Astaxanthin, a natural antioxidant, lowers cholesterol and markers of cardiovascular risk in individuals with prediabetes and dyslipidaemia.

AIM: To determine the effects of astaxanthin treatment on lipids, cardiovascular disease (CVD) markers, glucose tolerance, insulin action and inflammation in individuals with prediabetes and dyslipidaemia. MATERIALS AND METHODS: Adult participants with dyslipidaemia and prediabetes (n = 34) underwent baseline blood draw, an oral glucose tolerance test and a one-step hyperinsulinaemic-euglycaemic clamp. They were then randomized (n = 22 treated, 12 placebo) to receive astaxanthin 12 mg daily or placebo for 24 weeks. Baseline studies were repeated after 12 and 24 weeks of therapy. RESULTS: After 24 weeks, astaxanthin treatment significantly decreased low-density lipoprotein (-0.33 ± 0.11 mM) and total cholesterol (-0.30 ± 0.14 mM) (both P < .05). Astaxanthin also reduced levels of the CVD risk markers fibrinogen (-473 ± 210 ng/mL), L-selectin (-0.08 ± 0.03 ng/mL) and fetuin-A (-10.3 ± 3.6 ng/mL) (all P < .05). While the effects of astaxanthin treatment did not reach statistical significance, there were trends toward improvements in the primary outcome measure, insulin-stimulated, whole-body glucose disposal (+0.52 ± 0.37 mg/m2 /min, P = .078), as well as fasting [insulin] (-5.6 ± 8.4 pM, P = .097) and HOMA2-IR (-0.31 ± 0.16, P = .060), suggesting improved insulin action. No consistent significant differences from baseline were observed for any of these outcomes in the placebo group. Astaxanthin was safe and well tolerated with no clinically significant adverse events. CONCLUSIONS: Although the primary endpoint did not meet the prespecified significance level, these data suggest that astaxanthin is a safe over-the-counter supplement that improves lipid profiles and markers of CVD risk in individuals with prediabetes and dyslipidaemia.

Altered Myokine Secretion Is an Intrinsic Property of Skeletal Muscle in Type 2 Diabetes.

Skeletal muscle secretes factors, termed myokines. We employed differentiated human skeletal muscle cells (hSMC) cultured from Type 2 diabetic (T2D) and non-diabetic (ND) subjects to investigate the impact of T2D on myokine secretion. Following 24 hours of culture concentrations of selected myokines were determined to range over 4 orders of magnitude. T2D hSMC released increased amounts of IL6, IL8, IL15, TNFa, Growth Related Oncogene (GRO)a, monocyte chemotactic protein (MCP)-1, and follistatin compared to ND myotubes. T2D and ND hSMC secreted similar levels of IL1ß and vascular endothelial growth factor (VEGF). Treatment with the inflammatory agents lipopolysaccharide (LPS) or palmitate augmented the secretion of many myokines including: GROa, IL6, IL8, IL15, and TNFa, but did not consistently alter the protein content and/or phosphorylation of IkBa, p44/42 MAPK, p38 MAPK, c-Jun N-terminal kinase (JNK) and NF-kB, nor lead to consistent changes in basal and insulin-stimulated glucose uptake or free fatty acid oxidation. Conversely, treatment with pioglitazone or oleate resulted in modest reductions in the secretion of several myokines. Our results demonstrate that altered secretion of a number of myokines is an intrinsic property of skeletal muscle in T2D, suggesting a putative role of myokines in the response of skeletal muscle to T2D.

Excessive secretion of IL-8 by skeletal muscle in type 2 diabetes impairs tube growth: potential role of PI3K and the Tie2 receptor.

