Predictors of adipose tissue lipoprotein lipase in middle-aged and older men: relationship to leptin and obesity, but not cardiovascular fitness

Metabolic changes in aging humans: current evidence and therapeutic strategies

Aging and metabolism are inextricably linked, and many age-related changes in body composition, including increased central adiposity and sarcopenia, have underpinnings in fundamental aging processes. These age-related changes are further exacerbated by a sedentary lifestyle and can be in part prevented by maintenance of activity with aging. Here we explore the age-related changes seen in individual metabolic tissues - adipose, muscle, and liver - as well as globally in older adults. We also discuss the available evidence for therapeutic interventions such as caloric restriction, resistance training, and senolytic and senomorphic drugs to maintain healthy metabolism with aging, focusing on data from human studies.

Aging and plasma triglyceride metabolism

The risk for metabolic disease, including metabolic syndrome, insulin resistance, and diabetes, increases with age. Altered plasma TG metabolism and changes in fatty acid partitioning are also major contributors to metabolic disease. Plasma TG metabolism itself is altered by age in humans and rodents. As discussed in this review, the age-induced changes in human TG metabolism include increased plasma TG levels, reduced postprandial plasma TG clearance rates, reduced postheparin LPL activity, decreased adipose tissue lipolysis, and elevated ectopic fat deposition, all of which could potentially contribute to age-associated metabolic diseases. Similar observations have been made in aged rats. We highlight the limitations of currently available data and propose that mechanistic studies are needed to understand the extent to which age-induced alterations in TG metabolism contribute to metabolic disease. Such mechanistic insights could aid in therapeutic strategies for preventing or managing metabolic disease in older individuals.

A Cross-sectional Study on the Prevalence of Physical Activity Among Primary Health Care Physicians in Aljouf Region of Saudi Arabia

BACKGROUND

Sedentary life style and consequent obesity prevail in both developed and developing nations; gender- and age-independently. Physical inactivity in a population in a life style transition-like Saudi Arabia-causes metabolic syndrome with its immediate and long-term complications. Healthcare workers are in a better position for role modeling and counseling of appropriate health behaviors. Personal physical activity and body built among physicians influences to some degree their exercise counseling. Realizing such principle necessitates gauging the extent of physical activity among physicians and assessing the likelihood of counseling the patients on physical activities.

METHODS

A cross-sectional study enrolled primary health care physicians (PHCPs) from primary health care centers and general hospitals of two cities (Sakaka and Dumat Al-Jandal) of Aljouf region, Saudi Arabia. Both genders were included. English version of step-wise questionnaire of World Health Organization was used for data collection.

RESULTS

The response rate was 64.2%. 65.2% of respondent PHCPs were doing moderate to vigorous physical exercise and 34.8% of them were physically inactive. Majority of physically inactive PHCPs had intention to increase their physical activity. Neither gender, nationality nor city-wise significant differences were recorded. However, physically active PHCPs significantly impart advice and role modeling on physical activity to their patients compared to physically inactive PHCPs (p<0.01).

CONCLUSION

Most PHCPs in Sakaka and Dumat Al-Jandal cities were physically active and were able to impart the healthy behavior counseling to their patients. A strong intention prevailed to increase physical activity among physically inactive Primary Health care Physicians (PHCPs).

The role of physician counseling in improving adherence to physical activity among the general population

The regular practice of physical activity at appropriate levels ensures various benefits for the individual over the short, medium and long terms. It is therefore important in health promotion. On the other hand, sedentary behavior has reached alarming levels among the general population, which qualifies it as a serious health problem of endemic proportions. The present review describes public health problems consequent to sedentary behavior and the importance of physician counseling for change their patients behavior and making them more physically active on a regular basis. Models and behavioral theories are presented to facilitate physicians understanding of how to approach patients during clinical practice. We also describe programs conducted in many countries based on physician counseling for reducing sedentary behavior, and we present many tools used to quantify and qualify patients attitudes towards becoming more physically active. Through understanding the barriers faced by patients, we suggest methodologies that will enable physicians to use physical activity promotion appropriately. We hope that this will provide support for physicians in conducting physical activity counseling, as a means for improving the health of the population.

Lipoprotein lipase activity/mass ratio is higher in omental than in subcutaneous adipose tissue

BACKGROUND

Lipoprotein lipase (LPL) is important for lipid deposition in adipose tissue (AT) and responds rapidly to changes in the nutritional state. Animal experiments indicate that short-term regulation of LPL is mainly post-translational. Different processing of LPL in different AT depots may play a role in the distribution of lipids in the body.

