Serum concentrations and expressions of serum amyloid A and leptin in adipose tissue are interrelated: the Genobin Study

OBJECTIVE

Serum amyloid A (SAA) is a novel link between increased adipose tissue mass and low-grade inflammation in obesity. Little is known about the factors regulating its serum concentration and mRNA levels. We investigated the association between SAA and leptin in obese and normal weight subjects and analyzed the effect of weight reduction on serum SAA concentration and gene expression in adipose tissue of the obese subjects.

METHODS

Seventy-five obese subjects (60+/-7 years, body mass index (BMI) 32.9+/-2.8 kg/m(2), mean+/-s.d.) with impaired fasting plasma glucose or impaired glucose tolerance and other features of metabolic syndrome, and 11 normal weight control subjects (48+/-9 years, BMI 23.7+/-1.9 kg/m(2)) were studied at the baseline. Twenty-eight obese subjects underwent a 12-week intensive weight reduction program followed by 5 months of weight maintenance. Blood samples and abdominal s.c. adipose tissue biopsies were taken at the baseline and after the follow-up. Gene expression was studied using real-time quantitative PCR.

RESULTS

The gene expressions in women and serum concentrations of leptin and SAA were interrelated independently of body fat mass in the obese subjects (r=0.54, P=0.001; r=0.24, P=0.039 respectively). In multiple linear regression analyses, leptin mRNA explained 38% of the variance in SAA mRNA (P=0.002) in the obese women. Weight loss of at least 5% increased SAA mRNA expression by 48 and 36% in men and women, but serum SAA concentrations did not change.

CONCLUSIONS

The association between SAA and leptin suggests an interaction between these two adipokines, which may have implications in inflammatory processes related to obesity and the metabolic syndrome.

Responses of surrogate markers of cholesterol absorption and synthesis to changes in cholesterol metabolism during various amounts of fat and cholesterol feeding among healthy men

Serum ratios to cholesterol of lathosterol, and of cholestanol, campesterol and sitosterol measure respective relative cholesterol synthesis and absorption, but their clinical applicability is not known in evaluation of cholesterol metabolism under different dietary conditions. We compared relative synthesis and absorption of cholesterol to the respective absolute ones in healthy male volunteers (n29) on four subsequent diets: baseline home (HD), low-cholesterol low-fat (LCLF), high-cholesterol low-fat (HCLF) and low-cholesterol high-fat (LCHF). Serum lipids, lipoproteins, sterols, fractional cholesterol absorption and sterol synthesis were examined. HCLF and LCHF decreased fractional cholesterol absorption by approximately 23–27 % from baseline HD (P < 0·05) and increased the levels of total and LDL-cholesterol in serum from LCLF by approximately 9–14 % (P < 0·05). On HCLF, bile acid synthesis was high (P < 0·05 for each), and absolute cholesterol synthesis tended to be higher than on HD and LCHF (NS). Relative synthesis was positively associated with absolute cholesterol synthesis, but inversely with relative absorption during each diet (P < 0·05). The relative absorption markers were interrelated in each diet, and were also associated with fractional absorption of cholesterol in each diet but HD. In conclusion, relative markers of cholesterol absorption and synthesis reflect changes in cholesterol metabolism despite the amount of dietary fat and cholesterol consumed, but their validity with this respect is strengthened by controlled diets in metabolic studies. Additions of cholesterol and fat to a diet low in fat and cholesterol cause practically equal changes in the serum lipid profiles, whereas synthesis of cholesterol (NS) and bile acids (P < 0·05) were higher with the high-cholesterol feeding.

Effect of weight loss on cytokine messenger RNA expression in peripheral blood mononuclear cells of obese subjects with the metabolic syndrome

Inflammation is associated with obesity, the metabolic syndrome, and diabetes. No data are available on the effect of weight reduction on the gene expression of cytokines in immune cells in obesity and the metabolic syndrome. We assessed how long-term weight loss affects expression of cytokines in peripheral blood mononuclear cells (PBMCs) in individuals with impaired glucose metabolism and the metabolic syndrome. Data from 34 subjects randomized to either a weight reduction or a control group for a 33-week period were analyzed. The messenger RNA (mRNA) expression of interleukins (ILs) in PBMCs was measured using real-time polymerase chain reaction. Measures of insulin and glucose metabolism (intravenous and oral glucose tolerance tests), body composition, and circulating adipokines and inflammatory markers were also assessed. Weight reduction resulted in a decrease in the mRNA expression of IL-1beta (IL1B), IL-1 receptor antagonist, and tumor necrosis factor alpha (P < .001) and an increase in expression of IL-6 (IL6) and IL-8 (P < .01). The increase in IL6 expression was associated with a decrease in fasting glycemia (r = -0.53, P < .01). Interestingly, the decrease in IL1B expression was correlated with an increase in insulin sensitivity index (r = -0.68, P < .01). In general, a decrease in circulating levels of adipokines and inflammatory markers was also observed after weight loss. Weight loss altered gene expression of cytokines related to inflammation and the immune response in PBMCs. Changes in IL6 mRNA expression were associated with changes in fasting glycemia. The decrease in IL-1 receptor antagonist expression after weight loss and the strong correlation between the decrease in IL1B expression and the increase in insulin sensitivity suggest a contribution of these genes to insulin-resistant states found in obesity and the metabolic syndrome.

