Katarina Borer | University of Michigan (original) (raw)
Papers by Katarina Borer
Abstract Background Postprandial hyperinsulinemia, hyperglycemia, and insulin resistance increase... more Abstract
Background
Postprandial hyperinsulinemia, hyperglycemia, and insulin resistance increase the risk of
type 2 diabetes (T2D) and cardiovascular disease mortality. Postprandial hyperinsulinemia
and hyperglycemia also occur in metabolically healthy subjects consuming high-carbohydrate
diets particularly after evening meals and when carbohydrate loads follow acute exercise.
We hypothesized the involvement of dietary carbohydrate load, especially when timed
after exercise, and mediation by the glucose-dependent insulinotropic peptide (GIP) in this
phenomenon, as this incretin promotes insulin secretion after carbohydrate intake in insulin-
sensitive, but not in insulin-resistant states.
Methods
Four groups of eight metabolically healthy weight-matched postmenopausal women were
provided with three isocaloric meals (a pre-trial meal and two meals during the trial day)
containing either 30% or 60% carbohydrate, with and without two-hours of moderate-intensity
exercise before the last two meals. Plasma glucose, insulin, glucagon, GIP, glucagonlike
peptide 1 (GLP-1), free fatty acids (FFAs), and D-3-hydroxybutyrate concentrations
were measured during 4-h postprandial periods and 3-h exercise periods, and their areas
under the curve (AUCs) were analyzed by mixed-model ANOVA, and insulin resistance
during fasting and meal tolerance tests within each diet was estimated using homeostasismodel
assessment (HOMA-IR).
Results
The third low-carbohydrate meal, but not the high-carbohydrate meal, reduced: (1) evening
insulin AUC by 39% without exercise and by 31% after exercise; (2) GIP AUC by 48%
without exercise and by 45% after exercise, and (3) evening insulin resistance by 37%
without exercise and by 24% after exercise. Pre-meal exercise did not alter insulin-,
PLOS ONE | DOI:10.1371/journal.pone.0165378 October 31, 2016 1 / 22
Conclusions
Evening postprandial insulin and GIP responses and insulin resistance declined by over
30% after three meals that limited daily carbohydrate intake to 30% compared to no such
changes after three 60%-carbohydrate meals, an effect that was independent of pre-meal
exercise. The parallel timing and magnitude of postprandial insulin and GIP changes
suggest their dependence on a delayed intestinal adaptation to a low-carbohydrate diet.
Pre-meal exercise exacerbated glucose intolerance with both diets most likely due to
impairment of insulin signaling by pre-meal elevation of FFAs.
Biomedicine & Pharmacotherapy, 2004
Chronoastrobiology: are we at the threshold of a new science? Is there a critical mass for scient... more Chronoastrobiology: are we at the threshold of a new science? Is there a critical mass for scientific research?'' A simple photograph of the planet earth from outer space was one of the greatest contributions of space exploration. It drove home in a glance that human survival depends upon the wobbly dynamics in a thin and fragile skin of water and gas that covers a small globe in a mostly cold and vast universe. This image raised the stakes in understanding our place in that universe, in finding out where we came from and in choosing a path for survival.
Biomedicine & Pharmacotherapy, 2004
Chronoastrobiology: are we at the threshold of a new science? Is there a critical mass for scient... more Chronoastrobiology: are we at the threshold of a new science? Is there a critical mass for scientific research?'' A simple photograph of the planet earth from outer space was one of the greatest contributions of space exploration. It drove home in a glance that human survival depends upon the wobbly dynamics in a thin and fragile skin of water and gas that covers a small globe in a mostly cold and vast universe. This image raised the stakes in understanding our place in that universe, in finding out where we came from and in choosing a path for survival.
