Western diet changes cardiac acyl-CoA composition in obese rats: a potential role for hepatic lipogenesis

Abstract

The "lipotoxic footprint" of cardiac maladaptation in diet-induced obesity is poorly defined. We investigated how manipulation of dietary lipid and carbohydrate influenced potential lipotoxic species in the failing heart. In Wistar rats, contractile dysfunction develops at 48 weeks on a high-fat/high-carbohydrate "Western" diet, but not on low-fat/high-carbohydrate or high-fat diets. Cardiac content of the lipotoxic candidates--diacylglycerol, ceramide, lipid peroxide, and long-chain acyl-CoA species--was measured at different time points by high-performance liquid chromatography and biochemical assays, as was lipogenic capacity in the heart and liver by qRT-PCR and radiometric assays. Changes in membranes fluidity were also monitored using fluorescence polarization. We report that Western feeding induced a 40% decrease in myocardial palmitoleoyl-CoA content and a similar decrease in the unsaturated-to-saturated fatty acid ratio. These changes were associated with impaired cardiac mitochondrial membrane fluidity. At the same time, hepatic lipogenic capacity was increased in animals fed Western diet (+270% fatty acid elongase activity compared with high-fat diet), while fatty acid desaturase activity decreased over time. Our findings suggest that dysregulation of lipogenesis is a significant component of heart failure in diet-induced obesity.

Figures

Fig. 1.

High-fat diet and Western diet induce similar changes in myocardial lipid byproducts content. Myocardial triacylglycerol (A), diacylglycerol (B), ceramide (C), and TBARS (D), the latter taken as an index of lipid peroxidation, were quantified in the heart of male Wistar rats fed either low-fat/high-carbohydrate diet (HCD; open bars), high-fat diet (HFD; hatched bars), or Western diet (WD; black bars) for short term (ST), intermediate term (IT), or long term (LT). Data are means ± SE of n = 13–18 animals per group per time point. One, two, and three symbols represent P < 0.05, P < 0.01, and P < 0.001, respectively. * = vs. HCD at same age; a = vs. short term; b = vs. intermediate term; c = vs. long term. TBARS, thiobarbituric acid reactive substances.

Fig. 2.

Myocardial long-chain acyl-CoA profile is more profoundly altered by Western diet. A: Total myocardial long-chain acyl-CoA content was determined for male Wistar rats fed either low-fat/high-carbohydrate diet (HCD; open bars), high-fat diet (HFD; hatched bars), or Western diet (WD; black bars) for short term (ST), intermediate term (IT), or long term (LT). Results are expressed in percentage of long-chain acyl-CoA levels determined for animals fed with low-fat/high-carbohydrate diet. B: Myocardial levels of myristoyl-CoA (14:0), palmitoyl-CoA (16:0), palmitoleoyl-CoA (16:1), stearoyl-CoA (18:0), oleoyl-CoA (18:1), and linoleoyl-CoA (18:2) were also quantified separately in the same animals. Data are means ± SE of n = 13–17 animals per group per time point. One, two, and three symbols represent P < 0.05, P < 0.01, and P < 0.001, respectively. * = vs. HCD at same age; # = vs. WD at same age; $ = vs. HFD at same age; a = vs. short term; c = vs. long term.

Fig. 3.

Western feeding induces a dramatic decrease in myocardial unsaturated-to-saturated fatty acid ratio. Myocardial palmitoleoyl-CoA–to–palmitoyl-CoA ratio (16:1)/(16:0) (A), oleoyl-CoA–to–stearoyl-CoA ratio (18:1)/(18:0) (B), and total unsaturated-to-saturated long-chain acyl-CoA species ratio (C) are given for rats fed either low-fat/high-carbohydrate diet (HCD; open bars), high-fat diet (HFD; hatched bars), or Western diet (WD; black bars) for short term (ST), intermediate term (IT), or long term (LT). Data are means ± SE of n = 13–17 animals per group per time point. * = P < 0.05; ** = P < 0.01 vs. HCD at same age; # = P < 0.05 vs. WD at same age; $ = P < 0.05; $$ = P < 0.01 vs. HFD at same age; a = P < 0.05 vs. short term.

Fig. 4.

Hepatic de novo lipogenesis is regulated by diet composition at the transcriptional level. Transcript levels of fatty acid synthase (fasn; A), acetyl-CoA carboxylase 1 (acc1; B), sterol regulatory element-binding proteins 1 (srebp1; C), and carbohydrate response element binding protein (chrebp; D) were quantified by real-time PCR in the liver of Wistar rats fed either low-fat/high-carbohydrate diet (HCD; open bars), high-fat diet (HFD; hatched bars), or Western diet (WD; black bars) for acute term (AT), short term (ST), intermediate term (IT), or long term (LT). Baseline mRNA levels (B; gray bar) were determined from 8-week-old rats fed standard rodent chow for 2 weeks before the beginning of the feeding protocol. Data are means ± SE of n = 13–17 animals per group per time point (except baseline; n = 7). One, two, and three symbols represent P < 0.05, P < 0.01, and P < 0.001, respectively. # = vs. WD at same age; $ = vs. HFD at same age; a = vs. baseline; b = vs. acute term; c = vs. short term; d = vs. intermediate term.

Fig. 5.