Reduced capillary density is a feature of skeletal muscle (SkM) in type 2 diabetes (T2D), which is associated with multiple metabolic and functional abnormalities. SkM has been identified as a secretory tissue, releasing myokines that regulate multiple processes, including vascularization. We sought to determine how myokines secreted from T2D myotubes might influence SkM angiogenesis. Conditioned media (CM) were generated by myotubes from T2D and nondiabetic (ND) subjects. Primary human endothelial cells (HUVEC) and SkM explants were exposed to CM or recombinant myokines, and tube number or capillary outgrowth was determined as well as measurement of protein expression and phosphorylation. CM from ND myotubes stimulated tube formation of HUVEC to a greater extent than T2D myotubes (T2D-CM = 100%, ND-CM = 288 ± 90% after 48 h, P < 0.05). The effects of T2D myotube CM were mediated by IL-8, not IL-15 or GROα, and were due not to cell damage but rather through regulating tube production and maintenance (response to T2D-IL-8 = 100%, response to ND-IL-8 = 263 ± 46% after 48 h, P < 0.05). A similar effect was seen in SkM explants with exposure to IL-8. The dose-dependent effect of IL-8 on tube formation was also observable in the PI3K and FAK signaling pathways and mediated at least in part by PI3K, leading to regulation of Tie2 expression. These results suggest that elevated levels of IL-8 secreted from T2D myotubes create a muscle microenvironment that supports reduced capillarization in T2D. Impaired vascularization of SkM limits the availability of substrates, including glucose and contributes to the T2D phenotype.

Inflammatory cytokines and chemokines, skeletal muscle and polycystic ovary syndrome: effects of pioglitazone and metformin treatment.

OBJECTIVE: Chronic low-grade inflammation is a common feature of insulin resistant states, including obesity and type 2 diabetes. Less is known about inflammation in Polycystic Ovary Syndrome (PCOS). Thus we evaluated the impact of PCOS on circulating cytokine levels and the effects of anti-diabetic therapies on insulin action, cytokine and chemokine levels and inflammatory signaling in skeletal muscle. METHODS: Twenty subjects with PCOS and 12 healthy normal cycling (NC) subjects of similar body mass index were studied. PCOS subjects received oral placebo or pioglitazone, 45 mg/d, for 6 months. All PCOS subjects then had metformin, 2 g/day, added to their treatment. Circulating levels of cytokines, chemokines, and adiponectin, skeletal muscle markers of inflammation and phosphorylation of signaling proteins, insulin action evaluated by the hyperinsulinemic/euglycemic clamp procedure and Homeostasis Model Assessment of Insulin Resistance were measured. RESULTS: Circulating levels of a number of cytokines and chemokines were generally similar between PCOS and NC subjects. Levels in PCOS subjects were not altered by pioglitazone or metformin treatment, even though whole body insulin action and adiponectin levels increased with pioglitazone. In spite of the lack of change in levels of cytokines and chemokines, several markers of inflammation in skeletal muscle were improved with Pio treatment. CONCLUSIONS: PCOS may represent a state of elevated sensitivity of inflammatory cells in skeletal muscle to cytokines and chemokines, a property that could be reversed by pioglitazone treatment together with improved insulin action.

Adipocyte differentiation-related protein in human skeletal muscle: relationship to insulin sensitivity.