Journal of Molecular Pathophysiology, 2015
Journal of Comparative and Physiological Psychology
ABSTRACT
Growth
Voluntary exercise permanently elevates body weight in adult hamsters (Borer, K.T. Physiol. Behav... more Voluntary exercise permanently elevates body weight in adult hamsters (Borer, K.T. Physiol. Behav. 12:589, 1974). Possible effects of such exercise on skeletal growth were examined in female hamsters in the asymptotic phase of growth, 14 of which had a 34-day access to horizontal disc exercisers, while 14 others remained sedentary. Skeletal measurements were taken from radiographs obtained at the start and at the end of exercise and on day 29 of retirement. Exercise was associated with more pronounced growth of axial than appendicular skeleton. Vertebral column, skull, humerous and femur of excercising hamsters grew 5.61 +/- 0.75 (p less than .001), 1.26 +/- 0.49 (p less than .05), 1.96 +/- 0.81 (p less than .02) and 2.80+/-1.34 (p less than .05) percent more, respectively, than the corresponding bones of sedentary hamsters. Appendicular skeleton continued to grow during retirement. Humerus and femur grew 1.96+/-0.65 (p less than .02) and 1.67+/-0.59 (p less than .02)% more, respectively, during retirement in exercised than in sedentary hamsters. Significantly greater weight gain was seen in active than in sedentary hamsters during both exercise (25.62 + 2.68%, p less than .001) and retirement (6.43 + 2.23, p less than .02). These data indicate that disc exercise accelerates skeletal and ponderal growth in adult hamsters and that axial and appendicular skeleton respond to this stimulus differently.
Behavioral and Brain Sciences
The American journal of physiology
In freely feeding adult hamsters, voluntary exercise induces accelerated somatic growth and incre... more In freely feeding adult hamsters, voluntary exercise induces accelerated somatic growth and increased food consumption that last through several days of retirement. We examined the effects of exercise on serum concentrations of growth hormone (GH) and insulin during ad libitum or restricted intake of food. Serum insulin and GH concentrations were measured by radioimmunoassays in exercising, retired, or sedentary hamsters during ad libitum or restricted intake of food. Linear growth was delayed in food-restricted, exercising hamsters until they were retired and unlimited food consumption was allowed. Serum GH concentrations were increased during exercise and after retirement; serum insulin concentrations were increased only after retirement during both dietary regimes. In food-restricted hamsters, endocrine changes were noted after 4 h of feeding but not after a 14-h fast. We conclude that 1) in adult hamsters voluntary exercise leads to increased secretion of GH even when ingested nutrients are insufficient to support increased growth, and 2) increased secretion of insulin is not related directly to exercise.
Medicine & Science in Sports & Exercise
The American journal of physiology
Physiological and behavioral responses of adult hamsters to starvation were studied by measuring ... more Physiological and behavioral responses of adult hamsters to starvation were studied by measuring food intake, weight recovery, serum concentrations of glucose, insulin, free fatty acids and beta-hydroxybutyrate, and ketonuria in animals subjected to different weight losses, diets, and durations of fast. Hamsters were debilitated by fasts longer than 12 h or leading to greater than 20% weight loss. Hamsters' feeding patterns were unmodified by fasts ranging between 5 and 12 h and showed no circadian periodicity. Hamsters predominantly recovered from weight losses without increasing their food consumption (unless they were offered a diet of pellets and seeds) and without changing their meal patterns, at a rate of weight gain proportional to the magnitude of preceding weight loss if provided with uninterrupted access to food. By 8 h of fast, blood metabolites were indicative of mobilization of body fat. Hamsters are thus behaviorally unresponsive to duration of fast, but compensate physiologically for weight losses with proportional increases in the rate of weight gain.
The American journal of physiology
Voluntary exercise inhibits the reproductive regression associated with a short photoperiod in ma... more Voluntary exercise inhibits the reproductive regression associated with a short photoperiod in male or female hamsters. The question addressed by the present study was whether exercise would also attenuate the reproductive regression associated with injection of exogenous melatonin. In male hamsters exercise inhibited the testicular regression, decline in gonadotropin secretion, and reduction in testosterone release associated with two daily injections (15 micrograms) of melatonin in pinealectomized hamsters on long days. After the reproductive system of the sedentary melatonin group had regressed, one-half of these hamsters were placed in cages with exercise wheels. Access to the exercise wheels stimulated testicular recrudescence and restored gonadotropin secretion to levels found in vehicle-injected hamsters. Sedentary female hamsters injected with melatonin tended to go into a state of constant diestrus associated with daily afternoon increases in serum luteinizing hormone, whereas most exercising hamsters injected with melatonin generally continued having regular estrous cycles with proestrus luteinizing-hormone surges. The ability of exercise to inhibit the effect of exogenous melatonin in pinealectomized hamsters suggests that exercise acts, at least in part, by mechanisms other than altering melatonin secretion.
