Resolving the Egg and Cholesterol Intake Controversy: New Clinical Insights Into Cholesterol Regulation by the Liver and Intestine.

OBJECTIVE: Cardiovascular disease is the number one cause of death. Achieving American Heart Association low-density lipoprotein (LDL) cholesterol treatment goals is very difficult for many patients. The importance of a low cholesterol diet is controversial and not emphasized by most physicians. Of critical importance is determining whether each individual is a "hyper- or hypo-absorber" of dietary cholesterol. Furthermore, the quantity of each individual's baseline daily dietary cholesterol and saturated fat intake is important in assessing the effect of added egg yolk cholesterol and saturated fat on blood LDL cholesterol. METHODS: Gut cholesterol is absorbed via a specific enteric receptor (the Niemann- Pick-like receptor). Dietary cholesterol contributes one fourth of the absorbed cholesterol, while the remaining gut cholesterol is derived from secreted bile cholesterol. This dietary quantity of cholesterol is significant when other determinants are constant. For some individuals, dietary cholesterol has no adverse effects and in others, a significant elevation in blood LDL cholesterol may occur. RESULTS: There are no readily available blood tests to determine the effect of egg yolk cholesterol and saturated fat on an individual's plasma LDL cholesterol. However, a one month trial of a low cholesterol and saturated fat diet will provide the needed information to make clinical decisions. CONCLUSION: This article delineates the mechanisms that are altered by genetic and environmental factors that determine the net effects of dietary cholesterol and saturated fat on circulating LDL cholesterol. It then makes a practical clinical recommendation based on these mechanisms.

Cholesterol Review: A Metabolically Important Molecule.

OBJECTIVE: Cholesterol is an important molecule in humans and both its excess and its deficiency cause disease. Most clinicians appreciate its role in stabilizing cellular plasma membranes but are unaware of its myriad other functions. METHODS: This review highlights cholesterol's newly recognized important roles in human physiology and pathophysiology. RESULTS: The basis for cholesterol's ubiquitous presence in eukaryote organisms is its three part structure involving hydrophilic, hydrophobic, and rigid domains. This structure permits cholesterol to regulate multiple cellular processes ranging from membrane fluidity and permeability to gene transcription. Cholesterol not only serves as a molecule of regulation itself, but also forms the backbone of all steroid hormones and vitamin D analogs. Cholesterol is responsible for growth and development throughout life and may be useful as an anticancer facilitator. Because humans have a limited ability to catabolize cholesterol, it readily accumulates in the body when an excess from the diet or a genetic abnormality occurs. This accumulation results in the foremost cause of death and disease (atherosclerosis) in the Western world. Identification of cholesterol's disease-producing capabilities dates back 5,000 years to the Tyrolean iceman and more recently to ancient mummies from many cultures throughout the world. In contrast, a deficiency of cholesterol in the circulation may result in an inability to distribute vitamins K and E to vital organs with serious consequences. CONCLUSION: Understanding the benefits and hazards of cholesterol in the clinical setting will improve the endocrinologist's ability to control diseases associated with this unique molecule. ABBREVIATIONS: CVD = cardiovascular disease; HDL = high-density lipoprotein; LDL = low-density lipoprotein; NPC1L1 = Niemann-Pick C-1-like-1 protein; U.S. = United States; USDA = U.S. Department of Agriculture.

INSULIN TIMING: A PATIENT-CENTERED APPROACH TO IMPROVE CONTROL IN TYPE 1 DIABETES.

OBJECTIVE: The goal of insulin therapy in type 1 diabetes (T1D) is to reduce hemoglobin A1C (A1C) to ≤7.0% (53 mmol/mol) with minimal hypoglycemia. We investigated the possibility that "insulin timing" would improve A1C without incurring severe hypoglycemia in volunteers with T1D over a 6-month observation period. METHODS: Forty healthy adult volunteers with T1D were randomly assigned for 6 months to either a control group or an insulin timing group. The primary endpoint was the difference in A1C between the two groups. As a secondary endpoint, both groups were further divided to assess the importance of the baseline A1C in determining the response to timing. The insulin timing algorithm altered the time when the meal dose of insulin was injected or infused from 30 minutes before the meal to 15 minutes after the meal, depending upon the premeal blood glucose concentration. RESULTS: An improvement in mean A1C was observed in the timing group compared with no change in the control group, but this improvement did not reach statistical significance (P>.05). In contrast, when the two groups were analyzed according to baseline A1C, the timing volunteers with baseline A1C values in the upper half (separated by the A1C median of 7.45% [57.9 mmol/mol]) of the timing group had a more robust response to timing (decline in A1C) than the upper half of the control group (P<.05). CONCLUSION: Insulin timing is a patient-centered translational approach that is safe and effective in improving A1C in individuals with T1D with an elevated A1C. ABBREVIATIONS: A1C = hemoglobin A1C ANOVA = analysis of variance CGM = continuous glucose monitoring CSII = continuous subcutaneous insulin infusion MDI = multiple daily injection T1D = type 1 diabetes.

Is the masked continuous glucose monitoring system clinically useful for predicting hemoglobin A1C in type 1 diabetes?

BACKGROUND: The masked continuous glucose monitoring system (Masked-CGMS) differs from standard CGMSs in three ways: (1) there is no feedback to the user so that no immediate regimen changes can be made; (2) it can only be worn for up to 5 days; and (3) there are no alarms to warn of hyperglycemia or hypoglycemia. Since 2008 masked-CGMS has become popular for identifying reasons that a patient's hemoglobin A1C does not correlate closely with his or her capillary blood glucose measurements. To date only one study addressing the clinical utility of Masked-CGMS for improving A1C in diabetes has been published. No studies are available specifically examining the variability and correlation of Masked-CGMS and A1C. SUBJECTS AND METHODS: We performed 156 Masked-CGMS studies (40 patients studied sequentially a maximum of four times each) in type 1 diabetes patients. We then analyzed the resulting interstitial glucose levels obtained from the Masked-CGMS compared with an A1C measurement performed within 1 week of the Masked-CGMS study. RESULTS: There was a very low correlation between the A1C and the Masked-CGMS-derived mean interstitial glucose level. This statistic did not provide sufficiently predictive information to be clinically useful for changing an individual patient's intensive insulin therapy regimen. CONCLUSIONS: Our data demonstrate that a very weak correlation exists between 5 days of masked CGMS and a concurrently measured A1C level. For the individual type 1 diabetes patient, this relationship would unlikely to be clinically useful in altering the individual's treatment regimen.