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ABSTRACT Intensive glucose control increases the all-cause mortality in type 2 diabetes mellitus (T2DM); however, the underlying mechanisms remain unclear. We hypothesized that strict diet

control to achieve euglycemia in diabetes damages major organs, increasing the mortality risk. To evaluate effects on major organs when euglycemia is obtained by diet control, we generated a

model of end-stage T2DM in 13-week-old Sprague-Dawley rats by subtotal pancreatectomy, followed by _ad libitum_ feeding for 5 weeks. We divided these rats into two groups and for the

subsequent 6 weeks provided _ad libitum_ feeding to half (AL, _n_=12) and a calorie-controlled diet to the other half (R, _n_=12). To avoid hypoglycemia, the degree of calorie restriction in

the R group was isocaloric (g per kg body weight per day) compared with a sham-operated control group (C, _n_=12). During the 6-week diet control period, AL rats ate three times more than

rats in the C or R groups, developing hyperglycemia with renal hyperplasia. R group achieved euglycemia but lost overall body weight significantly compared with the C or AL group (49 or 22%,

respectively), heart weight (39 or 23%, respectively) and liver weight (50 or 46%, respectively). Autophagy levels in the heart and liver were the highest in the R group (_P_<0.01),

which also had the lowest pAkt/Akt levels among the groups (_P_<0.05 in the heart; _P_<0.01 in the liver). In conclusion, glycemic control achieved by diet control can prevent

hyperglycemia-induced renal hyperplasia in diabetes but may be deleterious even at isocaloric rate when insulin is deficient because of significant loss of heart and liver mass via increased

autophagy. SIMILAR CONTENT BEING VIEWED BY OTHERS RENAL DENERVATION AMELIORATES CARDIAC METABOLIC REMODELING IN DIABETIC CARDIOMYOPATHY RATS BY SUPPRESSING RENAL SGLT2 EXPRESSION Article 13

November 2021 HIGH-FAT DIET PROMOTES RENAL INJURY BY INDUCING OXIDATIVE STRESS AND MITOCHONDRIAL DYSFUNCTION Article Open access 24 October 2020 COMPARATIVE EVALUATION OF METFORMIN AND

LIRAGLUTIDE CARDIOPROTECTIVE EFFECT IN RATS WITH IMPAIRED GLUCOSE TOLERANCE Article Open access 23 March 2021 INTRODUCTION Correction of hyperglycemia is the ultimate goal in diabetes care,

as uncontrolled long-term hyperglycemia can cause complications in both type 1 and type 2 diabetes mellitus (T2DM).1, 2 According to the Diabetes Control and Complications Trial, the

incidence of diabetic retinopathy, nephropathy and neuropathy increases as hemoglobin A1c (HbA1c, measure of mean blood glucose during the previous 2–3 months) increases, and intensive

therapy targeting near-euglycemia reduces the risk of microvascular complications compared with conventional therapy.2, 3 Similarly, the United Kingdom Prospective Diabetes Study 35 reported

that lower HbA1c level was associated with significant reductions in the risk of death related to diabetes, myocardial infarction and microvascular complications, suggesting that good

glycemic control can prevent diabetic complications.1 Data from subsequent studies have consistently supported that improved glycemic control is associated with lower risks of mortality and

diabetic complications.4, 5, 6, 7 However, recent studies have reported that intensive glucose-lowering treatment targeting euglycemia is not always beneficial to patients with diabetes.8,

9, 10 In fact, the Action to Control Cardiovascular Risk in Diabetes study terminated the intensive-therapy arm (target HbA1c<6.0%) in the middle of the trial because of higher mortality

compared with the standard-therapy arm (target HbA1c 7.0–7.9%).8 Moreover, the all-cause mortality and cardiac events of patients in the lowest HbA1c decile (mean HbA1c 6.4%) and patients in

the highest HbA1c decile (mean HbA1c 10.6%) were higher than those of the patients with the lowest hazard ratio (mean HbA1c 7.5%).11 However, causes of higher mortality and cardiovascular

events in intensive glycemic control have not yet been identified, although iatrogenic hypoglycemia has been suggested.8, 9, 11 Diet control to achieve optimal glycemia is emphasized in

