De novo lipogenesis and cholesterol synthesis in humans with long-standing type 1 diabetes are comparable to non-diabetic individuals

Lipidomic profiling of plasma free fatty acids in type-1 diabetes highlights specific changes in lipid metabolism

Type-1 diabetes mellitus (T1DM) is associated with metabolic changes leading to alterations in glucose and lipid handling. While T1DM-associated effects on many major plasma lipids have been characterised, such effects on plasma free fatty acids (FFA) have not been fully examined. Using gas chromatography–mass spectrometry, we measured the plasma concentrations of FFA species in individuals with T1DM (n = 44) and age/sex-matched healthy controls (n = 44). Relationships between FFA species and various parameters were evaluated. Plasma concentrations of myristate (14:0), palmitoleate (16:1), palmitate (16:0), linoleate (18:2), oleate (18:1c9), cis-vaccenate (18:1c11), eicosapentaenoate (20:5), arachidonate (20:4) and docosahexanoate (22:6) were reduced in the T1DM group (p < 0.0001 for all, except p = 0.0020 for eicosapentaenoate and p = 0.0068 for arachidonate); α-linolenate (18:3) and dihomo-γ-linolenate (20:3) concentrations were unchanged. The saturated/unsaturated FFA ratio, n-3/n-6 ratio, de novo lipogenesis index (palmitate (main lipogenesis product)/linoleate (only found in diet)) and elongase index (oleate/palmitoleate) were increased in the T1DM group (p = 0.0166, p = 0.0089, p < 0.0001 and p = 0.0008 respectively). The stearoyl-CoA desaturase 1 (SCD1) index 1 (palmitoleate/palmitate) and index 2 (oleate/stearate) were reduced in T1DM (p < 0.0001 for both). The delta-(5)-desaturase (D5D) index (arachidonate/dihomo-γ-linolenate) was unchanged. Age and sex had no effect on plasma FFA concentrations in T1DM, while SCD1 index 1 was positively correlated (p = 0.098) and elongase index negatively correlated with age (p = 0.0363). HbA1c was negatively correlated with all plasma FFA concentrations measured except α-linolenate and dihomo-γ-linolenate. Correlations were observed between plasma FFA concentrations and cholesterol and HDL concentrations, but not LDL concentration or diabetes duration. Collectively, these results aid our understanding of T1DM and its effects on lipid metabolism.

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Plasma concentrations of major FFA species are lower in T1DM compared to controls.

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Plasma FFA concentrations negatively correlates with HbA1c in T1DM.

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The SCD1 index is reduced in T1DM.

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Lipogenesis, elongase, n3/n6, saturated/unsaturated indices are increased in T1DM.

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Collectively, the data highlight specific changes in lipid metabolism in T1DM

Lipoprotein subfraction cholesterol distribution is more atherogenic in insulin resistant adolescents with type 1 diabetes

AIMS/HYPOTHESIS

Adolescents with type 1 diabetes (T1D) often have a less atherogenic-appearing fasting lipid profile than controls, despite increased rates of cardiovascular disease (CVD) as adults. We previously reported an atherogenic lipoprotein subfraction cholesterol distribution associated with insulin resistance (IR) in T1D adults. We sought to determine if T1D youth have more atherogenic profile than controls via a cross-sectional study.

METHODS

Following 3 days of controlled diet and restricted exercise, fasting plasma samples were drawn from 28 T1D youth [50% female, age 15.3 ± 2 yr, body mass index (BMI) 48%ile; diabetes duration 73 ± 52 months, hemoglobin A1c (HbA1c) 8.3 ± 1.4%] and 17 non-diabetic controls (47% female, age: 15.0 ± 2 yr, BMI 49%ile) prior to a hyperinsulinemic euglycemic clamp. Lipoproteins were fractionated by fast protein liquid chromatography (FPLC) and lipoprotein cholesterol distribution determined. Outcome measures were IR assessed by glucose infusion rate (GIR) and FPLC lipoprotein subfraction cholesterol distribution.

