J. Lipid Res. Did you know there is a large type edition? Click here.
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Originally published In Press as doi:10.1194/jlr.M600548-JLR200 on March 3, 2007

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
M600548-JLR200v1
48/6/1336    most recent
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Hogue, J.-C.
Right arrow Articles by Couture, P.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Hogue, J.-C.
Right arrow Articles by Couture, P.
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati  
What's this?

Journal of Lipid Research, Vol. 48, 1336-1342, June 2007
Copyright © 2007 by American Society for Biochemistry and Molecular Biology

Evidence of increased secretion of apolipoprotein B-48-containing lipoproteins in subjects with type 2 diabetes

Jean-Charles Hogue*, Benoît Lamarche{dagger}, André J. Tremblay*, Jean Bergeron*, Claude Gagné* and Patrick Couture1,*

* Lipid Research Center, Centre hospitalier de l'Université Laval Research Center, Québec, Canada
{dagger} Institute on Nutraceuticals and Functional Foods, Laval University, Québec, Canada

Published, JLR Papers in Press, March 3, 2007.

1 To whom correspondence should be addressed. e-mail: patrick.couture{at}crchul.ulaval.ca


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Patients with type 2 diabetes have high levels of triglyceride-rich lipoproteins (TRLs), including apolipoprotein B-48 (apoB-48)-containing TRLs of intestinal origin, but the mechanism leading to overaccumulation of these lipoproteins remains to be fully elucidated. Therefore, the objective of this study was to examine the in vivo kinetics of TRL apoB-48 and VLDL, intermediate density lipoprotein (IDL), and LDL apoB-100 in type 2 diabetic subjects (n = 11) and nondiabetic controls (n = 13) using a primed-constant infusion of L-[5,5,5-D3]leucine for 12 h in the fed state. Diabetic subjects had significantly higher fasting glycemia, higher fasting insulinemia, higher plasma triglyceride, and lower HDL-cholesterol levels than controls. Compared with controls, diabetic subjects had increased TRL apoB-48, VLDL apoB-100, and IDL apoB-100 pool sizes as a result of increased production rates (PRs) and reduced fractional catabolic rates of these lipoprotein subfractions. Furthermore, multiple linear regression analyses revealed that the diabetic/control status was an independent predictor of TRL apoB-48 PR and represented nearly 35% of its variance. These results suggest that the overaccumulation of TRLs seen in patients with type 2 diabetes is attributable to increased PRs of both intestinally derived apoB-48-containing lipoproteins and TRL apoB-100 of hepatic origin and to decreased catabolism of these subfractions.

Supplementary key words kinetic study • stable isotope • hypertriglyceridemia


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Type 2 diabetes is a complex disease known to increase triglyceride (TG) levels, decrease HDL-cholesterol levels, and promote the formation of small, dense LDL particles. Recent studies indicate that type 2 diabetes is associated with increased levels of triglyceride-rich lipoproteins (TRLs), including apolipoprotein B-48 (apoB-48)-containing TRLs of intestinal origin, in both the fasted and postprandial states (1, 2). This is of interest because substantial evidence exists indicating that high levels of intestine-derived lipoproteins are associated with increased cardiovascular disease risk (3). Chylomicrons are too large to be able to enter the subendothelial space, but once hydrolyzed by the lipoprotein lipase, chylomicron remnants of <700 Å are small enough to enter into the intima and to participate in atherosclerotic lesion development (4). Chylomicron remnants have been shown to impair normal endothelial function (5), to be chemically modified, and to accumulate in the subendothelial space in the same way as apoB-100-containing lipoproteins do (6, 7). However, the mechanisms underlying the overaccumulation of apoB-48-containing TRLs in type 2 diabetes have not been fully characterized. Studies have suggested a mixed contribution of VLDL overproduction leading to competition for the removal of apoB-48-containing TRLs, impaired lipoprotein lipase activity, modified composition of TRLs, and reduced recognition by hepatic receptors (8–10). Furthermore, a recent study (11) suggested that hyperinsulinemia was associated with an increased production rate (PR) of apoB-48-containing lipoproteins of intestinal origin in insulin-resistant humans. That study, however, did not specifically examine the impact of insulin resistance on TRL apoB-48 metabolism in subjects with type 2 diabetes. Therefore, the objectives of this study were to determine whether intestinal apoB-48-containing lipoprotein secretion and catabolism are impaired in patients with type 2 diabetes and severe hypertriglyceridemia and to examine correlations between apoB-48 and apoB-100 kinetics.