diabetes care,12, 13, 14 but the possibility of harmful effects on major organs when insulin deficiency is not completely corrected has not been well described. Although blood glucose levels

are high in diabetic patients, glucose uptake decreases in cells dependent on insulin for glucose transport but increases in cells that are not dependent on insulin. It is unclear how these

various cell types react to euglycemia obtained by diet control when insulin deficiency exists. In our previous study, we observed that insulin deficiency given physiological needs is

common in patients with T2DM receiving oral antidiabetic agents or insulin injections when they need to restrict calorie to achieve euglycemia and that they do not require calorie

restriction to achieve euglycemia when insulin requirements are corrected for physiological needs by continuous subcutaneous insulin infusion therapy.15 However, few patients with T2DM use

continuous subcutaneous insulin infusion therapy, and therefore they require calorie restriction in addition to medical treatment to achieve euglycemia. Based on these findings, to explain

the increased mortality in intensive glycemic control group we hypothesized that diet control strict enough to achieve euglycemia in diabetic patients with insulin deficiency may result in

loss of functional mass of major organs, such as the heart, liver and kidneys. Thus calorie restriction may lead to life-threatening events such as organ failure due to the additive effects

of decreased insulin signaling and restricted energy supply. We hypothesized that a molecular mechanism underlying the loss of functional mass in major organs is autophagy, which is a

crucial mechanism for cell survival during nutrient and growth factor deprivation but is also an inducer of cell death through apoptotic or non-apoptotic pathways.16, 17, 18 To confirm our

hypotheses, we generated insulin-deficient diabetic rats by subtotal pancreatectomy to mimic end-stage T2DM as β-cell function and mass decrease over time and diet control becomes more

important to control hyperglycemia.19, 20 We used mature 13-week-old rats in this study, because calorie restriction and insulin deficiency early in life are associated with decreased organ

weight/function and disease in later life.21, 22, 23 After pancreatectomy, we determined how much more energy diabetic rats naturally ingest compared with sham-operated control rats when fed

_ad libitum_. We fed one group of diabetic rats a reduced-calorie diet to control hyperglycemia and another group an _ad libitum_ diet. We expected that hyperglycemia could be controlled

without profound energy depletion or hypoglycemia in the calorie-controlled group by feeding them the same number of calories per kilogram body weight as the sham-operated control group,

using a diet designed according to the nutrition recommendations for diabetes management.14 Finally, we compared overall body weight, weights of major organs and insulin-dependent tissues

and autophagy levels of major organs in the three experimental groups to determine whether euglycemia obtained by diet control in insulin deficiency causes loss of functional mass in major

organs through increased autophagy. MATERIALS AND METHODS ETHICS STATEMENT All experiments were carried out in accordance with the National Institute of Health Guide for the Care and Use of

Laboratory Animals. The study protocol was approved by the Konkuk University Institutional Animal Care and Use Committee. ANIMALS Thirty-six 11-week-old specific pathogen-free male

Sprague-Dawley (SD) rats were purchased from OrientBio (Sungnam, South Korea). The rats were weighed upon arrival and housed individually for 2 weeks before surgery to minimize body weight

variation during the acclimation period. After surgery, the rats were maintained in individual cages for the control and measurement of daily food intake in a temperature- and

humidity-controlled environment with a 12-h light–dark cycle (lights on 0800–2000 hours, temperature 20–23 °C, relative humidity 40–65%). The rats were given a standard chow (GF 2005; Feed

Laboratory, Guri, South Korea), which is a modified AIN-76A diet (4.1 kcal g−1; 62% carbohydrate, 18% protein and 20% fat by calories). The rats had _ad libitum_ access to tap water

throughout the study. At the end of experiment, rats were anesthetized by CO2 after overnight fasting and euthanized. STUDY DESIGN After the 2-week acclimation period, the 13-week-old rats

were randomly divided into two groups: 12 rats underwent a sham operation (C group) and 24 rats subtotal pancreatectomy. Then all rats were fed _ad libitum_ for 5 weeks, which could induce

diabetes in pancreatectomized rats. When overt diabetes was confirmed 5 weeks after the pancreatectomy, the pancreatectomized rats were divided into two groups: an _ad libitum_-fed group (AL

group, _n_=12) and a calorie-controlled diet group (R group, _n_=12). During the subsequent 6 weeks of diet control period, the R group was fed a calorie-restricted diet compared with the