OBJECTIVE: To determine whether adipocyte differentiation-related protein (ADRP), a lipid droplet-associated protein that binds to and sequesters intracellular fatty acids, is 1) expressed in human skeletal muscle and 2) differentially regulated in human skeletal muscle obtained from obese non-diabetic (OND) and obese diabetic (OD) subjects. RESEARCH METHODS AND PROCEDURES: Ten OND subjects and 15 OD subjects underwent a weight loss or pharmacological intervention program to improve insulin sensitivity. Anthropometric data, hemoglobin A(1C), fasting glucose, lipids, and glucose disposal rate were determined at baseline and at completion of studies. Biopsies of the vastus lateralis muscle (SkM) were obtained in the fasting state from OND and OD subjects. Protein expression was determined by Western blotting. RESULTS: ADRP was highly expressed in SkM from OND (4.4 +/- 1.54 AU/10 microg, protein, n = 10) and OD (5.02 +/- 1.33 AU/10 microg, n = 12) subjects. OND subjects undergoing weight loss had decreased triglyceride levels and improved insulin action. SkM ADRP content increased with weight loss from 5.14 +/- 2.15 AU/10 microg to 9.92 +/- 1.57 AU/10 microg (p < 0.025). OD subjects were treated with either troglitazone or metformin, together with glyburide, for 3 to 4 months. Both treatments attained similar levels of glycemic control. OD subjects with lower baseline ADRP content (2.85 +/- 1.07 AU/10 microg, n = 6) displayed up-regulation of ADRP expression (to 9.27 +/- 2.76 AU/10 microg, p < 0.025). DISCUSSION: ADRP is the predominant lipid droplet-associated protein in SkM, and low ADRP expression is up-regulated in circumstances of improved glucose tolerance. Up-regulation of ADRP may act to sequester fatty acids as triglycerides in discrete lipid droplets that could protect muscle from the detrimental effects of fatty acids on insulin action and glucose tolerance.

Impaired fatty acid metabolism in type 2 diabetic skeletal muscle cells is reversed by PPARgamma agonists.

The impact of type 2 diabetes on the ability of muscle to accumulate and dispose of fatty acids and triglycerides was evaluated in cultured muscle cells from nondiabetic (ND) and type 2 diabetic (T2D) subjects. In the presence of 5 microM palmitate, T2D muscle cells accumulated less lipid than ND cells (11.5 +/- 1.2 vs. 15.1 +/- 1.4 nmol/mg protein, P < 0.05). Chronic treatment (4 days) with the peroxisome proliferator-activated receptor-gamma (PPARgamma) agonist troglitazone increased palmitate accumulation, normalizing uptake in T2D cells. There were no significant differences between groups with regard to the relative incorporation of palmitate into neutral lipid species. This distribution was also unaffected by troglitazone treatment. beta-Oxidation of both long-chain (palmitate) and medium-chain (octanoate) fatty acids in T2D muscle cells was reduced by approximately 40% compared with ND cells. Palmitate oxidation occurred primarily in mitochondrial ( approximately 40-50% of total) and peroxisomal (20-30%) compartments. The diabetes-related defect in palmitate oxidation was localized to the mitochondrial component. Both palmitate and octanoate oxidation were stimulated by a series of thiazolidinediones. Oxidation in T2D muscle cells was normalized after treatment. Troglitazone increased the mitochondrial component of palmitate oxidation. Skeletal muscle cells from T2D subjects express defects in free fatty acid metabolism that are retained in vitro, most importantly defects in beta-oxidation. These defects can be corrected by treatment with PPARgamma agonists. Augmentation of fatty acid disposal in skeletal muscle, potentially reducing intramyocellular triglyceride content, may represent one mechanism for the lipid-lowering and insulin-sensitizing effects of thiazolidinediones.

Continuous subcutaneous insulin infusion and multiple daily injection therapy are equally effective in type 2 diabetes: a randomized, parallel-group, 24-week study.

OBJECTIVE: Compare the efficacy, safety, and patient satisfaction of continuous subcutaneous insulin infusion (CSII) therapy with multiple daily injection (MDI) therapy for patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: A total of 132 CSII-naive type 2 diabetic patients were randomly assigned (1:1) to CSII (using insulin aspart) or MDI therapy (bolus insulin aspart and basal NPH insulin) in a multicenter, open-label, randomized, parallel-group, 24-week study. Efficacy was assessed with HbA(1c) and eight-point blood glucose (BG) profiles. Treatment satisfaction was determined with a self-administered questionnaire. Safety assessments included adverse events, hypoglycemic episodes, laboratory values, and physical examination findings. RESULTS: HbA(1c) values decreased similarly for both groups from baseline (8.2 +/- 1.37% for CSII, 8.0 +/- 1.08% for MDI) to end of study (7.6 +/- 1.22% for CSII, 7.5 +/- 1.22% for MDI). The CSII group showed a trend toward lower eight-point BG values at most time points (only significant 90 min after breakfast; 167 +/- 48 vs. 192 +/- 65 mg/dl for CSII and MDI, respectively; P = 0.019). A total of 93% of CSII-treated subjects preferred the pump to their previous injectable insulin regimen for reasons of convenience, flexibility, ease of use, and overall preference. Safety assessments were comparable for both treatment groups. CONCLUSIONS: Insulin aspart in CSII therapy provided efficacy and safety comparable to MDI therapy for type 2 diabetes. Patients with type 2 diabetes can be trained as outpatients to use CSII and prefer CSII to injections, indicating that pump therapy should be considered when initiating intensive insulin therapy for type 2 diabetes.

