Brian Barrows | OCAD University (original) (raw)

Papers by Brian Barrows

Research paper thumbnail of Testing and Validation of High Density Resequencing Microarray for Broad Range Biothreat Agents Detection

PLOS One, 2009

Rapid and effective detection and identification of emerging microbiological threats and potentia... more Rapid and effective detection and identification of emerging microbiological threats and potential biowarfare agents is very challenging when using traditional culture-based methods. Contemporary molecular techniques, relying upon reverse transcription and/or polymerase chain reaction (RT-PCR/PCR) provide a rapid and effective alternative, however, such assays are generally designed and optimized to detect only a limited number of targets, and seldom are capable of differentiation among variants of detected targets. To meet these challenges, we have designed a broad-range resequencing pathogen microarray (RPM) for detection of tropical and emerging infectious agents (TEI) including biothreat agents: RPM-TEI v 1.0 (RPM-TEI). The scope of the RPM-TEI assay enables detection and differential identification of 84 types of pathogens and 13 toxin genes, including most of the class A, B and C select agents as defined by the Centers for Disease Control and Prevention (CDC, Atlanta, GA). Due to the high risks associated with handling these particular target pathogens, the sensitivity validation of the RPM-TEI has been performed using an innovative approach, in which synthetic DNA fragments are used as templates for testing the assay's limit of detection (LOD). Assay specificity and sensitivity was subsequently confirmed by testing with full-length genomic nucleic acids of selected agents. The LOD for a majority of the agents detected by RPM-TEI was determined to be at least 10 4 copies per test. Our results also show that the RPM-TEI assay not only detects and identifies agents, but is also able to differentiate near neighbors of the same agent types, such as closely related strains of filoviruses of the Ebola Zaire group, or the Machupo and Lassa arenaviruses. Furthermore, each RPM-TEI assay results in specimen-specific agent gene sequence information that can be used to assess pathogenicity, mutations, and virulence markers, results that are not generally available from multiplexed RT-PCR/PCR-based detection assays.

Research paper thumbnail of Testing and Validation of High Density Resequencing Microarray for Broad Range Biothreat Agents Detection

PLOS One, 2009

Rapid and effective detection and identification of emerging microbiological threats and potentia... more Rapid and effective detection and identification of emerging microbiological threats and potential biowarfare agents is very challenging when using traditional culture-based methods. Contemporary molecular techniques, relying upon reverse transcription and/or polymerase chain reaction (RT-PCR/PCR) provide a rapid and effective alternative, however, such assays are generally designed and optimized to detect only a limited number of targets, and seldom are capable of differentiation among variants of detected targets. To meet these challenges, we have designed a broad-range resequencing pathogen microarray (RPM) for detection of tropical and emerging infectious agents (TEI) including biothreat agents: RPM-TEI v 1.0 (RPM-TEI). The scope of the RPM-TEI assay enables detection and differential identification of 84 types of pathogens and 13 toxin genes, including most of the class A, B and C select agents as defined by the Centers for Disease Control and Prevention (CDC, Atlanta, GA). Due to the high risks associated with handling these particular target pathogens, the sensitivity validation of the RPM-TEI has been performed using an innovative approach, in which synthetic DNA fragments are used as templates for testing the assay's limit of detection (LOD). Assay specificity and sensitivity was subsequently confirmed by testing with full-length genomic nucleic acids of selected agents. The LOD for a majority of the agents detected by RPM-TEI was determined to be at least 10 4 copies per test. Our results also show that the RPM-TEI assay not only detects and identifies agents, but is also able to differentiate near neighbors of the same agent types, such as closely related strains of filoviruses of the Ebola Zaire group, or the Machupo and Lassa arenaviruses. Furthermore, each RPM-TEI assay results in specimen-specific agent gene sequence information that can be used to assess pathogenicity, mutations, and virulence markers, results that are not generally available from multiplexed RT-PCR/PCR-based detection assays.

Research paper thumbnail of Contributions of Different Fatty Acid Sources to Very Low-Density Lipoprotein-Triacylglycerol in the Fasted and Fed States

