[Clinical science relating atherosclerotic diseases and hypertriglyceridemia]

Recent epidemiologic studies and meta-analysis with triglyceride levels are revealing that hypertriglyceridemia is associated with coronary heart diseases independent of other coronary risk factors, although the direct effect of serum triglycerides to atherosclerotic lesion is still uncertain. Multiple genetic and environmental factors from familial hyperlipidemia to food and alcohol intake are implicated in elevating triglycerides. Especially, a number of investigators demonstrated a relationship between atherosclerotic diseases and postprandial hyperlipidemia, which may lead to nonfasting TG elevation. The purpose of this article is to review several clinical studies relating serum fasting and nonfasting triglyceride levels and coronary heart disease, and to discuss whether hypertriglyceridemia initiates atherosclerosis or plays a role as a biomarker for metabolic abnormalities.

Butyrate attenuates inflammation and lipolysis generated by the interaction of adipocytes and macrophages

AIM

Paracrine interaction between macrophages and adipocytes in obese visceral fat tissues is thought to be a trigger of chronic inflammation. The immunomodulatory effect of the short chain fatty acid, butyric acid, has been demonstrated. We hypothesize that sodium butyrate (butyrate) attenuates inflammatory responses and lipolysis generated by the interaction of macrophages and adipocytes.

METHODS

Using contact or transwell co-culture methods with differentiated 3T3-L1 adipocytes and RAW264.7 macrophages, we investigated the effects of butyrate on the production of tumor necrosis factor alpha (TNF-α), monocyte chemoattractant protein 1 (MCP-1), interleukin 6 (IL-6), and the release of free glycerol, free fatty acids (FFAs) into the medium. We also examined the activity of nuclear factor-kappaB (NF-κB) and the phosphorylation of mitogen-activated protein kinases (MAPKs) in co-cultured macrophages, as well as lipase activity and expression in co-cultured adipocytes.

RESULTS

We found increased production of TNF-α, MCP-1, IL-6, and free glycerol, FFAs in the co-culture medium, and butyrate significantly reduced them. Butyrate inhibited the phosphorylation of MAPKs, the activity of NF-κB in co-cultured macrophages, and suppressed lipase activity in co-cultured adipocytes. Lipase inhibitors significantly attenuated the production of TNF-α, MCP-1 and IL-6 in the co-culture medium as effectively as butyrate. Butyrate suppressed the protein production of adipose triglyceride lipase, hormone sensitive lipase, and fatty acid-binding protein 4 in co-cultured adipocytes. Pertussis toxin, which is known to block GPR41 completely, inhibited the antilipolysis effect of butyrate.

CONCLUSION

Butyrate suppresses inflammatory responses generated by the interaction of adipocytes and macrophages through reduced lipolysis and inhibition of inflammatory signaling.

Fasting remnant lipoproteins can predict postprandial hyperlipidemia

BACKGROUND

Hypertriglyceridemia and postprandial hyperlipidemia is thought to play an important role in atherosclerosis, but to select patients at high-risk for cardiovascular diseases is difficult with triglycerides (TG) alone in these patients.

METHODS

To predict postprandial hyperlipidemia without inconvenient test meal loading, we examined lipid concentrations before and after test meal loading and fasting adiponectin, and investigated which of these other than TG were significant during the fasting period in 45 healthy individuals (men: women, 26:19).

RESULTS

TG, remnant-like particle-cholesterol and -triglyceride (RemL-C, RLP-C, and RLP-TG), and TG/apolipoprotein(apo)B were significantly elevated after loading and fasting values significantly and positively correlated with incremental area under the curve (iAUC) (r=0.80, r=0.79, r=0.63, r=0.58, r=0.54; p<0.0001). Fasting adiponectin positively correlated with fasting high-density lipoprotein-cholesterol (r=0.43, p<0.005) and apoA-I (r=0.34, p<0.05), and negatively correlated with iAUC of TG, RemL-C, RLP-C, RLP-TG, and TG/apoB (r=-0.37, r=-0.41, r=-0.37, r=-0.36, r=-0.37; p<0.05). We constructed the model of multivariable linear regression analysis without fasting TG. In the sex-, BMI-, age-, and waist circumference-adjusted analysis of postprandial TG elevation 2 h after test meal loading in all participants, RemL-C, RLP-C, RLP-TG, and TG/apoB were significant factors, but adiponectin was not.

