Simeon I Taylor

Familial Hypercholesterolemia and Type 2 Diabetes in the Old Order Amish

Alleles associated with lower levels of LDL cholesterol (LDL-C) have recently been associated with an increased risk of type 2 diabetes (T2D), highlighting the complex relationship between LDL-C and diabetes. This observation begs the question of whether LDL-C–raising alleles are associated with a decreased risk of T2D. This issue was recently addressed in a large familial hypercholesterolemia (FH) screening study, which reported a lower prevalence of self-reported diabetes in FH subjects than in age-matched relatives without FH. To extend this observation, we tested the association of FH with diabetes status and glycemia in a large Amish population enriched for the FH-associated APOB R3527Q variant that included 640 APOB R3527Q carriers and 4,683 noncarriers. Each copy of the R3527Q T allele was associated with a 74.9 mg/dL increase in LDL-C. There was little difference in T2D prevalence between subjects with (5.2%) and without (4.5%) the R3527Q allele (P = 0.23), and there was no association between R3527Q variant and impaired fasting glucose, fasting glucose or insulin, or oral glucose tolerance test–derived measures. Our data provide no evidence supporting an association between the APOB R3527Q variant and T2D or glycemia and highlight the asymmetry of the LDL-C–T2D relationship and/or the gene/variant-dependent specificity of the LDL-C–T2D association.

Diabetic ketoacidosis, sodium glucose transporter-2 inhibitors and the kidney.

Diabetic ketoacidosis is a serious metabolic condition that may occur in patients with either Type 1 or Type 2 diabetes. The accumulation of ketoacids in the serum is a consequence of insulin deficiency and glucagon excess. Sodium Glucose Transporter 2 (SGLT2) inhibitors are novel therapeutic treatments for improving glucose homeostasis in patients with diabetes. Through reductions in glucose reabsorption by the kidney, they lower serum glucose in patients with Type 2 diabetes and they improve glucose control whether used alone or in combination with other therapies. Mechanistically, these drugs increase serum ketoacids and increase glucagon production, which in some individuals, can lead to formation of diabetic ketoacidosis. This review will first focus in how the kidney normally handles ketoacids, and second will discuss how the SGLT2 inhibitors affect the kidney in such a way so as to enhance the risk for development of ketoacidosis in susceptible individuals.

Insulin Access and Affordability Working Group: Conclusions and Recommendations

There are more than 30 million Americans with diabetes, a disease that costs the U.S. more than

Human biallelic MFN2 mutations induce mitochondrial dysfunction, upper body adipose hyperplasia, and suppression of leptin expression

327 billion per year (1,2). Achieving glycemic control and controlling cardiovascular risk factors have been conclusively shown to reduce diabetes complications, comorbidities, and mortality. To achieve these desired outcomes, the medical community now has available many classes of medications and many formulations of insulin to effectively manage the metabolic abnormalities for people with diabetes. However, the affordability of medications in general, and for insulin specifically, is currently of great concern to people with diabetes, their families, health care providers, insurers, and employers. For millions of people living with diabetes, including all individuals with type 1 diabetes, access to insulin is literally a matter of life and death. The average list price of insulin has skyrocketed in recent years, nearly tripling between 2002 and 2013 (3). The reasons for this increase are not entirely clear but are due in part to the complexity of drug pricing in general and of insulin pricing in particular. As the price of insulin continues to rise, individuals with diabetes are often forced to choose between purchasing their medications or paying for other necessities, exposing them to serious short- and long-term health consequences (4–9). To find solutions to the issue of insulin affordability, there must be a better understanding of the transactions throughout the insulin supply chain, the impact each stakeholder has on what people with diabetes pay for insulin, and the relative efficacy of therapeutic options. Thus, as the nation’s leading voluntary health organization whose mission is “to prevent and cure diabetes and to improve the lives of all people affected by diabetes,” the American Diabetes Association (ADA) is committed to finding ways to provide relief for individuals and families who lack affordable access …