RESULTS

T1D youth were more IR (GIR 9.1 ± 3.6 vs. 14.7 ± 3.9 mg/kg/min, p < 0.0001) and had more cholesterol distributed as small dense low density lipoprotein-cholesterol (LDL-C) and less as large buoyant high density lipoprotein-cholesterol (HDL-C) than controls (p < 0.05), despite no differences in the fasting lipid panel. T1D girls lacked the typical female less-atherogenic profile, whereas control girls tended to have a shift toward less dense LDL-C and HDL-C vs. control boys. Among T1D, IR but not HbA1c was associated with a more atherogenic lipoprotein profile.

CONCLUSIONS/INTERPRETATIONS

Normal weight T1D youth, especially females, had more atherogenic LDL-C and HDL-C distributions which correlated with lower insulin sensitivity. IR may contribute to the increased CVD burden in T1D.

Red Blood Cell Fatty Acids and Incident Diabetes Mellitus in the Women's Health Initiative Memory Study

Context

The relations between dietary and/or circulating levels of fatty acids and the development of type 2 diabetes is unclear. Protective associations with the marine omega-3 fatty acids and linoleic acid, and with a marker of fatty acid desaturase activity delta-5 desaturase (D5D ratio) have been reported, as have adverse relations with saturated fatty acids and D6D ratio.

Objective

To determine the associations between red blood cell (RBC) fatty acid distributions and incident type 2 diabetes.

Design

Prospective observational cohort study nested in the Women’s Health Initiative Memory Study.

Setting

General population.

Subjects

Postmenopausal women.

Main Outcome Measures

Self-reported incident type 2 diabetes.

Results

There were 703 new cases of type 2 diabetes over 11 years of follow up among 6379 postmenopausal women. In the fully adjusted models, baseline RBC D5D ratio was inversely associated with incident type 2 diabetes [Hazard Ratio (HR) 0.88, 95% confidence interval (CI) 0.81–0.95) per 1 SD increase. Similarly, baseline RBC D6D ratio and palmitic acid were directly associated with incident type 2 diabetes (HR 1.14, 95% CI 1.04–1.25; and HR 1.24, 95% CI 1.14–1.35, respectively). None of these relations were materially altered by excluding incident cases in the first two years of follow-up. There were no significant relations with eicosapentaenoic, docosahexaenoic or linoleic acids.

Conclusions

Whether altered fatty acid desaturase activities or palmitic acid levels are causally related to the development of type 2 diabetes cannot be determined from this study, but our findings suggest that proportions of certain fatty acids in RBC membranes are associated with risk for type 2 diabetes.

The relation of saturated fatty acids with low-grade inflammation and cardiovascular disease

The mantra that dietary (saturated) fat must be minimized to reduce cardiovascular disease (CVD) risk has dominated nutritional guidelines for decades. Parallel to decreasing intakes of fat and saturated fatty acids (SFA), there have been increases in carbohydrate and sugar intakes, overweight, obesity and type 2 diabetes mellitus. The "lipid hypothesis" coined the concept that fat, especially SFA, raises blood low-density lipoprotein-cholesterol and thereby CVD risk. In view of current controversies regarding their adequate intakes and effects, this review aims to summarize research regarding this heterogenic group of fatty acids and the mechanisms relating them to (chronic) systemic low-grade inflammation, insulin resistance, metabolic syndrome and notably CVD. The intimate relationship between inflammation and metabolism, including glucose, fat and cholesterol metabolism, revealed that the dyslipidemia in Western societies, notably increased triglycerides, "small dense" low-density lipoprotein and "dysfunctional" high-density lipoprotein, is influenced by many unfavorable lifestyle factors. Dietary SFA is only one of these, not necessarily the most important, in healthy, insulin-sensitive people. The environment provides us not only with many other proinflammatory stimuli than SFA but also with many antiinflammatory counterparts. Resolution of the conflict between our self-designed environment and ancient genome may rather rely on returning to the proinflammatory/antiinflammatory balance of the Paleolithic era in consonance with the 21st century culture. Accordingly, dietary guidelines might reconsider recommendations for SFA replacement and investigate diet in a broader context, together with nondietary lifestyle factors. This should be a clear priority, opposed to the reductionist approach of studying the effects of single nutrients, such as SFA.