CONCLUSION

Fasting triglyceride-rich lipoprotein-related values, especially RemL-C, RLP-C, RLP-TG, and TG/apoB are useful predictors of postprandial hyperlipidemia in young healthy individuals. Although fasting adiponectin concentration correlated with the iAUCs for TG, RemL-C, RLP-C, RLP-TG, and TG/apoB, it was not a significant predictor of postprandial hyperlipidemia in multivariable linear regression analysis.

A study on how a 6-month aerobic exercise program can modify coronary risk factors depending on their severity in middle-aged sedentary women

It is well known that physical exercise can reduce coronary risk factors. But how an aerobic exercise modifies coronary risk factors in relation to severity and physical fitness is still controversial.Fifty-four middle-aged women (mean age, 55 years) completed a 6-month on-site and home-based anaerobic threshold-level exercise program. The changes in coronary risk factor profiles were observed during the pre-intervention and intervention periods. Before the intervention (during control period), most coronary risk factors showed a rather unfavorable trend. After the program, their mean body weight decreased from 56.7 to 55.7 kg (p>0.05) and the proportion of body fat from 30.9 to 27.9% (p>0.05) without any reduction in lean body mass. Systolic blood pressure (SBP) decreased from 129.0 to 125.0 mm Hg (p>0.05) and diastolic blood pressure from 79.5 to 76.6 mm Hg (p>0.05). Fasting plasma glucose (FPG) declined from 109.6 to 103.4 mg/dl (p>0.05). Changes in SBP and FPG were most remarkable in their respective worst tertile. Serum lipids improved only modestly. Maximum oxygen uptake increased from 23.6 to 26.1 ml/kg/min (p>0.01). However, no significant correlations were found between changes in coronary risk factors and those in physical fitness. We conclude that the 6-month aerobic exercise program would modify women's coronary risk factors depending on their initial values, probably independently of the changes in physical fitness.

Adding diet and exercise counseling to the health promotion plan alleviates anthropometric and metabolic complications in patients with metabolic syndrome

We investigated the effects of individual (IC) and group (GC) diet and exercise counseling in men with metabolic syndrome. Participants received exercise instruction and exercise load was monitored. IC participants received individual diet counseling sessions and general consultations at baseline and monthly. GC participants received a group diet counseling session at baseline and general consultations at baseline and monthly. In the IC group, body mass index (BMI) percent body fat, waist circumference, diastolic blood pressure, low-density lipoprotein cholesterol, glycosylated hemoglobin A_1c, and liver function levels were reduced significantly after 3 months, whereas in the GC group, waist circumference and levels of liver function were reduced. Exercise load was negatively correlated with change in BMI and waist circumference in the IC group, and positively correlated with changes in high-density lipoprotein cholesterol levels in all subjects and in the GC group. Diet and exercise counseling, especially IC, may benefit patients with metabolic syndrome.

[What is a good marker for serum cholesterol to identify high-risk patients at general health checks?]