MATERIALS AND METHODS

Lipoprotein lipase mRNA, mass and activity were measured in pieces of omental adipose tissue (OAT) and subcutaneous adipose tissue (SAT) from 15 subjects undergoing gastrointestinal surgery (four male and 11 female subjects, mean age 54 +/- 5 years, BMI 28 +/- 2 kg m(-2)).

RESULTS

Lipoprotein lipase activity was higher in OAT than in SAT (18 +/- 2.1 compared with 12 +/- 1.6 mU g(-1), P < 0.01), whereas LPL mass was lower in OAT than in SAT (100 +/- 9 compared with 137 +/- 16 mU g(-1), P < 0.05). Consequently, the specific LPL activity (ratio of activity over mass) was approximately twofold greater in OAT compared with SAT. There was correlation between LPL mRNA and LPL activity in SAT (P < 0.05) and a similar tendency in OAT (P = 0.08). There were strong correlations (P < 0.01) for mRNA abundance as well as for LPL activity between the two depots. In contrast there was no correlation between the LPL mass and LPL mRNA or activity in any of the depots.

CONCLUSIONS

These results indicate that long-term regulation, as reflected in the mRNA abundance, is similar in the two types of adipose tissue. The displayed activity reflects the mRNA abundance and the fraction of newly synthesized LPL molecules which the post-translational mechanism allows to become/remain active. This fraction was on average twofold greater in OAT compared with SAT.

Tissue leptin and plasma insulin are associated with lipoprotein lipase activity in severely obese patients

The development of metabolic complications of obesity has been associated with the existence of depot-specific differences in the biochemical properties of adipocytes. The aim of this study was to investigate, in severely obese men and women, both gender- and depot-related differences in lipoprotein lipase (LPL) expression and activity, as well as the involvement of endocrine and biometric factors and their dependence on gender and/or fat depot. Morbidly obese, nondiabetic, subjects (9 men and 22 women) aged 41.1+/-1.9 years, with a body mass index (BMI) of 54.7+/-1.7 kg/m(2) who had undergone abdominal surgery were studied. Both expression and activity of LPL and leptin expression were determined in adipose samples from subcutaneous and visceral fat depots. In both men and women, visceral fat showed higher LPL mRNA levels as well as lower ob mRNA levels and tissue leptin content than the subcutaneous one. In both subcutaneous and visceral adipose depots, women exhibited higher protein content, decreased fat cell size and lower LPL activity than men. The gender-related differences found in abdominal fat LPL activity could contribute to the increased risk for developing obesity-associated diseases shown by men, even in morbid obesity, in which the massive fat accumulation could mask these differences. Furthermore, the leptin content of fat depots as well as plasma insulin concentrations appear in our population as the main determinants of adipose tissue LPL activity, adjusted by gender, depot and BMI.

Enhanced glycerol 3-phosphate dehydrogenase activity in adipose tissue of obese humans

The primary purpose of this investigation was to determine whether adipose tissue glycerol 3-phosphate dehydrogenase activity is associated with human obesity. The data presented in this paper indicate that the glycerol 3-phosphate dehydrogenase activity in adipose tissue from morbidly obese subjects is approximately 2-fold higher than from lean individuals. Moreover, positive correlation between adipose tissue glycerol 3-phosphate dehydrogenase activity and body mass index (BMI) (r = 0.5; p < 0.01) was found. In contrast, the adipose tissue fatty acid synthase (FAS) and ATP-citrate lyase (ACL) activities in morbidly obese patients are significantly lower than in lean subjects. Furthermore, negative correlation between adipose tissue FAS activity and BMI (r = -0.3; p < 0.05) as well as between ACL activity and BMI (r = -0.3; p < 0.05) was found. These data indicate that elevated glycerol 3-phosphate dehydrogenase might contribute to the increase of triacylglycerol (TAG) synthesis in obese subjects, however, fatty acids necessary for glycerol 3-phosphate esterification must be derived (because of lower FAS and ACL activities) mainly from TAG in circulating lipoproteins formed in liver (VLDL), and/or from the intake with food (chylomicrons). The conclusion is, that the enhanced activity of glycerol 3-phosphate dehydrogenase, and hence the generation of more glycerol 3-phosphate in adipose tissue offers a novel explanation for increased TAG production in adipose tissue of obese subjects.

Seasonal variation in insulin sensitivity in healthy elderly people

OBJECTIVE

There is a seasonal variation in the incidence of diabetes mellitus and cardiovascular diseases. However, there is very little information about the seasonal variation in insulin sensitivity. We report the seasonal variation in insulin sensitivity in a group of elderly subjects followed for 1 y.

