A novel posttranscriptional mechanism for dietary cholesterol-mediated suppression of liver LDL receptor expression

In liver cells, when intracellular cholesterol levels rise, LDLR mRNA levels fall substantially along with transcripts of other SREBP target genes.

“In liver cells, when intracellular cholesterol levels rise, LDLR mRNA levels fall substantially along with transcripts of other SREBP target genes”

• cites [13] Sheng, 1995, Independent regulation of sterol regulatory element-binding pro­teins 1 and 2 in hamster liver, Proc. Natl. Acad. Sci. USA. sourcePartly supported

  The abstract (p. 935) links sterol depletion in hamster liver to increased transcription of the LDL receptor and HMG-CoA synthase genes. It also describes sterol overloading as blocking SREBP processing in cultured cells, but does not report that rising cholesterol substantially lowers LDLR mRNA and other SREBP-target transcripts in liver cells. (LLM, conf=0.82)

  Experimental — accuracy not yet measured

Ad-shHNRNPD expresses a shRNA that targets all isoforms of mouse and human HNRNPD.

“In our previous in vitro studies, we had generated an adenovirus (Ad-shHNRNPD) to express a shRNA that targets all isoforms of mouse and human HNRNPD.”

• cites [28] Singh, 2014, The Critical role of mRNA destabilizing protein heterogeneous nuclear ribonucleoprotein D in 3′ untranslated region-mediated decay of low-density lipoprotein receptor mRNA in liver tissue, Arterioscler. Thromb. Vasc. Biol. sourceSupported

LDLR gene expression is subject to posttranscriptional regulation at the point of mRNA stability.

“In addition to transcriptional regulation, LDLR gene expression is subject to posttranscriptional regulation at the point of mRNA stability”

• cites [8] Wilson, 1998, Stabilization and cytoskeletal-association of LDL receptor mRNA are mediated by distinct domains in its 3′ untranslated region, J. Lipid Res. sourceSupported
• cites [9] Wilson, 1997, Modulation of LDL receptor mRNA stability by phorbol esters in human liver cell culture models, J. Lipid Res. sourceNot checked — no full text of the source
• cites [10] Goto, 1997, Upregulation of low density lipoproteinreceptor by gemfibrozil, a hypolipidemic agent, in human hepatoma cells through stabilization of mRNA transcripts, Arterioscler. Thromb. Vasc. Biol. sourceSupported
• cites [11] Kong, 2004, Berberine is a promising novel cholesterol-lowering drug working through a unique mechanism distinct from statins, Nat. Med. sourceNot checked — no full text of the source

HNRNPD depletion does not affect hepatic mRNA levels of other SREBP2 target genes measured in hypercholesterolemic mice.

“In contrast to LDLR, HRNPD depletion did not affect mRNA levels of other SREBP2 target genes that were measured.”

A high cholesterol diet increases serum total cholesterol 4-fold in hamsters.

“The serum TC was increased 4-fold in hamsters fed a HCD as compared with hamsters fed a ND (supplementary Fig. IB).”

A high cholesterol diet increases hepatic HNRNPD p37 protein to 2.5-fold of control in mice.

“The results demonstrated that HCD feeding increased both HNRNPD p45 and p37 isoforms to 1.7- and 2.5-fold, respectively, of control and reduced LDLR protein abundance to 50% of control (Fig. 1C, D).”

Ad-shHNRNPD-infected livers had 3.2-fold higher Luc activity compared with control.

“We further measured ex vivo Luc activity of individual liver samples and observed a 3.2-fold higher Luc activity in Ad-shHNRNPD-infected livers as compared with control (Fig. 4C).”

A high cholesterol diet increases hepatic HNRNPD p45 protein to 1.7-fold of control in mice.

“The results demonstrated that HCD feeding increased both HNRNPD p45 and p37 isoforms to 1.7- and 2.5-fold, respectively, of control and reduced LDLR protein abundance to 50% of control (Fig. 1C, D).”

HCD-fed C57BL/6J mice had significant increases in HNRNPD mRNA and protein levels compared with ND-fed mice.

“Again, we detected significant increases in HNRNPD mRNA and protein levels in HCD-fed C57BL/6J mice.”

A high cholesterol diet increases hepatic HNRNPD mRNA levels by 1.9-fold in mice.

“Figure 1A shows that a HCD increased HNRNPD mRNA levels by 1.9-fold (P < 0.001) without affecting HNRNPI, KSRP, or HuR mRNA expressions.”

