Kathleen A. Page

Effects of fructose vs glucose on regional cerebral blood flow in brain regions involved with appetite and reward pathways.

IMPORTANCE Increases in fructose consumption have paralleled the increasing prevalence of obesity, and high-fructose diets are thought to promote weight gain and insulin resistance. Fructose ingestion produces smaller increases in circulating satiety hormones compared with glucose ingestion, and central administration of fructose provokes feeding in rodents, whereas centrally administered glucose promotes satiety. OBJECTIVE To study neurophysiological factors that might underlie associations between fructose consumption and weight gain. DESIGN, SETTING, AND PARTICIPANTS Twenty healthy adult volunteers underwent 2 magnetic resonance imaging sessions at Yale University in conjunction with fructose or glucose drink ingestion in a blinded, random-order, crossover design. MAIN OUTCOME MEASURES Relative changes in hypothalamic regional cerebral blood flow (CBF) after glucose or fructose ingestion. Secondary outcomes included whole-brain analyses to explore regional CBF changes, functional connectivity analysis to investigate correlations between the hypothalamus and other brain region responses, and hormone responses to fructose and glucose ingestion. RESULTS There was a significantly greater reduction in hypothalamic CBF after glucose vs fructose ingestion (-5.45 vs 2.84 mL/g per minute, respectively; mean difference, 8.3 mL/g per minute [95% CI of mean difference, 1.87-14.70]; P = .01). Glucose ingestion (compared with baseline) increased functional connectivity between the hypothalamus and the thalamus and striatum. Fructose increased connectivity between the hypothalamus and thalamus but not the striatum. Regional CBF within the hypothalamus, thalamus, insula, anterior cingulate, and striatum (appetite and reward regions) was reduced after glucose ingestion compared with baseline (P < .05 significance threshold, family-wise error [FWE] whole-brain corrected). In contrast, fructose reduced regional CBF in the thalamus, hippocampus, posterior cingulate cortex, fusiform, and visual cortex (P < .05 significance threshold, FWE whole-brain corrected). In whole-brain voxel-level analyses, there were no significant differences between direct comparisons of fructose vs glucose sessions following correction for multiple comparisons. Fructose vs glucose ingestion resulted in lower peak levels of serum glucose (mean difference, 41.0 mg/dL [95% CI, 27.7-54.5]; P < .001), insulin (mean difference, 49.6 μU/mL [95% CI, 38.2-61.1]; P < .001), and glucagon-like polypeptide 1 (mean difference, 2.1 pmol/L [95% CI, 0.9-3.2]; P = .01). CONCLUSION AND RELEVANCE In a series of exploratory analyses, consumption of fructose compared with glucose resulted in a distinct pattern of regional CBF and a smaller increase in systemic glucose, insulin, and glucagon-like polypeptide 1 levels.

Gestational Diabetes Mellitus: Risks and Management during and after Pregnancy

Gestational diabetes mellitus (GDM) carries a small but potentially important risk of adverse perinatal outcomes and a long-term risk of obesity and glucose intolerance in offspring. Mothers with GDM have an excess of hypertensive disorders during pregnancy and a high risk of developing diabetes mellitus thereafter. Diagnosing and treating GDM can reduce perinatal complications, but only a small fraction of pregnancies benefit. Nutritional management is the cornerstone of treatment; insulin, glyburide and metformin can be used to intensify treatment. Fetal measurements complement maternal glucose monitoring in the identification of pregnancies that require such intensification. Glucose testing shortly after delivery can stratify the short-term diabetes risk in mothers. Thereafter, annual glucose and HbA1c testing can detect deteriorating glycaemic control, a harbinger of future diabetes mellitus, usually type 2 diabetes mellitus. Interventions that mitigate obesity or its metabolic effects are most potent in preventing or delaying diabetes mellitus. Lifestyle modification is the primary approach; use of medications for diabetes prevention after GDM remains controversial. Family planning enables optimization of health in subsequent pregnancies. Breastfeeding may reduce obesity in children and is recommended. Families should be encouraged to help children adopt lifestyles that reduce the risk of obesity.

Circulating glucose levels modulate neural control of desire for high-calorie foods in humans

Obesity is a worldwide epidemic resulting in part from the ubiquity of high-calorie foods and food images. Whether obese and nonobese individuals regulate their desire to consume high-calorie foods differently is not clear. We set out to investigate the hypothesis that circulating levels of glucose, the primary fuel source for the brain, influence brain regions that regulate the motivation to consume high-calorie foods. Using functional MRI (fMRI) combined with a stepped hyperinsulinemic euglycemic-hypoglycemic clamp and behavioral measures of interest in food, we have shown here that mild hypoglycemia preferentially activates limbic-striatal brain regions in response to food cues to produce a greater desire for high-calorie foods. In contrast, euglycemia preferentially activated the medial prefrontal cortex and resulted in less interest in food stimuli. Indeed, higher circulating glucose levels predicted greater medial prefrontal cortex activation, and this response was absent in obese subjects. These findings demonstrate that circulating glucose modulates neural stimulatory and inhibitory control over food motivation and suggest that this glucose-linked restraining influence is lost in obesity. Strategies that temper postprandial reductions in glucose levels might reduce the risk of overeating, particularly in environments inundated with visual cues of high-calorie foods.