METHODS

Healthy elderly (>/=70 y) subjects living independently were included. Fifty percent of subjects received a daily nutritional supplement that provided 400 kcal, 15 g of protein, and 50% of vitamin daily reference values (DRVs). Those receiving and not receiving supplements were randomly assigned to a resistance exercise training program. Every 6 mo (winter, summer, and winter), body composition was measured by dual-energy x-ray absorptiometry and blood samples were used to measure serum lipids, fasting and postprandial glucose, and insulin levels.

RESULTS

One hundred eight subjects (31 supplemented and trained, 28 supplemented, 16 trained, and 33 without supplementation or training) completed the follow up. Higher homeostasis assessment of insulin sensitivity, postprandial insulin, and fasting triacylglycerol levels were observed during the summer than during the winter. Body fat increased steadily during the study period, and fat-free mass did not change. Serum low-density lipoprotein cholesterol decreased significantly in the supplemented and trained group and increased in the non-intervention group.

CONCLUSIONS

In this group of elderly subjects, insulin resistance and triacylglycerol levels were higher during the summer. Nutritional supplementation and training had a positive effect on serum low-density lipoprotein cholesterol.

Effect of sex and obesity on basal VLDL-triacylglycerol kinetics

BACKGROUND

Plasma fatty acid availability is a major regulator of VLDL-triacylglycerol production. Basal whole-body lipolysis is higher in women than in men and is higher in persons with abdominal obesity than in lean individuals.

OBJECTIVE

Our goal was to determine whether sex and abdominal obesity affect VLDL-triacylglycerol kinetics. We hypothesized that basal VLDL-triacylglycerol production would be greater in women than in men and greater in obese than in lean subjects.

DESIGN

VLDL-triacylglycerol kinetics were measured in 20 lean (10 men, 10 women; body mass index, in kg/m(2): 23 +/- 1) and 20 abdominally obese (10 men, 10 women; body mass index: 35 +/- 1) subjects by using a bolus injection of [(2)H(5)]glycerol and compartmental modeling analysis.

RESULTS

The rate of VLDL-triacylglycerol secretion was greater in the lean women than in the lean men (5.1 +/- 0.7 and 2.6 +/- 0.3 micro mol x L plasma(-1) x min(-1), respectively; P < 0.002). Obesity was associated with increased VLDL-triacylglycerol secretion in the men (P < 0.001) but not in the women, which resulted in greater rates of VLDL-triacylglycerol secretion in the obese men than in the obese women (6.8 +/- 0.5 and 5.0 +/- 0.5 micro mol x L plasma(-1) x min(-1), respectively; P < 0.05). The clearance of VLDL-triacylglycerol from plasma was greater (P < 0.05) in the lean women than in the lean men (42 +/- 7 and 27 +/- 4 mL plasma/min, respectively) or in the obese men and obese women (28 +/- 3 and 20 +/- 4 mL plasma/min, respectively). The plasma VLDL-triacylglycerol concentration was directly related to the rate of VLDL-triacylglycerol secretion in the men (R(2) = 0.79, P < 0.001) and inversely related to VLDL-triacylglycerol clearance in the women (R(2) = 0.84, P<0.001).

CONCLUSION

Sex and obesity have independent effects on basal VLDL-triacylglycerol kinetics.

Metabolic response to a mixed meal in obese and lean women from two South african populations

OBJECTIVE

Lower lipid and insulin levels are found during a glucose-tolerance test in obese black than obese white South African women. Therefore, beta-cell function and lipid metabolism were compared in these populations during a mixed meal.

RESEARCH METHODS AND PROCEDURES

Blood concentrations of glucose, free fatty acids (FFAs), insulin, lipograms, and in vivo FFA oxidation were determined at fasting and for 7 hours after oral administration of a mixed emulsion containing glucose-casein-sucrose-lipid and [1-(13)C] palmitic acid in 8 lean black women (LBW), 10 obese black women (OBW), 9 lean white women (LWW), and 10 obese white women (OWW). Subcutaneous and visceral fat mass was assessed by computerized tomography.

RESULTS

Visceral fat area was higher in OWW (152.7 +/- 17.0 cm(2)) than OBW (80.0 +/- 6.7 cm(2); p < 0.01). In OBW, 30-minute insulin levels were higher (604.3 +/- 117.6 pM) than OWW (311.0 +/- 42.9 pM; p < 0.05). Total triglyceride was higher in OWW (706.7 +/- 96.0 mM x 7 hours) than OBW (465.7 +/- 48.2 mM x 7 hours; p < 0.05) and correlated with visceral fat area (beta = 0.38, p = 0.05). Palmitate oxidation was higher in lean than obese women in both ethnic groups and correlated negatively with fat mass (beta = -0.58, p < 0.005).

DISCUSSION

The higher 30-minute insulin response in OBW may reflect a higher insulinotropic effect of FFAs or glucose. The elevated triglyceride level of OWW may be due to their higher visceral fat mass and possibly reduced clearance by adipose tissue.