Effects of plant stanol esters on serum cholesterol concentrations, relative markers of cholesterol metabolism and endothelial function in type 1 diabetes

We investigated the effect of plant stanol esters (STAEST) on serum total and LDL cholesterol concentrations and endothelial function in subjects with type 1 diabetes (T1D). In addition, the changes in the relative serum markers of cholesterol metabolism were recorded. In a parallel, randomized, double-blind study the intervention group (n = 11) consumed STAEST spread (2g/day stanols) and the control group (n=8) the same spread containing no added stanols for 12 weeks. At baseline, brachial artery diameter was negatively correlated with serum HDL cholesterol concentration (r = -0.476, P < 0.05), but not with total or LDL cholesterol concentrations or serum non-cholesterol sterol ratios to cholesterol. Flow-mediated dilatation was positively associated with serum absorption marker ratios to cholesterol, significantly so with the sitosterol ratio (r = 0.467, P < 0.05). During the intervention, serum total and LDL cholesterol concentrations were reduced by 4.9 and 6.9% from baseline in the STAEST group, and by 10.8 and 16.1% from controls, respectively (P < 0.05 for all). No significant changes in HDL cholesterol and serum triglyceride concentrations were found. The STAEST consumption reduced serum campesterol and sitosterol ratios by 17-21% (P<0.05) from baseline, but the relative serum synthesis markers were not changed. Brachial artery diameter and flow-mediated dilatation did not change during the investigation. In conclusion, STAEST significantly reduced serum total and LDL cholesterol concentrations and serum plant sterol ratios without affecting HDL and triglyceride concentrations in subjects with T1D. STAEST had no effect on endothelial function.

SREBP-1c gene polymorphism is associated with increased inhibition of cholesterol-absorption in response to ezetimibe treatment

OBJECTIVE

Sterol regulatory binding proteins 1 and 2 (SREBPs) are transcription factors regulating lipid metabolism. A recent study has associated the CC genotype of the SREBP-1c polymorphism G952G with increased cholesterol synthesis. Further evidence suggests that SREBPs play a role in cholesterol absorption and that SREBP polymorphisms modulate the response to statin therapy. The present study examines whether the G952G polymorphism alters cholesterol synthesis and/or absorption and whether it modulates the response to widely used lipid-lowering drugs such as inhibitors of cholesterol synthesis (simvastatin) or absorption (ezetimibe).

METHODS

Seventy-two healthy male subjects with LDL cholesterol <190 mg/dL participated in the study. Twenty four subjects were treated with ezetimibe (10 mg), simvastatin (40 mg) or their combination, respectively, for two weeks. Blood was drawn before and after the 2-week treatment period.

RESULTS

Eleven CC homozygous carriers of the gene were found (15%). There were no differences in cholesterol synthesis or absorption between the CC homozygotes and the G allele-carriers, as measured by the ratios to cholesterol of serum lathosterol, desmosterol and cholestenol (synthesis markers) and cholestanol, sitosterol and campesterol (absorption markers). Ezetimibe had a significantly more potent effect in blocking cholesterol absorption in the CC homozygotes compared to the G-carriers ( P=0.002).

CONCLUSIONS

The G/C (G952G) polymorphism of the SREBP-1 gene is not associated with cholesterol synthesis or absorption in a German male population. The CC homozygotes have a significantly increased response to the effects of ezetimibe on cholesterol absorption compared to the G allele-carriers, suggesting that SREBP-1 may be implicated in ezetimibe's mechanism of action.

Effects of ezetimibe and/or simvastatin on LDL receptor protein expression and on LDL receptor and HMG-CoA reductase gene expression: a randomized trial in healthy men

OBJECTIVE

The combination of simvastatin, an HMG-CoA reductase inhibitor, and ezetimibe, an inhibitor of Niemann-Pick C1-like 1 protein, decreases cholesterol synthesis and absorption and reduces circulating LDL-cholesterol concentrations. The molecular mechanisms underlying the pronounced lipid-lowering effects of this combination have not been fully elucidated in humans.