Journal of Clinical Endocrinology & Metabolism, 2006

The liver's regulation of fatty acids (FAs) postprandially may contribute... more The liver's regulation of fatty acids (FAs) postprandially may contribute to risk of metabolic diseases. Measurements of steady-state metabolism were used to investigate sources of FAs used for very low-density lipoprotein (VLDL)-triacylglycerol (TG) synthesis during fasting and feeding in vivo. Subjects were duodenally fed a formula labeled with the stable isotope glyceryl tri-palmitate-d(31) and iv infused with [1,2,3,4-(13)C(4)]-palmitatic acid and [1-(13)C(1)]-acetate to quantitate the liver's use of FAs originating from adipose tissue and de novo lipogenesis. This study of healthy men (n = 12; body mass index, 24.4 +/- 2.7 kg/m(2)) was conducted at a General Clinical Research Center. Concentrations of metabolites during fasting and feeding, sources of FAs used for lipoprotein synthesis, rate of appearance of serum nonesterified FA (NEFA), and VLDL-TG were measured. During fasting, 77.2 +/- 14.0% of VLDL-TG was derived from adipose FA recycling and 4.0 +/- 3.6% from lipogenesis; with feeding, 43.6 +/- 18.6% came from adipose FAs (P < 0.001), 8.2 +/- 5.1% from lipogenesis (P < 0.001), 15.2 +/- 13.7% from uptake of chylomicron-remnant TG, and 10.3 +/- 6.9% from dietary FA spillover into the serum NEFA pool. Fed-state VLDL-TG from NEFA reesterification decreased in proportion to the reduction in adipose NEFA appearance. These data: 1) quantify the extent to which the healthy liver manages its use of different sources of FAs that flow to it, 2) demonstrate how the postprandial reduction in adipose-NEFA flux may be partially replaced by other sources, and 3) highlight the potential for dietary FA spillover to support the continued dominance of NEFA as a substrate for VLDL-TG synthesis.

Research paper thumbnail of Spillover of Dietary Fatty Acids and Use of Serum Nonesterified Fatty Acids for the Synthesis of VLDL-Triacylglycerol Under Two Different Feeding Regimens

Diabetes, 2005

The present study quantified dietary fatty acid flux in healthy men (n ‫؍‬ 6) who were fed a liqu... more The present study quantified dietary fatty acid flux in healthy men (n ‫؍‬ 6) who were fed a liquid formula through a duodenal feeding tube (continuous feeding group) or who consumed the same formula in meals (meal feeding group). A triacylglycerol (TAG) stable isotope was added to the formula to determine the entry of dietary fatty acids into the serum and its clearance to the liver and resecretion into serum via VLDL. The contribution of dietary fatty acids to serum nonesterified fatty acids (NEFAs) was higher with meal feeding (24.4 ؎ 2.6%) compared with continuous feeding (10.8 ؎ 2.9%, P < 0.01) and, when multiplied by the NEFA concentration, resulted in similar absolute fatty acid spillover. Diet-derived NEFAs subsequently represented 10.6 ؎ 1.2% and 4.7 ؎ 1.3% of hepatic VLDL-TAG (meal feeding vs. continuous feeding, respectively, P ‫؍‬ 0.004). Chylomicron remnant uptake by the liver contributed 9.3 ؎ 1.9% of fatty acids to hepatic VLDL-TAG synthesis with meal feeding compared with continuous feeding (4.4 ؎ 0.8%, P < 0.03). These data suggest that the extent of dietary fatty acid recycling via serum NEFAs and VLDL-TAG is determined by the rate of delivery of dietary fat to the intestine. The inefficient removal of dietary fat from the circulation may maintain VLDL-TAG production but may also result in prolonged postprandial lipemia. Diabetes 54:2668 -2673, 2005 E levated postprandial lipemia has been shown to correlate with increased cardiovascular disease risk (1). Triacylglycerols (TAGs) taken in from the diet are primarily stored in adipose and utilized for energy by peripheral tissues, but a portion of these fatty acids can clear to the liver. That the liver may coordinate its use of fatty acids that flow to it from many different sources (e.g., adipose, diet, etc.) provides an elegant example of physiology. However, in settings of expansion of adipose stores, or higher dietary fat intake, the liver's ability to handle alterations in fatty acid flux may be compromised. Studies in fasting individuals have shown that dysregulation of hepatic fatty acid usage of adipose-derived nonesterified fatty acids (NEFAs) contributes to impaired glucose tolerance (2), and an understanding of liver fatty acid partitioning during fasting and feeding will be necessary to formulate future dietary and therapeutic strategies for the treatment of elevated blood lipids in insulin resistance and diabetes. In a companion article (3) in this issue of Diabetes, we have described the use of multiple stable isotopes to quantitate the flux of fatty acids into the liver, where they are subsequently reassembled to TAGs, incorporated into VLDL particles, and secreted from the liver. In that article, fatty acids derived from adipose, lipogenesis, and diet were quantified in healthy men. Little is known about the role dietary fatty acid flux plays in liver lipid metabolism, and in the present analysis, we focused specifically on routes of dietary fatty acid entry into the serum and liver. To assess the influence of the rate of fatty acid influx, we compared the metabolism of dietary fatty acids when they were infused slowly into the duodenum and when they were consumed by mouth in meals.

Research paper thumbnail of Contributions of Different Fatty Acid Sources to Very Low-Density Lipoprotein-Triacylglycerol in the Fasted and Fed States

The liver's regulation of fatty acids (FAs) postprandially may contribute to risk of metabolic di... more The liver's regulation of fatty acids (FAs) postprandially may contribute to risk of metabolic diseases.

