Body mass index changes and their association with SARS-CoV-2 infection: a real-world analysis

Objective

To study body mass index (BMI) changes among individuals aged 18-99 years with and without SARS-CoV-2 infection.

Subjects/Methods

Using real-world data from the OneFlorida+ Clinical Research Network of the National Patient-Centered Clinical Research Network, we compared changes over time in BMI in an Exposed cohort (positive SARS-CoV-2 test between March 2020 - January 2022), to a contemporary Unexposed cohort (negative SARS-CoV-2 tests), and an age/sex-matched Historical control cohort (March 2018 - January 2020). Body mass index (kg/m2) was retrieved from objective measures of height and weight in electronic health records. We used target trial approaches to estimate BMI at baseline and change per 100 days of follow-up for Unexposed and Historical cohorts relative to the Exposed cohort by categories of sex, race-ethnicity, age, and hospitalization status.

Results

The study sample consisted of 44,436 (Exposed cohort), 164,118 (Unexposed cohort), and 41,189 (Historical cohort). Cumulatively, 62% were women, 21.5% Non-Hispanic Black, 21.4% Hispanic and 5.6% Non-Hispanic Other. Patients had an average age of 51.9 years (SD: 18.9). At baseline, relative to the Exposed cohort (mean BMI: 29.3 kg/m2 [95%CI: 29.0, 29.7]), the Unexposed (-0.07 kg/m2 [95%CI; -0.12, -0.01]) and Historical controls (-0.27 kg/m2 [95%CI; -0.34, -0.20]) had lower BMI. Relative to no change in the Exposed over 100 days (0.00 kg/m2 [95%CI; -0.03,0.03]), the BMI of those Unexposed decreased (-0.04 kg/m2 [95%CI; -0.06, -0.01]) while the Historical cohort's BMI increased (+0.03 kg/m2 [95%CI;0.00,0.06]). BMI changes were consistent between Exposed and Unexposed cohorts for most population groups, except at start of follow-up period among Males and those 65 years or older, and in changes over 100 days among Males and Hispanics.

Conclusions

In a diverse real-world cohort of adults, mean BMI of those with and without SARS-CoV2 infection varied in their trajectories. The mechanisms and implications of weight retention following SARS-CoV-2 infection remain unclear.

Limitations of Noninvasive Tests-Based Population-Level Risk Stratification Strategy for Nonalcoholic Fatty Liver Disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) are highly prevalent but underdiagnosed.

AIMS

We used an electronic health record data network to test a population-level risk stratification strategy using noninvasive tests (NITs) of liver fibrosis.

METHODS

Data were obtained from PCORnet® sites in the East, Midwest, Southwest, and Southeast United States from patients aged [Formula: see text] 18 with or without ICD-10-CM diagnosis codes for NAFLD, NASH, and NASH-cirrhosis between 9/1/2017 and 8/31/2020. Average and standard deviations (SD) for Fibrosis-4 index (FIB-4), NAFLD fibrosis score (NFS), and Hepatic Steatosis Index (HSI) were estimated by site for each patient cohort. Sample-wide estimates were calculated as weighted averages across study sites.

RESULTS

Of 11,875,959 patients, 0.8% and 0.1% were coded with NAFLD and NASH, respectively. NAFLD diagnosis rates in White, Black, and Hispanic patients were 0.93%, 0.50%, and 1.25%, respectively, and for NASH 0.19%, 0.04%, and 0.16%, respectively. Among undiagnosed patients, insufficient EHR data for estimating NITs ranged from 68% (FIB-4) to 76% (NFS). Predicted prevalence of NAFLD by HSI was 60%, with estimated prevalence of advanced fibrosis of 13% by NFS and 7% by FIB-4. Approximately, 15% and 23% of patients were classified in the intermediate range by FIB-4 and NFS, respectively. Among NAFLD-cirrhosis patients, a third had FIB-4 scores in the low or intermediate range.