METHODS AND RESULTS

One center, prospective, randomized, parallel three-group study in 72 healthy men (mean age 32+/-9 years, mean body mass index 25.7+/-3.2 kg/m(2)). Each group of twenty-four subjects received a 14-day treatment with either ezetimibe (10mg/day), simvastatin (40 mg/day) or their combination. Lipid levels, the ratio of non-cholesterol sterols to cholesterol concentrations (used as markers of cholesterol synthesis and absorption), cell surface LDL receptor (LDLR) protein as well as LDLR and HMG-CoA reductase gene expression in mononuclear blood cells were measured at baseline and at the end of the study. LDL-C decreased in all groups. Simvastatin decreased, ezetimibe increased and their combination had no effect on HMG-CoA reductase activity. Simvastatin and the combination of ezetimibe and simvastatin increased the HMG-CoA reductase and LDLR gene expression while ezetimibe had no effect. The cell surface LDLR protein expression remained unchanged in all groups. The combination of ezetimibe and simvastatin increased the expression of the serine protease proprotein convertase subtilisin/kexin 9 (PCSK9), an enzyme shown to down-regulate LDLR protein levels.

CONCLUSIONS

The co-administration of ezetimibe and simvastatin abrogates the ezetimibe-induced increase in cholesterol synthesis and up-regulates the LDLR gene but not protein expression, an effect possibly mediated through a parallel upregulation of PCSK9 expression.

Cholesterol metabolism and non-cholesterol sterol distribution in lipoproteins of type 1 diabetes: The effect of improved glycemic control

In type 1 diabetes, the ratios to cholesterol of serum absorption markers, e.g., cholestanol, are elevated and those of synthesis markers, e.g., lathosterol, are reduced suggesting perturbed cholesterol metabolism. We studied 17 subjects with type 1 diabetes in poor glycemic control at baseline to assess whether improvement of glycemic control affects lathosterol and cholestanol ratios to cholesterol and their distribution in lipoproteins. Cholesterol and the non-cholesterol sterols were assayed directly from serum, and free and ester fractions after thin-layer chromatographic separation of lipoprotein sterols with gas-liquid chromatography. After the 2-6 months follow-up, the mean value of HbA1(c) decreased from 10.8% to 8.6% (p=0.001). Even though the concentrations of serum and lipoprotein cholesterol remained unchanged, the serum lathosterol to cholesterol ratio increased by 28% (p<0.05) and the lathosterol/cholestanol proportion by 23% (p<0.05). The ratios of total and esterified lathosterol to cholesterol in serum, chylomicrons and LDL, and free lathosterol to cholesterol in serum and IDL, were negatively associated with HbA1(c) at baseline and after follow-up, suggesting that the better glycemic control, the higher was cholesterol synthesis. The absorption markers were less consistently associated with HbA1(c). About half of the serum lathosterol and cholestanol was carried in LDL and one-fourth to one-fifth in HDL, but the lathosterol ratios were roughly similar in all lipoproteins. In contrast, cholestanol accumulated in chylomicrons and HDL. Glycemic control did not affect the distributions of lathosterol and cholestanol. In conclusion, improvement in glycemic control increased cholesterol synthesis, but had no effect on cholesterol absorption as measured by the serum or lipoprotein cholestanol to cholesterol ratio. From a clinical point of view, the better the glycemic control, the more antiatherogenic cholesterol metabolism may be in type 1 diabetes.

Weight reduction modulates expression of genes involved in extracellular matrix and cell death: the GENOBIN study

OBJECTIVE

Lifestyle and genetic factors interact in the development of obesity and the metabolic syndrome. The molecular mechanisms underlying the beneficial dietary modifications are, however, unclear. We aimed to examine the effect of the long-term moderate weight reduction on gene expression in adipose tissue (AT) and to identify genes and gene clusters responsive to treatment and thereby likely contributing to the development of the metabolic syndrome.

DESIGN

Randomized controlled and individualized weight reduction intervention.

SUBJECTS

Forty-six subjects with impaired fasting glycemia or impaired glucose tolerance and features of metabolic syndrome, aged 60+/-7 years were randomized either to a weight reduction (WR) (n=28) or a control (n=18) group lasting for 33 weeks.

MEASUREMENTS

Oral and intravenous glucose tolerance tests and subcutaneous AT biopsies were performed before and after the intervention. Gene expression of AT was studied using microarray technology in subgroups of WR (with weight reduction > or =5%, n=9) and control group (n=10). The results were confirmed using quantitative PCR.

RESULTS

In the WR group, glucose metabolism improved. Moreover, an inverse correlation between the change in S (I) and the change in body weight was found (r=-0.44, P=0.026). Downregulation of gene expression (P<0.01) involving gene ontology groups of extracellular matrix and cell death was seen. Such changes did not occur in the control group. The tenomodulin-gene was one of the most downregulated genes (-39+/-16%, P<0.0001). Moreover, its expression correlated with insulin sensitivity (r=-0.34, P=0.005) before the intervention and with body adiposity both before (r=0.42, P=0.007) and after (r=0.30, P=0.056) the intervention.

