Seasonal variation in insulin sensitivity in healthy elderly people

The effect of dose, frequency, and timing of protein supplementation on muscle mass in older adults: A systematic review and meta-analysis

Protein supplementation has shown to improve muscle mass in older adults. However, its effect may be influenced by supplementation dose, frequency and timing. This systematic review aimed to assess the effect of dose, frequency and timing of protein supplementation on muscle mass in older adults. Five databases were systematically searched from inception to 14 March 2023, for randomised controlled trials investigating the effect of protein supplementation on muscle mass in adults aged ≥65 years. Random effects meta-analyses were performed, stratified by population. Subgroups were created for dose (≥30 g, <30 g/day), frequency (once, twice, three times/day) and timing of supplementation (at breakfast, breakfast and lunch, breakfast and dinner, all meals, between meals). Heterogeneity within and between subgroups was assessed using I2 and Cochran Q statistics respectively. Thirty-eight articles were included describing community-dwelling (28 articles, n=3204, 74.6±3.4 years, 62.8 % female), hospitalised (8 articles, n=590, 77.0±3.7 years, 50.3 % female) and institutionalised populations (2 articles, n=156, 85.7±1.2 years, 71.2 % female). Protein supplementation showed a positive effect on muscle mass in community-dwelling older adults (standardised mean difference 0.116; 95 % confidence interval 0.032-0.200 kg, p=0.007, I2=15.3 %) but the effect did not differ between subgroups of dose, frequency and timing (Q=0.056, 0.569 and 3.084 respectively, p>0.05). Data including hospitalised and institutionalised populations were limited. Protein supplementation improves muscle mass in community-dwelling older adults, but its dose, frequency or timing does not significantly influence the effect.

Seasonal light hours modulate peripheral clocks and energy metabolism in mice

Except for latitudes close to the equator, seasonal variation in light hours can change dramatically between summer and winter. Yet investigations into the interplay between energy metabolism and circadian rhythms typically use a 12 h light:12 h dark photoperiod corresponding to the light duration at the equator. We hypothesized that altering the seasonal photoperiod affects both the rhythmicity of peripheral tissue clocks and energy homeostasis. Mice were housed at photoperiods representing either light hours in summer, winter, or the equinox. Mice housed at a winter photoperiod exhibited an increase in the amplitude of rhythmic lipid metabolism and a modest reduction in fat mass and liver triglyceride content. Comparing melatonin-proficient and -deficient mice, the effect of seasonal light on energy metabolism was largely driven by differences in the rhythmicity of food intake and not melatonin. Together, these data indicate that seasonal light impacts energy metabolism by modulating the timing of eating.

Characteristics of Holstein cows predisposed to ketosis during the post-partum transition period

BACKGROUND

Ketosis is a common metabolic disorder during the post-partum transition period of dairy cattle. How the method of reproduction, parturition time, and calf birth weight affect the occurrence of ketosis on dairy herds remains elusive.

OBJECTIVES

This study investigated factors associated with the severity of ketosis.

METHODS

We divided 186 Holstein cows into three classifications based on the highest β-hydroxybutyrate (BHBA) concentration during the post-partum transition period, namely non-ketosis (<1.2 mmol/L, n = 94), subclinical ketosis (1.2-2.9 mmol/L, n = 58), and clinical ketosis (≥3.0 mmol/L, n = 34). We evaluated characteristics of cows associated with the severity of ketosis.

RESULTS

Ketosis was not associated with the method of reproduction, parturition time, pregnancy wastage, premature delivery, retained placenta, and type of calf. Cows calving in spring and especially summer were at higher risk of severe ketosis (p < 0.01). Cows with increased body condition score (BCS) at parturition, age, lactation number, and calving interval were more likely to develop severe ketosis (p < 0.05). Cows with clinical ketosis produced most milk (29.9 ± 1.0 kg) from days four to six, whereas cows without ketosis produced the least (21.3 ± 0.8 kg) (p < 0.001). Heavier calf birth weight resulted in high risk of severe ketosis (p < 0.01), due to increased milk yield during the early lactation.

