Effect of weight loss with reduction of intra-abdominal fat on lipid metabolism in older men

PCSK9 and leptin plasma levels in anorexia nervosa

AIM

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a regulator of low-density-lipoprotein cholesterol (LDL-C), a major risk factor for cardiovascular (CV) disease. Since the hormone leptin has been suggested as having a role in CV risk regulation, possibly by modulating LDL receptor expression through the PCSK9 pathway, nutritional status may represent a potential regulator. Thus, evaluation of PCSK9 levels in human eating disorders appears to be of interest. In this report, we evaluate the lipoprotein profile, PCSK9, and leptin levels in subjects affected by anorexia nervosa (AN) to improve our understanding of the metabolic alterations in this disease.

METHODS AND RESULTS

We designed a case-control observational study, enrolling 20 anorexic adolescent females and 20 adolescent females without AN as the control group, age- and sex-matched. Subjects affected by AN showed lower BMI, total cholesterol, and LDL-C in comparison to the control group, with lipoprotein levels in the normal range. Furthermore, adolescent girls with AN show significantly higher PCSK9 (+24%, p < 0.005) and lower leptin levels (-43%, p < 0.01), compared to the control group.

CONCLUSIONS

The findings of increased levels of PCSK9 and reduced leptin levels among AN subjects warrant further research in order to unravel the role of the liver and adipose tissue in the management of PCSK9/LDL metabolism in adolescents affected by AN.

Cardiovascular-Kidney-Metabolic Health: A Presidential Advisory From the American Heart Association

Cardiovascular-kidney-metabolic health reflects the interplay among metabolic risk factors, chronic kidney disease, and the cardiovascular system and has profound impacts on morbidity and mortality. There are multisystem consequences of poor cardiovascular-kidney-metabolic health, with the most significant clinical impact being the high associated incidence of cardiovascular disease events and cardiovascular mortality. There is a high prevalence of poor cardiovascular-kidney-metabolic health in the population, with a disproportionate burden seen among those with adverse social determinants of health. However, there is also a growing number of therapeutic options that favorably affect metabolic risk factors, kidney function, or both that also have cardioprotective effects. To improve cardiovascular-kidney-metabolic health and related outcomes in the population, there is a critical need for (1) more clarity on the definition of cardiovascular-kidney-metabolic syndrome; (2) an approach to cardiovascular-kidney-metabolic staging that promotes prevention across the life course; (3) prediction algorithms that include the exposures and outcomes most relevant to cardiovascular-kidney-metabolic health; and (4) strategies for the prevention and management of cardiovascular disease in relation to cardiovascular-kidney-metabolic health that reflect harmonization across major subspecialty guidelines and emerging scientific evidence. It is also critical to incorporate considerations of social determinants of health into care models for cardiovascular-kidney-metabolic syndrome and to reduce care fragmentation by facilitating approaches for patient-centered interdisciplinary care. This presidential advisory provides guidance on the definition, staging, prediction paradigms, and holistic approaches to care for patients with cardiovascular-kidney-metabolic syndrome and details a multicomponent vision for effectively and equitably enhancing cardiovascular-kidney-metabolic health in the population.

Association between skeletal muscle mass and serum concentrations of lipoprotein lipase, GPIHBP1, and hepatic triglyceride lipase in young Japanese men

Background

Two important regulators for circulating lipid metabolisms are lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL). In relation to this, glycosylphosphatidylinositol anchored high-density lipoprotein binding protein 1 (GPIHBP1) has been shown to have a vital role in LPL lipolytic processing. However, the relationships between skeletal muscle mass and lipid metabolism, including LPL, GPIHBP1, and HTGL, remain to be elucidated. Demonstration of these relationships may lead to clarification of the metabolic dysfunctions caused by sarcopenia. In this study, these relationships were investigated in young Japanese men who had no age-related factors; participants included wrestling athletes with abundant skeletal muscle.

Methods

A total of 111 young Japanese men who were not taking medications were enrolled; 70 wrestling athletes and 41 control students were included. The participants’ body compositions, serum concentrations of lipoprotein, LPL, GPIHBP1 and HTGL and thyroid function test results were determined under conditions of no extreme dietary restrictions and exercises.

Results

Compared with the control participants, wrestling athletes had significantly higher skeletal muscle index (SMI) (p < 0.001), higher serum concentrations of LPL (p < 0.001) and GPIHBP1 (p < 0.001), and lower fat mass index (p = 0.024). Kruskal–Wallis tests with Bonferroni multiple comparison tests showed that serum LPL and GPIHBP1 concentrations were significantly higher in the participants with higher SMI. Spearman’s correlation analyses showed that SMI was positively correlated with LPL (ρ = 0.341, p < 0.001) and GPIHBP1 (ρ = 0.309, p = 0.001) concentration. The serum concentrations of LPL and GPIHBP1 were also inversely correlated with serum concentrations of triglyceride (LPL, ρ = − 0.198, p = 0.037; GPIHBP1, ρ = − 0.249, p = 0.008). Serum HTGL concentration was positively correlated with serum concentrations of total cholesterol (ρ = 0.308, p = 0.001), low-density lipoprotein-cholesterol (ρ = 0.336, p < 0.001), and free 3,5,3′-triiodothyronine (ρ = 0.260, p = 0.006), but not with SMI.