CONCLUSION

Genes regulating the extracellular matrix and cell death showed a strong downregulation after long-term weight reduction. This likely reflects a new stable state at the molecular level in AT. Further studies are warranted to elucidate the mechanisms of these genetic factors.

The distribution of squalene and non-cholesterol sterols in lipoproteins in type 2 diabetes

BACKGROUND

Lipoprotein distribution of non-cholesterol sterols was studied to evaluate in which lipoproteins they are carried in type 2 diabetes with body weight ranging from normal to overweight.

METHODS

Serum and lipoprotein squalene and non-cholesterol sterols were quantitated with gas-liquid chromatography in 33 diabetic subjects separated into normal (BMI < or = 25 kg/m2, n=10) and overweight (BMI > 25 kg/m2, n=23) groups.

RESULTS

Two-thirds of the non-cholesterol sterols were carried in LDL and one-fifth in HDL, whereas squalene was mainly in VLDL and LDL in both groups. In overweight versus normal weight subjects, the absorption marker concentrations and ratios to cholesterol in serum and lipoproteins were lower and those of synthesis higher. In both groups the synthesis and absorption markers were interrelated in all lipoproteins suggesting intact regulation of cholesterol metabolism. The absorption marker ratios to cholesterol were mostly carried in HDL (cholestanol) and IDL (campesterol and sitosterol), and synthesis markers in VLDL and IDL regardless of overweight. Synthesis marker ratios were underestimated in serum versus VLDL and IDL, and those of absorption markers in serum versus IDL and HDL (p<0.05 for all). Squalene was related to lathosterol in all lipoprotein fractions (e.g., in LDL r=+0.501, p<0.01) suggesting that in diabetes squalene, too, is an indicator of cholesterol synthesis.

CONCLUSIONS

The absorption sterols are carried in IDL and HDL, and the synthesis markers in VLDL and IDL regardless of weight. The lipoprotein squalene and non-cholesterol sterol ratios were under- or overestimated in serum, and whether their evaluation in lipoproteins versus in serum only gives better information on cholesterol metabolism should be investigated further also in normal population.

Serum high sensitivity C-reactive protein and cognitive function in elderly women

BACKGROUND

Inflammation has been linked to cognitive impairment. However, limited data are available on the association between inflammatory markers and cognitive function.

OBJECTIVES

We tested the hypothesis that elevated serum concentration of high sensitivity C-reactive protein (hs-CRP), an established marker of low-grade inflammation, predicts cognitive impairment in elderly women.

DESIGN

A 12-year population-based follow-up study.

PARTICIPANTS

A total of 97 women between 60 and 70 years of age at baseline.

METHODS

Serum hs-CRP concentration was measured by a high sensitivity assay. Global cognitive function was measured with the Mini-Mental State Examination (MMSE), and memory and cognitive speed were measured with a detailed cognitive test battery.

RESULTS

Higher baseline hs-CRP was associated with poorer memory at 12-year follow-up without adjustment and after adjustment for age, education and depression (standardised regression coefficient beta -0.842, 95% confidence interval -1.602 to -0.083, P = 0.030), and further adjustment for the use of hormone replacement therapy, smoking, serum LDL cholesterol and body mass index (standardised regression coefficient beta -0.817, 95% confidence interval -1.630 to -0.004, P = 0.049). Memory at 12-year follow-up worsened linearly with increasing hs-CRP at baseline (P = 0.048 for linear trend). There was no association between hs-CRP at baseline and cognitive speed or MMSE score at 12-year follow-up.

CONCLUSIONS

High serum hs-CRP concentration predicts poorer memory 12 years later in elderly women. Hs-CRP may be a useful biomarker to identify individuals at an increased risk for cognitive decline.

Markers of absorption and synthesis of cholesterol in men with type 1 diabetes

BACKGROUND AND METHODS

Serum cholestanol and plant sterol ratios to cholesterol, surrogate markers of cholesterol absorption, are assumed to be high in type 1 diabetes (T1D), and the ratios of cholesterol precursor sterols (markers of synthesis) are assumed to be low reflecting downregulated cholesterol synthesis. To this end, we measured serum sterols with gas-liquid-chromatography in 56 men with T1D and in 18 controls to evaluate cholesterol metabolism. Subjects were categorised into tertiles by the cholestanol to cholesterol ratio of controls indicating low to high absorption of cholesterol.

RESULTS

The ratios of the synthesis markers were negatively related to the absorption markers in controls, but less consistently in T1D. The absorption markers were positively related to each other, but interrelation of the synthesis markers was less consistent in T1D. In the low absorbers the absorption markers were higher in T1D than in controls (e.g. sitosterol ratio 173 +/- 9 in T1D vs 135 +/- 11 10(2) x mmol/mol of cholesterol in controls, p < 0.05). In the high absorbers, the absorption markers were similar in T1D and controls, but the synthesis markers were higher in T1D than in controls (e.g. lathosterol ratio 154 +/- 10 in T1D vs 120 +/- 5 10(2) x mmol/mol of cholesterol in controls, p < 0.05).