   METHODS
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Subjects
Eleven men with type 2 diabetes and severe hypertriglyceridemia and 13 normolipidemic nondiabetic controls were included in this study. Diabetic subjects had to suffer from type 2 diabetes as defined by the American Diabetes Association (12) and to have a clinical requirement for an oral hypoglycemic agent. All diabetic patients were treated with either metformin or a combination of metformin and a sulfonylurea. Three subjects received a thiazolidinedione. For all subjects, exclusion criteria were as follows: history of cardiovascular disease; microalbuminuria; a genetic condition affecting lipid metabolism (e.g., familial hypercholesterolemia, type III hyperlipidemia, LPL deficiency, etc.); body mass index (BMI) of <18.0 or >35.0 kg/m2; uncontrolled hypothyroidism; nephrotic syndrome; anorexia nervosa; history of alcohol or drugs abuse; persistent increased alanine aminotransferase, aspartate aminotransferase, or creatine phosphokinase; uncontrolled endocrine or metabolic disease; poor mental condition; or a positive test for human immunodeficiency virus. All diabetic subjects had to receive stable doses of oral hypoglycemic agents for at least 3 months before the study to achieve glycosylated hemoglobin (HbA1C) values of <9%. Lipid-lowering medications were withdrawn for at least 6 weeks before the kinetic study. Upon their entry into the study, subjects met with a dietician and were instructed to maintain their usual nutritional habits throughout the entire intervention. A standardized food frequency questionnaire was also administered to participants to estimate their diet composition, and no significant difference was observed between the two groups. Fasting plasma insulin and glucose levels were measured to compute the insulin resistance index based on the homeostasis model assessment model (13). The research protocol was approved by the Laval University Medical Center review committee, and written informed consent was obtained from each subject.

Experimental protocol for in vivo stable isotope kinetics
To determine the kinetics of TRL apoB-48 and VLDL, intermediate density lipoprotein (IDL), and LDL apoB-100, participants underwent a primed-constant infusion of L-[5,5,5-D3]leucine while they were in a constantly fed state. Starting at 7 AM, the subjects received 30 identical small cookies every half-hour for 15 h, each equivalent to 1/30th of their estimated daily food intake based on the Harris-Benedict equation (14), with 15% of calories as protein, 45% as carbohydrate, and 40% as fat (7% saturated, 26% monounsaturated, and 7% polyunsaturated) and 85 mg of cholesterol/1,000 kcal. At 10 AM, with two intravenous lines in place, one for the infusate and one for blood sampling, L-[5,5,5-D3]leucine (10 µmol/kg body weight) was injected as a bolus and then by continuous infusion (10 µmol/kg body weight/h) over a 12 h period. Blood samples (20 ml) were collected at 0, 0.5, 1, 1.5, 2, 3, 4, 5, 6, 8, 10, and 12 h.

Characterization of fasting plasma lipids and lipoproteins
Before the kinetic studies, 12 h fasting venous blood samples were obtained from an antecubital vein into Vacutainer tubes containing EDTA (0.1% final concentration). Samples were then immediately centrifuged at 4°C for 10 min at 3,000 rpm to obtain plasma and were stored at 4°C until processed. Plasma VLDL (d < 1.006 g/ml) were isolated by preparative ultracentrifugation, and the HDL fraction was obtained after precipitation of LDL in the infranatant (d > 1.006 g/ml) with heparin and MnCl2. The cholesterol and TG contents of the infranatant fraction were measured before and after the precipitation step. Cholesterol and TG levels were determined using an Olympus AU400e analyzer (Melville, NY) using reagents and calibrators provided by the manufacturer. ApoB concentrations were measured by nephelometry (Dade Behring, Mississauga, Ontario, Canada) in plasma and in TRL and LDL fractions using reagents and calibrators provided by the manufacturer.

Quantification and isolation of apoB-48 and apoB-100
Venous blood samples were obtained from an antecubital vein into Vacutainer tubes containing EDTA (0.1% final concentration) at various time intervals during the kinetic study. ApoB concentrations were determined in the TRL fraction by noncompetitive ELISA using immunopurified polyclocal antibodies (Alerchek, Inc., Portland, ME) to calculate the pool size (PS). The coefficient of variation for this apoB assay was between 6% and 10%, depending on the region of the standard curve. ApoB-100 and apoB-48 were separated by SDS 3–10% one-dimensional polyacrylamide gradient gel electrophoresis (1D-PAGGE), according to standardized procedures (15), using 50 µl of each sample. ApoB-48 was assessed in the TRL (VLDL) fraction only. Based on the assumption that apoB-48 and apoB-100 both have the same chromogenicity, the relative proportion of each apolipoprotein was assessed by performing a densitometric scan of the gels. We scanned the TRL gels from three different time points to calculate the apoB-48/apoB-100 ratios and to estimate the average concentrations of apoB-100 and apoB-48 in the TRL fraction using the total TRL apoB concentration.