A high cholesterol diet reduces hepatic LDLR protein abundance to 50% of control in mice.

“The results demonstrated that HCD feeding increased both HNRNPD p45 and p37 isoforms to 1.7- and 2.5-fold, respectively, of control and reduced LDLR protein abundance to 50% of control (Fig. 1C, D).”

Hepatic HuR protein levels do not differ between high cholesterol diet and normal diet groups in mice.

“Consistent with the gene expression analysis, protein levels of HuR did not differ between diet groups.”

A high cholesterol diet increases hepatic HNRNPD mRNA level approximately 2-fold in hamsters.

“A HCD increased the HNRNPD mRNA level approximately 2-fold and reduced the LDLR mRNA level by 2.6-fold as compared with a ND (Fig. 1E).”

Gene knockdown in albumin-luciferase-UTR transgenic mice provides strong evidence supporting the essential role of 3′UTR in HNRNPD-mediated LDLR mRNA degradation in liver tissue.

“Additional studies of gene knockdown in albumin-luciferase-untranslated region (UTR) transgenic mice provide strong evidence supporting the essential role of 3′UTR in HNRNPD-mediated LDLR mRNA degradation in liver tissue.”

A high cholesterol diet does not affect hepatic mRNA expressions of HNRNPI, KSRP, or HuR in mice.

“Figure 1A shows that a HCD increased HNRNPD mRNA levels by 1.9-fold (P < 0.001) without affecting HNRNPI, KSRP, or HuR mRNA expressions.”

In hypercholesterolemic mice, Ad-shHNRNPD injection reduces serum total cholesterol by 13.9% after 4 days compared with control.

“While on a HCD, serum cholesterol levels continued rising during the treatment in control mice (Ad-shGFP), a significant drop in serum TC level was observed after 4 days of injection in Ad-shHNRNPD-infected mice (−13.9%, P < 0.05 compared with control mice), and serum TC further declined to a level which was 18.2% (P < 0.001) lower than control mice after 7 days of injection (Fig. 2A).”

In hypercholesterolemic mice, Ad-shHNRNPD injection reduces serum LDL-C by approximately 22% after 4 days compared with control.

“The time-dependent reduction in serum LDL-C levels by Ad-shHNRNPD infection in HCD mice was even more pronounced, with ∼22% lowering after 4 days and 30% lowering after 7 days, as compared with control mice (Fig. 2B).”

Depletion of HNRNPD in the liver results in a substantial increase in liver LDLR expression in hyperlipidemic mice.

“Employing the approach of adenovirus-mediated gene knockdown, we further show that depletion of HNRNPD in the liver results in a marked reduction of serum LDL-cholesterol and a substantial increase in liver LDLR expression in hyperlipidemic mice.”

• Also stated in: § RESULTS · plain

  “Figure 2D shows that in Ad-shHNRNPD-infected mice, mRNA levels of p37 and p45 isoforms were both significantly reduced to approximately 40% of that in control mice (P < 0.001), which was associated with a marked increase in the LDLR mRNA level to 260% of control (P < 0.001).”

High cholesterol feeding does not affect expressions of other LDLR mRNA binding proteins (HNRNPI, KSRP, HuR) in vivo and in vitro.

“Our results demonstrate that high cholesterol feeding specifically elevates the hepatic expression of LDLR mRNA decay promoting factor heterogeneous nuclear ribonucleoprotein (HNRNP)D without affecting expressions of other LDLR mRNA binding proteins in vivo and in vitro.”

• Also stated in: § RESULTS · plain

  “Figure 1A shows that a HCD increased HNRNPD mRNA levels by 1.9-fold (P < 0.001) without affecting HNRNPI, KSRP, or HuR mRNA expressions.”

The increase in LDLR abundance by HNRNPD depletion was 159% compared with HCD control groups.

“Again, the increase in LDLR abundance by HNRNPD depletion was higher when compared with HCD control groups (159%).”

In normolipidemic mice, Ad-shHNRNPD injection increased LDLR protein levels to 130% of control.

“Western blot analysis further demonstrated that LDLR protein levels were increased to 130% of control by Ad-shHNRNPD injection while HNRNPD p45 and p37 isoforms were reduced to 50 and 69% of control in normolipidemic mice, respectively (Fig. 3E).”

In normolipidemic (ND) mice, hepatic depletion of HNRNPD increased LDLR mRNA levels to 173% of control.