CONCLUSIONS

The severity of ketosis is associated with the calving season, BCS at parturition, age, lactation number, calving interval, milk yield in the early lactation period, and calf birth weight. Nonetheless, it was not associated with the method of reproduction, parturition time, pregnancy wastage, premature delivery, retained placenta, and type of calf. This study is the first to investigate the associations between ketosis and calf birth weight. Our findings could help predict cows at risk of ketosis and take precautions.

Seasonality of Insulin Resistance, Glucose, and Insulin Among Middle-Aged and Elderly Population: The Rotterdam Study

CONTEXT

There are discrepancies in the seasonality of insulin resistance (IR) across the literature, probably due to age-related differences in the seasonality of lifestyle factors and thermoregulation mechanisms.

OBJECTIVE

To estimate the seasonality of IR according to the homeostatic model assessment-IR (HOMA-IR), glucose, and insulin levels and to examine the role of lifestyle markers [body mass index (BMI) and physical activity] and meteorological factors, according to age.

DESIGN, SETTING, AND PARTICIPANTS

Seasonality was examined using cosinor analysis among middle-aged (45 to 65 years) and elderly (≥65 years) participants of a population-based Dutch cohort. We analyzed 13,622 observations from 8979 participants (57.6% women) without diagnosis of diabetes and fasting glucose <7 mmol/L. BMI was measured, physical activity was evaluated using a validated questionnaire, and meteorological factors (daily mean ambient temperature, mean relative humidity, total sunlight hours, and total precipitation) were obtained from local records. Seasonality estimates were adjusted for confounders.

RESULTS

Among the middle-aged participants, seasonal variation estimates were: 0.11 units (95% confidence interval: 0.03, 0.20) for HOMA-IR, 0.28 µIU/mL (-0.05, 0.69) for insulin, and 0.05 mmol/L (0.01, 0.09) for glucose. These had a summer peak, and lifestyle markers explained the pattern. Among the elderly, seasonal variations were: 0.29 units (0.21, 0.37) for HOMA-IR, 0.96 µIU/mL (0.58, 1.28) for insulin, and 0.01 mmol/L (-0.01, 0.05) for glucose. These had a winter peak and ambient temperature explained the pattern.

CONCLUSION

Impaired thermoregulation mechanisms could explain the winter peak of IR among elderly people without diabetes. The seasonality of lifestyle factors may explain the seasonality of glucose.

Seasonality of Insulin Use in German Outpatients With Diabetes: A Retrospective Analysis

BACKGROUND

Seasonality in insulin sensitivity has been the focus of controversial literature in the past decades. The aim of this study was to analyze seasonality of insulin use in patients with diabetes who were followed in German general practices.

METHODS

This study included patients affected by type 1 (T1DM) or type 2 diabetes mellitus (T2DM) who received intensified conventional insulin therapy over a period of at least 12 months between 2013 and 2015. The main outcome was the median insulin dose per day (calculated daily insulin doses, CDDs) between June and August (summer) and between December and February (winter).

RESULTS

The present study included 1197 T1DM patients and 3836 T2DM patients from 492 general practitioner or diabetologist practices. The mean age was 45.4 years (SD = 16.2 years) in the T1DM group and 65.2 years (SD = 14.1 years) in the T2DM group. The most frequent basal insulin therapy was insulin glargine (T1DM: 45.7%; T2DM: 41.1%), and the most frequent bolus insulin therapy was insulin lispro in the T1DM group (38.7%) and human insulin in the T2DM group (45.2%). The consumption of basal and bolus insulins did not significantly differ between summer and winter in T1DM individuals (basal therapy: 30.8 international units (IU)/day versus 31.2 IU/day; bolus therapy: 39.4 IU/day versus 37.8 IU/day). This consumption was also similar between the two seasons in the T2DM group (basal therapy: 31.0 IU/day versus 30.6 IU/day; bolus therapy: 44.3 IU/day versus 44.1 IU/day).

CONCLUSIONS

There was no significant difference in the use of basal and bolus insulin therapies between summer and winter in German patients with T1DM or T2DM.