Thiazolidinediones upregulate impaired fatty acid uptake in skeletal muscle of type 2 diabetic subjects.

We examined the regulation of free fatty acid (FFA, palmitate) uptake into skeletal muscle cells of nondiabetic and type 2 diabetic subjects. Palmitate uptake included a protein-mediated component that was inhibited by phloretin. The protein-mediated component of uptake in muscle cells from type 2 diabetic subjects (78 +/- 13 nmol. mg protein-1. min-1) was reduced compared with that in nondiabetic muscle (150 +/- 17, P < 0.01). Acute insulin exposure caused a modest (16 +/- 5%, P < 0.025) but significant increase in protein-mediated uptake in nondiabetic muscle. There was no significant insulin effect in diabetic muscle (+19 +/- 19%, P = not significant). Chronic (4 day) treatment with a series of thiazolidinediones, troglitazone (Tgz), rosiglitazone (Rgz), and pioglitazone (Pio) increased FFA uptake. Only the phloretin-inhibitable component was increased by treatment, which normalized this activity in diabetic muscle cells. Under the same conditions, FFA oxidation was also increased by thiazolidinedione treatment. Increases in FFA uptake and oxidation were associated with upregulation of fatty acid translocase (FAT/CD36) expression. FAT/CD36 protein was increased by Tgz (90 +/- 22% over control), Rgz (146 +/- 42%), and Pio (111 +/- 37%, P < 0.05 for all 3) treatment. Tgz treatment had no effect on fatty acid transporter protein-1 and membrane-associated plasmalemmal fatty acid-binding protein mRNA expression. We conclude that FFA uptake into cultured muscle cells is, in part, protein mediated and acutely insulin responsive. The basal activity of FFA uptake is impaired in type 2 diabetes. In addition, chronic thiazolidinedione treatment increased FFA uptake and oxidation into cultured human skeletal muscle cells in concert with upregulation of FAT/CD36 expression. Increased FFA uptake and oxidation may contribute to lower circulating FFA levels and reduced insulin resistance in skeletal muscle of individuals with type 2 diabetes following thiazolidinedione treatment.

Inhaled insulin using the AERx Insulin Diabetes Management System in healthy and asthmatic subjects.

OBJECTIVE: The AERx insulin Diabetes Management System (AERx iDMS) (Aradigm, Hayward, CA) delivers an aerosol of liquid human insulin to the deep lung for systemic absorption. This study examined the effects on pulmonary function, pharmacokinetics, and pharmacodynamics of inhaled insulin in asthmatic and nonasthmatic subjects without diabetes. RESEARCH DESIGN AND METHODS: A total of 28 healthy and 17 asthmatic (forced expiratory volume during the first second [ FEV(1)] 50-80% of predicted value) subjects were enrolled in a two-part, open-label trial. To assess insulin pharmacokinetics and pharmacodynamics, a single inhalation dose of 1.57 mg (45 IU) was given on each of the 2 dosing days in part 1. A dose of 4.7 mg (135 IU) of insulin was inhaled in part 2 to assess effects on pulmonary function. RESULTS: Inhaled insulin showed area under the curve (AUC)((0-360 min)) values that were significantly greater for healthy subjects than for asthmatic subjects (P = 0.013), whereas no difference was observed for maximum concentration (C(max)) in the two groups. A greater reduction of serum glucose as indicated by area over the curve (AOC)((0-360 min)) was observed in healthy subjects (P = 0.007). Asthmatic subjects had greater intrasubject variations in insulin AUC((0-360 min)) and C(max) values than healthy subjects, but similar variations in glucose AOC((0-360 min)). No significant changes in FEV(1), forced vital capacity (FVC), and FEV(1)/FVC were observed from pre- to postdose times, and there were no observed safety issues. CONCLUSIONS: After inhaling insulin using the AERx iDMS, asthmatic subjects absorbed less insulin than healthy subjects, resulting in less reduction of serum glucose. No effects on airway reactivity were observed. Diabetic patients with asthma may need to inhale more insulin than patients with normal respiratory function in order to achieve similar glycemic control.