AL group, which, however, was isocaloric (g per kg body weight per day) compared with the C group, determined by using the average daily food intake (g day−1) and body weight (g) of each

animal in the C group during the previous week. Rats in the AL and C groups had continued _ad libitum_ access to food. SUBTOTAL PANCREATECTOMY To generate an insulin-deficient diabetes model

in adult rats, we performed a subtotal pancreatectomy at 13 weeks of age. Briefly, we opened the abdominal wall under anesthesia using 0.7 mg per kg body weight Zoletil 50 (Virbac, Carros,

France) and 0.2 mg per kg body weight Rompun (Bayer Korea, Ansan, South Korea). Pancreatic tissue was carefully removed with cotton swabs, from the attachment to the spleen to 1 mm from the

common bile duct. The pancreatectomized rats were covered with blankets to maintain normal body temperature. The sham operation was performed using the same procedure but without removing

pancreatic tissue. FOOD INTAKE, FASTING BLOOD GLUCOSE (FBG), BODY WEIGHT AND RATE OF DAILY FOOD INTAKE The food intake (g) of each rat was measured daily, and the average daily food intake

of each group (g day−1) was calculated weekly. Every other week FBG (mg dl−1) was measured after an overnight fast at 0900 a.m. from the tail vein blood using a portable glucometer (CareSens

II; Gentrol Co., Incheon, South Korea). Body weight (g) was measured every week and at the end of the study just before euthanasia. The rate of daily food intake (g per kg body weight per

day) was calculated for each rat every week by dividing average daily food intake by body weight. PLASMA INSULIN AND C-PEPTIDE AND SERUM TRIACYLGLYCEROL (TAG), HIGH-DENSITY LIPOPROTEIN

(HDL)-CHOLESTEROL AND ALBUMIN ANALYSIS Immediately before excision of organs, blood samples were taken from the inferior vena cava. Plasma insulin and C-peptide levels were analyzed using

radioimmunoassay kits (Millipore, Billerica, MA, USA) according to the manufacturer’s instructions, and radioactivity was measured by using a γ-counter (Beckman Coulter, Brea, CA, USA).

Serum TAG level was measured using an enzymatic TAG assay kit (Bio Clinical System Co., Ansan, South Korea) and serum albumin level using a bromcresol green-albumin assay kit (Bio Clinical

System Co.) according to the manufacturer’s instructions. HDL-cholesterol level was quantified using a polyethylene glycol precipitation kit (Young Dong, Seoul, South Korea) combined with

the cholesterol oxidase method for cholesterol measurement. TWENTY-FOUR HOUR URINE GLUCOSE AND ALBUMIN ANALYSIS At the fourth week of the diet control period, 24-h urine samples were

collected while the rats were placed in metabolic cages. The total amounts of glucose and albumin in 24-h urine samples were measured with an automated analyzer (TBA-200 FR, Toshiba Medical

Systems Corporation, Tokyo, Japan), using a glucose assay kit (Denka Seiken Co., Tokyo, Japan) and an albumin assay kit (Abbott Laboratries, Abbott Park, IL, USA). ORGANS AND TISSUES At the

end of the 6-week diet control period, the rats were fasted overnight and the liver, heart, both epididymal fat pads, both kidneys and both soleus muscle tissues were quickly excised after

CO2 anesthesia, weighed and immediately frozen in liquid nitrogen. Frozen organs and tissues were stored in a −80 °C freezer until use. WESTERN BLOTTING ANALYSIS Each tissue from the excised

organs was pulverized to a fine powder in liquid nitrogen and homogenized in ice-cold buffer ocntaining 25 mM HEPES, 25 mM benzamidine, 100 mM sodium fluoride, 10 mM sodium pyrophosphate, 2

 mM sodium orthovanadate, 1% Triton X-100, 4 mM EDTA, 5 μl ml−1 phosphatase inhibitor cocktail I (Sigma Aldrich, St Louis, MO, USA), 5 μl ml−1 phosphatase inhibitor cocktail II (Sigma