CONCLUSIONS

We identified several potential barriers to a population-level NIT-based screening strategy. HSI-based NAFLD screening appears unrealistic. Further research is needed to define merits of NFS- versus FIB-4-based strategies, which may identify different high-risk groups.

Objectively measured pediatric obesity prevalence using the OneFlorida Clinical Research Consortium

We characterized the prevalence of obesity among Florida children 2-19years old using electronic health records (EHRs). The obesity prevalence for 331,641 children was 16.9%. Obesity prevalence at 6-11years (19.5%) and 12-19years (18.9%) were approximately double the prevalence of obesity among children 2-5years (9.9%). The highest prevalence of severe obesity occurred in rural Florida (21.7%) and non-Hispanic children with multiple races had the highest obesity prevalence (21.1%) across all racial/ethnic groups. Our results highlight EHR as a low-cost alternative to estimate the prevalence of obesity and severe obesity in Florida children, both overall and within subpopulations.

Validation of an algorithm for identifying type 1 diabetes in adults based on electronic health record data

PURPOSE

Algorithms using information from electronic health records to identify adults with type 1 diabetes have not been well studied. Such algorithms would have applications in pharmacoepidemiology, drug safety research, clinical trials, surveillance, and quality improvement. Our main objectives were to determine the positive predictive value for identifying type 1 diabetes in adults using a published algorithm (developed by Klompas et al) and to compare it to a simple requirement that the majority of diabetes diagnosis codes be type 1.

METHODS

We applied the Klompas algorithm and the diagnosis code criterion to a cohort of 66 690 adult Kaiser Permanente Colorado members with diabetes. We reviewed 220 charts of those identified as having type 1 diabetes and calculated positive predictive values.

RESULTS

The Klompas algorithm identified 3286 (4.9% of 66 690) adults with diabetes as having type 1 diabetes. Based on chart reviews, the overall positive predictive value was 94.5%. The requirement that the majority of diabetes diagnosis codes be type 1 identified 3000 (4.5%) as having type 1 diabetes and had a positive predictive value of 96.4%. However, the algorithm criterion involving dispensing of urine acetone test strips performed poorly, with a positive predictive value of 20.0%.

CONCLUSIONS

Data from electronic health records can be used to accurately identify adults with type 1 diabetes. When identifying adults with type 1 diabetes, we recommend either a modified version of the Klompas algorithm without the urine acetone test strips criterion or the requirement that the majority of diabetes diagnosis codes be type 1 codes.

Characterization of adult obesity in Florida using the OneFlorida clinical research consortium

INTRODUCTION

With obesity rates and obesity-related healthcare costs increasing, policy makers must understand the scope of obesity across populations.

OBJECTIVE

This study sought to characterize adult obesity using electronic health records (EHRs) available from a statewide clinical data research network, the OneFlorida Clinical Research Consortium, which contains claims and EHR data from over 12 million patients in Florida. The primary aim was to compare EHR-based Florida obesity rates with those rates obtained from the Behavioural Risk Factor Surveillance System (BRFSS).

METHODS

Body mass index from OneFlorida patient data (2012-2016) was used to characterize obesity among adults 20-79 years old. Obesity rates from both OneFlorida and BRFSS (2013) were reported by demographics and by county.

RESULTS

Among the 1,344,015 adults in OneFlorida with EHR data and who met inclusion criteria, the obesity rate was 37.1%. Women had higher obesity rates compared with men. Obesity rates varied within racial/ethnic groups, with the highest rate among African-Americans (45.7%). Obesity rates from OneFlorida were consistently higher than those found in BRFSS (overall 27.8%).

CONCLUSIONS

Utilizing clinical big data available through hospital system and health partner collaborations provides an important view of the extent of obesity. Although these data are available only from healthcare users, they are large in scope, directly measured and are available sooner than commonly used national data sources.