Isotopic enrichment determinations
ApoB-48 and apoB-100 bands were excised from the gels and hydrolyzed in 6.0 N HCl at 110°C for 24 h (16). After heating, the tubes were centrifuged and decanted to remove most of the polyacrylamide. The amino acids were then converted into trifluoromethyloxalizone derivatives using the single-step trifluoroacetic acid/trifluoroacetic anhydride procedure developed by Dwyer et al. (17). The derivatives were analyzed on a Hewlett-Packard 6890/5973 gas chromatograph/mass spectrometer. Isotopic enrichment (%) and tracer-to-tracee ratio (%) were calculated from the observed ion current ratios. The isotopic enrichment of leucine in the apolipoprotein was expressed as tracer-to-tracee ratio (%) using standardized formulas (18).

Kinetic analysis
Kinetics of apoB-48 and apoB-100 were derived by a multicompartmental model as described previously (19). We assumed a constant enrichment of the precursor pool and used either the TRL apoB-48 or the VLDL apoB-100 plateau tracer-to-tracee ratio data as the forcing function to drive the appearance of tracer into apoB-48 and apoB-100, respectively (16). Under steady-state conditions, the fractional catabolic rate (FCR) is equivalent to the fractional synthetic rate. ApoB PRs were determined by the formula PR (mg/kg/day) = [FCR (pools/day) x apoB concentration (mg/l) x plasma volume (liters)]/body weight (kg) (20). Plasma volume was estimated as 4.5% of body weight. The SAAM II program (SAAM Institute, Seattle, WA) was used to fit the model to the observed tracer data.

Statistical analysis
Data from the two groups were compared using Chi-square tests for categorical measures and ANOVA tests for continuous variables. Plasma TG levels were log-transformed to normalize their distribution. Pearson correlation coefficients were determined to assess the significance of associations between parameters. Stepwise multiple linear regression analysis was used to interpret the relationship of these associations. All analyses were performed using JMP Statistical Software (version 6.0; SAS Institute, Cary, NC).


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
Demographic, anthropometric, and biochemical characteristics of subjects
Table 1 shows the demographic, anthropometric, and biochemical characteristics of subjects according to their diabetic/control status. Diabetic subjects were significantly older than controls (54.1 ± 7.4 vs. 36.2 ± 11.3 years; P = 0.0002). There was no significant difference in BMI between the two groups. Diabetic subjects had higher fasting glucose levels (8.7 ± 2.0 vs. 4.8 ± 0.4 mmol/l; P < 0.0001), higher fasting insulin levels (87 ± 45 vs. 57 ± 14 pmol/l; P = 0.03), and higher homeostasis model assessment-insulin resistant (5.6 ± 2.9 vs. 2.0 ± 0.6; P = 0.0002). The mean HbA1C value in diabetics was 7.4 ± 1.0%.


View this table:
[in this window]
[in a new window]

  		TABLE 1. Demographic, anthropometric, and biochemical characteristics of subjects according to status

 
Table 2 shows the fasting lipid/lipoprotein profiles of subjects according to their status. Diabetic subjects had significantly higher plasma TG (4.60 ± 1.73 vs. 1.23 ± 0.67 mmol/l; P < 0.0001) (range, 2.3–8.1 mmol/l), higher TRL cholesterol (2.12 ± 0.97 vs. 0.49 ± 0.32 mmol/l; P < 0.0001), higher TRL TG (4.17 ± 1.52 vs. 0.79 ± 0.57 mmol/l; P < 0.0001), higher TRL apoB (0.27 ± 0.07 vs. 0.18 ± 0.07 g/l; P = 0.005), and lower HDL-cholesterol (0.86 ± 0.16 vs. 1.19 ± 0.24 mmol/l; P = 0.0009).