Research paper thumbnail of Increased Dietary Substrate Delivery Alters Hepatic Fatty Acid Recycling in Healthy Men

Diabetes, 2005

Sources of fatty acids flowing to the liver may be used for triacylglycerol (TAG) synthesis. Our ... more Sources of fatty acids flowing to the liver may be used for triacylglycerol (TAG) synthesis. Our objective was to quantify contributions of nonesterified fatty acids (NEFAs), de novo lipogenesis, and dietary fatty acids to VLDL-TAG in the fed state after meal feeding in healthy subjects (n ‫؍‬ 6). The effect of substrate delivery rate was also determined by comparison with data obtained under a continuous-feeding regimen. A liquid diet was administered by mouth or via feeding tube. Contributions of NEFAs, de novo lipogenesis, and dietary fatty acids to VLDL-TAG were quantified using stable isotopes and gas chromatography-mass spectrometry. Contribution of NEFAs to VLDL-TAG was similar under meal feeding and continuous feeding, although insulin area under the curve (AUC) was greater under meal feeding (1,597 ؎ 455 vs. 471 ؎ 484 pmol ⅐ h ⅐ l ؊1 , P < 0.004). Lipogenesis achieved a higher AUC with meal feeding versus continuous feeding (88.7 ؎ 84.4 vs. 1.9 ؎ 19.3 mol ⅐ h ⅐ l ؊1 , P ‫؍‬ 0.03) supporting greater stimulation of de novo lipogenesis from increased glucose delivery rate. The contribution of dietary fatty acids to VLDL-TAG was also greater with meal feeding. These data demonstrate for the first time in humans the well-coordinated use of fatty acids by the liver during the transition from fasted to fed states and highlight the dominant role of NEFAs for VLDL-TAG synthesis in both states. Diabetes

Research paper thumbnail of Dietary ω-3 Polyunsaturated Fatty Acids Enhance Adiponectin Expression and Protect Against Pressure Overload-Induced Left Ventricular Hypertrophy and Dysfunction

Journal of Cardiac Failure, 2007

Research paper thumbnail of Transcription Profiles of Failing and Non-Failing Hearts after Two-Cycle RNA Amplification from Biopsy-Sized Samples

Journal of Cardiac Failure, 2006

Research paper thumbnail of Dietary supplementation with ω-3 PUFA increases adiponectin and attenuates ventricular remodeling and dysfunction with pressure overload

Cardiovascular Research, 2007

Objective-Epidemiological studies suggest that consumption of ω-3 polyunsaturated fatty acids (ω-... more Objective-Epidemiological studies suggest that consumption of ω-3 polyunsaturated fatty acids (ω-3 PUFA) decreases the risk of heart failure. We assessed the effects of dietary supplementation with ω-3 PUFA from fish oil on the response of the left ventricle (LV) to arterial pressure overload.

Research paper thumbnail of Low-Carbohydrate/High-Fat Diet Attenuates Pressure Overload–Induced Ventricular Remodeling and Dysfunction

Journal of Cardiac Failure, 2008

Background-It is not known how carbohydrate and fat intake impact the development of left ventric... more Background-It is not known how carbohydrate and fat intake impact the development of left ventricular (LV) hypertrophy and contractile dysfunction in response to pressure overload. We hypothesized that a low carbohydrate/high fat diet prevents LV hypertrophy and dysfunction compared to high carbohydrate diets.

Research paper thumbnail of Dietary supplementation with ω-3 PUFA increases adiponectin and attenuates ventricular remodeling and dysfunction with pressure overload

Objective: Epidemiological studies suggest that consumption of ω-3 polyunsaturated fatty acids (ω... more Objective: Epidemiological studies suggest that consumption of ω-3 polyunsaturated fatty acids (ω-3 PUFA) decreases the risk of heart failure. We assessed the effects of dietary supplementation with ω-3 PUFA from fish oil on the response of the left ventricle (LV) to arterial pressure overload. Methods: Male Wistar rats were fed a standard chow or a ω-3 PUFA-supplemented diet. After 1 week rats underwent abdominal aortic banding or sham surgery (n = 9-12/group). LV function was assessed by echocardiography after 8 weeks. In addition, we studied the effect of ω-3 PUFA on the cardioprotective adipocyte-derived hormone adiponectin, which may alter the pro-growth serine-threonine kinase Akt. Results: Banding increased LV mass to a greater extent with the standard chow (31%) than with ω-3 PUFA (18%). LV end diastolic and systolic volumes were increased by 19% and 105% with standard chow, respectively, but were unchanged with ω-3 PUFA. The expression of adiponectin was up-regulated in adipose tissue, and the plasma adiponectin concentration was significantly elevated. Treatment with ω-3 PUFA increased total Akt protein expression in the heart, but decreased the fraction of Akt in the active phosphorylated form, and thus did not alter the amount of active phospho-Akt. Conclusion: Dietary supplementation with ω-3 PUFA attenuated pressure overload-induced LV dysfunction, which was associated with elevated plasma adiponectin.