Investing in Obesity Treatment: Kaiser Permanente's Approach to Chronic Disease Management

Kaiser Permanente, an integrated health care delivery system in the USA, takes a "whole systems" approach to the chronic disease of obesity that begins with efforts to prevent it by modifying the environment in communities and schools. Aggressive case-finding and substantial investment in intensive lifestyle modification programs target individuals at high risk of diabetes and other weight-related conditions. Kaiser Permanente regions are increasingly standardizing their approach when patients with obesity require treatment intensification using medically supervised diets, prescription medication to treat obesity, or weight loss surgery.

Chronic use of opioid medications before and after bariatric surgery

IMPORTANCE

Obesity is associated with chronic noncancer pain. It is not known if opioid use for chronic pain in obese individuals undergoing bariatric surgery is reduced.

OBJECTIVES

To determine opioid use following bariatric surgery in patients using opioids chronically for pain control prior to their surgery and to determine the effect of preoperative depression, chronic pain, or postoperative changes in body mass index (BMI) on changes in postoperative chronic opioid use.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective cohort study in a distributed health network (10 demographically and geographically varied US health care systems) of 11,719 individuals aged 21 years and older, who had undergone bariatric surgery between 2005 and 2009, and were assessed 1 year before and after surgery, with latest follow-up by December 31, 2010.

MAIN OUTCOMES AND MEASURES

Opioid use, measured as morphine equivalents 1 year before and 1 year after surgery, excluding the first 30 postoperative days. Chronic opioid use is defined as 10 or more opioid dispensings over 90 or more days or as dispensings of at least a 120-day supply of opioids during the year prior to surgery.

RESULTS

Before surgery, 8% (95% CI, 7%-8%; n = 933) of bariatric patients were chronic opioid users. Of these individuals, 77% (95% CI, 75%-80%; n = 723) continued chronic opioid use in the year following surgery. Mean daily morphine equivalents for the 933 bariatric patients who were chronic opioid users before surgery were 45.0 mg (95% CI, 40.0-50.1) preoperatively and 51.9 mg (95% CI, 46.0-57.8) postoperatively (P < .001). For this group with chronic opiate use prior to surgery, change in morphine equivalents before vs after surgery did not differ between individuals with loss of more than 50% excess BMI vs those with 50% or less (>50% BMI loss: adjusted incidence rate ratio [adjusted IRR, 1.17; 95% CI, 1.07-1.28] vs ≤50% BMI loss [adjusted IRR, 1.03; 95% CI, 0.93-1.14] model interaction, P = .06). In other subgroup analyses of preoperative chronic opioid users, changes in morphine equivalents before vs after surgery did not differ between those with or without preoperative diagnosis of depression or chronic pain (depression only [n = 75; IRR, 1.08; 95% CI, 0.90-1.30]; chronic pain only [n = 440; IRR, 1.17; 95% CI, 1.08-1.27]; both depression and chronic pain [n = 226; IRR, 1.11; 95% CI, 0.96-1.28]; neither depression nor chronic pain [n = 192; IRR, 1.22; 95% CI, 0.98-1.51); and P values for model interactions when compared with neither were P = .42 for depression, P = .76 for pain, and P = .48 for both.

CONCLUSIONS AND RELEVANCE

In this cohort of patients who underwent bariatric surgery, 77% of patients who were chronic opioid users before surgery continued chronic opioid use in the year following surgery, and the amount of chronic opioid use was greater postoperatively than preoperatively. These findings suggest the need for better pain management in these patients following surgery.

