Postprandial chylomicron clearance rate in late teenagers with diabetes mellitus type 1

Dyslipidemia in Type 1 Diabetes: AMaskedDanger

Type 1 diabetes (T1D) patients show lipid disorders which are likely to play a role in their increased cardiovascular (CV) disease risk. Quantitative abnormalities of lipoproteins are noted in T1D with poor glycemic control. In T1D with optimal glycemic control, triglycerides and LDL-cholesterol are normal or slightly decreased whereas HDL-cholesterol is normal or slightly increased. T1D patients, even with good glycemic control, show several qualitative and functional abnormalities of lipoproteins that are potentially atherogenic. An association between these abnormalities and CV disease risk has been reported in recent studies. Although the mechanisms underlying T1D dyslipidemia remain unclear, the subcutaneous route of insulin administration, that is responsible for peripheral hyperinsulinemia, is likely to be an important factor.

Altered Skeletal Muscle Mitochondrial Proteome As the Basis of Disruption of Mitochondrial Function in Diabetic Mice

Insulin plays pivotal role in cellular fuel metabolism in skeletal muscle. Despite being the primary site of energy metabolism, the underlying mechanism on how insulin deficiency deranges skeletal muscle mitochondrial physiology remains to be fully understood. Here we report an important link between altered skeletal muscle proteome homeostasis and mitochondrial physiology during insulin deficiency. Deprivation of insulin in streptozotocin-induced diabetic mice decreased mitochondrial ATP production, reduced coupling and phosphorylation efficiency, and increased oxidant emission in skeletal muscle. Proteomic survey revealed that the mitochondrial derangements during insulin deficiency were related to increased mitochondrial protein degradation and decreased protein synthesis, resulting in reduced abundance of proteins involved in mitochondrial respiration and β-oxidation. However, a paradoxical upregulation of proteins involved in cellular uptake of fatty acids triggered an accumulation of incomplete fatty acid oxidation products in skeletal muscle. These data implicate a mismatch of β-oxidation and fatty acid uptake as a mechanism leading to increased oxidative stress in diabetes. This notion was supported by elevated oxidative stress in cultured myotubes exposed to palmitate in the presence of a β-oxidation inhibitor. Together, these results indicate that insulin deficiency alters the balance of proteins involved in fatty acid transport and oxidation in skeletal muscle, leading to impaired mitochondrial function and increased oxidative stress.

Secondary hypertriglyceridemia in children and adolescents

Secondary dyslipidemia with predominant hypertriglyceridemia may occur as a consequence of both common and rare causes. After accounting for obesity and associated insulin resistance, clinicians should carefully consider other contributing factors and conditions. Genetic background and causative factors prevail during gestation, infancy, and childhood and continue in adults. Elevations in triglyceride (TG) are associated with transfer of TG to high-density lipoprotein (HDL) and low-density lipoprotein (LDL) resulting in lipolysis, HDL degradation, and formation of atherogenic LDL particles. Defining and treating the underlying cause is the first step toward restoring the lipids and lipoproteins to normal, especially in cases with severe hypertriglyceridemia, who are at risk for acute pancreatitis. Disorders involving the liver, kidney, endocrine, and immune systems and medications need to be considered. Rare diseases such as lipodystrophy and glycogen storage disease are particularly challenging, and there have been promising new developments. Treatment depends on the severity; prevention of acute pancreatitis being a priority in severe cases and lifestyle modification being a foundation for general management followed by targeting TG and predictors of coronary artery disease such as LDL cholesterol and non-HDL cholesterol, when they exceed cutpoints.

Impaired endothelial function in adolescents with type 1 diabetes mellitus

OBJECTIVE

To evaluate the effect of a high-fat meal on endothelial function in adolescents with type 1 diabetes mellitus (T1D).

STUDY DESIGN

Twenty-three children with T1D, aged 12 to 18 years, and age- and sex-matched healthy control subjects were assessed for baseline macronutrient intake, and endothelial function was measured both fasting and after a standardized fast-food, high-fat breakfast.

RESULTS

Endothelial function, assessed noninvasively by peripheral arterial tonometry, was impaired in the T1D group in the fasting state as compared with control subjects (T1D 1.78 +/- 0.4, control subjects 2.06 +/- 0.4, P = .02), and worsened postprandially in both groups (T1D 1.45 +/- 0.3, control subjects 1.71 +/- 0.3, P = .01). Both groups demonstrated significantly elevated triglyceride levels 3.5 hours after ingestion of the high-fat meal (T1D 114.8 +/- 42.8 and control subjects 126.7 +/- 54.9 mg/dL). Nutrient intake in both groups showed higher than recommended intakes of total fat, saturated fat, and cholesterol.

CONCLUSIONS

Patients with T1D exhibited worse endothelial function both before and after a high-fat breakfast than their peers. This suggests that patients with T1D are at greater risk of vascular impairment after a high-fat meal, the cumulative effect of which may contribute to the higher atherosclerotic burden observed in T1D.