Nuclear magnetic resonance reveals postprandial low-density lipoprotein cholesterol determined by enzymatic method could be a misleading indicator

The accuracy of four formulas for LDL-C calculation at the fasting and postprandial states

Background

Elevated level of low-density lipoprotein cholesterol (LDL-C) is concerned as one of the main risk factors for cardiovascular disease, in both the fasting and postprandial states. This study aimed to compare the measured LDL-C with LDL-C calculated by the Friedewald, Martin–Hopkins, Vujovic, and Sampson formulas, and establish which formula could provide the most reliable LDL-C results for Chinese subjects, especially at the postprandial state.

Methods

Twenty-six subjects were enrolled in this study. The blood samples were collected from all the subjects before and after taking a daily breakfast. The calculated LDL-C results were compared with LDL-C measured by the vertical auto profile method, at both the fasting and postprandial states. The percentage difference between calculated and measured LDL-C (total error) and the number of results exceeding the total error goal of 12% were established.

Results

The calculated LDL-C_F levels showed no significant difference from LDL-C_VAP levels at the fasting state. The calculated LDL-C_S were significantly higher than LDL-C_VAP at the fasting state (P < 0.05), while the calculated LDL-C_s were very close to LDL-C_VAP levels after a daily meal. At the fasting state, the median total error of calculated LDL-C_F was 0 (quartile: −3.8 to 6.0), followed by LDL-C_S, LDL-C_MH, and LDL-C_V. At the postprandial states, the median total errors of LDL-C_S were the smallest, 1.0 (−7.5, 8.5) and −0.3 (−10.1, 10.9) at 2 and 4 h, respectively. The calculated LDL-C_F levels showed the highest correlation to LDL-C_VAP and accuracy in evaluating fasting LDL-C levels, while the Sampson formula showed the highest accuracy at the postprandial state.

Conclusion

The Friedewald formula was recommended to calculate fasting LDL-C, while the Sampson formula seemed to be a better choice to calculate postprandial LDL-C levels in Chinese subjects.

ANGPTL3 Is Involved in the Post-prandial Response in Triglyceride-Rich Lipoproteins and HDL Components in Patients With Coronary Artery Disease

It is well-established that there exists an inverse relationship between high-density lipoprotein (HDL) cholesterol and triglyceride (TG) levels in the plasma. However, information is lacking on the impact of post-prandial triglyceride-rich lipoproteins (TRLs) on the structure of HDL subclasses in patients with coronary artery disease (CAD). In this study, the data of 49 patients with CAD were analyzed to evaluate dynamic alterations in post-prandial lipid profiles using nuclear magnetic resonance-based methods. An enzyme-linked immunosorbent assay was used to quantify the serum angiopoietin-like protein 3 (ANGPTL3). After glucose supplementation, the expression of hepatic ANGPTL3 was evaluated both in vitro and in vivo. Compared to fasting levels, the post-prandial serum TG level of all participants was considerably increased. Although post-prandial total cholesterol in HDL (HDL-C) remained unchanged, free cholesterol in HDL particles (HDL-FC) was significantly reduced after a meal. Furthermore, the post-prandial decrease in the HDL-FC level corresponded to the increase in remnant cholesterol (RC), indicating the possible exchange of free cholesterol between HDL and TRLs after a meal. Moreover, CAD patients with exaggerated TG response to diet, defined as TG increase >30%, tend to have a greater post-prandial increase of RC and decrease of HDL-FC compared to those with TG increase ≤30%. Mechanistically, the fasting and post-prandial serum ANGPTL3 levels were significantly lower in those with TG increase ≤30% than those with TG increase >30%, suggesting that ANGPTL3, the key lipolysis regulator, may be responsible for the different post-prandial responses of TG, RC, and HDL-FC.

Non-fasting Changes in Blood Lipids After Three Daily Meals Within a Day in Chinese Inpatients With Cardiovascular Diseases

Background

Non-fasting (i.e., postprandial) lipid detection is recommended in clinical practice. However, the change in blood lipids in Chinese patients with cardiovascular diseases after three daily meals has never been reported yet.

Methods

Serum levels of blood lipids were measured or calculated in 77 inpatients (48 men and 29 women) at high or very high risk of atherosclerotic cardiovascular disease (ASCVD) in the fasting state and at 4 h after three meals within a day according to their diet habits.

Results

Female patients showed significantly higher level of high-density lipoprotein cholesterol (HDL-C) than male patients, and the gender difference in other lipid parameters did not reach statistical significance at any time-point. Levels of triglyceride (TG) and remnant cholesterol (RC) increased, while that of low-density lipoprotein cholesterol (LDL-C) decreased significantly after three meals (p < 0.05). Levels of HDL-C, total cholesterol (TC), and non-high-density lipoprotein cholesterol (non-HDL-C) showed smaller changes after three meals. Percent reductions in the non-fasting LDL-C levels after lunch and supper were around 20%, which were greater than that after breakfast. The percent reductions in the non-fasting non-HDL-C levels after three meals were smaller than those in the non-fasting LDL-C levels. Patients with TG level ≥ 2.0 mmol/L (177 mg/dL) after lunch had significantly greater absolute reduction of LDL-C level than those with TG level < 2.0 mmol/L (177 mg/dL) after lunch [–0.69 mmol/L (–27 mg/dL) vs. –0.36 mmol/L (–14 mg/dL), p<0.01]. There was a significant and negative correlation between absolute change in LDL-C level and that in TG level (r = −0.32) or RC level (r = −0.67) after lunch (both p<0.01).

Conclusion

LDL-C level decreased significantly after three daily meals in Chinese patients at high or very high risk of ASCVD, especially when TG level reached its peak after lunch. Relatively, non-HDL-C level was more stable than LDL-C level postprandially. Therefore, when LDL-C level was measured in the non-fasting state, non-HDL-C level could be evaluated simultaneously to reduce the interference of related factors, such as postprandial hypertriglyceridemia, on detection.