View this table:
[in this window]
[in a new window]

  		TABLE 2. Fasting lipid/lipoprotein profiles of subjects according to status

 
Kinetics of TRL apoB-48 and apoB-100
Table 3 shows the kinetics of TRL apoB-48 according to status. Diabetic subjects had higher plasma apoB-48 concentrations than controls (4.2 ± 2.0 vs. 0.9 ± 0.6 mg/dl; P < 0.0001). Compared with controls, TRL apoB-48 PS was also increased in diabetic subjects (162 ± 65 vs. 32 ± 23 mg; P < 0.0001) as a result of an increase in TRL apoB-48 PR (11.0 ± 5.2 vs. 3.0 ± 1.9 mg/kg/day; P < 0.0001) and a decrease in TRL apoB-48 FCR (5.8 ± 1.6 vs. 7.8 ± 2.0 pools/day; P = 0.01) in these subjects. Multiple linear regression analysis was performed to assess the independent contribution of different metabolic and anthropometric variables to the variance of TRL apoB-48 PR. Age, BMI, and diabetic/control status were included in the model. As shown in Table 4 , the diabetic/control status represented nearly 35% of the variance in TRL apoB-48 PR, whereas age contributed 26.7% to the variance of TRL apoB-48 PR. After adjustment for age and diabetic/control status, BMI was not found to significantly modulate TRL apoB-48 PR.


View this table:
[in this window]
[in a new window]

  		TABLE 3. Kinetics of TRL apoB-48 in controls and type 2 diabetic patients

 

View this table:
[in this window]
[in a new window]

  		TABLE 4. Multiple linear regression analysis showing independent contributions of age, BMI, and diabetic/control status to the variance of TRL apoB-48 PR

 
Table 5 shows the kinetics of apoB-100 according to status. Diabetics had higher VLDL apoB-100 PS (895 ± 243 vs. 321 ± 142 mg; P < 0.0001) as a result of a decreased VLDL apoB-100 FCR (4.1 ± 1.3 vs. 9.1 ± 3.4 pools/day; P = 0.0002) and a tendency toward an increased VLDL apoB-100 PR (41.1 ± 15.8 vs. 32.1 ± 7.7 mg/kg/day; P = 0.08). Similarly, IDL apoB-100 PS was increased in diabetic subjects (187 ± 62 vs. 33 ± 21 mg; P < 0.0001) as a result of a decreased IDL apoB-100 FCR (3.5 ± 1.2 vs. 7.3 ± 2.7 pools/day; P = 0.0003) and an increased IDL apoB-100 PR (6.7 ± 2.7 vs. 2.8 ± 1.6 mg/kg/day; P = 0.0002). No significant difference in LDL apoB-100 PS was seen between the two groups attributable to the concomitant increase in both LDL apoB-100 FCR and PR in diabetics. Only increased LDL apoB-100 PR, however, remained significant after adjustment for age and BMI. TRL apoB-48 PS was correlated with apoB-48 PR in controls (r = 0.82, P = 0.0005) and in diabetics (r = 0.81, P = 0.003). No significant correlation was found between TRL apoB-48 PS and FCR. In both groups, VLDL apoB-100 PS was correlated with FCR (controls, r = –0.82, P = 0.0005; diabetics, r = –0.62, P = 0.04) but not with PR (controls, r = 0.09, P = 0.76; diabetics, r = 0.16, P = 0.63). TRL apoB-48 PS and PR were correlated inversely with VLDL apoB-100 FCR (PS, r = –0.88, P < 0.0001; PR, r = –0.77, P = 0.002) in controls but not in diabetics (PS, r = –0.35, P = 0.28; PR, r = –0.24, P = 0.48). Figure 1 illustrates the correlation between plasma TG levels and TRL apoB-48 PR and VLDL apoB-100 FCR in diabetic subjects. No significant correlation was found between TRL apoB-48 FCR and direct catabolism of IDL apoB-100 in both groups. Finally, there was no significant difference between controls and diabetics in either VLDL-to-IDL (5.1 ± 4.1 vs. 3.7 ± 1.6 pools/day; P = 0.3) or IDL-to-LDL (1.5 ± 2.4 vs. 0.5 ± 0.4 pools/day; P = 0.2) transfer rate.


View this table:
[in this window]
[in a new window]

  		TABLE 5. Kinetics of TRL, IDL, and LDL apoB-100 in controls and type 2 diabetic patients

 

Figure 1
View larger version (10K):
[in this window]
[in a new window]

  		Fig. 1. Correlation between plasma triglyceride (TG) levels and triglyceride-rich lipoprotein apolipoprotein B-48 (TRL apoB-48) production rate (PR) (A) and VLDL apoB-100 fractional catabolic rate (FCR) (B) in patients with type 2 diabetes.