Conclusions

The results suggest that increased skeletal muscle mass leads to improvements in energy metabolism by promoting triglyceride-rich lipoprotein hydrolysis through the increase in circulating LPL and GPIHBP1.

Slim Body Weight Is Highly Associated With Enhanced Lipoprotein Functionality, Higher HDL-C, and Large HDL Particle Size in Young Women

There has been no information about the correlations between body weight distribution and lipoprotein metabolism in terms of high-density lipoproteins-cholesterol (HDL-C) and cholesteryl ester transfer protein (CETP). In this study, we analyzed the quantity and quality of HDL correlations in young women (21.5 ± 1.2-years-old) with a slim (n = 21, 46.2 ± 3.8 kg) or plump (n = 30, 54.6 ± 4.4 kg) body weight. Body weight was inversely correlated with the percentage of HDL-C in total cholesterol (TC). The plump group showed 40% higher body fat (26 ± 3 %) and 86% more visceral fat mass (VFM, 1.3 ± 0.3 kg) than the slim group, which showed 18 ± 2% body fat and 0.7 ± 0.2 kg of VFM. Additionally, the plump group showed 20% higher TC, 58% higher triglyceride (TG), and 12% lower HDL-C levels in serum. The slim group showed 34% higher apoA-I but 15% lower CETP content in serum compared to the plump group. The slim group showed a 13% increase in particle size and 1.9-fold increase in particle number with enhanced cholesterol efflux activity. Although the plump group was within a normal body mass index (BMI) range, its lipid profile and lipoprotein properties were distinctly different from those of the slim group in terms of CETP mass and activity, HDL functionality, and HDL particle size.

Human hepatic lipase overexpression in mice induces hepatic steatosis and obesity through promoting hepatic lipogenesis and white adipose tissue lipolysis and fatty acid uptake

Human hepatic lipase (hHL) is mainly localized on the hepatocyte cell surface where it hydrolyzes lipids from remnant lipoproteins and high density lipoproteins and promotes their hepatic selective uptake. Furthermore, hepatic lipase (HL) is closely associated with obesity in multiple studies. Therefore, HL may play a key role on lipid homeostasis in liver and white adipose tissue (WAT). In the present study, we aimed to evaluate the effects of hHL expression on hepatic and white adipose triglyceride metabolism in vivo. Experiments were carried out in hHL transgenic and wild-type mice fed a Western-type diet. Triglyceride metabolism studies included β-oxidation and de novo lipogenesis in liver and WAT, hepatic triglyceride secretion, and adipose lipoprotein lipase (LPL)-mediated free fatty acid (FFA) lipolysis and influx. The expression of hHL promoted hepatic triglyceride accumulation and de novo lipogenesis without affecting triglyceride secretion, and this was associated with an upregulation of Srebf1 as well as the main genes controlling the synthesis of fatty acids. Transgenic mice also exhibited more adiposity and an increased LPL-mediated FFA influx into the WAT without affecting glucose tolerance. Our results demonstrate that hHL promoted hepatic steatosis in mice mainly by upregulating de novo lipogenesis. HL also upregulated WAT LPL and promoted triglyceride-rich lipoprotein hydrolysis and adipose FFA uptake. These data support the important role of hHL in regulating hepatic lipid homeostasis and confirm the broad cardiometabolic role of HL.

Efficacy of a liquid low-energy formula diet in achieving preoperative target weight loss before bariatric surgery