CONCLUSIONS

Absorption and synthesis of cholesterol are less closely related to each other in T1D than in controls, but the markers of cholesterol absorption are interrelated also in T1D. Absorption of cholesterol is higher in T1D than in controls within the range of low absorption, but similar in those with relatively high cholesterol absorption.

Respective hydrolysis and esterification of esterified and free plant stanols occur rapidly in human intestine after their duodenal infusion in triacyl- or diacylglycerol

Esterification of dietary phytosterols and glycerols may affect intestinal absorption of cholesterol and non-cholesterol sterols. We infused plant stanol esters in triacylglycerol (TAG) (F1) and diacylglycerol (DG) (F2) oils, and free plant stanols in F1 and F2 (F3) to the duodenum of healthy human subjects and sampled the contents from the proximal jejunum (PJ). Free and ester sterols were analysed from the infusates, and intestinal contents before and after ultracentrifuge separation of oil, micelle and sediment phases. During the 60-cm intestinal passage, over 40% of plant stanol esters were hydrolysed (P < 0.05) but around 30% of the infused free plant stanols (P < 0.05) and up to 40% of cholesterol (P < 0.05) were esterified in PJ after infusions. TAG in F1 favoured accumulation of plant stanol esters in the oil phase of the PJ aspirates as compared with respective values of F2 and F3 (P < 0.05 for both). About one third of free plant stanols of F3 had been esterified (P < 0.05) and 17% precipitated mainly in free form in the PJ aspirates (P < 0.05 compared with F1 and F2). In conclusion, DG- and TAG-oils had no profound superiority over each other as intestinal carriers regarding hydrolysis/esterification of administered plant stanol esters and cholesterol and their partition in oil, micellar and sediment phases in the PJ. The unesterified plant stanols experienced partial esterification and sedimentation during their intestinal passage, which might influence their biochemical properties in that segment of the gut where cholesterol is absorbed.

Cholesterol synthesis prevails over absorption in metabolic syndrome

The objective of this study was to investigate cholesterol metabolism and its association with glucose metabolism and genetic regulation in metabolic syndrome. Overall, 74 subjects with clinically defined metabolic syndrome and sex and age-matched controls (n=74) were recruited. Cholesterol metabolism was assayed with serum non-cholesterol sterols, surrogate markers of synthesis, and fractional absorption of cholesterol and was related to variables of glucose and insulin action and to the common polymorphisms of the ABCG5 and ABCG8 genes. Serum squalene and non-cholesterol sterols were analyzed with gas-liquid chromatography (GLC) and presented as ratios to cholesterol. Also, synthesis marker/absorption marker ratios were calculated. The subjects with metabolic syndrome had higher cholesterol synthesis marker ratios, including squalene, and lower absorption marker ratios than controls. When adjusted with body mass index (BMI) and waist circumference, differences in some of the absorption markers (plant sterols), but not in the synthesis markers, disappeared. Plasma glucose, serum triglycerides, and homeostasis model assessment (HOMA) index were positively associated with cholesterol synthesis/absorption marker ratios (r=0.264 to 0.353, P<0.05 for all). In multivariate analysis, the serum squalene ratio was the best variable of those of cholesterol metabolism explaining the presence of metabolic syndrome. The polymorphisms of ABCG5 and ABCG8 genes did not differ between the cases and controls. In conclusion, cholesterol synthesis prevails over absorption in metabolic syndrome. The high serum squalene ratio turned out to be associated with the prevalence of metabolic syndrome. The perturbations of cholesterol metabolism seem to be related to abdominal obesity, and weight reduction might normalize cholesterol metabolism.

Serum adipokines are associated with cholesterol metabolism in the metabolic syndrome

BACKGROUND

The purpose of this study was to investigate whether cholesterol metabolism is associated with serum adipokines and inflammatory markers.

METHODS

In fifty-eight subjects with impaired fasting glucose or impaired glucose tolerance and features of the metabolic syndrome cholesterol metabolism was assayed with serum non-cholesterol sterol ratios to cholesterol, surrogate markers of synthesis (cholesterol precursors) and dietary absorption % of cholesterol (cholestanol and plant sterols) and related them to serum adiponectin, leptin, high-sensitive C-reactive protein (hs-CRP), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha).