Greater systemic lipolysis in women compared with men during moderate-dose infusion of epinephrine and/or norepinephrine

Women have lower circulating catecholamine levels during metabolic perturbations, such as exercise or hypoglycemia, but similar rates of systemic lipolysis. This suggests women may be more sensitive to the lipolytic action of catecholamines, while maintaining similar glucoregulatory effects. The aim of the present study, therefore, was to determine whether women have higher rates of systemic lipolysis compared with men in response to matched peripheral infusion of catecholamines, but similar rates of glucose turnover. Healthy, nonobese women (n = 11) and men (n = 10) were recruited and studied on 3 separate days with the following infusions: epinephrine (Epi), norepinephrine (NE), or the two combined. Tracer infusions of glycerol and glucose were used to determine systemic lipolysis and glucose turnover, respectively. Following basal measurements of substrate kinetics, the catecholamine infusion commenced, and measures of substrate kinetics continued for 60 min. Catecholamine concentrations were similarly elevated in women and men during each infusion: Epi, 182-197 pg/ml and NE, 417-507 pg/ml. There was a significant sex difference in glycerol rate of appearance and rate of disappearance with the catecholamine infusions (P < 0.0001), mainly due to a significantly greater glycerol turnover during the first 30 min of each infusion: glycerol rate of appearance during Epi was only 268 +/- 18 vs. 206 +/- 21 micromol/min in women and men, respectively; during NE, only 173 +/- 13 vs. 153 +/- 17 micromol/min, and during Epi+NE, 303 +/- 24 vs. 257 +/- 21 micromol/min. No sex differences were observed in glucose kinetics under any condition. In conclusion, these data suggest that women are more sensitive to the lipolytic action of catecholamines, but have no difference in their glucoregulatory response. Thus the lower catcholamine levels observed in women vs. men during exercise and other metabolic perturbations may allow women to maintain a similar or greater level of lipid mobilization while minimizing changes in glucose turnover.

Glucose kinetics differ between women and men, during and after exercise

As exercise can improve the regulation of glucose and carbohydrate metabolism, it is important to establish biological factors, such as sex, that may influence these outcomes. Glucose kinetics, therefore, were compared between women and men at rest, during exercise, and postexercise. It was hypothesized that glucose flux would be significantly lower in women than men during both the exercise and postexercise periods. Subjects included normal weight, healthy, eumenorrehic women and men, matched for habitual activity level and maximal oxygen uptake per kilogram lean body mass. Testing occurred following 3 days of diet control, with no exercise the day before. Subjects were tested in the overnight-fasted condition with women studied in the midluteal phase of the menstrual cycle. Resting (120 min), exercise (85% lactate threshold, 90 min), and postexercise (180 min) measurements of glucose flux and substrate metabolism were made. During exercise, women had a significantly lower rate of glucose appearance (Ra) (P<0.001) and disappearance (Rd) (P<0.002) compared with men. Maximal values were achieved at 90 min of exercise for both glucose Ra (mean+/-SE: 22.8+/-1.12 micromol.kg body wt-1.min-1 women and 33.6+/-1.79 micromol.kg body wt-1.min-1 men) and glucose Rd (23.2+/-1.26 and 34.1+/-1.71 micromol.kg body wt-1.min-1, respectively). Exercise epinephrine concentration was significantly lower in women compared with men (P<0.02), as was the increment in glucagon from rest to exercise (P<0.04). During the postexercise period, glucose Ra and Rd were also significantly lower in women vs. men (P<0.001), with differences diminishing over time. In conclusion, circulating blood glucose flux was significantly lower during 90 min of moderate exercise, and immediately postexercise, in women compared with men. Sex differences in the glucagon increase to exercise, and/or the epinephrine levels during exercise, may play a role in determining these sex differences in exercise glucose turnover.

Acute and 1-month effect of small-volume suction lipectomy on insulin sensitivity and cardiovascular risk

OBJECTIVE

The most common surgical procedure for obesity is liposuction, the majority of which are small-volume procedures. The effect of large-volume liposuction on cardiovascular risk and insulin sensitivity has been variable. This study was performed to evaluate the effect of the more common, smaller-volume liposuction on insulin sensitivity, inflammatory mediators, and cardiovascular risk factors.