The activity of lipogenic enzymes is differentially regulated with long-term Western feeding. Transcript levels of the long chain fatty acid elongase ELOVL family member 6 (elovl6; A) and stearoyl-CoA desaturase 1 (scd1; C) were quantified by real-time PCR in the liver of Wistar rats fed either low-fat/high-carbohydrate diet (HCD; open bars), high-fat diet (HFD; hatched bars), or Western diet (WD; black bars) for acute term (AT), short term (ST), intermediate term (IT), or long term (LT). Baseline mRNA levels (B; gray bar) were determined from 8-week-old rats fed standard rodent chow for 2 weeks before the beginning of the feeding protocol. Data are means ± SE of n = 13–17 animals per group per time point (except baseline; n = 7). To confirm the variations observed at the mRNA level, hepatic acyl-CoA elongase (B) and delta-9 desaturase (D) activities were also assessed over time. Data are means ± SE of n = 6 animals per group per time point. One, two, and three symbols represent P < 0.05, P < 0.01, and P < 0.001, respectively. # = vs. WD at same age; $ = vs. HFD at same age; a = vs. baseline; b = vs. acute term; c = vs. short term; d = vs. intermediate term.

Fig. 6.

Plasma monounsaturated-to-saturated fatty acid ratios are differentially altered by the diets. Plasma palmitoleate-to-palmitate (16:1)/(16:0) (A) and oleate-to-stearate (18:1)/(18:0) (B) ratios are given for rats fed either low-fat/high-carbohydrate diet (HCD; open bars), high-fat diet (HFD; hatched bars), or Western diet (WD; black bars) for short term (ST), intermediate term (IT), or long term (LT). Data are means ± SE of n = 9 animals per group per time point. ### = P < 0.001 vs. WD at same age; $$$ = P < 0.001 vs. HFD at same age; aaa = P < 0.001 vs. short term; bbb = P < 0.001 vs. intermediate term.

Fig. 7.

Low-fat/high-carbohydrate diet, but not Western diet, upregulates cardiac delta-9 desaturase gene expression. Transcript levels of fatty acid synthase (fasn; A), the long chain fatty acid elongase ELOVL family member 6 (elovl6; B), acetyl-CoA carboxylase 1 (acc1; C), stearoyl-CoA desaturase isoforms 1 and 2 (scd1 and scd2; D and E, respectively), sterol regulatory element-binding proteins 1 (srebp1; F), and carbohydrate response element binding protein (chrebp; G) were quantified by real-time PCR in the heart of Wistar rats fed either low-fat/high-carbohydrate diet (HCD; open bars), high-fat diet (HFD; hatched bars), or Western diet (WD; black bars) for acute term (AT), short term (ST), intermediate term (IT), or long term (LT). Baseline mRNA levels (B; gray bar) were determined from 8-week-old rats fed standard rodent chow for 2 weeks before the beginning of the feeding protocol. Data are means ± SE of n = 13–18 animals per group per time point (except baseline; n = 6). One, two, and three symbols represent P < 0.05, P < 0.01, and P < 0.001, respectively. # = vs. Western diet at same age; $ = vs. high-fat diet at same age; a = vs. baseline; b = vs. acute term; c = vs. short term.

Fig. 8.

High-fat diet and Western diet induce time-dependent, organelle-specific impairment in membrane fluidity. Microsomal (A) and inner mitochondrial (B) membranes fluidity were assessed for male Wistar rats fed either low-fat high/carbohydrate diet (HCD; black squares), high-fat diet (HFD; black triangles), or Western diet (WD; black circles) for short term (ST), intermediate term (IT), or long term (LT). Results are expressed in millipolarization (mP) units. An increase in mP units means a decrease in membrane fluidity. Data are means ± SE of n = 6 (A) or n = 5 to 6 (B) animals per group per time point. * = P < 0.05; **= P < 0.01 vs. low-fat/high-carbohydrate diet at same age; a = P < 0.05 vs. short term; b = P < 0.05 vs. intermediate term.

Fig. 9.

Model for the role of hepatic de novo lipogenesis in Western diet–induced alteration of cardiac LCACoA profile. The consumption of a low-fat/high-carbohydrate diet (HCD; left panel) and the resulting high plasma carbohydrate and insulin levels induce the transcriptional activation of de novo lipogenesis (DNL) in the liver. Delta-9 desaturase expression/activity is increased to supply the heart with a normal amount of monounsaturated fat. Conversely, dietary fat is the essential provider of saturated and monounsaturated fatty acids under high-fat diet (HFD; middle panel) consumption, which consequently, inhibits hepatic de novo lipogenesis. Western diet (WD; right panel) induces de novo lipogenesis in the long term, but significant amounts of dietary fat may combine to obesity and/or insulin resistance to avoid stearoyl-CoA desaturases upregulation both in the liver and in the heart. Insufficient desaturation of de novo synthesized fat thus induces a decrease in the cardiac monounsaturated-to-saturated fat ratio, which could indirectly impair the contractility of the heart. Bar heads show inhibition of target. 16:0, palmitate; 16:1, palmitoleate; 18:0, stearate; 18:1, oleate; ACC, acetyl-CoA carboxylase; Elovl-6, long chain fatty acid elongase ELOVL family member 6; FAS, fatty acid synthase; SCD, stearoyl-CoA desaturase.