RESULTS

Adiponectin was negatively related to synthesis markers (e.g. desmosterol r=-0.371, P<0.01), and positively to absorption markers (e.g. cholestanol r=0.269, P<0.05). Leptin was associated with synthesis markers (e.g. desmosterol r=0.271, P<0.05) and negatively with absorption markers (e.g. sitosterol r=-0.278, P<0.05). Hs-CRP was negatively associated with absorption markers (e.g. sitosterol r=-0.407, P<0.001). IL-6 and TNF-alpha were not related to cholesterol metabolism. When dividing the subjects into tertiles by the serum desmosterol/cholestanol ratio, the I tertile (high synthesis/low absorption) was associated with low adiponectin concentrations, high BMI and serum leptin concentrations (P<0.05 for all).

CONCLUSIONS

Adiponectin, leptin and hs-CRP were associated with variables of cholesterol metabolism. A high ratio of cholesterol synthesis to absorption is characterized by high serum leptin and low adiponectin concentrations.

Blood glucose and the metabolism of cholesterol in coronary patients with and without simvastatin treatment

BACKGROUND AND AIM OF THE STUDY

Association of blood glucose with cholesterol metabolism and with cholesterol lowering during simvastatin treatment has not been studied earlier in hypercholesterolemic subjects with coronary heart disease.

METHODS

Baseline blood glucose was compared with cholesterol synthesis (e.g. ratios of squalene and lathosterol) and absorption (e.g. sitosterol ratio) without and with simvastatin for one year in 806 non-diabetes Finnish subjects of the Scandinavian Simvastatin Survival Study.

RESULTS

Baseline blood glucose was positively correlated with the baseline synthesis and negatively with the absorption of cholesterol, and positively with the synthesis/absorption ratio (e.g. p=0.001 for lathosterol/sitosterol). Simvastatin decreased serum cholesterol by about 29% irrespective of glucose level, cholesterol synthesis by up to 34%, especially in the highest glucose quartile, and increased cholesterol absorption by up to 49%, especially in the lowest glucose quartile (p<0.01 for all). The one-year synthesis/absorption ratio was decreased proportionately to the baseline glucose, e.g. for lathosterol/sitosterol by over 40% (p<0.001) in different glucose quartiles (p<0.001 between quartiles).

CONCLUSIONS

Baseline blood glucose level is related positively to cholesterol synthesis and negatively to that of absorption. Despite a marked glucose-related decrease in cholesterol synthesis with simvastatin, serum cholesterol reduction was not dependent on the baseline glucose level.

Moderate increase in dietary sucrose does not influence fasting or postprandial serum lipids regardless of the presence of apolipoprotein E2 allele in healthy subjects

OBJECTIVE

To investigate whether a moderate increase in dietary sucrose intake induces different serum lipid responses in normolipidemic subjects with the epsilon 2 allele compared with subjects without the epsilon 2 allele.

DESIGN

Controlled, parallel study.

SUBJECTS

There were 15 subjects with the apolipoprotein E (APOE)3/2 genotype and 19 subjects with the APOE 3/3 or 3/4 genotype, whose mean+/-s.d. age was 48+/-14 and 35+/-10 years, respectively. All subjects had normal glucose metabolism.

INTERVENTIONS

The subjects were instructed to increase their sucrose intake by 40 g/day for 8 weeks and to decrease the intake of saturated and unsaturated fat to maintain energy balance. Dietary adherence was monitored using food records and the actual increase in sucrose intake was 39.8+/-18.4 g/day. Sixteen subjects (nine with APOE 3/2 genotype, seven with APOE 3/3 or 3/4 genotypes) participated also in an 8 h oral fat tolerance test at the beginning and at the end of the intervention.

RESULTS

Body weight remained stable during the intervention. Sucrose intake did not have a significant effect on fasting concentrations of serum total and lipoprotein lipids, plasma glucose, serum insulin, squalene and non-cholesterol sterols in either genotype group. Neither were there any changes in postprandial lipid or insulin responses.

CONCLUSIONS

Moderate increase in sucrose intake does not affect fasting or postprandial serum lipid responses in healthy subjects with or without the epsilon 2 allele.

Effect of ezetimibe and/or simvastatin on coenzyme Q10 levels in plasma: a randomised trial

BACKGROUND

HMG-CoA reductase inhibitors ('statins') have been associated with a decrease in ubidecarenone (ubiquinone) levels, a lipophilic enzyme also known as coenzyme Q10 (CoQ10), due to inhibition of mevalonate synthesis. There is speculation that a decrease in CoQ10 levels may be associated with statin-induced myopathy. The cholesterol absorption inhibitor ezetimibe increases endogenous cholesterol synthesis. The purpose of this study was to examine (i) the effects of ezetimibe and simvastatin on plasma CoQ10 levels and (ii) whether ezetimibe coadministered with simvastatin abrogates the suggested statin-induced decrease in the CoQ10 plasma levels.

METHODS

Seventy-two healthy male subjects were enrolled in a single-centre, randomised, parallel-group study with three arms. Subjects received ezetimibe 10 mg/day, simvastatin 40 mg/day or the combination of ezetimibe 10 mg/day plus simvastatin 40 mg/day for 14 days.