Hamsters feeding at greater than 2-h intermeal intervals (IMI) lose weight but recover from weigh... more Hamsters feeding at greater than 2-h intermeal intervals (IMI) lose weight but recover from weight losses without hyperphagia if they are allowed to feed at 2-h IMIs (Am. J. Physiol. 236 (Endocrinol. Metab. Gastrointest. Physiol. 5): E105-E112, 1979). To determine the relative importance of changes in energy expenditure and fat synthesis in their energy regulation, measurements were made of resting metabolic rate, respiration by brown adipose tissue (BAT), locomotion, fecal energy content, and insulin and hepatic lipogenic enzyme responses to feeding in underweight hamsters allowed to feed at 2- or 5-h IMIs. Energy deficit suppressed the resting metabolic rate and general locomotor activity and increased the activity of fatty acid synthetase (FAS). Heat production by BAT increased in underweight hamsters. Increase in IMIs blocked the postprandial insulin release, reduced plasma insulin concentration and FAS activity, and increased malic enzyme activity. Thus ad libitum feeding hamsters recover from energy deficit by reducing energy expenditure, whereas failure to add additional meals and impaired insulin and changed lipogenic responses to feeding produce energy deficits in infrequently feeding hamsters.
Physiology & behavior, 1991
We describe a design for the modular horizontal activity disc and tandem cages suitable for conti... more We describe a design for the modular horizontal activity disc and tandem cages suitable for continuous monitoring of spontaneous running and of core temperatures in golden hamsters. An acrylic disc is equipped with a short brass axle. It is mounted inside a brass rotation sleeve at a 15 degrees angle off the horizontal plane. The disc module fits firmly inside either half of the tandem cage when activity measurements are needed. Easy removal allows for alternative use of cages. Minor modifications of disc dimensions and of disc base permit the use of activity modules with juvenile hamsters. The short distance between disc surface and cage floor permits continuous measurement of core temperature as well as running activity.
World journal of diabetes, Jan 15, 2014
A re-examination of the mechanism controlling eating, locomotion, and metabolism prompts formulat... more A re-examination of the mechanism controlling eating, locomotion, and metabolism prompts formulation of a new explanatory model containing five features: a coordinating joint role of the (1) autonomic nervous system (ANS); (2) the suprachiasmatic (SCN) master clock in counterbalancing parasympathetic digestive and absorptive functions and feeding with sympathetic locomotor and thermogenic energy expenditure within a circadian framework; (3) interaction of the ANS/SCN command with brain substrates of reward encompassing dopaminergic projections to ventral striatum and limbic and cortical forebrain. These drive the nonhomeostatic feeding and locomotor motivated behaviors in interaction with circulating ghrelin and lateral hypothalamic neurons signaling through melanin concentrating hormone and orexin-hypocretin peptides; (4) counterregulation of insulin by leptin of both gastric and adipose tissue origin through: potentiation by leptin of cholecystokinin-mediated satiation, inhibition...
Sports medicine (Auckland, N.Z.), 1995
The way in which exercise influences statural, hypertrophic and reparative growth is examined fro... more The way in which exercise influences statural, hypertrophic and reparative growth is examined from the perspective of the human lifespan. Statural growth depends on a neuroendocrine programme which channels nutrient energy towards increments in lean body mass. Exercise can facilitate statural growth and is a necessary stimulus for reparative growth through its stimulatory effects on secretion of growth hormone (GH) and other anabolic hormones. An exercise-associated increase in GH secretion is a response to acute or prolonged exercise-induced fuel shortage that directs metabolism towards utilisation of lipids and promotes growth. Exercise can transiently block the expression of statural growth by competitively removing the necessary nutritional support for growth. Statural growth retardation can be corrected by catch-up growth, but stunting may also be permanent (depending on the timing and magnitude of the energy drain). Hypertrophic growth is less dependent on hormonal and nutriti...