Aldrich) and 5 μl ml−1 protease inhibitor cocktail (Sigma Aldrich). After centrifugation (18 400 _g_ for 30 min at 4 °C), the supernatant was collected, and the protein concentration was

determined using a BCA protein quantification kit (Pierce, Rockford, IL, USA) according to the manufacturer’s instructions. The proteins were separated by sodium dodecyl sulfate

polyacrylamide gel electrophoresis (13.5% gel for LC3 and 8% gel for Akt and p62) and transferred to nitrocellulose membranes (0.45 μm, Bio-Rad Laboratories Inc., Hercules, CA, USA) at 250 

mA for 90 min. After blocking with 5% bovine serum albumin in TBS-T buffer for 1 h at room temperature, the membranes were incubated overnight with an anti-LC3 antibody (Cell Signaling

Technology Inc., Danvers, MA, USA, 1:1000), an anti-p62 antibody (BD Biosciences, Franklin Lakes, NJ, USA, 1:1000) or an anti-Akt antibody (Cell Signaling Technology Inc., 1:5000) at 4 °C.

We also detected phospho-Ser473 Akt (Cell Signaling Technology Inc., 1:5000). The membranes were then incubated with a horseradish peroxidase-conjugated anti-rabbit IgG (Cell Signaling

Technology Inc., 1:5000) followed by detection with enhanced chemiluminescence (GE Healthcare, Wauwatosa, WI, USA). The immunoreactive protein bands were quantified using the MultiGauge

software (version 3.1; Fujifilm, Tokyo, Japan). STATISTICAL ANALYSIS Groups were compared by one-way analysis of variance followed by Tukey’s _post hoc_ test. Pearson’s correlation tests

were performed to determine the degree of correlation between organ weight and body weight or insulin level in pancreatectomized rats. Data are presented as mean±s.d.; _P_<0.05 was

considered significant. Statistical analysis was performed using the SPSS 18.0 software (SPSS Inc., Chicago, IL, USA). RESULTS PLASMA INSULIN AND C-PEPTIDE LEVELS To confirm the generation

of a rat model of insulin-deficient diabetes, we determined plasma insulin and C-peptide levels at the end of the study. The mean plasma insulin levels of pancreatectomized rats were 7.6%

(AL group) and 5.7% (R group) than that of the C group (Figure 1a; _P_<0.001 vs C group for both). The mean plasma C-peptide levels of pancreatectomized rats were 15.6% (AL group) and

8.6% (R group) than that of the C group (Figure 1b; _P_<0.001 vs C group for both). Insulin and C-peptide levels did not differ significantly between the AL and R groups. RATE OF DAILY

FOOD INTAKE As shown in Figure 2a, the rate of daily food intake did not differ significantly among the groups during the 2-week acclimation period (C group 78.2±16.4, AL group 80.0±17.2, R

group 76.9±15.5 g per kg body weight per day; _P_=0.893). However, the rate of daily food intake in the C group decreased over time (58.9±13.5 g per kg body weight per day during the 5-week

diabetes induction period), whereas that of the pancreatectomized rats fed _ad libitum_ for 5 weeks after surgery increased significantly (AL group 95.1±43.0, R group 93.9±39.3 g per kg body

weight per day; _P_<0.001 vs C group for both; Figure 2b). Rats in the AL group ate about three times more than rats in the C and R groups during the diet control period (_P_<0.001;

Figure 2c). FBG LEVELS Figure 2d shows sequential changes in FBG levels of all the groups throughout the experiment. Before surgery, FBG levels were within the normal range for all groups.

However, the pancreatectomized AL and R groups showed hyperglycemia during the 5 weeks after surgery, in which all groups were fed _ad libitum_ (C group 112.2±7.9 vs AL group 445.5±139.3 or

R group 454.5±152.7 mg dl−1; _P_<0.001 for both; Figure 2e), confirming that all pancreatectomized rats developed diabetes. However, the hyperglycemia in rats of the R group improved over

time to near-normoglycemic levels during the period of diet control (Figure 2d). Figure 2f shows that at the last week of the diet control period, FBG levels were within normal range for

both the C and R groups (113.0±15.9 and 125.2±14.9 mg dl−1, respectively; _P_=0.906); however, the mean FBG level of the AL group was 448.3±119.6 mg dl−1 (_P_<0.001 vs C and R groups).