Research paper thumbnail of Fish oil, but not flaxseed oil, decreases inflammation and prevents pressure overload-induced cardiac dysfunction

Cardiovascular Research, 2008

Aims Clinical studies suggest that intake of v-3 polyunsaturated fatty acids (v-3 PUFA) may lower... more Aims Clinical studies suggest that intake of v-3 polyunsaturated fatty acids (v-3 PUFA) may lower the incidence of heart failure. Dietary supplementation with v-3 PUFA exerts metabolic and antiinflammatory effects that could prevent left ventricle (LV) pathology; however, it is unclear whether these effects occur at clinically relevant doses and whether there are differences between v-3 PUFA from fish [eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] and vegetable sources [a-linolenic acid (ALA)].

Research paper thumbnail of Robust gene expression with amplified RNA from biopsy-sized human heart tissue

Journal of Molecular and Cellular Cardiology, 2007

The need to assess heart failure at an early stage highlights the importance of accurate microarr... more The need to assess heart failure at an early stage highlights the importance of accurate microarray analysis using small tissue samples. To test our ability to obtain high quality RNA from biopsy-sized cardiac specimens, amplification was performed on RNA from biopsy-sized samples of left ventricle (LV) tissue from one explanted failing human heart and one non-failing heart. Two methods were used: one-cycle (1C) amplification of 1.6 μg of RNA, and two-cycle (2C) amplification of 50 ng of RNA. The resulting cRNA was hybridized to Affymetrix GeneChip® arrays. Over 65% of all differentially expressed genes for failing vs non-failing hearts were concordant between 1C and 2C RNA amplification. Differentially expressed genes between 1C and 2C RNA amplification in our study were highly correlated (R 2 = 0.957 and changes in gene expression agreed with prior studies on genes and heart failure; e.g., decreased α-myosin heavy chain and α-tropomyosin, as well as increased expression of insulinlike growth factor). Two cycles of amplification from cardiac biopsies will permit accurate transcription profiling of heart failure at presymptomatic stages. Ability to measure gene expression from nanogram amounts of RNA will provide new opportunities to predict progression to symptomatic heart failure, and to identify potential targets for therapy.

Research paper thumbnail of High sugar diet adversely effects gene expression, cardiac function and survival with pressure overload

Journal of Molecular and Cellular Cardiology, 2007

We created a mouse model of cardiac-specific conditional overexpression of calstabin 2 in the B6/... more We created a mouse model of cardiac-specific conditional overexpression of calstabin 2 in the B6/D2 genetic background using the Tet-off model. In this model, transgene expression is repressed by adding doxycycline (Dox) to mouse chow. Because mice are submitted to thoracic aorta constriction (TAC), we wanted to know if Dox has an influence on the development of ventricular hypertrophy (VH) and progression to heart failure (HF). TAC or sham operation was performed in 1-month-old B6D2 male mice under anesthesia. Mice were randomly assigned to standard mouse chow (St) or St plus doxycycline (1 g/kg, Dox). One or two months post-TAC, mice underwent cardiac catheterization and were killed. BNP mRNA was quantified in ventricles by QRT-PCR. One month post-TAC, VH was larger in TAC + Dox than in TAC+ St (51 vs. 39%, p< 0.05). Similarly, the proportion of mice with HF (lung weight > lung weight in shams +2 SD) was higher in the former than in the latter (79 vs. 36%, p<0.05). Two months after TAC, VH was further increased to 91% in TAC + Dox and to 98% in TAC + St (ns, p <0.05 vs. 1 month after TAC). At this stage, the proportion of mice with HF was 74 and 60%, respectively (ns). These results were confirmed by the hemodynamic study. One month post-TAC, BNP mRNA level was 1.8 times higher in TAC + Dox than in TAC + St (p <0.05). We conclude that doxycycline regimen accelerates the development of VH and progression to HF following TAC in mice. This indicates that great care should be taken in the experimental plan and data interpretation in models of LVH performed in TG mice using the Tet-on/Tet-off conditional expression system.

Research paper thumbnail of High-sugar diets increase cardiac dysfunction and mortality in hypertension compared to low-carbohydrate or high-starch diets

Journal of Hypertension, 2008

Objective-Sugar consumption affects insulin release and, in hypertension, may stimulate cardiac s... more Objective-Sugar consumption affects insulin release and, in hypertension, may stimulate cardiac signaling mechanisms that accelerate left ventricular hypertrophy and the development of heart failure. We investigated the effects of high-fructose or sucrose diets on ventricular function and mortality in hypertensive Dahl salt-sensitive rats.