Journal of comparative and physiological psychology, 1971
ABSTRACT
Abstract Background Postprandial hyperinsulinemia, hyperglycemia, and insulin resistance increase... more Abstract
Background
Postprandial hyperinsulinemia, hyperglycemia, and insulin resistance increase the risk of
type 2 diabetes (T2D) and cardiovascular disease mortality. Postprandial hyperinsulinemia
and hyperglycemia also occur in metabolically healthy subjects consuming high-carbohydrate
diets particularly after evening meals and when carbohydrate loads follow acute exercise.
We hypothesized the involvement of dietary carbohydrate load, especially when timed
after exercise, and mediation by the glucose-dependent insulinotropic peptide (GIP) in this
phenomenon, as this incretin promotes insulin secretion after carbohydrate intake in insulin-
sensitive, but not in insulin-resistant states.
Methods
Four groups of eight metabolically healthy weight-matched postmenopausal women were
provided with three isocaloric meals (a pre-trial meal and two meals during the trial day)
containing either 30% or 60% carbohydrate, with and without two-hours of moderate-intensity
exercise before the last two meals. Plasma glucose, insulin, glucagon, GIP, glucagonlike
peptide 1 (GLP-1), free fatty acids (FFAs), and D-3-hydroxybutyrate concentrations
were measured during 4-h postprandial periods and 3-h exercise periods, and their areas
under the curve (AUCs) were analyzed by mixed-model ANOVA, and insulin resistance
during fasting and meal tolerance tests within each diet was estimated using homeostasismodel
assessment (HOMA-IR).
Results
The third low-carbohydrate meal, but not the high-carbohydrate meal, reduced: (1) evening
insulin AUC by 39% without exercise and by 31% after exercise; (2) GIP AUC by 48%
without exercise and by 45% after exercise, and (3) evening insulin resistance by 37%
without exercise and by 24% after exercise. Pre-meal exercise did not alter insulin-,
PLOS ONE | DOI:10.1371/journal.pone.0165378 October 31, 2016 1 / 22
Conclusions
Evening postprandial insulin and GIP responses and insulin resistance declined by over
30% after three meals that limited daily carbohydrate intake to 30% compared to no such
changes after three 60%-carbohydrate meals, an effect that was independent of pre-meal
exercise. The parallel timing and magnitude of postprandial insulin and GIP changes
suggest their dependence on a delayed intestinal adaptation to a low-carbohydrate diet.
Pre-meal exercise exacerbated glucose intolerance with both diets most likely due to
impairment of insulin signaling by pre-meal elevation of FFAs.
Biomedicine & Pharmacotherapy, 2004
Chronoastrobiology: are we at the threshold of a new science? Is there a critical mass for scient... more Chronoastrobiology: are we at the threshold of a new science? Is there a critical mass for scientific research?'' A simple photograph of the planet earth from outer space was one of the greatest contributions of space exploration. It drove home in a glance that human survival depends upon the wobbly dynamics in a thin and fragile skin of water and gas that covers a small globe in a mostly cold and vast universe. This image raised the stakes in understanding our place in that universe, in finding out where we came from and in choosing a path for survival.
Biomedicine & Pharmacotherapy, 2004
Chronoastrobiology: are we at the threshold of a new science? Is there a critical mass for scient... more Chronoastrobiology: are we at the threshold of a new science? Is there a critical mass for scientific research?'' A simple photograph of the planet earth from outer space was one of the greatest contributions of space exploration. It drove home in a glance that human survival depends upon the wobbly dynamics in a thin and fragile skin of water and gas that covers a small globe in a mostly cold and vast universe. This image raised the stakes in understanding our place in that universe, in finding out where we came from and in choosing a path for survival.
