Henry J. Pownall

Cardiovascular effects of intensive lifestyle intervention in type 2 diabetes

BACKGROUND Weight loss is recommended for overweight or obese patients with type 2 diabetes on the basis of short-term studies, but long-term effects on cardiovascular disease remain unknown. We examined whether an intensive lifestyle intervention for weight loss would decrease cardiovascular morbidity and mortality among such patients. METHODS In 16 study centers in the United States, we randomly assigned 5145 overweight or obese patients with type 2 diabetes to participate in an intensive lifestyle intervention that promoted weight loss through decreased caloric intake and increased physical activity (intervention group) or to receive diabetes support and education (control group). The primary outcome was a composite of death from cardiovascular causes, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for angina during a maximum follow-up of 13.5 years. RESULTS The trial was stopped early on the basis of a futility analysis when the median follow-up was 9.6 years. Weight loss was greater in the intervention group than in the control group throughout the study (8.6% vs. 0.7% at 1 year; 6.0% vs. 3.5% at study end). The intensive lifestyle intervention also produced greater reductions in glycated hemoglobin and greater initial improvements in fitness and all cardiovascular risk factors, except for low-density-lipoprotein cholesterol levels. The primary outcome occurred in 403 patients in the intervention group and in 418 in the control group (1.83 and 1.92 events per 100 person-years, respectively; hazard ratio in the intervention group, 0.95; 95% confidence interval, 0.83 to 1.09; P=0.51). CONCLUSIONS An intensive lifestyle intervention focusing on weight loss did not reduce the rate of cardiovascular events in overweight or obese adults with type 2 diabetes. (Funded by the National Institutes of Health and others; Look AHEAD ClinicalTrials.gov number, NCT00017953.).

Long-term effects of a lifestyle intervention on weight and cardiovascular risk factors in individuals with type 2 diabetes mellitus: Four-year results of the look AHEAD trial

BACKGROUND Lifestyle interventions produce short-term improvements in glycemia and cardiovascular disease (CVD) risk factors in individuals with type 2 diabetes mellitus, but no long-term data are available. We examined the effects of lifestyle intervention on changes in weight, fitness, and CVD risk factors during a 4-year study. METHODS The Look AHEAD (Action for Health in Diabetes) trial is a multicenter randomized clinical trial comparing the effects of an intensive lifestyle intervention (ILI) and diabetes support and education (DSE; the control group) on the incidence of major CVD events in 5145 overweight or obese individuals (59.5% female; mean age, 58.7 years) with type 2 diabetes mellitus. More than 93% of participants provided outcomes data at each annual assessment. RESULTS Averaged across 4 years, ILI participants had a greater percentage of weight loss than DSE participants (-6.15% vs -0.88%; P < .001) and greater improvements in treadmill fitness (12.74% vs 1.96%; P < .001), hemoglobin A(1c) level (-0.36% vs -0.09%; P < .001), systolic (-5.33 vs -2.97 mm Hg; P < .001) and diastolic (-2.92 vs -2.48 mm Hg; P = .01) blood pressure, and levels of high-density lipoprotein cholesterol (3.67 vs 1.97 mg/dL; P < .001) and triglycerides (-25.56 vs -19.75 mg/dL; P < .001). Reductions in low-density lipoprotein cholesterol levels were greater in DSE than ILI participants (-11.27 vs -12.84 mg/dL; P = .009) owing to greater use of medications to lower lipid levels in the DSE group. At 4 years, ILI participants maintained greater improvements than DSE participants in weight, fitness, hemoglobin A(1c) levels, systolic blood pressure, and high-density lipoprotein cholesterol levels. CONCLUSIONS Intensive lifestyle intervention can produce sustained weight loss and improvements in fitness, glycemic control, and CVD risk factors in individuals with type 2 diabetes. Whether these differences in risk factors translate to reduction in CVD events will ultimately be addressed by the Look AHEAD trial. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00017953.

Introduction to the plasma lipoproteins.