Deletion of interleukin 1 receptor associated kinase 1 (IRAK1) improves glucose tolerance primarily by increasing insulin sensitivity in skeletal muscle

MFN2 encodes mitofusin 2, a membrane-bound mediator of mitochondrial membrane fusion and inter-organelle communication. MFN2 mutations cause axonal neuropathy, with associated lipodystrophy only occasionally noted, however homozygosity for the p.Arg707Trp mutation was recently associated with upper body adipose overgrowth. We describe similar massive adipose overgrowth with suppressed leptin expression in four further patients with biallelic MFN2 mutations and at least one p.Arg707Trp allele. Overgrown tissue was composed of normal-sized, UCP1-negative unilocular adipocytes, with mitochondrial network fragmentation, disorganised cristae, and increased autophagosomes. There was strong transcriptional evidence of mitochondrial stress signalling, increased protein synthesis, and suppression of signatures of cell death in affected tissue, whereas mitochondrial morphology and gene expression were normal in skin fibroblasts. These findings suggest that specific MFN2 mutations cause tissue-selective mitochondrial dysfunction with increased adipocyte proliferation and survival, confirm a novel form of excess adiposity with paradoxical suppression of leptin expression, and suggest potential targeted therapies. DOI: http://dx.doi.org/10.7554/eLife.23813.001

Effect of Leptin Administration on Circulating Apolipoprotein CIII levels in Patients With Lipodystrophy

Chronic inflammation may contribute to insulin resistance via molecular cross-talk between pathways for pro-inflammatory and insulin signaling. Interleukin 1 receptor-associated kinase 1 (IRAK-1) mediates pro-inflammatory signaling via IL-1 receptor/Toll-like receptors, which may contribute to insulin resistance, but this hypothesis is untested. Here, we used male Irak1 null (k/o) mice to investigate the metabolic role of IRAK-1. C57BL/6 wild-type (WT) and k/o mice had comparable body weights on low-fat and high-fat diets (LFD and HFD, respectively). After 12 weeks on LFD (but not HFD), k/o mice (versus WT) had substantially improved glucose tolerance (assessed by the intraperitoneal glucose tolerance test (IPGTT)). As assessed with the hyperinsulinemic euglycemic glucose clamp technique, insulin sensitivity was 30% higher in the Irak1 k/o mice on chow diet, but the Irak1 deletion did not affect IPGTT outcomes in mice on HFD, suggesting that the deletion did not overcome the impact of obesity on glucose tolerance. Moreover, insulin-stimulated glucose-disposal rates were higher in the k/o mice, but we detected no significant difference in hepatic glucose production rates (± insulin infusion). Positron emission/computed tomography scans indicated higher insulin-stimulated glucose uptake in muscle, but not liver, in Irak1 k/o mice in vivo. Moreover, insulin-stimulated phosphorylation of Akt was higher in muscle, but not in liver, from Irak1 k/o mice ex vivo. In conclusion, Irak1 deletion improved muscle insulin sensitivity, with the effect being most apparent in LFD mice.

Metabolic syndrome: an ill wind that blows some good?

