Impaired glucose tolerance without hypertriglyceridemia does not enhance postprandial lipemia

Exercise and dietary-mediated reductions in postprandial lipemia

Postprandial hyperlipemia produces long-term derangements in lipid/lipoprotein metabolism, vascular endothelial dysfunction, hypercoagulability, and sympathetic hyperactivity which are strongly linked to atherogenesis. The purpose of this review is to (1) provide a qualitative analysis of the available literature examining the dysregulation of postprandial lipid metabolism in the presence of obesity, (2) inspect the role of adiposity distribution and sex on postprandial lipid metabolism, and (3) examine the role of energy deficit (exercise- and/or energy restriction-mediated), isoenergetic low-carbohydrate diets, and omega-3 (n-3) fatty acid supplementation on postprandial lipid metabolism. We conclude from the literature that central adiposity primarily accounts for sex-related differences in postprandial lipemia and that aerobic exercise attenuates this response in obese or lean men and women to a similar extent through potentially unique mechanisms. In contrast, energy restriction produces only mild reductions in postprandial lipemia suggesting that exercise may be superior to energy restriction alone as a strategy for lowering postprandial lipemia. However, isoenergetic very low-carbohydrate diets and n-3 fatty acid supplementation reduce postprandial lipemia indicating that macronutrient manipulations reduce postprandial lipemia in the absence of energy restriction. Therefore, interactions between exercise/energy restriction and alterations in macronutrient content remain top priorities for the field to identify optimal behavioral treatments to reduce postprandial lipemia.

Postprandial lipaemia in patients with impaired fasting glucose, impaired glucose tolerance and diabetes mellitus

AIMS

To compare the postprandial lipid responses in subjects with prediabetes (IFG and IGT), newly detected diabetes mellitus (NDDM) and normal glucose tolerance (NGT).

METHODS

Postprandial lipid responses to a standard oral fat challenge was studied in forty-four subjects who were divided after an OGTT into NGT, pure impaired fasting glucose (PIFG), pure impaired glucose tolerance (PIGT) and NDDM.

RESULTS

There was a significantly higher postprandial triglyceride (PPTg) response with a higher PPTg area under curve (p=0.004) and peak PPTg levels (p=0.003) in patients with NDDM but not with either PIFG (p>0.05) or PIGT (p>0.05) when compared with NGT. Overall, PPTg responses correlated significantly with fasting plasma glucose (p=0.001) and 2h plasma glucose (p=0.001) but not with age, sex, body mass index, waist, or insulin resistance.

CONCLUSION

Subjects with newly detected diabetes mellitus displayed postprandial hypertriglyceridemia after a standard oral fat meal challenge while no such abnormality could be demonstrated in subjects with IFG or IGT. This defect is probably related to glycemic status and insulin resistance.

Emerging risk factors and early atherosclerosis indices in subjects with impaired glucose tolerance

AIM

To evaluate the response to an oral lipid overload, inflammatory markers and carotid intima-media thickness in subjects with impaired glucose tolerance.

METHODS

54 subjects, both sexes, 58 y-old average were submitted to 1) Clinical evaluation 2) Glucose tolerance test with 75 g glucose; classified as normal (2 h plasma glucose<140 mg/dl, n=37) or IGT (2 h G 140-200 mg/dl, n=17), 3) 12 h fasting sample (plasma glucose, lipids, C-reactive protein, fibrinogen and HOMA-IR calculation); 4 and 6 h after the oral lipid overload (1000 kcal, lipids 65 g) glycemia, fibrinogen and triglycerides were reevaluated. Intima-media thickness was calculated by the average of 6 measurements (3 highest of each carotid) evaluated by ultrasonography (7 MHZ transducer).