BODY WEIGHTS Figure 2g shows sequential changes in body weights of all the groups throughout the experiment. Body weight did not differ significantly among the groups during the 2-week

acclimation period. Although the mean body weight of the C group steadily increased throughout the experimental period, body weight in the AL and R groups significantly decreased during the

5 weeks after pancreatectomy, even though they were fed _ad libitum_ (C group 469.3±37.4 g vs AL group 399.9±32.8 g and R group 404.0±29.6 g; _P_<0.001 for both; Figure 2h). As shown in

Figure 2g, the AL group maintained body weight during the rest of the study, whereas the R group lost body weight. Figure 2i shows that during the diet control period, the mean body weight

of the R group (336.5±62.5 g; 60 and 87% that of the C and AL groups, respectively) was significantly lower than that of the C group (563.5±38.5 g, _P_<0.001) and the AL group (389.0±50.7

 g, _P_=0.045). SERUM TAG, HDL-CHOLESTEROL AND ALBUMIN LEVELS AND 24-H URINE GLUCOSE AND ALBUMIN LEVELS As shown in Table 1, serum TAG, HDL-cholesterol and albumin levels were significantly

lower in the AL and R groups than the C group, but the AL and R groups did not differ significantly. Twenty-four hour urine glucose level increased in both the AL and R groups compared with

the C group, whereas the level of the AL group was five times greater than that of the R group (_P_<0.001). Moreover, the AL group showed albuminuria above microalbuminuria range (30–300 

mg 24 h−1), and the level was 10.5 times greater than that of the R group (_P_<0.01; Table 1). However, the C and R groups did not differ significantly. WEIGHTS OF ORGANS AND TISSUES To

determine whether reduced body weight due to insulin deficiency and/or diet control was accompanied by decreased weight of organs and tissues, we weighed the heart, liver, both epididymal

fat pads, both kidneys and both soleus muscle tissues of all rats at the end of the study. Figure 3a shows that the mean heart weights of the AL group (1.33±0.20 g) and R group (1.02±0.20 g)

were 80 and 61%, respectively, that of the C group (1.66±0.15 g; _P_<0.001 for both). It is noteworthy that the mean heart weight of the R group was only 77% that of the AL group

(_P_<0.001). Figure 3b shows that the mean liver weight of the R group (8.3±2.2 g) was 50% that of the C group (16.7±3.8 g) and 54% that of the AL group (15.4±1.9 g; _P_<0.001 for

both); the C and AL groups did not differ significantly. Figure 3c shows that the mean weight of both kidneys of the AL group (5.43±0.61 g) was 163% that of the C group (3.33±0.30 g) and

189% that of the R group (2.86±0.38 g; _P_<0.001 for both); the C and R groups did not differ significantly. Figure 3d shows that the mean weights of both soleus muscle tissues of the AL

group (0.364±0.049 g) and R group (0.318±0.063 g) were 77 and 67%, respectively, that of C group (0.471±0.047 g; _P_<0.001 for both); the AL and R groups did not differ significantly.

Figure 3e shows that the mean weights of both epididymal fat pads of the AL group (3.4±1.5 g) and R group (1.4±1.1 g) were 20 and 8%, respectively, that of C group (16.9±4.3 g; _P_<0.001

for both); the AL and R groups did not differ significantly. In pancreatectomized rats, the weights of all organs and tissues examined were significantly correlated with body weights and

plasma insulin levels (Table 2). PAKT/AKT RATIO AND AUTOPHAGY LEVEL To investigate potential mechanisms underlying differential changes in organ weights of insulin-deficient diabetic rats

fed _ad libitum_ or a calorie controlled diet, we investigated the ratio of phosphorylated Akt to total Akt, which is a crucial marker for insulin signaling, and the ratio of LC3 II to LC3 I

