The waist-to-hip ratio corrected for body mass index is related to serum triglycerides and high-density lipoprotein cholesterol but not to parameters of glucose metabolism in healthy premenopausal women

Relationship between the inhibition of phosphatidic acid phosphohydrolase-1 by oleate and oleoyl-CoA ester and its apparent translocation

Phosphatidic acid phosphohydrolase-1 (PAP-1) activity is reversibly inhibited by fatty acids and their acyl-CoA esters and it appears paradoxical that these effectors have been reported to increase the liver's esterification capacity by translocating the rate-limiting enzyme PAP-1 from cytosol to the endoplasmic reticulum. Therefore, we have examined the effect of oleate, oleoyl-CoA, and spermine on the activation and translocation of PAP-1 of rat liver. PAP-1 activity is directly inhibited by oleic acid and oleoyl-CoA ester in an allosteric manner, resulting in the formation of inactive PAP-1-fatty acid (or -acyl-CoA) complex, even in the absence of any subcellular structures. Such association/aggregation of PAP-1 can be easily collected by centrifugation and may explain the apparent translocation phenomenon of this enzyme to a particular structure in the presence of fatty acids or acyl-CoA esters as reported in many works. Indeed, incubation of cytosol fraction alone with oleate or oleoyl-CoA at 37 degrees C, followed by centrifugation, induces a significant increase (sevenfold) in PAP-1 activity in the pellet fraction. This displacement is accompanied by an increase in the specific activity of PAP-1 in the pellet fraction. Spermine is less effective than oleate in inducing the displacement of PAP-1 activity from cytosol to the pellet fraction in the absence of any membrane structures. This apparent translocation of PAP-1 is also promoted when homogenate fraction was incubated with oleate prior to the preparation of cytosol and microsomal fraction. Thus, many of the announced factors, including fatty acids, would promote the in vitro association/aggregation of PAP-1 enzyme rather than its translocation, and therefore, re-evaluation of the reported effects on PAP-1 translocation phenomenon is required. It is proposed that fatty acids and their esters would favour beta-oxidation over esterification by promoting the forming of inactive associated PAP-1 in situations such as starvation and metabolic stress in which there is an increased supply of fatty acids to the liver.

Exercise mitigates the association of abdominal obesity with high-density lipoprotein cholesterol in premenopausal women: results from the third National Health and Nutrition Examination Survey

OBJECTIVE

To examine the relationship between abdominal obesity, as measured by waist-to-hip ratio (WHR) and high-density lipoprotein cholesterol (HDL-C) level within the context of age, body fatness, exercise, saturated fat intake, and other plasma lipids.

DESIGN/SUBJECTS

Subjects were premenopausal, white, non-Hispanic women from the third National Health and Nutrition Examination Survey. Smokers, heavy drinkers, and women who took lipid-altering drugs were excluded. Of 1,188 subjects who met the inclusion criteria, complete data were available for 435 women.

STATISTICAL ANALYSES

Means were calculated using all subjects for each variable, then F-protected t tests and linear contrasts were performed to test differences in means between subgroups. A P < .05 was considered significant.

RESULTS

Age was not significantly associated with HDL-C level. Comparisons of HDL-C by WHR, percentage body fat (%BF), and exercise level revealed that HDL-C level was significantly lower at the higher levels of WHR and %BF and higher at the highest levels of exercise. Higher levels of HDL-C were generally accompanied by lower levels of triacylglycerol. When HDL-C was compared by exercise level within each WHR tertile and %BF tertile, the association of exercise with HDL-C diminished. Saturated fat intake was not associated with HDL-C.

CONCLUSIONS/APPLICATIONS

Increased exercise is associated with a lower WHR and subsequently a higher HDL-C level. This association between WHR and HDL-C appears to be mediated through %BF. Women exercisers with the highest WHR had consistently more favorable plasma lipid profiles and lower mean body mass index and %BF than nonexercisers. Thus, for women who exhibit abdominal obesity, exercise mitigates the association of WHR with HDL-C level. Vigorous exercise in the premenopausal years may promote a more favorable lipid profile, even in the presence of increased body fat and abdominal girth.

Are there any sex differences in fatty liver? A study of glucose metabolism and body fat distribution

BACKGROUND AND AIMS

Fatty liver is a common condition found more often in males. Whether sex differences affect its development is presently unknown. The hypothesis that glucose metabolism alterations or central body fat distribution are gender-related in fatty liver was investigated.

METHODS

Overall 199 consecutive subjects seen in the Division of Internal Medicine and Gastroenterology, Modena City Hospital, were enrolled. In the main arm of the present study, 44 men with sonographic fatty liver and 47 controls without, and 18 women with and 19 without fatty liver had their body mass index (an index of overall adiposity), hepatobiliary serum enzymes, serum cholesterol and triglycerides determined. All underwent oral glucose tolerance tests (estimated through the glucose area under the curve with the trapezoidal method). In the ancillary arm study, 17 other men with and 14 without, and 11 other women with and 29 without fatty liver had anthropometric measurements of body fat distribution (waist/hip, waist/height and skinfold thickness).

RESULTS

Following statistical evaluation including univariate and multivariate analyses (main study), elevated body mass index was found to be an independent predictor of fatty liver in either sex. Glucose area under the curve and a central-type body fat distribution (ancillary study) predicted FL only in women.

CONCLUSIONS

Fatty liver could be gender-related in the present series.

Hyperglycemia-induced inhibition of splanchnic fatty acid oxidation increases hepatic triacylglycerol secretion

The effect of hyperglycemia ( approximately 8 mmol/l) on splanchnic fatty acid oxidation and triacylglycerol (TG) secretion rates was investigated in five healthy men. U-13C-labeled fatty acids were infused to estimate fatty acid kinetics and oxidation across the splanchnic region, and in vivo labeled very low density lipoprotein (VLDL)-TG was infused to estimate TG secretion rate. Plasma fatty acid carbon enrichment and concentration were maintained constant by infusion of lipids and heparin in the hyperglycemia experiments. Fatty acid uptake by the splanchnic region was 1.4 +/- 0.2 and 2.2 +/- 0.9 micromol. kg-1. min-1 in the basal and clamp experiments, respectively, whereas fatty acid oxidation decreased from 0.4 +/- 0. 04 to 0.2 +/- 0.05 micromol. kg-1. min-1 (P < 0.05). Hepatic TG secretion increased from 0.35 +/- 0.07 micromol. kg-1. min-1 in the basal state to 0.53 +/- 0.11 micromol. kg-1. min-1 after 15 h of hyperglycemia (P < 0.05). Similarly, plasma VLDL-TG concentration increased from 0.28 +/- 0.06 to 0.43 +/- 0.05 mmol/l during the clamp (P < 0.05). In summary, hyperglycemia attenuates fatty acid oxidation in the splanchnic region in human volunteers, even when fatty acid availability is constant. This adaptation results in a significant increase in the VLDL-TG secretion rate and concentration in plasma.