 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
This study provides information on the relationships between TRL apoB-48 and VLDL, IDL, and LDL apoB-100 kinetics in 11 type 2 diabetic males with marked increases in plasma TG levels and 13 nondiabetic controls. Specifically, we have demonstrated that these diabetic men had higher plasma concentrations and PR as well as lower FCR of intestinally derived apoB-48-containing lipoproteins than control individuals with lower insulin levels and greater insulin sensitivity. Importantly, multiple linear regression analyses revealed that the effect of diabetes on TRL apoB-48 PR and FCR remained independent of BMI and age. Our results indicate that the higher BMI in the diabetic group did not contribute significantly to the observed variations in TRL apoB-48 PR and FCR. Our findings support and extend the results of a recent study by Duez et al. (11) showing a positive correlation between TRL apoB-48 PR and fasting insulin concentrations in nondiabetic insulin-resistant subjects. Therefore, these results provide new evidence that diabetic dyslipidemia could be associated with overproduction and reduced clearance of both intestinally derived apoB-48- and TRL apoB-100-containing lipoproteins.

Previous studies have shown that both chylomicrons and VLDL increase after the ingestion of a fat-rich meal (20, 21). It is also well established that diabetic individuals have high levels of TRLs, including apoB-48-containing TRLs, in both the fasted and postprandial states (1, 22). The data reported here showing that TRL apoB-48 PS is correlated with TRL apoB-48 PR and not FCR indicate that the increase in apoB-48-containing lipoproteins is attributable to increased production. These results are in agreement with and extend previous findings by Duez et al. (11) showing that intestinal secretion of apoB-48-containing lipoproteins is increased in insulin-resistant humans with hyperinsulinemia. Our study was not designed to address the cellular mechanisms underlying the increased production of apoB-48-containing lipoproteins by the intestine in individuals with type 2 diabetes. However, recent studies using cultured primary enterocytes from fructose-fed insulin-resistant hamsters have demonstrated an increased secretion of apoB-48-containing lipoproteins accompanied by increased intracellular apoB-48 stability, enhanced de novo lipid synthesis, and higher abundance of microsomal TG transfer protein mass (23, 24). Therefore, it is likely that enhanced intestinal lipogenesis may play an important role in increasing the secretion of apoB-48-containing lipoproteins by the intestine in subjects with type 2 diabetes. Several lines of evidence also indicate that increased FFA flux from adipose tissue to the liver stimulates the hepatic assembly and secretion of apoB-100-containing lipoproteins in insulin-resistant subjects (25, 26). Similarly, recent studies using hamster enterocytes in primary culture showed that oleic acid stimulated the secretion of apoB-48-containing lipoproteins (27) and that intestinal lipoprotein production was markedly increased by an acute increase of plasma FFA in hamsters (28). Further studies are required to assess the potential correlation between increased FFA flux from adipose tissue to the liver and the intestinal production of TRL apoB-48 in humans.

As reported previously (16), this study also indicates that VLDL apoB-100 PS is correlated with the catabolism of VLDL apoB-100 and not PR in both controls and diabetics. Consequently, the increase in VLDL apoB-100 after the ingestion of a fat-rich meal is related to decreased catabolism of VLDL apoB-100. Modest reductions in postheparin LPL activity have been reported in patients with type 2 diabetes (22), and this may contribute significantly to decreased TRL catabolism. In addition, our study shows an inverse correlation between TRL apoB-48 PS and PR and VLDL apoB-100 FCR in controls with relatively low TG levels, a finding supported by previous observations in humans (16, 29). However, the absence of correlation between TRL apoB-48 PS and PR and VLDL apoB-100 FCR in diabetics with severe hypertriglyceridemia suggests that the competition between TRL apoB-48 and VLDL apoB-100 for the same catabolic pathway could be dependent on the number of circulating TRLs. It is likely that high plasma concentrations of TRLs could saturate the catabolic pathway and greatly reduce the capacity of apoB-48-containing lipoproteins to compete with TRL apoB-100 for catabolism. Furthermore, because both IDL and chylomicron remnants are presumably cleared by the same catabolic pathway, one might expect a direct correlation between FCRs of TRL apoB-48 and IDL apoB-100. However, there was no significant correlation between TRL apoB-48 FCR and direct catabolism of IDL apoB-100 in both groups. These results are in agreement with findings of a previous study (16) examining correlations between apoB-48 and apoB-100 kinetics in control subjects and suggest the presence of significant differences between IDL and chylomicron remnant catabolism. Further animal and human studies examining factors involved in the regulation of IDL and chylomicron remnant catabolism are needed to clarify this issue.