Circulating leptin: a marker of health in female students

We studied the relationship between serum leptin concentration and lifestyle factors in female nursing students. Serum leptin was estimated by radioimmunoassay and the correlation between these concentrations with serum lipids, physical fitness and Health-promoting Lifestyle Profile score was investigated. A total of 247 students took part in the study: mean age, 19.0 +/- 2.0 years; mean body mass index (BMI), 21.7 +/- 2.9 kg/m2; and mean serum leptin concentration, 10.8 +/- 11.5 ng/ml. Serum leptin was positively correlated with BMI, systolic and diastolic blood pressure, total cholesterol and serum triglyceride. Serum leptin level concentration inversely correlated with physical fitness score and lifestyle score. When the subjects were grouped according to BMI, the high-BMI group (BMI: > or = 24 kg/m2; n = 40) showed significantly lower fitness and lifestyle scores than the low-BMI group (BMI < or = 20 kg/m2; n = 70). Higher leptin, blood pressure, total cholesterol and triglyceride were seen in high-BMI compared with low-BMI subjects. We suggest that leptin is a useful marker for monitoring good health and may be useful as a motivational aid towards achieving and maintaining a healthy lifestyle.

Hormone sensitive lipase expression and adipose tissue metabolism show gender difference in obese subjects after weight loss

OBJECTIVE

The effect of weight reduction on hormone sensitive lipase (HSL) and lipoprotein lipase (LPL) gene expression and their relationship with adipose tissue metabolism were studied in massively obese men and women.

SUBJECTS

Seventeen obese subjects (eight men, nine women) participated in the study (age 44+/-2 y, weight 145+/-8 kg, fat 40+/-2% of body mass, mean+/-s.e.m.), who were going through a gastric-banding operation for weight reduction.

MEASUREMENTS

HSL and LPL mRNA expressions were analyzed using the reverse transcription competitive polymerase chain reaction. Subcutaneous fat lipolysis was measured in vivo by microdialysis and in vitro in isolated subcutaneous abdominal adipocytes. Measurements were done before and after 1 y of weight reduction.

RESULTS

Significant reductions in weight (for men -20.3+/-2.5%, for women -18.3+/-2.1% (mean+/-s.e.m.) and fat mass (for men -27.6+/-7.9%, for women -21.8+/-3.9%) were observed in both genders. In women HSL mRNA expression decreased by 31% (P=0.008) and LPL expression increased slightly, but nonsignificantly (42%, P=0.110). These changes were not observed in men. In men, inhibition of lipolysis with alpha(2)-adrenergic and adenosine agonist was improved (P=0.001) in isolated adipocytes.

CONCLUSIONS

This study uncovers new differences between genders in adipocyte metabolism along with weight reduction. In women, the observed changes in HSL and LPL gene expression suggest that deposition of lipids into adipose tissue might be favored after weight reduction. In men, the results indicate improved responsiveness to inhibition in adipose tissue metabolism along with weight reduction.

Associations of leptin with body fat distribution and metabolic parameters in non-insulin-dependent diabetic patients: no effect of apolipoprotein E polymorphism

Leptin levels have been shown previously to be associated with anthropometric parameters such as the body mass index (BMI), total body fat, and subcutaneous fat. Since apolipoprotein E (apoE) polymorphism is known to be a genetic marker affecting the relationship between certain anthropometric and metabolic parameters, we evaluated whether the leptin level and/or associations between the leptin level and body composition in non-insulin-dependent diabetic patients could be determined by apoE polymorphism. In 171 type 2 diabetic patients (105 male and 66 female), body composition (BMI, waist to hip ratio [WHR], fat mass, and visceral fat) was measured and fasting blood samples were obtained to determine the apoE genotype, leptin, glucose, and insulin levels, and the lipid profile. The mean leptin level for the whole group was 11.7 +/- 9.3 ng/mL, with a significant difference (P < .001) between men (7.1 +/- 4.9 ng/mL) and women (19.0 +/- 10.1 ng/mL). No difference was found for leptin levels or anthropometric variables between the 3 different apoE genotypes (E3/E3 homozygotes, E2 carriers, and E4 carriers). Only low-density lipoprotein (LDL) cholesterol was significantly different between the 3 apoE subgroups. The correlations of leptin with anthropometric variables, especially visceral fat, tended to be different between the 3 apoE groups, but this was not independent and no effect was found after controlling for the other parameters in the model. A multiple regression model containing gender, subcutaneous fat, fasting glucose, triglycerides, and high-density lipoprotein (HDL) cholesterol explained 81% of the variance in leptin levels. We conclude that apoE polymorphism has no effect on the leptin level or its associations with other anthropometric and metabolic parameters.