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. 2023 Jun 15;15(12):2755.
doi: 10.3390/nu15122755.

Lipoprotein Lipase Activity Does Not Differ in the Serum Environment of Vegans and Omnivores

Natjan-Naatan Seeba  1 , Robert Risti  1 , Aivar Lõokene  1
Affiliations

Lipoprotein Lipase Activity Does Not Differ in the Serum Environment of Vegans and Omnivores

Natjan-Naatan Seeba et al. Nutrients. .

Abstract

Although vegan diets have been reported to be associated with a reduced risk of cardiovascular disease, it was not known whether this might be partly due to vegan diets' effects on plasma triglyceride metabolism. This study aimed to investigate if there are differences in the activity of lipoprotein lipase (LPL), an enzyme that functions at the vascular endothelium and is responsible for triglyceride breakdown, in sera obtained from vegans and omnivores. LPL activity was assessed using isothermal titration calorimetry, which allows measurements in undiluted serum samples, mimicking physiological conditions. Fasted sera from 31 healthy participants (12F 2M vegans, 11F 6M omnivores) were analyzed. The results indicated no significant differences in average LPL activity between the vegan and omnivore groups. Interestingly, despite similar triglyceride levels, there were considerable variations in LPL activity and total very-low-density lipoprotein triglyceride breakdowns between individuals within both groups. Biomarker analysis showed that vegans had lower total cholesterol and LDL-C levels compared to omnivores. These findings suggest that the lipid-related benefits of a vegan diet, in terms of atherogenic risk, may primarily stem from cholesterol reduction rather than affecting serum as a medium for LPL-mediated triglyceride breakdown. In healthy individuals, lipid-related changes in serum composition in response to a vegan diet are likely overshadowed by genetic or other lifestyle factors.

Keywords: isothermal titration calorimetry; lipoprotein lipase; omnivore; vegan.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
General step-by-step workflow of the applied ITC method for LPL activity measurements. The received blood sera of vegan and omnivore participants (1) were prepared (2) for insertion in the isothermal titration calorimeter measurement cell (C). (3) During the measurements, the burette (B) contained an LPL enzyme mixture, while the ITC reference cell (A) contained MiliQ water. While constantly stirring, a series of LPL injections were made into the measurement cell (C) containing the blood serum of the subject. Lipolysis was monitored and the results were obtained as heat released over time. The results were then calculated to changes in heat rate per µg of protein, which was proportional to the amount of fatty acids release per µg of protein (4).
Figure 2
Figure 2
Ad libitum energy intake and median macronutrient composition of both groups: (A) average energy intake of both groups during the seven-day food diary recording period. No significant difference in the median daily energy intake was noted between the vegan (formula image) and omnivore (formula image) participants; (B) Median macronutrient composition of both diets illustrating the carbohydrate rich diet of the vegan group > 45% of energy from carbohydrates and the fat-rich diet of the omnivore group > 35% of energy from fats. On average, vegan participants consumed more carbohydrates and less protein and fat than their omnivore counterparts.
Figure 3
Figure 3
Scatter plot of measured exogenous LPL activities against TG concentration, N = 31. Data for LPL activity in the blood serum of each participant are presented as the mean of three independent measurements. Data for vegan sera are shown in gray and data for omnivorous participants are in black. LPL activity is expressed as heat rate per LPL mass (µW/µg), which is proportional to fatty acids released per µg of LPL.
Figure 4
Figure 4
PCA loading plots of LPL activity and lipoprotein-associated blood parameters. In total, 81.66% of the variance is explained through two principal components: F1 (52.54%) and F2 (29.12%). Variables are depicted as vectors with the angle between vectors representing correlation. An acute angle between variables represents a positive correlation, while a right angle and obtuse angle represent no correlation and negative correlation, respectively. Omnivore participants are indicated in green and vegans in violet. Homogeneity in participants showed no difference in parameters except for TC and LDL-C, where omnivore participants were shifted towards higher values of the mentioned active variables.
Figure 5
Figure 5
Correlation matrices of LPL activity and lipoprotein-associated blood parameters of both groups. (A) Pearson correlation matrix of vegan participants; a statistically significant negative correlation, r = −0.55 (p = 0.039), was found between measured LPL activity and HDL-C concentration (highlighted in bold). (B) Pearson correlation matrix of omnivore participants; unlike in vegans, a positive but statistically insignificant correlation of r = 0.47 between measured LPL activity and TG levels (p = 0.06) was noted in omnivore participants.
Figure 6
Figure 6
Average consumption of fatty acids and a PCA plot of LPL activity related to daily fatty acid intake. (A) SFA consumption was highest in both groups followed by PUFA and MUFA consumption. Vegans consumed more PUFA and MUFA than their omnivore counterparts; (B) The PCA loading plot shows no statistically significant correlation between daily fatty acid consumption and LPL activity (vegans are indicated in violet and omnivores in green).
Figure 6
Figure 6
Average consumption of fatty acids and a PCA plot of LPL activity related to daily fatty acid intake. (A) SFA consumption was highest in both groups followed by PUFA and MUFA consumption. Vegans consumed more PUFA and MUFA than their omnivore counterparts; (B) The PCA loading plot shows no statistically significant correlation between daily fatty acid consumption and LPL activity (vegans are indicated in violet and omnivores in green).
Figure 7
Figure 7
SEC analysis of long-term lipolysis. (A1–A3) Comparison of VLDL fractions for pairs of serum samples with similar TG levels before and after long-term lipolysis with LPL. The effects of treatment with LPL on the VLDL peaks for pairs with similar serum TG levels were as follows: (A1)—two vegans, VGNF213 and VGNM251, serum TG levels—1.05 mmol/L; (A2)—two omnivores, OMF321 and OMF351, serum TG levels—0.53 mmolL; (A3)—a vegan VGNF262 and an omnivore OMM301, serum TG levels of 0.52 mmol/L and 0.53 mmol/L, respectively. (B) Scatter plot showing the relationship between measured LPL activity and the percentage change in the area of VLDL peaks. Vegans are indicated in green and omnivores in black.
Figure 7
Figure 7
SEC analysis of long-term lipolysis. (A1–A3) Comparison of VLDL fractions for pairs of serum samples with similar TG levels before and after long-term lipolysis with LPL. The effects of treatment with LPL on the VLDL peaks for pairs with similar serum TG levels were as follows: (A1)—two vegans, VGNF213 and VGNM251, serum TG levels—1.05 mmol/L; (A2)—two omnivores, OMF321 and OMF351, serum TG levels—0.53 mmolL; (A3)—a vegan VGNF262 and an omnivore OMM301, serum TG levels of 0.52 mmol/L and 0.53 mmol/L, respectively. (B) Scatter plot showing the relationship between measured LPL activity and the percentage change in the area of VLDL peaks. Vegans are indicated in green and omnivores in black.
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