Research paper thumbnail of Testing and Validation of High Density Resequencing Microarray for Broad Range Biothreat Agents Detection

PLOS One, 2009

Rapid and effective detection and identification of emerging microbiological threats and potentia... more Rapid and effective detection and identification of emerging microbiological threats and potential biowarfare agents is very challenging when using traditional culture-based methods. Contemporary molecular techniques, relying upon reverse transcription and/or polymerase chain reaction (RT-PCR/PCR) provide a rapid and effective alternative, however, such assays are generally designed and optimized to detect only a limited number of targets, and seldom are capable of differentiation among variants of detected targets. To meet these challenges, we have designed a broad-range resequencing pathogen microarray (RPM) for detection of tropical and emerging infectious agents (TEI) including biothreat agents: RPM-TEI v 1.0 (RPM-TEI). The scope of the RPM-TEI assay enables detection and differential identification of 84 types of pathogens and 13 toxin genes, including most of the class A, B and C select agents as defined by the Centers for Disease Control and Prevention (CDC, Atlanta, GA). Due to the high risks associated with handling these particular target pathogens, the sensitivity validation of the RPM-TEI has been performed using an innovative approach, in which synthetic DNA fragments are used as templates for testing the assay's limit of detection (LOD). Assay specificity and sensitivity was subsequently confirmed by testing with full-length genomic nucleic acids of selected agents. The LOD for a majority of the agents detected by RPM-TEI was determined to be at least 10 4 copies per test. Our results also show that the RPM-TEI assay not only detects and identifies agents, but is also able to differentiate near neighbors of the same agent types, such as closely related strains of filoviruses of the Ebola Zaire group, or the Machupo and Lassa arenaviruses. Furthermore, each RPM-TEI assay results in specimen-specific agent gene sequence information that can be used to assess pathogenicity, mutations, and virulence markers, results that are not generally available from multiplexed RT-PCR/PCR-based detection assays.

Research paper thumbnail of Testing and Validation of High Density Resequencing Microarray for Broad Range Biothreat Agents Detection

PLOS One, 2009

Rapid and effective detection and identification of emerging microbiological threats and potentia... more Rapid and effective detection and identification of emerging microbiological threats and potential biowarfare agents is very challenging when using traditional culture-based methods. Contemporary molecular techniques, relying upon reverse transcription and/or polymerase chain reaction (RT-PCR/PCR) provide a rapid and effective alternative, however, such assays are generally designed and optimized to detect only a limited number of targets, and seldom are capable of differentiation among variants of detected targets. To meet these challenges, we have designed a broad-range resequencing pathogen microarray (RPM) for detection of tropical and emerging infectious agents (TEI) including biothreat agents: RPM-TEI v 1.0 (RPM-TEI). The scope of the RPM-TEI assay enables detection and differential identification of 84 types of pathogens and 13 toxin genes, including most of the class A, B and C select agents as defined by the Centers for Disease Control and Prevention (CDC, Atlanta, GA). Due to the high risks associated with handling these particular target pathogens, the sensitivity validation of the RPM-TEI has been performed using an innovative approach, in which synthetic DNA fragments are used as templates for testing the assay's limit of detection (LOD). Assay specificity and sensitivity was subsequently confirmed by testing with full-length genomic nucleic acids of selected agents. The LOD for a majority of the agents detected by RPM-TEI was determined to be at least 10 4 copies per test. Our results also show that the RPM-TEI assay not only detects and identifies agents, but is also able to differentiate near neighbors of the same agent types, such as closely related strains of filoviruses of the Ebola Zaire group, or the Machupo and Lassa arenaviruses. Furthermore, each RPM-TEI assay results in specimen-specific agent gene sequence information that can be used to assess pathogenicity, mutations, and virulence markers, results that are not generally available from multiplexed RT-PCR/PCR-based detection assays.

Research paper thumbnail of Contributions of Different Fatty Acid Sources to Very Low-Density Lipoprotein-Triacylglycerol in the Fasted and Fed States