Conventional measurement of lipid concentrations includes total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), high-density lipoprotein-cholesterol (HDL-C), and triglycerides (TG). Several guidelines for cardiovascular diseases recommend using LDL-C as the primary target of therapy in conjunction with assessing risk factors for cardiovascular diseases (CVD); however, emerging findings have revealed that lowering LDL-C to the goal with statins is not enough to prevent primary and secondary CVD. Thus, we need new parameters to better integrate residual risks into CVD risk stratification. Recently, non-HDL-C, apolipoprotein B (apoB), and LDL-C/HDL-C have been suggested. Non-HDL-C, indicating the cholesterol contents of all atherogenic lipoproteins and retaining continuity with the concept of cholesterol, is quickly computed by subtracting HDL-C from TC, needs no additional costs, and includes atherogenic TG-rich lipoproteins, called remnant lipoproteins. In addition, non-HDL-C has been shown to be an excellent predictor of CVD, free from dietary variations. ApoB, the number of atherogenic lipoproteins, is also a valuable parameter with slightly better performance than non-HDL-C in epidemiological studies, but it costs more and takes longer than conventional lipid examinations. Several lipid parameters, such as TC/HDL-C, non-HDL-C/HDL-C, LDL-C/HDL-C, are also available in clinical practice and epidemiological study; however, we should note that LDL-C/HDL-C is not reliable in cases of high TG. Thus, in general health checks, we should first pay attention to the absolute values of LDL-C, HDL-C, and TG for the diagnosis and subsequently use non-HDL-C, apoB, and other parameters, considering the pathophysiological condition, convenience, and costs.

Butyrate enhancement of inteleukin-1β production via activation of oxidative stress pathways in lipopolysaccharide-stimulated THP-1 cells

Safe and effective methods for oral bacterial disinfection have been desired, since bacteria cause many infectious diseases such as dental caries, periodontal disease, and endodontic infections. Singlet oxygen (¹O₂) is attractive, because it is toxic to prokaryotic cells, but not to eukaryotic cells. We selected irradiation of titanium dioxide (TiO₂) as a source of ¹O₂, because it has been used in sunscreens and cosmetic products without complications. In order to establish the optimal oral photodynamic therapy conditions, we measured the rate of ¹O₂ formation from the irradiated anatase or rutile forms of TiO₂ using 365 or 405 nm lamps. The rate of ¹O₂ formation decreased in the following order: anatase, 365 nm > rutile, 405 nm > rutile, 365 nm > anatase, 405 nm. Therefore, we concluded that irradiation of the rutile form of TiO₂ by a 405 nm lamp is the most favorable photodynamic therapy condition, because visible light is more desirable than UV light from the viewpoint of patient safety. We also confirmed that there was no direct HO^• formation from the irradiated TiO₂.

Are circulating metabolites important in drug-drug interactions?: Quantitative analysis of risk prediction and inhibitory potency

The potential of metabolites to contribute to drug-drug interactions (DDIs) is not well defined. The aim of this study was to determine the quantitative role of circulating metabolites in inhibitory DDIs in vivo. The area under the plasma concentration-time curve (AUC) data related to at least one circulating metabolite was available for 71% of the 102 inhibitor drugs identified. Of the 80 metabolites characterized at steady state, 78% had AUCs >10% of that of the parent drug. A comparison of the inhibitor concentration/inhibition constant ([I]/K(i)) ratios of metabolites and the respective parent drugs showed that 17 of the 21 (80%) reversible inhibitors studied had metabolites that were likely to contribute to in vivo DDIs, with some metabolites predicted to have inhibitory effects greater than those of the parent drug. The in vivo drug interaction risks associated with amiodarone, bupropion, and sertraline could be identified from in vitro data only, when data pertaining to metabolites were included in the predictions. In conclusion, cytochrome P450 (CYP) inhibitors often have circulating metabolites that contribute to clinically observed CYP inhibition.