Modulation of circulating and adipose tissue adiponectin levels by antidiabetic therapy.

The relationship between insulin action and control of the adipocyte-derived factor adiponectin was studied in age- and weight-matched obese individuals with type 2 diabetes failing sulfonylurea therapy. After initial metabolic characterization, subjects were randomized to troglitazone or metformin treatment groups; all subjects received glyburide (10 mg BID) as well. Treatment was continued for 3 months. The extent of glycemic control after treatment was similar in both groups. However, the increase in maximal insulin-stimulated glucose disposal rate was greater following troglitazone therapy (+44%) compared with metformin treatment (+20%). Troglitazone treatment increased serum adiponectin levels nearly threefold. There was no change in serum adiponectin with metformin treatment. A positive correlation was found between increases in whole-body glucose disposal rates and serum adiponectin levels after troglitazone; no such relationship was seen with metformin. The adiponectin protein content of subcutaneous abdominal adipocytes was increased following troglitazone treatment and unchanged after metformin. Adiponectin release from adipocytes was also augmented with troglitazone treatment. Adiponectin was present in adipocytes and plasma in several multimeric forms; a trimer was the major form secreted from adipocytes. These results indicate that increases in adiponectin content and secretion are associated with improved insulin action but are not directly related to glycemic control. Modulation of adipocyte function, including upregulation of adiponectin synthesis and secretion, may be an important mechanism by which thiazolidinediones influence insulin action.

Impact of pramlintide on glucose fluctuations and postprandial glucose, glucagon, and triglyceride excursions among patients with type 1 diabetes intensively treated with insulin pumps.

OBJECTIVE: To assess the effects of adjunctive treatment with pramlintide, an analog of the beta-cell hormone amylin, on 24-h glucose fluctuations and postprandial glucose, glucagon, and triglyceride excursions in patients with type 1 diabetes intensively treated with continuous subcutaneous insulin infusion (CSII). RESEARCH DESIGN AND METHODS: In this study, 18 patients (16 of whom could be evaluated) with type 1 diabetes (age 44 +/- 11 years, HbA(1c) 8.2 +/- 1.3% [mean +/- SD]) were given mealtime injections of 30 micro g pramlintide t.i.d. for 4 weeks in addition to their preexisting CSII regimen (16 lispro, 2 regular insulin). Mealtime insulin boluses were reduced by a minimum of 10% during the first 3 days, and re-adjusted thereafter based on clinical judgment. At weeks 0 (baseline), 4 (on treatment), and 6 (2 weeks off treatment), 24-h interstitial glucose concentrations were measured using a continuous glucose monitoring system (CGMS), and postprandial plasma glucose, glucagon, and triglyceride concentrations were measured in response to a standardized test meal. RESULTS: At baseline, patients had excessive 24-h glucose fluctuations, with 59% of the CGMS measurements >140 mg/dl, 13% <80 mg/dl, and only 28% in the euglycemic range (80-140 mg/dl). After 4 weeks on pramlintide, measurements in the hyperglycemic range declined to 48% and measurements within the euglycemic range increased to 37%. This shift from the hyperglycemic to the euglycemic range occurred with a concomitant 17% reduction in mealtime insulin dosages and without relevant increases in measurements below the euglycemic range (15%) or any severe hypoglycemic events. After 4 weeks on pramlintide, postprandial glucose, glucagon, and triglyceride excursions were reduced by approximately 86, approximately 87, and approximately 72%, respectively (incremental areas under the curve, all P < 0.05 vs. baseline). At week 6 (off treatment), the 24-h glucose profile and postprandial glucose, glucagon, and triglyceride excursions approached pretreatment values. CONCLUSIONS: In this study, the addition of pramlintide to insulin therapy reduced excessive 24-h glucose fluctuations as well as postprandial glucose, glucagon, and triglyceride excursions in patients with type 1 diabetes intensively treated with insulin pumps.