Journal of Clinical Endocrinology & Metabolism, 2006

The liver&amp;amp;amp;amp;#39;s regulation of fatty acids (FAs) postprandially may contribute... more The liver&amp;amp;amp;amp;#39;s regulation of fatty acids (FAs) postprandially may contribute to risk of metabolic diseases. Measurements of steady-state metabolism were used to investigate sources of FAs used for very low-density lipoprotein (VLDL)-triacylglycerol (TG) synthesis during fasting and feeding in vivo. Subjects were duodenally fed a formula labeled with the stable isotope glyceryl tri-palmitate-d(31) and iv infused with [1,2,3,4-(13)C(4)]-palmitatic acid and [1-(13)C(1)]-acetate to quantitate the liver&amp;amp;amp;amp;#39;s use of FAs originating from adipose tissue and de novo lipogenesis. This study of healthy men (n = 12; body mass index, 24.4 +/- 2.7 kg/m(2)) was conducted at a General Clinical Research Center. Concentrations of metabolites during fasting and feeding, sources of FAs used for lipoprotein synthesis, rate of appearance of serum nonesterified FA (NEFA), and VLDL-TG were measured. During fasting, 77.2 +/- 14.0% of VLDL-TG was derived from adipose FA recycling and 4.0 +/- 3.6% from lipogenesis; with feeding, 43.6 +/- 18.6% came from adipose FAs (P &amp;amp;amp;amp;lt; 0.001), 8.2 +/- 5.1% from lipogenesis (P &amp;amp;amp;amp;lt; 0.001), 15.2 +/- 13.7% from uptake of chylomicron-remnant TG, and 10.3 +/- 6.9% from dietary FA spillover into the serum NEFA pool. Fed-state VLDL-TG from NEFA reesterification decreased in proportion to the reduction in adipose NEFA appearance. These data: 1) quantify the extent to which the healthy liver manages its use of different sources of FAs that flow to it, 2) demonstrate how the postprandial reduction in adipose-NEFA flux may be partially replaced by other sources, and 3) highlight the potential for dietary FA spillover to support the continued dominance of NEFA as a substrate for VLDL-TG synthesis.

Research paper thumbnail of Spillover of Dietary Fatty Acids and Use of Serum Nonesterified Fatty Acids for the Synthesis of VLDL-Triacylglycerol Under Two Different Feeding Regimens

Diabetes, 2005

The present study quantified dietary fatty acid flux in healthy men (n ‫؍‬ 6) who were fed a liqu... more The present study quantified dietary fatty acid flux in healthy men (n ‫؍‬ 6) who were fed a liquid formula through a duodenal feeding tube (continuous feeding group) or who consumed the same formula in meals (meal feeding group). A triacylglycerol (TAG) stable isotope was added to the formula to determine the entry of dietary fatty acids into the serum and its clearance to the liver and resecretion into serum via VLDL. The contribution of dietary fatty acids to serum nonesterified fatty acids (NEFAs) was higher with meal feeding (24.4 ؎ 2.6%) compared with continuous feeding (10.8 ؎ 2.9%, P < 0.01) and, when multiplied by the NEFA concentration, resulted in similar absolute fatty acid spillover. Diet-derived NEFAs subsequently represented 10.6 ؎ 1.2% and 4.7 ؎ 1.3% of hepatic VLDL-TAG (meal feeding vs. continuous feeding, respectively, P ‫؍‬ 0.004). Chylomicron remnant uptake by the liver contributed 9.3 ؎ 1.9% of fatty acids to hepatic VLDL-TAG synthesis with meal feeding compared with continuous feeding (4.4 ؎ 0.8%, P < 0.03). These data suggest that the extent of dietary fatty acid recycling via serum NEFAs and VLDL-TAG is determined by the rate of delivery of dietary fat to the intestine. The inefficient removal of dietary fat from the circulation may maintain VLDL-TAG production but may also result in prolonged postprandial lipemia. Diabetes 54:2668 -2673, 2005 E levated postprandial lipemia has been shown to correlate with increased cardiovascular disease risk (1). Triacylglycerols (TAGs) taken in from the diet are primarily stored in adipose and utilized for energy by peripheral tissues, but a portion of these fatty acids can clear to the liver. That the liver may coordinate its use of fatty acids that flow to it from many different sources (e.g., adipose, diet, etc.) provides an elegant example of physiology. However, in settings of expansion of adipose stores, or higher dietary fat intake, the liver's ability to handle alterations in fatty acid flux may be compromised. Studies in fasting individuals have shown that dysregulation of hepatic fatty acid usage of adipose-derived nonesterified fatty acids (NEFAs) contributes to impaired glucose tolerance (2), and an understanding of liver fatty acid partitioning during fasting and feeding will be necessary to formulate future dietary and therapeutic strategies for the treatment of elevated blood lipids in insulin resistance and diabetes. In a companion article (3) in this issue of Diabetes, we have described the use of multiple stable isotopes to quantitate the flux of fatty acids into the liver, where they are subsequently reassembled to TAGs, incorporated into VLDL particles, and secreted from the liver. In that article, fatty acids derived from adipose, lipogenesis, and diet were quantified in healthy men. Little is known about the role dietary fatty acid flux plays in liver lipid metabolism, and in the present analysis, we focused specifically on routes of dietary fatty acid entry into the serum and liver. To assess the influence of the rate of fatty acid influx, we compared the metabolism of dietary fatty acids when they were infused slowly into the duodenum and when they were consumed by mouth in meals.

Research paper thumbnail of Contributions of Different Fatty Acid Sources to Very Low-Density Lipoprotein-Triacylglycerol in the Fasted and Fed States

The liver's regulation of fatty acids (FAs) postprandially may contribute to risk of metabolic di... more The liver's regulation of fatty acids (FAs) postprandially may contribute to risk of metabolic diseases.