RESULTS

Baseline CoQ10 (0.99 +/- 0.30 mg/L) levels for the combined groups remained unchanged in the ezetimibe group (0.95 +/- 0.24 mg/L), and significantly decreased in the simvastatin and combination groups (0.82 +/- 0.18 mg/L, p = 0.0002 and 0.7 +/- 0.22 mg/L, p < 0.0001, respectively). There was a correlation between the percentage change in the levels of low-density lipoprotein-cholesterol (LDL-C) and the percentage change in CoQ10 levels in all treatment groups (correlation coefficient [R] = 0.67, p < 0.0001). The ratios of CoQ10 levels to LDL-C levels were significantly increased in all treatment groups (p < 0.0001). CoQ10 level was independent of cholesterol synthesis or absorption markers.

CONCLUSIONS

Simvastatin and the combination of simvastatin and ezetimibe significantly decrease plasma CoQ10 levels whereas ezetimibe monotherapy does not. There is a significant correlation between the CoQ10 level decrease and the decrease in total and LDL-C levels in all three treatment groups, suggesting that the CoQ10 decrease may reflect the decrease in the levels of its lipoprotein carriers and might not be statin-specific. The statin-associated CoQ10 reduction is not abrogated through ezetimibe coadministration. Changes of CoQ10 levels are independent of cholesterol synthesis and absorption.

Postprandial behavior of plasma squalene and non-cholesterol sterols in men with varying cholesterol absorption

BACKGROUND

The purpose of this study was to investigate, whether low vs. high absorption of cholesterol affects the postprandial lipid clearance (squalene as the surrogate marker) and postprandial cholesterol metabolism evaluated with plasma levels of cholesterol absorption (cholestanol and plant sterols) and synthesis markers (desmosterol and lathosterol).

METHODS

Fifteen normo- or mildly hypercholesterolemic men were divided into low or high cholesterol absorbers on the basis of plasma cholestanol to cholesterol ratio and they volunteered to an oral fat load test containing fat 35 g/m(2) body surface.

RESULTS

Plasma squalene to cholesterol ratio did not differ between the groups throughout the postprandial follow-up of 8 h. The level differences in the plasma absorption and synthesis markers seen at baseline remained between the groups, so that in high absorbers the absorption markers remained high and synthesis markers low throughout the postprandial follow-up. The postprandial response curves of desmosterol (p<0.05) and lathosterol (p=0.052) to cholestanol decreased linearly in the low, but not in the high absorbers.

CONCLUSIONS

Low vs. high absorption of cholesterol does not affect the first 8-h postprandial lipid clearance. The metabolic profile of cholesterol is maintained postprandially. The postprandial decrease in cholesterol synthesis differs in low vs. high absorbers especially through the desmosterol pathway.

Interaction between cholesterol and glucose metabolism during dietary carbohydrate modification in subjects with the metabolic syndrome

BACKGROUND

Carbohydrate modification based on rye bread and pasta enhances early insulin secretion in subjects with the metabolic syndrome.

OBJECTIVE

Because the actions of insulin and cholesterol metabolism are interrelated, the question is raised of whether it is possible to alter cholesterol metabolism by means of dietary carbohydrate modification.

DESIGN

We investigated the 12-wk effects of dietary carbohydrate modification on cholesterol synthesis and absorption by measuring the ratios of surrogate markers of precursor (cholestenol, desmosterol, and lathosterol) and absorption (cholestanol and plant sterols) sterols to cholesterol and their association to glucose metabolism in 74 subjects with the metabolic syndrome. The subjects were randomly assigned to diets with rye bread and pasta (RPa) or oat, wheat bread, and potato (OWPo) as the main carbohydrate source (34% and 37% of energy intake, respectively).

RESULTS

During the study, serum cholesterol concentrations remained unchanged. Cholesterol synthesis was lower (6-10% for cholestenol and lathosterol; P < 0.05) and absorption higher (9%; P < 0.05 for sitosterol) with the OWPo diet than at baseline. With the RPa diet, cholesterol absorption was lower and synthesis higher than with the OWPo diet. The increment in the glucose area under the curve with the RPa diet was positively related to baseline cholesterol synthesis (eg, lathosterol; r = 0.480, P < 0.05) and negatively to absorption (for cholestanol; r = -0.520, P < 0.05). In the combined group, the changes in the cholestanol ratio and the insulinogenic index were interrelated (r = -0.464, P < 0.001).

CONCLUSIONS

Carbohydrate modifications had dissimilar effects on cholesterol metabolism. Consumption of RPa, as compared with OWPo, may be clinically more favorable because it seems to inhibit the absorption of cholesterol, a factor crucial in the development of arterial atherosclerosis.