“Analysis of hepatic gene expression by real-time qRT-PCR showed that the substantial reductions of HNRNPD isoforms in ND mice increased LDLR mRNA levels to 173% of control (Fig. 3D).”

In Ad-shHNRNPD-infected hypercholesterolemic mice, hepatic LDLR protein level increases to 163% of control.

“This reduction of HNRNPD protein abundance was associated with an increase of 163% of control in the hepatic LDLR protein level (P < 0.01) (Fig. 2E).”

Depletion of HNRNPD in the liver results in a marked reduction of serum LDL-cholesterol in hyperlipidemic mice.

“Employing the approach of adenovirus-mediated gene knockdown, we further show that depletion of HNRNPD in the liver results in a marked reduction of serum LDL-cholesterol and a substantial increase in liver LDLR expression in hyperlipidemic mice.”

• Also stated in: § RESULTS · plain

  “The time-dependent reduction in serum LDL-C levels by Ad-shHNRNPD infection in HCD mice was even more pronounced, with ∼22% lowering after 4 days and 30% lowering after 7 days, as compared with control mice (Fig. 2B).”

Ad-shHNRNPD infection did not alter mRNA levels of HNRNPI, KSRP, HuR, PCSK9, HMG-CoA reductase, or SREBP2 in liver samples.

“The results showed that none of these mRNA levels were altered by Ad-shHNRNPD infection (data not shown).”

Serum HDL-C levels are not affected by HNRNPD depletion in hypercholesterolemic mice throughout the treatment duration.

“Serum HDL-C levels were not affected by HNRNPD depletion throughout the treatment duration (Fig. 2C).”

A high cholesterol diet markedly decreases hepatic mRNA levels of LDLR and other SREBP2 target genes, including PCSK9 and SREBP2, in mice.

“In contrast and as expected, mRNA levels of LDLR and other SREBP2 target genes, including PCSK9 and SREBP2, were markedly decreased by HCD feeding (Fig. 1B).”

Knockdown of HNRNPD expression in liver has no impact on serum PCSK9 concentration in hypercholesterolemic mice.

“As we expected, knockdown of HNRNPD expression in liver had no impact on serum PCSK9 concentration (supplementary Fig. IIIC).”

In HCD mice, mRNA levels of four out of five HNRNPD target transcripts (cyclin B2, cyclin D1, IL-1β, IL-6, TNFα) were significantly reduced compared with ND-fed mice.

“Consistent with an increased HNRNPD expression by HCD, mRNA levels of four out of five HNRNPD targeted transcripts were significantly reduced in liver samples of HCD mice compared with ND-fed mice.”

A high cholesterol diet reduces hepatic LDLR mRNA level by 2.6-fold in hamsters.

“A HCD increased the HNRNPD mRNA level approximately 2-fold and reduced the LDLR mRNA level by 2.6-fold as compared with a ND (Fig. 1E).”

In hypercholesterolemic mice, Ad-shHNRNPD injection reduces serum total cholesterol by 18.2% after 7 days compared with control.

“While on a HCD, serum cholesterol levels continued rising during the treatment in control mice (Ad-shGFP), a significant drop in serum TC level was observed after 4 days of injection in Ad-shHNRNPD-infected mice (−13.9%, P < 0.05 compared with control mice), and serum TC further declined to a level which was 18.2% (P < 0.001) lower than control mice after 7 days of injection (Fig. 2A).”

In normolipidemic mice, Ad-shHNRNPD injection decreases serum total cholesterol by 8% compared with control.

“Ad-shHNRNPD injection at the same dose into mice fed a ND resulted in a relatively modest decrease in TC (−8%, P < 0.05; Fig. 3A) and LDL-C (−13%, P < 0.05; Fig. 3B) compared with the control mice infected with Ad-shGFP.”

A high cholesterol diet induces hepatic HNRNPD p37 protein expression in hamsters.

“Western blot analysis further corroborated the induction of HNRNPD p37 protein expression in hamster liver by HCD feeding (Fig. 1F).”

High cholesterol feeding specifically elevates hepatic expression of LDLR mRNA decay promoting factor HNRNPD in vivo and in vitro.

“Our results demonstrate that high cholesterol feeding specifically elevates the hepatic expression of LDLR mRNA decay promoting factor heterogeneous nuclear ribonucleoprotein (HNRNP)D without affecting expressions of other LDLR mRNA binding proteins in vivo and in vitro.”