Research paper thumbnail of Increased Dietary Substrate Delivery Alters Hepatic Fatty Acid Recycling in Healthy Men

Diabetes, 2005

Sources of fatty acids flowing to the liver may be used for triacylglycerol (TAG) synthesis. Our ... more Sources of fatty acids flowing to the liver may be used for triacylglycerol (TAG) synthesis. Our objective was to quantify contributions of nonesterified fatty acids (NEFAs), de novo lipogenesis, and dietary fatty acids to VLDL-TAG in the fed state after meal feeding in healthy subjects (n ‫؍‬ 6). The effect of substrate delivery rate was also determined by comparison with data obtained under a continuous-feeding regimen. A liquid diet was administered by mouth or via feeding tube. Contributions of NEFAs, de novo lipogenesis, and dietary fatty acids to VLDL-TAG were quantified using stable isotopes and gas chromatography-mass spectrometry. Contribution of NEFAs to VLDL-TAG was similar under meal feeding and continuous feeding, although insulin area under the curve (AUC) was greater under meal feeding (1,597 ؎ 455 vs. 471 ؎ 484 pmol ⅐ h ⅐ l ؊1 , P < 0.004). Lipogenesis achieved a higher AUC with meal feeding versus continuous feeding (88.7 ؎ 84.4 vs. 1.9 ؎ 19.3 mol ⅐ h ⅐ l ؊1 , P ‫؍‬ 0.03) supporting greater stimulation of de novo lipogenesis from increased glucose delivery rate. The contribution of dietary fatty acids to VLDL-TAG was also greater with meal feeding. These data demonstrate for the first time in humans the well-coordinated use of fatty acids by the liver during the transition from fasted to fed states and highlight the dominant role of NEFAs for VLDL-TAG synthesis in both states. Diabetes

Research paper thumbnail of Dietary ω-3 Polyunsaturated Fatty Acids Enhance Adiponectin Expression and Protect Against Pressure Overload-Induced Left Ventricular Hypertrophy and Dysfunction

Journal of Cardiac Failure, 2007

Research paper thumbnail of Transcription Profiles of Failing and Non-Failing Hearts after Two-Cycle RNA Amplification from Biopsy-Sized Samples

Journal of Cardiac Failure, 2006

Research paper thumbnail of Dietary supplementation with ω-3 PUFA increases adiponectin and attenuates ventricular remodeling and dysfunction with pressure overload

Cardiovascular Research, 2007

Objective-Epidemiological studies suggest that consumption of ω-3 polyunsaturated fatty acids (ω-... more Objective-Epidemiological studies suggest that consumption of ω-3 polyunsaturated fatty acids (ω-3 PUFA) decreases the risk of heart failure. We assessed the effects of dietary supplementation with ω-3 PUFA from fish oil on the response of the left ventricle (LV) to arterial pressure overload.

Research paper thumbnail of Low-Carbohydrate/High-Fat Diet Attenuates Pressure Overload–Induced Ventricular Remodeling and Dysfunction

Journal of Cardiac Failure, 2008

Background-It is not known how carbohydrate and fat intake impact the development of left ventric... more Background-It is not known how carbohydrate and fat intake impact the development of left ventricular (LV) hypertrophy and contractile dysfunction in response to pressure overload. We hypothesized that a low carbohydrate/high fat diet prevents LV hypertrophy and dysfunction compared to high carbohydrate diets.

Research paper thumbnail of Dietary supplementation with ω-3 PUFA increases adiponectin and attenuates ventricular remodeling and dysfunction with pressure overload

Objective: Epidemiological studies suggest that consumption of ω-3 polyunsaturated fatty acids (ω... more Objective: Epidemiological studies suggest that consumption of ω-3 polyunsaturated fatty acids (ω-3 PUFA) decreases the risk of heart failure. We assessed the effects of dietary supplementation with ω-3 PUFA from fish oil on the response of the left ventricle (LV) to arterial pressure overload. Methods: Male Wistar rats were fed a standard chow or a ω-3 PUFA-supplemented diet. After 1 week rats underwent abdominal aortic banding or sham surgery (n = 9-12/group). LV function was assessed by echocardiography after 8 weeks. In addition, we studied the effect of ω-3 PUFA on the cardioprotective adipocyte-derived hormone adiponectin, which may alter the pro-growth serine-threonine kinase Akt. Results: Banding increased LV mass to a greater extent with the standard chow (31%) than with ω-3 PUFA (18%). LV end diastolic and systolic volumes were increased by 19% and 105% with standard chow, respectively, but were unchanged with ω-3 PUFA. The expression of adiponectin was up-regulated in adipose tissue, and the plasma adiponectin concentration was significantly elevated. Treatment with ω-3 PUFA increased total Akt protein expression in the heart, but decreased the fraction of Akt in the active phosphorylated form, and thus did not alter the amount of active phospho-Akt. Conclusion: Dietary supplementation with ω-3 PUFA attenuated pressure overload-induced LV dysfunction, which was associated with elevated plasma adiponectin.