A preoperative weight loss of 8 % is a prerequisite to undergo bariatric surgery (BS) in Denmark. The aim of the present study was to evaluate the efficacy of a 7- or an 11-week low-energy diet (LCD) for achieving preoperative target weight before BS. A total of thirty obese patients (BMI 46·0 (sd 4·4) kg/m(2)) followed an LCD (Cambridge Weight Plan(®), 4184 kJ/d (1000 kcal/d)) for 7 or 11 weeks as preparation for BS. Anthropometric measurements including body composition (dual-energy X-ray absorptiometry), blood parameters and blood pressure were assessed at weeks 0, 7 and 11. At week 7, the majority of patients (77 %) had reached their target weight, and this was achieved after 5·4 (sem 0·3) weeks. Mean weight loss was 9·3 (sem 0·5) % (P < 0·01) and consisted of 41·6 % fat-free mass (FFM) and 58·4 % fat mass. The weight loss was accompanied by a decrease in systolic and diastolic blood pressure (7·1 (sem 2·3) and 7·3 (sem 1·8) mmHg, respectively, all P < 0·01) as well as an improved metabolic profile (8·2 (sem 1·8) % decrease in fasting glucose (P < 0·01), 28·6 (sem 6·4) % decrease in fasting insulin (P < 0·01), 23·1 (sem 2·2) % decrease in LDL (P < 0·01), and 9·7 (sem 4·7) % decrease in TAG (P < 0·05)). Weight, FFM and fat mass continued to decrease from week 7 to 11 (all P < 0·01), whereas no additional improvements was observed in the metabolic parameters. Severely obese patients can safely achieve preoperative target weight on an LCD within 7 weeks as part of preparation for BS. However, the considerable reduction in FFM in severely obese subjects needs further investigation.

Gender specific effect of LIPC C-514T polymorphism on obesity and relationship with plasma lipid levels in Chinese children

Hepatic lipase (LIPC) is a key rate-limiting enzyme in lipoprotein catabolism pathways involved in the development of obesity. The C-514T polymorphism in the promoter region is associated with decreased LIPC activity. We performed a case-controlled study (850 obese children and 2119 controls) and evaluated the association between LIPC C-514T polymorphism, obesity and plasma lipid profile in Chinese children and adolescents. Additionally, we conducted a meta-analysis of all results from published studies as well as our own data. A significant association between the polymorphism and obesity is observed in boys (P = 0.042), but not in girls. And we observed a significant relationship of the polymorphism with total cholesterol (TC) and high density lipoprotein cholesterol (HDL-C) independent of obesity in boys. The T allele carriers have higher levels of low density lipoprotein cholesterol (LDL-C) in obese boys, and triglyceride (TG), TC and LDL-C in non-obese girls (all P < 0.05). In the meta-analysis, under dominant model the T allele increased body mass index (BMI) level in boys, while it decreased BMI in girls, and increased the levels of TC both in the overall and subgroups, TG and HDL-C in the overall and boys, and LDL-C in the overall (all P < 0.05). Our results suggest that the T allele might carry an increased risk of obesity in Chinese boys. The meta-analysis suggests that T allele acts as a risk allele for higher BMI levels in male childhood, while it is a protective allele in female childhood. And the polymorphism is associated with the levels of plasma lipids, which may be modulated by obesity and gender.

In vivo structure-function studies of human hepatic lipase: the catalytic function rescues the lean phenotype of HL-deficient (hl-/-) mice

The lean body weight phenotype of hepatic lipase (HL)-deficient mice (hl(-/-)) suggests that HL is required for normal weight gain, but the underlying mechanisms are unknown. HL plays a unique role in lipoprotein metabolism performing bridging as well as catalytic functions, either of which could participate in energy homeostasis. To determine if both the catalytic and bridging functions or the catalytic function alone are required for the effect of HL on body weight, we studied (hl(-/-)) mice that transgenically express physiologic levels of human (h)HL (with catalytic and bridging functions) or a catalytically-inactive (ci)HL variant (with bridging function only) in which the catalytic Serine 145 was mutated to Alanine. As expected, HL activity in postheparin plasma was restored to physiologic levels only in hHL-transgenic mice (hl(-/-)hHL). During high-fat diet feeding, hHL-transgenic mice exhibited increased body weight gain and body adiposity relative to hl(-/-)ciHL mice. A similar, albeit less robust effect was observed in female hHL-transgenic relative to hl(-/-)ciHL mice. To delineate the basis for this effect, we determined cumulative food intake and measured energy expenditure using calorimetry. Interestingly, in both genders, food intake was 5-10% higher in hl(-/-)hHL mice relative to hl(-/-)ciHL controls. Similarly, energy expenditure was ~10% lower in HL-transgenic mice after adjusting for differences in total body weight. Our results demonstrate that (1) the catalytic function of HL is required to rescue the lean body weight phenotype of hl(-/-) mice; (2) this effect involves complementary changes in both sides of the energy balance equation; and (3) the bridging function alone is insufficient to rescue the lean phenotype of hl(-/-)ciHL mice.

Lowering triglycerides to modify cardiovascular risk: will icosapent deliver?

Despite the clinical benefits of lowering levels of low-density lipoprotein cholesterol, many patients continue to experience cardiovascular events. This residual risk suggests that additional risk factors require aggressive modification to result in more effective prevention of cardiovascular disease. Hypertriglyceridemia has presented a considerable challenge with regard to understanding its role in the promotion of cardiovascular risk. Increasing evidence has established a clear causal role for elevated triglyceride levels in vascular risk. As a result, there is increasing interest in the development of specific therapeutic strategies that directly target hypertriglyceridemia. This has seen a resurgence in the use of omega-3 fatty acids for the therapeutic lowering of triglyceride levels. The role of these agents and other emerging strategies to reduce triglyceride levels in order to decrease vascular risk are reviewed.