Representative Freshwater Bacterioplankton Isolated from Crater Lake, Oregon

ABSTRACT High-throughput culturing (HTC) methods that rely on dilution to extinction in very-low-nutrient media were used to obtain bacterial isolates from Crater Lake, Oregon. 16S rRNA sequence determination and phylogenetic reconstruction were used to determine the potential ecological significance of isolated bacteria, both in Crater Lake and globally. Fifty-five Crater Lake isolates yielded 16 different 16S rRNA gene sequences. Thirty of 55 (55%) Crater Lake isolates had 16S rRNA gene sequences with 97% or greater similarity to sequences recovered previously from Crater Lake 16S rRNA gene clone libraries. Furthermore, 36 of 55 (65%) Crater Lake isolates were found to be members of widely distributed freshwater groups. These results confirm that HTC is a significant improvement over traditional isolation techniques that tend to enrich for microorganisms that do not predominate in their environment and rarely correlate with 16S rRNA gene clone library sequences. Although all isolates were obtained under dark, heterotrophic growth conditions, 2 of the 16 different groups showed evidence of photosynthetic capability as assessed by the presence of puf operon sequences, suggesting that photoheterotrophy may be a significant process in this oligotrophic, freshwater habitat.

Medium-Chain Fatty Acids Improve Cognitive Function in Intensively Treated Type 1 Diabetic Patients and Support In Vitro Synaptic Transmission During Acute Hypoglycemia

OBJECTIVE We examined whether ingestion of medium-chain triglycerides could improve cognition during hypoglycemia in subjects with intensively treated type 1 diabetes and assessed potential underlying mechanisms by testing the effect of β-hydroxybutyrate and octanoate on rat hippocampal synaptic transmission during exposure to low glucose. RESEARCH DESIGN AND METHODS A total of 11 intensively treated type 1 diabetic subjects participated in stepped hyperinsulinemic- (2 mU · kg−1 · min−1) euglycemic- (glucose ∼5.5 mmol/l) hypoglycemic (glucose ∼2.8 mmol/l) clamp studies. During two separate sessions, they randomly received either medium-chain triglycerides or placebo drinks and performed a battery of cognitive tests. In vitro rat hippocampal slice preparations were used to assess the ability of β-hydroxybutyrate and octanoate to support neuronal activity when glucose levels are reduced. RESULTS Hypoglycemia impaired cognitive performance in tests of verbal memory, digit symbol coding, digit span backwards, and map searching. Ingestion of medium-chain triglycerides reversed these effects. Medium-chain triglycerides also produced higher free fatty acids and β-hydroxybutyrate levels compared with placebo. However, the increase in catecholamines and symptoms during hypoglycemia was not altered. In hippocampal slices β-hydroxybutyrate supported synaptic transmission under low-glucose conditions, whereas octanoate could not. Nevertheless, octanoate improved the rate of recovery of synaptic function upon restoration of control glucose concentrations. CONCLUSIONS Medium-chain triglyceride ingestion improves cognition without adversely affecting adrenergic or symptomatic responses to hypoglycemia in intensively treated type 1 diabetic subjects. Medium-chain triglycerides offer the therapeutic advantage of preserving brain function under hypoglycemic conditions without causing deleterious hyperglycemia.

Small Decrements in Systemic Glucose Provoke Increases in Hypothalamic Blood Flow Prior to the Release of Counterregulatory Hormones

OBJECTIVE—The hypothalamus is the central brain region responsible for sensing and integrating responses to changes in circulating glucose. The aim of this study was to determine the time sequence relationship between hypothalamic activation and the initiation of the counterregulatory hormonal response to small decrements in systemic glucose. RESEARCH DESIGN AND METHODS—Nine nondiabetic volunteers underwent two hyperinsulinemic clamp sessions in which pulsed arterial spin labeling was used to measure regional cerebral blood flow (CBF) at euglycemia (∼95 mg/dl) on one occasion and as glucose levels were declining to a nadir of ∼50 mg/dl on another occasion. Plasma glucose and counterregulatory hormones were measured during both study sessions. RESULTS—CBF to the hypothalamus significantly increased when glucose levels decreased to 77.2 ± 2 mg/dl compared with the euglycemic control session when glucose levels were 95.7 ± 3 mg/dl (P = 0.0009). Hypothalamic perfusion was significantly increased before there was a significant elevation in counterregulatory hormones. CONCLUSIONS—Our data suggest that the hypothalamus is exquisitely sensitive to small decrements in systemic glucose levels in healthy, nondiabetic subjects and that hypothalamic blood flow, and presumably neuronal activity, precedes the rise in counterregulatory hormones seen during hypoglycemia.