Research paper thumbnail of Fish oil, but not flaxseed oil, decreases inflammation and prevents pressure overload-induced cardiac dysfunction

Cardiovascular Research, 2008

Aims Clinical studies suggest that intake of v-3 polyunsaturated fatty acids (v-3 PUFA) may lower... more Aims Clinical studies suggest that intake of v-3 polyunsaturated fatty acids (v-3 PUFA) may lower the incidence of heart failure. Dietary supplementation with v-3 PUFA exerts metabolic and antiinflammatory effects that could prevent left ventricle (LV) pathology; however, it is unclear whether these effects occur at clinically relevant doses and whether there are differences between v-3 PUFA from fish [eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] and vegetable sources [a-linolenic acid (ALA)].

Research paper thumbnail of Robust gene expression with amplified RNA from biopsy-sized human heart tissue

Journal of Molecular and Cellular Cardiology, 2007

The need to assess heart failure at an early stage highlights the importance of accurate microarr... more The need to assess heart failure at an early stage highlights the importance of accurate microarray analysis using small tissue samples. To test our ability to obtain high quality RNA from biopsy-sized cardiac specimens, amplification was performed on RNA from biopsy-sized samples of left ventricle (LV) tissue from one explanted failing human heart and one non-failing heart. Two methods were used: one-cycle (1C) amplification of 1.6 μg of RNA, and two-cycle (2C) amplification of 50 ng of RNA. The resulting cRNA was hybridized to Affymetrix GeneChip® arrays. Over 65% of all differentially expressed genes for failing vs non-failing hearts were concordant between 1C and 2C RNA amplification. Differentially expressed genes between 1C and 2C RNA amplification in our study were highly correlated (R 2 = 0.957 and changes in gene expression agreed with prior studies on genes and heart failure; e.g., decreased α-myosin heavy chain and α-tropomyosin, as well as increased expression of insulinlike growth factor). Two cycles of amplification from cardiac biopsies will permit accurate transcription profiling of heart failure at presymptomatic stages. Ability to measure gene expression from nanogram amounts of RNA will provide new opportunities to predict progression to symptomatic heart failure, and to identify potential targets for therapy.

Research paper thumbnail of High sugar diet adversely effects gene expression, cardiac function and survival with pressure overload

Journal of Molecular and Cellular Cardiology, 2007

We created a mouse model of cardiac-specific conditional overexpression of calstabin 2 in the B6/... more We created a mouse model of cardiac-specific conditional overexpression of calstabin 2 in the B6/D2 genetic background using the Tet-off model. In this model, transgene expression is repressed by adding doxycycline (Dox) to mouse chow. Because mice are submitted to thoracic aorta constriction (TAC), we wanted to know if Dox has an influence on the development of ventricular hypertrophy (VH) and progression to heart failure (HF). TAC or sham operation was performed in 1-month-old B6D2 male mice under anesthesia. Mice were randomly assigned to standard mouse chow (St) or St plus doxycycline (1 g/kg, Dox). One or two months post-TAC, mice underwent cardiac catheterization and were killed. BNP mRNA was quantified in ventricles by QRT-PCR. One month post-TAC, VH was larger in TAC + Dox than in TAC+ St (51 vs. 39%, p< 0.05). Similarly, the proportion of mice with HF (lung weight > lung weight in shams +2 SD) was higher in the former than in the latter (79 vs. 36%, p<0.05). Two months after TAC, VH was further increased to 91% in TAC + Dox and to 98% in TAC + St (ns, p <0.05 vs. 1 month after TAC). At this stage, the proportion of mice with HF was 74 and 60%, respectively (ns). These results were confirmed by the hemodynamic study. One month post-TAC, BNP mRNA level was 1.8 times higher in TAC + Dox than in TAC + St (p <0.05). We conclude that doxycycline regimen accelerates the development of VH and progression to HF following TAC in mice. This indicates that great care should be taken in the experimental plan and data interpretation in models of LVH performed in TG mice using the Tet-on/Tet-off conditional expression system.

Research paper thumbnail of High-sugar diets increase cardiac dysfunction and mortality in hypertension compared to low-carbohydrate or high-starch diets

Journal of Hypertension, 2008

Objective-Sugar consumption affects insulin release and, in hypertension, may stimulate cardiac s... more Objective-Sugar consumption affects insulin release and, in hypertension, may stimulate cardiac signaling mechanisms that accelerate left ventricular hypertrophy and the development of heart failure. We investigated the effects of high-fructose or sucrose diets on ventricular function and mortality in hypertensive Dahl salt-sensitive rats.