• Also stated in: § Abstract · plain

  “We observed that the hepatic expression of LDLR mRNA decay promoting factor HNRNPD was specifically induced by HCD in mice as well as in hamsters, while expressions of HNRNPI, KSRP, and HuR were unaffected by high cholesterol feeding.”

• Also stated in: § RESULTS · plain

  “Figure 1A shows that a HCD increased HNRNPD mRNA levels by 1.9-fold (P < 0.001) without affecting HNRNPI, KSRP, or HuR mRNA expressions.”

In hypercholesterolemic mice, Ad-shHNRNPD injection reduces serum LDL-C by 30% after 7 days compared with control.

“The time-dependent reduction in serum LDL-C levels by Ad-shHNRNPD infection in HCD mice was even more pronounced, with ∼22% lowering after 4 days and 30% lowering after 7 days, as compared with control mice (Fig. 2B).”

Cholesterol feeding elevates the LDLR mRNA degrading protein HNRNPD in mice.

“Collectively, the results of protein and mRNA analyses from ND and HCD mice clearly demonstrate that cholesterol feeding elevates the LDLR mRNA degrading protein HNRNPD, and that eliminating HNRNPD in cholesterol-loaded liver produced stronger effects in restoring LDLR mRNA and protein levels, which translated into a substantially improved removal of serum LDL-C in hypercholesterolemic mice.”

• AssumptionRests on an assumption: The effects of the high-cholesterol diet on HNRNPD expression are attributable to its cholesterol content rather than other dietary components.

In normolipidemic mice, Ad-shHNRNPD injection decreases serum LDL-C by 13% compared with control.

“Ad-shHNRNPD injection at the same dose into mice fed a ND resulted in a relatively modest decrease in TC (−8%, P < 0.05; Fig. 3A) and LDL-C (−13%, P < 0.05; Fig. 3B) compared with the control mice infected with Ad-shGFP.”

The HNRNPD p45 isoform could not be detected in hamster liver.

“The p45 isoform could not be detected in hamster liver.”

In Ad-shHNRNPD-infected hypercholesterolemic mice, hepatic HNRNPD p37 protein level is reduced to 71% of control.

“Western blot analysis of individual liver homogenates further demonstrated that the p45 protein level in Ad-shHNRNPD-infected mice was reduced to 36% of control and p37 protein was lowered to 71% of control by the expression of HNRNPD shRNA.”

A cholesterol diet lowered liver LDLR protein by 25% compared with ND in Ad-shGFP-infected mice.

“Results showed that a cholesterol diet lowered LDLR by 25% (P < 0.001) as compared with the ND group in Ad-shGFP-infected mice.”

In normolipidemic mice, HDL-C levels are not affected by Ad-shHNRNPD injection.

“Again, HDL-C levels were not affected by Ad-shHNRNPD injection (Fig. 3C).”

In Ad-shHNRNPD-infected hypercholesterolemic mice, hepatic HNRNPD p45 protein level is reduced to 36% of control.

“Western blot analysis of individual liver homogenates further demonstrated that the p45 protein level in Ad-shHNRNPD-infected mice was reduced to 36% of control and p37 protein was lowered to 71% of control by the expression of HNRNPD shRNA.”

In normolipidemic mice, Ad-shHNRNPD injection reduced HNRNPD p45 and p37 isoforms to 50% and 69% of control, respectively.

“Western blot analysis further demonstrated that LDLR protein levels were increased to 130% of control by Ad-shHNRNPD injection while HNRNPD p45 and p37 isoforms were reduced to 50 and 69% of control in normolipidemic mice, respectively (Fig. 3E).”

A high cholesterol diet increases serum cholesterol levels in mice.

“Feeding mice a HCD for 4 weeks increased serum cholesterol levels by ∼2-fold from 122 to 240 mg/dl and serum LDL-C by 5-fold from 36 to 181 mg/dl, as compared with mice fed a ND (supplementary Fig. IA).”

A high cholesterol diet increases serum LDL-C levels in mice.

“Feeding mice a HCD for 4 weeks increased serum cholesterol levels by ∼2-fold from 122 to 240 mg/dl and serum LDL-C by 5-fold from 36 to 181 mg/dl, as compared with mice fed a ND (supplementary Fig. IA).”

Ad-shHNRNPD infection increased bioluminescence signal 4.2-fold over control virus in Alb-Luc-UTR mice.