Differential effects of fructose versus glucose on brain and appetitive responses to food cues and decisions for food rewards

Significance Fructose compared with glucose may be a weaker suppressor of appetite. Here we sought to determine the effects of fructose versus glucose on brain, hormone, and appetitive responses to food cues and food-approach behavior. We show that the ingestion of fructose compared with glucose resulted in smaller increases in plasma insulin levels and greater brain responses to food cues in the visual cortex and left orbital frontal cortex. Ingestion of fructose versus glucose also led to greater hunger and desire for food and a greater willingness to give up long-term monetary rewards to obtain immediate high-calorie foods. These findings suggest that ingestion of fructose relative to glucose activates brain regions involved in attention and reward processing and may promote feeding behavior. Prior studies suggest that fructose compared with glucose may be a weaker suppressor of appetite, and neuroimaging research shows that food cues trigger greater brain reward responses in a fasted relative to a fed state. We sought to determine the effects of ingesting fructose versus glucose on brain, hormone, and appetitive responses to food cues and food-approach behavior. Twenty-four healthy volunteers underwent two functional magnetic resonance imaging (fMRI) sessions with ingestion of either fructose or glucose in a double-blinded, random-order cross-over design. fMRI was performed while participants viewed images of high-calorie foods and nonfood items using a block design. After each block, participants rated hunger and desire for food. Participants also performed a decision task in which they chose between immediate food rewards and delayed monetary bonuses. Hormones were measured at baseline and 30 and 60 min after drink ingestion. Ingestion of fructose relative to glucose resulted in smaller increases in plasma insulin levels and greater brain reactivity to food cues in the visual cortex (in whole-brain analysis) and left orbital frontal cortex (in region-of-interest analysis). Parallel to the neuroimaging findings, fructose versus glucose led to greater hunger and desire for food and a greater willingness to give up long-term monetary rewards to obtain immediate high-calorie foods. These findings suggest that ingestion of fructose relative to glucose results in greater activation of brain regions involved in attention and reward processing and may promote feeding behavior.

A patient with type B insulin resistance syndrome, responsive to immune therapy.

Background A 55-year-old woman with vitiligo, hypothyroidism, interstitial lung disease and diabetes mellitus developed severe insulin resistance during a hospital admission for respiratory failure. Before hospitalization, her HbA1c level was 8.1% on ∼100 U/day of insulin. Her interstitial lung disease had been treated with glucocorticoids, but after their withdrawal her insulin requirements had increased dramatically. She remained hyperglycemic (blood glucose levels 16.7–27.8 mmol/l), despite intravenous insulin at doses as high as 30,000 U/day.Investigations The patients serum creatinine level was 301 µmol/l and her liver function tests were normal. A mildly elevated white cell count was present. The patient was diagnosed with pneumonia due to Pseudomonas aeruginosa. When the patients plasma glucose level was 22.5 mmol/l, her plasma C-peptide level was 0.9 nmol/l and her serum insulin level was 294 pmol/l. At that time the patient was on 2,600 U/day of intravenous insulin aspart. Anti-insulin and anti-islet-cell antibodies were not detected, but anti-insulin-receptor antibodies were found.Diagnosis Type B insulin resistance syndrome.Management The patients insulin resistance responded to glucocorticoids and plasmapheresis. After the patient was treated with prednisone (60 mg/day), her insulin requirements decreased within 1 week to pre-admission doses. When steroids were subsequently discontinued, glycemic control deteriorated once again. Plasmapheresis was initiated, inducing a striking acute decline in insulin needs. On a maintenance dose of 10 mg prednisone/day, glucose control improved (HbA1c 5.8%) with an average of 60 U of isophane insulin twice daily.

Maternal obesity, gestational diabetes, breastfeeding and childhood overweight at age 2 years

Maternal obesity, excessive gestational weight gain (EGWG), gestational diabetes mellitus (GDM) and breastfeeding are four important factors associated with childhood obesity.

Abdominal fat is associated with a greater brain reward response to high‐calorie food cues in hispanic women

Exposure to high‐calorie foods may promote overeating by stimulating brain reward pathways and appetite. Abdominal fat has particularly adverse metabolic consequences and may alter brain pathways that regulate feeding behavior. Functional magnetic resonance imaging (fMRI) was used to test the hypothesis that high‐calorie food cues activate brain reward regions and increase appetite, and to examine the relationship between abdominal fat and brain reward responsiveness in Hispanic women.