Publisher Summary Current knowledge of the structure and function of lipoproteins and apolipoproteins and of the enzymes and receptors that mediate lipoprotein–lipid transport is making it possible to define discrete steps of lipoprotein metabolism at the molecular level. This chapter describes the plasma lipoproteins and the association of individual apolipoproteins with specific classes of lipoproteins from the surface properties of lipoprotein particles. The coupling of cellular regulatory mechanisms to the processes of intracellular lipoprotein biosynthesis and catabolism is beginning to yield to the powerful tools of contemporary cell and molecular biology. This chapter shows that a myriad of methods have been brought to bear upon the biology of the plasma lipoproteins. The policies of granting agencies have helped to increase communication and collaboration among investigators. Included in this interaction have been clinical scientists and pathologists whose important contributions have not been described in this survey of lipoprotein structure and metabolism. The chapter indicates that the current state of the field is conducive both to further understanding of normal processes and of the role of lipoproteins in atherosclerosis.

Association of an Intensive Lifestyle Intervention With Remission of Type 2 Diabetes

CONTEXT The frequency of remission of type 2 diabetes achievable with lifestyle intervention is unclear. OBJECTIVE To examine the association of a long-term intensive weight-loss intervention with the frequency of remission from type 2 diabetes to prediabetes or normoglycemia. DESIGN, SETTING, AND PARTICIPANTS Ancillary observational analysis of a 4-year randomized controlled trial (baseline visit, August 2001-April 2004; last follow-up, April 2008) comparing an intensive lifestyle intervention (ILI) with a diabetes support and education control condition (DSE) among 4503 US adults with body mass index of 25 or higher and type 2 diabetes. INTERVENTIONS Participants were randomly assigned to receive the ILI, which included weekly group and individual counseling in the first 6 months followed by 3 sessions per month for the second 6 months and twice-monthly contact and regular refresher group series and campaigns in years 2 to 4 (n=2241) or the DSE, which was an offer of 3 group sessions per year on diet, physical activity, and social support (n=2262). MAIN OUTCOME MEASURES Partial or complete remission of diabetes, defined as transition from meeting diabetes criteria to a prediabetes or nondiabetic level of glycemia (fasting plasma glucose <126 mg/dL and hemoglobin A1c <6.5% with no antihyperglycemic medication). RESULTS Intensive lifestyle intervention participants lost significantly more weight than DSE participants at year 1 (net difference, -7.9%; 95% CI, -8.3% to -7.6%) and at year 4 (-3.9%; 95% CI, -4.4% to -3.5%) and had greater fitness increases at year 1 (net difference, 15.4%; 95% CI, 13.7%-17.0%) and at year 4 (6.4%; 95% CI, 4.7%-8.1%) (P < .001 for each). The ILI group was significantly more likely to experience any remission (partial or complete), with prevalences of 11.5% (95% CI, 10.1%-12.8%) during the first year and 7.3% (95% CI, 6.2%-8.4%) at year 4, compared with 2.0% for the DSE group at both time points (95% CIs, 1.4%-2.6% at year 1 and 1.5%-2.7% at year 4) (P < .001 for each). Among ILI participants, 9.2% (95% CI, 7.9%-10.4%), 6.4% (95% CI, 5.3%-7.4%), and 3.5% (95% CI, 2.7%-4.3%) had continuous, sustained remission for at least 2, at least 3, and 4 years, respectively, compared with less than 2% of DSE participants (1.7% [95% CI, 1.2%-2.3%] for at least 2 years; 1.3% [95% CI, 0.8%-1.7%] for at least 3 years; and 0.5% [95% CI, 0.2%-0.8%] for 4 years). CONCLUSIONS In these exploratory analyses of overweight adults, an intensive lifestyle intervention was associated with a greater likelihood of partial remission of type 2 diabetes compared with diabetes support and education. However, the absolute remission rates were modest. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00017953.

