Figure 2 depicts both fasting and post-prandial modifications of the different lipoprotein sub-fractions prior to and after weight loss. As indicated in the graphics, the main involved sub-fractions were VLDL-1, VLDL-2, LDL-3 and the LDL-2/LDL-3 mass ratios.
After weight loss, VLDL-1 concentrations were significantly decreased both fasting (62.9 ± 37.6 mg/dl vs 23.7 ± 16.1 mg/dl; P<0.002) and at pp1 (76.2 ± 54.5 mg/dl vs 36.2 ± 17.2 mg/dl; P<0.05). At pp2 VLDL-1 concentrations decreased without reaching statistical significance (95.9 ± 63.4 mg/dl vs 68.2 ± 22.7 mg/dl; P=NS). Post-prandial (pp1 and pp2) VLDL-1
concentrations were significantly higher than fasting levels (23.7 ± 16.05 mg/dl - F- vs 36.2 ± 17.2 mg/dl–pp1- vs 68.2 ± 22.7 mg/dl–pp2-; P<0.01) after weight loss while the post-prandial rise (pp1 and pp2) in VLDL-1 concentrations upon admission did not reach statistical significance.
A significant correlation was found between delta ([pp2] – [F]) VLDL1-cholesterol and delta ([pp2] – [F]) triglycerides both prior to (r= 0.897 ; P<0.02) and after weight loss (r= -0.928;
P<0.01).
Moreover, multiple linear regression analyses disclosed delta fasting TG (before-after weight loss) as an independent variable accounting for the ability to predict delta fasting VLDL-1 (before-after weight loss) changes (dependent variable) (P<0.05).
After weight loss, VLDL-2 concentrations were significantly decreased both at F (33.3 ± 23.2 mg/dl vs 54.7 ± 30.5 mg/dl;
P<0.05), at pp1 (36.6 ± 11.6 mg/dl vs 63.7 ± 36.8 mg/dl;
P<0.05) and at pp2 (44.3 ± 21.1 mg/dl vs 72.4 ± 44.3 mg/dl;
P<0.05). Interestingly, a significant correlation between delta ([pp2] – [F]) VLDL-2 cholesterol and delta ([pp2] – [F]) triglyceride concentrations found at entry (r=0.933: P<0.01) was no longer apparent after weight loss (r=-0.173: P=NS).
No significant alterations were found for the smaller VLDL-3 sub-fractions or between post-prandial triglyceride and VLDL-3 concentrations.
Upon admission, LDL-1 concentrations significantly increased post-principally from 47.8 ± 15.8 mg/dl at F to 56.7 ± 19.3 mg/dl at pp1; (P<0.05). After weight loss, LDL-1 concentrations remained unchanged post-prandially while their pp1 and pp2 concentrations significantly decreased when compared to admission pp1 and pp2 values (56.7 ± 19.3 mg/dl vs 45.4 ± 14.1 mg/dl; (P<0.02) –pp1- and 54.4 ± 13.6 vs 44.4 ± 16.5 mg/dl; (P<0.001)–pp2-), respectively.
No significant fasting or post-prandial modifications were noted for the LDL-2 sub-fractions at entry and after weight loss.
LDL-3 concentrations were significantly decreased post-prandially after weight loss (117.5 ± 67.2 mg/dl vs 53.8 ± 20.9 mg/dl; P<0.01 at F) and (105 ± 48 mg/dl vs 58 ± 10 mg/dl;
P<0.05 at pp2).
The LDL-2/LDL-3 mass ratio showed a non-significant post-prandial rise upon admission while an opposite post-post-prandial behaviour was observed after weight loss when the fasting LDL-2/LDL-3 mass ratio significantly decreased from 4.5 ± 1.5 to 3.5 ± 1.9 at pp1 (P<0.02). Additionally, close-to-significance correlations were initially found between the LDL-2/LDL-3 mass ratio and TG (r=-0.625; P=0.07) at fasting was no longer apparent after weight loss (r=-0.234; P=NS). Moreover, a close-to-significance correlation between LDL-2/LDL-3 mass ratio and TG found initially at pp2 (r=-0.695; P=0.055) disappeared after weight loss (r=-0.348; P=NS). Interestingly,
multiple linear regression analyses disclosed delta fasting TG (before-after weight loss) as an independent variable accounting for the ability to predict delta fasting LDL-2/LDL-3 mass ratio (before-after weight loss) changes (dependent variable) (P<0.05).