(the conversion of LC3 I to LC3 II) and p62 level, which are markers for autophagy activity (the ratio increases as autophagy is active)24 and autophagy flux (p62 level decreases as

autophagosomes are cleared from cytoplasm by lysosomal degradation),25 respectively. We found that Akt activation in heart tissue decreased by 40% in the R group compared with the C and AL

groups (_P_<0.05 for both; Figures 4a and b). In addition, the ratio of LC3 II to LC3 I in heart tissue increased by 5.6-fold in the R group compared with the C and AL groups (_P_<0.01

for both; Figures 5a and b), while p62 level of the R group was the lowest among all groups (Figure 5c). However, Akt activation, LC3 conversion and p62 level in heart tissue did not differ

significantly between the C and AL groups. Akt activation in liver tissue decreased by 31% in the R group compared with the C and AL groups (_P_<0.01 for both; Figures 4c and d). And the

ratio of LC3 II to LC3 I in liver tissue increased in the R group compared with the C group (1.6-fold, _P_=0.017) and AL group (2.2-fold, _P_=0.002; Figures 5d and e), while p62 level of

the R group was the lowest among all groups (Figure 5f). However, Akt activation, LC3 conversion and p62 level in liver tissue did not differ significantly between the C and AL groups. Akt

activity in kidney tissue increased by 50% in the AL group compared with the C group (_P_<0.05; Figures 4e and f) and increased by 72% compared with the R group (_P_<0.01; Figures 4e

and f ). The ratio of LC3 II to LC3 I in kidney tissue decreased by 40% in the AL group compared with the C and R groups (_P_<0.01 for both; Figures 5g and h), while p62 level did not

differ between the C and AL groups and was the highest in the R group (Figure 5i). However, Akt activation and LC3 conversion in kidney tissue did not differ significantly between the C and

R groups. DISCUSSION In the present study, we demonstrated that pancreatectomized diabetic SD rats achieved euglycemia and were protected against diabetic renal hyperplasia and excessive

albuminuria through diet control (R group) but displayed significant loss of overall body weight and weight of the heart and liver compared with both rats that underwent a sham operation (C

group) and diabetic rats with _ad libitum_ access to food (AL group). Although hyperglycemia induced renal hyperplasia and excessive albuminuria in the AL group, the loss of heart weight was

less than that of the R group, and liver weight was maintained similar to that of the C group (Figures 3a and b). Euglycemia has been known to prevent hyperglycemia-induced microvascular

complications, including diabetic nephropathy;2, 3 however, our results suggest that a strict diet control to achieve euglycemia may be deleterious in insulin deficiency, resulting in the

loss of functional mass in heart and liver tissues (Figures 3a and b). To understand the mechanism underlying the loss of organ weight in the R group, we investigated autophagy level,

because excessive autophagy has been known to induce cell death, leading to a reduction in organ weight.17, 26, 27, 28, 29, 30 We found that autophagy activity as well as autophagy flux

significantly increased in heart and liver tissues of the R group compared with the C group (Figures 5a–f), even though their daily food intake per body weight was the same (Figures 2a and

c). Insulin inhibits autophagy via the class I PI3K-Akt pathway.18, 31, 32 The mean plasma insulin level of the R group was <10% that of the C group, and Akt activity in those tissues was

also significantly lower in the R group (Figures 4a–d). Although the mean plasma insulin level of the AL group was similar to that of the R group, neither Akt activity nor autophagy

activity and flux differed from those of the C group (Figures 4a–d and Figures 5a–f). These findings are consistent with organ weight in the AL group, in which a considerable loss of heart

weight appeared to develop during the 5 weeks of induction of diabetes, but subsequently, the weight appeared to be maintained until the end of the study with an _ad libitum_ diet (Figure

