suggests that cytosolic LD-associated TAG contribute to TAG-rich lipoprotein (TRL) production. To get insight into the mechanisms controlling the storage/secretion balance of TAG, we used as a tool hepatitis C virus core protein, which localizes onto LDs, and thus may modify their protein coat and decrease TRL secretion. We compared the proteome of LD fractions isolated from Caco-2/TC7 enterocytes expressing or not hepatitis C virus core protein by a differential proteomic approach (isobaric tag for relative and absolute quantitation (iTRAQ) labeling coupled with liquid chromatography and tandem mass spectrometry). We identified 42 proteins, 21 being involved in lipid metabolism. Perilipin-2/ADRP, which is suggested to stabilize long term-stored TAG, was enriched in LD fractions isolated from Caco-2/TC7 expressing core protein while perilipin-3/TIP47, which is involved in LD synthesis from newly synthesized TAG, was decreased. Endoplasmic reticulum-associated proteins were strongly decreased, suggesting reduced interactions between LD and endoplasmic reticulum, where TRL assembly occurs. For the first time, we show that 17β-hydroxysteroid dehydrogenase 2 (DHB2), which catalyzes the conversion of 17-keto to 17 β-hydroxysteroids and which was the most highly enriched protein in core expressing cells, is localized to LD and interferes with TAG secretion, probably through its capacity to inactivate testosterone. Overall, we identified potential new players of lipid droplet dynamics, which may be involved in the balance between lipid storage and secretion, and may be altered in enterocytes in pathological conditions such as insulin resistance, type II diabetes and obesity.

Vitamin E dose-dependently reduces aortic fatty lesion formation in orchidectomized aged rats

BACKGROUND AND AIMS

Although the cardioprotective effects of supplemental doses of vitamin E have been investigated in several conditions, its role in gonadectomy- induced fatty lesion formation is unclear. The present study was designed to examine the efficacy of vitamin E in a dose-dependent manner on indices of oxidative stress and in preventing the formation of aortic fatty lesions in orchidectomized (Orx) aged rats.

METHODS

Forty 12-month old male Sprague-Dawley rats were either sham-operated (Sham) or Orx and fed a semi-purified control diet for 120 days. Thereafter, rats were assigned to four treatment groups (n=10): Sham and one Orx group received 75 IU vitamin E and served as controls, and the other two Orx groups received either 250 or 500 IU vitamin E per kg diet for 90 days.

RESULTS

Vitamin E at the highest dose (500 IU) was able to lower serum total cholesterol by 16% and significantly increase superoxide dismutase by 9% compared to Orx controls. Similarly, this dose was able to significantly reduce the development of atherosclerotic lesion formation and aortic fatty streak area by 93% compared to Orx controls.

CONCLUSIONS

The findings of this study suggest that dietary vitamin E supplementation in Orx aged rats provide anti-atherogenic effects, in part, due to vitamin E's antioxidative properties. Clinical studies are needed to confirm whether supplemental doses of vitamin E can prevent the development of atherosclerosis in older men particularly with low testosterone level.