In this study, we observed that LDL apoB-100 PR and FCR were higher in subjects with type 2 diabetes than in controls. Only differences in LDL apoB-100 PR, however, remained significant after adjustment for age and BMI. This finding contrasts with results of previous studies with type 2 diabetics showing both a decrease in LDL catabolism attributed to the glycation of apoB-100 (30) and a reduction in the expression of LDL receptor (31) as well as a trend toward reduced LDL synthesis (32). In this regard, it is likely that the increased LDL apoB-100 PR observed in diabetic individuals was attributable to increased VLDL and IDL apoB-100 PS associated with relatively normal VLDL-to-IDL and IDL-to-LDL transfer rates. It is interesting that the difference in LDL apoB-100 PR between diabetics and controls is no longer significant after adjustment for VLDL apoB-100 PS or plasma TG levels. Therefore, further studies including diabetics and controls with comparable plasma TG levels are needed to clarify the influence of type 2 diabetes on LDL apoB-100 kinetics.

In this study, diabetic subjects were older and had higher BMI compared with controls, and we cannot exclude the possibility that these variables may have contributed to the observed increase in TRL apoB-48 PR or may have affected FCR. After adjustment for these two variables, however, type 2 diabetes was found to be independently associated with increased TRL apoB-48 secretion. Furthermore, it is important to emphasize that diabetic subjects included here are on average severely hypertriglyceridemic to an extent that is not typical of diabetic subjects, with glycated hemoglobin of <9%. Therefore, we cannot exclude the possibility that another factor, such as primary hyperlipidemia or some other secondary cause increasing plasma TG levels, is involved. Further studies with diabetic patients having more typical TG levels are needed to examine the correlation between plasma TG levels and TRL apoB-48 PR.

In conclusion, this study provides evidence that type 2 diabetes associated with severe hypertriglyceridemia is also associated with both increased production and decreased catabolism of intestinally derived apoB-48-containing lipoproteins. Additional studies are required to elucidate the molecular mechanisms responsible for the increased TRL apoB-48 PR in this condition and to assess the contribution of these lipoproteins to the development of atherosclerosis in these patients.


   ACKNOWLEDGMENTS
 
The authors are grateful to the participants for their invaluable contribution. J-C.H. is the recipient of a Doctoral Research Award from the Heart and Stroke Foundation of Canada. P.C. is the recipient of a Research Award from the Fonds de la Recherche en Santé du Québec. B.L. is Chair Professor in Nutrition, Functional Food, and Cardiovascular Health from the Canada Research Chair Program.

Manuscript received December 26, 2006 and in revised form February 15, 2007 and in re-revised form March 1, 2007.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
  1. Schaefer, E. J., J. R. McNamara, P. K. Shah, K. Nakajima, L. A. Cupples, J. M. Ordovas, and P. W. Wilson. 2002. Elevated remnant-like particle cholesterol and triglyceride levels in diabetic men and women in the Framingham Offspring Study. Diabetes Care. 25: 989–994.[Abstract/Free Full Text]

  2. Curtin, A., P. Deegan, D. Owens, P. Collins, A. Johnson, and G. H. Tomkin. 1996. Elevated triglyceride-rich lipoproteins in diabetes. A study of apolipoprotein B-48. Acta Diabetol. 33: 205–210.[Medline]

  3. Kolovou, G. D., K. K. Anagnostopoulou, S. S. Daskalopoulou, D. P. Mikhailidis, and D. V. Cokkinos. 2005. Clinical relevance of postprandial lipaemia. Curr. Med. Chem. 12: 1931–1945.[CrossRef][Medline]

  4. Nordestgaard, B. G., and A. Tybjaerg-Hansen. 1992. IDL, VLDL, chylomicrons and atherosclerosis. Eur. J. Epidemiol. 8 (Suppl. 1): 92–98.[CrossRef][Medline]

  5. Doi, H., K. Kugiyama, M. Ohgushi, S. Sugiyama, T. Matsumura, Y. Ohta, T. Nakano, K. Nakajima, and H. Yasue. 1998. Remnants of chylomicron and very low density lipoprotein impair endothelium-dependent vasorelaxation. Atherosclerosis. 137: 341–349.[CrossRef][Medline]

  6. Twickler, T. B., G. M. Dallinga-Thie, J. S. Cohn, and M. J. Chapman. 2004. Elevated remnant-like particle cholesterol concentration: a characteristic feature of the atherogenic lipoprotein phenotype. Circulation. 109: 1918–1925.[Free Full Text]

  7. Proctor, S. D., and J. C. Mamo. 2003. Intimal retention of cholesterol derived from apolipoprotein B100- and apolipoprotein B48-containing lipoproteins in carotid arteries of Watanabe heritable hyperlipidemic rabbits. Arterioscler. Thromb. Vasc. Biol. 23: 1595–1600.[Abstract/Free Full Text]