Soluble Cell Adhesion Molecules in Hypertriglyceridemia and Potential Significance on Monocyte Adhesion

Hypertriglyceridemia may contribute to the development of atherosclerosis by increasing expression of cell adhesion molecules (CAMs). Although the cellular expression of CAMs is difficult to assess clinically, soluble forms of CAMs (sCAMs) are present in the circulation and may serve as markers for CAMs. In this study, we examined the association between sCAMs and other risk factors occurring with hypertriglyceridemia, the effect of triglyceride reduction on sCAM levels, and the role of soluble vascular cell adhesion molecule-1 (sVCAM-1) in monocyte adhesion in vitro. Compared with normal control subjects (n=20), patients with hypertriglyceridemia and low HDL (n=39) had significantly increased levels of soluble intercellular adhesion molecule-1 (sICAM-1) (316+/-28.8 versus 225+/-16.6 ng/mL), sVCAM-1 (743+/-52.2 versus 522+/-43.6 ng/mL), and soluble E-selectin (83+/-5.9 versus 49+/-3.6 ng/mL). ANCOVA showed that the higher sCAM levels in patients occurred independently of diabetes mellitus and other risk factors. In 27 patients who received purified n-3 fatty acid (Omacor) 4 g/d for > or =7 months, triglyceride level was reduced by 47+/-4.6%, sICAM-1 level was reduced by 9+/-3.4% (P=.02), and soluble E-selectin level was reduced by 16+/-3.2% (P<.0001), with the greatest reduction in diabetic patients. These results support previous in vitro data showing that disorders in triglyceride and HDL metabolism influence CAM expression and treatment with fish oils may alter vascular cell activation. In a parallel-plate flow chamber, recombinant sVCAM-1 at the concentration seen in patients significantly inhibited adhesion of monocytes to interleukin-1-stimulated cultured endothelial cells under conditions of flow by 27.5+/-7.2%. Thus, elevated sCAMs may negatively regulate monocyte adhesion.

Correlation of serum triglyceride and its reduction by ω-3 fatty acids with lipid transfer activity and the neutral lipid compositions of high-density and low-density lipoproteins

Serum triglyceride (TG) and high-density lipoprotein cholesterol (HDL-C) concentrations are inversely correlated and mechanistically linked by means of lipid transfer activities. Phospholipid transfer activity (PLTA) moves phospholipids among serum lipoproteins; cholesteryl ester transfer activity (CETA), which exchanges cholesteryl esters (CE) and TG among lipoproteins, is stimulated by nonesterified fatty acids (NEFA). The aims of this study were (a) to develop a quantitative model that correlates the neutral lipid (NL = CE + TG) compositions of HDL and LDL with serum TG concentration; (b) identify the serum lipid determinants of CETA and PLTA, and; (c) identify the effects of serum TG reductions on the neutral lipid compositions of HDL and LDL, serum NEFA concentrations, and on PLTA and CETA. These aims were addressed in 40 hypertriglyceridemic subjects before and after treatment with an 85% concentrate of omega-3 fatty acids (Omacor) and in 16 untreated normolipidemic subjects. In vivo, the NL compositions of LDL and HDL were described by a mathematical model having the form of adsorption isotherms: HDL - (TG/NL) = (0.90 +/- 0.07) serum TG/(7.0 +/- 1.2 mmol/l + serum TG) and LDL - (TG/NL) = (0.65 +/- 0.08) serum TG/(4.9 +/- 1.5 mmol/l + serum TG). Reduction of serum TG was associated with reductions in HDL - (TG/NL), serum NEFA concentration, and serum CETA but not PLTA. These data suggest that both hypertriglyceridemia and the attendant elevated serum CETA but not PLTA are determinants of HDL and LDL composition and structure and that serum TG concentrations are good predictors of the NL compositions of HDL and LDL.

Structure of apolipoprotein B-100 of human low density lipoproteins.