RESULTS

The IGT group had higher (P<0.001) fasting plasma glucose (89.4 +/- 13 vs 104.4 +/- 8 mg/dl), HOMA-IR (1.69 +/- 1.2 vs 2.93 +/- 2.2) and waist (91 +/- 14 vs 101 +/- 9 cm), similar fasting lipids, intima-media thickness (P=0.58) and post-oral lipid overload triglycerides (P=0.74), but higher fibrinogen (284.3 +/- 6 and 305 +/- 10 mg/dl, P=0.05) and C-reactive protein (2.11 +/- 0.33 and 4.19 +/- 0.65 mg/l, P=0.003). C-reactive protein was positively correlated with HOMA-IR (r=0.45, P=0.001), fasting plasma glucose (r=0.43, P=0.002) and waist (r=0.45, P=0.0006), but not with postprandial lipids.

CONCLUSION

A higher C-reactive protein in IGT, and its positive correlation with insulin resistance indices, but not with postprandial lipaemia, suggests that the clustering of these factors, characteristic of the metabolic syndrome, occurs earlier than postprandial lipid abnormalities.

Metabolic response to oral lipid overload in diabetes and impaired glucose tolerance

Post-prandial hyperglycemia and hypertriglyceridemia have been related to atherogenesis. The aim of this study was to evaluate the response of plasma lipoproteins to a lipid overload in subjects with diabetes (DM), impaired glucose tolerance (IGT) and normals (N). Seventy-seven subjects were selected, 36-85 years, plasma glucose (G)<140 mg/dl and triglycerides (TG)<150 mg/dl; those without diabetes underwent a glucose tolerance test (GTT), which classified them into three groups: N, 2h G<140 mg/dl, n=37; IGT, 2h G 140-200mg/dl, n=20; and DM, previous diabetes or 2h G>200mg/dl, n=20. They were submitted to a clinical evaluation and an oral lipid overload (1000 kcal, 58% fat). Fasting, 4 and 6-h blood samples after the meal were collected for G, insulinaemia (I), TG, cholesterol and their fractions, and HOMA-IR. Fasting and post-lipid overload lipoproteins were similar between groups, but 6h TG was still high in DM versus IGT and N as compared to their 4h values. There was a positive correlation between fasting TG versus 6h TG (r=0.78, p<0.001). We conclude that individuals with impaired glucose tolerance and with diabetes mellitus have a slower plasma reduction of triglycerides after lipid overload, as well as an altered glucose and post-prandial insulin response.

Contribution of visceral adiposity to the exaggerated postprandial lipemia of men with impaired glucose tolerance

OBJECTIVE

Impaired glucose tolerance (IGT) has been associated with alterations in numerous coronary heart disease risk factors, including postprandial hyperlipidemia. An excess visceral adipose tissue accumulation is also predictive of IGT and of an exaggerated postprandial lipemia. The objective of the present study was therefore to compare the respective contributions of visceral adipose tissue accumulation versus IGT with the variation in postprandial lipemia.

RESEARCH DESIGN AND METHODS

Potential differences in postprandial triglyceride (TG)-rich lipoprotein (TRL) levels following a standardized breakfast with a high fat content were examined among men characterized by normal glucose tolerance (NGT) or IGT. Sixty-seven men were classified according to their glucose tolerance status (<7.8 mmol/l [NGT] or between 7.8 and 11.1 mmol/l [IGT] 2 h after a 75-g oral glucose test).

RESULTS

Men with IGT showed the highest TRL-TG concentrations (P < 0.05) at the 4-, 6-, and 8-h time points compared with men with NGT. These higher postprandial TRL-TG levels among men with IGT were also accompanied by a greater postprandial TG total area under the incremental curve in all TRL fractions (large, medium, and small) (P < 0.05). Furthermore, subjects characterized by IGT had also the highest visceral adipose tissue accumulation (P < 0.009). When subgroups of IGT and NGT men were individually matched (n = 11) for similar visceral adipose tissue accumulation, no significant difference was found in postprandial responses of all TRL-TG fractions between the two groups.

CONCLUSIONS

These results provide evidence that visceral adipose tissue accumulation is an important factor involved in the deterioration of postprandial lipemia noted among men with IGT.