Effects of a year-long pedometer-based walking program on cardiovascular disease risk factors in active older people

We assessed the relationship between the number of daily steps and changes in cardiovascular disease (CVD) risk factors in a year-long pedometer-based walking program for physically active older people. A total of 36 physically active older people (68.3 ± 5.8 years) completed this 59-week program. The CVD risk parameters were measured at baseline and at weeks 21 and 59. The mean number of steps increased by week 21 and was maintained at week 59 (approximately 10 000 steps, increase in 1500 steps from the baseline; P < .05). Following a significant reduction in body mass index at week 21, systolic blood pressure levels were significantly reduced, and high-density lipoprotein cholesterol levels were significantly increased at week 59 (P < .05). In summary, even active older people can achieve further protection against CVD risks by minor, but sustained, physical activity using pedometers for a period of more than 1 year.

Seasonal variations of insulin sensitivity from a euglycemic insulin clamp in elderly men

INTRODUCTION

Seasonal variations in hemoglobin-A1c have been reported in diabetic patients, but the underlying mechanisms have not been elucidated.

AIMS

To study if insulin sensitivity, insulin secretion, and fasting plasma glucose showed seasonal variations in a Swedish population-based cohort of elderly men.

METHODS

Altogether 1117 men were investigated with a euglycemic insulin clamp and measurements of fasting plasma glucose and insulin secretion after an oral glucose tolerance test. Values were analyzed in linear regression models with an indicator variable for winter/summer season and outdoor temperature as predictors.

RESULTS

During winter, insulin sensitivity (M/I, unit = 100 × mg × min(-1) × kg(-1)/(mU × L(-1))) was 11.0% lower (4.84 versus 5.44, P = 0.0003), incremental area under the insulin curve was 16.4% higher (1167 versus 1003 mU/L, P = 0.007). Fasting plasma glucose was, however, not statistically significantly different (5.80 versus 5.71 mmol/L, P = 0.28) compared to the summer season. There was an association between outdoor temperature and M/I (0.57 units increase (95% CI 0.29-0.82, P < 0.0001) per 10°C increase of outdoor temperature) independent of winter/summer season. Adjustment for life-style factors, type 2 diabetes, and medication did not alter these results.

CONCLUSIONS

Insulin sensitivity showed seasonal variations with lower values during the winter and higher during the summer season. Inverse compensatory variations of insulin secretion resulted in only minor variations of fasting plasma glucose. Insulin sensitivity was associated with outdoor temperature. These phenomena should be further investigated in diabetic patients.

Metabolic adaptation of mice in a cool environment

Homeothermic animals, including humans, live by adapting to changes in ambient temperature. Numerous studies have demonstrated cold exposure (at approximately 5 degrees C) improves glucose tolerance despite reducing insulin secretion and increasing energy expenditure. To determine the effects of a small reduction in ambient temperature on energy metabolism, we compared two groups of mice; one exposed to a cool environment (20 degrees C) and the other maintained in a near-thermoneutral environment (25 degrees C) for 10 days. Both glucose-induced insulin secretion and glucose response were significantly impaired in mice exposed to a cool environment. In the cool temperature-exposed mice, skin temperatures were reduced, and plasma norepinephrine levels were increased, suggesting that impairment of insulin secretion was facilitated by induction of sympathetic nervous activity due to skin cooling. In addition, expression of GLUT4 mRNA was increased significantly in inguinal subcutaneous adipose tissue (IWAT) but not in epididymal or brown adipose tissue or skeletal muscle in these mice. Moreover, expression of Dok1, a molecule linked to activation of insulin receptors in adipocyte hypertrophy, and Cd36, a molecule related to NEFA uptake, were also increased at mRNA and/or protein levels only in IWAT of the cool temperature-exposed mice. Fatty acid synthesis was also facilitated, and fat weights were increased only in IWAT from mice kept at 20 degrees C. These results suggest that a small reduction in ambient temperature can affect glucose homeostasis through regulation of insulin secretion and preferentially enhances fat storage in IWAT. These adaptations can be interpreted as preparation for a further reduction in ambient temperature.

Community-based study on summer-winter difference in insulin resistance in Kin-Chen, Kinmen, Taiwan

BACKGROUND

The aim of this community-based study was to explore the summer-winter difference in insulin resistance in Kin-Chen, Kinmen.