We have analyzed low density lipoproteins (LDL) apolipoprotein (apo) B structure by direct sequence analysis of LDL apo B-100 tryptlc peptides. Native LDL were digested with trypsin, and the products were fractionated on a Sephadex G-50 column. The partially digested apo B-100 still associated with liplds was recovered In the void volume (designated trypsln-nonreleasable, TN, peptides). The released peptides (designated trypsln-releasable, TR, peptides) in subsequent peaks were repurifled on two successive high-performance liquid chromatogaphy (HPLC) columns. The TN peak was dellpidated and redigested with trypsin, and the resulting peptides were purified on two successive HPLC columns. Using this approach, we sequenced over 88% of LDL apo B-100, extending and refining our previous study (Nature 1986;323:738–742) which covered 52% of the protein. TN peptides made up 31%, and the TR peptides, 34% of the apo B-100 sequence; 23.7% were found under both TN and TR categories. Based on its differential trypsin releasabllity, apo B-100 can be divided into five domains: 1) residues 1–1000, largely TR; 2) residues 1001–1700, alternating TR and TN; 3) residues 1701–3070, largely TN; 4) residues 3071–4100, mainly TR and mixed; and 5) residues 4101–4536, almost exclusively TN. Domain 1 contained 14 of the 25 Cys residues In apo B. Domain 4 encompassed seven N-glycosylat Ion sites, and contained the putative receptor binding domains. All 19 potential N-glycosylatlon sites were directly sequenced: 16 were found to be glycosylated and three were not Three pairs of dlsurfide bridges were also mapped. Finally, a combination of cDNA sequencing, direct mRNA sequencing, and comparison of published apo B-100 sequences allowed us to Identify specific amino acid residues within apo B-100 that seem to represent bona fide allellc variations. Our study provides information on LDL apo B-100 structure that will be important to our understanding of its conformation and metabolism.

Choline Deficiency Causes Reversible Hepatic Abnormalities in Patients Receiving Parenteral Nutrition: Proof of a Human Choline Requirement: A Placebo-Controlled Trial

BACKGROUND Previous studies have shown that plasma free choline concentrations are significantly decreased in many long-term home total parenteral nutrition (TPN) patients. Furthermore, low choline status has been associated with both hepatic morphologic and hepatic aminotransferase abnormalities. A preliminary pilot study suggested choline-supplemented TPN may be useful in reversal of these hepatic abnormalities. METHODS Fifteen patients (10 M, 5 F) who had required TPN for > or =80% of their nutritional needs were randomized to receive their usual TPN (n = 8), or TPN to which 2 g choline chloride had been added (n = 7) for 24 weeks. Baseline demographic data were similar between groups. Patients had CT scans of the liver and spleen, and blood for plasma free and phospholipid-bound choline, alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase, gamma glutamyl transferase (GGT), bilirubin, serum lipids, complete blood count (CBC), and chemistry profile obtained at baseline, and weeks 2, 4, 6, 12, 16, 20, 24, and 34. CT scans were analyzed for Hounsfield unit (HU) densities. RESULTS There were no significant differences in any measured parameters after 2 weeks. However, at 4 weeks, a significant difference in liver HU between groups was observed (13.3+/-5.0 HU [choline] vs 5.8+/-5.2 HU [placebo], p = .04). This significant trend continued through week 24. Recurrent hepatic steatosis and decreased HU were observed at week 34, 10 weeks after choline supplementation had been discontinued. A significant increase in the liver-spleen differential HU was also observed in the choline group (10.6+/-6.2 HU [choline] vs 1.3+/-3.3 HU [placebo], p = .01). Serum ALT decreased significantly (p = .01 to .05) in the choline group vs placebo at weeks 6,12, 20, and 24. Serum AST was significantly decreased in the choline group by week 24 (p = .02). The serum alkaline phosphatase was significantly reduced in the choline group at weeks 2, 12, 20, 24, and 34 (p = .02 to 0.07). Total bilirubin was normal in these patients and remained unchanged during the study. Serum GGT tended to decrease more in the choline group, but the greater decrease was not statistically significant. CONCLUSIONS Choline deficiency is a significant contributor to the development of TPN-associated liver disease. The data suggest choline is a required nutrient for long-term home TPN patients.