Free fatty acid metabolism in human skeletal muscle is regulated by PPARgamma and RXR agonists.

Free fatty acid (FFA) oxidation in human skeletal muscle cells can be stimulated, both independently and in a synergistic manner, by agonists for PPARgamma and RXR. Increased FFA disposal in muscle through augmented oxidation could reduce intramyocellular lipid accumulation. The abilities of such agents to improve glucose tolerance and insulin action may thus involve effects on both glucose and FFA metabolism.

Differential effects of metformin and troglitazone on cardiovascular risk factors in patients with type 2 diabetes.

OBJECTIVE: Traditional cardiovascular risk factors (CVRF) only partly explain the excessive risk of cardiovascular disease in patients with type 2 diabetes. There is now an increasing appreciation for many novel CVRF that occur largely as a result of insulin resistance and hyperinsulinemia. Therefore, we investigated whether diabetes medications that vary in their mechanism of action and ability to reduce insulin resistance may differ in their effects on both traditional and novel CVRF. RESEARCH DESIGN AND METHODS: We compared the addition of metformin or troglitazone therapy on CVRF in 22 subjects with type 2 diabetes who remained in poor glycemic control (with HbA1c >8.5%) while taking glyburide 10 mg twice daily. Subjects were initially randomized to either metformin 850 mg once daily or troglitazone 200 mg once daily. Both medications were then titrated upward as needed to achieve fasting plasma glucose <120 mg/dl. Measures of glucose control, insulin resistance, and CVRF (blood pressure, lipids, plasminogen activator inhibitor-1, C-reactive protein, fibrinogen, and small dense LDL) were assessed both before and after therapy. RESULTS: After 4 months of treatment, both metformin and troglitazone led to similar decreases in fasting plasma glucose and HbA1c. The reduction in insulin resistance determined by hyperinsulinemic-euglycemic clamp was nearly twofold greater with troglitazone than metformin. Metformin did not induce significant changes in blood pressure, LDL cholesterol, LDL size, HDL cholesterol, triglycerides, or plasminogen activator inhibitor-1. However, C-reactive protein did decrease by 33% (6 +/- 1 to 4 +/- 1 mg/l; P < 0.01) [corrected]. Troglitazone therapy was associated with increases in LDL size (26.21 +/- 0.22 to 26.56 +/- 0.25 nm; P=0.04) and HDL cholesterol (33 +/- 3 to 36 +/- 3 mg/dl; P=0.05) and decreases in triglycerides (197 +/- 19 to 155 +/- 23 mg/dl; P=0.07) and C-reactive protein by 60% (8 +/- 3 to 3 +/- 1 mg/l, P < 0.01) [corrected]. CONCLUSIONS: For patients with type 2 diabetes in whom maximal sulfonylurea therapy failed, the addition of the insulin sensitizer troglitazone seemed to have greater benefits on several traditional and novel CVRF than metformin therapy. These differences were not related to glycemic improvement but reflected, in part, the greater reduction in insulin resistance obtained with addition of troglitazone. These data suggest that medications that more effectively address this underlying metabolic defect may be more beneficial in reducing cardiovascular risk in type 2 diabetes.