Moderate intensity physical activity prevents increased blood glucose concentrations, fat pad deposition and cardiac action potential prolongation following diet-induced obesity in a juvenile-adolescent rat model

Background

Both obesity and a lack of physical activity have been associated with an elevated risk of cardiovascular disease (CVD). The incidence of obesity is increasing, especially in juvenile-adolescents. While there is limited research examining the chronic effects of obesity in adolescent humans and animal models of this condition, little is also known concerning how moderate physical activity might prevent or attenuate secondary cardiovascular complications induced by obesity during adolescence. We investigated the effects of diet-induced obesity (consisting of a high-fat, high-carbohydrate diet (HFHC)) on biometric indices, vascular and airway function, cardiovascular function, systemic oxidative stress and markers of inflammation in a juvenile-adolescent rodent model. Four groups were used: control (CON), physical activity (PA) treated, HFHC and HFHC + PA (n = 16 per group). HFHC feeding started at 4 weeks of age for a period of 12 weeks. Physical activity treatment was initiated (PA and HFHC + PA groups) when the animals were 8 weeks of age, for 8 weeks.

Results

Physical activity in juvenile-adolescent healthy rats showed no change in comparison to the CON group in all experimental parameters except for increases in lipid peroxidation, decreases in inflammatory cytokines, improvements in vascular reactivity and decreased atrial responses to positive chronotropic agents. The HFHC animals were mildly hyperglycemic, hypertensive, displayed renal hypertrophy and showed increased retroperitoneal fat pad deposition compared to the CON group. HFHC + PA rats were also hypertensive, however showed improvements in cardiac electrophysiology, body weight, fat pad deposition and inflammatory signaling, in comparison to the HFHC fed rats and CON animals.

Conclusion

In conclusion, in a juvenile-adolescent animal model of diet-induced obesity engagement in physical activity is beneficial in reducing the inflammatory effects of obesity.

Cholesteryl ester transfer protein protects against insulin resistance in obese female mice

Cholesteryl ester transfer protein (CETP) shuttles lipids between lipoproteins, culminating in cholesteryl ester delivery to liver and increased secretion of cholesterol as bile. Since gut bile acids promote insulin sensitivity, we aimed to define if CETP improves insulin sensitivity with high-fat feeding. CETP and nontransgenic mice of both sexes became obese. Female but not male CETP mice had increased ileal bile acid levels versus nontransgenic littermates. CETP expression protected female mice from insulin resistance but had a minimal effect in males. In liver, female CETP mice showed activation of bile acid-sensitive pathways including Erk1/2 phosphorylation and Fxr and Shp gene expression. In muscle, CETP females showed increased glycolysis, increased mRNA for Dio2, and increased Akt phosphorylation, known effects of bile acid signaling. These results suggest that CETP can ameliorate insulin resistance associated with obesity in female mice, an effect that correlates with increased gut bile acids and known bile-signaling pathways.

The effect of hepatic lipase on coronary artery disease in humans is influenced by the underlying lipoprotein phenotype

Increased or decreased hepatic lipase (HL) activity has been associated with coronary artery disease (CAD). This is consistent with the findings that gene variants that influence HL activity were associated with increased CAD risk in some population studies but not in others. In this review, we will explain the conditions that influence the effects of HL on CAD. Increased HL is associated with smaller and denser LDL (sdLDL) and HDL (HDL(3)) particles, while decreased HL is associated with larger and more buoyant LDL and HDL particles. The effect of HL activity on CAD risk is dependent on the underlying lipoprotein phenotype or disorder. Central obesity with hypertriglyceridemia (HTG) is associated with high HL activity that leads to the formation of sdLDL that is pro-atherogenic. In the absence of HTG, where large buoyant cholesteryl ester-enriched LDL is prominent, elevation of HL does not raise the risk for CAD. In HTG patients, drug therapy that decreases HL activity selectively decreases sdLDL particles, an anti-atherogenic effect. Drug therapy that raises HDL(2) cholesterol has not decreased the risk for CAD. In trials where inhibition of cholesterol ester transfer protein (CETP) or HL occurs, the increase in HDL(2) most likely is due to inhibition of catabolism of HDL(2) and impairment of reverse cholesterol transport (RCT). In patients with isolated hypercholesterolemia, but with normal triglyceride levels and big-buoyant LDL particles, an increase in HL activity is beneficial; possibly because it increases RCT. Drugs that lower HL activity might decrease the risk for CAD only in hypertriglyceridemic patients with sdLDL by selectively clearing sdLDL particles from plasma, which would override the potentially pro-atherogenic effect on RCT. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).