Cholesterol absorption and synthesis in children with type 1 diabetes

OBJECTIVE

The levels of the surrogate markers of cholesterol absorption (cholestanol and plant sterols) and synthesis (cholesterol precursors) in serum have suggested that in adult type 1 diabetes, cholesterol absorption is high and synthesis is low compared with type 2 diabetic or control subjects. Accordingly, these findings were further studied in children with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Forty-eight children with diabetes were compared with 79 age- and sex-matched control subjects. The serum ratios of cholesterol absorption and synthesis markers were measured with gas-liquid chromatography. The study population was divided into triads (combining the two lowest triads) by serum cholestanol ratios of the control subjects indicating low to high cholesterol absorption efficiency.

RESULTS

The ratios of the absorption and synthesis markers were similar in case and control subjects, and they were negatively related to each other in control subjects, being less consistent in diabetic patients. Thus, high cholesterol absorption was associated with low synthesis. Plant sterol ratios increased significantly with increasing cholestanol triads in both groups, but the values in the lowest triads were higher in case versus control subjects.

CONCLUSIONS

Homeostasis between cholesterol absorption and synthesis is maintained in control children and somewhat less consistently in those with diabetes. The higher plant sterol ratios in diabetic versus control subjects in the lowest cholestanol triads suggest that cholesterol absorption is higher in children with diabetes versus control subjects but only within the range of low cholesterol absorption.

Endothelial function in hypercholesterolemic subjects: Effects of plant stanol and sterol esters

We investigated the effects of stanol (STAEST) and sterol esters (STEEST) on endothelial function in hypercholesterolemic subjects. In addition, associations of variables of cholesterol metabolism with endothelial function were investigated. In a double-blind randomized cross-over study (n=39) with age-matched parallel control group (n=37) the subjects consumed STAEST or STEEST spread (total plant sterols and stanols 1.93-1.98g/day) for 10 weeks each. Controls consumed the spread without sterols or stanols for 20 weeks. At baseline, brachial artery diameter was positively correlated with serum triglycerides (r=0.375, p=0.001) and glucose (r=0.420, p<0.001) and with cholesterol synthesis marker ratios to cholesterol (e.g. desmosterol r=0.540, p<0.001) and negatively with HDL cholesterol (r=-0.309, p=0.008) and absorption marker ratios (e.g. campesterol r=-0.332, p=0.004). During the intervention, LDL cholesterol was reduced by 6-9% from baseline with STAEST and STEEST spreads (p<0.05), and by 9-12%, respectively, from controls (p<0.05). Flow-mediated dilatation did not change during the investigation. Brachial artery diameter was unchanged in controls and during STAEST periods, but it was reduced during STEEST by 2.2% (p=0.012) from STAEST. In conclusion, variables of cholesterol metabolism are associated with brachial artery diameter at baseline. STEEST diminishes brachial artery diameter, but its clinical relevance remains unclear.

Effects of plant stanol esters supplied in a fat free milieu by pastilles on cholesterol metabolism in colectomized human subjects

BACKGROUND AND AIM

Nutritional products containing fat-soluble phytosterol esters for serum cholesterol lowering have traditionally been oil-based. Their cholesterol-lowering efficacy when provided by low-fat vehicles with a diet of normal fat content is questionable. The aims of the present study were to find out whether 1-week consumption of plant stanol esters in pastilles alters absorption percentage of labeled esterified and free cholesterol and fecal elimination of sterols, including phytosterols (n = 9), and to define the impact of dietary fat on intestinal sterol ester hydrolysis (n = 8) in colectomized human subjects.

METHODS AND RESULTS

Levels of lipoprotein cholesterol and triacylglycerols, non-cholesterol sterols and squalene in serum, neutral sterols, non-cholesterol sterols, fat and bile acids in feces, cholesterol absorption efficiency and cholesterol synthesis were analyzed at baseline and at the end of the treatment period. Analyses of esterified and free cholesterol and phytosterols were performed during diets with normal and low-fat content. Serum levels of total and low-density lipoprotein cholesterol decreased by 9% and 14%, respectively (P < 0.01 for both), and absorption of 3H-esterified and 14C-free cholesterol decreased in proportion to baseline values (r = -0.58, P < 0.05) by over 40% (P < 0.01) in colectomized patients with stanol ester pastilles. Fecal elimination of cholesterol was increased by about 35% and almost 60% of campestanol and sitostanol esters were hydrolyzed during their transit in gastrointestinal tract when consumed with a normal fat diet (mean daily fat 93 +/- 13g ) for 1 week. The hydrolysis of plant stanol esters was more pronounced with a normal than with a low-fat diet (70% versus 40%, P < 0.001).

CONCLUSIONS

We conclude that plant stanol esters provided in fat free milieu exert favourable effects on serum lipid profile by decreasing absorption of cholesterol in colectomized human subjects, even though the intestinal hydrolysis of plant stanol esters is weaker on low than normal fat diet.