2g), as estimated by the relationship between organ and body weight (Table 2). Several studies support these observations in the AL group: hyperglycemia can activate Akt33, 34 and sufficient

nutrient levels within cells inhibit autophagy, independent of insulin level.18 Taken together, our findings suggest that although an _ad libitum_ diet after subtotal pancreatectomy can

result in renal hyperplasia and excessive albuminuria, indicating hyperglycemic damage to endothelial cells as explained elsewhere,35 this more natural eating behavior may compensate for

decreased insulin signaling in heart and liver tissues. By contrast, the amount of food consumed by the healthy control rats may not be sufficient to protect the R group against autophagic

destruction of heart and liver tissues in insulin deficiency. These findings may explain the reason that the T2DM patients with moderate degree of hyperglycemia showed the lowest mortality

compared with those with high degree of hyperglycemia or near-euglycemia,11 for, though even moderate hyperglycemia is toxic to vascular endothelial cells compared with euglycemia, the

glycemic level seems to be high enough to suppress autophagic response by increasing insulin signaling in heart and liver tissues of diabetic patients but low enough not to induce severe

damage on endothelial cells as shown in high degree of hyperglycemia. Our results are reminiscent of studies on the autophagic response during starvation. One study reported that autophagy

in the heart and liver was increased in mice after a 24-h starvation period.36 Another study reported that heart weight decreased by 21% and liver weight decreased by 55% in 16-week-old rats

after 10 days of starvation; these rats died approximately 2 days later, when starved persistently.37 Because of the comparable loss of heart and liver weight, we speculate that diet

control to achieve euglycemia has a starvation-like effect in insulin-deficient rats. Although calorie restriction can extend lifespan and prevent age-associated diseases such as diabetes,

cardiovascular disease and cancer,38, 39 our study demonstrates that in insulin deficiency, calorie-restricted diet control to achieve euglycemia can increase autophagy above the basal level

in the heart and liver. These findings may explain the reason that the intensive glycemic control group showed higher mortality from cardiovascular causes compared with the standard-therapy

group, whose HbA1c levels were 6.4 and 7.5%, respectively.8 Finally, we found that loss of soleus muscle and epididymal fat pad weight was similar in both the groups of diabetic rats

compared with the sham-operated control group, indicating that insulin-dependent tissues, including skeletal muscle and adipose tissues, may not be protected against weight loss by the _ad

libitum_ diet when insulin is deficient. In conclusion, although diet control becomes more important for optimal glycemic control especially in end-stage T2DM because of decreased β-cell

function and drug failure over time,40, 41, 42 strict diet control to achieve euglycemia should be avoided to prevent loss of functional mass of the heart and liver via increased autophagy.

The effects of calorie restriction (beneficial or deleterious) are dependent on insulin status. In addition, polyphagia may be a compensatory mechanism for insulin deficiency in diabetic

patients, by which resulting high glucose level may activate insulin signaling and maintain the heart and liver weights at the cost of renal hyperplasia. Further studies are needed to better

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1716–1730. Article  CAS  PubMed  Google Scholar  Download references AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * Department of Biochemistry, Konkuk University School of Medicine, Seoul,

Republic of Korea Jun-Ho Lee, Ju-Han Lee, Mingli Jin, Seonguk Kim, Sung-Young Kim & Yun-Hee Noh * Rmedica-Stem Cell, Seoul, Republic of Korea Ju-Han Lee * Department of Neurology, Konkuk

University School of Medicine, Chungju Hospital, Chungju, Republic of Korea Sang-Don Han * Department of Pulmonary and Critical Care Medicine, Konkuk University School of Medicine, Chungju

Hospital, Chungju, Republic of Korea Gyu-Rak Chon * Department of Surgery, Konkuk University School of Medicine, Chungju Hospital, Chungju, Republic of Korea Ick-Hee Kim * Department of

Internal Medicine, Konkuk University School of Medicine, Chungju Hospital, Chungju, Republic of Korea Soo-Bong Choi Authors * Jun-Ho Lee View author publications You can also search for this

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AUTHORS Correspondence to Soo-Bong Choi or Yun-Hee Noh. ETHICS DECLARATIONS COMPETING INTERESTS The authors declare no conflict of interest. RIGHTS AND PERMISSIONS This work is licensed

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JH., Jin, M. _et al._ Diet control to achieve euglycemia induces significant loss of heart and liver weight via increased autophagy compared with _ad libitum_ diet in diabetic rats. _Exp Mol

Med_ 46, e111 (2014). https://doi.org/10.1038/emm.2014.52 Download citation * Received: 25 April 2014 * Accepted: 30 June 2014 * Published: 29 August 2014 * Issue Date: August 2014 * DOI:

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