Sarcoidal granulomas in the spleen associated with multiple carcinomas

Sarcoid reactions are relatively rare manifestations of epithelioid cell granulomas associated with malignancy; they are especially found in the lymph nodes draining malignant tumors, but rarely found in other organs. We present a case of a 60-year-old female with sarcoid reactions in the spleen identified during the consecutive diagnosis and management of ovarian, breast, and thyroid carcinomas during a period of about 2 years. The symptoms and laboratory data suggestive of systemic sarcoidosis were absent except for a slight mediastinal lymphadenopathy detected only by a computed tomographic scan. The splenic granulomas were accompanied by dendritic cells of mature and immature types, the latter being different from the reported nodal counterparts. To our knowledge, this is the first reported case of splenic sarcoid reactions associated with multiple cancers, and the first reported immunohistochemical detection of dendritic cells in splenic granuloma.

Remnant lipoproteins as strong key particles to atherogenesis

Recent epidemiologic studies have revealed that hypertriglyceridemia is associated with atherosclerosis independent of other coronary risk factors. However, it is difficult to select patients at high risk for coronary artery disease using only serum triglyceride levels compared with low-density lipoprotein cholesterol levels since multiple factors are associated with elevating triglycerides. Atherosclerotic diseases with high triglyceride levels can be found in patients with familial combined hyperlipidemia, diabetes mellitus, and metabolic syndrome, in which remnant lipoproteins accumulate in the circulating blood. Recent researches have paid attention to remnant lipoproteins as atherogenic particles with the development of methods for measuring remnant cholesterol levels and apolipoprotein B-48 levels directly from human serum. Measurement of these parameters in addition to serum triglycerides may help to distinguish high-risk patients and enable us to prevent or suppress the progression of atherosclerotic diseases in those patients. However, questions remain to be answered to evaluate the significance of remnant lipoproteins. Here, we focus on three issues: the underlying problems in measuring remnant lipoprotein cholesterol, the assessment of postprandial hyperlipidemia as an atherogenic condition, and finally a review of our experimental and clinical findings about the mechanisms by which remnant lipoproteins induce atherosclerosis.

Search for a light pseudoscalar particle in the decay K_{L};{0}-->pi;{0}pi;{0}X

We performed a search for a light pseudoscalar particle X in the decay K_{L};{0}-->pi;{0}pi;{0}X, X-->gammagamma with the E391a detector at KEK. Such a particle with a mass of 214.3 MeV/c;{2} was suggested by the HyperCP experiment. We found no evidence for X and set an upper limit on the product branching ratio for K_{L};{0}-->pi;{0}pi;{0}X, X-->gammagamma of 2.4x10;{-7} at the 90% confidence level. Upper limits on the branching ratios in the mass region of X from 194.3 to 219.3 MeV/c;{2} are also presented.

[Comparison of remnant lipoprotein-cholesterol measurements: the immune adsorption method (RLP-C) and the direct assay with detergent (RemL-C)]

Elevation of serum remnant lipoprotein concentration is an emerging risk factor for coronary artery disease. An immunoseparation procedure for remnant-like particle cholesterol(RLP-C) has been evaluated extensively in recent years. In addition, a new detergent-based method has been developed and applied to automated analyzer as "MetaboLead RemL-C" (RemL-C, KYOWA MEDEX CO., LTD.). Then, we compared the concentrations of remnant lipoproteins as RemL-C with those as RLP-C in various conditions. RemL-C assay was intra-assay-reproducible (n=20, CVs: 0.6-2.2%), and reproducible for 2 days in the refrigeration and for 8 hours in room temperature. This assay was also inter-assay-reproducible (during 5 days in the deep freezing, CVs: 1.6-3.0%). The available range for RemL-C assay was between 0.09 and 121.1 mg/dl. There were no detectable interferences from hemoglobin, free/conjugated bilirubin, chyle, and Intrafat. However, heparin influenced the titer of RemL-C concentrations. Correlation of values between RLP-C and RemL-C in 123 samples was excellent (r=0.924, p<0.001). However, different responses to intermediate lipoprotein fraction derived from a patients with type III hyperlipidemia were observed. In conclusion, RemL-C and RLP-C measurements may have a similar clinical significance. Differences in sensitivity for intermediate lipoprotein fraction between both methods may exist.