“Figure 4B is the summarized imaging results (mean ± SEM) showing that Ad-shHNRNPD infection increased bioluminescence signal 4.2-fold over the control virus (P < 0.001).”

A high cholesterol diet does not change hepatic HuR mRNA or protein levels in hamsters.

“As observed in the mouse diet study, we did not detect changes in mRNA or protein levels of HuR in hamster livers upon HCD feeding (supplementary Fig. II).”

In AML12 cells, 24-OHC or 24,25-EC caused no substantial changes in HNRNPD mRNA levels despite huge increases in Idol and ABCA1 mRNA.

“Similar to the finding in HepG2 cells, we observed no substantial changes in HNRNPD mRNA levels in AML12 cells after 24 h treatment with 24-OHC or 24,25-EC, despite huge increases in Idol and ABCA1 mRNA levels (supplementary Fig. VI).”

There was a strong inverse correlation of HNRNPD cellular abundance with LDLR mRNA levels in Ad-shHNRNPD-infected C57BL/6J mice.

“Because our results showed the strong inverse correlation of HNRNPD cellular abundance with LDLR mRNA levels in Ad-shHNRNPD-infected C57BL/6J mice, it was crucial to demonstrate that the effect of HNRNPD was indeed mediated through LDLR3′UTR without the involvement of LDLR gene transcription in vivo.”

Compared with normolipidemic mice, reduction of hepatic HNRNPD protein in hyperlipidemic mice produced greater lowering of serum TC (−18.2% vs −8%) and LDL-C (−30% vs −13.2%).

“Our results clearly showed that compared with normolipidemic mice, reduction of hepatic HNRNPD protein in hyperlipidemic mice produced greater effects on elevation of liver LDLR mRNA levels (2.6-fold in HCD mice vs. 1.7-fold in ND mice) and on lowering serum TC (−18.2% vs. −8%) and LDL-C (−30% vs. −13.2%).”

RSV had no effect on HNRNPD expression in HepG2 and AML12 cells.

“Gene expression analysis by qRT-PCR shows that cholesterol supplementation increased HNRNPD mRNA levels to 131% (P < 0.001) of control in HepG2 cells (Fig. 5A) and elevated HNRNPD mRNA levels to 133% (P < 0.001) of control in AML12 cells (Fig. 5B) while RSV had no effect on HNRNPD expression in both cell lines.”

In Alb-Luc-UTR mice, hepatic mRNA levels of HNRNPI and KSRP were not affected by Ad-shHNRNPD injection.

“As observed in C57BL/6J mice, hepatic mRNA levels of other mRNA binding proteins (HNRNPI, KSRP) were not affected by Ad-shHNRNPD injection.”

In HepG2 cells, 24-OHC and 24,25-EC markedly elevated Idol and ABCA1 mRNA levels.

“Figure 5C shows that mRNA levels of inducible degrader of the LDLR (Idol) and ABCA1 were markedly elevated in cells treated with 24-OHC and 24,25-EC.”

In HepG2 cells, oxysterols strongly repressed mRNA levels of SREBP2 target genes LDLR, PCSK9, and SREBP2.

“As we expected, mRNA levels of SREBP2 target genes, including LDLR, PCSK9, and SREBP2, were strongly repressed by oxysterols.”

Compared with normolipidemic mice, reduction of hepatic HNRNPD protein in hyperlipidemic mice produced greater elevation of liver LDLR mRNA levels (2.6-fold vs 1.7-fold).

“Our results clearly showed that compared with normolipidemic mice, reduction of hepatic HNRNPD protein in hyperlipidemic mice produced greater effects on elevation of liver LDLR mRNA levels (2.6-fold in HCD mice vs. 1.7-fold in ND mice) and on lowering serum TC (−18.2% vs. −8%) and LDL-C (−30% vs. −13.2%).”

Alb-Luc-UTR is a unique in vivo model to study the function of 3′UTR in mediating LDLR mRNA decay in liver tissue.

“Alb-Luc-UTR is a unique in vivo model to study the function of 3′UTR in mediating LDLR mRNA decay in liver tissue.”

• cites [28] Singh, 2014, The Critical role of mRNA destabilizing protein heterogeneous nuclear ribonucleoprotein D in 3′ untranslated region-mediated decay of low-density lipoprotein receptor mRNA in liver tissue, Arterioscler. Thromb. Vasc. Biol. sourceNot checked yet

  Checked before — its earlier verdict is held back until a new check runs.