  8. Haffner, S. M., D. M. Foster, R. S. Kushwaha, and W. R. Hazzard. 1984. Retarded chylomicron apolipoprotein-B catabolism in type 2 (non-insulin-dependent) diabetic subjects with lipaemia. Diabetologia. 26: 349–354.[Medline]

  9. Mamo, J. C., T. Hirano, A. Sainsbury, A. K. Fitzgerald, and T. G. Redgrave. 1992. Hypertriglyceridemia is exacerbated by slow lipolysis of triacylglycerol-rich lipoproteins in fed but not fasted streptozotocin diabetic rats. Biochim. Biophys. Acta. 1128: 132–138.[Medline]

  10. Brunzell, J. D., W. R. Hazzard, D. Porte, Jr., and E. L. Bierman. 1973. Evidence for a common, saturable, triglyceride removal mechanism for chylomicrons and very low density lipoproteins in man. J. Clin. Invest. 52: 1578–1585.[Medline]

  11. Duez, H., B. Lamarche, K. D. Uffelman, R. Valero, J. S. Cohn, and G. F. Lewis. 2006. Hyperinsulinemia is associated with increased production rate of intestinal apolipoprotein B-48-containing lipoproteins in humans. Arterioscler. Thromb. Vasc. Biol. 26: 1357–1363.[Abstract/Free Full Text]

  12. The Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. 2004. Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Diabetes Care. 27 (Suppl. 1): 5–10.

  13. Wallace, T. M., and D. R. Matthews. 2002. The assessment of insulin resistance in man. Diabet. Med. 19: 527–534.[CrossRef][Medline]

  14. Harris, J., and F. Benedict. 1919. A Biometric Study of Basal Metabolism in Man. Carnegie Institution, Washington, DC.

  15. Kotite, L., N. Bergeron, and R. J. Havel. 1995. Quantification of apolipoproteins B-100, B-48, and E in human triglyceride-rich lipoproteins. J. Lipid Res. 36: 890–900.[Abstract]

  16. Welty, F. K., A. H. Lichtenstein, P. H. Barrett, G. G. Dolnikowski, and E. J. Schaefer. 1999. Human apolipoprotein (apo) B-48 and apoB-100 kinetics with stable isotopes. Arterioscler. Thromb. Vasc. Biol. 19: 2966–2974.[Abstract/Free Full Text]

  17. Dwyer, K. P., P. H. Barrett, D. Chan, J. I. Foo, G. F. Watts, and K. D. Croft. 2002. Oxazolinone derivative of leucine for GC-MS: a sensitive and robust method for stable isotope kinetic studies of lipoproteins. J. Lipid Res. 43: 344–349.[Abstract/Free Full Text]

  18. Cobelli, C., G. Toffolo, D. M. Bier, and R. Nosadini. 1987. Models to interpret kinetic data in stable isotope tracer studies. Am. J. Physiol. 253: E551–E564.

  19. Tremblay, A. J., B. Lamarche, J. S. Cohn, J. C. Hogue, and P. Couture. 2006. Effect of ezetimibe on the in vivo kinetics of apoB-48 and apoB-100 in men with primary hypercholesterolemia. Arterioscler. Thromb. Vasc. Biol. 26: 1101–1106.[Abstract/Free Full Text]

  20. Cohn, J., D. Wagner, S. Cohn, J. Millar, and E. Schaefer. 1990. Measurement of very low density and low density lipoprotein apolipoprotein (apo) B-100 and high density lipoprotein apo A-I production in human subjects using deuterated leucine. Effect of fasting and feeding. J. Clin. Invest. 85: 804–811.[Medline]

  21. Cohn, J., E. Johnson, J. Millar, S. Cohn, R. Milne, Y. Marcel, R. Russell, and E. Schaefer. 1993. Contribution of apoB-48 and apoB-100 triglyceride-rich lipoproteins (TRL) to postprandial increases in the plasma concentration of TRL triglycerides and retinyl esters. J. Lipid Res. 34: 2033–2040.[Abstract]

  22. Ginsberg, H. N. 1991. Lipoprotein physiology in nondiabetic and diabetic states. Relationship to atherogenesis. Diabetes Care. 14: 839–855.[Abstract]