SUBJECTS AND STUDY DESIGN

In all, 15 overweight or obese premenopausal women underwent metabolic evaluation prior to, 1 day following and 1 month following suction lipectomy of the abdomen. Metabolic evaluation included assessment of free fatty acids, glucose, insulin, insulin sensitivity by frequently sampled i.v. glucose tolerance test, and adipokines (IL-6, angiotensin II, leptin, PAI-1, adiponectin, and TNF-alpha).

RESULTS

Free fatty acids did not change acutely although there was an almost 30% decrease in free fatty acids at 1 month. Fasting insulin levels decreased at one month from 8.3 +/- 1.1 to 5.6 +/- 1.3 microU/ml (P = 0.006). Insulin sensitivity by i.v. glucose tolerance test did not change at 1 month (4.0 +/- 0.8 to 5.0 +/- 0.7, P = 0.12) although with subgroup analysis insulin sensitivity improved in obese but not overweight participants. Several adipokines worsened acutely (IL-6 increased 15 fold and angiotensin II increased 67%), but there was no change in PAI-1, and other adipokines (adiponectin, leptin, and TNF-alpha) decreased. At the 1-month follow-up, all adipokines were similar to baseline.

CONCLUSION

This study provides little evidence supporting increased or decreased cardiovascular risk although there is evidence supporting improved insulin sensitivity at one month, especially in obese women.

Insulin sensitivity determines the effectiveness of dietary macronutrient composition on weight loss in obese women

OBJECTIVE

To determine whether macronutrient composition of a hypocaloric diet can enhance its effectiveness and whether insulin sensitivity (Si) affects the response to hypocaloric diets.

RESEARCH METHODS AND PROCEDURES

Obese nondiabetic insulin-sensitive (fasting insulin < 10 microU/mL; n = 12) and obese nondiabetic insulin-resistant (fasting insulin > 15 microU/mL; n = 9) women (23 to 53 years old) were randomized to either a high carbohydrate (CHO) (HC)/low fat (LF) (60% CHO, 20% fat) or low CHO (LC)/high fat (HF) (40% CHO, 40% fat) hypocaloric diet. Primary outcome measures after a 16-week dietary intervention were: changes in body weight (BW), Si, resting metabolic rate, and fasting lipids.

RESULTS

Insulin-sensitive women on the HC/LF diet lost 13.5 +/- 1.2% (p < 0.001) of their initial BW, whereas those on the LC/HF diet lost 6.8 +/- 1.2% (p < 0.001; p < 0.002 between the groups). In contrast, among the insulin-resistant women, those on the LC/HF diet lost 13.4 +/- 1.3% (p < 0.001) of their initial BW as compared with 8.5 +/- 1.4% (p < 0.001) lost by those on the HC/LF diet (p < 0.04 between two groups). These differences could not be explained by changes in resting metabolic rate, activity, or intake. Overall, changes in Si were associated with the degree of weight loss (r = -0.57, p < 0.05).

DISCUSSION

The state of Si determines the effectiveness of macronutrient composition of hypocaloric diets in obese women. For maximal benefit, the macronutrient composition of a hypocaloric diet may need to be adjusted to correspond to the state of Si.

Relation between calcium intake and fat oxidation in adult humans

OBJECTIVE

To determine if total calcium (Ca(2+)) intake and intake of Ca(2+) from dairy sources are related to whole-body fat oxidation.

DESIGN

: Cross-sectional study.

SUBJECTS

A total of 35 (21 m, 14 f) non-obese, healthy adults (mean+/-s.d., age: 31+/-6 y; weight: 71.2+/-12.3 kg; BMI: 23.7+/-2.9 kg m(-2); body fat: 21.4+/-5.4%).

MEASUREMENTS

Daily (24 h) energy expenditure (EE) and macronutrient oxidation using whole-room indirect calorimetry; habitual Ca(2+) intake estimated from analysis of 4-day food records; acute Ca(2+) intake estimated from measured food intake during a 24-h stay in a room calorimeter.