Exchanging carbohydrate or protein for fat improves lipid-related cardiovascular risk profile in overweight men and women when consumed ad libitum

BACKGROUND

The impact of low-fat diets on the plasma lipoprotein profile is incompletely understood.

METHODS

We conducted two 16-week dietary studies to compare the effects of a moderate-fat (mod-FAT) baseline diet with isocaloric and ad libitum low-fat diets rich in either carbohydrates (high-CHO, n = 16) or protein (high-PRO, n = 19) on plasma lipids, post-heparin lipase activities, cholesteryl ester transfer protein, and phospholipid transfer protein.

RESULTS

Switching from the mod-FAT to the isocaloric high-CHO diet lowered plasma high-density lipoprotein cholesterol concentrations (P < 0.001) and tended to increase triglyceride levels (P = 0.087). Cholesterol content in the larger, buoyant low-density lipoprotein (LDL) fractions decreased, whereas those of the very-low-density lipoprotein, intermediate-density lipoprotein, and smaller, denser LDL fractions tended to increase. These changes were largely reversed when subjects lost weight by consuming this high-CHO diet ad libitum. Switching from the mod-FAT diet to the isocaloric high-PRO diet did not increase cholesterol content in the small-dense LDL fraction and led to decreases in both LDL and high-density lipoprotein cholesterol in plasma (P < 0.001 for both).Consumption of the high-protein ad libitum diet accompanied by weight loss did not change plasma lipids further, except for a shift of cholesterol from dense low-density lipoprotein fractions to more buoyant low-density lipoprotein fractions. Cholesteryl ester transfer protein concentrations decreased with high-cholesterol feeding, whereas cholesteryl ester transfer protein concentrations and hepatic lipase and phospholipid transfer protein activities all decreased during high-protein feeding.

CONCLUSIONS

Both high-CHO and high-PRO diets improve plasma lipid-related risk of cardiovascular disease when consumed ad libitum.

Mice lacking hepatic lipase are lean and protected against diet-induced obesity and hepatic steatosis

Hepatic lipase (HL)-mediated lipoprotein hydrolysis provides free fatty acids for energy, storage, and nutrient signaling and may play a role in energy homeostasis. Because HL-activity increases with increased visceral fat, we hypothesized that increased HL-activity favors weight gain and obesity and consequently, that HL deficiency would reduce body fat stores and protect against diet-induced obesity. To test this hypothesis, we compared wild-type mice (with endogenous HL) and mice genetically deficient in HL with respect to daily body weight and food intake, body composition, and adipocyte size on both chow and high-fat (HF) diets. Key determinants of energy expenditure, including rate of oxygen consumption, heat production, and locomotor activity, were measured by indirect calorimetry. HL-deficient mice exhibited reduced weight gain on both diets (by 32%, chow; by 50%, HF; both P < 0.0001, n = 6-7 per genotype), effects that were associated with reduced average daily food intake (by 22-30% on both diets, P < 0.0001) and a modest increase in the rate of oxygen consumption (by 25%, P < 0.003) during the light cycle. Moreover, in mice fed the HF diet, HL deficiency reduced both body fat (by 30%, P < 0.0001) and adipocyte size (by 53%, P < 0.01) and fully prevented the development of hepatic steatosis. Also, HL deficiency reduced adipose tissue macrophage content, consistent with reduced inflammation and a lean phenotype. Our results demonstrate that in mice, HL deficiency protects against diet-induced obesity and its hepatic sequelae. Inhibition of HL-activity may therefore have value in the prevention and/or treatment of obesity.

Reversal of small, dense LDL subclass phenotype by normalization of adiposity

Excess adiposity and high-carbohydrate diets have been associated with an atherogenic lipoprotein phenotype (ALP) characterized by increased concentrations of small, dense low-density lipoprotein (LDL) particles (pattern B). We tested whether weight loss and normalization of adiposity could reverse ALP in overweight men with pattern B. After consuming a moderate-carbohydrate, high-fat diet for 3 weeks, pattern B and nonpattern B (pattern A) men were randomized to a weight loss (n = 60 and n = 36, respectively) or control weight-stable arm (n = 20 and n = 17, respectively). Men in the weight loss arm consumed approximately 1,000 fewer calories per day over 9 weeks to induce an average approximately 9 kg weight loss. In the control group, weight stability was maintained for 4 weeks after randomization. Weight loss led to the conversion of pattern B to pattern A in 58% of baseline pattern B men. Among men who achieved BMIs of <25 kg/m(2) (62% of pattern B men vs. 83% of pattern A men), 81% of pattern B men converted to pattern A. Weight loss was associated with a significantly greater decrease in small, dense LDL subclass 3b in pattern B relative to pattern A men. The lipoprotein profiles of pattern A men who converted from pattern B were comparable to those of men with pattern A at baseline. Conversion of LDL subclass pattern B to pattern A and reversal of ALP can be achieved in a high proportion of overweight men by normalization of adiposity.

