Association between the rs3812316 Single Nucleotide Variant of the MLXIPL Gene and Alpha-Linolenic Acid Intake with Triglycerides in Mexican Mestizo Women

Abstract

The carbohydrate response element binding protein (ChREBP) is a key transcription factor to understand the gene−diet−nutrient relationship that leads to metabolic diseases. We aimed to analyze the association between the rs17145750 and rs3812316 SNVs (single nucleotide variants) of the MLXIPL gene with dietary, anthropometric, and biochemical variables in Mexican Mestizo subjects. This is a cross-sectional study of 587 individuals. Genotyping was performed by allelic discrimination. In addition, liver and adipose tissue biopsies were obtained from a subgroup of 24 subjects to analyze the expression of the MLXIPL gene. An in silico test of the protein stability and allelic imbalance showed that rs17145750 and rs3812316 showed a high rate of joint heritability in a highly conserved area. The G allele of rs3812316 was associated with lower triglyceride levels (OR = −0.070 ± 0.027, p < 0.011, 95% CI = −0.124 to −0.016), the production of an unstable protein (ΔΔG −0.83 kcal/mol), and probably lower tissue mRNA levels. In addition, we found independent factors that also influence triglyceride levels, such as insulin resistance, HDL-c, and dietary protein intake in women. Our data showed that the association of rs3812316 on triglycerides was only observed in patients with an inadequate alpha-linolenic acid intake (1.97 ± 0.03 vs. 2.11 ± 0.01 log mg/dL, p < 0.001).

Keywords: ChREBP; G dyslipidemias; MLXIPL; alpha-linolenic acid; omega-3; triglycerides.

Figure 1

Flowchart for recruitment of the subjects.

Figure 2

Triglyceride levels according to SNV’s in MLXIPL gene. Comparison of triglyceride levels in women and men according to (A) rs17145750 and (B) rs3812316 SNVs. Bars represent mean ± SD (standard deviation). Triglyceride concentrations were log10-transformed to ensure a normal distribution and comparisons between women and men were performed with Student’s t-test. A p-value < 0.05 was considered statistically significant. Bold numbers highlight statistical significance.

Figure 3

Factors associated with hypertriglyceridemia in women and men. Logistic regression models of hypertriglyceridemia in (A) women and (B) men. Binary logistic regression was performed with hypertriglyceridemia (triglycerides ≥ 150 mg/dL) as a dependent variable. Lines represent the Odds Ratio and the 95% Confidence Interval. A p-value < 0.05 was considered statistically significant. HDL-c: High-density lipoprotein cholesterol, TC: Total cholesterol, WC: Waist circumference, SNV: Single nucleotide variant.

Figure 4

Triglyceride levels according to the rs3812316 C > G SNV and its association with (A) Total fat intake, (B) Saturated fatty acids, (C) Monounsaturated fatty acids, (D) Polyunsaturated fatty acids, and (E) alpha-linolenic acid in women. Data are shown as estimated mean. Fat intake and specific fatty acid intake were categorized according to the position of the Academy of Nutrition and Dietetics [19]. Triglycerides were log10-transformed to apply ANCOVA (analysis of covariance) analysis, adjusted for HDL-c, total cholesterol, waist circumference, HOMA-IR, and energy intake; Bonferroni correction was used to test for multiple comparisons. A p-value < 0.05 was considered statistically significant. SFA: Saturated fatty acids, MUFA: Monounsaturated fatty acids, PUFA: Polyunsaturated fatty acids, ALA: alpha-linolenic acid, n-3: omega-3, HDL-c: High-density lipoprotein cholesterol, HOMA-IR: Homeostasis model assessment of insulin resistance, Ad: adequate, Ex: excessive, Ins: insufficient. * CC adequate fat vs. CG + GG adequate total fat, p < 0.05. ** CC excessive fat vs. CG + GG excessive fat, p < 0.05. ♦ CC excessive SFA vs. CG + GG excessive SFA, p < 0.05. ∞ CC insufficient MUFA vs. CG + GG insufficient MUFA, p < 0.05. Δ CC adequate PUFA vs. CG + GG adequate PUFA, p < 0.05. ΔΔ CC insufficient PUFA vs. CG + GG insufficient PUFA, p < 0.05. ± CC insufficient ALA vs. CG + GG insufficient ALA, p < 0.05.

Figure 5

Gene expression of ChREBP α and β isoforms according to the rs3812316 SNV of MLXIPL gene. Units of relative expression (A) of ChREBP-α and (B) ChREBP-β isoforms according to the rs3812316. Bars represent mean ± SD (standard deviation). Comparisons between genotypes were performed with the Mann–Whitney U test. A p-value < 0.05 was considered statistically significant. Gene expression was performed by qPCR and using the 2^−∆∆CT method. OAT: Omental adipose tissue, SAT: Subcutaneous adipose tissue, qPCR: quantitative polymerase chain reaction.