After weight loss, HDL-2 concentrations at F, pp1 and pp2 were increased from their F, pp1 and pp2 time-points counterparts upon admission even though differences did not reach statistical significance.
HDL-3 concentrations disclosed significant decreases both at F (212.4 ± 55.5 vs 168 ± 29.2 mg/dl; P<0.005) and at pp1 (244 ± 56.2 vs 186 ± 18.4 mg/dl; P<0.02) after weight loss. The HDL-3 decrements at pp2 did not reach statistical significance.
Additionally, HDL-3 concentrations disclosed a significant increment post-prandially after weight loss (167.6 ± 29.2 at F vs 193.7 ± 36.4 mg/dl at pp2; P<0.05).
V-Discussion
A small group of type II diabetic patients who were well controlled and slightly overweight underwent a rapid improvement (-10 days-) in prandial lipemia and post-prandial glycemic excursions through a modest weight loss.
The main lipoproteins sub-fractions involved were VLDL-1, VLDL-2, LDL-3 and the LDL-2/LDL3 mass ratio.
The design of this study was such that in order to minimize the effects of glycemic control amelioration on lipoprotein sub-fractions inclusion criteria accurately targeted a population of well controlled NIDDM patients. Thus, we were able to assess minimal changes in daily glycemic control throughout the study period.
Weight loss was found to account for the ability to significantly predict changes in the post-prandial triglyceride excursions (delta Triglyceride Area Under the Curve (TG-AUC) while Blood Glucose improvement did not show the ability to predict these changes.
As depicted in Figure 1, the post-prandial triglyceride excursions were significantly diminished after weight loss even though their kinetics very much paralleled every other one (prior to- vs -after weight loss). Moreover, fasting triglyceride values were, as expected, significantly lowered and the Triglyceride Area Under the Curve (TG-AUC) was significantly diminished by 23% at the end of the study. Thus, modest
weight loss in otherwise well controlled NIDDM patients rapidly and significantly improves triglyceride clearance and/or intolerance independently of improvements in glycemic control.
The latter is one of several key features in the constellation of findings the define the metabolic syndrome49-50. Additionally, triglyceride intolerance/impaired clearance is one key feature of insulin resistance observed through various degrees of glucose tolerance23;24;51 and whose phenotypic characterization is inherited as a dominant trait52,53.
Post-prandial triglyceride enrichment of VLDL sub-fractions was indirectly assessed by correlating their respective increments in [VLDL] vs the [TG] increments at identical time-points (pp2 [VLDL] – F [VLDL]) vs (pp2 [TG] – F [TG]). Weight loss did not have a significant effect on neither VLDL-1 nor VLDL-3 post-prandial triglyceride enrichment. Interestingly enough, the VLDL-2 sub-fractions disclosed the disappearance of triglyceride enrichment post-prandially at the end of the study.
The net effects of weight loss on LDL-2 sub-fractions disclosed a blunted post-prandial rise (both pp1 and pp2) even though the fasting LDL-2 concentrations were non-significantly raised after weight loss.
LDL-3 cholesterol concentrations decreased after ten days both at fasting and at pp2 sampling periods. Again this finding supports the concept of rapid improvement in the clearance of
LDL-2 sub-fractions by modest weight loss and is in accordance with the available literature54.
LDL-3 cholesterol post-prandial kinetics prior to and after weight loss were symmetrically opposed. Whilst fasting LDL-3 cholesterol concentrations decreased by 19 % at pp1 and by 11 % at pp2 prior to weight loss they increased by 36 % at pp1 and by 8 % at pp2.
LDL-2/LDL-3 mass ratios disclosed a significant rise at fasting at the end of the study while the post-prandial increments did not reach statistical significance. Again, these ratios displayed symmetrically opposed kinetics between prior to and after weight loss. Thus, the ratio increased by 28 % at pp1 and by 24 % at pp2 at entry and decreased by 22 % at pp1 and by 14
% at pp2 after weight loss.
LDL-2/LDL-3 mass ratios did not show any significant correlation with either weight loss or blood glucose improvement.
LDL-2/LDL-3 mass ratios correlation with serum triglycerides is a finding which has already been reported in a previous study by our group in which stepwise multiple regression analysis identified a three-parameter model comprising triglycerides, HbA1c, and high density lipoprotein cholesterol as best defining the variations in the LDL-2/LDL-3 mass ratio55. We could not find these correlations in our patient group probably due to reduced sample size and overall better controlled
diabetes. These observations are consistent with an independent impact of diabetes on the LDL distribution profile and the possibility that the latter may be subjected to multiple pathological influences in diabetic patients.