CONTEXT Apolipoprotein CIII (apoCIII), an inhibitor of lipoprotein lipase, plays an important role in triglyceride metabolism. However, the role of apoCIII in hypertriglyceridemia in lipodystrophy and the effects of leptin replacement on apoCIII levels are unknown. OBJECTIVE The objective of the study was to test the hypotheses that apoCIII is elevated in hypertriglyceridemic patients with lipodystrophy and that leptin replacement in these patients lowers circulating apoCIII. DESIGN, SETTING, STUDY PARTICIPANTS, INTERVENTION, AND OUTCOME MEASURES Using a post hoc cross-sectional case-control design, we compared serum apoCIII levels from patients with lipodystrophy not associated with HIV (n = 60) and age-, gender-, race-, and ethnicity-matched controls (n = 54) participating in ongoing studies at the National Institutes of Health. In a prospective, open-label, ongoing study, we studied the effects of 6–12 months of leptin replacement on apoCIII in lipodystrophy patients as an exploratory outcome. RESULTS ApoCIII was higher in lipodystrophy patients (geometric mean [25th and 75th percentiles]) (23.9 mg/dL [14.6, 40.3]) compared with controls (14.9 mg/dL [12.3, 17.7]) (P < .0001). ApoCIII and triglyceride levels were positively correlated in patients with lipodystrophy (R = 0.72, P < .0001) and healthy controls (R = 0.6, P < .0001). Leptin replacement (6–12 mo) did not significantly alter apoCIII (before leptin: 23.4 mg/dL [14.5, 40.1]; after leptin: 21.4 mg/dL [16.7, 28.3]; P = .34). CONCLUSIONS Leptin replacement in lipodystrophy did not alter serum apoCIII levels. Elevated apoCIII may play a role in the hypertriglyceridemia of lipodystrophy independent of leptin deficiency and replacement.

Adverse effects of SGLT2 inhibitors on bone health

In this issue of the journal, Brima et al. report thought‐provoking research providing a potential evolutionary rationale whereby natural selection might have preserved genes that predispose to metabolic syndrome. When CD‐1 mice were fed a high fat diet, this induced metabolic changes characteristic of metabolic syndrome. In addition, the high fat diet provided substantial protection from lethality due to infection with Trypanosoma cruzi. The authors hypothesize that the same genes predispose to both metabolic syndrome and protection against infectious disease. Thus, the selective advantage of not dying from infectious disease implicitly provides selective pressure predisposing to metabolic syndrome. This hypothesis follows a similar line of reasoning that has provided explanations for the survival of the HbS mutation for sickle cell disease and renal disease‐associated genetic variants in apolipoprotein L1. Variants in these two genes provide protection from malaria and Trypanosoma brucei rhodesiense, respectively. Copyright

Monocyte DPP4 Expression in Human Atherosclerosis Is Associated With Obesity and Dyslipidemia

Sodium–glucose cotransporter 2 (SGLT2) inhibitors provide metabolic and cardiorenal benefits for patients with type 2 diabetes but are associated with a number of safety issues. Here, we discuss evidence suggesting that indirect activation of the FGF23–1,25-dihydroxyvitamin D–parathyroid hormone axis by SGLT2 inhibition might contribute to adverse effects on bone health.

GLP-1 receptor agonists: differentiation within the class

Studies including ours indicate that systemic inhibition of dipeptidyl peptidase 4 (DPP4), an ubiquitously expressed peptidase, by pharmaceutical inhibitors improved atherosclerosis (1,2). However, the role of immune cell–derived DPP4 is not well defined in atherosclerosis. Our previous work demonstrated that DPP4 expression on monocytes/macrophages was increased in obesity and associated with the degree of insulin resistance (3). To test if the obesity-related increase of monocyte DPP4 plays a role in vascular disease, we investigated the relationship of monocyte DPP4 expression with human aortic atherosclerosis, obesity, and lipid metabolism. A total of 14 control volunteers and 27 atherosclerotic patients without diagnosed heart, lung, or liver diseases and without prescription drugs (except ACE inhibitors and angiotensin receptor blockers) were selected from Aliskiren Effect on Aortic Plaque Progression (ALPINE), a phase 4 clinical trial (clinical trial reg. no. NCT01417104, clinicaltrials.gov). Presence of aortic atherosclerotic plaque (Fig. 1 A ) was confirmed by high-resolution three-dimensional MRI. Figure 1 A : High-resolution three-dimensional dark-blood MRI was used to confirm the aortic atherosclerotic plaque in patients with atherosclerotic disease. Arrows indicate the thickening of the aortic wall. Scale bars, 10 mm. B and C : DPP4 expression on circulating immune cells. Peripheral blood mononuclear cells were isolated from healthy volunteers, and CD11b+ monocyte and CD3+ T cells were gated for …