RESULTS

Acute Ca(2+) intake (mg. kcal(-1)) was positively correlated with fat oxidation over 24 h (r=0.38, P=0.03), during sleep (r=0.36, P=0.04), and during light physical activity (r=0.32, P=0.07). Acute Ca(2+) intake was inversely correlated with 24-h respiratory quotient (RQ) (r=-0.36, P=0.04) and RQ during sleep (r=-0.31, P=0.07). After adjustment for fat mass, fat-free mass, energy balance, acute fat intake, and habitual fat intake, acute Ca(2+) intake explained approximately 10% of the variance in 24-h fat oxidation. Habitual Ca(2+) intake was not significantly correlated to fat oxidation or RQ. Total Ca(2+) intake and Ca(2+) intake from dairy sources were similarly correlated with fat oxidation. In backwards stepwise models, total Ca(2+) intake was a stronger predictor of 24 h fat oxidation than dairy Ca(2+) intake.

CONCLUSION

Higher acute Ca(2+) intake is associated with higher rates of whole-body fat oxidation. These effects were apparent over 24 h, during sleep and, to a lesser extent, during light physical activity. Calcium intake from dairy sources was not a more important predictor of fat oxidation than total Ca(2+) intake.

From instinct to intellect: the challenge of maintaining healthy weight in the modern world

The global obesity epidemic is being driven in large part by a mismatch between our environment and our metabolism. Human physiology developed to function within an environment where high levels of physical activity were needed in daily life and food was inconsistently available. For most of mankind's history, physical activity has 'pulled' appetite so that the primary challenge to the physiological system for body weight control was to obtain sufficient energy intake to prevent negative energy balance and body energy loss. The current environment is characterized by a situation whereby minimal physical activity is required for daily life and food is abundant, inexpensive, high in energy density and widely available. Within this environment, food intake 'pushes' the system, and the challenge to the control system becomes to increase physical activity sufficiently to prevent positive energy balance. There does not appear to be a strong drive to increase physical activity in response to excess energy intake and there appears to be only a weak adaptive increase in resting energy expenditure in response to excess energy intake. In the modern world, the prevailing environment constitutes a constant background pressure that promotes weight gain. We propose that the modern environment has taken body weight control from an instinctual (unconscious) process to one that requires substantial cognitive effort. In the current environment, people who are not devoting substantial conscious effort to managing body weight are probably gaining weight. It is unlikely that we would be able to build the political will to undo our modern lifestyle, to change the environment back to one in which body weight control again becomes instinctual. In order to combat the growing epidemic we should focus our efforts on providing the knowledge, cognitive skills and incentives for controlling body weight and at the same time begin creating a supportive environment to allow better management of body weight.

Percent body fat and lean mass explain the gender difference in leptin: analysis and interpretation of leptin in Hispanic and non-Hispanic white adults

OBJECTIVE

To reassess the relationship between body fat and fasting leptin concentrations comparing plasma vs. serum assessments of leptin; ratios vs. regression adjustment for body composition; fat and lean mass vs. percent body fat; and gender-, ethnic-, and age-related variations.

RESEARCH METHODS AND PROCEDURES

Subjects included 766 adults from the nondiabetic cohort of the San Luis Valley Diabetes Study examined at follow up (1997 to 1998). Body composition was determined by dual energy X-ray absorptiometry. Leptin concentrations were determined after an overnight fast.

RESULTS

Fasting serum and plasma assessments of leptin were correlated with percent body fat to the same degree. Women had significantly higher serum leptin concentrations than men when leptin concentrations were divided by body mass index, fat mass in kilograms or percent body fat. The methodological problem inherent in interpreting these ratio measures is pictorially demonstrated. In regression analysis, fat mass alone did not explain the gender difference. However, lean body mass was inversely related to leptin concentrations (p < 0.0001) and explained 71% of the gender difference at a given fat mass. Percent body fat explained all of the gender difference in leptin concentrations in both Hispanics and non-Hispanic whites. Similar to findings about gender differences, ethnic- and age-related variations in the leptin-body fat association were minimized when percent body fat was employed as the body fat measure.