Journal of Molecular Pathophysiology, 2015
Journal of Comparative and Physiological Psychology
ABSTRACT
Growth
Voluntary exercise permanently elevates body weight in adult hamsters (Borer, K.T. Physiol. Behav... more Voluntary exercise permanently elevates body weight in adult hamsters (Borer, K.T. Physiol. Behav. 12:589, 1974). Possible effects of such exercise on skeletal growth were examined in female hamsters in the asymptotic phase of growth, 14 of which had a 34-day access to horizontal disc exercisers, while 14 others remained sedentary. Skeletal measurements were taken from radiographs obtained at the start and at the end of exercise and on day 29 of retirement. Exercise was associated with more pronounced growth of axial than appendicular skeleton. Vertebral column, skull, humerous and femur of excercising hamsters grew 5.61 +/- 0.75 (p less than .001), 1.26 +/- 0.49 (p less than .05), 1.96 +/- 0.81 (p less than .02) and 2.80+/-1.34 (p less than .05) percent more, respectively, than the corresponding bones of sedentary hamsters. Appendicular skeleton continued to grow during retirement. Humerus and femur grew 1.96+/-0.65 (p less than .02) and 1.67+/-0.59 (p less than .02)% more, respectively, during retirement in exercised than in sedentary hamsters. Significantly greater weight gain was seen in active than in sedentary hamsters during both exercise (25.62 + 2.68%, p less than .001) and retirement (6.43 + 2.23, p less than .02). These data indicate that disc exercise accelerates skeletal and ponderal growth in adult hamsters and that axial and appendicular skeleton respond to this stimulus differently.
Behavioral and Brain Sciences
The American journal of physiology
In freely feeding adult hamsters, voluntary exercise induces accelerated somatic growth and incre... more In freely feeding adult hamsters, voluntary exercise induces accelerated somatic growth and increased food consumption that last through several days of retirement. We examined the effects of exercise on serum concentrations of growth hormone (GH) and insulin during ad libitum or restricted intake of food. Serum insulin and GH concentrations were measured by radioimmunoassays in exercising, retired, or sedentary hamsters during ad libitum or restricted intake of food. Linear growth was delayed in food-restricted, exercising hamsters until they were retired and unlimited food consumption was allowed. Serum GH concentrations were increased during exercise and after retirement; serum insulin concentrations were increased only after retirement during both dietary regimes. In food-restricted hamsters, endocrine changes were noted after 4 h of feeding but not after a 14-h fast. We conclude that 1) in adult hamsters voluntary exercise leads to increased secretion of GH even when ingested nutrients are insufficient to support increased growth, and 2) increased secretion of insulin is not related directly to exercise.
Medicine & Science in Sports & Exercise
The American journal of physiology
Physiological and behavioral responses of adult hamsters to starvation were studied by measuring ... more Physiological and behavioral responses of adult hamsters to starvation were studied by measuring food intake, weight recovery, serum concentrations of glucose, insulin, free fatty acids and beta-hydroxybutyrate, and ketonuria in animals subjected to different weight losses, diets, and durations of fast. Hamsters were debilitated by fasts longer than 12 h or leading to greater than 20% weight loss. Hamsters' feeding patterns were unmodified by fasts ranging between 5 and 12 h and showed no circadian periodicity. Hamsters predominantly recovered from weight losses without increasing their food consumption (unless they were offered a diet of pellets and seeds) and without changing their meal patterns, at a rate of weight gain proportional to the magnitude of preceding weight loss if provided with uninterrupted access to food. By 8 h of fast, blood metabolites were indicative of mobilization of body fat. Hamsters are thus behaviorally unresponsive to duration of fast, but compensate physiologically for weight losses with proportional increases in the rate of weight gain.
The American journal of physiology
Voluntary exercise inhibits the reproductive regression associated with a short photoperiod in ma... more Voluntary exercise inhibits the reproductive regression associated with a short photoperiod in male or female hamsters. The question addressed by the present study was whether exercise would also attenuate the reproductive regression associated with injection of exogenous melatonin. In male hamsters exercise inhibited the testicular regression, decline in gonadotropin secretion, and reduction in testosterone release associated with two daily injections (15 micrograms) of melatonin in pinealectomized hamsters on long days. After the reproductive system of the sedentary melatonin group had regressed, one-half of these hamsters were placed in cages with exercise wheels. Access to the exercise wheels stimulated testicular recrudescence and restored gonadotropin secretion to levels found in vehicle-injected hamsters. Sedentary female hamsters injected with melatonin tended to go into a state of constant diestrus associated with daily afternoon increases in serum luteinizing hormone, whereas most exercising hamsters injected with melatonin generally continued having regular estrous cycles with proestrus luteinizing-hormone surges. The ability of exercise to inhibit the effect of exogenous melatonin in pinealectomized hamsters suggests that exercise acts, at least in part, by mechanisms other than altering melatonin secretion.