Anti-Diabetic Effects of Madecassic Acid and Rotundic Acid

Anti-diabetic effects of madecassic acid (MEA) and rotundic acid (RA) were examined. MEA or RA at 0.05% or 0.1% was supplied to diabetic mice for six weeks. The intake of MEA, not RA, dose-dependently lowered plasma glucose level and increased plasma insulin level. MEA, not RA, intake dose-dependently reduced plasminogen activator inhibitor-1 activity and fibrinogen level; as well as restored antithrombin-III and protein C activities in plasma of diabetic mice. MEA or RA intake decreased triglyceride and cholesterol levels in plasma and liver. Histological data agreed that MEA or RA intake lowered hepatic lipid droplets, determined by ORO stain. MEA intake dose-dependently declined reactive oxygen species (ROS) and oxidized glutathione levels, increased glutathione content and maintained the activity of glutathione reductase and catalase in the heart and kidneys of diabetic mice. MEA intake dose-dependently reduced interleukin (IL)-1β, IL-6, tumor necrosis factor-α and monocyte chemoattractant protein-1 levels in the heart and kidneys of diabetic mice. RA intake at 0.1% declined cardiac and renal levels of these inflammatory factors. These data indicated that MEA improved glycemic control and hemostatic imbalance, lowered lipid accumulation, and attenuated oxidative and inflammatory stress in diabetic mice. Thus, madecassic acid could be considered as an anti-diabetic agent.

The role of dietary sugars and de novo lipogenesis in non-alcoholic fatty liver disease

Dietary sugar consumption, in particular sugar-sweetened beverages and the monosaccharide fructose, has been linked to the incidence and severity of non-alcoholic fatty liver disease (NAFLD). Intervention studies in both animals and humans have shown large doses of fructose to be particularly lipogenic. While fructose does stimulate de novo lipogenesis (DNL), stable isotope tracer studies in humans demonstrate quantitatively that the lipogenic effect of fructose is not mediated exclusively by its provision of excess substrates for DNL. The deleterious metabolic effects of high fructose loads appear to be a consequence of altered transcriptional regulatory networks impacting intracellular macronutrient metabolism and altering signaling and inflammatory processes. Uric acid generated by fructose metabolism may also contribute to or exacerbate these effects. Here we review data from human and animal intervention and stable isotope tracer studies relevant to the role of dietary sugars on NAFLD development and progression, in the context of typical sugar consumption patterns and dietary recommendations worldwide. We conclude that the use of hypercaloric, supra-physiological doses in intervention trials has been a major confounding factor and whether or not dietary sugars, including fructose, at typically consumed population levels, effect hepatic lipogenesis and NAFLD pathogenesis in humans independently of excess energy remains unresolved.

Update on screening, etiology, and treatment of dyslipidemia in children

CONTEXT

Cardiovascular disease is a leading cause of morbidity and mortality. Early identification and treatment of risk factors that accelerate this condition are paramount to preventing disease. To this effect, the National Heart Lung and Blood Institute (NHLBI), endorsed by the American Academy of Pediatrics, issued updated pediatric guidelines for cardiovascular risk reduction in 2011. Integration of these guidelines into pediatric practice may lessen cardiovascular morbidity.

EVIDENCE ACQUISITION

In addition to reviewing the NHLBI guidelines, a detailed literature search was performed on PubMed for clinical studies published between 2010 and 2013. Key search terms included "pediatric dyslipidemia/hyperlipidemia," "cardiovascular disease," "atherosclerosis," "familial hypercholesterolemia," "hypertriglyceridemia," and "diabetes." Additional citations from these publications were also reviewed. Final publications were selected for their relevance to the topic.

EVIDENCE SYNTHESIS

These guidelines contain several important recommendations relative to lipid management, including screening all children with nonfasting non-high-density lipoprotein-cholesterol at ages 9-11 years, incorporation of aggressive lifestyle changes to meet cholesterol targets, and initiation of statin therapy for those with low-density lipoprotein-cholesterol elevation. In addition, both type 1 and type 2 diabetes are now considered high-risk conditions and have stringent cholesterol targets. The primary aim is early identification of children with familial hypercholesterolemia; however, these recommendations have met with some controversy. The purpose of this update is to summarize these recent lipid guidelines, present the relevant controversies, highlight common cholesterol disorders, and discuss dyslipidemia specific to the pediatric diabetes population.

CONCLUSION

Identification and treatment of youth with dyslipidemia is of paramount importance to the reduction of future cardiovascular disease. Increasing the comprehension and application of the newest NHLBI guidelines is critical to improving cardiovascular outcomes.