Dietary cholesterol inhibits liver LDLR expression via inducing HNRNPD to accelerate LDLR mRNA degradation.

“Altogether, this work identifies a novel posttranscriptional regulatory mechanism by which dietary cholesterol inhibits liver LDLR expression via inducing HNRNPD to accelerate LDLR mRNA degradation.”

• Also stated in: § Abstract · hedged

  “This work provides the first evidence suggesting that dietary cholesterol inhibits LDLR gene expression through the dual action mechanisms of transcriptional suppression and acceleration of mRNA decay.”

HNRNPD plays a key role in modulation of hepatic LDLR expression under hypercholesterolemic conditions.

“Taken together, these results provided the first in vivo evidence demonstrating a key role of HNRNPD in modulation of hepatic LDLR expression under hypercholesterolemic conditions.”

Animals respond to a cholesterol-enriched diet by increasing HNRNPD expression in liver tissues where LDLR expressions are reduced.

“Altogether, these results demonstrate, for the first time, that animals responded to a cholesterol-enriched diet by increasing HNRNPD expression in liver tissues where LDLR expressions were reduced.”

Food intake is not a causing factor for reduced serum cholesterol levels in Ad-shHNRNPD-injected hypercholesterolemic mice.

“thereby ruling out the influence of food intake as a causing factor for reduced serum cholesterol levels.”

In this mouse model, depletion of HNRNPD can overcome dietary cholesterol-mediated repression of hepatic LDLR.

“These data suggest that in this mouse model, depletion of HNRNPD can overcome dietary cholesterol-mediated repression of hepatic LDLR.”

The stability of LDLR mRNA is modulated through its 3′ UTR.

“The stability of LDLR mRNA is modulated through its 3′ untranslated region (UTR)”

• cites [16] Yamamoto, 1984, The human LDL receptor: A cysteine-rich protein with multiple Alu sequence in its mRNA, Cell. sourceNot checked — no full text of the source

Feeding animals a HCD specifically and uniformly elevated the expression of HNRNPD in liver tissue.

“These investigations led us to discover that feeding animals a HCD, specifically and uniformly elevated the expression of HNRNPD in liver tissue.”

• AssumptionRests on an assumption: The effects of the high-cholesterol diet on HNRNPD expression are attributable to its cholesterol content rather than other dietary components.

Stabilizing LDLR mRNA by blocking HNRNPD-mediated mRNA decay might be a viable means to increase hepatic LDLR activity to remove excessive LDL-C from the circulation when intracellular cholesterol is elevated and SREBP is repressed.

“These new findings suggest that when the intracellular cholesterol level is elevated due to HCD and the SREBP pathway is repressed, stabilizing LDLR mRNA by blocking HNRNPD-mediated mRNA decay might be a viable means to increase hepatic LDLR activity to remove excessive LDL-C from the circulation.”

Alb-Luc-UTR transgenic mouse is the first in vivo model to exclusively study the function of 3′UTR in liver tissue in living mice.

“Our Alb-Luc-UTR transgenic mouse is the first in vivo model to exclusively study the function of 3′UTR in liver tissue in living mice.”

• cites [28] Singh, 2014, The Critical role of mRNA destabilizing protein heterogeneous nuclear ribonucleoprotein D in 3′ untranslated region-mediated decay of low-density lipoprotein receptor mRNA in liver tissue, Arterioscler. Thromb. Vasc. Biol. sourceNot checked yet

  Checked before — its earlier verdict is held back until a new check runs.

The two-tier regulation at transcriptional and posttranscriptional levels likely represents a natural response of liver tissue to cholesterol-enriched diets to reduce LDLR-mediated cholesterol uptake from circulation to maintain cellular cholesterol homeostasis.

“This unique two-tier regulation at the transcriptional and posttranscriptional levels likely represents a natural response of liver tissue to cholesterol-enriched diets to reduce LDLR-mediated cholesterol uptake from circulation in order to maintain cellular cholesterol homeostasis.”

• AssumptionRests on an assumption: The effects of the high-cholesterol diet on HNRNPD expression are attributable to its cholesterol content rather than other dietary components.

In vivo data validated that Ad-shHNRNPD acts by reducing HNRNPD-mediated LDLR mRNA degradation through 3′UTR.

“These in vivo data clearly validated the action mechanism of Ad-shHNRNPD via reducing HNRNPD-mediated LDLR mRNA degradation through 3′UTR.”