Transbilayer diffusion of phospholipids: dependence on headgroup structure and acyl chain length

The kinetics and thermodynamics of the transmembrane movement (flip-flop) of fluorescent analogs of phosphatidic acid (PA), phosphatidylglycerol (PG), phosphatidylcholine (PC), and phosphatidylethanolamine (PE) were investigated to determine the contributions of headgroup composition and acyl chain length to phospholipid flip-flop. The phospholipid derivatives containing n-octanoic, n-decanoic or n-dodecanoic acid in the sn-1 position and 9-(1-pyrenyl)nonanoic acid in the sn-2 position were incorporated at 3 mol% into sonicated single-bilayer vesicles of 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphocholine (POPC). The kinetics of diffusion of the pyrene-labeled phospholipids from the outer and inner monolayers of the host vesicles to a large pool of POPC acceptor vesicles were monitored by the time-dependent decrease of pyrene excimer fluorescence. The observed kinetics of transfer were biexponential, with a fast component due to the spontaneous transfer of pyrenyl phospholipids in the outer monolayer of labeled vesicles and a slower component due to diffusion of pyrenyl phospholipid from the inner monolayer of the same vesicles. Intervesicular transfer rates decreased approx. 8-fold for every two carbons added to the first acyl chain. Correspondingly, the free energy of activation for transfer increased approx. 1.3 kcal/mol. With the exception of PE, the intervesicular transfer rates for the different headgroups within a homologous series were nearly the same, with the PC derivative being the fastest. Transfer rates for the PE derivatives were 5-to 7-fold slower than the rates observed for PC. Phospholipid flip-flop, in contrast, was strongly dependent on headgroup composition with a smaller dependence on acyl chain length. At pH 7.4, flip-flop rates increased in the order PC less than PG less than PA less than PE, where the rates for PE were at least 10-times greater than those of the homologous PC derivative. Activation energies for flip-flop were large, and ranged from 38 kcal/mol for the longest acyl chain derivative of PC to 25 kcal/mol for the PE derivatives. Titration of the PA headgroup at pH 4.0 produced an approx. 500-fold increase in the flip-flop rate of PA, while the activation energy decreased 10 kcal/mol. Increasing acyl chain length reduced phospholipid flip-flop rates, with the greatest change observed for the PC analogs, which exhibited an approx. 2-fold decrease in flip-flop rate for every two methylene carbons added to the acyl chain at the sn-1 position.(ABSTRACT TRUNCATED AT 400 WORDS)

Hyperhomocysteinemia Decreases Circulating High-Density Lipoprotein by Inhibiting Apolipoprotein A-I Protein Synthesis and Enhancing HDL Cholesterol Clearance

We previously reported that hyperhomocysteinemia (HHcy), an independent risk factor of coronary artery disease (CAD), is associated with increased atherosclerosis and decreased plasma high-density lipoprotein cholesterol (HDL-C) in cystathionine &bgr;-synthase–/apolipoprotein E–deficient (CBS−/−/apoE−/−) mice. We observed that plasma homocysteine (Hcy) concentrations are negatively correlated with HDL-C and apolipoprotein A1 (apoA-I) in patients with CAD. We found the loss of large HDL particles, increased HDL-free cholesterol, and decreased HDL protein in CBS−/−/apoE−/− mice, and attenuated cholesterol efflux from cholesterol-loaded macrophages to plasma in CBS−/−/apoE−/− mice. ApoA-I protein was reduced in the plasma and liver, but hepatic apoA-I mRNA was unchanged in CBS−/−/apoE−/− mice. Moreover, Hcy (0.5 to 2 mmol/L) reduced the levels of apoA-I protein but not mRNA and inhibited apoA-1 protein synthesis in mouse primary hepatocytes. Further, plasma lecithin:cholesterol acyltransferase (LCAT) substrate reactivity was decreased, LCAT specific activity increased, and plasma LCAT protein levels unchanged in apoE−/−/CBS−/− mice. Finally, the clearance of plasma HDL cholesteryl ester, but not HDL protein, was faster in CBS−/−/apoE−/− mice, correlated with increased scavenger receptor B1, and unchanged ATP-binding cassette transporter A1 protein expression in the liver. These findings indicate that HHcy inhibits reverse cholesterol transport by reducing circulating HDL via inhibiting apoA-I protein synthesis and enhancing HDL-C clearance.