DISCUSSION

Regression analysis and percent body fat measured with dual energy X-ray absorptiometry are recommended when assessing the relationship between leptin and body fat. Gender differences in leptin concentrations were accounted for by percent body fat in free living (no diet control), Hispanic and non-Hispanic white adults.

Comparison of risk factors for obesity in young, nonobese African-American and Caucasian women

OBJECTIVE

To determine whether specific risk factors for obesity were more evident in young, normal-weight African-American (AA) compared to Caucasian-American (CA) women.

DESIGN

Cross-sectional age-matched study.

SUBJECTS

Young, nonobese, sedentary AA (n= 13, 22.5y of age, 23.6% body fat) and CA women (n = 11, 21.5y of age, 24.0% body fat).

MEASUREMENTS

Aerobic physical fitness (peak VO2), resting metabolic rate (RMR), resting and submaximal exercise fat oxidation rates, total daily energy expenditure (TDEE) by the doubly-labeled water method, physical activity energy expenditure (PAEE), skeletal muscle glycolytic (phosphofructokinase activity (PFK)) and beta-oxidative (beta-hydroxy-acyl CoA dehydrogenase (beta-HADH)) activity, and insulin sensitivity estimated by the insulin-augmented frequently sampled intravenous glucose tolerance test.

RESULTS

The AA and CA subjects were similar in age, body mass index and body composition, but the AA women exhibited lower peak VO2. There were no group differences in RMR adjusted for body composition, or in the rates of submaximal exercise energy expenditure or fat oxidation, and no difference in skeletal muscle beta-HADH or PFK activity. The AA women exhibited lower insulin sensitivity and greater acute insulin response to glucose. The mean TDEE for the AA women was only 74% that of the CA women, primarily due to a lower physical activity energy expenditure (AA group: xPAEE = 1,246+/-438 kJ/day; CA group: x= 3,310+/-466 kJ/day.

CONCLUSION

These data indicate that PAEE and its correlates of peak aerobic capacity and insulin sensitivity are lower in young, nonobese AA women compared to their CA counterparts.

Seasonal variation in lipoprotein lipase and plasma lipids in physically active, normal weight humans

Adipose tissue lipoprotein lipase (ATLPL) provides free fatty acids (FFA) for storage in adipocytes, whereas in skeletal muscle LPL (SMLPL) provides FFA for oxidation. In hibernating animals, the level of SMLPL is relatively higher in summer than winter (promoting fat oxidation), whereas the opposite is seen with ATLPL. A patient-controlled study was designed to determine whether such seasonal variation occurs in normal weight humans. Eighteen subjects were studied in the summer and winter. After 2 days of a standardized diet, they underwent muscle and adipose biopsies for LPL activity, assessment of fitness by VO2 max, and determination of body composition by hydrostatic weighing. The percentages of body fat, body mass index, VO2 max, insulin, glucose, FFA, glycerol, and leptin were not affected by the season. Total cholesterol was higher in the winter than in the summer (157 +/- 5.5 vs. 148 +/- 4.2 mg/dL respectively; P = 0.03). The ATLPL activity was also higher in the winter than in the summer (4.4 +/- 0.8 vs. 2.3 +/- 0.6 nmol FFA/10(6) cells-min; P = 0.04). SMLPL activity trended to be higher in the winter than in the summer (1.9 +/- 0.5 vs. 1.0 +/- 0.1 nmol FFA/g x min; P = 0.06). In summary, ATLPL is seasonally regulated. It appears that SMLPL is similarly regulated by season. For physically active lean subjects, this increase in SMLPL may be a compensatory mechanism to help protect from seasonal weight gain.