Low plasma adiponectin levels are associated with increased hepatic lipase activity in vivo

OBJECTIVE

Hepatic lipase plays a key role in hydrolyzing triglycerides and phospholipids present in circulating plasma lipoproteins. Plasma hepatic lipase activity is known to be regulated by several hormonal and metabolic factors, but hepatic lipase responsiveness to insulin is still controversial. Hypoadiponectinemia is known to be associated with insulin resistance, diabetes, and obesity. These conditions are often characterized by high plasma triglyceride and low HDL cholesterol levels, and they have been shown to be associated with high plasma hepatic lipase activity. We therefore raised the question whether adiponectin may be associated with plasma hepatic lipase activity in vivo.

RESEARCH DESIGN AND METHODS

We measured plasma adiponectin and postheparin hepatic lipase activity in 206 nondiabetic men and in a second group of 110 patients with type 2 diabetes. The correlation of these parameters with markers of insulin resistance and systemic inflammation was investigated.

RESULTS

In nondiabetic patients, adiponectin levels were significantly inversely correlated with plasma hepatic lipase activity (r = -0.4, P < 0.01). These results were confirmed in the group of patients with type 2 diabetes (r = -0.32, P = 0.004). Multivariate analysis revealed that adiponectin was the strongest factor influencing hepatic lipase activity. The association was independent of age, sex, BMI, plasma triglycerides, insulin, HDL cholesterol, and high-sensitivity C-reactive protein and accounted for approximately 10 and 12% of the variation in hepatic lipase activity in the two different patient cohorts, respectively.

CONCLUSIONS

These results demonstrate for the first time a significant inverse association between adiponectin and postheparin plasma hepatic lipase activity that is independent of other factors such as markers of insulin resistance or inflammation. Therefore, adiponectin, rather than insulin, may represent an important factor contributing to the regulation of hepatic lipase activity in both nondiabetic individuals and patients with type 2 diabetes. The effect of adiponectin on hepatic lipase activity may also help to explain the HDL cholesterol-elevating action of adiponectin.

Diet and low-density lipoprotein particle size

Small, dense low-density lipoprotein (LDL) particles are being increasingly recognized as an important risk factor for cardiovascular disease. This paper provides an overview of how different diets and macronutrients modulate the LDL size phenotype. Data reviewed indicated that several components of the LDL size phenotype should be measured concurrently in order to fully appreciate the impact of diet on this complex trait. Data also suggested that numerous dietary elements have a significant impact on several characteristics of the LDL size phenotype, thus providing further evidence to the concept that specific dietary modifications can beneficially alter cardiovascular disease risk beyond their known and demonstrated effects on plasma LDL cholesterol concentrations.

Hepatic lipase mRNA, protein, and plasma enzyme activity is increased in the insulin-resistant, fructose-fed Syrian golden hamster and is partially normalized by the insulin sensitizer rosiglitazone

Postheparin plasma hepatic lipase (HL) activity has been shown to correlate with features of the metabolic syndrome and type 2 diabetes in humans. We examined HL postheparin plasma enzyme activity, hepatocyte mRNA, and protein mass in the insulin-resistant, fructose-fed Syrian golden hamster, and the response of the insulin-sensitizing peroxisome proliferator-activated receptor-gamma agonist rosiglitazone. Male Syrian golden hamsters were treated for 5 weeks with 1) normal diet (DIET group), 2) 60% fructose diet (FRUC group), or 3) 60% fructose and rosiglitazone (20 mmol . kg(-1) . day(-1)) (FRUC+RSG group). Hepatocyte HL mRNA, protein mass, and postheparin plasma HL activity were increased in FRUC compared with DIET hamsters. FRUC+RSG hamsters had partial normalization of HL mRNA, mass, and activity. There was a shift in the size of LDL particles from large to small in FRUC animals and a shift back to large LDL size in FRUC+RSG. This is the first demonstration that HL hepatocyte mRNA, mass, and plasma enzymatic activity increase concomitantly with induction of an insulin-resistant state and can be partially normalized by treatment with an insulin sensitizer. The increase in HL in insulin-resistant states may play an important role in the typical dyslipidemia of these conditions, and reduction of HL could explain some of the beneficial effects of insulin sensitizers on the plasma lipid profile.