METHODS

A total of 2,412 residents aged 40 and over was enrolled in a mass survey in Kin-Chen, Kinmen, by the Yang-Ming Crusade, a volunteer organization of well-trained medical students from National Yang-Ming University. All participants were investigated in winter (first phase, January and February, before Chinese New Year) and summer (secondary phase, July and August) in 2002. Structured questionnaires, demographic and physical data, lifestyle, and blood chemistry parameters were collected.

RESULTS

Higher levels of fasting insulin, HOMA-insulin resistance and triglycerides, but lower levels of high-density lipoprotein cholesterol were found in summer than in winter. The prevalence of metabolic syndrome was higher in summer than in winter, with differences of 7.7% in both genders (p = 0.0092 in men, p = 0.0037 in women). Body mass index (BMI), age and physical activity were significantly correlated with metabolic syndrome. After controlling for BMI and other risk profiles, summer was independently and positively associated with fasting insulin and insulin resistance regardless of metabolic syndrome.

CONCLUSION

Fasting insulin, insulin resistance and prevalence of metabolic syndrome were higher in summer than in winter. BMI and season were 2 major determinants of the variation in fasting insulin. The contextual impacts of seasonal variation in shaping metabolic syndrome or insulin resistance in populations need to be reemphasized.

Gastric emptying, diabetes, and aging

Gastric emptying is mildly slowed in healthy aging, although generally remains within the normal range for young people. The significance of this is unclear, but may potentially influence the absorption of certain drugs, especially when a rapid effect is desired. Type 2 diabetes is common in the elderly, but there is little data regarding its natural history, prognosis, and management. This article focuses on the interactions between gastric emptying and diabetes, how each is influenced by the process of aging, and the implications for patient management.

Community-based study on summer-winter differences of component of metabolic syndrome in Kinmen, Taiwan

BACKGROUND

A community-based study was conducted to investigate summer-winter differences of component of metabolic syndrome in Kinmen, Taiwan.

METHODS

A total of 8251 residents aged 40 and over were enrolled in the mass survey in Kinmen. They were investigated while on summer (July and August) and winter vacation (January and February) during 2000-2003. Demographics, physical examination findings, lifestyle variables and biochemical data were collected.

RESULTS

After controlling for age, body mass index, diet, lifestyle and other risk factors for component of metabolic syndrome, there were independent and significant relationships between summer-winter difference and component of metabolic syndrome. Winter season was positively correlated with blood pressure, fasting plasma glucose level, high-density lipoprotein-cholesterol (HDL-C) and waist circumference, but was negatively associated with fasting triglycerides and metabolic syndrome.

CONCLUSIONS

Summer season is positively associated with hypertriglyceridemia, low HDL-C and metabolic syndrome. These findings imply that cross-sectional, experimental and cohort studies of component of metabolic syndrome or metabolic syndrome should take season into account as possible confounding effects.

Seasonal patterns in monthly hemoglobin A1c values

The purpose of this study was to investigate seasonal variations in population monthly hemoglobin A(1c) (A1c) values over 2 years (from October 1998 to September 2000) among US diabetic veterans. The study cohort included 285,705 veterans with 856,181 A1c tests. The authors calculated the monthly average A1c values for the overall population and for subpopulations defined by age, sex, race, insulin use, and climate regions. A1c values were higher in winter and lower in summer with a difference of 0.22. The proportion of A1c values greater than 9.0% followed a similar seasonal pattern that varied from 17.3% to 25.3%. Seasonal autoregressive models including trigonometric function terms were fit to the monthly average A1c values. There were significant seasonal effects; the seasonal variation was consistent across different subpopulations. Regions with colder winter temperatures had larger winter-summer contrasts than did those with warmer winter temperatures. The seasonal patterns followed trends similar to those of many physiologic markers, cardiovascular and other diabetes outcomes, and mortality. These findings have implications for health-care service research in quality-of-care assessment, epidemiologic studies investigating population trends and risk factors, and clinical trials or program evaluations of treatments or interventions.