Leptin levels in restricting and purging anorectics

Patients with anorexia nervosa of the restricting (AN-R) and purging (AN-P) subtypes were studied to determine if there was a differential effect on leptin levels. It was hypothesized that the AN-P subgroup would have elevated leptin compared to the AN-R subgroup. Fasting plasma and anthropormorphic measurements were collected from 8 women with AN-R and 5 with AN-P. Eleven women served as controls. Overall, the plasma leptin correlated with body mass index (BMI; R = 0.432, p < .05). The AN-P subgroup had elevated leptin compared to the AN-R subgroup (3.8 +/- 0.8 vs. 1.5 +/- 0.2 ng/ml, p < .05) despite similar BMI (16.0 +/- 0.5 vs. 14.8 +/- 0.8 kg/m2). Additionally, the AN-P subgroup had similar plasma leptins as controls (3.8 +/- 0.8 vs. 3.6 +/- 0.1) despite different BMI (16.0 +/- 0.5 vs. 20.2 +/- 0.2, p < .001). Cortisol in the AN-P subgroup trended to be higher than in the restricting anorectics (21.8 +/- 3.0 vs. 15.6 +/- 1.3, p = .06). In AN, leptin was elevated in AN-P vs. AN. This may be due to increased glucocorticoid stimulation of leptin.

Drugs causing dyslipoproteinemia

Diuretics and beta-blockers have a strong tendency to affect serum lipids adversely, whereas the peripherally acting alpha-blocking agents consistently result in beneficial effects. Most of the other antihypertensive agents (calcium channel blockers, ACE inhibitors, angiotensin II receptor antagonists, and drugs that act centrally) are lipid neutral. The effect of steroid hormones varies with the drug, dose, and route of administration. In general, androgens lower HDL-C and have a variable effect on LDL-C. The effects of progestins vary greatly depending on their androgenicity, and estrogens are beneficial except when hypertriglyceridemia occurs with oral estrogens. Glucocorticoids raise HDL-C and may also increase triglycerides and LDL-C. Retinoids increase triglycerides and LDL-C and also reduce HDL-C. Interferons can cause hypertriglyceridemia. Following organ transplantation, a dyslipidemia often ensues. This is caused in part by the medications used to prevent rejection (glucocorticoids, cyclosporine, and FK-506) and requires close attention and, in some patients, drug therapy to prevent coronary artery disease.

Isoproterenol and somatostatin decrease plasma leptin in humans: a novel mechanism regulating leptin secretion

In cultured adipocytes, leptin is increased by insulin and decreased by cAMP. In animal models, insulin and agents that increase intracellular cAMP have been shown to similarly affect plasma leptin in vivo. This study was undertaken to test the hypothesis that in humans increased cAMP induced by isoproterenol would decrease leptin. Five groups of normal weight subjects were studied; 1) subjects infused with isoproterenol at a rate of 24 ng/kg/min (ISO24); 2) subjects infused with isoproterenol at a rate of 8 ng/kg/min (ISO8); 3) subjects infused with somatostatin/insulin/GH followed by coinfusion with 8 ng/kg/min isoproterenol (ISO8 + SRIH); 4) subjects infused with somatostatin/insulin/GH alone (SRIH); and 5) control subjects infused with saline (NS). ISO24 infusion resulted in a 27% decrease in plasma leptin over 120 min. ISO24 also increased plasma insulin over the infusion. ISO8 resulted in a 16% decrease in leptin. Saline did not change leptin. SRIH alone decreased leptin 19% over the first 120 min, however no additional fall was seen over the next 120 min the SRIH group. Nonetheless, the addition of 8 ng/kg/min ISO during the second 120 min (ISO8 + SRIH) caused a 15% further decline in plasma leptin. Therefore both isoproterenol and somatostatin reduce plasma leptin in humans. The effect of isoproterenol is likely mediated by beta-adrenergic receptors, whereas the effect of somatostatin suggests a novel mechanism for the regulation of leptin.