Relationship of adiponectin to body fat distribution, insulin sensitivity and plasma lipoproteins: evidence for independent roles of age and sex

AIMS/HYPOTHESIS

Increased intra-abdominal fat is associated with insulin resistance and an atherogenic lipoprotein profile. Circulating concentrations of adiponectin, an adipocyte-derived protein, are decreased with insulin resistance. We investigated the relationships between adiponectin and leptin, body fat distribution, insulin sensitivity and lipoproteins.

METHODS

We measured plasma adiponectin, leptin and lipid concentrations, intra-abdominal and subcutaneous fat areas by CT scan, and insulin sensitivity index (S(I)) in 182 subjects (76 M/106F).

RESULTS

Adiponectin concentrations were higher in women than in men (7.4+/-2.9 vs 5.4+/-2.3 micro g/ml, p<0.0001) as were leptin concentrations (19.1+/-13.7 vs 6.9+/-5.1 ng/ml, p<0.0001). Women were more insulin sensitive (S(I): 6.8+/-3.9 vs 5.9+/-4.4 x 10(-5) min(-1)/(pmol/l), p<0.01) and had more subcutaneous (240+/-133 vs 187+/-90 cm(2), p<0.01), but less intra-abdominal fat (82+/-57 vs 124+/-68 cm(2), p<0.0001). By simple regression, adiponectin was positively correlated with age ( r=0.227, p<0.01) and S(I) ( r=0.375, p<0.0001), and negatively correlated with BMI ( r=-0.333, p<0.0001), subcutaneous ( r=-0.168, p<0.05) and intra-abdominal fat ( r=-0.35, p<0.0001). Adiponectin was negatively correlated with triglycerides ( r=-0.281, p<0.001) and positively correlated with HDL cholesterol ( r=0.605, p<0.0001) and Rf, a measure of LDL particle buoyancy ( r=0.474, p<0.0001). By multiple regression analysis, adiponectin was related to age ( p<0.0001), sex ( p<0.005) and intra-abdominal fat ( p<0.01). S(I) was related to intra-abdominal fat ( p<0.0001) and adiponectin ( p<0.0005). Both intra-abdominal fat and adiponectin contributed independently to triglycerides, HDL cholesterol and Rf.

CONCLUSION/INTERPRETATION

These data suggest that adiponectin concentrations are determined by intra-abdominal fat mass, with additional independent effects of age and sex. Adiponectin could link intra-abdominal fat with insulin resistance and an atherogenic lipoprotein profile.

Exercise training, without weight loss, increases insulin sensitivity and postheparin plasma lipase activity in previously sedentary adults

OBJECTIVE

To determine the effects of exercise, without weight loss, on insulin sensitivity (S(I)), postheparin plasma lipase activity (PHPL), intravenous fat clearance rate (K(2)), and fasting lipids in sedentary adults.

RESEARCH DESIGN AND METHODS

At baseline and after 6 months of walk training (intensity 45-55 or 65-75% heart rate reserve, frequency 3-4 or 5-7 days/week, duration 30 min/session), anthropometric indexes, S(I), PHPL, K(2), and fasting lipids were measured in 18 sedentary adults (12 women, 6 men; 51.9 +/- 5.8 years of age, BMI 28.9 +/- 4.6 kg/m(2)).

RESULTS

Exercise increased S(I) (2.54 +/- 2.74 vs. 4.41 +/- 3.30 microU ml(-1) x min(-1), P < 0.005) and both lipoprotein lipase (LPL) (1890 +/- 1380 vs. 4926 +/- 1858 nEq free fatty acid [FFA]. ml(-1). h(-1)) and hepatic lipase (HL) activities (3326 +/- 1605 vs. 4636 +/- 1636 nEq FFA. ml(-1) x h(-1)) (both P < 0.001), without altering BMI, waist circumference, K(2), or fasting lipids. Correlations between changes in LPL and the total:HDL cholesterol ratio (r = -0.54) and changes in the LPL:HL ratio and waist circumference (r = -0.50) were significant (P < 0.05).

CONCLUSIONS

Exercise, without weight loss, increases S(I) and PHPL activity in previously sedentary adults, without changing K(2) or fasting lipid levels. Furthermore, increased LPL is associated with a decreased total:HDL ratio, and an increased LPL:HL ratio is associated with a decreased waist circumference. Therefore, even modest amounts of exercise in the absence of weight loss positively affect markers of glucose and fat metabolism in previously sedentary, middle-aged adults.