Hamsters feeding at greater than 2-h intermeal intervals (IMI) lose weight but recover from weigh... more Hamsters feeding at greater than 2-h intermeal intervals (IMI) lose weight but recover from weight losses without hyperphagia if they are allowed to feed at 2-h IMIs (Am. J. Physiol. 236 (Endocrinol. Metab. Gastrointest. Physiol. 5): E105-E112, 1979). To determine the relative importance of changes in energy expenditure and fat synthesis in their energy regulation, measurements were made of resting metabolic rate, respiration by brown adipose tissue (BAT), locomotion, fecal energy content, and insulin and hepatic lipogenic enzyme responses to feeding in underweight hamsters allowed to feed at 2- or 5-h IMIs. Energy deficit suppressed the resting metabolic rate and general locomotor activity and increased the activity of fatty acid synthetase (FAS). Heat production by BAT increased in underweight hamsters. Increase in IMIs blocked the postprandial insulin release, reduced plasma insulin concentration and FAS activity, and increased malic enzyme activity. Thus ad libitum feeding hamsters recover from energy deficit by reducing energy expenditure, whereas failure to add additional meals and impaired insulin and changed lipogenic responses to feeding produce energy deficits in infrequently feeding hamsters.
Physiology & behavior, 1991
We describe a design for the modular horizontal activity disc and tandem cages suitable for conti... more We describe a design for the modular horizontal activity disc and tandem cages suitable for continuous monitoring of spontaneous running and of core temperatures in golden hamsters. An acrylic disc is equipped with a short brass axle. It is mounted inside a brass rotation sleeve at a 15 degrees angle off the horizontal plane. The disc module fits firmly inside either half of the tandem cage when activity measurements are needed. Easy removal allows for alternative use of cages. Minor modifications of disc dimensions and of disc base permit the use of activity modules with juvenile hamsters. The short distance between disc surface and cage floor permits continuous measurement of core temperature as well as running activity.
World journal of diabetes, Jan 15, 2014
A re-examination of the mechanism controlling eating, locomotion, and metabolism prompts formulat... more A re-examination of the mechanism controlling eating, locomotion, and metabolism prompts formulation of a new explanatory model containing five features: a coordinating joint role of the (1) autonomic nervous system (ANS); (2) the suprachiasmatic (SCN) master clock in counterbalancing parasympathetic digestive and absorptive functions and feeding with sympathetic locomotor and thermogenic energy expenditure within a circadian framework; (3) interaction of the ANS/SCN command with brain substrates of reward encompassing dopaminergic projections to ventral striatum and limbic and cortical forebrain. These drive the nonhomeostatic feeding and locomotor motivated behaviors in interaction with circulating ghrelin and lateral hypothalamic neurons signaling through melanin concentrating hormone and orexin-hypocretin peptides; (4) counterregulation of insulin by leptin of both gastric and adipose tissue origin through: potentiation by leptin of cholecystokinin-mediated satiation, inhibition...
Sports medicine (Auckland, N.Z.), 1995
The way in which exercise influences statural, hypertrophic and reparative growth is examined fro... more The way in which exercise influences statural, hypertrophic and reparative growth is examined from the perspective of the human lifespan. Statural growth depends on a neuroendocrine programme which channels nutrient energy towards increments in lean body mass. Exercise can facilitate statural growth and is a necessary stimulus for reparative growth through its stimulatory effects on secretion of growth hormone (GH) and other anabolic hormones. An exercise-associated increase in GH secretion is a response to acute or prolonged exercise-induced fuel shortage that directs metabolism towards utilisation of lipids and promotes growth. Exercise can transiently block the expression of statural growth by competitively removing the necessary nutritional support for growth. Statural growth retardation can be corrected by catch-up growth, but stunting may also be permanent (depending on the timing and magnitude of the energy drain). Hypertrophic growth is less dependent on hormonal and nutriti...
Journal of comparative and physiological psychology, 1971
ABSTRACT