  23. Haidari, M., N. Leung, F. Mahbub, K. D. Uffelman, R. Kohen-Avramoglu, G. F. Lewis, and K. Adeli. 2002. Fasting and postprandial overproduction of intestinally derived lipoproteins in an animal model of insulin resistance. Evidence that chronic fructose feeding in the hamster is accompanied by enhanced intestinal de novo lipogenesis and apoB48-containing lipoprotein overproduction. J. Biol. Chem. 277: 31646–31655.[Abstract/Free Full Text]

  24. Lewis, G. F., K. Uffelman, M. Naples, L. Szeto, M. Haidari, and K. Adeli. 2005. Intestinal lipoprotein overproduction, a newly recognized component of insulin resistance, is ameliorated by the insulin sensitizer rosiglitazone: studies in the fructose-fed Syrian golden hamster. Endocrinology. 146: 247–255.[Abstract/Free Full Text]

  25. Lewis, G. F., A. Carpentier, K. Adeli, and A. Giacca. 2002. Disordered fat storage and mobilization in the pathogenesis of insulin resistance and type 2 diabetes. Endocr. Rev. 23: 201–229.[Abstract/Free Full Text]

  26. Lewis, G. F., K. D. Uffelman, L. W. Szeto, B. Weller, and G. Steiner. 1995. Interaction between free fatty acids and insulin in the acute control of very low density lipoprotein production in humans. J. Clin. Invest. 95: 158–166.[Medline]

  27. Guo, Q., R. K. Avramoglu, and K. Adeli. 2005. Intestinal assembly and secretion of highly dense/lipid-poor apolipoprotein B48-containing lipoprotein particles in the fasting state: evidence for induction by insulin resistance and exogenous fatty acids. Metabolism. 54: 689–697.[CrossRef][Medline]

  28. Lewis, G. F., M. Naples, K. Uffelman, N. Leung, L. Szeto, and K. Adeli. 2004. Intestinal lipoprotein production is stimulated by an acute elevation of plasma free fatty acids in the fasting state: studies in insulin-resistant and insulin-sensitized Syrian golden hamsters. Endocrinology. 145: 5006–5012.[Abstract/Free Full Text]

  29. Bjorkegren, J., S. Boquist, A. Samnegard, P. Lundman, P. Tornvall, C. G. Ericsson, and A. Hamsten. 2000. Accumulation of apolipoprotein C-I-rich and cholesterol-rich VLDL remnants during exaggerated postprandial triglyceridemia in normolipidemic patients with coronary artery disease. Circulation. 101: 227–230.[Abstract/Free Full Text]

  30. Steinbrecher, U. P., and J. L. Witztum. 1984. Glucosylation of low-density lipoproteins to an extent comparable to that seen in diabetes slows their catabolism. Diabetes. 33: 130–134.[Abstract]

  31. Wade, D. P., B. L. Knight, and A. K. Soutar. 1989. Regulation of low-density-lipoprotein-receptor mRNA by insulin in human hepatoma Hep G2 cells. Eur. J. Biochem. 181: 727–731.[Medline]

  32. Duvillard, L., F. Pont, E. Florentin, C. Galland-Jos, P. Gambert, and B. Verges. 2000. Metabolic abnormalities of apolipoprotein B-containing lipoproteins in non-insulin-dependent diabetes: a stable isotope kinetic study. Eur. J. Clin. Invest. 30: 685–694.[CrossRef][Medline]


Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati    What's this?


This article has been cited by other articles:


Home page
 Arterioscler. Thromb. Vasc. Bio.Home page
M. Pavlic, R. Valero, H. Duez, C. Xiao, L. Szeto, B. W. Patterson, and G. F. Lewis
Triglyceride-Rich Lipoprotein-Associated Apolipoprotein C-III Production Is Stimulated by Plasma Free Fatty Acids in Humans
Arterioscler. Thromb. Vasc. Biol., September 1, 2008; 28(9): 1660 - 1665.
[Abstract] [Full Text] [PDF]

Home page
 CirculationHome page
H. Duez, B. Lamarche, R. Valero, M. Pavlic, S. Proctor, C. Xiao, L. Szeto, B. W. Patterson, and G. F. Lewis
Both Intestinal and Hepatic Lipoprotein Production Are Stimulated by an Acute Elevation of Plasma Free Fatty Acids in Humans
Circulation, May 6, 2008; 117(18): 2369 - 2376.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
M600548-JLR200v1
48/6/1336    most recent
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Hogue, J.-C.
Right arrow Articles by Couture, P.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Hogue, J.-C.
Right arrow Articles by Couture, P.
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati  
What's this?

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
 All ASBMB Journals   Journal of Biological Chemistry 
 Molecular and Cellular Proteomics   ASBMB Today