Effects of identical weight loss on body composition and features of insulin resistance in obese women with high and low liver fat content

Our objective was to determine how 8% weight loss influences subcutaneous, intra-abdominal, and liver fat (LFAT), as well as features of insulin resistance, in obese women with high versus low LFAT. A total of 23 women with previous gestational diabetes were divided into groups of high (9.4 +/- 1.4%) and low (3.3 +/- 0.4%) LFAT based on their median LFAT (5%) measured with proton spectroscopy. Both groups were similar with respect to age, BMI, and intra-abdominal and subcutaneous fat. Before weight loss, women with high LFAT had higher fasting serum insulin and triglyceride concentrations than women with low LFAT. At baseline, LFAT correlated with the percent of fat (r = 0.44, P < 0.05) and saturated fat (r = 0.45, P < 0.05) of total caloric intake but not intra-abdominal or subcutaneous fat or fasting serum free fatty acids. Weight loss was similar between the groups (high LFAT -7.4 +/- 0.2 vs. low LFAT -7.7 +/- 0.3 kg). LFAT decreased from 9.4 +/- 1.4 to 4.8 +/- 0.7% (P < 0.001) in women with high LFAT and from 3.3 +/- 0.4 to 2.0 +/- 0.2% (P < 0.001) in women with low LFAT. The absolute decrease in LFAT was significantly higher in women with high than low LFAT (-4.6 +/- 1.0 vs. -1.3 +/- 0.3%, P < 0.005). The decrease in LFAT was closely correlated with baseline LFAT (r = -0.85, P < 0.001) but not with changes in the volumes of intra-abdominal or subcutaneous fat depots, which decreased similarly in both groups. LFAT appears to be related to the amount of fat in the diet rather than the size of endogenous fat depots in obese women. Women with initially high LFAT lost more LFAT by similar weight loss than those with low LFAT, although both groups lost similar amounts of subcutaneous and intra-abdominal fat. These data suggest that LFAT is regulated by factors other than intra-abdominal and subcutaneous fat. Therefore, LFAT does not appear to simply reflect the size of endogenous fat stores.

The relative contributions of insulin resistance and beta-cell dysfunction to the pathophysiology of Type 2 diabetes

The relative contributions of insulin resistance and beta-cell dysfunction to the pathophysiology of Type 2 diabetes have been debated extensively. The concept that a feedback loop governs the interaction of the insulin-sensitive tissues and the beta cell as well as the elucidation of the hyperbolic relationship between insulin sensitivity and insulin secretion explains why insulin-resistant subjects exhibit markedly increased insulin responses while those who are insulin-sensitive have low responses. Consideration of this hyperbolic relationship has helped identify the critical role of beta-cell dysfunction in the development of Type 2 diabetes and the demonstration of reduced beta-cell function in high risk subjects. Furthermore, assessments in a number of ethnic groups emphasise that beta-cell function is a major determinant of oral glucose tolerance in subjects with normal and reduced glucose tolerance and that in all populations the progression from normal to impaired glucose tolerance and subsequently to Type 2 diabetes is associated with declining insulin sensitivity and beta-cell function. The genetic and molecular basis for these reductions in insulin sensitivity and beta-cell function are not fully understood but it does seem that body-fat distribution and especially intra-abdominal fat are major determinants of insulin resistance while reductions in beta-cell mass contribute to beta-cell dysfunction. Based on our greater understanding of the relative roles of insulin resistance and beta-cell dysfunction in Type 2 diabetes, we can anticipate advances in the identification of genes contributing to the development of the disease as well as approaches to the treatment and prevention of Type 2 diabetes.

The atherogenic lipoprotein profile associated with obesity and insulin resistance is largely attributable to intra-abdominal fat

Obesity and insulin resistance are both associated with an atherogenic lipoprotein profile. We examined the effect of insulin sensitivity and central adiposity on lipoproteins in 196 individuals (75 men and 121 women) with an average age of 52.7 years. Subjects were subdivided into three groups based on BMI and their insulin sensitivity index (S(I)): lean insulin sensitive (n = 65), lean insulin resistant (n = 73), and obese insulin resistant (n = 58). This categorization revealed that both obesity and insulin resistance determined the lipoprotein profile. In addition, the insulin-resistant groups had increased central adiposity. Increasing intra-abdominal fat (IAF) area, quantified by computed tomography scan and decreasing S(I), were important determinants of an atherogenic profile, marked by increased triglycerides, LDL cholesterol, and apolipoprotein B and decreased HDL cholesterol and LDL buoyancy (Rf). Density gradient ultracentrifugation (DGUC) revealed that in subjects who had more IAF and were more insulin resistant, the cholesterol content was increased in VLDL, intermediate-density lipoprotein (IDL), and dense LDL fractions whereas it was reduced in HDL fractions. Multiple linear regression analysis of the relation between the cholesterol content of each DGUC fraction as the dependent variable and IAF and S(I) as independent variables revealed that the cholesterol concentration in the fractions corresponding to VLDL, IDL, dense LDL, and HDL was associated with IAF, and that S(I) additionally contributed independently to VLDL, but not to IDL, LDL, or HDL. Thus an atherogenic lipoprotein profile appears to be the result primarily of an increase in IAF, perhaps via insulin resistance.