In conclusion, a modest weight loss in overweight well controlled type II diabetic patients is associated with a significant improvement in post-prandial triglyceride excursions and the LDL2/LDL3 mass ratio kinetics independently from glycaemic control improvements.
VI-Annexes
Tables and figures
Table 1. Dietary habits and prescribed diet. Results are expressed as mean ± SD; *: P<0.05 between dietary habits recorded and prescribed data. Dietary habits: data collected from the dietary habits recorded at entry. Prescribed diet: diet followed during the study period.
Table 2. Physical characteristics before and after weight loss.
Results are expressed as mean ± SD; *: P<0.05 between before and after weight loss.
Table 3. Mean values ± SD are given for fasting and post-prandial blood samples obtained 4h after breakfast (pp1) and lunch (pp2). *: P<0.01 before vs after weight loss, **: P<0.005 before vs after weight loss.
Figure 1. Fasting and post-prandial capillary blood glucose values before and after weight loss. *: P<0.05 (before vs after weight loss).
Figure 2. Basal and post-prandial capillary triglyceride values before and after weight loss. *: P<0.05 (before vs after weight loss). #: P<0.05 (08:00 AM vs any other daytime)
Figure 3. VLDL-1, VLDL-2 and VLDL-3 cholesterol kinetics before and after weight loss. *: P<0.05 (before vs after weight loss). #: P<0.05 (F vs pp1/pp2).
Figure 4. LDL-2, LDL-3 cholesterol and LDL-2/LDL-3 mass ratio kinetics before and after weight loss. *: P<0.05 (before vs after weight loss). #: P<0.05 (F vs pp1/pp2).
Dietary habits Prescribed diet P
Kcal/day 2167 ± 178 (1600-3146) 1561 ± 39 (1400-1700) 0.01
Carbohydrates (gr.) 197 ± 13 196 ± 4 NS
Carbohydrates (%) 37.8 ± 3.3 50.3 ± 1.4
Fat (gr.) 96 ± 12 62 ± 4 0.03
Fat (%) 39.7 ± 3.2 35.5 ± 1.0
Protein (gr.) 92 ± 8 66 ± 3 0.02
Protein (%) 17.2 ± 1.2 16.9 ± 7.0
NaCl (gr./day) 5 5 NS
(Results are expressed as: mean values SD)± .
Before weight loss After weight loss
Weight (Kg) 79.2 ± 4.2 77.6 ± 4.0 *
Body Mass Index (Kg/m2) 28.0 ± 1.7 27.4 ± 1.6
Body Fat Mass (Kg) 27.8 ± 1.3 26.3 ± 1.9*
Waist circumference (cm) 95.0 ± 1.4 93.0 ± 3.0
Hip circumference (cm) 100.0 ± 3.0 98.0 ± 2.0 *
Waist/Hip ratio 0.95 ± 0.1 0.93 ± 0.1
Fasting blood sugar (mM/l) 7.3 ± 2.1 6.7 ± 2.6
Post-prandial blood sugar (mM/l) 8.2 ±2.6 6.5 ± 1.9 *
HbA1C (%) 7.3 ± 0.1 ---
Systolic Blood Pressure (mm Hg) 147 ± 6.0 142 ± 4.0
Diastolic Blood Pressure (mm Hg) 85 ± 3.0 82 ± 3.0
Before weight loss After weight loss
Fasting pp1 pp2 Fasting pp1 pp2 Cholesterol (mmol/L) 6.1 ± 0.7 6.1 ± 0.9 6.2 ± 0.6 5.3 ± 0.6** 5.2 ± 0.7 5.3 ± 0.5*
HDL-cholesterol (mmol/L) 1.1 ± 0.3 1.2 ± 0.3 1.2 ± 0.3 1.0 ± 0.3 1.0 ± 0.3 1.0 ± 0.3 Apo A-I (g/L) 111 ± 26 115 ± 22 118 ± 27 101 ± 25 103 ± 25 106 ± 26 Apo B (g/L) 93 ± 38 98 ± 21 99 ± 17 86 ± 14 83 ± 14 86 ± 13 Triglycerides (mmol/L) 2.1 ± 0.7 2.3 ± 0.9 2.6 ± 1.0 1.5 ± 0.4** 1.6 ± 0.5 2.1 ± 0.6*
0.00 1.00 2.00 3.00 4.00 5.00
08:00 10:00 12:00 14:00 16:00 18:00
Triglycerides (mmol/L)